JP4577815B2 - Film for transparent protective layer of optical disc - Google Patents

Description

  The present invention relates to an optical disc comprising a substrate that does not transmit light, an information signal portion formed on the substrate, and a light-transmitting protective layer comprising a transparent adhesive and a polycarbonate film formed thereon. The present invention relates to a polycarbonate film comprising a resin composition obtained by blending a polycarbonate resin (A) derived from a specific dihydroxy compound and a polycarbonate resin (B).

  Currently, light transmission type optical disk substrates are widely used. For example, an acrylic substrate, a polycarbonate substrate made of 2,2-bis (4-hydroxyphenyl) propane (common name: bisphenol A), an amorphous polyolefin substrate, or the like is a CD substrate (light transmission thickness 1.2 mm) or a DVD substrate. (Light transmission thickness 0.6mm) Widely used for applications. These discs are formed by transferring irregularities to a transparent substrate, forming an information recording layer made of a metal reflective film such as aluminum on the transfer surface, and further forming a protective film on the upper layer. A system is used to read the transferred irregularities using a red laser. At that time, the laser beam passes through the inside of the optical disk substrate both for the irradiation light and the reflected light. Therefore, it is known that if the birefringence of the optical disk substrate is large, a signal reading error is likely to occur. Therefore, the substrate of the current optical disk is strongly required to have a small birefringence.

  However, in recent years, a recording method for reading a signal using a blue laser has been developed, which can reduce the unevenness and dramatically increase the recording density of the optical disk. In this method, as in the current method, when an optical disk that transmits light through the substrate is used, a reading error occurs even with a slight birefringence. In order to eliminate such reading errors, it is necessary to reduce the thickness of the substrate to about 0.1 mm. However, it is technically extremely difficult to form such a thin substrate while transferring irregularities by injection molding. Have difficulty.

  Therefore, when reading information using a blue laser, the unevenness is transferred to a substrate that does not transmit light, and an information signal portion made of a recording film or a reflection film is formed on the transfer surface, Furthermore, a system was developed in which a protective layer having a thickness of 100 μm made of a light-transmitting protective film and a transparent adhesive was formed on the upper part, and a blue laser was irradiated from the protective film side to read information. The information signal portion is made of a reflective film, a film made of a magneto-optical material, a film made of a phase change material, or an organic dye film. When the optical disc is read-only, the information signal portion is composed of a single layer film or a laminated film having at least a reflection film. On the other hand, if the optical disc is a rewritable type, the information signal portion is composed of a single layer film or a laminated film having at least a film made of a magneto-optical material or a film made of a phase change material. For example, it is composed of a single layer film or a laminated film having at least a film made of an organic dye material (see, for example, Patent Documents 1, 2, and 3).

  In this system, light is transmitted only through the protective film and the transparent protective layer made of a transparent adhesive, but the protective film occupying most of the transparent protective layer substantially affects the light beam. Therefore, the protective film is strongly required to have a small retardation value (definition: birefringence x thickness, unit: nm), a smooth surface, and a uniform thickness. Furthermore, it is important that mass production is possible using a production method with high productivity from the viewpoint of economy. As a resin that satisfies the above conditions, for example, a polycarbonate resin made of bisphenol A can be used. However, several problems arise in this case.

  As a method for forming a film using a polycarbonate resin composed of bisphenol A, there are a wet forming method using a solvent and a melt extrusion forming method. In the former, a film obtained by dissolving polycarbonate resin composed of bisphenol A in a volatile solvent, continuously casting the resin solution on a rotating steel belt, and evaporating and removing the solvent on the steel belt is continuously obtained. This is a winding method. The film obtained by this method is a film having a smooth surface with small thickness unevenness and a non-stretched film, which has a small retardation value and is optically excellent. However, the wet molding method has the disadvantages that an expensive film forming facility is required and a solvent recovery facility is required because a volatile solvent is used, resulting in an increase in manufacturing cost. Further, since the solvent that could not be recovered is released into the atmosphere, it is not preferable from the viewpoint of the environment. Furthermore, since a fine defect due to bumping may occur during the evaporation of the solvent, there is a drawback that a fine void is generated on the surface and the yield of the product is deteriorated. On the other hand, the melt extrusion molding method is a molding method suitable for mass production since the film production equipment is relatively inexpensive and solvent recovery is not necessary. However, since stretching takes place during film formation, the polycarbonate resin made of bisphenol A has a drawback that the retardation value increases due to residual stress strain.

  For example, there is a method using a polycarbonate resin copolymerized with bisphenol having a fluorene skeleton (see, for example, Patent Document 4). However, when the amount of bisphenol having a fluorene skeleton is increased in order to sufficiently reduce the retardation value, the polycarbonate resin has a high glass transition temperature and poor fluidity, so it is difficult to form a film by a melt extrusion method. become. For this reason, the amount of bisphenol introduced is insufficient.

  For example, there is a film in which a polycarbonate resin using bisphenol having a fluorene skeleton and bisphenol having a siloxane bond as a copolymerization component is molded by a melt extrusion method, and the retardation value can be kept low even if residual stress distortion occurs. (For example, refer to Patent Document 5). Since the film has excellent moldability, high surface smoothness and almost no unevenness in thickness, it can be used as a protective film for the optical disk. However, since bisphenol having a siloxane bond is expensive, there is a problem in economy.

Japanese Patent Laid-Open No. 2002-8269 JP 2002-74749 A JP-A-10-283683 Japanese Patent Laid-Open No. 9-7222 JP 2002-317042 A

  The present invention is intended to solve the above-mentioned problems, and is formed by a melt extrusion method. Even if residual stress distortion occurs, the retardation value can be kept low, and surface smoothness, thickness uniformity, and economic efficiency are achieved. It is to provide an excellent film.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have made a light-transmitting protective layer formed on an upper layer of a substrate that does not transmit a light beam having an information signal portion formed on the substrate. The dihydroxy compound 95-5 mol% represented by the general formula (1) and the dihydroxy compound 5-95 mol% represented by the general formula (2) are carbonate-bonded with a carbonic acid diester. And (100 × (A)) / () a polycarbonate resin (B) formed by carbonate-bonding 2,2-bis (4-hydroxyphenyl) propane with a carbonic acid diester or phosgene. (A) + (B)) = 1 to 99% by weight A polycarbonate resin composition obtained by blending at a ratio of 1 to 99% by weight We have reached the present invention can solve the above problems by a transparent protective layer film.
(In the formula, R ₁ and R ₂ are a hydrogen atom or a methyl group.)
(Wherein, X is an alkylene group having 1 to 10 carbon atoms or a cycloalkylene group having 4 to 20 carbon atoms)

  According to the present invention, a low birefringence film having almost no thickness unevenness and a low retardation value can be efficiently produced by an extrusion molding method, which is useful. In addition, since it becomes possible to use the extrusion molding method, a solvent recovery facility is not necessary, and volatilization of the solvent into the environment is eliminated, which is useful. Further, the extruded film includes a substrate through which light does not transmit, an information signal portion formed on the substrate, a transparent adhesive layer formed on the upper layer, and a light-transmitting protective layer comprising a polycarbonate film. It can be suitably used as a protective film in an optical disc, which is very useful.

  As the dihydroxy compound represented by the general formula (1) for deriving the polycarbonate resin (A) used in the present invention, specifically, 9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy) -3-methylphenyl) fluorene and 9,9-bis (4- (2-hydroxyethoxy) -3,5-dimethylphenyl) fluorene are exemplified. Among them, 9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene is preferably used.

Specific examples of the dihydroxy compound represented by the general formula (2) for deriving the polycarbonate resin (A) used in the present invention include tricyclo [5.2.1.0 ^2,6 ] decanedimethanol, cyclohexane. -1,4-dimethanol, decalin-2,6-dimethanol, norbornane dimethanol, pentacyclopentadecanedimethanol, cyclopentane-1,3-dimethanol, 1,4-butanediol, 1,6-hexanediol Etc. are exemplified. Among them, a compound comprising at least one selected from tricyclo [5.2.1.0 ^2,6 ] decanedimethanol, cyclohexane-1,4-dimethanol or pentacyclopentadecanedimethanol is preferably used. The

  First, a method for producing a polycarbonate resin (A) according to the present invention will be described. A known melt polycondensation method in which a dihydroxy compound and a carbonic acid diester are reacted in the presence of a basic compound catalyst or a transesterification catalyst or a mixed catalyst composed of both is suitably used.

  Examples of the carbonic acid diester include diphenyl carbonate, ditolyl carbonate, bis (chlorophenyl) carbonate, m-cresyl carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, and dicyclohexyl carbonate. Of these, diphenyl carbonate is particularly preferred. The carbonic acid diester is preferably used in a ratio of 0.97 to 1.20 mol, more preferably 0.99 to 1.10 mol, relative to a total of 1 mol of the dihydroxy compound.

  Examples of the basic compound catalyst include alkali metal compounds and / or alkaline earth metal compounds, nitrogen-containing compounds, and the like.

  Examples of such compounds include organic acid salts such as alkali metal and / or alkaline earth metal compounds, inorganic salts, oxides, hydroxides, hydrides or alkoxides, quaternary ammonium hydroxides and salts thereof, and amines. Etc. are preferably used, and these compounds can be used alone or in combination.

  Specific examples of the alkali metal compound include sodium hydroxide, potassium hydroxide, cesium hydroxide, lithium hydroxide, sodium bicarbonate, potassium bicarbonate, cesium bicarbonate, lithium bicarbonate, sodium carbonate, potassium carbonate, carbonate Cesium, lithium carbonate, sodium acetate, potassium acetate, cesium acetate, lithium acetate, sodium stearate, potassium stearate, cesium stearate, lithium stearate, sodium borohydride, sodium phenyl borohydride, sodium benzoate, potassium benzoate Cesium benzoate, lithium benzoate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, dilithium hydrogen phosphate, disodium phenyl phosphate, disodium salt of bisphenol A, 2 potassium salt, 2 cesium , 2 lithium salt, sodium salt of phenol, potassium salt, cesium salt, lithium salt or the like is used.

  Specific examples of the alkaline earth metal compound include magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, magnesium hydrogen carbonate, calcium hydrogen carbonate, strontium hydrogen carbonate, barium hydrogen carbonate, magnesium carbonate, calcium carbonate. Strontium carbonate, barium carbonate, magnesium acetate, calcium acetate, strontium acetate, barium acetate, magnesium stearate, calcium stearate, calcium benzoate, magnesium phenyl phosphate, and the like are used.

  Specific examples of nitrogen-containing compounds include alkyl groups and aryl groups such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and trimethylbenzylammonium hydroxide. Secondary ammoniums such as quaternary ammonium hydroxides, triethylamine, dimethylbenzylamine and triphenylamine, secondary amines such as diethylamine and dibutylamine, primary amines such as propylamine and butylamine, 2-methylimidazole, 2 -Imidazoles such as phenylimidazole and benzimidazole, or ammonia, tetramethylammonium borohydride, tetrabutylammonium borohydride Tetrabutylammonium tetraphenylborate, basic or basic salts such as tetraphenyl ammonium tetraphenylborate, or the like is used.

  As the transesterification catalyst, zinc, tin, zirconium and lead salts are preferably used, and these can be used alone or in combination.

  Specific examples of the transesterification catalyst include zinc acetate, zinc benzoate, zinc 2-ethylhexanoate, tin (II) chloride, tin (IV) chloride, tin (II) acetate, tin (IV) acetate, and dibutyltin. Dilaurate, dibutyltin oxide, dibutyltin dimethoxide, zirconium acetylacetonate, zirconium oxyacetate, zirconium tetrabutoxide, lead (II) acetate, lead (IV) acetate and the like are used.

These catalysts are used in a ratio of 10 ⁻⁹ to 10 ⁻³ mol, preferably 10 ⁻⁷ to 10 ⁻⁴ mol, relative to a total of 1 mol of the dihydroxy compound.

  The melt polycondensation method according to the present invention is a method in which melt polycondensation is carried out using the above-mentioned raw materials and catalyst while removing by-products by a transesterification reaction under normal pressure or reduced pressure. The reaction is generally carried out in a multistage process of two or more stages.

  Specifically, the reaction at the first stage is allowed to react at a temperature of 120 to 260 ° C., preferably 180 to 240 ° C. for 0.1 to 5 hours, preferably 0.5 to 3 hours. Next, the reaction temperature is raised while raising the degree of decompression of the reaction system to carry out the reaction between the dihydroxy compound and the carbonic acid diester, and finally the polycondensation reaction is carried out at a temperature of 200 to 350 ° C. under a reduced pressure of 1 mmHg or less for 1 to 10 hours. I do. Such a reaction may be carried out continuously or batchwise. The reaction apparatus used for carrying out the above reaction is equipped with paddle blades, lattice blades, glasses blades, etc. even with vertical types equipped with vertical stirring blades, Max blend stirring blades, helical ribbon stirring blades, etc. It may be a horizontal type or an extruder type equipped with a screw, and it is preferable to use a reaction apparatus in which these are appropriately combined in consideration of the viscosity of the polymer.

  In the polycarbonate resin (A) according to the present invention, the catalyst is removed or deactivated after the polymerization reaction in order to maintain thermal stability and hydrolysis stability. In general, a method of deactivating a catalyst by adding a known acidic substance is preferably performed. Specific examples of these substances include esters such as butyl benzoate, aromatic sulfonic acids such as p-toluenesulfonic acid, and aromatic sulfonic acids such as butyl p-toluenesulfonate and hexyl p-toluenesulfonate. Esters, phosphoric acids such as phosphorous acid, phosphoric acid, phosphonic acid, triphenyl phosphite, monophenyl phosphite, diphenyl phosphite, monoethyl phosphite, diethyl phosphite, monobutyl phosphite, Phosphorous esters such as dibutyl phosphate, dioctyl phosphite, monooctyl phosphite, triphenyl phosphate, diphenyl phosphate, monophenyl phosphate, monoethyl phosphate, diethyl phosphate, dibutyl phosphate, phosphoric acid Phosphate esters such as dioctyl and monooctyl phosphate, diphenylphosphonic acid, dioctylphosphonic acid, dibutyl Phosphonic acids such as sulfonic acid, phosphonic acid esters such as diethyl phenylphosphonate, phosphines such as triphenylphosphine and bis (diphenylphosphino) ethane, boric acids such as boric acid and phenylboric acid, tetrabutyl dodecylbenzenesulfonate Aromatic sulfonates such as phosphonium salts, organic halides such as stearic acid chloride, benzoyl chloride and p-toluenesulfonic acid chloride, alkyl sulfuric acids such as dimethyl sulfate, and organic halides such as benzyl chloride are preferably used.

  After deactivation of the catalyst, a step of devolatilizing and removing low-boiling compounds in the polymer at a pressure of 0.1 to 1 mmHg and a temperature of 200 to 350 ° C. may be provided. For this purpose, paddle blades, lattice blades, glasses A horizontal apparatus provided with a stirring blade having excellent surface renewability such as a blade or a thin film evaporator is preferably used.

  Next, a method for producing the polycarbonate resin (B) according to the present invention will be described. The polycarbonate resin (B) is a homopolymer derived from 2,2-bis (4-hydroxyphenyl) propane (common name: bisphenol A), but a small amount of bisphenols other than bisphenol A is used as long as the physical properties are not impaired. It may be copolymerized. As one of the methods for producing the polycarbonate resin (B), a known melt polycondensation method in which a dihydroxy compound and a carbonic acid diester are reacted in the presence of a basic compound catalyst is preferably used. The production method conforms to the production method of the polycarbonate resin (A) except that a heavy metal transesterification catalyst is not used.

  Another suitable method for producing the polycarbonate resin (B) according to the present invention is an interfacial polymerization method in which a dihydroxy compound is reacted with phosgene in the presence of a solvent, a terminal terminator and an acid binder. Usually, a dihydroxy compound and a terminal terminator are dissolved in an aqueous solution of an acid binder and reacted in the presence of an organic solvent.

  As the acid binder, for example, pyridine, or an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide is preferably used. As the solvent, for example, methylene chloride, chloroform, chlorobenzene and xylene are preferably used. Furthermore, in order to accelerate the polymerization reaction, a tertiary amine such as triethylamine or a quaternary ammonium salt such as tetra-n-butylammonium bromide is used as a catalyst.

  Moreover, as a terminal terminator used for adjustment of a polymerization degree, monofunctional hydroxy compounds, such as a phenol, p-tert-butylphenol, p-cumylphenol, and a long-chain alkyl substituted phenol, are used.

  Furthermore, if desired, a small amount of an antioxidant such as sodium sulfite or hydrosulfite sodium may be added.

  The reaction is usually carried out in the range of 0 to 150 ° C, preferably 5 to 40 ° C. While the reaction time depends on the reaction temperature, it is generally 0.5 min-10 hr, preferably 1 min-2 hr. Moreover, it is preferable to maintain the pH of the reaction system at 10 or more during the reaction.

  The method for producing a blend resin composition according to the present invention may be produced by mixing solid polycarbonate resins (A) and (B) produced separately and kneading them with a kneader, or melting them. The solid (B) may be added to the resin (A) in the state, or the solid (A) may be added to the resin (B) in the melt and kneaded with a kneader. Alternatively, the molten resins (A) and (B) may be mixed and kneaded with a kneader. The kneading may be performed continuously or batchwise. As the kneading machine, an extruder, a lab plast mill, a kneader or the like is used, and an extruder is preferably used for continuous kneading, and a lab plast mill or kneader is preferably used for batch kneading. In addition, when using the polycarbonate resin manufactured by the melt polycondensation method, it is desirable to perform kneading | mixing after a catalyst deactivation from the viewpoint of avoiding the transesterification reaction at the time of kneading | mixing. However, the catalyst deactivator and the resin to be blended may be kneaded at the same time, or the catalyst deactivator may be kneaded after blending. However, in this case, it is necessary to keep it within a range where chemical resistance is not impaired by randomization by transesterification.

  As another method for producing the blend resin composition according to the present invention, there is a method in which the polycarbonate resins (A) and (B) are dissolved in a solvent, poured into a mold, and then the solvent is evaporated. As the solvent, for example, methylene chloride, chloroform, tetrahydrofuran, toluene and the like are used. When this method is used, it is convenient because the additive can be dissolved and added at the same time.

  Furthermore, it is preferable to add an antioxidant, a release agent, an ultraviolet absorber, a fluidity modifier, an antistatic agent, an antibacterial agent, or the like to the blend resin composition according to the present invention. These additives may be added in advance to the polycarbonate resins (A) and (B) or either of them before blend kneading, or they may be kneaded before blend kneading or simultaneously with blend kneading. It may be added and kneaded or kneaded after blending.

  Moreover, the preferable polystyrene conversion weight average molecular weight (Mw) of the polycarbonate resin (A) used for the blend resin composition concerning this invention is 20,000-300,000, More preferably, 35,000-150,000. It is. When Mw is smaller than 20,000, the protective film becomes brittle, which is not preferable. If Mw is larger than 300,000, the melt viscosity becomes high, so that it becomes difficult to take out the resin after production, and the melt viscosity becomes high, which causes problems such as difficulty in extrusion molding.

  The polystyrene-reduced weight average molecular weight (Mw) of the polycarbonate resin (B) used in the blend resin composition according to the present invention is 15,000 to 250,000, more preferably 20,000 to 110,000. . If Mw is less than 15,000, the protective film becomes brittle, which is not preferable. When Mw is larger than 250,000, the melt viscosity becomes high and the blending conditions become severe, which is not preferable, and since the melt viscosity becomes high, problems such as difficulty in extrusion molding occur.

  The polystyrene-converted weight average molecular weight difference ΔMw between the polycarbonate resins (A) and (B) used in the blend resin composition according to the present invention is preferably 0 to 120,000, more preferably 0 to 80, 000. When Mw exceeds 120,000, the difference in viscosity between (A) and (B) becomes remarkably large, so that the compatibility is deteriorated and the transparency of the blended resin composition is lowered, so that it can be used as a transparent protective film for optical disks. Since it disappears, it is not preferable.

  The polycarbonate resin (A) used in the blend resin composition according to the present invention contains random, block and alternating copolymer structures.

  The glass transition temperature (Tg) of the blend resin composition according to the present invention is preferably 90 to 180 ° C, more preferably 100 to 165 ° C. When Tg is lower than 90 ° C., the heat resistance of the protective film is lowered, and the operating temperature range of the optical disk becomes narrow, which is not preferable. On the other hand, if it exceeds 180 ° C., for example, the molding conditions for forming an extruded film become severe, which is not preferable.

  The polycarbonate film of the present invention can be easily formed by casting or melt extrusion of the polycarbonate resin composition, but the melt extrusion method is preferably carried out in that no solvent is used. In the melt extrusion method, a known film forming machine including an extruder, a T die, a plurality of mirror-polished rolls, and a winding device can be used. The temperature of the extruder or T die is appropriately selected according to the melt viscosity of the resin, but is preferably within the range of Tg + 40 ° C. to 200 ° C. of the resin. If it is less than Tg + 40 ° C., sufficient fluidity is not exhibited, and if it is higher than Tg + 200 ° C., depolymerization or thermal decomposition of the resin tends to occur. The roll temperature is suitably set to a temperature that does not cause uneven thickness or peeling, and is preferably set within Tg ± 80 ° C. of the resin. Also, in order to minimize the stress on the protective film and minimize the retardation value, it is preferable to set the winding speed so that the film is hardly stretched and the film does not sag.

  The thickness of the polycarbonate film of the present invention is preferably 20 μm to 200 μm, more preferably 40 μm to 150 μm. If the thickness of the film is less than 20 μm, the strength of the transparent protective layer becomes insufficient, which is not preferable. On the other hand, when the thickness is greater than 200 μm, handling during processing is deteriorated, and when the transparent protective layer of the optical disk is thick, signal writing errors and reading errors are liable to occur. Further, the thickness unevenness of the extruded film is preferably within ± 10%.

  The retardation value of the polycarbonate film of the present invention is preferably -20 nm to 20 nm. More preferably, it is −15 nm to 15 nm. When the retardation value is outside the range of −20 nm to 20 nm, it is not preferable because writing errors and reading errors of the optical disk are likely to occur. Moreover, it is desirable that the variation of the retardation value inside the film is within ± 5 nm.

Since the polycarbonate film of the present invention transmits light, it is desirable that the amount of dust is a highly purified low dust product, similar to the polycarbonate resin made of bisphenol A used in conventional CDs and DVDs. Specifically, it is desirable that dust having a diameter of 50 μm or more is not substantially detected, and dust having a diameter of 0.5 μm to 50 μm is 3 × 10 ⁴ or less. In addition, from the viewpoint of product durability, weather resistance, or hydrolysis resistance, it is possible to make criteria such as 2 ppm or less of residual inorganic and organic chlorine, 1000 ppm or less of residual hydroxyl group, 5 ppm or less of residual nitrogen, and 100 ppm or less of residual monomer. It is preferable to satisfy as much as possible.

  The polycarbonate film of the present invention has a higher light transmittance in the wavelength range of 390 nm to 420 nm of the blue laser, preferably 70% or more, more preferably 85% or more.

  An optical disk is formed by laminating the polycarbonate film of the present invention on a substrate provided with an information signal portion. For the bonding, it is preferable to use an adhesive that is highly transparent, hardly colored over time, and excellent in heat resistance, and specifically, an acrylic, epoxy, or urethane adhesive is preferably used. .

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In addition, the measured value in an Example was measured using the following method or apparatus.

[Measurement method of physical properties]
1) Polystyrene-converted weight average molecular weight (Mw): A calibration curve was prepared using standard polystyrene having a known molecular weight (molecular weight distribution = 1) using GPC and chloroform as a developing solvent. Based on this calibration curve, it was calculated from the retention time of GPC.
2) Glass transition temperature (Tg): measured by a differential thermal scanning calorimeter (DSC).
3) Retardation value: Measured at a measurement wavelength of 632.8 nm using an ellipsometer (ELP-200ADT manufactured by Mizoji Optics).

Example 1
9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene 10.11 kg (23.05 mol), tricyclo [5.2.1.0 ^2,6 ] decandimethanol 4.524 kg (23.05) Mol), 10.22 kg (47.71 mol) of diphenyl carbonate, and 0.01981 g (2.358 × 10 ⁻⁴ mol) of sodium bicarbonate were put into a 50 liter reactor equipped with a stirrer and a distiller, and a nitrogen atmosphere of 760 Torr. The mixture was heated to 215 ° C. over 1 hour and stirred.
Thereafter, the degree of vacuum was adjusted to 150 Torr over 15 minutes, and the transesterification reaction was carried out by maintaining for 20 minutes under the conditions of 215 ° C. and 150 Torr. Further, the temperature was raised to 240 ° C. at a rate of 37.5 ° C./hr, and maintained at 240 ° C. and 150 Torr for 10 minutes. Thereafter, the pressure was adjusted to 120 Torr over 10 minutes and maintained at 240 ° C. and 120 Torr for 70 minutes. Thereafter, the pressure was adjusted to 100 Torr over 10 minutes and held at 240 ° C. and 100 Torr for 10 minutes. The polymerization reaction was further carried out with stirring for 20 minutes under the conditions of 240 ° C. and 1 Torr or less at 40 ° C. over 1 Torr. After completion of the reaction, nitrogen was blown into the reactor to increase the pressure, and the produced polycarbonate resin was extracted while being pelletized. Mw = 92,800 of the obtained polycarbonate resin and Tg = 131 ° C. 10.0 kg of this polycarbonate resin was vacuum-dried at 100 ° C. for 24 hours, diethyl phosphite was added 10 times mol of sodium bicarbonate in the resin, and 300 ppm of glycerin monostearate was added to the resin, and 260 times by an extruder. The mixture was kneaded at 0 ° C. and pelletized to obtain pellets. The Mw of this pellet was 92,100.
The polycarbonate resin 1.5 kg and bisphenol A polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd., trade name: Iupilon S-3000) 4.5 kg were kneaded and pelletized in an extruder set at 260 ° C. Pellets were obtained. The obtained resin composition was transparent, and it was confirmed that Tg = 144 ° C. and only one inflection point was observed and they were compatible. The resin composition was extruded and molded under a cylinder of 220 ° C. and a die temperature of 220 ° C. to obtain an extruded film having a width of 26 cm and a film thickness of 150 μm ± 5 μm. The retardation value of the film is shown in Table 1.

Example 2
The same operation as in Example 1 was performed except that 3 kg of the polycarbonate resin synthesized in Example 1 and 3 kg of polycarbonate resin composed of bisphenol A (Mitsubishi Engineering Plastics Co., Ltd., trade name: Iupilon S-3000) were used. Then, an extruded film having a width of 26 cm and a film thickness of 150 μm ± 5 μm was obtained from the transparent blend pellet of Tg = 139 ° C. The retardation values of the film are shown in Table 1.

Example 3
Example 1 except that 4.2 kg of the polycarbonate resin synthesized in Example 1 and 1.8 kg of polycarbonate resin made of bisphenol A (Mitsubishi Engineering Plastics Co., Ltd., trade name: Iupilon S-3000) were used. The same operation was performed to obtain an extruded film having a width of 26 cm and a film thickness of 150 μ ± 5 μm from a transparent blend pellet having a Tg of 136 ° C. The retardation values of the film are shown in Table 1.

Example 4
In Example 1, 3.324 kg (23.05 mol) of cyclohexane-1,4-dimethanol was used in place of tricyclo [5.2.1.0 ^2,6 ] decane dimethanol, and over 45 minutes. The same operation as in Example 1 was performed except that the degree of vacuum was adjusted to 150 Torr. The obtained pellets had Mw = 90,000 and Tg = 120 ° C. Mw of the pellet after adding the same additive as in Example 1 was 89,400. 3 kg of the polycarbonate resin pellets and 3 kg of polycarbonate resin made of bisphenol A (trade name: Iupilon S-3000, manufactured by Mitsubishi Engineering Plastics Co., Ltd.) are kneaded in an extruder set at 260 ° C., pelletized by pelletizing. Obtained. The obtained resin composition was transparent, and it was confirmed that Tg = 132 ° C. and only one inflection point was observed and they were compatible. The resin composition was extruded and molded under a cylinder of 210 ° C. and a die temperature of 210 ° C. to obtain an extruded film having a width of 26 cm and a film thickness of 150 μm ± 5 μm. The retardation values of the film are shown in Table 1.

Comparative Example 1
Instead of the polycarbonate resin composition of Example 1, it was extruded using a polycarbonate resin made of bisphenol A (Mitsubishi Engineering Plastics Co., Ltd., trade name: Iupilon S-3000), width 26 cm, film thickness 150 μm ± An extruded film of 5 μm was obtained. The retardation values of the film are shown in Table 1.

Comparative Example 2
In Example 1, 5.057 kg (11.53 mol) of 9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene, 7.892 kg (34.57 mol) of bisphenol A, diphenyl carbonate 10. 47 kg (48.87 mol) and 0.01981 g (2.358 × 10 ⁻⁴ mol) of sodium hydrogen carbonate were placed in the reactor, and the polymerization reaction was further carried out under stirring at 240 ° C. and 1 Torr or less for 40 minutes. Except that, the same operation as in Example 1 was performed. The obtained pellets had Mw = 64,800 and Tg = 154 ° C. Mw of the pellet after adding the same additive as in Example 1 was 63,500. The polycarbonate resin was extruded and molded at a cylinder temperature of 240 ° C. to obtain an extruded film having a width of 26 cm and a film thickness of 150 μm ± 5 μm. The retardation values of the film are shown in Table 1.

Claims (6)

A dihydroxy compound represented by the general formula (1) is used for a light-transmitting protective layer formed on an upper layer of a substrate that does not transmit light having an information signal portion formed on the substrate. A polycarbonate resin (A) obtained by carbonate bonding of 95 to 5 mol% of a compound and 5 to 95 mol% of a dihydroxy compound represented by the general formula (2) with a carbonic acid diester or the like, and 2,2-bis (4- (100 × (A)) / ((A) + (B)) = 1 to 99% by weight of a polycarbonate resin (B) obtained by carbonate bonding of hydroxyphenyl) propane with carbonic acid diester or phosgene A film for a transparent protective layer of an optical disk, comprising a polycarbonate resin composition obtained by blending at a ratio.
(In the formula, R ₁ and R ₂ are a hydrogen atom or a methyl group.)
(In the formula, X is an alkylene group having 1 to 10 carbon atoms or a cycloalkylene group having 4 to 20 carbon atoms.) The compound represented by the general formula (2) is at least one selected from tricyclo [5.2.1.0 ^2,6 ] decane dimethanol, cyclohexane-1,4-dimethanol or pentacyclopentadecane dimethanol. The transparent protective layer film for an optical disk according to claim 1, wherein The film for transparent protective layers of an optical disk according to claim 1 or 2, wherein R ₁ in formula (1) is a hydrogen atom. The film for transparent protective layer of an optical disk according to claim 1, wherein R ₁ and R _{2 in} formula (1) are hydrogen atoms. The method for producing a film for a transparent protective layer of an optical disk according to any one of claims 1 to 4, wherein the film is formed by a melt extrusion method. The film for a transparent protective layer of an optical disk according to any one of claims 1 to 4 , wherein the film has a thickness of 20 µm to 200 µm and a retardation value of -20 nm to 20 nm.