JPWO2015159645A1 - Polarizing plate and liquid crystal display device - Google Patents

Abstract

An object of the present invention is to provide a polarizing plate having high polarizer stability when stored in a high temperature and high humidity environment, and a liquid crystal display device in which occurrence of display unevenness (bend unevenness) is suppressed. The polarizing plate of the present invention is a polarizing plate having a configuration in which a polarizer made of polyvinyl alcohol resin is sandwiched between a polarizing plate protective film and a retardation film, and the polarizing plate protective film is at least an aromatic vinyl monomer. And a copolymer (A) of an unsaturated carboxylic acid monomer or an unsaturated dicarboxylic acid anhydride monomer, the film thickness is in the range of 20 to 60 μm, and the film thickness of the polarizer is 5. It is in the range of 0 to 15 μm.

Description

  The present invention relates to a polarizing plate and a liquid crystal display device. More specifically, the present invention relates to a polarizing plate having high polarizer stability and a liquid crystal display device having the polarizing plate and having excellent bend unevenness resistance.

  The liquid crystal display device is composed of a liquid crystal cell having a structure in which a transparent electrode, a liquid crystal layer, a color filter, etc. are sandwiched between a pair of glass plates, and two polarizing plates provided on the surface side of each glass plate, Each polarizing plate is sandwiched between, for example, an optical film having two polarizers made of a polyvinyl alcohol-based resin, for example, a polarizing plate protective film located outside and a retardation film disposed on the liquid crystal cell side. It has been configured.

  As a polarizing plate protective film constituting this polarizing plate, mainly, it has high transparency, saponification treatment with an alkaline aqueous solution, and using a polyvinyl alcohol-based adhesive, good adhesion with a polarizer is obtained. Cellulose ester films have been mainly used because they are easy to be formed.

  Currently, portable liquid crystal display devices such as smart phones and tablets are widely used. These liquid crystal display devices are required to be thin. Thinning is required for all the constituent elements. However, it has been found that when both the polarizer and the cellulose ester film are thinned, there is a problem that the polarization performance is greatly lowered in the forced deterioration test assuming long-term use.

  As a polarizing plate protective film having an effect on the deterioration of the polarizer, a technique has been proposed in which an acrylic polymer that is an acrylic film material, such as a polymethyl methacrylate film, is used as a protective film for a polarizing plate (for example, , See Patent Document 1).

  However, in a polarizing plate having an acrylic polymer film mainly composed of polymethyl methacrylate as a polarizing plate protective film, the polarizing plate protective film is a thin film that is insufficient to prevent polarizer deterioration, and further improvements are made. It turned out to be necessary.

  Furthermore, thinning the glass plate used in the liquid crystal cell has a great effect on the thinning of the display device and is in the direction of adoption. However, it has been found that thinning the glass plate newly causes bend unevenness. It is coming. Bend unevenness is a phenomenon in which bending due to contraction and extension occurs in a polarizer or the like composed of a polyvinyl alcohol resin due to humidity fluctuations in a high or low humidity environment, and as a result, display unevenness develops. It has been found that this phenomenon tends to occur when the glass plate is thinned.

JP 2012-180423 A

  The present invention has been made in view of the above-described problems and situations, and a solution to the problem is a polarizing plate having high polarizer stability and display unevenness (bend unevenness) when stored in a high temperature and high humidity environment. It is an object of the present invention to provide a liquid crystal display device that suppresses the occurrence of the above.

  In order to solve the above-mentioned problems, the present inventor has a structure in which a polarizer composed of a polyvinyl alcohol-based resin is sandwiched between a polarizing plate protective film and a retardation film in the course of examining the cause of the above-described problem. A polarizing plate, wherein the polarizing plate protective film contains a copolymer (A) of at least an aromatic vinyl monomer and an unsaturated carboxylic acid monomer or an unsaturated dicarboxylic acid anhydride monomer, and the film thickness is specified. The polarizer has a high polarizer stability when stored in a high-temperature and high-humidity environment, and is a liquid crystal. It has been found that a polarizing plate capable of suppressing the occurrence of display unevenness (bend unevenness) when provided in a display device is obtained.

  That is, the said subject which concerns on this invention is solved by the following means.

1. A polarizer composed of a polyvinyl alcohol-based resin, a polarizing plate configured to be sandwiched between a polarizing plate protective film and a retardation film,
The polarizing plate protective film contains a copolymer (A) of an aromatic vinyl monomer and an unsaturated carboxylic acid monomer or an unsaturated dicarboxylic acid anhydride monomer, and the film thickness is in the range of 20 to 60 μm. ,
The polarizing plate, wherein the polarizer has a thickness in the range of 5.0 to 15 μm.

  2. The polarizing plate protective film further has an acid, alcohol, metal salt, nonionic surfactant and nonreactive quaternary ammonium salt type surface activity having a linear or branched alkyl group having 8 to 22 carbon atoms. The at least 1 type compound chosen from an agent is contained within the range of 0.1-1.0 mass% with respect to the total mass of the said copolymer (A), It is characterized by the above-mentioned. Polarizer.

  3. 3. The polarizing plate according to item 1 or 2, wherein the aromatic vinyl monomer contained in the polarizing plate protective film is styrene.

  4). The polarizing plate according to any one of items 1 to 3, wherein the unsaturated carboxylic acid monomer contained in the polarizing plate protective film is methacrylic acid.

  5. The polarizing plate according to any one of items 1 to 3, wherein the unsaturated dicarboxylic acid anhydride monomer contained in the polarizing plate protective film is maleic anhydride.

  6). The polarizing plate protective film further comprises at least one selected from core / shell type acrylic fine particles, styrene-butadiene copolymer, styrene-conjugated diene copolymer, and butyl acrylate compound. The polarizing plate according to any one of items 1 to 5, wherein the polarizing plate is contained in a range of 0.5 to 5.0% by mass with respect to the total mass.

  7). The polarizing plate according to any one of items 1 to 6, wherein at least the polarizing plate protective film and the polarizer are bonded with an active energy ray-curable adhesive.

  8). The degree of decrease in the degree of polarization (%) represented by the following formula (1) of the sample subjected to the forced degradation treatment for 120 hours in an environment of 80 ° C. and 90% RH with respect to the untreated sample is 1.0% or less. The polarizing plate according to any one of items 1 to 7, wherein the polarizing plate is adjusted to be

  9. The polarizing plate according to any one of items 1 to 8 is provided on at least one surface side of a liquid crystal cell having a glass plate having a thickness in the range of 0.3 to 0.7 mm on the surface. A liquid crystal display device comprising a retardation film surface constituting the polarizing plate and the glass plate bonded together.

  10. It is the structure which has arrange | positioned the polarizing plate as described in any one of Claim 1 to 8 on both surfaces of the said liquid crystal cell, and bonded the retardation film surface and the said glass plate which comprise the said polarizing plate. Item 10. A liquid crystal display device according to item 9, wherein:

  By the above means of the present invention, it is possible to provide a polarizing plate having high polarizer stability when stored in a high temperature and high humidity environment, and a liquid crystal display device in which occurrence of display unevenness (bend unevenness) is suppressed.

  The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.

  In the polarizing plate of the present invention, the polarizing plate protective film disposed at a position adjacent to the polarizer contains at least a copolymer of an aromatic vinyl monomer and an unsaturated carboxylic acid monomer or an unsaturated dicarboxylic anhydride monomer. It is characterized by doing.

  As described above, a film composed of a resin having a large amount of hydroxy groups such as cellulose ester is likely to contain moisture, and when a polarizing plate is constructed, it affects the adjacent polarizers and the like. Become. As a result, from the viewpoint of improving display unevenness (bend unevenness), when the film thickness of the polarizer is reduced, the stability of the polarizer in a high-temperature and high-humidity environment is reduced. The improvement in (bend unevenness) and the stability of the polarizer could not be achieved at the same time.

  As a result of diligent investigation on the above problem, when a copolymer (A) of an aromatic vinyl monomer and an unsaturated carboxylic acid monomer or an unsaturated dicarboxylic acid anhydride monomer is applied to the polarizing plate protective film, hydroxy In spite of the presence of the group, it was found that excellent heat resistance can be obtained and the influence on the polarizer is extremely small. In other words, the aromatic vinyl monomer that constitutes the polarizing plate protective film itself is hydrophobic, which improves water resistance and reduces the dimensional change of the film due to moisture in a high-temperature and high-humidity environment. It is assumed that the liquid crystal panel is less likely to warp and the display unevenness (bend unevenness) is improved.

  Furthermore, when an unsaturated carboxylic acid monomer or an unsaturated dicarboxylic acid anhydride monomer is applied as a constituent element of the copolymer (A), the hydroxyl group of each carboxylic acid monomer is hydrogen-bonded, thereby causing moisture in the film. In addition, the presence of the hydroxy group prevents the pH fluctuation of the adjacent polarizer, prevents the collapse of cross-linking by boric acid, etc., and high polarizer stability Can be realized. Furthermore, it is assumed that the heat resistance can be improved due to the presence of the hydroxy group interaction. Moreover, the polarizing plate protective film which has a film thickness in the range of 20-60 micrometers can be comprised with the copolymer (A) of an aromatic vinyl monomer, and an unsaturated carboxylic acid monomer or an unsaturated dicarboxylic anhydride monomer, Based on excellent water resistance and heat resistance, even if the polarizer is made thin (within a thickness of 5.0 to 15 μm), the deterioration and shrinkage of the polarizer can be suppressed. As a result, the liquid crystal display device When incorporated in the liquid crystal display, the liquid crystal panel is less likely to warp and display unevenness (bend unevenness) can be improved.

Schematic sectional view showing an example of the configuration of a polarizing plate provided with a polarizing plate protective film Schematic sectional view showing a part of the configuration of a liquid crystal display device provided with a polarizing plate Schematic diagram showing an example of a solution casting film forming process flow applicable to the production of a polarizing plate protective film

  The polarizing plate of the present invention has a configuration in which a polarizer made of polyvinyl alcohol resin is sandwiched between a polarizing plate protective film and a retardation film, and the polarizing plate protective film comprises at least an aromatic vinyl monomer and an unsaturated carboxylic acid. It contains a copolymer (A) with an acid monomer or an unsaturated dicarboxylic anhydride monomer, and the film thickness is in the range of 20 to 60 μm, and the film thickness of the polarizer is in the range of 5.0 to 15 μm. It is characterized by being within. This feature is a technical feature common to the inventions according to claims 1 to 10.

  As an embodiment of the present invention, a polarizing plate protective film further includes a linear or branched alkyl group having 8 to 22 carbon atoms as a peeling aid from the viewpoint that the effects of the present invention can be further expressed. At least one compound selected from acids, alcohols, metal salts, nonionic surfactants and nonreactive quaternary ammonium salt type surfactants having the following, with respect to the total mass of the copolymer (A): A copolymer (A) composed of an aromatic vinyl monomer and an unsaturated carboxylic acid monomer or an unsaturated dicarboxylic acid anhydride monomer is contained in the range of 0.1 to 1.0% by mass. By shifting to the vicinity of the metal belt at the time of filming, it becomes a cushion layer between the metal belt and the film, thereby facilitating peeling of the dope from the metal belt when forming the polarizing plate protective film, From the viewpoint of capable of suppressing the occurrence of rising or lateral stage size.

  Moreover, it is preferable that the said aromatic vinyl monomer which the said polarizing plate protective film contains is a styrene at the point which can obtain the polarizing plate which has the more outstanding heat resistance and polarizer stability.

  Further, the unsaturated carboxylic acid monomer contained in the protective film for polarizing plate is methacrylic acid, or the unsaturated dicarboxylic acid anhydride monomer is maleic anhydride. It is preferable at the point which can obtain the polarizing plate which has child stability.

  The polarizing plate protective film further comprises at least one selected from core / shell type acrylic fine particles, styrene-butadiene copolymer, styrene-conjugated diene copolymer, and butyl acrylate compound. It is preferable that it contains in the range of 0.5-5.0 mass% with respect to the total mass of (A) from the viewpoint which can obtain the polarizing plate protective film which is excellent in brittle resistance and toughness.

  Also, at least the polarizing plate protective film and the polarizer are bonded with an active energy ray-curable adhesive, and even in the polarizing plate protective film produced using an aromatic vinyl monomer, the polarizer and the stable It is preferable from the standpoint that a polarizing plate having excellent adhesion can be produced without causing delamination and that a desired degree of polarization stability can be obtained.

  Further, with respect to the untreated sample, the degree of decrease in the degree of polarization (%) represented by the formula (1) in the sample after being stored for 120 hours in an environment of 80 ° C. and 90% RH is 1.0% By adjusting to be as follows, it is preferable from the viewpoint of imparting excellent stability to the polarizer when stored in various environments.

  Further, as the liquid crystal display device, the polarizing plate of the present invention is configured on at least one surface side of a liquid crystal cell having a glass plate having a thickness in the range of 0.3 to 0.7 mm on the surface. The retardation film surface to be bonded and the glass plate are bonded to each other. Furthermore, the polarizing plate of the present invention is disposed on both surfaces of the liquid crystal cell, and the retardation film surface and the glass plate constituting the polarizing plate. Is preferable from the viewpoint that the characteristics of the polarizing plate of the present invention can be sufficiently exhibited and display unevenness (bend unevenness) of the liquid crystal display device can be suppressed due to high water resistance.

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

<< Basic configuration of polarizing plate and liquid crystal display device >>
[Basic structure of polarizing plate]
The polarizing plate of the present invention is characterized by having a polarizing plate protective film having a specific configuration and a polarizer.

  Furthermore, the polarizing plate of the present invention preferably has a configuration in which a polarizer is sandwiched between a polarizing plate protective film and a retardation film, and the polarizing plate protective film and the polarizer are bonded by an active energy ray-curable adhesive. It is a preferable aspect that it is the structure which has an active energy ray hardening-type resin layer to do.

  FIG. 1 is a schematic cross-sectional view showing an example of the configuration of a polarizing plate provided with a polarizing plate protective film according to the present invention.

In FIG. 1, a polarizing plate 101 has a polarizing plate protective film 102 containing a copolymer (A) of an aromatic vinyl monomer and an unsaturated carboxylic acid monomer or an unsaturated dicarboxylic anhydride monomer on the surface side. and, in its lower part has a radiation-curable resin layer 103A _1. The radiation-curable resin layer 103A ₁ is a layer that functions to adhere the polarizer protective film 102 and the polarizer 104 configured, the active energy ray, for example, a material that is cured by irradiating ultraviolet rays or the like Has been.

  In the polarizing plate 101 of the present invention, the thickness of the polarizing plate protective film 102 is in the range of 20 to 60 μm, and the thickness of the polarizer 104 is in the range of 5.0 to 15 μm. To do.

Furthermore, on the opposite side of the surface where the polarizing plate protective film 102 is arranged according to the present invention for polarizer 104, further through the active energy ray-curable resin layer 103A _2, a certain retardation value The provided retardation film 105 is laminated to constitute the polarizing plate 101.

  In this invention, the polarizing plate protective film which concerns on this invention is arrange | positioned on the surface side on the opposite side to the surface which touches a liquid crystal cell on both sides of a polarizer, when comprising a polarizing plate. In FIG. 1, the surface in contact with the liquid crystal cell in the present invention is the lower surface of the retardation film 105, which will be described in detail later with reference to FIG. 2, and is opposite to the surface with the polarizer 104 interposed therebetween. The polarizing plate protective film 102 according to the present invention is installed on the surface. That is, the polarizing plate protective film which concerns on this invention is an optical film located in the surface side among two types of optical films which comprise the polarizing plate of this invention.

  Although not shown in FIG. 2, on the further outer side (outermost surface portion) of the polarizing plate protective film 102 according to the present invention, for example, an antiglare layer, an antireflection layer, or an antifouling layer may be used as necessary. Various functional layers such as a hard coat layer may be provided.

[Basic Configuration of Liquid Crystal Display Device of the Present Invention]
Next, the outline of the configuration of the polarizing plate panel having the polarizing plate of the present invention constituting the liquid crystal display device of the present invention will be described.

  As the liquid crystal display device of the present invention, the polarizing plate of the present invention is disposed on at least one surface side of a liquid crystal cell having a glass plate having a thickness in the range of 0.3 to 0.7 mm on the surface. Is characterized in that the retardation film surface and the glass plate are laminated, and as a more preferred embodiment, the polarizing plate of the present invention is arranged on both surfaces of the liquid crystal cell to constitute the polarizing plate. It is a preferable configuration that the retardation film surface and the glass plate are bonded together.

  FIG. 2 is a schematic cross-sectional view showing an example of the configuration of the polarizing plate panel 106 provided with the polarizing plate 101 of the present invention described above. The configuration in which the polarizing plates are arranged on both surfaces of the liquid crystal cell is shown as an example. .

  In FIG. 2, a polarizing plate panel 106 is formed by sandwiching the liquid crystal cell 107 between the retardation film 105A constituting the polarizing plate 101A described in FIG. 1 and the retardation film 105B constituting the polarizing plate 101B. Yes.

  The liquid crystal cell 107 has a configuration in which glass plates 109 </ b> A and 109 </ b> B are disposed on both surfaces of the liquid crystal layer 108.

  In the configuration shown in FIG. 2, in the polarizing plate 101A on the upper surface side of the liquid crystal cell 107, the polarizing plate protective film 102A according to the present invention is disposed on the surface portion as an optical film. Further, a retardation film 105A is disposed below the polarizer 104A, and this is referred to as a retardation film T2.

Further, the polarizing plate 101A, the polarizing plate protective film 102A and the polarizer 104A is, are bonded through a radiation-curable resin layer 103A _1, similarly retardation film 105A and the polarizer 104A is active energy ray They are bonded through the cured resin layer 103A _2.

  In the configuration as described above, the retardation film 105A and the glass plate 109A of the liquid crystal cell 107 are bonded via an adhesive layer or the like.

  In addition, a polarizing plate 101B is disposed on the opposite surface of the liquid crystal cell 107, and a polarizing plate protective film 102B is disposed as an optical film from the outermost surface. In the present invention, this is referred to as a polarizing plate protective film T4. Further, a retardation film 105B is disposed on the liquid crystal cell side of the polarizer 104B, and this is referred to as a retardation film T3.

Further, the polarizing plate 101B, a polarizing plate protective film 102B and the polarizer 104B is, are bonded through a radiation-curable resin layer 103B _1, the polarizer 104B is similarly to the retardation film 105B, an active energy ray They are bonded through the cured resin layer 103B _2.

  In the configuration as described above, the retardation film 105B and the glass plate 109B of the liquid crystal cell 107 are bonded via an adhesive layer or the like.

  In the polarizing plate panel having such a configuration, the polarizing plate having the polarizing plate protective film defined in the present invention is disposed on at least one surface side of the liquid crystal cell 107, and on the other side, the polarizing plate is not applicable to the present invention. However, it is preferable that both of the polarizing plates 101A and 101B arranged on both surfaces of the liquid crystal cell 107 are polarizing plates having the characteristics defined in the present invention.

《Each component of polarizing plate》
[Polarizing film]
The polarizing plate protective film according to the present invention is characterized by containing a copolymer (A) of an aromatic vinyl monomer and an unsaturated carboxylic acid monomer or an unsaturated dicarboxylic acid anhydride monomer.

  The polarizing plate protective film according to the present invention is characterized by containing the copolymer (A). Preferably, 30 mol% or more of the thermoplastic resin constituting the polarizing plate protective film is present in the present invention. It is preferable that it is comprised with the copolymer (A) which concerns on this, More preferably, it is 50 mol% or more, More preferably, it is 70 mol% or more, Most preferably, it is 90 mol% or more. In addition, the monomer which comprises a copolymer is also called "-unit."

[Copolymer (A)]
(Aromatic vinyl monomer)
The aromatic vinyl monomer has a function of increasing the water resistance of the copolymer (A). The aromatic vinyl monomer is preferably a styrene compound.

  Specific examples of the styrenic compound include styrene; alkyl-substituted styrenes such as α-methylstyrene, β-methylstyrene, and p-methylstyrene; halogen-substituted styrenes such as 4-chlorostyrene and 4-bromostyrene; p- Hydroxystyrenes such as hydroxystyrene, α-methyl-p-hydroxystyrene, 2-methyl-4-hydroxystyrene, 3,4-dihydroxystyrene; vinylbenzyl alcohols; p-methoxystyrene, p-tert-butoxystyrene, alkoxy-substituted styrenes such as m-tert-butoxystyrene; vinyl benzoic acids such as 3-vinylbenzoic acid and 4-vinylbenzoic acid; 4-vinylbenzyl acetate; 4-acetoxystyrene; 2-butylamidostyrene, 4-methyl Amidostyrene, p- Amidostyrenes such as sulfonamide styrene; Aminostyrenes such as 3-aminostyrene, 4-aminostyrene, 2-isopropenylaniline and vinylbenzyldimethylamine; Nitrostyrenes such as 3-nitrostyrene and 4-nitrostyrene; Examples include cyanostyrenes such as 3-cyanostyrene and 4-cyanostyrene; vinylphenylacetonitrile; arylstyrenes such as phenylstyrene, and indenes.

  Among these, styrene and α-methylstyrene are preferable, and styrene is particularly preferable because it is compatible with other styrene resins and (meth) acrylic resins. These aromatic vinyl monomers may be used alone or in combination of two or more.

(Unsaturated carboxylic acid monomer)
Although there is no restriction | limiting in particular as an unsaturated carboxylic acid monomer used for forming the polarizing plate protective film which concerns on this invention, The monomer enumerated below can be mentioned.

  Examples of the unsaturated carboxylic acid monomer applicable to the present invention include acrylic acid, acetylene carboxylic acid, 1-adamantal carboxylic acid, benzoic acid, desodium benzoate, 9-anthracene carboxylic acid, isopentanoic acid, isobutyric acid, Undecanoic acid, 10-undecanoic acid, 4-ethylbenzoic acid, ethyl oleic acid, 2-ethylhexanoic acid, 2-ethylbutyric acid, octanoic acid, formic acid, crotonic acid, cinnamic acid, acetic acid, tetramethylammonium acetate, cyclobutanecarboxylic Acid, cyclopropanecarboxylic acid, cyclopropylacetic acid, cyclohexanecarboxylic acid, cyclopentanecarboxylic acid, diphenylacetic acid, 2,4-dimethylbenzoic acid, 2,6-dimethylbenzoic acid, 3,4-dimethylbenzoic acid, 3,5 -Dimethylbenzoic acid, stearic acid, tiglic acid, deca Acid, 2,4,6-trimethylbenzoic acid, o-tolylacetic acid, 2- (4-toluoyl) benzoic acid, 1-naphthylacetic acid, 2-naphthylacetic acid, 1-naphthoic acid, 2-naphthoic acid, nonane Acid, palmitic acid, 4-vinylbenzoic acid, vinylacetic acid, 4-biphenylylacetic acid, biphenyl-2-carboxylic acid, biphenyl-4-carboxylic acid, pivalic acid, 4- (1-pyrenyl) -butyric acid, phenylacetylenecarboxylic acid 2-phenylpropionic acid, 3-phenylpropionic acid, 4-phenylbutyric acid, 9-fluorenecarboxylic acid, 4-t-butylbenzoic acid, 4-t-butylcyclohexanecarboxylic acid, propionic acid, 2-propylvaleric acid, Hexanoic acid, heptanoic acid, pentadecanoic acid, pentanoic acid, 4-pentenoic acid, trans-2-pentenoic acid, myristic acid, methacrylate Acid, 2-methylbenzoic acid, 3-methylbenzoic acid, 4-methylbenzoic acid, 2-methylvaleric acid, 4-methylvaleric acid, α-methylcinnamic acid, 4-methylcinnamic acid, 3-methylpentanoic acid, Examples thereof include 2-methylbutyric acid and lauric acid. In the present invention, it is particularly preferable to use methacrylic acid as the unsaturated carboxylic acid monomer.

(Unsaturated dicarboxylic acid anhydride monomer)
Although there is no restriction | limiting in particular as an unsaturated dicarboxylic anhydride monomer used for forming the polarizing plate protective film which concerns on this invention, The monomer enumerated below can be mentioned.

  Examples of unsaturated dicarboxylic acid anhydride monomers applicable to the present invention include maleic acid anhydride, methylmaleic acid anhydride, 1,2-dimethylmaleic acid anhydride, ethylmaleic acid anhydride, and phenylmaleic acid anhydride. , Bromomaleic anhydride, itaconic anhydride, aconitic anhydride, glutaconic anhydride, succinic anhydride, fumaric anhydride, citraconic anhydride, mesaconic anhydride, 2-pentenedioic anhydride, Examples thereof include methylene succinic anhydride, allylmalonic anhydride, isopropylidene succinic anhydride, 2,4-hexadiene diacid anhydride, acetylenedicarboxylic acid anhydride, etc. In the present invention, among them, unsaturated dicarboxylic acid It is particularly preferable to use maleic anhydride as the acid anhydride monomer.

(Other monomer components)
In the copolymer (A) according to the present invention, other monomer components can be used in combination as long as the object effects of the present invention are not impaired.

  Examples of such other copolymerizable monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethyl (meth) acrylate, and 2-ethylhexyl. Examples thereof include alkyl (meth) acrylates such as methacrylate, maleimides such as N-phenylmaleimide, N-methylmaleimide, and N-cyclohexylmaleimide, and glycidyl group-containing monomers such as glycidyl methacrylate. Among these, alkyl (meth) acrylates such as methyl (meth) acrylate are preferable. Other monomer components may be used alone or in combination of two or more.

(Ratio of monomer units constituting copolymer (A))
The copolymer (A) according to the present invention has at least an aromatic vinyl monomer and an unsaturated carboxylic acid monomer or an unsaturated dicarboxylic anhydride monomer, and the aromatic vinyl in the copolymer (A). The monomer ratio is preferably within a range of 5 to 95 mol%, more preferably within a range of 30 to 95 mol%, still more preferably within a range of 50 to 95 mol%, and particularly preferably 75. It is in the range of ˜90 mol%.

  Moreover, as a ratio of an unsaturated carboxylic acid monomer or an unsaturated dicarboxylic anhydride monomer, it exists in the range of 5-95 mol%, More preferably, it exists in the range of 5-70 mol%, More preferably, it is 5-50 mol%. And particularly preferably within the range of 10 to 25 mol%.

  Moreover, as another monomer, the range which does not impair the objective effect of invention can be selected, For example, it can be made to copolymerize in 0-30 mol%.

(Synthesis of copolymer (A))
A well-known manufacturing method can be used for preparation of the copolymer (A) based on this invention. Examples of general polymerization methods for unsaturated carboxylic acid polymers include radical solution polymerization using radical heat and initiator, radical suspension polymerization, radical emulsion polymerization, anionic polymerization using organometallic compounds, and transition metal complexes. Examples thereof include coordination anionic polymerization, cationic polymerization using Lewis acid, and the like.

  Examples of the synthesis method using an aromatic vinyl monomer and an unsaturated carboxylic acid monomer or an unsaturated dicarboxylic anhydride monomer include, for example, JP-A-7-011081, JP-A-7-118508, 7-216184, JP-A-9-302173, JP-A-11-106579, JP-A-11-16751, JP-A 2000-178385, JP-A 2004-204064, JP-A 2004-2004. No. 3004344, JP-A No. 2004-339282, JP-A No. 2005-290207, JP-A No. 2006-124523, JP-A 2009-185141, JP-A 2010-024452, JP-A 2013-104402. It can be prepared with reference to the synthesis method described in the publication That.

  The molecular weight of the copolymer (A) according to the present invention is preferably in the range of 50,000 to 450,000, preferably in the range of 100,000 to 400,000, as the weight average molecular weight measured by GPC described below. More preferably, it is more preferably within the range of 150,000 to 300,000.

  If the weight average molecular weight is 450,000 or less, it is easy to dissolve in a solvent when forming a film by the solution casting method, and sufficient fluidity can be obtained when forming a film by the melt casting method. it can. Moreover, if a weight average molecular weight is 50,000 or more, the drawing process suitability can be obtained.

<Method for measuring weight average molecular weight by GPC>
The weight average molecular weight (Mw) of the copolymer (A) according to the present invention is gel permeation chromatography (HLC8220GPC manufactured by Tosoh Corporation), column (TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL series) manufactured by Tosoh Corporation. Can be measured.

  Specifically, 20 ± 0.5 mg of copolymer (A) is dissolved in 10 ml of tetrahydrofuran and filtered through a 0.45 mm filter. 100 ml of this filtrate is injected into the above column having a column temperature of 40 ° C., measured at a detector RI temperature of 40 ° C., and a weight average molecular weight in terms of styrene is measured.

[Polarizing plate protective film: various additives]
The polarizing plate protective film according to the present invention is provided with, for example, a peeling aid, an antistatic agent, an antioxidant, an ultraviolet absorber, and slipperiness, as necessary, within a range that does not impair the object effects of the present invention. Various additives such as fine particles (matting agent) and impact reinforcement for enhancing toughness can be further contained.

(Peeling aid, antistatic agent)
The polarizing plate protective film containing the aromatic vinyl (for example, styrene) copolymer according to the present invention has high adhesion to the metal support used when casting the dope in the film forming step. With respect to this phenomenon, for the purpose of stably peeling from the metal support, suppressing unnecessary elongation at the time of peeling, and uniforming the thickness of the resulting film, the polarizing plate protective film is provided with a peeling aid or a charge. It is preferable to contain an inhibitor.

  Although there is no restriction | limiting in particular as peeling adjuvant, The acid, alcohol, metal salt, nonionic surfactant, and non-reactive quaternary ammonium salt which have a C8-C22 linear or branched alkyl group It is possible to contain at least one compound selected from the type surfactants in the range of 0.1 to 1.0% by mass with respect to the total mass of the copolymer (A) according to the present invention. It is preferable from the viewpoint of improving the peelability to the body.

  Examples of the acid having a linear or branched alkyl group having 8 to 22 carbon atoms, which is the peeling aid, include alkyl sulfonates and alkyl benzene sulfonates. Examples of the salt include sodium salt, potassium salt, amine salt, ammonium salt, phosphonium salt and the like.

  Specific examples include sodium decylsulfonate, sodium decylbenzenesulfonate, potassium decylbenzenesulfonate, sodium dodecylsulfonate, potassium dodecylsulfonate, sodium dodecylbenzenesulfonate, potassium dodecylbenzenesulfonate, tetrabutyl dodecylbenzenesulfonate. Ammonium, tetrabutylphosphonium dodecylbenzenesulfonate, sodium tetradecylsulfonate, sodium tetradecylbenzenesulfonate, potassium tetradecylbenzenesulfonate, sodium hexadecylsulfonate, sodium hexadecylbenzenesulfonate, potassium hexadecylbenzenesulfonate, etc. Is mentioned.

  Moreover, as these commercially available products, Hostastat HS-1 manufactured by Clariant Japan Co., Ltd., Elecut S-412-2, Elecut S-418 manufactured by Takemoto Yushi Co., Ltd., Neo-Perex G65 manufactured by Kao Co., Ltd. Etc.

  Examples of the alcohol include, for example, octan-1-ol, nonan-1-ol, decan-1-ol, undecan-1-ol, dodecan-1-ol, tridecan-1-ol, and tetradecan-1-ol. , Pentadecan-1-ol, hexadecan-1-ol, heptadecan-1-ol, octadecan-1-ol, nonadecan-1-ol, icosan-1-ol, heneicosan-1-ol, docosan-1-ol, etc. And octadecan-1-ol (stearyl alcohol) is preferred.

  Examples of the nonionic surfactant include polyoxyalkylene glycols such as polyoxyethylene polyoxypropylene glycol, polyoxyalkylene styrenated phenyl ethers such as polyoxyethylene styrenated phenyl ether, and polyoxyethylene tridecyl ether. And nonionic surfactants such as polyoxyalkylene glycols such as polyoxyethylene lauryl ether, polyoxyethylene sorbitan monococoate, polyoxyethylene sorbitan monostearate and polyoxyalkylene fatty acid esters such as polyoxyethylene hydrogenated castor oil These may be used alone or in combination of two or more. Examples of these commercially available products include Epan manufactured by Daiichi Kogyo Seiyaku Co., Ltd., and electro stripper manufactured by Kao Corporation.

  Furthermore, it is also preferable to use a non-reactive quaternary ammonium salt type surfactant as a peeling aid. Among them, a non-reactive quaternary ammonium salt type surfactant having 2 or less methyl groups is useful. Examples of the surfactant include, for example, a non-reactive quaternary ammonium salt type surfactant having one methyl group, polyoxypropylene methyldiethylammonium chloride, methyldiethyl (2-methoxyethyl) ammonium chloride, octyl Examples include bispolyoxyethylene methylammonium chloride, lauryl bispolyoxyethylene methylammonium chloride, oleyl bispolyoxyethylene methylammonium chloride, and polyoxyethylene dodecyl monomethylammonium chloride. Non-reactive quaternary ammonium having two methyl groups Examples of the salt type surfactant include aliphatic alkyl quaternary ammonium salts such as octyl dimethyl ethyl ammonium ethyl sulfate, lauryl dimethyl ethyl amine. Nium ethyl sulfate, palmityldimethylethylammonium ethyl sulfate, didecyldimethylammonium chloride, distearyldimethylammonium chloride, lauryldimethylbenzylammonium chloride, stearyldimethylhydroxyethylammonium paratoluenesulfonate, alkylbenzyldimethylammonium chloride, ethyldimethyl (2- Methoxyethyl) ammonium chloride and the like are preferably used. Among these, it is particularly preferable that the surfactant contains an alkylene oxide group. As the alkylene oxide group, those contained in either or both of an anionic component and a cationic component of the surfactant can be used. Examples of those containing an alkylene oxide group include polyoxypropylene methyl diethyl ammonium chloride, methyl diethyl (2-methoxyethyl) ammonium chloride, octyl bis polyoxyethylene methyl ammonium chloride, and lauryl bis polyoxyethylene methyl ammonium chloride. It is also a more preferable embodiment to use oleyl bis polyoxyethylene methyl ammonium chloride, polyoxyethylene dodecyl monomethyl ammonium chloride, or ethyldimethyl (2-methoxyethyl) ammonium chloride. These surfactants may be used alone or in combination of two or more.

  As these non-reactive quaternary ammonium salt type surfactants, commercially available products can be used. For example, the trade name “ADEKA COAL CC-36” (number of methyl groups: 1, manufactured by ADEKA Corporation), “ADEKA COAL” CC-42 ”(number of methyl groups: 1, manufactured by ADEKA Corporation), trade name“ cationic L-207 ”(number of methyl groups: 1, manufactured by NOF Corporation), trade name“ Kathiogen ES-L ”( Number of methyl groups: 2, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), trade name “Katiogen ES-O” (number of methyl groups: 2, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), trade name “Katiogen ES-OW” ( Number of methyl groups: 2, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), trade name “Katiogen ES-WS-L-9” (number of methyl groups: 2, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), trade name “Katiogen ES” -P "(number of methyl groups: 2, Daiichi Kogyo Yakuhin Co., Ltd.), trade name “Katiogen DDM-PG” (methyl group number: 2, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), trade name “Katiogen S” (methyl group number: 2, manufactured by Daiichi Kogyo ( Product name) “Kachiogen D2” (number of methyl groups: 2, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), product name “Katiogen BC-50” (number of methyl groups: 2, Daiichi Kogyo Seiyaku Co., Ltd.) Etc.) can also be used.

(Antioxidant)
In the polarizing plate protective film according to the present invention, a conventionally known antioxidant can be used for the purpose of imparting stability. As the antioxidant, in particular, lactone, sulfur, phenol, double bond, hindered amine, and phosphorus compounds can be preferably used.

  For example, the phenolic compound preferably has a 2,6-dialkylphenol structure. For example, “Irganox 1076”, “Irganox 1010” commercially available from BASF Japan Ltd., and commercially available from ADEKA Corporation. "Adekastab AO-50" etc. which can be mentioned.

  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., "GSY-P101" commercially available from Sakai Chemical Industry Co., Ltd., "Irgafos XP40, Irgafos XP60" commercially available from BASF Japan Ltd., etc. Is mentioned.

  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”.

(UV absorber)
The polarizing plate protective film according to the present invention preferably contains an ultraviolet absorber from the viewpoint of improving the weather resistance. Examples of applicable ultraviolet absorbers include benzotriazole-based, 2-hydroxybenzophenone-based, and salicylic acid. Examples thereof include ultraviolet absorbers such as phenyl ester and triazine. 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.

  Commercially available products of these ultraviolet absorbers 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; as an example of a commercially available product, manufactured by ADEKA Corporation LA31) can be preferably used.

  Furthermore, among UV absorbers, UV absorbers having a molecular weight of 400 or more are less likely to volatilize at a high boiling point and are difficult to disperse during high temperature molding of a polarizing plate protective film. It is preferable from the viewpoint of imparting the property.

  The ultraviolet absorber having a molecular weight of 400 or more partially overlaps with the above exemplary compounds. For example, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2- Benzotriazoles such as benzotriazole, 2,2-methylenebis [4- (1,1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol], bis (2,2,6 , 6-tetramethyl-4-piperidyl) sebacate, hindered amines such as bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, and 2- (3,5-di-t-butyl) -4-hydroxybenzyl) -2-n-butylmalonate bis (1,2,2,6,6-pentamethyl-4-piperidyl), 1- [2- [3- (3,5-di-t- Butyl-4 -Hydroxyphenyl) propionyloxy] ethyl] -4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine The hybrid type | system | group which has both the structure of hindered phenol and 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.

(Matting agent)
In the polarizing plate protective film according to the present invention, a matting agent can be added for the purpose of imparting slipperiness.

  The matting agent applicable to the present invention may be either an inorganic compound or an organic compound as long as the material has heat resistance in the film forming process without impairing the transparency of the polarizing plate protective film to be obtained. 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 high transparency and slipperiness can be achieved.

  Among these, silicon dioxide fine particles are particularly preferably used from the viewpoint of excellent transparency (haze).

  Specific examples of the silicon dioxide fine particles include Aerosil 200V, Aerosil R972V, Aerosil R972, R974, R812, 200, 300, R202, OX50, TT600, NAX50 (above, manufactured by Nippon Aerosil Co., Ltd.), Sea Hoster KEP-10, Sea Hoster Names of products such as 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 Admatechs) A commercially available product having the same can be preferably used.

  The shape of the matting agent particles can be used without particular limitation, such as indefinite shape, needle shape, flat shape, and spherical shape. However, the use of spherical particles is particularly preferable because a film having high transparency can be obtained.

  The size of the matting agent particles is preferably smaller than the wavelength of visible light because the light is scattered and the transparency is lowered when the particle size is close to the wavelength of visible light. It is preferable that it is 2 or less. However, if the size of the matting agent particles is too small, the effect of improving slipperiness may not be exhibited, and therefore the particle diameter is particularly preferably in the range of 80 to 180 nm.

  The particle size means the size of an 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.

(Impact reinforcement)
The polarizing plate protective film according to the present invention may contain core / shell type acrylic fine particles, a styrene-conjugated diene compound, or a butyl acrylate compound as an impact reinforcing material in order to enhance impact resistance.

  In particular, a core / shell type graft copolymer obtained by grafting a (meth) acrylic resin to a copolymer of a (meth) acrylic rubber and an aromatic vinyl compound described in JP-A-2009-84574, or an international It is preferable to contain an impact reinforcing material such as core / shell type acrylic fine particles described in JP 2009/047924 A and styrene-butadiene-based elastic organic fine particles described in JP 2013-83907 A.

  For example, the core-shell type acrylic fine particles are obtained by polymerizing a mixture of 80 to 98.9% by mass of methyl methacrylate, 1 to 20% by mass of alkyl acrylate, and 0.01 to 0.3% by mass of a polyfunctional grafting agent. Mixture of the innermost hard layer (core part) obtained, alkyl acrylate 75-98.5 mass%, multifunctional crosslinking agent 0.01-5 mass%, and multifunctional grafting agent 0.5-5 mass% Fine particles having a soft layer obtained by polymerizing and an outermost hard layer (shell part) obtained by polymerizing a mixture of 80 to 99% by mass of methyl methacrylate and 1 to 20% by mass of alkyl acrylate.

  The styrene-conjugated diene compound is preferably a styrene-butadiene copolymer. The copolymer may be a rubbery elastic body or elastic organic fine particles. Specifically, it is preferably a core / shell type elastic organic fine particle. The core part is preferably composed of a soft polymer; and the shell part covering the periphery of the core part is preferably composed of another polymer having high compatibility with the copolymer according to the present invention and other resins.

  The soft polymer includes a structural unit derived from a conjugated diene monomer and, if necessary, a structural unit derived from another monomer. Examples of the conjugated diene monomer include 1,3-butadiene (hereinafter sometimes simply referred to as “butadiene”), isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 2 -Chloro-1,3-butadiene, myrcene and the like are included, and butadiene and isoprene are preferable. Examples of other monomers include styrene components such as styrene and α-methylstyrene. The content ratio of the structural unit derived from the conjugated diene monomer in the soft polymer is usually 50% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more.

  Examples of other polymers include a copolymer of acrylonitrile and styrene, a polymer mainly composed of a methacrylic ester such as methyl methacrylate, and the like.

  The volume average particle diameter of the elastic organic fine particles is preferably 0.35 μm or less, more preferably in the range of 0.01 to 0.35 μm, and still more preferably in the range of 0.05 to 0.30 μm. is there. If the volume average particle diameter is 0.01 μm or more, sufficient impact absorbability can be imparted to the film, and if the volume average particle diameter is 0.35 μm or less, the transparency of the resulting film is unlikely to be impaired.

  Commercially available products of elastic organic fine particles include, for example, Metabrene C-140A, C-215A (above, manufactured by Mitsubishi Rayon Co., Ltd.), Toughprene 126, Asaflex 800, Asaflex 825 (above, manufactured by Asahi Kasei Chemicals Co., Ltd.). , TR2000, TR2250 (above, manufactured by JSR Corporation) and the like.

  Examples of other rubber-like elastic bodies include acrylate-based rubber-like polymers, and rubber-like polymers containing acrylate-based polymers containing butyl acrylate as the main component are preferred.

  The rubber-like elastic body using butyl acrylate may be elastic particles or may have a structure in which two kinds of polymers are layered. A typical example is a grafted rubber elastic component of alkyl acrylate such as butyl acrylate and styrene, and a hard resin layer made of polymethyl methacrylate or a copolymer of methyl methacrylate and alkyl acrylate to form a layer with a core / shell structure. And elastic particles.

  The content of the impact reinforcing material is preferably 0.1 to 10% by mass and more preferably 1 to 5% by mass with respect to the total amount with the copolymer (A) and other resins.

  When the impact reinforcing material used in the present invention is acrylic fine particles, the refractive index is the same as that of the styrene-acrylonitrile copolymer used in the present invention, or the difference in refractive index is within a range of ± 0.01. It is preferable from the viewpoint that the transparency of the film can be maintained.

(About degree of polarization)
In the polarizing plate of the present invention, the degree of polarization obtained by the lower formula (1) of the untreated polarizing plate is set to 1 (%), and the forced deterioration treatment is performed for 120 hours in an environment of 80 ° C. and 90% RH. When the degree of polarization obtained by the following formula (1) after application is defined as the degree of polarization 2, the degree of decrease in the degree of polarization represented by the following formula (2) is preferably 1.0% or less. Preferably, it is 1.0% or less including 0%, and particularly preferably 0.6% or less including 0%.

Formula (2)
Degree of decrease in polarization degree (%) = polarization degree 1 (%) − polarization degree 2 (%)
Specifically, the degree of polarization in the present invention can be determined according to the following method.

  A reference untreated polarizing plate and a polarizing plate subjected to a forced deterioration treatment for 120 hours in an environment of 80 ° C. and 90% RH are prepared.

  Next, each was subjected to a humidity control treatment for 24 hours in an environment of 23 ° C. and 55% RH, and then the parallel transmittance and orthogonal transmittance of light having a wavelength of 550 nm were measured using an automatic polarizing film measuring device (VAP-7070, Japan). Measured using Spectroscopic Co., Ltd. Next, based on the measured values obtained, based on the above formula (1), the degree of polarization 1 of the untreated polarizing plate and the degree of polarization 2 of the polarizing plate subjected to the above-mentioned forced deterioration treatment are obtained, and the above formula According to (2), the reduction degree (%) of the polarization degree is obtained.

In the present invention, with respect to the degree of polarization 1 of the untreated polarizing plate, the reduction width (%) of the degree of polarization 2 of the polarizing plate after 120 hours of forced deterioration treatment in an environment of 80 ° C. and 90% RH. There is no particular limitation on the means for adjusting to 1.0% or less,
1) The thermoplastic resin constituting the polarizing plate protective film according to the present invention may be composed of a copolymer (A) of an aromatic vinyl monomer and an unsaturated carboxylic acid monomer or an unsaturated dicarboxylic anhydride monomer. The most preferred means, and besides,
2) Acid, alcohol, metal salt, nonionic surfactant, and non-reactive quaternary ammonium salt in which the polarizing plate protective film according to the present invention has a linear or branched alkyl group having 8 to 22 carbon atoms. Containing at least one compound selected from type surfactants in a range of 0.1 to 1.0% by mass relative to the total mass of the copolymer (A),
3) Use of styrene as the aromatic vinyl monomer constituting the polarizing plate protective film,
4) Use methacrylic acid as the unsaturated carboxylic acid monomer contained in the polarizing plate protective film, or use maleic anhydride as the unsaturated dicarboxylic acid anhydride monomer,
5) The polarizing plate protective film and the polarizer are bonded with an active energy ray-curable adhesive,
6) Forming a polarizing plate protective film by a solution casting method,
This can be achieved by appropriately selecting or combining the respective means.

  In particular, the method of forming a film of a styrene-methacrylic acid copolymer by a solution film forming method prevents the penetration of moisture into the film by hydrogen bonding of the hydroxy group of methacrylic acid, By the presence of the group, it is possible to suppress the pH fluctuation of the adjacent polarizer and to prevent the breakage of the cross-linking by boric acid, and by containing the highly hydrophobic styrene, High polarizer stability can be realized.

[Production method of polarizing plate protective film]
As a manufacturing method of the polarizing plate protective film according to the present invention, various film forming methods such as a normal inflation method, a T-die method, a calendar method, a cutting method, a casting method, an emulsion method, a hot press method, and the like are applied. However, from the viewpoints of suppressing coloring, suppressing defects of foreign matters, suppressing optical defects such as die lines, etc., the film casting method can be preferably selected from a solution casting method or a melt casting method. Applying it can control the distribution state of the resin to suppress panel bend and obtain a uniform and smooth surface. Furthermore, the degree of polarization of the polarizer constituting the polarizing plate in a high temperature and high humidity environment It is preferable from the viewpoint of suppressing the decrease.

(Solution casting method)
Hereinafter, the manufacture example which manufactures the polarizing plate protective film which concerns on this invention with a solution casting method is demonstrated.

  The production of the polarizing plate protective film according to the present invention includes the step of preparing a dope by dissolving the copolymer (A) according to the present invention, other resins and additives in a solvent, and filtering the prepared dope. The film is cast on a belt-shaped or drum-shaped metal support to form a web, the formed web is peeled from the metal support to form a film, the film is stretched and dried, and the film is dried. After the film is cooled, it is performed by each process such as a process of winding in a roll.

  Hereinafter, each process of manufacturing a polarizing plate protective film by a solution casting method will be described.

(1) Dissolution step The dissolution step is a dissolution pot in which the copolymer (A) and other additives according to the present invention are stored in an organic solvent mainly composed of a good solvent for the copolymer (A). The dope which is the main solution is prepared by mixing, stirring and dissolving to prepare the dope, or mixing the resin solution containing the copolymer (A) with a solution in which other additives are dissolved in a solvent. It is a process to do.

  When the polarizing plate protective film according to the present invention is produced by the solution casting method, the organic solvent useful for preparing the dope is limited as long as it dissolves the copolymer (A) and other additives at the same time. Can be used.

  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. Among them, methylene chloride, methyl acetate, ethyl acetate, and acetone can be preferably used as the main solvent. Particularly preferably down or ethyl acetate.

  In addition to the organic solvent, the dope preferably contains a linear or branched aliphatic alcohol having 1 to 4 carbon atoms in the range of 1 to 40% by mass. If the proportion of alcohol in the dope is 40% by mass or less, the web will gel, and peeling from the metal support will be easy, and if the proportion of alcohol is 1% by mass or more, the non-chlorine organic solvent There is also a role of promoting dissolution of the copolymer (A) according to the present invention and other additives in the system.

  In the formation of the polarizing plate protective film according to the present invention, a dope having an alcohol concentration in the range of 0.5 to 15.0% by mass is formed from the viewpoint of improving the flatness of the obtained polarizing plate protective film. A filming method can be applied.

  In particular, in a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms, the concentration of the copolymer (A) and other additives according to the present invention is 15 to 45 masses. It is preferable that it is the dope composition melt | dissolved in the range of%.

  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. . Among these, methanol and ethanol are preferable because they contribute to the stability of the dope, have a relatively low boiling point and good drying properties.

  For dissolving the copolymer (A) and other additives according to the present invention, a method carried out at normal pressure, a method carried out below the boiling point of the main solvent, a method carried out under pressure above the boiling point of the main solvent, JP-A-9 -95544, JP-A-9-95557, JP-A-9-95538, or the like, a method of performing a cooling dissolution method, or JP-A-11-21379, a method of performing at a high pressure Various dissolution methods such as, for example, can be used, but a method of pressurizing at a temperature equal to or higher than the boiling point of the main solvent is preferred.

  It is preferable that the density | concentration of the copolymer (A) based on this invention in dope exists in the range of 10-40 mass%. Various additives are added to the dope during or after dissolution of the copolymer (A) according to the present invention to dissolve and disperse it, and then filtered through a filter medium, defoamed, and sent to the next step with a liquid feed pump.

  Regarding dope filtration, it is preferable to filter the dope with a filter medium having a 90% collection particle diameter of 10 to 100 times the average particle diameter of fine particles, for example, with a main filter equipped with a leaf disk filter.

  In the present invention, the filter medium used for filtration preferably has a low absolute filtration accuracy. However, if the absolute filtration accuracy is too small, the filter medium is likely to be clogged, and the filter medium must be frequently replaced. There is a problem of lowering productivity.

  Therefore, in the present invention, the filter medium used for the dope preferably has an absolute filtration accuracy of 0.008 mm or less, more preferably in the range of 0.001 to 0.008 mm, and more preferably in the range of 0.003 to 0.006 mm. The filter medium is more preferable.

  There are no particular restrictions on the material of the filter medium, and ordinary filter media can be used. However, the filter medium is made of plastic fibers such as polypropylene and Teflon (registered trademark), and is made of metal such as stainless steel fibers that do not lose fibers. The filter medium is preferable.

In the present invention, the dope flow rate during filtration is in the range of 10 to 80 kg / (h · m ² ), preferably in the range of 20 to 60 kg / (h · m ² ). Here, if the dope flow rate during filtration is 10 kg / (h · m ² ) or more, the filtration efficiency is excellent in production suitability, and the dope flow rate during filtration is 80 kg / (h · m ^2). ) If it is below, the pressure applied to the filter medium is appropriate, and the filter medium is not damaged, which is preferable.

  The filtration pressure is preferably 3500 kPa or less, more preferably 3000 kPa or less, and even more preferably 2500 kPa or less. The filtration pressure can be controlled by appropriately selecting the filtration flow rate and the filtration area.

  FIG. 3 is a schematic diagram showing an example of a flow of a solution casting film forming step applicable to the production of a polarizing plate protective film according to the present invention.

  The dope prepared in the charging vessel 41 is removed from the large agglomerates by the filter 44 and then fed to the stock vessel 42. Thereafter, the dope is fed from the stock kettle 42 to the main dope dissolving kettle 1 and various additive solutions are added to prepare the main dope.

  Thereafter, the main dope is filtered by the main filter 3, and a matting agent dispersion liquid, an ultraviolet absorbent additive liquid, and the like are added in-line through the conduit 16 to the main dope.

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

  The return material is, for example, a product obtained by finely pulverizing the polarizing plate protective film according to the present invention. The raw material of the polarizing plate protective film exceeding the specified value is used.

  Moreover, as a raw material of resin used for dope preparation, what pelletized previously the copolymer (A) based on this invention, another additive, etc. can be used preferably.

(2) Casting step (2-1) Dope casting The dope prepared above is fed to the pressurizing die 30 through a feed pump (for example, a pressurized metering gear pump), and is transported infinitely. The dope is supplied from the slit portion of the pressurizing die 30 to the casting position on the metal support 31 of the loop shape, for example, a stainless steel belt or a metal support such as a rotating metal drum. is there.

  The metal support 31 in the casting (casting) step preferably has a mirror-finished surface, and the metal support 31 is preferably a stainless steel belt or a drum whose surface is plated with a casting. The cast width may be in the range of 1 to 4 m, preferably in the range of 1.5 to 3 m, and more preferably in the range of 2 to 2.8 m. The surface temperature of the metal support 31 in the casting step is set within a range of −50 ° C. to a temperature at which the solvent boils and does not foam, more preferably within a range of −30 to 100 ° C. A higher temperature is preferable because the web can be dried faster, but if the temperature is too high, the web may foam or the flatness may deteriorate. A preferable surface temperature of the metal support 31 is appropriately determined within a temperature range of 0 to 100 ° C, and more preferably within a range of 5 to 30 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent. The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing warm air or cold air, and a method of bringing hot water into contact with the back side of the metal support. It is preferable to use warm water from the viewpoint that heat can be efficiently transferred and the time until the temperature of the metal support becomes constant can be shortened. When using warm air, considering the temperature drop of the web due to the latent heat of vaporization of the solvent, while using warm air above the boiling point of the solvent, there is a case where wind at a temperature higher than the target temperature is used while preventing foaming. is there. In particular, it is preferable to perform efficient drying by appropriately adjusting the temperature of the metal support and the temperature of the drying air during the period from casting to peeling.

  As the pressurizing die 30, the pressurizing die 30 having a structure that can adjust the shape of the slit portion of the base portion and easily make the film thickness uniform is preferable. The pressure die 30 includes a coat hanger die and a T die, and any of them is preferably used. In order to increase the deposition rate, a method may be used in which two or more pressure dies 30 are provided on the metal support 31 in the transport direction and the dope amount is divided and stacked.

(3) Solvent evaporation step A web (hereinafter, the dope is cast on the casting metal support 31 and the formed dope film is referred to as a web) is heated on the casting metal support 31; This is a step of evaporating the solvent.

  Although a specific configuration is not shown in FIG. 3, in order to evaporate the solvent, a method of blowing air from the web side, a method of transferring heat from the back side of the metal support 31, or a method of transferring heat from the back side of the metal support 31, front and back surfaces by radiant heat are used. However, the method of transferring heat from the back side with a liquid is preferable from the viewpoint of good drying efficiency. It is also preferable to combine the above methods. The web on the metal support 31 after casting is preferably dried on the metal support 31 in an atmosphere of 40 to 100 ° C. In order to maintain an atmosphere of 40 to 100 ° C., a method of applying warm air of this temperature to the upper surface of the web or heating by a heating means using radiant heat such as infrared rays is preferable.

  From the viewpoint of surface quality, moisture permeability, and peelability, it is preferable to peel the formed web from the metal support 31 within 30 to 120 seconds.

(4) Peeling step This is a step of peeling the web that has been in a film state due to evaporation of the solvent on the metal support 31 at the peeling position 33 shown in FIG. The peeled web is made into a film and then sent to the subsequent drying and stretching steps.

  In addition, the amount of residual solvent at the time of peeling on the metal support 31 at the time of peeling is the amount of residual solvent represented by the following formula (Z) depending on the strength of drying conditions, the length of the metal support, and the like. (%) Is preferably peeled in the range of 50 to 120% by mass. When peeling under conditions with more residual solvent, since the web is too soft, the flatness at the time of peeling is impaired, and slippage and vertical lines due to peeling tension are likely to occur, so the amount of residual solvent at the time of peeling (%) Is determined by a balance between economic speed and quality. The residual solvent amount (%) of the web is defined by the following formula (Z).

Formula (Z)
Residual solvent amount (%) = [(mass before heat treatment of web−mass after heat treatment of web) / (mass after heat treatment of web)] × 100
Note that the heat treatment at the time of measuring the residual solvent amount is a heat treatment at 115 ° C. for 1 hour.

  The peeling tension when peeling the metal support from the film is usually preferably in the range of 196 to 245 N / m. However, if the wrinkles tend to occur during peeling, the tension is 190 N / m or less. Can also be peeled off.

  In the present invention, the temperature at the peeling position 33 on the metal support 31 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 preferable.

(5) Drying and stretching step The drying step can be performed by dividing it into a preliminary drying step and a main drying step.

<Preliminary drying process>
In the preliminary drying step, the web obtained by peeling from the metal support is dried. The web may be dried while being conveyed by a large number of rollers arranged above and below, or may be dried while being conveyed while fixing both ends of the web with clips like a tenter dryer. .

  The means for drying the web is not particularly limited, and can be performed by general hot air, infrared rays, a heating roller, microwave, or the like, but it is preferably performed by hot air from the viewpoint of simplicity.

  The drying temperature in the web drying step is preferably a glass transition temperature (Tg) of the polarizing plate protective film of −5 ° C. or lower, and it is effective to perform a heat treatment within a range of 5 to 20 minutes at a temperature of 100 ° C. or higher. Is. Drying is performed at a drying temperature in the range of 100 to 200 ° C, more preferably in the range of 110 to 160 ° C.

<Extension process>
The polarizing plate protective film according to the present invention can control the orientation of molecules in the film by being subjected to a stretching treatment, and can improve planarity and impart toughness.

  The stretching operation may be performed in multiple stages. Moreover, when performing biaxial stretching, you may perform simultaneous biaxial stretching and the method of extending | stretching in steps. In this case, stepwise means that, for example, stretching can be performed independently in the longitudinal direction and the width direction with different stretching directions, and stretching in the same direction is divided into multiple stages and different directions. It is also possible to add this stretching to any stage.

Thus, for example, the following stretching steps are possible:
(A) Stretch in the casting direction → Stretch in the width direction → Stretch in the casting direction → Stretch in the casting direction (b) Stretch in the width direction → Stretch in the width direction → Stretch in the casting direction → Casting direction In addition, simultaneous biaxial stretching includes stretching in one direction and contracting the other while relaxing the tension.

  The amount of residual solvent in the film at the start of stretching is preferably in the range of 2 to 10% by mass.

  If the amount of residual solvent in the film at the time of stretching is 2% by mass or more, the deviation of the film thickness is small, and it is preferable from the viewpoint of flatness. Improved and preferable.

  The polarizing plate protective film according to the present invention has (Tg + 15) when the glass transition temperature of the film is defined as Tg in the MD direction or TD direction, preferably in the TD direction so that the film thickness after stretching is in a desired range. ) To (Tg + 50) It is preferable to stretch in the temperature range. When stretched in the above temperature range, the stretching stress can be reduced, and the haze of the film can be kept low. Moreover, generation | occurrence | production of a film fracture | rupture is suppressed and the polarizing plate protective film excellent in planarity is obtained. The stretching temperature is preferably in the range of (Tg + 20) to (Tg + 40) ° C.

  The polarizing plate protective film according to the present invention preferably stretches the web within a range of 1.01 to 10 times at least in the MD direction or the TD direction. That is, the range of stretching is preferably in the range of 1.1 to 10 times, more preferably in the range of 1.2 to 8.0 times the original width. If it is in the said range, a film will become toughness, a film can be thinned, and the flatness of a film can be improved.

  In order to stretch in the MD direction, it is preferable to peel at a peeling tension of 130 N / m or more, and particularly preferably 150 to 170 N / m. Since the web after peeling is in a high residual solvent state, stretching in the MD direction can be performed by maintaining the same tension as the peeling tension. As the web dries and the residual solvent amount decreases, the stretch ratio in the MD direction decreases.

  For the stretching in the MD direction, a roller stretching machine utilizing the difference in peripheral speed of the rollers can be used, and the stretching ratio can be calculated from the rotational speed of the belt-shaped metal support and the operating speed of the roller stretching machine.

  In order to stretch in the TD direction, for example, the entire drying process or a part of the process as disclosed in Japanese Patent Application Laid-Open No. 62-46625 is performed while holding the width at both ends of the web with clips or pins in the width direction. A drying method (referred to as a tenter method), among them, a clip tenter method using a clip and a pin tenter method using a pin are preferably used.

  In stretching in the TD direction, stretching in the width direction of the film at a stretching speed of 250 to 500% / min is preferable from the viewpoint of improving the flatness of the film.

  If the stretching speed is 250% / min or more, the planarity is improved and the film can be processed at a high speed, which is preferable from the viewpoint of productivity, and if it is 500% / min or less, the film is broken. Therefore, the stretching process can be stably performed, which is preferable.

  A more preferable stretching speed is in the range of 300 to 400% / min. The stretching speed is defined by the following formula (E).

Formula (E)
Stretching speed (% / min) = [(d ₁ / d ₂ ) −1] × 100 (%) / t
In the above formula (E), d ₁ is the width dimension in the stretching direction of the polarizing plate protective film after stretching, d ₂ is the width dimension in the stretching direction of the polarizing plate protective film before stretching, and t is required for stretching. Time (min).

The in-plane retardation value Ro and the retardation value Rt in the thickness direction of the polarizing plate protective film according to the present invention are measured using an automatic birefringence meter Axoscan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axometrics). 23 ° C., under an environment of 55% RH, subjected to three-dimensional refractive index measured at a wavelength of 590 nm, the refractive index will be described later resulting _{n x, n y,} it can be calculated from _{n z.}

  The polarizing plate protective film according to the present invention has a retardation value (Rt) defined by the following formula (ii) within the range of the retardation value (Ro) defined by the following formula (i) of 0 to 70 nm. The range of −50 to 10 nm is particularly preferable when the polarizing plate protective film does not require retardation. In the polarizing plate protective film which concerns on this invention, it can be set as desired in-plane retardation value Ro and retardation value Rt by extending | stretching adjusting a draw ratio at least in the said MD direction or TD direction.

Formula _{(i): Ro = (n} x -n y) × d (nm)
Formula (ii): Rt = {(n _x + n _y ) / 2−n _z } × d (nm)
In the above 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 direction 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.

<Main drying process>
In the main drying step (drying step 35), the residual solvent is removed from the web that has been subjected to the stretching treatment and dried. The web may be dried while being conveyed by a large number of rollers arranged above and below, or may be dried while being conveyed while fixing both ends of the web with clips like a tenter dryer. . The amount of residual solvent in the web is preferably 2% by mass or less.

  The means for drying the web is not particularly limited, and can be performed by general hot air, infrared rays, a heating roller, microwave, or the like, but it is preferably performed by hot air from the viewpoint of simplicity.

  The drying temperature in the main drying step is preferably a glass transition temperature (Tg) of the polarizing plate protective film of −5 ° C. or lower, and it is effective to perform a heat treatment within a range of 10 to 60 minutes at a temperature of 100 ° C. or higher. It is. Drying is performed at a drying temperature in the range of 100 to 200 ° C, more preferably in the range of 110 to 160 ° C.

<Knurling>
After performing a predetermined heat treatment or cooling treatment, it is preferable to provide a slitter and take off the end portion before winding to obtain a good winding shape. Furthermore, it is preferable to apply a knurling process to both ends of the width.

  As the knurling process, a concavo-convex structure can be formed at both ends of the polarizing plate protective film by pressing a heated embossing roller against the formed polarizing plate protective film. Fine irregularities (embossing) are formed at both ends of the embossing roller, and by pressing this, irregularities can be formed at both ends of the polarizing plate protective film, and the ends can be made bulky.

  The height of the knurling at both ends of the width of the polarizing plate protective film according to the present invention is preferably in the range of 4 to 20 μm, and the width is preferably in the range of 5 to 20 mm.

  In the present invention, the knurling process is preferably provided after the drying process and before the winding process in the step of forming the polarizing plate protective film.

(6) Winding step This is a step of winding as a film after the amount of residual solvent in the web is 2% by mass or less. By making the residual solvent amount 0.4% by mass or less, good dimensional stability is obtained. A film can be obtained.

  As a winding method, a generally used method may be used, and 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.

(Melt casting method)
The polarizing plate protective film according to the present invention can be formed by a melt casting method in addition to the solution casting method described above. In the melt casting method, the film composition containing the copolymer (A) according to the present invention and other additives is heated and melted to a temperature showing fluidity, and then the fluid melt is cast. This is a method for forming a polarizing plate protective film.

  In the melt casting method, 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, that is, the copolymer (A) according to the present invention and other additives are preferably kneaded in advance and pelletized.

  Pelletization can be performed by a known method. For example, the copolymer (A) according to the present invention and other additives are supplied to an extruder by a feeder and mixed using a uniaxial or biaxial extruder. It can be pelletized by smelting, extruding into a strand form from a die, water cooling or air cooling, and then 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.

  The extruder is preferably processed at as low a temperature as possible within a range that can be pelletized so that the shearing force is suppressed and deterioration of the copolymer (A) or the like (for example, molecular weight reduction, coloring, gel formation, etc.) does not occur. . 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 with a feeder to form a film without pelletization.

  The melting temperature when extruding the above pellets using a single-screw or twin-screw type extruder is in the range of 200 to 300 ° C. After removing foreign matter by filtering with a leaf disk type filter or the like, the T die Then, a polarizing plate protective film can be formed by casting into a film, nip the film with a cooling roller and an elastic touch roller, and solidifying the film on the cooling roller.

  In addition, when supplying the copolymer (A) or the like from the supply hopper to the extruder, it is preferable to prevent oxidative decomposition or the like of the material under vacuum or reduced pressure or in an inert gas atmosphere.

  The extrusion flow rate is preferably stabilized 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 an integrated filter that creates an intricately intertwined state of the stainless steel fiber body and then compresses and sinters the contact area. The density is adjusted by the thickness and amount of compression of the stainless steel fiber. In addition, the filtration accuracy can be controlled.

  Additives such as antioxidants and matting agent particles may be previously mixed with the copolymer (A) or the like, or may be added and 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.

  The temperature of the polarizing plate protective film on the elastic touch roller side when the polarizing plate protective film is nipped between the cooling roller and the elastic touch roller is preferably in the range of Tg to (Tg + 110 ° C.) of the film.

  The elastic touch roller having an elastic body on the surface is also referred to as a pinching rotary body, and is not particularly limited, and a commercially available roller can be appropriately selected and 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 to stretch | stretch the film obtained as mentioned above by the same extending | stretching operation as the said solution casting method, after passing the process which contact | connects a cooling roller.

  As a stretching method, a known roller stretching machine, a tenter or the like can be preferably used. The stretching temperature is preferably carried out in the temperature range of Tg to (Tg + 60) ° C. of the resin that usually constitutes the film.

  Prior to winding, the end may be slit and cut to the width of the product, and the knurling process (embossing process) may be applied to both ends in order to prevent sticking and scratching during winding. As described above, the knurling method can be performed by heating or pressurizing using a metal roller having an uneven pattern at the end or a metal ring having an uneven pattern on the side as described above. In addition, since the polarizing plate protective film has deform | transformed and cannot use as a product, the holding part of the clip of the both ends of a film is normally cut out and reused.

[Physical properties of polarizing plate protective film]
<Haze>
In the polarizing plate protective film according to the present invention, the haze is preferably 1.0% or less, and more preferably 0.5% or less. By setting the haze to 1.0% or less, there is an advantage that the transparency of the film becomes higher and it becomes easier to use as a film for optical applications.

  The haze is measured with a haze meter (turbidimeter) (model: NDH 2000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K-7136.

<Total light transmittance>
The total light transmittance of the polarizing plate protective film according to the present invention is preferably 90% or more, and more preferably 93% or more. The total light transmittance can be measured in accordance with JIS K 7375: 2008 “Plastics—Determination of total light transmittance and total light reflectance”.

<Equilibrium moisture content>
In the polarizing plate protective film according to the present invention, the equilibrium water content at 25 ° C. and relative humidity 55% is preferably 3.0% by mass or less, and more preferably 2.0% by mass or less. By setting the equilibrium moisture content to 3.0% by mass or less, it is preferable to easily cope with a change in humidity and to hardly change the optical characteristics and dimensions.

<Film length, width, film thickness>
It is preferable that the polarizing plate protective film which concerns on this invention is a long specification, Specifically, it is preferable that it is about 100-10000m in length, and is wound up in the state laminated | stacked on roll shape. The width of the polarizing plate protective film according to the present invention is preferably 1 m or more, more preferably 1.4 m or more, and particularly preferably in the range of 1.4 to 4 m.

  The film thickness is in the range of 20 to 60 μm. When the film thickness is 20 μm or more, a certain level of film strength and retardation can be expressed. When the film thickness is 60 μm or less, the film has a desired retardation, and can be applied to thin the polarizing plate and the display device, and the bend unevenness and the thin film can be balanced.

<Moisture permeability>
In the polarizing plate protective film according to the present invention, the moisture permeability at 40 ° C. and 90% RH is preferably 300 g / m ² · day or less, more preferably 250 g / m ² · day or less, A range of 200 g / m ² · day is particularly preferable for suppressing bend unevenness. This is for suppressing a change in the size of the polarizer due to the transmitted water in a high temperature and high humidity environment. The moisture permeability is measured under the conditions of 40 ° C. and 90% RH in accordance with the method described in JIS Z 0208: 1976 “Moisture permeability test method for moisture-proof packaging material (cup method)”.

  The moisture permeability of the polarizing plate protective film can be adjusted by, for example, the content of an aromatic vinyl monomer such as a styrene monomer in the constituent unit of the copolymer (A) according to the present invention. When the moisture permeability is set low, for example, the content ratio of the structural unit derived from the aromatic vinyl monomer in the polymer (A) according to the present invention may be set large.

<Tear strength>
The tear strength of the polarizing plate protective film according to the present invention at 23 ° C. and 55% RH is preferably 15 mN or more, more preferably 20 mN or more, and further preferably 30 mN or more. The upper limit of the tear strength is about 50 mN.

  The tear strength of the polarizing plate protective film can be measured by the following method.

  The polarizing plate protective film is cut into a size of width 50 mm × length 64 mm to prepare a sample film. The sample film is conditioned for 24 hours in an environment of 23 ° C. and 55% RH, and then the Elmendorf tear strength is measured according to ISO 6383-2: 1983. Specifically, the Elmendorf tear strength can be measured using, for example, a light load tear tester manufactured by Toyo Seiki Co., Ltd. The tear strength was determined for each of the cases of tearing in the film length direction (MD direction) and film width direction (TD direction) in an environment of 23 ° C. and 55% RH. Calculated as a value.

  The tear strength of the polarizing plate protective film can be adjusted by, for example, the molecular weight of the copolymer (A) or other resin. In order to increase the tear strength, for example, the molecular weight of the copolymer (A) or other resin may be increased.

[Various functional layers that can be formed on the polarizing plate protective film]
In the polarizing plate protective film according to the present invention, a functional layer having various functions can be provided on at least one surface of the film. Examples of the functional layer include a hard coat layer, an antistatic layer, a back coat layer, an antireflection layer, a slippery layer, an adhesive layer, an antiglare layer, and a gas barrier layer.

  Since the polarizing plate protective film according to the present invention has high toughness and hardly causes uneven heat shrinkage, the polarizing plate protective film has excellent resistance to heat treatment when a functional layer is provided.

  Hereinafter, typical functional layers will be described.

(Hard coat layer)
The hard coat layer can be formed of a cured product of an actinic radiation curable compound. As an applicable actinic radiation curable compound, a component containing a monomer having an ethylenically unsaturated double bond can be preferably used. Examples of the actinic radiation curable compound include an ultraviolet curable compound and an electron beam curable compound, but an ultraviolet curable compound that is cured by ultraviolet irradiation is superior in mechanical film strength (abrasion resistance, pencil hardness). preferable.

  As the ultraviolet curable compound, for example, an ultraviolet curable urethane acrylate resin, an ultraviolet curable polyester acrylate resin, an ultraviolet curable epoxy acrylate resin, an ultraviolet curable polyol acrylate resin, or an ultraviolet curable epoxy resin is preferable. Used. Of these, UV curable acrylate resins are preferred.

  The hard coat layer is formed by applying a hard coat layer forming coating solution containing an actinic radiation curable compound and a photopolymerization initiator on the polarizing plate protective film according to the present invention, and then curing it by irradiation with actinic radiation. Can be formed.

  Examples of the photopolymerization initiator include acetophenone, benzophenone, hydroxybenzophenone, Michler's ketone, α-amyloxime ester, thioxanthone, and derivatives thereof, but are not particularly limited thereto. The amount of the photopolymerization initiator in the coating liquid for forming the hard coat layer is preferably within a range of photopolymerization initiator: active ray curable compound = 20: 100 to 0.01: 100 in terms of mass ratio.

  The hard coat layer forming coating solution preferably further contains inorganic fine particles or organic fine particles as necessary. Examples of inorganic fine particles include silicon oxide, titanium oxide, aluminum oxide, tin oxide, indium oxide, ITO, zinc oxide, zirconium oxide, magnesium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, and hydration. Calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate are included, and preferably silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, magnesium oxide and the like are used.

  Examples of the organic fine particles include polymethacrylic acid methyl acrylate resin powder, acrylic styrene resin powder, polymethyl methacrylate resin powder, and silicone resin powder.

  The average particle diameter of the fine particles is not particularly limited, but is preferably in the range of 0.01 to 5 μm in consideration of forming an antiglare layer in addition to the hard coat layer. More preferably, it is in the range of 01 to 1.0 μm. Further, two or more kinds of fine particles having different particle diameters may be mixed and used. The average particle diameter of the fine particles can be measured by, for example, a laser diffraction particle size distribution measuring device.

  It is preferable to mix | blend the content rate of microparticles | fine-particles so that it may exist in the range of 10-400 mass parts with respect to 100 mass parts of ultraviolet curable compounds, More preferably, it exists in the range of 50-200 mass parts.

  These hard coat layers, for example, using a known wet coating method such as a gravure coater, a dip coater, a reverse coater, a wire bar coater, a die coater, an ink jet method, a coating composition for forming a hard coat layer is applied, It can be formed by heating and drying after coating and applying a curing treatment by ultraviolet irradiation.

  The film thickness after drying of the hard coat layer is in the range of 0.1 to 30 μm, preferably 1 to 20 μm, particularly preferably 6 to 15 μm as the average film thickness.

  As a light source applied to the ultraviolet curing treatment, any light source that emits ultraviolet rays as active energy rays can be used without limitation. For example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, or the like can be used.

The irradiation conditions vary depending on individual lamps, irradiation of active energy rays, usually in the range of 5~500mJ / cm ^2, preferably in the range of 5 to 200 mJ / cm ^2.

(Antireflection layer)
In the polarizing plate protective film according to the present invention, an antireflection layer may be further provided on the upper surface of the hard coat layer. Thereby, the polarizing plate protective film according to the present invention can be used as an antireflection film having an external light antireflection function.

  The antireflection layer is preferably laminated in consideration of the refractive index, the film thickness, the number of layers, the layer order, and the like so that the reflectance is reduced by optical interference. The antireflection layer is composed of a low refractive index layer having a refractive index lower than that of the support (the above-mentioned optical film), or a combination of a high refractive index layer having a refractive index higher than that of the support and a low refractive index layer. Is preferred. Particularly preferably, it is an antireflection layer composed of three or more refractive index layers, and three layers having different refractive indexes from the support side are divided into medium refractive index layers (high refractive index layers having a higher refractive index than the support). Are preferably laminated in the order of a layer having a lower refractive index) / a high refractive index layer / a low refractive index layer. Alternatively, an antireflection layer having a layer structure of four or more layers in which two or more high refractive index layers and two or more low refractive index layers are alternately laminated is also preferably used.

  As the layer configuration of the antireflection film using the polarizing plate protective film according to the present invention, the following configurations may be considered, but the present invention is not limited to this.

Polarizing plate protective film / hard coat layer / low refractive index layer Polarizing plate protective film / hard coat layer / medium refractive index layer / low refractive index layer Polarizing plate protective film / hard coat layer / medium refractive index layer / high refractive index layer / Low refractive index layer Polarizing plate protective film / hard coat layer / high refractive index layer (conductive layer) / low refractive index layer Polarizing plate protective film / hard coat layer / antiglare layer / low refractive index layer Essential in antireflection film It is preferable that the low refractive index layer is a silica-based fine particle. The refractive index of the silica-based fine particles is preferably lower than the refractive index of the polarizing plate protective film as the support, and is preferably in the range of 1.30 to 1.45 at 23 ° C. and a wavelength of 550 nm. In particular, the silica-based fine particles preferably include at least one kind of particles having an outer shell layer and porous or hollow inside. The particles having the outer shell layer and having a porous or hollow interior are preferably hollow silica-based fine particles.

  The film thickness of the low refractive index layer is preferably 5 nm to 0.5 μm, more preferably 10 nm to 0.3 μm, and most preferably 30 nm to 0.2 μm.

  The low refractive index layer can be formed by applying and drying a coating solution for forming a low refractive index layer, followed by curing. The coating solution for forming a low refractive index layer contains the silica-based fine particles, and may further contain an organosilicon compound represented by the following formula (S), a hydrolyzate thereof, or a polycondensate thereof.

Formula (S): Si (OR) ₄
In the organosilicon compound represented by the above formula (S), R represents an alkyl group having 1 to 4 carbon atoms.

  Specifically, tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane and the like are preferably used.

  The coating solution for the low refractive index layer may further contain a solvent, a silane coupling agent, a curing agent, a surfactant and the like as necessary.

[Other components of polarizing plate]
In the polarizing plate of this invention, it is preferable that the polarizing plate protective film which concerns on this invention is the structure currently bonded on the one surface of the polarizer at least using the active energy ray hardening-type adhesive agent.

  In addition, a cellulose ester phase difference film is similarly applied to the surface of the polarizer opposite to the surface on which the polarizing plate protective film is bonded, using an active energy ray-curable adhesive. It is preferable from the viewpoint of handleability, reworkability, and optical characteristics, and also preferable from the viewpoint of simplification of the bonding process.

  In the present invention, when the outer films T1 and T4 (polarizing plate protective film) are films with low moisture permeability and the inner films T2 and T3 (retardation film) are cellulose ester films, It is preferable from the viewpoint that the influence of moisture can be reduced and internal moisture can be easily released, and the durability of the polarizing plate against humidity fluctuations is improved overall.

  Therefore, the polarizing plate of the present invention has a structure in which the polarizer is sandwiched between the polarizing plate protective film according to the present invention and the cellulose ester phase difference film, which improves durability, suppresses bend unevenness, and is excellent. From the viewpoint of imparting high visibility to the liquid crystal display device, this is a preferred embodiment.

  When the polarizing plate of the present invention is used as a polarizing plate on the viewing side, the polarizing plate protective film on the viewing side is an antiglare layer or a clear hard coat layer, an antireflection layer, an antistatic layer, an antifouling layer, etc. It is preferable to provide a functional layer. The polarizing plate protective film according to the present invention has a particularly high effect of suppressing variation in heat shrinkage after coating. Therefore, even if the functional layer is formed by coating, and then heated and dried to perform ultraviolet irradiation, Shrinkage is small, and generation of wrinkles in the film and cracks in the functional layer can be suppressed.

(Polarizer)
The polarizer, which is the main component of the polarizing plate of the present invention, 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, it is possible to use 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. . The film thickness of the polarizer is in the range of 5 to 15 μm, and particularly preferably in the range of 5 to 10 μm.

  Further, the ethylene unit content described in JP-A-2003-248123, JP-A-2003-342322, etc. is in the range of 1 to 4 mol%, the polymerization degree is in the range of 2000 to 4000, and saponification Ethylene-modified polyvinyl alcohol having a degree in the range of 99.0 to 99.99 mol% is also preferably used. Among these, an ethylene-modified polyvinyl alcohol film having a hot water cutting temperature in the range 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 little color unevenness, and is particularly preferably used for a large liquid crystal display device.

<Laminated film type polarizer>
In addition, the polarizing plate of the present invention is preferably a thin film, and the thickness of the polarizer is particularly preferably in the range of 2 to 15 μm from the viewpoint of achieving both the strength of the polarizing plate and the thinning.

  As such a thin film polarizer, for example, a method described in Japanese Patent Application Laid-Open No. 2011-1000016, Japanese Patent No. 4691205, Japanese Patent No. 4751481, Japanese Patent No. 4804589, and the like can be used. Is preferably produced.

<< Polarizing plate manufacturing method >>
The polarizing plate of the present invention can be produced by a general method. The surface of the polarizing plate protective film according to the present invention to be bonded to the polarizer is subjected to surface treatment such as corona treatment, plasma treatment, or excimer light treatment, and is then immersed in an iodine solution and drawn at least one of the polarizers. Attached to the surface using an active energy ray-curable adhesive.

  In that case, it is preferable that the retardation film and polarizer similarly demonstrated below are similarly bonded by the active energy ray hardening-type adhesive agent. When the retardation film is a cellulose ester film, the surface may be saponified.

  The direction of bonding with the polarizer is preferably bonded so that the absorption axis of the polarizer and the slow axis of the polarizing plate protective film are orthogonal, for example.

[Other polarizing plate protective film]
Another polarizing plate protective film can be bonded to the other surface of the polarizer. For example, as a conventional polarizing plate protective film, commercially available cellulose ester films (for example, Konica Minoltak KC8UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC4FR, KC4KR, KC4DR, KC4SR, KC8UY, KC6UY, KC, KC8UE, KC8UY-HA, KC8UX-RHA, KC8UXW-RHA-C, KC8UXW-RHA-NC, KC4UXW-RHA-NC, and the like, manufactured by Konica Minolta Co., Ltd.) are preferably used.

[Phase difference film]
On one surface of the polarizer, it is preferable to dispose retardation films as T2 and T3 in order to improve visibility such as widening the viewing angle and improving contrast provided in the VA liquid crystal auxiliary display device.

  The retardation film is not particularly limited, but is preferably a cellulose ester film, for example. Examples of cellulose esters constituting the cellulose ester film include cellulose triacetate, cellulose diacetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate benzoate, cellulose acetate propionate benzoate, cellulose propionate, and cellulose butyrate. , Cellulose acetate biphenylate, cellulose acetate propionate biphenylate, and the like.

  The cellulose ester preferably has a total acyl group substitution degree in the range of 1.5 to 2.5, and more preferably satisfies the following formulas (a) and (b).

Formula (a) 2.0 ≦ X + Y ≦ 2.5
Formula (b) 0 ≦ Y ≦ 1.5
In the above formulas (a) and (b), X represents the degree of substitution of the acetyl group, and Y represents the degree of substitution of the propionyl group, butyryl group, or a mixture thereof.

  The weight average molecular weight (Mw) of the cellulose ester is preferably 750,000 or more, more preferably 100,000 to 1,000,000, from the viewpoint of film strength and appropriate viscosity during film formation. It is especially preferable that it is ˜500,000.

  The cellulose ester film may be a single layer film or a laminated film. When the cellulose ester film is a laminated film, it is a laminate of a core layer mainly composed of a cellulose ester having a low degree of substitution and a skin layer mainly composed of a cellulose ester having a high degree of substitution disposed on both sides thereof. It is preferable. The cellulose ester having a low degree of substitution preferably satisfies the above formulas (a) and (b), and the cellulose ester having a high degree of substitution preferably has a total acyl group substitution degree of more than 2.5, and preferably 2.7. More preferably, it is in the range of ˜2.98, and it is particularly preferable that all the acyl groups contained in the cellulose ester are acetyl groups.

  The retardation of the retardation film can be set according to the type of liquid crystal cell to be combined. For example, the retardation value Ro in the in-plane direction measured at a wavelength of 590 nm under an environment of 23 ° C. and 55% RH of the retardation film is preferably in the range of 30 to 150 nm, and the retardation in the thickness direction The value Rt is preferably in the range of 70 to 300 nm. A retardation film having a retardation value in the above range can be preferably used as a retardation film such as a VA liquid crystal cell. Ro and Rt are defined as described above.

  The thickness of the retardation film is not particularly limited, but is preferably in the range of 10 to 250 μm, more preferably in the range of 10 to 100 μm, and particularly preferably in the range of 30 to 60 μm. preferable.

[Preparation of polarizing plate using active energy ray-curable adhesive]
In the polarizing plate of the present invention, the polarizing plate protective film according to the present invention described above and at least one surface side of the polarizer are preferably bonded with an active energy ray-curable adhesive. . In this case, as described above, it is preferable that the retardation film and the polarizer are similarly bonded with an active energy ray-curable adhesive. Furthermore, it is preferable that they are bonded by the same type of active energy ray-curable adhesive.

  In the present invention, by applying an active energy ray-curable adhesive to the bonding between the polarizing plate protective film and the polarizer according to the present invention, or the bonding between the retardation film and the polarizer, the productivity is high. The deformation of the polarizing plate can be suppressed, and excellent flatness can be obtained.

(Composition of active energy ray-curable adhesive)
The active energy ray-curable adhesive applicable to the production of the polarizing plate of the present invention includes a photo radical polymerization composition utilizing photo radical polymerization, a photo cation polymerization composition utilizing photo cation polymerization, and a photo radical. The hybrid polymerization type composition which used superposition | polymerization and photocationic polymerization together can be mentioned.

  As the radical photopolymerization type composition, for example, a specific ratio of a radical polymerizable compound containing a polar group such as a hydroxy group or a carboxy group described in JP-A-2008-009329 and a radical polymerizable compound not containing a polar group is specified. And the like are known. In particular, the radical polymerizable compound is preferably a compound having an ethylenically unsaturated bond capable of radical polymerization. Preferable examples of the compound having an ethylenically unsaturated bond capable of radical polymerization include a compound having a (meth) acryloyl group. Examples of the compound having a (meth) acryloyl group include an N-substituted (meth) acrylamide compound and a (meth) acrylate compound. (Meth) acrylamide means acrylamide or methacrylamide.

  Moreover, as a photocationic polymerization type composition, as described in JP2011-026234A, (α) a cationic polymerizable compound, (β) a photocationic polymerization initiator, and (γ) a wavelength longer than 380 nm. And an active energy ray-curable adhesive composition containing each of the components of a photosensitizer exhibiting maximum absorption in the light of (δ) and a naphthalene-based photosensitization aid. However, other active energy ray-curable adhesives may be used.

  As the active energy ray curable adhesive used in the present invention, an ultraviolet curable adhesive as described in the above publication is preferably used.

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

As a manufacturing process of the polarizing plate of the present invention, mainly,
1) Adhesive application step of applying the active energy ray-curable adhesive to at least one of the adhesive surfaces of the polarizer and the polarizing plate protective film according to the present invention;
2) A polarizer and a polarizing plate protective film are bonded through the formed adhesive layer, and a bonding process is performed.
3) A curing step of curing the adhesive layer in a state where the polarizer and the polarizing plate protective film are bonded via the adhesive layer,
Can be mentioned. Moreover, you may have the following pre-processing process of carrying out an easy adhesion process with respect to the surface which adhere | attaches the polarizer of a polarizing plate protective film.

  Next, details of each step will be described.

(Pretreatment process)
In the pretreatment step, an easy adhesion treatment is performed on the surface of the polarizing plate protective film adhered to the polarizer. As illustrated in FIG. 1, when bonding the respective polarizing plate protective film 102 and the retardation film 105 on both surfaces of the polarizer 104, through the active energy ray-curable adhesive 103A ₁ and 103A ₂ are respectively An easy adhesion treatment is performed on the adhesion surfaces of the polarizing plate protective film 102 and the retardation film 105.

In the adhesive coating process, which is the next process, the surface side of each film that has been subjected to easy adhesion treatment is treated as a bonding surface with the polarizer 104. Therefore, among the two surfaces of the polarizing plate protective film 102, the active energy ray-curable resin is used. the layer 103A ₁ and bonding a surface, subjected to easy adhesion treatment. Examples of the easy adhesion treatment include corona treatment, plasma treatment, and excimer light treatment.

(Adhesive application process)
In the adhesive application step, the active energy ray-curable adhesive is applied to at least one surface side of the adhesive surfaces of the polarizer 104 and the polarizing plate protective film 102. When applying an active energy ray hardening-type adhesive directly on the surface of a polarizer or a polarizing plate protective film, there is no special limitation in the coating method. 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 applied. Moreover, after casting an active energy ray hardening-type adhesive between a polarizer and a polarizing plate protective film, the method of pressing with a roller etc. and spreading it uniformly can also be applied.

(Bonding process)
After apply | coating an active energy ray hardening-type adhesive agent by said method, an adhesion | attachment process is given at the bonding process. In this bonding step, for example, when the active energy ray-curable adhesive is applied to the surface of the polarizer 104 in the previous adhesive application step, the polarizing plate protective film 102 is superimposed thereon. When an active energy ray-curable adhesive is applied to the surface of the polarizing plate protective film 102 in the previous adhesive application step, the polarizer 104 is superimposed thereon. When an active energy ray-curable adhesive is cast and inserted between the polarizer 104 and the polarizing plate protective film 102, the polarizer 104 and the polarizing plate protective film 102 are overlapped with each other in that state. In the case where the polarizing plate protective film 102 and the retardation film 105 are bonded to both surfaces of the polarizer 104 and both surfaces use an active energy ray-curable adhesive, the active energy ray-curable adhesive is bonded to both surfaces of the polarizer. The polarizing plate protective film 102 and the retardation film 105 are superposed through the applied active energy ray-curable adhesive.

  Usually, in this state, when a polarizing plate protective film is superimposed on both sides, for example, one side of a polarizer, a polarizing plate protective film and a retardation film are provided on the polarizer side and the polarizing plate protective film side, and on both sides of the polarizer. Are laminated with a roller or the like from both sides of the polarizing plate protective film and the retardation film side, and pressure is applied for pressure bonding. As the material of the roller, metal, rubber or the like can be used. The rollers arranged on both sides may be made of the same material or different materials.

(Curing process)
In the curing step, the applied 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). The active energy ray-curable resin layer containing the compound and the like is cured, and the polarizer and the polarizing plate protective film, or the polarizer and the retardation film, which are superposed via the active energy ray-curable adhesive, are adhered. When bonding a polarizing plate protective film to the single side | surface of a polarizer, you may irradiate an active energy ray from either a polarizer side or a polarizing plate protective film side. In addition, when a polarizing plate protective film and a retardation film are bonded to both sides of the polarizer, the polarizing plate protective film and the retardation film are overlaid on both sides of the polarizer via an active energy ray-curable adhesive, respectively. Therefore, it is advantageous to irradiate active energy rays and simultaneously cure the active energy ray-curable adhesive on both sides.

  Examples of active energy rays that can be used for curing include visible light, ultraviolet rays, X-rays, and electron beams. However, since they are easy to handle and have a sufficient curing rate, And ultraviolet rays are preferably used.

  As the ultraviolet light source, for example, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, or the like can be used. An ArF excimer laser, a KrF excimer laser, an excimer lamp, synchrotron radiation, or the like can also be used. Among these, an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a xenon arc, and a metal halide lamp are preferably used.

  Further, as the electron beam, 50 to 1000 keV emitted from various electron beam accelerators such as a cockroft Walton type, a bandegraph type, a resonance transformation type, an insulation core transformation type, a linear type, a dynamitron type, and a high frequency type, preferably 100 Mention may be made of electron beams having an energy in the range of ˜300 keV.

  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 in the range of 5 to 300 kV, more preferably in the range of 10 to 250 kV. If the acceleration voltage is 5 kV or more, the electron beam can reach the adhesive sufficiently to obtain desired curing conditions, and if the acceleration voltage is 300 kV or less, the irradiation energy and the penetration force may become excessively strong. Without damaging the transparent polarizing plate protective film and the polarizer.

  As an irradiation dose, it exists in the range of 5-100 kGy, More preferably, it exists in the range of 10-75 kGy. If the irradiation dose is 5 kGy or more, the active energy ray-curable adhesive is sufficiently cured, and if it is 100 kGy or less, the polarizing plate protective film and the polarizer are not damaged, and a desired adhesive strength is obtained. Can do.

Any appropriate conditions can be adopted as the irradiation condition of the ultraviolet rays as long as the active energy ray-curable adhesive can be cured. The dose of ultraviolet rays is preferably in accumulated light amount is within the range of 50~1500mJ / cm ^2, and even more preferably in the range of 100 to 500 mJ / cm ^2.

  When the production method is performed on a continuous line, the line speed depends on the curing time of the active energy ray-curable adhesive, but is preferably in the range of 1 to 500 m / min, more preferably 5 to 300 m / min, Preferably, it is within the range of 10 to 100 m / min. When the line speed is 1 m / min or more, appropriate productivity can be secured, damage to the transparent polarizing plate protective film can be suppressed, and a polarizing plate excellent in durability can be produced. Moreover, if the line speed is 500 m / min or less, the resulting adhesive is sufficiently cured, and the desired adhesiveness can be obtained.

  In the polarizing plate obtained as described above, the thickness of the active energy ray-curable adhesive layer is not particularly limited, but is usually in the range of 0.01 to 10 μm, preferably 0.5 to 5 μm. Within range.

<Liquid crystal display device>
In the liquid crystal display device of the present invention, at least the first polarizing plate A, the liquid crystal cell, and the second polarizing plate B are arranged in this order from the viewing surface side, and the first polarizing plate A from the viewing surface side. Is composed of a polarizing plate protective film T1, a polarizer and a retardation film T2, and a second polarizing plate B is composed of a retardation film T3, a polarizer and a polarizing plate protective film T4, and constitutes the polarizing plate of the present invention. The polarizing plate protective film is a polarizing plate protective film T1 constituting the polarizing plate A or a polarizing plate protective film T4 constituting the polarizing plate B, and any of the polarizing plate protective film T1 and the polarizing plate protective film T4 Is preferably a polarizing plate protective film having a structure defined in the present invention.

  Moreover, it is preferable to have functional layers, such as a hard-coat layer, a reflection prevention layer, or a glare-proof layer, in the visual recognition side surface of the said polarizing plate protective film T1.

  Since the polarizing plate protective film according to the present invention is excellent in water resistance, heat resistance, flatness and the like, the glass substrate constituting the liquid crystal cell is formed into a thin film by providing the liquid crystal display device with the polarizing plate of the present invention. As a result, it is possible to obtain a liquid crystal display device in which thinning is achieved.

  Examples of the glass substrate that can be used for the liquid crystal cell include soda lime glass, silicate glass, and the like, and preferably silicate glass, specifically, silica glass or borosilicate glass. More preferably.

  The glass constituting the glass base material is preferably a non-alkali glass that does not substantially contain an alkali component, specifically, a glass having an alkali component content of 1000 ppm or less. The content of the alkali component in the glass substrate is preferably 500 ppm or less, and more preferably 300 ppm or less. In a glass substrate containing an alkali component, cation substitution occurs on the film surface, and soda blowing phenomenon tends to occur. Thereby, the density of the film surface layer tends to be lowered, and the glass substrate is easily damaged.

  The thickness of the glass substrate of the liquid crystal cell constituting the liquid crystal display device is preferably within the range of 0.4 to 0.6 mm. Such a thickness is preferable in that it can contribute to the formation of a thin liquid crystal display device.

  The glass substrate can be formed by a known method such as a float method, a down draw method, an overflow down draw method or the like. Of these, the overflow downdraw method is preferred because the surface of the glass substrate does not come into contact with the molded member during molding and the surface of the resulting glass substrate is hardly damaged.

  Moreover, such a glass base material can also be obtained as a commercial item, for example, non-alkali glass AN100 (thickness 500 μm) manufactured by Asahi Glass Co., Ltd., a glass substrate EAGLE XG (r) Slim (thickness manufactured by Corning) 300 μm, 400 μm, etc.), a glass substrate (thickness: 100 to 200 μm) manufactured by Nippon Electric Glass Co., Ltd., and the like.

  By using the polarizing plate of the present invention, even if the screen using the thin film glass substrate for a liquid crystal cell is a large-screen liquid crystal display device of 30 type or more, display unevenness (bend unevenness) is suppressed and the front surface is suppressed. A liquid crystal display device having excellent visibility such as contrast can be obtained.

  The specific structure of the liquid crystal display device provided with the polarizing plate of the present invention is as described with reference to FIG. 2, and the description thereof is omitted here.

  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.

  In addition, the direction of bonding of the polarizing plate in the VA mode liquid crystal display device can be performed with reference to JP-A-2005-234431.

  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.

  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 "part" or "%" is used in an Example, unless otherwise indicated, "mass part" or "mass%" is represented.

Example 1
<< Synthesis of Copolymer (A) >>
[Synthesis of Copolymer A1]
As a monomer, 93.6 parts by mass (90 mol%) of styrene, 7.2 parts by mass (10 mol%) of acrylic acid, 29.4 parts by mass of ethylbenzene, and 3.3 parts by mass of 2-ethylhexanol are mixed. 0.04 parts by mass of 2,2-bis (4,4-ditertiary butyl peroxide) propane was added to the liquid, and this polymerization liquid was added to a polymerization apparatus having a 5.0 L complete mixing reactor. Charged continuously at 1.67 L / hr. At this time, the temperature of the complete mixing reactor was adjusted to 135 ° C. Next, the polymer solution continuously discharged from the polymerization reactor is supplied to a vent type screw type extruder having a reduced pressure of 2.7 to 4.0 kPa, and volatile components are removed to form a pellet-shaped copolymer A1. Got. The composition ratio of the monomer units in the copolymer A1 was 90 mol% for the styrene monomer and 10 mol% for the acrylic acid monomer, and the weight average molecular weight measured by GPC was 300,000.

[Synthesis of Copolymers A2 to A13]
According to the method for synthesizing the copolymer A1, the type of the monomer, the composition ratio (mol%), and the weight average molecular weight were similarly changed except that the composition described in Table 1 was used. A13 was synthesized.

  In addition, the detail of each monomer described by the abbreviation in Table 1 is as follows.

(* 1: aromatic vinyl monomer)
St: Styrene α-MSt: α-Methylstyrene (* 2: Unsaturated carboxylic acid monomer, unsaturated dicarboxylic acid anhydride monomer)
AA: acrylic acid MAA: methacrylic acid MAH: maleic anhydride SAH: succinic anhydride GAH: glutaric anhydride (other monomers)
MMA: Methyl methacrylate << Preparation of peeling aid >>
As the compound (1) which is an additive described in Table 1 described later, the following peeling aid was prepared.

1-1: Elecut S-412-2 (manufactured by Takemoto Yushi Co., Ltd.): sodium dodecylbenzenesulfonate 1-2: Epan 750 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): nonionic surfactant, polyalkylene Oxide block, ethylene oxide content: 50%
1-3: Stearyl alcohol << Preparation of impact reinforcement >>
The following impact reinforcement was prepared as a compound (2) which is an additive described in Table 1 described later.

2-1: Tufprene 126S (manufactured by Asahi Kasei Chemicals Corporation) styrene-butadiene copolymer 2-2: TR2003 (manufactured by JSR Corporation) styrene-butadiene copolymer 2-3: Particle 1 below
2-4: Particle 2 below
[Particle 1: Acrylic particles synthesized by the following method]
(Acrylic particles C1)
A reactor with a reflux condenser with an internal volume of 60 liters is charged with 38.2 liters of ion-exchanged water and 111.6 g of sodium dioctylsulfosuccinate and heated to 75 ° C. under a nitrogen atmosphere while stirring at a rotational speed of 250 rpm. The oxygen was not affected. Ammonium persulfate (abbreviation: APS) 0.36 g was added, and after stirring for 5 minutes, methyl methacrylate (abbreviation: MMA) 1657 g, n-butyl acrylate (abbreviation: BA) 21.6 g, allyl methacrylate (abbreviation: ALMA) 1.68 g A mixture of monomers consisting of 1 and 2 was added all at once, and after the exothermic peak was detected, the mixture was further maintained for 20 minutes to complete the polymerization of the innermost hard layer.

  Next, 3.48 g of APS was added, and after stirring for 5 minutes, a monomer mixture consisting of 8105 g of BA, 31.9 g of polyethylene glycol diacrylate (abbreviation: PEGDA, molecular weight 200), and 264.0 g of ALMA was obtained. The addition was continuously performed over 120 minutes, and after completion of the addition, the mixture was further maintained for 120 minutes to complete the polymerization of the soft layer.

  Next, 1.32 g of APS was added, and after stirring for 5 minutes, a monomer mixture consisting of 2106 g of MMA and 201.6 g of BA was continuously added over 20 minutes, and held for another 20 minutes after the addition was completed. Thus, the polymerization of the outermost hard layer 1 was completed.

  Next, 1.32 g of APS was added, and after 5 minutes, a monomer mixture consisting of 3148 g of MMA, 201.6 g of BA, and 10.1 g of n-octyl mercaptan (abbreviation: n-OM) was added. It was added continuously over a period of time and held for another 20 minutes after the addition was completed. Next, the temperature was raised to 95 ° C. and held for 60 minutes to complete the polymerization of the outermost hard layer 2.

  The polymer latex thus obtained was put into a 3% by weight sodium sulfate aqueous solution, salted out and coagulated, then repeatedly dehydrated and washed, and then dried to obtain a three-layer structure. Particles 1 which are acrylic particles were obtained. The average particle size determined by the absorbance method was 100 nm.

[Particle 2: Elastic organic fine particles synthesized by the following method]
(Elastic organic fine particles (B1)
In a pressure-resistant reaction vessel equipped with a stirrer, 70 parts of deionized water, 0.5 part of sodium pyrophosphate, 0.2 part of potassium oleate, 0.005 part of ferrous sulfate and 0.2 part of dextrose A mixture comprising 0.1 part of p-menthane hydroperoxide and 28 parts of 1,3-butadiene was added, the temperature was raised to 65 ° C., and a polymerization reaction was carried out for 2 hours. Next, 0.2 parts of p-menthane hydroperoxide is added to the resulting reaction mixture, followed by 72 parts of 1,3-butadiene, 1.33 parts of potassium oleate and 75 parts of deionized water. The mixture was continuously added dropwise over 2 hours. The reaction was continued for 21 hours from the start of polymerization to obtain a butadiene rubber polymer latex having a volume average particle size of 0.240 μm.

  Next, in a polymerization vessel equipped with a cooler and a stirrer, 120 parts of deionized water, 50 parts of the butadiene rubber polymer latex as a solid content, 1.5 parts of potassium oleate, sodium formaldehyde sulfone. 0.6 parts of xylate (abbreviation: SFS) was added, and the inside of the polymerization vessel was sufficiently replaced with nitrogen gas. Subsequently, after the internal temperature was raised to 70 ° C., a mixed monomer solution consisting of 36.5 parts of styrene, 13.5 parts of acrylonitrile, 0.27 parts of cumene hydroxy peroxide, deionized water Polymerization was carried out while continuously dropping a polymerization initiator solution consisting of 20 parts separately over 2 hours. After completion of the dropwise addition, the internal temperature was raised to 80 ° C. and polymerization was continued for 2 hours. Next, after cooling to an internal temperature of 40 ° C., the mixture was passed through a 300 mesh wire net to obtain an emulsion polymerization liquid of elastic organic fine particles. The obtained emulsion polymerization liquid of elastic organic fine particles was salted out and solidified with calcium chloride, washed with water and dried to obtain particles 2 which are powdery elastic organic fine particles. The volume average particle diameter of the elastic organic fine particles was 0.260 μm.

<< Production of polarizing plate protective film >>
[Preparation of Polarizing Plate Protective Film 1]
The following components were sufficiently dissolved with stirring and heating to prepare Dope 1.

(Composition of dope 1)
Copolymer A1 (styrene: 90 mol%, acrylic acid: 10 mol%, weight average molecular weight: 300,000) 100 parts by mass UV absorber 2- (2H-benzotriazol-2-yl) -6- (1-methyl-1) -Phenylethyl) -4- (1,1,3,3-tetramethylbutyl) phenol (Ti928 manufactured by BASF Japan) 3.0 parts by weight Matting agent R812 (manufactured by Nippon Aerosil Co., Ltd., silica particles, average particle size 8 nm) 0.30 parts by mass Compound (1): Compound 1-1 Peeling aid (Elecut S-412-2, sodium dodecylbenzenesulfonate, manufactured by Takemoto Yushi Co., Ltd.) 0.35 parts by mass Compound (2): Compound 2- 1 impact reinforcing agent (styrene-butadiene copolymer) 1.0 part by mass dichloromethane 150 parts by mass ethanol 5 parts by mass Using the extension device, the temperature 22 ° C., was uniformly cast on a stainless band support in 2m width. The solvent was evaporated on the stainless steel band support until the residual solvent amount reached 50%, and the obtained film-like material was peeled off from the stainless steel band support with a peeling tension of 162 N / m.

  Next, the peeled film-like material was dried at a drying temperature of 135 ° C. while evaporating the solvent at 35 ° C. and stretching it 1.25 times in the width direction (TD direction) by tenter stretching. The residual solvent amount at the start of stretching by zone stretching was 20.0%, and the residual solvent amount at the start of stretching by tenter was 8.0%.

  After stretching with a tenter, a relaxation treatment was performed at 130 ° C. for 5 minutes, and then drying was completed while conveying a drying zone at 120 ° C. and 140 ° C. with a number of rollers. The obtained film was slit to a width of 1.5 m, a knurling process having a width of 10 mm and a height of 5 μm was applied to both ends of the film, and then wound around a core to prepare a polarizing plate protective film 1. The produced polarizing plate protective film 1 had a film thickness of 40 μm and a winding length of 4000 m.

[Production of Polarizing Plate Protective Films 2 to 13]
In the production of the polarizing plate protective film 1, polarizing plate protective films 2 to 13 were produced in the same manner except that the copolymer A1 used for preparing the dope was changed to A2 to A13, respectively.

[Production of Polarizing Plate Protective Films 14 and 15]
Polarizer protective films 14 and 15 were produced in the same manner except that the thickness of the polarizing plate protective film 4 was changed from 40 μm to 25 μm and 60 μm.

[Preparation of Polarizing Plate Protective Film 16]
In the production of the polarizing plate protective film 4, a polarizing plate protective film 16 was produced in the same manner except that the compound (1) peeling aid (compound 1-1) and the compound (2) impact reinforcing agent were removed.

[Preparation of Polarizing Plate Protective Film 17]
In the production of the polarizing plate protective film 4, a polarizing plate protective film 17 was produced in the same manner except that the compound (1) peeling aid (compound 1-1) was removed.

[Production of Polarizing Plate Protective Film 18]
In the production of the polarizing plate protective film 4, compound 1-1 (sodium dodecylbenzenesulfonate), which is a peeling aid for compound (1), is converted into compound (1-2, Epan 750, nonionic surfactant). A polarizing plate protective film 18 was produced in the same manner except for the change.

[Preparation of Polarizing Plate Protective Film 19]
In preparation of the said polarizing plate protective film 4, except having changed the compound 1-1 (sodium dodecylbenzenesulfonate) which is a peeling adjuvant of a compound (1) into the compound (1-3, stearyl alcohol), it is the same. A polarizing plate protective film 19 was prepared.

[Preparation of Polarizing Plate Protective Films 20-22]
In the production of the polarizing plate protective film 4, the addition amount of compound 1-1, which is a peeling aid for compound (1), was 0.15% by mass, 0.90% by mass, A polarizing plate protective film 20-22 was produced in the same manner except that the content was changed to 20% by mass.

[Preparation of Polarizing Plate Protective Film 23]
In the production of the polarizing plate protective film 4, a polarizing plate protective film 23 was produced in the same manner except that the compound (2) impact reinforcing agent was removed.

[Preparation of Polarizing Plate Protective Film 24]
In the production of the polarizing plate protective film 4, compound 2-1 (styrene-butadiene copolymer), which is an impact reinforcing agent of compound (2), was changed to compound (2-2, styrene-butadiene copolymer). A polarizing plate protective film 24 was produced in the same manner except for the above.

[Preparation of Polarizing Plate Protective Film 25]
In preparation of the said polarizing plate protective film 4, except having changed the compound 2-1 (styrene-butadiene copolymer) which is an impact reinforcement agent of a compound (2) into the compound (2-3, acrylic particle), it is the same. Thus, a polarizing plate protective film 25 was produced.

[Preparation of Polarizing Plate Protective Film 26]
In preparation of the said polarizing plate protective film 4, it is the same except having changed the compound 2-1 (styrene-butadiene copolymer) which is an impact reinforcing agent of the compound (2) into the compound (2-4, elastic organic fine particles). Thus, a polarizing plate protective film 26 was produced.

[Preparation of Polarizing Plate Protective Films 27-30]
In the production of the polarizing plate protective film 4, the addition amount of compound 2-1 (styrene-butadiene copolymer), which is an impact reinforcing agent of compound (2), was 0.3% by mass with respect to copolymer A4. Polarizing plate protective films 27 to 30 were produced in the same manner except that the content was changed to 2.5 mass%, 4.5 mass%, and 6.0 mass%.

[Production of Polarizing Plate Protective Film 31]
A polarizing plate protective film 31 was produced by the melt casting method shown below.

(Preparation of pellets)
Copolymer A4 100 parts by mass UV absorber 2,2′-methylenebis [6- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol] (Inc. LA31 manufactured by ADEKA, molecular weight 659) 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 weight Compound (2): Compound 2-1 Impact reinforcement (styrene- Butadiene copolymer) 1.0 part by mass Each of the above constituent materials was dried at 70 ° C. under reduced pressure for 3 hours in a vacuum nauter mixer, and then cooled to room temperature. The obtained mixture was melt-kneaded at 235 ° C. with a twin-screw extruder and extruded into a strand shape. The resin composition extruded in a strand form was cooled with water and then cut to obtain pellets.

  The obtained pellets were put into a single screw extruder and melt kneaded at 250 ° C. in a nitrogen atmosphere. Then, it extruded from the die | dye on the 1st cooling roll whose surface temperature is 90 degreeC. And the resin extruded on the 1st cooling roll was pressed with the touch roll. The surface temperature of the touch roll was 80 ° C. Thereafter, the obtained resin was further cooled and solidified on the second and third cooling rolls to produce a polarizing plate protective film 31 having a thickness of 40 μm by a melt casting method.

[Production of Polarizing Plate Protective Films 32 and 33]
In the production of the polarizing plate protective film 4, polarizing plate protective films 32 and 33 were produced in the same manner except that the film thickness was changed from 40 μm to 18 μm and 65 μm, respectively.

  Table 1 shows the structure of each polarizing plate protective film produced as described above.

<Production of polarizing plate>
Next, a polarizing plate was produced according to the following method using each of the produced polarizing plate protective films.

[Preparation of Polarizing Plate 1]
(1) Production of Polarizer A polyvinyl alcohol film having a thickness of 30 μm 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 3 times. This uniaxially stretched film was washed with water and dried to obtain a polarizer having a thickness of 10 μm. Similarly, the draw ratio was adjusted to produce polarizers having thicknesses of 3 μm, 5 μm, 15 μm, and 20 μm.

(2) Preparation of active energy ray-curable adhesive liquid The following components were mixed and then defoamed to prepare an active energy ray-curable adhesive solution. 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 (3) Production of retardation film 1 A retardation film 1 (for T2 and T3) was produced according to the method described below.

(Preparation of fine particle dispersion 1)
11 parts by mass of Aerosil R812 (manufactured by Nippon Aerosil Co., Ltd.) as fine particles and 89 parts by mass of ethanol as a dispersion medium were stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin. Prepared.

(Preparation of fine particle additive solution)
While slowly adding 5 parts by mass of the prepared fine particle dispersion 1 to a dissolution tank containing 99 parts by mass of methylene chloride, the mixture was sufficiently stirred. The resulting solution was dispersed with an attritor so that the secondary particles had a predetermined particle size, and then filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution 1 did.

(Preparation of main dope)
A main dope having the following composition was prepared. First, after adding methylene chloride and ethanol to the pressure dissolution tank, the cellulose acetate, sugar ester 1, polycondensation ester, retardation increasing agent 1 and fine particle additive solution 1 having an acetyl group substitution degree of 2.40 are added with stirring. did. This was heated and dissolved completely with stirring. The obtained solution was used as Azumi filter paper No. manufactured by Azumi Filter Paper Co., Ltd. The main dope was prepared by filtration using 244.

<Composition of main dope>
Methylene chloride 365 parts by weight Ethanol 50 parts by weight Cellulose acetate (acetyl substitution degree 2.40) 84 parts by weight Sugar ester 1: Saccharose benzoate having an average substitution degree of 5.5
10 parts by mass Polycondensed ester: (phthalic acid / adipic acid / 1,2-propanediol = 25/75/100 molar ratio of condensate having both ends sealed with benzoic acid ester groups, molecular weight 440) 3 mass Part Retardation raising agent (compound A below) 3 parts by mass Particulate additive solution 1 1 part by mass

(Formation of retardation film)
The obtained main dope was cast (cast) on a stainless belt support, and the solvent was evaporated until the amount of residual solvent in the formed web reached 75% by mass. The obtained web was peeled from the stainless steel belt support with a peeling tension of 130 N / m. The web obtained by peeling was stretched 30% in the width direction using a tenter while being heated at 150 ° C. The residual solvent at the start of stretching was 15% by mass.

  Next, the drying zone was conveyed while being held by a large number of rolls to finish drying. The drying temperature was 130 ° C. and the transport tension was 100 N / m. As described above, a retardation film 1 having a dry film thickness of 35 μm was obtained.

(4) Production of Polarizing Plate One side of the produced retardation film 1 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 prepared above is applied to the surface of the retardation film 1 subjected to corona discharge treatment with a bar coater so that the film thickness after curing is about 3 μm. A line curable adhesive layer was formed. The produced polarizer having a thickness of 10 μm was bonded to the obtained active energy ray-curable adhesive layer.

  Next, the prepared polarizing plate protective film 1 was prepared as a polarizing plate protective film, and one surface side of the polarizing plate protective film 1 was subjected to corona discharge treatment in the same manner as described above. Next, the prepared active energy ray-curable adhesive liquid is applied to the surface side of the polarizing plate protective film 1 subjected to corona discharge treatment with a bar coater so that the film thickness after curing is about 3 μm. An active energy ray-curable adhesive layer was formed.

A polarizer bonded to one side of the retardation film 1 is bonded onto the active energy ray-curable adhesive layer of the polarizing plate protective film, and as shown in FIG. 1, the polarizing plate protective film 1 (10) Polarizing plate 1 in which / active energy ray-curable adhesive layer (103A ₁ ) / polarizer (104) / active energy ray-curable adhesive layer (103A ₂ ) / retardation film 1 (105) is laminated in this order Obtained. In addition, the number in a parenthesis has shown the code number of each applicable structural member in FIG.

  In the polarizing plate 1, the slow axis of the retardation film 1 (105) and the absorption axis of the polarizer (104) were arranged to be orthogonal to each other.

Next, the polarizing plate 1 is configured so that the accumulated light amount is 750 mJ / cm ² from the phase difference film 1 side using an ultraviolet irradiation device with a belt conveyor (the lamp uses a D bulb manufactured by Fusion UV Systems). Each active energy ray-curable adhesive layer was cured by irradiating with ultraviolet rays.

[Production of Polarizing Plates 2-31, 37, 38]
In the production of the polarizing plate 1, polarizing plates 2 to 31, 37 and 38 were produced in the same manner except that the polarizing plate protective films 2 to 31, 37 and 38 were used in place of the polarizing plate protective film 1, respectively. .

[Production of Polarizing Plates 32-35]
In the production of the polarizing plate 4, polarizing plates 32 to 35 were produced in the same manner except that the polarizers having thicknesses of 3 μm, 5 μm, 15 μm, and 20 μm were used instead of the 10 μm thick polarizer, respectively. did.

[Production of Polarizing Plate 36]
In the production of the polarizing plate 4, the polarizing plate protective film 4 and the polarizer, and the retardation film 1 and the polarizer are bonded by the water paste method described below instead of the bonding method using the active energy ray-curable adhesive. A polarizing plate 36 was produced in the same manner except that.

  As the polarizer, a 10 μm-thick polarizer similar to that used for the production of the polarizing plate 4 was used.

  According to the following steps 1 to 5, the retardation film 1 was bonded to one surface side of the polarizer, and the polarizing plate protective film 4 was bonded to the back surface side of the polarizer, to prepare a polarizing plate 36.

  Step 1: The surfaces of the retardation film 1 and the polarizing plate protective film 4 were 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.

  Step 2: A 10 μm-thick polarizer was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass for 1 to 2 seconds.

  Step 3: Excess polyvinyl alcohol adhesive adhered to the polarizer in Step 2 was lightly wiped off and placed on the retardation film 1 treated in Step 1. Subsequently, the polarizing plate protective film 4 was arrange | positioned in the surface on the opposite side to the surface which has arrange | positioned the phase difference film 1 of a polarizer.

Process 4: The polarizing plate protective film 4 is arrange | positioned on the polarizer surface on the opposite side to the surface which has arrange | positioned the phase difference film 1 of the laminated body produced at the process 3, The pressure of 20-30 N / cm < ² >, conveyance speed is Bonding was performed at about 2 m / min.

  Process 5: The laminated body which bonded the polarizer produced in the process 4, the phase difference film 1, and the polarizing plate protective film 4 in the 80 degreeC dryer was dried for 2 minutes, and the polarizing plate 36 was produced.

<Production of liquid crystal display device>
[Production of liquid crystal display device 1]
As a liquid crystal cell, a VA liquid crystal cell (107) having two glass substrates having a thickness of 0.5 mm and a liquid crystal layer disposed therebetween was prepared. Then, the prepared polarizing plates 1 (101A and 1010B) are attached to both surfaces of the prepared liquid crystal cell (107) via a 25 μm-thick double-sided tape (substrate-less tape MO-3005C) manufactured by Lintec. The liquid crystal display panel (106) was obtained by pasting together so as to have the structure shown in FIG. As shown in FIG. 3, the lamination was performed such that the retardation films 1 (105A and 105B) of the polarizing plates 1 (101A and 1010B) were in contact with the glass substrate of the liquid crystal cell (107).

  In the liquid crystal display panel 1 (106), the polarizing plate protective film (102A) is the polarizing plate protective film T1 referred to in the present invention, and the polarizing plate protective film (102B) is the polarizing plate protective film T4 referred to in the present invention. is there. Similarly, the retardation film (105A) in contact with the liquid crystal cell (107) is the retardation film T2 referred to in the present invention, and the retardation film (105B) is the retardation film T3 referred to in the present invention.

  Then, after removing the liquid crystal display panel (a laminate of the viewing side polarizing plate / liquid crystal cell / backlight side polarizing plate) from the SONY 40-inch display BRAVIA KLV-40J3000 (VA method), the liquid crystal display panel 1 produced as described above (106) was arranged, and the liquid crystal display device 1 was produced. In addition, it was made for the absorption axis of the polarizing plate of the attached liquid crystal display panel 1 (106) to be the same direction as the absorption axis of the polarizing plate previously stuck. In addition, the number in a parenthesis has shown the code number of the corresponding structural member in FIG.

[Production of liquid crystal display devices 2 to 38]
In the production of the liquid crystal display device 1, the liquid crystal display device 2 was similarly obtained except that the polarizing plates 1 (101 A and 1010 B) constituting the liquid crystal display panel 1 (106) were changed to the polarizing plates 2 to 38, respectively. -38 were made.

<< Evaluation of Polarizing Plate and Liquid Crystal Display >>
Polarizer stability was evaluated for each of the produced polarizing plates, and bent unevenness resistance was evaluated for the liquid crystal display device.

[Evaluation of Polarizer Stability: Measurement of Degree of Polarization Degree]
(Forced degradation 1)
Each polarizing plate immediately after the production was left in an environment of 23 ° C. and 55% RH for 24 hours, and then the parallel transmittance and orthogonal transmittance of light having a wavelength of 550 nm were measured using an automatic polarizing film measuring device (VAP-7070, Japan). (Manufactured by Spectroscopic Co., Ltd.). Subsequently, based on each measured value obtained, the degree of polarization 1 (%) was calculated based on the following formula (1).

  Next, each polarizing plate was allowed to stand for 120 hours in an environment of 80 ° C. and 90% RH, and then left for 24 hours in an environment of 23 ° C. and 55% RH, and the degree of polarization 2 (%) was calculated in the same manner. .

  Next, according to the following formula (2), a decrease degree 1 (%) of the degree of polarization was obtained and used as a measure of polarizer stability (forced deterioration 1).

Formula (2)
Degree of decrease in polarization degree 1 (%) = polarization degree 1 (%) − polarization degree 2 (%)
(Forced degradation 2)
Each polarizing plate was allowed to stand for 24 hours in an environment of 80 ° C. and 90% RH, and then allowed to stand for 24 hours in an environment of 80 ° C. and 10% RH. After that, the degree of polarization 3 (%) was calculated by the same method as described above.

  Next, from the measured degree of polarization 1 (%) and the measured degree of polarization 3 (%), the degree of polarization decrease 2 (%) was obtained according to the following formula (3), and this was determined as the stability of the polarizer. A scale (forced deterioration 2) was used.

Formula (3)
Degree of decrease in polarization degree 2 (%) = polarization degree 1 (%) − polarization degree 3 (%)
[Evaluation of resistance to bend unevenness]
About each produced said liquid crystal display device, the vent nonuniformity tolerance was evaluated in accordance with the following method.

  Each liquid crystal display device was left in an environment of 40 ° C. and 95% RH for 24 hours. Next, with the liquid crystal display device displaying black in a 40 ° C. dry environment, the difference between the luminance near the four vertices of the display screen and the luminance near the center of the display screen (image unevenness between the central portion and the peripheral portion) Was visually observed and evaluated for bend unevenness resistance based on the following criteria.

○: Bend unevenness is not recognized at all Δ: Bend unevenness is slightly recognized, but is acceptable in practical use ×: Clear bend unevenness is recognized Table 2 shows the results obtained as described above.

  As is apparent from the results shown in Table 2, a film prepared from a copolymer (A) composed of the aromatic vinyl monomer defined in the present invention and an unsaturated carboxylic acid monomer or unsaturated dicarboxylic anhydride monomer. The polarizing plate protective film having a thickness in the range of 20 to 60 μm and the polarizing plate of the present invention using the polarizer having a thickness in the range of 5.0 to 15 μm are high in the forced deterioration test. It can be seen that it has stability and has an excellent resistance to vent unevenness when it is provided in a liquid crystal display device.

  That is, in a polarizing plate using a polarizing plate protective film prepared from an aromatic vinyl monomer defined in the present invention and a copolymer (A) composed of an unsaturated carboxylic acid monomer or an unsaturated dicarboxylic acid anhydride monomer, It can be seen that when the thickness of the polarizer is in the range of 5.0 to 15 μm, both the polarizer stability and the vent unevenness resistance under a high temperature and high humidity environment are excellent. In the polarizing plate 32 in which the film thickness of the polarizer is not more than the range specified above, the polarization degree fluctuation range in a high temperature and high humidity environment is more than 1.0, and the film thickness of the polarizer is as described above. It can be seen that the occurrence of uneven venting is significant in the liquid crystal display device using the polarizing plate 35 that is not less than the specified range.

  In the polarizing plate or the liquid crystal display device of the present invention, in the sample in which the thickness of the polarizing plate protective film is changed from 18 to 65 μm, the thickness is 25 μm (polarizing plate 14), 40 μm (polarizing plate 4), 60 μm ( The polarizing plate 15) exhibits an excellent effect, but the polarizing plate 37 using a polarizing plate protective film having a film thickness of 18 μm, or the polarizing plate 38 using a polarizing plate protective film having a film thickness of 65 μm. Then, it can be seen that the stability of the polarizer and the resistance to bent unevenness are slightly deteriorated.

  Further, in the polarizing plate or the liquid crystal display device of the present invention, when each effect of the polarizing plates 1, 4, 7, 11 to 13 is verified, styrene is used as the aromatic vinyl monomer (the polarizing plate 4 and the polarizing plate 9). Comparison), using methacrylic acid as an unsaturated carboxylic acid monomer (comparison between polarizing plate 4 and polarizing plates 1 and 14), using maleic anhydride as an unsaturated dicarboxylic acid anhydride monomer (polarizing plate 7, It can be seen that the comparison of the polarizing plates 12 and 13 exhibits a more excellent effect.

  Further, a compound (compound) selected from acids, alcohols, metal salts, nonionic surfactants and nonreactive quaternary ammonium salt type surfactants having a linear or branched alkyl group having 8 to 22 carbon atoms It can be seen that by adding (1)), the isolation performance is improved and the foreign matter failure resistance is improved.

  Further, by adding at least one selected from core / shell type acrylic fine particles, styrene-butadiene copolymer, styrene-conjugated diene copolymer and butyl acrylate compound (compound (2)), heat resistance is improved. It can also be seen that the foreign matter failure resistance is improved.

  Moreover, when the polarizing plate 4 and the polarizing plate 31 are compared, it turns out that the foreign material failure tolerance and polarizer stability are more excellent by applying the solution casting method as a film-forming method of a polarizing plate protective film.

  In addition, the adhesive method (polarizing plate 4) with the active energy ray curable adhesive is superior to the water paste method (polarizing plate 36) as the bonding method, so that the polarizer stability and vent unevenness resistance are more excellent. I understand.

  Based on the above results, the present invention was constructed in which the thickness of the polarizer was in the range of 5.0 to 15 μm using the polarizing plate protective film having the thickness of 20 to 60 μm in the monomer configuration according to the present invention. The polarizing plate can provide a liquid crystal display device that is excellent in polarizer stability, includes the same, and suppresses occurrence of display unevenness (bend unevenness).

Example 2
<Production of polarizing plate>
[Production of Polarizing Plate 51]
In the production of the polarizing plate 3 described in Example 1, a polarizing plate 51 was produced in the same manner except that the polarizing plate protective film 3 was used instead of the retardation film 1 as the retardation film (105).

[Preparation of Polarizing Plate 52]
In the production of the polarizing plate 3 described in Example 1, a polarizing plate 52 was produced in the same manner except that the polarizing plate protective film 4 was used instead of the retardation film 1 as the retardation film (105).

[Preparation of Polarizing Plate 53]
In the production of the polarizing plate 4 described in Example 1, a polarizing plate 53 was produced in the same manner except that the polarizing plate protective film 4 was used instead of the retardation film 1 as the retardation film (105).

[Production of Polarizing Plate 54]
In the production of the polarizing plate 3 described in Example 1, a polarizing plate 54 was similarly obtained except that a cycloolefin polymer film (abbreviation: COP) was used instead of the retardation film 1 as the retardation film (105). Was made.

  In addition, as a cycloolefin polymer film, ZEONEA ZF14 film (film thickness: 100 μm) manufactured by Nippon Zeon Co., Ltd. was used.

[Preparation of Polarizing Plate 55]
In the production of the polarizing plate 4 described in Example 1, a polarizing plate was obtained in the same manner except that the above-mentioned cycloolefin polymer film (abbreviation: COP) was used instead of the retardation film 1 as the retardation film (105). 55 was produced.

<Production of liquid crystal display device>
Liquid crystal display devices 51 to 55 were produced in the same manner as in Example 1 using the produced polarizing plates 51 to 55.

<< Evaluation of Polarizing Plate and Liquid Crystal Display >>
About each produced polarizing plate and liquid crystal display device, and the polarizing plate 4 and liquid crystal display device 4 produced in the Example, the polarizer stability (forced deterioration 1 and forced deterioration 2) was carried out in the same manner as in the method described in Example 1. Table 3 shows the results obtained and the evaluation of the bent unevenness resistance of the liquid crystal display device.

  As is apparent from the results shown in Table 3, even when the polarizing plate protective film defined in the present invention is applied as a retardation film, the polarizer stability (forced deterioration 1 and forced deterioration 2) and the liquid crystal display device It is understood that there is no significant improvement in the resistance to bent unevenness of the polarizing plate, and that the polarizing plate protective film having the configuration defined in the present invention can exhibit a desired effect when used as a polarizing plate protective film. .

  The polarizing plate of the present invention has high polarizer stability when stored in a high-temperature and high-humidity environment, and can be applied to various drive-type liquid crystal display devices. Even so, it is possible to obtain a liquid crystal display device having excellent visibility such as unevenness of the liquid crystal display device.

DESCRIPTION OF SYMBOLS 1 Melting pot 3, 6, 12, 15 Filter 4, 13 Stock tank 5, 14 Liquid feed pump 8, 16 Pipe | tube 10 Ultraviolet absorber charging pot 17 Three-way valve 20 Merge pipe 21 Mixer 30 Pressure die 31 Metal support 32 Web 33 Peeling position 34 Tenter device 35 Roller dryer 41 Feeding tank 42 Stock tank 43 Pump 44 Filter 101 Polarizing plate 102 Polarizing plate protective film 102A Polarizing plate protective film T1
102B Polarizing plate protective film T4
103A ₁ , 103A ₂ , 103B ₁ , 103B ₂ Active energy ray curable adhesive layer 104, 104A, 104B Polarizer 105 Phase difference film 105A Phase difference film T2
105B retardation film T3
106 polarizing plate panel 107 liquid crystal cell 108 liquid crystal layer 109A, 109B glass plate

Claims (10)

A polarizer composed of a polyvinyl alcohol-based resin, a polarizing plate configured to be sandwiched between a polarizing plate protective film and a retardation film,
The polarizing plate protective film contains a copolymer (A) of an aromatic vinyl monomer and an unsaturated carboxylic acid monomer or an unsaturated dicarboxylic acid anhydride monomer, and the film thickness is in the range of 20 to 60 μm. ,
The polarizing plate, wherein the polarizer has a thickness in the range of 5.0 to 15 μm.   The polarizing plate protective film further has an acid, alcohol, metal salt, nonionic surfactant and nonreactive quaternary ammonium salt type surface activity having a linear or branched alkyl group having 8 to 22 carbon atoms. The at least 1 sort (s) of compound chosen from an agent is contained within the range of 0.1-1.0 mass% with respect to the total mass of the said copolymer (A), It is characterized by the above-mentioned. Polarizer.   The polarizing plate according to claim 1, wherein the aromatic vinyl monomer contained in the polarizing plate protective film is styrene.   The said unsaturated carboxylic acid monomer which the said polarizing plate protective film contains is methacrylic acid, The polarizing plate as described in any one of Claim 1- Claim 3 characterized by the above-mentioned.   The polarizing plate according to any one of claims 1 to 3, wherein the unsaturated dicarboxylic acid anhydride monomer contained in the polarizing plate protective film is maleic anhydride.   The polarizing plate protective film further comprises at least one selected from core / shell type acrylic fine particles, styrene-butadiene copolymer, styrene-conjugated diene copolymer, and butyl acrylate compound. The polarizing plate according to any one of claims 1 to 5, wherein the polarizing plate is contained in a range of 0.5 to 5.0 mass% with respect to the total mass.   The polarizing plate according to any one of claims 1 to 6, wherein at least the polarizing plate protective film and the polarizer are bonded with an active energy ray-curable adhesive. The degree of decrease in the degree of polarization (%) represented by the following formula (1) of the sample subjected to the forced degradation treatment for 120 hours in an environment of 80 ° C. and 90% RH with respect to the untreated sample is 1.0% or less. The polarizing plate according to any one of claims 1 to 7, wherein the polarizing plate is adjusted to be.

  The polarizing plate according to any one of claims 1 to 8 is provided on at least one surface side of a liquid crystal cell having a glass plate having a thickness in the range of 0.3 to 0.7 mm on the surface. A liquid crystal display device comprising a retardation film surface constituting the polarizing plate and the glass plate bonded together.   It is the structure which has arrange | positioned the polarizing plate as described in any one of Claim 1- Claim 8 on both surfaces of the said liquid crystal cell, and bonded the retardation film surface and the said glass plate which comprise the said polarizing plate. The liquid crystal display device according to claim 9.

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