The present invention relates to a write-once (information can be written once, thereafter it can only be reproduced) optical recording film, a method for manufacturing the same, an optical recording medium, a method for manufacturing the same, an information recording/reproducing apparatus using the same, a computer system using the same, and a video signal recording/reproducing system.

Recently, the amount of electronic information has risen dramatically, so that there is a need for the development of high-capacity low-cost optical information storage media. High-capacity low-cost optical information storage media are for example in high demand for recording video information of various formats and as supplemental storage media for computers. Most of the high-capacity optical information recording media that are currently under development use magnetic recording, optomagnetic recording or phase-change recording.

In magnetic recording, a super-thin layer of a metallic magnetic material is provided in a medium substrate, so that information is recorded by magnetizing the magnetic material by irradiation with magnetic force lines.

In optomagnetic recording, a magnetic chemisorptive thin film is heated partially to above the Curie temperature or the temperature compensation point, and information is written by extinguishing the coercivity of these portions and inverting the orientation of the magnetization into the direction of a magnetic recording field applied from outside.

In phase-change recording, a recording film made of a special alloy is irradiated with a laser beam, and information is recorded by switching the alloy between a crystalline state and an amorphous state.

However, when using any of these recording methods, the recording layer is formed by vacuum vapor deposition. Therefore, there is the problem that the manufacturing costs for these optical recording media are high.

Furthermore, with these methods, there is the problem that optical recording media that are compatible with various types of information recording/reproducing apparatuses cannot be manufactured easily.

In view of the above, it is a first object of the present invention to provide an optical recording film which an optical recording layer can be formed using an organic thin film, but without using vacuum vapor deposition, and a method for manufacturing the same.

It is a second object of the present invention to provide an inexpensive high-density write-once optical recording medium using this optical recording film.

It is a third object of the present invention to provide a computer system and a video signal recording/reproducing system using the write-once optical recording medium.

A first write-once optical recording film in accordance with the present invention includes:

• a chemisorptive thin film with orienting properties fixed directly or through a primer layer to a substrate surface; and
• a coating formed on a surface of the chemisorptive thin film;

A first method for manufacturing a write-once optical recording film in accordance with the present invention includes:

• forming a chemisorptive thin film on a substrate;
• subjecting the chemisorptive thin film to an orientation treatment;
• bringing a surface of the chemisorptive thin film in contact with polymerizable molecules by applying a solution in which the polymerizable molecules have been dissolved to the surface of the chemisorptive thin film, removing the solvent, and aligning a group of the polymerizable molecules in a predetermined direction at the surface of the chemisorptive thin film with the orientation regulating force of the chemisorptive thin film; and
• forming a coating by bonding (e.g. polymerizing or crosslinking) the polymerizable molecules to one another.

In accordance with the present invention, a first optical recording medium comprising an optical recording layer on at least one surface of a medium substrate includes an optical recording film comprising:

• a chemisorptive thin film with orienting properties fixed directly or through a primer layer to a substrate surface; and
• a coating formed on a surface of the chemisorptive thin film;

In accordance with the present invention, a first method for manufacturing an optical recording medium provided with a recording layer in which optical information can be recorded by changing an initial molecule orientation of a coating constituting the recording layer by selectively irradiating focused light, includes:

• forming a chemisorptive thin film on at least one surface of a medium substrate;
• subjecting the chemisorptive thin film to an orientation treatment;
• bringing a surface of the chemisorptive thin film in contact with polymerizable molecules by applying a solution in which the polymerizable molecules have been dissolved to the surface of the chemisorptive thin film, removing the solvent, and aligning a group of the polymerizable molecules in a predetermined direction at the surface of the chemisorptive thin film with the orientation regulating force of the chemisorptive thin film; and
• forming a coating by polymerizing the polymerizable molecules to one another.

In accordance with the present invention, a first method for optical recording on an optical recording medium provided with an optical recording layer on at least one surface of a substrate is provided,

wherein the optical recording layer comprises a chemisorptive thin film with orienting properties fixed directly or through a primer layer to the surface of the substrate, and a coating formed on a surface of the chemisorptive thin film;

wherein the coating has an initial molecule orientation attained by aligning a group of polymerizable molecules in a predetermined direction on the surface of the chemisorptive thin film, and polymerizing the polymerizable molecules to one another;

wherein regions with changed initial molecule orientation and regions with unchanged initial molecule orientation of the coating are formed when selectively irradiating the coating with light that changes the initial molecule orientation, thus recording optical information.

In accordance with the present invention, a first information recording/reproducing apparatus for recording and reproducing information on a write-once optical recording medium,

wherein the write-once optical recording medium is provided with an optical recording layer on at least one surface of a substrate;

wherein the optical recording layer comprises a chemisorptive thin film with orienting properties fixed directly or through a primer layer to the surface of the substrate, and a coating formed on a surface of the chemisorptive thin film;

wherein the coating has an initial molecule orientation attained by aligning a group of polymerizable molecules in a predetermined direction on the surface of the chemisorptive thin film, and polymerizing the polymerizable molecules to one another; and

wherein regions with changed initial molecule orientation and regions with unchanged initial molecule orientation of the coating can be formed by selectively irradiating the coating with light that changes the initial molecule orientation; comprises:

• a signal input/output portion;
• a recording light emitting portion selectively emitting recording light for writing information elements by changing the initial molecule orientation of the chemisorptive thin film constituting the recording layer, in accordance with an information signal from the signal input/output portion;
• an information recording portion including said optical recording medium, on which information is recorded by irradiating the recording light emitted from the recording light emitting portion;
• a reference light emitting portion for emitting reference light that does not change the initial molecule orientation of the coating constituting the recording layer, used for reproduction of information recorded on the optical recording medium of the information recording portion;
• an information element detecting portion which irradiates the reference light on the optical recording medium, detects with an optical sensor an intensity change of a polarized component of reflected light, transmitted light or scattered light of the reference light, due to differences in information elements, and outputs a predetermined electrical signal to the signal input/output portion, based on the detected results;
• a position control driving portion, which shifts or rotates the optical recording medium in order to selectively irradiate the recording light and the reference light on predetermined positions of the optical recording medium; and
• a control circuit portion for controlling the recording operation by coordinating the recording light emitting portion and the position control driving portion, and controlling the reproduction operation by coordinating the information element detecting portion and the position control driving portion.

A first computer system in accordance with the present invention includes:

• an arithmetic processing device including a main memory;
• an auxiliary recording device connected to the arithmetic processing device and serving as an auxiliary memory;
• an input device connected to the arithmetic processing device;
• an output device connected to the arithmetic processing device; and
• a control device for controlling data communication between the devices;

• a signal input/output portion;
• a recording light emitting portion selectively emitting recording light for writing information elements by changing and destroying the initial molecule orientation of the coating constituting the recording layer, in accordance with an information signal from the signal input/output portion;
• an information recording portion including said optical recording medium, on which information is recorded by irradiating the recording light emitted from the recording light emitting portion;
• a reference light emitting portion for emitting reference light that does not change the initial molecule orientation of the coating constituting the recording layer, used for reproduction of information recorded on the optical recording medium of the information recording portion;
• an information element detecting portion which irradiates the reference light on the optical recording medium, detects with an optical sensor an intensity change of a polarized component of reflected light, transmitted light or scattered light of the reference light that has passed through a polarizer, due to differences in information elements, and outputs a predetermined electrical signal to the signal input/output portion, based on the detected results;
• a position control driving portion, which shifts or rotates the optical recording medium in order to selectively irradiate the recording light and the reference light on predetermined positions of the optical recording medium; and
• a control circuit portion for controlling the recording operation by coordinating the recording light emitting portion and the position control driving portion, and controlling the reproduction operation by coordinating the information element detecting portion and the position control driving portion.

In another computer system making use of an optical information storage medium, an improvement is that the optical information storage medium comprises the first write-once optical recording film in accordance with the present invention.

A first video signal recording/reproducing system in accordance with the present invention includes:

• a video signal input/output control device controlling the input source and the output destination of a video signal;;
• a video recording/reproducing device connected to the video signal input/output control device;
• a video output device connected to the video signal input/output control device; and
• a control command input device for sending input/output control commands to the video signal input/output control device, connected to the video signal input/output control device;

• a signal input/output portion;
• a recording light emitting portion selectively emitting recording light for writing information elements by changing and destroying the initial molecule orientation of the coating constituting the recording layer, in accordance with an information signal from the signal input/output portion;
• an information recording portion including said optical recording medium, on which information is recorded by irradiating the recording light emitted from the recording light emitting portion;
• a reference light emitting portion for emitting reference light that does not change the initial molecule orientation of the coating constituting the recording layer, used for reproduction of information recorded on the optical recording medium of the information recording portion;
• an information element detecting portion which irradiates the reference light on the optical recording medium, detects with an optical sensor an intensity change of a polarized component of reflected light, transmitted light or scattered light of the reference light that has passed through a polarizer, due to differences in information elements, and outputs a predetermined electrical signal to the signal input/output portion, based on the detected results;
• a position control driving portion, which shifts or rotates the optical recording medium in order to selectively irradiate the recording light and the reference light on predetermined positions of the optical recording medium; and
• a control circuit portion for controlling the recording operation by coordinating the recording light emitting portion and the position control driving portion, and controlling the reproduction operation by coordinating the information element detecting portion and the position control driving portion.

In another video signal recording/reproducing system making use of an optical information storage medium, an improvement is that the optical information storage medium comprises the first write-once optical recording film in accordance with the present invention.

In a second aspect, a write-once optical recording film in accordance with the present invention comprises:

• a thin film made of chemisorptive molecules fixed directly or through a primer layer to a substrate surface by covalent bonding;

A second method for manufacturing a write-once optical recording film in accordance with the present invention, which comprises a thin film made of chemisorptive molecules fixed by covalent bonds directly or through a primer layer to a substrate surface, wherein optical information can be recorded on the thin film by irradiating light to degrade the molecules at the irradiated portions;

comprises bringing a chemisorptive compound including a chemisorptive group and a functional group that degrades when irradiated with light in contact with a substrate or a primer layer including active hydrogen at its surface to cause an elimination reaction between the chemisorptive group and the active hydrogen, and thereby fixing the chemisorptive compound by covalent bonding directly or through a primer layer to a substrate surface.

A second write-once optical recording medium including a write-once optical recording film comprises a substrate and a thin film made of chemisorptive molecules fixed by covalent bonds directly or through a primer layer to one or both sides of the substrate, in which optical information can be recorded;

wherein the optical recording film can be optically recorded by irradiating light to degrade the molecules at the irradiated portions.

A second method for manufacturing a write-once optical recording medium, which comprises a substrate and a thin film made of chemisorptive molecules fixed by covalent bonds directly or through a primer layer to one or both sides of the substrate, wherein optical information can be recorded in the thin film by irradiating light to degrade the molecules at the irradiated portions;

comprises bringing a chemisorptive compound including a chemisorptive group and a functional group that degrades when irradiated with light in contact with a substrate or a primer layer including active hydrogen at its surface to cause an elimination reaction between the chemisorptive group and the active hydrogen, and fixing the chemisorptive compound by covalent bonding directly or through a primer layer to the substrate surface.

A second method for recording/reproducing information on a write-once optical recording medium, which comprises a substrate and a thin film made of chemisorptive molecules fixed by covalent bonds directly or through a primer layer to one or both sides of the substrate, wherein optical information can be recorded in the thin film by irradiating light to degrade the molecules at the irradiated portions, comprises:

• a recording step of recording information by irradiating recording light on the optical recording film to degrade the irradiated portions into degraded portions, and by combining the degraded portions and non-degraded portions; and
• a reproduction step of reproducing information by irradiating reproduction light on the degraded portions and the non-degraded portions and detecting a difference in the optical intensity after the light has reached the degraded portions and the non-degraded portions.

A second apparatus for recording/reproducing information on a write-once optical recording medium, which comprises a substrate and a thin film made of chemisorptive molecules fixed by covalent bonds directly or through a primer layer to one or both sides of the substrate, wherein optical information can be recorded in the thin film by irradiating light to degrade the molecules at the irradiated portions, comprises:

• a signal input/output means for input/output of information signals of information converted into electrical signals and operation command signals to/from an external device;
• a recording light irradiation means for irradiating recording light in order to degrade the molecules constituting the optical recording film, in accordance with an information signal from the signal input/output means;
• a reproduction light irradiation means for irradiating reproduction light that does not degrade the molecules constituting the optical recording film, used for reproduction of information recorded on the optical recording medium of the information recording portion;
• an information element detecting means which irradiates the reference light on the optical recording medium, detects an intensity of reflected light or transmitted light after the reproduction light has reached the optical recording film, and outputs a predetermined electrical signal to the signal input/output means, based on the detected results;
• an optical recording medium driving means for irradiating the recording light or the reproduction light onto a predetermined position of the optical recording film; and
• a control circuit means for controlling the recording operation by coordinating the recording light irradiation means and the optical recording medium driving means, and controlling the reproduction operation by coordinating the reproduction light irradiation means, the optical recording medium driving means and the information element detecting means.

Fig. 1 is a diagram illustrating a chemisorptive thin film formation step for producing a monomolecular film on a substrate in accordance with Working Example 1 of the present invention.

Figs. 2A to 2C are diagrams schematically illustrating states of the chemisorptive thin film in Working Example 1 of the present invention. Fig. 2A is a diagram of the monomolecular film before the orientation treatment. Fig. 2B is a diagram illustrating the monomolecular film after the orientation treatment. Fig. 2C is a diagram illustrating the monomolecular film after crosslinking.

Figs. 3A to 3C are conceptual diagrams illustrating how the coating is formed in Working Example 1 of the present invention. Fig. 3A illustrates how polymerizable liquid crystal molecules are formed randomly. Fig. 3B illustrates the state of the polymerizable liquid crystal molecules after the orientation treatment. And Fig. 3C illustrates the state of the polymer liquid crystal molecules after polymerization.

Fig. 4 is a conceptual diagram showing how optical information is recorded on the optical recording film of Working Examples 1 to 4 of the present invention.

Figs. 5A to 5E are diagrams schematically illustrating variations of the recording regions formed on the optical recording medium in accordance with Embodiment 1 of the present invention.

Fig. 6 is a conceptual diagram showing an example of an information recording/reproducing apparatus in accordance with Working Example 4 of the present invention.

Fig. 7 is a conceptual diagram showing an example of a computer system using an optical recording medium in accordance with Working Example 5 of the present invention.

Fig. 8 is a conceptual diagram showing an example of a video recording/reproducing system using an optical recording medium in accordance with Working Example 6 of the present invention.

Figs. 9A and 9B illustrate a method for rubbing a polyimide film in Working Example 2 of the present invention. Fig. 9A is a plan view illustrating a method for rubbing with a rubbing roll, and Fig. 9B is a cross-sectional view taken from the right illustrating the method for rubbing with a rubbing roll.

Figs. 10A and 10B are conceptual diagrams showing, at the molecular level, a cross-sectional and a top view of the medium on which optical information has been recorded on an optical recording medium according to Working Example 3 of the present invention. Fig. 10A is a cross-sectional conceptual diagram of the medium on which optical information has been recorded. Fig. 10B is a conceptual diagram of the medium on which optical information has been recorded.

Fig. 11 is a cross-sectional view schematically illustrating a write-once optical recording film in accordance with Working Example 7 of the present invention.

Fig. 12 is a schematic diagram illustrating a method for manufacturing (film manufacturing step) a write-once optical recording film in accordance with Working Example 7 of the present invention.

Fig. 13 is a cross-sectional view schematically showing an optical recording medium in accordance with Working Example 9 of the present invention.

Figs. 14A to 14B are diagrams illustrating a recording method for an optical recording medium in accordance with Working Example 9 of the present invention. Fig. 14A is a schematic diagram illustrating the recording method. Fig. 14B is a plan view schematically illustrating the recorded state.

Fig. 15 is a schematic diagram illustrating a reproduction method for an optical recording medium in accordance with Working Example 9 of the present invention.

Fig. 16 is a schematic cross-sectional view illustrating another recording method for an optical recording medium in accordance with Working Example 9 of the present invention.

Fig. 17 is a schematic diagram illustrating a reproduction method for an optical recording medium in accordance with Working Example 10 of the present invention.

Fig. 18 is a schematic diagram illustrating the configuration of an information recording/reproducing apparatus in accordance with Working Example 11 of the present invention.

Fig. 19 is a schematic diagram illustrating the configuration of a computer system in accordance with Working Example 12 of the present invention.

Fig. 20 is a schematic diagram illustrating the configuration of a video signal recording/reproducing system in accordance with Working Example 13 of the present invention.

Fig. 21 is a diagram illustrating a method for evaluating the orientation of the molecules constituting the optical recording film in accordance with Working Example 14 of the present invention.

The polymerizable molecules of the present invention are aligned in accordance with the above-described orienting properties in a predetermined orientation and with a predetermined tilt on the surface of a chemisorptive thin film. Here, "chemisorptive thin film" refers to a thin film, in which a surface adsorbing agent having reactive groups, such as chlorosilyl groups alkoxysilyl groups, on its molecule ends is used to cause e.g. a dehydrochlorination reaction or dealcoholization reaction between the reactive groups and active hydrogen on the substrate surface, thus covalently bonding the surface adsorbing molecules to the substrate surface. Such films are also known as "self-assembling films" to the person skilled in the art.

The reason why in the present invention a coating is provided on a chemisorptive thin film with orienting properties is because it is necessary to orient the polymerizable molecules in a predetermined orientation. By simply providing the coating on a chemisorptive thin film without orienting properties, it may not be possible to orient the molecules in a certain orientation. Thus, the orientation regulating force of the chemisorptive thin film is utilized to orient the polymerizable molecules on the chemisorptive thin film. Here, "orientation regulating force" refers to a force that automatically orients the polymerizable molecules that are formed on top of the chemisorptive thin film and are influenced by the orientation of the chemisorptive thin film.

As long as the chemisorptive thin film has orienting properties, it can be a monomolecular film or a polymer film.

If the chemisorptive thin film with orienting properties is a monomolecular thin film, then the molecules constituting the chemisorptive thin film are aligned orderly, tilted in a certain direction. There are gaps between neighboring molecules constituting the chemisorptive thin film, and when the shape of the polymerizable molecules conforms to these gaps, they can be fitted into these gaps. As mentioned above, the molecules constituting the chemisorptive thin film are tilted in a predetermined direction, so that also the polymerizable molecules fitted into the gaps are tilted in a predetermined direction. Moreover, the polymerizable molecules are linked to one another by polymer coupling. Thus, also in the coating provided on the chemisorptive thin film, the polymerizable molecules are fixed while tilted in a certain direction and aligned orderly, so that it is possible to provide an optical recording film with high uniformity.

If the chemisorptive thin film having the above-described orienting function is a polymer film, then the polymer absorbs the irregularities of the layer below it, so that an optical recording film with superior flatness can be provided.

The monomolecular film or polymer film is made of molecules having photosensitive groups, and by crosslinking, the photosensitive groups in the chemisorptive thin film are bonded to one another by crosslinking. In this example, the photosensitive groups are bonded by crosslinking, and the molecules are fixed, so that the orientation state of the molecules constituting the chemisorptive thin film is three-dimensionally stable. As a result, a chemisorptive thin film with superior orientation regulating force with respect to polymerizable molecules is attained.

The photosensitive groups also can include double or triple bonds. Furthermore, the photosensitive groups also can be chalcone groups or cinnamate groups.

It is preferable that the polymerizable molecules are polymerizable liquid crystal molecules. Polymerizable liquid crystal molecules can be aligned orderly in accordance with the orienting properties of the chemisorptive thin film, and the polymerizable liquid crystal molecules can be polymer bonded to one another in this state. As a result, a coating with uniform initial molecule orientation is achieved, so that an optical recording film with a high contrast between the written positions and non-written positions of the optical recording and with superior recording stability can be provided. Here, "initial molecule orientation" means the orientation in which the polymerizable molecules are automatically oriented when they are formed on the chemisorptive thin film, influenced by the orientation chemisorptive thin film.

The polymerizable liquid crystal molecules can have groups including double or triple bonds. If the polymerizable liquid crystal molecules have groups including double or triple bonds, then the groups easily can be polymerized to one another. The polymerizable liquid crystal molecules also can be photopolymerizable liquid crystal molecules. If the polymerizable liquid crystal molecules are photopolymerizable liquid crystal molecules, then the molecules easily can be polymerized to one another by irradiation with light.

It is also possible to use the substance represented by the following general formula (A) for the polymerizable liquid crystal molecules:

In Formula 8, Q¹ represents a functional group selected from the group consisting of an acryloyloxy group, a methacryloyloxy group, ClCH=CHCOO-, an acryloamide group, a methacryloamide group, ClCH=CHCONH-, a vinyl group, CH₂=CCl-, CHCl=CH-, an epoxy group, an ethynyl group, a mercapto group and CH₂=CHO-; Q² represents a functional group selected from the group consisting of a hydrogen atom, an acryloyloxy group, a methacryloyloxy group, ClCH=CHCOO-, an acryloamide group, a methacryloamide group, ClCH=CHCONH-, a vinyl group, CH₂=CCl-, CHCl=CH-, an epoxy group, an ethynyl group, a mercapto group and CH₂=CHO-; R¹ and R² represent, independently, a straight-chain or branched bivalent hydrocarbon group with a carbon number of 1 to 18; Y¹ and Y² represent, independently, a linking group selected from the group consisting of a single bond, -O-, and -S-; u represents one of the integers 0 and 1; the 6-membered rings A, B and C , independently, are selected from the group consisting of p represents an integer of 1 to 4, Y³ and Y⁴ represent, independently, a linking chain selected from the group consisting of single bond, -CH₂CH₂-, -CH₂C(CH₃)H-, -C(CH₃)HCH₂-, -CH₂O-, -OCH₂-, -CF₂O-, -OCF₂-, -COO-, -OCO-, -C≡C-, -CH=CH-, -CF=CF-, -(CH₂)₄-, -CH₂CH₂CH₂O-, -OCH₂CH₂CH₂-, -CH=CH-CH₂CH₂- and -CH₂CH₂-CH=CH-.

This is because it is easy to obtain the desired polymer film when using these polymerizable liquid crystal molecules.

In the general formula (A), the portion represented by the following general formula (B) also can be one of the groups represented by the following formulas (C):

If the polymerizable liquid crystal molecules include such a group, then they react more readily to light, so that by irradiating them with light, it is possible to orient the polymerizable liquid crystal molecules better with the desired tilt angle.

In the above-noted general formula (A), the portion denoted by the general formula (D)



        (Formula 12)   Q¹-(R¹-Y¹)-   (D)



also can include an acryloyloxy group.

Acryloyloxy groups are photopolymer groups, so that it is possible to perform the polymerization of the liquid crystal molecules reliably.

In the above-noted general formula (A), the portion denoted by the general formula (D) and the portion denoted by the general formula (E)



        (Formula 13)   Q²-(R²-Y²)-   (E)



can also both include an acryloyloxy group.

When both the portion denoted by the general formula (D) and the portion denoted by the general formula (E) include an acryloyloxy group, the liquid crystal molecules can form at both ends crosslinking bonds with other liquid crystal molecules. As a result, a coating with superior orientation stability is attained.

In the general formula (A), the functional group denoted by the general formula (D) and the functional group denoted by the general formula (E) also can be the same.

This is because if in the general formula (A), the functional group denoted by the general formula (D) and the functional group denoted by the general formula (E) are the same, then the liquid crystal molecules have superior symmetry, so that it is possible to attain a coating with uniform orientation.

In the general formula (A), R² also can be a straight-chain or branched bivalent hydrocarbon group with a carbon number of 1 to 10. If R² is a straight-chain or branched bivalent hydrocarbon group with a carbon number of 1 to 10, then orientation in accordance with the orientation regulating force of the chemisorptive thin film becomes easier, so that a coating with superior orientation can be attained. More preferably, it is a straight-chain or branched bivalent hydrocarbon group with a carbon number of 1 to 3, which is even easier to orient.

The group of polymerizable liquid crystal molecules is tilted in a predetermined direction on the chemisorptive thin film in accordance with the orienting properties of the chemisorptive thin film having an orienting function, and the polymerizable liquid crystal molecules are polymerized/fixed to one another. With this configuration, the polymerizable liquid crystal molecules are oriented uniformly and have superior orientation stability, so that an optical recording film with a high contrast between the written positions and non-written positions of the optical recording and with superior recording stability can be provided.

There is no particular limitation with regard to the method for forming the chemisorptive thin film, and any of the methods known in the art can be used. For example, the step of forming the chemisorptive thin film can be the formation of a monomolecular film in a dry atmosphere by bringing a chemisorptive solution including a silane-based chemisorptive substance having a photosensitive group and a non-aqueous organic solvent in contact with the substrate surface, and chemisorbing the molecules of the chemisorptive substance in the chemisorptive solution to the substrate surface. With this configuration, it is possible to manufacture a chemisorptive thin film having gaps into which polymerizable molecules can be fitted between neighboring molecules constituting the chemisorptive thin film.

In the step of forming the chemisorptive thin film, it is also possible to form a polymer film by applying a solution in which a polymer precursor has been dissolved on the substrate, followed by drying or heating the substrate, and curing the precursor. With this configuration, it is possible to form a flat polymer film despite irregularities in the substrate, so that an optical recording film with superior flatness can be manufactured.

The above-mentioned orientation treatment step can be a polarized light orientation step of orienting by irradiating the substrate surface on which the chemisorptive thin film is formed with polarized light. With this configuration, the chemisorptive thin film surface can be oriented uniformly, so that a chemisorptive thin film having superior orientation regulating force can be attained and a uniform optical recording film can be manufactured.

The orientation treatment step also can be a step of irradiating polarized light on the monomolecular film or the polymer film including film molecules having photosensitive groups to polymerize or crosslink the photosensitive groups, and thus orientation treating the monomolecular film and the polymer film. With this configuration, the photosensitive groups are bonded by crosslinking to one another, and the molecules are fixed, so that the orientation of the molecules constituting the chemisorptive thin film is stabilized three-dimensionally. As a result, it is possible to attain a chemisorptive thin film with superior orientation regulating force with respect to the polymerizable molecules, so that it is possible to manufacture an optical recording film with which stable optical recording is possible.

In the orientation treatment step, the polarized light that is irradiated can be UV light. This is because by using UV light, it is possible to bond the photosensitive groups to one another efficiently by crosslinking.

The orientation treatment step also can be a step of orientation treating by rubbing the polymer film. When rubbing is used, then the orientation treatment of the chemisorptive thin film surface is facilitated.

In the polymerizable molecule orientation step, it is also possible to use polymerizable liquid crystal molecules as the polymerizable molecules, and to use an organic solvent as the solvent in which the polymerizable liquid crystal molecules are dissolved. With this configuration, liquid crystal molecules are used, so that it is possible to achieve a uniform orientation due to the orientation regulating force of the chemisorptive thin film. Also, the liquid crystal molecules easily can be bonded by crosslinking to one another, so that a coating with a three-dimensionally stable structure is attained, which makes it possible to manufacture an optical recording film on which optical information can be recorded stably. Furthermore, if an organic solvent is used as the solvent in which the polymerizable liquid crystal molecules are dissolved, then the polymerizable liquid crystal molecules can be dissolved with high efficiency.

It is more preferable that organic solvent that is used has a boiling point of at least 100°C and at most 250°C. If the boiling point is lower than 100°C, then the solvent is removed from the substrate surface before the polymerizable liquid crystal molecules are sufficiently oriented, which is undesirable. On the other hand, if the boiling point is higher than 250°C, then solvent remains on the substrate surface even after the polymerizable liquid crystal molecules have been oriented, thus lowering the stability of the orientation, which is also undesirable.

The coating formation step also can be a step of polymerizing the molecules by irradiating the polymerizable molecules with light. With this configuration, the photo-polymerization proceeds with high efficiency, so that an optical recording film can be manufactured with high efficiency.

In the coating formation step, it is also possible to use photo-polymerizable liquid crystal molecules for the polymerizable molecules. Such liquid crystal molecules easily can be polymerized by irradiation with light, because they are photo-polymerizable.

In the coating formation step, it is preferable that the light that is irradiated is UV light. Irradiating UV light promotes photo-polymerization, so that the optical recording film can be manufactured with high efficiency.

It is also possible to mix a substance as represented by the general formula (A) with a functional acrylate monomer that is different from that substance and use it as the polymerizable liquid crystal molecules. Functional acrylate monomers are cured when irradiated with UV light, so that an optical recording film with high film strength can be manufactured.

It is also possible to mix a substance as represented by the general formula (A) with a functional acrylate monomer that is different from that substance, further mix a sensitizing agent into that mixture, and use the result as the polymerizable liquid crystal molecules. Adding a sensitizing agent further promotes the polymerization of the polymer film.

For the sensitizing agent, it is possible to use a substance that responds to UV light. Mixing a substance that responds to UV light, the photo-polymerization of the polymer film is promoted, so that the optical recording film can be manufactured with high efficiency.

As the substance that responds to UV light, it is possible to use a substance containing -C₆H₄CO- in its molecules. A substance containing -C₆H₄CO- has higher sensitivity to UV light.

It is sufficient if the medium substrate of the present invention includes at least a substrate, but it also can include a protective layer, a reflective film and other layers, as desired.

The substrate can be made of metal, ceramic, glass or synthetic resin.

The medium substrate also can be made of the substrate and a reflective layer including a metal that is layered on the substrate. With this configuration, it is possible to provide a reflective optical recording medium.

The reflective layer can include aluminum. With this configuration, the reflectance of the light that is irradiated when writing optical information or reading out optical information is high, so that an optical recording medium is attained, which allows the reading and writing of optical information with high sensitivity. A preferable reflectance is about 97 to 98%.

It is also possible to provide a further transparent protective layer on the reflective layer. With this configuration, it is possible to improve the corrosion resistance of the surface of the reflective layer, providing an optical recording medium with high durability. It is preferable that such a transparent protective layer is made of an inorganic substance, and it is even more preferable that this inorganic substance is SiO₂ or SiN_x (stoichiometrically Si₃N₄, but the actual valence is not determined, so that x can be any suitable value).

It is also possible that a reflective film is layered on both sides of the substrate, forming optical recording layers on both sides of the optical recording medium. With this configuration, it is possible to record double the optical information on one optical recording medium.

The above-mentioned coating also can be provided over the entire surface of the chemisorptive thin film with orienting properties. Moreover, the coating can be provided partially on the chemisorptive thin film with orienting properties. It is possible to provide several kinds of films, in accordance with the intended use of the optical recording medium.

The optical recording layer has at least one optical recording region. With this configuration, it is possible to form a plurality of optical recording regions on one optical recording layer. As a result, it is possible to provide a plurality of optical recording regions conforming to a track pattern, and regions where optical recording is possible can be distinguished clearly from regions where optical recording is not possible, so that an optical recording medium with excellent contrast can be provided. It should be noted that a means for providing a plurality of optical regions should provide a plurality of the above-mentioned coatings on the medium substrate.

The medium substrate can be disk-shaped or tape-shaped. With such shapes, the shape is the same as for conventional optical recording media, so that it is possible to provide an optical recording medium that is easy to handle.

If the medium substrate is disk-shaped, then the optical information regions can be arranged in concentric rings or in a spiral shape on the medium substrate. For the optical recording regions, it is also possible to form the recording layer by arranging on the medium substrate linear groups parallel to a direction that intersects at a predetermined angle with the longitudinal direction of a tape. With this configuration, the coating is arranged in the regions where optical information recording takes place, so that an optical recording medium is attained in which the reading and writing of optical information is easy.

As described above, in the optical recording regions of the optical recording medium of the present invention, a group of polymerizable molecules, which are aligned in a predetermined direction and with a predetermined tilt on the surface of a chemisorptive thin film, are fixed to one another by polymerization. When light that is focused on the optical recording regions is irradiated selectively, then the initial molecule orientation of the coating is changed. Depending on whether the initial molecule orientation of the coating has been changed or not, it is possible to write information on the optical recording medium.

Here, "changing the initial molecule orientation of the coating" means the cutting of polymer bonds between the polymerizable molecules by irradiation of light, or the changing of the initial alignment state having a predetermined direction and a predetermined tilt on the surface of the chemisorptive thin film by degrading molecules constituting the coating other than the polymer bonds. Furthermore, it also includes the loss of the initial orientation state by melting or the like, which is not brought about by cutting the polymer bonds between the polymerizable molecules nor by the degrading of the molecules constituting the film.

What changes the initial molecule orientation of the film is the optical energy of the irradiated light or thermal energy converted from the optical energy.

It is preferable that the reflective film is formed before the chemisorptive thin film formation step. It is also possible to form the reflective film by vapor deposition of a film including aluminum on the substrate surface.

After the step of forming the metal reflective layer, it is also possible to form a transparent protective film made of an inorganic substance. Furthermore, it is also possible form the transparent protective film by any method selected from the group consisting of CVD, vapor deposition and sputtering using SiO₂ or SiN_x as the inorganic substance.

In the chemisorptive thin film formation step, it is also possible to form the chemisorptive thin film on at least one surface of the medium substrate on the entire surface. Furthermore, in the chemisorptive thin film formation step, it is also possible to form the chemisorptive thin film partially on at least one surface of the medium substrate. By changing the pattern of the formed chemisorptive thin film, it is possible to change the pattern of the coating formed on the chemisorptive thin film.

The chemisorptive thin film formation step may include a step of producing a chemisorptive solution by dissolving in an non-aqueous organic solvent chemisorptive thin film constituting molecules having, in their molecules, a photosensitive group and a functional group that reacts with the medium substrate surface forming chemical bonds, and a step of bringing the chemisorptive solution in contact with a substrate having active hydrogen at its surface, thus chemisorbing the chemisorptive thin film constituting molecules to the substrate surface.

Directly after the chemisorptive thin film formation, the substrate surface on which the chemisorptive thin film is formed can be rinsed with a rinsing solution made of a non-aqueous organic solvent, and non-adsorbed chemisorptive thin film constituting molecules can be removed. Thus, a monomolecular film can be formed. It is preferable that the non-aqueous organic solvent used above is a dehydrated hydrocarbon solvent, carbon fluoride solvent, carbon chloride solvent or silicone solvent, because then there is only little water present, and moisture absorbance is inhibited. Non-adsorbed chemisorptive thin film constituting molecules can be present on the monomolecular film formed in the chemisorptive thin film formation step. If the chemisorptive thin film is rinsed with the rinsing solution, then the non-adsorbed molecules are removed, and a high-quality monomolecular film can be formed, having many gaps for fitting the molecules constituting the polymer film.

If the substrate is a synthetic resin, then a step of introducing active hydrogen to the substrate surface is added, for example by subjecting the substrate surface before the chemisorptive thin film formation step to any of the methods selected from the group consisting of a plasma treatment, a corona treatment and a far UV light treatment. This is because, if the substrate is a synthetic resin, then it is necessary to have adsorbing groups for sufficient adsorption of the chemisorptive thin film forming molecules on the substrate surface.

It is also possible to add, before the chemisorptive thin film formation step, a step of forming a layer having active hydrogen on the substrate surface. The step of forming a layer having active hydrogen on the substrate surface also can be a step of forming a metal layer. Furthermore, this metal layer also can be used as a reflective layer. With this configuration, it is possible to simultaneously introduce active hydrogen to the surface of the medium substrate and form a reflective layer.

For the active hydrogen present in the medium substrate surface, it is possible to use hydroxyl groups. Hydroxyl groups have a high reactivity with chemisorptive thin film constituting molecules, so that in this way a uniform chemisorptive thin film can be formed.

The chemisorptive thin film formation step also can be a step of applying a solution in which a polymer has been dissolved in an organic solvent to the medium substrate surface, and after removing the solvent, heating and fixing the polymer to form a polymer film. With this configuration, a flat polymer film can be formed even if the medium substrate surface has irregularities, so that an optical recording medium with superior flatness can be manufactured.

The above-mentioned orientation treatment step can be carried out by orientation treating the entire chemisorptive thin film that has been formed. Or, the above-mentioned orientation treatment step also can be carried out by partially orientation treating the chemisorptive thin film that has been formed. It is also possible to change the pattern of the coating that is formed on the chemisorptive thin film by changing the orientation treatment parameters for the chemisorptive thin film.

The orientation treatment step also can be a polarized light orientation step of an orientation treatment by irradiating polarized light on the medium substrate surface on which the chemisorptive thin film has been formed. In the orientation treatment step, the polarized light can be irradiated on the entire chemisorptive thin film, or it can be irradiated onto a portion of the chemisorptive thin film. The chemisorptive thin film can be a monomolecular film or a polymer film, which can be made of chemisorptive thin film constituting molecules including photosensitive groups, and it is also possible to irradiate polarized light in dots on the chemisorptive thin film while moving the medium substrate. If the chemisorptive thin film is a monomolecular film, then the molecules at the polarized light irradiation position are arranged orderly, so that also the molecules constituting the polymer film are arranged orderly, and it is possible to form a recording format with high efficiency. On the other hand, if the chemisorptive thin film is a polymer film, then the polymer film absorbs surface irregularities when the substrate surface has an irregular shape, so that it is possible to manufacture a flat optical recording medium

If the medium substrate is disk-shaped, then it is possible to irradiate polarized light in dots along the tracks formed on the medium surface while rotating the medium substrate. With this configuration, it is possible to orient the chemisorptive thin film regularly at a plurality of positions, so that it is possible to manufacture an optical recording medium provided with recording regions on which optical information can be recorded at high densities.

It is preferable that the polarization direction of the polarized light irradiated in dots is the rotation direction of the medium substrate or a direction that intersects at right angles with the rotation direction. With this configuration, the polarization direction of the polarized light determines the orientation of the chemisorptive thin film, so that it also determines the orientation of the polymerizable molecules arranged on the chemisorptive thin film. Consequently, if the initial molecule orientation of the coating is changed by irradiating light when writing optical information, then the directions of reflected light, scattered light and transmitted light irradiated when reading the optical information are different in the changed regions and in the unchanged regions. Thus, it is possible to manufacture an optical recoding medium with which optical information can be read with high efficiency.

If the medium substrate is tape-shaped, then polarized light can be irradiated in dots along the tracks formed on the medium substrate while letting the medium substrate travel forward. With this configuration, it is possible to orient the chemisorptive thin film regularly at a plurality of different positions, so that it is possible to manufacture an optical recording medium provided with recording regions on which optical information can be recorded at high densities.

The orientation treatment step also can be a step of rubbing the polymer film while moving the medium substrate. If the medium substrate is disk-shaped, then it is also possible to rub the entire polymer film surface while rotating the medium substrate. If the medium substrate is tape-shaped, then it is also possible to rub the polymer film while letting the medium substrate travel forward. Furthermore, it is also possible to produce a tape-shaped optical recording medium by rubbing the polymer film while letting a wide medium substrate film travel forward and cutting the medium substrate after forming the polymer film. By rubbing, a chemisorptive thin film having an orienting function can be formed with high efficiency, so that it is possible to form an optical recording medium with high efficiency. It is also possible to produce a tape-shaped optical recording medium by rubbing the polymer film while letting a wide medium substrate film travel forward and cutting the medium substrate after forming the polymer film. Thus, it is possible to manufacture a plurality of optical recording media by rubbing once, which is even more efficient.

In the step of forming the coating, it is possible to form a coating on the entire surface of the chemisorptive thin film by applying a solution in which polymerizable molecules have been dissolved on the entire surface of the chemisorptive thin film to bring the polymerizable molecules in contact with the chemisorptive thin film surface, removing the solvent, orienting the polymerizable molecules with the orientation regulating force of the chemisorptive thin film, and polymerizing the polymerizable molecules to one another. Also, in the step of forming the coating, it is possible to form a coating on a portion of the chemisorptive thin film by applying a solution in which polymerizable molecules have been dissolved on the entire surface of the chemisorptive thin film to bring the polymerizable molecules in contact with the chemisorptive thin film surface, removing the solvent, orienting the polymerizable molecules with the orientation regulating force of the chemisorptive thin film, and polymerizing a portion of the group of polymerizable molecules to one another.

In the step of forming the coating, it is also possible to form a coating partially by applying a solution in which polymerizable molecules have been dissolved on a portion of the chemisorptive thin film to bring the polymerizable molecules in contact with the chemisorptive thin film surface, removing the solvent, orienting the polymerizable molecules with the orientation regulating force of the chemisorptive thin film, and polymerizing the polymerizable molecules that have been applied on the chemisorptive thin film to one another.

In the step of forming the coating, it is also possible to form the coating by irradiating a group of polymerizable molecules with dot-shaped polarized light while moving the medium substrate.

If the medium substrate is disk-shaped, then it is also possible to irradiate polarized light in dots onto a group of polymerizable molecules along tracks while rotating the medium substrate. It is preferable that the polarization direction of the polarized light that is irradiated in dots is the rotation direction of the medium substrate or a direction that intersects at right angles with the rotation direction.

If the medium substrate is tape-shaped, then it is also possible to irradiate polarized light in dots onto a group of polymerizable molecules along tracks while letting the medium substrate travel forward.

In the information recording/reproducing apparatus of the present invention, the reference light that is irradiated can be polarized light, and it is possible to detect the intensity change of a polarized light component only with an optical sensor, or to detect that light with an optical sensor after it has passed through a polarizer.

Furthermore, the reference light that is irradiated can be polarized light, and it is possible to detect the intensity change of a polarized light component only with an optical sensor, or to detect that light with an optical sensor after it has passed through a polarizer.

The emitted recording light also can be UV light. With this configuration, the beam diameter can be smaller when focusing the irradiated light.

The wavelength of the emitted recording light and the wavelength of the emitted reference light can be the same. With this configuration, the recording light and the reference light can be irradiated using the same light source, so that the apparatus can be made smaller.

The wavelength of the emitted recording light and the wavelength of the emitted reference light also can be different. With this configuration, the irradiation of the reference light has no influence on the initial orientation of the coating, so that it is possible to provide an information recording/reproducing apparatus with a stable recording state.

The emitted recording light and the emitted reference light can both be laser light. With this configuration, the irradiated beams can be made sharp, so that it is possible to provide an information recording/reproducing apparatus with which high-density recording is possible.

The irradiation area of the emitted recording light on the medium surface can be smaller than the irradiation area of the emitted reference light on the medium surface. With this configuration, it is possible to provide an information recording/reproducing apparatus with few reading errors during recording/reproducing.

The energy density of the emitted recording light can be made larger than the energy density of the emitted reference light. With this configuration, recorded information is not destroyed by irradiating the reference light, so that it is possible to provide an information recording/reproducing apparatus with stable recording information.

The reference light emitting portion and the optical sensor can be provided on the same side of the recording medium, and the intensity change of a polarized component of the reflected reference light that has been reflected by the recording medium or the scatted reference light that has been scatted at the recording medium surface can be detected with the optical sensor. Thus, a reflection-type information recording/reproducing apparatus can be provided.

It is also possible to arrange the recording medium between the reference light emitting portion and the optical sensor, and to detect the intensity change of a polarized component of transmitted reference light that has been transmitted through the recording medium. Thus, a transmission-type information recording/reproducing apparatus can be provided.

The information recording/reproducing apparatus can record and reproduce optical information with the following methods.

One possible method is a method for recording and reproducing information on/from a write-once optical recording medium as described above, which includes a recording layer on which optical information can be recorded depending on whether an initial molecule orientation of a coating constituting the recording layer is changed or not by selectively irradiating focused light. In this method, information is recorded by selectively irradiating recording light onto the recording layer to write information elements depending on whether the initial molecule orientation of the coating constituting the recording film has been changed or not. Information is reproduced by selectively irradiating reference light that does not destroy the orientation of the polymer film on the recording layer, and detecting with an optical sensor, from the light that has passed through a polarizer, intensity changes in a polarized component of reflected light, transmitted light or scattered light of the reference light, which depend on whether the initial molecule orientation of the coating in the recording layer has been changed or not.

When reading information, it is preferable that the polarizer is arranged such that the polarization direction is parallel or perpendicular to the initial orientation of the coating. Thus, at the portions maintaining the initial orientation of the coating, light with an oscillation direction that is parallel to the initial orientation is reflected or transmitted. On the other hand, at the portions where the initial orientation of the coating has been changed, the orientation plane has been disturbed, so that almost no light with an oscillation direction that is parallel to the initial orientation is reflected or transmitted. Consequently, if the polarizer is arranged such that the optical transmission axis is parallel to the initial orientation of the coating, then at the portions maintaining the initial orientation of the coating, the intensity of a polarized light component parallel to the initial orientation of the molecules is large. On the other hand, at the portions where the initial orientation of the coating has not been maintained, the intensity of a polarized light component of reflected light and transmitted light parallel to the initial orientation of the molecules is small, due to the disturbance of the initial orientation. As a result, there is a change in intensity of the polarized light component between the portions that have maintained the initial orientation of the coating and the portions that have not maintained the initial orientation of the coating. Consequently, optical information can be read with high sensitivity by arranging a polarizer such that its optical transmission axis is parallel to the initial orientation of the coating. Conversely, if the polarizer is arranged such that its optical transmission axis is perpendicular to the initial orientation of the coating, then the intensity of the polarized component of the reflected light, the transmitted light and the scattered light becomes opposite to the above. Also in this case, it is possible to read optical information with high sensitivity.

Another possible method is a method for recording and reproducing information on/from a write-once optical recording medium as described above, which includes a recording layer on which optical information can be recorded depending on whether an initial molecule orientation of a coating constituting the recording layer is changed or not by selectively irradiating focused light. In this method, information is recorded by selectively irradiating recording light onto the recording layer to write information elements depending on whether the initial molecule orientation of the coating constituting the recording film has been changed or not. Information is reproduced by selectively irradiating polarized light that does not change the initial molecule orientation of the coating as reference light on the recording layer, and detecting with an optical sensor intensity changes in a polarized component of reflected light, transmitted light or scattered light of the reference light, which depend on whether the initial molecule orientation of the coating in the recording layer has been changed or not.

It is preferable that the reference light irradiated when reading the information oscillates in a direction that is parallel or perpendicular with respect to the direction in which the coating is oriented initially. If, at the portions that have maintained the initial orientation of the coating, the reference light oscillates in a direction that is parallel to the direction in which the coating is oriented initially, then the reference light is transmitted by the coating. In this case, if a reflective layer is provided, then the reflected light again is transmitted through the coating in the same oscillation direction. Therefore, the intensity of a polarized component of reflected light or transmitted light is large. On the other hand, at the portions that have not maintained the initial orientation of the coating, the initial orientation is disturbed, so that the intensity of the polarized component of reflected light or transmitted light is small. As a result, there is a change in intensity of the polarized light component between the portions that have maintained the initial orientation of the coating and the portions that have not maintained the initial orientation of the coating. Consequently, optical information can be read with high sensitivity. Conversely, if the reference light is irradiated such that its oscillation direction is perpendicular to the initial orientation of the coating, then the intensity of the polarized component of the reflected light, the transmitted light and the scattered light becomes opposite to the above. Also in this case, it is possible to read optical information with high sensitivity, because there is a change in intensity in a polarized component, depending on whether or not the initial molecule orientation of the coating has been changed.

Yet another possible method is a method for recording and reproducing information on/from a write-once optical recording medium as described above, which includes a recording layer on which optical information can be recorded depending on whether an initial molecule orientation of a coating constituting the recording layer is changed or not by selectively irradiating focused light. In this method, information is recorded by selectively irradiating recording light onto the recording layer to write information elements depending on whether the initial molecule orientation of the coating constituting the recording film has been changed or not. Information is reproduced by selectively irradiating polarized light that does not change the initial molecule orientation of the coating as reference light on the recording layer, and detecting with an optical sensor, from the light that has passed through a polarizer, intensity changes in a polarized component of reflected light, transmitted light or scattered light of the reference light, which depend on whether the initial molecule orientation of the coating in the recording layer has been changed or not.

It is preferable that the irradiated light that is irradiated when reading information oscillates in a direction that is parallel or perpendicular with respect to the direction in which the coating is oriented initially. With this configuration, optical information can be read with high sensitivity.

It is also possible that the reference light irradiated when reading information oscillates parallel or perpendicular with respect to the direction in which the coating is oriented initially, and the polarizer is arranged such that the optical transmission axis is parallel or perpendicular with respect to the direction in which the coating is oriented initially. Thus, for the same reasons as explained above, it is possible to read optical information with high sensitivity.

It is also possible to write information by changing the initial molecule orientation of the coating using thermal energy of recording light that is irradiated when writing information. With this configuration, the initial molecule orientation of the coating can be changed easily, so that optical information can be written with high sensitivity.

The recording light that is irradiated when writing information and the reference light that is irradiated when reading information can be irradiated with different wavelengths.

UV light can be irradiated as the recording light.

The foregoing was an explanation of a first inventive concept (orientation changing optical recording film and application thereof).

The following is an explanation of a second inventive concept (photo-degradable or photothermally degradable optical recording film and application thereof).

According to the second inventive concept, information can be recorded by combining degraded portions and non-degraded portions obtained by classifying locally irradiated portions of an optical recording film as degraded portions and all other portions as non-degraded portions. Moreover, the monomolecular thin film can be formed without using vacuum vapor deposition, so that it can be used as an inexpensive recording layer. Also, with such an optical recording film, information is recorded using a degradation reaction (irreversible reaction), so that the storing properties of the recorded information are favorable. In the present invention, "substrate" includes both a substrate alone as well as a substrate with a thin film formed on its surface.

It is preferable that the degrading in the optical recording film is carried out by cleaving certain molecular bonds. Thus, information can be recorded with high precision, because the degraded portions are aligned by cleaving certain bonds. In particular with an optical recording film in which only one molecular bond is cleaved by irradiating light, information can be recorded with very high precision.

In the optical recording film, when the thin film is made of molecules having a photodegradable functional group, then that functional group is degraded by the irradiation of light, so that information can be recorded with high precision. Here, "photodegradable functional group" means a functional group that undergoes a degradation reaction through an excited state due to optical absorption. Using a molecule having such a functional group, the degradation reaction proceeds even at temperatures that are not very high, so that the substrate can be selected from a wider range. For the photodegradable functional group, it is possible to use any suitable functional group that can undergo a photodegradation reaction with UV light, such as a benzophenone residue, a benzyldimethylketal residue or a 1-hydroxy-cyclohexyl-phenylketone residue. With a functional group that undergoes a degradation reaction under UV light, fogging (unintended formation of degraded portions) will not occur when exposed to visible or infrared light during storage. Here, "residue" refers to the molecular form after reaction. For example, it can be a functional group or the like obtained by removing one or more hydrogen atoms from a chemical compound.

Also, if the thin film in the optical recording film is made of molecules including a thermally degradable functional group, then those functional groups are thermally degraded when irradiated with light, so that information recording can be carried out with high precision. Here, "thermally degradable functional group" refers to functional groups that undergo a degradation reaction utilizing the thermal effect of light. Using molecules having such a functional group, it is also possible to select the irradiated light without having to consider the absorbed wavelength, so that the recording light can be selected from a wider range. As the thermally degradable functional groups, a benzoin residue or a benzopinacole residue can be used.

It is preferable that the molecules constituting the thin film are straight-chain or rod-shaped molecules having a thermally degradable functional group or a photodegradable functional group on one molecule end, that the functional group on one molecule end is oriented in a direction pointing away from the substrate surface, and that the other end is covalently bonded to the substrate surface. Here, "straight-chain or rod-shaped molecules" (in the following also referred to simply as "straight-chain molecules") means molecules in which the group of atoms constituting the molecule is aligned in a straight line. With optical recording films made of such straight-chain molecules, the film constituting molecules are aligned as upright rods, and the thermally degradable functional groups or photodegradable functional groups are aligned at a predetermined position away from the substrate surface, so that the recording of information can be carried out with high precision. In particular, with straight-chain molecules including phenyl groups, the dipole moment in the molecules is large, so that there is the advantage that the energy for recording or reproducing can be small. Furthermore, if the light irradiation is constricted to a small region, then it is possible to record information at the molecule aggregate level (of several hundred to several thousand molecules), so that a recording medium with extremely high recording capacity can be provided.

For the functional group that is degraded when irradiated with light, it is suitable to use a photodegradable functional group or a thermally degradable functional group. Specific examples of those functional groups are noted above. As a chemisorptive group, it is preferable to use at least one functional group selected from the group consisting of halosilyl groups, alkoxysilyl groups and isocyanatosilyl groups. These functional groups are fixed by covalent bonds to the substrate by an elimination reaction with functional groups including active hydrogen, such as hydroxyl groups exposed at the substrate surface, so that an optical recording film with superior peel-off resistance and adhesiveness can be formed.

Moreover, for the substrate at which the functional groups reacting with the chemisorptive groups are exposed, it is preferable to use a substrate with exposed functional groups including active hydrogen. For the functional groups including active hydrogen, it is suitable to use hydroxyl groups. For reasons of availability and cost, it is preferable to use, as the substrate at which the functional groups including active hydrogen are exposed, a glass substrate, a ceramic substrate, a metal substrate, a synthetic resin substrate, or one of those substrates with a silica film or a silicon nitride film formed on it. The surface of these substrates is hydrophilic, so that the optical recording film can be formed efficiently. The silica film etc. can be formed easily by CVD, vacuum vapor deposition or sputtering, for example. If there is little exposed active hydrogen in these substrates, then it is preferable to increase the exposed active oxygen by at least one surface treatment method selected from the group consisting of plasma treatment, corona treatment and far UV light treatment.

It is preferable that after forming the film, the optical recording film formed on the substrate surface is rinsed with a non-aqueous organic solvent. This rinses away the chemisorptive molecules that have not been bonded to the substrate, so that an optical recording film can be provided in which the recording and reproducing of information can be carried out with high precision. As the non-aqueous organic solvent, it is possible to use a hydrocarbon solvent, a halogenized hydrocarbon solvent, a silicone-based hydrocarbon solvent, either alone or in a combination of two or more. With these solvents, the unreacted chemisorptive molecules can be removed reliably without reacting the optical recording film that has been formed.

It is preferable that the substrate is an optical reflective substrate or an optically transmissive substrate. If it is an optically reflective substrate, then the optical recording medium is one in which reflected light is detected after irradiation with reproduction light (reflective optical recording medium). For such an optically reflective substrate, it is preferable to use an optically reflective film such as a metal substrate, or to use a glass substrate, a ceramic substrate, a metal substrate or a synthetic resin substrate that has an optically reflective film formed on a suitable substrate surface. If a glass substrate, a ceramic substrate or a metal substrate is used, then the rigidity is high, so that an optical recording medium with superior durability can be provided. With a synthetic resin substrate, an optical recording medium with superior flexibility can be provided. Considering its high optical reflectance and low cost, it is preferable to use a film including aluminum as the optically reflective film. It is also possible to form an optically transmissive thin film on the uppermost surface of the substrate. If a silica film or a silicon nitride film is used for the optically transmissive thin film, then an optical recording medium with high recording density can be provided, because silica or silicon nitride films have a high density of exposed active hydrogen.

On the other hand, if the substrate is an optically transmissive substrate, then the optical recording medium is one in which after irradiation with reproduction light, the transmitted light is detected (transmissive optical recording medium). For such an optically transmissive substrate, it is suitable to use an optically transmissive substrate such as a glass substrate, or to use an optically transmissive substrate with an optically transmissive thin film formed on one or both sides. If a silica film or a silicon nitride film is used for the optically transmissive thin film, then an optical recording medium with high recording density can be provided.

If the optical recording medium has a plurality of information recording unit regions on which one information element can be written, depending on whether the film constituting molecules of the optical recording film are degraded or non-degraded, then an optical recording medium can be provided with which digital information can be recorded. Here, "information recording unit regions" means regions in which one information element is recorded on the optical recording film. "Information element" refers to the elements when the information has been broken down to its minimal units (information units). More specifically, in conventional binary recording formats, in which the information units are single bits of information expressed by "0"s and "1"s, those "0"s and "1"s are the information elements. If the information recording unit regions are dot-shaped, then more digital information can be recorded.

Regarding the shape of the substrate, disk shapes, tape shapes and card shapes are preferable, because this allows the utilization of technology for optical recording media that is already in existence. If the substrate is disk-shaped, then it is preferable that the information recording unit regions on the optical recording film are aligned in concentric rings or in a spiral shape, because this allows high recording densities. On the other hand, in the case of tape-shaped or card-shaped substrates, it is preferable that the information recording unit regions of the optical recording film are aligned in parallel straight-chain groups at a predetermined angle with respect to the longitudinal direction of the substrate, because this allows high recording densities.

If, in the information recording/reproducing method, a method is used as the recording method in which recording light is successively irradiated on the optical recording film, and degraded portions corresponding to the irradiated portions are formed successively, then information can be recorded sequentially. And if a method is used as the recording method, in which a light-blocking member provided with light-passing portions corresponding to irradiated portions on the optical recording film, or a light-passing member provided with light-blocking portions corresponding to the portions other than the irradiated portions on the optical recording film is placed in opposition to the optical recording film, recording light is irradiated via this member onto the optical recording film, and the degraded portions corresponding to the irradiated portions are formed all together, then a large amount of information can be recorded in a short time. Thus, the recording and the reproduction of information can be performed with high precision, since the degrading is performed by cleaving certain portions in the molecules.

If, in the information recording/reproducing method, a photodegradation reaction by optical irradiation or a thermal degradation reaction by optical irradiation is used when forming the degraded portions, then degraded portions can be formed in the optical recording film, and as a result, information can be recorded. If a photodegradation reaction is used, then the information recording can be carried out through a degradation reaction not involving high temperatures, so that the substrate can be selected from a broader range. On the other hand, if a thermal degradation reaction is used, then no consideration has to be given to the optical absorption wavelength with regard to the type of the optical recording film, so that the recording light can be selected from a broader range.

If UV light is used as the light for the recording, then the recording time (writing time) can be shortened, because of its high energy and its superior degradation efficiency. Furthermore, it can be constricted easily, so that recordings at high density are possible.

If infrared light or visible light is used for the light for reproduction, then the recorded information is hardly destroyed during reproduction, because of its low energy, so that reproduction can be carried out favorably.

Moreover, if the diameter of the recording light is smaller than the diameter of the reproduction light, then there is the advantage that the number of errors during recording can be decreased.

With the information recording/reproducing apparatus of the present invention, it is possible to carry out the recording and the reproduction of information on the above-described write-once optical recording medium with one apparatus.

Furthermore, it is preferable that in the information recording/reproducing apparatus of the present invention, the wavelength of the light that is irradiated from the recording light irradiation means is different from the wavelength of the light that is irradiated from the reproduction light irradiation means. This is, because if the recording light and the reproduction light have different wavelengths, then the recording of information during reproduction can be avoided. Furthermore, it is preferable that the recording light irradiation means irradiates UV light. It is also preferable that that the reproduction light irradiating means irradiates visible light or infrared light. Furthermore, if the diameter of the light that is irradiated by the recording light irradiation means is smaller than the diameter of the light that is irradiated by the reproduction light irradiation means, then recording errors can be inhibited. Moreover, if the power density of the reproduction light is smaller than the power density of the recording light, then recording during reproduction can be avoided.

It is also possible to devise an information recording/reproducing apparatus using the optical recording medium of the present invention as a computer system provided with an auxiliary storage device. With this configuration, a computer system that is inexpensive and has a high recording capacity can be provided. Here, "computer system" means a system that generally is provided with an arithmetic processing device having a main memory, an auxiliary storage device, an input device, an output device, and a communication control device controlling the communication among these devices, wherein upon a recording command entered from the input device, input information from the input device is transmitted as recording information signals of input information converted into electrical signals, via the arithmetic processing device to the auxiliary storage device, and recorded by the auxiliary storage device based on the transmitted recording information signals, and upon a reproduction command entered from the input device, the information recorded in the auxiliary storage device is read out as reproduction information signals from the auxiliary storage device, transferred via the arithmetic processing device to the output device, and reproduced by the output device based on the transferred reproduction information signals.

Also possible is a video signal recording/reproducing system provided with the information recording/reproducing apparatus of the present invention as a video storage device. With this configuration, a video signal recording/reproducing system that is inexpensive and has a high recording capacity can be provided. Here, "video signal recording/reproducing system" means a system that generally is provided with a video signal input/output control device controlling the input and the output of video signals, a video storage device, a video output device, and a control command input device for sending input/output control commands to the video signal input/output control device, wherein upon a recording command entered from the control command input device, video signals from an external video signal sender are transmitted via the video signal input/output control device to the video storage device, and the video information is recorded in the video storage device based on the transmitted video signals, and upon a reproduction command entered from the control command input device, the video information recorded in the video storage device is read out as reproduction video signals, transferred via the video signal input/output control device to the video output device, and reproduced by the video output device based on the transferred reproduction video signals.

As explained above, the present invention can provide an optical recording film made of an organic thin film formed by chemisorption and a method for manufacturing the same. Moreover, it can provide an inexpensive high-density write-once optical recording medium with which high-precision reading is possible. Furthermore, it can provide a computer system and a video signal recording/reproducing system using this write-once optical recording medium.

An embodiment of the optical recording film of the present invention is explained based on Figs. 1 to 3, showing an example of a method for manufacturing the optical recording film. Fig. 1 is a diagram illustrating the chemisorptive thin film formation step of producing a monomolecular film on the substrate. Figs. 2A to 2C schematically illustrate states of the chemisorptive thin film. Fig. 2A is a diagram illustrating the state of the monomolecular film before the orientation treatment. Fig. 2B is a diagram illustrating the state of the monomolecular film after the orientation treatment. Fig. 2C is a diagram illustrating the state of the monomolecular film after crosslinking.

First, the chemisorptive thin film formation step is performed, which forms a chemisorptive thin film on the substrate 1. There is no particular limitation regarding the material of the substrate 1, and depending on the purpose of use, it is possible to use a variety of materials known in the art. Regarding their ease of handling, it is preferable to use a metal, a ceramic or a synthetic resin, for example. If the substrate is disk-shaped, then it is preferable to use a metal, such as aluminum or an aluminum alloy, glass, a ceramic, or polycarbonate, because of the rigidity of those materials. If the substrate is tape-shaped, then it is preferable to use a synthetic resin with superior flexibility, such as polyester. There is no particular limitation regarding the shape of the substrate.

In the example in Fig. 1, a disk-shaped substrate 1 is used. The substrate does not have to be disk-shaped, and it also can be tape-shaped or card-shaped. Furthermore, also in the optically oriented film, it is possible to provide a reflective film 2 on a substrate 1, as for the optical recording medium. It should be noted that the reflective film 2 also can be a primer layer in accordance with the present invention.

For the chemisorptive thin film formed on the substrate, a chemisorptive solution 3 is prepared by dissolving in a non-aqueous organic solvent under a dry atmosphere a chemisorptive substance including a photosensitive group and a functional group (surface-active agent) that forms a chemical bond by reaction with the reflective layer 2. Then, the chemisorptive solution 3 is brought into contact with the substrate 1, and the molecules of the chemisorptive substance in the chemisorptive solution 3 are chemisorbed by the surface of the substrate 1.

A preferable chemisorptive substance is a silane-based chemisorptive substance including a photosensitive group. More specifically, using the compound C₆H₅-CH=CH-CO-C₆H₄-O-(CH₂)₆-O-SiCl₃, which includes a photosensitive group and a trichlorosilane group, as a silane-based compound, the chemisorptive reaction shown in the following chemical reaction (F) takes place. That is to say, the chlorosilyl groups in the compound and the OH-groups present at the surface of the substrate 1 undergo a dehydrochlorination reaction, and the compound is chemisorbed to the surface of the substrate 1.

Here, the silane compound is highly active with respect to water, so that it is deactivated when the water content in the chemisorptive solution is too high. Thus, to let the chemisorption reaction proceed smoothly, a non-aqueous organic solution is used, which contains no active hydrogen groups, such as -OH groups. Furthermore, it is preferable that the bringing into contact of the chemisorptive solution with the surface of the substrate 1 takes place in a dry atmosphere. Furthermore, "chemisorptive solution including a silane compound" means a solution in which a silane compound has been dissolved in a solvent, but it also can be one in which a portion of the silane compound is not dissolved. An example of such a solution is a supersaturated chemisorptive solution.

Examples of silane compounds that can be used for the present invention include the compounds listed below:



        (a1)   C₆H₅-CH=CH-CO-O-(CH₂)₆-O-SiCl₃



        (a2)   C₆H₅-CO-CH=CH-C₆H₄O-(CH₂)₆-O-SiCl₃



        (a3)   C₆H₅-CH=CH-CO-C₆H₄O-(CH₂)₆-O-SiCl₃

Of these compounds, the compound (a1) includes a cinnamoyl group as the photosensitive group, whereas the compounds (a2) and (a3) include a chalconyl group as the photosensitive group.

Furthermore, instead of the chlorosilane compound, it is also possible to use an isocyanate compound or an alkoxy compound, in which the chlorosilyl group has been replaced by an isocyanate group or an alkoxy group. For example, the following compounds can be given as examples:



        (b1)   C₆H₅-CH=CH-CO-O-(CH₂)₆-O-Si(OCH₃)₃



        (b2)   C₆H₅-CO-CH=CH-C₆H₄O-(CH₂)₆-O-Si(OCH₃)₃



        (b3)   C₆H₅-CH=CH-CO-C₆H₄O-(CH₂)₆-O-Si(OCH₃)₃



        (c1)   C₆H₅-CH=CH-CO-O-(CH₂)₆-O-Si(NCO)₃



        (c2)   C₆H₅-CO-CH=CH-C₆H₄O-(CH₂)₆-O-Si(NCO)₃



        (c3)   C₆H₅-CH=CH-CO-C₆H₄O-(CH₂)₆-O-Si(NCO)₃

The chlorosilane compound in (a1) to (a3) undergoes a dehydrochlorination reaction with the active hydrogen present at the primer surface, for example the hydrogen included in -OH groups, -COOH groups, -CHO groups, -NH₂ groups or >NH groups, forming covalent bonds.

Moreover, the alkoxy silane compound in (b1) to (b3) undergoes a dealcoholization reaction with the active hydrogen present at the primer surface, for example the hydrogen included in -OH groups, -COOH groups, -CHO groups, -NH₂ groups or >NH groups, forming covalent bonds.

Moreover, the isocyanate silane compound in (c1) to (c3) undergoes a deisocyanation reaction with the active hydrogen present at the primer surface, for example the hydrogen included in -OH groups, -COOH groups, -CHO groups, -NH₂ groups or >NH groups, forming covalent bonds.

The film obtained by such an elimination reaction is also called a "chemisorptive film" or "self-assembling film."

When an isocyanate compound or an alkoxy compound is used, and the chemisorption is carried out by contact with the substrate, then the generation of hydrogen chloride (HCl) can be prevented. Thus, there are the advantages that the substrate is not damaged, and that the workability is superior.

Moreover, examples of suitable organic solvents for dissolving the chemisorptive substance include dehydrated hydrocarbon-based solvents, carbon fluoride solvents and silicone solvents, and solvents that can be used as petroleum-based solvents include petroleum naphtha, solvent naphtha, petroleum ether, petroleum benzine, isoparaffin, normal paraffin, decalin, industrial gasoline/kerosene, ligroin, dimethylsilicone, phenylsilicone, alkyl modified silicone and polyester silicone. As a carbon fluoride solvent, it is possible to use a fluorocarbon based solvent, Fluorinate (trademark by 3M Corp.) or Afluide (trademark by Asahi Glass Corp.), for example. These solvents can be used alone or, if compatible solvents, in a mixture of two or more. In particular, silicone has a low water content, a low moisture absorbance, and easily dissolves chlorosilane compounds, so that it can prevent the direct contact between the chlorosilane compound and water. Consequently, with a chlorosilane compound and a solvent including silicone, it is possible to avert the adverse influence of hydrolysis due to the water components in the atmosphere during contact with the primer layer.

If, after the oriented film formation step, the substrate is rinsed with a rinsing solution made of a non-aqueous organic solvent to remove the non-adsorbed chemisorptive thin film constituting molecules present on the substrate, then a chemisorptive thin film of the monomolecular film 4 can be formed. Examples of a suitable rinsing method are immersion and steam rinsing. With steam rinsing, all the excessive non-adsorbed chemisorptive thin film constituting molecules on the entire surface of the substrate 1 can be removed aggressively by the osmotic force of the steam, so that it is particularly effective.

By rinsing, a monomolecular film 4 is attained, in which the lipophilic groups C₆H₅-CH=CH-CO-C₆H₄-O-(CH₂)₆-O-Si(-O-)₃ are exposed at the surface of the substrate 1.

The non-aqueous organic solvent that is used can be the solvent used for the dissolving of the chemisorptive substance. If a chlorosilane compound, which is one type of silane compounds, is used for the chemisorptive substance, then it is preferable that chloroform or N-methyl-2-pyrrolidone is used for the rinsing solution. Chloroform not only can rinse monomers, it is also superior in the removing of chlorosilane polymers which are generated by the reaction of the chlorosilane compound with water.

When the rinsing solution is dried, the monomolecular film 4 shown in Fig. 2A is obtained.

A polymer film can be formed as the chemisorptive thin film by applying a solution including the silane compound and a solvent to the substrate 1, initiating an elimination reaction with the active hydrogen at the substrate surface, then removing the solvent by drying, heating the substrate 1, and curing the precursor by hydrolysis.

If a polymer film is used as the chemisorptive thin film, and the film thickness of the polymer film is large, then the contrast during read-out between regions where the initial molecule orientation of the coating has changed and regions where it has not changed is small, so that a small film thickness is better. More specifically, it is preferable that the thickness of the chemisorptive thin film is in the range of 0.5nm to 20nm.

Next, the chemisorptive thin film formed on the substrate 1 is subjected to an orientation treatment by photo-orientation (polarized light orientation step; see Fig. 2B). Thus, a monomolecular film 4' that is oriented in a predetermined direction is obtained. This chemisorptive thin film is a monomolecular film resulting from the chemisorption of aggregate groups of silane compound molecules, wherein the majority of the chemisorptive thin film constituting molecules are exposed orderly at the surface. Therefore, it has superior sensitivity with respect to polarized light, and it is possible to give the film an anisotropic orientation by irradiation of polarized light of low intensity. Furthermore, since the thickness of the orientation film is that of a chemisorptive super-thin film, it is possible to read optical information with high sensitivity. Moreover, in the case of a polymer film with photosensitive groups, the orientation treatment can be carried out with an optical orientation method.

More specifically, optical orientation is performed by the following method. The following explanations refer to the case in which a disk-shaped substrate is subjected to an orientation treatment. Focused polarized UV light (for example, light centered around the i-line of an extra-high pressure mercury lamp of 313 nm wavelength) having a wavelength distribution near 300 nm to 400 nm is irradiated through a polarizer onto the entire substrate in a direction that is substantially perpendicular to the substrate surface while rotating the substrate and while shifting the focused light in a radial direction, such that the polarization direction is parallel to the shifting direction of the substrate.

The irradiation intensity of the polarized UV light can be in the range of for example 50 to 3000 mJ/cm² (wavelength: 365 nm). If the chemisorptive thin film is a polymer film with photosensitive groups, then the irradiation intensity of the polarized UV light can be in a range of 500 to 5000 mJ/cm² (wavelength: 365 nm), for example.

By performing this polarized light orientation step, it is possible to selectively photo-polymerize the photosensitive groups of the chemisorptive thin film constituting molecules in the chemisorptive thin film, and to bond the chemisorptive thin film constituting molecules at the surface of the substrate 1 by crosslinking along the substrate surface (see Fig. 2C). With this polarized light orientation treatment, the monomolecular film 4 is oriented in a predetermined direction and turned into a chemisorptive thin film 7 with orienting properties.

If the chemisorptive thin film is a polymer film without photosensitive groups, then it can be subjected to an orientation treatment by a conventional method known in the art, such as a rubbing method. In this case, the chemisorptive thin film 7 with orienting properties has an orientation regulating force in the rubbing direction.

Next, a solution in which polymerizable molecules have been dissolved is applied to the surface of the chemisorptive thin film 7 with orienting properties, thus bringing the polymerizable molecules in contact with the chemisorptive thin film surface, the solvent is removed, and with the orientation regulating force of the chemisorptive thin film, the group of polymerizable molecules is aligned with a predetermined tilt in a predetermined direction on the surface of the chemisorptive thin film. Figs. 3A to 3C are conceptual diagrams illustrating how the coating of the present invention is formed. Fig. 3A illustrates how a group of polymerizable liquid crystal molecules is present on the chemisorptive thin film. Fig. 3B illustrates the state of the group of the polymerizable liquid crystal molecules after the orientation treatment. And Fig. 3C illustrates the state of the monomolecular film after polymer bonding.

There is no particular limitation regarding the polymerizable molecules, as long as they can be aligned with the orientation regulating force of the chemisorptive thin film 7 with orienting properties, but polymerizable liquid crystal molecules are preferable. Polymerizable liquid crystal molecules can be aligned uniformly on the chemisorptive thin film surface with the orientation regulating force of the chemisorptive thin film.

In this initial polymerizable molecule orientation step, the polymerizable liquid crystal molecules are dissolved in an organic solvent. The organic solvent preferably has a boiling point of at least 100°C and at most 250°C. Examples of suitable organic solvents are xylene and toluene.

There is no particular limitation regarding the method for bringing the polymerizable molecules in contact with the substrate surface, and a suitable method is application with a spinner, for example.

When the substrate to which the liquid, in which the polymerizable molecules have been dissolved, is dried, the group 5 of polymerizable liquid crystal molecules is present in a non-oriented state on the chemisorptive thin film 7 with orienting properties (Fig. 3A). Thereafter, the entire substrate 1, on which this film of photo-polymerizable liquid crystal molecules is formed, is heated, and the polymerizable liquid crystal molecules are put into an isotropic state. Then, cooling down slowly to room temperature, a film 5' is attained in which the group 5 of photo-polymerizable liquid crystal molecules has been oriented by the orientation regulating force of the chemisorptive thin film on the substrate (Fig. 3B). The cooling speed can be slower than 10°C/10min from 100°C to 25°C, for example. It is preferable that the film thickness of the polymerizable molecules is in the range of 10nm to 100nm.

Next, a coating formation step of forming a coating 5" is carried out, in which the molecules are polymerized or crosslinked. There is no particular limitation regarding the coating formation step, as long as it is a method that can polymerize the polymerizable molecules, and it preferably polymerizes the polymerizable molecules by irradiation of light onto the polymerizable molecules (Fig. 3C).

In the coating formation step, it is preferable to use photo-polymerizable liquid crystal molecules as the polymerizable molecules. Thus, the molecules can be polymerized by irradiating light.

There is no particular limitation regarding the irradiation of light, as long as it can polymerize the polymerizable molecules, but UV light 6 promoting the polymerization is preferable.

For the polymerizable liquid crystal molecules, it is also possible to use the substance expressed by the above-noted general formula (A) mixed with functional acrylate monomers that are different from that substance. This promotes the polymerization reaction even more.

For the functional acrylate monomers, it is possible to use for example a monofunctional acrylate (such as methylmethacrylate, 2-ethylhexylacrylate, 2-hydroxyethylacrylate, 2-hydroxypropylacrylate, etc.), a 2-functional acrylate (such as 1,3-butanediol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, diethyleneglycol diacrylate, neopentylglycol diacrylate, etc.), a 3-functional acrylate (such as pentaerythritol triacrylate, trimethylolpropane triacrylate, etc.), a 4-functional acrylate (such as pentaerythritol tetraacrylate, trimethylolpropane tetraacrylate, etc.), a 5-functional acrylate (such as dipentaerythritol pentaacrylate, etc.), a 6-functional acrylate (such as dipentaerythritol hexaacrylate, etc.), or a >5-functional acrylate (such as dipentaerythritol penta- and hexaacrylate, etc.). Moreover, it is also possible to use functional oligomers, such as epoxy acrylate, urethane acrylate, polyester acrylate, polyether acrylate, silicon acrylate, for example.

Furthermore, it is also possible to add a substance that responds to UV light as a sensitizing agent. For example, a sensitizing agent containing a -C₆H₅CO- group can be used. Adding several percent of such a sensitizing agent (for example Irgacure™ 651, 184, 500 by Japan Ciba-Geigy Corp. or Kayacure™ BDMK, BP-100 by Nippon Kayaku Corp.) promotes the photoreaction, and shortens the polymerization time considerably.

Optical information can be recorded on the optical recording film obtained as described above, depending on whether the initial molecule orientation of the coating has been changed by irradiating focused light selectively or not. More specifically, the optical information recording is carried out as shown in Fig. 4. Fig. 4 is a conceptual diagram showing how optical information is recorded on the optical recording film of the present invention.

Focused light is irradiated as dots on the coating 5", while shifting the substrate 1. In regions 5"-1, in which light has been irradiated on the coating 5", the initial molecule orientation of the coating is changed. On the other hand, in regions 5"-2, in which light has not been irradiated on the coating 5", the initial molecule orientation of the coating stays the same. That is to say, with the optical recording film of the present invention, regions with a changed initial molecule orientation and regions with an unchanged initial molecule orientation are formed on the coating by selectively irradiating the coating with light that changes the initial orientation of the coating, thus writing the optical information.

The optical recording medium of this embodiment is an example using the above-described optical recording film as an optical recording layer. The aspects that are different from the above-described optical recording film are explained with reference to Fig. 4.

The optical recording medium of the present invention is made of a medium substrate and an optical recording layer. The medium substrate includes at least a substrate 1. Besides the substrate itself, the medium substrate also can include layers different from the optical recording layer, such as a reflective layer or a surface protection layer. As the material of the substrate 1, the material used for the optical recording film in Embodiment 1 can be used.

If the medium substrate is made of a substrate 1 and a reflective layer 2 including a metal that is layered on this substrate, a reflective optical recording medium is obtained. The reflective layer can include at least aluminum. Examples of this include aluminum and aluminum alloys (such as aluminum containing silicon, for example).

A reflective film 23 including such a metal can furnish active hydrogen to the surface of the medium substrate. Consequently, if a synthetic resin is used as the substrate, it also can function as a layer with active hydrogen.

There is no particular limitation to the method for layering the reflective layer 2 on the medium substrate, and any method known in the art can be used. For example, using vapor deposition, a thin and uniform layer can be formed, and is therefore preferable.

It is also possible to form a transparent protective layer made of an inorganic substance immediately after the metal reflective layer 2 has been formed. This prevents corrosion of the reflective film. As such an inorganic layer, SiO₂ or SiN_x can be used, for example. As the method for forming the transparent protective film, it is possible to use any method selected from the group consisting of CVD, vapor deposition and sputtering.

If the substrate is a synthetic resin, then active hydrogen can be introduced to the substrate surface by any method selected from the group consisting of plasma treatment, corona treatment and far UV treatment performed on the substrate surface before the chemisorptive thin film formation step. As the source of active hydrogen present on the medium substrate surface, it is possible to use hydroxyl groups.

In the recording layer, the coating 5" can be provided over the entire surface of the chemisorptive thin film 7 with orienting properties. Figs. 5A to 5E schematically illustrate how various types of recording regions are provided on an optical recording medium of the present invention. More specifically, the chemisorptive thin film 7 with orienting properties can be provided over the entire surface of the medium substrate 20, and the coating 5" can be provided on the entire surface of the chemisorptive thin film 7 (Fig. 5A). It is also possible to provide a chemisorptive thin film over the entire surface of the medium substrate 20, but let only a portion 7 of this chemisorptive thin film have orienting properties, and to provide the coating 5" on this portion 7 of the chemisorptive thin film with orienting properties (Fig. 5B). It is further possible to provide a chemisorptive thin film 7 with orienting properties partially on the surface of the medium substrate 20, and to provide the coating 5" on this chemisorptive thin film 7 with orienting properties (Fig. 5C). Moreover, it is also possible to provide the chemisorptive thin film 7 with orienting properties partially on the surface of the substrate medium 20, and to provide the film made of polymerizable molecules on the entire surface of the medium substrate 20, but to orient only the coating 5" provided on the chemisorptive thin film (Fig. 5D).

The coating 5" also can be provided partially on the surface of the chemisorptive thin film 7 with orienting properties. For example, it is possible to provide the chemisorptive thin film 7 with orienting properties over the entire surface of the medium substrate 20, and to provide the coating 5" partially on the surface of the chemisorptive thin film 7 (Fig. 5E).

A method for providing the chemisorptive thin film 7 partially on the surface of the medium substrate 20 is to form a monomolecular film or a polymer film partially on the surface of the medium substrate, and to subject the monomolecular film or polymer film to an orientation treatment, for example. Another possibility is to provide the chemisorptive thin film on the entire surface of the medium substrate 20, and then to perform a partial orientation treatment by masking the chemisorptive thin film.

A method for providing the coating 5" partially on the surface of the chemisorptive thin film can be, for example, as follows. The coating 5" can be formed by applying polymerizable molecules partially onto the chemisorptive thin film 7. Alternatively, the coating 5" can be formed by applying polymerizable molecules to the entire chemisorptive thin film, and partially subjecting it to an orientation treatment.

If the coating 5" is provided partially on the medium substrate 20 with the above-described methods, then the coating 5" functions as an optical recording region 19 of the optical recording layer.

If the medium substrate is disk-shaped or tape-shaped, then the following medium substrates can be obtained.

If the medium substrate is disk-shaped, and the coating 5" is provided in concentric rings or in a spiral shape along a track pattern on the medium substrate, then an optical recording film can be obtained in which optical recording regions are arranged in concentric rings or spiral shape on the medium substrate. Moreover, the coating can be continuous and linear, or it can be formed of aligned dots.

If the medium substrate is tape-shaped, and the coating 5" is provided on the medium substrate in linear groups that are parallel to a direction intersecting at a predetermined angle with the longitudinal direction of the tape along a track pattern, then an optical recording medium can be obtained, in which the recording layer is formed by arranging the optical recording regions on the medium substrate in linear groups that are parallel to a direction intersecting at a predetermined angle with the longitudinal direction of the tape.

If the chemisorptive thin film is oriented by rubbing, then, in the case of a disk-shaped medium substrate, the entire surface of the polymer film can be rubbed while rotating the medium substrate. In the case of a tape-shaped medium substrate, the polymer film can be rubbed while le