JP2009230115A - Manufacturing method of optical film, optical film, polarizing plate, liquid crystal panel, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an optical film using an inexpensive material having excellent working properties and having high retardation exhibiting properties, to provide the optical film, to provide a polarizing plate using the same, to provide a liquid crystal panel and to provide a liquid crystal display device. <P>SOLUTION: The manufacturing method of the optical film including a transparent film base material and an optical compensation layer and having an Nz coefficient defined by formula:(Nz coefficient)=(nx-nz)/(nx-ny) in the range of 0.9 to 2.0 includes a step of forming a coating film including a polyvinyl alcohol based resin containing a polyethylene part on the transparent film base material and a step of drawing the coating film and the transparent film base material. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical film manufacturing method, an optical film, a polarizing plate, a liquid crystal panel, and a liquid crystal display device.

  Conventionally, in various liquid crystal display devices, a retardation plate is used for the purpose of optical compensation. Examples of such a retardation plate include various polymer film stretching methods such as an inter-roll tensile stretching method, an inter-roll compression stretching method, and a tenter transverse uniaxial stretching method (for example, see Patent Document 1), and biaxial stretching. An optical biaxial retardation plate produced by a method of imparting anisotropy by the method (for example, see Patent Document 2). In addition to this, a retardation plate using both a uniaxially stretched polymer film having positive optical anisotropy and a biaxially stretched polymer film having negative optical anisotropy having a small in-plane retardation value, (For example, refer to Patent Document 3.) Instead of the stretching method as described above, for example, a retardation plate in which a soluble polyimide film is formed on a substrate due to the properties of polyimide (for example, refer to Patent Document 4). .

  A non-liquid crystal polymer such as polyimide exhibits optical characteristics of nx = ny> nz regardless of the orientation of the substrate. Further, by stretching the laminate of the substrate and the film together in one direction in the plane, the film exhibits a refractive difference in the plane and exhibits optical characteristics having a refractive index distribution of nx> ny> nz. Here, nx, ny, and nz respectively indicate the refractive indexes of the X-axis, Y-axis, and Z-axis in the film, and the X-axis is an axial direction that indicates the maximum refractive index in the film plane. , Y axis is an axial direction perpendicular to the X axis in the plane, and Z axis indicates a thickness direction perpendicular to the X axis and the Y axis. If the birefringent film having such optical characteristics is disposed between, for example, a liquid crystal cell of a liquid crystal display device and a polarizer, the display characteristics of the liquid crystal display device can be widened. It is useful as a viewing angle compensation film.

  However, even with a film having such optical characteristics, a retardation film obtained by stretching a polymer film has a thickness of several tens to several hundreds of μm, which leaves a major problem in terms of thinning a liquid crystal display device. . In order to reduce the thickness of the retardation film, a means for forming a soluble polyimide film on the substrate is useful, but since polyimide is very expensive, it has been a serious problem in terms of production cost. Furthermore, a film formed of polyimide has a high glass transition temperature (Tg), and molecules can be stacked, so that the film can be stretched only at a high temperature and cannot be stretched at a high magnification. Thus, since the processability of polyimide is not good, the design range of the optical characteristics of the retardation plate is very limited, and in particular, it is difficult to realize optical characteristics having a refractive index distribution of nx> ny≈nz. It was.

JP-A-3-33719 Japanese Patent Laid-Open No. 3-24502 JP-A-4-194820 Japanese National Patent Publication No. 8-511812

  Accordingly, the present invention provides a method for producing an optical film having a high retardation effect using a material that is less expensive than polyimide and has excellent processability, an optical film, a polarizing plate, a liquid crystal panel, and a liquid crystal display using the same An object is to provide an apparatus.

In order to achieve the above object, the method for producing an optical film of the present invention comprises:
A method for producing an optical film, comprising a transparent film substrate and an optical compensation layer, wherein the Nz coefficient defined by the following formula is in the range of 0.9 to 2.0, wherein polyethylene is formed on the transparent film substrate: It includes a step of forming a coating film containing a polyvinyl alcohol-based resin containing a part, and a step of stretching the coating film and the transparent film substrate.
Nz coefficient = (nx−nz) / (nx−ny)

The optical film of the present invention is an optical film including a transparent film substrate and an optical compensation layer, wherein the optical compensation layer includes a polyvinyl alcohol-based resin containing a polyethylene moiety, and is defined by the following formula of the optical film: The Nz coefficient is in the range of 0.9 to 2.0.
Nz coefficient = (nx−nz) / (nx−ny)

  The polarizing plate of the present invention is a polarizing plate including an optical film and a polarizer, and the optical film is the optical film of the present invention.

  The first liquid crystal panel of the present invention is a liquid crystal panel including a liquid crystal cell and an optical member, wherein the optical member is the optical film of the present invention or the polarizing plate of the present invention, and the optical member is It is arranged on at least one side of the liquid crystal cell.

The second liquid crystal panel of the present invention has a first polarizing plate, a second polarizing plate, and a liquid crystal cell, the first polarizing plate is disposed on the viewing side of the liquid crystal cell, and the second liquid crystal panel A polarizing plate is a liquid crystal panel disposed on the backlight side of the liquid crystal cell,
The first polarizing plate includes a first polarizer and a first optical compensation layer,
The first optical compensation layer is disposed between the first polarizer and the liquid crystal cell,
The refractive index of the first optical compensation layer has a relationship of nx> ny ≧ nz,
The second polarizing plate includes a second polarizer and a second optical compensation layer,
The second optical compensation layer is disposed between the second polarizer and the liquid crystal cell,
In the liquid crystal panel in which the refractive index of the second optical compensation layer shows a relationship of nx = ny> nz,
The first polarizing plate is the polarizing plate of the present invention, and the optical film contained in the polarizing plate of the present invention is the first optical compensation layer.

  The liquid crystal display device of the present invention is a liquid crystal display device including an optical member or a liquid crystal panel, wherein the optical member is the optical film of the present invention or the polarizing plate of the present invention, and the liquid crystal panel is the book of the present invention. It is the liquid crystal panel of the invention.

  According to the method for producing an optical film of the present invention, a polyvinyl alcohol resin having extremely excellent processability is used, and the resin is coated on a transparent film substrate and stretched. It was possible to manufacture an optical film satisfying nx> ny≈nz and having high retardation development at low cost.

FIG. 1 is a schematic cross-sectional view showing an example of the configuration of the polarizing plate of the present invention. FIG. 2 is a schematic cross-sectional view showing an example of the configuration of the first liquid crystal panel of the present invention. FIG. 3 is a schematic cross-sectional view showing an example of the configuration of the second liquid crystal panel of the present invention. FIG. 4 is a schematic cross-sectional view showing an example of the configuration of the liquid crystal cell provided in the liquid crystal panel of the present invention. FIG. 5 is a schematic cross-sectional view showing an example of the configuration of the liquid crystal display device of the present invention.

  In the method for producing an optical film of the present invention, it is preferable that the transparent film substrate and the coating film are both stretched in the stretching step.

  In the stretching step, the stretching direction is preferably the width direction of the transparent film substrate, and the stretching ratio in the stretching in the width direction is preferably in the range of 1.3 to 6.0 times.

  In the method for producing an optical film of the present invention, in the stretching step, the transparent film substrate and the coating film shrink in a range of 0.5 to 1.0 times in the longitudinal direction along with stretching in the width direction. It is preferred that

  In the method for producing an optical film of the present invention, an acrylic resin is preferably used as the material for the transparent film substrate.

  Examples of the acrylic resin include polyacrylic acid ester, polymethacrylic acid ester, methyl methacrylate-acrylic acid copolymer, methyl methacrylate-methacrylic acid copolymer, methyl methacrylate-acrylic acid ester copolymer, methyl methacrylate. -Methacrylic acid ester copolymer, Methyl methacrylate-Acrylic acid ester-Acrylic acid copolymer, Methyl methacrylate-Acrylic acid ester-Methacrylic acid copolymer, Methyl acrylate-Styrene copolymer, Methyl methacrylate-Styrene It is preferable to use at least one selected from the group consisting of a copolymer and a polymer having an alicyclic hydrocarbon group.

In the method for producing an optical film of the present invention, it is preferable to use a polymer containing a polymer containing repeating units represented by the following structural formulas (I) and (II) as the polyvinyl alcohol-based resin containing a polyethylene moiety. More preferably, the polymer has a molar ratio of (I) to (II) that satisfies the range of 50:50 to 99: 1.

  In the manufacturing method of the optical film of this invention, it is preferable to have a bridge | crosslinking process process after the said extending process.

  In the method for producing an optical film of the present invention, it is preferable to use a coating liquid to which no solvent is added in the step of forming the coating film.

  In the optical film of the present invention, the transparent film substrate is preferably an acrylic resin.

  The optical film of the present invention is preferably produced by the method for producing an optical film of the present invention.

  Next, the present invention will be described in detail. However, the present invention is not limited by the following description.

  In the method for producing an optical film of the present invention, a coating film is formed on a transparent film substrate by coating a polyvinyl alcohol resin containing a polyethylene moiety, which is a material for forming the optical compensation layer. By stretching the film and the transparent film substrate, an optical film having an Nz coefficient of 0.9 to 2.0 is produced. Here, the Nz coefficient is a value defined by the formula: Nz = (nx−nz) / (nx−ny).

  In the present invention, the refractive index “nx” is a refractive index in a direction (slow axis direction) in which the in-plane refractive index of the layer (birefringent layer, film, liquid crystal cell, etc. is the same) is maximum. The refractive index “ny” is a refractive index in a direction (fast axis direction) orthogonal to the nx direction in the plane of the layer. The refractive index “nz” is the refractive index in the thickness direction of the layer orthogonal to the nx and ny directions.

  In the present invention, the in-plane retardation value (Re [λ]) is, for example, an in-plane retardation value at a wavelength λ (nm) at 23 ° C. Re [λ] is calculated by the formula: Re [λ] = (nx−ny) × d, where d (nm) is the thickness of the layer. Re [λ] can be measured, for example, by the method described in Examples described later.

  In the present invention, the retardation value in the thickness direction of the layer (Rth [λ]) is, for example, a retardation value in the thickness direction of the layer at a wavelength λ (nm) at 23 ° C. Rth [λ] is calculated by the formula: Rth [λ] = (nx−nz) × d, where d (nm) is the thickness of the layer. Rth [λ] can be measured, for example, by the method described in Examples described later.

  In the present invention, the Nz coefficient is a value calculated also by the formula: Nz coefficient = Rth [λ] / Re [λ]. The λ can be set to 590 nm, for example.

  In the present invention, “nx = ny” or “ny = nz” includes not only the case where they completely match, but also the case where they are substantially the same. Therefore, for example, the description of nx = ny includes the case where Re [590] is less than 10 nm.

  In the present invention, the term “orthogonal” includes the case of being substantially orthogonal, and the case of being substantially orthogonal is, for example, a range of 90 ° ± 2 °, and preferably 90 °. The range is ± 1 °. Further, in the present invention, the term “parallel” includes a case of being substantially parallel, and the case of being substantially parallel is, for example, a range of 0 ° ± 2 °, and preferably 0 ° ± 1. It is in the range of °.

[Transparent film substrate]
As the transparent film substrate in the present invention, acrylic, acrylonitrile styrene (AS), acrylonitrile acrylic rubber styrene (AAS), acrylonitrile-butadiene-styrene (ABS), cyclic olefin copolymer (COC), cyclic olefin polymer (COP), Ethylene-vinyl alcohol (EVOH), ethylene-vinyl acetate (EVA), epoxy (EP), methacryl-styrene (MS), polyarylate (PAR), polyethylene terephthalate (PET), polyethersulfone (PES), polypropylene (PP ), Polystyrene (PS), polycarbonate (PC), polymethyl methacrylate (PMMA), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), hydrogenated styrene Butadiene styrene (SBS), polyamide (PA), polyethylene (PE), polymethylpentene (PMP), polysulfone (PSU), low density polyethylene (LDPE), triacetyl cellulose (TAC), and the like can be used.

  As the transparent film substrate, an acrylic resin is preferably used. The acrylic resin preferably has a glass transition temperature (Tg) of 115 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 125 ° C. or higher, and particularly preferably 130 ° C. or higher. When Tg is 115 ° C. or higher, the durability is excellent. Although the upper limit of Tg of the acrylic resin is not particularly limited, it is preferably 170 ° C. or less from the viewpoint of moldability and the like. The glass transition temperature (Tg) can be obtained by a DSC method according to JIS K7121.

  Any appropriate acrylic resin can be adopted as the acrylic resin within a range not impairing the effects of the present invention. Preferably, the acrylic resin includes polyacrylic acid ester, polymethacrylic acid ester ( For example, polymethyl methacrylate), methyl methacrylate-acrylic acid copolymer, methyl methacrylate-methacrylic acid copolymer, methyl methacrylate-acrylic acid ester copolymer, methyl methacrylate-methacrylic acid ester copolymer , Methyl methacrylate-acrylic acid ester-acrylic acid copolymer, methyl methacrylate-acrylic acid ester-methacrylic acid copolymer, methyl acrylate-styrene copolymer, methyl methacrylate-styrene copolymer and alicyclic Polymers having hydrocarbon groups (for example, methacrylic acid methyl ester) - cyclohexyl methacrylate copolymer, a methyl methacrylate - acrylic acid norbornyl copolymer, methyl methacrylate - methacrylate norbornyl copolymer) and the like. More preferred are polyalkyl acrylates and polyalkyl methacrylates such as polymethyl acrylate and polymethyl methacrylate. Here, the alkyl group preferably has 1 to 6 carbon atoms. More preferably, a methyl methacrylate resin containing methyl methacrylate as a main component (in the range of 50 to 100% by weight, preferably in the range of 70 to 100% by weight) can be used.

  Specific examples of the acrylic resin include, for example, Acrypet VH and Acrypet VRL20A manufactured by Mitsubishi Rayon Co., Ltd., an acrylic resin having a ring structure in the molecule described in JP-A-2004-70296, Examples thereof include a high Tg acrylic resin obtained by crosslinking or intramolecular cyclization reaction. As the acrylic resin, it is also preferable to use an acrylic resin having a lactone ring structure, an acrylic resin having a glutaric anhydride structure, or an acrylic resin having a glutarimide structure. This is because these acrylic resins have high heat resistance, high transparency, and high mechanical strength.

一般式（１）中、Ｒ^１、Ｒ^２およびＲ^３は、それぞれ独立に、水素原子または炭素数１〜２０の有機残基を表す。なお、有機残基は酸素原子を含んでいてもよい。 (Acrylic resin with lactone ring structure)
Examples of the acrylic resin having a lactone ring structure include JP 2000-230016, JP 2001-151814, JP 2002-120326, JP 2002-254544, and JP 2005-146084. Examples thereof include acrylic resins having a lactone ring structure, which are described in publications and the like. The acrylic resin having a lactone ring structure preferably has a lactone ring structure represented by the following general formula (1).

In General Formula (1), R ¹ , R ² and R ³ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom.

  The content of the lactone ring structural unit represented by the general formula (1) in the acrylic resin having the lactone ring structure is preferably 5 to 100% by weight in the acrylic resin having the lactone ring structure. The range is 90% by weight, more preferably 10 to 70% by weight, still more preferably 10 to 60% by weight, and particularly preferably 10 to 50% by weight. If the content is less than 5% by weight, heat resistance, solvent resistance and surface hardness may be insufficient, and if it is more than 90% by weight, molding processability may be poor. The content ratio can be calculated by the method described in JP-A-2002-254544.

  The acrylic resin having a lactone ring structure preferably has a weight average molecular weight in the range of 1,000 to 2,000,000, more preferably in the range of 5,000 to 1,000,000, and still more preferably 10, It is in the range of 000 to 500,000, particularly preferably in the range of 50,000 to 500,000. If the weight average molecular weight is out of the above range, the effects of the present invention may not be sufficiently exhibited.

  The acrylic resin having a lactone ring structure has a Tg of preferably 115 ° C. or higher, more preferably 125 ° C. or higher, still more preferably 130 ° C. or higher, particularly preferably 135 ° C. or higher, and most preferably 140 ° C. or higher. When Tg is 115 ° C. or higher, for example, when incorporated in a polarizing plate as a polarizer protective film, it can be excellent in durability. The upper limit of Tg of the acrylic resin having a lactone ring structure is not particularly limited, but is preferably 170 ° C. or less from the viewpoint of moldability and the like.

  The acrylic resin having the lactone ring structure is preferably as the total light transmittance of a molded product obtained by injection molding measured by a method according to ASTM-D-1003 is higher, preferably 85% or more. More preferably, it is 88% or more, and still more preferably 90% or more. The total light transmittance is a measure of transparency. If the total light transmittance is less than 85%, the transparency may be lowered.

一般式（２）中、Ｒ^１、Ｒ^２は、同一または相異なる水素原子または炭素数１〜５のアルキル基を表す。 (Acrylic resin with glutaric anhydride structure)
Examples of the acrylic resin having the glutaric anhydride structure include glutaric acid described in JP-A-2006-283013, JP-A-2006-335902, JP-A-2006-274118, International Publication WO2007 / 026659, and the like. An acrylic resin having an anhydride structure may be mentioned. The acrylic resin having a glutaric anhydride structure preferably contains a glutaric anhydride structure represented by the following general formula (2).

In the general formula ^{(2), R 1, R} 2 represents a same or different hydrogen atom or an alkyl group having 1 to 5 carbon atoms.

  More preferably, the acrylic resin having a glutaric anhydride structure includes (i) a glutaric anhydride structural unit represented by the general formula (2), and (ii) an unsaturated carboxylic acid alkyl ester unit. The copolymer which has is preferable.

  The content ratio of the glutaric anhydride structural unit represented by the general formula (2) in the acrylic resin having the glutaric anhydride structure is 100% by weight of the acrylic resin having the glutaric anhydride structure. Preferably, it is in the range of 25 to 50% by weight, more preferably in the range of 30 to 45% by weight. When the said content rate is less than 25 weight%, not only the heat resistance improvement effect will become small, but there exists a possibility that birefringence characteristics (optical isotropy) and solvent resistance may fall.

  The content of the unsaturated carboxylic acid alkyl ester unit in the acrylic resin having the glutaric anhydride structure is preferably 50 to 75% by weight in 100% by weight of the acrylic resin having the glutaric anhydride structure. More preferably, it is the range of 55 to 70% by weight.

  In addition to (i) the glutaric anhydride structure represented by the general formula (2) and (ii) the unsaturated carboxylic acid alkyl ester unit, the acrylic resin having the glutaric anhydride structure, It can contain (iii) unsaturated carboxylic acid units and / or (iv) other vinyl monomer units. Here, (iv) the other vinyl monomer unit is a copolymerizable vinyl monomer unit that does not belong to any of the above (i) to (iii).

  The content of the unsaturated carboxylic acid unit in the acrylic resin having the glutaric anhydride structure is preferably in the range of 0 to 10% by weight in 100% by weight of the acrylic resin having the glutaric anhydride structure. More preferably, it is in the range of 0 to 5% by weight, and most preferably in the range of 0 to 1% by weight. When the content ratio of the unsaturated carboxylic acid unit exceeds 10% by weight, colorless transparency and residence stability may be deteriorated.

  The content ratio of the other vinyl monomer units in the acrylic resin having the glutaric anhydride structure is preferably 0 to 10% in 100% by weight of the acrylic resin having the glutaric anhydride structure. % Range. As said other vinyl monomer unit, the vinyl monomer unit which does not contain an aromatic ring is preferable. When an aromatic vinyl monomer unit such as styrene is included, if the content ratio in the acrylic resin having the glutaric anhydride structure is high, colorless transparency, optical isotropy, and solvent resistance may be reduced. Therefore, the content is preferably in the range of 0 to 5% by weight, more preferably in the range of 0 to 3% by weight.

  The content ratio of each component unit in the acrylic resin having the glutaric anhydride structure can be calculated by the method described in JP-A-2006-274118.

一般式（３）中、Ｒ^３は水素または炭素数１〜５のアルキル基を表す。 As said unsaturated carboxylic acid unit, what has a structure represented by following General formula (3) is preferable.

In general formula (3), R ³ represents hydrogen or an alkyl group having 1 to 5 carbon atoms.

一般式（４）中、Ｒ^４は水素または炭素数１〜５のアルキル基を表し、Ｒ^５は炭素数１〜６の脂肪族もしくは脂環式炭化水素基、または１個以上炭素数以下の数の水酸基もしくはハロゲンで置換された炭素数１〜６の脂肪族もしくは脂環式炭化水素基を示す。 As the unsaturated carboxylic acid alkyl ester unit, those having a structure represented by the following general formula (4) are preferable.

In General Formula (4), R ⁴ represents hydrogen or an alkyl group having 1 to ⁵ carbon atoms, R ⁵ represents an aliphatic or alicyclic hydrocarbon group having 1 to 6 carbon atoms, or one or more carbon atoms. A C1-C6 aliphatic or alicyclic hydrocarbon group substituted with several hydroxyl groups or halogen.

  The acrylic resin having the glutaric anhydride structure preferably has a weight average molecular weight in the range of 30,000 to 150,000, more preferably in the range of 50,000 to 130,000, still more preferably 70,000 to The range is 110,000. When the weight average molecular weight is within this range, coloring during heat deaeration in the subsequent step can be reduced, a polymer having a small yellowness can be obtained, and the mechanical strength of the molded product can also be increased. .

  The acrylic resin having the glutaric anhydride structure has a Tg of preferably 130 ° C. or higher, more preferably 140 ° C. or higher, and further preferably 150 ° C. or higher. When Tg is 130 ° C. or higher, for example, when the optical film of the present invention is incorporated in a polarizing plate, it can be excellent in durability. The upper limit of Tg of the acrylic resin having the glutaric anhydride structure is preferably 170 ° C. or less from the viewpoint of moldability and the like.

一般式（５）中、Ｒ^１及びＲ^２は、それぞれ独立に、水素又は炭素数１〜８のアルキル基を示し、Ｒ^３は、炭素数１〜１８のアルキル基、炭素数３〜１２のシクロアルキル基、又は炭素数５〜１５の芳香環を含む置換基を示す。 (Acrylic resin with glutarimide structure)
Examples of the acrylic resin having a glutarimide structure include JP-A-2006-309033, JP-A-2006-317560, JP-A-2006-328329, JP-A-2006-328334, and JP-A-2006-337491. Examples thereof include acrylic resins having a glutarimide structure described in JP-A-2006-337492, JP-A-2006-337493, JP-A-2006-337569, JP-A-2007-009182, and the like. The acrylic resin having the glutarimide structure preferably contains a glutarimide structure represented by the following general formula (5).

In General Formula (5), R ¹ and R ² each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms, and R ³ represents an alkyl group having 1 to 18 carbon atoms or 3 to 12 carbon atoms. A cycloalkyl group or a substituent containing an aromatic ring having 5 to 15 carbon atoms is shown.

As the glutarimide structure, R ¹ and R ² are preferably hydrogen or a methyl group, and R ³ is hydrogen, a methyl group, a butyl group, or a cyclohexyl group. More preferably, R ¹ is a methyl group, R ² is hydrogen, and R ³ is a methyl group. The glutarimide structure may be a single type or may include a plurality of types in which R ¹ , R ² , and R ³ are different.

一般式（６）中、Ｒ^４及びＲ^５は、それぞれ独立に、水素又は炭素数１〜８のアルキル基を示し、Ｒ^６は、炭素数１〜１８のアルキル基、炭素数３〜１２のシクロアルキル基、又は炭素数５〜１５の芳香環を含む置換基を示す。 The glutarimide structure can be formed by imidizing an acrylic ester unit or a methacrylic ester unit described below. In addition, acid anhydrides such as maleic anhydride or half esters of these and linear or branched alcohols having 1 to 20 carbon atoms; acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, Α, β-ethylenically unsaturated carboxylic acids such as crotonic acid, fumaric acid, citraconic acid, and the like can also be imidized and can be used to form the glutarimide structure.
The acrylic resin having the glutarimide structure preferably contains an acrylic ester unit or a methacrylic ester unit represented by the following general formula (6).

In General Formula (6), R ⁴ and R ⁵ each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms, and R ⁶ represents an alkyl group having 1 to 18 carbon atoms or 3 to 12 carbon atoms. A cycloalkyl group or a substituent containing an aromatic ring having 5 to 15 carbon atoms is shown.

  When producing the acrylic resin having the glutarimide structure, first, an acrylate-aromatic vinyl copolymer, a methacrylic ester-aromatic vinyl copolymer, an acrylate polymer, or a methacrylic ester polymer In the case of forming a polymer by polymerizing and post-imidizing it, there are no particular restrictions on the raw material that gives the acrylic ester unit or methacrylic ester unit as a residue, but examples include methyl acrylate and ethyl acrylate. Butyl acrylate, isobutyl acrylate, t-butyl acrylate, benzyl acrylate, cyclohexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, benzyl methacrylate Acrylate and cyclohexyl methacrylate. Of these, methyl methacrylate is particularly preferred.

The acrylic ester unit or the methacrylic ester unit may be of a single type, or may include a plurality of types in which R ⁴ , R ⁵ , and R ⁶ are different. Similarly, a raw material that gives an acrylic ester unit or a methacrylic ester unit as a residue may be used in combination of a plurality of types.

一般式（７）中、Ｒ^７は、水素又は炭素数１〜８のアルキル基を示し、Ｒ^８は、炭素数６〜１０のアリール基を示す。 The acrylic resin having the glutarimide structure preferably contains an aromatic vinyl unit represented by the following general formula (7).

In General Formula (7), R ⁷ represents hydrogen or an alkyl group having 1 to 8 carbon atoms, and R ⁸ represents an aryl group having 6 to 10 carbon atoms.

Examples of the aromatic vinyl unit include styrene and α-methylstyrene. Styrene is particularly preferred. The aromatic vinyl unit may be of a single type, or may include a plurality of types in which R ⁷ and R ⁸ are different.

The content ratio of the glutarimide structural unit represented by the general formula (5) in the acrylic resin having the glutarimide structure may depend on the structure of R ³ , but the acrylic resin having the glutarimide structure is also included. In 100% by weight of the resin, it is preferably 20% by weight or more, more preferably in the range of 20 to 95% by weight, still more preferably in the range of 40 to 90% by weight, and particularly preferably in the range of 50 to 80% by weight. When the content rate of the said glutarimide structural unit is smaller than 20 weight%, there exists a possibility that the heat resistance of the acrylic resin which has a glutarimide structure obtained may be insufficient, or transparency may be impaired. In addition, if the content ratio of the glutarimide structural unit exceeds 95% by weight, the heat resistance and melt viscosity are unnecessarily increased, and the moldability may be deteriorated, and the mechanical strength of the obtained film is extremely high. There is a risk of becoming fragile and transparency may be impaired.

  The content of the aromatic vinyl unit represented by the general formula (7) in the acrylic resin having a glutarimide structure is preferably 10% by weight in 100% by weight of the acrylic resin having a glutarimide structure. More preferably, it is in the range of 10 to 40% by weight, more preferably in the range of 15 to 30% by weight, and particularly preferably in the range of 15 to 25% by weight. When the content ratio of the aromatic vinyl unit is larger than 40% by weight, the resulting acrylic resin having a glutarimide structure may be insufficient in heat resistance. If the content of the aromatic vinyl unit is less than 10% by weight, the mechanical strength of the resulting film may be lowered.

  The acrylic resin having the glutarimide structure is adjusted to various required physical properties by adjusting the structure and the content ratio of the units represented by the general formulas (5), (6), and (7). It is possible. For example, an acrylic resin having a glutarimide structure is polymerized with an acrylic ester-aromatic vinyl copolymer or a methacrylic ester-aromatic vinyl copolymer such as methyl methacrylate-styrene copolymer and then post-imidized. When forming, the content ratio of the aromatic vinyl unit represented by the general formula (7) is determined by adjusting the polymerization ratio of the acrylic ester or methacrylic ester and the aromatic vinyl (the general formula (7) In addition, the content ratio of the aromatic vinyl unit represented by general formula (5) may be set to 0), and further, the glutarimide structure represented by the general formula (5) or , Represented by the general formula (6), or the content ratio of the acrylate unit or methacrylate unit can be adjusted.

  The acrylic resin having the glutarimide structure may further be copolymerized with other structural units as necessary. Examples of other structural units include nitrile monomers such as acrylonitrile and methacrylonitrile; maleimide monomers such as maleimide, N-methylmaleimide, N-phenylmaleimide, and N-cyclohexylmaleimide; These may be directly copolymerized or graft copolymerized.

  In producing the acrylic resin having the glutarimide structure, first, a methacrylic acid ester-aromatic vinyl copolymer or an acrylic acid ester-aromatic vinyl copolymer such as methyl methacrylate-styrene copolymer, or When polymerizing a methacrylic acid ester polymer such as methyl methacrylate polymer or an acrylic acid ester polymer and converting it to an imide resin, a methacrylic acid ester-aromatic vinyl copolymer, acrylic acid ester-aromatic vinyl copolymer The polymer, methacrylic acid ester polymer and acrylic acid ester copolymer may be any of linear (linear) polymer, block polymer, core-shell polymer, branched polymer, ladder polymer, and cross-linked polymer as long as imidization reaction is possible. May be. The block polymer may be an AB type, an ABC type, an ABA type, or any other type of block polymer. The core-shell polymer may be composed of only one core and only one shell, or each may be a multilayer.

  The acrylic resin having the glutarimide structure preferably has a weight average molecular weight in the range of 10,000 to 500,000. When the weight average molecular weight is less than 10,000, the mechanical strength in the case of forming a film is insufficient, and when it exceeds 500,000, the viscosity at the time of melt extrusion is high, the molding processability is lowered, and molding is performed. Product productivity may be reduced.

[Optical compensation layer]
In the present invention, a polyvinyl alcohol resin having a polyethylene moiety is used as a material for forming the optical compensation layer. As the polyvinyl alcohol-based resin having a polyethylene moiety, any suitable polyvinyl alcohol-based resin having a polyethylene moiety can be used within a range not impairing the effects of the present invention. In particular, a polyvinyl alcohol-based resin containing a polyethylene moiety containing a repeating unit represented by the following structural formulas (I) and (II) has a hydroxyl group and thus has good adhesion to a transparent film, and further has a low Tg. Therefore, it is excellent in workability. Moreover, since the polyvinyl alcohol part is easy to line up with respect to the extending | stretching stress direction, it has the advantage that phase difference expression is good. In addition, the presence of the polyethylene moiety reduces the interaction of hydroxyl groups at the polyvinyl alcohol moiety and promotes orientation. Then, when the optical compensation layer is formed, optical characteristics of nx> ny≈nz can be imparted. Furthermore, the polyvinyl alcohol-based resin is very inexpensive as compared with a polyimide-based material, and has an advantage that it is excellent in terms of production cost.

  The polyvinyl alcohol-based resin having a polyethylene moiety preferably contains the repeating units represented by the structural formulas (I) and (II), but may contain components other than (I) and (II). Good. The molar ratio of (I) to (II) is preferably in the range of 50:50 to 99: 1. In the polymer containing each repeating unit, the arrangement order of the repeating units is not particularly limited, and may be any of alternating, random, or block.

  Although there is no limitation in particular about the molecular weight of the polyvinyl alcohol-type resin which has the said polyethylene part, As a weight average molecular weight (Mw), the range of 1,000-1,000,000 is preferable and the range of 2,000-500,000 is preferable. Further preferred.

  In order to form an optical compensation layer on the transparent film substrate, a coating film is formed on the transparent film substrate by coating a material for forming the optical compensation layer, and the coating film and the transparent film are formed. A method of stretching the substrate is used. The coating film formed on the transparent film substrate can be stretched together to form an optical compensation layer to obtain the optical film of the present invention.

  Examples of the method of applying the forming material of the optical compensation layer include a method of applying the melt by heating and melting the forming material, and a method of applying a solution in which the forming material is dissolved in a solvent. . In addition, a coating method such as a spin coating method, a roll coating method, a flow coating method, a printing method, a dip coating method, a casting film forming method, a bar coating method, or a gravure printing method can be appropriately selected.

  The solvent is not particularly limited as long as the forming material can be dissolved, and can be appropriately selected. For example, water, dimethyl sulfoxide (DMSO), isopropyl alcohol (IPA), or the like can be used as the solvent for the polyvinyl alcohol resin. These solvents can be used alone or in combination. From the viewpoint of viscosity, the solution is preferably used by mixing the forming material in a range of 5 to 50 parts by weight, preferably in a range of 10 to 40 parts by weight with respect to 100 parts by weight of the solvent.

  Moreover, it is also preferable to add the crosslinking agent which bridge | crosslinks the polyvinyl-alcohol-type resin which has the said polyethylene part to the said formation material, and has the crosslinking process process by heating, ultraviolet irradiation, electron beam irradiation, etc. after the said extending | stretching process.

  Any appropriate crosslinking agent can be adopted as the crosslinking agent. The crosslinking agent is preferably a compound having at least two functional groups having reactivity with the polyvinyl alcohol resin having the polyethylene moiety. Examples of the crosslinking agent include alkylenediamines having two alkylene groups and amino groups such as ethylenediamine, triethylenediamine, hexamethylenediamine, tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane tolylene diisocyanate adduct, Triphenylmethane triisocyanate, methylenebis (4-phenyl) methane triisocyanate, isophorone diisocyanate and isocyanates such as ketoxime block product or phenol block product, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether Glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, Epoxys such as methylolpropane triglycidyl ether, diglycidyl aniline, diglycidyl amine, monoaldehydes such as formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, glyoxal, malondialdehyde, succindialdehyde, glutardialdehyde, maleindialdehyde , Dialdehydes such as phthaldialdehyde, methylol urea, methylol melamine, alkylated methylol urea, alkylated methylolated melamine, acetoguanamine, amino-formaldehyde resins such as condensates of benzoguanamine and formaldehyde, sodium, potassium, magnesium, Examples include divalent or trivalent metal salts such as calcium, aluminum, iron, nickel, titanium, and oxides thereof. . Among these, amino-formaldehyde resins and dialdehydes are preferable. The amino-formaldehyde resin is preferably a compound having a methylol group. Glyoxal is preferred as the dialdehyde. Among them, a compound having a methylol group is preferable, and methylol melamine is particularly preferable. Examples of the aldehyde compound include a product name “Glyoxal” manufactured by Nippon Synthetic Chemical Co., Ltd., a product name “SECARETZ 755” manufactured by OMNOVA, and the like. Examples of the amine compound include trade name “metaxylenediamine” manufactured by Mitsubishi Gas Chemical Co., Ltd. Examples of the methylol compound include a trade name “Watersol” series manufactured by Dainippon Ink and Chemicals, Inc.

  The amount of the crosslinking agent is, for example, in the range of 1 to 60 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin having the polyethylene moiety. By setting the blending amount within the above range, an optical compensation layer excellent in transparency, adhesiveness, and water resistance can be formed.

  In addition, when using the polyvinyl alcohol-type resin which has the said polyethylene site | part of the polymerization degree of the polymer containing the repeating unit shown by said structural formula (I) and (II) in the range of 600-5,000, use a solvent. It can be applied without any problems. When such a resin is used, it is preferable to use a production method having the crosslinking treatment step.

  The stretching method of the laminate of the transparent film substrate and the coating film is not particularly limited. For example, a free end longitudinal stretching method in which the film is uniaxially stretched in the longitudinal direction, the width direction with the longitudinal direction of the film fixed. Examples thereof include a fixed end transverse stretching method in which uniaxial stretching is performed, a sequential or simultaneous biaxial stretching method in which stretching is performed in both the longitudinal direction and the width direction, and a method in which stretching is performed in the width direction and contracts in the longitudinal direction.

  And the stretching of the laminate was performed, for example, by coating the transparent film substrate with a polyvinyl alcohol resin containing the polyethylene moiety to form a coating film, and then drying the coating film Later, the dried coating film and the transparent film substrate may be stretched, or the transparent film substrate on which the coating film is formed is stretched before the coating film is dried. Also good. The stretching may be performed by pulling both the transparent film substrate and the coating film together. For example, for the following reason, the coating is performed by stretching only the transparent film substrate. It is also preferred to stretch the membrane indirectly. When only the transparent film substrate is stretched, the coating film on the transparent film substrate is indirectly stretched by the tension generated in the transparent film substrate by this stretching. And, since it is usually uniform stretching rather than stretching the laminate, if only the transparent film substrate is uniformly stretched as described above, the transparent This is because the coating film on the film substrate can also be stretched uniformly. By indirectly stretching the coating film by stretching only the transparent film substrate, the optical characteristics of the obtained optical film can be made more uniform, and in particular, variations in characteristics in the X-axis direction are effective. Therefore, the optical film obtained as described above can cope with a large screen of a liquid crystal display device.

  It does not specifically limit as extending | stretching conditions, Although it can determine suitably according to a transparent film base material, the kind of forming material, etc., it is preferable that an extending | stretching direction is the width direction of the said transparent film base material. By extending in the width direction of the transparent film substrate, when the optical film of the present invention is used for liquid crystal television applications, it is possible to cope with an increase in the size of the liquid crystal television screen. When using a polyvinyl alcohol-based material containing the structural formulas (I) and (II), the draw ratio in the width direction is preferably in the range of 1.3 to 6.0 times, more preferably 2.0 to 5 The range is .0 times. Further, the shrinkage factor in the longitudinal direction associated therewith is preferably in the range of 0.5 to 1.0 times, more preferably in the range of 0.7 to 1.0 times.

  According to the optical film of the present invention, it is possible to obtain optical characteristics satisfying not only the relationship of nx> ny> nz but also the relationship of nx> ny≈nz. That is, an optical film having a refractive index satisfying a relationship of nx> ny≈nz and having a desired Δn (difference between the in-plane maximum refractive index and the refractive index in the thickness direction: nx−nz) and an Nz coefficient is obtained. be able to. Here, ny≈nz includes not only the case where ny and nz are strictly equal, but also the case where ny and nz are substantially equal. In the present specification, for example, “ny and nz are substantially equal” is intended to include the case where ny and nz are different within a range that does not practically affect the overall optical characteristics of the optical film. Moreover, (DELTA) n in this invention is the range of 0.01-0.09, for example, Preferably it is the range of 0.015-0.06. More preferably, it is the range of 0.015-0.035. Moreover, the Nz coefficient in this invention is the range of 0.9-2.0, Preferably it is the range of 1.05-1.40.

[Polarizing plate of the present invention]
The polarizing plate of the present invention is a polarizing plate including an optical film and a polarizer, and the optical film is the optical film of the present invention. As a structure of the polarizing plate of this invention, a polarizer is laminated | stacked on the said transparent film base material side or the said optical compensation layer side which comprises the said optical film, and is comprised. In addition, the laminated body of the said optical compensation layer single layer which peeled the said optical compensation layer from the said transparent film base material, and a polarizer can also be used as a polarizing plate. A protective layer may be formed on the polarizer. An example of the configuration of the polarizing plate of the present invention is shown in the schematic cross-sectional view of FIG. In the figure, the size, ratio, and the like of each component are different from actual ones for easy understanding. As shown in the figure, the polarizing plate 10 is formed by laminating a protective layer 11, a polarizer 12, and the optical film 13 of the present invention in this order. The total thickness of the polarizing plate is, for example, in the range of 20 to 300 μm. By setting it as the thickness of the said range, the polarizing plate which was more excellent in mechanical strength can be obtained.

  Arbitrary adhesive layers and arbitrary optical members (preferably those exhibiting isotropic properties) may be disposed between the constituent members (optical members) of the polarizing plate. The “adhesive layer” refers to a layer that joins the surfaces of adjacent optical members and integrates them with practically sufficient adhesive force and adhesion time. Examples of the material for forming the adhesive layer include conventionally known adhesives, pressure-sensitive adhesives, anchor coating agents, and the like. The adhesive layer may have a multilayer structure in which an anchor coat layer is formed on the surface of an adhesive body and an adhesive layer is formed thereon. Further, it may be a thin layer (also referred to as a hairline) that cannot be visually recognized.

  The polarizer can be obtained, for example, by stretching a polymer film containing a polyvinyl alcohol resin containing iodine. The iodine content of the polarizer is, for example, in the range of 1.8 to 5.0% by weight, and preferably in the range of 2.0 to 4.0% by weight. The polarizer preferably further contains potassium. The potassium content is, for example, in the range of 0.2 to 1.0% by weight, preferably in the range of 0.3 to 0.9% by weight, and more preferably in the range of 0.4 to 0.00. It is in the range of 8% by weight. The polarizer preferably further contains boron. The boron content is, for example, in the range of 0.5 to 3.0% by weight, preferably in the range of 1.0 to 2.8% by weight, and more preferably in the range of 1.5 to 2.%. It is in the range of 6% by weight.

  The polyvinyl alcohol resin can be obtained, for example, by saponifying a vinyl ester polymer obtained by polymerizing a vinyl ester monomer. The degree of saponification of the polyvinyl alcohol resin is preferably in the range of 95.0 to 99.9 mol%. By using a polyvinyl alcohol-based resin having a saponification degree within the above range, a polarizer having more excellent durability can be obtained. The average degree of polymerization of the polyvinyl alcohol-based resin can be appropriately selected depending on the purpose. The average degree of polymerization is preferably in the range of 1200 to 3600. The average degree of polymerization can be determined according to, for example, JIS K 6726 (1994 edition).

  As a method for obtaining the polymer film containing the polyvinyl alcohol-based resin, any appropriate forming method can be adopted. Examples of the molding method include the method described in JP-A No. 2001-315144 [Example 1].

  The polymer film containing the polyvinyl alcohol resin preferably contains at least one of a plasticizer and a surfactant. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. Examples of the surfactant include nonionic surfactants. The content of the plasticizer and the surfactant is preferably in the range of 1 to 10 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin. For example, the plasticizer and the surfactant improve the dyeability and stretchability of the polarizer.

  As the polymer film containing the polyvinyl alcohol-based resin, for example, a commercially available film can be used as it is. Examples of the polymer film containing the commercially available polyvinyl alcohol resin include, for example, “Kuraray Vinylon Film” manufactured by Kuraray Co., Ltd., “Tose Cello Vinylon Film” manufactured by Tosero Co., Ltd., Nippon Synthetic Chemical Industry The product name "Nippon Vinylon Film" manufactured by Co., Ltd. and the like can be mentioned.

  The protective layer is used, for example, to prevent the polarizer from contracting or expanding, or to prevent deterioration due to ultraviolet rays. The thickness of the protective layer is preferably in the range of 20 to 100 μm. The transmittance (T [590]) at a wavelength of 590 nm of the protective layer is preferably 90% or more.

  Any appropriate material can be selected as the material for forming the protective layer. The protective layer is preferably a polymer film containing a cellulose resin, a norbornene resin, or an acrylic resin. The polymer film containing the cellulose resin can be obtained, for example, by the method described in Example 1 of JP-A-7-112446. The polymer film containing the norbornene resin can be obtained, for example, by the method described in JP-A-2001-350017. The polymer film containing the acrylic resin can be obtained, for example, by the method described in Example 1 of JP-A-2004-19892.

  The protective layer may have a surface treatment layer on the side opposite to the polarizer side. As the surface treatment, an appropriate treatment can be appropriately employed depending on the purpose. Examples of the surface treatment layer include treatment layers such as hard coat treatment, antistatic treatment, antireflection treatment (also referred to as antireflection treatment), and diffusion treatment (also referred to as antiglare treatment). These surface treatments are used for the purpose of preventing the screen from becoming dirty or damaged, or preventing the display screen from becoming difficult to see due to the reflection of indoor fluorescent light or sunlight on the screen. In general, the surface treatment layer is used in which a treatment agent for forming the treatment layer is fixed on the surface of a base film. The base film may also serve as the protective layer. Further, the surface treatment layer may have a multilayer structure in which a hard coat treatment layer is laminated on an antistatic treatment layer, for example.

  As the protective layer, for example, a commercially available polymer film subjected to surface treatment can be used as it is. Alternatively, the commercially available polymer film can be used after being subjected to any surface treatment. Examples of the commercially available film subjected to the diffusion treatment (anti-glare treatment) include trade names “AG150, AGS1, AGS2” manufactured by Nitto Denko Corporation. Examples of the commercially available film subjected to the antireflection treatment (antireflection treatment) include trade names “ARS, ARC” manufactured by Nitto Denko Corporation. Examples of the commercially available film subjected to the hard coat treatment and the antistatic treatment include trade name “KC8UX-HA” manufactured by Konica Minolta Opto Co., Ltd. Examples of the commercially available film subjected to the antireflection treatment include a product name “ReoLook” series manufactured by NOF Corporation.

[First LCD panel]
As described above, the first liquid crystal panel of the present invention is a liquid crystal panel including a liquid crystal cell and an optical member, and the optical member is the optical film of the present invention or the polarizing plate of the present invention, An optical member is disposed on at least one side of the liquid crystal cell. An example of the configuration of the first liquid crystal panel of the present invention is shown in the schematic cross-sectional view of FIG. In this figure, the same parts as those in FIG. As shown in the figure, in the first liquid crystal panel 30, the polarizing plate 10 of the present invention is in a state in which the optical film 13 is located on the liquid crystal cell 41 side (the upper side in the figure). ) And the backlight side (lower side in the figure). In the first liquid crystal panel of this example, the polarizing plate of the present invention is arranged on both the viewing side and the backlight side of the liquid crystal cell. However, the present invention is not limited to this. In the first liquid crystal panel of the present invention, the polarizing plate of the present invention may be disposed on at least one of the viewing side and the backlight side of the liquid crystal cell.

  Examples of the liquid crystal cell include an active matrix type using a thin film transistor. Examples of the liquid crystal cell include a simple matrix type as employed in a super twist nematic liquid crystal display device.

  The liquid crystal cell generally has a configuration in which a liquid crystal layer is sandwiched between a pair of substrates. FIG. 4 shows an example of the configuration of the liquid crystal cell. As illustrated, in the liquid crystal cell 41 of this example, a spacer 412 is disposed between a pair of substrates 411a and 411b, thereby forming a space, and a liquid crystal layer 413 is sandwiched in the space. Although not shown, one of the pair of substrates (active matrix substrate) has, for example, a switching element (for example, TFT) for controlling the electro-optical characteristics of the liquid crystal, and scanning that applies a gate signal to the active element. Lines and signal lines that carry source signals are provided. For example, a color filter is provided on the other of the pair of substrates.

  The color filter may be provided on the active matrix substrate. Or, for example, when an RGB three-color light source (which may further include a multicolor light source) is used as the illumination means of the liquid crystal display device as in the field sequential method, the color filter is omitted. Also good. The distance (cell gap) between the pair of substrates is controlled by a spacer, for example. The cell gap is, for example, in the range of 1.0 to 7.0 μm. For example, an alignment film made of polyimide is provided on the side of each substrate in contact with the liquid crystal layer. Alternatively, for example, when the initial alignment of liquid crystal molecules is controlled using a fringe electric field formed by a patterned transparent substrate, the alignment film may be omitted.

  The refractive index of the liquid crystal cell preferably shows a relationship of nz> nx = ny. As the liquid crystal cell having a refractive index of nz> nx = ny, according to the drive mode classification, for example, vertical alignment (VA) mode, twisted nematic (TN) mode, vertical alignment type electric field control Birefringence (ECB) mode, optical compensation birefringence (OCB) mode, etc. are mentioned. In the present invention, the driving mode of the liquid crystal cell is preferably the VA mode.

  Rth [590] of the liquid crystal cell in the absence of an electric field is preferably in the range of −500 to −200 nm, more preferably in the range of −400 to −200 nm. The Rth [590] is appropriately set by adjusting the birefringence of the liquid crystal molecules and the cell gap, for example.

  The VA mode liquid crystal cell uses a voltage-controlled birefringence effect to cause liquid crystal molecules aligned in a homeotropic alignment to respond to the substrate with an electric field in a normal direction in the absence of an electric field. Specifically, as described in, for example, Japanese Patent Application Laid-Open No. 62-210423 and Japanese Patent Application Laid-Open No. 4-153621, in the case of a normally black method, liquid crystal molecules are formed on a substrate in the absence of an electric field. Therefore, when the upper and lower polarizing plates are arranged orthogonally, black display can be obtained. On the other hand, in the presence of an electric field, the liquid crystal molecules operate so as to tilt in a 45 ° azimuth direction with respect to the absorption axis of the polarizing plate, whereby the transmittance increases and white display is obtained.

  The VA mode liquid crystal cell can be made multi-domain by using a substrate in which slits are formed on electrodes or a substrate on which protrusions are formed on the surface as described in JP-A-11-258605, for example. It may be what you did. Such a liquid crystal cell is, for example, a product name “ASV (Advanced Super View) mode” manufactured by Sharp Corporation, a product name “CPA (Continuous Pinwheel Alignment) mode” manufactured by the same company, and a product name manufactured by Fujitsu Limited. "MVA (Multi-domain Vertical Alignment) mode", product name "PVA (Patterned Vertical Alignment) mode" manufactured by Samsung Electronics Co., Ltd. "SURVIVE (Super Ranged Viewing Vertical Alignment) mode" and the like.

  In the present invention, it is also preferable that the driving mode of the liquid crystal panel is an in-plane switching (IPS) mode.

  The IPS mode liquid crystal cell uses a voltage controlled birefringence (ECB) effect and liquid crystal molecules that are homogeneously aligned in the absence of an electric field, for example, a counter electrode and a pixel electrode formed of metal. The substrate is caused to respond with an electric field (also referred to as a transverse electric field) parallel to the substrate. More specifically, for example, Techno Times Publishing “Monthly Display July” p. 83-p. 88 (1997 edition) and “Liquid Crystal vol.2 No. 4” published by the Japanese Liquid Crystal Society. 303-p. 316 (1998 edition), in the normally black method, the alignment direction of the liquid crystal cell when no electric field is applied is aligned with the absorption axis of the polarizer on one side so that the upper and lower polarizing plates are If they are arranged orthogonally, the display is completely black without an electric field. When an electric field is present, the transmittance according to the rotation angle can be obtained by rotating the liquid crystal molecules while keeping them parallel to the substrate. The IPS mode includes a super-in-plane switching (S-IPS) mode and an advanced super-in-plane switching (AS-IPS) mode employing a V-shaped electrode or a zigzag electrode.

The homogeneously aligned liquid crystal molecules are those in which the alignment vector of the liquid crystal molecules is aligned in parallel and uniformly with respect to the substrate plane as a result of the interaction between the aligned substrate and the liquid crystal molecules. In the present specification, the case where the alignment vector is slightly inclined with respect to the substrate plane, that is, the case where the liquid crystal molecules have a pretilt is also included in the homogeneous alignment. When the liquid crystal molecules have a pretilt, the pretilt angle is preferably 20 ° or less from the viewpoint of maintaining a high contrast ratio and obtaining good display characteristics.
As the nematic liquid crystal, any appropriate nematic liquid crystal can be adopted depending on the purpose. For example, the nematic liquid crystal may have a positive or negative dielectric anisotropy. A specific example of a nematic liquid crystal having a positive dielectric anisotropy is a product name “ZLI-4535” manufactured by Merck & Co., Inc. A specific example of a nematic liquid crystal having a negative dielectric anisotropy is a product name “ZLI-2806” manufactured by Merck & Co., Inc.

  As the liquid crystal cell, for example, a liquid crystal cell mounted on a commercially available liquid crystal display device may be used as it is. Examples of the commercially available liquid crystal display device including the VA mode liquid crystal cell include a product name “AQUAS” series of a liquid crystal television manufactured by Sharp Corporation, a product name “BRAVIA” series of a liquid crystal television manufactured by Sony, and a 32V product manufactured by Samsunung. The product name “LN32R51B” of the type wide liquid crystal television, the product name “FORIS SC26XD1” of the liquid crystal television manufactured by Nanao Co., Ltd., the product name “T460HW01” of the liquid crystal television manufactured by AU Optronics, and the like. As a commercially available liquid crystal display device including the IPS mode liquid crystal cell, for example, Hitachi, Ltd. 20V wide liquid crystal television product name “Wooo”, Eyama Co., Ltd. 19 type liquid crystal display product name “ProLite E481S- 1 ”, the trade name“ FlexScan L565 ”of 17 type TFT liquid crystal display manufactured by Nanao Corporation, and the like.

[Second LCD panel]
An example of the configuration of the second liquid crystal panel of the present invention is shown in the schematic cross-sectional view of FIG. In this figure, the same parts as those in FIG. As shown in the drawing, the second liquid crystal panel 40 includes a first polarizing plate 10, a second polarizing plate 20, and a liquid crystal cell 41 as main constituent members. The first polarizing plate 10 is the polarizing plate 10 of the present invention. In the first polarizing plate 10, the protective layer 11 is the first protective layer 11, the polarizer 12 is the first polarizer 12, and the optical film 13 is the first optical compensation. Layer 13. The second polarizing plate 20 includes a second protective layer 21, a second polarizer 22, and a second optical compensation layer 23 stacked in this order. The first polarizing plate 10 is disposed on the viewing side (upper side in the figure) of the liquid crystal cell 41 with the first optical compensation layer 13 positioned on the liquid crystal cell 41 side. The second polarizing plate 20 is disposed on the backlight side (lower side in the figure) of the liquid crystal cell 41 with the second optical compensation layer 23 positioned on the liquid crystal cell 41 side.

  As described above, in the second liquid crystal panel, the refractive index of the first optical compensation layer shows a relationship of nx> ny ≧ nz, and the refractive index of the second optical compensation layer is nx = ny>. It is configured to show the relationship of nz. By doing so, the contrast ratio in the front direction is significantly higher than that of a conventional liquid crystal panel (typically, the transmittance of two polarizing plates arranged on both sides of the liquid crystal cell is the same). A high liquid crystal panel can be obtained.

  The second protective layer is the same as the protective layer (the first protective layer).

  The second polarizer is the same as the polarizer (the first polarizer).

  The refractive index of the second optical compensation layer exhibits, for example, a relationship of nx = ny> nz (negative uniaxiality). The second optical compensation layer may be a single layer or a laminate composed of a plurality of layers. The thickness of the second optical compensation layer is preferably in the range of 0.5 to 200 μm. The transmittance (T [590]) at a wavelength of 590 nm of the second optical compensation layer is preferably 90% or more.

  Re [590] of the second optical compensation layer is, for example, less than 10 nm, preferably 5 nm or less, and more preferably 3 nm or less.

  Rth [590] of the second optical compensation layer can be appropriately set according to, for example, a retardation value in the thickness direction of the liquid crystal cell. The Rth [590] is, for example, in the range of 100 to 400 nm, preferably in the range of 120 to 350 nm, and more preferably in the range of 150 to 300 nm.

  As the material for forming the second optical compensation layer, any appropriate material can be adopted as long as the refractive index exhibits a relationship (negative uniaxiality) of nx = ny> nz. Examples of the material include poly (4,4′-hexafluoroisopropylidene-bisphenol) terephthalate-co-isophthalate, poly (4,4′-hexahydro-4,7-methanoindane-5-ylidene-bisphenol) terephthalate. Poly (4,4′-isopropylidene-2,2 ′, 6,6′-tetrachlorobisphenol) terephthalate-co-isophthalate, poly (4,4′-hexafluoroisopropylidene) -bisphenol-co- ( 2-norbornylidene) -bisphenol terephthalate, poly (4,4′-hexahydro-4,7-methanoindene-5-ylidene) -bisphenol-co- (4,4′-isopropylidene-2,2 ′, 6,6 ′ -Tetrabromo) -bisphenol terephthalate, poly (4 '- isopropylidene - bisphenol - co-4,4' - (2-norbornylidene) bisphenol) terephthalate - co - isophthalate or may employ these copolymers. These may be used alone or in combination of two or more.

  In addition, as the second optical compensation layer, for example, a retardation film containing a thermoplastic resin such as a polyimide resin, a cellulose resin, a norbornene resin, a polycarbonate resin, or a polyamide resin may be used. These retardation films preferably contain 60 to 100 parts by weight of a thermoplastic resin with respect to 100 parts by weight of the total solid content.

  The second optical compensation layer is preferably a retardation layer (B1) containing a polyimide resin, a retardation layer (B2) containing a cellulose resin, and the retardation film (B1) and the retardation. It is either a laminate (C) with a film (B2). In the laminate (C), the retardation film (B1) is bonded to the retardation film (B2) via an adhesive layer, or the retardation film (B1) is It is preferably formed directly on the surface of the retardation film (B2) by a method such as melting.

[Polyimide resin]
When the polyimide resin is formed into a sheet by the solvent casting method, the molecules are likely to spontaneously orientate during the solvent evaporation process, so the ellipse has a relationship of nx = ny> nz (negative uniaxiality). The retardation film shown can be made very thin. The thickness of the retardation film (B1) containing the polyimide resin is preferably in the range of 0.5 to 10 μm, more preferably in the range of 1 to 5 μm. The birefringence (Δn _xz [590]) in the thickness direction of the retardation film (B1) is preferably in the range of 0.01 to 0.12, more preferably 0.02 to 0.08. It is a range. Such a polyimide resin can be obtained, for example, by the method described in US Pat. No. 5,344,916.

  Preferably, the polyimide resin has at least one of a hexafluoroisopropylidene group and a trifluoromethyl group. More preferably, the polyimide resin has at least a repeating unit represented by the following general formula (8) or a repeating unit represented by the following general formula (9). Since the polyimide resin containing these repeating units is excellent in solubility in a general-purpose solvent, film formation by a solvent casting method is possible. Furthermore, a thin layer of the polyimide resin can be formed on a substrate having poor solvent resistance such as a TAC film without excessively eroding the surface.

前記一般式（８）および（９）において、ＧおよびＧ’は、それぞれ、共有結合、ＣＨ_２基、Ｃ（ＣＨ_３）_２基、Ｃ（ＣＦ_３）_２基、Ｃ（ＣＸ_３）_２基（ここで、Ｘは、ハロゲンである。）、ＣＯ基、Ｏ原子、Ｓ原子、ＳＯ_２基、Ｓｉ（ＣＨ_２ＣＨ_３）_２基、および、Ｎ（ＣＨ_３）基からなる群から選択される基であり、ＧおよびＧ’は同一でも異なっていてもよい。

前記一般式（８）において、Ｌは、置換基であり、ｅは、その置換数を表す。Ｌは、例えば、ハロゲン、炭素原子数１〜３のアルキル基、炭素原子数１〜３のハロゲン化アルキル基、フェニル基、または置換フェニル基であり、Ｌが複数の場合、各Ｌは同一でも異なっていてもよい。ｅは、０〜３までの整数である。

前記一般式（９）中、Ｑは、置換基であり、ｆは、その置換数を表す。Ｑは、例えば、水素、ハロゲン、アルキル基、置換アルキル基、ニトロ基、シアノ基、チオアルキル基、アルコキシ基、アリール基、置換アリール基、アルキルエステル基、および置換アルキルエステル基からなる群から選択される原子または基であって、Ｑが複数の場合、各Ｑは同一でも異なっていてもよい。ｆは、０〜４までの整数であり、ｇおよびｈは、それぞれ、１〜３までの整数である。

In the general formulas (8) and (9), G and G ′ are a covalent bond, a CH ₂ group, a C (CH ₃ ) ₂ group, a C (CF ₃ ) ₂ group, and a C (CX ₃ ) ₂ group, respectively. (Wherein X is a halogen), selected from the group consisting of a CO group, an O atom, an S atom, a SO ₂ group, a Si (CH ₂ CH ₃ ) ₂ group, and an N (CH ₃ ) group. G and G ′ may be the same or different.

In the said General formula (8), L is a substituent and e represents the substitution number. L is, for example, halogen, an alkyl group having 1 to 3 carbon atoms, a halogenated alkyl group having 1 to 3 carbon atoms, a phenyl group, or a substituted phenyl group. May be different. e is an integer from 0 to 3.

In the general formula (9), Q is a substituent, and f represents the number of substitutions. Q is selected from the group consisting of, for example, hydrogen, halogen, alkyl group, substituted alkyl group, nitro group, cyano group, thioalkyl group, alkoxy group, aryl group, substituted aryl group, alkyl ester group, and substituted alkyl ester group. When Q is plural, each Q may be the same or different. f is an integer from 0 to 4, and g and h are integers from 1 to 3, respectively.

  The polyimide resin can be obtained, for example, by a reaction between tetracarboxylic dianhydride and diamine. As the repeating unit of the general formula (8), for example, 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl is used as a diamine, and a tetracarboxylic acid having at least two aromatic rings. It can be obtained by reacting with dianhydride. As the repeating unit of the general formula (9), for example, 2,2′-bis (3,4-dicarboxyphenyl) hexafluoropropanoic dianhydride is used as a tetracarboxylic dianhydride, and this is combined with an aromatic ring. Can be obtained by reacting with a diamine having at least two. The reaction may be, for example, chemical imidization that proceeds in two stages, or thermal imidization that proceeds in one stage.

  Any appropriate tetracarboxylic dianhydride may be selected. Examples of the tetracarboxylic dianhydride include 2,2′-bis (3,4-dicarboxyphenyl) hexafluoropropanoic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic acid dianhydride. Anhydride, 2,3,3 ′, 4-benzophenone tetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenone tetracarboxylic dianhydride, 2,2′-dibromo-4,4 ′, 5,5′-biphenyltetracarboxylic dianhydride, 2,2′-bis (trifluoromethyl) -4,4 ′, 5,5′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4 4′-biphenyltetracarboxylic dianhydride, 4,4′-bis (3,4-dicarboxyphenyl) ether dianhydride, 4,4′-oxydiphthalic dianhydride, 4,4′-bis (3 , 4-Dicarboki Phenyl) sulfone dianhydride, bis (2,3-carboxyphenyl) methane dianhydride, bis (3,4-carboxyphenyl) diethyl silane dianhydride, and the like.

  Any appropriate diamine can be selected. Examples of the diamine include 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl, 4,4′-diaminobiphenyl, 4,4′-diaminophenylmethane, 4,4 ′-( 9-fluorenylidene) -dianiline, 3,3′-dichloro-4,4′-diaminophenylmethane, 2,2′-dichloro-4,4′-diaminobiphenyl, 4,4′-diaminophenyl ether, 3,4 Examples include '-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl thioether, and the like.

  The polyimide-based resin is a polyethylene oxide standard weight average molecular weight (Mw) using a dimethylformamide solution (a solution obtained by adding 10 mM lithium bromide and 10 mM phosphoric acid to make a 1 L dimethylformamide solution). However, Preferably, it is the range of 20000-180000. The polyimide resin preferably has an imidization ratio of 95% or more. The imidation ratio of the polyimide resin can be determined from, for example, an integral intensity ratio between a proton peak derived from polyamic acid, which is a polyimide precursor, and a proton peak derived from polyimide.

  The retardation film (B1) containing the polyimide resin can be obtained by any appropriate forming method. Preferably, the retardation film (B1) is produced by being formed into a sheet shape by a solvent casting method.

[Cellulosic resin]
Any appropriate cellulose-based resin can be adopted. The cellulose-based resin is preferably a cellulose organic acid ester or a cellulose mixed organic acid ester in which part or all of the hydroxyl groups of cellulose are substituted with at least one group of an acetyl group, a propionyl group, and a butyl group. Examples of the cellulose organic acid ester include cellulose acetate, cellulose propionate, and cellulose butyrate. Examples of the cellulose mixed organic acid ester include cellulose acetate propionate and cellulose acetate butyrate. The cellulose resin can be obtained, for example, by the method described in JP 2001-188128 A [0040] to [0041].

  The weight average molecular weight (Mw) of the cellulose resin is preferably in the range of 20000 to 1000000, as measured by gel permeation chromatography (polystyrene standard) using a tetrahydrofuran solvent. The glass transition temperature (Tg) of the cellulose resin is preferably in the range of 110 to 185 ° C. The glass transition temperature (Tg) can be obtained by a DSC method according to JIS K7121. If it is said resin, it can have the further excellent thermal stability and can obtain the retardation film which was further excellent in mechanical strength.

  The retardation film (B2) containing the cellulose resin can be obtained by any appropriate forming method. Preferably, the retardation film (B2) is produced by being formed into a sheet shape by a solvent casting method. As the retardation film (B2), for example, a polymer film containing a commercially available cellulose resin can be used as it is. Alternatively, a film obtained by subjecting the commercially available film to secondary processing such as at least one of stretching and shrinking can be used. Examples of the commercially available film include “Fujitac” series (ZRF80S, TD80UF, TDY-80UL) manufactured by Fuji Photo Film Co., Ltd., and “KC8UX2M” manufactured by Konica Minolta Opto Co., Ltd. .

  The retardation film used as the second optical compensation layer may further contain any appropriate additive. Examples of the additive include a plasticizer, a heat stabilizer, a light stabilizer, a lubricant, an antioxidant, an ultraviolet absorber, a flame retardant, a colorant, an antistatic agent, a compatibilizer, a crosslinking agent, and a thickener. Is mentioned. The content of the additive is preferably more than 0 and 10 parts by weight or less with respect to 100 parts by weight of the main component resin.

  The second optical compensation layer may be a liquid crystal composition. When the liquid crystalline composition is used, the second optical compensation layer is a solidified or cured layer of a liquid crystalline composition containing a rod-like liquid crystal compound aligned in a planar alignment, or a discotic aligned in a columnar alignment. A solidified layer or a cured layer of a liquid crystal composition containing a liquid crystal compound is included. When the liquid crystal compound is used, a thin retardation film can be obtained because the birefringence in the thickness direction is large.

  A retardation film composed of a solidified layer or a cured layer of a liquid crystalline composition containing a rod-like liquid crystal compound aligned in the planar arrangement can be obtained, for example, by the method described in JP-A No. 2003-287623. Further, a retardation film comprising a solidified layer or a cured layer of a liquid crystalline compound containing a discotic liquid crystal compound aligned in the columnar arrangement can be obtained by, for example, a method described in JP-A No. 9-117983.

  The liquid crystal cell is the same as the liquid crystal cell in the first liquid crystal panel.

  It is preferable that the first polarizing plate and the second polarizing plate are arranged so that their absorption axes are orthogonal to each other. The thickness of the second polarizing plate is the same as that of the polarizing plate of the present invention (first polarizing plate).

The degree of polarization of at least one of the first polarizing plate and the second polarizing plate is preferably 99% or more. By setting the degree of polarization to 99% or more, a liquid crystal panel with a higher contrast ratio in the front direction can be obtained. The degree of polarization is more preferably 99.5% or more, and further preferably 99.8% or more. The degree of polarization can be measured using, for example, a spectrophotometer (trade name “DOT-3” manufactured by Murakami Color Research Laboratory Co., Ltd.). As a specific method for measuring the degree of polarization, parallel transmittance (H ₀ ) and orthogonal transmittance (H ₉₀ ) of the first polarizing plate and the second polarizing plate are measured, and the formula: degree of polarization ( %) = {(H ₀ −H ₉₀ ) / (H ₀ + H ₉₀ )} ^1/2 × 100. The parallel transmittance (H ₀ ) is a transmittance value of a parallel laminated polarizing plate produced by superposing two identical polarizing plates so that their absorption axes are parallel to each other. The orthogonal transmittance (H ₉₀ ) is a value of the transmittance of an orthogonal laminated polarizing plate prepared by superposing two identical polarizing plates so that their absorption axes are orthogonal to each other. In addition, these transmittance | permeability is Y value which performed visibility correction | amendment by the 2nd visual field (C light source) of JISZ8701 (1982 edition).

  The liquid crystal display device of the present invention includes the polarizing plate or the liquid crystal panel of the present invention. An example of the configuration of the liquid crystal display device of the present invention is shown in the schematic sectional view of FIG. In the figure, the size, ratio, and the like of each component are different from actual ones for easy understanding. As illustrated, the liquid crystal display device 200 includes at least a liquid crystal panel 100 and a direct-type backlight unit 80 disposed on one side of the liquid crystal panel 100. The direct-type backlight unit 80 includes at least a light source 81, a reflection film 82, a diffusion plate 83, a prism sheet 84, and a brightness enhancement film 85. In the liquid crystal display device 200 of this example, the case where the direct type is adopted as the backlight unit is shown, but the present invention is not limited to this, and is, for example, a sidelight type backlight unit. May be. The sidelight type backlight unit further includes at least a light guide plate and a light reflector in addition to the configuration of the direct type. In addition, as long as the effects of the present invention are obtained, some of the components illustrated in FIG. 5 can be omitted depending on the application, such as the illumination method of the liquid crystal display device and the drive mode of the liquid crystal cell, or Other optical members can be substituted.

  The liquid crystal display device of the present invention may be a transmissive type in which light is irradiated from the backlight side of the liquid crystal panel and the screen is viewed, or a reflective type in which light is irradiated from the viewing side of the liquid crystal panel and the screen is viewed. Alternatively, it may be a transflective type having both transmissive and reflective properties.

  The liquid crystal display device of the present invention is used for any appropriate application. Applications include, for example, OA devices such as personal computer monitors, laptop computers, and copy machines, mobile phones, watches, digital cameras, personal digital assistants (PDAs), portable devices such as portable game machines, video cameras, televisions, microwave ovens, etc. Household electrical equipment, back monitor, car navigation system monitor, car audio and other in-vehicle equipment, display equipment for commercial store information monitors, security equipment such as monitoring monitors, nursing care monitors, medical monitors, etc. Nursing care / medical equipment.

  A preferred application of the liquid crystal display device of the present invention is a television. The screen size of the television is preferably a wide 17 type (373 mm × 224 mm) or more, more preferably a wide 23 type (499 mm × 300 mm) or more, and further preferably a wide 32 type (687 mm × 412 mm). That's it.

  Next, examples of the present invention will be described together with comparative examples. However, the present invention is not limited at all by the following examples and comparative examples. In addition, various physical properties and characteristics in each example and each comparative example were evaluated or measured by the following methods.

(In-plane retardation value Re [550] at a wavelength of 550 nm, thickness direction retardation value Rth [550], Δn and Nz coefficient)
The in-plane retardation value Re [550], thickness direction retardation value Rth [550], Δn, and Nz coefficient at a wavelength of 550 nm were measured using a product name “KOBRA-21ADH” manufactured by Oji Scientific Instruments.

(Thickness)
When the thickness was less than 10 μm, the measurement was performed using a thin film spectrophotometer (trade name “instant multiphotometry system MCPD-2000” manufactured by Otsuka Electronics Co., Ltd.). When the thickness was 10 μm or more, measurement was performed using a digital micrometer “KC-351C type” manufactured by Anritsu.

[Example 1]
As a transparent film base material, a mixture of 90 parts by weight of a lactone ring-containing acrylic resin (LMMA) represented by the general formula (1) and 10 parts by weight of acrylonitrile-styrene resin was formed by extrusion film formation, 2.0 times in length, A film stretched 2.4 times (thickness 40 μm, Re = 0 nm, Rth = 0 nm) was used. As the lactone ring-containing acrylic resin, in general formula (1), R ¹ is a hydrogen atom, R ² and R ³ are methyl groups, and methyl methacrylate and methyl 2- (hydroxymethyl) acrylate A resin having a copolymerization monomer weight ratio of 8: 2 and a lactone cyclization rate of about 100% was used. Further, as the acrylonitrile-styrene resin, Toyo Styrene Co., Ltd., trade name “Toyo AS AS20” was used.

  On the other hand, as a material for forming the optical compensation layer, a polyvinyl alcohol resin containing a repeating unit represented by the structural formulas (I) and (II) and containing a polyethylene moiety (trade name “EXVAL” manufactured by Kuraray Co., Ltd.) RS-2117) was used. This and water were mixed at a weight ratio of 1: 9 and stirred at room temperature for 20 minutes. Thereafter, the mixed solution was heated to 95 ° C. with a water bath, and stirring was continued for 2 hours. Subsequently, it was taken out from the water bath and further stirred at room temperature for 2 hours to obtain a coating liquid of the forming material.

  Next, the coating liquid was applied to a thickness of about 150 μm on the transparent film substrate (thickness: 40 μm), and this was subjected to a drying treatment at 100 ° C. for 10 minutes. As a result, a laminate in which a polyvinyl alcohol layer having a thickness of about 16 μm was laminated on the transparent film substrate was obtained. Thereafter, this laminate is stretched at a temperature of 160 ° C. at a stretching ratio of 3.00 in the width direction, whereby an optical film in which a polyvinyl alcohol layer having a thickness of about 5 μm is laminated on the transparent film substrate. Got. This optical film was an optical film having optical characteristics satisfying the relationship of nx> ny≈nz.

[Example 2]
In the stretching process, the optical film was formed in the same manner as in Example 1 except that the stretching process was performed at a stretching ratio of 3.00 times in the width direction and the shrinking process was performed at a contraction ratio of 0.90 in the longitudinal direction. Produced. As a result, an optical film in which a polyvinyl alcohol layer having a thickness of about 5.6 μm was laminated on the transparent film substrate was obtained.

[Example 3]
In the stretching process, the optical film was formed in the same manner as in Example 1 except that the stretching process was performed at a stretching ratio of 3.00 times in the width direction and the shrinking process was performed at a shrinking ratio of 0.70 times in the longitudinal direction. Produced. As a result, an optical film in which a polyvinyl alcohol layer having a thickness of about 7 μm was laminated on the transparent film substrate was obtained.

[Example 4]
In the stretching process, an optical film was produced in the same manner as in Example 1 except that the stretching process was performed at a stretching ratio in the width direction of 1.80. As a result, an optical film in which a polyvinyl alcohol layer having a thickness of about 8 μm was laminated on the transparent film substrate was obtained.

[Example 5]
An optical film was produced in the same manner as in Example 1 except that the stretching treatment was performed at a stretching ratio of 4.00 in the width direction. As a result, an optical film in which a polyvinyl alcohol layer having a thickness of about 3.8 μm was laminated on the transparent film substrate was obtained.

[Comparative Example 1] TAC / polyimide (stretched 1.22 times)
2,2′-bis (3,4-dicarboxyphenyl) hexafluoropropane and 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl were used as starting materials, and polyimide was prepared according to a conventional method. It was adjusted. A solution prepared by dissolving the obtained polyimide in cyclohexanone so as to be 15 wt% is obtained on a triacetyl cellulose (TAC) film (manufactured by Fuji Film Co., Ltd., trade name “TD-80UL”, thickness: 80 μm). To a thickness of about 20 μm. Subsequently, the laminated body by which the polyimide layer about 3 micrometers thick was laminated | stacked on the said TAC film by performing the drying process for 10 minutes at 120 degreeC. Thereafter, the laminated body is stretched at a temperature of 160 ° C. at a stretching ratio of 1.22 times in the width direction, whereby an optical film in which a polyimide layer having a thickness of about 2.4 μm is laminated on the TAC film. Obtained. This optical film was an optical film having optical properties satisfying the relationship of nx>ny> nz.

[Comparative Example 2]
A polyimide solution prepared in the same manner as in Comparative Example 1 was applied on the transparent film substrate (LMMA-containing film, thickness: 40 μm) used in Example 1 with a thickness of about 20 μm. Subsequently, the laminated body by which the polyimide layer about 3 micrometers thick was laminated | stacked on the said LMMA film by performing the drying process for 10 minutes at 120 degreeC. Thereafter, the laminated body is stretched at a temperature of 160 ° C. at a stretching ratio of 1.22 times in the width direction, whereby an optical film in which a polyimide layer having a thickness of about 2.4 μm is laminated on the LMMA film. Obtained. This optical film was an optical film having optical properties satisfying the relationship of nx>ny> nz.

[Comparative Example 3]
A polyimide solution prepared in the same manner as in Comparative Example 1 was applied on the TAC film (thickness: 50 μm) used in Comparative Example 1 to a thickness of about 20 μm. Subsequently, the laminated body by which the polyimide layer about 3 micrometers thick was laminated | stacked on the TAC film by performing a drying process for 10 minutes at 120 degreeC. Then, when this laminate was stretched at a temperature of 160 ° C. at a stretch ratio of 1.23 in the width direction, the polyimide layer was whitened.

[Comparative Example 4] LMMA / ethylene-free PVA stretching (3.00 times stretching)
As a material for forming the optical compensation layer, a polyvinyl alcohol-based resin having no polyethylene portion (trade name “Poval 124” manufactured by Kuraray Co., Ltd.) was used. This and water were mixed at a weight ratio of 1: 9 and stirred at room temperature for 20 minutes. Thereafter, the mixed solution of water and poval was heated to 95 ° C. with a water bath, and stirring was continued for 2 hours. Subsequently, the mixed solution was taken out from the water bath and further stirred at room temperature for 2 hours to obtain a coating liquid for forming material.

  Next, the coating solution was applied to a thickness of about 153 μm on the transparent film substrate (LMMA-containing film, thickness: 40 μm) used in Example 1. Subsequently, the laminated body by which the polyvinyl alcohol layer about 15.1 micrometers in thickness was laminated | stacked on the said transparent film base material by performing the drying process for 10 minutes at 100 degreeC. Thereafter, the laminate was stretched at a temperature of 160 ° C. at a stretching ratio of 3.00 in the width direction, whereby a polyvinyl alcohol layer having a thickness of about 4.8 μm was laminated on the transparent film substrate. An optical film was obtained. This optical film was an optical film having optical characteristics satisfying the relationship of nx> ny≈nz.

[Evaluation]
Table 1 shows the refractive index anisotropy, Δn (= nx−nz), and Nz coefficient ((nx−nz) / (nx−ny)) of the optical films obtained in the above Examples and Comparative Examples. In Examples 1 to 5, formation of an optical film satisfying nx> ny≈nz, expressing a desired phase difference, and having optical characteristics with an Nz coefficient in the range of 0.9 to 2.0 was realized. On the other hand, in Comparative Examples 1 to 4, desired optical characteristics could not be obtained. In Comparative Example 3, since the polyimide layer was whitened in the stretching step, the optical characteristics could not be measured. For the optical film obtained in Comparative Example 4, optical characteristics satisfying nx> ny≈nz were obtained, but the Δn value was very small as 0.0024, and the same retardation as that of the optical compensation layer of this example. In order to obtain the thickness, a thickness of about 10 times is required, and it cannot be said that it is suitable for applications where a reduction in thickness is desired.

  According to the method for producing an optical film of the present invention, it is possible to obtain an optical film that is less expensive than conventional ones and can be easily designed with optical characteristics. Applications of the obtained optical film, polarizing plate including the optical film, liquid crystal panel, and liquid crystal display device using the same include, for example, OA equipment such as desktop personal computers, notebook personal computers, copiers, mobile phones, watches, digital cameras , Portable devices such as personal digital assistants (PDAs), portable game machines, household electrical devices such as video cameras, televisions, and microwave ovens, back monitors, monitors for car navigation systems, in-vehicle devices such as car audio, for commercial stores Display equipment such as information monitors, security equipment such as monitoring monitors, nursing care and medical equipment such as nursing monitors and medical monitors, and the like are not limited and can be applied to a wide range of fields.

10 Polarizing plate (first polarizing plate)
11 Protective layer (first protective layer)
12 Polarizer (first polarizer)
13 Optical film (first optical compensation layer)
20 Second polarizing plate 21 Second protective layer 22 Second polarizer 23 Second optical compensation layer 30, 40, 100 Liquid crystal panel 41 Liquid crystal cell 411a, 411b Substrate 412 Spacer 413 Liquid crystal layer 80 Backlight unit 81 Light source 82 Reflective film 83 Diffusion plate 84 Prism sheet 85 Brightness enhancement film 200 Liquid crystal display device

Claims (18)

A method for producing an optical film, comprising a transparent film substrate and an optical compensation layer, wherein the Nz coefficient defined by the following formula is in the range of 0.9 to 2.0, wherein polyethylene is formed on the transparent film substrate: The manufacturing method of the optical film characterized by including the process of forming the coating film containing the polyvinyl alcohol-type resin containing a site | part, and the process of extending | stretching the said coating film and the said transparent film base material.
Nz coefficient = (nx−nz) / (nx−ny) The manufacturing method of the optical film of Claim 1 which extends | stretches both the said transparent film base material and the said coating film in the said extending process.   The method for producing an optical film according to claim 1 or 2, wherein in the stretching step, a stretching direction is a width direction of the transparent film substrate.   The manufacturing method of the optical film of Claim 3 whose draw ratio in the extending | stretching of the said width direction is the range of 1.3-6.0 times.   5. The stretching process according to claim 3, wherein, in the stretching step, the transparent film substrate and the coating film are contracted in the longitudinal direction in a range of 0.5 to 1.0 times along with stretching in the width direction. Manufacturing method of optical film. The manufacturing method of the optical film as described in any one of Claim 1 to 5 which uses acrylic resin as a material of the said transparent film base material. Examples of the acrylic resin include polyacrylic acid ester, polymethacrylic acid ester, methyl methacrylate-acrylic acid copolymer, methyl methacrylate-methacrylic acid copolymer, methyl methacrylate-acrylic acid ester copolymer, methyl methacrylate. -Methacrylic acid ester copolymer, Methyl methacrylate-Acrylic acid ester-Acrylic acid copolymer, Methyl methacrylate-Acrylic acid ester-Methacrylic acid copolymer, Methyl acrylate-Styrene copolymer, Methyl methacrylate-Styrene The method for producing an optical film according to claim 6, wherein at least one selected from the group consisting of a copolymer and a polymer having an alicyclic hydrocarbon group is used. The polyvinyl alcohol-based resin containing the polyethylene moiety is one containing a polymer containing a repeating unit represented by the following structural formulas (I) and (II). Manufacturing method of the optical film.

The method for producing an optical film according to claim 8, wherein the polymer has a molar ratio of (I) to (II) satisfying a range of 50:50 to 99: 1. The method for producing an optical film according to any one of claims 1 to 9, further comprising a crosslinking treatment step after the stretching step. The manufacturing method of the optical film as described in any one of Claims 1-10 using the coating liquid in which the solvent is not added in the process of forming the said coating film. An optical film comprising a transparent film substrate and an optical compensation layer, wherein the optical compensation layer comprises a polyvinyl alcohol-based resin containing a polyethylene moiety, and the Nz coefficient defined by the following formula of the optical film is 0. An optical film having a range of 9 to 2.0.
Nz coefficient = (nx−nz) / (nx−ny) The optical film according to claim 12, wherein the transparent film substrate is an acrylic resin. It is an optical film, Comprising: It manufactures with the manufacturing method of the optical film as described in any one of Claims 1-11, The optical film of Claim 12 or 13 characterized by the above-mentioned. It is a polarizing plate containing an optical film and a polarizer, Comprising: The said optical film is an optical film as described in any one of Claims 12-14, The polarizing plate characterized by the above-mentioned. A liquid crystal panel including a liquid crystal cell and an optical member,
The optical member is the optical film according to any one of claims 12 to 14 or the polarizing plate according to claim 15.
The liquid crystal panel, wherein the optical member is disposed on at least one side of the liquid crystal cell. A first polarizing plate, a second polarizing plate, and a liquid crystal cell, wherein the first polarizing plate is disposed on a viewing side of the liquid crystal cell, and the second polarizing plate is a backlight of the liquid crystal cell. A liquid crystal panel arranged on the side,
The first polarizing plate includes a first polarizer and a first optical compensation layer,
The first optical compensation layer is disposed between the first polarizer and the liquid crystal cell,
The refractive index of the first optical compensation layer has a relationship of nx> ny ≧ nz,
The second polarizing plate includes a second polarizer and a second optical compensation layer,
The second optical compensation layer is disposed between the second polarizer and the liquid crystal cell,
In the liquid crystal panel in which the refractive index of the second optical compensation layer shows a relationship of nx = ny> nz,
The liquid crystal panel according to claim 15, wherein the first polarizing plate is the polarizing plate according to claim 15, and the optical film contained in the polarizing plate according to claim 15 is the first optical compensation layer.   A liquid crystal display device comprising an optical member or a liquid crystal panel, wherein the optical member is the optical film according to any one of claims 12 to 14 or the polarizing plate according to claim 15, wherein the liquid crystal panel is A liquid crystal display device which is a liquid crystal panel according to claim 16.

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