JPH04132027A - Information recording medium and production thereof - Google Patents

Abstract

PURPOSE:To allow coloration to arbitrary colors of a wide range and to obtain reproduction signals satisfying DC standards by confining the difference between the optical film thickness of the dye layer of pit parts and the optical film thickness of the dye layer of inter-bit parts. CONSTITUTION:The dye layer 12 contg. dyes and a reflection layer 13 consisting of metals are provided in this order on a substrate 11 having the prepits. The difference between the optical film thickness t2 of the pit part 16 of the dye layer 12 and the optical film thickness t1 of the inter-pit part 15 is confined to lambda/8 (where lambda is the wavelength of a laser beam for reproducing) at this time. The arbitrary coloration a substrate 11 similar to the substrate for conventional CDs to various colors of a wide range is possible in this way and simultaneously the reproduction signals satisfying the CD standards are obtd. A tracking servo gain is thus increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to an information recording medium capable of reproducing information using laser light, and a method for manufacturing the same.

[Technical Background of the Invention] In recent years, information recording media that use high energy density beams such as laser light have been developed and put into practical use.

This information recording medium is called an optical disk and can be used as a video disk, an audio disk, a large-capacity still image file, and a large-capacity computer disk memory. Among these information recording media, compact discs (CDs) are widely used for audio reproduction of music and the like. Compact discs are used only to reproduce information consisting of pit rows formed on a substrate during manufacturing. That is, a compact disc is manufactured by molding a suitable plastic material to form pits in a spiral shape, and then forming a metal layer as a reflective layer on the surface of the pit. In this way, compact discs are playback-only recording media.

Information on a compact disc is read by irradiating a laser beam from the substrate side while rotating the disc. Information is reproduced by detecting changes in the amount of reflected light depending on the presence or absence of pits on the disc. Play-only compact discs are based on the CD standard.
It is designed to be read (reproduced) while rotating at a constant linear speed of 2 to 1.4 m/s, and the inner diameter of the signal surface is 46 mm.
It is also required to have a maximum recording time of about 74 minutes at a track pitch of 1.6 μm within a signal surface outer diameter of 116 mm.

As mentioned above, audio CDs are currently widely used. Therefore, commercially available CD players used to play audio CDs are also widely used, and mass production has led to lower prices and improved performance.

Conventional CDs have a structure in which a reflective layer made of metal is provided on the pre-pitted surface of the substrate as described above, so the color of the CD seen from the substrate side depends on the metal forming the reflective layer. For example, when the reflective layer was formed from aluminum, it was silver-colored, and when the reflective layer was formed from gold, it was gold-colored. Since the material forming the reflective layer is selected from the viewpoint of the performance of the reflective layer, the color of the reflective layer, that is, the color of the CD viewed from the substrate side, is limited and often tasteless.

As CDs have become more commonly used, there has been a trend towards CDs colored in a wide range of colors.
It is desirable that D can be colored in any color and pattern.

As a means for coloring a CD, a method has been proposed in which a dye is kneaded into the substrate and the substrate itself is colored. However, when a dye is kneaded into a substrate, it becomes difficult to mold a substrate with fine pre-pits, and it is necessary to delicately adjust the molding conditions of the substrate in response to the characteristics of the substrate and dye materials and their combination. Therefore, it is difficult to manufacture a substrate that can stably maintain excellent performance. Furthermore, since CD playback is performed by irradiating laser light from the substrate side,
It is also necessary to consider the influence of the color of the board on the reproduction of information.

As a means of coloring a CD, it is possible to write (record) information. RAW (Direct Read Af)
It is conceivable to provide a dye layer between the prepit-forming surface of the substrate and the reflective layer, similar to the type of information recording medium.

However, if a dye layer is provided on the surface of a substrate on which pre-pits are formed, there is a problem in that the degree of modulation of the pre-pit signal becomes small, making it impossible to practically reproduce information on a CD.

In other words, the dye layer is generally formed by applying a dye solution and drying it, and when the dye solution is applied to the pre-pit formation surface, the thickness of the dye layer at the pit portions (holes) becomes smaller than the area between the pits. The depth of the holes on the surface of the dye layer that reflect the shape of the pits on the substrate is larger than the thickness of the dye layer (the part between the pits). Since the depth becomes shallower than the pit depth and the phase difference between the pit portion and the inter-pit portion becomes smaller, the modulation degree of the pre-pit becomes smaller.

For example, Japanese Patent Laid-Open No. 2-42652 discloses an information recording medium having a ROM area in which pits are formed in advance on a substrate, and a recordable area in which pits for data reproduction are formed by irradiation with laser light. However, in this information recording medium, the dye layer is provided only in the recordable area, and the dye layer is not provided in the ROM area in which pre-pits are formed. In other words, if a dye layer is provided in the area where pre-pits are formed, the degree of modulation of the prepit signal becomes small and information in the ROM area cannot be practically reproduced. In other words, only a reflective layer is provided without providing a reflective layer.

[Object of the Invention] The present invention is an information recording medium having a structure in which a dye layer containing a dye is formed on a surface of a substrate on which pre-pits are formed, and a reflective layer is provided on this dye layer. It is an object of the present invention to provide an information recording medium that is colored in the same color as the CD standard and at the same time can obtain a reproduction signal that satisfies the CD standard.

A further object of the present invention is to provide a method for manufacturing an information recording medium having the above-mentioned excellent features.

[Summary of the Invention] The present inventors have discovered that when the thickness of the dye layer in the prepit portion of the substrate and the thickness of the dye layer in the area between the pits become almost the same, the phase difference between the prepits becomes large, and therefore the modulation degree of the prepit signal increases. They came up with the idea of making it into a large information recording medium and completed the present invention.

In the present invention, on a disk-shaped substrate on which pre-pits are formed,
A read-only information recording medium comprising a dye layer containing a dye and a reflective layer made of metal on the dye layer, wherein the optical thickness of the dye layer in the pits and the dye in the areas between the pits are different from each other. The information recording medium is characterized in that the difference between the optical thickness of the layer is λ/8 (where λ is the wavelength of a reproduction laser beam) or less.

The present invention also provides a dye solution prepared by dissolving a dye in a solvent on a disk-shaped substrate on which pre-pits are formed, and in which the solvent is evaporated from the dye solution at the coating temperature of the dye solution. A dye solution having a concentration limit of 99 to 20%, defined as the ratio of the volume of the dye suspension solution to the original volume of the dye solution when dye precipitation begins, is applied by spin coating and dried. By doing this, the difference between the optical thickness of the pit area and the optical thickness of the area between the pits is λ/8 (where λ is the wavelength of the reproduction laser beam).
The following method for manufacturing an information recording medium, which comprises forming a dye layer containing a dye on the surface of the substrate on which pre-pits are formed, and then providing a reflective layer made of metal on the dye layer. It is.

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

1) The difference between the optical thickness of the dye layer in the pit area and the optical thickness of the dye layer in the area between the pits is λ/16 or less (where, e is the wavelength of the reproduction laser beam). The above information recording medium.

2) The thickness of the pigment layer between the pits is 40 to 4
00 nm.

3) The pre-pit has a half width of 0.2 to 1.4 μm,
The information recording medium described above has a depth of 60 to 200 nm.

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

5) The information recording medium characterized in that an enhancement layer is formed between the dye layer and the reflective layer.

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

1) The difference between the optical thickness of the dye layer in the pit area and the optical thickness of the dye layer in the area between the pits is λ/16 or less (where λ is the wavelength of the reproduction laser beam). A method for manufacturing the above information recording medium.

2) The thickness of the pigment layer between the pits is 40 to 4
00 nm, the method for manufacturing the above information recording medium.

3) The pre-pit has a half width of 0.2 to 1.4 μm,
The method for manufacturing the information recording medium described above, characterized in that the medium has a depth of 60 to 200 nm.

4) The method for producing the information recording medium, characterized in that the dye solution has a concentration limit of 90 to 50%.

5) The method for producing the information recording medium, wherein the solvent is a single solvent.

6) The above solvent is a good solvent for the dye used (preferably,
A solvent capable of dissolving 2% by weight or more of the dye used at the coating temperature of the dye solution) and a poor solvent for the dye used that is compatible with the good solvent (preferably a solvent capable of dissolving 2% or more of the dye used at the coating temperature of the dye solution). The above-mentioned method for producing an information recording medium, characterized in that it is a mixture with a solvent in which the medium does not dissolve by more than % by weight.

f) The method for producing the information recording medium, characterized in that the concentration of the dye in the dye solution is 0.5 to 15% by weight.

8) The above dye solution was heated at a temperature of 0 to 100 t, and
10.00 Or, p, w+, (D) The method for manufacturing the above-mentioned information recording medium, characterized in that coating is carried out at the rotational speed of the above-mentioned substrate.

9) The method for manufacturing the information recording medium, further comprising forming a protective layer on the reflective layer.

10) The method for manufacturing the information recording medium, comprising forming an enhancement layer between the dye layer and the reflective layer.

[Effects of the Invention] The information recording medium of the present invention has a structure in which a dye layer containing a dye is formed on the surface of a substrate on which pre-pits are formed, and a reflective layer is formed on the dye layer. Therefore, the board can be the same as that of a conventional CD, can be arbitrarily colored in a wide variety of colors, and at the same time can obtain a playback signal that satisfies the CD standard, and has a large tracking servo gain. This is an information recording medium that exhibits remarkable effects.

Furthermore, since the information recording medium of the present invention is provided with a dye layer between the substrate and the reflective layer, it is possible to prevent or reduce attack by harmful components (for example, chlorine, moisture, etc.) from the substrate to the reflective layer. It has excellent effects.

Furthermore, the information recording medium of the present invention can display various pictures, designs, and patterns (including barcodes, etc.) when viewed from the substrate side by containing a photosensitive dye or a dye and a photosensitive material in the dye layer. It can be formed, and has remarkable effects both visually and practically.

Furthermore, the method for manufacturing the information recording medium of the present invention uses conventionally adopted means, except for using a coating liquid for forming a dye layer having specific properties, which is prepared by controlling the type of solvent and the concentration of the dye. This is a method for manufacturing an information recording medium which has a remarkable effect that it is possible to easily manufacture an information recording medium having the above-mentioned excellent features.

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

The material of the disk-shaped substrate in the present invention can be arbitrarily selected from various materials used as substrates of conventional information recording media. In terms of optical properties, flatness, processability, handling, stability over time, and manufacturing costs, examples of substrate materials include glass, 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, mention may be made of polycarbonate, polyolefin, glass and polymethyl methacrylate.

The surface of the substrate on which the dye layer is provided has improved flatness,
An undercoat layer may be provided for the purpose of improving adhesive strength, improving 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/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, epoxy resin polymeric substances such as; organic substances such as silane coupling agents and titanate coupling agents; and inorganic dielectrics (S i 02 , ZnS, A I
N, Si3N, etc.), and inorganic substances such as inorganic fluoride (MgFz).

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

In the present invention, the substrate surface (or undercoat layer surface)
, various audio signals, application software,
Pre-pits are formed in which information such as address signals is recorded in advance. The shape of the pre-pit is such that the pit depth (dt in the attached Figure 1) is in the range of 60 to 200 nm and the half width of the pit (width of the pit at 1/2 the depth of the pit) is 0. It is preferable that the pit depth is in the range of .2 to 1.4 μm, and it is more preferable that the pit depth is in the range of 70 to 180 nm and the half width of the pit is in the range of 0.3 to 1.0 μm. It is most preferable that the pit is in the range of 150 nm to 150 nm and the half width of the pit is 0.4 to 0.7 μm.

When the substrate material is plastic, the pre-pits may be directly provided on the substrate surface by injection molding, extrusion molding, or the like. Further, a prepit layer for forming the prepits may be provided on the surface of the substrate.

The material for the pre-pit layer is at least one type of acrylic acid monoester, diester, triester, and tetraester (or oligomer).
and a photoinitiator can be used.

The pre-pit layer is formed by first coating a mixed solution consisting of the above acrylic ester and polymerization initiator on a M-dense matrix (stambar), and then placing a substrate on top of this coating solution layer. Then, the liquid layer is cured by irradiation with ultraviolet rays through the substrate or the matrix, thereby fixing the substrate and the liquid phase. Next, by peeling the substrate from the mother mold, a substrate provided with a pre-pit layer is obtained. The thickness of the pre-pit layer is generally in the range of 0.1 to 100 μm, preferably 0.1 to 100 μm.
It is in the range of 1 to 50 μm.

Using a material similar to the material for forming the undercoat layer on the substrate (or pre-pit layer) on which pre-pits are formed,
A dye layer containing a dye is provided on a substrate (or undercoat layer) which may be provided with a solvent-resistant layer for protection from a solvent in a coating solution for forming the dye layer.

The dye used in the present invention is not particularly limited, and any dye may be used. For example, cyanine dyes,
Phthalocyanine dyes, naphthalocyanine dyes, biryllium dyes, thiopyrylium dyes, azulenium dyes, squarylium dyes, metal complex dyes such as Ni and Cr, naphthoquinone dyes, anthraquinone dyes, indophenol dyes, indoaniline Examples include dyes such as triphenylmethane dyes, triallylmethane dyes, aminium dyes, diimmonium dyes, nitroso dyes, leuco dyes, and croconium dyes.

These dyes may be used alone or as a mixture of two or more. Further, when using a cyanine dye, the above metal complex dye, aminium dye, or diimmonium dye may be used together as a quencher.

In the information recording medium of the present invention, the difference between the optical thickness of the pit portion of the dye layer and the optical thickness of the portion between the pits is λ/8.
(However, λ is the wavelength of the reproduction laser beam) or less.

The optical thickness of the dye layer in the information recording medium of the present invention will be explained in detail with reference to the accompanying drawings.

FIG. 1 is a sectional view schematically showing a part of a pre-pit section of an embodiment of an information recording medium of the present invention.

Figure 2 shows the case where a dye layer is formed by a conventionally known method.
FIG. 2 is a cross-sectional view schematically showing a part of a pre-pit section of an information recording medium.

In FIG. 2, a dye layer 22 made of a dye is formed on the surface of a substrate 21 made of plastic, and a reflective layer 23 made of metal is formed on the dye layer 22. Substrate 21
Pre-pits 24 are formed therein. The dye layer 22 is formed by applying a dye layer forming solution prepared by dissolving a dye in its solvent by spin coating and drying. The thickness t4 of the dye layer 22 in the pit portions 26 of the pre-pits 24 is larger than the thickness t3 of the dye layer 22 in the inter-pit portions 25 of the substrate 21. As a result, the depth of the groove shape at the contact surface of the dye layer 22 with the reflective layer 23 becomes smaller than the depth d2 of the pre-pits 24, and when laser light is irradiated to reproduce information, the dye layer 22
Since the phase difference between the top (corresponding to the part between the pits of the substrate) and the bottom of the groove No. 2 becomes small, there is a problem that the degree of modulation of the reproduced signal becomes small. Therefore, a dye layer is not formed on the ore or pre-pit in the conventional CD or ROM area.

In FIG. 1, a dye layer 12 made of a dye is formed on the surface of a substrate 11 made of plastic, and a reflective layer 13 made of metal is formed on the dye layer 12. Board 1
1, pre-pits 14 are formed. Dye layer 12
is formed by applying a dye layer-forming solution having specific properties as described above, prepared by dissolving a dye in a solvent, by spin coating and drying.

Optical thickness (n, -tz) of the dye layer 12 in the pit portion 16 of the pre-pit 14 (where n is the refractive index of the dye layer, and tl is the thickness of the dye layer 12 in the pit portion 16)
and the optical thickness (nr-tl) of the dye layer 12 in the inter-pit areas 15 of the substrate 11 (where n is the refractive index of the dye layer, and 1. is the optical thickness of the dye layer 12 in the inter-pit areas 15). thick)
The difference is λ/8 or less. As a result, the depth of the hole formed in the contact surface of the dye layer 12 with the reflective layer 13 is the same as the depth dl of the pre-pits 14, or the optical film thickness is as small as λ/8 or less, and the dye layer 1
There is a large phase difference between the pit portion of No. 2 and the inter-pit portion, and the degree of modulation of the pit signal is large. As a result, even if a dye layer is formed on the pre-pit formation surface of the substrate, it is possible to reproduce the pit signal of the substrate with a high degree of modulation.

The difference between the above n,...tI and n, -tl is λ/1! It is preferably at most λ/13, more preferably at most λ/16, even more preferably at most λ/16.

In the information recording medium of the present invention, a reflective layer is further formed on the dye layer. The same effect can be applied to an information recording medium that does not have a .

The film thickness of the pigment layer between the pits is 40 to 400.
nm, especially 60-300nm, more especially 80-250n
It is preferable that it is m.

In the information recording medium of the present invention, the dye layer having a specific optical thickness, that is, the difference between the optical thickness of the dye layer in the pit portion and the optical thickness of the dye layer in the portion between the pits is λ/8 or less The dye layer can be formed by the method for manufacturing an information recording medium of the present invention.

In the production method of the present invention, the dye layer is formed by dissolving the above dye in a solvent to prepare a dye solution, and then applying this dye solution to the surface of the substrate by spin coating to form a coating film. This is done by post-drying.

The above dye solution used in the production method of the present invention has specific properties, i.e., a concentration limit of 99 to 2.
0% dye solution. As used herein, the term "concentration limit" refers to the volume of the dye suspension solution at which precipitation of the dye begins by evaporating the solvent from the dye solution at the coating temperature of the dye solution. Defined as meaning the ratio to the original volume. For example, when a dye solution in which a dye is dissolved in a solvent is maintained at the coating temperature to form a dye layer and the solvent evaporates, the volume decreases as the solvent evaporates, and eventually the dissolved dye will start to precipitate, but if the concentration limit is It is called a 90% dye solution.

Therefore, the concentration limit of a dye solution is determined by the combination of dye and solvent (single solvent or mixed solvent), the type and ratio of the combination of two or more solvents, the concentration of the dye in the dye solution, and the application It changes depending on temperature, etc. For this reason, it is difficult for those skilled in the art to determine whether it is not possible to uniformly determine a dye solution having a specific concentration limit for a specific dye, or to prepare a dye solution having a desired concentration limit by varying the above-mentioned conditions. This can be done easily.

The dye solution used in the production method of the present invention is a dye solution with a concentration limit of 99 to 20%, and the concentration limit is 99 to 30%, particularly 95 to 40%, more particularly 90 to 50%.
% of the dye solution is preferred. If the concentration limit of the dye solution is larger than the above range, the thickness of the dye layer will become non-uniform as a whole, and if it is smaller than the above range, the optical thickness of the dye layer between the pits and the areas between pits will become uneven. The difference becomes larger.

The solvent used to prepare the dye solution may be a single solvent or a mixed solvent of two or more solvents, as long as it satisfies the concentration limit of the dye solution. When the above-mentioned solvent is a mixed solvent, a good solvent for the dye to be used (preferably a solvent capable of dissolving 2% by weight or more of the dye to be used at the coating temperature of the dye solution) and a poor solvent for the dye to be used (preferably, It is preferably a mixture with a solvent that does not dissolve 2% by weight or more of the dye used at the coating temperature of the dye solution. In this case, it is necessary that the good solvent and the poor solvent are compatible, and that the evaporation rate of the poor solvent is not greater than the evaporation rate of the good solvent at the above coating temperature.

Generally, the concentration limit increases as the mixing ratio of the poor solvent increases.

The above solvents include benzene, toluene, xylene,
Aromatic hydrocarbon solvents such as ethylhenzen; aliphatic hydrocarbon solvents such as hexane, octane, nonane, cyclohexane, etc.; organic acid solvents such as acetic acid;
Ester solvents such as ethyl acetate, butyl acetate, amyl acetate, ethylene glycol monoethyl ether acetate, cellosolve acetate, etc. Ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc. Nidichloromethane, 1.2
- halogenated hydrocarbon solvents such as dichloroethane, chloroform, methylchloroform, tricrene, carbon tetrachloride, tetrachloroethylene, etc.; ethereal solvents such as tetrahydrofuran, ethyl ether, isopropyl ether, dioxane, diglyme, etc.; ethanol, n- Alcoholic solvents such as propatool, isopropatool, n-butanol, amyl alcohol, diacetone alcohol, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, benzyl alcohol, etc.; amides such as dimethylformamide Fluorinated alcohols, fluorinated ketones, fluorinated esters, fluorinated amides, fluorinated ethers, fluorinated aromatic hydrocarbons, fluorinated fats, such as 2.2.3.3, tetrafluoropropanol, etc. Examples include fluorinated solvents such as group hydrocarbons.

In the manufacturing method of the present invention, the dye solution is not particularly limited as long as it satisfies the above-mentioned limit concentration, but for convenience of handling and spin coating, a uniform film thickness can be formed on the entire substrate. In order to form a dye layer, the concentration of the dye in the dye solution is preferably from 0.5 to 15% by weight, especially from 1 to 10% by weight, and even more preferably from 1.5 to 8% by weight.

The dye solution further contains antioxidants, UV absorbers,
Various additives such as plasticizers and lubricants may be added depending on the purpose.

When a binder is used, examples of the binder include cellulose conductors such as gelatin, nitrocellulose, and cellulose acetate; natural organic polymeric substances such as dextran, rosin, and rubber; and polyethylene, polypropylene, polystyrene, and polyisobutylene. Hydrocarbon resins, 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 polyolefins, Examples include synthetic organic polymeric substances such as epoxy resins, butyral resins, rubber derivatives, and initial condensates of thermosetting resins such as phenol/formaldehyde resins.

When applying the above-mentioned dye solution onto a substrate by a spin coating method, it can be performed using a device and method that are known per se. The above dye solution is generally 0 to 100%
It is preferred to apply at a temperature of 0.degree. C., especially 5 to 80.degree. C., more particularly 10 to 60.degree. The rotation speed of the substrate is generally 10 to 1000 r, p, m, when applying a dye solution.
In particular, it is preferable to set the temperature to 100 to 500 r, p, +a, and when drying a pigment coating, it is generally 300 to 500 to
oo.

r p m, especially 500-7000 r, p, m,,
More particularly, it is preferably 700 to 4000 r, p, m.

A reflective layer is further provided on the dye layer of the information recording medium of the present invention.

The materials for the reflective layer include Be, B, and 0%Sc.

Rb, Sr, As, Os, TI, At% Fr.

Ra, Mg, Se, Y, Ti, Zr%Hf, V, Nb
% Ta, Cr% Mo, W, Mn%
Re.

Fe% Co, Ni, Ru, Rh, P
d% Ir.

Pt, Cu, Ag, Au, 2n,
Cd, AIL.

Ga, In, Si, Ge, Te,
Pb% Mention may be made of metals and metalloids such as Po, Sn, Bi, and Sb. Among these, C, Au, Zn
.

Particularly preferred are Cu, Pt, AN%Ni, In 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 dye layer by, for example, vapor deposition, sputtering, or ion-blating the above-mentioned light-reflective material.

In particular, it is preferable to form the reflective layer by sputtering. The thickness of the reflective layer is generally 100-3000λ
, preferably in the range of 400 to 2000.

When a noble metal reflective layer is provided as a reflective layer, A
A metal adhesion layer such as No. 1 or an organic adhesion layer may be provided.

A protective layer may be provided on this reflective layer for the purpose of physically and chemically protecting the entire information recording medium, especially the dye layer and the reflective layer. Further, this protective layer may be provided on the side of the substrate where the dye layer is not provided in order to improve scratch resistance and moisture resistance.

Examples of materials used for the protective layer include inorganic substances such as SiO, SiO□, 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.

The protective layer can be formed by, for example, 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. In the case of a UV curable resin, the protective layer can be formed by applying the coating solution as it is or by dissolving it in an appropriate solvent and then applying the coating solution and curing it by irradiating it with UV light. . Examples of UV-curable resins include (meth)acrylates such as urethane (meth)acrylate, epoxy (meth)acrylate, and polyester (meth)acrylate.
Ordinary UV irradiation of acrylate oligomers, polymers such as (meth)acrylic esters, etc. and photopolymerization initiators, etc.
Curable resins 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. It is preferable to use UV-curable resin as the material for the protective layer.

The thickness of the protective layer is generally in the range of 0.1 to 100 μm, preferably 0.5 to 20 μm.

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 deposition, sputtering, and coating.

In the information recording medium of the present invention, an enhancement layer may be provided between the dye layer and the reflective layer to improve reflectance.

The substance for forming the enhancement layer is 60 to 40%
Glass transition temperature within the range of 0°C, preferably 100-300''C1, more preferably 100-250°C, 60-s
melting point within the range of oo'c, preferably 100-400°C, more preferably 100-350"C, 80-600°C
, preferably 120 to 500°C, more preferably 120°C
boiling point or decomposition point within the range of ~450°C, and 1.1~
1°8, preferably 1.2 to 1.7, more preferably 1
．． The material is preferably a material having a refractive index (n) at the wavelength of the reproducing laser beam within the range of 3 to 1.6 and an extinction coefficient (k) of 0.3 or less, preferably 0.1 or less. The substance forming the enhancement layer may be organic or inorganic as long as it has the above characteristics. Although the enhancement layer can be formed by vapor deposition, sputtering, etc., it is preferable to form the enhancement layer by coating and drying a solution containing the above-mentioned substance because it can be formed easily and economically. As the material for forming the film, it is preferable to use a material that can be formed into a film by coating, such as polybutadiene, silicone resin, fluororesin, or the like.

The method of forming the enhancement layer by coating is not particularly limited, and a solution in which the enhancement layer forming substance is dissolved in a suitable solvent is applied by a conventional coating method, for example, a spin coating method, and then the solvent is removed by drying. It is also possible to adopt a method of forming a film. At this time, the film thickness (dimensional film thickness) of the enhancement layer may be thicker in the pit area than in the area between the pits, but even in that case, the optical film of the enhancement layer is There is almost no difference in thickness between the pits and between the pits. Therefore, in the information recording medium of the present invention, by providing the enhancement layer, the reflectance can be improved without adversely affecting the reproduction of prepit signals.

The enhancement layer preferably has a thickness of 50 to 600 nm at the bottom of the group and pits, and a thickness of 50 to 600 nm at the land and between the pits.

Since the information recording medium of the present invention has a high reflectance, it is possible to obtain a reproduced signal with a high modulation degree that satisfies the CD standard.

Examples and comparative examples of the present invention are described below. However, these aspects do not limit the present invention.

[Example 1] A disc-shaped polycarbonate substrate (outer diameter: 120 mm
, inner diameter: 15 mm, thickness: 1.2 mm, pit width at half maximum = 0.6 μm, pit depth: 130 nm).

On the other hand, a dye (A) having the following structural formula: was dissolved in propylene glycol monoethyl ether to prepare a dye solution containing 2.4% by weight of the dye (A). The limit concentration of this dye solution at 23° C. is 70%.

This dye solution was maintained at 23°C, and the dye solution was spin-coated onto the substrate at 23°C at a substrate rotation speed of 200.
After coating for 4 seconds at speeds of r, p, m, rotation speed 70
A light absorption layer was formed by drying with Or, p, m for 30 seconds.

On the formed light absorption layer, AI was DC sputtered to a film thickness of 11 nm under the conditions of 480 W, target-substrate distance #95 mm, gas pressure 2 Pa, and rate 2 nm/sec.
A reflective layer made of 00n AI was formed.

A UV curable resin (trade name: 3070, manufactured by ThreeBond) was applied as a protective layer onto the reflective layer by spin coating at a rotation speed of 1500 r, p, m, and then UV rays were applied using a high-pressure mercury lamp. Irradiate and cure to a layer thickness of 2μ
A protective layer of m was formed.

In this way, an information recording medium consisting of a substrate, a dye layer, a reflective layer, and a protective layer was manufactured. This information recording medium was green when viewed from the substrate side and silver when viewed from the reflective layer side.

Regarding the obtained information recording medium, the optical thickness of the dye layer in the pits, the optical thickness of the dye layer in the areas between the pits, the IIT modulation degree, and the tracking servo gain were measured by the following evaluation methods. The evaluation results are listed in Table 1.

[Comparative Example 1] Using the same substrate as used in Example 1, using 2°2.3.3-tetrafluoropropanol instead of propylene glycol monoethyl ether as the solvent for preparing the dye solution. The dye (A) prepared by 2.
A dye layer was formed as in Example 1, except that a dye solution containing 3% by weight (the limiting concentration of this dye solution at 23° C. was less than 20%), and then
A reflective layer and a protective layer were sequentially formed on a substrate in the same manner as in Example 1 to produce an information recording medium.

The obtained information recording medium was evaluated in the same manner as in Example 1. The evaluation results are listed in Table 1.

[Comparative Example 2] Using the same substrate as that used in Example 1, a reflective layer made of A1 was directly formed on the substrate in the same manner as in Example 1 without providing a dye layer, and then the reflective layer was formed directly on the substrate in the same manner as in Example 1. A protective layer was formed on the layer in the same manner as in Example 1 to produce an information recording medium. The obtained information recording medium had a silver color on both sides.

The obtained information recording medium was evaluated in the same manner as in Example 1. The evaluation results are listed in Table 1.

[Evaluation of information recording media] 1) Optical thickness of the dye layer in the pit part The absolute film thickness of the dye layer was measured using an ultra-high resolution electron microscope (
5900 manufactured by Hitachi, Ltd.) Measured by observation,
The refractive index of the dye layer was determined from the results of measuring the reflectance, transmittance, and absolute film thickness of a separately formed dye thin film, and the optical film thickness was calculated from the absolute film thickness and the refractive index.

2) Optical thickness of dye layer between pits It was determined in the same manner as the method 1) above.

3) 11T modulation degree Among the CD format signals recorded above, the recording length is 11
Regarding the DC reproduction signal of T, the signal strength of the signal part and the mirror part (the bright part of the signal) was measured, and its modulation degree (C) was determined by the following formula.

SH-5L C=X100H (SH: (maximum intensity of E, SL: minimum intensity of signal)
4) Apply a disturbance with a tracking servo cane oscillator, measure it with a servo analyzer,
Expressed as gain compared to CD.

Margin below Table 1 Note: TSG = Tracking servo gain.

As is clear from Table 1, the information recording medium of the example is:
The degree of modulation is large, and the tracking servo gain is increased compared to the information recording medium of Comparative Example 2 in which no dye layer is provided, indicating excellent performance.

On the other hand, the information recording medium of Comparative Example 1 has a small modulation degree and the tracking servo gain is lower than that of the information recording medium of Comparative Example 2 in which no dye layer is provided.

[Brief explanation of drawings]

FIG. 1 is a sectional view schematically showing a part of a pre-pit section of an embodiment of the information recording medium of the present invention. FIG. 2 is a cross-sectional view schematically showing a part of a pre-pit section of an information recording medium in which a dye layer is formed by a conventionally known method. 11.21: Substrate, 12.22: Dye layer, 13.23: Reflective layer, 14.24: Pre-pit, 15.25: Inter-pit area, 16.26: Pit area, Figure 1. Patent applicant Fuji Photo Film Co., Ltd. Agent Patent Attorney Yasushi Yanagawa Procedural Amendment (Voluntary) August 20, 1991 1990 Patent Application No. 253645 2. Title of invention Information recording medium and its manufacturing method 3. Amendments made Patent applicant name (520) Fuji Photo Film Co., Ltd. 4, agent address: 8th floor, Miyya Yotsuya Pill, 2-14 Yotsuya, Shinjuku-ku, Tokyo Correct as expected. -" - 1゜ Change the "concentration limit" at the bottom of page 22 or line 63 of the specification to "
concentration limit (hereinafter sometimes referred to as limit concentration). 2゜Page 25, lines 13-14 of the specification “2.2.3.
3. Tetrafluoropropertool” r2, 2.3.3-
Tetrafluoropropertool” is corrected. 3゜ "Dye recording layer" on page 30, line 13 of the specification is corrected to "reflection layer." 4゜ In the specification, page 26, line 1, page 34, line 2, and page 35, lines 14-15 [limit concentration j is corrected to ``concentration limit''. −1 or more

Claims (1)

[Claims] 1. A read-only information recording medium comprising a dye layer containing a dye provided on a disc-shaped substrate on which pre-pits are formed, and a reflective layer made of metal further provided on the dye layer. and that the difference between the optical thickness of the dye layer in the pit area and the optical thickness of the dye layer in the area between the pits is λ/8 or less (where λ is the wavelength of the reproduction laser beam). Characteristic information recording media. 2. A dye solution prepared by dissolving a dye in a solvent on a disk-shaped substrate on which pre-pits are formed, and precipitation of the dye by evaporating the solvent from the dye solution at the coating temperature of the dye solution. By applying a dye solution with a concentration limit of 99 to 20%, defined as the ratio of the volume of the dye suspension solution at the start of the process to the original volume of the dye solution, by spin coating and drying, The difference between the optical film thickness in the pit area and the optical film thickness in the area between the pits is λ/
8 (where λ is the wavelength of the reproduction laser beam) or less, a dye layer containing a dye is formed on the surface of the substrate on which prepits are formed, and then a reflective layer made of metal is formed on the dye layer. 1. A method of manufacturing an information recording medium, comprising: