JPS61289555A - Optical disk - Google Patents

Abstract

PURPOSE:To prevent the deterioration of a recording film by injection-molding a bisalkane polycarbonate resin contg. a specific phosphite and providing the recording film thereon. CONSTITUTION:The bisalkane polycarbonate resin contg. <=0.005wt% phosphite expressed by the formula and having 130,000-22,000 average mol. wt. is injection-molded and the recording film is formed thereon. R1, R2 in the formula are an alkyl group or aryl group and R3 is a hydrogen atom or compd. consisting of an alkyl group or aryl group. The content of the phosphite is <=0.0025wt% by the weight of the polycarbonate resin. An adverse influence is exerted to the recording film and the deterioration of the film is accelerated if the phosphite is excessively added. The optical disk which has no adverse influence on the recording film, has good double refractions, lessens the decrease of a CN ratio and has excellent quality is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical disc on which signals are recorded and recorded signals are read by reflecting or transmitting laser light.

2. Description of the Related Art Digital audio discs (compact discs) and optical video discs are currently commercially available as optical discs. These are read-only optical discs, and software is preloaded on the disc. As these read-only optical discs have come into practical use, write-once or rewritable optical discs for recording information are also being actively developed. This write-once type, rewritable type optical disk has a high possibility of becoming a promising memory medium for information such as images, documents, and data.

Glass or transparent resin is used as the substrate material for these optical discs, and in the case of resin, the following performance is generally required.

(1) Good moldability and good mold transferability (11) High light transmittance (iiD) Small optical anisotropy (hereinafter referred to as birefringence) (V) Mechanical strength Good weatherability) Excellent weather resistance and retention of initial physical properties for as long as possible QB Good vapor deposition properties of the recording material As resins for optical disks, optical properties such as acrylic resin and polycarbonate resin are used. A resin with excellent properties is used.

On the other hand, regarding the vapor deposition material, in the case of a read-only optical disk, aluminum is vapor-deposited on the disk substrate. For recordable and rewritable optical discs, there are melting type and phase change type.

A wide variety of materials have been developed for both magneto-optical and sublimation types. As described above, the optical disk substrate does not chemically react with these recording films and have no adverse effects such as corrosion. That is, it is necessary to contain as little material as possible that has high bleeding properties and volatility and promotes deterioration of the recording film.

Problems that the invention seeks to solve Polycarbonate resins usually suffer from thermal deterioration during molding (
Phosphorus-based antioxidants are added to suppress thermal decomposition. However, if this antioxidant is present in excess, it will have an adverse effect on the recording film. Especially in high-temperature environments,
It is thought that the antioxidant reacts with moisture in the air and turns into an acidic substance, and this acidic substance promotes the deterioration of the recording film. The present invention solves the problem that polycarbonate resin has an adverse effect on the recording film on the disc substrate, and has developed a polycarbonate resin for optical discs that does not chemically react and corrode the recording film. The present invention provides an optical disc using polycarbonate resin.

Means to Solve the Problems The optical disc of the present invention is made of a bis(hydroxyphenyl)alkane-based polycarbonate resin having an average molecular weight of 13,000 to 22ooO and containing 0.006% by weight or less of a phosphite represented by the following structural formula. is obtained by injection molding and applying a recording film thereon.

As bis(hydroxyphenyl) alkanes, 2.
2-bis(4-hydroxyphenyl)furopane (hereinafter abbreviated as bisphenol A), 2°2-bis(4-hydroxyphenyl)butane, 2°2-bis(4-hydroxyphenyl)pentane.

2.2-bis(4-hydroxyphenyl)octane, 1
, 1-bis(4-hydroxyphenyl)ethane, and the like. Moreover, the average molecular weight of the polycarbonate resin needs to be 13,000 to 22,000. Note that the average molecular weight is a value calculated by a normal viscosity method. When attempting to make an optical disk substrate by injection molding a polycarbonate resin having an average molecular weight of 22,000 or more, the birefringence of the optical disk substrate increases because the melt viscosity is high and fluidity is reduced. On the other hand, in the case of a polycarbonate resin having an average molecular weight of 13,000 or less, the mechanical properties are significantly reduced and it cannot be used as an optical disk substrate.

In addition, the phosphorous acid ester represented by the above structural formula may be an alkyl group such as a butyl group, a hexyl group, a decyl group, a cyclohexyl group, a phenyl group, a nonylphenyl group, etc. An aryl group such as υ
, R3 is a hydrogen atom or the above-mentioned alkyl group or aryl group, specific examples thereof include triphenyl phosphite, tris(nonylphenyl) phosphite, tris(2,4-ditertiary-butylphenyl phosphite) , 2-ethylhexyl diphenyl phosphite, didecyl-monophenyl phosphite, and the like.

The amount of phosphite ester is 0.0025% by weight or less based on the polycarbonate resin. When the amount of phosphite added is large, it begins to have a negative effect on the recording film,
Deterioration of the membrane will be accelerated.

On the other hand, phosphite is an antioxidant added to improve the thermal stability of polycarbonate resin during molding, and if it is not added at all, there will be problems with stability in the heated molten state during molding. may occur.

As shown in the examples, when the error rate of an optical disk is measured as an electrical signal using a measurement and evaluation deck, when no phosphite is added, a large number of large defects that cannot be corrected occur. Even if a very small amount of phosphite is added, the number of defects will be reduced to less than the number of replacement tracks.

Function: By suppressing the amount of antioxidant added to the polycarbonate resin, corrosion deterioration of the recording film can be suppressed.

Example Hereinafter, specific examples of the present invention will be described.

Examples 1-9 Average molecular weight is 16,000, 17,000.

The three types of phosphorous esters in 20,000 are tris(nonylphenyl) phosphite, tris(2,4-ditertiary-butylphenyl) phosphite, and 2-ethylhexyldiphenyl phosphite, and the amount added is determined by the resin. Using pellets of polycarbonate resin from bisphenol A of 0.0005.0.001.00026 wt.
An optical disk substrate for data files was injection molded, and the birefringence of this substrate was measured. In addition, tellurium-based oxide was applied on the pregroup surface of the obtained optical disk substrate at 300~SO.
An optical disk was obtained by vapor deposition to a thickness of O. The number of disk defects having a length of 3 μm or more along the circumferential direction of this optical disk was examined using a measurement and evaluation deck to determine how many disk defects were present on the entire disk surface. Furthermore, the obtained optical disc was
0"0 Leave it in an atmosphere of 80% RH and turn it on after a certain period of time.
The N ratio was measured. These results are shown in Table 1.

For comparison, one with an average molecular weight of 25,000, one without phosphite, and one with an added amount of 0.0
The case of 1% by weight is also listed in Table 1. Birefringence was measured using an optical microscope equipped with a Nippon Kogaku Co., Ltd. equipped with a Senarmon compensator on a 110 ff diameter portion of the optical fiber substrate.

(The following is a blank space) Table 1-1 Table 1-2 Example 1 Tris (with an average molecular weight of 15000.0.002% by weight)
Using pellets of polycarbonate resin from bisphenol A (nonylphenyl) phosphite added to a thickness of 1.20. An optical disk substrate for a data file having a diameter of 12 On was molded, and a GdTbFe-based recording material was formed on this substrate by sputtering to obtain an optical disk. The number of disk defects having a length of 30 microns or more along the circumferential direction of this optical disk was examined using an evaluation deck.

Furthermore, the obtained optical disc was heated to 80'CB O%RH.
After a predetermined period of time, the 0M ratio was measured.

As a result, the number of large defects was 20, and 8
After 2000 hours in a 0°C 80% FIH (7) atmosphere, the ON ratio decreased by 0.9 dB compared to the initial state.

For comparison, an optical disc was obtained in the same manner as in Example 10, except that the amount of phosphite added was 0.01% by weight, and the same measurements were performed. As a result, the number of large defects was 6, but the ON ratio after 2000 hours in an atmosphere of 80% RH was 4d compared to the initial value.
B was decreasing.

Although the above embodiments mainly describe the structure and effects of tellurium-based oxides and magneto-optical recording films, they are of course also effective for compact discs having aluminum vapor deposition and CD-ROMs developed from them.

Effects of the invention As is clear from the above explanation, 0
．． Contains 0.05% by weight or less, average molecular weight is 13000
By injection molding bis(hydroxyphenyl)alkane-based polycarbonate resin of ~22,000 and applying a recording film on top of this, it has excellent quality with no adverse effects on the recording film, good birefringence, and little decrease in ON ratio. It is possible to obtain an optical disc.

Claims (1)

[Claims] A phosphite represented by the following structural formula is 0.00
Contains 25% by weight or less, and has an average molecular weight of 13,000 to 2.
An optical disc obtained by injection molding 2000 bis(hydroxyphenyl)alkane-based polycarbonate resin and applying a recording film thereon. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ However, R_1 and R_2 are alkyl groups or aryl groups, R
_3 represents a hydrogen atom, an alkyl group, or an aryl group.