JP2020090677A - Polycarbonate resin and optical film - Google Patents

Abstract

To provide a polycarbonate resin having wavelength dispersion characteristics close to an ideal wide range, high retardation developability, low photoelasticity and excellent melt processability, and an optical film made of the resin.SOLUTION: The polycarbonate resin comprises a carbonate unit (A) derived from 6,6'-dihydroxy-3,3,3',3'-tetramethyl-1,1'-spirobiindane and a carbonate unit (B) derived from isosorbide, in which a molar ratio (A/B) of the unit (A) to the unit (B) is 5/95 to 95/5, and the resin shows a relative viscosity of 0.20 to 0.45 measured in a methylene chloride solution at 20°C.SELECTED DRAWING: None

Description

TECHNICAL FIELD 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 from the same.

Generally, an optical film, especially a retardation film is used for a display device such as a liquid crystal display device and has functions such as color compensation, widening of a viewing angle, and antireflection.

As the retardation film, λ/4 plate and λ/2 plate are known, and as the material thereof, a thermoplastic polymer such as polycarbonate in which bisphenol A is polycondensed, polyether sulfone, or polysulfone is used. The λ/4 plate and the λ/2 plate obtained by stretching the film of these materials have a property that the retardation becomes larger as the wavelength becomes shorter. Therefore, there is a problem that the wavelength that can function as a λ/4 plate or a λ/2 plate is limited to a specific wavelength.

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 dependence of retardation are laminated at a specific angle to manufacture. (For example, refer to Patent Document 1) In these cases, since a plurality of retardation films are used, a step of laminating them or adjusting a laminating angle is necessary, which causes a problem in productivity. Further, since the thickness of the entire retardation film becomes large, there is a problem that the light transmittance is lowered, and becomes thicker or darker when incorporated into the device.

In recent years, a method has been proposed in which the band is widened by a single film without such lamination (see Patent Document 2). The film is a method of stretching a polymer film composed of a polymer monomer unit having a positive refractive index anisotropy and a polymer monomer unit having a negative refractive index anisotropy. However, since the film specifically disclosed has a high photoelastic constant, there is a problem that the birefringence due to stress is large and light leakage occurs when it is used as a retardation film. Further, since an aromatic polycarbonate having a fluorene-based bisphenol skeleton is used, there is a problem that when melt processing, the melting temperature is high and a gel substance is apt to be generated due to decomposition. Also. Since it has a high Tg (glass transition temperature), it requires a high temperature for stretching processing of the film, and requires special processing equipment different from the conventional ones, but the workability is not always sufficient. Absent.

As a film capable of being melt-formed 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 and the like using a polycarbonate copolymer of -(2-hydroxyethoxy)phenyl]fluorene and isosorbide have been reported (see Patent Documents 3 and 4). Further, although a retardation film using a polycarbonate copolymer containing spirobiindane has been reported, it has a high photoelastic constant and does not describe wavelength dispersion (see Patent Document 5).

JP-A-02-120804 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 wavelength dispersion characteristics close to an ideal broadband, high retardation expression, low photoelasticity, and excellent melt processability, and an optical film formed from the same. is there.

As a result of earnest studies aimed at achieving such an object, the present inventors have found that by using a specific monomer in combination, a film made of a polycarbonate resin obtained has an inverse wavelength dispersion close to an ideal wide band, 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.

A carbonate unit (A) derived from 1.6,6′-dihydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobiindane and a carbonate unit (B) derived from isosorbide The molar ratio (A/B) of the unit (A) and the unit (B) is 5/95 to 95/5, and the specific viscosity measured from a methylene chloride solution at 20° C. is 0.20 to 0. 45 polycarbonate resin.

2. The polycarbonate resin according to item 1 above, 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} polycarbonate resin has a photoelastic constant of 40×10 ⁻¹² Pa ⁻¹ or less.

4. The polycarbonate resin according to item 1, further comprising a carbonate unit (C) derived from a dihydroxy compound having a fluorene skeleton.

5. An optical film formed from the polycarbonate resin according to any one of items 1 to 4.

6. The optical film according to the above item 5, wherein the optical film is formed by a melt extrusion method.

7. 6. The optical film according to item 5, which is a retardation film formed by stretching an unstretched film.

8. The optical film as described in 7 above, wherein the in-plane retardation values R(450), R(550), and R(650) 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)

9. A liquid crystal display device or an organic EL display device comprising the optical film according to the above item 8.

The optical film of the present invention is composed of a polycarbonate copolymer resin having a low photoelastic constant, high transparency and excellent processability, has a desired wavelength dispersibility by a stretching treatment, and can be used for a wide band with one sheet. And is extremely useful as an optical film for liquid crystal display devices, organic EL displays, and the like.

It is explanatory drawing of the heat 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 which may contain an aromatic group having 1 to 10 carbon atoms, or a halogen atom. As the hydrocarbon group, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aralkyl group having 7 to 10 carbon atoms, and an alkenyl group having 1 to 10 carbon atoms. 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 that induces 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 which 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 pamphlet and International Publication No. 2011/021720 pamphlet, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol and the like. Oxyalkylene glycols may be mentioned.

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-propanediol, 2-methyl-2-propyl-1,3-propanediol, etc. Can be mentioned.

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 cyclohexanedimethanol, tricyclodecanedimethanol, 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 are preferred. , 2,2,4,4-Tetramethyl-1,3-cyclobutanediol is particularly preferred.
Further, a polyester carbonate can be partially formed by copolymerizing an acid component.

(Unit (C))
The unit (C) is a carbonate unit (which may partially include an ester unit) derived from a dihydroxy compound having a fluorene skeleton.
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 which may contain an aromatic group having 1 to 10 carbon atoms, or a halogen atom. As the hydrocarbon group, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aralkyl group having 7 to 10 carbon atoms, and an alkenyl group having 1 to 10 carbon atoms. 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 which 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 are each - _(R 5 -O) - and - _{(O-R 6)} - represents the number of repetitions of. p and q are each independently an integer of 0 or more, preferably an integer of 0-20, more preferably an integer of 0-12, even more preferably an integer of 0-8, particularly preferably 0-4. Is an integer, most preferably 0 or 1.
m and n each independently represent an integer of 0 to 4.

(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 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- Examples include units derived from bis(4-hydroxy-3-cyclohexylphenyl)fluorene, 9,9-bis(4-hydroxy-3-phenylphenyl)fluorene and the like. The compounds that induce these units (C1a) can be used alone or in combination of two or more kinds.

Particularly, 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 of a solution of 10 g dissolved in 50 ml of ethanol measured with an optical path length of 30 mm, preferably 6.0 or less, more preferably 5.5 or less, It is preferably 5.0 or less. When this b value is within the above range, the optical film formed from the polycarbonate copolymer has a 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 the 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 of o-cresol and fluorenone, the unreacted o-cresol is distilled off, and the residue is dissolved in an alcohol-based, ketone-based or benzene-derivative solvent, and activated clay or activated carbon is added thereto. In addition, after filtration, the product crystallized from the filtrate can be filtered to obtain purified 9,9-bis(4-hydroxy-3-methylphenyl)fluorene. Impurities to be removed include 2,4'-dihydroxy body, 2,2'-dihydroxy body and impurities of unknown structure. As the alcohol solvent used for such purification, lower alcohols such as methanol, ethanol, propanol and butanol are preferable. As the ketone-based solvent, lower aliphatic ketones such as acetone, methyl ethyl ketone, methyl isopropyl ketone, cyclohexanone and the like and mixtures thereof are preferable. As the benzene derivative-based solvent, toluene, xylene, benzene and a mixture thereof are preferable. The solvent may be used in an amount sufficient to dissolve the fluorene compound, and is usually about 2 to 10 times the amount of the fluorene compound. As the activated clay, a commercially available powdery or granular material containing silica-alumina as a main component is used. Further, as the activated carbon, commercially available powdery or granular ones are used.

(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 unit (C1b)).

(R ₃ , R ₄ , R ₅ , R ₆ , m and n are the same as 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)-3-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-hydroxy) Ethoxy)-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)s Examples include units derived from fluorene. Further, 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.

Particularly, a unit (C1b-i) derived from 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene (BPEF) represented by the following formula is preferable.

The compounds that induce these units (C1b-i) can be used alone or in combination of two or more kinds.

The compound deriving the unit (C1b-i) is obtained by reacting 9,9-bis(hydroxyphenyl)fluorene with a compound (alkylene oxide, haloalkanol, etc.) corresponding to the groups R ₃ and R _4. Be done. For example, 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene can be obtained by adding ethylene oxide to 9,9-bis(4-hydroxyphenyl)fluorene. 9,9-bis[4-(3-hydroxypropoxy)phenyl]fluorene can be obtained, for example, by reacting 9,9-bis[4-hydroxyphenyl]fluorene with 3-chloropropanol under alkaline conditions. Be done. Note that 9,9-bis(hydroxyphenyl)fluorene can be obtained by reacting fluorenone (9-fluorenone or the like) with a corresponding phenol. 9,9-bis(4-hydroxyphenyl)fluorene can be obtained, for example, by reacting phenol with 9-fluorenone.

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

In the 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, or 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 optionally substituted aralkylene groups 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, optionally substituted arylene group having 4 to 10 carbon atoms, or optionally substituted It is an aralkylene group having 6 to 10 carbon atoms, and R _{10 to} R ₁₁ are each independently a hydrogen atom, an optionally substituted alkyl group having 1 to 10 carbon atoms, or an optionally substituted carbon atom of 4 to 10 10 aryl groups, optionally substituted C 1-10 acyl groups, optionally substituted C 1-10 alkoxy groups, optionally substituted C 1-10 aryloxy groups , 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 value 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, 1,2. -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-hydroxymethylfluoren-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 polyester carbonate.

In the above formula (C3), R _{7 to} R ₁₁ , u and v have the same meaning as in the above formula (C2), and X represents an aliphatic group or an alicyclic group].
Specific examples of the compound for deriving the general formula (C3) include bis[9-(2-ethoxycarbonylethyl)fluoren-9-yl]methane and 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)
The polycarbonate resin used in the present invention has a main repeating unit containing a unit (A) and a unit (B), and their molar ratio (A/B) is 5/95 to 95/5. When the molar ratio (A/B) is 5/95 to 95/5, the heat resistance is high, which is preferable. The molar ratio (A/B) of the unit (A) and the unit (B) is preferably 5/95 to 85/15, more preferably 8/92 to 80/20. In the range of this composition, reverse wavelength dispersibility is obtained, which is preferable. It may also contain units (C). 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 Ltd.

The main repeating unit means that the total of the units (A) and the units (B) is preferably 30 mol% or more, more preferably 50 mol% or more, still more preferably 60 mol% or more, based on all repeating units. ..

(Other units)
Examples of the diol compound for deriving the other copolymerization structural unit include aromatic dihydroxy compounds, and 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.

Further, a polyester carbonate can be partially formed by copolymerizing an acid component such as terephthalic acid.

(Specific viscosity: η _SP )
The polycarbonate resin used in the present invention has a specific viscosity (η _SP ) of 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.

When the specific viscosity of the polycarbonate resin of the present invention is less than 0.2, the strength of the injection-molded molded piece decreases, while when it is more than 0.45, the moldability during injection molding decreases.

The specific viscosity referred to in the present invention is obtained from a solution of 0.7 g of polycarbonate resin dissolved 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 the number of seconds of methylene chloride drop, t is the number of seconds of drop of sample solution]
The specific viscosity can be measured in the following manner, for example. First, the polycarbonate resin is dissolved in 20 to 30 times its weight of methylene chloride, and the soluble component is collected by filtration through Celite, and then the solution is removed and sufficiently dried to obtain a solid component of the methylene chloride soluble component. The specific viscosity at 20° C. of a solution prepared by dissolving 0.7 g of this solid in 100 ml of methylene chloride is determined using an Ostwald viscometer.

<Glass transition temperature: Tg>
The glass transition temperature (Tg) of the polycarbonate resin used in the optical film of the present invention is preferably 70 to 180°C, more preferably 130 to 175°C, further preferably 135 to 175°C, and particularly preferably 140 to 170°C. The range is. When the glass transition temperature (Tg) is lower than 70° C., the heat resistance stability may be poor, and the retardation value may change with time to affect the display quality. Further, if the glass transition temperature (Tg) is higher than 180° C., the viscosity may be too high and it may be difficult to perform melt film formation. The glass transition temperature (Tg) is measured by using a 2910 type DSC manufactured by TA Instruments Japan Co., Ltd. at a temperature rising rate of 20° C./min.

<Photoelastic constant>
The photoelastic constant of the polycarbonate resin used in 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, 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 , the birefringence due to stress is large and light leakage easily occurs when used as a retardation film. The photoelastic constant is measured by cutting out a test piece having a length of 50 mm and a width of 10 mm from the film and using a spectroscopic instrument M-220 manufactured by JASCO Corporation.

(Method for producing polycarbonate resin)
The polycarbonate resin can be produced by melt-polymerizing a component containing a monomer that induces the unit (A) and the unit (B) and a carbonic acid diester.

Examples of the carbonic acid diester include an optionally substituted ester such as an aryl group having 6 to 12 carbon atoms and an aralkyl group. Specific examples include diphenyl carbonate, ditolyl carbonate, bis(chlorophenyl)carbonate and bis(m-cresyl)carbonate. Of these, diphenyl carbonate is particularly preferable.

The amount of diphenyl carbonate used is preferably 0.97 to 1.10 mol, and more preferably 1.00 to 1.06 mol, based on 1 mol of the total of the monomer components.

Further, in the melt polymerization method, a polymerization catalyst can be used in order to accelerate the polymerization rate, and examples of such a polymerization catalyst include an alkali metal compound, an alkaline earth metal compound, a nitrogen-containing compound and a metal compound.

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, and these compounds are They can be used alone or in combination.

As the alkali metal compound, sodium hydroxide, potassium hydroxide, cesium hydroxide, lithium hydroxide, sodium hydrogen carbonate, 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 Dilithium oxyhydrogen, disodium phenylphosphate, disodium salt of bisphenol A, 2 potassium salt, 2 cesium salt, 2 lithium salt, sodium salt of potassium, potassium salt, cesium salt, lithium salt and the like.

As the alkaline earth metal compound, magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, magnesium diacetate, calcium diacetate, strontium diacetate, diacetate Examples include barium.

Examples of the nitrogen-containing compound include quaternary ammonium hydroxides having alkyl or aryl groups 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 mentioned. Further, bases or basic salts such as ammonia, tetramethylammonium borohydride, tetrabutylammonium borohydride, tetrabutylammonium tetraphenylborate, tetraphenylammonium tetraphenylborate, etc. may be mentioned. Examples of the metal compound include a zinc aluminum compound, a germanium compound, an organic tin compound, an antimony compound, a manganese compound, a titanium compound and a zirconium compound. 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 equivalents, preferably 1×10 ⁻⁸ to 1×10 ⁻⁵ equivalents, and more preferably 1×, relative to 1 mol of the monomer component. It is selected within the range of 10 ⁻⁷ to 1×10 ⁻³ equivalent.

The melt polycondensation reaction is carried out by distilling off the monohydroxy compound produced by stirring under heating in an inert gas atmosphere and under reduced pressure as is conventionally known.

The reaction temperature is usually in the range of 120 to 350° C., and in the latter stage of the reaction, the degree of vacuum of the system is increased to 10 to 0.1 Torr to facilitate the distilling of the produced monohydroxy compound to complete the reaction. You may add a terminal terminator, an antioxidant, etc. as needed.

A catalyst deactivator can also be added in the latter stage of the reaction. As the catalyst deactivator used, known catalyst deactivators are effectively used, and among these, ammonium salts and phosphonium salts of sulfonic acid are preferable. Further, 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 benzene sulfonate, ethyl benzene sulfonate, butyl benzene sulfonate, octyl benzene sulfonate, phenyl benzene sulfonate, methyl paratoluene sulfonate, ethyl paratoluene sulfonate, butyl paratoluene sulfonate, Octyl paratoluenesulfonate, phenyl paratoluenesulfonate and the like are preferably used. Among them, dodecylbenzenesulfonic acid tetrabutylphosphonium salt is most preferably used. When at least one polymerization catalyst selected from alkali metal compounds and/or alkaline earth metal compounds is used, the amount of these catalyst deactivators is preferably 0.5 to 50 mol per mol of the catalyst. A ratio of 0.5 to 10 mol is more preferable, and a ratio of 0.8 to 5 mol is more preferable.

In addition, heat stabilizers, plasticizers, light stabilizers, metal deactivators, flame retardants, lubricants, antistatic agents, surfactants, antibacterial agents, ultraviolet absorbers, release agents, etc. Additives can be added.

<Optical film>
The optical film of the present invention will be described. This optical film is a film used for optical applications. Specific examples thereof include a retardation film, a plastic substrate film, a polarizing plate protective film, an antireflection film, a brightness enhancement film, an optical disc protective film, and a diffusion film. Particularly, a retardation film, a polarizing plate protective film and an antireflection film are preferable.

Examples of the method for producing the optical film include known methods such as a solution casting method, a melt extrusion method, a hot pressing method, and a calender 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 in which a resin is extruded using a T die and sent 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, and more preferably in the range of 200°C to 320°C. If it is lower than 180° C., the viscosity becomes high, and the polymer orientation and stress strain tend to remain, which is not preferable. Further, if the temperature is higher than 350° C., problems such as heat deterioration, coloring, and die lines (streaks) from the T die are likely to occur.

Further, 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 in terms of heat resistance.

The thickness of the unstretched optical film of the present invention is preferably in the range of 20 to 400 μm, more preferably 20 to 300 μm. When the film is further stretched to form a retardation film, it may be appropriately determined within the above range in consideration of the desired retardation value and thickness of the optical film.

The unstretched optical film thus obtained is stretch-oriented and becomes a retardation film. As the stretching method, a known method such as longitudinal uniaxial stretching, lateral uniaxial stretching using a tenter, or simultaneous biaxial stretching in which these are combined and sequential biaxial stretching can be used. Further, it is preferable to carry out the reaction continuously, from the viewpoint of productivity, but it may be carried out in a batch system. 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. Within this temperature range, 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, which is preferable.

The stretching ratio is determined depending on the intended retardation value, and is 1.05 to 5 times in the length and width, and more preferably 1.1 to 4 times. This stretching may be performed in one step or in multiple steps. The above Tg in the case of stretching a film obtained by the solution casting method is a glass transition temperature containing a trace amount of a solvent in the film.

(Thickness, etc.)
The thickness of the optical film of the present invention is preferably 20 to 200 μm, more preferably 20 to 150 μm. Within this range, a desired retardation value due to stretching is easily obtained, and film formation is easy, which is preferable.

The polycarbonate resin constituting the optical film of the present invention has a low photoelastic constant. Therefore, the change in retardation due to stress is small, and the liquid crystal display device provided with such retardation film has excellent display stability.

Further, 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 of wavelength 400 to 800 nm, the retardation in the film plane becomes smaller as the wavelength becomes shorter, and thus it exhibits reverse wavelength dispersion. An optical film can be obtained. It is desirable that the stretched retardation film satisfy 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 formula, and is a characteristic that expresses a phase delay between the X direction of light transmitted in the direction perpendicular to the film and the Y direction perpendicular thereto.
_{R = (n x -n y)} × d
However, n _x is the refractive index in the main stretching direction in the film plane, n _y is the refractive index in the direction perpendicular to the main stretching direction in the film plane, and d is the film thickness. Here, the main stretching direction means a stretching direction in the case of uniaxial stretching, and a stretching direction so as to increase the degree of orientation in the case of biaxial stretching. Refers to the orientation direction.

Further, the in-plane retardation value R(550) of the optical film at a wavelength of 550 nm is preferably R(550)≧50 nm. The optical films can be used as a wide band λ/4 plate or a λ/2 plate without being laminated. For such applications, it is further desirable that 100 nm≦R(550)≦180 nm for a λ/4 plate and 220 nm≦R(550)≦330 nm for a λ/2 plate.

The wavelength dispersibility of the optical film is measured by using a Spectroellipsimeter 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 above retardation film. In the present invention, a circularly polarizing film composed of the above retardation film and a polarizing layer can be suitably used as an antireflection film. Further, the above retardation film can be suitably used as a polarizing plate protective film or an optical compensation film of an image display device.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto. In addition, "part" in an Example means a "weight part." The resins used and the evaluation methods used in the examples are as follows.

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

2. Specific viscosity was measured using a Ostwald viscometer from a solution of 0.7 g of polycarbonate resin dissolved in 100 ml of methylene chloride at 20°C.
Specific viscosity (η _SP )=(t−t ₀ )/t ₀
[T ₀ is the number of seconds of methylene chloride drop, t is the number of seconds of drop of sample solution]
3. Tg (glass transition temperature)
It was measured using a 2910 type DSC manufactured by TA Instruments Japan Co., Ltd. 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 a Spectroellipometer M-220 manufactured by JASCO Corporation.

5. Retardation and wavelength dispersibility A test piece with a length of 100 mm and a width of 70 mm was cut out from a film and longitudinally stretched 2.0 times at a stretching temperature of Tg+10°C. The retardation wavelength dispersion was measured using -220.

6. Evaluation of heat unevenness A linear polarizing plate with a structure in which a polarizer film in which iodine is adsorbed and oriented in polyvinyl alcohol is sandwiched between two triacetyl cellulose films, and an acrylic pressure-sensitive adhesive layer is provided on one surface of the polarizer film is prepared. did. The stretched films prepared in the examples were subjected to corona discharge treatment under the condition of an integrated irradiation amount of 1500 J, and the corona discharge treated surface was attached to the linear polarizing plate on the acrylic pressure-sensitive adhesive layer side at an angle of 45°. Two sheets of the above polarizing plate were prepared and bonded to non-alkali glass (manufactured by Corning Japan Co., trade name: EAGLE2000) via an adhesive as shown in FIG. Visually evaluate the light leakage of the transmitted light when a backlight was applied immediately after storing the configured circularly polarizing plate for 240 minutes at 90° C. If there was no light leakage, ○, if light leakage was observed overall It was set to x.

[Reference Example 1]
<Production 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 a catalyst 1.8×10 ⁻² parts of ammonium hydroxide and 1.6×10 ⁻⁴ parts of sodium hydroxide were heated to 180° C. under a nitrogen atmosphere to be melted. Then, the degree of pressure reduction was adjusted to 13.4 kPa over 30 minutes. Then, the temperature was raised to 260° C. at a rate of 20° C./hr, the temperature was maintained for 10 minutes, and then the degree of pressure reduction was 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, dodecylbenzenesulfonic acid tetrabutylphosphonium salt in an amount 4 times the catalyst amount was added to deactivate the catalyst. Then, nitrogen was discharged from the bottom of the reaction tank under nitrogen pressure and cut with a pelletizer while cooling in a water tank. To obtain pellets.

<Manufacture of optical film>
Next, a T-die having a width of 150 mm and a lip width of 500 μm and a film take-up device were attached to a 15φ biaxial extrusion kneader manufactured by Technovel Co., and the obtained polycarbonate copolymer was melt-extruded at 290° C. to form a film. A transparent extruded film was obtained. The evaluation results are shown in Table 1.

[Reference Example 2]
<Production of polycarbonate copolymer resin>
Except for using 60.4 parts of SBI and 59.6 parts of SPG, the same operation as in Reference Example 1 was carried out to obtain an aliphatic aromatic polycarbonate copolymer.

<Manufacture of optical film>
Next, a film was prepared in the same manner as in Reference Example 1. The evaluation results are shown in Table 1.

[Reference Example 3]
<Production of polycarbonate copolymer resin>
Except that SBI 48.3 parts and SPG 71.5 parts were used, the same operation as in Reference 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 Reference Example 1. The evaluation results are shown in Table 1.

[Reference Example 4]
<Production of polycarbonate copolymer resin>
9,9-Bis[4-(2-hydroxyethoxy)phenyl]fluorene (hereinafter abbreviated as BPEF) 17.2 parts, SBI 48.3 parts, SPG 59.6 parts except that the same as in Reference Example 1 was used. The 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 Reference Example 1. The evaluation results are shown in Table 1.

[Reference Example 5]
<Production of polycarbonate copolymer resin>
The same operation as in Reference Example 1 except that 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 were used. Then, an aliphatic aromatic polycarbonate copolymer was obtained.

<Manufacture of optical film>
Next, a film was prepared in the same manner as in Reference Example 1. The evaluation results are shown in Table 1.

[Example 6]
<Production of polycarbonate copolymer resin>
An aliphatic aromatic polycarbonate copolymer was obtained in the same manner as in Reference Example 1 except that 28.6 parts of isosorbide (hereinafter abbreviated as ISS), 24.2 parts of SBI, and 44.5 parts of BPEF were used.

<Manufacture of optical film>
Next, a film was prepared in the same manner as in Reference Example 1. The evaluation results are shown in Table 1.

[Reference Example 7]
<Production of polycarbonate copolymer resin>
Except that 80 parts of spirobichroman (hereinafter abbreviated as SBC) and 22.9 parts of SPG were used, the same operation as in Reference Example 1 was carried out to obtain an aliphatic aromatic polycarbonate copolymer.

<Manufacture of optical film>
Next, a film was prepared in the same manner as in Reference Example 1. The evaluation results are shown in Table 1.

[Comparative Example 1]
<Production of polycarbonate copolymer resin>
Except for using 86.0 parts of BPEF and 28.6 parts of ISS, the same operation as in Reference Example 1 was carried out to obtain an aliphatic aromatic polycarbonate copolymer.

<Manufacture of optical film>
Next, a film was prepared in the same manner as in Reference Example 1. The evaluation results are shown in Table 1. As a result of thermal unevenness evaluation, color loss due to thermal unevenness due to photoelastic coefficient occurred.

[Comparative example 2]
<Production of polycarbonate copolymer resin>
Except for using 50.4 parts of BCF and 37.8 parts of ISS, the same operation as in Reference Example 1 was carried out to obtain an aliphatic aromatic polycarbonate copolymer.

<Manufacture of optical film>
Next, a film was prepared in the same manner as in Reference Example 1, but the resin was decomposed and foaming occurred because Tg was too high, and the quality as an optical film was not satisfied.

[Comparative Example 3]
<Production of polycarbonate copolymer resin>
Except that 86 parts of BPEF and 59.6 parts of SPG were used, the same operation as in Reference Example 1 was carried out to obtain an aliphatic aromatic polycarbonate copolymer.

<Manufacture of optical film>
Next, a film was prepared in the same manner as in Reference Example 1. The evaluation results are shown in Table 1. As a result of evaluation of heat unevenness, heat resistance was low, and thus color loss due to heat unevenness occurred.

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

1. Polarizer 2. Stretched film 3. Inorganic glass 4. Stretched film 5. Polarizer

Claims (9)

A carbonate unit (A) derived from 6,6′-dihydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobiindane and a carbonate unit (B) derived from isosorbide, The molar ratio (A/B) between the unit (A) and the unit (B) is 5/95 to 95/5, and the specific viscosity measured with a methylene chloride solution at 20° C. is 0.20 to 0.45. A polycarbonate resin. The polycarbonate resin according to claim 1, wherein the glass transition temperature of the polycarbonate resin is 70°C to 180°C. The polycarbonate resin according to claim 1, wherein the polycarbonate resin has a photoelastic constant of 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. An optical film formed from the polycarbonate resin according to claim 1. The optical film according to claim 5, wherein the optical film is formed by a melt extrusion method. The optical film according to claim 5, wherein the optical film is a retardation film formed by stretching an unstretched film. The optical film according to claim 7, wherein the in-plane retardation values R(450), R(550), and R(650) 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 8.

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