JP2016204430A - Polycarbonate resin and optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polycarbonate resin having wavelength dispersion property near an ideal wide band, high in phase contrast development property, low in photoelasticity and excellent in melt processing property, and an optical film consisting of the same.SOLUTION: There is provided a polycarbonate resin containing a structural unit (A) represented by the formula (A) and a carbonate unit (B) derived from an aliphatic diol compound and/or an alicyclic diol compound with molar ratio (A/B) of the unit (A) and the unit (B) of 5/95 to 95/5. In the formula (A), Rand Rare each independently H, a hydrocarbon group which may contain a C1 to 10 aromatic group or a halogen atom, and W is a single bond, C, O, S.SELECTED DRAWING: None

Description

  The present invention relates to a polycarbonate resin and an optical film, and relates to a polycarbonate resin having desired wavelength dispersion characteristics, a low photoelastic constant, high heat resistance, and excellent melt processability, and an optical film formed therefrom.

In general, an optical film, particularly a retardation film, is used in a display device such as a liquid crystal display device, and has functions such as color compensation, viewing angle expansion, and antireflection.
As the retardation film, λ / 4 plate and λ / 2 plate are known, and thermoplastic polymers such as polycarbonate, polyethersulfone, polysulfone and the like obtained by polycondensation of bisphenol A are used as the material. The λ / 4 plate and λ / 2 plate obtained by stretching films of these materials have the property that the phase difference increases as the wavelength becomes shorter. For this reason, there is a problem that the wavelengths that can function as the λ / 4 plate and the λ / 2 plate are limited to specific wavelengths.

  As a method for controlling the wavelength in a wide band, a method is known in which two or more specific birefringent films having different wavelength dependences of the retardation are laminated at a specific angle. (For example, refer to Patent Document 1) In these cases, since a plurality of retardation films are used, a process of bonding them together or adjusting the bonding angle is necessary, and there is a problem in productivity. In addition, since the entire thickness of the retardation film is increased, there is a problem that the light transmittance is lowered and becomes thicker or darker when incorporated in an apparatus.

  In recent years, there has been proposed a method of widening a band with a single film without performing such lamination (see Patent Document 2). The film is a method of stretching a polymer film comprising a polymer monomer unit having a positive refractive index anisotropy and a polymer monomer unit having a negative refractive index anisotropy. However, since the specifically disclosed film has a high photoelastic constant, the birefringence due to stress is large, and there is a problem that light leakage occurs when used as a retardation film. In addition, since an aromatic polycarbonate having a fluorene-based bisphenol skeleton is used, there is a problem that when melt processing is performed, a gel material is easily generated due to a high melting temperature. Also. Although it has a high Tg (glass transition temperature), it requires a high temperature for film stretching and the like, and requires special processing equipment different from conventional ones. Absent.

  As a film capable of melt film formation with a low photoelastic constant, a polycarbonate copolymer of 9,9-bis (4-hydroxy-3-methylphenyl) fluorene, isosorbide and an aliphatic diol, or 9,9-bis [4 A retardation film using a polycarbonate copolymer of-(2-hydroxyethoxy) phenyl] fluorene and isosorbide has been reported (see Patent Documents 3 and 4). Moreover, although the retardation film using the polycarbonate copolymer containing spirobiindane has been reported, the photoelastic constant is high and there is no description about wavelength dispersion (refer patent document 5).

Japanese Patent Laid-Open No. 2-120804 International Publication No. 2000/026705 Pamphlet International Publication No. 2006/041190 Pamphlet JP 2010-134232 A JP 2006-131789 A

  An object of the present invention is to provide a polycarbonate resin having a wavelength dispersion characteristic close to an ideal broadband, high retardation development, low photoelasticity, and excellent melt processability, and an optical film formed therefrom. is there.

As a result of diligent research to achieve this object, the present inventors have used a specific monomer in combination so that the resulting film made of polycarbonate resin has reverse wavelength dispersion close to an ideal broadband and photoelasticity. The inventors have found that the retardation film has a low coefficient, and have reached the present invention.
That is, the present invention is as follows.

［式中、Ｒ_１およびＲ_２は夫々独立して、水素原子、炭素原子数１〜１０の芳香族基を含んでもよい炭化水素基またはハロゲン原子を示す。Ｗは単結合、炭素原子、酸素原子、硫黄原子を示す。］
と、脂肪族ジオール化合物および／または脂環族ジオール化合物から誘導されるカーボネート単位（Ｂ）を含み、単位（Ａ）と単位（Ｂ）とのモル比（Ａ／Ｂ）が５／９５〜９５／５であり、２０℃の塩化メチレン溶液で測定された比粘度が０．２０〜０．４５であるポリカーボネート樹脂。
２．ポリカーボネート樹脂のガラス転移温度が７０℃〜１８０℃である前項１記載のポリカーボネート樹脂。
３．ポリカーボネート樹脂の光弾性定数が４０×１０^−１２Ｐａ^−１以下である前項１記載のポリカーボネート樹脂。
４．さらにフルオレン骨格を有するジヒドロキシ化合物から誘導されるカーボネート単位（Ｃ）を含む前項１記載のポリカーボネート樹脂。
５．単位（Ａ）が６，６´−ジヒドロキシ−３，３，３´，３´−テトラメチル−１，１´−スピロビインダンから誘導されるカーボネート単位である前項１記載のポリカーボネート樹脂。
６．単位（Ａ）がスピロビクロマンから誘導されるカーボネート単位である前項１記載のポリカーボネート樹脂。
７．前項１〜６のいずれかに記載のポリカーボネート樹脂から形成される光学フィルム。
８．光学フィルムが溶融押出法により成形したものである前項７記載の光学フィルム。
９．光学フィルムが、未延伸フィルムを延伸してなる位相差フィルムである前項７記載の光学フィルム。
１０．波長４５０ｎｍ、５５０ｎｍ、及び６５０ｎｍにおけるフィルム面内の位相差値Ｒ（４５０）、Ｒ（５５０）、及びＲ（６５０）が、下記式（１）及び（２）を満たす前項９記載の光学フィルム。
０．６０ ≦ Ｒ（４５０）／Ｒ（５５０）≦ １．００ （１）
１．０１ ≦ Ｒ（６５０）／Ｒ（５５０）≦ １．４０ （２）
１１．前項１０記載の光学フィルムを具備した液晶表示装置または有機ＥＬ表示装置。 1. Unit represented by the following formula (A)

[Wherein, R ₁ and R ₂ each independently represent a hydrogen atom, a hydrocarbon group which may contain an aromatic group having 1 to 10 carbon atoms, or a halogen atom. W represents a single bond, a carbon atom, an oxygen atom, or a sulfur atom. ]
And a carbonate unit (B) derived from an aliphatic diol compound and / or an alicyclic diol compound, the molar ratio (A / B) of the unit (A) to the unit (B) is 5/95 to 95 / 5, a polycarbonate resin having a specific viscosity of 0.20 to 0.45 measured with a 20 ° C. methylene chloride solution.
2. 2. The polycarbonate resin according to item 1, wherein the glass transition temperature of the polycarbonate resin is 70 ° C. to 180 ° C.
3. 2. The polycarbonate resin according to item ^{1, wherein the} photoelastic constant of the polycarbonate resin is 40 × 10 ⁻¹² Pa ⁻¹ or less.
4). 2. The polycarbonate resin according to item 1, further comprising a carbonate unit (C) derived from a dihydroxy compound having a fluorene skeleton.
5. 2. The polycarbonate resin according to item 1, wherein the unit (A) is a carbonate unit derived from 6,6′-dihydroxy-3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane.
6). 2. The polycarbonate resin according to item 1, wherein the unit (A) is a carbonate unit derived from spirobichroman.
7). 7. An optical film formed from the polycarbonate resin according to any one of 1 to 6 above.
8). 8. The optical film as described in 7 above, wherein the optical film is formed by a melt extrusion method.
9. 8. The optical film as described in 7 above, wherein the optical film is a retardation film formed by stretching an unstretched film.
10. 10. The optical film according to item 9, wherein retardation values R (450), R (550), and R (650) in the film plane at wavelengths of 450 nm, 550 nm, and 650 nm satisfy the following formulas (1) and (2).
0.60 ≦ R (450) / R (550) ≦ 1.00 (1)
1.01 ≦ R (650) / R (550) ≦ 1.40 (2)
11. A liquid crystal display device or organic EL display device comprising the optical film according to the item 10 above.

  The optical film of the present invention is composed of a polycarbonate copolymer resin having a low photoelastic constant, high transparency and excellent workability, has a desired wavelength dispersion by stretching treatment, and can be broadened with a single sheet. It is extremely useful as an optical film for liquid crystal display devices and organic EL displays.

It is explanatory drawing of the thermal nonuniformity evaluation of an Example.

Hereinafter, the present invention will be described in detail.
<Polycarbonate resin>
The present invention is formed from a polycarbonate resin containing units (A) and units (B).

(Unit (A))
The unit (A) is represented by the following formula.

In the unit (A), R ₁ and R ₂ each independently represent a hydrogen atom, a hydrocarbon group that may contain an aromatic group having 1 to 10 carbon atoms, or a halogen atom. As a hydrocarbon group, a C1-C10 alkyl group, a C5-C10 cycloalkyl group, a C6-C10 aryl group, a C7-C10 aralkyl group, a C1-C10 alkenyl group Is mentioned. Examples of the halogen atom include a fluorine atom, a chlorine atom, and a bromine atom. W represents a single bond, a carbon atom, an oxygen atom, or a sulfur atom.
Preferred examples of the compound for deriving the unit (A) include 6,6′-dihydroxy-3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane and spirobichroman.

(Unit (B))
The unit (B) is a carbonate unit derived from a diol compound that is an aliphatic diol compound and / or an alicyclic diol compound. Examples of the aliphatic diol compound and the alicyclic diol compound include diol compounds described in International Publication No. 2004/111106, International Publication No. 2011/021720, and diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, and the like. Examples include oxyalkylene glycols.

  Examples of the aliphatic diol compound include 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1.9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-n-butyl-2-ethyl- 1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 1,2-hexane glycol, 1,2-octyl glycol, 2-ethyl -1,3-hexanediol, 2,3-diisobutyl-1,3-propanediol, 2,2-diisoamyl-1,3-propanedio Le, 2-methyl-2-propyl-1,3-propanediol.

  Examples of the alicyclic diol compound include cyclohexanedimethanol, tricyclodecanedimethanol, adamantanediol, pentacyclopentadecanedimethanol, 3,9-bis (2-hydroxy-1,1-dimethylethyl) -2,4, Examples include 8,10-tetraoxaspiro [5.5] undecane, isosorbide, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, and the like.

The diol compound is preferably an alicyclic diol, and cyclohexane dimethanol, tricyclodecane dimethanol, 3,9-bis (2-hydroxy-1,1-dimethylethyl) -2,4,8,10-tetraoxa. Spiro [5.5] undecane and isosorbide are more preferable, and 3,9-bis (2-hydroxy-1,1-dimethylethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane and isosorbide 2,2,4,4-tetramethyl-1,3-cyclobutanediol is particularly preferred.
Moreover, it can also be set as a polyester carbonate partially by copolymerizing an acid component.

(Unit (C))
The unit (C) is a carbonate unit derived from a dihydroxy compound having a fluorene skeleton (some of which may include an ester unit).
As the unit (C), a carbonate unit represented by the following formula (C1) is preferably used.

In the unit (C1), R ₃ and R ₄ each independently represent a hydrogen atom, a hydrocarbon group that may contain an aromatic group having 1 to 10 carbon atoms, or a halogen atom. As a hydrocarbon group, a C1-C10 alkyl group, a C5-C10 cycloalkyl group, a C6-C10 aryl group, a C7-C10 aralkyl group, a C1-C10 alkenyl group Is mentioned. Examples of the halogen atom include a fluorine atom, a chlorine atom, and a bromine atom.

R ₅ and R ₆ each independently represent a hydrocarbon group that may contain an aromatic group having 1 to 10 carbon atoms. The hydrocarbon group is preferably an alkylene group having 1 to 10 carbon atoms, more preferably an alkylene group having 1 to 4 carbon atoms, and more preferably an ethylene group.
p and q represent the number of repetitions of — (R ₅ —O) — and — (O—R ₆ ) —, respectively. p and q are each independently an integer of 0 or more, preferably an integer of 0 to 20, more preferably an integer of 0 to 12, still more preferably an integer of 0 to 8, particularly preferably 0 to 4. And is most preferably 0 or 1.
m and n each independently represents an integer of 0 to 4.

（Ｒ_３およびＲ_４は単位（Ｃ１）と同じである。） (When p and q are 0)
When p and q are 0, the unit (C1) is represented by the following formula (hereinafter sometimes referred to as the unit (C1a)).

(R ₃ and R ₄ are the same as the unit (C1).)

  As the unit (C1a), 9,9-bis (4-hydroxyphenyl) fluorene, 9,9-bis (4-hydroxy-3-methylphenyl) fluorene, 9,9-bis (4-hydroxy-3-ethylphenyl) ) Fluorene, 9,9-bis (4-hydroxy-3-n-propylphenyl) fluorene, 9,9-bis (4-hydroxy-3-isopropylphenyl) fluorene, 9,9-bis (4-hydroxy-3) -N-butylphenyl) fluorene, 9,9-bis (4-hydroxy-3-sec-butylphenyl) fluorene, 9,9-bis (4-hydroxy-3-tert-butylphenyl) fluorene, 9,9- Bis (4-hydroxy-3-cyclohexylphenyl) fluorene, 9,9-bis (4-hydroxy-3-phenylphenyl) fluorene It includes units derived from alkylene and the like. The compound which derives these units (C1a) can be used alone or in combination of two or more.

In particular, a unit (C1a-i) represented by the following formula derived from 9,9-bis (4-hydroxy-3-methylphenyl) fluorene is preferable.

The polycarbonate copolymer containing the unit (C1a-i) has a b value measured by measuring a solution of 10 g in 50 ml of ethanol at an optical path length of 30 mm, preferably 6.0 or less, more preferably 5.5 or less, Preferably it is 5.0 or less. If this b value is in the above range, the optical film formed from the polycarbonate copolymer has good hue and high strength.
9,9-bis (4-hydroxy-3-methylphenyl) fluorene, which is a raw material of the unit (C1a-i), is obtained by a reaction of o-cresol and fluorenone. 9,9-bis (4-hydroxy-3-methylphenyl) fluorene having a small b value can be obtained by removing impurities.

  Specifically, after the reaction between o-cresol and fluorenone, unreacted o-cresol is distilled off, and the residue is dissolved in an alcohol, ketone, or benzene derivative solvent, and activated clay or activated carbon is added thereto. In addition, after filtration, the crystallized product from the filtrate can be filtered to obtain purified 9,9-bis (4-hydroxy-3-methylphenyl) fluorene. Examples of impurities to be removed include 2,4'-dihydroxy form, 2,2'-dihydroxy form, and impurities whose structure is unknown. As the alcohol solvent used for such purification, lower alcohols such as methanol, ethanol, propanol and butanol are preferred. As the ketone solvent, lower aliphatic ketones such as acetone, methyl ethyl ketone, methyl isopropyl ketone, cyclohexanone and mixtures thereof are preferable. As the benzene derivative solvent, toluene, xylene, benzene and a mixture thereof are preferable. The amount of the solvent used is sufficient if the fluorene compound is sufficiently dissolved, and is usually about 2 to 10 times the amount of the fluorene compound. As the activated clay, a commercially available powdery or granular silica-alumina main component is used. Further, as the activated carbon, commercially available powdery or granular materials are used.

（Ｒ_３、Ｒ_４、Ｒ_５、Ｒ_６、ｍおよびｎは単位（Ｃ１）と同じである。ｐおよびｑは、夫々独立して、１以上の整数である。） (When p and q are integers of 1 or more)
When p and q are integers of 1 or more, the unit (C1) is represented by the following formula (hereinafter sometimes referred to as the unit (C1b)).

(R ₃ , R ₄ , R ₅ , R ₆ , m and n are the same as in the unit (C1). P and q are each independently an integer of 1 or more.)

  As the unit (C1b), 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene, 9,9-bis [4- (3-hydroxypropoxy) phenyl] fluorene, 9,9-bis [4- (4-Hydroxybutoxy) phenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3-methylphenyl] fluorene, 9,9-bis [2- (2-hydroxyethoxy) -5-methyl Phenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3-ethylphenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3-propylphenyl] fluorene, 9, 9-bis [4- (2-hydroxyethoxy) -3-isopropylphenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy)- -N-butylphenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3-isobutylphenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3- (1- Methylpropyl) phenyl] fluorene, 9,9-bis [4- (3-hydroxypropoxy) -3-methylphenyl] fluorene, 9,9-bis [4- (4-hydroxybutoxy) -3-methylphenyl] fluorene 9,9-bis [4- (2-hydroxyethoxy) -3,5-dimethylphenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) -2,5-dimethylphenyl] fluorene, 9 , 9-bis [4- (2-hydroxyethoxy) -3,5-diethylphenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) 3,5-dipropylphenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3,5-diisopropylphenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3 , 5-Di-n-butylphenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3,5-diisobutylphenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3,5-bis (1-methylpropyl) phenyl] fluorene, 9,9-bis [4- (3-hydroxypropoxy) -3,5-dimethylphenyl] fluorene, 9,9-bis [4- (4 -Hydroxybutoxy) -3,5-dimethylphenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3-cyclohexylphenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3-phenylphenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3,5-diphenylphenyl] fluorene, 9,9- Bis [4- (2-hydroxyethoxy) -3-benzylphenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3,5-dibenzylphenyl] fluorene, 9,9-bis [4 -(2-hydroxyethoxy) -3-propenylphenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3-fluorophenyl] fluorene, and their 9,9-bis (hydroxyalkoxyphenyl) Examples include units derived from fluorene. Moreover, a unit derived from 9,9-bis [hydroxypoly (alkyleneoxy) phenyl] fluorene or the like in which p and q are 2 or more can be mentioned.

Of these, 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3-methylphenyl] fluorene} and the like are preferable.
In particular, a unit (C1b-i) derived from 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene (BPEF) represented by the following formula is preferred.

The compound which derives these units (C1b-i) can be used alone or in combination of two or more.
The compound for deriving the unit (C1b-i) is obtained by reacting 9,9-bis (hydroxyphenyl) fluorenes with compounds corresponding to the groups R ₃ and R ₄ (alkylene oxide, haloalkanol, etc.). It is done. For example, 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene is obtained by adding ethylene oxide to 9,9-bis (4-hydroxyphenyl) fluorene. 9,9-bis [4- (3-hydroxypropoxy) phenyl] fluorene is obtained, for example, by reacting 9,9-bis [4-hydroxyphenyl] fluorene with 3-chloropropanol under alkaline conditions. It is done. 9,9-bis (hydroxyphenyl) fluorene can be obtained by reaction of fluorenone (such as 9-fluorenone) with the corresponding phenol. 9,9-bis (4-hydroxyphenyl) fluorene can be obtained, for example, by reaction of phenol with 9-fluorenone.

As the unit (C), a carbonate unit represented by the following formula (C2) is also preferably used.

In the above formula (C2), R ₇ and R ₈ are each independently a direct bond, an optionally substituted alkylene group having 1 to 10 carbon atoms, or an optionally substituted arylene group having 4 to 10 carbon atoms. Or an optionally substituted aralkylene group having 6 to 10 carbon atoms, an optionally substituted alkylene group having 1 to 10 carbon atoms, an optionally substituted arylene group having 4 to 10 carbon atoms and a substituted group. Two or more groups selected from the group consisting of an optionally substituted aralkylene group having 6 to 10 carbon atoms are linked by an oxygen atom, an optionally substituted sulfur atom, an optionally substituted nitrogen atom or a carbonyl group a radicals, R ₉ is a direct bond, an optionally substituted alkylene group having 1 to 10 carbon atoms, an optionally substituted arylene group having 4 to 10 carbon atoms are also or optionally substituted An aralkylene group of 6 to 10 carbon _atoms, R 10 _{to R 11} are independently a hydrogen atom, an optionally substituted alkyl group having 1 to 10 carbon atoms, optionally carbon atoms 4 substituted 10 aryl groups, an optionally substituted acyl group having 1 to 10 carbon atoms, an optionally substituted alkoxy group having 1 to 10 carbon atoms, and an optionally substituted aryloxy group having 1 to 10 carbon atoms , An optionally substituted amino group, a sulfur atom having a substituent, a halogen atom, a nitro group, or a cyano group. u and v each independently represent an integer of 1 to 4, and w represents an integer of 1 to 5.

  Specific examples of the compound that derives the above formula (C2) include 9,9′-di (hydroxymethyl) -9,9′-bifluorenyl, bis (9-hydroxymethylfluoren-9-yl) methane, -Bis (9-hydroxymethylfluoren-9-yl) ethane, bis [9- (3-hydroxypropyl) -fluoren-9-yl] methane, bis {9- [2- (2-hydroxyethoxy) carbonylethyl] Fluoren-9-yl} methane, 9,9-bis [(9-hydroxymethylfluoren-9-yl) -methyl] fluorene, 1,2-bis [9- (3-hydroxypropyl) -fluoren-9-yl Ethane, α, α′-bis- (9-hydroxymethylfluoren-9-yl) -1,4-xylene, 1,2-bis (9-hydroxymethylfluorene- 9-yl) butane, 1-bis (9-hydroxymethylfluoren-9-yl) ethane, 1,2-bis (9-hydroxyfluoren-9-yl) ethane, bis-{[4- (2-hydroxyethoxy ) Phenyl] fluoren-9-yl} ethane is preferred.

As the unit (C), an ester unit represented by the following formula (C3) is also preferably used. In this case, it becomes a polyester carbonate.

In said formula (C3), R < ₇ > -R < ₁₁ >, u and v are synonymous with the said formula (C2), and X shows an aliphatic group or an alicyclic group.
Specific examples of the compound that derives the general formula (C3) include bis [9- (2-ethoxycarbonylethyl) fluoren-9-yl] methane, 1,2-bis [9- (2-ethoxycarbonylethyl). Fluoren-9-yl] ethane, 1,2-bis [9- (2-methoxycarbonylpropyl) fluoren-9-yl] ethane, bis [9- (2-methoxycarbonylethyl) fluoren-9-yl] methane, Bis [9- (2-phenoxycarbonylethyl) fluoren-9-yl] methane and 1,2-bis [9- (2-phenoxycarbonylethyl) fluoren-9-yl] ethane are preferred.

(composition)
In the polycarbonate resin used in the present invention, the main repeating unit includes the unit (A) and the unit (B), and the molar ratio (A / B) thereof is 5/95 to 95/5. A molar ratio (A / B) of 5/95 to 95/5 is preferred because the heat resistance is increased. The molar ratio (A / B) between the unit (A) and the unit (B) is preferably 5/95 to 85/15, more preferably 8/92 to 80/20. Within this composition range, reverse wavelength dispersion is preferable. A unit (C) can also be included. The molar ratio (A + B / C) is preferably 30/70 to 80/20. The molar ratio can be measured and calculated by proton NMR of JNM-AL400 manufactured by JEOL.
The main repeating unit is preferably 30 mol% or more, more preferably 50 mol% or more, still more preferably 60 mol% or more, based on the total repeating units, the sum of the units (A) and units (B). .

(Other units)
Examples of the diol compound for deriving other copolymerization structural units include aromatic dihydroxy compounds such as α, α′-bis (4-hydroxyphenyl) -m-diisopropylbenzene (bisphenol M), 9,9-bis ( 4-hydroxy-3-methylphenyl) fluorene, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane, 4,4′- Dihydroxy-3,3′-dimethyldiphenyl sulfide, bisphenol A, 2,2-bis (4-hydroxy-3-methylphenyl) propane (bisphenol C), 2,2-bis (4-hydroxyphenyl) -1,1 , 1,3,3,3-hexafluoropropane (bisphenol AF), and 1,1-bis (4- Hydroxyphenyl) decane and the like.
Moreover, it can also be made partially polyester carbonate by copolymerizing an acid component such as terephthalic acid.

(Specific viscosity: η _SP )
The specific viscosity (η _SP ) of the polycarbonate resin used in the present invention is 0.20 to 0.45. When the specific viscosity is 0.20 to 0.45, the strength and moldability are good. The specific viscosity (η _SP ) is preferably 0.25 to 0.40, more preferably 0.30 to 0.35.
If the specific viscosity of the polycarbonate resin of the present invention is less than 0.2, the strength of the injection-molded molded piece is lowered, and if it is greater than 0.45, the moldability during injection molding is lowered.
The specific viscosity referred to in the present invention is determined from an solution obtained by dissolving 0.7 g of polycarbonate resin in 100 ml of methylene chloride at 20 ° C. using an Ostwald viscometer.
Specific viscosity (η _SP ) = (t−t ₀ ) / t ₀
[T ₀ is methylene chloride falling seconds, t is sample solution falling seconds]

  In addition, as a specific measurement of specific viscosity, it can carry out in the following way, for example. First, the polycarbonate resin is dissolved in 20 to 30 times the weight of methylene chloride, and the soluble component is collected by celite filtration, and then the solution is removed and dried sufficiently to obtain a solid component soluble in methylene chloride. Using a Ostwald viscometer, the specific viscosity at 20 ° C. is determined from a solution of 0.7 g of the solid dissolved in 100 ml of methylene chloride.

<Glass transition temperature: Tg>
The glass transition temperature (Tg) of the polycarbonate resin used for the optical film of the present invention is preferably 70 to 180 ° C, more preferably 130 to 175 ° C, still more preferably 135 to 175 ° C, and particularly preferably 140 to 170 ° C. Range. When the glass transition temperature (Tg) is lower than 70 ° C., the heat resistance stability is inferior, and the retardation value may change over time and affect display quality. On the other hand, if the glass transition temperature (Tg) is higher than 180 ° C., the viscosity may be too high when melt film formation is attempted. The glass transition temperature (Tg) is measured at 29 ° C./min using a 2910 type DSC manufactured by TA Instruments Japan.

<Photoelastic constant>
The photoelastic constant of the polycarbonate resin used for the optical film of the present invention is preferably 40 × 10 ⁻¹² Pa ⁻¹ or less, more preferably 30 × 10 ⁻¹² Pa ⁻¹ or less, and further preferably 25 × 10 ^−12. Pa ⁻¹ or less, particularly preferably 20 × 10 ⁻¹² Pa ⁻¹ or less. When the absolute value is larger than 40 × 10 ⁻¹² Pa ⁻¹ , birefringence due to stress is large, and light leakage tends to occur when used as a retardation film. The photoelastic constant is measured using a Spectroellipometer M-220 manufactured by JASCO Corporation by cutting a test piece having a length of 50 mm and a width of 10 mm from the film.

(Production method of polycarbonate resin)
The polycarbonate resin can be produced by melt polymerization of a component containing a monomer that derives the unit (A) and the unit (B) and a carbonic acid diester.
Examples of the carbonic acid diester include esters such as an aryl group having 6 to 12 carbon atoms and an aralkyl group which may be substituted. Specific examples include diphenyl carbonate, ditolyl carbonate, bis (chlorophenyl) carbonate, and bis (m-cresyl) carbonate. Of these, diphenyl carbonate is particularly preferred.
The amount of diphenyl carbonate to be used is preferably 0.97 to 1.10 mol, more preferably 1.00 to 1.06 mol, per 1 mol of the total monomer components.

In the melt polymerization method, a polymerization catalyst can be used to increase the polymerization rate. Examples of the polymerization catalyst include alkali metal compounds, alkaline earth metal compounds, nitrogen-containing compounds, and metal compounds.
As such compounds, organic acid salts, inorganic salts, oxides, hydroxides, hydrides, alkoxides, quaternary ammonium hydroxides, and the like of alkali metals and alkaline earth metals are preferably used. It can be used alone or in combination.

  Examples of the alkali metal compound include 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, Sodium stearate, potassium stearate, cesium stearate, lithium stearate, sodium borohydride, sodium benzoate, potassium benzoate, cesium benzoate, lithium benzoate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, phosphorus Examples thereof include dilithium oxyhydrogen, disodium phenylphosphate, disodium salt of bisphenol A, dipotassium salt, cesium salt, dilithium salt, sodium salt of phenol, potassium salt, cesium salt, and lithium salt.

  Alkaline earth metal compounds include magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, magnesium diacetate, calcium diacetate, strontium diacetate, diacetate Barium etc. are mentioned.

Examples of nitrogen-containing compounds include quaternary ammonium hydroxides having alkyl, aryl groups, etc., such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and trimethylbenzylammonium hydroxide. Can be mentioned. Further, tertiary amines such as triethylamine, dimethylbenzylamine, and triphenylamine, and imidazoles such as 2-methylimidazole, 2-phenylimidazole, and benzimidazole can be used. Moreover, bases or basic salts such as ammonia, tetramethylammonium borohydride, tetrabutylammonium borohydride, tetrabutylammonium tetraphenylborate, tetraphenylammonium tetraphenylborate, and the like can be given. Examples of the metal compound include zinc aluminum compounds, germanium compounds, organotin compounds, antimony compounds, manganese compounds, titanium compounds, zirconium compounds and the like. These compounds may be used alone or in combination of two or more.
The amount of these polymerization catalysts used is preferably 1 × 10 ⁻⁹ to 1 × 10 ⁻² equivalent, preferably 1 × 10 ⁻⁸ to 1 × 10 ⁻⁵ equivalent, more preferably 1 ×, relative to 1 mol of the monomer component. It is selected in the range of 10 ⁻⁷ to 1 × 10 ⁻³ equivalents.

As conventionally known, the melt polycondensation reaction is carried out by distilling a monohydroxy compound produced by stirring under an inert gas atmosphere and under reduced pressure.
The reaction temperature is usually in the range of 120 to 350 ° C., and in the latter stage of the reaction, the monohydroxy compound formed by increasing the pressure reduction degree of the system to 10 to 0.1 Torr is facilitated to complete the reaction. You may add a terminal terminator, antioxidant, etc. as needed.

  In addition, a catalyst deactivator can be added at a later stage of the reaction. As the catalyst deactivator to be used, a known catalyst deactivator is effectively used. Among them, sulfonic acid ammonium salt and phosphonium salt are preferable. Furthermore, salts of dodecylbenzenesulfonic acid such as tetrabutylphosphonium salt of dodecylbenzenesulfonic acid and salts of paratoluenesulfonic acid such as tetrabutylammonium salt of paratoluenesulfonic acid are preferable.

Further, as esters of sulfonic acid, methyl benzenesulfonate, ethyl benzenesulfonate, butyl benzenesulfonate, octyl benzenesulfonate, phenyl benzenesulfonate, methyl paratoluenesulfonate, ethyl paratoluenesulfonate, butyl paratoluenesulfonate, Octyl paratoluenesulfonate, phenyl paratoluenesulfonate and the like are preferably used. Among these, dodecylbenzenesulfonic acid tetrabutylphosphonium salt is most preferably used. The amount of the catalyst deactivator used is preferably 0.5 to 50 mol per mol of the catalyst when at least one polymerization catalyst selected from alkali metal compounds and / or alkaline earth metal compounds is used. It can be used in a proportion, more preferably in a proportion of 0.5 to 10 mol, still more preferably in a proportion of 0.8 to 5 mol.
In addition, heat stabilizers, plasticizers, light stabilizers, polymerized metal deactivators, flame retardants, lubricants, antistatic agents, surfactants, antibacterial agents, ultraviolet absorbers, release agents, etc. Additives can be blended.

<Optical film>
The optical film of the present invention will be described. This optical film is a film used for optical applications. Specifically, a retardation film, a plastic substrate film, a polarizing plate protective film, an antireflection film, a brightness enhancement film, an optical disk protective film, a diffusion film, and the like can be given. In particular, a retardation film, a polarizing plate protective film, and an antireflection film are preferable.
Examples of the method for producing an optical film include known methods such as a solution casting method, a melt extrusion method, a hot pressing method, and a calendar method. As a method for producing the optical film of the present invention, a solution casting method and a melt extrusion method are preferable, and a melt extrusion method is particularly preferable from the viewpoint of productivity.

  In the melt extrusion method, a method of extruding a resin using a T die and feeding it to a cooling roll is preferably used. The temperature at this time is determined from the molecular weight, Tg, melt flow characteristics, etc. of the polycarbonate copolymer, but is in the range of 180 to 350 ° C, more preferably in the range of 200 to 320 ° C. When the temperature is lower than 180 ° C., the viscosity is increased, and the orientation and stress strain of the polymer tend to remain, which is not preferable. On the other hand, when the temperature is higher than 350 ° C., problems such as thermal deterioration, coloring, and die line (stripe) from the T-die are likely to occur.

  In addition, since the polycarbonate resin used in the present invention has good solubility in an organic solvent, a solution casting method can also be applied. In the case of the solution casting method, methylene chloride, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, dioxolane, dioxane and the like are preferably used as the solvent. The amount of residual solvent in the film used in the solution casting method is preferably 2% by weight or less, more preferably 1% by weight or less. If it exceeds 2% by weight, if the residual solvent is large, the glass transition temperature of the film is remarkably lowered, which is not preferable from the viewpoint of heat resistance.

As thickness of the unstretched optical film of this invention, the range of 20-400 micrometers is preferable, More preferably, it is the range of 20-300 micrometers. When such a film is further stretched to obtain a retardation film, it may be appropriately determined within the above range in consideration of a desired retardation value and thickness of the optical film.
The unstretched optical film thus obtained is stretched and oriented to form a retardation film. As the stretching method, a known method such as longitudinal uniaxial stretching, lateral uniaxial stretching using a tenter or the like, or simultaneous biaxial stretching or sequential biaxial stretching in combination thereof can be used. Moreover, although it is preferable from a point of productivity to perform continuously, you may carry out by a batch type. The stretching temperature is preferably in the range of (Tg-20 ° C) to (Tg + 50 ° C), more preferably (Tg-10 ° C) to (Tg + 30 ° C) with respect to the glass transition temperature (Tg) of the polycarbonate copolymer. It is a range. This temperature range is preferable because the molecular motion of the polymer is moderate, relaxation due to stretching is unlikely to occur, orientation is easily suppressed, and a desired Re value is easily obtained.

  Although the draw ratio is determined by the target retardation value, it is 1.05 to 5 times, more preferably 1.1 to 4 times in the vertical and horizontal directions, respectively. This stretching may be performed in a single stage or in multiple stages. In addition, said Tg in the case of extending | stretching the film obtained by the solution cast method means the glass transition temperature containing the trace amount solvent in this film.

(Thickness etc.)
The thickness of the optical film of the present invention is preferably in the range of 20 to 200 μm, more preferably 20 to 150 μm. If it is this range, the desired phase difference value by extending | stretching will be easy to obtain, and film forming will be easy and preferable.
The optical film of the present invention has a low photoelastic constant of the polycarbonate resin constituting it. Therefore, the change of the phase difference with respect to the stress is small, and the liquid crystal display device provided with such a retardation film has excellent display stability.
Moreover, the optical film of the present invention has high transparency. The total light transmittance of the optical film of the present invention having a thickness of 100 μm is preferably 85% or more, more preferably 88% or more. The haze value of the optical film of the present invention is preferably 5% or less, more preferably 3% or less.

(Wavelength dispersion)
By stretching an unstretched film using the polycarbonate resin used in the present invention, in the visible light region having a wavelength of 400 to 800 nm, the reverse wavelength dispersibility becomes smaller as the retardation in the film surface becomes shorter. An optical film can be obtained. Such a stretched retardation film preferably satisfies the conditions of the following formulas (1) and (2).
0.60 <R (450) / R (550) <1.00 (1)
1.01 <R (650) / R (550) <1.40 (2)
Preferably, the conditions of the following formulas (1-1) and (2-1) are satisfied.
0.65 <R (450) / R (550) <0.92 (1-1)
1.02 <R (650) / R (550) <1.35 (2-1)
More preferably, the conditions of the following formulas (1-2) and (2-2) are satisfied.
0.70 <R (450) / R (550) <0.90 (1-2)
1.03 <R (650) / R (550) <1.30 (2-2)
More preferably, the conditions of the following formulas (1-3) and (2-3) are satisfied.
0.70 <R (450) / R (550) <0.89 (1-3)
1.03 <R (650) / R (550) <1.20 (2-3)
Particularly preferably, the conditions of the following formulas (1-4) and (2-4) are satisfied.
0.70 <R (450) / R (550) <0.88 (1-4)
1.03 <R (650) / R (550) <1.10 (2-4)
Most preferably, the conditions of the following formulas (1-5) and (2-5) are satisfied.
0.70 <R (450) / R (550) <0.87 (1-5)
1.03 <R (650) / R (550) <1.10 (2-5)

Here, the in-plane retardation value R is defined by the following equation, and is a characteristic that expresses a phase delay between the X direction of light transmitted through the film in the vertical direction and the vertical Y direction.
_{R = (n x -n y)} × d
Where _nx is the refractive index in the main stretching direction in the film plane, _ny is the refractive index in the direction perpendicular to the main stretching direction in the film plane, and d is the thickness of the film. Here, the main stretching direction means a stretching direction in the case of uniaxial stretching, and a direction in which the degree of orientation is increased in the case of biaxial stretching. Refers to the orientation direction.

Moreover, it is preferable that retardation value R (550) in the film plane in wavelength 550nm of an optical film is R (550)> = 50nm. A single optical film can be used as a broadband λ / 4 plate or λ / 2 plate without being laminated. In such applications, it is further desirable that 100 nm ≦ R (550) ≦ 180 nm for the λ / 4 plate and 220 nm ≦ R (550) ≦ 330 nm for the λ / 2 plate.
The wavelength dispersibility of the optical film is measured using Spectroellipometer M-220 manufactured by JASCO Corporation.

  The optical film of the present invention can be suitably used particularly as a retardation film. The present invention includes an image display device (a liquid crystal display device or an organic EL display device) provided with the retardation film. In this invention, it is set as the circularly-polarizing film which consists of the said retardation film and a polarizing layer, and this can be used conveniently as an antireflection film. The retardation film can be suitably used as a polarizing plate protective film or an optical compensation film for an image display device.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to this. In the examples, “parts” means “parts by weight”. The resins used and the evaluation methods used in the examples are as follows.

1. Polymer composition ratio (NMR)
Measurement was performed by proton NMR of JNM-AL400 manufactured by JEOL Ltd., and the polymer composition ratio was calculated.

2. Specific viscosity The viscosity was determined using an Ostwald viscometer from a solution of 0.7 g of polycarbonate resin in 100 ml of methylene chloride at 20 ° C.
Specific viscosity (η _SP ) = (t−t ₀ ) / t ₀
[T ₀ is methylene chloride falling seconds, t is sample solution falling seconds]

3. Tg (glass transition temperature)
A 2910 type DSC manufactured by TA Instruments Japan Co., Ltd. was used, and measurement was performed at a temperature rising rate of 20 ° C./min in a nitrogen atmosphere.

4). Photoelastic constant A test piece having a length of 50 mm and a width of 10 mm was cut out from the film, and the photoelastic constant was measured using Spectroellipometer M-220 manufactured by JASCO Corporation.

5. Phase difference, wavelength dispersibility A test piece having a length of 100 mm and a width of 70 mm was cut out from the film, and longitudinally stretched 2.0 times at a stretching temperature of Tg + 10 ° C., and the center portion of the obtained film was Spectroellipometer M manufactured by JASCO Corporation. -220 was used to measure retardation wavelength dispersion.

6). Evaluation of thermal unevenness A linear polarizing plate with a structure in which a polarizer film in which iodine is adsorbed and oriented on polyvinyl alcohol is sandwiched between two triacetyl cellulose films and an acrylic pressure-sensitive adhesive layer is provided on one side is prepared. did. The stretched film prepared in the example was subjected to corona discharge treatment under the condition of an integrated irradiation amount of 1500 J, and the corona discharge treatment surface was bonded to the linear polarizing plate at an angle of 45 ° to the acrylic pressure-sensitive adhesive layer side. Two polarizing plates were prepared and bonded to non-alkali glass (Corning Japan, trade name: EAGLE2000) through an adhesive as shown in FIG. When the configured circularly polarizing plate is stored at 90 ° C. for 240 minutes, the light leakage of the transmitted light when the backlight is applied is visually evaluated. If there is no light leakage, ○, the light leakage is observed as a whole. X.

[Example 1]
<Manufacture of polycarbonate copolymer>
6,6′-dihydroxy-3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane (hereinafter sometimes abbreviated as “SBI”) 72.5 parts, 3,9-bis (2 -Hydroxy-1,1-dimethylethyl) -2,4,8,10-tetraoxaspiro (5.5) undecane (hereinafter abbreviated as SPG) 47.7 parts, diphenyl carbonate 85.7 parts and tetramethyl as catalyst 1.8 × 10 ⁻² parts of ammonium hydroxide and 1.6 × 10 ⁻⁴ parts of sodium hydroxide were heated to 180 ° C. in a nitrogen atmosphere and melted. Thereafter, the degree of vacuum was adjusted to 13.4 kPa over 30 minutes. Thereafter, the temperature was raised to 260 ° C. at a rate of 20 ° C./hr, held at that temperature for 10 minutes, and then the degree of vacuum was set to 133 Pa or less over 1 hour. The reaction was carried out under stirring for a total of 6 hours.
After completion of the reaction, 4 times mole of the catalyst amount of tetrabutylphosphonium salt of dodecylbenzene sulfonate is added to deactivate the catalyst, then discharged from the bottom of the reaction tank under nitrogen pressure, cut with a pelletizer while cooling in the water tank. To obtain pellets.
<Manufacture of optical film>
Next, by attaching a T-die having a width of 150 mm and a lip width of 500 μm and a film take-up device to a 15φ biaxial extrusion kneader manufactured by Technobel Co., Ltd., and melt-extruding the obtained polycarbonate copolymer at 290 ° C. to form a film A transparent extruded film was obtained. The evaluation results are shown in Table 1.

[Example 2]
<Manufacture of polycarbonate copolymer resin>
Except for using 60.4 parts of SBI and 59.6 parts of SPG, the same operation as in Example 1 was performed to obtain an aliphatic aromatic polycarbonate copolymer.
<Manufacture of optical film>
Next, a film was prepared in the same manner as in Example 1. The evaluation results are shown in Table 1.

[Example 3]
<Manufacture of polycarbonate copolymer resin>
Except for using 48.3 parts of SBI and 71.5 parts of SPG, the same operation as in Example 1 was performed to obtain an aliphatic aromatic polycarbonate copolymer.
<Manufacture of optical film>
Next, a film was prepared in the same manner as in Example 1. The evaluation results are shown in Table 1.

[Example 4]
<Manufacture of polycarbonate copolymer resin>
Except for using 17.2 parts of 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene (hereinafter abbreviated as BPEF), 48.3 parts of SBI, and 59.6 parts of SPG, the same as Example 1 was used. Operation was performed to obtain an aliphatic aromatic polycarbonate copolymer.
<Manufacture of optical film>
Next, a film was prepared in the same manner as in Example 1. The evaluation results are shown in Table 1.

[Example 5]
<Manufacture of polycarbonate copolymer resin>
Except for using 44.5 parts of 9,9-bis (4-hydroxy-3-methylphenyl) fluorene (hereinafter abbreviated as BCF), 12.1 parts of SBI, and 71.5 parts of SPG, the same operation as in Example 1 was performed. To obtain an aliphatic aromatic polycarbonate copolymer.
<Manufacture of optical film>
Next, a film was prepared in the same manner as in Example 1. The evaluation results are shown in Table 1.

[Example 6]
<Manufacture of polycarbonate copolymer resin>
Except that 28.6 parts of isosorbide (hereinafter abbreviated as ISS), 24.2 parts of SBI, and 44.5 parts of BPEF were used, the same operation as in Example 1 was performed to obtain an aliphatic aromatic polycarbonate copolymer.
<Manufacture of optical film>
Next, a film was prepared in the same manner as in Example 1. The evaluation results are shown in Table 1.

[Example 7]
<Manufacture of polycarbonate copolymer resin>
Except for using 80 parts of spirobichroman (hereinafter abbreviated as SBC) and 22.9 parts of SPG, the same operation as in Example 1 was performed to obtain an aliphatic aromatic polycarbonate copolymer.
<Manufacture of optical film>
Next, a film was prepared in the same manner as in Example 1. The evaluation results are shown in Table 1.

[Comparative Example 1]
<Manufacture of polycarbonate copolymer resin>
Except for using 86.0 parts of BPEF and 28.6 parts of ISS, the same operation as in Example 1 was performed to obtain an aliphatic aromatic polycarbonate copolymer.
<Manufacture of optical film>
Next, a film was prepared in the same manner as in Example 1. The evaluation results are shown in Table 1. As a result of thermal unevenness evaluation, color loss due to thermal unevenness caused by the photoelastic coefficient occurred.

[Comparative Example 2]
<Manufacture of polycarbonate copolymer resin>
Except for using 50.4 parts of BCF and 37.8 parts of ISS, the same operation as in Example 1 was performed to obtain an aliphatic aromatic polycarbonate copolymer.
<Manufacture of optical film>
Next, a film was produced in the same manner as in Example 1. However, since Tg was too high, the resin was decomposed and foaming occurred, and the quality as an optical film was not satisfied.

[Comparative Example 3]
<Manufacture of polycarbonate copolymer resin>
Except for using 86 parts of BPEF and 59.6 parts of SPG, the same operation as in Example 1 was performed to obtain an aliphatic aromatic polycarbonate copolymer.
<Manufacture of optical film>
Next, a film was prepared in the same manner as in Example 1. The evaluation results are shown in Table 1. As a result of thermal unevenness evaluation, color loss due to thermal unevenness occurred due to low heat resistance.

  The optical film of the present invention is useful as an optical film for liquid crystal display devices and organic EL displays.

1. Polarizing plate 2. Stretched film Inorganic glass Stretched film 5. Polarizer

Claims (11)

Unit represented by the following formula (A)

[Wherein, R ₁ and R ₂ each independently represent a hydrogen atom, a hydrocarbon group which may contain an aromatic group having 1 to 10 carbon atoms, or a halogen atom. W represents a single bond, a carbon atom, an oxygen atom, or a sulfur atom. ]
And a carbonate unit (B) derived from an aliphatic diol compound and / or an alicyclic diol compound, the molar ratio (A / B) of the unit (A) to the unit (B) is 5/95 to 95 / 5, a polycarbonate resin having a specific viscosity of 0.20 to 0.45 measured with a 20 ° C. methylene chloride solution.   The polycarbonate resin according to claim 1, wherein the glass transition temperature of the polycarbonate resin is 70C to 180C. The polycarbonate resin according to claim 1, wherein the photoelastic constant of the polycarbonate resin is 40 × 10 ⁻¹² Pa ⁻¹ or less.   The polycarbonate resin according to claim 1, further comprising a carbonate unit (C) derived from a dihydroxy compound having a fluorene skeleton.   The polycarbonate resin according to claim 1, wherein the unit (A) is a carbonate unit derived from 6,6'-dihydroxy-3,3,3 ', 3'-tetramethyl-1,1'-spirobiindane.   The polycarbonate resin according to claim 1, wherein the unit (A) is a carbonate unit derived from spirobichroman.   The optical film formed from the polycarbonate resin in any one of Claims 1-6.   The optical film according to claim 7, wherein the optical film is formed by a melt extrusion method.   The optical film according to claim 7, wherein the optical film is a retardation film formed by stretching an unstretched film. The optical film according to claim 9, wherein retardation values R (450), R (550), and R (650) in the film plane at wavelengths of 450 nm, 550 nm, and 650 nm satisfy the following formulas (1) and (2): .
0.60 ≦ R (450) / R (550) ≦ 1.00 (1)
1.01 ≦ R (650) / R (550) ≦ 1.40 (2)   A liquid crystal display device or an organic EL display device comprising the optical film according to claim 10.

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