WO2012111324A1

WO2012111324A1 - Stretched cellulose ester film, and method for producing same

Info

Publication number: WO2012111324A1
Application number: PCT/JP2012/000987
Authority: WO
Inventors: 真一郎鈴木; 光世長谷川
Original assignee: コニカミノルタオプト株式会社
Priority date: 2011-02-15
Filing date: 2012-02-15
Publication date: 2012-08-23
Also published as: JP2014079880A

Abstract

The objective of the present invention is to provide a stretched cellulose ester film wherein, at the time of large magnification stretching, "creases having grooves or ridges directed in the transfer direction" can be reduced, deviations of retardation (Ro) in various parts of the film in the in-plane direction are small even if the width is increased, and generation of folding creases at the film end can be reduced when the film is transferred at a high speed. On at least one side of a stretched cellulose ester film: the average value of the surface roughness (Ra) is in the range of 1.7 nm to 4.0 nm at the edge portion (H), which is 0.1 nm to 1.0 nm higher than the average value of the surface roughness (Ra) at the center portion (T); and the average value of the elastic modulus is in the range of 3.0 GPa to 8.0 GPa at the center portion (T), which is 0.1 GPa to 2.0 GPa higher than the average value of the elastic modulus at the edge portion (H).

Description

Stretched cellulose ester film and method for producing the same

The present invention relates to a stretched cellulose ester film and a production method thereof.

Recently, the demand for liquid crystal display devices (hereinafter also referred to as LCDs) is strong due to the widespread use of liquid crystal displays mounted on automobiles, large liquid crystal television displays, mobile phones, laptop computers, and the like. In such LCDs, various optical films such as a polarizing film and a retardation film are used.

Demand for LCDs has increased, and there is a demand for polarizing plates used to meet this demand for thinner, lighter and higher production. Furthermore, along with the increase in the screen size of LCDs, the optical film as a member is also required to be thinned and widened with high production, and studies to improve film properties centering on mechanical strength properties are also being promoted. Yes.

Cellulose ester films are commonly used as polarizing plate protective films, but when manufacturing such thin and wide films, in order to adjust the optical properties and flatness, and the film thickness and width of the resulting film. In general, the film is stretched at a high magnification by a tenter after film formation. (For example, refer to Patent Document 1.)

JP 2010-1383 A

However, when a cellulose ester film is stretched at a high magnification at a high temperature in order to make it wider and thinner, particularly when producing a film having a width exceeding 1.6 m, “wrinkles where the direction of grooves or peaks is the transport direction” There was a problem that occurred. In addition, there is a problem that disorder of cellulose orientation is likely to occur due to high-stretching, and the deviation of the retardation Ro in the in-plane direction, which is important for optical characteristics, increases in each part of the film. Furthermore, when the film is transported at a high speed, there is a problem that “folding wrinkles” occur at the end of the film and productivity is lowered.

Therefore, the object of the present invention is to suppress the “wrinkles in which the direction of the groove or the mountain is the conveying direction” when stretching at a high magnification in order to widen the width, and even if the width is widened, the retardation Ro in the in-plane direction is reduced. An object of the present invention is to provide a stretched cellulose ester film in which deviation at each part of the film is small and bending wrinkles at the end of the film when the film is conveyed at a high speed is suppressed, and a method for producing the stretched cellulose ester film.

The above object of the present invention is achieved by the following configurations.
[1] Let the width of the stretched cellulose ester film be L; the portion from the end of the stretched cellulose ester film to L × 0.05 in the width direction of the film is the end H; and the stretched cellulose ester film in the width direction of the film The average value of the surface roughness (Ra) of the end portion H of at least one surface of the stretched cellulose ester film is 1.7 nm when the portion from the center to ± L × 0.1 is the central portion T. In the range of ~ 4.0 nm, the average value of the surface roughness (Ra) of the central portion T is 0.1 nm to 1.0 nm higher, and the average elastic modulus of the central portion T is 3.0 GPa to 8. A stretched cellulose ester film that is 0.1 GPa to 2.0 GPa higher than the average value of the elastic modulus of the end H in the range of 0 GPa.
[2] The average surface roughness (Ra) of the end H on at least one surface of the stretched cellulose ester film is in the range of 2.2 nm to 3.5 nm, and the surface roughness (T Ra is 0.3 nm to 1.0 nm higher than the average value of Ra, and the average value of the elastic modulus of the central portion T is in the range of 4.0 GPa to 7.0 GPa. The stretched cellulose ester film according to [1], which is 0.3 GPa to 1.0 GPa higher.
[3] The stretched cellulose ester film according to [1] or [2], wherein the stretched cellulose ester film has a width of 2 to 3 m and a film thickness of 20 to 70 μm.
[4] The stretched cellulose ester film according to any one of [1] to [3], wherein the stretched cellulose ester film is a wound body wound in a direction perpendicular to the width direction of the film.

[5] A step of preparing a dope by dissolving cellulose ester in a solvent; a step of casting the dope on an endless metal support; and drying the cast dope and then peeling the dope from the metal support The stretched cellulose ester film according to any one of [1] to [4], comprising a step of obtaining an unstretched cellulose ester film and a step of stretching the unstretched cellulose ester film to obtain a stretched cellulose ester film. The width of the unstretched cellulose ester film is Lo; the portion from the end of the unstretched cellulose ester film to Lo × 0.05 in the width direction of the film is the end Ho; When the portion from the center of the unstretched cellulose ester film to ± Lo × 0.1 in the direction is the central portion To, the unstretched portion The surface temperature of the end portion Ho of the surface A opposite to the surface in contact with the metal support of the stretched cellulose ester film is 10 ° C. to 50 ° C. higher than the surface temperature of the central portion To of the surface A The manufacturing method of the extending | stretching cellulose-ester film which carries out extending | stretching process.
[6] At least a pair of end hot air generating portions for adjusting the surface temperature is disposed so as to face an end portion of the surface A of the unstretched cellulose ester film, and from the end hot air generating portion, Stretching the unstretched cellulose ester film while blowing hot air at a temperature 10 ° C. to 50 ° C. higher than the surface temperature of the central portion To of the surface A to the end portion Ho of the surface A of the unstretched cellulose ester film The method for producing a stretched cellulose ester film according to [5].
[7] The method for producing a stretched cellulose ester film according to [5] or [6], further comprising a winding step of winding the stretched cellulose ester film in a direction perpendicular to the width direction of the film.
[8] The stretched cellulose ester film according to any one of [5] to [7], wherein in the stretching treatment, the unstretched cellulose ester film is stretched at a stretch ratio of 25% to 100% in the width direction of the film. Manufacturing method.

According to the present invention, there is no occurrence of “wrinkles in which the direction of the groove or mountain is the conveying direction” when stretching at a high magnification in an attempt to widen the film, and the retardation Ro film in the in-plane direction even when widened It is possible to provide a stretched cellulose ester film in which deviation at each portion is small, and further, generation of folding wrinkles at the end of the film when the film is conveyed at a high speed and a method for producing the stretched cellulose ester film can be provided.

It is a schematic diagram of the stretched cellulose ester film of this invention. It is a schematic side block diagram of the manufacturing apparatus which manufactures the stretched cellulose-ester film of this invention. It is a schematic plane block diagram of a extending | stretching apparatus (tenter). It is the schematic diagram which showed the preferable extending | stretching processing method for this invention.

Hereinafter, modes for carrying out the present invention will be described in detail, but the present invention is not limited to these.

In the present invention, the cellulose ester film after the stretching treatment is referred to as “stretched cellulose ester film”, and the cellulose ester film before the stretching treatment is referred to as “unstretched cellulose ester film” or “web”.

The stretched cellulose ester film of the present invention contains a cellulose ester and fine particles, and further contains a plasticizer as necessary.

<Cellulose ester>
The cellulose ester used in the stretched cellulose ester film of the present invention preferably has an average degree of acetyl group substitution of the whole cellulose ester ≧ 1.9. Preferably, when the cellulose ester has a total acyl group substitution degree that satisfies the relationship of formulas (1) to (3) to be described later, it contributes to lowering the maximum stress during stretching, and the effects of the present invention are obtained. Can do. On the other hand, if it is less than 1.9, the cellulose ester becomes too soft and the surface becomes rough when the solvent or additive volatilizes, which is not preferable.

The measuring method of the substitution degree of the acyl group of the cellulose ester can be measured according to ASTM-D817-96.

The cellulose ester used in the present invention is not particularly limited as long as the acetyl group substitution degree is satisfied, but the cellulose ester is a carboxylic acid ester having about 2 to 22 carbon atoms, and may be an aromatic carboxylic acid ester. A lower fatty acid ester of cellulose is preferable. The lower fatty acid in the lower fatty acid ester of cellulose means a fatty acid having 6 or less carbon atoms. The acyl group bonded to the hydroxyl group may be linear or branched or may form a ring. Furthermore, another substituent may be substituted. In the case of the same degree of substitution, birefringence decreases when the number of carbon atoms is large. Therefore, the number of carbon atoms is preferably selected from acyl groups having 2 to 6 carbon atoms. The cellulose ester preferably has 2 to 4 carbon atoms, more preferably 2 to 3 carbon atoms.

The cellulose ester may be an acyl group derived from a mixed acid, and particularly preferably an acyl group having 2 and 3 carbon atoms, or 2 and 4 carbon atoms. In the present invention, as a cellulose ester, a mixed fatty acid ester of cellulose to which a propionate group or a butyrate group is bonded in addition to an acetyl group such as cellulose acetate propionate, cellulose acetate butyrate, or cellulose acetate propionate butyrate is used. Can do. The butyryl group forming butyrate may be linear or branched. As the cellulose ester preferably used in the present invention, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, and cellulose acetate phthalate are particularly preferably used.

Preferred cellulose esters for the present invention are those that simultaneously satisfy the following formulas (1) to (3).

Formula (1) 2.0 <= X + Y <= 3.0
Formula (2) 1.9 <= X <= 3.0
Formula (3) 0 ≦ Y ≦ 1.1
In the formula, X is the degree of substitution of the acetyl group, Y is the degree of substitution of the propionyl group or butyryl group, and X + Y is the degree of substitution of the total acyl group.

Of these, triacetyl cellulose and cellulose acetate propionate are particularly preferably used. In the case of cellulose acetate propionate, 1.9 ≦ X ≦ 2.5, and preferably 0.2 ≦ Y ≦ 1.0.

If the substitution degree of the acetyl group is too low, there will be many unreacted parts with respect to the hydroxyl groups of the pyranose ring constituting the skeleton of the cellulose resin, and a large amount of the hydroxyl groups will leave dimensional changes, warpage, and slits. The physical properties as a binder, such as defects, are likely to deteriorate.

The stretched cellulose ester film of the present invention preferably contains two or more cellulose esters having a weight average molecular weight (Mw) of Mw ≧ 260,000 and different Mw of 10,000 or more.

The smaller the molecular weight of the cellulose ester, the less the haze rises during the stretching process, but the peelability from the belt during casting tends to deteriorate, and by mixing two or more cellulose esters having different molecular weights, the peelability is improved. At the same time, the compatibility between the plasticizer and the cellulose ester, which will be described later, can also be improved, so that there is an effect of suppressing increase in haze and enhancing dimensional stability.

The weight average molecular weight (Mw) is preferably in the range of 260000-500000, more preferably in the range of 290000-400000. The difference in Mw between two or more cellulose esters is preferably 10,000 or more and 100,000 or less, and more preferably 20,000 or more and 50,000 or less.

The mixing ratio of the cellulose ester having a low molecular weight and the cellulose ester having a high molecular weight can be in the range of 99: 1 to 1:99, preferably 90:10 to 50:50, more preferably 90:10 to 60:40. Particularly preferred is the range of 85:15 to 60:40.

The weight average molecular weight (Mw) of the cellulose ester can be measured as follows.

Measured by high performance liquid chromatography under the following conditions.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (GL Science Co., Ltd.)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Co., Ltd.) Mw = 1000,000 to 500 calibration curves with 13 samples were used. The 13 samples are preferably used at approximately equal intervals.

The cellulose used as a raw material for the cellulose ester used in the present invention is not particularly limited, and wood pulp (coniferous pulp, hardwood pulp), cotton linter, and the like can be used. The Mw of the cellulose ester can be controlled by the type of cellulose and the use of a plurality of raw material celluloses. For example, if esterification is performed using pre-hydrolysis kraft pulp, the Mw of the cellulose ester increases, and if softwood sulfite pulp is used, the Mw tends to decrease. Therefore, cellulose may be used singly or in combination of two or more. For example, softwood pulp and cotton linter or hardwood pulp may be used in combination. As cellulose, usually pulp (particularly softwood pulp) is often used. The α-cellulose content (mass%) of cellulose is usually from 94 to 99 (eg, 95 to 99), preferably from about 96 to 98.5 (eg, 97.3 to 98). .

When the acylating agent of the cellulose raw material is an acid anhydride (acetic anhydride, propionic anhydride, butyric anhydride), the cellulose ester according to the present invention uses an organic solvent such as acetic acid or an organic solvent such as methylene chloride. The reaction is carried out using a protic catalyst such as sulfuric acid. When the acylating agent is acid chloride (CH ₃ COCl, C ₂ H ₅ COCl, C ₃ H ₇ COCl), the reaction is carried out using a basic compound such as an amine as a catalyst. Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

In addition, cellulose ester is also affected by trace metal components in cellulose ester. These are considered to be related to water used in the production process, but it is preferable that there are few components that can become insoluble nuclei, and metal ions such as iron, calcium, and magnesium contain organic acidic groups. Insoluble matter may be formed by salt formation with a polymer degradation product or the like that may be present, and it is preferable that the amount is small. The iron (Fe) component is preferably 10 ppm or less, and more preferably 8 ppm or less. As for the calcium (Ca) component, it is easy to form a coordination compound, that is, a complex with an acidic component such as carboxylic acid or sulfonic acid, and many ligands. Starch, turbidity).

The calcium (Ca) component is 60 ppm or less, preferably 0 to 30 ppm. The magnesium (Mg) component is preferably in the range of 0 to 70 ppm, and more preferably in the range of 0 to 20 ppm. Metal components such as iron (Fe) content, calcium (Ca) content, magnesium (Mg) content, etc. are pre-processed by completely digesting cellulose ester with micro digest wet cracking equipment (sulfuric acid decomposition) and alkali melting. After being performed, it can be analyzed using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometer).

(Plasticizer)
The stretched cellulose ester film of the present invention can contain an appropriate amount of a plasticizer as necessary to obtain the effects of the present invention. The plasticizer is not particularly limited, but is preferably a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a phthalate ester plasticizer, a fatty acid ester plasticizer, a polyhydric alcohol ester plasticizer, or a polyester plasticizer. Agent, acrylic plasticizer and the like. Of these, when two or more plasticizers are used, at least one plasticizer is preferably a polyhydric alcohol ester plasticizer.

The polyhydric alcohol ester is composed of an ester of a divalent or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule.

The polyhydric alcohol used is represented by the following general formula (1).

General formula (1) R1- (OH) n (wherein R1 represents an n-valent organic group, and n represents a positive integer of 2 or more)
Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these. Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, xylitol, pentaerythritol, dipentaerythritol and the like. Of these, trimethylolpropane and pentaerythritol are preferable.

There is no restriction | limiting in particular as monocarboxylic acid used for polyhydric alcohol ester, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferable in terms of improving moisture permeability and retention. Examples of preferred monocarboxylic acids include the following, but are not limited thereto.

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

Preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, tridecylic acid , Saturated fatty acids such as myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, melicic acid, laccelic acid, undecylenic acid, Examples thereof include unsaturated fatty acids such as oleic acid, sorbic acid, linoleic acid, linolenic acid and arachidonic acid. Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof. Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid, and tetralin carboxylic acid. The aromatic monocarboxylic acid which has, or those derivatives can be mentioned. In particular, benzoic acid is preferred.

The molecular weight of the polyhydric alcohol ester is preferably in the range of 300 to 1500, more preferably in the range of 350 to 750. A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose ester. The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are. The specific compound of a polyhydric alcohol ester is shown below.

In addition, trimethylolpropane triacetate, pentaerythritol tetraacetate, and the like are also preferably used.

The glycolate plasticizer is not particularly limited, but alkylphthalylalkyl glycolates can be preferably used. Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate, methyl phthalyl ethyl Glycolate, ethyl phthalyl methyl glycolate, ethyl phthalyl propyl glycolate, methyl phthalyl butyl glycolate, ethyl phthalyl butyl glycolate, butyl phthalyl methyl glycolate, butyl phthalyl ethyl glycolate, propyl phthalyl butyl glycol Butyl phthalyl propyl glycolate, methyl phthalyl octyl glycolate, ethyl phthalyl octyl glycolate, octyl phthalyl methyl glycolate, octyl phthalate Ethyl glycolate, and the like.

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

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

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

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

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

The polyvalent carboxylic acid is represented by the following general formula (2).

General formula (2) R2 (COOH) m (OH) n (where R2 is an (m + n) -valent organic group, m is a positive integer of 2 or more, n is an integer of 0 or more, COOH group is a carboxyl group, OH Group represents an alcoholic or phenolic hydroxyl group)
Examples of preferred polyvalent carboxylic acids include the following, but the present invention is not limited to these. Trivalent or higher aromatic polyvalent carboxylic acids such as trimellitic acid, trimesic acid, pyromellitic acid or derivatives thereof, succinic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid, fumaric acid, maleic acid, tetrahydrophthal An aliphatic polyvalent carboxylic acid such as an acid, an oxypolyvalent carboxylic acid such as tartaric acid, tartronic acid, malic acid and citric acid can be preferably used. In particular, it is preferable to use an oxypolycarboxylic acid from the viewpoint of improving retention.

The alcohol used in the polyvalent carboxylic acid ester compound that can be used in the present invention is not particularly limited, and known alcohols and phenols can be used. For example, an aliphatic saturated alcohol or aliphatic unsaturated alcohol having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. More preferably, it has 1 to 20 carbon atoms, and particularly preferably 1 to 10 carbon atoms. In addition, alicyclic alcohols such as cyclopentanol and cyclohexanol or derivatives thereof, aromatic alcohols such as benzyl alcohol and cinnamyl alcohol, or derivatives thereof can also be preferably used.

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

As the aliphatic monocarboxylic acid, a straight-chain or side-chain fatty acid having 1 to 32 carbon atoms can be preferably used. More preferably, it has 1 to 20 carbon atoms, and particularly preferably 1 to 10 carbon atoms.

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

Examples of preferable alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, and derivatives thereof.

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

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

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

The acid value of the polycarboxylic acid ester compound is preferably 1 mgKOH / g or less, more preferably 0.2 mgKOH / g or less. Setting the acid value in the above range is preferable because the environmental fluctuation of the retardation is also suppressed.

(Acid value)
The acid value means the number of milligrams of potassium hydroxide necessary for neutralizing the acid (carboxyl group present in the sample) contained in 1 g of the sample. The acid value is measured according to JIS K0070.

Examples of particularly preferred polyvalent carboxylic acid ester compounds are shown below, but the present invention is not limited thereto. For example, triethyl citrate, tributyl citrate, acetyl triethyl citrate (ATEC), acetyl tributyl citrate (ATBC), benzoyl tributyl citrate, acetyl triphenyl citrate, acetyl tribenzyl citrate, dibutyl tartrate, diacetyl dibutyl tartrate, Examples include tributyl trimellitic acid and tetrabutyl pyromellitic acid.

(Sugar ester compound)
The stretched cellulose ester film of the present invention contains a compound represented by the following general formula (3) (referred to as a sugar ester compound in the present invention) to prevent haze due to stretching and promote stable retardation development. Is preferable.

The average degree of substitution of the compound represented by the general formula (3) used in the present invention is 3.0 to 6.0, which is effective for suppressing a haze increase and developing a stable phase difference in the stretching treatment. It is. The average degree of substitution is more preferably in the range of 4.5 to 6.5.

In the present invention, the degree of substitution of the compound represented by the general formula (3) represents the number of substituents other than hydrogen among the eight hydroxyl groups contained in the general formula (3). Of R ₁ to R _{8 in} the general formula (3), this represents a number containing a group other than hydrogen. Therefore, when all of R ₁ to R ₈ are substituted with a substituent other than hydrogen, the degree of substitution is 8.0, the maximum value, and when all of R ₁ to R ₈ are hydrogen atoms, 0.0 It becomes.

In the compound having the structure represented by the general formula (3), it is difficult to synthesize a single kind of compound in which the number of hydroxyl groups and the number of OR groups are fixed. Since it is known that it becomes a compound in which several different components are mixed, it is appropriate to use the average substitution degree as the substitution degree of the general formula (3) in the present invention. The average substitution degree can be measured from the area ratio of the chart showing the substitution degree distribution.

In the general formula (3), R ₁ to R ₈ represent a substituted or unsubstituted alkylcarbonyl group or a substituted or unsubstituted allylcarbonyl group, and R ₁ to R ₈ may be the same or different. It may be.

Examples of the sugar as a raw material for synthesizing the sugar ester compound used in the present invention include the following, but the present invention is not limited to these.

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

Other examples include gentiobiose, gentiotriose, gentiotetraose, xylotriose, and galactosyl sucrose.

The monocarboxylic acid used in the synthesis of the sugar ester compound used in the present invention is not particularly limited, and known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid and the like can be used. . The carboxylic acid used may be one type or a mixture of two or more types.

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

Examples of preferred aromatic monocarboxylic acids include aromatic monocarboxylic acids in which 1 to 5 alkyl groups or alkoxy groups are introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, cinnamic acid, benzylic acid, An aromatic monocarboxylic acid having two or more benzene rings such as biphenyl carboxylic acid, naphthalene carboxylic acid, tetralin carboxylic acid, or a derivative thereof can be exemplified, and benzoic acid is particularly preferable.

Some specific examples are shown below, but these are cases where R ₁ to R ₈ are all the same substituent R, and the present invention is not limited thereto.

The sugar ester compound used in the present invention can be produced by reacting a sugar ester with an acylating agent (also called an esterifying agent, for example, an acid halide of acetyl chloride, an anhydride such as acetic anhydride). The distribution of the degree of substitution is made by adjusting the amount of acylating agent, the timing of addition, and the esterification reaction time, but it is possible to mix sugar ester compounds with different degrees of substitution, or purely isolated degrees of substitution. By mixing the compounds, it is possible to adjust a component having a target average substitution degree and a substitution degree of 4 or less.

(Synthesis example: synthesis of a compound according to the present invention)

Four-headed Kolben equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube were charged with 34.2 g (0.1 mol) of sucrose, 135.6 g (0.6 mol) of benzoic anhydride, 284. 8 g (3.6 mol) was charged, the temperature was raised while bubbling nitrogen gas through a nitrogen gas introduction tube with stirring, and an esterification reaction was carried out at 70 ° C. for 5 hours.

Next, the inside of the Kolben is depressurized to 4 × 10 ² Pa or less, and after excess pyridine is distilled off at 60 ° C., the inside of the Kolben is depressurized to 1.3 × 10 Pa or less and the temperature is raised to 120 ° C. Most of the acid and benzoic acid formed were distilled off. Then, 1 L of toluene and 300 g of a 0.5% by mass aqueous sodium carbonate solution were added, and the mixture was stirred at 50 ° C. for 30 minutes and then allowed to stand to separate a toluene layer. Finally, 100 g of water is added to the collected toluene layer, and after washing with water at room temperature for 30 minutes, the toluene layer is separated, and toluene is distilled off at 60 ° C. under reduced pressure (4 × 10 ² Pa or less). A sugar ester compound 1 which is a mixture of A-1, A-2, A-3, A-4, A-5 and the like was obtained.

The obtained mixture was analyzed by high performance liquid chromatography-mass spectrometry (HPLC-MS). As a result, A-1 was 1.2% by mass, A-2 was 13.2% by mass, and A-3 was 14.2% by mass. %, A-4 was 35.4% by mass, A-5 and the like were 40.0% by mass. The average degree of substitution was 5.2.

Similarly, 158.2 g (0.7 mol) of benzoic anhydride, 146.9 g (0.65 mol), 135.6 g (0.6 mol), 124.3 g (0.55 mol) and equimolar pyridine. To obtain sugar esters of components as shown in Table 1.

Next, a part of the obtained mixture was purified by column chromatography using silica gel to obtain 100% pure A-1, A-2, A-3, A-4, A-5, etc. Obtained.

A-5 etc. means a mixture of all components having a substitution degree of 4 or less, that is, compounds having substitution degrees of 4, 3, 2, 1. The average degree of substitution was calculated with A-5 and the like being the degree of substitution 4.

In the present invention, the average degree of substitution was adjusted by adding in combination the sugar ester close to the desired degree of average substitution and the isolated A-1 to A-5 etc. by the method prepared here.

<Measurement conditions for HPLC-MS>
1) LC section Equipment: Column oven (JASCO CO-965) manufactured by JASCO Corporation, detector (JASCO UV-970-240 nm), pump (JASCO PU-980), degasser (JASCO DG-980-50)
Column: Inertsil ODS-3 Particle size 5 μm 4.6 × 250 mm (manufactured by GL Sciences Inc.)
Column temperature: 40 ° C
Flow rate: 1 ml / min
Mobile phase: THF (1% acetic acid): H ₂ O (50:50)
Injection volume: 3 μl
2) MS unit Device: LCQ DECA (manufactured by Thermo Quest Co., Ltd.)
Ionization method: Electrospray ionization (ESI) method Spray Voltage: 5 kV
Capillary temperature: 180 ° C
Vaporizer temperature: 450 ° C
The stretched cellulose ester film of the present invention preferably contains 1 to 20% by mass, particularly 3 to 15% by mass of the sugar ester compound in the stretched cellulose ester film. Within this range, it is preferable that the excellent effects of the present invention are exhibited and there is no bleeding out during storage of the raw material.

(Ester compound)
The stretched cellulose ester film of the present invention preferably contains an ester compound represented by the following general formula (4) from the viewpoint of preventing haze due to stretching and suppressing breakage and the like.

As the ester compound, an ester compound having an aromatic ring or a cycloalkyl ring in the molecule is preferably used. As the ester compound, an aromatic terminal ester plasticizer represented by the following general formula (4) is preferably used.

General formula (4) B- (GA) nGB (wherein B is a benzene monocarboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, or aryl having 6 to 12 carbon atoms) A glycol residue or an oxyalkylene glycol residue having 4 to 12 carbon atoms, A represents an alkylene dicarboxylic acid residue having 4 to 12 carbon atoms or an aryl dicarboxylic acid residue having 6 to 12 carbon atoms, and n is 1 or more Represents an integer.)
In the general formula (4), a benzene monocarboxylic acid residue represented by B and an alkylene glycol residue, oxyalkylene glycol residue or aryl glycol residue represented by G, an alkylene dicarboxylic acid residue or aryl dicarboxylic group represented by A It is composed of an acid residue and can be obtained by a reaction similar to that of a normal polyester plasticizer.

Examples of the benzene monocarboxylic acid component of the polyester plasticizer include benzoic acid, para-tert-butyl benzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethyl benzoic acid, ethyl benzoic acid, normal propyl benzoic acid, and aminobenzoic acid. And acetoxybenzoic acid and the like, and these can be used as one kind or a mixture of two or more kinds, respectively.

Examples of the alkylene glycol component having 2 to 12 carbon atoms of the polyester plasticizer include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1, 2-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2 -Diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylolheptane), 3-methyl-1, 5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl 1,3-pentanediol, 2-ethyl 1 There are 3-hexanediol, 2-methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, etc., and these glycols are one kind or two kinds or more Used as a mixture. In particular, alkylene glycols having 2 to 12 carbon atoms are particularly preferable because of excellent compatibility with cellulose esters.

Examples of the oxyalkylene glycol component having 4 to 12 carbon atoms of the aromatic terminal ester include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. These glycols include 1 It can be used as a seed or a mixture of two or more.

Examples of the alkylene dicarboxylic acid component having 4 to 12 carbon atoms of the aromatic terminal ester include succinic acid, maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. These are used as one kind or a mixture of two or more kinds. Examples of the arylene dicarboxylic acid component having 6 to 12 carbon atoms include phthalic acid, terephthalic acid, isophthalic acid, 1,5 naphthalene dicarboxylic acid, and 1,4 naphthalene dicarboxylic acid.

The number average molecular weight of the polyester plasticizer is preferably 300 to 1500, more preferably 400 to 1000. The acid value is 0.5 mgKOH / g or less, the hydroxyl value is 25 mgKOH / g or less, more preferably the acid value is 0.3 mgKOH / g or less, and the hydroxyl value is 15 mgKOH / g or less.

Hereinafter, synthesis examples of aromatic terminal ester plasticizers will be shown.

<Sample No. 1 (Aromatic terminal ester sample)>
A reaction vessel was charged with 410 parts of phthalic acid, 610 parts of benzoic acid, 737 parts of dipropylene glycol, and 0.40 part of tetraisopropyl titanate as a catalyst. While the monohydric alcohol was refluxed, heating was continued at 130 to 250 ° C. until the acid value became 2 or less, and water produced was continuously removed. Next, the distillate was removed under reduced pressure of 1.33 × 104 Pa to 4 × 102 Pa or less at 200 to 230 ° C., and then filtered to obtain an aromatic terminal ester plasticizer having the following properties. .
Viscosity (25 ° C., mPa · s); 43400
Acid value: 0.2

<Sample No. 2 (Aromatic terminal ester sample)>
Sample No. 1 was used except that 410 parts of phthalic acid, 610 parts of benzoic acid, 341 parts of ethylene glycol, and 0.35 part of tetraisopropyl titanate as a catalyst were used in the reaction vessel. In the same manner as in No. 1, an aromatic terminal ester having the following properties was obtained.
Viscosity (25 ° C., mPa · s); 31000
Acid value: 0.1

<Sample No. 3 (Aromatic terminal ester sample)>
Sample No. 1 was used except that 410 parts of phthalic acid, 610 parts of benzoic acid, 418 parts of 1,2-propanediol, and 0.35 part of tetraisopropyl titanate as the catalyst were used in the reaction vessel. In the same manner as in No. 1, an aromatic terminal ester having the following properties was obtained.
Viscosity (25 ° C., mPa · s); 38000
Acid value: 0.05

<Sample No. 4 (Aromatic terminal ester sample)>
Sample No. 1 was used except that 410 parts of phthalic acid, 610 parts of benzoic acid, 418 parts of 1,3-propanediol, and 0.35 part of tetraisopropyl titanate as a catalyst were used in the reaction vessel. In the same manner as in No. 1, an aromatic terminal ester having the following properties was obtained.
Viscosity (25 ° C., mPa · s); 37000
Acid value: 0.05

Although the specific compound of an aromatic terminal ester plasticizer is shown below, this invention is not limited to this.

The stretched cellulose ester film of the present invention preferably contains 1 to 20% by mass, particularly 3 to 11% by mass of the ester compound in the stretched cellulose ester film. If it is in this range, while exhibiting the outstanding effect of this invention, failures, such as a fracture | rupture, can be suppressed.

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

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

For example, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxylphenyl) -2H-benzotriazole, (2-2H-benzotriazol-2-yl) -6- (linear and side Chain dodecyl) -4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone, 2,4-benzyloxybenzophenone, etc., and tinuvin 109, tinuvin 171, tinuvin 234, tinuvin 326, tinuvin 327, tinuvin 328, etc. These are commercially available products made by BASF Japan and can be preferably used.

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

Specific examples of the benzotriazole-based ultraviolet absorber used in the present invention are listed below, but the present invention is not limited to these.

UV-1: 2- (2'-hydroxy-5'-methylphenyl) benzotriazole UV-2: 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole UV-3 : 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole UV-4: 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl)- 5-Chlorobenzotriazole UV-5: 2- (2′-hydroxy-3 ′-(3 ″, 4 ″, 5 ″, 6 ″ -tetrahydrophthalimidomethyl) -5′-methylphenyl) benzotriazole UV-6: 2,2-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol)
UV-7: 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole UV-8: 2- (2H-benzotriazol-2-yl) -6- (Linear and side chain dodecyl) -4-methylphenol (TINUVIN171)
UV-9: Octyl-3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl- Mixture of 4-hydroxy-5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate (TINUVIN109)

Specific examples of the benzophenone-based ultraviolet absorber are shown below, but the present invention is not limited thereto.
UV-10: 2,4-dihydroxybenzophenone UV-11: 2,2'-dihydroxy-4-methoxybenzophenone UV-12: 2-hydroxy-4-methoxy-5-sulfobenzophenone UV-13: Bis (2-methoxy -4-hydroxy-5-benzoylphenylmethane)
In addition, a discotic compound such as a compound having a 1,3,5 triazine ring is also preferably used as the ultraviolet absorber.

The stretched cellulose ester film according to the present invention preferably contains two or more ultraviolet absorbers.

Also, as the ultraviolet absorber, a polymeric ultraviolet absorber can be preferably used, and in particular, a polymer type ultraviolet absorber described in JP-A-6-148430 is preferably used.

The method for adding the UV absorber is to add the UV absorber to the dope after dissolving the UV absorber in an alcohol such as methanol, ethanol or butanol, an organic solvent such as methylene chloride, methyl acetate, acetone or dioxolane, or a mixed solvent thereof. Or you may add directly in dope composition. For an inorganic powder that does not dissolve in an organic solvent, a dissolver or a sand mill is used in the organic solvent and cellulose ester to disperse and then added to the dope.

The amount of the UV absorber used is not uniform depending on the type of UV absorber, usage conditions, etc., but when the stretched cellulose ester film has a dry film thickness of 30 to 200 μm, it is 0.5% relative to the stretched cellulose ester film. Is preferably 10 to 10% by mass, and more preferably 0.6 to 4% by mass.

(Fine particles)
The stretched cellulose ester film of the present invention preferably contains fine particles from the viewpoint of improving slipperiness and eliminating poor conveyance such as wrinkles.

As fine particles, examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, Examples thereof include magnesium silicate and calcium phosphate. Fine particles containing silicon are preferable in terms of low turbidity, and silicon dioxide is particularly preferable.

The average primary particle size of the fine particles is preferably 5 to 400 nm, and more preferably 10 to 300 nm. These may be mainly contained as secondary aggregates having a particle size of 0.05 to 0.3 μm, and may be contained as primary particles without being aggregated if the particles have an average particle size of 100 to 400 nm. preferable. The content of these fine particles in the stretched cellulose ester film is preferably 0.01 to 1% by mass, particularly preferably 0.05 to 0.5% by mass. In the case of a stretched cellulose ester film having a multilayer structure by the co-casting method, it is preferable to contain fine particles of this addition amount on the surface.

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

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

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

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

(dye)
A dye can also be added to the stretched cellulose ester film of the present invention for color adjustment. For example, a blue dye may be added to suppress the yellowness of the film. Preferred examples of the dye include anthraquinone dyes.

The anthraquinone dye can have an arbitrary substituent at any position from the 1st position to the 8th position of the anthraquinone. Preferred substituents include an anilino group, hydroxyl group, amino group, nitro group, or hydrogen atom. In particular, it is preferable to contain a blue dye described in JP-A-2001-154017, particularly an anthraquinone dye.

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

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

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

Physical Properties of Stretched Cellulose Ester Film The stretched cellulose ester film of the present invention has an average value of the surface roughness (Ra) of the end H of at least one surface in the range of 1.7 nm to 4.0 nm, and the central portion of the film surface. 0.1 nm to 1.0 nm higher than the average value of the surface roughness (Ra) of T; in the range where the average value of the elastic modulus of the central portion T of the film is 3.0 GPa to 8.0 GPa, the edge H of the film It is characterized by being 0.1 GPa to 2.0 GPa higher than the average value of the elastic modulus.

At least one surface (film surface A) is a metal support surface when a dope solution containing a cellulose ester and a solvent is cast on an endless metal support (belt or drum) in a film manufacturing process described later. The surface opposite to the side in contact with the belt surface or drum surface.

“End H” refers to a portion from the end of the film to L × 0.05 in the width direction of the film, where L is the width (full width) of the stretched cellulose ester film. The “center portion T” refers to a portion up to ± L × 0.1 from the center portion of the film in the width direction of the stretched cellulose ester film when the width (full width) of the stretched cellulose ester film is L.

In order to increase productivity, it is required to stretch the web at a high magnification and transport the film at a high speed.

For example, when an attempt is made to obtain a stretched cellulose ester film that has been widened to a width of 1.6 m or more, more preferably 2 m or more, by a stretching treatment, a problem that has not occurred conventionally occurs. For example, there is a problem that wrinkles in which the direction of the groove or the mountain is the transport direction occur, or the deviation between the end portion and the center portion of the retardation Ro in the in-plane direction becomes large. When the deviation between the end portion and the central portion of the retardation Ro film in the in-plane direction is large, the visibility of the polarizing plate or the liquid crystal display device including the cellulose ester film is deteriorated, or the contrast is varied. Therefore, even when the width is increased, the retardation Ro in the in-plane direction is required to be uniform between the end portion and the central portion of the film.

In the present invention, as a result of diligent investigations on these problems, when the stretching process at a high magnification of 25% to 100% is performed while heating the entire surface of the web to a uniform and high temperature, the elastic modulus of the entire web rapidly increases. It was found that the deformation caused by the force that narrows the web in the width direction works and wrinkles in which the direction of the groove or the mountain is the transport direction are generated.

In order to suppress the deformation, it is effective to change the elastic modulus of the stretched web in the width direction (TD direction) of the web; It has been found that the higher the tension) and the lower the elastic modulus at the edge of the web, the more effective the suppression of wrinkles in which the direction of the groove or mountain is the conveying direction is suppressed. It was. In addition, since the stress applied to the web during stretching can be made uniform in the web surface (excluding the end portion Ho), the end portion of the retardation Ro film on the film surface (excluding the end portion H) and It has been found that the deviation at the central portion T can be reduced.

Also, there is a problem that wrinkles are generated at the end of the film when the film is conveyed at high speed with a roll or wound up.

On the other hand, a film having a distribution in the width direction so that the surface roughness of the end portion H of the film is large and the surface roughness of the central portion T is small has a difference in holding force by the roll in the width direction of the film. As a result, the tensile tension in the transport direction applied to the film does not concentrate on the central portion T of the film, and is easily dispersed uniformly in the width direction of the film. Specifically, since the end in the width direction of the film is easily held by the roll, the film is unlikely to shrink in the width direction. As a result, the film can be held at a constant width when the film is transported at high speed or taken up, so that not only is it difficult to produce wrinkles in which the direction of the groove or mountain is the transport direction, but also the end portion It was also found that it was difficult to cause wrinkles.

Therefore, the average value of the surface roughness (Ra) of the end portion H of at least one surface (for example, the film surface A) is in the range of 1.7 nm to 4.0 nm, and the surface roughness (Ra) of the central portion T is It is 0.1 nm to 1.0 nm higher than the average value, and the average value of the elastic modulus of the central portion T is in the range of 3.0 GPa to 8.0 GPa. The stretched cellulose ester film adjusted so as to increase by 2.0 GPa suppresses a sudden decrease in the elastic modulus of the web during the stretching process as described above, and deforms due to a force that narrows the web in the width direction. Since it can suppress, the wrinkle extended in a conveyance direction can be suppressed. In addition, since the entire web (excluding the web end Ho) can be stretched with a uniform stress during the stretching process, the center and end surfaces of the stretched cellulose ester film (excluding the film end H) It is possible to reduce the deviation of the internal retardation Ro (Ro value at the central portion−Ro value at the end portion). Furthermore, since the film can be held at a certain width when the film is conveyed at high speed or taken up, not only can the wrinkles extending in the conveying direction be made difficult to occur, but also the wrinkles at the end of the film can be folded. As a result, the present invention has been made.

FIG. 1 is a schematic view of a stretched cellulose ester film of the present invention. In FIG. 1, the stretched cellulose ester film shows a portion above the line b.

In the stretched cellulose ester film F of the present invention, the average value of the surface roughness (Ra) of the end portion H is different from the average value of the surface roughness of the central portion T, and the average value of the elastic modulus of the end portion H and the central portion. The average value of the elastic modulus of T is different. The end H refers to a portion from the end of the stretched cellulose ester film to L × 0.05 in the width direction, where L is the width (full width) of the stretched cellulose ester film. An area that is Further, the center portion T refers to a portion from the center (L / 2) of the film to ± L × 0.1 in the width direction, where L is the width (full width) of the stretched cellulose ester film, and FIG. Then, it refers to the area indicated by T.

The average value of the surface roughness (Ra) of the end H of at least one surface (for example, the film surface A) of the stretched cellulose ester film F of the present invention is in the range of 1.7 nm to 4.0 nm, It is characterized by being 0.1 nm to 1.0 nm higher than the average value of the surface roughness (Ra).

The average value of the surface roughness (Ra) of the end H of at least one surface (for example, film surface A) of the stretched cellulose ester film F of the present invention is preferably in the range of 2.2 nm to 3.5 nm. In addition, it is preferably 0.3 nm to 1.0 nm higher than the average value of the surface roughness (Ra) of the central portion T.

The average value of the surface roughness (Ra) of the end portion H is obtained by measuring the surface roughness (Ra) of at least 5 points in the width direction of the film from the end of the film, and obtaining the average value thereof. The average value of the surface roughness (Ra) of the central portion T is obtained by measuring the surface roughness (Ra) of at least five points in the width direction of the film across the center of the film and calculating the average value thereof. .

The surface roughness (Ra) is a numerical value defined in JIS B 0601, and examples of the measuring method include a stylus method or an optical method. The surface roughness (Ra) in the present invention can be measured using a non-contact surface fine shape measuring device WYKO NT-2000.

The stretched cellulose ester film F of the present invention has an average elastic modulus of the central portion T in the range of 3.0 GPa to 8.0 GPa, and 0.1 GPa to 2. It is characterized by being 0 GPa high.

In the stretched cellulose ester film F of the present invention, the average value of the elastic modulus of the central portion T is in the range of 4.0 GPa to 7.0 GPa, and is 0.3 GPa to 1. It is preferably 0 GPa high.

The average value of the elastic modulus of the end portion H is obtained by measuring the elastic modulus of at least five points from the end of the film in the width direction of the film, and obtaining the average value thereof. The average value of the elastic modulus of the central portion T is obtained by measuring the elastic modulus of at least five points in the width direction of the film across the center of the film, and obtaining the average value thereof.

In the present invention, the elastic modulus means a tensile elastic modulus, and a specific measuring method thereof includes, for example, the method of JISK7217. That is, the elastic modulus is 23 ° C. and 55% RH in accordance with the method described in JIS-K-7127 using a tensile tester (TG-2KN, manufactured by Minebea Co., Ltd.), ORIENTEC tensile tester RTC-1225A, and the like. Obtained by measuring below.

(Refractive index control)
For the stretched cellulose ester film of the present invention, adjusting the retardation by stretching is also an important operation. The stretched cellulose ester film of the present invention preferably has a retardation value Ro represented by the following formula of 0 to 20 nm and Rt of −100 to 100 nm, more preferably Ro ≦ 5 nm and −50 nm ≦ Rt ≦ 50 nm. A range is preferable.

Further, increasing the retardation value by stretching treatment is preferable for use as a retardation film. In that case, the retardation value Ro is preferably 30 to 100 nm and the Rt is preferably 70 to 400 nm.

Formula (i) Ro = (nx−ny) × d
Formula (ii) Rt = ((nx + ny) / 2−nz) × d
(In the formula, Ro is the retardation value in the film plane, Rt is the retardation value in the film thickness direction, nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, (nz represents the refractive index in the thickness direction of the film, and d represents the thickness (nm) of the film.)
The refractive index can be obtained at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH using, for example, KOBRA-WR (Oji Scientific Instruments).

The slow axis or the fast axis of the stretched cellulose ester film of the present invention exists in the film plane, and θ1 is preferably −1 ° or more and + 1 ° or less, assuming that the angle formed with the film forming direction is θ1, More preferably, it is 0.5 ° or more and + 0.5 ° or less. This θ1 can be defined as an orientation angle, and the measurement of θ1 can be performed using an automatic birefringence meter KOBRA-21ADH (Oji Scientific Instruments). Each of θ1 satisfying the above relationship can contribute to obtaining high luminance in a display image, suppressing or preventing light leakage, and contributing to obtaining faithful color reproduction in a color liquid crystal display device.

(Other physical properties)
The moisture permeability of the stretched cellulose ester film of the present invention is preferably 10 to 1200 g / m ² · 24 h at 40 ° C. and 90% RH, more preferably 20 to 1000 g / m ² · 24 h, and 20 to 850 g / m ² · 24 h. Is particularly preferred. The moisture permeability can be measured according to the method described in JIS Z 0208.

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

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

2. Production method of stretched cellulose ester film The stretched cellulose ester film of the present invention may be produced by a solution casting method or a melt casting method.

FIG. 2 is a schematic diagram showing an example of an apparatus for producing a stretched cellulose ester film by a solution casting method. As shown in FIG. 2, the stretched cellulose ester film manufacturing apparatus includes a support 1 made of a rotating metal endless belt, and a die 2 that casts a dope that is a raw material solution of the cellulose ester film on the support 1. A peeling roll 3 for peeling the web W formed on the support 1 by the die 2 from the support 1, and a tenter 4 for transporting and drying the film F peeled from the support 1 in the width direction, And a drying device 5 that dries the film F while being conveyed via a plurality of conveying rolls 6, and a winding roll 8 that winds the stretched cellulose ester film F obtained by drying.

The film A surface referred to in the present invention refers to a surface opposite to the side in contact with the belt surface or drum surface when the dope is cast on the belt or drum.

In FIG. 2, before entering the stretching process by the tenter 4, the heat retaining process 4-1 is performed so that the temperature of the unstretched cellulose ester film Fo does not become too low, and after the tenter 4 (stretching process), A cooling step 4-2 for performing slow cooling is provided. Further, before the drying step by the drying device 5, a heat retaining step 5-1 is performed so that the temperature of the stretched cellulose ester film F does not become too low, and after the drying device 5 (drying step), the film is gradually cooled. A cooling step 5-2 for performing the above is provided.

The stretched cellulose ester film of the present invention by the solution casting method includes 1) a step of preparing a dope by dissolving the cellulose ester and the additive in a solvent, and 2) a step of casting the dope on an endless metal support. 3) A process of drying the cast dope and then peeling it from the metal support to obtain a web (unstretched cellulose ester film). 4) Stretching the web (unstretched cellulose ester film) to form a stretched cellulose ester film. It can be manufactured through a step of obtaining, 5) a step of drying the film, and 6) a step of winding up the film.

1) Process for preparing dope A process for preparing a dope will be described. The concentration of cellulose ester in the dope is preferably higher because the drying load after casting on the metal support can be reduced. However, if the concentration of cellulose ester is too high, the load during filtration increases and the filtration accuracy is poor. Become. The concentration that achieves both of these is preferably 10 to 35% by mass, and more preferably 15 to 25% by mass.

The solvent used in the dope may be used alone or in combination of two or more, but it is preferable to use a mixture of a good solvent and a poor solvent of cellulose ester in terms of production efficiency, and there are many good solvents. This is preferable from the viewpoint of the solubility of the cellulose ester. The preferable range of the mixing ratio of the good solvent and the poor solvent is 70 to 98% by mass for the good solvent and 2 to 30% by mass for the poor solvent. With a good solvent and a poor solvent, what dissolve | melts the cellulose ester to be used independently is defined as a good solvent, and what poorly swells or does not melt | dissolve is defined as a poor solvent. Therefore, depending on the average acetylation degree (acetyl group substitution degree) of the cellulose ester, the good solvent and the poor solvent change. For example, when acetone is used as the solvent, the cellulose ester acetate ester (acetyl group substitution degree 2.4), cellulose Acetate propionate is a good solvent, and cellulose acetate (acetyl group substitution degree 2.8) is a poor solvent.

The good solvent is not particularly limited, and examples thereof include organic halogen compounds such as methylene chloride, dioxolanes, acetone, methyl acetate, and methyl acetoacetate. Particularly preferred is methylene chloride or methyl acetate.

The poor solvent is not particularly limited, but for example, methanol, ethanol, n-butanol, cyclohexane, cyclohexanone, etc. are preferably used. The dope preferably contains 0.01 to 2% by mass of water. Moreover, the solvent used for melt | dissolution of a cellulose ester collect | recovers the solvent removed from the film by drying at the film-forming process, and uses this again. The recovery solvent may contain trace amounts of additives added to the cellulose ester, such as plasticizers, UV absorbers, polymers, monomer components, etc., but even if these are included, they are preferably reused. Can be purified and reused if necessary.

A general method can be used as a method for dissolving the cellulose ester when the dope is prepared. When heating and pressurization are combined, it is possible to heat above the boiling point at normal pressure. It is preferable to stir and dissolve while heating at a temperature that is equal to or higher than the boiling point of the solvent at normal pressure and that the solvent does not boil under pressure, in order to prevent the generation of massive undissolved materials called gels and mamacos. Moreover, after mixing a cellulose ester with a poor solvent and making it wet or swell, the method of adding a good solvent and melt | dissolving is also used preferably.

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

The heating temperature with the addition of the solvent is preferably higher from the viewpoint of the solubility of the cellulose ester, but if the heating temperature is too high, the required pressure increases and the productivity deteriorates. A preferred heating temperature is 45 to 120 ° C, more preferably 60 to 110 ° C, and still more preferably 70 ° C to 105 ° C. The pressure is adjusted so that the solvent does not boil at the set temperature.

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

Next, the cellulose ester solution is filtered using an appropriate filter medium such as filter paper. As the filter medium, it is preferable that the absolute filtration accuracy is small in order to remove insoluble matters and the like, but there is a problem that the filter medium is likely to be clogged if the absolute filtration accuracy is too small. For this reason, a filter medium with an absolute filtration accuracy of 0.008 mm or less is preferable, a filter medium with 0.001 to 0.008 mm is more preferable, and a filter medium with 0.003 to 0.006 mm is more preferable.

There are no particular restrictions on the material of the filter medium, and ordinary filter media can be used. However, plastic filter media such as polypropylene and Teflon (registered trademark), and metal filter media such as stainless steel do not drop off fibers. preferable. It is preferable to remove and reduce impurities, particularly bright spot foreign matter, contained in the raw material cellulose ester by filtration.

The bright spot foreign matter is placed in a crossed Nicols state with two polarizing plates, a stretched cellulose ester film is placed between them, light is applied from the side of one polarizing plate, and observed from the side of the other polarizing plate. It is a point (foreign matter) where light from the opposite side sometimes leaks, and the number of bright spots having a diameter of 0.01 mm or more is preferably 200 / cm ² or less. More preferably, it is 100 pieces / cm ² or less, further preferably 50 pieces / cm ² or less, and further preferably 0 to 10 pieces / cm ² . Further, it is preferable that the number of bright spots of 0.01 mm or less is small.

The dope can be filtered by a normal method, but the method of filtering while heating at a temperature not lower than the boiling point of the solvent at normal pressure and in a range where the solvent does not boil under pressure is the filtration pressure before and after filtration. The increase in the difference (referred to as differential pressure) is small and preferable. A preferred temperature is 45 to 120 ° C., more preferably 45 to 70 ° C., and still more preferably 45 to 55 ° C.

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

2) Process of casting dope on endless metal support The metal support in the casting process is preferably a mirror-finished surface, and the metal support is made of stainless steel belt or casting. A drum plated with is preferably used. The cast width can be 1 to 4 m. Since the width of the optical film of the present invention is preferably 2 m to 4 m, the cast width is necessarily wide.

The surface temperature of the metal support may be the same as the surface temperature of the metal support in the step of drying the dope described later and then peeling the dope from the metal support to obtain a web.

3) Step of drying the cast dope and then peeling off from the metal support to obtain a web The surface temperature of the metal support is from −50 ° C. to below the boiling point of the solvent, and the higher the temperature, the more the web is dried. This is preferable because the speed can be increased, but if it is too high, the web may foam or the flatness may deteriorate. The support temperature is preferably 0 to 40 ° C, more preferably 5 to 30 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent. The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing hot air or cold air, and a method of contacting hot water with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short. When warm air is used, wind at a temperature higher than the target temperature may be used.

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

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

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

Next, the peeled web is conveyed to the above-described stretching process (preferably a tenter), and the stretching process according to the present invention is performed.

4) Step of Stretching Web to Obtain Stretched Cellulose Ester Film An example of the mechanism of the tenter 4 is shown in FIG. As shown in FIG. 3, the tenter 4 has a large number of clips 11 connected in a chain state on both left and right sides of the housing 10, and these clips 11 form a single wheel and run on the rail 12. The unstretched cellulose ester film Fo is gripped and conveyed. Although not shown in the drawings, each clip 11 is provided with a swingable presser arm. On both the left and right sides of the tenter 4, both ends in the width direction of the unstretched cellulose ester film Fo on the cradle are pressed by the tenter 4. It is sandwiched (clipped) between the curved surface tip of the arm and the cradle and conveyed together while being stretched, and at the same time dried.

In the tenter 4, the unstretched cellulose ester film Fo has a film width holding zone A, a film width direction stretching zone B, and a film width holding zone C in the stretched state in a state where both ends in the width direction are gripped. Passing sequentially, the film width direction stretching treatment is performed, and a stretched cellulose ester film F is obtained.

Here, the film width holding zone A in the tenter 4 is a zone in which the distance between grip clips of the film width (both ends of the base) from the entrance of the tenter 4 to the stretching start point a is constant. The stretching zone B refers to a zone in which the distance between grip clips of the film width (both ends of the base) from the stretching start point a to the stretching end point b of the tenter 4 spreads in the traveling direction (conveying direction). The film width holding zone C in the stretched state is a zone in which the distance between the grip clips of the stretched film width (both ends of the base) from the stretch end point b of the tenter 4 to the grip clip release point c is constant. In the latter half of the film width holding zone C, if the stress in the width direction on the post-stretching film F is too strong, it is also preferable to provide a relaxation treatment.

The rail 12 in the tenter 4 is normally a bendable rail. When the rail 12 is bent, the distance between the left and right clips changes, and the width holding zone A, the stretching zone B, and the width holding zone C are configured. can do. The stretching zone B corresponds to the stretching process of the present invention. Note that the combinations of these zones are not limited to those shown in the drawings, and may be combined in any order.

Moreover, although the illustrated tenter 4 is a clip tenter method, this may be a pin tenter method, and in any case, the tenter method can be dried while maintaining the width of the stretched cellulose ester film F. In order to improve flatness and dimensional stability, it is preferable.

In the stretching treatment, it is preferable to stretch the unstretched cellulose ester film Fo in the width direction of the film at a stretch ratio of 25% to 100% in order to widen the film, from the viewpoint of improving productivity and avoiding breakage and the like. The draw ratio is more preferably 30% to 50%.

The stretching operation can also be performed in the longitudinal direction (MD direction) of the film. For example, a method of stretching a circumferential speed difference between a plurality of rolls and stretching in the MD direction using the roll circumferential speed difference therebetween, a web And a method of extending the gap between the clips and pins in the traveling direction and extending in the MD direction, or a method of expanding the MD / TD direction simultaneously and extending in both the MD / TD directions.

The film transport tension in the film forming process such as in the tenter depends on the temperature, but is preferably 120 N / m to 200 N / m, and more preferably 140 N / m to 200 N / m. 140 N / m to 160 N / m is most preferable.

When stretching, the glass transition temperature of the stretched cellulose ester film of the present invention is defined as Tg (Tg-30) to (Tg + 100) ° C., more preferably (Tg-20) to (Tg + 80) ° C., and even more preferably (Tg− 5) to (Tg + 20) ° C.

The Tg of the cellulose ester film can be controlled by the material type constituting the film and the ratio of the constituting materials. In the application of the present invention, the Tg when the film is dried is preferably 110 ° C. or higher, more preferably 120 ° C. or higher.

Therefore, the glass transition temperature is preferably 190 ° C. or lower, more preferably 170 ° C. or lower. At this time, the Tg of the film can be determined by the method described in JIS K7121.

The stretching time is appropriately selected, but is preferably a relatively short time from the viewpoint of flatness and dimensional stability. Specifically, the range is preferably 1 to 10 seconds, and more preferably 4 to 10 seconds. Further, the stretching speed in the width direction may be constant or may be changed. The stretching speed is preferably 50 to 500% / min, more preferably 100 to 400% / min, and most preferably 200 to 300% / min.

FIG. 4 is a schematic diagram showing a stretching method preferred for the present invention.

The unstretched cellulose ester film Fo is conveyed to a tenter, the end is gripped with a clip or the like, and stretched at a predetermined stretch ratio.

As a preferable method for producing the stretched cellulose ester film of the present invention, the surface temperature of the end portion Ho of the surface A of the unstretched cellulose ester film Fo is the surface temperature of the central portion To of the surface A of the unstretched cellulose ester film Fo. For example, stretching may be performed while raising the temperature by 10 ° C to 50 ° C. However, it is not limited to this method.

The surface A of the unstretched cellulose ester film Fo refers to the surface opposite to the side in contact with the metal support surface when the dope solution is cast on the metal support to produce a film.

The end Ho refers to a portion from the end of the film to Lo × 0.05 in the width direction of the film, where Lo is the width (full width) of the unstretched cellulose ester film Fo. The center portion To refers to a portion from the center of the film to ± Lo × 0.1 in the width direction of the film when the width (full width) of the unstretched cellulose ester film Fo is Lo.

The surface temperature of the end portion Ho and the central portion To of the unstretched cellulose ester film can be measured using a contact-type handy thermometer (ANITSU DIGITAL THREMOMETER HA-100K). Specifically, 5 points can be measured for each of the width directions at the point a at which the stretching process of the film being transported is started, and the average value can be set as the film temperature of the part.

Thus, the mechanism in which the surface roughness (Ra) and the elastic modulus change by changing the surface temperature of the film during the stretching treatment between the end portion Ho and the central portion To does not yet go beyond the estimation range. Is estimated as follows.

That is, when the surface temperature of the end portion Ho of the web at the time of the stretching process is raised, the web at that portion is softened and softened, and the matting agent embedded in the web of the end portion Ho flows to the surface and the surface. Easy to gather in the vicinity. Thereby, it is considered that fine irregularities are formed on the surface of the end portion Ho of the web, and the surface roughness (Ra) of the end portion Ho of the web is increased.

In addition, since the surface temperature of the film during the stretching process is different between the end portion Ho and the central portion To, the arrangement of the polymer chains of the cellulose ester resin is changed between the end portion Ho and the central portion To of the web. A difference occurs in the stress applied to the web by stretching. Specifically, since the polymer chain in the central portion To that is relatively low in temperature is harder than the polymer chain in the end portion Ho, the central portion To of the web is easily stretched with a higher stress than the end portion Ho of the web. . Thereby, it is estimated that the elasticity modulus of the center part To of a web rises.

The method for adjusting the temperature is preferably a method in which hot air is blown locally on the end portion. Specifically, at least a pair of end hot air generating portions G1 for adjusting the surface temperature is disposed so as to face the end portion of the surface A of the unstretched cellulose ester film, and from the end hot air generating portions, A method in which stretching is performed while spraying hot air having a temperature 10 ° C. to 50 ° C. higher than the surface temperature of the central portion To of the surface A of the film A on the end portion Ho of the surface A of the unstretched cellulose ester film Fo is preferable.

The end hot air generating part preferably blows hot air, the temperature of which is controlled by a hot air generator (not shown), from the nozzle-like outlet to the entire end of the unstretched cellulose ester film Fo. The distance from the film end to the film end can be appropriately selected, but it is preferable to cover at least the point a before and after the point a at which the unstretched cellulose ester film Fo starts to be stretched. Moreover, as an area | region which sprays hot air, when the width | variety (full width) of the unstretched cellulose-ester film Fo is set to Lo, it can cover the part from the edge of this film to Lox0.2 in the width direction of a film, It is preferable because the temperature of the end portion and the center portion can be adjusted efficiently.

In the stretching step, it is preferable that the temperature distribution in the film width direction of the atmosphere is small from the viewpoint of improving the uniformity of the film, and the temperature distribution in the width direction at the end and the center is preferably within ± 5 ° C, Within ± 2 ° C is more preferred, and within ± 1 ° C is most preferred.

In FIG. 4, a pair of end hot air generating portions G1 are provided in the vicinity of the stretching start point a so as to cover both ends of the unstretched cellulose ester film Fo. The position of the end hot air generating part G1 in FIG. 4 shows a preferable position, and is not limited to this.

Furthermore, it is also preferable to provide an end hot air generating portion G2 after the stretching end point b, and by setting the hot air temperature between the center temperature and the end temperature of the stretched cellulose ester film, the high-speed conveyance suitability is further improved. You can also.

The stretched cellulose ester film obtained in the stretching process is conveyed to the film drying process.

5) Step of drying film In the film drying step, the amount of residual solvent is preferably 1% by mass or less, more preferably 0.1% by mass or less, and particularly preferably 0 to 0.01% by mass or less. It is.

In the film drying process, generally, a roll drying method (a method in which a plurality of rolls arranged at the top and bottom are alternately passed through the web for drying) or a tenter method for drying while transporting the web is employed.

The means for drying the film is not particularly limited, and can be generally performed with hot air, infrared rays, heating rolls, microwaves, etc., but it is preferably performed with hot air in terms of simplicity.

The drying temperature in the film drying step is preferably 90 ° C. to 200 ° C., more preferably 110 ° C. to 160 ° C. The drying temperature is preferably increased stepwise.

The preferred drying time depends on the drying temperature, but is preferably 5 minutes to 60 minutes, more preferably 10 minutes to 30 minutes.

The film thickness of the stretched cellulose ester film is not particularly limited, but is preferably 10 to 200 μm, more preferably 10 to 100 μm, and still more preferably 20 to 70 μm from the viewpoint of thin film and weight reduction.

The stretched cellulose ester film of the present invention has a width of 2 to 4 m, more preferably 2 to 3 m. If it exceeds 4 m, conveyance becomes difficult.

The stretched cellulose ester film is preferably heat-set after the stretching treatment described above, but the heat-set is preferably heat-set within a temperature range of Tg-20 ° C. or lower, usually for 0.5 to 300 seconds. At this time, it is preferable to perform heat fixing while sequentially raising the temperature in a range where the temperature difference is 1 to 100 ° C. in the region divided into two or more.

The heat-fixed film is usually cooled to Tg or less, and the clip gripping portions at both ends of the film are cut and wound. The cooling is preferably performed by gradually cooling from the final heat setting temperature to Tg at a cooling rate of 100 ° C. or less per second. Means for cooling and relaxation treatment are not particularly limited, and can be performed by a conventionally known means. In particular, it is preferable to carry out these treatments while sequentially cooling in a plurality of temperature ranges from the viewpoint of improving the dimensional stability of the film.

More optimal conditions of these heat setting conditions, cooling, and relaxation treatment conditions vary depending on the type of additives such as cellulose ester and plasticizer constituting the film, so the physical properties of the obtained stretched film are measured and preferable characteristics are obtained. Thus, it may be determined by adjusting as appropriate.

6) Step of winding film In the step of winding film, the obtained stretched cellulose ester film is wound in a direction perpendicular to the width direction of the film to obtain a wound body.

<Polarizing plate>
A polarizing plate using the stretched cellulose ester film of the present invention and a liquid crystal display device using the polarizing plate will be described.

The polarizing plate of the present invention has a polarizer and a stretched cellulose ester film of the present invention disposed on at least one surface thereof. In order to make the optical properties of the polarizing plate uniform in the plane, the stretched cellulose ester film used for the polarizing plate has at least a part of the end portion H (for example, L × 0.01 to 0.02 from the width direction end of the film). It is preferable that the region up to is removed by slit.

The polarizing plate can be produced by a general method. The polarizer side of the stretched cellulose ester film of the present invention is preferably bonded to at least one surface of a polarizer prepared by alkali saponification treatment and immersed in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. . The stretched cellulose ester film may be used on the other surface, or another optical film may be used. Commercially available cellulose ester films (for example, Konica Minoltack KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC12UR, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC4FR-1, KC4DR, KC4KR, K4SR, KC4KR, K4SR KC8UY-HA, KC8UX-RHA, KC2UA, KC4UA, KC6UA, KC4CZ, KC2CZ or higher, manufactured by Konica Minolta Opto, Fujitac 8TD, 6TD, 4TD, NRT, or Fujifilm, Inc. are also preferably used.

Furthermore, when the stretched cellulose ester film of the present invention was an optical film A, the optical film B was measured at a wavelength of 590 nm when the optical film used for the polarizing plate on the opposite side via a liquid crystal cell was an optical film B. An optical film having a retardation function with an in-plane retardation Ro of 20 to 100 nm and Rt = 70 to 300 nm is also preferable.

The optical film B is not particularly limited, and these can be produced, for example, by the methods described in JP-A-2005-196149 and JP-A-2005-275104. It is also preferable to use an optical film that also serves as an optical compensation film having an optically anisotropic layer formed by aligning a liquid crystal compound such as a discotic liquid crystal. For example, the optically anisotropic layer can be formed by the method described in JP-A-2005-275083. When the optical film B is used in combination with the optical film A of the present invention, a polarizing plate and a liquid crystal display device having a stable viewing angle expansion effect can be obtained.

A polarizer, which is a main component of a polarizing plate, is an element that allows only light of a plane of polarization in a certain direction to pass. A typical polarizer currently known is a polyvinyl alcohol-based polarizing film, which is polyvinyl alcohol. There are one in which iodine is dyed on a system film and one in which dichroic dye is dyed. For the polarizer, a polyvinyl alcohol aqueous solution is formed into a film and dyed by uniaxial stretching or dyed or uniaxially stretched and then preferably subjected to a durability treatment with a boron compound. The film thickness of the polarizer is preferably 5 to 30 μm, particularly preferably 10 to 20 μm.

Further, the ethylene unit content described in JP-A-2003-248123, JP-A-2003-342322, etc. is 1 to 4 mol%, the degree of polymerization is 2000 to 4000, and the degree of saponification is 99.0 to 99.99 mol%. Ethylene-modified polyvinyl alcohol is also preferably used. Of these, an ethylene-modified polyvinyl alcohol film having a hot water cutting temperature of 66 to 73 ° C. is preferably used. The difference in hot water cutting temperature between two points 5 cm away in the TD direction of the film is more preferably 1 ° C. or less in order to reduce color spots, and two points separated 1 cm in the TD direction of the film. In order to reduce color spots, it is more preferable that the difference in the hot water cutting temperature is 0.5 ° C. or less.

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

The polarizer obtained as described above is generally used as a polarizing plate with a protective film pasted on both sides or one side thereof. As an adhesive used for pasting, a PVA-based adhesive is used. In particular, a PVA-based adhesive is preferably used.

<Liquid crystal display device>
By incorporating the polarizing plate into the display device, various liquid crystal display devices with excellent visibility can be manufactured. As the liquid crystal display device, a reflection type, a transmission type, a transflective type liquid crystal display device, or a liquid crystal display device of various drive systems such as a TN type, STN type, OCB type, VA type, IPS type, ECB type, particularly VA type. It is preferably applied to a liquid crystal display device of (MVA type, PVA type).

The liquid crystal display device has a liquid crystal cell and a pair of polarizing plates that sandwich the liquid crystal cell. And at least one of a pair of polarizing plates contains the stretched cellulose ester film of this invention. It is preferable that the stretched cellulose ester film of this invention is arrange | positioned at the surface at the side of the liquid crystal cell of the polarizer which comprises a polarizing plate.

Since the stretched cellulose ester film of the present invention has a small deviation in the film plane of the retardation value Ro, the polarizing plate using it has good visibility when used in a large-screen liquid crystal display device, In addition, excellent front contrast can be imparted.

In a large-screen liquid crystal display device having a 17-inch or larger screen, particularly a 30-inch or larger screen, there is no distortion such as uneven color and wavy unevenness, and there is an effect that eyes are not tired even during long-time viewing.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
Preparation of Fine Particle Dispersion 1 The following components were stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.
(Composition of fine particle dispersion 1)
Fine particles (Aerosil R812V manufactured by Nippon Aerosil Co., Ltd.): 11 parts by mass Ethanol: 89 parts by mass

Preparation of Fine Particle Additive Solution 1 The fine particle dispersion 1 was slowly added to a dissolution tank containing methylene chloride with sufficient stirring. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution 1.
(Composition of fine particle additive liquid 1)
Methylene chloride: 99 parts by mass Fine particle dispersion 1: 5 parts by mass

Preparation of dope solution A dope solution having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. A cellulose acetate having an acetyl group substitution degree of 2.88, an ester compound, tinuvin 928, and the fine particle additive solution 1 were charged into a pressure dissolution tank containing a solvent while stirring. This was heated and dissolved completely with stirring. This was designated as Azumi Filter Paper No. A dope solution was prepared by filtration using 244.
(Dope solution composition)
Methylene chloride: 550 parts by mass Ethanol: 40 parts by mass Cellulose acetate (acetyl group substitution degree 2.88, number average molecular weight 130,000): 100 parts by mass Ester compound (aromatic terminal ester exemplified compound 2-16): 9 parts by mass Tinuvin 928 (Manufactured by BASF Japan): 2.6 parts by mass Fine particle additive solution 1: 5 parts by mass

Next, an endless belt casting apparatus was used to uniformly cast the dope solution on a stainless steel belt support at a temperature of 33 ° C. and a width of 1600 mm. The temperature of the stainless steel belt was controlled at 30 ° C.

On the stainless steel belt support, the solvent was evaporated until the amount of residual solvent in the cast (cast) film reached 75%, and then peeled off from the stainless steel belt support with a peeling tension of 130 N / m.

The peeled cellulose acetate film is adjusted so that the temperature of the housing 10 is adjusted using the tenter 4 shown in FIG. The hot air generating part G1 was installed, and the film was stretched in the width direction at a stretching ratio of 46% while adjusting the temperature so that the stretching temperature at the film end surface was 190 ° C. The residual solvent at the start of stretching was 10%.

The temperature of the film surface at the edge part and the central part was measured for each of the five points in the width direction of the film being conveyed using a contact-type handy thermometer (ANRITSU DIGITAL THREMOMETER HA-100K), and the average value was measured. It was set as the film temperature of the part.

Next, drying was completed and wound up while the drying zone was conveyed by a number of rolls. The drying temperature was 130 ° C. and the transport tension was 100 N / m.

Thus, a stretched cellulose ester film 1 having a film width of 2200 mm, a dry film thickness of 60 μm, and a length of 5000 m was produced.

Samples at 10 arbitrary positions were taken from the film, and the average values of retardation Ro and Rt were measured. As a result, they were Ro 5 nm and Rt 45 nm.

(Examples 2 to 13 and Comparative Examples 1 to 6)
In the production of the stretched cellulose ester film 1, the stretched cellulose ester film was similarly prepared except that the end stretching temperature, the center stretching temperature, the stretching ratio, the film thickness, and the film width after stretching were set as shown in Table 2. 2 to 19 were produced.

In addition, the stretched cellulose ester film 9 was produced by moving the end hot air generating portion G1 to the central portion so that the stretching temperature at the central portion was higher than that at the end.

<Evaluation>
The produced stretched cellulose ester films 1 to 19 were evaluated as follows.

(Measurement of surface roughness (Ra))
The average value of the surface roughness (Ra) of the edge H of the film was determined by measuring the surface roughness (Ra) at least 5 points in the width direction of the film from the end of the film, and calculating the average value thereof. The average value of the surface roughness (Ra) of the central portion T of the film was determined by measuring the surface roughness (Ra) at least 5 points in the width direction of the film across the center of the film, and calculating the average value thereof.

The surface roughness (Ra) was measured using a non-contact surface fine shape measuring apparatus WYKO HD3300 in accordance with JIS B 0601.

(Measurement of elastic modulus)
The average value of the elastic modulus at the end H of the film was determined by measuring the elastic modulus at a minimum of 5 points in the width direction of the film from the end of the film. The average value of the elastic modulus of the central portion T of the film was determined by measuring the elastic modulus of at least 5 points across the center of the film in the width direction of the film, and calculating the average value thereof.

The elastic modulus was measured in an environment of 23 ° C. and 55% RH using an ORIENTEC tensile tester RTC-1225A according to the method described in JIS-K-7127.

(Wrinkles where the direction of the groove or mountain is the transport direction)
Generation | occurrence | production of the wrinkle whose direction of a groove | channel or a peak is a conveyance direction was visually evaluated by the following evaluation criteria.
◎: Wrinkles whose groove or mountain direction is the conveyance direction were not confirmed at all ○: Wrinkles whose groove or mountain direction was the conveyance direction were not confirmed very much, or even if confirmed, there was a problem as a product ○ △: Wrinkles whose groove or mountain direction is the conveyance direction are confirmed even a little. ×: Wrinkles whose groove or mountain direction is the conveyance direction that cannot satisfy the product properties are confirmed. Xx: Wrinkles where the direction of the groove or mountain that does not satisfy the product is the conveying direction are continuously confirmed

(Folder wrinkles at high speed)
Generation | occurrence | production of the edge part wrinkle at the time of high-speed conveyance was visually evaluated on the following references | standards.
◎: No end wrinkling when transporting the film at high speed ○: Almost no wrinkling at the end when transporting the film at high speed ○ △: The film was transported at high speed Occasionally wrinkles occur at the end. ×: Frequent wrinkles occur at the end when the film is conveyed at high speed.

(Ro deviation)
After the end H of the stretched cellulose ester film produced by slitting removed, the resulting film samples were taken from the width direction end portion H ₁ and the central portion T (hereinafter, also referred to as a slit-removed film). Then, in the environment of 23 ° C. and 55% RH, the in-plane retardation Ro at a wavelength of 590 nm was measured using KOBRA-WR (Oji Scientific Instruments).
Formula (i) Ro = (nx−ny) × d
Formula (ii) Rt = ((nx + ny) / 2−nz) × d
(In the formula, Ro is the retardation value in the film plane, Rt is the retardation value in the film thickness direction, nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, (nz represents the refractive index in the thickness direction of the film, and d represents the thickness (nm) of the film.)

The end H ₁ refers to a portion extending from the end of the film to L ₁ × 0.05 in the width direction when the width (full width) of the slit-removed film is L ₁ ; the center T is the film The portion from the center of the line to ± L ₁ × 0.1 in the width direction.

And the dispersion | variation (Ro deviation) for every site | part of the film of retardation Ro of an in-plane direction was evaluated on the following evaluation criteria.
○: Ro deviation - less than (the value of the central portion T value of the end portion _{H 1)} 0.5 ○ △: deviation Ro (the value of the central portion T - value of the end portion _{H 1)} is 0.5 or more 1 Less than 0.0 Δ: Deviation of Ro (value of central portion T−value of edge H ₁ ) is 1.0 or more and less than 2.0 ×: Deviation of Ro (value of central portion T−value of edge H ₁ ) Is 2.0 or more

The above evaluation results are shown in Table 2.

From the results shown in Table 2, the stretched cellulose ester films 1 to 3, 5, 7 to 8, 10, 12, and 15 to 19 of the present invention generated wrinkles extending in the transport direction with respect to the stretched cellulose ester film of the comparative example. , occurrence of wrinkles broken end of a high speed transport is suppressed, and since the deviation of the in-plane retardation value of the central portion T and the end portion H ₁ in the slit-removed film is small, it is also suppressed variations in the optical properties I understood that.

(Example 14)
A dope solution having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose ester having a acetyl group substitution degree of 1.90, a propionyl group substitution degree of 0.70, and a total acyl group substitution degree of 2.60, a sugar ester compound, an ester compound, and tinuvin 928 The fine particle addition liquid 1 was added while stirring. This was heated and dissolved completely with stirring. This was designated as Azumi Filter Paper No. A dope solution was prepared by filtration using 244.
(Dope solution composition)
Methylene chloride: 550 parts by weight Ethanol: 40 parts by weight Cellulose acetate (acetyl group substitution degree 1.90, propionyl group substitution degree 0.70, total acyl group substitution degree 2.60, number average molecular weight 120,000): 100 parts by weight sugar ester Compound (Exemplary Compound 1-7): 5 parts by mass Ester Compound (Aromatic Terminal Ester Exemplified Compound 2-16): 5 parts by mass Tinuvin 928 (manufactured by BASF Japan): 2.6 parts by mass Fine particle additive solution 1: 4 parts by mass Part

Next, an endless belt casting apparatus was used to uniformly cast the dope solution on a stainless steel belt support at a temperature of 33 ° C. and a width of 1800 mm. The temperature of the stainless steel belt was controlled at 30 ° C.

Thus, a stretched cellulose ester film 21 having a film width of 2400 mm, a dry film thickness of 60 μm, and a length of 5000 m was produced.

When samples of 10 points at arbitrary positions were collected from the film and the average values of the retardations Ro and Rt were measured, they were Ro 50 nm and Rt 135 nm and had good phase difference performance.

(Examples 15 to 17)
In the production of the stretched cellulose ester film 21, stretched cellulose ester films 22 to 24 were produced in the same manner except that the types of sugar ester compound and ester compound were changed as shown in Table 3. When the sugar ester compound and the ester compound were used alone, 10 parts by mass were added.

Using the obtained stretched cellulose ester films 21 to 24, in the same manner as in Example 1, measurement of surface roughness (Ra), measurement of elastic modulus, evaluation of wrinkles, end wrinkles at high speed conveyance, Ro deviation, and When the following haze was evaluated, as shown in Table 3, it was a stretched cellulose ester film that reproduced Example 1 and had good characteristics, and it was confirmed that haze was lowered when a sugar ester compound was used.

(Haze)
One film sample is measured according to ASTM-D1003-52 using T-2600DA manufactured by Tokyo Denshoku Industries Co., Ltd., and the haze is ranked and evaluated as follows.

◎: Haze less than 0.15% ○: Haze 0.15% or more and less than 0.3% △: Haze 0.3% or more and less than 0.5% ×: Haze 0.5% or more

This application claims priority based on Japanese Patent Application No. 2011-029477 filed on Feb. 15, 2011. The contents described in the application specification and the drawings are all incorporated herein.

Fo Unstretched cellulose ester film F Stretched cellulose ester film 1 Stainless steel endless belt (support)
3 Peeling roll 4 Tenter 5 Drying device 6 Transport roll 8 Winding roll

Claims

The width of the stretched cellulose ester film is L; the portion from the end of the stretched cellulose ester film to L × 0.05 in the width direction of the film is the end H; and the center of the stretched cellulose ester film in the width direction of the film When the portion up to ± L × 0.1 is the central portion T,
The average value of the surface roughness (Ra) of the end portion H of at least one surface of the stretched cellulose ester film is in the range of 1.7 nm to 4.0 nm, and the surface roughness (Ra) of the central portion T is 0.1 nm to 1.0 nm higher than the average value,
A stretched cellulose ester film having an average elastic modulus of the central portion T in a range of 3.0 GPa to 8.0 GPa and higher by 0.1 GPa to 2.0 GPa than an average elastic modulus of the end portion H.
The average value of the surface roughness (Ra) of the end portion H of at least one surface of the stretched cellulose ester film is in the range of 2.2 nm to 3.5 nm, and the surface roughness (Ra) of the central portion T is 0.3 nm to 1.0 nm higher than the average value,
The stretching according to claim 1, wherein the average value of the elastic modulus of the central portion T is 0.3 GPa to 1.0 GPa higher than the average value of the elastic modulus of the end portion H in the range of 4.0 GPa to 7.0 GPa. Cellulose ester film.
2. The stretched cellulose ester film according to claim 1, wherein the stretched cellulose ester film has a width of 2 to 3 m and a film thickness of 20 to 70 μm.
The stretched cellulose ester film according to claim 1, wherein the stretched cellulose ester film is a wound body wound in a direction perpendicular to the width direction of the film.
A step of preparing a dope by dissolving cellulose ester in a solvent; a step of casting the dope on an endless metal support; and drying the cast dope, and then peeling off the metal support from the metal support. The method for producing a stretched cellulose ester film according to claim 1, comprising a step of obtaining a stretched cellulose ester film and a step of stretching the unstretched cellulose ester film to obtain a stretched cellulose ester film.
The width of the unstretched cellulose ester film is Lo; the portion from the end of the unstretched cellulose ester film to Lo × 0.05 is the end Ho in the width direction of the film; and the unstretched cellulose ester is in the width direction of the film When the portion from the center of the film to ± Lo × 0.1 is the central portion To,
The surface temperature of the end portion Ho of the surface A opposite to the surface in contact with the metal support of the unstretched cellulose ester film is 10 ° C. to 50 ° C. than the surface temperature of the central portion To of the surface A. A method for producing a stretched cellulose ester film, wherein the stretched cellulose ester film is stretched while being raised at a temperature.
Arranging at least a pair of end hot air generating portions for adjusting the surface temperature so as to face the end of the surface A of the unstretched cellulose ester film,
While blowing hot air having a temperature 10 ° C. to 50 ° C. higher than the surface temperature of the central portion To of the surface A to the end portion Ho of the surface A of the unstretched cellulose ester film from the end hot air generating portion, The method for producing a stretched cellulose ester film according to claim 5, wherein the unstretched cellulose ester film is stretched.
The method for producing a stretched cellulose ester film according to claim 5, further comprising a winding step of winding the stretched cellulose ester film in a direction perpendicular to the width direction of the film.
6. The method for producing a stretched cellulose ester film according to claim 5, wherein, in the stretching treatment, the unstretched cellulose ester film is stretched at a stretch ratio of 25% to 100% in the width direction of the film.