JP4733964B2 - Low birefringence aromatic polycarbonate copolymer and optical disk substrate formed therefrom - Google Patents

Description

  The present invention relates to an aromatic polycarbonate copolymer having extremely low orientation birefringence and having both a low photoelastic coefficient and high rigidity, and an optical disk substrate and an optical disk formed therefrom. More specifically, in the optical disk field such as CD (Compact Disk), MO (magneto-optical disk), DVD (Digital Versatile Disk), BD (Blu-ray Disk), and HD-DVD (High Density Digital Versatile Disk). The present invention relates to an optical disc substrate and an optical disc having low surface deflection and low birefringence. In particular, the present invention relates to a substrate for a high-density optical disk having a very large recording capacity.

The recording density of optical discs is steadily improving from 0.6 GB for CD to 4.7 GB for DVD. For example, a 4.7 GB capacity has been realized in a DVD-R, DVD-RW, and DVD-RAM that can be recorded and reproduced, as well as a read-only DVD-ROM. Recently, BD and HD-DVD, which are large-capacity recording media compatible with digital high-definition broadcasting, have achieved 15 to 25 GB. However, with the advancement of information technology, the market development in the optical disc field has been remarkably developed, and in the future, a high-density optical disc capable of recording a larger amount of information is expected. For example, there is a demand for an optical disc having a recording density of 100 GBit / inch ² or higher that can record high-definition video such as digital broadcasting for a long time.

  Conventionally, a polycarbonate resin obtained by reacting a carbonate precursor with 2,2-bis (4-hydroxyphenyl) propane (hereinafter referred to as bisphenol A) has excellent transparency, heat resistance, mechanical properties, and dimensional stability. Therefore, it has been widely used in many fields as an engineering plastic. Furthermore, in recent years, utilization of the transparency as an optical material in the fields of optical discs, optical fibers, lenses and the like has been developed, and in particular, in the field of optical discs, it is widely used as a material for information recording medium substrates.

  However, as the volume of recorded information increases, the rotational speed of the optical disk tends to increase when recording / reproducing the optical disk. If the rigidity of the disk substrate itself, that is, the flexural modulus is low, the surface vibration of the optical disk during high-speed rotation is low. Becomes a big problem for high-density information recording media.

  In high-density information recording media, when reading a signal by focusing a laser in a miniaturized groove, it is important that the optical disk substrate is optically uniform because the influence of the obliquely incident light component is strong. It becomes. Usually, when a laser beam is passed through an optical disk substrate, birefringence occurs due to molecular orientation, residual stress, and the like generated during the injection molding process. This high birefringence can be said to be a fatal defect for an optical disc of a type that reads a signal by passing a laser beam through the substrate.

  Therefore, various methods are being studied as improvement measures for the above problems. First, it is known that it is effective to use a rigid material having a high bending or tensile elastic modulus as a measure for preventing surface vibration during high-speed rotation of the optical disk. For this reason, for the purpose of improving the rigidity of the polycarbonate resin, a method of blending additives such as glass fibers and fillers has been attempted. However, the above additive improves the rigidity of the polycarbonate resin, but has a problem of lowering the transfer accuracy because it tends to lower the fluidity during injection molding. Furthermore, there are many problems that the surface of the molded product is often raised, resulting in poor appearance of the substrate.

  In response to demands for reducing birefringence, aromatic polycarbonate copolymers for optical disk substrates obtained by carbonate bonding of bisphenol with a specific structure that can reduce the photoelastic constant of the resin itself are widely used in the expression format. Is disclosed. (For example, see Patent Documents 1 to 3)

  A polycarbonate copolymer in which a specific proportion of 6,6′-dihydroxy-3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane structural unit has been proposed has also been proposed. Is a composition region exceeding 200 ° C. and is difficult to use as an injection molding material such as a substrate or a lens for an optical recording medium. (For example, see Patent Document 4)

  In addition, for example, an optical disk based on a polycarbonate copolymer obtained from a bis (hydroxyphenyl) fluorene compound is disclosed, and it is specifically shown that this has a lower birefringence than a polycarbonate resin obtained from bisphenol A. Has been. (For example, see Patent Document 5)

  Further, it has been shown that a polycarbonate copolymer obtained from a bis (hydroxyphenyl) fluorene compound is excellent as an optical disk. (For example, see Patent Documents 6 and 7)

  However, although all of the copolymers specifically shown have good characteristics as optical disk substrate materials having a high recording density, they are not necessarily used as optical disk substrate materials that require a higher recording capacity in recent years. There is a need for an optical disk substrate material that is not sufficient but has high rigidity and a small photoelastic constant.

JP-A-2-99521 JP-A-2-128336 JP-A-2-208840 JP-A-6-313035 Japanese Patent Laid-Open No. 2-304741 Japanese Patent Laid-Open No. 8-34845 JP-A-8-34846

  An object of the present invention is to provide an optical disk substrate having a low orientation birefringence, a low birefringence formed by a specific polycarbonate copolymer having a low photoelastic coefficient and a high rigidity, and a small surface deflection during high-speed rotation. is there. As a result of intensive studies to achieve the above object, the inventors of the present invention have extremely low orientation birefringence, higher rigidity, and lower photoelastic constant by copolymerizing a dihydric phenol having a specific structure. In addition, the present inventors have found that by using the resin as an optical molding material, an optical disk substrate having a small surface deflection during high-speed rotation and low birefringence can be obtained. The present invention has been completed based on this finding.

（式中、Ｒ_１〜Ｒ_２は夫々水素原子、炭素原子数１〜６のアルキル基、炭素原子数６〜１０のアリール基、炭素原子数１〜６のアルコキシ基、またはハロゲン原子である。）
で表される二価フェノール（Ａ）に由来する繰り返し単位（Ａ１）と、
下記式［２］

（式中、複数のＲ_３は各々独立に、水素原子、炭素原子数１〜６のアルキル基、炭素原子数６〜１０のアリール基または炭素原子数１〜６のアルコキシ基を表す。また、Ｒ_４、Ｒ_５は各々水素原子または炭素原子数１〜９のアルキル基を表す。ただし、Ｒ_４、Ｒ_５の炭素原子数の合計は９〜１０である。）
で表される二価フェノール（Ｂ）に由来する繰り返し単位（Ｂ１）より実質的に構成され、全カーボネート繰り返し単位における単位（Ａ１）と単位（Ｂ１）の割合がモル比で（Ａ１）：（Ｂ１）＝７０：３０〜９５：５である低複屈折性芳香族ポリカーボネート共重合体からなる光ディスク基板が提供される。 Hereinafter, the present invention will be described in detail. In order to solve the above problems, the present invention provides the following formula [1].

(Wherein R _{1 to} R ₂ are each a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 10 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. )
A repeating unit (A1) derived from a dihydric phenol (A) represented by:
Following formula [2]

(In the formula, each of R ₃ independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 10 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. R ₄ and R ₅ each represent a hydrogen atom or an alkyl group having 1 to 9 carbon atoms, provided that the total number of carbon atoms of R ₄ and R ₅ is 9 to 10).
Is substantially composed of a repeating unit (B1) derived from the dihydric phenol (B) represented by the formula (A1) :( A1) :( A) in the molar ratio of the unit (A1) to the unit (B1) in all carbonate repeating units. B1) = 70: 30~95: low birefringence aromatic polycarbonate copolymer or Ranaru optical disk substrate which is a 5 are provided.

  When an optical disk substrate is produced by injection molding of a polycarbonate resin, a birefringence (orientation birefringence) that cannot be ignored occurs when the resin is subjected to processing that undergoes orientation. That is, the birefringence at the time of molding an optical disc requires low birefringence not only in birefringence due to stress but also in birefringence due to orientation. Accordingly, in order to reduce the birefringence caused by stress as in the prior art, a sufficient birefringence reduction effect cannot be obtained when molding is performed using a material having a low photoelastic coefficient.

  When the present inventors examined the birefringence in detail, in order to reduce the birefringence due to the orientation, two or more dihydric phenols having different positive and negative signs of the intrinsic birefringence values were copolymerized to cause the orientation. It has been found that birefringence can be reduced. That is, an alkylidene moiety of the bisphenol A skeleton as represented by the above formula [2] is used as a dihydric phenol having a different sign of the intrinsic birefringence from the spiro ring-containing dihydric phenol represented by the above formula [1]. By using a modified dihydric phenol, the absolute value of the intrinsic birefringence value can be made lower than that of the conventional bisphenol A polycarbonate resin, and the content of the spiro ring-containing dihydric phenol can be reduced. It was found that the moldability was improved. Furthermore, it has also been found that a low photoelastic coefficient and high rigidity can be expressed simultaneously by using a spiro ring-containing dihydric phenol as a copolymerization partner. From the above knowledge, the following formula [1]

（式中、Ｒ_１〜Ｒ_２は夫々水素原子、炭素原子数１〜６のアルキル基、炭素原子数６〜１０のアリール基、炭素原子数１〜６のアルコキシ基、またはハロゲン原子である。）
で表される二価フェノール（Ａ）に由来する繰り返し単位（Ａ１）と、下記式［２］

(Wherein R _{1 to} R ₂ are each a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 10 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. )
A repeating unit (A1) derived from a dihydric phenol (A) represented by the following formula [2]

（式中、複数のＲ_３は各々独立に、水素原子、炭素原子数１〜６のアルキル基、炭素原子数６〜１０のアリール基または炭素原子数１〜６のアルコキシ基を表す。また、Ｒ_４、Ｒ_５は各々水素原子または炭素原子数１〜９のアルキル基を表す。ただし、Ｒ_４、Ｒ_５の炭素原子数の合計は９〜１０である。）
で表される二価フェノール（Ｂ）に由来する繰り返し単位（Ｂ１）より実質的に構成され、全カーボネート繰り返し単位における単位（Ａ１）と単位（Ｂ１）の割合がモル比で（Ａ１）：（Ｂ１）＝７０：３０〜９５：５である芳香族ポリカーボネート共重合体が上記課題を満足する光ディスク基板を高効率で得られる材料であることが判明した。

(In the formula, each of R ₃ independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 10 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. R ₄ and R ₅ each represent a hydrogen atom or an alkyl group having 1 to 9 carbon atoms, provided that the total number of carbon atoms of R ₄ and R ₅ is 9 to 10).
Is substantially composed of a repeating unit (B1) derived from the dihydric phenol (B) represented by the formula (A1) :( A1) :( A) in the molar ratio of the unit (A1) to the unit (B1) in all carbonate repeating units. It has been found that the aromatic polycarbonate copolymer of B1) = 70: 30 to 95: 5 is a material capable of obtaining an optical disk substrate satisfying the above-mentioned problems with high efficiency.

As the component (A), compounds in which R ₁ and R ₂ are the same or different and are a hydrogen atom, an alkyl group having 1 to 3 carbon atoms or a phenyl group are preferable. For example, 6,6′-dihydroxy-3,3, 3 ′, 3′-tetramethyl-1,1′-spirobiindane, 7,7′-dimethyl-6,6′-dihydroxy-3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane, 7,7′-diphenyl-6,6′-dihydroxy-3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane and the like as component (B), wherein R ₃ is a hydrogen atom Certain compounds are preferred, such as 1,1-bis (4-hydroxyphenyl) decane, 1,1-bis (3-methyl-4-hydroxyphenyl) decane, 1,1-bis (2,3-dimethyl-4-hydroxy). Phenyl) decane etc. It is below. Among them, in particular, the component (A) is 6,6′-dihydroxy-3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane, and the component (B) is 1,1-bis (4- Hydroxyphenyl) decane is preferred.

  The ratio of the unit (A1) to the unit (B1) ((A1) :( B1)) is more preferably 75:25 to 90:10, and most preferably 80:20 to 90:10.

  Further, by using them as molding materials, a high-density optical disk substrate having extremely low birefringence can be obtained. When the unit (A1) is 70 mol% or less, the moldability is improved, but the intrinsic birefringence value and the photoelastic coefficient are increased, and the rigidity is lowered, so that it is insufficient for use in a high-density information recording medium. It is. When the unit (A1) is 95 mol% or more, the photoelastic coefficient is low, but the absolute value of the intrinsic birefringence value is large, so that it is insufficient for use in a high-density information recording medium.

  Furthermore, according to the present invention, when 6,6′-dihydroxy-3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane is used as the component (A), (A1): (B1) When a polycarbonate copolymer of 80:20 to 90:10 is used, a resin having low birefringence is obtained, and in the component (A), 7,7′-dimethyl-6,6′-dihydroxy-3,3 , 3 ′, 3′-tetramethyl-1,1′-spirobiindane, birefringence is more likely when a polycarbonate copolymer of (A1) :( B1) = 78: 22 to 88:12 is used. When a low resin is obtained and 7,7′-diphenyl-6,6′-dihydroxy-3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane is used as the component (A), A1): (B1) = 70: 0-80: that birefringence is obtained a lower resin was found by the case of using the polycarbonate copolymer is 20.

  In addition, the optical disk must not be deformed under the usage environment (in the optical disk drive device, in the leaving environment). In that sense, the glass transition temperature of the aromatic polycarbonate copolymer of the present invention is desirably 110 ° C. or higher, and more preferably 125 ° C. or higher. When the glass transition temperature is less than 110 ° C., the substrate is likely to be thermally deformed in a severe use environment, for example, when left in an automobile for a long time, and a focus error or a tracking error is likely to occur. It is not preferable. The glass transition temperature in the present invention is a value obtained by using a differential scanning calorimeter (DSC) and measuring in a temperature rising process at a rate of 20 ° C./min.

The viscosity average molecular weight of the aromatic polycarbonate copolymer of the present invention is preferably controlled in the range of 10,000 to 30,000, more preferably in the range of 12,000 to 20,000. preferable. A polycarbonate resin optical molding material having such a viscosity average molecular weight is preferable because it has sufficient strength as an optical material, has good melt fluidity during molding, and does not cause molding distortion. If the molecular weight is excessively low, there is a problem in the strength as a substrate after molding. Conversely, if the molecular weight is excessively high, melt flowability at the time of molding is poor, and undesirable optical distortion increases in the substrate. The viscosity average molecular weight in the present invention is obtained by inserting the specific viscosity (η _sp ) at 20 ° C. of a solution obtained by dissolving a resin (0.7 g) used for measurement in 100 ml of methylene chloride 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

In addition, the aromatic polycarbonate copolymer of the present invention is 45 × 10 ⁻¹² m ² / N (45 × 10 ⁻¹³ cm ² / dyne) or less, more preferably 40 × 10 ⁻¹² m ² / N (43 × It is preferable to show a photoelastic coefficient of 10 ⁻¹³ cm ² / dyne). When the value of the photoelastic coefficient is within such a range, the birefringence due to stress is reduced, and it is advantageously used particularly in a high-density optical disc.

The aromatic polycarbonate copolymer of the present invention preferably has an absolute value of birefringence (birefringence = phase difference / film thickness) measured by the method described later of less than 4 × 10 ⁻³ . When the value of the birefringence index is in such a range, the birefringence due to the orientation becomes small, and it is advantageously used particularly in a high-density optical disc.

  Furthermore, the aromatic polycarbonate copolymer of the present invention has a flexural modulus measured according to ASTM D-0790 of 2,800 MPa to 4,000 MPa, more preferably 2,900 MPa to 3,900 MPa. If the flexural modulus is less than 2,800 MPa, the surface runout that occurs when the molded optical disk rotates at a high speed increases, which is not preferable as an optical disk substrate having a high recording capacity. On the other hand, if the flexural modulus is greater than 4,000 MPa, the molded optical disk becomes brittle and difficult to mold.

The polycarbonate resin optical molding material of the present invention has a groove or pit optical depth of λ / 8n to λ / 2n with respect to the wavelength λ of the laser beam used for recording and reproduction and the refractive index n of the substrate, preferably Can obtain an optical disk substrate in the range of λ / 6n to λ / 2n, more preferably λ / 4n to λ / 2n. Thus, a base material for a high-density optical disk recording medium having a recording density of 100 Gbit / inch ² or more can be easily provided.

  The aromatic polycarbonate copolymer can be produced by reacting the component (A) and the component (B) with a carbonate precursor by a solution polymerization method or a melt polymerization method.

  Further, according to the present invention, a carbonate bond repeating unit derived from another dihydric phenol as a dihydric phenol is a ratio of 10 mol% or less, preferably 5 mol% or less, unless the object and characteristics of the present invention are impaired. You may make it copolymerize in the ratio. Representative examples of such other dihydric phenols 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 (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-H Roxy-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, 3,3-bis (4-hydroxyphenyl) pentane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -4-isopropylcyclohexane, 1,1- (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 1,1′-bis- (4-hydroxyphenyl) -ortho-diisopropylbenzene, 1,1′-bis- (4-hydroxypheny ) -Meta-diisopropylbenzene, 1,1′-bis- (4-hydroxyphenyl) -para-diisopropylbenzene, 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (4-hydroxy-3) -Methylphenyl) fluorene, 9,9-bis (4-hydroxy-3-ethylphenyl) fluorene, 9,9-bis (4-hydroxy-2-methylphenyl) fluorene, 1,3-bis (4-hydroxyphenyl) ) -5,7-dimethyladamantane, 4,4′-dihydroxydiphenyl sulfone, 4,4′-dihydroxydiphenyl sulfoxide, 4,4′-dihydroxydiphenyl sulfide, 4,4′-dihydroxydiphenyl ketone, 4,4′- Dihydroxydiphenyl ether and 4,4′-dihydroxydiphenyl ester, 1 1,1-bis (4-hydroxyphenyl) -2-methyl propane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, and the like, it can be used alone or in combination.

  Examples of the carbonate precursor include carbonyl halide, carbonate ester, and haloformate. Specific examples include phosgene, diphenyl carbonate, dihaloformate of dihydric phenol, and the like, and phosgene or diphenyl carbonate is preferable. When producing polycarbonate resin by reacting the above dihydric phenol and carbonate precursor by interfacial polymerization method or melt polymerization method, use catalyst, terminal terminator, dihydric phenol antioxidant, etc. as necessary May be.

  The reaction by the interfacial 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 having the following general formula [3]

（式中、Ａは水素原子または炭素原子数１〜９の直鎖または分岐のアルキル基あるいはフェニル置換アルキル基であり、ｒは１〜５、好ましくは１〜３の整数である。）
で表される単官能フェノール類を示すことができる。

(In the formula, A is a hydrogen atom, a linear or branched alkyl group having 1 to 9 carbon atoms or a phenyl-substituted alkyl group, and r is an integer of 1 to 5, preferably 1 to 3).
The monofunctional phenol represented by these can be shown.

  Specific examples of the monofunctional phenols include phenol, phenylphenol, 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 polymer, they not only function as end terminators or molecular weight regulators, but also improve the melt fluidity of the resin and facilitate the molding process, It is preferably used because it has the effect of lowering the physical properties of the resin, particularly the water absorption rate of the resin, and the effect of reducing the birefringence of the substrate.

  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 typically a transesterification reaction between a dihydric phenol and a carbonate ester. The alcohol produced by mixing the dihydric phenol and the carbonate ester with heating in the presence of an inert gas. Or it is performed by the method of distilling phenol. 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 system is evacuated to about 10 to 0.1 Torr (1,300 Pa to 13 Pa) 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 aryl group having 6 to 10 carbon atoms, an aralkyl group, or an alkyl group having 1 to 4 carbon atoms which may have a substituent. 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. A catalyst may be used independently and may be used in combination of 2 or more types. The amount of the polymerization catalyst 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 the dihydric phenol as a raw material. Selected by range.

  Further, in this polymerization reaction, for example, 2-chlorophenylphenyl carbonate, 2-methoxycarbonylphenylphenyl carbonate and 2-ethoxycarbonylphenylphenyl carbonate are added at the later stage or after completion of the polycondensation reaction in order to reduce the phenolic end groups. In particular, 2-methoxycarbonylphenyl phenyl carbonate is preferably used.

  Considering that the purpose of use of the aromatic polycarbonate copolymer of the present invention is to produce an optical disk substrate, the aromatic polycarbonate copolymer is produced by a conventionally known conventional method (solution polymerization method, melt polymerization method, etc.) and then filtered in a solution state. It is preferable to remove impurities such as unreacted components and foreign matters by performing treatment. Further, in the extrusion process (pelletizing process) for obtaining a pellet-like polycarbonate resin for use in injection molding (including injection compression molding), foreign matters are removed by passing a sintered metal filter or the like in the molten state. Is desirable. As the filter, those having a filtration accuracy of 10 μm are preferably used. In any case, it is necessary that the raw material resin before injection molding (including injection compression molding) has a low content of foreign matters, impurities, solvents and the like as much as possible.

  In the present invention, if necessary, the aromatic polycarbonate copolymer is blended with at least one phosphorus compound selected from the group consisting of phosphoric acid, phosphorous acid, phosphonic acid, phosphonous acid and esters thereof. be able to. The amount of the phosphorus compound is preferably 0.0001 to 0.05% by weight, more preferably 0.0005 to 0.02% by weight, and 0.001 to 0.01 based on the aromatic polycarbonate copolymer. Weight percent is particularly preferred. By blending this phosphorus compound, the thermal stability of the aromatic polycarbonate copolymer is improved, and a decrease in molecular weight and a deterioration in hue during molding are prevented.

［式中、Ｒ^５〜Ｒ^１６は、それぞれ独立して、水素原子、メチル、エチル、プロピル、イソプロピル、ブチル、イソブチル、ｔｅｒｔ−ブチル、ペンチル、ヘキシル、ヘプチル、オクチル、ノニル、デシル、ドデシル、ヘキサデシル、オクタデシルなどの炭素原子数１〜２０のアルキル基、フェニル、トリル、ナフチルなどの炭素原子数６〜１５のアリール基またはベンジル、フェネチルなどの炭素原子数７〜１８のアラルキル基を表し、また１つの化合物中に２つのアルキル基が存在する場合は、その２つのアルキル基は互いに結合して環を形成していてもよい。］
よりなる群から選択された少なくとも１種のリン化合物である。 The phosphorus compound is at least one phosphorus compound selected from the group consisting of phosphoric acid, phosphorous acid, phosphonic acid, phosphonous acid, and esters thereof, preferably the following general formula

[Wherein, R ^{5 to} R ¹⁶ are each independently a hydrogen atom, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, hexadecyl. Represents an alkyl group having 1 to 20 carbon atoms such as octadecyl, an aryl group having 6 to 15 carbon atoms such as phenyl, tolyl and naphthyl, or an aralkyl group having 7 to 18 carbon atoms such as benzyl and phenethyl; When two alkyl groups are present in one compound, the two alkyl groups may be bonded to each other to form a ring. ]
At least one phosphorus compound selected from the group consisting of:

  Examples of the phosphorus compound represented by the above formula (1) include triphenyl phosphite, trisnonylphenyl phosphite, tris (2,4-di-tert-butylphenyl) phosphite, tridecyl phosphite, and trioctyl phosphite. , Trioctadecyl phosphite, didecyl monophenyl phosphite, dioctyl monophenyl phosphite, diisopropyl monophenyl phosphite, monobutyl diphenyl phosphite, monodecyl diphenyl phosphite, monooctyl diphenyl phosphite, bis (2,6-di -Tert-butyl-4-methylphenyl) pentaerythritol diphosphite, 2,2-methylenebis (4,6-di-tert-butylphenyl) octyl phosphite, bis (nonylphenyl) pentae Sri diphosphite, bis (2,4-di -tert- butylphenyl) pentaerythritol diphosphite, and distearyl pentaerythritol phosphite.

  Examples of the phosphorus compound represented by the formula (2) include tributyl phosphate, trimethyl phosphate, triphenyl phosphate, triethyl phosphate, diphenyl monoorthoxenyl phosphate, dibutyl phosphate, dioctyl phosphate, diisopropyl phosphate, and the like (3 ) The phosphorus compound represented by the formula includes tetrakis (2,4-di-tert-butylphenyl) -4,4-diphenylenephosphonite, and the compound represented by the formula (4) Examples thereof include dimethyl benzenephosphonate, diethyl benzenephosphonate, and dipropyl benzenephosphonate.

  Among these phosphorus compounds, trisnonylphenyl phosphite, tris (2,4-di-tert-butylphenyl) phosphite, tetrakis (2,4-di-tert-butylphenyl) -4,4-diphenylene Phosphonite is preferably used.

  Furthermore, a higher fatty acid ester of a monohydric or polyhydric alcohol can be added to the aromatic polycarbonate copolymer of the present invention as necessary.

  The higher fatty acid ester is preferably a partial ester or a total ester of a monovalent or polyhydric alcohol having 1 to 20 carbon atoms and a saturated fatty acid having 10 to 30 carbon atoms. Further, partial esters or total esters of monohydric or polyhydric alcohols and saturated fatty acids include stearic acid monoglyceride, stearic acid monosorbate, behenic acid monoglyceride, pentaerythritol monostearate, pentaerythritol tetrastearate, propylene glycol. Examples thereof include monostearate, stearyl stearate, palmityl palmitate, butyl stearate, methyl laurate, isopropyl palmitate, 2-ethylhexyl stearate, among which stearic acid monoglyceride and pentaerythritol tetrastearate are preferably used. . The amount of ester of such alcohol and higher fatty acid is preferably 0.01 to 2% by weight, more preferably 0.015 to 0.5% by weight, more preferably 0.02 to 0.5% by weight based on the aromatic polycarbonate copolymer. More preferred is 0.2% by weight. If the blending amount is within this range, it is preferable that the release property is excellent and the release agent does not migrate and adhere to the metal surface.

  To the aromatic polycarbonate resin of the invention, an antioxidant generally known for the purpose of antioxidant can be added. Examples thereof include phenolic antioxidants, specifically, for example, triethylene glycol-bis (3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate), 1,6 -Hexanediol-bis (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate), pentaerythritol-tetrakis (3- (3,5-di-tert-butyl-4-hydroxyphenyl) Propionate), octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl) -4-hydroxybenzyl) benzene, N, N-hexamethylenebis (3,5-di-tert-butyl-4-hydroxy-hydride) Cinnamide), 3,5-di-tert-butyl-4-hydroxy-benzylphosphonate-diethyl ester, tris (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, 3,9-bis {1 , 1-dimethyl-2- [β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl} -2,4,8,10-tetraoxaspiro (5,5) undecane, etc. Is mentioned. The range of the preferable addition amount of these antioxidants is 0.0001 to 0.05 weight% with respect to the aromatic polycarbonate resin.

  The optical disk substrate molded from the polycarbonate resin has a small surface shake during high-speed rotation and a low birefringence. The birefringence of this substrate is preferably 50 nm or less, and more preferably 30 nm or less. Further, the oblique incident birefringence phase difference measured at an incident angle of 30 degrees is preferably 30 nm or less, and more preferably 20 nm or less.

  When manufacturing an optical disk substrate from the polycarbonate resin, an injection molding machine (including an injection compression molding machine) is used. Although generally used as this injection molding machine, from the viewpoint of suppressing the generation of carbides and improving the reliability of the disk substrate, the adhesion to the resin as a cylinder or screw is low, and the corrosion resistance and resistance It is preferable to use a material made of a material that exhibits wear.

  As conditions for injection molding, a cylinder temperature of 300 to 450 ° C. and a mold temperature of 50 to 180 ° 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.

The optical disk substrate formed in this way is a transparent disk with a thickness of 0.1 mm that covers the disk substrate as well as the current optical disk such as a compact disk (CD), a magneto-optical disk (MO), and a DVD (Digital Versatile Disk). It is also suitably used as a high-density optical disk substrate typified by Blu-ray Disc (BD) for recording / reproducing through a simple cover layer and HD-DVD bonded with the same 0.6 mm substrate as DVD.
The optical disk substrate is produced by the following method.

  For example, in the case of DVD and HD-DVD, it is created by bonding two substrates each having a recording film, a recording layer made of a recording film protective film, and a light reflection layer on a 0.6 mm thick substrate. In the case of a Blu-ray Disc, it is created by forming a light reflection layer, a recording film, a recording layer comprising a recording film protective film and a transparent protective layer on a 1.1 mm thick substrate. A plurality of these layers may be formed.

  In the case of a write-once optical disk, the recording film is a recording film on which a irreversible optical characteristic is changed or a concavo-convex shape is formed on a transparent substrate by laser light irradiation. For example, the recording film is decomposed by heating by laser light irradiation. Cyanine-based, phthalocyanine-based, and azo-based organic dyes that change the optical constant and cause deformation of the substrate by volume change are used.

  In the case of a rewritable optical disc, the recording film is a material (phase change recording type) in which a reversible phase structure change between the amorphous state and the crystalline state of the substance caused by laser light irradiation, or perpendicular to the film surface This is a magnetic thin film (magneto-optical recording type) having a magneto-optic effect that has an easy magnetization direction in any 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 a chalcogenide-based material such as GeSbTe, InSbTe, InSe, InTe, AsTeGe, TeOx-GeSn, TeSeSn, FeTe, SbSeBi, and BiSeGe. Although it is used, a film made of GeSbTe is preferable because of its 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. A two-layer film, an artificial lattice multilayer film such as Co / Pt or Co / Pd, or a CoPt alloy 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. Thereby, the difference in reflectance between the crystalline phase and the amorphous phase as a medium, and the magneto-optical effect can be enhanced. In this case, 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. Eg, SiO-based, _{SiON-based, Ta 2 O 3, TiO 2} , Al 2 O 3, Y 2 O 3, CeO, La 2 O 3, In 2 O 3, GeO, GeO 2, PbO, SnO, SnO 2, Bi ₂ O ₃ , TeO ₂ WO ₂ , WO ₃ , Sc ₂ O ₃ , ZrO _{2 and} other oxides, nitrides such as TaN, AlN, SiN and AlSiN, ZnS, Sb ₂ S ₃ , CdS and In ₂ It is preferable to use a sulfide such as S ₃ , Ga ₂ S ₃ , GeS, SnS ₂ , PbS, Bi ₂ S ₃ , a mixed material thereof, a laminate thereof, or the like as the protective film.

  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 recording a signal by heating with laser light, if the thermal conductivity of the light reflecting 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 that 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 a material satisfying such conditions, one or more elements such as Au, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Tc, Re, Ru, Os, Ir, etc. as Al or Ag An alloy to which is added. In these alloys, if the amount of the additive element is less than 0.5 atomic%, the effect of the above-described decrease in heat conduction is small. This is disadvantageous. Therefore, the content of the additive element is preferably within the range of 0.5 to 20 atomic%. In particular, Ti, Zr, Hf, Ta, Cr, and Re are preferable in the specific element group in terms of enhancing durability of the metal reflective film itself. 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.

  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.

  The aromatic polycarbonate copolymer of the present invention exhibits high rigidity, and has a low intrinsic birefringence value and a small photoelastic coefficient. Therefore, the aromatic polycarbonate copolymer has excellent birefringence and surface deflection during high-speed rotation, particularly high density. It is suitably used as a material for an optical disk substrate, and the industrial effect exerted by it is exceptional.

  Hereinafter, although an example is given and explained in detail, the present invention is not limited to this unless it exceeds the purpose. In the examples and comparative examples, “parts” is parts by weight. Evaluation was according to the following method.

(1) Viscosity average molecular weight M
0.7 g of polycarbonate resin powder was dissolved in 100 ml of methylene chloride, and the specific viscosity (η _sp ) of the solution at 20 ° C. was calculated by 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

(2) Glass transition temperature Using a polycarbonate resin powder and using a thermal analysis system DSC-2910 manufactured by TA Instruments, under a nitrogen atmosphere (nitrogen flow rate: 40 ml / min), rate of temperature increase: 20 ° C./min The measurement was performed under the following conditions.

(3) Photoelastic coefficient 5.0 g of polycarbonate resin was dissolved in 100 ml of methylene chloride, and the solution was cast on a flat glass plate and left overnight to prepare a cast film. After the film was dried at 60 ° C. for 2 hours, a film having a length of 50 mm, a width of 20 mm, and an average thickness of 150 μm was prepared and measured with an ellipsometer M-220 manufactured by JASCO Corporation.

(4) Birefringence index Polycarbonate resin powder is dissolved in methylene chloride to prepare a solution with a solid content concentration of 15% by weight, and the dope is cast on a flat glass plate, resulting in an average thickness of 60 μm and thickness variation in the width direction. A 1.1 μm film was produced. The end of the film was cut off to a width of 100 mm and a length of 100 mm, and the film was dried at 120 ° C. for 2 hours in order to remove the methylene chloride solution. The obtained film was uniaxially stretched 2.0 times in the length direction at a predetermined stretching temperature (glass transition temperature + 10 ° C.) at a stretching speed of 15 mm / min to obtain a stretched film having a width of 71 mm, an average thickness of 42 μm, and a length of 200 mm. Obtained. When the film was observed with a polarizing plate, it was confirmed that the film was uniformly stretched. Thereafter, the phase difference was measured with an ellipsometer M-220 manufactured by JASCO Corporation. The birefringence was calculated from the obtained phase difference according to the following formula.
Δn = Ret / d
Δn: birefringence Ret: retardation d: film thickness

(5) Flexural modulus After drying the polycarbonate resin pellets at 120 ° C. for 5 hours, using a test piece injection-molded at a cylinder temperature of 340 ° C. with an injection molding machine [SG-150 manufactured by Sumitomo Heavy Industries, Ltd.], ASTM- Measured according to D0790.

(6) Diagonal incidence birefringence phase difference Using an Ellipsometer ADR-200B automatic birefringence measuring device manufactured by Oak Co., Ltd., the incidence angle was 30 degrees.

[Example 1]
A reactor equipped with a thermometer, a stirrer and a reflux condenser was charged with 69.1 parts of a 48% aqueous sodium hydroxide solution and 301.6 parts of ion-exchanged water, and 6,6'-dihydroxy-3,3, After dissolving 54.8 parts of 3 ′, 3′-tetramethyl-1,1′-spirobiindane, 10.2 parts of 1,1-bis (4-hydroxyphenyl) decane and 0.13 part of hydrosulfite, chlorination was performed. 231.5 parts of methylene was added, and 28.0 parts of phosgene was blown in at about 15 to 25 ° C. over about 60 minutes with stirring. After completion of the phosgene blowing, 8.6 parts of a 48% aqueous sodium hydroxide solution and 0.31 part of p-tert-butylphenol were added, stirring was resumed, 0.07 part of triethylamine was added after emulsification, and 1 at 28 to 33 ° C. The reaction was terminated by stirring for a period of time. After completion of the reaction, the product is diluted with methylene chloride, washed with water, acidified with hydrochloric acid, washed with water, and further washed with water until the conductivity of the aqueous phase becomes substantially the same as that of ion-exchanged water. Obtained. Next, this solution is passed through a filter having an aperture of 0.3 μm, and further dropped into warm water in a kneader with an isolation chamber having a foreign matter outlet at the bearing, and the polycarbonate resin is flaked while distilling off methylene chloride. The liquid-containing flakes were pulverized and dried to obtain a powder. Thereafter, 0.0025% by weight of tris (2,4-di-tert-butylphenyl) phosphite and 0.05% by weight of stearic acid monoglyceride are added to the powder and mixed uniformly. The mixture was melt-kneaded while degassing with a twin screw extruder [KTX-46 manufactured by Kobe Steel Co., Ltd.] to obtain polycarbonate resin pellets. Table 1 shows the viscosity average molecular weight, glass transition temperature, photoelastic constant, flexural modulus, and birefringence of the pellet. From this pellet, an injection molding machine (M35B-D-DM manufactured by Meiki Seisakusho), a mold with a cavity thickness of 0.6 mm, a diameter of 120 mm, a stamper, a cylinder set temperature of 380 ° C., a mold temperature of 175 ° C., and a filling time of 0 The optical disk substrate was molded under the conditions of 2 seconds, cooling time 15 seconds, and clamping force 30 tons. The oblique incident birefringence phase difference was measured using this substrate, and is also shown in Table 1.

[Example 2]
7,7′-dimethyl-6,6′-dihydroxy-3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane, 56.3 parts, 1,1-bis (4-hydroxyphenyl) decane Except for using 13.6 parts, the same procedure as in Example 1 was carried out to obtain polycarbonate resin pellets having the characteristics shown in Table 1. Further, the optical disk substrate was molded in the same manner as in Example 1 except that the mold temperature was 168 ° C., and the oblique incident birefringence phase difference was measured using the substrate, and the results are also shown in Table 1.

[Example 3]
7,7′-diphenyl-6,6′-dihydroxy-3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane 72.2 parts, 1,1-bis (4-hydroxyphenyl) decane Except for the amount of 17.1 parts, the same procedure as in Example 1 was carried out to obtain polycarbonate resin pellets having the characteristics shown in Table 1. Further, an optical disk substrate was molded in the same manner as in Example 1 except that the mold temperature was set to 160 ° C., and the oblique incident birefringence phase difference was measured using the substrate.

[Comparative Example 1]
Except for 38.7 parts of 6,6′-dihydroxy-3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane and 27.3 parts of 1,1-bis (4-hydroxyphenyl) decane Were the same as in Example 1, and polycarbonate resin pellets having the characteristics shown in Table 1 were obtained. Further, the optical disk substrate was molded in the same manner as in Example 1 except that the mold temperature was set to 137 ° C., and the oblique incident birefringence phase difference was measured using the substrate, and the results are also shown in Table 1.

[Comparative Example 2]
Except for 12.9 parts of 6,6′-dihydroxy-3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane and 54.6 parts of 1,1-bis (4-hydroxyphenyl) decane Were the same as in Example 1, and polycarbonate resin pellets having the characteristics shown in Table 1 were obtained. Further, the optical disk substrate was molded in the same manner as in Example 1 except that the mold temperature was set to 55 ° C., and the oblique incident birefringence phase difference was measured using the substrate.

[Comparative Example 3]
An optical disk substrate in the same manner as in Example 1 except that a polycarbonate resin (panlite AD-5503 manufactured by Teijin Chemicals Ltd.) obtained from 2,2-bis (4-hydroxyphenyl) propane was used and the mold temperature was 122 ° C. The obliquely incident birefringence phase difference was measured using the substrate, and is also shown in Table 1.

Claims (7)

Following formula [1]

Wherein R _{1 and} R ₂ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 10 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a halogen atom. is there.)
The repeating unit (A1) derived from the dihydric phenol (A) represented by the following formula [2]

(In the formula, each of R ₃ independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 10 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. R ₄ and R ₅ each represent a hydrogen atom or an alkyl group having 1 to 9 carbon atoms, provided that the total number of carbon atoms of R ₄ and R ₅ is 9 to 10).
Is substantially composed of a repeating unit (B1) derived from the dihydric phenol (B) represented by the formula (A1) :( A1) :( A) in the molar ratio of the unit (A1) to the unit (B1) in all carbonate repeating units. B1) An optical disk substrate molded using an optical molding material made of a low birefringence aromatic polycarbonate copolymer of 70:30 to 95: 5. The optical disk substrate according to claim 1, wherein R ₁ and R ₂ in the formula [1] are the same or different and are formed from an aromatic polycarbonate copolymer which is a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a phenyl group. . The dihydric phenol represented by the formula [1] is 6,6′-dihydroxy-3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane, 7,7′-dimethyl-6,6. '-Dihydroxy-3,3,3', 3'-tetramethyl-1,1'-spirobiindane or 7,7'-diphenyl-dihydroxy-3,3,3 ', 3'-tetramethyl-1,1 '- a spirobiindan, the formula dihydric phenol component represented by [2] 1,1-bis (4-hydroxyphenyl) optical disc substrate according to claim 1 or 2, wherein the decane. The optical disk substrate according to any one of claims 1 to 3, wherein the polycarbonate copolymer has a viscosity average molecular weight measured in a methylene chloride solution at 20 ° C in a range of 10,000 to 30,000. 2. The optical disk substrate according to claim 1 , wherein the interval between the groove rows or pit rows is 0.1 μm to 0.8 μm. 2. The optical disk substrate according to claim 1 , wherein the optical depth of the groove or pit is in the range of [lambda] / 8n to [lambda] / 2n with respect to the wavelength [lambda] of the laser beam used for recording and reproduction and the refractive index n of the substrate. Optical recording medium using any of the optical disk substrate of claims 1-6, wherein.