JP5428045B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a cellulose ester film, a polarizing plate using the same, and a liquid crystal display device.

  Liquid crystal display devices are widely used as image display devices because of the advantages of low power consumption and space saving.

  The VA mode liquid crystal display device has a merit that the contrast is higher than that of other liquid crystal display modes, but has a problem that a change in contrast and color is large depending on a viewing angle. In order to solve this problem, an improved method using an optical compensation film and a combination thereof has been proposed. For example, a method of disposing two biaxial films on both sides so as to sandwich a liquid crystal cell is disclosed (for example, see Patent Document 1).

  In recent years, with the further thinning of liquid crystal display devices, the optical compensation film is required to have high durability against heat and humidity.

  This is because the distance between the backlight and the polarizing plate is reduced with the thinning of the panel, and the influence of heat generation from the backlight unit is increased.

  The low durability of the optical compensation film to heat and humidity is undesirable because it causes corner unevenness. Corner unevenness refers to a phenomenon in which four corners are whitened when a shrinkage stress is applied to the optical compensation film constituting the polarizing plate and the screen is displayed in black. Although the corner unevenness can be improved by thinning the retardation film, high retardation development per unit film thickness is required for thinning the optical compensation film.

  Examples of the increase in retardation include the use of a cellulose ester having a low degree of substitution and the addition of a triazine compound, but in each case, the retardation development is insufficient.

  In a combination of a cellulose ester having a high degree of substitution and a triazine compound (see, for example, Patent Document 2), there is a problem in retardation film stability due to large deterioration over time such as fluctuations in retardation values and bleeding out of additive compounds.

  On the other hand, from the viewpoint of productivity of a liquid crystal display, a method of disposing a biaxial film having a large retardation value only on one side is disclosed (for example, see Patent Document 3).

  In this configuration, a high retardation value is required on one side, but a retardation film is often disposed on the backlight side, and further improvements in heat and humidity fluctuations are required.

  There are combinations of cellulose esters and aromatic terminal ester compounds (see, for example, Patent Documents 4 and 5), but the stability over time was insufficient.

  Under the circumstances described above, cellulose exhibits a high retardation value even in a thin film, and also has small environmental fluctuations (small corner unevenness) and excellent temporal stability (especially phase difference fluctuations, bleed-out properties). It was difficult to obtain an ester film.

JP 2003-294944 A JP 2003-344655 A JP 2003-344856 A WO2006 / 121026 Pamphlet JP 2007-138121 A

  An object of the present invention is to provide a cellulose ester film having high contrast, small environmental fluctuation (small corner unevenness), good temporal stability (especially retardation value fluctuation, bleeding out property), and a polarizing plate using the same. There is to do.

  The inventor has found that a film having high retardation value and high stability (color unevenness, fluctuation of retardation value, suitability for additive compound bleed-out) can be achieved by the following constitution 1.

  Furthermore, it has been found that the use of a cellulose ester having a bulky substituent such as a propyl substituent has better performance, and has led to the present invention.

  The above object of the present invention can be achieved by the following configuration.

  1. Contains at least one cellulose ester having a residual hydroxyl group of 0.3 or more and 1.0 or less and a compound that increases the retardation value, and has a film thickness of 20 μm to 60 μm, and a refractive index at 590 nm. nx, ny, nz satisfy | fills following formula (1), The cellulose-ester film characterized by the above-mentioned.

Formula (1)
6.7 × 10 ⁻⁴ <(nx−ny) <5.0 × 10 ⁻³ , and
3.3 × 10 ⁻³ <(nx + ny) / 2−nz <1.5 × 10 ⁻²
(In the formula, nx and ny represent the refractive index in the plane of 590 nm (where nx> ny), and nz represents the refractive index in the thickness direction of 590 nm.)
2. 2. The cellulose ester film as described in 1 above, which contains at least one compound represented by the following general formula (1).

General formula (1) B- (GA) n-GB
(In the formula, B is a benzene monocarboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms, A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.)
3. 3. The cellulose ester film as described in 1 or 2 above, wherein the compound that increases the retardation value is a compound represented by the following general formula (2).

(Wherein X ¹ represents a single bond, —NR ⁴ —, —O— or —S—, X ² represents a single bond, —NR ⁵ —, —O— or —S—, and X ³ Represents a single bond, —NR ⁶ —, —O— or —S—, and R ¹ , R ² and R ³ each independently represents an alkyl group or an alkenyl group, each of which may have a substituent. Represents an aromatic ring group or a heterocyclic group, and R ⁴ , R ⁵ and R ⁶ are each independently a hydrogen atom or an alkyl group, an alkenyl group, an aromatic group, each of which may have a substituent. Represents a cyclic group or a heterocyclic group.)
4). 4. The cellulose ester film as described in any one of 1 to 3 above, wherein the cellulose ester is a cellulose ester substituted with propionyl.

  5. The cellulose ester film according to any one of 1 to 4 is bonded to one side of a polarizer composed of polyvinyl alcohol, and the film thickness is 20 μm to 70 μm on the opposite side of the polarizer. The polarizing plate characterized by having bonded.

  6). The polarizing plate characterized by the cellulose-ester film of any one of said 1-4 being bonded on the one side of the polarizer comprised from polyvinyl alcohol.

  7). 7. A liquid crystal display device using the polarizing plate described in 5 or 6 above.

  8). A liquid crystal cell; two polarizing plates disposed on both sides of the liquid crystal cell; and an optical compensation film disposed on at least one of the polarizing plate and the liquid crystal cell, wherein the polarizing plate is a polarizer. And at least one sheet on the side close to the liquid crystal cell among the cellulose ester films is the cellulose ester film according to any one of 1 to 4 above. There is a liquid crystal display device.

  9. 9. The liquid crystal display device as described in 7 or 8 above, wherein the liquid crystal cell of the liquid crystal display device is in a VA mode.

  INDUSTRIAL APPLICABILITY According to the present invention, a cellulose ester film having high contrast, small environmental fluctuation (small corner unevenness), and good temporal stability (particularly phase difference fluctuation and bleeding out property), a polarizing plate using the same, and a liquid crystal display device Could be provided.

  The present invention will be described in more detail.

<Refractive index>
The cellulose ester film of the present invention has a thickness of 20 μm to 55 μm, and the in-plane refractive indexes nx and ny at 590 nm and the refractive index nz in the thickness direction satisfy the formula (1). However, nx> ny.

More preferably, 9.1 × 10 ⁻⁴ <(nx−ny) <3.0 × 10 ⁻³ and
3.5 × 10 ⁻³ <(nx + ny) / 2−nz <8.3 × 10 ⁻³
More preferably, 1.2 × 10 ⁻³ <(nx−ny) <2.3 × 10 ⁻³ and
It is 4.0 * 10 < ^-3 ><(nx + ny) / 2-nz <6.6 * 10 < ^-3 >.

  These refractive indexes are measured by the following method.

  The average refractive index nave of the optical film was measured using an Abbe refractometer 1T (manufactured by Atago Co., Ltd.) and a spectral light source device. Moreover, the thickness of the film was measured using a commercially available micrometer.

  Using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments Co., Ltd.), the retardation of the film at a wavelength of 590 nm was measured under the same environment for 24 hours in an environment of 23 ° C. and 55% RH. It was. Nx, ny, and nz were obtained from the following formulas using the average refractive index nave, the film thickness, the in-plane retardation Ro, and the retardation Rt in the thickness direction.

Ro = (nx−ny) × d
Rt = {(nx + ny) / 2−nz} × d
nave = (nx + ny + nz) / 3
In the formula, the refractive index in the slow axis direction in the plane is nx, the refractive index in the direction perpendicular to the slow axis in the plane is ny, the refractive index in the thickness direction of the film is nz, and d is the thickness of the film (nm ) Respectively.

<Cellulose ester>
The cellulose ester of the present invention is not particularly limited, and is a cellulose ester having a residual hydroxyl group of 0.3 to 1.0, but a residual hydroxyl group of 0.5 to 1.0 is more preferable. The cellulose ester is a carboxylic acid ester having about 2 to 22 carbon atoms and may be an aromatic carboxylic acid ester, and is particularly preferably a lower fatty acid ester having 6 or less carbon atoms.

  The acyl group bonded to the hydroxyl group may be linear or branched or may form a ring. Furthermore, another substituent may be substituted. When the degree of substitution is the same, birefringence decreases when the number of carbon atoms is large, and therefore, the number of carbon atoms is preferably selected from acyl groups having 2 to 6 carbon atoms. The cellulose ester preferably has 2 to 4 carbon atoms, more preferably 2 to 3 carbon atoms.

  Specifically, the cellulose ester includes cellulose acetate propionate, cellulose acetate butyrate, or a mixed fatty acid ester of cellulose to which a propionate group or a butyrate group is bonded in addition to an acetyl group such as cellulose acetate propionate butyrate. Can be used.

  The butyryl group forming butyrate may be linear or branched. The cellulose ester preferably used in the present invention is a cellulose ester in which the cellulose ester is particularly substituted with propionyl.

  The number average molecular weight of the cellulose ester used in the present invention is preferably in the range of 60,000 to 300,000 because the mechanical strength of the resulting film is strong. Furthermore, the thing of 70000-200000 is used preferably.

  The weight average molecular weight Mw and number average molecular weight Mn of the cellulose ester were measured using gel permeation chromatography (GPC).

  The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (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 Corporation) Mw = 100000 to 500 calibration curves with 13 samples were used. Thirteen samples are used at approximately equal intervals.

  The cellulose used as a raw material of the cellulose ester used in the present invention is not particularly limited, and examples thereof include cotton linter, wood pulp, and kenaf. Moreover, the cellulose ester obtained from them can be mixed and used in arbitrary ratios, respectively.

  The cellulose ester such as cellulose acetate phthalate of the present invention can be produced by a known method. Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

<Ester compound in which at least one of pyranose structure or furanose structure is 1 or more and 12 or less and all or part of OH groups of the structure are esterified>
The cellulose ester film of the present invention preferably contains an ester compound having at least one pyranose structure or furanose structure and having all or part of OH groups in the structure esterified.

  The proportion of esterification is preferably 70% or more of the OH groups present in the pyranose structure or furanose structure.

  The compound represented by the general formula (2) described later has a high polarizability and easily develops a phase difference, but at the same time has high cohesiveness. In particular, when used in combination with a cellulose ester having a large number of hydroxyl groups and a low degree of substitution, the aging stability decreases due to large aggregation of the compounds over time. However, when an ester compound containing a pyranose structure or a furanose structure is combined, aggregation is inhibited and the compatibility between the compound represented by the general formula (2) and the cellulose ester is improved. This phenomenon is presumed to be an interaction between the residual hydroxyl group of the cellulose ester and the hydroxyl group contained in the compound represented by the general formula (2). Furthermore, even in cellulose having a low degree of substitution, aggregation is inhibited by the introduction of a bulky substituent, and higher stability is exhibited.

  In the present invention, ester compounds are collectively referred to as sugar ester compounds.

  Examples of the ester compound of the present invention include the following, but the present invention is not limited thereto.

  Glucose, galactose, mannose, fructose, xylose or arabinose, lactose, sucrose, nystose, 1F-fructosyl nystose, stachyose, maltitol, lactitol, lactulose, cellobiose, maltose, cellotriose, maltotriose, raffinose or kestose .

  In addition, gentiobiose, gentiotriose, gentiotetraose, xylotriose, galactosyl sucrose, and the like are also included.

  Among these compounds, compounds having both a pyranose structure and a furanose structure are particularly preferable.

  Examples include sucrose, kestose, nystose, 1F-fructosyl nystose, stachyose, and more preferably sucrose.

  The monocarboxylic acid used for esterifying all or part of the OH groups in the pyranose structure or furanose structure of the present invention is not particularly limited, and known aliphatic monocarboxylic acids, alicyclic monocarboxylic acids, An aromatic monocarboxylic acid or the like can be used. The carboxylic acid used may be one type or a mixture of two or more types.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid , Saturated fatty acids such as tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid, Examples include unsaturated fatty acids such as undecylenic acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid and octenoic acid.

  Examples of preferable alicyclic monocarboxylic acids include acetic acid, cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid, and derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include aromatic monocarboxylic acids having an alkyl group or alkoxy group introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, cinnamic acid, benzylic acid, biphenylcarboxylic acid, and naphthalene. Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as carboxylic acid and tetralin carboxylic acid, or derivatives thereof. More specifically, xylyl acid, hemelic acid, mesitylene acid, prenylic acid, γ-isoduric acid, jurylic acid, mesitic acid, α-isoduric acid, cumic acid, α-toluic acid, hydroatropic acid, atropic acid, hydrocinnamic acid, salicylic acid, o-anisic acid, m-anisic acid, p-anisic acid , Creosote acid, o-homosalicylic acid, m-homosalicylic acid, p-homosalicylic acid, o-pyroca Succinic acid, β-resorcylic acid, vanillic acid, isovanillic acid, veratromic acid, o-veratrumic acid, gallic acid, asaronic acid, mandelic acid, homoanisic acid, homovanillic acid, homoveratrumic acid, o-homoveratrumic acid, phthalonic acid, p- Although coumaric acid can be mentioned, benzoic acid and naphthylic acid are particularly preferable.

  The oligosaccharide ester compound can be applied as a compound having 1 to 12 at least one of the pyranose structure or furanose structure according to the present invention.

  Oligosaccharides are produced by allowing an enzyme such as amylase to act on starch, sucrose, etc. Examples of oligosaccharides that can be applied to the present invention include maltooligosaccharides, isomaltoligosaccharides, fructooligosaccharides, galactooligosaccharides, xylooligos. Sugar.

Moreover, the said ester compound is a compound which condensed 1 or more and 12 or less of at least 1 sort (s) of the pyranose structure or furanose structure represented with the following general formula (A). However, R < ₁₁ > -R < ₁₅ >, R < ₂₁ > -R < ₂₅ > represents a C2-C22 acyl group or a hydrogen atom, m and n represent the integer of 0-12 respectively, and m + n represents the integer of 1-12.

R _{11 to} R ₁₅ and R _{21 to} R ₂₅ are preferably a benzoyl group or a hydrogen atom. The benzoyl group may further have a substituent, for example, an alkyl group, an alkenyl group, an alkoxyl group, and a phenyl group. Further, these alkyl group, alkenyl group, and phenyl group may have a substituent. Good. Oligosaccharides can also be produced by the same method as the ester compound of the present invention.

  Although the specific example of the ester compound which concerns on this invention is given to the following, this invention is not limited to this.

  The cellulose ester film of the present invention preferably contains a sugar ester compound in an amount of 0.5 to 30% by mass of the cellulose ester film in order to suppress the fluctuation of the retardation value and stabilize the display quality. 5 to 20% by mass is preferable.

  In the present invention, a compound that increases the retardation value is added. The compound that increases the retardation value is the case where the addition of 3 to 5 parts by mass with respect to 100 parts by mass of the cellulose ester results in no addition of the retardation value in the thickness direction of the cellulose film measured at a wavelength of 590 nm. It means a compound having a function of increasing to 1.5 times or more (preferably 2.0 times or more). Specifically, the compound etc. which are represented by the said General formula (2) can be mentioned.

<Compound represented by formula (1)>
The cellulose ester film of the present invention preferably contains a compound represented by the general formula (1). In the general formula (1), a benzene monocarboxylic acid residue represented by B and an alkylene glycol residue, oxyalkylene glycol residue or aryl glycol residue represented by G, an alkylene dicarboxylic acid residue or aryl dicarboxylic group represented by A It is composed of an acid residue and can be obtained by a normal reaction.

  Examples of the benzene monocarboxylic acid component of the compound represented by the general formula (1) of the present invention include benzoic acid, para-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, and ethylbenzoic acid. Normalpropyl benzoic acid, aminobenzoic acid, acetoxybenzoic acid, and the like, which can be used as one kind or a mixture of two or more kinds.

  Examples of the alkylene glycol component having 2 to 12 carbon atoms of the compound represented by the general formula (1) of the present invention include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 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-1,3propanediol (3,3-dimethylolheptane), 3-methyl- 1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl 1,3-pentanediol, 2-ethyl 1,3-hexa Diol, 2-methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, etc., and these glycols are used as one kind or a mixture of two or more kinds. used.

  Examples of the oxyalkylene glycol component having 4 to 12 carbon atoms of the compound represented by the general formula (1) of the present invention include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. Yes, these glycols can be used as one or a mixture of two or more.

  Examples of the aryl glycol component having 6 to 12 carbon atoms of the compound represented by the general formula (1) of the present invention include hydroquinone, resorcin, bisphenol A, bisphenol F, bisphenol, and the like. It can be used as one kind or a mixture of two or more kinds.

  Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of the compound represented by the general formula (1) of the present invention include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, There are dodecanedicarboxylic acid and the like, and these are used as one kind or a mixture of two or more kinds, respectively. Examples of the aryl dicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, isophthalic acid, terephthalic acid, 1,5 naphthalenedicarboxylic acid, and 1,4 naphthalenedicarboxylic acid.

  The compound represented by the general formula (1) of the present invention has a number average molecular weight of preferably 300 to 2000, more preferably 500 to 1500. The acid value is preferably 0.5 mgKOH / g or less, the hydroxyl value is 25 mgKOH / g or less, more preferably the acid value is 0.3 mgKOH / g or less, and the hydroxyl value is 15 mgKOH / g or less.

  Although the specific example of a compound represented by General formula (1) below is given, this invention is not limited to these.

<Compound represented by formula (2)>
The cellulose ester film of the present invention preferably contains a compound represented by the general formula (2). By containing the compound represented by the general formula (2), a high retardation value can be obtained.

In the general formula (2), when R ^{1 to} R ³ are an aromatic ring group or a heterocyclic group, as a substituent, a halogen atom, a hydroxyl group, a cyano group, a nitro group, a carboxyl group, an alkyl group, an alkenyl group, Aryl group, alkoxy group, alkenyloxy group, aryloxy group, acyloxy group, alkoxycarbonyl group, alkenyloxycarbonyl group, aryloxycarbonyl group, sulfamoyl group, alkyl-substituted sulfamoyl group, alkenyl-substituted sulfamoyl group, aryl-substituted sulfamoyl group, sulfone At least one selected from amide group, carbamoyl, alkyl-substituted carbamoyl group, alkenyl-substituted carbamoyl group, aryl-substituted carbamoyl group, amide group, alkylthio group, alkenylthio group, arylthio group, and acyl group It is preferred to have a group.

The aromatic ring represented by each of R ^{1 to} R ³ is preferably phenyl or naphthyl, and particularly preferably phenyl. The heterocyclic group preferably has aromaticity. The heterocycle having aromaticity is generally an unsaturated heterocycle, preferably a heterocycle having the largest number of double bonds. The heterocyclic ring is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring, and most preferably a 6-membered ring. The hetero atom of the heterocyclic ring is preferably a nitrogen atom, a sulfur atom or an oxygen atom, and particularly preferably a nitrogen atom. As the heterocyclic ring having aromaticity, a pyridine ring (2-pyridyl or 4-pyridyl as the heterocyclic group) is particularly preferable.

As the substituents for R ^{1 to} R ³ , a halogen atom, an alkyl group, an alkoxy group, and an alkoxycarbonyl group are preferable.

-X ¹ -R ^1, and ^-X 2 -R ² are preferably the same substituents.

  Specific examples of the compound represented by the general formula (2) include those described in (1) to (445) and JP-A-2001-235621 described in paragraph numbers 0028 to 0071 of JP-A No. 2001-166144. (I-1) to (I-10) described in paragraph numbers 0028 to 0071, or I- (1) to (50) described in paragraph numbers 0044 to 0056 of JP-A-2003-344655. ), II- (1) to (9), III- (1) to (12) and IV- (1) to (10), but are not limited thereto.

  Content of the compound represented by General formula (2) of this invention is 0.01-20 mass% with respect to a cellulose ester, Preferably it is 0.1-10%.

<Other additives>
(Plasticizer)
The cellulose ester film of the present invention can contain a plasticizer as necessary to obtain the effects of the present invention.

  The plasticizer is not particularly limited, but is preferably a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a phthalate ester plasticizer, a fatty acid ester plasticizer, a polyhydric alcohol ester plasticizer, or a polyester plasticizer. Agent, acrylic plasticizer and the like.

  Of these, when two or more plasticizers are used, at least one plasticizer is preferably a polyhydric alcohol ester plasticizer.

  The polyhydric alcohol ester plasticizer is a plasticizer comprising an ester of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule. Preferably it is a 2-20 valent aliphatic polyhydric alcohol ester.

  The polyhydric alcohol preferably used in the present invention is represented by the following general formula (a).

Formula _{^{(a) R 11 - (OH}} ) n11
R ¹¹ represents an n-valent organic group, n ¹¹ represents a positive integer of 2 or more, and an OH group represents an alcoholic and / or phenolic hydroxyl group.

  Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these.

  Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane- Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol and the like.

  In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

  There is no restriction | limiting in particular as monocarboxylic acid used for polyhydric alcohol ester, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferred in terms of improving moisture permeability and retention.

  Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-10. When acetic acid is contained, the compatibility with the cellulose ester is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanoic acid, undecylic acid, lauric acid, tridecylic acid, Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid, undecylenic acid, olein Examples thereof include unsaturated fatty acids such as acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which 1 to 3 alkoxy groups such as an alkyl group, a methoxy group or an ethoxy group are introduced into the benzene ring of benzoic acid such as benzoic acid or toluic acid, biphenylcarboxylic acid, Examples thereof include aromatic monocarboxylic acids having two or more benzene rings such as naphthalenecarboxylic acid and tetralincarboxylic acid, or derivatives thereof. Benzoic acid is particularly preferable.

  The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably 300 to 1500, and more preferably 350 to 750. A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose ester.

  The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

  Below, the specific compound of a polyhydric alcohol ester is illustrated.

  The glycolate plasticizer is not particularly limited, but alkylphthalylalkyl glycolates can be preferably used.

  Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl Glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl glycol Butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, octyl phthalate Ethyl glycolate, and the like.

  Examples of the phthalate ester plasticizer include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, and dicyclohexyl terephthalate.

  Examples of the citrate plasticizer include acetyl trimethyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate.

  Examples of fatty acid ester plasticizers include butyl oleate, methylacetyl ricinoleate, and dibutyl sebacate.

  Examples of the phosphate ester plasticizer include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate and the like.

  The polyvalent carboxylic acid ester compound is composed of an ester of divalent or higher, preferably divalent to 20 valent polyvalent carboxylic acid and alcohol. The aliphatic polyvalent carboxylic acid is preferably 2 to 20 valent, and in the case of an aromatic polyvalent carboxylic acid or an alicyclic polyvalent carboxylic acid, it is preferably 3 to 20 valent.

  The polyvalent carboxylic acid is represented by the following general formula (b).

Formula (b) R ¹² (COOH) _m12 (OH) _n12
^{However, R 12} represents (m12 + n12) -valent organic group, m12 represents a positive integer of 2 or more, n12 is an integer of 0 or more, COOH group is a carboxyl group, OH group of the alcohol or phenolic hydroxyl group.

  Examples of preferred polyvalent carboxylic acids include the following, but the present invention is not limited to these.

  Trivalent or higher aromatic polyvalent carboxylic acids such as trimellitic acid, trimesic acid, pyromellitic acid or derivatives thereof, succinic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid, fumaric acid, maleic acid, tetrahydrophthal An aliphatic polyvalent carboxylic acid such as an acid, an oxypolyvalent carboxylic acid such as tartaric acid, tartronic acid, malic acid and citric acid can be preferably used. In particular, it is preferable to use an oxypolycarboxylic acid from the viewpoint of improving retention.

  There is no restriction | limiting in particular as alcohol used for the polyhydric carboxylic acid ester compound which can be used for this invention, Well-known alcohol and phenols can be used.

  For example, an aliphatic saturated alcohol or aliphatic unsaturated alcohol having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

  In addition, alicyclic alcohols such as cyclopentanol and cyclohexanol or derivatives thereof, aromatic alcohols such as benzyl alcohol and cinnamyl alcohol, or derivatives thereof can also be preferably used.

  When an oxypolycarboxylic acid is used as the polycarboxylic acid, the alcoholic or phenolic hydroxyl group of the oxypolycarboxylic acid may be esterified with a monocarboxylic acid. Examples of preferred monocarboxylic acids include the following, but the present invention is not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

  Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, tridecylic acid, Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, and laccelic acid, undecylenic acid, olein Examples thereof include unsaturated fatty acids such as acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid, and tetralin carboxylic acid. The aromatic monocarboxylic acid which has, or those derivatives can be mentioned. Particularly preferred are acetic acid, propionic acid, and benzoic acid.

  The molecular weight of the polyvalent carboxylic acid ester compound is not particularly limited, but is preferably in the range of 300 to 1000, and more preferably in the range of 350 to 750. The larger one is preferable in terms of improvement in retention, and the smaller one is preferable in terms of moisture permeability and compatibility with cellulose ester.

  The alcohol used for the polyvalent carboxylic acid ester that can be used in the present invention may be one kind or a mixture of two or more kinds.

  The acid value of the polyvalent carboxylic acid ester compound that can be used in the present invention is preferably 1 mgKOH / g or less, and more preferably 0.2 mgKOH / g or less. It is preferable to set the acid value within the above range since the environmental fluctuation of the retardation is also suppressed.

  In addition, an acid value means the milligram number of potassium hydroxide required in order to neutralize the acid (carboxyl group which exists in a sample) contained in 1g of samples. The acid value is measured according to JIS K0070.

  Examples of particularly preferred polyvalent carboxylic acid ester compounds are shown below, but the present invention is not limited thereto.

  For example, triethyl citrate, tributyl citrate, acetyl triethyl citrate (ATEC), acetyl tributyl citrate (ATBC), benzoyl tributyl citrate, acetyl triphenyl citrate, acetyl tribenzyl citrate, dibutyl tartrate, diacetyl dibutyl tartrate, Examples include tributyl trimellitic acid and tetrabutyl pyromellitic acid.

(UV absorber)
The cellulose ester film according to the present invention can also contain an ultraviolet absorber. The ultraviolet absorber is intended to improve durability by absorbing ultraviolet rays of 400 nm or less, and in particular, the transmittance at a wavelength of 370 nm is preferably 10% or less, more preferably 5% or less, and further Preferably it is 2% or less.

  Although the ultraviolet absorber used in the present invention is not particularly limited, for example, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, triazine compounds, nickel complex compounds, inorganic powders Examples include the body.

  For example, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxylphenyl) -2H-benzotriazole, (2-2H-benzotriazol-2-yl) -6- (linear and side Chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc., and tinuvin 109, tinuvin 171, tinuvin 234, tinuvin 326, tinuvin 327, tinuvin 328, There are tinuvins such as tinuvin 928, all of which are commercially available from Ciba Japan and can be preferably used.

  The UV absorbers preferably used in the present invention are benzotriazole UV absorbers, benzophenone UV absorbers, and triazine UV absorbers, particularly preferably benzotriazole UV absorbers and benzophenone UV absorbers. .

  In addition, a discotic compound such as a compound having a 1,3,5 triazine ring is also preferably used as the ultraviolet absorber.

  It is preferable that the polarizing plate protective film concerning this invention contains 2 or more types of ultraviolet absorbers.

  As the UV absorber, a polymer UV absorber can also be preferably used, and in particular, a polymer type UV absorber described in JP-A-6-148430 is preferably used.

  The method of adding the UV absorber can be added to the dope after dissolving the UV absorber in an alcohol such as methanol, ethanol or butanol, an organic solvent such as methylene chloride, methyl acetate, acetone or dioxolane or a mixed solvent thereof. Or you may add directly in dope composition.

  For an inorganic powder that does not dissolve in an organic solvent, a dissolver or a sand mill is used in the organic solvent and cellulose ester to disperse and then added to the dope.

  The amount of the UV absorber used is not uniform depending on the type of UV absorber, the operating conditions, etc., but when the dry film thickness of the polarizing plate protective film is 30 to 200 μm, it is 0.5 with respect to the polarizing plate protective film. -10 mass% is preferable, and 0.6-4 mass% is still more preferable.

(Antioxidant)
Antioxidants are also referred to as deterioration inhibitors. When a liquid crystal image display device or the like is placed in a high humidity and high temperature state, the cellulose ester film may be deteriorated.

  The antioxidant has a role of delaying or preventing the cellulose ester film from being decomposed by, for example, a residual solvent amount of halogen in the cellulose ester film or phosphoric acid of a phosphoric acid plasticizer. It is preferable to make it contain in a film.

  As such an antioxidant, a hindered phenol compound is preferably used. For example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di- -T-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino)- 1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octa Sil-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxy Benzyl) -isocyanurate and the like.

  In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3 -(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di- A phosphorus processing stabilizer such as t-butylphenyl) phosphite may be used in combination.

  The addition amount of these compounds is preferably 1 ppm to 1.0%, more preferably 10 to 1000 ppm in terms of mass ratio with respect to the cellulose derivative.

(Fine particles)
The cellulose ester film according to the present invention preferably contains fine particles.

  As fine particles used in the present invention, examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, and hydrated silicic acid. Mention may be made of calcium, aluminum silicate, magnesium silicate and calcium phosphate. Further, fine particles of an organic compound can also be preferably used. Examples of organic compounds include polytetrafluoroethylene, cellulose acetate, polystyrene, polymethyl methacrylate, polypropyl methacrylate, polymethyl acrylate, polyethylene carbonate, acrylic styrene resin, silicone resin, polycarbonate resin, benzoguanamine resin, melamine resin Also, pulverized and classified products of organic polymer compounds such as polyolefin-based powders, polyester-based resins, polyamide-based resins, polyimide-based resins, polyfluorinated ethylene-based resins, and starches. Alternatively, a polymer compound synthesized by a suspension polymerization method, a polymer compound made spherical by a spray dry method or a dispersion method, or an inorganic compound can be used.

  Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable.

  The average primary particle diameter of the fine particles is preferably 5 to 400 nm, and more preferably 10 to 300 nm.

  These 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. preferable.

  The content of these fine particles in the polarizing plate protective film is preferably 0.01 to 1% by mass, particularly preferably 0.05 to 0.5% by mass. In the case of a polarizing plate protective film having a multilayer structure by the co-casting method, it is preferable to contain fine particles of this addition amount on the surface.

  Silicon dioxide fine particles are commercially available, for example, under the trade names Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above Nippon Aerosil Co., Ltd.). it can.

  Zirconium oxide fine particles are commercially available, for example, under the trade names Aerosil R976 and R811 (manufactured by Nippon Aerosil Co., Ltd.), and can be used.

  Examples of the polymer include silicone resin, fluororesin and acrylic resin. 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.) It is marketed by name and can be used.

  Among these, Aerosil 200V and Aerosil R972V are particularly preferably used because they have a large effect of reducing the friction coefficient while keeping the turbidity of the polarizing plate protective film low. In the polarizing plate protective film used in the present invention, the dynamic friction coefficient of at least one surface is preferably 0.2 to 1.0.

  Various additives may be batch-added to a dope that is a cellulose ester-containing solution before film formation, or an additive solution may be separately prepared and added in-line. In particular, it is preferable to add a part or all of the fine particles in-line in order to reduce the load on the filter medium.

  When the additive solution is added in-line, it is preferable to dissolve a small amount of cellulose ester in order to improve mixing with the dope. The amount of the cellulose ester is preferably 1 to 10 parts by mass, more preferably 3 to 5 parts by mass with respect to 100 parts by mass of the solvent.

  In order to perform in-line addition and mixing in the present invention, for example, an in-line mixer such as a static mixer (manufactured by Toray Engineering), SWJ (Toray static type in-tube mixer Hi-Mixer) or the like is preferably used.

<Method for producing cellulose ester film>
Next, the manufacturing method of the cellulose-ester film of this invention is demonstrated.

  The cellulose ester film according to the present invention can be preferably used regardless of whether it is a film produced by a solution casting method or a film produced by a melt casting method.

  The cellulose ester film of the present invention is prepared by dissolving a cellulose ester and an additive in a solvent to prepare a dope, casting a dope onto an endless metal support that moves infinitely, and casting the dope. It is carried out by a step of drying as a web, a step of peeling from a metal support, a step of stretching or maintaining the width, a step of further drying, and a step of winding up the finished film.

  The process for preparing the dope will be described. The concentration of cellulose ester in the dope is preferably higher because the drying load after casting on the metal support can be reduced. However, if the concentration of cellulose ester is too high, the load during filtration increases and the filtration accuracy is poor. Become. As a density | concentration which makes these compatible, 10-35 mass% is preferable, More preferably, it is 15-25 mass%.

  The solvent used in the dope may be used alone or in combination of two or more, but it is preferable to use a mixture of a good solvent and a poor solvent of cellulose ester in terms of production efficiency, and there are many good solvents. This is preferable from the viewpoint of the solubility of the cellulose ester.

  The preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass for the good solvent and 2 to 30% by mass for the poor solvent. With a good solvent and a poor solvent, what melt | dissolves the cellulose ester to be used independently is defined as a good solvent, and what poorly swells or does not dissolve is defined as a poor solvent.

  Therefore, depending on the average acetylation degree (acetyl group substitution degree) of the cellulose ester, the good solvent and the poor solvent change. For example, when acetone is used as the solvent, the cellulose ester acetate ester (acetyl group substitution degree 2.4), cellulose Acetate propionate is a good solvent, and cellulose acetate (acetyl group substitution degree 2.8) is a poor solvent.

  Although the good solvent used for this invention is not specifically limited, Organic halogen compounds, such as a methylene chloride, dioxolanes, acetone, methyl acetate, methyl acetoacetate, etc. are mentioned. Particularly preferred is methylene chloride or methyl acetate.

  Moreover, although the poor solvent used for this invention is not specifically limited, For example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone, etc. are used preferably. Moreover, it is preferable that 0.01-2 mass% of water contains in dope.

  Moreover, the solvent used for melt | dissolution of a cellulose ester collect | recovers the solvent removed from the film by drying at the film-forming process, and uses this again.

  The recovery solvent may contain trace amounts of additives added to the cellulose ester, such as plasticizers, UV absorbers, polymers, monomer components, etc., but even if these are included, they are preferably reused. Can be purified and reused if necessary.

  A general method can be used as a dissolution method of the cellulose ester when preparing the dope described above. When heating and pressurization are combined, it is possible to heat above the boiling point at normal pressure.

  It is preferable to stir and dissolve while heating at a temperature that is equal to or higher than the boiling point of the solvent at normal pressure and that the solvent does not boil under pressure, in order to prevent the generation of massive undissolved materials called gels and mamacos.

  A method in which a cellulose ester is mixed with a poor solvent and wetted or swollen, and then a good solvent is added and dissolved is also preferably used.

  The pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or a method of increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

  The heating temperature with the addition of a solvent is preferably higher from the viewpoint of the solubility of the cellulose ester, but if the heating temperature is too high, the required pressure increases and the productivity deteriorates.

  A preferable heating temperature is 45 to 120 ° C, more preferably 60 to 110 ° C, and still more preferably 70 ° C to 105 ° C. The pressure is adjusted so that the solvent does not boil at the set temperature.

  Alternatively, a cooling dissolution method is also preferably used, whereby the cellulose ester can be dissolved in a solvent such as methyl acetate.

  Next, this cellulose ester solution is filtered using a suitable filter medium such as filter paper. As the filter medium, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matters and the like, but there is a problem that the filter medium is likely to be clogged if the absolute filtration accuracy is too small.

  For this reason, a filter medium with an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium with 0.001 to 0.008 mm is more preferable, and a filter medium with 0.003 to 0.006 mm is still more preferable.

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

  It is preferable to remove and reduce impurities, particularly bright spot foreign matter, contained in the raw material cellulose ester by filtration.

Bright spot foreign matter means that when two polarizing plates are placed in a crossed Nicol state, an optical film or the like is placed between them, light is applied from one polarizing plate side, and observation is performed from the other polarizing plate side. It is a point (foreign matter) where light from the opposite side appears to leak, and the number of bright spots having a diameter of 0.01 mm or more is preferably 200 / cm ² or less.

More preferably, it is 100 pieces / cm < ² > or less, More preferably, it is 50 pieces / m < ² > or less, More preferably, it is 0-10 pieces / cm < ² > or less. Further, it is preferable that the number of bright spots of 0.01 mm or less is small.

  The dope can be filtered by a normal method, but the method of filtering while heating at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil under pressure is the filtration pressure before and after filtration. The increase in the difference (referred to as differential pressure) is small and preferable.

  A preferred temperature is 45 to 120 ° C, more preferably 45 to 70 ° C, and still more preferably 45 to 55 ° C.

  A smaller filtration pressure is preferred. The filtration pressure is preferably 1.6 MPa or less, more preferably 1.2 MPa or less, and further preferably 1.0 MPa or less.

  Here, the dope casting will be described.

  The metal support in the casting (casting) step preferably has a mirror-finished surface. As the metal support, a stainless steel belt or a drum whose surface is plated with a casting is preferably used.

  The cast width can be 1 to 4 m. The surface temperature of the metal support in the casting step is −50 ° C. to a temperature lower than the boiling point of the solvent, and a higher temperature is preferable because the web can be dried faster. May deteriorate.

  A preferable support temperature is 0 to 55 ° C, and more preferably 25 to 50 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent.

  The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing hot air or cold air, and a method of contacting hot water with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short. When warm air is used, wind at a temperature higher than the target temperature may be used.

  In order for the cellulose ester film to exhibit good flatness, the residual solvent amount when peeling the web from the metal support is preferably 10 to 150% by mass, more preferably 20 to 40% by mass or 60 to 130% by mass. Especially preferably, it is 20-30 mass% or 70-120 mass%.

  In the present invention, the amount of residual solvent is defined by the following formula.

Residual solvent amount (% by mass) = {(MN) / N} × 100
M is the mass of a sample collected during or after the production of the web or film, and N is the mass after heating M at 115 ° C. for 1 hour.

  Further, in the drying step of the cellulose ester film, the web is peeled off from the metal support, and further dried, and the residual solvent amount is preferably 1% by mass or less, more preferably 0.1% by mass or less, Especially preferably, it is 0-0.01 mass% or less.

  In the film drying step, generally, a roll drying method (a method in which webs are alternately passed through a plurality of rolls arranged above and below) and a method in which the web is dried while being conveyed by a tenter method are employed.

  In order to produce the cellulose ester film of the present invention, it is particularly preferable to perform stretching in the width direction (lateral direction) by a tenter method in which both ends of the web are held with clips or the like. Peeling is preferably performed at a peeling tension of 300 N / m or less.

  The means for drying the web is not particularly limited, and can be generally performed with hot air, infrared rays, a heating roll, microwave, or the like, but it is preferably performed with hot air in terms of simplicity.

  The drying temperature in the web drying step is preferably increased stepwise from 40 to 200 ° C.

  Although the film thickness of a cellulose-ester film is 20-60 micrometers, 30-55 micrometers is preferable and 35-50 micrometers is more preferable. A width of 1 to 4 m is used. In particular, those having a width of 1.4 to 4 m are preferably used, and particularly preferably 1.6 to 3 m. If it exceeds 4 m, conveyance becomes difficult.

  In order to obtain the target retardation values Ro and Rt in the present invention, it is preferable that the cellulose ester film has the structure of the present invention, and the refractive index is controlled by controlling the transport tension and stretching. In the present invention, preferable retardation values are 40 to 100 for Ro and 180 to 300 for Rt, more preferably 50 to 90 for Ro, 190 to 250 for Rt, and still more preferably 60 to 80 for Ro. And Rt is 200-230.

  For example, it is possible to change the phase difference value by lowering or increasing the tension in the longitudinal direction.

  Further, biaxial stretching or uniaxial stretching can be performed sequentially or simultaneously with respect to the longitudinal direction (film forming direction) of the film and the direction orthogonal to the longitudinal direction of the film, that is, the width direction.

  The draw ratios in the biaxial directions perpendicular to each other are preferably in the range of 0.8 to 1.5 times in the casting direction and 1.1 to 2.5 times in the width direction, respectively. It is preferable to perform in a range of 0.8 to 1.0 times in the direction and 1.2 to 2.0 times in the width direction.

  The stretching temperature is preferably 120 ° C. to 200 ° C., more preferably 150 ° C. to 200 ° C., and more preferably 150 ° C. to 190 ° C. or less.

  The residual solvent in the film is preferably 20 to 0%, more preferably 15 to 0%.

  Specifically, it is preferable that the residual solvent is stretched by 11% at 155 ° C., or the residual solvent is stretched by 2% at 155 ° C. Alternatively, it is preferable that the residual solvent is stretched at 11% at 160 ° C, or the residual solvent is stretched at less than 1% at 160 ° C.

  There is no particular limitation on the method of stretching the web. For example, a method in which a difference in peripheral speed is applied to a plurality of rolls, and the roll peripheral speed difference is used to stretch in the longitudinal direction, the both ends of the web are fixed with clips and pins, and the interval between the clips and pins is increased in the traveling direction. And a method of stretching in the vertical direction, a method of stretching in the horizontal direction and stretching in the horizontal direction, a method of stretching in the vertical and horizontal directions and stretching in both the vertical and horizontal directions, and the like. Of course, these methods may be used in combination.

  In the case of the so-called tenter method, driving the clip portion by the linear drive method is preferable because smooth stretching can be performed and the risk of breakage and the like can be reduced.

  These width maintenance or lateral stretching in the film forming step is preferably performed by a tenter, and may be a pin tenter or a clip tenter.

  The slow axis or the fast axis of the cellulose ester film of the present invention is present in the film plane, and θ1 is preferably −1 ° or more and + 1 ° or less, assuming that the angle formed with the film forming direction is θ1. More preferably, it is 5 ° or more and + 0.5 ° or less.

  This θ1 can be defined as an orientation angle, and θ1 can be measured using an automatic birefringence meter KOBRA-21ADH (Oji Scientific Instruments). Each of θ1 satisfying the above relationship can contribute to obtaining high luminance in a display image, suppressing or preventing light leakage, and contributing to obtaining faithful color reproduction in a color liquid crystal display device.

<Physical properties of cellulose ester film>
The moisture permeability of the cellulose ester film according to the present invention is preferably 300 to 1800 g / m ² · 24 h at 40 ° C. and 90% RH, more preferably 400 to 1500 g / m ² · 24 h, and 40 to 1300 g / m ² · 24 h. Is particularly preferred. The moisture permeability can be measured according to the method described in JIS Z 0208.

  The cellulose ester film according to the present invention preferably has a breaking elongation of 10 to 80%, more preferably 20 to 50%.

  The visible light transmittance of the cellulose ester film according to the present invention is preferably 90% or more, and more preferably 93% or more.

  The haze of the cellulose ester film according to the present invention is preferably less than 1%, particularly preferably 0 to 0.1%.

  Further, by further applying a liquid crystal layer to the cellulose ester film of the present invention, retardation values over a wider range can be obtained.

<Polarizer>
The cellulose ester film of the present invention can be used in a polarizing plate having a polarizing plate protective film and the liquid crystal display device of the present invention using the polarizing plate.

  The polarizing plate of the present invention is characterized in that it is a polarizing plate bonded to at least one surface of a polarizer using the cellulose ester film of the present invention as a polarizing plate protective film. The liquid crystal display device of the present invention is characterized in that the polarizing plate according to the present invention is bonded to at least one liquid crystal cell surface via an adhesive layer.

  The polarizing plate of the present invention can be produced by a general method. The cellulose ester film of the present invention is preferably bonded to at least one surface of a polarizer produced by subjecting the polarizer side to alkali saponification treatment and immersion drawing in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution.

  Even if it uses this cellulose-ester film for another surface, it is preferable to paste another polarizing plate protective film. The film thickness is 20 μm to 60 μm, preferably 25 μm to 55 μm.

  For example, commercially available cellulose ester films (for example, Konica Minoltack KC8UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UY, KC4UE, KC8UE, KC8UY-HA, KC8UX-RWA, KC8UX-RHA, KC8UX-RHA, KC8UX KC4UXW-RHA-NC, manufactured by Konica Minolta Opto, Inc.) is also preferably used.

  In addition to the antiglare layer or the clear hard coat layer, the polarizing plate protective film used on the surface side of the display device preferably has an antireflection layer, an antistatic layer, an antifouling layer, and a backcoat layer.

  A polarizer, which is a main component of a polarizing plate, is an element that allows only light of a plane of polarization in a certain direction to pass. A typical polarizer currently known is a polyvinyl alcohol-based polarizing film, which is polyvinyl alcohol. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed.

  For the polarizer, a polyvinyl alcohol aqueous solution is formed into a film and dyed by uniaxial stretching or dyed or uniaxially stretched and then preferably subjected to a durability treatment with a boron compound. The film thickness of the polarizer is preferably 5 to 30 μm, particularly preferably 10 to 20 μm.

  Further, the ethylene unit content described in JP-A-2003-248123, JP-A-2003-342322, etc. is 1 to 4 mol%, the degree of polymerization is 2000 to 4000, and the degree of saponification is 99.0 to 99.99 mol%. Ethylene-modified polyvinyl alcohol is also preferably used.

  Among them, an ethylene-modified polyvinyl alcohol film having a hot water cutting temperature of 66 to 73 ° C. is preferably used.

  The difference in hot water cutting temperature between two points 5 cm away in the TD direction of the film is more preferably 1 ° C. or less in order to reduce corner unevenness, and two points 1 cm away in the TD direction of the film. It is more preferable that the difference in the hot water cutting temperature is 0.5 ° C. or less in order to reduce corner unevenness.

  A polarizer using this ethylene-modified polyvinyl alcohol film is excellent in polarization performance and durability performance and has little corner unevenness, and is particularly preferably used for a large liquid crystal display device.

  The polarizer obtained as described above is usually used as a polarizing plate with a protective film bonded to both sides or one side thereof. Examples of the adhesive used for pasting include a PVA-based adhesive and a urethane-based adhesive. Among them, a PVA-based adhesive is preferably used.

<Liquid crystal display device>
By using the polarizing plate of the present invention for a liquid crystal display device, the liquid crystal display device of the present invention having various visibility can be produced.

  The cellulose ester film of the present invention can be used in liquid crystal display devices of various drive systems such as STN, TN, OCB, HAN, VA (MVA, PVA), IPS, OCB.

  A VA (MVA, PVA) type liquid crystal display device is preferable.

  In particular, even a large-screen liquid crystal display device with a 30-inch or larger screen can provide a liquid crystal display device with excellent visibility such as uneven coloring and front contrast with little environmental fluctuation and reduced light leakage.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1
<< Production of Cellulose Ester Films 101-121 >>
(Preparation of cellulose ester film 101)
<Fine particle dispersion>
Fine particles (Aerosil R812 manufactured by Nippon Aerosil Co., Ltd.) 11 parts by weight Ethanol 89 parts by weight The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

<Fine particle additive solution>
Cellulose ester B (acetyl group substitution degree 2.9, residual hydroxyl group 0.1, Mn 80000, Mw / Mn 2.4) was added to the dissolution tank containing methylene chloride and heated to completely dissolve it. Azumi Filter Paper No. manufactured by Azumi Filter Paper Co., Ltd. Filtered using 244. The fine particle dispersion was slowly added thereto while sufficiently stirring the filtered cellulose ester solution. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution.

Methylene chloride 99 parts by weight Cellulose ester B 4 parts by weight Fine particle dispersion 11 parts by weight Cellulose ester (acetyl group substitution degree 1.56, propyl group substitution degree 0.9, residual hydroxyl group 0.54, Mn 55000, Mw / Mn 2.4) Was used to prepare a main dope liquid having the following composition. First, methylene chloride and ethanol were added to the pressure dissolution tank. The cellulose ester was added to the pressure dissolution tank containing the solvent while stirring. This was heated and stirred to completely dissolve, and a plasticizer and an ultraviolet absorber were further added and dissolved. This was designated as Azumi Filter Paper No. The main dope solution was prepared by filtration using 244.

  2 parts by mass of the fine particle additive solution is added to 100 parts by mass of the main dope solution and mixed thoroughly with an in-line mixer (Toray static type in-pipe mixer Hi-Mixer, SWJ). It was cast uniformly on the band support. On the stainless steel band support, the solvent was evaporated until the residual solvent amount became 110%, and the stainless steel band support was peeled off. The film was stretched so that the longitudinal (MD) stretch ratio was 1.02 by applying tension at the time of peeling, and then the both ends of the web were gripped by a tenter, and the stretch ratio in the width (TD) direction was 1.3. Residual solvent at the start of stretching, which was stretched to double, was 30%. After stretching, hold for several seconds while maintaining its width, release the width holding after relaxing the tension in the width direction, further carry for 30 minutes in the third drying zone set at 125 ° C., and perform drying, A cellulose ester film 101 of the present invention having a film thickness of 40 μm having a width of 1.5 m, a knurling having a width of 1 cm at the end and a height of 8 μm was produced.

<Composition of main dope solution>
Methylene chloride 300 parts by weight Ethanol 57 parts by weight Cellulose ester 100 parts by weight Phase difference increasing compound (Compound a) 5 parts by weight Ester compound (Compound 5) 8 parts by weight Compound (3) represented by the general formula (1) 5 parts by weight 3 parts by mass of plasticizer (polyhydric alcohol ester 54)

(Production of cellulose ester films 102 to 121)
The cellulose ester films 102 to 121 of the present invention are produced in the same manner as described above except that the cellulose ester, the ester compound, the retardation increasing compound, and the compound represented by the general formula (1) are changed as shown in Table 1. did.

  The average refractive index of the obtained cellulose ester films 101-121 was measured using an Abbe refractometer (1T) and a spectral light source. Moreover, the thickness of each sample of the cellulose ester film was measured using a commercially available micrometer.

  Using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments Co., Ltd.), each sample of a cellulose ester film that was allowed to stand for 24 hours in an environment at a temperature of 23 ° C. and a humidity of 55% RH was measured at a wavelength of 589 nm. Retardation measurement of each sample of the retardation film was performed.

  The above-described average refractive index and film thickness were input to the following formula, and the in-plane retardation value Ro and the thickness direction retardation value Rt were determined. The direction of the slow axis was also measured at the same time.

Ro = (nx−ny) × d
Rt = {(nx + ny) / 2−nz} × d
In the formula, nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the film thickness direction, and d is the film thickness (nm). It is.

<Evaluation items and evaluation methods>
The following evaluation was performed using the obtained cellulose ester film.

<Bleed-out evaluation>
The cellulose ester film was allowed to stand for 1000 hours in a high-temperature and high-humidity atmosphere at 80 ° C. and 90% RH, and then the bleeding out of the film surface was evaluated.

◎: No bleed-out on the film surface ○: Partial bleed-out on the film surface is faint, but there is no problem in use △: Full bleed-out is found on the film surface ×: Entire surface on the film surface Clear bleed out <Haze>
About the produced said cellulose-ester film, the haze value after 60 degreeC, 90% and 120-hour storage was measured. The measurement was carried out according to JIS-K7136 using NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd. with one film sample.

(Fluctuation of phase difference value due to temperature and humidity change)
The prepared cellulose ester film was conditioned for 5 hours or more in an environment of 23 ° C. and 55% RH and 50 ° C. and 20% RH, and then the ratio of the retardation value (Rt) measured in the same environment was taken to obtain the retardation value. Variation was evaluated.

◎: Phase difference fluctuation is less than 5% ○: Phase difference fluctuation is 5% to 14%
Δ: Phase difference fluctuation is 15% to 24%
×: Variation in retardation value is 25% or more << Preparation of polarizing plate >>
Production of (Polarizing plate A) Using the obtained cellulose ester films 101 to 121, a polarizing plate A was produced by the following method.

  A polyvinyl alcohol film having a thickness of 120 μm was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times). This was immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide and 100 g of water for 60 seconds, and then immersed in an aqueous solution of 68 ° C. composed of 6 g of potassium iodide, 7.5 g of boric acid and 100 g of water. This was washed with water and dried to obtain a polarizing film.

  Next, the polarizing film and the cellulose ester films 101 to 121 according to the following steps 1 to 5, and the back side cellulose ester film prepared in the production of the following polarizing plate B are bonded to the back side as a polarizing plate protective film. Was made.

  Step 1: Cellulose ester films 101 to 121 were immersed in a 2 mol / l sodium hydroxide solution at 60 ° C. for 90 seconds, then washed with water and dried to obtain a cellulose ester film having a saponified surface.

  Step 2: The polarizing film was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by mass for 1 to 2 seconds.

  Step 3: Excess adhesive adhered to the polarizing film in Step 2 was gently wiped off, and this was placed on the cellulose ester film treated in Step 1, and further placed on the back side cellulose ester film.

Step 4: The cellulose ester films 101 to 121, the polarizing film, and the back side cellulose ester film laminated in Step 3 were bonded at a pressure of 20 to 30 N / cm ² and a conveyance speed of about 2 m / min.

  Step 5: A polarizing plate prepared in Step 4 in a drier at 80 ° C., the sample obtained by bonding the cellulose ester films 101 to 121 and the back side cellulose ester film were dried for 2 minutes, and a polarizing plate A was prepared.

(Preparation of polarizing plate B)
In making the polarizing plate A, instead of using the cellulose ester films 101 to 121, a polarizing plate B is prepared in the same manner except that the polarizing plate is prepared using the following backside cellulose ester film. did.

(Preparation of the back side cellulose ester film)
<Fine particle dispersion>
Fine particles 11 parts by weight Ethanol 89 parts by weight The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

<Fine particle additive solution>
Cellulose ester B was added to a dissolution tank containing methylene chloride and heated to completely dissolve, and this was then added to Azumi filter paper No. 3 manufactured by Azumi Filter Paper Co., Ltd. Filtered using 244. While finely stirring the filtered cellulose ester solution, the fine particle dispersion was slowly added thereto. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution.

Methylene chloride 99 parts by weight Cellulose ester B 4 parts by weight Fine particle dispersion 11 parts by weight A main dope solution having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose ester B (acetyl group substitution degree 2.9, Mn 80000, Mw / Mn 2.4) was added to a pressure dissolution tank containing a solvent while stirring. This was heated and stirred to completely dissolve, and a plasticizer and an ultraviolet absorber were further added and dissolved. This was designated as Azumi Filter Paper No. The main dope solution was prepared by filtration using 244.

  In addition to adding 100 parts by mass of the main dope solution and 5 parts by mass of the fine particle additive solution, mix thoroughly with an in-line mixer (Toray static type in-pipe mixer Hi-Mixer, SWJ), and then use a belt casting device to It was cast uniformly on a 2 m stainless steel band support. On the stainless steel band support, the solvent was evaporated until the residual solvent amount became 110%, and the stainless steel band support was peeled off. When peeling, the film is stretched so that the longitudinal (MD) stretch ratio is 1.1 times, and then both ends of the web are gripped by a tenter, and the stretch ratio in the width (TD) direction is 1.1. It extended | stretched so that it might become double. After stretching, hold for several seconds while maintaining its width, release the width holding after relaxing the tension in the width direction, further carry for 30 minutes in the third drying zone set at 125 ° C., and perform drying, A cellulose ester film having a thickness of 60 μm, a retardation value Ro = 3 nm, and Rt = 50 nm having a width of 1.5 m, a width of 1 cm at the end, and a height of 8 μm was prepared.

<Composition of main dope solution>
Methylene chloride 300 parts by weight Ethanol 57 parts by weight Cellulose ester B 100 parts by weight Plasticizer (triphenyl phosphate) 9.5 parts by weight Plasticizer (ethylphthalylethyl glycolate) 2.2 parts by weight Ultraviolet absorber (Tinbin 928 (Ciba)・ Japan Co., Ltd.) 1.1 parts by mass UV absorber (Tinubin 171 (Ciba Japan Co., Ltd.)) 0.6 parts by mass << Preparation of liquid crystal display device >>
Using the obtained polarizing plate, a liquid crystal display device was produced as follows.

  The polarizing plates on both sides of the Sony 20-type display KLV-20AP2 previously bonded were peeled off, and the prepared polarizing plates A and B were each bonded to the glass surface of the liquid crystal cell.

  At that time, the polarizing plate A was used on the backlight side, and the direction of bonding of the polarizing plate was previously bonded so that the surfaces of the cellulose ester films 101 to 121 were on the liquid crystal cell side. Liquid crystal display devices 101 to 121 were produced by performing the absorption axis in the same direction as the polarizing plate.

<Evaluation>
<Evaluation of corner unevenness>
Each liquid crystal display device obtained by the above method was stored for 24 hours in an environment of a temperature of 45 ° C. ± 2 ° C. and a humidity of 95 ± 3% RH. Immediately after that, the room is moved to a room with a temperature of 23 ° C. and a humidity of 55% RH, and the panel backlight is turned on. 24 hours after lighting, the front luminance at the four corners in the state of black display is measured, and the average value is calculated. Note that the “four corners” here are on the diagonal line of the effective display screen and the distance from the corner is 50 mm.

  For each liquid crystal display device, the occurrence of corner unevenness was evaluated in the following four stages by the ratio of the average value of the front luminance at the four corners and the front luminance at the center of the screen. The evaluation rank is as follows. The front luminance at the center of the screen of the liquid crystal display device was set to 1. The obtained results are shown in Table 1 below.

Evaluation rank A: No corner unevenness (Four-corner front luminance average; 1.00 to 1.05)
○: Corner unevenness cannot be recognized with the naked eye (Four-corner front luminance average: 1.06 to 1.10)
Δ: Appears as corner irregularity, but does not hinder use (average brightness at front of four corners; 1.11 to 1.20)
X: There is a problem in display quality (four corner front luminance average; 1.21 or more).

(Contrast unevenness)
Each manufactured liquid crystal display device was lit for 1000 hours, and then the viewing angle characteristics of the liquid crystal display device were evaluated by measuring the amount of transmitted light during black display and white display using EZ-contrast manufactured by ELDIM. The viewing angle was evaluated by calculating contrast = (transmitted light amount during white display) / (transmitted light amount during black display) and evaluated according to the following criteria.

  Evaluation was made as to whether or not there was contrast unevenness using the angle indicating the viewing angle of contrast 10 as an index.

◎: Contrast unevenness is not generated ○: Contrast unevenness is slightly generated, but there is no problem in use. It is shown in Table 1.

  From the results of Table 1, the cellulose ester film of the present invention is excellent in bleed-out performance, retardation value fluctuation, and haze value, and the liquid crystal display device comprising the polarizing plate of the present invention has uneven corners and uneven contrast. Is also clearly superior.

Claims (7)

Having a first polarizing plate, a liquid crystal cell, a second polarizing plate, and a backlight in order,
The first polarizing plate has a first polarizer and a cellulose ester film T2 disposed on the surface of the first polarizer on the liquid crystal cell side ,
The second polarizing plate includes a second polarizer and a cellulose ester film T3 disposed on the surface of the second polarizer on the liquid crystal cell side ,
The cellulose ester film T2 contains cellulose triacetate as a main component, and
The cellulose ester film T3 contains a cellulose ester having a hydroxyl group residual ratio of 0.3 or more and 1.0 or less, and at least one compound that increases a retardation value, and has a film thickness of 20 μm to 60 μm. Furthermore, the refractive index at 590 nm nx, ny, nz is a cellulose ester film satisfying the following formulas (1),
Formula (1)
6.7 × 10 ⁻⁴ <(nx−ny) <5.0 × 10 ⁻³ , and
3.3 × 10 ⁻³ <(nx + ny) / 2−nz <1.5 × 10 ⁻²
(In the formula, nx and ny represent the refractive index in the plane of 590 nm (where nx> ny), and nz represents the refractive index in the thickness direction of 590 nm.)
The liquid crystal display device in which the retardation of the cellulose ester film T3 is larger than the retardation of the cellulose ester film T2 . The liquid crystal display device according to claim 1, wherein a residual hydroxyl group of the cellulose ester contained in the cellulose ester film T3 is 0.5 or more and 1.0 or less . The cellulose ester film T3 contains at least one compound represented by the following general formula (1), a liquid crystal display device according to claim 1 or 2.
General formula (1) B- (GA) n-GB
(In the formula, B is a benzene monocarboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, or an oxyalkylene glycol residue having 4 to 12 carbon atoms, A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n represents an integer of 1 or more.) Compounds that increase the phase difference value included in the cellulose ester film T3 is a compound represented by the following general formula (2), a liquid crystal display device according to any one of claims 1-3.

(Wherein X ¹ represents a single bond, —NR ⁴ —, —O— or —S—, X ² represents a single bond, —NR ⁵ —, —O— or —S—, and X ³ Represents a single bond, —NR ⁶ —, —O— or —S—, and R ¹ , R ² and R ³ each independently represents an alkyl group or an alkenyl group, each of which may have a substituent. Represents an aromatic ring group or a heterocyclic group, and R ⁴ , R ⁵ and R ⁶ are each independently a hydrogen atom or an alkyl group, an alkenyl group, an aromatic group, each of which may have a substituent. Represents a cyclic group or a heterocyclic group.) Cellulose ester contained in the cellulose ester film T3 is a cellulose ester which is propionyl substitution, a liquid crystal display device according to any one of claims 1-4. The liquid crystal display device according to claim 1, wherein the first polarizer and the second polarizer are polarizers made of polyvinyl alcohol. The liquid crystal cell is a VA mode liquid crystal display device according to any one of 請 Motomeko 1-6.