CN117120890A - Phase difference film, circularly polarizing plate using the same, and image display device - Google Patents

Abstract

The invention provides a reverse dispersion phase difference film with excellent durability under high-temperature and high-humidity environment. The phase difference film of the present invention comprises: a resin that contains at least 1 kind of bonding group selected from the group consisting of a carbonate bond and an ester bond, and at least 1 kind of structural unit selected from the group consisting of a structural unit represented by the following general formula (1) and a structural unit represented by the following general formula (2), and has positive refractive index anisotropy; and a compound (A) having an aromatic structure and a molecular weight of 500 to 2000, wherein the compound (A) is contained in an amount of more than 0.5% by mass and not more than 4.0% by mass, re (550) is 100 to 200nm, and Re (450)/Re (550) is more than 0.5 and less than 1.0.

Description

Phase difference film, circularly polarizing plate using the same, and image display device

Technical Field

The present invention relates to a retardation film, a circularly polarizing plate using the retardation film, and an image display device.

Background

In recent years, there has been an increasing opportunity for use of display devices such as smart devices typified by smart phones and digital signage and window displays under intense external light. With this, there are problems such as reflection of external light and reflection of background due to the display device itself or a reflector such as a glass substrate or a metal wiring used in the display device. In particular, organic Electroluminescent (EL) display devices, which have been put into practical use in recent years, have a metal layer having high reflectivity, and thus are prone to problems such as reflection of external light and reflection of background. Therefore, it is known to prevent the above-described problem by providing a circular polarizing plate having a phase difference film (typically, λ/4 plate) as an antireflection film on the viewing side. Further, in order to achieve good retardation characteristics at each wavelength in the visible light range, development of a retardation film (hereinafter, sometimes simply referred to as a reverse dispersion retardation film) exhibiting wavelength dependence of so-called reverse dispersion in which a retardation value becomes larger with the wavelength of the measurement light has been advanced. In the development of a reverse dispersion retardation film, continuous studies are being conducted to further improve the characteristics.

Prior art literature

Patent literature

Patent document 1: japanese patent No. 3325560

Disclosure of Invention

Problems to be solved by the invention

The main object of the present invention is to provide a reverse dispersion retardation film having excellent durability in a high-temperature and high-humidity environment.

Means for solving the problems

The phase difference film of the present invention comprises: a resin that contains at least 1 kind of bonding group selected from the group consisting of a carbonate bond and an ester bond, and at least 1 kind of structural unit selected from the group consisting of a structural unit represented by the following general formula (1) and a structural unit represented by the following general formula (2), and has positive refractive index anisotropy; and a compound (A) having an aromatic structure and a molecular weight of 500 to 2000, wherein the compound (A) is contained in an amount of more than 0.5% by mass and not more than 4.0% by mass, re (550) is 100 to 200nm, re (450)/Re (550) is more than 0.5 and less than 1.0,

[ chemical 1]

[ chemical 2]

In the general formulae (1) and (2), R ¹ ～R ³ Each independently is a direct bond, a substituted or unsubstituted alkylene group having 1 to 4 carbon atoms, R ⁴ ～R ⁹ Each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted aryl group having 4 to 10 carbon atoms, a substituted or unsubstituted acyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms substituted or unsubstituted aryloxy group having 1 to 10 carbon atoms, substituted or unsubstituted amino group, substituted or unsubstituted vinyl group having 1 to 10 carbon atoms, substituted or unsubstituted ethynyl group having 1 to 10 carbon atoms, sulfur atom having substituent, or a compound having a substituent A silicon atom, a halogen atom, a nitro group or a cyano group; wherein R is ⁴ ～R ⁹ May be the same or different from each other, R ⁴ ～R ⁹ At least two adjacent groups of the two groups may be bonded to each other to form a ring; re (550) is the in-plane retardation of the film measured at 23℃with light having a wavelength of 550nm, and Re (450) is the in-plane retardation of the film measured at 23℃with light having a wavelength of 450 nm.

In one embodiment, the resin having positive refractive index anisotropy contains 1 to 40% by mass of at least 1 structural unit selected from the group consisting of the structural unit represented by the general formula (1) and the structural unit represented by the general formula (2).

In one embodiment, the resin having positive refractive index anisotropy further comprises a structural unit represented by the following general formula (3).

[ chemical 3]

In one embodiment, the resin having positive refractive index anisotropy further includes a structural unit represented by the following general formula (4).

[ chemical 4]

In one embodiment, the retardation film further comprises an acrylic resin, and the content of the acrylic resin is 0.5 to 2.0 mass%.

In one embodiment, the content of the compound (a) is 1.0 to 3.0 mass%.

In one embodiment, the compound (a) has a partial structure represented by the following formula (5).

[ chemical 5]

According to another aspect of the present invention, there is provided a circularly polarizing plate. The circularly polarizing plate comprises a polarizer and the phase difference film, wherein the angle between the absorption axis of the polarizer and the slow axis of the phase difference film is 40-50 DEG or 130-140 deg.

According to still another aspect of the present invention, there is provided an image display device. The image display device includes the circular polarizing plate on the viewing side, and a polarizer of the circular polarizing plate is disposed on the viewing side.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the embodiment of the present invention, a specific compound is blended into a resin having a specific positive refractive index anisotropy (typically, a polycarbonate-based resin, a polyester-based resin, or a polyester carbonate-based resin), thereby obtaining a reverse dispersion retardation film excellent in durability under a high-temperature and high-humidity environment.

Drawings

Fig. 1 is a schematic cross-sectional view of a circularly polarizing plate according to an embodiment of the present invention.

Detailed Description

Hereinafter, representative embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

(definition of terms and symbols)

The definitions of terms and symbols in the present specification are as follows.

(1) Refractive index (nx, ny, nz)

"nx" is a refractive index in a direction in which the in-plane refractive index becomes maximum (i.e., the slow axis direction), "ny" is a refractive index in a direction orthogonal to the slow axis (i.e., the fast axis direction), and "nz" is a refractive index in the thickness direction.

(2) In-plane phase difference (Re)

"Re (λ)" is the in-plane retardation of the film measured at 23℃using light of wavelength λnm. For example, "Re (450)" is the in-plane retardation of the film measured at 23℃using light having a wavelength of 450 nm. When the film thickness is d (nm), re (λ) is represented by the formula: re= (nx-ny) x d.

(3) Retardation in thickness direction (Rth)

"Rth (λ)" is a phase difference in the thickness direction of the film measured at 23℃using light having a wavelength of λnm. For example, "Rth (450)" is a retardation in the thickness direction of the film measured at 23 ℃ using light having a wavelength of 450 nm. When the film thickness is d (nm), rth (λ) is represented by the formula: rth= (nx-nz) ×d.

(4) Nz coefficient

The Nz coefficient is obtained by nz=rth/Re.

(5) Angle of

In the present specification, when referring to an angle, the angle includes angles in both a clockwise direction and a counterclockwise direction unless otherwise specified.

A. Retardation film

The phase difference film of the present invention comprises: a resin that contains at least 1 kind of bonding group selected from the group consisting of a carbonate bond and an ester bond, and at least 1 kind of structural unit selected from the group consisting of a structural unit represented by the following general formula (1) and a structural unit represented by the following general formula (2), and has positive refractive index anisotropy; and a compound (hereinafter sometimes referred to as compound (A)) having an aromatic structure and a molecular weight of 500 to 2000, wherein the content of the compound (A) is more than 0.5% by mass and not more than 4.0% by mass, re (550) is 100nm to 200nm, and Re (450)/Re (550) is more than 0.5 and less than 1.0. By providing the retardation film with the above-described constitution, a reverse dispersion retardation film excellent in durability under a high-temperature and high-humidity environment can be obtained.

[ chemical 6]

[ chemical 7]

A-1 constituent material of retardation film

The retardation film of the embodiment of the present invention contains a resin containing at least 1 kind of bonding group selected from the group consisting of carbonate bonds and ester bonds. In other words, the retardation film contains a polycarbonate-based resin, a polyester-based resin, or a polyester-carbonate-based resin (hereinafter, these may be collectively referred to as a polycarbonate-based resin or the like). The polycarbonate resin and the like contain at least 1 structural unit selected from the group consisting of the structural unit represented by the above general formula (1) and/or the structural unit represented by the above general formula (2). These structural units are structural units derived from 2-valent oligofluorene, and are sometimes referred to as oligofluorene structural units hereinafter. Such polycarbonate-based resins and the like have positive refractive index anisotropy.

The retardation film of the embodiment of the present invention further contains a modifier. The modifier is a compound (A) having an aromatic structure and a molecular weight of 500 to 2000. The content of the compound (a) is more than 0.5 mass% and 4.0 mass% or less as described above. In the present specification, the percentage or part of the "mass" unit is the same as the percentage or part of the "weight" unit.

The retardation film may further contain an acrylic resin. The content of the acrylic resin is 0.5 to 1.5 mass% as described above.

A-1-1. Polycarbonate resin and the like

< Oligofluorene structural unit >

The oligofluorene structural unit is represented by the above general formula (1) or (2). In the general formulae (1) and (2), R ¹ ～R ³ Each independently is a direct bond, a substituted or unsubstituted alkylene group having 1 to 4 carbon atoms, R ⁴ ～R ⁹ Each independently is a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted aryl group having 4 to 10 carbon atoms, a substituted or unsubstituted acyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms, a substituted or unsubstituted aryloxy group having 1 to 10 carbon atoms, a substituted or unsubstituted amino group, a substituted or unsubstituted vinyl group having 1 to 10 carbon atoms, a substituted or unsubstituted ethynyl group having 1 to 10 carbon atoms, a sulfur atom having a substituent, a silicon atom having a substituent, a halogen atom, Nitro or cyano. Wherein R is ⁴ ～R ⁹ May be the same or different from each other, R ⁴ ～R ⁹ At least two adjacent groups of (a) may be bonded to each other to form a ring.

As R ¹ R is R ² For example, the following alkylene groups may be used: straight-chain alkylene groups such as methylene, ethylene, n-propylene, n-butylene, and the like; and branched alkylene groups such as methyl methylene, dimethyl methylene, ethyl methylene, propyl methylene, (1-methylethyl) methylene, 1-methylethylene, 2-methylethylene, 1-ethylethylene, 2-ethylethylene, 1-methylpropylene, 2-methylpropylene, 1-dimethylethylene, 2-dimethylpropylene, and 3-methylpropylene. Here, R is ¹ R is R ² The positions of the branches in (a) are indicated by numbers given so that the carbon on the fluorene ring side becomes the 1-position.

R ¹ R is R ² May be related to the behavior of the reverse dispersion wavelength dependence. Polycarbonate resins and the like exhibit the strongest wavelength dependence of reverse dispersion in a state where fluorene rings are oriented perpendicularly to the main chain direction (extending direction). In order to bring the orientation state of the fluorene ring close to such a state and exhibit a strong dependence on the wavelength of reverse dispersion, R having 2 to 3 carbon atoms in the main chain of alkylene group is preferably used ¹ R is R ² . In the case where the carbon number is 1, there is a case where the reverse dispersion wavelength dependence is not unexpectedly exhibited. This is thought to be because, for example, the orientation of the fluorene ring is immobilized in a direction not perpendicular to the main chain direction due to steric hindrance of the carbonate group or the ester group as a linking group of the oligofluorene structural unit. On the other hand, if the number of carbons is too large, the alignment fixation of the fluorene ring is weakened, and thus the reverse dispersion wavelength dependence may become insufficient. Further, there are cases where heat resistance of polycarbonate resin and the like is lowered.

As R ³ For example, the following alkylene groups may be used: straight-chain alkylene groups such as methylene, ethylene, n-propylene, n-butylene, and the like; methyl methylene, dimethyl methylene, ethyl methylene, propyl methylene, (1-methylethyl) methylene, 1-methylethyleneAlkylene groups having a branched chain such as a group, 2-methylethylene group, 1-ethylethylene group, 2-ethylethylene group, 1-methylpropylene group, 2-methylpropylene group, 1-dimethylethylene group, 2-dimethylpropylene group, and 3-methylpropylene group. R is R ³ The number of carbon atoms in the main chain of the alkylene group is preferably 1 to 2, more preferably 1. In the case where the number of carbons in the main chain is excessive, R ¹ R is R ² In the same manner, immobilization of fluorene ring is weakened, which may lead to a decrease in wavelength dependence of reverse dispersion, an increase in photoelastic modulus, a decrease in heat resistance, and the like. On the other hand, when the number of carbons in the main chain is small, optical characteristics and heat resistance are good, but when the 9-positions of the two fluorene rings are connected by a direct bond, thermal stability may be poor.

As R ¹ ～R ³ Examples of the substituent(s) in (a) may include: a halogen atom (fluorine atom, chlorine atom, bromine atom or iodine atom); alkoxy groups having 1 to 10 carbon atoms such as methoxy and ethoxy; acyl groups having 1 to 10 carbon atoms such as acetyl and benzoyl; an amide group having 1 to 10 carbon atoms such as an acetamido group and a benzamido group; a nitro group; cyano group; aryl groups having 6 to 10 carbon atoms such as phenyl groups and naphthyl groups which may be substituted with 1 to 3 hydrogen atoms such as the halogen atom, the alkoxy group, the acyl group, the amide group, the nitro group and the cyano group.

As R ⁴ ～R ⁹ For example, the following alkyl groups may be used as the substituted or unsubstituted alkyl groups: straight-chain alkyl groups such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, and n-decyl; alkyl groups having a branched chain such as isopropyl group, 2-methylpropyl group, 2-dimethylpropyl group, and 2-ethylhexyl group; cyclic alkyl groups such as cyclopropyl, cyclopentyl, cyclohexyl, and cyclooctyl. The carbon number of the alkyl group is preferably 4 or less, more preferably 2 or less. When the number of carbons is within this range, steric hindrance of the fluorene rings is less likely to occur, and desired optical characteristics derived from the fluorene rings are easily obtained. As the substituent of the alkyl group, the above-mentioned one can be exemplified ¹ ～R ³ Said substituents.

As R ⁴ ～R ⁹ For example, the following aryl groups may be used as the substituted or unsubstituted aryl groups: phenyl, 1-naphthylAryl groups such as 2-naphthyl; heteroaryl groups such as 2-pyridyl, 2-thienyl, 2-furyl, and the like. The carbon number of the aryl group is preferably 8 or less, more preferably 7 or less. When the number of carbons is within this range, steric hindrance of the fluorene rings is less likely to occur, and desired optical characteristics derived from the fluorene rings are easily obtained. As the substituent for the aryl group, the above-mentioned ones can be exemplified ¹ ～R ³ Said substituents.

As R ⁴ ～R ⁹ For example, the following acyl groups may be used as the substituted or unsubstituted acyl groups: aliphatic acyl groups such as formyl, acetyl, propionyl, 2-methylpropanoyl, 2-dimethylpropionyl and 2-ethylhexanoyl; aromatic acyl groups such as benzoyl, 1-naphthylcarbonyl, 2-naphthylcarbonyl and 2-furylcarbonyl. The carbon number of the acyl group is preferably 4 or less, more preferably 2 or less. When the number of carbons is within this range, steric hindrance of the fluorene rings is less likely to occur, and desired optical characteristics derived from the fluorene rings are easily obtained. As the substituent for the acyl group, the above-mentioned one can be exemplified ¹ ～R ³ Said substituents.

As R ⁴ ～R ⁹ Examples of the substituted or unsubstituted alkoxy or aryloxy group include methoxy, ethoxy, isopropoxy, t-butoxy, trifluoromethoxy and phenoxy. The carbon number of the alkoxy group or the aryloxy group is preferably 4 or less, more preferably 2 or less. When the number of carbons is within this range, steric hindrance of the fluorene rings is less likely to occur, and desired optical characteristics derived from the fluorene rings are easily obtained. As the substituent for the alkoxy group or the aryloxy group, the above-mentioned ones can be exemplified ¹ ～R ³ Said substituents.

As R ⁴ ～R ⁹ For example, the following amine groups may be used as the substituted or unsubstituted amine groups: an amine group; aliphatic amine groups such as N-methylamino, N-dimethylamino, N-ethylamino, N-diethylamino, N-methylethylamino, N-propylamino, N-dipropylamino, N-isopropylamino, N-diisopropylamino and the like; an aromatic amine group such as an N-phenylamino group and an N, N-diphenylamino group; amide groups such as carboxamide group, acetamido group, decanoamide group, benzamido group, chloroacetamido group, and the like; alkyl such as benzyloxycarbonylamino group and t-butoxycarbonylamino groupAnd an oxycarbonylamino group. Preferably N, N-dimethylamino, N-ethylamino, or N, N-diethylamino, more preferably N, N-dimethylamino. They do not have protons with higher acidity, have small molecular weight, and can increase fluorene ratio.

As R ⁴ ～R ⁹ For example, vinyl, 2-methylethenyl, 2-dimethylvinyl, 2-phenylethenyl, 2-acetylvinyl, ethynyl, methylethynyl, t-butylethynyl, phenylethynyl, acetylethynyl, trimethylsilylethynyl may be used. The carbon number of the vinyl group or the acetylene group is preferably 4 or less. When the number of carbons is within this range, steric hindrance of the fluorene rings is less likely to occur, and desired optical characteristics derived from the fluorene rings are easily obtained. Further, a longer conjugated system of the fluorene ring facilitates a stronger wavelength dependence of the reverse dispersion.

As R ⁴ ～R ⁹ The sulfur atom having a substituent in (b) may be, for example, the following sulfur-containing group: a sulfo group; alkylsulfonyl groups such as methanesulfonyl, ethanesulfonyl, propanesulfonyl, and isopropylsulfonyl; arylsulfonyl groups such as benzenesulfonyl and p-toluenesulfonyl; alkylsulfinyl groups such as methylsulfinyl, ethylsulfinyl, propylsulfinyl and isopropylsulfinyl; arylsulfinyl groups such as phenylsulfinyl and p-tolylsulfinyl; alkylthio groups such as methylthio and ethylthio; arylthio groups such as phenylthio and p-tolylthio; an alkoxysulfonyl group such as a methoxysulfonyl group or an ethoxysulfonyl group; aryloxy sulfonyl groups such as phenoxy sulfonyl; sulfamoyl; alkylsulfonyl groups such as N-methylaminosulfonyl, N-ethylaminosulfonyl, N-t-butylaminosulfonyl, N-dimethylaminosulfonyl, N-diethylaminosulfonyl and the like; arylamino sulfonyl groups such as N-phenylaminosulfonyl and N, N-diphenylsulfamoyl. Further, the sulfo group may also form a salt with lithium, sodium, potassium, magnesium, ammonium, or the like. Preferably a methylsulfinyl, ethylsulfinyl, or phenylsulfinyl group, more preferably a methylsulfinyl group. They do not have protons with higher acidity, have small molecular weight, and can increase fluorene ratio.

As R ⁴ ～R ⁹ The silicon atom having a substituent in (a) may be, for example, the following silane group: trialkylsilyl groups such as trimethylsilyl and triethylsilyl; trialkoxysilyl groups such as trimethoxysilyl and triethoxysilyl. Preferably a trialkylsilyl group. The reason is that the stability and the operability are excellent.

The content of the oligofluorene structural unit in the polycarbonate resin or the like is preferably 1 to 40% by mass, more preferably 10 to 35% by mass, further preferably 15 to 30% by mass, and particularly preferably 18 to 25% by mass, relative to the entire resin. If the content of the oligofluorene structural unit is too large, there is a possibility that the photoelastic modulus becomes too large, the reliability becomes insufficient, and the phase difference manifestation becomes insufficient. Further, since the ratio of the oligofluorene structural unit to the resin becomes high, the range of molecular design becomes narrow, and there is a case where improvement is difficult when resin modification is required. On the other hand, there are cases where: even if the desired wavelength dependence of the reverse dispersion is obtained by a very small amount of the oligofluorene structural unit, in this case, the optical characteristics are sensitively changed due to a small deviation in the content of the oligofluorene structural unit, thereby making it difficult to manufacture in such a manner that each characteristic falls within a certain range.

Examples of the method for adjusting the ratio of the oligofluorene structural unit in the resin include a method of copolymerizing a monomer having an oligofluorene structural unit with another monomer, and a method of blending a resin containing an oligofluorene structural unit with another resin. The method of copolymerizing a monomer having an oligofluorene structural unit with other monomers is preferable in that the content of the oligofluorene structural unit can be precisely controlled, high transparency can be obtained, and uniform characteristics can be obtained over the entire surface of the film.

< other structural Unit >

The polycarbonate resin may typically contain other structural units in addition to the oligofluorene structural unit. In one embodiment, the other structural units may preferably be derived from a dihydroxy compound or a diester compound. In order to exhibit the target inverse wavelength dispersion, a structural unit having positive intrinsic birefringence must be incorporated into the polymer structure together with an oligofluorene structural unit having negative intrinsic birefringence, and therefore, a dihydroxy compound or a diester compound as a raw material for the structural unit having positive birefringence is more preferable as another monomer to be copolymerized.

Examples of the comonomer include: a compound into which a structural unit containing an aromatic ring can be introduced; and a compound having an aliphatic structure without introducing a structural unit containing an aromatic ring.

Specific examples of the above-mentioned compounds having an aliphatic structure are shown below. Dihydroxy compounds of linear aliphatic hydrocarbons such as ethylene glycol, 1, 3-propanediol, 1, 2-propanediol, 1, 4-butanediol, 1, 3-butanediol, 1, 2-butanediol, 1, 5-heptanediol, 1, 6-hexanediol, 1, 9-nonanediol, 1, 10-decanediol, and 1, 12-dodecanediol; dihydroxy compounds of branched aliphatic hydrocarbons such as neopentyl glycol and hexanediol; examples of the dihydroxy compound of the secondary alcohol and tertiary alcohol of the alicyclic hydrocarbon include 1, 2-cyclohexanediol, 1, 4-cyclohexanediol, 1, 3-dihydroxyadamantane, hydrogenated bisphenol A, 2, 4-tetramethyl-1, 3-cyclobutanediol, and the like; examples of the dihydroxy compound which is a primary alcohol of an alicyclic hydrocarbon include dihydroxy compounds derived from terpene compounds such as 1, 2-cyclohexanedimethanol, 1, 3-cyclohexanedimethanol, 1, 4-cyclohexanedimethanol, tricyclodecanedimethanol, pentacyclopentadecanedimethanol, 2, 6-decalin dimethanol, 1, 5-decalin dimethanol, 2, 3-norbornane dimethanol, 2, 5-norbornane dimethanol, 1, 3-adamantane dimethanol and limonene; alkylene oxide glycols such as diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, and polypropylene glycol; dihydroxyl compounds having a cyclic ether structure such as isosorbide; dihydroxy compounds having a cyclic acetal structure such as spiroglycol and dioxane glycol; alicyclic dicarboxylic acids such as 1, 2-cyclohexanedicarboxylic acid, 1, 3-cyclohexanedicarboxylic acid and 1, 4-cyclohexanedicarboxylic acid; aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and the like.

Specific examples of the above-mentioned compound into which the structural unit containing an aromatic ring can be introduced are as follows. 2, 2-bis (4-hydroxyphenyl) propane, 2-bis (3-methyl-4-hydroxyphenyl) propane, 2-bis (4-hydroxy-3, 5-dimethylphenyl) propane, 2-bis (4-hydroxy-3, 5-diethylphenyl) propane 2, 2-bis (4-hydroxy- (3-phenyl) propane, 2-bis (4-hydroxy- (3, 5-diphenyl) phenyl) propane, 2-bis (4-hydroxy-3, 5-dibromophenyl) propane, bis (4-hydroxyphenyl) methane 1, 1-bis (4-hydroxyphenyl) ethane, 2-bis (4-hydroxyphenyl) butane, 2-bis (4-hydroxyphenyl) pentane, 1-bis (4-hydroxyphenyl) -1-phenylethane, bis (4-hydroxyphenyl) diphenylmethane 1, 1-bis (4-hydroxyphenyl) -2-ethyl hexane, 1-bis (4-hydroxyphenyl) decane, bis (4-hydroxy-3-nitrophenyl) methane, 3-bis (4-hydroxyphenyl) pentane, 1, aromatic bisphenol compounds such as 3-bis (2- (4-hydroxyphenyl) -2-propyl) benzene, 1, 3-bis (2- (4-hydroxyphenyl) -2-propyl) benzene, 2-bis (4-hydroxyphenyl) hexafluoropropane, 1-bis (4-hydroxyphenyl) cyclohexane, bis (4-hydroxyphenyl) sulfone, 2,4 '-dihydroxydiphenyl sulfone, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxy-3-methylphenyl) sulfide, bis (4-hydroxyphenyl) disulfide, 4' -dihydroxydiphenyl ether, 4 '-dihydroxy-3, 3' -dichlorodiphenyl ether; dihydroxy compounds having an ether group bonded to an aromatic group, such as 2, 2-bis (4- (2-hydroxyethoxy) phenyl) propane, 2-bis (4- (2-hydroxypropoxy) phenyl) propane, 1, 3-bis (2-hydroxyethoxy) benzene, 4' -bis (2-hydroxyethoxy) biphenyl, and bis (4- (2-hydroxyethoxy) phenyl) sulfone; aromatic dicarboxylic acids such as terephthalic acid, phthalic acid, isophthalic acid, 4' -diphenyldicarboxylic acid, 4' -diphenylether dicarboxylic acid, 4' -benzophenone dicarboxylic acid, 4' -diphenoxyethane dicarboxylic acid, 4' -diphenylsulfone dicarboxylic acid, and 2, 6-naphthalene dicarboxylic acid.

The aliphatic dicarboxylic acid and the aromatic dicarboxylic acid component exemplified above may be obtained by using the dicarboxylic acid itself as a raw material of the polyester carbonate, or may be obtained by using a dicarboxylic acid ester such as a methyl ester or a phenyl ester, or a dicarboxylic acid derivative such as a dicarboxylic acid halide, according to a production method.

As the comonomer, a dihydroxy compound having a fluorene ring such as 9, 9-bis (4- (2-hydroxyethoxy) phenyl) fluorene, 9-bis (4-hydroxyphenyl) fluorene, 9-bis (4-hydroxy-3-methylphenyl) fluorene, or a dicarboxylic acid compound having a fluorene ring may be used in combination with an oligofluorene compound, which has been previously known as a compound containing a structural unit having negative birefringence.

From the viewpoint of optical characteristics, the resin used in the present invention preferably uses a structural unit containing no aromatic component as a structural unit other than the oligofluorene structural unit. That is, a compound having an aliphatic structure is preferably used as the comonomer. If the main chain of the polymer contains an aromatic component, the inverse wavelength dispersion exhibited by the oligofluorene structural unit is offset, and therefore the content of the oligofluorene structural unit must be increased, and thus the photoelastic modulus and the mechanical properties may be deteriorated. By using the above-mentioned other structural unit containing no aromatic component, the incorporation of an aromatic component derived from the structural unit into the main chain can be prevented. Among the compounds having an aliphatic structure, compounds having an alicyclic structure having excellent mechanical properties and heat resistance are more preferable.

On the other hand, there are also the following cases: in order to secure optical characteristics and to achieve a balance between optical characteristics and heat resistance, mechanical characteristics, and the like, it is effective to incorporate an aromatic component into the main chain or side chain of the polymer. From the viewpoint of achieving a balance of the respective characteristics, the content of the structural unit containing an aromatic group (excluding the oligofluorene structural unit) in the resin is preferably 5 mass% or less.

The resin used in the present invention preferably contains a structural unit represented by the following formula (3) as a copolymerization component in the structural unit that can be introduced by the above-mentioned compound having an alicyclic structure.

[ chemical 8]

As the dihydroxy compound into which the structural unit of the above formula (3) can be introduced, spiroglycol can be used.

The resin used in the present invention preferably contains 5 to 90% by mass of the structural unit represented by the formula (3). The upper limit is more preferably 70 mass% or less, particularly preferably 50 mass% or less. The lower limit is more preferably 10 mass% or more, still more preferably 20 mass% or more, and particularly preferably 25 mass% or more. When the content of the structural unit represented by the above formula (3) is not less than the above lower limit, sufficient mechanical properties, heat resistance and a low photoelastic modulus can be obtained. Furthermore, the compatibility with the acrylic resin is improved, and the transparency of the obtained resin composition can be further improved. Further, since the polymerization reaction of the spiroglycol is relatively slow, the polymerization reaction can be easily controlled by controlling the content to be not more than the above upper limit.

The resin used in the present invention preferably further contains a structural unit represented by the following formula (4) as a copolymerization component.

[ chemical 9]

Examples of the dihydroxy compound into which the structural unit represented by formula (4) can be introduced include Isosorbide (ISB), isomannide and isoidide having a stereoisomeric relationship. They may be used singly or in combination of 1 kind or 2 or more kinds.

The resin used in the present invention preferably contains 5 to 90% by mass of the structural unit represented by the formula (4). The upper limit is more preferably 70 mass% or less, particularly preferably 50 mass% or less. The lower limit is more preferably 10 mass% or more, particularly preferably 15 mass% or more. When the content of the structural unit represented by the above formula (4) is not less than the above lower limit, sufficient mechanical properties, heat resistance and low photoelastic modulus can be obtained. Further, since the structural unit represented by the above formula (4) has a characteristic of high water absorption, if the content of the structural unit represented by the above formula (4) is not more than the above upper limit, the dimensional change of the molded body due to water absorption can be suppressed to be within an allowable range.

The resin used in the present invention may further contain other structural units. Further, this structural unit is sometimes referred to as "other structural unit". As the monomer having another structural unit, 1, 4-cyclohexanedimethanol, tricyclodecanedimethanol, 1, 4-cyclohexanedicarboxylic acid (and derivatives thereof) are more preferably used, and 1, 4-cyclohexanedimethanol and tricyclodecanedimethanol are particularly preferred. The resin containing the structural unit derived from the above monomer is excellent in balance of optical properties, heat resistance, mechanical properties, and the like. Further, since the polymerization reactivity of the diester compound is relatively low, it is preferable not to use a diester compound other than the diester compound containing an oligofluorene structural unit from the viewpoint of improving the reaction efficiency.

The dihydroxy compound or diester compound used for introducing other structural units may be used alone or in combination of 2 or more kinds depending on the desired properties of the obtained resin. The content of the other structural unit in the resin is preferably 1 to 50% by mass, more preferably 5 to 40% by mass, and particularly preferably 10 to 30% by mass. Since other structural units particularly serve to adjust the heat resistance and impart flexibility or toughness to the resin, if the content is too small, there is a possibility that the mechanical properties and melt processability of the resin will be deteriorated; if the content is too large, heat resistance and optical characteristics may be deteriorated.

The molecular weight of the polycarbonate resin can be expressed by, for example, reduced viscosity. The reduced viscosity was measured by using a Ubbelohde viscosity tube at a temperature of 20.0deg.C.+ -. 0.1 ℃ while precisely adjusting the concentration of the polycarbonate resin to 0.6g/dL using methylene chloride as a solvent. The lower limit of the reduced viscosity is usually preferably 0.30dL/g or more, more preferably 0.35dL/g or more, and particularly preferably 0.40dL/g or more. The upper limit of the reduced viscosity is usually preferably 1.00dL/g or less, more preferably 0.80dL/g or less, and particularly preferably 0.60dL/g or less. If the reduced viscosity is less than the lower limit value, there is a case where the mechanical strength of the obtained film becomes insufficient. On the other hand, if the reduced viscosity exceeds the upper limit, the formability, the handleability, and the productivity may be insufficient.

The melt viscosity of the polycarbonate resin was at 240℃and the shear rate was 91.2sec ^-1 The measurement conditions of (2) are preferably 700 pas to 5000 pas or less. The upper limit is more preferably 4000pa·s or less, still more preferably 3500pa·s or less, and particularly preferably 3000pa·s or less. The lower limit is more preferably 1000pa·s or more, still more preferably 1500pa·s or more, and particularly preferably 2000pa·s or more. The melt viscosity was measured by using a capillary rheometer (manufactured by Toyo Seisakusho Co., ltd.).

The glass transition temperature (Tg) of the resin used in the present invention is preferably 110℃to 160 ℃. The upper limit is more preferably 155℃or less, still more preferably 150℃or less, and particularly preferably 145℃or less. The lower limit is more preferably 120℃or higher, particularly preferably 130℃or higher. If the glass transition temperature is outside the above range, heat resistance tends to be poor, and there is a possibility that the size after film formation may be changed or the quality reliability of the retardation film under the use conditions may be deteriorated. On the other hand, if the glass transition temperature is too high, there are cases where film thickness unevenness occurs during film formation, or the film becomes brittle and the stretchability becomes poor, and there are cases where the transparency of the film is impaired.

Details of the constitution of the polycarbonate resin and the production method thereof are described in, for example, international publication No. 2015/159928. This description is incorporated by reference into this specification.

A-1-2. Modifier

The retardation film in the embodiment of the present invention contains a modifier. As the modifier, a compound (A) having an aromatic structure and a molecular weight of 500 to 2000 is used. The content of the compound (a) exceeds 0.5 mass% and is 4.0 mass% or less. By setting the content of the compound (a) in the retardation film to be within the above range, a reverse dispersion retardation film excellent in durability under a high-temperature and high-humidity environment can be obtained. The reason for this is inferred as: by compounding the compound (a) with the resin, the mobility of the polymer molecules is suppressed, and the effect of suppressing the relaxation of the orientation of the polymer molecules due to heat or moisture absorption, the effect of suppressing moisture absorption of the resin, and the like are combined. From the same viewpoint, the lower limit of the content is more preferably 1.0 mass% or more, particularly preferably 1.5 mass% or more. The upper limit of the content is more preferably 3.5 mass% or less.

The molecular weight of the compound (A) is 500 to 2000 as described above. By setting the range as described above, the compound (a) is compatible with the resin, and the decrease in the glass transition temperature (Tg) of the resin is small, and a high durability improving effect can be obtained. In addition, when melt extrusion kneading or melt extrusion film formation is performed, the occurrence of defects such as contamination of a vacuum vent or a film forming roll due to volatilization or bleeding of the compound (a) can be reduced. From the same viewpoint, the lower limit is more preferably 600 or more, still more preferably 700 or more, and particularly preferably 800 or more. The upper limit of the molecular weight is more preferably 1800 or less, particularly preferably 1500 or less.

The compound (a) preferably has a partial structure represented by the following formula (5). It is assumed that the compound containing the above-mentioned partial structure has better compatibility with the polycarbonate resin used in the present invention, and the effect of suppressing the mobility of the polymer molecule is further enhanced due to its bulky structure.

[ chemical 10]

As the compound (a), for example, a compound known as an antioxidant having a hindered phenol structure or an ultraviolet absorber can be used, and examples thereof include: pentaerythritol-tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ]: trade name "Irganox1010" (manufactured by BASF corporation), 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-t-butyl-4-hydroxybenzyl) benzene: trade name "Irganox1330" (manufactured by BASF corporation), tris (3, 5-di-tert-butyl-4-hydroxybenzyl) isocyanurate: trade name "Irganox3114" (manufactured by BASF corporation), stearyl 3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate: trade name "Irganox1076" (manufactured by BASF corporation), 2' -thiodiethyl bis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ]: trade name "Irganox1035" (manufactured by BASF corporation), N' -hexamethylenebis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionamide ]: trade name "Irganox 1098" (manufactured by BASF corporation), bis [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionic acid ] [ ethylenebis (ethylene oxide) ]: trade names "Irganox245" (manufactured by BASF corporation), 1, 6-hexanediol bis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ] trade names "Irganox259" (manufactured by BASF corporation), 4- [ [4, 6-bis (octylthio) -1,3, 5-triazin-2-yl ] amino ] -2, 6-di-tert-butylphenol: trade name "Irganox565" (manufactured by BASF corporation), 2' -methylenebis [6- (2H-benzotriazol-2-yl) -4- (1, 3-tetramethylbutyl) phenol: trade name "Adekastab LA-31" (manufactured by ADEKA corporation) trade name "Adekastab LA-F70" (manufactured by ADEKA corporation), and the like. Among them, from the viewpoint of having a large molecular weight and a large volume structure, trade names "Irganox1010" (manufactured by BASF corporation), trade names "Irganox1330" (manufactured by BASF corporation), trade names "Irganox3114" (manufactured by BASF corporation), trade names "adekasab LA-31" (manufactured by ADEKA corporation), and trade names "adekasab LA-F70" (manufactured by ADEKA corporation) may be preferably used. Particularly preferred are pentaerythritol-tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ] or 2,2' -methylenebis [6- (2H-benzotriazol-2-yl) -4- (1, 3-tetramethylbutyl) phenol ], most preferred is pentaerythritol-tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ].

A-1-3 acrylic resin

The retardation film in the embodiment of the present invention may contain an acrylic resin. By containing the acrylic resin, the breaking strength and ultimate stretch ratio at the time of film stretching are improved, and higher orientation can be exhibited. In addition, by reducing the fracture frequency, the yield of the stretching process can be improved.

As the acrylic resin, an acrylic resin is used as the thermoplastic resin. Examples of the monomer that becomes a structural unit of the acrylic resin include the following compounds: methyl methacrylate, methacrylic acid, methyl acrylate, acrylic acid, benzyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, glycidyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, and norbornyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, acryl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2- (meth) acryloyloxyethyl succinate, 2- (meth) acryloyloxyethyl maleate, 2- (meth) acryloyloxyethyl phthalate, 2- (meth) acryloyloxyethyl hexahydrophthalate, 2- (meth) acryloyloxyethyl (meth) acrylate, pentamethylpiperidine (meth) acrylate, tetramethylpiperidine (meth) acrylate, and, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, cyclopentyl methacrylate, cyclopentyl acrylate, cyclohexyl methacrylate, cyclohexyl acrylate, cycloheptyl methacrylate, cycloheptyl acrylate, cyclooctyl methacrylate, cyclooctyl acrylate, cyclododecyl methacrylate, cyclododecyl acrylate. They may be used alone or in combination of 2 or more. Examples of the mode of using 2 or more monomers in combination include: copolymerization of 2 or more monomers, blending of homopolymers of 2 or more 1 monomer, and combinations thereof. Further, other monomers (for example, olefin monomers and vinyl monomers) which can be copolymerized with these acrylic monomers may be used in combination.

The acrylic resin preferably contains a structural unit derived from methyl methacrylate. The content of the structural unit derived from methyl methacrylate in the acrylic resin is preferably 70 to 100% by mass. The lower limit is more preferably 80 mass% or more, still more preferably 90 mass% or more, and particularly preferably 95 mass% or more. When the amount is within this range, excellent compatibility with the polycarbonate resin of the present invention can be obtained. As the structural unit other than methyl methacrylate, methyl acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, and styrene are preferably used. Thermal stability can be improved by copolymerizing methyl acrylate. The refractive index of the acrylic resin can be adjusted by using phenyl (meth) acrylate, benzyl (meth) acrylate, and styrene, and thus the transparency of the obtained resin composition can be improved by matching the refractive index of the combined resin.

The weight average molecular weight Mw of the acrylic resin is preferably 10,000 to 200,000. The lower limit is preferably 30,000 or more, particularly preferably 50,000 or more. The upper limit is preferably 180,000 or less, particularly preferably 150,000 or less. When the molecular weight is within this range, compatibility with the polycarbonate-based resin of the present invention can be obtained, and thus the transparency of the final retardation film can be improved, and the effect of sufficiently improving the stretchability upon stretching can be obtained. The weight average molecular weight is a molecular weight in terms of polystyrene measured by GPC (GelPermeation Chromatography ). Details of the measurement method are described later. In addition, from the viewpoint of compatibility, the acrylic resin preferably contains substantially no branched structure. The absence of the branched structure can be confirmed by unimodal GPC curve of the acrylic resin.

The content of the acrylic resin in the resin composition (as a result of the retardation film) is preferably 0 to 2.0 mass%. The upper limit is preferably 1.5 mass% or less, more preferably 1.0 mass% or less, still more preferably 0.9 mass% or less, and particularly preferably 0.8 mass% or less. In this way, by blending the acrylic resin into the polycarbonate resin at a very limited ratio, the stretchability and the retardation manifestation can be significantly increased. Further, haze can be suppressed. The above-described effects are not theoretically clear, and are unexpected excellent effects obtained by trial and error. If the content of the acrylic resin is too small, the above-mentioned effects may not be obtained. On the other hand, if the content of the acrylic resin is too large, there is a case where haze becomes high. In addition, the extensibility and the phase difference performance are often insufficient or reduced as compared with those in the above range.

A-1-4. Resin composition

A method for producing a retardation film by blending a polycarbonate resin or the like with the above-mentioned modifier or acrylic resin and supplying the resultant to the retardation film as a resin composition (the production method is described in item A-3). The polycarbonate resin and the like are preferably blended with the modifier or the acrylic resin in a molten state. As a method of blending in a molten state, melt kneading using an extruder can be exemplified. The kneading temperature (molten resin temperature) is preferably 200 to 280 ℃, more preferably 220 to 270 ℃, and even more preferably 230 to 260 ℃. When the kneading temperature is within the above range, pellets of the resin composition in which the thermal decomposition is suppressed and the modifier or the acrylic resin is uniformly blended can be obtained. If the temperature of the molten resin in the extruder exceeds 280 ℃, coloration and/or thermal decomposition of the resin may occur. On the other hand, if the temperature of the molten resin in the extruder is lower than 200 ℃, the viscosity of the resin may become too high, causing an excessive load on the extruder or insufficient melting of the resin. Any suitable structure may be used as the structure of the extruder, the structure of the screw, and the like. In order to obtain transparency or uniform dispersibility of the resin which can withstand the use of the optical film, a twin screw extruder is preferably used. Further, since the low molecular weight components remaining in the resin or the low molecular weight thermally decomposed components in the extrusion kneading may contaminate the cooling roll or the conveying roll in the film forming step or the stretching step, an extruder having a vacuum vent is preferably used for removing the components.

For modifying the mechanical properties and/or the solvent resistance, the resin composition may further contain synthetic resins such AS aromatic polycarbonate, aliphatic polycarbonate, aromatic polyester, aliphatic polyester, polyamide, polystyrene, polyolefin, acrylic acid, amorphous polyolefin, ABS (acrylonitrile-butadiene-styrene copolymer), AS (acrylonitrile-styrene copolymer), polylactic acid, polybutylene succinate, rubber, or a combination thereof.

The resin composition may further contain an additive. Specific examples of the additive include: heat stabilizers, antioxidants, catalyst deactivators, ultraviolet absorbers, light stabilizers, mold release agents, dye pigments, impact modifiers, antistatic agents, slip agents, lubricants, plasticizers, compatibilizers, nucleating agents, flame retardants, inorganic fillers, foaming agents. The kind, amount, combination, content, and the like of the additives contained in the resin composition can be appropriately set according to the purpose.

A-2 characteristics of phase-difference film

The in-plane retardation Re (550) of the retardation film is, as described above, 100nm to 200nm, preferably 110nm to 180nm, more preferably 120nm to 160nm, and still more preferably 130nm to 150nm. That is, the retardation film can function as a so-called λ/4 plate.

The retardation film typically satisfies the relationship Re (450) < Re (550) < Re (650). That is, the phase difference film exhibits a reverse dispersion wavelength dependence in which the phase difference value becomes larger with the wavelength of the measurement light. Re (450)/Re (550) of the retardation film exceeds 0.5 and is less than 1.0 as described above, and is preferably 0.7 to 0.95, more preferably 0.75 to 0.92, and still more preferably 0.8 to 0.9.Re (650)/Re (550) is preferably 1.0 or more and less than 1.15, more preferably 1.03 to 1.1.

The retardation film has a relationship of nx > ny because of the in-plane retardation as described above. The retardation film exhibits any appropriate refractive index ellipsoid as long as it has a relationship of nx > ny. The refractive index ellipsoids of retardation films typically show a relationship of nx > ny.gtoreq.nz. Further, "ny=nz" herein includes not only the case where ny is completely equal to nz but also the case where ny is substantially equal to nz. Therefore, ny < nz may be present within a range that does not impair the effects of the present invention. The Nz coefficient of the retardation film is preferably 0.9 to 2.0, more preferably 0.9 to 1.5, and even more preferably 0.9 to 1.2. By satisfying the above relation, when the circularly polarizing plate including the phase difference film is used for an image display device, a very excellent reflection hue can be achieved.

The thickness of the retardation film can be set so as to function most appropriately as a lambda/4 plate. In other words, the thickness may be set in such a manner as to obtain a desired in-plane retardation. Specifically, the thickness is preferably 15 μm to 60. Mu.m, more preferably 20 μm to 55. Mu.m, and most preferably 20 μm to 50. Mu.m. According to the embodiment of the present invention, a retardation film excellent in retardation expression can be obtained, and therefore the thickness of the retardation film can be made thinner than a usual λ/4 plate.

The haze value of the retardation film is preferably 1.5% or less, more preferably 1.0% or less, and further preferably 0.5% or less. According to the embodiment of the present invention, a reverse dispersion retardation film excellent in both of the retardation expression and the haze value can be realized. The smaller the haze value, the better. The lower limit of the haze value may be, for example, 0.1%.

The birefringence Δn of the retardation film is preferably 0.0025 or more, more preferably 0.0030 or more, further preferably 0.0035 or more, and particularly preferably 0.0040 or more. The upper limit of the birefringence Δn may be, for example, 0.0070. The birefringence can be obtained by dividing the in-plane retardation Re of the film at the highest stretch ratio without breaking by the film thickness d.

The absolute value of the photoelastic modulus of the retardation film is preferably 20×10 ^-12 (m ² N) or less, more preferably 1.0X10 ^-12 (m ² /N)～15×10 ^-12 (m ² N), more preferably 2.0X10 ^-12 (m ² /N)～12×10 ^-12 (m ² /N). If the absolute value of the photoelastic modulus is within the above range, display unevenness can be suppressed in the case where the phase difference film is applied to an image display device.

A-3 method for producing retardation film

The retardation film described in the above item A-1 and item A-2 is obtained by: a film is formed from the resin composition described in item A-1, and the film is stretched. As a method for forming a film from the resin composition, any suitable molding method may be used. Specific examples thereof include: compression molding, transfer molding, injection molding, extrusion molding, blow molding, powder molding, FRP (Fiber Reinforced Plastics, fiber reinforced plastic) molding, cast coating (e.g., casting), calendaring, hot pressing, and the like. Among them, an extrusion molding method or a cast coating method is preferable, which can improve the smoothness of the obtained film and can obtain good optical uniformity. Since the cast coating method may cause problems due to residual solvents, extrusion molding is particularly preferred, and among them, melt extrusion molding using a T-die is preferred from the viewpoint of productivity of the film or easiness of subsequent stretching treatment. The molding conditions may be appropriately set according to the composition or type of the resin used, the characteristics required for the retardation film, and the like. Thus, a resin film containing a polycarbonate resin or the like can be obtained.

The thickness of the resin film (unstretched film) may be set to any appropriate value according to the desired thickness of the obtained phase difference film, the desired optical characteristics, stretching conditions described later, and the like. Preferably 50 μm to 300. Mu.m.

The stretching may be performed by any suitable stretching method or stretching conditions (e.g., stretching temperature, stretching ratio, stretching direction). Specifically, various stretching methods such as free end stretching, fixed end stretching, free end shrinkage, fixed end shrinkage and the like may be used alone, or the above stretching methods may be used simultaneously or sequentially. The stretching direction can be performed in various directions or dimensions such as a longitudinal direction, a width direction, a thickness direction, and an oblique direction.

By appropriately selecting the stretching method and the stretching conditions, a retardation film having the above-described desired optical characteristics (for example, refractive index characteristics, in-plane retardation, nz coefficient) can be obtained.

In one embodiment, the retardation film is produced by uniaxially stretching or uniaxially stretching the resin film at the fixed end. A specific example of the uniaxial stretching is a method of stretching a resin film in a traveling direction (longitudinal direction) while traveling in the longitudinal direction. As a specific example of the fixed-end uniaxial stretching, a method of stretching a resin film in the width direction (transverse direction) while moving in the longitudinal direction can be exemplified. The stretching ratio is preferably 1.1 to 3.5 times.

In another embodiment, the retardation film can be produced by continuously stretching a long resin film obliquely in a direction at a specific angle with respect to the longitudinal direction. By using oblique stretching, a long stretched film having an orientation angle (a slow axis in a direction of a specific angle) of a specific angle with respect to the longitudinal direction of the film can be obtained, and for example, roll-to-roll can be used when stacking with a polarizer, thereby simplifying the manufacturing process. Further, the above-mentioned specific angle may be an angle formed by an absorption axis of a polarizer and a slow axis of a retardation film in a circularly polarizing plate (described later). As described below, the angle is preferably 40 ° to 50 °, more preferably 42 ° to 48 °, further preferably 44 ° to 46 °, particularly preferably about 45 °; or preferably 130 to 140, more preferably 132 to 138, even more preferably 134 to 136, and particularly preferably about 135.

Examples of the stretching machine used in the diagonal stretching include a tenter stretching machine capable of applying a feeding force, a stretching force, or a drawing force having different lateral speeds in the lateral and/or longitudinal directions. Examples of the tenter type stretching machine include a transverse uniaxial stretching machine and a simultaneous biaxial stretching machine, but any suitable stretching machine may be used as long as the long resin film can be continuously and obliquely stretched.

By appropriately controlling the left and right speeds of the stretching machine, a retardation film (substantially long retardation film) having the desired in-plane retardation and having a slow axis in the desired direction can be obtained.

Examples of the method of the oblique stretching include those described in JP-A-50-83482, JP-A-2-113920, JP-A-3-182701, JP-A-2000-9912, JP-A-2002-86554, and JP-A-2002-22944.

In one embodiment, the stretching temperature of the film is a temperature equal to or lower than the glass transition temperature (Tg) of a polycarbonate resin or the like. In general, when a film such as a polycarbonate resin is stretched, the film is in a glass state at a temperature of Tg or less, and thus stretching is substantially impossible. According to the embodiment of the present invention, by blending a small amount of an acrylic resin (typically polymethyl methacrylate), stretching can be performed at Tg or lower without substantially changing Tg of a polycarbonate resin or the like. Further, although not clearly shown in theory, by stretching at a temperature of Tg or lower, a reverse dispersion retardation film excellent in stretchability and retardation expression and having a small haze can be obtained. Specifically, the stretching temperature is preferably from Tg to Tg-10deg.C, more preferably from Tg to Tg-8deg.C, and still more preferably from Tg to Tg-5deg.C. The film may be stretched at a temperature higher than Tg, for example, about Tg+5℃, and at a temperature of about Tg+2℃.

B. Circular polarizer

The retardation film according to the embodiment of the present invention described in item a above can be suitably used for a circularly polarizing plate. Accordingly, embodiments of the present invention also include circular polarizers. Fig. 1 is a schematic cross-sectional view of a circularly polarizing plate according to an embodiment of the present invention. The circularly polarizing plate 100 illustrated in the figure has a polarizing plate 10 and a retardation film 20. The retardation film 20 is the retardation film according to the embodiment of the present invention described in item a above. The polarizing plate 10 includes: a polarizer 11; a 1 st protective layer 12 disposed on one side of the polarizer 11; and a 2 nd protective layer 13 disposed on the other side of the polarizer 11. One of the 1 st protective layer 12 and the 2 nd protective layer 13 may be omitted according to purposes. For example, since the retardation film 20 according to the embodiment of the present invention can also function as a protective layer of the polarizer 11, the 2 nd protective layer 13 can be omitted. The angle between the slow axis of the retardation film 20 and the absorption axis of the polarizer 11 is preferably 40 ° to 50 °, more preferably 42 ° to 48 °, further preferably 44 ° to 46 °, and particularly preferably about 45 °; or preferably 130 to 140, more preferably 132 to 138, even more preferably 134 to 136, and particularly preferably about 135.

In another embodiment, another retardation layer and/or a conductive layer or an isotropic substrate with a conductive layer (not shown) may be provided. The other retardation layer and the conductive layer or the isotropic substrate with the conductive layer are typically provided outside the retardation film 20 (on the opposite side of the polarizing plate 10). The refractive index characteristic of the other retardation layer typically shows a relationship of nz > nx=ny. By providing the above-described other retardation layer, reflection in an oblique direction can be satisfactorily prevented, and a wide viewing angle of an antireflection function can be achieved. The other retardation layer and the conductive layer or the isotropic substrate with the conductive layer are typically provided in order from the retardation film 20 side. The other retardation layer and the conductive layer or the isotropic substrate with the conductive layer are typically any layers provided as needed, and either or both of them may be omitted. Further, in the case of an isotropic substrate provided with a conductive layer or with a conductive layer, the circular polarizer may be applied to a so-called internal touch panel type input display device in which a touch sensor is assembled between an image display unit (for example, an organic EL unit) and a polarizer.

The circularly polarizing plate may also have a further retardation layer. The further retardation layer may be provided in combination with another retardation layer or may be provided separately (i.e., without providing another retardation layer). The optical characteristics (for example, refractive index characteristics, in-plane retardation, nz coefficient, photoelastic modulus), thickness, arrangement position, and the like of the retardation layer can be appropriately set according to the purpose.

The circular polarizer may be monolithic or elongated. In the present specification, the term "elongated" means an elongated shape having a length long enough to the width, and includes, for example, an elongated shape having a length 10 times or more, preferably 20 times or more, the width. The elongated circular polarizer may be wound into a roll. In the case where the circularly polarizing plate is elongated, the polarizing plate and the retardation film are also elongated. In this case, the polarizer preferably has an absorption axis in the longitudinal direction. The retardation film is preferably an obliquely stretched film having a slow axis in a direction at an angle of 40 ° to 50 ° or 130 ° to 140 ° with respect to the longitudinal direction, as described above. If the polarizer and the retardation film are configured as described above, a circularly polarizing plate can be manufactured by roll-to-roll.

In terms of practicality, an adhesive layer (not shown) may be provided on the opposite side of the retardation film from the polarizing plate to attach the circular polarizing plate to the image display unit. Further, it is preferable that a release film is temporarily adhered to the surface of the pressure-sensitive adhesive layer until the circularly polarizing plate is used. By temporarily adhering the release film, the adhesive layer can be protected, and a roll of the circularly polarizing plate can be formed.

Hereinafter, the constituent elements of the circularly polarizing plate will be described.

B-1 polarizer

As the polarizer 11, any suitable polarizer may be used. For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

Specific examples of the polarizer composed of a single-layer resin film include: a polarizer obtained by dyeing and stretching a hydrophilic polymer film such as a polyvinyl alcohol (PVA) film, a partially formalized PVA film, or an ethylene-vinyl acetate copolymer partially saponified film, a polyvinyl orientation film such as a dehydrated product of PVA or a dehydrochlorination product of polyvinyl chloride, and the like with a dichroic substance such as iodine or a dichroic dye. In terms of excellent optical characteristics, a polarizer obtained by dyeing a PVA-based film with iodine and uniaxially stretching the film is preferably used.

The dyeing with iodine is performed, for example, by immersing the PVA-based film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after dyeing treatment or may be performed while dyeing. Alternatively, dyeing may be performed after stretching. The PVA-based film is optionally subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, and the like. For example, by immersing the PVA-based film in water and washing it with water before dyeing, not only stains or anti-blocking agents on the surface of the PVA-based film can be washed, but also the PVA-based film can be swelled to prevent uneven dyeing.

Specific examples of the polarizer obtained by using the laminate include a laminate of a resin base material and a PVA-based resin layer (PVA-based resin film) laminated on the resin base material, and a polarizer obtained by coating a laminate of a resin base material and a PVA-based resin layer formed on the resin base material. A polarizer obtained by using a laminate of a resin substrate and a PVA-based resin layer formed on the resin substrate can be produced, for example, by applying a PVA-based resin solution to a resin substrate and drying the same to form a PVA-based resin layer on the resin substrate, thereby obtaining a laminate of a resin substrate and a PVA-based resin layer; the laminate was stretched and dyed to prepare a polarizer from the PVA-based resin layer. In the present embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution to perform stretching. Further, stretching may optionally further include stretching the laminate in air at a high temperature (for example, 95 ℃ or higher) before stretching in an aqueous boric acid solution. The obtained laminate of the resin substrate and the polarizer may be used as it is (that is, the resin substrate may be used as a protective layer for the polarizer), or the resin substrate may be peeled from the laminate of the resin substrate and the polarizer, and any appropriate protective layer depending on the purpose may be laminated on the peeled surface. Details of the method for producing the polarizer are described in, for example, japanese patent application laid-open nos. 2012-73580 (5414738) and 6470455. The description of this patent document is incorporated by reference into the present specification.

The thickness of the polarizer is preferably 15 μm or less, more preferably 1 μm to 12 μm, still more preferably 3 μm to 10 μm, particularly preferably 3 μm to 8 μm. When the thickness of the polarizer is within the above range, curling at the time of heating can be favorably suppressed, and excellent durability of appearance at the time of heating can be obtained. Further, if the thickness of the polarizer is within the above range, the circularly polarizing plate (as a result, the organic EL display device) can be made thinner.

The polarizer preferably exhibits absorption dichroism at any one of wavelengths 380nm to 780 nm. The monomer transmittance of the polarizer is preferably 43.0% to 46.0%, more preferably 44.5% to 46.0%. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and still more preferably 99.9% or more.

B-2. Protective layer

The 1 st protective layer 12 and the 2 nd protective layer 13 are each formed of any suitable film that can be used as a protective layer of a polarizer. Specific examples of the material that becomes the main component of the film include: cellulose resins such as triacetyl cellulose (TAC), transparent resins such as polyester resins, polyvinyl alcohol resins, polycarbonate resins, polyamide resins, polyimide resins, polyether sulfone resins, polysulfone resins, polystyrene resins, polynorbornene resins, polyolefin resins, (meth) acrylic resins, acetate resins, and the like. Further, it is also possible to exemplify: and (meth) acrylic, urethane, thermosetting resins such as urethane (meth) acrylate, epoxy and silicone resins, ultraviolet curable resins, and the like. In addition, for example, a vitreous polymer such as a siloxane polymer may be used. In addition, a polymer film described in Japanese patent application laid-open No. 2001-343529 (WO 01/37007) can be used. As a material of the film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in a side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in a side chain, for example, a resin composition containing an alternating copolymer of isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer can be used. The polymer film may be, for example, an extrusion molded product of the above resin composition.

As described below, the circular polarizer is typically disposed on the viewing side of the image display device, and the 1 st protective layer 12 is typically disposed on the viewing side. Therefore, the 1 st protective layer 12 may be subjected to surface treatments such as hard coat treatment, antireflection treatment, anti-sticking treatment, antiglare treatment, and the like, as necessary. Further, the 1 st protective layer 12 may be optionally subjected to a treatment for improving visibility when it is visually recognized through polarized sunglasses (typically, an (elliptical) polarized function or an ultra-high phase difference is given). By performing the above-described processing, even when the display screen is visually recognized through a polarized lens such as polarized sunglasses, excellent visibility can be achieved. Therefore, the circularly polarizing plate can be preferably applied to an image display device that can be used outdoors.

The thickness of the 1 st protective layer is typically 300 μm or less, preferably 100 μm or less, more preferably 5 μm to 80 μm, and still more preferably 10 μm to 60 μm. When the surface treatment is performed, the thickness of the outer protective layer includes the thickness of the surface treatment layer.

The 2 nd protective layer 13 is preferably optically isotropic in one embodiment. In the present specification, the term "having optical isotropy" means that the in-plane retardation Re (550) is from 0nm to 10nm, and the retardation Rth (550) in the thickness direction is from-10 nm to +10nm.

C. Image display device

The circularly polarizing plate as defined in item B above, which is applicable to an image display device. Accordingly, the embodiment of the present invention also includes an image display device using the circularly polarizing plate. As typical examples of the image display device, a liquid crystal display device and an organic EL display device are given. The image display device according to the embodiment of the present invention includes the circularly polarizing plate described in the above item B on the viewing side. The circularly polarizing plate is disposed so that the polarizer is on the viewing side.

Examples (example)

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. The measurement method of each characteristic is as follows.

(1) Thickness of (L)

The measurement was performed using a dial gauge (manufactured by PEACOCK Co., ltd., product name "DG-205 typepds-2").

(2) Glass transition temperature (Tg)

The glass transition temperature of the resin and the film was measured by using a differential scanning calorimeter DSC6220 manufactured by Seiko electronic nanotechnology Co. About 10mg of the resin sample was charged into an aluminum pot manufactured by Seiko electronic nanotechnology corporation and sealed, and the temperature was raised from 30℃to 200℃at a temperature-raising rate of 20℃per minute under a nitrogen gas stream of 50 mL/minute. After maintaining this temperature for 3 minutes, it was cooled to 30℃at a rate of 20℃per minute. The temperature was maintained at 30℃for 3 minutes and again raised to 200℃at a rate of 20℃per minute. From DSC (Differential Scanning Calorimetry ) data obtained at the 2 nd temperature rise, an extrapolated glass transition start temperature, which is a temperature at which an intersection of a straight line obtained by extending a base line on a low temperature side toward a high temperature side and a tangent line made at a point at which a gradient of a curve of a stepwise change portion of the glass transition reaches a maximum, is obtained and taken as a glass transition temperature (Tg).

(3) Water absorption rate

The films obtained in examples and comparative examples were used and measured according to the "test method for water absorption and boiling water absorption of plastics" described in JISK 7209. The test piece was square with a side length of 50mm, and the water absorption was determined by immersing the test piece in water at a water temperature of 25℃for 24 hours and then measuring the weight change before and after immersion. The unit is%.

(4) Content of modifier in resin

By passing through ¹ H-NMR( ¹ The actual content of modifier (compound (a)) in the resin was analyzed by Hydrogen nuclear magnetic Resonance. About 15mg of the retardation film obtained in examples and comparative examples was weighed and dissolved in about 0.7mL of deuterated chloroform, and the resulting solution was placed in a tube for NMR having an inner diameter of 5mm, and the measurement was performed ¹ H-NMR spectrum. In addition, the resin and modifier containing no modifier were precisely weighed, samples of known contents were prepared, and the same manner was used for measurement ¹ H-NMR. According to the obtained ¹ The H-NMR spectrum is obtained by calculating the integral value of each proton from the signals from the components constituting the resin and the signals from the modifier, multiplying the integral value by the molecular weight of each component, and calculating the value corresponding to the weight of the resin and the weight of the modifier. When the values were X, Y, the modifier content was determined by the following formula. Here, the coefficient α is determined from the measurement result of a sample of a known content.

Content of modifier [ mass% ] =α×y/(x+y) ×100

The apparatus and conditions used are as follows.

Device: JNM-ECZ400S (manufactured by Japanese electronics Co., ltd.)

Measurement temperature: 30 DEG C

Relaxation time: 6 seconds

Cumulative number of times: 64 times

(5) Phase difference value

From the retardation films obtained in examples and comparative examples, 50 mm. Times.50 mm samples were cut out as measurement samples, and were measured using Axoscan manufactured by Axometrics corporation. The measurement wavelength was 450nm, 550nm, 590nm, 650nm, and the measurement temperature was 23 ℃.

(6) Phase difference variation in humidification test

The retardation films obtained in examples and comparative examples were laminated on glass via an adhesive layer to prepare samples, and the retardation was measured in the same manner as in the measurement of the retardation. After the sample after measurement was left at 60℃for 500 hours in 90% RH, the sample was taken out, and the phase difference was measured again to determine the rate of change (%) of Re (550).

Good: the absolute value of the phase difference change rate (%) is lower than 1.40%

Poor: the absolute value of the phase difference change rate (%) is 1.40% or more

(7) Dimensional change in humidification test

The stretched films or the retardation films obtained in examples and comparative examples were cut into 20mm (slow axis direction) ×4mm (fast axis direction) as measurement samples. After the measurement sample was left at 60℃for 500 hours in a 90% RH atmosphere, the dimensional change rate of the measurement sample in the longitudinal direction was measured.

Good: the absolute value of the dimensional change rate (%) is lower than 0.12%

Poor: the absolute value of the dimensional change rate (%) is 0.12% or more

(8) Dimensional change in heating and humidification experiments

The stretched films or the retardation films obtained in examples and comparative examples were cut into 20mm (slow axis direction) ×4mm (fast axis direction) as measurement samples. After the measurement sample was left at 85℃for 500 hours in an environment of 85% RH, the dimensional change rate of the measurement sample in the longitudinal direction was measured.

Good: the absolute value of the dimensional change rate (%) is less than 0.30%

Poor: the absolute value of the dimensional change rate (%) is 0.30% or more

[ short for Compounds ]

The following synthesis examples, examples and comparative examples are given by way of short.

BPFM: bis [9- (2-phenoxycarbonylethyl) fluoren-9-yl ] methane

Synthesized by the method described in Japanese patent application laid-open No. 2015-25111 (Japanese patent application laid-open No. 6311264).

[ chemical 11]

ISB: isosorbide (manufactured by Roquetteffreres Co.)

SPG: spiro glycol (Mitsubishi gas chemical Co., ltd.)

DPC: diphenyl carbonate (manufactured by mitsubishi chemical Co., ltd.)

PHL: phenol [ Mitsubishi chemical company manufacturing ]

Irganox1010: pentaerythritol-tetrakis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ] [ BASF Co., ltd. ] … molecular weight 1178

Irganox1330:1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-t-butyl-4-hydroxybenzyl) benzene [ BASF corporation ] … molecular weight 775

Irganox3114: tris (3, 5-di-tert-butyl-4-hydroxybenzyl) isocyanurate [ manufactured by BASF corporation ] … molecular weight 784

LA-31:2,2' -methylenebis [6- (2H-benzotriazol-2-yl) -4- (1, 3-tetramethylbutyl) phenol [ ADEKA Co., ltd. ] … molecular weight 659

LA-F70:6,6' - (1, 3, 5-triazine-2, 4, 6-triyl) tris (3-hexyloxy-2-methylphenol) [ manufactured by ADEKA Co., ltd. ] … molecular weight 700

TPP: triphenyl phosphate (manufactured by tokyo chemical industry Co., ltd.) … molecular weight 326

DMT: dimethyl terephthalate manufactured by tokyo chemical industry Co., ltd.) … molecular weight 194

PEP36:3, 9-bis (2, 6-di-tert-butyl-4-methylphenoxy) -2,4,8, 10-tetraoxa-3, 9-diphosphaspiro [5.5] undecane [ ADEKA Co., ltd. ] … molecular weight 633

BR80: acrylic resin [ Mitsubishi chemical Co., ltd. ]

Production example 1

The polyester carbonate resin was polymerized using a continuous polymerization apparatus comprising a vertical stirring reactor 3 stage, a horizontal stirring reactor 1 stage, and a biaxial extruder. ISB, SPG and PHL, BPFM and DPC were melted in each melting vessel (PHL is a solvent used to dissolve SPG). At this time, the mixture was carried out so that the weight ratio of SPG to PHL became 55.0/45.0 and the weight ratio of BPFM to DPC became 30.3/69.7. The ISB melt was continuously fed to the 1 st vertical stirring reactor at a flow rate of 49.9 parts by weight/hr, the SPG-PHL blend at 68.5 parts by weight/hr, and the BPFM-DPC blend at 75.3 parts by weight/hr (ISB/SPG/BPFM/dpc=0.734/0.266/0.126/0.874 in terms of molar ratio). Meanwhile, an aqueous solution of calcium acetate monohydrate as a polymerization catalyst was supplied to the 1 st vertical agitation reactor in such a manner that the addition amount of calcium acetate monohydrate became 12. Mu. Mol with respect to 1mol of all the dihydroxy compounds. The internal temperature, internal pressure, and residence time of each reactor were set as follows: 1 st vertical stirred reactor: 195℃and 27kPa for 90 minutes; 2 nd vertical stirring reactor: 205 ℃, 20kPa, 70 minutes; 3 rd vertical stirred reactor: 220 ℃ and 10kPa for 60 minutes; 4 th horizontal stirring reactor: 235 deg.c, 0.1-1.0 kPa for 150 min. The operation is performed while the vacuum pressure of the 4 th horizontal stirring reactor is finely adjusted so that the reduced viscosity of the finally obtained resin becomes 0.45 to 0.47 dL/g. The resin withdrawn from the 4 th horizontal type stirring reactor was supplied in a molten state to a vented twin screw extruder [ manufactured by japan steel company ]. The extruder had 2 vacuum vents, where the low molecular weight components remaining in the resin were devolatilized and 3.7 weight ppm of phosphonic acid relative to the polyester carbonate resin was added as a catalyst deactivator before vent 1. After the 2 nd vent, irganox1010 in an amount of 1000 mass ppm with respect to the polyester carbonate resin and PEP36 in an amount of 100 mass ppm with respect to the polyester carbonate resin were added as heat stabilizers. Further, irganox1010 and PEP36 added here are compounds corresponding to the compound (a) in the present invention, and are contained in the content of the modifier. The polycarbonate resin passed through the extruder was continuously passed through a Upleat candle filter [ PALL Co., ltd.) having a mesh size of 10 μm in a molten state to filter out foreign matters. Thereafter, the molten resin is extruded from the die into a linear shape, cooled with water, solidified, and then cut by a rotary cutter, whereby pellets are produced. The ratio of structural units derived from each monomer was BPFM/ISB/SPG/dpc=21.5/39.4/30.0/9.1 mass%.

Example 1

The polyester-carbonate resin obtained in production example 1 was used for extrusion kneading. The pellets of the polyester carbonate resin were mixed with Irganox1010 2.0 mass% as a modifier, and fed into a twin-screw extruder TEX30HSS [ manufactured by Japanese Steel Co., ltd.) using a quantitative feeder. The extruder cylinder temperature was set at 240℃and extrusion was carried out at a throughput of 12 kg/hr and a screw speed of 120 rpm. The extruder was equipped with a vacuum vent, and the molten resin was extruded while being volatilized under reduced pressure. The molten resin was extruded from a die into a strand form, cooled with water, solidified, and then cut by a rotary cutter to obtain pellets. After the pellets of the resin composition obtained in this manner were dried under vacuum at 100℃for 6 hours or more, a long unstretched film having a length of 10m, a width of 350mm and a thickness of 110 μm was produced using a film-forming apparatus equipped with a single-screw extruder (manufactured by Technovel, screw diameter: 30mm, cylinder set temperature: 235℃with vacuum vent), T-die (width: 400mm, set temperature: 245 ℃), cooling rolls (set temperature: 125 to 135 ℃) and a winder. After the film was removed, the surface of the chill roll was confirmed, and as a result, no stains on the roll were observed. The glass transition temperature (Tg) of the obtained film was 137℃and the water absorption was 1.6%. Then, a sample of 120mm (conveyance direction of the film at the time of production: MD (machine direction)) ×150mm (direction perpendicular to the conveyance direction: TD (transverse direction)) was cut out from the long unstretched film. A retardation film was produced by uniaxially stretching a sample at a fixed end in the TD direction with the stretching temperature set to "tg+4℃" of the resin sample using a laboratory stretcher "blueknerkkariv", and adjusting the in-plane retardation Re (measurement wavelength 590 nm) to 145 nm. The results are shown in Table 1.

Example 2

A retardation film was produced in the same manner as in example 1, except that Irganox1330 was incorporated in an amount of 1 mass% as a modifier. It was confirmed that a small amount of adhering matter was present on the surface of the cooling roll. The Tg of the film was 140℃and the water absorption was 1.7%. The obtained retardation film was subjected to the same evaluation as in example 1. The results are shown in Table 1.

Example 3

A retardation film was produced in the same manner as in example 1, except that Irganox1330 was incorporated in an amount of 2 mass% as a modifier. It was confirmed that a small amount of adhering matter was present on the surface of the cooling roll. The film had a Tg of 139℃and a water absorption of 1.6%. The obtained retardation film was subjected to the same evaluation as in example 1. The results are shown in Table 1.

Example 4

A retardation film was produced in the same manner as in example 1, except that Irganox3114 was incorporated in an amount of 2 mass% as a modifier. It was confirmed that a small amount of adhering matter was present on the surface of the cooling roll. The film had a Tg of 139℃and a water absorption of 1.7%. The obtained retardation film was subjected to the same evaluation as in example 1. The results are shown in Table 1.

Example 5

A retardation film was produced in the same manner as in example 1, except that 2 mass% of LA-31 was blended as a modifier. No staining of the chill roll surface was observed. The film had a Tg of 138℃and a water absorption of 1.7%. The obtained retardation film was subjected to the same evaluation as in example 1. The results are shown in Table 1.

Example 6

A retardation film was produced in the same manner as in example 1, except that 2 mass% of Irganox1010 was used as a modifier and 0.7 mass% of BR80 was used as an acrylic resin. No staining of the chill roll surface was observed. The Tg of the film was 137℃and the water absorption was 1.6%. A retardation film was obtained in the same manner as in example 1, except that the stretching temperature was set to "Tg-2 ℃. The results are shown in Table 1.

Example 7

A retardation film was produced in the same manner as in example 1, except that 1.5 mass% of Irganox1010 as a modifier, 0.3 mass% of LA-F70, and 0.7 mass% of BR80 as an acrylic resin were blended. No staining of the chill roll surface was observed. The Tg of the film was 137℃and the water absorption was 1.7%. The obtained retardation film was subjected to the same evaluation as in example 1. The results are shown in Table 1.

Comparative example 1

A retardation film was produced in the same manner as in example 1, except that 0.2 mass% of Irganox1010 was blended as a modifier. No staining of the chill roll surface was observed. The Tg of the film was 140℃and the water absorption was 1.8%. The obtained retardation film was subjected to the same evaluation as in example 1. The results are shown in Table 1.

Comparative example 2

Extrusion kneading was performed in the same manner as in example 1 except that 5 mass% of Irganox1010 was blended as a modifier, but the ejection state of the molten resin was unstable, and a pellet sample could not be obtained.

Comparative example 3

A retardation film was produced in the same manner as in example 1, except that 2 mass% of TPP was blended as a modifier. No staining of the chill roll surface was observed. The film had a Tg of 134℃and a water absorption of 1.5%. The obtained retardation film was subjected to the same evaluation as in example 1. The results are shown in Table 1.

Comparative example 4

A retardation film was produced in the same manner as in example 1, except that 2 mass% of DMT was blended as a modifier. It was confirmed that a small amount of adhering matter was present on the surface of the cooling roll. The film had a Tg of 131℃and a water absorption of 1.5%. The obtained retardation film was subjected to the same evaluation as in example 1. The results are shown in Table 1.

TABLE 1

[ evaluation ]

As is clear from table 1, by the constitution having the example of the present invention, a retardation film in which the change in retardation under the humidified condition, the change in dimension, and the change in dimension under the heated and wet condition were suppressed was obtained.

[ Industrial applicability ]

The retardation film of the present invention can be suitably used for a circularly polarizing plate, and the circularly polarizing plate can be suitably used for an image display device (typically, a liquid crystal display device or an organic EL display device).

Symbol description

10: polarizing plate

11: polarizer

12: 1 st protective layer

13: 2 nd protective layer

20: retardation film

100: circular polarizer

Claims (9)

1. A retardation film, comprising: a resin that contains at least 1 kind of bonding group selected from the group consisting of a carbonate bond and an ester bond, and at least 1 kind of structural unit selected from the group consisting of a structural unit represented by the following general formula (1) and a structural unit represented by the following general formula (2), and has positive refractive index anisotropy; and a compound (A) having an aromatic structure and a molecular weight of 500 to 2000,

the content of the compound (A) exceeds 0.5% by mass and is 4.0% by mass or less,

re (550) is 100nm to 200nm, re (450)/Re (550) exceeds 0.5 and is lower than 1.0,

in the general formulae (1) and (2), R ¹ ～R ³ Each independently is a direct bond, a substituted or unsubstituted alkylene group having 1 to 4 carbon atoms, R ⁴ ～R ⁹ Each independently is a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted aryl group having 4 to 10 carbon atoms, a substituted or unsubstituted acyl group having 1 to 10 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms, a substituted or unsubstituted aryloxy group having 1 to 10 carbon atoms, a substituted or unsubstituted amino group, a substituted or unsubstituted vinyl group having 1 to 10 carbon atoms, a substituted or unsubstituted ethynyl group having 1 to 10 carbon atoms, a sulfur atom having a substituent, a silicon atom having a substituent, a halogen atom, a nitro group or a cyano group; wherein R is ⁴ ～R ⁹ Can be identical to each otherOr may be different, R ⁴ ～R ⁹ At least two adjacent groups of the two groups may be bonded to each other to form a ring;

re (550) is the in-plane retardation of the film measured at 23℃with light having a wavelength of 550nm, and Re (450) is the in-plane retardation of the film measured at 23℃with light having a wavelength of 450 nm.

2. The retardation film as claimed in claim 1, wherein the resin having positive refractive index anisotropy contains 1 to 40 mass% of at least 1 structural unit selected from the group consisting of the structural unit represented by the general formula (1) and the structural unit represented by the general formula (2).

3. The retardation film as claimed in claim 1 or 2, wherein the resin having positive refractive index anisotropy further comprises a structural unit represented by the following general formula (3),

4. the retardation film as claimed in any one of claims 1 to 3, wherein the resin having positive refractive index anisotropy further comprises a structural unit represented by the following general formula (4).

5. The retardation film as claimed in any one of claims 1 to 4, further comprising an acrylic resin, wherein the content of the acrylic resin is 0.5 to 2.0 mass%.

6. The retardation film as claimed in any one of claims 1 to 5, wherein the content of the compound (a) is 1.0 to 3.0 mass%.

7. The retardation film as claimed in any one of claims 1 to 6, wherein the compound (A) has a partial structure represented by the following formula (5),

8. a circularly polarizing plate comprising a polarizer and the retardation film according to any one of claims 1 to 7,

the angle formed by the absorption axis of the polarizer and the slow axis of the phase difference film is 40-50 degrees or 130-140 degrees.

9. An image display device comprising the circularly polarizing plate according to claim 8 on a viewing side, wherein a polarizer of the circularly polarizing plate is disposed on the viewing side.