JP2006259621A - Polarizer protection film and polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizer protection film having excellent transparency, moisture resistance and heat resistance, having a small photoelastic coefficient, and moreover, excellent film conveying property, film processability and rework property in a production line, and to provide a polarizing plate excellent in optical characteristics and durability. <P>SOLUTION: The polarizer protection film is obtained by forming the film of a resin composition which contains an olefin-maleimide copolymer by 50 to 90 wt% comprising a maleimide structural component by 30 to 98 mol% and an olefin structural component by 70 to 2 mol% and having 1×10<SP>3</SP>to 5×10<SP>6</SP>weight average molecular weight, and contains a polycarbonate resin having an acrylonitrile-styrene copolymer in a side chain by 50 to 10 wt%. The polarizer comprises the polarizer protection film laminated on at least one surface of a polarizer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polarizer protective film and a polarizing plate suitably used for a thin liquid crystal display device (LCD) requiring high durability.

  In recent years, along with downsizing, thinning, and weight reduction of notebook personal computers, word processors, mobile phones, personal digital assistants, etc., LCDs that take advantage of the features of light weight and compactness are often used. In this type of LCD, various plastic optical films such as polarizing plates and retardation films are used to maintain the display quality. In addition, in order to further reduce the weight of LCDs for portable information terminals and mobile phones, LCDs using plastic films instead of glass substrates have been put into practical use.

  In addition to being optically transparent, optical homogeneity is required for optical films used in devices that handle polarized light such as LCDs. Furthermore, a film substrate for a plastic LCD in which the glass substrate is replaced with a plastic film is required to hardly change a phase difference (expressed by a product of birefringence and thickness) due to an external stress or the like. In particular, when the optical film is used as a polarizer protective film, the above-described characteristics are strongly demanded for wide viewing angle and large screen. Also, when applied to optical films for various LCDs, it is required that changes in phase difference due to stress during processing or use be small.

  As plastic optical films used for LCDs, films made of engineering plastics such as polycarbonate, polyarylate, polysulfone, and polyethersulfone, and cellulose plastics such as triacetylcellulose are known. When manufacturing these plastic films, various stresses are applied to the film during molding due to the flow when the plastic melts, the shrinkage when drying the solvent, the shrinkage when heating, the tension during transportation, etc. Remains a phase difference due to molecular orientation induced by stress.

  For this reason, if necessary, a special treatment for the film such as thermal annealing must be performed to reduce the remaining phase difference, and there is a problem that the manufacturing process of the film becomes complicated. Furthermore, even with a film with reduced residual retardation, a new retardation is generated due to the orientation of molecules caused by deformation during bonding with the polarizer and deformation stress after forming the polarizing plate. This is a problem in terms of stability.

  In order to solve these problems, attempts have been made to obtain a plastic optical film in which retardation due to molecular orientation is difficult to develop, such as a film made of a cyclic olefin resin or an olefin resin having a maleimide component. A film has been proposed. This type of resin film is excellent in transparency, moisture resistance, heat resistance and the like, has a small photoelastic coefficient, and has preferable performance as an optical film for LCD.

  However, the cyclic olefin resin film and the olefin resin film having a maleimide component have a problem that a phase difference due to molecular orientation is hardly exhibited in the film plane direction, but a phase difference is easily generated in the film thickness direction. However, there is still a problem to be improved as a polarizer protective film that is strongly required optically isotropic.

In particular, when the cyclic olefin-based resin is formed into a film having a general thickness (50 to 90 μm) as a polarizer protective film, the water vapor permeability is 10 g / m ² · 24 hr at 40 ° C. and 90% RH. The adhesion failure between the polarizer protective film and the polarizer has been a problem. That is, when manufacturing a polarizing plate, a polarizer protective film is bonded to both sides of the polarizer with an adhesive, but since a water-based adhesive is mainly used, the water vapor permeability of the polarizer protective film is low. If it is too high, the drying becomes insufficient, resulting in poor adhesion.

In addition, the triacetyl cellulose film (80 μm thickness) generally used conventionally as a polarizer protective film has a water vapor permeability as large as about 250 g / m ² · 24 hr at 40 ° C. and 90% RH. Although there is no problem of such poor adhesion, the permeation of water vapor from the outside after bonding cannot be suppressed, and a polarizing plate using a triacetyl cellulose-based polarizer protective film tends to cause a long-term deterioration in durability.

  Further, the olefin resin film having a maleimide component has a tensile elongation at break of only about 2 to 3% and is very brittle. Therefore, in the process of producing a film from the above resin composition and the process of producing a polarizing plate using this film, when the film is pulled while being bent or stretched under tension to make the film slack, There is a problem that various troubles such as the film may be broken and the productivity is deteriorated.

  In order to solve such problems, the following Patent Document 1 describes 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. A polarizer protective film made of a resin composition containing a resin has been proposed. This polarizer protective film is excellent in transparency, moisture resistance, heat resistance, etc., has a small photoelastic coefficient, a small phase difference between the film plane direction and the thickness direction, and has an appropriate water vapor transmission rate. Excellent performance as a protective film.

However, the polarizer protective film proposed in Patent Document 1 contains a substituted or unsubstituted phenyl group and a nitrile group in the side chain so that the side chain has a substituted or unsubstituted imide group. Although the mechanical strength of the thermoplastic resin is considerably improved, it is still satisfactory in terms of productivity because it is easily broken and brittle, so it is easy to break in the film forming process and the film cannot be transported stably. It is not a thing. Also, when a polarizing plate is produced by laminating this film to a polarizer, the film often breaks in the process of laminating with the polarizer, and it is not yet satisfactory in terms of workability.
Further, in the production of a liquid crystal display device, a step of attaching a polarizing plate to a liquid crystal cell is performed. However, it is inevitable that bubbles or foreign substances are involved in the attachment, or that the polarizing plate itself has a defect. Therefore, an inspection is performed after the step of attaching the polarizing plate to the liquid crystal cell, and if there is a defect, a step called rework is performed in which the polarizing plate is removed and the expensive liquid crystal cell is reused. In order to enable such reuse, it is necessary that the polarizing plate can be easily peeled at the time of peeling, but polarization using a polarizer protective film or a retardation film made of a brittle maleimide copolymer resin film. In the case of the plate, there is also a problem that the maleimide copolymer resin film is broken at the time of peeling and inferior in reworkability.
JP 2001-343529 A

  The present invention solves the above problems, and its object is to have excellent transparency, moisture resistance, heat resistance, a small photoelastic coefficient, and film transportability and film processing in a production line. It is providing the polarizer protective film excellent in property and rework property, and a polarizing plate using the same.

  As a result of intensive studies to achieve the above object, the present inventor uses a film made of a resin composition in which an olefin-maleimide resin is blended with a polycarbonate resin having an acrylonitrile-styrene copolymer in the side chain. Thus, the inventors have found that the above object can be achieved, and have completed the present invention.

That is, in the polarizer protective film of the present invention, the component represented by the following general formula (1) is 30 to 98 mol% and the component represented by the following general formula (2) is 70 to 2 mol%. 50 to 90% by weight of an olefin-maleimide resin having a polystyrene-equivalent weight average molecular weight of 1 × 10 ^{3 to} 5 × 10 ⁶ and a polycarbonate resin having a side chain of acrylonitrile-styrene copolymer 50 to 10% by weight % Of the resin composition. Each of these films preferably has a tensile elongation at break of 4% or more and a tensile elastic modulus of 2500 MPa or more.
(Here, R ¹ represents an alkyl group having 1 to 18 carbon atoms or a cycloalkyl group having 3 to 12 carbon atoms.)
(Here, R ² represents hydrogen or an alkyl group having 1 to 8 carbon atoms, and R ³ and R ⁴ represent an alkyl group having 1 to 8 carbon atoms.)
The polarizing plate of the present invention is characterized in that the polarizer protective film is bonded to at least one surface of the polarizer.

  The olefin-maleimide copolymer used in the present invention is produced, for example, by a radical copolymerization reaction between an N-substituted or unsubstituted maleimide monomer that provides the component (1) and an olefin monomer that provides the component (2). Can do. As the polymerization method, any of a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method can be employed.

  Examples of N-substituted or unsubstituted monomers that give component (1) include N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, Ni-propylmaleimide, Nn-butylmaleimide, N- i-butylmaleimide, Ns-butylmaleimide, Nt-butylmaleimide, Nn-pentylmaleimide, Nn-hexylmaleimide, Nn-heptylmaleimide, Nn-octylmaleimide, N-lauryl Maleimide, N-stearylmaleimide, N-cyclopropylmaleimide, N-cyclobutylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N- (2-methylphenyl) maleimide, N- (2-ethylphenyl) maleimide, N -(2-Isopropylphenyl) maleimide, N- ( -Methylphenyl) maleimide, N- (3-ethylphenyl) maleimide, N- (4-methylphenyl) maleimide, N- (4-ethylphenyl) maleimide, N- (2,6-dimethylphenyl) maleimide, N- (2,6-diethylphenyl) maleimide, N- (2,6-diisopropylphenyl) maleimide, N- (2,4,6-trimethylphenyl) maleimide, N-carboxyphenylmaleimide, N- (2-chlorophenyl) maleimide N- (2,6-dichlorophenyl) maleimide, N- (2-bromophenyl) maleimide, N- (perbromophenyl) maleimide, N- (2,4-dimethylphenyl) maleimide, p-tolylmaleimide, etc. Substituted maleimides and maleimides are used. Of these monomers, N-methylmaleimide, N-ethylmaleimide, N-isopropylmaleimide, and N-cyclohexylmaleimide are preferable. These monomers can be used alone or in combination of two or more.

  Examples of the olefin monomer that gives component (2) include isobutene, 2-methyl-1-butene, 2-methyl-1-pentene, 2-methyl-1-hexene, 1-methyl-1-heptene, 1-isooctene, Olefins such as 2-methyl-1-octene, 2-ethyl-1-pentene, 2-methyl-2-butene, 2-methyl-2-pentene, 2-methyl-2-hexene, and the like. Of these, isobutene is preferred. These monomers can be used alone or in combination of two or more.

  Content of the structural component (1) is 30 to 98 mol% of the whole olefin-maleimide copolymer, preferably 40 to 85 mol%, and more preferably 45 to 80 mol%. When the component (1) exceeds 98 mol%, the produced copolymer becomes brittle. On the contrary, when it is less than 30 mol%, the heat resistance of the produced copolymer is lowered, which is not preferable.

  These olefin-maleimide copolymers may be further modified with a reactive group. Examples of reactive groups include carboxylic acids and their derivatives or metal salts, acid anhydride groups, epoxy groups, amino groups, hydroxyl groups, thiol groups, alkoxysilyl groups, isocyanate groups, and the like. It is 0-25 mol% with respect to an olefin-maleimide-type copolymer, Preferably it is 0.01-20 mol%, More preferably, it is 0.02-5 mol%. When the reactive group exceeds 25 mol%, the thermal stability and mechanical strength of the resulting copolymer tend to decrease.

  These modified olefin-maleimide copolymers include, for example, maleic anhydride, citraconic anhydride, itaconic anhydride, (meth) acrylic acid, itaconic acid, fumaric acid, glycidyl (meth) acrylate, 2-aminoethyl (meta ) Acrylate, 2-hydroxyethyl (meth) acrylate, triethoxysilylpropyl (meth) acrylate, allylamine and other unsaturated compounds can be copolymerized. As will be described later, when an olefin-maleimide copolymer is obtained by post-imidation of maleic anhydride and an olefin copolymer, it is produced by adjusting the amount of imidization to leave the acid anhydride unit. it can.

  Furthermore, if necessary, other vinyl monomers can be copolymerized with the above-mentioned copolymer within a range not impairing the object of the present invention. Examples of other vinyl monomers include styrene, α-methylstyrene, vinyltoluene, 1,3-butadiene, isoprene and halogen-substituted derivatives thereof, methyl methacrylate, ethyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, methacrylic acid. Methacrylic acid esters such as benzyl, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, acrylic acid esters such as benzyl acrylate, vinyl esters such as vinyl acetate and vinyl benzoate, Vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, vinyl chloride, vinylidene chloride, acrylonitrile, ethylene, propylene, 1-butene, 2-butyl Emissions, one or more monomers selected from the 1-hexene is used.

  As polymerization initiators used for radical copolymerization reaction of the above various monomers, benzoyl peroxide, lauryl peroxide, octanoyl peroxide, acetyl peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, dicumyl Organic peroxides such as peroxide, t-butylperoxyacetate, t-butylperoxybenzoate, or 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2- Butyronitrile), 2,2′-azobisisobutyronitrile, dimethyl-2,2′-azobisisobutyrate, 1,1′-azobis (cyclohexane-1-carbonitrile) and the like. It is done.

  Examples of the solvent that can be used in the solution polymerization method include benzene, toluene, xylene, ethylbenzene, cyclohexane, dioxane, tetrahydrofuran, acetone, methyl ethyl ketone, dimethylformamide, isopropyl alcohol, and butyl alcohol. The polymerization temperature can be appropriately set according to the decomposition temperature of the initiator, but generally it is preferably performed in the range of 40 to 150 ° C.

  The olefin-maleimide copolymer used in the present invention can also be obtained by post-imidizing a copolymer obtained by copolymerization of maleic anhydride and olefins with alkylamine or the like. Such a post-imidation reaction is performed, for example, by dissolving or dispersing a maleic anhydride-isobutene copolymer in a molten state or an alcohol solvent such as methanol, ethanol or propanol or an aromatic solvent such as benzene or toluene. Can be reacted with a primary amine such as methylamine at a temperature of 100 to 350 ° C.

The weight average molecular weight of the olefin-maleimide copolymer used in the present invention needs to be 1 × 10 ^{3 to} 5 × 10 ⁶ , and preferably 1 × 10 ⁵ to 1 × 10 ⁶ . When the weight average molecular weight exceeds 5 × 10 ⁶ , the film formability is deteriorated. Conversely, when the weight average molecular weight is less than 1 × 10 ³ , the resulting resin film becomes brittle. Here, the weight average molecular weight (Mw) is determined by gel permeation chromatography (GPC).

Hereinafter, the manufacturing method of the polycarbonate resin which has the acrylonitrile styrene copolymer used for this invention in a side chain is illustrated.
The polycarbonate resin used in the present invention is 4,4-dioxydiallylalkane polycarbonate including 4,4-dihydroxydiphenyl-2,2-propane (commonly called bisphenol A). A polycarbonate of 4-dihydroxydiphenyl-2,2-propane having a number average molecular weight of 15,000 to 80,000 is preferred. These polycarbonates are produced by an arbitrary method. For example, for the production of polycarbonate of 4,4-dihydroxydiphenyl-2,2-propane, 4,4-dihydroxydiphenyl-2,2-propane is used as the dioxy compound, and phosgene is present in the presence of a caustic aqueous solution and a solvent. Or a method of transesterifying 4,4-dihydroxydiphenyl-2,2-propane and carbonic acid diester in the presence of a catalyst, and the like.

The method for producing a polycarbonate resin having the acrylonitrile-styrene copolymer of the present invention in the side chain is, for example, by suspending the polycarbonate resin in water and separately adding acrylonitrile and styrene to the following general formula (3) or (4). Addition of a solution in which at least one or a mixture of two or more of the radical (co) polymerizable organic peroxides represented is dissolved in the acrylonitrile and styrene, and the radical polymerization initiator is not substantially decomposed. Heating under the conditions, impregnating polycarbonate resin with acrylonitrile and styrene, radical (co) polymerizable organic peroxide and radical polymerization initiator, and subsequently raising the temperature of this aqueous suspension, acrylonitrile and styrene and radical Copolymerized (co) polymerizable organic peroxide in polycarbonate resin Shimete, acrylonitrile - obtain a polycarbonate resin having a styrene copolymer in a side chain.
Moreover, the kneading | mixing of the polycarbonate resin which has the acrylonitrile styrene copolymer manufactured in this way in a side chain under 100-300 degreeC melt | fusion can be anticipated.

The radical (co) polymerizable organic peroxide represented by the general formula (3) is a formula
(In the formula, R ⁵ is a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, R ⁶ is a hydrogen atom or a methyl group, R ⁷ and R ⁸ are each an alkyl group having 1 to 4 carbon atoms, and R ⁹ is 1 carbon atom. Represents a -12 alkyl group, a phenyl group, an alkyl-substituted phenyl group or a cycloalkyl group having 3 to 12 carbon atoms, m is 1 or 2.
The radical (co) polymerizable organic peroxide represented by the general formula (4) is a formula
(Wherein R ¹⁰ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ¹¹ is a hydrogen atom or a methyl group, R ¹² and R ¹³ are each an alkyl group having 1 to 4 carbon atoms, and R ¹⁴ is 1 carbon atom) Represents a -12 alkyl group, a phenyl group, an alkyl-substituted phenyl group or a cycloalkyl group having 3 to 12 carbon atoms, where n is 0, 1 or 2.

  Specific examples of the radical (co) polymerizable organic peroxide represented by the general formula (3) include t-butylperoxyacryloyloxyethyl carbonate, t-amylperoxyacryloyloxyethyl carbonate, and t-hexylperoxyacrylic. Leuoxyethyl carbonate, 1,1,3,3-tetramethylbutylperoxyacryloyloxyethyl carbonate, cumylperoxyacryloyloxyethyl carbonate, p-isopropylcumylperoxyacryloyloxyethyl carbonate, t-butylperoxymethacryloyl Loxyethyl carbonate, t-amylperoxymethacryloyloxyethyl carbonate, t-hexylperoxymethacryloyloxyethyl carbonate, 1,1,3,3-tetramethylbutylperoxy Tacryloyloxyethyl carbonate, cumylperoxymethacryloyloxyethyl carbonate, p-isopropylcumylperoxymethacryloyloxyethyl carbonate, t-butylperoxymethacryloyloxyethyl carbonate, t-amylperoxyacryloyloxyethoxyethyl carbonate, t- Hexylperoxyacryloyloxyethoxyethyl carbonate, 1,1,3,3-tetramethylbutylperoxyacryloyloxyethoxyethyl carbonate, cumylperoxyacryloyloxyethoxyethyl carbonate, p-isopropylcumylperoxyacryloyloxyethoxyethyl carbonate , T-butylperoxymethacryloyloxyethoxyethyl carbonate, t-amylperoxymethacrylate Loyloxyethoxyethyl carbonate, t-hexylperoxymethacryloyloxyethoxyethyl carbonate, 1,1,3,3-tetramethylbutylperoxymethacryloyloxyethoxyethyl carbonate, cumylperoxymethacryloyloxyethoxyethyl carbonate, p-isopropyl Milperoxymethacryloyloxyethoxyethyl carbonate, t-butylperoxyacryloyloxyisopropyl carbonate, t-amylperoxyacryloyloxyisopropyl carbonate, t-hexylperoxyacryloyloxyisopropyl carbonate, 1,1,3,3-tetramethylbutyl Peroxyacryloyloxyisopropyl carbonate, cumyl peroxyacryloyloxyisopropyl carbonate , P-isopropylcumylperoxyacryloyloxyisopropyl carbonate, t-butylperoxymethacryloyloxyisopropyl carbonate, t-amylperoxymethacryloyloxyisopropyl carbonate, t-hexylperoxymethacryloyloxyisopropyl carbonate, 1,1,3,3 Examples thereof include tetramethylbutyl peroxymethacryloyloxyisopropyl carbonate, cumyl peroxymethacryloyloxyisopropyl carbonate, p-isopropylcumyl peroxymethacryloyloxyisopropyl carbonate, and the like.

Furthermore, as the compound represented by the general formula (4), t-butyl peroxyallyl carbonate, t-amyl peroxyallyl carbonate, t-hexyl peroxyallyl carbonate, 1,1,3,3-tetramethylbutyl peroxyallyl carbonate, p-menthane peroxyallyl carbonate, cumyl peroxyallyl carbonate, t-butyl peroxymethallyl carbonate, t-amyl peroxymethallyl carbonate, t-hexyl peroxymethallyl carbonate, 1,1,3,3-tetramethylbutyl peroxymeta Ryl carbonate, p-menthane peroxymethallyl carbonate, cumyl peroxymethallyl carbonate, t-butylperoxyallyloxyethyl carbonate, t-amylperoxyallyloxy Ethyl carbonate, t-hexylperoxyallyloxyethyl carbonate, t-butylperoxymetalloxyethyl carbonate, t-amylperoxymetalloxyethyl carbonate, t-hexylperoxymetalloxyethyl carbonate, t-butylperoxyallyloxyisopropyl carbonate, t- Examples thereof include amylperoxyallyloxyisopropyl carbonate, t-hexylperoxyallyloxyisopropyl carbonate, t-butylperoxymetalloxyisopropyl carbonate, t-amylperoxymetalloxyisopropyl carbonate, t-hexylperoxymetalloxyisopropyl carbonate, and the like. Among these, t-butyl peroxyacryloyloxyethyl carbonate, t-butyl peroxymethacryloyloxyethyl carbonate, t-butyl peroxyallyl carbonate, and t-butyl peroxymethallyl carbonate are preferable.
Examples of the polycarbonate resin having the acrylonitrile-styrene copolymer thus produced in the side chain include MODIFER C series manufactured by NOF Corporation.

The weight average molecular weight of the obtained polycarbonate resin having acrylonitrile-styrene copolymer in the side chain is preferably 1 × 10 ^{4 to} 5 × 10 ⁵ . When the weight average molecular weight exceeds 5 × 10 ⁶ , the film moldability deteriorates. Conversely, when the weight average molecular weight is less than 1 × 10 ³ , the resulting resin film tends to be brittle. Here, the weight average molecular weight (Mw) is determined by gel permeation chromatography (GPC).

  The ratio of the acrylonitrile component to the styrene component is preferably 20 to 50% by weight for the former, 80 to 50% by weight for the latter, more preferably 25 to 35% by weight for the former, and 75 to 65 for the latter. % By weight. In particular, when the former is 25 to 30% by weight and the latter is 75 to 70% by weight, more preferable results are obtained. When the acrylonitrile component or the styrene component exceeds this range, the compatibility with the olefin-maleimide copolymer becomes poor, and a polarizer protective film having excellent transparency may not be obtained. The acrylonitrile component and the styrene component may contain a third component. In this case, the content of the third component in the polycarbonate resin having an acrylonitrile-styrene copolymer in the side chain is 5% by weight or more, 30 It is preferable to set it as weight% or less.

  The ratio of the acrylonitrile-styrene copolymer component and the polycarbonate resin component is preferably 5 to 70% by weight for the former, 95 to 30% by weight for the latter, and more preferably 15 to 50% by weight for the former. The latter is 85 to 50% by weight. When the acrylonitrile-styrene copolymer component or the polycarbonate resin component exceeds this range, the grafting efficiency is lowered, and one of them is ungrafted, which is not preferable.

  The polarizer protective film of the present invention is obtained by simply mixing 50 to 90% by weight of the olefin-maleimide copolymer and 50 to 10% by weight of a polycarbonate resin having the acrylonitrile-styrene copolymer in the side chain. Or a resin composition obtained by melt-kneading the same, and is produced by a known film forming method such as a solution casting method or a melt extrusion method. The thickness of each film is preferably 10 μm to 100 μm, more preferably 20 μm to 80 μm.

  Here, in the above resin composition, when the content of the polycarbonate resin having an acrylonitrile-styrene copolymer in the side chain is less than 10% by weight, the obtained film does not stretch, so that even a slight deformation or tension breaks. It is easy to handle, film transportability and film processability on the production line are poor, and handling becomes difficult, which is not preferable. On the other hand, if the content of the polycarbonate resin having an acrylonitrile-styrene copolymer in the side chain exceeds 50% by weight, the physical properties essential for a polarizer protective film such as transparency and mechanical strength are lowered. It is not preferable because it cannot perform a proper function.

  The polarizer protective film of the present invention thus obtained preferably has a tensile elongation at break of 4% or more, more preferably 7% or more, measured according to JIS K 7127. When the tensile elongation at break is less than 4%, the film does not stretch, so it is easy to break even with slight deformation and tension, and the film transportability and film processability on the production line are poor. When used as a polarizer protective film The reworkability of the polarizing plate may be inferior and handling becomes difficult.

  In addition, the polarizer protective film of the present invention preferably has a tensile elastic modulus measured according to JIS K 7113 of 2500 MPa or more, more preferably 3000 MPa or more. When the tensile elastic modulus is less than 2500 MPa, the film easily deforms even with a small stress, and cannot function sufficiently as an optical film. The tensile modulus is preferably 6000 MPa or less. When the tensile modulus exceeds 6000 MPa, the film becomes brittle and easily broken, and the film transportability, film processability, and reworkability on the production line are poor, and handling becomes difficult.

  In addition, the above-described resin composition may include a compatibilizer, a dispersant, a plasticizer, a heat stabilizer, an antioxidant, an ultraviolet absorber, a lubricant, and an antistatic agent as long as the purpose of the present invention is not impaired. You may contain well-known additives, such as an agent and a filler, and another polymer.

  In particular, 2,6-di-t-butyl-4-methylphenol, 2- (1-methylcyclohexyl) -4,6, dimethylphenol, 2,2-methylene-bis- (4-ethyl-6-t- Butylphenol), tris (di-nonylphenyl phosphite) and other antioxidants; pt-butylphenyl salicylate, 2,2′-dihydroxy-4-methoxy-benzophenone, 2- (2′-dihydroxy-4′-) It is preferable to contain an ultraviolet absorber such as m-octoxyphenyl) benzotriazole; a lubricant such as paraffin phenos and hydrogenated oil; and an antistatic agent such as stearoazitopropyldimethyl-β-hydroxyethylammonium trate.

  Further, the surface on the front side of the polarizer protective film of the present invention may be subjected to surface treatment such as hard coat treatment, anti-transfer, anti-reflection, anti-diffusion and anti-glare treatment according to the application of the LCD.

  When producing a film that is a polarizer protective film and also has a retardation compensation function, a film produced by a known film forming method is further produced by uniaxial stretching or biaxial stretching. By imparting orientation by uniaxial or biaxial stretching, it can be suitably used as a retardation film that compensates for distortion of light when passing through a liquid crystal substance.

  The polarizing plate of the present invention has the polarizer protective film of the present invention bonded to at least one surface of the polarizer. The polarizer refers to a PVA film or sheet having the function of a polarizer. The polarizer is not particularly limited, and a conventionally known one can be used. For example, PVA film that adsorbs iodine to PVA film and then uniaxially stretched in boric acid bath, PVA film that diffuses and absorbs dichroic direct dye on PVA film, and then uniaxially stretched PVA and dye A PVA / polyene polarizing film having a polyene structure formed by adsorbing iodine on a PVA film and stretching is used.

  When the polarizer protective film of the present invention is bonded to one surface of the polarizer, a conventionally known polarizer protective film or a conventionally known retardation film other than the present invention may be bonded to the other surface. In particular, considering the durability, it is preferable that the polarizer protective film of the present invention is bonded to both sides of the polarizer. In addition, when the polarizer protective film of the present invention is bonded to one side of the polarizer, when the obtained polarizing plate is bonded to the liquid crystal cell, the polarizer protection of the present invention is provided on the surface facing the liquid crystal cell. It is preferable to stick so that a film may be arrange | positioned.

  The method for bonding the polarizer protective film and the polarizer is preferably a wet laminating method that has been widely used conventionally. Wet lamination is a method in which a water-based adhesive or a solvent-based adhesive is applied or dripped onto the adhesive surface between the polarizer protective film and the polarizer, passed through a pair of rolls to remove excess adhesive, and then passed through the film with water or solvent. Is a method of evaporating and drying. As the adhesive, water-based adhesives such as polyvinyl alcohol (PVA) adhesives, acrylic adhesives, polyurethane adhesives and the like are suitable. In addition, in order to improve adhesiveness, it is preferable to perform hydrophilic treatment, such as a corona discharge process, an ultraviolet irradiation process, and a primer process, to the bonding surface of a polarizer protective film.

  According to the present invention, by using a film made of a resin composition in which an olefin-maleimide-based resin is blended with a polycarbonate resin having an acrylonitrile-styrene copolymer in the side chain, the film is excellent in transparency, moisture resistance, and heat resistance. In addition, a polarizer protective film having a small photoelastic coefficient and excellent film transportability, film processability and reworkability on a production line can be obtained, and a polarizing plate excellent in optical performance and durability performance can be obtained.

  It should be noted that sufficient compatibility cannot be obtained simply by combining acrylonitrile-styrene copolymer and polycarbonate resin with an olefin-maleimide resin, and the obtained film has transparency and toughness. The film is insufficient as a polarizer protective film, and the effect of the present invention cannot be obtained. Since the compatibility is poor only by adding a polycarbonate resin to an olefin-maleimide resin, the obtained film is transparent. Not only decreases, but also the mechanical strength decreases, and the effect of the present invention cannot be obtained.

  Hereinafter, the present invention will be described in more detail by giving specific examples of the present invention. In addition, this invention is not limited to a following example.

(Synthesis of olefin-maleimide resin copolymer)
In a 30 L autoclave equipped with a stirrer, a nitrogen introduction tube, a thermometer and a deaeration tube, 1180 g of N-methylmaleimide, 23 g of maleic anhydride, 8 g of perbutyl neodecanate and a toluene / methanol mixed solvent (1/1 weight ratio) After charging 15 L and purging with nitrogen 5 times, 8.5 liters of liquefied isobutene was charged and reacted at 60 ° C. for 12 hours. The particulate polymer obtained by the reaction was separated by centrifugation and dried at 60 ° C. under reduced pressure for 24 hours to obtain an N-methylmaleimide-isobutene copolymer. The yield was 1750g.

From the results of elemental analysis of the obtained polymer and the results of elemental analysis and ¹ H-NMR analysis of the sample obtained by methyl esterification of the maleic anhydride part of the obtained polymer, the maleimide component in the resulting polymer was 49 mol%, anhydrous The maleic acid component was 1 mol% and the isobutene component was 50 mol%. The weight average molecular weight (Mw) determined by GPC was 270,000. The refractive index was 1.525.

(Preparation of polarizer protective film)
A polycarbonate resin (Nippon Yushi Co., Ltd .: Modiper C) having an N-methylmaleimide-isobutene copolymer and an acrylonitrile-styrene copolymer obtained in the above manner in the side chain at a weight ratio of 2 is 80:20. The resin composition melt-kneaded using an axial melt extruder was melt-extruded into a film using a single-screw extruder equipped with a T-die to form a 40 μm thick polarizer protective film.

(Production of polarizer)
A 75 μm-thick unstretched PVA film made of polyvinyl alcohol (PVA) having a polymerization degree of 2400 and a saponification degree of 99 mol% was washed with water at room temperature, and then stretched 5 times in the longitudinal direction. While maintaining the tension state of this film, it was immersed in a dyeing bath (an aqueous solution containing 0.5% by weight of iodine and 5% by weight of potassium iodide) to adsorb the dichroic dye. Thereafter, a crosslinking treatment (an aqueous solution containing 10% by weight of boric acid and 10% by weight of potassium iodide) was performed at 50 ° C. for 5 minutes, and this was dried at 70 ° C. for 5 minutes to obtain a moisture content of 8% by weight. An adjusted film-like polarizer was produced.

(Preparation of polarizing plate)
One side of the polarizer protective film was subjected to corona discharge treatment. A / B agent of a two-component mixed aqueous urethane adhesive (Toyo Morton Co., Ltd .: EL-436A / B) is mixed to 10/3 (weight ratio) so that the solid content becomes 10% by weight. The solution was diluted with water to prepare an adhesive solution. This adhesive solution was applied to the corona discharge-treated surface of the polarizer protective film using a Mayer bar # 8, and this was applied to both sides of the polarizer to obtain a sandwich-like laminate. This laminate was held in a 45 ° C. constant temperature bath for 72 hours, dried and cured to produce a polarizing plate.

  A weight of 70:30 of a polycarbonate resin (manufactured by NOF Corporation: Modiper C) having an N-methylmaleimide-isobutene copolymer and an acrylonitrile-styrene copolymer obtained in the same manner as in Example 1 in the side chain. A polarizer protective film was produced in the same manner as in Example 1 except that the ratio was mixed, and a polarizing plate was produced in the same manner as in Example 1.

(Comparative Example 1)
Using the N-methylmaleimide-isobutene copolymer obtained in the same manner as in Example 1, and without adding a polycarbonate resin having an acrylonitrile-styrene copolymer in the side chain, polarization is performed in the same manner as in Example 1. A child protective film was produced, and a polarizing plate was produced in the same manner as in Example 1.

(Comparative Example 2)
Use acrylonitrile-styrene copolymer (manufactured by Mitsubishi Kasei Polytech Co., Ltd .: Sanrex) instead of polycarbonate resin (manufactured by NOF Corporation: Modiper C) having acrylonitrile-styrene copolymer in the side chain. A polarizer protective film was produced in the same manner as in Example 1, and a polarizing plate was produced in the same manner as in Example 1.

(Comparative Example 3)
A polycarbonate resin (manufactured by Teijin Kasei Co., Ltd .: Panlite K1300) was used in place of the polycarbonate resin having a acrylonitrile-styrene copolymer in the side chain (manufactured by Nippon Oil & Fats Co., Ltd .: Modiper C), and the others were the same as in Example 1. Then, a polarizer protective film was produced, and a polarizing plate was produced in the same manner as in Example 1.

(Comparative Example 4)
Instead of a polycarbonate resin having an acrylonitrile-styrene copolymer in the side chain (manufactured by NOF Corporation: Modiper C), 7% by weight of an acrylonitrile-styrene copolymer (manufactured by Mitsubishi Kasei Polytech Co., Ltd .: Sanrex) and a polycarbonate resin (Teijin) A polarizer protective film was produced in the same manner as in Example 1 except that 13% by weight of a product made by Kasei Co., Ltd .: Panlite K1300) was used in combination, and a polarizing plate was produced in the same manner as in Example 1.

  About the polarizer protective film obtained by the said Example and comparative example, evaluation and determination were performed with the evaluation method shown below. The results are shown in Table 1.

(Evaluation methods)
Tensile elongation at break: Measured according to JIS K 7127.
Tensile modulus: Measured according to JIS K 7113.
Line transportability: Polarizer protective film (700 mm width) is transferred to a film transport line consisting of multiple (15) guide rolls at a line speed of 20 m / min, and the frequency of troubles caused by film breakage is counted. / 5 hours were marked as ◯, 1-2 times / 5 hours as △, 3 times or more / 5 hours as x.
Reworkability: The polarizing plate was cut into 15 cm × 15 cm, then corona-treated again, and attached to a non-alkali glass substrate using a double-sided pressure-sensitive adhesive sheet (180 ° peel strength: 10 N / 25 mm width). The polarizing plate was peeled off from the corner in the vertical direction at an angle of 45 ° toward the center, and the case where the glass was completely peeled without any adhesive residue on the glass was marked with ○, and the case where tearing occurred halfway was marked with ×. .
A: N-methylmaleimide-isobutene copolymer (copolymer synthesized in Example 1)
B: Polycarbonate resin having acrylonitrile-styrene copolymer in the side chain (manufactured by NOF Corporation: Modiper C)
C: Acrylonitrile-styrene copolymer (manufactured by Mitsubishi Kasei Polytech Co., Ltd .: Sunrex)
D: Polycarbonate resin (Teijin Chemicals Ltd .: Panlite K1300)

Claims (3)

Consists of 30 to 98 mol% of the structural component represented by the following general formula (1) and 70 to 2 mol% of the structural component represented by the following general formula (2), and the weight average molecular weight in terms of polystyrene is 1 × 10. ^A polarizer comprising a resin composition comprising 50 to 90% by weight of an olefin-maleimide copolymer of ^{3 to} 5 × 10 ⁶ and 50 to 10% by weight of a polycarbonate resin having an acrylonitrile-styrene copolymer in the side chain. Protective film.
(Here, R ¹ represents an alkyl group having 1 to 18 carbon atoms or a cycloalkyl group having 3 to 12 carbon atoms.)
(Here, R ² represents hydrogen or an alkyl group having 1 to 8 carbon atoms, and R ³ and R ⁴ represent an alkyl group having 1 to 8 carbon atoms.)   The polarizer protective film according to claim 1, which has a tensile elongation at break of 4% or more and a tensile elastic modulus of 2500 MPa or more.   A polarizing plate comprising the polarizer protective film according to claim 1 or 2 bonded to at least one surface of a polarizer.