JPH08194968A - Protective coating agent for high density optical disc and hardened matter thereof - Google Patents

Abstract

PURPOSE: To obtain a protective coating agent, and a hardened matter thereof, for optical disc excellent in mechanical strength and having a radiation curing resin layer where warping under high temperature high humidity environment is suppressed by employing a resin composition having tensile fracture elongation of predetermined value or above. CONSTITUTION: The protective coating agent for optical disc is produced by coating the memory part of an optical disc with a radiation curing resin composition having tensile fracture elongation, regulated by JISK7127, of 15% or above at 25 deg.C. The composition of the protective coating agent for optical disc contains more than one (meta) acrylate, i.e., monofunctional monomer or oligomer, in a molecule. The protective coating agent for optical disc is applied covering the recording part on a transparent substrate in order to isolate the recording part from oxygen and moisture in the air thus protecting the recording part from corrosion or the like. Furthermore, the coating agent prevent the optical disc from warping and ensures high quality recording/reproduction for a long term under high temperature high humidity environment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective coating agent for an optical disk, and more particularly to a protective coating agent for an optical disk which is hard to warp in a high temperature and high humidity environment and which is cured by irradiation with radiation having excellent mechanical properties.

[0002]

2. Description of the Related Art Conventionally, various types of media such as magneto-optical discs, various write-once optical discs, compact discs and laser discs have been put into practical use as optical discs for recording / reproducing information by irradiating laser light.

In this optical disc, the generation of cracks in the inorganic layer laminated on the substrate is prevented, the invasion of oxygen and water into the recording layer is more completely prevented, and recording is performed for a long time even in an environment of high temperature and high humidity. The one in which a cured product of an acrylate resin composition is used as an organic protective film on a dielectric layer for the purpose of maintaining reproduction characteristics is disclosed in, for example, JP-A-61-12.
3593, JP-A-61-133067, JP-A-61-1
39961, JP-A-61-153844, JP-A2-1
07630, JP-A-2-132664, and the like.

Further, when the optical disk substrate is warped, the apparatus may misread or unreadable the recorded information, so that it is required that the protective coating agent has a low shrinkage ratio. Generally, in order to lower the curing shrinkage ratio, for example, JP-A-56-135526 and JP-A-2-123172 propose a protective coating agent containing a high-molecular weight oligomer.

On the other hand, as the next generation, research has been conducted on increasing the density for introducing a larger amount of information and image data into an optical disc. The warp of the disk has become a problem again with the increase in density. It is difficult to apply a high-density optical disc because the current disc has a large warp. Currently, studies are being conducted on warpage due to improvements in disk substrates and protective coating agents. In particular, as a protective coating agent, which is considered to be one of the factors of warpage, a satisfactory one is not provided under high temperature and high humidity environment.

[0006]

Even if a protective layer made of a cured product of the radiation-curable resin composition having a low shrinkage ratio of the above-mentioned conventional example is provided, it is satisfactory at room temperature, but at 80 ° C. and 90% RH. Warpage occurs under severe high temperature and high humidity environment.

[0007]

The present inventors have arrived at the present invention as a result of intensive studies to solve the above problems. That is, the occurrence of warpage in a high temperature and high humidity environment was found that the occurrence of warpage can be suppressed if the tensile fracture elongation of the cured product of the radiation-curable resin composition to be applied is appropriate, leading to the invention. It was

The present invention has been proposed on the basis of such an invention, and the tensile breaking elongation defined by JIS K 7127 at 25 ° C. on the recording portion of an optical disk is 1
Provided is a protective coating agent for an optical disk, which is formed by applying a radiation curable resin composition of 5% or more and curing the composition.

The protective coating agent of the present invention is formed on a transparent substrate so as to cover a recording portion composed of a functional film of a recording layer and a reflective layer, and the recording portion is isolated from oxygen and moisture in the air for recording. This is to prevent corrosion of the parts.

Examples of the transparent substrate include general optical disc substrate materials such as polycarbonate resin, polymethylmethacrylate resin, and amorphous polyolefin resin. A recording layer formed on the transparent substrate,
The reflective layer can be arbitrarily selected according to the application. For example, a metal reflective film is formed on a transferred pattern of a CD, a CD-ROM, or the like. Rare earth-transition metal alloy amorphous film is formed on the perpendicular magnetization film of magneto-optical disk. In addition, it can be applied to an optical disc having a recording layer such as a low melting point metal thin film, a phase change film, and a film containing an organic dye.

Next, the components constituting the protective coating agent for an optical disk of the present invention (hereinafter simply referred to as "composition") will be described. The composition of the present invention contains two or more (meth) acrylates in the molecule as a monofunctional monomer or oligomer, but further contains a photopolymerization initiator depending on the type of radiation used for curing the same. can do.

As the monofunctional monomer used in the present invention,
For example, tricyclodecane (meth) acrylate, dicyclopentadieneoxyethyl (meth) acrylate, dicyclopentanyl (meth) acrylate, isobornyl (meth) acrylate, adamantyl (meth) acrylate, phenyloxyethyl (meth) acrylate, benzyl ( Examples thereof include (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, monophorine acrylate, phenylglycidyl (meth) acrylate, and 2-hydroxy (meth) acrylate.

Examples of the monomer having two or more (meth) acryloyl groups in the molecule include neopentyl glycol di (meth) acrylate, tricyclodecane dimethylol di (meth) acrylate and hydroxypivalic acid di (meth). ) Acrylate, polyethylene glycol di (meth) acrylate, dicyclopentanyl di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, tripropylene glycol di (meth) acrylate, neopentyl glycol modified trimethylolpropane di (Meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, alkyl-modified dipentaerythritol penta (meth) acrylate,
Acrylic modified dipentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, caprolite modified dipentaerythritol hexa (meth) acrylate, pentaerythritol tetra (meth) acrylate, tris [(meth) acryloxyethyl] isocyanurate , Caprolactone-modified tris [(meth) acryloxyethyl] isocyanurate, ditrimethylolpropane tetra (meth) acrylate, and the like.

These monomers may be used alone or in combination of two or more, and may be used in an arbitrary ratio. The amount used in the composition is preferably 5 to 90 parts by weight.

Examples of the oligomer having two or more (meth) acryloyl groups in the molecule include bisphenol type epoxy resins (for example, bisphenol A type epoxy resins such as Epicoat 828, 1001, 1004 manufactured by Yuka Shell Epoxy Co., Ltd., and Epicoat 4001P, 400
2P, 4003P and other bisphenol F type epoxy resins) or novolac type epoxy resins (for example, Epicat 152, 154 manufactured by Yuka Shell Epoxy Co., Ltd.) and other epoxy resins obtained by reaction with (meth) acrylic acid (meta). ) Acrylate. Further, polyhydric alcohols (for example, nerpentyl glycol, ethylene glycol, propylene glycol, 1,6-hexanediol, trimethylolpropane, pentaerythritol, tricyclodecane dimethylol, bis- [hydroxymethyl] -cyclohexane, etc.) Basic acid (eg,
(Succinic acid, phthalic acid, hexahydrophthalic anhydride, terephthalic acid, adipic acid, azelaic acid, tetrahydrophthalic anhydride, etc.) and a polyester (meth) obtained by reacting a polyester polyol with (meth) acrylic acid Acrylate. Furthermore, polypropylene glycol, polyether polyol such as polytetramethylene glycol, polyester polyol obtained by the reaction of the polyhydric alcohol and the polybasic acid, by the reaction of the polyhydric alcohol and the polybasic acid and ε-caprolactone The resulting caprolactone polyol, and polycarbonate polyol (for example,
Polycarbonate polyols obtained by reaction of 1,6-hexanediol and diphenyl carbonate) and organic polyisocyanates (for example, isophorone diisocyanate, hexamethylenediisocyanate, tolylene diisocyanate, xylene diisocyanate,
Examples of the resin include a polymer unsaturated group-containing resin such as urethane (meth) acrylate obtained by the reaction of diphenylmethane-4,4'-diisocyanate, dicyclopentanyl diisocyanate and the like) with a hydroxy (meth) acrylate compound.

Among these, bisphenol type epoxy acrylate is particularly preferable in terms of viscosity and curability. These oligomers may be used alone or in combination of two or more, and may be used in an arbitrary ratio, and the amount used in the composition is preferably 5 to 70 parts by weight.

The viscosity of the composition of the present invention is preferably 5 to 300 cps · 25 ° C., particularly preferably 5 to 100 cps · 25 ° C. when applied by a spin coater.

The composition of the present invention contains each component at room temperature to 80 ° C.
It can be obtained by mixing and dissolving. The cured product of the composition of the present invention can be obtained by irradiating with radiation such as ultraviolet rays or electron beams by a conventional method. In the case of ultraviolet curing, it is preferable to use a photopolymerization initiator.

The photopolymerization initiator used in the present invention includes:
Various photopolymerization initiators and photopolymerization initiation assistants used for general UV-curable resins can be used. For example, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin butyl ether, 2-methylbenzoin, benzophenone, Michler's ketone, benzyl, benzyl dimethyl ketal, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, benzoin. Benzoic acid, benzoyl methyl benzoate, 4-benzoyl-4'-methyldiphenyl sulfide, 3,3'-dimethyl-4-methoxybenzophenone, 1- (4-dodecylphenyl) -2-hydroxy-2-methylpropane-1. -One, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-methyl-
1- [4- (methylthiophenyl)]-2-morpholinopropane-1,2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diisopropylthioxanthone, isopropylthioxanthone, 2,4,6-
Examples thereof include trimethylbenzoyldiphenylphosphine oxide, and these photopolymerization initiators may be used alone, in combination of two or more, and may be used in a mixture at an arbitrary ratio. It can also be used together with.

The amount of the photopolymerization initiator used in the present invention is usually 0. 0 with respect to the amount obtained by removing volatile components such as a solvent from the composition.
5 to 20 parts by weight is preferable.

Examples of the photopolymerization initiator such as amines include 2-dimethylaminoethylbenzoate, dimethylaminoacetophenone, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate and the like.

The amount of the photopolymerization initiation aid used is usually preferably 0.5 to 15 parts by weight based on the amount obtained by removing volatile components such as a solvent from the composition.

Further, in the present invention, an organic solvent, a silane coupling agent, a polymerization inhibitor, a leveling agent, a light stabilizer,
Antioxidants, antistatic agents, surface lubricants, fillers and the like can also be used in combination. The curing of the composition of the present invention by ultraviolet irradiation is specifically carried out by irradiating ultraviolet rays using a low pressure or high pressure mercury lamp, a xenon lamp or the like.

The composition of the present invention is particularly useful as a protective coating agent for optical discs. The protective coating agent for an optical disk of the present invention preferably has a dry coating film thickness of 1 to 1 on a recording film of an optical disk by using a coating device such as a spin coater.
The protective film is formed by applying the coating so as to have a thickness of 50 μm and curing by irradiating with ultraviolet rays. In these methods, the present composition may be irradiated with electron beams instead of ultraviolet rays.

[0025]

EXAMPLES The present invention will be described in more detail below with reference to examples. The parts in the examples are parts by weight. Example 1. 20 parts by weight of commercially available bisphenol epoxy acrylate and neopentyl glycol diacrylate hydropivalate shown in Table 1 below (Nippon Kayaku Co., Ltd.)
Manufactured by Kayarad MANDA, 30 parts by weight and phenyloxyethyl acrylate (manufactured by Nippon Kayaku Co., Ltd.,
50 parts by weight of the product name "Kayarad R-561" and 7 parts by weight of a photopolymerization initiator benzophenone (manufactured by Nippon Kayaku Co., Ltd., product name "Kayacure BP-100"). Further, a photopolymerization initiation aid, dimethylaminobenzoic acid. A protective coating agent for an optical disk was prepared by mixing 3 parts by weight of isoamyl acid (manufactured by Nippon Kayaku Co., Ltd., trade name “Kayacure DMBI”).

Protective coating agents for optical disks having the compositions shown in Table 1 were prepared in the same manner as in Example 1 (in Table 1, Examples 1, 2, 3 and Comparative Examples 1, 2 and SD-17 [commodity) Name: Dainippon Ink and Chemicals, Inc., protective coating agent for optical disks]).

The abbreviations of the compositions shown in the table are as follows. EPA-1: Bisphenol type epoxy acrylate,
Nippon Kayaku Co., Ltd. THE-330: Ethylene oxide modified trimethylolpropane triacrylate, Nippon Kayaku Co., Ltd. NPGDA: Neopentyl glycol diacrylate,
Nippon Kayaku Co., Ltd. MANDA: Hydropivalic acid neopentyl glycol diacrylate, Nippon Kayaku Co., Ltd. TC-101: Tetrahydrofurfuryl acrylate,
Nippon Kayaku Co., Ltd. R-561: Phenyloxyethyl acrylate, Nippon Kayaku Co., Ltd. FA-513A: Tricyclodecane acrylate, Hitachi Chemical Co., Ltd. BP-100: Benzophenone, Nippon Kayaku Co., Ltd. Photopolymerization initiator DMBI: Isoamyl p-dimethylaminobenzoate, manufactured by Nippon Kayaku Co., Ltd. Photopolymerization initiation aid Irg-651: 2,2-dimethoxy-2-phenylacetophenone, manufactured by Ciba Geigy Co., Ltd. Polymerization initiator

[0028]

Table 1 Table 1 Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 SD-17 EPA-1 20 30 20 20 20 30 THE-330 --- --30 NPGDA-20 --- MANDA 30-40 30 40 TC-101-10 10-10 R-561 50-30 30-FA-513A-35-20-BP-100 7 5 3 3 3 3 DMBI 3 3 3 1 1 1 Irg-651--3 3 3 3 Curing shrinkage. Rate (%) 8 8 9 8 8 10 Tensile fracture elongation (%) 45 20 27 10 7 5 Warp appearance Immediately after curing ○ ○ ○ △ △ × 25 ℃, 50%, 1hr After durability test ○ △ ○ × × × × 85 ℃, 90%, 3days crack occurred

The liquid specific gravity of each composition obtained and the solid specific gravity of the cured product of the composition were measured to calculate the cure shrinkage, and the results are shown in Table 1.

Each composition thus obtained was measured according to JIS K 7127.
Create a No. 4 type test piece with a film thickness of 200 μm according to the regulations,
The results of the tensile test at 25 ° C are shown in Table 1.

Each composition obtained was applied to a polycarbonate plate having a thickness of 0.5 mm so as to have a film thickness of 50 μm, and cured by a curing device having a high pressure mercury lamp (80 w / cm), and immediately after curing (25 ° C., The degree of warpage was observed after 50% RH, after 1 hour) and after the durability test (85 ° C., 90% RH, after 3 days). The degree of warpage is expressed as follows. ○ ・ ・ ・ ・ No warpage is observed △ ・ ・ ・ ・ Slight warpage is observed × ・ ・ ・ ・ Warp is observed considerably ×× ・ ・ ・ ・ War is greatly warped

[0032]

EFFECTS OF THE INVENTION The cured product of the composition of the present invention has little warpage in a high temperature and high humidity environment and has excellent mechanical properties, and is particularly useful as a protective coating agent for high density optical disks.

Claims (2)

[Claims] 1. A radiation-curable high-density optical disc protective code agent having a tensile elongation at break of not less than 15%. 2. A cured product of the protective coating agent for an optical disk according to claim 1.