JPS63267596A - Optical disk - Google Patents

Abstract

PURPOSE:To obtain an optical disk with a small retardation superior in transparency, heat resistance, moisture resistance, impact resistance, and optical uniformity, by using a polycarbonate resin which is shown by a specific formula and has a softening point in a specific range as a substrate. CONSTITUTION:A polycarbonate resin which is shown by a formula (1) and has a softening point ranging 150-300 deg.C is used as a substrate, here R1, R2 are hydrogen or methyl and m/n=1/4-4/1. A softening point lower than 150 deg.C causes an optical disk to be susceptible to deformation, such as warping and distortion, due to heat, and a softening point higher than 300 deg.C causes a markedly difficult molding; thus, neither conditions are preferable. On the other hand, a condition of m/n<1/4 results in a larger retardation, and that of m/n>1/4 results in a lower mechanical strength; thus, both of said conditions are not desirable. The disk substrate is molded by an injection molding, a press molding, or the like in which a bit to be a recording signal is transferred by a mold provided with a stamper.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disc, and particularly to a base material for an optical disc.

[Conventional technology]

The optical information recording and reproducing method, in which a spot beam of a laser beam is directed onto a disk and the signals recorded by minute pits on the disk are read out by detecting the amount of reflected light or transmitted light, has outstanding image and sound quality. Because of its characteristics, it is expected to be widely used for recording and reproducing images and sounds, recording and reproducing large amounts of information, etc.

Disks used in the above-mentioned optical information recording and reproducing system must be transparent because laser beams pass through the disk base material, and optical homogeneity is strongly required. For the disk, methacrylic resin or the like is used, for example, as described in Nikkei Electronics, No. 292 (June 7, 1982 issue).

[Problem that the invention seeks to solve]

When the above-mentioned methacrylic resin or the like is used for a disk, it is still difficult to say that it has sufficient heat resistance, moisture resistance, and impact resistance. In addition, polycarbonate resin obtained by reacting bisphenol A (2,2-bis(4'-hydroxyphenyl)propane) with phosgene, diphenyl carbonate, etc. has excellent heat resistance, moisture resistance, and impact resistance.
The reddation (birefringence value) is large and the optical properties are poor, causing problems such as reduced sensitivity in reading information recorded on the disc and the occurrence of errors.

The present invention eliminates the problems of the prior art described above, provides transparency,
An object of the present invention is to provide an optical disc that has excellent heat resistance, moisture resistance, and impact resistance, small retardation, and excellent optical homogeneity.

[Means for solving problems]

The above object is achieved by an optical disc whose base material is a polycarbonate resin represented by the following general formula +11 and whose softening point is in the range of 150 to 300°C. (However, R
1-R1 is hydrogen or a methyl group. However, if the softening point is lower than 150°C, the optical disk will easily undergo changes such as warping or twisting due to heating, and if the softening point is higher than 300°C, molding will be extremely difficult. Therefore, either case is not preferable.

Also, in the case of n x 4, the retardation becomes large, and n>
In the case of 1, the mechanical strength decreases, and both are unfavorable.

Furthermore, the base material of the optical disc of the present invention may contain, for example, silicone, in order to improve the releasability from the stamper during molding.
Auxiliary agents such as waxes, fatty acids, fatty acid esters, fatty acid metal salts, and aliphatic alcohols, as well as auxiliary agents such as higher alcohol sulfonates and quaternary ammonium salts for antistatic purposes, can be used to achieve the present invention. It may be added as long as it does not interfere.

In the optical disc of the present invention, a disc base material is formed by transferring the bits serving as a recording signal from the polycarbonate resin according to the present invention using a mold equipped with a stamper using a method such as injection molding or press molding.

Furthermore, in the case of a duplicate disc, a reflective layer is generally formed on the bit transfer surface by a method such as vacuum deposition of metal, sputtering, or ion blasting, and if necessary, a protective layer for the reflective layer is formed. can be manufactured. In the case of a memory disk, bits that serve as tracking signals are transferred to the disk in the same manner as described above, and a user-writable disk made of, for example, an amorphous rare metal or a compound that can be thermally decomposed by a laser is written on the bit surface. The recording layer can be formed by sputtering, vapor deposition, coating, etc., and if necessary, a reflective layer or a protective layer as described above can be formed.

〔Example〕

Next, the present invention will be explained in more detail by way of examples.

Six types of resins (2) to (7) shown below were used as test resins.

(However, rrV'n = 1/4 Softening point is 200
°C) with the chemical formula (2) above, n1/n
= 271 and the softening point is 250℃ ・So・Song・
Curved surface... Curved surface Curved surface + 31 The chemical formula of (2) above, ny'n = 4/1 Softening point power 300
℃Nomono ......Curved surface...Song...Curved surface...+41 (However, Iv/n = 174
, with a softening point of 200 t:) With the chemical formula (5) above, IV/n = 2/l is softened Al at 150°C ... curved surface for curved curved surface old curved surface・+61 Formula 1 in (6) above, with ny'n = 471 and a softening point of 300℃ ・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・(7) Also, for comparison, it consists of a repeating unit represented by the following two flashes and has a softening point of 190
A conventional polycarbonate resin at 100°C was also used.

Next, a method for manufacturing an optical disc and a method for measuring the characteristics of the manufactured disc will be described.

Manufacture of optical discs The above seven types of polycarbonate resin pellets were injection molded into a mold equipped with a stamper, and the thickness was 1.
A disk with a diameter of 2M and a diameter of 1208 cm was obtained.

Next, a reflective layer made of aluminum was formed by sputtering on the surface of the disk on which the signal bits were engraved, and an acrylic lacquer was applied on this anti-St+ω surface and dried to form a protective layer to obtain an optical disk.

Method for Measuring Properties (Softening Point) Flat plates were prepared using each of the seven types of polycarbonate resins listed above, and the Vicat softening point was determined according to J I 8 K7206.

(2) Heat resistance Seven types of optical discs produced as described above were heated to 120
After being left at ℃ for 4 hours, the presence or absence of warpage and twisting was visually determined.

(31 Optical homogeneity) The retardation of the optical disc tabulated as above was measured using an ellipsometer (manufactured by Mizojiri Optical Industry Co., Ltd.).
A He--Ne laser beam with a wavelength of 632.8 Mm was irradiated to measure 10 locations from the inside to the outside of the optical disc. The maximum value was then indicated as the maximum retardation. The smaller the maximum retardation value, the better the optical homogeneity.

(4) Tensile strength This is necessary as a guideline for the mechanical strength with which an optical disk can withstand high-speed rotation of 50 Orpm or more.
It was determined according to JIa K6911 at ℃.

Anything above 45 FvlPa can withstand practical use.

Next, the results of measuring the characteristics of the above-mentioned type 7a are shown below.

Characteristic measurement results The measurement results are summarized in Table 1. As is clear from Table 1, polycarbonate 41 according to the present invention! The original discs manufactured using resin have a higher softening point than optical discs manufactured using ordinary polycarbonate resin, superior heat resistance, and a tensile strength that satisfies a practical level, and in particular have a small maximum retardation. It was found that the optical homogeneity (including transparency) was very good, and the information reading sensitivity was also high.

Furthermore, the moisture resistance and impact resistance s% were also good.

* Regarding heat resistance. Check for warping or twisting of the optical disc after being left at 120°C for 4 hours.

Hayashi Regarding the optical homogeneity of optical discs. The smaller the maximum retardation, the better.

Rin All resins have a pressure of 45 MPa or higher, which is at a practical level.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain an optical disc that has excellent transparency, heat resistance, moisture resistance, and mechanical strength, has particularly small retardation, is excellent in optical homogeneity, and has high information reading sensitivity. , /−′,.

Agent: Patent Attorney Katsuo Ogawa
I Procedural Amendment (Saba) Case Description 1988 Patent Application No. 101945 Title of Invention 11 cases of fraud with those who make optical disc corrections Patent Applicant R Name 15101 Stock Company 11 Manufactured by Hitachi
(1 person) Target of amendment by agent Scope of claims in the description and Part 1 of the invention,
The scope of claims is amended as shown in the attached sheet.

2 General formula (1) from line 17 to line 20 on page 3 of the specification of the present application is corrected as follows.

[5] General formula (2) k from page 6, line 1 to line 6 of the specification of the present application is amended as follows.

XcH/'' 4. General formula (5) from page 6, line 12 to line 17 of the specification of the present application? I-, knee. Correct it accordingly.

[Attachment Claim 1, lower F+e general formula (covered with Ri, and with a softening point of 1
Base material is polycarbonate resin in the range of 50 to 30"C.

A former Dinuk who is famous for his character.

(However, R1 and bird are hydrogen or methyl groups, and G1=i
～T is C large “

Claims (1)

[Claims] 1. It is represented by the following general formula (1) and has a softening point of 150
An optical disc characterized in that the base material is a polycarbonate resin having a temperature in the range of ~300°C. (However, R_1 and R_2 are hydrogen or methyl groups, and m/n = 1/4 to 4/1.) ▲There are mathematical formulas, chemical formulas, tables, etc.▼... (1)