JPH02152037A - Optical disk substrate - Google Patents

Abstract

PURPOSE:To suppress optical distortion and to reduce errors on reading or writing by molding a substrate from polyformal copolymers having a specific structure with recurrent units. CONSTITUTION:The substrate is molded from the polyformal copolymer having recurrent units represented by formulae I and II (wherein, X represents formula III or -SO2- group. The molar ratio of the unit I and unit II, p:q, satisfies [p/(p+q)] X 100 = 95 to 5 and [q/(p+q)] X 100 = 5 to 95). By this method, the substrate has good heat resistance, humidity resistance and shock resistance, and moreover, it has less optical distortion, in particular smaller birefringent for oblique incident light. Consequently, errors on reading or writing can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disk substrate used for optical memory disks and the like.

[Conventional technology]

Optical disc substrates are required to have excellent transparency and low optical distortion. Particularly in optical discs in which information is read or written using digital signals, optical distortion is required to be 20 nm or less as a phase difference in actual molded products. Further, in order to focus the light beam onto the recording film of the substrate, the light beam travels obliquely through the substrate. At this time, the obliquely incident light beam exhibits a large phase difference, which causes errors when reading or writing information.

Conventionally, optical disc substrates have been made of polymethyl methacrylate or 2
, polycarbonate made from 2-bis(4-hydroxyphenyl)propane, etc. are used. However, although the former has excellent optical properties, it has poor heat resistance and
Does not have sufficient performance in terms of moisture resistance and impact resistance.

In addition, although the latter has excellent heat resistance, moisture resistance, and impact resistance, it has large optical distortion, which increases birefringence and reduces information reading sensitivity and causes errors. There are some difficulties.

The purpose is to provide a short circuit board.

[Means to solve the problem]

As a result of extensive research to achieve the above object, the present inventors have discovered that the above object can be achieved by an optical disc substrate made of an aromatic polyformal copolymer having a specific structure with a high density of aromatic nuclei. Based on this knowledge, the present invention was completed.

That is, the present invention provides an optical disc substrate formed by molding a polyformal copolymer having a repeating unit represented by the following formula.

[Problem to be solved by the invention]

The present invention has excellent heat resistance, moisture resistance, and impact resistance, and
Optical device molded from resin with excellent fluidity, with reduced optical distortion, especially birefringence at oblique incidence, and fewer errors during reading or writing CH3C) 13), with a molar ratio of repeating unit I to repeating unit ■ p:
When q, (p/ (p+q)) x 100 is 95 to 5, and (q/ (p+q)) x 100 is 5 to 95.
It is. ] The reduced viscosity [η sp/c ) of the polyformal copolymer used in the present invention at 20°C of 0.5 d1/gfi when dichloromethane is used as a solvent is usually 0.20 to 1.
．． 00cU/g, preferably 0.25-0.50d/g
It is. If the reduced viscosity is less than 0.20 a/g, the molded article will not have sufficient mechanical strength, and if it exceeds 1.0 Odl/g, the fluidity may decrease and the optical strength of the molded article may decrease.

If the copolymer composition of repeating unit (1) and repeating unit (II) (p/ (p+q)) If so, the heat resistance will decrease.

The polyformal copolymer of the present invention is, for example, 4.4'
-dihydroxytetraphenylmethane and 2,2-bis(
3-phenyl-4-hydroxyphenyl)propane, ■
-Phenyl-1,1-bis(3-phenyl-4-hydroxyphenyl)ethane, 1,1-bis(3-phenyl-
4-hydroxyphenyl)cyclohexane, bis(3-
Using a mixed bisphenol consisting of at least one type of bisphenol selected from phenyl-4-hydroxyphenyl) sulfone as a raw material, this mixed bisphenol and methylene cybaride are prepared from ? In each section, it can be obtained by reacting in the presence of an alkali metal hydroxide.

Dichloromethane, dibromomethane, and short methane are used as methylene cybaride, and dichloromethane is preferably used.

Further, as the alkali metal hydroxide, sodium hydroxide, potassium hydroxide, etc. are used.

Further, as a solvent, for example, N-methylpyrrolidone, N-methylpyrrolidone,
, N-dimethylformamide, dimethylacetamide,
Dimethylimidazolidinone, sulfolane, and dimethylsulfoxide are used.

The amount of each reactant to be used is such that the weight ratio of methylene cybaride to 1 of bisphenol is preferably 1.05 to 5, and the alkali metal hydroxide is preferably 2.1 to 3.
．． The concentration of bisphenol in the solvent is preferably 0.0, more preferably 2.2 to 2.8.
1-3 mol/I! , more preferably 0.5 to 2 or above 2
It is used to give moles.

The reaction is usually carried out at 20-150°C2, preferably at 50-100°C.
It is carried out in the temperature range of °C. The reaction time depends on the reaction temperature, but is usually 1 to 20 hours, preferably 3 to 7 hours.
It's time.

Further, the reaction may be carried out by adding a degree of polymerization regulator such as pt-butylphenol to the reaction system.

In the present invention, the polyformal copolymer may be molded as it is, but as long as the optical properties are not affected, antioxidants, 'R' fuel agents, ultraviolet absorbers, antistatic agents, lubricants, etc. may be added as necessary. Additives such as those normally added to polyformal can be added.

Examples of the antioxidants used include 2゜6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, stearyl-β-(3゜5-di-t-butyl-4-
hydroxyphenyl) propionate, 2,2'-methylenebis(4-methyl-6-t-butylphenol),
2.2'methylene-bis(4-ethyl-6-t-butylphenol), 4.4'-thiobis(3-methyl-6-
L-butylphenol), 4.4'~butylidene bis(
3-methyl-6-t-butylphenol), tetrakis[methylene-3-(3',5-di-t-butyl-4-hydroxyphenyl)propionate]methane, 1,1.
3-1-Lis(2-methyl-4-hydroxy-5-t-
phenolic compounds such as butylphenyl)butane, amine compounds such as phenyl-β-naphthylamine, N N'-diphenyl-p-phenylenediamine, tris(nonylphenyl)phosphite, triphenylphosphite, triotadecylphosphite, Examples include phosphorus compounds such as diphenylisodecyl phosphite, sulfur compounds such as dilaurylthiodipropionate, simiristylthiodipropionate, and distearylthiodipropionate.

Examples of the UV absorbers used include salicylic acid UV absorbers such as phenyl salicylate and pt-butylphenyl salicylate, and benzophenone UV absorbers such as 2°4-dihydroxybenzophenone and 2-hydroxy-4-methoxybenzophenone. agent, 2- (2'
Examples include benzotriazole ultraviolet absorbers such as -hydroxy-5'-methylphenyl)benzotriazole and 2-(2'-hydroxy-5'-t-butylphenyl)benzotriazole.

Examples of the antistatic agent used include nonionic antistatic agents such as polyoxyethylene alkylamine and polyoxyethylene alkylamide, anionic antistatic agents such as alkyl sulfonate and alkylbenzene sulfonate, and quaternary ammonium chloride. , cationic antistatic agents such as quaternary ammonium sulfate, and amphoteric antistatic agents such as alkyl hetain type and alkylimidacilline type.

Molding of polyformal copolymer is usually 260 to 400
C1 Preferably carried out at 280-350°C. 26
If the temperature is less than 0°C, the melting of the resin will be insufficient, resulting in decreased fluidity, resulting in optical distortion, or incomplete filling of the resin, which may cause problems in transferability. Also, 400°
At high temperatures exceeding C, the resin may decompose, resulting in yellowing or other discoloration, a decrease in molecular weight, and silver streaks, which may impair the transparency of the molded product.

Mold temperature is usually 80 to 140°C, preferably 100 to
Performed at 120°C. If the temperature is less than 80°C, birefringence tends to occur due to residual stress, and if it exceeds 140'C, the molded product may be deformed.

〔Example〕

Hereinafter, the present invention will be explained in detail based on Examples, but the present invention is not limited thereto.

The copolymer was found to consist of the following repeating units by NMR spectrum analysis.

Example 1 845 g of 4,4'-dihydroxytetraphenylmethane (2,4mo I) and 228 g of 2,2-bis(3-phenyl-4-hydroxyphenyl)propane were added to the reactor.
(0,6mo I), 316 g of sodium hydroxide (
7,9mo I), dichloromethane 383g (4,5
mol), 3.02 mol of 1,3-dimethyl-4-imidazolidinone as a solvent, and 10 g (0,067 m) of pt-butylphenol as a molecular weight regulator.

1) was added, and the reaction was carried out at 80°C for 6 hours with stirring.

After the reaction was completed, the product was cooled, diluted with 101 g of dichloromethane, washed with 0.01 N hydrochloric acid and water, and the organic layer was separated. This was converted into acetone to obtain a polyformal copolymer. The reduced viscosity (ηsp/c) of this polyformal copolymer obtained was 0.29 di/g.
Met. In addition, the glass transition temperature (Tg) is 147.2
It was °C. The result of measuring the photoelastic coefficient (Cm) during melting is 1',000X 10-"cni/dyne
Met. This photoelastic coefficient during melting refers to the slope of a straight line when the resin is melt-spun and wound using a cavilograph, and the stress applied to the thread is taken on the horizontal axis and the birefringence of the thread is taken on the vertical axis. It is something.

Further, for an optical disk substrate having a diameter of 130 mm obtained by injection molding this polyformal copolymer at 340° C., the birefringence at normal incidence and at an oblique incidence of 30° was measured at a position 60 degrees from the center.

The value of this birefringence is -10 nm perpendicular, +25 r at oblique incidence.
+m (double pulse). In addition, moisture permeability, water absorption rate,
These results are summarized in Table 1 together with the hardness and pencil hardness.

Example 2 634 g (1,8 mol) of 4,4'-dihydroxytetraphenylmethane and 456 g of 2,2-bis(3-phenyl-4-hydroxyphenyl)propane were added to the reactor.
(1,2mo 1), 316 g of sodium hydroxide
(7,9mo 1), dichloromethane 383g (4,
5 mol), 1,3-dimethyl-4-imidazolidinone 3.01 as a solvent, and 10 g (0,067 m) of pt-butylphenol as a molecular tt1 moderator.

1), and polymerization and post-treatment were carried out in the same manner as in Example 1. The resulting polyformal copolymer was found to consist of the following repeating units by NMR spectrum analysis.

Reduced viscosity of this polyformal copolymer [ηsp/c]
was 0.30d17g. Further, physical properties such as optical properties and heat resistance of this polyformal copolymer are shown in Table 1.

Example 3 422 g (1,2 mo 1) of 4,4'-dihydroxytetraphenylmethane and 77 g of 1,1-bis(3-phenyl-4-hydroxyphenyl)cyclohexane were placed in a reactor.
8 g (1,8 mo 1), sodium hydroxide 31
6 g (7,9 mo 1), dichloromethane 383
g (4,5 mo 1), the solvent 1,3-dimethyl-4-imidazolidinone 3.01, and the molecular weight adjustment pt-butylphenol 10 g (0°067 mol
), and polymerization and post-treatment were performed in the same manner as in Example 1. The resulting polyformal copolymer was found to consist of the following repeating units by NMR spectrum analysis.

-1,1-bis(3-phenyl-4-hydroxyphenyl)ethane 1061g (2.4mol), sodium hydroxide 316g (7.9mol), dichloromethane 3
83 g (4,5 mo 1), 1,3-dimethyl-4-imidazolidinone 3.02 as a solvent, and 10 g (0,0
67 mol), and polymerization and post-treatment were performed in the same manner as in Example 1. The resulting polyformal copolymer was found to consist of the following repeating units by NMR spectrum analysis.

Reduced viscosity of this polyformal copolymer [ηsp/c]
was 0.33 dl/g. Further, physical properties such as optical properties and heat resistance of this polyformal copolymer are shown in Table 1.

Example 4 211 g (0.6 mo 1) of 4,4'-dihydroxytetraphenylmethane and 1-phenyl were placed in a reactor. The reduced viscosity of this polyformal copolymer [ηsp/c] was 0.
It was 30clf/g. Further, physical properties such as optical properties and heat resistance of this polyformal copolymer are shown in Table 1.

Example 5 528 g (1,5 mo I) of 4,4'-dihydroxytetraphenylmethane, bis(3-phenyl-
4-hydroxyphenyl) sulfone 603g (1,5m
of), 316 g (7.9 mol) of sodium hydroxide,
782 g (4.5 mol) of dibromomethane, 1.
3-dimethyl-4-imidazolidinone 3.0! ! , , and the molecular weight regulator p-L-butylphenol 10
g (0,067 mo 1) was added, and polymerization and post-treatment were performed in the same manner as in Example 1. The obtained polymer is N
According to MR spectrum analysis, it was found to consist of the following repeating units.

Physical properties such as optical properties and heat resistance of this polyformal resin are shown in Table 1.

Comparative Example 1 As a comparative resin, a commercially available polycarbonate resin made from bisphenol was measured in the same manner as in Example 1, and its physical properties such as optical properties and heat resistance were measured and are shown in Table 1.

The reduced viscosity (ηsp/c) of this B15A-PC is 0°3
It was 8a/g.

Comparative Example 2 As a resin for comparison, commercially available polymethyl methacrylate was used in the same manner as in Example 1, and its physical properties such as optical properties and heat resistance were measured and are shown in Table 1.

[Effects of the Invention] The present invention not only has good heat resistance, moisture resistance, and impact resistance, but also reduces optical distortion, especially birefringence at oblique incidence, and prevents errors during reading or writing. Fewer optical disk substrates can be obtained.

Claims (1)

[Claims] 1. An optical disc substrate formed by molding a polyformal copolymer having a repeating unit represented by the following formula. ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [ I ] ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [ II ] [In the formula, X is ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ There are ▼, ▲There are mathematical formulas, chemical formulas, tables, etc.▼ or -SO_2-, repeating unit I
When the molar ratio of repeating unit II is p:q, [p/
(p+q)]×100 is 95-5, [q/(p+q)
]×100 is 5 to 95. ]