WO2016111316A1

WO2016111316A1 - Polarizing plate protective film, production method therefor, polarizing plate, and liquid crystal display device

Info

Publication number: WO2016111316A1
Application number: PCT/JP2016/050251
Authority: WO
Inventors: 洋介水谷
Original assignee: コニカミノルタ株式会社
Priority date: 2015-01-09
Filing date: 2016-01-06
Publication date: 2016-07-14
Also published as: JPWO2016111316A1; KR20170088974A

Abstract

The purpose of the present invention is to provide a polarizing plate protective film that, even if made thinner, has high surface hardness and is capable of having suppressed reduction in punching workability and suppressed polarizer deterioration, during polarizing plate production. This polarizing plate protective film includes a substrate film and an active energy ray cured product layer. The substrate film includes a cellulose ester and a polyester-based additive indicated by formula (1). The substrate film has a film thickness of 15-50 µm and a storage elastic modulus in an in-plane phase delay axis direction at 30°C of 5.0-7.0 GPa. Formula (1): B - (G - A) n - G - B (in the formula (1), B indicates a group induced from a hydroxyl group-containing monocarboxylic acid including a ring structure.)

Description

Polarizing plate protective film and manufacturing method thereof, polarizing plate and liquid crystal display device

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

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

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

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

As another polarizing plate protective film, a film containing a cellulose ester and a high molecular weight plasticizer (Patent Document 3); a film containing a cellulose ester and a polyester diol having OH groups at both ends (Patent Document 4); A cellulose ester film (Patent Document 5) produced under the stretching conditions is also known.

JP2013-127058A JP 2010-228314 A Patent No. 5028251 Patent No. 5422165 International Publication No. 2012/073692

However, the base films of Patent Documents 1 and 2 do not have sufficient hardness (or elastic modulus). Therefore, there has been a problem that when the substrate film is thinned, sufficient surface hardness of the polarizing plate protective film cannot be obtained.

On the other hand, since the polarizing plate protective films of Patent Documents 3 and 5 contain a polyester-based additive end-capped with an aromatic monocarboxylic acid, a certain degree of hardness is easily obtained, but they are easily fragile. When a polarizing plate including such a polarizing plate protective film is punched into a predetermined size, there is a problem in that cracks and flaking tend to occur on the cut surface of the polarizing plate.

The polarizing plate protective film of Patent Document 4 contains a non-end-sealed polyester-based additive, so that the water resistance tends to decrease. Therefore, for example, when water paste is used at the time of preparing the polarizing plate, it is difficult to remove moisture from the protective film, and there is a possibility that the polarizer is deteriorated by moisture.

As described above, it is desired to obtain a polarizing plate having a high surface hardness without causing a decrease in punching processability or polarizer deterioration during the production of the polarizing plate even if the film thickness is reduced. The present invention has been made in view of such circumstances. Even when the film is thinned, the polarizing plate protection has high surface hardness and can suppress the deterioration of the punching processability and the polarizer deterioration during the production of the polarizing plate. The object is to provide a film.

[1] A polarizing plate protective film including a base film and an active energy ray cured product layer, wherein the base film includes a cellulose ester and a polyester-based additive represented by the following formula (1). And the base film has a film thickness of 15 to 50 μm and a storage elastic modulus in the in-plane slow axis direction at 30 ° C. of 5.0 to 7.0 GPa.
Formula (1): B- (GA) n-GB
(In the formula (1), B is a group derived from a hydroxyl group-containing monocarboxylic acid containing a ring structure; G is an alkylene diol having 2 to 12 carbon atoms, or a cycloalkylene having 6 to 12 carbon atoms. A group derived from at least one selected from the group consisting of a diol, an oxyalkylene diol having 4 to 12 carbon atoms, and an arylene diol having 6 to 12 carbon atoms; A is an alkylene dicarboxylic acid having 4 to 12 carbon atoms; A group derived from at least one selected from the group consisting of acids, cycloalkylene dicarboxylic acids having 6 to 16 carbon atoms, and arylenedicarboxylic acids 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 polarizing plate 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 with respect to 100 parts by mass of the cellulose ester. Protective film.
[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 coat layer or an antiglare layer.
[6] A method for producing a polarizing plate protective film according to any one of [1] to [5], comprising a cellulose ester and a polyester-based additive represented by the following formula (1) A base film obtained by stretching the film at a temperature of 140 to 180 ° C. at a magnification of 5 to 30%, and after applying the active energy ray cured product composition on the base film, drying and curing are performed. And a step of obtaining a cured active energy ray layer, and a method for producing a polarizing plate protective film.
Formula (1): B- (GA) n-GB
(In the formula (1), B is a group derived from a hydroxyl group-containing monocarboxylic acid containing a ring structure; G is an alkylene diol having 2 to 12 carbon atoms, or a cycloalkylene having 6 to 12 carbon atoms. A group derived from at least one selected from the group consisting of a diol, an oxyalkylene diol having 4 to 12 carbon atoms, and an arylene diol having 6 to 12 carbon atoms; A is an alkylene dicarboxylic acid having 4 to 12 carbon atoms; A group derived from at least one selected from the group consisting of acids, cycloalkylene dicarboxylic acids having 6 to 16 carbon atoms, and arylenedicarboxylic acids having 8 to 16 carbon atoms; n represents an integer of 0 or more )
[7] A polarizing plate comprising a polarizer and the polarizing plate protective film according to any one of [1] to [5], wherein a base film of the polarizing plate protective film is in contact with the polarizer.
[8] A liquid crystal cell, and a first polarizing plate and a second polarizing plate sandwiching the liquid crystal cell, wherein the first polarizing plate includes a first polarizer and the first polarizer. A polarizing plate protective film disposed on a surface opposite to the liquid crystal cell, and the second polarizing plate includes a second polarizer and a side opposite to the liquid crystal cell of the second polarizer. The polarizing plate protective film of the first polarizing plate is the polarizing plate protective film according to any one of [1] to [5], and The substrate film of the polarizing plate protective film of the first polarizing plate is in contact with the first polarizer, or the protective film of the second polarizing plate is any one of [1] to [5] And the base film of the polarizing plate protective film of the second polarizing plate is in contact with the second polarizer A liquid crystal display device.

According to the present invention, it is possible to provide a polarizing plate protective film that has a high surface hardness even when it is thinned, and that can suppress the deterioration of punching processability and polarizer deterioration during the production of the polarizing plate.

It is an example which shows the fundamental structure of the liquid crystal display device of this invention.

As described above, a cellulose ester film containing 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, It tends to be brittle.

On the other hand, the inventors of the present invention have a high elastic modulus, a cellulose ester film containing a polyester-based additive end-capped with a “monocarboxylic acid having a ring structure and containing a hydroxyl group”, and I found it difficult to become brittle. Although this cause is not necessarily clear, it is estimated as follows. In the polyester-based additive end-capped with “monocarboxylic acid having a ring structure and containing a hydroxyl group”, the hydroxy groups are likely to interact with each other. As a result, it is considered that the polyester-based additive is easily oriented by stretching and the elastic modulus is likely to increase. Moreover, it is thought that by having a ring structure, the interaction of hydroxyl groups tends to occur stably, and the elastic modulus tends to increase more effectively. Furthermore, it is considered that due to the interaction between hydroxyl groups, toughness is easily imparted despite having a ring structure, and it is difficult to become brittle.

And the cellulose ester film which has a high storage elastic modulus and favorable toughness can be obtained by further optimizing content and extending | stretching conditions of the said polyester type additive. By using such a film as a base film, a hard coat film having a high surface hardness and a good polarizing plate punching property can be obtained.

On the other hand, a polyester-based additive end-capped with a “monocarboxylic acid containing a hydroxyl group” usually has poorer water resistance than a polyester-based additive end-capped with a “monocarboxylic acid not containing a hydroxyl group”. Tend. In the present invention, since the monocarboxylic acid containing a hydroxyl group has a ring structure (which can impart hydrophobicity), the water resistance of the polyester-based additive can be ensured. The present invention has been made based on these findings.

1. Polarizing plate protective film The polarizing plate protective film has a base film and an active energy ray cured product layer.

1-1. Base film The base film contains a cellulose ester and a polyester-based additive.

<Cellulose ester>
The cellulose ester is a compound obtained by esterifying cellulose and a carboxylic acid 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 birefringence is lowered when the number of carbon atoms of the acyl group is large, and therefore the number of carbon atoms of the acyl group is preferably 2 to 6. The cellulose ester may contain two or more types of acyl groups having different carbon atoms; preferably an acyl group having 2 and 3 carbon atoms, or an acyl group having 2 and 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 that simultaneously satisfy the following formulas (1) and (2) are preferable. In the formula, X is the substitution degree of the acetyl group, and Y is the substitution degree of the propionyl group or butyryl group.
Formula (1) 2.0 <= X + Y <= 3.0
Formula (2) 0 ≦ Y ≦ 1.5

In particular, triacetyl cellulose and cellulose acetate propionate are preferably used. Triacetyl cellulose may preferably have Y = 0 and 2.5 ≦ X + Y ≦ 2.98, more preferably Y = 0 and 2.7 ≦ X + Y ≦ 2.95. The cellulose acetate propionate may preferably satisfy 1.0 ≦ X ≦ 2.5, 0.1 ≦ Y ≦ 1.5 and 2.0 ≦ X + Y ≦ 3.0. The method for measuring the substitution degree of the acyl group can be measured according to ASTM-D817-96.

By setting the substitution degree of the acyl group to a certain level or more, the number of hydroxyl groups remaining in the pyranose ring constituting the cellulose skeleton can be reduced, and the occurrence of unnecessary birefringence and the influence of humidity can be suppressed.

The weight average molecular weight (Mw) of the cellulose ester is preferably 80,000 to 300,000, more preferably 100,000 to 280000, and further preferably 230000 to 280000. The ratio Mw / Mn of the weight average molecular weight (Mw) and 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 a cellulose ester can be measured using commercially available gel permeation chromatography (GPC). The measurement conditions can be as follows.
(Measurement condition)
Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three products manufactured by Showa Denko KK)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Co., Ltd.) Mw = 1000000-500 13 calibration curves are used. Thirteen samples are used at approximately equal intervals.

The calcium content of the cellulose ester is preferably 50 ppm or less, more preferably 10 to 50 ppm. When the calcium content of the cellulose ester is below a certain level, an increase in the haze of the substrate film over time can be effectively suppressed. The calcium content of the cellulose ester can be adjusted by the selection of the raw material of the cellulose ester and the production conditions.

The cellulose used as the raw material for the cellulose ester can be wood pulp (conifer pulp, hardwood pulp), cotton linter, or the like. The calcium content of the cellulose ester can be adjusted by the type of cellulose and the combination of a plurality of celluloses. As the raw material pulp, pulp having a low calcium content; specifically, a pulp having a calcium content of 20 ppm or less, preferably 10 ppm or less, more preferably 5 ppm or less is used. Such raw pulp can be obtained by the method described in paragraphs 0062 to 0088 of JP2012-48214A.

<Polyester additive>
The polyester-based additive is obtained by subjecting a diol and a dicarboxylic acid to a dehydration condensation reaction; a hydroxyl group (derived from a diol) at the molecular end of the resulting reaction product is converted into a carboxyl group of a hydroxyl group-containing monocarboxylic acid having a ring structure. And a compound obtained by a dehydration condensation reaction.

The polyester-based additive is preferably a compound represented by the following formula (1).
Formula (1): B- (GA) n-GB

B in the formula (1) is a group derived from a hydroxyl group-containing monocarboxylic acid having a ring structure. The ring structure refers to a structure having an aliphatic hydrocarbon ring, an aliphatic hetero ring, an aromatic hydrocarbon ring or an aromatic hetero ring, preferably a structure having an aliphatic hydrocarbon ring or an aromatic hydrocarbon ring. . The hydroxyl group-containing monocarboxylic acid having a ring 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 alicyclic monocarboxylic acids include 4-hydroxycyclohexylacetic acid, 3-hydroxycyclohexylacetic acid, 2-hydroxycyclohexylacetic acid, 4-hydroxycyclohexylpropionic acid, 4-hydroxycyclohexylbutyric acid, 4-hydroxycyclohexylglycolic acid, 4 -Hydroxy-o-methylcyclohexylacetic acid, 4-hydroxy-m-methylcyclohexylacetic acid, 4-hydroxy-p-methylcyclohexylacetic acid, 5-hydroxy-m-methylcyclohexylacetic acid, 6-hydroxy-o-methylcyclohexylacetic acid, 2 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-1 -Me Ruechiru) cyclohexyl acetate, 3- (1-hydroxy-1-methylethyl) cyclohexyl acetate, 4- (1-hydroxy-1-methylethyl) cyclohexyl acetate and the like.

The aromatic monocarboxylic acid having 5 to 20 carbon atoms is preferably an aromatic monocarboxylic acid having 6 to 15 carbon atoms. Examples of aromatic monocarboxylic acids include 4-hydroxybenzoic acid, 3-hydroxybenzoic acid, 2-hydroxybenzoic acid, 4-hydroxy-o-toluic acid, 3-hydroxy-p-toluic acid, 5-hydroxy- m-toluic acid, 6-hydroxy-o-toluic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2- (hydroxymethyl) benzoic acid, 3- (hydroxymethyl) benzoic acid, 4- (Hydroxymethyl) benzoic acid, 2- (1-hydroxy-1-methylethyl) benzoic acid, 3- (1-hydroxy-1-methylethyl) benzoic acid, 4- (1-hydroxy-1-methylethyl) benzoic acid Acid etc. are included.

Among these, a hydroxyl group-containing monocarboxylic acid containing an aromatic hydrocarbon ring (an aromatic containing a hydroxyl group) from the point of imparting sufficient hydrophobicity to the polarizing plate protective film and easily suppressing deterioration of the polarizer due to moisture. Monocarboxylic acids) are preferred.

G in formula (1) 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. A group derived from at least one selected from the group consisting of:

Examples of alkylene diols having 2 to 12 carbon atoms include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,2-propane. Diol, 2-methyl 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2-diethyl- 1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3-methyl-1,5-pentane Diol 1,6-hexanediol, 2,2,4-trimethyl 1,3-pentanediol, 2-ethyl 1,3-hexanediol, - methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, include 1,12-octadecanediol 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 are included.

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 arylene diols having 6 to 12 carbon atoms include bisphenol A and bisphenol B.

Diol is used as one kind or a mixture of two or more kinds. Among these, alkylene glycols having 2 to 12 carbon atoms are preferable in terms of excellent compatibility with cellulose esters.

A in the formula (1) is at least one selected from the group consisting of alkylene dicarboxylic acids having 4 to 12 carbon atoms, cycloalkylene dicarboxylic acids having 6 to 16 carbon atoms, and arylenedicarboxylic acids having 8 to 16 carbon atoms. Is a group derived from

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 cycloalkylene dicarboxylic acids having 6 to 16 carbon atoms include 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,5-decahydronaphthalenedicarboxylic acid, 1,4-decahydronaphthalenedicarboxylic acid and the like are included.

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

Dicarboxylic acid is used as one kind or a mixture of two or more kinds. The dicarboxylic acid is preferably a mixture of alkylene dicarboxylic acid and arylene dicarboxylic acid. The content ratio of alkylene dicarboxylic acid and arylene dicarboxylic acid is preferably alkylene dicarboxylic acid: arylene dicarboxylic acid = 40: 60 to 99: 1, and more preferably 50:50 to 90:10.

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

In terms of facilitating increasing the storage elastic modulus of the base film, G in the formula (1) contains a group derived from a cycloalkylene diol having 6 to 12 carbon atoms; or A in the formula (1) is carbon. It preferably contains a group derived from a cycloalkylene dicarboxylic acid having 6 to 12 atoms or an arylenedicarboxylic acid having 8 to 16 carbon atoms. Since the polyester-based additive containing these groups has a rigid structure, it is easy to increase the storage elastic modulus of the base film.

The number average molecular weight of the polyester-based additive is preferably 300 to 30,000, more preferably 300 or more and less than 700, and more preferably 300 to 600. If the number average molecular weight is above a certain level, bleeding out is likely to be suppressed. When the number average molecular weight is not more than a certain value, the compatibility with the cellulose ester is not impaired and it is easy to suppress an increase in haze, and it is easy to be oriented by stretching and to increase the storage elastic modulus.

The number average molecular weight of the polyester-based additive can be measured by gel permeation chromatography. Specifically, using a gel permeation chromatography (GPC) measuring device (“HLC-8330” manufactured by Tosoh Corporation), the number average molecular weight (Mn) of the ester compound in terms of standard polystyrene is measured under the following measurement conditions. Can be measured.
(Measurement condition)
Column: "TSK gel SuperHZM-M" x 2 and "TSK gel SuperHZ-2000" x 2 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, more preferably 15 mgKOH / g or less.

The synthesis of the polyester-based additive is carried out by a conventional method of hot-melt condensation by esterification reaction or transesterification reaction of dicarboxylic acid, diol, and end-capping monocarboxylic acid; or dicarboxylic acid and end-capping monocarboxylic acid It can be performed by any of the interfacial condensation methods of acid chloride and diol. The charging ratio of the diol and the dicarboxylic acid is adjusted so that the molecular terminal is 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 with respect to 100 parts by mass of the cellulose ester. When the content of the polyester-based additive is a certain level or more, the storage elastic modulus of the base film can be sufficiently increased without increasing brittleness. If the content of the polyester-based additive is below a certain level, there is no possibility of causing bleed-out or increased internal haze.

<Acrylic copolymer>
The base film may further contain an acrylic copolymer as necessary in order to adjust the retardation value.

The acrylic copolymer is an acrylic polymer having a weight average molecular weight of 500 to 30,000; preferably an ethylenically unsaturated monomer having no aromatic ring and no hydrophilic group in the molecule and an aromatic ring in the molecule. A polymer having a weight average molecular weight of 5,000 to 30,000 obtained by copolymerization with an ethylenically unsaturated monomer having a hydrophilic group; more preferably an ethylenically unsaturated group having no aromatic ring and no hydrophilic group in the molecule. A polymer having a weight average molecular weight of 5,000 to 30,000 obtained by copolymerization of a saturated monomer and an ethylenically unsaturated monomer having no hydrophilic ring in the molecule and having a hydrophilic group, and ethylenic having no aromatic ring It may be a mixture with a polymer having a weight average molecular weight of 500 or more and 3000 or less obtained by polymerizing an unsaturated monomer.

<Ultraviolet absorber>
The base film may further contain an ultraviolet absorber as 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, and even more preferably 2% or less.

Examples of ultraviolet absorbers include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, nickel complex compounds, inorganic powders, and the like. Among these, benzotriazole ultraviolet absorbers, benzophenone ultraviolet absorbers, and triazine ultraviolet absorbers are preferable, and benzotriazole ultraviolet absorbers and benzophenone ultraviolet absorbers are more preferable.

The content of the UV absorber is preferably 0.5 to 10% by mass with respect to the base film when the thickness of the base film is 30 to 200 μm, although it depends on the type and use conditions of the UV absorber. 0.6 to 4% by mass is more preferable.

<Fine particles (matting agent)>
The base film can further contain fine particles (matting agent) in order to impart slipperiness or the like to the surface. The fine particles may be composed of an inorganic compound or a resin.

Examples of inorganic compounds 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, calcium phosphate, etc. Is mentioned.

Examples of the resin include silicone resin, fluororesin and acrylic resin. Among them, silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120 and 240 (manufactured by Toshiba Silicone Co., Ltd.) What is marketed with a brand name is mentioned.

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

The average primary particle diameter 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 size of 0.05 to 0.3 μm, and may be contained as primary particles without being aggregated if the particles have an average particle size of 100 to 400 nm.

The fine particles are preferably added so that the dynamic friction coefficient of the base film surface is 0.2 to 1.0. Specifically, the content of the fine particles can be 0.01 to 1% by mass, preferably 0.05 to 0.5% by mass with respect to the base film.

1-2. Production method of base film The base film can be produced by any method, but it is preferably produced by a solution casting method from the viewpoint of easy film formation even with a resin having a relatively large molecular weight. Specifically, the base film is 1) a step of preparing a dope solution by dissolving the above-described components in a solvent, 2) a step of casting the dope solution on an endless metal support, and 3) casting. The dope is dried and then peeled off to obtain a film-like material. 4) The film-like material is dried and stretched.

In the step 4), the film-like material is preferably stretched while being dried in order to increase the storage elastic modulus of the base film. Stretching can be performed in the width direction, the film forming direction, or both.

The stretching ratio in the maximum stretching direction (the direction in which the stretching ratio becomes maximum) is preferably 5 to 30%, more preferably 12 to 28%. For example, when stretching in biaxial directions perpendicular to each other, it can be 0 to 15% in the transport direction (MD direction) and 5 to 30% in the width direction (TD direction). The draw ratio (%) is defined by the following formula.
Stretch ratio (%) = {((Stretch direction) length of stretched film− (Stretch direction) length of stretched film) / (Stretch direction) length of stretched film)} × 100

The stretching temperature can be 120 to 180 ° C, preferably 140 to 180 ° C, more preferably 145 to 165 ° C. By stretching at the above 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-like material at the start of stretching is preferably less than 5% by mass, more preferably 4% by mass or less, and even more preferably 2% by mass or less, from the viewpoint of suppressing an increase in haze. In order to keep the residual solvent at the start of stretching at less than 5% by mass, it is preferable to provide the drying step in the process of peeling the cast dope from the metal support and transporting it to evaporate the solvent.

The method of stretching the film-like material is not particularly limited, and a method of stretching a difference in peripheral speed between a plurality of rolls and using the difference in the peripheral speed of the roll between them in the MD direction; It may be a method of fixing with a clip or a pin and extending the gap between the clip or the pin in the TD direction. Among them, the stretching in the TD direction is preferably performed by a tenter, and may be a pin tenter or a clip tenter.

The other steps may be the same as known solution casting methods; for example, paragraphs 0109 to 0140 of JP2012-48214A.

<Physical properties of base film>
(Storage modulus)
The storage elastic modulus of the base film in the in-plane slow axis direction at 30 ° C. 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 is cut into a size of 5 mm wide × length (length in the in-plane slow axis direction) 50 mm, and used as a sample. The sample is conditioned for 24 hours at 23 ° C. and 55% RH. The obtained sample is pulled in the length direction while raising the temperature under the following conditions in an environment of 23 ° C. and 55% RH to obtain a temperature-storage modulus curve. From the obtained curve, the value of the storage elastic modulus at 30 ° C. is read, and is set as “the storage elastic modulus in the in-plane slow axis direction at 30 ° C.”.
Measuring device: RSA III manufactured by TI Instruments
Sample size: width 5mm, length 50mm
Gap: 20mm
Measurement conditions: Tensile mode Measurement temperature: 25-210 ° C
Temperature rising condition: 5 ° C / min
Frequency: 1Hz

The in-plane slow axis of the substrate film is an axis in the direction in which the in-plane refractive index is maximum. The in-plane slow axis is usually the maximum stretching direction, and can be, for example, the TD direction (width direction) in the roll body of the long base film. The angle θ1 (orientation angle) between the in-plane slow axis and the film width direction can be ± 1 ° or less, preferably ± 0.5 ° or less. The in-plane slow axis direction and the angle θ1 formed by the film width direction or longitudinal direction (preferably the width direction) are measured using an automatic birefringence meter KOBRA-21ADH or KOBRA-WR (Oji Scientific Instruments). It 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 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 5 parts by mass or more with respect to 100 parts by mass of the cellulose ester; and the stretching temperature is 140 ° C. or more, and the stretching ratio is 5%. The above is preferable. In addition, the storage elastic modulus can be increased by making the polyester-based additive “a structure containing an aromatic ring or an aliphatic ring” or by making the molecular weight below a certain level.

(Elongation at break)
The elongation at break of the base film can be preferably 10 to 80%, more preferably 20 to 50%.

(Internal haze)
The internal haze of the base film measured by a method according to JIS K-7136 may be less than 1%, preferably 0.1% or less, more preferably 0.05% or less.

The internal haze can be adjusted by the molecular weight and content of the polyester-based additive. In order to reduce the internal haze, for example, the molecular weight and content of the polyester-based additive are kept below a certain level, or the hydroxyl group-containing monocarboxylic acid that is end-capped has an aromatic hydrocarbon ring that has high affinity with the cellulose ester. Is preferably introduced.

(Thickness)
The base film can be preferably 10 to 80 μm, more preferably 10 to 60 μm, and even more preferably 15 to 50 μm. As described above, since the base film has a sufficient storage elastic modulus even when the thickness is as thin as 50 μm or less, the hardness of the polarizing plate protective film can be increased to a certain level or more.

1-3. Active energy ray cured product layer The active energy ray cured product layer may be preferably a hard coat layer or an antiglare layer. By providing the active energy ray cured product layer on the base film, the surface hardness of the entire film can be increased.

The active energy ray cured product layer may be a cured product of a coating film composed of a coating solution for an active energy ray cured product layer containing a curable compound, a photopolymerization initiator, and a solvent.

<Curable compound>
The curable compound contained in the coating solution for the active energy ray-curable layer is a compound that is cured by irradiation with active energy rays, preferably a compound having an ethylenically unsaturated double bond, and more preferably an acrylate compound. sell.

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

<Photopolymerization initiator>
Examples of the photopolymerization initiator contained in the coating solution for the active energy ray curable layer include acetophenone, benzophenone, hydroxybenzophenone, Michler's ketone, α-amyloxime ester, thioxanthone, and derivatives thereof. The content ratio of the photopolymerization initiator may be 0.01 to 20 parts by mass with respect to 100 parts by mass of the curable compound.

<Solvent>
Examples of the solvent contained in the coating solution for the active energy ray cured layer include:
Ketones such as methyl ethyl ketone, acetone, cyclohexanone, methyl isobutyl ketone;
Esters such as methyl acetate, ethyl acetate, butyl acetate, propyl acetate, propylene glycol monomethyl ether acetate;
Alcohols such as ethanol, methanol, butanol, n-propyl alcohol, isopropyl alcohol, diacetone alcohol;
Hydrocarbons such as toluene, xylene, benzene, cyclohexane;
Examples include glycol ethers such as propylene glycol monomethyl ether, propylene glycol monopropyl ether, and ethylene glycol monopropyl ether. Of these, 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) alkyl ether ester is preferable. More preferably, it is contained in an amount of at least 5% by mass, more preferably 5-80% by mass.

The coating solution for the active energy ray-cured layer may further contain a leveling agent for enhancing the coatability, fine particles for adjusting the hardness and refractive index of the active energy ray-cured product layer, if necessary.

<Leveling agent>
Preferred examples of the leveling agent include a fluorine-siloxane graft compound. The fluorine-siloxane graft compound is a copolymer obtained by grafting polysiloxane and / or organopolysiloxane containing siloxane and / or organosiloxane alone to at least a fluorine-based resin. Examples of commercially available fluorine-siloxane graft compounds include ZX-022H, ZX-007C, ZX-049, and ZX-047-D manufactured by Fuji Kasei Kogyo Co., Ltd.

<Fine particles>
From the viewpoint of adjusting the hardness and refractive index of the cured product and imparting unevenness to the surface to provide an antiglare function (antiglare function), the active energy ray cured layer coating solution contains fine particles as necessary. It may further include. The fine particles may be organic fine particles or inorganic fine particles.

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

Examples of the inorganic fine particles include those similar to the fine particles added as a matting agent to the above-described base film, and are preferably silicon dioxide (silica) fine particles. The silica fine particles may be reactive silica fine particles described in paragraphs 0230 to 0258 of International Publication No. 2011/158626 from the viewpoint of improving dispersibility.

The active energy ray-cured layer coating solution may contain metal oxide fine particles from the viewpoint of making it easier to adjust the refractive index of the cured product. The metal oxide fine particles preferably have a refractive index measured at a wavelength of 550 nm of 1.80 to 2.60, 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. May be zinc antimonate particles.

The average primary particle diameter 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 micrograph taken with a scanning electron microscope (SEM) or the like.

For example, the refractive index of the hard coat layer measured at 23 ° C. and 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 amount of the metal oxide fine particles added.

The thickness of the active energy ray cured product layer is preferably 3 to 30 μm, more preferably 5 to 15 μm, from the viewpoint of obtaining sufficient hardness. Since the above-mentioned base film has high hardness, high hardness is easily obtained even if the thickness of the active energy ray cured product layer is reduced to, for example, 15 μm or less.

The polarizing plate protective film of the present invention may further have functional layers such as an antistatic layer, a backcoat layer, a slippery layer, an adhesive layer, a barrier layer, and an antireflection layer as necessary.

1-4. Manufacturing method of polarizing plate protective film The polarizing plate protective film of the present invention includes 1) a step of preparing the above-mentioned base film, and 2) after applying a coating solution for an active energy ray cured product layer on the base film. , Drying and curing to obtain an active energy ray cured product layer.

The step of preparing the base film of 1) above is the above described 1-2. It can be the same as the manufacturing method of a base film.

The application of the coating solution for the active energy ray cured layer in the above 2) can be performed by any means such as a dipping method, a die coater method, a wire bar method, and a spray method.

Curing of the coating film of the coating solution for active energy ray cured layer of 2) can be performed by irradiating active energy rays. Examples of the light source that irradiates active energy rays (preferably ultraviolet rays) include 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, and a xenon lamp. Irradiation light amount is sufficient if 20 ~ 10000mJ / cm ² degrees, and preferably 50 ~ 2000mJ / cm ^2. The irradiation time is preferably 0.5 seconds to 5 minutes, and more preferably 3 seconds to 2 minutes from the viewpoint of work efficiency.

1-5. Physical properties (hardness) of protective film for polarizing plate
The polarizing plate protective film can 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 further preferably 4H or more. Thereby, for example, the surface of the liquid crystal display device can be hardly damaged during use.

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

(Retardation)
The retardation R ₀ in the in-plane direction measured under the conditions of a measurement wavelength of 590 nm and 23 ° C. and 55% RH of the polarizing plate protective film is, for example, 0 to 10 nm; and the retardation Rth in the thickness direction is, for example, −5 to It can be 20 nm. A polarizing plate protective film having a retardation value within the above range is suitable as a protective film (F1, F4) for a liquid crystal display device described later.

Retardation _R0 and Rth are defined by the following equations, respectively.
Formula (I): R ₀ = (nx−ny) × d (nm)
Formula (II): Rth = {(nx + ny) / 2−nz} × d (nm)
(In formulas (I) and (II),
nx represents the refractive index in the slow axis direction x where the refractive index is maximum in the in-plane direction of the film;
ny represents the refractive index in the direction y perpendicular to the slow axis direction x in the in-plane direction of the film;
nz represents the refractive index in the thickness direction z of the film;
d (nm) represents the thickness of the film)

The retardations _R0 and Rth can be determined by the following method, for example.
1) Condition the polarizing plate protective film at 23 ° C. and 55% RH. The average refractive index of the polarizing plate protective film after humidity adjustment is measured with an Abbe refractometer or the like.
A polarizing plate protective film after 2) humidity, measuring the _{R 0} when the light is incident in parallel to the measurement wavelength 590nm to normal of the film surface, KOBRA21DH, in Oji Scientific Corporation.
3) With KOBRA21ADH, the slow axis in the plane of the polarizing plate protective film is set as the tilt axis (rotation axis), and the measurement wavelength is 590 nm from the angle (incident angle (θ)) with respect to the normal to the surface of the film. The retardation value R (θ) when light is incident is measured. The retardation value R (θ) can be measured at 6 points every 10 °, with θ ranging from 0 ° to 50 °. The in-plane slow axis is an axis having the maximum refractive index in the film plane, and can be confirmed by KOBRA21ADH.
4) nx, ny, and nz are calculated by KOBRA21ADH from the measured R ₀ and R (θ) and the above-described average refractive index and film thickness, and Rth at a measurement wavelength of 590 nm is calculated. The measurement of retardation can be performed under conditions of 23 ° C. and 55% RH.

2. Polarizing plate The polarizing plate of this invention contains a polarizer and the above-mentioned polarizing plate protective film. The polarizing plate protective film is disposed so that the base film is in contact with the polarizer.

2-1. Polarizer A polarizer is an element that passes only light having a polarization plane in a certain direction, and a typical polarizer known at present 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.

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

For example, the ethylene unit content described in JP-A-2003-248123, JP-A-2003-342322, etc. is 1 to 4 mol%, the degree of polymerization is 2000 to 4000, and the degree of saponification is 99.0 to 99.99 mol%. Ethylene-modified polyvinyl alcohol or the like is used. Among these, an ethylene-modified polyvinyl alcohol film having a hot water cutting temperature of 66 to 73 ° C. is preferably used.

The thickness of the polarizer is preferably 5 to 30 μm, and more preferably 10 to 20 μm in order to reduce the thickness of the polarizing plate.

2-2. Other polarizing plate protective film The other polarizing plate protective film may be arrange | positioned on the other surface of a polarizer as needed, and the above-mentioned polarizing plate protective film and base film may be arrange | positioned as needed.

Examples of other polarizing plate protective films include a commercially available cellulose acylate film (for example, Konica Minoltack® 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 or higher, manufactured by Konica Minolta Opto Co., Ltd.).

The retardation of other polarizing plate protective films depends on the type of liquid crystal cell to be combined. For example, the in-plane retardation Ro (590) measured at a wavelength of 590 nm at 23 ° C. and RH 55% is 20 to 100 nm. The retardation Rt (590) in the thickness direction is preferably 70 to 300 nm. A protective film having a retardation in the above range is suitable as a retardation film (protective films (F2, F3) described later) such as a VA liquid crystal cell. Each retardation value can be measured by the same method as described above.

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

The polarizing plate of the present invention can be obtained through a step of bonding the polarizer and the polarizing plate protective film of the present invention through an adhesive; and a step of cutting the bonded laminate into a predetermined size. it can.

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

As described above, the polarizing plate protective film of the present invention can have appropriate toughness. Therefore, in the step of cutting the polarizing plate into a predetermined size, it is possible to suppress the occurrence of cracks and crushing on the cut surface, and the workability of the polarizing plate can be improved. Moreover, since the polarizing plate protective film of this invention has high surface hardness, the polarizing plate obtained can also have high surface hardness.

Moreover, since the polarizing plate protective film of the present invention contains a terminal-capped 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 Device The liquid crystal display device of the present invention includes a liquid crystal cell and a pair of polarizing plates that sandwich the liquid crystal cell.

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

The display mode of the liquid crystal cell 30 may be various display modes such as STN, TN, OCB, HAN, VA (MVA, PVA), and IPS. For obtaining high contrast, the VA (MVA, PVA) mode is used. It is preferable that

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

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

And at least one of the polarizing plate protective film 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) includes 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 high scratch resistance on the surface, so that the display screen can be hardly damaged.

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

Hereinafter, the present invention will be described with reference to examples. By way of example, the scope of the invention is not construed as limiting.

1. Materials (1) Cellulose ester <Synthesis of cellulose ester 1>
50 parts by mass of acetic acid was added to raw pulp (α cellulose 93% or more, water content 8.5%, calcium content in pulp 25 ppm: manufactured by Nippon Paper Industries Co., Ltd.), and an activation treatment was performed for 1 hour. The obtained acetic acid-containing pulp was put into a reactor, and further 500 parts by mass of acetic anhydride and 12 parts by mass of sulfuric acid were added, and the temperature was gradually raised from room temperature to 40 ° C. And it heat-retained for 1 hour, keeping at 40 degreeC, and esterification reaction was advanced.

Next, 250 parts of 30% acetic acid aqueous solution was added to neutralize (primary neutralization step); to neutralize sulfuric acid, 15 parts by mass of 30% by weight magnesium acetate aqueous solution was added to neutralize (reaction stopping step) ); In order to hydrolyze the remaining carboxylic anhydrides, 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 process).

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

Thereafter, the precipitated cellulose acylate was filtered off, washed 5 times with warm water at 50 ° C., and the remaining acetic acid aqueous solution was eluted, followed by drying at 70 ° C. for 3 hours. A triacetyl cellulose having an acyl group substitution degree of 2.89 was obtained. The weight average molecular weight (Mw) was 260,000 as a result of measurement by the method described above.

(Measurement of calcium content)
The obtained triacetyl cellulose sample (3.0 g) was placed in a crucible and carbonized on an electric heater, and then placed in an electric furnace and ashed at 800 ± 10 ° C. for about 2 hours. This was covered and allowed to cool, then 25 ml of 0.07% hydrochloric acid solution was added and dissolved by heating on a hot plate. After allowing to cool, the solution was transferred to a 200 ml Nalgel flask. The crucible was washed with distilled water, the liquid was also transferred to a Nalgel flask, and distilled water was poured up to the marked line. Using this as a test solution, the absorbance was measured using an atomic absorption photometer to determine the amount of Ca in the sample. As a result, the calcium content was 25 ppm.

(2) Polyester-based additive <Synthesis of polyester compound T1>
341 parts of ethylene glycol, 410 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 are thermometer, stirrer and slow cooling Charge to a 2L four-necked flask equipped with a tube and heat at 230 ° C until the acid value becomes 2 or less while refluxing excess monohydric alcohol with a reflux condenser while stirring in a nitrogen stream. The water produced was continuously removed. Next, unreacted ethylene glycol was distilled off at 200 ° C. under reduced pressure of 4 × 10 ² Pa or less to obtain a polyester compound T1.

<Synthesis of polyester compounds T2 to T5>
Polyester compounds T2 to T5 were obtained in the same manner except that the types or molecular weights of the diol, dicarboxylic acid, and end-capping monocarboxylic acid 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 types or molecular weights of the diol, dicarboxylic acid, and end-capping monocarboxylic acid were changed as shown in Table 1.

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

(Measurement of number average molecular weight (Mn))
Using a gel permeation chromatography (GPC) measuring device (“HLC-8330” manufactured by Tosoh Corporation), the number average molecular weight (Mn) of the polyester compound in terms of standard polystyrene was measured under the following conditions.
Column: "TSK gel SuperHZM-M" x 2 and "TSK gel SuperHZ-2000" x 2 Guard column: "TSK SuperH-H"
Developing solvent: Tetrahydrofuran Flow rate: 0.35 ml / min

2. Production of Polarizing Plate Protective Film <Example 1>
(1) Production of base film (Preparation of silicon dioxide diluted dispersion)
Aerosil R812 (manufactured by Nippon Aerosil Co., Ltd.) 10 parts by mass and ethanol 90 parts by mass were stirred and mixed with a dissolver for 30 minutes, and then dispersed with Manton Gorin to obtain a silicon dioxide dispersion.
88 parts by mass of methylene chloride was added to the obtained silicon dioxide dispersion while stirring, and the mixture was stirred and mixed with a dissolver for 30 minutes to obtain a silicon dioxide dispersion dilution. The obtained solution was filtered with a fine particle dispersion dilution filter (Advantech Toyo Co., Ltd. polypropylene wind cartridge filter TCW-PPS-1N).

(Preparation of main dope solution)
The following components were charged into a sealed container, and then completely dissolved while being heated and stirred. Then, the obtained solution was filtered to obtain a main dope solution.
Triacetyl cellulose (acetyl group substitution degree 2.89, Mw = 19000): 100 parts by mass Tinuvin 928 (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 obtained main dope solution, 4 parts by mass of the prepared silicon dioxide dispersion dilution was added while stirring, and further stirred for 30 minutes to obtain a dope solution.

(Film formation)
The obtained dope solution was uniformly cast on a stainless steel band support at a temperature of 35 ° C. and a width of 2 m using a belt casting apparatus. On the stainless steel band support, the cast film was peeled off from the stainless steel band support after the solvent was evaporated until the amount of the residual solvent reached 100% by mass. The film-like material obtained by peeling was conveyed while being dried at 50 ° C., and then slitted.
The obtained film was stretched with a tenter in the TD direction (direction perpendicular to the film transport direction) at a temperature of 160 ° C. at a magnification of 20%, and then dried at 160 ° C. The residual solvent amount of the film-like material when stretching with a tenter was 4.5%.
Next, the obtained film-like material was dried for 15 minutes while being transported in a drying apparatus at 120 ° C. by a number of rolls, slitted, and knurled with a width of 15 mm and a height of 10 μm at both ends of the film. A base film having a thickness of 40 μm was obtained. The draw ratio in the MD direction calculated from the rotational speed of the stainless steel band support and the operating speed of the tenter was 1.05.

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

[Storage modulus]
The base film was cut into a size of 5 mm wide × 50 mm long (length in the in-plane slow axis direction) to prepare a sample. This sample was conditioned at 23 ° C. and 55% RH for 24 hours. This sample was pulled in the length direction while raising the temperature under the following conditions in an environment of 23 ° C. and 55% RH to obtain a temperature-storage modulus curve. From the obtained curve, the value of the storage elastic modulus at 30 ° C. was read out and taken as “the storage elastic modulus in the in-plane slow axis direction at 30 ° C.”.
Measuring device: RSA III manufactured by TI Instruments
Gap: 20mm
Measurement conditions: Tensile mode Measurement temperature: 25-210 ° C
Temperature rising condition: 5 ° C / min
Frequency: 1Hz

[Internal haze]
The internal haze was measured by the following method according to JIS K-7136.
1) One drop (0.05 ml) of glycerin was dropped on the washed slide glass. At this time, care was taken to prevent bubbles from entering the droplets. Next, a cover glass was placed on the dropped glycerin. The glycerin spreads without holding the cover glass. The obtained blank measurement sample (cover glass / glycerin / slide glass) was set on a haze meter, and haze 1 (blank haze) was measured.
2) In the same manner as in 1) above, glycerin was dropped on the washed slide glass. Then, the base film conditioned at 23 ° C. and 55% RH for 5 hours or more was placed on the dropped glycerin so that no bubbles would enter. Further, 0.05 ml of glycerin was dropped on the substrate film, and then a cover glass was further placed. The obtained sample for measurement (cover glass / glycerin / base film / glycerin / slide glass) was set on the aforementioned haze meter, and haze 2 was measured.
3) The haze 1 of the base film was calculated by applying the haze 1 obtained in 1) and the haze 2 obtained in 2) to the following formula.
Internal haze of substrate film (%) = Haze 2 (%) − Haze 1 (%)

The internal haze was measured under conditions of 23 ° C. and 55% RH. The glass used for the measurement was MICRO SLIDE GLASS S9213 MATSUNAMI; the glycerin used for the measurement was Kanto Chemical's deer special grade (purity> 99.0%) and a refractive index of 1.47. As a measuring device, NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd. was used.

The measured haze value was evaluated according to 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) Preparation of hard coat film (polarizing plate protective film) The following components were mixed to obtain a hard coat layer coating solution.
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 Ciba Japan): 5 parts by mass Fluoro-siloxane Graft polymer I (35% by mass): 5 parts by mass Sea Hoster KEP-50 (powdered silica particles, average particle size 0.47 to 0.61 μm, manufactured by Nippon Shokubai Co., Ltd.): 24.3 parts by mass Propylene glycol monomethyl ether: 20 Part by mass Methyl acetate: 40 parts by mass Methyl ethyl ketone: 60 parts by mass 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 hard coat layer was applied on the prepared base film with a die coater so that the thickness after curing was 7 μm. After drying the obtained coating layer at 70 ° C., the coating layer was cured by irradiating with ultraviolet rays under the conditions of illuminance of 300 mW / cm ² and irradiation amount of 0.3 J / cm ^{2 in} a nitrogen atmosphere. The base film having the cured coating layer was heat-treated at 130 ° C. for 5 minutes while being transported at a transport tension of 300 N / m to obtain a hard coat film.

[surface hardness]
The surface hardness of the hard coat layer of the obtained hard coat film was measured by a pencil height evaluation method based on JIS K5400. Specifically, the hard coat film was conditioned at 23 ° C. and 55% RH for 24 hours. Thereafter, the operation of scratching the surface of the hard coat layer with a pencil of each hardness using a 1 kg weight was repeated five times, and the maximum value of the hardness at which one scratch 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 μm 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 ° C. to a stretching ratio of 6 times in the transport direction. A polarizer having a thickness of 20 μm was obtained.

The obtained polarizer was subjected to alkali saponification treatment under the following conditions.
Saponification step: 2.5 M NaOH 50 ° C. 90 seconds Water washing step: Water 30 ° C. 45 seconds Neutralization step: 10 parts by mass HCl 30 ° C. 45 seconds Water washing step: water 30 ° C. 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 bonded to both surfaces of the prepared polarizer through a completely saponified polyvinyl alcohol aqueous solution. The laminated laminate was dried to obtain a long polarizing plate. The bonding was performed so that the transmission axis of the polarizer and the in-plane slow axis 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 polarizing plate]
The obtained polarizing plate sample was cut (punched) with a compression force of 50 kN using a 10 cm square Thomson blade (40 °) in a size of 576 × 324 mm to obtain a polarizing plate.
About the edge part (cut surface) of the polarizing plate after a punching process, the state of the edge part (cut surface) was observed using the 10 times loupe, and the crack and the crack were evaluated on the following references | standards.
◎: Level at which no cracking / crushing occurs ○: Cracking / crushing is slightly observed but there is no practical problem △: Cracking / crushing is slightly observed ×: Cracking・ Level where occurrence of sasare is seen

[Polarizer degradation]
The transmittance T0 of the obtained polarizing plate was measured using NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd. in accordance with JIS K7136. Next, after this polarizing plate was treated at 80 ° C. and 90% RH for 120 hours, the transmittance Td was measured by the same method as described above. The obtained value was applied to the following formula to determine the transmittance difference ΔT.
Transmittance difference ΔT (%) = Td (transmittance after processing) −T0 (transmittance before processing)
Then, polarizer deterioration was evaluated according to the following criteria.
◎: ΔT is less than 1% ○: ΔT is 1% or more and less than 5% △: ΔT is 5% or more and less than 10% ×: ΔT is 10% or more and less than 15% XX: ΔT is 15% or more

<Examples 2 to 5, Comparative Examples 1 to 8>
A base film was produced in the same manner as in Example 1 except that the type of the polyester-based additive was changed as shown in Table 2. Moreover, the polarizing plate protective film and the polarizing plate were produced like Example 1, and the same evaluation was performed.

<Examples 6 to 8, Comparative Example 9>
A base film was produced in the same manner as in Example 1 except that the thickness of the base film was changed as shown in Table 3. Moreover, the polarizing plate protective film and the polarizing plate were produced like Example 1, and the same evaluation was performed.

<Examples 9 to 12>
A base film was produced in the same manner as in Example 1 except that the addition amount of the polyester-based additive was changed as shown in Table 4. Moreover, the polarizing plate protective film and the polarizing plate were produced like Example 1, and the same evaluation was performed.

<Example 13 and Comparative Example 10>
A base film of Example 13 was produced in the same manner as in Example 1 except that the stretching conditions were changed as shown in Table 5; Comparative Example 4 was changed except that the stretching conditions were changed as shown in Table 5 Similarly, a base film of Comparative Example 10 was produced. And the polarizing plate protective film and the polarizing plate were produced like Example 1, and the same evaluation was performed.

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, and the evaluation results of Examples 9 to 12 are shown in Table 4. Table 5 shows the evaluation results of Example 13 and Comparative Example 10.

As shown in Table 2, it can be seen that Examples 1 to 5 have higher surface hardness of the polarizing plate protective film and better punchability of the polarizing plate than Comparative Examples 1 to 8. This is 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 ring structure, so that the storage elastic modulus of the base film is high, and This is considered to be because of having good toughness.

Further, it can be seen that the polarizing plate of Example 1 has less polarizer deterioration than the polarizing plates of Comparative Examples 1, 6 and 7. This is considered to be because the hydrophobicity of the base film was enhanced by sealing the molecular ends of the polyester-based additive; particularly by sealing with a monocarboxylic acid containing an aromatic ring having high hydrophobicity.

Moreover, it turns out that the base film of Example 1 has a higher storage elastic 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 because the polyester-based additive has a lower molecular weight than the polyester-based plasticizer of Example 5, and is therefore highly compatible with the cellulose ester. . The reason why the storage elastic modulus of Example 1 is high is considered to be that since the compatibility of the polyester plasticizer with the cellulose ester is high, the ordering property is high and the film is easily oriented by stretching.

As shown in Table 3, it can be seen that when the film thickness of the substrate film is 15 μm or more, the surface hardness of the polarizing plate protective film can be increased and the punching property of the polarizing plate can be improved. It is shown that it is advantageous from a viewpoint of thin film formation that the film thickness of a base film is 50 micrometers or less.

As shown in Table 4, when the content of the polyester-based additive is 20 parts by mass or less with respect to 100 parts by mass of the cellulose ester, the storage elastic modulus of the base film is increased without excessively increasing the internal haze. It is shown that It is shown that a polarizer deterioration can be suppressed as it is 5 mass parts or more. 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, it can be seen that the base films of Example 1 and Comparative Example 4 stretched at high temperatures have lower internal haze than the base films of Example 13 and Comparative Example 10 stretched at low temperatures. This is considered to be because an excessive stretching stress can be suppressed by stretching at a high temperature.

This application claims priority based on Japanese Patent Application No. 2015-003496 filed on Jan. 9, 2015. The contents described in the application specification and the drawings are all incorporated herein.

According to the present invention, it is possible to provide a polarizing plate protective film that has a high surface hardness even when it is thinned, and that can suppress a decrease in punching processability and polarizer deterioration during the production of a polarizing plate.

DESCRIPTION OF SYMBOLS 10 Liquid crystal display device 30 Liquid crystal cell 50 1st polarizing plate 51 1st polarizer 53 Protective film (F1)
55 Protective film (F2)
70 Second polarizing plate 71 Second polarizer 73 Protective film (F3)
75 Protective film (F4)
90 backlight

Claims

A polarizing plate protective film comprising a base film and an active energy ray cured product layer,
The base film includes a cellulose ester and a polyester-based additive represented by the following formula (1),
The substrate film is a polarizing plate protective film having a film thickness of 15 to 50 μm and a storage elastic modulus in the in-plane slow axis direction at 30 ° C. of 5.0 to 7.0 GPa.
Formula (1): B- (GA) n-GB
(In the formula (1),
B is a group derived from a hydroxyl group-containing monocarboxylic acid containing a ring structure;
G is selected from the group consisting of alkylene diols having 2 to 12 carbon atoms, cycloalkylene diols having 6 to 12 carbon atoms, oxyalkylene diols having 4 to 12 carbon atoms, and arylene diols having 6 to 12 carbon atoms. A group derived from at least one species,
A represents a group derived from at least one selected from the group consisting of alkylene dicarboxylic acids having 4 to 12 carbon atoms, cycloalkylene dicarboxylic acids having 6 to 16 carbon atoms, and arylenedicarboxylic acids having 8 to 16 carbon atoms. And
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 hydroxyl group-containing monocarboxylic acid containing an aromatic hydrocarbon ring.
The polarizing plate protective film according to claim 1, wherein the polyester-based additive has a number average molecular weight of 300 or more and less than 700.
2. 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 with respect 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 coat layer or an antiglare layer.
It is a manufacturing method of the polarizing plate protective film according to claim 1,
Stretching a film-like material containing a cellulose ester and a polyester-based additive represented by the following formula (1) at a temperature of 140 to 180 ° C. at a magnification of 5 to 30% to obtain a base film;
The manufacturing method of a polarizing plate protective film including the process of apply | coating the composition for active energy ray hardened | cured material layers on the said base film, and making it dry and harden | cure and obtaining an active energy ray hardened | cured material layer.
Formula (1): B- (GA) n-GB
(In the formula (1),
B is a group derived from a hydroxyl group-containing monocarboxylic acid containing a ring structure;
G is selected from the group consisting of alkylene diols having 2 to 12 carbon atoms, cycloalkylene diols having 6 to 12 carbon atoms, oxyalkylene diols having 4 to 12 carbon atoms, and arylene diols having 6 to 12 carbon atoms. A group derived from at least one species,
A represents a group derived from at least one selected from the group consisting of alkylene dicarboxylic acids having 4 to 12 carbon atoms, cycloalkylene dicarboxylic acids having 6 to 16 carbon atoms, and arylenedicarboxylic acids having 8 to 16 carbon atoms. And
n represents an integer of 0 or more)
Including a polarizer and the polarizing plate protective film according to claim 1,
The polarizing plate with which the base film of the said polarizing plate protective film is in contact with the said polarizer.
A liquid crystal cell, and a first polarizing plate and a second polarizing plate sandwiching the liquid crystal cell,
The first polarizing plate has a first polarizer and a polarizing plate protective film disposed on a surface opposite to the liquid crystal cell of the first polarizer,
The second polarizing plate has a second polarizer and a polarizing plate protective film disposed on the surface opposite to the liquid crystal cell of the second polarizer,
The polarizing plate protective film of the first polarizing plate is the polarizing plate protective film according to claim 1, and the base film of the polarizing plate protective film of the first polarizing plate is the first polarizer. The polarizing plate protective film of the second polarizing plate is the polarizing plate protective film according to claim 1, and the base film of the polarizing plate protective film of the second polarizing plate is the second polarizing plate. A liquid crystal display device in contact with the polarizer.