JPH0645678B2 - Material for optical disc - Google Patents

Description

TECHNICAL FIELD The present invention relates to a material suitable for optical disc materials, particularly for digital audio discs, optical memory discs and the like.

[Problems to be Solved by Prior Art and Invention]

Generally, various performances are required for the materials for the optical disc as described above. For example, it is necessary to have excellent transparency, heat resistance, low moisture permeability, mechanical strength and the like as well as excellent optical properties. Conventionally, a polycarbonate resin has been known as one having such properties, but a commonly used bisphenol A is used.
Polycarbonate resin obtained by reacting (2,2-bis (4'-hydroxyphenyl) propane) with phosgene or diphenyl carbonate is excellent in heat resistance, low moisture permeability and impact resistance, but has a photoelastic coefficient. Is relatively large, and the fluidity during molding is also unsatisfactory. Therefore, the distortion of the molded product due to the residual strain after the molding process becomes large, the birefringence of the molded product becomes large due to these, and the reading sensitivity of the information recorded on the disk is lowered. As described above, there has not yet been obtained a sufficiently satisfactory optical disc material.

Therefore, the present inventors have conducted extensive studies to develop a polycarbonate resin having improved optical properties by improving the photoelastic coefficient and fluidity, which are the drawbacks of conventional polycarbonate resins.

[Means for solving problems]

As a result, they have found that a specific polycarbonate resin can achieve the above object, and completed the present invention based on this finding.

That is, the present invention has the general formula [In the formula, R ¹ and R ² each represent an alkyl group having 1 to 5 carbon atoms, an alkoxyl group having 1 to 5 carbon atoms, an aryl group, a cycloalkyl group or a halogen atom, and R ³ and R ⁴
Each represents an alkyl group or an aryl group having 1 to 5 carbon atoms (provided that R ³ and R ⁴ are both methyl groups)] and has a concentration of 0 at 20 ° C. Reduced viscosity of a 5 g / dl methylene chloride solution [ηsp /
c] is 0.3 to 1.0 dl / g, and a material for an optical disc made of a polycarbonate resin is provided.

There are various polymers having a repeating unit represented by the above general formula [I] depending on the types of R ^{1 to} R ⁴ , but if the specific structure of the repeating unit is shown, And so on.

The degree of polymerization of the polymer having the repeating unit may be appropriately determined according to the type of optical disc, but the reduced viscosity [ηsp at 20 ° C. of a solution having a concentration of 0.5 g / dl in a methylene chloride solution as a solvent] / C] is 0.3 to 1.0 dl / g,
It should preferably be polymerized to give a polymer of 0.3 to 0.8 dl / g. Here, the reduced viscosity is 0.3 dl / g
If it is less than, heat resistance and mechanical strength will be poor,
On the other hand, if it exceeds 1.0 dl / g, the fluidity is lowered and the molding processability is lowered, resulting in a large residual strain and poor optical properties.

Although the above-mentioned polymer can be produced by various methods, it can be usually produced in the same manner as a general polycarbonate resin having bisphenol A as a starting material. For example, the general formula ^Wherein, R 1 to R ¹ are as defined above. The desired polymer can be obtained by the phosgene method in which phosgene is added to the bisphenol represented by the formula and reacted in the presence of an alkali and optionally a molecular weight modifier in a suitable solvent. It can also be produced by a transesterification method using diphenyl carbonate or the like instead of phosgene.

When molding a disk or the like using the polymer of the present invention, usual additives such as an antioxidant and an ultraviolet absorber may be added.

〔The invention's effect〕

The polymer of the present invention thus obtained has a smaller photoelastic coefficient than conventional polycarbonate resins, and also has good moldability and little molding strain, resulting in small birefringence and excellent optical properties. It is a thing. Moreover, it has excellent heat resistance and mechanical strength. Therefore, when the polymer of the present invention is used as a material for various optical discs, the optical properties are improved, and thus the optical device has high reading sensitivity of information recorded on the disc and little error. Further, since it is a material which is good both in terms of heat and mechanically, the optical disc manufactured using it can operate stably under various conditions.

Therefore, the material of the present invention can be effectively used as a material for optical disks such as digital audio disks and optical memory disks.

〔Example〕

 Next, the present invention will be described in more detail with reference to examples.

Example 1 A solution of 31.8 g of 1-phenyl-1,1-bis (3-methyl-4-hydroxyphenyl) ethane dissolved in 200 m of a 2N aqueous sodium hydroxide solution and p-tert- which is a molecular weight modifier. A solution of 0.1 g of butylphenol dissolved in 250 m of methylene chloride was mixed and stirred, and triethylamine (0.1%) was used as a solvent in the mixed solution.
5 m was added, and then phosgene gas was blown at a rate of 300 m / min. When the pH of the reaction system reached 9, the blowing of phosgene gas was stopped. Next, the reaction solution was separated by separation, and the obtained organic layer was washed with water and then poured into methanol to precipitate and collect a polymer.

The obtained polymer has 0.5 g of methylene chloride as a solvent.
Reduced viscosity [ηsp / c] of a solution with a concentration of / dl at 20 ° C
Was 0.5 dl / g. The glass transition temperature of this polymer was 151 ° C. Furthermore, this copolymer is
The photoelastic coefficient was measured at a wavelength of 633 nm using a sheet having a thickness of 0.3 mm obtained by press molding at 80 ° C. The results are summarized in Table 1.

Example 2 In place of 1-phenyl-1,1-bis (3-methyl-4-hydroxyphenyl) ethane in Example 1, 4-
Example 1 was repeated except that 31.2 g of methyl-2,2-bis (4-hydroxy-3-methylphenyl) pentane was used. The results are shown in Table 1.

Example 3 In place of 1-phenyl-1,1-bis (3-methyl-4-hydroxyphenyl) ethane, 32.6 g of 2,2-bis (4-hydroxy-3-methylphenyl) heptane was used. Other than that was the same as that of Example 1. The results are shown in Table 1.

Example 4 28.4 g of 3,3-bis (4-hydroxy-3-methylphenyl) pentane was used instead of 1-phenyl-1,1-bis (3-methyl-4-hydroxyphenyl) ethane. Other than that was the same as that of Example 1. The results are shown in Table 1.

Example 5 Instead of 1-phenyl-1,1-bis (3-methyl-4-hydroxyphenyl) ethane, 4-methyl-2,2-
The same procedure as in Example 1 was performed except that 34.4 g of bis (4-hydroxy-3-methoxyphenyl) pentane was used. The results are shown in Table 1.

Example 6 32.5 g of 2,2-bis (4-hydroxy-3-chlorophenyl) pentane was used instead of 1-phenyl-1,1-bis (3-methyl-4-hydroxyphenyl) ethane. Was the same as in Example 1. The results are shown in Table 1.

Comparative Example 1 A commercially available 2,2-bis (4-hydroxyphenyl) propane was used as a raw material to obtain a polycarbonate by an ordinary phosgene method. Various physical properties of this polycarbonate were measured in the same manner as in the examples. The results are shown in Table 1.

From the above results, it is understood that the material of the present invention has an excellent photoelastic coefficient as compared with the polycarbonate of Comparative Example 1, and suppresses the birefringence of light of the molded product to be low.

Claims (1)

[Claims] 1. A general formula [In the formula, R ¹ and R ² each represent an alkyl group having 1 to 5 carbon atoms, an alkoxyl group having 1 to 5 carbon atoms, an aryl group, a cycloalkyl group or a halogen atom, and R ³ and R ⁴
Each represents an alkyl group or an aryl group having 1 to 5 carbon atoms (provided that R ³ and R ⁴ are both methyl groups)] and has a temperature of 20 ° C.
A material for optical discs made of a polycarbonate resin having a reduced viscosity [ηsp / c] of 0.3 to 1.0 dl / g in a methylene chloride solution having a concentration of 0.5 g / dl.