KR102580448B1 - Retardation film and manufacturing method thereof, circular polarizer and image display device using the retardation film - Google Patents

Abstract

An inverse dispersion retardation film with excellent stretchability and retardation development properties and low haze is provided. The retardation film of the present invention includes a resin comprising at least one bonding group selected from the group consisting of a carbonate bond and an ester bond, a structural unit derived from divalent oligofluorene, and having positive refractive index anisotropy; Contains acrylic resin. The content of acrylic resin is 0.5% by mass to 2.0% by mass. The acrylic resin contains 70% by mass or more of structural units derived from methyl methacrylate, and its weight average molecular weight (Mw) is 10,000 to 200,000. The Re(550) of the retardation film is 100 nm to 200 nm, and Re(450)/Re(550) exceeds 0.5 and is less than 1.0.

Description

Retardation film and manufacturing method thereof, circular polarizer and image display device using the retardation film

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

Recently, the opportunities for smart devices such as smartphones and display devices such as digital signage and window displays to be used under strong external light are increasing. As a result, problems such as external light reflection and background mirroring caused by the display device itself or reflectors such as a touch panel unit, glass substrate, or metal wiring used in the display device arise. In particular, organic electroluminescence (EL) display devices that have been put into practical use in recent years are prone to problems such as external light reflection and background reflection because they contain a highly reflective metal layer. Therefore, it is known to prevent these problems by providing a circularly polarizing plate containing a retardation film (typically a λ/4 plate) as an antireflection film on the viewer side. In addition, in order to realize good retardation characteristics at each wavelength in the visible region, the development of a retardation film (hereinafter sometimes simply referred to as an inverse dispersion retardation film) exhibiting the so-called wavelength dependence of inverse dispersion, in which the retardation value increases depending on the wavelength of the measurement light. This is going on. In the development of inverse dispersion retardation films, continuous studies are being conducted to further improve the characteristics.

Japanese Patent No. 3325560

The main object of the present invention is to provide a reverse dispersion retardation film that is excellent in extensibility and retardation development and has small haze.

The retardation film of the present invention is selected from the group consisting of at least one bonding group selected from the group consisting of a carbonate bond and an ester bond, a structural unit represented by the following general formula (1), and a structural unit represented by the following general formula (2) A resin containing at least one structural unit and having positive refractive index anisotropy; Contains acrylic resin. The content of the acrylic resin is 0.5% by mass to 2.0% by mass. Additionally, the acrylic resin contains 70% by mass or more of structural units derived from methyl methacrylate, and its weight average molecular weight (Mw) is 10,000 to 200,000. Additionally, Re(550) of the retardation film is 100 nm to 200 nm, and Re(450)/Re(550) exceeds 0.5 and is less than 1.0.

In general formulas (1) and (2), R ¹ to R ³ are each independently a directly bonded, substituted or unsubstituted alkylene group having 1 to 4 carbon atoms, and R ⁴ to R ⁹ are each independently a hydrogen atom, a substituted or unsubstituted alkylene group. Unsubstituted alkyl group with 1 to 10 carbon atoms, substituted or unsubstituted aryl group with 4 to 10 carbon atoms, substituted or unsubstituted acyl group with 1 to 10 carbon atoms, substituted or unsubstituted alkoxy group with 1 to 10 carbon atoms, substituted or unsubstituted carbon atoms 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 a substituent, silicon atom having a substituent, It is a halogen atom, nitro group or cyano group; However, R ⁴ to R ⁹ may be the same or different from each other, and at least two adjacent groups among R ⁴ to R ⁹ may be bonded to each other to form a ring. Re(550) is the in-plane retardation of the film measured with light with a wavelength of 550 nm at 23°C, and Re(450) is the in-plane retardation of the film measured with light with a wavelength of 450 nm at 23°C.

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

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

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

In one embodiment, the retardation film has a haze value of 1.5% or less.

In one embodiment, the retardation film has an elongation at break of 200% or more.

In one embodiment, the retardation film has a limiting birefringence (Δn) of 0.0039 or greater.

According to another aspect of the present invention, a method for manufacturing the retardation film is provided. This manufacturing method includes stretching a resin film containing the resin having the positive refractive index anisotropy and the acrylic resin, and the stretching is performed at a temperature below the glass transition temperature of the resin having the positive refractive index anisotropy. Lose.

In one embodiment, the stretching is performed while conveying the elongated resin film in the elongate direction, and the slow axis direction of the obtained elongated retardation film is 40° to 50° or 130° to 140° with respect to the elongate direction. is the direction of

According to another aspect of the present invention, a circularly polarizing plate is provided. This circularly polarizing plate includes a polarizer and the retardation film, and the angle formed between the absorption axis of the polarizer and the slow axis of the retardation film is 40° to 50° or 130° to 140°.

According to another aspect of the present invention, an image display device is provided. This image display device is equipped with the above circularly polarizing plate on the viewer's side, and the polarizer of the circularly polarizing plate is disposed on the viewer's side.

According to an embodiment of the present invention, by containing a resin (typically polycarbonate-based resin, polyester-based resin, or polyestercarbonate-based resin) and acrylic resin having a specific positive refractive index anisotropy, extensibility and retardation are improved. A reverse dispersion retardation film with excellent expression properties and small haze can be obtained.

1 is a schematic cross-sectional view of a circularly polarizing plate according to one embodiment of the present invention.
Figure 2 is a schematic cross-sectional view of a circularly polarizing plate according to another embodiment of the present invention.

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 this specification are as follows.

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

'nx' is the refractive index in the direction where the in-plane refractive index is maximum (i.e., slow axis direction), 'ny' is the refractive index in the direction orthogonal to the slow axis in the plane (i.e., fast axis direction), and 'nz' is It is the refractive index in the thickness direction.

(2) In-plane phase difference (Re)

'Re(λ)' is the in-plane retardation of the film measured with light of wavelength λnm at 23°C. For example, 'Re(450)' is the in-plane retardation of the film measured with light with a wavelength of 450 nm at 23°C. Re(λ) is obtained by the formula: Re=(nx-ny)×d when the thickness of the film is d(nm).

(3) Phase difference in the thickness direction (Rth)

'Rth(λ)' is the phase difference in the thickness direction of the film measured with light with a wavelength of λ nm at 23°C. For example, 'Rth(450)' is the phase difference in the thickness direction of the film measured with light with a wavelength of 450 nm at 23°C. Rth (λ) is obtained by the formula: Rth = (nx-nz) × d, when the thickness of the film is d (nm).

(4) Nz coefficient

The Nz coefficient is obtained by Nz=Rth/Re.

(5) angle

When referring to an angle in this specification, unless otherwise specified, the angle includes angles in both clockwise and counterclockwise directions.

A. Phase contrast film

A-1. Materials of retardation film

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

The retardation film further contains an acrylic resin. The content of acrylic resin is 0.5% by mass to 1.5% by mass. Additionally, in this specification, the percentage or part of the 'mass' unit is the same as the percentage or part of the 'weight' unit.

A-1-1. Polycarbonate-based resin, etc.

<Oligofluorene structural unit>

The oligofluorene structural unit is represented by the above general formula (1) or (2). In general formulas (1) and (2), R ¹ to R ³ are each independently a directly bonded, substituted or unsubstituted alkylene group having 1 to 4 carbon atoms, and R ⁴ to R ⁹ are each independently a hydrogen atom, a substituted or unsubstituted alkylene group. Unsubstituted alkyl group with 1 to 10 carbon atoms, substituted or unsubstituted aryl group with 4 to 10 carbon atoms, substituted or unsubstituted acyl group with 1 to 10 carbon atoms, substituted or unsubstituted alkoxy group with 1 to 10 carbon atoms, substituted or unsubstituted carbon atoms 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 a substituent, silicon atom having a substituent, It is a halogen atom, a nitro group, or a cyano group. However, R ⁴ to R ⁹ may be the same or different, and at least two adjacent groups among R ⁴ to R ⁹ may be bonded to each other to form a ring.

As R ¹ and R ² , for example, the following alkylene groups can be employed: linear alkylene groups such as methylene group, ethylene group, n-propylene group, and n-butylene group; Methylmethylene group, dimethylmethylene group, ethylmethylene group, propylmethylene group, (1-methylethyl)methylene group, 1-methylethylene group, 2-methylethylene group, 1-ethylethylene group, 2-ethylethylene group, 1 -Alkylene groups having branched chains such as methylpropylene group, 2-methylpropylene group, 1,1-dimethylethylene group, 2,2-dimethylpropylene group, and 3-methylpropylene group. Here, the positions of the branch chains in R ¹ and R ² are indicated by numbers assigned so that the carbon on the fluorene ring side is in the 1st position.

The choice of R ¹ and R ² may relate to the development of the inverse dispersion wavelength dependence. Polycarbonate-based resins and the like show the strongest reverse dispersion wavelength dependence when the fluorene ring is oriented perpendicular to the main chain direction (stretching direction). In order to bring the orientation state of the fluorene ring close to this state and to develop strong reverse dispersion wavelength dependence, it is preferable to employ R ¹ and R ² having 2 to 3 carbon atoms on the main chain of the alkylene group. When the number of carbon atoms is 1, surprisingly, there are cases where inverse dispersion does not show wavelength dependence. The cause of this is thought to be that the orientation of the fluorene ring is fixed in a direction other than perpendicular to the main chain direction due to steric hindrance of the carbonate group and/or ester group, which are linking groups of the oligofluorene structural unit. On the other hand, if the number of carbon atoms is too large, the fixation of the orientation of the fluorene ring becomes weak, and there is a risk that the reverse dispersion wavelength dependence may become insufficient. Additionally, the heat resistance of polycarbonate-based resins and the like may decrease.

As R ³ , for example, the following alkylene groups can be employed: linear alkylene groups such as methylene group, ethylene group, n-propylene group, and n-butylene group; Methylmethylene group, dimethylmethylene group, ethylmethylene group, propylmethylene group, (1-methylethyl)methylene group, 1-methylethylene group, 2-methylethylene group, 1-ethylethylene group, 2-ethylethylene group, 1 -Alkylene groups having branched chains such as methylpropylene group, 2-methylpropylene group, 1,1-dimethylethylene group, 2,2-dimethylpropylene group, and 3-methylpropylene group. R ³ preferably has 1 to 2 carbon atoms on the main chain of the alkylene group, and more preferably has 1 carbon number. If the number of carbon atoms on the main chain is too large, as in the case of R ¹ and R ² , the immobilization of the fluorene ring may be weakened, which may lead to a decrease in the reverse dispersion wavelength dependence, an increase in the photoelastic coefficient, a decrease in heat resistance, etc. On the other hand, the smaller the number of carbon atoms on the main chain, the better the optical properties and heat resistance, but when the 9th position of two fluorene rings is directly bonded, thermal stability may deteriorate.

Substituents for R ¹ to R ³ include, for example, a halogen atom (fluorine atom, chlorine atom, bromine atom or iodine atom); Alkoxy groups having 1 to 10 carbon atoms, such as methoxy group and ethoxy group; Acyl groups having 1 to 10 carbon atoms, such as acetyl group and benzoyl group; Acylamino groups having 1 to 10 carbon atoms, such as acetamide group and benzoylamide group; nitro group; Cyano group; An aryl group having 6 to 10 carbon atoms, such as a phenyl group or a naphthyl group, where 1 to 3 hydrogen atoms may be substituted by the halogen atom, the alkoxy group, the acyl group, the acylamino group, the nitro group, or the cyano group.

As the substituted or unsubstituted alkyl group at R ⁴ to R ⁹ , for example, the following alkyl groups can be employed: methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl, n-decyl. linear alkyl groups such as; Alkyl groups having branched chains such as isopropyl group, 2-methylpropyl group, 2,2-dimethylpropyl group, and 2-ethylhexyl group; Cyclic alkyl groups such as cyclopropyl group, cyclopentyl group, cyclohexyl group, and cyclooctyl group. The number of carbon atoms in the alkyl group is preferably 4 or less, and more preferably 2 or less. If the carbon number is within this range, steric hindrance between fluorene rings is unlikely to occur, and desired optical properties derived from the fluorene ring are easy to obtain. Substituents of the alkyl group include the substituents mentioned above for R ¹ to R ³ .

As the substituted or unsubstituted aryl group at R ⁴ to R ⁹ , for example, the following aryl groups can be employed: aryl groups such as phenyl group, 1-naphthyl group, and 2-naphthyl group; Heteroaryl groups such as 2-pyridyl group, 2-thienyl group, and 2-furyl group. The number of carbon atoms in the aryl group is preferably 8 or less, and more preferably 7 or less. If the carbon number is within this range, steric hindrance between fluorene rings is unlikely to occur, and desired optical properties derived from the fluorene ring are easy to obtain. Substituents of the aryl group include the substituents mentioned above for R ¹ to R ³ .

As the substituted or unsubstituted acyl group at R ⁴ to R ⁹ , for example, the following acyl groups can be adopted: formyl group, acetyl group, propionyl group, 2-methylpropionyl group, 2,2-dimethylpropionyl group. , aliphatic acyl groups such as 2-ethylhexanoyl group; Aromatic acyl groups such as benzoyl group, 1-naphthylcarbonyl group, 2-naphthylcarbonyl group, and 2-furylcarbonyl group. The number of carbon atoms of the acyl group is preferably 4 or less, and more preferably 2 or less. If the carbon number is within this range, steric hindrance between fluorene rings is unlikely to occur, and desired optical properties derived from the fluorene ring are easy to obtain. Substituents for the acyl group include the substituents mentioned above for R ¹ to R ³ .

As the substituted or unsubstituted alkoxy group or aryloxy group at R ⁴ to R ⁹ , for example, the following can be adopted: methoxy group, ethoxy group, isopropoxy group, tert-butoxy group, trifluoromethoxy group, Phenoxy group. The number of carbon atoms of the alkoxy group or aryloxy group is preferably 4 or less, and more preferably 2 or less. If the carbon number is within this range, steric hindrance between fluorene rings is unlikely to occur, and desired optical properties derived from the fluorene ring are easy to obtain. Substituents for the alkoxy group or aryloxy group include the substituents mentioned above for R ¹ to R ³ .

As the substituted or unsubstituted amino group at R ⁴ to R ⁹ , for example, the following amino groups can be employed: amino group; N-methylamino group, N,N-dimethylamino group, N-ethylamino group, N,N-diethylamino group, N,N-methylethylamino group, N-propylamino group, N,N-dipropylamino group, N-isopropyl Aliphatic amino groups such as amino group and N,N-diisopropylamino group; Aromatic amino groups such as N-phenylamino group and N,N-diphenylamino group; Acylamino groups such as formamide group, acetamide group, decanoylamide group, benzoylamide group, and chloroacetamide group; Alkoxycarbonylamino groups such as benzyloxycarbonylamino group and tert-butyloxycarbonylamino group. N,N-dimethylamino group, N-ethylamino group, or N,N-diethylamino group is preferred, and N,N-dimethylamino group is more preferred. They do not have highly acidic protons and have a low molecular weight, allowing the fluorene ratio to be increased.

As the substituted or unsubstituted vinyl or ethynyl group at R ⁴ to R ⁹ , for example, the following can be adopted: vinyl group, 2-methylvinyl group, 2,2-dimethylvinyl group, 2-phenylvinyl group, 2-acetylvinyl group, ethynyl group, methylethynyl group, tert-butylethynyl group, phenylethynyl group, acetylethynyl group, trimethylsilylethynyl group. It is preferable that the carbon number of the vinyl group or ethynyl group is 4 or less. If the carbon number is within this range, steric hindrance between fluorene rings is unlikely to occur, and desired optical properties derived from the fluorene ring are easy to obtain. Additionally, as the conjugate system of the fluorene ring becomes longer, it becomes easier to obtain stronger reverse dispersion wavelength dependence.

As the sulfur atom having a substituent at R ⁴ to R ⁹ , for example, the following sulfur-containing groups can be employed: sulfo group; Alkylsulfonyl groups such as methylsulfonyl group, ethylsulfonyl group, propylsulfonyl group, and isopropylsulfonyl group; Arylsulfonyl groups such as phenylsulfonyl group and p-tolylsulfonyl group; Alkylsulfinyl groups such as methylsulfinyl group, ethylsulfinyl group, propylsulfinyl group, and isopropylsulfinyl group; Arylsulfinyl groups such as phenylsulfinyl group and p-tolylsulfinyl group; Alkylthio groups such as methylthio groups and ethylthio groups; Arylthio groups such as phenylthio group and p-tolylthio group; Alkoxysulfonyl groups such as methoxysulfonyl group and ethoxysulfonyl group; Aryloxysulfonyl groups such as phenoxysulfonyl groups; aminosulfonyl group; Alkylsulfonyl groups such as N-methylaminosulfonyl group, N-ethylaminosulfonyl group, N-tert-butylaminosulfonyl group, N,N-dimethylaminosulfonyl group, and N,N-diethylaminosulfonyl group; Arylaminosulfonyl groups such as N-phenylaminosulfonyl group and N,N-diphenylaminosulfonyl group. Additionally, the sulfo group may form a salt with lithium, sodium, potassium, magnesium, ammonium, etc. A methylsulfinyl group, an ethylsulfinyl group, or a phenylsulfinyl group is preferable, and a methylsulfinyl group is more preferable. They do not have highly acidic protons and have a low molecular weight, allowing the fluorene ratio to be increased.

As the silicon atom having a substituent at R ⁴ to R ⁹ , for example, the following silyl groups can be employed: trialkyl silyl groups such as trimethylsilyl group and triethylsilyl group; Trialkoxysilyl groups such as trimethoxysilyl group and triethoxysilyl group. Trialkylsilyl groups are preferred. This is because it has excellent stability and handling properties.

The content of the oligofluorene structural unit in polycarbonate-based resin, etc. is preferably 1% by mass to 40% by mass, more preferably 10% by mass to 35% by mass, and even more preferably 15% by mass, based on the entire resin. It is ~30 mass%, especially preferably 18 mass% ~ 25 mass%. If the content of the oligofluorene structural unit is too high, there is a risk that problems such as an excessively large photoelastic coefficient, insufficient reliability, or insufficient retardation generation may occur. Additionally, because the proportion of the oligofluorene structural unit in the resin increases, the scope for molecular design narrows, and when modification of the resin is required, modification may become difficult. On the other hand, even if the desired inverse dispersion wavelength dependence is obtained by a very small amount of oligofluorene structural units, in this case, the optical properties change sensitively depending on slight deviations in the content of oligofluorene structural units. There are times when it becomes difficult to manufacture products so that various characteristics fall within a certain range.

Methods for controlling the ratio of oligofluorene structural units in the resin include, for example, a method of copolymerizing a monomer having an oligofluorene structural unit with another monomer, or a method of blending a resin containing an oligofluorene structural unit with another resin. I can hear it. A method of copolymerizing a monomer having an oligofluorene structural unit with another monomer in that the content of the oligofluorene structural unit can be precisely controlled, high transparency can be obtained, and uniform properties can be obtained over the entire surface of the film. This is desirable.

<Other structural units>

Polycarbonate-based resins and the like may typically contain other structural units in addition to oligofluorene structural units. In one embodiment, the other structural units may preferably be from dihydroxy compounds or diester compounds. In order to develop the desired reverse wavelength dispersion, it is necessary to introduce a structural unit with a positive intrinsic birefringence into the polymer structure along with an oligofluorene structural unit with a negative intrinsic birefringence. As the monomer, a dihydroxy compound or diester compound that serves as a raw material for a structural unit having positive birefringence is more preferable.

Examples of the copolymerizable monomer include compounds capable of introducing a structural unit containing an aromatic ring, and compounds that do not introduce a structural unit containing an aromatic ring, that is, have an aliphatic structure.

Specific examples of compounds composed of the above aliphatic structure are given below. Ethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 1,3-butanediol, 1,2-butanediol, 1,5-heptanediol, 1,6-hexanediol, 1 , dihydroxy compounds of straight-chain aliphatic hydrocarbons such as 9-nonanediol, 1,10-decanediol, and 1,12-dodecanediol; Dihydroxy compounds of branched aliphatic hydrocarbons such as neopentyl glycol and hexylene glycol; Examples include 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,3-adamantanediol, hydrogenated bisphenol A, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, etc. secondary alcohols of alicyclic hydrocarbons, and dihydroxy compounds that are tertiary alcohols; 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, tricyclodecanedimethanol, pentacyclopentadecanedimethanol, 2,6-decalindimethanol, 1, Dihydroxy derived from terpene compounds such as 5-decalin dimethanol, 2,3-decalin dimethanol, 2,3-norbonane dimethanol, 2,5-norbonane dimethanol, 1,3-adamantane dimethanol, limonene, etc. Examples of such compounds include dihydroxy compounds, which are primary alcohols of alicyclic hydrocarbons; Oxyalkylene glycols such as diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, and polypropylene glycol; Dihydroxy 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, sberic acid, azelaic acid, and sebacic acid.

Specific examples of compounds into which a structural unit containing the aromatic ring can be introduced are given below. 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(3-methyl-4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl) Propane, 2,2-bis(4-hydroxy-3,5-diethyl phenyl)propane, 2,2-bis(4-hydroxy-(3-phenyl)phenyl)propane, 2,2-bis(4 -Hydroxy-(3,5-diphenyl)phenyl)propane, 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, bis(4-hydroxyphenyl)methane, 1, 1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)pentane, 1,1-bis(4-hydroxy) Phenyl)-1-phenylethane, bis(4-hydroxyphenyl)diphenylmethane, 1,1-bis(4-hydroxyphenyl)-2-ethylhexane, 1,1-bis(4-hydroxyphenyl) Decane, bis(4-hydroxy-3-nitrophenyl)methane, 3,3-bis(4-hydroxyphenyl)pentane, 1,3-bis(2-(4-hydroxyphenyl)-2-propyl) Benzene, 1,3-bis(2-(4-hydroxyphenyl)-2-propyl)benzene, 2,2-bis(4-hydroxyphenyl)hexafluoropropane, 1,1-bis(4-hyde Roxyphenyl)cyclohexane, bis(4-hydroxyphenyl)sulfone, 2,4'-dihydroxydiphenyl sulfone, bis(4-hydroxyphenyl)sulfide, bis(4-hydroxy-3-methylphenyl)sulfide , aromatic bisphenol compounds such as bis(4-hydroxyphenyl)disulfide, 4,4'-dihydroxydiphenyl ether, and 4,4'-dihydroxy-3,3'-dichlorodiphenyl ether; 2,2-bis(4-(2-hydroxyethoxy)phenyl)propane, 2,2-bis(4-(2-hydroxypropoxy)phenyl)propane, 1,3-bis(2-hydroxy dihydroxy compounds having an ether group bonded to an aromatic group such as ethoxy)benzene, 4,4'-bis(2-hydroxyethoxy)biphenyl, and bis(4-(2-hydroxyethoxy)phenyl)sulfone; Terephthalic acid, phthalic acid, isophthalic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-benzophenonedicarboxylic acid, 4,4'-diphenoxyethanedicarboxylic acid, Aromatic dicarboxylic acids such as 4,4'-diphenylsulfonedicarboxylic acid and 2,6-naphthalenedicarboxylic acid.

In addition, the above-mentioned aliphatic dicarboxylic acid and aromatic dicarboxylic acid components can be used as dicarboxylic acids themselves as raw materials for the polyester carbonate, but depending on the manufacturing method, dicarboxylic acid esters such as methyl ester, phenyl ester, or dicarboxylic acid halide. Dicarboxylic acid derivatives such as these can also be used as raw materials.

As copolymerized monomers, 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene and 9,9-bis(4-hyde), which are conventionally known as compounds having a structural unit with negative birefringence. Dihydroxy compounds having a fluorene ring such as oxyphenyl)fluorene and 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, and dicarboxylic acid compounds having a fluorene ring are also used as oligofluorene compounds. Can be used in combination.

From the viewpoint of optical properties, it is preferable to use a resin used in the present invention that does not contain an aromatic component as structural units other than the oligofluorene structural unit. That is, it is preferable to use a compound composed of an aliphatic structure as a copolymerization monomer. If the main chain of the polymer contains an aromatic component, the reverse wavelength dispersion expressed by the oligofluorene structural unit is canceled out, so the content of the oligofluorene structural unit must be increased, which causes the photoelastic coefficient and mechanical properties to deteriorate. There is a risk that it will happen. By employing the above-described other structural units that do not contain an aromatic component, introduction of aromatic components into the main chain originating from the structural unit can be prevented. Among compounds composed of an aliphatic structure, compounds having an alicyclic structure with excellent mechanical properties and heat resistance are more preferable.

On the other hand, in order to secure optical properties while maintaining a balance with heat resistance and mechanical properties, there are cases where it is effective to introduce an aromatic component into the main chain or side chain of the polymer. From the viewpoint of balancing various characteristics, it is preferable that the content of the structural unit containing an aromatic group (however, excluding the oligofluorene structural unit) in the resin is 5% by 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 among the structural units that can be introduced by the compound having the above-mentioned alicyclic structure.

As a dihydroxy compound into which the structural unit of the formula (3) can be introduced, spiro glycol can be used.

In the resin used in the present invention, it is preferable that the structural unit represented by the above formula (3) is contained in an amount of 5% by mass or more and 90% by mass or less. As for the upper limit, 70 mass% or less is more preferable, and 50 mass% or less is especially preferable. As for the lower limit, 10 mass% or more is more preferable, 20 mass% or more is more preferable, and 25 mass% or more is especially preferable. When the content of the structural unit represented by the above formula (3) is more than the above lower limit, sufficient mechanical properties, heat resistance, and a low photoelastic coefficient are obtained. Additionally, compatibility with acrylic resin is improved, and the transparency of the resulting resin composition can be further improved. Additionally, since the rate of polymerization reaction of spiroglycol is relatively slow, it becomes easy to control the polymerization reaction by suppressing the content below the above upper limit.

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

Examples of dihydroxy compounds into which the structural unit represented by the formula (4) can be introduced include isosorbide (ISB), isomannide, and isoidide, which are stereoisomers. These may be used individually or in combination of two or more types.

In the resin used in the present invention, it is preferable that the structural unit represented by the above formula (4) is contained in an amount of 5% by mass or more and 90% by mass or less. As for the upper limit, 70 mass% or less is more preferable, and 50 mass% or less is especially preferable. As for the lower limit, 10 mass% or more is more preferable, and 15 mass% or more is especially preferable. If the content of the structural unit represented by the above formula (4) is more than the above lower limit, sufficient mechanical properties, heat resistance, and a low photoelastic coefficient are obtained. In addition, since the structural unit represented by the above formula (4) has the characteristic of high water absorption, if the content of the structural unit represented by the above formula (4) is below the upper limit, the dimensional change of the molded article due to absorption can be suppressed to an acceptable range. You can.

The resin used in the present invention may contain another structural unit. Additionally, these structural units are sometimes referred to as 'other structural units'. As monomers having other structural units, it is more preferable to employ 1,4-cyclohexanedimethanol, tricyclodecanedimethanol, and 1,4-cyclohexanedicarboxylic acid (and derivatives thereof), and 1,4-cyclohexanedicarboxylic acid (and derivatives thereof) is more preferably used. Hexanedimethanol and tricyclodecanedimethanol are particularly preferred. Resins containing structural units derived from these monomers have excellent balance in optical properties, heat resistance, mechanical properties, etc. Additionally, since the polymerization reactivity of diester compounds is relatively low, from the viewpoint of increasing reaction efficiency, it is preferable not to use diester compounds other than diester compounds containing oligofluorene structural units.

In addition, dihydroxy compounds and diester compounds for introducing structural units may be used individually or in combination of two or more types, depending on the required performance of the resulting resin. The content of other structural units in the resin is preferably 1 mass% or more and 50 mass% or less, more preferably 5 mass% or more and 40 mass% or less, and particularly preferably 10 mass% or more and 30 mass% or less. Since other structural units play a role in adjusting the heat resistance of the resin and providing flexibility and toughness, if the content is too small, the mechanical properties and melt processability of the resin will deteriorate, and if the content is too high, the heat resistance and optical properties will decrease. There is a risk that this will worsen.

The molecular weight of polycarbonate-based resin can be expressed, for example, in terms of reduced viscosity. The reduced viscosity is measured using methylene chloride as a solvent, precisely adjusting the concentration of the polycarbonate resin to 0.6 g/dL, and using an Ubberod viscometer at a temperature of 20.0°C ± 0.1°C. The lower limit of the reduced viscosity is generally preferably 0.30 dL/g or more, more preferably 0.35 dL/g or more, and particularly preferably 0.40 dL/g or more. The upper limit of reduced viscosity is generally preferably 1.00 dL/g or less, more preferably 0.80 dL/g or less, and especially preferably 0.60 dL/g or less. If the reduced viscosity is less than the lower limit, the mechanical strength of the resulting film may become insufficient. On the other hand, if the reduced viscosity is greater than the upper limit, moldability, handleability, and productivity may become insufficient.

The melt viscosity of the polycarbonate-based resin is preferably 700 Pa·s or more and 5000 Pa·s or less under measurement conditions of a temperature of 240°C and a shear rate of 91.2 sec ^-1 . The upper limit is more preferably 4000 Pa·s or less, more preferably 3500 Pa·s or less, and especially preferably 3000 Pa·s or less. The lower limit is more preferably 1000 Pa·s or more, more preferably 1500 Pa·s or more, and especially preferably 2000 Pa·s or more. In addition, melt viscosity is measured using a capillary rheometer (manufactured by Toyo Seiki Co., Ltd.).

The glass transition temperature (Tg) of the resin used in the present invention is preferably 110°C or higher and 160°C or lower. The upper limit is more preferably 155°C or lower, more preferably 150°C or lower, and especially preferably 145°C or lower. The lower limit is more preferably 120°C or higher, and particularly preferably 130°C or higher. If the glass transition temperature is outside the above range, heat resistance tends to deteriorate, dimensional changes may occur after film forming, or quality reliability under the use conditions of the retardation film may deteriorate. On the other hand, if the glass transition temperature is too high, uneven film thickness may occur during film forming, the film may become brittle, stretchability may deteriorate, and transparency of the film may be impaired.

Details of the composition and production method of polycarbonate-based resin, etc. are described, for example, in the pamphlet of International Publication No. 2015/159928. This description is incorporated herein by reference.

A-1-2. Acrylic resin

As the acrylic resin, an acrylic resin as a thermoplastic resin is used. Monomers that serve as structural units of acrylic resin include, for example, the following compounds: methyl methacrylate, methacrylic acid, methyl acrylate, acrylic acid, benzyl (meth)acrylate, n-butyl (meth)acrylate, i -Butyl (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, iso Bornyl (meth)acrylate, norbornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, acrylic (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl maleic acid, phthalic acid 2-(meth)acryloyloxyethyl, hexahydrophthalic acid 2-(meth)acryloyloxyethyl, pentamethylpiperidyl(meth)acrylate, tetramethylpiperidyl(meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, cyclopentyl methacrylate, cyclopentyl acrylate, cyclohexyl methacrylate, cyclohexyl acrylate, cycloheptyl methacrylate, cycloheptyl acrylate, cycloheptyl acrylate Octyl methacrylate, cyclooctylacrylate, cyclododecyl methacrylate, cyclododecyl acrylate. These may be used individually, or two or more types may be used in combination. Forms in which two or more types of monomers are used in combination include copolymerization of two or more types of monomers, blends of two or more homopolymers of one type of monomer, and combinations thereof. Additionally, other monomers (e.g., olefin monomers, vinyl monomers) that can be copolymerized with these acrylic monomers may be used in combination.

Acrylic resin contains structural units derived from methyl methacrylate. The content of the structural unit derived from methyl methacrylate in the acrylic resin is preferably 70% by mass or more and 100% by mass or less. As for the lower limit, 80 mass% or more is more preferable, 90 mass% or more is still more preferable, and 95 mass% or more is especially preferable. Within this range, excellent compatibility with the polycarbonate-based resin of the present invention is obtained. As structural units other than methyl methacrylate, it is preferable to use methyl acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, and styrene. Thermal stability can be improved by copolymerizing methyl acrylate. Since the refractive index of the acrylic resin can be adjusted by using phenyl (meth)acrylate, benzyl (meth)acrylate, and styrene, the transparency of the resin composition obtained can be improved by matching the refractive index of the resin to be combined. By using such an acrylic resin, a reverse-dispersion retardation film with excellent extensibility and retardation development properties and small haze can be obtained.

The weight average molecular weight (Mw) of the acrylic resin is 10,000 or more and 200,000 or less. The lower limit is preferably 30,000 or more, and particularly preferably 50,000 or more. The upper limit is preferably 180,000 or less, and particularly preferably 150,000 or less. If the molecular weight is within this range, compatibility with the polycarbonate-based resin of the present invention can be achieved, thereby improving the transparency of the final retardation film, and also achieving the effect of sufficiently improving extensibility during stretching. In addition, the above weight average molecular weight is the molecular weight in terms of polystyrene measured by GPC. Details of the measurement method are described later. Additionally, it is preferable from the viewpoint of compatibility that the acrylic resin does not contain substantially a branched structure. That it does not contain a branched structure can be confirmed by the fact that the GPC curve of the acrylic resin is unimodal.

A-1-3. Blends with acrylic resins such as polycarbonate resins

Polycarbonate-based resin, etc., and acrylic-based resin are blended and used as a resin composition in the production method of the retardation film (the production method is described later in Section A-3). Acrylic resins such as polycarbonate resins can be blended, preferably in a molten state. A typical method of blending in a molten state includes melt kneading using an extruder. The kneading temperature (molten resin temperature) is preferably 200°C to 280°C, more preferably 220°C to 270°C, and even more preferably 230°C to 260°C. If the kneading temperature is within this range, pellets of a resin composition in which both resins are uniformly blended can be obtained while suppressing thermal decomposition. If the temperature of the molten resin in the extruder exceeds 280°C, coloring 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°C, the resin viscosity may become too high, which may place an excessive load on the extruder or cause insufficient melting of the resin. Additionally, any appropriate configuration may be adopted as the extruder configuration, screw configuration, etc. In order to obtain resin transparency that can withstand optical film applications, it is preferable to use a twin-screw extruder. In addition, the remaining low molecular components in the resin or the low molecular weight thermally decomposed components during extrusion kneading may contaminate the cooling rolls and conveyance rolls during the film forming process and stretching process, so it is recommended to use an extruder equipped with a vacuum vent to remove them. desirable.

The content of acrylic resin in the resin composition (as a result, retardation film) is 0.5% by mass or more and 2.0% by mass or less as described above. As for the lower limit, 0.6 mass% or more is more preferable. The upper limit is preferably 1.5% by mass or less, more preferably 1.0% by weight or less, more preferably 0.9% by weight or less, and especially preferably 0.8% by weight or less. In this way, by mixing acrylic resin with polycarbonate resin in an extremely limited ratio, extensibility and retardation development can be significantly increased. Additionally, haze can be suppressed. This effect is not clear in theory and is an unexpected and excellent effect obtained through trial and error. Additionally, if the content of acrylic resin is too small, the above effects may not be obtained. On the other hand, if the content of acrylic resin is too high, the haze may become high. In addition, extensibility and phase difference development often become insufficient or rather deteriorate compared to those within the above range.

Resin compositions include aromatic polycarbonate, aliphatic polycarbonate, aromatic polyester, aliphatic polyester, polyamide, polystyrene, polyolefin, acrylic, amorphous polyolefin, ABS, AS for the purpose of modifying properties such as mechanical properties and/or solvent resistance. , synthetic resins such as polylactic acid and polybutylene succinate, rubber, and combinations thereof may be further blended.

The resin composition may further contain additives. Specific examples of additives include heat stabilizers, antioxidants, catalyst deactivators, ultraviolet absorbers, light stabilizers, mold release agents, dye pigments, impact modifiers, antistatic agents, lubricants, lubricants, plasticizers, compatibilizers, nucleating agents, flame retardants, inorganic fillers, and foaming agents. I can hear it. The type, number, combination, content, etc. of additives included in the resin composition can be appropriately set depending on the purpose.

A-2. Characteristics of retardation film

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

Retardation films typically satisfy the relationship Re(450)<Re(550)<Re(650). In other words, the retardation film exhibits wavelength dependence of inverse dispersion in which the retardation value increases depending on the wavelength of the measurement light. Re(450)/Re(550) of the retardation film exceeds 0.5 and is less than 1.0 as mentioned above, 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, and more preferably 1.03 to 1.1.

Since the retardation film has an in-plane retardation as described above, it has the relationship nx>ny. The retardation film represents any suitable refractive index ellipsoid as long as it has the relationship nx>ny. The refractive index ellipsoid of the retardation film typically exhibits the relationship nx>ny≥nz. Additionally, here, 'ny=nz' includes not only cases where ny and nz are completely equal, but also cases where they are substantially equal. Therefore, there may be cases where ny < nz within a range that does not impair the effect 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 still more preferably 0.9 to 1.2. By satisfying this relationship, when a circularly polarizing plate containing a retardation film is used in an image display device, very excellent reflected color can be achieved.

The thickness of the retardation film can be set to function most appropriately as a λ/4 plate. In other words, the thickness can be set so that the desired in-plane retardation is obtained. Specifically, the thickness is preferably 15 μm to 60 μm, more preferably 20 μm to 55 μm, and most preferably 20 μm to 45 μm. According to the embodiment of the present invention, a retardation film with excellent retardation development property is obtained, and therefore the thickness of the retardation film can be significantly thinner compared to a typical λ/4 plate.

The haze value of the retardation film is preferably 1.5% or less, more preferably 1.0% or less, and even more preferably 0.5% or less. According to the embodiment of the present invention, an inverse dispersion retardation film excellent in both retardation development and haze value can be realized. The smaller the haze value, the more preferable it is. The lower limit of the haze value may be, for example, 0.1%.

The breaking elongation of the retardation film is preferably 200% or more, more preferably 210% or more, further preferably 220% or more, and particularly preferably 245% or more. The upper limit of the elongation at break may be, for example, 500%. Since the retardation film according to an embodiment of the present invention has excellent retardation development properties as well as excellent extensibility, the desired in-plane retardation can be realized at a very thin thickness due to their synergistic effect. In addition, in this specification, 'elongation at break' refers to the elongation rate when the film breaks during fixed-end uniaxial stretching at a predetermined stretching temperature (eg, Tg-2°C).

The limiting birefringence (Δn) of the retardation film is preferably 0.0039 or more, more preferably 0.0040 or more, further preferably 0.0041 or more, and particularly preferably 0.0044 or more. The upper limit of the limiting birefringence (Δn) may be, for example, 0.0070. In this way, since the retardation film according to an embodiment of the present invention has very high birefringence, a desired in-plane retardation can be achieved with a very thin thickness. In addition, in this specification, 'limiting birefringence' means birefringence at the highest stretching ratio that does not break when the stretching ratio is increased at a predetermined stretching temperature. Birefringence can be determined by dividing the in-plane retardation (Re) of the film at the highest stretching ratio without fracture by the film thickness (d).

The absolute value of the retardation film's photoelastic coefficient is preferably 20 × 10 ^-12 (m ² /N) or less, more preferably 1.0 × 10 ^-12 (m ² /N) to 15 × 10 ^-12 (m ² /N), and more preferably 2.0 × 10 ^-12 (m ² /N) to 12 × 10 ^-12 (m ² /N). If the absolute value of the photoelastic coefficient is within this range, display unevenness can be suppressed when the retardation film is applied to an image display device.

A-3. Method for manufacturing retardation film

The retardation film described in paragraphs A-1 and A-2 is obtained by forming a film from the resin composition described in paragraph A-1 and further stretching the film. As a method of forming a film from the resin composition, any suitable molding processing method can be employed. Specific examples include compression molding, transfer molding, injection molding, extrusion molding, blow molding, powder molding, FRP molding, casting coating method (e.g., casting method), calender molding method, and heat pressing method. Among them, the extrusion molding method or casting coating method is preferable because it can increase the smoothness of the resulting film and obtain good optical uniformity. Since the casting coating method may cause problems due to residual solvent, the extrusion molding method, especially the melt extrusion molding method using a T die, is preferable from the viewpoint of film productivity and ease of subsequent stretching processing. . Molding conditions can be appropriately set depending on the composition or type of the resin used, the characteristics desired for the retardation film, etc. In this way, a resin film containing polycarbonate-based resin and the like and acrylic-based resin can be obtained.

The thickness of the resin film (unstretched film) can be set to any appropriate value depending on the desired thickness of the resulting retardation film, desired optical properties, stretching conditions described later, etc. Preferably it is 50㎛~300㎛.

For the stretching, any appropriate stretching method and stretching conditions (eg, stretching temperature, stretching ratio, stretching direction) may be employed. Specifically, various stretching methods such as free end stretching, fixed end stretching, free end shrinking, and fixed end shrinking can be used singly, simultaneously, or sequentially. Regarding the stretching direction, it can be carried out in various directions or dimensions, such as the longitudinal direction, the width direction, the thickness direction, and the oblique direction.

By appropriately selecting the stretching method and stretching conditions, a retardation film having the desired optical properties (eg, refractive index properties, in-plane retardation, Nz coefficient) can be obtained.

In one embodiment, the retardation film is produced by uniaxial stretching or fixed-end uniaxial stretching of a resin film. A specific example of uniaxial stretching includes a method of stretching the resin film in the running direction (long-length direction) while running it in the long-length direction. A specific example of fixed-end uniaxial stretching includes a method of stretching the resin film in the width direction (transverse direction) while running it in the direction of a long picture. The stretching ratio is preferably 1.1 to 3.5 times.

In another embodiment, the retardation film can be produced by continuously obliquely stretching a long resin film in a direction at a predetermined angle with respect to the long picture direction. By employing oblique stretching, a long stretched film having an orientation angle of a predetermined angle (slow axis in the direction of the predetermined angle) with respect to the long direction of the film is obtained, and, for example, roll-to-roll when laminated with a polarizer. This becomes possible, and the manufacturing process can be simplified. Additionally, the predetermined angle may be the angle formed between the absorption axis of the polarizer and the slow axis of the retardation film in the circularly polarizing plate (described later). As described later, the angle is preferably 40° to 50°, more preferably 42° to 48°, further preferably 44° to 46°, and particularly preferably about 45°; Alternatively, it is preferably 130° to 140°, more preferably 132° to 138°, further preferably 134° to 136°, and particularly preferably about 135°.

As a stretching machine used for diagonal stretching, for example, a tenter-type stretching machine capable of adding feed force, tension force, or pull force at different speeds on the left and right in the transverse and/or longitudinal directions. Tenter-type stretching machines include transverse single-axis stretching machines and simultaneous two-axis stretching machines. Any suitable stretching machine can be used as long as it can continuously diagonally stretch a long resin film.

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

As a method of oblique stretching, for example, Japanese Patent Application Laid-Open No. 50-83482, Japanese Patent Application Laid-Open No. 2-113920, Japanese Patent Application Laid-Open No. 3-182701, Japanese Patent Application Laid-Open No. 2000-9912, Japanese Patent Application Laid-Open No. 2-113920. Methods described in No. 2002-86554, Japanese Patent Application Publication No. 2002-22944, etc. may be mentioned.

In one embodiment, the stretching temperature of the film is a temperature equal to or lower than the glass transition temperature (Tg) of polycarbonate-based resin. Normally, when stretching a film of polycarbonate-based resin or the like, stretching is practically impossible because the film is in a glass state at a temperature below Tg. According to an embodiment of the present invention, by blending a small amount of acrylic resin (typically polymethyl methacrylate), stretching below Tg is possible without substantially changing the Tg of polycarbonate resin or the like. In addition, although it is not clear in theory, by performing stretching below Tg, a reverse-dispersion retardation film with excellent stretchability and retardation development properties and small haze can be realized. Specifically, the stretching temperature is preferably Tg to Tg-10°C, more preferably Tg to Tg-8°C, and even more preferably Tg to Tg-5°C. In addition, the film can be appropriately stretched even at a temperature higher than Tg, for example, to about Tg+5°C, or to about Tg+2°C, for example.

[Reason for effectiveness]

The reason why the film made of the resin composition of the present invention exhibits excellent properties is assumed as follows. As shown in the examples described later, for a resin composition in which an acrylic resin of an appropriate composition is mixed in a limited ratio, the critical fracture ratio during stretching is clearly improved while maintaining transparency almost equal to that of the polycarbonate resin alone. there is. It is presumed that the polycarbonate-based resin and acrylic resin are completely compatible, and the polymer chains of the acrylic resin dissolved in the polycarbonate-based resin increase the entanglement of the polymer chains of the polycarbonate-based resin, improving the breaking strength of the film. It is thought that Since the intrinsic birefringence of a single acrylic resin is almost zero, it is expected that by mixing an acrylic resin, the intrinsic birefringence of the resin composition will decrease and the orientation birefringence that develops upon stretching will decrease. However, in the present invention, since the blending amount of the acrylic resin is extremely small, it is believed that the effect of lowering the intrinsic birefringence due to the acrylic resin was suppressed to almost zero while the stretching strength of the resin composition was improved, and the orientation birefringence was improved. .

B. Circular polarizer

The retardation film according to the embodiment of the present invention described in Item A above can be suitably used in a circularly polarizing plate. Accordingly, embodiments of the present invention also include circularly polarizing plates. 1 is a schematic cross-sectional view of a circularly polarizing plate according to one embodiment of the present invention. The circular polarizing plate 100 in the illustrated example includes a polarizing plate 10 and a retardation film 20. The retardation film 20 is a retardation film according to the embodiment of the present invention described in item A above. The polarizer 10 includes a polarizer 11, a first protective layer 12 disposed on one side of the polarizer 11, and a second protective layer 13 disposed on the other side of the polarizer 11. do. Depending on the purpose, one of the first protective layer 12 and the second protective layer 13 may be omitted. For example, since the retardation film 20 according to an embodiment of the present invention can also function as a protective layer of the polarizer 11, the second protective layer 13 may be omitted. The angle formed by 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°, and even more preferably 44° to 46°. and is particularly preferably about 45°; Or preferably 130° to 140°, more preferably 132° to 138°, further preferably 134° to 136°, and particularly preferably about 135°.

As shown in FIG. 2 , in the circularly polarizing plate 101 according to another embodiment, another retardation layer 50 and/or a conductive layer or an isotropic base material 60 with a conductive layer may be provided. The other retardation layer 50 and the conductive layer or the isotropic base material with a conductive layer 60 are typically provided outside the retardation film 20 (on the side opposite to the polarizing plate 10). The refractive index characteristics of other retardation layers typically show the relationship nz>nx=ny. By providing such a different phase difference layer, reflection in the oblique direction can be prevented satisfactorily, and wide viewing angle of the anti-reflection function becomes possible. The other retardation layer 50 and the conductive layer or the isotropic base material with a conductive layer 60 are typically prepared in this order from the retardation film 20 side. The other retardation layer 50 and the conductive layer or the isotropic base material with a conductive layer 60 are typically arbitrary layers provided as needed, and either or both may be omitted. In addition, when a conductive layer or an isotropic substrate with a conductive layer is provided, the circularly polarizing plate can be applied to a so-called inner touch panel type input display device in which a touch sensor is embedded between an image display cell (e.g., an organic EL cell) and a polarizing plate. You can.

The circularly polarizing plate may include an additional retardation layer. The additional retardation layer may be provided in combination with the other retardation layer 50, or may be provided alone (that is, without providing the other retardation layer 50). The optical properties (e.g., refractive index properties, in-plane retardation, Nz coefficient, photoelastic coefficient), thickness, arrangement position, etc. of the additional retardation layer can be appropriately set depending on the purpose.

The circularly polarizing plate may be sheet-shaped or elongated. In this specification, 'elongated shape' means an elongated shape with a sufficiently long length relative to the width, and includes, for example, an elongated shape with a length of 10 or more times the width, preferably 20 times or more. A long circular polarizing plate can be wound into a roll. When 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 long direction. The retardation film is preferably, as described above, an inclined stretched film having a slow axis in a direction forming an angle of 40° to 50° or 130° to 140° with respect to the long direction. If the polarizer and retardation film have this configuration, the circularly polarizing plate can be manufactured by roll-to-roll.

In practical terms, an adhesive layer (not shown) is provided on the side opposite to the polarizing plate of the retardation film, and the circularly polarizing plate can be attached to the image display cell. In addition, it is preferable that a release film is temporarily attached to the surface of the adhesive layer until the circularly polarizing plate is provided for use. By temporarily attaching the release film, the adhesive layer is protected and roll formation of the circularly polarizing plate becomes possible.

Hereinafter, the components of the circularly polarizing plate will be described.

B-1. polarizer

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

A specific example of a polarizer composed of a single layer of resin film is a hydrophilic polymer film such as a polyvinyl alcohol (PVA)-based film, a partially formalized PVA-based film, and an ethylene-vinyl acetate copolymer-based partially saponified film, with iodine or dichroism (double-colored). Examples include those that have been dyed and stretched with dichroic substances such as dyes, and polyene-based oriented films such as dehydrated PVA products and dechlorinated polyvinyl chloride products. Preferably, a polarizer obtained by dyeing a PVA-based film with iodine and uniaxially stretching is used because it has excellent optical properties.

The dyeing with iodine is performed, for example, by immersing the PVA-based film in an aqueous iodine solution. The draw ratio of the uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after dyeing treatment or may be performed while dyeing. Additionally, it may be dyed after stretching. If necessary, the PVA-based film is subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, etc. For example, by immersing the PVA-based film in water and washing it before dyeing, not only can contamination and anti-blocking agents on the surface of the PVA-based film be removed, but also the PVA-based film can be swelled to prevent staining, etc.

Specific examples of the polarizer obtained using the laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a PVA-based resin layer applied to the resin substrate and the resin substrate. A polarizer obtained by using a laminate of . A polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer formed by applying to the resin substrate is, for example, applied to a resin substrate and dried to form a PVA-based resin layer on the resin substrate. and obtaining a laminate of a PVA-based resin layer; It can be produced by stretching and dyeing the laminate and using the PVA-based resin layer as a polarizer. In this embodiment, stretching typically includes stretching the laminate by immersing it in an aqueous boric acid solution. In addition, stretching may further include air stretching the laminate at a high temperature (eg, 95°C or higher) before stretching in an aqueous boric acid solution, if necessary. The obtained resin substrate/polarizer laminate may be used as is (i.e., the resin substrate may be used as a protective layer for the polarizer), or the resin substrate may be peeled from the resin substrate/polarizer laminate and applied to the peeled surface for the purpose. Any appropriate protective layer may be laminated and used. Details of the manufacturing method of such a polarizer are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580 and Japanese Patent Application Publication No. 6470455. The descriptions of these patent documents are incorporated herein by reference.

The thickness of the polarizer is preferably 15 μm or less, more preferably 1 μm to 12 μm, further preferably 3 μm to 10 μm, and particularly preferably 3 μm to 8 μm. If the thickness of the polarizer is within this range, curling during heating can be suppressed well, and good external appearance durability during heating can be obtained. Additionally, if the thickness of the polarizer is within this range, it can contribute to thinning the circularly polarizing plate (and, as a result, the organic EL display device).

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

B-2. protective layer

The first protective layer 12 and the second protective layer 13 are each formed of any suitable film that can be used as a protective layer of a polarizer. Specific examples of materials that become the main component of the film include cellulose-based resins such as triacetylcellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, Transparent resins such as polysulfone-based, polystyrene-based, polynorbornene-based, polyolefin-based, (meth)acrylic-based, and acetate-based resins can be mentioned. In addition, thermosetting resins or ultraviolet curing resins such as (meth)acrylic, urethane, (meth)acrylic urethane, epoxy, silicone, etc. may also be included. In addition to these, for example, glassy polymers such as siloxane polymers can also be mentioned. Additionally, the polymer film described in Japanese Patent Application Laid-Open No. 2001-343529 (WO01/37007) can also be used. As a material for this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain can be used, for example, isobutene and N -A resin composition containing an alternating copolymer made of methylmaleimide and an acrylonitrile/styrene copolymer can be mentioned. The polymer film may be, for example, an extrusion molded product of the resin composition.

As will be described later, the circularly polarizing plate is typically placed on the viewer's side of the image display device, and the first protective layer 12 is typically placed on its viewer's side. Therefore, the first protective layer 12 may be subjected to surface treatment such as hard coat treatment, anti-reflection treatment, anti-sticking treatment, or anti-glare treatment as necessary. In addition,/or the first protective layer 12 may be treated, if necessary, to improve visibility when viewed through polarized sunglasses (typically, imparting an (other) circularly polarized function or imparting an ultra-high phase difference). It may be implemented. By performing such processing, excellent visibility can be achieved even when the display screen is viewed through polarized lenses such as polarized sunglasses. Therefore, the circular polarizer can also be suitably applied to an image display device that can be used outdoors.

The thickness of the first 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. In addition, when surface treatment is performed, the thickness of the outer protective layer is a thickness including the thickness of the surface treatment layer.

The second protective layer 13 is preferably optically isotropic in one embodiment. In this specification, 'optically isotropic' means that the in-plane phase difference Re (550) is 0 nm to 10 nm, and the phase difference Rth (550) in the thickness direction is -10 nm to +10 nm.

C. Image display device

The circularly polarizing plate described in item B above can be applied to an image display device. Accordingly, embodiments of the present invention also include an image display device using such a circularly polarizing plate. Representative examples of image display devices include liquid crystal display devices and organic EL display devices. An image display device according to an embodiment of the present invention is provided with the circularly polarizing plate described in item B above on its viewer side. The circularly polarizing plate is arranged so that the polarizer is on the viewer's side.

Example

Hereinafter, the present invention will be described in detail through examples, but the present invention is not limited to these examples. Additionally, the measurement method for each characteristic is as follows.

(1) Reduced viscosity

The resin sample was dissolved in methylene chloride to prepare a resin solution with a concentration of 0.6 g/dL. Measurements were made at a temperature of 20.0°C ± 0.1°C using an Ubberod-type viscosity tube manufactured by Morito Morika Industries, Ltd., and the passage time of the solvent (t0) and the passage time of the solution (t) were measured. Using the obtained values of t ₀ and t, calculate the relative viscosity (η _rel ) by the following equation (i), and also use the obtained relative viscosity (η _rel ) to obtain the specific viscosity (η _sp ) by the following equation (ii) was obtained.

η _rel =t/t ₀ … (i)

η _sp =(η-η ₀ )/η ₀ =η _rel -1… (ii)

Afterwards, the obtained specific viscosity (η _sp ) was divided by the concentration c [g/dL], and the reduced viscosity η _sp /c was obtained. The higher this value, the larger the molecular weight.

(2) Melt viscosity

The pellet-like resin was dried by placing it in a hot air dryer at 100°C for more than 6 hours. Measurements were made with a capillary rheometer manufactured by Toyo Seki Co., Ltd. using dried pellets. The measurement temperature was 240°C, the melt viscosity was measured at a shear rate of 6.08 to 1824 sec ^-1 , and the melt viscosity value at 91.2 sec ^-1 was used. Additionally, a die with a diameter of 1 mm and a length of 10 mm was used as the orifice.

(3) Glass transition temperature

The glass transition temperature of the resin was measured using a differential scanning calorimeter DSC6220 manufactured by SI Nanotechnology. Approximately 10 mg of the resin sample was placed in an aluminum pan manufactured by the company and sealed, and the temperature was raised from 30°C to 200°C at a temperature increase rate of 20°C/min under a nitrogen stream of 50 mL/min. After maintaining the temperature for 3 minutes, it was cooled to 30°C at a rate of 20°C/min. The temperature was maintained at 30°C for 3 minutes, and the temperature was again raised to 200°C at a rate of 20°C/min. According to the DSC data obtained at the second temperature increase, the temperature of the intersection of the straight line extending the base line on the low temperature side to the high temperature side and the tangent line drawn at the point where the gradient of the curve in the stepwise change portion of the glass transition is maximum is, The extrapolated glass transition start temperature was determined, and it was set as the glass transition temperature.

(4) GPC

Approximately 0.1 g of the resin sample was dissolved in 2 mL of methylene chloride, and the solution was filtered through a 0.2 μm disk filter to measure GPC. GPC was similarly measured for standard polystyrene, and the number average molecular weight (Mn) and weight average molecular weight (Mw) in terms of polystyrene were calculated. The devices and conditions are as follows.

・Pump: LC-20AD (manufactured by Shimadzu Corporation)

· Degasser: DGU-20A5 (manufactured by Shimadzu Corporation)

Column oven: CTO-20AC (manufactured by Shimadzu Corporation)

・Detector: Differential refractive index detector RID-10A (manufactured by Shimadzu Corporation)

Column: PLgel 10㎛ Guard, 2 PLgel 10㎛ MIXED-B (manufactured by Agilent)

·Oven temperature: 40℃

·Eluent: Chloroform

·Flow rate: 1mL/min

·Injection volume: 10μL

(5) Refractive index

Approximately 4 g of resin pellets dried in a hot air dryer at 100°C for more than 6 hours were placed on top and bottom of the sample using a spacer measuring 14 cm long, 14 cm wide, and 0.1 mm thick. Polyimide film was placed on the top and bottom of the sample, and then dried for 3 hours at a temperature of 200 to 230° C. After preheating for a minute and pressurizing at a pressure of 7 MPa for 5 minutes, each spacer was taken out and cooled to produce a film. From the obtained film, a rectangular test piece with a width of 8 mm and a length of 40 mm was cut out and used as a measurement sample. Using interference filters with wavelengths of 656 nm (C line), 589 nm (D line), and 486 nm (F line), the refractive index n _C , n of each wavelength was measured using a multi-wavelength Abbe refractometer DR-M4/1550 manufactured by Atago Co., Ltd. _D and n _F were measured. The measurement was performed at 20°C using monobromonaphthalene as the interfacial liquid.

(6) Photoelastic coefficient

Measurements were made using a device combining a birefringence measurement device consisting of a He-Ne laser, a polarizer, a compensating plate, an analyzer, and a photodetector, and a vibration-type viscoelasticity measurement device (DVE-3 manufactured by Rheology Co., Ltd.) (For details, see Rheology Japan) (See Journal Vol. 19, p93-97 (1991)). A sample of 5 mm in width and 20 mm in length was cut from the film produced by the same method as (5) described above, fixed to a viscoelasticity measuring device, and the storage modulus (E') was measured at a frequency of 96 Hz at a room temperature of 25°C. did. At the same time, the emitted laser light is passed through the polarizer, sample, compensation plate, and analyzer in that order, captured by a photodetector (photodiode), and passed through a lock-in amplifier to produce an angular frequency of ω or 2ω. For the waveform, its amplitude and phase difference for deformation were obtained, and the deformation optical coefficient (O') was determined. At this time, the directions of the absorption axes of the polarizer and the analyzer were perpendicular to each other and were adjusted to form an angle of π/4 with respect to the elongation direction of the sample. The photoelastic coefficient (C) was obtained by the following equation using the storage modulus (E') and the optical strain coefficient (O').

C=O'/E'

(7) Thickness of film

It was measured using a dial gauge.

(8) Phase difference value of phase difference film

A sample of 50 mm x 50 mm was cut from the retardation film obtained in Examples and Comparative Examples and used as a measurement sample. For this measurement sample, Re(450) and Re(550) were measured using Axoscan manufactured by Axometrics. The measurement temperature was 23°C.

(9) Haze value

It was measured using a haze meter (manufactured by Murakami Color Research Laboratories, brand name 'HN-150') according to JIS K 7136. If it was less than 1.5%, it was judged as passing. Since it was judged that a transparent retardation film could not be obtained even if the pellet was cloudy at the time of extrusion and kneading, even if this was used, the retardation film was not evaluated.

(10) Elongation at break and limiting birefringence (Δn)

A sample of 120 mm (film transport direction during manufacturing: MD) x 150 mm (direction perpendicular to the transport direction: TD) was cut from the long unstretched film used in the examples and comparative examples. Using the lab stretcher 'Bluckner KARO IV', this sample was stretched at a fixed end uniaxially in the TD direction by setting the stretching temperature to 'Tg-2℃' of the resin sample and changing the stretching ratio. The maximum elongation at break was measured with a steel ruler. Additionally, the in-plane retardation (Re) and film thickness (d) of the film at the highest stretching ratio without breaking were measured, and the limiting birefringence (Δn) was obtained by dividing the in-plane retardation (Re) by the film thickness (d). . Film thickness was measured with a dial gauge as above. The in-plane retardation (Re) was measured using 'Axoscan' manufactured by Axometrics. The measurement wavelength was 590 nm.

[Symbol of compound]

The abbreviations of the compounds used in the following synthesis examples, examples, and comparative examples are as follows.

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

It was synthesized by the method described in Japanese Patent Publication No. 2015-25111.

・ISB: Isosorbide (manufactured by Rocket Fleure)

SPG: Spiroglycol [manufactured by Mitsubishi Gas Chemical Co., Ltd.]

DPC: Diphenyl carbonate (manufactured by Mitsubishi Chemical Co., Ltd.)

BPEF: 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene (manufactured by Osaka Gas Chemical Co., Ltd.)

PEG1000: polyethylene glycol, number average molecular weight 1000 [manufactured by Sanyo Chemical Industry Co., Ltd.]

[Modifier resin]

·Dianal BR80 (manufactured by Mitsubishi Chemical Co., Ltd.)

·Dianal BR85 (manufactured by Mitsubishi Chemical Co., Ltd.)

· Kuraity LA4285 (manufactured by Kuraray Co., Ltd.)

· Metablen P570A (Mitsubishi Chemical Co., Ltd.)

・Estyrene MS-600 (manufactured by Nippon Chemical Co., Ltd.)

· Estyrene MS-200 (manufactured by Nippon Chemical Co., Ltd.)

·G9504 (manufactured by Nippon Polystyrene Co., Ltd.)

The composition and physical properties of each resin are shown in Table 1.

[Example 1]

Polymerization was performed using a batch polymerization apparatus consisting of two vertical stirring reactors equipped with stirring blades and a reflux condenser. BPFM is 30.31 parts by mass (0.047 mol), ISB is 39.94 parts by mass (0.273 mol), SPG is 30.20 parts by mass (0.099 mol), DPC is 69.67 parts by mass (0.325 mol), and calcium acetate monohydrate as a catalyst is 7.88 × 10 ^{- 4} mass parts (4.47×10 ^-6 mol) were introduced. After purging the reactor with reduced pressure nitrogen, heating was performed using a heating medium, and stirring was started when the internal temperature reached 100°C. 40 minutes after the start of the temperature increase, the internal temperature reached 220°C, and while controlling to maintain this temperature, pressure reduction was started, and 90 minutes after reaching 220°C, the temperature was 13.3 kPa. The phenol vapor produced by-product with the polymerization reaction was guided to a reflux cooler at 110°C, the monomer component contained in a small amount in the phenol vapor was returned to the reactor, and the uncondensed phenol vapor was guided to a condenser at 45°C for recovery. After nitrogen was introduced into the first reactor and the pressure was restored to atmospheric pressure, the oligomerized reaction solution in the first reactor was transferred to the second reactor. Next, temperature increase and pressure reduction in the second reactor were started, and the internal temperature was 240°C and the pressure was 20 kPa in 40 minutes. Thereafter, the pressure was further lowered and polymerization was allowed to proceed until the predetermined stirring power was reached. When the predetermined power was reached, nitrogen was introduced into the reactor, the pressure was restored, the resulting polyester carbonate was extruded into water, and the strand was cut to obtain pellets. This resin is referred to as 'PC1'. The ratio of structural units derived from each monomer is BPFM/ISB/SPG/DPC=21.5/39.4/30.0/9.1% by mass. The reduced viscosity of PC1 is 0.46dL/g, Mw is 48,000, refractive index n _D is 1.526, melt viscosity is 2480Pa·s, glass transition temperature is 139℃, photoelastic coefficient is 9×10 ^-12 [m ² /N], wavelength The variance Re(450)/Re(550) was 0.85.

BR80 was used as an acrylic resin, and extrusion kneading was performed with the obtained polyester carbonate. A mixture of polycarbonate pellets (99.5 parts by mass) and BR80 powder (0.5 parts by mass) was fed into a twin-screw extruder TEX30HSS manufactured by Nihon Steel Works Co., Ltd. using a quantitative feeder. The extruder cylinder temperature was set at 250°C, and extrusion was performed at a throughput of 12 kg/hr and a screw rotation speed of 120 rpm. In addition, the extruder was equipped with a vacuum vent, and the molten resin was extruded while devolarizing under reduced pressure. The pellets of the resin composition obtained in this way were vacuum dried at 100°C for more than 6 hours, and then extruded using a single screw extruder (manufactured by Isuzu Chemical Engineering Co., Ltd., screw diameter 25 mm, cylinder setting temperature: 250°C) and a T-die (width 300 mm, setting temperature: 250°C). A long unstretched film with a length of 3 m, a width of 200 mm, and a thickness of 100 μm was produced using a film forming apparatus equipped with a cooling roll (set temperature: 220°C), a cooling roll (set temperature: 120 to 130°C), and a winder. Next, using this long unstretched film, the breaking elongation and limiting birefringence (Δn) were determined according to the procedure described in (10) above. In addition, separately from the film used for the above-mentioned evaluation, the retardation film obtained by setting the stretching temperature to Tg and the stretching ratio to 2.4 times showed the refractive index characteristic of nx>ny>nz. Additionally, Re(550) of the obtained retardation film was 145 nm, Re(450)/Re(550) was 0.85, and haze was 0.3%. The results are shown in Table 1.

[Example 2]

A retardation film was produced in the same manner as in Example 1, except that the mixing ratio of BR80 was set to 0.7% by mass. The obtained retardation film was subjected to the same evaluation as 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 the mixing ratio of BR80 was set to 0.9% by mass. The obtained retardation film was subjected to the same evaluation as 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 the mixing ratio of BR80 was 1.5% by mass. The obtained retardation film was subjected to the same evaluation as 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 acrylic resin was not used (that is, the acrylic resin content was set to zero) and the stretching temperature was set to Tg+2°C. The obtained retardation film was subjected to the same evaluation as Example 1. The results are shown in Table 1.

[Comparative Example 2]

A retardation film was produced in the same manner as in Example 1, except that the mixing ratio of BR80 was set to 0.3% by mass. The obtained retardation film was subjected to the same evaluation as Example 1. The results are shown in Table 1.

[Comparative Example 3]

A retardation film was produced in the same manner as in Example 1, except that the mixing ratio of BR80 was 3.0% by mass. The obtained retardation film was subjected to the same evaluation as 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 the mixing ratio of BR80 was 10% by mass and the stretching temperature was Tg+2°C. The obtained retardation film was subjected to the same evaluation as Example 1. The results are shown in Table 1.

[Comparative Example 5]

Extrusion kneading and production of an unstretched film were performed in the same manner as in Example 1, except that BR85 was used as the acrylic resin and the mixing ratio of BR85 was 1% by mass. Although the unstretched film was transparent at first glance, fine insoluble components were generated.

[Comparative Example 6]

Extrusion kneading was performed in the same manner as in Example 1 except that LA4285 was used as the acrylic resin and the mixing ratio of LA4285 was set to 1% by mass. The pellets after kneading were cloudy.

[Comparative Example 7]

P570A was used as the acrylic resin, and extrusion kneading was performed in the same manner as in Example 1, except that the mixing ratio of P570A was 1% by mass. The pellets after kneading were cloudy.

[Comparative Example 8]

MS-600 was used as the acrylic resin, and the same evaluation as Example 1 was conducted except that the mixing ratio of MS-600 was 1% by mass. The results are shown in Table 1.

[Comparative Example 9]

MS-200 was used as the acrylic resin, and extrusion kneading was performed in the same manner as in Example 1, except that the mixing ratio of MS-200 was 1% by mass. The pellets after kneading were cloudy.

[Comparative Example 10]

Extrusion kneading was performed in the same manner as in Example 1, except that G9504, a non-acrylic resin, was used as the modifier resin, and the mixing ratio of G9504 was set to 1% by mass. The pellets after kneading were cloudy.

[Comparative Example 11]

BPEF/ISB/PEG1000 copolycarbonate was synthesized by the method described in Japanese Patent Application Laid-Open No. 2014-43570. This resin is called 'PC2'. The ratio of structural units derived from each monomer is BPEF/ISB/PEG1000/DPC=63.7/26.1/1.0/9.2% by mass. The reduced viscosity of PC2 is 0.35 dL/g, Mw is 36,000, refractive index (n _D ) is 1.599, melt viscosity is 3100 Pa·s, glass transition temperature is 145°C, and photoelastic coefficient is 30×10 ^-12 [m ² /N]. , wavelength dispersion Re(450)/Re(550) was 0.89. PC2 was used as the base resin, BR80 was used as the acrylic resin, and extrusion kneading was performed in the same manner as in Example 1 except that the mixing ratio of BR80 was 1% by mass. The pellets after kneading were cloudy.

[Table 1]

[evaluation]

As is clear from Table 1, according to the examples of the present invention, by using an acrylic resin with an optimal composition and molecular weight, the breaking elongation is large (i.e., excellent extensibility) and the limiting birefringence is large (i.e., phase difference excellent expression properties), and an inverse dispersion retardation film with small haze can be obtained. It can be seen that Comparative Examples 1 and 2, in which the acrylic resin addition amount was less than 0.5% by mass, had a small elongation at break (i.e., could not be sufficiently elongated), and the limiting birefringence (Δn) was significantly smaller than that of the Examples. On the other hand, it can be seen that Comparative Examples 3 and 4, in which the amount of acrylic resin added exceeds 2.0 mass%, have high haze and insufficient transparency, and if the amount of acrylic resin added is too large, the limiting birefringence actually decreases. From Comparative Examples 6 to 10, acrylic resins and non-acrylic resins containing a large amount of components other than methyl methacrylate are not compatible with the resin of the present invention, so the transparency of the resin required as an optical film is low. You can see that it is not obtained. Additionally, in Comparative Example 8, the resin composition after extrusion was transparent, but the haze increased after stretching. This is because the refractive index of the polyester carbonate resin and MS-600 are close, so it was transparent in appearance, but in reality, it is incompatible and the phases are separated, so when a large strain such as stretching is applied, separation between the phases occurs and the haze is thought to have increased.

[Example 5]

(Production of polarizer)

A long roll of 30㎛ thick polyvinyl alcohol (PVA)-based resin film (manufactured by Kuraray, product name 'PE3000') is stretched uniaxially in the longitudinal direction by a roll stretching machine to a length of 5.9 times, while simultaneously swelling, dyeing, and crosslinking. , a washing process was performed, and finally a drying process was performed to produce a polarizer with a thickness of 12 μm.

Specifically, the swelling treatment was performed with pure water at 20°C and stretched 2.2 times. Next, the dyeing treatment was carried out in an aqueous solution at 30°C with a weight ratio of iodine and potassium iodide of 1:7, where the iodine concentration was adjusted so that the resulting polarizer had a single transmittance of 45.0%, and was stretched 1.4 times. In addition, the crosslinking treatment adopted a two-stage crosslinking treatment, and the first crosslinking treatment was stretched 1.2 times while being treated in an aqueous solution of boric acid and potassium iodide at 40°C. The boric acid content of the aqueous solution in the first stage crosslinking treatment was 5.0% by weight, and the potassium iodide content was 3.0% by weight. In the second stage of crosslinking treatment, the material was stretched 1.6 times while being treated in an aqueous solution of boric acid and potassium iodide at 65°C. The boric acid content of the aqueous solution in the second stage crosslinking treatment was 4.3% by weight, and the potassium iodide content was 5.0% by weight. Additionally, the washing treatment was performed with an aqueous potassium iodide solution at 20°C. The potassium iodide content of the aqueous solution for washing treatment was 2.6% by weight. Finally, the drying treatment was performed at 70°C for 5 minutes to obtain a polarizer.

(Production of polarizer)

A triacetylcellulose film (thickness 40 μm, manufactured by Konica Minolta, brand name 'KC4UYW') was bonded to one side of the polarizer through a polyvinyl alcohol adhesive, and a polarizing plate having a protective layer/polarizer configuration was obtained.

(Production of circular polarizer)

The polarizer surface of the polarizer obtained above and the retardation film prepared in the same manner as in Example 1 except that the stretching ratio was adjusted so that Re (550) was 140 nm were bonded together through an acrylic adhesive. Additionally, the retardation film was cut so that its slow axis and the absorption axis of the polarizer formed an angle of 45 degrees when bonded together. Additionally, the absorption axis of the polarizer was arranged to be parallel in the longitudinal direction. In this way, a circularly polarizing plate having a structure of protective layer/polarizer/retardation film was obtained.

(Production of image display device)

An organic EL panel was taken out from a commercially available organic EL display device (manufactured by Samsung, product name 'Galaxy 5'), the polarizing film attached to the organic EL panel was peeled off, and the circularly polarizing plate obtained above was used instead. They were bonded together to obtain an image display device (organic EL display device). The obtained organic EL display device was displayed entirely in black, and the image (black display screen) was observed with the naked eye. The image was good with little reflection and no undesirable coloring.

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

10 polarizer
11 polarizer
12 First protective layer
13 Second protective layer
20 phase contrast film
100 circular polarizer
101 circular polarizer

Claims (11)

At least one linking group selected from the group consisting of a carbonate bond and an ester bond, and at least one 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) Contains a resin having positive refractive index anisotropy and an acrylic resin,
The content of the acrylic resin is 0.5% by mass to 2.0% by mass,
The acrylic resin contains 70% by mass or more of structural units derived from methyl methacrylate, and its weight average molecular weight (Mw) is 10,000 to 200,000,
Re(550) is 100nm to 200nm, Re(450)/Re(550) is more than 0.5 but less than 1.0,
Retardation film:

In general formulas (1) and (2), R ¹ to R ³ are each independently a directly bonded, substituted or unsubstituted alkylene group having 1 to 4 carbon atoms, and R ⁴ to R ⁹ are each independently a hydrogen atom, a substituted or unsubstituted alkylene group. Unsubstituted alkyl group with 1 to 10 carbon atoms, substituted or unsubstituted aryl group with 4 to 10 carbon atoms, substituted or unsubstituted acyl group with 1 to 10 carbon atoms, substituted or unsubstituted alkoxy group with 1 to 10 carbon atoms, substituted or unsubstituted carbon atoms 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 a substituent, silicon atom having a substituent, It is a halogen atom, nitro group or cyano group; At this time, R ⁴ to R ⁹ may be the same or different from each other, and at least two adjacent groups among R ⁴ to R ⁹ may be bonded to each other to form a ring;
Re(550) is the in-plane retardation of the film measured with light with a wavelength of 550 nm at 23°C, and Re(450) is the in-plane retardation of the film measured with light with a wavelength of 450 nm at 23°C. According to paragraph 1,
The resin having the positive refractive index anisotropy contains 1% by mass to 40% by mass of at least one 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). Containing retardation film. According to paragraph 1,
A retardation film in which the resin having the positive refractive index anisotropy further includes a structural unit represented by the following general formula (3):

. According to paragraph 1,
A retardation film in which the resin having the positive refractive index anisotropy further includes a structural unit represented by the following general formula (4):

. According to paragraph 1,
Retardation film with a haze value of 1.5% or less. According to paragraph 1,
Retardation film with a breaking elongation of 200% or more. According to paragraph 1,
A retardation film with a limiting birefringence (Δn) of 0.0039 or greater. A method for producing the retardation film according to any one of claims 1 to 7, comprising:
It includes stretching a resin film containing the resin having the positive refractive index anisotropy and the acrylic resin,
The stretching is performed at a temperature below the glass transition temperature of the resin having the positive refractive index anisotropy.
method. According to clause 8,
The stretching is performed while conveying the elongated resin film in the elongate direction,
The slow axis direction of the obtained long-length retardation film is a direction of 40° to 50° or 130° to 140° with respect to the long-length direction,
Method for manufacturing retardation film. Comprising a polarizer and the retardation film according to any one of claims 1 to 7,
The angle between the absorption axis of the polarizer and the slow axis of the retardation film is 40° to 50° or 130° to 140°,
Circular polarizer. An image display device comprising the circularly polarizing plate according to claim 10 on the viewer's side, and wherein a polarizer of the circularly polarizing plate is disposed on the viewer's side.

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