JPWO2010092960A1 - Optical disk substrate manufacturing method and optical disk substrate molding material - Google Patents

Abstract

An object of the present invention is to provide an optical disc excellent in resistance to high-speed rotation and capable of reading / writing information at high speed, and a method for manufacturing the same. The present invention relates to a method for producing a substrate of an optical disc by molding a molding material, the optical disc having a substrate on which a fine concavo-convex pattern is formed, a light reflecting layer and a cover layer, and rotating the cover layer An optical disk for reading and writing recorded information from the side. As a molding material, in tensile strength measurement at 80 ° C. according to IS0527-1 and 527-2, the nominal fracture strain is 80 to 180% and the fracture stress is 40 to 80 MPa. This is a method using a certain thermoplastic resin.

Description

  The present invention relates to a method of manufacturing an optical disk substrate and a molding material for the optical disk substrate. More specifically, the present invention relates to a molding material suitable for an optical disc of information read / write system represented by BD (Blu-ray Disc). The present invention relates to a method of manufacturing an optical disk substrate that improves the accuracy of the optical disk substrate and the durability for high-speed reading and writing.

In the field of optical disks, with the progress in information technology such as high-definition video, an increase in capacity of information recording media is required, and various methods have been proposed. Further, as the capacity of the recording medium is increased, a higher transfer rate of recorded information is required. Therefore, the rotational speed of the optical disc when recording or reproducing the optical disc tends to increase.
The present applicant has already proposed that a molding material mainly composed of an aromatic polycarbonate copolymer composed of a specific unit derived from a specific dihydric phenol has a small amount of birefringence and deformation at high-speed rotation, and is an optical disk that rotates at high speed. (See Patent Document 1). In Patent Document 1, an optical disk manufactured from a general-purpose optical disk substrate material made of a bisphenol A type polycarbonate resin cannot sufficiently withstand a rotation test at 30,000 rpm. On the other hand, optical disks made from the copolymer have been shown to withstand such rotation tests. However, since such a copolymer requires the use of a special dihydric phenol, it is expensive and insufficient for use in a wide range of fields. In addition, since it is different from general-purpose polycarbonate, recyclability is insufficient.
On the other hand, it is known that in a bonded type disc such as a DVD, a substrate in a layer where no signal is recorded is formed of a polycarbonate resin having a viscosity average molecular weight of 18,000 or more (see Patent Document 2). The object of the invention in Patent Document 2 is to improve manufacturing efficiency and reduce manufacturing cost by replacing a smooth substrate without a signal with an extruded sheet. That is, the invention described in Patent Document 2 is merely one using a high molecular weight polycarbonate resin suitable for extrusion molding.
JP 2006-328106 A Japanese Patent Laid-Open No. 10-049917

An object of the present invention is to provide a method of manufacturing an optical disk substrate that has excellent resistance to high-speed rotation and can read and write information at high speed. Another object of the present invention is to provide a molding material for a substrate of an optical disk that has excellent resistance to high-speed rotation and can read and write information at high speed.
An optical disc, which is represented by a BD (Blu-ray Disc) and has a substrate with a fine uneven pattern, a light reflection layer, and a cover layer, and reads and writes recorded information from the cover layer side by rotating, is hereinafter referred to as “BD”. May be abbreviated as "." The BD preferably has a recording layer between the light reflecting layer and the cover layer.
Conventionally, it has been recognized that bisphenol A-type polycarbonate resin is not suitable for high-speed discs. In addition, it is recognized that it is difficult to use high-viscosity polycarbonate resin for substrates with signals. However, the present inventors have surprisingly found that even a bisphenol A type polycarbonate resin can be a substrate having high resistance to high-speed rotation as long as it satisfies the tensile fracture nominal strain and tensile fracture stress measured under specific conditions. I found. As a result of further investigation based on this finding, the present invention has been completed.
That is, the present invention relates to a method of manufacturing a substrate of an optical disc by molding a molding material, and the optical disc has a substrate on which a fine concavo-convex pattern is formed, a light reflection layer, and a cover layer, and is rotated to cover. It is an optical disk for reading and writing recorded information from the layer side. As a molding material, in tensile strength measurement at 80 ° C. according to IS0527-1 and 527-2, the fracture nominal strain is 80 to 180% and the fracture stress is 40 to 80 MPa. This is a method using a thermoplastic resin.
In addition, the present invention has IS0527-1 and 527 as molding materials for optical disk substrates that have a substrate with a fine concavo-convex pattern, a light reflection layer, and a cover layer, and are rotated to read / write recorded information from the cover layer side. This is a method using a thermoplastic resin having a fracture nominal strain of 80 to 180% and a fracture stress of 40 to 80 MPa in tensile strength measurement at 80 ° C. according to -2.
The present invention can be applied to an optical disc in which the maximum peripheral speed of the outer peripheral portion is in the range of 50 to 200 m / sec when reading / writing recorded information.
The present invention can also be applied to an optical disc having a recording layer between a light reflecting layer and a cover layer.
Further, the present invention has a fine concavo-convex pattern on the substrate, the fine concavo-convex pattern has groups and pit rows in the track direction, the track pitch is 0.1 to 0.8 μm, and the optical depth thereof. Is λ / 8n to λ / 2n (where λ is the wavelength of the laser beam used for recording and reproduction. N is the refractive index of the substrate on which the concave / convex pattern is formed at the wavelength λ). It can be applied to an optical disc having a substrate.
The molding material is preferably substantially composed of a polycarbonate resin having a viscosity average molecular weight of 1.7 × 10 ^{4 to} 2.4 × 10 ⁴ , which is composed of a carbonate constituent unit derived from bisphenol A.
The molding material is composed of a carbonate constituent unit derived from bisphenol A and has a fatty acid ester of 0.005 with respect to 100 parts by weight of a polycarbonate resin having a viscosity average molecular weight in the range of 1.7 × 10 ^{4 to} 2.4 × 10 ^4. It is preferable to contain -0.2 weight part.

  Details of the present invention will be described below.
  The present invention relates to a method for producing a substrate of an optical disk by molding a molding material, and the fracture nominal strain is 80 in the tensile strength measurement at 80 ° C. measured according to IS0527-1 and 527-2 as the molding material. This is a method of using a thermoplastic resin having a fracture stress of 40 to 80 MPa.
  The present invention is also a method of using the thermoplastic resin as a molding material for an optical disk substrate.
(Tensile strength)
  In the present invention, the molding material is a thermoplastic resin having a fracture nominal strain of 80 to 180% and a fracture stress of 40 to 80 MPa in tensile strength measurement at 80 ° C. according to IS0527-1 and 527-2. .
  By satisfying such specific fracture nominal strain and fracture stress, an optical disc that can withstand high-speed rotation and is less susceptible to breakage is provided. The reason is presumed as follows. Centrifugal force generated by high-speed rotation causes the disk to be deformed by high-speed rotation of the disk, and tensile force acts from the center of the disk toward the outer periphery. It is considered that when such a tensile force is repeatedly applied by high-speed continuous rotation, microcracks are generated and propagated from the central portion of the substrate, leading to final destruction. The correlation between the resistance to high-speed rotation and the tensile properties is presumably due to the mechanism that is damaged by high-speed rotation.
  On the other hand, the measurement at 80 ° C was performed for the purpose of accelerating and accelerating polymer behavior at high temperature, and although there was no clear critical meaning, the inside of equipment such as drives used for reading and writing information was closed. Considering that the temperature rises to some extent due to frictional heat between the substrate and the air rotating at high speed, it is considered to be an appropriate condition. By satisfying such characteristics, it is presumed that the generation and progress of microcracks are delayed, and the resistance to final destruction is improved.
  The lower limit of the fracture nominal strain at 80 ° C. is 80%, preferably 100%. The upper limit is 180%, preferably 160%. On the other hand, the lower limit of the fracture stress is 40 MPa, preferably 50 MPa, and the upper limit is 80 MPa, preferably 70 MPa.
(Thermoplastic resin)
  The thermoplastic resin may be any thermoplastic resin as long as the above tensile properties are satisfied.
  As thermoplastic resins, polycarbonate resins, polyarylate resins, polysulfone resins, polyethersulfone resins, polyphenylene resins, polyglutmethacrylate resins partially glutarimided, and various polymer compositions based on such resins, etc. Is exemplified. A more suitable thermoplastic resin is a polycarbonate resin in terms of moldability, cost, and enormous knowledge of conventional optical disks.
  A polycarbonate resin (hereinafter sometimes simply referred to as “polycarbonate”) is obtained by reacting a dihydric phenol, an aliphatic difunctional alcohol or an alicyclic bifunctional alcohol with a carbonate precursor. Examples of the reaction method include an interfacial polycondensation method, a melt transesterification method, a solid phase transesterification method of a carbonate prepolymer, and a ring-opening polymerization method of a cyclic carbonate compound.
  The polycarbonate resin may be various polycarbonate resins having a low crystallinity, a high heat resistance, or a low water absorption rate, which are polymerized using other dihydric phenols, in addition to the commonly used bisphenol A type polycarbonate. . The polycarbonate resin may be produced by any production method, and in the case of interfacial polycondensation, a terminal stopper of a monohydric phenol is usually used. The polycarbonate resin may be a branched polycarbonate obtained by polymerizing a trifunctional or higher polyfunctional component in addition to the dihydric phenol or difunctional alcohol. Further, it may be a branched polycarbonate resin obtained by polymerizing polyfunctional phenols such as trifunctional phenols, and further, an aliphatic dicarboxylic acid or aromatic dicarboxylic acid, a polyorganosiloxane component, and a vinyl monomer may be copolymerized. Copolymer polycarbonate may also be used.
  In the present invention, a bisphenol A type polycarbonate resin composed of a carbonate constituent unit derived from bisphenol A is more preferred. This is because it is one of the objects of the present invention to improve the high-speed rotation resistance by using a general-purpose thermoplastic resin. Even in such a bisphenol A type polycarbonate resin, it is possible to copolymerize a small proportion of other carbonate constituent units and to mix a polycarbonate resin composed of other carbonate constituent units.
  Examples of such dihydric phenols that derive other carbonate structural units include 4,4′-biphenol, 4,4′-bis (2,6-dimethyl) diphenol, α, α′-bis (4-hydroxy). Phenyl) -o-diisopropylbenzene, α, α′-bis (4-hydroxyphenyl) -m-diisopropylbenzene, α, α′-bis (4-hydroxyphenyl) -p-diisopropylbenzene, 9,9-bis ( 4-hydroxyphenyl) fluorene, 9,9-bis (4-hydroxy-3-methylphenyl) fluorene, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -3 , 3,5-trimethylcyclohexane, 1,1-bis (4-hydroxy-3-methylphenyl) cyclohexane, 1,1 Bis (4-hydroxyphenyl) -4-isopropylcyclohexane, 1,1-bis (3-cyclohexyl-4-hydroxyphenyl) cyclohexane, 4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxy-3,3′- Dimethyl diphenyl ether, 4,4′-dihydroxydiphenyl sulfone, 2,4′-dihydroxydiphenyl sulfone, 4,4′-dihydroxydiphenyl sulfoxide, 4,4′-dihydroxydiphenyl sulfide, 3,3′-dimethyl-4,4 ′ -Dihydroxydiphenyl sulfide, bis (3,5-dimethyl-4-hydroxyphenyl) sulfone, 1,1-bis (4-hydroxyphenyl) methane, 2,4'-dihydroxydiphenylmethane, bis (2-hydroxyphenyl) methane, Bi (4-hydroxyphenyl) methane, bis (4-hydroxy-5-nitrophenyl) methane, bis (4-hydroxy-2,6-dimethyl-3-methoxyphenyl) methane, bis (4-hydroxyphenyl) cyclohexylmethane, Bis (4-hydroxyphenyl) diphenylmethane, 1,1-bis (4-hydroxyphenyl) ethane, 1,1-bis (4-hydroxy-2-phenyl) -1-phenylethane, 1,1-bis (4- Hydroxy-2-chlorophenyl) ethane, 2,2-bis (3-phenyl-4-hydroxyphenyl) propane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, 2,2-bis (4- Hydroxy-3-ethylphenyl) propane, 2,2-bis (4-hydroxy-3-isopropylphenyl) pro Bread, 2,2-bis (3-tert-butyl-4-hydroxyphenyl) propane, 2,2-bis (3-bromo-4-hydroxyphenyl) propane, 2,2-bis (3,5-dibromo- 4-hydroxyphenyl) propane, 2,2-bis (4-hydroxyphenyl) -1-phenylpropane, 2,2-bis (4-hydroxyphenyl) -1,1,1,3,3,3-hexafluoro Propane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) pentane, 2,2-bis (4-hydroxyphenyl) butane, 4,4-bis (4-hydroxy) Phenyl) heptane, 2,2-bis (4-hydroxyphenyl) octane, 1,1-bis (4-hydroxyphenyl) decane, 1,1-bis (3-methyl-4-hydro) Roxyphenyl) decane, 1,1-bis (2,3-dimethyl-4-hydroxyphenyl) decane, 2,6-dihydroxynaphthalene, hydroquinone, resorcinol, resorcinol substituted with 1 to 3 alkyl groups, 3 -(4-hydroxyphenyl) -1,1,3-trimethylindan-5-ol, 1- (4-hydroxyphenyl) -1,3,3-trimethylindan-5-ol, 6,6'-dihydroxy- 3,3,3 ′, 3′-tetramethylspiroindan, 1-methyl-1,3-bis (4-hydroxyphenyl) -3-isopropylcyclohexane, 1-methyl-2- (4-hydroxyphenyl) -3 -[1- (4-hydroxyphenyl) isopropyl] cyclohexane, 1,6-bis (4-hydroxyphenyl) -1, - hexanedione, and ethylene glycol bis (4-hydroxyphenyl) ether, and the like.
  Among the dihydric phenols, α, α′-bis (4-hydroxyphenyl) -m-diisopropylbenzene, 9,9-bis (4-hydroxy-3-methylphenyl) fluorene, 1,1-bis (4- Hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxy-3-methylphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 3,3′-dimethyl- Preferred examples include 4,4′-dihydroxydiphenyl sulfide, 2,2-bis (4-hydroxy-3-methylphenyl) propane, and 1,1-bis (4-hydroxyphenyl) decane.
  As the bifunctional alcohol for deriving the structural unit of the polycarbonate, an alicyclic diol is more preferable. For example, cyclohexanedimethanol, cyclohexanediol, tricyclo (5.2.1.0).^2,6) Decandimethanol, norbornane dimethanol, decalin-2,6-dimethanol, spiroglycol, 1,4; 3,6-dianhydro-D-glucitol, 1,4; 3,6-dianhydro-D-mannitol, and 1,4; 3,6-dianhydro-L-iditol and the like are exemplified.
  Units other than the carbonate structural unit derived from bisphenol A are preferably 20 mol% or less, more preferably 5 mol% or less, and still more preferably 2 mol% or less, per 100 mol% of all the structural units. The glass transition temperature (Tg) of the polycarbonate used in the present invention is preferably adjusted to 130 ° C. or higher, more preferably 140 ° C. or higher. The upper limit is preferably 180 ° C. or lower, more preferably 175 ° C. or lower. By setting it as the range of this Tg, the tensile strength characteristic of this invention can be achieved under appropriate moldability. Tg is measured in accordance with JIS K-7121 at a temperature increase rate of 20 ° C./min.
  The viscosity average molecular weight (M) of the polycarbonate is preferably 1.7 × 10.⁴~ 2.4 × 10⁴Range. The lower limit is more preferably 1.8 × 10⁴More preferably, 1.85 × 10⁴It is. The upper limit is more preferably 2.2 × 10⁴, More preferably 2.15 × 10⁴It is. Such molecular weight may be achieved by mixing polycarbonate resins of different molecular weights, but in such mixing the molecular weight difference is 1.0 × 10⁴It is preferable to be within.
  The viscosity average molecular weight of polycarbonate is first calculated by the specific viscosity (η_SP) At 20 ° C. using a Ostwald viscometer from a solution of 0.7 g polycarbonate dissolved in 100 ml methylene chloride,
  Specific viscosity (η_SP) = (T−t₀) / T₀
  [T₀Is the drop time of methylene chloride, t is the drop time of the sample solution]
Calculated specific viscosity (η_SP) To calculate the viscosity average molecular weight M by the following formula.
  η_SP/C=[η]+0.45×[η]²c (where [η] is the intrinsic viscosity)
  [Η] = 1.23 × 10^-4M^0.83
  c = 0.7
  The molding material is composed of a carbonate constituent unit derived from bisphenol A, and has a viscosity average molecular weight of 1.7 × 10⁴~ 2.4 × 10⁴It is preferable to consist substantially of a polycarbonate resin in the range. In the present invention, “substantially” means preferably 80 mol% or more, more preferably 95 mol% or more, and still more preferably 98 mol% or more of all structural units.
  The molding material is composed of a carbonate constituent unit derived from bisphenol A, and has a viscosity average molecular weight of 1.7 × 10⁴~ 2.4 × 10⁴It is preferable to contain 0.005-0.2 weight part of fatty acid ester with respect to 100 weight part of polycarbonate resin of the range. By including the fatty acid ester, good releasability can be obtained, and an optical disk that forms a good pit or groove shape and has less warpage and deformation under a wide range of molding conditions. On the other hand, the presence of such fatty acid esters does not reduce the resistance to high-speed rotation.
  The molding material is composed of a carbonate constituent unit derived from bisphenol A, and has a viscosity average molecular weight of 1.7 × 10⁴~ 2.4 × 10⁴What mixed 2 or more types of polycarbonate resin of the range of can be used.
(Ingredients other than resin)
  In the present invention, the molding material is more preferably blended with the following release agent, heat stabilizer and the like.
(I) Release agent
  It is preferable to add a release agent to the thermoplastic resin used in the present invention, particularly the polycarbonate resin.
  A well-known thing can be used as a mold release agent. For example, fatty acid ester, polyolefin wax (polyethylene wax, 1-alkene polymer, etc., which may be modified with a functional group-containing compound such as acid modification), silicone compound, fluorine compound (represented by polyfluoroalkyl ether) Fluorinated oil), paraffin wax, beeswax and the like. Of these, fatty acid esters are preferred from the standpoints of availability, releasability and transparency. Such a release agent is preferably 0.005 to 0.2 parts by weight, more preferably 0.007 to 0.1 parts by weight, and still more preferably 0.01 to 0.06 parts per 100 parts by weight of the thermoplastic resin. Parts by weight. When the addition amount is less than the lower limit of the above range, the releasability is not sufficiently improved, and when the addition amount exceeds the upper limit, contamination of the stamper tends to be adversely affected.
  Among the above, fatty acid ester is mentioned as a preferable release agent. Such fatty acid esters are esters of aliphatic alcohols and aliphatic carboxylic acids. Such an aliphatic alcohol may be a monohydric alcohol or a dihydric or higher polyhydric alcohol. Moreover, as carbon number of this alcohol, it is the range of 3-32 suitably, More preferably, it is the range of 5-30. Examples of such monohydric alcohols include dodecanol, tetradecanol, hexadecanol, octadecanol, eicosanol, tetracosanol, seryl alcohol, and triacontanol. Examples of such polyhydric alcohols include pentaerythritol, dipentaerythritol, tripentaerythritol, polyglycerol (triglycerol to hexaglycerol), ditrimethylolpropane, xylitol, sorbitol, and mannitol. In the fatty acid ester of the present invention, a polyhydric alcohol is more preferable.
  On the other hand, the aliphatic carboxylic acid preferably has 3 to 32 carbon atoms, and particularly preferably an aliphatic carboxylic acid having 10 to 22 carbon atoms. Examples of the aliphatic carboxylic acid include decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid (palmitic acid), heptadecanoic acid, octadecanoic acid (stearic acid), nonadecanoic acid, icosanoic acid, And saturated aliphatic carboxylic acids such as docosanoic acid (behenic acid) and unsaturated aliphatic carboxylic acids such as palmitoleic acid, oleic acid, linoleic acid, linolenic acid, eicosenoic acid, eicosapentaenoic acid, and cetreic acid it can. Among the above, aliphatic carboxylic acids having 14 to 20 carbon atoms are preferable. Of these, saturated aliphatic carboxylic acids are preferred. Such aliphatic carboxylic acids are usually produced from natural fats and oils such as animal fats (such as beef tallow and pork fat) and vegetable fats and oils (such as palm oil). Of other carboxylic acid components. Therefore, in the production of the aliphatic carboxylic acid used in the present invention, it is produced from such natural fats and oils and is in the form of a mixture containing other carboxylic acid components. The acid value in the fatty acid ester is preferably 20 or less (can take substantially 0). However, in the case of all esters (full esters), it is preferable to contain at least a free fatty acid in order to improve releasability. In this respect, the acid value in the full ester is preferably in the range of 3 to 15. The iodine value of the fatty acid ester is preferably 10 or less (can take substantially 0). These characteristics can be obtained by a method defined in JIS K 0070.
  The fatty acid ester may be a partial ester or a full ester. In the present invention, a partial ester is more preferable in terms of good releasability and durability. Of these, glycerin monoester is preferred. Glycerin monoester is mainly composed of monoester of glycerin and fatty acid. Suitable fatty acids include saturated fatty acids such as stearic acid, palmitic acid, behenic acid, arachidic acid, montanic acid, lauric acid, oleic acid, and linoleic acid. And unsaturated fatty acids such as sorbic acid, and those having glycerin monoesters of stearic acid, behenic acid, and palmitic acid as main components are particularly preferred. Such fatty acids are synthesized from natural fatty acids and become a mixture as described above. The glycerin monoester can be used in combination with other release agents, particularly fatty acid full esters, but even when used in combination, it is preferable that the glycerin monoester is the main component. That is, it is preferably 60% by weight or more in 100% by weight of the release agent.
  In addition, partial esters are often inferior to full esters in terms of thermal stability. In order to improve the thermal stability of such a partial ester, the partial ester preferably has a sodium metal content of less than 20 ppm, more preferably less than 5 ppm, and even more preferably less than 1 ppm. The fatty acid partial ester having a sodium metal content of less than 1 ppm can be produced by producing the fatty acid partial ester by an ordinary method and then purifying it by molecular distillation or the like.
  Specifically, after removing gas components and low-boiling substances with a spray nozzle type degassing apparatus, glycerin is used under the conditions of a distillation temperature of 120 to 150 ° C. and a vacuum degree of 0.01 to 0.03 kPa using a falling film distillation apparatus. For example, a high molecular weight fatty acid ester is distilled off using a centrifugal molecular distillation apparatus at a distillation temperature of 160 to 230 ° C. and a vacuum of 0.01 to 0.2 Torr. The sodium metal can be removed as a distillation residue. By subjecting the resulting distillate to repeated molecular distillation, it is possible to further increase the purity and obtain a fatty acid partial ester having a lower sodium metal content. It is also important to prevent the contamination of the sodium metal component from the external environment by thoroughly washing the inside of the molecular distillation apparatus by an appropriate method in advance and improving airtightness. Such a fatty acid ester is available from a specialist (for example, Riken Vitamin Co., Ltd.).
(Ii) Phosphorus stabilizer
  In the present invention, it is preferable that various thermoplastic stabilizers are further blended in the thermoplastic resin, particularly the polycarbonate resin, mainly for the purpose of improving the thermal stability during the molding process. Examples of such phosphorus stabilizers include phosphorous acid, phosphoric acid, phosphonous acid, phosphonic acid, and esters thereof. In addition, such phosphorus stabilizers include tertiary phosphines.
  Specifically, as the phosphite compound, for example, triphenyl phosphite, tris (nonylphenyl) phosphite, tridecyl phosphite, trioctyl phosphite, trioctadecyl phosphite, didecyl monophenyl phosphite, dioctyl monophenyl Phosphite, diisopropyl monophenyl phosphite, monobutyl diphenyl phosphite, monodecyl diphenyl phosphite, monooctyl diphenyl phosphite, 2,2-methylenebis (4,6-di-tert-butylphenyl) octyl phosphite, tris ( Diethylphenyl) phosphite, tris (di-iso-propylphenyl) phosphite, tris (di-n-butylphenyl) phosphite, tris (2,4-di-tert-butylpheny) ) Phosphite, tris (2,6-di-tert-butylphenyl) phosphite, distearyl pentaerythritol diphosphite, bis (2,4-di-tert-butylphenyl) pentaerythritol diphosphite, bis (2 , 6-Di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite, bis (2,6-di-tert-butyl-4-ethylphenyl) pentaerythritol diphosphite, phenylbisphenol A pentaerythritol diphosphite Phyto, bis (nonylphenyl) pentaerythritol diphosphite, dicyclohexyl pentaerythritol diphosphite, and the like.
  Further, as other phosphite compounds, those which react with dihydric phenols and have a cyclic structure can be used. For example, 2,2′-methylenebis (4,6-di-tert-butylphenyl) (2,4-di-tert-butylphenyl) phosphite, 2,2′-methylenebis (4,6-di-tert- Butylphenyl) (2-tert-butyl-4-methylphenyl) phosphite, 2,2′-methylenebis (4-methyl-6-tert-butylphenyl) (2-tert-butyl-4-methylphenyl) phosphite 2,2′-ethylidenebis (4-methyl-6-tert-butylphenyl) (2-tert-butyl-4-methylphenyl) phosphite.
  Examples of the phosphate compound include tributyl phosphate, trimethyl phosphate, tricresyl phosphate, triphenyl phosphate, trichlorophenyl phosphate, triethyl phosphate, diphenyl cresyl phosphate, diphenyl monoorxenyl phosphate, tributoxyethyl phosphate, dibutyl phosphate, dioctyl phosphate, Examples thereof include diisopropyl phosphate, and triphenyl phosphate and trimethyl phosphate are preferable.
  Examples of the phosphonite compound include tetrakis (2,4-di-tert-butylphenyl) -4,4′-biphenylenediphosphonite, tetrakis (2,4-di-tert-butylphenyl) -4,3′-biphenylenedi. Phosphonite, tetrakis (2,4-di-tert-butylphenyl) -3,3′-biphenylenediphosphonite, tetrakis (2,6-di-tert-butylphenyl) -4,4′-biphenylenediphosphonite Tetrakis (2,6-di-tert-butylphenyl) -4,3′-biphenylene diphosphonite, tetrakis (2,6-di-tert-butylphenyl) -3,3′-biphenylene diphosphonite, bis (2,4-di-tert-butylphenyl) -4-phenyl-phenylphosphonite, bis (2,4-di tert-butylphenyl) -3-phenyl-phenylphosphonite, bis (2,6-di-n-butylphenyl) -3-phenyl-phenylphosphonite, bis (2,6-di-tert-butylphenyl)- Examples include 4-phenyl-phenylphosphonite, bis (2,6-di-tert-butylphenyl) -3-phenyl-phenylphosphonite. Of these, tetrakis (di-tert-butylphenyl) -biphenylenediphosphonite and bis (di-tert-butylphenyl) -phenyl-phenylphosphonite are preferable. In particular, tetrakis (2,4-di-tert-butylphenyl) -biphenylenediphosphonite and bis (2,4-di-tert-butylphenyl) -phenyl-phenylphosphonite are preferable. Such a phosphonite compound is preferable because it can be used in combination with a phosphite compound having an aryl group in which two or more alkyl groups are substituted.
  Examples of the phosphonate compound include dimethyl benzenephosphonate, diethyl benzenephosphonate, and dipropyl benzenephosphonate.
  Tertiary phosphine includes triethylphosphine, tripropylphosphine, tributylphosphine, trioctylphosphine, triamylphosphine, dimethylphenylphosphine, dibutylphenylphosphine, diphenylmethylphosphine, diphenyloctylphosphine, triphenylphosphine, tri-p-tolyl. Examples include phosphine, trinaphthylphosphine, and diphenylbenzylphosphine. A particularly preferred tertiary phosphine is triphenylphosphine.
  The phosphorus stabilizer can be used not only in one kind but also in a mixture of two or more kinds. Among the phosphorus stabilizers, phosphite compounds or phosphonite compounds are preferable. In particular, tris (2,4-di-tert-butylphenyl) phosphite, tetrakis (2,4-di-tert-butylphenyl) -4,4′-biphenylenediphosphonite and bis (2,4-di-) tert-Butylphenyl) -phenyl-phenylphosphonite is preferred. A combination of these and a phosphate compound is also a preferred embodiment.
(Iii) Hindered phenol stabilizer
  A hindered phenol stabilizer can be blended with the thermoplastic resin, particularly the polycarbonate resin in the present invention, mainly for the purpose of improving the heat stability during molding and heat aging resistance. Examples of such hindered phenol stabilizers include α-tocopherol, butylhydroxytoluene, sinapyl alcohol, vitamin E, n-octadecyl-β- (4′-hydroxy-3 ′, 5′-di-tert-butyl). Phenyl) propionate, 2-tert-butyl-6- (3′-tert-butyl-5′-methyl-2′-hydroxybenzyl) -4-methylphenyl acrylate, 2,6-di-tert-butyl-4- (N, N-dimethylaminomethyl) phenol, 3,5-di-tert-butyl-4-hydroxybenzylphosphonate diethyl ester, 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 2,2 '-Methylenebis (4-ethyl-6-tert-butylphenol), 4,4'-me Tylene bis (2,6-di-tert-butylphenol), 2,2′-methylene bis (4-methyl-6-cyclohexylphenol), 2,2′-dimethylene-bis (6-α-methyl-benzyl-p-cresol) ), 2,2′-ethylidene-bis (4,6-di-tert-butylphenol), 2,2′-butylidene-bis (4-methyl-6-tert-butylphenol), 4,4′-butylidenebis (3 -Methyl-6-tert-butylphenol), triethylene glycol-N-bis-3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate, 1,6-hexanediol bis [3- (3 , 5-di-tert-butyl-4-hydroxyphenyl) propionate], bis [2-tert-butyl-4-methyl 6- (3-tert-butyl-5-methyl-2-hydroxybenzyl) phenyl] terephthalate, 3,9-bis {2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) Propionyloxy] -1,1-dimethylethyl} -2,4,8,10-tetraoxaspiro [5.5] undecane, 4,4′-thiobis (6-tert-butyl-m-cresol), 4, 4′-thiobis (3-methyl-6-tert-butylphenol), 2,2′-thiobis (4-methyl-6-tert-butylphenol), bis (3,5-di-tert-butyl-4-hydroxybenzyl) ) Sulfide, 4,4′-di-thiobis (2,6-di-tert-butylphenol), 4,4′-tri-thiobis (2,6-di-tert-butyl) Phenol), 2,2-thiodiethylenebis- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,4-bis (n-octylthio) -6- (4-hydroxy -3 ′, 5′-di-tert-butylanilino) -1,3,5-triazine, N, N′-hexamethylenebis- (3,5-di-tert-butyl-4-hydroxyhydrocinnamide), N, N′-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyl] hydrazine, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butyl Phenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, tris (3,5-di-tert) Butyl-4-hydroxyphenyl) isocyanurate, tris (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, 1,3,5-tris (4-tert-butyl-3-hydroxy-2, 6-dimethylbenzyl) isocyanurate, 1,3,5-tris 2 [3 (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] ethyl isocyanurate, and tetrakis [methylene-3- (3 ', 5'-di-tert-butyl-4-hydroxyphenyl) propionate] methane and the like. All of these are readily available. The said hindered phenolic antioxidant can be used individually or in combination of 2 or more types.
  The amount of the (ii) phosphorus stabilizer and (iii) hindered phenol antioxidant is preferably 0.0001 to 1 part by weight, more preferably 0.001 to 100 parts by weight of the thermoplastic resin. 0.1 parts by weight, more preferably 0.005 to 0.1 parts by weight. When the amount of the stabilizer is less than the above range, it is difficult to obtain a good stabilizing effect. When the amount exceeds the above range, the physical properties of the material may be deteriorated or the stamper may be contaminated.
  In the present invention, an antioxidant other than the hindered phenol-based antioxidant can be appropriately used for the thermoplastic resin. Examples of such other antioxidants include pentaerythritol tetrakis (3-mercaptopropionate), pentaerythritol tetrakis (3-lauryl thiopropionate), and glycerol-3-stearyl thiopropionate. The amount of these other antioxidants used is preferably 0.001 to 0.05 parts by weight with respect to 100 parts by weight of the thermoplastic resin.
  In the present invention, the thermoplastic resin may also include an ultraviolet absorber, a light stabilizer, a bluing agent, a fluorescent dye, an antistatic agent, a heat ray absorbent, a dye / pigment, a flame retardant, a hydrolysis improver, an inorganic filler, An antibacterial agent, a photocatalytic antifouling agent, a light diffusing agent, and a white pigment for high light reflection can be contained. These can be contained by appropriately selecting agents and blending amounts that do not hinder the production of the optical disk.
  The bluing agent preferably comprises 0.05 to 3.0 ppm (weight ratio) in the resin material. Representative examples of the bluing agent include Macrolex Violet B and Macrolex Blue RR manufactured by Bayer, and Polysynthrene Blue RLS manufactured by Clariant.
  Examples of fluorescent dyes (including fluorescent brighteners) include coumarin fluorescent dyes, benzopyran fluorescent dyes, perylene fluorescent dyes, anthraquinone fluorescent dyes, thioindigo fluorescent dyes, xanthene fluorescent dyes, and xanthone fluorescent dyes. And thioxanthene fluorescent dyes, thioxanthone fluorescent dyes, thiazine fluorescent dyes, and diaminostilbene fluorescent dyes. The blending amount of the fluorescent dye (including the fluorescent brightening agent) is preferably 0.0001 to 0.1 parts by weight with respect to 100 parts by weight of the thermoplastic resin.
  In the present invention, the molding material tends to have a yellowish color as compared with the conventional optical disk substrate material, so that it can be adjusted to an appropriate hue by adding a dye. Furthermore, it is also preferable to make a clear hue to make it easy to sort by purpose and to clearly indicate that it is a high-speed rotating disk. In addition, the molding material for substrates of the present invention can be used to adjust the hue of a material when a resin molded product collected from the market is partially added to form a resin material. Preferred examples of the resin molded product recovered from the market include vehicle headlamp lenses, CDs, and DVDs. The blending amount of the dye / pigment is preferably 0.0001 to 1 part by weight with respect to 100 parts by weight of the thermoplastic resin.
  Examples of the hydrolysis improver include epoxy compounds, oxetane compounds, silane compounds, and phosphonic acid compounds.
(Manufacture of molding materials)
  For the production of the molding material, a known method for producing an optical disk material made of polycarbonate resin can be used. That is, after the polycarbonate resin and the additive are premixed, they are put into an extruder and melt-kneaded, and the extruded thread is cooled and cut by a pelletizer to produce a pellet-shaped molding material.
  As the extruder, any of a single screw extruder and a twin screw extruder can be used, but a twin screw extruder is preferable from the viewpoint of productivity and kneadability. A typical example of such a twin screw extruder is ZSK (trade name, manufactured by Werner & Pfleiderer). Specific examples of similar types include TEX (trade name, manufactured by Nippon Steel Works, Ltd.), TEM (trade name, manufactured by Toshiba Machine Co., Ltd.), KTX (product name, manufactured by Kobe Steel, Ltd.), and the like. Can be mentioned. As the extruder, one having a vent capable of degassing moisture in the raw material and volatile gas generated from the melt-kneaded resin can be preferably used. From the vent, a vacuum pump is preferably installed for efficiently discharging generated moisture and volatile gas to the outside of the extruder. It is also possible to remove a foreign substance from the resin composition by installing a screen for removing the foreign substance mixed in the extrusion raw material in the zone in front of the extruder die. Examples of such a screen include a wire mesh, a screen changer, a sintered metal plate (such as a disk filter), and the like.
  Although the additive can be independently supplied to the extruder, it is preferably premixed with the resin raw material as described above. Examples of such premixing means include a Nauter mixer, a V-type blender, a Henschel mixer, a mechanochemical apparatus, and an extrusion mixer. A more suitable method is to prepare a master agent by mixing a part of the raw material and an additive with a high-speed stirrer such as a Henschel mixer, and then leave the total amount of the resin raw material and the high-speed component such as a Nauter mixer. It is a method of mixing with a stirrer not.
  The resin extruded from the extruder is directly cut into pellets, or after forming strands, the strands are cut with a pelletizer and pelletized. When it is necessary to reduce the influence of external dust or the like, it is preferable to clean the atmosphere around the extruder. Further, in the production of such pellets, various methods already proposed for polycarbonate resin for optical discs are used to narrow the shape distribution of pellets, further reduce miscuts, and generate fine powder during transportation or transportation. It is preferable to further reduce the amount of bubbles and the bubbles (vacuum bubbles) generated in the strands and pellets. Miscuts can be reduced by controlling the thread temperature during cutting with a pelletizer, blowing ionic air during cutting, optimizing the rake angle of the pelletizer, and properly blending the release agent, and cutting. And a method of filtering the mixture of the pellets and water to separate the pellets, water and miscuts. An example of the measuring method is disclosed in, for example, Japanese Patent Application Laid-Open No. 2003-200421. By these prescriptions, it is possible to increase the molding cycle and reduce the occurrence rate of defects such as silver.
  In the present invention, the miscut amount in the molding material is preferably 10 ppm or less, more preferably 5 ppm or less. Here, the miscut means a granular material finer than a pellet having a desired size that passes through a JIS standard sieve having an opening of 1.0 mm. The shape of the pellet can take a general shape such as a cylinder, a prism, and a sphere, but is more preferably a cylinder (including an elliptic cylinder), and the diameter of the cylinder is preferably 1.5 to 4 mm, more preferably Is 2 to 3.5 mm. In the elliptic cylinder, the ratio of the minor axis to the major axis is preferably 60% or more, more preferably 65% or more. On the other hand, the length of the cylinder is preferably 2 to 4 mm, more preferably 2.5 to 3.5 mm.
(Molding)
  An injection molding machine (including an injection compression molding machine) is used when manufacturing a BD substrate from a molding material, more specifically, a molding material having a pellet shape. 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 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, the cylinder temperature is preferably 300 to 450 ° C., more preferably 320 to 400 ° C., the mold temperature is preferably 50 to 180 ° C., more preferably 80 to 140 ° C., and these are more excellent. A BD substrate having excellent mechanical properties and shape 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.
  The optical disk substrate of the present invention can be used not only for injection molding including injection compression molding, but also for hot press molding, vacuum compression molding, melt thermal transfer molding, and the like. However, injection molding, especially injection compression molding is preferred from the viewpoint of productivity. That is, by injection compression molding, a substrate that is excellent in productivity and excellent in resistance to high-speed rotation is manufactured.
(substrate)
  The thickness of the substrate of the optical disk is preferably 1.1 mm. The substrate of the optical disk has a fine concavo-convex pattern, the fine concavo-convex pattern has groups and pit rows in the track direction, the track pitch is 0.1 to 0.8 μm, and the optical depth is It is preferable that λ / 8n to λ / 2n (where λ is the wavelength of the laser beam used for recording / reproduction. n is the refractive index of the substrate on which the concave / convex pattern at the wavelength λ is formed. ). The present invention is applicable to an optical disk substrate having such a fine uneven pattern.
(optical disk)
  In the present invention, the optical disk is an optical disk having a substrate on which a fine concavo-convex pattern is formed, a light reflection layer, and a cover layer, and reading and writing recorded information from the cover layer side by rotating.
  According to the present invention, an optical disc excellent in resistance to high-speed rotation is provided. The present invention can be applied to an optical disc in which the maximum peripheral speed of the outer peripheral portion is in the range of 50 to 200 m / sec when reading / writing recorded information. The lower limit of the maximum peripheral speed is preferably 70 m / sec, more preferably 100 m / sec.
  In BD (Blu-ray Disc), at least a light reflection layer and a cover layer are formed on a substrate. Preferably, a recording layer made of a single layer or a plurality of recording films and a recording film protective film is formed between the light reflecting layer and the cover layer. A plurality of these layers may be formed, and in particular, a two-layer system is widely known. In an optical disc having a recording layer such as a write-once type BD-R and a rewritable type BD-RE, there is a high demand for high-speed rotation, and the present invention is more suitably utilized.
  Further, a moisture-proof film is usually formed on the surface opposite to the layer provided with the cover layer in order to prevent warping of the substrate during use. If necessary, a hard coat layer is provided on the outermost cover layer.
(Recording film)
  In the case of a write-once type optical disc, the recording film is a film in which the optical characteristics are irreversibly changed by the irradiation of laser light or an uneven shape is formed. For example, cyanine-based, phthalocyanine-based, azo-based, and indoaniline-based organic dyes that decompose when heated by laser light irradiation to change their optical constants and cause deformation of the recording film due to volume changes are used. . In particular, organic dyes of azo metal complexes and indoaniline metal complex compounds are preferably used. Such complexes can be matched with other organic dyes to increase the sensitivity of the laser light. Details of the combination of the azo metal complex and the metal complex compound of the indoaniline metal complex compound with other organic dyes are described in, for example, Japanese Patent Application Laid-Open Nos. 2005-271587 and 2008-262661. Yes.
  In the case of a rewritable optical disc, the recording film is a film made of a material that causes a reversible phase structure change between an amorphous state and a crystalline state upon irradiation with laser light (phase change recording type), or perpendicular to the film surface. It is a magnetic thin film (magneto-optical recording type) having a magneto-optical effect that has an easy magnetization direction in the direction and can record, reproduce, and erase information by creating an arbitrary inversion magnetic domain.
  Examples of the phase change recording type recording film include GeSbTe-based, InSbTe-based, InSe-based, InTe-based, AsTeGe-based, TeOx-GeSn-based, TeSeSn-based, FeTe-based, SbSeBi-based, and BiSeGe-based chalcogenide-based materials. However, a film made of a GeSbTe system is preferable because of stable operation during repeated recording / erasing.
  Examples of magneto-optical recording films include amorphous alloy thin films of rare earth elements and transition metal elements such as TbFe, TbFeCo, GdTbFe, NdDyFeCo, NdDyTbFeCo, NdFe, PrFe, and CeFe, and those utilizing exchange coupling Bilayer films of the above, artificial lattice multilayer films such as Co / Pt and Co / Pd, and CoPt alloys can be used.
  In the present invention, it is preferable to use a dielectric material as the recording film protective film for sandwiching the recording film. As a result, the reflectance difference between the crystalline phase and the amorphous phase as a medium, and the magneto-optical effect can be increased, and further, the storage stability of the recording layer, the adhesion between the recording layer and the cover layer, and the heat Conductivity adjustment can be performed.
  The dielectric material is preferably a material having a high refractive index n, that is, a material satisfying n ≧ 1.6, more preferably a material satisfying n ≧ 1.8. Specifically, materials composed of nitrides, oxides, carbides, and sulfides such as Zn, Si, Ti, Te, Sn, Mo, Ge, Nb, and Ta are preferable. For example, SiO, SiON, Ta₂O₃TiO₂, Al₂O₃, Y₂O₃, CeO, La₂O₃, In₂O₃, GeO, GeO₂, MoO₂, Nb₂O₅, PbO, SnO, SnO₂, Bi₂O₃, Ta₂O₅, TeO, TeO₂WO₂TiO₂, WO₃, Sc₂O₃, ZnO, ZrO₂Oxides such as TaN, AlN, SiN, AlSiN, etc., ZnS, ZnO—Ga₂O₃, Sb₂S₃, CdS, In₂S₃, Ga₂S₃, GeS, SnS₂, PbS, Bi₂S₃It is preferable to use a sulfide such as the above or a mixed material thereof or a laminate thereof as a protective film.
(Light reflecting layer)
  The light reflecting layer is preferably a material having higher reflectivity than the recording layer with respect to the laser beam of the drive head used for evaluation. Specifically, it is preferable to select a material in which the refractive index n and the extinction coefficient k, which are optical constants at the used laser light wavelength, satisfy n ≦ 3.5 and k ≧ 3.5. More preferably, n ≦ 2.5 and 4.5 ≦ k ≦ 8.5. With a medium manufactured under these conditions, the reproduction signal characteristics can be further improved.
  On the other hand, when a signal is recorded by heating with laser light, if the thermal conductivity of the light reflection layer is too high, thermal diffusion is large and strong laser power is required. For this reason, in order to enable signal recording with a semiconductor laser having a power of 15 mW or less, which is widely used at present, the thermal conductivity of the material used for the light reflection layer is 100 [W / (m · K)] or less. It is more preferable that it is 80 [W / (m · K)] or less.
  As materials satisfying such conditions, Al, Ag, Au, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Tc, Re, Ru, Os, Ir, Pd, Pt, Cu, And an alloy to which one or more elements such as Nd are added. Specifically, for example, an AgPdCu alloy, an AgCuAu alloy, an AgCuAuNd alloy, an AgCuNd alloy, or the like. In these alloys, the content of the additive element is preferably in the range of 0.1 to 10 atomic%. As a material other than metal, a multilayer film can be formed by alternately stacking a low refractive index thin film and a high refractive index thin film, and this can be used as a light reflecting layer. The film thickness range of these reflective layers is 10 to 500 nm, but preferably 30 to 200 nm, particularly in order to suppress the deterioration of the reproduction signal characteristics due to the decrease in reflectance and to enable recording at a laser power of 15 mW. Preferably it is 40-100 nm. The light reflecting layer can be formed on the substrate by vacuum deposition, sputtering or ion plating. In the case of a read-only optical disc medium, only the light reflecting layer described above is formed on the substrate, but the same materials can be used.
(Cover layer)
  The cover layer is formed by applying and curing a curable resin such as an ultraviolet curable resin (hereinafter simply referred to as “UV curable resin”) by a method typified by spin coating (so-called spin coating method), In addition, any of methods for attaching and forming an optical film typified by a polycarbonate resin film (so-called sheet attaching method) can be used. As such an optical film for the cover layer, Pure Ace (registered trademark) is commercially available from Teijin Chemicals. In the sheet pasting method, after applying a curable compound such as a UV curable resin to the substrate side, the sheet is pasted, and a sheet pre-coated with an adhesive or adhesive is pasted on the sheet side, if necessary Any method of curing can be used. Examples of such pressure-sensitive adhesives include acrylic pressure-sensitive adhesives and silicone pressure-sensitive adhesives, and acrylic pressure-sensitive adhesives are particularly preferably used. In the write-once type system using an organic dye of an azo-based metal complex and an indoaniline-based metal complex compound, it is preferable to use a sheet sticking method and an adhesive for such sticking in order to facilitate the formation of voids. The Tg of the pressure-sensitive adhesive is preferably 0 ° C. or lower, more preferably −15 ° C. or lower, and further preferably −25 ° C. or lower.

発明の効果
本発明の光ディスク基板の製造方法によれば、高速回転に対する耐性に優れ、情報の高速の読み書きが可能な光ディスクが提供される。本発明の特定の熱可塑性樹脂を用いる方法によれば、高速回転に対する耐性に優れ、情報の高速の読み書きが可能な光ディスクが提供される。
本発明は、汎用のビスフェノールＡ型のポリカーボネート樹脂であっても、特定の物性を有するものを、光ディスクの基板材料として用いると、高速回転に対する耐性に優れた光ディスク基板が得られることを見出したものであり、低コスト、リサイクル性にも優れる方法である。Hereinafter, the present invention will be described in detail by way of examples. However, the present invention is not limited to these. In addition, the measurement of the various characteristics in an Example was based on the following method.
(I) Evaluation item (I-1) Viscosity average molecular weight The viscosity average molecular weight of the pellet is calculated by the following formula using an Ostwald viscometer from a solution obtained by dissolving 0.7 g of polycarbonate pellets in 100 ml of methylene chloride at 20 ° C. The specific viscosity (η _SP ) was determined, and the viscosity average molecular weight (M) was calculated from the specific viscosity (η _SP ) by the following formula.
Specific viscosity (η _SP ) = (t−t ₀ ) / t ₀
[T ₀ is methylene chloride falling seconds, t is sample solution falling seconds]
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
(I-2) Measurement of Tensile Fracture Stress and Tensile Fracture Nominal Strain A pellet having a length of 175 mm, a width of 10 mm, and a thickness of 4 mm was prepared by injection molding, and 23 ° C. in accordance with ISO527-1 and 527-2. And tensile fracture stress (unit: MPa) and tensile fracture nominal strain (unit:%) at 80 ° C. were measured. The test speed was 5 mm / min.
(I-3) Evaluation of warpage amount of optical disk An optical disk substrate having a diameter of 120 mmφ and a thickness of 1.1 mm was formed by the method of (2) described later, and a reflective film was sputter deposited on the signal surface side of the optical disk substrate. A cover layer film made of polycarbonate resin (Pure Ace (registered trademark) D92 manufactured by Teijin Chemicals Ltd.) was bonded to the optical disk to produce an optical disk. As a warp change amount of the optical disc, a radial tilt at 55 mm from the center of the optical disc was measured using a three-dimensional shape measuring device DLD-3000U manufactured by Japan EM Co., Ltd.
(I-4) Rotational strength test of optical disc Using the optical disc with the cover layer bonded as in the evaluation in (I-3) above, the optical disc was rotated at 30,000 rpm for 5 minutes at high speed, and the rotational strength was measured. A test was conducted. In this evaluation, ten optical disks were used. Even if any one piece is broken at high speed, no breakage, but no breakage occurs even if any one piece is cracked on the signal surface (radius 25mm to 55mm). In addition, the case where no cracks occurred on the signal surface was judged as ◯.
Examples 1 to 4 and Comparative Example 1
(1) Production of substrate molding material A substrate molding material having the blending ratio shown in Table 1 was prepared in the following manner. That is, according to the charging composition shown in Table 1, each raw material was weighed into a polyethylene bag and the bag was sufficiently rotated up and down and left and right to uniformly dry-blend the charged material. The dry blended mixture was supplied to the first inlet at the rearmost part using a vent type twin screw extruder (TEX30α-35BW-3V manufactured by Nippon Steel Works, Ltd.) having a screw diameter of 30 mm. The cylinder temperature and the die temperature were 255 ° C., 260 ° C., 265 ° C., and 275 ° C. in Examples 1 to 4, respectively. The screw rotation speed was 250 rpm, the discharge rate per hour was 15 kg / hour, and the vacuum degree of the vent was 10 kPa. In addition, the structure of the screw segment had the kneading | mixing zone comprised with the kneading disk in the upstream and downstream of the position of a vent. The extruded strand was cooled in a water bath, then cut with a pelletizer and pelletized. The obtained pellets had a number average diameter of 2.8 mm, a number average length of 3.0 mm, and a miscut of 3 ppm. The pellets were dried in a hot air dryer at 120 ° C. for 6 hours.
(2) Preparation of optical disk for evaluation The optical disk used for evaluation was prepared as follows. First, using each pellet obtained in (1), an optical disk substrate having a diameter of 120 mmφ and a thickness of 1.1 mm was injection molded at the cylinder temperature and the mold temperature shown in Table 1. The used injection molding machine [SD-40E manufactured by Sumitomo Heavy Industries, Ltd.] was equipped with a BD-R stamper (having a groove with a track pitch of 0.32 μm and a depth of 0.03 μm).
A thin film having a thickness of 100 nm was deposited on the signal surface side of the obtained optical disk substrate by DC sputtering using a high frequency magnetron sputtering apparatus (ILC3102 type manufactured by Anelva). Such sputtering was performed using an Ag alloy sputtering target containing 5.0 atomic% of Nd and 1.0 atomic% of Bi at a discharge power of 500 W. Other film formation conditions were substrate temperature: 22 ° C., argon gas pressure: 2 mTorr, film formation rate: 5 nm / sec, and back pressure: <5 × 10 ⁻⁶ Torr.
The substrate on which the light reflecting layer was formed was taken out of the sputtering apparatus and attached to a spin coater. While rotating the disk, after applying UV curable phenol novolac epoxy acrylate resin, vacuum cover layer film (panlite film (registered trademark) D92 manufactured by Teijin Kasei Co., Ltd.) cut to 15mmφ inner diameter and 120mmφ outer diameter Pasted together. Thereafter, an ultraviolet ray irradiating apparatus was passed to cure the ultraviolet curable resin, thereby producing an optical disc.
In the evaluation of the present invention, the presence or absence of the recording layer does not have a great influence on the warp amount and the rotational strength of the optical disk, and therefore they are omitted. The obtained optical disk was evaluated for warpage and a rotational strength test, and the results are shown in Table 1.
As is apparent from the results in Table 1, by using a resin material whose tensile properties at 80 ° C. satisfy a specific value, good rotational strength that cannot be obtained with a polycarbonate resin material for general-purpose optical disks can be obtained. I understand.
In addition, the symbol in a table | surface shows the following.
(Thermoplastic polymer as the main component)
PC-1: Linear aromatic polycarbonate resin powder having a viscosity average molecular weight of 15,900 (Panlite (registered trademark) CM-1000 manufactured by Teijin Chemicals Ltd.)
PC-2: Linear aromatic polycarbonate resin powder having a viscosity average molecular weight of 19,700 (Panlite (registered trademark) L-1225WX manufactured by Teijin Chemicals Ltd.)
PC-3: Linear aromatic polycarbonate resin powder having a viscosity average molecular weight of 20,800 (Panlite (registered trademark) L-1225WS manufactured by Teijin Chemicals Ltd.)
PC-4: Linear aromatic polycarbonate resin powder having a viscosity average molecular weight of 22,400 (Panlite (registered trademark) L-1225WP manufactured by Teijin Chemicals Ltd.)
(Comparative material)
AD: Polycarbonate resin pellet for optical disk having a viscosity average molecular weight of 15,500 (Panlite (registered trademark) AD-5503 manufactured by Teijin Chemicals Ltd.)
(Other additives)
RA: monoester composed of glycerin having a molecular weight of 343 and an aliphatic carboxylic acid (manufactured by Riken Vitamin Co., Ltd .: Riquemar S-100A)
ST: Phosphite heat stabilizer (manufactured by Ciba Specialty Chemicals: Irgafos 168; tris (2,4-di-tert-butylphenyl) phosphite)

Advantageous Effects of Invention According to the method for manufacturing an optical disk substrate of the present invention, an optical disk having excellent resistance to high-speed rotation and capable of reading and writing information at high speed is provided. According to the method using the specific thermoplastic resin of the present invention, an optical disc that has excellent resistance to high-speed rotation and can read and write information at high speed is provided.
The present invention has found that an optical disk substrate excellent in resistance to high-speed rotation can be obtained when a general-purpose bisphenol A type polycarbonate resin having specific physical properties is used as a substrate material for an optical disk. It is a low cost and excellent recyclability method.

  The method of the present invention can be used for production of BD (Blu-ray Disc).

Claims (12)

  A method of manufacturing a substrate of an optical disc by molding a molding material, the optical disc having a substrate with a fine concavo-convex pattern, a light reflection layer, and a cover layer, and rotating the recording information from the cover layer side Is a thermoplastic resin having a fracture nominal strain of 80 to 180% and a fracture stress of 40 to 80 MPa in a tensile strength measurement at 80 ° C. according to IS0527-1 and 527-2 as a molding material. Method using.   The method according to claim 1, wherein the optical disk has a maximum peripheral speed in the range of 50 to 200 m / sec when reading / writing recorded information.   The method according to claim 1, wherein the optical disc has a recording layer between the light reflecting layer and the cover layer.   An optical disk substrate has a fine concavo-convex pattern, and the fine concavo-convex pattern has groups and pit rows in the track direction, the track pitch is 0.1 to 0.8 μm, and the optical depth is The method according to claim 1, wherein λ / 8n to λ / 2n (where λ is a wavelength of laser light used for recording / reproduction. n is an uneven pattern at the wavelength λ. Is the refractive index of the substrate on which is formed.) The molding material is substantially composed of a polycarbonate resin having a viscosity average molecular weight of 1.7 × 10 ^{4 to} 2.4 × 10 ⁴ , which is composed of a carbonate constituent unit derived from bisphenol A. The method according to claim 1. The molding material is composed of a carbonate constituent unit derived from bisphenol A and has a fatty acid ester of 0.005 with respect to 100 parts by weight of a polycarbonate resin having a viscosity average molecular weight in the range of 1.7 × 10 ^{4 to} 2.4 × 10 ^4. The method according to any one of claims 1 to 5, comprising -0.2 parts by weight.   80 ° C. according to IS0527-1 and 527-2 as a molding material for an optical disc substrate having a substrate with a fine concavo-convex pattern, a light reflection layer and a cover layer, and rotating and rotating the recording information from the cover layer side A method of using a thermoplastic resin having a fracture nominal strain of 80 to 180% and a fracture stress of 40 to 80 MPa in the measurement of tensile strength in.   8. The method according to claim 7, wherein the optical disk has a maximum peripheral speed in the range of 50 to 200 m / sec when reading / writing recorded information.   9. The method according to claim 7, wherein the optical disc has a recording layer between the light reflecting layer and the cover layer.   An optical disk substrate has a fine concavo-convex pattern, and the fine concavo-convex pattern has groups and pit rows in the track direction, the track pitch is 0.1 to 0.8 μm, and the optical depth is The method according to claim 7, wherein λ / 8n to λ / 2n (where λ is a wavelength of laser light used for recording / reproduction. n is an uneven pattern formed at the wavelength λ. Is the refractive index of the processed substrate.) The molding material is substantially composed of a polycarbonate resin having a viscosity average molecular weight of 1.7 × 10 ^{4 to} 2.4 × 10 ⁴ , which is composed of a carbonate constituent unit derived from bisphenol A. The method according to claim 1. The molding material is composed of a carbonate constituent unit derived from bisphenol A and has a fatty acid ester of 0.005 with respect to 100 parts by weight of a polycarbonate resin having a viscosity average molecular weight in the range of 1.7 × 10 ^{4 to} 2.4 × 10 ^4. The method according to any one of claims 7 to 11, comprising -0.2 parts by weight.