JPH0954982A - Optical disk substrate and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical disk substrate attaining accurate transfer of pits, ensuring a low error rate and less liable to warp by moisture absorption with polycarbonate resin from 2,2-bis(3-methyl-4-hydroxyphenyl)propane. SOLUTION: This optical disk substrate is formed with polycarbonate resin obtd. by allowing a carbonate precursor to react with dihydric phenol, mainly 2,2-bis(3-methyl-4-hydroxyphenyl)propane. The specific viscosity of the polycarbonate resin is 0.2-0.4. When the resin is dissolved in methylene chloride, the number of undissolved particles each having >=0.5μm diameter measured in the resultant soln. is <=25,000 per 1g of the resin and the number of undissolved particles each having >=1μm diameter is <=500. The resin has <=0.2wt.% water absorption.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk substrate and a method for manufacturing the same. More specifically, the present invention relates to an optical disk substrate that has less warpage due to moisture absorption, accurately transfers pits, and has a good error rate (BLER), and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, as a typical polycarbonate resin, a polycarbonate resin obtained by reacting 2,2-bis (4-hydroxyphenyl) propane (commonly called bisphenol A) with a carbonate precursor such as phosgene or diphenyl carbonate is transparent. It is widely used as an engineering plastic because of its excellent properties, heat resistance, mechanical properties, and dimensional accuracy. In recent years, it has been widely used as an optical disk substrate material, particularly as a compact disk material for music. As a method for manufacturing such an optical disk substrate, a bis (hydroxyphenyl) alkane-based polycarbonate resin having a specific molecular weight is used at a resin temperature of 33.
It has been proposed to perform injection molding at 0 to 400 ° C. and a mold temperature of 50 to 110 ° C. (Japanese Patent Publication No. 63-56043). However, a polycarbonate resin made from bisphenol A has a large birefringence and is apt to warp. These problems are extremely serious problems when used for an optical disc substrate having a larger amount of information than a compact disc for music, and it is difficult to use for such an optical disc substrate unless these problems are solved.

Further, the polycarbonate resin obtained by reacting 2,2-bis (3-methyl-4-hydroxyphenyl) propane with a carbonate precursor has a small birefringence as compared with the polycarbonate resin from bisphenol A, It has excellent transparency, solution stability, and mechanical properties and is used in the field of electrophotographic photoreceptors. In recent years, the use of optical disc substrates has also been proposed by utilizing its excellent optical characteristics (Japanese Patent Laid-Open No. 62-39624). However, when the above injection molding conditions are applied to this polycarbonate resin, there are problems such as insufficient transfer of pits from the stamper and a large error rate (BLER). Therefore, a good optical disk substrate cannot be obtained by the conventional injection molding method. It was

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide:
A pit is accurately transferred by using a polycarbonate resin from 2-bis (3-methyl-4-hydroxyphenyl) propane, and an optical disk substrate having a good error rate (BLER) and less warpage due to moisture absorption is provided. .

The present inventor has conducted earnest studies as an attempt to achieve this object, and as a result, achieved the above object for the first time by using the above-mentioned polycarbonate resin satisfying extremely strict specific conditions and adopting specific injection molding conditions. The inventors have found out what can be done and have reached the present invention.

[0006]

The first aspect of the present invention is 2,2-
Formed from a polycarbonate resin obtained by reacting a carbonate precursor with a dihydric phenol mainly containing bis (3-methyl-4-hydroxyphenyl) propane,
The polycarbonate resin (A) has a specific viscosity of 0.2 to 0.4 measured at 20 ° C. in a solution of 0.7 g thereof dissolved in 100 ml of methylene chloride, and (B) is measured in the methylene chloride solution. There are 2 undissolved particles with a particle equivalent diameter of 0.5 μm or more per 1 g of polycarbonate resin.
The present invention relates to an optical disk substrate characterized in that it is formed of a resin that satisfies the following conditions: 5,000 or less, 1 μm or more, 500 or less, and (C) a water absorption coefficient of 0.2% by weight or less. It is a thing.

The second aspect of the present invention is a polycarbonate resin obtained by reacting a dihydric phenol mainly containing 2,2-bis (3-methyl-4-hydroxyphenyl) propane with a carbonate precursor (A). The specific viscosity of the solution of 0.7 g dissolved in 100 ml of methylene chloride at 20 ° C. was 0.2 to 0.4, and (B) the undissolved particles measured in the methylene chloride solution were polycarbonate resins. Polycarbonate resin having a particle diameter of 0.5 μm or more per 1 g is 25,000 or less, 1 μm or more is 500 or less, and (C) a water absorption rate is 0.2 wt% or less. ˜60 tons, resin temperature 290 to 330 ° C., mold temperature 60 to 110 ° C., injection molding is performed.

In the present invention, the polycarbonate resin used as the material for the optical disk substrate is 2,2-bis (3-methyl-4-).
It is obtained by reacting a dihydric phenol mainly containing hydroxyphenyl) propane with a carbonate precursor. It is preferable that the 2,2-bis (3-methyl-4-hydroxyphenyl) propane used here has a high purity of 99.0% or more in which impurities by-produced during the synthesis are removed as much as possible. If it is less than 99.0%, the obtained polycarbonate resin becomes colored. Further, a part of 2,2-bis (3-methyl-4-hydroxyphenyl) propane is replaced with another dihydric phenol within a range not departing from the gist of the present invention (usually 20 mol% or less, preferably 10 mol% or less). It may be replaced. Examples of the other dihydric phenol include 2,2-bis (4-hydroxyphenyl) propane (commonly called bisphenol A), 2,2-bis (4-hydroxy-3-ethylphenyl) propane, 2,2-bis- ( 4-hydroxy-3-propylphenyl) propane, 2,2-bis (4-hydroxy-3-sec-butylphenyl) propane, 2,2-bis (4-hydroxy-tert-butylphenyl) propane, 4,4 -Bis (4-hydroxyphenyl) heptane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl)
Examples include pentane. It is also possible to use a small amount of a trifunctional compound together. Examples of the carbonate precursor to be reacted with the dihydric phenol include phosgene and diphenyl carbonate.

The reaction for producing a polycarbonate resin from the above dihydric phenol and the carbonate precursor is a reaction adopted when producing a polycarbonate resin from a usual bisphenol A, for example, an interfacial polycondensation reaction between a dihydric phenol and phosgene, Alternatively, a transesterification reaction between a dihydric phenol and diphenyl carbonate is preferably adopted.

In the interfacial polycondensation reaction, the reaction is usually carried out in the presence of an acid binder and an organic solvent. As the acid binder, for example, hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide, pyridine and the like are used. As the organic solvent, for example, halogenated hydrocarbons such as methylene chloride and chlorobenzene are used. A catalyst such as a tertiary amine or a quaternary ammonium salt can be used to accelerate the reaction, and as a molecular weight regulator, for example, phenol or p-te.
It is desirable to use an end-capping agent such as an alkyl-substituted phenol such as rt-butylphenol. The reaction temperature is usually 0 to 40 ° C, the reaction time is several minutes to 5 hours, and the pH during the reaction is
Is preferably maintained at 10 or more.

In the transesterification reaction, dihydric phenol and diphenyl carbonate are mixed in the presence of an inert gas, and the reaction is usually performed at 120 to 350 ° C. under reduced pressure. The degree of pressure reduction is changed stepwise, and finally the phenols produced at 1 mmHg or less are distilled out of the system. The reaction time is usually about 1 to 4 hours. Moreover, you may add a molecular weight regulator and antioxidant as needed.

The polycarbonate resin thus obtained must have a specific viscosity of 0.2 to 0.4, preferably 0.25 to 0.33. When the specific viscosity is less than 0.2, the obtained optical disk substrate becomes fragile, and when the specific viscosity is higher than 0.4, the melt fluidity is deteriorated and molding defects occur, and it becomes difficult to obtain an optically good optical disk substrate. This specific viscosity is the specific viscosity measured by dissolving 0.7 g of polycarbonate resin in 100 ml of methylene chloride at 20 ° C. In order to produce a polycarbonate resin having the above specific viscosity, for example, in the phosgene method, a predetermined amount of a terminal stopper is used. It may be used, and in the transesterification method, it may be adjusted by controlling the melt viscosity of the reaction system or the amount of distillate phenol.

The polycarbonate resin must have a number of undissolved particles measured in a methylene chloride solution that is less than a specific value. That is, the polycarbonate resin 20
A liquid particle counter model 41 manufactured by HYAC-ROCO Co., Ltd. is prepared by dissolving g in 1 liter of methylene chloride.
The number of undissolved particles having a diameter of 0.5 μm or more obtained by converting the scattered light into the scattered light of latex particles by the laser sensor method using 00 is 25,000 or less and 1 μm or more per 1 g of the polycarbonate resin. It is necessary that the number is 500 or less. When the number of undissolved particles of 0.5 μm or more exceeds 25,000 and the number of undissolved particles of 1 μm or more exceeds 500, the information pits written on the optical disk are adversely affected and the error rate (BLER) increases. More preferably, the number of undissolved particles of 0.5 μm or more is 20,000 or less and the number of undissolved particles of 1 μm or more is 200 or less. In addition, substantially no undissolved particles of 10 μm or more should be present. In order to produce the above-mentioned polycarbonate resin in which the amount of undissolved particles is not more than the specified amount, it is necessary to employ a means that does not mix or can remove undissolved particles in the polycondensation process and the granulation process. As such means, for example, the operation is performed in a clean room, a granulating device equipped with a device for removing undissolved particles (a kneader provided with an isolation chamber having a foreign matter extraction port in a bearing portion used in Example 1 described later as a specific example). ) Is used, and granulation is performed with an apparatus having a structure in which the resin particles do not touch the sliding portion (for example, a spray dryer type granulator). Further, as a means for removing undissolved particles, a resin solution is opened (0.5 to 1).
A method of filtering with a filter having a small (μm), a method of melting the resin and removing solid particles with a filter (opening of 10 to 40 μm), and the like are adopted.

Further, the above polycarbonate resin is AST
The water absorption measured by MD-0570 is required to be 0.2% by weight or less, and preferably 0.17% by weight or less. When the water absorption rate exceeds 0.2% by weight, the optical disk having the metal film formed on the surface of the optical disk substrate is liable to warp due to water absorption, which easily causes a tracking error. Particularly preferred water absorption is 0.1
5% by weight or less.

The total light transmittance measured by ASTM D-1003 using Sigma 80 manufactured by Nippon Denshoku Co., Ltd. is preferably 85% or more, more preferably 90% or more. Also, using an automatic birefringence measuring device Ellipsometer ADR-200B manufactured by Oak Co., Incident angle 3
The value of the oblique incident birefringence phase difference measured at 0 ° is preferably 60 nm or less, and more preferably 40 nm or less. When the value of the oblique incident birefringence phase difference exceeds 60 nm, reading of recording will be hindered when used as an optical disc. Further, the value of photoelastic constant measured using a photoelasticity measuring device PA-150 manufactured by Riken Keiki Co., Ltd. is preferably 60 × 10 ^-13 cm ² / dyn or less,
It is more preferably 50 × 10 ⁻¹³ cm ² / dyn or less. When the above polycarbonate resin is produced by an interfacial polycondensation reaction using phosgene as a carbonate precursor and a chlorine-based solvent such as methylene chloride, a large amount of chlorine remains. If the residual amount of chlorine is large, the molding die is corroded, the thermal stability of the polycarbonate resin is deteriorated, and the metal film of the optical disk is corroded, which is not desirable. Therefore, the amount of chlorine contained is preferably 10ppm or less, and 5ppm
The following is particularly preferable. The content of chlorine was determined by a method in which a total amount of organic halogen analyzer TOX10 manufactured by Mitsubishi Chemical Corporation was used, a predetermined amount of sample was burned, the combustion gas was dehydrated, and then potentiometric titration was performed using an acetic acid cell. In order to produce the above polycarbonate resin having a chlorine content of 10 ppm or less, for example, when it is produced by a transesterification reaction or an interfacial polycondensation reaction, a porous powdery granule which is easily dried at the time of granulation is produced. , Dry enough,
It can be produced by a method such as substituting a chlorine-based solvent with a non-chlorine-based solvent during or after granulation.

The above polycarbonate resin preferably contains 10% or less of oligomers, and particularly preferably 5% or less. When the amount of the oligomer is more than 10%, the mold surface is contaminated during molding, and the transferability is deteriorated, and it becomes difficult to obtain the intended optical disk substrate.
In order to control the amount of the oligomer in the polycarbonate resin within the above range, it is necessary to strictly control the polycondensation conditions to promote the polymerization of the oligomer. In the interfacial polycondensation reaction, optimization of alkali concentration, reaction temperature, reaction time and amount of catalyst is important, and in transesterification reaction, optimization of reaction temperature, degree of reduced pressure and reaction time is important. When the oligomer content exceeds the above range, it may be removed by a means such as oligomer extraction. This extraction is a method of dropping a solution of a polycarbonate resin (for example, a methylene chloride solution) into a poor solvent or a non-solvent (for example, acetone, ethanol, etc.) of the resin, or immersing the polycarbonate resin in a poor solvent or a non-solvent to form an oligomer. It can be carried out by means such as extraction. In the present invention, the amount of the oligomer is TSKgel G2000HXL manufactured by Tosoh Corp. and one G3000HXL column are connected in series, and chloroform is used as an eluent to stabilize at a flow rate of 0.7 ml / min, and then a chloroform solution of a polycarbonate resin is injected. The retention time of the GPC chart measured by the method is the ratio of the total oligomer peak area after 19 minutes to the total peak area.

When the specific viscosity, undissolved particle content and water absorption of the above polycarbonate resin all satisfy the above specified amounts, more preferably the total light transmittance, the oblique incident birefringence retardation value, the photoelastic constant value, When the chlorine content and the oligomer content satisfy the above specified values,
Accurate transfer of pits using a polycarbonate resin from 2-bis (3-methyl-4-hydroxyphenyl) propane to provide an optical disk substrate with a good error rate (BLER) and less warpage due to moisture absorption. Therefore, even if any one of the specific viscosity, the oligomer content, the undissolved particle content, and the water absorption rate deviates, the object cannot be achieved.

The optical disk substrate of the present invention can be obtained by molding the above polycarbonate resin by an arbitrary method such as an injection molding method, a compression molding method, an extrusion molding method or a solution casting method. Among them, the injection molding method is preferable. The injection molding used for manufacturing the optical disk substrate of the present invention is performed in a clean room using a normal precision injection molding machine for optical disk molding. The cleanliness of the clean room is preferably class 1000 or less. The mold clamping force during injection molding should be 10 tons or more. If the mold clamping force is lower than 10 tons, the mold is loosened and it becomes impossible to obtain an optical disk substrate having a predetermined shape. Further, it is necessary to set the resin temperature at the time of molding, that is, the cylinder temperature to 290 to 330 ° C. and the mold temperature to the range of 60 to 110 ° C., set the resin temperature to 300 to 320 ° C. and the mold temperature to 80 to 100 ° C. Preferably. When the resin temperature is lower than 290 ° C or the mold temperature is lower than 60 ° C, the melt flowability of the resin on the mold surface is lowered, and the oblique incident birefringence phase difference of the obtained optical disk substrate increases. , Again, the pit depth will be insufficient. If the resin temperature is higher than 330 ° C. or the mold temperature is higher than 110 ° C., it takes a long time to cool the obtained optical disk substrate, not only the molding cycle becomes long but also the resin does not harden sufficiently at the time of mold release. The optical disk substrate to be warped is warped. In addition, it is preferable to set the injection speed to 50 to 700 mm / sec. If it is less than 50 mm / sec, the fluidity of the resin in the mold is poor, and the transferability and birefringence are deteriorated.
When it exceeds 700 mm / sec, burrs are easily generated, and gas burn, silver, etc. are likely to occur. The holding pressure (secondary pressure) is 25
It is preferably about 60 kg / cm ² . If it is lower than 25 kg / cm ² , sink marks are likely to occur, and if it is higher than 60 kg / cm ² , large stress is applied to the optical disc substrate and distortion remains, making it difficult to obtain an optical disc substrate having excellent optical characteristics.

In molding the optical disk substrate of the present invention, a phosphorus-based stabilizer can be added to the above polycarbonate resin, which is preferable. Phosphorous acid esters and phosphoric acid esters are preferably used as the phosphorus-based stabilizer. Examples of the phosphite include triphenylphosphite, trisnonylphenylphosphite, tris (2,4-di-tert-butylphenyl) phosphite, tridecylphosphite, trioctylphosphite, trioctadecylphosphite, didecyl. Monophenyl phosphite, dioctyl monophenyl phosphite, diisopropyl monophenyl phosphite,
Distearyl pentaerythritol diphosphite, monobutyl diphenyl phosphite, monodecyl diphenyl phosphite, monooctyl diphenyl phosphite, bis (2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite, 2 , 2-
Methylenebis (4,6-di-tert-butylphenyl) octylphosphite, bis (nonylphenyl) pentaerythritol diphosphite, bis (2,4-di-tert.
-Butylphenyl) pentaerythritol diphosphite, tetrakis (2,4-di-tert-butylphenyl) -4,4-diphenylenephosphonite and other phosphorous acid triesters, diesters, monoesters, and the like. However, trisnonylphenyl phosphite, distearyl pentaerythritol diphosphite and the like are preferable. Examples of the phosphoric acid ester include tributyl phosphate, trimethyl phosphate, triethyl phosphate, tricresyl phosphate, triphenyl phosphate, trichlorophenyl phosphate, tributoxyethyl phosphate, diphenyl cresyl phosphate, diphenylmonoorthoxenyl phosphate, dibutyl phosphate, dioctyl phosphate, Examples thereof include diisopropyl phosphate, and among them, triphenyl phosphate, triethyl phosphate and the like are preferable. These phosphorus-based stabilizers may be used alone or in combination of two or more. The blending amount of these phosphorus stabilizers is
If it is too small, it is difficult to obtain a sufficient stabilizing effect, especially the heat stabilizing effect, and if it is too large, the deterioration of the optical disk substrate is promoted during long-term storage. Therefore, the phosphorus-based stabilizer is converted to phosphorus atoms to be 1 to 150 ppm. The amount contained is suitable. Special attention is required when using a phosphite stabilizer, and it is preferable not to use it from the viewpoint of deterioration during long-term storage, but it is effective in suppressing initial deterioration.
It is preferable to use a very small amount, and it is 1 to 2 in terms of phosphorus atom.
It is preferable to use about 5 ppm. Phosphate ester-based stabilizers have less adverse effects on deterioration during long-term storage than phosphorous acid ester-based stabilizers, and are preferably used at 1 to 150 ppm, more preferably 1 to 100 ppm, in terms of phosphorus atoms.

Further, in molding the optical disk substrate of the present invention, a higher fatty acid ester of a polyhydric alcohol can be blended with the above polycarbonate resin. By blending this higher fatty acid ester, the thermal stability of the polycarbonate resin is improved, the fluidity of the resin at the time of molding is improved, and the releasability of the optical disk substrate from the mold after molding is further improved and the resin is released. It is possible to prevent the deformation of the optical disk substrate due to mold defects. Examples of such higher fatty acid esters include polyhydric alcohols having 2 to 5 carbon atoms and 10 to 30 carbon atoms.
Partial or total esters with saturated fatty acids of are preferred. Examples of the polyhydric alcohol include glycols, glycerol, pentaerythritol and the like. The amount of the higher fatty acid ester compounded is preferably an amount contained in the polycarbonate resin in an amount of 50 to 2000 ppm. 50ppm
If it is less than 2000 ppm, the above effect cannot be obtained, and if it is more than 2000 ppm, it causes stains on the mold surface, which is not preferable.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be further described below with reference to examples. Parts and% in the examples are parts by weight and% by weight, and evaluation was made by the following method. (1) Specific viscosity: 0.7 g of polycarbonate resin was dissolved in 100 ml of methylene chloride and measured at 20 ° C. (2) Oligomer content (%): CPC columns TSKgel G2000HXL and TSKgel G3 manufactured by Tosoh Corporation
Using 000HXL, 50 mg of sample was mixed with chloroform while flowing chloroform as an eluent at a flow rate of 0.7 ml / min.
GP obtained by the method of injecting 20 μl of the solution dissolved in ml
The ratio of the peak area of the oligomer component after the retention time of 19 minutes on the C chart to the total peak area is%.
Indicated by (3) Number of particles not dissolved in methylene chloride (particles / g): A solution prepared by dissolving 20 g of a polycarbonate resin in 1 liter of methylene chloride is a latex of scattered light by a laser sensor method using a liquid particle counter model 4100 manufactured by Hyac-Leuco. It was obtained by the method of converting it into scattered light of particles. (4) Water absorption rate (%): Measured by ASTM D-0570. (5) Total light transmittance (%): Sigma 8 manufactured by Nippon Denshoku Co., Ltd.
0 was used to measure by ASTM D-1003. (6) Oblique incidence birefringence phase difference (nm): Measured at an incident angle of 30 ° using an oak ellipsometer ADR-200B automatic birefringence measuring device. (7) Photoelastic constant (× 10 ⁻¹³ cm ² / dyn): Measured with a photoelastic measuring device PA-150 manufactured by Riken Keiki Co., Ltd. (8) Content of chlorine (ppm): Using a total organic halogen analyzer TOX10 manufactured by Mitsubishi Chemical Corporation, the sample was burned, the combustion gas was dehydrated, and then the potentiometric titration was performed using an acetic acid cell. (9) Pit depth (nm): injection molding machine [DI manufactured by Sumitomo Heavy Industries, Ltd.] using a stamper with a pit depth of 112 nm
A substrate having a thickness of 1.2 mm and a diameter of 120 mm was molded with SK3], and the pit depth at a position of 40 mm from the center of the disk was measured with an atomic force microscope manufactured by Seiko Denshi Kogyo Co., Ltd., and the pit depth was 100 nm. The above was passed. (10) BLER: An aluminum film is applied to one side of the disk formed in (9) by sputtering, and CDP-3
BLER (Cl peak) was measured using 000. (11) Warp (mm): An aluminum film is applied to one side of the disk formed in (9) by sputtering and the temperature is set to 80 ° C. for 8 hours.
After standing in a thermo-hygrostat at 5% RH for 1,000 hours, measurement was performed using an LM-1200 optical disk inspection device manufactured by Ono Sokki Co., Ltd., and 0.25 mm or less was determined to be acceptable.

[Examples 1 to 3] A. Synthesis of polycarbonate resin 48. in a reaction tank equipped with a stirrer, a thermometer and a reflux condenser.
2691 parts of 5% aqueous sodium hydroxide solution and 184 water
62 parts were charged, and nitrogen gas was bubbled for 30 minutes to deoxygenate. 2,387 parts of 2,2-bis (3-methyl-4-hydroxyphenyl) propane and 2.52 parts of hydrosulfite were dissolved in this, and 12681 parts of methylene chloride deoxygenated by nitrogen gas bubbling were added to give 20 parts.
1200 parts of phosgene was bubbled in at 60 ° C. over 60 minutes. Then, 769 parts of a 48.5% sodium hydroxide solution deoxidized in the same manner and 69.9 parts of p-tert-butylphenol were added to emulsify the mixture, and then 6.5 parts of trierylamine was added to the mixture at 30 ° C. for about 2 hours. The reaction was completed by stirring. After completion of the reaction, the organic phase is separated, washed with water, acidified with hydrochloric acid, and repeatedly washed with water. When the conductivity of the aqueous phase becomes equal to that of ion-exchanged water, the washing is stopped and the bearing has a foreign matter extraction port. Methylene chloride was evaporated with a kneader provided with a chamber to obtain a polycarbonate resin. The specific viscosity of this resin is 0.27
9, water absorption was 0.14%, chlorine content was 5 ppm, and oligomer content was 3.5%.

B. Fabrication of optical disk substrate Tris (2,
4-di-tert-butylphenyl) phosphite 0.07
1 part (1.4 ppm of phosphorus atom), trimethyl phosphate 0.1
19 parts (11 ppm of phosphorus atom) and 1.07 parts of stearic acid monoglyceride (450 ppm) were added, and the pit depth was 1
Using a 12 nm stamper, a disk substrate having a thickness of 1.2 mm and a diameter of 120 mm was injection molded by an injection molding machine [DISK3 manufactured by Sumitomo Heavy Industries, Ltd.] under the molding conditions shown in Table 1. The injection speed is 100 mm / sec and the holding pressure is 40 kg / cm ^2.
The undissolved particles of the obtained disk substrate are 24,500 particles / g with a particle equivalent diameter of 0.5 μm or more, 1 μm.
200 or more per m or more, total light transmittance of 89%,
The value of photoelastic constant is 55 × 10 ⁻¹³ cm ² / dyn, and other properties are shown in Table 1.

[Example 4] To 100 parts of the polycarbonate resin synthesized in Example 1, 0.01 parts of trimethyl phosphate (22 ppm by phosphorus atom) and 0.045 parts (450 ppm) of stearic acid monoglyceride were added. A disk substrate was injection molded in the same manner as in Example 1. The number of undissolved particles on the obtained disk substrate is 24,500 particles / g with a particle equivalent diameter of 0.5 μm or more, and 200 particles / g with a particle diameter of 1 μm or more.
, Total light transmittance is 89%, photoelastic constant value is 55 × 1
0 ^-13 cm ² / dyn, and other characteristics are shown in Table 1.

Comparative Example 1 The characteristics of the disk substrate obtained by injection molding in the same manner as in Example 2 except that the mold temperature was 50 ° C. are shown in Table 1. The BLER was as large as 320 pieces / sec, the pit depth was insufficient, and the warpage was large.

[Comparative Example 2] Granulation was carried out in the same manner as in Example 1 except that an ordinary kneader having no isolation chamber for taking out foreign matters was used in the granulation step. The specific viscosity of this resin is 0.27
9, water absorption was 0.16%, chlorine content was 6 ppm, and oligomer content was 3.3%. Then, injection molding was carried out in the same manner as in Example 1, and the total light transmittance of the obtained disk substrate was 8
9%, the value of photoelastic constant was 56 × 10 ⁻¹³ cm ² / dyn, and other properties are shown in Table 1. Many undissolved particles,
The BLER of the disk substrate became a large value of 490 pieces / second.

COMPARATIVE EXAMPLE 3 Injection molding was carried out in the same manner as in Example 1 except that the mold clamping force was set to 9 t and the cylinder temperature was set to 300 ° C. However, a good disk substrate could not be obtained due to burrs.

Comparative Example 4 The characteristics of the disk substrate obtained by injection molding in the same manner as in Example 1 except that the mold clamping force was 12 t and the cylinder temperature was 280 ° C. are shown in Table 1. Oblique incidence birefringence Phase difference becomes large and BLER is 350
The number of pieces / second was large, the pit depth was insufficient, and the warpage was large.

Comparative Example 5 The characteristics of the disk substrate obtained by injection molding in the same manner as in Example 1 except that the mold clamping force was 12 t and the cylinder temperature was 340 ° C. are shown in Table 1. The warpage was great.

COMPARATIVE EXAMPLE 6 The characteristics of the disk substrate obtained by injection molding in the same manner as in Example 2 except that the cylinder temperature was 350 ° C. and the mold temperature was 120 ° C. are shown in Table 1. The warpage was great.

Comparative Example 7 A polycarbonate resin was synthesized in the same manner as in Example 1-A except that the amount of p-tert-butylphenol used was 100.6 parts. The resin had a specific viscosity of 0.198, a water absorption rate of 0.15%, a chlorine content of 5 ppm, and an oligomer content of 4.8%. When injection molding was performed using this resin in the same manner as in Example 3, a crack was generated at the time of release and a disk substrate could not be obtained.

Comparative Example 8 A polycarbonate resin was synthesized in the same manner as in Example 1-A except that the amount of p-tert-butylphenol used was 55.9 parts. The resin had a specific viscosity of 0.420, a water absorption rate of 0.16%, a chlorine content of 5 ppm, and an oligomer content of 3.0%. Injection molding was performed in the same manner as in Example 1 using this resin. The obtained disk substrate had a total light transmittance of 89% and a photoelastic constant of 5
6 × 10 ⁻¹³ cm ² / dyn, and other characteristics are shown in Table 1. The value of the birefringence phase difference of oblique incidence becomes large, and BLE
The R was as large as 380 pieces / second, the pit depth was insufficient, and the warpage was large.

COMPARATIVE EXAMPLE 9 Bisphenol A was reacted with phosgene to give a specific viscosity of 0.283 and a water absorption of 0.2.
3, injection molding was carried out in the same manner as in Example 2 using a polycarbonate resin [AD5503 manufactured by Teijin Chemicals Ltd.] having a photoelastic constant of 80, a chlorine content of 7 ppm and an oligomer content of 3.2%. The total light transmittance of the obtained disk substrate was 89.
%, The value of photoelastic constant was 80 × 10 ⁻¹³ cm ² / dyn, and other properties are shown in Table 1. The value of the birefringent phase difference of oblique incidence was large, the pit depth was insufficient, and the warpage was large.

[0034]

[Table 1]

[0035]

According to the present invention, a polycarbonate resin made from 2,2-bis (3-methyl-4-hydroxyphenyl) propane is used to accurately transfer pits, and the error rate (BLER) is good. It is possible to provide an optical disk substrate that is less likely to warp due to moisture absorption, and the effect produced by the optical disk substrate is exceptional.

Claims (17)

[Claims] 1. A polycarbonate resin obtained by reacting a dihydric phenol mainly containing 2,2-bis (3-methyl-4-hydroxyphenyl) propane with a carbonate precursor, wherein the polycarbonate resin is (A). ) A solution of 0.7 g of this in 100 ml of methylene chloride has a specific viscosity measured at 20 DEG C. of 0.2-0.1.
4 (B) The undissolved particles measured in the methylene chloride solution are 25,000 particles having a diameter of 0.5 μm or more in terms of particle diameter per 1 g of the polycarbonate resin, 1 μm
An optical disk substrate formed of a resin satisfying the following conditions: 500 or less and (C) a water absorption rate of 0.2% by weight or less. 2. The optical disk substrate according to claim 1, wherein the polycarbonate resin has a total light transmittance of at least 85%. 3. The optical disk substrate according to claim 1, wherein the polycarbonate resin has an oblique incident birefringence retardation value of 60 nm or less. 4. The polycarbonate resin has a photoelastic constant value of 60 × 10 ⁻¹³ cm ² / dyn or less.
An optical disc substrate according to any one of 1. 5. The optical disk substrate according to claim 1, wherein the polycarbonate resin has a chlorine content of 10 ppm or less. 6. The polycarbonate resin has an oligomer content of 10% measured by the method defined in the text.
The optical disk substrate according to any one of claims 1 to 5, which is as follows. 7. The polycarbonate resin contains 1 to 150 ppm of a phosphorus stabilizer in terms of phosphorus atoms.
6. The optical disc substrate according to any one of 6 above. 8. The optical disk substrate according to claim 7, wherein the phosphorus-based stabilizer is a phosphoric acid ester. 9. The phosphorus-based stabilizer is 1 to 1 in terms of phosphorus atoms.
1 to 25 in terms of 00ppm phosphoric acid ester and phosphorus atom
8. The optical disk substrate according to claim 7, which is ppm phosphite ester. 10. The polycarbonate resin comprises 50 to 20 partial or total esters of a polyhydric alcohol having 2 to 5 carbon atoms and a saturated fatty acid having 10 to 30 carbon atoms.
The optical disk substrate according to any one of claims 1 to 9, which contains 00 ppm. 11. A polycarbonate resin obtained by reacting a dihydric phenol mainly containing 2,2-bis (3-methyl-4-hydroxyphenyl) propane with a carbonate precursor, which is 0.7 g of (A). The specific viscosity measured at 20 ° C. of a solution prepared by dissolving 100 ml of methylene chloride at 0.2 ° C. is 0.2 to 0.4, and (B) the undissolved particles measured in the methylene chloride solution are converted into particles per 1 g of the polycarbonate resin. 25.0 with a diameter of 0.5 μm or more
00 or less, 500 or less 1 μm or more, and (C) a polycarbonate resin having a water absorption of 0.2 wt% or less, a mold clamping force of 10 to 60 tons, and a resin temperature of 290 to 3
A method for manufacturing an optical disk substrate, which comprises performing injection molding at 30 ° C. and a mold temperature of 60 to 110 ° C. 12. The injection speed during injection molding is 50 to 700.
The method for manufacturing an optical disk substrate according to claim 11, wherein the manufacturing method is mm / sec. 13. The holding pressure during injection molding is 25 to 60 kg / cm.
^{2. The} term claim 11 or 12 optical disk substrate manufacturing method according. 14. The method for producing an optical disk substrate according to claim 11, wherein the polycarbonate resin to be injection-molded is a resin composition containing a phosphorus-based stabilizer in an amount of 1 to 150 ppm in terms of phosphorus atoms. . 15. The method for manufacturing an optical disk substrate according to claim 14, wherein the phosphorus-based stabilizer is a phosphoric acid ester. 16. The phosphorus-based stabilizer is 1 to 1 in terms of phosphorus atoms.
1 to 2 in terms of 100 ppm phosphoric acid ester and phosphorus atom
15. The method for manufacturing an optical disk substrate according to claim 14, wherein the phosphorous acid ester is 5 ppm. 17. The polycarbonate resin to be injection-molded comprises a polyhydric alcohol having 2 to 5 carbon atoms and 1 carbon atom.
The method for producing an optical disk substrate according to any one of claims 11 to 16, which is a resin composition containing 50 to 2000 ppm of a partial ester or a total ester of 0 to 30 saturated fatty acids.