KR102015658B1 - Cellulose acetate film, method for producing cellulose acetate film, polarizer and liquid crystal display device - Google Patents

Abstract

(Problem) Providing the manufacturing method of the cellulose acetate film which is easy to peel from a metal support, and is favorable in the corrosiveness of a manufacturing installation, and is excellent in the expression property of Rth when solution casting.
(Solution means) A dope containing cellulose acetate having a total substitution degree of 2.0 to 2.7, a solvent, and an organic acid satisfying the requirements of 0.01 to 20 mass% of the following (1) to (3) with respect to the cellulose acetate: The manufacturing method of the cellulose acetate film containing the process of solution casting on a metal support body, and the process of peeling off the said dope film from the said metal support body.
(1) It contains the structure which the polyhydric alcohol and polyhydric carboxylic acid couple | bonded and formed the ester bond.
(2) The sum total of the number of molecules of the polyhydric alcohol and polyhydric carboxylic acid which forms the compound is three or more.
(3) It has at least 1 unsubstituted carboxyl group derived from polyhydric carboxylic acid.

Description

Cellulose Acetate Film, Manufacturing Method Thereof, Polarizing Plate and Liquid Crystal Display Device {CELLULOSE ACETATE FILM, METHOD FOR PRODUCING CELLULOSE ACETATE FILM, POLARIZER AND LIQUID CRYSTAL DISPLAY DEVICE}

The present invention relates to a cellulose acetate film and a method for producing a cellulose acetate film. Moreover, it also relates to the polarizing plate and liquid crystal display device which contain this cellulose acetate film.

Conventionally, various optical films are used as a liquid crystal display device use, and the optical film which added various additives is known. Such optical films are produced by various film production methods. As a typical method, the optical films are widely manufactured by a solution casting method in which a dope in which a cellulose acylate is dissolved in a solvent is cast on a support to produce a film.

In recent years, using the cellulose dicylate which has a low degree of total acyl substitution from the viewpoint of manufacturing at low cost the film which expressed the retardation Rth of the film thickness direction has been examined. On the other hand, about the case where the film using the cellulose diacetate which has a low total acyl substitution degree was manufactured by solution casting, it was the present situation that the method of improving the peelability from a support body was still not fully examined.

PTL 1 controls the water content of cellulose acetate dope before solution casting to a specific range with respect to cellulose acetate having a low degree of substitution of all acyl groups at 2.1 to 2.7, and the ΔSP value of the cellulose acetate and the solvent (solvent) (solubility value). It is disclosed that whitening of the film obtained can be suppressed by making) into an appropriate range. In this document, peelability was not examined at all. In Examples of the same document, citric acid half ester was used as the release agent (peeling accelerator).

Japanese Unexamined Patent Publication No. 2009-263619

When the present inventors produced the film using the cellulose diacetate (henceforth DAC) with low total acyl substitution degree by solution casting | flow_spread, expression of Rth compared with the case where the cellulose triacetate with high total acyl substitution degree was used. Although it became favorable, it turned out that peeling from a support body becomes more difficult.

On the other hand, the present inventors use a relatively expensive cellulose acetate propionate (hereinafter also referred to as CAP) in which the degree of substitution of the entire acyl group is about 2.0 to 2.7 and has a certain amount of propionyl group as the acyl group. As a result of solution casting film production, it was surprisingly found that peelability was better than that of an inexpensive cellulose diacetate film having the same degree of total acyl substitution degree and having only an acetyl group as an acyl group.

Although not bound by any theory, the difference in the peelability from the support of CAP and DAP in the same amount of hydroxyl groups is due to the fact that the side chain propionyl chain of cellulose acetate is longer than the acetyl chain, and thus the distance between the support and the unsubstituted hydroxyl group. Apart, the interaction between the support and hydroxyl groups decreases, so that the peeling load is expected to decrease.

Therefore, the problem of the improvement of peelability from a support body at the time of reducing the total acyl substitution degree came to find out that it is a problem peculiar to DAC.

Thus, the present inventors have found that improving the peelability of the film from the support, which is peculiar when producing a solution cast film using cellulose diacetate, which is lower in cost than this CAP and lower in manufacturing cost, has a lower total acyl substitution degree. The purpose of this study was to conduct a polite study.

On the other hand, the present inventors refer to the method described in Patent Literature 1, and 40% monoester of citric acid ethyl ester and diester as cellulose acetate having a low degree of substitution of all acyl groups at 2.1 to 2.7 and citric acid half ester as a peeling accelerator. As a result of solution casting film formation on the metal support using a mixture of 40% and 10% of the ester, the peelability of the film from the metal support was somewhat improved, but it was found that there was a problem of corrosion of the metal support. Therefore, in the solution casting film production using the cellulose diacetate which has low total acyl substitution degree, earnest research is made for the purpose of reducing the maintenance cost of manufacturing equipment by improving the corrosiveness of a metal support body, a dope preparation tank, a piping, and a die. It was decided as follows.

That is, the problem to be solved by this invention is providing the manufacturing method of the cellulose acetate film which is easy to peel from a metal support, and is favorable in the corrosiveness of a manufacturing installation, and is excellent in the expression property of Rth when it is solution casting.

Under the above-mentioned problems, the present inventors earnestly examined and studied the peeling property of the cellulose acetate film from the metal support and the improvement of the corrosiveness of the metal support, the dope preparation tank, the piping, and the die. By using an organic acid in which the carboxylic acid forms an ester bond and also satisfies specific requirements, it has been found that the corrosion of the metal support, the dope preparation tank, the piping and the die can be improved while the film is well peeled from the support. The invention has been completed.

Specifically, the problem was solved by the following means.

[1] A dope containing metal cellulose acetate having a total substitution degree of 2.0 to 2.7, a solvent, and an organic acid satisfying the requirements of 0.01 to 20 mass% of the following (1) to (3) with respect to the cellulose acetate. And a step of solution casting on the support, and a step of peeling off the dope film from the metal support.

(1) It contains the structure which the polyhydric alcohol and polyhydric carboxylic acid couple | bonded and formed the ester bond.

(2) The sum total of the number of molecules of the polyhydric alcohol and polyhydric carboxylic acid which forms the compound is three or more.

(3) It has at least 1 unsubstituted carboxyl group derived from polyhydric carboxylic acid.

[2] In the method for producing a cellulose acetate film according to [1], 15 mass% or more of the solvent is preferably an alcohol, and the average carbon number of the alcohol is preferably 1.5 to 4.

[3] The method for producing a cellulose acetate film according to [2] preferably contains ethanol as the alcohol.

[4] The method for producing a cellulose acetate film according to any one of [1] to [3], wherein the metal support is a band-like support to which the metal support moves, and in the region where the dope film of the metal support is peeled off, the metal It is preferable to bring the cooling body whose surface temperature is 10 degrees C or less into the surface on the opposite side to the dope film peeling side of a support body.

[5] It is preferable that the manufacturing method of the cellulose acetate film in any one of [1]-[4] contains the retardation Rth control agent of the film thickness direction in the said dope.

[6] A cellulose produced by the method for producing a cellulose acetate film according to any one of [1] to [5], wherein the retardation value Rth in the film thickness direction measured at a wavelength of 590 nm is 80 nm or more. Acetate film.

[7] The cellulose acetate film according to [6], preferably has a haze of less than 0.5%.

[8] The cellulose acetate film according to [6] or [7] is preferably a retardation value Re of the film in-plane direction measured at a wavelength of 590 nm of 30 to 100 nm.

[9] A polarizing plate comprising a polarizer and at least one cellulose acetate film according to any one of [6] to [8].

[10] A liquid crystal display device comprising the cellulose acetate film according to any one of [6] to [8].

According to the present invention, when the solution is cast, it is possible to provide a method for producing a cellulose acetate film that is easily peeled from the metal support and exhibits good Rth expression with good corrosiveness of the manufacturing equipment.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic diagram which shows the outline | summary of the preferable apparatus for controlling the casting | flow_spread manufacturing and peeling conditions in the manufacturing method of this invention in the solution casting apparatus of the aspect which has the endless band spanned between two rolls. to be.

EMBODIMENT OF THE INVENTION Below, the content of this invention is demonstrated in detail. Although description of the element | module described below may be made | formed based on typical embodiment of this invention, this invention is not limited to such embodiment. In addition, in this specification, "-" is used by the meaning which includes the numerical value described before and after that as a lower limit and an upper limit.

[Method for producing cellulose acetate film]

The manufacturing method (henceforth a manufacturing method of this invention) of the cellulose acetate film of this invention is 0.01 mass%-20 mass% of the following (based on the cellulose acetate of total substitution degree 2.0-2.7, a solvent, and this cellulose acetate) The process of carrying out solution casting of the dope containing organic acid which satisfy | fills the requirements of 1)-(3) on a metal support body, and the process of peeling off the said dope film from the said metal support body are included.

(1) It contains the structure which the polyhydric alcohol and polyhydric carboxylic acid couple | bonded and formed the ester bond.

(2) The sum total of the number of molecules of the polyhydric alcohol and polyhydric carboxylic acid which forms the compound is three or more.

(3) It has at least 1 unsubstituted carboxyl group derived from polyhydric carboxylic acid.

Hereinafter, the manufacturing method of this invention is demonstrated.

The cellulose acetate film (henceforth the film of this invention) of this invention is manufactured by the solution film manufacturing method (solvent cast method). Regarding the production examples of the cellulose acetate film using the solvent cast method, each specification of US Pat. Nos. 2,336,310, 2,367,603, 2,492,078, 2,492,977, 2,492,978, 2,607,704, 2,739,069 and 2,739,070. Each specification of British Patent No. 640731 and 736892, and Japanese Patent Publication Nos. 45-4554, 49-5614, 60-176834, 60-203430, 62-115035, etc. See the publication of. Moreover, although it is preferable that extending | stretching process is performed for the film of this invention, About the method and conditions of extending | stretching process other than what is prescribed | regulated in this specification, For example, Unexamined-Japanese-Patent No. 62-115035, Unexamined-Japanese-Patent No. References such as Japanese Patent Publication Nos. 4-152125, 4-284211, 4-298310, and 11-48271 may be referred to.

<Preparation of dope>

In the solvent cast method, a film can be manufactured using the solution (dope) which melt | dissolved cellulose acetate in the organic solvent.

(Dope)

The dope used by the manufacturing method of this invention is cellulose acetate whose substitution degree of all acyl groups is 2.0-2.7, 0.01 mass%-20 mass% of following (1)-(3) with respect to a solvent and this cellulose acetate It is characterized by containing an organic acid which satisfies the requirements. By using such dope, the cellulose acetate film with favorable expression of Rth can be obtained. Hereinafter, each component contained in dope and dope used for the film of this invention is demonstrated.

(Cellulose acetate)

The cellulose acetate used for this invention will not be specifically determined if the substitution degree of all the acyl groups is 2.0-2.7. If it is 2.0 or more, compatibility with water is high enough, and the film obtained does not whiten well. As a cellulose which is a raw material of cellulose acetate, there are cotton linter, wood pulp (softwood pulp, softwood pulp), and the like, and cellulose acetate obtained from any raw material cellulose may be used, and may be mixed and used if necessary. For detailed descriptions of these raw celluloses, see, for example, Maruzawa, Utaze, "Plastic Material Course (17) Fibrin-Based Resin," Nikkan Kogyo Shimbun (Issued in 1970), and the Society for Invented Publications Publication No. 2001-1745. The cellulose described in (pages 7 to 8) can be used.

First, the cellulose acetate used preferably for this invention is described in detail. The glucose unit which binds (beta) -1,4 which comprises a cellulose has free hydroxyl groups in 2, 3, and 6 positions. Cellulose acetate is a polymer (polymer) in which some or all of these hydroxyl groups are esterified by acyl groups having 2 or more carbon atoms. Acyl substitution degree means the ratio (100% esterification is substitution degree 1) in which the hydroxyl group of the cellulose located in 2nd, 3rd, and 6th positions is esterified.

As for all acyl substitution degree, ie, DS2 + DS3 + DS6, 2.1-2.55 are preferable, More preferably, it is 2.2-2.55, Especially preferably, it is 2.35-2.50, Especially preferably, it is 2.40-2.50. In addition, the DS6 / (DS2 + DS3 + DS6) is preferably 0.08 to 0.66, more preferably 0.15 to 0.60, still more preferably 0.20 to 0.45. Here, DS2 is the substitution degree by the acyl group of the hydroxyl group of 2-position of a glucose unit (henceforth "acyl substitution degree of 2-position"), and DS3 is the substitution degree by the implementation of the hydroxyl group of 3-position (hereinafter, " 3 position is acyl substitution degree ", DS6 is a substitution degree by the acyl group of the hydroxyl group of 6-position (henceforth" acyl substitution degree of 6-position "). In addition, DS6 / (DS2 + DS3 + DS6) is a ratio of the 6-position acyl substitution degree with respect to all acyl substitution degree, and is also called "the 6-position acyl substitution rate."

The acyl group of the cellulose acetate used for the said dope is an acetyl group.

In the acylation of cellulose, when an acid anhydride or an acid chloride is used as an acylating agent, as an organic solvent which is a reaction solvent, an organic acid, for example, acetic acid, methylene chloride, etc. are used.

As the catalyst, when the acylating agent is an acid anhydride, a protic catalyst such as sulfuric acid is preferably used, and when the acylating agent is an acid chloride (for example, CH ₃ CH ₂ COCl), a basic compound is used.

The most common method for industrial synthesis of mixed fatty acid esters of cellulose is a method of acylating cellulose with a mixed organic acid component containing fatty acids (acetic acid, propionic acid, valeric acid, etc.) corresponding to acetyl groups or their acid anhydrides.

The cellulose acetate used for this invention can be synthesize | combined, for example by the method of Unexamined-Japanese-Patent No. 10-45804.

In the dope used for this invention, it is preferable to adjust the quantity of cellulose acetate in 10-40 mass% in the dope obtained. The amount of cellulose acetate is more preferably 10 to 30% by mass.

(menstruum)

As a solvent used for this invention, if it is a solvent used for solution casting, a well-known thing can be employ | adopted, From a viewpoint of lowering haze more, Ether of 3-12 carbon atoms, Ketone of 3-12 carbon atoms, Carbon atom It is preferred to contain a solvent selected from esters having 3 to 12 carbon atoms and halogenated hydrocarbons having 1 to 6 carbon atoms. Ethers, ketones and esters may have a cyclic structure. Compounds having two or more of functional groups of ethers, ketones and esters (ie, -O-, -CO- and -COO-) can also be used as the solvent. The solvent may have other functional groups, such as an alcoholic hydroxyl group. In the case of the solvent which has two or more types of functional groups, the carbon atom number should just be in the prescribed range of the compound which has any functional group.

Examples of ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phentol This includes.

Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone.

Examples of esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate.

Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.

The number of carbon atoms of the halogenated hydrocarbon is preferably 1 or 2, most preferably 1. The halogen of the halogenated hydrocarbon is preferably chlorine. It is preferable that the ratio in which the hydrogen atom of a halogenated hydrocarbon is substituted by halogen is 25-75 mol%, It is more preferable that it is 30-70 mol%, It is further more preferable that it is 35-65 mol%, It is 40-60 mol% Most preferred. Examples of halogenated hydrocarbons include dichloromethane (hereinafter also referred to as methichlor), chloroform, methyl chloride, carbon tetrachloride, trichloracetic acid, methyl bromide, methyl iodide, tri (tetra) chloroethylene, and the like. It is preferable to contain.

In this invention, it is preferable to further contain a poor solvent in the ratio of 3-40 weight%, and it is more preferable to contain in the ratio of 5-20 weight%. By containing the said poor solvent within the said range, compatibility with cellulose acetate improves and haze tends to fall further, and it is preferable.

Moreover, it is preferable that it is 120 degrees C or less, and, as for the boiling point of a poor solvent, it is more preferable that it is 40-100 degreeC. By setting a boiling point to 120 degrees C or less, the drying speed of a solvent can be made faster and it is preferable.

As such a poor solvent, alcohol (methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-pentanol, n-hexanol) and water are mentioned as a preferable example. Especially, in the manufacturing method of this invention, it is more preferable to use a primary alcohol (methanol, ethanol, n-propanol, n-butanol, n-pentanol, n-hexanol), and ethanol has peelability and a drying rate. Most preferable from the standpoint of compatibility.

In the said dope, 15 mass% or more of the said solvent is an alcohol (preferably primary alcohol), and the average carbon number of the said alcohol is 1.5-4 in the said dope, It is characterized by the above-mentioned.

Here, the primary alcohol having 2 or more carbon atoms includes ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-pentanol, n-hexanol and the like, among which ethanol, n-propanol, Isopropanol, n-butanol, and isobutanol are mentioned as a preferable example. In addition, although the primary alcohol here may contain glycols etc. which are C3 or more polyhydric alcohols, Ethylene glycol which is a C2 glycol is not a primary alcohol naturally.

Moreover, as long as the alcohol average carbon number contained in dope is 1.5-4, you may mix and use 2 or more types of said alcohols. In addition, as long as the average carbon number is 1.5-4, you may naturally use methanol or C5 or more alcohol. Specifically, the solvent which mixed ethanol which is C2 alcohol, C1 methanol, and ethanol / methanol = 1/1 (mass ratio) or more can be used.

It is preferable that the average carbon number of the alcohol contained 15 mass% or more as a solvent in the said dope is 1.5-4, It is more preferable that it is 1.5-2.5, It is especially preferable that it is 1.5-2.

Moreover, as for content of the alcohol contained as a solvent in the said dope, it is preferable that it is 18-40 mass% of the said solvent from a viewpoint of improving peelability, and it is especially preferable that it is 20-30 mass%.

Moreover, it is preferable that the total content of the said C2 or more alcohol with respect to the total mass of the said solvent is 10-40 mass%.

Moreover, it is preferable from a viewpoint of further improving peelability that the total content of the said C2 or more alcohol is 10 mass% or more with respect to the total mass of the said solvent, It is more preferable that it is 10-40 mass%, It is 15-40 weight It is especially preferable to contain in the ratio of%, and it is especially preferable to contain in the ratio of 20-30 weight%. By containing the said C2 or more alcohol within the said range, compatibility with a cellulose acetate improves and it exists in the tendency for a haze to fall further, and it is preferable.

Moreover, it is preferable that it is 120 degrees C or less, and, as for the boiling point of the said C2 or more alcohol, it is more preferable that it is 40-100 degreeC. By setting a boiling point to 120 degrees C or less, the drying speed of a solvent can be made faster and it is preferable.

<Peeling accelerator>

(Organic acid that satisfies the requirements of (1) to (3))

The film of this invention contains 0.01 mass%-20 mass% of organic acids which satisfy | fill the requirements of following (1)-(3) with respect to the resin, It is characterized by the above-mentioned.

(1) It contains the structure which the polyhydric alcohol and polyhydric carboxylic acid couple | bonded and formed the ester bond.

(2) The sum total of the number of molecules of the polyhydric alcohol and polyhydric carboxylic acid which forms the compound is three or more.

(3) It has at least 1 unsubstituted carboxyl group derived from polyhydric carboxylic acid.

In the organic acid that satisfies the requirements of (1) to (3) above, the peelability from the solution film production facility (metal support when dope is cast) can be improved by an unsubstituted carboxyl group. Organic acids that satisfy the requirements of (1) to (3) can be used as the peeling accelerator.

In addition, the unsubstituted carboxyl group is attached to the metal surface of the support, and the polyhydric alcohol moiety or the hydrophobic group moiety substituted therewith blocks the metal surface of the support from an oxidizing agent such as oxygen, whereby the polyhydric alcohol moiety or the hydrophobic group moiety substituted therewith Compared with the organic acid which does not contain, it is possible to prevent the corrosion of the metal.

Hereinafter, the organic acid which satisfy | fills the requirements of said (1)-(3) which can be used as a peeling accelerator for the film of this invention, and the other peeling promoter which may be used together elsewhere are demonstrated.

Although it does not specifically limit as polyhydric carboxylic acid used for the organic acid which satisfy | fills the requirements of said (1)-(3), For example, succinic acid, citric acid, tartaric acid, diacetyl tartaric acid, malic acid, adipic acid is preferable. .

It is preferable that the number of molecules of polyhydric carboxylic acid is 1-20, It is more preferable that it is 1-15, and it is especially preferable that it is 1-10 in the organic acid which satisfy | fills the requirements of said (1)-(3).

Moreover, as a polyhydric alcohol used for the organic acid which satisfy | fills the requirements of said (1)-(3), it is adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2- Propanediol, 1,3-butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol , Mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol, glycerin and the like. Especially, glycerin is preferable.

It is preferable that the number of molecules of a polyhydric alcohol is 1-20, It is more preferable that it is 1-15, and it is especially preferable that it is 1-10 in the organic acid which satisfy | fills the requirements of said (1)-(3).

As for the organic acid which satisfy | fills the requirements of said (1)-(3), in addition to the polyhydric alcohol and polyhydric carboxylic acid which comprise this organic acid, the monovalent acid which has a C4 or more substituent is the hydride of a part of the polyhydric alcohol further. You may have a structure which formed the ester bond with the hydroxyl group. Specific examples of the monovalent acid having the substituent having 4 or more carbon atoms are given below. In addition, the substituent in the monovalent acid which has a C4 or more substituent means R when the monovalent acid which has a C4 or more substituent is represented by RCOOH.

"fatty acid"

Caproic acid, heptyl acid, caprylic acid, pelagonic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, ricinonoic acid, undecanoic acid.

<< alkyl sulfuric acid >>

Myristyl sulfuric acid, cetyl sulfuric acid, oleyl sulfuric acid.

<< alkylbenzene sulfonic acid >>

Dodecylbenzenesulfonic acid, pentadecylbenzenesulfonic acid.

<< alkyl naphthalene sulfonic acid >>

Cesky butyl naphthalene sulfonic acid, diisobutyl naphthalene sulfonic acid.

Among these, monovalent acids having 4 or more substituents, which are fatty acids, are preferred, caprylic acid, lauric acid, stearic acid and oleic acid are more preferred, and oleic acid is particularly preferred.

In the organic acid which satisfy | fills the requirements of said (1)-(3), it is preferable that the number of molecules of the monovalent acid which has a C4 or more substituent is 0-4, It is more preferable that it is 0-3, It is 0-2 Is particularly preferred.

As for the organic acid which satisfy | fills the requirements of said (1)-(3), the sum total of the number of molecules of the polyhydric alcohol and polyhydric carboxylic acid which forms the compound is 3 or more, It is preferable that it is 3-30, It is 3-20 More preferred.

There is no restriction | limiting in particular in the ratio of the monovalent acid which has a polyhydric carboxylic acid, a polyhydric alcohol, and a C4 or more substituent among the organic acids which satisfy | fill the requirements of said (1)-(3), Two or more unsubstituted hydroxides in an organic acid The actual group may remain and an unsubstituted hydroxyl group may remain.

It is preferable that the organic acid which satisfy | fills the requirements of said (1)-(3) has at least 1 unsubstituted carboxyl group derived from polyhydric carboxylic acid, has 1-40 unsubstituted carboxyl group derived from polyhydric carboxylic acid, and it is 1- It is more preferable to have 30.

The organic acid which satisfy | fills the requirements of said (1)-(3) may be used independently, and may be used as a some mixture. In addition, the organic acid which satisfy | fills the requirements of said (1)-(3) may be ionized as needed, and may form salt with arbitrary metal ions etc. as needed.

The preferable compound example of the organic acid which satisfy | fills the requirements of said (1)-(3) used for this invention below is shown.

The organic acid (partial condensate of organic acid) which consists of the following compositions is preferable.

The addition amount of the organic acid which satisfy | fills the requirements of said (1)-(3) contained in the film of this invention is the ratio of 0.01-20 mass% with respect to the said resin, and it is especially preferable that it is 0.05-10 mass%. And it is still more preferable that it is 0.1 mass%-5 mass%. In addition, the addition amount of the organic acid which satisfy | fills the requirements of said (1)-(3) is the requirement of all said (1)-(3) when the organic acid which satisfy | fills the requirements of said (1)-(3) is a mixture. It means the total amount of the organic acid satisfying.

A polarizer durability improvement effect and peelability improvement effect become enough that addition amount is 0.001% or more. Moreover, if it is the addition amount of 20 mass% or less, organic acid does not bleed out well in the passage of high temperature, high humidity time, and the orthogonal transmittance of a polarizing plate does not rise easily, and it is preferable.

Moreover, even if it is an addition amount of 0.01% or less, peelability improvement can be anticipated also with the addition amount of about 0.001-0.01% by a combination with peelability improvement techniques, such as peeling site cooling of a flexible support body.

(additive)

In the film of this invention, in addition to the organic acid which is a peeling accelerator as an additive, Rth control agent (containing a non-phosphate ester type compound); inorganic fine particles (mat agent); plasticizers, such as a phthalate ester and a phosphate ester type compound; Re expression agent UV absorbers; Additives, such as antioxidant, can also be added.

(A) Rth control agent

In the manufacturing method of this invention, it is preferable to contain the retardation Rth control agent of the film thickness direction in the said dope from a viewpoint of controlling the expression property of Rth of a film to 80 nm or more.

As said Rth control agent, the Rth control agent which is a non-phosphate ester type compound can be used.

It is also preferable that the said high molecular weight additive is a compound of a phosphate ester type or a non-phosphate ester type compound from a viewpoint which can reduce haze.

It is preferable that the film of this invention contains the Rth control agent which is the said non-phosphate ester type compound. By containing such a non-phosphate ester type compound, the film of this invention shows the effect that it does not whiten well.

In addition, in this specification, a "non-phosphate ester type compound" means "a compound which has an ester bond, and whose acid which contributes to this ester bond is other than phosphoric acid." That is, a "non-phosphate ester compound" means a compound that does not contain phosphoric acid and is an ester system.

Moreover, a low molecular weight compound may be sufficient as the said non-phosphate ester type compound, and a polymer (high molecular weight compound) may be sufficient as it. Hereinafter, the non-phosphate ester type compound which is a polymer (polymer compound) is also called a non-phosphate ester type polymer.

As a Rth control agent which is the said non-phosphate ester type compound, well-known high molecular weight additives and low molecular weight additives can be employ | adopted widely as an additive of a cellulose acylate film.

The high molecular weight additive used as the Rth control agent which is the said non-phosphate ester type compound has a repeating unit in the compound, and it is preferable that number average molecular weights are 700-10000. The high molecular weight additive has a function of increasing the volatilization rate of the solvent and a function of reducing the amount of residual solvent in the solution casting method. Moreover, it shows a useful effect from a viewpoint of film modification, such as mechanical property improvement, flexibility provision, water absorption provision, and water transmittance reduction.

Moreover, in the Rth control agent which is the said high molecular weight additive, the high molecular weight additive of Unexamined-Japanese-Patent No. 2009-263619 can be used preferably.

Here, the number average molecular weight of the high molecular weight additive which is the said non-phosphate ester type compound becomes like this. More preferably, it is the number average molecular weight 700-8000, More preferably, it is the number average molecular weight 700-5000, Especially preferably, the number average molecular weight 1000 -5000.

Hereinafter, although the high molecular weight additive which is the said non-phosphate ester type compound is demonstrated in detail, giving the specific example, it cannot be overemphasized that the high molecular weight additive which is the said non-phosphate ester type compound is not limited to these things. .

As a polymeric additive which is a non-phosphate ester type compound, the polyester type polymer (aliphatic polyester type polymer, aromatic polyester type polymer etc.), the copolymer of a polyester type component and other components, etc. are mentioned, Polyester polymer, aromatic polyester polymer, copolymer of polyester polymer (aliphatic polyester polymer, aromatic polyester polymer, etc.) and acrylic polymer and polyester polymer (aliphatic polyester polymer, aromatic polyester) Copolymer of a styrene polymer) and a styrene polymer are preferable, and it is more preferable that it is a polyester compound containing an aromatic ring at least as one of a copolymerization component.

As said aliphatic polyester-type polymer, it is obtained by reaction with a C2-C20 aliphatic dicarboxylic acid, a C2-C12 aliphatic diol, and a C4-C20 alkyl ether diol selected from at least 1 type or more of diols. In addition, although both the terminals of a reactant may be a reactant, you may make monosolic acid, monoalcohols, or a phenol react, and seal what is called a terminal. This terminal sealing is especially effective from the point of preservation | storage etc., in order not to contain free carboxylic acid. The dicarboxylic acid used for the polyester polymer in the present invention is preferably an aliphatic dicarboxylic acid residue having 4 to 20 carbon atoms or an aromatic dicarboxylic acid residue having 8 to 20 carbon atoms.

Examples of the aliphatic dicarboxylic acid having 2 to 20 carbon atoms that are preferably used in the present invention include oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, pimeric acid, and suber. Acids, azelaic acid, sebacic acid, dodecanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid.

Among these, preferable aliphatic dicarboxylic acids are malonic acid, succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, and 1,4-cyclohexanedicarboxylic acid. Particularly preferably, the aliphatic dicarboxylic acid component is succinic acid, glutaric acid, adipic acid.

The diol used for the said high molecular weight additive is chosen from a C2-C20 aliphatic diol and a C4-C20 alkyletherdiol, for example.

Examples of the aliphatic diols having 2 to 20 carbon atoms include alkyldiols and alicyclic diols. For example, ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentylglycol), 2, 2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3 propanediol (3,3-dimethylolheptane), 3-methyl- 1,5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol , 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, and the like, and glycols thereof are used as one kind or a mixture of two or more kinds.

Preferred aliphatic diols include ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4- Butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, and particularly preferably ethane Diol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1, 4-cyclohexanediol and 1,4-cyclohexanedimethanol.

As a C4-C20 alkyl ether diol, Preferably, polytetramethylene ether glycol, polyethylene ether glycol, polypropylene ether glycol, and a combination thereof are mentioned. Although the average polymerization degree is not specifically limited, Preferably it is 2-20, More preferably, it is 2-10, Furthermore, it is 2-5, Especially preferably, it is 2-4. Examples of these typically available commercially available polyetherglycols include Carbowax resin, Pluronics resin and Niax resin.

In this invention, it is especially preferable that the terminal is a high molecular weight additive sealed by the alkyl group or the aromatic group. This is a factor which is effective against time-lapse deterioration in high temperature, high humidity by protecting a terminal by a hydrophobic functional group, and exhibits the role which delays the hydrolysis of an ester group.

It is preferable to protect with a monoalcohol residue or a monocarboxylic acid residue so that both ends of the said polyester additive may not become a carboxylic acid or an OH group.

In this case, as the monoalcohol, a substituted or unsubstituted monoalcohol having 1 to 30 carbon atoms is preferable, and methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, isopentanol, hexanol, isohexanol and cyclo Hexyl alcohol, octanol, isooctanol, 2-ethylhexyl alcohol, nonyl alcohol, isononyl alcohol, tert-nonyl alcohol, decanol, dodecanol, dodecahexanol, dodecaoctanol, allyl alcohol, oleyl alcohol, etc. And substituted alcohols such as aliphatic alcohols, benzyl alcohol, and 3-phenylpropanol.

Terminal sealing alcohols that may be preferably used are methanol, ethanol, propanol, isopropanol, butanol, isobutanol, isopentanol, hexanol, isohexanol, cyclohexyl alcohol, isooctanol, 2-ethylhexyl alcohol, isononyl alcohol And oleyl alcohol and benzyl alcohol, in particular methanol, ethanol, propanol, isobutanol, cyclohexyl alcohol, 2-ethylhexyl alcohol, isononyl alcohol and benzyl alcohol.

In the case of sealing with a monocarboxylic acid residue, the monocarboxylic acid used as the monocarboxylic acid residue is preferably a substituted or unsubstituted monocarboxylic acid having 1 to 30 carbon atoms. These may be aliphatic monocarboxylic acids or aromatic ring-containing carboxylic acids. When describing preferable aliphatic monocarboxylic acid, acetic acid, propionic acid, butanoic acid, caprylic acid, caproic acid, decanoic acid, dodecanoic acid, stearic acid, and oleic acid are mentioned, As an aromatic ring containing monocarboxylic acid, Examples include benzoic acid, p-tert-butylbenzoic acid, p-tert-amylbenzoic acid, orthotoluic acid, metatoluic acid, paratoluic acid, dimethylbenzoic acid, ethylbenzoic acid, normalpropylbenzoic acid, aminobenzoic acid, acetoxybenzoic acid, and the like. These can use 1 type (s) or 2 or more types, respectively.

Synthesis of such high molecular weight additives is carried out by thermal melting condensation by polyesterification or transesterification of the aliphatic dicarboxylic acid with diol and / or terminal carboxylic acid or monoalcohol by a conventional method. Or by any method of interfacial condensation of acid chlorides and glycols of these acids. About these polyester additives, there is a detailed description in Murai Koichi horseshoe "The additive and the theory and application" (the Saisho Shobo Co., Ltd., the first edition of March 1, 1983). Japanese Unexamined Patent Application Publication Nos. Hei 05-155809, Japanese Unexamined Patent Publication No. 05-155810, Japanese Unexamined Patent Application Publication No. 5-197073, Japanese Unexamined Patent Application Publication No. 2006-259494 and Japanese Unexamined Patent Application Publication No. 07-330670 The material described in each of Unexamined-Japanese-Patent No. 2006-342227, Unexamined-Japanese-Patent No. 2007-003679, etc. can also be used.

The aromatic polyester polymer is obtained by copolymerizing a monomer having an aromatic ring in the polyester polymer. As a monomer which has an aromatic ring, it is at least 1 sort (s) or more of monomers chosen from C8-C20 aromatic dicarboxylic acid and C6-C20 aromatic diol.

Examples of the aromatic dicarboxylic acid having 8 to 20 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,8-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and the like. Among these, preferred aromatic dicarboxylic acids are phthalic acid, terephthalic acid and isophthalic acid.

Although it does not specifically limit as C6-C20 aromatic diol, Bisphenol A, 1,2-hydroxybenzene, 1, 3-hydroxybenzene, 1, 4- hydroxybenzene, 1, 4- benzene dimethanol is mentioned. And bisphenol A, 1,4-hydroxybenzene, and 1,4-benzenedimethanol.

The aromatic polyester-based polymer is used by combining at least one of aromatic dicarboxylic acids or aromatic diols with the polyesters described above, but the combination is not particularly limited, and even if various kinds of components are combined, there is a problem. none. In the present invention, as described above, it is particularly preferable that the terminal is a high molecular weight additive sealed with an alkyl group or an aromatic group, and the method described above can be used for sealing.

As Rth control agents other than the said non-phosphate ester type compound, a compound other than a well-known ester type as an additive of a phosphate ester compound and a cellulose acylate film can be employ | adopted widely, for example.

As a high molecular weight Rth reducing agent, it is chosen from a phosphate type polymer, a styrene type polymer, an acryl type polymer, these copolymers, and the like, and an acrylic type polymer and a styrene type polymer are preferable. Moreover, it is preferable that at least one kind of polymer which has negative intrinsic birefringence, such as a styrene polymer and an acryl-type polymer, is contained.

As a low molecular weight Rth reducing agent which is a compound other than a non-phosphate ester type, the following is mentioned. These may be solid or an oily substance may be sufficient as them. That is, it is not specifically limited in the melting point or boiling point. For example, it is mixing of 20 degrees C or less and 20 degrees C or more ultraviolet absorbing material, similarly mixing deterioration inhibitor, etc. Moreover, as an infrared absorbing dye, it is described, for example in Unexamined-Japanese-Patent No. 2001-194522. Moreover, although the addition time may be added in any in a cellulose acetate solution (dope) manufacturing process, you may add and implement the process of adding and preparing an additive to the last preparation process of a dope preparation process. In addition, the addition amount of each raw material is not specifically limited as long as a function expresses.

Although it does not specifically limit as a low molecular weight Rth reducing agent which is a compound other than a non-phosphate ester type, The detail is described in Unexamined-Japanese-Patent No. 2007-272177.

The compound described as general formula (1) in Unexamined-Japanese-Patent No. 2007-272177 can be manufactured with the following method.

The compound of the general formula (1) can be obtained by condensation reaction of a sulfonyl chloride derivative and an amine derivative.

The compound of Unexamined-Japanese-Patent No. 2007-272177 General formula (2) is a dehydration condensation reaction of carboxylic acids and amines using a condensing agent (for example, dicyclohexylcarbodiimide (DCC), etc.) or car It can obtain by substitution reaction of an acid chloride derivative and an amine derivative, and the like.

As an Rth reducing agent, an acrylic polymer and a styrene polymer, the low molecular compound of Unexamined-Japanese-Patent No. 2007-272177 General formula (3)-(7), etc. are mentioned, Especially, an acryl-type polymer and a styrene-type polymer are preferable, Acrylic polymers are more preferred.

It is preferable to add the said Rth control agent in the ratio of 0.01-30 mass% with respect to cellulose acetate.

By making the said addition amount 30 mass% or less, compatibility with a cellulose resin can be improved and whitening can be suppressed. When using two or more types of said Rth control agents, it is preferable that the total amount exists in the said range.

From the viewpoint of further reducing the haze of the resulting film, the Rth control agent is more preferably added at a ratio of 10 to 30 mass%, and particularly preferably at a ratio of 15 to 30 mass%, relative to cellulose acetate. Do.

(B) inorganic fine particles

It is preferable that the film of this invention contains an inorganic fine particle in at least one outermost layer.

It is preferable to add an inorganic fine particle (mat agent) to the film of this invention. Examples of the inorganic fine particles used in the present invention include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, calcium silicate hydrate, aluminum silicate, magnesium silicate and phosphoric acid. Calcium is mentioned. Inorganic fine particles are preferable in that silicon contains turbidity, and silicon dioxide is particularly preferable. The fine particles of silicon dioxide preferably have a primary average particle diameter of 20 nm or less and an apparent specific gravity of 70 g / liter or more. It is more preferable that the average particle diameter of a primary particle is 5-30 nm from a viewpoint which can control the whole haze of a film in the range of this invention. The apparent specific gravity is preferably 10 to 100 g / liter or more, and more preferably 30 to 80 g / liter or more.

When the film of this invention is a laminated structure of two layers, the said inorganic fine particle is contained in at least one outermost layer. Moreover, when the film of this invention is a laminated structure of three or more layers, it is preferable that the said inorganic fine particle is contained in both of the said surface layers.

These microparticles | fine-particles usually form the secondary particle which is 0.1-3.0 micrometers in average particle diameter, and these microparticles | fine-particles exist as aggregate of a primary particle in a film, and form unevenness | corrugation of 0.1-3.0 micrometers in a film surface. The secondary average particle diameter is preferably 0.2 µm to 1.5 µm, more preferably 0.4 µm to 1.2 µm, and most preferably 0.6 µm to 1.1 µm. Primary and secondary particle diameters were made into the particle size by observing the particle | grains in a film with the scanning electron microscope, and having the diameter of the circle circumscribed to particle | grains. In addition, 200 particles were observed at different locations, and the average value was used as the average particle diameter.

As microparticles | fine-particles of silicon dioxide, commercial items, such as aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above Nippon Aerosil Co., Ltd. make) are used, for example. Can be. The fine particles of zirconium oxide are commercially available under the trade names of Aerosil R976 and R811 (above Nippon Aerosil Co., Ltd.) and can be used, for example.

Among them, aerosil R972 is particularly preferable from the viewpoint of cohesiveness in preparing the inorganic fine particle dispersion solution.

In this invention, in order to obtain the film which has a particle | grain with small secondary average particle diameter, some methods can be considered when preparing the dispersion liquid of microparticles | fine-particles. For example, there is a method in which a fine particle dispersion obtained by stirring and mixing a solvent and fine particles is prepared in advance, and the fine particle dispersion is added to a small amount of separately prepared cellulose acetate solution, stirred and dissolved, and further mixed with a main cellulose acetate dope solution. . This method is a preferable preparation method in that the dispersibility of the silicon dioxide fine particles is good and the silicon dioxide fine particles are not reaggregated better. In addition, a small amount of cellulose ester is added to the solvent, followed by stirring to dissolve it, and then fine particles are added thereto to be dispersed with a disperser, which is used as a fine particle addition liquid, and the fine particle addition liquid is sufficiently mixed with the dope liquid with an in-line mixer. There is also a way. Although this invention is not limited to these methods, 5-30 mass% is preferable, as for the density | concentration of silicon dioxide at the time of disperse | distributing silicon dioxide fine particles mixed with a solvent etc., 10-25 mass% is more preferable, 15-20 Mass% is the most preferable. The higher the dispersion concentration, the lower the liquid turbidity with respect to the added amount, and the haze and aggregates are positive, which is preferable.

As the lower alcohols, the solvent used is preferably methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like. Although it does not specifically limit as solvent other than lower alcohol, It is preferable to use the solvent used at the time of film production of a cellulose ester.

(C) plasticizer

As the plasticizer used in the present invention, many compounds known as plasticizers of cellulose acylate can also be usefully used. As a plasticizer, a phosphate ester type compound or carboxylic acid ester is used. Examples of the phosphate ester compound include triphenylphosphate (TPP) and tricresylphosphate (TCP). Phthalic acid ester and citric acid ester are typical as carboxylic acid ester. Examples of phthalate esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethylhexyl phthalate (DEHP). . Examples of citric acid ester include O-acetyl citrate triethyl (OACTE) and O-acetyl citrate tributyl (OACTB). Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Phthalate ester plasticizers (DMP, DEP, DBP, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularly preferred.

(D) Re expression agent

Although the film of this invention may contain Re expression agent, even if it does not contain, although the retardation of a desired in-plane direction can be expressed, it may contain Re expression agent further. By employing a Re expression agent, high Re expressionability is obtained at a low draw ratio. Although it does not specifically determine as a kind of Re expression agent, The thing which consists of a rod-shaped or disk shaped compound, and the compound which shows Re expression property in the said non-phosphate ester type compound are mentioned. As the rod-shaped or disk-shaped compound, a compound having at least two aromatic rings can be preferably used as the Re expression agent.

You may use together 2 or more types of Re expression agents.

It is preferable that the Re expression agent has a maximum absorption in the wavelength region of 250 to 400 nm, and preferably does not have substantially the absorption in the visible region.

As the Re expression agent, for example, the compounds described in JP-A-2004-50516 and JP-A-2007-86748 can be used, but the present invention is not limited to these.

Examples of the discotic compound include, for example, a compound described in European Patent Application Publication No. 0911656A2, a triazine compound described in Japanese Patent Laid-Open No. 2003-344655, and Japanese Patent Laid-Open Nos. 2008-150592. The triphenylene compound described in the above may also be preferably used.

A discotic compound can be synthesize | combined by a well-known method, such as the method of Unexamined-Japanese-Patent No. 2003-344655, the method of Unexamined-Japanese-Patent No. 2005-134884, for example.

In addition to the disk-like compound described above, a rod-shaped compound having a linear molecular structure can also be preferably used. For example, the rod-like compound described in JP 2008-150592 A [0127] can be preferably used. .

In the ultraviolet absorption spectrum of a solution, you may use together 2 or more types of rod-like compounds whose maximum absorption wavelength ((lambda) max) is longer than 250 nm.

The rod-like compound can be synthesized with reference to the method described in the literature. According to the literature, Mol. Cryst. Liq. Cryst., Vol. 53, p. 229 (1979), p. 89, p. 93 (1982), p. 145, p. 111 (1987), p. 170, p. 43 (1989), J. Am. Chem.Soc., Vol. 113, p. 1349 (1991), p. 118, p. 5346 (1996), p. 92, p. 1582 (1970), J.Org.Chem., P. 40, p. 420 ( 1975), Tetrahedron, Vol. 48, No. 16, page 3437 (1992).

It is more preferable to add the said Re expression agent in the ratio of 0.2-10 mass% with respect to cellulose acetate, It is more preferable to add in the ratio of 0.5-5 mass%, It is added in the ratio of 1-4 mass% It is particularly preferable to.

Moreover, it is preferable to use the said Re expression agent together with the said Rth control agent suitably from a viewpoint which can manufacture Re cellulose R film with a low haze while controlling Re and Rth to a preferable range.

(Production of dope)

In the manufacturing method of this invention, the said dope can be prepared by a general method. A general method means processing at the temperature (normal temperature or high temperature) of 0 degreeC or more. Preparation of the solution can be carried out using a method and apparatus for preparing dope in a conventional solvent cast method. The dope can be prepared by stirring cellulose acetate and a solvent at normal temperature (0-40 degreeC). The high concentration solution may be stirred under pressurized and heated conditions. Specifically, the cellulose acetate and the solvent are placed in a pressurized container and sealed, and the mixture is stirred while heating to a temperature not lower than the boiling point at normal temperature of the solvent and the solvent does not boil under pressure. Heating temperature is 40 degreeC or more normally, Preferably it is 60-200 degreeC, More preferably, it is 80-110 degreeC.

Each component may be previously mixed in a bath and then put in a container (tank or the like). Moreover, you may inject into a container one by one. The container needs to be comprised so that stirring is possible. The vessel can be pressurized by injecting an inert gas such as nitrogen gas. Moreover, you may use the raise of the vapor pressure of a solvent by heating. Or after sealing a container, you may add each component under pressure.

When heating, it is preferable to heat from the exterior of a container. For example, a jacket type heating device can be used. Moreover, the whole container can also be heated by providing a plate heater in the exterior of a container, piping, and circulating a liquid.

It is preferable to form a stirring blade inside a container, and to stir using this. The stirring vane is preferably a length reaching the vicinity of the wall of the vessel. In order to update the liquid film of the wall of a container, it is preferable to form a deodorant blade at the end of a stirring blade.

Instruments may be provided with instruments such as a pressure gauge and a thermometer. It is preferable to dissolve each component in a solvent in a container. The prepared dope is preferably taken out of the container after cooling or taken out, and then cooled using a heat exchanger or the like.

The said dope can also be prepared by a cooling dissolution method. In the cooling dissolution method, cellulose acetate can be dissolved in a solvent that is difficult to dissolve by the usual dissolution method. Moreover, even if it is a solvent which can melt | dissolve cellulose acetate by a conventional dissolution method, there exists an effect that a uniform solution can be obtained quickly by a cooling dissolution method.

In the cooling dissolution method, the cellulose acetate is slowly added at first to the organic solvent at room temperature with stirring. It is preferable to adjust the amount of cellulose acetate so that it may contain 10-40 mass% in this mixture. The amount of cellulose acetate is more preferably 10 to 30% by mass.

Next, the mixture is cooled to -100 to -10 占 폚 (preferably -80 to -10 占 폚, more preferably -50 to -20 占 폚, most preferably -50 to -30 占 폚). Cooling can be performed, for example in a dry ice methanol bath (-75 degreeC) or the cooled diethylene glycol solution (-30--20 degreeC). With this cooling, the mixture of cellulose acetate and organic solvent is solidified.

The cooling rate is preferably 4 ° C / minute or more, more preferably 8 ° C / minute or more, and most preferably 12 ° C / minute or more. The faster the cooling rate is, the more preferable it is, but the theoretical upper limit is 10000 ° C / sec, the technical upper limit is 1000 ° C / sec, and 100 ° C / sec is the practical upper limit. The cooling rate is a value obtained by dividing the difference between the temperature at the start of cooling and the final cooling temperature by the time from the start of cooling until the final cooling temperature is reached.

Moreover, when this is heated to 0-200 degreeC (preferably 0-150 degreeC, More preferably, 0-120 degreeC, most preferably 0-50 degreeC), a cellulose acetate will melt | dissolve in an organic solvent. An elevated temperature may be left to stand only at room temperature and may be heated in a warm bath. It is preferable that a heating rate is 4 degree-C / min or more, It is more preferable that it is 8 degree-C / min or more, It is most preferable that it is 12 degree-C / min or more. The higher the heating rate is, the more preferable it is, but the theoretical upper limit is 10000 ° C / sec, the technical upper limit is 1000 ° C / sec, and 100 ° C / sec is the practical upper limit. The heating rate is a value obtained by dividing the difference between the temperature at the start of heating and the final heating temperature by the time from the start of heating until the final heating temperature is reached.

As described above, a uniform solution is obtained. Moreover, when melt | dissolution is inadequate, you may repeat operation of cooling and a heating. Whether the dissolution is sufficient can be judged only by visually observing the appearance of the solution.

In the cooling dissolution method, in order to avoid moisture mixing due to condensation at the time of cooling, it is preferable to use a sealed container. Moreover, in cooling heating operation, when it pressurizes at the time of cooling and depressurizes at the time of heating, a dissolution time can be shortened. In order to perform pressurization and pressure reduction, it is preferable to use a pressure-resistant container.

In addition, the 20 mass% solution which melt | dissolved cellulose acetate (total acetyl substitution degree: 60.9%, viscosity average degree of polymerization: 299) in methyl acetate by the cooling dissolution method showed the vicinity of 33 degreeC according to differential scanning calorimetry (DSC). There is a similar phase transition point between the sol state and the gel state, resulting in a uniform gel state below this temperature. Therefore, this solution needs to be stored at a temperature above the pseudo phase transition temperature, preferably at a temperature of about 10 ° C. plus the gel phase transition temperature. However, this pseudo phase transition temperature changes with total acetyl substitution degree of cellulose acetate, viscosity average polymerization degree, solution concentration, and the organic solvent to be used.

In this invention, Preferably, drying of a cellulose acetate is performed previously with a silo, and after that, it mixes with the said solvent and prepares dope. Moreover, More preferably, the additive added to dope is previously dried by a silo, and it mixes with the said solvent and cellulose acetate after that, and prepares dope.

<Film production process and peeling process>

According to the production method of the present invention, 0.01 to 20% by mass of the cellulose acetate having a total degree of substitution of 2.0 to 2.7, a solvent, and the cellulose acetate, on the metal support, satisfy the following requirements (1) to (3). And a step of forming a dope film by solution casting of the dope containing a satisfactory organic acid (hereinafter also referred to as a film production step), and a step of peeling the dope film from the support (hereinafter also referred to as a peeling step). do. That is, in this invention, a cellulose acetate film can be manufactured by the solvent casting method from the prepared dope.

Moreover, it is preferable that the manufacturing method of this invention is a strip | belt-shaped support body to which the said metal support body moves.

Moreover, in the manufacturing method of this invention, it is preferable to control the amount of residual solvent at the time of peeling off the said dope film | membrane to 100% or less, and in the area | region which peels off the said dope film | membrane of the said support body, with the dope film peeling side of the said support body. It is also preferable to contact the cooling surface whose surface temperature is 10 degrees C or less on the opposite surface.

EMBODIMENT OF THE INVENTION Hereinafter, the preferable aspect about the said film manufacturing process and the said peeling process in the manufacturing method of this invention is demonstrated.

The equipment used in the film production process in the method for producing the cellulose acetate film of the present invention having a low degree of acyl substitution is used by the same solution casting film production method and solution casting film production apparatus as those used for conventional cellulose triacetate film production. do. In the manufacturing method of this invention, the manufacturing apparatus of Unexamined-Japanese-Patent No. 2004-359379 can be used preferably, for example.

About the casting | flow_spread in the solvent-cast method and the drying method mentioned later, US patent 2336310, 2367603, 2492078, 2492977, 2492978, 2607704, 2739069, 2739070, and British patent 640731, the description of each of 736892, Japanese Patent Publication No. 45-4554, 49-5614, Japanese Unexamined Patent Publication No. 60-176834, 60-203430, 62-115035 have.

In addition, Japanese Unexamined Patent Publication No. 2000-301555, Japanese Unexamined Patent Publication No. 2000-301558, Japanese Unexamined Patent Publication No. Hei 7-032391, Japanese Unexamined Patent Publication No. 3-193316, Japanese Unexamined Patent Application Publication No. 5-086212, Japan Each of Unexamined-Japanese-Patent No. 62-037113, Unexamined-Japanese-Patent No. 2-276607, Unexamined-Japanese-Patent No. 55-014201, Unexamined-Japanese-Patent No. 2-111511, and Unexamined-Japanese-Patent No. 2-208650. The cellulose acylate film production technique described in the publication can be applied in the present invention.

Hereinafter, more specifically, a preferable aspect is demonstrated about the said film manufacturing process and the said peeling process.

It is preferable to store the dope (cellulose acetate solution) prepared from the dissolver (kiln) once in a storage kiln, and defoaming the bubble contained in the dope for final preparation.

In the manufacturing method of this invention, it is preferable that the prepared dope is solution cast on the moving strip | belt-shaped support body. The prepared dope is preferably sent from the dope outlet to a press die through a pressurized metering gear pump capable of quantitatively feeding the fluid at high precision according to the rotational speed, and is solution-flexible on the moving band-like support. .

The moving band support is not particularly limited, but is preferably a band or a belt, and more preferably an endless band or a belt. By using such an endless support body, dope can be moved endlessly. Moreover, although the said band-shaped support body may move in what aspect, it is especially preferable that it is an endless belt spanned between two or more rolls (drum).

The material of the strip-shaped support is not particularly limited except that it is made of metal, but more preferably made of SUS (for example, SUS 316).

It is preferable that the specific heat of the said band-shaped support body is 0.1-1.0 J / (m <3> * K).

It is preferable that the width | variety of the said strip | belt-shaped support body is 1-3 m, It is more preferable that it is 1.5-3 m, It is especially preferable that it is about 2 m. In addition, about 2 m here means the range of 2 m +/- 30 cm.

It is preferable that the length (so-called band length) of the said band-shaped support body is 80-100 m.

It is preferable that the surface roughness (Ra value) of the said band-shaped support body is 0.01 micrometer or less. Moreover, it is preferable to finish the surface of the said strip | belt-shaped support body in a mirror surface state. In addition, mirror surface finish means smoothing a band surface by repeating grinding | polishing. Moreover, it is more preferable that the said band surface is finished by what is called a superhard surface which has higher thickness precision in the width direction.

It is preferable that the thickness of the said strip | belt-shaped support body is 1.5-2 mm.

In the strip | belt-shaped peeling area | region, the said band-shaped support body is in contact with the cooling body on the surface opposite to the peeling side. There is no restriction | limiting in particular in a shape, The said cooling body may be a cooling plate or a cooling curved body, Especially, it is preferable that it is a cylindrical cooling body. Moreover, it is preferable that the said cooling body is a drive roll or a driven roll, and the said band-shaped support body is wound around any of these rolls. It is preferable that the diameter of the said roll is 2-3 m. Moreover, when there are a plurality of said rolls, it is preferable that at least one is a drive roll which can actively rotate the said strip | belt-shaped support body by a motor. In addition, the roll on which the said band-shaped support body is wound may be a drive roll, or the driven roll which turns together with a drive roll may be sufficient.

It is preferable that the moving speed of the said strip | belt-shaped support body driven by the said drive roll is 15-80 m / s.

In the manufacturing method of this invention, it is preferable that the said dope is peeled uniformly on the said metal support body (it is preferable that it is a strip-shaped support body), and then peeling off the said dope film from the said metal support body, controlling on specific conditions. In the manufacturing method of this invention, there is no restriction | limiting in particular about the area | region (henceforth a peeling point) which peels off the said dope, The amount of residual solvent at the time of peeling off the said dope film is controlled to 100% or less, and the said dope film is further controlled. In the area | region peeled off from a metal support body, it is preferable to contact the cooling body whose surface temperature is 10 degrees C or less on the surface opposite to the dope film peeling side of the said metal support body. Thus, after evaporating a solvent on the said metal support body (preferably a strip-shaped support body), peeling off a less dry dope film | membrane (also called a web) from this metal support body (preferably a strip-shaped support body) is peelable. It is preferable from a viewpoint of improving.

As a specific aspect, when the said strip | belt-shaped support body is an endless belt, it is preferable to make the point which traveled about 1 week as a peeling point.

As a method of controlling the amount of residual solvent at the time of peeling off the said dope film | membrane, for example, it is described in Unexamined-Japanese-Patent No. 5-17844, and after making said dope cast on the said band-shaped support body, Air drying for 2 seconds or more. Moreover, the method etc. which are 10 degreeC-40 degreeC are mentioned in the area | region which controls the residual solvent amount until the surface temperature of the said strip | belt-shaped support body reaches near peeling point.

In addition, the residual solvent amount can be represented by the following formula.

Residual Solvent Amount (mass%) = {(M-N) / N} × 100

Here, M is the mass at the arbitrary time of a web, N is the mass when the web which measured M was dried at 110 degreeC for 3 hours.

It is more preferable to control the amount of the residual solvent at the time of peeling off the said dope film, It is especially preferable to control to 45 mass% or less, It is especially preferable to control to less than 45 mass%. It is preferable to make the amount of the residual solvent at the time of peeling off the said dope film into 30 mass% or more from a viewpoint which expresses Rth of a film more.

In the manufacturing method of this invention, in the area | region which peels off the said dope film from a metal support body, it is preferable to contact the cooling body whose surface temperature is 10 degrees C or less on the surface opposite to the dope film peeling side of the said metal support body. It is preferable that the said cooling body also serves as the roll which can rotate the moving strip | belt-shaped support body. As a control method of the surface temperature of the said cooling body, For example, surface temperature resulting from cooling with a blind chiller using an antifreeze is 10 degrees C or less (The upper limit becomes like this. Preferably it is 5 degrees C or less, More preferably, it is 0 degrees C or less, Especially preferably, it is -5 degrees C or less). As for the surface temperature of the roll closest to the said peeling area | region, it is more preferable that it is -25 degreeC-5 degreeC, It is especially preferable that it is -25 degreeC-0 degreeC, It is especially preferable that it is -20 degreeC --5 degreeC.

By controlling the surface temperature of the cooling body in such a temperature range and controlling the amount of residual solvent in the dope in the above range, the dope can be gelated at the surface temperature of the band-like support during casting, and remarkably The peelability of the cellulose acetate web of low acyl substitution degree can be improved.

On the other hand, in the area | region which peels the said dope film from a metal support body, about surface temperature of the surface of the dope film peeling side of the said metal support body, although not necessarily 10 degrees C or less, it is preferable that it is 10 degrees C or less, and it is in a more preferable range. Also, it is the same as the preferable range of the surface temperature of the said cooling body.

It is preferable to control to 15%-25% of solid content concentration contained in flexible dope from a viewpoint of the film surface after drying, It is more preferable to control to 16%-23%, and to control to 17%-22% Particularly preferred.

The aspect of the band flexible apparatus used preferably for the manufacturing method of this invention is shown in FIG.

Fig. 1 shows an example of a cellulose acetate film continuous production machine using a single metal endless belt 101 having a super mirror surface processing having high thickness accuracy in the belt width direction. This film continuous production machine is made of, for example, the metal endless belt 101 made of stainless steel, its thickness is about 1.5 mm, the belt width is about 3 m, the belt speed is 2 to 100 m / min, and the product thickness is 10. It is preferable that it is micrometer or less. In addition, depending on the apparatus, it can also be applied to a thicker film or sheet. The endless belt 101 made of metal is spread over the driven roll 102 on the product conveying side and the driving roll 103 on the raw material resin supply side, and can be actively rotated by the driving roll 103.

In the film continuous manufacturing machine of the illustrated example, cellulose acetate dope is quantitatively supplied from the high-precision gear pump 104 to the upper surface of the belt on the driving roll 103 side, and extruded to the required width through the T die 105 exclusively designed. The three-stage heating is performed by the residual solvent amount control device 108 while the copper belt 101 is transferred to the driven roll side. Thereafter, it is conveyed to the drive roll 103 side while being supported on the lower surface of the belt 101 by rotating the endless belt 101 via the belt turning part on the follower roll 102 side, and the dope film is peeled off ( It peels from the endless belt 101 in 107, and winds around a winding part not shown through the take-up roll group 106 arrange | positioned from the endless belt 101 to the outer side of the drive roll 103. As shown in FIG. Here, the drive roll 103 is equipped with the cooling apparatus 109, and in the peeling area | region 107, the surface temperature of the drive roll 103, ie, a cooling body, is controlled to a specific range. Moreover, it is more preferable that the operation part of the belt meandering prevention device 110 is arrange | positioned at the driven roll 102 side.

<Drying process>

The drying method of the web dried on the said strip | belt-shaped support body and peeled is described. The web stripped at the peeling position just before the band-like support is rotated once is alternately passed through the roll group arranged in a zigzag manner, or is conveyed in a non-contact manner by holding both ends of the peeled web with a clip or the like. Conveyed by Drying is performed by the method of blowing a predetermined temperature on both surfaces of the web (film) in conveyance, the method of using heating means, such as a microwave. Since rapid drying may impair the planarity of the film to be formed, it is preferable to dry at a temperature such that the solvent does not foam at the initial stage of drying, and to perform drying at a high temperature after the drying proceeds. In the drying process after peeling from a support body, a film tries to shrink | contract in the longitudinal direction or the width direction by evaporation of a solvent. Shrinkage increases with drying at high temperatures. Drying while suppressing this shrinkage as much as possible is preferred in order to improve the planarity of the finished film. From this point, for example, as shown in Japanese Patent Laid-Open No. 62-46625, a method for carrying out the entire drying process or a part of the drying process while maintaining both ends of the width of the web with a clip or pin in the width direction. (Tenter system) is preferable. It is preferable that the drying temperature in the said drying process is 100-145 degreeC. Although drying temperature, drying air volume, and drying time differ according to the solvent used, what is necessary is just to select suitably according to the kind and combination of solvents used. The residual solvent may be evaporated by drying with hot air, whose temperature is changed in sequence.

<Stretching process>

It is preferable that the manufacturing method of this invention includes the process of extending | stretching the web (film) peeled from a metal support body at the temperature which satisfy | fills following formula (1) from a viewpoint of achieving both optical expression and suppression of film whitening. .

160-Numerical value when the residual solvent amount is expressed by mass% ≤ Stretching temperature (° C) ≤ 190-Numerical value when the residual solvent amount is expressed by mass% (1)

In addition, the residual solvent amount can be represented by the following formula.

Residual Solvent Amount (mass%) = {(M-N) / N} × 100

Here, M is the mass at the arbitrary time of a web, N is the mass when the web which measured M was dried at 110 degreeC for 3 hours. If the amount of residual solvent in the web is too large, the effect of stretching is not obtained. If the amount of the solvent is too small, the stretching may be remarkably difficult, resulting in breakage of the web. The more preferable range of the amount of residual solvent in a web is 10 mass%-50 mass%, Most preferably, 12 mass%-30 mass%. Moreover, when a draw ratio is too small, sufficient phase difference will not be obtained, and when too large, drawing may become difficult and breakage may arise.

In the present invention, the solution cast film can be stretched without heating at a high temperature as long as the amount of the residual solvent in a specific range is used. However, the process may be shorter when combined with drying and stretching. However, since the plasticizer volatilizes when the temperature of a web is too high, the range of room temperature (15 degreeC)-145 degreeC or less is preferable. Moreover, extending | stretching in the biaxial direction orthogonal to each other is an effective method in order to put the refractive index Nx, Ny, Nz of a film in the scope of the present invention. For example, when extending | stretching in a casting | flow_spread direction, when the shrinkage of the width direction is too large, the value of Nz will become large too much. In this case, it can improve by suppressing the width shrinkage of a film or extending | stretching also in the width direction. When extending | stretching in the width direction, distribution may arise in refractive index in width. Although this may be seen, for example, when using the tenter method, it is a phenomenon which arises by shrinkage | strength force generate | occur | produced in the film center part by extending | stretching in the width direction, and the edge part is being fixed, and is called what is called a boeing phenomenon. Also in this case, by extending | stretching to a casting | flow_spread direction, a bowing phenomenon can be suppressed and the distribution of the phase difference of width can be improved little. Moreover, the film thickness variation of the film obtained by extending | stretching in the biaxial direction orthogonal to each other can be reduced. When the film thickness fluctuation of an optical film is too big | large, it will become a nonuniformity of phase difference. It is preferable to make the film thickness variation of an optical film into the range of +/- 3%, and also +/- 1%. For the above purposes, the method of extending | stretching in the biaxial direction orthogonal to each other is effective, and it is preferable to make the draw ratio of the biaxial direction orthogonal to each other be 1.2 to 2.0 times, and 0.7 to 1.0 times, respectively. Here, extending | stretching 1.2-2.0 times with respect to one direction, and making another one orthogonal 0.7-1.0 times makes the space | interval of the clip and pin which support a film into the range of 0.7-1.0 times with respect to the space | interval before extending | stretching. It means.

Generally, when extending | stretching so that it may become 1.2 to 2.0 times the space | interval in the width direction using a biaxial stretching tenter, a decreasing force acts on the longitudinal direction which is the perpendicular direction.

Therefore, if the force continues to be stretched in only one direction, the width in the right-angle direction decreases, which means that the reduced amount is held down against the reduced amount without controlling the width. It means that is regulated in the range of 0.7-1.0 times with respect to before extending | stretching. At this time, the force which the film is trying to reduce by extending | stretching to the width direction acts in the longitudinal direction. The interval between the clips or pins in the longitudinal direction is prevented from applying more tension than necessary in the longitudinal direction. There is no restriction | limiting in particular in the method of extending a web. For example, a circumferential speed difference is applied to a plurality of rolls, and a longitudinal axial speed difference is used therebetween, both ends of the web are fixed with clips or pins, and the distance between the clips and pins is extended in the advancing direction. The method of extending | stretching to a longitudinal direction, the method of extending | stretching to a horizontal direction and extending | stretching to a horizontal direction similarly, or the method of extending | stretching to a horizontally-vertical direction by extending | stretching simultaneously longitudinally and horizontally, etc. are mentioned. Of course, you may use these methods in combination. Moreover, in the so-called tenter method, when the clip portion is driven by the linear drive method, smooth stretching can be performed, and the risk of breakage or the like can be reduced, which is preferable.

It is preferable that it is 1.2-2.0 times, and, as for the film elongation (it may be called draw ratio) in the said extending process, it is more preferable that it is 1.3-1.5 times.

By setting it as the extending | stretching temperature prescribed | regulated by the said Formula (1), even when extending | stretching the film containing a residual solvent, the rate of change of the dimensional degree at the time of passing the obtained film in a wet heat environment can be remarkably improved. Although not bound by any theory, in consideration of the influence of the residual solvent, the stretching temperature is corrected and extended by the above formula (1), and surprisingly, even when the film containing the residual solvent is drawn, the rate of change of the dimension is remarkably remarkable. Is improved.

As a method of extending | stretching in the direction orthogonal to a film conveyance direction, Unexamined-Japanese-Patent No. 62-115035, Unexamined-Japanese-Patent No. 4-152125, 4-284211, 4-298310, copper It is described in each publication, such as 11-48271. In the case of extending | stretching of a film conveyance direction (length direction), for example, when the speed of the conveyance roll of a film is adjusted and the winding speed of a film is made faster than the peeling speed of a film, a film is stretched. In the case of extending | stretching of the direction orthogonal to a film conveyance direction, it can convey, maintaining a width of a film with a tenter, and extending | stretching a film can also extend | stretch the width of a tenter gradually. After drying of the film, stretching using a stretching machine (preferably uniaxial stretching using a long stretching machine) is also possible.

When using an optical film as a protective film of a polarizer, it is necessary to arrange | position the transmission axis of a polarizer and the in-plane slow axis of an optical film in parallel, in order to suppress the light leakage when the polarizing plate is seen from the inclined direction. Since the transmission axis of the roll film-shaped polarizer manufactured continuously is parallel in the width direction of a roll film, in order to bond together the protective film which consists of said roll film-shaped polarizer and roll film optical film continuously, a roll The in-plane slow axis of the film-form protective film needs to be parallel to the width direction of a film. Therefore, it is preferable to extend | stretch a lot by the width direction. Moreover, although extending | stretching process may be performed in the middle of a film manufacturing process, and the raw material which wound and produced the film may be extended | stretched, In the manufacturing method of this invention, since extending | stretching is carried out in the state containing residual solvent, extending | stretching in the middle of a film manufacturing process It is desirable to.

<Heat Treatment Step>

It is preferable that the manufacturing method of the film of this invention forms a heat processing process after completion | finish of a drying process. The heat treatment in the heat treatment step may be carried out after the completion of the drying step, may be carried out immediately after the stretching / drying step, or may be separately formed only after winding once by the method described later after the drying step is completed. In this invention, it is preferable to form the said heat processing process again after cooling to room temperature-100 degrees C or less once after completion | finish of a drying process. This is because it is advantageous in that the film which is more excellent in thermal dimensional stability is obtained. For the same reason, it is preferable that the residual solvent amount is dried to less than 2% by mass, preferably less than 0.4% by mass, immediately before the heat treatment step.

Although it is not clear why the shrinkage of the film can be reduced by such a treatment, in the film subjected to the stretching by the stretching step, since the residual stress in the stretching direction is large, the residual stress is eliminated by heat treatment. The shrinkage force in the region below the heat treatment temperature is estimated to be reduced.

The heat treatment is performed by a method of blowing air at a predetermined temperature to the film being conveyed, or by using a heating means such as microwave.

It is preferable to perform heat processing at the temperature of 150-200 degreeC, and it is more preferable to carry out at the temperature of 160-180 degreeC. Moreover, it is preferable to perform heat processing for 1 to 20 minutes, and it is more preferable to carry out for 5 to 10 minutes.

If the heat treatment temperature is higher than 200 ° C. for a long time, the scattering amount of the plasticizer contained in the film increases, which may cause a problem.

Moreover, in the said heat processing process, a film is going to shrink | contract in the longitudinal direction or the width direction. It is preferable to heat-treat while suppressing this shrinkage as much as possible in order to improve the flatness of a finished film, and the method (tenter system) which carries out width maintaining both ends of a web with a clip or a pin in the width direction is preferable. . Moreover, it is preferable to extend | stretch by 0.9 time-1.5 time in the width direction and the conveyance direction of a film, respectively.

<Winding process>

Moreover, it is preferable that both ends of the web obtained are interposed with a clip, it conveys with a tenter, it dries, it conveys to the roll group of a drying apparatus, finishes drying, and winds up to a predetermined length with a winder. The combination of a tenter and the drying apparatus of a roll group can be changed according to the objective.

The winding machine generally used can be used for the winding machine which winds up the obtained film, and can be wound up by winding methods, such as the static tension method, the static torque method, the taper tension method, and the program tension control method with constant internal stress. Can be. In the optical film roll obtained as mentioned above, it is preferable that the slow-axis direction of a film is +/- 2 degree with respect to a winding direction (the longitudinal direction of a film), and also it is preferable that it is the range of +/- 1 degree. Or it is preferable that it is +/- 2 degree with respect to the direction orthogonal to the winding direction (width direction of a film), and it is preferable to exist in the range of +/- 1 degree further. It is preferable that especially the slow-axis direction of a film is within +/- 0.1 degree with respect to the winding direction (the longitudinal direction of a film). Or it is preferable that it is within +/- 0.1 degree with respect to the width direction of a film.

The film thickness may be adjusted by adjusting the solid content concentration contained in the dope, the slit gap in the die of the die, the extrusion pressure from the die, the speed of the metal support, and the like so as to have a desired thickness.

It is preferable to wind the length of the optical film obtained as mentioned above at 100-10000m per roll, More preferably, it is 500-7000m, More preferably, it is 1000-6000m. 0.5-5.0 m are preferable, as for the width | variety of an optical film, More preferably, it is 1.0-3.0 m, More preferably, it is 1.0-2.5 m. When winding up, it is preferable to give a knurling at least one end, 3 mm-50 mm are preferable, as for the width of a knurling, More preferably, 5 mm-30 mm, and 0.5-500 micrometers of height are preferable, More preferably, it is 1-200 micrometers. This may be one-side press or both-side press.

Generally, in the large-screen display apparatus, since the fall of the contrast of a diagonal direction and formation of color taste become remarkable, the film of this invention is suitable for using it especially for a large-screen liquid crystal display device. When using as an optical compensation film for big screen liquid crystal display devices, it is preferable to shape | mold it, for example to make film width 1470 mm or more. Moreover, not only the film of the aspect of the film piece cut | disconnected to the magnitude | size which can be attached to a liquid crystal display device as it is to the optical compensation film of this invention, but also the film of the aspect produced by the continuous production and wound up in roll shape by continuous production Included. The optical compensation film of the latter aspect is cut | disconnected and used for a desired size, when it is stored and conveyed in the state, when it is actually attached to a liquid crystal display device, or is bonded together with a polarizer etc. Moreover, after bonding together in the elongate state with the polarizer etc. which consist of a polyvinyl alcohol film etc. produced in the elongate shape similarly, it is cut | disconnected and used for a desired size when it is actually mounted in a liquid crystal display device. As an aspect of the optical compensation film wound up in roll shape, the aspect wound up to the roll shape whose roll length is 2500 m or more is mentioned.

In the solution casting film manufacturing method used for the functional protective film for electronic displays, in addition to a solution casting film manufacturing apparatus, a coating apparatus is added for surface processing to films, such as a servant layer, an antistatic layer, an anti-halation layer, a protective layer, etc. There are many cases.

[Cellulose acetate film]

(Retardation)

The film of this invention is manufactured by the manufacturing method of the cellulose acetate film of this invention, It is characterized by the retardation value Rth of the film thickness direction measured by the wavelength of 590nm being 80 nm or more. In addition, Rth preferably satisfies 80 nm ≤ Rth ≤ 300 nm, and more preferably 80 nm ≤ Rth ≤ 150 nm. By setting it as such Rth, VA phase difference film with less color shift can be manufactured.

It is preferable that the retardation value Re of the film surface direction measured by the wavelength of 590 nm of the film of this invention is 30-100 nm.

Re is preferably 35 nm ≤ Re ≤ 80 nm, more preferably 40 nm ≤ Re ≤ 60 nm.

In this specification, Re ((lambda)) and Rth ((lambda)) represent the in-plane retardation in the wavelength (lambda), and the retardation of the thickness direction, respectively. In this specification, when there is no description in particular, wavelength (lambda) shall be 590 nm. Re ((lambda)) is measured by injecting light of wavelength (lambda) nm in a film normal line direction in KOBRA 21ADH or WR (Oji Measurement Instruments Co., Ltd. product). In the selection of the measurement wavelength λ nm, the wavelength selection filter can be replaced by manual, or the measured value can be converted into a program or the like and measured.

When the film to be measured is represented by a refractive index ellipsoid of one axis or two axes, Rth (λ) is calculated by the following method.

Rth (λ) is the Re (λ) as the in-plane slow axis (determined by KOBRA 21ADH or WR) as the inclination axis (rotation axis) (when there is no ground axis, any direction in the film plane as the rotation axis 6 points are measured by injecting light having a wavelength of λ nm from the inclined direction at 10 degrees from the normal direction to 50 degrees on one side with respect to the film normal direction, and measuring all 6 points, and the assumption of the measured retardation value and the average refractive index. And KOBRA 21ADH or WR is calculated based on the input film thickness value.

In the above description, in the case of a film having a direction in which the retardation value becomes zero at any inclination angle from the normal axis direction as the rotation axis, the retardation value at the inclination angle greater than the inclination angle is denoted by the symbol. After changing to negative, KOBRA 21ADH or WR is calculated.

In addition, the slow axis is set as the inclination axis (rotation axis) (when there is no ground axis, any direction in the film plane is used as the rotation axis), and the retardation value is measured from any inclined two directions to determine the value and the average refractive index. Rth can also be calculated from the following formulas (A) and (B) based on the assumptions and the input film thickness values.

Formula (A) ：

[Equation 1]

The said Re ((theta)) shows the retardation value in the direction which inclined angle (theta) from a normal line direction.

Nx in Formula (A) represents the refractive index of the slow-axis direction in surface inside, ny represents the refractive index of the direction orthogonal to nx in surface, and nz represents the refractive index of the direction orthogonal to nx and ny. d is the film thickness.

Formula (B):

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

In the case where the film to be measured cannot be expressed by one or two refractive index ellipsoids, or a so-called optical axis-free film, Rth (λ) is calculated by the following method.

Rth (λ) is the Re (λ) at a 10-degree step from -50 to +50 degrees with respect to the film normal direction using the in-plane slow axis (judged by KOBRA 21ADH or WR) as the inclined axis (rotation axis). 11 points of light were measured by injecting light having a wavelength of λ nm from the inclined direction, and KOBRA 21ADH or WR was calculated based on the measured retardation value, the assumption value of the average refractive index, and the input film thickness value.

In the said measurement, the hypothesis of average refractive index can use the value of the catalog of a polymer handbook (JOHN WILEY & SONS, INC) and various optical films. If the value of the average refractive index is not already known, it can be measured with an Abbe refractometer. The value of the average refractive index of a main optical film is illustrated below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), and polystyrene (1.59). By inputting the assumption values and film thicknesses of these average refractive indices, KOBRA 21ADH or WR calculates nx, ny, and nz. Nz = (nx−nz) / (nx−ny) is further calculated by the calculated nx, ny, and nz.

(Film thickness)

Although the thickness of the film of this invention can be suitably determined according to the kind etc. of the polarizing plate to be used, Preferably it is 30-60 micrometers, More preferably, it is 35-55 micrometers. By making thickness of a film 60 micrometers or less, cost can be reduced and it is preferable.

(Haze)

It is preferable that haze is 1% or less, It is more preferable that it is 0.8% or less, It is especially preferable that it is less than 0.5%, and, as for the film of this invention, it is especially preferable that it is 0.3% or less.

(Polarizing plate)

The polarizing plate of the present invention comprises a polarizer and at least one cellulose acetate film of the present invention.

The cellulose acetate film of this invention is suitable for the protective film for polarizing plates. A polarizing plate is formed by bonding a protective film to at least one surface of a polarizer, and laminating | stacking. A polarizer can use what is known conventionally, For example, it extends | stretches by treating a hydrophilic polymer film like a polyvinyl alcohol film with a dichroic dye like iodine. Although bonding of a cellulose acetate film and a polarizer does not have limitation in particular, It can carry out by the adhesive agent which consists of aqueous solution of a water-soluble polymer. As this water-soluble polymer adhesive, the fully saponified polyvinyl alcohol aqueous solution is used preferably.

The cellulose acetate film of this invention is a protective film for polarizing plates / polarizer / protective film for polarizing plates / liquid crystal cell / composition of the cellulose acetate film / polarizer / polarizing plate protective film of this invention, or protective film for polarizing plates / polarizer / cellulose of this invention It can use preferably with the structure of the acetate film / liquid crystal cell / the protective film for polarizing plates / polarizer / polarizing plate of this invention. In particular, by bonding to liquid crystal cells such as TN type, VA type, and OCB type, the display device can be provided with excellent viewing angle and excellent visibility with little coloration. Moreover, the polarizing plate using the cellulose acetate film of this invention has little deterioration under high temperature, high humidity conditions, and can maintain the long-term stable performance.

The aspect of the polarizing plate of this invention is not only the polarizing plate of the aspect of the film piece cut | disconnected to the magnitude | size which can be attached to a liquid crystal display device, but also the aspect produced by the long picture by continuous production, and wound up in roll shape (for example, The polarizing plate of 2500 m or more of roll form and 3900 m or more of aspect) is also included. In order to use for a big screen liquid crystal display device, as above-mentioned, it is preferable that the width of a polarizing plate shall be 1470 mm or more.

There is no restriction | limiting in particular about the specific structure of the polarizing plate of this invention, A well-known structure can be employ | adopted, for example, the structure of FIG. 6 of Unexamined-Japanese-Patent No. 2008-262161 can be employ | adopted.

(Liquid crystal display device)

The liquid crystal display device of this invention is characterized by including the cellulose acetate film of this invention.

The film of this invention can be applied to the liquid crystal display device which has a polarizing plate of this invention.

The liquid crystal display device of the present invention is a liquid crystal display device having a liquid crystal cell and a pair of polarizing plates disposed on both sides of the liquid crystal cell, wherein at least one of the polarizing plates is the polarizing plate of the present invention, wherein the polarizer is an IPS, OCB or VA mode. It is preferable that it is a liquid crystal display device of.

There is no restriction | limiting in particular as a specific structure of the liquid crystal display device of this invention, A well-known structure can be employ | adopted. Moreover, the structure of FIG. 2 of Unexamined-Japanese-Patent No. 2008-262161 can also be employ | adopted suitably.

Example

An Example is given to the following and this invention is demonstrated to it further more concretely. The materials, usage amounts, ratios, treatment contents, treatment procedures, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific example shown below.

In this invention, it measured by the following measuring method.

(Peel aptitude)

In each Example and the comparative example, the fluctuation range of the peeling point at the time of peeling a casting film from a support body as a wet film (peeling before extending | stretching) was measured, and peeling aptitude was evaluated.

(Double-circle): It does not fluctuate by 0 mm of variation of peeling point (very light).

(Circle): The fluctuation | variation range of a peeling point exceeds 0 mm and fluctuates within 2 mm (light).

▲: The fluctuation range of the peeling point exceeds 2 mm and fluctuates within 5 mm (slightly heavy).

X: It fluctuates more than 5 mm and 10 mm or more of fluctuation range of a peeling point (heavy).

Xx: It fluctuates more than 10 mm of variation of a peeling point (it is very heavy).

According to the above evaluation, the peeling aptitude was evaluated and the result obtained is shown in following Table 6 and Table 7. In addition, about the comparative examples 1 and 3, peeling aptitude was not evaluated.

(Re, Rth)

Re and Rth were measured with the wavelength of 590 nm by KOBRA 21ADH (Oji Scientific Instruments Co., Ltd. product) by the said method. The results are shown in Tables 6 and 7 below.

(Haze)

The haze was measured according to JIS K-6714 with a haze meter (HGM-2DP, Suga Tester) at 25 ° C and 60% relative humidity at a film sample of 40 mm x 80 mm of the present invention. The results are shown in Tables 6 and 7 below.

(Corrosion evaluation of organic acid: SUS corrosion)

In each Example and the comparative example, 20 g of the prepared dope was weighed in the autoclave, and the test piece of SUS 316 of thickness 0.5cm cut | disconnected 2 cm in width x 3 cm in length was immersed in it. After closing the autoclave and passing 72 hours at 90 ° C., the autoclave was opened and the corrosion of the test piece of SUS 316 and the change in dope caused by this were observed and evaluated according to the following criteria.

(Double-circle): The smoothness of the test piece surface does not change, and an organic acid solution is colorless and transparent.

(Circle): Although the change of the smoothness of the test piece surface is small, the organic acid solution is colored yellow.

X: The test piece surface is rough, and the organic acid solution is dark brown.

According to the above evaluation, the corrosiveness of organic acid was evaluated, and the result obtained is shown in following Table 6 and Table 7.

[Examples 1-57 and Comparative Examples 1-8: film production of a cellulose acetate film]

(1) Preparation of cellulose acetate dope

The cellulose acetate of the acyl substitution degree of Table 6 and Table 7 was prepared. Sulfuric acid (7.7 parts by mass relative to 100 parts by mass of cellulose) was added as a catalyst, and carboxylic acid was added to carry out an acylation reaction at 40 ° C. Thereafter, the total substitution degree and the 6-position substitution degree were adjusted by adjusting the sulfuric acid catalyst amount, water content, and aging time. Aging temperature was performed at 40 degreeC. In addition, the low molecular weight component of this cellulose acetate was removed by washing with acetone.

(Cellulose acetate solution)

The cellulose acetate, dichloromethane, and alcohol shown in Tables 6 and 7 shown in Tables 6 and 7 below were added to the mixing tank, stirred to dissolve each component, and further heated at 90 ° C. for about 10 minutes, Filtration was carried out with a filter paper having an average pore diameter of 34 μm and a sintered metal filter having an average pore diameter of 10 μm. Inorganic microparticles | fine-particles, each additive of following Table 6 and Table 7 were further thrown in, and the following cellulose acetate solutions were prepared. In addition, the inorganic fine particles were put into a disperser to prepare, and each additive was stirred and dissolved while heating. The composition of the dope of Example 1 is shown below.

(Each additive)

Here, the addition amount of a Rth control agent and a Re expression agent (additive 2) is as showing in Table 6 and Table 7, and is represented by the mass% with respect to cellulose acetate. In Table 7, AA is

[Formula 1]

, AB is

[Formula 2]

AC is

[Formula 3]

Are shown respectively.

Moreover, about additive A, it is compound D-1 of Unexamined-Japanese-Patent No. 2009-222994. The structure of the said additive A is described below.

[Formula 4]

Additive A

The additives B to H are listed in Table 5 below. In Table 5, EG represents ethylene glycol, PG represents propylene glycol, BG represents butylene glycol, TPA represents terephthalic acid, PA represents phthalic acid, AA represents adipic acid, and SA represents succinic acid. .

In addition, the addition amount of the said additive is the mass% with respect to the thermoplastic resin contained in dope.

In Comparative Example 5, citric acid ethyl ester (40% monoester, 40% diester, triester 10%) was used as a peeling accelerator, and in Comparative Example 6, citric acid (manufactured by Tokyo Chemical) was shown in Table 6 or Table 7 below. The amount described was mixed and the dope for film manufacture was prepared. The final addition ratios of cellulose acetate, each solvent, and each additive were as described in Tables 6 and 7 below.

In addition, the thing which dried 2 hours at 120 degreeC using the silo made from Nara Machinery Co., Ltd. beforehand was used for the cellulose acetate and various additives which were used as a raw material of dope.

Moreover, solid content concentration contained in dope at this time was measured, and it shows in Table 6 and Table 7 below.

(2) Flexible film making, peeling

The dope mentioned above was flexible using the band softener of the structure shown in FIG. The band is made of SUS 316, the band width is about 2 m, the band is an endless belt, the band length is about 80 m, the surface roughness Ra value is 0.01 μm, and the thickness of the band is about 1.5 to 2 mm It was finished. The endless metal belt of the band flexible machine is wound around two rolls, the diameter of which is about 2.5 m, and the cooling apparatus is provided and attached to the roll by which the dope film | membrane is peeled out of the roll. The cooling apparatus became able to cool a roll using a blind chiller, and made the roll into a cooling body, and controlled the surface temperature to the surface temperature described as roll temperature in Table 6 and Table 7 below. Moreover, the moving speed of the endless metal belt was 40 m / s.

By the residual solvent amount control apparatus which can be suitably controlled in the range of the air supply temperature 80 degreeC-130 degreeC (exhaust temperature is 75 degreeC-120 degreeC) on a band, it shows in Table 6 and Table 7 in a peeling area | region. After drying to the amount of residual solvent, the dope film was peeled off from the band.

In addition, in Table 6 and Table 7, after "37-> after drying 0" of Example 56 peeled off at the time of 37% of solvent residual amount, it does not extend | stretch and dries a film at 120 degreeC for 30 minutes, without extending | stretching. It means to carry out extending | stretching about the film dried after that and it became a dry film. Example 57 was also performed with respect to the film that became a dry film in the same manner as in Example 56.

(3) stretching

The obtained web (film) was peeled off from the band, sandwiched in a clip, and the residual solvent amount relative to the mass of the entire film is shown in Tables 6 and 7 below, except that Examples 56 and 57 were further added to the residual solvent amount of 0%. In the state after fixed), it extended | stretched in the direction (horizontal direction) orthogonal to a film conveyance direction using a tenter by drawing ratio 1.3 times at the extending | stretching temperature of following Table 6 and Table 7 on the conditions of fixed edge uniaxial stretching.

The clip was then removed from the film and dried at 130 ° C. for 20 minutes. At this time, the flexible film thickness was adjusted so that the film thickness after extending | stretching might become the film thickness (unit: micrometer) of Table 6 and Table 7. In this way, the cellulose acetate film of each Example and the comparative example of the characteristic shown in Table 6 and Table 7 was manufactured, and the roll of 1280 mm in roll width and 2600 mm in roll length was made into the above conditions for the purpose of judging its aptitude. A minimum of 24 rolls were produced. The sample (width 1280 mm) of length 1m was cut out at 100m interval with respect to 1 roll in 24 rolls continuously manufactured, and each measurement was performed.

According to the present invention, it can be seen from Table 6 and Table 7 that when the solution is cast, peeling from the metal support is easy, the corrosiveness of the manufacturing equipment is good, and the cellulose acetate film with good Rth expression can be provided. .

On the other hand, the comparative examples 1 and 3 made the total acyl substitution degree of the cellulose acetate used lower than the range of this invention, and the obtained film was bad in peeling aptitude, and the optical characteristic and haze could not be measured. Comparative Examples 2 and 4 made the total acyl substitution degree of the used cellulose acetate higher than the range of the present invention, and the resulting film had a poor expression of Rth. Comparative Examples 5 and 6 are comparative examples using ethyl citrate and citric acid, respectively, which are organic acids that do not satisfy the requirements of (1) to (3) as peeling accelerators. Comparative Example 7 is a comparative example in which an organic acid that satisfies the requirements of (1) to (3) was added in excess of the upper limit of the amount defined in the present invention, and the resulting film had poor Rth expression. Comparative Example 8 is a comparative example in which no peeling accelerator such as an organic acid was added, and the peelability was poor.

101 metal endless belt
102 driven rolls
103 Drive Roll (Cooling Body)
104 gear pump
105 T die
106 snatch roll group
107 Peel off area
108 Residual Solvent Level Control
109 roll cooling unit
110 belt meandering device

Claims (10)

A dope containing cellulose acetate having a total substitution degree of 2.0 to 2.7, a solvent, and an organic acid satisfying the requirements of 0.01 to 20 mass% of the following (1) to (3) with respect to the cellulose acetate is formed on the metal support. Solution softening process,
And a step of peeling off the dope film from the metal support.
(1) It contains the structure which the polyhydric alcohol and polyhydric carboxylic acid couple | bonded and formed the ester bond, and the monovalent acid which has a C4 or more substituent includes the structure which formed ester bond with some hydroxyl groups of the polyhydric alcohol. .
(2) The sum total of the number of molecules of the polyhydric alcohol and polyhydric carboxylic acid which forms the compound is three or more.
(3) It has at least 1 unsubstituted carboxyl group derived from polyhydric carboxylic acid. The method of claim 1,
15 mass% or more of the said solvent is an alcohol whose average carbon number of the said alcohol is 1.5-4, The manufacturing method of the cellulose acetate film characterized by the above-mentioned. The method of claim 2,
Method for producing a cellulose acetate film, characterized in that it comprises ethanol as the alcohol. The method of claim 1,
The metal support is a band-like support to move,
In the area | region which peels off the said dope film | membrane of the said metal support body, the manufacturing method of the cellulose acetate film characterized by making a cooling body whose surface temperature is 10 degrees C or less contact with the surface opposite to the dope film peeling side of the said metal support body. The method of claim 1,
The retardation Rth control agent of a film thickness direction is contained in the said dope, The manufacturing method of the cellulose acetate film characterized by the above-mentioned. It is manufactured by the manufacturing method of the cellulose acetate film of any one of Claims 1-5,
The retardation value Rth of the film thickness direction measured by the wavelength of 590 nm is 80 nm or more, The cellulose acetate film characterized by the above-mentioned. The method of claim 6,
A cellulose acetate film, wherein haze is less than 0.5%. The method of claim 6,
The retardation value Re of the film in-plane direction measured at the wavelength of 590 nm is 30-100 nm, The cellulose acetate film characterized by the above-mentioned. A polarizing plate, comprising a polarizer and at least one cellulose acetate film according to claim 6. The cellulose acetate film of Claim 6 is included, The liquid crystal display device characterized by the above-mentioned.

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