JP2006224589A - Cellulose ester film, manufacturing process of cellulose ester film, polarizing plate, and display unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new manufacturing process of cellulose ester film by a melt-flow-casting method not using a halogen based solvent with high environmental load, thereby to provide a cellulose ester film which has improved planarity, curling nature, dimensional stability which are physical properties and retardation uniformity which is optical property, further to use such a cellulose ester film for a polarizing plate or a liquid crystal display, and thereby to provide a quality display unit. <P>SOLUTION: The manufacturing process of the cellulose ester film comprises: combining a composition containing a cellulose ester and a plasticizer with a thermoplastic resin of non-adhesiveness with this cellulose ester in the shape of a layer and in the state of melting of both of them; arranging layers (B) containing this thermoplastic resin that may differ or be the same kind to both sides of this layer (A) containing the cellulose ester and the plasticizer; and extruding this layer (A) and (B) in the shape of a laminated film having at least three layers from a flat die to be cooled. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  Cellulose ester film is a film that protects photographic negative film supports and polarizers used in liquid crystal displays because of its high transparency, low birefringence, and easy adhesion to polarizers. Has been used a lot.

  Due to the thinness and lightness of the liquid crystal display, the production volume has increased greatly in recent years, and the demand for liquid crystal displays has increased. In addition, TVs using liquid crystal displays are thin and light, and large-scale TVs that have not been achieved with TVs using Brown 菅 are now being produced. The demand for polarizers and polarizer protective films is also increasing.

  Until now, these cellulose ester films have been produced exclusively by the solution casting method. The solution casting method is a film forming method in which a solution obtained by dissolving cellulose ester in a solvent is cast to obtain a film shape, and then the solvent is evaporated and dried to obtain a film. Since a film formed by the solution casting method has high flatness, a high-quality liquid crystal display without unevenness can be obtained using this film.

  However, the solution casting method requires a large amount of an organic solvent and has a large environmental load. Cellulose ester film is formed using a halogen-based solvent with high environmental impact due to its dissolution characteristics, so it is particularly required to reduce the amount of solvent used, and the production of cellulose ester film is increased by solution casting film formation. It has become difficult to do.

  Therefore, in recent years, attempts have been made to melt and form a cellulose ester for silver salt photography (for example, see Patent Document 1) or for a polarizer protective film (for example, see Patent Document 2). Because it is a polymer with a very high viscosity at the time of melting and a high glass transition temperature, it is difficult to level even if the cellulose ester is melted and extruded from a die and cast on a cooling drum or cooling belt. Since it solidifies in a short time after extrusion, the flatness and curl properties that are the physical properties of the resulting film, as well as dimensional stability and retardation properties that are optical properties, particularly retardation uniformity in the width direction of the film, It became clear that it had the subject that it was lower than a rolled film.

In the actual manufacturing stage, it is also required to prevent the take-up roll from being soiled, prevent the process from being contaminated, and prevent the dust from adhering to the take-up roll due to static electricity in the production process.
Japanese National Patent Publication No. 6-501040 JP 2000-352620 A

  Accordingly, the present invention has been intensively studied in view of the above problems, and its object is to provide a novel method for producing a cellulose ester film by a melt casting method that does not use a halogen-based solvent having a high environmental load. By providing a cellulose ester film with improved properties of flatness, curl, dimensional stability, and optical properties of retardation uniformity, and further using such a cellulose ester film for polarizing plates and liquid crystal displays. It is to provide a high-quality display device.

  It is another object of the present invention to provide a method for producing a cellulose ester film that can simultaneously achieve take-out roll contamination prevention, process contamination prevention, and prevention of dust adhesion on a take-up roll by antistatic processing in a production process.

  As a result of intensive investigations aimed at improving these problems, the present inventor has volatilized a part of the added plasticizer from the inside of the film by heating at the time of melt film formation, and as a result, the film surface or internal film density It has been found that the distribution of the plasticizer becomes uneven and the flatness, curling property, dimensional stability and retardation uniformity deteriorate. Therefore, as a method for preventing a part of the plasticizer from volatilizing during melt film formation, a film forming method having a laminated film structure in which layers containing cellulose ester and a plasticizer are sandwiched from both sides by protective layers has been studied.

  For laminated films, the thermoplastic resin protective film is formed on the outside of the cellulose dioxide resin film by coextrusion inflation molding when obtaining a cellulose dioxide resin film for the purpose of protecting the film surface during melt film formation from environmental changes and air oxidation. Or a method of forming a three-layer film by placing the polymer B layer on the at least one surface of the polymer resin A layer by melt extrusion molding. In the present invention, a method of forming a laminate and then surface-treating after peeling off the polymer B layer (Japanese Patent Laid-Open No. 2002-103410) is disclosed. It does not suggest a method for producing such cellulose ester film, but has physical properties such as flatness, curl, dimensional stability, and optical properties. That is not mentioned at all in relation to the retardation uniformity of improvement.

  Therefore, the above-described problem of the present invention is achieved by the following configuration.

(Claim 1)
A composition comprising a cellulose ester and a plasticizer, and the cellulose ester and a non-adhesive thermoplastic resin are both combined in a layered state in a molten state, and are formed on both sides of the layer (A) containing the cellulose ester and the plasticizer. The layer (B) containing the thermoplastic resin, which may be the same or different, is disposed, and the layers (A) and (B) are extruded into a film in a state where three or more layers are laminated from a flat die, A method for producing a cellulose ester film comprising cooling.

(Claim 2)
The method for producing a cellulose ester film according to claim 1, wherein the plasticizer is a polyhydric alcohol ester plasticizer.

(Claim 3)
3. The cellulose ester according to claim 1, wherein the cellulose ester is one or a mixture of two or more selected from cellulose acetate, cellulose propionate, cellulose acetate propionate, and cellulose acetate butyrate. A method for producing a cellulose ester film.

(Claim 4)
The method for producing a cellulose ester film according to any one of claims 1 to 3, wherein the flat die is a multi-manifold die.

(Claim 5)
The method for producing a cellulose ester film according to any one of claims 1 to 4, wherein the resin contained in the layer (B) containing the thermoplastic resin is the same kind of thermoplastic resin.

(Claim 6)
The method for producing a cellulose ester film according to any one of claims 1 to 5, wherein the resin contained in the layer (B) containing the thermoplastic resin is at least one of polyolefin resins.

(Claim 7)
The method for producing a cellulose ester film according to any one of claims 1 to 6, wherein the layer (B) containing the thermoplastic resin has antistatic properties.

(Claim 8)
The method for producing a cellulose ester film according to any one of claims 1 to 7, wherein a surface specific resistance value of the front and back surfaces of the laminated cellulose ester film is 1 × 10 ¹⁴ Ω / □ or less.

(Claim 9)
The method for producing a cellulose ester film according to any one of claims 1 to 8, wherein the cellulose ester film is stretched in at least one direction.

(Claim 10)
The method for producing a cellulose ester film according to any one of claims 1 to 9, wherein the layer (B) containing the thermoplastic resin is peeled off and only the cellulose ester film is wound up.

(Claim 11)
The method for producing a cellulose ester film according to any one of claims 1 to 9, wherein the layer (B) containing a thermoplastic resin is wound up without peeling from the cellulose ester film.

(Claim 12)
The cellulose-ester film manufactured by the manufacturing method of the cellulose-ester film of any one of Claims 1-11.

(Claim 13)
A polarizing plate comprising the cellulose ester film according to claim 12 on at least one surface.

(Claim 14)
A display device comprising the cellulose ester film according to claim 12 or the polarizing plate according to claim 13.

  According to the present invention, it is possible to provide a novel method for producing a cellulose ester film by a melt casting method that does not use a halogen-based solvent with a high environmental load, and are flatness, curl, dimensional stability, and optical properties that are physical properties. A cellulose ester film with improved retardation uniformity can be provided. Further, by using such a cellulose ester film for a polarizing plate or a liquid crystal display, a high-quality display device can be provided.

  Furthermore, in the production process, it is possible to provide a method for producing a cellulose ester film that can simultaneously achieve take-up roll contamination prevention, process contamination prevention, and prevention of dust adhesion of the take-up roll by antistatic processing.

  The best mode for carrying out the present invention will be described in detail below, but the present invention is not limited thereto.

  The present invention provides a cellulose ester film having sufficient flatness and curling properties, and improved retardation uniformity, which is dimensional stability and optical properties, even if it is a melt-formed cellulose ester. is there.

  By using such a cellulose ester film, it is possible to obtain high-quality optical films such as a polarizing plate protective film, an antireflection film, and a retardation film, and further to obtain a liquid crystal display device with high display quality. I can do it.

  As a result of diligent research, the inventors of the present invention have excellent optical characteristics and flatness, curl properties, and dimensions in a thermal melting method, that is, a method of forming a film by a melt casting method that does not use a halogen-based solvent with a large environmental load. In order to obtain a cellulose ester film having high stability, a composition comprising a cellulose ester and a plasticizer, and the cellulose ester and a non-adhesive thermoplastic resin are both combined in a layered state in a molten state, and the cellulose ester and A layer (B) containing the thermoplastic resin, which may be the same or different, is arranged on both sides of the layer (A) containing the plasticizer, and the layers (A) and (B) are separated from the flat die 3 It has been found that by extruding into a film form in a state where more than one layer is laminated and cooling, volatilization and uneven distribution of a film composition such as a plasticizer can be prevented and the object of the present invention can be achieved.

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

(Cellulose ester)
First, the cellulose ester used in the layer (A) containing the cellulose ester and the plasticizer according to the present invention will be described in detail.

  The cellulose ester film of the present invention is produced by a melt casting method. Since the melt casting method can significantly reduce the amount of organic solvent used during film production, the film is much more environmentally friendly than conventional solution casting methods that use a large amount of organic solvent. Is obtained.

  The melt casting in the present invention is a method in which a cellulose ester is heated and melted to a temperature showing fluidity without substantially using a solvent, and a film is formed using this, for example, extruding a fluid cellulose ester from a die. This is a method for forming a film. In addition, although a solvent may be used in a part of the process of preparing the molten cellulose ester, in the melt film forming process in which the film is formed into a film, the forming process is substantially performed without using the solvent.

  The cellulose ester constituting the optical film is not particularly limited as long as it is a meltable film-forming cellulose ester. For example, an aromatic carboxylic acid ester is also used, but in view of the characteristics of the obtained film such as optical characteristics. It is preferable to use a lower fatty acid ester of cellulose. In the present invention, the lower fatty acid in the lower fatty acid ester of cellulose means a fatty acid having 5 or less carbon atoms. For example, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose pivalate and the like are preferable lower cellulose esters of cellulose. It is mentioned as a thing. This is because cellulose ester substituted with a fatty acid having 6 or more carbon atoms has good melt film-forming properties, but the resulting cellulose ester film has low mechanical properties and is substantially difficult to use as an optical film. . In order to achieve both mechanical properties and melt film-forming properties, mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may be used. From the above, cellulose acetate, cellulose propionate, cellulose acetate propionate, and cellulose acetate butyrate are preferably used in the present invention.

  Note that triacetyl cellulose, which is a cellulose ester generally used in solution casting film formation, is a cellulose ester having a decomposition temperature higher than the melting temperature, and thus is difficult to use for melt film formation.

  Therefore, the most preferable lower fatty acid ester of cellulose has an acyl group having 2 to 4 carbon atoms as a substituent, the substitution degree with acetic acid, that is, the substitution degree of acetyl group is X, and the organic acid has 3 to 5 carbon atoms. When the substitution degree, that is, the substitution degree with an acyl group derived from an aliphatic organic acid having 3 to 5 carbon atoms, for example, an acyl group such as a propionyl group or a butyryl group, is Y, the following formulas (2) and (3 A cellulose ester satisfying the above is preferred.

Formula (2) 2.5 <= X + Y <= 2.9
Formula (3) 0.1 <= Y <= 2.0
Among these, cellulose acetate propionate is particularly preferably used, and among them, a cellulose ester satisfying 1.5 ≦ X ≦ 2.5 and 0.5 ≦ Y ≦ 1.0 is preferably used. The portion not substituted with an acyl group usually exists as a hydroxyl group. These can be synthesized by known methods.

  The cellulose ester used in the present invention has a weight average molecular weight Mw / number average molecular weight Mn ratio of 1.0 to 5.5, particularly preferably 1.4 to 5.0, and more preferably 2 0.0-3.0. Mw is preferably 100,000 to 500,000, and more preferably 200,000 to 400,000.

  The average molecular weight and molecular weight distribution of the cellulose ester can be measured by a known method using high performance liquid chromatography. Using this, the number average molecular weight and the weight average molecular weight are calculated.

The measurement conditions are as follows.
Solvent: Tetrahydrofuran column: Shodex K806, K805, K803 (3 connected by Showa Denko KK were used)
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 Corp.) Mw = 100000-500 calibration curves with 13 samples were used. It is preferable that the 13 samples are substantially equally spaced.

  The cellulose ester raw material cellulose used in the present invention may be wood pulp or cotton linter, and the wood pulp may be softwood or hardwood, but softwood is more preferred. A cotton linter is preferably used from the viewpoint of peelability during film formation. The cellulose ester made from these can be mixed suitably or can be used independently.

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

  The cellulose ester can be obtained, for example, by substituting the hydroxyl group of the raw material cellulose with acetic anhydride, propionic anhydride and / or butyric anhydride in the usual manner using an acetyl group, propionyl group and / or butyl group within the above range. . The method for synthesizing such a cellulose ester is not particularly limited, and for example, it can be synthesized with reference to the method described in JP-A-10-45804 or JP-A-6-501040.

  The degree of substitution of acyl groups such as acetyl, propionyl, and butyl groups can be measured according to ASTM-D817-96.

  In addition, cellulose ester is synthesized industrially using sulfuric acid as a catalyst, but this sulfuric acid is not completely removed, and the residual sulfuric acid causes various decomposition reactions during melt film formation, resulting in cellulose ester obtained. In order to affect the quality of the film, the residual sulfuric acid content in the cellulose ester used in the present invention is in the range of 0.1 to 40 ppm in terms of elemental sulfur. These are considered to be contained in the form of salts. If the residual sulfuric acid content exceeds 40 ppm, the thermal decomposition of the cellulose polymer is accelerated at the time of thermal melting, and the strength of the resulting film is lowered or colored, such being undesirable. Moreover, since it becomes easy to fracture | rupture at the time of slitting at the time of hot drawing or after hot drawing, it is not preferable. A smaller amount is preferable, but if it is less than 0.1, it is not preferable because the burden of the washing step of the cellulose resin becomes too large. This is not well understood, although an increase in the number of washings may affect the resin. Furthermore, the range of 0.1-30 ppm is preferable. The residual sulfuric acid content can be similarly measured by ASTM-D817-96.

  By washing the synthesized cellulose ester more sufficiently than when used in the solution casting method, the residual sulfuric acid content can be made within the above range, and when producing a film by the melt casting method. Further, adhesion to the lip portion is reduced, and a film having excellent flatness can be obtained, and a film having favorable dimensional change, mechanical strength, transparency, moisture resistance, Rt value and Ro value described later can be obtained.

The intrinsic viscosity of the cellulose resin is preferably 1.5 to 1.75 g / cm ³ , and more preferably 1.53 to 1.63.

  Moreover, it is preferable that the cellulose ester used by this invention is a thing with few bright spot foreign materials when it is made into a film. A bright spot foreign material is an arrangement in which two polarizing plates are arranged orthogonally (crossed Nicols), a cellulose ester film is arranged between them, light from the light source is applied from one side, and the cellulose ester film is applied from the other side. This is the point where the light from the light source appears to leak when observed. At this time, the polarizing plate used for the evaluation is desirably composed of a protective film having no bright spot foreign matter, and a polarizing plate using a glass plate for protecting the polarizer is preferably used. The bright spot foreign matter is considered to be one of the causes due to the unacetylated or low acetylated cellulose contained in the cellulose ester, and use a cellulose ester with a little bright spot foreign matter (use a cellulose ester with a small dispersion of substitution degree). And filtering the melted cellulose ester, or removing the bright spot foreign matters through the filtration process in the same way once in the solution state in at least one of the process of synthesizing the cellulose ester and the process of obtaining the precipitate You can also. Since the molten resin has a high viscosity, the latter method is more efficient.

As the film thickness decreases, the number of bright spot foreign matter per unit area decreases, and as the cellulose ester content in the film decreases, the bright spot foreign matter tends to decrease. 0.01 mm or more is preferably 200 pieces / cm ² or less, more preferably 100 pieces / cm ² or less, further preferably 50 pieces / cm ² or less, and 30 pieces / cm ² or less. Preferably, it is preferably 10 pieces / cm ² or less, but 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.

  When removing bright spot foreign matter by melt filtration, it is more effective to filter the composition mixed with a plasticizer, deterioration inhibitor, antioxidant, etc. than to filter the melted cellulose ester alone. The removal efficiency of is preferable. Of course, the cellulose ester may be dissolved in a solvent during the synthesis and reduced by filtration. It is possible to filter a mixture of UV absorbers and other additives as appropriate. Filtration is preferably performed at a viscosity of the melt containing cellulose ester of 10,000 PaS or less, more preferably 5000 PaS or less, still more preferably 1000 PaS or less, and even more preferably 500 PaS or less. As the filter medium, conventionally known materials such as glass fibers, cellulose fibers, filter paper, and fluorine resins such as tetrafluoroethylene resin are preferably used, and ceramics and metals are particularly preferably used. The absolute filtration accuracy is preferably 50 μm or less, more preferably 30 μm or less, still more preferably 10 μm or less, and even more preferably 5 μm or less. These can also be used in appropriate combinations. The filter medium can be either a surface type or a depth type, but the depth type is preferably used because it is relatively less clogged.

  In another embodiment, the cellulose ester obtained by dissolving the raw material cellulose ester at least once in a solvent and then drying the solvent may be used. In that case, a cellulose ester which is dissolved in a solvent together with at least one of a plasticizer, an ultraviolet absorber, a deterioration inhibitor, an antioxidant and a matting agent and then dried is used. As the solvent, a good solvent used in a solution casting method such as methylene chloride, methyl acetate or dioxolane can be used, and a poor solvent such as methanol, ethanol or butanol may be used at the same time. In the process of dissolution, it may be cooled to -20 ° C or lower, or heated to 80 ° C or higher. When such a cellulose ester is used, each additive when melted can be easily made uniform, and optical characteristics can be made uniform.

  The optical film of the present invention may be appropriately mixed with polymer components other than cellulose ester. The polymer component to be mixed is preferably one having excellent compatibility with the cellulose ester, and the transmittance when formed into a film is preferably 80% or more, more preferably 90% or more, and further preferably 92% or more.

(Plasticizer)
The addition of a compound known as a plasticizer to the cellulose ester film of the present invention is essential from the viewpoint of improving the film, such as improving mechanical properties, imparting flexibility, imparting water absorption resistance, and reducing moisture permeability. is there. In addition, in the melt casting method performed in the present invention, the plasticizer is added for the purpose of lowering the melting temperature of the film constituting material by adding the plasticizer, rather than the glass transition temperature of the cellulose ester used alone, or at the same heating temperature. This includes the purpose of reducing the viscosity of the film constituting material containing a plasticizer.

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

  If the cellulose ester alone is lower than the glass transition temperature, the fluidity for forming a film is not exhibited. However, the cellulose ester has a lower elastic modulus or viscosity due to the absorption of heat at a glass transition temperature or higher, and exhibits fluidity. In order to melt the film constituent material, the plasticizer to be added preferably has a melting point or glass transition temperature lower than the glass transition temperature of the cellulose ester in order to satisfy the above-mentioned purpose.

  Although it does not specifically limit as a plasticizer used for this invention, It is preferable to contain the following plasticizers. Examples of plasticizers include phosphate ester plasticizers, polyhydric alcohol ester plasticizers, phthalate ester plasticizers, trimellitic ester plasticizers, pyromellitic acid plasticizers, glycolate plasticizers, Citric acid ester plasticizers, polyester plasticizers, fatty acid ester plasticizers, polycarboxylic acid ester plasticizers, and the like can be preferably used.

  Among these, polyhydric alcohol ester plasticizers, phthalate ester plasticizers, citrate ester plasticizers, fatty acid ester plasticizers, glycolate plasticizers, polycarboxylic acid ester plasticizers, and the like are preferable. In particular, it is preferable to use a polyhydric alcohol ester plasticizer.

  The polyhydric alcohol ester plasticizer is a plasticizer comprising an ester of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule. Preferably it is a 2-20 valent aliphatic polyhydric alcohol ester.

  The polyhydric alcohol preferably used in the present invention is represented by the following general formula (I).

Formula (I) R _1- (OH) _n
However, R ₁ represents an n-valent organic group, n represents a positive integer of 2 or more, and the OH group represents an alcoholic and / or phenolic hydroxyl group.

  Examples of preferred polyhydric alcohols include the following, but the present invention is not limited to these. Adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3- Butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, galactitol, mannitol, 3-methylpentane- Examples include 1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, and xylitol. In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

  There is no restriction | limiting in particular as monocarboxylic acid used for the polyhydric alcohol ester of this invention, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferred in terms of improving moisture permeability and retention.

  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. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-10. When acetic acid is contained, the compatibility with the cellulose ester is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

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

  Examples of preferable alicyclic monocarboxylic acids include cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclooctanecarboxylic acid, and derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenylcarboxylic acid, naphthalenecarboxylic acid, and tetralincarboxylic acid. The aromatic monocarboxylic acid which has, or those derivatives can be mentioned. Benzoic acid is particularly preferable.

  The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably 300 to 1500, and more preferably 350 to 750. A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose ester.

  The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

  Below, the specific compound of a polyhydric alcohol ester is illustrated.

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

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

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

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

  Polycarboxylic acid ester plasticizers can also be preferably used. Specifically, it is preferable to add the polyvalent carboxylic acid ester described in paragraphs [0015] to [0020] of JP-A No. 2002-265639 as one of the plasticizers.

  Examples of phosphate plasticizers include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, and the like. Since the agent has high volatility, it is preferable that the agent is not substantially contained in the cellulose ester film constituting the present invention. “Substantially not contained” means that the content is less than 1% by mass, preferably less than 0.1% by mass, and it is particularly preferable not to contain at all.

  The total content of the plasticizer in the cellulose ester film is preferably 5 to 20% by mass, more preferably 6 to 16% by mass, and particularly preferably 8 to 13% by mass with respect to the total solid content. The contents of the two kinds of plasticizers are each at least 1% by mass, preferably 2% by mass or more.

  The polyhydric alcohol ester plasticizer is preferably contained in an amount of 1 to 12% by mass, particularly preferably 3 to 11% by mass. If the amount is too small, deterioration of flatness and curling property is recognized, and if too much, bleeding out tends to occur. The mass ratio between the polyhydric alcohol ester plasticizer and the other plasticizer is preferably in the range of 1: 4 to 4: 1, more preferably 1: 3 to 3: 1. If the amount of the plasticizer added is too large or too small, the film is liable to be deformed, which is not preferable.

  Among the plasticizers, it is generally preferable that no volatile component is generated during heat melting. Specifically, among the above exemplary compounds, trimethylolpropane tribenzoate, which is a polyhydric alcohol ester plasticizer, is preferable, but is not limited thereto. When the volatile component is due to thermal decomposition of the plasticizer, the thermal decomposition temperature Td (1.0) of the plasticizer is higher than the melting temperature of the film-forming material when defined as the temperature at which the mass decreases by 1.0% by mass. Is required. This is because, for the above purpose, the plasticizer is added to the cellulose ester in a larger amount than other film constituent materials, and the presence of the volatile component has a great influence on the quality of the obtained film. The thermal decomposition temperature Td (1.0) can be measured with a commercially available differential thermogravimetric analysis (TG-DTA) apparatus.

  In addition, this invention expands the selection range of the said plasticizer generally considered preferable. That is, when the film constituent material is an integral molded product, the resin and the additive are in close contact with each other, and the contact area with air (especially oxygen and water) is reduced. Therefore, it is expected that the melting point of the film forming material and the thermal decomposition temperature of the plasticizer are lower than those of the single material, and the melting point of the film forming material is lowered and the thermal decomposition temperature of the plasticizer is increased. Further, the best mode in the film formation of the present invention is characterized by extruding at a temperature as low as possible in a short time. For example, the thermal decomposition temperature Td (1.0) of the plasticizer is the melting temperature of the film forming material. Even if it is lower, if the value is close to Td (1.0) = melting temperature of the film-forming material to melting temperature of the film-forming material−about 30 ° C., it is inferior to film quality such as mechanical strength. There is no.

(Other additives)
The cellulose ester film of the present invention includes, in addition to cellulose ester and a plasticizer, a stabilizer, a slip agent, a matting agent, a filler, an inorganic polymer, an organic polymer, a dye, a pigment, a phosphor, an ultraviolet absorber, and an infrared ray. Various functions such as absorbent, dichroic dye, refractive index adjuster, retardation control agent, gas permeation suppressor, antibacterial agent, conductivity imparting agent, biodegradability imparting agent, anti-gelling agent, viscosity modifier If desired, an additive having the following may be added.

  Since the cellulose ester of the present invention is melted and formed at a high temperature of 200 to 250 ° C., the cellulose ester is a process in which decomposition and deterioration of the cellulose ester occurs more easily than conventional solution casting film formation. Among the agents, a stabilizer is preferably added to the film forming material.

  Examples of stabilizers include antioxidants, acid scavengers, hindered amine light stabilizers, ultraviolet absorbers, peroxide decomposers, radical scavengers, metal deactivators, and the like. It is not limited. These are described in JP-A-3-199201, JP-A-5-1907073, JP-A-5-194789, JP-A-5-271471, JP-A-6-107854, and the like. It is preferable that at least one selected from these is included in the film-forming material.

  Further, when the cellulose ester film of the present invention is used as a polarizer protective film, a retardation film, etc., since the polarizer is weak against ultraviolet rays, at least the cellulose ester film on the light incident side with respect to the polarizer has ultraviolet rays. It preferably contains an absorbent.

  Moreover, when using the cellulose-ester film of this invention as a retardation film, the additive for adjusting retardation can be contained. As the compound to be added for adjusting the retardation, a retardation control agent as described in EP 911,656A2 can be used.

  In addition, an organic polymer or an inorganic polymer can be added to the cellulose ester film in order to control the viscosity at the time of heating and melting and adjust the film physical properties after film processing.

  When these additives are added to the cellulose ester resin, the total amount including them is preferably 1 to 30% by mass with respect to the mass of the cellulose resin. If it is 1% by mass or less, the melt film-forming property is lowered, and if it is 30% by mass or more, the mechanical properties and storage stability of the obtained cellulose ester film may not be ensured.

(Antioxidant)
Cellulose ester is preferably decomposed not only by heat but also by oxygen in a high temperature environment where melt film formation is performed. Therefore, the optical film of the present invention preferably contains an antioxidant as a stabilizer. .
The antioxidant useful in the present invention can be used without limitation as long as it is a compound that suppresses deterioration of the melt-molded material due to oxygen. Among these useful antioxidants are hindered phenol antioxidants, Examples thereof include phosphorus antioxidants, sulfur antioxidants, heat-resistant processing stabilizers, oxygen scavengers, etc. Among them, phenol antioxidants, particularly hindered phenol antioxidants are preferable. By blending these antioxidants, it is possible to prevent coloring and strength reduction of the molded product due to heat during heat molding or thermal oxidative degradation without lowering transparency and heat resistance. These antioxidants can be used alone or in combination of two or more.

  Among the above antioxidants, hindered phenol antioxidants are preferable. The hindered phenolic antioxidant compound is a known compound, and is described in, for example, columns 12 to 14 of U.S. Pat. No. 4,839,405, and includes a 2,6-dialkylphenol derivative compound. It is. Among such compounds, preferred compounds include compounds represented by the following general formula (1).

In the formula, R ₁ , R ₂ and R ₃ represent a further substituted or unsubstituted alkyl substituent. Specific examples of hindered phenol compounds include n-octadecyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) -propionate, n-octadecyl 3- (3,5-di-t-butyl- 4-hydroxyphenyl) -acetate, n-octadecyl 3,5-di-tert-butyl-4-hydroxybenzoate, n-hexyl 3,5-di-tert-butyl-4-hydroxyphenylbenzoate, n-dodecyl 3, 5-di-t-butyl-4-hydroxyphenylbenzoate, neo-dodecyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, dodecyl β (3,5-di-t-butyl- 4-hydroxyphenyl) propionate, ethyl α- (4-hydroxy-3,5-di-t-butylphenyl) isobutyrate, octade Sil α- (4-hydroxy-3,5-di-t-butylphenyl) isobutyrate, octadecyl α- (4-hydroxy-3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2- (n -Octylthio) ethyl 3,5-di-t-butyl-4-hydroxy-benzoate, 2- (n-octylthio) ethyl 3,5-di-t-butyl-4-hydroxy-phenylacetate, 2- (n- Octadecylthio) ethyl 3,5-di-t-butyl-4-hydroxyphenyl acetate, 2- (n-octadecylthio) ethyl 3,5-di-t-butyl-4-hydroxy-benzoate, 2- (2- Hydroxyethylthio) ethyl 3,5-di-t-butyl-4-hydroxybenzoate, diethyl glycol bis- (3,5-di-t-butyl-4) -Hydroxy-phenyl) propionate, 2- (n-octadecylthio) ethyl 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, stearamide N, N-bis- [ethylene 3- (3 5-di-t-butyl-4-hydroxyphenyl) propionate], n-butylimino N, N-bis- [ethylene 3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2- (2-stearoyloxyethylthio) ethyl 3,5-di-tert-butyl-4-hydroxybenzoate, 2- (2-stearoyloxyethylthio) ethyl 7- (3-methyl-5-tert-butyl-4- Hydroxyphenyl) heptanoate, 1,2-propylene glycol bis- [3- (3,5-di-tert-butyl-4-hydroxyl Nyl) propionate], ethylene glycol bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], neopentyl glycol bis- [3- (3,5-di-t-butyl-) 4-hydroxyphenyl) propionate], ethylene glycol bis- (3,5-di-t-butyl-4-hydroxyphenyl acetate), glycerin-1-n-octadecanoate-2,3-bis- (3 5-di-t-butyl-4-hydroxyphenyl acetate), pentaerythritol-tetrakis- [3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate], 1,1,1 -Trimethylolethane-tris- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], sorbite Ruhexa- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2-hydroxyethyl 7- (3-methyl-5-tert-butyl-4-hydroxyphenyl) propionate, 2- Stearoyloxyethyl 7- (3-methyl-5-t-butyl-4-hydroxyphenyl) heptanoate, 1,6-n-hexanediol-bis [(3 ', 5'-di-t-butyl-4-hydroxy Phenyl) propionate], pentaerythritol-tetrakis (3,5-di-t-butyl-4-hydroxyhydrocinnamate). Hindered phenol compounds of the type described above are commercially available, for example, from Ciba Specialty Chemicals under the trade names “Irganox 1076” and “Irganox 1010”.

  The antioxidant is preferably added in an amount of 0.1 to 10% by mass, more preferably 0.2 to 5% by mass, and further preferably 0.5 to 2% by mass. Two or more of these may be used in combination.

(Acid scavenger)
Cellulose ester is preferably decomposed by an acid in a high temperature environment where melt film formation is performed. Therefore, the optical film of the present invention preferably contains an acid scavenger as a stabilizer. Any acid scavenger useful in the present invention can be used without limitation as long as it is a compound that reacts with an acid to inactivate the acid, but is described in US Pat. No. 4,137,201. A compound having an epoxy group is preferred. Epoxy compounds as such acid scavengers are known in the art and are derived by condensation of various polyglycol diglycidyl ethers, particularly about 8-40 moles of ethylene oxide per mole of polyglycol. Glycol, diglycidyl ether of glycerol, metal epoxy compounds (such as those conventionally used in and together with vinyl chloride polymer compositions), epoxidized ether condensation products, diphenols of bisphenol A Glycidyl ether (i.e., 4,4'-dihydroxydiphenyldimethylmethane), epoxidized unsaturated fatty acid ester (especially an ester of an alkyl of about 4 to 2 carbon atoms of a fatty acid of 2 to 22 carbon atoms (e.g. butyl Epoxy stearate Epoxidized vegetable oils and other unsaturated natural oils, which may be represented and exemplified by compositions of various epoxidized long chain fatty acid triglycerides and the like (eg, epoxidized soybean oil, epoxidized linseed oil, etc.) As epoxidized natural glycerides or unsaturated fatty acids, which generally contain from 12 to 22 carbon atoms). Further, as a commercially available epoxy group-containing epoxide resin compound, EPON 815C and other epoxidized ether oligomer condensation products of the following general formula (2) can also be preferably used.

In formula, n is an integer of 0-12. Other acid scavengers that can be used include those described in paragraphs 87 to 105 of JP-A-5-194788.
The acid scavenger is preferably added in an amount of 0.1 to 10% by mass, more preferably 0.2 to 5% by mass, and further preferably 0.5 to 2% by mass. Two or more of these may be used in combination.

  The acid scavenger may be referred to as an acid scavenger, an acid scavenger, an acid catcher, etc., but can be used in the present invention without any difference due to their names.

(UV absorber)
The ultraviolet absorber is excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of the polarizer and the display device with respect to ultraviolet rays, and has little absorption of visible light having a wavelength of 400 nm or more from the viewpoint of liquid crystal display properties. Those are preferred. Examples of the ultraviolet absorber used in the present invention include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, triazine compounds, and the like. A benzophenone compound, a benzotriazole compound with little coloring, and a triazine compound are preferable. Moreover, you may use the ultraviolet absorber of Unexamined-Japanese-Patent No. 10-182621 and 8-337574, and the polymeric ultraviolet absorber of Unexamined-Japanese-Patent No. 6-148430.

  Specific examples of the benzotriazole ultraviolet absorber include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) benzo Triazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5 Chlorobenzotriazole, 2- (2′-hydroxy-3 ′-(3 ″, 4 ″, 5 ″, 6 ″ -tetrahydrophthalimidomethyl) -5′-methylphenyl) benzotriazole, 2,2-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2'-hydroxy- '-Tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -6- (straight and side chain dodecyl) -4-methylphenol, octyl- 3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy-5 A mixture of (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate can be mentioned, but is not limited thereto.

  In addition, as commercially available products, TINUVIN 171, TINUVIN 234, and TINUVIN 360 (all manufactured by Ciba Specialty Chemicals) can be mentioned.

  Specific examples of benzophenone compounds include 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, bis (2-methoxy-4-hydroxy- 5-benzoylphenylmethane) and the like, but are not limited thereto.

In the present invention, the ultraviolet absorber is preferably added in an amount of 0.1 to 5% by mass, more preferably 0.2 to 3% by mass, and further preferably 0.5 to 2% by mass. Two or more of these may be used in combination.
These benzotriazole structures and benzophenone structures may be partly or regularly pendant to the polymer, and the molecular structure of other additives such as plasticizers, antioxidants, and acid scavengers. Some may be introduced.

(Hindered amine compounds)
In addition to the above antioxidants, acid scavengers, and UV absorbers, hindered amine compounds can be cited as additives that can suppress the decomposition of cellulose esters by heat and light. It may be added.

  Examples of the hindered amine compound (HALS) used in the present invention include, for example, columns 5 to 11 of U.S. Pat. No. 4,619,956 and columns 3 to 5 of U.S. Pat. No. 4,839,405. 2,2,6,6-tetraalkylpiperidine compounds, or their acid addition salts or complexes of them with metal compounds. Such a compound includes a compound represented by the following general formula (3).

In the formula, R ₁ and R ₂ are H or a substituent. Specific examples of hindered amine compounds include 4-hydroxy-2,2,6,6-tetramethylpiperidine, 1-allyl-4-hydroxy-2,2,6,6-tetramethylpiperidine, 1-benzyl-4- Hydroxy-2,2,6,6-tetramethylpiperidine, 1- (4-t-butyl-2-butenyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine, 4-stearoyloxy-2 , 2,6,6-tetramethylpiperidine, 1-ethyl-4-salicyloyloxy-2,2,6,6-tetramethylpiperidine, 4-methacryloyloxy-1,2,2,6,6-penta Methylpiperidine, 1,2,2,6,6-pentamethylpiperidin-4-yl-β (3,5-di-t-butyl-4-hydroxyphenyl) -propionate, 1-ben L-2,2,6,6-tetramethyl-4-piperidinylmaleate, (di-2,2,6,6-tetramethylpiperidin-4-yl) -adipate, (di-2 , 2,6,6-tetramethylpiperidin-4-yl) -sebacate, (di-1,2,3,6-tetramethyl-2,6-diethyl-piperidin-4-yl) -sebacate, (di- 1-allyl-2,2,6,6-tetramethyl-piperidin-4-yl) -phthalate, 1-acetyl-2,2,6,6-tetramethylpiperidin-4-yl-acetate, trimellitic acid-tri -(2,2,6,6-tetramethylpiperidin-4-yl) ester, 1-acryloyl-4-benzyloxy-2,2,6,6-tetramethylpiperidine, dibutyl-malonic acid-di- (1 , 2,2,6,6-pentamethyl-piperidin-4-yl) -ester, dibenzyl-malonic acid-di- (1,2,3,6-tetramethyl-2,6-diethyl-piperidin-4-yl) Ester, dimethyl-bis- (2,2,6,6-tetramethylpiperidin-4-oxy) -silane, tris- (1-propyl-2,2,6,6-tetramethylpiperidin-4-yl) -Phosphite, tris- (1-propyl-2,2,6,6-tetramethylpiperidin-4-yl) -phosphate, N, N'-bis- (2,2,6,6-tetramethylpiperidine- 4-yl) -hexamethylene-1,6-diamine, N, N′-bis- (2,2,6,6-tetramethylpiperidin-4-yl) -hexamethylene-1,6-diacetamide, 1 -Acetyl-4- N-cyclohexylacetamide) -2,2,6,6-tetramethyl-piperidine, 4-benzylamino-2,2,6,6-tetramethylpiperidine, N, N'-bis- (2,2,6, 6-tetramethylpiperidin-4-yl) -N, N'-dibutyl-adipamide, N, N'-bis- (2,2,6,6-tetramethylpiperidin-4-yl) -N, N'- Dicyclohexyl- (2-hydroxypropylene), N, N′-bis- (2,2,6,6-tetramethylpiperidin-4-yl) -p-xylylene-diamine, 4- (bis-2-hydroxyethyl) -Amino-1,2,2,6,6-pentamethylpiperidine, 4-methacrylamide-1,2,2,6,6-pentamethylpiperidine, α-cyano-β-methyl-β- [N- ( 2, 2, 6, 6 Tetramethylpiperidin-4-yl)] - amino - acrylic acid methyl ester. Examples of preferred hindered amine compounds include, but are not limited to, the following HALS-1 and HALS-2.

  It is preferable to contain at least one of the above compounds, and the content is preferably 0.01 to 5% by mass, more preferably 0.1 to 3% by mass with respect to the mass of the cellulose ester resin. Preferably it is 0.2-2 mass%.

  When the content of the compound is less than the above range, the cellulose ester resin is likely to be thermally decomposed, and when the content is more than the range of the addition amount, transparency as a polarizing plate protective film from the viewpoint of compatibility with the resin. This is not preferable because it causes a decrease and the film becomes brittle.

(Matting agent)
A matting agent can be added to the cellulose ester film of the present invention in order to impart slipperiness, optical and mechanical functions. Examples of the matting agent include inorganic compound fine particles and organic compound fine particles.

  The shape of the matting agent is preferably a spherical shape, a rod shape, a needle shape, a layer shape, a flat shape or the like. Examples of the matting agent include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. Examples thereof include inorganic fine particles such as oxides, phosphates, silicates, carbonates, and crosslinked polymer fine particles. Among these, silicon dioxide is preferable because it can reduce the haze of the film. These fine particles are preferably surface-treated with an organic substance because the haze of the film can be reduced.

  The surface treatment is preferably performed with halosilanes, alkoxysilanes, silazane, siloxane, or the like. The larger the average particle size of the fine particles, the greater the sliding effect, and the smaller the average particle size, the better the transparency. The average primary particle size of the fine particles is in the range of 0.01 to 1.0 μm. The average particle diameter of primary particles of preferable fine particles is preferably 5 to 50 nm, and more preferably 7 to 14 nm. These fine particles are preferably used for generating irregularities of 0.01 to 1.0 μm on the surface of the cellulose ester film.

  Examples of the fine particles of silicon dioxide include Aerosil 200, 200V, 300, R972, R972V, R974, R202, R812, OX50, TT600 manufactured by Nippon Aerosil Co., Ltd., preferably Aerosil 200V, R972. , R972V, R974, R202, R812. Two or more kinds of these fine particles may be used in combination.

  When using 2 or more types together, it can mix and use in arbitrary ratios. Fine particles having different average particle sizes and materials, for example, Aerosil 200V and R972V can be used in a mass ratio of 0.1: 99.9 to 99.9: 0.1.

  These matting agents are preferably added by kneading. Further, as another form, after mixing and dispersing a matting agent previously dispersed in a solvent and a cellulose ester and / or a plasticizer and / or an ultraviolet absorber, a solid material obtained by volatilizing or precipitating the solvent is obtained. It is preferable to use it in the production process of the ester melt from the viewpoint that the matting agent can be uniformly dispersed in the cellulose resin.

  The matting agent can be added to improve the mechanical, electrical and optical properties of the film.

  The slipperiness of the resulting cellulose ester film improves as the fine particles are added, but the haze increases as the fine particles are added. Therefore, the content is preferably 0.001 to 5% by mass, more preferably 0. 0.005 to 1% by mass, and more preferably 0.01 to 0.5% by mass.

  As the cellulose ester film of the present invention, if the haze value exceeds 1.0%, the haze value is preferably less than 1.0%, more preferably less than 0.5%, because it affects the optical material. . The haze value can be measured based on JIS-K7136.

(Formation of laminated film by melt casting method)
The laminated cellulose ester film of the present invention comprises a layer (B) containing a non-adhesive thermoplastic resin to a cellulose ester which may be the same or different on both sides of the layer (A) containing the cellulose ester. (Hereinafter also referred to as a surface layer), and the layers (A) and (B) are extruded into a film in a state where three or more layers are laminated from a flat die, and cooled. The “surface layer” in the present invention is a thermoplastic resin layer located on the outermost layer of the laminated cellulose ester film of the present invention, and there are two layers on the front side and the back side, both of which are referred to as the surface layer. The surface conveyed in contact with the cooling roll at the time of thickness or melt casting can be identified as the roll surface, and the surface in contact with air on the opposite side can be identified as the air surface.

  The number of layers constituting the cellulose ester film of the present invention may be laminated as long as it is 3 or more, but generally 3 layers are preferable from the viewpoint of complicating production equipment. “Lamination” in the present invention means that at least two or more molten resins are joined together with fluidity and processed into an integral sheet film. The layer (A) containing the cellulose ester preferably has a thickness of 10 to 500 μm, particularly preferably 20 μm or more, and more preferably 35 μm or more, as the cellulose ester film used for the final polarizing plate protective film. Moreover, 100 micrometers or less, Furthermore, 85 micrometers or less are preferable. Especially preferably, it is the range of 20-80 micrometers. The layer (B) containing a non-adhesive thermoplastic resin in the cellulose ester is preferably 5 μm or more in order to exhibit the function of the present invention, and has a thickness of 5 to 100 μm from an economical viewpoint. preferable. From the viewpoint of the above reasons and the effective barrier property of the plasticizer, the range of 10 to 30 μm is particularly preferable. Although the thickness of the surface side surface layer or the back surface side surface layer may be the same or different, it is preferable that the thickness is the same in improving the curling property described later.

  In the present invention, once a solid sheet is formed and pasted, so-called laminating processing or coating processing with a paint or the like is performed during the course from the conveyance of the raw material to the winding, and the “lamination” defined in the present invention is used. Is not included.

  In the present invention, the cellulose ester and the non-adhesive thermoplastic resin are thermoplastic resins that are incompatible with the cellulose ester and can be peeled off without being bonded when the layers (A) and (B) are laminated. means. As such a thermoplastic resin, after cooling the extruded sheet obtained by laminating the two sheets of the layer (A) and the layer (B) in a molten state, the peeling force between the layer (A) and the layer (B) Is preferably 100 g / cm or less, more preferably about 1 g / cm to 50 g / cm, and it is preferable to have an adhesive strength that can be easily peeled off. Therefore, the above range is preferable.

  The thermoplastic resin used in the present invention is preferably laminated with cellulose in a molten state as a surface layer resin, and therefore preferably exhibits a melt viscosity close to the melt viscosity of cellulose at the set temperature of the die. If resins having greatly different melt viscosities are laminated, it is difficult to control the film thickness uniformity of the resulting cellulose film. Further, since the surface layer is not a product, a resin with a low cost is preferable. From these two points, polyolefin resins, particularly polyethylene and polypropylene are preferred. Polyethylene and polypropylene are commercially available in many varieties with different melt viscosities due to differences in molecular weight, branching degree, stereoregularity, etc., and those having melt viscosities suitable for the purpose of the present invention can be selected. .

  The term “polyolefin resin” as used herein refers to a resin that contains a large amount of a polyolefin portion and mainly has the properties of a polyolefin resin. The polyolefin may be used alone or in combination.

  That is, the polyolefin resin is a chemically modified polyolefin (hereinafter referred to as a modified polyolefin) alone, or a modified polyolefin blended with an unmodified polyolefin resin such as polypropylene (hereinafter referred to as a polyolefin resin, to be distinguished from a polyolefin resin). Means a blended thermoplastic rubber such as a polyolefin elastomer.

  That is, the polyolefin resin or polyolefin resin preferably used in the present invention means a polymer mainly composed of olefins and a mixture thereof, and includes an olefin homopolymer, an olefin and another olefin and a copolymer, or Various copolymers with other monomers, other differences in chemical structure (straight chain, branched, stereoregularity, etc.), etc., do not matter.

  As the polyolefin resin, polypropylene having an isotactic structure as a main component, low density or high density polyethylene, a copolymer with these other olefins, and a mixture thereof are used, particularly the polypropylene homopolymer resin and the polypropylene copolymer. A resin or a resin mainly composed of polypropylene is preferably used.

  Accordingly, even when a polyolefin resin alone, a modified polyolefin added for the purpose of improving mechanical properties, a polyolefin elastomer, or the like is blended, the polyolefin resin composition preferably has high fluidity.

  In the present invention, the thermoplastic composition preferably has a melt index (sometimes abbreviated as MI) of 20 to 100. The measurement of MI is an index measured according to condition 4 in Table 1 of JISK7210 or condition L in Table 1 of ASTM D1238, both of which are well known to those skilled in the art.

  The layer (B) containing these thermoplastic resins is used in combination with various additives such as slipping materials, stabilizers, antioxidants, viscosity modifiers, antistatic agents, colorants, pigments, etc. I can do it. In particular, it is preferable to contain an antistatic agent in the production process, because it is possible to prevent dust adhesion during roll conveyance and dust adhesion of the take-up roll. The antistatic agent that can be used is not particularly limited, and any antistatic agent that can be added to the resin can be used. Examples of the anionic antistatic agent include fatty acid salts, higher alcohol sulfate esters, Liquid fatty oil sulfate esters, aliphatic amine and aliphatic amide sulfates, aliphatic alcohol phosphate esters, dibasic fatty acid ester sulfonates, aliphatic amide sulfonates, alkylallyl sulfonates, formalin Examples of the cationic antistatic agent including condensed naphthalene sulfonates include aliphatic amine salts, quaternary ammonium salts, and alkylpyridinium salts. Examples of nonionic antistatic agents include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters, polyoxyethylene sorbitan alkyl esters, and the like. Examples of antistatic agents include imidazoline derivatives, betaine-type higher alkylamino derivatives, sulfate ester derivatives, phosphate ester derivatives, etc. Specific compounds include “Antistatic Agent Surface Modification of Polymers” by Hideo Marumo. Shobo, Augmented "Practical Handbook for Additives for Plastics and Rubbers p333-p455" published by Chemical Industry Co., Ltd., JP-A-11-256143, JP-B-52-32572, JP-A-10-158484, and the like. Commercially available antistatic agents can also be used.

  Preferable antistatic agents include ionic polymer compounds such as anionic antistatic agents and cationic antistatic agents. Examples of the ionic polymer compound include anionic polymer compounds such as those described in JP-B-49-23828, JP-A-49-23827, and JP-A-47-28937; JP-B-55-734, JP-A-50-54672 Ionene type polymers having a dissociating group in the main chain as seen in JP-B Nos. 59-14735, 57-18175, 57-18176, 57-56059, etc .: JP-B 53-13223 No. 57-15376, No. 53-45231, No. 55-145783, No. 55-65950, No. 55-67746, No. 57-11342, No. 57-19735, No. 58-56858. No., JP-A 61-27853, 62-9346, and a cationic pendant type having a cationic dissociation group in the side chain Rimmer, graft copolymers such as those found in JP-A-5-230161 and the like.

Another preferable antistatic agent is a metal oxide having conductivity. As an example of the metal oxide, ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ , SiO ₂ , MgO, BaO, MoO ₂ , V ₂ O ₅ , or a composite oxide thereof is preferable. In particular, ZnO, TiO ₂ and SnO ₂ are preferred. Examples of containing different atoms include, for example, addition of Al, In, etc. to ZnO, addition of Nb, Ta, etc. to TiO ₂ , and addition of Sb, Nb, halogen elements, etc. to SnO ₂ . Addition is effective. The amount of these different atoms added is preferably in the range of 0.01 mol% to 25 mol%, but is particularly preferably in the range of 0.1 mol% to 15 mol%.

Further, the volume resistivity of these conductive metal oxide powders is 10 ⁷ Ωcm or less, particularly 10 ⁵ Ωcm or less, the primary particle diameter is 10 nm or more and 0.2 μm or less, and the major structure has a long diameter. It is preferable that the conductive layer contains a powder having a specific structure with a thickness of 30 nm to 6 μm in a volume fraction of 0.01% to 20%.

A particularly preferable antistatic agent is preferably one having a surface specific resistance value of 1 × 10 ¹⁴ Ω / □ or less of the laminated cellulose ester film in view of the relationship between the antistatic performance and the addition amount. Particularly preferably, it is 1 × 10 ¹² Ω / □ or less.

  The surface specific resistance value is measured according to ASTM D257 using a superinsulator after the sample is conditioned for 24 hours in an atmosphere of 23 ° C. and 50% RH.

  A particularly preferable antistatic agent desirably contains an ionene conductive polymer described in JP-A-9-203810 or a quaternary ammonium cation conductive polymer having intermolecular crosslinking.

  The characteristic of the cross-linked cationic conductive polymer is the dispersible granular polymer obtained, and the cationic component in the particles can be given a high concentration and high density. The compatibility with the resin is good, and high transparency is selected. Furthermore, no deterioration in conductivity is observed even under a low relative humidity.

  The laminated cellulose ester film of the present invention is produced by the melt casting method. First, the cellulose ester and the thermoplastic resin are supplied to separate extruders, melt-kneaded, and the layer (A) containing the cellulose ester is formed. A layer (B) containing the thermoplastic resin, which may be the same or different, is arranged on both sides, and the layers (A) and (B) are formed into a film in a state where three or more layers are laminated from a flat die. Extruded, cooled and molded.

  More specifically, the molding method by melt casting that heats and melts 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 polarizing plate protective film excellent in mechanical strength, surface accuracy, etc., the melt extrusion method is excellent, and is particularly preferably used in the present invention. Considering the physical properties of the resulting cellulose ester film, the molten resin temperature is preferably in the range of 120 to 300 ° C, more preferably 200 to 270 ° C. In that case, the cylinder temperature is appropriately set in the range of usually 150 to 400 ° C, preferably 200 to 350 ° C, more preferably 230 to 330 ° C. If the resin temperature is excessively low, the fluidity is deteriorated, sinking or distortion is caused in the film, and it may be difficult to adjust the film thickness. If the resin temperature is excessively high, voids or silver streaks due to thermal decomposition of the resin may occur, or molding defects such as yellowing of the film may occur.

  The actual flow is as follows. After the raw material cellulose ester and the thermoplastic resin formed into a powder or pellet form are dried with hot air or vacuum, they are heated and melted together with the film constituting material, and the fluidity is expressed. It is melt extruded, extruded into a sheet form from a T-die, and brought into close contact with a cooling roll or an endless belt by an electrostatic application method, for example, and solidified by cooling to obtain an unstretched sheet. The temperature of the cooling roll is preferably maintained at 50 to 150 ° C.

  FIG. 1 is a schematic view of a coextrusion die melting film forming apparatus preferable for the present invention.

  The thermoplastic resin molded into powder or pellets is melt-kneaded by a single screw extruder (A) and a single screw extruder (C), and the cellulose ester is melt-kneaded by a twin screw extruder (B). Since the cellulose ester resin of the present invention contains additives such as a plasticizer and an antioxidant, it is preferable to use a biaxial extruder in order to uniformly knead them. The twin screw extruder is subjected to a stronger shearing force than the single screw extruder by two screws, and the effect of mixing the materials is high. There are two types of twin-screw extruders, the same direction rotating type and the different direction rotating type. In the present invention, the same direction type capable of obtaining a stronger shearing force is preferably used. Furthermore, segments such as screw feed and kneading can be designed to be an optimal combination for melt-kneading the material of the present invention. For example, a kneading disk that can disperse a material that is difficult to disperse such as an inorganic fine particle matting agent to a desired degree of dispersion is incorporated, and the diameter of the screw can be selected so as to obtain a desired extrusion amount. When the raw materials are supplied to the co-rotation type twin screw extruder, the respective raw materials may be supplied separately or after being mixed in advance. In order to supply the raw material to the extruder, a continuous feeder such as a known screw feeder, electromagnetic vibration feeder, forced push-type screw feeder or the like can be used. As will be described later, the cellulose polymer is preferably dried before being supplied to the extruder, and the drying temperature is preferably equal to or lower than the Tg of the polymer. However, the glass transition point and melting point of an additive such as a plasticizer are the drying temperature of the cellulose polymer. The following is not preferable because when it is dried together, it is fused to the machine wall. In such a case, it is preferable to dry and supply the cellulose and the additive separately. When cellulose and an additive are mixed and supplied in advance, the drying temperature may be set to the lowest Tg among the respective materials or a temperature not higher than the melting point. In order not to absorb moisture after drying, it is preferable that the dried material is promptly supplied to the extruder. Therefore, a dryer can be installed immediately above the extruder, and the dried raw material can be supplied to the extruder by the continuous feeder described above. Moreover, in order to efficiently dry and prevent moisture absorption of the dried raw material, vacuum drying, reduced pressure drying, or drying while introducing an inert gas is also preferably used. For the same purpose, a reduced pressure or an inert gas atmosphere is preferably performed between the dryer and the feeder, and between the feeder and the extruder inlet. In the case of supplying the cellulose and the additive in powder form, it is preferable that the particle size and the particle size distribution are the same or approximate for uniform mixing regardless of whether they are a separate feed or a mixed feed. Therefore, it is also preferable to pulverize the mixed raw materials with a pulverizer. Moreover, the method of melt-molding after once pelletizing or granulating the mixed raw material can also be taken. In this case, it is completely melted and extruded into a rod shape, cut into a shape of about 3 mm square, pelletized, and completely melted and compressed in a softened state, etc. to be granulated. It is distinguished from. In addition, defective products of melt-formed films and ear portions (hereinafter referred to as recovered products) that do not become products at the time of molding can be pulverized and used as molding raw materials again. This recovered product may also be pelletized or granulated. The recovered product may be pelletized or granulated, or may be mixed with the virgin raw material to be pelletized or granulated. Of course, it may be supplied to the extruder separately from the virgin raw material, or, for example, cellulose and a recovered product can be mixed and supplied.

  Then, each melted resin flow is laminated with a confluencer called a feed block, or a resin flow widened by a manifold is joined and laminated at the base land portion, and from a co-extrusion die (flat die in the present invention) The melt-extruded sheet (A) containing cellulose ester is laminated on both sides of a layer (B) containing a thermoplastic resin, and the molten resin laminate sheet is drawn in the figure. A cast sheet is obtained by tightly cooling and solidifying a moving cooling medium such as a drum as a take-up roll.

  FIG. 2 shows a schematic view of another coextrusion die melt film forming apparatus preferable for the present invention.

  In this case, a single-layer extruder (A) that melts and kneads the thermoplastic resin is used as a single unit, and a sheet having a three-layer structure can be produced by a method of supplying a diverted flow before the co-extrusion die.

  In melt extrusion, the coextrusion slit die is preferably a flat die such as a T-type die, an L-type die, or a fishtail die, and the die lip interval is desirably 50 μm to 2 mm. The type of coextrusion die may be any of the die having the feed block shown in FIG. 3, the multi-manifold die shown in FIG. 4, the multi-slot die, etc. Particularly preferred from the viewpoint of imparting sex. By combining the feed block and the multi-manifold die, it is possible to form a multilayer film such as 5 layers or 7 layers. In this case, what is necessary is just to set so that a thermoplastic resin which does not adhere to cellulose may be the outermost layer, and the inner cellulose film can have a multilayer structure.

  In the multi-manifold die shown in FIG. 4 which is a preferred flat die in the present invention, the cellulose ester or the thermoplastic resin melt-kneaded by a single screw extruder or a twin screw extruder is a gear pump (not shown) for flow rate control. ) Is introduced into the extrusion sections A, B, and C, and the extrusion amount is stabilized by the manifolds A, B, and C, which are liquid pools, and melt extrusion film formation is performed with a film thickness controlled by the lip adjustment bolt 1 . It is also preferred to place a filter between the extruder and the die.

  As the material of the flat die, the molten resin is easy to adhere to a metal material such as a die, and therefore, a fixed streak called a die streak is likely to occur, and there is a possibility that it cannot be used for optical applications. The material in contact with the surface is preferably not a typical chrome plating or nitrided steel, but a ceramic material having excellent releasability, such as TiN, or a SUS material.

  Since the molten resin sheet laminated in three layers is brought into close contact with the cooling roll and cooled and solidified, when the sheet slides on the drum, molecular orientation occurs, so that the retardation becomes 5 nm or more, and it cannot be said to be optically isotropic. Therefore, it is important that the sheet is cast by an adhesion improving means such as a method selected from an air knife, an air chamber, a press roll method, a liquid paraffin coating method, a static electricity application method and the like. A matting agent or the like can also be added to the surface layer (B). Furthermore, in order for the three-layer laminated sheet to be completely adhered onto the cooling roll and cooled, it is preferable to further use an adhesion improving means at the end of the sheet.

  FIG. 5 is a view showing another embodiment of taking the molten film. In this case, the film composition supplied from the die is cooled and solidified to a desired thickness by a cooling drum and a close contact means (air knife or the like) to form a film via a peeling roll.

  In the case of the present invention, the press roll method shown in FIG. 1 is most preferable from the viewpoints of flatness and retardation stability. The press roll method preferably has the same diameter as shown in the take-up roll of FIG. If the diameters are different, there may be a difference in temperature difference or degree of orientation between the front and back surfaces of the extruded film.

  The surface roughness Ra of the cooling roll is preferably 0.4 μm or less, more preferably 0.2 μm or less for a mirror roll, and it is important for improving adhesion and smoothness of the sheet. However, when it is desired to cast at a high speed, the surface roughness Ra obtained by applying a reverse electric field to chrome plating to form a microcrack drum may be a rough roll of about 1 to 4 μm.

  The width of the melt-formed cellulose ester film is preferably 1.4 m or more from the viewpoint of productivity. More preferably, it is the range of 1.4-6m. In the conventional melt-formed cellulose ester film, if the width exceeds 1.4 m, it was difficult to widen because wrinkles or curls were likely to occur in the manufacturing process. The point can be remarkably improved.

The cellulose ester film of the present invention preferably has a hook-shaped curl (curl in the width direction) of 30 m ⁻¹ or less. More preferably 20 m ^-1, further preferably 10 m ^-1 or less, particularly preferably in the range of 0~5m ^-1. The curl value referred to here is the reciprocal of the radius of curvature of the curl (measured in units of m), and the larger the value, the stronger the curl. The curl measurement method is shown below. When the curl is strong, the cellulose ester film may be curled instead of being cocoon-shaped. It is preferable to be within this range even after the film has been heat-treated. The wrinkled curl can be improved by the surface layer (B) containing the thermoplastic resin according to the present invention, and the surface layer (B) is preferably the same kind of thermoplastic resin.

<Measurement method of curl>
The film sample was left for 3 days in an environment of 25 ° C. and 55% RH, and then the film was cut into a width direction of 50 mm and a longitudinal direction of 2 mm. Further, the film piece can be conditioned for 24 hours in an environment of 23 ° C. ± 2 ° C. and 55% RH, and the curl value of the film can be measured using a curvature scale. The degree of curl was measured according to method A of JIS-K7619-1988.

  The curl value is represented by 1 / R, where R is a radius of curvature and the unit is m.

  Thus, the cellulose ester film which is the layer (A) obtained in the present invention is sent to the next step through the transport roll in a state covered with the thermoplastic resin which is the surface layer (B).

  FIG. 6 shows an example of the structure of the laminated cellulose ester film of the present invention.

  In the present invention, the non-adhesive thermoplastic resin layer which is the surface layer (B) may be peeled off and only the cellulose ester film may be wound up, or the thermoplastic resin layer may be wound up without being peeled off. . In particular, the latter case is preferable because it can be used as a protective film for preventing scratches during the production of a polarizing plate, and can prevent dust from adhering even during long-term storage.

  In addition, the film obtained by peeling from the cooling roll is reheated through one or a plurality of roll groups and / or a heating device such as an infrared heater, and then cooled after being stretched in one or more stages in the longitudinal or transverse direction. I can do it. At this time, the non-adhesive thermoplastic resin layer may or may not be peeled off, but is preferably peeled off after passing through the heating step.

  When the glass transition temperature of the cellulose ester film of the present invention is defined as Tg, the stretching is heated in the range of (Tg-30) to (Tg + 100) ° C., more preferably (Tg-20) to (Tg + 80) ° C. It is preferable to stretch in the (longitudinal direction; MD) or width direction (TD). It is preferable to perform transverse stretching within the temperature range of (Tg-20) to (Tg + 20) ° C. and then heat-set. It is also preferable to perform relaxation treatment after the stretching step. Simultaneous biaxial stretching is also preferably used.

  The Tg of the cellulose ester film can be controlled by the material type constituting the film and the ratio of the constituting materials. In the application of the present invention, the Tg of the film is preferably 120 ° C. or higher, and more preferably 135 ° C. or higher. This is because when the cellulose ester film of the present invention is used in a liquid crystal display device, if the Tg of the film is lower than the above, the orientation of molecules fixed inside the film due to the influence of the temperature of the use environment and the heat of the backlight The state is affected, and there is a high possibility that the retardation value and the dimensional stability and shape as a film are greatly changed. Conversely, if the Tg of the film is too high, it becomes difficult to produce because it approaches the decomposition temperature of the film constituting material, and the presence of a volatile component or coloring may occur due to the decomposition of the material itself used when forming a film. Accordingly, it is preferably 200 ° C. or lower, more preferably 170 ° C. or lower. At this time, the Tg of the film can be determined by the method described in JIS K7121.

  In the case of transverse stretching (width direction: TD), it is preferable to perform transverse stretching while sequentially raising the temperature difference in the range of 1 to 50 ° C. in the stretching region divided into two or more, so that the distribution of physical properties in the width direction can be reduced. . Further, after the transverse stretching, it is preferable that the film is held at a temperature of Tg-40 ° C. or higher at a temperature equal to or lower than the final transverse stretching temperature for 0.01 to 5 minutes because the distribution of physical properties in the width direction can be further reduced.

  In the heat setting, heat setting is usually performed for 0.5 to 300 seconds at a temperature higher than the final transverse stretching temperature and within a temperature range of Tg-20 ° C or lower. At this time, it is preferable to heat-fix while sequentially raising the temperature difference in the range of 1 to 100 ° C. in the region divided into two or more.

  The heat-set film is usually cooled to Tg or less, and clip holding portions at both ends of the film are cut and wound. At this time, it is preferable to perform a relaxation treatment of 0.1 to 10% in the lateral direction and / or the longitudinal direction within a temperature range of not more than the final heat setting temperature and not less than Tg. In addition, it is preferable that the cooling is gradually performed from the final heat setting temperature to Tg at a cooling rate of 100 ° C. or less per second. Means for cooling and relaxation treatment are not particularly limited, and can be performed by a conventionally known means. In particular, it is preferable to perform these treatments while sequentially cooling in a plurality of temperature ranges from the viewpoint of improving the dimensional stability of the film. The cooling rate is a value obtained by (T1-T2) / t, where T1 is the final heat setting temperature and t is the time until the film reaches T2 from the final heat setting temperature.

  More optimal conditions of these heat setting conditions, cooling, and relaxation treatment conditions vary depending on the cellulose ester constituting the film, so the physical properties of the obtained biaxially stretched film should be measured and adjusted appropriately to have desirable characteristics. It may be determined by.

  The preferred stretch ratio of the cellulose ester film is that stretched by 1.01 to 3.00 in both the longitudinal direction and the width direction. More preferably, the film is stretched 1.01 to 2.50 times, and more preferably 1.01 to 2.00 times. Accordingly, a cellulose ester film excellent in optical isotropy can be preferably obtained, and a cellulose ester film having excellent flatness can be obtained. It is preferable to perform the width maintenance or the transverse stretching in the film forming process by a tenter, and it may be a pin tenter or a clip tenter.

  In the case of obtaining a retardation film, by changing the stretching ratio in the longitudinal direction and the width direction and stretching so that one of the stretching ratios is larger than the other stretching ratio, optical anisotropy is achieved. A film can be obtained. In this case, the draw ratio between the width direction and the longitudinal direction is preferably 1.1 to 2.0, more preferably 1.2 to 1.5.

  When the cellulose ester film of the present invention is used as a protective film for a polarizing plate, the thickness of the protective film is preferably 10 to 500 μm as described above. 10-100 micrometers is especially preferable, and 20-80 micrometers is especially preferable. When the cellulose ester film is thicker than the above region, for example, when used as a polarizing plate protective film, the polarizing plate after polarizing plate processing becomes too thick, and is particularly thin in liquid crystal displays used for notebook computers and mobile electronic devices. Not suitable for lightweight purposes. On the other hand, if the thickness is smaller than the above region, it is difficult to develop retardation as a retardation film, and the moisture permeability of the film is increased, so that the ability to protect the polarizer from humidity is reduced.

  In the solution casting method, when the film thickness is increased, the drying load is remarkably increased. However, in the present invention, since a drying step is not necessary, a film having a large film thickness can be produced with high productivity. Therefore, there is an advantage that it is easier than ever to increase the thickness of the film in accordance with the purpose of providing a necessary phase difference or reducing moisture permeability. Moreover, even if it is a film with a thin film thickness, it has the effect that it can be produced with high productivity by extending | stretching such a thick film.

  The film thickness variation of the cellulose ester film support is preferably within a range of ± 3%, further ± 1%, and more preferably ± 0.1%.

  The winding length is preferably 500 to 5000 m, more preferably 1000 to 5000 m. It is also preferable to wind up by providing a knurling with a height of 0 to 25% of the film thickness at both ends of the width.

(Volatile component removal)
In order to stably produce such a very long film, it is important that volatile components are not mixed in the material to be cast. Film formation by the melt casting method differs significantly from the solution casting method in the temperature at the time of film formation, and if there are volatile components in the material to be cast, these additives volatilize and adhere to the film forming apparatus at the time of film formation. However, since it causes various failures, it is not preferable from the viewpoint of ensuring the flatness and transparency of the film for utilizing the function as a film or a polarizing plate protective film. In particular, when it adheres to the die, it may cause a streak on the film surface and induce flatness deterioration. Therefore, when a film constituent material is formed into a film, it is not preferable that a component that volatilizes exists in a region lower than the melting temperature for film formation from the viewpoint of avoiding generation of a volatile component during heating and melting.

  The volatile components include moisture absorbed by any of the film constituent materials, mixed oxygen, nitrogen and other gases, or solvents or impurities mixed before the material is purchased or synthesized, plasticizers, oxidation Examples thereof include additives such as an inhibitor, and examples thereof include evaporation by heating, sublimation or volatilization by decomposition. The solvent here is different from the solvent for adjusting the resin as a solution as a solution casting, and is contained in a trace amount in the film constituting material. Therefore, selection of the film constituent material is important in avoiding the generation of volatile components.

  In the present invention, the film constituent material used for melt casting is preferably removed before film formation or heating, when the volatile components typified by the moisture and the solvent are formed. A method by drying can be applied to this removal method, and it can be performed by a method such as a heating method, a reduced pressure method, or a heated reduced pressure method. Drying may be performed in air or in an atmosphere in which an inert gas such as nitrogen or argon is selected as the inert gas. These inert gases preferably have a low content of water or oxygen, and preferably do not substantially contain them. When these known drying methods are performed, it is preferable in terms of film quality to be performed in a temperature range where the film constituting material does not decompose. For example, the moisture or solvent remaining after removal in the drying step is preferably 3% by mass or less, more preferably 1% by mass or less, based on the total mass of the film constituent materials. .

  In particular, the moisture content of the cellulose ester resin is preferably less than 0.5% by mass. These characteristic values can be measured by ASTM-D817-96. The cellulose ester is preferably used as 0.1 to 1000 ppm by further reducing the moisture by heat treatment.

  The film constituent material can reduce the generation of volatile components by drying before film formation, and the resin alone, or at least one mixture or compatible material other than the resin among the resin and the film constituent material. It can be divided and dried. The preferable drying temperature is preferably 80 ° C. or higher and the Tg or melting point of the material to be dried. Including the viewpoint of avoiding fusion between materials, the drying temperature is more preferably 100 to (Tg-5) ° C, and still more preferably 110 to (Tg-20) ° C. A preferable drying time is 0.5 to 24 hours, more preferably 1 to 18 hours, and further preferably 1.5 to 12 hours. Below these ranges, the removal rate of volatile components may be low, or drying may take too long, and when Tg is present in the material to be dried, heating to a drying temperature higher than Tg will cause the material to be removed. May be difficult to handle due to fusion. Drying is preferably performed at 1 atm or less, and particularly preferably performed while reducing the pressure from vacuum to 1/2 atm. Drying is preferably performed while appropriately stirring the material such as resin, and the fluidized bed system in which drying air or dry nitrogen is fed from the lower part in the drying container can perform necessary drying in a shorter time. It is preferable because it is possible.

  The drying process may be separated into two or more stages. For example, the material may be formed using a material that has been subjected to storage of the material in the preliminary drying process and drying immediately before film formation to immediately before a week. .

(Retardation value)
The in-plane retardation value (Ro) and the retardation value (Rt) in the thickness direction of the cellulose ester film according to the present invention are preferably 0 ≦ Ro and Rt ≦ 70 nm when used as a polarizer protective film. . More preferably, 0 ≦ Ro ≦ 30 nm and 0 ≦ Rt ≦ 50 nm, and more preferably 0 ≦ Ro ≦ 10 nm and 0 ≦ Rt ≦ 30 nm. When used as a retardation film, 30 ≦ Ro ≦ 100 nm and 70 ≦ Rt ≦ 400 nm, and more preferably 35 ≦ Ro ≦ 65 nm and 90 ≦ Rt ≦ 180 nm. Further, the variation of Rt and the width of the distribution are preferably less than ± 50%, preferably less than ± 30%, and preferably less than ± 20%. Further, it is preferably less than ± 15%, preferably less than ± 10%, preferably less than ± 5%, particularly preferably less than ± 1%. Most preferably, there is no variation in Rt.

  In the present invention, the retardation fluctuation particularly in the width direction is improved, and excellent visibility can be provided when mounted on a polarizing plate or a liquid crystal display device.

  The retardation values Ro and Rt can be obtained by the following equations.

Ro = (nx−ny) × d
Rt = ((nx + ny) / 2−nz) × d
Here, d is the thickness (nm) of the film, the refractive index nx (also referred to as the maximum refractive index in the plane of the film, the refractive index in the slow axis direction), ny (in the direction perpendicular to the slow axis in the film plane). ) (Refractive index of the film in the thickness direction).

  The retardation values (Ro) and (Rt) can be measured using an automatic birefringence meter. For example, it can be obtained at a wavelength of 590 nm using KOBRA-21ADH (Oji Scientific Instruments) under an environment of 23 ° C. and 55% RH.

  The slow axis is preferably in the width direction ± 1 ° or the longitudinal direction ± 1 ° of the film. More preferably, it is ± 0.7 ° with respect to the width direction or the longitudinal direction, and further preferably ± 0.5 ° with respect to the width direction or the longitudinal direction.

(Residual solvent, moisture content)
Since the cellulose ester film of the present invention does not substantially use a solvent in the film forming step, the amount of residual organic solvent contained in the cellulose ester film wound up after film formation is stably less than 0.1% by mass. Thus, it is possible to provide a cellulose ester film having flatness and dimensional stability that are more stable than before and Rt. In particular, it has become possible to provide a cellulose ester film having stable planarity and Rt even in a long roll of 100 m or longer. The cellulose ester film is not particularly limited as to the winding length, and is preferably used even if it is 1500 m, 2500 m, or 5000 m.

  The amount of residual organic solvent can be measured by the headspace gas chromatography method. That is, a known amount of cellulose ester film is heated in a sealed container at 120 ° C. for 20 minutes, and the organic solvent contained in the gas phase in the sealed container is quantified by gas chromatography. From this result, the residual organic solvent amount (%) can be calculated.

  Moreover, when a film contains a water | moisture content, the moisture content (g) further contained in the cellulose-ester film is calculated | required by another method, and the mass of a water | moisture content from the mass difference (g) of the cellulose-ester film before and behind the said heat processing. The residual organic solvent content (%) can be obtained from the value obtained by subtracting (g).

  It is difficult to reduce the residual organic solvent amount (%) of the cellulose ester film produced by the solution casting method to 0.1% by mass or less, and this requires a long drying step. For example, a cellulose ester film having a very low residual organic solvent content can be obtained at low cost, and a cellulose ester film having excellent characteristics as an optical film can be obtained.

  When the film constituting material is heated and melted, the decomposition reaction becomes remarkable, and this decomposition reaction may be accompanied by coloring or deterioration. Moreover, generation | occurrence | production of the unfavorable volatile component may be accompanied by a decomposition reaction. When volatile components are generated, the conventional method may deposit these components on the surface of the take-up roll, and after continuous production for a certain period of time, it was necessary to interrupt production and clean the roll. In the invention, since both sides of cellulose are covered with a resin film, the degree of contamination of the roll is very small compared to the conventional method, and production can be continued continuously over a long period of time, so the productivity is greatly increased. Be improved.

  The film constituent material can be stored as one or more kinds of pellets for the purpose of avoiding material alteration and hygroscopicity, and a melt can be produced using this. Pelletization can improve the mixability or compatibility of the film constituent materials at the time of melting, and contributes to obtaining optical uniformity of the film. Mixing the constituent materials other than the cellulose resin uniformly with the resin before melting can contribute to providing uniform meltability when heated and melted.

(Application to deflection plate)
When forming and using a polarizing plate using the cellulose ester film of the present invention as a polarizing plate protective film for a liquid crystal display device, the polarizing plate on at least one surface is preferably the polarizing plate of the present invention, and both surfaces are polarizing plates of the present invention. It is more preferable that

  In addition, as a conventional polarizing plate protective film, Konica Minoltak KC8UX, KC4UX, KC5UX, KC8UY, KC4UY, KC8UCR-3, KC8UCR-4, KC12UR, KC8UXW-H, KC8UYW-HA, KC8UX-RHA Cellulose ester films such as those manufactured by KK) are used.

  In the polarizing plate using the cellulose ester film of the present invention, other functional layers can be disposed in order to improve the quality of the display device and to give various functions. For example, a known functional layer such as an antistatic layer, a transparent conductive layer, a hard coat layer, an antireflection layer, an antifouling layer, a slippery layer, an easy adhesion layer, an antiglare layer, or a gas barrier layer may be applied. . In addition, an optically anisotropic layer formed of liquid crystal, polyimide, or the like can be provided, and optimal optical compensation can be performed by combining the polarizing plate protective film and these optically anisotropic layers. At this time, various surface treatments such as corona discharge treatment, plasma treatment, and chemical treatment can be performed as necessary.

(Preparation of deflection plate)
The production method of the polarizing plate of the present invention is not particularly limited, and can be produced by a general method. The obtained polarizing plate protective film was treated with an alkali, and a polyvinyl alcohol film was immersed and stretched in an iodine solution, using a completely saponified polyvinyl alcohol aqueous solution on both sides of the polarizer, and polarizing plate protective films on both sides of the polarizer. Can be pasted together. This method is preferable in that the polarizing plate protective film of the present invention can be directly bonded to a polarizer on at least one side.

  Further, instead of the alkali treatment, easy-adhesion processing as described in JP-A-6-94915 and JP-A-6-118232 may be applied to perform polarizing plate processing.

  The polarizing plate is composed of a polarizer and a protective film for protecting both surfaces of the polarizer, and can further be constructed by laminating a protective film on one surface of the polarizing plate and a separate film on the opposite surface. The protective film and the separate film are used for the purpose of protecting the polarizing plate when the polarizing plate is shipped or transported. In this case, the protect film is bonded for the purpose of protecting the surface of the polarizing plate, and is used on the side opposite to the surface where the polarizing plate is bonded to the liquid crystal plate. The separate film is used for the purpose of covering the adhesive layer. The surface layer (B) of the present invention can also be used as a protective film.

(Liquid crystal display device)
Since the liquid crystal display device comprised of the polarizing plate containing the cellulose ester film of the present invention has good flatness and retardation uniformity of the cellulose ester film used for the polarizing plate, high display quality can be exhibited. In particular, the effect of the present invention can be further exerted when used in a multi-domain liquid crystal display device, more preferably in a multi-domain liquid crystal display device by a birefringence mode.

  Multi-domaining is also suitable for improving the symmetry of image display, and various methods have been reported "Okita, Yamauchi: Liquid Crystal, 6 (3), 303 (2002)". The liquid crystal display cell is also shown in “Yamada, Yamahara: Liquid Crystal, 7 (2), 184 (2003)”, but is not limited thereto.

  The polarizing plate of the present invention includes an MVA (Multi-domain Vertical Alignment) mode represented by a vertical alignment mode, in particular, an MVA mode divided into four, a known PVA (Patterned Vertical Alignment) mode and an electrode multi-domained by electrode arrangement. It can be effectively used in a CPA (Continuous Pinwheel Alignment) mode in which arrangement and chiral ability are fused. In addition, a proposal of an optically biaxial film in the adaptation to the OCB (Optical Compensated Bend) mode has been disclosed, and “T. Miyashita, T. Uchida: J. SID, 3 (1), 29 ( 1995) ", the polarizing plate according to the present invention can also exhibit the effect of the present invention in display quality. If the effect of this invention can be expressed by using the polarizing plate of this invention, arrangement | positioning of a liquid crystal mode and a polarizing plate will not be limited.

  Liquid crystal display devices are being applied to color display and moving image display devices, and the display quality in the present invention is less fatigued and more faithful to display moving images due to improved contrast and resistance to polarizing plates. It becomes.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

  The following cellulose ester was used as a raw material polymer.

<Cellulose ester>
C-1: cellulose acetate propionate (acetyl group substitution degree 1.9, propionyl group substitution degree 0.8, molecular weight Mn = 90000, molecular weight Mw = 220,000, Mw / Mn = 2.4)
C-2: Cellulose acetate propionate (CAP482-20 (manufactured by Eastman Chemical Co.))
C-3: Cellulose acetate butyrate (CAB171-15 (manufactured by Eastman Chemical Co.))
<Thermoplastic resin: polymer for surface layer>
E-1: Low density polyethylene NUC-8000 (manufactured by Nihon Unicar)
E-2: Low density polyethylene F522N (manufactured by Ube Industries)
E-3: High density polyethylene 730F (made by Idemitsu Petrochemical Co., Ltd.)
E-4: High density polyethylene 640UF (made by Idemitsu Petrochemical Co., Ltd.)
E-5: Polypropylene F704NP (made by Idemitsu Petrochemical Co., Ltd.)
E-6: Polypropylene F744NP (made by Idemitsu Petrochemical Co., Ltd.)
E-7: Polypropylene WFX4T (manufactured by Nippon Polypro)
<Plasticizer>
P-1: Trimethylolpropane tribenzoate P-2: Triphenyl phosphate <Antioxidant>
A-1: IRGANOX-1010 (Ciba Specialty Chemicals)
A-2: TINUVIN 144 (Ciba Specialty Chemicals)
A-3: Sumilizer GP (manufactured by Sumitomo Chemical Co., Ltd.)
Example 1
(Film forming of the present invention-1)
100 parts by weight of cellulose ester C-1, plasticizer P-1: 10 parts by weight, antioxidant A-1: 0.5 parts by weight, A-2: 0.5 parts by weight in a tumbler mixer After mixing for a minute, the obtained mixture was dried with a dehumidifying hot air dryer (Matsui Seisakusho DMZ2) at a hot air temperature of 70 ° C. and a dew point of −56 ° C. for 5 hours. Then, it supplied to the biaxial extruder (B) shown in FIG. 1, and shape | molded in the film form. At this time, the polymer E-1 for surface layer which is a thermoplastic resin is supplied to two single-screw extruders (A) and (C), and a co-extrusion die is used. It was molded so that E-1 would come. Although not shown in the figure, a filter and a gear pump are installed at the tip of the extruder.

  The set temperatures of the three extruders were all set to 240 ° C, and the coextrusion die was set to 250 ° C. The coextrusion die was a coat hanger type three-layer multi-manifold die, and the lip gap was 200 μm. The gap can be adjusted by push-pull bolts according to the thickness of the film formed. The thickness of each layer can be arbitrarily adjusted by changing the number of rotations of each gear pump.

  Silica particles (particle size: 2 μm) were added as a slip agent from the opening of the additive hopper provided in the middle part of the twin screw extruder (B) by a continuous feeder so as to be 0.02% of the extrusion amount. . Similarly, a UV absorber (Tinuvin 360: manufactured by Ciba Specialty Chemicals) was added from the same opening so that the amount of extrusion was 0.5%. The melt-extruded film was sandwiched between two chrome-plated mirror rolls adjusted to 100 ° C., slit at the edge, and wound around a winder. The surface film is not peeled off.

  Among the wound films, the rotation speed of each gear pump, the rotation speed of the extruder, and the rotation speed of the take-up roll were adjusted so that the thickness of the cellulose film was 80 μm and both of the surface layer films were 20 μm.

(Film forming of the present invention-2-15)
Films of the present inventions 2 to 14 in the same manner as the film forming of the present invention-1 in the combinations shown in Table 1 using cellulose esters C-1, 2, 3 and E-1 to 7 as the polymer for the surface layer. Was molded. When producing the film of the present invention-13, 2% of A-3 was added instead of A-1 and A-2. When producing the film of the present invention-14, 1% of A-3 was added instead of A-1. When the film of the present invention-1 was prepared, the film of the present invention-15 was formed using the same amount of P-2 instead of the plasticizer P-1.

(Film forming of the present invention-16)
The same raw materials as those of Invention-1 were used, and films were formed under the same conditions except that the final cellulose ester film thickness was adjusted to 96 μm. The surface film of the obtained three-layer film was peeled off, the cellulose ester film was guided to a tenter, and stretched by 20% in the width direction at 130 ° C.

(Film forming of the present invention-17)
The same raw material as in the present invention-1 was used, and a film was formed under the same conditions except that the final cellulose ester film thickness was adjusted to 115 μm. After peeling off the surface film of the obtained three-layer film, the film was stretched by 20% in the longitudinal direction due to the difference in peripheral speed of the rolls, then led to a tenter, and stretched by 20% in the width direction at 130 ° C.

  In addition, the transmittance | permeability of the cellulose-ester film of this invention-1 to this invention-17 measured the transmittance | permeability of visible light whole region using the Hitachi Ltd. spectrophotometer, after peeling the surface layer of the obtained film. As a result, all were 90% or more and excellent in transparency. In addition, none of the die muscles was observed. Furthermore, the contamination of the take-up roll and the process contamination in the production process were improved compared to the film formation of the comparative example.

(Film forming of Comparative Example-1)
A cellulose film was formed using the same raw material as in the present invention-1 and using only a twin screw extruder and no surface layer. The die used was a coat hanger type single layer die.

(Film forming of Comparative Example-2)
A cellulose film was formed using the same raw material as that of the present invention-15 using P-2 as a plasticizer, without using a surface layer, using only a twin screw extruder. The die used was a coat hanger type single layer die.

(Film forming of Comparative Example-3)
The same raw materials as in the present invention-1 were used, except that two single-screw extruders (A) and (C) were cellulose ester C-2: 100 parts by mass, plasticizer P-1: 10 parts by mass, oxidation Inhibitors A-1: 0.5 parts by mass, A-2: 0.5 parts by mass were mixed for 30 minutes with a tumbler mixer, and then heated with a dehumidifying hot air dryer (Matsui Seisakusho DMZ2). A composition dried at 70 ° C. and a dew point of −56 ° C. for 5 hours was supplied. The number of revolutions of the extruders (A), (B), and (C) and the gear pump was adjusted so that the formed film had a thickness of 10 μm for the surface layer, 60 μm for the center layer, and 80 μm in total thickness. Three layers of the obtained film were completely adhered and could not be peeled off.

(Film forming of Comparative Example-4)
In the same manner as in Comparative Example-3, the thickness of the film was set to 10 μm for the surface layer, 80 μm for the center layer, and 100 μm in total thickness. Three layers of the obtained film were completely adhered and could not be peeled off.

<Evaluation>
(Flatness)
The surface layer is peeled off from the formed film, each cellulose ester film sample is cut into a size of 90 cm in width and 100 cm in length, and a height of 1. is set so that five 50 W fluorescent lamps are arranged and the sample stage can be illuminated from a 45 ° angle. The film sample was fixed on a height of 5 m, each film sample was placed on a sample stage, and the unevenness that was reflected on the film surface was visually observed, and the following determination was made. By this method, it is possible to determine “tsun” and “wrinkle”.

◎: All five fluorescent lamps looked straight ○: Fluorescent lamps appear to be slightly bent △: Fluorescent lamps appear to be slightly bent as a whole ×: Fluorescent lamps appear to swell greatly (dimensional stability)
The surface layer was peeled off from the formed film, two 10-character scratches were placed as marks on the cellulose ester film sample and placed in an atmosphere of 23 ° C. and 55% RH for 24 hours, and the distance ( X0) is measured. Next, the sample is put in an oven maintained at 80 ° C. and 90% RH, left for 100 hours, then placed in an atmosphere of 23 ° C. and 55% RH for 24 hours, and then the scratch distance X1 is measured. The following formula D is defined as a dimensional change rate.

D = (X1-X0) / X0 × 100 (%)
(Evaluation of curling properties)
The surface layer is peeled off from the molded film, a 5 mm × 5 cm cellulose ester film sample is cut out, left in a constant temperature and humidity chamber at a temperature of 23 ° C. and 55% RH for 24 hours, placed on a flat plate, and a curvature scale is set. The radius of curvature having a curve matching the sample was obtained, and the curl size and ease of handling were ranked as follows.

Curvature radius: 1 / radius of a circle with a curve that matches the sample (1 / m)
◎: Less than 0-5 ◯: Less than 5-10 △: Less than 10-30 x: 30 or more Here, ◎ and ○ are easy to handle, but below △ are extremely difficult to handle.

(Retardation Ro, Rt variation)
The surface layer was peeled from the formed film, the retardation was measured at 1 cm intervals in the width direction of the obtained cellulose ester film sample, and expressed by the variation coefficient (CV) of the retardation obtained from the following formula It is. For measurement, an automatic birefringence meter KOBURA 21ADH (manufactured by Oji Scientific Instruments Co., Ltd.) is used and is three-dimensionally spaced at 1 cm intervals in the width direction of the sample at a wavelength of 590 nm in an environment of 23 ° C. and 55% RH The birefringence was measured and the measured value was substituted into the following equation.

In-plane retardation Ro = (nx−ny) × d
Thickness direction retardation Rt = ((nx + ny) / 2−nz) × d
Here, d is the thickness (nm) of the film, the refractive index nx (also referred to as the maximum refractive index in the plane of the film, the refractive index in the slow axis direction), ny (in the direction perpendicular to the slow axis in the film plane). ) (Refractive index of the film in the thickness direction).

  The standard deviation by the (n-1) method was calculated | required for the obtained in-plane and thickness direction retardation, respectively. For the retardation distribution, the coefficient of variation (CV) shown below was obtained and used as an index. In actual measurement, n was set to 130 to 140.

Coefficient of variation (CV) = standard deviation / retardation average value ◎: variation (CV) is less than 1.5% ○: variation (CV) is 1.5% or more and less than 5% Δ: variation (CV) is 5% Above, less than 10% x: Table 1 shows the evaluation results with a variation (CV) of 10% or more.

  From the above results, the cellulose ester films of the present invention-1 to 17 are superior to the cellulose ester films of Comparative Examples-1 to 4 in flatness, dimensional change rate, curling property, and uniformity of retardation. I understand that.

  Comparing Comparative Example-2 using triphenyl phosphate with relatively high volatility and the cellulose ester film of the present invention-15, the structure of the present invention has a remarkable flatness, dimensional change rate, curling property, and retardation uniformity. It is clear that it will be improved. However, from the comparison between the present invention-1 and the present invention-15, it is preferable to use a polyhydric alcohol ester plasticizer as the plasticizer because each characteristic is further improved.

  Further, C-1 as the cellulose ester, the same type as the polymer species for the surface layer, and the cellulose ester having a thickness of 80 μm or less were excellent overall.

Example 2
In the film forming of the present invention-1, 30 parts by mass of an antistatic agent Hiboron (manufactured by Boron International Co., Ltd.) is added to the thermoplastic resin: polymer E-1 for the surface layer, and the film is formed in the same manner. The film of invention-18 was produced, and the surface layer film was wound around a winder without peeling off. At this time, in order to knead high boron and E-1, a twin screw extruder was used instead of the single screw extruders (A) and (C).

When the surface specific resistance value of the film was measured with an insulation resistance measuring instrument (such as VE-30 manufactured by Kawaguchi Electric Co., Ltd.), the surface specific resistance value on the front and back of the film of the present invention-18 was 1 × 10 ¹¹ Ω / □. The surface specific resistance value of the front and back surfaces of the film-1 of the present invention was 5 × 10 ¹⁴ Ω / □.

  The wound film was stored in a warehouse for one month in an environment of 23 ° C. and 30% RH. Compared to the film 1 of the present invention wound in the same manner, the surface of the roll was visually observed. No dust adhesion was observed, and it was found that the effect of preventing dust adhesion by antistatic processing was excellent.

Example 3
(Preparation of polarizing plate)
A 120 μm-thick polyvinyl alcohol film was immersed in an aqueous solution containing 1 part by mass of iodine, 2 parts by mass of potassium iodide, and 4 parts by mass of boric acid, and stretched 4 times at 50 ° C. to produce a polarizer.
The cellulose ester films of the present invention-1-18 prepared in Examples 1 and 2 and the surface layers were peeled off, and the films of Comparative Examples-1-4 were alkali-treated with a 2.5N sodium hydroxide aqueous solution at 40 ° C. for 60 seconds. The surface was further washed and dried to saponify the surface.

  On both sides of the polarizer, the cellulose ester film of the present invention-1-18 or the alkali-treated surface of the film of Comparative Examples-1-4 was bonded from both sides with a fully saponified polyvinyl alcohol 5% aqueous solution as an adhesive, The polarizing plates 1-18 of this invention in which the protective film was formed, and the polarizing plates 1-4 of the comparative example were produced.

  In the cellulose ester films of the present invention-1 to 18, there was no failure that caused a problem particularly during the processing of the polarizing plate. Further, the cellulose ester film of the present invention-18 had good processability without adhesion of dust even during polarizing plate processing.

(Characteristic evaluation as a liquid crystal display device)
The both-sided polarizing plates of the 15-inch display VL-150SD manufactured by Fujitsu were peeled off, and the prepared polarizing plates were cut according to the size of the liquid crystal cell and bonded to the glass surface.

  The two prepared polarizing plates were bonded so as to be orthogonal to each other so that the polarizing axes of the polarizing plates were not changed, and liquid crystal display devices were respectively prepared.

  The liquid crystal display device using the polarizing plates 1 to 18 of the present invention had high contrast and exhibited excellent display properties without color unevenness due to variation in retardation. Thereby, it was confirmed that it is excellent as a polarizing plate for image display apparatuses, such as a liquid crystal display.

1 is a schematic view of a preferred co-extrusion die melting film forming apparatus for the present invention. A schematic view of another coextrusion die melt film forming apparatus preferable for the present invention is shown. 1 is a schematic view of a die having a feed block. FIG. It is the schematic of a multi-manifold die. It is another form figure of taking over of a molten film. It is an example which shows the structure of the laminated | stacked cellulose-ester film of this invention.

Explanation of symbols

1 Lip adjustment bolt 2 Extruded part A
3 Extrusion part B
4 Extrusion part C
5 Manifold A
6 Manifold B
7 Manifold C
8 Feed block 9 Choke bar 10 Adjustment bolt

Claims (14)

A composition comprising a cellulose ester and a plasticizer, and the cellulose ester and a non-adhesive thermoplastic resin are both combined in a layered state in a molten state, and are formed on both sides of the layer (A) containing the cellulose ester and the plasticizer. The layer (B) containing the thermoplastic resin, which may be the same or different, is disposed, and the layers (A) and (B) are extruded into a film in a state where three or more layers are laminated from a flat die, A method for producing a cellulose ester film comprising cooling. The method for producing a cellulose ester film according to claim 1, wherein the plasticizer is a polyhydric alcohol ester plasticizer. 3. The cellulose ester according to claim 1, wherein the cellulose ester is one or a mixture of two or more selected from cellulose acetate, cellulose propionate, cellulose acetate propionate, and cellulose acetate butyrate. A method for producing a cellulose ester film. The method for producing a cellulose ester film according to any one of claims 1 to 3, wherein the flat die is a multi-manifold die. The method for producing a cellulose ester film according to any one of claims 1 to 4, wherein the resin contained in the layer (B) containing the thermoplastic resin is the same kind of thermoplastic resin. The method for producing a cellulose ester film according to any one of claims 1 to 5, wherein the resin contained in the layer (B) containing the thermoplastic resin is at least one of polyolefin resins. The method for producing a cellulose ester film according to any one of claims 1 to 6, wherein the layer (B) containing the thermoplastic resin has antistatic properties. The method for producing a cellulose ester film according to any one of claims 1 to 7, wherein a surface specific resistance value of the front and back surfaces of the laminated cellulose ester film is 1 × 10 ¹⁴ Ω / □ or less. The method for producing a cellulose ester film according to any one of claims 1 to 8, wherein the cellulose ester film is stretched in at least one direction. The method for producing a cellulose ester film according to any one of claims 1 to 9, wherein the layer (B) containing the thermoplastic resin is peeled off and only the cellulose ester film is wound up. The method for producing a cellulose ester film according to any one of claims 1 to 9, wherein the layer (B) containing a thermoplastic resin is wound up without peeling from the cellulose ester film. The cellulose-ester film manufactured by the manufacturing method of the cellulose-ester film of any one of Claims 1-11. A polarizing plate comprising the cellulose ester film according to claim 12 on at least one surface. A display device comprising the cellulose ester film according to claim 12 or the polarizing plate according to claim 13.

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