JPS63110203A - Optical disk substrate - Google Patents

Abstract

PURPOSE:To obtain a disk substrate, hardly warping by optical strain and moisture absorption and having improved surface hardness, heat resistance as well as mechanical strength with high reliability for a long period, by photopolymerizing a resin composition consisting of specific two kinds of polymerizable compounds and photopolymerizable monomer. CONSTITUTION:An optical disk substrate obtained by injecting a resin composition consisting of (A) a polymerizable compound expressed by formula I (R is H or CH3; X1-X8 are H, Cl or Br; m is 0-3), (B) a polymerizable compound expressed by formula II (Y1-Y4 are H, Cl or Br; n1 and n2 are 0-3) and (C) a photopolymerizable acrylate monomer, oligomer or vinyl group-containing monomer, e.g. (meth)acrylate, N-vinylpyrrolidone, etc., into a gap between a glass plate and stamper with a given interval, preferably kept by a spacer and photo-setting the composition while irradiating with ultraviolet rays.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an optically readable disk or screen substrate, particularly to an optical disk substrate such as a digital audio disk, video disk, or memory disk.

(Prior art) A method of manufacturing a disk substrate for an optical disk memory is to mold polycarbonate resin or acrylic resin using the indie exion method. Another method is to pour a photocurable resin onto a flat plate of glass, acrylic resin, polycarbonate resin, epoxy resin, etc., press a metal stamper over it, and irradiate radiation from the substrate side. A so-called 2P method is known in which an optical disc substrate is manufactured by curing the resin and peeling off the stamper.

Furthermore, JP-A-60-112409, JP-A-60-2
02557, JP 61-44689, JP 61-98710, JP 61-11591
Publication No. 3, JP-A-61-159411, JP-A-6
Japanese Patent No. 1-176618 proposes a method of manufacturing an optical disc substrate by photocuring an acrylic resin.

(Problems to be solved by the invention) Although the method of molding optical disk substrates by injection method has excellent productivity, it is easy for foreign matter to get mixed in (not only is the C/N ratio low, but polycarbonate resin is Optical distortion (birefringence) due to orientation of molecules due to residual stress
It has the disadvantage of being thick and easily scratched during the manufacturing process due to its low surface hardness, and polymethyl methacrylate resin has a high hygroscopicity, making the disc easy to warp and having low heat resistance. Therefore, there is a problem that the thermal stability of the groove provided with the recording film is low.

In addition, in the case of using the 2P method, the optical disk substrate is created in two steps, which takes time from a work perspective, and also requires high reliability in the adhesion between the substrate and the photocuring resin. Acrylic resin has a problem of warping due to its low Tg and hygroscopicity, polycarbonate resin has a large birefringence, and epoxy resin has problems such as a long curing time during molding.

JP-A-60-112409, JP-A-60-202
557, JP 61-44689, JP 61-98710, JP 61-115913, JP 61-159411, JP 61-1987-
The method proposed in Publication No. 176618 reduces warpage,
It is said to have characteristics such as low water absorption, low moisture absorption, and heat resistance, but none of these have yet been put into practical use.

The present invention provides an optical disk substrate that is less warped due to optical distortion (birefringence) and moisture absorption, has excellent surface hardness, heat resistance, and mechanical strength, and has high long-term reliability.

(Means for solving problems) Invention 1, A general formula (+) (In the formula, R is HSCH3, and X+-Xs is H%CI.

Br%m is 0-3) A polymerizable compound represented by B general formula (n) (In the formula, R is H, CH:+, Y+ to Y4 are H, CI.

Br, n, n is 0 to 3) A polymerizable compound represented by: C: a photopolymerizable acrylate monomer, oligomer,
A resin composition comprising a vinyl group-containing monomer 1 is photocured into a predetermined shape to form an optical disc substrate.

Photopolymerizable acrylate monomers, oligomers, and vinyl group-containing monomers include epoxy (meth)acrylate, polyester (meth)acrylate, and urethane (
meth)acrylate, silicone (meth)acrylate, 1.6 hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, ethoxytrimethylolpropane tri(meth)acrylate ) acrylate, neopentyl glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, isobonyl(meth)acrylate, tricyclodecanyl(meth)acrylate, styrene, N-vinylpyrrolidone, etc. are used. The molecular weight of the oligomer is preferably 200 to 300.

Components A and B can be copolymerized, and components A, B, and C are used in combination. The mixing ratio varies depending on the type and amount used, but if the A component exceeds 80% (the same below weight%), the hygroscopicity tends to increase, while if it is less than 5%, the mechanical strength, heat resistance, surface Hardness tends to decrease, which is not preferable.

Moreover, if the B component exceeds 80%, it tends to become brittle and the impact resistance decreases, while if it is less than 10%, the hygroscopicity increases.

It is preferable to use 50% or more of each component C, although it cannot be determined unambiguously because it varies depending on its own structure, number of functional groups, etc.

In order to polymerize the above resin composition and manufacture a disk substrate,
A resin composition is injected between a transparent plate and a metal or transparent plate stamper, which are kept at a predetermined distance by a spacer, or between two transparent plates, and is photocured by irradiating ultraviolet rays or the like from one side or the entire surface. In the latter case, a resin layer having the grooves of the stamper transferred thereto is formed on the photocured substrate.

The resin composition of the present invention may contain commonly known photosensitizers, such as dibenzoyl, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2-hydroxy-2-benzoylpropane, azobisisobutyl ether, etc. Butyronitrile, benzyl, thioxanthone, diphenyl disulfide, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 2-hydroxy-
2-methyl-1-phenyl-propan-1-one, 2.
2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, etc. can be used. These photosensitizers are used in amounts of at most 5% based on the resin composition.

Additives such as an anti-yellowing agent, a leveling agent, and an ultraviolet absorber can be added to the resin composition of the present invention, if necessary, within a range that does not interfere with polymerization and curing.

Example 1 A glass mold consisting of two glass plates and a spacer was prepared, and a double portion of 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-
Various resin compositions of NotmNO4 in Table 1, which had been added and mixed with On, were injected and irradiated with ultraviolet rays from the surroundings using an 80-/bi high-pressure mercury lamp. After curing for 60 seconds, release the mold and check the thickness! , 2 tm, and a uniform thickness of 30 cm in diameter was obtained. Using this substrate, the following characteristics (I1 to (4)) were measured and the results shown in Table 1 were obtained.

(I) Water absorption rate: left in water at 60°C for 300 hours, JI
S- was measured according to 6911.

(2) Heat resistant temperature: Glass transition temperature was measured by DMA method.

(3) Optical properties: 830r on a resin plate with a thickness of 1.2H
+a+ light was applied, and the light transmittance was determined using a spectrophotometer.

In addition, retardation was also measured by irradiating light of 830 nm to determine birefringence.

(4) Surface hardness: Pencil hardness was determined.

(5) Bending strength: Measured according to JIS-6911.

(Left below) As can be seen from Table 1, the substrate of the present invention has lower water absorption and higher heat resistance than polymethyl methacrylate substrates, and has lower retardation than polycarbonate substrates. Excellent hardness and surface hardness.

Example 2 A glass plate coated with a release agent was placed facing a groove-patterned Ni stamper, and 1.
A resin injection mold was formed with a 2 m space.

In this mold, the first table N01 to NO shown in Example 1
Each of the resins No. 4 was injected, and the glass plate was irradiated with ultraviolet rays for 60 seconds using an 80 W/am high-pressure mercury lamp to harden the resins, thereby obtaining a grooved patterned substrate.

After a Te-based recording film was deposited to a thickness of about 30 μm on the surface of a grooved transparent substrate, the entire substrate was exposed to an atmosphere at 100° C. for 1 hour to crystallize the recording film, thereby producing an optical disc recording medium. The obtained optical disc recording medium had a good output level when outputting information, and the substrate did not warp.

Example 3 A resin injection mold was prepared in the same manner as in Example 2 using a glass plate coated with a release agent and a grooved patterned glass stamper coated with a release agent. Furthermore, each resin of Table 1 No. 1 to No. 4 shown in Example 1 was injected into this mold. Using an 801 f/am high pressure mercury lamp, ultraviolet rays were irradiated from the glass plate side for 30 seconds, and then ultraviolet rays were irradiated from the stamper side for 30 seconds to cure the resin. The obtained grooved patterned substrate was subjected to the same treatment as in Example 2 to produce an optical disc recording medium.

No warping was observed in the obtained optical disc recording medium, and information could be written and read smoothly.

(Effects of the Invention) The optical disk substrate of the present invention has less optical distortion (birefringence) and warping due to moisture absorption, and has excellent surface hardness, mechanical strength, and heat resistance, and can be molded in a short time by photocuring, so it can be manufactured. productivity is increased.

Furthermore, the resin composition is injected between the glass plate and the stamper, which are maintained at a predetermined distance by a spacer, and is photocured by irradiation with ultraviolet rays or the like to produce an optical disc substrate, thereby significantly increasing the productivity of its production.

Claims (1)

[Claims] 1.A: General formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (In the formula, R is H, CH_3, X_1 to X_9 are H, Cl,
Br, m are 0 to 3) B: General formula (II) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (II) (In the formula, R is H, CH_3, Y_1 to Y_4 are H ,Cl,
Br, n_1n_2 is 0 to 3) and C: a photopolymerizable acrylate monomer, oligomer,
An optical disc substrate formed by photocuring a resin composition comprising a vinyl group-containing monomer into a predetermined shape. 2. The optical disc substrate according to claim 1, wherein a resin composition is injected between a glass plate and a stamper, which are maintained at a predetermined distance by a spacer, and is photocured by irradiating ultraviolet rays.