JPH1135671A - Polycarbonate resin composition for optical disk substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polycarbonate resin composition excellent in strength and transferability on injection molding and used for optical disk substrates by including a prescribed amount of a specific low mol.wt. polymer. SOLUTION: This polycarbonate resin composition contains 3.5-8 wt.% of a low mol.wt. polymer comprising repeating units represented by the formula [X is a 1-4C alkylene, a 2-3C alkylidene, O, S, CO, SO, SO2 ; (n) is 1-4] (cases containing 14-30C aliphatic acid monoglyceride in amounts of 0.06-0.1 wt.% are excluded). The optical disk substrate is an optical disk substrate or DVD substrate comprising a molded substrate having a thickness of <=1 mm, preferably <=0.6 mm, or the laminate of the two molded substrates. The substrate is obtained by injection-molding the resin composition at a resin temperature of >=350 deg.C and at a mold temperature of >=100 deg.C. The viscosity-average mol.wt. of the polycarbonate resin is preferably 10,000-25,000.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polycarbonate resin composition for an optical disc substrate, and more particularly, to D.
The present invention relates to a polycarbonate resin composition for an optical disk substrate useful as a VD substrate.

[0002]

2. Description of the Related Art Conventionally, as a material for an optical disk substrate,
Polycarbonate resins are mainly used in terms of transparency, strength, heat resistance and the like. However, polycarbonate resins have a bulky benzene ring in the main chain of the polymer, and their moldability is not always sufficient. When forming an optical disc substrate having a thickness of 1 mm or less using such a polycarbonate resin, the thickness is relatively thin, the gate thickness is small, the shortest pit length is as small as about 0.4 μm, and the interval between pits and grooves is also small. In order to obtain a substrate excellent in transferability because it is as short as about 0.74 μm, for example, it was necessary to reduce the molecular weight of the polycarbonate resin.

[0003] However, although the fluidity is improved by reducing the molecular weight of the resin, there is a problem that the strength of the substrate is significantly reduced when the molecular weight is reduced. Therefore, it was difficult to obtain a polycarbonate resin having excellent strength and transferability.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polycarbonate resin composition for an optical disk substrate which is excellent in transferability during injection molding and excellent in strength.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and the gist of the present invention is to provide a low molecular weight compound comprising a repeating unit represented by the following general formula (1): 0.5 to 8% by weight of the polycarbonate resin composition for an optical disk substrate (excluding the case where a fatty acid monoglyceride having 14 to 30 carbon atoms is contained in an amount of 0.06 to 0.1% by weight).

[0006]

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(Wherein, X represents an alkylene group having 1 to 4 carbon atoms, an alkylidene group having 2 to 3 carbon atoms, an oxygen atom, a sulfur atom, a carbonyl group, a sulfinyl group, or a sulfone group; 4 represents an integer.)

Hereinafter, the present invention will be described in detail. The polycarbonate resin in the present invention is produced by reacting a dihydric phenol and a carbonate precursor by a solution method or a melting method, and is preferably obtained by reacting phosgene and a dihydric phenol by interfacial polymerization. Polycarbonate resin.

As the dihydric phenol, 2,2-bis (4-hydroxyphenyl) propane [bisphenol A], bis (4-hydroxyphenyl) methane, 1,1
-Bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, bis (4- (Hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfone and the like. As the dihydric phenol, preferably, a bis (4-hydroxyphenyl) alkane-based compound, particularly one containing bisphenol A as a main raw material is used. Examples of the carbonate precursor include carbonyl halide, carbonyl ester, and haloformate, and more specifically, phosgene, diphenyl carbonate, dihaloformate of divalent phenol, and a mixture thereof, and preferably phosgene. In producing the polycarbonate resin, the dihydric phenol may be used alone or in combination of two or more. Further, a branching agent may be used in combination with the above dihydric phenol compound.

The viscosity average molecular weight of a polycarbonate resin is determined by using methylene chloride as a solvent at a temperature of 25 ° C.
Is the viscosity average molecular weight calculated from the solution viscosity measured in 1.
It is between 000 and 25,000. Viscosity average molecular weight of 1
If it is less than 000, the strength of the obtained optical disk is not sufficient, and if it exceeds 25,000, the transferability tends to be reduced in molding the optical disk. The viscosity average molecular weight is preferably from 11,000 to 20, from the viewpoint of strength and transferability.
2,000, more preferably 12,000 to 18.0
00. When producing a polycarbonate resin having such a viscosity average molecular weight, a suitable molecular weight regulator, a catalyst for accelerating the reaction, and the like can be added.

[0011] The polycarbonate resin composition for an optical disk substrate of the present invention contains a low molecular weight compound comprising a repeating unit represented by the following general formula (1).

[0012]

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In the formula, X represents an alkylene group having 1 to 4 carbon atoms, an alkylidene group having 2 to 3 carbon atoms, an oxygen atom, a sulfur atom, a carbonyl group, a sulfinyl group or a sulfone group, and n represents 1 to 4 Indicates an integer.

[0014] The content of the low molecular weight compound comprising the repeating unit represented by the general formula (1) is 3.5 to 8% by weight of the polycarbonate resin composition for an optical disk substrate. When the content of the low-molecular-weight substance is less than 3.5% by weight, the flowability of the resin on the surface of the optical disk substrate is not improved because the amount of the low-molecular-weight substance transferred to the skin layer is small, and exceeds 8% by weight. Then, white spots occur due to hydrolysis after the high-temperature and high-humidity test of the optical disk substrate.

[0015] The low molecular weight substance comprising the repeating unit represented by the general formula (1) easily migrates to a surface layer called a skin layer within 10 to 30 μm in the thickness direction of the surface of the optical disk substrate, and the flow on the surface of the optical disk substrate It greatly affects sex. The pit depth and groove height, which are signals of the optical disk substrate, are about 1000 to 2000 ° and are located in the skin layer of the substrate. Therefore, the amount of the low molecular weight skin layer affects the transferability of the signal of the optical disk. .
For example, when molding a molded substrate having a thickness of 0.6 mm, since the resin temperature is as high as about 380 ° C. and the mold temperature is as high as about 120 ° C., the transition of the low molecular weight substance to the skin layer is remarkable, These effects are significant.

If the low molecular weight of the polycarbonate resin composition is 3.5 to 8% by weight, the glass transition temperature of the skin layer at the time of molding the optical disc substrate is the glass transition temperature of the core layer, that is, the central portion in the thickness direction of the substrate. About 20 ° C. lower than the glass transition temperature, and the fluidity of the molten resin on the surface of the substrate is improved. Along with this, the transferability of the signal is 9
The temperature of the molten resin required to secure 0% or more is 20 to
It is possible to lower the temperature by about 30 ° C. At this time, the glass transition temperature of only the skin layer on the surface of the optical disk substrate decreases, and the decrease of the glass transition temperature of the core layer is small. Therefore, the strength of the optical disk substrate hardly decreases.

In order to increase the content of the low molecular weight compound composed of the repeating unit represented by the general formula (1) in the polycarbonate resin, for example, (a) a method in which the stirring conditions of the polymerization reaction are relaxed; ) A method of accelerating the addition of a polymerization terminator; (c) acetone,
Methyl ethyl ketone, toluene, a method of extracting a low molecular weight substance with a solvent such as xylene, and a method of melting and kneading the extracted low molecular weight substance and a polycarbonate resin with an extruder or the like. The above operation may be performed, and the content can be controlled by adjusting these conditions.

The polycarbonate resin composition for an optical disk substrate of the present invention is preferably a low molecular weight polymer comprising a repeating unit represented by the above general formula (1) in order to avoid a reduction in molecular weight due to coloring or thermal decomposition during molding. In addition, it contains a heat stabilizer. Examples of the heat stabilizer include phosphorous acid, phosphite, hindered phenol and the like. The content of the heat stabilizer is preferably 10 to 10 with respect to the resin composition.
1000 ppm.

The polycarbonate resin composition for an optical disk substrate of the present invention is produced by mixing the above-mentioned components with a mixer such as a tumbler, a V-type blender, a Nauta mixer, a Banbury mixer, a kneading roll, and an extruder. Can be. In the production of the polycarbonate resin composition of the present invention, the method of mixing the components and the order of mixing are not particularly limited.

In the polycarbonate resin composition of the present invention, various additives, such as various stabilizers, release agents, ultraviolet absorbers, dyes and pigments, are added in amounts not to impair the effects of the present invention. Etc. can be contained. In the polycarbonate resin composition of the present invention, for example, a fatty acid monoglyceride can be blended in order to improve releasability from a mold at the time of molding. The present inventor has filed Japanese Patent Application No.
No. 2-2368, a fatty acid monoglyceride having 14 to 30 carbon atoms is contained in an amount of 0.06 to 0.1% by weight, and a low molecular weight compound comprising a repeating unit represented by the general formula (1) is contained in an amount of 3.5 to 8% by weight. It describes that the polycarbonate resin composition for an optical disc substrate containing the compound is excellent in transferability, and excellent in release property and strength.

As the optical disk substrate in the present invention,
For example, CD, LD, C having a molded substrate thickness of 1.2 mm
Substrates such as a D-ROM, a CD-R, a magneto-optical disc, and a phase-change disc can be cited. Also, by bonding two molded substrates for DVD, which are single plates having a diameter of 120 mm and a thickness of 0.6 mm, The resulting DVD substrate is an example. As a DVD substrate, for example, a DVD-ROM,
Substrates such as a DVD-R and a DVD-RAM can be used. The polycarbonate resin composition for an optical disk substrate of the present invention is excellent in transferability even when molded at a relatively low temperature, particularly for an optical disk substrate comprising a molded substrate having a thickness of 1 mm or less and a thickness of 1 mm or less. It is useful for an optical disk substrate formed by bonding two molded substrates, and particularly useful for a DVD substrate.

[0022]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. The evaluation method in Examples and Comparative Examples was performed as follows. (1) Measurement of content of low molecular weight substance 90 mg of polycarbonate material in 20 ml of chloroform
And the four peaks (excluding peaks of unreacted monomers and chloroform, etc.) are counted by liquid chromatography under the following conditions from the longer separation time, and the content of the weight fraction is determined. I asked. Column configuration: Shode
x, L-803L, 2 in series, solvent: chloroform, flow rate: 1 ml / min. As an example of measurement, Table 1 shows an example of an analysis result of a liquid chromatograph of a polycarbonate resin having a low molecular weight content of 3.5% by weight.

[0023]

[Table 1]

(2) Measurement of glass transition temperature of skin layer 10 μm in the thickness direction from the surface of the substrate obtained by molding
10 mg of a thin section of m was collected with a microtome, and the glass transition temperature was determined by DSC. (3) Measurement of molten resin temperature to achieve transfer rate of 90% The pit depth of the molded substrate was measured with an atomic force microscope, and the ratio to the pit height of the stamper was taken as the transfer rate. The molten resin temperature to achieve was determined. The molten resin temperature was the highest temperature set in the molding machine cylinder.
The measurement conditions with the atomic force microscope are as follows. Measuring machine: Olympus NV2100, cantilever: conical, number of scanning lines: 128, scanning speed: 5 sec / li
ne, measuring range: 2000 × 2000 nm, load value: 3
0 nN.

(4) Measurement of Number of Hydrolysis White Spots after High-Temperature and High-Humidity Test The molded substrate was treated at 50 ° C. under the conditions of 80 ° C. and 90% by weight RH.
After treating for 0 hour, the number of hydrolyzed white spots of 50 μm or more in one substrate was observed under polarized light, and the number of hydrolyzed white spots was measured.

Reference Example 1 Phosgene and bisphenol A
In the reaction by the interfacial polymerization of alkaline water and methylene chloride, the timing of addition of paratertiary butyl phenol, which is a polymerization terminator, was changed during polymerization to obtain a polycarbonate resin containing a low molecular weight compound. After the polymerization, a solid polycarbonate resin was obtained by adding heptane, a poor solvent, to the methylene chloride solution. The content of the low molecular weight substance in the obtained polycarbonate resin was 2% by weight. Acetone was added to the polycarbonate resin to extract a low molecular weight substance, and the solvent was removed by a dryer to obtain a low molecular weight substance represented by the general formula (1).

[Examples 1 to 4 and Comparative Examples 1 and 2] To the polycarbonate resin obtained in the reference example, the low molecular weight compound of the reference example was added in a predetermined amount shown in Table 2, and phosphoric acid was added at 10 ppm as a heat stabilizer. Was added and pelletized by an extruder.
Using the obtained pellets, an optical disk substrate was obtained by the following method. The molding machine was for Sumitomo Heavy Industries DISK3, the stamper was for DVD-ROM, and the pit depth was 1200 mm. As the molding conditions, the mold temperature was 120 ° C., the injection speed was 250 mm / sec, the cycle was 5.0 sec, the substrate thickness was 0.6 mmt, and the cylinder temperature of the molding machine was 380.
° C. Table 2 shows the evaluation results.

[0028]

[Table 2]

[0029]

The polycarbonate resin composition for an optical disk substrate of the present invention is excellent in signal transferability and strength during molding, and is excellent in optical disk substrate, especially 1 mm thick.
It is useful for an optical disk substrate formed by bonding two sheets of the following molded substrate and a molded substrate having a thickness of 1 mm or less, and is very useful, for example, as a DVD substrate.

[0030]

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view of a substrate measured by an atomic force microscope in evaluating a molten resin temperature for achieving a transfer rate of 90%.

[Explanation of symbols]

 1. The height of the swell. 2. Pit depth. 3. Land part

Claims (5)

[Claims] 1. A polycarbonate resin composition for an optical disk substrate, comprising 3.5 to 8% by weight of a low molecular weight compound comprising a repeating unit represented by the following general formula (1). (However,
The fatty acid monoglyceride having 14 to 30 carbon atoms is 0.06 to
Excludes cases containing 0.1% by weight. ) (Wherein X is an alkylene group having 1 to 4 carbon atoms, 2 carbon atoms)
Represents an alkylidene group, an oxygen atom, a sulfur atom, a carbonyl group, a sulfinyl group, or a sulfone group,
Represents an integer of 1 to 4. ) 2. The polycarbonate resin composition for an optical disk substrate according to claim 1, wherein the optical disk substrate is a molded substrate having a thickness of 1 mm or less or an optical disk substrate formed by laminating two molded substrates. 3. An optical disc substrate obtained by bonding two molded substrates each having a thickness of 0.6 mm to each other.
The polycarbonate resin composition for an optical disk substrate according to claim 1, which is a D substrate. 4. The optical disk according to claim 2, wherein the molded substrate is a molded substrate obtained by injection molding at a molten resin temperature of 350 ° C. or more and a mold temperature of 100 ° C. or more. A polycarbonate resin composition for a substrate. 5. The polycarbonate resin composition for an optical disk substrate according to claim 1, wherein the viscosity average molecular weight of the polycarbonate resin is 10,000 to 25,000.