JP3530316B2 - Polycarbonate resin composition for optical disc substrate - Google Patents

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 optical disk substrates, and more specifically, D
The present invention relates to a polycarbonate resin composition for an optical disk substrate which is useful as a VD (digital video disk) substrate.

[0002]

2. Description of the Related Art Conventionally, as materials for optical disk substrates,
Polycarbonate resin is mainly used from the viewpoint of transparency, strength, heat resistance, etc. However, the polycarbonate resin has a bulky benzene ring in the main chain of the polymer, and its moldability was not always sufficient. When molding an optical disk substrate with 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 about 0.4 μm, and the pit and groove intervals are also small. Since it becomes as short as 0.74 μm, it is necessary to raise the cylinder temperature of the molding machine to about 350 to 380 ° C. and the mold temperature to about 100 to 120 ° C. in order to obtain a substrate having excellent transferability.

However, when the molding temperature is increased and the molding cycle is shortened to 4 to 6 seconds to improve the productivity, when a substrate made of a polycarbonate resin is taken out of the mold, a mold release defect occurs and pits and grooves are formed. The problem that the shape of is deformed occurs. Further, although the fluidity is improved by lowering the molecular weight of the resin, the lowering of the molecular weight causes a problem that the strength of the substrate is significantly reduced. Therefore, it has been difficult to obtain a polycarbonate resin having excellent strength and transferability and excellent releasability.

[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 is excellent in mold releasability and strength. .

[0005]

The present invention has been made in order to solve the above-mentioned problems, and its gist is to use a fatty acid monoglyceride having 14 to 30 carbon atoms in an amount of 0.06 to 0.
The present invention provides a polycarbonate resin composition for an optical disk substrate, which contains 1% by weight and a low molecular weight substance composed of a repeating unit represented by the following general formula (1) in an amount of 3.5 to 8% by weight.

[0006]

[Chemical 2]

(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 is 1 to 1). Indicates an integer of 4.)

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

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- Examples thereof include hydroxyphenyl) sulfide and bis (4-hydroxyphenyl) sulfone. As the dihydric phenol, preferably, a bis (4-hydroxyphenyl) alkane-based one, particularly one containing bisphenol A as a main raw material is used. Examples of the carbonate precursor include carbonyl halide, carbonyl ester, haloformate, and the like, and more specifically, phosgene, diphenyl carbonate, dihaloformate of divalent phenol, and a mixture thereof are preferable, and phosgene is preferable. In producing the polycarbonate resin, the dihydric phenol may be used alone or in combination of two or more kinds. Further, a branching agent may be used in combination with the above dihydric phenol compound.

The viscosity average molecular weight of the polycarbonate resin is 25 ° C. when methylene chloride is used as a solvent.
The viscosity average molecular weight converted from the solution viscosity measured in 1.
It is 20,000 to 25,000. Viscosity average molecular weight is 1
If it is less than 10,000, the strength of the obtained optical disk is not sufficient, and if it exceeds 25,000, the transferability tends to be lowered in the molding of the optical disk. The viscosity average molecular weight is preferably 11,000 to 20, from the viewpoint of strength and transferability.
2,000, and more preferably 12,000 to 18.0.
00. When producing a polycarbonate resin having these viscosity average molecular weights, an appropriate molecular weight modifier, a catalyst for accelerating the reaction and the like can be added.

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]

[Chemical 3]

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 is 1 to 4 Indicates an integer.

The content of the low molecular weight substance composed of the repeating unit represented by the general formula (1) is 3.5 to 8% by weight of the polycarbonate resin composition for optical disk substrates. If the content of the low molecular weight substance is less than 3.5% by weight, the fluidity of the resin on the surface portion 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 due to hydrolysis occur after the high temperature and high humidity test of the optical disk substrate.

The low molecular weight compound consisting of 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. Greatly affects sex. The pit depth and groove height that are signals of the optical disk substrate are about 1000 to 2000 Å and are located in the skin layer of the substrate. Therefore, the transferability of the signal of the optical disk is affected by the amount of the low molecular weight substance in the skin layer. .
For example, when a molded substrate having a thickness of 0.6 mm is molded, the resin temperature is about 380 ° C. and the mold temperature is about 120 ° C., which is a high temperature. These effects are significant.

When the low molecular weight component in the polycarbonate resin composition is 3.5 to 8% by weight, the glass transition temperature of the skin layer during the molding of the optical disk substrate is the glass transition temperature of the core layer, that is, the central portion in the thickness direction of the substrate. The glass transition temperature of the molten resin is lowered by about 20 ° C., and the fluidity of the molten resin on the surface of the substrate is improved. Along with that, 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 disc substrate decreases, and the glass transition temperature of the core layer does not decrease so much, so that the strength of the optical disc substrate hardly decreases.

In order to increase the content of the low molecular weight substance consisting of the repeating unit represented by the general formula (1) in the polycarbonate resin, for example, (a) a method of relaxing the stirring conditions of the polymerization reaction, (b) ) A method of accelerating the timing of addition of the polymerization terminator, (c) acetone from the resin after the polymerization is completed,
Examples include a method in which a low molecular weight substance is extracted with a solvent such as methyl ethyl ketone, toluene, xylene, and the extracted low molecular weight substance and a polycarbonate resin are melt-kneaded with an extruder or the like. The operation may be performed, and the content rate can be controlled by adjusting these conditions.

The polycarbonate resin composition for an optical disk substrate of the present invention contains a fatty acid monoglyceride having 14 to 30 carbon atoms, together with a low molecular weight substance composed of the repeating unit represented by the above general formula (1). Examples of the fatty acid monoglyceride having 14 to 30 carbon atoms include stearic acid monoglyceride, behenic acid monoglyceride, arachidic acid monoglyceride, montanic acid monoglyceride, and a mixture thereof can be used. As the fatty acid monoglyceride, stearic acid monoglyceride, behenic acid monoglyceride and the like are preferable from the viewpoint of releasing effect.

The content of the fatty acid monoglyceride having 14 to 30 carbon atoms is 0.06 to 0.1% by weight of the polycarbonate resin composition for optical disk substrates. 14 to 3 carbon atoms
When the content of the fatty acid monoglyceride of 0 is less than 0.06% by weight, pits and grooves are likely to be deformed due to defective release, and particularly in the case of molding a DVD having a thickness of 0.6 mm, due to defective release, Signal interference is likely to occur because the distance between adjacent pits and grooves is small, and if it exceeds 0.1% by weight, hydrolysis white spots are likely to occur in the high temperature and high humidity test of the substrate due to impurities such as fatty acid monoglyceride.

The polycarbonate resin composition for an optical disk substrate of the present invention is preferably a low molecular weight compound comprising a repeating unit represented by the above general formula (1) in order to avoid a decrease in molecular weight due to coloring during molding or thermal decomposition. , Carbon number 14 ~
Contains a heat stabilizer with 30 fatty acid monoglycerides. As the heat stabilizer, phosphorous acid, phosphite ester,
A hindered phenol etc. are mentioned. The content of the heat stabilizer is preferably 10 to 1000 p based on the resin composition.
pm.

The polycarbonate resin composition for optical disk substrates of the present invention is produced by mixing the above-mentioned components by a mixer such as a tumbler, a V-type blender, a Nauter mixer, a Banbury mixer, a kneading roll and an extruder. You can In the production of the polycarbonate resin composition of the present invention, the mixing method of each component and the order of mixing are not particularly limited.

The polycarbonate resin composition of the present invention contains various additives such as various stabilizers, ultraviolet absorbers, dyes and pigments, etc. in an amount that produces the effects of the present invention, within a range that does not impair the effects of the present invention. be able to.

As the optical disk substrate in the present invention,
For example, a molded substrate having a thickness of 1.2 mm, such as CD, LD, and C
Substrates such as D-ROMs, CD-Rs, magneto-optical discs, phase-change discs, etc. can be mentioned, and by bonding two molded substrates for DVDs, which are single plates with a diameter of 120 mm and a thickness of 0.6 mm. The obtained DVD substrate is mentioned. As the DVD substrate, for example, a DVD-ROM,
Examples of substrates include DVD-R and DVD-RAM. INDUSTRIAL APPLICABILITY 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, and is particularly useful for an optical disk substrate having a thickness of 1 mm or less and for a DVD substrate. is there.

[0024]

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

[0025]

[Table 1]

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

(4) Measurement of Deformation Deformation Amount The height of the portion raised from the land portion shown in FIG. 1 on the surface of the molded substrate was measured with an atomic force microscope. The measurement conditions with an atomic force microscope are the same as in (3). (5) Measurement of number of hydrolysis white spots after high temperature and high humidity test The substrate after molding was subjected to 50 ° C. at 80 ° C. and 90% by weight RH.
After treatment for 0 hour, the number of hydrolysis white spots of 50 um or more in one substrate was observed under polarized light to measure the number of hydrolysis white spots.

Reference Example 1 Phosgene and Bisphenol A
In the reaction of the interfacial polymerization of alkaline water with methylene chloride, a polycarbonate resin containing a low molecular weight substance was obtained by changing the addition time of para-tertiary butylphenol, which is a polymerization terminator, during the polymerization. After the polymerization, heptane, which is a poor solvent, was added to the methylene chloride solution to obtain a solidified granular polycarbonate resin. The content of the low molecular weight product in the obtained polycarbonate resin was 2% by weight. Acetone was added to this polycarbonate resin to extract a low molecular weight product, and the solvent was removed by a dryer to obtain a low molecular weight product represented by the general formula (1).

[Examples 1 to 7 and Comparative Examples 1 to 8] In the polycarbonate resin obtained in Reference Example, a predetermined amount of the low molecular weight substance of Reference Example shown in Table 2 and 10 ppm of phosphorous acid as a heat stabilizer were added. Then, a predetermined amount of stearic acid monoglyceride as a release agent was added and pelletized by an extruder. An optical disk substrate was obtained by the following method using the obtained pellets. The molding machine is for Sumitomo Heavy Industries DISK3, the stamper is for DVD-ROM, and the pit depth is 120.
It was 0Å. Mold temperature is 120
℃, injection speed 250mm / sec, cycle 5.0s
ec, the substrate thickness was 0.6 mmt, and the cylinder temperature of the molding machine was 380 ° C. The evaluation results are shown in Table-2.

[0030]

[Table 2]

[0031]

INDUSTRIAL APPLICABILITY The polycarbonate resin composition for an optical disk substrate of the present invention is excellent in signal transferability at the time of molding, and is excellent in mold releasability and strength.
It is very useful in the application of the optical disc substrate of less than mm.

[0032]

[Brief description of drawings]

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

[Explanation of symbols]

1. Height of rising part. 2. Pit depth. 3. Land section

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) C08G 64/00-64/42 C08L 69/00

Claims (5)

(57) [Claims] 1. A fatty acid monoglyceride having 14 to 30 carbon atoms is used in an amount of 0.06 to 0.1% by weight, and a low molecular weight substance having a repeating unit represented by the following general formula (1) is used in an amount of 3.5 to 8% by weight. A polycarbonate resin composition for an optical disk substrate, which comprises: [Chemical 1] (In the formula, X is an alkylene group having 1 to 4 carbon atoms and 2 carbon atoms.
~ 3 alkylidene group, oxygen atom, sulfur atom, carbonyl group, sulfinyl group, or sulfone group,
Represents an integer of 1 to 4. ) 2. The polycarbonate resin composition for an optical disc substrate according to claim 1, wherein the optical disc substrate is an optical disc substrate having a thickness of 1 mm or less. 3. A DV obtained by laminating two molded substrates having an optical disc substrate thickness of 0.6 mm.
The polycarbonate resin composition for an optical disk substrate according to claim 1, which is a D substrate. 4. The optical disc according to claim 2 or 3, wherein the molded substrate is a molded substrate obtained by injection molding under conditions of a molten resin temperature of 350 ° C. or higher and a mold temperature of 100 ° C. or higher. Polycarbonate resin composition for substrates. 5. The polycarbonate resin composition for an optical disc substrate according to claim 1, wherein the polycarbonate resin has a viscosity average molecular weight of 10,000 to 25,000.