JP7279366B2 - Polycarbonate resin and optical film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polycarbonate resin that can be used for a retardation film and an optical film containing the polycarbonate resin. More particularly, it relates to polycarbonate resins and optical films having high retardation and small wavelength dependence.

Flat panel displays (FPDs) such as liquid crystals and organic ELs are widely used as the most important display devices in the multimedia society, including mobile phones, computer monitors, laptop computers and televisions. Many optical films are used in FPDs to improve display characteristics. In particular, the retardation film is a member necessary for improving visibility when viewed from the front or obliquely.

Quarter-wave and half-wave plates are known as retardation films, and examples of materials thereof include polycarbonate resins and cyclic polyolefins. Polycarbonate resin has high transparency and excellent impact resistance, and is suitable for use as an optical member. In addition, it is known to exhibit a high retardation when used as a retardation film. However, a resin obtained by polymerizing an aromatic monomer such as bisphenol A exhibits a high photoelastic constant of 80×10 ⁻¹² Pa ⁻¹ or more, and has a large birefringence due to stress. reduction is an issue. In addition, the resin has a large wavelength dependence of retardation, and there is a problem that color unevenness becomes large when used as a retardation film. Here, the wavelength dependence of the phase difference means that the phase difference changes depending on the measurement wavelength, and the ratio of the phase difference (R450) measured at a wavelength of 450 nm and the phase difference (R550) measured at a wavelength of 550 nm It can be expressed as (R450/R550).

Polycarbonate resins obtained by copolymerizing positive and negative aromatic monomers are known as polycarbonate resins with reduced wavelength dependence (see, for example, Patent Documents 1 to 4). Here, the positive or negative aromatic monomer means an aromatic monomer that makes a film consisting of only a resin obtained by homopolymerization of the monomer exhibiting positive or negative birefringence, respectively. Further, the aromatic monomer means a monomer containing at least one or more aromatic rings in its structure. However, these resins have a problem that the retardation is small.

Patent No. 3919997 Patent No. 3325560 Patent No. 5760396 Patent No. 5204358

The present invention has been made in view of the above problems, and an object of the present invention is to obtain a polycarbonate resin that exhibits a high retardation and has a small wavelength dependence, and an optical film containing the polycarbonate resin. .

As a result of intensive studies to solve the above problems, the present inventors have found that a polycarbonate resin containing a specific structural unit and an optical film containing the polycarbonate resin can solve the above problems, and the present invention is based on the findings. was completed.

That is, the present invention provides a structural unit (I) represented by the following general formula (1), a structural unit (II) represented by the following general formula (2), and a structure represented by the following general formula (3) Characterized in that it contains the unit (III), and the molar fraction of the structural unit (III) is 8 mol% or more with respect to the total of the structural unit (I), the structural unit (II), and the structural unit (III). A polycarbonate resin and an optical film containing the polycarbonate resin.

(In the formula, R ₁ and R ₂ are each independently an unsubstituted alkyl group having 1 to 4 carbon atoms, Z is an alkylene group having 1 to 14 carbon atoms, and n is an integer of 0 to 4.)

(wherein R ₃ and R ₄ each independently represent a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 6 to 20 carbon atoms, a cycloalkyl group having 6 to 20 carbon atoms, or a A cycloalkoxy group, an aryl group having 6 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, an aryloxy group having 6 to 10 carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, and q and r are each independently an integer of 0 to 4, X is a single bond, or

wherein R ₅ to R ₁₀ are each independently a hydrogen atom, a halogen atom, a phenyl group, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or an alkyl group having 1 to 10 carbon atoms. It is a carboxylic acid or a carbon halide having 1 to 10 carbon atoms, and s is an integer of 1 to 6. )

(Wherein Y is an alkylene group having 1 to 20 carbon atoms, a cycloalkylene group having 3 to 20 carbon atoms, an ether group having 1 to 20 carbon atoms, a cyclic ether group having 6 to 20 carbon atoms, a cyclic ether group having 1 to 20 carbon atoms, a thioether group, a cyclic thioether group having 6 to 20 carbon atoms, an imino group having 1 to 20 carbon atoms, a cyclic imino group having 6 to 20 carbon atoms, and a halogenated alkylene group having 1 to 20 carbon atoms.)
The present invention will be described in detail below.

The polycarbonate resin of the present invention is a polymer in which dihydroxy compounds are linked by carbonate bonds.

The polycarbonate resin of the present invention comprises an aromatic structural unit (I) represented by the general formula (1), a structural unit (II) represented by the general formula (2), and a structure represented by the general formula (3) It is characterized by including the unit (III), and the molar fraction of the structural unit (III) is 8 mol % or more with respect to the total of the structural unit (I), the structural unit (II), and the structural unit (III).

In the present invention, the aromatic structural unit (I) represented by the general formula (1), the structural unit (II) represented by the general formula (2), and the structural unit (III) represented by the general formula (3) ) and the structural unit (III) satisfies the above molar fraction, the polycarbonate resin of the present invention has a low photoelastic coefficient, and the optical film containing the polycarbonate resin has a position It has excellent retardation characteristics and wavelength dependence.

In order for the obtained transparent film to express a higher retardation, the molar fraction of the structural unit (III) is the structural unit (I), the structural unit (II), and the total of the structural unit (III), preferably 10 mol % or more, more preferably 10 to 70 mol %, still more preferably 20 to 70 mol %, particularly preferably 30 to 70 mol %.

Furthermore, the polycarbonate resin of the present invention is suitable for expressing an equivalent retardation in a wider wavelength range, so the ratio of the molar fractions of the structural unit (I) and the structural unit (II) is the structural unit (I ) / structural unit (II) = 30/70 to 90/10, more preferably 40/60 to 90/10, and a ratio of 50/50 to 80/20. More preferred.

R ₁ and R ₂ in general formula (1) are each independently an unsubstituted alkyl group having 1 to 4 carbon atoms, and Z is an alkylene group having 1 to 14 carbon atoms.

Examples of the alkyl group having 1 to 4 carbon atoms for R ₁ and R ₂ include methyl group, ethyl group, propyl group, butyl group and the like.

Examples of the alkylene group having 1 to 14 carbon atoms in Z include methylene group, ethylene group, n-propylene group, n-butylene group, isobutylene group, tert-butylene group, n-pentylene group, neopentylene group and n-hexylene. group, n-heptylene group, n-octylene group, n-nonylene group, n-decylene group and the like.

Further, in the present invention, the structural unit (I) is preferably a structural unit represented by the following general formula (4) or the following general formula (5) in order to obtain a polycarbonate resin with more excellent wavelength dependence. , and more preferably the following general formula (5). Here, R ₁ and R ₂ in formulas (4) and (5) have the same designations as in general formula (1).

More preferably, the structural unit (I) is a structural unit represented by the following formula (6) or (7), more preferably formula (7).

R ₃ and R ₄ in general formula (2) each independently represent a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 6 to 20 carbon atoms, or a cycloalkyl group having 6 to 20 carbon atoms. ~20 cycloalkoxy group, 6-10 carbon aryl group, 7-20 carbon aralkyl group, 6-10 carbon aryloxy group or 7-20 carbon aralkyloxy group , q and r are each independently an integer from 0 to 4, X is a single bond, or

wherein R ₅ to R ₁₀ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, or an alkoxy group having 1 to 10 carbon atoms, and s is an integer of 1 to 6 is.

Halogen atoms for R ₃ and R ₄ include, for example, fluorine, chlorine, and bromine.

Examples of alkyl groups having 1 to 10 carbon atoms for R ₃ and R ₄ include methyl group, ethyl group, n-propyl group, n-butyl group, isobutyl group, tert-butyl group, n-pentyl group and neopentyl group. , n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group and the like.

Examples of alkoxy groups having 1 to 10 carbon atoms for R ₃ and R ₄ include methoxy, ethoxy, n-propoxy, n-butoxy, isobutoxy, tert-butoxy, n-pentyloxy, neopentyloxy, roxy group, n-hexyloxy group, n-heptyloxy group, n-octyloxy group, n-nonyloxy group, n-decyloxy group and the like.

Examples of the cycloalkyl group having 6 to 20 carbon atoms for R ₃ and R ₄ include cyclohexyl group and cyclooctyl group.

The cycloalkoxy group having 6 to 20 carbon atoms in R ₃ and R ₄ includes, for example, 2-ethylhexyloxy group, cyclohexyloxy group, cyclooctyloxy group and the like.

Examples of the aryl group having 6 to 10 carbon atoms in R ₃ and R ₄ include a phenyl group, p-tolyl group, p-(n-hexyl)phenyl group, p-(n-octyl)phenyl group, p -(2-ethylhexyl)phenyl group and the like.

Examples of the aralkyl group having 7 to 20 carbon atoms for R ₃ and R ₄ include benzyl group and phenethyl group.

Examples of the aryloxy group having 6 to 18 carbon atoms in R ₃ and R ₄ include phenoxy group, 2-methylphenoxy group, 3-methylphenoxy group, 4-methylphenoxy group, 2-methoxyphenoxy group, 3- methoxyphenoxy group, 4-methoxyphenoxy group, 2-cyanophenoxy group, 3-cyanophenoxy group, 4-cyanophenoxy group, 4-methylphenyloxy group, 3-methylphenyloxy group, 4-biphenylyloxy group, 3 -biphenyloxy group, 1-naphthyloxy group, 2-naphthyloxy group and the like.

Examples of the aralkyloxy group having 7 to 20 carbon atoms for R ₃ and R ₄ include benzyloxy and phenethyloxy groups.

Halogen atoms for R ₅ to R ₁₀ include, for example, fluorine, chlorine and bromine.

Examples of alkyl groups having 1 to 10 carbon atoms in R ₅ to R ₁₀ include methyl group, ethyl group, n-propyl group, n-butyl group, isobutyl group, tert-butyl group, n-pentyl group and neopentyl group. , n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group and the like.

Examples of alkoxy groups having 1 to 10 carbon atoms in R ₅ to R ₁₀ include methoxy, ethoxy, n-propoxy, n-butoxy, isobutoxy, tert-butoxy, n-pentyloxy, neopentyloxy, and neopentyloxy. roxy group, n-hexyloxy group, n-heptyloxy group, n-octyloxy group, n-nonyloxy group, n-decyloxy group and the like.

Y in the general formula (3) is an alkylene group having 1 to 20 carbon atoms, a cycloalkylene group having 3 to 20 carbon atoms, an ether group having 1 to 20 carbon atoms, a cyclic ether group having 6 to 20 carbon atoms, and 1 to 2 carbon atoms. 20 thioether groups, cyclic thioether groups having 6 to 20 carbon atoms, imino groups having 1 to 20 carbon atoms, cyclic imino groups having 6 to 20 carbon atoms, and halogenated alkylene groups having 1 to 20 carbon atoms.

The alkylene group having 1 to 20 carbon atoms in Y may be either a linear or branched alkylene group, and examples thereof include a methylene group, an ethylene group, a propylene group, a 2-methylpropylene group, and a 2,2-dimethylpropylene group. group, isopropylene group, butylene group, 2-methylbutylene group, 3-methylbutylene group, 2-butylene group, 3-methylbutan-2-ylene group, tert-butylene group, pentylene group, 2-methylpentylene group, 3-ethylpentylene group, 2,4-dimethylpentylene group, 2-pentylene group, 2-methylpentan-2-ylene group, 4,4-dimethylpentan-2-ylene group, 3-pentyl group, 3- ethylpentan-3-ylene group, 2,5-dimethylcyclopentylene group, hexylene group, 2-methylhexylene group, 3,3-dimethylhexylene group, 4-ethylhexylene group, 2-hexylene group, 2 -methylhexane-2-ylene group, 5,5-dimethylhexane-2-ylene group, 3-hexylene group, 2,4-dimethylhexane-3-ylene group, heptylene group, 2-heptylene group, 3-heptylene group , 4-heptylene group, octylene group, 2-octylene group, 3-octylene group, 4-octylene group, nonylene group, 5-nonylene group, decylene group, 2-decylene group, 5-decylene group, undecylene group, dodecylene group , tridecylene group, tetradecylene group, pentadecylene group, hexadecylene group, heptadecylene group, octadecylene group, nonadecylene group, eicosilene group and the like.

The cycloalkylene group having 3 to 20 carbon atoms in Y includes, for example, cyclohexylmethylene group, 2-cyclopentylethylene group, 3-cyclopropylpropylene group, cyclopropylene group, cyclobutylene group, cyclopentylene group, 3-ethylcyclo pentylene group, cyclohexylene group, 4-ethylcyclohexylene group, 4-propylcyclohexylene group, 4,4-dimethylcyclohexylene group, bicyclo[2.2.1]heptylene group, cyclooctylene group, bicyclo[2 .2.2] octylene group and the like.

The ether group having 1 to 20 carbon atoms in Y includes, for example, methyl ether group, methyl ethyl ether group, ethyl ether group, n-propyl ether group, n-butyl ether group, isobutyl ether group, tert-butyl ether group, n- Pentyl ether group, neopentyl ether group, n-hexyl ether group, n-heptyl ether group, n-octyl ether group, n-nonyl ether group, n-decyl ether group and the like.

Examples of the cyclic ether group having 6 to 20 carbon atoms in Y include a cyclohexyl ether group and a cyclooctyl ether octyloxy group. Further, as the structural unit (III) having the cyclic ether group,

is mentioned.

Examples of the thioether group having 1 to 20 carbon atoms in Y include -CH ₂ SCH ₂ -, -CH ₂ SCH ₂ SCH ₂ -, -CH ₂ CH ₂ SCH ₂ CH ₂ -, -CH ₂ SCH ₂ CH ₂ CH ₂ SCH ₂ - and the like.

The cyclic thioether group having 6 to 20 carbon atoms in Y includes, for example,

etc.

Examples of the imino group having 1 to 20 carbon atoms in Y include -CH ₂ NHCH ₂ -, -CH ₂ NHCH ₂ NHCH ₂ -, -CH ₂ CH ₂ NHCH ₂ CH ₂ -, -CH ₂ CH ₂ NHCH ₂ CH _{2NHCH 2} CH ₂ -, -CH ₂ NHCH ₂ CH ₂ CH ₂ NHCH ₂ - groups and the like.

The cyclic imino group having 6 to 20 carbon atoms in Y includes, for example,

etc.

Examples of the halogenated alkylene group having 1 to 20 carbon atoms in Y include -CF ₂ -, -(CF ₂ ) ₂ -, -(CF ₂ ) ₃ -, -(CF ₂ ) ₄ -, -(CF ₂ ) ₅ -, -(CF ₂ ) ₆ -, -(CF ₂ ) ₇ -, -(CF ₂ ) ₈ -, -(CF ₂ ) ₉ -, -(CF ₂ ) ₁₀ - and the like.

Further, as the structural unit (III),

(In the formula, R is hydrogen or a methyl group.)
is also mentioned.

Further, in the present invention, in order to obtain a polycarbonate resin with more excellent retardation properties, the structural unit (III) is preferably a structural unit represented by the following (8) or the following general formula (9), more preferably It is general formula (9).

Here, in general formula (9), n is an integer of 3-10. Hereinafter, the compound that is the starting material for the structural unit of formula (9) is also referred to as "nD". That is, in formula (9), when n is 3, i.e. propanediol, it is called 3D, and when n is 10, i.e. decanediol, it is sometimes called 10D.

In general formula (9), n is preferably 4-9.

The polycarbonate resin of the present invention is characterized by a low photoelastic constant. As a result, the polycarbonate resin of the present invention is less likely to cause birefringence due to stress, and is therefore suitable for preventing light leakage when used as an optical film. Particularly, the photoelastic constant preferably satisfies the following formula (A). .
35×10 ⁻¹² Pa ⁻¹ ≦photoelastic constant<80×10 ⁻¹² Pa ⁻¹ (A)

Since the polycarbonate resin of the present invention is excellent in impact resistance and good handleability, it preferably has a weight average molecular weight of 10,000 to 200,000, more preferably 30,000 to 100,000.

The glass transition temperature (hereinafter referred to as "Tg") of the polycarbonate resin of the present invention is preferably 100°C or higher and 180°C or lower. As a result, when the resin of the present invention is used to form a retardation film, it can be applied to a wide range of applications such as mobile phones, tablet terminals, and in-vehicle displays. The Tg of the polycarbonate resin of the present invention is preferably 160°C or less.

As a specific polycarbonate resin of the present invention, for example, the structural unit (I) is a 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene residue unit, and the structural unit (II) is a bisphenol A residue. units, and a polycarbonate resin in which the structural unit (III) is a cyclohexanedimethanol residue unit, a structural unit (I) is a 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene residue unit, a structural unit ( II) is a 4,4'-biphenol residue unit and a polycarbonate resin in which the structural unit (III) is a cyclohexanedimethanol residue unit, the structural unit (I) is a 9,9-bis(4-(2- hydroxyethoxy)phenyl)fluorene residue unit, structural unit (II) is bisphenol P residue unit, and structural unit (III) is cyclohexanedimethanol residue unit polycarbonate resin, structural unit (I) is 9,9- Bis(4-(2-hydroxyethoxy)phenyl)fluorene residue units, structural units (II) are bisphenol AF residue units, and structural units (III) are cyclohexanedimethanol residue units, polycarbonate resins, and the like. .

The polycarbonate resin of the present invention comprises an aromatic monomer exhibiting a specific negative birefringence, an aromatic monomer exhibiting a specific positive birefringence, and an aliphatic monomer exhibiting a specific positive birefringence. It is preferably obtained by a production method involving copolymerization. Here, an aliphatic monomer means a monomer that does not contain an aromatic ring in its structure. The aromatic monomer exhibiting negative birefringence, the aromatic monomer exhibiting positive birefringence, and the aliphatic monomer exhibiting positive birefringence are each used to obtain the polycarbonate resin of the present invention. When it becomes a structural unit (I), a structural unit (II), and a structural unit (III).

The polycarbonate resin of the present invention may be produced by any commonly used polymerization method, such as the phosgene method and the transesterification method. Polymerization by the phosgene method is preferably carried out under the same conditions and operations as in Japanese Patent No. 5544681. The polymerization method by transesterification is preferably carried out under the same conditions and operations as in Japanese Patent No. 4938151.

The aromatic monomer exhibiting negative birefringence used in the production of the polycarbonate resin of the present invention contains at least one or more aromatic rings in its structure, and only the polycarbonate resin obtained by homopolymerizing the monomer is used. Any film can be used as long as the film exhibits negative birefringence, and one type or a plurality of types may be used. Examples of aromatic monomers exhibiting negative birefringence include 9,9-bis(4-hydroxyphenyl)fluorene, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 9,9- Bis(4-(2-hydroxyethoxy)phenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-methylphenyl)fluorene, 2,2-bis(4-(2-hydroxyethoxy) phenyl)propane, 1,3-bis(2-hydroxyethoxy)benzene, 4,4'-bis(2-hydroxyethoxy)biphenyl, biscresol fluorene, etc., and are expected to exhibit high retardation when copolymerized. Therefore, preferably 9,9-bis(4-hydroxyphenyl)fluorene, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)phenyl ) fluorene and biscrezol fluorene.

The aromatic monomer exhibiting positive birefringence used in the production of the polycarbonate resin of the present invention contains at least one or more aromatic rings in its structure, and only the polycarbonate resin obtained by homopolymerizing the monomer is used. Any film can be used as long as the film exhibits positive birefringence, and one type or a plurality of types may be used.

Examples of aromatic monomers exhibiting positive birefringence include 2,2-bis(4-hydroxyphenyl)propane (commonly known as bisphenol A), 4,4′-biphenol, bis(4- hydroxyphenyl)sulfone, 4,4-dihydroxybenzophenone, 3,3',5,5'-tetramethylbiphenyl-4,4'-diol, 4,4-ethylidenebisphenol, 4,4'- dihydroxydiphenylmethane, α,α'-bis(4-hydroxyphenyl)-1,4-diisopropylbenzene, 1,3-bis[2-(4-hydroxyphenyl)-2-propyl]benzene, 1,1-bis( 4-hydroxyphenyl)cyclohexane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 4,4'-(1,3-dimethylbutylidene)diphenol, 4,4'-methylenebis (2,6-dimethylphenol), 2,2-bis(4-hydroxy-3-methylphenyl)propane, 4,4'-methylenebis(2,6-di-tert-butylphenol), 4, 4'-butylidenebis(6-tert-butyl-m-cresol), 2,2-bis(4-hydroxyphenyl)butane, diphenolic acid, 2,2-bis(4-hydroxyphenyl)hexafluoropropane , 1,1-dichloro-2,2-bis(4-hydroxyphenyl)ethylene, 4,4′-isopropylidenebis(2,6-dibromophenol), 2,2-bis(3,5-dichloro -4-hydroxyphenyl)propane, 4,4'-(α-methylbenzylidene)bisphenol, 4,4'-dihydroxytetraphenylmethanebis(4-(2-hydroxyethoxy)phenyl)sulfone, bisphenol Z, α , α'-Bis(4-hydroxy-3,5-dimethylphenyl)-1,4-diisopropylbenzene and the like, and are expected to exhibit a high phase difference when copolymerized, so 2,2-bis (4-Hydroxyphenyl)propane, 4,4'-biphenol, 2,6-dihydroxynaphthalene, 4,4-ethylidenebisphenol, 4,4'-dihydroxydiphenylmethane, α,α'-bis(4 -hydroxyphenyl)-1,4-diisopropylbenzene, 1,1-bis(4-hydroxyphenyl)cyclohexane, diphenolic acid, bisphenol Z, α,α'-bis(4-hydroxy-3,5-dimethylphenyl )-1,4-diisopropylbenzene.

As the aliphatic monomer exhibiting positive birefringence used in the production of the polycarbonate resin of the present invention, a film containing only a resin obtained by homopolymerizing the monomer without containing an aromatic ring in its structure is positive. Any material can be used as long as it exhibits birefringence, and one type or a plurality of types may be used. Aliphatic monomers exhibiting positive birefringence include, for example, ethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 1,3 -butanediol, 1,2-butanediol, 1,5-heptanediol, 1,6-hexanediol, 1,8-octanediol, 1,2-cyclohexanedimethanol, 1,3- Cyclohexanedimethanol, 1,4-cyclohexanedimethanol, tricyclodecanedimethanol, pentacyclopentadecanedimethanol, 2,6-decalindimethanol, 1,5-decalindimethanol, 2, 3-decalinedimethanol, 2,3-norbornanedimethanol, 2,5-norbornanedimethanol, 1,3-adamantanedimethanol, 1,4-cyclohexanediol, 2,2-bis (4-hydroxycyclohexyl)propane, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4, 8,10-tetraoxaspiro[5,5]undecane and the like, and are expected to exhibit a high retardation when copolymerized. 1,8-octanediol, tricyclodecanedimethanol, 2,2-bis(4-hydroxycyclohexyl)propane.

The polycarbonate resin of the present invention is suitably used as an optical film containing the polycarbonate resin. The optical film may be an optical film using only the polycarbonate resin, or an optical film using a composition mixed with another resin. At this time, the other resin to be mixed may be a resin exhibiting negative birefringence or a resin exhibiting positive birefringence.

The optical film of the present invention can be suitably used as a transparent film.

The transparent film of the present invention preferably has a light transmittance of 85% or more, preferably 90% or more. The haze (cloudiness) of the transparent film is preferably 2% or less, more preferably 1% or less.

The method for producing the transparent film of the present invention is not particularly limited, and examples thereof include methods such as a melt film-forming method and a solution casting method.

The method of melt film formation specifically includes a melt extrusion method using a T-die, a calendar molding method, a hot press method, a co-extrusion method, a co-melting method, a multi-layer extrusion method, an inflation molding method, and the like. Although not limited, a melt extrusion method using a T-die is preferred because of ease of subsequent stretching treatment.

When a transparent film is formed by a melt film-forming method, the forming temperature is preferably 200° C., because the forming method is suitable for making the film thickness more uniform and preventing defects and coloring of the film. ~265°C, more preferably 210 to 260°C, particularly preferably 220 to 258°C. Here, the molding temperature is the temperature at the time of molding in the melt film-forming method, and is usually a value obtained by measuring the temperature at the outlet of the die for extruding the molten resin.

In the solution casting method, a solution obtained by dissolving the polycarbonate resin of the present invention in a solvent (hereinafter referred to as "dope") is cast on a support substrate, and then the solvent is removed by heating or the like to obtain a transparent film. The method. At that time, the method of casting the dope onto the support base includes the T-die method, the doctor blade method, the bar coater method, the roll coater method, and the lip coater method. etc. are used. Particularly industrially, the most common method is to continuously extrude the dope from a die onto a belt-shaped or drum-shaped support substrate. Examples of supporting substrates that can be used include glass substrates, metal substrates such as stainless steel and ferrotype, and films such as polyethylene terephthalate. In the solution casting method, the solution viscosity of the dope is an extremely important factor when forming a film having high transparency and excellent thickness accuracy and surface smoothness, and is preferably 10 to 20000 cPs. , 100 to 10000 cPs.

The transparent film of the present invention may contain a polymer or fine particles for the purpose of adjusting the out-of-plane retardation and ensuring a wide viewing angle. Examples of the polymer capable of adjusting the out-of-plane retardation include those described in JP-A-2016-145290 and JP-A-2016-145291.

The transparent film of the present invention contains other polymers, surfactants, polymer electrolytes, conductive complexes, inorganic fillers, pigments, antistatic agents, antiblocking agents, lubricants, etc., within the scope of the invention. You may

The transparent film of the present invention is preferably obtained as one containing the resin of the present invention. Group structural unit (a), and an aliphatic structural unit (c) that exhibits positive birefringence, and the molar fraction of the structural unit (c) is the structural unit (a), the structural unit (b), the structural unit ( c) with respect to the total of 10 mol% or more, a polycarbonate resin having a photoelastic constant satisfying the following formula (B), and a stretched film made of the polycarbonate resin has a retardation R450 measured at 450 nm and a wavelength of 550 nm. The ratio (R450/R550) to the retardation R550 measured in is 1.00 ≤ R450/R500 ≤ 1.05, and the ratio (Re/d) of the in-plane retardation Re to the film thickness d is 6. It is particularly preferably used as a transparent film which is a stretched film having a thickness of 5 (nm/μm) or more. Here, a structural unit exhibiting positive or negative birefringence means that a film made of only a resin obtained by homopolymerizing a monomer relating to the structural unit exhibits positive or negative birefringence, respectively. means a constituent unit. Further, the aromatic structural unit means a structural unit containing at least one or more aromatic rings in its structure, and the aliphatic structural unit means a structural unit not containing an aromatic ring in its structure.
35×10 ⁻¹² Pa ⁻¹ ≦photoelastic constant<80×10 ⁻¹² Pa ⁻¹ (B)

The transparent film using the polycarbonate resin of the present invention can be suitably used as a retardation film because it has a high retardation even in a thin film when stretched.

Since the retardation film of the present invention exhibits an equivalent retardation in a wide wavelength range, the ratio of the retardation R450 measured at 450 nm and the retardation R550 measured at a wavelength of 550 nm (R450/R550) is 1.00 ≤ It is preferable that R450/R500≦1.05.

Since the retardation film of the present invention exhibits a high retardation compared to conventional retardation films, the ratio (Re / d) of the in-plane retardation Re and the film thickness d is 6.5 (nm / μm) or more. is preferred. Here, the in-plane retardation Re can be expressed by the following formula.
Re=(nx−ny)×d

In the retardation film of the present invention, when nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the film in-plane direction perpendicular to it, and nz is the refractive index in the thickness direction of the film, after stretching is suitable as a retardation film in which the respective relationships of nx>ny and nx>nz are satisfied.

The retardation film of the present invention can be obtained by uniaxially or biaxially stretching and orienting a transparent film containing a polycarbonate resin.

The transparent film using the polycarbonate resin of the present invention preferably has a thickness of 50 μm or less. This enables application to a foldable flexible display or the like.

Examples of the uniaxial stretching method include free width uniaxial stretching, a method of stretching with a tenter, and a method of stretching between rolls. Examples of the biaxial stretching method include a method of stretching with a tenter, a method of stretching with a -There is a method of inflating and stretching. As the stretching conditions at that time, the thickness unevenness is unlikely to occur, and the mechanical properties and the retardation film are excellent in optical properties. to (Tg+20°C), preferably (Tg-10°C) to (Tg+10°C). The draw ratio is preferably 1.5 to 3.5 times, more preferably 2 to 2.5 times.

The stretching rate is also appropriately selected depending on the purpose, and can be selected so that the strain rate represented by the following formula is usually 50 to 1000%/min, preferably 100 to 500%/min.
Strain rate (%/min) = {stretching rate (mm/min)/length of transparent film (mm)} x 100

Polycarbonate resin of the present invention, the wavelength dependence of the transparent film using the polycarbonate resin is small, and has a high retardation compared to conventional ones, especially when used as a retardation film, the thin film of the retardation film is possible.

<Glass transition temperature (Tg)>
Using a differential scanning calorimeter (manufactured by Seiko Electronics Industry Co., Ltd., trade name DSC2000), 10 ° C./min. was measured at a heating rate of .
<Measurement of retardation characteristics>
The retardation properties of the retardation film were measured using light with a wavelength of 589 nm using a tilt sample automatic birefringence meter (manufactured by AXOMETRICS, trade name: AxoScan).
<Measurement of wavelength dependence>
Using a sample tilting automatic birefringence meter (manufactured by AXOMETRICS, trade name: AxoScan), the wavelength dispersion of the optical film was measured as the ratio of the retardation Re450 due to light with a wavelength of 450 nm to the retardation Re550 due to light with a wavelength of 550 nm (R450/R550). properties were measured.
<Measurement of photoelastic constant>
It was calculated from the birefringence measurement with respect to the change in load using light with a wavelength of 589 nm using a sample tilt type automatic birefringence meter (manufactured by Oji Scientific Instruments, trade name: KOBRA-WR).

[Example 1]
44.4 g (0.10 mol) of 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene (manufactured by Osaka Gas Chemicals, abbreviated as “BPEF”) and 1,4-cyclohexanedimethano- (manufactured by Tokyo Chemical Industry Co., Ltd., abbreviated as "CHDM") 12.5 g (0.087 mol) and 2,2-bis(4-hydroxyphenyl) propane (manufactured by Tokyo Chemical Industry Co., Ltd., abbreviated as "BPA" ) 23.1 g (0.10 mol) and diphenyl carbonate (manufactured by Tokyo Kasei Co., Ltd., hereinafter abbreviated as “DPC”) 62.0 g (0.29 mol), and sodium hydrogen carbonate as a catalyst (Wako Pure Chemical Industries, Ltd. 0.146 × 10 ^-3 g (1.74 × 10 ^-6 mol) of (manufacturer) was put into a reaction vessel equipped with a cooling pipe for phenol recovery. In a nitrogen atmosphere, the heating bath temperature was heated to 200° C. as the first step of the reaction, and the raw materials were dissolved with stirring as necessary (about 15 minutes). Next, as the second step, the temperature of the heating bath was raised to 220° C., and the generated phenol was discharged out of the reaction vessel. Further, as the third step, the pressure was changed from normal pressure to 13.3 kPa, and the generated phenol was discharged out of the reaction vessel. After holding the entire reaction vessel for 15 minutes, as the fourth step, the pressure in the reaction vessel is increased to 6.67 kPa, the heating tank temperature is raised to 230° C. in 15 minutes, and the generated phenol is removed from the reaction vessel. pulled out. Since the stirring torque of the stirrer increased, the temperature was raised to 250° C. in 8 minutes as the final step, and the pressure in the reaction vessel reached 0.200 kPa or less. After completion of the polymerization reaction, the resulting reaction product was dissolved in methylene chloride and poured into methanol for reprecipitation. The precipitated polymer was filtered, washed with methanol, and dried in vacuum to obtain a polycarbonate resin. The obtained resin had a photoelastic coefficient of 48×10 ⁻¹² Pa ⁻¹ and Mw=4.0×10 ⁴ .

[Example 2]
Example 1 was repeated except that BPEF was changed to 38.0 g (0.087 mol), CHDM to 16.7 g (0.12 mol), and BPA to 19.8 g (0.087 mol). to obtain a polycarbonate resin. The obtained resin had a photoelastic coefficient of 43×10 ⁻¹² Pa−1 and Mw=3.4×10 ⁴ .

[Example 3]
Example 1 was repeated except that BPEF was changed to 31.7 g (0.072 mol), CHDM to 20.9 g (0.15 mol), and BPA to 16.5 g (0.072 mol). to obtain a polycarbonate resin. The resulting resin had a photoelastic coefficient of 46×10 ⁻¹² Pa ⁻¹ and Mw=5.8×10 ⁴ .

[Example 4]
In Example 1, 60.9 g (0.14 mol) of BPEF, 16.7 g (0.12 mol) of CHDM, 23.1 g of BPA, and 4,4′-biphenol (manufactured by Tokyo Chemical Industry Co., Ltd., “BPh ".) A polycarbonate resin was obtained in the same manner except that the amount was changed to 6.5 g (0.035 mol). The resulting resin had a photoelastic coefficient of 42×10 ⁻¹² Pa ⁻¹ and Mw=4.4×10 ⁴ .

[Example 5]
Example 4 was carried out in the same manner except that BPEF was changed to 50.7 g (0.12 mol), CHDM to 20.9 g (0.14 mol), and BPh to 5.4 g (0.029 mol). to obtain a polycarbonate resin. The obtained resin had a photoelastic coefficient of 42×10 ⁻¹² Pa ⁻¹ and Mw=5.7×10 ⁴ .

[Example 6]
Example 4 was carried out in the same manner except that BPEF was changed to 40.6 g (0.093 mol), CHDM to 4.3 g (0.17 mol), and BPh to 4.3 g (0.0023 mol). to obtain a polycarbonate resin. The resulting resin had a photoelastic coefficient of 46×10 ⁻¹² Pa ⁻¹ and Mw=6.5×10 ⁴ .

[Example 7]
In Example 1, 38.0 g (0.087 mol) of BPEF, 20.9 g (0.15 mol) of CHDM, and 23.1 g of BPA were bisphenol P (manufactured by Tokyo Chemical Industry Co., Ltd., abbreviated as "BPP"). A polycarbonate resin was obtained in the same manner except that the content was changed to 20.0 g (0.058 mol). The resulting resin had a photoelastic coefficient of 44×10 ⁻¹² Pa ⁻¹ and Mw=4.7×10 ⁴ .

[Example 8]
In Example 1, 31.7 g (0.072 mol) of BPEF, 20.9 g (0.15 mol) of CHDM, and 23.1 g of BPA were bisphenol Z (manufactured by Tokyo Chemical Industry Co., Ltd., abbreviated as "BPZ"). A polycarbonate resin was obtained in the same manner except that the content was changed to 19.4 g (0.072 mol). The resulting resin had a photoelastic coefficient of 42×10 ⁻¹² Pa ⁻¹ and Mw=5.4×10 ⁴ .

[Example 9]
In Example 7, the amount of BPEF is 22.8 g (0.052 mol), the amount of BPP is 12.0 g (0.035 mol), the amount of DPC is 31.6 g (0.15 mol), and A polycarbonate resin was obtained in the same manner except that 6.0 g (0.058 mol) of 1,5-pentanediol (manufactured by Tokyo Chemical Industry Co., Ltd., abbreviated as "5D") was changed to CHDM. rice field. The resulting resin had a photoelastic coefficient of 43×10 ⁻¹² Pa ⁻¹ and Mw=6.4×10 ⁴ .

[Example 10]
In Example 7, the amount of BPEF was 30.4 g (0.069 mol), the amount of BPP was 16.0 g (0.046 mol), the amount of DPC was 31.6 g (0.15 mol), and A polycarbonate resin was obtained in the same manner except that 4.2 g (0.029 mol) of 1,8-octanediol (manufactured by Tokyo Chemical Industry Co., Ltd., abbreviated as "8D") was used instead of CHDM. rice field. The resulting resin had a photoelastic coefficient of 43×10 ⁻¹² Pa ⁻¹ and Mw=8.0×10 ⁴ .

[Example 11]
In Example 7, the amount of BPEF was 34.2 g (0.078 mol), the amount of BPP was 18.0 g (0.052 mol), the amount of DPC was 31.6 g (0.15 mol), and 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro[5,5]undecane (manufactured by Tokyo Chemical Industry Co., Ltd., "SPG" instead of CHDM) ) was changed to 4.4 g (0.014 mol) to obtain a polycarbonate resin. The obtained resin had a photoelastic coefficient of 40×10 ⁻¹² Pa ⁻¹ and Mw=7.3×10 ⁴ .

[Example 12]
In Example 1, the amount of CHDM was 14.6 g (0.101 mol), the amount of DPC was 31.6 g (0.15 mol), and biscresol fluorene (manufactured by Osaka Gas Chemicals Co., Ltd., " BCF”) is 9.9 g (0.026 mol), and α,α′-bis(4-hydroxy-3,5-dimethylphenyl)-1,4-diisopropylbenzene ( A polycarbonate resin was obtained in the same manner, except that 7.0 g (0.017 mol) of BXP (manufactured by Tokyo Chemical Industry Co., Ltd.) was changed to 7.0 g (0.017 mol). The resulting resin had a photoelastic coefficient of 37×10 ⁻¹² Pa ⁻¹ and Mw=6.4×10 ⁴ .

[Example 13]
In Example 10, the amount of 8D was 8.3 g (0.057 mol), the amount of BPP was 11.7 g (0.034 mol), the amount of DPC was 31.6 g (0.15 mol), and the BPEF was A polycarbonate resin was obtained in the same manner except that the amount of BCF was changed to 19.4 g (0.051 mol). The resulting resin had a photoelastic coefficient of 47×10 ⁻¹² Pa ⁻¹ and Mw=6.0×10 ⁴ .

[Synthesis Example 1]
A reaction vessel equipped with a stirrer, a thermometer and a reflux condenser was charged with an aqueous sodium hydroxide solution and ion-exchanged water, and 58.9 g (0.168 g) of bisphenol fluorene (manufactured by Osaka Gas Chemicals Co., Ltd., abbreviated as "BPFL") was added. mol) and 16.5 g (0.072 mol) of BPA were dissolved and a small amount of hydrosulfite was added. Next, methylene chloride was added to this, and phosgene was blown in at 20° C. for about 60 minutes. Further, p-tert-butylphenol was added and emulsified, then triethylamine was added and stirred at 30° C. for about 3 hours to complete the reaction. After completion of the reaction, the organic phase was separated and the methylene chloride was evaporated to obtain a polycarbonate resin.

[Synthesis Example 2]
In Synthesis Example 1, 58.9 g of BPFL was combined with 33.3 g (0.088 mol) of 9,9-bis(4-hydroxymethylphenyl)fluorene (manufactured by Osaka Gas Chemicals, abbreviated as “BCF”) and 16.5 g of BPA. (0.072 mol) was carried out in the same manner.

[Synthesis Example 3]
In Synthesis ^Example 1, isosorbide ("ISB ), 21.72 g (0.058 mol) of BCF (0.058 mol), 138.49 g (0.646 mol) of DPC, and 5.1 × 10 ^{− 4} (manufactured by Ardrich) was carried out in the same manner except that the aqueous solution was changed to g (1.61×10 ⁻⁶ mol).

[Synthesis Example 4]
In Synthesis Example 1, instead of making an aqueous solution of 44.4 g of BPEF, 12.5 g of CHDM, 23.1 g of BPA, 62.0 g of DPC, and 0.146×10 ⁻³ g of sodium hydrogen carbonate as a catalyst, 84.91 g of ISB (0.581 g of mol), 24.44 g (0.065 mol) of BCF, 138.49 g (0.646 mol) of DPC, and 5.1×10 ⁻⁴ (Ardrich) g (1.61×10 ^-6 mol) was carried out in the same manner.

[Example 14]
The polycarbonate resin obtained in Example 1 was dissolved in methylene chloride to form a 24% by weight resin solution, cast on a polyethylene terephthalate film by a coater, and dried at a temperature of 40° C. (1 hour). After that, it was dried in two stages at 100° C. (15 minutes) to prepare a polycarbonate resin film. The obtained polycarbonate resin film was cut into a 50 mm×15 mm square and stretched 2.5 times (stretched at 133° C.). Retardation properties and wavelength dependence of the stretched polycarbonate resin film were measured. Table 1 shows the results. Here, the retardation power in Table 1 indicates a value converted to a film thickness of 30 μm, and the same converted value is indicated in other examples.

The polycarbonate resin film after stretching was transparent, had a high retardation, and had a small wavelength dependence.

[Example 15]
A polycarbonate resin film was obtained in the same manner as in Example 14 except that the polycarbonate resin obtained in Example 2 was changed, and then stretched 2.5 times (122° C. stretching). Retardation properties and wavelength dependence of the stretched polycarbonate resin film were measured. The results are also shown in Table 1. The polycarbonate resin film after stretching was transparent, had a high retardation, and had a small wavelength dependence.

[Example 16]
A polycarbonate resin film was obtained in the same manner as in Example 14, except that the polycarbonate resin obtained in Example 3 was changed, and then stretched 2.5 times (117° C. stretching). Retardation properties and wavelength dependence of the stretched polycarbonate resin film were measured. The results are also shown in Table 1. The polycarbonate resin film after stretching was transparent, had a high retardation, and had a small wavelength dependence.

[Example 17]
A polycarbonate resin film was obtained in the same manner as in Example 14, except that the polycarbonate resin obtained in Example 4 was changed, and then stretched 2.5 times (130° C. stretching). Retardation properties and wavelength dependence of the stretched polycarbonate resin film were measured. The results are also shown in Table 1. The polycarbonate resin film after stretching was transparent, had a high retardation, and had a small wavelength dependence.

[Example 18]
A polycarbonate resin film was obtained in the same manner as in Example 14, except that the polycarbonate resin obtained in Example 5 was changed, and then stretched 2.5 times (120° C. stretching). Retardation properties and wavelength dependence of the stretched polycarbonate resin film were measured. The results are also shown in Table 1. The polycarbonate resin film after stretching was transparent, had a high retardation, and had a small wavelength dependence.

[Example 19]
A polycarbonate resin film was obtained in the same manner as in Example 14 except that the polycarbonate resin obtained in Example 6 was changed, and then stretched 2.5 times (108° C. stretching). Retardation properties and wavelength dependence of the stretched polycarbonate resin film were measured. The results are also shown in Table 1. The polycarbonate resin film after stretching was transparent, had a high retardation, and had a small wavelength dependence.

[Example 20]
A polycarbonate resin film was obtained in the same manner as in Example 14 except that the polycarbonate resin obtained in Example 7 was used, and then stretched 2.5 times (114° C. stretching). Retardation properties and wavelength dependence of the stretched polycarbonate resin film were measured. The results are also shown in Table 1. The polycarbonate resin film after stretching was transparent, had a high retardation, and had a small wavelength dependence.

[Example 21]
A polycarbonate resin film was obtained in the same manner as in Example 14 except that the polycarbonate resin obtained in Example 8 was changed, and then stretched 2.5 times (119° C. stretching). Retardation properties and wavelength dependence of the stretched polycarbonate resin film were measured. The results are also shown in Table 1. The polycarbonate resin film after stretching was transparent, had a high retardation, and had a small wavelength dependence.

[Example 22]
A polycarbonate resin film was obtained in the same manner as in Example 14 except that the polycarbonate resin obtained in Example 9 was used, and then stretched 2.5 times (110° C. stretching). Retardation properties and wavelength dependence of the stretched polycarbonate resin film were measured. The results are also shown in Table 1. The polycarbonate resin film after stretching was transparent, had a high retardation, and had a small wavelength dependence.

[Example 23]
A polycarbonate resin film was obtained in the same manner as in Example 14, except that the polycarbonate resin obtained in Example 10 was changed, and then stretched 2.5 times (120° C. stretching). Retardation properties and wavelength dependence of the stretched polycarbonate resin film were measured. The results are also shown in Table 1. The polycarbonate resin film after stretching was transparent, had a high retardation, and had a small wavelength dependence.

[Example 24]
A polycarbonate resin film was obtained in the same manner as in Example 14 except that the polycarbonate resin obtained in Example 11 was changed, and then stretched 2.5 times (133° C. stretching). Retardation properties and wavelength dependence of the stretched polycarbonate resin film were measured. The results are also shown in Table 1. The polycarbonate resin film after stretching was transparent, had a high retardation, and had a small wavelength dependence.

[Example 25]
A polycarbonate resin film was obtained in the same manner as in Example 14 except that the polycarbonate resin obtained in Example 12 was changed, and then stretched 2.5 times (116° C. stretching). Retardation properties and wavelength dependence of the stretched polycarbonate resin film were measured. The results are also shown in Table 1. The polycarbonate resin film after stretching was transparent, had a high retardation, and had a small wavelength dependence.

[Example 26]
A polycarbonate resin film was obtained in the same manner as in Example 14 except that the polycarbonate resin obtained in Example 13 was changed, and then stretched 2.5 times (134° C. stretching). Retardation properties and wavelength dependence of the stretched polycarbonate resin film were measured. The results are also shown in Table 1. The polycarbonate resin film after stretching was transparent, had a high retardation, and had a small wavelength dependence.

[Comparative Example 1]
The polycarbonate resin obtained in Synthesis Example 1 was dissolved in methylene chloride to form a 15% by weight resin solution, cast on a polyethylene terephthalate film by a coater, and dried at a drying temperature of 140° C. (2 hours). Then, a polycarbonate resin film was produced. The obtained polycarbonate resin film was cut into a 50 mm×15 mm square, and then stretched 2.0 times. Retardation properties and wavelength dependence of the stretched polycarbonate resin film were measured. The results are also shown in Table 1. The polycarbonate resin film after stretching was transparent, but had a low retardation and a wavelength dependence of less than 1.00.

[Comparative Example 2]
A polycarbonate resin film was obtained in the same manner as in Comparative Example 1, except that the polycarbonate resin obtained in Synthesis Example 2 was changed, and then stretched 1.7 times. Retardation properties and wavelength dependence of the stretched polycarbonate resin film were measured. The results are also shown in Table 1. The polycarbonate resin film after stretching was transparent, but had a low retardation and a wavelength dependence of less than 1.00.

Claims (3)

A structural unit (I) represented by at least one of the following general formula (4) or (5) , a structural unit (II) represented by the following general formula (2), and the following formula (8) or the following general Containing the structural unit (III) represented by the formula (9) , the ratio of the molar fractions of the structural unit (I) and the structural unit (II) is structural unit (I) / structural unit (II) = 40/60 to 90/10, and the molar fraction of the structural unit (III) is 20 to 70 mol% with respect to the total of the structural unit (I), the structural unit (II), and the structural unit (III). A retardation film obtained by stretching an optical film containing a polycarbonate resin in one or more directions, the retardation film having a thickness of 50 μm or less.

(In the formula, R ₁ and R ₂ are each independently an unsubstituted alkyl group having 1 to 4 carbon atoms.)

(wherein R ₃ and R ₄ are each independently an alkyl group having 1 to 10 carbon atoms , q and r are each independently an integer of 1 to 4, X is a single bond, or

wherein R ₅ and R ₆ are each independently an alkyl group having 1 to 10 carbon atoms, R ₇ and R ₈ are hydrogen atoms, and s is an integer of 1 to 6. )

(Wherein, n is an integer of 3 to 10.) 2. The retardation film according to claim 1, wherein the photoelastic constant of the polycarbonate resin satisfies the following formula (A).
35×10 ⁻¹² Pa ⁻¹ ≦photoelastic constant<80×10 ⁻¹² Pa ⁻¹ (A) 3. The retardation film according to claim 1, wherein the polycarbonate resin has a weight average molecular weight of 10,000 to 200,000.