JP2009298826A - Cellulose derivative, cellulose derivative film and its application - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new film having high retardation developing properties and excellent kinetic properties. <P>SOLUTION: The film includes a cellulose derivative having a polymerization unit represented by general formula (1) and satisfying the expression (I): DS<SB>B</SB>≥DS<SB>C</SB>(wherein DS<SB>B</SB>is a number of aliphatic groups present as R<SP>2</SP>, R<SP>3</SP>and R<SP>6</SP>, respectively, in the unit; DS<SB>C</SB>is a number of aliphatic carbamate groups present as R<SP>2</SP>, R<SP>3</SP>and R<SP>6</SP>, respectively, in the unit; DS<SB>C</SB>>0; and DS<SB>B</SB>+DS<SB>C</SB>≤3). In the formula, R<SP>2</SP>, R<SP>3</SP>and R<SP>6</SP>each independently represents H, an aliphatic group or an aliphatic carbamate group. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a film having high retardation development properties and excellent mechanical properties, an optical compensation sheet using the same, a polarizing plate, and a liquid crystal display device. The present invention also relates to a novel cellulose derivative useful for producing a film.

Cellulose acylate films have been widely used as polarizing plate protective films for liquid crystal display devices because of their moderate water permeability and high optical isotropy (low retardation value).
In recent years, a method has been proposed in which a phase difference is imparted to a cellulose acylate film so as to have an optical compensation function in addition to a function as a polarizing plate protective film. For example, Patent Document 1 discloses a method in which a triazine type compound having high planarity is added to cellulose acylate to develop retardation.
Patent Documents 2 and 3 each disclose an optical film satisfying predetermined optical properties containing a cellulose mixed ester having two or more different substituents, and the optical film production method includes predetermined conditions. Discloses a method of stretching treatment.

  On the other hand, there are few examination examples of optical film use regarding cellulose derivatives other than cellulose acylate. For example, Patent Document 4 proposes an optical film made of cellulose ether acetate that satisfies a predetermined condition.

JP 2003-170492 A JP 2002-71957 A JP 2005-8803 A JP 2005-283997 A

An object of the present invention is to provide a novel film having high retardation development properties and excellent mechanical properties, an optical compensation sheet, a polarizing plate, and a liquid crystal display device using the same.
Another object of the present invention is to provide a novel cellulose derivative that has good film-forming properties and is useful for producing a film.

  As a result of intensive studies, the present inventors have determined that the degree of substitution between the ether substituent and the carbamate substituent in the cellulose derivative has a large effect on retardation development, and that an ether carbamate hybrid satisfying predetermined conditions is obtained. Thus, it has been found that good mechanical properties can be obtained, and further studies have been made based on this finding, and the present invention has been completed.

［式中、Ｒ²、Ｒ³及びＲ⁶は、それぞれ独立に水素原子、脂肪族基又は脂肪族カルバメート基を表す。］
（Ｉ） ＤＳ_B≧ＤＳ_C
［式中、ＤＳ_Bは、上記単位中にＲ²、Ｒ³及びＲ⁶としてそれぞれ存在する脂肪族基の数であり、ＤＳ_Cは、同単位中にＲ²、Ｒ³及びＲ⁶としてそれぞれ存在する脂肪族カルバメート基の数であり、ＤＳｃ＞０であり、且つＤＳ_B＋ＤＳ_C≦３である。］ That is, the means for solving the above problems are as follows.
[1] A film comprising a cellulose derivative having at least a polymerization unit represented by the following general formula (1) and satisfying the following mathematical formula (I).

[Wherein, R ² , R ³ and R ⁶ each independently represents a hydrogen atom, an aliphatic group or an aliphatic carbamate group. ]
(I) DS _B ≧ DS _C
[Wherein DS _B is the number of aliphatic groups present as R ² , R ³ and R ⁶ in the above unit, respectively, and DS _C is R ² , R ³ and R ^{6 in} the same unit, respectively. The number of aliphatic carbamate groups present, DSc> 0, and DS _B + DS _C ≦ 3. ]

［式中、Ｒ²、Ｒ³及びＲ⁶は、それぞれ独立に水素原子、脂肪族基又は脂肪族カルバメート基を表す。］
（Ｉ） ＤＳ_B≧ＤＳ_C
（II） ０≦ＤＳ_A≦１．２
［式中、ＤＳ_Aは、上記単位中にＲ²、Ｒ³及びＲ⁶として存在する水素原子の数であり、ＤＳ_Bは、同単位中にＲ²、Ｒ³及びＲ⁶としてそれぞれ存在する脂肪族基の数であり、及びＤＳ_Cは、同単位中にＲ²、Ｒ³及びＲ⁶としてそれぞれ存在する脂肪族カルバメート基の数であり、ＤＳｃ＞０であり、且つＤＳ_A＋ＤＳ_B＋ＤＳ_C＝３である。］ [2] The film of [1], wherein the cellulose derivative satisfies the following formula (II).
(II) 0 ≦ DS _A ≦ 1.2
[Wherein DS _A is the number of hydrogen atoms present as R ² , R ³ and R ^{6 in} the above unit, and DS _A + DS _B + DS _C = 3. ]
[3] The film according to [1] or [2], wherein the cellulose derivative satisfies the following mathematical formulas (III) to (V).
(III) 1.6 ≦ DS _B ≦ 2.8
(IV) 0.1 ≦ DS _C ≦ 1.2
(V) 0 ≦ DS _A ≦ 0.5
[4] The film according to any one of [1] to [3], wherein the aliphatic group is a methyl group or an ethyl group.
[5] An optical compensation sheet comprising or including the film according to any one of [1] to [4].
[6] A polarizing plate comprising at least a polarizer and the film of any one of [1] to [4].
[7] A liquid crystal display device comprising the film according to any one of [1] to [4].
[8] A cellulose derivative having at least a polymerization unit represented by the following general formula (1) and satisfying the following mathematical formulas (I) and (II).

[Wherein, R ² , R ³ and R ⁶ each independently represents a hydrogen atom, an aliphatic group or an aliphatic carbamate group. ]
(I) DS _B ≧ DS _C
(II) 0 ≦ DS _A ≦ 1.2
[Wherein DS _A is the number of hydrogen atoms present as R ² , R ³ and R ⁶ in the unit, and DS _B is present as R ² , R ³ and R ^{6 in} the same unit, respectively. DS _C is the number of aliphatic carbamate groups present as R ² , R ³ and R ⁶ , respectively, in the same unit, DSc> 0, and DS _A + DS _B + DS _C = 3. ]

[9] The cellulose derivative according to [8], wherein the following formulas (III) to (V) are satisfied.
(III) 1.6 ≦ DS _B ≦ 2.8
(IV) 0.1 ≦ DS _C ≦ 1.2
(V) 0 ≦ DS _A ≦ 0.5
[10] The cellulose derivative according to [8] or [9], wherein the aliphatic group is a methyl group or an ethyl group.

The film obtained from the cellulose derivative of the present invention has good mechanical properties and is useful for producing optical films and the like. In particular, there is a characteristic that the retardation expression at the time of film formation is high.
Therefore, by using the cellulose derivative of the present invention, it is possible to provide a film with high retardation that is suitable for use as an optical film for liquid crystal display devices, particularly as an optical compensation sheet.
Further, by using the film of the present invention as a protective film for a polarizing plate, an optical compensation function can be added to the polarizing plate without increasing the number of components of the polarizing plate.
Further, the optical compensation sheet of the present invention and the polarizing plate using the optical compensation sheet of the present invention as a protective film are useful for liquid crystal display devices, particularly VA mode and OCB mode liquid crystal display devices. It is possible to provide a liquid crystal display device with high contrast and small color change due to viewing angle.

  Hereinafter, the present invention will be described in detail. Hereinafter, typical embodiments of the present invention will be described, but the present invention is not limited to such embodiments. In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value. Further, in this specification, the term “cellulose derivative” is used to include both a cellulose compound and a compound having a cellulose skeleton obtained by introducing a functional group biologically or chemically using cellulose as a raw material.

[Cellulose derivative film]
The present invention relates to a film containing a cellulose derivative in which the hydrogen atoms of the hydroxyl groups at the 2nd, 3rd and 6th positions of the β-glucose ring which is a structural unit of cellulose are substituted with an aliphatic group and an aliphatic carbamate group. Specifically, the present invention relates to a film containing a cellulose derivative having at least a polymer unit having an aliphatic group and an aliphatic carbamate group represented by the following general formula (1).

In the formula, R ² , R ³ and R ⁶ each independently represent a hydrogen atom, an aliphatic group or an aliphatic carbamate group. In the present invention, a film is obtained by using a cellulose derivative in which the hydrogen atoms of the hydroxyl groups at the 2nd, 3rd and 6th positions of the β-glucose ring which is a structural unit of cellulose are substituted with an aliphatic group and an aliphatic carbamate group. As a film having a sufficient mechanical strength and exhibiting retardation.

In the present invention, a cellulose derivative satisfying the following formula (I) is used.
(I) DS _B ≧ DS _C
In the formula (I), DS _B is the number of aliphatic groups present as R ² , R ³ and R ^{6 in} the same unit, respectively, and DS _C is R ² , R ³ and R in the same unit. ⁶ is the number of each aliphatic carbamate group present. That, DS _B the 2-position, a substitution degree of aliphatic groups to 3-position and the 6-hydroxyl group, and DS _C the 2-position, with substitution degree of aliphatic carbamate groups for the 3-position and the 6-hydroxyl group is there. In the cellulose derivative used in the present invention, at least a part of the hydrogen atoms of the hydroxyl groups at the 2nd, 3rd and 6th positions of the β-glucose ring which is a structural unit of cellulose is substituted with an aliphatic group and an aliphatic carbamate group. Therefore, DS _B > 0 and DS _C > 0 are satisfied, and DS _B + DS _C is 3 or less.

Since aliphatic carbamate groups is the polarizability and hydrogen bonding is large substituent, if the degree of substitution DS _C is increased, the intermolecular hydrogen bonds, improved orientation ratio during the film, the retardation is large Tend to be. On the other hand, when the substitution degree DSc is too high, the film formability is lowered, the surface state of the obtained film is deteriorated, and the film tends to become clouded. Also, the mechanical strength tends to decrease. In the present invention, by using a cellulose acylate derivative satisfying the above formula (I), a film having a good surface shape, sufficient mechanical strength as a film, and a retardation is provided. .

On the other hand, the aliphatic group, the polarizability and hydrogen bonding is a small substituent, if the degree of substitution DS _B is high, there is a tendency that retardation is decreased. Since the aliphatic group has a high density, its presence contributes to the improvement of film moldability and film mechanical properties, but on the other hand, because there is less entanglement, when the proportion of unsubstituted hydroxyl groups in the cellulose derivative increases, There is a tendency that the mechanical strength in the film form is insufficient. In order to express an appropriate intermolecular interaction and impart mechanical strength during film formation, it is preferable to use a cellulose derivative that satisfies the following formula (II).
(II) 0 ≦ DS _A ≦ 1.2
In the formula (II), DS _A is the number of hydrogen atoms present as R ² , R ³ and R ^{6 in} the above unit, that is, DS _A has no hydroxyl groups at the 2nd, 3rd and 6th positions. The percentage that is the substitution. Therefore, DS _A + DS _B + DS _C is 3.

Preferred examples of the cellulose derivative are cellulose derivatives that satisfy the following formulas (III) to (V).
(III) 1.6 ≦ DS _B ≦ 2.8
(IV) 0.1 ≦ DS _C ≦ 1.2
(V) 0 ≦ DS _A ≦ 0.5
Further, more preferred examples of the cellulose derivative are cellulose derivatives that satisfy the following formulas (III) ′ to (V) ′.
(III) '1.8 ≦ DS _B ≦ 2.7
(IV) '0.3 ≦ DS _C ≦ 1.2
(V) '0 ≦ DS _A ≦ 0.2
Cellulose derivatives satisfying the above formulas (III) to (V) and the above formulas (III) ′ to (V) ′ are preferred from the viewpoints of film forming properties and optical properties.

DS _A , DS _B and DS _C are obtained by using the method described in Cellulose Communication 6, 73-79 (1999) and Chrality 12 (9), 670-674, ¹ H-NMR or ¹³ C-NMR. Can be determined.

In the formula (I), the aliphatic groups represented by R ² , R ³ and R ⁶ may be any of linear, branched and cyclic aliphatic groups, and the aliphatic group has 1 to 20 carbon atoms. Are preferable, 1-12 are more preferable, and 1-6 are still more preferable. Of these, a methyl group and an ethyl group are particularly preferable.

In the formula (I), the aliphatic carbamate groups represented by R ² , R ³ and R ⁶ may be any of linear, branched and cyclic aliphatic groups in the aliphatic moiety. 1-20 are preferable, as for the carbon atom number of an aliphatic acyl group, 1-12 are more preferable, and 1-8 are more preferable. Of these, a butyl carbamate group, a hexyl carbamate group or an octyl carbamate group is preferable.

The aliphatic group and the aliphatic carbamate group may have one or more substituents. Examples of the substituent can be selected from the substituent group T listed below.
Substituent group T:
An alkyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, particularly preferably 1 to 8 carbon atoms such as a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, an n-octyl group, n-decyl group, n-hexadecyl group, cyclopropyl group, cyclopentyl, cyclohexyl group, etc.), alkenyl group (preferably having 2 to 20 carbon atoms, more preferably 2 to 12, more preferably 2 to 8). For example, a vinyl group, an allyl group, a 2-butenyl group, a 3-pentenyl group, etc.), an alkynyl group (preferably having 2 to 20 carbon atoms, more preferably 2 to 12 carbon atoms, particularly preferably 2 to 2 carbon atoms). 8, for example, propargyl group, 3-pentynyl group, etc.), aryl group (preferably having 6 to 30 carbon atoms, more preferred) Is 6 to 20, particularly preferably 6 to 12, and examples thereof include a phenyl group, a biphenyl group, a naphthyl group, and the like, an amino group (preferably having 0 to 20 carbon atoms, more preferably 0 to 10, and particularly preferably). Is 0-6, for example, an amino group, a methylamino group, a dimethylamino group, a diethylamino group, a dibenzylamino group, etc., an alkoxy group (preferably having 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms). And particularly preferably 1 to 8, for example, methoxy group, ethoxy group, butoxy group and the like, and aryloxy group (preferably having 6 to 20 carbon atoms, more preferably 6 to 16 and particularly preferably 6 to 6). 12 such as a phenyloxy group and a 2-naphthyloxy group), an acyl group (preferably having 1 to 20 carbon atoms, More preferably, it is 1-16, Most preferably, it is 1-12, for example, an acetyl group, a benzoyl group, a formyl group, a pivaloyl group etc. are mentioned, An alkoxycarbonyl group (preferably C2-C20, More preferably 2 to 16, particularly preferably 2 to 12, for example, methoxycarbonyl group, ethoxycarbonyl group and the like, and aryloxycarbonyl group (preferably having 7 to 20 carbon atoms, more preferably 7 to 16 carbon atoms, particularly preferably Is 7 to 10, for example, a phenyloxycarbonyl group, etc.), an acyloxy group (preferably 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 10 carbon atoms such as an acetoxy group, A benzoyloxy group, etc.), an acylamino group (preferably having 2 carbon atoms) -20, more preferably 2-16, particularly preferably 2-10, for example, acetylamino group, benzoylamino group and the like, alkoxycarbonylamino group (preferably having 2-20 carbon atoms, more preferably 2 to 16, particularly preferably 2 to 12, and examples thereof include a methoxycarbonylamino group and the like, an aryloxycarbonylamino group (preferably having 7 to 20 carbon atoms, more preferably 7 to 16 and particularly preferably 7). -12, such as phenyloxycarbonylamino group), sulfonylamino group (preferably 1-20 carbon atoms, more preferably 1-16, particularly preferably 1-12, for example methanesulfonylamino) Group, benzenesulfonylamino group, etc.), sulfamoyl group ( The number of carbon atoms is preferably 0 to 20, more preferably 0 to 16, particularly preferably 0 to 12, and examples thereof include a sulfamoyl group, a methylsulfamoyl group, a dimethylsulfamoyl group, and a phenylsulfamoyl group. Carbamoyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms such as carbamoyl group, methylcarbamoyl group, diethylcarbamoyl group, and phenylcarbamoyl group). ), An alkylthio group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16, particularly preferably 1 to 12, and examples thereof include a methylthio group and an ethylthio group), an arylthio group (preferably having a carbon atom number). 6-20, more preferably 6-16, particularly preferably 6-12, examples A phenylthio group, etc.), a sulfonyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16, particularly preferably 1 to 12, such as mesyl group and tosyl group), sulfinyl A group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms such as methanesulfinyl group and benzenesulfinyl group), ureido group (preferably having 1 carbon atom) To 20, more preferably 1 to 16, particularly preferably 1 to 12, and examples thereof include a ureido group, a methylureido group, and a phenylureido group), a phosphoric acid amide group (preferably having 1 to 20 carbon atoms, More preferably, it is 1-16, Most preferably, it is 1-12, for example, diethyl phosphoric acid amide, phenylphosphoric acid amide Hydroxy group, mercapto group, halogen atom (eg fluorine atom, chlorine atom, bromine atom, iodine atom), cyano group, sulfo group, carboxyl group, nitro group, hydroxamic acid group, sulfino group, hydrazino group , An imino group, a heterocyclic group (preferably having 1 to 30 carbon atoms, more preferably 1 to 12, and examples of the hetero atom include a nitrogen atom, an oxygen atom and a sulfur atom, specifically, for example, an imidazolyl group and a pyridyl group. Group, quinolyl group, furyl group, piperidyl group, morpholino group, benzoxazolyl group, benzimidazolyl group, benzthiazolyl group, etc.), silyl group (preferably having 3 to 40 carbon atoms, more preferably 3 to 3 carbon atoms). 30, particularly preferably 3 to 24, such as trimethylsilyl group and triphenylsilyl group. And the like).
These substituents may be further substituted. Moreover, when there are two or more substituents, they may be the same or different. If possible, they may be linked together to form a ring.

  However, it is preferable that the aliphatic group does not contain a substituent. If the aliphatic group contains a substituent, the bulkiness increases, the density decreases, and the mechanical strength tends to deteriorate.

  The cellulose derivative can be produced by referring to a known method, for example, a method for synthesizing an aliphatic ether or an aromatic carbamate described in “Encyclopedia of Cellulose” pages 131 to 164 (Asakura Shoten, 2000). it can. Specifically, cellulose ether in which a part of hydroxyl groups at the 2nd, 3rd and 6th positions is substituted with an ether group is used as a raw material, or the corresponding alkyl halide is allowed to act in the presence of a base such as sodium hydroxide. Thus, a cellulose ether having a desired degree of substitution can be prepared, and an aliphatic isocyanate can be produced as a raw material in the presence of a base such as pyridine. A known raw material can be used for the raw material cotton of the cellulose ether to be used.

  The average degree of polymerization of the cellulose derivative is preferably 15 to 5000, more preferably 50 to 5000, and still more preferably 50 to 4000. By increasing the degree of polymerization, crystallization during film formation can be suppressed. On the other hand, when the degree of polymerization is too large, there is a problem that the viscosity at the time of preparing the dope becomes too high.

The film of the present invention preferably contains 50% by mass or more, and more preferably 70% by mass or more, of the cellulose derivative in the total components (solid content). By containing in the said range, the property of the said cellulose derivative is utilized effectively, It becomes a film with the high expression property of retardation (absolute value is large), and its dynamic strength. The film of this invention may contain the additive with the said cellulose derivative depending on necessity. Hereinafter, various additives that can be added to the film of the present invention will be described.
(Plasticizer)
A plasticizer can be added to the film of the present invention in order to improve mechanical properties or increase the drying speed. As the plasticizer, phosphoric acid ester or carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP). Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethyl hexyl phthalate (DEHP). Examples of citrate esters include triethyl O-acetylcitrate (OACTE) and tributyl O-acetylcitrate (OACTB). Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Phthalate plasticizers (DMP, DEP, DBP, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularly preferred.
The amount of the plasticizer added is preferably 0.1 to 25% by mass of the amount of the cellulose derivative, more preferably 1 to 20% by mass, and still more preferably 3 to 15% by mass.

(UV absorber)
The film of the present invention may contain an ultraviolet absorber.
Examples of ultraviolet absorbers include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like, but less benzotriazole compounds Compounds are preferred. Further, ultraviolet absorbers described in JP-A-10-182621 and JP-A-8-337574, and polymer ultraviolet absorbers described in JP-A-6-148430 are also preferably used. When the film of the present invention is used as a protective film for a polarizing plate, the ultraviolet absorber is excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less and has a liquid crystal display property from the viewpoint of preventing the deterioration of a polarizer and liquid crystal. In view of the above, those that absorb less visible light having a wavelength of 400 nm or more are preferable.

  Specific examples of the benzotriazole ultraviolet absorber useful in the present invention include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-t -Butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-t-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-t-butyl Phenyl) -5-chlorobenzotriazole, 2- [2'-hydroxy-3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl] benzotriazole, 2,2 -Methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- (2'-hydroxy-3'-t-butyl-5) '-Methylph Nyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, octyl-3- [3-t-butyl-4 -Hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy-5- (5-chloro-2H-benzotriazole- Examples include, but are not limited to, mixtures of 2-yl) phenyl] propionate.

In addition, as commercial products, “TINUVIN 109”, “TINUVIN 171”, “TINUVIN 326”, “TINUVIN 328” {all trade names, Ciba Specialty Chemicals Co., Ltd. )} Can be preferably used.
The addition amount of the ultraviolet absorber is preferably 0.1 to 5.0% by mass and more preferably 0.5 to 5.0% by mass with respect to the cellulose derivative.

(Deterioration inhibitor)
A degradation inhibitor (for example, an antioxidant, a peroxide decomposer, a radical inhibitor, a metal deactivator, an acid scavenger, an amine) may be added to the film of the present invention. The deterioration preventing agents are described in JP-A-3-199201, JP-A-51907073, JP-A-5-194789, JP-A-5-271471, and JP-A-6-107854. The amount of the deterioration inhibitor added is 0.01 to 1 of the solution (dope) to be prepared from the viewpoint that the effect of addition of the deterioration inhibitor is manifested and that the deterioration inhibitor is prevented from bleeding out on the film surface. It is preferable that it is mass%, and it is further more preferable that it is 0.01-0.2 mass%. Examples of particularly preferred deterioration inhibitors include butylated hydroxytoluene (BHT) and tribenzylamine (TBA).

(Matting agent fine particles)
It is preferable to add fine particles as a matting agent to the film of the present invention. Examples of the fine particles include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate. Can be mentioned. Among these fine particles, those containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable. The fine particles of silicon dioxide preferably have a primary average particle size of 1 nm to 20 nm and an apparent specific gravity of 70 g / liter or more. The average diameter of the primary particles is preferably 1 nm to 20 nm, and a smaller one of 5 nm to 16 nm is more preferable because it can reduce the haze of the film. The apparent specific gravity is preferably 90 to 200 g / liter, more preferably 100 to 200 g / liter. A higher apparent specific gravity is preferable because a high-concentration dispersion can be produced, and haze and aggregates are improved.

  These fine particles usually form secondary particles having an average particle size of 0.05 to 2.0 μm, and these fine particles are present in the film as aggregates of primary particles, and 0.05 to 2.0 on the film surface. An unevenness of 2.0 μm is formed. The secondary average particle size is preferably 0.05 μm to 1.0 μm, more preferably 0.1 μm to 0.7 μm, and still more preferably 0.1 μm to 0.4 μm. For the primary and secondary particle sizes, the particles in the film were observed with a scanning electron microscope, and the diameter of a circle circumscribing the particles was defined as the particle size. Also, 200 particles are observed at different locations, and the average value is taken as the average particle size.

  As the silicon dioxide fine particles, for example, commercially available products such as Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above, Nippon Aerosil Co., Ltd., trade name) may be used. 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.

  Among these, Aerosil 200V and Aerosil R972V are fine particles of silicon dioxide having a primary average particle size of 20 nm or less and an apparent specific gravity of 70 g / liter or more, and the coefficient of friction is maintained while keeping the haze of the optical film low. It is particularly preferable because it has a great effect of reducing the effect.

  The matting agent is preferably prepared by the following method. That is, a fine particle dispersion prepared by stirring and mixing a solvent and fine particles is prepared in advance, and this fine particle dispersion is separately added to a first additive solution having a cellulose derivative concentration of less than 5% by mass and a molecular weight of 200 to 2000, and stirring and dissolving. After that, a method of further adding the second additive solution, stirring and dissolving, and further mixing with the main cellulose derivative dope solution is preferable.

  Since the surface of the matting agent is hydrophobized, when a hydrophobic additive is added, the additive is adsorbed on the surface of the matting agent, and aggregates of the additive tend to be generated using this as a nucleus. After mixing a relatively hydrophilic additive in advance with the matting agent dispersion, by mixing the hydrophobic additive, aggregation of the additive on the surface of the matting agent can be suppressed, and the haze is low. It is preferable because light leakage in black display when incorporated in a liquid crystal display device is small.

  It is preferable to use an in-line mixer for mixing the matting agent dispersant and the additive solution and mixing the cellulose derivative dope liquid. Although not limited to these methods, the concentration of silicon dioxide when the silicon dioxide fine particles are mixed and dispersed with a solvent or the like is preferably 5 to 30% by mass, more preferably 10 to 25% by mass, and 15 to 20% by mass. Even more preferred. A higher dispersion concentration is preferable because the turbidity with respect to the same amount of addition becomes low, and haze and aggregates are improved. The addition amount of the matting agent in the final cellulose derivative dope solution is preferably 0.001 to 1.0% by mass, more preferably 0.005 to 0.5% by mass, and 0.01 to 0.1% by mass. % Is even more preferred.

[Production of cellulose derivative film]
The film of the present invention can be produced by various methods. One example is the solvent cast method. In the solvent cast method, a film is produced using a solution (dope) in which a cellulose derivative is dissolved in an organic solvent.
The organic solvent used for the preparation of the dope is an ether having 3 to 12 carbon atoms, a ketone having 3 to 12 carbon atoms, an ester having 3 to 12 carbon atoms, and a halogenated carbonization having 1 to 6 carbon atoms. It is preferable to include a solvent selected from hydrogen.
The ether, ketone and ester may have a cyclic structure. A compound having two or more functional groups of ether, ketone, and ester (that is, —O—, —CO—, and —COO—) can also be used as the organic solvent. The organic solvent may have another functional group such as an alcoholic hydroxyl group. In the case of an organic solvent having two or more types of functional groups, the number of carbon atoms is preferably within the above-described preferable number of carbon atoms range of the solvent having any functional group.

Examples of the ether having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole.
Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone.
Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate.

Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.
The number of carbon atoms of the halogenated hydrocarbon is preferably 1 or 2, and most preferably 1. The halogen of the halogenated hydrocarbon is preferably chlorine. The proportion of halogen atoms substituted by halogen in the halogenated hydrocarbon is preferably 25 to 75 mol%, more preferably 30 to 70 mol%, and more preferably 35 to 65 mol%. More preferably, it is still more preferably 40 to 60 mol%. Methylene chloride is a representative halogenated hydrocarbon.

  For the preparation of the dope, it is preferable to use a mixed solvent of methylene chloride and alcohol, and the ratio of alcohol to methylene chloride is preferably 1 to 50% by mass, more preferably 10 to 40% by mass, and more preferably 12 to 30% by mass. Further preferred. As the alcohol, methanol, ethanol, and n-butanol are preferable, and two or more kinds of alcohols may be mixed and used.

  The dope can be prepared by a general method under a temperature of 0 ° C. or higher (room temperature or high temperature). The solution can be prepared by using a dope preparation method and apparatus in a normal solvent cast method. In the case of a general method, it is preferable to use a halogenated hydrocarbon (particularly methylene chloride) as the organic solvent.

  The concentration of the cellulose derivative in the dope is preferably 10 to 40% by mass, and more preferably 10 to 30% by mass. Various additives described above may be added to the organic solvent (main solvent).

The dope can be prepared by stirring a cellulose derivative and an organic solvent at room temperature (0 to 40 ° C.). The high concentration solution may be stirred under pressure and heating conditions. Specifically, the cellulose derivative and the organic solvent are sealed in a pressure vessel, and stirred while heating to a temperature not lower than the boiling point of the solvent at room temperature and in a range where the solvent does not boil under pressure.
The heating temperature is usually 40 ° C. or higher, preferably 60 to 200 ° C., and more preferably 80 to 110 ° C.

  Each component may be coarsely mixed in advance and then placed in a container. Moreover, you may put into a container sequentially. The container needs to be configured so that it can be stirred. The container can be pressurized by injecting an inert gas such as nitrogen gas. Moreover, you may utilize the raise of the vapor pressure of the solvent by heating. Or after sealing a container, you may add each component under pressure.

  When heating, it is preferable to heat from the outside of the container. For example, a jacket type heating device can be used. The entire container can also be heated by providing a plate heater outside the container and piping to circulate the liquid.

  It is preferable to provide a stirring blade inside the container and stir using this. The stirring blade preferably has a length that reaches the vicinity of the wall of the container. A scraping blade is preferably provided at the end of the stirring blade in order to renew the liquid film on the vessel wall.

  Instruments such as a pressure gauge and a thermometer may be installed in the container. Each component is dissolved in a solvent in a container. The prepared dope is taken out of the container after cooling, or is taken out and then cooled using a heat exchanger or the like.

  A solution can also be prepared by a cooling dissolution method. In the cooling dissolution method, the cellulose derivative can be dissolved in an organic solvent that is difficult to dissolve by a normal dissolution method. In addition, even if it is a solvent which can melt | dissolve a cellulose derivative with a normal melt | dissolution method, there exists an effect that a uniform solution can be obtained rapidly according to a cooling melt | dissolution method.

  In the cooling dissolution method, first, a cellulose derivative is gradually added to an organic solvent at room temperature while stirring. The amount of the cellulose derivative is preferably adjusted so as to be contained in the mixture in an amount of 10 to 40% by mass. The amount of the cellulose derivative is more preferably 10 to 30% by mass. Furthermore, you may add the arbitrary additive mentioned later in a mixture.

  Next, the mixture is cooled to -100 to -10 ° C (preferably -80 to -10 ° C, more preferably -50 to -20 ° C, still more preferably -50 to -30 ° C). The cooling can be performed, for example, in a dry ice / methanol bath (−75 ° C.) or a cooled diethylene glycol solution (−30 to −20 ° C.). The mixture of the cellulose derivative and the organic solvent is solidified by cooling.

  The cooling rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and even more preferably 12 ° C./min or more. The faster the cooling rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The cooling rate is a value obtained by dividing the difference between the temperature at the start of cooling and the final cooling temperature by the time from the start of cooling to the final cooling temperature.

  Furthermore, when this is heated to 0 to 200 ° C. (preferably 0 to 150 ° C., more preferably 0 to 120 ° C., and still more preferably 0 to 50 ° C.), the cellulose derivative is dissolved in the organic solvent. The temperature may be increased by simply leaving it at room temperature or in a warm bath.

  The heating rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and even more preferably 12 ° C./min or more. The higher the heating rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The heating rate is the value obtained by dividing the difference between the temperature at the start of heating and the final heating temperature by the time from the start of heating until the final heating temperature is reached. is there.

  A uniform solution is obtained as described above. If the dissolution is insufficient, the cooling and heating operations may be repeated. Whether or not the dissolution is sufficient can be determined by merely observing the appearance of the solution with the naked eye.

  In the cooling dissolution method, it is preferable to use an airtight container in order to avoid moisture mixing due to condensation during cooling. In the cooling and heating operation, when the pressure is applied during cooling and the pressure is reduced during heating, the dissolution time can be shortened. In order to perform pressurization and pressure reduction, it is preferable to use a pressure-resistant container.

  A cellulose derivative film is produced from the prepared cellulose derivative solution (dope) by a solvent cast method.

  The dope is cast on a drum or band and the solvent is evaporated to form a film. The concentration of the dope before casting is preferably adjusted so that the solid content is 18 to 35%. The surface of the drum or band is preferably finished in a mirror state. The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less.

  The drying method in the solvent cast method is described in U.S. Pat. Nos. 2,336,310, 2,367,603, 2,429,2078, 2,429,297, 2,429,978, 2,607,704, 2,273,069, and 2,739,070. Each specification, British Patent Nos. 640731 and 736892, and Japanese Patent Publication Nos. 45-4554, 49-5614, JP-A-60-176634, 60-203430, and 62- There is a description in each publication of No. 115035. Drying on the band or drum can be performed by blowing an inert gas such as air or nitrogen.

  Using the prepared cellulose derivative solution (dope), two or more layers can be cast to form a film. In this case, it is preferable to produce a cellulose derivative film by a solvent cast method. The dope is cast on a drum or band and the solvent is evaporated to form a film. It is preferable to adjust the concentration of the dope before casting so that the solid content is in the range of 10 to 40%. The surface of the drum or band is preferably finished in a mirror state.

  When casting a plurality of cellulose derivative liquids of two or more layers, it is possible to cast a plurality of cellulose derivative solutions, and cellulose derivatives from a plurality of casting openings provided at intervals in the traveling direction of the support. A film may be produced while casting and laminating solutions each containing. For example, the methods described in JP-A-61-158414, JP-A-1-122419, and JP-A-11-198285 can be used. Moreover, it can also be formed into a film by casting a cellulose derivative solution from two casting ports. For example, JP-B-60-27562, JP-A-61-94724, JP-A-61-947245, JP-A-61-104413, JP-A-61-158413, and JP-A-6-134933. The method described in the publication can be used. Furthermore, a method for casting a cellulose derivative film described in JP-A-56-162617, which wraps a flow of a high-viscosity cellulose derivative solution with a low-viscosity cellulose derivative solution and simultaneously extrudes the high- and low-viscosity cellulose derivative solution. It can also be used.

  In addition, after peeling off the film formed on the support by the first casting port using the two casting ports, the second casting is performed on the side of the film that is in contact with the support surface. Thus, a film can also be produced. For example, the method described in Japanese Patent Publication No. 44-20235 can be mentioned.

  As the cellulose derivative solution to be cast, the same solution may be used, or different cellulose derivative solutions may be used. In order to give a function to a plurality of cellulose derivative layers, a cellulose derivative solution corresponding to the function may be extruded from each casting port. Furthermore, the cellulose derivative solution used in the above method can be cast simultaneously with other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, an ultraviolet absorption layer, a polarizing layer, etc.).

  In the conventional single-layer liquid, it is necessary to extrude a cellulose derivative solution having a high concentration and a high viscosity in order to obtain a necessary film thickness. In that case, the stability of the cellulose derivative solution is poor and solids are generated, which often causes problems such as defects and poor flatness. As a solution to this problem, by casting a plurality of cellulose derivative solutions from the casting port, it is possible to extrude a highly viscous solution onto the support at the same time. Not only can it be produced, but also the use of a concentrated cellulose derivative solution can achieve a reduction in drying load and increase the production speed of the film.

(Extension process)
The film of the present invention may be stretched. Stretching can be performed in the film conveyance direction (longitudinal direction) and / or in the direction perpendicular to the film conveyance direction (width direction).
Methods for stretching in the width direction are described in, for example, JP-A-62-115035, JP-A-4-152125, 4-284221, 4-298310, and 11-48271. Yes. In the case of stretching in the longitudinal direction, for example, the film is stretched by adjusting the speed of the film transport roller so that the film winding speed is higher than the film peeling speed. In the case of stretching in the width direction, the film can also be stretched by conveying while holding the width of the film with a tenter and gradually widening the width of the tenter. After the film is dried, it can be stretched using a stretching machine (preferably uniaxial stretching using a long stretching machine).
In order to improve both Re developability and Rth developability, it is particularly preferable to stretch in both the transport direction and the width direction.

[Characteristics of cellulose derivative film]
The film of this invention is manufactured so that the characteristic may become a preferable range according to various uses. Below, the characteristic preferable in using the film of this invention as a member of a liquid crystal display device is demonstrated.
(Film thickness)
The thickness of the cellulose derivative film of the present invention is preferably 30 μm to 200 μm. More preferably, they are 40 micrometers-150 micrometers, More preferably, they are 40 micrometers-100 micrometers.

(Film retardation)
The cellulose derivative film of the present invention has high expression of retardation, particularly retardation in the thickness direction. Specifically, the retardation Rth (589) in the thickness direction at a wavelength of 589 nm can achieve about 50 nm to 400 nm, and about 100 nm to 300 nm.
On the other hand, the in-plane retardation Re (589) at a wavelength of 589 nm of the cellulose derivative film of the present invention can achieve about 0 nm to 200 nm, and can achieve about 0 nm to 100 nm.
Films that exhibit these ranges of optical properties are useful in a variety of applications.

  In the present specification, Re and Rth represent front retardation and retardation in the thickness direction, respectively. Re is measured by making light with a wavelength of 589 nm incident in the normal direction of the film in KOBRA 21ADH (trade name, manufactured by Oji Scientific Instruments). Rth is a letter measured by making light with a wavelength of 589 nm incident from a direction inclined + 40 ° with respect to the film normal direction with the slow axis of the front (determined by KOBRA 21ADH) as the tilt axis (rotation axis). 3 directions of retardation value and retardation value measured by making light with a wavelength of 589 nm incident from a direction inclined by −40 ° with respect to the normal direction of the film with the in-plane slow axis as the tilt axis (rotation axis) KOBRA 21ADH is calculated based on the retardation value measured in (1). Here, as the assumed value of the average refractive index, the values of “Polymer Handbook” (JOHN WILEY & SONS, INC) and catalogs of various optical films can be used. Those whose average refractive index is not known can be measured with an Abbe refractometer. The average refractive index values of main optical films are exemplified below: cellulose derivative (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), polystyrene (1.59). KOBRA 21ADH calculates nx, ny, and nz by inputting these assumed values of average refractive index and film thickness.

(Haze)
The cellulose derivative film of the present invention preferably has a value measured using, for example, a haze meter (1001DP type, trade name, manufactured by Nippon Denshoku Industries Co., Ltd.) of 0.1 to 0.8. More preferably, it is 0.1-0.7, More preferably, it is 0.1-0.60. By controlling the haze within the above range, a high-contrast image can be obtained when incorporated in a liquid crystal display device as an optical compensation sheet.

(Equilibrium moisture content of film)
The water absorption rate of the cellulose derivative film can be evaluated by measuring the equilibrium water content at a constant temperature and humidity. The equilibrium moisture content is calculated by measuring the moisture content of the sample that has reached equilibrium after being left at a constant temperature and humidity for 24 hours by the Karl Fischer method, and dividing the moisture content (g) by the sample mass (g). .
It is preferable that the equilibrium moisture content in the cellulose derivative film of this invention in 25 degreeC80% RH is 5.0 mass% or less. More preferably, it is 4.5 mass% or less, More preferably, it is 4.0 mass% or less.
By setting the equilibrium moisture content of the film within the above range, the change in retardation of the film can be reduced.

(Retardation change due to environmental humidity)
The cellulose derivative film of the present invention preferably has a small change in change retardation due to environmental humidity, and Re and Rth preferably satisfy the relationship of the following formulas (7) and (8).

であり、よりさらに好ましくは、

である。 Formula (7) is more preferably

And even more preferably

It is.

であり、よりさらに好ましくは、

である。 Further, the formula (8) is more preferably

And even more preferably

It is.

  By controlling the retardation change due to the environmental humidity within the above range, a liquid crystal display device having a small tint change due to the environmental humidity when incorporated in the liquid crystal display device can be obtained.

(Mechanical properties of film)
The film of the present invention can achieve the following ranges of elastic modulus, elongation at break, and stress at break, and it can be said that these characteristics have sufficient mechanical strength as a film.
-Elastic modulus The elastic modulus of a film can be measured according to JIS K 7162. The film of the present invention can achieve an elastic modulus of 1.0 to 4.0 GPa. The elastic modulus of the film of the present invention is preferably 1.0 to 3.0 GPa.
-Breaking elongation The breaking elongation of a film can be measured according to JIS K 7162. The film of the present invention can achieve a breaking elongation of 1 to 100%. The elongation at break of the film of the present invention is preferably 2 to 80%.
-Breaking stress The breaking stress of a film can be measured according to JIS K 7162. The film of the present invention can achieve a breaking stress of 20 to 100 MPa. The breaking stress of the film of the present invention is preferably 20 to 80 MPa.

(Surface failure)
The cellulose derivative film of the present invention has, for example, a value obtained by sampling the cellulose derivative film and counting the number of foreign matters or aggregates of 30 μm or more present on both ends 30 cm width and length 1 m of the obtained film. 50 is preferable. More preferably, it is 0-40, Most preferably, it is 0-30.

(Surface treatment of cellulose derivative film)
A surface treatment may be applied to the cellulose derivative film. Examples of the surface treatment include saponification treatment, plasma treatment, flame treatment, and ultraviolet irradiation treatment. Saponification treatment includes acid saponification treatment and alkali saponification treatment. Plasma treatment includes corona discharge treatment and glow discharge treatment. In order to maintain the flatness of the film, in these surface treatments, the temperature of the cellulose derivative film is preferably set to a glass transition temperature (Tg) or lower, specifically 150 ° C. or lower. The surface energy of the cellulose derivative film after these surface treatments is preferably 55 to 75 mN / m.
The glow discharge treatment may be low-temperature plasma that occurs under a low pressure gas of 10 ^{−3 to} 20 Torr (0.133 Pa to 2.67 kPa), and plasma treatment under atmospheric pressure is also preferable. A plasma-excitable gas is a gas that is plasma-excited under the above conditions, and examples thereof include chlorofluorocarbons such as argon, helium, neon, krypton, xenon, nitrogen, carbon dioxide, and tetrafluoromethane, and mixtures thereof. It is done. Details of these are described in detail on pages 30 to 32 of the Japan Society of Invention Disclosure Technical Bulletin (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society of Invention). In the plasma treatment at atmospheric pressure, which has been attracting attention in recent years, for example, irradiation energy of 20 to 500 kGy is used under 10 to 1000 keV, and more preferably irradiation energy of 20 to 300 kGy is used under 30 to 500 keV. Among these, alkali saponification treatment is particularly preferable, and it is extremely effective as the surface treatment of the cellulose derivative film.

  The alkali saponification treatment is preferably carried out by a method of directly immersing the cellulose derivative film in a saponification solution tank or a method of applying a saponification solution to the cellulose derivative film. Examples of the coating method include a dip coating method, a curtain coating method, an extrusion coating method, a bar coating method, and an E-type coating method. The solvent of the alkali saponification coating solution has good wettability because it is applied to the transparent support of the saponification solution, and the surface state remains good without forming irregularities on the surface of the transparent support by the saponification solution solvent. It is preferred to select a solvent to keep. Specifically, an alcohol solvent is preferable, and isopropyl alcohol is particularly preferable. An aqueous solution of a surfactant can also be used as a solvent. The alkali of the alkali saponification coating solution is preferably an alkali that dissolves in the above solvent, and more preferably KOH or NaOH. The pH of the saponification coating solution is preferably 10 or more, more preferably 12 or more. The reaction conditions at the time of alkali saponification are preferably 1 second to 5 minutes at room temperature, more preferably 5 seconds to 5 minutes, and particularly preferably 20 seconds to 3 minutes. After the alkali saponification reaction, it is preferable to wash the surface on which the saponification solution is applied with water or with an acid and then with water.

  The surface energy of the solid obtained by these methods can be determined by the contact angle method, the wet heat method, and the adsorption method as described in “Basics and Applications of Wetting” (Realize, 1989.12.10). it can. In the case of the cellulose derivative film of the present invention, it is preferable to use a contact angle method. Specifically, two types of solutions having known surface energies are dropped on a cellulose derivative film, and at the intersection between the surface of the droplet and the film surface, the angle formed by the tangent line drawn on the droplet and the film surface The surface angle of the film can be calculated by defining the angle containing the droplet as the contact angle.

  By carrying out the above-mentioned surface treatment on the cellulose derivative film, a cellulose derivative film having a surface energy of 55 to 75 mN / m can be obtained. By using this cellulose derivative film as a transparent protective film for a polarizing plate, the adhesion between the polarizing film and the cellulose derivative film can be improved. When the cellulose derivative film of the present invention is used in an OCB mode liquid crystal display device, an optically anisotropic layer comprising an alignment film formed on the cellulose derivative film of the present invention and a discotic compound or a rod-shaped liquid crystal compound thereon. May be provided. The optically anisotropic layer is formed by aligning a discotic compound (or rod-shaped liquid crystal compound) on the alignment film and fixing the alignment state.

[Use of cellulose derivative film]
[Optical compensation sheet]
The cellulose derivative film of the present invention can be used as an optical compensation sheet.

〔Polarizer〕
The cellulose derivative film of the present invention can be used as one member of a polarizing plate. A polarizing plate consists of a polarizing film and two transparent protective films arrange | positioned at the both sides. As one protective film, the above cellulose derivative film can be used. The other protective film may be a normal cellulose acetate film.
Examples of the polarizing film include an iodine polarizing film, a dye polarizing film using a dichroic dye, and a polyene polarizing film. The iodine polarizing film and the dye polarizing film are generally produced using a polyvinyl alcohol film.
The slow axis of the cellulose derivative film of the present invention and the transmission axis of the polarizing film are preferably arranged so as to be substantially parallel.

(Antireflection layer)
It is preferable to provide an antireflection layer on the transparent protective film disposed on the opposite side of the polarizing plate from the liquid crystal cell. An example of the antireflection layer is (1) an antireflection layer in which at least a light scattering layer and a low refractive index layer are laminated in this order on the transparent protective film, and other examples are (2) medium refraction on the transparent protective film. This is an antireflection layer in which a refractive index layer, a high refractive index layer and a low refractive index layer are laminated in this order.

[Liquid Crystal Display]
The cellulose derivative film of the present invention can be used as an optical member of a liquid crystal display device. For example, it can be bonded to a polarizing film and used as a member of a polarizing plate in a liquid crystal display device. The film of the present invention can be used for liquid crystal cells in various display modes. TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferroelectric Liquid Crystal), AFLC (Anti-ferroelectric Liquid Crystal), OCB (Optically Compensatory Bend), STN (Supper Twisted Nematic), VA (Vertically Aligned) and Various display modes such as HAN (Hybrid Aligned Nematic) have been proposed. Among these, it can be preferably used for the OCB mode or the VA mode.

  The OCB mode liquid crystal cell is a liquid crystal display device using a bend alignment mode liquid crystal cell in which rod-like liquid crystalline molecules are aligned in a substantially opposite direction (symmetrically) between an upper portion and a lower portion of the liquid crystal cell. OCB mode liquid crystal cells are disclosed in US Pat. Nos. 4,583,825 and 5,410,422. Since the rod-like liquid crystal molecules are aligned symmetrically between the upper part and the lower part of the liquid crystal cell, the bend alignment mode liquid crystal cell has a self-optical compensation function. Therefore, this liquid crystal mode is also called an OCB (Optically Compensatory Bend) liquid crystal mode. The bend alignment mode liquid crystal display device has an advantage of high response speed.

In a VA mode liquid crystal cell, rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied.
The VA mode liquid crystal cell includes (1) a narrowly defined VA mode liquid crystal cell in which rod-like liquid crystalline molecules are aligned substantially vertically when no voltage is applied, and substantially horizontally when a voltage is applied (Japanese Patent Laid-Open No. Hei 2-). 176625) (2) Liquid crystal cell (SID97, Digest of tech. Papers (Preliminary Proceed) 28 (1997) 845 in which the VA mode is converted into a multi-domain (MVA mode) for widening the viewing angle ), (3) A liquid crystal cell in a mode (n-ASM mode) in which rod-like liquid crystalline molecules are substantially vertically aligned when no voltage is applied and twisted multi-domain alignment is applied when a voltage is applied (Preliminary collections 58-59 of the Japan Liquid Crystal Society) (1998)) and (4) SURVAVAL mode liquid crystal cells (announced at LCD International 98).
In the OCB mode and VA mode liquid crystal display devices, the liquid crystal cell and two polarizing plates may be arranged on both sides thereof. In the VA mode, the polarizing plate may be arranged on the backlight side of the cell. The liquid crystal cell carries a liquid crystal between two electrode substrates.

EXAMPLES The present invention will be specifically described below with reference to examples, but the scope of the present invention is not limited to the specific examples shown below.
The raw materials used in the examples and comparative examples were all commercially available and used as they were.

<Synthesis Example 1: Synthesis of methylcellulose ethyl carbamate (P-1)>
Into a 3 L three-necked flask equipped with a mechanical stirrer, thermometer, condenser, and dropping funnel, 10 g of methylcellulose (methoxy substitution degree 1.8) and 200 mL of pyridine were weighed and stirred at room temperature. Ethyl isocyanate 18mL was dripped here slowly, and it stirred at 60 degreeC for 5 hours. After the reaction, the reaction solution was returned to room temperature and quenched by adding 10 mL of methanol under ice cooling. The reaction solution was diluted with 200 mL of acetone and then added to 2 L of hexane with vigorous stirring, whereby a yellow amorphous solid precipitated. After removing the solvent by decantation, washing with a large amount of hexane was performed three times. The obtained yellow amorphous solid was vacuum-dried at 100 ° C. for 6 hours to obtain the target cellulose derivative (P-1) as a yellow amorphous solid (12.5 g).
The obtained cellulose derivative was identified by ¹ HNMR, and DS _A , DS _B and DS _C were determined by the method described above. The same applies to any of the following compounds.

<Synthesis Example 2: Synthesis of methylcellulose butyl carbamate (P-2)>
The target cellulose derivative (P-2) was obtained as a yellowish white solid in the same manner as in Synthesis Example 1 except that ethyl isocyanate was changed to butyl isocyanate (11.1 g).

<Synthesis Example 3: Synthesis of methylcellulose octylcarbamate (P-3)>
The target cellulose derivative (P-3) was obtained as a pale yellow solid in the same manner as in Synthesis Example 1 except that ethyl isocyanate was changed to octyl isocyanate (12.7 g).

<Synthesis Example 4: Synthesis of methylcellulose octylcarbamate (P-4)>
The target cellulose derivative (P-4) was obtained as a yellowish white solid in the same manner as in Synthesis Example 1 except that ethyl isocyanate was changed to octyl isocyanate and the reaction time was changed to 1 hour (11.3 g).

<Synthesis Example 5: Synthesis of methylcellulose tert-octylcarbamate (P-5)>
The target cellulose derivative (P-5) was obtained as a white solid (9.6 g) in the same manner as in Synthesis Example 1 except that ethyl isocyanate was changed to tert-octyl isocyanate.

<Synthesis Example 6: Synthesis of methylcellulose cyclohexyl carbamate (P-6)>
The target cellulose derivative (P-6) was obtained as a white solid (3.6 g) in the same manner as in Synthesis Example 1 except that ethyl isocyanate was changed to cyclohexyl isocyanate.

<Synthesis Example 7: Synthesis of methylcellulose octylcarbamate (P-7)>
The target cellulose derivative (P-7) was obtained as a white solid in the same manner as in Synthesis Example 1 except that methyl cellulose (methoxy substitution degree 1.8) was changed to methyl cellulose (methoxy substitution degree 2.2) (11. 7g).

<Synthesis Example 8: Synthesis of ethyl cellulose hexyl carbamate (P-8)>
In the same manner as in Synthesis Example 1, except that methyl cellulose (methoxy substitution degree 1.8) was changed to ethyl cellulose (ethoxy substitution degree 2.6) and ethyl isocyanate was changed to hexyl isocyanate, the desired cellulose derivative (P-8) was white powder. Obtained as a body (3.2 g).

<Synthesis Example 9: Synthesis of ethyl cellulose octyl carbamate (P-9)>
In the same manner as in Synthesis Example 1, except that methyl cellulose (methoxy substitution degree 1.8) was changed to ethyl cellulose (ethoxy substitution degree 2.6) and ethyl isocyanate was changed to octyl isocyanate, the desired cellulose derivative (P-9) was white powder. Obtained as a body (5.4 g).

<Synthesis Example 10: Synthesis of ethyl cellulose benzyl carbamate (P-10)>
In the same manner as in Synthesis Example 1, except that methyl cellulose (methoxy substitution degree 1.8) was changed to ethyl cellulose (ethoxy substitution degree 2.6) and ethyl isocyanate was changed to benzyl isocyanate, the target cellulose derivative (P-10) was white pink. Obtained as a powder (6.0 g).

<Synthesis Example 11: Synthesis of cellulose ethyl carbamate (CTC-1)>
In a 3 L three-necked flask equipped with a mechanical stirrer, thermometer, condenser, and dropping funnel, 10 g of KC-Flock and 200 mL of DMAc were weighed and stirred and dispersed at room temperature. After 44 ml of ethyl isocyanate was slowly added dropwise thereto, 0.5 ml of dibutyltin dilaurate was added and stirred at 80 ° C. for 5 hours. After the reaction, the temperature was returned to room temperature and quenched by adding 10 mL of methanol. When the reaction solution was diluted with 200 mL of acetone and then poured into 2 L of hexane with vigorous stirring, an amorphous solid precipitated. After removing the solvent by decantation, washing with a large amount of hexane was performed three times. The obtained amorphous solid was vacuum-dried at 100 ° C. for 6 hours to obtain the target comparative compound cellulose ethyl carbamate (CTC-1) as an amorphous solid (15.6 g).

<Synthesis Example 12: Synthesis of methylcellulose ethyl carbamate (P-11)>
The target comparative compound (P-11) was obtained as a white solid in the same manner as in Synthesis Example 11 except that KC-Flock was changed to methylcellulose (methoxy substitution degree 1.6) (4.0 g).

<Synthesis Example 13: Synthesis of methylcellulose ethyl carbamate (MCEC-1)>
In a 3 L three-necked flask equipped with a mechanical stirrer, thermometer, condenser, and dropping funnel, 10 g of KC-Flock and 200 mL of DMAc were weighed and stirred and dispersed at room temperature. To this was added 14.8 g of powdered sodium hydroxide, and the mixture was stirred at 60 ° C. for 1 hour. After returning to room temperature, 52.5 g of methyl iodide was slowly added dropwise and stirred at 50 ° C. for 3 hours. Further, 44 mL of ethyl isocyanate was slowly added dropwise thereto, 0.5 mL of dibutyltin dilaurate was added, and the mixture was stirred at 80 ° C. for 5 hours. After the reaction, the temperature was returned to room temperature and quenched by adding 10 mL of methanol. When the reaction solution was diluted with 200 mL of acetone and then poured into 2 L of hexane with vigorous stirring, an amorphous solid precipitated. After removing the solvent by decantation, washing with a large amount of hexane was performed three times. The obtained amorphous solid was vacuum-dried at 100 ° C. for 6 hours to obtain the target comparative compound (MCEC-1) as an amorphous solid (9.6 g).

[Film production]
4 g of each cellulose derivative (P-1 to P-11) obtained above was dissolved in a mixed solvent of methylene chloride / methanol / butanol (53 g / 14 g / 4 g), and this was subjected to pressure filtration. The obtained dope was cast on an A3 large hydrophobic glass plate using an applicator. This was leveled for 1 minute in a 25 ° C. closed system and subsequently dried in a blow dryer at 45 ° C. for 8 minutes. The film is peeled off from the glass plate and sandwiched between stainless steel frames, which are then dried in a dryer at 100 ° C. for 10 minutes and in a dryer at 140 ° C. for 30 minutes. Produced.
Similarly, cellulose ethyl carbamate (CTC-1), methyl cellulose (MC, methoxy substitution degree 1.8), ethyl cellulose (EC, ethoxy substitution degree 2.6), and methyl cellulose ethyl synthesized in Synthesis Example 13 above. Carbamate (MCEC-1) was formed, and films F-12 to F-15 were prepared.

[Film physical property measurement]
The surface shape of each produced film was evaluated functionally as follows. The results are shown in Table 1 below.
(Surface shape) ○: Transparent and uniform state △: Cloudy state ×: Cannot be formed into a film

  Moreover, Rth in wavelength 589nm of each produced film was measured as mentioned above. Further, the elastic modulus, elongation at break, and stress at break were also measured as described above. The results are shown in Table 1 below.

As is clear from the results in Table 1, the films F-1 to F-10 of Examples prepared using the cellulose derivative of the present invention exhibit a very large Rth, and also have a certain degree of elasticity. It can be seen that the tensile strength and elongation at break are compatible, and the mechanical strength is also excellent. In addition, although the film F-11 had a poor surface shape and was slightly cloudy as compared with F1 to F10, Rth could not be measured. However, the film F-11 functions as a self-supporting film and is useful depending on applications. .
On the other hand, the film F-12 of Comparative Example 1 produced using CTC-1 consisting only of an aliphatic carbamate group had poor film-forming suitability and could not be formed.
In addition, methyl cellulose and ethyl cellulose have poor film moldability, and the films F-13 and 14 of Comparative Examples 2 and 3 prepared using them have poor mechanical strength and surface shape, and did not lead to optical property evaluation. .
MCEC-1 having both ether and carbamate substituents but DS _B <DS _C has poor film moldability as in Comparative Examples 2 and 3, and film F-15 of Comparative Example 4 in which it was formed. The mechanical strength and surface shape were poor, and the optical properties were not evaluated.
That is, by replacing the hydrogen atom of the hydroxyl group in cellulose with both an aliphatic group and an aliphatic carbamate group, it is expected that film-forming properties (appropriate mechanical strength) and predetermined optical properties (large Rth) are exhibited. It can be understood that an unexpected effect was obtained.
Therefore, it can be understood that the effect of the present invention can be obtained by a cellulose derivative having both ether and carbamate substituents and satisfying a predetermined relational expression.

<Example 2: Production and evaluation of polarizing plate>
The produced film F-1 and a cellulose acylate film (Fuji Film Co., Ltd., Fuji TAC) were immersed in an aqueous 1.5N sodium hydroxide solution at 60 ° C. for 2 minutes. Then, after immersing in a 0.1N sulfuric acid aqueous solution for 30 seconds, a saponified F-1 and FujiTAC were obtained through a water washing bath.

  According to Example 1 of Japanese Patent Laid-Open No. 2001-141926, a peripheral speed difference is given between two pairs of nip rolls, and a 75 μm-thick polyvinyl alcohol film (manufactured by Kuraray Co., Ltd., 9 × 75RS) is stretched in the longitudinal direction. A polarizing film was obtained.

  The polarizing film thus obtained and the saponified F-1 were subjected to 45 ° in the longitudinal direction of the film with a 3% by weight aqueous solution of polyvinyl alcohol (PVA) (manufactured by Kuraray Co., Ltd., PVA-117H) as an adhesive. As described above, the polarizing plate Pol-1 was prepared by laminating with a layer configuration of “saponified F-1 / polarizing film / saponified FujiTAC”.

<Example 3: Production and evaluation of liquid crystal display device>
Of two pairs of polarizing plates installed with a liquid crystal layer sandwiched between 26-inch and 40-inch liquid crystal display devices (manufactured by Sharp Corporation) using VA type liquid crystal cells, a polarizing plate on one side on the viewer side is used. It peeled off and the said polarizing plate Pol-1 was affixed instead using the adhesive. A liquid crystal display device was manufactured by arranging the transmission axis of the polarizing plate on the viewer side and the transmission axis of the polarizing plate on the backlight side to be orthogonal to each other. Color unevenness of the obtained liquid crystal display device was observed. The liquid crystal display device incorporating the polarizing plate Pol-1 of the present invention had no color unevenness and was very excellent.

Claims (10)

A film comprising a cellulose derivative having at least a polymerization unit represented by the following general formula (1) and satisfying the following mathematical formula (I).

[Wherein, R ² , R ³ and R ⁶ each independently represents a hydrogen atom, an aliphatic group or an aliphatic carbamate group. ]
(I) DS _B ≧ DS _C
[Wherein DS _B is the number of aliphatic groups present as R ² , R ³ and R ⁶ in the above unit, respectively, and DS _C is R ² , R ³ and R ^{6 in} the same unit, respectively. The number of aliphatic carbamate groups present, DSc> 0, and DS _B + DS _C ≦ 3. ] The film according to claim 1, wherein the cellulose derivative satisfies the following formula (II).
(II) 0 ≦ DS _A ≦ 1.2
[Wherein DS _A is the number of hydrogen atoms present as R ² , R ³ and R ^{6 in} the above unit, and DS _A + DS _B + DS _C = 3. ] The film according to claim 1 or 2, wherein the cellulose derivative satisfies the following mathematical formulas (III) to (V).
(III) 1.6 ≦ DS _B ≦ 2.8
(IV) 0.1 ≦ DS _C ≦ 1.2
(V) 0 ≦ DS _A ≦ 0.5   The said aliphatic group is a methyl group or an ethyl group, The film of any one of Claims 1-3 characterized by the above-mentioned. An optical compensation sheet comprising or including the film according to claim 1. A polarizing plate comprising at least a polarizer and the film according to claim 1. A liquid crystal display device comprising the film according to claim 1. A cellulose derivative having at least a polymerization unit represented by the following general formula (1) and satisfying the following mathematical formulas (I) and (II).

[Wherein, R ² , R ³ and R ⁶ each independently represents a hydrogen atom, an aliphatic group or an aliphatic carbamate group. ]
(I) DS _B ≧ DS _C
(II) 0 ≦ DS _A ≦ 1.2
[Wherein DS _A is the number of hydrogen atoms present as R ² , R ³ and R ⁶ in the unit, and DS _B is present as R ² , R ³ and R ^{6 in} the same unit, respectively. DS _C is the number of aliphatic carbamate groups present as R ² , R ³ and R ⁶ , respectively, in the same unit, DSc> 0, and DS _A + DS _B + DS _C = 3. ] The cellulose derivative according to claim 8, wherein the following mathematical formulas (III) to (V) are satisfied.
(III) 1.6 ≦ DS _B ≦ 2.8
(IV) 0.1 ≦ DS _C ≦ 1.2
(V) 0 ≦ DS _A ≦ 0.5 The cellulose derivative according to claim 8 or 9, wherein the aliphatic group is a methyl group or an ethyl group.