JPH04255930A - Information recording medium - Google Patents

Abstract

PURPOSE:To facilitate an information recording medium excellent in durability by providing a recording made of dyestuff and/or a reflective layer made of a metal excellent in adhesive strength with a protective layer. CONSTITUTION:The recording layer containing dyestuff is provided on a substrate, the reflective layer is provided on the reflective layer, and in some case, the protective layer is further provided on the reflective layer. The reflective layer is made of the metal A having <=3 refractive index, >=2 extinctive coefficient in a recording or reproducing wave length, and an element having higher m.p. than m.p. of the metal A, and wt. ratio of the metal A:the element is 100:0.1-8.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an information recording layer having a recording layer containing a dye and a metal reflective layer capable of recording (writing) and/or reproducing (reading) information using a high-energy-density laser beam. It's about the medium.

0002

2. Description of the Related Art In recent years, information recording media using high energy density beams such as laser beams 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.

[0003] The basic structure of an optical disk is a disk-shaped substrate made of glass, synthetic resin, etc., and a metal or metalloid such as Bi, Sn, In, Te, etc.; , and a recording layer made of a quinone-based dye. 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.

In addition, in order to improve the durability of the information recording medium, a protective layer is provided on the recording layer, or a recording layer is provided on at least one of the two disk-shaped substrates as a disk structure. An air sandwich structure has been proposed in which the two substrates are bonded via a ring-shaped inner spacer and a ring-shaped outer spacer so that the recording layer is located inside and a space is formed. There is. In optical discs provided with such a protective layer or optical discs with an air sandwich structure, the recording layer is not in direct contact with the outside air, and information is recorded and reproduced using laser light that passes through the substrate. It has the advantage that it will not be physically or chemically damaged, or that dust will not adhere to its surface, which will impede information recording and reproduction.

[0005] Writing and reading information to and from an optical disc is normally performed by the following method. That is,
Information is written by irradiating this optical disc with a laser beam, and the irradiated portion of the recording layer absorbs the light, causing a local temperature rise, causing physical or chemical changes (for example, the formation of pits). information is recorded by changing its optical properties. Information is also read by irradiating the optical disk with a laser beam, and the information is reproduced by detecting reflected or transmitted light depending on changes in the optical characteristics of the recording layer.

As described above, metals, pigments, and the like are known as recording materials for 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 generally has a drawback that it has a low reflectance or that it is difficult to obtain a high C/N.

[0007] In order to improve the drawback that the recording layer made of the above dye has a low reflectance, it has been proposed to provide a reflective layer made of metal on the recording layer. However, a reflective layer made of metal has poor adhesion with a recording layer made of a dye and a protective layer made of an organic substance in general. Information recording media in which a protective layer is further provided on the reflective layer generally have low durability.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an information recording medium with excellent durability by providing a reflective layer made of a metal that has excellent adhesion to a recording layer made of a dye and/or a protective layer.

[0009]

[Means for Solving the Problems] The present invention provides a disk-shaped substrate with a recording layer containing a dye that can record and/or reproduce information using a laser beam, and a metal layer on the recording layer. An information recording medium provided with a reflective layer comprising: a metal A having a refractive index of 3 or less and an extinction coefficient of 2 or more at a recording or reproduction wavelength; The information recording medium is characterized in that the metal A:element weight ratio is 100:0.1 to 8.

Preferred embodiments of the information recording medium of the present invention are as follows. (1) The information recording medium described above, further comprising a protective layer provided on the reflective layer.

(2) The metal A is Au, Ag, Cu,
The information recording medium described above is made of at least one metal selected from the group consisting of Pt, Al, and Mg.

(3) The above elements are Be, B, C, Mg,
Si, Sc, Ti, V, Cr, Mn, Fe, Co, Ni
, Cu, Ge, Y, Zr, Nb, Mo, Tc, Ru, R
h, Pd, Ag, Hf, Ta, W, Re, Os, Ir,
Pt, Au, La, Ce, Pf, Nd, Pm, Sm, E
The above information recording medium is characterized in that it is at least one element selected from the group consisting of u, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

(4) The information recording medium described above, wherein the reflective layer is made of a combination of the metal A and an element having a melting point 100° C. or more higher than the melting point of the metal A.

(5) The reflective layer has a thickness of 20 to 500 nm,
Preferably 40-300 nm, more preferably 60-2
The above information recording medium is characterized in that it has a film thickness of 00 nm.

(6) The reflective layer has a hole diameter of 50 nm or more,
The above information recording medium preferably does not have holes larger than 20 nm.

(7) The above dye is a cyanine dye, an azulenium dye, a squarylium dye, a phthalocyanine dye, a pyrylium dye, a thiopyrylium dye,
It is characterized by being composed of one or more types of dyes selected from indophenol dyes, indoaniline dyes, triphenylmethane dyes, quinone dyes, aminium dyes, diimmonium dyes, metal complex dyes, etc. The above information recording medium.

The information recording medium of the present invention has a basic structure in which a dye recording layer and a metal reflective layer are provided on a disk-shaped substrate.

The disc-shaped substrate in the present invention can be arbitrarily selected from various resin materials used as substrates for conventional information recording media. In terms of substrate optical properties, flatness, processability, handling, stability over time, manufacturing cost, etc., examples of substrate materials include acrylic resins such as cell cast polymethyl methacrylate and injection molded polymethyl methacrylate; Examples include vinyl chloride resins such as vinyl chloride and vinyl chloride copolymers; epoxy resins; polycarbonate resins, amorphous polyolefins, and polyesters. Preferably, mention may be made of polycarbonate, polyolefin and cell-cast polymethyl methacrylate.

An undercoat layer is provided on the surface of the substrate on the side on which the recording layer is provided for the purpose of improving flatness, improving adhesive strength, improving solvent resistance of the substrate, and preventing deterioration of the recording layer. Good too. Examples of materials for the undercoat layer include polymethyl methacrylate, acrylic acid/methacrylic acid copolymer, styrene/maleic anhydride copolymer, polyvinyl alcohol,
N-methylolacrylamide, styrene/sulfonic acid copolymer, styrene/vinyltoluene copolymer, chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate/vinyl chloride copolymer, Polymer substances such as ethylene/vinyl acetate copolymer, polyethylene, polypropylene, and polycarbonate; organic substances such as silane coupling agents; and inorganic oxides (SiO2, Al2
(O3, etc.), and inorganic substances such as inorganic fluoride (MgF2).

[0020] The undercoat layer is prepared by, for example, dissolving or dispersing the above substances in a suitable 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. It can be formed by The layer thickness of the undercoat layer is generally 0.0
in the range of 0.05 to 20 μm, preferably 0.01 to 1
It is in the range of 0 μm.

Further, 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 unevenness representing information such as address signals. Materials for the pregroove layer, etc.
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 pregroove layer is formed by first coating a mixture of the above acrylic acid ester and polymerization initiator on a precisely made matrix (stamper), and then placing the substrate on top of this coating solution layer. Thereafter, the liquid layer is cured by irradiation with ultraviolet rays through the substrate or the matrix, thereby fixing the substrate and the liquid phase. Next, by peeling the substrate from the mother mold, a substrate provided with a pregroove layer is obtained. The thickness of the pregroove layer is generally in the range of 0.05 to 100 μm, preferably in the range of 0.1 to 50 μm. When the substrate material is plastic as in the present invention, pregrooves and/or prepits may be directly provided on the substrate by injection molding, extrusion molding, or the like.

A recording layer containing a dye that can record and/or reproduce information using a laser beam is provided on the substrate (or the pregroove layer, etc.). The dye used in the present invention is not particularly limited, and any dye may be used. For example, cyanine dyes, azulenium dyes, squalirium dyes, phthalocyanine dyes, pyrylium dyes, thiopyrylium dyes, indophenol dyes, indoaniline dyes, triphenylmethane dyes,
Examples include quinone dyes, aminium dyes, diimmonium dyes, and metal complex dyes. Preferably, cyanine dyes and phthalocyanine dyes can be mentioned.

Among these, dyes with a high absorption rate for light in the near-infrared region of 700 to 900 nm are preferred, since semiconductor lasers that emit near-infrared light have been put into practical use as recording and reproducing lasers. .

[0025] These dyes may be used alone or as a mixture of two or more. Furthermore, when a cyanine dye is used, it is preferable to use the above metal complex dye, aminium dye, or diimmonium dye together as a quencher. In that case, the quencher is preferably contained in an amount of 0.001 to 0.1 mole part per mole part of the total dye.

The recording layer is 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 it. can be done.

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, dichloromethane,
, halogenated hydrocarbons such as 2-dichloroethane and chloroform, ethers such as tetrahydrofuran, ethyl ether and dioxane, alcohols such as ethanol, n-propanol, isopropanol and n-butanol, amides such as dimethylformamide, 2,2,3, 3
- Fluorinated solvents such as tetrafluoropropanol can be mentioned. In addition, these non-hydrocarbon organic solvents may include aliphatic hydrocarbon solvents, as long as the amount is within 50% by volume.
It may also contain hydrocarbon solvents such as alicyclic hydrocarbon solvents and aromatic hydrocarbon solvents.

Various additives such as antioxidants, UV absorbers, plasticizers, and lubricants may be further added to the coating liquid depending on the purpose.

[0029] When a binder is used, the binder includes:
For example, cellulose derivatives such as gelatin, nitrocellulose, and cellulose acetate, natural organic polymer substances such as dextran, rosin, and rubber; and hydrocarbon resins such as polyethylene, polypropylene, polystyrene, and polyisobutylene, 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, epoxy resins, butyral resins, rubber derivatives, phenol/formaldehyde resins Synthetic organic polymer substances such as initial condensates of thermosetting resins such as

[0030] Examples of the coating method include a spray method, a spin coat method, a dip method, a roll coat method, a blade coat method, a doctor roll method, and a screen printing method. In order to form a good alignment state of the dye, it is preferable to use a spin coating method.

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

In the information recording medium of the present invention, a reflective layer made of metal is further provided on the dye recording layer. By providing a reflective layer, the effect of improving reflectance,
It is also possible to obtain the effects of improving S/N when reproducing information and improving sensitivity when recording information.

The information recording medium of the present invention is characterized by the components constituting the reflective layer. That is,
By having the above-described specific configuration of the above-mentioned reflective layer, the adhesion between the above-mentioned reflective layer and the dye recording layer is significantly improved without impairing the effects provided by the above-mentioned reflective layer. Furthermore, when a protective layer is further provided on the reflective layer, the adhesion between the reflective layer and the protective layer is also significantly improved. As a result, the durability of the information recording medium is significantly improved.

In the information recording medium of the present invention, the reflective layer includes a metal A having a refractive index of 3 or less and an extinction coefficient of 2 or more at the recording or reproduction wavelength, and a metal A having a melting point higher than that of the metal A. The metal A:element weight ratio is 100:0.1 to 8.

[0035] The above metal A includes Au, Ag, Cu,
At least one metal selected from the group consisting of Pt, Al, and Mg is preferred, and Au, Ag, or Pt is particularly preferred.

[0036] The above elements include Be, B, C, M
g, Si, Sc, Ti, V, Cr, Mn, Fe, Co,
Ni, Cu, Ge, Y, Zr, Nb, Mo, Tc, Ru
, Rh, Pd, Ag, Hf, Ta, W, Re, Os, I
r, Pt, Au, La, Ce, Pf, Nd, Pm, Sm
, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb,
and at least one element selected from the group consisting of Lu, particularly Si, Cu, Ge, Mo, Rh, Pd.
, Au, Ag, Ta, or W are preferred.

Examples of the above-mentioned metal A are also included in the above-mentioned examples of the elements, but when these metals are selected as the above-mentioned element, in order to distinguish them from the metal A, in this specification, the metal Shown as B.

In the reflective layer of the information recording medium of the present invention,
The metal A and the above-mentioned element preferably have a 1% content such that the melting point of the above-mentioned element is higher than the melting point of the selected specific metal A.
The above elements are selected and combined so that the temperature becomes higher than 00°C. When Metal A is combined with the above element having a lower melting point than Metal A, the crystal grains tend to become larger due to the lower melting point. It is thought that the surface irregularities that contribute to adhesion are reduced, and the effect of improving adhesion is reduced.

Further, in the reflective layer of the information recording medium of the present invention, the weight ratio of metal A to element must be 100:0.1 to 8. The weight ratio of metal A:element is 100:
It is preferable that it is 0.3-6. If the amount of the above-mentioned element is larger than the above-mentioned range, the extinction coefficient becomes small and the reflectance decreases, which is not preferable.

The above-mentioned reflective layer is formed by a conventional method for forming a reflective layer of an information recording medium, except that an alloy or mixture of metal A and an element selected to satisfy the above-mentioned conditions is used as the material for forming the reflective layer. For example, it can be formed by methods such as vapor deposition, sputtering, and ion plating.

[0041] The thickness of the above reflective layer is 20 to 500 nm.
, particularly preferably from 40 to 300 nm, more particularly from 60 to 200 nm.

In addition, when a protective layer is further provided on the above reflective layer by coating, the dye in the recording layer is washed out by the solvent in the coating solution for forming the protective layer, and the C/N value of the information recording medium is reduced. Therefore, the reflective layer has a hole diameter of 50 nm.
As mentioned above, it is preferable that there be substantially no holes having a hole diameter of 20 nm or more. Such a reflective layer having substantially no holes can be formed, for example, by the method described in the patent application specification of Japanese Patent Application No. 2-224112.

That is, the target-substrate distance is L (cm)
When the sputtering gas pressure is P (Pa), the above steps are performed so that the reflective layer with the above thickness is formed under conditions such that L and P satisfy the following formula: L×P≦30. It can be formed by sputtering a reflective layer forming material such as.

The above sputtering can be performed by any method such as direct current sputtering, high frequency sputtering, magnetron sputtering, and ion beam sputtering. In particular, direct current magnetron sputtering is preferred. Further, the sputtering is performed at a temperature of 10-2 to 102 Pa
It is preferable to carry out the sputtering at a sputtering gas pressure of .

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

Examples of materials used for the protective layer include inorganic materials such as SiO, SiO2, SiN4, M
Examples include gF2, SnO2, and the like. Also,
Organic substances include thermoplastic resins, thermosetting resins, UV
Examples include curable resins, preferably UV curable resins. 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, etc. in a suitable solvent to prepare a coating solution, and then applying this coating solution and drying it. In the case of a UV curable resin, it can also be formed by preparing a coating liquid as it is or by dissolving it in an appropriate solvent, applying this coating liquid, and curing it by irradiating it with UV light. Examples of UV-curable resins include oligomers of (meth)acrylate such as urethane (meth)acrylate, epoxy (meth)acrylate, and polyester (meth)acrylate, monomers such as (meth)acrylic acid ester, and photopolymerization initiators. Common UV curable resins such as UV 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. 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 100 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 recording layer via an adhesive layer. Alternatively, it may be provided by methods such as vacuum deposition, sputtering, and coating.

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

[Example 1] A disc-shaped polycarbonate substrate (outer diameter: 120 mm) provided with a tracking guide.
, inner diameter: 15 mm, thickness: 1.2 mm, track pitch: 1.6 μm, groove depth: 80 nm).

On the other hand, a dye having the following structural formula (A) (
A) was dissolved in 2,2,3,3-tetrafluoropropanol to prepare a coating liquid for forming a recording layer containing 2.25% by weight of the dye (A).

[0052]

[Chemical formula 1]

The coating liquid for forming a light absorption layer is applied onto the substrate by spin coating at a substrate rotation speed of 1000 rpm. p. m
．． After coating at a speed of 2000r. p. m.
The film was dried for 1 minute to form a recording layer with a thickness of 130 nm.

[0054] On the recording layer formed as described above,
An alloy of gold (Au) as metal A and tungsten (W) as metal B (weight ratio of Au:W is 100:5) was used, Ar was used as sputtering gas, target-substrate distance L = 187 mm, DC sputtering was performed at a sputtering gas pressure of 0.2 Pa and a sputtering speed of 100 nm/50 seconds to form a reflective layer with a thickness of 100 nm.

When the above information recording medium was observed in an area of 10 μm×10 μm using an electron microscope, no holes with a diameter of 50 nm or more were present in the reflective layer.

A UV curable resin (trade name: UV3070, manufactured by ThreeBond) was applied as a protective layer onto the reflective layer of the information recording medium by spin coating at a rotational speed of 1500 r.
After coating at a speed of 2 pm, the coating was cured by irradiation with ultraviolet rays using a high-pressure mercury lamp to form a protective layer with a thickness of 2 μm, thereby producing an information recording medium having a protective layer.

The reflectance of the mirror portion of the obtained information recording medium was measured by the following method and was found to be 80%. In addition, when the adhesion between the reflective layer and the protective layer was evaluated by the following method, it was evaluated as "excellent". In this adhesion test, no peeling occurred between the reflective layer and the recording layer.

[Reflectance of Mirror Part] Measurement was performed using a spectrophotometer (UV130 manufactured by Shimadzu Corporation) using an aluminum plate with a known reflectance as a reference.

[Adhesion] 1 cm of the protective layer of the information recording medium
Using a cutter, make 10 x 10 square cuts in a 1cm square part, paste cellophane tape on top of the cuts, peel off the cellophane tape, and remove the grid-like strips of the protective layer that adhere to the cellophane tape. Adhesion was evaluated by the number of .

Number of strips 0 to 10: "Excellent", number of strips 11 to 60: "Good", number of strips 61 to 100: "Poor".

[Example 2] The material for forming the reflective layer was gold (A
u) and nickel (Ni) as metal B (Au
An information recording medium in which a recording layer, a reflective layer, and a protective layer were provided on a substrate was manufactured in the same manner as in Example 1, except that the weight ratio of :Ni was changed to 100:7).

When the reflective layer of the intermediate product was observed in the same manner as in Example 1, no holes with a diameter of 50 nm or more were present in the reflective layer.

When the reflectance of the mirror portion of the obtained information recording medium was measured by the method described above, it was found to be 78%. Furthermore, when the adhesion between the reflective layer and the protective layer was evaluated by the method described above, it was evaluated as "excellent". In this adhesion test, no peeling occurred between the reflective layer and the recording layer.

[Example 3] The material for forming the reflective layer was gold (A
u) and tantalum (Ta) as metal B (Au
An information recording medium in which a recording layer, a reflective layer, and a protective layer were provided on a substrate was manufactured in the same manner as in Example 1, except that the weight ratio of :Ta was changed to 100:4).

When the reflective layer of the intermediate product was observed in the same manner as in Example 1, no holes with a diameter of 50 nm or more were present in the reflective layer.

When the reflectance of the mirror portion of the obtained information recording medium was measured by the method described above, it was found to be 80%. Furthermore, when the adhesion between the reflective layer and the protective layer was evaluated by the method described above, it was evaluated as "excellent". In this adhesion test, no peeling occurred between the reflective layer and the recording layer.

[Comparative Example 1] A substrate was prepared in the same manner as in Example 1, except that the material for forming the reflective layer was changed to only gold (99.9% purity) (no element to be combined with metal A was used). An information recording medium was manufactured in which a recording layer, a reflective layer, and a protective layer were provided.

When the reflective layer of the intermediate product was observed in the same manner as in Example 1, no holes with a diameter of 50 nm or more were present in the reflective layer.

When the reflectance of the mirror portion of the obtained information recording medium was measured by the method described above, it was found to be 83%. Furthermore, when the adhesion between the reflective layer and the protective layer was evaluated by the method described above, it was evaluated as "poor." In this adhesion test, no peeling occurred between the reflective layer and the recording layer.

[0070]

Effects of the Invention In the information recording medium of the present invention, since the reflective layer is formed from a material with specific components, the adhesion with the recording layer and/or the protective layer containing the dye is significantly excellent, and the recording medium has excellent durability. It is an information recording medium with excellent performance.

Claims (2)

[Claims] Claim 1: Information comprising a disk-shaped substrate, a recording layer containing a dye that can record and/or reproduce information using a laser beam, and a reflective layer made of metal provided on the recording layer. A recording medium, wherein the reflective layer is made of a metal A having a refractive index of 3 or less and an extinction coefficient of 2 or more at a recording or reproduction wavelength, and an element having a melting point higher than the melting point of the metal A. , the weight ratio of metal A:element is 100:0.1~
An information recording medium characterized by being 8. 2. The information recording medium according to claim 1, further comprising a protective layer provided on the reflective layer.