JP2010217846A - Cellulose ester film, polarizing plate, liquid crystal display device, and melt-cast film forming method of cellulose ester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cellulose ester film and a method for producing the film, in which the film has a large Ro, a small Nz coefficient, and small variation in the internal haze and orientation angle, and also to provide a polarizing plate and a liquid crystal display device with high productivity and high contrast. <P>SOLUTION: The cellulose ester film is characterized in that: Ro and Nz described below satisfy 100≤Ro≤180 and 0.8≤Nz≤1.3; the whole haze Ht of a single film satisfies 0.1≤Ht≤0.3; a ratio Hi/Ht of the internal haze Hi to the whole haze satisfies 0.1≤Hi/Ht≤0.5; the film has a slow phase axis in a width direction, the variance of orientation angles of the slow phase axis is ±0.2 degree; and the amount of solvents included in the cellulose ester film with respect to the whole mass of the film is not more than 0.01 mass%. Ro and Nz are defined by a formula 1: Ro=(nx-ny)×d and a formula 2: Nz=(nx-nz)/(nz-ny), wherein Ro represents an in-plane retardation value of the cellulose ester film, nx represents the refractive index in the direction of the slow phase axis in the film plane, ny represents the refractive index in a direction perpendicular to the slow phase axis, nz represents the refractive index in the film thickness direction, and d represents the film thickness (nm) of the film. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a cellulose ester film, a polarizing plate, a liquid crystal display device, and a method for producing a cellulose ester.

  The demand for liquid crystal display devices is expanding in applications such as liquid crystal televisions and personal computer liquid crystal displays. In general, a liquid crystal display device is composed of a liquid crystal cell in which a transparent electrode, a liquid crystal layer, a color filter, etc. are sandwiched between glass plates, and two polarizing plates provided on both sides thereof. The optical element (polarizing plate protective film) is sandwiched between a child (also referred to as a polarizing film or a polarizing film).

  As this polarizing plate protective film, a cellulose ester film is usually used.

  As a retardation film used for a high-contrast VA liquid crystal display device, it is known that a film having 100 ≦ Ro ≦ 200 nm and a small Nz coefficient is suitable (Patent Documents 1 to 3).

  As a method for producing a retardation film that achieves this condition, Patent Document 1 describes a method for producing a film in an ideal Rt / Ro range by stretching at a high stretch ratio. Is too high, the haze (especially internal haze) tends to be high, and there is a problem that the contrast does not increase as expected.

  Further, Patent Document 2 describes a method of stretching in the transport direction at the free end in solution casting film formation. However, in this method, the slow axis is directed in the transport direction, and therefore roll tow The roll (Roll to Roll) could not be bonded to the polarizer, the sheet was bonded, the productivity was poor, and the problem of haze (particularly internal haze) has not yet been solved.

  Patent Document 3 proposes a method in which the film is stretched in the width direction by a tenter and then thermally contracted in the transport direction.

  With this method, it is possible to bond with a polarizer in Roll to Roll, and the productivity is improved. However, since Ro and Rt change at the same time, adjustment to a target retardation value is difficult. In addition, it is difficult to control the orientation angle, and the improvement of haze (particularly internal haze) is insufficient, and a desired high contrast has not been obtained yet.

  Patent Document 4 proposes a technique regarding a cellulose ester in which a specific plasticizer is used and the retardation distribution is stabilized.

JP 2002-62430 A JP 2008-279724 A JP 2008-287218 A JP 2008-257220 A

  An object of the present invention is to provide a cellulose ester film having a large Ro, a small Nz coefficient and a small variation in internal haze and orientation angle, and a method for producing the same, and a polarizing plate and a liquid crystal display device having high productivity and high contrast. Is to provide.

  The above object of the present invention is achieved by the following configurations.

  1.100 ≦ Ro ≦ 180 and 0.8 ≦ Nz ≦ 1.3 are satisfied, the total haze Ht in one film is 0.1 ≦ Ht ≦ 0.3, and the ratio of the internal haze Hi to the total haze Hi / Ht is 0.1 ≦ Hi / Ht ≦ 0.5, has a slow axis in the width direction, variation in orientation angle of slow axis is ± 0.2 degrees, and the whole cellulose ester film A cellulose ester film, wherein the content of the solvent is 0.01% by mass or less based on the mass.

Formula 1 Ro = (nx−ny) × d
Formula 2 Nz = (nx−nz) / (nx−ny)
(Ro represents the in-plane retardation value of the cellulose ester film. The refractive index in the slow axis direction in the film plane is nx, the refractive index in the direction perpendicular to the slow axis is ny, and the refractive index in the film thickness direction. Nz and d represent the film thickness (nm), respectively.)
Total haze (Ht): Haze value (%) measured according to JISK7136.

  Internal haze (Hi): Haze value (%) measured by dropping a few drops of glycerin on the surface of the film and sandwiching it from two sides with two 1.3 mm thick glass plates (MICRO SLIDE GLASS part number S9213, manufactured by MATSANAMI) ) Is a value (%) obtained by subtracting the haze value measured in a state where a few drops of glycerin are dropped between two glasses.

  2. A polarizing plate comprising the cellulose ester film as described in 1 above.

  3. 3. A liquid crystal display device comprising the polarizing plate described in 2 above.

  4). A step of producing a melt by heating and melting a composition containing a cellulose ester to a temperature exhibiting fluidity, a step of casting and cooling the melt to form a film, and a width of the film by a tenter A step of stretching in the direction, a step of heat-treating the stretched film-like material at Tg−20 ° C. to Tg + 20 ° C., and a step of stretching in the width direction while shrinking the heat-treated film-like material in the transport direction. A method for melt casting a cellulose ester film.

  In addition, Tg represents the glass transition temperature of the composition containing a cellulose ester.

  INDUSTRIAL APPLICABILITY According to the present invention, a cellulose ester film having a large Ro, a small Nz coefficient and a small variation in internal haze and orientation angle, and a method for producing the same, and a highly productive and high contrast cellulose ester film, polarizing plate, and liquid crystal display An apparatus and a method for producing a cellulose ester can be provided.

It is a schematic diagram which shows the state which dripped glycerin on the slide glass. It is a schematic diagram which shows the state which put the sample film on glycerol. It is a schematic diagram which shows the state which dripped glycerin on the sample film. It is a schematic diagram which shows the state which put the cover glass on glycerol. It is the outline | summary of the apparatus which manufactures the cellulose ester of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described in detail.

  As a result of intensive studies in view of the above problems, the present inventors have satisfied 100 ≦ Ro ≦ 180 and 0.8 ≦ Nz ≦ 1.3, and the total haze Ht of one film is 0.1 ≦ Ht ≦ 0.3. The ratio of the internal haze Hi to the total haze is 0.1 ≦ Hi / Ht ≦ 0.5, the slow axis is in the width direction, and the variation of the orientation angle of the slow axis is within ± 0.2 degrees. And a cellulose ester film characterized in that the content of the solvent is 0.01% by mass or less with respect to the total mass of the cellulose ester film, whereby a polarizing plate and a liquid crystal display device having high productivity and high contrast are obtained. As a result, the inventors have found that the present invention can be obtained and have made the present invention.

  The retardation Ro in the in-plane direction of the cellulose ester film of the present invention is preferably in the range of 100 to 180 nm, and Nz is in the range of 0.8 to 1.3.

Formula 1 Ro = (nx−ny) × d
Formula 2 Nz = (nx−nz) / (nx−ny)
(Where nx is the maximum refractive index in the film plane, ny is the refractive index in the direction perpendicular to nx, nz is the refractive index in the film thickness direction, and d is the thickness (nm) of the film.)
In addition, Ro calculates | requires the average refractive index of a sample from the Abbe's refractometer, and also in 23 degreeC and 55% RH environment using automatic birefringence meter KOBRA-21ADH (made by Oji Scientific Instruments). Thus, three-dimensional refractive index measurement is performed at a wavelength of 590 nm, and the obtained value of the phase difference and the average refractive index can be obtained by calculation.

  The haze of the retardation film of the present invention was measured in a turbidimeter (NDH2000, Nippon Denshoku Industries Co., Ltd.) in a film that was allowed to stand for 24 hours in an environment of 23 ° C. and 55% RH. .

Total haze (Ht): Haze value measured according to JISK7136 Internal haze (Hi): A few drops of glycerin are dropped on the surface of the film, and a glass plate having a thickness of 1.3 mm (MICRO SLIDE GLASS product number S9213, manufactured by MATSUNAMI) It means a value (%) obtained by subtracting a haze value measured in a state where several drops of glycerin are dropped between two sheets of glass from a haze value (%) measured with two sheets sandwiched from both sides.

  The internal haze measurement is performed as follows. Description will be given with reference to FIGS.

First, the blank haze 1 of a measuring instrument other than a film is measured.
1. Drip a drop (0.05 ml) of glycerin on a cleaned glass slide. At this time, care is taken so that bubbles do not enter the droplet. Be sure to use glass that has been cleaned with a detergent because it may look dirty even if it looks clean. See FIG. Place the cover glass on top of it. Glycerin spreads without pressing the cover glass.
3. Set on a haze meter and measure blank haze 1.

Next, the haze 2 including the sample is measured.
4). Glycerol is dropped on the slide glass. (0.05 ml) See FIG. A sample film to be measured is placed thereon. See FIG. Glycerol is dropped on the sample film. (0.05 ml) See FIG. Place the cover glass on top of it. See FIG. Set in a haze meter and measure haze 2.
9. (Haze 2) − (Haze 1) = (Internal haze of the present invention) is calculated.

  The glass and glycerin used in the above measurement are as follows.

Glass: MICRO SLIDE GLASS S9213 MATUNAMI
Glycerin: Kanto Kagaku Deer Special Grade The total haze of the retardation film of the present invention is preferably 0.1 ≦ Ht ≦ 0.3, more preferably 0.1 ≦ Ht ≦ 0.2.

  In addition, OPTIPRO (XY scanning stage, halogen lamp light + 550 nm interference filter) was used for the variation in orientation angle. At this time, the measurement area was 60 mm × 60 mm, and measurement was performed at intervals of 4 mm using a beam with a diameter of 3 mm. The difference between the maximum value and the minimum value of the orientation angle in the range of 60 mm × 60 mm measured in this way was regarded as variation.

  In the present invention, the front contrast is defined as a front contrast value in black display measured using EZ-Contrast 160D manufactured by ELDIM.

  Hereinafter, each element of the present invention will be described in detail.

<Cellulose ester>
The cellulose ester used in the present invention is a carboxylic acid ester having about 2 to 22 carbon atoms, may be an aromatic carboxylic acid ester, and is particularly preferably a lower fatty acid ester of cellulose.

  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.

  When the substitution degree is the same, the number of carbon atoms is preferably selected from an acyl group having 2 to 6 carbon atoms. The cellulose ester of the present invention preferably satisfies the following formulas (i) and (ii) at the same time.

Formula (i) 2.2 ≦ X + Y ≦ 2.7
Formula (ii) 0.5 ≦ Y ≦ 1.5
In the formula, X represents the degree of substitution of the acetyl group, Y represents the degree of substitution of the propionyl group or butyryl group, and X + Y represents the degree of substitution of the total acyl group.

  Of these, cellulose acetate propionate is particularly preferably used. The measuring method of the substitution degree of an acyl group can be measured according to ASTM-D817-96.

  The molecular weight of the cellulose ester is preferably 60000-300000, more preferably 60000-200000 in terms of number average molecular weight (Mn).

  The cellulose ester used in the present invention preferably has a weight average molecular weight (Mw) / number average molecular weight (Mn) ratio of 4.0 or less, more preferably 1.2 to 3.5.

  Since the average molecular weight and molecular weight distribution of cellulose ester can be measured using gel permeation chromatography (GPC), the number average molecular weight (Mn) and the weight average molecular weight (Mw) are calculated using this, and the ratio is calculated. be able to.

  The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min Calibration curve:
Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corp.) Mw = 1,000,000-500 calibration curves with 13 samples were used. The 13 samples are preferably used at approximately equal intervals.

  The cellulose ester of the present invention can be synthesized by a known method. However, the synthesized cellulose ester can be purified to remove low molecular weight components, or components having no acetylation or low acetylation degree can be removed by filtration. Is also preferably performed.

  Cellulose esters are also affected by trace metal components in cellulose esters. 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 residual sulfuric acid content in the cellulose ester of the present invention is preferably in the range of 0.1 to 45 ppm in terms of elemental sulfur. These are considered to be contained in the form of salts.

  When the residual sulfuric acid content exceeds 45 ppm, there is a tendency that deposits on the die lip portion during heat melting increase. In addition, there is a tendency to break easily during slitting at the time of hot drawing or after hot drawing. Therefore, the range of 1-30 ppm is more preferable. The residual sulfuric acid content can be measured by the method prescribed in ASTM D817-96.

  The free acid content in the cellulose ester of the present invention is preferably 1 to 500 ppm. Within the above range, there is no increase in deposits on the die lip and it is difficult to break.

  Furthermore, about this invention, it is preferable that it is the range of 1-100 ppm, and the range of 1-70 ppm is especially preferable. The free acid content can be measured by the method prescribed in ASTM D817-96. By washing the synthesized cellulose ester more sufficiently than when used in the solution casting method, the residual alkaline earth metal content, residual sulfuric acid content, and residual acid content are within the above ranges. Can be preferred.

  In addition to washing with water, cellulose ester can be washed with a poor solvent such as methanol or ethanol, or as a result, a poor solvent and a mixed solvent of a good solvent can be used. Low molecular organic impurities can be removed.

Moreover, it is preferable that the cellulose ester of this invention has few bright spot foreign materials when it is made into a film. The bright spot foreign matter preferably has a bright spot diameter of 0.01 mm or more and 200 pieces / cm ² or less, more preferably 100 pieces / cm ² or less, and preferably 50 pieces / cm ² or less. 30 / cm ² or less, preferably 10 / cm ² or less, and most preferably none.

Moreover, it is preferable that it is 200 pieces / cm < ² > or less also about a bright spot of 0.005-0.01 mm or less, Furthermore, it is preferable that it is 100 pieces / cm < ² > or less, and it is 50 pieces / cm < ² > or less. The number is preferably 30 pieces / cm ² or less, more preferably 10 pieces / cm ² or less, and most preferably none.
<Additives>
The cellulose ester film in the present invention includes a plasticizer that imparts processability, flexibility, and moisture resistance to the film, an antioxidant that prevents deterioration of the film, a colorant that adjusts the yellow index and reduces haze, and ultraviolet light. You may contain the ultraviolet absorber which provides an absorption function, the microparticles | fine-particles (matting agent) which provide slipperiness to a film, the retardation adjusting agent which adjusts the retardation of a film, etc.

<Plasticizer>
There are no particular limitations on the plasticizer used, but a cellulose derivative or a polycondensate of a reactive metal compound capable of hydrolytic polycondensation and hydrogen so as not to generate haze, bleed out or volatilize from the film. It preferably has a functional group capable of interacting by bonding or the like.

  Examples of such functional groups include hydroxyl groups, ether groups, carbonyl groups, ester groups, carboxylic acid residues, amino groups, imino groups, amide groups, imide groups, cyano groups, nitro groups, sulfonyl groups, sulfonic acid residues, Examples thereof include a phosphonyl group and a phosphonic acid residue, and a carbonyl group, an ester group and a phosphonyl group are preferred.

Examples of such plasticizers include phosphate ester plasticizers, phthalate ester plasticizers, trimellitic ester plasticizers, pyromellitic acid plasticizers, polyhydric alcohol plasticizers, glycolate plasticizers. Citric acid ester plasticizers, fatty acid ester plasticizers, carboxylic acid ester plasticizers, polyester plasticizers, sugar plasticizers, acrylic polymers, etc. can be preferably used, especially polyhydric alcohol plasticizers It is preferable to use a polyester plasticizer.
(Polyhydric ester plasticizer)
The organic acid of the present invention is represented by the following general formula (1).

In the formula, R _{1 to} R ₅ represent a hydrogen atom or a cycloalkyl group, an aralkyl group, an alkoxy group, a cycloalkoxy group, an aryloxy group, an aralkyloxy group, an acyl group, a carbonyloxy group, an oxycarbonyl group, or an oxycarbonyloxy group. These may be further substituted. L represents a linking group and represents a substituted or unsubstituted alkylene group, an oxygen atom, or a direct bond.

The cycloalkyl group represented by R ₁ to R _5, preferably a cycloalkyl group having 3 to 8 carbon atoms, specifically cyclopropyl, cyclopentyl, groups such as cyclohexyl. These groups may be substituted, and preferred substituents include halogen atoms such as chlorine atom, bromine atom, fluorine atom, hydroxyl group, alkyl group, alkoxy group, cycloalkoxy group, aralkyl group (this phenyl group). The group may be further substituted with an alkyl group or a halogen atom), an alkenyl group such as a vinyl group or an allyl group, or a phenyl group (this phenyl group may be further substituted with an alkyl group or a halogen atom). Phenoxy group (this phenyl group may be further substituted by an alkyl group or a halogen atom), an acyl group having 2 to 8 carbon atoms such as an acetyl group or a propionyl group, an acetyloxy group, or a propionyloxy group. And an unsubstituted carbonyloxy group having 2 to 8 carbon atoms such as a group.

The aralkyl group represented by R _{1 to} R ₅ represents a group such as a benzyl group, a phenethyl group, and a γ-phenylpropyl group, and these groups may be substituted. Preferred substituents include The group which may be substituted with the said cycloalkyl group can be mentioned similarly.

Examples of the alkoxy group represented by R _{1 to} R ₅ include an alkoxy group having 1 to 8 carbon atoms, specifically, methoxy, ethoxy, n-propoxy, n-butoxy, n-octyloxy, isopropoxy. , Alkoxy groups such as isobutoxy, 2-ethylhexyloxy, or t-butoxy.

  These groups may be substituted, and preferred substituents include halogen atoms such as chlorine atom, bromine atom, fluorine atom, hydroxyl group, alkoxy group, cycloalkoxy group, aralkyl group (this phenyl group). May be substituted with an alkyl group or a halogen atom), an alkenyl group, a phenyl group (this phenyl group may be further substituted with an alkyl group or a halogen atom), an aryloxy group (for example, phenoxy) An acyl group such as an acetyl group or a propionyl group, or an aryl group such as an acetyloxy group or a propionyloxy group (the phenyl group may be further substituted with an alkyl group or a halogen atom). Arylcarbonyl groups such as unsubstituted acyloxy groups and benzoyloxy groups Shi group.

Examples of the cycloalkoxy group represented by R _{1 to} R ₅ include an unsubstituted cycloalkoxy group having 1 to 8 carbon atoms, specifically cyclopropyloxy, cyclopentyloxy, cyclohexyloxy. And the like.

  In addition, these groups may be substituted, and preferred substituents include the same groups that may be substituted with the cycloalkyl group.

Examples of the aryloxy group represented by R _{1 to} R ₅ include a phenoxy group, and the phenyl group includes a substituent that may be substituted with the cycloalkyl group such as an alkyl group or a halogen atom. May be substituted.

Examples of the aralkyloxy group represented by R _{1 to} R ₅ include a benzyloxy group and a phenethyloxy group, and these substituents may be further substituted. Preferred substituents include the above cycloalkyl The group which may be substituted with a group can be mentioned similarly.

Examples of the acyl group represented by R _{1 to} R ₅ include an unsubstituted acyl group having 2 to 8 carbon atoms such as an acetyl group and a propionyl group (the hydrocarbon group of the acyl group includes alkyl, alkenyl, alkynyl). These substituents may be further substituted, and preferred substituents include the same groups that may be substituted with the cycloalkyl group.

As the carbonyloxy group represented by R _{1 to} R ₅ , an unsubstituted acyloxy group having 2 to 8 carbon atoms such as acetyloxy group and propionyloxy group (the hydrocarbon group of the acyl group is alkyl, alkenyl, alkynyl). And arylcarbonyloxy groups such as a benzoyloxy group, and these groups may be further substituted with the same groups as those which may be substituted with the cycloalkyl group.

The oxycarbonyl group represented by R _{1 to} R ₅ represents an alkoxycarbonyl group such as a methoxycarbonyl group, an ethoxycarbonyl group or a propyloxycarbonyl group, or an aryloxycarbonyl group such as a phenoxycarbonyl group.

  These substituents may be further substituted, and preferred examples of the substituent include the same groups that may be substituted with the cycloalkyl group.

The oxycarbonyloxy group represented by R _{1 to} R ₅ represents an alkoxycarbonyloxy group having 1 to 8 carbon atoms such as a methoxycarbonyloxy group, and these substituents may be further substituted and are preferably substituted. Examples of the group include the same groups that may be substituted on the cycloalkyl group.

Any one of R _{1 to} R ₅ may be connected to each other to form a ring structure.

The linking group represented by L represents a substituted or unsubstituted alkylene group, an oxygen atom, or a direct bond, and the alkylene group is a group such as a methylene group, an ethylene group, or a propylene group. These groups may be further substituted with the groups mentioned as groups that may be substituted with the groups represented by R _{1 to} R ₅ .

  Among these, a direct bond and an aromatic carboxylic acid are particularly preferable as the linking group represented by L.

In addition, the organic acid represented by the general formula (1) constituting the ester compound serving as a plasticizer in the present invention includes at least R ₁ or R ₂ having the alkoxy group, acyl group, oxycarbonyl group, carbonyl group. Those having an oxy group or an oxycarbonyloxy group are preferred. A compound having a plurality of substituents is also preferred.

  In the present invention, the organic acid for substituting the hydroxyl group of the trivalent or higher alcohol may be a single type or a plurality of types.

  In the present invention, the trihydric or higher alcohol compound that reacts with the organic acid represented by the general formula (1) to form a polyhydric alcohol ester compound is preferably a 3-20 valent aliphatic polyhydric alcohol. In the present invention, the trihydric or higher alcohol is preferably represented by the following general formula (2).

General formula (2) R '-(OH) m
In the formula, R ′ represents an m-valent organic group, m represents a positive integer of 3 or more, and the OH group represents an alcoholic hydroxyl group. Particularly preferred is a polyhydric alcohol having 3 or 4 as m.

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

  Adonitol, arabitol, 1,2,4-butanetriol, 1,2,3-hexanetriol, 1,2,6-hexanetriol, glycerin, diglycerin, erythritol, pentaerythritol, dipentaerythritol, tripentaerythritol, ga Examples include lactitol, inositol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, and xylitol.

  In particular, glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol are preferable.

  The ester of the organic acid represented by the general formula (1) and the trihydric or higher polyhydric alcohol represented by the general formula (2) can be synthesized by a known method. In the examples, typical synthesis examples are shown. For example, the organic acid represented by the general formula (1) and the polyhydric alcohol represented by the general formula (2) are condensed and esterified in the presence of an acid. There are a method, an organic acid in advance as an acid chloride or an acid anhydride, a method of reacting with a polyhydric alcohol, a method of reacting a phenyl ester of an organic acid and a polyhydric alcohol, etc. It is preferable to select a method with good yield.

  As a plasticizer comprising an organic acid represented by the general formula (1) and an ester of a trihydric or higher polyhydric alcohol represented by the general formula (2), a compound represented by the following general formula (3) is preferable. .

In the formula, R _{6 to} R ₂₀ represent a hydrogen atom or a cycloalkyl group, an aralkyl group, an alkoxy group, a cycloalkoxy group, an aryloxy group, an aralkyloxy group, an acyl group, a carbonyloxy group, an oxycarbonyl group, or an oxycarbonyloxy group. These may be further substituted. R ₂₁ represents a hydrogen atom or an alkyl group.

The cycloalkyl group, the aralkyl group, the alkoxy group, the cycloalkoxy group, the aryloxy group, the aralkyloxy group, the acyl group, the carbonyloxy group, the oxycarbonyl group, and the oxycarbonyloxy group of R _{6 to} R ₂₀ are represented by the general formula ( The same group as R < ₁ > -R < ₅ > of 1) is mentioned.

  Below, the specific compound of the polyhydric alcohol ester concerning this invention is illustrated.

The content of the polyhydric alcohol ester according to the present invention is preferably 1 to 30% by mass and particularly preferably 5 to 20% by mass in the cellulose ester film.
(Polyester plasticizer)
Among polyester plasticizers, it is particularly preferable to use a polyester polyol. The polyester polyol has a dehydration condensation reaction between a glycol (a) having an average carbon number of 2 to 3.5 and a dibasic acid (b) having an average carbon number of 4 to 5.5, or the glycol (a ) And a dibasic acid anhydride (b) having an average carbon number of 4 to 5.5, and a conventional method by dehydration condensation reaction.

  Examples of the glycol (a) used in the polyester polyol include ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 2-methyl-1,3-propanediol, and 1,4-butylene glycol. , Neopentyl glycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, and the like. These may be used alone or in combination of two or more. For example, ethylene glycol, or ethylene glycol and diethylene glycol A mixture of these is particularly preferably used.

  Regarding the glycol (a), it is important that the average number of carbon atoms of the glycol (a) is in the range of 2 to 3.5. When the average number of carbon atoms of the glycol (a) is smaller than 2, it is difficult to produce a polyester polyol, and when it is larger than 3.5, the compatibility with cellulose is deteriorated, and the cellulose ester having poor physical properties such as transparency. Become a film. The glycol (a) preferably has an average carbon number of 2.1 to 2.8 or 3.2 to 3.5, and by using the glycol (a) in such a range, The crystallinity and melting point are close to those of conventional ones, and the productivity itself is good.

  When a mixture of ethylene glycol and diethylene glycol is used as the glycol (a), the ethylene glycol / diethylene glycol molar ratio is preferably 25 to 100/75 to 0, and is excellent in compatibility with the cellulose ester. More preferably, it is 25-40 / 75-60, and 60-95 / 40-5, and by adjusting to such a range, the crystallinity and melting point of the polyester polyol are close to those of conventional ones, Productivity is also improved.

  Next, examples of the dibasic acid (b) constituting the polyester polyol used in the present invention include succinic acid, glutaric acid, adipic acid, and sebacic acid. These may be used alone or in combination of two or more. For example, succinic acid or a mixture of succinic acid and terephthalic acid is particularly preferably used.

  Moreover, regarding the above-mentioned dibasic acid (b), it is important that the average carbon number of the dibasic acid (b) is in the range of 4 to 5.5. When the average number of carbon atoms of the dibasic acid (b) is smaller than 4, it is difficult to produce a polyester polyol, and when it is larger than 5.5, the compatibility with cellulose is deteriorated and physical properties such as transparency are deteriorated. It becomes an inferior cellulose film.

  The dibasic acid (b) preferably has an average carbon number of 4.1 to 4.8 or 5.2 to 5.5, and by using the dibasic acid (b) in such a range, The crystallinity and melting point of the polyester polyol are close to conventional ones, and the productivity and storage stability of the polyester polyol are also good.

  When a mixture of succinic acid and terephthalic acid is used as the dibasic acid (b), the succinic acid / terephthalic acid molar ratio is preferably 25 to 100/75 to 0.

  The glycol (a) and dibasic acid (b) constituting the polyester polyol used in the present invention include combinations other than the above, but the average number of carbon atoms of the glycol (a) and dibasic acid (b) The combination whose total with the average of carbon number is 6-7.5 is preferable.

  The polyester polyol obtained from the glycol (a) and the dibasic acid (b) may have a number average molecular weight in the range of 1,000 or more and 200,000 or less, more preferably 1000 to 5,000 basically hydroxyl-terminated polyester. A number average molecular weight of 1200 to 4000 is particularly preferably used. By using a polyester polyol having a number average molecular weight in such a range, the compatibility with the cellulose ester is excellent.

  In order to obtain the effects of the present invention, the polyester polyol having the number average molecular weight of 1000 or more is preferably contained in the film in an amount of 10 to 30% by mass. More preferably, it is 10-20 mass%. When the number average molecular weight is larger than the above range, the compatibility is deteriorated and the effect of reducing moisture permeability is thin, but rather the retention property tends to be deteriorated. Therefore, the range of the number average molecular weight as described above is preferable.

  Actually, the content of the polymer in the film depends on the type of polymer and the weight average molecular weight, and the performance such as dimensional stability, retentivity, and transmittance is within the range where dope, web, and phase separation does not occur after film formation. It is decided accordingly.

  On the other hand, the carboxyl group terminal in the polyester polyol used in the present invention reduces the effect of improving the physical properties of the cellulose ester modifier of the present invention, so its content is less than 1/20 mol of the hydroxyl terminal. It is preferable that it is a number, and it is more preferable to stop at 1/40 or less.

  In producing the above-described polyester polyol, conventionally known esterification catalysts such as metal organic acid salts or metal chelate compounds such as titanium, zinc, lead and zirconium, or antimony oxide can be used. As the esterification catalyst, for example, tetraisopropyl titanate, tetrabutyl titanate and the like are preferably used, and 0.0005 to 0.02 mass relative to 100 mass parts in total of glycol (a) and dibasic acid (b) used. Are preferably used.

  Polycondensation of the polyester polyol is performed by a conventional method. For example, a direct reaction between the dibasic acid and glycol, the dibasic acid or an alkyl ester thereof, for example, a polyesterification reaction or transesterification reaction between a dibasic acid methyl ester and a glycol, or a hot melt condensation method, Alternatively, the polyester polyol which can be easily synthesized by any method of dehydrohalogenation reaction of acid chloride of these acids and glycol, but the polyester polyol whose number average molecular weight is not so large is preferably by direct reaction.

  The polyester polyol having a high distribution on the low molecular weight side has very good compatibility with the cellulose ester, and after forming the film, a water vapor permeability is small, and a cellulose ester film rich in transparency can be obtained.

  A conventional method can be used as a method for adjusting the molecular weight without particular limitation. For example, although depending on the polymerization conditions, the amount of these monovalent compounds can be controlled by a method of blocking the molecular ends with a monovalent acid or monovalent alcohol. In this case, a monovalent acid is preferable from the viewpoint of polymer stability. For example, acetic acid, propionic acid, butyric acid, pivalic acid, benzoic acid and the like can be mentioned, but during the polycondensation reaction, such monovalent acid is not removed from the system but stopped and removed from the reaction system. Those which are easy to be distilled off when being removed from the system are selected, but these may be mixed and used.

  In the case of direct reaction, the number average molecular weight can also be adjusted by measuring the timing at which the reaction is stopped by the amount of water distilled off during the reaction. In addition, it can be adjusted by biasing the number of moles of glycol or dibasic acid to be charged or by controlling the reaction temperature.

<Antioxidant>
In this invention, what is generally known can be used as an antioxidant.

  In particular, lactone, sulfur, phenol, double bond, hindered amine, and phosphorus compounds can be preferably used.

  For example, the thing containing what is marketed by the brand name "IrgafosXP40" and "IrgafosXP60" from Ciba Japan KK is preferable.

  The phenolic compound preferably has a 2,6-dialkylphenol structure. For example, Ciba Japan Co., Ltd., “Irganox 1076”, “Irganox 1010”, ADEKA “ADEKA STAB AO-50” And those commercially available.

  Examples of the phosphorous compounds are Sumitomo Chemical Co., Ltd., “Sumilizer GP”, ADEKA Co., Ltd., “ADK STAB PEP-24G”, “ADK STAB PEP-36” and “ADK STAB 3010”, Ciba Japan Co., Ltd. “IRGAFOS P-EPQ”, commercially available from Sakai Chemical Industry Co., Ltd. under the trade name “GSY-P101” is preferable.

  As the hindered amine compound, for example, those commercially available from Ciba Japan Co., Ltd. under the trade names “Tinuvin 144” and “Tinvin 770”, and from ADEKA Co., Ltd. as “ADK STAB LA-52” are preferable.

  The sulfur compound is preferably commercially available from Sumitomo Chemical Co., Ltd. under the trade names “Sumilizer TPL-R” and “Sumilizer TP-D”.

  The above-mentioned double bond type compounds are preferably those commercially available from Sumitomo Chemical Co., Ltd. under the trade names “Sumilizer GM” and “Sumilizer GS”.

  Furthermore, it is possible to contain a compound having an epoxy group as described in US Pat. No. 4,137,201 as an acid scavenger.

  The amount of these antioxidants and the like to be appropriately added is determined in accordance with the process at the time of recycling, but generally 0.05 to 20% by mass, preferably with respect to the resin as the main raw material of the film Is added in the range of 0.1 to 1% by mass.

  These antioxidants can obtain a synergistic effect by using several different types of compounds in combination rather than using only one kind. For example, the combined use of lactone, phosphorus, phenol and double bond compounds is preferred.

<Colorant>
In the present invention, a colorant can also be used. The colorant means a dye or a pigment. In the present invention, the colorant means an effect of making the color tone of a liquid crystal screen blue, adjusting the yellow index, and reducing haze. Various dyes and pigments can be used as the colorant, but anthraquinone dyes, azo dyes, phthalocyanine pigments and the like are effective.

<Ultraviolet absorber>
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. It is good also as a polymer type ultraviolet absorber.

<Matting agent>
In the present invention, it is preferable to add a matting agent in order to impart film slipperiness.

  As the matting agent used in the present invention, any inorganic compound or organic compound may be used as long as it has heat resistance at the time of melting without impairing the transparency of the obtained film. For example, talc, mica, zeolite, diatomaceous earth, Calcined siliceous clay, kaolin, sericite, bentonite, smectite, clay, silica, quartz powder, glass beads, glass powder, glass flakes, milled fiber, wollastonite, boron nitride, boron carbide, titanium boride, magnesium carbonate, Heavy calcium carbonate, light calcium carbonate, calcium silicate, aluminum silicate, magnesium silicate, magnesium aluminosilicate, alumina, silica, zinc oxide, titanium dioxide, iron oxide, magnesium oxide, zirconium oxide, aluminum hydroxide, calcium hydroxide, water Magnesium oxide Beam, calcium sulfate, barium sulfate, silicon carbide, aluminum carbide, titanium carbide, aluminum nitride, silicon nitride, titanium nitride, and white carbon. These matting agents can be used alone or in combination of two or more.

  By using particles having different particle sizes and shapes (for example, acicular and spherical), both transparency and slipperiness can be made highly compatible. Among these, silicon dioxide is particularly preferably used since it has a refractive index close to that of cellulose ester and is excellent in transparency (haze).

  Specific examples of silicon dioxide include Aerosil 200V, Aerosil R972V, Aerosil R972, R974, R812, 200, 300, R202, OX50, TT600, NAX50 (manufactured by Nippon Aerosil Co., Ltd.), Sea Hoster KEP-10, Sea Hoster KEP- 30, Seahoster KEP-50 (manufactured by Nippon Shokubai Co., Ltd.), Silo Hovic 100 (manufactured by Fuji Silysia), nip seal E220A (manufactured by Nippon Silica Industry), Admafine SO (manufactured by Admatechs) Goods etc. can be preferably used.

  The shape of the particles can be used without particular limitation, such as indefinite shape, needle shape, flat shape, spherical shape, etc. However, the use of spherical particles is particularly preferable because the transparency of the resulting film can be improved.

  When the particle size is close to the wavelength of visible light, light is scattered and the transparency is deteriorated. Therefore, the particle size is preferably smaller than the wavelength of visible light, and more preferably ½ or less of the wavelength of visible light. . If the size of the particles is too small, the slipperiness may not be improved, so the range of 80 nm to 180 nm is particularly preferable.

  The particle size means the size of the aggregate when the particle is an aggregate of primary particles. Moreover, when a particle is not spherical, it means the diameter of a circle corresponding to the projected area.

<Viscosity reducing agent>
In the present invention, a hydrogen bonding solvent can be added for the purpose of reducing the melt viscosity. The hydrogen bonding solvent is J.I. N. As described in Israel Ativili, “Intermolecular Forces and Surface Forces” (Takeshi Kondo, Hiroyuki Oshima, Maglow Hill Publishing, 1991) and electrically negative atoms (oxygen, nitrogen, fluorine, chlorine) An organic solvent capable of producing a hydrogen atom-mediated “bond” between a hydrogen atom covalently bonded to an electronegative atom, ie, a bond having a large bond moment and containing hydrogen, such as O—H (Oxygen hydrogen bond), N—H (nitrogen hydrogen bond), and organic solvent that can arrange adjacent molecules by including F—H (fluorine hydrogen bond).

  These have the ability to form stronger hydrogen bonds with cellulose than intermolecular hydrogen bonds of cellulose resin. In the melt casting method performed in the present invention, the glass transition temperature of the cellulose resin used alone is higher than that. The melting temperature of the cellulose resin composition can be lowered by the addition of a hydrogen bonding solvent, or the melt viscosity of the cellulose resin composition containing a hydrogen bonding solvent can be lowered at the same melting temperature as the cellulose resin. .

  Examples of the hydrogen bonding solvent include alcohols: for example, methanol, ethanol, propanol, isopropanol, n-butanol, sec-butanol, t-butanol, 2-ethylhexanol, heptanol, octanol, nonanol, dodecanol, ethylene glycol, Propylene glycol, hexylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, methyl cellosolve, ethyl cellosolve, butyl cellosolve, hexyl cellosolve, glycerin, etc., ketones: acetone, methyl ethyl ketone, etc., carboxylic acids: eg formic acid, acetic acid, propionic acid, Butyric acid, etc., ethers: eg, diethyl ether, tetrahydrofuran, dioxane, etc., Pyrrolidones: eg, N-methyl Pyrrolidone, etc., amines: for example, can be exemplified trimethylamine, pyridine, etc., and the like. These hydrogen bonding solvents can be used alone or in admixture of two or more. Among these, alcohol, ketone, and ether are preferable, and methanol, ethanol, propanol, isopropanol, octanol, dodecanol, ethylene glycol, glycerin, acetone, and tetrahydrofuran are particularly preferable. Furthermore, water-soluble solvents such as methanol, ethanol, propanol, isopropanol, ethylene glycol, glycerin, acetone, and tetrahydrofuran are particularly preferable. Here, water-soluble means that the solubility in 100 g of water is 10 g or more.

<Retardation adjuster>
The cellulose ester film of the present invention may contain a compound for adjusting the retardation.

  As the compound to be added for adjusting the retardation, an aromatic compound having two or more aromatic rings as described in EP 911,656A2 can also be used.

Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic heterocyclic ring in addition to the aromatic hydrocarbon ring. An aromatic heterocyclic ring is particularly preferred, and the aromatic heterocyclic ring is generally an unsaturated heterocyclic ring. Of these, compounds having a 1,3,5-triazine ring are particularly preferred.
<Melt casting method of cellulose ester film>
In the melt casting film forming method of the present invention, a composition containing a cellulose ester is heated and melted to a temperature showing fluidity to form a melt, then the melt is cast and cooled, and then the width is measured by a tenter. After stretching in the hand direction, heat treatment is performed at Tg−20 ° C. to Tg + 20 ° C., and then stretching in the width direction while shrinking in the transport direction (simultaneous biaxial stretching).

  By using the melt casting film forming method, a highly transparent film having desired optical characteristics can be obtained. More specifically, the heating and melting molding method can be classified into a melt extrusion molding method, a press molding method, an inflation method, an injection molding method, a blow molding method, a stretch molding method, and the like. Among these, in order to obtain a cellulose ester film excellent in mechanical strength and surface accuracy, the melt extrusion method is excellent.

(Production method)
Hereinafter, the manufacturing method of a film is demonstrated.

(Step of pelletizing a composition containing cellulose ester)
It is preferable that a plurality of raw materials used for melt extrusion are usually kneaded and pelletized in advance. Pelletization may be performed by a known method. For example, dry cellulose ester, plasticizer, and other additives are fed to an extruder using a feeder and kneaded using a single-screw or twin-screw extruder, and then formed into a strand from a die. It can be done by extrusion, water cooling or air cooling and cutting.

  It is important to dry the raw material before extruding to prevent decomposition of the raw material. In particular, since the cellulose ester easily absorbs moisture, it is preferable to dry it at 70 to 140 ° C. for 3 hours or more with a dehumidifying hot air dryer or a vacuum dryer to keep the moisture content at 200 ppm or less, and further 100 ppm or less.

  The additives may be mixed before being supplied to the extruder, or may be supplied by individual feeders. A small amount of an additive such as an antioxidant is preferably mixed in advance in order to mix uniformly. Mixing of the antioxidants may be performed by mixing solids, and if necessary, the antioxidant may be dissolved in a solvent, impregnated with cellulose ester and mixed, or sprayed and mixed. Also good.

A vacuum nauter mixer or the like is preferable because drying and mixing can be performed simultaneously. Further, if the contact with air, such as the exit from the feeder unit or die, it is preferable that the atmosphere such as dehumidified air and dehumidified N ₂ gas.

  In addition, it is preferable to keep the supply hopper and the like to the extruder warm because moisture absorption can be prevented.

  A matting agent, an ultraviolet absorber and the like may be applied to the obtained pellets or added in an extruder during film formation.

  The extruder is preferably processed at a temperature as low as possible so as to suppress the shearing force and prevent the resin from deteriorating (molecular weight reduction, coloring, gel formation, etc.). For example, in the case of a twin screw extruder, it is preferable to rotate in the same direction using a deep groove type screw. From the uniformity of kneading, the meshing type is preferable.

  Kneader discs can improve kneadability, but care must be taken for shearing heat generation, and the mixability is sufficient even without using a kneader disc. The suction from the vent hole may be performed as necessary. Since the volatile component is hardly generated at a low temperature, the vent hole may be omitted.

  The color of the pellet is preferably such that the b * value, which is an index of yellowness, is in the range of -5 to 10, more preferably in the range of -1 to 8, and in the range of -1 to 5. More preferred. The b * value can be measured at a viewing angle of 10 ° using a spectrocolorimeter CM-3700d (manufactured by Konica Minolta Sensing Co., Ltd.) using D65 (color temperature 6504K) as a light source.

  A film is formed using the pellets obtained as described above. Of course, the raw material powder can be directly fed to the extruder by a feeder without being pelletized to form a film as it is.

(Process of heating and melting the pelletized cellulose ester composition to a temperature showing fluidity to produce a melt)
Dehydrated hot air or polymer dried under vacuum or reduced pressure using a single or twin screw type extruder with a melting temperature of about 200-300 ° C and filtered through a leaf disk type filter to remove foreign matter A melt is produced.

(Process of casting and cooling the melt to form a film)
The produced melt is cast from a T die and solidified on a cooling roll to form a film.

  When introducing from the supply hopper to the extruder, it is preferable to prevent oxidative decomposition or the like under vacuum, reduced pressure, or inert gas atmosphere.

  The extrusion flow rate is preferably performed stably by introducing a gear pump or the like. Further, a stainless fiber sintered filter is preferably used as a filter used for removing foreign substances.

  A stainless steel fiber sintered filter is an integrated stainless steel fiber body that is intricately entangled and then compressed and sintered at the contact point. The density is changed according to the thickness of the fiber and the amount of compression, and the filtration accuracy is improved. Can be adjusted.

  It is preferable to use a multilayer body in which the filtration accuracy is repeated coarsely and densely a plurality of times. Further, it is preferable to adopt a configuration in which the filtration accuracy is sequentially increased or a method in which coarse and dense filtration accuracy is repeated, so that the filtration life of the filter can be extended and the accuracy of supplementing foreign matters and gels can be improved.

  If flaws or foreign matter adhere to the die, streaky defects may occur. Such a defect is also called a die line, but in order to reduce surface defects such as a die line, it is preferable to have a structure in which the resin retention portion is minimized in the piping from the extruder to the die. . It is preferable to use a die that has as few scratches as possible inside the lip.

  The inner surface that contacts the molten resin such as an extruder or a die is preferably subjected to surface treatment that makes it difficult for the molten resin to adhere to the surface by reducing the surface roughness or using a material having a low surface energy. Specifically, a hard chrome plated or ceramic sprayed material is polished so that the surface roughness is 0.2 S or less.

  Additives such as plasticizers may be mixed with the resin in advance, or may be kneaded in the middle of the extruder, but it is preferable to use a mixing device such as a static mixer in order to add uniformly. .

  The film temperature on the touch roll side when the film-like material is nipped by the cooling roll and the elastic touch roll is preferably Tg or more and Tg + 110 ° C. or less of the film. A well-known roll can be used for the roll which has the elastic body surface used for such a purpose.

  When peeling the film-like material from the cooling roll, it is preferable to prevent the deformation of the film-like material by controlling the tension.

(Stretching the film-like material in the width direction with a tenter)
As the stretching method in the present invention, a known roll stretching machine or tenter can be preferably used, but it is desirable to use a tenter for stretching in the width direction.

  The stretching temperature is preferably performed in a temperature range of Tg-20 to Tg + 20 ° C. of the composition. Here, Tg is the glass transition temperature of the composition constituting the film, and in the present invention, it can be adjusted by selecting the amount and type of the plasticizer described above. Tg is 110 ° C. or higher, preferably 125 ° C. or higher and 250 ° C. or lower.

  Tg was measured with a differential scanning calorimeter (DSC-7, manufactured by Perkin Elmer) at a rate of temperature increase of 20 ° C./min. To do.

  The draw ratio is preferably 1.3 times (30%) to 2.5 (150%) times, and more preferably 1.5 times (50%) to 2.0 (100%) times.

  In the liquid crystal display device, in the image display state, the temperature environment of the film changes due to the temperature rise of the device itself, for example, the temperature rise derived from the light source. At this time, if the Tg of the film is lower than the use environment temperature of the film, the retardation value derived from the orientation state of the molecules fixed inside the film by stretching and the dimensional shape as the film are greatly changed.

  If the Tg of the film is too high, the temperature is increased when the film constituent material is made into a film, so that the energy consumption for heating is increased, and the material itself may be decomposed when it is made into a film, resulting in coloring. Therefore, Tg is preferably 250 ° C. or lower.

  If the stretching temperature is too low, it may break, and if it is too high, the desired retardation may not be obtained.

  The stretching is preferably performed under a uniform temperature distribution controlled in the width direction. The temperature is preferably within ± 2 ° C, more preferably within ± 1 ° C, and particularly preferably within ± 0.5 ° C.

(The process of heat-treating the stretched film-like material at Tg-20 ° C to Tg + 20 ° C)
In this invention, after extending | stretching to a lateral direction, it is preferable to heat-process in the temperature range of Tg-20-Tg + 20 degreeC. In particular, by performing heat treatment in the temperature range of Tg-20 to Tg ° C., only the retardation in the thickness direction (Rt) can be changed, and a desired in-plane retardation (Ro) and Nz coefficient can be easily obtained. Become. Further, by performing the heat treatment, the resin and plasticizer in the film are easily distributed uniformly, and a highly transparent film can be obtained.

(Step of stretching in the width direction while shrinking the heat-treated film in the transport direction (simultaneous biaxial stretching) step)
In the present invention, after a stretching process in the width direction, a heat treatment process, and a simultaneous biaxial stretching process, the desired Ro and Nz coefficients are obtained, the variation in the orientation angle of the slow axis is small, and the productivity is high. A film can be obtained. In particular, this process is responsible for final optical characteristics and alignment angle adjustment.

  Although it was possible to obtain the desired optical characteristics even in the conventional free end stretching in the transport direction, because the slow axis is directed in the transport direction, it can not be bonded to the roll-to-roll polarizer, Productivity was bad. Further, in the conventional stretching in the width direction at the fixed end, since the slow axis is directed in the width direction, bonding with a roll-to-roll was possible, but desired optical characteristics could not be obtained.

  In the present invention, the film is contracted in the conveying direction by 1 to 50%, preferably 10% to 30%, and stretched in the width direction by 1 to 50%, preferably 10% to 30%. The temperature at this time is preferably Tg-20 to Tg + 20 ° C.

  Such simultaneous biaxial stretching is achieved by stretching in the width direction while lowering the transport speed of the clip in the transport in the tenter than the transport speed of the clip being stretched.

  Here, the shrinkage rate (MD shrinkage rate) was determined as the MD shrinkage rate using the following equation from the speed of the tenter inlet (V2) and the speed of the tenter outlet (V1).

MD shrinkage (%) = 100 × (V1−V2) / V1
By performing simultaneous biaxial stretching, it is possible to reduce variations in the orientation angle in the width direction. This simultaneous biaxial stretching may be carried out after the stretching in the width direction, or may be carried out by feeding out the material once wound after the transverse stretching.

  Moreover, it is preferable that the film thickness of the retardation film of this invention is 20-55 micrometers. If it is less than 20 μm, it is a thin film and the temperature at the time of stretching is low, so that mechanical strength is insufficient, failure such as breakage during production is likely to occur, and the film surface may be poor. When it is 55 μm or more, shrinkage in the transport direction is difficult to occur, and it is difficult to obtain the target Ro and Nz coefficients.

  The film thickness variation of the cellulose ester film of the present invention is preferably in the range of ± 3%, and more preferably ± 1%.

  After stretching, after slitting the end of the film to a product width with a slitter, the film is subjected to knurling (embossing) on both ends of the film by a knurling device consisting of an embossing ring and a back roll, and a winder By taking up with, it prevents the cellulose ester film (original winding) from sticking and the generation of scratches.

The knurling method can process a metal ring having an uneven pattern on its side surface by heating or pressing. In addition, since the grip part of the clip of the both ends of a film is deform | transforming normally and cannot be used as a film product, it is cut out and reused as a raw material.
<Polarizing plate and liquid crystal display device>
The polarizing plate of the present invention will be described.

  The polarizing plate of the present invention can be produced by a general method. For example, there is a method in which a cellulose ester film is subjected to alkali saponification treatment and then bonded to both sides of a polarizer using a completely saponified polyvinyl alcohol aqueous solution. The alkali saponification treatment is a treatment in which the cellulose ester film is immersed in a strong alkaline solution at high temperature in order to improve the wetness of the aqueous adhesive and improve the adhesion.

  A conventionally well-known thing can be used as a polarizer used for the polarizing plate of this invention. For example, a film made of a hydrophilic polymer such as polyvinyl alcohol or ethylene-modified polyvinyl alcohol having an ethylene unit content of 1 to 4 mol%, a polymerization degree of 2000 to 4000, and a saponification degree of 99.0 to 99.99 mol%, A film stretched by treatment with a dichroic dye such as the above, or a film oriented by treating a plastic film such as vinyl chloride is used.

  The film thickness of the polarizer is preferably 5 to 30 μm. The polarizer thus obtained is bonded to a cellulose ester film.

  At this time, the cellulose film of the present invention is used as at least one of the cellulose ester films. Another cellulose ester film can be used on the other surface.

  For example, a commercially available cellulose ester film (KC8UX, KC4UX, KC4UY, KC8UY (manufactured by Konica Minolta Opto)) can be used as a polarizing plate protective film.

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

  Moreover, at the time of producing the polarizing plate, it is preferable to bond the retardation film of the present invention so that the in-plane slow axis and the transmission axis of the polarizer are parallel or orthogonal.

  The liquid crystal display device of the present invention can be produced by arranging and bonding the polarizing plate of the present invention obtained on the both sides of the liquid crystal cell. The cellulose ester film of the present invention is used in liquid crystal display devices of various drive systems such as TN, VA, OCB, HAN, etc., and is particularly preferably used in liquid crystal display devices of VA system.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these.

<Preparation of cellulose ester film 1>
Acetyl group substitution degree 1.30, propionyl group substitution degree 1.20, total acyl group substitution degree 2.5, number average molecular weight 65000 (weight average molecular weight 200000) dried at 80 ° C. for 6 hours (water content 200 ppm) 100 parts by mass of cellulose acetate propionate, 12 parts by mass of compound 48 (ADEKA), 0.01 parts by mass of PEP-36 (ADEKA) as a phosphorus compound, Irganox 1010 (manufactured by Ciba Japan) 0 .5 parts by mass, Sumilizer GS (manufactured by Sumitomo Chemical Co., Ltd.) 0.24 parts by mass, and Aerosil R972V (manufactured by Nippon Aerosil Co., Ltd.) 0.1 parts by mass with a vacuum Nauter mixer at 80 ° C. and 1 Torr for 3 hours Further dried.

  The obtained mixture was melt-mixed at 235 ° C. using a twin-screw extruder and pelletized. The cellulose ester film was produced by the production apparatus shown in FIG.

  Pellets (moisture content 50 ppm) were melt extruded from a T die onto a first cooling roll having a surface temperature of 90 ° C. at a melting temperature of 240 ° C. using a single screw extruder to obtain a 120 μm cast film. At this time, the film was pressed on the first cooling roll with an elastic touch roll having a 2 mm thick metal surface.

  The obtained film is introduced into a tenter having a preheating zone, a stretching zone, a holding zone, and a cooling zone (there is also a neutral zone between each zone to ensure thermal insulation between the zones). The film was stretched at 60 ° C. for 60%, then cooled to 120 ° C. and maintained at 120 ° C. for heat treatment.

  After that, while the transport speed of the clip in the tenter was slower than the transport speed of the clip being stretched, it was contracted 30% in the transport direction and stretched 30% in the width direction. Thereafter, the clip gripping part was cut off to obtain a cellulose ester film 1 having a film thickness of 40 μm and a film width of 2300 mm.

The present invention and comparative cellulose ester films 2 to 8, 12, and 13 were obtained in the same manner as the cellulose ester film 1 of the present invention except that the cellulose ester, the plasticizer, and the production conditions were changed as shown in Table 1.
(Sample 7: prepared according to JP-A-2008-287218, Example 1, a-15. Sample 12: prepared according to JP-A-2008-257220, Example 1, F-1)
Compound A: polyester polyol (reaction product of ethylene glycol and succinic acid / terephthalic acid = 50/50 molar ratio Mw = 2000)
<Preparation of cellulose ester film 9>
<Preparation of fine particle dispersion>
Aerosil R972V (manufactured by Nippon Aerosil Co., Ltd.) 11 parts by weight Ethanol 89 parts by weight The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin to prepare a fine particle dispersion.

<Preparation of fine particle additive solution>
The following cellulose ester was added to a dissolution tank containing methylene chloride, and heated to completely dissolve, then, this was added to Azumi Filter Paper No. Filtered using 244.

  The fine particle dispersion was slowly added thereto while sufficiently stirring the filtered cellulose ester solution. Furthermore, dispersion was carried out with an attritor. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution.

99 parts by mass of methylene chloride Cellulose triacetate (acetyl group substitution degree 2.54, number average molecular weight 60000)
4 parts by mass Fine particle dispersion 11 parts by mass <Preparation of main dope liquid>
A main dope solution having the following composition was prepared.

  First, methylene chloride and ethanol were added to the pressure dissolution tank. A part of methylene chloride (about 40 parts by mass) was divided in advance and used when the cellulose ester was charged into the pressurized dissolution tank containing the solvent (while stirring the pressurized dissolution tank).

  This was heated and stirred to dissolve completely, and the polymers listed in Table 1 were added and dissolved. This was designated as Azumi Filter Paper No. The main dope solution was prepared by filtration using 244.

PETB: pentaerythritol tetrabenzoate TPP: triphenyl phosphate BDPP: biphenyl diphenyl phosphate <composition of main dope solution>
Methylene chloride 300 parts by weight Ethanol 40 parts by weight Cellulose triacetate (total substitution degree 2.54) 100 parts by weight Tricresyl phosphate 10 parts by weight In addition to the main dope solution 100 parts by weight and the fine particle additive liquid 2 parts by weight, an in-line mixer (Toray static type in-pipe mixer Hi-Mixer, SWJ) was sufficiently mixed, and then uniformly cast on a stainless steel band support having a width of 2 m by a belt casting apparatus. On the stainless steel band support, the solvent is evaporated until the residual solvent amount becomes 30% by mass, and after peeling off from the stainless steel band support, the both ends of the web are gripped by the tenter part, and at 150 ° C. in the width direction. Stretched 0 times.

Comparative cellulose ester films 10 to 11 were obtained in the same manner as the cellulose ester film 9 of the present invention except that the cellulose ester, the plasticizer, and the production conditions were changed as shown in Table 1.
(Sample 11: produced in accordance with Example 1 of JP-A-2008-279724)

  A polarizing plate and a liquid crystal display device were produced using the produced cellulose ester films 1 to 13 in the following manner.

<Production of polarizing plate>
Using the prepared cellulose ester film sample, the alkali saponification treatment described below and a polarizing plate were prepared.

<Alkali saponification treatment>
Saponification process 2N-NaOH 50 ° C. 90 seconds Water washing process Water 30 ° C. 45 seconds Neutralization process 10% HCl 30 ° C. 45 seconds Water washing process Water 30 ° C. 45 seconds After saponification treatment, water washing, neutralization, water washing are performed in this order. Subsequently, it dried at 80 degreeC.

<Production of polarizer>
A 120 μm-thick long roll polyvinyl alcohol film was immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid, and stretched in the transport direction 6 times at 50 ° C. to form a polarizing film.

  KC4UY manufactured by Konica Minolta Opto Co., Ltd., which was similarly saponified on one side of the polarizing film, and a cellulose ester film subjected to the alkali saponification treatment on the opposite side thereof as a fully saponified polyvinyl alcohol 5% aqueous solution, The polarizing plates 1 to 11 were produced by laminating them by roll-to-roll so that the transmission axis of the polarizer and the in-plane slow axis of the film were parallel to each other and drying.

<Production of liquid crystal display device>
About the obtained polarizing plate, in combination with Sharp liquid crystal panel LL-T1620, the polarizing plate previously bonded to the liquid crystal panel is peeled off, and polarized so that the arrangement configuration shown in FIG. The polarizing plate was bonded via an adhesive so that the transmission axis of the plate was in the same direction as the transmission axis of the polarizing plate previously bonded. As a polarizing plate on the backlight side, a Konica Minolta-tack film KC4UY (manufactured by Konica Minolta Opto Co., Ltd.) is used as a polarizer, and a phase difference of Ro = 0 nm and Rt = 200 nm prepared on the opposite surface of the polarizer is as follows. Liquid crystal display devices 1 to 11 were prepared by pasting a polarizing plate pasted with a retardation film.

<< Evaluation of Cellulose Ester Film and Liquid Crystal Display >>
The obtained cellulose ester film, polarizing plate and liquid crystal display device were evaluated by the methods shown below.

<Evaluation of film>
[Measurement of Ro and Rt]
The average refractive index of the film constituting material was measured using an Abbe refractometer (4T). Moreover, the thickness of the film was measured using a commercially available micrometer.

  Using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments), film retardation measurement at a wavelength of 590 nm was performed under the same environment for 24 hours in an environment of 23 ° C. and 55% RH. went. The average refractive index and film thickness described above were input, and values for in-plane retardation (Ro) and thickness direction retardation (Rt) were obtained.

[Measurement of haze]
Using a turbidimeter (NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.), haze measurement of the film was carried out in the same environment in a film that was allowed to stand for 24 hours in an environment of 23 ° C. and 55% RH.
Total haze (Ht): Haze value (%) measured according to JISK7136.
Internal haze (Hi): measured in a state where several drops of glycerin are dropped on the surface of the obtained retardation film and sandwiched between two glass plates (MICRO SLIDE GLASS part number S9213, manufactured by MATSUNAMI) having a thickness of 1.3 mm. The value (%) obtained by subtracting the haze measured in a state where several drops of glycerin were dropped between two glasses.
(Orientation angle variation)
Using OPTPRO (XY scanning stage, halogen lamp light + 550 nm interference filter), the orientation angle was measured on a film that was allowed to stand for 24 hours in an environment of 23 ° C. and 55% RH. At this time, the measurement area was 60 mm × 60 mm, and measurement was performed at intervals of 4 mm using a beam with a diameter of 3 mm.

  The difference between the maximum value and the minimum value of the orientation angle in the range of 60 mm × 60 mm measured in this way was regarded as variation.

<Evaluation of liquid crystal display device>
[Front contrast]
First, the contrast of the liquid crystal display device was evaluated by measuring the front contrast in black display using EZ-contrast manufactured by ELDIM.

  The front contrast was evaluated using the front contrast value as an index.

  Since the front contrast was high, it was set as ◎, ○, ×.

From the above table, it was found that a liquid crystal display device having a high front contrast can be provided by using the retardation film of the present invention.
<Preparation of retardation film for backlight side polarizing plate>
Acetyl group substitution degree 1.20, propionyl substitution degree 1.10, total acyl group substitution degree 2.3, number average molecular weight 65000 (weight average molecular weight 200000) dried at 80 ° C. for 6 hours (water content 200 ppm) 100 parts by mass of cellulose acetate propionate, 12 parts by mass of compound 48 (ADEKA), 0.01 parts by mass of PEP-36 (ADEKA) as a phosphorus compound, Irganox 1010 (manufactured by Ciba Japan) 0 .5 parts by mass, Sumilizer GS (manufactured by Sumitomo Chemical Co., Ltd.) 0.24 parts by mass, and Aerosil R972V (manufactured by Nippon Aerosil Co., Ltd.) 0.1 parts by mass with a vacuum Nauter mixer at 80 ° C. and 1 Torr for 3 hours Further dried.

  The obtained mixture was melt-mixed at 235 ° C. using a twin-screw extruder and pelletized.

  Pellets (moisture content 50 ppm) were melt extruded from a T die onto a first cooling roll having a surface temperature of 90 ° C. at a melting temperature of 240 ° C. using a single screw extruder to obtain a film having a thickness of 70 μm. At this time, the film was pressed on the first cooling roll with an elastic touch roll having a 2 mm thick metal surface.

  Next, this film-like material was stretched 30% in the conveying direction at 130 ° C. by a stretching machine utilizing the difference in the peripheral speed of the roll, and further, a preheating zone, a stretching zone, a holding zone, a cooling zone (between each zone, between each zone). It is also introduced into a tenter, which is a stretching machine in the width direction with a neutral zone for ensuring heat insulation), stretched at 130 ° C in the width direction by 30%, cooled to 30 ° C, and then released from the clip Then, the clip gripping part was cut off to obtain a retardation film for a backlight-side polarizing plate having a film thickness of 40 μm.

  When this film was measured for Ro and Rth at a wavelength of 590 nm and a relative humidity of 55% at 23 ° C. using KOBRA 21-ADH manufactured by Oji Scientific Instruments, Ro = 0 nm and Rt = 200 nm.

DESCRIPTION OF SYMBOLS 1 Extruder 2 Filter 3 Static mixer 4 Casting die 5 Rotating support body (1st cooling roll)
6 Nipping pressure rotating body (touch roll)
7 Rotating support (second cooling roll)
8 Rotating support (3rd cooling roll)
9, 11, 13, 14, 15 Transport roll 10 Cellulose ester film 16 Winding machine F film

Claims (4)

100 ≦ Ro ≦ 180 and 0.8 ≦ Nz ≦ 1.3 are satisfied, the total haze Ht in one film is 0.1 ≦ Ht ≦ 0.3, and the ratio of the internal haze Hi to the total haze Hi / Ht 0.1 ≦ Hi / Ht ≦ 0.5, having a slow axis in the width direction, variation in orientation angle of slow axis is ± 0.2 degrees, and the total mass of the cellulose ester film On the other hand, a cellulose ester film characterized in that the content of the solvent is 0.01% by mass or less.
Formula 1 Ro = (nx−ny) × d
Formula 2 Nz = (nx−nz) / (nx−ny)
(Ro represents the in-plane retardation value of the cellulose ester film. The refractive index in the slow axis direction in the film plane is nx, the refractive index in the direction perpendicular to the slow axis is ny, and the refractive index in the film thickness direction. Nz and d represent the film thickness (nm), respectively.)
Total haze (Ht): Haze value (%) measured according to JISK7136.
Internal haze (Hi): Haze value (%) measured by dropping a few drops of glycerin on the surface of the film and sandwiching it from two sides with two 1.3 mm thick glass plates (MICRO SLIDE GLASS part number S9213, manufactured by MATSANAMI) ) Is a value (%) obtained by subtracting the haze value measured in a state where a few drops of glycerin are dropped between two glasses.   A polarizing plate comprising the cellulose ester film according to claim 1.   A liquid crystal display device comprising the polarizing plate according to claim 2. A step of producing a melt by heating and melting a composition containing a cellulose ester to a temperature exhibiting fluidity, a step of casting and cooling the melt to form a film, and a width of the film by a tenter A step of stretching in the direction, a step of heat-treating the stretched film-like material at Tg−20 ° C. to Tg + 20 ° C., and a step of stretching in the width direction while shrinking the heat-treated film-like material in the transport direction. A method for melt casting a cellulose ester film.
In addition, Tg represents the glass transition temperature of the composition containing a cellulose ester.

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