JPH0670859B2 - Optical disk substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an optical disk substrate. More specifically, the present invention relates to an optical disk substrate having a tracking groove structure formed by using an ultraviolet curable resin on a transparent substrate and having particularly excellent storage stability.

[Conventional technology and its problems]

On the surface of the substrate for the optical disc, fine tracking grooves are provided in a concentric circle or spiral shape.
This groove is formed by a method of transferring the unevenness of the mold.

The main transfer methods are the injection molding method and the method using an ultraviolet curable resin. The latter is said to be capable of forming a highly accurate tracking groove without problems such as the occurrence of birefringence. There is.

As the UV-curable resin used here, an addition-polymerizable liquid resin having bisphenol A in the skeleton structure is already known (Japanese Patent Laid-Open No. 56-77905). However, an optical disk substrate is constructed using this resin. Even in this case, some problems still needed to be solved. In particular, optical disk substrates manufactured using these UV-curable resins usually have poor long-term storage stability and reliability, and accordingly, UV-curable resins satisfying those requirements have been strongly desired. .

[Object of the Invention]

The present invention satisfies these needs, and an object thereof is to provide an optical disk substrate which is easy to manufacture, has sufficient heat resistance and strength, and has excellent long-term storage stability. It is in.

[Structure of Invention]

Such an object is achieved by using an ultraviolet curable resin composition containing a specific (meth) acrylate compound.

That is, the gist of the present invention is that in an optical disk substrate having an ultraviolet curable resin film having a groove for tracking on the surface thereof formed on one or both sides of a transparent support, the ultraviolet curable resin film is made of a polyester. The present invention resides in an optical disk substrate which is a composition obtained by photocuring a composition containing a functional (meth) acrylate compound.

The polyfunctional (meth) acrylate compound of polyester is produced by subjecting a polyhydric alcohol, a polycarboxylic acid and (meth) acrylic acid to a condensation reaction.

As the polyhydric alcohol, for example, ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, trimethylolethane, glycerin, pentaerythritol, sorbitol, diethylene glycol, Triethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, dipentaerythritol, 1,4-cyclohexanediol, 1,4
-Cyclohexanedimethanol and the like can be mentioned.

Examples of the polycarboxylic acid include phthalic acid, isophthalic acid, terephthalic acid, tetrachlorophthalic acid, dihydroterephthalic acid, tetrahydroterephthalic acid, trimellitic acid, pyromellitic acid, benzophenonedicarboxylic acid,
Examples thereof include maleic acid, fumaric acid, itaconic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, sebacic acid and dodecanoic acid. The polyfunctional (meth) acrylate compound of polyester can be produced by adding the above-mentioned polyhydric alcohol, polyvalent carboxylic acid, and (meth) acrylic acid and subjecting them to a condensation reaction in the presence of a catalyst.

A more preferable polyfunctional acrylate compound is one whose main structure is represented by the following general formula I.

(General formula I) [In the formula, A represents a (meth) acryloyl group, X represents a polyhydric alcohol residue, and Y represents a polycarboxylic acid residue. n is 1
Represents an integer of ~ 10. These compounds can be easily obtained as commercial products, and, for example, oligoester acrylate “Aronix” manufactured by Toagosei Kagaku KK can also be used.

It is advantageous to add a photopolymerization initiator to the photosensitive composition for forming the ultraviolet curable resin film of the present invention in order to increase the photocuring rate. The photopolymerization disclosure agent absorbs ultraviolet light,
Any compound that generates radicals can be used.

As typical ones, p-tert-butyltrichloroacetophenone, 2,4-diethoxyacetophenone, 2-
Hydroxy-2-methyl-1-phenylpropane-1-
On, acetophenones such as 1-hydroxycyclohexyl phenyl ketone; benzophenones such as benzophenone and Michler's ketone (4,4′-bisdimethylaminobenzophenone); 2-chlorothioxanthone, 2-methylthioxanthone, 2-ethylthioxanthone, Examples thereof include thioxanthones such as 2-isopropylthioxanthone; benzoyl and benzoin ethers such as benzoin methyl ether, benzoin isopropyl ether, and benzoin isobutyl ether; benzyls; benzyl ketals such as benzyl dimethyl ketal and benzyl diethyl ketal.

A sensitizer may be added together with such a photopolymerization initiator to accelerate the photocuring rate. As a sensitizer, for example, when using a benzyl compound as a photopolymerization disclosure agent,
Amine compounds such as dimelaminobenzoic acid ethyl ester, di-n-butylamine, triethanolamine and diethylaminoethyl methacrylate are suitable.

The ultraviolet curable resin composition may further contain an addition polymerizable compound having a low viscosity, in addition to the polyfunctional (meth) acrylate compound of polyester, in order to impart an appropriate liquid viscosity. The viscosity of the ultraviolet curable resin composition at room temperature is preferably 10,000 cps or less, more preferably 100 to 4,000 cps, and thereby it becomes possible to completely cover the irregularities on the mold surface.

Examples of the low-viscosity addition-polymerizable compound include monofunctional (meth) acrylate compounds such as 2-ethylhexyl acrylate, lauryl methacrylate, and hydroxyethyl (meth) acrylate; 1,3-butanediol di (meth) acrylate, 1,4 -Butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate,
Difunctional (meth) acrylate compounds such as diethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and hydroxypivalate neopentyl glycol diacrylate; trimethylolpropane tri (meth) acrylate, trimethylolethane trimethacrylate. Examples thereof include trifunctional (meth) acrylate compounds such as pentaerythritol tri (meth) acrylate. In order to obtain a photo-curable resin film having particularly sufficient hardness, one of the addition-polymerizable compounds described above may be used. Preference is given to using functional (meth) acrylate compounds.

The content of the polyfunctional (meth) acrylate compound of the polyester in the ultraviolet curable resin composition is 10 to 99.5% by weight, preferably 25 to 98% by weight, and the content of the photopolymerization initiator is 0.5 to 10% by weight, It is preferably 1 to 6% by weight,
The content of the low-viscosity addition-polymerizable compound is 0 to 89.5% by weight, preferably 0 to 60% by weight.

The liquid UV-curable resin composition thus obtained is obtained, for example, by coating the liquid UV-curable resin composition on the surface of a mold in which a groove for tracking is engraved, and then pressing a transparent support on the surface of the mold for uniform application. After making it to a thickness (10 to 100 μm), irradiating it with ultraviolet light through the support to cure the liquid resin, the support is peeled off from the mold together with the cured resin film adhered to the optical disc. A substrate for is obtained.

As the transparent support, a vinyl chloride / vinyl acetate copolymer, polymethacrylic acid ester, polystyrene, polycarbonate, epoxy resin, glass or the like is used.

By applying an organic or inorganic recording medium to the surface of the obtained substrate provided with the grooves for tracking by vapor deposition, coating, or the like, an optical disk is formed, and recording with a semiconductor laser is possible.

Next, examples and comparative examples of the present invention will be shown, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Example 1 "Aronix M-8060" (manufactured by Toagosei Co., Ltd.) as a polyfunctional (meth) acrylate compound of polyester 50
g, 45 g of trimethylolpropane triacrylate, and further 5 g of "Irgakiure-651" (manufactured by Ciba Geigy) were blended and uniformly dissolved in a stirrer at room temperature, and then passed through a Millipore filter to obtain an ultraviolet curable resin composition. Obtained. A glass support, which is coated with the UV curable resin composition, is spin-coated with a silane coupling agent (Nippon Yunika A-1120), and the glass substrate is coated with the UV curable resin composition. To 50 μm and irradiated with 1.5 Joule / cm ² of ultraviolet light, the support is peeled from the mold together with the cured resin film, and the depth is 700Å.
An optical disk substrate having a groove of 1.6 μm pitch on the surface was obtained. In order to test the heat resistance of the UV curable resin film on the substrate, the substrate surface is irradiated with a laser beam of 830 nm while raising the temperature at 15 ° C / min, and the obtained diffraction image light intensity and transmitted light intensity are obtained. Was measured. As a result, no abnormalities were observed even at 280 ° C. Further, the pencil hardness of the surface of the photocured film was 7H, and the mechanical strength had sufficient characteristics. Next, a GdFe recording medium was formed on the obtained disk substrate using a magnetron sputtering device (430H machine manufactured by Anerva) to a film thickness of 700Å, and the C / N ratio at 1MHz was 50 dB or more. It was possible to record various information. Next, this disk substrate was subjected to an accelerated deterioration test under the conditions of 65 ° C. and 80% relative humidity, but no abnormality was observed even after 600 hours.

Comparative Example 1 2,2-bis (4-acryloyloxydiethyleneoxyphenyl) propane described in JP-A-56-77905
95 g and 5 g of "Irgakiure-651" were mixed and dissolved, and an ultraviolet curable resin composition was prepared and evaluated in the same manner as in Example 1. As a result, the heat resistance and C / N ratio were almost the same as those of Example 1, but the pencil hardness was 1H, and cracks occurred in 75 hours in the accelerated deterioration test, and small craters on the surface in 200 hours. Deformation occurred and gradually increased.

Example 2 95 g of "Aronix M-8030" and "Irgakiure-6"
5 g of 51 "was mixed and dissolved, and an ultraviolet curable resin composition was prepared and evaluated in the same manner as in Example 1. As a result, the heat resistance, pencil hardness, and C / N ratio were almost the same as in Example 1, and no change was observed in the properties of the accelerated deterioration test at 600 hours.

Example 3 25 g of "Aronix M-7100", "Aronix M-806"
0 "20g, trimethylolpropane triacrylate 50g
Then, 5 g of "Irgakiyu-651" was dissolved and mixed, and an ultraviolet curable resin composition was prepared and evaluated in the same manner as in Example 1. As a result, the same results as in Example 1 were obtained in each evaluation item.

[Effects of the Invention] The optical disk substrate of the present invention is very effective in practical use because the grooves for tracking are formed by the special UV-effect resin film having excellent storage stability, heat resistance and strength.

Claims (3)

[Claims] 1. An optical disk substrate having a transparent support on one or both sides of which an ultraviolet curable resin film having a groove for tracking on the surface thereof is applied, wherein the ultraviolet curable resin film is a polyfunctional (meth) acrylate of polyester. An optical disc substrate, which is obtained by photo-curing a composition containing a compound. 2. The optical disk substrate according to claim 1, wherein the polyfunctional (meth) acrylate compound of polyester has a main structure represented by the following general formula I. (General formula I) [In the formula, A represents a (meth) acryloyl group, X represents a polyhydric alcohol residue, and Y represents a polycarboxylic acid residue. n is 1
Represents an integer of ~ 10. ] 3. The ultraviolet curable resin film contains at least 10 polyfunctional (meth) acrylate compounds of the polyester.
The optical disk substrate according to claim (1), which is a composition obtained by photocuring a composition containing 0.5% by weight of a photopolymerization initiator in an amount of 0.5% by weight.