JPH0373385A - Information recording medium - Google Patents

Abstract

PURPOSE:To obtain an information recording medium which is high in durability to repetitive reproduction of information and high in reflectance, C/N, and modulation factor by a method wherein a coloring matter of a recording layer is composed of a mixture of a first coloring matter having a specific complex index refraction to a wavelength of a laser beam for recording or reproduction of information and a second coloring matter having larger absorption and higher transformation temperature than the first coloring matter. CONSTITUTION:An information recording medium provides a recording layer containing a coloring matter capable of recording or reproducing information by lase beam on a disk like substrate and a reflection layer thereon. Then, the coloring matter of the recording layer is composed of a mixture of a first coloring matter having a complex index of refraction of which a real part is 1.5 or over and of which an imaginary part absolute value is 0.1 or under to a wavelength of a beam for recording or reproduction of information, and a second coloring matter having larger absorption than the first coloring matter at said wavelength and having higher transformation temperature than the transformation temperature of the first coloring matter. Further, for the composite index of refraction to light of said wavelength of the mixture of both coloring matters, the real part is 1.5 or over and the imaginary part absolute value is 0.03 to 0.5. Further, a filter layer for interrupting light of a wavelength of an absorption range of this first coloring matter is provided to a surface on a side wherein light is incident on the recording layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to an information recording medium capable of recording (writing) and/or reproducing (reading) information using a high-energy-density laser beam, and particularly to an information recording medium capable of recording (writing) and/or reproducing (reading) information using a high-energy-density laser beam. The present invention relates to an information recording medium that can obtain a high C/N ratio.

[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.

The basic structure of an optical disk is a disk-shaped substrate made of glass, synthetic resin, etc., and Bi, Sn, etc.
, In, Te, and other metals or metalloids; or cyanine-based, metal complex-based, quinone-based, and other dyes. Note that an intermediate layer made of a polymeric substance is usually provided on the surface of the substrate on the side where the recording layer is provided, in order to improve the flatness of the substrate, improve the adhesive force with the recording layer, or improve the sensitivity of the optical disc. often.

Recording of information on an optical disk and reproduction of information from the optical disk are normally performed by the following method.

Information is recorded 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 and causing physical or chemical changes (for example, the formation of pits). information is recorded by changing its optical properties. Information is also reproduced by irradiating the optical disk with a laser beam, and by detecting reflected or transmitted light depending on changes in the optical characteristics of the recording layer.

As described above, metals, dyes, and the like are known as recording materials forming the recording layer of such information recording media. Information recording media using dyes have advantages in the characteristics of the recording medium itself, such as higher sensitivity compared to recording materials such as metals, as well as manufacturing advantages in that the recording layer can be easily formed by a coating method. It has great advantages. However, a recording layer made of a dye has a drawback that it generally has a low C reflectance, or that it is difficult to obtain a high C/N or modulation degree.

In general, optical discs with high reflectance provide high reliable strength, high servo gain, and high C/N.
and modulation degree can be easily obtained. Therefore, since it can be widely applied to various drives, improving its characteristics is an important issue. However, dyes with high reflectance (generally high refractive index) have the disadvantage that they have low absorption at the laser oscillation wavelength and are difficult to record.

On the other hand, dyes with high absorption have low reflectance and also have the problem of being easily degraded by light.

An information recording medium in which a metal reflective layer is provided on a dye recording layer to improve reflectance has been published by Nikkei Electronics J.
(Published January 23, 1989, p. 107). Although reflectance can be improved by forming an optical disc in such a form, sensitivity is generally lowered, and susceptibility to deterioration by laser light during reproduction cannot be improved.

On the other hand, in order to solve the above problem, Japanese Patent Laid-Open No. 64-4039
No. 0 discloses an optical disk using an indolenine cyanine dye that has a high reflectance at the laser oscillation wavelength and an aminium dye that has a low reflectance but a large absorption coefficient. However, both of these dyes have large absorption at the dye laser's oscillation wavelength (the absolute value of the imaginary part of the complex refractive index is large) and low transformation temperatures, so the resulting optical disk has a low modulation degree and C/N. Therefore, these dyes are excellent materials for the recording layer of optical discs, but they are easily degraded by laser light during playback, so they do not have sufficient durability (playback life) for repeated playback of information. Also, the reflectance cannot be said to be high.

Therefore, the information recording medium is provided with a recording layer using a dye that is advantageous in terms of productivity, has sufficiently high durability for repeated reproduction of information, has high reflectance during recording or reproduction of information, and has a high modulation degree and An information recording medium with a sufficiently high C/H is also desired.

[Summary of the Invention] The present inventors have made repeated studies in order to obtain an information recording medium that has sufficiently high durability against repeated information reproduction, high reflectance, and also high C/N and modulation.

In order to obtain the above-mentioned excellent information recording medium, the present invention aims to solve the problems of the above-mentioned optical disc having a configuration in which a reflective layer is provided on the recording layer that can easily obtain a high reflectance.
That is, repeated studies have been made to obtain a recording layer with improved durability against reduction in reflectance and repeated reproduction of information.

Therefore, in general, optical disks have a high refractive index to improve reflectance, and have low absorption near the laser oscillation wavelength (that is, the absolute value of the imaginary part of the complex refractive index is small) to improve the durability of repeated playback. As a result of repeated studies on recording layers containing dyes as main components, which are considered unsuitable for use as recording layers in The inventors have discovered that the dyes having a high refractive index and low absorption are also useful and valuable for solving the above problems, and have arrived at the present invention.

Therefore, the present invention provides a recording layer containing a dye on a substrate, which has a high reflectance when recording or reproducing information, has excellent durability against repeated reproduction of information, and has a large signal modulation degree and a high C/N. The purpose is to provide an information recording medium that has the following characteristics.

Another object of the present invention is to provide an information recording medium that has the above-mentioned excellent properties and has significantly improved light resistance.

The present invention provides an information recording medium in which a recording layer containing a dye on which information can be recorded or reproduced by laser light is provided on a disc-shaped substrate, and a reflective layer is provided thereon. The real part is 1 for the wavelength of the reproduction laser beam.
．． A first dye having a complex refractive index of 5 or more and an absolute value of the imaginary part of 0.1 or less, and a transformation temperature that has a larger absorption than the first dye at the wavelength and a transformation temperature higher than that of the first dye. Further, the complex refractive index of the mixture of both of the above-mentioned dyes for light of the wavelength has a real part of 1.
The information recording medium is characterized in that the absolute value of the imaginary part is 5 or more and the absolute value of the imaginary part is 0.03 to 0.5.

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

1) The above information characterized in that a filter layer that blocks light with a wavelength within the absorption range of the first dye is provided on at least the surface of the information recording medium on the side where light is incident on the recording layer. recoding media.

2) The above information characterized in that the above pigment is a combination of pigments selected from cyanine pigments, azulenicum pigments, squalirium pigments, merocyanine pigments, oxonol pigments, indoaniline pigments, or phthalocyanine pigments. recoding media.

3) The information recording medium, wherein the transformation temperature of the second dye is 30° C. or more higher than the transformation temperature of the first dye.

4) The information recording medium, wherein the transformation temperature of the second dye is 50° C. or more higher than the transformation temperature of the first dye.

5) The information recording medium, wherein the absorption maximum of the first dye is between less than 5% of the wavelength of the laser beam and a wavelength of 5% or more of the wavelength of the laser beam.

6) The information recording medium, wherein the composition ratio of the first dye and the second dye is within a range of 70.30 to 99.9:0.1 in terms of weight ratio.

7) The information recording medium according to claim 1, wherein the recording layer further contains 0.001 to 0.1 mole part of a metal complex dye based on 1 mole part of the dye mixture.

8) The above-mentioned information recording medium, wherein the thickness of the above-mentioned recording layer is in the range of 500 to 2000X.

9) The above-mentioned information characterized in that a filter layer that blocks light having a wavelength within the absorption range of the first dye is provided on at least the surface of the above-mentioned information recording medium on the side where light is incident on the above-mentioned recording layer. recoding media.

10) The information recording medium, wherein the filter layer has a transmittance of 10% or less for light having a wavelength within the absorption range of the first dye.

11) The reflective layer is made of Au, Ag, Cu, Pt, Cr,
The information recording medium described above is made of at least one metal or alloy selected from the group consisting of Ti, AIL, and stainless steel.

12) The information recording medium, wherein the reflective layer has a thickness in the range of 500 to 2000.

13) The information recording medium described above, further comprising a protective layer provided on the reflective layer.

The information recording medium of the present invention has outstanding durability against repeated reproduction of information, high reflectance when reading information, and has a large f/34 degree equivalent to that of a compact disc and a high C/N. It is an information recording medium that has excellent effects.

In addition, by using the two specific dyes of the present invention in Section L, it is possible to effectively utilize dyes that are not commonly used in recording layers of optical disks, and to obtain optical disks with excellent characteristics as described above. be able to.

Furthermore, in particular, the information recording medium provided with the filter layer of the present invention has excellent properties such as those listed in J-List, and furthermore, the information recording medium has a significantly superior effect of improving light resistance by 1. It is a recording medium.

[Detailed Description of the Invention] The information recording medium of the present invention has a basic configuration in which a recording layer containing a mixture of two types of dyes with different properties is provided on a disc-shaped substrate, and a reflective layer is provided on the recording layer. has.

Preferably, the substrate is made of plastic, and the plastic can be arbitrarily selected from various materials used as substrates for conventional information recording media. Examples of substrate materials include acrylic resins such as polymethyl methacrylate, polyvinyl chloride,
Examples include vinyl chloride resins such as vinyl chloride copolymers; epoxy resins: polycarbonate resins, amorphous polyolefins, and polyesters. Preferably, polycarbonate, polyolefin, and polymethyl methacrylate are used from the viewpoint of substrate optical properties, flatness, processability, handleability, stability over time, manufacturing cost, and the like.

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 substrate, 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/vinylhenzenesulfonic acid copolymer, styrene/donyltoluene copolymer, chlorosulfonated polyethylene, High molecular substances such as nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate/vinyl chloride copolymer, ethylene/vinyl acetate copolymer, polyethylene, polypropylene, polycarbonate; organic materials such as silane coupling agents substance; and mR oxide (SiO□, A
Q, 01, etc.), inorganic fusides (MgF2), and other inorganic substances.

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

Furthermore, a pre-groove layer and/or a pre-pit layer may be provided on the substrate (or undercoat layer) for the purpose of forming tracking grooves or depressions representing information such as address signals. The material for the pre-groove layer etc. is at least one monomer selected from monoesters, diesters, triesters and tetraesters of acrylic acid (
or oligomer) and a photopolymerization initiator can be used.

The pregroove layer is formed by first applying a mixture of the above acrylic ester and polymerization initiator onto a precisely made matrix (stambar), and then placing the substrate on top of this coating liquid layer. After that, 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, the substrate with the pregroove layer is obtained by peeling the substrate from the matrix. The layer H of the pregroove layer is generally in the range of 0.1 to 100 μm, preferably in the range of 0.1 to 50 μm. When the substrate material is plastic as in the present invention, injection molding, extrusion molding, etc. Pregroove and/or
Alternatively, a pre-pit may be provided.

A recording layer containing a dye that can record (write) or reproduce (read) information using a laser beam is provided on the substrate (or the pregroove layer, etc.). The present invention is particularly characterized by the composition of the dye in the recording layer.

That is, the dye of the recording layer in the present invention is a mixture of two specific dyes (referred to as a first dye and a second dye in this specification).

The first dye is a dye that has a specific complex refractive index as described below in order to obtain excellent durability against repeated reproduction, high reflectance and modulation degree, and the second dye is a dye that easily absorbs laser light and It is a pigment that is less likely to undergo transformation than the first pigment so that it can efficiently provide heat energy to the first pigment.

The first dye is a dye having a complex refractive index with a real part of 1.5 or more and an imaginary part of an absolute value of 0.1 or less with respect to a laser beam for recording or reproducing information. The complex refractive index (n) is expressed by the formula: %Formula %) The first dye has an rlo of 1.5 or more with respect to the wavelength of the laser beam for recording or reproducing information.
Preferably it is 2.0 or more, k.

is 0.1 or less, preferably 0.09 or less, particularly preferably 0.05 or less. The complex refractive index of a dye varies depending on the state of the dye at the time of measurement (e.g., solvent, concentration, etc.), but in this specification, including the following description, the value measured while coated on a substrate is used. means.

Although the complex refractive index of the dye changes depending on the wavelength of light, the complex refractive index of the first dye should be determined for the laser light used for recording or reproducing information on the information recording medium.

Therefore, the first dye in the present invention cannot be uniquely determined because it must be selected in accordance with the laser beam used for recording or reproducing information on the information recording medium, but it can be used in a wide variety of colors. A person skilled in the art can easily select one of the following dyes by considering the above conditions.

In addition, in order to obtain excellent durability against repeated reproduction (reproduction life) and high reflectance, the first dye in the present invention has the above-mentioned specific complex refractive index as well as a laser beam for recording or reproducing information. It is preferable that the dye has an absorption range (wavelength range of half-value width of maximum absorption) in a wavelength shorter than the wavelength of light by 5% or more.

Further, the second dye in the present invention is a dye that absorbs at the wavelength of the laser beam for recording or reproducing the information. It is necessary that the absorption of the second dye at the wavelength be greater than the absorption of the first dye. Furthermore, it is preferable that the dye has an absorption maximum between less than 5% of the wavelength of the laser beam and a wavelength of 5% or more of the wavelength of the laser beam. There is no need to particularly consider the complex refractive index of the second dye, but in the present invention, as described later, it is necessary to set the a-prime refractive index of the dye mixture within a specific range, and the complex refractive index of the first dye mixture and Considering the content of the first dye in the recording layer (this is also related to the ratio of the first dye to the second dye in the dye mixture), the real part is 1 or more and the absolute value of the imaginary part is Preferably, the dye has a complex refractive index of 0.1 or more. The second dye can also be readily selected from a wide variety of dyes by those skilled in the art.

In the information recording medium of the present invention, the correlation between the transformation temperature of the first dye and the transformation temperature of the second dye is particularly important.

As used herein, "transformation temperature" means the temperature at which transformation from solid to liquid or gas begins, such as melting point, decomposition temperature, etc., and the temperature at which crystal transformation from one crystalline form to another begins. do. In the information recording medium of the present invention, the correlation between the transformation temperatures is such that the transformation temperature of the second dye is higher than the transformation temperature of the first dye, preferably 30°C or more higher, and more preferably 50°C or more higher. It is. In the information recording medium of the present invention, the second dye absorbs the laser beam used for recording information, and the first dye is chemically and/or physically changed by the heat generated by the absorption, and the first dye is changed chemically and/or physically. The result information is recorded. In the information recording medium of the present invention, information can be stored by combining the first dye and the second dye so that the correlation between the transformation temperature of the first dye and the transformation temperature of the second dye is as described above. In addition to increasing the reflectance of the recording medium, it becomes possible to significantly increase the modulation degree and C/N of the signal.

-1-1 The recording format is estimated as follows.

By irradiating the recording layer with laser light, the second dye absorbs Toko and generates thermal energy. The first dye, which has a lower heptamorphic density than the second dye, causes transformations such as melting and vaporization by absorbing the heat. As a result, cavities or changes in the crystalline state of the recording layer occur in the recording layer on the side that is in contact with the reflective layer, and information is recorded. In the present invention, in order to obtain high reflectance and excellent durability against repeated reproduction, a large amount of the primary dye that absorbs little laser light is contained, so that the capacity for transformation as described above is also large. Therefore, the recorded signal will be larger,
Modulation degree and contrast are improved.

Furthermore, since the first pigment has a high refractive index, the diffraction of light becomes large in the area where the signal is recorded, and the difference in reflectance between the recorded area and the unrecorded area of No. 13 is greatly reduced. It is estimated that the degree of modulation of the recorded signal will be significantly higher.

In the present invention, furthermore, the mixture of the first dye and the second dye has a real part of 1.5 or more -L, preferably 2.0 or more, with respect to light having the wavelength of a laser beam for recording or reproducing information. and
The absolute value of the imaginary part is 0.03 to 0.5, preferably 0.05
It is necessary to have a complex refractive index of ~0.11. Since the L complex refractive index is additive, the complex refractive index of the mixture can be easily determined from the complex refractive index of each of the first dye and the second dye. Further, the mixing ratio of the first dye and the second dye can be easily determined in accordance with the complex refractive index of the desired mixture. However, since it is preferable to have a large amount of the first dye in order to obtain a high modulation degree and reflectance, the composition ratio of the first dye and the second dye is approximately 70:30 to 99.9:0.1. The ratio is preferably within the range of 90:10 to 99.9:0.1, particularly preferably 90:10 to 99.9:0.1.

In the information recording medium of the present invention, if the real part of the complex refractive index of the dye mixture is smaller than the above range, the reproduction No. 3 amplitude intensity tends to decrease; If the absolute value of the imaginary part is smaller than the above range, the recording sensitivity will decrease, and if it is larger than the E range, the reflectance will decrease.

Thus, in the present invention, the second dye functions to absorb the laser light used for recording information. On the other hand, the first dye is not recorded by the information recording laser beam, but is chemically and/or physically changed by the heat generated when the second dye absorbs the information recording laser beam, resulting in Information is mainly recorded in the first dye.

Information is reproduced by recording the information as described above, and comparing the optical properties of the first dye that has changed through the change of the second dye by the recording laser beam and the second dye of the part that is not irradiated with the recording laser beam. This is done by detecting the difference in the optical properties of one dye by reflecting the reproduction laser beam. The reflectance of the dye is greater on the longer wavelength side than the absorption range of the dye, so the first dye does not absorb the laser beam for information recording, but serves to increase the reflectance for the laser beam for reproduction. . The second dye only needs to function to change the first dye when recording information, and does not need to be involved when reproducing information.

However, in the present invention, the dye for recording and accumulating information is the first dye, and the second dye only has to function to absorb the information recording laser beam (as described above,
(The heat generated when the second dye absorbs the information recording laser beam changes the first dye and information is recorded.)The second dye deteriorates slightly due to the general light absorption of the environment before information recording, and the information is recorded. Even if the sensitivity to the recording laser beam decreases slightly, it will hardly affect the information recording to the first dye, and the first dye will be able to obtain a sufficiently high reflectance, and a sufficiently high contrast and a significantly high degree of modulation. Obtainable.

Therefore, in the present invention, the above-mentioned dyes are used as the second dye. In addition, as the first dye, a dye having a complex refractive index as described above, that is, a large real part (refractive index) of 1.5 or more and an absolute value of the imaginary part (extinction coefficient) of 0
．． A dye having a small complex refractive index of 1 or less is used.

From what has been explained in detail above, the smaller the extinction coefficient (related to the absorption coefficient) of the first dye, the better the light resistance of the recording layer will be (the durability of repeated playback of the optical disc will also be improved), and moreover, when recording information It is clear that the sensitivity of Furthermore, the greater the refractive index of the dye, the greater the reflectance.

The reflectance of a dye is generally larger on the long wavelength side C than the absorption range of the dye, so the first dye has an absorption range (C) that is at least 5% shorter than the wavelength of the laser beam for recording or reproducing information. It is preferable that the dye has a wavelength range of half width of maximum absorption. In the present invention, the first dye is
Since it is not directly involved in the absorption of the information recording laser beam, it can be selected to maximize the reflectance for the reproduction laser beam without particularly considering the absorption of the information recording laser beam.

In the present invention, the first dye and the second dye are determined in relation to the wavelength of the laser beam for recording or reproducing information. Therefore, depending on the wavelength of the laser beam used for recording or reproducing information, the same dye may function as the second dye or may function as the second dye.

In the present invention, the first dye is usually a dye that has an absorption range at least 5% shorter than the wavelength of the laser beam for recording or reproducing information, so that light is incident on at least the recording layer of the information recording medium. It is preferable that a filter layer that blocks light having a wavelength within the absorption range of the first dye is provided on the side where the first dye is absorbed. This filter layer preferably has a transmittance of 10% or less, particularly 1% or less in the absorption range of the first dye. Information recording on the information recording medium and information reproduction from the information recording medium are performed by laser light irradiation from the substrate, so the recording layer is exposed to light from the substrate side, so the filter layer is Provided on either side.

Since a reflective layer is provided on the recording layer (on the side opposite to the substrate), there is no need to provide a filter layer.
If it is necessary to consider the incidence of general light from the reflective layer side, a filter layer may be provided on any layer on the surface of the recording layer opposite to the substrate. This filter layer may be made into a separate film and attached to a desired location (for example, the surface of a substrate), or the filter layer may be formed at a desired location using a filter layer forming solution, etc. You may.

By forming such a filter layer, the first dye, which plays the role of recording and storing information, will not be affected by environmental light (e.g. sunlight) before recording information, so that it will not be affected by environmental light (e.g. sunlight) during storage of the information recording medium. The primary dye does not deteriorate,
The light resistance of the information recording medium is significantly improved.

As the filter layer, any commercially available filter that transmits light around the wavelength of the laser beam used and blocks light at the absorption wavelength of the first dye can be arbitrarily selected and used.

The first dye and the second dye used in the present invention may be of any type as long as they satisfy the above conditions. For example, cyanine dyes, phthalocyanine dyes, pyrylium/thiopyrylium dyes, azulenium dyes, squarylium dyes, metal complex dyes such as Ni and Cr, naphthoquinone/anthraquinone dyes, indophenol dyes, and indoaniline dyes. Examples include dyes, triphenylmethane dyes, triallylmethane dyes, aluminum diimmonium dyes, merocyanine dyes, oxonol dyes, pyridone dyes, and nitroso compounds. Preferably, a cyanine dye,
Examples include azulenium dyes and squarylium dyes, and among cyanine dyes, naphthoindolenine dyes and imidazoquinoxaline dyes can be mentioned.

As a specific example of the dye used in the present invention, for example, when a 780 nm laser beam is used as a laser beam for recording and reproduction, a preferable dye as the first dye is the following merocyanine dye compound (1). A preferable dye as the second dye is the following indolenine dye compound (2).

Compound (1) Compound (2) IO4 Furthermore, when a cyanine dye is used, it is preferable to use the above metal complex dye or aminium diimmonium dye as a quencher. In that case, it is preferable to contain 0.001 to 0.1 mole part of a metal complex dye or the like as a quencher per 1 mole part of the total dye.

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 this coating solution to the surface of the substrate to form a coating film, and then drying the coating solution. can.

Examples of the solvent for preparing the dye coating solution 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; Examples include needles such as tetrahydrofuran, ethyl ether, and dioxane, alcohols such as ethanol, n-propanol, isopropanol, and n-butanol, amides such as dimethylformamide, and fluorocarbon solvents such as 2,2,3°3-tetrafluorolobanol. be able to. Note that these non-hydrocarbon organic solvents may contain hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents, as long as the amount is within 50% by volume. .

Paint! Depending on the purpose, various additives such as antioxidants, UV absorbers, plasticizers, and lubricants may be added to the liquid.

When a binder is used, examples of the binder include cellulose derivatives such as gelatin, nitrocellulose, and cellulose acetate; natural organic polymeric substances such as dextran, rosin, and rubber; and carbonized materials such as polyethylene, polypropylene, polystyrene, and polyisobutylene. Hydrogen resins, vinyl resins such as polyvinyl chloride, polyvinylidene chloride, polyvinyl chloride/polyvinyl acetate coelectrolyte, acrylic resins such as polymethyl acrylate, polymethyl methacrylate,
Examples include synthetic organic polymeric substances such as polyvinyl alcohol, chlorinated polyolefins, epoxy resins, butyral resins, rubber derivatives, and initial condensates of thermosetting resins such as phenol/formaldehyde resins.

Examples of the coating method include a spray method, a spin code method, a dip method, a roll coat method, a blade coat method/doctor roll method, and a screen printing method. In order to form a good alignment state of the dye, it is preferable to use a spin code method.

When a binder is used as a material for the recording layer, the ratio of dye to binder is generally 0.01 to 99% (weight ratio).
It is 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 λ, preferably 500 to 2000 λ.

A reflective layer is provided on the recording layer. By providing a reflective layer, it is possible to obtain the effect of improving reflectance, improving S/N during information reproduction, and improving sensitivity during recording.

Materials for the reflective layer include Mg, Se, Y, Ti, and Zr.
, Hf, V, Nb, Ta, Cr, Mo.

W, Mn, Re, Fe, Co, Ni, Ru, Rh, Pd
, Ir, Pt, Cu, Ag, Au.

Zn, Cd, ALL, Ga, In, Si, Ge, Te,
Mention may be made of metals and metalloids such as Pb, Po, Sn, Bi and the like. Furthermore, alloys such as stainless steel may be used. Among these, Au, Ag%Cu, Pt, A
Particularly preferred are 11, Cr, Ni and stainless steel.

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-blating the above-mentioned light-reflective material.

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

A protective layer may be 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 scratch resistance and moisture resistance on the side of the substrate where the recording layer is not provided.

Examples of materials used for the protective layer include inorganic substances such as SiO, 5i02, Si3N4, 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. In the present invention, remarkable effects can be obtained when the above-mentioned substance is provided by coating. This is particularly effective when the organic substance is applied by coating.

That is, it can also be formed by dissolving a thermoplastic resin, a thermosetting resin, or the like in a suitable solvent to prepare a coating solution, and then applying the coating solution and drying it. U
In the case of V-curable resin, apply the coating solution as it is or dissolve it in an appropriate solvent to prepare a coating solution,
It can also be formed by curing by irradiating UV light. Examples of UV-curable resins include oligomers of (meth)acrylate such as urethane (meth)acrylate, epoxy (meth)acrylate, and polyester (meth)acrylate, and monomers such as (meth)acrylic acid ester. Conventional UV curable resins such as initiators can be used. Various additives such as antistatic agents, antioxidants, and UV absorbers may be further added to these coating liquids depending on 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 of 0.1 to Zooμm.

In addition to the above, the protective layer can be formed, for example, by laminating a film obtained by extrusion of plastic onto the dye recording layer via an adhesive layer.

Alternatively, it may be provided by methods such as vacuum evaporation, sputtering, coating, etc.) Examples and comparative examples of the present invention will be described below in the margins. However, each of these aspects does not limit the invention.

[Example 1] A dye having the following structural formula: was used as the first dye, a dye having the following structural formula: 104 was used as the second dye, and the weight ratio of the first dye:second dye = 95:5 Dissolve it in 2,2,3,3-tetrafluoropropanol and add the recording layer coating solution (total dye concentration: 2.0 weight!+
1%) was manufactured by A.

In addition, the wavelength 780 of each dye measured as described above
Real part (no) of double refractive index for rnm laser light
and the absolute value of the imaginary part (ko), as well as the melting point and decomposition temperature measured by DSC, were as follows.

no ko - Shiri L-m First dye 2.8 0.0'1 150℃
None 1st, pigment 2. B 1.5 280℃
330°C mixed dye 2.7 0.10 In addition, the absorption range of the first dye is 510 to 690 nm,
The maximum absorption of the 7th dye is 750 nm! child .

Disc-shaped polycarbonate substrate with tracking guide (outer diameter: 130 mm, inner diameter = 15 mm, thickness:
1.2mm, track pitch: 1.6μtn, group depth: 800 Dry for 10 minutes at a temperature of 100%
A 0X recording layer was formed.

On the recording layer made of the dye, a reflective layer having a thickness of 1300 mm was formed by DC sputtering of Au.

-Reflective layer"Second, as a protective layer, t+V curable resin (
After applying 3070 (manufactured by Three Bond Co., Ltd., product name: 3070) using the spin code method at a speed of 850 rpm and 1 m,
Cured by irradiating ultraviolet rays with a high-pressure mercury lamp to a layer thickness of 3 μm.
A protective layer was formed.

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

[Comparative Example 1] An information recording medium was produced in the same manner as in Example 1, except that only the first dye was used and a recording layer coating liquid was prepared at a dye concentration of 2.0% by weight.

[Comparative Example 2] An information recording medium was produced in the same manner as in Example 1, except that only the second dye was used and a recording layer coating liquid was prepared at a dye concentration of 2.0% by weight.

[Comparative Example 3] In Example 1, the second dye was a dye with the following structural formula: [Comparative Example 4] In Example 1, the first dye was a general dye with the following structural formula (indolenine, which is said to have a high reflectance). An information recording medium was produced in the same manner as in Example 1 except that the dye was changed to:

In addition, the absolute values of the real part (no) and imaginary part (ko) of the complex refractive index of each dye used in Comparative Example 3 with respect to the laser beam with a wavelength of 780 nm measured as described above, and D
The melting point and decomposition temperature measured by SC were as follows.

no ko - Riichi Kakitoshi Ikkakusai Watari First dye 2.8 0.03 150℃ None Second dye 1.4 2.0 90℃ 1
90°C mixed dye 2.7 0.2 Same as Example 1 except that the second dye was changed to an aminium dye having the following structural formula and the weight ratio of the first dye:second dye was 80:20. An information recording medium was manufactured in the same manner.

In addition, the absolute value of the real part (n, ) and imaginary part (ko) of the complex refractive index of each dye used in Comparative Example 4 with respect to the laser beam with a wavelength of 780 nm measured as described above, and D
The melting point and decomposition temperature measured by SC were as follows.

no ko n fresh limb emperor and first pigment 2.9 0.11 155℃ 27
4℃ secondary dye 1.5 0.2 128℃ 2
79°C mixed dye 2.6 0.12 The information recording media obtained in the above examples and comparative examples were evaluated for reflectance, C/N, and modulation using a semiconductor laser beam with a wavelength of 780 nm according to the evaluation method below. The degree of regeneration and regeneration life were measured.

[Evaluation of information recording medium] A single signal with a modulation frequency of 720 kHz (duty: 33%) was recorded on the information recording medium using a semiconductor laser beam with a wavelength of 780 nm at a constant linear velocity of 1.3 cm/sec and a recording power of 6 mW. was recorded.

(Reflectance) When an unrecorded area for tracking/no group was reproduced, the energy of the laser incident light and the energy of the reflected light were measured, and the ratio was determined as a percentage.

(C/N) The output level of the carrier and noise was measured using a spectrum analyzer (RBW: 10kHz, VBW: toOHz) under the conditions of reproduction power 0.5mW and constant linear velocity 1.3m/sec for the information recorded under the above conditions. The ratio (C/N) was measured.

(Degree of Modulation) When information recorded under the above conditions is reproduced, the maximum value of the reflected light level of the DC reproduced waveform is A, the minimum value is B, and the reflected light level in an area without a pregroove is R. The modulation degree was calculated as (A-B)/RX100%.

(Reproduction life) Using an optical disk drive (DDU-1000; manufactured by Pulstic ■) on each of the obtained information recording media,
EFM signals were recorded by irradiating with a 780 nm semiconductor laser at a recording power of 6 mW and a linear velocity of 1.3 m/sec. Playback power 1.5mW using the same drive
The information recorded was played back. Reproduction was performed repeatedly on the same track on the recording medium. The number of plays was counted as one play of one track. The jitter was measured every 100 times of reproduction, and the number of reproductions when the measured value increased to a value exceeding the initial value by 10 nsec was defined as the reproduction life.

The above results are shown in Table 1.

Table 1 As is clear from Table 1, the information recording medium of the present invention of Example 1 has a higher reflectance than the recording media of Comparative Examples 1 and 3, and has a significantly higher C/N and modulation degree. It shows excellent properties. The optical disc of Comparative Example 2 has good reproduction characteristics, but has low reflectance and short reproduction life. Second
The optical disc of Comparative Example 3, which uses a dye having a lower transformation temperature than the first dye, has an extremely low degree of modulation. The optical disc of Comparative Example 4 using two conventional dyes has a significantly shorter playback life than the recording medium of the present invention.

[Example 2] As a substrate, a filter layer (manufactured by Fuji Photo Film Co., Ltd.) that cuts light of 740 nm or less was placed on the surface of a substrate similar to the polycarbonate substrate used in Example 1, opposite to the surface on which the recording layer is formed. Company-made sharp cut filter 5
An information recording medium was manufactured in the same manner as in Example 1, except that a substrate to which C74) was attached with an adhesive was used.

When this information recording medium was evaluated in the same manner as in Example 1, it had the same performance as the information recording medium of Example 1, except that the reflectance was 71%.

The reflectance of this information recording medium after being irradiated with a xenon lamp for 24 hours was 73%. On the other hand, the reflectance of the information recording medium of Example 1 after being irradiated with a xenon lamp for 24 hours was 98%.

From this result, it is clear that the light resistance of the information recording medium of the present invention is increased by providing the filter layer without degrading the performance.

Claims (1)

[Claims] 1. An information recording medium in which a recording layer containing a dye that can record or reproduce information with a laser beam is provided on a disk-shaped substrate, and a reflective layer is provided on the recording layer, in which the dye is formed by a laser beam for recording or reproducing information. a first dye having a complex refractive index whose real part is 1.5 or more and the absolute value of the imaginary part is 0.1 or less with respect to the wavelength; It consists of a mixture with a second dye having a transformation temperature higher than that of the dye, and furthermore, the complex refractive index of the mixture of both dyes for light of this wavelength has a real part of 1.5 or more and an imaginary part of absolute An information recording medium having a value of 0.03 to 0.5. 2. 2. A filter layer for blocking light having a wavelength within the absorption range of the first dye is provided on at least the surface of the information recording medium on which light is incident on the recording layer. information recording medium.