JPH0419838A - Information recording medium - Google Patents

Abstract

PURPOSE:To improve durability by continuously providing a reflecting layer from above a recording layer to the outer peripheral edge of a substrate and continuously providing a protective layer from above the reflecting layer to the outer peripheral end face of the substrate. CONSTITUTION:The reflecting layer 16 is formed on the recording layer 13, i.e. up to the outer peripheral edge of the substrate 11 and there is no need for using a mask. The generation of troubles, such as sticking of dust and generation of flaws, is thereby obviated and the stage for mounting a mask is saved. The protective layer 17 to be provided on the reflecting layer 16 is provided not only on the reflecting layer 16 but on the end face on the outer peripheral side of the substrate 11 as well. Since the outer peripheral edge of the reflecting layer 16 is completely coated with the protective layer 17 in such a manner, the peeling from the end at the outer peripheral edge of the reflecting layer 16 (particularly the boundary between the reflecting layer 16 and the recording layer 13 or between the substrate 11 and the recording layer 13) at the time of long-term preservation or long-term use is prevented. The optical disk having the excellent durability is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to an information recording medium on which information can be recorded using a laser.

[Technical Background of the Invention] In recent years, information recording media using high energy density beams such as laser light have been developed and put into practical use. Information can be written in RAW (Direct
The basic structure of the Read After Write (Read After Write) type optical disk is a disc-shaped transparent substrate made of plastic, glass, etc., and Bi, Sn, and I
It has a recording layer made of a metal or semimetal such as n, Te, or a dye. Writing information to an optical disc is
For example, this is done by irradiating the optical disc with a laser beam.

In order to record information on the optical disc, it is necessary to guide a laser beam irradiated onto the disc and track it to a predetermined position. For this reason, groups (generally called pregrooves) of spiral or concentric recesses (grooves) are generally formed on the surface of the substrate.

When a dye is used as the material for the recording layer provided on the substrate having the pregrooves, there is a great manufacturing advantage in that the recording layer can be formed by coating. However, in general, a dye recording layer is more easily degraded by light than a metal recording layer, and a degraded dye recording layer may become unable to record. Further, the dye recording layer has a low reflectance, and in order to improve the reflectance, a reflective layer made of metal is generally provided on the recording layer.

In order to prevent the dye recording layer and the reflective layer from being scratched and to prevent dust from adhering to them from the outside world, a protective layer is provided on the reflective layer (on the recording layer) or two optical discs are placed so that the reflective layers face each other. A sandwich structure is being used in which the materials are bonded together to create a sandwich structure.

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, published January 23, 1989, p. 107). Although such optical disks have a high reflectance, there is a problem that the protective layer is easily peeled off from the interface between the dye recording layer and the reflective layer or between the substrate and the dye recording layer.

Generally, an optical disk in which a recording layer and a protective layer are provided in this order on a substrate has a shape as shown in the radial partial cross-sectional view of FIG. Such cross-sectional shapes or similar ones are disclosed in Japanese Patent Application Laid-Open Nos. 62-270036 and 1-276442.

In FIG. 3, the pregroove 22 is formed in an area other than the inner substrate area 24 on the inner circumference side and the outer circumference side substrate area 25 on the outer circumference side of the disc-shaped substrate 2, and recording is performed on the pregroove of the substrate. A layer 23 is formed, and a protective layer 27 is further provided on the recording layer and the outer substrate region 25. When a reflective layer is provided on the recording layer as in the optical disc described in Nikkei Electronics, it is not disclosed in what condition it is provided, but according to the analysis of the present inventors, the radius shown in FIG. As shown in the partial cross-sectional view, it has become clear that the reflective layer is generally formed only on the recording layer, and the protective layer is formed on the reflective layer and on the outer peripheral portion of the substrate. The optical disc shown in FIG.
A recording layer 23 is formed on one pre-groove 22, a reflective layer 26 is formed thereon, and a protective layer 27 is further provided on the recording layer and the outer substrate region 25.

According to studies conducted by the present inventors, an optical disc having a cross-sectional structure as shown in FIG. 4 has insufficient adhesion between the recording layer and the reflective layer as described above. It has become clear that the reflective layer tends to peel off from the recording layer while attached to the protective layer due to the shrinkage of the protective layer.

[Object of the Invention] In order to simplify the manufacturing process, the present inventors applied a dye recording layer to the vicinity of the outer periphery of the substrate by a spin code method.
The reflective layer is also provided on the dye layer without using a mask for the outer periphery of the substrate, that is, up to the outer periphery of the substrate, and on optical discs with a protective layer formed on it, or up to the outer periphery of the substrate to expand the recording area. When examining an optical disk in which the three layers described above were laminated on a substrate provided with pregrooves, it was found that the portion where the protective layer directly contacts the substrate is almost eliminated, further reducing the adhesion of the protective layer as described above.

Therefore, an object of the present invention is to provide an information storage medium with durability that allows good recording and reproducing characteristics to be maintained over a long period of time.

Another object of the present invention is to provide an information recording medium that has high reflectance and excellent durability and can maintain good recording and reproducing characteristics over a long period of time.

A further object of the present invention is to provide a highly durable information recording medium that has a wide recording area and can maintain good recording and reproducing characteristics over a long period of time.

[Summary of the Invention] The present invention provides a disc-shaped substrate having a hole in the center and a tracking pregroove on the surface thereof, and a recording layer made of a dye on which information can be written by a laser; In an information recording medium in which a reflective layer made of a metal and a protective layer made of a cured product of an ultraviolet curable resin are provided in this order, the reflective layer is provided continuously from above the recording layer to the outer periphery of the substrate. The information recording medium is characterized in that the protective layer is provided continuously from the reflective layer to the outer peripheral end surface of the substrate.

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

1) The information recording medium described above, wherein the pregroove is provided up to or near the outer periphery of the substrate.

2) The information recording medium described above, wherein the recording layer and the reflective layer are provided up to or near the outer periphery of the substrate.

3) The information recording medium described above, wherein the protective layer is provided over the entire outer peripheral end surface of the substrate.

4) The information recording medium, wherein the protective layer is colored.

[Effects of the Invention] In the information recording medium of the present invention, the reflective layer provided on the recording layer is formed up to the outer peripheral edge of the substrate as described above, and the protective layer is provided up to the outer peripheral end face of the substrate. The protective layer formed in this way completely covers the recording layer and the reflective layer, so it does not cause peeling at the interface between the reflective layer and the recording layer or the separation between the recording layer and the substrate, which is likely to occur due to the formation of the protective layer. No peeling occurs at the interface. Therefore, the protective layer can remain attached for a long period of time without peeling off.

In addition, since the reflective layer is formed up to the outer edge of the substrate, there is no need to use a mask during vapor deposition such as sputtering, so there are no problems such as dust adhesion or scratches caused by attaching or removing the mask. Moreover, the number of steps required for attaching the mask can be reduced.

Therefore, it is possible to obtain a highly durable information recording medium that has a high reflectance and can maintain good recording and reproducing characteristics over a long period of time.

[Detailed Description of the Invention] The present invention provides a disc-shaped substrate provided with a tracking pregroove, and a recording layer on which information can be written by a laser, a reflective layer made of metal, and a protective layer are provided on the pregroove. , has a basic configuration provided in this order.

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

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

FIG. 1 shows a central hole 10, a recording layer 13, an inner substrate area (exposed area of the substrate where no recording layer is provided) 14, and a reflective layer provided on the recording layer 13. layer 16
FIG. 2 is a plan view of an optical disc, viewed from the recording layer side, which includes a protective layer 17 provided on a reflective layer.

FIG. 2 shows the right half of the 1-1 sectional view of FIG. 1 from the center.

In FIG. 2, a pregroove 12, a recording layer 13, a reflective layer 16, and a protective layer 17 are provided on a disk-shaped substrate 11 having a central hole 10, and an inner substrate area ( Exposed areas of the substrate where no recording layer is provided)! 4 is shown.

In the above optical disc, the pregroove 12 is formed in an area other than the inner circumference 1 substrate area 14. The pre-croup is formed up to the outer periphery of the substrate, and the recording layer 13 is also formed above the outer periphery of the substrate. The stiffness allows the recording area to be expanded. Of course, the pregroove does not have to be provided all the way to the outer periphery of the substrate (for example, as shown in FIG. 4). The reflective layer 16 is formed on the recording layer, that is, on the outer peripheral edge of the substrate. The reflective layer is generally formed of metal by sputtering, vacuum deposition, or the like. In the present invention, since the reflective layer is formed up to the outer periphery of the substrate, there is no need to use a mask, so problems such as dust adhesion and scratches do not occur.
Moreover, the number of steps required for attaching the mask can be reduced. The protective layer 17 provided on the reflective layer 16 is provided not only on the reflective layer 16 but also on the end face on the outer peripheral side of the substrate.

Therefore, since the outer periphery of the reflective layer is completely covered by the protective layer, the outer periphery of the reflective layer (particularly the interface between the reflective layer and the recording layer or the substrate and the recording layer) during long-term storage or long-term use. can prevent peeling. Furthermore, by providing the protective layer in this manner, the protective layer is strongly adhered to the outer circumferential end surface of the substrate, thereby eliminating the occurrence of peeling between the reflective layer and the recording layer. Therefore, it is possible to form a protective layer of ultraviolet curable resin with high hardness, excellent durability, and high productivity without causing peeling, and the protective layer sufficiently protects the recording layer as described above. Since the optical disk is formed in a circular shape, it is possible to obtain an optical disk with excellent durability.

The protective layer may be formed only on the recording layer, but as shown in FIG. 2, it is preferable to form the protective layer on the inner surface of the substrate beyond the inner peripheral edge of the recording layer.

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

The substrate used in the present invention can be arbitrarily selected from various materials used as substrates for conventional information recording media. Examples of substrate materials include glass, acrylic resins such as polymethyl methacrylate; vinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymers; epoxy resins; polycarbonate resins, amorphous polyolefins, and polyesters. Preferably, polycarbonate, polyolefin, and polymethyl methacrylate are used from the viewpoint of substrate optical properties, flatness, processability, handleability, stability over time, manufacturing cost, and the like.

Pre-grooves or pre-grooves and pre-pits may be provided on the substrate for the purpose of forming tracking grooves or unevenness representing information such as address signals. When the substrate material is plastic, it is preferable to form pregrooves directly on the substrate by injection molding, extrusion molding, or the like.

Alternatively, by providing a pre-groove layer on the substrate,
A pre-groove may also be formed. Materials for the pre-groove layer include acrylic acid monoester, diester,
A mixture of at least one triester (or oligomer) of triesters and tetraesters and a photopolymerization initiator can be used.

The pre-groove layer was formed by first coating a mixture of the above acrylic acid ester and polymerization initiator on a densely prepared matrix, and then placing the substrate on top of this coating solution layer. Thereafter, the liquid layer is cured by irradiation with ultraviolet rays through the substrate or the matrix, thereby fixing the substrate and the liquid phase.

Next, by peeling the substrate from the mother mold, a substrate provided with a pregroove layer is obtained. The thickness of the pregroove layer is generally in the range of 0.05 to 100 μm, preferably in the range of 0.1 to 50 μm.

A recording layer made of a dye is provided on the substrate (or pregroove layer, etc.).

The dyes used in the present invention include, for example, cyanine dyes such as indolenine dyes, imidazoquinoxaline dyes, and indolizine dyes, phthalocyanine dyes, biryllium/thiopyrylium dyes, azulenium dyes,
Squalilium dyes, metal complex dyes with Ni and Cr, naphthoquinone/anthraquinone dyes, indophenol dyes, indoaniline dyes, triphenylmethane dyes, triallylmethane dyes, merocyan dyes, oxonol dyes Mention may be made of dyes, aminium-based and diimmonium-based dyes, and nitroso compounds.

Formation of the dye layer involves adding the above dye, optionally a binder,
Dissolving a metal complex dye or aminium/diimmonium dye (quencher) in a solvent to prepare a coating solution, then applying this coating solution to the substrate surface to form a coating film, and then drying. It's coming.

Examples of the solvent for preparing the dye coating solution include esters such as ethyl acetate, butyl acetate, and cellosolve acetate, ketones such as methyl ethyl ketone, cyclohexanone, and methyl isobutyl ketone, halogenated hydrocarbons such as dichloromethane, 1,2-dichloroethane, and chloroform; Ethers such as tetrahydrofuran, ethyl ether, dioxane, alcohols such as ethanol, n-propanol, impropanol, n-butanol, amides such as dimethylformamide, fluorocarbons such as 2.2.3.3-tetrafluoropropanol, etc. Examples include solvents. Note that these non-hydrocarbon organic solvents may contain hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents, as long as the amount is within 50% by volume. .

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

When a binder is used, examples of the binder include cellulose derivatives such as gelatin, nitrocellulose, and cellulose acetate; natural organic polymeric substances such as dextran, rosin, and rubber; and carbonized materials such as polyethylene, polypropylene, polystyrene, and polyisobutylene. Hydrogen resins, vinyl resins such as polyvinyl chloride, polyvinylidene chloride, polyvinyl chloride/polyvinyl acetate copolymers, acrylic resins such as polymethyl acrylate, polymethyl methacrylate,
Examples include synthetic organic polymeric substances such as polyvinyl alcohol, chlorinated polyolefins, epoxy resins, butyral resins, rubber derivatives, and initial condensates of thermosetting resins such as phenol/formaldehyde resins.

Examples of the coating method include a spray method, a spin code method, a dip method, a roll coat method, a blade coat method, a doctor roll method, and a screen printing method.

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

The dye layer may be a single layer or a multilayer, but its layer thickness is generally in the range of 100 to 5,500 mm, preferably 200 mm.
It is in the range of ~3000.

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 light-reflective substance that is the material of the reflective layer is a substance that has a high reflectance to laser light, and examples thereof include Mg, Se,
, Y, Ti, Zr, Hf%V, Nb, Ta, Cr, M
o, W, Mn, Re.

Fe, Co, Ni, Ru, Rh, Pd, 1r, Pt, C
u, Ag, Au% Zn, Cd, , Al1, Ga, In
, Si%Ge, Te, Pb, Po, Sn, Bi, and other metals and semimetals. Among these, preferred are Al1, Au, Cr and Ni.

These substances may be used alone, or in combination of two or more or as an alloy.

The reflective layer can be formed on the substrate by, for example, vapor deposition, sputtering, or ion-blating the light-reflecting material described above. The thickness of the reflective layer is generally in the range of 100 to 3000 mm.

The reflective layer of the present invention is formed up to the outer periphery of the substrate. Therefore, sputtering metal onto the substrate on which the recording layer is formed does not use a mask for the outer periphery (used to avoid providing a reflective layer on the outer periphery of the substrate),
．． This is carried out in a state in which the substrate is fitted into a recess of a dish-shaped mounting table that is approximately 0.1 to 0.5 mm larger and has a depth that is greater than or equal to the thickness of the substrate and less than or equal to 3 times the thickness of the substrate. This allows the metal layer to be formed on the outer periphery of the substrate and not on the outer periphery end surface of the substrate. Therefore, the problem of dust adhesion due to attaching and removing the outer circumferential mask does not occur, and there is an advantage that manufacturing is facilitated by reducing the number of steps for attaching the mask.

A protective layer made of an ultraviolet curable resin is provided on the reflective layer.

As the ultraviolet curable resin, those conventionally used can be used. The use of ultraviolet curable resins in protective layers of optical discs is known, and is described, for example, in Japanese Patent Publication No. 63-42333.

The above-mentioned ultraviolet curable resin is composed of a polymer having a polymerizable double bond, an oligomer, a photopolymerization initiator, and the like.

Examples of the polymers and oligomers having polymerizable double bonds include the following (meth)acrylates (a) to (j).

(a) Poly(meth)acrylates of aliphatic, cycloaliphatic and aromatic polyhydric alcohols and polyalkylene gelicols; for example, ethylene glycol, propylene glycol, 1
, 3- or 1,4-butanediol, hexanediol, neopentyl glycol, cyclohexanediol, trimethylolethane, trimethylolpropane, glycerin, sorbitol, pentaerythritol, dipentaerythritol, hydrogenated bisphenol A and other polyhydric alcohols; Examples include poly(meth)acrylates of polyhydric alcohols such as diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, and the like.

(b) Poly(meth)acrylates of polyhydric alcohols in the form of aliphatic, alicyclic, and aromatic polyhydric alcohols with 2 to 6 slightly added alkylene oxides; for example, bisphenol A dioxyethyl ether, etc. Examples include poly(meth)acrylates of polyhydric alcohols obtained by adding ethylene oxide or propylene oxide to polyhydric alcohols such as trimethylolpropane, pentaerythritol, glycerin, and bisphenol A.

(C) Poly(meth)acryloyloxyalkyl phosphate ester; Obtained by reaction of hydroxyl group-containing (meth)acrylate with phosphorus pentoxide, such as poly(meth)acryloyloxyethyl phosphate, poly(meth)acryloyloxy Examples include propyl phosphate.

(d) Polyester poly(meth)acrylate; Polyester poly(meth)acrylate is usually (meth)
It is synthesized by esterifying acrylic acid, polyhydric alcohol, and polyhydric carboxylic acid. It is assumed that poly(meth)acrylate, which is a polyester type polyhydric alcohol, is the main component.

For example, di(meth)acrylate of polyester diol of succinic acid and ethylene glycol, di(meth)acrylate of polyester diol of maleic acid and ethylene glycol
Acrylate, di(meth)acrylate of polyester diol with phthalic acid and diethylene glycol, poly(meth)acrylate of polyester diol with adipic acid and triethylene glycol, poly(meth)acrylate of polyester polyol with tetrahydrophthalic acid and trimethylolpropane Examples include acrylate, poly(meth)acrylate of polyester polyol of tetrahydrophthalic acid and pentaerythritol, and the like. Among these polyester poly(meth)acrylates, when using aliphatic or alicyclic polycarboxylic acid-based polyester poly(meth)acrylates rather than aromatic polycarboxylic acid-based ones such as phthalic acid, This has the advantage that the cross-linked cured product has better physical properties such as unicompatibility and toughness.

(e) Epoxy poly(meth)acrylate: 2 in the molecule
(meth)acrylic acid, (meth)acrylate having a carboxyl group, or (meth)acrylic acid or (meth)acrylate having a carboxyl group and a polybase in an epoxy resin having more than one epoxy group. It is synthesized by reacting a mixture with an acid. Alternatively, there is also a method of reacting an epoxy group-containing (meth)acrylate with a polyhydric carboxylic acid.

For example, addition reaction products of epoxy resins such as bisphenol A diglycidyl ether type, glycerin diglycidyl ether type, polyalkylene glycol diglycidyl ether type, polybasic acid diglycidyl ester type, and cyclohexene oxide type, and (meth)acrylic acid. etc.

(f) Polyurethane poly(meth)acrylate; Polyurethane poly(meth)acrylate has the structure of a polyhydric alcohol (meth)acrylate having a polyurethane bonding unit in the main chain, and usually contains a hydroxyl group (meth)acrylate.
It is synthesized by a method such as reacting an acrylate with a polyisocyanate and, if necessary, a polyhydric alcohol.

For example, the addition reaction product of 2-hydroxylethyl (meth)acrylate or 2-hydroxypropyl (meth)acrylate and diisocyanate, the addition reaction product of 2-hydroxylethyl (meth)acrylate, diisocyanate, and dihydric alcohol, etc. Corresponds to an example.

(g) Polyamide poly(meth)acrylate: It has the structure of polyhydric alcohol (meth)acrylate having a polyamide bonding unit in the main chain, and is usually combined with polyamide-type polycarboxylic acid and droxy group-containing (meth)acrylate or It is synthesized by reacting an epoxy group-containing (meth)acrylate or by reacting a polyamide-type polyhydric alcohol with (meth)acrylic acid.

For example, a reaction product of a polyamide-type polycarboxylic acid obtained by the reaction of ethylenediamine and phthalic acid and 2-hydroxyethyl (meth)acrylate or glycidyl (meth)acrylate corresponds to this example.

(h) Polysiloxane poly(meth)acrylate: It has the structure of a (meth)acrylate of a polyhydric alcohol with a polysiloxane bonding unit in the main chain, and (meth)acrylate is usually added to a polyhydric alcohol with a polysiloxane bonding unit. It is synthesized by a method such as a reaction.

(i) A vinyl or diene-based low polymer having a (meth)acryloyloxy group in the side chain and/or the terminal; a side chain of a vinyl-based or diene-based low-density vinyl or diene-based low polymer having a cy group; Or via an ester bond, urethane bond, amide bond, ether bond, etc. at the terminal (meta)
It has a structure in which an acryloyloxy group is bonded.

Hydroxy group, carboxyl group, usually in the side chain or terminal,
Low polymers containing epoxy groups, etc. contain (meth)acrylic acid, carboxyl group-containing (meth)acrylates, hydroxyl group-containing (meth)acrylates, epoxy group-containing (meth)acrylates, and isocyanate groups that are reactive with these groups. (meth)acrylate, amino group-containing (meth)
Synthesized by reacting acrylate etc.

Examples include reaction products obtained by reacting glycidyl (meth)acrylate with copolymers of <meth)acrylic acid and other vinyl polymers.

In addition, crosslinkable oligomers belonging to this system generally tend to become highly viscous or solid when their molecular weight becomes high, so they are used by dissolving them in liquid low viscosity liquid (crosslinkable monomer) etc. as described below. It is preferable to use a liquid oligomer with a high molecular weight or a low molecular weight (usually a number average molecular weight of 3000 or less).

(j) Modified products of the crosslinkable monomers described in (a) to (i) above; - At least a part of the hydroxyl group or carboxyl group remaining in each crosslinkable monomer of item F is replaced with these groups. reactive acid chlorides, acid anhydrides, isocyanates or
It is a modified product that is modified by reacting with an epoxy compound, and the method and specific examples of modification are, for example, JP-A No. 49-1999-
This method is disclosed in JP-A No. 128994, Japanese Unexamined Patent Publication No. 128088-1988, and the like.

The compounds are as follows.

1) CH2=CHCoo Cn H2n++, where n is an integer from 1 to 12++) GH2=CII COO((:IhCt12
o) RR=CnH2n+ where n is an integer from 1 to 12 l1l) CI(2=(:HCOO(CH2CI+2
0)2 RR=CnH2n, - However, n is an integer of 1 to 12 iv) ii) and jii) (7) -CthCH20
-&nv) CH2= CH-COO-X -OH
Clb Cyclopentadienyloxyethyl acrylate R': -C)12CH2OH.

-CH2 CHCH3 H -CH3 viii) N-vinylpyrrolidone Depending on the material, disk structure, etc., they can be used alone or in an appropriate mixture.

A photoinitiator is necessary for curing with ultraviolet light (
Examples are benzoin alkyl ethers, benzyl ketals, acetals,
Examples include acetophenone derivatives, benzophenone conductors, xanthone derivatives, and benzaldehyde derivatives.

Specific examples of compounds that can be used as sensitizers 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-
Examples include hydroxy-2-propiophenone, 4,4'-bisdiethylaminobenzophenone, dimethylaminohenzaldehyde, ethyl-4,4'-bisdimethylaminohensiphenone, ethylanthraquinone, and 2-chlorothioxanthone. These sensitizers can be used alone or in appropriate combinations.

In the present invention, a coating solution is prepared by preparing the above-mentioned ultraviolet curable resin as it is or by dissolving it in an organic solvent, and applying the coating solution onto the reflective layer and the outer peripheral edge surface of the substrate. After drying, the coating layer is irradiated with ultraviolet rays and cured. Provide a protective layer.

The protective layer may be colored to improve light resistance. As the coloring agent, inorganic pigments, organic pigments, dyes, etc. can be used.

Depending on the purpose, various additives such as an organic solvent, an antistatic agent, an antioxidant, and a UV absorber may be added to the coating liquid for forming a protective layer made of the ultraviolet curable resin. It can be formed by applying this coating liquid to the surface of the substrate by a coating method such as spin cording, dip coating, or extrusion coating (after drying if it contains an organic solvent), and then curing it by irradiating it with ultraviolet rays.

When the above coating liquid is cured with ultraviolet rays, the coating layer is cured by irradiating ultraviolet rays from a distance of 1 to 100 cm for 0.1 to 60 seconds using a high-pressure mercury lamp to form an antireflection layer. can do. When curing with an electron beam, an electron accelerator such as a linear accelerator or a hump graph accelerator is used. When curing a protective layer with low transmittance, electron beam irradiation is more advantageous in ensuring sufficient internal curing.

The thickness of the protective layer is generally 0.01 to 50 μm, preferably 0.1 to 20 μm, particularly preferably 0.5 to 20 μm.
It is in the μm range. Further, the thickness of the protective layer on the outer peripheral end surface of the substrate is preferably 1 μm or more, and particularly preferably in the range of 2 to 50 μm.

In the present invention, the protective layer is formed not only on the surface of the substrate but also on the outer peripheral end surface of the substrate. Therefore, by applying and drying the coating using the method described below, it is possible to simultaneously coat the substrate surface and the outer peripheral end surface of the substrate, which is preferable.

The substrate on which the recording layer and the reflective layer have been formed is mounted on a spinner, and the coating solution for forming the protective layer (viscosity is preferably 1 to 100 cps at the coating temperature, and if it contains an organic solvent, the organic solvent The substrate was rotated at a speed of 100 to 300 r while discharging from a spinner a content of 80% by weight or less).
Coating is started while rotating at a speed of 1000 to 2500 rpm, maintained for 3 to 10 seconds, and then completed, and the number of rotations is increased in 0.1 to 60 seconds to a final number of rotations of 1000 to 2500 rpm. This allows the protective layer to be applied onto the recording layer and up to the outer peripheral end surface of the substrate. Next, a protective layer can be formed by immediately irradiating the coated layer with ultraviolet rays.

The protective layer of the present invention may contain other resins in addition to the above-mentioned ultraviolet curable resins within a range that does not impair the object of the present invention. In general, the surface becomes easily damaged and the protective effect tends to decrease.

The protective layer of the present invention is provided on the substrate surface, the outer peripheral end face, and the reflective layer. Therefore, the present invention can be applied to any information recording medium as long as it is possible to form a protective layer and the effect can be obtained.

Such information recording media include read-only type, postscript (
It can be applied to any type of medium, such as DRAW type, rewritable type, magneto-optical type, etc., regardless of whether it is recordable or not, or the type of recording layer.

Recording on the information recording medium is performed, for example, as follows.

First, while rotating the information recording BtB body at a constant linear velocity or constant angular velocity, a laser beam for recording such as a semiconductor laser beam is irradiated from the substrate side to the group of pregrooves to generate an EFM signal of CD format. A signal is recorded by forming various shape changes in the recording layer of the group (a cavity at the interface between the dye recording layer and the reflective layer, a convex portion on the substrate surface, etc.). Generally, the recording light is 750~8
A semiconductor laser beam with an oscillation wavelength in the range of 50 nm is used. Generally recorded with a laser power of 1-15 mW.

During recording, tracking control is performed by a push-pull method or the like using the tracking pregroove. Information is recorded in groups of break loops or on lands between groups.

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

Margin below less than, Examples and comparative examples of the present invention are described. Ru.

however, Each of these does not limit the invention. It's not.

[Example 1] The following indolenine dye: g and the following dye (IRG-023 manufactured by Nippon Kayaku ■): 0.17 g were placed in 100 ml of 2,2,3,3-tetrafluoropropanol by ultrasonication. A dye coating solution was prepared by dissolving the dye while applying it for 1 hour.

A disc-shaped polycarbonate substrate provided with a pregroove (outer diameter: 120 mm, inner diameter = 15 mm, thickness: 1.
2mm, track pitch: 1.6μm, group width:
0.45. um, group depth: 900, group area: diameter 44 mm to It, 7 mm) on the surface of the substrate on the side where the pregroove is provided, a dye coating solution was applied using a spin code method at a rotational speed of 200 mm. Apply at a speed of pIIl for 5 seconds, gradually increase the rotation speed by 50 rpm per second for 16 seconds.The final rotation speed is 1000 rpm, hold for 30 seconds, and dry until the layer thickness within the group is 1400 rpm.
Another dye recording layer was formed up to the outer periphery of the substrate.

A state in which the substrate provided with the recording layer is fitted into a recess of a dish-shaped mounting table with the recording layer facing upward and having a depth of 0.1 mm larger than the outer diameter of the substrate and twice the thickness of the substrate. A reflective layer was formed by sputtering as described below.

Ar
A reflective layer having a layer thickness of 1 oooX was formed on the surface from the recording layer to the outer periphery of the substrate by sputtering under the conditions of a pressure of 2 Pa and a power of 200 W.

Further, on the reflective layer, apply the above-mentioned coating liquid for forming a protective layer (product name: 3070, which is an ultraviolet curable resin, manufactured by ThreeBond).
Using the spin code method, coating was started at a rotational speed of 200 rpm, maintained for 5 seconds to complete the coating, and then the rotational speed was increased and dried by spinning at a final rotational speed of 1500 "pI!l" for 10 seconds. Next, the coating layer was irradiated with ultraviolet rays (200 W/cm 2 mercury lamp for 10 seconds) to form a protective layer from above the reflective layer to the outer peripheral edge surface of the substrate.

The layer thickness on the reflective layer is 2 μm, and the layer thickness on the outer peripheral edge of the substrate is 2 μm.
It was ~10 μm.

In this way, an information recording medium (see FIG. 2) in which a dye recording layer, a reflective layer, and a protective layer were provided on a substrate was manufactured.

[Comparative Example 1] An information recording medium was prepared in the same manner as in Example 1, except that the protective layer was not provided on the outer peripheral end surface of the substrate by applying the protective layer forming coating liquid under the following conditions. Manufactured.

The coating solution for forming a protective layer was applied onto the reflective layer using a spin code method at a rotational speed of 100 rpm, which was maintained for 2 seconds to complete the coating, and then the rotational speed was increased to a final rotational speed of 1.
It was maintained at 500 rpm for 10 seconds to dry. Next, the coating layer was irradiated with ultraviolet rays (a 200 W/Cm2 mercury lamp was used once).
0 seconds) to form a protective layer with a thickness of 2 μm on the recording layer. Almost no protective layer was formed on the outer peripheral edge surface of the substrate.

[Evaluation of information recording media] 1) Tape peel test PET from the inner circumferential side of the protective layer of the optical disk to the outer circumferential edge of the substrate
Apply adhesive tape (Mylar tape, manufactured by Nitto Denko),
It peeled off from the outer periphery at once. The recording layer, reflective layer, and protective layer on the disk side were observed for peeling.

The test was performed 10 times and the number of times the film did not peel off was shown.

The above measurement results are shown in Table 1.

Table 1 As is clear from Table 1 above, an optical disc ( Example 1) has excellent adhesion.

On the other hand, the optical disc in which the protective layer was formed only up to the outer periphery of the substrate (Comparative Example 1) had poor adhesion.

[Brief explanation of drawings]

FIG. 1 is an example of a plan view showing the basic configuration of the information recording medium of the present invention. FIG. 2 is an example of a partial sectional view of FIG. 1 showing the basic structure of the information recording medium of the present invention. 3 and 4 are examples of cross-sectional views of conventional information recording media, respectively. Hole: 10.2 Substrate: 11.2 Pre-groove: Recording layer: 13, Inner circumferential side substrate area, Outer circumferential side substrate area Reflective layer: 16, Protective layer: 17, Substrate outer circumferential end face: 12, 22 = 14, 24: 25 18. Patent applicant Fuji Photo Film Co., Ltd. Agent Patent attorney Yasushi Yanagawa Application No. 124398 Invention Name Information Recording Medium 3, Relationship with the Amendment Person Case Patent Applicant

Claims (1)

[Claims] 1. A recording layer made of a dye on which information can be written by a laser, a reflective layer made of a metal, and an ultraviolet curing type are formed on the pregroove of a disc-shaped substrate having a hole in the center and a pregroove for tracking on the surface. In an information recording medium in which a protective layer made of a cured resin is provided in this order, the reflective layer is provided continuously from the recording layer to the outer periphery of the substrate, and the protective layer An information recording medium characterized in that a reflective layer is provided continuously from the top of the reflective layer to the outer peripheral end surface of the substrate.