JP2002092957A - Material of surface protecting layer for optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material of a surface protecting layer for an optical recording medium, forming the protecting layer excellent in transparency, film thickness uniformity and adhesive properties. SOLUTION: A transparent adhesive (B) containing a cationically polymeric copolymer (B-1), a cationically polymeric monomer (B-2) and a photopolymerization initiator (B-3) is applied on one surface of a transparent film (A) to form the material of the surface protecting layer for the optical recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material for protecting a recording layer of an optical recording medium, and to a surface protective layer material for an optical recording medium which is excellent in transparency, film thickness uniformity and adhesiveness. Further, the present invention relates to an optical recording medium obtained by using the surface protective layer material.

[0002]

2. Description of the Related Art In recent years, DVDs (digital video discs or digital versatile discs) capable of recording a large amount of information among optical recording media have attracted attention, and the use of a blue-violet light source having a wavelength of about 405 nm has been attracting attention. And the protective layer covering the recording layer is made as thin as 0.1 mm to 0.3 mm to increase the storage capacity of the optical disc to 20 G on one side.
A technology to increase the size to bytes to 30 GB has been proposed (Japanese Journal Applied Physics. Vol. 30 (200
0)). Unlike a conventional structure in which two disks are bonded to each other, this DVD is basically composed of one disk, and therefore requires a material for protecting the surface. Proposals for materials for this protective layer include (Japanese Journal Appli
ed Physics. Vol.39 775-778 (2000)) and UV curable resin (Dainiure, manufactured by Dainippon Ink and Chemicals, Inc.)
SD645) is spin-coated on an optical disc and then irradiated with UV light in a nitrogen atmosphere to form a protective layer.
A method of forming a protective layer by spin-coating (EQUES Coatings), adhering to an optical disc, and irradiating with UV light is introduced. For the requirements of thickness accuracy and transparency of 100 ± 2 μm, the method is 100 μm
It is expected that it is difficult to control the film thickness by controlling the film thickness, which is the upper limit, and to cure the entire film by UV curing due to the problem of distortion due to curing shrinkage in order to obtain by the ordinary spin coating method. On the other hand, a problem that adhesion to the polycarbonate film is low is expected.

In addition, a hot melt adhesive which has been conventionally used as a DVD adhesive for bonding two substrates can be used. However, since a thermoplastic resin is used, it is necessary to melt the adhesive when applying the adhesive. There is a problem in deformation of the substrate due to heat applied to the substrate, dimensional stability at high temperature, and adhesiveness.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a protective layer material for an optical recording medium for forming a protective layer having excellent transparency, uniform film thickness and adhesiveness, and an optical recording medium using the material. It is to provide.

[0005]

Means for Solving the Problems The present inventors have conducted various studies in order to solve the above-mentioned problems. As a result, (A-1) a cationic polymerizable copolymer (B-2) )
By using a material for a surface protective layer formed by applying a transparent adhesive (B) containing a cationic polymerizable monomer and (B-3) a photopolymerization initiator, transparency, film thickness uniformity, and adhesion can be improved. It is possible to form an excellent protective layer.

That is, the present invention provides the following (1) to (11)
Is provided. (1) A transparent adhesive (B) containing a cationically polymerizable copolymer (B-1), a cationically polymerizable monomer (B-2) and a photopolymerization initiator (B-3) on one surface of the transparent film (A) ) Is applied to the surface protective material for optical recording media. (2) The surface protective layer material for an optical recording medium according to (1), wherein the curing shrinkage of the transparent adhesive (B) is 3% or less. (3) The surface protective layer material for an optical recording medium according to (1), wherein the transparent film (A) is a polyolefin. (4) The surface protective layer material for an optical recording medium according to (3), wherein the polyolefin is a cyclic polyolefin. (5) The cationic polymerizable copolymer (B-1) is an acrylic copolymer containing oxetanyl (meth) acrylate and / or glycidyl (meth) acrylate. The surface protective layer material for an optical recording medium according to any one of claims 1 to 7. (6) The cationic polymerizable monomer (B-2) is a compound or a mixture having an oxetane ring and / or an oxirane ring in the molecule, or any one of (1) to (5). Surface protective layer material for optical recording media. (7) The compound having an oxirane ring in the cationically polymerizable monomer (B-2) is at least one compound selected from alicyclic epoxy compounds and aliphatic glycidyl ethers (6). 4. The surface protective layer material for an optical recording medium according to item 1. (8) The surface protective layer material for an optical recording medium according to any one of (1) to (7), wherein the photopolymerization initiator (B-3) is an onium salt. (9) The content ratio of each component in the transparent adhesive (B) is as follows: (B-1) 63 to 99.5% by mass of the cationically polymerizable copolymer, (B-2) 0.2 to 10% by mass of the cationically polymerizable monomer. 30% by mass; (B-3) 0.3 to 7% by mass of a photopolymerization initiator, any one of (1) to (8).
Item 14. A surface protective layer material for an optical recording medium according to item 8.

(10) The transparent film (A) in the optical recording medium surface protective layer material described in any of (1) to (9) above is replaced with the transparent adhesive (B) in the optical recording medium surface protective layer material. An optical recording medium obtained by holding on a substrate using (11) The substrate comprises a support, on which a reflective layer and a recording layer are sequentially formed. The transparent film (A) is bonded on the recording layer with a transparent adhesive (B), and the transparent adhesive ( The optical recording medium according to (10), further comprising: a protective layer obtained by curing B), wherein information recording / reproduction is performed from the protective layer side. (12) The optical recording medium according to (10) or (11), which is attached to the substrate in the form of the surface protective material for an optical recording medium according to any one of (1) to (9).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a material for a surface protective layer for an optical recording medium according to the present invention, which is capable of forming a protective layer having excellent transparency, uniform film thickness and adhesiveness, will be described.

[Surface Protective Layer Material for Optical Recording Medium] The surface protective layer material for an optical recording medium of the present invention comprises (A) a cationic polymerizable copolymer (B-1) on the surface of a transparent film;
It has a configuration in which a transparent adhesive (B) containing a cationically polymerizable monomer (B-3) photopolymerization initiator is applied.

Hereinafter, each component will be described in detail.

<(A) Transparent film> The material usable as the transparent film (A) of the present invention is not particularly limited as long as it is a film material having excellent transparency. Examples include methyl methacrylate, polyether sulfone, and polyethylene terephthalate.

Depending on the purpose of use, polycarbonate is excellent in rigidity, heat resistance, heat aging resistance, and impact resistance, but is inferior in chemical resistance. High refraction and high water absorption (water resistance)
Is also not sufficiently small. Polymethyl methacrylate is excellent in mechanical properties, but has a problem of poor chemical resistance, heat resistance, and weather resistance.Polyethylene terephthalate has excellent heat resistance and mechanical properties, but strong acid. Or weak to alkali,
There is a problem that it is susceptible to hydrolysis. Polyethersulfone is excellent in heat resistance, impact resistance, and moldability, but has the problem of poor transparency, birefringence, and weather resistance.

Among these, polyolefins are excellent in transparency, and can be preferably used particularly in view of a good balance between rigidity and transparency, and more preferably, transparency, low birefringence, moisture resistance (low water absorption), A cyclic polyolefin derived from a bulky cyclic olefin having an excellent balance of electrical properties such as heat resistance, chemical resistance, solvent resistance, precision molding processability, and dielectric properties, mechanical properties, and rigidity can be used.

As the cyclic olefin, for example, JP-A-6
Nos. 0-168708, 61-120816, 61-115912, 61-15991
No. 6, No. 61-271308, No. 61-27
In addition to those described in JP-A Nos. 2216, 62-252406 and 62-252407, 2,3-dihydroxydicyclopentadiene (U.S. Pat. No. 2,883,372) and 5-ethylidene norbornene are mentioned. Can be

The cyclic olefin used in the present invention may contain two or more units derived from the above cyclic olefin.

The cyclic polyolefin used in the present invention can be prepared by using the above-mentioned cyclic olefins, for example, in JP-A Nos. 60-168708 and 61-120816.
JP-A-6-115912 and JP-A-61-11512
Nos. 916, 61-271308, 61-
According to the methods described in JP-A-272216, JP-A-62-252406 and JP-A-62-252407, they can be produced by appropriately selecting the conditions.

The transparent film used in the present invention can be obtained by molding the above-mentioned material into a desired shape by a known molding method. For example, it can be formed into a sheet or film by a molding method such as an injection molding method, an injection blow molding method, a direct blow molding method, a T-die extrusion method, an inflation method, and a pressing method.

The thickness of the transparent film is 50 to 300 μm
Is preferably 80 to 150 μm, more preferably 1 to 150 μm.
It is preferably about 00 μm.

[(B) Transparent adhesive] Next, each component of the transparent adhesive (B) will be described in detail.

<(B-1) Cationic polymerizable copolymer> The cationic polymerizable copolymer (B-1) used in the present invention.
Is preferably an acrylic copolymer such as oxetanyl (meth) acrylate and / or glycidyl (meth) acrylate in which a cationic polymerizable group is introduced into a polymer using an acrylic monomer having an oxetane ring or an oxirane ring.

Other copolymerizable copolymers include:
Copolymerizable with these monomers, 380 to 800
The monomer is not particularly limited as long as it is a highly transparent monomer having no absorption in the wavelength region of nm. Specific examples include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (acrylate),
2-ethylhexyl (meth) acrylate, amyl (meth) acrylate, hexadecyl (meth) acrylate, octadecyl (meth) acrylate, butoxyethyl (meth) acrylate, phenoxyethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, etc. Can be mentioned. These can be used alone or in combination of two or more. The content of oxetanyl (meth) acrylate and glycidyl (meth) acrylate in the cationically polymerizable copolymer (B-1) is preferably from 5% by mass to 50% by mass. When the amount is 5% by mass or more, sufficient adhesive strength is obtained due to an increase in cohesive force due to curing, and when the amount is 50% by mass or less, the cured film has sufficient flexibility and good adhesion. is there.

The method of synthesizing the cationically polymerizable copolymer is not particularly limited, but it is possible to carry out synthesis by generally known radical solution polymerization.

The glass transition temperature (hereinafter, Tg) of the cationically polymerizable copolymer (B-1) is preferably 0 ° C. or less, and when Tg is 0 ° C. or less, the desired adhesive strength can be exhibited. .

The cationically polymerizable copolymer (B-
The molecular weight of 1) is preferably from 2,000 to 50,000 as a number average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC). More preferably, it is 4000 to 30,000. When the number average molecular weight is 2,000 to 50,000, good coating properties can be obtained.

These cationically polymerizable copolymers (B-1)
Is used in an amount of 63% by mass based on the entire transparent adhesive (B).
It is preferably from 9 to 99.5% by mass. 6 used
When the content is 3% by mass or more, the curing shrinkage is reduced, and the uniformity of the film thickness and the adhesive strength are improved. On the other hand, when the content is 99.5% by mass or less, the curability can be maintained.

<(B-2) Cationic polymerizable monomer> Cationic polymerizable monomer (B-2) used in the present invention
Is not particularly limited, but is preferably a compound or a mixture having an oxetane ring and / or an oxirane ring in the molecule. The amount of the compound having an oxetane ring used is 5 in the cationically polymerizable monomer (B-2).
It is preferably from 80 to 80% by mass, more preferably from 10 to 50% by mass. By setting the amount to be 5% by mass or more, the curability is improved and curing can be performed in a short time. When the amount is 80% by mass or less, the adhesiveness at a high temperature is improved. The use amount of the compound having an oxirane ring is preferably 20 to 95% by mass, and 30 to 85% by mass.
Is more preferred. When the amount is 20% by mass or more, the adhesiveness at a high temperature is improved, and when the amount is 95% by mass or less, the curability is improved, and the curing can be performed in a short time.

The amount of the cationically polymerizable monomer (B-2) used in the transparent adhesive (B) is preferably from 0.2 to 30% by mass. When the amount is 0.2% by mass or more, the curability increases, and when the amount is 30% by mass or less, the shrinkage ratio before and after curing is reduced to improve the adhesive strength.

Hereinafter, the cationically polymerizable monomer (B-2)
Will be described in more detail.

[Polymerizable monomer having oxetane ring]
The polymerizable monomer having an oxetane ring used in the present invention is not particularly limited as long as it is a compound having 1 to 5 oxetane rings in the molecule and having no absorption in a wavelength region of 380 to 800 nm. is not.

Specific examples of the polymerizable monomer having one oxetane ring include 3-ethyl-3-hydroxymethyloxetane, 3- (meth) allyloxymethyl-3-ethyloxetane, (3-ethyl-3-oxetanyl) Methoxy) methylbenzene, 4-fluoro- [1- (3-ethyl-3-oxetanylmethoxy) methyl] benzene,
4-methoxy- [1- (3-ethyl-3-oxetanylmethoxy) methyl] benzene, [1- (3-ethyl-3
-Oxetanylmethoxy) ethyl] phenyl ether,
Isobutoxymethyl (3-ethyl-3-oxetanylmethyl) ether, isobornyloxyethyl (3-ethyl-3-oxetanylmethyl) ether, isobornyl (3-ethyl-3-oxetanylmethyl) ether, 2
-Ethylhexyl (3-ethyl-3-oxetanylmethyl) ether, ethyldiethylene glycol (3-ethyl-3-oxetanylmethyl) ether, dicyclopentadiene (3-ethyl-3-oxetanylmethyl) ether, dicyclopentenyloxyethyl (3 -Ethyl-
3-oxetanylmethyl) ether, dicyclopentenylethyl (3-ethyl-3-oxetanylmethyl) ether, tetrahydrofurfuryl (3-ethyl-3-oxetanylmethyl) ether, tetrabromophenyl (3
-Ethyl-3-oxetanylmethyl) ether, 2-tetrabromophenoxyethyl (3-ethyl-3-oxetanylmethyl) ether, tribromophenyl (3-ethyl-3-oxetanylmethyl) ether, 2-tribromophenoxyethyl ( 3-ethyl-3-oxetanylmethyl) ether, 2-hydroxyethyl (3-ethyl-3-oxetanylmethyl) ether, 2-hydroxypropyl (3-ethyl-3-oxetanylmethyl) ether, butoxyethyl (3-ethyl- 3-oxetanylmethyl) ether, pentachlorophenyl (3-ethyl-3-oxetanylmethyl) ether, pentabromophenyl (3-ethyl-3-oxetanylmethyl) ether, bornyl (3-ethyl-3-oxetanylmethyl)
Ether and the like.

Specific examples of the polymerizable monomer having two oxetane rings include 1,4-bis {[(3-ethyl-3
-Oxetanyl) methoxy] methyl} benzene, bis {[(1-ethyl) 3-oxetanyl] methyl} ether, 1,4-bis [(3-ethyl-3-oxetanyl)
Methoxy] benzene, 1,3-bis [(3-ethyl-3
-Oxetanyl) methoxy] benzene, 3,7-bis (3-oxetanyl) -5-oxa-nonane, 1,4-
Bis [(3-ethyl-3-oxetanylmethoxy) methyl] benzene, 1,2-bis [(3-ethyl-3-oxetanylmethoxy) methyl] ethane, 1,2-bis [(3-ethyl-3-oxetanyl) Methoxy) methyl
Propane, ethylene glycol bis (3-ethyl-3-
Oxetanylmethyl) ether, dicyclopentenylbis (3-ethyl-3-oxetanylmethyl) ether,
Triethylene glycol bis (3-ethyl-3-oxetanylmethyl) ether, tetraethylene glycol bis (3-ethyl-3-oxetanylmethyl) ether,
Tricyclodecanediyl dimethylenebis (3-ethyl-
3-oxetanylmethyl) ether, 1,4-bis [(3-ethyl-3-oxetanylmethoxy) methyl]
Butane, 1,6-bis [(3-ethyl-3-oxetanylmethoxy) methyl] hexane, polyethylene glycol bis (3-ethyl-3-oxetanylmethyl) ether, EO-modified bisphenol A bis (3-ethyl-3-
Oxetanylmethyl) ether, PO-modified bisphenol A bis (3-ethyl-3-oxetanylmethyl) ether, EO-modified hydrogenated bisphenol A bis (3-ethyl-3-oxetanylmethyl) ether, PO-modified hydrogenated bisphenol Abis (3 -Ethyl-3-oxetanylmethyl) ether, EO-modified bisphenol F bis (3-
Ethyl-3-oxetanylmethyl) ether and the like.

Specific examples of the polymerizable monomer having 3 to 5 oxetane rings include trimethylolpropane tris (3-ethyl-3-oxetanylmethyl) ether,
Pentaerythritol tris (3-ethyl-3-oxetanylmethyl) ether, pentaerythritol tetrakis (3-ethyl-3-oxetanylmethyl) ether, dipentaerythritol pentakis (3-ethyl-)
3-oxetanylmethyl) ether and the like.

[Polymerizable monomer having oxirane ring]
The polymerizable monomer having an oxirane ring used in the present invention is not particularly limited as long as it is a compound having 1 to 4 oxirane rings in the molecule.

The polymerizable monomer having an oxirane ring will be described with reference to specific examples. Examples of the compound having one oxirane ring (epoxy group) include phenyl glycidyl ether and butyl glycidyl ether. Examples of the compound having two or more oxirane rings (epoxy group) include:
Examples thereof include hexanediol diglycidyl ether, tetraethylene glycol diglycidyl ether, trimethylolpropane triglycidyl ether, and bisphenol A diglycidyl ether. Further, alicyclic epoxies such as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate and bis- (3,4-epoxycyclohexyl) adipate are also included. These cationically polymerizable monomers may be used alone or in combination of two or more.

<(B-3) Photopolymerization Initiator> The photopolymerization initiator (B-3) of the present invention is a compound which initiates cationic polymerization of the components (B-1) and (B-2) by light. If it is, there is no particular limitation, and any of them can be used.

A preferred example of the photopolymerization initiator (B-3) is an onium salt. This onium salt is a compound that reacts with light and releases a Lewis acid.

Specifically, it is represented by the following general formula (1).

[R ¹ _a R ² _b R ³ _c R ⁴ _d W] ^{m +} [MX _{n + m} ] ^m− (1) (where the cation is an onium ion, and W is S,
Se, Te, P, As, Sb, Bi, O, I, Br, C
l, or

[Outside 1] It is. R ¹ , R ² , R ³ , and R ⁴ are the same or different organic groups, a, b, c, and d are each an integer of 0 to 3, and (a + b + c + d) is equal to the valence of W. M is a metal or metalloid constituting the central atom of the halogenated complex [MX _{n + m} ], for example, B, P,
As, Sb, Fe, Sn, Bi, Al, Ca, In, T
i, Zn, Sc, V, Cr, Mn, Co and the like. X is, for example, a halogen atom such as F, Cl, or Br; m is the net charge of the halide complex ion; and n is the valence of M. )

In the general formula (1), specific examples of the onium ion include diphenyliodonium, 4-methoxydiphenyliodonium, bis (4-methylphenyl)
Iodonium, bis (4-tert-butylphenyl)
Iodonium, bis (dodecylphenyl) iodonium, triphenylsulfonium, diphenyl-4-thiophenoxyphenylsulfonium, bis [4- (diphenylsulfonio) -phenyl] sulfide, bis [4
- (di (4- (2-hydroxyethyl) phenyl) sulfonio) - phenyl] sulfide, eta ^{5-2,4-(cyclopentadienyl)} [1,2,3,4,5,6-.eta.
(Methylethyl) benzene] -iron (1+).

In the general formula (1), specific examples of the anion include tetrafluoroborate, hexafluorophosphate, hexafluoroantimonate, hexafluoroarsenate, hexachloroantimonate and the like.

These photopolymerization initiators (B-3) can be used alone or in combination of two or more.

In the transparent adhesive (B) of the present invention, (B-
3) The content ratio of the component is preferably 0.3 to 7% by mass.
And more preferably 0.5 to 4% by mass.

The content ratio of the component (B-3) is 0.3% by mass.
With the above, the curing condition of the transparent adhesive (B) becomes better, and by setting the content to 7% by mass or less, the elution of the initiator during the curing process and after the curing can be reduced.

Further, other additives can be used for the transparent adhesive (B) of the present invention, if necessary.

<Other Additive Components> Examples of materials that can be added to the transparent adhesive (B) of the present invention include tackifiers, antioxidants, ultraviolet absorbers, and diluents.

(Tackifier) Specific examples of the tackifier used in the present invention include, for example, aliphatic petroleum resins, alicyclic petroleum resins, aromatic petroleum resins, rosin petroleum resins, and terpene-based petroleum resins. It is preferable to use at least one selected from the group of petroleum resins or each hydrogenated resin.

(Antioxidant) Specific examples of the antioxidant used in the present invention include a hindered phenol compound and a phosphate compound. An antioxidant can be added for the purpose of preventing thermal deterioration.

(Ultraviolet absorber) The ultraviolet absorber used in the present invention is, for example, a salicylic acid ultraviolet absorber such as p-tert-butylphenyl salicylate.
-Hydroxy-4-octoxybenzophenone, 2,2
Benzophenone-based ultraviolet absorbers such as dihydroxy-4-methoxybenzophenone, 2 ′-(2-hydroxy-
5-methylphenyl)) benzotriazole, 2- (2
-Hydroxy-3-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2-
Hydroxy-3,5-di-tert-butylphenyl)
Benzotriazole-based ultraviolet absorbers such as benzotriazole are exemplified. An ultraviolet absorber can be added for the purpose of preventing ultraviolet deterioration.

(Diluent) The diluent can be used for imparting coatability or improving the coatability. As a diluent, an organic solvent is usually used. Although the physical properties of the organic solvent are not particularly limited, a compound or a mixture having a boiling point at 200 ° C. or less at 1 atm is preferred, the boiling point is more preferably 150 ° C. or less, and even more preferably 70 ° C. or more and 130 ° C. or less.

These diluents can be used alone or in combination of two or more. The amount of the diluent is not particularly limited, and the amount is selected according to the suitability for coating.

These diluents include alcohols, glycol ethers, ethylene glycol ether acetates, aromatic hydrocarbons, ketones, esters,
Ethers and the like. Specific examples of these compounds include the following.

Examples of alcohols include methanol,
Ethanol, propanol, butanol and the like can be mentioned.

Examples of the glycol ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether,
3-methoxybutanol, 3-methyl-3-methoxybutanol and the like.

Examples of the ethylene glycol ether acetates include ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, 3-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, and ethyl ethoxyprote. Piolate and the like.

Examples of the aromatic hydrocarbons include toluene, xylene and the like. Ketones include methyl ethyl ketone, cyclohexanone, 4-hydroxy-4-methyl-2-pentanone and the like.

Esters include methyl acetate, ethyl acetate, propyl acetate, butyl acetate, 2-hydroxy-2-
Methyl methyl propionate, ethyl 2-hydroxy-2-methylpropionate, methyl hydroxyacetate, ethyl hydroxyacetate, butyl hydroxyacetate, methyl lactate,
Ethyl lactate, butyl lactate, methyl 3-hydroxypropionate, ethyl 3-hydroxypropionate, propyl 3-hydroxypropionate, butyl 3-hydroxypropionate, propyl 2-hydroxy-3-methylbutanoate, methyl methoxyacetate, methoxyacetic acid Ethyl, propyl methoxyacetate, butyl methoxyacetate, methyl ethoxyacetate, ethyl ethoxyacetate, propyl ethoxyacetate,
Butyl ethoxyacetate, methyl 2-methoxypropionate, ethyl 2-methoxypropionate, propyl 2-methoxypropionate, butyl 2-methoxypropionate, methyl 2-ethoxypropionate, ethyl 2-ethoxypropionate, 2-ethoxypropion Propyl acetate, butyl 2-ethoxypropionate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate,
Propyl 3-methoxypropionate, butyl 3-methoxypropionate, methyl 3-ethoxypropionate, 3
-Ethyl ethoxypropionate, propyl 3-ethoxypropionate, butyl 3-ethoxypropionate and the like. Examples of ethers include tetrahydrofuran.

[Preparation of Transparent Adhesive (B)] The transparent adhesive (B) of the present invention comprises a cationically polymerizable copolymer (B-1), a cationically polymerizable monomer (B-2), and a photopolymerization initiator. (B
-3) Other additives are uniformly mixed and adjusted to have a viscosity of 0.01 to 1 Pa · s at 25 ° C.
When the viscosity is in the range of 0.01 to 1 Pa · s, the control of the film thickness is facilitated, and the coating workability can be more efficiently performed. The viscosity range is more preferably from 0.02 to 0.5 Pa · s. The viscosity can be adjusted by the ratio between the cationically polymerizable copolymer (B-1) and the cationically polymerizable monomer (B-2), and a diluent can be used.

[Production Method of Surface Protective Layer Material for Optical Recording Medium] The surface protective layer material for an optical recording medium of the present invention is prepared by applying the above transparent film (A) to the transparent adhesive prepared by a coating apparatus such as a comma coater. It is obtained by applying the agent (B) and, if necessary, drying. The surface protective layer material of the present invention can be stored, transported and distributed as a sheet or roll product by protecting the surface with a release paper or a release film on the adhesive side, if necessary.

[Method of Forming Optical Recording Medium] The optical recording medium of the present invention is, for example, as shown in a schematic sectional view of FIG. 1, on a support 1 made of a transparent resin having a pregroove formed thereon. The substrate on which the layer 2, the recording layer 3, and the intermediate layer 4 are sequentially formed and the transparent film 6 according to the present invention are bonded together via the transparent adhesive layer 7 and cured to form the protective layer 5, and the information Recording and reproduction are performed from the protective layer 5 side.

Alternatively, a two-sided recordable medium may be formed by laminating two disks on the support side or forming a recording layer on both sides of the support.

As the support, for example, organic polymer materials such as polycarbonate, polyacrylate, polymethacrylate, polystyrene, polyester, polyolefin, and epoxy resin, and inorganic materials such as glass can be used. Particularly, a polycarbonate resin which is excellent in balance between light transmittance and heat resistance and is easy to mold is more desirable. Polyolefins having a ring skeleton are also desirable in that they have low optical anisotropy, low water absorption, and excellent transparency in the blue-violet region.

These substrate surfaces may have guide grooves and pits indicating recording positions, and pre-pits for partially read-only information. Although these guide grooves and pits are usually provided when a substrate is formed by injection molding, they may be formed by a laser cutting method or a 2P method.

In the case of a CD or DVD compatible optical disk, the support may be a disk having a diameter of 120 mm or 80 mm and having a hole of about 15 mm at the center thereof. It can also be applied to other various shapes such as a sheet shape.

Au, Al, Pt, A
A reflective layer using a metal such as g or Ni or an alloy thereof may be provided. In particular, it is desirable to use gold which is stable against oxygen and moisture. The reflection layer is formed by vapor deposition, sputtering, ion plating or the like.

The thickness of the reflective layer is 10 nm to 300 nm,
Desirably, it is 30 nm to 150 nm.

A recording layer containing an organic dye is formed on the reflective layer. Examples of the organic dye include macrocyclic azaannulene dyes (phthalocyanine dye, naphthalocyanine dye, azaporphyrin dye, etc.) and polymethine dyes (cyanine dye, Merocyanine dyes, squarylium dyes, etc.), anthraquinone dyes, azurenium dyes, azo dyes,
And indoaniline dyes.

The recording layer containing the above dye can be formed into a film by a coating method such as spin coating, spray coating, dip coating and roll coating. At the time of coating, a dye, a resinous binder, or other substance that forms a recording layer is dissolved in a solvent that does not damage the substrate, and is dried after coating. Examples of the solvent used include aliphatic and alicyclic hydrocarbons such as hexane, heptane, octane, decane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; ethers such as diethyl ether, dibutyl ether and tetrahydrofuran; Solvents such as alcohols such as methanol, ethanol, isopropanol, tetrafluoropropanol, and methylcellosolve; and halogen compounds such as chloroform, dichloromethane, and 1,2-dichloroethane can be preferably used. These solvents may be used alone or in combination. When two or more recording layers are laminated, it is desirable to select a solvent that does not attack the previously applied layer.

As a method for forming the recording layer, a vacuum evaporation method may be used. This method is effective when the recording layer material is hardly soluble in a solvent or when a solvent that does not damage the substrate cannot be selected.

The thickness of the recording layer is from 10 nm to 300 nm.
nm, preferably 40 nm to 150 nm.

An undercoat layer may be provided between the metal reflective layer and the recording layer for the purpose of improving the adhesion between the layers or increasing the reflectance.

Further, between the recording layer and the transparent adhesive, for example, a layer made of an organic substance such as polystyrene or polymethyl methacrylate or an inorganic substance such as SiO ₂ can be used. These may be used alone or may be mixed. Also, two or more kinds may be used in a stacked state.

When laminating a transparent film, a transparent adhesive may be applied on the intermediate layer and the transparent film may be laminated. Preferably, the transparent adhesive is applied to the transparent film in advance, and It is desirable to form a protective layer material, cut it into a desired shape, and then bond it to a substrate. For example, 0.3 Pa. The transparent adhesive (B) whose viscosity has been adjusted is applied to the transparent film with a comma coater, and dried if necessary.

The transparent adhesive layer is applied by adjusting the coating speed and the amount of diluent so as to have a thickness of 1 ± 0.5 μm to form a surface protective layer material.

The surface protective layer material thus formed is applied to an optical recording medium substrate having a reflective layer, a recording layer, and if necessary, an intermediate layer such as silicon oxide provided on a stamper-molded support such as polycarbonate. 500 ° C, 100 g / cm ²
And hot-press to bond. Thereafter, an arbitrary amount of light is irradiated from the transparent film surface using a high-pressure mercury lamp or a metahalide lamp. An optical recording medium having improved adhesiveness and reliability under high temperature and high humidity conditions is formed by photocuring.

[0075]

The present invention will be described below in more detail with reference to Examples and Comparative Examples.

(Evaluation Method) Table 1 shows the results of evaluation by the following test methods.

1. Light transmittance test 80% (toluene /
A transparent adhesive in a solution of a mixed solvent of methyl ethyl ketone) is applied with a comma coater. After evaporating the solvent at 50 ° C. for 20 minutes, UV light is irradiated to cure the solvent. The transmittance of the sheet coated with the obtained 16 μm transparent adhesive was measured in the range of 400 nm to 700 nm using an ultraviolet-visible spectrophotometer. In Table 1, the value of the transmittance for each 100 nm is described in%.

2. Film Thickness Distribution Measurement Test A transparent adhesive of a 5% (toluene / methyl ethyl ketone mixed solvent) solution is applied on a transparent film having a film thickness of 100 μm using a comma coater. After evaporating the solvent at 50 ° C. for 60 minutes, it was cut out into a circular shape having a diameter of 12 cm and a thickness of 0.1 cm.
After bonding to a 600 mm polycarbonate substrate with a 50 ° C. hot-press roll, the substrate was photo-cured by irradiation with UV light. As a result of measuring the film thickness of the sheet coated with the obtained 1 μm transparent adhesive at arbitrary 100 points,
The maximum and minimum values are listed.

3. Adhesive force test A transparent adhesive of a 5% (toluene / methyl ethyl ketone mixed solvent) solution is applied on a transparent film having a thickness of 100 μm by using a comma coater. After evaporating the solvent at 50 ° C. for 60 minutes, cut out into a circle having a diameter of 12 cm. On the other hand, a transparent dielectric film of silicon nitride or the like was formed on a polycarbonate substrate having a thickness of 0.600 mm by sputtering, and an aluminum film was used as a reflective layer and sputtered. After laminating the aluminum film and the transparent adhesive layer with a hot-press roll at 50 ° C., photo-curing was performed by irradiation with UV light. After leaving the obtained optical disk at 20 ° C. for 24 hours, the results of measuring the peel strength of the surface protective layer are described.

4. High-temperature high-humidity test 85
The film thickness distribution after standing for 120 hours at 85 ° C. and the presence or absence of a change in adhesive strength are described.

5. Curing Shrinkage Measurement The value calculated from the specific gravity before and after curing of the curing shrinkage of the transparent adhesive is described.

<Synthesis of Cationic Polymerizable Copolymer 1> 200 g of toluene was charged into a separable flask equipped with a cooling tube, two feed ports, and a thermometer, and purged with nitrogen. After the temperature was increased to 120 ° C. with stirring, 6 g of perbutyl octanoate and 0.1 g of n-dodecyl mercaptan were fed through the first feed port.
4 g, a mixed solution of 40 g of glycidyl methacrylate, 40 g of methyl methacrylate, and 120 g of 2-ethylhexyl acrylate were continuously fed from the second feed port for 4 hours. After adding 1 g of perbutyl octanoate, polymerization was continued at 120 ° C. for 3 hours to obtain a cationically polymerizable copolymer 1 (a 50.9% solids solution in toluene). The number average molecular weight of this cationically polymerizable copolymer 1 is 8
000 (GPC: polystyrene equivalent), Tg is -32 ° C
(Viscoelasticity measuring device).

<Synthesis of Cationic Polymerizable Copolymer 2> 200 g of toluene was charged into a separable flask equipped with a cooling tube, two feed ports, and a thermometer, and purged with nitrogen. After the temperature was increased to 120 ° C. with stirring, 6 g of perbutyl octanoate and 0.1 g of n-dodecyl mercaptan were fed through the first feed port.
4 g, a mixed solution of oxetanyl methacrylate 40 g, methyl methacrylate 40 g, and 2-ethylhexyl acrylate 120 g are continuously fed from the second feed port for 4 hours. Perbutyl octanoate 1g
After the addition, polymerization was continued at 120 ° C. for 3 hours to obtain a cationically polymerizable copolymer 1 (a toluene solution having a solid content of 50.9%). The number average molecular weight of this cationically polymerizable copolymer 1 was 10,000 (GPC: converted to polystyrene), and Tg was -2.
The temperature was 8 ° C (viscoelasticity measuring device).

(Example 1) Cationic polymerizable copolymer 1
138.7 g of methyl ethyl ketone was added to 200 g and uniformly mixed to obtain a 30% solution of the cationically polymerizable copolymer 1 in toluene / methyl ethyl ketone. 3 g of 3-ethyl-3-hydroxymethyloxetane, 2 g of diphenyl-4-thiophenoxyphenylsulfonium, and 10 g of hydrogenated rosin ester (KE-100: Arakawa Chemical)
Was stirred and mixed in a brown glass container to obtain a transparent adhesive 1. Further, after adding a toluene / ethyl acetate = 1/1 mixed solution or distilling off the solvent, evaluations 1 to 4 were performed using a transparent adhesive solution whose concentration was adjusted with a toluene / ethyl acetate = 1/1 mixed solution. Carried out. Table 1 shows the results.

Examples 2 to 6 A composition was obtained in accordance with Example 1 except that the composition shown in Table 1 was used, and the composition was evaluated. Table 1 shows the results.

(Comparative Examples 1 to 3) The compositions shown in Table 1 were evaluated in comparison with Examples. Table 1 shows the results.

[0087]

[Table 1]

As is clear from the above table, it is found that the transparent adhesive (B) according to the present invention has higher adhesive strength than the conventionally known adhesive. In addition, it can be seen that a protective layer having excellent durability can be formed by using a polyolefin, particularly a cyclic polyolefin, as the transparent film.

[0089]

The transparent adhesive (B) of the present invention has transparency,
With excellent film thickness uniformity and excellent adhesion, a thin protective layer can be formed, and a DVD having a high storage capacity can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an optical recording medium according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Support 2 Reflective layer 3 Recording layer 4 Intermediate layer 5 Protective layer 6 Transparent film 7 Transparent adhesive layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08F 220/26 C08F 220/26 5D121 C08G 65/10 C08G 65/10 65/18 65/18 C08J 7/04 CER C08J 7/04 CERV CEZ CEZ G11B 7/26 531 G11B 7/26 531 // C08L 101: 00 C08L 101: 00 (72) Inventor Yugo Yamamoto 1190 Kasama-cho, Sakae-ku, Yokohama, Kanagawa Prefecture Mitsui Chemicals, Inc. (72) Inventor Yasushi Takamatsu 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa F-term in Mitsui Chemicals Co., Ltd. AL01B BA02 CA30B CB02B GB41 JA03B JB12B JK06 JL12B JN01A JN01B YY00B 4J005 AA04 AA07 BB01 BB02 4J100 A L03Q AL04Q AL05Q AL08P AL08Q AL09Q AL10P BA02Q BA04Q BC43Q BC53P CA04 DA01 DA25 JA03 5D029 HA05 KA03 LA03 LA04 RA38 5D121 AA04 AA07 EE28 FF03 FF13 GG02

Claims (12)

[Claims] 1. A transparent adhesive comprising a cationically polymerizable copolymer (B-1), a cationically polymerizable monomer (B-2) and a photopolymerization initiator (B-3) on one surface of a transparent film (A). A surface protective material for an optical recording medium coated with (B). 2. The surface protective layer material for an optical recording medium according to claim 1, wherein the curing shrinkage of the transparent adhesive (B) is 3% or less. 3. The material for a surface protective layer for an optical recording medium according to claim 1, wherein the transparent film (A) is a polyolefin. 4. The material for a surface protective layer for an optical recording medium according to claim 3, wherein the polyolefin is a cyclic polyolefin. 5. The cationically polymerizable copolymer (B-1)
The surface protective layer material for an optical recording medium according to any one of claims 1 to 4, wherein the material is an acrylic copolymer containing oxetanyl (meth) acrylate and / or glycidyl (meth) acrylate. 6. The cationic polymerizable monomer (B-2) is
2. A compound or a mixture having an oxetane ring and / or an oxirane ring in a molecule.
6. The surface protective layer material for an optical recording medium according to any one of claims 5 to 5. 7. The compound having an oxirane ring in the cationically polymerizable monomer (B-2) is at least one compound selected from alicyclic epoxy compounds and aliphatic glycidyl ethers. Item 7. A surface protective layer material for an optical recording medium according to Item 6. 8. The surface protective layer material for an optical recording medium according to claim 1, wherein the photopolymerization initiator (B-3) is an onium salt. 9. The content ratio of each component in the transparent adhesive (B) is (B-1) 63 to 99.5% by mass of a cationically polymerizable copolymer, and (B-2) a cationically polymerizable monomer. The surface protective layer for an optical recording medium according to any one of claims 1 to 8, wherein 2 to 30% by mass, and (B-3) 0.3 to 7% by mass of a photopolymerization initiator. material. 10. The transparent film (A) in the surface protective layer material for an optical recording medium according to claim 1, wherein the transparent adhesive (B) in the surface protective layer material for the optical recording medium is used. An optical recording medium obtained by using and holding on a substrate. 11. The substrate comprises a support, on which a reflective layer and a recording layer are sequentially formed. The transparent film (A) is laminated on the recording layer with a transparent adhesive (B), and the transparent adhesive The optical recording medium according to claim 10, further comprising a protective layer obtained by curing the agent (B), wherein information is recorded and reproduced from the protective layer side. 12. The optical recording medium according to claim 10, wherein the optical recording medium is bonded to the substrate in a form of the surface protective material for an optical recording medium according to any one of claims 1 to 9.