JPH01167315A - Optical disc base plate - Google Patents

Abstract

PURPOSE:To obtain the title base plate excellent in e.g., surface hardeness, by photocuring, to a specified shape, a composition produced by incorporating a specified amount of a self-scission-type photopolymerization initiator in a composition comprising a specific polymerizable compound and photopolymerizable (meth)acrylate monomer, etc. CONSTITUTION:(I) a composition comprising (A) pref. 5-50wt.% of a polymerizable compound of the formula (R1 is H or CH3; R2 is H, 1-6C alkyl, etc.) and (B) pref. 50-80wt.% of at least one kind of compound selected from (meth)acrylate monomers, vinyl group-contg. monomers each photopolymerizable with the component A is incorporated with (II) 0.5-5wt.%, based on the composition I, of a self-scission-type photopolymerization initiator to produce a composition with a viscosity of <=800cp (at 25 deg.C). This composition is injected, pref. between a transparent plate and stamper with such integral as to be designed to keep a desired level by spacer, followed by ultraviolet irradiation to effect photocuring, thus obtaining the objective optical disc base plate little in optical strain and warpage due to moisture absorption, excellent in heat resistance, mechanical strength, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disc substrate for storing, recording, and reproducing audio, images, information, and the like.

[Conventional technology]

Disk substrates for optical disk memories are manufactured by pouring plastic with a low degree of polymerization into a mold with a stand bar installed on one side of polycarbonate resin or acrylic resin at high temperature and pressure, or by molding plastic with glass or acrylic resin. , a photocurable resin is poured onto a flat plate of polycarbonate resin, epoxy resin, etc., a metal stand bar is pressed onto it, radiation is irradiated from the substrate side to harden the resin, and the stand bar is peeled off to produce an optical disk substrate. ,
The so-called 22 method is known.

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.

[Problem that the invention seeks to solve]

The method of molding optical disk substrates by injection method has excellent productivity, but not only does it allow foreign matter to get mixed in and the C/N ratio is low, but in the case of polycarbonate resin, residual stress during molding causes the molecules to become oriented, resulting in optical problems. Distortion (birefringence)
Polymethyl methacrylate resin has the disadvantage of easily becoming large and easily scratched during the manufacturing process due to its low surface hardness.Polymethyl methacrylate resin has high hygroscopicity, which causes the disc to warp easily, and its heat resistance is low, making it difficult to record. There is a problem that the thermal stability of the groove with the film is low.

Furthermore, in the case of using the 2P method, the optical disc substrate is created in two steps, which takes time, and also requires high reliability in adhesion between the substrate and the photocuring resin, and it is also necessary to select a transparent substrate. Acrylic resins have a problem of warping due to their low Tg and hygroscopicity, polycarbonate resins have large birefringence, and epoxy resins have problems such as a long curing time during molding.

JP-A-60-112409, JP-A-61-202
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.

has not yet been reached.

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]

The present invention is based on the A knee formula % formula % [wherein R6 represents 11 or CH3, R2 represents H, C,
-C6 alkyl group or phenyl group.

] A composition containing a polymerizable compound represented by B: at least one selected from photopolymerizable (meth)acrylate monomers, vinyl group-containing monomers, and oligomers thereof; Provided is an optical disc substrate made by photocuring a resin composition containing 0.5 to 5% by weight of a self-cleavable photopolymerization initiator and having a viscosity of 800 cp (25°C) or less into a predetermined shape. It is something to do.

The polymerizable compound of component A is a low-viscosity liquid monomer typically synthesized from neopentyl glycol and pivalic acid.

Photopolymerizable acrylate monomers, vinyl group-containing monomers, and oligomers thereof as component B include epoxy (meth)acrylates such as bisphenol A epoxy (meth)acrylate, polyester (meth)acrylates, urethane (meth)acrylates, silicone (
meth)acrylate, 2.2-bis(4-methacryloyloxyethoxyphenyl)propane, 2.2-bis(
4-Acryloyloxyethoxybiphenyl)propane, 2,2-bis(4-acryloyloxyethoxyphenyl)sulfone, 2,2-bis(4-acryloyloxyethoxyfer)sulfone, 1,6-hexanethiol di(meth)acrylate , trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethoxytrimethylolpropane tri(meth)acrylate, neopentyl glycol di(meth)acrylate, tripropylene Glycol di(meth)acrylate, isobonyl(meth)acrylate, tricyclodecanyl(meth)acrylate, styrene, N-vinylpyrrolidone, oligomers thereof, and the like are used. The molecular weight of the oligomer is 200-10
00 is preferred.

Components A and B are used in combination, and their mixing ratio varies depending on the type and amount used,
If the A component exceeds 50% (same as below weight %), hygroscopicity tends to increase, and if it is less than 5%, heat resistance tends to decrease, which is not preferable. Regarding each of the B components,
Although it cannot be determined unambiguously because it varies depending on the structure itself, the number of functional groups, the viscosity after mixing, etc., it is usually used in an amount of 50% or more, preferably 50 to 80%.

The photopolymerization initiator used in the present invention is a self-cleavable type from the viewpoint of non-coloring of the cured product. These may be known ones, and typically include benzoin methyl ether, benzoin ethyl ether, 2゜2-dimethoxy-2-phenylacetophenone, ■-hydroxycyclohexylphenyl ketone, 1-(4-isopropylphenyl )-2
-Hydroxy-2-methylpropane and the like. These are used in an amount of 0.5 to 5% by weight based on both components A and B. Two or more of these may be used in combination.

Additives such as anti-yellowing agents, ultraviolet absorbers, antioxidants, leveling agents, polymerization inhibitors, mold release agents, and antistatic agents may be added to the resin composition of the present invention as necessary to achieve the effects of the present invention. It can be added as long as it does not interfere.

Furthermore, since the resin composition is injected into a mold and cured, the viscosity at room temperature is preferably as low as possible. There is a method of heating the resin composition as a means of lowering the viscosity.
This is undesirable because it causes disadvantages due to heating, such as a shortened pot life and generation of residual stress due to curing in an expanded state of the resin.

The viscosity of the above resin composition is 800 cp (25
°C) or less. When the viscosity exceeds 800 cp, pouring and defoaming becomes very difficult.

To polymerize the above resin composition and manufacture a disk substrate, the resin composition is injected between a transparent plate and a metal or transparent plate stamper, or between two transparent plates, keeping a predetermined distance with a spacer. It is photocured by irradiating it with ultraviolet rays, etc. from one side or the entire surface. In the latter case, a resin layer having the grooves of the stamper transferred thereon is then formed on the photocured substrate.

In order to obtain a substrate without warpage, it is preferable to make the center 4, transparent plate temperature, resin composition temperature, and stamper temperature as uniform as possible during photocuring. The temperature difference between the three is less than 20°C.
Preferably, the temperature is 5°C or less. If a temperature difference of more than 20°C occurs between the three, the warpage of the substrate will increase.

In addition, during light irradiation, the light source, transparent plate, and stamper are It is desirable to photocure by moving or rotating.

〔Example〕

Hereinafter, the present invention will be explained in detail based on Examples, but the present invention is not limited thereto.

Examples 1 to 4, Comparative Example 1.2 A glass mold consisting of two pieces of temporary glass and a spacer was prepared, and in this mold, 2 parts by weight of 1-(4-isopropylphenyl)-2-hydroxy-2 -Methylpropane-
1-one added and mixed Table 1 No. 1 to No.
Various resin compositions having a viscosity of 800 cp (25° C.) or less were injected into the sample, and ultraviolet rays were irradiated from the surrounding area using an 80 W/cll + high-pressure mercury lamp.

After curing for 60 seconds, the mold was released to obtain a uniform substrate with a thickness of 1.2 m+ and a diameter of 30 ctn. Using this substrate, we measured the following characteristics (1) to (5).
Obtained the results in the table. Also, for comparison, No. 5, No.
The specificity was also measured for a substrate using the resin shown in No. 6.

(1) Water absorption rate: The sample was left in water at 60''C for 300 hours and measured according to JIS-6911.

(2) Heat Resistant Temperature i The glass transition temperature was measured by the DMA method.

(3) Optical properties: 830n on a resin plate with a thickness of 1.2m + w
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-691N.

As can be seen from Table 1, the substrate of the present invention has a lower water absorption rate (and higher heat resistance) than a polymethyl methacrylate substrate.Also, compared to a polycarbonate substrate, it has lower retardation and surface hardness. Excellent.

Examples 5 to 8 A glass plate coated with a release agent was placed facing a Ni stamper with a grooved pattern, and 1.2 mm was placed between the two.
A resin injection mold was formed with a space of nv. At this time,
Water at 25°C was circulated through the stamper base, and air at 25°C was continuously blown onto the glass plate using a blower.

Example 1~ kept in this mold at 25°C in a constant temperature bath
Inject each resin No. 1 to No. 4 in Table 1 shown in No. 4, and heat it using an 80 W/cm high pressure mercury lamp.
The resin was cured by irradiating ultraviolet rays from the glass plate side for 0 seconds to obtain a grooved patterned substrate. After depositing a Te-based recording film on a grooved transparent substrate to a thickness of 30 μm, the entire substrate was
An optical disc recording medium was prepared by exposing the recording film to an atmosphere of 10°C for a period of time to crystallize the recording film. The obtained optical disc recording medium had a good output level when outputting information, and the substrate did not warp.

Examples 9 to 10 A resin injection agent was prepared in the same manner as in Examples 5 to 8 using a glass plate coated with a release agent and a grooved patterned glass stamper coated with a release agent. Furthermore, in this mold,
Table 1 No. 1 to No. shown in Examples 1 to 4,
3 resins were injected. Using an 80 W/cm high pressure mercury lamp, ultraviolet rays were irradiated from the glass plate side for 15 seconds and from the stamper side for 15 seconds to cure the resin. The obtained grooved patterned substrate was subjected to the same treatment as in Examples 5 to 8 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.

〔Effect of the invention〕

The optical disc substrate of the present invention has low optical distortion (birefringence), low warpage due to moisture absorption, excellent surface hardness, and heat resistance, and is excellent in productivity because it can be molded in a short time by photocuring.

Furthermore, productivity can be further improved by injecting a resin composition between the glass plate and the stamper, which are maintained at a predetermined distance by a spacer, and photocuring the resin composition by irradiating it with ultraviolet rays or the like to produce an optical disk substrate.

Claims (1)

[Claims] 1. A: General formula ▲ Numerical formula, chemical formula, table, etc. ▼ [In the formula, R_1 represents H or CH_3, R_2 represents H,
Indicates an alkyl group or a phenyl group from C_1 to C_6. ] A composition containing a polymerizable compound represented by B: at least one selected from photopolymerizable (meth)acrylate monomers, vinyl group-containing monomers, and oligomers thereof; An optical disc substrate formed by photocuring into a predetermined shape a resin composition containing 0.5 to 5% by weight of a self-cleavable photopolymerization initiator and having a viscosity of 800 cp (25°C) or less. 2. The optical disc substrate according to claim 1, wherein a resin composition is injected between the transparent plate and the stamper, which are maintained at a desired distance by a spacer, and is photocured by irradiation with ultraviolet rays. 3. When photocuring, the temperature of the transparent plate, the temperature of the resin composition,
3. The optical disk substrate according to claim 2, which is photocured at a uniform stamper temperature.