JP2006139105A - Optical film and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film having excellent characteristics of a polyurethane resin and birefringence, an optical film obtained by combining a transparent base film or other birefringent film with a birefringent film formed from the polyurethane resin, and also to provide a liquid crystal display device or the like provided with the optical film. <P>SOLUTION: The optical film includes at least the polyurethane based film having 10-100 μm thickness as a 1st birefringent layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an optical film and a liquid crystal display device including the optical film.

Conventionally, for example, when producing a polarizing plate composed of a polarizer and a transparent protective film, a polyurethane-based resin is mainly used as an adhesive for bonding the polarizer and the transparent protective film.
The reason is that the polyurethane-based resin has good adhesion, high moisture resistance, and excellent transparency.

  Due to the excellent properties of such polyurethane resins, it can be considered to be used as an optical film. However, at present, no film formed from such polyurethane resins exhibits birefringence. is there.

  The present invention provides a film having excellent properties and birefringence of a polyurethane resin, and also has birefringence formed from a transparent base film or other birefringent film and the polyurethane resin. It is an object to provide an optical film combined with a film, a liquid crystal display device including the optical film, and the like.

  As a result of intensive research to solve the above-mentioned problems, the inventors have developed a birefringence by forming a polyurethane-based resin whose birefringence has not been confirmed at present into a film having a predetermined thickness. As a result, the present invention has been completed.

  That is, the present invention provides an optical film comprising a polyurethane-based film having a thickness of 10 to 100 μm as at least the first birefringent layer.

  Birefringence is expressed by molding a polyurethane resin into a film having a thickness of 10 to 100 μm.

  The optical film of the present invention has excellent properties and birefringence of a polyurethane resin.

The optical film according to the present invention will be described.
The optical film of the present invention comprises at least a first birefringent layer, which is a polyurethane film having a thickness of 10 to 100 μm, as a birefringent layer.

  Examples of polyurethane resins used as raw materials for polyurethane films include modified polyester urethanes, water-dispersed polyester urethanes, solvent-based polyester urethanes, polyether-based urethanes, polycarbonate-based urethanes, etc., or self-emulsifying types and forced emulsifying types of the above resins. Examples thereof include resins. The polyurethane resin is generally produced from a polyol and a polyisocyanate.

  Examples of the polyol include polyester polyol, polyether polyol, and other polyols.

  The polyester polyol is a reaction product of a fatty acid and a polyol. Examples of the fatty acid include ricinoleic acid, oxycaproic acid, oxycapric acid, oxyundecanoic acid, oxylinoleic acid, oxystearic acid, and oxyhexanedecenoic acid. Examples thereof include hydroxy-containing long chain fatty acids. Examples of polyols that react with fatty acids include glycols such as ethylene glycol, propylene glycol, butylene glycol, hexamethylene glycol and diethylene glycol, trifunctional polyols such as glycerin, trimethylolpropane and triethanolamine, and tetrafunctionals such as diglycerin and pentaerythritol. Polyols, hexafunctional polyols such as sorbitol, octafunctional polyols such as sugar, addition polymerization products of alkylene oxides corresponding to these polyols with aliphatic, alicyclic and aromatic amines, and the alkylene oxides and polyamide polyamines. Examples include addition polymerization products.

  Examples of the polyether polyol include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, 4,4′-dihydroxyphenylpropane, and 4,4′-dihydroxyphenylmethane. Trivalent or higher polyhydric alcohol such as divalent alcohol such as glycerin, 1,1,1-trimethylolpropane, 1,2,5-hexanetriol, pentaerythritol, and Examples include addition polymerization products with alkylene oxides such as oxide, propylene oxide, butylene oxide, and α-olefin oxide.

  Other polyols include those whose main chain is carbon-carbon, such as acrylic polyol, polybutadiene polyol, polyisoprene polyol, hydrogenated polybutadiene polyol, AN (acrylonitrile) and SM. Examples thereof include a polyol obtained by graft polymerization of (styrene monomer) onto the carbon-carbon polyol described above, a polycarbonate polycarbonate, and PTMG (polytetramethylene glycol).

  Examples of the polyisocyanate include aromatic polyisocyanate, aliphatic polyisocyanate, alicyclic polyisocyanate and the like. Examples of the aromatic polyisocyanate include diphenylmethane diisocyanate (MDI), polymethylene polyphenylene polyisocyanate (crude MDI), tolylene diisocyanate (TDI), and polytolylene polyisocyanate. (Crude TDI), xylene diisocyanate (XDI), naphthalene diisocyanate (NDI) and the like. Examples of the aliphatic polyisocyanate include hexamethylene diisocyanate (HDI). Examples of the alicyclic polyisocyanate include isophorone diisocyanate (IPDI). In addition, polyisocyanate obtained by modifying the above polyisocyanate with carbodiimide (carbodiimide-modified polyisocyanate), isocyanurate-modified polyisocyanate, urethane prepolymer (for example, reaction between polyol and excess polyisocyanate) And products having an isocyanate group at the molecular end). These may be used alone or as a mixture.

The polyurethane-based film of the present embodiment is a polyurethane-based resin film having a thickness of 10 to 100 μm.
When the thickness is less than 10 μm, the in-plane retardation (Δnd) and the thickness retardation (Rth) do not appear and the birefringent film does not function.
Further, when the thickness exceeds 100 μm, a phase difference appears, but there is a problem in terms of thinness and weight reduction.
The thickness direction retardation (Rth) is calculated according to the following equation.
Rth = (nx−nz) × d
In the formula, nx is the refractive index in the slow axis direction in the plane of the optical film (maximum refractive index in the plane), nz is the refractive index in the thickness direction, and d is the thickness (nm) of the optical film. is there.
The in-plane retardation (Δnd) is calculated according to the following formula.
Δnd = (nx−ny) × d
In the equation, nx is a refractive index in the slow axis direction in the plane of the optical film (maximum refractive index in the plane), ny is a refractive index in a direction perpendicular to the slow axis in the plane, and d is optical It is the thickness (nm) of the film.
In addition, the polyurethane-type film of this embodiment has the optical characteristic of what is called a negative C plate which has a relationship of nx≈ny> nz when not stretched.
By stretching or shrinking the unstretched film having a relationship of nx≈ny> nz while heating, an optically biaxial film having a relationship of nx>ny> nz is obtained.

The polyurethane film of the present embodiment has a birefringence Δn = 0.0001 to 0.001, preferably 0.0005 to 0.0008.
If the birefringence index Δn is in the range of 0.0001 to 0.001, the optimum thickness direction retardation (Rth) and in-plane retardation (Δnd) can be obtained. In addition, the weight can be reduced.
The birefringence is measured by the method described in the examples.

  As a method for forming the polyurethane-based resin into a film having a predetermined thickness, for example, the polyurethane resin is dissolved in a solvent, adjusted to a predetermined solution concentration, applied onto a substrate, and then dried under a predetermined temperature condition to be transparent. A smooth film or a self-emulsifying type or forced emulsifying type polyurethane resin solution is added to a solvent, adjusted to a predetermined solution concentration, coated on a substrate, and then dried under a predetermined temperature condition. There is a method of making a transparent and smooth film.

  The concentration of the solution may be determined as appropriate, but in consideration of applicability to the substrate (contamination of foreign matter, unevenness and streaks during coating), usually 5 to 50% by weight, preferably 10 to 40% by weight. can do. If the solution concentration is less than 5% by weight, the solution viscosity is too low, so that it is difficult to apply up to a predetermined film thickness, and if it exceeds 50% by weight, the solution viscosity is too high and the coating surface becomes rough. Such a problem may occur.

  The solvent for dissolving the polyurethane resin can be appropriately selected according to the polyurethane resin to be used. Specifically, for example, halogenated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, o-dichlorobenzene, phenols such as phenol and parachlorophenol, benzene, Aromatic hydrocarbons such as toluene, xylene, methoxybenzene, 1,2-dimethoxybenzene, acetone, ethyl acetate, t-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol , Dipropylene glycol, 2-methyl-2,4-pentanediol, ethyl cellosolve, butyl cellosolve, 2-pyrrolidone, N-methyl-2-pyrrole , Pyridine, triethylamine, dimethylformamide, dimethylacetamide, acetonitrile, butyronitrile, methyl isobutyl ketone, methyl ether ketone, cyclopentanone, carbon disulfide, methanol, ethanol, isopropyl alcohol, water, and a mixed solvent thereof are used. .

The method for applying the solution onto the substrate is not particularly limited, and can be performed by a spin coating method, a roll coating method, a die coating method, a blade coating method, or the like. The film can be obtained by arranging the solution on the substrate so that the resulting film has a desired film thickness by these methods and then drying the solution. Although drying temperature can be suitably selected according to the kind etc. of solvent, Usually, 80-200 degreeC, Preferably it can be set as 100-150 degreeC. Drying may be performed at a constant temperature or may be performed by increasing the temperature stepwise.
The drying time is usually 5 to 30 minutes, preferably 10 to 20 minutes. If the drying time is less than 5 minutes, a large amount of solvent may remain, causing a problem in product reliability. If it exceeds 30 minutes, it is not suitable for industrial productivity.

  The optical film of the present invention may further include a transparent substrate film in addition to the birefringent film formed from the polyurethane resin.

As the transparent substrate film, those having excellent transparency, mechanical strength, thermal stability, moisture shielding property, isotropy and the like are preferable. Examples of the material for the transparent base film include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, polystyrene, acrylonitrile / styrene copolymer Examples thereof include styrene polymers such as coalesced (AS resin), polycarbonate polymers and the like.
In addition, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Examples thereof include polymer blends.

  Various additives, such as a light stabilizer, a ultraviolet absorber, antioxidant, a filler, can be mix | blended with the said transparent base film as needed. Moreover, well-known surface modification processes, such as a corona process, can also be performed.

  The thickness of the transparent substrate film is not particularly limited, but is preferably about 3 to 300 μm, and particularly preferably about 10 to 100 μm.

In the case of further laminating a transparent base film on a film showing birefringence formed from a polyurethane-based resin, a coating solution prepared from the polyurethane-based resin is directly applied on the transparent base film, A film having a predetermined thickness of birefringence can be laminated.
Moreover, the film which shows the birefringence formed from a polyurethane-type resin, and a transparent base film can also be laminated | stacked using a well-known adhesive agent or an adhesive.
As the adhesive or pressure-sensitive adhesive, for example, acrylic, silicone, or isocyanate can be used.

  The optical film of the present invention is at least selected from the group consisting of polyamide, polyimide, polyester, polyether ketone, polyamideimide and polyesterimide as the second birefringent layer which is a layer different from the first birefringent layer. A birefringent film formed from a kind of polymer may be further included.

As a material for the birefringent film, for example, a non-liquid crystal material, particularly a non-liquid crystal polymer can be preferably used. The non-liquid crystalline material is different from the liquid crystalline material, and forms a film exhibiting optical uniaxiality of nx> nz and ny> nz by its own property regardless of the orientation of the applied substrate. is there. For this reason, even if the said film (base material) is a non-orientation thing, the process of apply | coating an orientation film on the surface, the process of laminating | stacking an orientation film, etc. are not required.
Optical biaxiality of nx>ny> nz can be imparted by stretching or shrinking the substrate coated with the non-liquid crystalline material while heating.

  Examples of the non-liquid crystalline polymer include polymers such as polyamide, polyimide, polyester, polyetherketone, polyamide-imide, and polyester-imide because they are excellent in heat resistance, chemical resistance, transparency, and rigidity. preferable. Any one kind of these polymers may be used alone, or for example, a mixture of two or more kinds having different functional groups such as a mixture of polyetherketone and polyamide. Among such polymers, polyimide is particularly preferable because of its high transparency, high orientation, and high stretchability.

  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 hydrogen, halogen, a phenyl group, a phenyl group substituted with ₁ to 4 halogen atoms or a C ₁ to ₁₀ alkyl group, and a C ₁ to ₁₀ alkyl. It is at least one kind of substituent each independently selected from the group consisting of groups. Preferably, R ³ to R ⁶ is a halogen, a phenyl group, respectively, from the group consisting of 1-4 a halogen atom or an alkyl group C ₁ phenyl group substituted with an alkyl group of _1-10, and C ₁ ~ _10, It is at least one kind of substituent selected independently.

In the formula (1), Z represents a tetravalent aromatic group C ₆ ~ _20, preferably a pyromellitic group, a polycyclic aromatic group, a derivative of a polycyclic aromatic group, or, It is group represented by following formula (2).

In the formula (2), Z ′ is, for example, a covalent bond, C (R ⁷ ) ₂ groups, CO groups, O atoms, S atoms, SO ₂ groups, Si (C ₂ H ₅ ) ₂ groups, or NR ⁸ groups, and when there are plural groups, they are the same or different.
W represents an integer of 1 to 10. Each R ⁷ is independently hydrogen or C (R ⁹ ) ₃ . R ⁸ is hydrogen, an alkyl group having 1 to 20 carbon atoms, or an aryl group having ₆ to ₂₀ carbon atoms, 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. The substitution Examples of the substituted derivatives of polycyclic aromatic group, for example, an alkyl group of C ₁ ~ _10, at least one group selected from the group consisting of halogen, such as its fluorinated derivatives, and F and Cl The polycyclic aromatic group thus prepared can be mentioned.

  In addition to this, 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 can be mentioned. 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 a 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, It represents independently selected groups, and may be the same or different.

In said Formula (3) and Formula (5), L is a substituent and d and e represent the substitution number. L is, for example, a halogen, an alkyl group of _{C 1 ~ 3, C 1 ~} 3 halogenated alkyl group, a phenyl group, or a substituted phenyl group and when there are plural Ls, they may be the same or different. Examples of the substituted phenyl group, for example, halogen, be mentioned substituted phenyl group having at least one substituent selected from the group consisting of halogenated alkyl groups of C ₁ ~ ₃ alkyl group, and C ₁ ~ ₃ Can do. 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 the formula (5), M ¹ and M ² are the same or different, for example, a halogen, a halogenated alkyl group of C ₁ ~ ₃ alkyl group, C ₁ ~ _3, a phenyl group, or a substituted phenyl It is a group.
Examples of the halogen include fluorine, chlorine, bromine and iodine.
The above-mentioned substituted phenyl group, for example, a halogen, an alkyl group of C ₁ ~ _3, and a substituted phenyl group having at least one substituent selected from the group consisting of halogenated alkyl groups of C ₁ ~ ₃ Can be mentioned.

  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 , 2'-substituted biphenyltetracarboxylic dianhydride and the like.

Examples of the pyromellitic dianhydride include pyromellitic dianhydride, 3,6-diphenylpyromellitic dianhydride, 3,6-bis (trifluoromethyl) pyromellitic dianhydride, 3, Examples thereof include 6-dibromopyromellitic 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′-benzophenone tetracarboxylic 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. And pyridine-2,3,5,6-tetracarboxylic dianhydride.
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 be mentioned.

  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 ′-(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′-diphenylsulfonetetracarboxylic 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 dianhydride Etc.

  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 benzenediamine, diaminobenzophenone, naphthalenediamine, heterocyclic aromatic diamine, 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 naphthalenediamine 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.

  Examples of the polyetherketone that is a film forming material for the second birefringent layer include polyaryletherketone represented by the following general formula (7) described in JP-A No. 2001-49110. be able to.

  In the formula (7), X represents a substituent, and q represents the number of substitutions. X is, for example, a halogen atom, a lower alkyl group, a halogenated alkyl group, a lower alkoxy group, or a halogenated alkoxy group, and when there are a plurality of X, they are the same or different.

Examples of the halogen atom include a fluorine atom, a bromine atom, a chlorine atom, and an iodine atom, and among these, a fluorine atom is preferable. Examples of the lower alkyl group, for example, preferably a lower alkyl group having a linear or branched C ₁ ~ _6, more preferably a straight-chain or branched-chain alkyl group of C ₁ ~ _4. Specifically, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group are preferable, and a methyl group and an ethyl group are particularly preferable. Examples of the halogenated alkyl group include halides of the lower alkyl group such as a trifluoromethyl group. Examples of the lower alkoxy group include an alkoxy group having a linear or branched chain preferably of C ₁ ~ _6, more preferably a straight-chain or branched-chain alkoxy group of C ₁ ~ _4. Specifically, a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a sec-butoxy group, and a tert-butoxy group are more preferable, and a methoxy group and an ethoxy group are particularly preferable. . Examples of the halogenated alkoxy group include a halide of the lower alkoxy group such as a trifluoromethoxy group.

  In the formula (7), q is an integer from 0 to 4. In the above formula (7), it is preferable that q = 0 and that the carbonyl group bonded to both ends of the benzene ring and the oxygen atom of the ether are present in the para position.

In the formula (7), R ¹ is a group represented by the following formula (8), and m is an integer of 0 or 1.

  In the formula (8), X ′ represents a substituent, and is the same as X in the formula (7), for example. In Formula (8), when there are a plurality of X ′, they are the same or different. q ′ represents the number of substitutions of X ′, and is an integer from 0 to 4, preferably q ′ = 0. P is an integer of 0 or 1.

In the formula (8), R ² represents a divalent aromatic group. Examples of the divalent aromatic group include an o-, m- or p-phenylene group, or naphthalene, biphenyl, anthracene, o-, m- or p-terphenyl, phenanthrene, dibenzofuran, biphenyl ether, or And divalent groups derived from biphenylsulfone. In these divalent aromatic groups, hydrogen directly bonded to the aromatic group may be substituted with a halogen atom, a lower alkyl group or a lower alkoxy group. Among these, R ² is preferably an aromatic group selected from the group consisting of the following formulas (9) to (15).

In the formula (7), R ¹ is preferably a group represented by the following formula (16). In the following formula (16), R ² and p have the same meanings as the formula (8).

  Furthermore, in said Formula (7), n represents a polymerization degree, for example, is the range of 2-5,000, Preferably, it is the range of 5-500. Further, the polymerization may be composed of repeating units having the same structure, or may be composed of repeating units having different structures. In the latter case, the polymerization mode of the repeating unit may be block polymerization or random polymerization.

  Furthermore, the end of the polyaryl ether ketone represented by the formula (7) is preferably fluorine on the p-tetrafluorobenzoylene group side and a hydrogen atom on the oxyalkylene group side. For example, it can be represented by the following general formula (17). In the following formula, n represents the same degree of polymerization as in formula (7).

  Specific examples of the polyaryletherketone represented by the formula (7) include those represented by the following formulas (18) to (21). In each formula below, n represents the formula (7). Represents the same degree of polymerization.

  In addition to these, examples of the polyamide or polyester that is the film forming material of the second birefringent layer include polyamides and polyesters described in JP-T-10-508048, and those The repeating unit can be represented by, for example, the following general formula (22).

In the formula (22), Y is O or NH. E is, for example, a covalent bond, a C ₂ alkylene group, a halogenated C ₂ alkylene group, a CH ₂ group, a C (CX ₃ ) ₂ group (where X is a halogen or hydrogen), a CO group, At least one group selected from the group consisting of O atom, S atom, SO ₂ group, Si (R) ₂ group, and N (R) group, which may be the same or different.
In the E, R is at least one of a halogenated alkyl group of C ₁ ~ ₃ alkyl and C ₁ ~ _3, in the meta or para to the carbonyl functional group or a Y group.

  Moreover, in said (22), A and A 'are substituents, and t and z represent the number of each substitution. Moreover, p is an integer from 0 to 3, q is an integer from 1 to 3, and r is an integer from 0 to 3.

Wherein A is selected from hydrogen, a halogen, an alkyl group of C ₁ ~ _3, a halogenated alkyl group of C ₁ ~ _3, OR (wherein, R represents those defined above.) The alkoxy group represented by , an aryl group, a substituted aryl group by a halogen, etc., C ₁ - ₉ alkoxycarbonyl group, C ₁ alkylcarbonyloxy group _1-9, ants C ₁ - ₁₂ - Le oxycarbonyl group, C ₁ ~ ₁₂ Ali - Le carbonyl group and substituted derivatives thereof, ants C ₁ ~ ₁₂ - carbamoyl group, as well as ants C ₁ ~ ₁₂ - is selected from the group consisting of Le carbonylamino group and substituted derivatives thereof, in the case of a plurality, each identical Is or different. Wherein A 'is, for example, a halogen, an alkyl group of C ₁ ~ _3, a halogenated alkyl group of C ₁ ~ _3, is selected from phenyl and the group consisting of substituted phenyl group and when there are plural, or are respectively the same Different. The substituent on the phenyl ring of the substituted phenyl group, for example, a halogen, an alkyl group of C ₁ ~ _3, a halogenated alkyl group and combinations thereof C ₁ ~ _3. The t is an integer from 0 to 4, and the z is an integer from 0 to 3.

  Among the repeating units of polyamide or polyester represented by the formula (22), those represented by the following general formula (23) are preferable.

  In the formula (23), A, A ′ and Y are as defined in the formula (22), and v is an integer of 0 to 3, preferably an integer of 0 to 2. x and y are each 0 or 1, but are not 0 at the same time.

  Moreover, as polyester, the repeating unit may be represented by the following general formulas (24) and (25).

  In the formulas (24) and (25), X and Y are substituents. X is selected from the group consisting of hydrogen, chlorine and bromine. The Y is selected from the group consisting of the following formulas (26) (27) (28) (29).

  Further, the polyester may be a copolymer in which the polyesters represented by the general formulas (24) and (25) are combined.

  The optical film of the present invention can be used as a polarizing plate in combination with a polarizer. The polarizer is not particularly limited, and is prepared by adsorbing and dying dichroic substances such as iodine and dichroic dyes on various films by conventional known methods, stretching, crosslinking, and drying. Can be used. Among them, a polarizer that transmits linearly polarized light when natural light is incident is preferable, and one that is excellent in light transmittance and degree of polarization is preferable. Examples of the film for adsorbing the dichroic material include hydrophilic polymer films such as polyvinyl alcohol (PVA) film, partially formalized PVA film, ethylene / vinyl acetate copolymerized saponified film, and cellulose film. Can be mentioned. In addition to these, polyene oriented films such as dehydrated PVA and polyvinyl chloride dehydrochlorination can be used. Among these, a PVA film is preferable. The thickness of the polarizer is usually in the range of 1 to 80 μm, but is not limited thereto.

  When the polarizing plate is produced by laminating the optical film of the present invention and the polarizer, for example, an adhesive can be used for laminating. Examples of the adhesive include acrylic, vinyl alcohol, silicone, polyester, polyurethane, and polyether pressure sensitive adhesives and rubber pressure sensitive adhesives. An adhesive composed of a water-soluble cross-linking agent of vinyl alcohol polymers such as glutaraldehyde, melamine, and oxalic acid can also be used. As these adhesives and the like, those which are not easily separated by the influence of temperature and heat and are excellent in light transmittance and degree of polarization are preferable. Specifically, when the polarizer is a PVA-based film, a PVA-based adhesive is preferable from the viewpoint of, for example, the stability of the adhesion treatment.

  The optical film and polarizing plate of the present invention can be preferably used for the formation of image display devices such as liquid crystal display devices, organic EL display devices, and PDPs.

  The polarizing plate of the present invention can be preferably used for forming various devices such as a liquid crystal display device. For example, a reflective liquid crystal display device or a transflective liquid crystal in which a polarizing plate is disposed on one side or both sides of a liquid crystal cell. It can be used for a display device or a liquid crystal display device such as a transmission / reflection type. The liquid crystal cell substrate may be either a plastic substrate or a glass substrate. The liquid crystal cell forming the liquid crystal display device is arbitrary. For example, an appropriate type such as an active matrix drive type represented by a thin film transistor type, a simple matrix drive type represented by a twist nematic type or a super twist nematic type, etc. A liquid crystal cell may be used.

Examples of the transmissive liquid crystal display device include a VA (Vertical aligned) mode liquid crystal display device and an OCB (Optically compensated bend) mode liquid crystal display device.
These liquid crystal display devices are composed of a cell and two polarizing plates disposed on both sides thereof. A liquid crystal cell of a transmissive liquid crystal display device has a liquid crystal supported between two electrode substrates. The reflective liquid crystal display device includes a liquid crystal cell sandwiched between a polarizing plate and a reflecting plate.

  A VA mode liquid crystal cell uses a voltage controlled birefringence (ECB) effect, and nematic liquid crystal with negative dielectric anisotropy between transparent electrodes is vertically aligned when no voltage is applied. I mean. Specific examples include liquid crystal cells described in JP-A-62-210423 and JP-A-4-153621. In addition, as described in JP-A-11-258605, the VA mode liquid crystal cell uses a substrate provided with a slit in a pixel or a substrate on which a projection is formed in order to enlarge a viewing angle. Thus, a multi-domain MVA mode liquid crystal cell may be used. Further, as described in Japanese Patent Application Laid-Open No. 10-123576, a VATN mode in which a chiral agent is added to a liquid crystal, the liquid crystal is substantially vertically aligned when no nematic liquid crystal voltage is applied, and twisted multi-domain alignment is applied when a voltage is applied. A liquid crystal cell may be used.

  The OCB mode liquid crystal cell is a liquid crystal display device using a bend alignment mode liquid crystal cell in which rod-like liquid crystal molecules are aligned in substantially opposite directions (symmetrical) between an upper portion and a lower portion of the liquid crystal cell. Since the rod-like liquid crystal molecules are symmetrically aligned at the upper and lower portions of the liquid crystal cell, the bend alignment mode liquid crystal cell has a self-optical compensation function. The bend alignment mode liquid crystal display device has an advantage of high response speed. In the OCB mode liquid crystal display device, it is preferable to combine an optical compensation layer containing a discotic compound or a rod-like liquid crystal compound with the polarizing plate with an optical compensation layer.

  Next, an organic electroluminescence device (organic EL display device) will be described. Generally, in an organic EL display device, a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light emitter (organic electroluminescent light emitter). Here, 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 and the like and a light emitting layer made of a fluorescent organic solid such as anthracene, It is also known to have various combinations such as a laminate of such a light emitting layer and an electron injection layer composed of a perylene derivative, etc., or a laminate of these hole injection layer, light emitting layer, and electron injection layer. It has been.

  In organic EL display devices, holes and electrons are injected into the organic light-emitting layer by applying a voltage to the transparent electrode and the metal electrode, and the energy generated by recombination of these holes and electrons excites the fluorescent material. Then, light is emitted on the principle that the excited fluorescent material emits light when returning to the ground state. The mechanism of recombination in the middle is the same as that of a general diode, and as can be expected from this, the current and the emission intensity show strong nonlinearity due to rectification with respect to the 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 must be transparent, and usually a transparent electrode formed of a transparent conductor such as indium tin oxide (ITO) is used. 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, and 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 formed of a very thin film having a thickness of about 10 nm. For this reason, the organic light emitting layer transmits light almost completely like the transparent electrode. As a result, light that is incident from the surface of the transparent substrate at the time of non-light emission, passes through the transparent electrode and the organic light emitting layer, and is reflected by the metal electrode is again emitted to the surface side of the transparent substrate. The display surface of the organic EL display device looks like a mirror surface.

  In an organic EL display device comprising an organic electroluminescent light emitting device comprising a transparent electrode on the surface side of an organic light emitting layer that emits light upon application of a voltage and a metal electrode on the back side of the organic light emitting layer, the surface of the transparent electrode While providing a polarizing plate on the side, a retardation film can be provided between the transparent electrode and the polarizing plate.

  Since the retardation film and the polarizing plate have a function of polarizing light incident from the outside and reflected by the metal electrode, there is an effect that the mirror surface of the metal electrode is not visually recognized by the polarization function. In particular, the mirror surface of the metal electrode can be completely shielded by configuring the retardation film with a quarter-wave plate and adjusting the angle formed by the polarization direction of the polarizing plate and the retardation film to π / 4. .

  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. This linearly polarized light is generally elliptically polarized light by the retardation film, but becomes circularly polarized light especially when the retardation film is a quarter wavelength plate and the angle formed by the polarization direction of the polarizing plate and the retardation film is π / 4. .

  This circularly polarized light is transmitted through the transparent substrate, the transparent electrode, and the organic thin film, is reflected by the metal electrode, is again transmitted through the organic thin film, the transparent electrode, and the transparent substrate, and becomes linearly polarized light again by the retardation film. And since this linearly polarized light is orthogonal to the polarization direction of a polarizing plate, it cannot permeate | transmit a polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded.

  Examples will be described below, but the present invention is not limited thereto. In addition, each analysis method used in the Example is as follows.

(Measurement of birefringence and phase difference)
Measurement was performed using an automatic birefringence meter (KOBRA-21ADH manufactured by Oji Scientific Instruments).
The measurement was carried out at a wavelength of 590 nm and a measurement temperature of 25 ° C.

(Film thickness measurement)
Calculation was performed by an optical interference method with a wavelength of 700 to 900 nm (manufactured by Otsuka Electronics, self-recording spectrophotometer MCPD-2000).

Example 1
A 20 wt% solution of Asahi Denka Co., Ltd., trade name “Adekabon titer HUX320” was prepared using water / isopropyl alcohol (1/1), and the solution was applied onto a triacetyl cellulose film (thickness 80 μm).
Thereafter, the film was dried at 120 ° C. for 30 minutes, stretched 1.3 times, and a transparent and smooth birefringent film having a thickness of 30 μm was formed.
The birefringence film had birefringence Δn = 0.001 and had optical characteristics of nx>ny> nz. The thickness and in-plane retardation of the film were Δnd = 100 nm and Rth = 200 nm.

(Example 2)
Δn≈0.04 nm synthesized from 2,2′-bis (3,4-dicarboxyphenyl) hexafluoropropane and 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl Was dissolved in cyclohexanone to prepare a 23 wt% coating solution. The coating solution was applied to the film prepared in Example 1 and dried at 140 ° C. for 15 minutes to obtain a transparent and smooth optical film (polyimide layer thickness 6 μm).
In the film, the polyimide layer had optical characteristics of nx≈ny> nz, and the film as a whole had optical characteristics of nx>ny> nz.
The thickness and in-plane retardation of the film were Δnd = 100 nm and Rth = 440 nm.

Claims (10)

  An optical film comprising a polyurethane-based film having a thickness of 10 to 100 μm as at least a first birefringent layer. The optical film according to claim 1, wherein the first birefringent layer has optical characteristics of nx ≧ ny> nz.
However, nx, ny, and nz respectively indicate refractive indexes in the X-axis direction, the Y-axis direction, and the Z-axis direction in the first birefringent layer. The X-axis direction is an axial direction showing the maximum refractive index in the in-plane direction of the first birefringent layer, and the Y-axis direction is an axial direction perpendicular to the X-axis direction in the plane. And the Z-axis direction indicates a thickness direction perpendicular to the X-axis direction and the Y-axis direction.   Furthermore, the optical film of Claim 1 or 2 containing a transparent base film.   Further, the second birefringent layer includes a film formed of at least one polymer selected from the group consisting of polyamide, polyimide, polyester, polyetherketone, polyamideimide and polyesterimide. The optical film described in 1. The optical film according to claim 4, wherein the second birefringent layer has optical characteristics of nx ≧ ny> nz.
However, nx, ny, and nz respectively indicate the refractive indexes in the X-axis direction, the Y-axis direction, and the Z-axis direction in the second birefringent layer. The X-axis direction is an axial direction showing the maximum refractive index in the in-plane direction of the second birefringent layer, and the Y-axis direction is an axial direction perpendicular to the X-axis direction in the plane. And the Z-axis direction indicates a thickness direction perpendicular to the X-axis direction and the Y-axis direction.   A polarizing plate comprising the optical film according to claim 1 and a polarizer.   A liquid crystal cell comprising the optical film according to claim 1 or the polarizing plate according to claim 6.   The liquid crystal cell according to claim 7, which is in a VA mode or an OCB mode.   A liquid crystal display device comprising the liquid crystal cell according to claim 7 or 8.   An image display device comprising the optical film according to claim 1 or the polarizing plate according to claim 6.