JPH07130003A - Optical disk forming substrate - Google Patents

Abstract

PURPOSE:To obtain an optical disk forming substrate having low double refraction and small warpage with superior mass productivity by molding a transparent thermoplastic resin by injection molding or injection-compression molding. CONSTITUTION:A transparent thermoplastic resin is molded by injection molding or injection-compression molding to produce the objective optical disk forming substrate having <=1.0mm thickness, <=¦20¦nm double refraction in a double-path state and <=200mum warpage. At this time, acrylic resin or polycarbonate resin capable of injection molding or injection-compression molding may be used as the transparent thermoplastic resin. A polymer of a methacrylic ester monomer or an acrylic ester monomer may be used as the acrylic resin and the polycarbonate resin may be produced from bisphenol A and phosgene or bisphenol A and diphenyl carbonate. The optical disk forming substrate capable of high density input of images is obtd. with superior mass productivity at a low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk molding substrate injection-molded or injection-compression molded with a transparent thermoplastic resin.

[0002]

2. Description of the Related Art Optical discs have been rapidly spreading since the market of compact discs (CDs) and laser discs (LDs) in the early 1980's. Nowadays, however, optical discs of CD size are comparable to those of LDs. Is desired to be recorded digitally, and various studies have been made on development of a thin and high-density one. (Lecture 17p-T-11 at "The Society of Applied Physics", Autumn 1992,
17p-T-13, Lecture 29a-B-8, 29a-B-5, etc. at the "Applied Physics Society" in the spring of 1993)
As a method for manufacturing a thin high-density disk, a 2P method, which is one of the transfer methods, is used to apply or inject a curable resin onto a glass substrate or a resin plate, and then stack the masters having pits or grooves formed thereon. Pits or grooves are formed on the substrate by a method of curing a curable resin or an etching method. However, these methods cannot be said to be excellent in terms of mass productivity and cost.

Under such circumstances, as a manufacturing method excellent in mass productivity and cost, a method of obtaining a thin high-density disk molded substrate by injection molding or injection compression molding of a transparent thermoplastic resin has been strongly developed. Is desired.

[0004]

The object of the present invention is to form a transparent thermoplastic resin which has hitherto not been obtained, by an injection molding method or an injection compression molding method.
An object is to provide an optical disk molded substrate having low birefringence and small warpage.

[0005]

The gist of the present invention is that the thickness is 1.0 mm or less, the birefringence is double pass | 20 | nm or less, and the warp of the substrate is 200 μm or less. A characteristic is an optical disk molded substrate injection-molded or injection-compressed with a transparent thermoplastic resin.

As the transparent thermoplastic resin used in the present invention, those which can be injection-molded or injection-compression-molded, such as acrylic resins and polycarbonate resins which have been conventionally used for optical disks, are used.

Specific examples of acrylic resins include, for example, methacrylic acid ester monomers and acrylic acid ester monomers, and if necessary, N-substituted maleimides, maleic anhydride, itaconic anhydride, and other acid anhydrides. Examples of the copolymer include other copolymerizable monomers such as substances.

Examples of the methacrylic acid ester monomer include methyl methacrylate, ethyl methacrylate, propyl methacrylate, cyclohexyl methacrylate, trimethyl cyclohexyl methacrylate, phenyl methacrylate, fluorophenyl methacrylate, chlorophenyl methacrylate, bromomethacrylate. Phenyl, benzyl methacrylate, cyclopentyl methacrylate, norbornyl methacrylate, norbornyl methyl methacrylate, isobornyl methacrylate, bornyl methacrylate, menthyl methacrylate, fentyl methacrylate, adamantyl methacrylate, dimethyl adamantyl methacrylate, tricyclomethacrylate. [5,2,1,0 ^2,6 ] deca-8-yl, tricyclomethacrylate [5,2,1,
[0 ^2,6 ] deca-4-methyl, tricyclodecyl methacrylate, 2,2,2-trifluoroethyl methacrylate, etc., or a mixture thereof.

The acrylic ester monomers include methyl acrylate, ethyl acrylate, propyl acrylate, cyclohexyl acrylate, trimethyl cyclohexyl acrylate, phenyl acrylate, fluorophenyl acrylate, chlorophenyl acrylate, acrylic acid. Bromophenyl, benzyl acrylate, cyclopentyl acrylate, norbornyl acrylate, norbornyl methyl acrylate, isobornyl acrylate, bornyl acrylate, menthyl acrylate, fentyl acrylate, adamantyl acrylate, dimethyl adamantyl acrylate, acrylic acid Tricyclo [5,2,1,0
^2,6 ] deca-8-yl, tricyclo acrylate [5,
2,1,0 ^2,6 ] deca-4-methyl, tricyclodecyl acrylate, 2,2,2-trifluoroethyl acrylate, etc., or a mixture thereof.

Further, other copolymerizable monomers include
For the purpose of improving the heat resistance of the base material, N-substituted maleimides such as N-cyclohexylmaleimide, N-phenylmaleimide, N-chlorophenylmaleimide, N-methylphenylmaleimide and N-bromophenylmaleimide, maleic anhydride. Acid anhydrides and acid anhydrides such as itaconic anhydride may be mentioned.

When a sputtering method is used as a method for forming a metal film on an optical disk molding substrate in the acrylic resin, a mixture containing 20 mol% or more of a methacrylic acid ester monomer and an acrylic acid ester monomer is used. In the copolymer obtained by polymerization, the ratio of methacrylic acid ester in the copolymer is 80 mol% or less,
Intrinsic viscosity measured in chloroform at ℃ 0.3-1.5
It is preferred to use copolymers in the range of dl / g.

Examples of the polycarbonate resin used in the present invention include those obtained from bisphenol A and phosgene, or bisphenol A and diphenyl carbonate.

In the present invention, the optical disk substrate is molded by the injection molding method or the injection compression molding method. The molding conditions are cylinder temperature, mold temperature, mold clamping pressure, injection speed, etc. depending on the material to be used. The target substrate can be obtained by setting.

In the present invention, the thickness of the obtained optical disk molded substrate must be 1.0 mm or less. "Optical Technology Contact" 23 , No. 7,1985
As described in the equation (4) on page 451, a coma aberration having a size proportional to the plate thickness and the cube of the numerical aperture occurs on the tilted optical disk molding substrate. Therefore, the thickness is 1.0
If it exceeds mm, when an objective lens with a high numerical aperture is used to densify the optical disc, coma aberration becomes large, and as a result, crosstalk becomes large when the disc substrate is tilted, and at the same time, the disc from the disc becomes larger. Since the amount of returning light decreases, the S / N ratio deteriorates and the jitter increases too much, which is not preferable.

Further, in the present invention, the birefringence of the obtained optical disk molded substrate needs to be │20│nm or less. If the birefringence exceeds │20│nm, the data error rate of the read signal becomes high and the tracking becomes unstable, which is not preferable.

Further, in the present invention, it is necessary that the warp of the obtained optical disk molded substrate is 200 μm or less. If the warp exceeds 200 μm, tracking and focus become unstable, which makes it impossible to accurately read the data recorded on the optical disc, which is not preferable.

In the present invention, the pits or grooves on the surface of the optical disk molded substrate to be obtained are preferably 1.0 μm or less from the viewpoint of increasing the density of the optical disk molded substrate.

[0018]

The present invention will be described in more detail with reference to the following examples.

In the present invention, an injection molding machine (Dynamelter M-70A-DM manufactured by Meiki Seisakusho Co., Ltd.) is used.
Using a mold equipped with a stamper having pits and grooves having a pitch of 8 to 1.0 μm, an outer diameter of 120 m
An optical disk molding substrate having a thickness of m and a thickness of 0.6 mm was injection-compression-molded, and the substrate was evaluated for birefringence and warpage.

A polarization microscope is used for measuring the birefringence of the substrate.
The value in the double pass was measured with a light beam having a wavelength of 546 nm.

Regarding the warp of the optical disk, the amount of warp of the substrate, which was left at room temperature for one day or more after molding, was measured as the amount of vertical displacement at the outermost periphery with respect to the central portion of the disk substrate.

Example 1 As a transparent thermoplastic resin, 90 parts by weight of methyl methacrylate and 10 parts of methyl acrylate were used.
An optical disk molding substrate was molded under the molding conditions of a cylinder temperature of 280 ° C., a mold temperature of 80 ° C., and a mold clamping pressure of 20 tons using an acrylic resin composed of parts by weight, and a track pitch of 0.8 to 1.0 μm was formed on the substrate surface. A substrate having pits and grooves was obtained. The birefringence of this substrate is 10 nm and the warp is 100.
was μm.

A gold thin film having a film thickness of about 200 angstrom was formed on the surface of this substrate by a sputtering method, and the shape of the pits and grooves was examined by a scanning tunneling microscope (STM). Even the shape of the stamper was reproduced.

Example 2 A disk-molded substrate was prepared in the same manner as in Example 1 except that the molding conditions were a cylinder temperature of 290 ° C., a mold temperature of 70 ° C., and a mold clamping pressure of 20 tons.

The birefringence of the obtained substrate is 10 nm,
The warp was 100 μm. When the shapes of the pits and the grooves were examined in the same manner as in Example 1, the shape of the stamper was reproduced up to the grooves having a pitch of 0.9 μm.

[Example 3] Polycarbonate resin AD9000TG manufactured by Teijin Chemicals Ltd. was used as the transparent thermoplastic resin, and the molding conditions were cylinder temperature 375 ° C, mold temperature 140 ° C and mold clamping pressure 10 tons. A disk molded substrate was prepared in the same manner as in Example 1.

The birefringence of the obtained substrate was -15 nm and the warpage was 180 μm. Further, when the shapes of the pit and the groove were examined in the same manner as in Example 1, it was found that 1.0 μ
The groove of m pitch reproduced the shape of the stamper.

Example 4 A disk-molded substrate was prepared in the same manner as in Example 3 except that the molding conditions were a cylinder temperature of 390 ° C., a mold temperature of 135 ° C., and a mold clamping pressure of 10 tons.

The birefringence of the obtained substrate was -10 nm and the warpage was 120 μm. Further, when the shapes of the pit and the groove were examined in the same manner as in Example 1, it was found that 1.0 μ
The groove of m pitch reproduced the shape of the stamper.

[Comparative Example 1] An optical disk molded substrate was prepared in the same manner as in Example 1 except that the molding temperature was 270 ° C, the mold temperature was 70 ° C, and the mold clamping pressure was 10 tons.

The warp of the obtained substrate was 100 μm, but the birefringence of the substrate was as large as 30 nm.

[Comparative Example 2] An optical disk molded substrate was prepared in the same manner as in Example 1 except that the molding temperature was 290 ° C, the mold temperature was 90 ° C, and the mold clamping pressure was 30 tons.

The birefringence of the obtained substrate was 5 nm, but the warpage was as large as 350 μm.

Comparative Example 3 An optical disk molded substrate was prepared in the same manner as in Example 3 except that the molding temperature was 370 ° C., the mold temperature was 130 ° C., and the mold clamping pressure was 10 tons.

The warp of the obtained substrate was 50 μm, but the birefringence of the substrate was as large as −40 nm.

Comparative Example 4 An optical disk molded substrate was prepared in the same manner as in Example 3 except that the molding temperature was 390 ° C., the mold temperature was 140 ° C., and the mold clamping pressure was 30 tons.

The birefringence of the obtained substrate was -20 nm, but the warpage was as large as 300 μm.

[0038]

The optical disk molded substrate of the present invention is molded by an injection molding method or an injection compression molding method using a transparent thermoplastic resin, which has been heretofore not obtained. It is very excellent in terms of surface, and since the obtained disk-molded substrate has low birefringence and small warpage, high-density image input is possible, and its effect is extremely large as a next-generation optical disk substrate. Is.

Claims (2)

[Claims] 1. A thickness of 1.0 mm or less, birefringence of | 20 | nm or less in a double pass, and a substrate warp of 200.
An optical disk molding substrate injection-molded or injection-compression-molded with a transparent thermoplastic resin, which has a thickness of less than μm. 2. The optical disk molding substrate according to claim 1, wherein the substrate surface has pits or grooves having a pitch of 1.0 μm or less.