JPS6288155A - Optical disk substrate - Google Patents

Abstract

PURPOSE:To obtain a substrate having films of a UV-curing resin which are easily strippable from a metallic mold and have highly accurate and heat resistance groove structure and substantial hardness by forming the films of the specific novolack resin curable by UV rays having grooves for tracking on one or both faces of a prescribed transparent substrate. CONSTITUTION:The film which have the tracking grooves on the surface and consist of the novolak resin curable by UV rays expressed by constitutional formula are formed on one or both faces of the transparent substrate. In formula, n is 0-20 integer, R<1>, R<4> are a hydrogen atom, methyl group, R<2>, R<3> are a hydrogen atom, alkyl group or phenyl group of 1-6C. Any of a polymethyl methacrylate, polycarbonate, polystyrene, epoxy resin, vinyl chloride/vinyl acetate copolymer or glass is used as the transparent substrate. The film of the US-curing resin is formed by photocuring a compsn. consisting of 10-99.5% concn. of the novolak resin and 0.5-10wt% concn. of a polymn. initiator.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an optical disk substrate.

Specifically, an ultraviolet curing resin was used to create a transparent support surface with excellent heat resistance. The present invention relates to an original disk substrate on which a tracking groove structure is formed.

[Conventional technology and its problems]

Concentric or spiral fine grooves are provided on the surface of the original disk substrate for tracking during reading and writing. This groove.

Usually, concentric or spiral grooves are formed on the surface of a mold and then transferred during molding.

The main transfer methods are injection molding or a method using ultraviolet curing resin, but the latter does not cause problems such as birefringence in the resulting groove structure and allows for highly accurate groove formation. is said to be possible.

As the ultraviolet curing resin used here, an addition polymerizable liquid resin having a bisphenol skeleton in its skeleton structure is already known. (Japanese Unexamined Patent Publication No. 36-7), l However, it cannot be said that the groove precision and heat resistance are still sufficient, and a disk with a more reliable groove structure is needed, that is, a high-performance ultraviolet ray. Resin is desired.

[Purpose of the invention]

The first objective is to provide a substrate that is easy to peel off from the mold and has a highly accurate groove structure formed therein.

The first objective is to provide a substrate in which the edge shape of the formed groove structure has sufficient heat resistance even at high temperatures.

The third object is to provide a substrate in which the formed ultraviolet curable resin film has sufficient heat resistance even at high temperatures, especially in the wavelength range of semiconductor lasers.

The second purpose is to provide a substrate in which the formed ultraviolet curable resin film has sufficient hardness.

This objective was achieved by using ultraviolet curable resin compositions containing specific novolak resin derivatives.

[Structure of the invention]

The gist of the present invention is to provide an optical disk substrate in which an ultraviolet curable resin film having tracking grooves on the surface is formed on one or both sides of a transparent support, wherein the ultraviolet curable resin film has the following structural formula (1). The substrate for an optical disk is characterized by being made of a photocured novolak resin shown in the following.

O=0 R'-0 8H! n is an integer of O-10.

R' and R' represent a hydrogen atom or a methyl group.

R1 and R1 represent a hydrogen atom, an alkyl group having 7 to 7 carbon atoms, or a phenyl group.

The novolak resin of structural formula (1) is synthesized by reacting a novolak resin with a glycidyl (meth)acrylate derivative. Novolac resin.

It can be synthesized by a condensation reaction between phenol derivatives such as phenol and cresol and carbonyl compounds such as formaldehyde, acetone, and penzaldehyde.

In order to increase the photocuring speed, the ultraviolet curable resin composition generally contains a photopolymerization initiator in addition to the novolak resin.

The photopolymerization initiator is not particularly limited as long as it is a compound that absorbs ultraviolet light and generates radicals.

Representative examples include p-tart-butyltrichloroacetophenone, ! , 2'-jethoxyacetophenone, cohydroxy-umethyl-/-phenylpropan-7-one and other a7tophenones; benzophenone, Michler's ketone (da, da'-bisdimethylaelectronobenzophenone)% cochlorothioxanthone, -monomethylthioxanthone , coethylthioxane, and -isopropynethioxane; benzoin ethers such as benzoin ether; benzyl and benzyl dimethyl ketal; and pencil tars such as hydroxycyclohexylphenyl lactone.

It is preferable to add sensitizing chemical 11 together with such a photopolymerization initiator because it accelerates the photocuring rate. As a sensitizer,
For example, when using benzyl as a photoinitiator, n
Amine compounds such as -butylamine, di-n-butylamine, triethylamine, diethylaminoethyl methacrylate, etc. are suitable.

In order to maintain an appropriate liquid viscosity, the ultraviolet curable resin composition
In addition to the novolak resin, an addition polymerizable compound with a lower viscosity may be contained. The viscosity of the ultraviolet curable W resin composition in heavy hot water is preferably /aOOOapa or less, more preferably in the range of 10θ to II 000 cpa, which makes it possible to completely remove the unevenness of the mold surface. becomes.

Examples of low-viscosity addition polymerizable compounds include monofunctional (meth)acrylate compounds such as λ-ethylhexyl acrylate, lacryl methacrylate, and hydroxyethyl (meth)acrylate: l,3-butanediol di(meth)acrylate; hedarbutanediol di(meth)acrylate, /, A-hexanediol di(meth)acrylate, diethylene glycol di(meth)acrylate,
Difunctional (meth)acrylate compounds such as neopentyl glycol di(meth)acrylate and hydroxypiparic acid ester neopentyl glycol diacrylate Trifunctional (such as nitrimethylolpropane tri(meth)acrylate and trimethylolethane trimethacrylate)
Examples include meth)acrylate compounds.

In particular, in order to obtain a photocurable resin film having sufficient hardness, it is advantageous to use polyfunctional (meth)acrylate compounds from among the above-mentioned addition polymerizable compounds.

The concentration of the resin of the novolac yarn in the ultraviolet curable resin composition is 1 OX to Tade, 3 wt.
It is preferably 7 to 5% by weight, and the concentration of the addition polymerizable compound is 0 to 70% by weight, preferably 0 to 70% by weight.
It is.

Thus obtained. After curing the 1g resin by irradiating the liquid ultraviolet curable resin pellets with ultraviolet light through a gold support with grooves carved for tracking, the support was added to it and the gold was applied together with the hardened resin film. By peeling it off, a substrate for the original disk is obtained.

As the transparent support, vinyl chloride/vinyl acetate copolymer, polymethacrylate, polystyrene, polycarbonate, epoxy resin, glass, etc. are used.

Obtained. By applying an organic or inorganic recording medium to the surface of the substrate provided with tracking grooves by vapor deposition or gold stone, it becomes possible to record and read from the original disk using a semiconductor laser or the like.

〔Example〕

Examples will be shown below, but the present invention is not limited to the following examples as long as they do not exceed the gist of the invention.

Production Example O Preparation of UV Curable Resin Composition Liquid UV curable resin compositions A and B were prepared by blending Novolak Resin Derivative 1 polymerization initiator and addition polymerizable compound at room temperature under yellow lighting with UV rays removed. , used in the following examples.

In addition, a liquid ultraviolet curable resin composition O containing an addition polymerizable composition described in JP-A-36-Kukude O was prepared and used in the following comparative example.

A composition Novo 2 Tsuku resin derivative 3 parts ■ Addition polymerizable compound Hiro θ part OH, -0-0-OH=O3lt.

■ Polymerization initiator 3 parts B composition Novolak resin derivative 50 parts Oh.

Addition polymerizable compound 75 parts OR, -0-0-OH=OH.

Polymerization initiator 3 parts 00B.

0 composition Addition polymerizable compound 93 parts OCR, 0 Polymerization initiator 3 parts 00H.

Example/Comparative Example 1 A nickel-plated mold was coated with the above-mentioned tow line curing resin compositions A, B, and O, and then spin-coated with a comb springing agent (Nippon Konica). A glass support was pressed so that the film thickness of the ultraviolet curable resin composition was roμ.

After irradiation with ultraviolet rays of 8z:f/di, the support was peeled off from the mold together with the cured resin film to obtain an original disk substrate having grooves on the surface with a depth of 7θθ^ and a pitch of 86μ.

A heat resistance test of the photocured film on the substrate was conducted as follows.

Changes in tracking groove depth and transmission depth due to heating can be observed by heating the substrate sample from room temperature at a heating rate of /r°C/min, and then irradiating the track groove surface with a laser beam of g J Orm. The light intensity and transmitted light intensity of the obtained diffraction image were measured, and each light intensity was 90% of that at the start of temperature rise (ioo%).
Find the temperature when the temperature drops to %. Table 7 shows the results. 7 Reference Example 11 Next, Te was deposited on the original disk substrate obtained in Example 1-2.
8. When a recording medium having a composition of S"Is was deposited to a film thickness of 1) 3oo^ using a commercially available magnetron type sputtering device (Anelva's IJOB machine), both /M
O/N in n2! Good information recording was possible with rOdE or higher. Note that a Nakamichi fissure evaluation device (oMslooo) was used for recording and reproduction.

Examples J, 4 (Comparative Example) The above-mentioned ultraviolet curable resin compositions A to 0 were applied to a conical plated mold, a shibori carbonate support was pressed onto the mold, and after irradiation with ultraviolet light, the support was cured. It was peeled off from the mold together with the resin film to obtain an optical disk substrate having a groove shape on the surface similar to that of Examples/--.When the pencil hardness of the obtained cured resin film was measured, it was shown in Table--. Good results were obtained.

Table Co Reference Example 3, G Next, the original disk substrate obtained in Examples 3 to 1I
When a magneto-optical recording medium with a film thickness of J00^ having a composition of .
+1! Good results were obtained with a C/N of 4 (j-dB or more) in H2.

〔Effect of the invention〕

According to the present invention, peeling from the mold is easy.

A disk substrate with a highly precise groove structure and excellent heat resistance and hardness can be obtained.

Claims (4)

[Claims] (1) In an optical disk substrate in which an ultraviolet curable resin film having tracking grooves on the surface is formed on one or both sides of a transparent support, the ultraviolet curable resin film is a novolak represented by the following structural formula (I). An optical disc substrate characterized by being made of a photo-cured resin. ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(I) n is an integer from 0 to 20. R^1 and R^4 represent a hydrogen atom or a methyl group. R^2 and R^3 represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a phenyl group. (2) The transparent support is any one of polymethyl methacrylate, polycarbonate, polystyrene, epoxy resin, vinyl chloride/vinyl acetate copolymer, and glass. Optical disc substrate. (3) The optical disc substrate according to claim 1, wherein the novolac resin is represented by the following structural formula. ▲There are mathematical formulas, chemical formulas, tables, etc.▼n=0-5 (4) The ultraviolet curable resin film is characterized in that it is obtained by photo-curing a composition containing at least 10% by weight of a novolac resin and 0.5 to 10% by weight of a photopolymerization initiator. An optical disc substrate according to claim 1, which is coated with an ultraviolet curable resin film.