KR20170088974A - Polarizing plate protective film, production method therefor, polarizing plate, and liquid crystal display device - Google Patents

Abstract

An object of the present invention is to provide a polarizing plate protective film which has a high surface hardness even when it is made thin and can suppress the punching workability at the time of producing a polarizing plate and deterioration of the polarizer. The polarizing plate protective film of the present invention comprises a base film and an active energy pre-cured product layer, wherein the base film comprises a cellulose ester and a polyester-based additive represented by the following formula (1) The film thickness is 15 to 50 占 퐉, and the storage elastic modulus in the in-plane slow axis direction at 30 占 폚 is 5.0 to 7.0 GPa. Wherein B is a group derived from a hydroxyl group-containing monocarboxylic acid containing a cyclic structure, B is a group represented by the following formula (1): B- (GA)

Description

FIELD OF THE INVENTION [0001] The present invention relates to a polarizing plate protective film, a polarizing plate protective film, a polarizing plate protective film, a polarizing plate protective film, a polarizing plate protective film,

The present invention relates to a polarizing plate protective film, a manufacturing method thereof, a polarizing plate, and a liquid crystal display.

BACKGROUND ART Liquid crystal display devices (LCDs) are widely used as displays for large-size liquid crystal TVs, notebook computers, mobile phones, and the like. Such a liquid crystal display device includes a liquid crystal cell and a pair of polarizing plates for supporting the liquid crystal cell.

Among the pair of polarizing plates constituting the liquid crystal display device, in particular, the polarizing plate on the viewer side is required to have high scratch resistance in order to prevent the surface from being scratched. Therefore, it has been studied to increase the surface hardness of the polarizing plate protective film used for the polarizing plate on the viewing side.

As a method of increasing the surface hardness of the polarizing plate protective film, there is known a method of laminating a hard coating layer on a base film (for example, Patent Document 1). Further, as a method of increasing the surface hardness of the base film itself, a film comprising a cellulose ester and a hindered amine compound is known (for example, Patent Document 2).

As another polarizing plate protective film, a film comprising a cellulose ester and a high molecular weight plasticizer (Patent Document 3); A cellulose ester and a polyester diol having OH groups at both terminals (Patent Document 4); And a cellulose ester film produced under a specific stretching condition (Patent Document 5).

Japanese Patent Application Laid-Open No. 2013-127058 Japanese Patent Application Laid-Open No. 2010-228314 Japanese Patent No. 5028251 Japanese Patent No. 5422165 International Publication No. 2012/073692

However, the base film of Patent Document 1 or 2 does not have sufficient hardness (or elastic modulus). Therefore, when the base film is made thin, there is a problem that sufficient surface hardness of the polarizing plate protective film can not be obtained.

On the other hand, the polarizing plate protective films of Patent Documents 3 and 5 contain a polyester-based additive end-capped with an aromatic monocarboxylic acid, which tends to be harder than a certain degree, but tends to become brittle. When the polarizing plate including such a polarizing plate protective film is punched to a predetermined size, there is a problem that cracks or tip cracks are likely to occur at the cut surface of the polarizing plate.

The polarizing plate protective film of Patent Document 4 is liable to be deteriorated in water resistance because it contains a polyester-based additive at the end unsealed. For this reason, for example, when a water-repellent film is used at the time of producing a polarizing plate, moisture is hardly released from the protective film and the polarizer deterioration due to moisture may occur.

Thus, it is desired to obtain a polarizing plate having a high surface hardness without causing deterioration of the punching workability and polarizer deterioration at the time of polarizing plate production even if it is made thin. SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and an object thereof is to provide a polarizing plate protective film having a high surface hardness and capable of suppressing punching workability and polarizer deterioration at the time of producing a polarizing plate.

[1] A polarizing plate protective film comprising a base film and an active energy pre-cured product layer, wherein the base film comprises a cellulose ester and a polyester-based additive represented by the following formula (1) A film thickness of 15 to 50 占 퐉 and a storage elastic modulus in an in-plane slow axis direction at 30 占 폚 of 5.0 to 7.0 GPa.

(1): B- (GA) n-G-B

(Wherein B is a group derived from a hydroxyl group-containing monocarboxylic acid containing a cyclic structure, G is an alkylene diol having 2 to 12 carbon atoms, a cycloalkyl having 6 to 12 carbon atoms A group derived from at least one member selected from the group consisting of lanediol, an oxyalkylene diol having 4 to 12 carbon atoms and an arylene diol having 6 to 12 carbon atoms, A is an alkyl group having 4 to 12 carbon atoms A cycloalkylene dicarboxylic acid having 6 to 16 carbon atoms, and an arylene dicarboxylic acid having 8 to 16 carbon atoms; n Represents an integer of 0 or more)

[2] The polarizing plate protective film according to [1], wherein B in the formula (1) is a group derived from a hydroxyl group-containing monocarboxylic acid containing an aromatic hydrocarbon ring.

[3] The polarizing plate protective film according to [1] or [2], wherein the polyester-based additive has a number average molecular weight of 300 or more and less than 700.

[4] The polarizer protective film according to any one of [1] to [3], wherein the content of the polyester-based additive in the base film is 5 to 20 parts by mass relative to 100 parts by mass of the cellulose ester.

[5] The polarizing plate protective film according to any one of [1] to [4], wherein the active energy ray cured product layer is a hard coating layer or an antiglare layer.

[6] A method for producing a polarizing plate protective film according to any one of [1] to [5], wherein the film material containing a cellulose ester and a polyester-based additive represented by the following formula (1) At a temperature of 5 to 30% to obtain a base film; applying a composition for active energy ray cured product layer onto the base film, followed by drying and curing to obtain an active energy ray cured product layer Wherein the polarizing plate protective film comprises a polarizing plate.

(1): B- (GA) n-G-B

(Wherein B is a group derived from a hydroxyl group-containing monocarboxylic acid containing a cyclic structure, G is an alkylene diol having 2 to 12 carbon atoms, a cycloalkyl having 6 to 12 carbon atoms A group derived from at least one member selected from the group consisting of lanediol, an oxyalkylene diol having 4 to 12 carbon atoms and an arylene diol having 6 to 12 carbon atoms, A is an alkyl group having 4 to 12 carbon atoms A cycloalkylene dicarboxylic acid having 6 to 16 carbon atoms, and an arylene dicarboxylic acid having 8 to 16 carbon atoms; n Represents an integer of 0 or more)

[7] A polarizer comprising a polarizer and the polarizer protective film according to any one of [1] to [5], wherein the base film of the polarizer protective film is in contact with the polarizer.

[8] A liquid crystal display device comprising: a liquid crystal cell; a first polarizer plate and a second polarizer plate for supporting and supporting the liquid crystal cell, the first polarizer plate including a first polarizer and a polarizer Wherein the second polarizer has a second polarizer and a polarizer protective film disposed on a surface opposite to the liquid crystal cell of the second polarizer, wherein the polarizer protective film of the first polarizer comprises a protective film, Wherein the polarizing plate protective film according to any one of [1] to [5], wherein the base film of the polarizing plate protective film of the first polarizing plate is in contact with the first polarizing element, or the protective film of the second polarizing plate is [ And the base film of the polarizing plate protective film of the second polarizing plate is in contact with the second polarizing film.

According to the present invention, it is possible to provide a polarizing plate protective film which has a high surface hardness and can suppress the punching workability at the time of producing a polarizing plate and the deterioration of polarizer even if the film is thinned.

1 is an example showing a basic configuration of a liquid crystal display device of the present invention.

As described above, a cellulose ester film comprising a polyester-based additive end-capped with a " monocarboxylic acid having a ring structure but not containing a hydroxyl group " such as an aromatic monocarboxylic acid has a high elastic modulus However, it is likely to become brittle.

On the other hand, the inventors of the present invention found that a cellulose ester film comprising a polyester-based additive end-capped with a "monocarboxylic acid having a ring structure and containing a hydroxyl group" has a high elastic modulus and is hardly brittle I found out. This cause is not necessarily obvious, but it is assumed as follows. In a polyester-based additive having a "ring structure and also end-capped with a monocarboxylic acid containing a hydroxyl group", hydroxyl groups are likely to interact with each other. As a result, it is considered that the polyester-based additive is liable to be oriented by stretching and the elastic modulus tends to be high. In addition, it is considered that, by having a ring structure, the interaction of hydroxyl groups is likely to occur stably and the modulus of elasticity tends to be more effectively increased. In addition, toughness is likely to be imparted even though the ring structure is present due to the mutual action of the hydroxyl groups, and it is considered that it is hard to become brittle.

By further optimizing the content of the polyester-based additive and the stretching conditions, a cellulose ester film having a high storage modulus and a good toughness can be obtained. By making such a film a base film, a hard coating film having high surface hardness and punching workability of a good polarizing plate can be obtained.

On the other hand, a polyester-based additive end-capped with a "monocarboxylic acid containing a hydroxyl group" has water resistance lower than that of a polyester-based additive end-capped with a "monocarboxylic acid not containing a hydroxyl group" There is a tendency. In the present invention, since the monocarboxylic acid containing a hydroxyl group has a cyclic structure (capable of imparting hydrophobicity), the water resistance of the polyester-based additive can be secured. The present invention is based on these findings.

1. Polarizer protective film

The polarizer protective film has a base film and an active energy precursor layer.

1-1. Base film

The base film includes a cellulose ester and a polyester-based additive.

<Cellulose Ester>

Cellulose esters include cellulose, and carboxylic acids having 2 to 22 carbon atoms; Preferably an aliphatic carboxylic acid having 6 or less carbon atoms.

The acyl group contained in the cellulose ester may be linear or branched or may form a ring. The acyl group may be further substituted with another substituent. When the total substitution degree of the acyl group is the same, the number of carbon atoms of the acyl group is preferably 2 to 6 in view of reduction in birefringence when the number of carbon atoms in the acyl group is large. The cellulose ester includes two or more kinds of acyl groups having different carbon atoms; Preferably an acyl group having 2 or 3 carbon atoms or an acyl group having 2 or 4 carbon atoms.

Examples of cellulose esters include cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate propionate butyrate, cellulose acetate phthalate and the like.

Among these, cellulose esters satisfying the following formulas (1) and (2) are preferable. Wherein X is the degree of substitution of the acetyl group and Y is the degree of substitution of the propionyl group or the butyryl group.

2.0? X + Y? 3.0

(2) 0? Y? 1.5

Particularly, triacetyl cellulose and cellulose acetate propionate are preferably used. The triacetyl cellulose preferably has Y = 0 and also 2.5? X + Y? 2.98, more preferably Y = 0 and 2.7? X + Y? 2.95. The cellulose acetate propionate may preferably be 1.0? X? 2.5, 0.1? Y? 1.5 and 2.0? X + Y? 3.0. The degree of substitution degree of the acyl group can be measured according to ASTM-D817-96.

By setting the degree of substitution of the acyl group to a certain value or more, it is possible to suppress the occurrence of unnecessary birefringence or the influence of humidity by reducing the number of hydroxyl groups remaining in the pyranose ring constituting the cellulose skeleton.

The weight average molecular weight (Mw) of the cellulose ester is preferably from 80000 to 300000, more preferably from 100000 to 280000, and still more preferably from 230000 to 280000. The ratio Mw / Mn of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the cellulose ester is preferably 1.4 to 3.0, more preferably 1.7 to 2.2.

The weight average molecular weight of the cellulose ester can be measured using a commercially available gel permeation chromatography (GPC). The measurement conditions can be as follows.

(Measuring conditions)

Solvent: methylene chloride

Column: Shodex K806, K805, K803G (connected with three of the products manufactured by Showa Denko K.K.)

Column temperature: 25 ° C

Sample concentration: 0.1 mass%

Detector: RI Model 504 (manufactured by GL Science)

Pump: L6000 (manufactured by Hitachi Seisakusho Co., Ltd.)

Flow rate: 1.0 ml / min

Calibration curve: Standard polystyrene STK standard A calibration curve of 13 samples of polystyrene (manufactured by Tosoh Corporation) Mw = 1000000 to 500 is used. 13 samples are used at almost equal intervals.

The calcium content of the cellulose ester is preferably 50 ppm or less, more preferably 10 to 50 ppm. If the calcium content of the cellulose ester is less than a certain level, the increase in the haze over time of the base film can be effectively suppressed. The calcium content of the cellulose ester can be adjusted depending on the raw material selection and production conditions of the cellulose ester.

Cellulose to be a raw material for the cellulose ester may be wood pulp (softwood pulp, hardwood pulp), cotton linter, or the like. The calcium content of the cellulose ester can be adjusted by the kind of cellulose or the combination of plural kinds of cellulose. Pulp having a low calcium content as raw pulp; Specifically, a pulp having a calcium content of 20 ppm or less, preferably 10 ppm or less, and more preferably 5 ppm or less is used. Such raw pulp can be obtained by the method described in paragraphs 0062 to 0088 of Japanese Patent Laid-Open Publication No. 48214/1986.

&Lt; Polyester Additive >

The polyester-based additive may be obtained by subjecting a diol and a dicarboxylic acid to dehydration condensation reaction; Condensation reaction of a hydroxyl group (derived from a diol) at the molecular end of the obtained reaction product with a carboxyl group of a hydroxyl group-containing monocarboxylic acid having a cyclic structure.

The polyester-based additive is preferably a compound represented by the following formula (1).

(1): B- (GA) n-G-B

B in the formula (1) is a group derived from a monocarboxylic acid containing a hydroxyl group having a cyclic structure. The ring structure refers to a structure having an aliphatic hydrocarbon ring, an aliphatic heterocycle, an aromatic hydrocarbon ring or an aromatic heterocycle, and preferably refers to a structure having an aliphatic hydrocarbon ring or an aromatic hydrocarbon ring. The hydroxyl group-containing monocarboxylic acid having a cyclic structure may be an alicyclic monocarboxylic acid having 5 to 20 carbon atoms, an aromatic monocarboxylic acid having 7 to 20 carbon atoms, and a mixture thereof.

The alicyclic monocarboxylic acid having 5 to 20 carbon atoms is preferably an alicyclic monocarboxylic acid having 6 to 15 carbon atoms. Examples of the alicyclic monocarboxylic acid include 4-hydroxycyclohexyl acetic acid, 3-hydroxycyclohexyl acetic acid, 2-hydroxycyclohexyl acetic acid, 4-hydroxycyclohexylpropionic acid, 4-hydroxycyclohexylbutyric acid, 4-hydroxy cyclohexyl acetic acid, 4-hydroxy cyclohexyl acetic acid, 4-hydroxy cyclohexyl acetic acid, 4-hydroxycyclohexyl acetic acid, dihydroxycyclohexyl acetic acid, 2,4-dihydroxycyclohexyl acetic acid, 2,5-dihydroxycyclohexyl acetic acid, 2- (hydroxymethyl) cyclohexyl Acetic acid, 3- (hydroxymethyl) cyclohexyl acetic acid, 4- (hydroxymethyl) cyclohexyl acetic acid, 2- (1-hydroxy- -Methylethyl) cyclohexyl acetic acid, 4- (1-hydroxy-1-methylethyl) cyclohexyl acetic acid And the like.

The aromatic monocarboxylic acid having 5 to 20 carbon atoms may preferably be an aromatic monocarboxylic acid having 6 to 15 carbon atoms. Examples of the aromatic monocarboxylic acids include 4-hydroxybenzoic acid, 3-hydroxybenzoic acid, 2-hydroxybenzoic acid, 4-hydroxy-o-tolylic acid, 3-hydroxy- dihydroxybenzoic acid, 2- (hydroxymethyl) benzoic acid, 3- (hydroxymethyl) benzoic acid, 2-hydroxybenzoic acid, Benzoic acid, 4- (hydroxymethyl) benzoic acid, 2- (1-hydroxy-1-methylethyl) -Methylethyl) benzoic acid and the like.

Of these, from the viewpoint of imparting sufficient hydrophobicity to the polarizing plate protective film and suppressing deterioration of the polarizer by moisture, it is preferable to use a monocarboxylic acid containing a hydroxyl group containing an aromatic hydrocarbon ring (aromatic monocarboxylic acid containing a hydroxyl group Is preferred.

G in the formula (1) represents an alkylene diol having 2 to 12 carbon atoms, a cycloalkylene diol having 6 to 12 carbon atoms, an oxyalkylene diol having 4 to 12 carbon atoms and an oxyalkylene diol having 6 to 12 carbon atoms Arylenediols, and arylene diols.

Examples of the alkylene diol having 2 to 12 carbon atoms include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, -Methyl 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2- Propanediol (3,3-dimethylol pentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3- Hexanediol, 2,2,4-trimethyl 1,3-pentanediol, 2-ethyl 1,3-hexanediol, 2-methyl 1,8-octanediol, 1,9- Decanediol, 1,12-octadecanediol, and the like.

Examples of cycloalkylene diols having 6 to 12 carbon atoms include hydrogenated bisphenol A (2,2-bis (4-hydroxycyclohexyl) propane), hydrogenated bisphenol B (2,2-bis (4-hydroxycyclohexyl ) Butane and the like.

Examples of the oxyalkylene diol having 4 to 12 carbon atoms include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol and the like.

Examples of the arylene diol having 6 to 12 carbon atoms include bisphenol A, bisphenol B, and the like.

The diol is used as one or a mixture of two or more kinds. Of these, alkylene glycols having 2 to 12 carbon atoms are preferable because they are excellent in compatibility with cellulose esters.

A in the formula (1) represents an alkylene dicarboxylic acid having 4 to 12 carbon atoms, a cycloalkylene dicarboxylic acid having 6 to 16 carbon atoms, and an arylene dicarboxylic acid having 8 to 16 carbon atoms &Lt; / RTI &gt; is a group derived from at least one species selected from the group consisting of

Examples of the alkylene dicarboxylic acid having 4 to 12 carbon atoms include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid and the like.

Examples of the cycloalkylene dicarboxylic acid having 6 to 16 carbon atoms include 1,2-cyclohexane dicarboxylic acid, 1,3-cyclohexane dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid, 1,5-decahydronaphthalene dicarboxylic acid, 1,4-decahydronaphthalene dicarboxylic acid, and the like.

Examples of the arylene dicarboxylic acid having 8 to 16 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalene dicarboxylic acid, 1,4-naphthalene dicarboxylic acid and the like.

The dicarboxylic acid is used as one kind or a mixture of two or more kinds. The dicarboxylic acid is preferably a mixture of an alkylene dicarboxylic acid and an arylene dicarboxylic acid. The content of the alkylene dicarboxylic acid and the arylene dicarboxylic acid is preferably from 40:60 to 99: 1, and more preferably from 50:50 to 90:10, Is more preferable.

N in the formula (1) is an integer of 0 or more, and the number average molecular weight can be set to be in the range described later.

G in the formula (1) includes a group derived from a cycloalkylene diol having 6 to 12 carbon atoms in view of facilitating the storage elastic modulus of the base film. Or a group derived from a cycloalkylene dicarboxylic acid having 6 to 12 carbon atoms or an arylene dicarboxylic acid having 8 to 16 carbon atoms in the formula (1). Since the polyester-based additives including these groups have a rigid structure, it is easy to increase the storage modulus of the base film.

The number average molecular weight of the polyester-based additive is preferably 300 to 30,000, more preferably 300 to less than 700, and still more preferably 300 to 600. If the number average molecular weight is more than a certain value, it is easy to suppress bleeding out. When the number average molecular weight is less than a certain value, compatibility with the cellulose ester is hardly impaired, haze rise is suppressed easily, and orientation is easily caused by stretching and the storage elastic modulus is easily increased.

The number average molecular weight of the polyester-based additive can be measured by gel permeation chromatography. Specifically, the number average molecular weight (Mn) of the ester compound in terms of standard polystyrene was measured using a gel permeation chromatography (GPC) measuring device ("HLC-8330" manufactured by Tosoh Corp.) under the following measurement conditions can do.

(Measuring conditions)

Column: Two "TSK gel SuperHZM-M" and two "TSK gel SuperHZ-2000"

Guard column: "TSK SuperH-H"

Developing solvent: tetrahydrofuran

Flow rate: 0.35 ml / min

The number average molecular weight of the polyester-based additive can be adjusted by the reaction time of condensation or polycondensation.

The acid value of the polyester-based additive is preferably 0.5 mgKOH / g or less, more preferably 0.3 mgKOH / g or less. The hydroxyl value of the polyester-based additive is preferably 25 mgKOH / g or less, and more preferably 15 mgKOH / g or less.

The synthesis of the polyester-based additive can be carried out by a thermal melt-condensation method by an esterification reaction or transesterification reaction of a dicarboxylic acid, a diol and a terminal-sealing monocarboxylic acid by a usual method; Or an interfacial condensation method of an acid chloride of a dicarboxylic acid and a monocarboxylic acid for terminal sealing with a diol. The charging ratio of the diol and the dicarboxylic acid is adjusted so that the molecular end becomes a diol.

The content of the polyester-based additive in the base film is preferably 5 to 20 parts by mass, more preferably 8 to 15 parts by mass based on 100 parts by mass of the cellulose ester. If the content of the polyester-based additive is more than a certain level, the storage elastic modulus of the base film can be sufficiently increased without increasing the brittleness. If the content of the polyester-based additive is less than a certain level, there is no possibility of bleeding out or increase in internal haze.

&Lt; Acrylic copolymer &

The base film may further comprise an acrylic copolymer, if necessary, for adjusting the retardation value and the like.

The acrylic copolymer is an acrylic polymer having a weight average molecular weight of 500 to 30000; Preferably a polymer having a weight average molecular weight of 5000 to 30000 obtained by copolymerizing an ethylenically unsaturated monomer having no aromatic ring and a hydrophilic group in a molecule with an ethylenically unsaturated monomer having a hydrophilic group without an aromatic ring in the molecule; More preferably a polymer having a weight average molecular weight of 5000 to 30000 that is obtained by copolymerizing an ethylenically unsaturated monomer having no aromatic ring and a hydrophilic group in the molecule with an ethylenically unsaturated monomer having a hydrophilic group having no aromatic ring in the molecule, Or a mixture of polymers having a weight average molecular weight of 500 to 3000 obtained by polymerizing an ethylenically unsaturated monomer.

<Ultraviolet absorber>

The base film may further include an ultraviolet absorber if necessary in order to improve the weather resistance. The ultraviolet absorber may preferably have a transmittance at a wavelength of 370 nm of 10% or less, more preferably 5% or less, further preferably 2% or less.

Examples of ultraviolet absorbers include oxybenzophenone compounds, benzotriazole compounds, salicylic ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, nickel complex salts compounds and inorganic powders . Above all, a benzotriazole-based ultraviolet absorber, a benzophenone-based ultraviolet absorber and a triazine-based ultraviolet absorber are preferable, and a benzotriazole-based ultraviolet absorber and a benzophenone-based ultraviolet absorber are more preferable.

The content of the ultraviolet absorber varies depending on the kind of the ultraviolet absorber and the conditions of use. When the thickness of the base film is 30 to 200 mu m, the content is preferably 0.5 to 10 mass%, more preferably 0.6 to 4 mass% desirable.

&Lt; Particles (Mat) >

The base film may further include fine particles (made of a mat) for imparting slippery properties to the surface. The fine particles may be composed of an inorganic compound or a resin.

Examples of the inorganic compound include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate.

Examples of the resin include a silicone resin, a fluororesin, and an acrylic resin. Among them, silicone resin is preferable, and it is particularly preferable to have a three-dimensional network structure. For example, Tosepearl 103, Copper 105, Copper 108, Copper 120, Copper 145, Copper 3120 and Copper 240 ), Which is commercially available under the trade name of Mitsubishi Chemical Corporation.

Of these, fine particles of silicon dioxide are preferable in that the turbidity of the film can be lowered. Examples of fine particles of silicon dioxide include Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50 and TT600 (manufactured by Nippon Aerosil Co., Ltd.) Aerosil 200V and Aerosil R972V are preferable in that the effect of lowering the friction coefficient is great.

The average particle diameter of the primary particles of the fine particles is preferably 5 to 400 nm, more preferably 10 to 300 nm. The fine particles may be mainly contained as secondary aggregates having a particle diameter of 0.05 to 0.3 탆 or may be contained as primary particles without aggregation if the particles have an average particle diameter of 100 to 400 nm.

The fine particles are preferably added so that the kinetic friction coefficient of the surface of the base film is 0.2 to 1.0. Specifically, the content of the fine particles may be 0.01 to 1% by mass, preferably 0.05 to 0.5% by mass, based on the base film.

1-2. Method for producing base film

The base film can be produced by any method, but it is preferable that the base film is produced by a solution casting method, from the viewpoint of easy film formation even if the resin has a relatively large molecular weight. Specifically, the base film is formed by 1) a step of dissolving each of the above-mentioned respective components in a solvent to prepare a dope solution, 2) a step of softening the dope liquid on an endless metal support, 3) A step of obtaining a film-like material, and 4) a step of drying and drawing the film-like material.

In the step 4), it is preferable to stretch the film-like material while drying it, in order to increase the storage elastic modulus of the base film. The stretching can be performed in the width direction or the film formation direction, or both of them.

The stretching ratio in the maximum stretching direction (direction in which the stretching ratio is maximized) is preferably 5 to 30%, more preferably 12 to 28%. For example, in the case of stretching in two axial directions orthogonal to each other, 0 to 15% in the transport direction (MD direction) and 5 to 30% in the width direction (TD direction) can be set. The draw ratio (%) is defined by the following formula.

(Elongation direction) length of the film before stretching) / (length of stretching direction) of the film before stretching)} x 100

The stretching temperature may be 120 to 180 占 폚, preferably 140 to 180 占 폚, and more preferably 145 to 165 占 폚. By stretching at the above-mentioned temperature and magnification, sufficient stretching stress can be applied to the film, so that the storage elastic modulus of the resulting film can be effectively increased.

The residual solvent of the film-shaped material at the start of the stretching may preferably be less than 5% by mass, more preferably 4% by mass or less, and still more preferably 2% by mass or less, from the viewpoint of suppressing the rise in haze. In order to maintain the residual solvent at the time of starting the drawing at less than 5 mass%, it is preferable that the drying step is carried out to evaporate the solvent in the process of separating and transporting the flexible dope from the metal support.

A method of stretching the film-like material is not particularly limited, and a method in which a peripheral speed difference is placed on a plurality of rolls, and the film is stretched in the MD direction using a roll speed difference; A method in which both ends of the film-like material are fixed with clips or fins by a tenter, and the intervals between the clips and the fins are extended in the TD direction. Among them, stretching in the TD direction is preferably performed by a tenter, and it may be a pin tenter or a clip tenter.

For other processes, known solution casting methods; For example, in paragraphs 0109 to 0140 of Japanese Patent Laid-Open Publication No. 2012-48214.

<Physical Properties of Base Film>

(Storage elastic modulus)

The storage elastic modulus of the base film in the in-plane slow axis direction at 30 캜 is preferably 5.0 to 7.0 GPa, more preferably 5.5 to 7.0 GPa.

The storage elastic modulus can be measured by the following method. The base film was cut into a size of 5 mm width × length (length in the in-plane slow axis direction) of 50 mm, and used as a sample. The sample is conditioned at 23 ° C and 55% RH for 24 hours. The obtained sample is stretched in the longitudinal direction under an environment of 23 占 폚 and 55% RH while heating at the following conditions, and a temperature-storage elastic modulus curve is obtained. From the obtained curve, the value of the storage elastic modulus at 30 占 폚 is read and is referred to as &quot; storage elastic modulus in the in-plane slow axis direction at 30 占 폚. &Quot;

Measuring apparatus: manufactured by TS Instruments RSAIII

Sample size: width 5mm, length 50mm

Gap: 20mm

Measurement conditions: Tensile mode

Measuring temperature: 25 to 210 DEG C

Temperature rise condition: 5 ° C / min

Frequency: 1Hz

The in-plane slow axis in the base film is the axis in the direction in which the refractive index in the plane becomes maximum. The in-plane slow axis is usually the maximum stretching direction, and may be, for example, the TD direction (width direction) in the rolled base material film. The angle? 1 (orientation angle) formed by the film width direction of the in-plane slow axis can be set to be ± 1 ° or less, preferably, ± 0.5 ° or less. The measurement of the angle? 1 formed by the in-plane slow axis direction and the film width direction or the longitudinal direction (preferably the width direction) thereof is carried out using an automatic birefringence system KOBRA-21ADH or KOBRA-WR (Oji Keisoku Kikuchi) And can be performed at a wavelength of 590 nm.

The storage elastic modulus of the base film can be adjusted by the content of the above-described polyester-based additive and the stretching conditions. In order to increase the storage elastic modulus of the base film, the content of the polyester-based additive is set to 5 parts by mass or more based on 100 parts by mass of the cellulose ester; It is also preferable that the stretching temperature is 140 占 폚 or more and the stretching magnification is 5% or more. In addition, it is also possible to increase the storage elastic modulus by setting the polyester-based additive to "a structure containing an aromatic ring or an aliphatic ring" or by setting the molecular weight to a certain value or less.

(Breaking extension)

The elongation at break of the base film may preferably be 10 to 80%, more preferably 20 to 50%.

(Internal haze)

The internal haze of the base film measured by the method in accordance with JIS K-7136 may be less than 1%, preferably not more than 0.1%, more preferably not more than 0.05%.

The internal haze can be adjusted by the molecular weight or the content of the polyester-based additive. In order to lower the internal haze, for example, the molecular weight and content of the polyester-based additive may be set to a certain value or less, or an aromatic hydrocarbon ring having a high affinity with the cellulose ester may be introduced into the monocarboxylic acid containing a hydroxyl group, Or the like.

(thickness)

The base film may preferably be 10 to 80 占 퐉, more preferably 10 to 60 占 퐉, and still more preferably 15 to 50 占 퐉. As described above, since the substrate film has a sufficient storage elastic modulus even if the thickness is as thin as 50 m or less, the hardness of the polarizing plate protective film can be increased to a certain level or higher.

1-3. Active energy ray hardened layer

The active energy ray cured layer may preferably be a hard coating layer or an antiglare layer. By providing the active energy ray ray cured product layer on the base film, the surface hardness of the whole film can be increased.

The active energy pre-cured layer may be a cured product of a coating film containing a curable compound, a photopolymerization initiator, and a coating liquid for a curable active energy ray layer containing a solvent.

<Curable compound>

The curable compound contained in the coating liquid for the active energy ray curable layer is a compound that cures upon irradiation with an active energy ray and is preferably a compound having an ethylenically unsaturated double bond and more preferably an acrylate compound.

The acrylate compound is preferably a polyfunctional acrylate having at least two acryloyloxy groups and / or a methacryloyloxy group in the molecule. The polyfunctional acrylate is at least one selected from the group consisting of pentaerythritol polyfunctional acrylate, dipentaerythritol polyfunctional acrylate, pentaerythritol polyfunctional methacrylate and dipentaerythritol polyfunctional methacrylate desirable.

<Photopolymerization initiator>

Examples of the photopolymerization initiator contained in the coating liquid for the active energy ray curing layer include acetophenone, benzophenone, hydroxybenzophenone, Michler's ketone,? -Amyloxime ester, thioxanthone, and derivatives thereof. The content of the photopolymerization initiator may be 0.01 to 20 parts by mass based on 100 parts by mass of the curable compound.

<Solvent>

Examples of the solvent contained in the coating liquid for the active energy ray-

Ketones such as methyl ethyl ketone, acetone, cyclohexanone and methyl isobutyl ketone;

Esters such as methyl acetate, ethyl acetate, butyl acetate, propyl acetate, and propylene glycol monomethyl ether acetate;

Alcohols such as ethanol, methanol, butanol, n-propyl alcohol, isopropyl alcohol and diacetone alcohol;

Hydrocarbons such as toluene, xylene, benzene, and cyclohexane;

And glycol ethers such as propylene glycol monomethyl ether, propylene glycol monopropyl ether, and ethylene glycol monopropyl ether. Among them, esters, glycol ethers and alcohols are preferable, and propylene glycol mono (alkyl group having 1 to 4 carbon atoms) alkyl ether or propylene glycol mono (alkyl group having 1 to 4 carbon atoms) By mass or more, and more preferably 5 to 80% by mass or more.

The coating liquid for the active energy ray curing layer may further include a leveling agent for increasing the coating property as required, and fine particles for adjusting the hardness and refractive index of the active energy ray cured layer.

<Leveling agent>

Preferred examples of leveling agents include fluorine-siloxane graft compounds. The fluorine-siloxane graft compound is a copolymer obtained by grafting at least a polysiloxane and / or an organopolysiloxane containing a siloxane and / or an organosiloxane group to a fluorine resin. Commercially available examples of the fluorine-siloxane graft compound include ZX-022H, ZX-007C, ZX-049 and ZX-047-D manufactured by Fuji Kasei Kogyo K.K.

&Lt; Particles >

The coating liquid for the active energy ray-curing layer may further contain fine particles as necessary in order to adjust the hardness and refractive index of the cured product, or to impart irregularities to the surface to impart an antiglare function (anti-glare function). The fine particles may be organic fine particles or inorganic fine particles.

As the organic fine particles, particles comprising a methyl methacrylate-divinylbenzene copolymer resin, a polysiloxane resin, a polystyrene resin, a melamine resin, a benzoguanamine resin and a composite of these resins are preferably used.

The inorganic fine particles may be the same as the fine particles added as the matting agent to the above-mentioned base film, and are preferably fine particles of silicon dioxide (silica). The fine particles of silica may be the reactive silica fine particles of paragraphs 0230 to 0258 of International Publication No. 2011/158626 from the viewpoint of enhancing the dispersibility.

The coating liquid for the active energy rays hardening layer may contain metal oxide fine particles in view of making it easier to adjust the refractive index of the cured product. The refractive index of the metal oxide fine particles measured at a wavelength of 550 nm is preferably 1.80 to 2.60, and more preferably 1.85 to 2.50. Examples of such metal oxide fine particles include zirconium oxide, antimony oxide, tin oxide, zinc oxide, indium tin oxide (ITO), antimony doped tin oxide (ATO) and zinc antimonate, Zinc particles.

The average particle diameter of the primary particles of the metal oxide fine particles is preferably 10 nm to 200 nm, more preferably 10 to 150 nm. The average particle diameter of the metal oxide fine particles can be measured from an electron microscope photograph by a scanning electron microscope (SEM) or the like.

For example, the refractive index of the hard coating layer measured at 23 DEG C and at a wavelength of 550 nm may be 1.4 to 2.2. The refractive index of the hard coat layer can be adjusted by the addition amount of the metal oxide fine particles or the like.

The thickness of the active energy ray ray hardened layer is preferably 3 to 30 占 퐉, more preferably 5 to 15 占 퐉, from the viewpoint of obtaining sufficient hardness. In view of the high hardness of the base film described above, even if the thickness of the active energy rays pre-cured product layer is reduced to, for example, 15 占 퐉 or less, high hardness is likely to be obtained.

The polarizing plate protective film of the present invention may further include functional layers such as an antistatic layer, a back coat layer, an active facilitating layer, an adhesive layer, a barrier layer, and an antireflection layer, if necessary.

1-4. Method for producing polarizing plate protective film

The polarizing plate protective film of the present invention comprises the steps of 1) preparing the base film described above, and 2) applying a coating liquid for curing an active energy ray curable material layer onto the base film, drying and curing the active energy ray curable material layer And can be produced through a process of obtaining.

The step of preparing the base film of 1) It can be carried out in the same manner as the production method of the base film.

Application of the coating liquid for the active energy ray-cured layer in the above 2) can be performed by any means such as dipping, die coatering, wirebinding, spraying and the like.

Coating hardening of the coating liquid for the active energy rays hardening layer in the above 2) can be carried out by irradiating active energy rays. Examples of the light source for irradiating the active energy ray (preferably ultraviolet ray) include a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra high pressure mercury lamp, a carbon arc lamp, a metal halide lamp and a xenon lamp. The irradiation light amount may be about 20 to 10,000 mJ / cm2, preferably 50 to 2,000 mJ / cm2. The irradiation time is preferably 0.5 seconds to 5 minutes, more preferably 3 seconds to 2 minutes from the viewpoint of working efficiency and the like.

1-5. Properties of Protective Film for Polarizer

(Hardness)

The polarizing plate protective film may have a high hardness. Specifically, the hardness of the polarizing plate protective film is a pencil hardness of 2.8H or more, preferably 3H or more, more preferably 3.5H or more, and even more preferably 4H or more. Thereby, it is possible to make it difficult to scratch the surface of the liquid crystal display device, for example, in use.

The pencil hardness can be measured by a pencil height evaluation method in accordance with JIS K5400. Specifically, the polarizing plate protective film is humidity-conditioned at 23 캜 and 55% RH for 24 hours. Thereafter, the surface of the active energy ray cured product layer was scratched with a test pencil of each hardness specified in JIS S 6006 using a weight of 1 kg, and the operation was repeated five times. Then, the maximum value of the hardness at which the scratch becomes one or less is obtained. The larger the maximum value, the higher the hardness.

(Retardation)

The retardation R ₀ in the in-plane direction of the polarizing plate protective film measured under conditions of a measurement wavelength of 590 nm and 23 캜 55% RH is, for example, 0 to 10 nm; The retardation Rth in the thickness direction may be, for example, -5 to 20 nm. The polarizing plate protective film whose retardation value is within the above range is suitable as the protective films F1 and F4 of a liquid crystal display device described later.

The retardation R ₀ and Rth are respectively defined by the following formulas.

Formula _{(I): R 0 = (} nx-ny) × d (nm)

Rth = {(nx + ny) / 2-nz} xd (nm)

(In the formulas (I) and (II)

nx represents a refractive index in the slow axis direction x at which the refractive index becomes the maximum in the in-plane direction of the film;

ny represents a refractive index in an in-plane direction of the film in a direction y perpendicular to the slow axis direction x;

nz represents the refractive index in the thickness direction z of the film;

d (nm) denotes the thickness of the film)

The retardation R ₀ and Rth can be obtained, for example, by the following methods.

1) Moisture the polarizing plate protective film at 23 ° C and 55% RH. The average refractive index of the polarizing plate protective film after humidity control is measured by an Abbe refractometer or the like.

2) R ₀ when light with a measurement wavelength of 590 nm is incident on the polarizing plate protective film after humidity control parallel to the normal line of the film surface is measured by KOBRA21DH, Oji Keisuke Co., Ltd.

3) When the light in a wavelength of 590 nm was incident on the retardation axis (rotation axis) of the polarizing plate protective film of the polarizing plate protective film by using KOBRA21ADH from the angle of the angle (incident angle (?)) (?) Is measured. The measurement of the retardation value R ([theta]) can be performed at six points every 10 degrees within the range of 0 DEG to 50 DEG. The in-plane slow axis refers to the axis at which the medium refractive index in the film surface is maximized, and can be confirmed by KOBRA21ADH.

4) From the measured R ₀ and R (θ) and the above-described average refractive index and film thickness, nx, ny and nz are calculated by KOBRA 21ADH to calculate Rth at a measurement wavelength of 590 nm. The measurement of the retardation can be performed under conditions of 23 占 폚 and 55% RH.

2. Polarizer

The polarizing plate of the present invention comprises a polarizer and the above-mentioned polarizing plate protective film. The polarizing plate protective film is disposed such that the base film is in contact with the polarizer.

2-1. Polarizer

The polarizer is an element which allows only the birefringent light in a certain direction to pass therethrough, and a typical polarizer currently known is a polyvinyl alcohol polarizing film. The polyvinyl alcohol polarizing film includes a polyvinyl alcohol film stained with iodine and a dichroic dye stained.

The polyvinyl alcohol polarizing film may be a film obtained by uniaxially stretching a polyvinyl alcohol film and then dyed with iodine or a dichroic dye (preferably a film which is also subjected to a durability treatment with a boron compound); The film may be a uniaxially stretched film (preferably, a film obtained by durability treatment with a boron compound) after the polyvinyl alcohol film is dyed with iodine or a dichroic dye. The absorption axis of the polarizer is parallel to the stretching direction of the film.

For example, an ethylene-modified (meth) acrylate having an ethylene unit content of 1 to 4 mol%, a degree of polymerization of 2000 to 4000 and a degree of saponification of 99.0 to 99.99 mol% as disclosed in Japanese Patent Application Laid-Open Nos. 2003-248123 and 2003-342322 Polyvinyl alcohol and the like are used. Among them, an ethylene-modified polyvinyl alcohol film having a hot water cutting temperature of 66 to 73 占 폚 is preferably used.

The thickness of the polarizer is preferably from 5 to 30 占 퐉, and more preferably from 10 to 20 占 퐉, from the viewpoint of thinning the polarizing plate.

2-2. Another polarizer protective film

On the other side of the polarizer, the aforementioned polarizing plate protective film or base film may be arranged if necessary; Another polarizing plate protective film may be disposed.

Examples of other polarizing plate protective films include commercially available cellulose acylate films (for example, Konica Minolta Tact KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC4FR-1 , KC8UY-HA, KC8UX-RHA, KC8UE, KC4UE, KC4HR-1, KC4KR-1, KC4UA, KC6UA and more) available from Konica Minolta Opto.

The retardation of the other polarizing plate protective film may vary depending on the type of the liquid crystal cell to be combined. For example, the in-plane retardation Ro (590) measured at a wavelength of 590 nm under a condition of 23% RH and 55% , And the retardation Rt (590) in the thickness direction is preferably 70 to 300 nm. The protective film having the retardation within the above range is suitable as a retardation film (protective films (F2, F3) described later) such as a VA type liquid crystal cell. Each retardation value can be measured in the same manner as described above.

The thickness of the other polarizing plate protective film is not particularly limited, but is preferably 10 to 250 占 퐉, more preferably 10 to 100 占 퐉, and particularly preferably 30 to 60 占 퐉.

The polarizing plate of the present invention comprises a step of bonding a polarizer and a polarizing plate protective film of the present invention via an adhesive; And then cutting the bonded laminate to a predetermined size.

The adhesive to be used for bonding may be a completely saponified polyvinyl alcohol aqueous solution (water-soluble) or an active energy ray-curable adhesive.

The polarizing plate protective film of the present invention may have an appropriate toughness, as described above. Therefore, in the step of cutting the polarizing plate to a predetermined size, it is possible to suppress occurrence of cracks or tip cracks on the cut surface, and the workability of the polarizing plate can be enhanced. In addition, since the polarizing plate protective film of the present invention has a high surface hardness, the obtained polarizing plate can also have a high surface hardness.

Further, since the polarizing plate protective film of the present invention includes a terminally-sealed polyester-based additive, it can have water resistance. Therefore, the polarizing plate protective film of the present invention can suppress deterioration of the polarizer due to moisture.

3. Liquid crystal display

A liquid crystal display device of the present invention includes a liquid crystal cell and a pair of polarizing plates for supporting the liquid crystal cell.

1 is a schematic diagram showing an example of a basic configuration of a liquid crystal display device. 1, the liquid crystal display 10 of the present invention includes a liquid crystal cell 30, a first polarizing plate 50 and a second polarizing plate 70 for supporting and supporting the liquid crystal cell 30, and a backlight 90 .

The display mode of the liquid crystal cell 30 may be any of various display modes such as STN, TN, OCB, HAN, VA (MVA, PVA), and IPS. In order to obtain high contrast, .

The first polarizing plate 50 includes a first polarizer 51 and a polarizing plate protective film 53 (F1) disposed on the side opposite to the liquid crystal cell of the first polarizing bar 51, And a polarizing plate protective film 55 (F2) disposed on the side of the liquid crystal cell.

The second polarizing plate 70 includes a second polarizer 71 and a polarizing plate protective film 73 (F3) disposed on the side of the liquid crystal cell side of the second polarizing plate 71 and a liquid crystal cell of the second polarizing plate 71 A polarizing plate protective film 75 (F4) disposed on the opposite side. One of the polarizer protective films 55 (F2) and 73 (F3) may be omitted if necessary.

At least one of the polarizing plate protective films 53 (F1) and 75 (F4); Preferably, the polarizing plate protective film 53 (F1) may be the polarizing plate protective film of the present invention. The polarizing plate protective film 53 (F1) has a base film 53A and an active energy ray cured product layer 53B and the base film 53A is in contact with the first polarizer 51. The liquid crystal display device in which the polarizing plate protective film 53 (F1) is the polarizing plate protective film of the present invention has a high scratch resistance on the surface, so that the display screen can be hardly scratched.

The polarizing plate protective film of the present invention can be preferably used not only as a polarizing plate protective film of a liquid crystal display device but also as a protective film for an image display device provided with a touch panel or an image display device such as an organic EL display or a plasma display .

Example

Hereinafter, the present invention will be described with reference to Examples. The scope of the present invention is not limited by the examples.

1. Materials

(1) Cellulose ester

<Synthesis of cellulose ester 1>

50 parts by mass of acetic acid was added to raw pulp (93% or more of? -Cellulose, water content 8.5%, calcium content in pulp 25 ppm: manufactured by Nippon Seishi Co., Ltd.) and activation treatment was performed for 1 hour. The resulting acetic acid-containing pulp was put in a reactor, and 500 parts by mass of acetic anhydride and 12 parts by mass of sulfuric acid were added thereto, and the temperature was gradually raised from room temperature to 40 占 폚. Then, the mixture was incubated at 40 캜 for one hour to proceed the esterification reaction.

Subsequently, 250 parts of a 30% aqueous acetic acid solution was added to neutralize (primary neutralization step); To neutralize the sulfuric acid, 15 parts by mass of an aqueous solution of 30% by mass of magnesium acetate was added and neutralized (reaction stopping step); To hydrolyze the remaining carboxylic anhydride, 150 parts by mass of an 80% by mass aqueous acetic acid solution was added and the mixture was kept at 60 ° C and stirred for 1 hour (aging step).

Subsequently, to neutralize the sulfuric acid, 15 mass parts of an aqueous solution of magnesium acetate of 30 mass% was added (the aging reaction stopping step). Hydrophilic silica particles having a hydrophilic group and having an average particle size of 30 占 퐉 were added to the dope after the termination of the aging reaction, stirred for 5 minutes, and then dope with acetic acid was filtered with a glass filter (filtration step).

Thereafter, the precipitated cellulose acylate was separated by filtration, washed with hot water at 50 占 폚 five times, and the remaining aqueous acetic acid solution was eluted and then dried at 70 占 폚 for 3 hours to obtain a cellulose acylate having an acetyl group substitution degree of 2.89, To obtain the triacetylcellulose of Figure 2.89. The weight average molecular weight (Mw) was measured by the above-mentioned method and found to be 260,000.

(Calcium amount measurement)

3.0 g of the obtained triacetylcellulose sample was employed as a crucible, carbonized on a heater, put into an electric furnace, and stirred at 800 占 폚 for about 2 hours. This was covered with a lid and allowed to cool. Then, 25 ml of 0.07% hydrochloric acid solution was added, and the mixture was heated on a hot plate. After this was allowed to cool, the solution was transferred to a 200 ml flask. The crucible was rinsed with distilled water, and the solution was transferred to a flask, and distilled water was injected to the top. Using this as a sample solution, the absorbance was measured using an atomic absorption spectrophotometer, and the amount of Ca in the sample was determined. As a result, the calcium amount was 25 ppm.

(2) Polyester additive

&Lt; Synthesis of polyester compound T1 >

410 parts of ethylene glycol, 341 parts of terephthalic acid and succinic acid in a molar ratio of 5: 5, 610 parts of 4-hydroxybenzoic acid, and 0.35 part of tetraisopropyl titanate as an esterification catalyst were added to a 2 L flask equipped with a thermometer, The flask was charged into a four-necked flask, and a reflux condenser was attached thereto with stirring in a nitrogen stream. Heating was continued at 230 캜 until the acid value became 2 or less while refluxing an excessive amount of monohydric alcohol, Respectively. Subsequently, unreacted ethylene glycol was distilled off at 200 DEG C under a reduced pressure of 4 x 10 &lt; ² &gt; Pa or less to obtain a polyester compound T1.

&Lt; Synthesis of polyester compounds T2 to T5 >

Polyester compounds T2 to T5 were obtained in the same manner as in Example 1, except that the kinds or molecular weights of the diol, dicarboxylic acid and monocarboxylic acid for terminal sealing were changed as shown in Table 1.

<Synthesis of Comparative Polyester Compounds H1 to H8>

Comparative polyester compounds H1 to H8 were obtained in the same manner, except that the kind or molecular weight of the diol, dicarboxylic acid and monocarboxylic acid for terminal sealing was changed as shown in Table 1.

The number average molecular weight of the obtained polyester compound was measured by the following method. The results are shown in Table 1.

(Measurement of Number Average Molecular Weight (Mn)) [

The number average molecular weight (Mn) of the polyester compound in terms of standard polystyrene was measured under the following conditions using a gel permeation chromatography (GPC) measuring device ("HLC-8330" manufactured by Tosoh Corporation).

Column: Two "TSK gel Super HZM-M" and two "TSK gel SuperHZ-2000"

Guard column: "TSK SuperH-H"

Developing solvent: tetrahydrofuran

Flow rate: 0.35 ml / min

2. Preparation of polarizer protective film

&Lt; Example 1 >

(1) Production of base film

(Preparation of diluted silicon dioxide dispersion)

10 parts by mass of Aerosil R812 (manufactured by Nippon Aerosil Co., Ltd.) and 90 parts by mass of ethanol were mixed with stirring in a dissolver for 30 minutes and then dispersed with mannitol to obtain a silicon dioxide dispersion.

To the silicon dioxide dispersion thus obtained, 88 parts by mass of methylene chloride was added with stirring, and the mixture was stirred with a dissolver for 30 minutes to obtain a diluted silicon dioxide dispersion. The obtained solution was filtered with a fine particle dispersion diluent filter (Polyvinyl Chloride filter cartridge TCW-PPS-1N, manufactured by ADVANTEK TOYO CO., LTD.).

(Preparation of the main doping solution)

The following components were put in a hermetically sealed container and completely dissolved while being heated and stirred, and the obtained solution was filtered to obtain a main dope solution.

Triacetyl cellulose (acetyl group degree of substitution: 2.89, Mw = 190000): 100 parts by mass

Tinuvin 928 (manufactured by BASF Japan Ltd.): 3 parts by mass

Polyester-based additive T1: 10 parts by mass

Methylene chloride: 700 parts by mass

Ethanol: 40 parts by mass

To the main doping solution thus obtained, 4 parts by mass of the diluted silicon dioxide dispersion was added while stirring, and further stirred for 30 minutes to obtain a dope solution.

(Film forming)

The obtained dope was uniformly plied on a stainless steel band support at a temperature of 35 DEG C and a width of 2 m by using a belt softener. On the stainless steel band support, a flexible film was evaporated on the stainless steel band support until the residual solvent amount became 100% by mass. The film-like material obtained by peeling was transported while being dried at 50 캜 and slit.

The film-like material thus obtained was stretched in a TD direction (direction orthogonal to the conveying direction of the film) at a temperature of 160 캜 at a magnification of 20% by a tenter, and then dried at 160 캜. The amount of residual solvent of the film material when the stretching was started with a tenter was 4.5%.

Subsequently, the film-like material thus obtained was dried in a drying apparatus at 120 캜 for 15 minutes while being conveyed in a plurality of rolls, and then slit and knurled at both ends of the film to a width of 15 mm and a height of 10 탆, &Lt; / RTI &gt; The draw ratio in the MD direction calculated from the rotating speed of the stainless steel band support and the running speed of the tenter was 1.05 times.

The storage modulus and internal haze of the obtained base film were measured by the following methods.

[Storage elastic modulus]

The base film was cut into a size of 5 mm width x length (length in the in-plane slow axis direction) of 50 mm and used as a sample. This sample was humidity-conditioned at 23 占 폚 and 55% RH for 24 hours. This sample was stretched in the longitudinal direction under an environment of 23 占 폚 and 55% RH while being heated under the following conditions to obtain a temperature-storage elastic modulus curve. From the obtained curve, the value of the storage elastic modulus at 30 캜 was read, and the storage elastic modulus in the in-plane slow axis direction at 30 캜 was obtained.

Measuring apparatus: manufactured by TS Instruments RSAIII

Gap: 20mm

Measurement conditions: Tensile mode

Measuring temperature: 25 to 210 DEG C

Temperature rise condition: 5 ° C / min

Frequency: 1Hz

[Internal Hayes]

The internal haze was measured by the following method in accordance with JIS K-7136.

1) One drop of glycerin (0.05 ml) was dropped onto the washed slide glass. At this time, care was taken to prevent air bubbles from entering the droplet. Then, a cover glass was placed on the dropped glycerin. Glycerin spread even though the cover glass was not pressed. A sample (cover glass / glycerin / slide glass) for measurement of the obtained blank was set on a haze meter, and haze 1 (blank haze) was measured.

2) Glycerin was added dropwise to the washed slide glass in the same manner as in 1) above. Then, the substrate film, which was humidified at 23 DEG C and 55% RH for 5 hours or more, was placed on the dropped glycerin so that air bubbles would not enter. Further, 0.05 ml of glycerin was dropped onto the substrate film, and then a cover glass was further placed thereon. The sample for measurement (cover glass / glycerin / base film / glycerin / slide glass) was set on the above-mentioned haze meter, and haze 2 was measured.

3) The haze of the base film was calculated by applying the haze 1 obtained in the above 1) and the haze 2 obtained in the above 2) to the following formula.

Internal Haze (%) of Base Film = Haze 2 (%) - Haze 1 (%)

The measurement of the internal haze was carried out under the conditions of 23 ° C and 55% RH. The glass used for the measurement was MICRO SLIDE GLASS S9213 MATSUNAMI; The glycerin used in the measurement was Kanto Chemical Industries, Limited (purity > 99.0%) and a refractive index of 1.47. NDH2000 manufactured by Nippon Denshoku Kogyo Co., Ltd. was used as the measuring apparatus.

The measured haze value was evaluated by the following criteria.

A: less than 0.04

B: 0.04 or more and less than 0.08

C: 0.08 or more and less than 0.12

D: 0.12 or more

(2) Production of hard coating film (polarizer protective film)

The following components were mixed to obtain a coating liquid for a hard coating layer.

Pentaerythritol triacrylate: 20 parts by mass

Pentaerythritol tetraacrylate: 50 parts by mass

Dipentaerythritol hexaacrylate: 30 parts by mass

Dipentaerythritol pentaacrylate: 30 parts by mass

Irgacure 184 (manufactured by Shiba Japan): 5 parts by mass

Fluorine-siloxane graft polymer I (35 mass%): 5 mass parts

Sihosta KEP-50 (silica particles in powder, average particle diameter 0.47 to 0.61 mu m, manufactured by Nippon Shokubai Co., Ltd.): 24.3 parts by mass

Propylene glycol monomethyl ether: 20 parts by mass

Methyl acetate: 40 parts by mass

Methyl ethyl ketone: 60 parts by mass

Further, the fluorine-siloxane graft polymer I was synthesized by the method described in paragraphs 0299 to 0302 of International Publication No. 2011/158626.

The obtained coating liquid for the hard coating layer was applied on the prepared base film with a die coater so that the thickness after curing became 7 占 퐉. The obtained coating layer was dried at 70 占 폚 and irradiated with ultraviolet rays under a nitrogen atmosphere at an illuminance of 300 mW / cm2 and an irradiation dose of 0.3 J / cm2 to cure the coating layer. The base film having the cured coating layer was heat-treated at 130 캜 for 5 minutes while conveying at a conveying tension of 300 N / m to obtain a hard coating film.

[Surface hardness]

The surface hardness of the hard coat layer of the obtained hard coat film was measured by a pencil altimetric method according to JIS K5400. Specifically, the hard coating film was humidity-conditioned at 23 캜 and 55% RH for 24 hours. Thereafter, the surface of the hard coat layer was scratched with a pencil of each hardness using a weight of 1 kg five times, and the maximum value of the hardness at which scratches became one or less was obtained. The larger the maximum value, the higher the hardness.

(3) Production of Polarizing Plate

A polyvinyl alcohol film having a thickness of 120 占 퐉 was immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid and stretched at 50 占 폚 at a stretching magnification of 6 times in the carrying direction to obtain a polarizer with a thickness of 20 占 퐉.

The obtained polarizer was subjected to alkali saponification under the following conditions.

Saponification process: 2.5M-NaOH 50 캜 90 sec

Washing process: water 30 ℃ 45 seconds

Neutralization process: 10 parts by mass HCl 30 占 폚 45 seconds

Washing process: water 30 ℃ 45 seconds

After the saponification treatment, washing with water, neutralization and washing with water were carried out in this order, followed by drying at 80 ° C. Thereafter, the prepared polarizing plate protective films were respectively bonded to both sides of the prepared polarizer via a completely saponified polyvinyl alcohol aqueous solution. The bonded laminate was dried to obtain a long polarizing plate. The bonding was carried out such that the transmission axis of the polarizer and the in-plane slow axis in the plane of the polarizing plate protective film were parallel and the base film of the polarizing plate protective film was in contact with the polarizer.

[Punching Workability of Polarizer]

The obtained polarizing plate sample was cut (punching) at a compression force of 50 kN using a square Thomson blade (40 DEG) having a size of 576 x 324 mm and a side length of 10 cm to obtain a polarizing plate.

The end of the polarizing plate (cut surface) after the punching was observed by observing the state of the end (cut surface) using a 10-fold loupe, and the crack and the end crack were evaluated according to the following criteria.

?: Level at which there is no generation of cracks or tip cracks

○: Cracks and tip cracks were observed very little, but practically no problem level

B: Level where cracks and tip cracks are slightly observed

X: Level at which cracks and tip cracks are observed

[Polarizer deterioration]

The transmittance T0 of the obtained polarizing plate was measured using NDH2000 manufactured by Nippon Denshoku Kogyo Co., Ltd. in accordance with JIS K7136. Subsequently, after the polarizing plate was treated at 80 DEG C and 90% RH for 120 hours, the transmittance Td was measured in the same manner as described above. The obtained value was applied to the following formula to determine the difference in transmittance? T.

Difference in transmittance? T (%) = Td (transmittance after processing) -T0 (transmittance before processing)

Polarizer deterioration was evaluated by the following criteria.

?: DELTA T is less than 1%

○: ΔT is 1% or more and less than 5%

Δ: ΔT is 5% or more and less than 10%

×: ΔT is 10% or more and less than 15%

××: ΔT is 15% or more

&Lt; Examples 2 to 5 and Comparative Examples 1 to 8 >

A base material film was produced in the same manner as in Example 1 except that the kind of the polyester-based additive was changed as shown in Table 2. In the same manner as in Example 1, a polarizing plate protective film and a polarizing plate were produced and evaluated in the same manner.

&Lt; Examples 6 to 8 and Comparative Example 9 >

A base film was prepared in the same manner as in Example 1 except that the film thickness of the base film was changed as shown in Table 3. [ In the same manner as in Example 1, a polarizing plate protective film and a polarizing plate were produced and evaluated in the same manner.

&Lt; Examples 9 to 12 >

A substrate film was prepared in the same manner as in Example 1 except that the amount of the polyester-based additive was changed as shown in Table 4. [ In the same manner as in Example 1, a polarizing plate protective film and a polarizing plate were produced and evaluated in the same manner.

&Lt; Example 13 and Comparative Example 10 >

The base film of Example 13 was prepared in the same manner as in Example 1 except that the stretching conditions were changed as shown in Table 5; The base film of Comparative Example 10 was produced in the same manner as in Comparative Example 4 except that the stretching conditions were changed as shown in Table 5. [ Then, in the same manner as in Example 1, a polarizing plate protective film and a polarizing plate were produced and evaluated in the same manner.

The evaluation results of Examples 1 to 5 and Comparative Examples 1 to 8 are shown in Table 2; The evaluation results of Examples 6 to 8 and Comparative Example 9 are shown in Table 3; The evaluation results of Examples 9 to 12 are shown in Table 4; The evaluation results of Example 13 and Comparative Example 10 are shown in Table 5.

As shown in Table 2, in Examples 1 to 5, the surface hardness of the polarizing plate protective film is higher than that of Comparative Examples 1 to 8, and the punching property of the polarizing plate is also good. This is presumably because the base film of Examples 1 to 5 contains a polyester-based additive end-capped with an OH group-containing monocarboxylic acid having a cyclic structure and has a high storage modulus of the base film and good toughness .

Further, it can be seen that the polarizer of Example 1 has less polarizer deterioration than the polarizer of Comparative Examples 1, 6, and 7. This is accomplished by sealing the molecular end of the polyester-based additive; In particular, it is considered that sealing with a monocarboxylic acid containing an aromatic ring having a high hydrophobicity increases the hydrophobicity of the base film.

It can also be seen that the base film of Example 1 has higher storage modulus and lower internal haze than the base film of Example 5. [ The reason why the internal haze of the base film of Example 1 is low is considered to be that the polyester-based additive has a lower molecular weight than that of the polyester-based plasticizer of Example 5, and therefore is highly compatible with the cellulose ester. The reason why the storage elastic modulus of Example 1 is high is that it is highly compatible with the cellulose ester of the polyester plasticizer and therefore is highly ordered and easy to be oriented by stretching.

As shown in Table 3, when the thickness of the base film is 15 m or more, it is understood that the surface hardness of the polarizing plate protective film can be increased and the polarizing plate can be punched well. When the film thickness of the base film is 50 m or less, it is shown advantageous from the viewpoint of thinning.

As shown in Table 4, it is shown that when the content of the polyester-based additive is 20 parts by mass or less based on 100 parts by mass of the cellulose ester, the storage modulus of the base film can be increased without excessively increasing the internal haze. When it is 5 parts by mass or more, deterioration of the polarizer can be suppressed. This is considered to be because the moisture permeability of the base film is reduced (see Examples 9 to 12).

As shown in Table 5, the base film of Example 1 or Comparative Example 4 stretched at a high temperature had lower internal haze than the base film of Example 13 or Comparative Example 10 stretched at a low temperature. This is believed to be because it is possible to inhibit an excessive drawing stress from being applied by stretching at a high temperature.

This application claims priority to Japanese Patent Application No. 2015-003496, filed on January 9, 2015. The contents of the present specification and drawings are all incorporated herein by reference.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a polarizing plate protective film which has a high surface hardness and can suppress the punching workability at the time of producing a polarizing plate, deterioration of polarizers and the like.

10 Liquid crystal display
30 liquid crystal cell
50 first polarizer plate
51 first polarizer
53 Protective film (F1)
55 Protective film (F2)
70 second polarizer plate
71 Second polarizer
73 Protective film (F3)
75 Protective film (F4)
90 backlight

Claims (8)

A polarizing plate protective film comprising a base film and an active energy pre-
Wherein the base film comprises a cellulose ester and a polyester-based additive represented by the following formula (1)
Wherein the base film has a film thickness of 15 to 50 占 퐉 and a storage elastic modulus in an in-plane slow axis direction at 30 占 폚 of 5.0 to 7.0 GPa.
Formula (1): B- (GA) nGB
(In the formula (1)
B is a group derived from a monocarboxylic acid containing a hydroxyl group containing a cyclic structure,
G is an alkylene diol having 2 to 12 carbon atoms, a cycloalkylene diol having 6 to 12 carbon atoms, an oxyalkylene diol having 4 to 12 carbon atoms, and an arylene diol having 6 to 12 carbon atoms And R &lt; 2 &gt;
A is selected from the group consisting of an alkylene dicarboxylic acid having 4 to 12 carbon atoms, a cycloalkylene dicarboxylic acid having 6 to 16 carbon atoms and an arylene dicarboxylic acid having 8 to 16 carbon atoms A group derived from at least one species,
n represents an integer of 0 or more) The polarizing plate protective film according to claim 1, wherein B in the formula (1) is a group derived from a monocarboxylic acid containing a hydroxyl group containing an aromatic hydrocarbon ring. The polarizing plate protective film according to claim 1, wherein the number average molecular weight of the polyester-based additive is 300 or more and less than 700. The polarizing plate protective film according to claim 1, wherein the content of the polyester-based additive in the base film is 5 to 20 parts by mass relative to 100 parts by mass of the cellulose ester. The polarizing plate protective film according to claim 1, wherein the active energy ray cured product layer is a hard coating layer or an antiglare layer. A method for producing a polarizing plate protective film according to claim 1,
A step of stretching a film material containing a cellulose ester and a polyester-based additive represented by the following formula (1) at a temperature of 140 to 180 占 폚 at a magnification of 5 to 30% to obtain a base film;
Applying a composition for an active energy ray pre-cured product layer onto the base film, and then drying and curing the product to obtain an active energy ray pre-cured product layer.
Formula (1): B- (GA) nGB
(In the formula (1)
B is a group derived from a monocarboxylic acid containing a hydroxyl group containing a cyclic structure,
G is an alkylene diol having 2 to 12 carbon atoms, a cycloalkylene diol having 6 to 12 carbon atoms, an oxyalkylene diol having 4 to 12 carbon atoms, and an arylene diol having 6 to 12 carbon atoms And R &lt; 2 &gt;
A is selected from the group consisting of an alkylene dicarboxylic acid having 4 to 12 carbon atoms, a cycloalkylene dicarboxylic acid having 6 to 16 carbon atoms and an arylene dicarboxylic acid having 8 to 16 carbon atoms A group derived from at least one species,
n represents an integer of 0 or more) A polarizer, and a polarizing plate protective film according to claim 1,
Wherein the base film of the polarizing plate protective film is in contact with the polarizer. A liquid crystal cell, a first polarizer plate and a second polarizer plate for supporting and supporting the liquid crystal cell,
Wherein the first polarizer comprises a first polarizer and a polarizer protective film disposed on a surface of the first polarizer opposite to the liquid crystal cell,
Wherein the second polarizer comprises a second polarizer and a polarizer protective film disposed on a surface of the second polarizer opposite to the liquid crystal cell,
Wherein the polarizing plate protective film of the first polarizing plate is the polarizing plate protective film of claim 1 and the base film of the polarizing plate protective film of the first polarizing plate is in contact with the first polarizing plate,
Wherein the polarizing plate protective film of the second polarizing plate is the polarizing plate protective film of claim 1 and the base film of the polarizing plate protective film of the second polarizing plate is in contact with the second polarizing plate.

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