JP3791806B2 - Manufacturing method of optical film - Google Patents

Description

  The present invention relates to a method for producing an optical film.

  Various optical films are used for liquid crystal display devices in order to improve display performance. For example, an optical film (retardation film) that satisfies the following condition (1) is disposed between the liquid crystal cell and the polarizing plate, and is used for compensating the viewing angle of the liquid crystal display device. Such an optical film is produced by stretching a polymer film (see Patent Documents 1, 2, and 3).

nx ≧ ny> nz (1)
In the formula (1), nx, ny, and nz represent refractive indexes in the X-axis direction, the Y-axis direction, and the Z-axis direction, respectively, in the optical film.
The X-axis direction is an axial direction showing the maximum refractive index in the in-plane direction of the optical film, and the Y-axis direction is an axial direction perpendicular to the X-axis direction in the plane, The Z-axis direction indicates a thickness direction perpendicular to the X-axis direction and the Y-axis direction.

  However, in the manufacturing method based on the stretching method, detailed setting of conditions such as the stretching ratio and the stretching direction is necessary, and the stretching process needs to be precisely controlled, and the process becomes complicated. In the stretching method, it is necessary to solve the bowing phenomenon. Furthermore, in the stretching method, it is necessary to use a polymer film having a certain thickness. Therefore, the obtained optical film has a film thickness, and as a result, there is a problem that the liquid crystal display device becomes thick.

  On the other hand, there is a method for producing an optical film without depending on the stretching treatment. For example, a solution of a polymer such as polyamide, polyimide, polyester, polyetherketone, polyamideimide and polyesterimide may be applied to a substrate having a smooth surface, and the solvent of the solution may be removed by evaporation to form an optical film. Yes (see Patent Documents 4, 5, 6, 7, and 8). As the base material, an inorganic base material such as a SUS belt, a copper thin plate, a glass plate, or a Si wafer is mainly used. However, when an inorganic base material is used, it cannot be used for a liquid crystal display device itself, so it is necessary to transfer an optical film from the base material to a polarizer or the like. Moreover, the optical film formed on the base material is also peeled off from the base material and wound. Thus, when an inorganic base material is used, manufacture of an optical film will become complicated and there also exists a problem that the cost of an inorganic base material is high.

Thus, although the conventional optical film has a problem in the manufacturing method, the improvement of the further optical characteristic is calculated | required also with respect to optical film itself.
JP-A-3-33719 Japanese Patent Laid-Open No. 3-24502 JP-A-4-194820 US Pat. No. 5,344,916 US Pat. No. 5,395,918 (Japanese Patent Publication No. 8-511812) US Pat. No. 5,480,964 US Pat. No. 5,580,950 US Pat. No. 6,074,709

  Therefore, an object of this invention is to provide the manufacturing method of the optical film which can be manufactured simply and at low cost, and was excellent in the optical characteristic.

In order to solve the above problems, an optical film manufacturing method of the present invention is an optical film manufacturing method in which a transparent polymer film layer and a birefringent layer are laminated, and an in-plane retardation is 50 nm or less. A transparent polymer film made of resin is prepared. A birefringent layer is formed by applying a solution containing polyimide and methyl isobutyl ketone, which are non-liquid crystalline polymers, and evaporating and removing the solvent in the solution. Then, by shrinking the laminate of the transparent polymer film layer and the birefringent layer, the birefringent layer is made to satisfy the condition of the following formula (1), and the birefringence index Δn ( In the production method, both layers are formed so that the birefringence Δn (b) of a) and the transparent polymer film layer satisfies the condition of the following formula (2).
nx>ny> nz (1)
Δn (a)> Δn (b) × 10 (2)

In the formula (1), nx, ny, and nz represent refractive indexes in the X-axis direction, the Y-axis direction, and the Z-axis direction, respectively, in the birefringent layer. The X-axis direction is an axial direction showing the maximum refractive index in the in-plane direction of the birefringent layer, and the Y-axis direction is an axial direction perpendicular to the X-axis direction in the plane, The Z-axis direction indicates a thickness direction perpendicular to the X-axis direction and the Y-axis direction.

  Thus, the optical film obtained by the production method of the present invention (hereinafter also referred to as the optical film of the present invention) uses a transparent polymer film layer as a base material, and has a birefringent layer laminated thereon, It can be used as it is in a laminated state, does not require peeling work or winding work from the substrate, and the transparent polymer film layer is low in cost. For this reason, the optical film of this invention can be manufactured simply and at low cost compared with the past. In the optical film of the present invention, the in-plane retardation of the transparent polymer film layer is 50 nm or less. For this reason, the retardation of the entire optical film can be set in an appropriate range, and the optical characteristics such as contrast and viewing angle characteristics are excellent.

  Next, the present invention will be described in detail.

  In the optical film of the present invention, the birefringent layer needs to satisfy the conditional expression (1). FIG. 4 shows an example of the refractive indexes nx, ny and nz in the birefringent layer. As shown in the figure, nx, ny, and nz respectively indicate refractive indexes in the X-axis direction, the Y-axis direction, and the Z-axis direction in the birefringent layer. The X-axis direction is an axial direction showing the maximum refractive index in the in-plane direction of the birefringent layer, and the Y-axis direction is an axial direction perpendicular to the X-axis direction in the plane, The Z-axis direction indicates a thickness direction perpendicular to the X-axis direction and the Y-axis direction.

  When it has an optical characteristic of nx = ny> nz, it is an optically uniaxial characteristic, and such an optical film is usually called a C plate. Moreover, when it has the optical characteristic of nx> ny> nz, it is an optically biaxial characteristic. In the case of an optically uniaxial characteristic, nx and ny are in principle coincident with each other, but an actual measurement value has an error. When the thickness (d) of the birefringent layer is 0.1 μm to 50 μm, for example, if Δnd = (nx−ny) · d <5 nm, it can be said to be an optically uniaxial characteristic and exceeds the above range. Is optically biaxial.

  In the method for producing an optical film of the present invention, the birefringence Δn (a) of the birefringent layer and the birefringence Δn (b) of the transparent polymer film layer are replaced by the following formula (2): It is preferable to satisfy any one of the conditions (3) to (7). By satisfying this condition, optical characteristics such as contrast and viewing angle characteristics are further improved. In the following formula, the formula (3) to formula (7) are preferred.

Δn (a)> Δn (b) × 15 (3)
Δn (a)> Δn (b) × 20 (4)
Δn (a)> Δn (b) × 30 (5)
Δn (a)> Δn (b) × 40 (6)
Δn (a)> Δn (b) × 50 (7)

In the method for producing an optical film of the present invention, the birefringence (Δn) of the entire optical film is preferably in the range of 0.0005 to 0.5. If Δn is 0.0005 or more, the optical film can be made thin, and if it is 0.5 or less, there is an advantage that the phase difference can be easily controlled. A more preferable range of Δn is 0.001 to 0.2, and a further preferable range is 0.002 to 0.15.

  In the method for producing an optical film of the present invention, the non-liquid crystalline polymer forming the birefringent layer is polyimide.

  In the method for producing an optical film of the present invention, the resin forming the transparent polymer film layer is a cellulose resin. An example of the cellulose resin is triacetyl cellulose.

In the method for producing an optical film of the present invention, the transparent polymer film layer is not particularly limited, and may be produced by forming the forming material resin into a film shape and stretching the resin. Moreover, in the manufacturing method of the optical film of this invention, after laminating | stacking the said transparent polymer film layer and the said birefringent layer, this laminated body is shrink | contracted.

  In the method for producing an optical film of the present invention, the transparent polymer film layer may be used as a transparent protective film for a polarizing plate.

  The polarizing plate of this invention is a polarizing plate containing an optical film and a polarizer, Comprising: The said optical film is an optical film obtained by the manufacturing method of the said this invention. It is preferable that the transparent polymer film layer of the optical film also serves as a transparent protective film of the polarizing plate. The optical film preferably functions as an optical compensation layer.

  The 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 disposed on at least one surface of the liquid crystal cell, and the optical member is obtained by the manufacturing method of the present invention. The optical film to be produced or the polarizing plate of the present invention. The type of the liquid crystal cell of the present invention is not particularly limited, and for example, an STN (Super Twisted Nematic) cell, a TN (Twisted Nematic) cell, an IPS (In-Plane Switching) cell, a VA (Vertical Alighned) cell, an OCB (OCB) There are an optically asymmetric birefringence (HAN) cell, a hybrid algebraic nematic (HAN) cell, an axially symmetrical microcell (ASM) cell, and the like. In this, it is preferable to apply the optical film obtained by the manufacturing method of this invention to a VA cell and an OCB cell.

  The liquid crystal display device of the present invention is a liquid crystal display device including the liquid crystal panel of the present invention.

  The self-luminous display device of the present invention is a self-luminous display device including at least one of the optical film obtained by the production method of the present invention and the polarizing plate of the present invention. Examples of the self-luminous display measure include an organic EL display.

  Below, the manufacturing method of the optical film of this invention is demonstrated. The optical film of the present invention is prepared, for example, by preparing a transparent polymer film made of a cellulose resin having an in-plane retardation of 50 nm or less, applying a polyimide solution thereon, and evaporating and removing the solvent in the solution. It can be manufactured by forming a birefringent layer and satisfying the condition of the above formula (1).

  As described above, the non-liquid crystalline polymer used for forming the birefringent layer is, for example, excellent in heat resistance, chemical resistance and transparency, rich in rigidity, highly transparent, highly oriented, and highly stretched. Because of its properties, it is polyimide.

  Although the molecular weight of the polymer is not particularly limited, for example, the weight average molecular weight (Mw) is preferably in the range of 1,000 to 1,000,000, more preferably in the range of 2,000 to 500,000. is there.

  As the polyimide, for example, a polyimide that has high in-plane orientation and is soluble in an organic solvent is preferable. Specifically, for example, it includes a condensation polymerization product of 9,9-bis (aminoaryl) fluorene and an aromatic tetracarboxylic dianhydride disclosed in JP 2000-511296 A, and has the following formula ( A polymer containing one or more repeating units shown in 1) can be used.

In the formula (1), R ^{3 to} R ⁶ are a group consisting of hydrogen, halogen, a phenyl group, a phenyl group substituted with 1 to 4 halogen atoms or a C1-10 alkyl group, and a C1-10 alkyl group. Are at least one kind of substituents independently selected from the above. Preferably, R ^{3 to} R ⁶ are each independently selected from the group consisting of halogen, phenyl groups, phenyl groups substituted with 1 to 4 halogen atoms or C 1-10 alkyl groups, and C 1-10 alkyl groups. At least one kind of substituent.

  In the formula (1), Z is, for example, a C6-20 tetravalent aromatic group, preferably a pyromellitic group, a polycyclic aromatic group, a derivative of a polycyclic aromatic group, or the following It is group represented by Formula (2).

In the formula (2), Z ′ is, for example, a covalent bond, C (R ⁷ ) ₂ group, CO group, O atom, S atom, SO ₂ group, Si (C ₂ H ₅ ) ₂ group, or NR ^{There are 8} groups, and when there are multiple groups, they are the same or different. W represents an integer from 1 to 10. Each R ⁷ is independently hydrogen or C (R ⁹ ) ₃ . R ⁸ is hydrogen, a C1 to C20 alkyl group, or a C6 to 20 aryl group, and in a plurality of cases, they are the same or different. Each R ⁹ is independently hydrogen, fluorine, or chlorine.

  Examples of the polycyclic aromatic group include a tetravalent group derived from naphthalene, fluorene, benzofluorene or anthracene. Examples of the substituted derivative of the polycyclic aromatic group include a C1-10 alkyl group, a fluorinated derivative thereof, and at least one group selected from the group consisting of halogens such as F and Cl. In addition, the polycyclic aromatic group is exemplified.

  In addition, for example, a homopolymer described in JP-A-8-511812, wherein the repeating unit is represented by the following general formula (3) or (4), or the repeating unit is represented by the following general formula (5): The polyimide etc. which are shown are mention | raise | lifted. In addition, the polyimide of following formula (5) is a preferable form of the homopolymer of following formula (3).

In the general formulas (3) to (5), G and G ′ are, for example, a covalent bond, a CH ₂ group, a C (CH ₃ ) ₂ group, a C (CF ₃ ) ₂ group, or a C (CX ₃ ) ₂ group. (Wherein X is halogen), from the group consisting of CO group, O atom, S atom, SO ₂ group, Si (CH ₂ CH ₃ ) ₂ group, and N (CH ₃ ) group, respectively It represents independently selected groups, and may be the same or different.

  In the above formulas (3) and (5), L is a substituent, and d and e represent the number of substitutions. L is, for example, a halogen, a C1-3 alkyl group, a C1-3 halogenated alkyl group, a phenyl group, or a substituted phenyl group, and in a plurality of cases, they are the same or different. Examples of the substituted phenyl group include substituted phenyl groups having at least one type of substituent selected from the group consisting of halogen, C1-3 alkyl groups, and C1-3 halogenated alkyl groups. Examples of the halogen include fluorine, chlorine, bromine and iodine. d is an integer from 0 to 2, and e is an integer from 0 to 3.

  In the formulas (3) to (5), Q is a substituent, and f represents the number of substitutions. Q is, for example, selected from the group consisting of 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 And when Q is plural, they are the same or different. Examples of the halogen include fluorine, chlorine, bromine and iodine. Examples of the substituted alkyl group include a halogenated alkyl group. Examples of the substituted aryl group include a halogenated aryl group. f is an integer from 0 to 4, and g and h are integers from 0 to 3 and 1 to 3, respectively. Further, g and h are preferably larger than 1.

In the formula (4), R ¹⁰ and R ¹¹ are groups independently selected from the group consisting of hydrogen, halogen, phenyl group, substituted phenyl group, alkyl group, and substituted alkyl group. Among these, R ¹⁰ and R ¹¹ are preferably each independently a halogenated alkyl group.

In Formula (5), M ¹ and M ² are the same or different and are, for example, halogen, C1-3 alkyl group, C1-3 halogenated alkyl group, phenyl group, or substituted phenyl group. Examples of the halogen include fluorine, chlorine, bromine and iodine. Examples of the substituted phenyl group include substituted phenyl groups having at least one type of substituent selected from the group consisting of halogen, C1-3 alkyl groups, and C1-3 halogenated alkyl groups.

  Specific examples of the polyimide represented by the formula (3) include those represented by the following formula (6).

  Furthermore, examples of the polyimide include a copolymer obtained by appropriately copolymerizing an acid dianhydride other than the skeleton (repeating unit) as described above and a diamine.

  Examples of the acid dianhydride include aromatic tetracarboxylic dianhydrides. Examples of the aromatic tetracarboxylic dianhydride include pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride, naphthalene tetracarboxylic dianhydride, heterocyclic aromatic tetracarboxylic dianhydride, 2, And 2'-substituted biphenyltetracarboxylic dianhydride.

  Examples of the pyromellitic dianhydride include pyromellitic dianhydride, 3,6-diphenylpyromellitic dianhydride, 3,6-bis (trifluoromethyl) pyromellitic dianhydride, and 3,6-dibromo. Examples include pyromellitic dianhydride and 3,6-dichloropyromellitic dianhydride. Examples of the benzophenone tetracarboxylic dianhydride include 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2,3,3 ′, 4′-benzophenone tetracarboxylic dianhydride, 2 , 2 ′, 3,3′-benzophenonetetracarboxylic dianhydride and the like. Examples of the naphthalenetetracarboxylic dianhydride include 2,3,6,7-naphthalene-tetracarboxylic dianhydride, 1,2,5,6-naphthalene-tetracarboxylic dianhydride, 2,6 -Dichloro-naphthalene-1,4,5,8-tetracarboxylic dianhydride and the like. Examples of the heterocyclic aromatic tetracarboxylic dianhydride include thiophene-2,3,4,5-tetracarboxylic dianhydride and pyrazine-2,3,5,6-tetracarboxylic dianhydride. Pyridine-2,3,5,6-tetracarboxylic dianhydride and the like. Examples of the 2,2′-substituted biphenyltetracarboxylic dianhydride include 2,2′-dibromo-4,4 ′, 5,5′-biphenyltetracarboxylic dianhydride and 2,2′-dichloro. -4,4 ', 5,5'-biphenyltetracarboxylic dianhydride, 2,2'-bis (trifluoromethyl) -4,4', 5,5'-biphenyltetracarboxylic dianhydride, etc. can give.

  Other examples of the aromatic tetracarboxylic dianhydride include 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and bis (2,3-dicarboxyphenyl) methane dianhydride. Bis (2,5,6-trifluoro-3,4-dicarboxyphenyl) methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3 3-hexafluoropropane dianhydride, 4,4′-bis (3,4-dicarboxyphenyl) -2,2-diphenylpropane dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, 4,4′-oxydiphthalic dianhydride, bis (3,4-dicarboxyphenyl) sulfonic dianhydride, 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic dianhydride, 4,4 ′ -[4,4'-isopropylidene Di (p-phenyleneoxy)] bis (phthalic anhydride), N, N- (3,4-dicarboxyphenyl) -N-methylamine dianhydride, bis (3,4-dicarboxyphenyl) diethylsilane And dianhydrides.

  Among these, the aromatic tetracarboxylic dianhydride is preferably 2,2′-substituted biphenyltetracarboxylic dianhydride, more preferably 2,2′-bis (trihalomethyl) -4,4. ', 5,5'-biphenyltetracarboxylic dianhydride, more preferably 2,2'-bis (trifluoromethyl) -4,4', 5,5'-biphenyltetracarboxylic dianhydride It is.

  Examples of the diamine include aromatic diamines, and specific examples include benzene diamine, diaminobenzophenone, naphthalene diamine, heterocyclic aromatic diamines, and other aromatic diamines.

  Examples of the benzenediamine include o-, m- and p-phenylenediamine, 2,4-diaminotoluene, 1,4-diamino-2-methoxybenzene, 1,4-diamino-2-phenylbenzene, and 1, Examples include diamines selected from the group consisting of benzenediamines such as 3-diamino-4-chlorobenzene. Examples of the diaminobenzophenone include 2,2'-diaminobenzophenone and 3,3'-diaminobenzophenone. Examples of the naphthalene diamine include 1,8-diaminonaphthalene and 1,5-diaminonaphthalene. Examples of the heterocyclic aromatic diamine include 2,6-diaminopyridine, 2,4-diaminopyridine, and 2,4-diamino-S-triazine.

  In addition to these, the aromatic diamine includes 4,4′-diaminobiphenyl, 4,4′-diaminodiphenylmethane, 4,4 ′-(9-fluorenylidene) -dianiline, 2,2′-bis ( Trifluoromethyl) -4,4′-diaminobiphenyl, 3,3′-dichloro-4,4′-diaminodiphenylmethane, 2,2′-dichloro-4,4′-diaminobiphenyl, 2,2 ′, 5 5′-tetrachlorobenzidine, 2,2-bis (4-aminophenoxyphenyl) propane, 2,2-bis (4-aminophenyl) propane, 2,2-bis (4-aminophenyl) -1,1, 1,3,3,3-hexafluoropropane, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 1,3-bis (3-aminophenoxy) benzene 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-bis (3-amino Phenoxy) biphenyl, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3 -Hexafluoropropane, 4,4'-diaminodiphenyl thioether, 4,4'-diaminodiphenyl sulfone and the like.

  Next, as described above, the in-plane retardation (Δnd) of the transparent polymer film may be 50 nm or less, preferably 20 nm or less, more preferably 10 nm or less. In the present invention, the in-plane retardation (Δnd), the thickness direction retardation (Rth), and the birefringence (Δn) are expressed by the following equations. When the transparent polymer film is a single layer, the lower limit of the in-plane retardation (Δnd) is a value exceeding 0. Therefore, the range of the in-plane retardation (Δnd) of the transparent polymer film is preferably in the range of 50 nm or less and over 0 nm, more preferably in the range of 20 nm or less and over 0 nm, and further preferably in the range of 10 nm or less and over 0 nm. is there. In the following formula, nx, ny and nz are the same as those in the birefringent layer described above. That is, nx, ny, and nz represent the refractive indexes in the X-axis direction, the Y-axis direction, and the Z-axis direction, respectively, in the transparent polymer film. The X-axis direction is an axial direction showing the maximum refractive index in the in-plane direction of the transparent polymer film, and the Y-axis direction is an axial direction perpendicular to the X-axis direction in the plane. The Z-axis direction indicates a thickness direction perpendicular to the X-axis direction and the Y-axis direction. d is the thickness of the film.

Δnd = (nx−ny) · d
Rth = [(nx + ny) / 2−nz] · d
Δn = [(nx + ny) / 2−nz] · d / d

The material for forming the transparent polymer film is a cellulose resin. A polymer having excellent transparency is preferable, and a cellulose resin such as triacetyl cellulose (TAC) is specifically used because it is suitable for a stretching treatment and a shrinking treatment as described later.

  The thickness of the transparent polymer film is, for example, about 10 to 1000 μm, preferably 20 to 500 μm, and more preferably 30 to 100 μm.

  The transparent polymer film layer of the present invention may be formed in advance using the transparent polymer film having the in-plane retardation (Δnd) of the present invention. May be subjected to a treatment such as stretching or shrinking to the predetermined range.

  Next, a solution of the non-liquid crystal polymer is applied to the transparent polymer film in the form of a film, and the solvent in the solution is removed by evaporation to form a birefringent layer.

  The solvent of the solution to be applied only needs to contain methyl isobutyl ketone. The solvent used in combination is not particularly limited. For example, halogenated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, and orthodichlorobenzene; phenols such as phenol and parachlorophenol Aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene, 1,2-dimethoxybenzene; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone, N-methyl-2-pyrrolidone Ketone solvents such as ethyl acetate and butyl acetate; t-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ester Alcohol solvents such as ter, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol, 2-methyl-2,4-pentanediol; amide solvents such as dimethylformamide and dimethylacetamide; nitrile solvents such as acetonitrile and butyronitrile Ether solvents such as diethyl ether, dibutyl ether and tetrahydrofuran; carbon disulfide, ethyl cellosolve, butyl cellosolve and the like. One type of these solvents may be used, or two or more types may be used in combination.

  For example, the coating solution may further contain various additives such as a stabilizer, a plasticizer, and metals as necessary.

  The coating solution may contain other different resins. Examples of the other resin include various general-purpose resins, engineering plastics, thermoplastic resins, and thermosetting resins.

  Examples of the general-purpose resin include polyethylene (PE), polypropylene (PP), polystyrene (PS), polymethyl methacrylate (PMMA), ABS resin, and AS resin. Examples of the engineering plastic include polyacetate (POM), polycarbonate (PC), polyamide (PA: nylon), polyethylene terephthalate (PET), and polybutylene terephthalate (PBT). Examples of the thermoplastic resin include polyphenylene sulfide (PPS), polyethersulfone (PES), polyketone (PK), polyimide (PI), polycyclohexanedimethanol terephthalate (PCT), polyarylate (PAR), and liquid crystal polymer. (LCP) and the like. Examples of the thermosetting resin include an epoxy resin and a phenol novolac resin.

  Thus, when said other resin etc. are mix | blended with the said coating solution, the compounding quantity is 0-50 mass% with respect to the said polymer material, Preferably, it is 0-30 mass%. is there.

  Examples of the solution coating method include spin coating, roll coating, flow coating, printing, dip coating, casting film formation, bar coating, and gravure printing. Moreover, in the case of coating, the superposition | polymerization method of a polymer layer is also employable as needed.

  After the coating, for example, the solvent in the solution is evaporated and removed by natural drying, air drying, or heat drying (for example, 60 to 250 ° C.) to form a film-like birefringent layer. This birefringent layer satisfies the condition of the formula (1). The thickness of the birefringent layer is not particularly limited, but is, for example, 0.1 to 50 μm, preferably 0.5 to 30 μm, more preferably from the viewpoint of thinning the liquid crystal display device, viewing angle compensation, film homogeneity, and the like. Is in the range of 1-20 μm.

The birefringent layer of the present invention is formed with optically uniaxial characteristics (nx = ny> nz) unless treatment other than the layer forming step by solvent evaporation removal of the non-liquid crystalline polymer solution is performed. However, for example, if the following processing is performed, a difference in refractive index (nx> ny) can be provided in the surface, and optical biaxiality (nx>ny> nz) is obtained. Examples of a method for giving a difference in refractive index in the plane of the birefringent layer include the following methods. First, a transparent polymer film having in-plane shrinkage in one direction is used, and the solution is applied onto the film and dried to form the in-plane shrinkage of the transparent polymer film. The birefringent layer can have an in-plane refractive index difference .

  Thus, an optical film in which a transparent polymer film layer and a birefringent layer formed of a non-liquid crystalline polymer are laminated, satisfying the condition of the formula (1), and the transparent polymer film The optical film of the present invention in which the in-plane retardation of the layer is 50 nm or less is obtained.

  In the present invention, the birefringent layer may be formed on one surface of the transparent polymer film layer, or may be formed on both surfaces. Further, the birefringent layer may be a single layer or a multilayer structure formed of a single forming material or a plurality of forming materials.

  The optical film of the present invention preferably further has at least one of an adhesive layer and a pressure-sensitive adhesive layer. This is because adhesion between the optical film of the present invention and other members such as other optical layers and liquid crystal cells can be facilitated, and peeling of the optical film of the present invention can be prevented. Therefore, the adhesive layer and the pressure-sensitive adhesive layer are preferably laminated on the outermost layer of the optical film, and may be one outermost layer of the optical film or may be laminated on both outermost layers.

  The material of the adhesive layer is not particularly limited. For example, a pressure sensitive adhesive made of a polymer such as acrylic, vinyl alcohol, silicone, polyester, polyurethane, or polyether, or a rubber pressure sensitive adhesive. Etc. can be used. Alternatively, these materials may contain fine particles to form a layer exhibiting light diffusibility. Among these, for example, a material excellent in hygroscopicity and heat resistance is preferable. With such a property, for example, when used in a liquid crystal display device, it can prevent foaming and peeling due to moisture absorption, deterioration of optical characteristics due to a difference in thermal expansion, warpage of the liquid crystal cell, etc., and high quality and durability. The display device is also excellent.

  As described above, the optical film of the present invention may be used alone, or may be used in various optical applications as a laminate in combination with other optical members as necessary. Specifically, it is useful as an optical compensation member, particularly as a visual compensation member. Although it does not restrict | limit especially as said other optical member, For example, the polarizer etc. which are shown below are mention | raise | lifted.

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

  The configuration of such a polarizing plate is not particularly limited as long as it has the optical film of the present invention, and examples thereof include those shown in FIG. 1 or FIG. FIG. 1 and FIG. 2 are cross-sectional views showing examples of the polarizing plate of the present invention, in which the same parts are denoted by the same reference numerals. In addition, the polarizing plate of this invention is not limited to the following structures, Furthermore, the other optical member etc. may be included.

  The polarizing plate shown in FIG. 1 has the optical film 1, the polarizer 2 and the transparent protective layer 3 of the present invention, and the optical film 1 is laminated on one surface (the upper surface in the figure) of the polarizer 2, The transparent protective layer 3 is laminated on the other surface (the lower surface in the figure). Since the optical film 1 is a laminate of a birefringent layer and a transparent polymer film layer as described above, any surface may face the polarizer 2, but the transparent polymer film layer When also serving as the transparent protective layer 3, it is preferable that the transparent polymer film layer is in contact with the polarizer. The optical film 1, the polarizer 2 and the transparent protective layer 3 may be laminated by forming an adhesive layer or an adhesive layer between the respective layers, for example.

  The polarizing plate shown in FIG. 2 has the optical film 1, the polarizer 2 and the two transparent protective layers 3 of the present invention, and the transparent protective layers 3 are laminated on both sides of the polarizer 2, respectively. An optical film 1 is further laminated on the protective layer 3. Since the optical film 1 is a laminate of a birefringent layer and a transparent polymer film as described above, any surface may face the transparent protective layer 3.

  In addition, a transparent protective layer may be laminated | stacked on both sides of a polarizer as shown in the figure, and may be laminated | stacked only on either one surface. Moreover, when laminating | stacking on both surfaces, the same kind of transparent protective layer may be used, for example, and a different kind of transparent protective layer may be used.

  The polarizer is not particularly limited, and for example, by dying dichroic substances such as iodine and dichroic dyes on various films by using a conventionally known method, dyeing, crosslinking, stretching, and drying. The prepared one can be used. Among these, a film that transmits linearly polarized light when natural light is incident is preferable, and a film that is excellent in light transmittance and degree of polarization is preferable. Examples of the various films that adsorb the dichroic substance include high hydrophilicity such as polyvinyl alcohol (PVA) film, partially formalized PVA film, ethylene / vinyl acetate copolymer partially saponified film, and cellulose film. In addition to these, for example, polyene oriented films such as PVA dehydrated products and polyvinyl chloride dehydrochlorinated products can be used. Among these, PVA film is preferable. Moreover, although the thickness of the said polarizing film is the range of 1-80 micrometers normally, it is not limited to this.

  The transparent protective layer is not particularly limited, and a conventionally known transparent film can be used. For example, a layer having excellent transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, and the like is preferable. Specific examples of the material for such a transparent protective layer include cellulose resins such as triacetyl cellulose, polyester, polycarbonate, polyamide, polyimide, polyethersulfone, polysulfone, polystyrene, and polynorbornene. Transparent resins such as polyethylene, polyolefin, acrylic, and acetate. Further, examples thereof include thermosetting resins such as acrylic, urethane, acrylic urethane, epoxy, and silicone, or ultraviolet curable resins. Among these, a TAC film whose surface is saponified with alkali or the like is preferable from the viewpoint of polarization characteristics and durability.

  Moreover, as a transparent protective layer, the polymer film as described in Unexamined-Japanese-Patent No. 2001-343529 (WO01 / 37007) is mention | raise | lifted. Examples of the polymer material include a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain. For example, a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer can be used. The polymer film may be, for example, an extruded product of the resin composition.

  Moreover, it is preferable that the said transparent protective layer does not have coloring, for example. Specifically, the retardation value (Rth) in the film thickness direction represented by the following formula is preferably in the range of −90 nm to +75 nm, more preferably −80 nm to +60 nm, and particularly preferably −70 nm. It is in the range of ˜ + 45 nm. When the retardation value is in the range of −90 nm to +75 nm, the coloring (optical coloring) of the polarizing plate due to the protective film can be sufficiently eliminated. In the following formula, nx, ny, and nz are the same as described above, and d indicates the film thickness.

Rth = [(nx + ny) / 2−nz] · d

The transparent protective layer may further have an optical compensation function. As described above, the transparent protective layer having an optical compensation function is intended to prevent coloring or increase the viewing angle for good viewing caused by a change in viewing angle based on a phase difference in a liquid crystal cell, for example. A well-known thing can be used. Specifically, for example, various stretched films obtained by uniaxially or biaxially stretching the above-described transparent resin, alignment films such as liquid crystal polymers, and laminates in which alignment layers such as liquid crystal polymers are arranged on a transparent substrate. It is done. Among these, since it is possible to achieve a wide viewing angle with good visibility, the alignment film of the liquid crystal polymer is preferable, and in particular, the optical compensation layer composed of the inclined alignment layer of the discotic or nematic liquid crystal polymer is used as described above. An optical compensation retardation plate supported by a triacetyl cellulose film or the like is preferable. Examples of such an optical compensation retardation plate include commercially available products such as “WV film” manufactured by Fuji Photo Film Co., Ltd. The optical compensation retardation plate may be one in which optical properties such as retardation are controlled by laminating two or more film supports such as the retardation film and triacetyl cellulose film. The thickness of the transparent protective layer is not particularly limited, and can be appropriately determined according to, for example, the phase difference or the protective strength, but is usually 500 μm or less, preferably 5 to 300 μm, more preferably 5 to 150 μm. It is.

  The transparent protective layer is appropriately formed by a conventionally known method such as a method of applying the various transparent resins to a polarizing film, a method of laminating the transparent resin film, the optical compensation retardation plate, or the like on the polarizing film. It is also possible to use a commercial product.

  The transparent protective layer may be further subjected to, for example, a hard coat treatment, an antireflection treatment, a treatment for preventing sticking or diffusion, antiglare, and the like. The hard coat treatment is for the purpose of preventing scratches on the surface of the polarizing plate, for example, a treatment for forming a cured film having excellent hardness and slipperiness composed of a curable resin on the surface of the transparent protective layer. It is. As the curable resin, for example, a silicone-based, urethane-based, acrylic-based, or epoxy-based ultraviolet curable resin can be used, and the treatment can be performed by a conventionally known method. The purpose of preventing sticking is to prevent adhesion between adjacent layers. The antireflection treatment is intended to prevent reflection of external light on the surface of the polarizing plate, and can be performed by forming a conventionally known antireflection layer or the like.

  The anti-glare treatment is intended to prevent visual interference of the light transmitted through the polarizing plate due to reflection of external light on the surface of the polarizing plate, for example, on the surface of the transparent protective layer by a conventionally known method, This can be done by forming a fine uneven structure. Examples of a method for forming such a concavo-convex structure include a roughening method by sandblasting or embossing, a method of forming the transparent protective layer by blending transparent fine particles in the transparent resin as described above, and the like. It is done.

  Examples of the transparent fine particles include silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, and the like. In addition, conductive inorganic fine particles, crosslinked or uncrosslinked Organic fine particles composed of polymer particles and the like can also be used. The average particle size of the transparent fine particles is not particularly limited, but is, for example, in the range of 0.5 to 20 μm. The blending ratio of the transparent fine particles is not particularly limited, but is generally preferably in the range of 2 to 70 parts by mass and more preferably in the range of 5 to 50 parts by mass per 100 parts by mass of the transparent resin as described above.

The antiglare layer containing the transparent fine particles can be used as, for example, the transparent protective layer itself, or may be formed as a coating layer on the surface of the transparent protective layer. Furthermore, the anti-glare layer may also serve as a diffusion layer (visual compensation function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.
The antireflection layer, anti-sticking layer, diffusion layer, anti-glare layer, etc. are laminated on the polarizing plate as an optical layer composed of, for example, a sheet provided with these layers, separately from the transparent protective layer. May be.

  The method for laminating the components (optical film, polarizer, transparent protective layer, etc.) is not particularly limited, and can be performed by a conventionally known method. In general, the same pressure-sensitive adhesives and adhesives as described above can be used, and the type thereof can be appropriately determined depending on the material of each component. Examples of the adhesive include polymer adhesives such as acrylic, vinyl alcohol, silicone, polyester, polyurethane, and polyether, and rubber adhesives. Further, an adhesive composed of a water-soluble crosslinking agent of vinyl alcohol polymers such as glutaraldehyde, melamine and oxalic acid can be used. The pressure-sensitive adhesives and adhesives as described above are hardly peeled off due to, for example, the influence of humidity and heat, and are excellent in light transmittance and degree of polarization. Specifically, when the polarizer is a PVA-based film, for example, a PVA-based adhesive is preferable from the viewpoint of the stability of the adhesion treatment. These adhesives and pressure-sensitive adhesives may be applied to the surface of the polarizer or the transparent protective layer as they are, for example, or a layer such as a tape or sheet composed of the adhesive or pressure-sensitive adhesive is disposed on the surface. May be. For example, when prepared as an aqueous solution, other additives and catalysts such as acids may be blended as necessary. In addition, when apply | coating the said adhesive agent, you may mix | blend another additive and catalysts, such as an acid, with the said adhesive agent aqueous solution, for example. The thickness of such an adhesive layer is not particularly limited, but is, for example, 1 nm to 500 nm, preferably 10 nm to 300 nm, and more preferably 20 nm to 100 nm. The method is not particularly limited, and for example, a conventionally known method using an adhesive such as an acrylic polymer or a vinyl alcohol polymer can be employed. In addition, an adhesive containing a water-soluble cross-linking agent of PVA polymer such as glutaraldehyde, melamine, oxalic acid and the like can be obtained because it can form a polarizing plate that is hardly peeled off by humidity, heat, etc. and has excellent light transmittance and polarization degree. preferable. These adhesives can be used by, for example, applying the aqueous solution to the surface of each component and drying. In the aqueous solution, for example, other additives and a catalyst such as an acid can be blended as necessary. Among these, as the adhesive, a PVA adhesive is preferable from the viewpoint of excellent adhesiveness with a PVA film.

  In addition to the polarizer as described above, the optical film of the present invention can be used in combination with conventionally known optical members such as various retardation plates, diffusion control films, brightness enhancement films, and the like. Examples of the retardation plate include a uniaxially or biaxially stretched polymer film, a Z-axis aligned treatment, a liquid crystalline polymer coating film, and the like. Examples of the diffusion control film include films utilizing diffusion, scattering, and refraction, and these can be used for, for example, control of viewing angle, glare related to resolution, and control of scattered light. As the brightness enhancement film, for example, a brightness enhancement film using selective reflection of a cholesteric liquid crystal and a quarter wavelength plate (λ / 4 plate), a scattering film using anisotropic scattering by the polarization direction, or the like is used. it can. Moreover, the said optical film can also be combined with a wire grid type polarizer, for example.

  In practical use, the polarizing plate of the present invention may further contain other optical layers in addition to the optical film of the present invention. Examples of the optical layer include conventionally known various optical layers used for forming a liquid crystal display device and the like such as a polarizing plate, a reflecting plate, a transflective plate, and a brightness enhancement film as shown below. One kind of these optical layers may be used, two or more kinds may be used in combination, one layer may be used, or two or more layers may be laminated. The laminated polarizing plate further including such an optical layer is preferably used as an integrated polarizing plate having an optical compensation function, for example, and is suitable for use in various image display devices such as being disposed on the surface of a liquid crystal cell. ing.

Hereinafter, such an integrated polarizing plate will be described.
First, an example of a reflective polarizing plate or a transflective polarizing plate will be described. The reflective polarizing plate further includes a reflective plate on the laminated polarizing plate of the present invention, and the transflective polarizing plate further includes a semi-transmissive reflective plate stacked on the laminated polarizing plate of the present invention.

  The reflective polarizing plate is usually disposed on the back side of a liquid crystal cell, and can be used for a liquid crystal display device (reflective liquid crystal display device) of a type that reflects incident light from the viewing side (display side). Such a reflective polarizing plate, for example, has an advantage that the liquid crystal display device can be thinned because the built-in light source such as a backlight can be omitted.

  The reflective polarizing plate can be produced by a conventionally known method such as a method of forming a reflective plate made of metal or the like on one surface of a polarizing plate exhibiting the elastic modulus. Specifically, for example, one surface (exposed surface) of the transparent protective layer in the polarizing plate is mat-treated as necessary, and a metal foil or a vapor deposition film made of a reflective metal such as aluminum is formed on the surface as a reflection plate. The reflective polarizing plate formed as follows.

  In addition, as described above, a reflective polarizing plate or the like in which a reflecting plate reflecting the fine uneven structure is formed on a transparent protective layer containing fine particles in various transparent resins and having a fine uneven structure on the surface. It is done. A reflector having a fine concavo-convex structure on its surface has an advantage that, for example, incident light can be diffused by irregular reflection to prevent directivity and glaring appearance and to suppress uneven brightness. Such a reflector is, for example, directly on the uneven surface of the transparent protective layer by a conventionally known method such as a vacuum deposition method, an ion plating method, a sputtering method, or a plating method. It can form as a metal vapor deposition film.

  In addition, instead of the method of directly forming the reflective plate on the transparent protective layer of the polarizing plate as described above, a reflective sheet having a reflective layer provided on a suitable film such as the transparent protective film is used as the reflective plate. May be. Since the reflective layer in the reflective plate is usually composed of metal, for example, from the viewpoint of preventing the decrease in reflectance due to oxidation, and thus the long-term persistence of the initial reflectance, and the separate formation of a transparent protective layer, etc. The usage form is preferably a state in which the reflective surface of the reflective layer is covered with the film, a polarizing plate or the like.

  On the other hand, the transflective polarizing plate has a transflective reflective plate instead of the reflective plate in the reflective polarizing plate. Examples of the transflective reflector include a half mirror that reflects light through a reflective layer and transmits light.

  The transflective polarizing plate is usually provided on the back side of a liquid crystal cell. When a liquid crystal display device or the like is used in a relatively bright atmosphere, the incident light from the viewing side (display side) is reflected to display an image. In a relatively dark atmosphere, it can be used for a liquid crystal display device of a type that displays an image using a built-in light source such as a backlight built in the back side of the transflective polarizing plate. That is, the transflective polarizing plate can save the energy of using a light source such as a backlight in a bright atmosphere, and can be used with the built-in light source in a relatively dark atmosphere. It is useful for the formation of etc.

  Next, an example of a polarizing plate in which a brightness enhancement film is further laminated on the polarizing plate of the present invention will be described.

  The brightness enhancement film is not particularly limited, and for example, a linear multi-layer thin film of dielectric material or a multi-layer laminate of thin film films having different refractive index anisotropy transmits linearly polarized light having a predetermined polarization axis, Other light can be used that reflects light. As such a brightness enhancement film, for example, trade name “D-BEF” manufactured by 3M Co., Ltd. may be mentioned. Also, a cholesteric liquid crystal layer, in particular an oriented film of a cholesteric liquid crystal polymer, or a film in which the oriented liquid crystal layer is supported on a film substrate can be used. These reflect the right and left circularly polarized light and transmit the other light. For example, the product name “PCF350” manufactured by Nitto Denko Corporation, the product name “Transmax” manufactured by Merck, etc. can give.

  The various polarizing plates of the present invention as described above may be, for example, an optical member obtained by laminating the polarizing plate of the present invention and two or more optical layers.

  An optical member in which two or more optical layers are laminated in this manner can be formed by a method of sequentially laminating separately, for example, in the manufacturing process of a liquid crystal display device or the like. There are advantages such as excellent quality stability and assembly workability, and improvement in manufacturing efficiency of liquid crystal display devices and the like. For the lamination, various adhesive means such as an adhesive layer can be used as described above.

  The various polarizing plates as described above preferably have a pressure-sensitive adhesive layer or an adhesive layer because they can be easily laminated on other members such as a liquid crystal cell. It can be placed on one or both sides of the plate. The material of the adhesive layer is not particularly limited, and a conventionally known material such as an acrylic polymer can be used. In particular, foaming and peeling due to moisture absorption are prevented, optical characteristics are deteriorated due to a difference in thermal expansion, and a liquid crystal cell is warped. For example, it is preferable to form a pressure-sensitive adhesive layer having a low moisture absorption rate and excellent heat resistance, for example, from the viewpoints of prevention, and hence formability of a liquid crystal display device having high quality and excellent durability. Moreover, the adhesion layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient. The pressure-sensitive adhesive layer is formed on the surface of the polarizing plate by, for example, adding a solution or a melt of various pressure-sensitive adhesive materials directly to a predetermined surface of the polarizing plate by a developing method such as casting or coating. In the same manner, a pressure-sensitive adhesive layer is formed on a separator, which will be described later, and transferred to a predetermined surface of the polarizing plate. Such a layer may be formed on any surface of the polarizing plate, for example, on the exposed surface of the retardation plate in the polarizing plate.

  Thus, when the surface of the pressure-sensitive adhesive layer or the like provided on the polarizing plate is exposed, it is preferable to cover the surface with a separator for the purpose of preventing contamination until the pressure-sensitive adhesive layer is put to practical use. This separator is formed on a suitable film such as the above-mentioned transparent protective film by a method of providing one or more release coats with a release agent such as silicone, long chain alkyl, fluorine, molybdenum sulfide, etc., if necessary. it can.

  For example, the pressure-sensitive adhesive layer may be a single layer or a laminate. As the laminate, for example, a laminate in which different compositions and different types of single layers are combined can be used. Moreover, when arrange | positioning on the both surfaces of the said polarizing plate, the same adhesive layer may respectively be sufficient, for example, a different composition and a different kind of adhesive layer may be sufficient.

  The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to, for example, the configuration of the polarizing plate, and is generally 1 to 500 μm.

  As the pressure-sensitive adhesive that forms the pressure-sensitive adhesive layer, for example, one that is excellent in optical transparency and exhibits appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties is preferable. Specific examples include pressure-sensitive adhesives prepared by appropriately using polymers such as acrylic polymers, silicone polymers, polyesters, polyurethanes, polyethers, and synthetic rubbers as base polymers.

  Control of the adhesive property of the pressure-sensitive adhesive layer is, for example, the degree of cross-linking depending on the composition and molecular weight of the base polymer forming the pressure-sensitive adhesive layer, the crosslinking method, the content ratio of the crosslinkable functional group, the blending ratio of the crosslinking agent, and the like. It can be suitably carried out by a conventionally known method such as adjusting the molecular weight.

  The optical film and polarizing plate of the present invention as described above, and various layers such as a polarizing film, a transparent protective layer, an optical layer, and a pressure-sensitive adhesive layer forming various optical members (various polarizing plates laminated with optical layers) are, for example, salicylic acid. It may have an ultraviolet absorbing ability by appropriately treating with an ultraviolet absorber such as an ester compound, a benzophenone compound, a benzotriazole compound, a cyanoacrylate compound, or a nickel complex salt compound.

  As described above, the optical film or polarizing plate of the present invention is preferably used for forming various devices such as a liquid crystal display device. For example, the optical film or polarizing plate of the present invention is disposed on one side or both sides of a liquid crystal cell. Thus, a liquid crystal panel can be used for a liquid crystal display device such as a reflective type, a transflective type, or a transmissive / reflective type.

  The type of the liquid crystal cell forming the liquid crystal display device can be arbitrarily selected, for example, an STN (Super Twisted Nematic) cell, a TN (Twisted Nematic) cell, an IPS (In-Plane Switching) cell, a VA (Vertical Alighned) cell, OCB (Optically Alighned Birefringence) cell, HAN (Hybrid Alighned Nematic) cell, ASM (Axially Symmetric Alighned Microcell) cell, ferroelectric / antiferroelectric cell and those with regular alignment division, random alignment division Various cells such as objects are included. Among these, the optical film and polarizing plate of the present invention are extremely useful for optical compensation of VA cells and OCB cells, and are very useful as viewing angle compensation films for VA mode and OCB mode liquid crystal display devices. is there.

  In addition, the liquid crystal cell has a structure in which liquid crystal is usually injected into a gap between opposing liquid crystal cell substrates, and the liquid crystal cell substrate is not particularly limited, and for example, a glass substrate or a plastic substrate can be used. The material for the plastic substrate is not particularly limited, and conventionally known materials can be used.

  Moreover, when providing a polarizing plate and an optical member on both surfaces of a liquid crystal cell, they may be the same kind and may differ. Furthermore, when forming the liquid crystal display device, for example, appropriate components such as a prism array sheet, a lens array sheet, a light diffusing plate, and a backlight can be arranged in one or more layers at appropriate positions.

  Furthermore, the liquid crystal display device of the present invention includes a liquid crystal panel, and is not particularly limited except that the liquid crystal panel of the present invention is used as the liquid crystal panel. In the case of including a light source, the light source is not particularly limited. However, for example, a planar light source that emits polarized light is preferable because light energy can be used effectively.

  An example of the liquid crystal panel of the present invention is shown in the sectional view of FIG. As shown in the figure, the liquid crystal panel has a liquid crystal cell 21, an optical film 1, a polarizer 2, and a transparent protective layer 3. The optical film 1 is laminated on one surface of the liquid crystal cell 21, and an optical The polarizer 2 and the transparent protective layer are laminated in this order on the other surface. The liquid crystal cell has a configuration in which liquid crystal is held between two liquid crystal cell substrates (not shown). The optical film 1 is a laminate of a birefringent layer and a transparent polymer film layer as described above, the birefringent layer side facing the liquid crystal cell 21, and the transparent polymer film side facing the polarizer 2. is doing.

  In the liquid crystal display device of the present invention, for example, a diffusion plate, an antiglare layer, an antireflection film, a protective layer and a protective plate are further arranged on the viewing-side optical film (polarizing plate), or a liquid crystal cell in a liquid crystal panel. A compensation retardation plate or the like may be appropriately disposed between the polarizing plate and the polarizing plate.

  In addition, the optical film and polarizing plate of this invention are not limited to the above liquid crystal display devices, For example, it can be used also for self-luminous display devices, such as an organic electroluminescent (EL) display, PDP, and FED. When used in a self-luminous flat display, for example, by setting the in-plane retardation value Δnd of the birefringent optical film of the present invention to λ / 4, circularly polarized light can be obtained. Available.

  Hereinafter, an electroluminescence (EL) display device including the polarizing plate of the present invention will be described. The EL display device of the present invention is a display device having the optical film or polarizing plate of the present invention, and this EL device may be either organic EL or inorganic EL.

  In recent years, it has been proposed to use, for example, an optical film such as a polarizer or a polarizing plate together with a λ / 4 plate in an EL display device as an antireflection from an electrode in a black state. The polarizer or optical film of the present invention is slanted even when linearly polarized light, circularly polarized light or elliptically polarized light is emitted from the EL layer or when natural light is emitted in the front direction. This is very useful when the emitted light in the direction is partially polarized.

  First, a general organic EL display device will be described here. The organic EL display device generally has a light emitter (organic EL light emitter) in which a transparent electrode, an organic light emitting layer, and a metal electrode are laminated in this order on a transparent substrate. The organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative or the like and a light emitting layer made of a fluorescent organic solid such as anthracene, or the like. Various combinations such as a laminate of a light-emitting layer and an electron injection layer made of a perylene derivative, or a laminate of the hole injection layer, the light-emitting layer, and the electron injection layer can be given.

  In such an organic EL display device, by applying a voltage to the anode and the cathode, holes and electrons are injected into the organic light emitting layer, and the holes and electrons are recombined. The generated energy emits light on the principle that it excites the phosphor and emits light when the excited phosphor returns to the ground state. The mechanism of recombination of holes and electrons is the same as that of a general diode, and current and emission intensity show strong nonlinearity with rectification with respect to applied voltage.

  In the organic EL display device, in order to extract light emitted from the organic light emitting layer, at least one of the electrodes needs to be transparent. Therefore, the organic EL display device is usually formed of a transparent conductor such as indium tin oxide (ITO). A transparent electrode is used as the anode. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode. Usually, metal electrodes such as Mg—Ag and Al—Li are used.

  In the organic EL display device having such a configuration, the organic light emitting layer is preferably formed of an extremely thin film having a thickness of about 10 nm, for example. This is because the organic light-emitting layer transmits light almost completely as in the transparent electrode. As a result, at the time of non-light emission, the light incident from the surface of the transparent substrate, transmitted through the transparent electrode and the organic light emitting layer, and reflected by the metal electrode again returns to the surface side of the transparent substrate. For this reason, when viewed from the outside, the display surface of the organic EL display device looks like a mirror surface.

  The organic EL display device of the present invention is, for example, an organic EL display device including the organic EL light emitting device including a transparent electrode on a front surface side of the organic light emitting layer and a metal electrode on a back surface side of the organic light emitting layer. The optical film (polarizing plate or the like) of the present invention is preferably disposed on the surface of the transparent electrode, and a λ / 4 plate is preferably disposed between the polarizing plate and the EL element. Thus, by arranging the optical film of the present invention, it becomes an organic EL display device that has the effect of suppressing reflection from the outside and improving the visibility. Moreover, it is preferable that a phase difference plate is further disposed between the transparent electrode and the optical film.

  For example, the retardation film and the optical film (polarizing plate, etc.) have a function of polarizing the light incident from the outside and reflected by the metal electrode, so that the mirror surface of the metal electrode is visually recognized from the outside by the polarization action. There is an effect of not letting it. In particular, if a quarter-wave plate is used as a retardation plate and the angle formed by the polarization direction of the polarizing plate and the retardation plate is adjusted to π / 4, the mirror surface of the metal electrode is completely shielded. can do. That is, only the linearly polarized light component of the external light incident on the organic EL display device is transmitted by the polarizing plate. The linearly polarized light becomes generally elliptically polarized light by the retardation plate, but becomes circularly polarized light particularly when the retardation plate is a quarter wavelength plate and the angle is π / 4.

  For example, this circularly polarized light is transmitted through the transparent substrate, the transparent electrode, and the organic thin film, reflected by the metal electrode, again transmitted through the organic thin film, the transparent electrode, and the transparent substrate, and again by the retardation plate. Become. And since this linearly polarized light is orthogonal to the polarization direction of the polarizing plate, it cannot pass through the polarizing plate, and as a result, the mirror surface of the metal electrode can be completely shielded as described above. .

  Next, examples of the present invention will be described together with comparative examples. However, the present invention is not limited to the following examples. In the following examples and the like, the characteristics of the optical film were evaluated by the following methods.

(Measurement of phase difference value Δnd, orientation axis accuracy)
The retardation value Δnd and the orientation axis accuracy were measured using a retardation meter (trade name KOBRA21ADH, manufactured by Oji Scientific Instruments).

(Measurement of refractive index)
The refractive index was measured at 590 nm using a trade name KOBRA21ADH manufactured by Oji Scientific Instruments.

(Film thickness measurement)
The film thickness was measured using an Anritsu brand name digital micrometer K-351C type.

  Weight average molecular weight synthesized from 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride and 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl ( Mw) A polyimide having 70,000 and a birefringence (Δn) of about 0.04 was dissolved in MIBK (methyl isobutyl ketone) to obtain a solution having a solid content concentration of 15% by weight. This solution was applied on a triacetylcellulose (TAC) film having a thickness of 75 μm that was stretched 1.3 times at 150 ° C. by fixed-end transverse stretching. Δnd of this TAC film was 20 nm. Thereafter, the solution was evaporated and removed by heating at 100 ° C. for 10 minutes to form a layer, and the TAC film was contracted to contract the layer to obtain a completely transparent and smooth optical film. . The optical properties of the obtained birefringent layer were nx> ny> nz.

(Comparative Example 1)
The same solution as in Example 1 was used, and this was applied onto a PET film having a thickness of 75 μm and Δnd = 4000 nm. Thereafter, the solution was subjected to solvent evaporation removal at 150 ° C. for 10 minutes to form a birefringent layer to obtain a completely transparent and smooth optical film. The birefringent layer of this optical film had optical characteristics of nx = ny> nz. However, since the in-plane retardation of the PET film is too large, there is a problem with the optical characteristics of the optical film, and it is necessary to peel off the birefringent layer from the PET film and transfer it to an optical member such as a polarizer. It was.

(Comparative Example 2)
The same solution as in Example 1 was applied on a TAC film having a thickness of 150 μm that was stretched 1.5 times by free end longitudinal stretching at 150 ° C. Δnd of this TAC film was 70 nm. Thereafter, the solution was subjected to solvent evaporation removal at 100 ° C. for 10 minutes to form a birefringent layer to obtain a completely transparent and smooth optical film. The birefringent layer of this optical film had optical characteristics of nx = ny> nz. However, since the in-plane retardation of the TAC film is too large, there is a problem with the optical characteristics of the optical film, and it is necessary to peel off the birefringent layer from the TAC film and transfer it to an optical member such as a polarizer. It was.

  For the optical films obtained in the above Examples and Comparative Examples, the thickness, the in-plane retardation A (Δnd) of the optical film, the in-plane retardation B (Δnd) of the transparent polymer film, and the birefringence of the birefringent layer Table 1 below shows the results of examining the refractive index (Δn (a)) and the birefringence (Δn (b)) of the transparent polymer film.

(Table 1)
Thickness (μm) A (Δnd) B (Δnd) Δn (a) Δn (b)
Example 1 6 135 20 0.04 0.0006
Comparative Example 1 6 0.9 4000 0.04 0.08
Comparative Example 2 6 150 70 0.04 0.0007

  About the optical film obtained by the said each Example and the comparative example, it investigated about the liquid crystal display characteristic (LCD display characteristic). That is, first, an optical film and a polarizing plate (manufactured by Nitto Denko Corporation, trade name “HEG1425DU”) were laminated via an acrylic adhesive to obtain an optical compensation layer integrated polarizing plate. This was adhered to the backlight side of the liquid crystal cell so that the polarizing plate was on the outside, thereby producing a liquid crystal display device. Then, the front contrast of the liquid crystal display device was examined. The results are shown in Table 2 below. Further, for Example 1 and Comparative Example 1, the presence or absence of rainbow unevenness was examined. The results are shown in the photographs of FIG. 5 (Example 1) and FIG. 6 (Comparative Example 1). The front contrast was measured by the following method.

(Front contrast)
A white image and a black image were displayed on the liquid crystal display device, and the Y value, the x value, and the y value of the XYZ display system on the front surface of the display screen were measured by a product name Ez contrast 160D (manufactured by ELDIM). Then, the front (viewing angle 0 °) contrast (YW / YB) was calculated from the Y value (YW) in the white image and the Y value (YB) in the black image.

(Table 2)
Front contrast *
Example 1 ○
Comparative Example 1 ×
Comparative Example 2 ×
* A contrast of 100 or more was given as ◯, and a contrast of less than 100 as x.

  As shown in Table 2, all examples were excellent in contrast. In contrast, the comparative example had a problem with contrast. Moreover, as shown in FIG. 5, in Example 1, the rainbow nonuniformity did not generate | occur | produce. In contrast, as shown in FIG. 6, in Comparative Example 1, rainbow unevenness occurred.

  As described above, the optical film of the present invention is excellent in optical properties and can be produced easily and at low cost. Therefore, the optical film of the present invention is useful as an optical member of a display device such as a liquid crystal display device or a self-luminous display device.

It is a cross-sectional schematic diagram which shows an example of the polarizing plate of this invention. It is a cross-sectional schematic diagram which shows the other example of the polarizing plate of this invention. It is a cross-sectional schematic diagram which shows an example of the liquid crystal display device of this invention. It is a figure which shows an example of the axial direction of the optical film of this invention. It is the photograph which evaluated the rainbow nonuniformity in one Example of the optical film of this invention. It is the photograph which evaluated the rainbow nonuniformity in the optical film of a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Birefringent layer 2 ... Polarizer 3 ... Protective film 11 ... Polarizing plate 21 ... Liquid crystal cell

Claims (8)

A method for producing an optical film in which a transparent polymer film layer and a birefringent layer are laminated, and a transparent polymer film made of a cellulose resin having an in-plane retardation of 50 nm or less is prepared. Applying a solution containing a polymer polyimide and methyl isobutyl ketone, forming a birefringent layer by evaporating and removing the solvent in the solution, a laminate of the transparent polymer film layer and the birefringent layer , By shrinking , the birefringent layer is made to satisfy the condition of the following formula (1), the birefringence Δn (a) of the birefringent layer and the birefringence Δn (b of the transparent polymer film layer) ) Forms the both layers so as to satisfy the condition of the following formula (2).

nx>ny> nz (1)
Δn (a)> Δn (b) × 10 (2)

In the formula (1), nx, ny, and nz represent refractive indexes in the X-axis direction, the Y-axis direction, and the Z-axis direction, respectively, in the birefringent layer. The X-axis direction is an axial direction showing the maximum refractive index in the plane of the birefringent layer, and the Y-axis direction is an axial direction perpendicular to the X-axis direction in the plane, The Z-axis direction indicates a thickness direction perpendicular to the X-axis direction and the Y-axis direction. The manufacturing method according to claim 1, wherein the polyimide is a polyimide represented by the following general formula (3).

The manufacturing method according to claim 1, wherein the polyimide is a polyimide represented by the following general formula (6).

As the transparent polymer film layer, a transparent polymer film having in-plane shrinkage in one direction is used, and the solution is applied onto the film and then dried to utilize the in-plane shrinkage of the transparent polymer film. And the manufacturing method as described in any one of Claims 1-3 which gives the difference of an in-plane refractive index to the said birefringent layer formed. The manufacturing method as described in any one of Claims 1-4 which makes the birefringence ((DELTA) n) of the whole optical film the range of 0.0005-0.5. The production method according to claim 1, wherein the resin forming the transparent polymer film layer is triacetyl cellulose. The manufacturing method as described in any one of Claims 1-6 which manufactures the said transparent polymer film layer by extending | stretching, after forming the forming material resin into a film form. The manufacturing method according to any one of claims 1 to 7, wherein the transparent polymer film layer is a single layer, and an in-plane retardation thereof exceeds 0 and is 50 nm or less.

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