JPH04264166A - Overcoating composition for optical disc - Google Patents

Abstract

PURPOSE:To obtain the title composition which can be cured with ultraviolet rays or the like and can give a cured film excellent in adhesion to a recording medium and humidity resistance and being capable of preventing the thin metallic film of an optical disc from being corroded for a long time. CONSTITUTION:This composition contains a compound of the formula (wherein R is H or CH3) and a photopolymerization initiator (e.g. 1-hydroxycyclohexyl phenyl ketone).

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an overcoat composition for optical recording media that is useful as a recording medium for high-speed data files, video recording, etc. , relates to a radiation-curable overcoat composition with good moisture resistance.

0002

2. Description of the Related Art Optical disks such as compact disks and magneto-optical recording disks have a structure in which a thin metal film layer is formed on a transparent substrate such as polycarbonate by vapor deposition or sputtering.

Since this metal thin film layer is easily affected by oxygen and moisture in the atmosphere and its properties deteriorate, conventionally, thermoplastic resins mainly composed of nitrocellulose and ultraviolet curing resins mainly composed of acrylic esters have been used. Although molded resins have been used as overcoating agents, they have insufficient adhesion and moisture resistance, and corrosion has sometimes been observed in the metal thin film layer during environmental resistance tests.

0004

[Problems to be Solved by the Invention] The problem to be solved by the present invention is to provide an optical disc that is capable of forming a cured film that has excellent adhesiveness and moisture resistance, and shows no corrosion on the metal thin film layer of the optical disc even in an environmental resistance test. An object of the present invention is to provide an overcoat composition for

[0005]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present inventors have made extensive studies and have completed the present invention. That is, in order to solve the above problems, the present invention provides general formula (I)

[0006]

[Case 2]

An overcoat composition for an optical disc (wherein R represents a hydrogen atom or a methyl group) and a photopolymerization initiator.
Hereinafter, it will be referred to as the composition of the present invention. )I will provide a.

The compound represented by the general formula (I) used in the present invention is available as a commercial product, such as "Kayarad R-604" manufactured by Nippon Kayaku Co., Ltd.

The compound represented by the general formula (I) used in the present invention has excellent adhesion to metal thin film layers and substrates,
It is a monomer with low hygroscopicity and moderate hardness, and is a central component of the composition of the present invention.

The compounding ratio of the compound represented by formula (I) in the composition of the present invention is preferably in the range of 40 to 95% by weight. When the proportion of the compound represented by general formula (I) used is less than 40% by weight, the characteristics of the compound represented by general formula (I), which are excellent adhesion to metal thin film layers and substrates and low hygroscopicity, are This is not desirable because it tends not to make the most of it.

[0011] As the photopolymerization initiator used in the present invention,
Various photopolymerization initiators and photopolymerization sensitizers used in general ultraviolet curable resins can be used. For example, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isobutyl ether, 2-methylbenzoin, benzophenone, Michler's ketone, benzyl, benzyl dimethyl ketal, 2,2-diethoxyacetophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4- Benzoyl-4'-methyldiphenyl sulfide, 3,3'-dimethyl-4-methoxybenzophenone, 1-(4-dodecylphenyl)-2-hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexylphenyl 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 include trimethylbenzoyldiphenylphosphine oxide, and these photopolymerization initiators can also be used in combination with sensitizing aids such as amines.

The proportion of the photopolymerization initiator used in the composition of the present invention is preferably in the range of 1 to 10% by weight.

Examples of sensitizing aids such as amines include:
Examples include 2-dimethylaminoethylbenzoate, dimethylaminoacetophenone, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, and the like. The usage ratio of these sensitizing aids is 0% of the photopolymerization initiator.
．． A range of 1 to 10% by weight is preferred.

[0014] In the composition of the present invention, a compound having a (meth)acryloyl group (hereinafter referred to as the third component) other than the compound represented by the general formula (I) can be used in combination as the third component. .

The third component is used for the purpose of adjusting the viscosity and curability of the composition of the present invention and the hardness of the cured product,
Particularly preferred are hydrophobic compounds. Examples of the third component include isodecyl (meth)acrylate, isooctyl (meth)acrylate), phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and dicyclopentenyl (meth)acrylate. , isobornyl (meth)acrylate, phenoxyethyl (meth)acrylate, ethylene oxide-modified bisphenol A di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, long-chain aliphatic di(meth)acrylate, etc. ) Acrylate monomers are particularly preferred because they are relatively hydrophobic. Furthermore, trimethylolpropane tri(meth)acrylate, pentaerythol tetra(meth)acrylate, and dipentaerythol tetra(meth)acrylate are components that are not strongly hydrophobic but can increase the hardness of the cured coating film. , dipentaerythol tetra(meth)acrylate, and other polyfunctional monomers can also be used in combination within a range that does not significantly reduce hydrophobicity.

Although the composition of the present invention can sufficiently achieve the desired purpose with the above-mentioned components alone, in order to further improve the performance, a silane coupling agent, a polymerization agent, etc. Additives such as inhibitors, leveling agents, adhesion promoters, etc. can also be added.

[0017] As the silane coupling agent, for example,
γ-methacryloxypropyltrimethoxysilane, γ-
Examples include (2-aminoethyl)aminopropyltrimethoxysilane and γ-mercaptopropyltrimethoxysilane.

Examples of the polymerization inhibitor include hydroquinone monomethyl ether, t-butylcatechol, p-
Benzoquinone, 2,5-t-butyl-hydroquinone,
Examples include phenothiazine.

[0019] As the leveling agent, for example, "Modaflow" manufactured by Monsanto Company, "FC-430" manufactured by 3M Company, etc.
etc.

Examples of the adhesion promoter include carboxyl groups, phosphoric acid groups, or hydroxyl groups such as ethylene oxide-modified succinic acid (meth)acrylate, ethylene oxide-modified phthalic acid (meth)acrylate, and ethylene oxide-modified phosphoric acid (meth)acrylate. Examples include (meth)acrylates having the following.

The amount of these additives used is preferably in the range of 0 to 5% by weight of the composition of the present invention.

The composition of the present invention is applied onto the metal thin film layer of an optical disk using a coating device such as a spin coater so that the dry coating thickness is 5 to 10 μm, and is further irradiated with radiation such as ultraviolet rays. As a result, an overcoat (protective) layer is formed on the metal thin film.

[0023]

EXAMPLES The present invention will be explained in more detail below using Examples and Comparative Examples. In addition, in the following, "%" represents "weight %".

(Example 1) "Kayarad R-604" (
Neopentyl glycol-modified trimethylolpropane diacrylate (manufactured by Nippon Kayaku Co., Ltd.) and 9% of "Irgacure 184" (1-hydroxycyclohexylphenyl ketone, manufactured by Ciba-Geigy) were mixed, and an overcoat for ultraviolet curable optical discs was prepared by a conventional method. A coating composition was prepared.

[0025] Next, the obtained overcoat composition for an ultraviolet curable optical disc was applied onto the recording film of an optical disc in which aluminum was vapor-deposited on a polycarbonate substrate using a spin coater so that the dry film thickness was 7 μm. Then, the coating film was cured by irradiation with a metal halide lamp (120 W/cm, manufactured by Eye Graphic).

After the obtained overcoated optical disk was left in a constant temperature and humidity chamber at 75° C. and 85 RH% for 50 hours, the recording film was observed, and no abnormality was observed.

(Comparative Example 1) An overcoat for ultraviolet curing optical discs was prepared in the same manner as in Example 1, except that "TMP3A" (manufactured by Osaka Organic Co., Ltd.) was used in place of "Kayarad R-604". A coating composition was prepared and an overcoated optical disc was obtained.

[0028] In the same manner as in Example 1, 5
After being left for 0 hours, the surface of the recording film was observed, and as a result, the entire surface of the recording film was corroded.

[0029]

[Effects of the Invention] The composition of the present invention has good adhesion and moisture resistance of the cured coating film to recording media, and can effectively prevent corrosion of the metal thin film layer of optical discs for a long period of time. .

Therefore, the composition of the present invention is extremely useful as an overcoat agent for optical discs.

Claims (1)

[Claims] 1. An overcoat composition for an optical disc, comprising a compound represented by the general formula [Formula 1] (wherein R represents a hydrogen atom or a methyl group) and a photopolymerization initiator.