JP2013064145A - Method for producing cellulose ester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a cellulose ester film with a small phase difference value even when stretched, and hardly leaking light; an optical film; a polarizer; a liquid crystal display device; and a method for producing the cellulose ester film.SOLUTION: This production method of a cellulose ester film is obtained by polymerizing a cellulose ester satisfying formulae (1) and (2), and ethylenically unsaturated monomers, wherein the cellulose ester film includes a polymer in which at least one monomer has a nitrogen atom. The method comprises: a step of obtaining an original film including the cellulose ester and the polymer; and a step of stretching the original film in the carrying direction and width direction so that the total value of magnification ratios in the carrying direction and width direction becomes 2.5 times or larger, and obtaining the cellulose ester film satisfying Ro≤10 nm and -20 nm≤Rt≤20 nm. The formula (1): 2.70≤X+Y≤2.95. The formula (2): 0.5≤Y≤2.3.

Description

  The present invention relates to a method for producing a cellulose ester film, and more particularly relates to a method for producing a cellulose ester film that has a small retardation value and hardly leaks light even when stretched.

  Liquid crystal display devices are widely used as display devices for TVs, personal computers, and the like because they have low power consumption and can be particularly thinned. A liquid crystal display device has polarizing plates on both sides of a liquid crystal cell, and the polarizing plate has a structure in which both sides of a polarizing film adsorbed and oriented with iodine or dye are sandwiched between transparent resin layers.

  This transparent resin layer has the purpose of protecting the polarizer, but is often used because the cellulose ester film is suitable for this purpose.

  In recent years, with the spread of liquid crystal display devices, further reduction in thickness, size, and performance have been demanded. Accordingly, the TN mode liquid crystal display device that has been used in the past is difficult to perform a complete black display due to its characteristics. Therefore, an IPS mode liquid crystal display device capable of a substantially complete black display in a non-driven state. Has become widespread.

  However, in the IPS mode, almost complete black display is possible in the normal direction of the panel, but when the panel is observed from a direction deviated from the normal direction, light leakage occurs, resulting in a narrow viewing angle. There was a problem. This is because the viewing angle becomes narrow due to the birefringence of a commonly used triacetyl cellulose film.

  Recently, with the increase in size of liquid crystal display devices, a film having a wider width than before has been demanded. Generally, in order to increase the film width, the film is stretched in the width direction. .

  Furthermore, in order to improve the durability, cellulose ester films with a high degree of substitution have been frequently used. However, a cellulose ester film with a high degree of substitution is uniform in the width direction of the retardation when the stretch ratio is set to a certain value or more. As a result, it is difficult to ensure the property, and the problem of facilitating the occurrence of light leakage occurred.

  Patent Document 1 discloses an example in which a triacetyl cellulose (TAC) film having a small retardation value is used. However, when the film is stretched, white turbidity occurs or the film breaks. There was a problem that a wide film could not be made.

  Patent Document 2 discloses an example of obtaining a wide film without stretching. Patent Document 3 discloses a film obtained by a melt film-forming method having a cellulose ester, an acrylic polymer, and a terminal aromatic polyester plasticizer, but it is difficult to suppress the expression of retardation. The light leakage could not be improved.

JP 2007-178992 A JP 2005-154664 A JP 2007-231157 A

  An object of the present invention is to provide a cellulose ester film, a polarizing plate, and a liquid crystal display device that have a small absolute value of retardation and hardly leak light even when stretched to produce a wide film.

The object of the present invention has been achieved by the following.
1. In the cellulose ester film containing a cellulose ester satisfying the following formulas (1) and (2) and a polymer obtained by polymerizing an ethylenically unsaturated monomer, at least one of the monomers has a nitrogen atom, An in-plane retardation Ro and a retardation Rt in the thickness direction are in the following ranges.

Formula (1) 2.70 ≦ X + Y ≦ 2.95
Formula (2) 0.5 ≦ Y ≦ 2.3
Ro ≦ 10nm
−20 nm ≦ Rt ≦ 20 nm
In the formula, X represents the degree of substitution of the acetyl group, and Y represents the degree of substitution of the propionyl group or butyryl group.

Ro = (nx−ny) × d, Rt = {(nx + ny) / 2−nz} × d (where the refractive index in the slow axis direction in the film plane at the measurement wavelength of 590 nm is nx, and orthogonal to the slow axis. Ny is the refractive index in the direction of the film, nz is the refractive index in the film thickness direction, and d is the film thickness (nm) of the film.)
2. 2. The cellulose ester film as described in 1 above, wherein the monomer has an amide structure.
3. A polarizing plate characterized by using the cellulose ester film described in 1 as a polarizing plate protective film.
4). A liquid crystal display device using the cellulose ester film as described in 1 above.

  According to the present invention, it is possible to provide a cellulose ester film, a polarizing plate, and a liquid crystal display device that have a small absolute value of retardation even when stretched and hardly leak light.

It is a general | schematic flow sheet of the apparatus which enforces the manufacturing method of the cellulose-ester film of this invention.

<Cellulose ester film>
The cellulose ester film of the present invention includes a cellulose ester and a polymer obtained by polymerizing an ethylenically unsaturated monomer in which at least one of the monomers has a nitrogen atom.
<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 preferably a lower carbon number 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.

  In the case of the same degree of substitution, since the film loses its elasticity when the number of carbon atoms is large, the number of carbon atoms is preferably selected from acyl groups having 2 to 6 carbon atoms.

  The cellulose ester of the present invention preferably satisfies the following formulas (1) and (2) at the same time.

Formula (1) 2.70 ≦ X + Y ≦ 2.95
Formula (2) 0.5 ≦ Y ≦ 2.3
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 70000-200000 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 1.4 to 2.3.

  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: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) 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 also it becomes difficult to fracture | rupture. A range of 1 to 70 ppm is particularly 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. This is preferable.

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

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.
<Polymer obtained by polymerizing ethylenically unsaturated monomer>
The polymer obtained by polymerizing the ethylenically unsaturated monomer of the present invention is characterized in that at least one of the monomers has a nitrogen atom.

  And when it is made to contain in a cellulose-ester film, it is preferable as a function to show negative birefringence with respect to the extending | stretching direction, and the weight average molecular weight obtained by superposing | polymerizing an ethylenically unsaturated monomer is 500-30000 or less. A polymer is preferred.

  The polymer obtained by polymerizing the ethylenically unsaturated monomer of the present invention is preferably an acrylic polymer.

  The acrylic polymer used in the present invention is represented by the following general formula (X).

Formula (X)
-[Xa] m- [Xb] n-
In the general formula (X), Xa represents an ethylenically unsaturated monomer having an amide structure in the molecule, and Xb represents an ethylenically unsaturated monomer copolymerizable with Xa. m and n each represent a mass composition ratio. However, m ≠ 0 and m + n = 100. There may be a plurality of Xa and Xb.

  Although the monomer as a monomer unit which comprises the polymer X of this invention is mentioned below, it is not limited to this.

  As monomer units having an amide structure as Xa, N-vinylpyrrolidone, N-acryloylmorpholine, N-methacryloylmorpholine, N-vinylpiperidone, N-vinylcaprolactam, acrylamide, N, N-dimethylacrylamide, N-isopropylacrylamide, N, N-dimethylaminopropylacrylamide, N, N-diethylacrylamide, N-hydroxyethylacrylamide, N-vinylacetamide and the like can be mentioned.

  Examples of Xb include methyl acrylate, ethyl acrylate, propyl acrylate (i-, n-), butyl acrylate (n-, i-, s-, t-), and pentyl acrylate (n-, i-). -, S-), hexyl acrylate (n-, i-), heptyl acrylate (n-, i-), octyl acrylate (n-, i-), nonyl acrylate (n-, i-), Examples include myristyl acrylate (n-, i-), acrylic acid (2-ethylhexyl), acrylic acid ([epsilon] -caprolactone), and the like, or those obtained by replacing the acrylic ester with a methacrylic ester. Among them, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate (i-, n-) and the like can be mentioned.

  In addition, Xb is preferably a monomer having a hydroxyl group, and is preferably acrylic acid or methacrylic acid ester. For example, acrylic acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), acrylic acid (3-hydroxypropyl) ), Acrylic acid (4-hydroxybutyl), acrylic acid (2-hydroxybutyl), or those obtained by replacing these acrylic acids with methacrylic acid, preferably acrylic acid (2-hydroxyethyl) and methacrylic acid. Acid (2-hydroxyethyl), acrylic acid (2-hydroxypropyl), and acrylic acid (3-hydroxypropyl).

  Xb may be, for example, styrene, vinyl acetate or the like.

  The molar composition ratio m: n of Xa and Xb is preferably in the range of 99: 1 to 65:35, more preferably in the range of 95: 5 to 75:25.

  The birefringence of the acrylic polymer can be determined by the following test method.

  The acrylic polymer is dissolved in a solvent, cast into a film, and then dried by heating. The film having a transmittance of 80% or more is evaluated for birefringence.

  Refractive index measurement was performed using an Abbe refractometer-4T (manufactured by Atago Co., Ltd.) using a multi-wavelength light source. The refractive index ny in the stretching direction and the refractive index in the orthogonal in-plane direction were nx. For a film where (ny-nx) <0 for each refractive index at 550 nm, the (meth) acrylic polymer is judged to be negatively birefringent with respect to the stretch direction.

  The weight average molecular weight of the polymer X of the present invention can be adjusted by a known molecular weight adjusting method. Examples of such a molecular weight adjusting method include a method of adding a chain transfer agent such as carbon tetrachloride, lauryl mercaptan, octyl thioglycolate, and the like.

  The polymerization temperature is usually from room temperature to 130 ° C., preferably from 50 ° C. to 100 ° C., and this temperature or the polymerization reaction time can be adjusted.

  The weight average molecular weight Mw and the number average molecular weight Mn can be measured using gel permeation chromatography (GPC). The measurement conditions are as described above.

  In order to synthesize the acrylic polymer X of the present invention, an ordinary polymerization method can be used. However, when it is necessary to strictly control the molecular weight, the molecular weight should be set as much as possible by a method that does not increase the molecular weight. It is desirable to use a method that can be aligned.

  Such polymerization methods include a method using a peroxide polymerization initiator such as cumene peroxide and t-butyl hydroperoxide, a method using a polymerization initiator in a larger amount than normal polymerization, and a mercapto compound in addition to the polymerization initiator. And a method using a chain transfer agent such as carbon tetrachloride, a method using a polymerization terminator such as benzoquinone and dinitrobenzene in addition to the polymerization initiator, and further disclosed in JP 2000-128911 or 2000-344823 Examples thereof include a compound having one thiol group and a secondary hydroxyl group, or a bulk polymerization method using a polymerization catalyst in which the compound and an organometallic compound are used in combination. Used.

  For example, a polymerization method using a compound having a thiol group and a secondary hydroxyl group in the molecule as a chain transfer agent is preferable. In this case, the terminal of the polymer Y has a hydroxyl group and a thioether resulting from the polymerization catalyst and the chain transfer agent. The compatibility of X and cellulose ester can be adjusted by this terminal residue.

  The above-mentioned polymer X is excellent in compatibility with cellulose ester, excellent in productivity without evaporation and volatilization, good in retention as a protective film for polarizing plates, low in water vapor permeability, and excellent in dimensional stability.

Polymer X can be added directly to the cellulose ester as a molten composition.
<Other additives>
The cellulose ester film in the present invention includes a plasticizer that imparts processability to the film, an antioxidant that prevents deterioration of the film, an ultraviolet absorber that imparts an ultraviolet absorbing function, and fine particles that impart slipperiness to the film (matting agent). ), And an additive such as a retardation adjusting agent for adjusting the retardation of the film is preferably contained.

<Plasticizer>
In the production of the cellulose ester film according to the present invention, it is preferable that the film forming material contains at least one plasticizer.

  The plasticizer that can be used is preferably a polyhydric alcohol ester plasticizer, a polycarboxylic acid ester plasticizer, a glycolate plasticizer, a phthalate ester plasticizer, a citrate ester plasticizer, It is selected from phosphoric ester plasticizers, fatty acid ester plasticizers, polyacrylic plasticizers, sugar ester plasticizers, polyester plasticizers, and the like. As for the usage-amount of a plasticizer, 1-20 mass% is preferable with respect to a cellulose ester.

<Polyhydric ester plasticizer>
The organic acid for forming the polyhydric alcohol ester plasticizer 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 is preferably a cycloalkyl group having 3 to 8 carbon atoms, specifically, a group such as cyclopropyl, cyclopentyl, or 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, for example. 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.

<Sugar ester plasticizer>
In the cellulose ester film of the present invention, it is also preferable to use a sugar ester plasticizer obtained by esterifying a hydroxyl group of a sugar compound in which 1 to 12 at least one structure selected from a furanose structure and a pyranose structure is bonded.

  Examples of the sugar ester compound used in the present invention include glucose, galactose, mannose, fructose, xylose, arabinose, lactose, sucrose, cellobiose, cellotriose, maltotriose, raffinose, etc. What has is preferable. An example is sucrose.

The sugar ester plasticizer used in the present invention is a compound obtained by condensing at least one pyranose structure or furanose structure represented by the following general formula (A) by 1 or more and 12 or less. However, R < ₁₁ > -R < ₁₅ >, R < ₂₁ > -R < ₂₅ > represents a C2-C22 acyl group or a hydrogen atom, m and n represent the integer of 0-12 respectively, and m + n represents the integer of 1-12.

R _{11 to} R ₁₅ and R _{21 to} R ₂₅ are preferably a benzoyl group or a hydrogen atom. The benzoyl group may further have a substituent R ₂₆ (p is 0 to 5), and examples thereof include an alkyl group, an alkenyl group, an alkoxyl group, and a phenyl group, and further, these alkyl groups, alkenyl groups, and phenyl groups. May have a substituent. Oligosaccharides can also be produced by the same method as the ester compound of the present invention.

  Although the specific example of the ester compound which concerns on this invention is given to the following, this invention is not limited to this.

  The cellulose ester film of the present invention preferably contains the sugar ester compound of the present invention in an amount of 1 to 30% by mass of the cellulose ester film in order to suppress the fluctuation of the retardation value and stabilize the display quality. It is preferable to contain 5-30 mass%.

<Glycolate plasticizer>
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.

<Phthalate ester plasticizer>
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.

<Citric acid ester plasticizer>
Examples of the citrate plasticizer include acetyl trimethyl citrate, acetyl triethyl citrate, and acetyl tributyl citrate.

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

<Phosphate plasticizer>
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.

<Polycarboxylic acid ester plasticizer>
The polyvalent carboxylic acid ester plasticizer is composed of an ester of a divalent or higher, preferably a divalent to 20 valent polyvalent carboxylic acid and an alcohol. The aliphatic polyvalent carboxylic acid is preferably 2 to 20 valent, and in the case of an aromatic polyvalent carboxylic acid or an alicyclic polyvalent carboxylic acid, it is preferably 3 to 20 valent.

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

Formula (b) R2 (COOH) m (OH) n
(Wherein 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, a COOH group is a carboxyl group, and an OH group is 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.

  There is no restriction | limiting in particular as alcohol used for the polyhydric carboxylic acid ester plasticizer which can be used for this invention, Well-known alcohol 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. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

  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 fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms can be preferably used. It is more preferable that it is C1-C20, and it is especially preferable that it is C1-C10.

  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 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. 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 plasticizer 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 alcohol used for the polyvalent carboxylic acid ester that can be used in the present invention may be one kind or a mixture of two or more kinds.

  The acid value of the polyvalent carboxylic acid ester plasticizer that can be used in the present invention is preferably 1 mgKOH / g or less, and 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.

  In addition, an acid value means the milligram number of potassium hydroxide required in order to neutralize the acid (carboxyl group which exists in a sample) contained in 1g of samples. The acid value is measured according to JIS K0070.

  Examples of particularly preferred polycarboxylic acid ester plasticizers 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.

<Polyester plasticizer>
As the polyester plasticizer, a polyester plasticizer having an aromatic ring or a cycloalkyl ring in the molecule can be used. An aromatic terminal ester plasticizer represented by the following general formula (c) can be preferably used.

General formula (c) B- (GA) n-GB
(In the formula, B is a benzene monocarboxylic acid residue, G is an alkylene glycol residue having 2 to 12 carbon atoms, an aryl glycol residue having 6 to 12 carbon atoms, 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 represents an integer of 1 or more.)
In the general formula (c), 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 used in the present invention include benzoic acid, para-tert-butylbenzoic acid, orthotoluic acid, metatoluic acid, p-toluic acid, dimethylbenzoic acid, ethylbenzoic acid, and normalpropyl. There exist benzoic acid, aminobenzoic acid, acetoxybenzoic acid, etc., and these can be used as 1 type, or 2 or more types of mixtures, respectively.

  Examples of the alkylene glycol component having 2 to 12 carbon atoms of the polyester plasticizer that can be used in the present invention 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 (neo Pentyl glycol), 2,2-diethyl-1,3-propanediol (3,3-dimethylolpentane), 2-n-butyl-2-ethyl-1,3propanediol (3,3-dimethylolheptane) 3-methyl-1,5-pentanediol 1,6-hexanediol, 2,2,4-trimethyl 1,3-penta Diol, 2-ethyl 1,3-hexanediol, 2-methyl 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-octadecanediol, and the like. It is used as one kind or a mixture of two or more kinds.

  In particular, an alkylene glycol having 2 to 12 carbon atoms is particularly preferable because of excellent compatibility with a cellulose ester.

  In addition, 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. 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 polyester plasticizer used in the present invention has a number average molecular weight of 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.

  Although the specific compound of the aromatic terminal ester plasticizer which can be used for this invention below is shown, this invention is not limited to this.

<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”, and ADEKA “ADEKA STAB AO-50” are trade names. And those commercially available.

  Examples of the phosphorus compound include Sumitizer GP (AO2) from Sumitomo Chemical Co., Ltd., “ADK STAB PEP-24G”, “ADK STAB PEP-36” (AO1) and “ADK STAB 3010” from ADEKA Co., Ltd. What is marketed by the brand name "IRGAFOS P-EPQ" (AO4) from Ciba Japan Co., Ltd. and "GSY-P101" (AO3) from Sakai Chemical Industry Co., Ltd. is preferable.

  As the hindered amine compound, for example, those commercially available from Ciba Japan Co., Ltd. under the trade names “Tinuvin 144 (AO2)” and “Tinvin 770” and ADEKA Co., Ltd. under the name “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 of “Sumilizer GM” (AO5) and “Sumilizer GS” (AO3).

  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.
<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.
<Colorant>
In the present invention, it is preferable to use a colorant. 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 (above Nippon Aerosil Co., Ltd.), Sea Hoster KEP-10, Sea Hoster KEP-30, Commercial products having trade names such as Sea Hoster KEP-50 (above, Nippon Shokubai Co., Ltd.), Silo Hovic 100 (Fuji Silysia), Nip Seal E220A (Nihon Silica Kogyo), Admafine SO (Admatechs), 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.
<Melt casting method of cellulose ester film>
In the melt casting film-forming method of the present invention, a composition containing a cellulose ester and an acrylic polymer is heated and melted to a temperature showing fluidity to form a melt, and then the melt is cast and cooled. The film temperature is Tg + 10 to Tg + 50 ° C. of the composition, and the film is stretched 1.3 to 6.5 times in combination with the conveyance direction magnification and the width direction magnification. In particular, the effect of the present invention is remarkable in the case of a high draw ratio of 2.5 times or more in combination of the conveyance direction magnification and the width direction magnification. If it is 6.5 times or more, the cellulose ester film is easily broken, and the production stability is deteriorated.

  The combination of the conveyance direction magnification and the width direction magnification is, for example, 1.2 + 2.0 when the magnification is 1.2 times in the conveyance direction and 2.0 times the magnification in the width direction. It means 3.2 times.

  More specifically, the heat 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.

(Process for producing molten pellets of cellulose ester and additives)
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.

  Matting agents, UV absorbers, and the like may be applied to the obtained pellets or added in an extruder during film formation.

  The extruder is preferably processed at as low a temperature as possible so that the shearing force is suppressed and the resin can be pelletized so as not to deteriorate (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 against shearing heat generation. Mixability is sufficient without using a kneader disk. The suction from the vent hole may be performed as necessary. Since there is almost no volatile component at low temperatures, there may be no vent hole.

  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 extruding a melt of cellulose ester and additive from the die)
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 Then, it is cast into a film from a T die and solidified on a cooling roll.

  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 defects are also referred to as die lines, but in order to reduce surface defects such as die lines, 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. In order to add uniformly, it is preferable to use a mixing apparatus such as a static mixer.

(Process of casting while pressing the melt extruded from the die between the cooling roll and the elastic touch roll)
The film temperature on the touch roll side when the film is nipped between 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 from the cooling roll, it is preferable to control the tension to prevent deformation of the film.

(Stretching process)
In this invention, a film is extended | stretched 1.3 to 4 times according to a conveyance direction and a width direction.

  As a method of stretching, a known roll stretching machine or tenter can be preferably used.

  The stretching temperature is preferably performed in the temperature range of Tg + 10 to Tg + 50 ° 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 using a differential scanning calorimeter (DSC-7, manufactured by Perkin Elmer) at a rate of temperature increase of 20 ° C./min, and the intermediate glass transition temperature (Tmg) determined according to JIS K7121 (1987) To do.

  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.

  The stretching step may be performed by known heat setting conditions, cooling, and relaxation treatment, and may be appropriately adjusted so as to have the characteristics required for the target optical film.

  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.

  Prior to winding, the ends may be slit and cut to the width of the product, and knurling (embossing) may be applied to both ends to prevent sticking or scratching during winding. The knurling method can process a metal ring having an uneven pattern on its side surface by heating or pressing. In addition, since the film has deform | transformed and cannot use as a product normally, the holding | grip part of the clip of both ends of a film is cut out and reused.

  Hereinafter, the stretching method will be described.

  Stretching is performed by stretching in the conveying direction (longitudinal stretching), stretching in the width direction (transverse stretching), and combinations thereof. Longitudinal stretching includes roll stretching (stretching in the transport direction using two or more pairs of nip rolls with increased peripheral speed on the outlet side) and fixed end stretching (gripping both ends of the film and transporting them gradually and quickly in the transport direction) Stretching in the direction) or the like. Further, the transverse stretching can be performed by tenter stretching (holding both ends of the film with a chuck and stretching the film in the transverse direction (perpendicular to the conveying direction)) or the like.

  These longitudinal stretching and lateral stretching may be performed independently (uniaxial stretching) or may be performed in combination (biaxial stretching). In the case of biaxial stretching, it may be carried out in the longitudinal and transverse sequential manners (sequential stretching) or simultaneously (simultaneous stretching).

  The stretching speed in the transport direction and the width direction is represented by stretching speed (% / min) = {(post-stretching dimension / pre-stretching dimension) -1} × 100 (%) (time required for stretching (min)), It is preferably 200% / min to 30000% / min, more preferably 300% / min to 20000% / min, and even more preferably 500% / min to 20000% / min. In the case of multistage stretching, the stretching speed refers to the average value of the stretching speed of each stage.

  More preferably, stretching is performed at 400% / min to 1500% / min. More preferably, they are 500% / min-1400% / min, More preferably, they are 600% / min-1300% / min.

  Following such stretching, it is also preferable to relax by 0% to 10% in the longitudinal or transverse direction. Furthermore, it is also preferable to heat-fix at 150-250 degreeC for 1 second-3 minutes following extending | stretching.

  In the cellulose ester film of the present invention, it is necessary to stretch 1.3 to 4 times by combining the conveyance direction magnification and the width direction magnification, and to stretch 1.05 times or more in at least one direction.

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

  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.

  In general, it is known that the melt-extrusion tends to increase the residence time on the end side due to the shape of the casting die, and this is thought to promote the coloring of the film end.

  In the present invention, the yellow index Ye at the end in the width direction of the film immediately after melt extrusion and the yellow index Yc at the center of the film preferably satisfy the following formula, and more preferably, Ye / Yc is 3.0 or less.

  If Ye / Yc is greater than 5.0, the color of the produced film increases when the film edge is cut off and reused as a raw material. In the present invention, the yellow index at the end is defined as the maximum value within 30 mm from both ends in the width direction of the film.

Formula 1.0 ≦ Ye / Yc ≦ 5.0
<Optical film>
The cellulose ester film of the present invention is preferably an optical film used as a polarizing plate protective film used for a liquid crystal display device.
<Polarizing plate>
The optical film of the present invention can be used as a polarizing plate protective film of a polarizing plate having a structure in which a polarizer is sandwiched between two polarizing plate protective films.

  The polarizing plate can be produced by a general method. The cellulose ester film of the present invention is preferably subjected to alkali saponification treatment, and the treated film is bonded to at least one surface of a polarizer prepared by immersing and stretching in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. .

  The polarizer of the present invention includes a polyvinyl alcohol polarizing film, which is a polyvinyl alcohol film dyed with iodine and a dichroic dye 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.

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

The long cellulose ester film produced by the melt casting film-forming method according to the present invention can be bonded with a long polarizer (polarizing film) by subjecting it to alkali saponification treatment. The productive effect is obtained with a long length of 1, and the longer the length is 1500 m, 2500 m, and 5000 m, the higher the productive effect of manufacturing the polarizing plate.
<Liquid crystal display device>
The polarizing plate containing the cellulose ester film of the present invention can exhibit high display quality as compared with a normal polarizing plate.

  The polarizing plate of the present invention includes a multi-domain vertical alignment (MVA) mode, a patterned vertical alignment (PVA) mode, a continuous pinwheel alignment (CPA) mode, an OCB (Optical Compensation InP mode, OCB (Optical Compensation InP) mode, and the like. Can be used.

  The liquid crystal display device is applied as a device for colorization and moving image display, and the display quality is improved by the present invention, and the contrast is improved and the resistance of the polarizing plate is improved. .

  In the case of an optical film, the thickness of the film is preferably 10 to 500 μm. In particular, the lower limit is 20 μm or more, preferably 30 μm or more. The upper limit is 150 μm or less, preferably 120 μm or less.

  A particularly preferred range is 25 to 90 μm. If the film is thick, the polarizing plate after polarizing plate processing becomes too thick, and it is not suitable for the purpose of thin and light in liquid crystal displays used for notebook computers and mobile electronic devices.

  On the other hand, if the film is thin, the moisture permeability of the film increases, and the ability to protect the polarizer from humidity tends to be reduced.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
Example 1
Cellulose acetate propionate having an acetyl group substitution degree of 1.60, a propionyl group substitution degree of 1.20, a total acyl group substitution degree of 2.80, and a number average molecular weight of 60000 dried at 80 ° C. for 6 hours (water content 200 ppm) 100 parts by mass, 12 parts by mass of AC1, 1.1 parts by mass of Tinuvin 928 (manufactured by Ciba Japan Co., Ltd.), 0.25 parts by mass of GSY-P101 (manufactured by Sakai Chemical Industry Co., Ltd.) as a phosphorus compound, Irganox 1010 (Ciba. Japan Co., Ltd.) 0.5 parts by mass, Sumilizer GS (Sumitomo Chemical Co., Ltd.) 0.24 parts by mass, polyhydric alcohol ester plasticizer No. 3 parts by mass of 63, 0.2 parts by mass of Aerosil NAX50 (manufactured by Nippon Aerosil Co., Ltd.), 0.02 parts by mass of Sea Hoster KEP-30 (manufactured by Nippon Shokubai Co., Ltd.) at 80 ° C. and 1 Torr at 3 ° C. Further drying while mixing for a period of time.

  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 was stretched 1.6 times in the transport direction at 175 ° C. (Tg + 35 ° C.) by a stretching machine utilizing the difference in peripheral speed of the roll. Next, it 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 for ensuring thermal insulation between the zones), and is 175 ° C. (Tg + 35 in the width direction). The film was cooled to 30 ° C., then released from the clip, and the clip holding part was cut off to obtain a cellulose ester film 1 having a film thickness of 40 μm and a film width of 2500 mm.

  The cellulose ester film 1 of the present invention except that the cellulose ester and the acrylic polymer were changed as shown in Table 2, the production temperature was changed to Tg + 30 ° C., and the draw ratio and the film thickness before drawing were changed as shown in Table 2. In the same manner as above, the present invention and comparative cellulose ester films 2 to 20 having a film thickness of 40 μm were finally obtained.

(Abbreviations of monomers in Table 1)
MMA: methyl methacrylate VP: N-vinyl pyrrolidone ACMO: acryloylmorpholine HEMA: 2-hydroxyethyl methacrylate HEA: 2-hydroxyethyl acrylate MA: methyl acrylate BA: n-butyl acrylate St: styrene Sumilizer GP: manufactured by Sumitomo Chemical Co., Ltd. Phosphite-based antioxidant TINUVIN111: Hindered amine light stabilizer manufactured by Ciba Japan Co., Ltd. << Evaluation >>
(Measurement method of retardation value)
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.

  Retardation of a film having a wavelength of 590 nm under the same environment using an automatic birefringence meter KOBRA-21ADH (manufactured by Oji Scientific Instruments) for 24 hours in an environment of 23 ° C. and 55% RH. Measurements were made. 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. The direction of the slow axis was also measured at the same time.

Formula (1) Ro = (nx−ny) × d
Formula (2) Rt = {(nx + ny) / 2−nz} × d (where 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 film thickness The refractive index in the direction is nz and d is the film thickness (nm) of the film.)
(Transparency of film)
The film was cut out in the width direction, and white turbidity and dirt generated on the film were visually observed under a fluorescent lamp and a green lamp.
○: There is no cloudiness or dirt Δ: There is weak cloudiness or dirt ×: There is strong cloudiness or dirt The above evaluation results are shown in Table 2 below.

From Table 2, it can be seen that the acrylic polymer of the present invention shows little retardation even at a high draw ratio.
<Production of polarizing plate and liquid crystal display device>
(Preparation of polarizing plate)
Using the raw fabric samples of the cellulose ester films 1 to 20 prepared above, the alkali saponification treatment and the polarizing plate described below were prepared.

<Alkali saponification treatment>
Saponification process 2M-NaOH 50 ° C. 90 seconds Water washing process Water 30 ° C. 45 seconds Neutralization process 10% by mass 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 6 times at 50 ° C. in the transport direction to produce a polarizer.

  Kk4UY manufactured by Konica Minolta Opto Co., Ltd., which was similarly saponified on one side of the polarizer, and the cellulose ester film of the present invention which had been subjected to the alkali saponification treatment on the opposite side was bonded with a 5% aqueous solution of saponified polyvinyl alcohol. As the agent, the polarizing plates 1 to 20 were prepared by bonding them 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)
The obtained polarizing plate carefully peels off the polarizing plate previously bonded to Hitachi liquid crystal display device Wooo W32L-H90, which is an IPS type liquid crystal display device, according to the transmission axis of the polarizing plate originally applied, A polarizing plate was attached so that the cellulose ester film of the present invention produced through the pressure-sensitive adhesive was on the liquid crystal cell side, and a liquid crystal display device was produced. Thereafter, the backlight was continuously turned on for 5 hours in an environment of 23 ° C. and 55% RH, and the entire black display state was visually observed in a dark room to evaluate light leakage.
The results are shown in Table 3.
<Light leakage>
Light leakage during black display was visually evaluated according to the following criteria.
◎: No light leakage ○: There are 1 to 2 weak light leaks △: There are 1 to 2 strong light leaks X: There are 3 or more strong light leaks There is no problem in practical use.

  From Table 3, it can be seen that the acrylic polymer of the present invention has small light leakage even at a high draw ratio.

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 device

Claims (6)

A cellulose ester film comprising: a cellulose ester satisfying the following formulas (1) and (2); and a polymer obtained by polymerizing an ethylenically unsaturated monomer, wherein at least one of the ethylenically unsaturated monomers has a nitrogen atom. A manufacturing method comprising:
Obtaining a raw film containing the cellulose ester and the polymer;
The film original fabric is stretched in each of the conveyance direction and the width direction so that the conveyance direction magnification and the width direction magnification are 2.5 times or more, and in-plane retardation Ro and thickness direction retardation are obtained. And a step of obtaining a cellulose ester film having Rt in the following range.
Formula (1) 2.70 ≦ X + Y ≦ 2.95
Formula (2) 0.5 ≦ Y ≦ 2.3
Ro ≦ 10nm
−20 nm ≦ Rt ≦ 20 nm
In the formula, X represents the degree of substitution of the acetyl group, and Y represents the degree of substitution of the propionyl group or butyryl group.
Ro = (nx−ny) × d, Rt = {(nx + ny) / 2−nz} × d (where the refractive index in the slow axis direction in the film plane at the measurement wavelength of 590 nm is nx, and orthogonal to the slow axis. Ny is the refractive index in the direction of the film, nz is the refractive index in the film thickness direction, and d is the film thickness (nm) of the film.)   The method for producing a cellulose ester film according to claim 1, wherein the ethylenically unsaturated monomer having a nitrogen atom has an amide structure.   The manufacturing method of the cellulose-ester film of Claim 1 or 2 which obtains the said film original fabric by the melt-casting film forming method.   A polymer obtained by polymerizing the ethylenically unsaturated monomer, wherein at least one of the ethylenically unsaturated monomers has a nitrogen atom, N-vinylpyrrolidone, N-acryloylmorpholine, N-methacryloylmorpholine, N-vinylpiperidone, N -Selected from the group consisting of vinylcaprolactam, acrylamide, N, N-dimethylacrylamide, N-isopropylacrylamide, N, N-dimethylaminopropylacrylamide, N, N-diethylacrylamide, N-hydroxyethylacrylamide and N-vinylacetamide A homopolymer of one or more monomers Xa or a copolymer of the monomer Xa and one or more ethylenically unsaturated monomers Xb that are copolymerizable with the monomer Xa and do not contain a nitrogen atom. ~ The method for producing a cellulose ester film of any one of.   The Xb in the copolymer is methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate (i-, n-), butyl (meth) acrylate (n-, i-, s-, t-), pentyl (meth) acrylate (n-, i-, s-), hexyl (meth) acrylate (n-, i-), heptyl (meth) acrylate (n-, i- ), Octyl (meth) acrylate (n-, i-), nonyl (meth) acrylate (n-, i-), myristyl (meth) acrylate (n-, i-), (meth) acrylic acid ( 2-ethylhexyl), (meth) acrylic acid (ε-caprolactone), (meth) acrylic acid (2-hydroxyethyl), (meth) acrylic acid (2-hydroxypropyl), (meth) acrylic acid (3-hydroxypropyl) ), (Meta) The manufacturing method of the cellulose-ester film of Claim 4 which is one or more monomers chosen from the group which consists of lauric acid (4-hydroxybutyl), (meth) acrylic acid (2-hydroxybutyl), styrene, and vinyl acetate. .   The method for producing a cellulose ester film according to claim 4 or 5, wherein a content ratio of the Xa in the copolymer is 20% by mass or more based on a total mass of the Xa and the Xb.

Images