JP2883618B2 - Information recording medium and optical information reproducing method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an optical information recording / reproducing method capable of writing and reading (reproducing) information using a high energy density laser beam, an information recording medium and information recording. The present invention relates to a method for manufacturing a medium.

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

The optical disk has a basic structure of a disk-shaped substrate made of glass, synthetic resin, etc., and Bi, Sn,
A recording layer made of a metal or semimetal such as In or Te; or a dye such as cyanine, metal complex, or quinone.
In general, an intermediate layer made of a polymer substance is provided on the surface of the substrate on which the recording layer is provided, from the viewpoint of improving the flatness of the substrate, improving the adhesive force with the recording layer, or improving the sensitivity of the optical disc. Is often done.

Further, for the purpose of improving the durability of the information recording medium, a protective layer is provided on the recording layer, or as a disk structure, a recording layer is provided on at least one of the two disc-shaped substrates, An air sandwich structure has been proposed in which the two substrates are joined via a ring-shaped inner spacer and a ring-shaped outer spacer so that the recording layer is located inside and a space is formed. In an optical disk provided with such a protective layer or an optical disk having an air sandwich structure, the recording layer does not come into direct contact with the outside air, and information is recorded and reproduced by laser light transmitted through the substrate. This has the advantage that it does not suffer physical or chemical damage, or dust adheres to its surface and does not hinder the recording and reproduction of information.

Writing and reading of information to and from the optical disk are usually performed by the following method.

Writing of information is performed by irradiating the optical disk with a laser beam, and the irradiated portion of the recording layer absorbs the light and locally raises the temperature, causing a physical or chemical change (for example, generation of pits). Information is recorded by changing its optical properties. Reading of information is also performed by irradiating the optical disk with a laser beam, and information is reproduced by detecting reflected light or transmitted light corresponding to a change in the optical characteristics of the recording layer.

As the recording material for forming the recording layer of such an information recording medium, metals and dyes are known as described above. An information recording medium using a dye has advantages in characteristics of the recording medium itself, such as higher sensitivity than a recording material such as a metal, and also has a manufacturing advantage that a recording layer can be easily formed by a coating method. Has great advantages. However, the recording layer made of a dye generally has a low reflectance,
Alternatively, there is a disadvantage that it is difficult to obtain a high C / N.

Recording of information using a dye as a recording layer is performed by forming pits in the dye recording layer. As described above, dyes have high sensitivity, but require relatively large recording power to form complete pits. That is, in order to obtain a high C / N recording signal, a large recording power is required, and therefore, in many cases, the sensitivity is not truly high.
Further, when a reflective layer is provided in order to improve the low reflectivity, which is a drawback of the dye recording layer, there is a problem that it is more difficult to form pits in the dye recording layer.

On the other hand, there has been disclosed an information recording medium in which a light-absorbing substance such as the above dye is provided on a substrate as a light-absorbing layer, and a metal recording layer is provided thereon to perform recording by forming pits (Japanese Patent Publication No. 63-1988). No. 38773). However, since the metal used for the metal layer must be capable of forming pits, it has a low melting point and cannot be said to have a sufficiently high reflectivity. Further, since pits are formed, the reflectivity decreases during reproduction. There is. Furthermore, recording sensitivity was not sufficient because pits were formed in the dye layer and the metal layer.

Therefore, it is desired to propose an information recording medium which is a recording layer using a dye advantageous in productivity, has a high reflectance, and has a high C / N with a high recording signal.

[Object of the Invention] An object of the present invention is to provide an information recording medium having a C / N having a high reflectance and a high recording signal, comprising a dye recording layer and a reflective layer on a substrate.

An object of the present invention is to provide an optical information reproducing method that is advantageous for reading (reproducing) recorded information from an information recording medium on which information is recorded by changing a dye recording layer in an oriented state to a non-oriented state. And

Another object of the present invention is to provide an information recording medium that can be reproduced by a commercially available CD player by recording a CD format signal by the optical information recording method.

[Summary of the Invention] In the present invention, a recording layer made of a dye in which information is changed from an oriented state to a non-oriented state by laser light irradiation and information is recorded on a disc-shaped substrate, and a reflective layer made of a metal are provided in this order. An information recording medium for reproducing recorded information by reading a difference in reflectance between an oriented region and a non-oriented region in a recording layer, and reading the difference in reflectance between them. In the medium.

The present invention also provides an information recording medium in which a recording layer made of a dye on which information is recorded by changing from an oriented state to a non-oriented state by irradiation of a laser beam on a disc-shaped substrate, and a reflective layer made of a metal are provided in this order. While rotating the laser beam from the substrate side at a constant linear velocity to the recording layer, the difference in the reflectance between the oriented region and the non-oriented region in the recording layer, the difference in the reflectance between them There is also an optical information reproducing method characterized in that recorded information is reproduced by reading the information.

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

1) The information recording medium as described above, wherein the dye is at least one dye selected from a cyanine dye, an azulenium dye, and a squarylium dye.

2) The information recording medium as described above, wherein the dye is a naphthoindolenine dye or a cyanine dye of an imidazoquinoxaline dye.

3) The information recording medium as described above, wherein the dye recording layer contains 0.001 to 0.1 mol part of a metal complex salt dye per 1 mol part of the dye.

4) The optical information recording method as described above, wherein the dye recording layer has a thickness in the range of 500 to 2000 °.

5) The information recording medium, wherein the material of the substrate is polycarbonate, polyolefin, or cell cast polymethyl methacrylate.

6) The information recording medium, wherein the metal is at least one metal or alloy selected from the group consisting of Au, Ag, Cu, Pt, Cr, Ti, Al, and stainless steel.

7) The information recording medium as described above, wherein the thickness of the reflective layer is in the range of 500 to 2000 °.

Preferred embodiments of the method for recording information on the information recording medium of the present invention are described below.

1) The recording of the information is performed by irradiating the dye recording layer with laser light from the substrate side at a constant linear speed of 1.2 to 2.8 m / sec while rotating the information recording medium. Optical information recording method.

2) The optical information recording described above, wherein the recording of the information is performed by irradiating the dye recording layer with a laser beam from the substrate side at a constant linear speed with a CD format signal while rotating the information recording medium. Method.

3) The optical information recording method as described above, wherein the dye is at least one dye selected from a cyanine dye, an azulenium dye, and a squarylium dye.

4) The optical information recording method, wherein the dye is a naphthoindolenin dye or a cyanine dye of an imidaquinoxaline dye.

5) The optical information recording method as described above, wherein the dye recording layer contains 0.001 to 0.1 mol part of a metal complex dye based on 1 mol part of the dye.

6) The optical information recording method, wherein the thickness of the dye recording layer is in the range of 500 to 2000 °.

7) The optical information recording method, wherein the material of the substrate is polycarbonate, polyolefin, or cell cast polymethyl methacrylate.

8) The optical information recording method as described above, wherein the metal is at least one metal or alloy selected from the group consisting of Au, Ag, Cu, Pt, Cr, Ti, Al and stainless steel.

9) The optical information recording method as described above, wherein the thickness of the reflective layer is in the range of 500 to 2000 °.

[Effect of the Invention] The information recording medium of the present invention has a recording layer made of a dye in an oriented state, and a reflective layer thereon. Since information is recorded according to the presence or absence of an orientation state by the recording method of the present invention, in the information recording medium of the present invention, the reflection layer on the dye recording layer remains in a state before recording without forming pits. . This results in high reflectivity and high C / N
Can be obtained.

In the optical information recording method of the present invention, the recording layer made of a dye in an oriented state is melted by irradiation with laser light,
The heat is immediately transmitted to the reflective layer made of metal, so that the dye recording layer does not form pits, but solidifies immediately after melting and changes from an oriented state to a non-oriented state. Information is recorded in this manner. Therefore, the optical information recording method of the present invention,
Since information can be recorded based on the presence or absence of an alignment state, that is, a phase change without forming pits, a high C / N signal can be recorded with a low laser power.

In particular, an information recording medium on which a CD format signal is recorded by the optical information recording method can be reproduced by a commercially available CD player.

[Detailed Description of the Invention] The information recording medium of the present invention has a basic configuration in which a dye recording layer and a reflective layer are provided in this order on a substrate.

The information recording medium of the present invention is characterized by having a dye recording layer in an oriented state. In the present invention, it can be said that the entire surface of the dye recording layer is in the alignment state. When recording information using conventional pits,
In general, the dye layer was provided in a non-oriented state in terms of good smoothness and the like.

In the present invention, instead of recording information by forming pits in a conventional dye recording layer, information can be recorded by a phase change of changing the dye recording layer in the above-mentioned alignment state to a non-alignment state.

The dye used in the information recording medium of the present invention desirably has a property that pit formation hardly occurs, that is, a difference between a melting point and a thermal decomposition temperature is large and an alignment state is easily formed. In order to form the alignment state of the dye, the coating is performed by applying a coating liquid for forming a dye layer in a certain direction while applying a force, and is preferably performed by, for example, spin coating. It can be said that the dye in the oriented state is likely to be melted by heating and become non-oriented, but if the cooling after heating takes too much time, reorientation proceeds. Therefore, in the present invention, by providing a reflective layer made of a metal having a high thermal conductivity on the dye recording layer, the heat applied to the dye recording layer by laser light during recording, on the dye recording layer The dye recording layer is cooled rapidly by conduction to the reflective layer. As a result, the molten dye solidifies while being changed to a non-oriented state without re-orientation. Thus, the recording of the information of the present invention is performed. The thickness of the dye recording layer is preferably in the range of 500 to 2000 ° so that the dye recording layer can be easily coagulated in a non-oriented state without forming pits. The reflective layer preferably has a thickness in the range of 500 to 2000 ° because the dye recording layer needs to be cooled rapidly.

In the recording layer on which information is thus recorded, the dye is in an oriented state in a non-recording part, and a part corresponding to a conventional pit on which information is recorded is in a non-oriented state. Since the reflectance differs depending on the presence or absence of the alignment state, the reproduction can be performed by detecting this.

The state change caused by the phase change at the time of recording can be determined by heating the recording layer and observing the polarization of the recording layer using a polarizing microscope. When there is polarized light, there is birefringence, and when there is no polarized light, there is no birefringence. By observing polarized light, the presence or absence of birefringence can be determined. In general, it is known that a material having birefringence is in an oriented state, and a material having no birefringence is in a non-oriented state. Therefore, by heating (for example, by laser light)
If the state changes from the state with polarized light to the state without polarized light, it can be said that the state has changed from the aligned state to the non-oriented state. In the information recording medium of the present invention, the change in the polarization is observed.

The information recording medium on which information is recorded according to the presence or absence of the orientation state as described above has a reflection layer on the dye recording layer, and since no pits are formed, the reflection layer remains in a state before recording. This results in high reflectivity and high C /
It can be said that this is an information recording medium on which a recording signal having N is recorded.

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

The plastic substrate used in the present invention can be arbitrarily selected from various materials used as a substrate of a conventional information recording medium. In view of the optical characteristics, flatness, workability, handleability, stability over time, and manufacturing cost of the substrate, examples of the substrate material include acrylic resins such as cell cast polymethyl methacrylate and injection-molded polymethyl methacrylate; Examples thereof include vinyl chloride resins such as vinyl chloride and vinyl chloride copolymer; epoxy resins; polycarbonate resins, amorphous polyolefins and polyesters. Preferably, polycarbonate, polyolefin and cell cast polymethyl methacrylate can be mentioned.

An undercoat layer may be provided on the surface of the substrate on which the recording layer is provided, for the purpose of improving flatness, improving adhesion, improving solvent resistance of the substrate, and preventing deterioration of the recording layer. Examples of the material for the undercoat layer include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, suriten / maleic anhydride copolymer, polyvinyl alcohol, N-methylolacrylamide, styrene / sulfonic acid copolymer, and styrene / vinyl. Toluene copolymer, chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, polyethylene, polypropylene, polycarbonate, etc. Molecular substances; organic substances such as silane coupling agents; and inorganic oxides (SiO ₂ , Al ₂ O _3, etc.);
Inorganic substances such as inorganic fluoride (MgF ₂ ) can be exemplified.

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

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

The pre-groove layer is formed by first applying a mixed solution composed of the above-mentioned acrylate and a polymerization initiator on a precisely formed master (stamper), and then placing a substrate on the coating solution layer. The liquid layer is cured by irradiating ultraviolet rays through the substrate or the matrix to fix the substrate and the liquid phase. Next, the substrate provided with the pre-groove layer is obtained by peeling the substrate from the matrix. The thickness of the pregroove layer is generally in the range of 0.05 to 100 μm, preferably in the range of 0.1 to 50 μm. When the substrate material is plastic as in the present invention, the substrate may be directly provided with pregrooves and / or prepits by injection molding or extrusion molding.

On a substrate (or a pre-groove layer or the like), a recording layer made of a dye is provided. The dye used in the present invention is not particularly limited, and any dye may be used. For example, cyanine dyes, phthalocyanine dyes, pyrylium / thiopyrylium dyes, azulenium dyes,
Squarylium dyes, metal complex salt dyes such as Ni and Cr,
Naphthoquinone / anthraquinone dyes, indophenol dyes, indoaniline dyes, triphenylmethane dyes, triallylmethane dyes, aluminum dyes
Diimmonium dyes and nitroso compounds can be mentioned. Preferably, a cyanine-based dye, an azulenium-based dye, and a squarylium-based dye can be used. Among the cyanine-based dyes, a naphthoindolenin-based dye and an imidazoquinoxaline-based dye can be used. These are preferable because they have a large difference between the melting point and the thermal decomposition temperature and can easily form an oriented state.

Among these, a dye having a high absorptivity to light in the near-infrared region of 700 to 900 nm is preferable because a semiconductor laser that emits near-infrared light is practically used as a recording / reproducing laser.

Preferred examples thereof include: i) cyanine dyes: Indolenine ring residue, thiazole ring residue, oxazole ring residue, selenazole ring residue, imidazole ring residue, pyridine ring residue, thiazolopyrimidine ring residue or imidazoquinoxaline ring residue which may be condensed And L is a linking group for forming monocarbocyanine, dicarbocyanine, tricarbocyanine or tetracarbocyanine, X ^m- is a m-valent anion, m is 1 or 2, and X ^m- may be substituted on Φ, L or Ψ to form an inner salt, and Φ and L or L and Ψ
May be further linked to form a ring) Examples of specific compounds represented by the above general formula include the following a) to h).

ii) Squalilium dyes: iii) Azulhenium dyes: (However, at least one combination of R ¹ and R ² , R ² and R ³ , R ³ and R ⁴ , R ⁴ and R ⁵ , R ⁵ and R ^6, and R ⁶ and R ⁷ is substituted or unsubstituted. R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ when forming a ring with a substituted heterocyclic or aliphatic ring and not forming the ring
And R ⁷ are each a hydrogen atom, a halogen atom or a monovalent organic residue, or R ¹ and R ² , R ³ and R ⁴ , R ⁴ and R ⁵ ,
At least one combination of R ⁵ and R ⁶ and R ⁶ and R ⁷ may form a substituted or unsubstituted aromatic ring, and A is a divalent organic residue linked by a double bond. And Z ^- is an anionic residue. Note that at least one carbon atom constituting the azulene ring may be replaced with a nitrogen atom to form an azaazulene ring. Iv) Indophenol dyes: (Where X and Y are each a hydrogen atom, an alkyl group, an acylamino group, an alkoxy group or a halogen atom, and R ¹ , R ² and R ³ are each a hydrogen atom, C ₁ -C ₂₀
A substituted or unsubstituted alkyl group, aryl group, heterocyclic ring or cyclohexyl group, wherein A is -NHCO- or-
V) metal complex dyes: (Where R ^{1 to} R ⁴ are an alkyl group or an aryl group, respectively, and M is a divalent transition metal atom) (Where R ¹ and R ² are an alkyl group or a halogen atom, respectively, and M is a divalent transition metal atom) (However, R ¹ and R ² are each a substituted or unsubstituted alkyl group or aryl group, and R ³ is an alkyl group, a halogen atom or (Where R ⁴ and R ⁵ are each a substituted or unsubstituted alkyl group or aryl group), M is a transition metal atom, and n is an integer of 0 to 3. (Where [Cat] is a cation necessary to neutralize the complex salt, M is Ni, Cu, Co, Pd or Pt, and n is 1 or 2) (Where [Cat] is a cation necessary to neutralize the complex salt, M is Ni, Cu, Co, Pd or Pt, and n is 1 or 2) (Where X is a hydrogen atom, a chlorine atom, a bromine atom or a methyl group, n is an integer of 1 to 4, and A is a quaternary ammonium group) (Where X ¹ and X ² are each a nitro group and / or a halogen atom, n ₁ and n ₂ are each an integer of 1 to 3, R ¹ and R ² are an amino group, a monoalkylamino group, X ¹ and X ² , n ₁ and n _2, and R ¹ and R ² may be the same or different even if they are the same as dialkylamino, acetylamino, and benzoylamino (including substituted benzoylamino). M is Cr or
A Co atom and Y is hydrogen, sodium, potassium, ammonium, aliphatic ammonium (including substituted aliphatic ammonium) or alicyclic ammonium) vi) naphthoquinone-based, anthraquinone-based dyes: (Where R is a hydrogen atom, an alkyl group, an allyl group, an amino group or a substituted amino group) (Where R is a hydrogen atom, an alkyl group, an allyl group, an amino group or a substituted amino group) (Where R is a hydrogen atom, an alkyl group, an allyl group, an amino group or a substituted amino group) (Where X is a halogen atom and n is an integer of 0 to 10) (Where X is a halogen atom) And the like.

Among these dyes, those to which the method of the present invention can be preferably applied include cyanine dyes, azurenium dyes and squalilium dyes, and among the cyanine dyes, naphthoindolenine dyes and An imidazoquinoxaline dye can be mentioned. These are preferable because they have a large difference between the melting point and the thermal decomposition temperature and can easily form an oriented state. These dyes may be used alone or as a mixture of two or more.
When a cyanine dye is used, the metal complex salt dye or the aminium / diimmonium dye is preferably used together as a quencher. In such a case, a metal complex salt dye or the like is used as a quencher for all dyes 1
It is preferable to contain 0.001 to 0.1 mol part to mol part.

The recording layer can be formed by dissolving the dye and, if desired, a binder in a solvent to prepare a coating solution, then applying the coating solution to the substrate surface to form a coating film, and then drying the coating solution. it can.

Ethyl acetate, as a solvent for the dye coating solution preparation,
Esters such as 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; ethers such as tetrahydrofuran, ethyl ether and dioxane; ethanol; n- Examples thereof include alcohols such as propanol, isopropanol and n-butanol, amides such as dimethylformamide, and fluorine-based solvents such as 2,2,3,3 and tetrafluoropropanyl. These non-hydrocarbon organic solvents account for 50% by volume.
As long as it is within, it may contain a hydrocarbon-based solvent such as an aliphatic hydrocarbon solvent, an alicyclic hydrocarbon solvent, or an aromatic hydrocarbon solvent.

Antioxidants, UV absorbers, plasticizers,
Various additives such as a lubricant may be added according to the purpose.

When a binder is used, examples of the binder include cellulose derivatives such as gelatin, nitrocellulose, and cellulose acetate; natural organic polymer substances such as dextran, rosin, and rubber; and carbonized materials such as polyethylene, polypropylene, polystyrene, and polyisobutylene. Hydrogen resin, polyvinyl chloride, polyvinylidene chloride, polyvinyl chloride
Thermal curing of vinyl resins such as polyvinyl acetate copolymers, acrylic resins such as polymethyl acrylate and polymethyl methacrylate, polyvinyl alcohol, chlorinated polyolefins, epoxy resins, butyral resins, rubber derivatives, phenol / formaldehyde resins, etc. And synthetic organic polymer substances such as a precondensate of a hydrophilic resin.

Examples of the application method include a spray method, a spin coating method, a dip method, a roll coating method, a blade coating method, a doctor roll method, and a screen printing method. In order to form a favorable alignment state of the dye, it is preferable to use a spin coating method. Further, it is preferable that the spinner be rotated at a spinning speed in the range of 500 to 5,000 rpm and the drying time be in the range of 1 to 60 seconds in order to promote good orientation of the dye.

When a binder is used as a material for the recording layer, the ratio of the dye to the binder is generally in the range of 0.01 to 99% (weight ratio), preferably in the range of 1.0 to 95% (weight ratio).

The thickness of the dye recording layer is generally in the range of 200 to 3000 °. Further, in the present invention, since the dye of the dye recording layer needs to be maintained in a molten state without forming pits, the thickness of the layer is reduced.
Preferably, it is in the range of 500 to 2000 °.

The reflective layer of the present invention is provided on the dye recording layer. By providing a reflective layer, the effect of improving the reflectance,
The information can also have the effect of improving the S / N during reproduction and the sensitivity during recording.

Materials for the reflective layer include Mg, Se, Y, Ti, Zr, Hf,
V, Nb, Ta, Cr, MoW, Mn, Re, Fe, Co, Ni, Ru, Rh, P
d, Ir, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Si, G
Metals and metalloids such as e, Te, Pb, Po, Sn, Bi and the like can be mentioned. Further, an alloy such as stainless steel may be used. In the present invention, it is preferable to provide a reflective layer made of a metal having a high thermal conductivity at a temperature of 400K and having a value of at least 10 w / mk. Thereby, the heat when the dye recording layer is irradiated with the laser beam can be rapidly transmitted to the reflection layer. Among these, Au, Ag, Cu, Pt, Al, C
r, Ni and stainless steel are particularly preferred. These substances may be used alone or in combination of two or more kinds or as an alloy.

The reflection layer can be formed on the recording layer by, for example, vapor deposition, sputtering, or ion plating of the above-mentioned light reflective substance. The thickness of the reflective layer is generally in the range from 100 to 3000 °. The dye of the dye recording layer is
In order to change from an oriented state to a non-oriented state, it is necessary to rapidly cool after melting the dye, so that heat must be quickly released from the dye layer.
It is preferable to set the range of Å.

A protective layer is provided on the reflective layer for the purpose of physically and chemically protecting the recording layer and the entire information recording medium. This protective layer also has the effect of increasing the scratch resistance and moisture resistance on the side of the substrate where the recording layer is not provided.

Examples of the material used for the protective layer include inorganic substances such as SiO, SiO ₂ , SIN ₄ , MgF ₂ , and SnO ₂ . Further, examples of the organic substance include a thermoplastic resin, a thermosetting resin, a UV-curable resin, and the like, and a UV-curable resin is preferable. In the present invention, a remarkable effect can be obtained when the above substance is provided by coating. This is particularly effective when the organic substance is provided by coating.

That is, it can also be formed by dissolving a thermoplastic resin, a thermosetting resin, or the like in an appropriate solvent to prepare a coating solution, applying the coating solution, and drying.
In the case of a UV curable resin, a coating solution is prepared as it is or dissolved in an appropriate solvent, and then this coating solution is applied.
It can also be formed by curing by irradiating UV light. UV-curable resins include oligomers of (meth) acrylates such as urethane (meth) acrylate, epoxy (meth) acrylate, and polyester (meth) acrylate, and monomers such as (meth) acrylate, and a photopolymerization initiator. And the like can be used. Various additives such as an antistatic agent, an antioxidant and a UV absorber may be added to these coating solutions according to the purpose. In the present invention, it is preferable to use a UV curable resin.

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

In addition to the above, the protective layer can be formed, for example, by laminating a film obtained by extrusion of a plastic onto the dye recording layer via an adhesive layer. Alternatively, it may be provided by a method such as vacuum deposition, sputtering, or coating.

Hereinafter, Examples and Comparative Examples of the present invention will be described. However, these examples do not limit the present invention.

[Example 1] Structural formulas [4] to [d] of the above dyes: And the following dyes in addition to the above dyes: 3 g to which 0.01 mol% was added was dissolved in 2,2,3,3-tetrafluoropropanol to prepare a dye recording layer coating solution (concentration: 3% by weight).

On a disc-shaped polycarbonate substrate (outer diameter: 130 mm, inner diameter: 15 mm, thickness: 1.2 mm, track pitch: 1.6 μm, groove depth: 800 mm) provided with a tracking guide,
After applying the coating solution at a rotation speed of 1000 rpm by a spin coating method, dried at 70 ° C. for 10 seconds to form a film having a thickness of 13
A recording layer of 00 ° was formed.

Au is vapor-deposited on the recording layer made of a dye to have a thickness of 1000 mm.
Was formed.

A UV curable resin (trade name: SD17, Dainippon Ink and Chemicals, Inc.) is applied as a protective layer on the reflective layer by a spin coating method at a rotation speed of 850 rpm, and then irradiated with ultraviolet light from a high-pressure mercury lamp. And cured to form a protective layer having a thickness of 1 μm.

Thus, an information recording medium including the substrate, the dye recording layer, the reflective layer, and the protective layer was manufactured.

Example 2 An information recording medium was manufactured in the same manner as in Example 1, except that the following imidazoquinoxaline dye was used as the dye.

Structural formula [4]-[i] of the above dye [Evaluation of Information Recording Medium] Laser power (recording power) at the time of recording the information recording medium obtained above using a disk evaluation device (Nakmich Disk evaluation device OMS-1000) and an EFM encoder (KEN-WOOD). ) Was recorded at 7 mW, constant linear velocity: 1.3 m / sec, and modulation frequency: 8.75 kHz.

Then, the recorded signal was reproduced at a reproduction power of 0.5 mW using a CD player (Sony, D-50Mk II) that detects a difference in reflectance in a commercially available recording layer and reproduces recorded information.

As a result, Example 1 obtained by the manufacturing method of the present invention was used.
It can be seen that the information recording media of Nos. 1 and 2 can be reproduced by the CD player, that is, have a high reflectivity and a high C / N signal recorded thereon.

When the recording layers of these recording media were observed with a scanning electron microscope, it was confirmed that no pits were formed. Therefore, since information is recorded without forming pits, it is considered that the phase change occurs in the dye layer by irradiating the dye recording layer with laser light, and the information is thus recorded. For the state change of the phase change, use a polarizing microscope and a heating device (Mettler).
And observing the polarization of the recording phase while applying heat to the recording phase. This is to observe the change in birefringence. When there is birefringence, polarized light is generated, but when there is no birefringence, no polarized light is generated. It is known that a material having birefringence is in an oriented state, and a material having no birefringence is in a non-oriented state. The recording layer of the recording medium obtained in the above example shows polarized light at the low temperature of the above observation, but shows high temperature (Example 1:
(170 ° C., Example 2: 250 ° C.), the polarized light disappeared. At this point, heating was stopped. This is because the dye was melted and immediately solidified by heating, and thus changed from the oriented state to the non-oriented state. Therefore, it can be said that the optical recording of the present invention was performed by changing the dye recording layer from the oriented state to the non-oriented state.

Claims (2)

(57) [Claims] 1. An information recording apparatus comprising: a recording layer made of a dye on which information is changed from an oriented state to a non-oriented state by irradiating a laser beam on a disc-shaped substrate, and a reflective layer made of a metal are provided in this order. An information recording medium for reproducing recorded information by reading a difference in reflectance between an oriented region and a non-oriented region in a recording layer, and reading the difference in reflectance between them. 2. An information recording medium in which a recording layer made of a dye and a reflective layer made of a metal are provided in this order on a disc-shaped substrate by irradiating a laser beam from an oriented state to a non-oriented state by laser light irradiation. While rotating the laser beam from the substrate side at a constant linear velocity to the recording layer, the difference in the reflectance between the oriented region and the non-oriented region in the recording layer, the difference in the reflectance between them An optical information reproducing method characterized by reproducing recorded information by reading the information.