JP2006302504A - Method for manufacturing optical disk substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a highly reliable optical disk substrate which can be obtained in a high nondefective rate. <P>SOLUTION: The method for manufacturing an optical disk substrate by molding a polycarbonate resin is a method for manufacturing an optical disk substrate, wherein in the polycarbonate resin, the total number of contaminations whose particle size is ≥15 μm is ≥1 piece/40g and ≤37 pieces/40g, and copper or contaminations containing copper among the contaminations are ≤12 pieces/40g. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical disc substrate with reduced foreign matter, and not only restricts the total amount of foreign matter, but also takes into account its thermal properties, in particular, an optical disc substrate made of a polycarbonate resin with a restricted proportion of foreign matters having specific thermal properties. It is about.

  Transparent thermoplastic resins include acrylic resin, styrene resin, polycarbonate resin, and amorphous polyolefin resin. These are used as optical materials such as compact discs and magneto-optical discs. Yes. Optical discs use micron-sized irregularities formed on a substrate to record and reproduce information using laser light, so that foreign matter (dust, carbides, etc.) in the substrate is responsible for the reliability of information recording and reproduction. Have a huge impact. Therefore, a small amount of foreign matter is required for the transparent thermoplastic resin constituting the substrate. Among these series of transparent thermoplastic resins, polycarbonate resins are particularly widely used worldwide because they are excellent in heat resistance and low water absorption, and are particularly excellent in transparency. As an example of this optical disk substrate material, polycarbonate resin that is used for general purposes will be described as an example. Conventionally, since the transparent thermoplastic resin constituting the substrate is required to have a small amount of foreign matter, Foreign substances in the raw material are reduced by filtering them through a filter in the purification process, granulation process, etc., for example, Japanese Patent Application Laid-Open No. 61-90345, Japanese Patent Application Laid-Open No. 63-91231, Techniques such as those described in Japanese Patent Application Laid-Open Nos. 7-109655 and 2000-173101 have been proposed.

Of these, JP-A-61-90345 discloses that the amount of foreign matter having a particle size of 0.5 μm or more contained in an optical disk substrate is 1 × 10 ⁵ particles / g or less, and this condition is satisfied. In addition, it is disclosed that it is necessary to remove foreign substances in raw materials used such as monomers by distillation and / or filtration, and to prevent foreign substances from being mixed during cleaning of the manufacturing equipment and the manufacturing process.

  Japanese Patent Application Laid-Open No. 63-91231 requires that the amount of foreign matter having a particle size of 1 μm or more be 10,000 pieces / g or less in order to obtain a highly reliable optical disc substrate. In addition, a technique for forming an optical disk substrate with a resin composition in which foreign particles are removed by filtering a solution dissolved in an organic solvent in order to satisfy this condition or by passing a sintered metal filter in a molten state. Is disclosed.

In Japanese Patent Publication No. 7-109655, in order to obtain sufficient reliability for recording and reproduction of information on an optical disk substrate, the concept of foreign matter strength is used, and in particular, the particle size is 1.1 μm or less. It is disclosed that the amount of foreign matter needs to be reduced to 10,000 μm ² / g or less.

  Japanese Patent Application Laid-Open No. 2000-173101 discloses that in order to obtain an optical disk substrate with few errors and extremely high reliability, in particular, the number of foreign matters for each particle size category is taken into consideration, and foreign matters are reduced for all particle size categories. A technique for an optical polycarbonate resin molding material and an optical disk substrate made of the material is disclosed.

  In the above prior art, the relationship between the total amount of foreign matter or the amount of foreign matter for each detailed particle size category and the information error of the final recording medium is examined in detail, but it does not necessarily eliminate defects in the actual disk manufacturing process. It does not reflect the actual situation. Currently, in general substrate materials for compact discs, sufficient reproduction reliability is obtained only by reducing the total amount of minute foreign matter. This is due to the idea that foreign matter) is also reduced. However, in the case of substrate materials for high-density optical discs represented by digital versatile discs (DVD-ROM, DVD-video, DVD-R, DVD-RAM, etc.), quality and economic efficiency can be achieved only by restricting all foreign substances indiscriminately. It turned out that it was not necessarily satisfied from both sides. In fact, manufacturers that produce optical disk substrates routinely inspect products with defect inspection machines to determine whether they are good or defective. A defect inspection machine is a device that determines whether a product is non-defective or defective by irradiating a substrate with light and detecting a minute shadow in the transmitted or reflected light obtained. As a matter of course, an optical disk substrate having a defect exceeding a specific value determined by the inspection machine has a high error and is inferior in reliability, and thus is excluded as a defective product.

  Thus, while the demand for quality improvement of optical transparent thermoplastic resin molding materials typified by polycarbonate and optical disk substrates made of such materials is increasing, the amount of production accompanying the recent spread of optical disk substrates has increased. Due to the increase, the demand for improved substrate productivity is also increasing. Since optical disk substrates are currently mass-produced, even if the yield rate is improved by several percent, the economic merit for optical disk substrate producers is enormous.

  As a result of repeated studies by the present inventors, if a foreign material having a large difference in thermal properties with the resin is present in the resin for substrate formation, the foreign material in the resin cooling process when obtaining a substrate by injection molding. It has been found that optical distortion is generated in the surrounding resin. Optical distortion generated around a foreign material having a large difference in thermophysical properties from these resins is detected as a defect by a defect inspection machine. In other words, a foreign material having a large difference in thermophysical property with the resin is likely to be detected including the optical distortion in the vicinity thereof, and is inspected as a foreign material defect larger than the actual size of the foreign material. It is judged by the opportunity. This has been a hindrance to obtaining a high-quality and highly reliable optical optical substrate.

  The present invention has been made in view of the above problems, and as a result of intensive studies on the problems, among various foreign substances present in the resin, copper or copper-containing foreign substances are different in thermophysical properties from the resin. It is found that the optical distortion is large because of the large thermal conductivity, and that the difference in thermal conductivity is greatly effective as the difference in thermal properties. On the other hand, in the resin production process, the reduction of foreign matters is generally accompanied by an increase in manufacturing cost. The inventors of the present invention have also found that enormous cost increases in the resin production process when aiming for a foreign matter content of a certain amount or less. In this way, the amount of foreign matter of a specific size in the resin is limited within the allowable range in terms of product quality and manufacturing cost, of which the proportion of foreign matter whose thermal conductivity difference from the resin exceeds a specific value By defining the ratio, especially the ratio of copper or copper-containing foreign matters to a specific value or less, it is possible to suppress the occurrence of large optical distortion around the foreign matters, and surprisingly high yield and high reliability. The present inventors have found that an optical disk substrate can be obtained and have reached the present invention.

According to the present invention, the following optical disk substrate manufacturing methods (1) to (5) are provided.
(1) A method for producing an optical disk substrate by molding a polycarbonate resin, wherein the total number of foreign matters having a particle diameter of 15 μm or more is 1/40 g or more and 37/40 g or less, A manufacturing method of an optical disk substrate, wherein copper or copper-containing foreign matter is 12 pieces / 40 g or less.
(2) The method according to (1) above, wherein the polycarbonate resin has a viscosity average molecular weight of 10,000 to 22,000.
(3) The method according to (1) or (2), wherein the molding is performed by injection molding.
(4) The method according to (3) above, wherein the injection molding is performed at a cylinder temperature of 300 to 400 ° C and a mold temperature of 50 to 140 ° C.
(5) The method according to any one of (1) to (4) above, wherein the optical disk substrate is a DVD substrate.

  The present invention not only restricts the total amount of foreign matter present in the resin, but also selectively restricts the proportion of the foreign matter among these various foreign matters based on the difference in thermal conductivity with the resin. The present invention relates to a featured optical disk substrate manufacturing method, which can provide a high-quality and highly reliable optical optical disc substrate, and is particularly effective for providing a high-density optical disc such as a digital video disc (DVD). The effect is exceptional.

  In the present invention, “foreign matter” refers to contaminants mixed in from any process until the polycarbonate resin is produced from the raw material and further the optical disk substrate is molded. For example, impurities contained in the used raw material (monomer, solvent, etc.) All components that are insoluble in solvents such as methylene chloride, such as dust, dust adhering to manufacturing equipment, or carbides generated during the molding process.

  According to the present invention, in order to obtain a high-quality and highly reliable optical disk substrate used for a high-density optical disk such as a digital video disk, the molding material to be used for molding the substrate is described in the above item (1). It must be a polycarbonate resin that satisfies the conditions shown. The molding material of the present invention needs to satisfy the condition of the above item (1), and a high density optical disk substrate molded from a material out of the condition is economically high and has high reliability and high reliability. An optical disk substrate cannot be obtained.

In the present invention, the particle size for counting the total number of foreign particles is set to 15 μm or more. When the defect inspection machine recognizes the optical distortion around the foreign particles, there is a foreign particle having a particle size larger than this, especially copper-containing foreign particles. This is because, in many cases, the defect is specifically detected as a defect exceeding the allowable limit (for example, 100 μm or more). However, the degree of optical distortion varies depending on the position of the foreign substance of the same size in the thickness direction of the substrate. In the thickness direction, the strain decreases as it moves away from the central portion.
This does not mean that any foreign material less than 15 μm may be present. It is better that the number of foreign matters less than 15 μm is small from another viewpoint.

In the present invention, the lower limit of the total number of foreign matters is set to 1/40 g because of the burden on the manufacturing cost of the foreign matter removing step. From the viewpoint of reducing the burden, it is possible to allow up to 3/40 g, and further to 5/40 g.
When the total number of foreign matters is close to these lower limit values, the ratio of copper or copper-containing foreign matters can be obtained as an average value by increasing the number of measurement samples to increase the total number of foreign matters.

The resin used in the present invention is a polycarbonate resin having transparency that can be used for optical applications.
The production method of the polycarbonate resin is not limited, but a polycarbonate resin is usually obtained by reacting a dihydric phenol and a carbonate precursor by a solution polymerization method or a melt polymerization method. Representative examples of the dihydric phenol used here include hydroquinone, resorcinol, 4,4'-dihydroxydiphenyl, bis (4-hydroxyphenyl) methane, bis {(4-hydroxy-3,5-dimethyl). Phenyl} methane, 1,1-bis (4-hydroxyphenyl) ethane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 2,2-bis (4-hydroxyphenyl) propane (commonly referred to as bisphenol A) ), 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane, 2,2-bis {(4-hydroxy-3,5-dimethyl) phenyl} propane, 2,2-bis {(3 , 5-Dibromo-4-hydroxy) phenyl} propane, 2,2-bis {(3-isopropyl-4-hydroxy) phenyl} propane 2,2-bis {(4-hydroxy-3-phenyl) phenyl} propane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) -3-methylbutane, 2, 2-bis (4-hydroxyphenyl) -3,3-dimethylbutane, 2,4-bis (4-hydroxyphenyl) -2-methylbutane, 2,2-bis (4-hydroxyphenyl) pentane, 2,2- Bis (4-hydroxyphenyl) -4-methylpentane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -4-isopropylcyclohexane, 1,1-bis (4 -Hydroxyphenyl) -3,3,5-trimethylcyclohexane, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bi {(4-hydroxy-3-methyl) phenyl} fluorene, α, α′-bis (4-hydroxyphenyl) -o-diisopropylbenzene, α, α′-bis (4-hydroxyphenyl) -m-diisopropylbenzene, α, α'-bis (4-hydroxyphenyl) -p-diisopropylbenzene, 1,3-bis (4-hydroxyphenyl) -5,7-dimethyladamantane, 4,4'-dihydroxydiphenylsulfone, 4,4 ' -Dihydroxydiphenyl sulfoxide, 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxydiphenyl ketone, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl ester, etc. The above can be mixed and used.

  Among them, bisphenol A, 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) -3 -Methylbutane, 2,2-bis (4-hydroxyphenyl) -3,3-dimethylbutane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 1,1-bis (4-hydroxyphenyl) A homopolymer or copolymer obtained from at least one bisphenol selected from the group consisting of 3,3,5-trimethylcyclohexane and α, α'-bis (4-hydroxyphenyl) -m-diisopropylbenzene In particular, a homopolymer of bisphenol A and 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethyl Preferred is a copolymer of rucyclohexane and bisphenol A, 2,2-bis {(4-hydroxy-3-methyl) phenyl} propane or α, α'-bis (4-hydroxyphenyl) -m-diisopropylbenzene. Is done.

  As the carbonate precursor, carbonyl halide, carbonate ester, haloformate or the like is used, and specific examples include phosgene, diphenyl carbonate, dihaloformate of dihydric phenol, and the like.

  When producing polycarbonate resin by reacting the above dihydric phenol and carbonate precursor by solution polymerization method or melt polymerization method, use catalyst, terminal terminator, dihydric phenol antioxidant, etc. as necessary. May be. The polycarbonate resin may be a branched polycarbonate resin copolymerized with a trifunctional or higher polyfunctional aromatic compound, or may be a polyester carbonate resin copolymerized with an aromatic or aliphatic difunctional carboxylic acid, Moreover, the mixture which mixed 2 or more types of the obtained polycarbonate resin may be sufficient.

  The reaction by the solution polymerization method is usually a reaction between a dihydric phenol and phosgene, and is reacted in the presence of an acid binder and an organic solvent. As the acid binder, for example, an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide or an amine compound such as pyridine is used. As the organic solvent, for example, halogenated hydrocarbons such as methylene chloride and chlorobenzene are used. In order to accelerate the reaction, a catalyst such as a tertiary amine such as triethylamine, tetra-n-butylammonium bromide or tetra-n-butylphosphonium bromide, a quaternary ammonium compound or a quaternary phosphonium compound may be used. it can. At that time, the reaction temperature is usually 0 to 40 ° C., the reaction time is preferably about 10 minutes to 5 hours, and the pH during the reaction is preferably maintained at 9 or more.

  In such a polymerization reaction, a terminal stopper is usually used. Monofunctional phenols can be used as such end terminators. Monofunctional phenols are commonly used as end terminators for molecular weight control, and the resulting polycarbonate resins are compared to those that do not because the ends are blocked by groups based on monofunctional phenols. Excellent thermal stability. Such monofunctional phenols are generally phenols or lower alkyl-substituted phenols, and can be monofunctional phenols represented by the following general formula (1).

[Wherein, A is a hydrogen atom or an aliphatic hydrocarbon group having 1 to 9, preferably 1 to 8 carbon atoms, and r is an integer of 1 to 5, preferably 1 to 3].

  Specific examples of the monofunctional phenols include phenol, p-tert-butylphenol, p-cumylphenol and isooctylphenol.

  In addition, as other monofunctional phenols, phenols or benzoic acid chlorides having long chain alkyl groups or aliphatic ester groups as substituents, or long chain alkyl carboxylic acid chlorides can be used, When these are used to block the ends of the polycarbonate copolymer, they not only function as end terminators or molecular weight regulators, but also improve the melt fluidity of the resin, facilitating the molding process, It is preferably used because it has the effect of lowering the physical properties, particularly the water absorption of the resin, and the effect of reducing the birefringence of the substrate. Of these, phenols having a long-chain alkyl group represented by the following general formulas (2) and (3) as a substituent are preferably used.

[Wherein, X is —R—O—, —R—CO—O— or —R—O—CO—, wherein R is a single bond or a carbon number of 1 to 10, preferably 1 to 5; A valent aliphatic hydrocarbon group, and n represents an integer of 10 to 50. ]
As the substituted phenols of the formula (2), those having n of 10 to 30, particularly 10 to 26 are preferable. Specific examples thereof include decylphenol, dodecylphenol, tetradecylphenol, hexadecylphenol, octadecylphenol, eico. Examples include silphenol, docosylphenol, and triacontylphenol.

  Further, as the substituted phenols of the formula (3), those in which X is —R—CO—O— and R is a single bond are suitable, and those in which n is 10 to 30, particularly 10 to 26 are suitable. Specific examples thereof include decyl hydroxybenzoate, dodecyl hydroxybenzoate, tetradecyl hydroxybenzoate, hexadecyl hydroxybenzoate, eicosyl hydroxybenzoate, docosyl hydroxybenzoate and triacontyl hydroxybenzoate.

  These end terminators are desirably introduced at the end of at least 5 mol%, preferably at least 10 mol% with respect to all the ends of the obtained polycarbonate resin, and the end terminators may be used alone or in combination of two or more. You may mix and use.

  The reaction by the melt polymerization method is usually a transesterification reaction between a dihydric phenol and a carbonate ester. In the presence of an inert gas, the dihydric phenol and the carbonate ester are mixed with heating, and the resulting alcohol or phenol is mixed. It is performed by the method of distilling. The reaction temperature varies depending on the boiling point of the alcohol or phenol produced, but is usually in the range of 120 to 350 ° C. In the latter stage of the reaction, the reaction system is decompressed to about 10 to 0.1 Torr to facilitate the distillation of the alcohol or phenol produced. The reaction time is usually about 1 to 4 hours.

  Examples of the carbonate ester include esters such as an optionally substituted aryl group having 6 to 10 carbon atoms, an aralkyl group, or an alkyl group having 1 to 4 carbon atoms. Specific examples include diphenyl carbonate, ditolyl carbonate, bis (chlorophenyl) carbonate, m-cresyl carbonate, dinaphthyl carbonate, bis (diphenyl) carbonate, dimethyl carbonate, diethyl carbonate, and dibutyl carbonate. Is preferred.

A polymerization catalyst can be used to increase the polymerization rate. Examples of such polymerization catalyst include sodium hydroxide, potassium hydroxide, sodium salt of dihydric phenol, alkali metal compounds such as potassium salt, calcium hydroxide, Alkaline earth metal compounds such as barium hydroxide and magnesium hydroxide, nitrogen-containing basic compounds such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, trimethylamine and triethylamine, alkoxides of alkali metals and alkaline earth metals, alkali metals And organic earth salts of alkaline earth metals, zinc compounds, boron compounds, aluminum compounds, silicon compounds, germanium compounds, organotin compounds, lead compounds, osmium compounds, antimony compounds, manganese compounds , Tan compounds, usually the esterification reaction, such as zirconium compounds, there can be used a catalyst used in the transesterification reaction. A catalyst may be used independently and may be used in combination of 2 or more types. The amount of these polymerization catalysts used is preferably 1 × 10 ⁻⁸ to 1 × 10 ⁻³ equivalent, more preferably 1 × 10 ^{−7 to} 5 × 10 ⁻⁴ equivalent, relative to 1 mol of dihydric phenol as a raw material. Selected by range.

The molecular weight of the polycarbonate resin is preferably 10,000 to 22,000, more preferably 12,000 to 20,000, and particularly preferably 13,000 to 18,000 in terms of viscosity average molecular weight (M). A polycarbonate resin having such a viscosity average molecular weight is preferable because it provides sufficient strength as an optical material and has good melt fluidity during molding and does not cause molding distortion. The viscosity average molecular weight referred to in the present invention is obtained by inserting the specific viscosity (η _sp ) obtained from a solution obtained by dissolving 0.7 g of a polycarbonate resin in 100 mL of methylene chloride at 20 ° C. into the following equation.
η _sp /c=[η]+0.45×[η] ² c (where [η] is the intrinsic viscosity)
[Η] = 1.23 × 10 ⁻⁴ M ^0.83
c = 0.7

  The raw material polycarbonate resin is produced by a conventionally known method (solution polymerization method, melt polymerization method, etc.), and then subjected to filtration treatment in a solution state or the granular raw material after granulation (desolvation) is heated, for example, under acetone. It is preferable to remove impurities and foreign matters such as low molecular weight components and unreacted components by washing with a poor solvent such as Furthermore, in the extrusion process (pelletizing process) for obtaining a pellet-like polycarbonate resin for use in injection molding, it is preferable to remove foreign matters by passing it through a sintered metal filter having a filtration accuracy of 10 μm in the molten state. In particular, in order to obtain a foreign material having a difference in thermal conductivity of 5 [W / (m · K)] or more from the resin, especially a resin having a small amount of copper or copper-containing foreign material, the foreign material as a polymerization raw material It is also desired to select a small amount of raw material and to use an apparatus with little occurrence of such foreign matter. Also in the step after the pelletization, it is also preferable to remove copper or copper-containing foreign matters by installing a magnetic separator. Furthermore, as a fundamental measure, it is also preferable that piping, equipment, and equipment of materials considered to be related to the generation of the foreign matter specified in the present invention are not used in the process as much as possible. If necessary, it is also preferable to add additives such as phosphorus-based antioxidants. In any case, it is necessary for the raw material resin before injection molding to keep the content of foreign matters, impurities, solvents, etc. as low as possible.

  When manufacturing an optical disk substrate from the polycarbonate resin, an injection molding machine (including an injection compression molding machine) is used. This injection molding machine may be generally used, but it has low adhesion to the resin as a cylinder or screw from the viewpoint of suppressing the generation of carbides and increasing the reliability of the disk substrate, and also has corrosion resistance and wear resistance. It is preferable to use a material made of a material exhibiting properties. As conditions for injection molding, a cylinder temperature of 300 to 400 ° C. and a mold temperature of 50 to 140 ° C. are preferable, and an optically excellent optical disk substrate can be obtained. The environment in the molding process is preferably as clean as possible in view of the object of the present invention. It is also important to take into consideration that the material used for molding is sufficiently dried to remove moisture, and that no retention that causes decomposition of the molten resin occurs.

Example 1
A bisphenol-A type polycarbonate resin powder having a viscosity average molecular weight of 15,000 was obtained by a solution polymerization method under the conditions in which mixing of external foreign matters and generation of internal foreign matters was controlled, and then pellets were obtained by pelletizing. The pellet was dissolved in methylene chloride filtered in advance with a 0.05 μm filter, and this sample was filtered with a 15 μm filter to obtain a filter collection, and the number of foreign matters was counted visually. The total number of foreign matters was 35/40 g. Further, when these collected foreign substances were analyzed in more detail using Link ISIS 300-I manufactured by XMA analyzer OXFORD, 8/40 g of copper-containing foreign substances were detected.
Next, using an optical disk substrate injection molding machine M-35B-D-DM, 1,000 DVD substrates were continuously molded at a cylinder temperature of 370 ° C and a mold temperature of 118 ° C. Then, the yield rate of the obtained substrate was measured in-line by a Basler defect inspection machine. This defect inspection machine uses a line scan camera with a resolution of 2,048 pixels and processes the image on the entire surface of the DVD substrate obtained by rotating in the circumferential direction of the DVD substrate and scanning it for 12,000 on a personal computer. In this case, it is determined whether the substrate is non-defective or defective. The quality of the defect inspection machine was determined based on 100 μm. Table 1 shows the obtained yield rate values.
In addition, when the defect part recognized / determined to be about 100 μm of the substrate determined to be defective by the defect inspection machine was visually observed using a polarizing plate and a microscope, there was a case where foreign matter of almost the same size was present. However, there were many cases where foreign matter of about 15 μm was present. When a portion of the resin containing about 15 μm of foreign matter was dissolved in a solvent (chloroform), the foreign matter was taken out from the resin and analyzed using the XMA analyzer, Cu was detected in many places.

Example 2
A bisphenol-A type polycarbonate resin powder having a viscosity average molecular weight of 15,000 was obtained by a solution polymerization method under conditions in which mixing of external foreign matters and generation of internal foreign matters were controlled. Copper powder having a particle size of 15 to 20 μm was added to this powder, and pellets were obtained by pelletizing. The pellet was dissolved in methylene chloride filtered in advance with a 0.05 μm filter, and this sample was filtered with a 15 μm filter to obtain a filter collection, and the number of foreign matters was counted visually. The total number of foreign matters was 37/40 g. Moreover, when these collected foreign materials were analyzed in detail using Link ISIS 300-I manufactured by XMA analyzer OXFORD, 12/40 g of copper-containing foreign materials were detected.
Next, the yield rate evaluation similar to Example 1 was performed. Table 1 shows the obtained yield rate values.

Comparative Example A bisphenol-A type polycarbonate resin powder having a viscosity average molecular weight of 15,000 was obtained by a solution polymerization method under the conditions in which mixing of external foreign matters and generation of internal foreign matters were controlled. Copper powder having a particle size of 15 to 20 μm was added to this powder, and pellets were obtained by pelletizing. The pellet was dissolved in methylene chloride filtered in advance with a 0.05 μm filter, and this sample was filtered with a 15 μm filter to obtain a filter collection, and the number of foreign matters was counted visually. The total number of foreign matters was 39/40 g. Further, when these collected foreign substances were analyzed in more detail using Link ISIS 300-I manufactured by XMA analyzer OXFORD, 29/40 g of copper-containing foreign substances were detected.
The same experiment as in Example 1 was performed except that this pellet was used. Table 1 shows the obtained yield rate values. Here, the thermal conductivity of copper is 336 [W / (m · K)] or more (Chemical Handbook (edited by the Chemical Society of Japan / Maruzen Co., Ltd.)), and the thermal conductivity of polycarbonate resin is 0.203. [W / (m · K)] or less (Chemical Equipment Handbook (Chemical Industry Association / Maruzen Co., Ltd.)), the difference in thermal conductivity between the two being 5 [W / (m · K)] or more

  From this result, in order to obtain a high-quality and highly reliable optical optical disc substrate, according to the present invention, not only the total amount of foreign matter present in the resin is limited, but among these various foreign matters, It can be seen that it is necessary to use a polycarbonate resin that selectively restricts the proportion of the foreign matter based on the difference in thermal conductivity with the resin.

Claims (5)

A method for producing an optical disk substrate by molding a polycarbonate resin, wherein the total number of foreign matters having a particle size of 15 μm or more is 1/40 g or more and 37/40 g or less, and copper or copper A manufacturing method of an optical disk substrate, wherein the number of contained foreign matters is 12 pieces / 40 g or less. The method of claim 1 wherein the polycarbonate resin has a viscosity average molecular weight of 10,000 to 22,000. The method according to claim 1 or 2, wherein the molding is performed by injection molding. The method according to claim 3, wherein the injection molding is performed at a cylinder temperature of 300 to 400 ° C and a mold temperature of 50 to 140 ° C. 5. The method according to claim 1, wherein the optical disk substrate is a DVD substrate.