JP2014013283A - Polarizing plate and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing plate excellent in surface uniformity (wrinkle resistance), unevenness resistance under a high humidity environment and flatness (panel warpage resistance), and a liquid crystal display device equipped with the same.SOLUTION: A polarizing plate at least comprises a protective film, an active energy ray-curable resin layer and a polarizer, laminated in this order, and is configured to be installed in a liquid crystal display device. The protective film includes an acrylic resin (A) and a cellulose ester resin (B) within a range of 95:5-50:50 of a mass ratio (A:B), and is arranged on a surface opposite to a surface making contact with a liquid crystal cell.

Description

  The present invention relates to a polarizing plate and a liquid crystal display device including the polarizing plate.

  The liquid crystal display device is composed of a liquid crystal cell in which a transparent electrode, a liquid crystal layer, a color filter and the like are sandwiched between glass plates, and two polarizing plates provided on both sides thereof. A polarizer or a polarizing film) is sandwiched between two polarizing plate protective films.

  As this polarizing plate protective film, cellulose ester has been mainly used. This cellulose ester film has a high water vapor transmission rate, and can be immersed in an alkaline aqueous solution to saponify and hydrophilize the surface, thereby realizing excellent adhesion with a polarizer. However, since the cellulose ester film has high moisture permeability, the film easily undergoes a dimensional change due to moisture absorption or dehydration due to temperature and humidity changes, and the retardation of the retardation film is increased by allowing moisture to penetrate inside. In other words, the liquid crystal display device has a problem of unevenness in the liquid crystal display device.

  Thus, when applied as a polarizing plate protective film, since there is a limit to moisture resistance as a cellulose ester film, an acrylic resin, such as a polymethyl methacrylate film, which is an acrylic film material having low hygroscopicity, is provided on both sides. The technique used as a polarizing plate protective film is proposed (for example, refer patent document 1).

  However, a polarizing plate using an acrylic resin film as a polarizing plate protective film is brittle in film quality, and is usually poor in adhesiveness in a polyvinyl alcohol-based aqueous solution used in a saponification treatment process at the time of polarizing plate preparation. An active energy ray curable adhesive such as an ultraviolet curable adhesive having a higher adhesiveness, which is different from the polyvinyl alcohol-based adhesive, is used.

  By using this active energy ray-curable adhesive, unevenness due to moisture permeability that the cellulose ester film has is less likely to occur, but the acrylic film is inferior in heat resistance compared to the cellulose ester film. In recent years, there is a high demand for thinning the protective film for the polarizing plate in order to reduce the thickness of the panel. However, especially when the acrylic film is thinned, deformation (wrinkles) occurs in the ultraviolet irradiation process during the production of the polarizing plate. There was a problem.

  On the other hand, Patent Document 2 discloses a film in which a polarizing plate protective film is blended with a cellulose ester and an acrylic resin, but an active energy ray-curable adhesive is not used as an adhesion method with a polarizer. For this reason, there has been a problem that the film and the polarizer are peeled off when used for a long time in a high-humidity heat environment.

JP 2011-123169 A International Publication No. 2010/001668

  The present invention has been made in view of the above problems, and the problem to be solved is a polarizing plate excellent in surface uniformity (wrinkle resistance), unevenness resistance in a high-humidity environment, and flatness (panel warpage resistance). It is to provide a liquid crystal display device provided with the same.

  As a result of intensive studies in view of the above problems, the present inventor at least forms a polarizing plate by laminating at least a protective film, an active energy ray-curable resin layer, and a polarizer in this order, and the protective film. Contains an acrylic resin (A) and a cellulose ester resin (B) in a mass ratio (A: B) ratio of 95: 5 to 50:50, and the protective film and the polarizer are active constituent curable resins. When the polarizing plate and the liquid crystal cell are contacted to form a liquid crystal display device, the protective film is disposed on the surface of the polarizing plate opposite to the surface in contact with the liquid crystal cell. By arranging the protective film according to the present invention on the surface side of the liquid crystal display device, it is excellent in surface uniformity (wrinkle resistance), unevenness resistance under high humidity environment and flatness (panel warpage resistance). Realized polarizing plate It found that can Rukoto, is up which led to the present invention.

  That is, the said subject of this invention is solved by the following means.

  1. At least a protective film, an active energy ray-curable resin layer, and a polarizer are laminated in this order to form a polarizing plate provided in a liquid crystal display device, wherein the protective film is an acrylic resin (A) and cellulose The ester resin (B) is contained within a mass ratio (A: B) of 95: 5 to 50:50, and is disposed on the surface opposite to the surface in contact with the liquid crystal cell. A polarizing plate.

  2. An active energy ray-curable resin layer and a retardation film satisfying all of the following conditions 1 to 3 are laminated on the polarizer surface opposite to the surface on which the protective film is disposed. The polarizing plate according to item 1.

  Condition 1: An in-plane retardation value Ro (590) represented by the following formula (I) measured at a wavelength of 590 nm under an environment of a temperature of 23 ° C. and a relative humidity of 55% is in the range of 30 to 150 nm.

Formula (I): Ro (590) = (n x -n y) × d
Condition 2: Retardation value Rt (590) in the thickness direction represented by the following formula (II) measured at a wavelength of 590 nm under an environment of a temperature of 23 ° C. and a relative humidity of 55% is within a range of 70 to 300 nm. is there.

Formula (II): Rt (590) = {(n _x + n _y ) / 2−n _z } × d
Condition 3: The amount of change in the retardation value Rt (590) in the thickness direction when the humidity is changed from 20 to 80% in an environment of a temperature of 23 ° C. is in the range of 1 to 30 nm.
In [Formula (I) and formula (II), n _x represents a refractive index in the direction x in which the refractive index is maximized in the plane direction of the film. n _y, in-plane direction of the film, the refractive index in the process y perpendicular to the direction x. _nz represents the refractive index in the thickness direction z of the film. d represents the thickness (nm) of the film. ]
3. When the moisture permeability of the protective film containing the acrylic resin (A) and the cellulose ester resin (B) is measured according to JIS Z 0208 in an environment of 40 ° C. and 90% RH, 50 to 350 g / m ^2. The polarizing plate according to the first or second item, which is within a range of 24 hours.

  4). The polarizing plate according to any one of Items 1 to 3, wherein the acrylic resin (A) has a weight average molecular weight Mw in the range of 100,000 to 1,000,000.

  5. A liquid crystal display device comprising the polarizing plate according to any one of items 1 to 4.

  By the above means of the present invention, a polarizing plate excellent in surface uniformity (wrinkle resistance), unevenness resistance in a high humidity environment and flatness (panel warpage resistance), and a liquid crystal display device including the polarizing plate are provided. Can do.

  It is presumed that the above problem can be solved by the configuration defined in the present invention for the following reason.

  A film made of a conventional cellulose ester resin, because of its high moisture permeability, permeates moisture from the external environment into the inside of the polarizing plate and the liquid crystal display device. The retardation value (retardation value) of the retardation film is likely to fluctuate, and as a result, the liquid crystal display device is uneven in a high humidity environment.

  However, by disposing the film with low moisture permeability according to the present invention on the surface opposite to the surface in contact with the liquid crystal cell, for example, the fluctuation of the retardation value (phase difference value) due to water content is large. However, since it is possible to prevent moisture from penetrating into the retardation film, unevenness of the liquid crystal display device in a high humidity environment can be suppressed.

  Furthermore, by using an active energy ray curable adhesive instead of a water-soluble polyvinyl alcohol adhesive, it was possible to suppress the penetration of moisture into the retardation film side.

  In addition, the protective film according to the present invention is mainly composed of an acrylic resin to reduce moisture permeability, but by blending the cellulose ester resin to supplement heat resistance and brittleness, the presence of the cellulose ester resin, Since the active energy ray-curable adhesive easily penetrates into the protective film, it is considered that the adhesion to the polarizer is improved, and the heat resistance is higher than that of a general acrylic film. Deformation (wrinkles) and yellowing could be suppressed in the ultraviolet irradiation process when using the curable adhesive. In addition, with the thinning of the liquid crystal display device, not only the film of the present invention but also the polarizer can be made a thin film, and the shrinkage of the polarizer can be suppressed, and the flatness (warpage) of the liquid crystal display device can be improved. I guess it was made.

Sectional drawing which shows an example of a structure of the polarizing plate of this invention Sectional drawing which shows an example of a structure of the liquid crystal display device of this invention Schematic diagram showing an example of the dope preparation step, casting step and drying step of the solution casting film forming method preferred for the present invention

  The polarizing plate of the present invention is at least a protective film, an active energy ray curable resin layer, and a polarizer laminated in this order, and is provided in a liquid crystal display device, wherein the protective film comprises: The acrylic resin (A) and the cellulose ester resin (B) are contained within a mass ratio (A: B) of 95: 5 to 50:50, and on the surface side opposite to the surface in contact with the liquid crystal cell. It is characterized by being disposed, and a polarizing plate excellent in surface uniformity (wrinkle resistance), unevenness resistance in a high humidity environment and flatness (panel warpage resistance) can be realized. This feature is a technical feature common to the inventions according to claims 1 to 5.

  As an embodiment of the present invention, an active energy ray-curable resin layer is further provided on the polarizer surface on the side opposite to the surface on which the protective film is disposed, from the viewpoint that the effects intended by the present invention can be further expressed. And it is a preferable aspect that the retardation film provided with the specific retardation value is laminated | stacked.

Moreover, when the moisture permeability of the protective film containing the acrylic resin (A) and the cellulose ester resin (B) is measured according to JIS Z 0208 in an environment of 40 ° C. and 90% RH, 50 to 350 g / m. The range is preferably ² · 24 hours. Moreover, it is preferable that the weight average molecular weight Mw of the said acrylic resin (A) is the range of 100,000-1 million.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, "-" shown in this invention is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

<< Configuration of polarizing plate and liquid crystal display device >>
First, configurations of the polarizing plate and the liquid crystal display device of the present invention will be described with reference to the drawings.

  The polarizing plate of the present invention is characterized in that at least a protective film, an active energy ray-curable resin layer, and a polarizer are laminated in this order, and further, a surface on which the protective film is disposed, Is a configuration in which an active energy ray-curable resin layer and a retardation film having a specific litter value are laminated on the opposite polarizer surface.

  FIG. 1 is a schematic cross-sectional view showing an example of the configuration of the polarizing plate of the present invention.

  In FIG. 1, the polarizing plate 101 of this invention has the protective film 102 containing an acrylic resin (A) and a cellulose-ester resin (B) in a specific range from the surface side, and active energy ray hardening is carried out in the lower part. A mold resin layer 103A is provided. This active energy ray-curable resin layer 103A is a layer that functions to bond the protective film 101 and the polarizer 104, and is made of a material that is cured by irradiation with active energy rays, for example, ultraviolet rays. .

  In the polarizing plate 101 of the present invention, the surface of the polarizer 104 opposite to the surface on which the protective film 102 is disposed further includes an active energy ray-curable resin layer 103B and a specific retardation value. A configuration in which the retardation film 105 is laminated is preferable.

  Moreover, although not described in FIG. 1, for example, an antiglare layer, an antireflection layer, an antifouling layer, a hard coat layer, etc. are provided on the outer side (outermost surface portion) of the protective film as necessary. May be.

  FIG. 2 is a schematic cross-sectional view showing an example of the configuration of the liquid crystal display device 106 including the polarizing plate 101 of the present invention described above.

  In FIG. 2, a liquid crystal cell 106 is sandwiched between the retardation film 105 of the polarizing plate 101A and the retardation film 105 of the polarizing plate 101B described in FIG.

  The polarizing plate having such a configuration is characterized in that the protective film 101 according to the present invention is disposed at a position opposite to the surface in contact with the liquid crystal cell 107.

<Components of polarizing plate>
Next, details of the protective film, the active energy ray-curable resin layer, the polarizer, the retardation film, and the like constituting the polarizing plate of the present invention will be sequentially described.

〔Protective film〕
The protective film according to the present invention includes at least an acrylic resin (A) and a cellulose ester resin (B) in a mass ratio (A: B) range of 95: 5 to 50:50. To do.

(Acrylic resin (A))
Acrylic resins applicable to the present invention include methacrylic resins. Although it does not restrict | limit especially as an acrylic resin, The thing which a methylmethacrylate unit consists of 50-99 mass% and the total amount of the other monomer unit copolymerizable with this is 1-50 mass% is preferable. .

  Examples of other copolymerizable monomers include alkyl methacrylates having 2 to 18 carbon atoms, alkyl acrylates having 1 to 18 carbon atoms, and amides such as acryloylmorpholine and N, N-dimethylacrylamide. Vinyl monomers having a group, methacrylic acid ester or acrylic acid ester having an alicyclic hydrocarbon group having 5 to 22 carbon atoms in the ester portion, α, β-unsaturated acid such as acrylic acid, methacrylic acid, maleic acid, Unsaturated divalent carboxylic acids such as fumaric acid and itaconic acid, aromatic vinyl compounds such as styrene and α-methylstyrene, α and β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride, and the like. These may be used alone or in combination of two or more. A monomer can be used in combination.

  The acrylic resin of the present invention may have a ring structure, specifically, a lactone ring structure, a glutaric anhydride structure, a glutarimide structure, an N-substituted maleimide structure and a maleic anhydride structure, a pyran ring. Structure is mentioned.

  Among these, from the viewpoint of thermal decomposition resistance and fluidity of the copolymer, alkyl acrylate having 1 to 18 carbon atoms, vinyl monomer having an amide group such as acryloylmorpholine and dimethylacrylamide, and carbon number in the ester portion. A methacrylic acid ester or acrylic acid ester having 5 to 22 alicyclic hydrocarbon groups, an N-substituted maleimide structure, a pyran ring structure and the like are preferable.

  Specific examples of the alkyl acrylate having 1 to 18 carbon atoms are methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, etc., preferably And methyl acrylate.

  Specific examples of the vinyl monomer having an amide group include acrylamide, N-methylacrylamide, N-butylacrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, acryloylmorpholine, N-hydroxyethylacrylamide, acryloylpyrrolidine, Acryloylpiperidine, methacrylamide, N-methylmethacrylamide, N-butylmethacrylamide, N, N-dimethylmethacrylamide, N, N-diethylmethacrylamide, methacryloylmorpholine, N-hydroxyethylmethacrylamide, methacryloylpyrrolidine, methacryloylpiperidine, N-vinylformamide, N-vinylacetamide, vinylpyrrolidone and the like can be mentioned. Preferably, acryloylmorpholine, N, N-dimethylacrylamide, N-butylacrylamide, and vinylpyrrolidone are used.

Specific examples of the methacrylic acid ester or acrylic acid ester having an alicyclic hydrocarbon group having 5 to 22 carbon atoms in the ester portion include, for example, cyclopentyl acrylate, cyclohexyl acrylate, methyl cyclohexyl acrylate, trimethyl cyclohexyl acrylate, Norbornyl acrylate, norbornyl acrylate, cyano norbornyl acrylate, isobornyl acrylate, bornyl acrylate, menthyl acrylate, fentyl acrylate, adamantyl acrylate, dimethyladamantyl acrylate, tricycloacrylate [5.2 .1.0 ^2,6 ] dec-8-yl, tricyclo [5.2.1.0 ^2,6 ] dec-4-methyl acrylate, cyclodecyl acrylate, cyclopentyl methacrylate, cyclohex methacrylate Sil, methyl cyclohexyl methacrylate, trimethyl cyclohexyl methacrylate, norbornyl methacrylate, norbornyl methyl methacrylate, cyano norbornyl methacrylate, phenyl norbornyl methacrylate, isobornyl methacrylate, bornyl methacrylate, menthyl methacrylate, methacryl Fentyl acid, adamantyl methacrylate, dimethyladamantyl methacrylate, tricyclo [5.2.1.0 ^2,6 ] deca-8-yl methacrylate, tricyclo [5.2.1.0 ^2,6 ] decamethacrylate Examples include 4-methyl, cyclodecyl methacrylate, and dicyclopentanyl methacrylate.

  Preferable examples include isobornyl methacrylate, dicyclopentanyl methacrylate, dimethyladamantyl methacrylate and the like.

  Examples of the N-substituted maleimide include N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, Ni-propylmaleimide, N-butylmaleimide, Ni-butylmaleimide, Nt-butylmaleimide, N-laurylmaleimide, N-cyclohexylmaleimide, N-benzylmaleimide, N-phenylmaleimide, N- (2-chlorophenyl) maleimide, N- (4-chlorophenyl) maleimide, N- (4-bromophenyl) phenylmaleimide, N -(2-methylphenyl) maleimide, N- (2-ethylphenylmaleimide), N- (2-methoxyphenyl) maleimide, N- (2,4,6-trimethylphenyl) maleimide, N- (4-benzylphenyl) Maleimide, N- (2,4,6-tribromophe Le) maleimide and the like.

  Preferably, N-methylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, etc. are mentioned.

  Commercially available monomers can be used as they are.

  The acrylic resin (A) used for the acrylic resin-containing film according to the present invention has a weight average molecular weight (Mw) in the range of 100,000 to 1,000,000 in terms of mechanical strength as a film and fluidity when producing the film. It is preferable that it exists, More preferably, it exists in the range of 300000-500000.

  The weight average molecular weight of the acrylic resin (A) according to the present invention can be measured by gel permeation chromatography. The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (GL Science Co., Ltd.)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 2,800,000-500 calibration curves with 13 samples were used. The 13 samples are preferably used at approximately equal intervals.

  There is no restriction | limiting in particular as a manufacturing method of the acrylic resin (A) in this invention, You may use any well-known methods, such as suspension polymerization, emulsion polymerization, block polymerization, or solution polymerization. Here, as a polymerization initiator, a normal peroxide type and an azo type can be used, and a redox type can also be used. Regarding the polymerization temperature, suspension or emulsion polymerization can be carried out in the range of 30 to 100 ° C, and bulk or solution polymerization in the range of 80 to 160 ° C. In order to control the reduced viscosity of the obtained copolymer, polymerization can be carried out using alkyl mercaptan or the like as a chain transfer agent.

  A commercially available thing can also be used as an acrylic resin which concerns on this invention. For example, Delpet 60N, 80N (above, manufactured by Asahi Kasei Chemicals Co., Ltd.), Dianal BR52, BR80, BR83, BR85, BR88 (above, manufactured by Mitsubishi Rayon Co., Ltd.), Parapet HR-S (manufactured by Kuraray Co., Ltd.) ) And the like. Two or more acrylic resins can be used in combination.

(Cellulose ester resin (B))
The cellulose ester resin (B) according to the present invention is preferably selected from the following two types from the viewpoint of transparency, particularly when it is improved in brittleness and is compatible with the acrylic resin (A).

  As one of the cellulose ester resins (B) according to the present invention, it is preferable to use cellulose acetate having an average degree of substitution of acetyl groups in the range of 2.0 to 3.0.

  The average substitution degree of acetyl group here means the average number of esterified (acetylated) hydroxy groups (hydroxyl groups) among the three hydroxy groups (hydroxyl groups) of each anhydroglucose constituting cellulose. A value is shown, and a value within a range of 2.0 or more and less than 3.0 is shown.

  When the average degree of acetyl group substitution of cellulose acetate is 2.0 or more, it is possible to prevent the deterioration of film surface quality due to an increase in the dope viscosity, and a high-quality film can be obtained.

  In the present invention, the portion not substituted with an acetyl group is usually present as a hydroxy group (hydroxyl group). The cellulose acetate according to the present invention can be synthesized by a known method.

  In addition, the substitution degree of an acetyl group is calculated | required by the method prescribed | regulated to ASTM-D817-96 (test methods, such as a cellulose acetate).

  As another one of the cellulose ester resins (B), the average substitution degree (T) of acyl groups is 2.0 to 3.0, and the substitution degree of acyl groups having 3 to 7 carbon atoms is 0.5 to 3. Is preferably in the range of 0.0.

  That is, the cellulose ester resin (B) according to the present invention is a cellulose ester resin substituted with an acyl group having 3 to 7 carbon atoms. Specifically, propionyl, butyryl and the like are preferably used.

  When the average substitution degree of the acyl group of the cellulose ester resin (B) is less than 2.0, that is, when the residual degree of the hydroxyl groups at the 2, 3, and 6 positions of the cellulose ester molecule is more than 1.0, the acrylic ester When the resin (A) is not sufficiently compatible with the resin (A) and used as an optical film, haze becomes a problem.

  Moreover, even if the average substitution degree of the acyl group is 2.0 or more, if the substitution degree of the acyl group having 3 to 7 carbon atoms is less than 0.5, sufficient compatibility cannot be obtained.

  The average substitution degree (T) of the acyl group of the cellulose ester resin (B) is more preferably in the range of 2.5 to 3.0.

  Therefore, the cellulose ester resin (B) according to the present invention is selected from cellulose diacetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate benzoate, cellulose propionate, and cellulose butyrate in addition to cellulose triacetate. It is preferable that it is at least one kind.

  Among these, cellulose ester resins (B) that are particularly preferable are cellulose triacetate, cellulose acetate propionate, and cellulose acetate butyrate.

  The portion not substituted with an acyl group is usually present as a hydroxy group. These can be synthesized by known methods.

  In addition, the substitution degree of an acetyl group and the substitution degree of other acyl groups are obtained by a method prescribed in ASTM-D817-96.

  The weight average molecular weight (Mw) of the cellulose ester resin according to the present invention is 75,000 or more, particularly from the viewpoint of improving compatibility with the acrylic resin (A) and brittleness, and is preferably in the range of 100,000 to 1,000,000. It is particularly preferable that it is in the range of ˜500000.

  When the weight average molecular weight (Mw) of the cellulose ester resin is less than 75,000, the effect of improving heat resistance and brittleness decreases. Moreover, when it exceeds 1000000, a viscosity becomes high and film formation becomes difficult.

  Moreover, in this invention, 2 or more types of cellulose resins can also be mixed and used.

  The weight average molecular weight of the cellulose ester resin according to the present invention can be measured by the GPC.

  In the protective film according to the present invention, the acrylic resin (A) and the cellulose ester resin (B) are preferably contained in a compatible state within a mass ratio range of 95: 5 to 50:50. Is 90: 10-70: 30.

  When the mass ratio of the acrylic resin (A) and the cellulose ester resin (B) is more than 95: 5, the heat resistance and the adhesion to the polarizer cannot be sufficiently obtained, and the same mass ratio. However, if the amount of acrylic resin is less than 50:50, the moisture permeability increases.

  In the protective film according to the present invention, the acrylic resin (A) and the cellulose ester resin (B) are preferably contained in a compatible state. The physical properties and quality required for an optical film are achieved by supplementing each other by dissolving different resins.

  Whether the acrylic resin (A) and the cellulose ester resin (B) are in a compatible state can be determined by, for example, the glass transition temperature Tg.

  For example, when the two resins have different glass transition temperatures, when the two resins are mixed, there are two or more glass transition temperatures for each resin because there is a glass transition temperature for each resin. When they are compatible, the glass transition temperature specific to each resin disappears and becomes one glass transition temperature, which is the glass transition temperature of the compatible resin.

  In addition, the glass transition temperature here is the intermediate | middle calculated | required according to JISK7121 (1987), using the differential scanning calorimeter (DSC-7 type | mold by Perkin Elmer), measured with the temperature increase rate of 20 degree-C / min. The point glass transition temperature (Tmg).

  The weight average molecular weight (Mw) of the acrylic resin (A) in the protective film according to the present invention, the weight average molecular weight (Mw) of the cellulose ester resin (B), and the degree of substitution are based on the difference in solubility of both resins in the solvent. Thus, it is obtained by measuring each after the separation.

  When fractionating the resin, it is possible to extract and separate the soluble resin by adding a compatible resin in a solvent that is soluble only in either one. At this time, heating operation or reflux is performed. May be.

  A combination of these solvents may be combined in two or more steps to separate the resin. The dissolved resin and the resin remaining as an insoluble matter are filtered off, and the solution containing the extract can be separated by an operation of evaporating the solvent and drying.

  These fractionated resins can be identified by general structural analysis of polymers. Even when the protective film according to the present invention contains a resin other than the acrylic resin (A) or the cellulose ester resin (B), it can be separated by the same method.

  If the weight average molecular weights (Mw) of the compatible resins are different, the high molecular weight substances are eluted earlier by gel permeation chromatography (GPC), and the lower molecular weight substances are eluted after a longer time. Therefore, it can be easily fractionated and the molecular weight can be measured.

  In addition, the molecular weight of the compatible resin is measured by GPC, and at the same time, the resin solution eluted every time is separated, the solvent is distilled off, and the dried resin is different by quantitatively analyzing the structure. By detecting the resin composition for each molecular weight fraction, it is possible to identify each compatible resin.

  By measuring the molecular weight distribution of each of the resins separated in advance based on the difference in solubility in a solvent by GPC, it is possible to detect each of the compatible resins.

  The total mass of the acrylic resin (A) and the cellulose ester resin (B) in the protective film according to the present invention is preferably 55% by mass or more of the total mass of the protective film, more preferably 60% by mass or more, in particular. Preferably, it is 70 mass% or more.

(Other additive resins)
In the protective film according to the present invention, when a resin other than the acrylic resin (A) and the cellulose ester resin (B) is used, the addition amount is preferably adjusted within a range not impairing the function of the polarizing plate of the present invention. .

  As a preferable resin, a low molecular acrylic resin obtained by polymerizing an ethylenically unsaturated monomer described in paragraphs (0072) to (0123) of JP2010-32655A (weight average molecular weight Mw is 500 or more, Polymer having a molecular weight of 30000 or less).

  Particularly preferably, Mw is in the range of 2000 to 30000. If it is 2000 or less, a problem occurs in bleed out, and if it exceeds 30000, the transparency is deteriorated.

  Moreover, the vinyl polymer which has an amide bond as described in Unexamined-Japanese-Patent No. 2009-249588, paragraph number (0038)-(0045) can also be used.

  In this invention, it is 0-15 mass% with respect to the total mass of a protective film, and it is preferable that the low molecular acrylic resin and the vinyl polymer which has an amide bond are the range of 0-10 mass%.

(Various additives)
The protective film according to the present invention includes a retardation (phase difference) control agent for the purpose of controlling retardation, a plasticizer that imparts processability to the film, an antioxidant that prevents deterioration of the film, and UV absorption. Various additives such as an ultraviolet absorber for imparting a function, fine particles (matting agent) for imparting slipperiness to the film, and acrylic fine particles for improving toughness can be contained as necessary.

<Polyester polyol of glycol and dibasic acid>
The polyester polyol that can be used in the present invention includes a dehydration condensation reaction between a glycol having an average carbon number of 2 to 3.5 and a dibasic acid having an average carbon number of 4 to 5.5, or the glycol. It is preferable to be produced by a conventional method by addition of a dibasic anhydride having an average carbon number of 4 to 5.5 and a dehydration condensation reaction.

<Polyester of aromatic dicarboxylic acid and alkylene glycol>
In the present invention, an aromatic terminal polyester represented by the following general formula (I) can be used as a retardation control agent.

Formula (I)
B- (GA) _n -GB
In the general formula (I), B is a benzene monocarboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene having 4 to 12 carbon atoms. A glycol residue, A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.

  In the general formula (I), a benzene monocarboxylic acid residue represented by B and an alkylene glycol residue, oxyalkylene glycol residue or aryl glycol residue represented by G, an alkylene dicarboxylic acid residue or aryl dicarboxylic group represented by A It is composed of an acid residue and can be obtained by a reaction similar to that of ordinary polyester.

  In the present invention, specific compounds of the aromatic terminal polyester include compounds described in paragraph numbers (0183) to (0186) of JP2010-32655A.

  The content of the aromatic terminal polyester is preferably 0 to 20% by mass, particularly preferably 1 to 11% by mass, in the protective film according to the present invention.

<Polyhydric ester compound>
The protective film according to the present invention may contain a polyhydric alcohol ester compound.

  Examples of the polyhydric alcohol ester compound include compounds described in paragraph numbers (0218) to (0170) of JP2010-32655A.

<Sugar ester compound>
In the present invention, sugar ester compounds other than cellulose ester can be contained. As the sugar ester compound according to the present invention, a sugar ester compound in which at least one of the pyranose structure or furanose structure is 1 to 12 and all or a part of the OH groups of the structure is esterified is used. Is preferred.

  Examples of the sugar ester compound used in the present invention include glucose, galactose, mannose, fructose, xylose, arabinose, lactose, sucrose, cellobiose, cellotriose, maltotriose, raffinose and the like. What has is preferable. An example is sucrose.

  The sugar ester compound used in the present invention is one in which a part or all of the hydroxy group of the sugar compound is esterified or a mixture thereof.

  Specific examples of the sugar ester compound applicable to the present invention include compounds described in paragraphs (0060) to (0070) of JP 2010-32655 A.

<Retardation control agent>
As the retardation control agent, a known retardation control agent can be used, and in particular, it is used for controlling the retardation value in the thickness direction.

  Specific examples include those containing bisphenol A in the molecule, and compounds having ethylene oxide and propylene oxide added to both ends of bisphenol A can be used.

  For example, BP series such as New Pole BP-2P, BP-3P, BP-23P, BP-5P, BPE-20 (F), BPE-20NK, BPE-20T, BPE-40, BPE-60, BPE-100 BPE series such as BPE-180 (manufactured by Sanyo Chemical Co., Ltd.) and BPX series such as Adeka polyether BPX-11, BPX-33, BPX-55 (manufactured by Adeka Co., Ltd.).

  Diallyl bisphenol A, dimethallyl bisphenol A, tetrabromobisphenol A with bisphenol A substituted with bromine, oligomers and polymers obtained by polymerizing this, bisphenol A bis (diphenyl phosphate) substituted with diphenyl phosphate, etc. Can be used.

  Polycarbonate obtained by polymerizing bisphenol A, polyarylate obtained by polymerizing bisphenol A with a dibasic acid such as terephthalic acid, and an epoxy oligomer or polymer polymerized with an epoxy-containing monomer can also be used.

  Modiper CL130D or L440-G obtained by graft polymerization of bisphenol A and styrene, styrene acrylic, or the like can also be used.

  A compound having a riadine structure is also preferable. Examples of these compounds include compounds described in JP-A No. 2001-166144.

<Antioxidant>
In this invention, what is generally known can be used as an antioxidant. In particular, lactone, sulfur, phenol, double bond, hindered amine, and phosphorus compounds can be preferably used.

  For example, “IrgafosXP40, IrgafosXP60 (trade name)” commercially available from BASF Japan Ltd. and the like can be mentioned.

  As the phenolic compound, those having a 2,6-dialkylphenol structure are preferable. For example, “Irganox 1076”, “Irganox 1010” commercially available from BASF Japan Ltd., and “Analyzed by ADEKA” ADEKA STAB AO-50 "and the like.

  Examples of the phosphorus compounds include “Sumizer GP” commercially available from Sumitomo Chemical Co., Ltd., “ADK STAB PEP-24G”, “ADK STAB PEP-36” and “ADK STAB 3010” commercially available from ADEKA Corporation. “IRGAFOS P-EPQ” commercially available from BASF Japan Ltd. and “GSY-P101” commercially available from Sakai Chemical Industry Co., Ltd.

  Examples of the hindered amine compound include “Tinvin 144” and “Tinvin 770” commercially available from BASF Japan, and “ADK STAB LA-52” commercially available from ADEKA.

  Examples of the sulfur compound include “Sumilizer TPL-R” and “Sumilizer TP-D” commercially available from Sumitomo Chemical Co., Ltd.

  The above double bond compounds are commercially available from Sumitomo Chemical Co., Ltd. under the trade names “Sumilizer GM” and “Sumilizer GS”.

<Acid supplement>
Furthermore, it is possible to contain a compound having an epoxy group as described in US Pat. No. 4,137,201 as an acid scavenger.

  The amount of these antioxidants and the like to be appropriately added is determined in accordance with the process at the time of recycling and use. Is added in the range of 0.1 to 1% by mass.

  These antioxidants can obtain a synergistic effect by using several different types of compounds in combination rather than using only one kind. For example, the combined use of lactone, phosphorus, phenol and double bond compounds is preferred.

<Colorant>
In the present invention, it is preferable to use a colorant. The colorant means a dye or a pigment. In the present invention, the colorant refers to a colorant having an effect of making a color tone of a liquid crystal screen a blue tone, a yellow index adjustment, or a haze reduction.

  Various dyes and pigments can be used as the colorant, but anthraquinone dyes, azo dyes, phthalocyanine pigments and the like are effective.

<Ultraviolet absorber>
Examples of the ultraviolet absorber used in the present invention include benzotriazole-based, 2-hydroxybenzophenone-based, and salicylic acid phenyl ester-based ultraviolet absorbers. For example, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3 Triazoles such as 5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone And benzophenones.

  Of the UV absorbers, UV absorbers having a molecular weight of 400 or more are not sublimated or are not easily volatilized at a high boiling point. From the viewpoint of improving weather resistance, it is preferable.

  Examples of the ultraviolet absorber having a molecular weight of 400 or more include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2-methylenebis [4- ( 1,1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] and the like, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, Hindered amines such as bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and further 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butyl Bis (1,2,2,6,6-pentamethyl-4-piperidyl) malonate, 1- [2- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy Cis] ethyl] -4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine The hybrid type | system | group which has the structure of a hindered amine is mentioned, These can be used individually or in combination of 2 or more types. Among these, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole and 2,2-methylenebis [4- (1,1,3,3- Tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] is particularly preferred.

  As these ultraviolet absorbers, commercially available products may be used, for example, Tinuvin 109, Tinuvin 171, Tinuvin 234, Tinuvin 326, Tinuvin 327, Tinuvin 328, Tinuvin 928, etc. manufactured by BASF Japan, or 2, 2'-methylenebis [6- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol] (molecular weight 659; examples of commercially available products are manufactured by ADEKA Corporation LA31) can be preferably used.

<Matting agent>
In the present invention, it is preferable to add a matting agent in order to impart film slipperiness.

  The matting agent used in the present invention may be either an inorganic compound or an organic compound as long as it does not impair the transparency of the resulting film and has heat resistance during melting. These matting agents can be used alone or in combination of two or more.

  By using particles having different particle sizes and shapes (for example, acicular and spherical), both transparency and slipperiness can be made highly compatible.

  Among these, silicon dioxide is particularly preferably used since it has a refractive index close to that of cellulose ester and is excellent in transparency (haze).

  Specific examples of silicon dioxide include Aerosil 200V, Aerosil R972V, Aerosil R972, R974, R812, 200, 300, R202, OX50, TT600, NAX50 (manufactured by Nippon Aerosil Co., Ltd.), Sea Hoster KEP-10, Sea Hoster KEP- 30, Seahoster KEP-50 (manufactured by Nippon Shokubai Co., Ltd.), Silo Hovic 100 (manufactured by Fuji Silysia), nip seal E220A (manufactured by Nippon Silica Industry), Admafine SO (manufactured by Admatex) Goods etc. can be preferably used.

  The shape of the particles can be used without particular limitation, such as indefinite shape, needle shape, flat shape, spherical shape, etc. However, the use of spherical particles is particularly preferable because the transparency of the resulting film can be improved.

  When the particle size is close to the wavelength of visible light, light is scattered and the transparency is deteriorated. Therefore, the particle size is preferably smaller than the wavelength of visible light, and more preferably ½ or less of the wavelength of visible light. . If the size of the particles is too small, the slipperiness may not be improved, so the range of 80 nm to 180 nm is particularly preferable.

  The particle size means the size of the aggregate when the particle is an aggregate of primary particles. Moreover, when a particle is not spherical, it means the diameter of a circle corresponding to the projected area.

<Acrylic particles>
The protective film according to the present invention may contain acrylic particles (D) described in International Publication No. 2010/001668.

  As an example of a commercial item of such a multilayer structure acrylic granular composite, for example, “Metablene W-341” manufactured by Mitsubishi Rayon Co., “Kaneace” manufactured by Kaneka Chemical Co., Ltd., “ "Parroid", "Acryloid" manufactured by Rohm and Haas, "Staffroid" manufactured by Gantz Kasei Kogyo, Chemisnow MR-2G, MS-300X (above, manufactured by Soken Chemical Co., Ltd.) and "Parapet SA manufactured by Kuraray Co., Ltd." These may be used alone or in combination of two or more.

<Hydrogen bondable solvent>
In the present invention, when a film is used in the solution casting method, a hydrogen bonding solvent can be added to the solvent for dissolving the constituent material of the film for the purpose of adjusting the solution viscosity. The hydrogen bonding solvent is J.I. N. As described in Israel Ativili, “Intermolecular Forces and Surface Forces” (Takeshi Kondo, Hiroyuki Oshima, Maglow Hill Publishing, 1991) and electrically negative atoms (oxygen, nitrogen, fluorine, chlorine) An organic solvent capable of producing a hydrogen atom-mediated “bond” between a hydrogen atom covalently bonded to an electronegative atom, ie, a bond having a large bond moment and containing hydrogen, such as O—H (Oxygen hydrogen bond), N—H (nitrogen hydrogen bond), and organic solvent that can arrange adjacent molecules by including F—H (fluorine hydrogen bond).

  These can be inferred by forming a stronger hydrogen bond between the resin and the hydrogen bonding solvent than the intermolecular hydrogen bond of the cellulose resin, the acrylic resin, or the resin mixture itself to be compatibilized.

  In the solution casting method performed in the present invention, in addition to adjusting the solution viscosity with respect to the resin solution to be used, in order to reduce the peeling force at the time of film formation, a hydrogen bond is added to the solvent for dissolution. A part or all of the solvent may be used.

(Physical properties of protective film)
Hereinafter, the characteristic about the physical property etc. of the protective film in this invention is demonstrated.

  As the protective film according to the present invention, the ductile fracture is not caused by breakage such as breakage even when a large stress is applied to the film in two at 23 ° C. and 55% RH. Shall be evaluated.

  As the protective film according to the present invention, if the tension softening point in an atmosphere of 23 ° C. and 55% RH is 85 ° C. to 135 ° C., it can be judged that sufficient heat resistance is exhibited. In particular, it is more preferable to control to 100 ° C to 115 ° C.

  As an index for judging the transparency of the protective film according to the present invention, a haze value (turbidity) is used. In particular, in a liquid crystal display device used outdoors, it is required that sufficient brightness and high contrast are obtained even in a bright place. Therefore, the haze value is preferably 1.0% or less, and is 0.5% or less. More preferably. When used as a scattering film, the haze value may exceed the above range.

  The thickness of the protective film according to the present invention is preferably 10 μm or more. More preferably, it is 30 μm or more.

  The protective film according to the present invention preferably has a total light transmittance of 90% or more, more preferably 93% or more. Moreover, as a realistic upper limit, it is about 99%.

  The protective film according to the present invention can be particularly preferably used as a polarizing plate protective film for a large-sized liquid crystal display device or a liquid crystal display device for outdoor use as long as the physical properties as described above are satisfied.

(Method for producing protective film)
Subsequently, although the example of the manufacturing method of the protective film which concerns on this invention is demonstrated, this invention is not limited to this.

  As a production method of the protective film according to the present invention, production methods such as a normal inflation method, a T-die method, a calendering method, a cutting method, a casting method, an emulsion method, and a hot press method can be used. From the viewpoints of suppressing foreign matter defects and optical defects such as die lines, the film forming method can be selected from a solution casting film forming method and a melt casting film forming method. Preferred for obtaining a surface.

<Solution casting film forming method>
When the protective film according to the present invention is produced by the solution casting method, the organic solvent useful for forming the dope is one that simultaneously dissolves the acrylic resin (A), the cellulose ester resin (B), and other additives. If it is, it can be used without limitation.

  For example, as the chlorinated organic solvent, methylene chloride, as the non-chlorinated organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro- Examples include 2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, and nitroethane. Methylene chloride, methyl acetate, ethyl acetate, and acetone can be preferably used.

  In addition to the organic solvent, the dope preferably contains 1 to 40% by mass of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. When the ratio of alcohol in the dope increases, the web gels and peeling from the metal support becomes easy. When the ratio of alcohol is small, acrylic resin (A) and cellulose ester in non-chlorine organic solvent system. There is also a role of promoting dissolution of the resin (B).

  In particular, a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms contains acrylic resin (A) and cellulose ester resin (B) at least 15 to 45 mass% in total. A dissolved dope composition is preferred.

  Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Ethanol is preferred because of the stability of these dopes, the relatively low boiling point, and good drying properties.

  Hereinafter, the preferable film forming method of the protective film according to the present invention will be described.

1) Dissolution step In an organic solvent mainly composed of a good solvent for the acrylic resin (A) and the cellulose ester resin (B), the acrylic resin (A), the cellulose ester resin (B), and optionally acrylic particles ( C), a step of dissolving other additives while stirring to form a dope, or the acrylic resin (A) and cellulose ester resin (B) solutions, optionally with acrylic particle (C) solutions and other additive solutions Are mixed to form a dope which is a main solution.

  For dissolving the acrylic resin (A) and the cellulose ester resin (B), a method performed at normal pressure, a method performed below the boiling point of the main solvent, a method performed under pressure above the boiling point of the main solvent, JP-A-9-95544 Various dissolution methods such as a method performed by a cooling dissolution method as described in JP-A-9-95557, or JP-A-9-95538, a method performed at a high pressure as described in JP-A-11-21379 However, a method in which pressure is applied at a temperature equal to or higher than the boiling point of the main solvent is preferable.

  The concentration of the acrylic resin (A) and the cellulose ester resin (B) in the dope is preferably in the range of 15 to 45% by mass. An additive is added to the dope during or after dissolution to dissolve and disperse, then filtered through a filter medium, defoamed, and sent to the next step with a liquid feed pump.

  It is preferable to use a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml.

  In this method, the aggregate remaining at the time of particle dispersion and the aggregate generated when the main dope is added are aggregated by using a filter medium having a collected particle diameter of 0.5 to 5 μm and a drainage time of 10 to 25 sec / 100 ml. Can only be removed. In the main dope, the concentration of particles is sufficiently thinner than that of the additive solution, so that aggregates do not stick together at the time of filtration and the filtration pressure does not increase suddenly.

  FIG. 3 is a diagram schematically showing an example of a dope preparation step, a casting step, and a drying step of a solution casting film forming method preferable for the present invention.

  Large agglomerates are removed from the charging kettle 41 by the filter 44 and fed to the stock kettle 42. Thereafter, various additive solutions are added from the stock kettle 42 to the main dope dissolving kettle 1.

  Thereafter, the main dope solution is filtered by the main filter 3, and an ultraviolet absorbent additive solution is added in-line from 16 to this.

  In many cases, the main dope may contain about 10 to 50% by mass of the recycled material.

  Recycled material is a product obtained by finely pulverizing a protective film, which is produced when a protective film is formed, such as a film that has been cut off on both sides of the film, or a protective film that has been speculated out of scratches. .

  Moreover, as a raw material of resin used for dope preparation, what pelletized acrylic resin, cellulose ester resin, etc. previously can be used preferably.

2) Casting process An endless metal belt 31 such as a stainless steel belt or a rotating metal drum that feeds the dope to a pressure die 30 through a liquid feed pump (for example, a pressurized metering gear pump) and transfers it indefinitely. This is a step of casting a dope from a pressure die slit to a casting position on a metal support.

  A pressure die that can adjust the slit shape of the die base portion and can easily make the film thickness uniform is preferable. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used. The surface of the metal support is a mirror surface. In order to increase the film forming speed, two or more pressure dies may be provided on the metal support, and the dope amount may be divided and stacked. Or it is also preferable to obtain the film of a laminated structure by the co-casting method which casts several dope simultaneously.

3) Solvent evaporation step In this step, the web (the dope is cast on the casting support and the formed dope film is called a web) is heated on the casting support to evaporate the solvent.

  In order to evaporate the solvent, there are a method of blowing air from the web side and / or a method of transferring heat from the back side of the support by a liquid, a method of transferring heat from the front and back by radiant heat, and the like. The drying efficiency is good and preferable. A method of combining them is also preferably used. The web on the support after casting is preferably dried on the support in an atmosphere of 40 to 100 ° C. In order to maintain the atmosphere at 40 to 100 ° C., it is preferable to apply hot air at this temperature to the upper surface of the web or to heat by means such as infrared rays.

  From the viewpoint of surface quality, moisture permeability, and peelability, it is preferable to peel the web from the support within 30 to 120 seconds.

4) Peeling process It is the process of peeling the web which the solvent evaporated on the metal support body in a peeling position. The peeled web is sent to the next process.

  The temperature at the peeling position on the metal support is preferably 10 to 40 ° C, more preferably 11 to 30 ° C.

  In addition, it is preferable that the residual solvent amount at the time of peeling of the web on the metal support at the time of peeling is peeled in the range of 50 to 120% by mass depending on the strength of drying conditions, the length of the metal support, and the like. If the web is peeled off at a time when the amount of residual solvent is larger, if the web is too soft, the flatness at the time of peeling will be lost, and slippage and vertical stripes are likely to occur due to the peeling tension. The amount of solvent is determined.

  The residual solvent amount of the web is defined by the following formula.

Residual solvent amount (%) = (mass before web heat treatment−mass after web heat treatment) / (mass after web heat treatment) × 100
Note that the heat treatment for measuring the residual solvent amount represents performing heat treatment at 140 ° C. for 1 hour.

  The peeling tension at the time of peeling the metal support and the film is usually 196 to 245 N / m, but when wrinkles are easily formed at the time of peeling, it is preferable to peel with a tension of 190 N / m or less.

  In the present invention, the temperature at the peeling position on the metal support is preferably in the range of −50 to 40 ° C., more preferably in the range of 10 to 40 ° C., and in the range of 15 to 30 ° C. Is most preferred.

5) Drying and stretching step After peeling, a drying device 35 that transports the web alternately through rolls arranged in the drying device and / or a tenter stretching device 34 that clips and transports both ends of the web with clips. And dry the web.

  Generally, the drying means blows hot air on both sides of the web, but there is also a means for heating by applying microwaves instead of the wind. Too rapid drying tends to impair the flatness of the finished film. Drying at a high temperature is preferably performed from about 8% by mass or less of the residual solvent. Throughout, the drying is generally performed within a range of 40 to 250 ° C. It is particularly preferable to dry within the range of 40 to 200 ° C.

  When using a tenter stretching apparatus, it is preferable to use an apparatus that can independently control the film gripping length (distance from the start of gripping to the end of gripping) left and right by the left and right gripping means of the tenter. In the tenter process, it is also preferable to intentionally create sections having different temperatures in order to improve planarity.

  It is also preferable to provide a neutral zone between different temperature zones so that the zones do not interfere with each other.

  The stretching operation may be performed in multiple stages, and it is particularly preferable to perform biaxial stretching in the casting direction and the width direction. When biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be performed stepwise. The draw ratio is 1.1 to 9 times, preferably 1.2 to 5 times, by adding the casting direction and the width direction.

  In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, stretching in the same direction is divided into multiple stages, and stretching in different directions is added to any one of the stages. Is also possible. That is, for example, the following stretching steps are possible.

-Stretch in the casting direction-> Stretch in the width direction-> Stretch in the casting direction-> Stretch in the casting direction-Stretch in the width direction-> Stretch in the width direction-> Stretch in the casting direction-> Stretch in the casting direction Simultaneous biaxial stretching includes stretching in one direction and contracting the other while relaxing the tension. The preferable draw ratio of simultaneous biaxial stretching is in the range of 1.01 to 1.5 times in both the width direction and the longitudinal direction.

  When the tenter is used, the residual solvent amount of the web is preferably in the range of 20 to 100% by mass at the start of the tenter, and drying is performed while the tenter is applied until the residual solvent amount of the web becomes 10% by mass or less. Is more preferable, and more preferably 5% by mass or less.

  The drying temperature when performing the tenter is preferably in the range of 30 to 160 ° C, more preferably in the range of 50 to 150 ° C.

  In the tenter process, it is preferable that the temperature distribution in the width direction of the atmosphere is small from the viewpoint of improving the uniformity of the film. The temperature distribution in the width direction in the tenter process is preferably within ± 5 ° C, and within ± 2 ° C. Is more preferable, and within ± 1 ° C is most preferable.

6) Winding process This is a process in which the amount of residual solvent in the web becomes 2% by mass or less and is wound by the winder 37 as a protective film, and the dimensional stability is achieved by making the residual solvent amount 0.4% by mass or less. A film having good properties can be obtained. In particular, it is preferable to wind up in the range of 0.00 to 0.10% by mass.

  As a winding method, a generally used method may be used. There are a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, and the like.

  The protective film according to the present invention is preferably a long film. Specifically, the protective film has a thickness of about 100 m to 10000 m, and is usually provided in a roll shape. Moreover, it is preferable that the width | variety of a film is 1-4m, and it is more preferable that it is 1.4-2m.

<Melt casting method>
The protective film according to the present invention can also be formed by a melt casting method.

  The melt film-forming method refers to a method in which a composition containing additives such as a resin and a plasticizer is heated and melted to a temperature exhibiting fluidity, and then a melt containing fluid cellulose acetate is cast.

  The molding method for heating and melting can be classified in detail into a melt extrusion molding method, a press molding method, an inflation method, an injection molding method, a blow molding method, a stretch molding method, and the like. Among these molding methods, the melt extrusion method is preferable from the viewpoint of mechanical strength and surface accuracy. The plurality of raw materials used in the melt extrusion method are usually preferably kneaded in advance and pelletized.

  Pelletization may be performed by a known method. For example, dry cellulose acetate, plasticizer, and other additives are fed to an extruder using a feeder, kneaded using a single or twin screw extruder, and then formed into a strand from a die. It can be carried out by extruding, water cooling or air cooling and cutting.

  The additives may be mixed before being supplied to the extruder, or may be supplied by individual feeders.

  A small amount of additives such as particles and antioxidants are preferably mixed in advance in order to mix uniformly.

  It is preferable that the extruder can be pelletized so as to suppress the shearing force and prevent the resin from deteriorating (molecular weight reduction, coloring, gel formation, etc.) and processing at as low a temperature as possible. For example, in the case of a twin screw extruder, it is preferable to rotate in the same direction using a deep groove type screw. From the uniformity of kneading, the meshing type is preferable.

  A film is formed using the pellets obtained as described above. Of course, the raw material powder can be directly fed to the extruder by a feeder without being pelletized to form a film as it is.

  The melting temperature when extruding the above pellets using a single-screw or twin-screw type extruder is set to a temperature range of 200 to 300 ° C., filtered through a leaf disk type filter, etc. A film is cast from the die, the film is nipped by a cooling roller and an elastic touch roller, and solidified on the cooling roller.

  A method of preventing oxidative decomposition or the like under vacuum or reduced pressure or in an inert gas atmosphere when introducing from the supply hopper to the extruder is also preferable.

  The extrusion flow rate is preferably performed stably by introducing a gear pump or the like. Further, a stainless fiber sintered filter is preferably used as a filter used for removing foreign substances. The stainless steel fiber sintered filter is made by compressing the intricately intertwined state of the stainless steel fiber body and sintering and integrating the contact points. The density changes depending on the thickness of the fiber and the amount of compression, and the filtration accuracy Can be adjusted.

  Additives such as plasticizers and particles may be mixed with the resin in advance, or may be kneaded in the middle of the extruder. In order to add uniformly, it is preferable to use a mixing apparatus such as a static mixer.

  When the film is nipped by the cooling roller and the elastic touch roller, the film temperature on the touch roller side is preferably in the temperature range of Tg to Tg + 110 ° C. of the film. A known roller can be used as the roller having an elastic surface used for such a purpose.

  The elastic touch roller is also referred to as a pinching rotator. A commercially available elastic touch roller can also be used.

  When peeling the film from the cooling roller, it is preferable to control the tension to prevent deformation of the film.

  Moreover, it is preferable that the film obtained as described above is stretched by the stretching operation after passing through the step of contacting the cooling roller.

  As a stretching method, a known roller stretching machine or tenter can be preferably used. The stretching temperature is usually preferably performed in the temperature range of Tg to Tg + 60 ° C. of the resin constituting the film.

  Prior to winding, the ends may be slit and cut to the width of the product, and knurling (embossing) may be applied to both ends to prevent sticking or scratching during winding. The knurling method can process a metal ring having an uneven pattern on its side surface by heating or pressing. Note that the clip holding portions at both ends of the film are usually cut off because the film is deformed and cannot be used as a product. If the material has not deteriorated due to heat, it is reused after recovery.

[Active energy ray-curable resin layer]
The active energy ray-curable resin layer according to the present invention preferably contains an active energy ray-curable adhesive for bonding the protective film and the polarizer. The active energy ray-curable adhesive includes a cationic polymerization type and a radical polymerization type.

  Preferable examples of the active energy ray-curable adhesive that can be suitably used in the present invention include active energy ray-curable adhesive compositions containing the following components (α) to (δ).

(Α) Cationic polymerizable compound (β) Photocationic polymerization initiator (γ) Photosensitizer exhibiting maximum absorption for light having a wavelength longer than 380 nm (δ) Naphthalene photosensitizer (cationic polymerizable compound (α ))
The cationic polymerizable compound (α), which is a main component of the active energy ray-curable adhesive composition and serves as a component that imparts adhesive force by polymerization and curing, may be any compound that cures by cationic polymerization. It is preferable to include an epoxy compound having two epoxy groups. The epoxy compound includes an aromatic epoxy compound having an aromatic ring in the molecule, an alicyclic epoxy compound having at least two epoxy groups in the molecule, and at least one of which is bonded to the alicyclic ring. A fatty acid that does not have an aromatic ring in the molecule and one carbon atom of the ring containing the two carbon atoms to which it is bonded (usually an oxirane ring) is bonded to another aliphatic carbon atom Group epoxy compounds. The active energy ray-curable adhesive composition used in the present invention is preferably an epoxy resin not containing an aromatic ring and an alicyclic epoxy compound as a main component, particularly as the cationic polymerizable compound (α). If a cationically polymerizable compound having an alicyclic epoxy compound as a main component is used, a cured product having a high storage elastic modulus is provided, and a protective film and a polarizer are bonded via the cured product (adhesive layer). In this case, the polarizer is difficult to break.

  The alicyclic epoxy compound has at least two epoxy groups in the molecule, and at least one of them is bonded to the alicyclic ring. Here, the epoxy group bonded to the alicyclic ring is, as shown in the following formula (ep), two bonds in which two bonds of the epoxy group (—O—) constitute the alicyclic ring. Each of the carbon atoms (usually adjacent carbon atoms). In the following general formula (ep), m represents an integer of 2 to 5.

A compound in which a group in which one or more hydrogen atoms in (CH ₂ ) _m in the general formula (ep) are removed is bonded to another chemical structure can be an alicyclic epoxy compound. Hydrogen constituting the alicyclic ring may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Of these, compounds having an epoxycyclopentane ring (m = 3 in the above formula (ep)) or an epoxycyclohexane ring (m = 4 in the above formula (ep)) are preferable.

  Among the alicyclic epoxy compounds, any of the following compounds (ep-1) to (ep-11) is more preferable because they are easily available and have a large effect of increasing the storage elastic modulus of the cured product.

In the above formula, R ^{1 to} R ²⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and when R ^{1 to} R ²⁴ are alkyl groups, the position bonded to the alicyclic ring is 1 It is an arbitrary number of the first to sixth positions. The alkyl group having 1 to 6 carbon atoms may be a straight chain, may have a branch, or may have an alicyclic ring. Y ⁸ represents an oxygen atom or an alkanediyl group having 1 to 20 carbon atoms. Y ^{1 to} Y ⁷ each independently represents a straight chain, may have a branch, and represents an alkanediyl group having 1 to 20 carbon atoms which may have an alicyclic ring. n, p, q and r each independently represents a number of 0 to 20.

Among the compounds represented by the above formulas (ep-1) to (ep-11), the alicyclic diepoxy compound represented by the formula (ep-2) is preferable because it is easily available. The alicyclic diepoxy compound of the formula (ep-2) is composed of 3,4-epoxycyclohexylmethanol (an alkyl group having 1 to 6 carbon atoms may be bonded to the cyclohexane ring) and 3,4-epoxycyclohexane. An ester compound with a carboxylic acid (an alkyl group having 1 to 6 carbon atoms may be bonded to the cyclohexane ring). Specific examples of such ester compounds include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (a compound in which R ⁵ = R ⁶ = H and n = 0 in the formula (ep-2)) 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate (in the formula (ep-2), R ⁵ = 6-methyl, R ⁶ = 6-methyl, n = Compound which is 0) and the like.

  In addition, it is effective to use an alicyclic epoxy compound in combination with an epoxy resin having substantially no alicyclic epoxy group. If a cation-polymerizable compound containing an alicyclic epoxy compound as the main component and an epoxy resin substantially free of an alicyclic epoxy group is used as a cationically polymerizable compound, the cured product has a high storage elastic modulus. However, the adhesion between the polarizer and the protective film can be further enhanced. As used herein, an epoxy resin having substantially no alicyclic epoxy group means that one carbon atom of a ring (usually an oxirane ring) containing an epoxy group and two carbon atoms to which the epoxy group is bonded in the molecule. A compound bonded to another aliphatic carbon atom. Examples thereof include polyglycidyl ether of polyhydric alcohol (phenol). Among these, a diglycidyl ether compound represented by the following general formula (ge) is preferable because it is easily available and has a great effect of improving the adhesion between the polarizer and the protective film.

〔式中、Ｘは直接結合、メチレン基、炭素原子数１〜４のアルキリデン基、脂環式炭化水素基、Ｏ、Ｓ、ＳＯ_２、ＳＳ、ＳＯ、ＣＯ、ＯＣＯ又は下記式（ｇｅ−１）〜（ｇｅ−３）で表される３種の置換基からなる群から選ばれる置換基を表し、アルキリデン基はハロゲン原子で置換されていてもよい。〕

[Wherein, X represents a direct bond, a methylene group, an alkylidene group having 1 to 4 carbon atoms, an alicyclic hydrocarbon group, O, S, SO ₂ , SS, SO, CO, OCO, or the following formula (ge-1 )-(Ge-3) represents a substituent selected from the group consisting of three types of substituents, and the alkylidene group may be substituted with a halogen atom. ]

In the formula (ge-1), R ²⁵ and R ²⁶ may each independently be substituted with a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 10 carbon atoms, or an alkoxy group. Represents a cycloalkyl group having 3 to 10 carbon atoms which may be substituted by a phenyl group, an alkyl group having 1 to 10 carbon atoms or an alkoxy group, and R ²⁵ and R ²⁶ may be linked to each other to form a ring. Good.

  In the formula (ge-2), A and D are each independently an alkyl group having 1 to 10 carbon atoms which may be substituted with a halogen atom, or 6 carbon atoms which may be substituted with a halogen atom. Represents an aryl group having ˜20, an arylalkyl group having 7 to 20 carbon atoms which may be substituted with a halogen atom, a heterocyclic group having 2 to 20 carbon atoms which may be substituted with a halogen atom, or a halogen atom; The methylene group in the alkyl group, aryl group or arylalkyl group may be interrupted by an unsaturated bond, -O- or -S-. a represents a number of 0 to 4, and d represents a number of 0 to 4.

  Examples of the diglycidyl ether compound represented by the general formula (ge) include bisphenol type epoxy resins such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, and diglycidyl ether of bisphenol S; Polyfunctional epoxy resin such as glycidyl ether of methane, glycidyl ether of tetrahydroxybenzophenone, epoxidized polyvinylphenol; polyglycidyl ether of aliphatic polyhydric alcohol; polyglycidyl ether of alkylene oxide adduct of aliphatic polyhydric alcohol A diglycidyl ether of alkylene glycol, and the like. Among them, a polyglycidyl ether of an aliphatic polyhydric alcohol is preferable.

  Examples of the aliphatic polyhydric alcohol include those having 2 to 20 carbon atoms. More specifically, for example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,4-butanediol, neopentyl glycol, 3-methyl-2,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2-methyl -2,4-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 3,5-heptanediol, 1,8-octanediol, 2 -Aliphatic diols such as methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol; cyclohexanedi Cycloaliphatic diols such as butanol, cyclohexanediol, hydrogenated bisphenol A, hydrogenated bisphenol F; trimethylolethane, trimethylolpropane, hexitols, pentitols, glycerin, polyglycerin, pentaerythritol, dipentaerythritol, tetramethylol Examples include trivalent or higher polyols such as propane.

  When using together an alicyclic epoxy compound and an epoxy resin substantially free of an alicyclic epoxy group, the blending ratio of both is 50 to 50 based on the total amount of the cationically polymerizable compound. It is preferable that 95% by mass and an epoxy resin substantially not having an alicyclic epoxy group be 5% by mass or more. By blending 50% by mass or more of the alicyclic epoxy compound in the whole cationic polymerizable compound, the storage elastic modulus at 80 ° C. of the cured product becomes 1,000 MPa or more, and such a cured product (adhesive layer) is obtained. In the polarizing plate in which the polarizer and the protective film are bonded to each other, the polarizer is hardly broken. Moreover, the adhesiveness of a polarizer and a protective film improves by mix | blending 5 mass% or more of epoxy resins which do not have an alicyclic epoxy group substantially with respect to the whole cationically polymerizable compound. The amount of the epoxy resin having substantially no alicyclic epoxy group is 50 based on the total amount of the cation polymerizable compound when the cation polymerizable compound is a two-component system with the alicyclic epoxy compound. However, if the amount is too large, the storage elastic modulus of the cured product is lowered and the polarizer is easily broken, so that it is 45% by mass or less based on the total amount of the cationically polymerizable compound. It is preferable to do this.

  As the cationic polymerizable compound (α) constituting the active energy ray-curable adhesive composition according to the present invention, an alicyclic epoxy compound and an epoxy resin substantially free of an alicyclic epoxy group as described above When these are used in combination, other cationically polymerizable compounds may be included in addition to these in the range in which each amount is as described above. Examples of other cationic polymerizable compounds include epoxy compounds other than formulas (ep-1) to (ep-11) and general formula (ge), oxetane compounds, and the like.

  Epoxy compounds other than formulas (ep-1) to (ep-11) and formula (ge) include at least one alicyclic ring in a molecule other than formulas (ep-1) to (ep-11). An alicyclic epoxy compound having an epoxy group to be bonded, an aliphatic epoxy compound having an oxirane ring bonded to an aliphatic carbon atom other than the formula (ge), an aromatic epoxy compound having an aromatic ring and an epoxy group in the molecule, aromatic There are hydrogenated epoxy compounds in which aromatic rings in group epoxy compounds are hydrogenated.

  Examples of alicyclic epoxy compounds having an epoxy group bonded to at least one alicyclic ring in a molecule other than those represented by formulas (ep-1) to (ep-11) include 4-vinylcyclohexene diepoxide, 2: diepoxides of vinylcyclohexenes such as 8,8,9-diepoxy limonene.

  Examples of the aliphatic epoxy compound having an oxirane ring bonded to an aliphatic carbon atom other than the general formula (ge) include triglycidyl ether of glycerin, triglycidyl ether of trimethylolpropane, and diglycidyl ether of polyethylene glycol.

  The aromatic epoxy compound having an aromatic ring and an epoxy group in the molecule can be a glycidyl ether of an aromatic polyhydroxy compound having at least two phenolic hydroxy groups (hydroxyl groups) in the molecule. Bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, phenol novolac resin glycidyl ether, and the like.

  A hydrogenated epoxy compound in which an aromatic ring in an aromatic epoxy compound is hydrogenated is an aromatic polyhydroxy compound having at least two phenolic hydroxy groups (hydroxyl groups) in a molecule as a raw material of the aromatic epoxy compound. Can be obtained by performing a hydrogenation reaction selectively under pressure in the presence of a catalyst and glycidyl etherifying the resulting hydrogenated polyhydroxy compound. Specific examples include diglycidyl ether of hydrogenated bisphenol A, diglycidyl ether of hydrogenated bisphenol F, diglycidyl ether of hydrogenated bisphenol S, and the like.

  Among the epoxy compounds other than these formulas (ep-1) to (ep-11) and the general formula (ge), they have an epoxy group bonded to an alicyclic ring and are classified as the alicyclic epoxy compounds defined above. When the compound to be blended is added, the sum of the alicyclic epoxy compounds represented by the formulas (ep-1) to (ep-11) does not exceed 95% by mass based on the total amount of the cationically polymerizable compounds. Used in a range.

  An oxetane compound that can be any cationically polymerizable compound is a compound having a 4-membered ring ether (oxetanyl group) in the molecule. Specific examples thereof include 3-ethyl-3-hydroxymethyloxetane, 1,4-bis [(3-ethyl-3-oxetanyl) methoxymethyl] benzene, 3-ethyl-3- (phenoxymethyl) oxetane, di [ (3-ethyl-3-oxetanyl) methyl] ether, bis [(3-ethyl-3-oxetanyl) methyl] ether, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, 3-ethyl-3- ( (Cyclohexyloxymethyl) oxetane, phenol novolac oxetane, 1,3-bis [(3-ethyloxetane-3-yl) methoxy] benzene, oxetanylsilsesquioxane, oxetanyl silicate and the like.

  By blending the oxetane compound at a ratio of 30% by mass or less based on the total amount of the cationic polymerizable compound, an effect of improving curability is expected compared to the case where only the epoxy compound is used as the cationic polymerizable compound. There are things you can do.

(Photocationic polymerization initiator (β))
In the present invention, the cationically polymerizable compound as described above is cationically polymerized by irradiation with active energy rays and cured to form an adhesive layer. Therefore, the active energy ray-curable adhesive composition includes a photocation. It is preferable to blend a polymerization initiator (β).

  The cationic photopolymerization initiator generates a cationic species or a Lewis acid upon irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams, and initiates a polymerization reaction of the cationic polymerizable compound (α). It is. Since the cationic photopolymerization initiator acts catalytically by light, it is excellent in storage stability and workability even when mixed with the cationically polymerizable compound (α). Examples of compounds that generate cation species and Lewis acids upon irradiation with active energy rays include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; iron-allene complexes, and the like.

  Examples of the aromatic diazonium salt include benzenediazonium hexafluoroantimonate, benzenediazonium hexafluorophosphate, and benzenediazonium hexafluoroborate.

  Examples of the aromatic iodonium salt include diphenyliodonium tetrakis (pentafluorophenyl) borate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, di (4-nonylphenyl) iodonium hexafluorophosphate, and the like.

  Examples of the aromatic sulfonium salt include triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis (pentafluorophenyl) borate, 4,4′-bis [diphenylsulfonio] diphenyl sulfide bishexa. Fluorophosphate, 4,4'-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl sulfide bishexafluoroantimonate, 4,4'-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl sulfide bis Hexafluorophosphate, 7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone hexafluoroantimonate, 7- [di (p-toluyl) sulfoni O] -2-Isopropylthioxanthone tetrakis (pentafluorophenyl) borate, 4-phenylcarbonyl-4'-diphenylsulfonio-diphenylsulfide hexafluorophosphate, 4- (p-tert-butylphenylcarbonyl) -4'-diphenylsulfo Nio-diphenyl sulfide hexafluoroantimonate, 4- (p-tert-butylphenylcarbonyl) -4'-di (p-toluyl) sulfonio-diphenyl sulfide tetrakis (pentafluorophenyl) borate, and the like.

  Examples of the iron-allene complex include xylene-cyclopentadienyl iron (II) hexafluoroantimonate, cumene-cyclopentadienyl iron (II) hexafluorophosphate, xylene-cyclopentadienyl iron (II) tris ( (Trifluoromethylsulfonyl) methanide and the like.

  These cationic photopolymerization initiators may be used alone or in combination of two or more. Among these, aromatic sulfonium salts are particularly preferably used because they have ultraviolet absorption characteristics even in the wavelength region near 300 nm, and thus can provide a cured product having excellent curability and good mechanical strength and adhesive strength. .

  The compounding quantity of a photocationic polymerization initiator ((beta)) shall be 1-10 mass parts with respect to 100 mass parts of the whole cationic polymerizable compound ((alpha)). By blending 1 part by mass or more of the cationic photopolymerization initiator per 100 parts by mass of the cationic polymerizable compound (α), the cationic polymerizable compound (α) can be sufficiently cured, and the resulting polarizing plate has high mechanical strength. And give adhesive strength. On the other hand, when the amount is increased, the ionic substance in the cured product increases, so that the hygroscopic property of the cured product increases and the durability performance of the polarizing plate may be lowered. ) Is 10 parts by mass or less per 100 parts by mass of the cationically polymerizable compound (α).

  The amount of the cationic photopolymerization initiator (β) is preferably 2 parts by mass or more and preferably 6 parts by mass or less per 100 parts by mass of the cationic polymerizable compound (α).

(Photosensitizer (γ))
The active energy ray-curable adhesive composition according to the present invention can be used for light having a wavelength longer than 380 nm in addition to the cationic polymerizable compound (α) and the cationic photopolymerization initiator (β) including the epoxy compound as described above. Contains a photosensitizer (γ) exhibiting maximum absorption. The cationic photopolymerization initiator (β) exhibits maximum absorption at a wavelength near or shorter than 300 nm, generates a cationic species or a Lewis acid in response to light having a wavelength near the wavelength, and generates a cationic polymerizable compound (α ) Is initiated, but a photosensitizer (γ) that exhibits maximum absorption in light having a wavelength longer than 380 nm is blended so as to be sensitive to light having a longer wavelength than that.

  As such a photosensitizer (γ), an anthracene compound represented by the following general formula (at) is advantageously used.

〔式中、Ｒ^５及びＲ^６は、それぞれ独立に炭素数１〜６のアルキル基又は炭素数２〜１２のアルコキシアルキル基を表す。Ｒ^７は、水素原子又は炭素数１〜６のアルキル基を表す。〕
一般式（ａｔ）で示されるアントラセン系化合物の具体例としては、９，１０−ジメトキシアントラセン、９，１０−ジエトキシアントラセン、９，１０−ジプロポキシアントラセン、９，１０−ジイソプロポキシアントラセン、９，１０−ジブトキシアントラセン、９，１０−ジペンチルオキシアントラセン、９，１０−ジヘキシルオキシアントラセン、９，１０−ビス（２−メトキシエトキシ）アントラセン、９，１０−ビス（２−エトキシエトキシ）アントラセン、９，１０−ビス（２−ブトキシエトキシ）アントラセン、９，１０−ビス（３−ブトキシプロポキシ）アントラセン、２−メチル又は２−エチル−９，１０−ジメトキシアントラセン、２−メチル又は２−エチル−９，１０−ジエトキシアントラセン、２−メチル又は２−エチル−９，１０−ジプロポキシアントラセン、２−メチル又は２−エチル−９，１０−ジイソプロポキシアントラセン、２−メチル又は２−エチル−９，１０−ジブトキシアントラセン、２−メチル又は２−エチル−９，１０−ジペンチルオキシアントラセン、２−メチル又は２−エチル−９，１０−ジヘキシルオキシアントラセン等が挙げられる。

[Wherein, R ⁵ and R ⁶ each independently represent an alkyl group having 1 to 6 carbon atoms or an alkoxyalkyl group having 2 to 12 carbon atoms. R ⁷ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. ]
Specific examples of the anthracene compound represented by the general formula (at) include 9,10-dimethoxyanthracene, 9,10-diethoxyanthracene, 9,10-dipropoxyanthracene, 9,10-diisopropoxyanthracene, 9 , 10-dibutoxyanthracene, 9,10-dipentyloxyanthracene, 9,10-dihexyloxyanthracene, 9,10-bis (2-methoxyethoxy) anthracene, 9,10-bis (2-ethoxyethoxy) anthracene, 9 , 10-bis (2-butoxyethoxy) anthracene, 9,10-bis (3-butoxypropoxy) anthracene, 2-methyl or 2-ethyl-9,10-dimethoxyanthracene, 2-methyl or 2-ethyl-9, 10-diethoxyanthracene, 2-methyl or 2 Ethyl-9,10-dipropoxyanthracene, 2-methyl or 2-ethyl-9,10-diisopropoxyanthracene, 2-methyl or 2-ethyl-9,10-dibutoxyanthracene, 2-methyl or 2-ethyl Examples include -9,10-dipentyloxyanthracene, 2-methyl or 2-ethyl-9,10-dihexyloxyanthracene.

  By incorporating the photosensitizer (γ) as described above into the active energy ray-curable adhesive composition, the curability of the active energy ray-curable adhesive composition is improved compared to the case where it is not incorporated. To do. By setting the blending amount of the photosensitizer (γ) to 100 parts by mass of the cationic polymerizable compound (α) constituting the active energy ray-curable adhesive composition to be 0.1 parts by mass or more, curability is improved. The improvement effect is manifested. On the other hand, when the blending amount of the photosensitizer (γ) increases, problems such as precipitation during low-temperature storage occur, so the blending amount of 2 parts by weight or less with respect to 100 parts by weight of the cationic polymerizable compound (α) To do. From the viewpoint of maintaining the neutral gray of the polarizing plate, it is advantageous to reduce the blending amount of the photosensitizer (γ) within a range in which the adhesiveness between the polarizer and the protective film is appropriately maintained. For example, with respect to 100 parts by mass of the cationically polymerizable compound (α), the amount of the photosensitizer (γ) is 0.1 to 0.5 parts by mass, and further 0.1 to 0.3 parts by mass Is preferred.

(Photosensitizer (δ))
The active energy ray-curable adhesive composition according to the present invention includes the above-described cationic polymerizable compound (α) containing an epoxy compound, a photo cationic polymerization initiator (β), and a photosensitizer (γ), A naphthalene-based photosensitization aid (δ) represented by the general formula (nf) can be contained.

〔式中、Ｒ^１及びＲ^２はそれぞれ、炭素数１〜６のアルキル基である。〕
ナフタレン系光増感助剤（δ）の具体例としては、１，４−ジメトキシナフタレン、１−エトキシ−４−メトキシナフタレン、１，４−ジエトキシナフタレン、１，４−ジプロポキシナフタレン、１，４−ジブトキシナフタレン等が挙げられる。

[Wherein, R ¹ and R ² are each an alkyl group having 1 to 6 carbon atoms. ]
Specific examples of the naphthalene photosensitizing aid (δ) include 1,4-dimethoxynaphthalene, 1-ethoxy-4-methoxynaphthalene, 1,4-diethoxynaphthalene, 1,4-dipropoxynaphthalene, 1, 4-dibutoxynaphthalene etc. are mentioned.

  In the active energy ray-curable adhesive composition according to the present invention, by adding the naphthalene photosensitizing aid (δ), the active energy ray-curable adhesive composition is compared with the case where it is not added. Curability is improved. Curing is achieved by setting the blending amount of the naphthalene photosensitizer (δ) to 0.1 parts by mass or more with respect to 100 parts by mass of the cationic polymerizable compound (α) constituting the active energy ray-curable adhesive composition. The effect of improving the properties is manifested. On the other hand, if the amount of the naphthalene-based photosensitization aid (δ) increases, problems such as precipitation during low-temperature storage occur, and therefore the amount is 10 parts by mass or less with respect to 100 parts by mass of the cationic polymerizable compound (α). The blending amount. Preferably, the blending amount is 5 parts by mass or less with respect to 100 parts by mass of the cationic polymerizable compound (α).

  Furthermore, the active energy ray-curable adhesive composition according to the present invention can contain an additive component as another component that is an optional component as long as the effects of the present invention are not impaired. As additive components, in addition to the above-mentioned photocationic polymerization initiator and photosensitizer (γ), photosensitizers other than the photosensitizer (γ), thermal cationic polymerization initiators, polyols, ion trapping agents , Antioxidants, light stabilizers, chain transfer agents, tackifiers, thermoplastic resins, fillers, flow regulators, plasticizers, antifoaming agents, leveling agents, dyes, organic solvents, and the like.

  When the additive component is contained, the amount of the additive component used is preferably 1000 parts by mass or less with respect to 100 parts by mass of the cationic polymerizable compound (α). When the amount used is 1000 parts by mass or less, a cationically polymerizable compound (α), a photocationic polymerization initiator (β), a photointensifier which are essential components of the active energy ray-curable adhesive composition that can be used in the present invention. The combination of the sensitizer (γ) and the photosensitization aid (δ) can exhibit the effects of improving storage stability, preventing discoloration, improving the curing speed, and ensuring good adhesion.

  As a preferable example of the active energy ray-curable adhesive that can be suitably used in the present invention, an N-substituted amide monomer having a hydroxy group is contained as a curable component of the active energy ray-curable adhesive. The hydroxy group may have at least one substituent bonded to the nitrogen atom (N) forming the amide group, and may have two or more. As the N-substituted amide monomer having a hydroxy group, either monofunctional or bifunctional or more can be used. Moreover, the N-substituted amide monomer which has a hydroxyl group can select 1 type, or can be used in combination of 2 or more type.

  The N-substituted amide monomer having a hydroxy group exhibits good adhesion even to a low moisture content polarizer and a transparent protective film using a material having low moisture permeability. In particular, the following monomers exhibit good adhesion. For example, N-substituted amide monomers include N-hydroxyethyl (meth) acrylamide, N- (2,2-dimethoxy-1-hydroxyethyl)-(meth) acrylamide, N-hydroxymethyl (meth) acrylamide, p -Hydroxyphenyl (meth) acrylamide, N, N '-(1,2-dihydroxyethylene) bis (meth) acrylamide and the like. Among these, N-hydroxyethyl (meth) acrylamide is preferable. In addition, (meth) acrylamide means an acrylamide group and / or a methacrylamide group.

  In addition to the N-substituted amide monomer having a hydroxy group, the curable component may contain other monomers. Examples of other monomers that can be used as the curable component include compounds having a (meth) acryloyl group, compounds having a vinyl group, and the like. As the other monomer used as the curable component, either monofunctional or bifunctional or more can be used. These curable components may be used alone or in combination of two or more.

  As other monomers used as the curable component, for example, N-substituted amide monomers other than N-substituted amide monomers having a hydroxy group are preferably used. The N-substituted amide monomer is represented by the following general formula (1).

General formula (1)
_{CH 2 = C (R 1)} -CONR 2 (R 3)
In the general formula (1), R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents a hydrogen atom, a mercapto group, an amino group, or a quaternary ammonium group, which may have a straight chain having 1 to 4 carbon atoms. Alternatively, it represents a branched alkyl group, and R ₃ represents a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms. However, the case where R ₂ and R ₃ are hydrogen atoms at the same time is excluded. R ₂ and R ₃ are bonded to form a 5-membered ring or a 6-membered ring that may contain an oxygen atom.

In the general formula (1), examples of the linear or branched alkyl group having 1 to 4 carbon atoms in R ₂ or R ₃ include a methyl group, an ethyl group, an isopropyl group, and a t-butyl group. Examples of the alkyl group having an amino group include an aminomethyl group and an aminoethyl group. Moreover, when R < ₂ > and R < ₃ > _couple | bond together and form the 5-membered ring or 6-membered ring which may contain an oxygen atom, it has a heterocyclic ring which has nitrogen. Examples of the heterocyclic ring include morpholine ring, piperidine ring, pyrrolidine ring, piperazine ring and the like.

  Specific examples of the N-substituted amide monomer include, for example, N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-isopropylacrylamide, N- Butyl (meth) acrylamide, N-hexyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylol-N-propane (meth) acrylamide, aminomethyl (meth) acrylamide, aminoethyl (meth) acrylamide, mercaapt Examples include methyl (meth) acrylamide and mercaptoethyl (meth) acrylamide. Examples of the heterocyclic-containing monomer having a heterocyclic ring include N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, and N-acryloylpyrrolidine. These N-substituted amide monomers can be used singly or in combination of two or more.

  When the N-substituted amide monomer having a hydroxy group and the N-substituted amide monomer represented by the general formula (1) are used in combination as a curable component, durability, coatability, adhesion From the viewpoint of sex, a combination of N-hydroxyethyl (meth) acrylamide and N-acryloylmorpholine is preferred. Moreover, in the case of the said combination, the ratio of N-hydroxyethyl (meth) acrylamide with respect to the total amount of N-hydroxyethyl (meth) acrylamide and N-acryloyl morpholine is 40 mass% or more, and it has favorable adhesiveness. It is preferable in obtaining. As for the said ratio, 40-95 mass% is more preferable, Furthermore, it is preferable that it is 60-90 mass%.

  Moreover, as a monomer which can be used in combination with an N-substituted amide monomer having a hydroxy group as a curable component, in addition to the above, as a compound having a (meth) acryloyl group, for example, various epoxy (meth) acrylates and urethanes Examples include (meth) acrylate, polyester (meth) acrylate, and various (meth) acrylate monomers. Among these, epoxy (meth) acrylates, particularly monofunctional (meth) acrylates having an aromatic ring and a hydroxy group are preferably used.

  As the monofunctional (meth) acrylate having an aromatic ring and a hydroxy group, various monofunctional (meth) acrylates having an aromatic ring and a hydroxy group can be used. The hydroxy group may be present as a substituent on the aromatic ring, but is preferably present as an organic group that binds the aromatic ring and the (meth) acrylate (bonded to a hydrocarbon group, particularly an alkylene group). .

  Examples of the monofunctional (meth) acrylate having an aromatic ring and a hydroxy group include a reaction product of a monofunctional epoxy compound having an aromatic ring and (meth) acrylic acid. Examples of the monofunctional epoxy compound having an aromatic ring include phenyl glycidyl ether, t-butylphenyl glycidyl ether, and phenyl polyethylene glycol glycidyl ether. Specific examples of the monofunctional (meth) acrylate having an aromatic ring and a hydroxy group include, for example, 2-hydroxy-3-phenoxypropyl (meth) acrylate and 2-hydroxy-3-t-butylphenoxypropyl (meth). Examples thereof include acrylate and 2-hydroxy-3-phenyl polyethylene glycol propyl (meth) acrylate.

  Moreover, a carboxyl group monomer is mentioned as a compound which has a (meth) acryloyl group. A carboxyl group monomer is also preferable in terms of adhesiveness. Examples of the carboxyl group monomer include (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, and the like. Of these, acrylic acid is preferred.

  In addition to the above, compounds having a (meth) acryloyl group include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, and isononyl. Alkyl (meth) acrylates having 1 to 12 carbon atoms such as (meth) acrylate and lauryl (meth) acrylate; (meth) acrylic acid alkoxyalkyl systems such as (meth) acrylic acid methoxyethyl and (meth) acrylic acid ethoxyethyl Monomer; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxy (meth) acrylate Octyl, (meth) a Hydroxy group-containing monomers such as 10-hydroxydecyl laurate, 12-hydroxy lauryl (meth) acrylate and (4-hydroxymethylcyclohexyl) -methyl acrylate; Acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; Caprolactone adduct of acrylic acid; styrene sulfonic acid and allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyloxynaphthalene Examples thereof include sulfonic acid group-containing monomers such as sulfonic acid; phosphoric acid group-containing monomers such as 2-hydroxyethylacryloyl phosphate. (Meth) acrylamide; maleimide, N-cyclohexylmaleimide, N-phenylmaleimide, etc .; aminoethyl (meth) acrylate, aminopropyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate , (Meth) acrylic acid alkylaminoalkyl monomers such as (meth) acrylic acid t-butylaminoethyl, 3- (3-pyridinyl) propyl (meth) acrylate; N- (meth) acryloyloxymethylene succinimide and N- ( And nitrogen-containing monomers such as succinimide monomers such as (meth) acryloyl-6-oxyhexamethylene succinimide and N- (meth) acryloyl-8-oxyoctamethylene succinimide.

  In addition to the above curable components, bifunctional or higher curable components can be used. The bifunctional or higher curable component is preferably a bifunctional or higher (meth) acrylate, particularly a bifunctional or higher epoxy (meth) acrylate. The bifunctional or higher functional epoxy (meth) acrylate is obtained by reacting a polyfunctional epoxy compound with (meth) acrylic acid. Various examples of the polyfunctional epoxy compound can be exemplified. Examples of the polyfunctional epoxy compound include aromatic epoxy resins, alicyclic epoxy resins, and aliphatic epoxy resins.

  Examples of the aromatic epoxy resin include bisphenol type epoxy resins such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, diglycidyl ether of bisphenol S; phenol novolac epoxy resin, cresol novolac epoxy resin, hydroxybenzaldehyde Examples include novolak-type epoxy resins such as phenol novolac epoxy resins; glycidyl ethers of tetrahydroxyphenylmethane, glycidyl ethers of tetrahydroxybenzophenone, and polyfunctional epoxy resins such as epoxidized polyvinylphenol.

  Examples of the alicyclic epoxy resin include hydrogenated aromatic epoxy resins, cyclohexane-based, cyclohexylmethyl ester-based, cicyclohexylmethyl ether-based, spiro-based, and tricyclodecane-based epoxy resins.

  Examples of the aliphatic epoxy resin include polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof. Examples include 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, propylene. Polyethers of polyether polyols obtained by adding one or more alkylene oxides (ethylene oxide or propylene oxide) to aliphatic polyhydric alcohols such as glycol diglycidyl ether, ethylene glycol, propylene glycol, and glycerin Examples thereof include glycidyl ether.

  The epoxy equivalent of the epoxy resin is usually in the range of 30 to 3000 g / equivalent, preferably 50 to 1500 g / equivalent.

  The bifunctional or higher epoxy (meth) acrylate is preferably an epoxy (meth) acrylate of an aliphatic epoxy resin, particularly preferably an epoxy (meth) acrylate of a bifunctional aliphatic epoxy resin.

  As the curable component in the active energy ray-curable adhesive, an N-substituted amide monomer having a hydroxy group is used, and the N-substituted monomer represented by the general formula (1) is used as a monomer in combination therewith. Amide monomers are preferred. In addition, when using together the monofunctional (meth) acrylate which has an aromatic ring and a hydroxy group as a sclerosing | hardenable component, it is 0-50 mass% with respect to the ratio of the N-substituted amide type monomer which has a hydroxy group, 1 It is preferable to make it -40 mass% further 5-30 mass%.

  When using an epoxy-type compound for the monomer used together, it is preferable to set it as 0-50 mass%, 1-30 mass%, and 5-15 mass% with respect to the N-substituted amide type monomer which has a hydroxyl group.

  The active energy ray-curable adhesive contains a curable component, but in addition to the above components, an additive may be appropriately added if necessary. The active energy ray curable adhesive can be used in an electron beam curable type or an ultraviolet curable type. When the adhesive is used as an electron beam curable type, it is not particularly necessary for the adhesive to contain a photopolymerization initiator, but when used as an ultraviolet curable type, a photopolymerization initiator is used. . The usage-amount of a photoinitiator is about 0.1-10 mass parts normally per 100 mass parts of sclerosing | hardenable components, Preferably, it is the range of 0.5-3 mass parts.

  Examples of additives include sensitizers that increase the curing speed and sensitivity of the electron beam typified by carbonyl compounds, adhesion promoters typified by silane coupling agents and ethylene oxide, and wettability with transparent protective films. Additives to improve, such as acryloxy group compounds and hydrocarbons (natural and synthetic resins), additives that improve mechanical strength and processability, UV absorbers, anti-aging agents, dyes, processing aids, Examples include ion trapping agents, antioxidants, tackifiers, fillers (other than metal compound fillers), plasticizers, leveling agents, foaming inhibitors, and antistatic percents. Moreover, you may contain oxetanes, polyols, etc.

  In addition, the formation method and hardening method of an active energy ray hardening-type resin layer are mentioned later.

[Polarizer]
The polarizer, which is the main component of the polarizing plate, is an element that passes only light having a plane of polarization in a certain direction, and a typical known polarizer is a polyvinyl alcohol polarizing film. The polyvinyl alcohol polarizing film includes those obtained by dyeing iodine on a polyvinyl alcohol film and those obtained by dyeing a dichroic dye.

  As the polarizer, a polarizer obtained by forming a polyvinyl alcohol aqueous solution into a film and dyeing it by uniaxial stretching or dyeing and then uniaxially stretching and then preferably performing a durability treatment with a boron compound may be used. The film thickness of the polarizer is preferably 5 to 30 μm, and particularly preferably 5 to 15 μm.

  Further, the ethylene unit content described in JP-A-2003-248123, JP-A-2003-342322, etc. is 1 to 4 mol%, the degree of polymerization is 2000 to 4000, and the degree of saponification is 99.0 to 99.99 mol%. The ethylene-modified polyvinyl alcohol is also preferably used. Among these, an ethylene-modified polyvinyl alcohol film having a hot water cutting temperature of 66 to 73 ° C. is preferably used. A polarizer using this ethylene-modified polyvinyl alcohol film is excellent in polarization performance and durability, and has few color spots, and is particularly preferably used for a large-sized liquid crystal display device.

[Phase difference film]
In the polarizing plate of the present invention, as shown in FIG. 1 and FIG. 2, an active energy ray curable resin layer is further interposed on the polarizer surface opposite to the surface on which the protective film according to the present invention is disposed. The retardation film is preferably laminated.

  Furthermore, the retardation film according to the present invention preferably satisfies all of the following conditions 1 to 3.

  Condition 1: An in-plane retardation value Ro (590) measured at a wavelength of 590 nm in an environment of a temperature of 23 ° C. and a relative humidity of 55% represented by the following formula (I) is in the range of 30 to 150 nm.

Formula (I): Ro (590) = (n x -n y) × d
Condition 2: Retardation value Rt (590) in the thickness direction measured at a wavelength of 590 nm under the environment of temperature 23 ° C. and relative humidity 55% represented by the following formula (II) is in the range of 70 to 300 nm. .

Formula (II): Rt (590) = {(n _x + n _y ) / 2−n _z } × d
Condition 3: The amount of change in the retardation value Rt (590) in the thickness direction when the humidity is changed from 20 to 80% in an environment of a temperature of 23 ° C. is in the range of 1 to 30 nm.

In the above formulas (I) and (II), n _x represents a refractive index in the direction x in which the refractive index is maximized in the plane direction of the film. n _y, in-plane direction of the film, the refractive index in the process y perpendicular to the direction x. _nz represents the refractive index in the thickness direction z of the film. d represents the thickness (nm) of the film. ]
Each retardation value can be measured using an automatic birefringence meter. As an automatic birefringence meter, for example, an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments Co., Ltd.) or Axoscan made by Axometric is used. The wavelength dependence by refraction or birefringence measurement at each wavelength (450 nm, 550 nm and 650 nm) is measured, and the retardation value with respect to the wavelength is calculated from the thickness of the film.

  The retardation film according to the present invention can be obtained by the same film forming method using the cellulose ester resin (B) used in the preparation of the protective film alone.

  In addition, the retardation film according to the present invention can be obtained as a commercial product. For example, as a retardation film for VA, Konica Minoltack KC8UCR3, KC8UCR4, KC8UCR5, KC4FR, KC4KR, KC4DR, KC4SR (hereinafter, Konica Minolta Advanced Layer Co., Ltd.). In addition, examples of the film that can be used other than the retardation film for VA include KC4UE, KC8UE, KC8UX, KC5UX, KC8UY, KC4UY, KC4CZ, KC6UA, KC4UA, KC2UA (manufactured by Konica Minolta Advanced Layer Co., Ltd.) and the like. .

  The thickness of the retardation film according to the present invention is not particularly limited, but is preferably in the range of 10 to 250 μm, and more preferably in the range of 10 to 100 μm. Especially preferably, it exists in the range of 30-60 micrometers.

  The retardation film according to the present invention is used in the range of 1 to 4 m in width. Particularly, those having a width in the range of 1.4 to 4 m are preferably used, and particularly preferably in the range of 1.6 to 3 m.

<< Polarizing plate manufacturing method >>
A polarizing plate can be manufactured by bonding the protective film described above to one surface of a polarizer using an active energy ray-curable adhesive. When adhesiveness differs on both surfaces of a protective film, it is preferable to stick together on the one with good adhesiveness.

  Hereinafter, an example of the manufacturing method of the polarizing plate using an active energy ray hardening adhesive is demonstrated.

  The polarizing plate includes an adhesive application step of applying the following active energy ray-curable adhesive to at least one of the adhesive surfaces of the polarizer and the protective film, and the polarizer and the protective film via an adhesive layer. Can be manufactured by a manufacturing method including a bonding step of bonding and bonding, and a curing step of curing the adhesive layer in a state where the polarizer and the protective film are bonded via the adhesive layer. Moreover, there may be a pretreatment process for easily bonding the surface of the protective film to which the polarizer is bonded.

(Pretreatment process)
In the pretreatment step, the surface of the protective film that adheres to the polarizer is easily adhered. When the protective film and the retardation film are respectively bonded to both surfaces of the polarizer, an easy adhesion treatment is performed on each protective film and the retardation film. In the next adhesive application process, the surface subjected to the easy adhesion treatment is treated as the bonding surface with the polarizer, and therefore, the surface to be bonded to the active energy ray-curable resin layer is easily selected on both surfaces of the protective film. Apply adhesive treatment. As easy adhesion treatment. Examples include corona treatment and plasma treatment.

(Adhesive application process)
In the adhesive application step, the active energy ray-curable adhesive is applied to at least one of the adhesive surfaces of the polarizer and the protective film. When the active energy ray-curable adhesive is applied directly to the surface of the polarizer or the protective film, the application method is not particularly limited. For example, various wet coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. Moreover, after casting an active energy ray hardening adhesive between a polarizer and a protective film, the method of pressurizing with a roll etc. and spreading it uniformly can also be utilized.

(Bonding process)
After apply | coating an active energy ray hardening adhesive agent by said method, it processes by a bonding process. In this bonding step, for example, when an active energy ray-curable adhesive is applied to the surface of the polarizer in the previous application step, a protective film is superimposed thereon. When the active energy ray-curable adhesive is applied to the surface of the protective film in the previous application step, a polarizer is superimposed thereon. Moreover, when an active energy ray-curable adhesive is cast between the polarizer and the protective film, the polarizer and the protective film are superposed in that state. When a protective film and a retardation film are adhered to both sides of a polarizer, and both sides use an active energy ray-curable adhesive, both sides of the polarizer are each via an active energy ray-curable adhesive. A protective film and a retardation film are overlaid. And usually both sides in this state (If a protective film is overlaid on one side of the polarizer, the polarizer side and the protective film side, and if the protective film and retardation film are overlaid on both sides of the polarizer, The pressure is sandwiched between rollers on both sides of the protective film and the retardation film side). As the material of the roll, metal, rubber or the like can be used. The rolls arranged on both sides may be the same material or different materials.

(Curing process)
In the curing step, an active energy ray curable adhesive is irradiated with active energy rays, and a cationic polymerizable compound (eg, epoxy compound or oxetane compound) or a radical polymerizable compound (eg, acrylate compound, acrylamide type). The active energy ray-curable resin layer containing the compound or the like is cured, and the polarizer and the protective film, or the polarizer and the retardation film, which are superposed via the active energy ray-curable adhesive, are adhered. When bonding a protective film to the single side | surface of a polarizer, you may irradiate an active energy ray from either a polarizer side or a protective film side. In addition, when the protective film and the retardation film are bonded to both sides of the polarizer, the active energy is applied in a state where the protective film and the retardation film are superposed on both sides of the polarizer via an active energy ray-curable adhesive, respectively. It is advantageous to irradiate the line and simultaneously cure the active energy ray curable adhesive on both sides.

  Visible light, ultraviolet rays, X-rays, electron beams, etc. can be used as the active energy rays applied for curing, but electron beams and ultraviolet rays are generally preferred because they are easy to handle and have a sufficient curing rate. Used.

  Any appropriate condition can be adopted as the electron beam irradiation condition as long as the adhesive can be cured. For example, in the electron beam irradiation, the acceleration voltage is preferably 5 kV to 300 kV, and more preferably 10 kV to 250 kV. If the acceleration voltage is less than 5 kV, the electron beam may not reach the adhesive and may be insufficiently cured. If the acceleration voltage exceeds 300 kV, the penetration force through the sample is too strong and the electron beam rebounds, There is a risk of damaging the polarizer. The irradiation dose is 5 to 100 kGy, more preferably 10 to 75 kGy. When the irradiation dose is less than 5 kGy, the adhesive becomes insufficiently cured, and when it exceeds 100 kGy, the transparent protective film and the polarizer are damaged, resulting in a decrease in mechanical strength and yellowing, thereby obtaining predetermined optical characteristics. I can't.

Arbitrary appropriate conditions can be employ | adopted for the irradiation conditions of an ultraviolet-ray, if it is the conditions which can harden the said adhesive agent. The dose of ultraviolet rays is preferably in the range of 50~1500mJ / cm ² in accumulated light quantity, and even more preferably in the range of 100 to 500 mJ / cm ^2.

  When the production method is performed in a continuous line, the line speed depends on the curing time of the adhesive, but is preferably in the range of 1 to 500 m / min, more preferably 5 to 300 m / min, and still more preferably 10 to 100 m. / Min. When the line speed is too slow, the productivity is poor, or the damage to the transparent protective film is too great, and a polarizing plate that can withstand the durability test cannot be produced. When the line speed is too high, the adhesive is not sufficiently cured, and the target adhesiveness may not be obtained.

  In the polarizing plate obtained as described above, the thickness of the adhesive layer is not particularly limited, but is usually within a range of 0.01 to 10, and preferably within a range of 0.5 to 5 μm.

<Liquid crystal display device>
The polarizing plate of the present invention can be suitably used for a liquid crystal display device. Since the liquid crystal display device using the polarizing plate of the present invention uses a protective film having low moisture permeability, unevenness of the liquid crystal display device due to water content is difficult to occur.

  The bonding between the surface of the polarizing plate on the side of the retardation film and at least one surface of the liquid crystal cell can be performed by a known method. Depending on the case, it may be bonded through an adhesive layer.

  The mode (driving method) of the liquid crystal display device is not particularly limited, and liquid crystal display devices in various drive modes such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS, and OCB can be used. In particular, a VA (MVA, PVA) type liquid crystal display device is preferable. By using the polarizing plate according to the present invention for these liquid crystal display devices, a liquid crystal display device having excellent visibility such as unevenness of the liquid crystal display device can be obtained even for a liquid crystal display device with a large screen of 30 type or more. be able to. The polarizing plate of the present invention is preferably used as a polarizing plate for organic EL using a λ / 4 plate obliquely stretched on one polarizing plate protective film.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "%" is used in an Example, unless otherwise indicated, "mass%" is represented.

Example 1
<Production of protective film>
[Preparation of acrylic resin (A)]
Acrylic resins A1 to A20 having the configuration described in Table 1 were prepared.

  In addition, the detail of each constituent material described with the abbreviation in Table 1 is as follows.

MMA: methyl methacrylate ACMO: acryloylmorpholine MA: methyl acrylate * 1: isobornyl methacrylate * 2: dicyclopentanyl methacrylate * 3: 3,5-dimethyladamantyl methacrylate DMAAm: N, N-dimethylacrylamide TBAAm: Nt -Butylacrylamide BR80: Dynal BR80, manufactured by Mitsubishi Rayon Co., Ltd., Tg = 105 ° C., Mw = 95,000 BR85: Dynal BR85, manufactured by Mitsubishi Rayon Co., Ltd., Tg = 105 ° C., Mw = 280,000 BR88: Dynal BR88, Mitsubishi Rayon Tg = 105 ° C., Mw = 480,000 [Preparation of cellulose ester resin (B)]
According to a conventional method, cellulose ester resins B1 to B5 having the acetyl group substitution degree, propionyl group substitution degree, and butyryl group substitution degree shown in Table 2 were prepared.

[Preparation of Protective Film 1]
(Preparation of dope 1)
Acrylic resin (A) A1 90 parts by weight Cellulose ester resin (B) B1 10 parts by weight UV absorber: 2,2′-methylenebis [6- (2H-benzotriazol-2-yl) -4- (1,1, 3,3-tetramethylbutyl) phenol] (molecular weight 659, LA31 manufactured by ADEKA Corporation) 3.0 parts by weight Matting agent: R972V (manufactured by Nippon Aerosil Co., Ltd., silica particles, average particle size = 16 nm)
0.30 parts by mass Peeling aid: ELECUT S412 (manufactured by Takemoto Yushi Co., Ltd.) 0.50 parts by mass Methylene chloride 300 parts by mass Ethanol 40 parts by mass Prepared.

(Protective film formation)
The prepared dope 1 was uniformly cast on a stainless steel band support at a temperature of 22 ° C. and a width of 2 m using a belt casting apparatus. With the stainless steel band support, the solvent was evaporated until the amount of residual solvent reached 100%, and peeling was performed from the stainless steel band support with a peeling tension of 162 N / m.

  Next, the solvent of the peeled dope 1 is evaporated at 35 ° C., slit to 1 m width, and then 2.0 times in the transport direction (MD direction) by zone stretching and the width direction (TD direction) by tenter stretching. The film was dried at a drying temperature of 135 ° C. while being stretched 2.0 times. At this time, the residual solvent amount when starting stretching with the tenter was 8%.

  After stretching with a tenter, it was relaxed at 130 ° C for 5 minutes, and then dried while being transported by a large number of rolls at 120 ° C and 140 ° C, and slitted to a width of 1.5 m. Was subjected to a knurling process having a width of 10 mm and a height of 5 μm, and then wound around a core to prepare the protective film 1 according to the present invention.

  The produced protective film had a residual solvent amount of 700 ppm, a film thickness of 40 μm, and a winding length of 4000 m.

[Preparation of protective film 2 to 37]
In the production of the protective film 1, the types and composition ratios of the acrylic resin (A) and the cellulose ester resin (B) used for the preparation of the dope, the presence or absence of the additive 1, the type of the ultraviolet absorber, and the film thickness are shown in Table 3. Protective films 2 to 37 were produced in the same manner except that the combinations were changed to those described in 1.

  In addition, the detail of the additive and ultraviolet absorber which were described by the abbreviation in Table 3 is as follows.

  1) Additive 1: An ester compound 1 described in JP 2011-52205 A was prepared according to the following synthesis method.

<Synthesis of ester compound 1>
251 g of 1,2-propylene glycol, 278 g of phthalic anhydride, 91 g of adipic acid, 610 g of benzoic acid, 0.191 g of tetraisopropyl titanate as an esterification catalyst, 2 L four-neck equipped with a thermometer, stirrer, and slow cooling tube The flask was charged and gradually heated with stirring until it reached 230 ° C. in a nitrogen stream. The ester compound 1 was obtained by making it dehydrate-condense for 15 hours, and depressurizingly distilling unreacted 1, 2- propylene glycol at 200 degreeC after completion | finish of reaction. The acid value was 0.10 mg / g and the number average molecular weight was 450.

2) LA31: 2,2′-methylenebis [6- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol] (molecular weight 659, manufactured by ADEKA Corporation) LA31)
3) Ti928: 2- (2H-benzotriazol-2-yl) -6- (1-methyl-1-phenylethyl) -4- (1,1,3,3-tetramethylbutyl) phenol (tinuvin 928, (Made by BASF Japan)
<Evaluation of protective film>
About each produced said protective film, the following characteristic value was measured and evaluated.

[Measurement of moisture permeability]
In accordance with JIS Z-0208, each protective film was conditioned for 24 hours in an environment of 40 ° C. and 90% RH, and then moisture content per unit area before and after humidity adjustment using a moisture permeation test device. Was calculated (g / m ² ). And moisture permeability was calculated | required from the moisture content after humidity control-the moisture content before humidity control.

(Measurement of tension softening point: heat resistance evaluation)
Each protective film conditioned for 24 hours in an environment of 23 ° C. and 55% RH was cut into a size of 30 mm (length) × 2 mm (width) under the same conditions, and a TMA (thermomechanical analysis) tester (manufactured by Rigaku Corporation). Using Thermo plus II TMA8310), the temperature was increased at a rate of temperature increase of 5 ° C./min while pulling with a tension of 0.7 N, and the temperature when the slope of the elongation with respect to the temperature changed was measured three times. This was determined as the tension softening point.

(Evaluation of ductile fracture: brittleness evaluation)
Each protective film was conditioned for 24 hours under an environment of 23 ° C. and 55% RH, and was cut into a size of 100 mm (vertical) × 10 mm (width) under the same conditions, with a radius of curvature of 0 mm at the center in the vertical direction, The folding angle was 180 °, and the film was folded once in a mountain fold and a valley fold so that the films were exactly overlapped. The evaluation was measured three times, and ductile fracture was evaluated according to the following criteria. Note that “break” in this evaluation means that the material has broken into two or more pieces.

○: No occurrence of folding in 3 times. ×: At least 1 out of 3 times, folding occurred. Table 3 shows the results obtained as described above.

  As is clear from the results shown in Table 3, the protective films 22 and 23 made of only the acrylic resin have low moisture permeability and excellent moisture barrier properties, but are inferior to ductile fracture and are brittle films. I understand. Moreover, although the protective films 24 and 25 formed only with the cellulose ester resin have the flexibility as a film, it turns out that moisture permeability is too high and has a problem as a protective film. On the other hand, the protective film according to the present invention that satisfies the conditions specified in the present invention has an excellent balance in the three performances of moisture permeability, tension softening point, and ductile fracture with respect to the comparative example. Recognize.

Example 2
<Production of polarizing plate>
[Preparation of Polarizing Plate 1]
(Preparation of polarizer)
A 70 μm thick polyvinyl alcohol film was swollen with water at 35 ° C. The obtained film was immersed in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and further immersed in an aqueous solution at 45 ° C. consisting of 3 g of potassium iodide, 7.5 g of boric acid and 100 g of water. . The obtained film was uniaxially stretched under conditions of a stretching temperature of 55 ° C. and a stretching ratio of 5 times. This uniaxially stretched film was washed with water and dried to obtain a polarizer having a thickness of 25 μm.

(Preparation of active energy ray-curable adhesive solution R: radical polymerization type)
What mixed 3 mass parts of photoinitiators (BASF Japan Co., Ltd .; brand name Irgacure 127) with 100 mass parts of N-hydroxyethyl acrylamide was used as active energy ray-curable adhesive liquid R.

(Preparation of polarizing plate)
A polarizing plate 1 having the configuration shown in FIG. 1 was produced according to the following method. The numerical value in parentheses indicates the number of each component described in FIG.

  First, as the retardation film (105), a KC4DR film (manufactured by Konica Minolta Advanced Layer Co., Ltd., details will be described later) is prepared, and the above-prepared active energy ray-curable adhesive liquid R is prepared using a microgravure coater ( A gravure roll: # 300, rotational speed 140% / line speed) was applied to a thickness of 5 μm to form an active energy ray-curable resin layer (103B).

  Next, the active energy ray-curable adhesive liquid R prepared above was applied to the protective film 1 (102) so as to have a thickness of 5 μm, as described above, and the active energy ray-curable resin layer (103A). Formed.

  Between the active energy ray-curable resin layers (103A) and (103B), the produced polyvinyl alcohol-iodine polarizer (104) is placed and bonded with a roll machine, and the protective film 1 (102). A laminate in which / active energy ray-curable resin layer (103A) / polarizer (104) / active energy ray-curable resin layer (103B) / retardation film (105) was laminated was obtained. In that case, it bonded by the roll machine so that the slow axis of retardation film (105) and the absorption axis of polarizer (104) might become mutually orthogonal.

A polarizing plate 1 (101) was produced by irradiating an electron beam from both sides of the laminate.
The line speed was 20 m / min, the acceleration voltage was 250 kV, and the irradiation dose was 20 kGy.

[Production of Polarizing Plate 2]
(Preparation of polarizer)
A 70 μm thick polyvinyl alcohol film was swollen with water at 35 ° C. The obtained film was immersed in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and further immersed in an aqueous solution at 45 ° C. consisting of 3 g of potassium iodide, 7.5 g of boric acid and 100 g of water. . The obtained film was uniaxially stretched under conditions of a stretching temperature of 55 ° C. and a stretching ratio of 5 times. This uniaxially stretched film was washed with water and dried to obtain a polarizer having a thickness of 25 μm.

(Preparation of active energy ray-curable adhesive liquid C: cationic polymerization type)
After mixing the following components, defoaming was performed to prepare an active energy ray-curable adhesive solution C. Triarylsulfonium hexafluorophosphate was blended as a 50% propylene carbonate solution, and the solid content of triarylsulfonium hexafluorophosphate was shown below.

3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate 45 parts by mass Epolide GT-301 (alicyclic epoxy resin manufactured by Daicel Chemical Industries) 40 parts by mass 1,4-butanediol diglycidyl ether 15 parts by mass Triarylsulfonium hexafluorophosphate 2.3 parts by mass 9,10-dibutoxyanthracene 0.1 parts by mass 1,4-diethoxynaphthalene 2.0 parts by mass (Preparation of polarizing plate)
A polarizing plate 2 having the configuration shown in FIG. 1 was produced according to the following method. The numerical value in parentheses indicates the number of each component described in FIG.

  First, as the retardation film (105), a KC4SR film (manufactured by Konica Minolta Advanced Layer) was used, and the surface thereof was subjected to corona discharge treatment. The corona discharge treatment was performed at a corona output intensity of 2.0 kW and a line speed of 18 m / min. Next, the active energy ray-curable adhesive liquid C prepared above is applied to the corona discharge-treated surface of the retardation film (105) with a bar coater so that the film thickness after curing is about 3 μm. A line curable resin layer (103B) was formed. The produced polyvinyl alcohol-iodine polarizer (104) was bonded to the obtained active energy ray-curable resin layer (103B).

  Subsequently, the surface of the protective film 1 (102) was subjected to corona discharge treatment. The conditions for the corona discharge treatment were a corona output intensity of 2.0 kW and a line speed of 18 m / min. Next, the active energy ray-curable adhesive liquid C prepared above is applied to the corona discharge-treated surface of the protective film 1 (102) with a bar coater so that the film thickness after curing is about 3 μm. A line curable resin layer (103A) was formed.

  A polarizer (104) bonded to one side of the retardation film (105) is bonded to the active energy beam curable resin layer (103A), and the protective film 1 (102) / active energy beam curable resin is bonded. A laminate in which layer (103A) / polarizer (104) / active energy ray-curable resin layer (103B) / retardation film (105) was laminated was obtained. In that case, it bonded so that the slow axis of retardation film (105) and the absorption axis of polarizer (104) might become mutually orthogonal.

From the phase difference film (105) side of this laminate, using an ultraviolet irradiation device with a belt conveyor (the lamp uses a D bulb manufactured by Fusion UV Systems), the ultraviolet light is adjusted so that the integrated light quantity becomes 750 mJ / cm ^2. Was applied to cure the active energy ray-curable adhesive layer to produce Polarizing Plate 1 (101).

[Preparation of polarizing plates 3 to 45]
Table 4 shows the types of the protective film, the retardation film, the active energy ray-curable resin layer (radical type or cationic type), and the thickness of the polarizer in the production of the polarizing plate 1 and the polarizing plate 2. Polarizing plates 3 to 45 were produced in the same manner except that the combinations were changed.

  In addition, the detail of the phase difference film described with the abbreviation in Table 4 is as follows.

4DR: Cellulose acylate film manufactured by Konica Minolta Advanced Layer
Retardation value Ro (590): 52 nm
Retardation value Rt (590): 125 nm
Change amount of retardation value Rt (590): 15 nm
4SR: Cellulose acylate film manufactured by Konica Minolta Advanced Layer
Retardation value Ro (590): 52 nm
Retardation value Rt (590): 125 m
Change amount of retardation value Rt (590): 22 nm
F1: Film described in Example 1 of JP-A-2006-235085
Retardation value Ro (590): 55 nm
Retardation value Rt (590): 125 nm
Change amount of retardation value Rt (590): 1 nm
F2: Film described in Example 34 of JP2011-12186A
Retardation value Ro (590): 52 nm
Retardation value Rt (590): 118 nm
Change amount of retardation value Rt (590): 20 nm
<Production of liquid crystal display device>
Using a commercially available VA type liquid crystal display device (SONY 40 type display KLV-40J3000), the polarizing plate bonded to both sides of the liquid crystal cell was peeled off, and the produced polarizing plates 1 to 40 were used as both sides of the liquid crystal cell. The liquid crystal display devices 1-40 were produced by bonding to each other.

<< Evaluation of Polarizing Plate and Liquid Crystal Display >>
Each evaluation below was performed about each produced said liquid crystal display device and each polarizing plate used for the production.

(Evaluation of wrinkle resistance)
The presence or absence of wrinkles on the surface of each polarizing plate after irradiation of ultraviolet light used for the production of each liquid crystal display device and the presence or absence of film interface peeling were visually observed, and wrinkle resistance was evaluated according to the following criteria.

A: Generation of wrinkles, peeling between film interfaces, or film peeling is not observed at all. ○: Generation of either extremely weak wrinkles or film peeling between film interfaces is observed, but practical use △: Generation of weak wrinkles and film peeling between film interfaces are recognized, but acceptable quality ×: Generation of strong wrinkles and peeling between film interfaces This is a quality that poses practical problems (evaluation of panel warpage resistance).
After the liquid crystal display device (also referred to as a panel) prepared as described above was stored for 24 hours in an environment of 40 ° C. and 90% RH, a durability test was performed for 2 hours in an environment of 40 ° C. and 10% RH. The liquid crystal display device was left in an environment of 23 ° C. and 55% RH for 24 hours. Next, the panel was placed on a flat quartz plate, and the average value of the height of lifting from the four quartz plate surfaces was measured, and the warpage resistance of the panel was evaluated according to the following criteria.

A: The average lift height of the four corners is less than 1 mm. O: The average lift height of the four corners is 1 mm or more and less than 3 mm. Δ: The average lift height of the four corners is 3 mm or more (moisture resistance Evaluation of color unevenness due to humidity fluctuation)
Bencot (manufactured by Asahi Kasei Fibers Co., Ltd.) soaked in water was placed on the surface of the liquid crystal display device produced as described above and held for 24 hours in a state where moisture did not evaporate. Next, each liquid crystal display device was turned on, the uniformity of the display screen was visually evaluated, and the moisture resistance was evaluated according to the following criteria.

A: No occurrence of color unevenness is observed at all. ○: Slightly weak color unevenness is observed, but the quality has no problem in practical use. Δ: Although the occurrence of weak color unevenness is observed, it is practically acceptable. Table 4 shows the results obtained as described above. The results obtained are as follows.

  As is clear from the results shown in Table 4, the liquid crystal display device using the polarizing plate of the present invention has excellent characteristics in any of wrinkle resistance, panel warpage resistance and moisture resistance. Recognize.

DESCRIPTION OF SYMBOLS 1 Melting pot 3, 6, 12, 15 Filter 4, 13 Stock tank 5, 14 Liquid feed pump 8, 16 Conduit 10 Ultraviolet absorber charging pot 20 Merge pipe 21 Mixer 30 Die 31 Metal support 32 Web 33 Peeling position 34 Tenter device 35 Roll drying device 41 Feeding pot 42 Stock tank 43 Pump 44 Filter 101, 101A, 101B Polarizing plate 102 Protective film 103A, 103B Active energy ray curable resin layer 104 Polarizer 105 Phase difference film 106 Liquid crystal display device 107 Liquid crystal cell

Claims (5)

  At least a protective film, an active energy ray-curable resin layer, and a polarizer are laminated in this order to form a polarizing plate provided in a liquid crystal display device, wherein the protective film is an acrylic resin (A) and cellulose The ester resin (B) is contained within a mass ratio (A: B) of 95: 5 to 50:50, and is disposed on the surface opposite to the surface in contact with the liquid crystal cell. A polarizing plate. An active energy ray-curable resin layer and a retardation film satisfying all of the following conditions 1 to 3 are laminated on the polarizer surface opposite to the surface on which the protective film is disposed. The polarizing plate according to claim 1.
Condition 1: An in-plane retardation value Ro (590) represented by the following formula (I) measured at a wavelength of 590 nm under an environment of a temperature of 23 ° C. and a relative humidity of 55% is in the range of 30 to 150 nm.
Formula (I): Ro (590) = (n x -n y) × d
Condition 2: Retardation value Rt (590) in the thickness direction represented by the following formula (II) measured at a wavelength of 590 nm under an environment of a temperature of 23 ° C. and a relative humidity of 55% is within a range of 70 to 300 nm. is there.
Formula (II): Rt (590) = {(n _x + n _y ) / 2−n _z } × d
Condition 3: The amount of change in the retardation value Rt (590) in the thickness direction when the humidity is changed from 20 to 80% in an environment of a temperature of 23 ° C. is in the range of 1 to 30 nm.
In [Formula (I) and formula (II), n _x represents a refractive index in the direction x in which the refractive index is maximized in the plane direction of the film. n _y, in-plane direction of the film, the refractive index in the process y perpendicular to the direction x. _nz represents the refractive index in the thickness direction z of the film. d represents the thickness (nm) of the film. ] When the moisture permeability of the protective film containing the acrylic resin (A) and the cellulose ester resin (B) is measured according to JIS Z 0208 in an environment of 40 ° C. and 90% RH, 50 to 350 g / m ^2. The polarizing plate according to claim 1 or 2, wherein the polarizing plate is within a range of 24 hours.   The weight average molecular weight Mw of the said acrylic resin (A) exists in the range of 100,000-1 million, The polarizing plate as described in any one of Claim 1- Claim 3 characterized by the above-mentioned.   A liquid crystal display device comprising the polarizing plate according to any one of claims 1 to 4.

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