JP2686841B2 - Information recording medium and optical information recording method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an information recording medium capable of recording (writing) information by using a laser beam having a high energy density, particularly, an information recording medium having high reflectance and excellent durability. The present invention relates to an information recording 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.

A DRAW (Direct Read After Write) type optical disk has a disk-shaped substrate made of glass, synthetic resin, and the like, and a metal or semimetal such as Bi, Sn, In, Te, etc. provided thereon, or cyanine. And a recording layer comprising a dye of a metal, metal complex, or quinone type. 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.

Recording of information on the optical disk and reproduction (reading) of information from the optical disk are usually performed by the following method.

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

As described above, metals and dyes are known as recording materials for forming the recording layer of such an information recording medium. 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,
It has problems such as characteristics such as low C / N of the reproduction signal, and disadvantages such that the dye recording layer is liable to deteriorate with time due to light irradiation.

Japanese Unexamined Patent Publication (Kokai) No. 64-27995 discloses an optical information recording medium having an organic dye recording layer capable of high-sensitivity recording and high-contrast reproduction using a single pickup, which comprises a main cyanine dye and an auxiliary cyanine dye. A record containing a mixed cyanine dye in which the reflection maximum wavelength range of the auxiliary cyanine dye substantially matches the absorption maximum wavelength range of the main cyanine dye, and the number of methine groups in the auxiliary cyanine dye is less than the number of methine groups in the main cyanine dye. An optical information recording medium provided with layers is described.

However, in such an information recording medium, the absorption maximum wavelength range of the main cyanine dye is almost the same as the wavelength of the laser beam used for recording and reproduction [where the wavelength of the laser beam is λ, the absorption maximum wavelength range is The range is (λ-20) to (λ + 20)], so that the reflectance is low.

Further, in JP-A-64-40387, a dicarbocyanine dye having a benzoindolenin skeleton (a structure in which a benzene ring is condensed on an indolenine skeleton) (methine chain is 5
And a tricarbocyanine dye (7 methine chains) having an indolenine skeleton (7 methine chains). This is to improve the C / N by using a tricarbocyanine dye having an indolenine skeleton while maintaining a high reflectance of a dicarbocyanine dye having a benzoindolenine skeleton.

However, the information recording medium having such a dye recording layer has a relatively good C / N,
The reflectance and light resistance are not satisfactory.

Further, according to the studies by the present inventors, the cyanine dye used in the above information recording medium tends to crystallize in the recording layer during long-term storage or use of the information recording medium. Therefore, it was found that the information recording medium was deteriorated and the durability was deteriorated due to this.

In general, a reflective layer is further provided on the dye recording layer in order to increase the reflectance. Such an example is described in Nikkei Electronics (p. 107, issued January 23, 1989), which shows that the dye used in the recording layer of the recording medium is unknown, but the recording method is However, the dye is melted by the absorption of the laser beam in the dye recording layer, the plastic substrate is heated accordingly, and the substrate rises toward the recording layer to form pits. Has been done. This reflection layer is a deposited film of gold. According to the study of the present inventors, the use of the cyanine dye having the benzoindolenin skeleton in the dye recording layer makes it possible to obtain an optical disk having a relatively high C / N and an improved reflectance. .

Even with DRAW type optical discs, in high-density recording of CD format signals (CD-DRAW), it is necessary to record the above signals at a constant linear velocity of 1.2 to 1.4 m / sec. It is required to play on a CD player. It is desirable that the reflectivity of the optical disk be at least 70% or more for reproduction by a CD player. However, even if a CD format signal is recorded on the optical disc, some CD players cannot reproduce the CD format signal. Further, the above-mentioned cyanine dyes do not have sufficient light fastness, and a singlet oxygen quencher is generally added to improve the light fastness. However, since the addition of such a quencher significantly lowers the reflectance, there is a problem that the reflectance decreases as the light resistance improves.

[Object of the Invention] An object of the present invention is to provide an information recording medium having high reflectance and excellent durability, and an optical information recording method using the information recording medium.

SUMMARY OF THE INVENTION The present invention relates to a dye A having a long-wavelength side end of an absorption curve at a wavelength of 780 nm and a complex refractive index having an absolute value of an imaginary part of 0.2 or less at a wavelength of 780 nm, and the dye A. A recording layer capable of recording information by laser light, containing a mixture with a trimethine cyanine dye (dye B) having an absorption maximum wavelength on a shorter wavelength side than the absorption maximum wavelength of It is a characteristic information recording medium.

Another aspect of the present invention is to use a laser beam having an oscillation wavelength in the range of 750 to 810 nm as the recording light, and have the long wavelength side end of the absorption curve at a wavelength of 780 nm, and the absolute value of the imaginary part at a wavelength of 780 nm. By a laser beam containing a mixture of a dye A having a complex index of refraction of 0.2 or less and a trimethine cyanine dye (dye B) having an absorption maximum wavelength shorter than the absorption maximum wavelength of the dye A. A recording layer capable of recording information is recorded on the recording layer by irradiating the laser beam from the substrate side on the recording layer while rotating the information recording medium provided on the substrate. This is an information recording method.

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

1) The above dye A has the following general formula (I); [However, R ¹ , R ² and R ³ each independently represent an alkyl group which may have a substituent having 1 to 8 carbon atoms, and X ⁻ represents an anion, And p represents 1 or 2], which is a cyanine dye having a benzoindolenine skeleton.

2) The above dye B is represented by the following general formula (II); [However, R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ and R
^16's each independently represent an alkyl group which may have a substituent having 1 to 8 carbon atoms, and X represents
^q- represents an anion, q represents 1 or 2, and A ₁ and A ₂ each independently represent an atomic group for forming a naphthalene ring or a benzene ring which may have a substituent. The above information recording medium is a trimethine cyanine dye having an indolenine skeleton represented by

3) The information recording medium, wherein the recording layer contains a quencher having an absorption maximum on the long wavelength side of the absorption maximum wavelength of any of the dyes contained in the recording layer.

4) The information recording medium, wherein the absorption maximum of the dye B is lower than the absorption maximum of the cyanine dye represented by the general formula (I) by 20 nm or more.

5) The above information recording medium, wherein the mixing ratio of the dye A and the dye B is in the range of Dye A: Dye B = 20: 80 to 95: 5.

6) The information recording medium, wherein the material of the substrate is plastic.

7) The information recording medium, wherein a reflective layer made of metal is further provided on the recording layer.

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

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

1) The above optical information recording method, wherein the recorded information is a CD format signal.

2) An optical information recording method, wherein the information recording medium is rotated at a constant linear velocity of 1.2 to 2.8 m / sec.

Incidentally, the absorption maximum of the dye of the present invention refers to the absorption maximum of the dye layer formed on the substrate.

[Effects of the Invention] The information recording medium of the present invention comprises the dye A having the above-mentioned specific absorption curve and complex refractive index on the substrate as described above, and a wavelength shorter than the absorption maximum wavelength of the dye A. The information recording medium is provided with a recording layer containing a mixture with the dye B, which is a trimethine cyanine dye having an absorption maximum wavelength.

The above dye A and the above dye B, when used alone, tend to crystallize in the recording layer during long-term storage or use of the information recording medium. By using the mixture with B, the information recording medium does not crystallize in the recording layer even if it is stored or used for a long period of time, and therefore the durability of the information recording medium is remarkably improved.

Further, since the above-mentioned dye A and the above-mentioned dye B have the absorption characteristics and the absorption characteristics relations specified as described above, the information recording medium of the present invention has a C / N, a modulation degree, etc. This is an information recording medium in which the recording / reproducing characteristics are hardly deteriorated and the reflectance is greatly improved.

Furthermore, since the obtained optical disc has a remarkably high reflectance, it can be recorded on a CD format signal and reproduced by a commercially available CD player, and thus is useful as a CD-DRAW.

[Detailed Description of the Invention] The information recording medium of the present invention comprises a dye A having a specific absorption curve and a complex refractive index as described above, and a dye A on a substrate.
The recording layer is provided with a recording layer containing a mixture with dye B, which is a trimethine cyanine dye having an absorption maximum wavelength on the shorter wavelength side than the absorption maximum wavelength.

The above-mentioned substrate can be arbitrarily selected from various materials used as the substrate of the conventional information recording medium. Examples of the substrate material include glass; polycarbonate; acrylic resin such as polymethylmethacrylate; vinyl chloride resin such as polyvinyl chloride and vinyl chloride copolymer; epoxy resin; amorphous polyolefin and polyester. You may use together. Note that these materials can be used in the form of a film or a rigid substrate. Among the above materials, polycarbonate is preferred from the viewpoint of moisture resistance, dimensional stability, cost, and the like.

On the surface of the substrate on which the recording layer is provided, for the purpose of improving flatness, improving adhesive strength and preventing deterioration of the recording layer,
An undercoat layer may be provided. Examples of the material of the undercoat layer include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleinanhydride copolymer,
Polyvinyl alcohol, N-methylol acrylamide, styrene / sulfonato copolymer, styrene / vinyl toluene copolymer, chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer Examples thereof include polymer materials such as polymer, ethylene / vinyl acetate copolymer, polyethylene / polypropylene and polycarbonate; and organic materials such as silane coupling agents.

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, it is preferable that irregularities representing information such as tracking grooves or address signals are formed on the substrate (or the undercoat layer). When a resin material such as the above polycarbonate is used, it is preferable that grooves are provided directly on the substrate by injection molding or extrusion molding of the resin material.

The groove may be formed by providing a pre-groove layer. As the material of the pre-groove layer,
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.

A recording layer containing a dye capable of recording or reproducing information by laser light is provided on the substrate. The present invention is particularly characterized in that the dye in the recording layer is a specific dye, that is, a mixture of the dye A and the dye B.

The dye A is a dye A having a long wavelength side end of the absorption curve at a wavelength of 780 nm and a complex refractive index having an absolute value of an imaginary part of 0.2 or less at a wavelength of 780 nm. Therefore, dye A is 780n
It has an absorption maximum in a wavelength much shorter than m, generally in a wavelength range of 710 ± 30 nm. The wavelength of 780 nm is the wavelength of laser light generally used for recording / reproducing information recording media, and the absorption maximum wavelength of the dye A is shorter than the wavelength of laser light used for recording / reproducing. Is off. In this respect, the dye A in the present invention is the main cyanine dye (where the absorption maximum wavelength region is the wavelength of the laser light used for recording / reproducing in the optical information recording medium described in JP-A-64-27995). They are chosen to be nearly identical) and are quite different. Therefore, in the selection of the dye for the recording layer, the present invention and the invention described in Japanese Patent Application Laid-Open No. 64-27995 differ from each other in the idea of the invention.

As the dye A in the present invention, any dye can be used as long as it has the above-mentioned properties. The dye A preferable as the dye A has a structure represented by the following general formula (I). It is a cyanine dye having a benzoindolenine skeleton.

General formula (I); [However, R ¹ , R ² and R ³ each independently represent an alkyl group which may have a substituent having 1 to 8 carbon atoms, and X ⁻ represents an anion, And p represents 1 or 2.] In the general formula (I), the alkyl group represented by R ¹ is a methyl group having 1 to 8 carbon atoms, which may have a substituent. , Ethyl, n-propyl, n-butyl, isobutyl, 2-ethylhexyl and the like can be mentioned, preferably an alkyl group having 1 to 6 carbon atoms (for example, methyl, ethyl, n-).
Propyl, n-butyl and isobutyl), and examples of the substituent which may be substituted include a fluorine atom and an alkoxy group. Particularly preferred is an alkyl group having no substituent.

The alkyl group represented by R ² and R ³ is an unsubstituted alkyl group having 1 to 8 carbon atoms (specific example, methyl,
Ethyl and propyl), and particularly preferably a methyl group or an ethyl group.

Preferred examples of the anion represented by X include halide ion (eg Cl ⁻ , Br ⁻ , I ⁻ ), sulfonate ion (eg CH ₃ SO ₃ ⁻ , CF ₃ SO ₃ ⁻ , CH ₃ OSO ₃ ^- , Naphthalene-1,5-disulfonate ion), Cl
O ₄ ⁻ , BF ₄ ⁻ , metal complex ion (for example, And phosphate ions (for example, PF ₆ ^-, Can be mentioned.

Of these, particularly preferred anions are ClO ₄ ⁻ , PF ₆
^- and However, I ^- and May be mixed in a trace amount.

The cyanine dye having the benzoindolenine skeleton represented by the general formula (I) has high reflectance among dyes and is excellent in recording sensitivity and recording / reproducing characteristics such as C / N. The cyanine dye having a benzoindolenin skeleton represented by the general formula (I) generally has an absorption maximum wavelength of 71 ± 30 nm and absorbs in a wavelength band around 780 nm which is an oscillation wavelength of laser light used for recording and reproduction. It has a characteristic that the long wavelength side end of the curve (the complex refractive index at the wavelength of 780 nm has an absolute value of the imaginary part of 0.2 or less) and the light absorption is relatively small and the reflectance is high. Have.

Specific examples of the compound represented by the above general formula include the following I-1 to I-16.

The cyanine dye having the indolenine skeleton represented by the general formula (I) as specifically shown above is included in the general formula of the dye used in the recording layer of the optical disk described in JP-A-64-40387. It is what is done.

The dye B is a trimethine cyanine dye having an absorption maximum on the shorter wavelength side than the absorption maximum wavelength of the dye A. The dyes used in the recording layer of the optical disk described in JP-A-64-40387 include indolenine dicarbocyanine dyes (5 methine chains) and indolenine tricarbocyanine dyes (7 methine chains). It is a mixture with. Some of the indolenine-based dicarbocyanine dyes are the same as the dye A in the present invention, but the indolenine-based tricarbocyanine dyes are absorbed on the longer wavelength side than the absorption maximum of the indolenine-based dicarbocyanine dyes. It is a dye that has a maximum. Therefore, the information recording medium of the present invention is disclosed in JP-A-64-4.
In comparison with the information recording medium described in JP-A No. 0387, in the present invention, a mixture of Dye A and Dye B (three methine chains) having an absorption maximum on the shorter wavelength side than the absorption maximum of Dye A is used. On the other hand, in the information recording medium described in JP-A-64-40387, an indolenine dicarbocyanine dye (corresponding to dye A) and an absorption maximum on the longer wavelength side than the absorption maximum of this dye. Since it is a mixture with an indolenine-based tricarbocyanine dye, the combination form of the two dyes is completely opposite, and in the selection of the dye for the recording layer, the present invention and JP-A-64-40387 are described. The invention that has been made is different from the thought of the invention. By the way, JP-A 64-403
When the combination as described in Japanese Patent No. 87 is used, the reflectance of the information recording medium is lowered.

The absorption maximum wavelength of the dye B is preferably 20 nm or more shorter than the absorption maximum wavelength of the dye A to be combined in order to obtain high reflectance.

The trimethine cyanine dye B having the above-mentioned absorption characteristics is not particularly limited as long as the above conditions are satisfied, but a trimetine skeleton having an indolenine skeleton or a benzoindolenine skeleton represented by the following general formula (II) is particularly preferable. It is preferably a tincyanine dye.

[However, R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ and R
^16's each independently represent an alkyl group which may have a substituent having 1 to 8 carbon atoms, and X represents
^q- represents an anion, q represents 1 or 2, and A ₁ and A ₂ each independently represent an atomic group for forming a naphthalene ring or a benzene ring which may have a substituent. In the general formula (II), the alkyl group represented by R ¹¹ and R ¹² is an alkyl group which may have a substituent having 1 to 8 carbon atoms, such as methyl, ethyl and n. -Propyl, n-butyl, isobutyl and 2-
Examples thereof include a group such as ethylhexyl, preferably an alkyl group having 1 to 6 carbon atoms (eg, methyl, ethyl, n-propyl, n-butyl, isobutyl), which may be substituted. Examples of the group include a fluorine atom and an alkoxy group. Particularly preferred is an alkyl group having no substituent.

The alkyl group represented by R ¹³ , R ¹⁴ , R ¹⁵ or R ¹⁶ is independently preferably an unsubstituted alkyl group having 1 to 6 carbon atoms (specific example, methyl, ethyl), particularly preferably methyl. Group or ethyl group.

A ¹ and A ₂ are preferably each independently an atomic group for forming an unsubstituted benzene ring, or a methyl group,
It represents an atomic group for forming a benzene ring or a naphthalene ring substituted with one or two groups selected from a chlorine atom, a fluorine atom, a methoxy group or an ethoxy group.

Preferred examples of the anion represented by Y include the preferable anion represented by X in the above general formula (I).

Examples of specific compounds represented by the above general formula include the following II-1 to II-20.

The specific cyanine dye represented by the above general formula (II) is partly included in the general formula of the dye used for the recording layer of the optical disk disclosed in JP-A-59-55795.
The cyanine dyes are cyanine dyes and related compounds (Cyanine Dyes) of the Chemistry of Heterocyclic Compound series as dyes.
and Related Compounds, John Wiley & Sons, New Yor
k, London, published 1964).

Further, the mixing ratio of the dye A and the dye B is preferably in the range of 20:80 to 95: 5 by weight, and more preferably in the range of 40:60 to 90:10, in order to obtain good recording sensitivity. Is preferred. When the ratio of the dye A is larger than the above range, the reflectance of the information recording medium is not improved and the durability is deteriorated. on the other hand,
When the proportion of the dye B is larger than the above range, the sensitivity of the information recording medium is lowered and the durability is deteriorated.

In order to improve light resistance, it is preferable to use various dyes known as a so-called singlet oxygen quencher, for example, a compound represented by the following general formula (III) or (IV).

(However, [Cat] ⁺ represents a non-metal cation such as tetraalkylammonium, M represents a transition metal atom such as Ni, and Z and Z ′ represent an optionally substituted benzene ring, 2-thioxo-1 Represents an atomic group for completing a 5- or 6-membered aromatic ring or hetero ring such as a 3,3-dithiol ring) [Wherein R represents an alkyl group which may have a substituent and Q represents the same anion as represented by X in the general formula (I)] The above general formula (III) or (IV) Specific examples of the quencher represented by are PA-1006 (Mitsui Toatsu Fine Co., Ltd.), IRG-023 (Nippon Kayaku Co., Ltd.) and the like.

The recording layer is formed by dissolving the dye, and optionally the quencher, the binder, and the like in a solvent to prepare a coating solution, and then coating the coating solution on the substrate surface to form a coating film and then drying. It can be done by doing.

Examples of the solvent for preparing the dye layer coating solution of the present invention include: esters such as ethyl acetate, butyl acetate, and cellosolve acetate; ketones such as methyl ethyl ketone, cyclohexanone, and methyl isobutyl ketone;
Chlorinated hydrocarbons such as dichloroelan and chloroform;
Amides such as dimethylformamide; hydrocarbons such as cyclohexane; tetrahydrofuran, ethyl ether,
Ethers such as dioxane; alcohols such as ethanol, n-propanol, isopropanol and n-butanol; and fluorinated solvents such as 2,2,3,3-tetrafluoropropanol.

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 natural organic high molecular substances such as gelatin, cellulose derivatives, dextran, rosin, and rubber; hydrocarbon resins such as polyethylene, polypropylene, polystyrene, and polyisobutylene; and polyvinyl chloride. , Polyvinylidene chloride,
Vinyl resins such as polyvinyl chloride / polyvinyl acetate copolymers, acrylic resins such as polymethyl acrylate and polymethyl methacrylate, polyvinyl alcohol, chlorinated polyethylene, epoxy resins, butyral resins, rubber derivatives, phenol / formaldehyde resins And the like. Synthetic organic polymer substances such as an initial condensate of a thermosetting resin.

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 concentration of the coating solution prepared in this way is generally 0.
01 to 10% (weight ratio), preferably 0.1 to 5%
% (Weight ratio).

The recording layer may be a single layer or a multilayer, but the layer thickness is generally
It is in the range of 200-3000 °, preferably in the range of 500-2500 °. The recording layer may be provided not only on one side of the substrate but also on both sides.

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.

Further, the information recording medium of the present invention may have a reflective layer provided on the recording layer for the purpose of improving the C / N and the reflectance when reproducing information.

The light-reflecting substance that is the material of the reflecting layer is a substance having a high reflectance for laser light, and examples thereof include Mg, Se,
Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, F
e, Co, Ni, Ru, Rh, Pd, Ir, Pt, Cu, Ag, Au, Zn, C
Examples thereof include metals such as d, Al, Ga, In, Si, Ge, Te, Pb, Po, Sn, and Bi and semimetals or stainless steel. Of these, preferred are Cr, Ni, Pt, C
u, Ag, Au, Al and stainless steel. 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 °.

Further, a protective layer may be provided on the reflective layer for the purpose of physically and chemically protecting the recording layer and the like. This protective layer may be provided on the side of the substrate on which the recording layer is not provided for the purpose of improving the scratch resistance and the moisture resistance.

Examples of materials used for the protective layer include SiO, SiO ₂ , M
gF _2, inorganic substances such as SnO _2, Si ₃ N _4; thermoplastic resins, thermosetting resins, and organic materials such as UV curable resin.

The protective layer can be formed, for example, by laminating a film obtained by extrusion processing of a plastic on a recording layer (or a silver salt layer or a reflective layer) and / or a substrate via an adhesive layer. Or vacuum deposition,
It may be provided by a method such as sputtering or coating. In the case of a thermoplastic resin or a thermosetting resin, they can also be formed by dissolving these in an appropriate solvent to prepare a coating solution, applying the coating solution, and drying. In the case of a UV curable resin, it can also be formed by preparing a coating solution as it is or by dissolving it in an appropriate solvent, applying the coating solution, and irradiating with UV light to cure. Various additives such as an antistatic agent, an antioxidant and a UV absorber may be added to these coating solutions according to the purpose.

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

In the present invention, the information recording medium may be a single plate having the above-described configuration, or two substrates having the above-described configuration are arranged such that the recording layer faces inside,
By bonding using an adhesive or the like, a bonding type recording medium can also be manufactured. Alternatively, an air sandwich type recording medium is manufactured by joining a substrate having the above configuration to at least one of the two disk-shaped substrates via a ring-shaped inner spacer and a ring-shaped outer spacer. You can also.

A method for recording and reproducing information using the information recording medium is performed, for example, as follows.

First, while rotating the information recording medium at a constant linear velocity (1.2 to 1.4 m / sec in the case of the CD format) or a constant angular velocity, a 780 nm recording light such as a semiconductor laser beam is irradiated from the substrate side. By this light irradiation, in the present invention, a cavity is formed at the interface between the recording layer and the reflective layer (the cavity is formed by deforming the recording layer or the reflective layer, or deforming both layers). Alternatively, it is considered that information is recorded when the substrate is overlaid and deformed, or when the refractive index changes due to discoloration or change in the association state of the recording layer.

Information can be reproduced by irradiating the semiconductor laser light from the substrate side while rotating the information recording medium at the same constant linear velocity as above, and detecting the reflected light.

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

Example 1 As dye A, 1.0 g of the benzoindolenine-based cyanine dye of the dye I-1 and as dye B, 1.0 g of the benzoindolenine-based trimethine cyanine dye of the dye II-1,
A recording layer coating solution was prepared by dissolving it in 100 cc of 2,2,3,3-tetrafluoropropanol.

On a disc-shaped polycarbonate substrate (outer diameter: 120 mm, inner diameter: 15 mm, thickness: 1.2 mm, track pitch: 1.6 μm, groove width: 0.5 μm, groove depth: 900 Å) provided with a tracking guide, The coating solution for recording layer was applied by a spin coating method at a rotation speed of 1000 rpm and dried for 30 seconds to form a recording layer having a layer thickness of 1300Å.

Au is further DC-sputtered on the recording layer to obtain a layer thickness.
A 1300 mm reflective layer was formed.

A UV-curable resin (trade name: 3070, manufactured by ThreeBond Co., Ltd.) as a protective layer was applied on the reflective layer by a spin coating method at a rotation speed of 1500 rpm, and then cured by irradiating ultraviolet rays with a high-pressure mercury lamp to cure the layer. A protective layer having a thickness of 3 μm was formed.

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

[Example 2] An information recording medium was produced in the same manner as in Example 1 except that the dye A was changed to the benzoindolenine type cyanine dye of the dye I-6.

Comparative Example 1 In Example 1, the dye I-1 was used as the dye A in 2.
An information recording medium was produced in the same manner as in Example 1 except that 0 g was used and Dye B was not used.

Regarding the dyes used in the above Examples and Comparative Examples,
A coating solution was prepared by dissolving it in 2,2,3,3-tetrafluoropropanol and coating it on a glass plate to form a dye layer having a layer thickness of about 1300Å, and the absorption maximum wavelength was determined. The results were as follows.

I-1: 710nm I-6: 715nm II-1: 619nm [Evaluation of Information Recording Medium] 1) Reflectivity About the obtained information recording medium, using a spectrophotometer (manufactured by Hitachi, Ltd.), the substrate side Further, the light having a wavelength of 780 nm was irradiated to measure the reflectance of the unrecorded portion.

2) C / N The information recording medium obtained above was recorded on a semiconductor laser beam having a wavelength of 780 nm at a constant linear velocity of 1.3 m / sec and recording power.
At 7.0 mW, a signal with a modulation frequency of 720 kHz (duty: 33%) was recorded. Then, the recorded signal was reproduced with a reproduction power of 0.5 mW, and the C / N during the reproduction was measured using a spectrum analyzer (TR4135: manufactured by Advantest).

3) Durability The information recording medium obtained above was used at a temperature of 80 ° C and a humidity of 80%.
After left in a RH constant temperature and humidity chamber for 96 hours, the recording layer was observed from the substrate side with an optical microscope to determine the presence or absence of crystals. It has been separately confirmed that the information recording medium having crystals in the recording layer has many errors when recording / reproducing information. Therefore, those without crystals are regarded as durability “poor” and those with crystals are present. The durability was defined as "poor".

 Table 1 shows the measurement results.

As is clear from Table 1, the information recording medium having the recording layer composed of the two specific types of cyanine dyes of the examples has extremely high reflectance and maintains a high C / N level. The information recording medium of the comparative example has a low reflectance and is inferior in durability as compared with the examples, while having excellent durability.

Claims (4)

(57) [Claims] 1. A dye A having a long-wavelength side end of an absorption curve at a wavelength of 780 nm and a complex refractive index having an absolute value of an imaginary part of 0.2 or less at a wavelength of 780 nm, and a maximum absorption wavelength of the dye A. Information comprising a mixture of a trimethine cyanine dye having an absorption maximum wavelength on the shorter wavelength side (dye B) and capable of recording information by laser light, provided on the substrate. recoding media. 2. The information recording medium according to claim 1, wherein the dye A is a cyanine dye having a benzoindolenine skeleton and the dye B is a trimethine cyanine dye having an indolenine skeleton. 3. The information recording medium according to claim 1, further comprising a reflective layer made of metal provided on the recording layer. 4. A laser beam having an oscillation wavelength in the range of 750 to 810 nm is used as the recording light, and the long wavelength side end of the absorption curve is at 780 nm, and the absolute value of the imaginary part at the wavelength of 780 nm is
A dye A having a complex refractive index of 0.2 or less, and the dye A
A mixture with a trimethine cyanine dye (dye B) having an absorption maximum wavelength on a shorter wavelength side than the absorption maximum wavelength of
A recording layer capable of recording information with a laser beam records information by irradiating the laser beam from the substrate side onto the recording layer while rotating the information recording medium provided on the substrate. A characteristic optical information recording method.