JPH0353984A - Data recording medium and preparation thereof - Google Patents

Abstract

PURPOSE:To provide a data recording medium having high recording sensitivity and a high C/N ratio and excellent in durability by using polyurethane having a specific polar group and/or a vinyl chloride/vinyl acetate copolymer as a binder. CONSTITUTION:A recording layer wherein carbon black, org. pigment, inorg. pigment or a fine light absorbent metal powder are dispersed in a binder is provided on a substrate. As the binder, polyurethane having at least one polar group selected from -OH, -COOM and -SO3M (wherein M is a hydrogen atom, Na or K) or a vinyl chloride/vinyl acetate copolymer must be used. As the polar group, -COOH and -SO3H is pref. and the conc. of the polar group is pref. within a range of 1X10<-6>-1X10<-3> equivalent per 1g of the resin.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to an information recording medium on which information can be recorded using a high energy density laser beam, and a method for manufacturing the same.

[Technical Background of the Invention] In recent years, information recording media that use high energy density beams such as laser light have been developed and put into practical use. This information recording medium is called an optical disk, and is used as a video disk, an audio disk, a large-capacity still image file, a large-capacity computer disk memory, and the like.

Carbon black, metals, pigments, and the like are known as recording materials that form the recording layer of information recording media. Information recording media that use light-absorbing fine powder such as carbon black or pigments have the manufacturing advantage of being able to easily form a recording layer by coating these materials as they are or by dispersing them in a binder. '4-f has great advantages. Comparing the recording layers that can be formed by such coating, in the case of recording layers made of dyes, the sensitivity and C/
Although N is high, durability such as reading durability or weather resistance is not sufficient, and recording layers with light-absorbing fine powder such as carbon black dispersed in a binder have high sensitivity and C/N. However, it has excellent durability.

Writing and reading information to and from an optical disc is usually performed by the following method.

Information is written by irradiating this optical disc with a laser beam, and the irradiated portion of the recording layer absorbs the light, causing a local temperature rise, causing physical or chemical changes (for example, the formation of pits). information is recorded by changing its optical properties. Information is also read by irradiating the optical disk with a laser beam, and the information is reproduced by detecting reflected or transmitted light that corresponds to changes in the optical characteristics of the recording layer.

Optical discs using the above light-absorbing fine powder such as carbon black include an optical disc having a recording layer using a self-oxidizing compound as a binder (Japanese Patent Application Laid-Open No. 57-24291), and an optical disc using a specific nitrocellulose as a binder. The optical disc used (Japanese Unexamined Patent Publication No. 58-102348), the optical disc with a reflective layer of pigment or metal under the light absorption layer of carbon black (Japanese Unexamined Patent Publication No. 58-224447), and the recording of Rikiichi Bon Black An optical disk in which layers are bonded together (Japanese Unexamined Patent Publication No. 61-99951) has been proposed. However, these do not sufficiently consider the particle size of the light-absorbing fine powder such as carbon black or its dispersion state, so it cannot be said that a recording layer in which fine particles are uniformly dispersed is formed. The recording sensitivity and C/N ratio were not sufficiently improved.

Using ultrafine powder of metals, nonmetals, metal compounds, etc. as a dispersing agent, acids having 10 to 12 carbon atoms and 3 COOH groups and 3 OH groups, their lactones, salts, or esters are used to disperse nitrofluorocarbons. An information recording medium having a recording layer dispersed in a binder such as cellulose is disclosed in JP-A-63-264996. By using the above dispersant-
The ultrafine powder described in L can be uniformly dispersed, and as a result,
It is said that uniform optical characteristics can be obtained over a wide range. However, when the recording layer of the optical disc obtained in this way is irradiated with a laser, there is relatively little change in optical properties (transmittance) due to differences in the irradiated position, but the recording sensitivity and C/N are significantly affected. I can't say it's improving.

[Object of the Invention] The present invention provides a recording layer having a recording layer made of light-absorbing fine particle powder formed on a substrate, which has high recording sensitivity and C/N, and has excellent durability such as reading durability and weather resistance. The purpose is to provide information recording media.

SUMMARY OF THE INVENTION An object of the present invention is to provide a simple method for manufacturing an information recording medium, which allows a recording layer made of light-absorbing fine particles to be formed on a substrate by a coating method.

[Summary of the Invention] The present invention provides an information recording medium in which a recording layer capable of recording with a laser is provided on a substrate, the recording layer having light-absorbing fine particles dispersed in a binder, the binder comprising: The following polar groups: O H , C 0 0 M , S O 3 M
and CH-CH2\/O [where M is a hydrogen atom, Na or K] and/or a polyurethane and/or a vinyl chloride/vinyl acetate copolymer. The information recording medium is characterized by:

The above information recording medium is as follows (a) to (C): (a
) light-absorbing fine particle powder; (b) at least one polar group selected from the group consisting of the following polar groups: OH, -COOM, -SO3M, and [where M is a hydrogen atom, Na or K]; A recording layer is formed by coating a substrate with a coating solution consisting of a dispersion in which polyurethane and/or vinyl chloride/vinyl acetate copolymer and (C) an organic solvent are mixed, and then drying the coating layer. This can be advantageously obtained by a method for manufacturing an information recording medium p characterized by forming.

Preferred embodiments of the information recording medium of the present invention are as follows.

1) The light-absorbing fine particle powder is carbon black,
The above information recording medium is characterized in that it is at least one kind of powder selected from the group consisting of organic pigments, deep pigments, and metal powders.

2)-E The above-mentioned information recording medium, wherein the light-absorbing fine particle powder is carbon black.

3) The above polar group is -COOH or The above information recording medium is characterized in that it is SO3H.

Preferred embodiments of the method for manufacturing an information recording medium of the present invention are as follows.

1) The light-absorbing fine particle powder is carbon black,
The method for producing the information recording medium described above, characterized in that the powder is at least one kind of powder selected from the group consisting of organic pigments, inorganic pigments, and metal powders.

2) The method for producing the information recording medium, wherein the light-absorbing fine particle powder is carbon black.

3) The method for producing the information recording medium, wherein the polar group is -COOH or S03H.

[Effects of the Invention] As described above, the information recording medium of the present invention has light-absorbing fine particles uniformly distributed in a binder in the form of extremely fine particles on a substrate.
A recording layer is formed in which the recording sensitivity and C/
It has a high N content and is also excellent in durability such as reading durability and weather resistance.

Generally, it is advantageous for the particle size of light-absorbing fine particles such as carbon black to be as small as possible in order to improve sensitivity and C/N. In the present invention, by dispersing the light-absorbing powder such as the fine particles of carbon black using polyurethane or vinyl chloride/vinyl acetate copolymer having a polar group as a binder as shown in -L, This makes it possible to uniformly disperse it in the binder and organic solvent in the form of extremely fine particles. In the case of carbon black, it is dispersed in the form of primary particles. Also,
The resulting dispersion is also a stable dispersion in which flocculation, in which dispersed fine particles aggregate again, is unlikely to occur.

By coating a well-dispersed dispersion liquid onto a substrate to form a recording layer, light-absorbing fine particles such as carbon blocks can be absorbed into the binder without agglomeration as fine particles. A uniformly dispersed recording layer can be formed. As a result, each particle of the light-absorbing microparticle powder is thought to exist in a relatively separate state, making it easier to form a bit corresponding to the area irradiated with the laser, making the bit shape clearly visible. In addition, the recording sensitivity is improved and the C/N is also significantly improved. Also,
Since the recording layer of the present invention is composed of light-absorbing fine particles such as carbon black dispersed in a binder, it is essentially a system with excellent light resistance (reading durability) and weather resistance. It also has excellent durability.

Furthermore, the above-mentioned excellent information recording medium can be easily manufactured by the simple manufacturing method of the present invention in which a recording layer made of light-absorbing fine particle powder is formed on a substrate by the coating method as described above.

[Detailed Description of the Invention] The information recording medium of the present invention is provided with a recording layer formed by dispersing light-absorbing fine particles of carbon black, an organic pigment, an inorganic pigment, or a metal powder in a binder on a substrate. It has a basic configuration.

The present inventors can manufacture it by a simple method,
We have made extensive efforts to obtain an information recording medium with high recording sensitivity, high C/N, and excellent durability. Sensitivity, C/N
Information recording media obtained using dye materials are known as optical disks that have a high level of resistance and can form a recording layer by coating. Due to its tendency to easily scratch, it is not possible to obtain sufficient performance in terms of durability such as reading durability and weather resistance. On the other hand, by dispersing a light-absorbing fine particle powder such as carbon black in a binder such as nitrocenolose, it is possible to form a recording layer more easily by coating. However, such a recording layer generally has not only low reflectance but also low recording sensitivity and C/N. The inventors of the present invention have repeatedly investigated the cause of this problem. In general, light-absorbing fine particles such as carbon black used to improve sensitivity etc. are preferably as fine as possible, but even if such fine particles are used, the state of fine particles remains in the binder. It cannot be said that the particles are uniformly dispersed, and the particles are partially or entirely aggregated or not sufficiently dispersed. This revealed that improvements in properties cannot be obtained by making the powder into fine particles. In order to improve this dispersion state, the inventors of the present invention, Nagisa et al., have made detailed studies on fine particle powder, dispersants, binders, etc., and have found that the binders include polyurethane having the above polar group and/or vinyl chloride/vinyl acetate copolymer. It has become clear that by using coalescence, the above-mentioned fine particle powder can be made into a uniformly dispersed state in an extremely fine particle state. Of course, in addition to using the resin having a polar group as the bonding agent, the light-absorbing fine particle powder may be carbon black, an organic pigment, an inorganic pigment, or a metal powder, each of which is preferable. It is desirable to use a material with a particle size, and it is further preferable to use, for example, a metal salt of a fatty acid as a dispersant in order to obtain an excellent C/N.

As a result, it is possible to obtain an information recording medium with high recording sensitivity and high C/N while maintaining the excellent durability that is an advantage of a recording layer made of light-absorbing fine particle powder.

The information recording medium of the present invention can be manufactured using, for example, the materials described below.

The substrate used in the present invention can be arbitrarily selected from various materials used as substrates for conventional information recording media. Optical properties, flatness, processability of the substrate,
In terms of ease of handling, stability over time, and manufacturing cost,
Examples of substrate materials include glass: acrylic resins such as cell cast polymethyl methacrylate and injection molded polymethyl methacrylate; vinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymers; epoxy resins: polycarbonate resins: amorphous polyolefins and Mention may be made of polyester. Preferably, mention may be made of polycarbonates, polyolefins and cell-cast polymethyl methacrylate.

The surface of the substrate on which the recording layer is provided has improved flatness,
An undercoat layer may be provided for the purpose of improving adhesive strength, improving the solvent resistance of the plate, and preventing deterioration of the recording layer. Examples of materials for the undercoat layer include polymethyl methacrylate,
Acrylic acid/methacrylic acid copolymer, styrene/maleic anhydride copolymer, polyvinyl alcohol, N-methylolacrylamide, styrene/sulfonic acid copolymer,
Styrene/vinyltoluene copolymer, chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate/vinyl chloride copolymer, ethylene/vinyl acetate copolymer, polyethylene, polypropylene, polycarbonate polymeric substances such as; organic substances such as silane coupling agents; and inorganic oxides (SiO2, Aft203, etc.)
, inorganic substances such as inorganic fluoride (MgF2).

The undercoat layer can be formed by, for example, preparing a coating solution by dissolving or dispersing the above substances in an appropriate solvent, and then applying this coating solution to the substrate surface by a coating method such as spin coating, dip coating, or extrusion coating. It can be formed by The layer thickness of the undercoat layer is generally 0.005 to 20
It is in the range of μm, preferably in the range of 0.01 to 10 μm.

Further, a pre-group layer and/or a pre-pit layer may be provided on the substrate (or undercoat layer) for the purpose of forming tracking grooves or unevenness representing information such as an address signal. As a material for the pregroup layer and the like, a mixture of at least one type of monomer (or oligomer) of acrylic acid monoester, diester, triester, and tetraester 15 ter and a photopolymerization initiator can be used.

To form the pregroup layer, first, a mixed solution consisting of an acrylic ester and a polymerization initiator described in -E is applied onto a densely formed matrix (stamper), and then a substrate is placed on top of this coating solution layer. Thereafter, the liquid layer is cured by irradiation with ultraviolet rays through the substrate or the matrix, thereby fixing the substrate and the liquid phase. Next, by peeling the substrate from the matrix, a substrate provided with a pregroup layer is obtained. The thickness of the pregroup layer generally ranges from 0.05 to 100 μm, preferably from 0.1 to 50 μm. If the substrate material is plastic, the pregroups and/or prepits may be provided directly on the substrate by injection molding, extrusion molding, or the like.

A recording layer is provided on the substrate (or the pregroup layer, etc.) in which the heat-absorbing fine particle powder described above is dispersed in the polar group-containing binder of the present invention.

Examples of the light-absorbing fine particle powder include Carphone 16 Black, organic pigments, inorganic pigments, and metal powders.

As the carbon black that can be used in the present invention, furnace carbon black, furnace carbon black for rubber, thermal black for rubber, black for color, etc. can be used.

Examples of specific products include Conductec, 7, [
CONDUCTEX] S C {Average particle size 18m
μ} (manufactured by Columbia Carbon); BLACK PEARLS 8 0 0 {18mμ}
, 1 300 {1 3 mμ} (manufactured by Cabot); @60 {50 mμ} (manufactured by Asahi Carbon ■);
L/-pen [REVEN] 4 5 0 { 6 2m
u}. 410 {7omμ} (manufactured by E-Columbia Carbon).

The average primary particle size of these carbon blacks used in the present invention is preferably in the range of 10 to 100 mμ (electron microscopy m), and more preferably in the range of 10 to 30 mμ. When it exceeds 100 mμ, the C/N decreases, and when it is less than 10 mμ, dispersion becomes difficult. Nitrogen adsorption method specific surface area (SRE
T) is preferably from 50 to 1500 rn2/g, more preferably from 100 to 900 rn'/g. 15
If it exceeds 00rn'/g, dispersion becomes difficult;
If it is less than '/g, the C/N will decrease. DBP oil absorption (JI
S standard K-6221-1982 method) is 40 to 400 m
l/100 g is preferred, and more preferably 45 to 150 m/100 g. 400m 1
/ If it exceeds 100 g, the C/N will decrease and the
If it is less than 7100 g, dispersion becomes difficult. Further, these carbon blacks may be used after being surface-treated with a dispersant described below or grafted with a resin. Further, it is also possible to use carbon black whose surface is partially graphitized by treating the furnace at a temperature of 2000 DEG C. or higher.

Furthermore, hollow carbon black can be used as a special carbon black.

The weight ratio of the carbon black to the binder described below is preferably in the range of 1.99 to 99:1, particularly preferably in the range of 10:90 to 9010.

Examples of organic pigments that can be used in the present invention include phthalocyanine-based, naphthalocyanine-based, and anthraquinone-based organic pigments. The average particle size of these organic pigments is preferably in the range of 10 to 100 mμ (electron microscope), more preferably in the range of 10 to 30 mμ.

When it exceeds 100 mμ, the C/N decreases, and when it is less than 10 mμ, dispersion becomes difficult.

The weight ratio of the organic pigment to the binder described below is preferably in the range of 1=99 to 99:1, particularly preferably in the range of 10:90 to 90:10.

Inorganic pigments that can be used in the present invention include a
Examples include Fe203, Fe304 and TiO. The average particle diameter of these inorganic pigments is 10
The range is preferably from 100 mμ to 100 mμ (electron microscope), and more preferably from 10 to 30 mμ. When it exceeds 100 mμ, the C/N decreases, and when it is less than 10 mμ, dispersion becomes difficult. The ratio of the amounts of the above-mentioned inorganic pigment to the binder described below is preferably in the range of 1=99 to 99:1, particularly preferably in the range of 10:90 to 90:10.

Metals that can be used in the present invention include Cu, A
Examples include g and In.

The average particle size of these metals is 10 to 100 mμ (
electron microscope) range, more preferably 10
It is in the range of ~30 mμ. C/N when exceeding 100mμ
If the particle diameter is less than 10 mμ, dispersion becomes difficult.

The weight ratio of the metal powder to the binder described below is preferably in the range of 1=99 to 99:1, particularly preferably in the range of 10:90 to 90:10.

The recording layer is formed using the light-absorbing fine particle powder as follows. After mixing the light-absorbing fine particle powder of the present invention with the polar group-containing resin of the present invention and a solvent (a dispersant may be added as desired), or without mixing, knead or disperse the same to prepare a dispersion liquid. . This dispersion is used as it is or with addition of solvents, binders, additives, etc. as desired, and stirred to prepare a coating solution for forming a recording layer.Then, this coating solution is applied to the surface of the substrate to form a coating film. A recording layer can be formed by forming and drying.

The binder, which is a characteristic requirement used in the present invention, is as follows:
It is necessary that the material is a polyurethane or a vinyl chloride/vinyl acetate copolymer having at least one type of polar group selected from the following polar groups.

OH, -COOM, -SO3 M and CH-CH2\/O [where M is a hydrogen atom, Na or K] Among these polar groups, preferably -COOH and -SO3H
It is. It is desirable that the concentration of these polar groups be as high as possible in order to improve the dispersibility of the fine particle powder.
If it is too high, the water resistance etc. will decrease and the durability of the recording layer will also decrease, so IXIO-6 to 1 per gram of resin
It is preferable from the viewpoint of dispersibility and durability that the amount is in the range of 10 x 10, and the range of IXIO-5 to 1 x lO' equivalent is particularly preferable.

The polyurethane is not particularly limited as long as it is a resin containing a urethane bond, and examples thereof include polyester polyurethane, polyether polyurethane, and polycarbonate polyurethane. These may be used alone or in combination, and the polyurethane may further contain two or more of an ester component, an ether component, and a carbonate component. The weight average molecular weight of the above polyurethane is generally 10,000 to 2,000.
00, preferably 15,000 to 60,000
is within the range of

The vinyl chloride/vinyl acetate copolymer is not particularly limited as long as vinyl chloride and vinyl acetate are contained in the polymer. Examples include vinyl chloride/vinyl acetate copolymers, vinyl chloride/vinyl acetate/vinyl alcohol copolymers, and vinyl chloride/vinyl acetate/maleic acid copolymers. These may be used alone or in combination. The degree of polymerization of the above polymer is generally 20
In the range of 0 to 2000, preferably 300 to 100
It is 0.

In addition to the polyurethane and vinyl chloride/vinyl acetate copolymer of the present invention, the following binders may be used as desired.

Examples of natural organic polymeric substances include gelatin, cellulose derivatives such as nitrocellulose and cellulose acetate, dextran, rosin, and rubber.

Examples of thermoplastic resins include vinyl chloride/vinylidene chloride copolymer, acrylic resin (e.g., vinyl chloride/acrylonitrile copolymer, vinylidene chloride/acrylonitrile copolymer, (meth)acrylic acid ester/acrylonitrile copolymer, ) Acrylic acid ester/vinylidene chloride copolymer, (meth)acrylic acid ester/styrene copolymer, butadiene/acrylonitrile copolymer), cellulose derivatives (e.g., cellulose acetate butyrate, cellulose diacetate, cellulose triacetate, Cellulose propionate, cellulose acetate propionate, nitrocellulose, cellulose acetate), various synthetic rubber thermoplastic resins (polybutadiene, chloroprene, polyisoprene, styrene butadiene copolymer), polyurethane resins, polyvinyl fluoride, Polyamide net resin, polyvinyl butyrate, styrene,
Examples include butadiene copolymers and polystyrene resins.

Thermosetting resins or reactive resins are generally resins with an average molecular weight of 200,000 or less in the coating liquid state, and resins whose molecular weight becomes almost infinite due to condensation reaction or addition reaction after coating. . However, when these resins are thermosetting resins, it is preferable that the resins do not soften or dissolve due to heating during the process leading to curing. Examples of such resins include phenol and
Formalin/nopolac resin, phenol/formalin/resol resin, phenol/furfurer 24 resin, xylene/formalin resin, urea resin, melamine resin, drying oil-modified alkyd resin, phenol resin-modified alkyd resin, maleic acid resin-modified alkyd resin, Unsaturated polyester resins, combinations of epoxy resins and curing agents (e.g. polyamines, acid anhydrides, polyamide resins), terminal isocyanate polyether moisture-curable resins, polyisocyanate brevolimers (e.g. combinations of diisocyanates and low molecular weight triols) Reaction products (compounds with three or more isocyanate groups in one molecule, diisocyanate trimers and tetramers), polyisocyanate brevolimers and resins containing active hydrogen (e.g., polyester polyols, polyether polyols, acrylic acids) copolymers, maleic acid copolymers, 2-hydroxyethyl methacrylate copolymers, p-hydroxystyrene copolymers), and these can be used alone or in combination. .

Examples of the solvent include esters such as ethyl acetate, butyl acetate, and cellosolve acetate, ketones such as methyl ethyl ketone, cyclohexanone, and methyl isobutyl ketone, halogenated hydrocarbons such as dichloromethane, 1,2-dichloroethane, and chloroform, tetrahydrofuran,
Examples include ethers such as ethyl ether and dioxane, alcohols such as ethanol, n-probanol, isoprobanol, and n-butanol, amides such as dimedylformamide, and fluorinated solvents such as 2,2,3,3-tetrafluoropropanol. be able to. Note that these solvents consisting of non-hydrocarbon organic solvents do not include hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents, as long as the amount is within 50% by volume. It's okay to stay.

As the dispersant, it is preferable to use the following metal salts of fatty acids. Particularly preferred are metal salts of fatty acids having from 11 to 22 carbon atoms.

Examples of metal salts of fatty acids include alkali metal salts (e.g. Li,
Na, K) salts, alkaline earth metals (e.g., Mg, Ca.B
a) Salt or metals other than these (e.g. Ni, Tll.Z
n, Sn, Cu, Co, Cd, Pb, Afi, Zr, G
e) Salts may be mentioned. These can be used alone or in combination. Among these, metal salts other than alkali and alkaline earth metals of the above-mentioned fatty acids are preferred, and copper or zinc salts of the above-mentioned fatty acids are particularly preferred.

In addition to the metal salts of the fatty acids mentioned above, compounds in which part or all of the hydrogen atoms in fatty acid compounds are replaced with fluorine atoms, amides of the fatty acids listed in L, aliphatic amines, higher alcohols, polyalkylene oxide alkyl phosphates, alkyl phosphoric acids Esters, alkyl borates, sarcosinates, alkyl ether esters, trialkyl polyolefin oxy quaternary ammonium salts and lenti 2
A known dispersant such as 7-N may also be used in combination. The dispersant is generally 0.00 to 100 ffT of binder.
1 to 100 parts by weight are used, preferably 0.1 to 10 parts by weight.
Parts by weight.

In addition to the above dispersant, a dialkyl phthalate plasticizer such as dibutyl phthalate (DBP) may be used in order to shorten the dispersion time.

The method for preparing a dispersion having such a composition is not particularly limited as long as it is a commonly used dispersion method, and the order of addition of each component can be determined as appropriate.

For the preparation of the dispersion, a conventional kneading machine or dispersing machine is used, such as a Niki roll mill, a three-roll mill, a ball mill, a vebble mill, a trom mill, a sand glider, a Zegvariator lighter, a high-speed inveler dispersion machine, a high-speed stone mill,
High-speed impact mills, dispersers, kneaders, high-speed mixers, homogenizers, and ultrasonic dispersers are manufactured by Sengawa.

When preparing a dispersion liquid, a1! ; Antistatic agent and acid 2
8. Known additives such as antifouling agents may also be used.

If desired, a binder and a solvent may be added to the dispersion, and various additives such as an antioxidant, a UV absorber, a plasticizer, and a lubricant may be added depending on the purpose.

Examples of the coating method include a spray method, a spin coat method, a dip method, a roll coat method, a blade coat method, a doctor roll method, and a screen printing method.

The recording layer may be a single layer or a multilayer, but the layer thickness is generally 1.
It is in the range of 00 to ioooo, preferably 500 to
It is in the range of 2000. Furthermore, the recording layer may be provided not only on one side of the substrate but also on both sides.

A protective layer may be provided on the recording layer of the present invention for the purpose of physically and chemically protecting the recording layer and the entire information recording medium. Further, this protective layer may be provided on the side of the substrate where the recording layer is not provided for the purpose of increasing scratch resistance and moisture resistance.

Examples of materials used for the protective layer include inorganic materials such as Sin, Sin2, Si3Na, MgF2, and SnO.
2nd place can be mentioned. In addition, as organic substances,
Examples include thermoplastic resins, thermosetting resins, UV curable resins, etc., with UV curable resins being preferred.

The protective layer can be formed, for example, by laminating a film obtained by extrusion of plastic onto the -12 of the recording layer via an adhesive layer. Alternatively, it may be provided by methods such as vacuum deposition, sputtering, and coating. In addition, in the case of thermoplastic resins and thermosetting resins,
After preparing a coating solution by dissolving these in an appropriate solvent,
It can also be formed by applying this coating liquid and drying it. In the case of a UV curable resin, it can also be shaped by preparing a coating liquid as it is or by dissolving it in an appropriate solvent, applying this coating liquid, and curing it by irradiating it with UV light. Examples of UV curable resins include urethane (meth)acrylate, epoxy (meth)acrylate, polyester (meth)acrylate,
Monomers such as meth)acrylate oligomers and (meth)acrylic acid esters, as well as ordinary UV-curable resins such as photopolymerization initiators can be used. These Coating II liquids further contain an itF antistatic agent, an antioxidant, and a U
Various additives such as V absorbers may be added depending on the purpose.

The thickness of the protective layer is generally in the range of 0.1 to 100 μm.

A reflective layer may be provided on the recording layer for the purpose of improving C/N when reproducing information and improving sensitivity during recording.

The light-reflective material that is the material of the reflective layer is a material that has a high reflectance to laser light, and examples thereof include Mg, Se,
%Y, Ti, Zr. Hf%V, Nb. Ta. Cr,Mo
, W, Mn% Re, Fe, Co, Ni, Ru, Rh,
Pd, l r, Pt. Cu, Ag, Au, Zn% Cd
, Afl, Ga. In, Si. Ge. Te. Pb,Po
, Sn, Bi, and metalloid metals. Among these, preferred are Au, An,
These are Cr and Ni. These substances may be used alone, or in combination of two or more or as an alloy.

The reflective layer can be formed on the recording layer by, for example, vapor deposition, sputtering, or ion plating of the above-mentioned light reflective material.

The thickness of the reflective layer is generally in the range of 100 to 3000X,
Preferably it is 500-2000X.

In the present invention, the information recording medium may be a single board having the above-mentioned structure, or alternatively, two substrates having the above-mentioned structure may be placed facing each other so that the recording layer is on the inside, and adhesive or the like is used. By joining, a laminated type recording medium can also be manufactured. Alternatively, by using a substrate having the above configuration as at least one of the two disc-shaped substrates and joining them via a ring-shaped inner substrate and a ring-shaped outer substrate, an air sand arch type recording medium can be used. can also be manufactured.

3 2 Next, the method for recording information on the information recording medium of the present invention is carried out, for example, as follows.

First, while rotating the information recording medium at a constant linear velocity (for example, within the range of 1.2 to 1.4 m/sec for CD format signals) or a constant angular velocity, a recording light such as a semiconductor laser beam is emitted from the substrate side. irradiate. Generally, a semiconductor laser beam having an oscillation wavelength in the range of 770 to 830 nm is used as the recording light.

Note that during recording, it is preferable to perform tracking control using tracking grooves.

Information can be reproduced by irradiating semiconductor laser light from the substrate side while rotating the recording medium at the same constant speed as described above, and detecting the reflected light or transmitted light.

Margin below Next, Examples and Comparative Examples of the present invention will be described.

However, these examples do not limit the invention.

[Example 1] Distribution ゛ 10 parts of carbon black (primary particle diameter: 13 mμ, S BET: 750 rn”/g
, DBP absorption amount: 125ml/l00g) Polyurethane 10 parts (polar group: -(:
OOH, polar group concentration: 2×10 −5 equivalents/g) diacetone alcohol 1000 parts The materials having the above composition were mixed and then dispersed in a kneader for 2 hours and then in a sand mill for 2 hours to prepare a dispersion. This was directly used as a coating solution for forming a recording layer on a disc-shaped polycarbonate substrate (outer diameter +
1 20mm, inner diameter: 15mm, thickness: 1.2mm, track width: 1.0μm: track pitch: 1.6μm,
Group depth: 800X) was coated using the above coating I5 coating method at a rotational speed of 1000 rpm, and then dried to form a recording layer having a film thickness of 1000X.

In this way, an information recording medium consisting of a substrate and a recording layer was manufactured.

[Example 2] In Example 1, polyurethane having -SO3H as a polar group instead of polyurethane having -COOI{ as a polar group (trade name: UR-8300, manufactured by Toyobo ■, polar group concentration: 6xlO-5 equivalent) An information recording medium was manufactured in the same manner as in Example 1, except that 1/g) was used.

[Example 3] In Example 1, instead of the polyurethane having -COOH as a polar group, a vinyl chloride/vinyl acetate/maleic acid copolymer (vinyl chloride: vinyl acetate:?lz{:/ = 88: 8: 4, degree of polymerization = 400, ゛Product name: 400X110A, manufactured by Nippon Zeon ■), polar group concentration: 6X10-' equivalent/g) Information was obtained in the same manner as in Example 1 except that Recording medium 3 5 was manufactured.

[Comparative Example 1] Example 1 except that polyurethane having no polar group (trade name: N-2301, manufactured by Nippon Polyurethane ■) was used instead of the polyurethane having −(;OOH) as the polar group. An information recording medium was manufactured in the same manner.

[Comparative Example 2] The same procedure as in Example 1 was carried out except that nitrocellulose having no polar group (Hercules method viscosity: t/2 seconds) was used instead of polyurethane having -COOH as a polar group. An information recording medium was manufactured.

[Evaluation of information recording media] Regarding the information recording media obtained in the above examples and comparative examples, laser power (recording power) during recording was 6 mW.
, constant linear velocity 1.3 m/s and modulation frequency 720 kHz
The C/N was measured using a spectrum analyzer (TR4235: manufactured by Advantest) using a decomposition band 3 6 width 30 kHz. There was 10 playbacks.

The above results are shown in Table 1.

Table 1 Conducted at 8 mW Binder resin type Polar group C/N (dB) Example 1 Example 2 Example 3 Polyurethane Polyurethane VC/VA [:00H -SO3H coot+ 5 2 5 2 5 3 Comparative example 1, Polyurethane none
4 0 Comparative example z No NC
40 However, VC/VA in Table 1 represents vinyl chloride/vinyl acetate copolymer, and NC represents nitrocellulose.

As is clear from Table 1, the information recording medium (Examples 1 and 2) having a recording layer using the polar group-containing polyurethane or vinyl chloride/vinyl acetate copolymer of the present invention as a binder is C/ It can be seen that the optical disc has a high N content and has excellent recording and reproducing properties.On the other hand, when polyurethane without polar groups (Comparative Example 1) or nitrocellulose (Comparative Example 2), which is a conventional binder, was used as a binder, Optical disks having a recording layer have a low C/N and cannot be said to have sufficient recording and reproducing characteristics.This is thought to be because carbon black is not uniformly dispersed in the binder in the form of fine particles.

Claims (1)

[Claims] 1. An information recording medium in which a laser-recordable recording layer in which light-absorbing fine particles are dispersed in a binder is provided on a substrate, and the binder contains the following polar groups: -OH, - Polyurethane and/or vinyl chloride/acetic acid having at least one polar group selected from the group consisting of COOM, -SO_3M and ▲Mathematical formulas, chemical formulas, tables, etc.▼ [However, M is a hydrogen atom, Na or K] An information recording medium characterized by being made of a vinyl copolymer. 2. The following (a) to (c): (a) Light-absorbing fine particle powder, (b) The following polar groups; -OH, -COOM, -SO_3M and ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [However, M is a hydrogen atom, Na or K], and (c) a dispersion containing a polyurethane and/or a vinyl chloride/vinyl acetate copolymer having at least one polar group selected from the group consisting of a hydrogen atom, Na or K, and (c) an organic solvent. 1. A method for manufacturing an information recording medium, comprising: coating a substrate with a coating liquid, and then drying the coating layer to form a recording layer.