JP2011123165A - Retardation film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retardation film having a new composition which allows optical compensation over a wide range of wavelength. <P>SOLUTION: The retardation film is constituted of a thermoplastic resin composition (C), containing a cellulose-based resin (A) and an acrylic resin (B) having (I) a glass transition temperature of ≥110°C, exhibiting (II) a negative intrinsic birefringence, and having (III) α,β-unsaturated monomer unit having a specific molecular structure or a heteroaromatic group, and the retardation film has wavelength dispersion properties such that the in-plane retardation Re becomes small the shorter the wavelength becomes. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a retardation film made of a thermoplastic resin including a cellulose resin and an acrylic resin, and a liquid crystal display device including the film.

  Optical films having birefringence utilizing birefringence generated by polymer orientation are widely used in the image display field. For example, an optical film using a phase difference caused by birefringence is widely used for color tone compensation and viewing angle compensation of an image display device. As a specific example, in a reflection type liquid crystal display device (LCD), a retardation plate (λ /) whose optical path length difference (retardation) based on the phase difference caused by birefringence is 1/4 of the wavelength. 4 plates) is used. These optical films having birefringence (hereinafter, also simply referred to as “birefringent film” or “retardation film”) are expected to expand further in the future.

  Conventionally, polycarbonate, cyclic olefin, etc. have been mainly used for retardation films, but these general polymers have higher birefringence as the wavelength of light becomes shorter (i.e. (The phase difference increases). In order to obtain an image display device having excellent display characteristics, on the contrary, at least in the visible light region, the birefringence becomes smaller (that is, the phase difference is reduced) as the wavelength of light becomes shorter. A birefringent film is desired. In this specification, a wavelength that a general polymer (and a birefringent film formed of the polymer) has a wavelength dispersibility in which birefringence decreases as the wavelength of light becomes shorter at least in the visible light region. Based on the reverse of dispersibility, it is called “reverse wavelength dispersibility”.

  Until now, in order to obtain a birefringent film having reverse wavelength dispersion, two types of birefringent films having different phase differences or wavelength dispersion are laminated, or fine particles having specific optical characteristics are added to a member. (For example, see Patent Document 1 for the addition of fine particles). However, in order to achieve the reverse wavelength dispersion by laminating two kinds of birefringent films, it is required to cut both members precisely at a predetermined angle and to laminate them precisely at a predetermined angle. As a result, the manufacturing process becomes complicated, resulting in significant problems in cost and productivity of the birefringent film. In addition, image display devices used in mobile devices are highly demanded for miniaturization and weight reduction. However, a birefringent film obtained is thicker in a method that achieves reverse wavelength dispersion by laminating two kinds of members. It is difficult to respond to this request. On the other hand, in the method of adding fine particles, the manufacturing process becomes complicated, and the major problems remain in the cost and productivity of the birefringent film.

  Apart from these techniques, Patent Document 2 discloses a retardation plate having reverse wavelength dispersion obtained by blending a polymer having positive intrinsic birefringence and a polymer having negative intrinsic birefringence. Is disclosed. In this document, a norbornene resin is exemplified as a polymer having positive intrinsic birefringence, and a styrene polymer is exemplified as a polymer having negative intrinsic birefringence. Patent Document 3 discloses a position having reverse wavelength dispersion formed using a composition comprising a copolymer having a molecular chain having positive intrinsic birefringence and a molecular chain having negative intrinsic birefringence. A phase difference plate is disclosed. In this document, a norbornene chain is exemplified as a molecular chain having positive intrinsic birefringence, and a styrene molecular chain such as a styrene chain is exemplified as a molecular chain having negative intrinsic birefringence.

  Patent Document 4 discloses that the cellulose-based resin has a single layer and reverse wavelength dispersion depending on the structure. Conventionally, a cellulose resin has been used for a polarizer protective film and the like, and development as a retardation film having a function of a polarizer protective film has been actively performed.

JP 2005-156864 A JP 2001-337222 A JP 2001-235622 A JP 2000-137116 A

  However, when a cellulose resin is used as a retardation film having reverse wavelength dispersibility, the photoelastic coefficient is large. For example, in the stretching process during film production, there is a variation in retardation due to slight fluctuations in tension. When exposed to high temperatures, the retardation of the film tends to be non-uniform, and when used in a large liquid crystal display device, contrast unevenness tends to occur. Furthermore, the cellulose-based resin also has a problem that the retardation in the thickness direction tends to be large. For example, the Nz coefficient tends to be large even if uniaxial stretching of the free end is performed, and the film surface is positive in the film plane. There was also a phenomenon that it was not easy to produce a uniaxial film. The present invention has been made in view of such circumstances, and an object thereof is to provide a retardation film having a novel composition capable of optical compensation in a wide range of wavelengths.

  The retardation film of the present invention has a cellulose resin (A) and (I) a glass transition temperature of 110 ° C. or higher, (II) a negative intrinsic birefringence, and (III) the following formula (1) ), (2) or (3) a thermoplastic resin composition (C) containing an acrylic resin (B) having an α, β-unsaturated monomer unit having a molecular structure or heteroaromatic group The in-plane retardation Re becomes smaller as the wavelength becomes shorter.

(In the formula (1), n is a natural number in the range of 1 to 4, and R ¹ and R ² are each independently a hydrogen atom or a methyl group.)
The liquid crystal display device of the present invention includes the retardation film of the present invention.

  The retardation film of the present invention is composed of a thermoplastic resin composition (C) containing a cellulose resin (A) and a specific acrylic resin (B), thereby exhibiting excellent optical properties and reverse wavelength dispersion. Therefore, optical compensation in a wide range of wavelengths is possible.

In the following description, “%” means “% by weight” and “parts” means “parts by weight” unless otherwise specified. In addition, “A to B” indicating a range indicates that the range is A or more and B or less.

<< Cellulose Resin (A) >>
The cellulose-based resin according to the present invention is not particularly limited. For example, aromatic carboxylic acid esters and the like are used, but in view of the characteristics of the obtained film such as optical characteristics, lower fatty acid esters of cellulose are used. Is preferred. In the present invention, the lower fatty acid in the lower fatty acid ester of cellulose means a fatty acid having 5 or less carbon atoms. For example, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose pivalate and the like are preferable lower cellulose esters of cellulose. It is mentioned as a thing. In order to achieve both mechanical properties and melt film-forming properties, mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may be used. Among them, cellulose acetates such as triacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate are preferably used because of their high compatibility with acrylic polymers. Among these, cellulose acetate propionate is particularly preferable from the viewpoint of wavelength dispersion of retardation.
The cellulosic resin (A) preferably has a number average molecular weight (Mn) of 50,000 to 150,000, more preferably a number average molecular weight of 55,000 to 120,000, and most preferably a number average molecular weight of 60000 to 100,000. preferable. A weight average molecular weight (Mw) / number average molecular weight (Mn) ratio of 1.3 to 5.5 is preferably used, particularly preferably 1.5 to 5.0, and more preferably 1.7. It is -4.0, More preferably, the cellulose resin of 2.0-3.5 is used preferably.
The raw material cellulose of the cellulose resin (A) may be wood pulp or cotton linter, and the wood pulp may be softwood or hardwood, but softwood is more preferable. A cotton linter is preferably used from the viewpoint of releasability during film formation. Cellulosic resins made from these can be mixed appropriately or used alone.
The cellulose resin (A) can be obtained, for example, by substituting the hydroxyl group of the raw material cellulose with an acetyl group, a propionyl group and / or a butyl group by a conventional method using acetic anhydride, propionic anhydride and / or butyric anhydride. The method for synthesizing such a cellulose-based resin is not particularly limited, and for example, it can be synthesized with reference to the method described in JP-A-10-45804 or JP-A-6-501040.

Cellulosic resin (A) may contain a known additive. Examples of additives include UV absorbers, antioxidants, light stabilizers, weathering stabilizers, heat stabilizers, and other stabilizers; reinforcing materials such as glass fibers and carbon fibers; near infrared absorbers; tris (dibromopropyl) ) Flame retardants such as phosphate, triallyl phosphate and antimony oxide; antistatic agents represented by anionic, cationic and nonionic surfactants; colorants such as inorganic pigments, organic pigments and dyes; organic fillers and inorganics Filler; resin modifier; anti-blocking agent; matting agent; acid scavenger; metal deactivator; plasticizer; lubricant; flame retardant; rubber mass such as ASA and ABS. The additive amount of the additive is, for example, 0.01 to 20%, preferably 0.1 to 5%, and more preferably 0.1 to 0.5%.

<< Acrylic resin (B) >>
The acrylic resin (B) according to the present invention has (I) a glass transition temperature of 110 ° C. or higher, (II) a negative intrinsic birefringence, and (III), the following formulas (1), ( It has an α, β-unsaturated monomer unit having the molecular structure shown in 2) or (3) or a heteroaromatic group.

(In the formula (1), n is a natural number in the range of 1 to 4, and R ¹ and R ² are each independently a hydrogen atom or a methyl group.)
Here, the acrylic resin is a resin having a (meth) acrylic acid ester unit and / or a (meth) acrylic acid unit as a structural unit. The total ratio of (meth) acrylic acid ester units and (meth) acrylic acid units in all structural units of the acrylic resin is preferably 10% by weight or more, more preferably 30% by weight or more, and particularly preferably 50% by weight. That's it. In addition, the acrylic resin (B) may introduce a ring structure into the main chain by a cyclization reaction after polymerization or the like. In this case, if the total of the (meth) acrylic acid ester unit and the ring structure is 50% by weight or more of all the structural units, the acrylic resin (B) is used.

  (Meth) acrylic acid ester units are, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, t- (meth) acrylic acid t- Butyl, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxy (meth) acrylate Ethyl, 3-hydroxypropyl (meth) acrylate, 2,3,4,5,6-pentahydroxyhexyl (meth) acrylate, 2,3,4,5-tetrahydroxypentyl (meth) acrylate, 2- Α-hydroxyacrylates such as methyl (hydroxymethyl) acrylate and methyl 2- (hydroxyethyl) acrylate Methyl acid, a structural unit derived from the monomers such. The acrylic resin (B) particularly preferably has a methyl (meth) acrylate unit, and in this case, the optical properties and thermal stability of the molded product are improved. The acrylic resin (B) may have two or more of these structural units as (meth) acrylic acid ester units.

  The glass transition temperature of the acrylic resin (B) is 110 ° C. or higher. Preferably, they are 110 degreeC-200 degreeC, More preferably, it is 115 degreeC-200 degreeC, More preferably, it is 120 degreeC-200 degreeC, Especially preferably, it is 125 degreeC-190 degreeC, Most preferably, it is 130 degreeC-180 degreeC. If it is less than 110 ° C., the heat resistance may be insufficient with respect to a severe use environment, which is not preferable. On the other hand, if it exceeds 200 ° C., the molding processability may be deteriorated.

  The acrylic resin (B) exhibits negative intrinsic birefringence. Although the intrinsic birefringence of a general acrylic resin is weakly negative, it is known that the heat-resistant acrylic resin has a positive intrinsic birefringence because a cyclic structure is introduced into the main chain. The acrylic resin (B) according to the present invention has an α, β-unsaturated monomer unit having a molecular structure represented by the formula (1), (2) or (3) or a heteroaromatic group. Therefore, even when a ring structure is introduced into the main chain, it exhibits negative intrinsic birefringence.

  In addition, the positive / negative of the intrinsic birefringence of the polymer is the molecular chain in the layer out of light incident perpendicularly to the principal surface of the layer in a layer (for example, a sheet or film) in which the molecular chain of the polymer is uniaxially oriented. Can be determined based on a value “n1−n2” obtained by subtracting the refractive index n2 of the layer with respect to the vibration component perpendicular to the alignment axis from the refractive index n1 of the layer with respect to the vibration component parallel to the direction (orientation axis) of the film. The intrinsic birefringence value can be determined by calculation based on the molecular structure of each polymer. Further, the positive / negative of the intrinsic birefringence of the resin is determined by the balance of birefringence generated by each polymer contained in the resin.

  The acrylic resin (B) has a molecular structure or a heteroaromatic group represented by the formula (1), (2) or (3). When the molecular structure and the heteroaromatic group represented by the formulas (1), (2), and (3) are defined as the molecular structure X, for example, the acrylic resin (B) includes a structural unit (repeating unit) to which the molecular structure X is bonded. ). The acrylic resin (B) may have two or more molecular structures X.

An example of the acrylic resin (B) has a unit represented by the following formula (4), (5) or (6) or an α, β-unsaturated monomer unit having a heteroaromatic group as a constituent unit. It is a polymer (B-1). In other words, the acrylic resin (B) comprises a unit represented by the following formula (4), (5) or (6) or an α, β-unsaturated monomer unit having a heteroaromatic group as a constituent unit. As a polymer (B-1). Moreover, a polymer (B-1) may have 2 or more types of structural units Y.

(In Formula (4), n is a natural number in the range of 1 to 4, and R ¹ and R ² are each independently a hydrogen atom or a methyl group.)
Hereinafter, the unit represented by the formulas (4), (5), and (6) and the α, β-unsaturated monomer unit having a heteroaromatic group are referred to as a structural unit Y. An α, β-unsaturated monomer unit having a heteroaromatic group is simply referred to as an unsaturated monomer unit.

  Among the structural units Y, the units represented by the formulas (4), (5), and (6) are vinyl groups that are polymerizable groups in the molecular structures represented by the formulas (1), (2), and (3), respectively. It is a structural unit formed by polymerization of a monomer to which a group or a methylene group is bonded. The unsaturated monomer unit is typically a constituent unit formed by polymerization of a monomer in which a vinyl group or methylene group which is a polymerizable group is bonded to a heteroaromatic group.

  The polymer (B-1) preferably has a unit represented by the formula (4) or (5) or an unsaturated monomer unit, and has a unit represented by the formula (4) or an unsaturated monomer unit. More preferably.

  The unit represented by the formula (4) is formed by polymerization of a monomer (vinyl lactam) in which a vinyl group as a polymerizable group is bonded to the lactam structure represented by the formula (1). Examples of the unit represented by the formula (4) include an N-vinyl-2-pyrrolidone unit, an N-vinyl-ε-caprolactam unit, an N-vinyl-2-piperidone unit, and an N-vinyl-4-methyl-2-pyrrolidone unit. , N-vinyl-5-methyl-2-pyrrolidone unit and N-vinyl-ω-heptalactam unit.

  The unit shown in Formula (5) is a vinylanthracene unit. The unit is formed by polymerization of a monomer (vinyl anthracene) in which a vinyl group which is a polymerizable group is bonded to the anthracene structure represented by the formula (2). In addition, a part of hydrogen atom on the ring shown in Formula (5) may be substituted by the group illustrated as an organic residue in Formula (8) described later.

  The unit shown in Formula (6) is a dibenzofulvene unit. The unit is formed by polymerization of a monomer (dibenzofulvene) in which a methylene group as a polymerizable group is bonded to the fluorene structure represented by the formula (3). In addition, a part of hydrogen atom on the ring shown in Formula (6) may be substituted by the group exemplified as the organic residue in Formula (8) described later.

  The heteroaromatic group is at least one selected from, for example, a carbazole group, a pyridine group, an imidazole group, and a thiophene group. Among them, a carbazole group is preferable from the viewpoint of compatibility with the cellulose resin.

The unsaturated monomer unit is, for example, at least one selected from a vinyl carbazole unit, a vinyl pyridine unit, a vinyl imidazole unit, and a vinyl thiophene unit. The vinyl carbazole unit is shown in the following formula (7). In addition, a part of hydrogen atom on the ring shown in Formula (7) may be substituted by the group illustrated as an organic residue in Formula (8) described later.

  The acrylic resin (B) can be produced by a known method. For example, the polymer (B) having an unsaturated monomer unit (for example, a vinyl carbazole unit) and an acrylate ester unit as a constituent unit is an α, β-unsaturated acrylate ester and a heteroaromatic group. It can be formed by polymerizing a monomer group including a monomer (for example, a vinyl carbazole monomer represented by the formula (7)). By selecting the type of (meth) acrylic acid ester contained in the monomer group and cyclizing and condensing the polymer formed, it has an unsaturated monomer unit as a constituent unit and a ring structure in the main chain. Acrylic resin (B) may be used.

  The polymerization method is not particularly limited, and polymerization using a radical or ionic initiator is possible. The polymerization form is not particularly limited, and bulk polymerization, solution polymerization, emulsion polymerization and suspension polymerization can be performed. Moreover, after polymerization, if necessary, treatment such as drying or devolatilization can be performed to obtain powder or pellets.

  The acrylic resin (B) preferably has a ring structure in the main chain. By having a ring structure in the main chain, heat resistance is improved. When the acrylic resin (B) has a ring structure in the main chain, the total amount of the (meth) acrylic acid ester unit, the (meth) acrylic acid unit and the ring structure is 50% by weight or more. An acrylic resin having a ring structure is used.

  As the ring structure of the main chain, N-substituted maleimides such as cyclohexylmaleimide, methylmaleimide, phenylmaleimide, benzylmaleimide, or a ring structure derived from N-substituted maleimide by copolymerization with maleic anhydride or anhydride-derived Or a lactone ring structure, a glutaric anhydride structure, a glutarimide structure, a ring structure derived from an N-substituted maleimide, or the like may be introduced into the main chain by a cyclization reaction after polymerization. Good. From heat resistance, lactone ring structure, cyclic imide structure (ring structure derived from N-alkyl-substituted maleimide, glutarimide ring, etc.) and cyclic acid anhydride structure (ring structure derived from maleic anhydride, glutaric anhydride, etc.) Those having a lactone ring structure in the main chain are particularly preferred from the viewpoint of optical properties.

  The lactone ring structure of the main chain may be a 4- to 8-membered ring, but a 5- to 6-membered ring is more preferable, and a 6-membered ring is still more preferable in terms of structural stability. In addition, when the main chain lactone ring structure is a 6-membered ring, the synthesis yield is high in synthesizing the polymer before introducing the lactone ring structure into the main chain, and the content ratio of the lactone ring structure is high. A structure represented by the following general formula (8) is preferable from the viewpoint of easily obtaining a polymer and further having good copolymerizability with a (meth) acrylic acid ester such as methyl methacrylate.

(In the formula, R ³ , R ⁴ and R ⁵ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom. Examples of the group include an alkyl group having 1 to 20 carbon atoms such as a methyl group, an ethyl group, and a propyl group; an unsaturated aliphatic hydrocarbon group having 1 to 20 carbon atoms such as an ethenyl group and a propenyl group. An aromatic hydrocarbon group having 1 to 20 carbon atoms, such as a phenyl group or a naphthyl group; one or more hydrogen atoms in the alkyl group, the unsaturated aliphatic hydrocarbon group and the aromatic hydrocarbon group; Is a group substituted with at least one group selected from a hydroxyl group, a carboxyl group, an ether group and an ester group.)
When the acrylic resin (B) has a ring structure, the content of the ring structure is not particularly limited, but is usually 5 to 90% by weight, preferably 10 to 70% by weight, and more preferably 10 to 60% by weight. 10 to 50% by weight is more preferable. When the said content rate becomes small too much, the heat resistance of the resin molded product obtained by shape | molding a resin composition may fall, or solvent resistance and surface hardness may become inadequate. On the other hand, when the said content rate becomes large too much, the moldability and handling property of a resin composition will fall.

  The ring structure can be introduced into the acrylic resin (B) by a known method. An acrylic resin whose ring structure is a glutaric anhydride structure or a glutarimide structure can be produced, for example, by the method described in WO2007 / 26659 or WO2005 / 108438. An acrylic resin whose ring structure is a maleic anhydride structure or an N-substituted maleimide structure can be produced, for example, by the method described in JP-A-57-153008 and JP-A-2007-31537. An acrylic resin whose ring structure is a lactone ring structure can be produced, for example, by the method described in JP-A-2006-96960, JP-A-2006-171464, or JP-A-2007-63541.

The acrylic resin (B) may contain a known additive. Examples of additives include UV absorbers, antioxidants, light stabilizers, weathering stabilizers, heat stabilizers, and other stabilizers; reinforcing materials such as glass fibers and carbon fibers; near infrared absorbers; tris (dibromopropyl) ) Flame retardants such as phosphate, triallyl phosphate and antimony oxide; antistatic agents represented by anionic, cationic and nonionic surfactants; colorants such as inorganic pigments, organic pigments and dyes; organic fillers and inorganics Filler; resin modifier; anti-blocking agent; matting agent; acid scavenger; metal deactivator; plasticizer; lubricant; flame retardant; rubber mass such as ASA and ABS. The additive amount of the additive is, for example, 0.01 to 20%, preferably 0.1 to 5%, and more preferably 0.1 to 0.5%.

<< Thermoplastic resin composition (C) >>
The thermoplastic resin composition (C) of the present invention contains the cellulose resin (A) and the acrylic resin (B). Preferably, it contains 5 to 95% by weight of the cellulose resin (A) and 95 to 5% by weight of the acrylic resin (B), more preferably 20 to 80% by weight of the cellulose resin (A) and an acrylic resin ( B) 20 to 80% by weight, more preferably 30 to 70% by weight of the cellulose resin (A) and 30 to 70% by weight of the acrylic resin (B). If the proportion of the cellulose resin (A) is too high, the moisture resistance and optical properties are lowered, and if it is too low, the flexibility is lowered.

  The glass transition temperature of the thermoplastic resin composition (C) of the present invention is preferably 110 ° C or higher, more preferably 110 ° C to 200 ° C, further preferably 115 ° C to 200 ° C, particularly preferably 120 ° C to 190 ° C, Most preferably, it is 130 to 180 ° C. If it is less than 110 ° C., the heat resistance may be insufficient with respect to a severe use environment, which is not preferable. On the other hand, if it exceeds 200 ° C., the molding processability may be deteriorated.

  In the thermoplastic resin composition (C) of the present invention, components other than the cellulose resin (A) and the acrylic resin (B) are preferably used in a proportion of the composition, and preferably less than 50% by weight. May be included in a range of 30% by weight, more preferably less than 10% by weight.

  When other thermoplastic resins are included, the other thermoplastic resins are, for example, olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, poly (4-methyl-1-pentene); vinyl chloride, chlorinated vinyl Halogen-containing polymers such as resins; styrene polymers such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene block copolymer; polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc. Polyamides such as nylon 6, nylon 66 and nylon 610; polyacetal: polycarbonate; polyphenylene oxide; polyphenylene sulfide: polyether ether Ton; polyether nitrile; polysulfone; polyether sulfone; polyoxyethylene benzylidene alkylene; polyamideimide; and the like.

  Among the thermoplastic resins exemplified above, the composition derived from the vinyl cyanide monomer is excellent in compatibility with the acrylic polymer, particularly in compatibility with the acrylic polymer having a ring structure in the main chain. A copolymer containing a unit and a structural unit derived from an aromatic vinyl monomer is preferred. The copolymer is, for example, a styrene-acrylonitrile copolymer.

  The thermoplastic resin composition (C) of the present invention may contain an ultraviolet absorber. When an ultraviolet absorber is included, examples of the ultraviolet absorber include benzophenone compounds, salicinate compounds, benzoate compounds, triazole compounds, and triazine compounds. Examples of the benzophenone compounds include 2,4-dihydroxybenzophenone, 4-n-octyloxy-2-hydroxybenzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, 2-hydroxy-4-n-octyl. Examples thereof include oxybenzophenone, bis (5-benzoyl-4-hydroxy-2-methoxyphenyl) methane, 1,4-bis (4-benzoyl-3-hydroxyphenone) -butane and the like. Examples of the silicate compound include pt-butylphenyl silicate. Examples of the benzoate compound include 2,4-di-t-butylphenyl-3 ', 5'-di-t-butyl-4'-hydroxybenzoate. Examples of triazole compounds include 2,2′-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- (3 , 5-Di-tert-butyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -p-cresol, 2- (2H-benzotriazol-2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol, 2-benzotriazol-2-yl-4,6-di-tert-butylphenol, 2- [5-chloro (2H) -benzotriazole- 2-yl] -4-methyl-6- (tert-butyl) phenol, 2- (2H-benzotriazol-2-yl) -4,6-di-tert-butyl Enol, 2- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol, 2- (2H-benzotriazol-2-yl) -4-methyl-6 -(3,4,5,6-tetrahydrophthalimidylmethyl) phenol, methyl 3- (3- (2H-benzotriazol-2-yl) -5-tert-butyl-4-hydroxyphenyl) propionate / polyethylene glycol 300 reaction products, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-Hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 3- (2H-ben Triazol-2-yl) -5- (1,1-dimethylethyl) -4-hydroxy -C7-9 side chain and straight chain alkyl esters. Further, triazine compounds include 2,4-diphenyl-6- (2-hydroxy-4-methoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-). Ethoxyphenyl) -1,3,5-triazine, 2,4-diphenyl- (2-hydroxy-4-propoxyphenyl) -1,3,5-triazine, 2,4-diphenyl- (2-hydroxy-4-) Butoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-butoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2- Hydroxy-4-hexyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-octyloxyphenyl) -1,3,5-tria 2,4-diphenyl-6- (2-hydroxy-4-dodecyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-benzyloxyphenyl)- 1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-butoxyethoxy) -1,3,5-triazine, 2,4-bis “2-hydroxy-4-butoxyphenyl” -6- (2,4-dibutoxyphenyl) -1,3-5-triazine, 2,4-bis (2,4-dimethylphenyl) -6- [2-hydroxy-4- (3-alkyloxy- 2-hydroxypropyloxy) -5-α-cumylphenyl] -s-triazine skeleton (alkyloxy; long-chain alkyloxy groups such as octyloxy, nonyloxy, decyloxy, etc.) A line absorber is mentioned. Commercially available products include, for example, “Tinuvin 1577”, “Tinuvin 460”, “Tinuvin 477” (manufactured by Ciba Specialty Chemicals) as a triazine UV absorber, and “Adeka Stub LA-31” (Asahi Denka) as a triazole UV absorber. Manufactured by Kogyo Co., Ltd.).

  These can be used alone or in combination of two or more. Although the compounding quantity of the said ultraviolet absorber is not specifically limited, It is preferable that it is 0.01-25 weight% in a film, More preferably, it is 0.05-10 weight%. If the amount added is too small, the contribution to improving the weather resistance is low, and if it is too large, the mechanical strength may be lowered or yellowing may be caused.

  The thermoplastic resin composition (C) of the present invention may contain an antioxidant. Although antioxidant is not specifically limited, For example, well-known antioxidants, such as a hindered phenol type, a phosphorus type, or a sulfur type, can be used by 1 type or in combination of 2 or more types.

  The antioxidant may be a phenolic antioxidant. Examples of the phenolic antioxidant include n-octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, n-octadecyl-3- (3,5-di-t-butyl- 4-hydroxyphenyl) acetate, n-octadecyl-3,5-di-t-butyl-4-hydroxybenzoate, n-hexyl-3,5-di-t-butyl-4-hydroxyphenylbenzoate, n-dodecyl- 3,5-di-t-butyl-4-hydroxyphenylbenzoate, neododecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, dodecyl-β- (3,5-di-t -Butyl-4-hydroxyphenyl) propionate, ethyl-α- (4-hydroxy-3,5-di-t-butylphenyl) isobutyrate, Kutadecyl-α- (4-hydroxy-3,5-di-t-butylphenyl) isobutyrate, octadecyl-α- (4-hydroxy-3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2- (N-octylthio) ethyl-3,5-di-t-butyl-4-hydroxybenzoate, 2- (n-octylthio) ethyl-3,5-di-t-butyl-4-hydroxyphenyl acetate, 2- ( n-octadecylthio) ethyl-3,5-di-t-butyl-4-hydroxyphenyl acetate, 2- (n-octadecylthio) ethyl-3,5-di-t-butyl-4-hydroxybenzoate, 2- (2-hydroxyethylthio) ethyl-3,5-di-t-butyl-4-hydroxybenzoate, diethyl glycol bis- (3,5-di- t-butyl-4-hydroxy-phenyl) propionate, 2- (n-octadecylthio) ethyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, stearamide-N, N-bis- [Ethylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], n-butylimino-N, N-bis- [ethylene-3- (3,5-di-t-butyl- 4-hydroxyphenyl) propionate], 2- (2-stearoyloxyethylthio) ethyl-3,5-di-t-butyl-4-hydroxybenzoate, 2- (2-stearoyloxyethylthio) ethyl-7- ( 3-methyl-5-tert-butyl-4-hydroxyphenyl) heptanoate, 1,2-propylene glycol bis- [3- (3,5-di- -Butyl-4-hydroxyphenyl) propionate], ethylene glycol bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], neopentyl glycol bis- [3- (3,5- Di-t-butyl-4-hydroxyphenyl) propionate], ethylene glycol bis- (3,5-di-t-butyl-4-hydroxyphenyl acetate), glycerin-1-n-octadecanoate-2,3 -Bis- (3,5-di-t-butyl-4-hydroxyphenyl acetate), pentaerythritol tetrakis- [3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate], 1,1,1-trimethylolethanetris- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propyl Pionate], sorbitol hexa- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2-hydroxyethyl-7- (3-methyl-5-tert-butyl-4-hydroxyphenyl) ) Propionate, 2-stearoyloxyethyl-7- (3-methyl-5-tert-butyl-4-hydroxyphenyl) heptanoate, 1,6-n-hexanediol bis [(3 ′, 5′-di-t- Butyl-4-hydroxyphenyl) propionate], pentaerythritol tetrakis (3,5-di-t-butyl-4-hydroxyhydrocinnamate), 3,9-bis [1,1-dimethyl-2- [β- ( 3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl] -2,4,8,10-tetraoxaspir [5,5] - it is undecane.

  The phenolic antioxidant is preferably used in combination with a thioether antioxidant or a phosphoric acid antioxidant. The amount of antioxidant added in combination is 0.01% or more of each of the phenolic antioxidant and the thioether antioxidant relative to the acrylic polymer, or the phenolic antioxidant and the phosphoric acid antioxidant. Each of the agents is 0.025% or more.

  Examples of the thioether-based antioxidant include pentaerythrityl tetrakis (3-laurylthiopropionate), dilauryl-3,3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate, distearyl- 3,3′-thiodipropionate.

  Examples of the phosphoric acid antioxidant include tris (2,4-di-t-butylphenyl) phosphite, 2-[[2,4,8,10-tetrakis (1,1-dimethylethyl) dibenzo [d. , F] [1,3,2] dioxaphosphin-6-yl] oxy] -N, N-bis [2-[[2,4,8,10-tetrakis (1,1 dimethylethyl) dibenzo [D, f] [1,3,2] dioxaphosphin-6-yl] oxy] -ethyl] ethanamine, diphenyltridecyl phosphite, triphenyl phosphite, 2,2-methylenebis (4,6- Di-t-butylphenyl) octyl phosphite, bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite, distearyl pentaerythritol diphosphite Cyclic neopentanetetraylbis is (2,6-di -t- butyl-4-methylphenyl) phosphite. The addition amount of the antioxidant in the thermoplastic resin composition of the present invention is, for example, 0.001 to 10%, preferably 0.001 to 5%, more preferably 0.01 to 2%, More preferably, it is 0.05 to 1%. When the amount of the antioxidant added is excessively large, the antioxidant bleed out or silver streaks may occur during molding.

  The thermoplastic resin composition (C) of the present invention may contain other additives. Other additives include, for example, retardation adjusting agents such as retardation increasing agents and retardation reducing agents; stabilizers such as retardation stabilizing agents, light stabilizers, weathering stabilizers, thermal stabilizers; glass fibers, carbon fibers Near infrared absorbers; flame retardants such as tris (dibromopropyl) phosphate, triallyl phosphate, antimony oxide; antistatic agents typified by anionic, cationic, and nonionic surfactants; inorganic pigments Colorants such as organic pigments and dyes; organic fillers, inorganic fillers; resin modifiers; antiblocking agents; matting agents; acid scavengers; metal deactivators; plasticizers; lubricants, flame retardants; Rubber mass body. The amount of the other additive added in the thermoplastic resin composition of the present invention is, for example, 0.01 to 5%, preferably 0.1 to 2%, and more preferably 0.1 to 0. 5%.

The method for producing the thermoplastic resin composition (C) of the present invention is not particularly limited, and can be produced by mixing the cellulose resin (A) and the acrylic resin (B) by a known method. For example, after each resin is dissolved in a solvent and mixed, a film-shaped thermoplastic resin composition can be produced by film formation and drying by a solution casting method. Further, both resins may be melted and mixed with an extruder or the like, and may be pelletized with a pelletizer or the like, if necessary.

<Phase difference film>
The retardation film of this invention consists of the said thermoplastic resin composition (C).

  In the retardation film of the present invention, the birefringence decreases as the wavelength decreases in the visible light region. The wavelength dispersibility of the film can be evaluated by measuring the phase difference of the film at different wavelengths. For example, the phase difference value at the other wavelength is measured with the phase difference value at the measurement wavelength of 589 nm as a reference (R0). When the ratio (R / R0) is less than 1 at 589 nm or less and more than 1 at a wavelength exceeding 589 nm, the birefringence decreases as the wavelength decreases in the visible light region, that is, the reverse wavelength Dispersion. R / R0 is preferably from 0.6 to less than 1 at 447 nm / 589 nm, more preferably from 0.7 to less than 0.95, still more preferably from 0.75 to less than 0.93, and 1.0 at 750 nm / 589 nm. Is preferably 1.4 or less and more preferably 1.02 or more and 1.3 or less.

The photoelastic coefficient of the retardation film of the present invention is preferably less than 10 × 10 ⁻¹² / Pa. More preferably, it is less than 5 * 10 < ^-12 > / Pa, More preferably, it is 3 * 10 < ^-12 > / Pa. When the photoelastic coefficient is 10 × 10 ⁻¹² / Pa or more, a change in phase difference due to an external force becomes large and image unevenness occurs.

  The in-plane retardation Re of the retardation film of the present invention is not particularly limited, and can be designed according to the characteristics of a liquid crystal cell or other optical compensation film. In the retardation film according to the present invention, the in-plane retardation Re at a measurement wavelength of 589 nm is preferably 50 to 400 nm. More preferably, it is 50-300 nm, More preferably, it is 50-200 nm. When the in-plane phase difference Re takes the above value, the image quality is improved particularly in a VA mode liquid crystal display device. The thickness direction retardation Rth is preferably 50 to 400 nm, and more preferably 50 to 200 nm.

The in-plane retardation Re here is
Re = (nx−ny) × d
The thickness direction retardation Rth is
Rth = [(nx + ny) / 2−nz] × d
Defined. Nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the direction perpendicular to nx in the film plane, nz is the refractive index in the film thickness direction, and d is the thickness (nm) of the film. . The slow axis direction is the direction in which the in-plane refractive index is maximized.

  The retardation film of the present invention can be a film (positive A film) optically uniaxial in the film plane. Uniaxiality means that two types of refractive indexes among the three types of refractive indexes (nx, ny, nz) of the film are substantially the same, and another type of refractive index is different. To have optically positive uniaxiality in the film plane means that ny and nz are almost the same, and nx is larger than ny and nz (nx> ny≈nz). A film that has optically positive uniaxiality in the film plane is also referred to as a positive A film.

  When the retardation film of the present invention is a positive A film, the in-plane retardation Re is not particularly limited, but is preferably 100 to 400 nm, and more preferably 120 to 300 nm. When the in-plane phase difference Re takes the above value, the image quality is improved particularly in a VA mode liquid crystal display device. The thickness direction retardation Rth is not particularly limited, but is preferably 50 to 200 nm, and more preferably 60 to 150 nm.

Although the thickness of the retardation film of this invention is not specifically limited, For example, they are 10 micrometers-500 micrometers, 20 micrometers-300 micrometers are preferable, and 30 micrometers-150 micrometers are especially preferable.
The retardation film of the present invention preferably has a total light transmittance of 85% or more. More preferably, it is 90% or more, More preferably, it is 91% or more. The total light transmittance is a measure of transparency, and if it is less than 85%, the transparency is lowered and it is not suitable as a retardation film.

  The retardation film of the present invention is less colored, and the b value per 250 μm thickness is preferably 0.5 or less, more preferably 0.3 or less.

  The retardation film of the present invention preferably has a haze of 5% or less, more preferably 3% or less. If the haze exceeds 5%, the transmittance is lowered and may not be suitable for optical applications.

  The glass transition temperature of the retardation film of the present invention is preferably 110 ° C. or higher, more preferably 110 ° C. to 200 ° C., further preferably 115 ° C. to 200 ° C., particularly preferably 120 ° C. to 190 ° C., and most preferably 130 ° C. ~ 180 ° C. If it is less than 110 ° C., the heat resistance may be insufficient with respect to a severe use environment, which is not preferable. Moreover, since workability may fall when it exceeds 200 degreeC, it is unpreferable.

  Next, the manufacturing method of the retardation film of this invention is demonstrated. The manufacturing method of the retardation film of this invention is not specifically limited except consisting of a thermoplastic resin composition (C), A well-known manufacturing method is possible. Examples of the film forming method include known film forming methods such as a solution casting method (solution casting method), a melt extrusion method, a calendar method, and a compression molding method. Among these, the solution casting method (solution casting method) and the melt extrusion method are preferable.

  As a specific example of the melt extrusion method, the kneader used for extrusion kneading is not particularly limited. For example, a known kneader such as a single screw extruder, a twin screw extruder, or a pressure kneader is used. Can be used. Moreover, after adding a thermoplastic resin and an additive as needed, and pre-blending with mixers, such as an omni mixer, the obtained mixture may be extrusion-kneaded from a kneader.

  Examples of the melt extrusion method include a T-die method and an inflation method, and the molding temperature at that time is preferably 200 to 350 ° C., more preferably 250 to 300 ° C., still more preferably 255 to 300 ° C., and particularly preferably. Is 260-300 ° C.

  When the T-die method is used, a resin film wound into a roll can be obtained by attaching a T-die to the tip of the extruder and winding the film extruded from the T-die. At this time, it is also possible to control the temperature and speed of winding and to stretch (uniaxial stretching) in the extrusion direction of the film. Further, the film may be stretched in a direction perpendicular to the extrusion direction, and sequential biaxial stretching or simultaneous biaxial stretching may be performed.

  When an extruder is used for extrusion molding, the type is not particularly limited and may be uniaxial, biaxial, or multiaxial, but its L / D value is (L is the value of the extruder) Cylinder length, D is cylinder inner diameter), in order to sufficiently plasticize the thermoplastic resin composition to obtain a good kneaded state, it is preferably 10 or more and 100 or less, more preferably 15 or more and 80 or less, More preferably, it is 20 or more and 60 or less. When the L / D value is less than 10, the thermoplastic resin composition may not be sufficiently plasticized and a good kneaded state may not be obtained. On the other hand, if the L / D value exceeds 100, the resin in the composition may be thermally decomposed due to excessive heat generation from the thermoplastic resin composition.

  In this case, the set temperature of the cylinder is preferably 200 to 350 ° C or less, more preferably 250 to 300 ° C or less. If setting temperature is less than 200 degreeC, the melt viscosity of a thermoplastic resin composition will become high too much, and the productivity of a resin film will fall. On the other hand, if the set temperature exceeds 350 ° C., the resin in the thermoplastic resin composition may be thermally decomposed.

  When an extruder is used for extrusion molding, the shape is not particularly limited, but the extruder preferably has one or more open vent portions. By using such an extruder, the decomposition gas can be sucked from the open vent portion, and the amount of volatile components remaining in the obtained resin film can be reduced. In order to suck the decomposition gas from the open vent portion, for example, the open vent portion may be in a reduced pressure state, and the degree of pressure reduction is preferably in the range of 931 to 1.3 hPa as the pressure of the open vent portion, 798 A range of ˜13.3 hPa is more preferable. When the pressure in the open vent is higher than 931 hPa, volatile components or monomer components generated by the decomposition of the resin are likely to remain in the thermoplastic resin. On the other hand, it is industrially difficult to keep the pressure of the open vent part lower than 1.3 hPa.

  When producing the retardation film of the present invention, it is preferable to incorporate a filtration step such as filtration with a polymer filter. By incorporating the filtration step, foreign substances present in the thermoplastic resin composition can be removed, and thus defects in the appearance of the obtained film can be reduced. In addition, at the time of filtration with a polymer filter, a thermoplastic resin composition will be in a high temperature molten state. For this reason, the thermoplastic resin composition deteriorates when passing through the polymer filter, and gas components and colored deterioration products formed by the deterioration start to flow into the composition. Defects such as flow streaks may be observed. This defect is particularly apt to be observed during the continuous forming of a film. Therefore, when molding a thermoplastic resin composition filtered through a polymer filter, the molding temperature decreases the melt viscosity of the thermoplastic resin and shortens the residence time of the thermoplastic resin in the polymer filter. For example, it is 255-350 degreeC, and 260-320 degreeC is preferable.

  The configuration of the polymer filter is not particularly limited, but a polymer filter in which a large number of leaf disk filters are arranged in a housing can be suitably used. The filter material of the leaf disk type filter may be any of a type in which a metal fiber nonwoven fabric is sintered, a type in which metal powder is sintered, a type in which several metal meshes are laminated, or a hybrid type in which they are combined. The sintered type is most preferred.

  The filtration accuracy by the polymer filter is not particularly limited, but is usually 15 μm or less, preferably 10 μm or less, more preferably 5 μm or less. When the filtration accuracy is 1 μm or less, the residence time of the thermoplastic resin composition becomes longer, so that the thermal deterioration of the composition increases, and the productivity of the resin film decreases. On the other hand, when the filtration accuracy exceeds 15 μm, it is difficult to remove foreign substances in the thermoplastic resin composition.

  The filtration area with respect to the resin composition throughput per hour in the polymer filter is not particularly limited, and can be appropriately set according to the throughput of the thermoplastic resin composition. The filtration area is, for example, 0.001 to 0.15 m2 / (kg / hour).

  The shape of the polymer filter is not particularly limited. For example, an inner flow type having a plurality of resin flow ports and a resin flow path in the center pole; the inner peripheral surface of the leaf disk filter at a plurality of vertices or faces And an external flow type having a resin flow path on the outer surface of the center pole. In particular, it is preferable to use an external flow type in which the resin stays are small.

  Although there is no restriction | limiting in particular in the residence time of the thermoplastic resin in a polymer filter, Preferably it is 20 minutes or less, More preferably, it is 10 minutes or less, More preferably, it is 5 minutes or less. Further, the filter inlet pressure and the filter outlet pressure during filtration are, for example, 3 to 15 MPa and 0.3 to 10 MPa, respectively, and the pressure loss (the pressure difference between the filter inlet pressure and the outlet pressure) is 1 MPa to 15 MPa. A range is preferred. When the pressure loss is 1 MPa or less, the flow path through which the thermoplastic resin passes the filter tends to be biased, and the quality of the obtained film tends to deteriorate. On the other hand, when the pressure loss exceeds 15 MPa, the polymer filter is easily damaged.

  What is necessary is just to set suitably the temperature of the thermoplastic resin composition introduce | transduced into a polymer filter according to the melt viscosity, for example, it is 250-300 degreeC, Preferably it is 255-300 degreeC, More preferably, it is 260-300. ° C.

  There are no particular limitations on the specific steps for obtaining a film with less foreign matter and color by filtration using a polymer filter. For example, (1) a process of forming and filtering a thermoplastic resin composition in a clean environment, and subsequently molding the thermoplastic resin in a clean environment; (2) a thermoplastic resin composition having foreign matter or colored matter A process in which a product is filtered in a clean environment, and then a thermoplastic resin composition is molded in a clean environment. (3) A thermoplastic resin composition having foreign matters or colored products is filtered in a clean environment. And a process of forming at the same time as the treatment. You may perform the filtration process of the thermoplastic resin composition by a polymer filter in multiple times for each process.

  When filtering a thermoplastic resin composition with a polymer filter, it is preferable to install a gear pump between the extruder and the polymer filter to stabilize the pressure of the thermoplastic resin composition in the filter.

  It is preferable that the thermoplastic resin composition is extruded as it is after production to form a film. Since the thermal history can be reduced compared to the case of remelting the obtained pellets and forming a film after pelletizing the thermoplastic resin composition, thermal deterioration of the thermoplastic resin composition can be suppressed. Moreover, in this method, since contamination of foreign matter from the environment can be suppressed, it is possible to suppress the presence of foreign matter in the obtained film or coloring of the obtained film. A gear pump and a polymer filter are preferably arranged between the extruder and the T die.

  In the case of the solution casting method, a film-like thermoplastic resin composition can be produced by preparing a solution containing the cellulose resin (A) and the acrylic resin (B), forming a film by the casting method, and drying. is there. The process includes (1) a dissolution process, (2) a casting process, and (3) a drying process.

(1) Dissolution process:
When the cellulose resin and the acrylic resin are dissolved in the solvent, the solutions may be mixed after dissolving in the solvent individually, or the resin composition containing the cellulose resin and the acrylic resin may be dissolved in the solvent. May be. The acrylic resin can be used in the dissolution step without passing through the devolatilization step and the polymerization solution containing the polymerization solvent. While stirring the separately prepared cellulose resin solution, By adding them one by one, a dope used for solution film formation can be prepared. Additives necessary for the dope during or after dissolution are added and dissolved, then filtered with a filter medium, defoamed, and sent to the next step with a liquid feed pump. The filter medium for filtration preferably has an absolute filtration accuracy of 0.04 mm or less, and more preferably in the range of 0.01 to 0.02 mm. There is no particular limitation on the material of the filter medium, and a normal filter medium can be used. However, a filter medium made of plastic fibers such as polypropylene and Teflon and a metal filter medium such as stainless steel fibers are preferable because they do not drop off fibers.

  As the solvent, a good solvent used in a solution casting method such as methylene chloride, methyl acetate or dioxolane can be used, and a poor solvent such as methanol, ethanol or butanol may be used at the same time. In the present invention, a polymerization solvent contained in a polymerization solution of an acrylic resin can also be used. Among these, a plurality of solvents may be included in the solution. You may cool to -20 degrees C or less in the process of dissolution, or you may heat to 80 degrees C or more.

  In order to prepare a cellulose resin solution, the cellulose resin is dissolved in an organic solvent mainly composed of a good solvent for the cellulosic resin (flaked), an acrylic polymer having a ring structure in the main chain, It is conceivable to dissolve the additive while stirring to form a dope, or to mix a cellulose resin solution with an acrylic resin solution or an additive solution to form a dope. Cellulosic resins can be dissolved at normal pressure, below the boiling point of the main solvent, under pressure above the boiling point of the main solvent, or disclosed in JP-A-9-95544, 9-95557 or 9 Various dissolution methods such as a method performed by a cooling dissolution method as described in JP-A-95538 and a method performed at a high pressure as described in JP-A-11-21379 can be used, but the concentration of the cellulose-based resin in the dope Is preferably 10 to 35% by weight.

(2) Casting process:
This is a step of casting a dope on a support to obtain a uniform film.

  Generally, if a deformation stress is applied in the film forming process, the orientation proceeds and the birefringence value of the film increases. As the birefringence value increases, it becomes difficult to maintain the uniformity of the film, and the variation in optical characteristics also increases. Therefore, it is desirable to form a film under a relatively low stress with a low viscosity. In addition, it is preferable that the dope has a low viscosity because the film thickness is uniformed by the leveling effect after coating. The preferred viscosity of the solution is from 10 poise to 100 poise, more preferably from 15 poise to 70 poise. In addition, since it will flow out from a support body when it is lower than 10 poise, measures, such as providing a partition plate suitably, are needed.

  As a coating method, a die coater, a doctor blade coater, a roll coater, a comma coater, a lip coater, and the like are preferable, but various methods that are usually used are possible without being limited to these examples.

  As a preferable support, a metal support such as a stainless steel endless belt or a rotating metal drum, or a film such as a polyimide film or a biaxially stretched polyethylene terephthalate film can be used.

(3) Drying process:
This is a step of heating a dope film in which a dope is cast on a metal support and evaporating the solvent to obtain a dry film.

  Heat drying is performed in a state where the liquid film immediately after casting or coating is not dried, and if there is a rapid flow of air or heating, thickness unevenness is likely to occur. That is, there are also means for preventing direct wind from being applied to the film or heating by applying microwaves instead of wind. It is also important to prevent rapid heating and cooling. Furthermore, since the dope film is foamed by the humidity in the atmosphere, the humidity control is also important. Thereafter, it is preferably dried so as to reduce the residual solvent by blowing hot air after the semi-solidified state.

  The drying after casting can be carried out while being supported on the support, but if necessary, the predried film can be peeled off from the support until it has self-supporting property, and further dried. In general, a float method, a tenter or a roll conveying method can be used for drying the film. In the case of the float process, the film itself is subjected to complicated stress, and optical characteristics are likely to be uneven. In the case of the tenter method, it is necessary to balance the film width shrinkage due to solvent drying and the tension to support its own weight depending on the distance between the pins or clips that support both ends of the film. There is a need. On the other hand, in the case of the roll conveyance method, since the tension for stable film conveyance is in principle applied to the film flow direction (MD direction), it has a characteristic that the direction of stress is easily made constant. Therefore, the film is most preferably dried by a roll conveyance method. Above all, in order to reduce the stress caused by gravity, the vertical path method (vertical suspension path method) that arranges multiple rolls on the top and bottom and passes the film up, down, up, down, etc. is a long drying path while omitting the oven installation space Can be ensured.

  Further, drying in an atmosphere kept at a low humidity so that the film does not absorb moisture when the solvent is dried is an effective method for obtaining a film having high mechanical strength and transparency.

  As the stretching method for obtaining the retardation film of the present invention, conventionally known stretching methods can be applied as long as the retardation film can be optically uniaxially imparted. From the standpoint of developing the necessary in-plane retardation Re and thickness direction retardation Rth, free end uniaxial stretching is preferred. Sequential biaxial stretching is also one of the preferred forms in that the bending resistance to any two orthogonal directions in the film plane is improved. Examples of the two orthogonal directions in the plane include a direction parallel to the slow axis in the film plane and a direction perpendicular to the slow axis in the film plane. In addition, what is necessary is just to set extending | stretching conditions, such as a draw ratio, extending | stretching temperature, an extending | stretching speed, suitably according to a desired phase difference and desired bending resistance, and there is no limitation in particular.

  Examples of the stretching apparatus include a roll stretching machine, a tenter-type stretching machine, an oven stretching machine, and a small experimental stretching apparatus such as a tensile tester, a uniaxial stretching machine, and a sequential biaxial stretching machine. The retardation film of the present invention can also be obtained using this apparatus.

  The stretching temperature is preferably around the glass transition temperature of the film raw material polymer or the film before stretching. Specifically, it is preferably performed at (glass transition temperature−30) ° C. to (glass transition temperature + 50) ° C., more preferably (glass transition temperature−20) ° C. to (glass transition temperature + 20) ° C., more preferably. It is (glass transition temperature−10) ° C. to (glass transition temperature + 10) ° C. When it is lower than (glass transition temperature-30) ° C., a sufficient draw ratio cannot be obtained, which is not preferable. When the temperature is higher than (glass transition temperature + 50) ° C., resin flow occurs and stable stretching cannot be performed.

  The draw ratio defined by the area ratio is preferably in the range of 1.1 to 25 times, more preferably in the range of 1.2 to 10 times, and still more preferably in the range of 1.3 to 5 times. If it is smaller than 1.1 times, it is not preferable because it does not lead to the development of retardation performance accompanying to stretching and the improvement of toughness. If it is larger than 25 times, the effect of increasing the draw ratio is not recognized.

  When stretching in a certain direction, the stretching ratio in one direction is preferably in the range of 1.05 to 10 times, more preferably in the range of 1.1 to 5 times, and still more preferably in the range of 1.2 to 3 times. Done. If it is smaller than 1.05 times, a desired phase difference may not be obtained, which is not preferable. When it is larger than 10 times, the effect of only increasing the draw ratio is not recognized, and the film may be broken during the drawing, which is not preferable.

  The stretching speed (one direction) is preferably in the range of 10 to 20000% / min, more preferably in the range of 100 to 10000% / min. If it is slower than 10% / min, it takes time to obtain a sufficient draw ratio, and the production cost is increased, which is not preferable. If it is faster than 20000% / min, the stretched film may be broken, which is not preferable.

  The retardation film of the present invention can also be used as a polarizer protective film. A polarizer protective film is used in the state joined to the single side | surface or both surfaces of the polarizer. A polarizer is typically formed by dyeing a polyvinyl alcohol film with a dichroic material such as iodine or a dichroic dye, but since an aqueous solution is used for dyeing, the polarizer is bonded to the polarizer. The protective film preferably originally has water permeability. The use of a water-based adhesive for bonding the polarizer and the polarizer protective film is one of the reasons why a polarizer protective film having water permeability is preferable. For example, a film made of a cycloolefin polymer exhibits little water permeability due to the strong hydrophobicity of the polymer, and is not necessarily suitable as a polarizer protective film. In contrast, the molecular structure represented by the formula (1) has high hydrophilicity. For this reason, the film of the present invention having a layer made of the thermoplastic resin composition (C) having the structure depends on the specific structure such as the content of the structure in the thermoplastic resin composition (C). It exhibits high water permeability and is suitable as a polarizer protective film.

  When the retardation film of the present invention is used as a polarizer protective film, for example, one or both sides of a polarizer obtained by dyeing a polyvinyl alcohol-based fat film with a dichroic substance (such as iodine or a dichroic dye) and uniaxially stretching it. In addition, the retardation film can be bonded via an adhesive layer or an anchor layer.

  The polarizer may be any polarizer as long as it has a function of transmitting only light having a specific vibration direction. For example, a polyvinyl alcohol film stretched and dyed with iodine or a dichroic dye. Alcohol polarizers; polyene polarizers such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride; reflective polarizers using multilayer laminates or cholesteric liquid crystals; thin film crystal polarizers Among them, a polarizer obtained by uniaxially stretching a polyvinyl alcohol-based fat film dyed with a dichroic material is preferably used. The thickness of these polarizers is not particularly limited, and is generally about 5 to 100 μm.

  The retardation film of the present invention is preferably bonded to the polarizer via an adhesive layer. Preferred adhesives include, for example, polyvinyl alcohol resins, polyacrylic resins, polyurethane resins, polyester resin adhesives, adhesives that cure with active energy rays such as ultraviolet rays and electron beams, acrylic resins, silicon resins, Examples thereof include rubber-based pressure-sensitive adhesives. In addition, it cannot be overemphasized that it may heat-press on the conditions which the polarizing function of a polarizer does not fall, and in that case, it can adhere | attach on gentle thermo-compression conditions.

  The method of adhering using the adhesive is not particularly limited. For example, kiss coat, spin coat, roll coat, dip coat, curtain coat, bar coat, doctor blade coat, knife coat, air knife coat, die coat, gravure coat Using various methods such as micro gravure coating, offset gravure coating, lip coating, spray coating, comma coating, etc., applying adhesive on the adhesive surface of the polarizing film and / or the film to be joined, and overlaying the two Is possible. After applying the adhesive, the polarizing film and the film bonded thereto are sandwiched by nip rolls and bonded together. When bonding, it is preferable to arrange | position the optical axis of the said retardation film, and the absorption axis of a polarizer orthogonally or in parallel.

The retardation film of the present invention can be subjected to an easy adhesion treatment for improving adhesiveness on the surface in contact with the polarizer. Examples of the easy adhesion treatment include a plasma treatment, a corona treatment, an ultraviolet irradiation treatment, a flame (flame) treatment, a saponification treatment, and a method for forming an anchor layer, and these can be used in combination. Among these, a corona treatment, a method of forming an anchor layer, and a method of using these in combination are preferable. The anchor layer is not particularly limited, and a known anchor layer is used, and acrylic, cellulose, polyurethane, silicone, polyester, polyethyleneimine, polymers containing amino groups in the molecule, etc. are used. The These anchor layers may be used alone, or two or more of them may be used in combination or laminated.
The thickness of the anchor layer is the thickness after drying / curing or drying, and is, for example, preferably 0.01 to 10 μm, more preferably 0.05 to 3 μm, and further preferably 0.1 to 1 μm. When the thickness of the anchor layer is less than 0.01 μm, the adhesive strength between the polarizer and the film may be insufficient. On the other hand, when the thickness of the anchor layer exceeds 10 μm, color loss or discoloration of the polarizing plate may easily occur in the water resistance or moisture resistance test.
The method for applying the anchor layer coating composition to the surface of the retardation film of the present invention that faces the polarizer is not particularly limited as long as a normal coating technique using a bar coater, roll coater, gravure coater, or the like is employed. It is not something. Moreover, the method and conditions for drying the applied anchor layer coating composition are not particularly limited. For example, using a hot air dryer or an infrared dryer, preferably 50 to 130 ° C., more preferably 75. What is necessary is just to dry at the temperature of -110 degreeC. Moreover, there is no problem even if a curing step is provided for the urethane bond formation reaction and / or curing of the anchor layer coating composition. When a curing process is required, the curing temperature is preferably 20 to 100 ° C., more preferably 20 to 50 ° C., but it proceeds to some extent with the heat used for drying the composition, and an adhesive is used. Since the process proceeds further in the bonding process between the polarizer and the retardation film, sufficient physical properties can be obtained even at room temperature curing.
In addition, in order to adjust the surface wetting tension, the surface of the anchor layer of the film provided with the anchor layer is subjected to, for example, corona discharge treatment, plasma treatment, ozone spraying, ultraviolet irradiation, before the subsequent bonding step. Flame treatment, chemical treatment, and other conventionally known surface treatments can be performed.

  The retardation film may have an adhesive layer as at least one of the outermost layers. An adhesive layer for adhering to other members such as other optical films and liquid crystal cells can be provided. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, a silicone-based polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based or rubber-based polymer is appropriately used as a base polymer. Can be selected and used.

The attachment of the pressure-sensitive adhesive layer can be performed by an appropriate method. For example, a pressure sensitive adhesive solution of about 10 to 40% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of a suitable solvent alone or a mixture such as toluene and ethyl acetate is prepared. A method of attaching it directly on the film by an appropriate development method such as a casting method or a coating method, or a method of forming an adhesive layer on a separator according to the above and transferring it to the film surface, etc. The retardation film of the present invention can be a laminate, and can be laminated before and after stretching. As the laminating method, known methods such as co-extrusion and bonding via a sticky / adhesive layer are possible.

  The retardation film of the present invention may be used in combination with other optical members depending on the embodiment and application. Also, adhesive layer, adhesive layer, anchor layer, if necessary, UV shielding layer, heat ray shielding layer, antireflection layer, antiglare layer (non-glare) layer, hard coat layer, antistatic layer, photocatalyst layer, etc. Various functional coating layers such as antifouling layer, electromagnetic wave shielding layer, gas barrier property, etc. are each laminated and applied, or a member coated with each individual functional coating layer is applied via an adhesive or adhesive. It may be laminated. In addition, the stacking order of each layer is not particularly limited, and the stacking method is not particularly limited.

The retardation film of the present invention can be used for various image display devices. Specific examples are not particularly limited, and it is preferably used for various image display devices such as a liquid crystal display (LCD), an electroluminescence (EL) display, a plasma display (PD), and a field emission display (FED: Field Emission Display). I can do it.

[Liquid Crystal Display]
The liquid crystal display device of the present invention includes the retardation film of the present invention. FIG. 1 is an example of a schematic cross-sectional view of an image display surface of a liquid crystal display device. The liquid crystal display device mainly includes a liquid crystal cell 4 (including a liquid crystal layer, a glass substrate, a transparent electrode, an alignment film, and the like), polarizing plates 9 and 10 disposed with the liquid crystal cell 4 interposed therebetween, and a back surface. A light unit 8 (including a light source, a reflection sheet, a light guide plate, a diffusion plate, a diffusion sheet, a prism sheet, a brightness enhancement film, and the like) is provided. The polarizing plates 9 and 10 include the polarizer 2 and the polarizer 6, and the polarizer protective films 1, 3, 5, and 7 disposed with the polarizer interposed therebetween. It is preferable that the first polarizer (polarizer 2) and the second polarizer (polarizer 6) are arranged on both sides of the liquid crystal cell and the polarization axes are orthogonal to each other.

  In the liquid crystal display device of the present invention, the retardation film of the present invention includes a first polarizer and a second polarizer whose polarization axes are orthogonal to each other, that is, in FIG. It is preferable to be located between the polarizer 2 and the polarizer 6. Although there is no particular limitation, it is one of the preferred embodiments that it is located between the liquid crystal cell 4 and the polarizing plate 9 and / or between the liquid crystal cell 4 and the polarizing plate 10. Furthermore, in the liquid crystal display device of the present invention, the retardation film according to the present invention can be used as a polarizer protective film. In this case, the polarizer protective film 3 and / or 5 is the retardation of the present invention. Become a film.

  As a polarizer protective film other than the retardation film according to the present invention, a known resin can be employed. For example, cellulose resins such as triacetyl cellulose, polycarbonates, cyclic polyolefins, (meth) acrylic resins, Examples thereof include polyethylene terephthalate and polynaphthalene terephthalate. An acrylic resin is preferable from the viewpoint of suppressing optical properties and curling of the polarizing plate.

  As the acrylic resin, an acrylic resin film having a ring structure in the main chain is particularly preferable from the viewpoint of heat resistance. The ring structure that the acrylic resin has in the main chain is, for example, a ring structure having an ester group, an imide group, or an acid anhydride group. More specific examples of the ring structure are at least one selected from a lactone ring structure, a glutarimide structure, a glutaric anhydride structure, and a structure derived from N-substituted maleimide or maleic anhydride. Among them, from the viewpoint of optical properties and heat resistance, at least one selected from a lactone ring structure and a glutarimide structure is preferable, and a lactone ring structure is more preferable. A specific lactone ring structure is not particularly limited, but is a structure represented by the above formula (8).

  Known functionality can be imparted to the polarizer protective film. For example, the polarizer protective films 1 and 7 contain an ultraviolet absorber to impart ultraviolet absorbing ability, or the polarizer protective film 1 that is the outermost surface is hard-coated and / or anti-reflective, low-reflective, etc. Anti-glare treatment can also be performed.

  Specific examples of the liquid crystal display device of the present invention are not particularly limited, and various drive systems such as a reflective type, a transmissive type, a transflective type LCD, or a TN type, STN type, OCB type, HAN type, VA type, IPS type, etc. Used in a liquid crystal display device (LCD). Among these, a VA mode liquid crystal display device is preferable, and by providing the retardation film according to the present invention, it is possible to display a high-quality image with particularly high contrast.

It should be noted that the specific embodiments and the following examples made in the section of the best mode for carrying out the invention are intended to clarify the technical contents of the present invention, and to such specific examples. It is not to be construed as limiting in any way whatsoever, and those skilled in the art can implement the invention within the spirit of the invention and the scope of the appended claims.

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to the examples shown below.

[Weight average molecular weight]
The weight average molecular weight was determined in terms of polystyrene using gel permeation chromatography (GPC). The apparatus and measurement conditions used for the measurement are as follows.

System: manufactured by Tosoh Corporation Column: TSK-GEL superHZM-M 6.0 × 150 2 in series
TSK-GEL superHZ-L 4.6 × 35 1 column Reference column: TSK-GEL superH-RC 6.0 × 150 2 columns Eluent: Chloroform Flow rate 0.6 mL / min Column temperature: 40 ° C.
[Glass-transition temperature]
The glass transition temperature (Tg) was determined according to JIS K7121. Specifically, using a devolatilization differential operation calorimeter (DSC-8230, manufactured by Rigaku Corporation), a sample of about 10 mg was heated from normal temperature to 200 ° C. (temperature increase rate: 20 ° C./min) in a nitrogen gas atmosphere. From the DSC curve obtained in this way, the starting point method was used for evaluation. Α-alumina was used as a reference.

[In-plane retardation Re]
In-plane retardation (per 100 μm thickness) at a measurement wavelength of 589 nm of the film was evaluated using a fully automatic birefringence meter (manufactured by Oji Scientific Instruments, KOBRA-WR).

[Thickness direction retardation Rth, Nz coefficient]
The thickness direction retardation (per 100 μm thickness) and the Nz coefficient at a measurement wavelength of 589 nm of the film were evaluated using a fully automatic birefringence meter (manufactured by Oji Scientific Instruments, KOBRA-WR).

[Photoelastic coefficient]
The photoelastic coefficient of the stretched film was evaluated using an ellipsometer (manufactured by JASCO Corporation, M-150).

[Flexibility]
The flexibility (folding resistance) of the film is an appearance when a film having a thickness of 100 μm is folded at 90 ° at a folding radius of 1 mm in an atmosphere of 25 ° C. and 65% RH so that the stretching direction becomes a crease. Was observed.

(Production Example 1)
A reactor equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introduction pipe was mixed with 30 parts by weight of methyl 2- (hydroxymethyl) acrylate (MHMA), 54 parts by weight of methyl methacrylate (MMA), and N-vinylcarbazole 6 Part by weight, 10 parts by weight of butyl methacrylate (BMA), and 90 parts by weight of toluene were charged. While introducing nitrogen gas into the reaction vessel, the temperature was raised to 105 ° C., and when refluxing was started, 0.04 part by weight of t-amyl peroxyisononanoate (Lupelox 570, manufactured by Arkema Yoshitomi) was used as a polymerization initiator. At the same time as the addition, a solution prepared by dissolving 0.08 part by weight of t-amyl peroxyisononanoate (Lupelox 570, manufactured by Arkema Yoshitomi) in 10 parts by weight of toluene was added dropwise over 3 hours while refluxing at about 105 ° C. Solution polymerization was performed at ˜110 ° C., and the mixture was further heated for 4 hours.
To the obtained polymer solution, 0.2 part by weight of a stearyl phosphate / distearyl mixture was added, and a cyclization condensation reaction was performed at 80 ° C. to 105 ° C. under reflux for 2 hours. Furthermore, it was heated at 240 ° C. for 90 minutes in an autoclave to obtain a transparent solution of an acrylic resin having a lactone ring structure in the main chain. The solution thus obtained was subjected to a barrel temperature of 250 ° C., a rotation speed of 100 rpm, a reduced pressure of 13.3 to 670 hPa (10 to 500 mmHg), a rear vent number of 1 and a fore vent number of 4 (first and second from the upstream side Introduced into a vent type screw twin screw extruder (Φ = 29.75 mm, L / D = 40) at a processing rate of 2 kg / hour in terms of resin amount and devolatilized As a result, a polymer (A-1) was obtained. At the time of devolatilization, separately prepared antioxidant / deactivator mixed solution was injected after the second vent at an injection rate of 0.04 kg / hour. In the antioxidant / deactivator mixed solution, 2.3 parts by weight of Irganox 1010 manufactured by Ciba Specialty Chemicals, 2.3 parts by weight of ADEKA Adekastab AO-412S and 10 parts by weight of zinc octylate (manufactured by Nippon Chemical Industry, A solution of 3.6% of Nikka octix zinc) in 86 parts by weight of toluene was used. The weight average molecular weight of the obtained polymer (A-1) was 110,000, and the glass transition temperature was 137 ° C.

Example 1
The polymer (A-1) obtained in Production Example 1 and a commercially available cellulose compound (manufactured by Acros Organics, cellulose acetate propionate, number average molecular weight 75,000) are polymer (A-1) / Cellulose compound = A thermoplastic resin composition containing an acrylic resin and a cellulose resin, kneaded at a temperature of 250 ° C using a twin screw extruder while feeding using a feeder at a weight ratio of 60/40 ( SB-1) was obtained.

The obtained thermoplastic resin composition (SB-1) was press-molded at 250 ° C. with a press molding machine to obtain a film (FB-1) having a thickness of about 150 μm. Next, the produced film (FB-1) was uniaxially stretched by an autograph (manufactured by Shimadzu Corporation) at a stretching temperature of 135 ° C. so that the stretching ratio was 2.0 times, and a stretched film (XB) having a thickness of 100 μm was used. -1) was obtained. In-plane retardation Re and thickness direction retardation Rth of the obtained stretched film (XB-1) were evaluated using a fully automatic birefringence meter (manufactured by Oji Scientific Instruments, KOBRA-WR). The evaluation results of wavelength dispersion are shown in Table 1 below. The retardation shown in the table is a value converted per film thickness of 100 μm. In addition, the photoelastic coefficient of the obtained film (FB-1) was −7 × 10 ⁻¹² / Pa. The Nz coefficient of the obtained stretched film (XB-1) was 1.07. In Table 1, the phase difference when the measurement wavelength is 589 nm is used as a reference (R0), and the ratio (R / R0) between the phase differences R and R0 at other wavelengths is also shown. Moreover, although the obtained film (XB-1) was folded at 90 ° so that the stretching direction was a crease, no cracking or the like of the film was confirmed.

(Comparative Example 1)
A film made of a cellulose resin (FB-2) in the same manner as in Example 1 except that only a commercially available cellulose resin (manufactured by Acros Organics, cellulose acetate propionate, number average molecular weight 75,000) was used. And the stretched film (XB-2) was obtained. In-plane retardation Re and thickness direction retardation Rth in the obtained stretched film (XB-2) were evaluated using a fully automatic birefringence meter (manufactured by Oji Scientific Instruments, KOBRA-WR). The evaluation results are shown in Table 2. The retardation shown in the table is a value converted per film thickness of 100 μm. In addition, the photoelastic coefficient of the obtained film (FB-2) was −15 × 10 ⁻¹² / Pa. The stretched film (XB-2) obtained had an Nz coefficient of 1.21. In Table 2, the phase difference when the measurement wavelength is 589 nm is used as a reference (R0), and the ratio (R / R0) between the phase differences R and R0 at other wavelengths is also shown. Moreover, although the obtained film (XB-2) was folded at 90 ° so that the stretching direction was a crease, no cracking or the like of the film was confirmed.

(Comparative Example 2)
A film (FB-3) made of an acrylic resin having a lactone ring structure in the main chain and a stretched film in the same manner as in Example 1 except that only the resin (A-1) produced in Production Example 1 was used. (XB-3) was obtained. In-plane retardation Re and thickness direction retardation Rth of the obtained stretched film (XB-3) were evaluated using a fully automatic birefringence meter (manufactured by Oji Scientific Instruments, KOBRA-WR). The evaluation results are shown in Table 3. The retardation shown in the table is a value converted per film thickness of 100 μm. In addition, the photoelastic coefficient of the obtained film (FB-3) was −2 × 10 ⁻¹² / Pa. The Nz coefficient of the obtained stretched film (XB-3) was 1.00. In Table 3, the phase difference when the measurement wavelength is 589 nm is used as a reference (R0), and the ratio (R / R0) between the phase differences R and R0 at other wavelengths is also shown. Moreover, when the obtained film (XB-3) was folded at 90 ° so that the stretching direction was a crease, the film was confirmed to be cracked.

The retardation film of the present invention can be widely used in image display devices including liquid crystal display devices (LCD). By using this retardation film, optical compensation in a wide range of wavelengths is possible, and the display characteristics in the image display device can be improved.

It is an example of schematic sectional drawing of the image display surface of a liquid crystal display device.

Liquid crystal cell 4 (including liquid crystal layer, glass substrate, transparent electrode, alignment film, etc.)
Polarizing plates 9 and 10 arranged with the liquid crystal cell 4 interposed therebetween.
Backlight unit 8 (including light source, reflection sheet, light guide plate, diffusion plate, diffusion sheet, prism sheet, brightness enhancement film, etc.)
Polarizers 2 and 6
Polarizer protective films 1, 3, 5, 7 arranged with a polarizer in between

Claims (7)

Cellulosic resin (A) and (I) glass transition temperature of 110 ° C. or higher, (II) negative intrinsic birefringence, and (III) the following formulas (1), (2) or (3 ), A thermoplastic resin composition (C) containing an acrylic resin (B) having an α, β-unsaturated monomer unit having a molecular structure or a heteroaromatic group shown in FIG. A retardation film exhibiting wavelength dispersion that reduces the internal retardation Re.

(In the formula (1), n is a natural number in the range of 1 to 4, and R ¹ and R ² are each independently a hydrogen atom or a methyl group.)   The position according to claim 1, wherein the α, β-unsaturated monomer unit having a heteroaromatic group is at least one selected from a vinylcarbazole unit, a vinylpyridine unit, a vinylimidazole unit, and a vinylthiophene unit. Phase difference film. The retardation film according to claim 1, wherein the acrylic resin is an acrylic resin having a ring structure in the main chain.   The retardation film according to claim 3, wherein the ring structure is at least one selected from a lactone ring structure, a cyclic imide structure, and a cyclic acid anhydride structure.   The retardation film according to claim 4, wherein the cellulose resin is cellulose acetate. The retardation film according to claim 1, wherein the photoelastic coefficient is less than 10 × 10 ⁻¹² / Pa. A liquid crystal display provided with the phase difference film according to any one of claims 1 to 6.

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