JPS62184639A - Optical disk - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 Currently, digital audio discs (compact discs) and optical video discs are commercially available as optical discs. These are read-only optical discs, and information is stored in advance 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 disks, but in the case of resin, the following performance is required for -i.

(1) Good moldability and good mold transferability.

(ii) High light transmittance.

(iii) Small optical anisotropy (hereinafter referred to as birefringence).

(iv) Good mechanical strength.

(v) It should have excellent weather resistance and retain its initial physical properties for as long as possible.

(vi) Good adhesion of the recording material.

As the resin for optical discs, resins with excellent optical properties such as acrylic resins and polycarbonate resins are 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 transition quizzes.

Various materials have been developed for each magneto-optical type.

As described above, the optical disc substrate does not have any adverse effects such as chemical reaction and corrosion on these recording films.

That is, it is necessary that the material has high bleeding properties and volatility, and does not contain anything that promotes deterioration of the recording film.

Problems that the invention seeks to solve Polycarbonate resins usually suffer from thermal deterioration during molding (
Antioxidants made of organic phosphorus compounds are added to suppress thermal decomposition. However, this antioxidant itself has a negative effect on the recording film or reflective film.Especially in a high-temperature atmosphere, the antioxidant reacts with moisture in the air and turns into an acidic substance. It is thought that if there is a film, it promotes the deterioration of the reflective film.

The present invention solves the problem that polycarbonate resin has an adverse effect on the recording film or reflective film on the disk substrate. An object of the present invention is to provide an optical disc using a polycarbonate resin for optical discs that does not cause any adverse effects.

Means for Solving the Problems The optical disc of the present invention contains an organic phosphorus compound (1,002% by weight or less in terms of phosphorus atoms) and has an average molecular weight of 13
It can be obtained by comprising an optical disc substrate made of a bis(hydroxyphenyl)alkane-based polycarbonate resin having a molecular weight of 000 to 22,000, a dielectric layer, and a recording film or a reflective film.

Function By suppressing the amount of organic phosphorus compound added to the polycarbonate resin below a certain value and by providing a dielectric layer between the optical disk substrate made of polycarbonate resin and the recording film or reflective film, the recording! Corrosion and deterioration of the 3-layer film or reflective film can be suppressed.

Example In the present invention, the cough bis(hydroxyphenyl)alkanes include 2.2-bis(4-hydroxyphenyl)propane (hereinafter abbreviated as bisphenol), 2.2-bis(hydroxyphenyl)propane (hereinafter abbreviated as bisphenol),
-bis(4-hydroxyphenyl)butane, 2.2-bis(4-hydroxyphenyl)pentane, 2.2-bis(4-hydroxyphenyl)octane, 1.1-bis(
Examples include 4-hydroxyphenyl)ethane. In addition, the average molecular weight of polycarbonate resin is 13,000~
Must be 22000.

Note that the average molecular weight is a value calculated by a normal viscosity method. When attempting to obtain 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 due to the high melt viscosity and decreased fluidity. On the other hand, the average molecular weight is 130
In the case of a polycarbonate resin having a molecular weight of 0.00 or less, the mechanical properties are significantly deteriorated and the resin cannot be used as an optical disc substrate.

In addition, the organic phosphorus compound used in the present invention is added as an antioxidant for the purpose of suppressing thermal deterioration (thermal decomposition) during molding, and is a phosphite ester or Trimethyl phosphate is preferred.

As for the phosphorous acid ester represented by the above structural formula, R1 and R2 in the formula are a butyl group and a hexyl group.

A compound in which R3 is an alkyl group such as a decyl group or a cyclohexyl group, or an allyl group such as a phenyl group or a nonylphenyl group, and R3 is a hydrogen atom or the above-mentioned alkyl group or allyl group; specific examples thereof include: , triphenyl phosphite, tris(nonylphenyl) phosphite, tris(2,4-di-t-butylphenyl) phosphite, 2-ethylhexyldiphenyl phosphite, didecyl-monophenyl phosphite, and the like.

The amount of these organic phosphorus compounds added is 0.002% by weight or less in terms of phosphorus atoms based on the polycarbonate resin. When the dielectric layer of the present invention is not provided between the optical disc substrate made of polycarbonate resin and the recording film or reflective film, the amount of the organic phosphorus compound added is as small as 0.00045% by weight in terms of phosphorus atoms. Even if it is, it will have an adverse effect on the recording film or reflective film. However, by providing a dielectric layer on an optical disk substrate made of polycarbonate resin, the organic phosphorus compound can be added up to 0.002% by weight in terms of phosphorus atoms, as described above. However, if the amount added is even larger, it begins to have an adverse effect on the recording film or reflective film, and the deterioration of the film is accelerated.

As mentioned above, the dielectric layer in the present invention prevents the organic phosphorus compound contained in the polycarbonate resin that is the material of the optical disc substrate or the reaction product of the organic phosphorus compound and water from coming into contact with the recording film or the reflective film. It also needs to be transparent at the wavelengths of light used in the optical disc system. Preferred dielectrics suitable for these purposes include z, ns, s, and o□.

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

Examples 1 to 15 Three types of organic phosphorus compounds with average molecular weights of 15,000.17,000 and 20,000, tris(nonylphenyl)phosphite, (2,4-di-t-butylphenyl)phosphite, and 2-ethylhexyl Four types of diphenyl phosphite and trimethyl phosphate, and the amount added is 0.00005 o, ooos, o, in terms of phosphorus atom.
ooi, 0.002% by weight of polycarbonate resin pellets from bisphenol A in four different ways.
Thickness lJw with a spiral pre-group on one side,
An optical disk substrate for a data file with a diameter of 120mm was injection molded, and the birefringence of this substrate was measured. Moreover, Z is formed on the pregroup surface of the obtained optical disc substrate. S from 300 to 1
0,000 thick, and then T as a recording film on top of this.
An optical disk was obtained by depositing an e-based low oxide to a thickness of 300 to 500 layers. 30 along the circumferential direction of this optical disc.
The number of disk defects having a length of .mu.m or more present on the entire disk surface was investigated using a measurement and evaluation deck. Further, the obtained optical disc was left in an atmosphere of 80° C. and 80% RH, and the CN ratio was measured after a predetermined period of time. These results are shown in Table 1.

(Margins below) For comparison, the results for the case where the average molecular weight is 25,000, the case where the amount of organic phosphorus compound added is 0.005% by weight in terms of phosphorus atoms, and the case where there is no ZnS layer are also shown in the first table.
Also listed in the table. Birefringence was measured at the diameter 1)0 fin portion of the optical disk substrate using a Nippon Kogaku Kogyo fissure light microscope equipped with a Senarmon compensator.

Examples 16-18 Example 1.3. and ZnS as dielectric layer in 6
An optical disk was obtained by using S and O2 in place of , and all other substances were carried out in the same manner, and the same items as in Example 1 were measured. The results are shown in Table 2.

(Left below) Example 19 A polycarbonate resin pellet made from bisphenol resin having an average molecular weight of 15,000 and containing 0.001% by weight of tris(nonylphenyl)phosphite (calculated as a phosphorus atom) was used, and one side of the polycarbonate resin was coated with a spiral line. An optical disk substrate for a data file with a thickness of 1.2 fl and a diameter of 12 on is injection molded, and Zn is coated on the pre-group surface.
Apply S to a thickness of 500 people, and then apply GdT on top of this.

An optical disc was obtained by applying a Fe-based recording material. It was investigated how many disc defects having a length of 30 μm or more were present on the entire disc surface along the circumferential direction of this optical disc. As a result, the number of defects was 25. Furthermore, the obtained optical disc was placed in an atmosphere of 80°C and 80% RH for 200 minutes.
The CN ratio after being left for 0 hours was 0.8 dB lower than the initial value.

Example 20 A pellet of polycarbonate resin from bisphenol resin having an average molecular weight of 15,000 and containing o, ooi weight percent of tris(nonylphenyl) phosphite in terms of phosphorus atoms was used, and the thickness was 1.2 with a bit hole as information in advance.
++*, injection molded optical disc substrate with a diameter of 120 m,
After ZnS was applied thereon, AIL was deposited to obtain an optical disk. After leaving this optical disc in an atmosphere of 80°C and 80% RH for 2000 hours, the reflectance was 10% compared to the initial state.
It decreased by a certain amount.

Effects of the Invention As is clear from the above explanation, an optical disk substrate made of a bis(hydroxyphenyl)alkane-based polycarbonate resin having an average molecular weight of 13,000 to 22,000 and containing an organic phosphorus compound in an amount of 0.002% by weight or less in terms of phosphorus atoms. By being composed of a dielectric layer and a recording film or a reflective film, there is no adverse effect on the recording film or reflective film, the birefringence is good, and the CN ratio decreases little.
An optical disc of excellent quality can be obtained.

Claims (7)

[Claims] (1) Contains an organic phosphorus compound of 0.002% by weight or less in terms of phosphorus atoms, and has an average molecular weight of 13,000 to 22,000.
An optical disc comprising an optical disc substrate made of bis(hydroxyphenyl)alkane-based polycarbonate resin, a dielectric layer, and a recording film or a reflective film. (2) Claim No. (2) characterized in that the organic phosphorus compound is a phosphite represented by the following structural formula.
The optical disc described in section 1). ▲There are mathematical formulas, chemical formulas, tables, etc.▼ However, R_1 and R_2 represent an alkyl group or an allyl group, and R_3 represents a hydrogen atom, an alkyl group, or an allyl group. (3) The optical disc according to claim (1), wherein the organic phosphorus compound is trimethyl phosphate. (4) The optical disc according to claim (1), wherein the dielectric layer is Z_nS or S_iO_3. (5) The optical disc according to claim (1), wherein the recording film is a T_e-based low oxide. (6) The optical disc according to claim (1), wherein the recording film is of G_dT_bF_e system. (7) The optical disc according to claim (1), wherein the reflective film is made of Al.