JPS63100402A - Optical disk - Google Patents

Abstract

PURPOSE:To obtain an optical disk having small retardation characteristic and superior optical uniformness nd high sensitivity for reading information recorded in the disk by using polysulfone resin having 2,000-200,000 number average mol.wt. and consisting of specified recurrent groups. CONSTITUTION:A polysulfone resin having 2,000-200,000 number average mol.wt. and consisting of recurrent groups expressed by the formula I is used as the base material. In the formula, R1 is H or phenyl group; R2 is H, methyl, phenyl, or biphenyl group. If the number average mol.wt. is <2,000, the optical disk is warped or twisted, etc. easily by the change of heat. If the number average mol.wt. is >200,000, the disk will become hardly moldable. By this constitution, an optical disk causing hardly retardation, having superior optical uniformness and high sensitivity for reading of information recorded in the disk is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disc, and particularly to an optical disc that has small retardation, excellent optical homogeneity, and high information reading sensitivity.

[Conventional technology]

Optical information that records information by irradiating a spot beam of laser light onto the disk to form minute bits on the disk, and then reads the information by detecting the amount of light reflected from or transmitted through these bits. The recording and reproducing method can significantly increase the information recording density.

Furthermore, since the above-mentioned optical type, information recording, and reproducing method has excellent characteristics of reproduced images and sound quality, it is expected that it will be widely put to practical use in recording and reproducing images and sounds.

In the disc used in the above recording and reproducing method, since laser light passes through the disc base material, the disc base material is required not only to be transparent but also to be optically homogeneous.

[Problem that the invention seeks to solve]

Conventionally, methacrylic resin or the like has been applied to optical discs. However, methacrylic resin has a problem in that its heat resistance, moisture resistance, and impact resistance are still far from satisfactory.

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, impact resistance, etc. , the retardation (birefringence value) is large and the optical properties are poor, resulting in problems such as reduced sensitivity for reading information recorded on the disc and errors. (Nikkei Electronics, No. 292, 1982) June 7 issue).

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical disc with a small retardation, excellent optical homogeneity, and high sensitivity for reading information recorded on the disc.

[Means for solving problems]

The above object is achieved by an optical disc based on a polysulfone resin having a number average molecular weight of λ000 to 2 (1000), which is composed of the following repeating unit (1).

However, in the above repeating unit +11, R1 is hydrogen or a phenyl group, and R2 is hydrogen, a methyl group, a phenyl group, or a biphenyl group.

The polysulfone resin used in the present invention has a number average molecular weight of 2.
．． 000~200. Those of OOQ are preferred.

When the number average molecular weight is less than 2.000, the optical disc becomes susceptible to changes such as warping and twisting due to heat.
When the number average molecular weight is higher than 200[]00, it becomes difficult to mold.

Furthermore, the disc base material of the present invention contains auxiliary agents such as silicone, wax, fatty acids, fatty acid esters, fatty acid metal salts, and aliphatic alcohols to improve release properties from the stamper during molding, and to prevent static electricity on the optical disc. Add auxiliary agents such as higher alcohol sulfonates and quaternary ammonium salts to
They may be added to the extent that they do not impede achievement of the objectives of the present invention.

The above-mentioned auxiliary agents may be used alone or in combination of two or more.

In the case of a duplicate disc, the optical disc of the present invention has a number average molecular weight of 2.000 to 2.000, which is composed of the repeating unit (1).
2001) 00 polysulfone resin is injection molded or press molded, a stamper is set on Venus, and the bits that become the information recording signal (tracking signal) are transferred to form the disk base material, and then the signal bits are transferred to the film force. It can be manufactured by forming a reflective layer on the surface of a metal by a method such as vacuum evaporation, sputtering, or ion blating, and further forming a protective layer on the reflective layer if necessary.

In the case of a memory disk, the bits that become the information recording signal are transferred in the same way as above, and a user-writable record made of amorphous rare metal or a compound that can be thermally decomposed by a laser is recorded on the bit surface. It can be manufactured by forming a layer by sputtering, vacuum deposition, coating, etc., and forming a reflective layer or a protective layer as described above on this recording layer, if necessary.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

Polysulfone resin has a number average molecular weight 2 (ILOOO
~180.000 was used.

Number average molecular weight: 2 to 000 Number average molecular weight: 5 to 000 Number average molecular weight: 4 to 000 and 180,000 As comparative samples, commercially available polycarbonates with a number average molecular weight of 3QOOO consisting of repeating units represented by the following formula (A) were used. A commercially available polysulfone resin having a number average molecular weight of 30.000 and consisting of a resin and a repeating unit represented by the following formula (B) was used.

The optical disc was manufactured as follows. That is, the six types of resin pellets mentioned above were injected and dispersed into a mold equipped with a stand bar to obtain 120 disks with a thickness of 1.21111% and a diameter having signal bits engraved thereon. A reflective layer of aluminum was formed by sputtering on the surface on which the signal bits were engraved, and an acrylic lacquer was applied on the reflective layer and dried to form a protective layer.

The characteristics of the optical disc were measured by the methods shown in (+) and (II) below.

(1) Heat-resistant optical discs were left at 120° C. for 4 hours, and the presence or absence of warpage or twisting of the discs was examined.

(11) Optical homogeneity The retardation of an optical disc was measured from the inside to the outside using an ellipsometer (manufactured by Mizojiri Optical Industry Co., Ltd.).
Measurements were taken at 0 locations, and the largest value was taken as the maximum retardation. The smaller the measured value, the better the optical homogeneity. In addition, when measuring retardation carbon,
A He--Ne laser beam with a wavelength of 632° and 8 nm was used as a light source.

Next, the results of measuring the optical disc using the above method are shown in the table. From the table, it was found that the optical discs manufactured using the four types of polysulfone resins according to the present invention had the same heat resistance as optical discs manufactured using commercially available polycarbonate resins and commercially available polysulfone resins.

Furthermore, it has been found that the optical disc manufactured using the polysulfone resin according to the present invention has an extremely smaller maximum retardation density and significantly superior optical homogeneity than optical discs manufactured using commercially available polycarbonate resins or commercially available polysulfone resins.

Furthermore, the optical disks manufactured using the four types of polysulfone resins according to the present invention shown in the table had high practical value and sufficiently satisfied characteristics other than those mentioned above.

table (*) Regarding heat resistance. Leave at 120°C for 4 hours.

〔Effect of the invention〕

As described above, according to the present invention, an optical disc having a small retardation area, excellent optical homogeneity, and high sensitivity for reading information recorded on the disc can be obtained.

Claims (1)

[Claims] 1. Number average molecular weight consisting of the following repeating unit (1) 2.
An optical disc characterized in that the base material is a polysulfone resin having a molecular weight of 000 to 200,000. ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・(1) However, in the above repeating unit (1), R_1 is hydrogen or a phenyl group, and R_2 is hydrogen, a methyl group, a phenyl group, or a biphenyl group. .