JPH113539A - Information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to stably maintain an adhesive state without allowing the peeling of a protective layer for a long time by forming a protective layer to the outer peripheral edge of a substrate, which protective layer completely covers a recording layer and a reflection layer. SOLUTION: Pregrooves 12 are formed to the outer peripheral edge of the substrate of the region exclusive of an inner peripheral side substrate region 14. The recording layer 13 is also disposed up to the outer peripheral edge of the substrate. The reflection layer 16 is formed to the outer peripheral edge on the recording layer, i.e., the substrate. Since the reflection layer is formed to the outer peripheral edge of the substrate, there is no need for using a mask and the problems, such as pickup of dust and generation of flaws, do not arise. The protective layer 17 to be formed on the surface of the reflection layer 16 is formed not only the reflection layer 16 but on the end face on the outer peripheral side of the substrate as well. The respective outer peripheral edges of the recording layer and the recording layer are thereby completely covered by the protective layer and, therefore, the peeling from the outer peripheral edge end (more specifically the boundary between the reflection layer and the recording layer or between the substrate and the recording layer) of the reflection layer when the medium is preserved for a long time or used for a long time is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording medium on which information can be recorded by a laser.

[0002]

2. Description of the Related Art In recent years, information recording media using a beam of high energy density such as laser light have been developed and put into practical use. DRAW (D
The direct read after write (optical) type optical disk has a disc-shaped transparent substrate made of plastic, glass, or the like, and a B-type optical disc provided thereon.
a recording layer made of a metal or semimetal such as i, Sn, In, Te or the like, or a dye. Writing of information to the optical disk is performed, for example, by irradiating the optical disk with a laser beam.

In order to record information on the optical disk, it is necessary to guide a laser beam applied to the disk to track the laser beam at a predetermined position. Therefore, generally, a spiral or concentric concave portion (groove) is formed on the substrate surface.
(Generally called a pre-groove).

When a dye is used as a material for the recording layer provided on the substrate having the pregroove, there is a great advantage in production that the recording layer can be formed by coating. However, in general, the dye recording layer is more likely to be deteriorated by light irradiation than the metal recording layer, and the deteriorated dye recording layer may not be able to be recorded. Further, the dye recording layer has a low reflectance, and in order to improve the reflectance, a reflection layer made of metal is generally provided on the recording layer. From the viewpoint of preventing the dye recording layer and the reflective layer from being damaged and preventing dust from adhering to the outside, a protective layer may be provided on the reflective layer (on the recording layer) or two optical discs may be used. 2. Description of the Related Art A sandwich structure bonded to face each other has been used.

[0005] An information recording medium comprising such a substrate, a dye recording layer, a metal reflective layer and a protective layer is disclosed, for example, in Nikkei Electronics (No. 465, issued January 23, 1989, p. 107).

In general, an optical disc having a recording layer and a protective layer provided on a substrate in this order has a shape as shown in a partial radial sectional view of FIG. Such a cross-sectional shape or the like is disclosed in JP-A-62-270036 and JP-A-1-276442. In FIG. 3, a pregroove 22 is formed in a region other than the inner peripheral substrate region 24 on the inner peripheral side and the outer peripheral substrate region 25 on the outer peripheral side of the disk-shaped substrate 21, and a recording layer is formed on the pregrave of the substrate. 23, and a protective layer 27 is provided on the recording layer and the outer peripheral side substrate region 25.

[0007] When the reflective layer is provided on the recording layer as in the optical disk described in the above-mentioned "Nikkei Electronics", the state in which the reflective layer is provided is not disclosed. It is presumed that the reflective layer is generally formed only on the recording layer as shown in the partial radial sectional view of FIG. 4, and the protective layer is formed from the reflective layer to the outer peripheral edge of the substrate. The optical disc shown in FIG. 4 has a recording layer 23 on a pre-groove 22 of a disc-shaped substrate 21.
Is formed thereon, a reflective layer 26 is formed thereon, and a protective layer 27 is provided on the recording layer and the outer peripheral side substrate region 25.

According to the studies made by the present inventors, an optical disk having a sectional structure as shown in FIG. 4 has a high reflectance. However, by providing a protective layer, a dye recording layer and a reflective layer or a substrate are provided. From the interface between the dye and the dye recording layer. That is, since the adhesiveness between the recording layer and the reflective layer is not sufficient, forming the protective layer tends to cause the reflective layer to be easily separated from the recording layer with the protective layer attached to the protective layer due to shrinkage of the resin or the like. .

[0009]

SUMMARY OF THE INVENTION In order to simplify the manufacturing process, the present inventors have applied a dye recording layer to the vicinity of the outer peripheral edge of a substrate by a spin coating method, and a reflective layer also has a function of shielding the outer peripheral portion of the substrate. Without using a mask for the outer periphery of the above, on the dye layer, that is, on the optical disk having a protective layer formed on the outer peripheral edge of the substrate, or on a substrate provided with a pre-groove up to the outer peripheral edge of the substrate for enlarging the recording area. Examination of an optical disc having three stacked layers revealed that there was almost no portion where the protective layer was in direct contact with the substrate, and that the adhesion of the protective layer as described above was further reduced.

Accordingly, an object of the present invention is to provide an information recording medium which can maintain good recording / reproducing characteristics for a long period of time and has excellent durability. Another object of the present invention is to provide an information recording medium having high reflectivity and excellent durability which can maintain good recording / reproducing characteristics for a long period of time. Another object of the present invention is to provide an information recording medium having a wide recording area and excellent durability, which can maintain good recording / reproducing characteristics for a long period of time.

[0011]

SUMMARY OF THE INVENTION The present invention is directed to a method of writing information by a laser on a disc-shaped substrate having a hole at the center and a pre-groove for tracking on the surface of the disc-shaped substrate. Mg, Se, Y, Ti, Zr, Hf, V, N
b, Ta, Cr, Mo, W, Mn, Re, Fe, Co,
Ni, Ru, Rh, Pd, Ir, Cu, Zn, Cd, A
1, Ga, In, Si, Ge, Te, Pb, Po, S
n, and a reflective layer containing at least one metal or metalloid selected from Bi and a protective layer made of a cured product of an ultraviolet curable resin are formed in this order on the information recording medium, the reflective layer and the dye recording And the protective layer is continuously formed up to the outer peripheral edge of the substrate, and the protective layer is formed on the outer peripheral end surface of the reflective layer, the outer peripheral end surface of the recording layer, and the outer peripheral end surface of the substrate. An information recording medium characterized by being provided continuously.

Preferred embodiments of the information recording medium of the present invention are as follows. 1) The information recording medium as described above, wherein the pre-groove is provided up to an outer peripheral edge of the substrate or in the vicinity thereof. 2) The information recording medium as described above, wherein the protective layer is provided on the entire outer peripheral end surface of the substrate. 3) The information recording medium, wherein the protective layer is colored.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An information recording medium according to the present invention has a recording layer on which information can be written by a laser, a reflective layer made of metal, and a recording medium on a disc-shaped substrate provided with a tracking pregroove. The protective layer has a basic structure provided in this order. The information recording medium of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a plan view showing the basic structure of an information recording medium according to the present invention.
3, an inner peripheral side substrate region of the inner peripheral portion of the substrate (exposed region of the substrate on which the recording layer is not provided) 14, a reflective layer 16 provided on the recording layer 13, and a protective layer provided on the reflective layer 1
7 is a plan view of an optical disk (information recording medium) made of No. 7 viewed from a recording layer side.

FIG. 2 shows a half on the right side of the center of the II sectional view of FIG. FIG. 2 shows a pre-groove 12 and a recording layer 1 on a disc-shaped substrate 11 having a central hole 10.
3, there is shown an optical disk in which a reflective layer 16 and a protective layer 17 are provided, and an inner peripheral side substrate area (exposed area of a substrate not provided with a recording layer) 14 is set in an inner peripheral portion of the substrate.

In the optical disk shown in FIG.
2 is formed in an area other than the inner peripheral substrate area 14.
The pre-groove is formed up to the outer peripheral edge of the substrate, and the recording layer 13 is also provided up to the outer peripheral edge of the substrate. Thereby, the enlargement of the recording area is realized. Of course, the pre-groove need not be provided up to the outer peripheral edge of the substrate (see FIG. 4 attached). The reflection layer 16 is formed on the recording layer, that is, up to the outer peripheral edge of the substrate. The reflective layer is generally formed by sputtering metal, vacuum deposition, or the like. In the present invention, since the reflective layer is formed up to the outer peripheral edge of the substrate, there is no need to use a mask, so that problems such as adhesion of dust and generation of scratches do not occur, and the number of mask mounting steps is reduced. be able to. Protective layer 1 provided on surface of reflective layer 16
7 is provided not only on the reflective layer 16 but also on the end face on the outer peripheral side of the substrate. For this reason, since the outer peripheral edge of each of the recording layer and the reflective layer is completely covered with the protective layer, the outer peripheral edge of the reflective layer during long-term storage or long-term use (particularly, the reflective layer and the recording layer or the substrate and the recording layer). (Layer interface) can be prevented. Further, by providing the protective layer in this manner, the protective layer is strongly adhered to the outer peripheral end surface of the substrate, so that separation between the reflective layer and the recording layer does not occur. Therefore, it is possible to form a protective layer of a UV-curable resin having high hardness, excellent durability, and high productivity without causing peeling, and therefore, the protective layer can sufficiently form the recording layer as described above. Since the optical disk is formed in a protected form, an optical disk having excellent durability can be obtained.

The formation position of the protective layer on the inner peripheral side of the substrate may be only on the recording layer, but it is preferable that the protective layer be provided on the inner peripheral surface of the substrate beyond the inner peripheral line of the recording layer as shown in FIG. preferable.

The information recording medium of the present invention can be manufactured by using, for example, the following materials.

The substrate used in the present invention can be arbitrarily selected from various materials used as conventional substrates for information recording media. Examples of substrate materials include:
Glass, acrylic resin such as polymethyl methacrylate,
Examples thereof include polyvinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymer, epoxy resins, polycarbonate resins, amorphous polyolefins and polyesters. Preferably, polycarbonate, polyolefin, and polymethyl methacrylate are used in view of the optical properties, flatness, workability, handleability, stability over time, and production cost of the substrate.

On the substrate, a pre-groove or a pre-groove or a pre-pit may be provided for the purpose of forming irregularities representing information such as tracking grooves or address signals. When the substrate material is plastic, it is preferable to form a pregroove or the like directly on the substrate by injection molding or extrusion molding. Alternatively, the pre-groove may be formed by providing a pre-groove layer on the substrate. As a material for the pregroove layer and the like, 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 pregrave layer is formed by first applying a mixed solution comprising the above-mentioned allylic ester and a polymerization initiator on a precisely formed master (stamper), and then placing a substrate on the coating solution layer. Then, the liquid layer is cured by irradiating ultraviolet rays through the substrate or the matrix to fix the substrate and the cured liquid layer. Next, the substrate provided with the pre-groove layer is obtained by peeling the substrate from the matrix. 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.

On the substrate (or pre-groove layer etc.)
A recording layer made of a dye is provided. This dye recording layer is
It is formed on the surface of the substrate up to the outer peripheral edge. Dyes used in the recording layer of the information recording medium of the present invention include, for example, indolenine dyes, imidazoquinoxaline dyes, cyanine dyes such as indolizine dyes, phthalocyanine dyes, pyrylium / thiopyrylium dyes, azurenium Dyes, squarylium dyes, metal complex dyes such as Ni and Cr, naphthoquinone / anthraquinone dyes, indophenol dyes, indoaniline dyes,
Triphenylmethane dye, triallylmethane dye,
Examples include merocyanine dyes, oxonol dyes, aminium / diimmonium dyes, and nitroso compounds.

The dye layer is formed by dissolving the above dye and, if desired, a binder, a metal complex salt dye or an aminium / diimmonium dye (quencher) in a solvent to prepare a coating solution. It can be carried out by applying the composition on the substrate surface to form a coating film and then drying.

Solvents for preparing the dye coating solution include esters such as ethyl acetate, butyl acetate and cellosolve acetate; ketones such as methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone;
Halogenated hydrocarbons such as 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; Fluorinated solvents such as tetrafluoropropanol can be exemplified. In addition, these non-hydrocarbon organic solvents,
As long as the content is within 50% by volume, a hydrocarbon solvent such as an aliphatic hydrocarbon solvent may be contained.

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.

When the binder is used, examples of the binder include natural derivatives of gelatin, nitrocellulose, cellulose derivatives such as cellulose acetate, dextran, rosin, rubber and the like, and polyethylene, polypropylene, polystyrene, polyisobutylene. Such as hydrocarbon resins, polyvinyl chloride, polyvinylidene chloride, vinyl resins such as vinyl chloride / vinyl acetate copolymer, acrylic resins such as polymethyl acrylate and polymethyl methacrylate, polyvinyl alcohol, chlorinated polyolefin, Synthetic organic polymer substances such as an epoxy resin, a butyral resin, a rubber derivative, and an initial polymer of a thermosetting resin such as a phenol / formaldehyde resin can be given.

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.

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

The dye layer may be a single layer or a multilayer, and the layer thickness is generally in the range of 100 to 5500 angstroms, preferably in the range of 200 to 3000 angstroms.

An intermediate layer made of chlorinated polyolefin, nitrocellulose or fluororesin may be provided between the recording layer and the substrate.

A reflective layer is provided on the recording layer. The reflection layer is a layer containing a light-reflective substance, and is composed of Mg, Se, Y, T
i, Zr, Hf, V, Nb, Ta, Cr, Mo, W, M
n, Re, Fe, Co, Ni, Ru, Rh, Pd, I
r, Cu, Zn, Cd, Al, Ga, In, Si, G
It is a layer containing at least one metal or metalloid selected from e, Te, Pb, Po, Sn, and Bi. The reflective layer is formed, for example, by vapor deposition, sputtering or ion plating of one or more of these light-reflective substances.
Can be formed on the substrate. The thickness of the reflective layer is generally in the range of 100-3000 Å.

The reflection layer of the present invention is formed up to the outer peripheral edge of the substrate. Therefore, metal sputtering on the substrate on which the recording layer is formed does not use a mask for outer periphery (used to prevent a reflective layer from being provided on the outer periphery of the substrate), and is 0.01 to 0 mm from the outer diameter of the substrate. It is performed in a state of being fitted into a dish-shaped mounting recess of a plate-shaped mounting base having a thickness of about 0.5 mm and a depth not less than the thickness of the substrate and not more than three times the thickness. Thus, the metal layer can be formed on the outer peripheral edge of the substrate, and can be prevented from being formed on the outer peripheral end surface of the substrate. Therefore, there is an advantage that the problem of adhesion of dust due to the attachment and detachment of the outer peripheral mask does not occur, and the manufacturing is facilitated by reducing the number of mask attaching steps.

On the reflective layer, a protective layer made of an ultraviolet curable resin is provided. As the ultraviolet-curable resin, those conventionally used can be used. It is known to use an ultraviolet-curable resin for a protective layer of an optical disk, and is described in, for example, Japanese Patent Publication No. 63-43333.

UV-curable resins include monomers and oligomers having a polymerizable double bond as exemplified below,
And a photopolymerization initiator. (A) Aliphatic, alicyclic and aromatic di- to hexavalent polyhydric alcohols and poly (meth) acrylates of polyalkylene glycols (b) Aliphatic, alicyclic and aromatic di- to hexavalent polyhydric alcohols Poly (meth) acrylate of polyhydric alcohol in the form of alkylene oxide added to polyhydric alcohol (c) poly (meth) acryloyloxyalkyl phosphate ester (d) polyester poly (meth) acrylate (e) epoxy poly (meth) Acrylate (f) Polyurethane poly (meth) acrylate (g) Polyamide poly (meth) acrylate (h) Polysiloxane poly (meth) acrylate (i) Vinyl based having a (meth) acryloyloxy group at a side chain and / or terminal Diene-based low polymer (j) Modified product of the crosslinkable monomer described in (a) to (i) above

These oligomers and monomers (monofunctional vinyl compounds) can be used alone or in an appropriate mixture depending on the adherend, the disk structure and the like.

The photopolymerization initiator is necessary for curing with ultraviolet rays (not required in the case of electron beam curing). Derivatives and benzaldehyde derivatives. Specific examples of the compound that can be used as a sensitizer include benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzophenone, benzyl, 2,2-dimethoxy-2-phenylacetophenone, 2,2- Dimethoxy-2-hydroxyacetophenone, diphenyl disulfide, 2-hydroxy-2-propiophenone, 4,4'-bisdiethylaminobenzophenone, dimethylaminobenzaldehyde, ethyl-
4,4'-bisdimethylaminobenzophenone, ethylanthraquinone, 2-chlorothioxanthone and the like can be mentioned. These sensitizers can be used alone or in an appropriate combination.

In the present invention, a coating solution is prepared by directly dissolving the above-mentioned UV-curable resin or by dissolving it in an organic solvent. The coating solution is applied on the reflective layer and the outer peripheral end surface of the substrate. Then, a protective layer is provided. The protective layer may be colored to improve light resistance. As the coloring agent, an inorganic pigment, an organic pigment, a dye, or the like can be used.

Various additives such as an organic solvent, an antistatic agent, an antioxidant, and a UV absorber may be further added to the coating liquid for forming a protective layer comprising the above-mentioned UV-curable resin according to the purpose. . Spin coating, dip coating,
It can be formed by applying to the substrate surface by an application method such as extrusion coating (after drying when an organic solvent is contained), and then irradiating with ultraviolet light to cure.

When the above coating solution is cured with ultraviolet light,
Using a high-pressure mercury lamp or the like, the coating layer is irradiated with ultraviolet rays from a distance of 1 to 100 cm for 0.1 to 60 seconds to cure the coating layer, thereby forming an anti-reflection layer.
In the case of curing with an electron beam, the curing is performed using an electron accelerator such as a linear accelerator or a handicap accelerator. When curing a protective layer having a low transmittance, electron beam irradiation is more advantageous for sufficiently performing internal curing.

The thickness of the protective layer is generally 0.01 to 50 μm.
m, preferably 0.1 to 20 μm, particularly preferably 0.1 μm.
The range is 5 to 20 μm. Further, the thickness of the protective layer on the outer peripheral end face of the substrate is preferably 1 μm or more, and particularly preferably in the range of 2 to 50 μm.

In manufacturing the information recording medium of the present invention,
The protective layer is formed not only on the substrate surface but also on the outer peripheral end surface of the substrate. Therefore, by applying and drying by the following method, the substrate surface and the outer peripheral end surface can be simultaneously applied, which is preferable.

The substrate on which the dye recording layer and the reflective layer are formed is mounted on a spinner, and a coating liquid for forming a protective layer (having a viscosity of preferably 1 to 100 cps at the temperature at the time of coating and containing an organic solvent, Organic solvent content of 80% by weight or less)
Is discharged from the spinner, and the substrate is rotated at 100 to 100 rpm.
Coating is started while rotating at a speed of 300 rpm, and 3
The coating is completed by maintaining the coating speed for 10 seconds to 10 seconds, and the rotation speed is increased in 0.1 to 60 seconds to a final rotation speed of 1000 to 2500 rpm. Thereby, the protective layer can be applied to the recording layer and the outer peripheral end surface of the substrate. Then, the protective layer can be formed by immediately irradiating the coating layer with ultraviolet rays.

The protective layer of the information recording medium of the present invention may contain other resins besides the above-mentioned ultraviolet curable resin within a range not to impair the object of the present invention. In general, the surface is easily damaged and the protection effect is easily reduced.

The protective layer of the information recording medium of the present invention is provided on the surface of the substrate and the outer peripheral end face, and on the reflective layer. Therefore, a protective layer can be formed, and the present invention can be applied to any information recording medium as long as the effect can be obtained.
Such an information recording medium can be applied to any type of medium, such as a read-only type, a write-once (DRAW) type, a rewritable type, and a magneto-optical type, irrespective of the type of the recording layer, such as recordable or unrecordable. .

Recording on the information recording medium of the present invention is performed, for example, as follows. First, while rotating an information recording medium (optical disc) at a constant linear velocity or a constant angular velocity, a recording light such as a semiconductor laser beam is irradiated onto the groove of the pre-groove from the substrate side, and the EFM of the CD format is performed.
A signal such as a signal is recorded by forming various shape changes (cavities at the interface between the dye recording layer and the reflective layer, projections on the substrate surface, etc.) in the recording layer of the groove. In general,
As the recording light, a semiconductor laser beam having an oscillation wavelength in the range of 750 to 850 nm is used. In general, recording is performed with a laser power of 1 to 15 mW.

At the time of recording, tracking control by push-pull or the like is performed using the tracking pre-groove. Recording of information is performed on the pre-groove grooves or lands between the grooves.

The information is reproduced by, for example, irradiating a laser beam such as a semiconductor laser from the substrate side while rotating the recording medium at the same constant linear velocity or constant angular velocity as described above, and detecting the reflected light. Information can be reproduced while performing tracking control by a method or the like.

[0048]

According to the information recording medium of the present invention, the recording layer and the reflective layer provided thereon are both formed up to the outer peripheral edge of the substrate, and the protective layer is provided up to the outer peripheral surface of the substrate. Since the protective layer thus formed completely covers the recording layer and the reflective layer, peeling at the interface between the reflective layer and the recording layer, which is likely to occur by forming the protective layer, or the separation between the recording layer and the substrate. No peeling at the interface. For this reason,
The protective layer can stably maintain the adhered state without peeling for a long time.

Further, since the reflective layer is formed up to the outer peripheral edge of the substrate, it is not necessary to use a mask at the time of vapor deposition such as sputtering, so that problems such as attachment of dust and generation of scratches due to attachment and detachment of the mask also occur. And the number of mask mounting steps can be reduced.

Accordingly, it is possible to obtain an information recording medium having a high reflectivity and excellent durability which can maintain good recording / reproducing characteristics for a long period of time.

[Brief description of the drawings]

FIG. 1 is an example of a plan view showing a basic configuration of an information recording medium of the present invention.

FIG. 2 shows a basic configuration of the information recording medium of the present invention.
FIG.

FIG. 3 is an example of a cross-sectional view of a conventional information recording medium.

FIG. 4 is another example of a cross-sectional view of a conventional information recording medium.

[Explanation of symbols]

 10, 20 hole portion 11, 21 substrate 12, 22 pregroove 13, 23 recording layer 14, 24 inner peripheral side substrate region 25 outer peripheral side substrate region 16, 26 reflective layer 17, 27 protective layer 18, substrate outer peripheral end surface

Claims (1)

[Claims] 1. A recording layer made of a dye to which information can be written by a laser, and a light-reflective substance on a disc-shaped substrate having a hole in the center and having a pre-groove for tracking on its surface. As Mg, Se, Y,
Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W,
Mn, Re, Fe, Co, Ni, Ru, Rh, Pd, I
r, Cu, Zn, Cd, Al, Ga, In, Si, G
e, Te, Pb, Po, Sn, and an information recording medium in which a reflective layer containing at least one metal or semimetal selected from Bi, and a protective layer made of a cured product of an ultraviolet curable resin are formed in this order. The reflective layer and the dye recording layer are continuously formed up to the outer peripheral edge of the substrate, and the protective layer is formed on the outer peripheral end face of the reflective layer and the outer peripheral end face of the recording layer from above the reflective layer. An information recording medium characterized by being provided continuously to the outer peripheral end surface of the substrate.