JP2001155379A - Optical information recording medium for both-side reading - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information recording medium having a high capacity and high production efficiency. SOLUTION: This optical information recording medium for both-side reading is provided with a recording layer formed in at least one side of a substrate, and a groove and/or a pit provided in the other side of the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an optical information recording medium.

[0002]

2. Description of the Related Art Hitherto, a CD-R (write-once compact disc) has been developed and put into practical use as an optical information recording medium having a high recording capacity. As a medium having a higher capacity, a DVD-R (write-once digital video disk) has also been developed.

In order to increase the recording capacity, it is conceivable to increase the number of recording layers. For DVD-R, a medium provided with two recording layers and reading from both sides has been proposed. Further, in a read-only DVD, not only two recording layers are provided, but also a medium in which these two layers can be read from one side has been put to practical use. Also, rewritable DVD
Then, a medium that can be recorded and reproduced from one side has also been developed.

[0004]

However, in these optical information recording media, two substrates are bonded to each other, so that the production efficiency of the substrate molding is low and a bonding step is required. There were many.

The present invention has been made in view of the above-mentioned circumstances, and has as its object to obtain an optical information recording medium having high capacity and high production efficiency.

[0006]

That is, the present invention provides an optical information recording medium for double-side reading in which a recording layer is provided on at least one of the substrates and grooves and / or pits are provided on the other of the substrates.

In the present invention, pits and grooves are provided on both sides of the substrate, so that the capacity is high, the production efficiency of substrate molding is good, and the number of steps is small because bonding is unnecessary.

Further, since reading is performed from both sides of the substrate, the recording and reproducing light does not pass through the substrate and the recording layer, and does not require the optical information recording medium to have a contradictory characteristic of a certain amount of light absorption and light transmission.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The substrate can be arbitrarily selected from various materials used as a substrate of a conventional optical information recording medium.

Examples of the substrate material include glass; polycarbonate; acrylic resins such as polymethyl methacrylate; vinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymer; epoxy resins; amorphous polyolefins and polyesters. They can be used together if desired. Note that these materials can be used in the form of a film or a rigid substrate. Among the above materials, polycarbonate is preferred from the viewpoints of moisture resistance, dimensional stability, cost, and the like. The substrate is
Its diameter is 120 ± 3mm and thickness is 1.2 ± 0.1m
m, or its diameter is 80 ± 3mm and its thickness is 1.2 ±
One having a diameter of 0.1 mm is generally used.

One surface of the substrate (hereinafter referred to as a first surface)
Are formed with tracking grooves or irregularities (pre-grooves) representing information such as address signals. On the other surface of the substrate (hereinafter, referred to as a second surface), similar pre-grooves, tracking grooves, or unevenness (pits) representing information such as digital signals are formed. The pregrooves or pits are preferably formed directly on the substrate when injection molding or extrusion molding of a resin material such as polycarbonate.

FIG. 1 is a schematic sectional view showing the shape of a pregroove. D is the groove depth, which is the distance from the substrate surface before the groove is formed to the deepest point of the groove. W is the groove width,
The width of the groove at a depth of D / 2. The groove inclination angle is an angle formed by a straight line passing through a position at a depth of D / 10 from the substrate surface and a position at a depth of 9D / 10 from the substrate surface, and a straight line parallel to the substrate surface.

The groove width of the pregroove is 700 nm or less, preferably 600 nm or less, and more preferably 500 nm or less. If the groove width exceeds 700 nm, it is not possible to prevent uneven spread of the pits. The lower limit of the groove width is preferably 50 nm or more, more preferably 100 nm or more, and even more preferably 150 nm or more.

The groove depth of the pregroove is preferably 300 nm or less, more preferably 250 nm or less,
200 nm or less is more preferable. 300nm groove depth
If it is deeper, the reflectance decreases. The lower limit of the groove depth is 5
0 nm or more is preferable, 70 nm or more is more preferable,
80 nm or more is more preferable. If the groove depth is less than 50 nm, uneven spread of the pits cannot be prevented.

The pit has a groove width of 800 nm or less.
00 nm or less is preferable, and 600 nm or less is more preferable.

The pit has a groove depth of 200 nm or less, preferably 150 nm or less, and more preferably 100 nm or less.

The track pitch is about 1600 nm.

The pre-groove may be formed by providing a pre-groove layer. As a material for the pregroove layer, a mixture of at least one monomer (or oligomer) of acrylic acid monoester, diester, triester and tetraester and a photopolymerization initiator can be used. The formation of the pre-groove layer is performed, for example, by first forming a precisely formed master (stamper).
A mixture comprising the above acrylate and a polymerization initiator is applied thereon, and after further placing the substrate on this coating liquid layer, the coating layer is cured by irradiating ultraviolet rays through the substrate or the matrix. The substrate and the coating layer are fixed. Next, it can be obtained by peeling the substrate from the matrix. The thickness of the pregroove layer is generally 0.05 to 100.
It is in the range of μm, preferably in the range of 0.1 to 50 μm.

An undercoat layer may be provided on the surface of the substrate for the purpose of improving flatness, improving adhesive strength, preventing deterioration of the recording layer, and the like. Examples of the material of the undercoat layer include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleic anhydride copolymer, polyvinyl alcohol, N-methylol acrylamide, styrene / vinyl toluene copolymer, and chlorosulfonation. Polymeric substances such as polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, polyethylene, polypropylene, polycarbonate, etc .; and silane coupling agents And other surface modifiers. The undercoat layer is prepared by dissolving or dispersing the above substance in an appropriate solvent to prepare a coating solution, and then applying the coating solution to the substrate surface using a coating method such as spin coating, dip coating, or extrusion coating. Can be formed. The thickness of the undercoat layer is generally in the range of 0.005 to 20 μm, preferably in the range of 0.01 to 10 μm.

A recording layer is provided on the first surface of the substrate.
Examples of the recording layer include a phase change recording layer and an organic dye-containing recording layer. As a phase change substance, T
and chalcogen-containing compounds such as e. Further, as organic dyes, cyanine dyes, azo dyes,
Examples include phthalocyanine dyes, oxonol dyes, and pyrromethene dyes, with cyanine dyes, azo dyes, and oxonol dyes being preferred, and cyanine dyes and oxonol dyes being particularly preferred.

The recording layer may be formed, for example, by dissolving a phase-change substance and a binder as required in a solvent to prepare a coating solution, or dissolving an organic dye, an anti-fading agent and a binder as required in a solvent. To prepare a coating solution, and then apply the coating solution to the surface of the substrate on which the pregroove is formed to form a coating film, followed by drying.

Solvents for the coating solution for forming the recording layer include esters such as butyl acetate and cellosolve acetate; ketones such as methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone; chlorinated hydrocarbons such as dichloromethane, 1,2-dichloroethane and chloroform. Amides such as dimethylformamide; hydrocarbons such as cyclohexane; ethers such as tetrahydrofuran, ethyl ether and dioxane; ethanol, n-propanol;
Alcohols such as isopropanol, n-butanol and diacetone alcohol; fluorinated solvents such as 2,2,3,3-tetrafluoropropanol; glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether and propylene glycol monomethyl ether And the like.

Among them, in the case of the organic dye-containing recording layer, from the viewpoints of solubility in the dye and drying property of the coating solution,
1,2-dichloroethane, chloroform, cyclohexane, ethanol, n-propanol, isopropanol, n-butanol, 2,2,3,3-tetrafluoropropanol, ethylene glycol monomethyl ether,
Preferred are ethylene glycol monoethyl ether and propylene glycol monomethyl ether;
3-Tetrafluoropropanol is particularly preferred.

The above solvents can be used alone or in combination of two or more in consideration of the solubility of the compound used. Various additives such as an antioxidant, a UV absorber, a plasticizer, and a lubricant may be further added to the coating solution according to the purpose.

Representative examples of the anti-fading agent include a tetracyanoquinodimethane derivative (TCNQ derivative), a nitroso compound, a metal complex, a diimmonium salt, and an aminium salt. These examples are described, for example, in JP-A-2-300288 and JP-A-3-224793.
Or each of the publications such as JP-A No. 4-146189. When an anti-fading agent is used, its amount is usually in the range of 0.1 to 50% by weight, preferably in the range of 0.5 to 45% by weight, more preferably in the amount of the dye. Ranges from 3 to 40% by weight, in particular from 5 to 25% by weight.

Examples of binders include, for example, gelatin,
Natural organic high molecular substances such as cellulose derivatives, dextran, rosin and rubber; and hydrocarbon resins such as polyurethane, polyethylene, polypropylene, polystyrene and polyisobutylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl chloride and polyvinyl acetate Initial stage of thermosetting resins such as vinyl resins such as polymers, acrylic resins such as polymethyl acrylate and polymethyl methacrylate, polyvinyl alcohol, chlorinated polyethylene, epoxy resins, butyral resins, rubber derivatives, and phenol / formaldehyde resins. Synthetic organic polymers such as condensates can be mentioned. Of these, polyurethane is particularly preferred. By using a binder, it is also possible to improve the temporal stability of the recording layer. Further, the storage stability of the recording layer can be improved. When a binder is used in combination as a material for the recording layer, the amount of the binder used is 0.2 to 20 parts by weight, preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the dye or phase change substance. More preferably, 1 to 7
Parts by weight.

The concentration of the dye or phase change substance in the coating solution is
Generally, it is in the range of 0.01 to 10% by weight, preferably in the range of 0.1 to 5% by weight.

Examples of the coating method include a spray method, a spin coating method, a dip method, a roll coating method, a blade coating method, a doctor roll method, and a screen printing method. The recording layer may be a single layer or a multilayer. The layer thickness at the groove of the recording layer is preferably in the range of 40 to 230 nm because if the thickness is too large, the pits easily spread.
The range of 60 to 200 nm is more preferable, and 70 to 180 nm.
The range of nm is more preferred.

A reflective layer can be provided between the first surface of the substrate and the recording layer. As the material of the reflection layer, it is preferable that the light-reflective substance is a substance having a high reflectance with respect to laser light, and examples thereof include Mg, Se, Y, Ti and Z.
r, Hf, V, Nb, Ta, Cr, Mo, W, Mn, R
e, Fe, Co, Ni, Ru, Rh, Pd, Ir, P
t, Cu, Ag, Au, Zn, Cd, Al, Ga, I
Examples include metals and semimetals such as n, Si, Ge, Te, Pb, Po, Sn, and Bi, and stainless steel. Of these, preferred are Cr, Ni, P
t, Cu, Ag, Au, Al and stainless steel. These substances may be used alone, or in combination of two or more kinds, or may be used as an alloy. Particularly preferably, Au, Ag or Pt, C and these are used.
It is an alloy containing at least one metal selected from u and Al.

The thickness of the reflective layer is generally from 10 to 350.
nm, preferably in the range of 30 to 300 nm, more preferably in the range of 40 to 250 nm.

The reflection layer can be formed on the substrate by, for example, vacuum deposition, sputtering or ion plating of the above-mentioned light-reflective substance.

In the present invention, for the purpose of improving the storage stability or changing the appearance, the reflective layer may be formed by laminating the above-mentioned materials in a single layer or by laminating two or more kinds of materials in a multilayer. .

By providing the reflective layer, water and oxygen are hardly permeated, so that the storage property is improved, and unnecessary light is prevented from being transmitted, so that the weather resistance is also improved.

It is preferable to provide a protective layer on the recording layer for the purpose of physically and chemically protecting the recording layer. Examples of the material used for the protective layer include SiO, S
Examples include inorganic substances such as iO ₂ , MgF ₂ , SnO ₂ , and Si ₃ N ₄ , and organic substances such as a thermoplastic resin, a thermosetting resin, and a UV-curable resin.

The protective layer can be formed, for example, by laminating a film obtained by extrusion of a plastic on the recording layer via an adhesive. Alternatively, it may be provided by a method such as vacuum deposition, sputtering, or coating. In the case of a thermoplastic resin or a thermosetting resin, they can also be formed by dissolving these in an appropriate solvent to prepare a coating solution, applying the coating solution, and drying. In the case of a UV curable resin, it is also formed by applying a coating liquid as it is without using a solvent or dissolving in an appropriate solvent to prepare a coating liquid, and then irradiating with UV light to cure the coating liquid. be able to. Various additives such as an antistatic agent, an antioxidant, and a UV absorber may be added to these coating solutions according to the purpose. The hardness of the protective layer is preferably F or higher, more preferably H or higher in terms of scratch hardness of the pencil, in order to prevent uneven spread of the pits in the protective layer direction. The thickness of the protective layer is preferably in the range of 2.5 to 23 μm, more preferably 3.5 to 20 μm, and still more preferably 4.0 to 15 μm.

Between the protective layer and the recording layer, between the substrate and the reflective layer,
An intermediate layer may be provided between the reflective layer and the recording layer, if necessary. The intermediate layer between the protective layer and the recording layer has an effect of preventing the recording layer from being attacked by the protective layer.

The material of the intermediate layer is transparent and thermally stable.
Good substance, Mg, Se, Y, Ti, Zr, Hf, V,
Nb, Ta, Cr, Mo, W, Mn, Re, Fe, C
o, Ni, Ru, Rh, Pd, Ir, Pt, Cu, A
g, Au, Zn, Cd, Al, Ga, In, Si, G
Metals such as e, Te, Pb, Po, Sn, Bi and half-metals
Genus or SiO_Two, SiO, Al_TwoO_Three, GeO_Two,
In_TwoO_Three, Ta_TwoO_Five, TeO _Two, MoO_Three, WO_Three, Zr
O_Two, Si_ThreeN_Four, AlN, BN, TiN, ZnS, Cd
S, CdSe, ZnSe, ZnTe, AgF, Pb
F_Two, MnF_Two, NiF_TwoAcid of metals and metalloids such as SiC
Chloride, nitride, chalcogenide, fluoride, carbide, etc.
A single substance or a mixture thereof is used.

When a pre-groove is formed on the second surface of the substrate, a recording layer is provided on the second surface.
Further, a reflective layer may be provided between the recording layer and the second surface, and a protective layer may be provided on the recording layer. Also,
An intermediate layer may be provided between the protective layer and the recording layer, between the second surface of the substrate and the reflective layer, and between the reflective layer and the recording layer. When pits are formed on the second surface of the substrate, a reflective layer or a protective layer can be provided on the second surface. As the recording layer, the reflective layer, the protective layer, and the intermediate layer, those described above can be used.

The present invention relates to DVD and CD (read only,
Write-once type and rewritable type).

It is preferable that the total thickness of the optical information recording medium of any embodiment is adjusted to 1.2 ± 0.2 mm.

[0042]

EXAMPLES Examples and comparative examples of the present invention will be described below. [Example 1] A polycarbonate substrate having a spiral pre-groove formed on both sides by injection molding (thickness: 1.2 m)
m, outer diameter: 120 mm, inner diameter: 15 mm).
The groove depth, groove width, groove pitch, and groove inclination angle of the pregroove were measured by an atomic force microscope (AFM) and are as follows.

Groove depth: 180 nm Groove width: 500 nm Groove pitch: 1600 nm Groove inclination angle: 50 ° This substrate is placed in a chamber with an internal pressure of 1 Pa, and silver reflection is performed on both surfaces of the substrate by DC magnetron sputtering in an argon atmosphere. The film was formed with a thickness of 100 nm.

1 g of the following cyanine dye was added to 2,2,3,3-
A coating solution for forming a recording layer dissolved in 100 ml of tetrafluoro-1-propanol was applied to the reflection layers on both sides of the substrate by spin coating, and dried to form recording layers on both sides of the substrate. Scanning electron microscope (SEM)
The thickness of one recording layer (hereinafter, referred to as a first recording layer) was found to be 14 in the pregroove.
0 nm, and 80 nm at the land. The thickness of the other recording layer (hereinafter, referred to as a second recording layer) was 180 nm in the pre-groove and 100 nm in the land. Further, the reflectance of the pre-groove portion was 70%.

[0045]

Embedded image

Thus, the recording layer / reflection layer / substrate /
A DVD-R type optical disk having a structure of a reflective layer / recording layer was manufactured.

The recording light is irradiated from the first recording layer side,
When the recording layer was focused, information could be recorded on the first recording layer. When the recording light was irradiated from the side of the second recording layer to focus on the second recording layer, information could be recorded on the second recording layer. In the same way,
The information recorded on the first and second recording layers could be reproduced.
Also, the jitter was good.

[0048]

According to the present invention, an optical information recording medium having high capacity and high production efficiency is provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing the shape of a pregroove.

Claims (1)

[Claims] A recording layer provided on at least one of the substrates;
An optical information recording medium for double-sided reading in which grooves and / or pits are provided on the other side of the substrate.