JP2000311384A - Optical information recording medium - Google Patents

Abstract

(57) [Problem] To provide a write-once optical information recording medium of a one-side reading system, which has two light absorbing layers and is capable of recording with high capacity. SOLUTION: A first light absorbing layer 2 and a second light absorbing layer 6 containing an organic dye and capable of recording information by irradiating a laser beam from the substrate side are provided in this order on a substrate, Between the light absorbing layer 2 and the second light absorbing layer 6, a light transmitting first barrier layer 3 adjacent to the first light absorbing layer 2 and a light transmitting first barrier layer 3 adjacent to the second light absorbing layer 6. Two barrier layers 5 are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium, and more particularly, to a one-side read-only write-once optical information recording medium capable of recording a large amount of data.

[0002]

2. Description of the Related Art Digital Video Disk (DVD)
Has been developed as a medium having a higher capacity than a compact disk (CD), and is a read-only type R
In an OM type DVD, a bonded recording medium is generally used in which two disks each having a recording layer are bonded and turned upside down, but a single-side reading system capable of reading two recording layers from one side is used. Two-layer recording media have also been developed. Such a two-layer recording medium of the one-side reading method is useful in a field where random access is frequently required, in particular, in a computer field because it can be accessed without turning over the disk.

However, conventionally, a DVD-R (DV-R) is a write-once medium on which information is recorded by irradiating a laser beam.
D-Rewritable), there was no single-sided reading two-layer recording medium. This is presumed to be due to the following reasons. When the DVD-R is a one-sided reading type two-layer recording medium such as a ROM type DVD, it is necessary to bond two recording layers. However, dyes for recording layers of write-once recording media such as cyanine dyes are relatively unstable,
When laminated with a curable adhesive such as an ultraviolet curable resin used in a laminated recording medium, the recording layer dyes dissolve and deteriorate in the adhesive, and eventually the recording / reproducing characteristics of the recording medium are deteriorated. This is because there is a great risk of lowering.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a one-side reading system having two light absorbing layers and capable of recording a large amount of data. An object of the present invention is to provide a write-once optical information recording medium.

[0005]

As a result of intensive studies, the present inventors have found that the above-mentioned problems can be solved by the following means, and have completed the present invention. That is, the optical information recording medium of the present invention comprises, between a substrate and a counter substrate facing the substrate, a first light absorbing layer containing an organic dye and capable of recording information by irradiating a laser beam; A transparent intermediate layer, a second light absorbing layer separated from the first light absorbing layer by the intermediate layer,
Are stacked in this order, and a first light-transmissive barrier layer that reflects a part of the laser light transmitted through the first light-absorbing layer while simultaneously blocking material transmission from the intermediate layer to the first light-absorbing layer is formed. ,
A light interposed between the intermediate layer and the first light absorbing layer for blocking a substance from passing from the intermediate layer to the second light absorbing layer and reflecting a laser beam transmitted through the first light absorbing layer; A second transparent barrier layer is inserted between the intermediate layer and the second light absorbing layer, and information is recorded and reproduced by irradiating a laser beam from a substrate side close to the first light absorbing layer. It is characterized by. The first barrier layer has a transmittance to recording light of 30.
The second barrier layer preferably has a reflectance to recording light of 10 to 90%.

Further, the optical information recording medium of the present invention comprises a first light absorbing layer containing an organic dye and capable of recording information by irradiating a laser beam between a substrate and a counter substrate facing the substrate. A light-transmitting intermediate layer, and a second light-absorbing layer separated from the first light-absorbing layer by the intermediate layer, in this order, and a substance permeates from the intermediate layer to the first light-absorbing layer. And a light-transmitting first barrier layer that reflects a part of the laser light transmitted through the first light-absorbing layer.
A light-transmitting second barrier layer interposed between the intermediate layer and the second light-absorbing layer, the light-transmitting second barrier layer being interposed between the intermediate layer and the second light-absorbing layer to prevent a substance from passing from the intermediate layer to the second light-absorbing layer; A reflective layer is provided adjacent to a surface of the second light absorbing layer opposite to the substrate side, and information is recorded and irradiated by laser light irradiation from a substrate side close to the first light absorbing layer. It is characterized by reproducing. The second barrier layer has a transmittance to recording light of 30.
It is preferably in the range of ~ 95%.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a specific structure of an optical information recording medium according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing the structure of an optical information recording medium according to a first embodiment of the present invention. In FIG. 1, 1 is a substrate, 2 is a first light absorption layer, 3 is a first barrier layer,
4 is an intermediate layer, 5 is a second barrier layer, 6 is a second light absorbing layer, 7
Is a counter substrate.

The optical information recording medium according to the first embodiment of the present invention is provided with two light absorbing layers, that is, a first light absorbing layer 2 and a second light absorbing layer 6, and an intermediate point between the two. It is characterized in that the first barrier layer 3 and the second barrier layer 5 are provided between the first and second layers.

[0010] Information recording using this optical information recording medium is performed, for example, as follows. First, while rotating the optical information recording medium at a predetermined constant linear velocity or a predetermined constant angular velocity, recording laser light such as semiconductor laser light is condensed from the substrate 1 side through an optical system and irradiated. A part of the recording light from the substrate 1 side is absorbed by the first light absorbing layer 2, and the irradiated part of the first light absorbing layer 2 absorbs the light to locally increase the temperature, and the physical or chemical The information is recorded on the first light-absorbing layer 2 by changing the optical characteristics of the first light-absorbing layer 2 while the remaining light is changed by the first light-absorbing layer 2.
Through. Next, part of the light transmitted through the first light absorbing layer 2 is reflected by the first barrier layer 3, and the remaining light is transmitted through the first barrier layer 3. Then, the first barrier layer 3
Is partially reflected by the second barrier layer 5, and the remaining light is transmitted through the second barrier layer 5,
The light absorption layer 6 absorbs the light and locally raises the temperature, causing a physical or chemical change to change its optical characteristics, whereby information is recorded on the second light absorption layer 6.

The recording light is a laser light in a visible region, usually 600 nm to 700 nm (preferably 620 to 680 nm).
m, more preferably, a semiconductor laser beam having an oscillation wavelength in the range of 630 to 660 nm). The recording light is preferably collected through an optical system having an NA of 0.55 to 0.7.

The information recorded as described above is reproduced by irradiating a semiconductor laser beam having the same wavelength as at the time of recording from the substrate side while rotating the optical information recording medium at a predetermined constant linear speed, and reflecting the reflected light. Can be detected by detecting The optical information recording medium of the present invention is capable of recording / reproducing at a high speed as well as at a normal speed of the normal DVD format.

In the optical information recording medium according to the first embodiment, the first optical absorption layer 2 and the second optical absorption layer 6 are recorded from the one side of the disk in order to perform good recording or reproduction. The barrier layer 3 and the second barrier layer 5 have the following roles.

That is, the first barrier layer 3 has the following three roles. (1) The role of the first light absorbing layer 2 as a reflection film. (2) The recording light passing through the first light absorbing layer 2 is absorbed and absorbed.
The second light absorbing layer 6 is transmitted to some extent without scattering.
(3) Role as an impermeable film for preventing elution of the dye contained in the first light absorbing layer 2

Therefore, the reflectance of the first barrier layer 3 with respect to the recording light is preferably in the range of 3 to 50%, more preferably 7 to 40%, and still more preferably 10 to 35%.
It is. The transmittance of the first barrier layer 3 for recording light is preferably in the range of 30 to 95%, more preferably 40 to 90%, and still more preferably 50 to 85%. Further, the absorptance of the first barrier layer 3 for recording light is preferably in the range of 1 to 30%, more preferably 2 to 20%, and further preferably 3 to 10%.
Adjustment of these optical characteristics is performed by changing the material type and layer thickness of the first barrier layer, as described later.
Further, when a protective layer or an intermediate layer is formed on the first light absorbing layer 2 without providing the first barrier layer 3, a dye is eluted from the first light absorbing layer 2 to the protective layer or the intermediate layer and the first light absorbing layer is formed. The coloring inherent in the layer 2 disappears and the layer 2 becomes transparent. Therefore, the first barrier layer 3 needs to have a light absorbing layer component elution inhibiting ability that can maintain the coloring of the first light absorbing layer 2 by providing the first barrier layer 3. As a guide, a resin that is liquid at the time of application and solidifies after application, such as an ultraviolet curable resin, is applied to the barrier layer provided on the light absorption layer, and is applied from application to solidification (usually, If the coloration of the light absorbing layer does not disappear at about 1 minute), it can be said that the light absorbing layer component elution inhibiting ability of the barrier layer is good.

The second barrier layer 5 has the following three roles. (1) A role as a reflection film for the second light absorption layer 6 (2) The recording light that has passed through the first barrier layer 3 is transmitted, and at least the recording light that has reached the second light absorption layer 6 raises the temperature. A role as a light transmitting film that reaches the second light absorbing layer 6 to the extent that pits are formed and deformation and alteration occur. (3) An impermeable film that prevents elution of the dye contained in the second light absorbing layer 6 Role

Accordingly, the reflectance of the second barrier layer with respect to the recording light is preferably in the range of 10 to 90%, more preferably 20 to 80%, and still more preferably 30 to 70%.
%. Further, the transmittance of the first barrier layer with respect to the recording light is preferably in the range of 5 to 80%, more preferably 10 to 70%, and still more preferably 30 to 70%. Further, the absorptance of the first barrier layer for recording light is 1
It is preferably in the range of 30% to 30%, more preferably 2% to 20%, and still more preferably 3% to 30%. Adjustment of these optical characteristics is performed according to the material type and layer thickness of the barrier layer, as described later. Also, the second barrier layer 5
As with the first barrier layer 3, the second light absorbing layer 6
It is necessary to have a light absorbing layer component elution inhibiting ability that can maintain the coloring of the light absorbing layer.

Hereinafter, the structure of each layer will be described according to the manufacturing process. The substrate 1 can be arbitrarily selected from various materials used as a substrate of a conventional optical information recording medium. As the substrate material, for example, glass; polycarbonate; acrylic resin such as polymethyl methacrylate;
Examples thereof include polyvinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymer; epoxy resins; amorphous polyolefins and polyesters. These may be used in combination, 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 has a diameter of 120 ± 3 mm and a thickness of 0.6 ± 0.1 mm, or a diameter of 80 ± 3 mm and a thickness of 0.6 ± 0.1 m.
m are generally used.

On the substrate (or undercoat layer), it is preferable to form tracking grooves or irregularities (pre-grooves) representing information such as address signals. This pregroove is preferably formed directly on the substrate when injection molding or extrusion molding of a resin material such as polycarbonate.

FIG. 2 is a schematic sectional view showing the shape of the 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 slope width is the difference between the groove width W1 at a depth of D / 10 from the substrate surface before the formation of the groove and the groove width W2 at a height of D / 10 from the deepest point of the groove.

The groove width of the pre-groove is 450 nm or less, preferably 400 nm or less, more preferably 350 nm or less. If the groove width exceeds 450 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 slope width is 180 nm or less, preferably 160 nm or less,
It is more preferably 150 nm or less. Groove slope width 180n
If it exceeds m, the inclination of the groove becomes gentle and uneven spread of the pits cannot be prevented. In addition, the lower limit of the groove slope width is preferably 20 nm or more, more preferably 40 nm or more, and even more preferably 50 nm or more.

The groove depth is preferably 300 nm or less, more preferably 250 nm or less, and even more preferably 200 nm or less. When the groove depth is deeper than 300 nm, the reflectivity decreases. Further, the lower limit of the groove depth is preferably 50 nm or more, more preferably 70 nm or more, and further preferably 80 nm or more. If the groove depth is less than 50 nm, uneven spread of the pits cannot be prevented. The track pitch is preferably 1200 nm or less, and 10
00 nm or less is more preferable, and 900 nm or less is further preferable. The lower limit of the track pitch is preferably 100 nm or more, more preferably 200 nm or more, and 300 nm or more.
nm or more is more preferable.

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 1 on the side where the first light absorbing layer 2 is provided, for the purpose of improving flatness, improving adhesive strength, preventing deterioration of the light absorbing layer, and the like. Good. 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, chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, polyethylene ,
Examples include polymer substances such as polypropylene and polycarbonate; and surface modifiers such as silane coupling agents. 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 0.00
In the range of 5 to 20 μm, preferably 0.01 to 10
It is in the range of μm.

A first light absorbing layer 2 containing an organic dye is provided on the surface of the substrate 1 (or the undercoat layer) on which the pregroove is formed. Examples of the organic dye include a cyanine dye, an azo dye, a phthalocyanine dye, an oxonol dye, and a pyrromethene dye.A cyanine dye, an azo dye, and an oxonol dye are preferable.
Cyanine dyes and oxonol dyes are particularly preferred.

The first light absorbing layer 2 is formed, for example, by dissolving, in addition to an organic dye, an anti-fading agent and a binder as required in a solvent to prepare a coating solution, and then applying the coating solution to a pre-groove of the substrate. Can be carried out by applying the composition on the surface on which is formed, forming a coating film, and then drying.

The first light absorbing layer 2 preferably has an absorptivity of 2 to 30%, and preferably 5 to 20%, in order to allow recording light or reproducing light to reach the second light absorbing layer 6. % Is more preferable, and 7 to 15% is particularly preferable.

As the solvent of the coating solution for forming the light absorbing layer,
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; tetrahydrofuran; Ethers such as ethyl ether and dioxane; alcohols such as ethanol, n-propanol, isopropanol, n-butanol and diacetone alcohol; fluorinated solvents such as 2,2,3,3-tetrafluoropropanol; ethylene glycol monomethyl ether And glycol ethers such as ethylene glycol monoethyl ether and propylene glycol monomethyl ether. Among these, 1,2-dichloroethane, chloroform, cyclohexane, ethanol, n-propanol, isopropanol, n-butanol, 2,2,3,3-tetrafluoropropanol are preferred from the viewpoint of solubility in a dye and drying property of a coating solution. , Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether and propylene glycol monomethyl ether are preferred,
2,3,3-tetrafluoropropanol is particularly preferred. The above-mentioned solvents can be used alone or in combination of two or more in consideration of the solubility of the dye used.

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.

Typical 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 the binder 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 as a material for the light absorbing layer, the amount of the binder used is
0.2 to 20 parts by weight, preferably 0 part by weight,
It is 0.5 to 10 parts by weight, more preferably 1 to 7 parts by weight.

The concentration of the dye in the coating solution is generally 0.01
-10% by weight, preferably in the range of 0.1-5% by weight.

Examples of the coating method include a spray method, a spin coating method, a dipping method, a roll coating method, a blade coating method, a doctor roll method, and a screen printing method. The light absorbing layer may be a single layer or a multilayer. First
The layer thickness of the light absorbing layer 2 in the groove portion is preferably in the range of 40 to 230 nm, more preferably in the range of 60 to 200 nm, and further preferably in the range of 70 to 180 nm, because if the thickness is too large, the pits are likely to spread. preferable.

On the first light absorbing layer 2, a first barrier layer 3
Is formed, and the laminate (1) is produced. The material of the first barrier layer 3 is preferably a transparent and thermally stable substance, for example, 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
e, Te, Pb, Po, Sn, Bi and other metals and metalloids, or SiO ₂ , SiO, Al ₂ O ₃ , GeO ₂ ,
In ₂ O ₃ , Ta ₂ O ₅ , TeO ₂ , MoO ₃ , WO ₃ , Zr
O ₂ , Si ₃ N ₄ , AlN, BN, TiN, ZnS, Cd
S, CdSe, ZnSe, ZnTe, AgF, Pb
Metals such as F ₂ , MnF ₂ , NiF ₂ , SiC and the like, and oxides, nitrides, chalcogenides, fluorides, carbides and the like of metal or semimetals, or mixtures thereof can be mentioned. Among these, a material having an optical constant satisfying the following relational expression (1) is preferable, and a material satisfying the following relational expression (2) is more preferable. Here, k represents an extinction coefficient, and n represents a refractive index. k <−4n + 10 Relational expression (1) k <−4n + 7 Relational expression (2) Further, k is preferably 0.0001 or more, and 0.1.
The above is more preferable. n is preferably 0.001 or more, more preferably 0.01 or more. Speaking of specific materials, a simple metal such as Al, Au, Ag, and Cu or an alloy mainly containing them is particularly preferable.

The thickness of the first barrier layer 3 is adjusted according to the material so that the optical characteristics of the first barrier layer 3, such as transmittance, reflectance, and absorptance, fall within the above ranges. For example, 650 nm
At a wavelength of, Cu preferably has a layer thickness of 30 nm or less, and Ag preferably has a layer thickness of 30 nm or less.
Preferably, Au has a layer thickness of 40 nm or less, and Al has a layer thickness of 20 nm or less. The lower limit of the thickness of the first barrier layer 3 is approximately 6 nm in terms of barrier performance.
It is.

On the other hand, the counter substrate 7 can be manufactured using the same material as that of the substrate 1 and has the same diameter as the substrate and a thickness of 0.1 to 2.0 mm, preferably 0.1 to 2.0 mm.
2 to 1.3 mm, more preferably 0.3 to 0.7 mm
Is preferably within the range. It is preferable that the material and the thickness of the opposing substrate 7 and the substrate 1 be the same, because the secular deformation due to heat is small. Also, like the substrate 1, it is preferable to form tracking grooves or irregularities (pre-grooves) representing information such as address signals on the opposite substrate 7.

On the substrate-side surface of the opposing substrate 7 corresponding to the inside of the medium, a second light absorbing layer 6 containing an organic dye is provided. The second light absorbing layer 6 preferably has an absorptance of 4 to 35%, more preferably 7 to 25%, and particularly preferably 9 to 20%. Generally, since the amount of recording light incident on the second light absorbing layer 6 is smaller, the absorptance of the second light absorbing layer 6 is
In the above range, it is preferable to set higher than the absorptance of the first light absorbing layer 2.

The second light absorbing layer 6 is formed using the same material as that of the first light absorbing layer 2 in the same manner as the first light absorbing layer.

On the second light absorbing layer 6, the second barrier layer 5
Is formed, and the laminate (2) is produced. The material of the second barrier layer 5 is common to the first barrier layer 3 in that a transparent and thermally stable substance is preferable, and is used as a material of the first barrier layer 3. Alternatively, simple substances such as oxides, nitrides, chalcogenides, fluorides, and carbides of these metals and metalloids, and mixtures thereof are used. As a material of the second barrier layer 5, a material having an optical constant satisfying the following relational expression (3) is preferable, and a material satisfying the following relational expression (4) is more preferable. k <−5n + 15 Relational expression (3) k <−5n + 10 Relational expression (4) Furthermore, k is preferably 0.0001 or more, and 0.1
The above is more preferable. n is preferably 0.001 or more, more preferably 0.01 or more.

The thickness of the second barrier layer 5 is adjusted in accordance with the material so that the optical characteristics of the second barrier layer 5, such as transmittance, reflectance, and absorptance, fall within the above ranges. For example, 650 nm
At a wavelength of, Cu preferably has a layer thickness of 40 nm or less, and Ag preferably has a layer thickness of 30 nm or less.
Au preferably has a layer thickness of 40 nm or less. In addition,
The lower limit of the thickness of the second barrier layer 5 is approximately 6 nm in terms of barrier performance.

Through the above steps, the laminate (1) in which the first light absorbing layer 2 and the first barrier layer 3 are provided on the substrate 1,
The laminate (2) in which the second light absorbing layer 6 and the second barrier layer 5 are provided on the counter substrate 7 can be manufactured. Then, the obtained two laminates are bonded via the intermediate layer 4 so that each barrier layer is on the inside, whereby a DVD-R type optical information recording medium having two light absorption layers is manufactured. be able to.

As a material of the intermediate layer 4, an ultraviolet curable resin or a synthetic adhesive is used. Examples of the synthetic adhesive include a slow-acting adhesive such as a cation-curable epoxy resin and a spin-curable adhesive such as an ultraviolet-curable acrylate resin, and a spin-curable adhesive is more preferable. The function of the protective layer can also be used for the intermediate layer 4. The ultraviolet curable resin and the synthetic adhesive are liquid at the time of application, and solidify after application to form the intermediate layer 4. In order to record and reproduce information independently on the two light absorbing layers, the first light absorbing layer and the second light absorbing layer, the first light absorbing layer and the second light absorbing layer need to be separated by a certain distance. , Middle layer 4
Is preferably 10 μm or more, more preferably 20 μm or more, and further preferably 30 μm or more. On the other hand, the thickness of the intermediate layer 4 is preferably 200 μm or less, more preferably 100 μm or less, and still more preferably 60 μm or less, in order to prevent warpage and enable correction of optical aberration. Further, the bonding of the two laminates may be performed using a double-sided tape or the like. Regardless of the method of bonding the two laminates together, it is preferable that voids such as air bubbles are not formed at the interface between the barrier layer and the intermediate layer 4.

Between the first barrier layer 3 and the intermediate layer 4 or between the second barrier layer 5 and the intermediate layer 4, a light absorbing layer or the like is physically and chemically protected. Preferably, a layer is provided. Examples of the material used for the protective layer include SiO, SiO 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 barrier 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, a coating solution is prepared as it is without using a solvent or dissolved in an appropriate solvent, and then the coating solution is applied.
It can also be formed by irradiating light and curing. 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 determined by the scratch hardness of a pencil in order to prevent uneven spread of the pits toward the protective layer.
Or more, and more preferably H or more. 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.

A buffer layer may be further provided between the protective layer and the intermediate layer 4 in order to improve storability and adhesion. Materials used for the buffer layer include:
For example, SiO, SiO ₂ , MgF ₂ , SnO ₂ , Si ₃ N
Inorganic substances such as ₄ , thermoplastic resin, thermosetting resin, UV
An organic substance such as a curable resin can be used. This buffer layer can be formed using vacuum film formation, spin coating, or the like.

The optical information recording medium according to the first embodiment of the present invention is configured as described above to prevent the dye contained in the light-absorbing layer from being eluted into the intermediate layer. Degradation can be prevented, and good recording or reproduction can be performed for different light absorbing layers from one side of the disc. That is, it is possible to independently read and write each of the first light absorbing layer and the second light absorbing layer through the substrate 1.

FIG. 3 is a sectional view showing the structure of an optical information recording medium according to the second embodiment of the present invention. In FIG. 3, 1 is a substrate, 2 is a first light absorption layer, 3 is a first barrier layer,
4 is an intermediate layer, 5 is a second barrier layer, 6 is a second light absorbing layer, 8
Is a reflective layer, and 7 is a counter substrate.

The optical information recording medium according to the second embodiment of the present invention is characterized in that two light absorbing layers, that is, a first light absorbing layer 2 and a second light absorbing layer 6, are provided. In addition to the point that the first barrier layer 3 and the second barrier layer 5 are provided between the second light absorbing layer 4 and the second light absorbing layer 4, a reflective layer 8 is provided between the second light absorbing layer 6 and the counter substrate 7.

In this optical information recording medium, a part of the recording light from the substrate 1 is absorbed by the first light absorbing layer 2,
The irradiated portion of the light absorbing layer 2 absorbs the light and locally rises in temperature, causing a physical or chemical change to change its optical characteristics, whereby information is recorded on the first light absorbing layer 2. On the other hand, the remaining light passes through the first light absorbing layer 2. Next, part of the light transmitted through the first light absorbing layer 2 is reflected by the first barrier layer 3, and the remaining light is transmitted through the first barrier layer 3. Most of the light transmitted through the first barrier layer 3 is transmitted through the second barrier layer 5, and a part of the light is absorbed by the second light absorption layer 6, and the temperature is locally increased. Information is recorded on the second light absorbing layer 6 by causing a chemical change to change its optical characteristics.

In the optical information recording medium according to the second embodiment, in order to perform recording or reproduction on both the first light absorbing layer 2 and the second light absorbing layer 6 from one side of the disk, the first
The role played by the barrier layer 3 is the same as in the first embodiment, and the first barrier layer 3 can be formed in the same manner as in the first embodiment. However, since the reflective layer 8 is separately provided, the role of the second barrier layer 5 in the optical information recording medium according to the second embodiment is changed to the following two. (1) A role as a light transmitting film for transmitting the recording light passing through the first barrier layer 3 and reaching the second light absorbing layer 6 (2) Preventing the elution of the dye contained in the second light absorbing layer 6 Role as an impermeable membrane

Therefore, when the reflection layer 8 is provided thereon,
The transmittance of the second barrier layer 5 to recording light is preferably high, specifically, preferably in the range of 30 to 95%, more preferably 40 to 90%, and still more preferably 50 to 85%. is there. The reflectance with respect to the recording light is preferably in the range of 3 to 70%, more preferably 7 to 60%, and still more preferably 10 to 50%. Further, the absorptance of the second barrier layer 5 with respect to recording light is preferably in the range of 1 to 30%, more preferably 2 to 20%, and still more preferably 3 to 10%.

When the reflective layer 8 is provided on the second light absorbing layer 6, the material of the second barrier layer 5 is preferably a transparent and thermally stable substance such as a metal or semimetal oxide, Nitrides, chalcogenides, fluorides, carbides, and the like, and mixtures thereof; specifically, SiO ₂ , SiO, Al ₂ O
₃ , GeO ₂ , In ₂ O ₃ , Ta ₂ O ₅ , TeO ₂ , MoO ₃ ,
_{WO 3, ZrO 2, Si 3} N 4, AlN, BN, TiN, Z
nS, CdS, CdSe, ZnSe, ZnTe, Ag
It is a simple substance such as F, PbF ₂ , MnF ₂ , NiF ₂ , SiC or a mixture thereof. Further, a material whose optical constant satisfies the following relational expression (5) is preferable.
Materials satisfying the above are more preferable. k <−5n + 15 Relational expression (5) k <−5n + 6 Relational expression (6) Further, k is preferably 0.0001 or more, and 0.1 is preferable.
The above is more preferable. n is preferably 0.001 or more, more preferably 0.01 or more.

The thickness of the second barrier layer 5 depends on the material, and the optical characteristics such as transmittance, reflectance and absorptance of the second barrier layer 5 are considered to be suitable when the reflective layer 8 is provided. Adjust to be within the range. For example, at a wavelength of 650 nm, Cu preferably has a layer thickness of 40 nm or less.
g is preferably 30 nm or less, and Au is 4 nm.
The layer thickness is preferably 0 nm or less. Note that the lower limit of the thickness of the second barrier layer 5 is approximately 6 nm in terms of barrier performance.

When the reflective layer 8 is provided on the second light absorbing layer 6, the absorption of the second light absorbing layer 6 with respect to the recording light is 5-6.
0% is preferred, 10 to 50% is more preferred, and 15 to 15%.
40% is particularly preferred. The second light-absorbing layer 6 has the same structure as the first light-absorbing layer 2 except that the absorptance for the recording light is within the above range.
The first light absorbing layer 2 can be formed using the same material as in the first embodiment.

The reflectivity of the reflective layer 8 is preferably at least 50%, more preferably at least 60%, further preferably at least 70%. The material of the reflection layer 8 is a light-reflective substance having a high reflectance with respect to laser light, and examples thereof include Mg, Se, Y, Ti, Zr, Hf, V, and N.
b, Ta, Cr, Mo, W, Mn, Re, Fe, Co,
Ni, Ru, Rh, Pd, Ir, Pt, Cu, Ag, A
u, Zn, Cd, Al, Ga, In, Si, Ge, T
e, Pb, Po, Sn, Bi, and other metals and semi-metals or stainless steel. Of these, preferred are Cr, Ni, Pt, Cu, Ag, A
u, 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, A
g or an alloy containing at least one metal selected from Pt, Cu, and Al.

The reflection layer 8 can be formed on the counter substrate 7 by, for example, vacuum evaporation, sputtering or ion plating of the above-mentioned light-reflective substance.
The thickness of the reflective layer 8 is generally in the range of 10 to 350 nm, preferably in the range of 30 to 300 nm, and more preferably in the range of 40 to 250 nm. In the present invention, for the purpose of improving storage stability or changing the appearance, the reflective layer may be formed by laminating the above-mentioned material in a single layer.
More than one kind of material may be laminated in multiple layers.

An adjusting layer may be provided between the reflecting layer 8 and the counter substrate 7 to adjust optical characteristics such as improvement of reflectance. As a material used for the adjustment layer, for example, Si
Examples include inorganic substances such as O, SiO ₂ , MgF ₂ , SnO ₂ , and Si ₃ N ₄ . In addition, this adjustment layer can be formed by vacuum film formation such as evaporation or sputtering.

The optical information recording medium according to the second embodiment of the present invention is configured as described above to prevent the dye contained in the light-absorbing layer from being eluted into the intermediate layer. Degradation can be prevented, and good recording or reproduction can be performed for different light absorbing layers from one side of the disc. That is, it is possible to independently read and write each of the first light absorbing layer and the second light absorbing layer through the substrate 1. Further, by providing the reflection layer, the reflectance from the second light absorption layer is increased, and the quality of the reproduction signal from the second light absorption layer is improved. In addition, water and oxygen are hardly permeated, so that storage stability is improved, and light transmission from the counter substrate side is prevented, and weather resistance is also improved.

In any of the optical information recording media of the DVD-R type, the overall thickness is 1.2 ± 0.2 m.
It is preferable to prepare m.

In any of the optical information recording media of the DVD-R type, a printable layer may be provided on the surface of the recording medium opposite to the side on which the light for recording and reproduction is incident. it can. That is, a layer suitable for printing with an inkjet printer or the like to display the content recorded on the medium is formed on the protective layer or the like. In ink-jet printing, the ink is usually hydrophilic, so that the printable layer preferably has a hydrophilic surface. For example, a layer in which hydrophilic particles such as protein particles are uniformly dispersed in an ultraviolet curable resin is formed as a printable layer. The background printed on the printable layer may be colored by the influence of light transmitted from the metal reflective layer or the dye recording layer. Include a pigment for determining the background color in the printable layer to prevent such coloring, and further form a colored shielding layer under the printable layer to enhance the aesthetics of the printed image Can also. Various additives such as an antistatic agent, an antifungal agent, and a coloring agent can be contained in the printable layer according to the purpose.

EXAMPLES Examples and comparative examples of the present invention will be described below.

Example 1 A polycarbonate substrate having a spiral pregroove formed on its surface by injection molding (thickness: 0.6 mm, outer diameter: 120 mm, inner diameter: 15 mm,
A product name “Panlite AD5503” manufactured by Teijin Limited was produced. The groove depth, groove width, groove pitch, and width of the groove inclined portion of the pre-groove are as follows. Measurement of groove depth, groove width, groove pitch, width of groove inclined part by atomic force microscope (AFM)
I went in. Groove depth: 150 nm Groove width: 330 nm Groove pitch: 800 nm Width of groove slope: 120 nm (60 nm on one side)

1 g of the following cyanine dye was added to 2,2,3,3
-Dissolved in 100 ml of tetrafluoro-1-propanol, applied this coating solution for forming a light-absorbing layer to the pre-groove surface of the obtained substrate by spin coating while changing the rotation speed from 300 to 3000 rpm, and dried. Thus, a first light absorbing layer was formed. The thickness of the first light absorbing layer was 80 nm in the pregroove and 50 nm in the land as measured by observing the cross section of the light absorbing layer with a scanning electron microscope (SEM). The transmittance of the first light absorbing layer is 75
% And the absorptivity were 12%.

[0063]

Embedded image

Next, by DC sputtering, the first
A first barrier layer made of Au having a thickness of about 15 nm was formed on the light absorbing layer. At this time, the pressure in the chamber is 0.5
Pa. The transmittance of the first barrier layer was 57%, the absorption was 8%, and the reflectance was 35%. Note that the optical characteristics of the barrier layer are measured by forming a barrier layer directly on a substrate under the same conditions without interposing a light absorbing layer, and irradiating light from the substrate side.

Further, a UV curable resin (trade name “SD-318”, manufactured by Dainippon Ink and Chemicals, Inc.) is applied on the first barrier layer by spin coating while changing the rotation speed from 300 rpm to 4000 rpm. did. After the application, the coating was irradiated with ultraviolet light from a high-pressure mercury lamp to cure the coating, thereby forming a protective layer having a thickness of 8 μm. The surface hardness was 2H as the pencil hardness.

In this way, a laminate (1) in which a light absorbing layer, a barrier layer, and a protective layer were sequentially provided on the substrate was obtained.

On the other hand, a counter substrate made of polycarbonate (thickness: 0.6 mm, outer diameter: 120 mm, inner diameter: 15 mm,
1 g of the above-mentioned cyanine dye was dissolved in 100 ml of 2,2,3,3-tetrafluoro-1-propanol on Teijin Co., Ltd. (trade name “Panlite AD5503”). Was applied to the pre-groove surface of the obtained substrate by a spin coating method while changing the rotation speed from 300 to 3000 rpm, and dried to form a second light absorption layer. The thickness of the second light absorbing layer was 90 nm in the pregroove and 60 nm in the land as measured by observing the cross section of the light absorbing layer by SEM. The transmittance of the second light absorption layer was 78%, and the absorption was 13%.

Next, the second sputtering was performed by DC sputtering.
A second barrier layer made of Au having a thickness of about 20 nm was formed on the light absorbing layer. At this time, the pressure in the chamber is 0.5
Pa. The transmittance of the second barrier layer was 41%, the absorption was 9%, and the reflectance was 50%.

Further, a UV curable resin (trade name “SD-318”, manufactured by Dainippon Ink and Chemicals, Inc.) is applied on the second barrier layer by spin coating while changing the rotation speed from 300 rpm to 4000 rpm. did. After the application, the coating was irradiated with ultraviolet light from a high-pressure mercury lamp to cure the coating, thereby forming a protective layer having a thickness of 8 μm. The surface hardness was 2H as the pencil hardness.

Thus, a laminate (2-1) in which the light absorbing layer, the barrier layer, and the protective layer were sequentially provided on the substrate was obtained.

The laminate (1) obtained above and the laminate (2-
1) and an ultraviolet-curable acrylate adhesive “XNR552” manufactured by Ciba-Geigy Co., Ltd. so that the thickness of the intermediate layer is 40 μm.
2 "to manufacture a DVD-R type optical disk according to the present invention.

Example 2 Instead of the laminate (2-1),
Under the following conditions, the reflective layer, the second light absorbing layer, the second
A laminated body in which a barrier layer and a protective layer are sequentially provided (2-
2) was produced.

A counter substrate made of polycarbonate (thickness:
0.6 mm, outer diameter: 120 mm, inner diameter: 15 mm, manufactured by Teijin Limited, trade name “Panlite AD5503”)
A reflective layer made of Au having a thickness of about 100 nm was formed by DC sputtering. At this time, the pressure in the chamber was 0.5 Pa.

Then, 1 g of the cyanine dye was added to 2,2,2
3,3-tetrafluoro-1-propanol 100 ml
And the coating solution for forming a light absorbing layer is applied to the pre-groove surface of the obtained substrate at a rotation speed of 300 to 3000 rpm.
The coating was applied by a spin coating method while being changed to the above, and dried to form a second light absorption layer. The thickness of the second light absorbing layer is
Observation and measurement of the cross section of the light absorbing layer by SEM showed that it was 90 nm in the pre-groove and 60 nm in the land. The transmittance of the second light absorption layer is 78%, and the absorption is 13
%Met.

Next, a second barrier layer of Au having a thickness of about 25 nm was formed on the reflective layer by DC sputtering. At this time, the pressure in the chamber was 0.5 Pa. The transmittance of the second barrier layer is 32%, and the absorption is 10
% And reflectance were 58%.

Further, a UV curable resin (trade name “SD-318”, manufactured by Dainippon Ink and Chemicals, Inc.) is applied on the second barrier layer by spin coating while changing the rotation speed from 300 rpm to 4000 rpm. did. After the application, the coating was irradiated with ultraviolet light from a high-pressure mercury lamp to cure the coating, thereby forming a protective layer having a thickness of 8 μm. The surface hardness was 2H as the pencil hardness.

The laminate (1) produced in Example 1 and the laminate (2-2) were overlapped so that the protective layer side was on the inside, and the thickness of the intermediate layer was set to 40 μm.・
Geigy's UV curable acrylate adhesive "XN
R5522 "and a DVD according to the present invention.
-An R type optical disk was manufactured.

[Evaluation as Optical Disk] Wavelength 635n
The recording / reproducing characteristics were evaluated using an optical recording / reproducing evaluator (DDU1000, manufactured by Pulstec Co., Ltd.) equipped with a pickup of m and NA of 0.6. Table 1 shows the results. 3.
Focus each layer at a constant linear speed of 9 m / sec, and increase the laser power by 0.5 m every 4 to 10 mW.
The recording was performed while changing the value every W. Recording signal is 1MHz
Was input. The degree of modulation was calculated from the amplitude of the reproduced signal from the recorded medium. The modulation degree is a value obtained by dividing the amplitude of the reproduction signal by a high level (reflectance of an unrecorded portion).

Table 1 First absorption layer modulation degree Second absorption layer modulation degree Example 1 45 35 Example 2 45 40

Comparative Example In Example 1, an attempt was made to form an intermediate layer on the first light-absorbing layer without forming a barrier layer. As a result, the light absorbing layer became transparent.

[0081]

According to the present invention, there is provided a one-side read-only write-once optical information recording medium having two light absorbing layers and capable of high-capacity recording.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a layer configuration of an optical information recording medium of the present invention.

FIG. 2 is a schematic sectional view illustrating a shape of a pregroove.

FIG. 3 is a schematic sectional view showing another layer configuration of the optical information recording medium of the present invention.

[Explanation of symbols]

 D Groove depth W Groove width 1 Substrate 2 First light absorbing layer 3 First barrier layer 4 Intermediate layer 5 Second barrier layer 6 Second light absorbing layer 7 Counter substrate 8 Reflecting layer

Claims (5)

[Claims] A first light-absorbing layer containing an organic dye and capable of recording information by irradiating a laser beam, and a light-transmitting intermediate layer between a substrate and a counter substrate facing the substrate; And a second light absorbing layer separated from the first light absorbing layer by the intermediate layer in this order, so that the first light absorbing layer and the first light absorbing layer are prevented from transmitting the substance from the intermediate layer to the first light absorbing layer. A light-transmissive first barrier layer that reflects a part of the laser light transmitted through the layer is inserted between the intermediate layer and the first light-absorbing layer, and from the intermediate layer to the second light-absorbing layer. A light-transmissive second barrier layer that reflects the laser light transmitted through the first light-absorbing layer while intercepting the material is inserted between the intermediate layer and the second light-absorbing layer; An optical information recording medium for recording and reproducing information by irradiating a laser beam from a substrate side close to a light absorbing layer. 2. The optical information recording medium according to claim 1, wherein the first barrier layer has a transmittance for recording light in a range of 30 to 95%. 3. The optical information recording medium according to claim 1, wherein the second barrier layer has a reflectance to recording light in a range of 10 to 90%. 4. A first light-absorbing layer containing an organic dye and capable of recording information by irradiating a laser beam, and a light-transmitting intermediate layer between a substrate and a counter substrate facing the substrate. And a second light absorbing layer separated from the first light absorbing layer by the intermediate layer in this order, so that the first light absorbing layer and the first light absorbing layer are prevented from transmitting the substance from the intermediate layer to the first light absorbing layer. A light-transmissive first barrier layer that reflects a part of the laser light transmitted through the layer is inserted between the intermediate layer and the first light-absorbing layer, and from the intermediate layer to the second light-absorbing layer. A light-transmitting second barrier layer that blocks the transmission of a substance is inserted between the intermediate layer and the second light-absorbing layer, and is adjacent to a surface of the second light-absorbing layer opposite to the substrate side. Optical information recording for recording and reproducing information by irradiating a laser beam from a substrate side close to the first light absorbing layer Body. 5. The optical information recording medium according to claim 4, wherein the second barrier layer has a transmittance for recording light in a range of 30 to 95%.