JP2014228760A - Polarizing plate-protecting film, polarizing plate, and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing plate-protecting film excellent in resistance against moisture permeation, heat resistance, and resistance against fragility; a polarizing plate which is provided with the polarizing plate-protecting film, is excellent in adhesion with a polarizer, enhances durability (water resistance) of the polarizer, and is excellent in flatness (warp resistance of panel); and a liquid crystal display device provided with the same.SOLUTION: A polarizing plate-protecting film which is arranged on a surface in an opposite side to a liquid crystal cell of a polarizing plate provided on the liquid crystal cell contains a (meth)acrylic polymer (A) and a cellulose ester resin (B). The (meth)acrylic polymer (A) includes at least (meth)acrylic acid alkyl ester unit represented by general formula (1) as a constitutional unit.

Description

  The present invention relates to a polarizing plate protective film, a polarizing plate using the polarizing plate, and a liquid crystal display device provided with the polarizing plate, and more specifically, a surface of the polarizing plate provided on the liquid crystal cell opposite to the liquid crystal cell. The polarizing plate protective film arrange | positioned in this invention, the polarizing plate using the same, and the liquid crystal display device with which the said polarizing plate is comprised.

  The liquid crystal display device is composed of a liquid crystal cell in which a transparent electrode, a liquid crystal layer, a color filter, etc. are sandwiched between glass plates, and two polarizing plates provided on both sides thereof. The structure is sandwiched between two optical films, for example, a polarizing plate protective film located outside and a retardation film disposed on the liquid crystal cell side.

  As this polarizing plate protective film, cellulose ester has been mainly used. This cellulose ester film has a high water vapor transmission rate, and can be immersed in an alkaline aqueous solution to saponify and hydrophilize the surface, thereby realizing excellent adhesion with a polarizer.

  However, since the cellulose ester film has high moisture permeability, it becomes easy to cause dimensional changes due to moisture absorption or dehydration of the film due to changes in temperature and humidity due to thinning of the polarizer and simplification of packaging during distribution. In addition, the liquid crystal display device has a problem of unevenness and the degree of polarization deteriorates due to moisture permeating into the inside.

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

  However, a polarizing plate using an acrylic polymer film mainly composed of polymethyl methacrylate as a polarizing plate protective film has a poor film quality and water resistance is still insufficient.

  Furthermore, the acrylic polymer film usually has a higher adhesiveness than the conventional polyvinyl alcohol-based adhesive because the adhesiveness is poor in the polyvinyl alcohol-based aqueous solution used in the saponification process during the production of the polarizing plate. An active energy ray curable adhesive such as an ultraviolet curable adhesive is used.

  Furthermore, by using this active energy ray-curable adhesive, unevenness due to the dimensional change of the cellulose ester film is less likely to occur, but the acrylic film is more heat resistant than the cellulose ester film. With the recent demand for thinner panels, there has been a problem that deformation (wrinkles) occurs in the ultraviolet irradiation process during the production of the polarizing plate, especially when the acrylic film is made thinner.

  Moreover, although the film which blended (meth) acrylic polymer and cellulose ester resin is disclosed (for example, refer patent document 2), the acrylic polymer described in patent document 2 is mainly. It is an acrylic polymer with a long chain and a linear alkyl group, and even optical films to which these acrylic polymers are applied have problems of insufficient adhesion to the polarizer and poor heat resistance and brittleness. It was.

JP 2011-123169 A JP 2012-012594 A

  The present invention has been made in view of the above problems, and a solution to the problem is a polarizing plate protective film having low moisture permeability, excellent heat resistance and brittleness resistance, and the polarizing plate protective film. Provided are a polarizing plate excellent in adhesion to a polarizer, improved in durability of the polarizer (polarizer deterioration is less likely to occur), and excellent in flatness (panel warpage resistance), and a liquid crystal display device including the polarizing plate. That is.

  As a result of intensive studies in view of the above problems, the present inventor has a (meth) acrylic polymer (A) and a cellulose ester resin (B), and the (meth) acrylic polymer (A) is specified. And having a (meth) acrylic acid alkyl ester unit having a branched alkyl group as a substituent as a structural unit, and forming a polarizing plate, on the surface side opposite to the surface in contact with the liquid crystal cell A polarizing plate protective film characterized by being an optical film to be disposed, comprising a polarizing plate protective film having low moisture permeability, excellent heat resistance and brittleness resistance, and the polarizing plate protective film, A polarizing plate excellent in adhesiveness, improving the durability of the polarizer (polarizer deterioration is unlikely to occur) and having excellent flatness (panel warpage resistance) and a liquid crystal display device including the polarizing plate can be realized. Heading It has led to the present invention.

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

1. A polarizing plate protective film disposed on a surface opposite to the liquid crystal cell of the polarizing plate provided on the liquid crystal cell,
Containing (meth) acrylic polymer (A) and cellulose ester resin (B),
The polarizing plate protective film, wherein the (meth) acrylic polymer (A) has at least a (meth) acrylic acid alkyl ester unit represented by the following general formula (1) as a constituent unit.

〔式中、Ｒ^１は炭素数３〜１８の分枝アルキル基であり、Ｒ^２は水素原子又はメチル基である。〕
２．前記セルロースエステル樹脂（Ｂ）を構成するセルロースエステル単位が、置換基として炭素数が３〜１３の範囲内にあるアシル基を有し、かつ置換基の総炭素数が６〜１５の範囲内であることを特徴とする第１項に記載の偏光板保護フィルム。

[Wherein, R ¹ represents a branched alkyl group having 3 to 18 carbon atoms, and R ² represents a hydrogen atom or a methyl group. ]
2. The cellulose ester unit constituting the cellulose ester resin (B) has an acyl group having 3 to 13 carbon atoms as a substituent, and the total number of carbon atoms in the substituent is 6 to 15 The polarizing plate protective film according to Item 1, which is characterized in that it exists.

3. R ¹ in the general formula (1) is a branched alkyl group having a tertiary carbon atom, The polarizing plate protective film according to item 1 or 2,

  4). The polarizing plate protection according to any one of Items 1 to 3, wherein the (meth) acrylic polymer (A) has a weight average molecular weight in the range of 200,000 to 1,500,000. the film.

  5. Any one of Items 2 to 4 wherein the substituent of the cellulose ester unit constituting the cellulose ester resin (B) is an acyl group having 7 to 13 carbon atoms. The polarizing plate protective film according to one item.

  6). The ratio of said (meth) acrylic polymer (A) with respect to the film total mass exists in the range of 70-95 mass%, Polarized light as described in any one of Claim 1-5 characterized by the above-mentioned. Board protection film.

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

  8). 8. The polarizing plate according to item 7, wherein the polarizer has a thickness in the range of 2.0 to 15.0 μm.

9. A liquid crystal display device in which at least the first polarizing plate A, the liquid crystal cell, and the second polarizing plate B are arranged in this order from the display surface side,
From the display surface side, the first polarizing plate A is composed of a polarizing plate protective film T1, a polarizer and a retardation film T2, and the second polarizing plate B is a retardation film T3, a polarizer and a polarizing plate protective film. The polarizing plate protective film T1 and the polarizing plate protective film T1 and the polarizing plate protective film T4 are both polarizing plate protective films according to any one of items 1 to 6. Display device.

  By the above means of the present invention, the polarizing plate protective film having low moisture permeability, excellent heat resistance and brittleness resistance, and the polarizing plate protective film, having excellent adhesion to the polarizer, and durability of the polarizer It is possible to provide a polarizing plate with improved (polarizer deterioration hardly occurs) and excellent flatness (panel warpage resistance) and a liquid crystal display device including the polarizing plate.

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

  Films composed of conventional cellulose ester resins tend to cause dimensional changes due to moisture absorption or dehydration due to temperature and humidity changes due to their high moisture permeability, resulting in unevenness of liquid crystal display devices. In addition, there is a problem that the degree of polarization deteriorates due to moisture permeating into the interior.

  However, a film containing a (meth) acrylic polymer (A) having a (meth) acrylic acid alkyl ester unit having a branched alkyl group as a structural unit as a substituent according to the present invention and a cellulose ester resin (B) is used. Thus, it was possible to suppress unevenness of the liquid crystal display device in a high temperature and high humidity environment and to suppress deterioration of the polarization degree.

  Furthermore, unevenness and polarizer deterioration could be further suppressed by using an active energy ray-curable adhesive instead of a water-soluble polyvinyl alcohol adhesive.

  The polarizing plate protective film of the present invention is mainly composed of an acrylic polymer in order to reduce moisture permeability, but has a (meth) acrylic acid alkyl ester unit having a branched alkyl group as a substituent as a structural unit. Compared with typical (meth) acrylic film, heat resistance is higher (molecular motion is difficult to occur at high temperatures), and deformation (wrinkles) and yellowing occur in the ultraviolet irradiation process when using an active energy ray-curable adhesive. And so on.

  In addition, water resistance (low moisture permeability) could be further improved by having a long-chain substituent as compared with a general (meth) acrylic film.

  Thereby, even if the polarizer is made into a thin film, it is estimated that the deterioration and shrinkage of the polarizer can be suppressed, and the flatness (warpage) of the liquid crystal display device can be improved.

  Further, it is presumed that heat resistance, brittleness, and adhesiveness with a polarizer are also improved by blending the cellulose ester resin.

The schematic diagram which shows an example of the solution casting film forming process flow applicable to manufacture of the polarizing plate protective film of this invention Sectional drawing which shows an example of a structure of the polarizing plate of this invention Sectional drawing which shows an example of a structure of the liquid crystal display device of this invention

  The polarizing plate protective film of this invention is a polarizing plate protective film arrange | positioned on the surface on the opposite side to the said liquid crystal cell of the polarizing plate provided on a liquid crystal cell, Comprising: (meth) acrylic polymer (A) and cellulose An (meth) acrylic acid alkyl ester unit which contains an ester resin (B), the (meth) acrylic polymer (A) is represented by at least the general formula (1) and has a branched alkyl group as a substituent. A polarizing plate protective film having low moisture permeability, heat resistance, and brittleness resistance can be realized. This feature is a technical feature common to the inventions according to claims 1 to 9.

  As an embodiment of the present invention, the cellulose ester unit constituting the cellulose ester resin (B) has a carbon number in the range of 3 to 13 as a substituent from the viewpoint that the effect intended by the present invention can be further expressed. It has a certain acyl group, and the total carbon number of the substituent is in the range of 6 to 15, the affinity for water of (meth) acrylic polymer (A) and cellulose ester resin (B) is comparable. As a result, it is preferable because the transparency of the film can be further improved.

Moreover, it is preferable that R ¹ in the general formula (1) is a branched alkyl group having a tertiary carbon atom from the viewpoint that molecular motion hardly occurs at a high temperature and the heat resistance of the film can be further improved.

  Moreover, it is preferable that the weight average molecular weight of the said (meth) acrylic polymer (A) exists in the range of 200,000-1,500,000 from the point which can improve film strength (brittle resistance) further.

  Moreover, it is more hydrophobic that the substituent which the cellulose-ester unit which comprises the said cellulose-ester resin (B) has is an acyl group which has a carbon number in the range of 7-13. As a result, it is preferable from the viewpoint of obtaining more excellent low moisture permeability.

  Further, the ratio of the (meth) acrylic polymer (A) to the total film mass is preferably in the range of 70 to 95% by mass from the viewpoint of obtaining more excellent low moisture permeability.

  The polarizing plate of the present invention comprises the polarizing plate protective film of the present invention, wherein the polarizing plate protective film and the polarizer are bonded with an active energy ray-curable adhesive, and are bonded to the polarizer. It is possible to obtain a polarizing plate that is excellent in the durability, the durability of the polarizer (polarizer deterioration is unlikely to occur) and the flatness (the warpage resistance of the liquid crystal panel).

  In addition, the thickness of the polarizer is preferably in the range of 2.0 to 15.0 μm from the viewpoint of suppressing the warpage of the liquid crystal panel.

  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 display surface side, and the first polarized light from the side where the image can be visually recognized. The plate A is composed of a polarizing plate protective film T1, a polarizer and a retardation film T2, and the second polarizing plate B is composed of a retardation film T3, a polarizer and a polarizing plate protective film T4, and The polarizing plate protective film T1 and the light plate protective film T4 are both polarizing plate protective films according to any one of items 1 to 7.

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

<Polarizing plate protective film>
The polarizing plate protective film of the present invention contains a (meth) acrylic polymer (A) and a cellulose ester resin (B), and the (meth) acrylic polymer (A) is at least represented by the general formula (1). And a (meth) acrylic acid alkyl ester unit having a branched alkyl group as a substituent as a structural unit, and when the polarizing plate protective film of the present invention constitutes a polarizing plate, It is an optical film arranged on the surface side opposite to the surface in contact with it.

  Hereinafter, the detail of each component of the polarizing plate protective film of this invention is demonstrated.

[(Meth) acrylic polymer (A)]
The (meth) acrylic polymer (A) according to the present invention has at least a (meth) acrylic acid alkyl ester unit represented by the following general formula (1) as a structural unit as a (meth) acrylic acid alkyl ester unit. It is characterized by that.

In the general formula (1), R ¹ is a branched alkyl group having 3 to 18 carbon atoms, and R ² is a hydrogen atom or a methyl group.

R ¹ is not limited as long as it is a branched alkyl group having 3 to 18 carbon atoms. Examples of R ¹ include a branched propyl group having 3 carbon atoms (for example, isopropyl group), a branched butyl group having 4 carbon atoms (for example, isobutyl group, s-butyl group, t-butyl group), and 5 branched carbon atoms. Pentyl group (for example, isopentyl group, neopentyl group, s-pentyl group, t-pentyl group), branched hexyl group having 6 carbon atoms (for example, isohexyl group, neohexyl group, s-hexyl group, t-hexyl group), carbon A branched heptyl group having a number 7 (for example, isoheptyl group, neoheptyl group, s-heptyl group, t-heptyl group), a branched octyl group having 8 carbon atoms (for example, an isooctyl group, neooctyl group, s-octyl group, t-octyl group) Group), a branched nonyl group having 9 carbon atoms (for example, isononyl group, neononyl group, s-nonyl group, t-nonyl group), branched decanyl group having 10 carbon atoms. (For example, isodecanyl group, neodecanyl group, s-decanyl group, t-decanyl group), branched undecanyl group having 11 carbon atoms (for example, isoundecanyl group, neoundecanyl group, s-undecanyl group, t-undecanyl group), carbon number 12 Branched dodecanyl group (for example, isododecanyl group, neododecanyl group, s-dodecanyl group, t-dodecanyl group) and the like.

In the present invention, from the viewpoint of further improving the heat resistance and brittleness resistance of the polarizing plate protective film, R ¹ in the general formula (1) is a branched alkyl group having a tertiary carbon atom. For example, t-butyl group, neopentyl group, t-pentyl group, neohexyl group, t-hexyl group, neoheptyl group, t-heptyl group, neooctyl group, t-octyl group, neononyl group, t-nonyl group, A neodecanyl group, a t-decanyl group, a neoundecanyl group, a t-undecanyl group, a neododecanyl group, and a t-dodecanyl group can be exemplified. Furthermore, among the branched alkyl groups having the tertiary carbon atom, a t-butyl group is particularly preferable from the viewpoint of heat resistance and compatibility with the cellulose ester resin (B).

Since the alkyl group of R ¹ in the general formula (1) imparts more hydrophobicity than methyl, it is preferable to increase the number of carbon atoms. However, when the alkyl group is linear, the glass transition temperature of the polymer derived from the unit is lowered, and the strength as an optical film may not be maintained.

  When the alkyl group has a branched structure as defined in the present invention, the glass transition temperature of the polymer similarly derived can be imparted with the hydrophobicity of the resin without significantly decreasing.

  In this invention, the ratio of the (meth) acrylic-acid alkylester unit represented by General formula (1) to all the structural units of (meth) acrylic polymer (A) is represented by the said General formula (1). Although it varies depending on the specific molecular structure of the (meth) acrylic acid alkyl ester unit, it is approximately 5% by mass or more, and preferably 10% by mass or more from the viewpoint of further manifesting the effects of the present invention. More preferably, it is 15% by mass or more. As long as the objective effect of the present invention is obtained, the upper limit of the (meth) acrylic acid alkyl ester unit represented by the general formula (1) according to the present invention is not particularly limited, but is preferably 90% by mass or less, more preferably Is 80% by mass or less, more preferably 50% by mass or less.

The ratio of the (meth) acrylic acid alkyl ester unit represented by the general formula (1) to all the structural units of the (meth) acrylic polymer (A) according to the present invention is, for example, ¹ H nuclear magnetic resonance ( ¹ H -NMR) or infrared spectroscopic analysis (IR). In addition, the ratio of each monomer used for the polymerization of the (meth) acrylic polymer (A) and, if necessary, the reaction mechanism from the monomer to the (meth) acrylic polymer (A). It can also be obtained by reference.

  The (meth) acrylic polymer (A) according to the present invention may have a (meth) acrylic acid alkyl ester unit having two or more kinds of branched alkyl groups as a constituent unit.

  In the (meth) acrylic polymer (A) according to the present invention, a copolymerizable other monomer is used together with the (meth) acrylic acid alkyl ester unit represented by the general formula (1) described above. Can do.

  As the other copolymerizable monomer together with the (meth) acrylic acid alkyl ester unit represented by the general formula (1) according to the present invention, for example, a linear alkyl group having 2 to 18 carbon atoms. Alkyl methacrylate, linear alkyl acrylate having 1 to 18 carbon atoms, vinyl monomer having amide group such as acryloylmorpholine and N, N-dimethylacrylamide, isobornyl methacrylate, dicyclopentanyl methacrylate, methacrylic acid Methacrylic acid ester or acrylic acid ester having an alicyclic hydrocarbon group having 5 to 22 carbon atoms in the ester moiety such as dimethyladamantyl, α, β-unsaturated acid such as acrylic acid and methacrylic acid, maleic acid, fumaric acid , Unsaturated group-containing divalent carboxylic acids such as itaconic acid, styrene, α-methylstyrene, etc. Aromatic vinyl compounds, acrylonitrile, alpha, such as methacrylonitrile, beta-unsaturated nitrile and the like, which may be used alone or in combination of two or more monomers.

  The (meth) acrylic polymer (A) according to the present invention may have a ring structure, specifically, a lactone ring structure, a glutaric anhydride structure, a glutarimide structure, an N-substituted maleimide structure. And a maleic anhydride structure and a pyran ring structure.

  In the (meth) acrylic polymer (A) according to the present invention, the other copolymerizable monomer is preferably methyl acrylate, methyl methacrylate, styrene, maleic anhydride, glutaric anhydride, or a lactone ring structure. Methyl methacrylate is particularly preferred.

  Commercially available monomers can be used as they are.

  The (meth) acrylic polymer (A) used for the polarizing plate protective film of the present invention preferably has a weight average molecular weight (Mw) of 20 from the viewpoint of mechanical strength as a film and fluidity when producing the film. It is in the range of 10,000 to 1,500,000, more preferably in the range of 200,000 to 500,000.

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

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

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

[Cellulose ester resin (B)]
The cellulose ester resin (B) according to the present invention has a cellulose triacetate, a cellulose diacetate, a cellulose acetate pro, particularly from the viewpoint of improvement in brittleness and transparency when it is compatible with the (meth) acrylic polymer (A). It is preferably at least one selected from pionate, cellulose acetate butyrate, cellulose acetate benzoate, cellulose acetate propionate benzoate, cellulose propionate, cellulose butyrate, cellulose acetate biphenylate, and cellulose acetate propionate biphenylate. .

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

  Further, the cellulose ester unit constituting the cellulose ester resin (B) has an acyl group having 3 to 13 carbon atoms as a substituent, and the total carbon number of the substituent is 6 to 15 It is preferable to have an acyl group having a carbon number in the range of 7 to 13 as a substituent.

  Moreover, there is no restriction | limiting in particular as an average substitution degree of the said acyl group in a cellulose-ester unit, However, It is preferable to exist in the range of 2.0-3.0.

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

  In addition, the substitution degree of an acyl group etc. are calculated | required by the method prescribed | regulated to ASTM-D817-96.

  The weight average molecular weight (Mw) of the cellulose ester resin (B) according to the present invention is preferably 75000 or more, particularly from the viewpoint of compatibility with the (meth) acrylic polymer (A) and improvement in brittleness. More preferably, it is in the range of 100,000 to 1,000,000, and particularly preferably in the range of 100,000 to 500,000.

  When the weight average molecular weight (Mw) of the cellulose ester resin (B) is 75000 or more, an effect of improving heat resistance and brittleness can be obtained. Moreover, if it is 1000000 or less, the viscosity of dope etc. to prepare will not become high and film forming aptitude can be provided.

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

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

[Composition ratio of (meth) acrylic polymer (A) and cellulose ester resin (B)]
In the polarizing plate protective film of the present invention, the (meth) acrylic polymer (A) and the cellulose ester resin (B) are contained in a compatible state within a mass ratio of 95: 5 to 50:50. However, it is more preferably 95: 5 to 70:30.

  If the mass ratio of the (meth) acrylic polymer (A) to the cellulose ester resin (B) is lower than 95: 5, the heat resistance and the adhesion to the polarizer are sufficient. When the ratio of the meth) acrylic polymer (A) is higher than that of the 50:50 mass ratio, sufficient moisture permeability can be obtained.

  In the polarizing plate protective film of the present invention, the (meth) acrylic polymer (A) and the cellulose ester resin (B) are preferably contained in a compatible state. The physical properties and quality required as a polarizing plate protective film are achieved by supplementing each other by making different resins compatible.

  Whether or not the (meth) acrylic polymer (A) and the cellulose ester resin (B) are in a compatible state can be determined by, for example, the glass transition temperature (Tg).

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

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

  The total mass of the (meth) acrylic polymer (A) and the cellulose ester resin (B) in the polarizing plate protective film of the present invention is preferably 70% by mass or more of the total mass of the polarizing plate protective film, more preferably 80. It is at least 95% by mass, particularly preferably at least 95% by mass.

[Various additives]
The polarizing plate protective film of the present invention includes a peeling aid for improving the peelability of the film, a plasticizer for imparting processability to the film, an antioxidant for preventing deterioration of the film, and an ultraviolet absorber for imparting an ultraviolet absorbing function. Various additives such as fine particles (matting agent) for imparting slipperiness to the film and acrylic fine particles for improving toughness can be contained as required.

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

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

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

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

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

(Polyhydric alcohol ester)
The polarizing plate protective film of the present invention can contain a polyhydric alcohol ester.

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

(Sugar ester)
In the present invention, sugar esters other than cellulose esters can be contained. As the sugar ester according to the present invention, it is preferable to use a sugar ester in which at least one of the pyranose structure or the furanose structure is 1 to 12 and all or part of the OH groups in the structure are esterified. .

  Examples of the sugar ester used in the present invention include glucose, galactose, mannose, fructose, xylose, arabinose, lactose, sucrose, cellobiose, cellotriose, maltotriose, raffinose, etc., particularly having both a furanose structure and a pyranose structure. Those are preferred. An example is sucrose.

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

  Specific examples of the sugar ester applicable to the present invention include compounds described in paragraphs (0060) to (0070) of JP2010-32655A.

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

  For example, “Irgafos XP40, Irgafos XP60” commercially available from BASF Japan Ltd. can be mentioned.

  The phenolic compound preferably has a 2,6-dialkylphenol structure. For example, “Irganox 1076”, “Irganox 1010” commercially available from BASF Japan Ltd., and ADEKA Corporation are commercially available. "Adeka Stub AO-50" 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. and “GSY-P101” commercially available from Sakai Chemical Industry Co., Ltd.

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

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

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

(Peeling aid, antistatic agent)
The peeling aid and the antistatic agent are partly agglomerated on the metal belt surface, thereby improving the peelability of the dope.

  As said compound, an organic, inorganic acidic compound, surfactant, and a chelating agent can be used.

  The acidic compound is preferably an organic acid, a partial alcohol ester of a polyvalent carboxylic acid, a surfactant or a chelating agent.

  As the partial alcohol ester of polyvalent carboxylic acid, the compounds described in paragraph (0049) of JP-A-2006-45497 can be preferably used.

  As the surfactant, compounds described in paragraphs (0050) to (0051) of JP-A-2006-45497 can be preferably used.

  The chelating agent is a compound capable of coordinating (chelating) a metal ion such as an iron ion or an alkaline earth metal ion such as a calcium ion. 11-190892, JP-A-2000-18038, JP-A-2010-158640, JP-A-2006-328203, JP-A-2005-68246, JP-A-2006-306969 are used. it can.

Moreover, as these commercially available products, Clariant Japan Co., Ltd. Hostastat HS-1, Takemoto Yushi Co., Ltd. Elecut S-412-2, Elecut S-418, Kao Corporation Neo-Perex G65, etc. are mentioned. (UV absorber)
Examples of the ultraviolet absorber applicable to the polarizing plate protective film of the present invention include benzotriazole-based, 2-hydroxybenzophenone-based, and salicylic acid phenyl ester-based ultraviolet absorbers. For example, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3 Triazoles such as 5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone And benzophenones.

  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.

(Matting agent)
In the present invention, it is preferable to add a matting agent in order to impart slipperiness to the polarizing plate protective film.

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

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

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

  Specific examples of silicon dioxide include Aerosil 200V, Aerosil R972V, Aerosil R972, R974, R812, 200, 300, R202, OX50, TT600, NAX50 (above, Nippon Aerosil Co., Ltd.), Sea Hoster KEP-10, Sea Hoster KEP -30, Seahoster KEP-50 (above, 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 commercial item etc. can be used preferably.

  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 the resulting film can have good transparency.

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

(Acrylic particles)
The polarizing plate protective film of the present invention may contain acrylic particles (D) described in International Publication No. 2010/001668.

  Examples of such commercially available acrylic particles include, for example, “Metablene W-341” manufactured by Mitsubishi Rayon Co., “Kaneace” manufactured by Kaneka Chemical Co., Ltd., “Paralloid” manufactured by Kureha Chemical Co., Ltd., Rohm and “Acryloid” manufactured by Haas, “Staffyroid” manufactured by Gantz Kasei Kogyo Co., Ltd., Chemisnow MR-2G, MS-300X (manufactured by Soken Chemical Co., Ltd.) and “Parapet SA” manufactured by Kuraray These can be used alone or in combination of two or more.

(Physical properties of polarizing plate protective film)
Hereinafter, physical properties of the polarizing plate protective film in the present invention will be described.

  As a polarizing plate protective film of the present invention, as a ductile fracture, there is a characteristic that a fracture such as a fracture is not observed even when a large stress is applied such that the film is folded in two in an atmosphere of 23 ° C. and 55% RH. It is preferable.

  In the polarizing plate protective film of the present invention, the glass transition temperature (Tg) is preferably in the range of 110 to 130 ° C.

  The Tg of the polarizing plate protective film referred to in the present invention is measured, for example, using a differential scanning calorimeter (DSC-7 type manufactured by Perkin Elmer) at a heating rate of 20 ° C./min, according to JIS K7121 (1987). The determined intermediate point can be determined as the glass transition temperature (Tg).

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

  The thickness of the polarizing plate protective film of the present invention is preferably in the range of 10 to 60 μm, more preferably in the range of 20 to 40 μm.

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

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

(Other functional layers)
The polarizing plate protective film of the present invention has functional layers such as 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 barrier layer as necessary. Furthermore, you may have.

<Hard coat layer>
For the formation of the hard coat layer, a cured product of an actinic radiation curable compound is 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, a component containing a monomer having an ethylenically unsaturated double bond is particularly preferably used.

  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, ultraviolet curable acrylate resins are preferred.

  The hard coat layer is obtained by applying a hard coat layer coating solution containing an actinic radiation curable compound and a photopolymerization initiator on a polarizing plate protective film, and then curing the composition by actinic radiation, for example, ultraviolet irradiation. Can do.

  Specific 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 hard coat layer coating solution is preferably in a mass ratio of photopolymerization initiator: active ray curable compound = 20: 100 to 0.01: 100.

  It is preferable that the hard coat layer coating liquid further contains fine particles such as inorganic fine particles or organic fine particles, if 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, hydration Calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate are included, and preferable examples include silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, and magnesium oxide.

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

  The average particle size of the fine particles is not particularly limited, but for example, considering that an antiglare layer is formed thereon, it is preferably in the range of 0.01 to 5 μm, and more preferably 0.01 to More preferably within the range of 1.0 μm. Moreover, you may contain 2 or more types of microparticles | fine-particles from which average particle diameter differs. 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 are coated with a coating solution for forming a hard coat layer using a known method such as a gravure coater, dip coater, reverse coater, wire bar coater, die coater, ink jet method, etc., heat-dried, and then UV cured. It can be formed by processing.

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

  As a light source used for the UV curing treatment, any light source that generates ultraviolet 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 actinic rays is in the range of usually 5~500mJ / cm ^2, preferably in the range of 5 to 200 mJ / cm ^2.

[Production method of polarizing plate protective film]
Subsequently, although the example of the manufacturing method of the polarizing plate protective film of this invention is demonstrated, this invention is not limited to this.

  As a method for producing the polarizing plate protective film of the present invention, the usual inflation method, T-die method, calendar method, cutting method, casting method, emulsion method, hot press method and the like can be used. From the viewpoint of suppressing foreign matter defects and optical defects such as die lines, the film forming method is preferably selected from a solution casting film forming method and a melt casting film forming method. It is preferable to obtain high transparency and smoothness.

(Solution casting film forming method)
When the polarizing plate protective film of the present invention is produced by a solution casting method, the (meth) acrylic polymer according to the present invention is used as an organic solvent useful for forming a dope in which each component used for film formation is dissolved. If (A), cellulose-ester resin (B), and another additive can be melt | dissolved simultaneously, it can use without a restriction | limiting especially.

  For example, as the chlorinated organic solvent, dichloromethane and 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-2 -Methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, etc. Of these, dichloromethane, methyl acetate, ethyl acetate and acetone can be preferably used.

  The dope used for forming the polarizing plate protective film of the present invention includes, in addition to the organic solvent, a linear or branched aliphatic alcohol having 1 to 4 carbon atoms within a range of 1 to 40% by mass. It is preferable to contain. When the proportion of alcohol in the dope increases, the web gels, and peeling from the metal support becomes easy. When the proportion of alcohol is small, a (meth) acrylic polymer (non-chlorine organic solvent) ( There is also a role of promoting dissolution of A) and the cellulose ester resin (B).

  In particular, in a solvent containing dichloromethane and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms, the (meth) acrylic polymer (A) according to the present invention and the cellulose ester resin (B), A dope composition dissolved in a total amount of at least 15 to 45% by mass with respect to the total mass of the dope is preferable.

  Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, s-butanol, and t-butanol. it can. Of these, ethanol and butanol are preferred because they contribute to the stability of the dope, have a relatively low boiling point, and have good drying properties.

  Hereinafter, an example of the preferable film forming method of the polarizing plate protective film of the present invention will be described.

1) Dissolution process
(Meth) acrylic polymer (A) and cellulose ester resin (B) in an organic solvent mainly composed of a good solvent for (meth) acrylic polymer (A) and cellulose ester resin (B) The step of preparing a dope for film formation by adding and dissolving while stirring acrylic particles and other additives according to the above, or the (meth) acrylic polymer (A) and cellulose ester resin (B) solution This is a step of preparing a dope which is a main solution by mixing an acrylic particle solution and other additive solutions as necessary.

  To dissolve the (meth) acrylic polymer (A) and the cellulose ester resin (B), a method performed at normal pressure, a method performed at a temperature lower than the boiling point of the main solvent, a method performed at a pressure higher than the boiling point of the main solvent, A method of applying the cooling dissolution method described in JP-A-9-95544, JP-A-9-95557, or JP-A-9-95538, described in JP-A-11-21379 Various dissolution methods such as a method performed at a high pressure can be used, but a method performed by pressurizing at a temperature equal to or higher than the boiling point of the main solvent is particularly preferable.

  As described above, the concentration of the (meth) acrylic polymer (A) and the cellulose ester resin (B) in the dope is preferably in the range of 15 to 45% by mass with respect to the total mass of the dope.

  After the additive is added to the dope and dissolved and dispersed, the prepared dope is filtered through a filter medium, then defoamed, and sent to the next step by a liquid feed pump. As the filter medium to be applied, it is preferable to use a filter medium having a collected particle diameter in the range of 0.5 to 5 μm and a drainage time in the range of 10 to 25 sec / 100 ml. By using the filter medium having the above characteristics, only the aggregate remaining at the time of dope dispersion and the aggregate generated at the time of dope preparation can be efficiently removed. In the dope, since the concentration of particles is sufficiently lower than that of the particle additive solution, aggregates do not stick together during filtration, and the filtration pressure does not increase rapidly.

  FIG. 1 is a diagram schematically showing an example of a dope preparation step, a casting step, and a drying step of a solution casting method for forming a polarizing plate protective film of the present invention.

  In FIG. 1, a dope (for example, a solution in which a (meth) acrylic polymer (A) and a cellulose ester resin (B) are dissolved) is transferred from a storage tank 41 to a filter 44 where large aggregation occurs. The material is removed and the solution is fed to the stock pot 42. Then, it transfers to the dope preparation pot 1 from the stock pot 42, and various additive liquids are added there, and the main dope is prepared.

  Thereafter, the main dope is filtered by the main filter 3, and an ultraviolet absorbent additive solution or the like is added in-line through the conduit 16 to the main dope and mixed uniformly by the mixer 21 to prepare the final dope.

  In many cases, the dope may contain about 10 to 50% by mass of the recycled material. A return material is a product obtained by finely pulverizing a polarizing plate protective film, which is generated when a polarizing plate protective film is formed, and a polarizing plate that has been cut off from both sides of the film, or a polarizing plate that is out of specification due to scratches, etc. The original film of the protective film is used.

  In addition, as a raw material for the resin used for preparing the dope, a material obtained by pelletizing a (meth) acrylic polymer (A) and a cellulose ester resin (B) in advance can be preferably used.

2) Casting process The casting process is an endless metal belt 31 that feeds the dope to a pressure die 30 through a liquid feed pump (for example, a pressurized metering gear pump) and transfers it infinitely, such as a stainless steel belt, Alternatively, the dope is cast from a pressure die slit at a casting position on a metal support such as a rotating metal drum.

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

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

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

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

4) Peeling process A peeling process is a process of peeling the web which the solvent evaporated on the metal support body in the peeling position 33. FIG. The peeled web is sent to the next process.

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

  The residual solvent amount at the time of peeling of the web on the metal support at the time of peeling varies depending on the strength of drying conditions, the length of the metal support, etc., but the residual solvent amount is generally 50 to 120 mass. However, if the web is too soft, the flatness at the time of peeling will be lost, and it is easy to cause slippage and vertical stripes due to peeling tension. The balance of speed and quality determines the amount of residual solvent during stripping.

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

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

  The peeling tension when peeling the metal support and the web 32 is usually in the range of 196 to 245 N / m. However, if wrinkles are likely to occur during peeling, the peeling tension should be 190 N / m or less. Is preferred.

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

5) Drying and stretching step After peeling, a drying device 35 that transports the web 32 alternately through rollers 36 arranged in the drying device 35, or a tenter stretching device 34 that clips and transports both ends of the web 32 with clips. Is used to dry the web 32.

  As a drying means, hot air is generally blown on both surfaces of the web 32, but there is also a means for heating by applying microwaves instead of wind. Too rapid drying tends to impair the flatness of the finished film. The drying at a high temperature is preferably performed under the condition that the residual solvent is 8% by mass or less. Throughout the entire process, drying is generally performed within a range of 40 to 250 ° C. In particular, it is preferable to dry within a range of 40 to 200 ° C.

  When the tenter stretching device 34 is used, it is preferable to use a device that can independently control the film gripping length (distance from the start of gripping to the end of gripping) left and right by the left and right gripping means of the tenter. In the tenter process, it is also preferable to intentionally create sections having different temperatures in order to improve planarity.

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

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

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

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

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

  When performing the tenter, the drying temperature is preferably within the range of 30 to 160 ° C, and more preferably within the range of 50 to 150 ° C.

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

6) Winding process The winding process is a process in which the amount of residual solvent in the web is 2% by mass or less, and then wound by the winder 37 as a polarizing plate protective film, and the amount of residual solvent is 0.4 mass. By setting the ratio to not more than%, a film having good dimensional stability can be obtained. In particular, the amount of residual solvent is preferably wound in the range of 0.00 to 0.10% by mass.

  The winding method may be a generally used one, 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, etc. You can do it in combination.

  The polarizing plate protective film of the present invention is preferably a long film. Specifically, the polarizing plate protective film is in the range of 100 to 10,000 m, and is usually in a form provided in a roll shape. Moreover, it is preferable that the width | variety of a film exists in the range of 1-4 m, and it is more preferable that it exists in the range of 1.4-3 m.

<< Configuration of polarizing plate and liquid crystal display device >>
Subsequently, the outline of the structure of the polarizing plate and liquid crystal display device which comprised the polarizing plate protective film of this invention is demonstrated.

  The polarizing plate of the present invention has at least the polarizing plate protective film of the present invention, and further has a configuration in which an active energy ray-curable resin layer and a polarizer are laminated in this order. Further, a specific retardation value is further provided on the surface of the polarizer opposite to the surface on which the polarizing plate protective film of the present invention is disposed, via an active energy ray-curable resin layer. It is a preferable embodiment that the retardation film is laminated.

  FIG. 2 is a schematic cross-sectional view showing an example of the configuration of the polarizing plate provided with the polarizing plate protective film of the present invention.

  In FIG. 2, the polarizing plate 101 of the present invention comprises a (meth) acrylic polymer (A) having a (meth) acrylic acid alkyl ester unit having a branched alkyl group as a substituent on the surface side, and a cellulose ester resin. It has the polarizing plate protective film 102 of this invention containing (B), and has the active energy ray hardening-type resin layer 103A in the lower part. This active energy ray-curable resin layer 103A is a layer that functions to adhere the polarizing plate protective film 101 and the polarizer 104, and is made of a material that is cured by irradiation with active energy rays, for example, ultraviolet rays. ing.

  Further, the surface of the polarizer 104 opposite to the surface on which the polarizing plate protective film 102 of the present invention is disposed is further provided with a specific retardation value via the active energy ray-curable resin layer 103B. A retardation film 105 is laminated to form a polarizing plate.

  In this invention, when the polarizing plate protective film of this invention comprises a polarizing plate, it 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. In FIG. 2, 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 of the present invention is installed on the surface. That is, the polarizing plate protective film of this invention is an optical film located in the surface side among the 2 types of optical films which comprise a polarizing plate.

  Moreover, although not described in FIG. 2, on the further outer side (outermost surface portion) of the polarizing plate protective film of the present invention, for example, an antiglare layer, an antireflection layer, an antifouling layer, a hard layer, if necessary. Various functional layers such as a coat layer may be provided.

  Subsequently, the outline of the structure is demonstrated about the liquid crystal display device which comprised the polarizing plate which has the polarizing plate protective film of this invention.

  FIG. 3 is a schematic cross-sectional view showing an example of the configuration of the liquid crystal display device 106 including the polarizing plate 101 of the present invention described above.

  In FIG. 3, a liquid crystal cell 107 is sandwiched between the retardation film 105 constituting the polarizing plate 101A and the retardation film 105 constituting the polarizing plate 101B described in FIG. Yes.

  In the configuration shown in FIG. 3, in the polarizing plate 101A on the liquid crystal cell 107, as the optical film, a polarizing plate protective film 102A is disposed on the surface portion, which is referred to as a polarizing plate protective film T1, and further below the polarizer 104A. Is provided with a retardation film 105A, which is referred to as a retardation film T2.

  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 under the polarizer 104B (liquid crystal cell side), and this is referred to as a retardation film T3.

  In the liquid crystal display device having such a configuration, the polarizing plate protective film of the present invention is the polarizing plate protective film 102A (polarizing plate protective film T1) and the polarizing plate protective film 102B (polarizing plate protective film T4).

<Components of polarizing plate>
Next, the polarizer, the retardation film, the active energy ray-curable resin layer, etc., excluding the polarizing plate protective film described above, will be sequentially described with respect to the components of the polarizing plate of the present invention.

[Polarizer]
The polarizer, which is one of the components 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, a polarizer obtained by forming a polyvinyl alcohol aqueous solution into a film and dyeing it by uniaxial stretching or dyeing and then uniaxially stretching and then preferably performing a durability treatment with a boron compound may be used. The thickness of the polarizer is in the range of 2.0 to 30 μm, and in the present invention, it is particularly preferably in the range of 2.0 to 15 μm.

[Phase difference film]
In the polarizing plate of the present invention, as shown in FIG. 2 and FIG. 3, active energy ray curing is further performed on the surface opposite to the surface on which the polarizing plate protective film of the present invention is disposed. It is preferable that the retardation film is laminated via the mold resin layer.

  The retardation film according to the present invention is not particularly limited in its properties, but a retardation film satisfying all of the following conditions 1 to 3 is preferable.

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

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

Formula (II): Rt (590) = {(n _x + n _y ) / 2−n _z } × d
In the above formulas (I) and (II), n _x represents a refractive index in the direction x in which the refractive index is maximized in the plane direction of the film. n _y, in-plane direction of the film, the refractive index in the 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.

  Each retardation value can be measured using an automatic birefringence meter. As an automatic birefringence meter, for example, an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments Co., Ltd.) or Axoscan made by Axometric is used, and the birefringence meter at 590 nm is used at 23 ° C. and 55% RH. The wavelength dependence by refraction or birefringence measurement at each wavelength (450 nm, 550 nm and 650 nm) is measured, and the retardation value with respect to the wavelength is calculated from the thickness of the film.

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

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

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

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

[Active energy ray-curable adhesive]
In the polarizing plate of this invention, it is a preferable aspect that the polarizing plate protective film of this invention demonstrated above and at least one surface of a polarizer are bonded by the active energy ray hardening-type adhesive agent. Similarly, the retardation film and the polarizer are preferably bonded with an active energy ray-curable adhesive.

  In the present invention, by applying the active energy ray-curable adhesive to the bonding of the polarizing plate protective film and the polarizer of the present invention, or the bonding of the retardation film and the polarizer, with high productivity, A characteristic excellent in flatness can be obtained.

(Composition of active energy ray-curable adhesive)
Examples of the active energy ray-curable adhesive composition applicable to the production of polarizing plates include a photo radical polymerization composition utilizing photo radical polymerization, a photo cation polymerization composition utilizing photo cation polymerization, and photo radical polymerization. In addition, a hybrid composition using both photocationic polymerization and photocationic polymerization is known.

  As a radical photopolymerization type composition, 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 are contained in a specific ratio. Composition) and the like are known. In particular, the radical polymerizable compound is preferably a compound having a radical polymerizable ethylenically unsaturated bond. 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 disclosed in JP 2011-08234 A, (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.

<< Polarizing plate manufacturing method >>
The method for laminating the polarizing plate protective film of the present invention and the polarizer is not particularly limited, but may be performed using a fully saponified polyvinyl alcohol adhesive, an active energy ray curable adhesive, or the like. Can do. Among them, a method using an active energy ray-curable adhesive is preferable because the obtained adhesive layer has a high elastic modulus and can easily suppress deformation of the polarizing plate.

  Preferable examples of the active energy ray-curable adhesive include (α) cationic polymerizable compound, (β) photocationic polymerization initiator, and (γ) as described in, for example, JP-A-2011-028234. Examples thereof include a photosensitizing agent composition containing each component of a photosensitizer that exhibits maximum absorption in light having a wavelength longer than 380 nm and (δ) a naphthalene-based photosensitization aid. However, other photocurable adhesives may be 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 following active energy ray-curable adhesive to at least one of the adhesive surfaces of the polarizer and the polarizing plate protective film of the present invention;
2) A bonding step in which a polarizer and a polarizing plate protective film are bonded and bonded via an adhesive layer;
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.

(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. 2, when the polarizing plate protective film 102 and the retardation film 105 are bonded to both surfaces of the polarizer 104 through an active energy ray-curable adhesive, the respective polarizing plate protective films 102 are used. Further, easy adhesion treatment is performed on the adhesion surface of the retardation film 105.

  In the adhesive application step, which is the next step, the surface subjected to the easy adhesion treatment is treated as a bonding surface with the polarizer, and therefore the active energy ray-curable resin layer 103A is bonded to both surfaces of the polarizing plate protective film. The surface to be treated is subjected to an easy adhesion treatment. Examples of the easy adhesion treatment include corona treatment, plasma treatment, and excimer treatment.

(Adhesive application process)
In the adhesive application step, the active energy ray-curable adhesive is applied to at least one of the adhesive surfaces of the polarizer and the polarizing plate protective film. 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 used. Moreover, after casting an active energy ray hardening-type adhesive between a polarizer and a polarizing plate protective film, the method of pressurizing with a roller etc. and spreading uniformly can also be utilized.

(Bonding process)
After apply | coating an active energy ray hardening-type adhesive agent by said method, it processes by a bonding process. In this bonding step, for example, when an active energy ray-curable adhesive is applied to the surface of the polarizer in the previous application step, a polarizing plate protective film is superimposed there. When the active energy ray-curable adhesive is applied to the surface of the polarizing plate protective film in the previous application step, a polarizer is superimposed thereon. Moreover, when an active energy ray hardening-type adhesive agent is cast between a polarizer and a polarizing plate protective film, a polarizer and a polarizing plate protective film are piled up in that state. When a polarizing plate protective film and a retardation film are bonded to both sides of a polarizer, and both surfaces use an active energy ray-curable adhesive, an active energy ray-curable adhesive is applied to both sides of the polarizer. A polarizing plate protective film and a retardation film are superimposed on each other. Usually, in this state, both sides (when a polarizing plate protective film is superimposed on one side of the polarizer, the polarizing plate protective film and the retardation film are provided on both sides of the polarizer and the polarizing plate protective film side. In the case of superimposing, pressure is applied between the polarizing plate protective film and the retardation film side of both surfaces with a roller or the like. 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, an active energy ray curable adhesive is irradiated with active energy rays, and a cationic polymerizable compound (for example, an epoxy compound or an oxetane compound) or a radical polymerizable compound (for example, an acrylate compound or an acrylamide compound). The active energy ray-curable resin layer containing the compound or the like is cured, and the polarizer and the polarizing plate protective film, or the polarizer and the retardation film are overlapped with each other via the active energy ray-curable adhesive. 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.

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

  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 the desired curing conditions, and if the acceleration voltage is 300 kV or less, the penetration force through the bonding unit becomes excessively strong. It can suppress that a transparent polarizing plate protective film and a polarizer are damaged.

  As an irradiation dose, it exists in the range of 5-100 kGy, More preferably, it exists in the range of 10-75 kGy. When the irradiation dose is 5 kGy or more, the active energy ray-curable adhesive is sufficiently cured. When the irradiation dose is 100 kGy or less, the polarizing plate protective film and the polarizer are not damaged, and the mechanical strength is reduced. Changes can be prevented, and predetermined optical characteristics can be obtained.

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

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

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

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

<< Preparation of (meth) acrylic polymer (A) >>
(Meth) acrylic polymers A1 to A15 having the composition shown in Table 1 (monomer species, ratio, weight average molecular weight) were prepared according to a conventional method.

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

MMA: methyl methacrylate t-BMA: tert-butyl methacrylate t-BA: tert-butyl acrylate s-BMA: sec-butyl methacrylate i-PrMA: iso-propyl methacrylate * 1: neopentyl methacrylate * 2: tert-pentyl methacrylate n -BMA: n-butyl methacrylate MA: methyl acrylate MHMA: 2- (hydroxymethyl) methyl acrylate << Preparation of cellulose ester resin (B) >>
According to a conventional method, cellulose ester resins B1 to B8 having a degree of substitution with each group described in Table 2 were prepared.

  The details of each substituent described in abbreviations in Table 2 are as follows.

Ac: Acetyl group Pro: Propionyl group Bu: Butanoyl group Bz: Benzoyl group Bp: Biphenoyl group << Preparation of polarizing plate protective film >>
[Preparation of Polarizing Plate Protective Film 1]
(Preparation of dope 1)
(Meth) acrylic polymer A1 90 parts by weight Cellulose ester resin B1 10 parts by weight UV absorber: 2,2′-methylenebis [6- (2H-benzotriazol-2-yl) -4- (1,1,3, 3-tetramethylbutyl) phenol] (molecular weight 659, LA31 manufactured by ADEKA Corporation) 3.0 parts by weight Matting agent: R972V (manufactured by Nippon Aerosil Co., Ltd., silica particles, average particle size = 16 nm)
0.30 parts by mass Peeling aid: Elecut S412 (manufactured by Takemoto Yushi Co., Ltd.) 0.50 parts by mass Dichloromethane 300 parts by mass Ethanol 40 parts by mass The above compositions are sufficiently dissolved with stirring and heating to prepare Dope 1. did.

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

  Next, the solvent of the peeled dope 1 is evaporated at 35 ° C., slit to 1 m width, and then 2.0 times in the transport direction (MD direction) by zone stretching and the width direction (TD direction) by tenter stretching. The film was dried at a drying temperature of 135 ° C. while being stretched 2.0 times. At this time, the residual solvent amount when starting stretching with the tenter was 8.0%.

  After stretching with a tenter, 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, slitting to a width of 1.5 m, and both ends of the film Was subjected to a knurling process having a width of 10 mm and a height of 5 μm, and then wound around a core to prepare the polarizing plate protective film 1 of the present invention.

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

[Formation of hard coat layer]
Next, a hard coat layer coating solution prepared by filtering the following hard coat layer coating composition through a polypropylene filter having a pore diameter of 0.4 μm is applied onto the prepared polarizing plate protective film 1 using an extrusion coater. After drying at a temperature of 80 ° C. for 50 seconds, using an ultraviolet lamp, the illuminance of the irradiated part is 300 mW / cm ² , the irradiation amount is 0.3 J / cm ² , the coating layer is cured, and the dry film thickness is 10 μm. A hard coat layer was formed, and a polarizing plate protective film 1 was produced.

(Preparation of hard coat layer composition)
After dissolving 3.8 parts by mass of acrylic resin (Mw 280000, trade name: Dianal BR85, manufactured by Mitsubishi Rayon Co., Ltd.) with 100 parts by mass of methyl ethyl ketone, the following additives are added and mixed while stirring. Then, a hard coat layer composition was prepared.

<Radically polymerizable compound>
Dipentaerythritol hexaacrylate (NK ester A-DPH, manufactured by Shin-Nakamura Chemical Co., Ltd.) 180 parts by mass <Photopolymerization initiator>
Irgacure 184 (manufactured by BASF Japan) 6.0 parts by mass Irgacure 907 (manufactured by BASF Japan) 8.0 parts by mass <Silicone-based surfactant>
Polyether-modified silicone compound (trade name: KF-355A, manufactured by Shin-Etsu Chemical Co., Ltd.)
9.0 parts by mass <solvent>
Propylene glycol monomethyl ether 10.0 parts by mass Methyl acetate 80.0 parts by mass [Preparation of polarizing plate protective film 2-30]
Table 3 shows the types, mixing ratios (A / B) and film thicknesses of the (meth) acrylic polymer (A) and the cellulose ester resin (B) used for preparing the dope in the production of the polarizing plate protective film 1. Polarizing plate protective films 2 to 30 were produced in the same manner except that the combination was changed.

<< Evaluation of polarizing plate protective film >>
About each produced said polarizing plate protective film, each following evaluation was performed.

[Evaluation of low moisture permeability]
In accordance with JIS Z-0208, each polarizing plate protective film was conditioned for 24 hours in an environment of 40 ° C. and 90% RH, and then per unit area before and after humidity adjustment using a moisture permeation test device. The water content was calculated (g / m ² · 24 hr). Subsequently, the amount of moisture after conditioning-the amount of change in moisture content before conditioning (g / m ² · 24 hr) was determined, and this was used as a measure of moisture permeability, and low moisture permeability was evaluated according to the following criteria.

A: Change amount of moisture (moisture permeability) is less than 100 (g / m ² · 24 hr) ○: Change amount of moisture (moisture permeability) is 100 (g / m ² · 24 hr) or more, 150 Less than (g / m ² · 24 hr) Δ: Change amount of moisture (moisture permeability) is 150 (g / m ² · 24 hr) or more and less than 500 (g / m ² · 24 hr) ×: moisture The amount of change (moisture permeability) is 500 (g / m ² · 24 hr) or more [Evaluation of Glass Transition Temperature (Tg)]
The glass transition temperature (Tg) of each polarizing plate protective film was measured according to JIS K7121, using a differential scanning calorimeter DSC220 manufactured by Seiko Instruments Inc.

  About the glass transition temperature (Tg) of each polarizing plate protective film measured by the above, glass transition temperature was evaluated according to the following reference | standard.

A: The glass transition temperature is in the range of 120 ° C. or higher and 130 ° C. or lower. ○: The glass transition temperature is in the range of 110 ° C. or higher and lower than 120 ° C. Δ: The glass transition temperature is 100 ° C. or higher, 110 Within the range of less than ℃ ×: Glass transition temperature is less than 100 ℃ [Evaluation of transparency]
The haze of each produced polarizing plate protective film was measured using a haze meter (1001DP type, manufactured by Nippon Denshoku Industries Co., Ltd.), and the transparency was evaluated according to the following criteria.

○: Haze is less than 0.5% Δ: Haze is 0.5 or more and less than 1.5% ×: Haze is 1.5% or more [Evaluation of vulnerability]
Each protective film was conditioned for 24 hours under an environment of 23 ° C. and 55% RH, and was cut into a size of 100 mm (vertical) × 10 mm (width) under the same conditions, with a radius of curvature of 0 mm at the center in the vertical direction, Folding angle was 180 °, and the film was folded once in two such as mountain fold and valley fold so that the films were exactly overlapped, and this evaluation was performed 10 times, and the brittleness resistance was evaluated according to the following criteria. Note that “break” in this evaluation means that the material has broken into two or more pieces.

◎: No breakage was observed in all 10 times ○: Partial cracking occurred in 1 out of 10 times, but not broken △: Breaking occurred in 1 out of 10 times X: The breakage occurred at least 2 times out of 10 times. Table 3 shows the results obtained as described above.

  As is clear from the results shown in Table 3, the polarizing plate protective film of the present invention has an appropriate glass transition temperature (Tg), and moisture permeability, transparency (haze resistance) and resistance to brittleness relative to the comparative example. It can be seen that there is an excellent balance in the three performances.

More specifically, the polarizing plate protective film 1 is a branched alkyl group in which the (meth) acrylic polymer (A) has a tertiary carbon atom as the substituent R ¹ as compared with the polarizing plate protective films 12 and 13. From this, it was found that heat resistance (glass transition temperature) was excellent.

  Moreover, since the polarizing plate protective film 1 has a large weight average molecular weight of the (meth) acrylic polymer (A) compared with the polarizing plate protective film 6, it turns out that it is excellent in brittle resistance.

  Moreover, since the polarizing plate protective films 21-25 have the acyl group in which the cellulose ester resin (B) has a carbon number in the range of 7-13 compared with the polarizing plate protective film film 1, it has low permeability. It can be seen that the wettability is particularly excellent.

Example 2
<Production of polarizing plate>
[Preparation of Polarizing Plate 1]
(Preparation of polarizer)
A 70 μm thick polyvinyl alcohol film was swollen with water at 35 ° C. The obtained film was immersed in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and further immersed in an aqueous solution of 45 ° C. consisting of 3 g of potassium iodide, 7.5 g of boric acid and 100 g of water. . The obtained film was uniaxially stretched under conditions of a stretching temperature of 55 ° C. and a stretching ratio of 5 times. This uniaxially stretched film was washed with water and dried to obtain a polarizer having a thickness of 10 μm.

(Preparation of retardation film A)
As the retardation film A, a cellulose acylate film 4DR (film thickness: 40 μm) manufactured by Konica Minolta was prepared.

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

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

  First, as the retardation film (105), the retardation film A (cellulose acylate film 4DR film thickness 40 μm manufactured by Konica Minolta Co., Ltd.) was prepared, and the surface thereof was subjected to corona discharge treatment. The corona discharge treatment was performed at a corona output intensity of 2.0 kW and a line speed of 18 m / min. Next, the active energy ray-curable adhesive liquid prepared above is applied to the corona discharge-treated surface of the retardation film (105) with a bar coater so that the film thickness after curing is about 3 μm. A curable resin layer (103B) was formed. The produced polyvinyl alcohol-iodine polarizer (104) was bonded to the obtained active energy ray-curable resin layer (103B).

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

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

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

[Production of Polarizing Plates 2-28, 31-40]
In the production of the polarizing plate 1, the same applies except that the type of polarizing plate protective film, the type of retardation film, the method of bonding the polarizer and each film, and the thickness of the polarizer are changed to the combinations shown in Table 4. Thus, polarizing plates 2 to 28 and 31 to 40 were produced.

[Preparation of Polarizing Plate 29]
In the production of the polarizing plate 1, a polarizing plate 29 was produced in the same manner except that the polarizing plate protective film 1 and the polarizer, and the retardation film A and the polarizer were adhered by the water paste method 1 described below. .

  As the polarizer, a 10 μm-thick polarizer similar to that used for the production of the polarizing plate 1 was used.

  Subsequently, according to the following processes 1-5, the polarizer, the produced retardation film A, and the produced polarizing plate protective film 1 were bonded together on the back side, and the polarizing plate 29 was produced.

  Step 1: The surfaces of the retardation film A and the polarizing plate protective film 1 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: The prepared 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 adhesive adhered to the polarizer in Step 2 was gently wiped off and placed on the retardation film A processed in Step 1.

Step 4: Step 3 phase was laminated with film A polarizer and pressure polarizing plate protective film 1 on the back side 20-30 N / cm ^2, the conveyance speed was pasted at approximately 2m / min.

  Step 5: A sample obtained by bonding the polarizer, the retardation film A, and the polarizing plate protective film 1 prepared in Step 4 in a dryer at 80 ° C. was dried for 2 minutes to prepare a polarizing plate 29.

[Production of Polarizing Plate 30]
In the production of the polarizing plate 29, Step 1 of the water paste method 1 is the same except that the water paste method 2 changed to the following step 1A is used, and the polarizing plate protective film 1, the polarizer, and the retardation film A polarizing plate 30 was produced in the same manner except that A and a polarizer were bonded.

  Step 1A: Excimer light was irradiated under the following conditions using an excimer irradiation apparatus (MECL-M-1-200) manufactured by M.D.

(Irradiation conditions)
Lamp filled gas: Xe
Wavelength: 172nm
Excimer light intensity: 130 mW / cm ² (172 nm)
Oxygen concentration in irradiation device: 0.3% (nitrogen purge)
Integrated light quantity of light having a wavelength shorter than 200 nm: 1600 mJ / cm ²
[Phase difference films A to G]
Below, it shows about the detailed content and preparation method of retardation film AG described in Table 4 by the abbreviation.

(Phase difference film A)
As the retardation film A, a cellulose acylate film 4DR (film thickness: 40 μm) manufactured by Konica Minolta was prepared.

(Phase difference film B)
The following components were sufficiently stirred and dissolved while heating to prepare a dope.

<Dope composition>
Cellulose ester (diacetyl cellulose having an acetyl group substitution degree of 2.3 and a weight average molecular weight (Mw) of 185,000) 100 parts by weight Compound A (retardation increasing agent) 4 parts by weight Sugar ester 1 10 parts by weight Compound B (phthalic acid) / Adipic acid / 1,2-propanediol = 50/50/100 molar ratio of both ends of the condensate sealed with a benzoate group, molecular weight 440) 2 parts by weight Matting agent: R972V (manufactured by Nippon Aerosil Co., Ltd.) , Silica particles, average particle size = 16 nm)
0.20 parts by mass Dichloromethane 300 parts by mass Ethanol 40 parts by mass

  The obtained dope was uniformly cast on a stainless steel band support at a temperature of 22 ° C. and a width of 2 m using a belt casting apparatus. With the stainless steel band support, the solvent was evaporated until the amount of residual solvent reached 100%, and peeling was performed from the stainless steel band support with a peeling tension of 162 N / m. Next, the solvent of the peeled dope web is evaporated at 35 ° C., slit to 1 m width, and then 1.1 times in the transport direction (MD direction) by zone stretching and in the lateral direction (TD direction) by tenter stretching. The film was dried at a drying temperature of 135 ° C. while being stretched 1.5 times. The residual solvent amount at the start of stretching by the tenter was 8%.

  After stretching with a tenter, 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, slitting to a width of 1.5 m, and both ends of the film Was subjected to a knurling process having a width of 10 mm and a height of 5 μm, and then wound around a core to obtain a retardation film B having a thickness of 30 μm.

(Phase difference film C)
A core layer dope, a skin B layer dope and a skin A layer dope having the following compositions were prepared.

<Dope composition for core layer>
Cellulose acetate (total substitution degree 2.45, acetyl group substitution degree 2.45)
100 parts by mass Compound C (retardation enhancer) 3 parts by mass Compound D (terephthalic acid / succinic acid / ethanediol / propanediol (80/20/50/50 molar ratio)) Sealed)
10 parts by mass Dichloromethane 406 parts by mass Methanol 61 parts by mass

<Dope composition for skin B layer>
Cellulose acetate (total substitution degree 2.93, acetyl group substitution degree 2.93)
100 parts by mass Compound E (terephthalic acid / succinic acid / ethylene glycol copolymer (50/50/100 molar ratio), molecular weight 2000, retardation developer) 4 parts by mass Aerosil R972 (manufactured by Nippon Aerosil Co., Ltd., silicon dioxide) Fine particles (average particle size 15 nm, matting agent) 0.12 parts by weight Citric acid half ethyl ester (manufactured by Fuso Chemical Industry Co., Ltd., peeling accelerator) 2 parts by weight Dichloromethane 406 parts by weight Methanol 61 parts by weight <Dope for skin A layer Composition>
In the preparation of the skin B layer dope, a skin A layer dope was obtained in the same manner except that the citric acid partial ethyl ester compound (peeling accelerator) was not included.

  Each of these dopes was put into a mixing tank and stirred to dissolve each component, and then filtered through a filter paper having an average pore size of 34 μm and a sintered metal filter having an average pore size of 10 μm to prepare a dope.

  The obtained core layer dope, skin A layer dope, and skin B layer dope were co-cast from a casting die on a traveling casting band (simultaneous multilayer casting). The co-casting was performed so that the dope for the skin B layer was in contact with the casting band. The cast film was peeled off from the cast band, made into a wet film, and then dried with a tenter to obtain a web. The amount of residual solvent immediately after stripping the dope was about 30% by mass. The web was stretched to a stretch ratio of 30% with a tenter and then relaxed at 140 ° C. for 60 seconds to obtain a retardation film C having a thickness of 40 μm having a three-layer structure of skin B layer / core layer / skin A layer. Obtained.

(Retardation film D)
A core layer dope, a skin B layer dope and a skin A layer dope having the following compositions were prepared.

<Dope composition for core layer>
Cellulose acetate (total substitution degree 2.45, acetyl group substitution degree 2.45)
100 parts by mass Compound F (retardation enhancer) 3 parts by mass Compound G (succinic acid / adipic acid / ethylene glycol copolymer (copolymerization ratio = 3: 2: 5, molecular weight 2000), retardation reducing agent) 10 parts by mass Parts dichloromethane 406 parts by mass methanol 61 parts by mass

<Dope composition for skin B layer>
Cellulose acetate (total substitution degree 2.93, acetyl group substitution degree 2.93)
100 parts by mass Compound E (terephthalic acid / succinic acid / ethylene glycol copolymer (50/50/100 molar ratio), molecular weight 2000, retardation developer) 4 parts by mass Aerosil R972 (manufactured by Nippon Aerosil Co., Ltd., silicon dioxide) Fine particles (average particle size 15 nm, matting agent) 0.12 parts by weight N- (2,6-diethylphenylcarbamoylmethyl) iminodiacetic acid 2 parts by mass Dichloromethane 406 parts by mass Methanol 61 parts by mass <Dope composition for skin A layer>
In the preparation of the skin B layer dope, a skin A layer dope was obtained in the same manner except that the citric acid partial ethyl ester compound (peeling accelerator) was not included.

  Each of these dopes was put into a mixing tank and stirred to dissolve each component, and then filtered through a filter paper having an average pore size of 34 μm and a sintered metal filter having an average pore size of 10 μm to prepare a dope.

  The obtained core layer dope, skin A layer dope, and skin B layer dope were co-cast from a casting die on a traveling casting band (simultaneous multilayer casting). The co-casting was performed so that the dope for the skin B layer was in contact with the casting band. The cast film was peeled off from the cast band, made into a wet film, and then dried with a tenter to obtain a web. The amount of residual solvent immediately after stripping the dope was about 30% by mass. The web is stretched to a stretch ratio of 30% with a tenter and then relaxed at 140 ° C. for 60 seconds to obtain a retardation film D having a thickness of 40 μm and having a three-layer structure of skin B layer / core layer / skin A layer. Obtained.

(Phase difference film E)
As the retardation film E, a cycloolefin resin film (film described in Example 1 of JP-A-2006-235085) having a film thickness of 40 μm was prepared.

(Retardation film F)
The following components were sufficiently stirred and dissolved while heating to prepare a dope.

<Dope composition>
Cellulose ester (triacetyl cellulose having an acetyl group substitution degree of 2.75 and a weight average molecular weight (Mw) of 280,000) 100 parts by mass The following compound H 4 parts by mass Polyester phthalate 10 parts by mass Matting agent: R972V (produced by Nippon Aerosil Co., Ltd., silica particles Average particle size = 16 nm)
0.20 parts by mass Dichloromethane 280 parts by mass Ethanol 60 parts by mass

  The obtained dope was uniformly cast on a stainless steel band support at a temperature of 22 ° C. and a width of 2 m using a belt casting apparatus. With the stainless steel band support, the solvent was evaporated until the amount of residual solvent reached 100%, and peeling was performed from the stainless steel band support with a peeling tension of 162 N / m. Next, the solvent of the peeled dope web is evaporated at 35 ° C., slit to 1 m width, and then 1.1 times in the transport direction (MD direction) by zone stretching and in the lateral direction (TD direction) by tenter stretching. The film was dried at a drying temperature of 140 ° C. while being stretched 1.2 times. The residual solvent amount at the start of stretching by the tenter was 8%.

  After stretching with a tenter, 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, slitting to a width of 1.5 m, and both ends of the film Was subjected to a knurling process having a width of 10 mm and a height of 5 μm, and then wound around a core to obtain a retardation film F having a thickness of 60 μm.

(Retardation film G)
As the retardation film G, a cellulose acylate film 4KR (film thickness: 40 μm) manufactured by Konica Minolta was prepared.

<Production of liquid crystal display device>
Using a commercially available VA type liquid crystal display device (40 type display KLV-40J3000 made by SONY), the polarizing plate bonded to both surfaces of the liquid crystal cell was peeled off, and as shown in FIG. , 101B) 1 to 40 were bonded to both surfaces of the liquid crystal cell (107) to prepare liquid crystal display devices (106) 1 to 40.

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

(Evaluation of moisture resistance of polarizer)
The obtained polarizing plate was allowed to stand for 1000 hours in an environment of 60 ° C. and 95% RH. Next, after being allowed to stand for 24 hours in an environment of 23 ° C. and 55%, the parallel transmittance and orthogonal transmittance of light having a wavelength of 550 nm are measured using an automatic polarizing film measuring device (VAP-7070, manufactured by JASCO Corporation). It was measured. Next, the degree of polarization was determined based on the following formula based on the obtained measured values.

  Using the obtained degree of polarization (%), the moisture resistance of the polarizer was evaluated based on the following evaluation rank.

A: The degree of polarization is 99.5% or more, and there is no problem at all. ○: The degree of polarization is 99.0% or more and less than 99.5%, and there is no problem. Δ: The degree of polarization is 98. 0.0% or more and less than 99.0%, but the quality has no problem in practical use. X: The degree of polarization is less than 98.0%, which is a problem in practical use. Evaluation)
The above-prepared liquid crystal display device (also referred to as a display panel) was stored for 24 hours in an environment of 40 ° C. and 90% RH, and then subjected to a durability test for 2 hours in an environment of 40 ° C. and 10% RH. . Next, the liquid crystal display device is placed on a flat quartz plate in an environment of 23 ° C. and 55% RH, and the average value of the lifting height from the quartz plate surface at the four corners is measured. The flatness (warpage resistance) of was evaluated.

A: The average value of the average lift height at the four corners is less than 1.0 mm. O: The average value of the average lift height at the four corners is 1.0 mm or more and less than 3.0 mm. The average value of the average lift height is 3.0 mm or more and less than 5.0 mm, but it is a quality that is practically acceptable. X: The average value of the average lift height of the four corners is 5.0 mm or more Table 4 shows the results obtained from the above, which is a quality that is a problem in practical use.

  As is clear from the results shown in Table 4, the polarizing plate provided with the polarizing plate protective film of the present invention has an excellent moisture resistance against the comparative example, preventing the influence of moisture on the constituting polarizer. It can be seen that the liquid crystal display device including the polarizing plate of the present invention is excellent in the flatness of the liquid crystal panel after being stored in a high humidity environment and a low humidity environment as compared with the comparative example.

  More specifically, the polarizing plate 1 uses an active energy ray-curable adhesive as compared with the polarizing plate 29, and thus it was found that the polarizer has excellent moisture resistance. The same applies to the polarizing plate 36.

  In addition, it was found that the liquid crystal display device 1 was excellent in the flatness of the liquid crystal panel because the thickness of the polarizer was smaller than that of the liquid crystal display device 33.

DESCRIPTION OF SYMBOLS 1 Dope preparation pot 3, 6, 12, 15, 44 Filter 4, 13, 42 Stock tank 2, 5, 11, 14, 43 Liquid feed pump 8, 16 Pipe | tube 10 Ultraviolet absorber preparation pot 20 Merge pipe 21 Mixer 30 Die 31 Metal Support 32 Web 33 Peeling Position 34 Tenter Stretching Device 35 Drying Device 36 Roller 37 Winder 41 Feeding Pot 101, 101A, 101B Polarizing Plate 102 Polarizing Plate Protective Film 103A, 103B Active Energy Ray Curing Resin Layer 104 Polarizer 105 Retardation film 106 Liquid crystal display device 107 Liquid crystal cell

Claims (9)

A polarizing plate protective film disposed on a surface opposite to the liquid crystal cell of the polarizing plate provided on the liquid crystal cell,
Containing (meth) acrylic polymer (A) and cellulose ester resin (B),
The polarizing plate protective film, wherein the (meth) acrylic polymer (A) has at least a (meth) acrylic acid alkyl ester unit represented by the following general formula (1) as a constituent unit.

[Wherein, R ¹ represents a branched alkyl group having 3 to 18 carbon atoms, and R ² represents a hydrogen atom or a methyl group. ]   The cellulose ester unit constituting the cellulose ester resin (B) has an acyl group having 3 to 13 carbon atoms as a substituent, and the total number of carbon atoms in the substituent is 6 to 15 The polarizing plate protective film according to claim 1, wherein the protective film is a polarizing plate protective film. The polarizing plate protective film according to claim 1, wherein R ¹ in the general formula (1) is a branched alkyl group having a tertiary carbon atom.   The polarizing plate protection according to any one of claims 1 to 3, wherein a weight average molecular weight of the (meth) acrylic polymer (A) is in a range of 200,000 to 1,500,000. the film.   The substituent which the cellulose-ester unit which comprises the said cellulose-ester resin (B) has is an acyl group which has a carbon number in the range of 7-13, Any one of Claim 2-4 The polarizing plate protective film according to one item.   The ratio of the (meth) acrylic polymer (A) to the total film mass is in the range of 70 to 95 mass%, and the polarized light according to any one of claims 1 to 5. Board protection film. A polarizing plate comprising the polarizing plate protective film according to any one of claims 1 to 6,
The polarizing plate, wherein the polarizing plate protective film and the polarizer are bonded with an active energy ray-curable adhesive.   The polarizing plate according to claim 7, wherein a thickness of the polarizer is in a range of 2.0 to 15.0 μm. A liquid crystal display device in which at least the first polarizing plate A, the liquid crystal cell, and the second polarizing plate B are arranged in this order from the display surface side,
From the display surface side, the first polarizing plate A is composed of a polarizing plate protective film T1, a polarizer and a retardation film T2, and the second polarizing plate B is a retardation film T3, a polarizer and a polarizing plate protective film. It consists of T4, and both the said polarizing plate protective film T1 and the said polarizing plate protective film T4 are polarizing plate protective films as described in any one of Claim 1- Claim 6 characterized by the above-mentioned. Display device.

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