JP5896893B2 - Method for producing optical film made of halogenated polycarbonate - Google Patents

Description

  The present invention relates to an optical film made of a halogenated polycarbonate. Specifically, the present invention relates to an optical film made of a halogenated polycarbonate, having little coloration, having high heat resistance, high thermal dimensional stability and flame retardancy, and having sufficient mechanical properties.

  In an electronic device in which an electrode is arranged on a transparent substrate and a display element, a light emitting element, or a light receiving element is formed thereon, such as a liquid crystal display, an organic EL display, an organic EL illumination, a thin film solar cell, an organic solar cell, Glass is generally used as the substrate. By replacing this glass with a resin, new functions difficult to achieve with a glass substrate, such as flexibility, lightness, and impact resistance, can be imparted. Therefore, various developments for replacing this glass with resin have been carried out.

  However, since resin has lower heat resistance and thermal dimensional stability than glass, electrode formation and element formation on a resin substrate are greatly restricted. Moreover, it is difficult for the resin substrate to achieve both transparency and flame retardancy. Therefore, a resin optical film having these characteristics has been demanded.

  Polycarbonate is well known as a resin for optical films used for displays and the like because of its high heat resistance and high transparency. However, a polycarbonate film having a thickness of 0.5 mm or less has insufficient flame retardancy even when a flame retardant is added. Furthermore, a general polycarbonate having bisphenol A as a monomer has a low glass transition temperature, which is an index of heat resistance, as low as about 150 ° C., and a linear expansion coefficient, which is an index of thermal dimensional stability, is as high as 80 ppm / ° C. . Therefore, in general polycarbonate, higher heat resistance and dimensional stability have been demanded.

  On the other hand, a halogen-substituted polycarbonate oligomer having a halogen-substituted dihydric phenol as a monomer has high flame retardancy, and is well known as an additive for imparting flame retardancy to a resin. However, even if these halogen-substituted polycarbonate oligomers are formed into films, they are mechanically fragile as optical films and are difficult to use.

  A high molecular weight halogenated polycarbonate obtained by increasing the molecular weight of such a halogen-substituted polycarbonate oligomer has been proposed (Patent Document 1). However, when such a high molecular weight halogenated polycarbonate is formed into a film by simply forming a film by extrusion, the high molecular weight halogenated polycarbonate itself is used as a film for optical applications because the film is highly colored. That was not taken into account.

JP-T 6-502216

  An object of the present invention is to provide an optical film with little coloring, high heat resistance, high thermal dimensional stability, flame retardancy, and sufficient mechanical properties.

  As a result of intensive studies to solve the above problems, the present inventors have unexpectedly found that the above object can be achieved by molding a halogenated polycarbonate having specific characteristics by a casting method, and reached the present invention. did. That is, the present inventors formed a halogenated polycarbonate having a high glass transition temperature and a large molecular weight and a small amount of oligomers by molding, thereby providing a mechanical strength due to a large molecular weight and a high heat resistance due to a high glass transition temperature. The present invention has been conceived by finding that an optical film having a combination of heat resistance and thermal dimensional stability, a cast method and at least a small coloration due to the oligomer content, and flame retardancy due to a halogenated polycarbonate can be obtained.

式中、
（Ｉ）Ｚは、下記の（Ａ）〜（Ｃ）のいずれかであり：
（Ａ）（ｉ）直鎖状、分岐状、環状又は二環式の二価の基、（ｉｉ）脂肪族又は芳香族の二価の基、及び（ｉｉｉ）飽和又は不飽和の二価の基から選択される二価の基であって、５個以下の硫黄及び／又はハロゲン原子、及び１〜１５個の炭素原子より成る二価の基；
（Ｂ）−Ｓ−基、−Ｓ_２−基、−ＳＯ−基、−ＳＯ_２−基、−Ｏ−基又は−ＣＯ−基；
（Ｃ）単結合；
（ＩＩ）各Ｘは独立的に、水素、Ｃ_１〜Ｃ_１２の直鎖状又は環状のアルキル基、アルコキシ基、アリール基、又はアリールオキシ基であり；
（ＩＩＩ）Ｄ^１及びＤ^２は、同一か又は異なるハロゲン基であり；
（ＩＶ）１≦ａ≦４及び１≦ｂ≦４；かつｃ＝４−ａ及びｄ＝４−ｂである）。
〈９〉上記の一般式（１）において、各Ｘは、それぞれに、水素又はメチル基であり、ａ及びｂがそれぞれ２以上４以下である、上記〈８〉項に記載の光学フィルム。
〈１０〉上記一般式（１）で示される構造単位が、２，２−ビス（３，５−ジハロゲノ，４−ヒドロキシフェニル）プロパンである、上記〈８〉項に記載の光学フィルム。That is, the present invention is as follows:
<1> Obtained by producing a halogenated polycarbonate by a solution casting method, and the halogenated polycarbonate has a glass transition temperature of 230 ° C. or more, a weight average molecular weight of more than 50,000, and an oligomer content of 0.6% by weight or less. Is,
Optical film.
<2> The optical film as described in <1> above, wherein the chromaticness index b ^* value of the L ^* a ^* b ^* color system is −1.0 to 3.0.
<3> The optical film according to <1> or <2>, wherein the linear expansion coefficient is 60 ppm / ° C. or less.
<4> The optical film according to any one of <1> to <3>, wherein the tensile elongation is 2.5% or more.
<5> The molecular weight distribution (Mw / Mn) obtained by dividing the weight molecular weight (Mw) by the number average molecular weight (Mn) is 4.5 or less, according to any one of <1> to <4> above. Optical film.
<6> The optical film according to any one of <1> to <5>, wherein the amount of residual solvent contained in the optical film is 0.1% by weight or less.
<7> The optical film according to any one of <1> to <6>, wherein the total light transmittance is 85% or more and the haze is 2% or less.
<8> The optical film according to any one of <1> to <7>, wherein the halogenated polycarbonate has a structural unit represented by the following general formula (1) as a main repeating unit:

Where
(I) Z is any of the following (A) to (C):
(A) (i) a linear, branched, cyclic or bicyclic divalent group, (ii) an aliphatic or aromatic divalent group, and (iii) a saturated or unsaturated divalent group A divalent group selected from the group consisting of up to 5 sulfur and / or halogen atoms and 1 to 15 carbon atoms;
(B) -S- group, -S ₂ - group, -SO- group, -SO ₂ - group, -O- group or -CO- group;
(C) a single bond;
(II) each X is, each independently, _hydrogen, straight-chain or cyclic alkyl group of C 1 _{-C 12,} alkoxy groups, aryl groups, or an aryloxy group;
(III) D ¹ and D ² are the same or different halogen groups;
(IV) 1 ≦ a ≦ 4 and 1 ≦ b ≦ 4; and c = 4-a and d = 4-b).
<9> The optical film according to <8>, wherein in the general formula (1), each X is hydrogen or a methyl group, and a and b are each 2 or more and 4 or less.
<10> The optical film according to <8>, wherein the structural unit represented by the general formula (1) is 2,2-bis (3,5-dihalogeno, 4-hydroxyphenyl) propane.

  According to the present invention, there is provided an optical film that is less colored and has high heat resistance, high thermal dimensional stability, good flame retardancy, and sufficient mechanical properties.

  More specifically, the optical film of the present invention has little coloration and has high heat resistance, high thermal dimensional stability, high flame retardancy, and sufficient mechanical properties, so that the display, organic EL lighting, It can be suitably used as a transparent electrode substrate for electronic devices such as solar cells. In addition, since it has good optical characteristics and heat resistance, it can be used for electrode formation and element formation. Furthermore, warpage of the substrate after electrode and element formation, wiring disconnection, pixel dot misalignment, etc. This problem is less likely to occur. In addition, since the flame retardancy is high, it is possible to suppress ignition due to an electrical short circuit. Furthermore, since it has sufficient mechanical characteristics when used as an electronic device, the handling property at the time of manufacturing an electronic device is also improved.

  The present invention will be described below.

<Halogenated polycarbonate-Repeating unit>
The halogenated polycarbonate in the present invention has, for example, a structural unit represented by the following general formula (1) as a main repeating unit. The main in the present invention means 70 mol% or more, preferably 80 mol% or more, particularly preferably 90 mol% or more, based on the number of moles of repeating units.

In the above formula, (I) Z is any one of the following (A) to (C):
(A) (i) a linear, branched, cyclic or bicyclic divalent group, (ii) an aliphatic or aromatic divalent group, and (iii) a saturated or unsaturated divalent group A divalent group selected from the group consisting of up to 5 sulfur and / or halogen atoms and 1 to 15 carbon atoms;
(B) -S- group, -S ₂ - group, -SO- group, -SO ₂ - group, -O- group or -CO- group;
(C) Single bond.

Further, in the above formula is (II) each X is, each independently, hydrogen, straight-chain or cyclic alkyl group of C ₁ -C _12, an alkoxy group, an aryl group, or an aryloxy group.

In the above formula, (III) D ¹ and D ² are the same or different halogen groups.

  In the above formula, (IV) 1 ≦ a ≦ 4 and 1 ≦ b ≦ 4; and c = 4-a and d = 4-b.

  More preferably, for (II), each X is independently hydrogen or a methyl group. Regarding (IV), it is preferable that 2 ≦ a ≦ 4 and 2 ≦ b ≦ 4; and c = 4-a and d = 4-b. When satisfy | filling this range, the flame retardance of a film expresses favorably.

  In the above formula (1), the halogen atom is, for example, a fluorine atom, an iodine atom, a chlorine atom or a bromine atom, and the halogen group is, for example, a fluoro group, a chloro group, a bromo group or an iodo group.

<Halogenated polycarbonate-dihydric phenol>
The halogenated polycarbonate in the present invention is synthesized by a method of reacting a halogen-substituted dihydric phenol component with a carbonate precursor such as phosgene or carbonic acid diester.

  Specific examples of the halogen-substituted dihydric phenol include 2,2-bis (3,5-dibromo-4-hydroxyphenyl) propane (commonly known as tetrabromobisphenol A), 2,2-bis (3,5-dichloro- 4-hydroxyphenyl) propane, 1,1-bis (3,5-dibromo-4-hydroxyphenyl) ethane, 1,1-bis (3,5-dichloro-4-hydroxyphenyl) ethane, 1,1-bis (3,5-dibromo-4-hydroxyphenyl) methane, 1,1-bis (3,5-dichloro-4-hydroxyphenyl) methane, bis (3,5-dibromo-4-hydroxyphenyl) sulfone, bis ( 3,5-dichloro-4-hydroxyphenyl) sulfone and the like. Tetrabromobisphenol A is particularly preferable. These can be used alone or in admixture of two or more.

  Moreover, a general dihydric phenol can also be introduce | transduced in the range which does not impair the heat resistance of a film, thermal dimensional stability, and a flame retardance as needed. Specific examples of such dihydric phenols include resorcinol, hydroquinone, 4,4′-dihydroxybiphenyl, 1,6-dihydroxynaphthalene, bis (4-hydroxyphenyl) methane, bis (4-hydroxyphenyl) diphenylmethane, 1 , 1-bis (4-hydroxyphenyl) ethane, 1,2-bis (4-hydroxyphenyl) ethane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 2,2-bis (4- Hydroxyphenyl) propane (ie, “bisphenol A”), 2,2-bis (4-hydroxyphenyl) butane, 1,1-bis (4-hydroxyphenyl) isobutane, 1,1-bis (4-hydroxyphenyl) Cyclohexane, 1,1-bis (4-hydroxyphenyl) cyclododecane, 2, -Bis (4-hydroxyphenyl) adamantane, 2,2-bis (3-methyl-4-hydroxyphenyl) propane, 2,2-bis (3-n-propyl-4-hydroxyphenyl) propane, 2,2- Bis (3-isopropyl-4-hydroxyphenyl) propane, 2,2-bis (3-sec-butyl-4-hydroxyphenyl) propane, 2,2-bis (3-tert-butyl-4-hydroxyphenyl) propane 2,2-bis (3-cyclohexyl-4-hydroxyphenyl) propane, 2,2-bis (4-hydroxyphenyl) hexafluoropropane, 4,4'-dihydroxybenzophenone, 3,3-bis (4-hydroxy) Phenyl) -2-butanone, bis (4-hydroxyphenyl) ether, bis (4-hydroxyphenyl) ) Sulfide, bis (4-hydroxyphenyl) sulfoxide, bis (4-hydroxyphenyl) sulfone, 9,9-bis (4-hydroxyphenyl) fluorene, and the like. The proportion of these copolymer components is 30 mol% or less, preferably 20 mol% or less, and particularly preferably 10 mol or less, based on the number of moles of repeating units.

<Halogenated polycarbonate-production method>
Next, basic means of the method for producing the halogenated polycarbonate will be briefly described.

  As the carbonate precursor, carbonyl halide, carbonate ester, haloformate or the like is used, and specifically, phosgene, diphenyl carbonate, dihaloformate of dihydric phenol or the like can be mentioned.

  In producing a polycarbonate resin by reacting the dihydric phenol and the carbonate precursor by an interfacial polymerization method, a catalyst, a terminal stopper, a dihydric phenol antioxidant, etc. may be used as necessary. Good.

<Halogenated polycarbonate-production method by interfacial polymerization>
The reaction by the interfacial polymerization method is usually a reaction between a halogenated dihydric phenol and phosgene, and is reacted in the presence of an acid binder and an organic solvent.

  As the acid binder, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, or amine compounds such as pyridine are used. As the organic solvent, halogenated hydrocarbons such as methylene chloride and chlorobenzene are used.

  In the reaction by the interfacial polymerization method, for example, an amine catalyst or a phosphonium catalyst can be used to promote the reaction. Examples of amine catalysts include trimethylamine, triethylamine, tripropylamine, tributylamine, trihexylamine, trioctylamine, tridecylamine, dimethyl-n-propylamine, diethyl-n-propylamine, N, N-dimethylcyclohexyl. Tertiary amines such as amine, pyridine, N, N-dimethylaniline, N, N-dimethyl-4-aminopyridine, N, N-diethyl-4-aminopyridine, trimethyldodecylammonium chloride, triethyldodecylammonium chloride, dimethylbenzyl Phenylammonium chloride, diethylbenzylphenylammonium chloride, trimethyldodecylbenzylammonium hydroxide, triethyldodecylbenzylammonium hydroxide, trime Le benzyl ammonium chloride, triethylbenzylammonium chloride, tetramethylammonium chloride, quaternary ammonium compounds such as tetraethylammonium chloride. Further, as the phosphonium catalyst, a quaternary phosphonium salt such as triphenyl-n-butylphosphonium bromide or triphenylmethylphosphonium bromide may be used. Of these catalysts, triethylamine is preferred. These catalysts can also be present during the phosgenation reaction. At that time, the reaction temperature is usually 0 to 40 ° C., the reaction time is about 10 minutes to 5 hours, and the pH during the reaction is preferably kept at 9 or more.

<Halogenated polycarbonate-Detailed production example>
As a halogen-substituted dihydric phenol, a structure in which a large halogen element is bonded to the 1,5-position of a hydroxyl group such as tetrabromobisphenol A has a reactivity with a carbonate precursor due to steric hindrance of the halogen element. In order to obtain a carbonate having a high molecular weight and a very small amount of oligomer, it is preferable to use a production method by the following interfacial polymerization method.

  That is, in producing a halogenated carbonate by reacting an alkaline aqueous solution of a halogen-substituted dihydric phenol with phosgene in the presence of an organic solvent, the following conditions (a) to (c) are preferably satisfied.

  (A) Until the end of the phosgenation reaction, the total amount of alkali used is controlled to 2.0 mol or less with respect to the halogenated dihydric phenol, and then transferred to the subsequent polymerization reaction.

  By this method, a monochloroformate body is produced as a main reactant, and the decomposition reaction of the produced oligomer can be suppressed, so that the subsequent polymerization reaction can proceed efficiently. However, when the amount of the alkali compound used is less than 1.0 mole, the production of chloroformate is reduced in the phosgenation reaction, and the unreacted halogenated dihydric phenol is increased. When the total amount of alkali used is more than 2.0 times the mole of the halogenated dihydric phenol, the decomposition reaction of the resulting oligomer is promoted, so a sufficient amount of monochloroformate required for the subsequent polymerization reaction. The body cannot be obtained.

  (B) An amine catalyst is used through a series of reactions.

  It is essential that the amount of amine catalyst used is 0.01 to 0.1 times the molar amount of the dihydric phenol. If the amount of the amine catalyst used is larger than the above range, the chloroformate group and the amine catalyst react through a series of reactions to form urethane bonds (carbamoyl), which deteriorates the thermal stability of the reaction product. . If the amount of amine catalyst used is less than the above range, the reaction does not proceed.

  (C) During the polymerization reaction, an alkali compound is added sequentially.

  This method suppresses decomposition due to excess alkali, allows polymerization to proceed efficiently even with a small amount of phosgene used, and also suppresses the decomposition reaction of the generated oligomer. Can be obtained.

  In the present invention, in the polymerization reaction, monofunctional phenols usually used as a terminal terminator can be used. Especially in the case of reactions using phosgene as a carbonate precursor, monofunctional phenols are generally used as end-capping agents for molecular weight control, and the polymers obtained are based on groups based on monofunctional phenols. Since it is blocked by, it is superior in thermal stability compared to other cases.

  Such monofunctional phenols may be those usually used as an end stopper for aromatic polycarbonate resins, and are generally phenols or lower alkyl-substituted phenols, and are monofunctional phenols represented by the following general formula: Can be preferably shown.

  In the formula, A represents a hydrogen atom, a linear or branched alkyl group having 1 to 9 carbon atoms or an arylalkyl group, and r represents an integer of 1 to 5, preferably 1 to 3.

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

  Further, as other monofunctional phenols, phenols or benzoic acid chlorides having a long chain alkyl group or an aliphatic ester group as a substituent, or long chain alkyl carboxylic acid chlorides may be used.

  Specific examples include, for example, decylphenol, dodecylphenol, tetradecylphenol, hexadecylphenol, octadecylphenol, eicosylphenol, docosylphenol, triacontylphenol, decyl hydroxybenzoate, dodecyl hydroxybenzoate, hydroxybenzoic acid Examples include tetradecyl, hexadecyl hydroxybenzoate, eicosyl hydroxybenzoate, docosyl hydroxybenzoate, and triacontyl hydroxybenzoate.

  Monofunctional phenols are preferably introduced at least 5 mol%, preferably at least 10 mol%, based on the number of moles of all terminals of the obtained halogenated polycarbonate. Moreover, you may use monofunctional phenols individually or in mixture of 2 or more types.

<Halogenated polycarbonate-additive>
In the halogenated polycarbonate in the present invention, at least one phosphorus compound selected from the group consisting of phosphoric acid, phosphorous acid, phosphonic acid, phosphonous acid and esters thereof is 0.0001 with respect to the copolymer. It is preferable to mix | blend in the ratio of -0.05weight%. By blending this phosphorus compound, the thermal stability of the halogenated polycarbonate is improved, and the molecular weight and hue are prevented from being deteriorated during molding.

  The amount of the phosphorus compound may be 0.0001 to 0.05% by weight, preferably 0.0005 to 0.02% by weight, and 0.001 to 0.01% by weight based on the halogenated polycarbonate. Is particularly preferred. If the amount is too small, it is difficult to obtain the above effect. If the amount is too large, the thermal stability of the halogenated polycarbonate is adversely affected, and the hydrolysis resistance tends to decrease.

  In the halogenated polycarbonate in the present invention, an antioxidant generally known for the purpose of antioxidant can be added. Examples thereof include phenolic antioxidants and lactone antioxidants. The range of preferable addition amount of these antioxidants is 0.0001 to 0.05% by weight based on the weight of the composition with the halogenated polycarbonate.

  Furthermore, the higher halogenated ester of monohydric or polyhydric alcohol can also be added to the halogenated polycarbonate in this invention as needed. By blending this higher fatty acid ester of mono- or polyhydric alcohol, the release property from the mold or belt during the molding of the halogenated polycarbonate is improved, and in the molding of the optical film, the release load is small. Deformation of the film due to mold failure can be prevented. 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.

  The halogenated polycarbonate in the present invention further includes a light stabilizer, a light absorber, a light diffusing agent, a filler, a colorant, an antistatic agent, for the purpose of improving the stability of the resin and imparting functionality to the film. Additives such as lubricants can be added as long as the heat resistance is not impaired.

<Halogenated polycarbonate-glass transition temperature>
The halogenated polycarbonate in the present invention has high heat resistance due to the thermally stable and bulky halogen group introduced into the aromatic group suppressing the thermal motion of the polymer chain, and thereby has a high glass transition temperature. . The halogenated polycarbonate in the present invention has a glass transition temperature of 230 ° C. or higher, preferably 250 ° C. or higher. More preferably, it is 260 degreeC or more. When the glass transition temperature is low, the heat resistance of the film is not sufficient, and for example, it is difficult to adapt to a high temperature process such as TFT formation on a display substrate.

  In the present invention, the glass transition temperature is measured using a differential scanning calorimeter (DSC) at a heating rate of 20 ° C./min, and the inflection point of the temperature-differential heat curve is evaluated as the glass transition temperature. To do.

<Halogenated polycarbonate-weight average molecular weight, number average molecular weight and molecular weight distribution>
The halogenated polycarbonate in the present invention has a weight average molecular weight (Mw) of more than 50,000, preferably Mw is more than 50,000 and not more than 500,000, more preferably Mw is 70,000. In the range of 300,000 or less. When Mw is low, the mechanical properties as a film are low, and the film becomes very brittle. On the other hand, when Mw is too high, the viscosity of the solution at the time of solution casting becomes too high, and it may be difficult to form a film having a good thickness or surface property.

  The halogenated polycarbonate in the present invention preferably has a molecular weight distribution (Mw / Mn) represented by a ratio of Mw and number average molecular weight (Mn) of 4.5 or less in order to improve thermal stability. .

Mw and Mn were measured by dissolving 40 mg of a dried sample in 5 ml of chloroform and introducing 200 μl into a GPC (gel permeation chromatography) apparatus under the following conditions.
Equipment: GPC system (LC-10A) manufactured by Shimadzu Corporation
Detector: RID-10A
Column: Shodex KF-801 + KF-802 + KF805L
Standard substance: TSK standard polystyrene Eluent: Chloroform, 40 ° C., 1 ml / min

<Halogenated polycarbonate-oligomer amount>
The halogenated polycarbonate in the present invention has an oligomer amount of 0.6% by weight or less, preferably 0.5% by weight or less, more preferably 0.45% by weight or less based on the weight of the halogenated polycarbonate. Since the oligomer is likely to be deteriorated by heat and the film is colored, the amount of the oligomer needs to be not more than the above upper limit.

  The oligomer in the present invention refers to a low molecular weight carbonate from a monomer dimer to a tetramer, which has no end capping agent bound thereto, or one molecule or two molecules bound. In addition, the oligomer in the present invention includes an unreacted monomer, a terminal blocking agent, a monomer in which a terminal blocking agent is bonded to one molecule or two molecules, and a low molecular weight monomer such as a dimer of the terminal blocking agent. included.

  The oligomer amount in the present invention indicates the proportion (% by weight) of the oligomer contained in the sample.

  The oligomer in the present invention is measured by dissolving 50 mg of a dried sample in 5 ml of chloroform and introducing 20 μl into a GPC (gel permeation chromatography) apparatus under the following conditions. The oligomer amount in the present invention corresponds to the ratio (%) of the peak area of the oligomer component observed after the retention time of the GPC chart obtained by the previous measurement method after 19 min to the total peak area.

The peak area of the oligomer component is obtained by connecting adjacent valleys sandwiched between the respective peaks with a straight line and converting it into the weight percent as the area between the straight line and the peak.
Apparatus: GPC system (Waters 2695) manufactured by Waters Co., Ltd.
Detector: Waters 2487
Column: TSKgel G2000H _XL + G3000H _X
Standard substance: TSK standard polystyrene Eluent: Chloroform, 40 ° C., 0.7 ml / min

<Film-Production Method>
General methods for producing an optical film include an extrusion molding method and a solution casting method. The extrusion molding method is a technique in which a resin is melted by heat in an extruder, flows out from a T die into a film shape, is cooled using a cooling roll or the like, and is continuously wound. On the other hand, the solution casting method creates a dope in which resin is dissolved in a solvent, casts it from a T-die onto a mirror belt, removes the solvent to some extent, removes the film from the belt, and then dries the film. And then winding it up.

  Since the optical film of the present invention has a high glass transition temperature, a high molecular weight, and a high melt viscosity, it is necessary to obtain an optical film with little coloring by performing a solution casting method instead of an extrusion molding method.

  The solvent for forming a halogenated polycarbonate into a film by the solution casting method is not particularly limited as long as it is a solvent capable of dissolving the halogenated polycarbonate. Preferable examples include methylene chloride, chloroform, 1,2-dichloroethane, 1,1-dichloroethane, 1,1,2-trichloroethane, chlorobenzene, dichlorobenzene, tetrahydrofuran, toluene, isophorone and the like. Methylene chloride and chloroform are particularly preferable from the viewpoint that the boiling point is relatively low and the film can be easily dried.

<Optical film-residual solvent amount>
Since the optical film of the present invention is prepared by a casting method, some solvent remains in the film. When an optical film is used as a substrate for a device such as a display, the residual solvent amount is constant because it causes a reduction in the degree of vacuum during device formation in a vacuum process and also causes corrosion of the formed metal wiring. Desirably less than the amount. For this reason, the residual solvent amount of the optical film of the present invention is preferably 0.1% by weight or less, more preferably 0.05% by weight or less, and particularly preferably 0.03% by weight or less, based on the weight of the film. .

  Since the halogenated polycarbonate of the present invention has high heat resistance, it can be easily dried at a high temperature, and the amount of residual solvent can be lowered more easily than general polycarbonate by drying in a short time.

The residual solvent amount of the film can be measured by ¹ H-NMR measurement, gas chromatograph or the like.

<Optical film-thickness>
The thickness of the optical film of the present invention is preferably 10 μm or more and 300 μm or less in view of mechanical properties and film productivity. More preferably, the thickness of the optical film of the present invention is 20 μm or more and 250 μm or less. More preferably, the thickness of the optical film of the present invention is 30 μm or more and 200 μm or less. When the film is too thin, it is difficult to produce the film, and mechanical properties such as the strength of the film tend to be low. On the other hand, when the film is too thick, the characteristics of the resin base material that is lightweight are lost, and a long time is required in the production by the casting method described above.

<Optical film-total light transmittance, haze>
As one embodiment of the optical film of the present invention, a highly transparent film that does not use a filler such as a light diffusing agent can be produced. Such a highly transparent film is preferably used as a transparent substrate for displays, organic EL lighting, thin film solar cells and the like. When used in applications requiring such transparency, the total light transmittance of a 10 to 300 μm thick film is preferably 85% or more, more preferably 87% or more, and particularly preferably 88% or more.

  Further, the haze of such a highly transparent optical film is preferably 2% or less, more preferably 1.5% or less, and particularly preferably 1% or less.

<Optical film-b ^* value>
In the optical film of the present invention, coloring can be extremely reduced by forming a halogenated polycarbonate with a small amount of oligomers by molding.

Therefore, the optical film of the present invention can exhibit an excellent hue with a chromaticness index b ^* value of the L ^* a ^* b ^* color system of −1.0 to 3.0. Preferred b ^* values are 0 to 2.0, more particularly 0 to 1.5. These values can be obtained particularly when the film is a transparent film having a transmittance of 85% or more without adding a diffusing agent or the like and without providing an optical interference layer or the like.

Here, in the present invention, the b ^* value is the chromaticness index b ^* value of the L ^* a ^* b ^* color system defined by JIS Z8729, and is measured in the transmission mode according to JIS Z8722. Value. In the measurement of the b ^* value, standard light D65 defined in Japanese Industrial Standard Z8720 is adopted as the light source, and the measurement is performed under the condition of a two-degree field of view.

<Optical film-linear expansion coefficient>
Since the optical film of the present invention uses a polycarbonate whose main repeating unit is a specific structural unit, the film is less susceptible to expansion and contraction due to temperature and has favorable characteristics as a display substrate.

  The linear expansion coefficient of the optical film of the present invention is preferably 60 ppm / ° C. or less, more preferably 55 ppm / ° C. or less, and particularly preferably 50 ppm / ° C. or less. When the linear expansion coefficient is large, for example, when used as a display substrate, it is likely to be difficult to align the optical film. In addition, when the linear expansion coefficient is large, when a metal film or an inorganic film having a low linear expansion coefficient is laminated to form a laminated body, a change in warpage of the laminated body due to temperature tends to be large.

The linear expansion coefficient (α _T ) of the optical film was determined by placing a 4 mm wide × 30 mm sample at 25 ° C. and 50% relative humidity (RH) for 24 hours, and then measuring the thermal / stress-strain measuring device (SII nanotechnology). The temperature is measured at a temperature rising rate of 5 ° C./minute using SS6100), and the temperature range is 50 ° C. to 150 ° C.

A linear expansion coefficient ((alpha) _T ) is calculated | required by the following formula | equation. In addition, a measurement is performed twice about each of the longitudinal direction of a film, and its perpendicular direction, and takes an average value.
α _T = (L ₁₅₀ −L ₅₀ ) / (L ₅₀ × 100) (ppm / ° C.)
L ₁₅₀ : film length at 150 ° C. L ₅₀ : film length at 50 ° C.

<Optical film-Flame resistance>
The optical film of the present invention has a high flame retardance because a halogen-containing monomer having a high flame retardancy is polymerized. In addition, a highly transparent optical film having a total light transmittance of 85% or more and a haze of 2% or less formed as one embodiment of the optical film of the present invention can achieve both transparency and flame retardancy. . Such an optical film having high transparency is preferably used as a transparent substrate for displays, organic EL lighting, thin film solar cells and the like. On the other hand, when the halogenated polycarbonate of the present invention is filled with a diffusing agent or a reflective agent and used as a diffusing film / reflective film, or when a reflective film is formed on a transparent film and used as a reflective film, it is similarly difficult. It can be used as a flammable optical film.

  In addition, the flame retardance of a film is evaluated by performing a vertical combustion test according to UL standard 94 using the prepared film. Based on the results of the test, the grade is evaluated as either V-0, V-1, or V-2out (not-V). Since the optical film of the present invention has high flame retardancy, it can have a V-0 or V-1 rating, preferably a V-0 rating. From the viewpoint of flame retardancy, the halogen contained in the halogenated polycarbonate is particularly preferably bromine. From the viewpoint of flame retardancy, the structural unit constituting the halogenated polycarbonate is preferably 2,2-bis (3,5-dihalogeno-4-hydroxyphenyl) propane.

<Film-Tensile elongation at break>
The optical film of the present invention is composed of a halogenated polycarbonate having a weight average molecular weight exceeding the above-mentioned lower limit, and has high mechanical properties, and therefore has a high tensile elongation.

  The tensile elongation of the film of the present invention is preferably 2.5% or more, more preferably 3.0% or more, and particularly preferably 3.5% or more.

In addition, the tensile elongation is measured under the following conditions using a film strong elongation automatic measuring device “Tensilon RTC-1210A” manufactured by Orientec Co., Ltd.
Sample size: width 10mm, length 140mm
Distance between chucks 100mm
Tensile speed: 5 mm / min Measurement environment: 25 ° C., relative humidity (RH) 50%, under atmospheric pressure

  Tensile elongation is obtained by multiplying the length obtained by subtracting the distance between chucks from the length at the time of film break by the distance between chucks and multiplying by 100. The measurement is performed 5 times for each of the longitudinal direction and the vertical direction of the film, and an average value is taken.

<Film-Functional layer>
In the optical film of the present invention, various functional layers such as a hard coat layer, a gas barrier layer, a transparent conductive layer, and a reflective film can be laminated in order to impart functions depending on the application.

  The optical film of the present invention may further have one or a plurality of hard coat layers as long as the characteristics are not lost for the purpose of imparting hardness and abrasion resistance of the film surface. The hard coat layer can be formed of a thermosetting resin, an active energy ray curable resin, or the like. Especially, the ultraviolet curable resin which used the ultraviolet-ray for the active energy ray is excellent in productivity and economical efficiency, and is suitable.

  The optical film of the present invention can further have a single or a plurality of gas barrier layers for preventing the permeation of gases such as oxygen and water vapor as long as the properties are not lost for the purpose of imparting gas barrier properties.

  For example, when the gas barrier layer is formed by a wet coating method, the barrier material is a polyvinyl alcohol polymer such as polyvinyl alcohol or polyvinyl alcohol-ethylene copolymer; a polyacrylonitrile, polyacrylonitrile-styrene copolymer or the like Known coating materials such as acrylonitrile polymers; polysilazane resins and polyvinylidene chloride can be used.

  Although there is no restriction | limiting in particular also about the coating method, Well-known methods, such as a reverse roll coating method, a gravure roll coating method, and a die coating method, can be used. In addition, when adhesion to the substrate or the surface of the base material, wettability, and the like are poor, an easy adhesion treatment such as a primer treatment can be appropriately performed.

  In the case of forming a gas barrier layer by a dry process such as sputtering or vacuum deposition, at least one metal selected from Si, Al, Ti, Mg, Zr, etc., which are known barrier materials, or two or more kinds An oxide, nitride, or oxynitride thin film of a metal mixture can be formed by a known method.

  The film thickness of these gas barrier layers may be set to a thickness that can achieve the desired performance. Two or more layers such as dry / wet, dry / dry, and wet / wet may be appropriately combined and stacked.

  The optical film of the present invention, the optical film with a hard coat layer, and the optical film with a gas barrier layer are provided in such a range that the characteristics are not lost for the purpose of imparting conductivity and antistatic function to the film surface depending on the application. Further, it may further have one or a plurality of transparent conductive layers. The transparent conductive layer is not particularly limited, and examples thereof include a thin film made of a crystalline metal layer or a crystalline metal compound layer, and a coating layer such as a conductive polymer, carbon nanotube, graphene, and metal nanofiber. . Among these, examples of the metal compound component constituting the transparent conductive layer include metal oxide layers such as silicon oxide, aluminum oxide, titanium oxide, magnesium oxide, zinc oxide, indium oxide, and tin oxide. The metal oxide layer constituting the transparent conductive layer is preferably a crystalline layer mainly composed of indium oxide, and a layer made of crystalline ITO (Indium Tin Oxide) is particularly preferably used.

  The transparent conductive layer can be formed by a known method according to the characteristics and composition of the transparent conductive layer to be used. As a method for forming the transparent conductive layer, for example, a DC magnetron sputtering method, an RF magnetron sputtering method, an ion plating method, a vacuum deposition method, a pulsed laser deposition method or the like, a chemical vapor deposition method (Chemical Vapor Deposition method). (Hereinafter referred to as “CVD”)), a sol-gel method, a chemical formation method, or a wet coating of a conductive component can also be used.

  The transparent conductive laminate thus obtained is used as a transparent electrode for a display element such as a liquid crystal display, an organic EL display, and electronic paper, a transparent electrode for organic EL lighting, and a thin film solar cell. When used as a transparent electrode, the surface resistance value of the transparent conductive layer is preferably 1 to 50Ω / □ (Ω / sq), more preferably 1 to 30Ω / □ (Ω / sq).

  In addition to the hard coat layer, gas barrier layer, and transparent conductive layer, the optical film of the present invention is separately provided with a functional layer as long as the characteristics as a film, hard coat film, gas barrier film, or transparent conductive film are not impaired. can do. The functional layer referred to here is a layer intended to express some function chemically, optically, electrically, and physically, and is not particularly limited. For example, antireflection, antiglare properties, etc. And a layer capable of exhibiting functions such as light emission, polarization, light scattering, light collection, light refraction, antifouling property, chemical resistance, slipperiness, and insulation.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to this Example. In the examples, “parts” and “%” are based on weight unless otherwise specified. Various measurements in the examples were performed as follows.

<Glass transition temperature (Tg)>
A film sample is pulverized, using a thermal analysis system DSC-2910 manufactured by TA Instruments, in accordance with JIS K7121, under a nitrogen atmosphere (nitrogen flow rate: 40 ml / min), temperature rising rate: 20 ° C./min. Measured below.

<Weight average molecular weight (Mw), number average molecular weight (Mn)>
The film sample was pulverized, 40 mg of the dried sample was dissolved in 5 ml of chloroform, and 200 μl was introduced into a GPC (gel permeation chromatography) apparatus under the following conditions for measurement. The weight average molecular weight (Mw) and the number average molecular weight (Mn) were calculated in terms of polystyrene by the above measurement method.
Equipment: GPC system (LC-10A) manufactured by Shimadzu Corporation
Detector: RID-10A
Column: Shodex KF-801 + KF-802 + KF805L
Standard substance: TSK standard polystyrene Eluent: Chloroform, 40 ° C., 1 ml / min

<Oligomer amount>
The film sample was pulverized, 50 mg of the dried sample was dissolved in 5 ml of chloroform, and 20 μl was introduced into a GPC (gel permeation chromatography) apparatus under the following conditions for measurement. The ratio (%) of the peak area of the oligomer component observed with the retention time of the GPC chart obtained by the above measuring method after 19 min or more to the total peak area was determined and converted to wt%. At this time, the peak area of the oligomer component was obtained by connecting adjacent valleys sandwiched between peaks with a straight line and converting it into an area between the straight line and the peak.
Apparatus: GPC system (Waters 2695) manufactured by Waters Co., Ltd.
Detector: Waters 2487
Column: TSKgel G2000H _XL + G3000H _XL
Standard substance: TSK standard polystyrene Eluent: Chloroform, 40 ° C., 0.7 ml / min

<Film thickness>
It was measured with an electronic micro film thickness meter manufactured by Anritsu Corporation.

<Residual solvent amount of film>
The residual solvent in the film was determined by dissolving 30 mg of polymer in 0.6 ml of deuterated chloroform and measuring the number of integrations 256 times using ¹ H-NMR of JNM-AL400 manufactured by JEOL. Specifically, when using methylene chloride as the solvent for the polymer component (peak (7.45 ppm) due to the aromatic moiety of tetrabromobisphenol A), it is due to the peak (5.34 ppm) due to methylene chloride. It was obtained from the integral ratio of the peak to be obtained.

<Total light transmittance of film>
The total light transmittance of the film was measured according to JIS K7361-1 using a Nippon Denshoku Co., Ltd. haze meter (MDH2000).

<Haze of film>
According to JIS K7136, the haze of the film was measured using the Nippon Denshoku Co., Ltd. haze meter (MDH2000).

<B ^* value of film>
In accordance with JIS Z8722, the chromaticness index b ^* value of the L ^* a ^* b ^* color system defined by JIS Z8729 was measured in the transmission mode. In addition, the standard light D65 prescribed | regulated to Japanese Industrial Standard Z8720 was employ | adopted as a light source, and it measured on condition of a 2 degree visual field.

<Linear expansion coefficient>
The linear expansion coefficient of the film was determined by placing a sample of 4 mm width × 30 mm at 25 ° C. and relative humidity (RH) 50% for 24 hours, and then using a thermal / stress-strain measuring device (SS6100 manufactured by SII Nanotechnology). The temperature was increased at a rate of 5 ° C./min, and the average linear expansion coefficient in the temperature range of 50 ° C. to 150 ° C. was calculated. The measurement was performed twice for each of the longitudinal direction of the film and the direction orthogonal to the thickness direction, and the average value of these four points was taken.

<Flame retardance>
For the flame retardancy of the film, a vertical combustion test was performed according to UL standard 94 using the prepared film. Based on the result of the test, it was evaluated as either V-0, V-1, or V-2out (not-V).

<Tensile elongation at break of film>
Measurement was carried out under the following conditions using a film tensile strength automatic measuring device “Tensilon RTC-1210A” manufactured by Orientec Co., Ltd.
Sample size: width 10mm, length 140mm
Distance between chucks 100mm
Tensile speed: 5 mm / min Measurement environment: 25 ° C., relative humidity (RH) 50%, under atmospheric pressure Multiply 100 times the distance obtained by subtracting the distance between chucks from the length at the time of film rupture. It was set as the tensile elongation. The measurement was performed 5 times for each of the longitudinal direction of the film and the direction orthogonal to the thickness direction, and the average value of these 10 points was taken.

[Example 1]
<Synthesis of Halogenated Polycarbonate A1 (Halogenated PC-A1)>
In a flask equipped with a phosgene blowing tube, thermometer and stirrer, 130 g (0.239 mol) of tetrabromobisphenol A, 161 ml of 7.0% aqueous sodium hydroxide solution (0.299 mol of sodium hydroxide), 393 ml of methylene chloride, and triethylamine 0.2 ml (0.002 mol) was charged and dissolved, and maintained at 20 to 25 ° C. with stirring, and 28.5 g (0.289 mol) of phosgene was blown in over 60 minutes. At the end of phosgene blowing, phosgenation reaction was carried out while maintaining the pH of the reaction mixture at 10.5 to 11.0 while adding 5 ml of 25% aqueous sodium hydroxide solution (0.041 mol of sodium hydroxide).

  After completion of the phosgenation reaction, 0.20 g (0.0013 mol) of p-tert-butylphenol was added, and 0.8 ml (0.008 mol) of triethylamine and 44 ml of 25% aqueous sodium hydroxide solution (0.363 mol of sodium hydroxide) ) Was added to the reaction mixture over about 60 minutes and reacted at a temperature of 35-40 ° C. for 90 minutes.

  The separated methylene chloride phase was acid washed and washed with water until inorganic salts and amines disappeared, and then methylene chloride was removed to obtain a halogenated polycarbonate A1. At this time, the weight average molecular weight was 214,000 and the glass transition temperature was 265 ° C.

<Creation of film>
This halogenated PC-A1 was dissolved in methylene chloride to prepare a 22% by weight solution. The prepared solution was poured onto a glass substrate, and a film was cast using a doctor blade having a clearance of 0.9 mm. Subsequently, after preliminary drying at 40 ° C. for 1 hour, the temperature was gradually raised to 200 ° C., and further dried at 200 ° C. for 1 hour. The physical properties of the obtained film are summarized in Table 1.

[Example 2]
<Synthesis of Halogenated Polycarbonate A2 (Halogenated PC-A2)>
The procedure in Example 1 was repeated except that the amount of p-tert-butylphenol after the phosgenation reaction was changed to 0.46 g (0.0030 mol). At this time, a halogenated polycarbonate A2 having a weight average molecular weight of 75,000 and a glass transition temperature of 263 ° C. was obtained.

<Creation of film>
A film was prepared in the same manner as in Example 1 except that the resin to be dissolved was halogenated PC-A2. The physical properties of the obtained film are summarized in Table 1.

[Example 3]
<Creation of film>
A film was prepared in the same manner as in Example 1 except that the clearance of the doctor blade was 0.27 mm. The physical properties of the obtained film are summarized in Table 1.

[Example 4]
<Creation of film>
In Example 2, the same operation was repeated except that the concentration when dissolved in methylene chloride was changed to 25% by weight and the clearance of the doctor blade was changed to 1.5 mm. The physical properties of the obtained film are summarized in Table 1.

[Comparative Example 1]
As a general polycarbonate resin using bisphenol A as a dihydric phenol, Teijin Chemicals Ltd. Panlite C-1400 (hereinafter referred to as PC-A) was used. This PC-A had a weight average molecular weight of 120,000 and a glass transition temperature of 155 ° C.

<Creation of film>
This PC-A was dissolved in methylene chloride to prepare a 22% by weight solution. The prepared solution was poured onto a glass substrate, and a film was cast using a doctor blade having a clearance of 0.6 mm. Subsequently, after preliminary drying at 40 ° C. for 1 hour, the temperature was gradually raised to 130 ° C., and further drying at 130 ° C. for 1 hour. The physical properties of the obtained film are summarized in Table 1.

[Comparative Example 2]
<Synthesis of Halogenated Polycarbonate A3 (Halogenated PC-A3)>
The procedure in Example 1 was repeated except that the amount of p-tert-butylphenol after completion of the phosgenation reaction was changed to 0.73 g (0.0048 mol). The weight average molecular weight obtained was 30,000, and the glass transition temperature was 254 ° C.

<Creation of film>
A film was prepared in the same manner as in Example 1 except that halogenated PC-A3 was used instead of halogenated PC-A1. The physical properties of the obtained film are summarized in Table 1.

[Comparative Example 3]
<Synthesis of Halogenated Polycarbonate A4 (Halogenated PC-A4)>
In a flask equipped with a phosgene blowing tube, a thermometer and a stirrer, 130 g (0.239 mol) of tetrabromobisphenol A, 322 ml of 7.0% aqueous sodium hydroxide solution (0.478 mol of sodium hydroxide), 640 ml of methylene chloride, and triethylamine 1.03 ml (0.01 mol) was charged and dissolved, and maintained at 20 to 25 ° C. with stirring, and 30.4 g (0.301 mol) of phosgene was blown in over about 60 minutes. During the phosgene blowing, the pH of the reaction mixture was maintained at 9 to 10 while adding 29 ml of 25% aqueous sodium hydroxide solution (0.239 mol of sodium hydroxide) as appropriate, to cause phosgenation reaction.

  After completion of the phosgenation reaction, 0.20 g (0.0013 mol) of p-tert-butylphenol was added, and 44 ml of 25% aqueous sodium hydroxide solution (0.363 mol of sodium hydroxide) was added over about 60 minutes. The reaction was carried out at a temperature of 40 ° C. for 90 minutes.

  The separated methylene chloride phase was acid washed and washed with water until inorganic salts and amines disappeared, and then methylene chloride was removed to obtain halogenated polycarbonate PC-A4. A halogenated polycarbonate having a weight average molecular weight of 41,000 was obtained.

<Creation of film>
A film was prepared in the same manner as in Example 1 except that the halogenated PC-A1 was changed to the halogenated PC-A4. The physical properties of the obtained film are summarized in Table 1.

[Comparative Example 4]
<Synthesis of Halogenated Polycarbonate A5 (Halogenated PC-A5)>
With reference to US Pat. No. 4,794,156, a method for producing a halogenated polycarbonate was additionally tested.

  Specifically, in a flask equipped with a phosgene blowing tube, a thermometer and a stirrer, 130 g (0.239 mol) of tetrabromobisphenol A, 37.9 g of 50% aqueous sodium hydroxide solution (0.474 mol of sodium hydroxide), water 480 ml, methylene chloride 320 ml, and p-tert-butylphenol 0.20 g (0.0013 mol) were charged and dissolved, and the mixture was kept at 22 to 28 ° C. with stirring, and phosgene 34.8 g (0.352 mol) was added to about 30. It took a long time. While the phosgene was being blown in, 4.7 g of a 50% aqueous sodium hydroxide solution (0.059 mol of sodium hydroxide) was added as appropriate, and the pH of the reaction mixture was maintained at 10 to cause a phosgenation reaction.

After completion of the phosgenation reaction, 630 ml of methylene chloride and 65 mg (0.00053 mol) of N, N-dimethylaminopyridine were added to start stirring, and 37.5 g of 50% aqueous sodium hydroxide solution (hydroxylation) was maintained so as to maintain pH 10. Sodium (0.468 mol) was added over about 30 minutes, and then 3.2 g (0.032 mol) of phosgene was added to adjust the pH to 7 and stirring was stopped. The reaction was carried out at a temperature of 35-40 ° C. for 90 minutes.
The separated methylene chloride phase was acid washed and washed with water until inorganic salts and amines disappeared, and then methylene chloride was removed to obtain halogenated polycarbonate PC-A5.

  A halogenated polycarbonate PC-A5 having a weight average molecular weight of 201,000, a dispersion of 4.9, and an oligomer amount of 0.62% was obtained.

<Creation of film>
A film was prepared in the same manner as in Example 1 except that the halogenated PC-A1 was changed to the halogenated PC-A5. The physical properties of the obtained film are summarized in Table 1.

[Comparative Example 5]
After drying the halogenated PC-A2 powder synthesized in Example 2 at 200 ° C. for 1 hour, the pellets were T-die at a resin temperature of 380 ° C. using a single-screw extruder with a T die having a screw with a diameter of 30 mm. The melt-extruded film was obtained by melt-extruding from the above and continuously winding through a cooling drum. The physical properties of the obtained film are summarized in Table 1.

As is clear from Table 1, all of the optical films of the examples have high heat resistance, a low b ^* value that is an index of coloring, and a high tensile elongation at break that is an index of mechanical strength of the film. It was a good flame retardant film as an optical film. On the other hand, as is clear from Table 1, the film of the comparative example was poor in at least one of the indicators of heat resistance, coloring, and mechanical strength of the film.

  The film of the present invention is a transparent substrate for an electronic device in which an electrode is arranged on a transparent substrate and a display element, a light emitting element or a light receiving element is formed thereon. For example, a liquid crystal display, an organic EL thin display, an organic EL illumination It is preferably used as a transparent substrate for thin film solar cells or organic solar cells. In such an application, by replacing a portion where glass is usually used with the film of the present invention, it is difficult to achieve a glass substrate, and new functions such as flexibility, weight reduction, and impact resistance are imparted. Is possible.

Claims (9)

A method for producing an optical film, comprising forming a halogenated polycarbonate into a film by a solution casting method,
The halogenated polycarbonate, a glass transition temperature of 230 ° C. or higher, a weight-average molecular weight of 50,000 ultra 500,000 or less and not more than 0.6 wt% oligomer content, and the halogenated polycarbonate is represented by the following general formula (1 ) As the main repeating unit:

(Where
(I) Z is any of the following (A) to (C):
(A) (i) a linear, branched, cyclic or bicyclic divalent group, (ii) an aliphatic or aromatic divalent group, and (iii) a saturated or unsaturated divalent group A divalent group selected from the group consisting of up to 5 sulfur and / or halogen atoms and 1 to 15 carbon atoms;
(B) -S- group, -S ₂ - group, -SO- group, -SO ₂ - group, -O- group or -CO- group;
(C) a single bond;
(II) each X is, each independently, _hydrogen, straight-chain or cyclic alkyl group of C 1 _{-C 12,} alkoxy groups, aryl groups, or an aryloxy group;
(III) D ¹ and D ² are the same or different halogen groups;
(IV) 1 ≦ a ≦ 4 and 1 ≦ b ≦ 4; and c = 4-a and d = 4-b)
Manufacturing method of optical film. The method according to claim 1, wherein the optical film has a chromaticness index b ^* value of L ^* a ^* b ^* color system of −1.0 to 3.0. The method of Claim 1 or 2 whose linear expansion coefficient of the said optical film is 60 ppm / degrees C or less. The method as described in any one of Claims 1-3 whose tensile elongation of the said optical film is 2.5% or more. Of the halogenated polycarbonate, number-average molecular weight weight molecular weight (Mw) is (Mn) molecular weight distribution, divided by (Mw / Mn), is 4.5 or less, according to any one of claims 1-4 Way . The method as described in any one of Claims 1-5 that the amount of residual solvent contained in the said optical film is 0.1 weight% or less. The method as described in any one of Claims 1-6 whose total light transmittance of the said optical film is 85% or more, and the haze of the said optical film is 2% or less. In said general formula (1), each X is hydrogen or a methyl group, respectively, and a and b are 2 or more and 4 or less, respectively, The method as described in any one of Claims 1-7. The method according to any one of claims 1 to 7, wherein the structural unit represented by the general formula (1) is 2,2-bis (3,5-dihalogeno, 4-hydroxyphenyl) propane.