JPS61206943A - Production of optical disk substrate - Google Patents

Abstract

PURPOSE:To obtain a substrate which obviates the thermal shear droop owing to the irradiation of laser light during recording and erasing by mixing a curing agent for epoxy resin with a copolymer consisting essentially of a methacrylate monomer and specific vinyl monomer and curing the mixture. CONSTITUTION:At least the curing agent for epoxy resin hardener out of the curing agent for epoxy resin and curing accelerator is mixed with the copolymer obtd. by using the methacrylate monomer A and the vinyl monomer B which has an epoxy group at the side chain and can be copolymerized with the methacrylic acid as essential components and the mixture is cured to obtain the disk substrate. A methyl methacrylate, etc. are more preferable as the monomer A when performances such as thermal deformation temp., water absorptivity and mechanical characteristics of the disk are taken into consideration. A glycidyl methacrylate is preferably used for the monomer B in terms of easy availability, low cost and the easy copolymerizability with the methacrylate. The content of the monomer B in the copolymer is preferably >=5wt% as the thermal deformation resistance is low if the content is too low.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to recording/reproducing/reproducing information by irradiating laser light.
The present invention relates to a method for manufacturing an erasable optical disc substrate.

[Background technology]

Optical discs have a read-only type in which information is carved into the substrate as uneven pits, and a tracking guide groove (hereinafter referred to as "
DRAW type, which records and reproduces information by changing the light reflectance or light transmittance of the recording material formed on the recording material (referred to as "group") by irradiating it with laser light; It is classified into three possible types: E-DRAW type (rewritable type).

Magneto-optical disks are also known as E-DRAW large disks, which record information by using a magnetic material capable of perpendicular magnetization as a recording material and reversing the direction of magnetization by irradiation with laser light. However, DRA
W-type and E-DRAW type optical optical zone discs include:
In order to effect a crystal-amorphous transition or a reversal of the magnetization direction of the recording material when recording information, it is necessary to heat the recording material to several hundred degrees or more by irradiation with laser light, albeit for a short time.

Therefore, as for the optical disk substrate adjacent to the recording material that is exposed to such high temperatures, the groups will not be thermally deformed even in the high temperature conditions (thermal deformation here does not mean thermal deformation under a normal load. A high degree of heat resistance is required.

Traditionally, it has been the first choice as a substrate material for read-only optical discs.
Thermoplastic resins such as methacrylic resins and polycarbonate resins have excellent optical properties, which is a requirement for There is a drawback that the resin softens due to the high temperature and the group becomes deformed. Therefore, such thermoplastic resins can be used for recording/erasing/
E/D requires repeated playback and reliability.
It cannot be used as a raw optical disc material.

[Purpose of the invention]

In view of the current situation, the present invention provides a method for manufacturing an optical disk substrate that has a high degree of heat resistance and does not cause thermal fluctuation of the group due to heat generated by laser beam irradiation during recording and erasing. It is something to do.

[Disclosure of the invention]

In order to achieve this purpose, the inventors investigated various substrate materials for optical discs that can withstand the heat of repeated recording and erasing and do not cause group thermal fluctuation, and have found that they have cross-linked bonds. We have discovered that a type of resin that no longer has thermoplasticity has good heat sag resistance, and in addition to heat sag resistance, it also has the properties necessary for optical disk substrate materials (transparency in the laser wavelength range). The inventors conducted intensive research on resins that also have high refraction (low birefringence, good mechanical properties, etc.), and finally completed this invention.

Therefore, this invention provides methacrylic acid ester monomer (
A) and a vinyl monomer (B) having an epoxy group in its side chain and copolymerizable with methacrylic acid as essential components, and at least an epoxy resin curing agent and a curing accelerator. The gist of this paper is a method for manufacturing an optical disc substrate by mixing a chemical agent and curing the mixture to obtain a disc substrate. The present invention will be explained in detail below.

First, a copolymer is obtained using as essential components a methacrylic acid ester monomer (A) and a vinyl monomer (B) having an epoxy group in its side chain and copolymerizable with methacrylic acid. Specifically, examples of the monomer (A) include methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, and isobutyl methacrylate.

Ester residues such as t-butyl methacrylate and cyclohexyl methacrylate (ester residue refers to the remaining group after removing the 10H group from the alcohol during the enylation reaction), Preference is given to methacrylic acid esters having 1 to 6 alkyl and cycloalkyl groups, and mixtures thereof. In particular, in consideration of performance such as heat distortion temperature, water absorption and mechanical properties of the disk, monomers such as methyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, and mixtures thereof are preferred. As the monomer (B), in addition to glycidyl ester of methacrylic acid, methyl-substituted glycidyl ester, vinyl monomer having a glycidyl group in the side chain, vinyl monomer having an alicyclic epoxy group in the side chain, etc. use Among these, glycidyl methacrylate is preferably used in terms of availability, price, and ease of copolymerization with methacrylate ester. The mixing ratio of these monomers in the copolymer is not particularly limited. However, monomer (B)
If the content is too small, the heat deformation resistance will decrease, so the content in the copolymer is preferably 5 wt% or more. In addition, within the scope of not hindering the purpose of this invention,
A monomer copolymerizable with the above monomers (A) and (B),
For example, styrenes, acrylic esters, two unsaturated groups,! Acid diesters, vinyl alcohol esters.

Monomers such as acrylonitrile may be used in combination. Any known method such as bulk polymerization, emulsion polymerization, suspension polymerization, and solution polymerization may be used as the co-electric method for obtaining this copolymer.

This copolymer is mixed with an epoxy resin curing agent and a curing accelerator, and the mixture is molded in a mold to obtain an optical disc substrate. Although a curing accelerator may or may not be used, it is preferable to use it in order to shorten the curing acceleration time. As curing agents, aliphatic polyamines, W (N-aminoethylpiperazine, dibutylaminopropylamine, etc.), alicyclic amines (isophorone diamine, 4.4'
-diaminodicyclohexylmethane, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane, etc.),
Aromatic amines [(4,4'-diaminodiphenylmethane, 2,4-1-lylene diamine.

metakylylene diamine, etc.), dibasic acid anhydrides (phthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, etc.), organic acids (cepatic acid, adipic acid, decamethylene dicarboxylic acids, etc.), polyamide resins, polyamide amines, imidazoles (2-methylimidazole,
2-ethyl, 4-methylimidazole, etc.), tertiary amines (triethanolamine, benzyldimethylamine,
dimethylaniline, etc.), alkali metal hydroxides, Lewis acids (BF3, T i Cla, A I C1
1, zinc chloride, tin chloride, etc.) and complexes of these with amines, mercaptans (pentaerythritol ester of thioglycolic acid, tris(mercaptopropyl) isocyanurate, etc.), and dicyanamide, dihydrazide as latent curing agents. (Adipic acid dihydrazide,
Known epoxy resin curing agents such as isophthalic acid dihydrazide, etc.) can be used. Among these, hydrogenated phthalic anhydrides are preferred from the viewpoint of colorless transparency of the cured product, but the invention is not limited thereto. Although the amount of these curing agents added varies depending on the type of curing agent, it is sufficient to use the amount added within the range normally used for epoxy resins based on the equivalent weight of the epoxy group in the copolymer. For example, when using a dibasic acid anhydride, curing accelerators that may be added in an amount of 0.5 to 1.0 times the chemical equivalent include amines, imidazoles, Lewis acids, etc. listed among the curing agents. -amine complex,
Mercaptans, tin octylate, sodium alconate, etc. are effective, and an appropriate curing accelerator is selected and used depending on the type of curing agent. For example, for dibasic acid anhydrides, 2. 4. 6-Tri(dimethylaminomethyl)phenol (trade name DMP-30) 1.8-
Diazabicyclo-(5,4,O)-undecene-7(D
BU) and its salts, such as DBU-paratoluenesulfonate, DBU-orthophthalate, DBU-octylate, and DBU-oleate, are useful as curing accelerators that do not impair transparency. The curing agent, curing accelerator, and the like are limited to those mentioned above, but can be employed as long as they are effective as curing agents and curing accelerators for epoxy resins. (
Crosslinker handbook.

(See Shiroshita, Kaneko, eds., published by Taiseisha, October 1981) Furthermore, fatty acids,
A release agent such as a fatty acid ester, an aliphatic alcohol, or a silicone, or an antistatic agent such as a quaternary ammonium salt for the purpose of preventing static electricity may be added to the copolymer within a range that does not impede the object of the present invention.

The above-mentioned copolymer, curing agent, curing accelerator, and other additives are uniformly mixed by a known method such as a kneading method in a molten state using a roll or a kneader, or a solution kneading method. However, kneading in a molten state using rolls or a kneader is more convenient than solution kneading in that there is no need to remove the solvent.

As a molding method, any of injection molding, transfer molding, and direct pressure molding may be used in the same manner as a normal thermosetting resin molding method using a mold set with a stamper on which the group has been transferred.

When manufacturing DRAW and E-DRAW type optical discs, a recording material,
For example, tellurium low oxide containing germanium, indium, lead, etc., iron, terbium, gatrilinium alloy, etc. are deposited, and a protective coating film is formed thereon.

Examples of the present invention and comparative examples will be described in detail below.

(Example 1) A copolymer with a weight average of 10,000 was obtained by copolymerizing 60 wt% of methyl methacrylate and 40 wt% of glycidyl methacrylate using a solution polymerization method.

70 parts by weight (hereinafter abbreviated as "parts") of this copolymer and 30 parts by weight of HHPA (hexahydrophthalic anhydride) as a curing agent.
A resin composition was prepared by mixing 1 part of DBU-paratoluenesulfonate as a curing accelerator. By transfer-molding this resin composition using a mold in which a stamper was set, a chemical formula disk substrate having a thickness of 1.2M and a diameter of 120 μm was obtained. The mold temperature during molding is 150
~160°C molding time was 60 to 90 minutes.

(Example 2) THPA (tetrahydrophthalic anhydride) as a curing agent
An optical disk substrate was obtained in the same manner as in Example 1, except that 30 parts of DMP-30 was used as the curing accelerator and 2 parts of DMP-30 was used.

(Example 3) A copolymer with a weight average of 9,000 was obtained by copolymerizing 50-t% of cyclohexyl methacrylate and 50-t% of glycidyl methacrylate using a solution polymerization method. A resin composition was prepared by mixing 29 parts of HHPA as a curing agent and 2 parts of DMP-30 as a curing accelerator with 71 parts of this copolymer. Thereafter, an optical disc substrate was obtained in the same manner as in Example 1.

(Example 4) An optical disk substrate was obtained in the same manner as in Example 3, except that the curing agent was 20 parts of THPA and the curing accelerator was 1 part of DBU para-toluene sulfonate.

(Example 5) Methyl methacrylate was 40i1t%, isobutyl methacrylate was 20wt%, and glycidyl methacrylate was 40-1t%.
Copolymerization was carried out by a solution polymerization method at a ratio of t% to obtain a copolymer having a weight average molecular weight of 11,000. This copolymer 72
28 parts of HHPA as a curing agent and DB as a curing accelerator
A resin composition was prepared by mixing 2 parts of U-orthophthalate. Thereafter, an optical disc substrate was obtained in the same manner as in Example 1.

(Comparative example) Methyl methacrylate with a weight average molecular weight of 100,000 (
An optical disc substrate similar to that in Example 1 was obtained from the MMA) polymer.

Table 1 shows the composition of the copolymer and the mixing ratio of the resin composition of the above-mentioned Examples, and the evaluation of the characteristics of the optical disc substrate made using the same, together with those of the Comparative Examples. In addition,
The presence or absence of birefringence was examined using a polariscope. Heat sagging resistance was determined by irradiating a disk substrate on which a recording film was deposited with a laser beam, repeating recording and erasing 100 times, and then checking for deformation of the group. The results are as follows:
It had no birefringence, had excellent heat sag resistance, and had very good characteristic evaluations.

(Margin below) [Effects of the Invention] According to the manufacturing method of the optical disc substrate of the present invention, the optical disc substrate has heat sag resistance sufficient to withstand repeated use of recording and erasing with laser light, and has excellent optical properties. You can get a formula disc.

Agent Patent Attorney Takehiko Matsumoto Related Patent Application Colonel Address: 1048 Kadoma, Kadoma City, Osaka Name (583) Matsushita Electric Works Co., Ltd. 1 Company Representative ((JlrIi Weight: Sadao Fujii 4, No agent \6, Specification subject to amendment 7, Amendment Contents (1) r120 μm (7
)Correct the phrase "chemical formula" to "optical formula of r120+m".

Claims (4)

[Claims] (1) An epoxy resin curing agent is added to a copolymer obtained as essential components of a methacrylic acid ester monomer (A) and a vinyl monomer (B) having an epoxy group in the side chain and copolymerizable with methacrylic acid. and a method for manufacturing an optical disk substrate, in which at least an epoxy resin curing agent among the curing accelerators is mixed, and the mixture is cured to obtain a disk substrate. (2) The optical formula according to claim 1, wherein the ester residue of the monomer (A) is one selected from the group consisting of an alkyl group having 1 to 6 carbon atoms and a cycloalkyl group. Manufacturing method for disk substrates. (3) The method for producing an optical disc substrate according to claim 1 or 2, wherein the monomer (B) is glycidyl methacrylate. (4) The method for manufacturing an optical disk substrate according to any one of claims 1 to 3, wherein the curing is performed in a heated mold equipped with a stamper.