JP2008163194A - Polycarbonate resin for optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an industrially producible polycarbonate resin for an optical film, having low birefringence, high transparency, and a high glass transition temperature, and an optical film. <P>SOLUTION: The polycarbonate resin for the optical film is obtained by carbonate-bonding two constituents of 99-51 mol% of 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene represented by formula (1) and 1-49 mol% of bisphenol A with a carbonic diester. The optical film is made of the resin. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polycarbonate resin for an optical film having a specific structure and an optical film using the same.

  As an optical element material used in an optical system of an image display device (so-called display), an optical glass plate or an optical film made of an optical transparent resin is used. Optical glass plates are excellent in heat resistance, transparency, dimensional stability, chemical resistance, etc., and there are many types of materials with various refractive indexes and Abbe numbers, but the material cost is high and the molding process The problem is that the productivity is poor and the productivity is low.

  On the other hand, optical transparent resins, especially optical films made of thermoplastic transparent resins, have the advantage that they can be mass-produced by various molding methods and can be further processed easily. It is used as For example, polycarbonate, polystyrene, poly-4-methylpentene, polymethyl methacrylate, amorphous polyolefin or the like made of bisphenol A is exemplified.

  However, when an optical transparent resin is used as an optical film, in addition to transparency, heat resistance and even low birefringence may be required, so the use location is limited by the balance of resin properties. There are weaknesses. For example, polystyrene has high transparency, but has a low glass transition temperature, low heat resistance, and a high birefringence. If the optical film has a birefringence higher than the designed birefringence, it has weak points such as lowering the quality of the image composed of polarized light and changing the color of the image depending on the viewing angle of the viewer. This is not preferable because the use place is limited. Poly-4-methylpentene and polymethylmethacrylate have a low birefringence, but have a low glass transition temperature and low heat resistance, so the use area is limited. Polycarbonate made of bisphenol A has high heat resistance, but double Since it has a weak point such as a large refraction and lowering the quality of an image composed of polarized light, it is not preferable because the use place is limited.

  In general, if the balance of properties of optical materials is low birefringence, high transparency, high glass transition temperature, and high heat resistance, it can be used for various purposes, and the types of constituent materials of video display devices are simple. This is very useful.

  Among optically transparent resins that have been put into practical use for optical film applications, both polycarbonate resin made of bisphenol A and polystyrene have a weak point that the birefringence is large, and therefore have limited applications. Therefore, development of resins for optical films having a high glass transition temperature, low birefringence and excellent physical property balance has been widely performed. In particular, in recent video display devices, as the resolution is increased by increasing the number of pixels, an optical film having a lower birefringence is required in order to perform the function as designed.

  As a method for reducing the birefringence of the above-described material, there is a method of canceling each other's birefringence between compositions having positive and negative birefringences having different signs. The sign of birefringence is determined by the difference between the polarizability in the polymer main chain direction and the polarizability in the polymer side chain direction. For example, a polycarbonate resin made of bisphenol A in which the polarizability in the polymer main chain direction is larger than the polarizability in the polymer side chain direction has a positive birefringence, and the polarizability in the polymer side chain direction is larger. A polycarbonate resin made of bisphenol having a fluorene structure has negative birefringence. For this reason, the composition ratio of the material composition having birefringence with different signs is very important.

  As a method for reducing the birefringence, bisphenols having a fluorene structure having a high polarizability in the polymer side chain direction have been reported (see Patent Document 1). However, as a result of the study by the present inventors, the composition ratio of the resin composition described in Patent Document 1 is insufficient to cancel the positive and negative intrinsic birefringence, and a material that does not achieve the desired low birefringence is obtained. I found out that

  Separately, polycarbonate resins having a fluorene structure are disclosed (see Patent Documents 2 and 3). However, these polycarbonate resins are only made into a film and the photoelastic coefficient is examined, and the birefringence as a so-called optical film molding including both orientation birefringence and photoelastic birefringence is not examined. Actually, as a result of the study by the present inventors, the composition ratios of the resin compositions described in Patent Document 2 and Patent Document 3 are insufficient to cancel out the positive and negative intrinsic birefringence, and as a so-called optical film molded body It became clear that the birefringence of was very large.

  Also disclosed are a resin composition containing a polycondensation or polyaddition polymer having a fluorene compound as a monomer unit and having at least one sulfur atom in the repeating unit, and an optical element formed by injection molding the resin composition (See Patent Document 4). As a result of the study by the present inventors, the resin composition disclosed in the patent document is insufficient to cancel out the positive and negative intrinsic birefringence, and the birefringence as a so-called optical film molded article is very large, In addition, the optical film molded body is colored from the low heat resistance, and the total light transmittance is significantly reduced. Furthermore, it has become clear that when forming continuously, the inside of the forming machine or the forming metal roll is corroded by the decomposition gas containing sulfur, making it difficult to implement industrially.

  Thus, an optical film having low birefringence, high transparency, and high glass transition temperature (heat resistance) in a well-balanced manner has not been known so far.

Japanese Unexamined Patent Publication No. 7-109342 Japanese Patent Laid-Open No. 10-101786 Japanese Patent Laid-Open No. 10-101787 Japanese Patent Laid-Open No. 2001-106761

The present invention is intended to solve the above-described problems, and provides an optical film having a low birefringence, high transparency, and a high glass transition temperature, which can be industrially produced, and is made of a polycarbonate resin having a specific structure. To do.

  As a result of intensive studies to solve the above problems, the inventors of the present invention have 9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene represented by the following formula (1) 99 to 51 mol%. And the above-mentioned problem can be solved by a polycarbonate resin for an optical film comprising a polycarbonate resin obtained by reacting a diol component consisting of 1 to 49 mol% of bisphenol A represented by the following formula (2) with a carbonic acid diester. The present invention was found.

That is, this invention provides the following polycarbonate resin for optical films, the optical film consisting of this polycarbonate resin, and the image display element consisting of this optical film.
1. 99-51 mol% of 9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene represented by formula (1) and 1-49 mol% of bisphenol A represented by formula (2) A polycarbonate resin for optical films, in which two components are carbonated by carbonic acid diester.
2. The polycarbonate resin for optical films according to 1, wherein the reduced viscosity at 20 ° C. of a 0.5 g / dl solution having methylene chloride as a solvent is 0.2 dl / g or more.
3. The polycarbonate resin for optical films according to 1, wherein the glass transition temperature is 120 ° C. or higher and 160 ° C. or lower.
4.1 An optical film obtained by molding the polycarbonate resin for an optical film described in 1.
5. The optical film as described in 4, wherein the total light transmittance is 85.0% or more.
6. The optical film according to 4, wherein the birefringence is 1 × 10 ⁻³ or less in the entire visible light region.
7.4 A device for an image display device using the optical film described in 4 above.

According to the present invention, optical films such as a Blu-ray Disc cover layer film, a polarizing protective film, a dimming protective film, a prism sheet, and an antireflection film, which have low birefringence, substantially no optical distortion, and excellent transparency and heat resistance. Can be obtained.

  The polycarbonate resin according to the present invention includes two types of 9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene represented by the formula (1) and bisphenol A represented by the formula (2). This diol component can be produced by a known melt polycondensation method in which a carbonic acid diester is reacted with a basic compound catalyst, a transesterification catalyst, or a mixed catalyst comprising both. 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 0.98 to 1.10 mol, relative to 1 mol of the diol component.

The polycarbonate resin according to the present invention has a reduced viscosity of 0.2 dl / g or more at 20 ° C. in a 0.5 g / dl solution containing methylene chloride as a solvent.

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

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

Examples of the alkali metal compound used in the present invention include alkali metal organic acid salts, inorganic salts, oxides, hydroxides, hydrides, and alkoxides.
Specifically, sodium hydroxide, potassium hydroxide, cesium hydroxide, lithium hydroxide, sodium bicarbonate, sodium carbonate, potassium carbonate, cesium carbonate, lithium carbonate, sodium acetate, potassium acetate, cesium acetate, lithium acetate, stearin Sodium phosphate, potassium stearate, cesium stearate, lithium stearate, sodium borohydride, sodium phenyl borohydride, sodium benzoate, potassium benzoate, cesium benzoate, lithium benzoate, disodium hydrogen phosphate, hydrogen phosphate 2 potassium, 2 lithium hydrogen phosphate, 2 sodium phenyl phosphate, disodium salt of bisphenol A, 2 potassium salt, 2 cesium salt, 2 lithium salt, sodium salt of phenol, potassium salt, cesium salt, lithium salt, etc. It is needed.

Examples of the alkaline earth metal compound include organic acid salts, inorganic salts, oxides, hydroxides, hydrides, and alkoxides of alkaline earth metal compounds.
Specifically, magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, magnesium bicarbonate, calcium bicarbonate, strontium bicarbonate, barium bicarbonate, magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, acetic acid Magnesium, calcium acetate, strontium acetate, barium acetate, magnesium stearate, calcium stearate, calcium benzoate, magnesium phenyl phosphate and the like are used.

Examples of the nitrogen-containing compound include quaternary ammonium hydroxide and salts thereof, amines and the like.
Specifically, quaternary ammonium hydroxides having alkyl, aryl, groups, etc. such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, trimethylbenzylammonium hydroxide, Tertiary amines such as triethylamine, dimethylbenzylamine and triphenylamine, secondary amines such as diethylamine and dibutylamine, primary amines such as propylamine and butylamine, 2-methylimidazole, 2-phenylimidazole and benzimidazole Imidazoles such as ammonia, tetramethylammonium borohydride, tetrabutylammonium borohydride, tetrabutylammonium tetra Eniruboreto, base 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 first stage reaction is performed 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 vacuum of the reaction system, and the reaction between the dihydroxy compound and the carbonic acid diester is carried out. Finally, the polycondensation reaction is carried out at a temperature of 200 to 350 ° C. for 0.05 to 2 hours under a reduced pressure of 1 mmHg or less. 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 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, diethyl phosphite, di-n-propyl phosphite, phosphorous acid Phosphorous esters such as di-n-butyl, di-n-hexyl phosphite, dioctyl phosphite, monooctyl phosphite, triphenyl phosphate, diphenyl phosphate, monophenyl phosphate, dibutyl phosphate, phosphorus Phosphate esters such as dioctyl acid and monooctyl phosphate, phosphonic acids such as diphenylphosphonic acid, dioctylphosphonic acid and dibutylphosphonic acid, Phosphonic acid esters such as diethyl nylphosphonate, phosphines such as triphenylphosphine and bis (diphenylphosphino) ethane, boric acids such as boric acid and phenylboric acid, and aromatic sulfonic acids such as tetrabutylphosphonium dodecylbenzenesulfonate Organic halides such as salts, stearic acid chloride, benzoyl chloride and p-toluenesulfonic acid chloride, alkylsulfuric acid such as dimethylsulfuric acid, and organic halides such as benzyl chloride are preferably used. These deactivators are used in an amount of 0.01 to 50 times mol, preferably 0.3 to 20 times mol for the amount of catalyst. When the amount is less than 0.01 times the amount of the catalyst, the deactivation effect is insufficient, which is not preferable. On the other hand, when the amount is more than 50 times the amount of the catalyst, the heat resistance is lowered, and the molded product is likely to be colored.

  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 blades, etc. A horizontal apparatus equipped with a stirring blade excellent in surface renewability or a thin film evaporator is preferably used.

The polycarbonate resin used in the present invention is obtained by reacting a diol component composed of the dihydroxy compound represented by the formula (1) and the dihydroxy compound represented by the formula (2) with a carbonic acid diester to form a carbonate bond. This is a polycarbonate resin. The proportion of the dihydroxy compound represented by formula (1) in the total diol component is preferably 99 to 51 mol%, more preferably 65 to 95 mol%, most preferably 80 to 95 mol%. is there. When the content of the dihydroxy compound represented by the formula (1) is less than 51 mol%, the positive birefringence of the optical film obtained from the polycarbonate resin is increased, which is not preferable. If it exceeds 99 mol%, negative birefringence increases, which is not preferable.

  Moreover, the polystyrene conversion weight average molecular weight (Mw) of the polycarbonate resin used for this invention is 20,000-300,000, More preferably, it is 35,000-120,000. If Mw is less than 20,000, the optical film becomes brittle, which is not preferable. If Mw is greater than 300,000, the melt viscosity will be high, and it will be difficult to remove the resin after production, and the fluidity will be poor, making it difficult to injection mold in the molten state.

The polycarbonate resin used in the present invention includes random, block and alternating copolymer structures.
Moreover, the preferable glass transition temperature (Tg) of the polycarbonate resin used for this invention is 95-180 degreeC, More preferably, it is 120-160 degreeC. When Tg is lower than 95 ° C., the operating temperature range becomes narrow, which is not preferable. On the other hand, if it exceeds 180 ° C., the molding conditions during film molding become severe, which is not preferable.

  Furthermore, an antioxidant, a release agent, an ultraviolet absorber, a fluidity modifier, a crystal nucleating agent, a reinforcing agent, a dye, an antistatic agent, an antibacterial agent, or the like may be added to the polycarbonate resin used in the present invention. It is preferably implemented.

  The polycarbonate resin used in the present invention is desired to have as little foreign matter content as possible, and filtration of the molten raw material and filtration of the catalyst solution are suitably performed. The filter mesh is preferably 5 μm or less, more preferably 1 μm or less. Furthermore, filtration of the produced resin with a polymer filter is suitably performed. The mesh of the polymer filter is preferably 100 μm or less, more preferably 30 μm or less. Further, the process of collecting the resin pellets must naturally be in a low dust environment, preferably class 1000 or less, more preferably class 100 or less.

  The optical film of the present invention can be obtained by molding the polycarbonate resin into a film shape by melt film molding or solution casting film molding. In order to avoid contamination of the optical film as much as possible, the molding environment must naturally be a low dust environment, preferably class 1000 or less, more preferably class 100 or less.

  A coating layer such as an antireflection layer or a hard coating layer may be provided on the surface of the optical film of the present invention, if necessary. The antireflection layer may be a single layer or a multilayer, and may be organic or inorganic, but is preferably inorganic. Specific examples include oxides or fluorides such as silicon oxide, aluminum oxide, zirconium oxide, titanium oxide, cerium oxide, magnesium oxide, and magnesium fluoride.

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.
1) Weight average molecular weight in terms of polystyrene (Mw): A calibration curve was prepared using standard polystyrene of known molecular weight (molecular weight distribution = 1) using GPC, 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 with a differential thermal scanning calorimeter (DSC).
3) Birefringence: Measured with an ellipsometer manufactured by JASCO Corporation.
5) Film forming machine: PSV-30 manufactured by Plaenegi Co., Ltd. was used.
6) Total light transmittance: Measured with MODEL1001DP manufactured by Nippon Denshoku Industries Co., Ltd.

<Example 1>
9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene 22.41 kg (51.11 mol), bisphenol A 0.1179 kg (0.5162 mol), diphenyl carbonate 8.869 kg (52.66 mol), and sodium bicarbonate 0.02602 g (3.097 × 10 ⁻⁴ mol) was placed in a 50 liter reactor equipped with a stirrer and a distillation apparatus, and heated to 215 ° C. and stirred for 1 hour under a nitrogen atmosphere of 760 Torr.
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 held 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 under stirring at 40 ° C. under 1 Torr for 10 minutes under a condition of 1 Torr or less over 40 minutes. 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 = 49,600 of the obtained polycarbonate resin and Tg = 160 ° C. 10.0 kg of this polycarbonate resin was vacuum-dried at 100 ° C. for 24 hours. Phosphorous acid was 1.5 ppm, diphenyl phosphite was 50 ppm, and ADK STAB PEP-36 (Asahi Denka Kogyo Co., Ltd.) was 500 ppm. 200 ppm of HP-136 (manufactured by Ciba Specialty Chemicals Co., Ltd.) and 300 ppm of glycerin monostearate were added and kneaded at 250 ° C. by an extruder to pelletize to obtain pellets. The Mw of this pellet was 49,100.
The pellets were vacuum dried at 100 ° C. for 24 hours, and then film-formed at a cylinder temperature of 250 ° C., a die temperature of 250 ° C., and a roll temperature of 155 ° C. to obtain a film having a thickness of 100 μm.
Further, when the birefringence of the resin film was measured, it was 56 nm, the birefringence was 0.56 × 10 ⁻³ , and it was confirmed that the film had a very small birefringence and no substantial optical distortion.
Further, the total light transmittance was measured and found to be 90%.

<Example 2>
9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene 15.46 kg (35.26 mol), bisphenol A 1.203 kg (5.269 mol), diphenyl carbonate 8.900 kg (41.55 mol), and sodium bicarbonate 0.02043 g (2.432 × 10 ⁻⁴ mol) was placed in a 50 liter reactor equipped with a stirrer and a distillation apparatus, and heated to 215 ° C. and stirred for 1 hour under a nitrogen atmosphere of 760 Torr.
Thereafter, the degree of vacuum was adjusted to 150 Torr over 15 minutes, and the transesterification reaction was carried out by maintaining at 215 ° C. and 150 Torr for 20 minutes. Further, the temperature was raised to 240 ° C. at a rate of 37.5 ° C./hr, and held 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 under stirring at 40 ° C. under 1 Torr for 10 minutes under a condition of 1 Torr or less over 40 minutes. 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. The polycarbonate resin obtained had Mw = 5,6800 and Tg = 158 ° C. 10.0 kg of this polycarbonate resin was vacuum-dried at 100 ° C. for 24 hours. Phosphorous acid was 1.5 ppm, diphenyl phosphite was 50 ppm, and ADK STAB PEP-36 (Asahi Denka Kogyo Co., Ltd.) was 500 ppm. 200 ppm of HP-136 (manufactured by Ciba Specialty Chemicals Co., Ltd.) and 300 ppm of glycerin monostearate were added and kneaded at 250 ° C. with an extruder to pelletize to obtain pellets. The Mw of this pellet was 56,100.
The pellets were vacuum dried at 100 ° C. for 24 hours, and then film-formed at a cylinder temperature of 250 ° C., a die temperature of 250 ° C., and a roll temperature of 153 ° C. to obtain a film having a thickness of 100 μm.
Further, when the birefringence of the resin film was measured, it was 37 nm, the birefringence was 0.37 × 10 ⁻³ , and it was confirmed that the film was a film having very little birefringence and no substantial optical distortion. Further, the total light transmittance was measured and found to be 90%.

<Example 3>
9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene 9.167 kg (20.90 mol), bisphenol A 4.585 kg (20.084 mol), diphenyl carbonate 9.000 kg (42.01 mol), and sodium bicarbonate 0.02066 g (2.459 × 10 ⁻⁴ mol) was placed in a 50 liter reactor equipped with a stirrer and a distillation apparatus, and heated to 215 ° C. and stirred for 1 hour under a nitrogen atmosphere of 760 Torr.
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 held 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 under stirring at 40 ° C. under 1 Torr for 10 minutes under a condition of 1 Torr or less over 40 minutes. 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. The obtained polycarbonate resin had Mw = 40,800 and Tg = 152 ° C. 10.0 kg of this polycarbonate resin was vacuum-dried at 100 ° C. for 24 hours. Phosphorous acid was 1.5 ppm, diphenyl phosphite was 50 ppm, and ADK STAB PEP-36 (Asahi Denka Kogyo Co., Ltd.) was 500 ppm. 200 ppm of HP-136 (manufactured by Ciba Specialty Chemicals Co., Ltd.) and 300 ppm of glycerin monostearate were added and kneaded at 250 ° C. by an extruder to pelletize to obtain pellets. The Mw of this pellet was 40,600.
The pellets were vacuum dried at 100 ° C. for 24 hours, and then film-formed at a cylinder temperature of 250 ° C., a die temperature of 250 ° C., and a roll temperature of 147 ° C. to obtain a film having a thickness of 100 μm.
Further, when the birefringence of the resin film was measured, it was 86 nm, the birefringence was 0.86 × 10 ⁻³ , and it was confirmed that the film was very small in birefringence and substantially free from optical distortion.
Further, the total light transmittance was measured and found to be 90%.

<Comparative Example 1>
9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene 12.04 kg (27.46 mol), diphenyl carbonate 6.000 kg (28.01 mol), and sodium bicarbonate 0.01384 g (1.648 × 10 ⁻⁴ mol) The mixture was placed in a 50 liter reactor equipped with a distillation apparatus, heated to 215 ° C. and stirred for 1 hour under a nitrogen atmosphere of 760 Torr.
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 held 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 under stirring at 40 ° C. under 1 Torr for 10 minutes under a condition of 1 Torr or less over 40 minutes. 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 = 76,900 of the obtained polycarbonate resin and Tg = 161 ° C. 10.0 kg of this polycarbonate resin was vacuum-dried at 100 ° C. for 24 hours. Phosphorous acid was 1.5 ppm, diphenyl phosphite was 50 ppm, and ADK STAB PEP-36 (Asahi Denka Kogyo Co., Ltd.) was 500 ppm. 200 ppm of HP-136 (manufactured by Ciba Specialty Chemicals Co., Ltd.) and 300 ppm of glycerin monostearate were added and kneaded at 250 ° C. by an extruder to pelletize to obtain pellets. The Mw of this pellet was 75,800.
The pellets were vacuum dried at 100 ° C. for 24 hours, and then film-formed at a cylinder temperature of 250 ° C., a die temperature of 250 ° C., and a roll temperature of 156 ° C. to obtain a film having a thickness of 100 μm.
Further, when the birefringence of the resin film was measured, it was 150 nm, the birefringence was 1.50 × 10 ⁻³ , and it was confirmed that the film had a large birefringence and a large optical distortion.

<Comparative Example 2>
9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene 6.944 kg (15.84 mol), bisphenol A 5.422 kg (23.75 mol), diphenyl carbonate 8.650 kg (40.38 mol), and sodium bicarbonate 0.01995 g (2.375 × 10 ⁻⁴ mol) was placed in a 50 liter reactor equipped with a stirrer and a distillation apparatus, and heated to 215 ° C. and stirred for 1 hour under a nitrogen atmosphere of 760 Torr.
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 held 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 under stirring at 40 ° C. under 1 Torr for 10 minutes under a condition of 1 Torr or less over 40 minutes. 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 = 59,800 of the obtained polycarbonate resin and Tg = 153 ° C. 10.0 kg of this polycarbonate resin was vacuum-dried at 100 ° C. for 24 hours. Phosphorous acid was 1.5 ppm, diphenyl phosphite was 50 ppm, and ADK STAB PEP-36 (Asahi Denka Kogyo Co., Ltd.) was 500 ppm. 200 ppm of HP-136 (manufactured by Ciba Specialty Chemicals Co., Ltd.) and 300 ppm of glycerin monostearate were added and kneaded at 250 ° C. by an extruder to pelletize to obtain pellets. The Mw of this pellet was 59,000.
The pellets were vacuum dried at 100 ° C. for 24 hours, and then film-formed at a cylinder temperature of 250 ° C., a die temperature of 250 ° C., and a roll temperature of 147 ° C. to obtain a film having a thickness of 100 μm.
Further, when the birefringence of the resin film was measured, it was 202 nm, the birefringence was 2.02 × 10 ⁻³ , and it was confirmed that the film was large in birefringence and large in optical distortion.

<Comparative Example 3>
As a polycarbonate resin made of bisphenol A, Iupilon H-4000 (manufactured by Mitsubishi Engineering Plastics Co., Ltd.) was used.
The pellets were vacuum dried at 100 ° C. for 24 hours, and then film-formed at a cylinder temperature of 250 ° C., a die temperature of 250 ° C., and a roll temperature of 133 ° C. to obtain a film having a thickness of 100 μm.
Further, when the birefringence of the resin film was measured, it was 287 nm, the birefringence was 2.87 × 10 ⁻³ , and it was confirmed that the resin film had a large birefringence and a large optical distortion.

The above-described Examples and Comparative Examples are summarized and listed in Tables 1, 2, and 3.

Claims (7)

Two types, 99-51 mol% of 9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene represented by the formula (1) and 1-49 mol% of bisphenol A represented by the formula (2) A polycarbonate resin for an optical film obtained by carbonate-bonding these components with a carbonic acid diester.

The polycarbonate resin for an optical film according to claim 1, wherein the reduced viscosity at 20 ° C of a 0.5 g / dl solution containing methylene chloride as a solvent is 0.2 dl / g or more. 2. The polycarbonate resin for an optical film according to claim 1, wherein the glass transition temperature is 120 ° C. or higher and 160 ° C. or lower. An optical film obtained by molding the polycarbonate resin for an optical film according to claim 1. The optical film according to claim 4, wherein the total light transmittance is 85.0% or more. 5. The optical film according to claim 4, wherein the birefringence is 1 × 10 ⁻³ or less in the entire visible light region. An element for an image display device using the optical film according to claim 4.