JP2009015045A - Optical film, deflection plate and method of manufacturing the same, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film which is free of stripe failure on the surface of the optical film, has good surface processability for the hard coat layer and reflection preventing layer, has high contrast, and is excellent in durability at high temperature and high humidity, to provide a deflection plate and a method of manufacturing the same, and to provide a liquid crystal display device using the deflection plate. <P>SOLUTION: The optical film is formed by heating and melting an optical film formation material containing cellulosic ester and forming a film by the molten flow stretching method. The optical film formation material contains a compound having an imido structure group expressed by a general formula (1). Here, in the formula, Z<SB>1</SB>expresses a nonmetallic atom group required for forming 5-6 member rings with a -C-N-C-part. L expresses a divalent connecting group. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical film, a polarizing plate, a method for producing the same, and a liquid crystal display device.

  In recent years, notebook computers have been developed to be thinner and lighter, larger screens, and higher definition. Along with this, various film for display devices, especially protective films for liquid crystal polarizing plates, are increasingly required to be thinner, wider and higher quality.

  In general, optical films are widely used as protective films for polarizing plates.

  Until now, these optical films have been produced exclusively by the solution casting method. However, since the solution casting method requires a large amount of an organic solvent and has a large environmental load and cost, attempts have been made to melt-form cellulose esters.

  However, the production of an optical film by the melt casting method is difficult and has not been put to practical use.

  For example, in the solution casting method, there is a problem that the low molecular weight compound of the optical film forming material contaminates the production process due to volatilization during heat processing.

  In melt casting where the heating temperature is higher than that of the solution casting method, the problem of process contamination due to volatilization is further serious.

  In particular, the volatiles are contaminated on the surface of the optical film, and the surface workability of the hard coat layer and the antireflection layer is deteriorated, the contrast is reduced, and the volatiles adhere to the lip of the die. There is a problem that streaks occur on the film surface.

  In order to solve the problem due to volatilization, in the solution casting method, studies have been made to polymerize an ultraviolet absorber (for example, see Patent Document 1).

  However, in the melt casting method, there is a problem that the optical film tends to be whitened depending on the compound used, and particularly when a polymer or a high molecular weight compound is used, the problem of whitening is very likely to occur.

In the melt casting method, polymers and high molecular weight compounds have been studied (for example, see Patent Document 2), but the problem of whitening of optical films has not been improved sufficiently, and durability during storage at high temperature and high humidity There are problems such as bad. Therefore, a compound having low volatility and low process contamination due to volatilization is required for a low molecular weight.
JP 2002-169020 A JP 2006-113175 A

  The present invention has been made in view of the above problems, and the object of the present invention is that there is no problem of streaking failure on the surface of the optical film, the surface processability of a hard coat layer, an antireflection layer, etc. is good, high contrast, and high temperature. An object of the present invention is to provide an optical film excellent in durability under high humidity, a polarizing plate and a method for producing the same, and a liquid crystal display device using the polarizing plate.

  The object of the present invention is achieved by the following constitution.

  1. In an optical film formed by melt-melting an optical film-forming material containing a cellulose ester and formed by a melt casting method, a compound having an imide structural group represented by the following general formula (1) is added to the optical film-forming material. An optical film characterized by containing.

(In the formula, Z ₁ represents a nonmetallic atom group necessary for forming a 5- to 6-membered ring together with the —C—N—C— moiety. L represents a divalent linking group.)
2. 2. The optical film as described in 1 above, wherein the compound having an imide structure group represented by the general formula (1) is an ultraviolet absorber, a plasticizer or an antioxidant.

  3. 3. The optical film as described in 1 or 2 above, which contains an ultraviolet absorber having an imide structure group represented by the following general formula (2).

Wherein R ₃₁ and R ₃₂ are each independently a hydroxyl group, alkoxy group, alkenyl group, aryl group, acyloxy group, aryloxy group, alkylthio group, arylthio group, mono- or dialkylamino group, acylamino group, acyl group Represents a sulfonyl group, an arylthio group, an amino group, an arylamino group, an acylamino group, a cyano group, a carbamoyl group, a sulfamoyl group, a sulfonamide group, an acyloxy group, and an oxycarbonyl group, and each of R ₃₃ , R ₃₄ , and R ₃₅ is independent. A halogen atom, alkyl group, alkoxy group, alkenyl group, aryl group, acyloxy group, aryloxy group, alkylthio group, arylthio group, mono- or dialkylamino group, acylamino group, acyl group, sulfonyl group, arylthio group, amino group , Arylamino Represents an acylamino group, cyano, carbamoyl, sulfamoyl groups, sulfonamide group, an acyloxy group or an oxycarbonyl group.

  l, m, and n represent an integer of 0-4.

Z ₁ represents a nonmetallic atom group necessary for forming a 5- to 6-membered ring together with the —C—N—C— moiety. L represents a divalent linking group. )
4). 3. The optical film as described in 1 or 2 above, which contains an ultraviolet absorber having an imide structure group represented by the following general formula (3).

(Wherein R ₁₁ represents a hydrogen atom, an acyloxy group, an oxycarbonyl group, a carbamoyl group, an acyl group, an aliphatic group or an aryl group. R ₁₂ and R ₁₃ each independently represents a halogen atom, an alkyl group, an aryl group, Acyl, sulfonyl, alkoxy, aryloxy, alkylthio, arylthio, amino, alkylamino, arylamino, acylamino, hydroxyl, cyano, carbamoyl, sulfamoyl, sulfonamido, acyloxy Represents a group or an oxycarbonyl group, m represents an integer of 0 to 3, n represents an integer of 0 to 5. Z ₁ forms a 5- to 6-membered ring together with the —C—N—C— moiety. Represents a group of non-metallic atoms necessary for the above, L represents a divalent linking group.)
5). 3. The optical film as described in 1 or 2 above, which comprises a plasticizer having an imide structure group represented by the following general formula (4).

(Wherein, X is an alkyl group, a cycloalkyl group, an aryl group, .Z ₁ represents a heterocycle are, -C-N-C- with parts, non-metallic atoms necessary to form a 5- or 6-membered ring L represents a divalent linking group.

p represents an integer of 0 to 5, q represents an integer of 1 to 6, 2 ≦ p + q ≦ 6, and A represents a p + q valent polyhydric alcohol residue. )
6). 3. The optical film as described in 1 or 2 above, which contains a benzofuranone-based compound having an imide structure group represented by the general formula (1).

  7. 7. The optical film as described in 6 above, which contains a benzofuranone compound represented by the following general formula (5).

(Wherein R ₂ is an alkyl group, acyl group, alkoxy group, aryloxy group, alkylthio group, arylthio group, amino group, alkylamino group, arylamino group, acylamino group, hydroxyl group, cyano group, carbamoyl group, sulfamoyl group) Group, a sulfonamide group, an acyloxy group or an oxycarbonyl group, R ₆ represents a hydrogen atom or an alkyl group, or an acyl group, and n represents 1 or 2. Z ₁ represents a —C—N—C— moiety. And a non-metallic atom group necessary for forming a 5- to 6-membered ring, and L represents a divalent linking group.

When n is 1, R ₁ represents an aryl group, a hydroxyl group, or an acyl group. When n is 2, R ₁ represents a divalent linking group. m represents an integer of 0 to 3. )
8). 3. The optical film as described in 1 or 2 above, which comprises a phosphonite compound containing an imide structural group represented by the general formula (1).

  9. 9. The optical film as described in 8 above, wherein the phosphonite compound contains a partial structure represented by the following general formula (C-2).

(In the formula, Ph ₂ and Ph ′ ₂ represent a substituted or unsubstituted phenyl group or biphenyl group.)
10. 10. The optical film as described in any one of 1 to 9 above, wherein the imide structure group is represented by the following general formula (6).

(In the formula, Z ₂ represents a non-metallic atom group necessary for forming a 5- to 6-membered ring together with C... C part. L represents a divalent linking group. Represents a single bond or a double bond.)
11. 11. The optical film as described in 10 above, wherein the general formula (6) is represented by the following general formula (7).

(In the formula, R ₁₀₁ represents a halogen atom, an alkyl group, an aryl group, an acyl group, a sulfonyl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an amino group, an alkylamino group, an arylamino group, an acylamino group, A hydroxyl group, a cyano group, a carbamoyl group, a sulfamoyl group, a sulfonamide group, an acyloxy group or an oxycarbonyl group, L represents a divalent linking group, and r represents an integer of 0 to 8.)
12 A polarizing plate comprising the optical film according to any one of 1 to 11 on at least one surface.

  13. The optical film of any one of said 1-11 is saponified, and is bonded with a polarizer, The manufacturing method of the polarizing plate characterized by the above-mentioned.

  14 13. A liquid crystal display device using the polarizing plate described in 12 above on at least one surface of a liquid crystal cell.

  15. 14. A liquid crystal display device using the polarizing plate produced by the method for producing a polarizing plate as described in 13 above on at least one surface of a liquid crystal cell.

  According to the present invention, by reducing process contamination due to volatiles generated when the optical film forming material is melted by heat, there is no problem of streaking of the surface of the optical film, and surface processing properties such as a hard coat layer and an antireflection layer are good, An optical film, a polarizing plate and a method for producing the same, and a liquid crystal display device using the polarizing plate, which are excellent in durability at high contrast and high temperature and high humidity, can be provided.

  Hereinafter, the present invention will be described in more detail.

  The present invention provides an optical film obtained by heating and melting an optical film-forming material containing a cellulose ester, and forming the film by a melt casting method. The optical film-forming material includes an imide structure group represented by the general formula (1). It contains the compound which has this.

  Examples of the compound having an imide structure group represented by the general formula (1) include an ultraviolet absorber, a moisture permeability adjusting agent, a plasticizer, an antioxidant, a peeling aid, a mechanical property improving agent, a retardation control agent, and a wavelength dispersing agent. And a flatness improving agent.

  Preferably, the compound having an imide structure group represented by the general formula (1) is preferably an ultraviolet absorber, a moisture permeability adjusting agent, a plasticizer, or an antioxidant.

  First, the compound which has a structure represented by General formula (1) of this invention is demonstrated.

Z ₁ represents a nonmetallic atom group necessary for forming a 5- to 6-membered ring together with the —C—N—C— moiety.

  Examples of the 5- to 6-membered ring formed include a succinimide ring, a maleimide ring, a urazole ring, a hydantoin ring, an oxazoline dindione ring, and a thiazoline dindione ring. preferable.

  The ring formed may have a substituent and may form a condensed ring with another ring.

  Examples of the substituent include, but are not particularly limited to, for example, an alkyl group (for example, methyl group, ethyl group, propyl group, isopropyl group, t-butyl group, pentyl group, hexyl group, octyl group, dodecyl group, trimethyl group). Fluoromethyl group etc.), cycloalkyl group (eg cyclopentyl group, cyclohexyl group etc.), aryl group (eg phenyl group, naphthyl group etc.), acylamino group (eg acetylamino group, benzoylamino group etc.), alkylthio group (Eg, methylthio group, ethylthio group, etc.), arylthio group (eg, phenylthio group, naphthylthio group, etc.), alkenyl group (eg, vinyl group, 2-propenyl group, 3-butenyl group, 1-methyl-3-propenyl group) 3-pentenyl group, 1-methyl-3-butenyl group, 4-hexenyl group, cycl Hexenyl group etc.), halogen atoms (eg fluorine atom, chlorine atom, bromine atom, iodine atom etc.), alkynyl groups (eg propargyl group etc.), heterocyclic groups (eg pyridyl group, thiazolyl group, oxazolyl group, imidazolyl) Group), alkylsulfonyl group (eg methylsulfonyl group, ethylsulfonyl group etc.), arylsulfonyl group (eg phenylsulfonyl group, naphthylsulfonyl group etc.), alkylsulfinyl group (eg methylsulfinyl group etc.), arylsulfinyl Group (for example, phenylsulfinyl group), phosphono group, acyl group (for example, acetyl group, pivaloyl group, benzoyl group, etc.), carbamoyl group (for example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, butylaminocarbonyl group) Bonyl group, cyclohexylaminocarbonyl group, phenylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, Cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), sulfonamide group (for example, methanesulfonamide group, benzenesulfonamide group, etc.) , Cyano group, alkoxy group (eg methoxy group, ethoxy group, propoxy group etc.), aryloxy group (eg phenoxy group, naphthyloxy group etc.), heterocyclic ring Oxy group, siloxy group, acyloxy group (for example, acetyloxy group, benzoyloxy group, etc.), sulfonic acid group, sulfonic acid salt, aminocarbonyloxy group, amino group (for example, amino group, ethylamino group, dimethylamino group) , Butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, etc.), anilino group (for example, phenylamino group, chlorophenylamino group, toluidino group, anisidino group, naphthylamino group, 2-pyridylamino group, etc.) Imide group, ureido group (for example, methylureido group, ethylureido group, pentylureido group, cyclohexylureido group, octylureido group, dodecylureido group, phenylureido group, naphthylureido group, 2-pyridylaminoureido group), alkoxy Rubonylamino group (for example, methoxycarbonylamino group, phenoxycarbonylamino group, etc.), alkoxycarbonyl group (for example, methoxycarbonyl group, ethoxycarbonyl group, phenoxycarbonyl, etc.), aryloxycarbonyl group (for example, phenoxycarbonyl group, etc.), Examples include heterocyclic thio groups, thioureido groups, carboxyl groups, carboxylic acid salts, hydroxyl groups, mercapto groups, and nitro groups. These substituents may be further substituted with the same substituent.

  L represents a divalent linking group.

  Examples of the divalent linking group include an alkylene group that may have a substituent, an arylene group that may have a substituent, an oxygen atom, a nitrogen atom, a sulfur atom, or a combination of these linking groups. it can. Of these, an alkylene group and an arylene group are preferred.

  Next, the compound represented by the general formula (6) will be described.

Z ₂ represents a nonmetallic atom group necessary for forming a 5- to 6-membered ring together with the C... C part.

  Preferably, an aliphatic hydrocarbon ring, an aromatic hydrocarbon ring, or a heterocyclic ring is preferable, and a cyclohexane ring, a cyclohexene ring, a cyclopentane ring, a cyclobutane ring, a furan ring, a thiophene ring, a pyrrole ring, a pyridine ring, an imidazole ring, and a thiazole. And a ring, an oxazole ring, an oxadiazole ring, a thiadiazole ring, a pyrazole ring, and a benzene ring.

  Among these, a cyclohexane ring, a cyclohexene ring, and a benzene ring are preferable.

  The ring formed may have a substituent and may form a condensed ring with another ring.

  As the substituent, a halogen atom, a nitro group, a hydroxyl group, an alkyl group, an alkenyl group, an aryl group, an alkoxy group, an acyloxy group, and an aryloxy group are preferable.

  L represents a divalent linking group. As the divalent linking group, the linking groups mentioned in formula (1) are preferable. ... represents a single bond or a double bond.

  Next, the compound represented by the general formula (7) will be described.

R ₁₀₁ is a halogen atom (eg, fluorine atom, chlorine atom, bromine atom, iodine atom), nitro group, hydroxyl group, alkyl group (eg, methyl group, ethyl group, propyl group, isopropyl group, t-butyl group). Pentyl group, hexyl group, octyl group, dodecyl group, trifluoromethyl group, etc.), alkenyl group (for example, vinyl group, 2-propenyl group, 3-butenyl group, 1-methyl-3-propenyl group, 3-pentenyl group) Group, 1-methyl-3-butenyl group, 4-hexenyl group, cyclohexenyl group, etc.), aryl group (eg, phenyl group, naphthyl group, etc.), alkoxy group (eg, methoxy group, ethoxy group, propoxy group, etc.) , Acyloxy groups (eg, acetyloxy group, benzoyloxy group, etc.), aryloxy groups (eg, phenoxy group, naphthy A ruoxy group, etc.). r represents an integer of 0 to 8.

  Among these, a hydrogen atom is particularly preferable.

  L represents a divalent linking group. As the divalent linking group, the linking groups mentioned in formula (1) are preferable.

  In the present invention, the compound having the partial structure (imide partial structural group) represented by the general formula (1) is the compound represented by the general formula (6) or the general formula (7). It is more preferable at the point which produces an effect.

(UV absorber)
The ultraviolet absorber is excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of the polarizer and the display device with respect to ultraviolet rays, and has little absorption of visible light having a wavelength of 400 nm or more from the viewpoint of liquid crystal display properties. Those are preferred.

  Examples of ultraviolet absorbers preferably used in the present invention include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, triazine compounds, and the like. However, benzophenone compounds, benzotriazole compounds and triazine compounds with little coloration are preferred.

  The optical film of the present invention preferably contains an ultraviolet absorber having an imide structure group represented by the general formula (1).

  Further preferred are benzotriazole compounds, benzophenone compounds, and triazine compounds having an imide structure group represented by the general formula (1).

  In the present invention, it is particularly preferable to use the compounds represented by the general formulas (2) and (3).

  Especially, it is preferable to use the ultraviolet absorber which has an imide structure group represented by General formula (2).

  Next, the compound represented by the general formula (2) will be described.

R ₃₁ and R ₃₂ are each independently a hydroxyl group, an alkoxy group (for example, methoxy group, ethoxy group, propoxy group, etc.), an alkenyl group (for example, vinyl group, 2-propenyl group, 3-butenyl group, 1-methyl group). -3-propenyl group, 3-pentenyl group, 1-methyl-3-butenyl group, 4-hexenyl group, cyclohexenyl group, etc.), aryl group (for example, phenyl group, naphthyl group, etc.), acyloxy group (for example, acetyl) Oxy group, benzoyloxy group, etc.), aryloxy group (eg, phenoxy group, naphthyloxy group, etc.), alkylthio group (eg, methylthio group, ethylthio group, etc.), arylthio group (eg, phenylthio group, naphthylthio group, etc.), Mono- or dialkylamino group, acylamino group (for example, acetylamino group, benzoylamino group) Group), acyl group (eg, acetyl group, pivaloyl group, benzoyl group, etc.), sulfonyl group, arylthio group (eg, phenylthio group, naphthylthio group, etc.), amino group (eg, amino group, ethylamino group, dimethyl group). Amino group, butylamino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, etc.), arylamino group, acylamino group (eg, acetylamino group, benzoylamino group, etc.), cyano group, carbamoyl group (eg, Aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, butylaminocarbonyl group, cyclohexylaminocarbonyl group, phenylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), sulfamoyl group (for example, aminosulfonyl group, methyl Minosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc. ), Sulfonamide groups (eg, methanesulfonamide groups, benzenesulfonamide groups, etc.), acyloxy groups (eg, acetyloxy groups, benzoyloxy groups, etc.), oxycarbonyl groups (eg, methoxycarbonyl groups, ethoxycarbonyl groups, phenoxy) Carbonyl etc.). In particular, the alkoxy group is preferably a methoxy group, an ethoxy group, or a propoxy group.

R ₃₃ , R ₃₄ and R ₃₅ are each independently a halogen atom (eg, fluorine atom, chlorine atom, bromine atom, iodine atom), alkyl group (eg, methyl group, ethyl group, propyl group, isopropyl group, t -Butyl group, pentyl group, hexyl group, octyl group, dodecyl group, trifluoromethyl group, etc.), alkoxy group (eg, methoxy group, ethoxy group, propoxy group, etc.), alkenyl group (eg, vinyl group, 2-propenyl) Group, 3-butenyl group, 1-methyl-3-propenyl group, 3-pentenyl group, 1-methyl-3-butenyl group, 4-hexenyl group, cyclohexenyl group, etc.), aryl group (for example, phenyl group, naphthyl) Group), acyloxy group (eg, acetyloxy group, benzoyloxy group, etc.), aryloxy group (eg, phenoxy group, naphtho group, etc.) Alkyloxy group (eg methylthio group, ethylthio group etc.), arylthio group (eg phenylthio group, naphthylthio group etc.) mono- or dialkylamino group, acylamino group (eg acetylamino group, benzoylamino group etc.) An acyl group (eg, acetyl group, pivaloyl group, benzoyl group), sulfonyl group, arylthio group (eg, phenylthio group, naphthylthio group, etc.), amino group (eg, amino group, ethylamino group, dimethylamino group, butyl) Amino group, cyclopentylamino group, 2-ethylhexylamino group, dodecylamino group, etc., arylamino group, acylamino group (eg, acetylamino group, benzoylamino group, etc.), cyano group, carbamoyl group (eg, aminocarbonyl group, Methylaminoca Sulfonyl group, dimethylaminocarbonyl group, butylaminocarbonyl group, cyclohexylaminocarbonyl group, phenylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), sulfamoyl group (for example, aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, Butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), sulfonamide group (for example, methane) Sulfonamide group, benzenesulfonamide group, etc.), acyloxy group (eg, acetyloxy group, benzoyloxy group, etc.), oxycarbonyl group ( Eg to represent a methoxycarbonyl group, an ethoxycarbonyl group, a phenoxycarbonyl etc.).

  In particular, the halogen atom is preferably a chloro group, the alkyl group is preferably a methyl group, and the alkoxy group is preferably a methoxy group or a propoxy group.

l, m, and n represent an integer of 0-4. Z ₁ represents a nonmetallic atom group necessary for forming a 5- to 6-membered ring together with the —C—N—C— moiety. Z ₁ is preferably the structure given in general formula (1). L represents a divalent linking group. As the divalent linking group, the linking groups mentioned in formula (1) are preferable.

  Hereinafter, although the typical example of a compound represented by General formula (2) preferably used for this invention is illustrated, this invention is not limited to these.

  Next, the compound represented by the general formula (3) will be described.

R ₁₁ is a hydrogen atom, an acyloxy group (eg, acetyloxy group, benzoyloxy group, etc.), an oxycarbonyl group (eg, phenoxycarbonyl group, etc.), a carbamoyl group (eg, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group). Butylaminocarbonyl group, cyclohexylaminocarbonyl group, phenylaminocarbonyl group, 2-pyridylaminocarbonyl group etc.), acyl group (eg acetylamino group, benzoylamino group etc.), aliphatic group (eg methyl group, ethyl group) Propyl group, isopropyl group, t-butyl group, pentyl group, hexyl group, octyl group, dodecyl group, trifluoromethyl group and the like) or aryl group (for example, phenyl group, naphthyl group and the like). R ₁₂ and R _{13 are} each independently a hydrogen atom, a halogen atom (eg, fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), alkyl group (eg, methyl group, ethyl group, propyl group, isopropyl group, t- Butyl group, pentyl group, hexyl group, octyl group, dodecyl group, trifluoromethyl group, etc.), aryl group (eg, phenyl group, naphthyl group, etc.), acyl group (eg, acetylamino group, benzoylamino group, etc.), A sulfonyl group, an alkoxy group (eg, methoxy group, ethoxy group, propoxy group, etc.), an aryloxy group (eg, phenoxy group, naphthyloxy group, etc.), an alkylthio group (eg, methylthio group, ethylthio group, etc.), an arylthio group ( For example, phenylthio group, naphthylthio group, etc.), amino group, alkylamino group (for example, the number of carbon atoms) To 4 alkylamino groups), arylamino groups, (for example, acetylamino group, benzoylamino group, etc.) acylamino groups (for example, acetylamino group, propionylamino group, etc.), alkylthio groups (for example, methylthio group, ethylthio group, butylthio group) Etc.), hydroxyl group, cyano group, carbamoyl group (eg methylcarbamoyl group, ethylcarbamoyl group, dimethylcarbamoyl group etc.), sulfamoyl group (eg ethylsulfamoyl group, dimethylsulfamoyl group etc.), sulfonamide group (eg , A methanesulfonamide group, a benzenesulfonamide group, etc.), an acyloxy group (eg, acetyloxy group, benzoyloxy group, etc.) or an oxycarbonyl group (eg, phenoxycarbonyl group, etc.). m represents an integer of 0 to 3, and n represents an integer of 0 to 5. Z ₁ represents a nonmetallic atom group necessary for forming a 5- to 6-membered ring together with the —C—N—C— moiety. Z ₁ is preferably the structure given in general formula (1). L represents a divalent linking group. As the divalent linking group, the linking groups mentioned in formula (1) are preferable.

  Hereinafter, although the typical example of a compound represented by General formula (3) preferably used for this invention is illustrated, this invention is not limited to these.

  Moreover, you may add a conventionally well-known ultraviolet absorber to such an extent that the effect of this invention is not impaired.

  Examples include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, triazine compounds, and the like. Triazole compounds and triazine compounds are preferred.

  Examples thereof include ultraviolet absorbers described in JP-A Nos. 10-182621 and 8-337574, and polymer ultraviolet absorbers described in JP-A Nos. 6-148430 and 2003-113317.

  In the present invention, the ultraviolet absorber is preferably added in an amount of 0.1 to 20 parts by weight, more preferably 0.5 to 10 parts by weight, and further 1 to 5 parts by weight, based on the cellulose ester. It is preferable.

  Two or more of these may be used in combination.

(Plasticizer)
It is preferable to add a plasticizer to the optical film of the present invention.

  In general, it is preferable to add a compound known as a plasticizer from the viewpoint of modification of an optical film such as improvement of mechanical properties, imparting flexibility, imparting water absorption resistance, and reducing moisture permeability.

  Further, in the melt casting method, the plasticizer is contained more than the cellulose ester at the same heating temperature for the purpose of lowering the melting temperature of the optical film constituting material by adding a plasticizer, rather than the glass transition temperature of the cellulose ester used alone. This includes the purpose of reducing the viscosity of the optical film constituting material.

  Here, in the present invention, the melting temperature of the optical film constituting material means a temperature at which the material is heated in a state where the material is heated and fluidity is developed.

  If the cellulose ester alone is lower than the glass transition temperature, the fluidity for forming an optical film is not expressed. However, the cellulose ester exhibits a fluidity due to a decrease in elastic modulus or viscosity due to heat absorption above the glass transition temperature. In order to melt the optical film constituting material, the plasticizer to be added preferably has a melting point or glass transition temperature lower than the glass transition temperature of the cellulose ester in order to satisfy the above object.

  As the plasticizer having, as a partial structure, an imide structural group represented by the general formula (1) preferably used in the present invention, an ester plasticizer comprising a polyhydric alcohol and a monovalent carboxylic acid, a polyvalent carboxylic acid and 1 And ester plasticizers composed of monovalent alcohols, phosphate ester plasticizers, and carbohydrate ester plasticizers.

  In the present invention, it is preferable to add an ester plasticizer comprising a polyhydric alcohol represented by the general formula (4) and a monovalent carboxylic acid.

  Next, the compound represented by the general formula (4) will be described.

In the general formula (4), X is an alkyl group (for example, methyl group, ethyl group, propyl group, isopropyl group, t-butyl group, pentyl group, hexyl group, octyl group, dodecyl group, trifluoromethyl group, etc.), It represents a cycloalkyl group (for example, cyclopentyl group, cyclohexyl group, etc.), an aryl group (for example, phenyl group, naphthyl group, etc.), and a heterocyclic ring (for example, pyridyl group, thiazolyl group, oxazolyl group, imidazolyl group, etc.). Z ₁ represents a nonmetallic atom group necessary for forming a 5- to 6-membered ring together with the —C—N—C— moiety. Z ₁ is preferably the structure given in general formula (1). L represents a divalent linking group. As the divalent linking group, the linking groups mentioned in formula (1) are preferable.

  p represents an integer of 0 to 5, q represents an integer of 1 to 6, 2 ≦ p + q ≦ 6, and A represents a p + q valent polyhydric alcohol residue.

  X is preferably a substituted or unsubstituted aryl group.

  Preferably, A is a trivalent polyhydric alcohol, p represents an integer of 0 to 2, and q represents an integer of 1 to 3.

  Hereinafter, although the representative example of a compound represented by General formula (4) preferably used for this invention is illustrated, it is not limited to these.

  Furthermore, the following plasticizers are preferable.

  These plasticizers may be used singly or in combination of two or more as required.

Moreover, you may add a conventionally well-known plasticizer to such an extent that the effect of this invention is not impaired.
Conventionally known plasticizers include ester plasticizers composed of polyhydric alcohols and monovalent carboxylic acids, ester plasticizers composed of polyvalent carboxylic acids and monovalent alcohols, phosphate ester plasticizers, and carbohydrate ester plasticizers. Agents, polymer plasticizers and the like.
Moreover, it is preferable to make the addition amount of a plasticizer contain 1-30 mass% with respect to a cellulose ester, More preferably, it is 2-25 mass%, Most preferably, it is 7-20 mass%.

"Antioxidant"
The following general formula (A), general formula (B), general formula (C-1), general formula (C-3), general formula (C-4), general formula (C-5) and the above general formula (C -2) will be described.

  Cellulose ester is preferably decomposed not only by heat but also by oxygen, and therefore the optical film of the present invention preferably contains an antioxidant as a stabilizer.

  In particular, in a high temperature environment where melt film formation is performed, decomposition of the optical film molding material with heat and oxygen is promoted, and therefore, an antioxidant is preferably contained.

  The antioxidant useful in the present invention can be used without limitation as long as it is a compound that suppresses the deterioration of the optical film molding material due to oxygen. Among them, the useful antioxidants include phenolic compounds and hindered amine compounds. , Phosphorus compounds, sulfur compounds, heat-resistant processing stabilizers, oxygen scavengers and the like. Among these, phenol compounds, hindered amine compounds, and phosphorus compounds are particularly preferable.

  By blending these compounds, it is possible to prevent coloration or strength reduction of the molded product due to heat, thermal oxidation deterioration, or the like without reducing transparency, heat resistance, and the like. These antioxidants can be used alone or in combination of two or more.

  In the present invention, it is preferable to use an antioxidant having an imide structure group represented by the general formula (1).

  Preferably, the following general formula (A), general formula (B), general formula (C-1), general formula (C-3), general formula (C) having an imide structure group represented by general formula (1) -4), a compound represented by the general formula (C-5) and the one-spot formula (C-2) is preferably used, and more preferably a compound having an imide structure group represented by the general formula (1). It is preferable to use compounds represented by the formulas (A) and (C-2).

(Phenolic compounds)
Phenol compounds are known compounds and are described, for example, in columns 12 to 14 of US Pat. No. 4,839,405, and include 2,6-dialkylphenol derivative compounds. Among such compounds, a compound represented by the following general formula (A) having an imide structure group represented by the general formula (1) is preferable.

  The compound represented by the following general formula (A) will be described.

In formula (A), R ¹¹ ~R ¹⁶ represents a substituent. Examples of the substituent include a halogen atom (eg, fluorine atom, chlorine atom), an alkyl group (eg, methyl group, ethyl group, isopropyl group, hydroxyethyl group, methoxymethyl group, trifluoromethyl group, t-butyl group, etc.), A cycloalkyl group (eg, cyclopentyl group, cyclohexyl group, etc.), an aralkyl group (eg, benzyl group, 2-phenethyl group, etc.), an aryl group (eg, phenyl group, naphthyl group, p-tolyl group, p-chlorophenyl group, etc.), alkoxy Groups (eg methoxy, ethoxy, isopropoxy, butoxy), aryloxy (eg phenoxy), cyano, acylamino (eg acetylamino, propionylamino), alkylthio (eg methylthio) Group, ethylthio group, butylthio group, etc.), aryl O group (for example, phenylthio group), sulfonylamino group (for example, methanesulfonylamino group, benzenesulfonylamino group, etc.), ureido group (for example, 3-methylureido group, 3,3-dimethylureido group, 1,3-dimethylureido) Group), sulfamoylamino group (dimethylsulfamoylamino group etc.), carbamoyl group (eg methylcarbamoyl group, ethylcarbamoyl group, dimethylcarbamoyl group etc.), sulfamoyl group (eg ethylsulfamoyl group, dimethylsulfamoyl group) Moyl group etc.), alkoxycarbonyl group (eg methoxycarbonyl group, ethoxycarbonyl group etc.), aryloxycarbonyl group (eg phenoxycarbonyl group etc.), sulfonyl group (eg methanesulfonyl group, butanesulfonyl group, phenylsulfonyl group) Group), acyl group (eg, acetyl group, propanoyl group, butyroyl group, etc.), amino group (methylamino group, ethylamino group, dimethylamino group, etc.), cyano group, hydroxy group, nitro group, nitroso group, amine oxide Group (for example, pyridine-oxide group), imide group (for example, phthalimide group, etc.), disulfide group (for example, benzene disulfide group, benzothiazolyl-2-disulfide group, etc.), carboxyl group, sulfo group, heterocyclic group (for example, pyrrole group, Pyrrolidyl group, pyrazolyl group, imidazolyl group, pyridyl group, benzimidazolyl group, benzthiazolyl group, benzoxazolyl group, etc.). These substituents may be further substituted.

Moreover, the phenol type compound whose R < ¹¹ > is a hydrogen atom and R < ¹² >, R < ¹⁶ > is a t-butyl group is preferable.

(Hindered amine compounds)
As one of the antioxidants useful in the present invention, a hindered amine compound represented by the following general formula (B) having an imide structure group represented by the general formula (1) is preferable.

  The compound represented by formula (B) will be described.

In the general formula (B), R ²¹ ~R ²⁷ represents a substituent. As a substituent, it is synonymous with the substituent represented by R < ¹¹ > -R < ¹⁶ > of the said general formula (A). R ²⁴ is a hydrogen atom, a methyl group, R ²⁷ is a hydrogen ^{atom, R 22, R 23, R} 25, R 26 is preferably a methyl group.

(Phosphorus compounds)
As one of the antioxidants useful in the present invention, the following general formula (C-1), general formula (C-3), and general formula (C-4) having an imide structure group represented by the general formula (1) ), A compound having a partial structure represented by the general formula (C-5) and the general formula (C-2) in the molecule.

  The compound represented by formula (C-1) will be described.

In the general formula (C-1), Ph ₁ and Ph ′ ₁ represent a substituent. As a substituent, it is synonymous with the substituent represented by R < ¹¹ > -R < ¹⁶ > of the said general formula (A).

More preferably, Ph ₁ and Ph ′ ₁ represent a phenylene group, and the hydrogen atom of the phenylene group is a phenyl group, an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, or 6 to 12 carbon atoms. Or an alkyl cycloalkyl group or an aralkyl group having 7 to 12 carbon atoms. Ph ₁ and Ph ′ ₁ may be the same as or different from each other.

X represents a single bond, a sulfur atom or a —CHR ₆ — group. R ₆ represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms. Moreover, these may be substituted by a substituent having the same meaning as the substituent represented by R ^{11 to} R ¹⁶ in the general formula (A).

  The compound represented by the general formula (C-2) will be described.

In the general formula (C-2), Ph ₂ and Ph ′ ₂ represent a substituent. As a substituent, it is synonymous with the substituent represented by R < ¹¹ > -R < ¹⁶ > of the said general formula (A). More preferably, Ph ₂ and Ph ′ ₂ represent a phenyl group or a biphenyl group, and the hydrogen atom of the phenyl group or biphenyl group is an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, or a carbon number. It may be substituted with a 6-12 alkylcycloalkyl group or an aralkyl group having 7-12 carbon atoms. Ph ₂ and Ph ′ ₂ may be the same as or different from each other. Moreover, these may be substituted by a substituent having the same meaning as the substituent represented by R ^{11 to} R ¹⁶ in the general formula (A).

  The compound represented by the following general formula (C-3) will be described.

In the general formula (C-3), Ph ₃ represents a substituent. As a substituent, it is synonymous with the substituent represented by R < ¹¹ > -R < ¹⁶ > of the said general formula (A). More preferably, Ph ₃ represents a phenyl group or a biphenyl group, and the hydrogen atom of the phenyl group or biphenyl group is an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, or a 6 to 12 carbon atom. It may be substituted with an alkylcycloalkyl group or an aralkyl group having 7 to 12 carbon atoms. Moreover, these may be substituted by a substituent having the same meaning as the substituent represented by R ^{11 to} R ¹⁶ in the general formula (A).

  The compound represented by the following general formula (C-4) will be described.

In the general formula (C-4), Ph ₄ represents a substituent. As a substituent, it is synonymous with the substituent represented by R < ¹¹ > -R < ¹⁶ > of the said general formula (A).

More preferably, Ph ₄ represents an alkyl group having 1 to 20 carbon atoms or a phenyl group, and the alkyl group or phenyl group is a substituent having the same meaning as the substituent represented by R ^{11 to} R ¹⁶ in the general formula (A). It may be substituted by a group.

  The compound represented by the following general formula (C-5) will be described.

In the general formula (C-5), Ph ₅ , Ph ′ ₅ and Ph ″ ₅ represent substituents. The substituents have the same meaning as the substituents represented by R ^{11 to} R ¹⁶ in the general formula (A). is there.

More preferably, Ph ₅ , Ph ′ ₅ and Ph ″ ₅ represent an alkyl group or phenyl group having 1 to 20 carbon atoms, and the alkyl group or phenyl group is represented by R ^{11 to} R ¹⁶ in the general formula (A). It may be substituted with a substituent having the same meaning as the substituent.

  The antioxidant is preferably removed from impurities such as residual acids, inorganic salts, organic low molecules, etc. that are carried over from production or generated during storage, more preferably 99% or more in purity, like the cellulose ester described above. It is. The residual acid and water are preferably from 0.01 to 100 ppm, and when melt-forming cellulose ester, thermal degradation can be suppressed, and film-forming stability, optical physical properties and mechanical properties of optical films are improved. .

  Below, although the representative example of the antioxidant which has an imide structure group represented by General formula (1) in this invention is illustrated, this invention is not limited to these.

  Moreover, you may add a conventionally well-known antioxidant to such an extent that the effect of this invention is not impaired.

  For example, the following compounds are mentioned.

IRGANOX 1010: Ciba Specialty Chemicals IRGAFOS P-EPQ: Ciba Specialty Chemicals TINUVIN 770: Ciba Specialty Chemicals TINUVIN 144: Ciba Specialty Chemicals ADK STABLA LA-52: Sumitizer GP manufactured by ADK: PEP-24G manufactured by Sumitomo Chemical Co., Ltd. Sumitizer TP-D manufactured by ADK Corporation GSY-P101 manufactured by Sumitomo Chemical Co., Ltd. Sumizer GM manufactured by Sumitomo Chemical Co., Ltd. Sumitizer manufactured by Sumitomo Chemical Co., Ltd. GS: manufactured by Sumitomo Chemical Co., Ltd. The antioxidant is preferably added in an amount of 0.1 to 10% by mass, more preferably 0.2 to 5% by mass, and further 0.5 to 2% by mass. Are preferred. Two or more of these may be used in combination.

  If the added amount of the antioxidant is too small, the stabilizing effect is low at the time of melting, so the effect cannot be obtained, and if the added amount is too large, the transparency as an optical film is lowered from the viewpoint of compatibility with the cellulose ester. And the optical film may become brittle.

  Moreover, it is preferable to add the compound represented by the general formula (5) because the stability of the cellulose ester during melt film formation is enhanced.

  The compound represented by the general formula (5) will be described.

In the general formula (5), R ₂ is an alkyl group (for example, methyl group, ethyl group, propyl group, isopropyl group, t-butyl group, pentyl group, hexyl group, octyl group, dodecyl group, trifluoromethyl group, etc.) , Acyl groups (eg acetyl group, pivaloyl group, benzoyl group etc.), alkoxy groups (eg methoxy group, ethoxy group, propoxy group etc.), aryloxy groups (eg phenoxy group, naphthyloxy group etc.), alkylthio groups (Eg, methylthio group, ethylthio group, etc.), arylthio group (eg, phenylthio group, naphthylthio group, etc.), amino group, alkylamino group (eg, alkylamino group having 1 to 4 carbon atoms), arylamino group, acylamino group (For example, acetylamino group, benzoylamino group, etc.), hydroxyl group, Group, carbamoyl group (for example, aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, butylaminocarbonyl group, cyclohexylaminocarbonyl group, phenylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), sulfamoyl group (for example, Aminosulfonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, butylaminosulfonyl group, hexylaminosulfonyl group, cyclohexylaminosulfonyl group, octylaminosulfonyl group, dodecylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2 -Pyridylaminosulfonyl group etc.), sulfonamide group (eg methanesulfonamide group, benzenesulfonamide group etc.), acyloxy group (eg Acetyloxy group, benzoyloxy group and the like) or oxycarbonyl group (for example, phenoxycarbonyl group and the like).

R ₆ is a hydrogen atom or an alkyl group (for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a t-butyl group, a pentyl group, a hexyl group, an octyl group, a dodecyl group, a trifluoromethyl group), or an acyl group (For example, acetyl group, pivaloyl group, benzoyl group, etc.).

n represents 1 or 2. Z ₁ represents a nonmetallic atom group necessary for forming a 5- to 6-membered ring together with the —C—N—C— moiety. Z ₁ is preferably the structure given in general formula (1).

  L represents a divalent linking group. As the divalent linking group, the linking groups mentioned in formula (1) are preferable.

When n is 1, R ₁ represents an aryl group, a hydroxyl group, or an acyl group. When n is 2, R ₁ represents a divalent linking group. As the divalent linking group, the linking groups mentioned in formula (1) are preferable. m represents an integer of 0 to 3.

In general formula (5), n is preferably 1, R ₁ is preferably a substituted or unsubstituted phenyl group, more preferably an alkyl group or a phenyl group substituted with an acyloxy group, and R ₂ is a hydrogen atom or an alkyl group. Is preferred.

  Although the typical example of the compound which has an imide structure group represented by General formula (5) below is illustrated, this invention is not limited to these.

  Moreover, you may add a conventionally well-known benzofuranone type compound to such an extent that the effect of this invention is not impaired. Examples thereof include benzofuranone compounds as described in JP-A-7-233160 and JP-A-7-247278.

  These compounds represented by the general formula (5) can be used singly or in combination of two or more, and the blending amount is appropriately selected within a range not impairing the object of the present invention. It is 0.001-10.0 mass part normally with respect to a mass part, Preferably it is 0.01-5.0 mass part, More preferably, it is 0.1-3.0 mass part.

(Cellulose ester)
Next, the cellulose ester preferably used in the present invention will be described in detail.

  The optical film of the present invention is produced by a melt casting method.

  In the melt casting method, a cellulose ester melted by heating (melt) is cast on a support to form an optical film. Since the melt casting method can significantly reduce the amount of organic solvent used in the production of optical films, it is significantly more environmentally friendly than conventional solution casting methods that use large amounts of organic solvents. Since an improved optical film can be obtained, it is preferable to produce the optical film by a melt casting method.

  The melt casting in the present invention is a method in which a cellulose ester is heated and melted to a temperature showing fluidity without using a solvent, and a film is formed using this, for example, a film is formed by extruding a fluid cellulose ester from a die. It is a method to do.

  In addition, although a solvent may be used in a part of the process for preparing the molten cellulose ester, in the melt film forming process for forming into a film shape, the forming process is performed without using the solvent.

  The cellulose ester constituting the optical film is not particularly limited as long as it is a meltable film-forming cellulose ester. For example, an aromatic carboxylic acid ester or the like is also used, but in consideration of the characteristics of the obtained optical film such as optical characteristics. And lower fatty acid esters of cellulose are preferably used.

  The lower fatty acid ester of cellulose preferably used in the present invention has 5 or less carbon atoms in the lower fatty acid. Specifically, for example, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose pivalate and the like are lower in cellulose. It is mentioned as a preferable thing of fatty acid ester.

  If the cellulose ester is substituted with a fatty acid having 5 or less carbon atoms, the melt film-forming property is good, the mechanical properties of the resulting optical film are excellent, and it can be easily used as an optical film.

  In order to achieve both mechanical properties and melt film-forming properties, mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may be used.

  Next, the substitution degree of the acyl group of the cellulose ester preferably used in the present invention will be described.

  Cellulose has a total of three hydroxyl groups, one at each of the 2nd, 3rd and 6th positions of 1 glucose unit. The total degree of substitution is the average number of acyl groups bonded to 1 glucose unit. It is a numerical value indicating whether or not. Therefore, the maximum substitution degree is 3.0. These acyl groups may be substituted on the 2nd, 3rd and 6th positions of the glucose unit on average, or may be substituted with a distribution.

  As the substitution degree of the mixed fatty acid ester, more preferred cellulose acetate propionate and cellulose acetate butyrate lower fatty acid ester have an acyl group having 2 to 4 carbon atoms as a substituent, and the substitution degree of the acetyl group is X, When the substitution degree of propionyl group or butyryl group is Y, it is a cellulose resin containing a cellulose ester that simultaneously satisfies the following formulas (I), (II) and (III).

  In addition, the substitution degree of an acetyl group and the substitution degree of another acyl group are determined by a method prescribed in ASTM-D817-96.

Formula (I) 2.4 ≦ X + Y ≦ 3.0
Formula (II) 0 ≦ X ≦ 2.4
Formula (III) 0.5 ≦ Y ≦ 2.9
Of these, cellulose acetate propionate is particularly preferably used. Among them, 1.2 ≦ X ≦ 2.1 and 0.6 ≦ Y ≦ 1.4 are preferable. More preferably, 1.3 ≦ X ≦ 1.8 and 0.9 ≦ Y ≦ 1.4.

  Cellulose esters having different degrees of substitution of acyl groups may be blended so that the entire optical film falls within the above range. The part not substituted with the acyl group is usually present as a hydroxyl group. These can be synthesized by known methods.

  The cellulose ester preferably used in the present invention preferably has a number average molecular weight (Mn) of 50,000 to 150,000, more preferably a number average molecular weight of 55,000 to 120,000, Most preferably, it has a number average molecular weight of 000-100,000.

  Furthermore, the cellulose ester used in the present invention preferably has a weight average molecular weight (Mw) / number average molecular weight (Mn) ratio of 1.3 to 5.5, particularly preferably 1.5 to 5.0. More preferably, it is 1.7-3.5, More preferably, the cellulose ester of 2.0-3.0 is used preferably.

  Mn and Mw / Mn were calculated by gel permeation chromatography in the following manner.

  The measurement conditions are as follows.

Solvent: Tetohydrofuran Equipment: HLC-8220 (manufactured by Tosoh Corporation)
Column: TSKgel SuperHM-M (manufactured by Tosoh Corporation)
Column temperature: 40 ° C
Sample concentration: 0.1% by mass
Injection volume: 10 μl
Flow rate: 0.6 ml / min
Calibration curve: Standard polystyrene: PS-1 (manufactured by Polymer Laboratories) Mw = 2, 560,000 to 580, a calibration curve with 9 samples was used.

  The cellulose ester raw material cellulose preferably used in the present invention may be wood pulp or cotton linter, and the wood pulp may be softwood or hardwood, but softwood is more preferred.

  A cotton linter is preferably used from the viewpoint of peelability during film formation. The cellulose ester made from these can be mixed suitably or can be used independently.

  For example, the ratio of cellulose ester derived from cellulose linter: cellulose ester derived from wood pulp (coniferous): cellulose ester derived from wood pulp (hardwood) is 100: 0: 0, 90: 10: 0, 85: 15: 0, 50:50: 0, 20: 80: 0, 10: 90: 0, 0: 100: 0, 0: 0: 100, 80:10:10, 85: 0: 15, 40:30:30.

  The cellulose ester can be obtained, for example, by substituting the hydroxyl group of the raw material cellulose with acetic anhydride, propionic anhydride and / or butyric anhydride in the usual manner using an acetyl group, propionyl group and / or butyl group within the above range. .

  The method for synthesizing such a cellulose ester is not particularly limited, and for example, it can be synthesized with reference to the method described in JP-A-10-45804 or JP-A-6-501040.

  The alkaline earth metal content of the cellulose ester preferably used in the present invention is preferably in the range of 1 to 50 ppm.

  If the alkaline earth metal content is in the above range, lip deposits are reduced, and no breakage occurs at the slitting part during or after hot stretching.

  Furthermore, the range of 1-30 ppm is preferable.

  The alkaline earth metal as used herein refers to the total content of Ca and Mg, and can be measured using an X-ray photoelectron spectrometer (XPS).

  The residual sulfuric acid content in the cellulose ester preferably used in the present invention is preferably in the range of 0.1 to 45 ppm in terms of elemental sulfur. These are considered to be contained in the form of salts.

  When the residual sulfuric acid content is in the above range, the deposit on the die lip portion during heat melting is reduced, and breakage does not occur during slitting during heat stretching or after heat stretching.

  Furthermore, the range of 1-30 ppm is preferable. The residual sulfuric acid content can be measured by a method prescribed in ASTM-D817-96.

  The free acid content in the cellulose ester preferably used in the present invention is preferably 1 to 500 ppm.

  When the free acid content is within the above range, the deposits on the die lip are reduced, and no breakage occurs during hot stretching or slitting after hot stretching.

  A range of 1 to 70 ppm is particularly preferable. The free acid content can be measured by a method prescribed in ASTM-D817-96.

  Compared to the case where the synthesized cellulose ester is washed in a solution casting method, the residual acid content can be made within the above range by manufacturing the optical film by the melt casting method. In this case, an optical film with reduced adhesion to the lip portion and excellent flatness can be obtained, and an optical film with good dimensional change, mechanical strength, transparency, moisture resistance, Rt value, and Ro value can be obtained. it can.

  Ro indicates in-plane retardation, the difference between the refractive index in the longitudinal direction MD in the plane and the refractive index in the width direction TD multiplied by the thickness, Rt indicates the thickness direction retardation, and the in-plane refractive index ( The difference between the average of the longitudinal direction MD and the width direction TD) and the refractive index in the thickness direction is multiplied by the thickness.

  In addition to washing with water, cellulose ester can be washed with a poor solvent such as methanol or ethanol, or as a result, a mixed solvent of a poor solvent and a good solvent can be used if it is a poor solvent. Low molecular organic impurities can be removed. Furthermore, washing of the cellulose ester is preferably performed in the presence of an antioxidant such as a hindered amine or a phosphite, which improves the heat resistance and film formation stability of the cellulose ester.

  In order to improve the heat resistance, mechanical properties, optical properties, etc. of cellulose ester, it can be dissolved in a good solvent of cellulose ester and then reprecipitated in a poor solvent to remove low molecular weight components and other impurities of cellulose ester. it can. At this time, it is preferable to carry out in the presence of an antioxidant as in the case of washing the cellulose ester.

  Furthermore, another polymer or a low molecular weight compound may be added after the cellulose ester reprecipitation treatment.

  In the present invention, in addition to cellulose ester resins, cellulose ether resins, vinyl resins (including polyvinyl acetate resins, polyvinyl alcohol resins, etc.), cyclic olefin resins, polyester resins (aromatic polyesters, aliphatic polyesters, Or a copolymer containing them), an acrylic resin (including a copolymer), and the like.

  As content of resin other than a cellulose ester, 0.1-30 mass% is preferable.

(Matting agent)
Further, it is preferable to add fine particles as a matting agent to the optical film of the present invention. As fine particles used in the present invention, for example, silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, Mention may be made of aluminum silicate, magnesium silicate and calcium phosphate.

  The average primary particle diameter of the silicon dioxide fine particles is preferably 5 to 16 nm, and more preferably 5 to 12 nm. A smaller primary particle average diameter is preferred because haze is low. The apparent specific gravity is preferably 90 to 200 g / L, more preferably 100 to 200 g / L. A larger apparent specific gravity is preferable because a high-concentration dispersion can be produced, and haze and aggregates are improved.

The addition amount of the matting agent is preferably 0.01 to 1.0 g, more preferably 0.03 to 0.3 g, and particularly preferably 0.10 to 0.18 g per 1 m ² .

  Examples of the silicon dioxide fine particles include AEROSIL R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600, and NAX50 manufactured by Nippon Aerosil Co., Ltd., KE-P10 manufactured by Nippon Shokubai Co., Ltd. KE-P30, KE-P100, KE-P150 etc. are mentioned.

  Among these, AEROSIL 200V and R972V are fine particles of silicon dioxide having a primary average particle diameter of 20 nm or less and an apparent specific gravity of 70 g / L or more, and the effect of lowering the friction coefficient while keeping the turbidity of the optical film low. Particularly preferred because of its large size.

  Further, NAX50, KE-P30, and KE-P100 are particularly preferable because they have a large effect of reducing the friction coefficient in a small amount.

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

  Examples of the polymer include silicone resin, fluorine resin, and acrylic resin.

  Among them, silicone resins are preferable, and those having a three-dimensional network structure are particularly preferable. For example, Tospearl 103, 105, 108, 120, 145, 3120, and 240 (manufactured by Toshiba Silicone Co., Ltd.) It is commercially available under the trade name and can be used.

  These fine particles usually preferably form secondary particles having an average particle diameter of 0.01 to 1.0 μm, more preferably 0.1 to 0.8 μm, and most preferably 0.2 to 0.5 μm.

  These fine particles are present as aggregates of primary particles in the optical film and form irregularities of 0.01 to 1.0 μm on the surface of the optical film.

  The content of these fine particles is preferably 0.005 to 0.3% by mass, more preferably 0.05 to 0.2% by mass, and most preferably 0.1 to 0.2% by mass with respect to the optical film. Two or more kinds of these fine particles may be used in combination.

(Retardation control agent)
In the optical film of the present invention, in order to improve liquid crystal display quality, a retardation control agent is added to the optical film, or an alignment film is formed to provide a liquid crystal layer. The optical compensation ability can be imparted by combining the foundation.

  As the compound to be added to adjust the retardation, an aromatic compound having two or more aromatic rings as described in the specification of European Patent 911,656A2 may be used as a retardation control agent. it can. Or the rod-shaped compound of Unexamined-Japanese-Patent No. 2006-2025 is mentioned. Two or more aromatic compounds may be used in combination.

  The aromatic ring of the aromatic compound is particularly preferably an aromatic heterocyclic ring including an aromatic heterocyclic ring in addition to an aromatic hydrocarbon ring, and the aromatic heterocyclic ring is generally an unsaturated hetero ring. It is a ring.

  Of these, the 1,3,5-triazine ring described in JP-A-2006-2026 is particularly preferable.

(Melt casting method)
The optical film of the present invention is formed by melt casting.

  The molding method by melt casting that heats and melts without using the solvent (for example, methylene chloride, etc.) used in the solution casting method, more specifically, melt extrusion molding method, press molding method, inflation method, injection molding method And can be classified into blow molding, stretch molding and the like. Among these, the melt extrusion method is excellent for obtaining an optical film having excellent mechanical strength, surface accuracy, and the like.

  Hereinafter, the manufacturing method of the optical film of the present invention will be described by taking the melt extrusion method as an example.

  FIG. 1 is a schematic flow sheet diagram showing an example of one embodiment of an apparatus for carrying out the method for producing an optical film of the present invention.

  FIG. 2 is a flow sheet showing an example of an enlarged main part of the manufacturing apparatus of FIG.

  The optical film is produced by mixing an optical film material such as a cellulose resin, and then using the extruder 1 to melt and extrude from the casting die 4 onto the first cooling roll 5 so as to circumscribe the first cooling roll 5. In addition, the optical film 10 is obtained by sequentially circumscribing a total of three cooling rolls, that is, the second cooling roll 7 and the third cooling roll 8, and cooling and solidifying.

  Next, the optical film 10 peeled off by the peeling roll 9 is then stretched in the width direction by holding both ends of the optical film by the stretching device 12, and then wound by the winding device 16.

  Moreover, 6 which clamps a molten film on the surface of the 1st cooling roll 5 in order to correct flatness is provided. The touch roll 6 has an elastic surface and forms a nip with the first cooling roll 5. Details of the touch roll 6 will be described later.

  In the method for producing an optical film, the conditions for melt extrusion can be performed in the same manner as the conditions used for other thermoplastic resins such as polyester. The material is preferably dried beforehand. It is desirable to dry the moisture to 1000 ppm or less, preferably 200 ppm or less by using a vacuum or reduced pressure drier or a dehumidifying hot air drier.

  For example, the cellulose ester resin dried under hot air, vacuum or reduced pressure is melted at an extrusion temperature of about 200 to 300 ° C. using the extruder 1, filtered through a leaf disk type filter 2, etc. to remove foreign matters.

  When introducing into the extruder 1 from a supply hopper (not shown), it is preferable to prevent oxidative decomposition or the like under vacuum, reduced pressure, or inert gas atmosphere.

  When additives such as a plasticizer are not mixed in advance, they may be kneaded in the middle of the extruder. In order to add uniformly, it is preferable to use a mixing apparatus such as a static mixer.

  In the present invention, the cellulose resin and other additives such as a stabilizer added if necessary are preferably mixed before melting, and more preferably mixed before heating. . Mixing may be performed by a mixer or the like, or may be mixed in the cellulose resin preparation process as described above. When a mixer is used, a general mixer such as a V-type mixer, a conical screw type mixer, a horizontal cylindrical type mixer, a Henschel mixer, a ribbon mixer, or the like can be used.

  After mixing the optical film constituting material as described above, the mixture may be directly melted and formed into a film using the extruder 1, but once the optical film constituting material is pelletized, the pellet May be melted by the extruder 1 to form a film.

  Further, when the optical film constituting material includes a plurality of materials having different melting points, a so-called braided semi-melt is once produced at a temperature at which only a material having a low melting point is melted, and the semi-melt is extruded into the extruder 1. It is also possible to form a film by putting it into the film.

  If the optical film material contains materials that are easily pyrolyzed, in order to reduce the number of melting times, a method of directly forming a film without producing pellets, or making a braided semi-melt as described above A method of forming a film from is preferred.

  As the extruder 1, various commercially available extruders can be used, but a melt-kneading extruder is preferable, and a single-screw extruder or a twin-screw extruder may be used.

  When forming a film directly without producing pellets from the optical film constituent material, it is preferable to use a twin screw extruder because an appropriate degree of kneading is required. However, even with a single screw extruder, the screw shape can be changed to Maddock. By changing to a kneading type screw such as a mold, unimelt, dalmage, etc., moderate kneading can be obtained, which can be used. When a pellet or braided semi-melt is used as the optical film constituent material, it can be used with either a single screw extruder or a twin screw extruder.

  In the extruder 1 and the cooling step after extrusion, it is preferable to reduce the oxygen concentration by replacing with an inert gas such as nitrogen gas or reducing the pressure.

  The melting temperature of the optical film constituting material in the extruder 1 varies depending on the viscosity and discharge amount of the optical film constituting material, the thickness of the sheet to be produced, etc., but is preferably 150 to 300 ° C, more preferably 180 to 270 ° C. Preferably, 200-250 degreeC is more preferable. The melt viscosity at the time of extrusion is 10 to 100,000 poise, preferably 100 to 10,000 poise. Further, the residence time of the optical film constituting material in the extruder 1 is preferably shorter, and is within 5 minutes, preferably within 3 minutes, and more preferably within 2 minutes.

  Although the residence time depends on the type of the extruder 1 and the extrusion conditions, it can be shortened by adjusting the material supply amount, L / D, screw rotation speed, screw groove depth, etc. It is.

  The shape, rotation speed, etc. of the screw of the extruder 1 are appropriately selected depending on the viscosity, discharge amount, etc. of the optical film constituting material. In the present invention, the shear rate in the extruder 1 is 1 / second to 10000 / second, preferably 5 / second to 1000 / second, more preferably 10 / second to 100 / second.

  The extruder 1 that can be used in the present invention is generally available as a plastic molding machine.

  The optical film constituting material extruded from the extruder 1 is sent to the casting die 4 and extruded from the slit of the casting die 4 into an optical film shape. The casting die 4 is not particularly limited as long as it is used for producing a sheet or an optical film.

  The material of the casting die 4 is sprayed or plated with hard chromium, chromium carbide, chromium nitride, titanium carbide, titanium carbonitride, titanium nitride, super steel, ceramic (tungsten carbide, aluminum oxide, chromium oxide), etc. Processing such as buffing, lapping using a # 1000 or higher grinding wheel, plane cutting using a # 1000 or higher diamond grinding wheel (the cutting direction is perpendicular to the resin flow direction), electrolytic polishing, electrolytic composite polishing, etc. And the like. A preferred material for the lip portion of the casting die 4 is the same as that of the casting die 4. The surface accuracy of the lip is preferably 0.5S or less, and more preferably 0.2S or less.

  The slit of the casting die 4 is configured so that the gap can be adjusted.

  FIG. 3A is an external view showing an example of the main part of the casting die, and FIG. 3B is a cross-sectional view showing an example of the main part of the casting die.

  Of the pair of lips forming the slit 32 of the casting die 4, one is a flexible lip 33 having low rigidity and easily deformed, and the other is a fixed lip 34.

  A large number of heat bolts 35 are arranged at a constant pitch in the width direction of the casting die 4, that is, in the length direction of the slits 32. Each heat bolt 5 is provided with a block 36 having an embedded electric heater 37 and a cooling medium passage, and each heat bolt 35 penetrates each block 36 vertically.

  The base of the heat bolt 35 is fixed to the die body 31, and the tip is in contact with the outer surface of the flexible lip 33. While the block 36 is always air-cooled, the input of the embedded electric heater 37 is increased or decreased to raise or lower the temperature of the block 36, thereby causing the heat bolt 35 to thermally expand and contract, thereby displacing the flexible lip 33 to change the thickness of the optical film. Adjust.

  Thickness gauges are installed at the required locations in the wake of the die, and the web thickness information detected thereby is fed back to the control device. The thickness information is compared with the set thickness information by the control device, and correction control comes from the same device. It is also possible to control the power or the ON rate of the heat bolt heating element by the amount signal.

  The heat bolt preferably has a length of 20 to 40 cm and a diameter of 7 to 14 mm, and a plurality of, for example, several tens of heat bolts are preferably arranged at a pitch of 20 to 40 mm.

  Instead of the heat bolt, a gap adjusting member mainly composed of a bolt for adjusting the slit gap by manually moving back and forth in the axial direction may be provided.

  The slit gap adjusted by the gap adjusting member is usually 200 to 1000 μm, preferably 300 to 800 μm, more preferably 400 to 600 μm.

  The first to third cooling rolls are made of seamless steel pipe having a wall thickness of about 20 to 30 mm, and the surface is finished to a mirror surface. A pipe for flowing a cooling liquid is arranged inside the pipe, and the cooling liquid flowing through the pipe can absorb heat from the optical film on the roll.

  On the other hand, the touch roll 6 in contact with the first cooling roll 5 has an elastic surface and is deformed along the surface of the first cooling roll 5 by the pressing force to the first cooling roll 5. A nip is formed between the two. That is, the touch roll 6 corresponds to the pinching rotary body of the present invention.

  FIG. 4 is a cross-sectional view showing an example of the first embodiment of the pinching rotator. (One Embodiment of touch roll 6 (henceforth, schematic cross section of touch roll A)) is shown. As shown in the drawing, the touch roll A has an elastic roller 42 disposed inside a flexible metal sleeve 41.

  The metal sleeve 41 is made of stainless steel having a thickness of 0.3 mm and has flexibility. If the metal sleeve 41 is too thin, the strength is insufficient, whereas if it is too thick, the elasticity is insufficient.

  For these reasons, the thickness of the metal sleeve 41 is preferably 0.1 to 1.5 mm.

  The elastic roller 42 is formed in a roll shape by providing a rubber 44 on the surface of a metal inner cylinder 43 that is rotatable via a bearing.

  When the touch roll A is pressed toward the first cooling roll 5, the elastic roller 42 presses the metal sleeve 41 against the first cooling roll 5, and the metal sleep 41 and the elastic roller 42 have the shape of the first cooling roll 5. It deforms corresponding to the familiar shape, and forms a nip with the first cooling roll. Cooling water 45 flows in a space formed between the metal sleeve 41 and the elastic roller 42.

  FIG. 5 is a cross-sectional view in a plane perpendicular to the rotation axis showing an example (hereinafter referred to as touch roll B) of the second embodiment of the pinching rotator.

  FIG. 6 is a cross-sectional view showing an example of a plane including the rotation axis of the second embodiment (touch roll B) of the pinching rotator.

  5 and 6, the touch roll B is a flexible and seamless outer tube 51 made of a stainless steel pipe (thickness 4 mm), and a high rigidity arranged in the same axial center inside the outer tube 51. The metal inner cylinder 52 is generally configured.

  A coolant 54 flows in the space 53 between the outer cylinder 51 and the inner cylinder 52. Specifically, in the touch roll B, outer cylinder support flanges 56a and 56b are attached to the rotation shafts 55a and 55b at both ends, and a thin metal outer cylinder 51 is attached between the outer peripheral portions of the both outer cylinder support flanges 56a and 56b. Yes.

  A fluid supply pipe 59 is disposed in the same axial center in a fluid discharge hole 58 formed in the axial center portion of one rotary shaft 55a and forming a fluid return passage 57. The fluid supply pipe 59 is thin-walled. It is connected and fixed to a fluid shaft cylinder 60 arranged at the axial center in the metal outer cylinder 51.

  Inner cylinder support flanges 61a and 61b are attached to both ends of the fluid shaft cylinder 60, respectively, and a thickness of about 15 to 20 mm between the outer periphery of the inner cylinder support flanges 61a and 61b and the other end side outer cylinder support flange 56b. A metal inner cylinder 52 having a thickness is attached.

  A cooling liquid flow space 53 of, for example, about 10 mm is formed between the metal inner cylinder 52 and the thin metal outer cylinder 51, and the metal inner cylinder 52 has a flow space 53 and an inner space near both ends. An outlet 52a and an inlet 52b are formed to communicate with the intermediate passages 62a and 62b outside the cylinder support flanges 61a and 61b, respectively.

  Further, the outer cylinder 51 is thinned within a range in which the thin cylinder theory of elastic mechanics can be applied in order to have flexibility, flexibility, and resilience close to rubber elasticity.

  The flexibility evaluated by the thin-walled cylinder theory is expressed by the thickness t / roll radius r, and the flexibility increases as t / r decreases.

  In this touch roll B, the flexibility is the optimum condition when t / r ≦ 0.03.

  Usually, the touch roll generally used has a roll diameter R = 200 to 500 mm (roll radius r = R / 2), a roll effective width L = 500 to 1600 mm, and a horizontally long shape with r / L <1. is there.

  As shown in FIG. 6, for example, when the roll diameter R = 300 mm and the roll effective width L = 1200 mm, the appropriate range of the wall thickness t is 150 × 0.03 = 4.5 mm or less, but the molten sheet width is 1300 mm. On the other hand, when the average linear pressure is clamped at 98 N / cm, the equivalent spring constant is equal by setting the wall thickness of the outer cylinder 51 to 3 mm compared to the rubber roll of the same shape. The nip width k in the roll rotation direction of the nip is also about 9 mm, which is almost the same as the nip width of this rubber roll of about 12 mm.

  The deflection amount at the nip width k is about 0.05 to 0.1 mm.

  Here, t / r ≦ 0.03. However, in the case of a general roll diameter R = 200 to 500 mm, flexibility is sufficiently obtained especially in the range of 2 mm ≦ t ≦ 5 mm. Thinning by processing can be easily performed, and it is an extremely practical range. If the wall thickness is 2 mm or less, high-precision processing cannot be performed due to elastic deformation during processing.

  The converted value of 2 mm ≦ t ≦ 5 mm is 0.008 ≦ t / r ≦ 0.05 with respect to a general roll diameter, but in practical use, the roll diameter under the condition of t / r ≦ 0.03. The wall thickness should be increased in proportion to

  For example, when roll diameter: R = 200, t = 2 to 3 mm, and when roll diameter: R = 500, t = 4 to 5 mm.

  The touch rolls A and B are urged toward the first cooling roll by the urging means. The urging force of the urging means is F, and the value F / W (linear pressure) obtained by dividing the width W of the optical film in the nip along the rotation axis of the first cooling roll 5 is 9.8 to 147 N / Set to cm.

  In the present invention, it is preferable that a nip is formed between the touch rolls A and B and the first cooling roll 5 and the flatness is corrected while the optical film passes through the nip. Accordingly, the optical film is sandwiched over a long time with a small linear pressure, compared to the case where the touch roll is formed of a rigid body and no nip is formed between the first cooling roll and the flatness is more reliably corrected. be able to.

  That is, when the linear pressure is smaller than 9.8 N / cm, the die line cannot be sufficiently eliminated. On the other hand, if the linear pressure is greater than 147 N / cm, the optical film is difficult to pass through the nip, resulting in unevenness in place of the thickness of the optical film.

  In addition, since the surfaces of the touch rolls A and B are made of metal, the surfaces of the touch rolls A and B can be made smoother than when the surface of the touch roll is rubber. Can be obtained. In addition, as a material of the elastic body 44 of the elastic roller 42, ethylene propylene rubber, neoprene rubber, silicon rubber, or the like can be used.

  Now, in order to eliminate the die line satisfactorily by the touch roll 6, it is important that the viscosity of the optical film when the touch roll 6 sandwiches the optical film is in an appropriate range.

  Cellulose esters are known to have a relatively large change in viscosity with temperature.

  Therefore, in order to set the viscosity when the touch roll 6 clamps the optical film to an appropriate range, it is important to set the temperature of the optical film when the touch roll 6 clamps the cellulose film to an appropriate range. It becomes.

  When the glass transition temperature of the optical film is Tg, it is preferable to set the temperature T of the optical film immediately before the optical film is sandwiched between the touch rolls 6 so as to satisfy Tg <T <Tg + 110 ° C.

  That is, when the temperature T of the optical film immediately before being sandwiched between the touch rolls 6 is within the above range, the viscosity of the optical film when sandwiching the optical film can be set to an appropriate range, and the die line can be corrected. Further, the surface of the optical film and the roll are uniformly bonded, and the die line can be corrected.

  Tg + 10 ° C. <T <Tg + 90 ° C., more preferably Tg + 20 ° C. <T <Tg + 70 ° C.

  In order to set the temperature of the optical film when the touch roll 6 clamps the optical film to an appropriate range, the first cooling is performed from the position P1 at which the melt extruded from the casting die 4 contacts the first cooling roll 5. The length L of the nip between the roll 5 and the touch roll 6 along the rotation direction of the first cooling roll 5 may be adjusted.

  In the present invention, preferred materials for the first roll 5 and the second roll 6 include carbon steel, stainless steel, resin, and the like. The surface accuracy is preferably increased, and the surface roughness is set to 0.3 S or less, more preferably 0.01 S or less.

  In the present invention, by reducing the pressure from the opening (lip) of the casting die 4 to the first roll 5 to 70 kPa or less, the above-mentioned die line correction effect is more manifested. Preferably, the reduced pressure is 50 to 70 kPa. It is. Although there is no restriction | limiting in particular as a method of keeping the pressure of the part from the opening part (lip | rip) of the casting die 4 to the 1st roll 5 below 70 kPa, Cover the roll periphery from the casting die 4 with a pressure | voltage resistant member, and reduce pressure. There are methods.

  At this time, the suction device is preferably subjected to a treatment such as heating with a heater so that the device itself does not become a place where the sublimate is attached. In the present invention, if the suction pressure is too small, the sublimate cannot be sucked effectively, so it is necessary to set the suction pressure to an appropriate value.

  In the present invention, a film-like cellulose ester resin in a molten state is transferred from the T die 4 to the first roll (first cooling roll) 5, the second cooling roll 7, and the third cooling roll 8 in order and conveyed. While being cooled and solidified, an unstretched optical film 10 is obtained.

  In the embodiment of the present invention shown in FIG. 1, the cooled and solidified unstretched optical film 10 separated from the third cooling roll 8 by the peeling roll 9 passes through a dancer roll (optical film tension adjusting roll) 11 and a stretching machine 12. Then, the optical film 10 is stretched in the transverse direction (width direction). By this stretching, the molecules in the optical film are oriented.

  As a method for stretching the optical film in the width direction, a known tenter or the like can be preferably used.

  In particular, it is preferable to set the stretching direction to the width direction because lamination with a polarizing film can be performed in a roll form. By stretching in the width direction, the slow axis of the optical film made of the cellulose ester resin film is in the width direction.

  On the other hand, the transmission axis of the polarizing film is also usually in the width direction. By incorporating a polarizing plate in which the transmission axis of the polarizing film and the slow axis of the optical film are parallel to each other into the liquid crystal display device, the display contrast of the liquid crystal display device can be increased and a good viewing angle can be obtained. Is obtained.

  The glass transition temperature Tg of the optical film constituting material can be controlled by making the material type constituting the optical film and the ratio of the constituting material different.

  When a retardation film is produced as an optical film, Tg is preferably 120 ° C. or higher, preferably 135 ° C. or higher. In the liquid crystal display device, in the image display state, the temperature environment of the optical film changes due to the temperature rise of the device itself, for example, the temperature rise derived from the light source.

  At this time, if the Tg of the optical film is 120 ° C. or higher than the operating environment temperature of the optical film, the retardation value derived from the orientation state of the molecules fixed inside the optical film by stretching and the dimensional shape as the optical film are adjusted. Is easy.

  When the Tg of the optical film is 250 ° C. or less, the temperature when the optical film constituting material is made into an optical film can be optimized, energy consumption for heating is drastically reduced, and the material itself is decomposed when it is made into an optical film. There is no coloration.

  Therefore, Tg is preferably 120 ° C to 250 ° C.

  In the stretching step, known heat setting conditions, cooling, and relaxation treatment may be performed, and adjustment may be made as appropriate so as to have characteristics required for the target optical film.

  In order to provide the physical properties of the phase film and the function of the phase film for expanding the viewing angle of the liquid crystal display device, the stretching step and the heat setting treatment are appropriately selected and performed. When such a stretching step and heat setting treatment are included, the heating and pressurizing step is performed before the stretching step and heat setting treatment.

  When producing a retardation film as an optical film and further combining the functions of a polarizing plate protective film, it is necessary to control the refractive index. However, the refractive index can be controlled by a stretching operation. Is a preferred method. Hereinafter, the stretching method will be described.

  In the retardation film stretching process, it is required by stretching 1.0 to 2.0 times in one direction of the cellulose resin and 1.01 to 2.5 times in the direction perpendicular to the optical film plane. Retardation Ro and Rth can be controlled. Here, Ro indicates in-plane retardation, the difference between the refractive index in the longitudinal direction MD in the plane and the refractive index in the width direction TD is multiplied by the thickness, and Rth indicates the thickness direction retardation. The difference between the refractive index (average of the longitudinal direction MD and the width direction TD) and the refractive index in the thickness direction is multiplied by the thickness.

  Stretching can be performed, for example, sequentially or simultaneously in the longitudinal direction of the optical film and the direction orthogonal to the longitudinal direction of the optical film, that is, the width direction. At this time, if the stretching ratio in at least one direction is too small, a sufficient phase difference cannot be obtained, and if it is too large, stretching becomes difficult and film breakage may occur.

  Stretching in biaxial directions perpendicular to each other is an effective method for putting the refractive indexes nx, ny, and nz of the optical film within a predetermined range. Here, nx is the refractive index in the longitudinal MD direction, ny is the refractive index in the width TD direction, and nz is the refractive index in the thickness direction.

  For example, when stretching in the melt casting direction, if the shrinkage in the width direction is too large, the value of nz becomes too large. In this case, it can be improved by suppressing the width shrinkage of the optical film or stretching in the width direction. When stretching in the width direction, the refractive index may be distributed in the width direction.

  This distribution may appear when the tenter method is used. By stretching the optical film in the width direction, a contraction force is generated at the center of the optical film, and the phenomenon is caused by the end being fixed. The so-called Boeing phenomenon is considered. Even in this case, by stretching in the casting direction, the bowing phenomenon can be suppressed and the distribution of the phase difference in the width direction can be reduced.

  By stretching in the biaxial directions perpendicular to each other, the film thickness variation of the obtained optical film can be reduced. When the film thickness variation of the retardation film is too large, the retardation becomes uneven, and unevenness such as coloring may be a problem when used in a liquid crystal display.

  The film thickness variation of the optical film is preferably in the range of ± 3%, and more preferably ± 1%. For the purposes as described above, the method of stretching in the biaxial directions perpendicular to each other is effective, and the stretching ratio in the biaxial directions perpendicular to each other is finally 1.0 to 2.0 times in the casting direction. The width direction is preferably 1.01 to 2.5 times, preferably 1.01 to 1.5 times in the casting direction and 1.05 to 2.0 times in the width direction. It is more preferable to obtain the required retardation value.

  When the absorption axis of the polarizer exists in the longitudinal direction, the transmission axis of the polarizer coincides with the width direction. In order to obtain a long polarizing plate, the retardation film is preferably stretched so as to obtain a slow axis in the width direction.

  When cellulose ester that obtains positive birefringence with respect to stress is used, the slow axis of the retardation film can be imparted in the width direction by stretching in the width direction from the above-described configuration.

  In this case, in order to improve the display quality, it is preferable that the slow axis of the retardation film is in the width direction, and in order to obtain the target retardation value, the following equation must be satisfied. is there.

Formula (Stretch ratio in the width direction)> (Stretch ratio in the casting direction)
After stretching, the end of the optical film is slit to a product width by the slitter 13 and cut off, and then knurled (embossing) is applied to both ends of the optical film by a knurling device comprising the embossing ring 14 and the back roll 15. Application and winding by the winder 16 prevents sticking in the optical film (original winding) F and generation of scratches.

  The knurling method can process a metal ring having an uneven pattern on its side surface by heating or pressing. In addition, since the grip part of the clip of the optical film both ends is deform | transforming normally and cannot be used as an optical film product, it is cut out and reused as a raw material.

  Next, the winding process of the optical film is performed by keeping the shortest distance between the outer peripheral surface of the cylindrically wound optical film and the outer peripheral surface of the mobile transport roll immediately before the optical film as a winding roll. It is to be wound up. In addition, a means such as a static elimination blower for removing or reducing the surface potential of the optical film is provided in front of the winding roll.

  The winder related to the production of the optical film of the present invention may be generally used, and it may be a winding method such as a constant tension method, a constant torque method, a taper tension method, or a program tension control method with a constant internal stress. Can be wound up. In addition, it is preferable that the initial winding tension at the time of winding of the optical film is 90.2 to 300.8 N / m.

  In the winding process of the optical film in the method of the present invention, the optical film is preferably wound under environmental conditions of a temperature of 20 to 30 ° C. and a humidity of 20 to 60% RH.

  Thus, the tolerance of the humidity change of the thickness direction retardation (Rt) improves by prescribing | regulating the temperature and humidity in the winding-up process of an optical film.

  If the temperature in the winding process is in the range of 20 to 30 ° C., there will be no wrinkles, and there will be no deterioration of the optical film winding quality.

  Moreover, if the humidity in the winding process of the optical film is 20 to 60% RH, it is difficult to be charged, the optical film winding quality deterioration is reduced, the winding quality is excellent, there is no sticking failure, and the transportability is not deteriorated. .

  When winding the optical film into a roll, the wound core may be any material as long as it is a cylindrical core, but is preferably a hollow plastic core, and the plastic material is heated. Any heat-resistant plastic that can withstand the processing temperature may be used, and examples thereof include phenol resins, xylene resins, melamine resins, polyester resins, and epoxy resins.

  A thermosetting resin reinforced with a filler such as glass fiber is preferred. For example, a hollow plastic core: a wound core made of FRP having an outer diameter of 6 inches (hereinafter, 1 inch is 2.54 cm) and an inner diameter of 5 inches is used.

  The number of turns to these winding cores is preferably 100 turns or more, more preferably 500 turns or more, the winding thickness is preferably 5 cm or more, and the width of the optical film substrate is 80 cm or more. It is preferable that it is 1 m or more.

  The production effect obtained by the present invention is particularly remarkable in a long roll of an optical film having a length of 100 m or more and a width of a film having a width of 1.35 m or more, and the length is 1500 m, 2500 m, and 5000 m. The longer the length is, the more wide the width is 2 m and 4 m, the more suitable for the production of the optical film.

  In the production of the optical film of the present invention, the length of the roll is preferably 10 to 5000 m, more preferably 50 to 4500 m in consideration of productivity and transportability.

  The width of the optical film at this time can be selected from the width of the polarizer and the width suitable for the production line, but the optical film has a width of 0.5 to 4.0 m, preferably 0.6 to 3.0 m. Is preferably wound up into a roll.

<Optical film>
The optical film of the present invention is a functional film used for various display devices such as a liquid crystal display, a plasma display, and an organic EL display, and more specifically, a polarizing plate protective film, a retardation film, and an antireflection for a liquid crystal display device. Films, brightness enhancement films, hard coat films, antiglare films, antistatic films, optical compensation films such as viewing angle expansion, and the like.

  The optical film of the present invention is preferably used for a polarizing plate protective film, a retardation film, and an optical compensation film, and particularly preferably used for a polarizing plate protective film.

  When the retardation film is a polarizing plate protective film, the thickness of the protective film is preferably 10 to 500 μm.

  In particular, the lower limit is 20 μm or more, preferably 35 μm or more. The upper limit is 150 μm or less, preferably 120 μm or less. A particularly preferable range is 25 to 90 μm.

  When the thickness of the retardation film is 500 μm or less, the liquid crystal display used for a notebook personal computer or a mobile electronic device is particularly suitable for the purpose of being thin and light.

  On the other hand, when the thickness of the retardation film is 10 μm or more, retardation as a retardation film can be developed, and in addition, the moisture permeability of the optical film is lowered, and the ability to protect the polarizer from humidity is improved.

  When the slow axis or the fast axis of the retardation film exists in the film plane and the angle formed with the film forming direction is θ1, θ1 is −1 to + 1 °, preferably −0.5 to + 0.5 °. To be.

  This θ1 can be defined as an orientation angle, and θ1 can be measured using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments).

  When each θ1 satisfies the above relationship, it contributes to obtaining high luminance in a display image, suppressing or preventing light leakage, and contributing to faithful color reproduction in a color liquid crystal display device.

  When the retardation film is used for the multi-domain VA mode, the retardation film is arranged in the above region with the fast axis of the retardation film being θ1, which contributes to the improvement of display image quality. When the plate and the liquid crystal display device are in the MVA mode, for example, the configuration shown in FIG. 7 can be adopted.

  FIG. 7 is a perspective view showing an example of an exploded view schematically showing a configuration diagram of the liquid crystal display device.

  In FIG. 7, 21a and 21b are protective films, 22a and 22b are retardation films, 25a and 25b are polarizers, 23a and 23b are slow axis directions of the optical film, 24a and 24b are transmission axis directions of the polarizer, and 26a. 26b are polarizing plates, 27 is a liquid crystal cell, and 29 is a liquid crystal display device.

  The retardation Ro distribution in the in-plane direction of the optical film is preferably adjusted to 5% or less, more preferably 2% or less, and particularly preferably 1.5% or less.

  The retardation Rt distribution in the thickness direction of the optical film is preferably adjusted to 10% or less, more preferably 2% or less, and particularly preferably 1.5% or less.

  In the retardation film, it is preferable that the retardation value distribution fluctuation is small. When a polarizing plate including a retardation film is used in a liquid crystal display device, the retardation distribution fluctuation is preferably small from the viewpoint of preventing color unevenness and the like.

  The retardation film is adjusted so as to have a retardation value suitable for improving the display quality of the liquid crystal cell of VA mode or TN mode, and is preferably used in the MVA mode by dividing the retardation film into the above multi-domain as the VA mode. For this purpose, it is required to adjust the in-plane retardation Ro to a value greater than 30 nm and 95 nm or less, and the thickness direction retardation Rt to a value greater than 70 nm and 400 nm or less.

  The in-plane retardation Ro is observed from the normal direction of the display surface when the two polarizing plates are arranged in crossed Nicols and the liquid crystal cell is arranged between the polarizing plates, for example, in the configuration shown in FIG. When in a crossed Nicol state with respect to time, when observed obliquely from the normal line of the display surface, the polarizing plate deviates from the crossed Nicol state, and light leakage caused by this is mainly compensated.

  The retardation in the thickness direction mainly compensates for the birefringence of the liquid crystal cell similarly observed when viewed from an oblique direction when the liquid crystal cell is in the black display state in the TN mode or VA mode, particularly in the MVA mode. Contribute to.

  As shown in FIG. 7, in the liquid crystal display device, when two polarizing plates are arranged above and below the liquid crystal cell, 22a and 22b in the figure can select the distribution of the thickness direction retardation Rt. The total value of both of the above-mentioned ranges and the thickness direction retardation Rt is preferably larger than 140 nm and 500 nm or less.

  In this case, in-plane retardation Ro and thickness direction retardation Rt of 22a and 22b are preferably the same for improving productivity of an industrial polarizing plate. Particularly preferably, the in-plane retardation Ro is larger than 35 nm and not larger than 65 nm, and the thickness direction retardation Rt is larger than 90 nm and not larger than 180 nm, and is applied to the MVA mode liquid crystal cell in the configuration of FIG.

  In the liquid crystal display device, for example, a TAC film having an in-plane retardation Ro = 0 to 4 nm and a thickness direction retardation Rt = 20 to 50 nm and a thickness of 35 to 85 μm as one commercially available polarizing plate protective film is shown in FIG. When used at the position 22b, the polarizing film disposed on the other polarizing plate, for example, the retardation film disposed on 22a in FIG. 7, has an in-plane retardation Ro of more than 30 nm and not more than 95 nm, and By using a film having a thickness direction retardation Rt of greater than 140 nm and not greater than 400 nm, the display quality is improved and the production of the optical film is preferred.

"Polarizer"
When using the optical film of this invention as a polarizing plate protective film, the preparation methods of a polarizing plate are not specifically limited, It can manufacture by a general method.

  The back side of the optical film of the present invention is subjected to alkali saponification treatment, and the treated optical film is bonded to at least one surface of a polarizing film prepared by immersing and stretching in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. It is preferable.

  The optical film of the present invention may be used on the other surface, or another polarizing plate protective film may be used.

  With respect to the optical film of the present invention, a commercially available optical film can be used as the polarizing plate protective film used on the other surface.

  For example, as a commercially available optical film, KC8UX2M, KC4UX, KC5UX, KC4UY, KC8UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UY-HA, KC8UX-RHA (manufactured by Konica Minolta Opto Co., Ltd. is preferably used), etc. It is done.

  Alternatively, it is also preferable to use a polarizing plate protective film that also serves as an optical compensation film having an optically anisotropic layer formed by aligning liquid crystal compounds such as discotic liquid crystal, rod-shaped liquid crystal, and cholesteric liquid crystal.

  For example, the optically anisotropic layer can be formed by the method described in JP-A-2003-98348.

  By using in combination with the optical film of the present invention, a polarizing plate having excellent flatness and a stable viewing angle expansion effect can be obtained.

  Or you may use optical films, such as cyclic olefin resin other than an optical film, an acrylic resin, polyester, a polycarbonate, as a polarizing plate protective film of the other surface.

  Instead of the alkali treatment, a polarizing plate may be processed by applying an easy adhesion process as described in JP-A-6-94915 and JP-A-6-118232.

  The polarizing film, which is the main component of the polarizing plate, is an element that transmits only light having a polarization plane in a certain direction. A typical polarizing film known at present is a polyvinyl alcohol polarizing film, which is a polyvinyl alcohol film. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed.

  As the polarizing film, a polyvinyl alcohol aqueous solution is formed and dyed by uniaxially stretching or dyed, or uniaxially stretched after dyeing, and then preferably subjected to a durability treatment with a boron compound.

  The thickness of the polarizing film is 5 to 40 μm, preferably 5 to 30 μm, and particularly preferably 5 to 20 μm.

  On the surface of the polarizing film, one side of the cellulose ester film of the present invention is bonded to form a polarizing plate. It is preferably bonded with an aqueous adhesive mainly composed of completely saponified polyvinyl alcohol or the like.

  Since the polarizing film is stretched in a uniaxial direction (usually the longitudinal direction), when the polarizing plate is placed in a high-temperature and high-humidity environment, the stretching direction (usually the longitudinal direction) shrinks, and the direction perpendicular to the stretching (usually the width direction) ) Will grow. As the thickness of the polarizing plate protective film becomes thinner, the expansion / contraction ratio of the polarizing plate increases, and in particular, the amount of contraction in the stretching direction of the polarizing film increases.

  Normally, the stretching direction of the polarizing film is bonded to the casting direction (MD direction) of the polarizing plate protective film. Therefore, when making the polarizing plate protective film thin, it is particularly important to suppress the stretching rate in the casting direction. It is. Since the optical film of the present invention is extremely excellent in dimensional stability, it is suitably used as such a polarizing plate protective film.

  That is, even when the durability test is performed at 60 ° C. and 90% RH, the wavy unevenness does not increase, and even if the polarizing plate has an optical compensation film on the back side, the viewing angle characteristics fluctuate after the durability test. Good visibility can be provided without doing so.

  The polarizing plate is composed of a polarizer and a protective film for protecting both surfaces of the polarizer, and can further be constructed by laminating a protective film on one surface of the polarizing plate and a separate film on the opposite surface.

  The protective film and the separate film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate and at the time of product inspection.

  In this case, the protect film is bonded for the purpose of protecting the surface of the polarizing plate, and is used on the side opposite to the surface where the polarizing plate is bonded to the liquid crystal plate.

  Moreover, a separate film is used in order to cover the contact bonding layer bonded to a liquid crystal board, and is used for the surface side which bonds a polarizing plate to a liquid crystal cell.

<Liquid crystal display device>
A polarizing plate comprising the optical film of the present invention as a polarizing plate protective film (including a case where it also serves as a retardation film) can exhibit higher display quality than a normal polarizing plate, and in particular, a multi-domain liquid crystal. It is suitable for use in a display device, more preferably a multi-domain liquid crystal display device by a birefringence mode.

  The polarizing plate of the present invention can be used for MVA (Multi-domain Vertical Alignment) mode, PVA (Patterned Vertical Alignment) mode, CPA (Continuous Pinweal Alignment) mode, OCB (Optical Compensated B mode, etc.). It is not limited to the mode and the arrangement of the polarizing plates.

  Liquid crystal display devices are being applied as devices for colorization and moving image display, and the display quality is improved by the present invention, and the improvement of contrast and the resistance of polarizing plates improve the display of moving images that are less fatigued and faithful. It becomes possible.

  In a liquid crystal display device including at least a polarizing plate including a retardation film, one polarizing plate including a polarizing plate protective film as the optical film of the present invention is disposed on the liquid crystal cell, or both sides of the liquid crystal cell. Place two in a row.

  At this time, it can contribute to the improvement of display quality by using the polarizing plate protective film side included in the polarizing plate so as to face the liquid crystal cell of the liquid crystal display device.

  In FIG. 7, the optical films 22a and 22b face the liquid crystal cell of the liquid crystal display device.

  In such a configuration, the polarizing plate protective film as the optical film of the present invention can optically compensate the liquid crystal cell.

  When the polarizing plate of the present invention is used in a liquid crystal display device, at least one polarizing plate in the liquid crystal display device may be the polarizing plate of the present invention.

  By using the polarizing plate of the present invention, a liquid crystal display device with improved display quality and excellent viewing angle characteristics can be provided.

  In the polarizing plate of the present invention, a polarizing plate protective film of a cellulose derivative is used on the surface opposite to the polarizing plate protective film as the optical film of the present invention as viewed from the polarizer, and a general-purpose TAC film or the like is used. Can do. The polarizing plate protective film located on the side far from the liquid crystal cell can be provided with another functional layer in order to improve the quality of the display device.

  For example, an anti-glare, anti-glare, scratch resistance, dust adhesion prevention, and an optical film containing a known functional layer as a display as a constituent for improving brightness, or may be attached to the polarizing plate surface of the present invention. It is not limited to these.

  In general, a retardation film is required to obtain stable optical characteristics that the fluctuation of Ro or Rt is small as the retardation value.

  In particular, in a liquid crystal display device in a birefringence mode, these fluctuations may cause image unevenness.

  Since the polarizing plate protective film produced by the melt casting film forming method according to the present invention is mainly composed of cellulose ester, the alkali treatment step can be utilized by utilizing saponification inherent to cellulose ester.

  When the resin which comprises a polarizer is polyvinyl alcohol, this can be bonded with a polarizing plate protective film using the completely saponified polyvinyl alcohol aqueous solution similarly to the conventional polarizing plate protective film. For this reason, this invention is excellent in the point which can apply the conventional polarizing plate processing method.

  In the present invention, particularly in the case of a long roll of 100 m or more, the productivity of the polarizing plate is significantly improved. The longer the length is 1500 m, 2500 m, and 5000 m, the more the improvement in productivity becomes. It is preferable to increase the length.

  For example, in the production of a polarizing plate protective film, the roll length is 10 to 5000 m, preferably 50 to 4500 m in consideration of productivity and transportability. At this time, the width of the film is the width of the polarizer or the production line. A suitable width can be selected.

  The width of the optical film may be 0.5 to 4.0 m, preferably 0.6 to 3.0 m, wound into a roll, and may be used for polarizing plate processing. After manufacturing an optical film and winding up on a roll, it may cut and obtain the roll of the target width, and you may make it use such a roll for polarizing plate processing.

  In the production of the polarizing plate protective film, functional layers such as an antistatic layer, a hard coat layer, a slippery layer, an adhesive layer, an antiglare layer, and a barrier layer may be coated before and / or after stretching. At this time, various surface treatments such as corona discharge treatment, plasma treatment, and chemical treatment can be performed as necessary.

  In the film forming process, the clip gripping portions at both ends of the cut optical film are pulverized or granulated as necessary, and then used as raw materials for the same type of optical film or different types of optical film. It may be reused as a raw material.

  An optical film having a laminated structure can be prepared by co-extrusion of a composition containing cellulose esters having different additive concentrations such as the plasticizer, the ultraviolet absorber, and the matting agent.

  For example, an optical film having a structure of skin layer / core layer / skin layer can be produced.

  For example, the matting agent can be contained in the skin layer in a large amount or only in the skin layer. The plasticizer and the ultraviolet absorber can be contained in the core layer more than the skin layer, and may be contained only in the core layer.

  In addition, the type of plasticizer and ultraviolet absorber can be changed between the core layer and the skin layer. For example, the skin layer contains a low-volatile plasticizer and / or an ultraviolet absorber, and the core layer has excellent plasticity. It is also possible to add a plasticizer or an ultraviolet absorber excellent in ultraviolet absorption.

  The glass transition temperature of the skin layer and the core layer may be different, and the glass transition temperature of the core layer is preferably lower than the glass transition temperature of the skin layer.

  At this time, the glass transition temperatures of both the skin layer and the core layer are measured, and an average value calculated from these volume fractions can be defined as the glass transition temperature Tg and similarly handled.

  Also, the viscosity of the melt containing the cellulose ester during melt casting may be different between the skin layer and the core layer, and the viscosity of the skin layer> the viscosity of the core layer or the viscosity of the core layer ≧ the viscosity of the skin layer may be used.

  The dimensional stability of the optical film of the present invention has a dimensional variation value of ± 2.0 at 80 ° C. and 90% RH, based on the dimensions of the optical film left at 23 ° C. and 55% RH for 24 hours. %, Preferably less than 1.0%, more preferably less than 0.5%.

  When using the optical film of the present invention as a retardation film for a polarizing plate protective film, if the retardation film itself has a variation beyond the above range, the retardation absolute value and the orientation angle as the polarizing plate are initially set. This shift is not preferable because it may cause a decrease in display quality improvement capability or display quality deterioration.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, the embodiment of this invention is not limited by these. In addition, “part” described below represents “part by mass”.

Example 1
(Preparation of optical film No. 1-1)
Using the following additives and cellulose ester, optical film No. 1-1 was produced.

Cellulose ester C-1 (cellulose acetate propionate (acetyl group substitution degree 1.4, propionyl group substitution degree 1.3, molecular weight Mn = 86,000, Mw / Mn = 2.5)) 100 parts by mass TMPTB 10 parts by mass Part IRGANOX-1010 (manufactured by Ciba Specialty Chemicals) 0.5 part by mass GSY-P101 (manufactured by Sakai Chemical Industry Co., Ltd.) 0.3 part by mass Sumizer-GS (manufactured by Sumitomo Chemical Co., Ltd.) 0.3 part by mass 2-5 2.5 parts by mass The structural formulas of the comparative compound and TMPTB compound used in the examples of the present invention are listed below.

  The cellulose ester was dried under reduced pressure at 70 ° C. for 3 hours and cooled to room temperature, and then the additive was mixed.

  The above mixture was melt-mixed at 230 ° C. using a twin-screw extruder and pelletized.

  Using this pellet, it is melted at 250 ° C. in a nitrogen atmosphere and extruded from the casting die 4 onto the first cooling roll 5, and an optical film is sandwiched between the first cooling roll 5 and the touch roll 6 to form it. did.

  Further, 200 V of silica particles (manufactured by Nippon Aerosil Co., Ltd.) was added as a slip agent from the hopper opening in the middle of the extruder 1 so as to be 0.5 parts by mass.

  The heat bolt was adjusted so that the gap width of the casting die 4 was 0.5 mm within 30 mm from the end in the width direction of the optical film and 1 mm at other locations. The touch roll A was used as the touch roll, and 80 ° C. water was poured as cooling water therein.

  From the position P1 at which the resin extruded from the casting die 4 contacts the first cooling roll 5 to the position P2 at the upstream end in the rotation direction of the first cooling roll 5 in the nip between the first cooling roll 5 and the touch roll 6. 1 The length L along the peripheral surface of the cooling roller 5 was set to 20 mm.

  The linear pressure of the touch roll 6 against the first cooling roll 5 was 14.7 N / cm.

  Furthermore, after being introduced into a tenter and stretched 1.15 times in the width direction at 160 ° C., it was cooled to 30 ° C. while relaxing 3% in the width direction, and then released from the clip. Both ends were subjected to a knurling process with a width of 10 mm and a height of 5 μm, and wound on a winding core with a winding tension of 220 N / m and a taper of 40%.

  In addition, the extrusion amount and the take-up speed were adjusted so that the optical film had a thickness of 80 μm, and the finished optical film was slit and wound so that the width of the finished optical film was 1430 mm.

  Furthermore, except for changing to the additives listed in Table 1, optical film No. In the same manner as in 1-1, the optical film No. 1-2 to 1-6, comparative optical film No. 1-7 to 1-9 were produced.

  In addition, the addition amount of an additive is No. It was replaced with the same amount as 1-1 compound 2-5.

  The obtained optical film sample was evaluated by the following method.

(Die line evaluation)
When the fluorescent lamp was viewed through the optical film, the distortion or fine disturbance was observed to evaluate the dilan, and the rank was classified into the following levels.

  Ranks B and C have no commercial value. The evaluation results are shown in Table 1.

A: Fluorescent lamp looks straight without distortion B: Fluorescent lamp appears partially distorted C: Fluorescent lamp outline appears jagged <Production of polarizing plate>
Optical film No. 1 of the present invention. 1-1 to 1-6 and comparative optical film No. 1-7 to 1-9, a hard coat layer was formed on one surface of the optical film No. 1 with the hard coat layer of the present invention. 1-1 to 1-6 and comparative optical film No. 1 with a hard coat layer. 1-7 to 1-9 were produced.

  Using this, polarizing plates 1 to 6 of the present invention and comparative polarizing plates 7 to 9 were produced.

<Production of optical film with hard coat layer>
The following composition was prepared:

(Antistatic layer coating composition (1))
Polymethyl methacrylate (weight average molecular weight 550,000, Tg: 90 ° C.) 0.5 part Propylene glycol monomethyl ether 60 parts Methyl ethyl ketone 16 parts Ethyl lactate 5 parts Methanol 8 parts Conductive polymer resin P-1 (0.1-0. 3 μm particles) 0.5 part (hard coat layer coating composition (2))
Dipentaerythritol hexaacrylate monomer 60 parts Dipentaerythritol hexaacrylate dimer 20 parts Dipentaerythritol hexaacrylate trimer or higher component 20 parts Diethoxybenzophenone photoinitiator 6 parts Silicone surfactant 1 part Propylene Glycol monomethyl ether 75 parts Methyl ethyl ketone 75 parts (Anti-curl layer coating composition (3))
Acetone 35 parts Ethyl acetate 45 parts Isopropyl alcohol 5 parts Diacetyl cellulose 0.5 part Ultrafine silica 2% acetone dispersion (Aerosil: 200 V, manufactured by Nippon Aerosil Co., Ltd.) 0.1 part Optical film with hard coat layer according to the following Was made.

  On one side of the optical film, the anti-curl layer coating composition (3) was gravure coated to a wet film thickness of 13 μm and dried at a drying temperature of 80 ± 5 ° C.

  On the other side of the optical film, the antistatic layer coating composition (1) was coated at an optical film conveyance speed of 30 m / min so that the wet film thickness was 7 μm in an environment of 28 ° C. and 82% RH. The film was applied at 1 m and then dried in a drying section set at 80 ± 5 ° C. to provide a resin layer having a dry film thickness of about 0.2 μm to obtain an optical film with an antistatic layer.

Further, the hard coat layer coating composition (2) was applied on the antistatic layer so as to have a wet film thickness of 13 μm, dried at a drying temperature of 90 ° C., and then irradiated with ultraviolet rays at 150 mJ / m ² . The clear hard coat layer having a dry film thickness of 5 μm was provided.

(Preparation of polarizing film)
A polyvinyl alcohol film having a thickness of 120 μm was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times). This was immersed for 60 seconds in an aqueous solution consisting of 0.075 g of iodine, 5 g of potassium iodide, and 100 g of water, and then immersed in an aqueous solution of 68 ° C. consisting 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.

  Then, according to the following processes 1-5, a polarizing film and optical film No. 1 with a hard-coat layer of this invention. 1-1 to 1-6 and Comparative No. 1-7 to 1-9, an optical film was bonded to the back side to prepare a polarizing plate.

  For the optical film on the back side, Konica Minolta-Tac KC8UCR-4 (manufactured by Konica Minolta Opto Co., Ltd.), which is a commercially available optical film, was used for polarizing plate No. 1 of the present invention. 1-6 and comparative polarizing plate No. 7-9.

  Step 1: Optical film with a hard coat layer of the present invention, which was immersed in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, then washed with water and dried to saponify the side to be bonded to the polarizing film. No. 1-1 to 1-6 and Comparative No. 1-7 to 1-9 were obtained.

  The saponification treatment was similarly performed for Konica Minolta Tack.

  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: Gently wipe off excess adhesive adhered to the polarizing film in Step 2, one side of the polarizing film with an optical film with a hard coat layer, the other side with Konica Minoltack, and the alkali saponification surface of Step 1 A polarizing plate was prepared by laminating as a polarizing film side.

Step 4: The optical film with a hard coat layer, the polarizing film, and the optical 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 sample obtained by bonding the polarizing film, the optical film, and the optical film with a hard coat layer prepared in Step 4 in a dryer at 80 ° C. was dried for 2 minutes to prepare a polarizing plate.

(Characteristic evaluation as a liquid crystal display device)
The polarizing plate of 32-type TFT color liquid crystal display Vega (manufactured by Sony Corporation) was peeled off, and each of the produced polarizing plates was cut according to the size of the liquid crystal cell.

  The two polarizing plates produced as described above were bonded so that the polarizing axes of the polarizing plates were not perpendicular to each other so as to sandwich the liquid crystal cell, so that a 32-type TFT color liquid crystal display was produced, and the polarizing plate of the optical film As the characteristics were evaluated.

(Front contrast evaluation)
In an environment of 23 ° C. and 55% RH, the backlight of the liquid crystal display was turned on and left for 30 minutes before measurement.

  For measurement, EZ-Contrast 160D manufactured by ELDIM was used to measure the front luminance of white display and black display with a liquid crystal TV, and the ratio was defined as the front contrast.

  The higher the value, the better the contrast. The evaluation results are shown in Table 1.

Front contrast = Front brightness of white display / Front brightness of black display (Durability evaluation when stored under high temperature and high humidity)
The prepared polarizing plate was treated at 80 ° C. and 90% RH for 200 hours, then left at 23 ° C. and 55% RH for 24 hours, and then observed from the front side of the polarizing plate having a polarizing plate / backlight configuration. Evaluation was performed according to the following criteria. The evaluation results are shown in Table 1.

A: Good with no change from before treatment B: Although it is faintly white and deteriorated, it is a level that is not problematic in practical use C: It is partially cloudy and has practical problems D: In a considerable area White turbidity is recognized and there is a problem in practical use.

  Sample No. of the present invention using the compound of the present invention. Although 1-1 to 1-6 use a compound having the same molecular weight as that of the comparative compound, no die line is generated, the flatness is good, and even if a hard coat layer is applied, brushing is performed. No cracks were observed after drying, and the coating property was good.

  Furthermore, when it was made into a polarizing plate, the contrast was high, the high-temperature and high-humidity resistance was good, and good performance was exhibited.

Example 2
(Preparation of optical film No. 2-1)
Using the following additives, cellulose ester, optical film No. In the same manner as in 1-1, the optical film no. 2-1.

Cellulose ester C-1 (cellulose acetate propionate (acetyl group substitution degree 1.4, propionyl group substitution degree 1.3, molecular weight Mn = 86,000, Mw / Mn = 2.5)) 100 parts by mass Compound 4-1 10 parts by weight IRGANOX-1010 (manufactured by Ciba Specialty Chemicals) 0.5 part by weight GSY-P101 (manufactured by Sakai Chemical Industry Co., Ltd.) 0.3 part by weight Sumizer-GS (manufactured by Sumitomo Chemical Co., Ltd.) 0 .3 parts by mass Further, except for changing to the additives listed in Table 2, optical film No. In the same manner as in 1-1, the optical film No. 2-2 to 2-5, comparative optical film No. 2-6 to 2-8 were produced. In addition, the addition amount of an additive is No. It was replaced with an equivalent amount of 2-1 compound 4-1.

  For the obtained optical film sample, a die line evaluation, a polarizing plate, and a liquid crystal display device were prepared in the same manner as in Example 1, and front contrast evaluation and durability evaluation during storage at high temperature and high humidity were performed. The results are shown in Table 2.

  As shown in Table 2, Sample No. Although 2-1 to 2-5 use a compound having the same molecular weight as that of the comparative compound, no die line is generated, and it can be seen that good performance is obtained when a polarizing plate is formed.

  Furthermore, sample No. 1 of the present invention. The optical film in which the hard coat layer was applied to 2-1 to 2-5 showed no good brushing and cracking and showed good coating properties.

Example 3
(Preparation of optical film No. 3-1)
Using the following additives, cellulose ester, optical film No. In the same manner as in 1-1, the optical film no. 3-1.

Cellulose ester C-1 (cellulose acetate propionate (acetyl group substitution degree 1.4, propionyl group substitution degree 1.3, molecular weight Mn = 86,000, Mw / Mn = 2.5)) 100 parts by mass TMPTB 10 parts by mass Part Compound A1 of the present invention 0.5 part by weight Compound C3 of the present invention 0.3 part by weight Sumilizer-GS (manufactured by Sumitomo Chemical Co., Ltd.) 0.3 part by weight Further, compounds A1 and C3 of the present invention are described in Table 3. Except for the change as in Example No. In the same manner as in 1-1, the optical film No. 3-2 to 3-7, comparative optical film No. 3-8 to 3-10 were produced.

  When the amount added is changed with respect to the compound A1 of the present invention, it is replaced with an equivalent amount of the compound A1 of the present invention. It was.

  About the obtained sample, evaluation of die line, a polarizing plate, and a liquid crystal display device were produced like Example 1, and front contrast evaluation and durability evaluation at the time of storage under high temperature and high humidity were performed. The results are shown in Table 3.

  As a result, sample no. Although 3-1 to 3-7 used a molecular weight similar to that of the comparative compound, no die line was generated, and good performance was obtained when the polarizing plate was formed.

  Furthermore, sample No. 1 of the present invention. The optical film provided with a hard coat layer on 3-1 to 3-7 did not cause brushing, no cracks were observed after drying, and the coating property was good.

Example 4
(Preparation of optical film No. 4-1)
Optical film No. 1 of Example 1 1-1, substituting 0.3 part by mass of Sumilizer-GS (manufactured by Sumitomo Chemical Co., Ltd.) with 0.3 part by mass of compound 5-1 of the present invention, 4-1.

  Furthermore, Example No. 5 was changed except that compound 5-1 of the present invention was changed as shown in Table 4. In the same manner as in 1-1, the optical film No. 4-2, Comparative optical film No. 4-3 was produced.

  The addition amount was replaced with an equivalent amount of the compound 5-1 of the present invention.

  About the obtained sample, evaluation of die line, a polarizing plate, and a liquid crystal display device were produced like Example 1, and front contrast evaluation and durability evaluation at the time of storage under high temperature and high humidity were performed. The results are shown in Table 4.

  As a result, sample no. Although 4-1 to 4-2 used the same degree of compound as the comparative compound, no die line was generated, and good performance was obtained when the polarizing plate was used.

  Furthermore, the optical film No. 1 of the present invention. The optical film in which the hard coat layer was applied to 4-1 to 4-2 showed no good brushing and cracking and showed good coating properties.

Example 5
(Preparation of optical film No. 5-1)
Optical film No. Except that the cellulose ester C-1 used in 1-1 was changed to the following C-2 to C-4, the optical film No. 5-1 to 5-3 were produced.

C-2: Cellulose acetate propionate (acetyl group substitution degree 1.3, propionyl group substitution degree 1.2, molecular weight Mn 65,000, Mw / Mn = 3.0, acyl group total carbon number 6.2)
C-3: Cellulose acetate propionate (acetyl group substitution degree 1.5, propionyl group substitution degree 1.3, molecular weight Mn 64,000 = 200,000, Mw / Mn = 3.0, acyl group total carbon number 6. 9)
C-4: Cellulose acetate propionate (acetyl group substitution degree 2.1, propionyl group substitution degree 0.7, molecular weight Mn 90,000, Mw / Mn = 2.5, acyl group total carbon number 6.3)
The obtained sample was evaluated in the same manner as in Example 1 for die line evaluation, front contrast evaluation, and durability evaluation during storage at high temperature and high humidity.

As a result, sample no. Nos. 5-1 to 5-3 were free of die lines and had good flatness, and the optical film coated with the hard coat layer did not show brushing or cracks, and showed good results.
Further, when the polarizing plate was used, the contrast was high, the high temperature and high humidity resistance was good, and good performance was exhibited.

  In particular, the optical film using cellulose esters C-2 and C-3 was more excellent in flatness and better in coating properties than when C-4 was used.

It is a general | schematic flow sheet which shows an example of one Embodiment of the apparatus which enforces the manufacturing method of the optical film of this invention. It is a flow sheet which shows an example of the principal part expansion of the manufacturing apparatus of FIG. FIG. 3A is an external view showing an example of the main part of the casting die, and FIG. 3B is a cross-sectional view showing an example of the main part of the casting die. It is sectional drawing which shows an example of 1st Embodiment of a pinching rotary body. It is sectional drawing in the plane perpendicular | vertical to the rotating shaft which shows an example of 2nd Embodiment of a pinching rotary body. It is sectional drawing which shows an example of the plane containing the rotating shaft of 2nd Embodiment of a pinching rotary body. It is a perspective view which shows an example of the decomposition | disassembly which shows the outline of the block diagram of a liquid crystal display device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Extruder 2 Filter 3 Static mixer 4 Casting die 5 Rotating support body (1st cooling roll)
6 Nipping pressure rotating body (touch roll)
7 Rotating support (second cooling roll)
8 Rotating support (3rd cooling roll)
9, 11, 13, 14, 15 Transport roll 10 Optical film 16 Winding device 21a, 21b Protective film 22a, 22b Phase difference film 23a, 23b Film slow axis direction 24a, 24b Polarizer transmission axis direction 25a, 25b Polarizers 26a, 26b Polarizing plate 27 Liquid crystal cell 29 Liquid crystal display device 31 Die body 32 Slit 41 Metal sleeve 42 Elastic roller 43 Metal inner cylinder 44 Rubber 45 Cooling water or heating medium 51 Outer cylinder 52 Inner cylinder 53 Space 54 Coolant 55a, 55b Rotating shaft 56a, 56b Outer cylinder support flange 60 Fluid shaft cylinder 61a, 61b Inner cylinder support flange 62a, 62b Intermediate passage

Claims (15)

In an optical film formed by melt-melting an optical film-forming material containing a cellulose ester and formed by a melt casting method, a compound having an imide structural group represented by the following general formula (1) is added to the optical film-forming material. An optical film characterized by containing.

(In the formula, Z ₁ represents a nonmetallic atom group necessary for forming a 5- to 6-membered ring together with the —C—N—C— moiety. L represents a divalent linking group.) The optical film according to claim 1, wherein the compound having an imide structure group represented by the general formula (1) is an ultraviolet absorber, a plasticizer, or an antioxidant. The optical film according to claim 1, further comprising an ultraviolet absorber having an imide structure group represented by the following general formula (2).

Wherein R ₃₁ and R ₃₂ are each independently a hydroxyl group, alkoxy group, alkenyl group, aryl group, acyloxy group, aryloxy group, alkylthio group, arylthio group, mono- or dialkylamino group, acylamino group, acyl group , a sulfonyl group, an arylthio group, an amino group, an arylamino group, an acylamino group, a cyano group, a carbamoyl group, a sulfamoyl group, a sulfonamido group, an acyloxy _{group, .R 33, R 34, R} 35 representing a oxycarbonyl group are each independently A halogen atom, alkyl group, alkoxy group, alkenyl group, aryl group, acyloxy group, aryloxy group, alkylthio group, arylthio group, mono- or dialkylamino group, acylamino group, acyl group, sulfonyl group, arylthio group, amino group , Arylamino Represents an acylamino group, a cyano group, a carbamoyl group, a sulfamoyl group, a sulfonamido group, an acyloxy group, an oxycarbonyl group.
l, m, and n represent an integer of 0-4.
Z ₁ represents a nonmetallic atomic group necessary for forming a 5- to 6-membered ring together with the —C—N—C— moiety. L represents a divalent linking group. ) The optical film according to claim 1 or 2, comprising an ultraviolet absorber having an imide structure group represented by the following general formula (3).

(Wherein R ₁₁ represents a hydrogen atom, an acyloxy group, an oxycarbonyl group, a carbamoyl group, an acyl group, an aliphatic group or an aryl group. R ₁₂ and R ₁₃ each independently represents a halogen atom, an alkyl group, an aryl group, Acyl, sulfonyl, alkoxy, aryloxy, alkylthio, arylthio, amino, alkylamino, arylamino, acylamino, hydroxyl, cyano, carbamoyl, sulfamoyl, sulfonamido, acyloxy Represents a group or an oxycarbonyl group, m represents an integer of 0 to 3, n represents an integer of 0 to 5. Z ₁ forms a 5- to 6-membered ring together with the —C—N—C— moiety. Represents a group of non-metallic atoms necessary for the above, L represents a divalent linking group.) The optical film according to claim 1, comprising a plasticizer having an imide structure group represented by the following general formula (4).

(In the formula, X represents an alkyl group, a cycloalkyl group, an aryl group or a heterocyclic ring. Z ₁ is a nonmetallic atom necessary for forming a 5- to 6-membered ring together with the —C—N—C— moiety. L represents a divalent linking group.
p represents an integer of 0 to 5, q represents an integer of 1 to 6, 2 ≦ p + q ≦ 6, and A represents a p + q valent polyhydric alcohol residue. ) The optical film according to claim 1, comprising a benzofuranone-based compound having an imide structure group represented by the general formula (1). The optical film according to claim 6, comprising a benzofuranone compound represented by the following general formula (5).

(Wherein R ₂ is an alkyl group, acyl group, alkoxy group, aryloxy group, alkylthio group, arylthio group, amino group, alkylamino group, arylamino group, acylamino group, hydroxyl group, cyano group, carbamoyl group, sulfamoyl group) Group, a sulfonamide group, an acyloxy group or an oxycarbonyl group, R ₆ represents a hydrogen atom or an alkyl group, or an acyl group, and n represents 1 or 2. Z ₁ represents a —C—N—C— moiety. And a non-metallic atom group necessary for forming a 5- to 6-membered ring, and L represents a divalent linking group.
When n is 1, R ₁ represents an aryl group, a hydroxyl group, or an acyl group. When n is 2, R ₁ represents a divalent linking group. m represents an integer of 0 to 3. ) The optical film according to claim 1, comprising a phosphonite compound containing an imide structure group represented by the general formula (1). The optical film according to claim 8, wherein the phosphonite compound contains a partial structure represented by the following general formula (C-2).

(In the formula, Ph ₂ and Ph ′ ₂ represent a substituted or unsubstituted phenyl group or biphenyl group.) The said imide structure group is represented by following General formula (6), The optical film of any one of Claims 1-9 characterized by the above-mentioned.

(In the formula, Z ₂ represents a non-metallic atom group necessary for forming a 5- to 6-membered ring together with C... C part. L represents a divalent linking group. Represents a single bond or a double bond.) The optical film according to claim 10, wherein the general formula (6) is represented by the following general formula (7).

(In the formula, R ₁₀₁ represents a halogen atom, an alkyl group, an aryl group, an acyl group, a sulfonyl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an amino group, an alkylamino group, an arylamino group, an acylamino group, A hydroxyl group, a cyano group, a carbamoyl group, a sulfamoyl group, a sulfonamide group, an acyloxy group or an oxycarbonyl group, L represents a divalent linking group, and r represents an integer of 0 to 8.) A polarizing plate comprising the optical film according to claim 1 on at least one surface. A method for producing a polarizing plate, wherein the optical film according to claim 1 is saponified and bonded to a polarizer. A liquid crystal display device comprising the polarizing plate according to claim 12 on at least one surface of a liquid crystal cell. A liquid crystal display device comprising: a polarizing plate produced by the method for producing a polarizing plate according to claim 13 on at least one surface of a liquid crystal cell.

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