JP2006232892A - Method for producing cellulose ester film, cellulose ester film, and optical film using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-saponified cellulose ester film suited as an optical film free from surface defects. <P>SOLUTION: The method for producing the cellulose ester film comprises the step of irradiating at least one surface of a filmlike cellulose ester satisfying all of the requirements specified by the following formulas (S-1) to (S-3) with electron beams at an intensity of 10 to 200 keV at a dose of 10 to 200 kGy and treating the film-like cellulose ester subjected to the irradiation with electron beams with an alkali saponifying solution: formula (S-1) 2.50≤A+B≤3.00, formula (S-2) 0≤A≤2.5, and formula (S-3) 0.5≤B≤3.00, (wherein A is the degree of substitution with acetyl groups; and B is the degree of substitution with 3 to 22C substituted acyl groups). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a cellulose ester film, a cellulose ester film, and an optical film using the same. In particular, the present invention relates to an optical film having functions such as polarization, reflection, and optical compensation useful for an image display device.

Technical background

  Various image display devices mounted on personal computers, televisions, mobile phones, and various instruments, etc., are able to observe visual information such as letters and figures through transparent protective substrates such as glass and plastic plates on the surface. ing. In recent years, many of the image display devices of equipment have become liquid crystal display devices. A liquid crystal display device usually comprises a liquid crystal cell, a polarizing plate, and an optical compensation sheet (retardation plate). In a transmissive liquid crystal display device, usually, two polarizing plates are attached to both sides of a liquid crystal cell, and one or two optical compensation sheets are disposed between the liquid crystal cell and the polarizing plate. In a reflection type liquid crystal display device, it usually comprises a reflection plate, a liquid crystal cell, one optical compensation sheet, and one polarizing plate.

  The liquid crystal cell is composed of a rod-like liquid crystal molecule, two substrates for encapsulating it, and an electrode layer for applying a voltage to the rod-like liquid crystal molecule. About TN (Twisted Nematic), IPS (In-Plane Switching), FLC (Ferro-electric Liquid Crystal), OCB (Optically Compensation Bend), STN (Super T e). Various display modes such as HAN (Hybrid Aligned Nematic) have been proposed. The polarizing plate generally comprises a polarizing film and two transparent protective films provided on both sides thereof. The polarizing film is generally obtained by impregnating polyvinyl alcohol with an aqueous solution of iodine or a dichroic dye, and further uniaxially stretching the film. A polarizing plate using a cellulose ester film as a protective film has excellent optical properties, high transmittance and polarization degree in a wide wavelength range, and excellent brightness and contrast. It is also frequently used as a plate.

  Optical compensation sheets are used in various liquid crystal display devices in order to eliminate image coloring and increase the viewing angle. As an optical compensation sheet, a stretched birefringent film has been conventionally used. It has been proposed to use an optical compensation sheet having an optically anisotropic layer formed of liquid crystalline molecules (particularly discotic liquid crystalline molecules) on a transparent support, instead of an optical compensation sheet comprising a stretched birefringent film. Yes. The optically anisotropic layer is formed by aligning liquid crystalline molecules and fixing the alignment state. By using liquid crystalline molecules in the optical compensation sheet, it has become possible to realize optical characteristics that could not be obtained with conventional stretched birefringent films. The optical properties of the optical compensation sheet are designed according to the optical properties of the liquid crystal cell, specifically, the difference in the display mode of the liquid crystal cell as described above. When liquid crystalline molecules, particularly discotic liquid crystalline molecules are used for the optical compensation sheet, optical compensation sheets having various optical characteristics corresponding to various display modes of the liquid crystal cell can be produced.

  Optical compensation sheets using discotic liquid crystalline molecules have been proposed for various display modes. For example, Patent Documents 1 to 4 describe optical compensation sheets for TN mode liquid crystal cells. An optical compensation sheet for liquid crystal cells in IPS mode or FLC mode is described in Patent Document 5. Furthermore, optical compensation sheets for liquid crystal cells in OCB mode or HAN mode are described in Patent Documents 6 and 7. Furthermore, an optical compensation sheet for liquid crystal cells in STN mode is described in Patent Document 8. A VA mode liquid crystal cell optical compensation sheet is described in Patent Document 9.

  If an elliptically polarizing plate is formed by laminating an optical compensation sheet using liquid crystalline molecules and a polarizing film, the optical compensation sheet can also function as one transparent protective film of the polarizing plate. Such an elliptically polarizing plate has a layer structure in which a transparent protective film, a polarizing film, a transparent support, and an optically anisotropic layer formed of liquid crystalline molecules are laminated in this order. Since the liquid crystal display device is required to have a thin and lightweight characteristic, if it can be reduced by combining one of the components (transparent protective film of polarizing plate and optical compensation sheet), the device can be made thinner and lighter. It becomes possible. Further, by reducing the number of components of the liquid crystal display device, it is preferable that the number of steps for attaching the components is also reduced, and the possibility that a failure or the like occurs when the device is assembled is reduced. For example, Patent Documents 10 to 12 describe an integrated elliptical polarizing plate in which a transparent support of an optical compensation sheet using liquid crystalline molecules and one protective film of a polarizing plate are used in common.

  Such a sheet-like material having optical functionality such as a polarizing plate and an optical compensation sheet is called an optical film, but as a transparent support of the optical film, it has excellent light transmittance and optical non-orientation. Thus, a cellulose ester film represented by a cellulose acetate film having excellent physical and mechanical properties and having characteristics such as little dimensional change with respect to temperature and humidity changes is used.

  A polarizing film or an optical compensation layer is provided on the cellulose ester film of the transparent support via an adhesive layer or an alignment film (usually polyvinyl alcohol). One of the adhesive layers and the alignment film is provided with adhesiveness. As a means, a method of immersing a cellulose ester film in an alkaline saponification aqueous solution to saponify and hydrophilize the surface (for example, paragraph No. [0008] of Patent Document 13, paragraph No. [0033] of Patent Document 14 and Patent Document 15). Paragraph number [0083] and paragraph number [0042] of Patent Document 16 are known.

  However, since these treatment solutions are treated with an aqueous solution containing only an alkali agent, it is difficult to uniformly saponify the hydrophobic film surface. On the other hand, a method of immersing in an alkaline saponification aqueous solution containing an organic solvent that does not dissolve or swell the polymer film (paragraph number [0034] of Patent Document 17), alkaline saponification There has been proposed a method (Patent Document 18) in which an aqueous saponification solution containing an aqueous solution or an organic solvent is applied onto a film surface to saponify at least one surface. By including an organic solvent in the alkaline saponification aqueous solution, the saponification reaction activity can be enhanced as compared with the alkaline saponification aqueous solution. However, on the other hand, depending on the increased reaction activity and the type or content of the organic solvent, a large amount of additive substances or film mixed substances contained in the film to be treated may elute, or a concentrated alkaline agent may adhere. Thus, there is a problem in that the quality as an optical film is deteriorated, such as an increase in film haze, adhesion failure, generation of foreign matter defects and orientation defects. Furthermore, in order to increase production volume due to rapid progress such as the recent enlargement of screens and mobile devices of image display devices and to reduce manufacturing costs, continuous production of long films is more stable. Is desired.

As this improvement, an electron beam process such as a corona discharge process is described (Patent Document 19). However, the adhesion with the polarizing plate was insufficient only by this surface treatment. Further, a cellulose ester film for an elliptically polarizing plate that is surface-treated by corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment, and ultraviolet treatment has been disclosed. It was difficult to achieve sufficient adhesion.
Moreover, the process of apply | coating an alkaline solution to a polymer film, especially a cellulose-ester film, and the process of washing off an alkaline solution from a polymer film are disclosed (patent document 20, patent document 21, patent document 22). Although these methods have been shown to improve saponification characteristics over conventional alkali saponification methods, surface treatment non-uniformity and by-products due to saponification (eg, cellulose degradation components, plasticizers, optical A major problem is that property control agents and surfactants) adhere to the surface of the cellulose ester film and cause deterioration of the surface state.
Furthermore, as a modification of these, a method for producing a polarizing plate protective film is disclosed (Patent Document 23), wherein at least one surface of the film is made hydrophilic by electron beam irradiation treatment (Patent Document 23). However, the film described in Patent Document 23 has a problem that an optical material (for example, cellulose triacetate) has a large humidity dependency of its optical characteristics, and further, the film strength is lowered and the adhesion to the polarizing plate is deteriorated. It was.

JP-A-6-214116 US Pat. No. 5,583,679 US Pat. No. 5,646,703 German Patent No. 3911620A1 Japanese Patent Laid-Open No. 10-54982 US Pat. No. 5,805,253 International Publication WO96 / 37804 JP-A-9-26572 Patent Registration No. 2866372 Japanese Patent Laid-Open No. 7-191217 JP-A-8-21996 JP-A-8-94838 JP-A-7-151914 JP-A-8-94838 JP 2001-166146 A JP 2001-188130 A JP 2002-82226 A International Publication WOO02 / 46809 JP 2003-195044 A JP 2003-203964 A JP 2003-203965 A JP 2003-313326 A JP 2004-109713 A

  An object of the present invention is to provide a cellulose ester film that is excellent in surface treatment characteristics and aims to solve the above-described problems.

  As a result of intensive studies by the inventor of the present application under the above problems, it has been found that the object of the present invention is achieved by the following means.

(1) An electron beam having an intensity of 10 to 200 keV and an irradiation amount of 10 to 200 kGy on at least one surface of a film-like cellulose ester satisfying all the requirements defined by the following formulas (S-1) to (S-3) A method for producing a cellulose ester film, comprising a step of performing irradiation and treating the film-like cellulose ester with an alkali saponification solution after the electron beam irradiation.
Formula (S-1) 2.50 ≦ A + B ≦ 3.00
Formula (S-2) 0 ≦ A ≦ 2.5
Formula (S-3) 0.5 ≦ B ≦ 3.00
(In formulas (S-1) to (S-3), A represents the degree of substitution of the acetyl group, and B represents the degree of substitution of the substituted acyl group having 3 to 22 carbon atoms.)

(2) The method for producing a cellulose ester film according to (1), wherein the electron beam irradiation is performed in an inert gas atmosphere.

(3) The cellulose ester according to (1) or (2), wherein the alkali saponification solution contains 0.2 to 5 mol / L of at least one of sodium hydroxide, potassium hydroxide, and lithium hydroxide. A method for producing a film.
(3-2) The alkali saponification solution contains 0.2 to 5 mol / L of at least one kind of sodium hydroxide, potassium hydroxide and lithium hydroxide and 0.005 to 1% by mass of a surfactant. The method for producing a cellulose ester film according to (1) or (2).
(3-3) The alkali saponification solution is 0.2 to 5 mol / L of at least one of sodium hydroxide, potassium hydroxide and lithium hydroxide, 0.005 to 1% by mass of a surfactant and 0 The manufacturing method of the cellulose-ester film as described in (1) or (2) containing 0.005 to 1 mass% antifoamer.

(4) The method for producing a cellulose ester film according to any one of (1) to (3), wherein the alkali saponification solution has a carbonate ion concentration of 3500 mg / L or less.
(4-2) The cellulose ester according to any one of (1) to (3), wherein the alkali saponification solution has a carbonate ion concentration of 3500 mg / L or less and a polyvalent metal ion concentration of 1000 mg / L or less. A method for producing a film.
(4-3) The alkali saponification solution has a carbonate ion concentration of 3500 mg / L or less, a polyvalent metal ion concentration of 1000 mg / L or less, and a chloride ion concentration of 1000 mg / L or less. The manufacturing method of the cellulose-ester film in any one of 1)-(3).

(5) The alkali saponification solution has a surface tension of 15 to 65 mN / m and a viscosity of 0.00. 6~20mPa · s, density of ^{0.9g / cm 3 ~1.4g / cm 3} , specific conductivity is 20mS / cm~2S / cm, cellulose according to any one of (1) to (4) A method for producing an ester film.
(6) The method for producing a cellulose ester film according to any one of (1) to (5), wherein an alkali saponification treatment is performed with an alkali saponification solution at 10 to 90 ° C. for 5 to 600 seconds.
(7) After the alkali saponification treatment, at least one water washing treatment and / or at least one acid treatment is performed at 5 to 90 ° C. for 5 seconds to 1200 seconds, (1) to (6) ) A method for producing a cellulose ester film according to any one of the above.
(8) The method includes the steps of heating the film-like cellulose ester to room temperature or higher in advance, applying an alkaline saponification aqueous solution to the film-like cellulose ester to saponify the cellulose ester, and then removing the cellulose ester. ) A method for producing a cellulose ester film according to any one of the above.
(9) Any of (1) to (8), wherein the film-like cellulose ester has a surface contact angle of 45 ° or less at 25 ° C. and 60% relative humidity after being treated with an alkali saponification solution. A method for producing a cellulose ester film according to claim 1.

(10) The method for producing a cellulose ester film according to any one of (1) to (9), wherein the film-like cellulose ester is solution cast or melt cast.
(11) The filmy cellulose ester is selected from halogenated organic solvents, ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, and esters having 3 to 12 carbon atoms. The method for producing a cellulose ester film according to (10), wherein the solution is cast using an organic solvent.

(12) The cellulose ester film has a polymerization degree of the cellulose ester of 140 to 400, contains 0.5 to 20% by mass of a plasticizer, contains 0.1 to 10% by mass of a UV agent, and The manufacturing method of the cellulose-ester film in any one of (1)-(11) containing 0.5-15 mass% of retardation raising agents.
(13) (1) The cellulose ester dispersed in an organic solvent is swollen at −10 to 55 ° C., the cellulose ester dispersion is heated to 0 to 57 ° C., and the cellulose ester is dissolved in the heated solution. Step (2) After swelling the cellulose ester dispersed in the organic solvent at −10 to 55 ° C., the cellulose ester dispersion is cooled to −100 to −10 ° C., and the cooled cellulose ester solution is changed to 0 to 57 A step of dissolving the cellulose ester in the heated solvent, or (3) swelling the cellulose ester dispersed in the organic solvent at −10 to 55 ° C. Heating at 2 to 30 MPa, 60 to 240 ° C., cooling the heated cellulose ester solution to 0 to 57 ° C., and dissolving the cellulose ester in the cooled solution Including, (1) to the cellulose ester film producing method according to any one of (12).

(14) A step of casting the cellulose ester on a support is included, and the maximum peeling load when peeling the cellulose ester from the support is 1 to 30 g / cm, and the peelable time is 30. The manufacturing method of the cellulose-ester film in any one of (1)-(13) which is -600 second.
(15) including a step of stretching the film-like cellulose ester by 1.03 to 3 times in at least one direction of the transport direction and / or the width direction, and the slow axis of the cellulose ester film with respect to the stretching direction The manufacturing method of the cellulose-ester film as described in (1)-(14) which is 0 +/- 5 degree or 90 degreeC +/- 5 degree.
(16) The cellulose ester film has an in-plane retardation (Re) of 0 ≦ Re ≦ 300 nm, a thickness direction retardation (Rth) of −100 ≦ Rth ≦ 500 nm, and a film thickness of 20 to 200 μm. The manufacturing method of the cellulose-ester film in any one of (1)-(15) which is.

(17) A cellulose ester film produced by the method for producing a cellulose ester film according to any one of (1) to (16).
(18) An optical film using the cellulose ester film according to (17).

  By the method for producing a cellulose ester film of the present invention, a cellulose ester film excellent in surface treatment characteristics (haze, foreign matter defect, adhesiveness) can be easily obtained.

  Hereinafter, the contents of the present invention will be described in detail. In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

(Cellulose ester)
The cellulose ester used in the present invention will be described in detail. The cellulose ester used in the present invention is a cellulose ester that satisfies all the requirements defined by the following formulas (S-1) to (S-3).
Formula (S-1) 2.50 ≦ A + B ≦ 3.00
Formula (S-2) 0 ≦ A ≦ 2.5
Formula (S-3) 0.5 ≦ B ≦ 3.00
(In general formulas (S-1) to (S-3), A represents the degree of substitution of the acetyl group, and B represents the degree of substitution of the substituted acyl group having 3 to 22 carbon atoms.)

  The glucose unit, which is a constituent component of cellulose, is bonded to beta-1,4 and has free hydroxyl groups at the 2-position, 3-position and 6-position. The cellulose ester is a polymer (polymer) obtained by esterifying some or all of these hydroxyl groups. The substitution degree of the acyl group means the sum of the ratios of esterification of cellulose for each of the 2-position, 3-position and 6-position (100% esterification has a substitution degree of 1). In the present invention, A + B is preferably 2.60 ≦ A + B ≦ 3.00, and more preferably 2.67 ≦ A + B ≦ 2.97. A is preferably 0 ≦ A ≦ 2.20, more preferably 0 ≦ A ≦ 2.0, and B is preferably 0.80 ≦ B ≦ 2.97, and more Preferably it is 1.25 <= B <= 2.97. In the present invention, the substitution degree of each hydroxyl group at the 2-position, 3-position and 6-position of the cellulose is not particularly limited, but the substitution degree at the 6-position of the cellulose ester is preferably 0.7 or more, more preferably 0. .8 or more, more preferably 0.85 or more. As a result, not only deterioration of the cellulose ester due to electron beam irradiation but also solubility and heat-and-moisture resistance can be improved.

Next, the C3-C22 acyl group represented by the substituent B of the cellulose ester of the present invention may be either an aliphatic acyl group or an aromatic acyl group.
When the acyl group of the cellulose ester of the present invention is an aliphatic acyl group, it is preferably 3 to 18 carbon atoms, more preferably 3 to 12 carbon atoms, and further preferably 3 to 8 carbon atoms. preferable. Examples of these aliphatic acyl groups include an alkylcarbonyl group, an alkenylcarbonyl group, and an alkynylcarbonyl group.
When the acyl group of the cellulose ester of the present invention is an aromatic acyl group, it is preferably 6 to 22 carbon atoms, more preferably 6 to 18 carbon atoms, and further preferably 6 to 12 carbon atoms. preferable.
Each of these acyl groups may further have a substituent.
Examples of preferred acyl groups include propionyl, butyryl, heptanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl, isobutyryl, Examples thereof include a t-butyryl group, a cyclohexanecarbonyl group, an oleoyl group, a benzoyl group, a naphthalenecarbonyl group, a phthaloyl group, and a cinnamoyl group. Among these, more preferred are propionyl group, butyryl group, dodecanoyl group, octadecanoyl group, t-butanoyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group, and more preferred are propionyl. Group, butyryl group.

  Preferred examples of the cellulose ester of the present invention include cellulose propionate, cellulose acetate propionate, cellulose acetate butyrate, cellulose propanoate butyrate, cellulose acetate propionate butyrate, cellulose acetate hexanoate, cellulose acetate octa Noate, cellulose acetate cyclohexanoate, cellulose acetate decanoate, cellulose acetate adamantane carboxylate, cellulose acetate sulfate, cellulose acetate carbamate, cellulose propionate sulfate, cellulose acetate propionate sulfate, cellulose acetate phthalate it can. More preferred examples include cellulose propionate, cellulose acetate propionate, cellulose butyrate, cellulose acetate butyrate, cellulose propanoate butyrate, cellulose acetate hexanoate, and cellulose acetate octanoate. More preferred examples include cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate. In this case, the substitution degree of acetyl and an acyl group having 3 or more carbon atoms is prepared within the above-described range, and desired characteristics (particularly optical characteristics) can be obtained depending on the substitution degree.

More detailed raw material cotton and synthesis method of the cellulose ester of the present invention can be synthesized in accordance with pages 7 to 12 of JIII Journal of Technical Disclosure (Technical No. 2001-1745, published on March 15, 2001, JIII).
(Cellulose ester raw material and pretreatment) As the cellulose raw material, those derived from hardwood pulp, softwood pulp, and cotton linter are preferably used. As a cellulose raw material, it is preferable to use a high-purity material having an α-cellulose content of 92 mass% to 99.9 mass%. In the case where the cellulose raw material is in the form of a sheet or a lump, it is preferable to pulverize in advance, and the pulverization proceeds until the cellulose has a fluffy form.

  Prior to acylation, the cellulose raw material is preferably subjected to a treatment (activation) in contact with an activator. As the activator, carboxylic acid or water can be used. However, when water is used, an excess of acid anhydride is added after activation to perform dehydration or to replace water. It is preferable to include a step of washing with an acid or adjusting acylation conditions. The activator may be added by adjusting to any temperature, and the addition method can be selected from spraying, dropping, dipping and the like.

  In the production of the cellulose ester in the present invention, it is preferable to acylate the hydroxyl group of cellulose by adding an acid anhydride of carboxylic acid to cellulose and reacting with Bronsted acid or Lewis acid as a catalyst. As the method for obtaining the cellulose mixed acylate of the present invention, a method of reacting two kinds of carboxylic acid anhydrides as an acylating agent by mixing or sequentially adding them, a mixed acid anhydride of two kinds of carboxylic acids (for example, acetic acid / propionic acid) Mixed acid anhydride), a mixed acid anhydride (for example, acetic acid / propionic acid mixed acid) in the reaction system using a carboxylic acid and another carboxylic acid anhydride (for example, acetic acid and propionic acid anhydride) as raw materials A method of synthesizing an anhydride) and reacting with cellulose, a method of once synthesizing a cellulose ester having a degree of substitution of less than 3, and further acylating a remaining hydroxyl group using an acid anhydride or an acid halide. it can.

  First, it is preferable to use a Bronsted acid or a Lewis acid as the acylation catalyst used in the production of the cellulose ester in the present invention. The definitions of Bronsted acid and Lewis acid are described in, for example, “Physical and Chemical Dictionary”, 5th edition (2000). Examples of preferable Bronsted acid include sulfuric acid, perchloric acid, phosphoric acid, methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid and the like. Examples of preferred Lewis acids include zinc chloride, tin chloride, antimony chloride, magnesium chloride and the like. As the catalyst, sulfuric acid or perchloric acid is more preferable, and sulfuric acid is particularly preferable. The addition amount of the catalyst is preferably 0.1 to 30% by mass, more preferably 1 to 15% by mass, and further preferably 3 to 12% by mass with respect to cellulose.

  Although acylation of cellulose is an exothermic reaction, in the production of the cellulose ester in the present invention, the highest temperature reached during acylation is preferably -50 to 50 ° C, more preferably -30 to 45 ° C, -20-40 degreeC is further more preferable, and -20-35 degreeC is the most preferable. The acylation time is preferably 0.5 to 24 hours, more preferably 1 to 12 hours, and particularly preferably 1.5 to 6 hours.

  In the method for producing a cellulose ester in the present invention, it is preferable to add a reaction terminator after the acylation reaction. The reaction terminator may be any as long as it decomposes the acid anhydride, and preferred examples include water, alcohol (eg, ethanol, methanol, propanol, isopropyl alcohol, etc.) or a composition containing these. be able to.

  The cellulose ester thus obtained has a total degree of substitution of cellulose hydroxyl groups close to about 3. However, for the purpose of obtaining a desired degree of substitution, a small amount of catalyst (generally, a residual acyl such as sulfuric acid) is obtained. The ester bond is partially hydrolyzed by keeping it at 20 to 90 ° C. for several minutes to several days in the presence of water and a catalyst, so that the cellulose ester has a desired degree of acyl substitution (so-called aging). ) Is generally performed. Since the cellulose sulfate ester is also hydrolyzed during the partial hydrolysis, the amount of sulfate ester bound to the cellulose can be reduced by adjusting the hydrolysis conditions. When the desired cellulose ester is obtained, it is preferable to completely neutralize the catalyst remaining in the system using the neutralizing agent or a solution thereof as described above to stop the partial hydrolysis. By adding a neutralizing agent (for example, magnesium carbonate, magnesium acetate, etc.) that generates a salt that is poorly soluble in the reaction solution, a catalyst (for example, sulfate ester) bound to the solution or to cellulose is effectively removed. It is also preferable to remove.

  For the purpose of removing or reducing unreacted substances, hardly soluble salts, and other foreign matters in the cellulose ester, it is preferable to filter the reaction mixture after acylation. Filtration may be performed in any step from completion of esterification to reprecipitation. For the purpose of controlling filtration pressure and handleability, it is also preferable to dilute with an appropriate solvent prior to filtration. When filtering, the filter medium is not particularly limited, and cloth, glass filter, cellulose filter paper, cellulose cloth filter, metal filter, polymer filter (for example, polypropylene filter, polyethylene filter, polyamide filter, fluorine filter) Filter). The filter aperture size is preferably 0.1 to 600 μm, more preferably 2 to 200 μm, and further preferably 3 to 60 μm.

  The cellulose ester after washing by hot water treatment is weakly alkaline (for example, carbonates such as sodium, potassium, calcium, magnesium, aluminum, hydrogen carbonate, It is also preferable to treat with an aqueous solution of hydroxide, oxide, etc.). The amount of residual impurities can be controlled by the amount of cleaning liquid, cleaning temperature, time, stirring method, shape of cleaning container, composition and concentration of stabilizer.

  In the present invention, in order to adjust the water content of the cellulose ester to a preferable amount, it is preferable to dry the cellulose ester. The drying method is not particularly limited as long as the desired moisture content can be obtained. However, it is preferable that the drying method be performed efficiently by using means such as heating, air blowing, decompression, and stirring alone or in combination. Preferably it is 0-200 degreeC as drying temperature, More preferably, it is 40-180 degreeC, More preferably, it is 50-160 degreeC. At this time, it is preferable to dry at a temperature lower than the glass transition point (Tg) of the cellulose ester, and it is more preferable that the drying temperature is 10 ° C. or less from the Tg. The moisture content of the cellulose ester of the present invention obtained by drying is preferably 2% by mass or less, more preferably 1% by mass or less, and further preferably 0.5% by mass or less.

The cellulose ester raw material is preferably in the form of particles or powder. The cellulose ester after drying may be pulverized or sieved for uniform particle size and improved handling. When the cellulose ester is in the form of particles, 90% by mass or more of the particles used preferably have a particle size of 0.5 to 5 mm. Moreover, it is preferable that 50 mass% or more of the particle | grains to be used have a particle size of 1-4 mm. The cellulose ester particles preferably have a shape as close to a sphere as possible.
The degree of polymerization of the cellulose ester used in the present invention is an average degree of polymerization, preferably 140 to 400, more preferably 150 to 350. When the cellulose ester is produced by the solution casting method, the average polymerization degree is particularly preferably 250 to 350, and when the cellulose ester is produced by the melt casting method, the average polymerization degree is particularly preferably 150 to 250.

  The average degree of polymerization was measured by molecular weight distribution by Uda et al.'S intrinsic viscosity method (Kazuo Uda, Hideo Saito, Journal of Textile Science, Vol. 18, No. 1, pages 105-120, 1962), gel permeation chromatography (GPC). It can be measured by such a method. Further details are described in JP-A-9-95538. These cellulose esters may use only 1 type and may mix 2 or more types. Moreover, what mixed suitably polymer components other than a cellulose ester may be used. 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. The obtained cellulose ester is preferably stored in a low-temperature dark place so that the storage is less affected by the environment. Furthermore, it is more preferable to store in a moisture-proof bag made of a prevention material such as aluminum, a SUS drum or a container for storage.

  The synthesis of cellulose esters having a high degree of substitution at the 6-position is described in JP-A Nos. 11-5851, 2002-212338 and 2002-338601. Other synthetic methods for cellulose esters include the presence of a base (sodium hydroxide, potassium hydroxide, barium hydroxide, sodium carbonate, pyridine, triethylamine, tert-butoxy potassium, sodium methoxide, sodium ethoxide, etc.) A method of reacting with a carboxylic acid anhydride or a carboxylic acid halide, or a method using a mixed acid anhydride (such as a mixed anhydride of carboxylic acid / trifluoroacetic acid or a mixed anhydride of carboxylic acid / methanesulfonic acid) as an acylating agent may be used. In particular, the latter method is effective when introducing an acyl group having a large number of carbon atoms or an acyl group that is difficult to be subjected to liquid phase acylation using a carboxylic acid anhydride-acetic acid-sulfuric acid catalyst.

In the present invention, the cellulose ester film is preferably produced by solution casting or melt casting.
First, solution casting will be described. The organic solvent used in the cellulose ester used in the solution casting of the present invention is not particularly limited, but is a halogen-based organic solvent, an ether having 3 to 12 carbon atoms, or a ketone having 3 to 12 carbon atoms. And organic solvents selected from esters having 3 to 12 carbon atoms. More recently, non-halogen organic solvents as environmentally friendly organic solvents may be used. The halogen-based organic solvent is preferably a halogenated hydrocarbon having 1 to 7 carbon atoms, more preferably dichloromethane or chloroform, and particularly preferably dichloromethane. In addition, there is no particular problem in mixing an organic solvent other than the chlorinated organic solvent.

  In that case, it is preferable to use at least 50% by mass or more of dichloromethane, and more preferably 70% by mass to 100% by mass. The solvent used in combination with the chlorinated organic solvent is preferably an alcohol, which may be a linear, branched or cyclic alcohol, and is a saturated aliphatic hydrocarbon alcohol. It is preferable. The hydroxyl group of the alcohol may be any of primary to tertiary. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 1-pentanol, 2-methyl-2-butanol and cyclohexanol.

  As the alcohol, fluorine-based alcohol is also used. Examples thereof include 2-fluoroethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol and the like. Furthermore, the hydrocarbon may be linear, branched or cyclic. Either aromatic hydrocarbons or aliphatic hydrocarbons can be used. The aliphatic hydrocarbon may be saturated or unsaturated. Examples of hydrocarbons include cyclohexane, hexane, benzene, toluene and xylene. Furthermore, methyl acetate, ethyl acetate, methyl formate, ethyl formate, acetone, dioxolane, dioxane, ketones having 4 to 7 carbon atoms or acetoacetate are also preferable. Preferred non-chlorine organic solvents used in combination are methyl acetate, acetone, methyl formate, ethyl formate, methyl ethyl ketone, cyclopentanone, cyclohexanone, methyl acetyl acetate, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and cyclohexanol, cyclohexane, and hexane. The organic solvent used in combination other than these halogen-based organic solvents is preferably 50% by mass or less, more preferably 50 to 10% by mass, and further preferably 40 to 10% by mass.

Although the following can be mentioned as a combination of the chlorinated organic solvent which is a preferable main solvent of this invention, It is not limited to these (the number in the following parenthesis shows a mass part).
(HSV-1) dichloromethane / methanol / ethanol / butanol (HSV-2) dichloromethane / acetone / methanol / propanol (HSV-3) dichloromethane / methanol / butanol (HSV-4) dichloromethane / methyl ethyl ketone / methanol / butanol (HSV-5) ) Dichloromethane / acetone / methyl ethyl ketone / ethanol / isopropanol (HSV-6) dichloromethane / cyclopentanone / methanol / isopropanol (HSV-7) dichloromethane / methyl acetate / butanol (HSV-8) dichloromethane / cyclohexanone / methanol / hexane

(HSV-9) dichloromethane / methyl ethyl ketone / acetone / methanol / ethanol (HSV-10) dichloromethane / 1, 3 dioxolane / methanol / ethanol (HSV-11) dichloromethane / dioxane / acetone / methanol / ethanol (HSV-12) dichloromethane / Acetone / cyclopentanone / ethanol / isobutanol / cyclohexane (HSV-13) dichloromethane / methyl ethyl ketone / acetone / methanol / ethanol (HSV-14) dichloromethane / acetone / ethyl acetate / ethanol / butanol / hexane (HSV-15) dichloromethane / Methyl acetoacetate / methanol / ethanol (HSV-16) dichloromethane / cyclopentanone / ethanol / butanol

  Next, the non-halogen organic solvent used for the cellulose ester of the present invention will be described. The preferred non-halogen organic solvent is preferably a solvent selected from esters, ketones or ethers having 3 to 12 carbon atoms. These esters, ketones and ethers may have a cyclic structure. A compound having two or more functional groups of esters, ketones and ethers (that is, —O—, —CO— and —COO—) can also be used as a main solvent, such as an alcoholic hydroxyl group. It may have other functional groups. In the case of the main solvent having two or more kinds of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group.

  Examples of esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate. Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone and methylcyclohexanone. Examples of ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole. Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.

  In the present invention, the preferred non-halogen solvent is a mixed solvent of three or more different from each other, and the first solvent is at least one selected from methyl acetate, ethyl acetate, methyl formate, ethyl formate, acetone, dioxolane and dioxane. And the second solvent is selected from ketones having 4 to 7 carbon atoms or acetoacetate, and the third solvent is selected from alcohols or hydrocarbons having 1 to 10 carbon atoms, more preferably 1 carbon atom. ~ 8 alcohols. In addition, when the 1st solvent is a 2 or more types of solvent liquid mixture, there may not be a 2nd solvent. The first solvent is more preferably methyl acetate, acetone, methyl formate or ethyl formate, or a mixture thereof, and the second solvent is preferably methyl ethyl ketone, cyclopentanone, cyclohexanone, or methyl acetyl acetate. It may be.

  The alcohol as the third solvent is preferably linear, branched or cyclic, and is preferably a saturated aliphatic hydrocarbon. The hydroxyl group of the alcohol may be any of primary to tertiary. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 1-pentanol, 2-methyl-2-butanol and cyclohexanol. As the alcohol, fluorine-based alcohol is also used. Examples thereof include 2-fluoroethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol and the like. Furthermore, the hydrocarbon may be linear, branched or cyclic. Either aromatic hydrocarbons or aliphatic hydrocarbons can be used. The aliphatic hydrocarbon may be saturated or unsaturated. Examples of hydrocarbons include cyclohexane, hexane, benzene, toluene and xylene. These alcohols and hydrocarbons as the third solvent may be used alone or in combination of two or more, and are not particularly limited. Preferred examples of the third solvent include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and cyclohexanol, cyclohexane, and hexane. Are methanol, ethanol, 1-propanol, 2-propanol, 1-butanol.

  The mixed solvent composed of the above three types preferably includes the first solvent at a ratio of 20 to 90% by mass, the second solvent at 5 to 60% by mass, and the third solvent at a ratio of 10 to 60% by mass. Furthermore, it is preferable that the first solvent is 30 to 86% by mass, the second solvent is 10 to 50% by mass, and further the third alcohol is 15 to 60% by mass. In particular, the first solvent is preferably 30 to 80% by mass, the second solvent is 10 to 50% by mass, and the third solvent is alcohol, and is preferably contained in an amount of 15 to 60% by mass. When the first solvent is a mixed solution and the second solvent is not used, it is preferable that the first solvent is contained in a ratio of 40 to 85% by mass, and the third solvent is contained in a ratio of 15 to 60% by mass. Furthermore, it is preferable that a 1st solvent is 45-85 mass%, and also a 3rd solvent is contained 15-55 mass%.

Specific examples of these solvent combinations preferable in the present invention include the following.
(SL-1) Methyl acetate / cyclopentanone / acetone / methanol / ethanol (SL-2) Methyl acetate / acetone / methanol / ethanol (SL-3) Methyl acetate / cyclopentanone / methanol / ethanol (SL-4) Methyl acetate / cyclopentanone / methanol / ethanol (SL-5) methyl acetate / cyclohexanone / methanol / hexane (SL-6) methyl acetate / methyl ethyl ketone / acetone / methanol / ethanol (SL-7) methyl acetate / 1, 3 dioxolane / Methanol / ethanol (SL-8) methyl acetate / dioxane / acetone / methanol / ethanol (SL-9) methyl formate / methyl ethyl ketone / acetone / methanol / ethanol

(SL-10) acetone / methyl acetoacetate / methanol / ethanol (SL-11) 3 dioxolane / cyclohexanone / methyl ethyl ketone / methanol / ethanol (SL-12) acetone / methanol / butanol (SL-13) acetone / ethanol / isopropanol ( SL-14) Acetone / ethanol / butanol (SL-14) Acetone / ethanol / butanol / dichloromethane Among these, a mixed solvent system of methyl acetate / acetone / methanol / ethanol is preferable, and the use ratio thereof is SL-2, SL- 6, solvent systems such as SL-10 and SL-12 are preferred.
In addition to the organic solvent of the present invention, the dope used in the present invention may contain methylene chloride in an amount of 10% by mass or less of the total organic solvent amount of the present invention to improve the transparency of the film or speed up the solubility. You may use it.

Regarding the preparation of the cellulose ester solution (dope) used in the present invention, the dissolution method is not particularly limited, and may be a room temperature dissolution method, a cooling dissolution method or a high temperature dissolution method, or a combination thereof.
A preferred method for dissolving cellulose ester in an organic solvent is described below.
(1) As a room temperature dissolution method, cellulose ester dispersed in an organic solvent is swollen at −10 to 55 ° C., the cellulose ester dispersion is heated to 0 to 57 ° C., and cellulose ester is added to the heated solution. The method of making it melt | dissolve is mentioned. Preferably, the cellulose ester dispersed in an organic solvent is swollen at 10 to 40 ° C., and the cellulose ester dispersion solution is heated to 20 to 57 ° C. Further, the cellulose ester dispersed in the organic solvent is 15 A method of swelling at ˜40 ° C. and warming the cellulose ester dispersion to 20-45 ° C. is preferred.
(2) As a cooling dissolution method, the cellulose ester dispersed in an organic solvent is swollen at −10 to 55 ° C., and then the cellulose ester dispersion solution is cooled to −100 to −10 ° C. The method of heating to 0-57 degreeC and dissolving a cellulose ester in this heated solvent is mentioned. Preferably, the cellulose ester dispersed in an organic solvent is swollen at 10 to 40 ° C., the cellulose ester dispersion solution is cooled to −85 to −30 ° C. and heated to 20 to 57 ° C., and further organic A method of swelling the cellulose ester dispersed in a solvent at 15 to 40 ° C., cooling the cellulose ester dispersion solution to −85 to −50 ° C., and heating to 15 to 45 ° C. is preferable.
(3) As a high temperature dissolution method, the cellulose ester dispersed in an organic solvent is swollen at −10 to 55 ° C., and the cellulose ester dispersion is heated to 60 to 240 ° C. at high pressure and high temperature at 0.2 to 30 MPa, A method in which the heated cellulose ester solution is cooled to 0 to 57 ° C., and the cellulose ester is dissolved in the cooled solution. Preferably, the cellulose ester dispersion is swollen at 10 to 40 ° C., heated to 90 to 200 ° C. at high pressure and high temperature at 0.5 to 30 MPa, and cooled to 0 to 57 ° C., and further 15 to 40 It is preferable that the cellulose ester dispersion is swollen at a temperature of 0.5 to 10 MPa, heated to 90 to 150 ° C. at a high pressure and a high temperature, and cooled to 15 to 45 ° C.
Regarding these, for example, JP-A-5-163301, JP-A-61-106628, JP-A-58-127737, JP-A-9-95544, JP-A-10-95854, JP-A-10-45950, JP-A-2000-53784, JP-A-11-322946, JP-A-11-322947, JP-A-2-276830, JP-A-2000-273239, JP-A-11-71463, JP-A-4-04 Nos. -259511, 2000-273184, 11-323017, 11-302388, etc. describe methods for preparing cellulose acylate solutions. These techniques can be applied to the method for dissolving the cellulose ester described above in the organic solvent without departing from the gist of the present invention. Further, the cellulose ester dope solution of the present invention is usually concentrated and filtered, and is described in detail on page 25 of the Japan Institute of Invention (Technical No. 2001-1745, published on March 15, 2001, Japan Institute of Invention). It is described in. In addition, when it melt | dissolves at high temperature, it is the case where it is more than the boiling point of the organic solvent to be used, and in that case, it uses in a pressurized state.

Next, a method for producing a film using a cellulose ester solution will be described. As a manufacturing method of the cellulose ester film of the present invention and equipment used therefor, for example, a conventionally known solution casting film forming method and solution casting manufacturing method referred to as a drum method or a band method used for manufacturing a cellulose triacetate film A membrane device can be employed. The film formation process will be described using the band method as an example. The dope (cellulose ester solution) prepared from the dissolving machine (kettle) is temporarily stored in the storage kettle, and the foam contained in the dope is defoamed for final preparation. do. The prepared dope is fed from the dope discharge port to the pressure die through a pressure metering gear pump capable of delivering a constant amount of liquid with high accuracy, for example, by the rotational speed, and the dope is run endlessly from the die (slit) of the pressure die. The dope film (also referred to as a web) is peeled off from the metal support at the peeling point where the metal support is almost cast around the metal support. Both ends of the obtained web are sandwiched between clips, transported by a tenter while keeping the width, dried, then transported by a roll group of a drying device, dried, and wound up to a predetermined length by a winder. The combination of the tenter and the roll group dryer varies depending on the purpose. About each of these manufacturing processes (classification into casting (including co-casting), metal support, drying, peeling, stretching, etc.), the Japan Society for Invention and Technology (Publication No. 2001-1745, March 2001) The contents described in detail on pages 25 to 30 of Jissu, Japan Institute of Invention). In the casting step, one type of cellulose ester solution may be cast as a single layer, or two or more types of cellulose ester solutions may be cast simultaneously and / or sequentially.
In particular, when the cellulose ester film of the present invention is produced by a solution casting method, the stripping load and stripping time are set as described below when stripping the cellulose ester solution in order to improve the film surface shape. It is preferable. That is, when the web comprising the cellulose ester of the present invention is peeled from the support, the peel load is preferably small, and the maximum peel load when peeling from the support is preferably 1 to 30 g / cm. 1 to 25 g / cm, particularly 1 to 20 g / cm is preferable. Further, at that time, it is preferable that the peelable time is 30 to 600 seconds, and more preferably 60 to 420 seconds. By controlling these peeling processes, a cellulose ester film having an excellent surface shape can be obtained.

Next, the cellulose ester produced by melt film formation in the present invention will be described below.
(Pelletized)
When melt film formation is performed, the cellulose ester to be used may be pelletized. Pellet preparation is performed as follows. First, the cellulose ester is sufficiently pre-dried (for example, at 80 to 150 ° C. for 0.1 to 24 hours). Next, various dry additives as described later (retardation increasing agents, plasticizers, deterioration inhibitors, UV inhibitors, matting agents, wavelength dispersion adjusting agents, infrared absorbers, surfactants, etc.) as necessary. Was added according to the required amount of cellulose ester. More preferably, the obtained mixture is put into a hopper with stirring and substituted with an inert gas such as nitrogen. Using a twin-screw kneading extruder, preferably 150 to 240 ° C., more preferably 160 to 240 ° C., further preferably 170 to 235 ° C., and the screw rotation speed is preferably 100 rpm to 800 rpm, more preferably 150 rpm to 600 rpm, More preferably, pellets are produced at 200 rpm to 400 rpm and a residence time of preferably 5 seconds to 3 minutes, more preferably 10 seconds to 2 minutes, and even more preferably 20 seconds to 90 seconds. The pellet preparation is preferably performed in an inert gas atmosphere in order to suppress deterioration. The inert gas is preferably nitrogen. The purity of nitrogen is preferably 95% or more, more preferably 99% or more, and most preferably 99.5% or more.

  It is preferable to provide a vent on the outlet side of the twin-screw kneading extruder and produce pellets while evacuating. This is because the mixed cellulose ester powder is hydrophilic, so that residual moisture of about 0.2% by mass remains, and the low acetylated substance is easily decomposed in the presence of water and easily becomes a crosslinkable foreign matter. The degree of vacuum in the vent portion is preferably in the range of 0.9 atmosphere to 0.001 atmosphere, more preferably 0.8 atmosphere to 0.01 atmosphere, and further preferably 0.7 atmosphere to 0.1 atmosphere. It is. Such evacuation can be achieved by providing an exhaust port in the screw casing of the twin-screw kneading extruder and piping this to a vacuum pump. After melting, it is solidified in a strand shape in warm water of preferably 30 ° C. to 90 ° C., more preferably 35 ° C. to 80 ° C., more preferably 37 ° C. to 60 ° C., and then cut and dried.

The size of the cellulose ester pellets is preferably 1 mm ^{3 to} 10 cm ³ , more preferably 1 mm ^{3 to} 7 cm ³ , and even more preferably 2 mm ^{3 to 5} cm ³ . At this time, it is preferable to pelletize the additive together. Then, it is dried so that the water content is 0.1% or less.

(Melting extrusion)
The above pelletized cellulose ester, retardation increasing agent and other additives as necessary (plasticizer, deterioration inhibitor, UV inhibitor, matting agent, wavelength dispersion adjusting agent, infrared absorber, etc.) Charge into the hopper of the melt extruder. As described above, when each additive is added in the cellulose ester synthesis step and the pelletizing step, it may not be added during the melt film forming step. The temperature of the hopper is preferably also described as a temperature that is 50 ° C. lower than the Tg of the cellulose ester used and 30 ° C. lower than the Tg (hereinafter referred to as (Tg-50) to (Tg + 30 ° C.). The same applies to the above.), More preferably (Tg−40 ° C.) to (Tg + 10 ° C.), still more preferably (Tg−30 ° C.) to Tg. Thereby, the re-adsorption of the water | moisture content in a hopper can be suppressed, and the said drying efficiency can be expressed more easily.

  Furthermore, by using the melt film-forming conditions of a low melt viscosity resin composition, a short time, high shear force (high rotation), and a stepped temperature screw temperature pattern, the fine polarized foreign matter mixed in the resin can be sufficiently melted. And by suppressing the heat of fusion history to a minimum, it is possible to reduce the finely polarized foreign matter and yellowness (YI value) of the formed cellulose ester. Specifically, the cellulose ester resin reduces the melt viscosity of the cellulose ester by adding various additives. Moreover, the screw of the single screw or twin screw extruder used for melt film formation rotates at a high speed, and the temperature pattern of the screw changes from the upstream supply part (hopper side) to the compression part (intermediate part), the downstream metering part (T- Increase the screw temperature up to the die side). This divides and controls the screw temperature, and gradually increases the temperature from the upstream supply unit to the downstream metering unit (T-die side), thereby promoting melting and requiring melting of undissolved fine foreign matter. By suppressing the minimum heat history, the thermal deterioration and yellowish coloring of the resin are reduced.

In the present invention, the setting is such that the screw temperature pattern is increased stepwise, preferably 5 ° C. to 50 ° C., more preferably 5 ° C. to 30 ° C., and further preferably 10 ° C. to 20 ° C., according to the upstream supply unit to the downstream metering unit. Preferably used. The temperature of the upstream supply section is preferably 150 to 190 ° C, more preferably 160 to 190 ° C, and further preferably 170 to 190 ° C. The temperature of the intermediate compression part is preferably 170 to 210 ° C, more preferably 180 to 210 ° C, and further preferably 190 to 210 ° C. The temperature on the downstream die side is preferably 190 to 240 ° C, more preferably 200 to 240 ° C, and still more preferably 210 to 240 ° C.
The screw rotation speed of the present invention is preferably 60 to 400 rpm, more preferably 700 to 300 rpm, further preferably 80 to 280 rpm, and the residence time is preferably 5 seconds to 10 minutes, more preferably 10 seconds to 8 minutes, and further Preferably, the cellulose ester is melt extruded in 30 seconds to 7 minutes. It is also preferable to carry out the inside of the melt extruder in an inert (nitrogen or the like) air flow. The inert gas is preferably nitrogen. The purity of nitrogen is preferably 95% or more, more preferably 99% or more, and most preferably 99.5% or more.

  In addition, by adjusting the screw compression ratio used in the present invention, it is possible to sufficiently knead and more effectively suppress the problem that fine polarized foreign matter is generated. Further, by adjusting the compression ratio, it is possible to more effectively suppress problems such as heat deterioration of the resin due to heat generation and an increase in yellowness of the melt-formed film. Moreover, by adjusting L / D (screw length to diameter ratio), deterioration of the resin due to insufficient kneading or excessive residence time can be more effectively suppressed. Specifically, the compression ratio is preferably 2.5 or more, more preferably 4.5 or less, further preferably 2.8 to 4.2, and particularly preferably 3 to 4. Moreover, 20-50 are preferable, as for L / D, More preferably, it is 22-45, More preferably, it is 24-40. In this way, by using the melt film formation conditions of high shear force (high rotation), short time, stepwise increase in the screw temperature pattern, the insoluble finely modified foreign matter mixed in the resin is sufficiently melted, In addition, by minimizing the heat of fusion history, it is possible to achieve both finely polarized foreign matters and yellowishness (YI value) of the formed cellulose ester.

0-8 are preferable, as for the yellowishness (YI value) of the film of this invention, 0-6 are more preferable, and 0-4 are the most preferable. Cellulose ester film fine polarization number of foreign matters in the molten casting of the present invention is by measurement described later, is preferably 0-5 / 5 × 10 ^-2 mm ^3, is 0-4 / 5 × 10 ^-2 mm ³ More preferably, 0 to 3 pieces / 5 × 10 ⁻² mm ³ is most preferable.

(filtration)
Next, the melted cellulose ester is passed through a gear pump to remove the pulsation of the extruder, and then filtered through a metal mesh filter, a sintered metal leaf disk, or the like. The mesh size is preferably 2 to 30 μm, more preferably 2 to 20 μm, and still more preferably 2 to 10 μm. At this time, it is preferable to pressurize and shorten the time required for filtration as much as possible. The filtration pressure is preferably 0.5 MPa to 15 MPa, more preferably 2 Pa to 15 MPa, and most preferably 10 Pa to 15 MPa. A higher filtration pressure is preferable because the filtration time can be shortened, but it is preferable to use a high pressure within a range in which the filter is not damaged.

The temperature during filtration is preferably 180 ° C to 230 ° C, more preferably 180 ° C to 220 ° C, and further preferably 190 ° C to 220 ° C. If the temperature during filtration is less than or equal to the upper limit value, it is preferable because problems such as thermal degradation are unlikely to occur. If the temperature is greater than or equal to the lower limit value, it takes too much time for filtration to cause thermal degradation. Is preferable because it is difficult to cause. The time required for filtration should be as short as possible to prevent yellowing of the cellulose ester film. Filtration rate of the filter 1 cm ² per minute, preferably 0.05～100Cm ^3, more preferably 0.1~100cm ^3, 0.5~100cm ³ being most preferred.

(Melting cast)
The filtered molten cellulose ester is extruded from a T-shaped die attached behind the filter. Extrusion may be performed in a single layer or may be performed in multiple layers using a multi-manifold die or a feed block die. At this time, the thickness unevenness in the width direction can be adjusted by adjusting the distance between the lips of the die. Thereafter, it is extruded onto a casting drum. At this time, it is preferable to use a method such as an electrostatic application method, an air knife method, an air chamber method, a vacuum nozzle method, or a touch roll method to increase the adhesion between the casting drum and the melt-extruded sheet. Such an adhesion improving method may be performed on the entire surface of the melt-extruded sheet or a part thereof.

  When extruding the molten cellulose ester from the die, it is preferably performed in an inert gas. The inert gas is preferably nitrogen. The purity of nitrogen is preferably 95% or more, more preferably 99% or more, and most preferably 99.5% or more.

  The die lip interval is preferably 1 to 10 times the film thickness of the film to be formed, more preferably 2 to 8 times, still more preferably 3 to 7 times. The sheet extruded from the die lip in this way is adjusted to a desired thickness by adjusting the peripheral speed of the CD. The preferable temperature of the die lip is 180 ° C to 250 ° C, more preferably 190 ° C to 240 ° C, and further preferably 200 ° C to 230 ° C. After this, the melt is extruded onto a metal casting support called a casting drum (CD). The temperature of CD is preferably (Tg-50 ° C) to (Tg + 10 ° C), more preferably (Tg-30 ° C) to (Tg + 5 ° C) of the resin (referring to Tg of the mixture of cellulose ester and additive), and further Preferably it is (Tg-20 degreeC)-TgdegreeC. The number of CD is preferably 1 to 10 and more preferably 2 to 5.

After the melt is solidified on the casting drum, it is peeled off, and after passing through a nip roll, it is wound up. The winding speed is preferably 10 m / min to 100 m / min, more preferably 15 m / min to 80 m / min, still more preferably 20 m / min to 70 m / min.
The film forming width is preferably 0.5 m to 5 m, more preferably 0.7 m to 4 m, and still more preferably 1 m to 3 m. After film formation, it is preferable to trim both ends and wind up. After trimming, the trimmed part is recycled as a raw material for film of the same type or as a raw material for film of a different type after being subjected to processing such as granulation treatment or depolymerization / repolymerization as necessary. May be used. Moreover, it is also preferable from a viewpoint of scratch prevention to attach a lami film to at least one surface before winding.

Modulus of the thus-obtained cellulose ester is preferably from ^{1.5kN / mm 2 ~2.9kN / mm 2} , more preferably ^{1.7kN / mm 2 ~2.8kN / mm 2} , more preferably 1. it is a ^{8kN / mm 2 ~2.6kN / mm 2} . Tg (referring to Tg of film, that is, Tg of a mixture of cellulose ester and additive) is preferably 95 ° C to 145 ° C, more preferably 100 ° C to 140 ° C, and further preferably 105 ° C to 135 ° C. The cellulose ester film obtained by the above melt film-forming process can be made to exhibit a predetermined characteristic by performing the extending | stretching process mentioned later further.

  As described above, various additives (for example, plasticizers, UV inhibitors, deterioration inhibitors, fine particles, optical property modifiers, etc.) according to the application may be added to the cellulose ester of the present invention in each preparation step. it can. Moreover, you may add at any time in the preparation process. As a plasticizer to be preferably added, phosphate ester or carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP), cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate.

  Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethyl hexyl phthalate (DEHP). Examples of citrate esters include triethyl O-acetylcitrate (OACTE) and tributyl O-acetylcitrate (OACTB), acetyltriethyl citrate, and acetyltributyl citrate.

  Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Examples of glycolic acid esters include triacetin, tributyrin, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, and butyl phthalyl butyl glycolate. Further trimethylolpropane tribenzoate, pentaerythritol tetrabenzoate, ditrimethylolpropane tetraacetate, ditrimethylolpropane tetrapropionate, pentaerythritol tetraacetate, sorbitol hexaacetate, sorbitol hexapropionate, sorbitol triacetate tripropionate, inositol pentaacetate Sorbitan tetrabutyrate is also preferably used.

  Among them, triphenyl phosphate, diphenyl biphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, tributyl phosphate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, diethyl hexyl phthalate, triacetin, ethyl phthalyl ethyl glycolate, trimethylol Propane tribenzoate, pentaerythritol tetrabenzoate, ditrimethylolpropane tetraacetate, pentaerythritol tetraacetate, sorbitol hexaacetate, sorbitol hexapropionate, sorbitol triacetate tripropionate and the like are preferable. In particular, triphenyl phosphate, diethyl phthalate, ethyl phthalyl ethyl glycolate, trimethylolpropane tribenzoate, pentaerythritol tetrabenzoate, ditrimethylolpropane tetraacetate, sorbitol hexaacetate, sorbitol hexapropionate, and sorbitol triacetate tripropionate are preferable. These plasticizers may be used alone or in combination of two or more. 0.5-20 mass% is preferable with respect to a cellulose ester, and, as for the addition amount of a plasticizer, 5-16 mass% is more preferable.

  Examples of these plasticizers include (di) pentaerythritol esters described in JP-A No. 11-124445, glycerol esters described in JP-A No. 11-246704, and diglycerol described in JP-A No. 2000-63560. Examples thereof include esters, citrate esters described in JP-A No. 11-92574, substituted phenyl phosphate esters described in JP-A No. 11-90946, and the like.

  A retardation increasing agent for adjusting optical anisotropy is optionally added. In order to adjust the retardation of the cellulose ester film, it is preferable to use an aromatic compound having at least two aromatic rings as a retardation increasing agent. The aromatic compound is preferably used in the range of 0.01 to 20 parts by mass with respect to 100 parts by mass of the cellulose ester. Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring. Examples thereof include compounds described in European Patent 0911656A2, JP-A Nos. 2000-1111914 and 2000-275434. Of these, those having a 1,3,5-triazine ring are particularly preferred.

  The cellulose ester solution (composition in which a cellulose ester is dispersed in a solvent) used in the present invention is further added with various additives (for example, an ultraviolet inhibitor, a deterioration inhibitor, fine particles, a release agent, an infrared ray) depending on the application. Absorbers, antistatic agents, etc.) can be added and they can be solid or oily. Moreover, when a cellulose-ester film is formed from a multilayer, the kind and addition amount of the additive of each layer may differ. For these details, materials described in detail on pages 16 to 22 of the Japan Society for Invention and Technology (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society of Invention) are preferably used. Although the usage-amount of these additives is not specifically limited as long as the function of the added raw material expresses, It is preferable to use suitably in the range of 0.001-20 mass% in the cellulose acylate whole composition.

(3) Stretching Stretching may be performed on-line after melt extrusion, or may be temporarily wound up after melt-extrusion and performed off-line. The stretching temperature is preferably Tg to (Tg + 50 ° C.), more preferably (Tg + 3 ° C.) to (Tg + 30 ° C.), and still more preferably (Tg + 5 ° C.) to (Tg + 20 ° C.). A preferable draw ratio is 1.03 to 3 times, more preferably 1.05 to 2.8 times, and still more preferably 1.05 to 2.5 times at least one side. These stretching operations may be performed in one stage or in multiple stages. The draw ratio here is determined using the following equation.
Stretch ratio = Length after stretching / Length before stretching Such stretching may be performed in the longitudinal direction using two or more pairs of nip rolls with increased peripheral speed on the outlet side (longitudinal stretching), film It is also possible to hold both ends of the substrate with a chuck and spread it in the orthogonal direction (perpendicular to the longitudinal direction) (lateral stretching). Moreover, you may use the simultaneous biaxial stretching method as described in Unexamined-Japanese-Patent No. 2000-37772, Unexamined-Japanese-Patent No. 2001-113591, and Unexamined-Japanese-Patent No. 2002-103445.

  Further, the ratio of Re and Rth can be freely controlled by controlling the value (aspect ratio) obtained by dividing the space between nip rolls by the film width in the case of longitudinal stretching. That is, the Rth / Re ratio can be increased by reducing the aspect ratio. In the case of lateral stretching, it can be controlled by stretching in the orthogonal direction and simultaneously stretching in the longitudinal direction, or conversely relaxing. That is, the Rth / Re ratio can be increased by stretching in the vertical direction, and the Rth / Re ratio can be decreased by relaxing in the vertical direction. Further, by combining longitudinal stretching and lateral stretching, Re and Rth are reduced by increasing Rth (increasing area magnification (longitudinal magnification x lateral magnification)) while reducing Re (making the longitudinal and lateral stretching ratios closer). Can be controlled. In the present invention, the difference between the stretching ratios in the longitudinal and lateral directions is preferably 10% to 100%, more preferably 20% to 80%, and further preferably 25% to 60%, and it is more preferable that the stretching is performed asymmetrically in the longitudinal and lateral directions. At this time, it is more preferable to increase the stretching ratio in the transverse direction. Such stretching speed is preferably 10% / min to 10000% / min, more preferably 20% / min to 1000% / min, and still more preferably 30% / min to 800% / min.

  Following such stretching, it is also preferable to relax by 0% to 10% in the longitudinal or transverse direction. Furthermore, it is also preferable to heat-fix at 100 to 160 degreeC for 1 second-2 minutes following extending | stretching. In addition, the above-mentioned stretching method carried out by melt film formation is applied in the same manner to a cellulose ester film obtained by solution film formation, and a cellulose ester film having desired excellent optical properties and physical properties is produced. can do.

Regarding the optical properties of the cellulose ester film of the present invention, Re and Rth of the cellulose ester film after stretching or stretching preferably satisfy the following formula.
Here, optical property evaluation is performed at 25 ° C. using an automatic birefringence meter (KOBRA-21ADH: manufactured by Oji Scientific Instruments) after conditioning the cellulose ester film at 25 ° C. and 60% relative humidity for 24 hours. At a relative humidity of 60%, the phase difference at a wavelength of 590 nm was measured from a plurality of directions inclined from the normal to the film surface with the direction perpendicular to the film surface and the slow axis as the rotation axis, and the in-plane retardation value (Re) The retardation value (Rth) in the film thickness direction was calculated and carried out.

  Preferable Re is 0 ≦ Re ≦ 300, more preferably 0 ≦ Re ≦ 200, and particularly preferably 0 ≦ Re ≦ 150. Further, Re is preferably −100 ≦ Rth ≦ 500, more preferably −100 ≦ Rth ≦ 350, and particularly preferably −100 ≦ Rth ≦ 300.

The difference between Re at 25 ° C. and 10% relative humidity and Re at 25 ° C. and 80% relative humidity at a wavelength of 590 nm of the cellulose ester film of the present invention is preferably 15 nm or less, and more preferably 10 nm or less.
Further, the difference between Rth at 25 ° C. and 10% relative humidity at a wavelength of 590 nm and Rth at 25 ° C. and 80% relative humidity is preferably 30 nm or less, and more preferably 20 nm or less. The angle θ formed by the film forming direction (longitudinal direction) and the slow axis of Re of the film is preferably closer to 0 °, + 90 °, or −90 °. That is, in the case of longitudinal stretching, it is preferably as close to 0 °, more preferably 0 ± 5 °, further preferably 0 ± 3 °, still more preferably 0 ± 2 °, and most preferably 0 ± 1 °. In the case of transverse stretching, 90 ± 5 ° is preferable, 90 ± 3 ° or −90 ± 3 ° is more preferable, 90 ± 2 ° or −90 ± 2 ° is more preferable, and still more preferably 90 ± 1. ° or -90 ± 1 °.

As for the thickness of the cellulose-ester film of this invention, 20 micrometers-200 micrometers are preferable, More preferably, they are 30 micrometers-170 micrometers, More preferably, they are 40 micrometers-140 micrometers. The thickness unevenness is preferably 0% to 2%, more preferably 0% to 1.5%, and still more preferably 0% to 1% in both the thickness direction and the width direction, both after unstretching and after stretching.
Modulus of the thus-obtained cellulose ester is preferably from ^{1.5kN / mm 2 ~2.9kN / mm 2} , more preferably ^{1.7kN / mm 2 ~2.8kN / mm 2} , more preferably 1. it is a ^{8kN / mm 2 ~2.6kN / mm 2} .

(Electron beam treatment of cellulose ester film)
Next, after producing the cellulose ester film of the present invention, an electron beam treatment is further performed, and then an alkali saponification treatment is performed. The cellulose ester film of the present invention is surface-activated and generally hydrophilized by electron beam treatment and subsequent alkali saponification treatment. In the present invention, as the degree of hydrophilicity of the membrane surface, the degree of hydrophilicity is expressed by evaluating a contact angle formed by dropping water drops on the surface and forming the water drops and the cellulose ester film surface. In the present invention, in order to measure hydrophilicity by wetting with water on the surface of the cellulose ester film after the electron beam treatment, 5 microliters of pure water is dropped, and a measuring device (Gonometer Elmer G1 manufactured by Elma Kogyo Co., Ltd.) is used. The contact angle between the water droplet and the protective film is measured at a temperature of 25 ° C. The higher the hydrophilicity, the greater the wettability with water, so the contact angle becomes smaller. Or less, more preferably 40 ° or less, and most preferably 35 ° or less. By this surface treatment, the adhesive strength between the cellulose ester film of the present invention and the polarizer film can be increased, and a good polarizing plate can be obtained.

First, the electron beam processing method in the cellulose ester film of the present invention will be described.
In the present invention, at least one surface of the film-like cellulose ester is subjected to an electron beam irradiation treatment.
In the electron beam treatment, the treatment depth is controlled by the electron beam irradiation intensity, and the surface elastic modulus is controlled by the irradiation amount. The electron beam irradiation intensity is 10 to 200 keV, preferably 50 to 150 keV. By setting it to 200 keV or less, it is possible to more effectively prevent the material from being decomposed. The irradiation amount is 10 to 200 kGy, preferably 50 to 150 kGy.
The temperature during electron beam irradiation is preferably 0 to 150 ° C, more preferably 5 to 120 ° C, and particularly preferably 10 to 100 ° C. The irradiation time is preferably 2 to 600 seconds, more preferably 5 to 240 seconds, and particularly preferably 10 to 120 seconds.

  The atmosphere during the electron beam treatment is not particularly limited, and may be an air atmosphere or an inert gas atmosphere (for example, nitrogen gas, helium gas, argon gas, fluorine gas, etc.). Further, water, oxygen, ammonia, alkylamines (for example, trimethylamine), carbon dioxide and the like may be contained in a small amount (0.001 to 5% by volume) in these air or inert gas. An inert gas atmosphere is preferable, and an argon or nitrogen atmosphere is more preferable.

  Next, the present invention is characterized in that alkali suitability is improved by performing an alkali saponification treatment after an electron beam irradiation treatment of a film-like cellulose ester. In that case, the alkali saponification treatment may be carried out at any time after the electron beam irradiation treatment, but is preferably within 24 hours, more preferably within 12 hours, particularly preferably within 6 hours, most preferably. Is within 3 hours. This is to avoid adverse effects caused by attenuation of activated surface properties (such as hydrophilicity) when a long time has elapsed since electron beam irradiation. For these electron beam treatments, methods described in JP-A Nos. 2002-318300 and 2003-248100 can be used.

[Alkaline saponification aqueous solution]
Next, the alkali saponification process of the present invention will be described. The alkali agent of the alkali saponification aqueous solution of the present invention is not particularly limited as long as it can have either an inorganic alkali agent or an organic alkali agent and has alkali saponification characteristics. Examples of strong inorganic alkali agents include alkali metal hydroxides (e.g., NaOH, KOH, LiOH), alkaline earth metal hydroxides, tribasic sodium phosphate, tripotassium, dibasic ammonium, dibasic sodium phosphate, The potassium, ammonium, sodium borate, potassium, and ammonium are preferred.

Organic alkali agents include ammonium hydroxide, amine (eg, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, n-butylamine, monoethanolamine, diethanolamine. , Triethanolamine, monoisopropanolamine, diisopropanolamine, ethyleneimine, ethylenediamine, pyridine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, triethylbutylammonium hydroxide, par Fluorotributylamine, triethylamine), and Free base _{(eg, [Pt (NH 3) 6} ] (OH) 4) salts are preferred. Among these, NaOH, KOH, and LiOH, which are alkali metal hydroxides, are more preferable to cause a saponification reaction at a low concentration, and NaOH and KOH are particularly preferable. These alkali agents can be used alone or in combination of two or more.

  The concentration of the alkaline agent in the alkaline saponification aqueous solution is determined according to the type of alkaline agent used, the reaction temperature, and the reaction time. In order to complete the saponification reaction in a short time, it is preferable to prepare a solution at a high concentration. However, if the alkali concentration is too high, the stability of the alkali saponification aqueous solution is impaired, and in some cases, it may be deposited in the liquid or gas-liquid interface as a solid content during long-time application. The concentration of the alkali saponification aqueous solution is preferably 0.2 to 5 mol / L, more preferably 0.5 to 5 mol / L, and most preferably 0.5 to 3 mol / L.

[Surfactant]
The surfactant optionally used in the alkaline saponification aqueous solution of the present invention can reduce the surface tension of the alkaline saponification aqueous solution to facilitate coating, prevent repelling failure, and concentrate the alkaline agent or film and alkali. The reaction product with the agent can be stably present in the alkaline saponification aqueous solution, and precipitation and solidification can be prevented in the subsequent water washing step. The concentration of the surfactant is preferably a concentration at which these substances can be stably dispersed in the alkaline saponification aqueous solution, and can be estimated to be 1% by mass at the maximum, but the concentration of the surfactant is actually 10 times this 10 It has been found that sufficient dispersion characteristics can be obtained by addition of mass%. On the other hand, depending on the type of surfactant, if it remains without being sufficiently washed away in the water washing step, it may interfere with the bonding (adhesion) between the film and the alignment film when the alignment film is applied on the cellulose ester film later. There is. Moreover, since it may interfere with the orientation of the liquid crystalline molecules when applying the liquid crystalline molecules, it is not preferable to add more than necessary. The addition concentration of the surfactant is preferably 0.005 to 1% by mass, and more preferably 0.02 to 1% by mass.

  The surfactant preferably used in the alkali saponification method of the present invention is not particularly limited as long as it can be dissolved or dispersed in the alkali saponification solution of the present invention. Any of nonionic surfactants (nonionic surfactants, fluorosurfactants), ionic surfactants (anions, cations, amphoteric surfactants) can be suitably used. Among the surfactants, nonionic surfactants and anionic surfactants are preferably used from the viewpoints of solubility and saponification performance. These surfactants may be added alone or in combination of one or more different ionic surfactants or nonionic surfactants. A nonionic surfactant may be added in combination.

  Hereinafter, the surfactants that can be used in the present invention will be sequentially described. (Anionic surfactant) Examples of the anionic surfactant include fatty acid salts, abietic acid salts, hydroxyalkane sulfonic acid salts, alkane sulfonic acid salts, dialkyl sulfosuccinic acid ester salts, α-olefin sulfonic acid salts, and linear alkylbenzene. Sulfonates, branched alkylbenzene sulfonates, alkylnaphthalene sulfonates, alkylphenoxy polyoxyethylene propyl sulfonates, polyoxyethylene alkyl sulfophenyl ether salts, N-methyl-N-oleyl taurine sodium salt, N-alkyl Sulfosuccinic acid monoamide disodium salt, petroleum sulfonates, sulfated beef oil, sulfate esters of fatty acid alkyl esters, alkyl sulfate esters, polyoxyethylene alkyl ethers Acid ester salts, fatty acid monoglyceride sulfates, polyoxyethylene alkylphenyl ether sulfates, polyoxyethylene styryl phenyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkyl Preferable examples include phenyl ether phosphate salts, partially saponified products of styrene / maleic anhydride copolymer, partially saponified products of olefin / maleic anhydride copolymer, and naphthalene sulfonate formalin condensates.

(Cationic surfactant)
Examples of the cationic surfactant include alkylamine salts, quaternary ammonium salts such as tetrabutylammonium bromide, polyoxyethylene alkylamine salts, polyethylene polyamine derivatives, and the like.
(Amphoteric surfactant)
Examples of amphoteric surfactants include carboxybetaines, alkylaminocarboxylic acids, sulfobetaines, aminosulfuric acid esters, imidazolines, and the like.

(Nonionic surfactant)
Nonionic surfactants include, for example, polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene polystyryl phenyl ethers, polyoxyethylene polyoxypropylene alkyl ethers, glycerin fatty acid partial esters, Sorbitan fatty acid partial esters, pentaerythritol fatty acid partial esters, propylene glycol mono fatty acid esters, sucrose fatty acid partial esters, polyoxyethylene sorbitan fatty acid partial esters, polyoxyethylene sorbitol fatty acid partial esters, polyethylene glycol fatty acid esters , Polyglycerin fatty acid partial esters, polyoxyethylenated castor oil, polyoxyethylene glycerin fatty acid partial esters, Fatty acid diethanol amides, N, N-bis-2-hydroxyalkylamines, polyoxyethylene alkylamines, triethanolamine fatty acid esters, trialkylamine oxides and the like.

  Specific examples thereof include, for example, polyethylene glycol, polyoxyethylene lauryl ether, polyoxyethylene nonyl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene behenyl ether, polyoxyethylene Oxyethylene polyoxypropylene cetyl ether, polyoxyethylene polyoxypropylene behenyl ether, polyoxyethylene phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene stearylamine, polyoxyethylene oleylamine, polyoxyethylene stearamide, polyoxy Ethylene oleamide, polyoxyethylene castor oil, polyoxyethylene ethylene abietic Ether, polyoxyethylene nonine ether, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene glyceryl monooleate, polyoxyethylene glyceryl monostearate, polyoxyethylene propylene glycol monostearate, oxyethyleneoxy Propylene block polymer, distyrenated phenol polyethylene oxide adduct, tribenzylphenol polyethylene oxide adduct, octylphenol polyoxyethylene polyoxypropylene adduct, glycerol monostearate, sorbitan monolaurate, polyoxyethylene sorbitan monolaurate, etc. It is done. These nonionic surfactants preferably have a weight average molecular weight of 300 to 50,000, more preferably 500 to 5,000.

In the present invention, among the nonionic surfactants, a compound represented by the following general formula (1) is preferable.
General formula (1)
R ¹ —O (CH ₂ CHR ² O) ₁ — (CH ₂ CHR ³ O) _m — (CH ₂ CHR ⁴ O) _n —R ⁵
In general formula (1), R ^{1 to} R ⁵ each represent a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an alkenyl group, an alkynyl group, an aryl group, a carbonyl group, a carboxylate group, a sulfonyl group, or a sulfonate group. To express. Specific examples of the alkyl group include a methyl group, an ethyl group, and a hexyl group. Specific examples of the alkenyl group include a vinyl group and a propenyl group. Specific examples of the alkynyl group include An acetyl group, a propynyl group, etc. are mentioned, As a specific example of the said aryl group, a phenyl group, 4-hydroxyphenyl group, etc. are mentioned. l, m, and n each represents an integer of 0 or more. However, all of l, m, and n are not 0. Specific examples of the compound represented by the general formula (1) include homopolymers such as polyethylene glycol and polypropylene glycol, copolymers of ethylene glycol and propylene glycol, and the like. The ratio of the copolymer is preferably 10/90 to 90/10 from the viewpoint of solubility in an alkaline saponification aqueous solution. Of the copolymers, graft polymers and block polymers are preferable from the viewpoint of solubility in an aqueous alkali saponification solution and ease of alkali saponification treatment.

(Fluorosurfactant)
The fluorosurfactant refers to a surfactant containing a perfluoroalkyl group in the molecule. Examples of such fluorosurfactants include perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, anionic types such as perfluoroalkyl phosphates, amphoteric types such as perfluoroalkyl betaines, and perfluoroalkyls. Cation type such as trimethylammonium salt, perfluoroalkylamine oxide, perfluoroalkylethylene oxide adduct, perfluoroalkyl group and hydrophilic group-containing oligomer, perfluoroalkyl group and lipophilic group-containing oligomer, perfluoroalkyl group, hydrophilic Nonionic types such as group and lipophilic group-containing oligomers, perfluoroalkyl groups and lipophilic group-containing urethanes. Among the above surfactants, those having “polyoxyethylene” can be read as polyoxyalkylenes such as polyoxymethylene, polyoxypropylene and polyoxybutylene, and these are also included in the surfactant. The The surfactants may be used alone or in combination of two or more as long as the effect is not impaired by the combined use.

  Among the above surfactants, the quaternary ammonium salts as the cationic surfactant, the various polyethylene glycol derivatives as the nonionic surfactant, and the polyethylene oxides such as the various polyethylene oxide adducts. Derivatives and betaine type compounds as amphoteric surfactants are also preferably used. In the alkaline saponification aqueous solution, it is also preferable to use a nonionic activator and an anionic activator or a nonionic activator and a cationic activator together in order to enhance the effect of the present invention.

When the cellulose ester film is treated with an alkaline saponification aqueous solution, the alkali agent is concentrated, and fatty acid salts and film additive substances produced by the saponification treatment are generated and extracted from the alkaline saponification aqueous solution. In order to prevent the generated and extracted components from depositing on the film surface, it is effective to set the carbonate ion concentration of this alkaline saponified aqueous solution to 3500 mg / L or less. More preferably, it is 1000 mg / L or less, and particularly preferably 100 mg / L or less. By setting the carbonate ion concentration to 3500 mg / L, an alignment film is applied to a saponified cellulose ester film, and after rubbing, foreign matter defects and alignment are formed when an optical anisotropic layer is formed by liquid crystalline molecules. Defects can be reduced. A high-concentration alkaline saponification aqueous solution easily absorbs CO ₂ in the environmental atmosphere, lowers the pH, and causes precipitation. In order to suppress the absorption of CO _{2 in} the ambient atmosphere, it is more preferable that the coating coater of the alkaline saponification aqueous solution has a semi-sealed structure, or is covered with dry air, an inert gas or an organic solvent saturated vapor of the alkaline saponification aqueous solution. .

  In addition, concentrated alkali agents, fatty acid salts, and film-added substances can be obtained by setting the chloride ions (preferably chloride ions) and the polyvalent metal ions such as calcium ions and magnesium ions in the alkaline saponification aqueous solution to 1000 mg / L or less, respectively. An optical anisotropic layer when an optically anisotropic layer of liquid crystalline molecules is installed after an alignment film is applied to a saponified cellulose ester film without rubbing the extracted substance on the film surface, and after rubbing. The adhesion failure can be reduced. The main solvent of the alkaline saponification aqueous solution is water, but the water to be used is preferably pure water. As pure water, the calcium concentration in the liquid is preferably 0.001 to 100 mg / L, and 0.001 to 50 mg. / L is more preferable, and 0.001 to 10 mg / L is particularly preferable. The magnesium concentration is preferably 0.001 to 50 mg / L, more preferably 0.001 to 30 mg / L, and particularly preferably 0.001 to 10 mg / L.

  Polyvalent metal ions other than calcium and magnesium, such as B, Sr, Ba, Al, Sn, Pb, Ti, Cr, Mn, Fe, Co, Ni, Cu (II), Co, and Zn may not be included. preferable. The concentration of the polyvalent metal ion is preferably 0.002 to 150 mg / L. On the other hand, it is preferable that the alkali saponification solution does not contain anions such as chloride ions and carbonate ions. The chloride ion concentration is preferably 0.001 to 100 mg / L, more preferably 0.001 to 50 mg / L, and particularly preferably 0.001 to 10 mg / L. Further, it is preferable that carbonate ions are not included. The carbonate ion concentration is preferably 0.001 to 500 mg / L, more preferably 0.001 to 100 mg / L, and particularly preferably 0.001 to 20 mg / L. The concentration of each of the above ionic species is preferably as low as possible, and the lower limit of 0.001 mg / L means that it is below the measurement limit. In these concentration ranges, generation of insoluble matters in the solution is suppressed. In these concentration ranges, generation of insoluble matters in the solution is suppressed.

  The surface tension of the alkaline saponification aqueous solution of the present invention is preferably 15 to 65 mN / m or less. More preferably, it is 15-60 mN / m, Most preferably, it is 15-50 mN / m. The viscosity of the alkali saponification aqueous solution of the present invention is preferably 0.6 to 20 mPa · s, more preferably 1 to 15 mPa · s. The surface tension of the alkali saponification aqueous solution is preferably as described above, and in this range, the wettability to the film surface, the retention of the solution applied to the film surface, the alkali liquid from the film surface after the saponification treatment Removability is sufficiently performed, and a stable coating operation can be realized.

The density of the alkali saponification aqueous solution of an alkali saponification method of the present invention is preferably 0.9~1.4g / cm ^3, more preferably 0.95~1.3g / cm ^3, 1 It is especially preferable that it is 0.0-1.2 g / cm < ³ >. If it is 0.9 g / cm ³ or less, wind unevenness due to wind pressure due to conveyance occurs, and the uniformity of processing is impaired. On the other hand, at 1.4 g / cm ³ or more, a coating streak parallel to the transport direction is generated due to its own weight, which also impairs the uniformity of processing and causes uneven thickness of the alignment film. Furthermore, the specific conductivity of the alkaline saponification aqueous solution of the alkaline saponification method of the present invention is preferably 20 mS / cm to 2 S / cm in order to minimize the load in the washing step described later, and 50 mS / cm to 1. It is more preferably 5 S / cm, and particularly preferably 100 mS / cm to 1 S / cm.
By setting the specific conductivity to 2 S / cm or less, a salt that causes a bright spot failure (foreign matter defect) is less likely to occur, and poor adhesion of the optical compensation layer is less likely to occur.

  Further, as the liquid characteristics of the alkaline saponification aqueous solution, the absorbance of the liquid at a measurement wavelength of 400 nm is 2. It is preferably less than 0. When a liquid having a high absorbance is used, a reaction product with the cellulose ester film and a film additive dissolved in the liquid adhere to the cellulose ester film and cause a bright spot failure (foreign substance defect). For controlling the absorbance of the alkaline saponified aqueous solution, activated carbon can be used to adsorb and remove the eluted components. Activated carbon only needs to have a function of removing colored components in the saponification solution, and there is no limitation on the form, material, and the like. It may be a method of directly putting activated carbon into an alkaline saponification aqueous solution tank, or a method of circulating a saponification aqueous solution between a saponification aqueous solution tank and a purification device filled with activated carbon.

  The alkali coating amount required for the saponification reaction is the total number of saponification sites obtained by multiplying the number of saponification reaction sites per unit area of the cellulose ester film by the saponification depth necessary to develop adhesion with the alignment film (= theoretical alkali coating) Amount) is a guide. As the saponification reaction proceeds, the alkali is consumed and the reaction rate decreases, so it is actually preferable to apply several times the theoretical alkali coating amount. Specifically, it is preferably 2 to 20 times the theoretical alkali coating amount, and more preferably 2 to 5 times.

[Defoaming agent]
The alkali saponification aqueous solution and the alkali dilution liquid may contain an antifoaming agent. The additive is preferably 0.005 to 1% by mass, more preferably 0. It can be contained at a concentration of 005 to 3% by mass. On the other hand, it can be contained in the alkali diluted solution at a concentration of preferably 0.001 to 2 mass%, particularly preferably 0.005 to 0.5 mass%. Within this range, there is no adhesion of minute bubbles to the film surface, and saponification by the alkali treatment proceeds uniformly without unevenness.

  Examples of antifoaming agents include oils and fats such as castor oil and linseed oil, fatty acids such as stearic acid and oleic acid, fatty acid esters such as natural wax, alcohols such as polyoxyalkylene monohydric alcohol, di-tert- Amylphenoxyethanol, heptylcellosolve, nonylcellosolve, ethers such as 3-heptylcarbitol, phosphate esters such as tributylphosphate and tris (butoxyethyl) phosphate, amines such as diamylamine, polyalkyleneamide, acylate polyamide, etc. Metal soaps such as amides, aluminum stearate, calcium stearate, potassium oleate, calcium wool oleate, sulfates such as sodium lauryl sulfate, dimethylpolysiloxane, methylphenol Silicone oil such as nylpolysiloxane, methylhydrogen polysiloxane, fluoropolysiloxane, copolymer of dimethylpolysiloxane and polyalkylene oxide, and silicone-based antifoaming agents such as solution type, emulsion type and paste type silicone oil Is mentioned.

In the alkaline saponification aqueous solution of the present invention, an organic solvent other than the organic solvents described above can be added as a solubilizing agent for the surfactant and antifoaming agent in the alkaline saponification aqueous solution. There is no particular limitation as long as it is preferably a solvent having solubility in water. For example, methanol, ethanol, n-propanol, isopropanol, butanol, ethylene glycol, diethylene glycol, ethoxyethanol, butoxyethanol, diethylene glycol monoethyl ether, ethylene glycol monobutyl ether, benzyl alcohol, fluorinated alcohol (for example, CnF _{2n + 1} (CH ₂ ) _k OH (n is an integer of 3 to 8, k is an integer of 1 or 2), 1,2,2,3,3-heptafluoropropanol, hexafluorobutanediol, perfluorocyclohexanol, etc. Etc. The content of these organic solvents is preferably 0.1 to 5% by mass with respect to the total weight of the liquid used.

[Antidepressant / Antimicrobial agent]
The alkaline saponification aqueous solution of the present invention may further contain a fungicide and / or a fungicide. The antifungal agent and antibacterial agent used in the present invention may be anything as long as they do not adversely affect alkali saponification. Specifically, thiazolylbenzimidazole compounds, isothiazolone compounds, chlorophenol compounds , Bromophenol compounds, thiocyanic acid and isothiocyanic acid compounds, acid azide compounds, diazines and triazine compounds, thiourea compounds, alkylguanidine compounds, quaternary ammonium salts, organotin and organozinc compounds, cyclohexylphenol compounds , Imidazole and benzimidazole compounds, sulfamide compounds, active halogen compounds such as chlorinated sodium isocyanurate, chelating agents, sulfites, and various antibacterial and antifungal agents such as antibiotics typified by penicillin .

  Others E. West, “Water Quality Criteria”, Photo. Sci. and Eng. , Vol9 No. 6 (1965), various antifungal agents described in JP-A-57-8542, 58-105145, 59-126533, 55-111942, and 57-157244, Use of chemicals such as those described in "History of fungi prevention" by Horiguchi Hiroshi, Sankyo Publishing (Sho 57), "Anti-bacteria prevention handbook" Specific examples are shown below, but are not limited thereto. The addition amount of the antifungal agent and / or the antibacterial agent is preferably 0.01 to 50 g / L, more preferably 0.05 to 20 g / L in the alkaline saponification aqueous solution.

  An organic solvent can be optionally added to the alkaline saponification aqueous solution used in the present invention. There is no particular limitation as long as it is a solvent having solubility in water. For example, methanol, ethanol, n-propanol, isopropanol, butanol, ethylene glycol, diethylene glycol, ethoxyethanol, butoxyethanol, diethylene glycol monoethyl ether, ethylene glycol monobutyl ether, benzyl alcohol, 3-phenyl-1-propanol, 4 -Phenyl-1-butanol, 4-phenyl-2-butanol, 2-phenyl-1-butanol, 2-phenoxyethanol, 2-benzyloxyethanol, o-methoxybenzyl alcohol, m-methoxybenzyl alcohol, p-methoxybenzyl alcohol Benzyl alcohol, cyclohexanol, 2-methylcyclohexanol, 3-methylcyclohexanol, 4-methylcyclohexanol, Alcohols (e.g. 1,2,2,3,3- heptafluoro fluoroalkyl propanol, hexafluoro-butanediol, perfluoro cyclohexanol), and the like. The content of the organic solvent is preferably 0.1 to 5% by mass with respect to the total weight of the liquid used. The amount used is closely related to the amount of surfactant used, and it is preferable to increase the amount of surfactant as the amount of organic solvent increases. This is because the amount of the surfactant is small, and when a large amount of the organic solvent is used, the organic solvent is not completely dissolved, so that it is not possible to ensure a good saponification treatment.

  The aqueous alkaline saponification solution of the present invention preferably contains at least one compound selected from non-reducing sugars because it has a pH buffering action in combination with an alkaline agent. Such non-reducing sugars are saccharides that do not have a free aldehyde group or ketone group and do not exhibit reducing properties, and are trehalose-type oligosaccharides in which reducing groups are bonded to each other, and glycosides in which a reducing group of saccharides and non-saccharides are bonded. These are classified into sugar alcohols reduced by hydrogenation of the body and saccharides, both of which are preferably used in the present invention. Trehalose type oligosaccharides include saccharose and trehalose. Examples of glycosides include alkyl glycosides, phenol glycosides, mustard oil glycosides, and the like. Examples of the sugar alcohol include D, L-arabit, rebit, xylit, D, L-sorbit, D, L-mannit, D, L-exit, D, L-talit, zulsiit and allozulcit. Further, a multibit obtained by hydrogenation of a disaccharide and a reduced form (reduced water candy) obtained by hydrogenation of an oligosaccharide are preferably used. Among these, preferred non-reducing sugars for the present invention are sugar alcohol and saccharose. Particularly, D-sorbite, saccharose, and reduced starch syrup are preferable because they have a buffering action in an appropriate pH region and are inexpensive. These non-reducing sugars can be used singly or in combination of two or more, and the proportion of them in the developer is preferably from 0.1 to 30% by mass, more preferably from 1 to 20% by mass.

[Other additives to alkaline saponification solution]
In addition, you may use together another additive for the alkali saponification liquid of this invention. For example, alkaline solution stabilizers (antioxidants etc.), known pH buffering agents and the like can be mentioned. In the present invention, the alkali saponification aqueous solution additive is not limited thereto. The temperature of the alkaline saponification aqueous solution is desirably equal to the reaction temperature (= temperature of the cellulose ester film). In order to perform stable coating, the temperature needs to be lower than the boiling point of water, preferably 10 ° C to 90 ° C, more preferably 15 to 80 ° C, particularly 25 to 25 ° C. It is preferable that it is 70 degreeC.
The processing time is preferably 5 seconds to 600 seconds.

[Alkali saponification method]
The surface treatment method of the cellulose ester film of the present invention includes a step of saponifying the surface of the cellulose ester film using an alkaline saponified aqueous solution at a temperature of room temperature or higher using an alkaline saponified aqueous solution, and a step of washing off the alkaline saponified aqueous solution from the cellulose ester film. Further, it is preferable to carry out the alkali saponification treatment by a step of neutralizing the alkaline aqueous solution with an acidic aqueous solution and a step of washing with water.
For the step of treating the cellulose ester film with the alkaline saponification aqueous solution, any conventionally known method may be used, and examples thereof include a dipping method, a spraying method, and a coating method.

  A method of immersing a cellulose ester film in a saponification solution bath that is generally performed will be described. The size of the treatment bath is not particularly limited as long as it is a container capable of a predetermined temperature and treatment time. As the arrangement of the treatment steps, a process arrangement of a sending-out part-electron beam treatment part-alkali saponification treatment tank-water washing tank-acid neutralization tank-water washing tank-drying process part-winding part is common. The temperature of each tank is not particularly limited as long as it is controlled at 5 to 90 ° C. and a processing time of 5 to 1200 seconds. The saponification bath is more preferably 15 to 80 ° C, particularly preferably 25 to 70 ° C. The treatment time is more preferably 10 seconds to 600 seconds, and particularly preferably 10 to 300 seconds. Moreover, as an acidic neutralization tank, it is more preferable that it is 5-80 degreeC, and it is especially preferable that it is 10-50 degreeC. The treatment time is more preferably 10 seconds to 600 seconds, and particularly preferably 10 to 300 seconds. About a water-washing tank, it is still more preferable that it is 5-80 degreeC, and it is more preferable that it is especially 10-50 degreeC. The treatment time is more preferably 10 seconds to 600 seconds, and particularly preferably 10 to 300 seconds.

  Moreover, 25-150 degreeC is preferable, as for the temperature of a drying process, 30-140 degreeC is more preferable, and 40-130 degreeC is further more preferable. The drying time is preferably 5 to 1500 seconds, more preferably 20 to 1200 seconds, and further preferably 60 to 1200 seconds. The processing method may be carried in a roll shape or may be processed in a sheet shape. In the case of a roll-like cellulose ester film, it may be handled consistently from sending out to drying, or it may be cut at any point in the process and further handled in a roll state of a certain length. However, the post-processing step may be performed in the sheet state. As a conveyance speed, 1-200 m / min is preferable, 3-150 m / min is more preferable, 10-150 m / min is further more preferable.

  Next, a coating method of a saponification treatment liquid used as a saponification treatment method for a cellulose ester film treated with an electron beam according to the present invention will be described. As a coating method of the alkali saponification solution, a conventionally known coating method can be used as described below. For the saponification treatment with an aqueous solution of alkali saponification of the cellulose ester film at a temperature of room temperature or higher, a step of heating to a room temperature or higher before coating, a step of warming an alkaline solution in advance, or a combination of these steps Etc. It is preferable to combine with the process of heating to room temperature or higher before application.

  First, in the step of previously heating the cellulose ester film to room temperature or more, hot air collision (direct heating by spraying), contact heat transfer by a heating roll, induction heating by microwaves, radiant heat heating by an infrared heater, or the like can be preferably used. In particular, contact heat transfer using a heating roll is preferable in that heat transfer efficiency is high and it can be performed with a small installation area, and that the rise of the film temperature at the start of conveyance is fast. A general double jacket roll or electromagnetic induction roll (manufactured by Tokuden) can be used. The film surface temperature after heating is preferably 25 to 150 ° C, more preferably 25 to 100 ° C, and most preferably 40 to 80 ° C.

In the step of applying an alkali saponification aqueous solution to the above-mentioned electron beam-treated cellulose ester film, a die coater (extrusion coater, slide coater), roll coater (forward roll coater, reverse roll coater, gravure coater), rod coater (narrow) A rod wound with a metal wire can be preferably used. The coating method is described in various documents (for example, Modern Coating and Drying Technology, Edward Cohen and Edgar B. Gutoff, Edits., VCH Publishers, Inc, 1992). The coating amount of the alkali saponification solution is then, taking into account the waste treatment to water washing removed as much as possible it is desirable to suppress, preferably ^{1~100cc / m 2, 1~50cc / m} 2 is more preferable. A rod coater, gravure coater, and blade coater that can be stably operated even in a small coating amount range are particularly preferred. Moreover, it is preferable to apply the alkaline saponification aqueous solution to the lower surface of the cellulose ester film in order to easily wash off the alkaline saponification aqueous solution from the cellulose ester film after applying the alkaline saponification aqueous solution and saponifying the cellulose ester film. The variation in the amount of water sprayed per unit time is preferably controlled to be less than 30% in both the longitudinal direction and the width direction of the cellulose ester film being conveyed. Moreover, a continuous application method can also be adopted.

  In the coating-type alkaline saponification method of the present invention, it is recommended that the temperature of the electron-treated cellulose ester film be kept at room temperature (20 ° C.) or higher after the alkaline saponification aqueous solution is coated until the saponification reaction is completed. The heating means is selected in consideration of the fact that one side of the cellulose ester film is wet with the alkaline saponification aqueous solution. Hot air collision (spraying) on the opposite surface of the coating, contact heat transfer with a heating roll, induction heating with a microwave, radiant heat heating with an infrared heater, etc. can be preferably used. Infrared heaters are preferred because they can be heated without contact and without the flow of air, so that the influence on the surface to which the alkaline saponification aqueous solution is applied can be minimized. As the infrared heater, an electric, gas, oil or steam far infrared ceramic heater can be used. A commercially available infrared heater (for example, manufactured by Noritake Company Limited) may be used. An oil-type or steam-type infrared heater using oil or steam as the heat medium is preferable from the viewpoint of explosion prevention in an atmosphere in which an organic solvent coexists.

  The temperature of the cellulose ester film may be the same as or different from the temperature heated before application of the alkaline saponification aqueous solution. Further, the temperature may be changed continuously or stepwise during the saponification reaction. The film temperature is preferably 20 ° C to 150 ° C, more preferably 25 ° C to 100 ° C, and further preferably 35 ° C to 80 ° C. For the detection of the film temperature, a commercially available non-contact infrared thermometer can be used. In order to control the temperature within the above temperature range, feedback control may be performed on the heating means. The time for applying the alkali saponification aqueous solution and maintaining the temperature range before washing off depends on the conveyance speed described later, but is preferably maintained for 1 second to 5 minutes, more preferably 2 to 100 seconds, It is particularly preferred to hold for 3 to 50 seconds.

  Although it is preferable to carry out each step treatment while carrying the cellulose ester film to carry out the alkali saponification treatment, the carrying speed of the cellulose ester film is determined by the combination of the composition of the alkali saponification aqueous solution and the coating method. Generally, 10 to 500 m / min is preferable, and 20 to 300 m / min is more preferable.

  Also, before the step of heating the electron beam-treated cellulose ester film above room temperature or the step of applying an alkaline saponification aqueous solution to the cellulose ester film, dust is removed and the wettability of the membrane surface is more uniform. In order to achieve this, a method known in the art can be used for these methods, in which a neutralization treatment, a dust removal treatment, or a wet treatment can be carried out, and the neutralization method is described in JP-A-62-131500. Examples of the method and the dust removal method include the method described in JP-A-2-43157.

  There are generally three methods for slowing or stopping the saponification reaction between the aqueous alkaline saponification solution and the cellulose ester film after the saponification reaction is allowed to proceed while maintaining the temperature of the cellulose ester film at room temperature or higher. The first is to dilute the applied alkaline saponification aqueous solution to lower the alkali concentration and reduce the reaction rate, and the second is to lower the temperature of the cellulose ester film coated with the alkaline saponification aqueous solution to react. The third is a method of reducing the speed, and the third is a method of neutralizing with an acidic liquid.

  In order to dilute the applied aqueous solution of alkali saponification, a method of applying a diluent, a method of spraying the diluent, or a method of immersing the cellulose ester film in a container containing the diluent can be employed. The method of applying the diluting solution and the method of spraying are preferable methods for carrying out the cellulose ester film while being continuously conveyed. The method of applying the diluent is most preferable because it can be carried out using the minimum amount of diluent.

  It is desirable that the dilution liquid is applied in such a manner that the dilution liquid can be applied again on the cellulose ester film already coated with the alkaline saponification aqueous solution. For coating, a die coater (extrusion coater, slide coater), roll coater (forward roll coater, reverse roll coater, gravure coater), and rod coater (rod wound with a thin metal wire) can be preferably used. The application method is described in various documents (for example, Modern Coating and Drying Technology, Edward Cohen and Edgar B. Gutoff, Edits., VCH Publis hers, Inc, 1992). In order to reduce the alkali concentration by quickly mixing the alkali saponification aqueous solution and the diluting solution, the flow is more laminar than the die coater in the micro area where the diluting solution is applied (sometimes called coating bead). However, a roll coater or a rod coater in which the flow is not uniform is preferable.

  The purpose of the alkaline diluting solution is to lower the alkali concentration and prevent the extraction material such as a film additive substance from adhering to the film, so it must be a solvent that dissolves the alkaline agent in the alkaline saponification aqueous solution. Therefore, it is preferable to use water or a mixed solution of water and an organic solvent, and two or more organic solvents may be mixed and used. The organic solvent used for the alkali saponification aqueous solution mentioned later can be used preferentially. A preferred solvent is water. In addition, it is preferable to include a surfactant in the alkaline diluent so that an extraction material such as a film additive substance does not adhere to the film. Although there is no limitation in particular as surfactant, the surfactant used for the alkali saponification aqueous solution mentioned later can be utilized advantageously. Furthermore, the alkali diluent contains an antifoaming agent, which will be described later, so that fine bubbles do not adhere to the film surface, and the alkaline saponification aqueous solution and the alkali dilution solution can be uniformly and uniformly washed. preferable.

  The coating amount of the diluent is determined according to the concentration of the alkaline saponification aqueous solution. In the case of a die coater in which the flow in the coating bead is a laminar flow, the coating amount is preferably diluted from 1.5 to 10 times the original alkali concentration, more preferably from 2 to 5 times. In the case of a roll coater or a rod coater, since the flow in the coating bead is not uniform, the alkaline saponification aqueous solution and the diluting liquid are mixed, and the mixed liquid is recoated. Therefore, in this case, since the dilution rate cannot be specified by the application amount of the diluent, it is necessary to measure the alkali concentration after application of the diluent. Also in the roll coater and the rod coater, the coating amount is preferably diluted from the original alkali concentration by 1.5 to 10 times, and more preferably from 2 to 5 times.

  An acid can also be used to quickly stop the saponification reaction with alkali. In order to neutralize with a small amount, it is preferable to use a strong acid. Furthermore, considering the ease of washing with water, it is preferable to select an acid having a high solubility in water for the salt produced after the neutralization reaction with the alkali. Hydrochloric acid, nitric acid, phosphoric acid, chromic acid, sulfonic acid, and methanesulfonic acid are particularly preferred. If the carbonate ion concentration or chloride ion concentration in the alkali saponification solution is high, precipitation may occur due to a rapid neutralization reaction. In this case, a buffering weak acid is added to the alkali neutralization solution. It is preferable. Such weak acids include sorbitol, saccharose, glucose, galactose, arabinose, xylose, fructose, ribose, mannose and L-ascorbic acid, etc. , Alcohols, aldehydes, compounds having phenolic hydroxyl groups, oximes, nucleic acid-related substances, and the like.

  In order to neutralize the applied alkaline saponification aqueous solution with an acid, a method of applying an acidic solution (alkali neutralizing solution), a method of spraying the acidic solution, or a method of immersing the cellulose ester film together in a container containing the acidic solution Can be adopted. The method of applying an acidic solution and the method of spraying are preferable when the cellulose ester film is continuously conveyed. The method of applying the acidic solution is most preferable because it can be carried out using the minimum necessary acidic solution.

  The application of the alkali neutralizing solution is desirably a continuous application method in which the acidic solution can be applied again on the cellulose ester film already coated with the alkaline saponification aqueous solution. For coating, a die coater (extrusion coater, slide coater), roll coater (forward roll coater, reverse roll coater, gravure coater), and rod coater (rod wound with a thin metal wire) can be preferably used. The coating method is described in various documents (for example, Modern Coating and Drying Technology, Edward Cohen and Edgar B. Gutoff, Edits., VCH Publishers, Inc, 1992). In order to reduce the alkalinity by quickly mixing the alkali saponification aqueous solution and the neutralizing solution, the die coater in which the flow is laminar in a minute region (sometimes called a coating bead) where the neutralizing solution is applied A roll coater or a rod coater in which the flow is not uniform is preferable.

  The coating amount of the alkali neutralizing solution is determined according to the type of alkali and the concentration of the alkali saponified aqueous solution. In the case of a die coater in which the flow in the coating bead is a laminar flow, the coating amount of the neutralizing solution is preferably 0.1 to 5 times the original alkali coating amount, and is preferably 0.5 to 2 times. Further preferred. In the case of a roll coater or a rod coater, since the flow in the coating bead is not uniform, mixing of the alkaline saponification aqueous solution and the neutralizing liquid occurs, and the mixed liquid is recoated. Therefore, in this case, since the neutralization rate cannot be specified by the application amount of the neutralization liquid, it is necessary to measure the alkali concentration after application of the neutralization liquid. In a roll coater or a rod coater, the application amount of the acidic solution is preferably determined such that the pH after application of the acidic solution is 4 to 9, and more preferably 6 to 8.

  The purpose of the alkali neutralization solution is to reduce alkalinity and prevent the extraction materials such as film additive substances from adhering to the film. I must. Therefore, it is preferable to use water or a mixed solution of water and an organic solvent, and two or more organic solvents may be mixed and used. The organic solvent used for the alkali saponification aqueous solution mentioned later can be used significantly. A preferred solvent is water. Moreover, it is preferable to include a surfactant in the alkali neutralization solution so that an extraction material such as a film additive substance does not adhere to the film. Although there is no limitation in particular as surfactant, the surfactant used for the alkali saponification aqueous solution mentioned later can be utilized advantageously. Furthermore, it is preferable that the alkali neutralizing solution contains a buffering agent described later in order to increase the cleaning efficiency.

  It is also possible to stop the saponification reaction by lowering the temperature of the cellulose ester film. In order to promote the reaction, the saponification reaction is substantially stopped by sufficiently lowering the temperature from a state maintained at room temperature or higher. The means for lowering the temperature of the cellulose ester film is determined considering that one side of the cellulose ester film is wet. Collision of cold air with the opposite surface of the coating or contact heat transfer with a cooling roll can be preferably employed. The film temperature after cooling is preferably 5 ° C to 60 ° C, more preferably 10 ° C to 50 ° C, and most preferably 15 ° C to 30 ° C. The film temperature is preferably measured with a non-contact infrared thermometer. It is also possible to adjust the cooling temperature by performing feedback control on the cooling means.

[Washing process]
The washing step is performed in order to remove the alkali saponification aqueous solution, the alkali dilution liquid or the alkali neutralization liquid. If extraction materials such as alkali agents, acids, salts, and film additives remain in these materials, the saponification reaction proceeds, the formation of alignment films and liquid crystal molecular layers applied later, and the alignment of liquid crystal molecules Affects. Cleaning can be performed by a method of applying cleaning water, a method of spraying cleaning water, or a method of immersing the cellulose ester film together in a container containing cleaning water. The method of applying washing water and the method of spraying are preferable for carrying out the cellulose ester film while continuously conveying it. The method of spraying the washing water is particularly preferable because the turbulent mixing of the washing water on the cellulose ester film and the alkaline coating liquid can be obtained by the jet.

  Water can be sprayed by a method using an application head (for example, a fountain coater or a frog mouth coater), or a method using a spray nozzle used for humidifying or painting air or automatically cleaning a tank. The coating method is described in “All about coating” edited by Masayoshi Araki, Research Institute for Processing Technology (1999). Conical or fan-shaped spray nozzles can be arranged in the width direction of the cellulose ester film so that the water flow collides with the entire width. Commercially available spray nozzles (for example, manufactured by Ikeuchi Co., Ltd., manufactured by Spraying Systems) may be used. The higher the water spray speed, the higher the turbulent mixing. However, if the speed is high, the conveyance stability of the cellulose ester film that is continuously conveyed may be impaired. The collision speed of spraying is preferably 50 to 1000 cm / second, more preferably 100 to 700 cm / second, and most preferably 100 to 500 cm / second.

  The variation in the amount of water sprayed per unit time is preferably controlled to be less than 30% in both the longitudinal direction and the width direction of the cellulose ester film being conveyed. However, at both ends in the width direction of the cellulose ester film, it often occurs that the coating amount of the alkaline saponification aqueous solution or the coating amount of the acidic solution used for neutralization is large. In order to ensure the cleanability of the portion where the coating amount is large, the amount of water spraying at both ends in the width direction can be increased. When using a coating head, the clearance of the slit from which water is discharged is set wide so that the flow rate at both ends is increased. In addition, a coater having a narrow width may be separately installed in order to locally supply water films to both ends. Multiple coaters with a narrow width can be installed. Also when using a spray nozzle, a nozzle for spraying water locally can be installed at both ends.

  When a certain amount of water is used in the water washing, a batch type washing method in which the whole amount is applied at once rather than being divided into several times is preferable. That is, the amount of water is divided into several parts and supplied to a plurality of water washing means sequentially installed in the conveying direction of the cellulose ester film. Appropriate time (distance) is provided between one water washing means and the next water washing means to dilute the alkaline coating liquid by diffusion. More preferably, if the cellulose ester film to be conveyed is inclined so that the water on the film flows along the film surface, mixed dilution by flow can be obtained in addition to diffusion. As the most preferable method, the water washing dilution efficiency can be further increased by providing a water draining means for removing the water film on the cellulose ester film between the water washing means and the water washing means. Specific examples of draining means include blades used for blade coaters, air knives used for air knife coaters, rods used for rod coaters, and rolls used for roll coaters. It is advantageous that the number of washing means arranged in sequence is large. However, from the viewpoint of installation space and equipment cost, preferably 2 to 10 stages, more preferably 2 to 5 stages are used. The water film thickness after the draining means is preferably thin, but the minimum water film thickness is limited depending on the type of draining means used. In the method of physically bringing a solid into contact with the cellulose ester film, such as a blade, rod, or roll, even if the solid is an elastic body with low hardness such as rubber, the film surface is scratched or the elastic body is not Since it is worn out, it is necessary to leave a finite water film as a lubricating fluid. Usually, a water film of preferably several μm or more, more preferably 10 μm or more is left as a lubricating fluid.

  An air knife is preferable as the draining means that can reduce the thickness of the water film to the limit. By setting a sufficient air volume and pressure, the water film thickness can be brought close to zero. However, if the amount of air blown out is too large, it may affect the transport stability of the cellulose ester film, such as flapping of the transport film and deviation to one side, so there is a preferable range. Although it depends on the original water film thickness on the cellulose ester film and the film conveyance speed, the wind speed is preferably 10 to 500 m / second, more preferably 20 to 300 m / second, more preferably 30 to 200 m 2 / second. . In order to remove the water film uniformly, the air supply to the outlet of the air knife and the air knife is adjusted so that the wind speed distribution in the width direction of the cellulose ester film is usually within 10%, preferably within 5%. Adjust the method. The narrower the gap between the surface of the cellulose ester film to be conveyed and the air knife outlet, the better the draining ability. However, there is an appropriate range because the possibility of damage due to contact with the cellulose ester film increases. Preferably, the air knife is installed with a gap of 10 μm to 10 cm, more preferably 100 μm to 5 cm, and even more preferably 500 μm to 1 cm. Furthermore, by setting up a backup roll on the side opposite to the water-washed surface of the cellulose ester film so as to face the air knife, the setting of the gap can be stabilized and the influence of fluttering, wrinkles, deformation, etc. of the film can be reduced. It is preferable because it is possible.

It is preferable to use pure water as the washing water. The pure water used in the present invention has a specific electric resistance of at least 0.1 MΩ or more, in particular, metal ions such as sodium, potassium, magnesium and calcium are less than 1 mg / L, and anions such as chloro ion and nitrate ion are 0. .1 is preferably less than 1 mg / L. Pure water can be obtained by a reverse osmosis membrane, an ion exchange resin, a simple substance such as distillation, or a combination thereof.
The higher the washing water, the higher the washing ability. However, in the method of spraying water on the cellulose ester film to be transported, the area of water that comes into contact with air is large, and the evaporation becomes more significant as the temperature increases, so that the surrounding humidity increases and the risk of condensation increases. For this reason, the temperature of the washing water is preferably set in the range of 5 to 90 ° C, more preferably 20 to 80 ° C, and further preferably 25 to 60 ° C.

  If the components of the alkaline saponification aqueous solution or the product of the saponification reaction are not easily soluble in water, a solvent washing step for removing water-insoluble components may be added before or after the water washing step. The solvent washing step can utilize the water washing method and draining means described above. As the organic solvent to be used, in addition to a solvent that can be used in an alkali saponification aqueous solution described later, a solvent described in a new edition solvent pocket book (Ohm, 1994) can be used.

  A drying step can also be performed after the washing step. Usually, the water film can be sufficiently removed with a draining means such as an air knife, and a drying step may not be necessary. However, before winding the cellulose ester film into a roll, heat drying to adjust the moisture content to a preferred level. May be. Conversely, the humidity can be adjusted with a wind having a set humidity. The temperature of the drying air is preferably 30 to 200 ° C, more preferably 40 to 150 ° C, and particularly preferably 50 to 120 ° C. The cellulose ester film subjected to the electron beam treatment and alkali saponification treatment of the present invention can be coated with a functional layer continuously after the alkali saponification treatment step described above. By applying saponification treatment to one side by coating and coating the functional layer on it, even if the film is wound into a roll after the functional layer is provided, it is between the functional layer surface and the opposite surface of the film. It can prevent sticking.

Next, the cellulose ester film of the present invention is applied as various optical films. Although the typical application example is given to the following, it is not limited to these.
[Optical compensation sheet]
The cellulose ester film of the present invention, which has been subjected to the electron beam treatment of the present invention and further subjected to alkali saponification treatment, is preferably used as a transparent support for an optical compensation sheet. The optical compensation sheet has a layer structure in which a cellulose ester film subjected to electron beam treatment and alkali saponification treatment, an alignment film forming resin layer, and an optical anisotropic layer in which the orientation of liquid crystal molecules is fixed are laminated in this order. In the formation of the alignment film, a step of heating the cellulose ester film, a step of applying an electron beam treatment to the surface of the cellulose ester film on the alignment film side and applying an alkali saponification aqueous solution, a step of maintaining the temperature of the surface of the alkali saponification aqueous solution application, reaction Next, a step of applying an alignment film and drying can be added to the step of stopping the step and the step of washing and removing the alkaline saponification aqueous solution from the surface of the film. Furthermore, after the alignment film is applied and dried, the surface of the alignment film is rubbed, and the liquid crystalline molecular layer is applied and dried to complete the final optical compensation sheet. High productivity can be obtained by consistently forming not only the alkali saponification treatment of the cellulose ester film but also the alignment film and the liquid crystalline molecular layer. If it is formed consistently, there will be no time lapse from electron beam treatment to alkali saponification treatment to alignment film coating, less degradation of the activated saponification surface, and the water washing process of saponification treatment may also be used as wet dust removal Another advantage is that no loss occurs at the end of the roll due to multiple feeding and winding.

  The optical compensation sheet is an optically anisotropic material having a transparent support comprising a cellulose ester film that has been subjected to electron beam treatment and then subjected to alkali saponification treatment, an alignment film provided thereon, and a disk-like structural unit formed on the alignment film. Consists of layers. The alignment film is preferably a rubbed film made of a crosslinked polymer. As the compound having a discotic structural unit used in the optically anisotropic layer, a low molecular weight discotic liquid crystalline compound (monomer) or a polymer obtained by polymerization of a polymerizable discotic liquid crystalline compound can be used. In general, discotic compounds (discotic compounds) can be broadly classified into compounds having a discotic liquid crystal phase (that is, a discotic nematic phase) and compounds having no discotic liquid crystal phase. The discotic compound generally has negative birefringence, and the optical anisotropic layer according to the present invention has this negative birefringence of the discotic compound. The optically anisotropic layer utilizes the negative birefringence of the discotic compound.

[Alignment film]
The alignment film of the optically anisotropic layer is preferably formed by rubbing a film made of a crosslinked polymer. The alignment film is more preferably composed of two types of crosslinked polymers. One of the two polymers is a polymer that is itself crosslinkable or a polymer that is crosslinked by a crosslinking agent. The alignment film is formed by reacting a polymer having a functional group or a polymer in which a functional group is introduced with light, heat, or pH change between the polymers, or a cross-linking agent that is a highly reactive compound. It can be formed by introducing a linking group derived from a crosslinking agent between the polymers and crosslinking the polymers.

  Crosslinking of the polymer can be carried out by applying a coating liquid containing a polymer or a mixture of a polymer and a crosslinking agent on a transparent support and then heating. You may perform the process which bridge | crosslinks in any step after obtaining an optical compensation sheet after coating an alignment film on a transparent support body. In consideration of the orientation of the compound having a discotic structure (optically anisotropic layer) formed on the alignment film, it is also preferable to carry out final crosslinking after orienting the compound having a discotic structure. That is, when a coating liquid containing a polymer and a crosslinking agent capable of crosslinking the polymer is applied on the transparent support, after heating and drying, an alignment film is formed by rubbing, and then a disk is formed on the alignment film. A coating liquid containing a compound having a structural unit is applied, heated to a discotic nematic phase formation temperature or higher, and then cooled to form an optically anisotropic layer.

  As the polymer used in the alignment film, either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent can be used, and a plurality of combinations thereof can be used. Examples of polymers include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleimide copolymer, polyvinyl alcohol and modified polyvinyl alcohol, poly (N-methylol acrylamide), styrene / vinyl toluene copolymer, Polymers such as chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, carboxymethyl cellulose, gelatin, polyethylene, polypropylene, and polycarbonate And compounds such as silane coupling agents. Examples of preferred polymers are water-soluble polymers such as poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvir alcohol and modified polyvinyl alcohol, and gelatin, polyvir alcohol and modified polyvinyl alcohol are preferred. Alcohol and modified polyvinyl alcohol are particularly preferable, and it is particularly preferable to use two types of polyvinyl alcohol or modified polyvinyl alcohol having different degrees of polymerization.

The saponification degree of polyvinyl alcohol is preferably 70 to 100%, more preferably 80 to 100%, and most preferably 85 to 95%. The polymerization degree of polyvinyl alcohol is preferably 100 to 3000. The modifying group of the modified polyvinyl alcohol can be introduced by copolymerization modification, chain transfer modification or block polymerization modification. Examples of the introduction group in the case of copolymerization modification include COONa, Si (OX) ₃ , N (CH ₃ ) ₃ .Cl, C ₉ H ₁₉ C OO, SO ₃ , Na 2 and C ₁₂ H ₂₅ . (X is a proton or cation). Examples of the introduction group in the case of the chain transfer modifying group include COONa, SH, and C ₁₂ H ₂₅ . Examples of the introduction group in the case of block polymerization modification include COOH, CONH ₂ , COOR, and C ₆ H ₅ (R is an alkyl group). Among these, unmodified polyvinyl alcohol or alkylthio-modified polyvinyl alcohol having a saponification degree of 85 to 95% is most preferable.

The modified polyvinyl alcohol is preferably a reactive organism between the compound represented by the following general formula (2) and polyvinyl alcohol.
General formula (2)

In the general formula (2), R ¹¹ is an unsubstituted alkyl group, an acrylolyl-substituted alkyl group, a methacryloyl-substituted alkyl group or an epoxy group-substituted alkyl group, W is a halogen atom, an alkyl group or an alkoxy group, and X Is an atomic group necessary to form an active ester, acid anhydride or acid halide, p is 0 or 1, and n is an integer of 0-4.
The modified polyvinyl alcohol is more preferably a reaction product of a compound represented by the following general formula (3) and polyvinyl alcohol.
General formula (3)

In the general formula (3), X ¹ is a group of atoms necessary to form an active ester, acid anhydride or acid halide, and, m is an integer of 2 to 24.
The polyvinyl alcohol to be reacted with the compounds represented by the general formula (2) and the general formula (3) may be modified polyvinyl alcohol (copolymerization modification, chain transfer modification, block polymerization modification). The method for synthesizing polyvinyl alcohol, measuring the visible absorption spectrum, and determining the introduction rate of the modifying group are described in detail in JP-A-8-33891.
Examples of cross-linking agents for polymers (preferably water-soluble polymers, more preferably polyvinyl alcohol or modified polyvinyl alcohol) include aldehydes (eg formaldehyde, glyoxal, glutaraldehyde), N-methylol compounds (eg dimethylol urea, methylol dimethyl). Hydantoin), dioxane derivatives (eg 2,3-dihydroxydioxane), compounds acting by activating carboxyl groups (eg carbenium, 2-naphthalenesulfonate, 1,1-bispyrrolidino-1-chloropyridinium, 1 -Morpholinocarbonyl-3- (sulfonatoaminomethyl)), active vinyl compounds (eg 1,3,5-triacroyl-hexahydro-s-triazine, bis (vinylsulfone) methane, N '-Methylenebis- [β- (vinylsulfonyl) propionamide]), active halogen compounds (eg 2,4-dichloro-6-hydroxy-S-triazine), isoxazoles and dialdehyde starch. Two or more kinds of crosslinking agents may be used in combination. Aldehydes having high reaction activity, particularly glutaraldehyde are preferred.

0.1-20 mass% is preferable with respect to a polymer, and, as for the addition amount of a crosslinking agent, 0.5-15 mass% is more preferable. The amount of the unreacted crosslinking agent remaining in the alignment film is preferably 1.0% by mass or less, and more preferably 0.5% by mass or less. If the crosslinking agent remains in the alignment film in an amount exceeding 1.0% by mass, sufficient durability cannot be obtained. When such an alignment film is used in a liquid crystal display device, reticulation may occur when used for a long time or when left in a high temperature and high humidity atmosphere for a long time.
The alignment film can be basically formed by applying the above polymer containing a crosslinking agent, which is an alignment film forming material, on a transparent support, followed by drying by heating (crosslinking) and rubbing treatment. As described above, the crosslinking reaction may be carried out at any time after coating on the transparent support. When a water-soluble polymer such as polyvinyl alcohol is used as the alignment film forming material, the coating solution is preferably a mixed solvent of an organic solvent (for example, methanol) having a defoaming action and water. The ratio of water: methanol is preferably 0: 100 to 99: 1, and more preferably 0: 100 to 91: 9. Thereby, generation | occurrence | production of a bubble is suppressed and the defect of the surface of an alignment film and also an optically anisotropic layer reduces remarkably.

  The alignment film is preferably applied by spin coating, dip coating, curtain coating, extrusion coating, rod coating, or roll coating. A rod coating method is particularly preferable. The film thickness after drying is 0. 1-10 micrometers is preferable. Heating and drying can be performed at 20 ° C to 110 ° C. In order to form sufficient cross-linking, 60 ° C to 100 ° C is preferable, and 80 ° C to 100 ° C is more preferable. The drying time can be 1 minute to 36 hours, preferably 1 minute to 30 minutes. The pH is also preferably set to an optimum value for the crosslinking agent to be used. When glutaraldehyde is used, pH 4.5 to 5.5 is preferable, and pH 5 is more preferable.

The alignment film is provided on the transparent support. The alignment film can be obtained by rubbing the surface after crosslinking the polymer layer as described above. The alignment film is provided in order to define the alignment direction of the discotic compound provided thereon.
For the rubbing treatment, a treatment method widely adopted as a liquid crystal alignment treatment process of LCD can be applied. That is, a method of obtaining alignment by rubbing the surface of the alignment film in a certain direction using paper, gauze, felt, rubber, nylon, polyester fiber, or the like can be used. Generally, it is carried out by rubbing several times using a cloth or the like in which fibers having a uniform length and thickness are planted on average.

[Optically anisotropic layer]
The optical anisotropic layer of the optical compensation sheet is formed on the alignment film. The optically anisotropic layer is preferably a layer composed of a compound having a discotic structural unit, and is formed by polymerization (curing) of a low molecular weight liquid crystalline discotic compound (monomer) layer or a polymerizable liquid crystalline discotic compound. More preferably, it is a layer of the resulting polymer. Examples of discotic compounds include C.I. Destrade et al., Mol. Cryst. 71, 111 (1 981), benzene derivatives, C.I. Destrade et al., Research Report, Mol. Cryst. 122, 141 (1985), Physicslett, A, 78, 82 (1990); Kohne et al., Angew. Chem. 96, page 70 (1984) and the cyclohexane derivatives described in J. Am. M.M. Lehn et al. Chem. Commun. , 1 794 (1985); Zhang et al., J. Am. Chem. Soc. 116, 2655 (1994), azacrown type and phenylacetylene type macrocycles are included.

  A discotic compound generally has a structure in which these are used as a mother nucleus at the center of a molecule, and a linear alkyl group, an alkoxy group, or a substituted benzoyloxy group is radially substituted as the linear chain. The discotic compound includes a discotic liquid crystalline compound exhibiting liquid crystallinity. The optically anisotropic layer formed from a discotic compound has a high molecular weight and loses liquid crystallinity by reacting with a low-molecular discotic liquid crystalline compound having a group that reacts with heat or light to cause polymerization or crosslinking. Is also included. Discotic compounds are described in JP-A-8-50206.

  The optically anisotropic layer is a layer having a negative birefringence made of a compound having a disk-like structural unit, and the surface of the disk-like structural unit is inclined with respect to the transparent support surface, and the disk-like structural unit has The angle formed between the surface and the transparent support surface is preferably changed in the depth direction of the optically anisotropic layer.

  In general, the angle (tilt angle) of the surface of the disk-like structural unit increases or decreases in the depth direction of the optical anisotropic layer and as the distance from the bottom surface of the alignment film of the optical anisotropic layer increases. The tilt angle preferably increases with increasing distance. In addition, examples of changes in the inclination angle include continuous increase, continuous decrease, intermittent increase, intermittent decrease, changes including continuous increase and continuous decrease, and intermittent changes including increase and decrease. it can. The intermittent change includes a region where the inclination angle does not change in the middle of the thickness direction. Even if the inclination angle includes a region that does not change, it is preferable that the inclination angle increases or decreases as a whole. Further, the inclination angle is preferably increased as a whole, and particularly preferably continuously changed.

  The optically anisotropic layer is generally formed by applying a solution obtained by dissolving a discotic compound and other compounds in a solvent onto an alignment film, drying it, and then heating it to a discotic nematic phase formation temperature, and then aligning it (discotic nematic). Obtained by maintaining the phase) and cooling. Alternatively, the optically anisotropic layer is formed by applying a solution obtained by dissolving a discotic compound and another compound (for example, a polymerizable monomer, a photopolymerization initiator) in a solvent onto the alignment film, drying, and then discotic nematic It is obtained by heating to the phase formation temperature, followed by polymerization (by irradiation with UV light, etc.) and further cooling. The discotic nematic liquid crystal phase-solid phase transition temperature of the discotic liquid crystalline compound used in the present invention is preferably 70 to 300 ° C, more preferably 70 to 170 ° C.

The inclination angle of the disk-shaped unit on the support side can be generally adjusted by selecting a disk-shaped compound or an alignment film material or by selecting a rubbing treatment method. Further, the inclination angle of the disk-like unit on the surface side (air side) is generally selected from a discotic compound or other compounds (for example, a plasticizer, a surfactant, a polymerizable monomer and a polymer) used together with the discotic compound. Can be adjusted. Furthermore, the degree of change in the tilt angle can also be adjusted by the above selection.
Any plasticizer, surfactant and polymerizable monomer may be used as long as they have moderate compatibility with the discotic compound and can change the tilt angle of the liquid crystalline discotic compound or do not inhibit the alignment. Compounds can also be used. Among these, a polymerizable monomer (for example, a compound having a vinyl group, a vinyloxy group, an acryloyl group, and a methacryloyl group) is preferable. The above compound is used in an amount of preferably 1 to 50% by mass, more preferably 5 to 30% by mass with respect to the discotic compound.

  As the polymer, any polymer can be used as long as it is compatible with the discotic compound and can change the tilt angle of the liquid crystalline discotic compound. A cellulose ester can be mentioned as an example of a polymer. Preferable examples of the cellulose ester include cellulose acetate, cellulose acetate propionate, hydroxypropyl cellulose and cellulose acetate butyrate. The polymer is preferably 0.1 to 10% by mass, more preferably 0.1 to 8% by mass, and still more preferably 0.1% by mass with respect to the discotic compound so as not to inhibit the alignment of the discotic liquid crystalline compound. Used in an amount of ˜5% by weight.

[Polarizer]
The polarizing plate has a layer structure in which an optical compensation sheet, a polarizing film, and a transparent protective film in which an alignment film and an optical anisotropic layer in which the alignment of liquid crystal molecules is fixed are provided on a polymer film are laminated in this order. A normal cellulose acetate film may be used for the transparent protective film. Examples of the polarizing film include an iodine polarizing film and a dye polarizing film using a dichroic dye and a polyene polarizing film. The iodine polarizing film and the dye polarizing film are generally produced using a polyvinyl alcohol film. The relationship between the slow axis of the polymer film and the transmission axis of the polarizing film varies depending on the type of liquid crystal display device to be applied. In the TN, MVA, and OCB modes, they are arranged so as to be substantially parallel. In the case of a reflective liquid crystal display device, it is preferably arranged so as to be substantially 45 degrees.

[Liquid Crystal Display]
The optical compensation sheet or the polarizing plate is advantageously used for a liquid crystal display device. A TN, VA, MVA, and OCB mode liquid crystal display device includes a liquid crystal cell and two polarizing plates disposed on both sides thereof. The liquid crystal cell carries a liquid crystal between two electrode substrates. One optical compensation sheet is disposed between the liquid crystal cell and one polarizing plate, or two optical compensation sheets are disposed between the liquid crystal cell and both polarizing plates. In the case of the OCB mode liquid crystal display device, the optical compensation sheet may have an optically anisotropic layer containing a discotic compound or a rod-shaped liquid crystal compound on a polymer film. The optically anisotropic layer is formed by aligning a discotic compound (or rod-shaped liquid crystal compound) and fixing the alignment state. A discotic compound generally has a large birefringence. The discotic compound has various orientation forms. Therefore, by using a discotic compound, an optical compensation sheet having optical properties that cannot be obtained by a conventional stretched birefringent film can be produced. Optical compensation sheets using discotic compounds are described in JP-A-6-214116, US Pat. Nos. 5,583,679, 5,646,703, and West German Patent 3,911,620A1.

  In the polarizing plate, the polymer film can be used as a transparent protective film disposed between the liquid crystal cell and the polarizing film. Only the transparent protective film (between the liquid crystal cell and the polarizing film) of one polarizing plate uses the above polymer film, or two transparent protective films (between the liquid crystal cell and the polarizing film) of both polarizing plates The above polymer film is used for the membrane. The liquid crystal cell is preferably OCB mode or TN mode. The OCB mode liquid crystal cell is a liquid crystal display device using a bend alignment mode liquid crystal cell in which rod-like liquid crystalline molecules are aligned in a substantially opposite direction (symmetrically) between the upper part and the lower part of the liquid crystal cell. This is disclosed in the specifications of Japanese Patent Nos. 4,583,825 and 5,410,422. Since the rod-like liquid crystal molecules are symmetrically aligned at the upper and lower portions of the liquid crystal cell, the bend alignment mode liquid crystal cell has a self-optical compensation function. Therefore, this liquid crystal mode is also referred to as an OCB (Optically Compensatory Bend) liquid crystal mode. The bend alignment mode liquid crystal display device has an advantage of a high response speed. In the TN mode liquid crystal cell, rod-like liquid crystal molecules are substantially horizontally aligned when no voltage is applied, and are twisted and aligned at 60 to 120 °. The TN mode liquid crystal cell is most frequently used as a color TFT liquid crystal display device, and is described in many documents.

  The present invention will be described more specifically with reference to the following examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

Example 1
(1-1) Synthesis of cellulose ester-A Cellulose ester-A was synthesized using cellulose collected from cotton as a raw material.
Cellulose ester-A has an acetyl group substitution degree of 1.00, a butyryl group substitution degree of 1.70, a total acyl group substitution degree of 2.70, a viscosity average polymerization degree of 220, and a water content of 0.2. It was a powder having a viscosity of 190 mPa · s, an average particle diameter of 1.5 mm, and a standard deviation of 0.5 mm. Further, the residual acetic acid amount is 0.1% by mass or less, the residual butanoic acid amount is 0.1% by mass or less, the Ca content is 80 ppm, the Mg content is 22 ppm, the Fe content is 0.5 ppm, It contained 105 ppm of sulfur as a sulfate group. The substitution degree of the 6-position acetyl group was 0.33, and the substitution degree of the 6-position butyryl group was 0.57, which was 33% of the total acyl groups. The methanol extraction amount was 5% by mass or less, the weight average molecular weight / number average molecular weight ratio (measured by GPC) was 2.8, and Tg (glass transition temperature; measured by DSC) was 128 ° C. Cellulose ester-A was made into a 20% by mass solution using a methylene chloride / methanol (mass ratio 9/1) solution and cast onto a glass plate to give a film having a thickness of 100 μm. The obtained cellulose ester-A film had a yellow index of 1.6, a haze of 0.07, and a transparency of 93.9%.

(1-2) Preparation of cellulose ester solution (dope) The following was used as a cellulose ester solution formulation.
-Cellulose ester-A 100 mass parts-Methylene chloride 267 mass parts-Methanol 48.5 mass parts-1-butanol 11.8 mass parts-Plasticizer A (triphenyl phosphate) 1.7 mass parts-Plasticizer B (biphenyl) Diphenyl phosphate) 1.3 parts by mass, 3 parts by mass of the following optical anisotropy control agent

UV agent a (2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine) 0.5 parts by mass UV Agent b (2 (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -5-chlorobenzotriazole) 0.2 parts by mass UV agent c: 2 (2′-hydroxy-3 ′, 5′-di-tert-amylphenyl) -5-chlorobenzotriazole) 0.1 part by mass / citric acid monoethyl ester / diethyl ester mixture (mixing ratio 1/1 mass ratio) 0.2% by mass
Fine particles (silicon dioxide, primary particle diameter 15 nm, Mohs hardness about 7) 0.05 parts by mass

The cellulose ester solution formulation solvent is mixed in a 500 L stainless steel dissolution tank having a stirring blade, and the cellulose ester-A powder (flakes) is gradually added while stirring and dispersing so that the total weight becomes 250 kg. Prepared. Here, all the solvents used had a water content of 0.5% by mass or less. First, the powder of cellulose ester-A is a dissolver type in which powder is put into a dispersion tank and stirred at a peripheral shear speed of 5 m / sec (shear stress 5 × 10 ⁴ kgf / m / sec ² ) at first. The mixture was dispersed for 30 minutes under the condition of having an eccentric stirring shaft and an anchor blade on the central shaft and stirring at a peripheral speed of 1 m / sec (shear stress 1 × 10 ⁴ kgf / m / sec ² ). The dispersion start temperature was 25 ° C. and the final temperature reached 34 ° C. After completion of the dispersion, high-speed stirring was stopped, the peripheral speed of the anchor blade was 0.5 m / sec, and stirring was further performed for 100 minutes to swell the cellulose ester-A flakes. Until the end of swelling, the inside of the tank was pressurized to 0.12 MPa using nitrogen gas. At this time, the oxygen concentration in the tank was set to less than 2% by volume, and a state with no problem in explosion prevention was maintained. Further, it was confirmed that the water content in the dope was 0.3 mass% or less.

(1-3) Dissolution / Filtering The swollen solution was heated from the tank to 50 ° C. with a jacketed pipe, and further heated to 90 ° C. under a pressure of 2 MPa to completely dissolve. The heating time was 15 minutes. Next, the temperature was lowered to 36 ° C., and coarse filtration was performed with cellulose filter paper having a pore diameter of 40 μm. Further, a dope was obtained by passing a filter medium having a pore diameter of 8 μm. At this time, the primary pressure of filtration was 1.5 MPa, and the secondary pressure was 1.2 MPa. The filters, housings, and pipes that were exposed to high temperatures were made of Hastelloy alloy and had excellent corrosion resistance, and those having a jacket for circulating a heat medium for heat insulation and heating were used.

(1-4) Concentration and Filtration The pre-concentration dope thus obtained was flushed at 80 ° C. in a normal pressure tank, and the evaporated solvent was recovered and separated by a condenser. The solid concentration of the dope after flashing was 28.8% by mass. The condensed solvent was sent to the recovery process to be reused as a solvent in the preparation process. The center axis of the flash tank has an anchor wing, which was used for defoaming by stirring at a peripheral speed of 0.5 m / sec. The temperature of the dope in the tank was 25 ° C., and the average residence time in the tank was 50 minutes. The shear viscosity measured at 25 ° C. after collecting this dope was 130 (Pa · s) at a shear rate of 10 (sec ⁻¹ ).

  Next, bubbles were removed by irradiating the dope with weak ultrasonic waves. Thereafter, under a pressure of 1.5 MPa, a sintered fiber metal filter having a pore size of 10 μm was passed, and then a sintered fiber filter having a pore size of 10 μm was passed. Respective primary pressures were 1.5 MPa and 1.2 MPa, and secondary pressures were 1.0 MPa and 0.8 MPa. The dope temperature after filtration was adjusted to 36 ° C. and stored in a 500 L stainless steel stock tank. The stock tank has an anchor blade on its central axis, and is constantly stirred at a peripheral speed of 0.3 m / sec. In addition, when the dope was prepared from the dope before concentration, no problem such as corrosion occurred at all in the wetted part of the dope.

(1-5) Casting Subsequently, the dope in the stock tank was fed by a feedback control using an inverter motor so that the primary pressure of the high-precision gear pump was 0.8 MPa with a gear pump for primary pressure increase. The high-precision gear pump had a volume efficiency of 99.2% and a discharge rate variation rate of 0.5% or less. The discharge pressure was 1.5 MPa. The casting die was equipped with a feed block adjusted for co-casting with a width of 1.8 m, and a device that was capable of forming a three-layer film by laminating on both sides in addition to the mainstream. . In the following description, a layer formed from the mainstream is referred to as an intermediate layer, a support surface side layer is referred to as a support surface, and an opposite surface is referred to as an air surface. In addition, the dope liquid supply flow path used three flow paths for the intermediate layer, the support surface, and the air surface. The support side dope and the air side dope for the outermost layer are prepared by using a dope prepared in (1-2) as a solvent comprising 267 parts by mass of methylene chloride / 48.5 parts by mass of methanol / 11.8 parts by mass of 1-butanol. A static mixer and a slew mixer were connected and diluted in-line installed in the pipe. Dilution was performed such that the original dope was at a concentration of 97% for the support-side dope and the air-side dope was at a concentration of 95% with respect to the original dope.

  The film thickness of the finished cellulose ester film sample is 4 μm, 92 μm, and 4 μm on the air surface, intermediate layer, and support surface, respectively, and the casting width is 1500 mm so that the thickness is 100 μm. Casting was performed by adjusting the dope flow rate. In order to adjust the temperature of each dope to 36 ° C., a jacket was provided on the casting die, and the inlet temperature of the heat transfer medium supplied into the jacket was set to 36 ° C.

  The die, feed block, and piping were all kept at 36 ° C. during the work process. The die was a coat hanger type die, with thickness adjusting bolts provided at a pitch of 20 mm, and having an automatic thickness adjusting mechanism using a heat bolt. This heat bolt can also set a profile according to the liquid feed amount of the high precision gear pump by a preset program, and feedback control can also be performed by an adjustment program based on the profile of the infrared thickness gauge installed in the film forming process It has performance. The thickness difference between two arbitrary points 50 mm apart in the film excluding the casting edge portion 20 mm was within 1 μm, and the largest difference in the width direction thickness was adjusted to 3 μm / m or less. The average thickness accuracy of each layer was controlled to ± 2% or less for both outer layers and ± 1% or less for the mainstream, and the overall thickness was adjusted to ± 1.5% or less.

  In addition, a chamber for decompressing was installed on the primary side of the die. The degree of decompression of the decompression chamber is such that a pressure difference of 1 Pa to 5000 Pa can be applied before and after the casting bead, and can be adjusted according to the casting speed. At that time, the pressure difference was set such that the bead length was 2 mm to 50 mm. Further, the chamber temperature was provided with a mechanism that can be set higher than the condensation temperature of the gas around the casting portion. In addition, a beat was provided at the front and a labyrinth at the rear. Openings were provided at both ends. Furthermore, from there, the one to which the edge suction device was attached in order to adjust the disturbance of the flow at both edges of the bead was used.

(1-6) Casting die Here, the material of the die is precipitation hardening stainless steel, the material has a thermal expansion coefficient of 2 × 10 ⁻⁵ (° C. ⁻¹ ) or less, and is forcedly corroded in an aqueous electrolyte solution. In the test, a material having approximately the same corrosion resistance as SUS316 was used. In addition, a material having corrosion resistance that does not cause pitting (opening) at the gas-liquid interface even when immersed in a mixed solution of dichloromethane, methanol, and water for 3 months was used. Furthermore, the surface of the cellulose ester solution was kept constant by grinding the one aged or longer after casting. The finishing accuracy of the wetted surfaces of the casting die and the feed block was 1 μm or less in terms of surface roughness, the straightness was 1 μm / m or less in any direction, and the slit clearance was adjusted to 1.5 mm by automatic adjustment. About the corner | angular part of the liquid-contact part of die-tip tip, it processed so that R might be 50 micrometers or less over the slit full width. The shear rate inside the die was in the range of 1 (1 / sec) to 5000 (1 / sec).

  Further, a casting die provided with a cured film was used at the lip tip. As a means for providing the hard film, a tungsten carbide (WC) coating formed by a thermal spraying method was used. Furthermore, in order to prevent the dope flowing out from the slit end of the die from locally drying and solidifying, a mixed solvent (sample 070), which is a solvent for solubilizing the dope, is applied to the gas-liquid interface between the bead end and the slit. Feeded at 0.5 ml / min on one side. The pulsation rate of the pump supplying this liquid was 5% or less. In addition, the pressure on the back surface of the bead was reduced by 150 Pa by the decompression chamber. A jacket was attached to keep the temperature of the vacuum chamber constant. A heat transfer medium adjusted to 35 ° C. was supplied into the jacket. The edge suction air volume that can be adjusted in the range of 1 L / min to 100 L / min was used, and in this example, it was appropriately adjusted in the range of 30 L / min to 40 L / min.

(1-7) Metal support A stainless steel endless band having a width of 2.1 m and a length of 70 m was used as a support. The band was 1.5 mm thick and polished so that the surface roughness was 0.05 μm or less. The material was made of SUS316 and had sufficient corrosion resistance and strength. The thickness unevenness of the entire band was 0.5% or less. The band is a type driven by two drums, and the tension of the band at that time is adjusted to 1.5 × 10 ⁴ kg / m, and the relative speed difference between the band and the drum is 0.01 m / min or less. It was a thing. The band drive speed fluctuation was 0.5% or less. Further, both ends of the band were detected and controlled so that the meandering in the width direction of one rotation was limited to 1.5 mm or less. Further, the positional fluctuation in the vertical direction accompanying the drum rotation on the surface of the support just below the casting die was set to 200 μm or less. The support was installed in a casing having wind pressure vibration suppression means. Three layers of dope were co-cast from this die on this support.

As the casting drum, a drum having equipment for circulating a heat transfer medium (refrigerant) therein was used so as to cool the support. Moreover, since the other drum supplies heat for drying, the heat transfer medium can pass water. The temperature of each heat transfer medium was 5 ° C. (casting die side) and 40 ° C. The surface temperature at the center of the support just before casting was 15 ° C. The temperature difference between both ends was 6 ° C. or less. The drum can be directly used as a casting support. In this case, the drum was rotated so that the rotation unevenness had an accuracy of 0.2 mm or less. Also in the drum, the average roughness of the surface is 0.01 μm or less, and it has sufficient hardness and durability by the chrome plating treatment. There should be no surface defects in either the drum or the band, there are no pinholes of 30 μm or more, 1 pinhole of 10 μm to 30 μm / m ² or less, and ² pinholes of 10 μm or less A support that was less than / m ² was used.

(1-8) Casting drying The temperature of the casting chamber provided with the casting die and the support was kept at 35 ° C. The dope cast on the band was first dried by sending parallel-flow drying air. The overall heat transfer coefficient from the drying air to the dope during drying was 24 kcal / m ² · hr · ° C. The temperature of the drying air was 135 ° C on the upstream side of the upper part of the band, and 140 ° C on the downstream side. The lower part of the band was set to 65 ° C. The saturation temperature of each gas was around -8 ° C. The oxygen concentration in the dry atmosphere on the support was kept at 5% by volume. The air was replaced with nitrogen gas in order to keep the oxygen concentration at 5% by volume. Moreover, in order to condense and collect the solvent in the casting chamber, a condenser (condenser) was provided, and the outlet temperature was set to −10 ° C.

  For 5 seconds after casting, the static pressure fluctuation in the immediate vicinity of the casting die was suppressed to ± 1 Pa or less so that the dry wind did not directly hit the dope with a wind shield. When the solvent ratio in the dope reached 50% by mass on a dry basis, the film was peeled off from the casting support. The peeling tension at this time was 10 kgf / m, and the peeling speed (peeling roll draw) with respect to the support speed was set so as to be properly peeled in the range of 100.1% to 110%. The surface temperature of the peeled film was 15 ° C. The drying rate on the support was an average of 60% by weight dry weight reference solvent / min. The solvent gas generated upon drying was led to a condenser, liquefied at −10 ° C., recovered, and reused as a charging solvent. The drying air from which the solvent was removed was heated again and reused as drying air. At that time, the water content in the solvent was adjusted to 0.5% or less and reused.

  The peeled film was conveyed by the transfer part provided with many rollers. The transition part was equipped with three rollers, and the temperature of the transition part was kept at 40 ° C. During conveyance with the roller of the crossing part, tension of 16N to 160N was applied to the film.

(1-9) Tenter Transport / Drying The peeled film was transported in the drying zone of the tenter while being fixed at both ends with a tenter having a clip, and dried with drying air. The clip was cooled by supplying a heat transfer medium at 20 ° C. The tenter was driven by a chain, and the speed fluctuation of the sprocket was 0.5% or less. Further, the inside of the tenter was divided into three zones, and the drying air temperature of each zone was set to 90 ° C., 100 ° C., and 110 ° C. from the upstream side. The gas composition of the drying air was set to a saturated gas concentration of −10 ° C. The average drying rate in the tenter was 120% by mass (dry weight reference solvent) / min. At the outlet of the tenter, the amount of residual solvent in the film was adjusted to 10% by mass or less, and in this experiment, the conditions of the drying zone were adjusted to 7% by mass. Stretching was also performed in the width direction while transporting in the tenter.

  The amount of widening when the width when conveyed to the tenter was 100% was 103%. The stretching ratio (tenter driven draw) from the peeling roller to the tenter inlet was 102%. As for the stretching ratio in the tenter, the difference in the substantial stretching ratio at a portion 10 mm or more away from the tenter biting portion was 10% or less, and the difference in the stretching ratio at any two points 20 mm apart was 5% or less. The ratio of the length of the base end fixed by the tenter was 90%. Further, the tenter clip was transported while being cooled so as not to exceed 50 ° C. The solvent evaporated in the tenter part was condensed and liquefied at a temperature of −10 ° C. and recovered. A condenser (condenser) was provided for condensation recovery, and the outlet temperature was set to -8 ° C. The water content contained in the solvent was adjusted to 0.5% by mass or less and reused.

Then, the ears were cut at both ends within 30 seconds from the tenter exit. Ears 50 mm on both sides were cut with an NT-type cutter, and the cut ears were blown by a cutter blower to a crusher and crushed into chips of about 80 mm ² on average. This chip was again usable as a raw material in the preparation process together with cellulose ester flakes as a raw material for preparation. The oxygen concentration in the dry atmosphere of the tenter part was kept at 5% by volume. The air was replaced with nitrogen gas in order to keep the oxygen concentration at 5% by volume. The film was preheated in a predrying zone supplied with 100 ° C. drying air before being dried at a high temperature in a roller conveyance zone described later.

(1-10) Post-drying The cellulose ester film after the end cutting obtained by the method described above was dried at high temperature in the roller transport zone. The roller conveyance zone was divided into four sections, and dry air at 100 ° C., 105 ° C., 105 ° C., and 110 ° C. was supplied from the upstream side. At this time, the roller conveyance tension of the film was 100 N / width, and the film was dried until the residual solvent amount finally reached 0.3% by mass (about 20 minutes). The wrap angle of this roller was 90 degrees and 180 degrees. The material of this roller was made of aluminum or carbon steel, and hard chrome plating was applied to the surface. As the surface shape of the roller, a flat one and a mat formed by blasting were used. All the shakes due to the rotation of the roller were 50 μm or less. The roller deflection at a tension of 100 N / width was selected to be 0.5 mm or less.

  A forced charge removal device (charge removal bar) was installed during the process so that the film voltage during conveyance was always in the range of -3 kV to 3 kV. Moreover, in the winding part, not only the static elimination bar but also ion wind static elimination was installed so that the charge would be -1.5 kV to 1.5 kV. The solvent gas contained in the drying air was adsorbed and recovered using an adsorbent. The adsorbent was activated carbon, and desorption was performed using dry nitrogen. The recovered solvent was adjusted to a water content of 0.3% by mass or less and reused as a charged solvent. The drying air contains plasticizers, UV absorbers, and other high-boiling substances in addition to solvent gas, so these were removed by a cooler and pre-adsorber that were cooled and removed, and were recycled and used. And adsorption / desorption conditions were set so that VOC in outdoor exhaust gas would be 10 ppm or less finally. Further, the amount of solvent recovered by the condensing method of all evaporated solvents was 90% by mass, and most of the rest was recovered by adsorption recovery.

  The dried film was conveyed to the 1st humidity control chamber. Dry air at 105 ° C. was supplied to the transition portion between the roller conveyance zone and the first humidity control chamber. Air having a temperature of 50 ° C. and a dew point of 20 ° C. was supplied to the first humidity control chamber. Further, the film was conveyed to a second humidity control chamber that suppresses the curling of the film. In the second humidity control chamber, air of 90 ° C. and humidity 70% was directly applied to the film.

(1-11) Post-treatment, winding The dried cellulose ester film was cooled to 30 ° C. or lower, and both ends were cut off, and further, both ends of the film were knurled. The knurling was imparted by embossing from one side, the knurling width was 10 mm, and the pressing pressure was set so that the maximum height was 12 μm higher than the average thickness on average.

  And the obtained film was conveyed to the winding chamber. The winding chamber was kept at a room temperature of 28 ° C. and a humidity of 70%. The width of the cellulose ester film sample-1 (thickness: 100 μm) thus obtained was 1475 mm. The tension pattern was 360 N / width at the start of winding and 250 N / width at the end of winding. The total winding length was 300 m. Moreover, the press roll was set to the winding roll, and the pressure was set to 50 N / width. The temperature of the film at the time of winding was 25 ° C., the water content was 1.4% by mass, and the residual solvent amount was 0.3% by mass or less. Moreover, there was no winding looseness, no wrinkles, and no winding slip occurred. The roll appearance was also good.

  The cellulose ester film sample-1 of the present invention contained 0.15% by mass of residual acetic acid, 0.03% by mass of butanoic acid, 66 ppm of Ca, and 8.3 ppm of Mg. The thickness of the cellulose ester film of the present invention was confirmed to be 100 μm ± 1.5 μm over the entire region. At this time, for each of the top, middle part and last in the length direction, further evaluation of both end parts and the center part in the width direction was performed, and it was confirmed that the error was substantially 0.2% or less. Further, the longitudinal and transverse average heat shrinkage (80 ° C./relative humidity 90% / 48 hours) of the film was within −0.3%.

  The cellulose ester film sample-1 of the present invention has a haze of 0.2%, a transparency (transparency) of 93.4%, a slope width of 19.6 nm, a limit wavelength of 392.6 nm, and an absorption edge of 374. Absorption at 3 nm and 380 nm is 1.9%, Re is 1.2 nm, Rth is 80 nm, axial deviation (molecular orientation axis) is 0.3 °, elastic modulus is 2.51 GPa in the longitudinal direction, width direction 2.46 GPa, tensile strength is 128 MPa in the longitudinal direction, 115 MPa in the width direction, elongation is 60% in the longitudinal direction, 56% in the width direction, the kishimi value (static friction coefficient) is 0.75, and the kishimi value (dynamic friction) The coefficient) was 0.51, the curl value was -0.3 at 25% relative humidity, and 1.1 when wet. The moisture content is 1.5% by mass (25 ° C./60% relative humidity), the residual solvent amount is 0.15% by mass, and the heat shrinkage is −0.19% in the longitudinal direction, which is the width direction. Was −0.18%. The foreign matter had a lint of less than 5 pieces / m. Further, the bright spots were 0.02 mm to 0.05 mm less than 10/3 m, 0.05 to 0.1 mm less than 4/3 m, and 0.1 mm or more. Through the above steps, a cellulose ester film sample-1 was formed.

(1-12) Electron beam treatment and alkali saponification treatment Next, the cellulose ester film sample-1 obtained above was subjected to a surface treatment according to Table 1.
(1-12-1) Electron Beam Method The electron beam treatment was performed under the irradiation conditions shown in Table 1. Here, an apparatus having an irradiation window with a width of 1.5 m was used for the electron beam treatment. This apparatus has a conveyance inlet and an outlet for conveying a film. The irradiation process is provided with a gas introduction part and a gas discharge part, and the irradiation part is designed to be isolated from the atmosphere by a box. About the sample substituted by other inert gas, the degree was controlled with the oxygen concentration meter, and electron beam irradiation was performed when oxygen became 0.2 volume% or less in air | atmosphere.

(1-12-2) Alkali Saponification Method Next, cellulose ester film samples 1-1 to 1-19 were prepared by electron beam treatment in (1-12-1) and subjected to alkali saponification according to the following alkali saponification method. .
(A) Preparation of alkali saponification solution (S-1)
The alkali saponification solution (1.0 mol / L) and alkali dilution liquid of the following prescription were prepared.

Alkali saponification solution (S-1) Formulation · KOH 560 parts by mass _{· C 14 H 29 -O- (CH} 2 CH 2 O) -H 100 parts by mass antifoaming agent Surfynol DF110D (Nissin Chemical Industry Co., (Made) 2 mass parts, water 9338 mass parts

(Preparation of saponification film)
A cellulose ester film sample treated with an electron beam according to Table 1 was passed through a dielectric heating roll heated to 60 ° C. and heated to 40 ° C., and then an alkali saponification aqueous solution (S-1) kept at 40 ° C. was added to a rod coater. 20 ml / m ^{2 was} applied. After retaining for 7 seconds under a steam far-infrared heater manufactured by Noritake Co., Ltd. heated to 110 ° C (the surface temperature of the film was 40-50 ° C), a rod coater was also used. Then, 20 ml / m ^{2 of} pure water was applied to wash off the alkaline solution. At this time, the film temperature was maintained at 40 to 45 ° C., and the KOH concentration of the coating film after application of pure water was 0.5 mol / L. Next, washing with a fountain coater and draining with an air knife were repeated three times to wash away the alkali, and then, the saponification film was produced by staying in a drying zone at 70 ° C. for 15 seconds and drying.

  Here, the surface tension of the alkaline saponification aqueous solution S-1 was 64 mN / m, the viscosity of the liquid was 1.8 mPa · s, the density of the liquid was 1.07, and the electric conductivity was 180 mS / cm. The carbonate ion concentration in the alkaline saponification aqueous solution was 1090 mg / L, the total concentration of polyvalent metal ions including calcium and magnesium was 190 mg / L, and the chloride ion concentration was 133 mg / L.

(Evaluation method of alkali saponification film)
About the cellulose-ester film which carried out the electron beam process and the alkali saponification process, the haze was measured using the Nippon Denshoku Co., Ltd. NDH-300A type | mold optical testing machine. The results are shown in Table 1.

(Formation of alignment film)
The following alignment film coating solution was applied to the alkali saponified surface of the above-mentioned electron beam-treated and alkali-saponified film with a rod coater at 30 ml / m ² , heated at 60 ° C. for 60 seconds, and further heated at 90 ° C. The film was dried for 150 seconds and then rubbed using a velvet cloth rubbing roll placed perpendicular to the conveying direction to form an alignment film.

(Orientation film coating solution composition)
・ Modified polyvinyl alcohol 100 mass parts ・ Water 1800 mass parts ・ Methanol 600 mass parts ・ Glutaraldehyde 2.5 mass parts

(Formation of optically anisotropic layer)
On the alignment film formed as described above, a discotic compound solution having the following formulation was applied with a # 4 wire bar. Subsequently, heating was performed for 2 minutes in a hot air zone of 130 ° C. to be connected to align the discotic compound. Finally, under an atmosphere of 80 ° C, with a film surface temperature of about 100 ° C, a 120 W / cm high-pressure mercury lamp is used for UV irradiation for 0.4 seconds to polymerize the discotic compound to form an optically anisotropic layer. Thus, an optical compensation sheet was produced.

(Discotic compound solution composition)
-2735 parts by mass of the following discotic compound-80 parts by mass of ethylene oxide modified trimethylolpropane triacrylate (V # 360, manufactured by Osaka Organic Chemical Co., Ltd.)-Multifunctional acrylate monomer (NK ester A-TMMT, manufactured by Shin-Nakamura Chemical ) 190 parts by mass cellulose acetate butyrate (CAB551-0.2, manufactured by Eastman Chemical Co.) 60 parts by mass cellulose acetate butyrate (CAB531-1 manufactured by Eastman Chemical Co.) 15 parts by mass photoinitiator ( Irgacure 907, manufactured by Ciba Geigy Co., Ltd.) 90 parts by mass, sensitizer (Kayacure DETX, manufactured by Nippon Kayaku Co., Ltd.) 30 parts by mass, 6800 parts by mass of methyl ethyl ketone

  Here, as for the representative sample 1-13 which implemented the electron beam process of this invention, the retardation value (Re) of the optically anisotropic layer measured at the wavelength of 633 nm of the optical compensation film was 39 nm. The angle (inclination angle) between the disk surface and the first transparent support (the support KF-1) was 36 ° on average.

(Evaluation method of optical compensation sheet)
(Foreign matter defect)
The obtained optical compensation sheet was sandwiched between two polarizing plates arranged in crossed Nichols, and foreign matter defects in which transmitted light became uneven due to foreign matter were visually observed. The number of bright spots on the 17-inch screen was counted. Table 1 shows the evaluation results.

(Adhesion)
Each optical compensation sheet was cut into 30 cm × 25 cm and left for 1 day under conditions of a temperature of 25 ° C. and a relative humidity of 25%, and then a cutter knife was placed on the optical anisotropic layer side with the obtained cellulose ester film. Then, 11 grid cuts having a depth of 200 μm and an angle of 45 ° were applied at right angles. Nichiban cellophane tape No. 405 and Nitto tape (PET tape) are firmly attached to the entire surface and left for 30 minutes, and the end is peeled off at right angles and peeled between the film and the alignment film. Observed and marked the number of peeled grids. It shows that adhesiveness is so bad that there are many.

As shown in Table 1, Samples 1-8 to 1-19 of the present invention, which were subjected to the alkali saponification treatment after the electron beam treatment of the present invention, had a low contact angle of the cellulose ester film after the electron beam treatment, and the optical compensation sheet The film after conversion also had excellent haze, foreign matter defects and adhesiveness. In particular, it was found that the optical compensation sheet samples 1-12 to 1-19 of the present invention after forming an optical compensation sheet using an inert gas as the atmosphere during the electron beam treatment have remarkably improved haze and foreign matter defects.
On the other hand, Sample 1-1 in which no electron beam treatment was performed and Samples 1-2 to 1-5 in which the irradiation intensity or irradiation amount was insufficient showed extremely poor foreign matter defects and adhesion. Further, Samples 1-6 and 1-7 having a high irradiation intensity or irradiation amount were improved in the foreign matter defects, but had extremely poor adhesion.

In addition, the film samples 1-8 to 1-19 of the present invention are 25 ° C / 60% relative humidity, -10 ° C / 10% relative humidity, 40 ° C / 95% relative humidity, and 80 ° C / dry (Dry) conditions. Each sample was stored for 1 month and examined for adhesion after being allowed to stand at 25 ° C./60% relative humidity for 1 day, but no deterioration in adhesion was observed under forced conditions.
From the above, by performing the electron beam treatment and the alkali saponification treatment in the present invention, an excellent surface treatment of the cellulose ester film can be performed, and an excellent optical compensation sheet can be produced.

[Example 2]
(Preparation of alkaline saponification aqueous solution S-2)
A 1.7 mol / L alkaline saponification aqueous solution (S-2) having the following formulation was prepared.
-NaOH 680 parts by mass-Sodium salt of tri (oxyethylene) decyl ether sulfate 110 parts by mass-Antifoaming agent: Pluronic TR701 (Asahi Denka Kogyo Co., Ltd. 1 part by mass)-Pure water 9209 parts by mass

(Creation of saponified cellulose triacetate film)
The sample 1-13 of the present invention that had been treated with the electron beam produced in Example 1 was collided with hot air at 100 ° C., heated to 55 ° C., and then the alkali saponification solution (S-2) kept at 35 ° C. was used as a rod coater. Then, 8 ml / m ^{2 was} applied and after 10 seconds, 15 ml / m ^{2 of} pure water was again applied using a rod coater. The film maintenance temperature at this time was 45 ° C. Next, 1000 ml / m ² of pure water was applied using an extrusion type coater, washed with water, and after 5 seconds, 100 m / second of wind was made to collide with the water application surface from an air knife. Washing with an extrusion coater and draining with an air knife were repeated twice, and then, the saponification film KF-2 was produced by staying in an 80 ° C. drying zone for 10 seconds and drying. The contact angle of water with this saponified film was 27 °, and the surface free energy of this saponified film was 36 mN / m.

  The surface tension of the alkali saponification solution S-2 was 60 mN / m, the viscosity of the solution was 1.6 mPa · s, the density of the solution was 1.05, and the specific conductivity was 300 mS / cm. The carbonate ion concentration in the alkali saponification aqueous solution was 70 mg / L, the total concentration of polyvalent metal ions including calcium and magnesium was 0.3 mg / L, and the chloride ion concentration was 0.1 mg / L.

(Adjustment of alkaline saponification aqueous solution S-3 to S-6)
The pure water of the alkaline saponification aqueous solution S-2 is changed to ultrapure water at the semiconductor device factory level and water mixed with this with city water or well water. Alkaline saponified aqueous solutions S-3 to S-6 were prepared in the same manner as the alkaline saponified aqueous solution S-2 except that the amount was changed.
The surface tension of the alkali saponification solution S-3 was 59 mN / m, the viscosity of the solution was 1.6 mPa · s, the density of the solution was 1.05, and the specific conductivity was 360 mS / cm. The carbonate ion concentration in the alkaline saponification aqueous solution was 280 mg / L, the total concentration of polyvalent metal ions including calcium and magnesium was 2.3 mg / L, and the chloride ion concentration was 1.5 mg / L.
The surface tension of the alkali saponification solution S-4 was 58 mN / m, the viscosity of the solution was 1.7 mPa · s, the density of the solution was 1.03, and the specific conductivity was 400 mS / cm. The carbonate ion concentration in the alkaline saponification aqueous solution was 850 mg / L, the total concentration of polyvalent metal ions including calcium and magnesium was 18 mg / L, and the chloride ion concentration was 11 mg / L.
The surface tension of the alkaline saponification solution S-5 was 56 mN / m, the viscosity of the solution was 1.7 mPa · s, the density of the solution was 1.06, and the specific conductivity was 410 mS / cm. The carbonate ion concentration in the alkaline saponification aqueous solution was 1260 mg / L, the total concentration of polyvalent metal ions including calcium and magnesium was 92 mg / L, and the chloride ion concentration was 73 mg / L.
The surface tension of the alkali saponification solution S-6 was 55 mN / m, the viscosity of the solution was 1.8 mPa · s, the density of the solution was 1.06, and the specific conductivity was 420 mS / cm. The carbonate ion concentration in the alkaline saponification aqueous solution was 3410 mg / L, the total concentration of polyvalent metal ions including calcium and magnesium was 470 mg / L, and the chloride ion concentration was 263 mg / L.
Alkali saponification-treated films were produced in the same manner as Sample 1-13 of the present invention that had been subjected to electron beam treatment, and optical compensation film sheets 2-1 to 2-5 were further produced. The results of performance evaluation are shown in Table 1.

  As shown in Table 1, the optical compensation sheet that had been subjected to the alkali saponification treatment using the preferred alkali saponification solution of the present invention was good with no foreign matter defects or poor adhesion. When the alkali ion saponification solution has a carbonate ion concentration of 3500 mg / L or less, a polyvalent metal ion concentration of 1000 mg / L or less, and a chlorine ion concentration of 1000 mg / L or less, it is possible to more effectively suppress an increase in haze. The range is more suitable for use.

[Example 3]
In Example 1-13, cellulose ester-A was converted to cellulose triacetate-X (acetyl group substitution degree 2.70, 6-position substitution degree 0.90, polymerization degree 305, Fe content 1.1 ppm, Ca content) 78 ppm, Mg content 7.2 ppm), cellulose triacetate-Y (acetyl group substitution degree 2.92, 6-position substitution degree 0.95, polymerization degree 323, Fe content 0.3 ppm, Ca content 29 ppm, Mg 7.2 ppm)), cellulose ester-PX (acetyl group substitution degree 2.50, propionyl group substitution degree 0.21, all acyl group substitution degree 2.71, 6-position substitution degree 0 .85, degree of polymerization 280, Fe content 2.3 ppm, Ca content 62 ppm, Mg content 14.6 ppm), cellulose triacetate-BY (substitution degree of all acyl groups is 2.82, butanoyl group Except that the degree of substitution is 0.42, the degree of substitution of the acetyl group is 2.40, the degree of substitution at the 6-position is 0.90, the degree of polymerization is 293, the Fe content is 0.05 ppm, the Ca content is 26 ppm, and the Mg content is 0.8 ppm. Were produced in the same manner as Example 1-13, and comparative samples 3-1 to 3-4 outside the present invention were prepared.
The characteristics of these samples were evaluated in the same manner as in Example 1 and listed in Table 1.

Both Comparative Samples 3-1 and 3-2, in which the substituents consisted only of acetyl, were remarkably poor in haze, foreign matter defects, and adhesion, despite the electron beam treatment and alkali saponification treatment of the present invention. . In addition, Comparative Samples 3-3 and 3-4 using a cellulose ester different from the formula of the present invention were at a level that could not be used, although the haze, foreign matter defects and adhesion were slightly improved.
Therefore, it was confirmed that it is effective to perform the surface treatment of the present invention using cellulose ester that satisfies all the requirements defined by the formulas (S-1) to (S-3) of the present invention.

[Example 4]
A polarizing film was prepared by adsorbing iodine to a stretched polyvinyl alcohol film, and using the polyvinyl alcohol-based adhesive, the optical compensation sheets prepared in Examples 1 and 2 (optical compensation sheet samples 1-8 and 1 of the present invention). -13, 1-17, 2-1 to 2-5, and comparative optical compensation sheet samples 1-1 and 1-6) on one side of the polarizing film, and on the other side a commercially available cellulose triacetate film (Fujitac TD80UF, A saponification treatment (not including a surfactant in particular) was applied to Fuji Photo Film Co., Ltd. by a conventional method, followed by drying at 80 ° C. for 10 minutes. The transmission axis of the polarizing film and the slow axis of the optical compensation sheet were arranged in parallel. The transmission axis of the polarizing film and the slow axis of the commercially available cellulose triacetate film were arranged so as to be orthogonal to each other. Thus, polarizing plate samples HB1-8, HB1-13, HB1-17, HB2-1 to HB2-5, and comparative optical compensation sheet sheets HB1-1 and HB1-6) of the present invention were prepared.

  A pair of polarizing plates provided in a liquid crystal display device (6E-A3, manufactured by Sharp Corporation) using a TN type liquid crystal cell is peeled off, and instead of the polarizing plate prepared above, the optical compensation sheet is on the liquid crystal cell side. Each sheet was attached to the observer side and the backlight side through an adhesive so that The transmission axis of the polarizing plate on the observer side and the transmission axis of the polarizing plate on the backlight side were arranged so as to be in the O mode, thereby producing a liquid crystal display device.

  About the produced liquid crystal display device, the drawing nonuniformity at the time of black display (L1) was visually observed using the measuring machine (EZ-Contrast 160D, ELDIM company make). In the liquid crystal display device using the polarizing plate HB1-1 using the optical compensation sheet that was only subjected to the alkali saponification treatment without the electron beam treatment of the present invention, the entire surface of the liquid crystal screen was clouded and the luminance was lowered. Similarly, in the comparative deflector plate sample 1-6 in which the electron beam treatment is within the scope of the present invention, the entire surface of the liquid crystal screen was clouded and the luminance was lowered. On the other hand, in the polarizing plate samples HB1-8, HB1-13, HB1-17, HB2-1 to HB2-5 of the present invention, high luminance was obtained.

[Example 5]
A pair of polarizing plates provided in a liquid crystal display device (VL-1530S, manufactured by Fujitsu Limited) using a vertical alignment type liquid crystal cell is peeled off, and the polarizing plate prepared in Example 4 above (the polarizing plate of the present invention) Plate samples HB1-8, HB1-13, HB1-17, HB2-1 to HB2-5, and comparative optical compensation sheet samples HB1-1, HB1-6)), and the optical compensation sheet on the liquid crystal cell side In this manner, the sheets were attached to the observer side and the backlight side one by one through the adhesive. The liquid crystal display device was assembled in a crossed Nicol arrangement so that the transmission axis of the polarizing plate on the viewer side was in the vertical direction and the transmission axis of the polarizing plate on the backlight side was in the horizontal direction.

About the produced liquid crystal display device, the drawing nonuniformity at the time of black display (L1) was visually observed using the measuring machine (EZ-Contrast 160D, ELDIM company make).
In the liquid crystal display device using the polarizing plate HB1-1 using the optical compensation sheet that was only subjected to the alkali saponification treatment without performing the electron beam treatment of the present invention, the entire surface of the liquid crystal screen was clouded and the luminance was lowered. Similarly, the comparative deflector plate sample 1-6 in which the electron beam processing is within the scope of the present invention also has a liquid crystal display device in which the brightness of the liquid crystal screen is reduced and the drawing unevenness is conspicuous.
The liquid crystal display device using the polarizing plate subjected to the electron beam treatment and alkali saponification treatment of the present invention had high luminance.

[Example 6]
A bend alignment type liquid crystal cell was prepared, and the polarizing plates prepared in Examples 1 and 2 (polarizing plate samples HB1-8, HB1-13, HB1-17, HB2 of the present invention) so as to sandwich the prepared bend alignment cell. -1 to HB2-5) were attached to the observer side and the backlight side one by one through an adhesive so that the optical compensation sheet was on the liquid crystal cell side. The rubbing direction of the liquid crystal cell and the rubbing direction of the optically anisotropic layer facing it were arranged so as to be antiparallel.
About the produced liquid crystal display device, the drawing nonuniformity at the time of black display (L1) was visually observed using the measuring machine (EZ-Contrast 160D, ELDIM company make). In the liquid crystal display device using the polarizing plate subjected to the electron beam treatment and alkali saponification treatment of the present invention, a good liquid crystal display device having high luminance and free from uneven drawing was obtained.

(Example 7)
(8-1) Stretching Using the film before electron beam treatment of the cellulose ester film sample 1-17 of the present invention obtained in Example 1, a temperature (120 ° C. higher than Tg (110 ° C.) of the cellulose ester film. ℃)) in the longitudinal direction (MD stretching) at a rate of 100% / second, and in the transverse direction (TD stretching) at a rate of 20% / second. Stretching was carried out by successive stretching (sample EA-1-17) in which transverse stretching was performed after longitudinal stretching and simultaneous biaxial stretching (EB-1-17) in which stretching was performed simultaneously in the longitudinal and transverse directions.

(8-2) Characteristic evaluation of stretched film Re and Rth of the obtained stretched film had optical characteristic values required as a polarizing plate. The cellulose ester film samples EA-1-17 and EB-1-17 samples of the present invention thus stretched were subjected to surface treatment according to Table 2. The characteristics of the obtained sample were exactly the same as those of Sample 1-17 of Example 1, and it was confirmed that the sample had excellent contact angle, haze, foreign matter defect and adhesiveness. From this, in the present invention, it was confirmed that the various properties were exhibited even by the surface treatment of the stretched film.
In addition, the optical properties after the surface treatment showed a change rate of 1% or less for both Re and Rth compared to those before the surface treatment, and it was found that the surface treatment method of the present invention has no problem.
Furthermore, in addition to the method of stretching after film formation and drying as described above, the sample is also stretched into an undried state during film formation (immediately after completion of temperature removal after peeling), and a sample having equivalent optical characteristics is obtained. The same excellent results were obtained by manufacturing and carrying out the surface treatment.

  Using a specific cellulose ester, a cellulose ester film having excellent surface treatment properties could be produced by electron beam treatment and subsequent alkali saponification treatment. As a result, the produced cellulose ester film can be easily incorporated into an optical film such as an optical compensation sheet for a liquid crystal display device having a large area without display defects. Moreover, the cellulose-ester film for transparent supports excellent in the adhesiveness of the transparent support body and alignment film of an optical compensation film was obtained.

(Example 8)
Using the cellulose ester film sample 1-17 of the present invention prepared in Example 1, the stretched cellulose ester film EA-1-17 of the present invention prepared according to Table 2 was used in Example 13 described in JP-A No. 2002-265636. Used in place of the cellulose triacetate film sample 1301. A bend-aligned liquid crystal cell was prepared in the same manner as in Example 13 described in JP-A-2002-265636 by preparing an optically anisotropic layer and a polarizing plate sample. The obtained liquid crystal cell had excellent viewing angle characteristics.

Example 9
(9-1) Film formation of unstretched cellulose ester film (1) Preparation of cellulose ester pellets The cellulose ester-A was used as the cellulose ester.
This cellulose ester A was dried at 120 ° C. for 3 hours, and the water content was adjusted to 0.1% by mass or less. Thereafter, 0.05% by mass of silicon dioxide particles (Aerosil R972V) and N, N ′ , N ″ -tri-m-toluyl-1,3,5-triazine-2,4,6-triamine was added in an amount of 4% by mass. These were mixed and put into a hopper of a twin-screw kneading extruder, and further kneaded at 200 ° C. with a screw rotation speed of 200 rpm and a residence time of 20 seconds to be melted. Furthermore, after extruding into a strand having a diameter of 3 mm in a water bath and immersing for 1 minute (strand solidification), the temperature was lowered by passing water at 10 ° C. for 30 seconds and cutting to 5 mm in length to obtain a pellet. The obtained pellets of cellulose ester-A were dried at 100 ° C. for 10 minutes and then stored in a moisture-proof bag made of a laminate film having aluminum.

(2) Filtration The cellulose ester formed into a cylindrical pellet having a diameter of 3 mm and a length of 5 mm was dried with a vacuum dryer at 110 ° C. for 3 hours. This was put into a hopper, melted at 200 ° C., and then pressure filtered at a rate of 0.1 cm / min at 10 MPa using a sintered metal filter having a diameter of 5 μm. The obtained filtrate was confirmed to have a transparent and homogeneous composition.

(3) Melt film formation The filtrate obtained in (2) above is put into a hopper adjusted to 118 ° C. (ie, Tg−10 ° C.), and has an upstream melting temperature of 180 ° C. and an intermediate melting temperature of 180 ° C. , Downstream melting temperature 180 ° C, compression ratio 14, T-die temperature is -7 ° C, distance between T-die and casting drum 8cm, solidification speed 30 ° C / sec, casting drum temperature is the first roll (upstream) (Tg -10) The second roll (upstream) (Tg-11) ° C and the third roll (upstream) (Tg-12) ° C at -10 ° C, and the cooling rate was -15 ° C. The melt was melt extruded over 10 minutes. At this time, each level electrostatic application method (a 10 kV wire was placed 10 cm from the point where the melt was attached to the casting drum) was used. The solidified melt was peeled off and wound with a winding tension of 6 kg / cm ² via a nip roll. In addition, after trimming both ends (each 3% of the total width) immediately before winding, the both ends were subjected to a thicknessing process (knurling) with a width of 10 mm and a height of 50 μm and wound. Each level was wound at a speed of 30 m / min and a width of 1.5 m and a length of 500 m. The film thickness of the obtained film was 100 μm. The obtained melt-formed cellulose ester sample 9-1 of the present invention was subjected to electron beam treatment and alkali saponification treatment in exactly the same manner as the cellulose ester sample 1-17 of the present invention of Example 1. The characteristics are shown in Table 1. As can be seen from the table, it was found to have excellent surface properties even for melt-formed cellulose ester films.

(Example 10)
(10-1) Preparation of cellulose ester (1-1) Cellulose ester-A in Example 1 was used.

(10-2) Preparation of cellulose ester solution (dope) Cellulose ester solution formulation Cellulose ester-A 100 parts by mass Methyl acetate 280.9 parts by mass Methanol 32.7 parts by mass 1-butanol 13.1 parts by mass Plasticizer A (tri 0.7 parts by weight Plasticizer B (biphenyl, diphenyl phosphate) 0.3 parts by weight Optical anisotropy control agent (same as in Example 1) 3 parts by weight

UV agent a (2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine) 0.5 part by mass UV agent b (2 (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -5-chlorobenzotriazole) 0.2 part by mass UV agent c: 2 (2′-hydroxy-3 ′, 5′- Di-tert-amylphenyl) -5-chlorobenzotriazole) 0.1 part by mass Polymer having fluorine atom (and comparative substance) Table 1 Fine particles (silicon dioxide, primary particle size 15 nm, Mohs hardness about 7)
0.05 parts by mass

A plurality of solvents are mixed in a 500 L stainless steel dissolution tank having a stirring blade, and cellulose ester powder (flakes) is gradually added while stirring and dispersing well as a mixed solvent, so that the whole becomes 250 kg. Prepared. In addition, all the solvents used that the water content is 0.5 mass% or less. First, the powder of cellulose ester-A is a dissolver type in which powder is put into a dispersion tank and stirred at a peripheral shear speed of 5 m / sec (shear stress 5 × 10 ⁴ kgf / m / sec ² ) at first. The mixture was dispersed for 30 minutes under the condition of having an eccentric stirring shaft and an anchor blade on the central shaft and stirring at a peripheral speed of 1 m / sec (shear stress 1 × 10 ⁴ kgf / m / sec ² ). The dispersion start temperature was 25 ° C., and the final temperature reached 45 ° C. After completion of the dispersion, the high-speed stirring was stopped, and the peripheral speed of the anchor blade was set to 0.5 m / sec and further stirred for 100 minutes to swell the cellulose ester flakes. Until the end of swelling, the inside of the tank was pressurized to 0.13 MPa with nitrogen gas. At this time, the oxygen concentration in the tank was less than 2% by volume, and no problem was found in terms of explosion protection. The water content in the dope was 0.2% by mass.

(10-3) Dissolution / filtration The swollen solution was heated from a tank to 50 ° C. with a jacketed pipe and completely dissolved. The heating time was 30 minutes. Next, the temperature was lowered to 45 ° C., and a dope was obtained by passing through a filter medium having a pore diameter of 8 μm. At this time, the primary pressure of filtration was 1.9 MPa, and the secondary pressure was 1.5 MPa. The filters, housings, and pipes exposed to high temperatures were made of Hastelloy alloy and had excellent corrosion resistance, and those having a jacket for circulating a heat medium for heat insulation and heating were used.

(10-4) Concentration / filtration The pre-concentration dope thus obtained was flushed in a tank under normal pressure at 110 ° C., and the evaporated solvent was recovered and separated by a condenser. The solid concentration of the dope after flashing was 28.9% by mass. The condensed solvent was sent to a recovery process to be reused as a solvent in the preparation process (recovery is carried out by a distillation process, a dehydration process, etc.). The flash tank had an anchor blade on the central axis, and deaerated by stirring at a peripheral speed of 0.5 m / sec. The temperature of the dope in the tank was 40 ° C., and the average residence time in the tank was 50 minutes. The shear viscosity measured at 25 ° C. after collecting this dope was 93 (Pa · s) at a shear rate of 10 (sec ⁻¹ ).

  Next, the dope was defoamed by irradiating weak ultrasonic waves. Then, after passing through a sintered fiber metal filter having a pore diameter of 10 μm while being pressurized to 1.5 MPa, it was passed through a 10 μm sintered fiber filter. Respective primary pressures were 1.5 and 1.2 MPa, and secondary pressures were 1.0 and 0.8 MPa. The dope temperature after filtration was adjusted to 40 ° C. and stored in a 500 L stainless steel stock tank. The stock tank had an anchor blade on the central axis, and was constantly stirred at a peripheral speed of 0.3 m / sec. In addition, when the dope was prepared from the dope before concentration, no problem such as corrosion occurred at all in the wetted part of the dope.

(10-5) Casting Subsequently, the dope in the stock tank was fed by a feedback control using an inverter motor so that the primary pressure of the high precision gear pump became 0.8 MPa with a gear pump for primary pressure increase. The high-precision gear pump had a volume efficiency of 99.2% and a discharge rate variation rate of 0.5% or less. The discharge pressure was 1.5 MPa. The casting die was equipped with a feed block adjusted for co-casting with a width of 1.8 m, and a device that was capable of forming a three-layer film by laminating on both sides in addition to the mainstream. . In the following description, a layer formed from the mainstream is referred to as an intermediate layer, a support surface side layer is referred to as a support surface, and an opposite surface is referred to as an air surface. In addition, the dope liquid supply flow path used three flow paths for the intermediate layer, the support surface, and the air surface. The support side dope and the air side dope for the outermost layer are prepared by using a dope prepared in (1-2) as a solvent comprising 267 parts by mass of methylene chloride / 48.5 parts by mass of methanol / 11.8 parts by mass of 1-butanol. A static mixer and a slew mixer were connected and diluted in-line installed in the pipe. Dilution was performed such that the original dope was at a concentration of 97% for the support-side dope and the air-side dope was at a concentration of 95% with respect to the original dope.

  The film thickness of the finished cellulose ester film sample is 4 μm, 92 μm, and 4 μm on the air surface, intermediate layer, and support surface, respectively, and the casting width is 1500 mm so that the thickness is 100 μm. Casting was performed by adjusting the dope flow rate. In order to adjust the dope temperature to 40 ° C, a jacket was provided on the casting die, and the inlet temperature of the heat transfer medium supplied into the jacket was 43 ° C.

  The die, feed block, and piping were all kept at 40 ° C. during the work process. The die was a coat hanger type die, with thickness adjusting bolts provided at a pitch of 20 mm, and having an automatic thickness adjusting mechanism using a heat bolt. This heat bolt can also set a profile according to the liquid feed amount of the high precision gear pump by a preset program, and feedback control can also be performed by an adjustment program based on the profile of the infrared thickness gauge installed in the film forming process It has performance. The thickness difference between two arbitrary points 50 mm apart in the film excluding the casting edge portion 20 mm was within 1 μm, and the largest difference in the width direction thickness was adjusted to 3 μm / m or less. The average thickness accuracy of each layer was controlled to ± 2% or less for both outer layers and ± 1% or less for the mainstream, and the overall thickness was adjusted to ± 1.5% or less.

  In addition, a chamber for decompressing was installed on the primary side of the die. The degree of decompression of the decompression chamber is such that a pressure difference of 1 Pa to 5000 Pa can be applied before and after the casting bead, and can be adjusted according to the casting speed. At that time, the pressure difference was set such that the bead length was 2 mm to 50 mm. Further, the chamber temperature was provided with a mechanism that can be set higher than the condensation temperature of the gas around the casting portion. In addition, a bead was provided for all and a labyrinth was provided for the rear. Openings were provided at both ends. Furthermore, from there, the one to which the edge suction device was attached in order to adjust the disturbance of the flow at both edges of the bead was used.

(10-6) Casting die Here, the material of the die is precipitation hardening stainless steel, and the material has a coefficient of thermal expansion of 2 × 10 ⁻⁵ (° C. ⁻¹ ) or less, and forced corrosion with an aqueous electrolyte solution. In the test, a material having approximately the same corrosion resistance as SUS316 was used. In addition, a material having corrosion resistance that does not cause pitting (opening) at the gas-liquid interface even when immersed in methyl acetate, acetone, methanol, butanol, or water for 3 months was used. Furthermore, the surface of the cellulose ester solution was kept constant by grinding the one aged or longer after casting. The finishing accuracy of the wetted surfaces of the casting die and the feed block was 1 μm or less in terms of surface roughness, the straightness was 1 μm / m or less in any direction, and the slit clearance was adjusted to 1.5 mm by automatic adjustment. About the corner | angular part of the liquid-contact part of die-tip tip, it processed so that R might be 50 micrometers or less over the slit full width. The shear rate inside the die was in the range of 1 (1 / sec) to 5000 (1 / sec).

  Further, a casting die provided with a cured film was used at the lip tip. As a means for providing the hard film, a tungsten carbide (WC) coating formed by a thermal spraying method was used.

  Furthermore, in order to prevent the dope flowing out at the slit end of the die from locally drying and solidifying, a mixed solvent (for example, 280.9 parts by mass of methyl acetate, 32.7 methanol) is a solvent for solubilizing the dope. The solvent comprising 1 part by mass and 13.1 parts by mass of 1-butanol was supplied at 0.5 ml / min on one side to the gas-liquid interface between the bead end and the slit. The pulsation rate of the pump supplying this liquid was 5% or less. In addition, the pressure on the back surface of the bead was reduced by 150 Pa by the decompression chamber. A jacket was attached to keep the temperature of the vacuum chamber constant. A heat transfer medium adjusted to 35 ° C. was supplied into the jacket. The edge suction air volume that can be adjusted in the range of 1 L / min to 100 L / min was used, and in this example, it was appropriately adjusted in the range of 30 L / min to 40 L / min.

(10-7) Metal support A stainless steel endless band having a width of 2.1 m and a length of 70 m was used as a support. The band was 1.5 mm thick and polished so that the surface roughness was 0.05 μm or less. The material was made of SUS316 and had sufficient corrosion resistance and strength. The thickness unevenness of the entire band was 0.5% or less. The band is a type driven by two drums, and the tension of the band at that time is adjusted to 1.5 × 10 ⁴ kg / m, and the relative speed difference between the band and the drum is 0.01 m / min or less. It was a thing. The band drive speed fluctuation was 0.5% or less. Further, both ends of the band were detected and controlled so that the meandering in the width direction of one rotation was limited to 1.5 mm or less. Further, the positional fluctuation in the vertical direction accompanying the drum rotation on the surface of the support just below the casting die was set to 200 μm or less. The support was installed in a casing having wind pressure vibration suppression means. Three layers of dope were co-cast from this die on this support.

As the casting drum, a drum having equipment for circulating a heat transfer medium (refrigerant) therein was used so as to cool the support. Moreover, since the other drum supplies heat for drying, the heat transfer medium can pass water. The temperature of each heat transfer medium was 5 ° C. (casting die side) and 35 ° C. The surface temperature at the center of the support just before casting was 15 ° C. The temperature difference between both ends was 6 ° C. or less. The drum can be directly used as a casting support. In this case, the drum was rotated so that the rotation unevenness had an accuracy of 0.2 mm or less. Also in the drum, the average roughness of the surface is 0.01 μm or less, and it has sufficient hardness and durability by the chrome plating treatment. There should be no surface defects in either the drum or the band, there are no pinholes of 30 μm or more, 1 pinhole of 10 μm to 30 μm / m ² or less, and ² pinholes of 10 μm or less A support that was less than / m ² was used.

(10-8) Casting Drying The temperature of the casting chamber provided with the casting die and the support was kept at 40 ° C. The dope cast on the band was first dried by sending parallel-flow drying air. The overall heat transfer coefficient from the drying air to the dope during drying was 24 kcal / m ² · hr · ° C. The temperature of the drying air was 135 ° C on the upstream side of the upper part of the band, and 140 ° C on the downstream side. The lower part of the band was set to 65 ° C. The saturation temperature of each gas was around -8 ° C. The oxygen concentration in the dry atmosphere on the support was kept at 5% by volume. The air was replaced with nitrogen gas in order to keep the oxygen concentration at 5% by volume. Further, in order to condense and recover the solvent in the casting chamber, a condenser (condenser) was provided, and the outlet temperature thereof was set to −10 ° C.

  For 5 seconds after casting, the wind pressure was prevented from directly hitting the dope by a wind shield device, and the static pressure fluctuation in the immediate vicinity of the casting die was suppressed to ± 1 Pa or less. When the solvent ratio in the dope became 50% by mass on a dry basis, the dope was peeled off as a film. The peeling tension at this time was 10 kgf / m, and the peeling speed (peeling roll draw) with respect to the support speed was set so as to be properly peeled in the range of 100.1% to 110%. The surface temperature of the peeled film was 15 ° C. The drying rate on the support was an average of 60% by weight dry weight reference solvent / min. The solvent gas generated upon drying was led to a condenser, liquefied at −10 ° C., recovered, and reused as a charging solvent. The drying air from which the solvent was removed was heated again and reused as drying air. At that time, the water content in the solvent was adjusted to 0.5% or less and reused.

  The peeled film was conveyed by the transfer part provided with many rollers. The transition part was equipped with three rollers, and the temperature of the transition part was kept at 40 ° C. A tension of 16 N / m to 160 N / m was applied to the film while the film was being transported by a roller at the transfer section.

(10-9) Tenter Transport / Drying The peeled film was transported in the drying zone of the tenter while being fixed at both ends with a tenter having a clip, and dried with drying air. The clip was cooled by supplying a heat transfer medium at 20 ° C. The tenter was driven by a chain, and the speed fluctuation of the sprocket was 0.5% or less. Further, the inside of the tenter was divided into three zones, and the drying air temperature of each zone was set to 90 ° C., 100 ° C., and 110 ° C. from the upstream side. The gas composition of the drying air was set to a saturated gas concentration of −10 ° C. The average drying rate in the tenter was 120% by mass (dry weight reference solvent) / min. At the outlet of the tenter, the amount of residual solvent in the film was adjusted to 10% by mass or less, and in this experiment, the conditions of the drying zone were adjusted to 7% by mass. In the tenter, the film was stretched in the width direction while being conveyed. The amount of widening when the width when conveyed to the tenter was 100% was 103%. The stretching ratio (tenter-driven draw) from the peeling roller to the tenter inlet was 102%.

  As for the stretching ratio in the tenter, the difference in the substantial stretching ratio at a portion 10 mm or more away from the tenter biting portion was 10% or less, and the difference in the stretching ratio at any two points 20 mm apart was 5% or less. The ratio of the length of the base end fixed by the tenter was 90%. Further, the tenter clip was transported while being cooled so as not to exceed 50 ° C. The solvent evaporated in the tenter part was condensed and liquefied at a temperature of −10 ° C. and recovered. A condenser (condenser) was provided for condensation recovery, and the outlet temperature was set to -8 ° C. The water content contained in the solvent was adjusted to 0.5% by mass or less and reused.

Then, the ears were cut at both ends within 30 seconds from the tenter exit. Ears 50 mm on both sides were cut with an NT-type cutter, and the cut ears were blown to a crusher by a cutter blower and crushed into chips of about 80 mm ² on average (this chip was again charged with cellulose ester flakes as a raw material for preparation) Can be used as a raw material). The oxygen concentration in the dry atmosphere of the tenter part was kept at 5% by volume. The air was replaced with nitrogen gas in order to keep the oxygen concentration at 5% by volume. The film was preheated in a predrying zone supplied with 100 ° C. drying air before being dried at a high temperature in a roller conveyance zone described later.

(10-10) Post-drying The cellulose ester film after the end cutting obtained by the above-described method was dried at high temperature in the roller transport zone. The roller conveyance zone was divided into four sections, and dry air at 100 ° C., 105 ° C., 105 ° C., and 110 ° C. was supplied from the upstream side. At this time, the roller conveyance tension of the film was set to 100 N / width, and the film was dried for about 30 minutes until the residual solvent amount finally reached 0.3% by mass. The wrap angle of the roller was 90 degrees and 180 degrees. The roller was made of aluminum or carbon steel, and a hard chrome plating was applied to the surface. As the surface shape of the roller, a flat one and a mat formed by blasting were used. All the shakes due to the rotation of the roller were 50 μm or less. The roller deflection at a tension of 100 N / width was selected to be 0.5 mm or less.

  A forced charge removal device (charge removal bar) was installed during the process so that the film voltage during conveyance was always in the range of -3 kV to 3 kV. Moreover, in the winding part, not only the static elimination bar but also ion wind static elimination was installed so that the charge would be -1.5 kV to 1.5 kV. The solvent gas contained in the drying air was adsorbed and recovered using an adsorbent. The adsorbent was activated carbon, and desorption was performed using dry nitrogen. The recovered solvent was adjusted to a water content of 0.3% by mass or less and reused as a charged solvent. The drying air contains plasticizers, UV absorbers, and other high-boiling substances in addition to solvent gas, so these were removed by a cooler and pre-adsorber that were cooled and removed, and were recycled and used. And adsorption / desorption conditions were set so that VOC in outdoor exhaust gas would be 10 ppm or less finally. Further, the amount of solvent recovered by the condensing method of all evaporated solvents was 90% by mass, and most of the rest was recovered by adsorption recovery.

  The dried film was conveyed to the 1st humidity control chamber. Dry air at 105 ° C. was supplied to the transition portion between the roller conveyance zone and the first humidity control chamber. Air having a temperature of 50 ° C. and a dew point of 20 ° C. was supplied to the first humidity control chamber. Further, the film was conveyed to a second humidity control chamber that suppresses the curling of the film. In the second humidity control chamber, air at 90 ° C. and 80% humidity was directly applied to the film.

(10-11) Post-treatment, winding The dried cellulose ester film was cooled to 30 ° C. or lower, and both ends were cut off, and further, both ends of the film were knurled. The knurling was imparted by embossing from one side, the knurling width was 10 mm, and the pressing pressure was set so that the maximum height was 12 μm higher than the average thickness on average.

  And the obtained film was conveyed to the winding chamber. The winding chamber was kept at a room temperature of 28 ° C. and a humidity of 70%. The width of the cellulose ester film (thickness 100 μm) thus obtained was 1475 mm. The diameter of the winding core was 169 mm, and the tension pattern was such that the tension at the start of winding was 360 N / width and the end of winding was 250 N / width. The total winding length was 300 m. Moreover, the press roll was set to the winding roll, and the pressure was set to 50 N / width. The temperature of the film at the time of winding was 25 ° C., the water content was 1.4% by mass, and the residual solvent amount was 0.1% by mass or less. Moreover, there was no winding looseness, no wrinkles, and no winding slip occurred. The roll appearance was also good. Through the above steps, a cellulose ester film sample 10-1 shown in Table 1 was formed.

(10-12) Surface treatment and characteristic evaluation The cellulose ester sample 10-1 of the present invention obtained above was treated with an electron beam in the same manner as the cellulose ester sample 1-17 of the present invention of Example 1 and further subjected to electron beam treatment. Alkaline saponification treatment was performed. The characteristics are shown in Table 1. As can be seen from the table, it was found that the cellulose ester film of the present invention which was solution-coated with a non-halogen organic solvent also had excellent surface characteristics.

(Example 11)
In the cellulose ester film sample 1-17 of the present invention produced in Example 1, the film thickness was 40 μ (inner layer 3 μm, intermediate layer 34 μm, outer layer 3 μm). Sample 11-1 was produced. The produced cellulose ester film sample 11-1 had Re of 1.1 nm and Rth of 82 nm. The surface-treated cellulose ester film of this film was used in place of the cellulose triacetate film sample 1401 in Example 14 described in JP-A No. 2002-265636. Then, a TN type liquid crystal cell was produced in the same manner as in Example 14 described in JP-A No. 2002-265636 by producing an optically anisotropic layer and a polarizing plate sample. The obtained liquid crystal cell had excellent viewing angle characteristics.

  The cellulose ester film of the present invention has an optical compensation by forming an alignment film on the alignment film, then applying liquid crystal molecules on the alignment film, and fixing the alignment of the liquid crystal molecules to form an optically anisotropic layer. Sheets can be manufactured. Further, the polarizing plate is composed of a polarizing film and two transparent protective films arranged on both sides thereof, and one of the transparent protective films fixes the alignment film and the alignment of the liquid crystalline molecules on the cellulose ester film. In the case where the optically anisotropic sheet is provided with the optically anisotropic layer in this order, a cellulose ester film having an alkali saponified surface on the side on which the alignment film is formed can be advantageously used as the cellulose ester film. That is, an optical film carrying an alignment film, an optical film provided with an optical anisotropic layer, an optical film such as a polarizing plate, an optical compensation sheet, and the like can be produced by using the cellulose ester film of the present invention to achieve interlayer adhesion. It can be excellent and has a uniform and good surface shape free from foreign matter defects and alignment defects, and can be used for various liquid crystal display devices and image display devices.

  The alkaline saponification aqueous solution of the present invention contains at least an alkaline agent and a surfactant, and the alkaline saponification aqueous solution has a carbonate ion concentration, a polyvalent metal ion concentration, and a chloride ion concentration within a predetermined range. And salts generated by saponification treatment (fatty acid salts, etc.) can be dissolved and dispersed to achieve more uniform alkali saponification treatment without increasing haze of the film, poor adhesion, generation of foreign matter defects and orientation defects.

  By attaching an optical film using the cellulose ester film of the present invention, it is possible to provide an image display device that enables clear image display. Furthermore, it can be easily incorporated into an optical film such as an optical compensation sheet for a liquid crystal display device having a large area without display defects. Moreover, it can be set as the cellulose-ester film for transparent supports excellent in the adhesiveness of the transparent support body and alignment film of an optical compensation film.

Claims (18)

At least one surface of a film-like cellulose ester that satisfies all the requirements defined by the following formulas (S-1) to (S-3) is irradiated with an electron beam with an intensity of 10 to 200 keV and an irradiation amount of 10 to 200 kGy. A method for producing a cellulose ester film, comprising a step of treating the film-like cellulose ester with an alkali saponification solution after the electron beam irradiation.
Formula (S-1) 2.50 ≦ A + B ≦ 3.00
Formula (S-2) 0 ≦ A ≦ 2.5
Formula (S-3) 0.5 ≦ B ≦ 3.00
(In formulas (S-1) to (S-3), A represents the degree of substitution of the acetyl group, and B represents the degree of substitution of the substituted acyl group having 3 to 22 carbon atoms.) The said electron beam irradiation is a manufacturing method of the cellulose-ester film of Claim 1 performed in inert gas atmosphere. The method for producing a cellulose ester film according to claim 1 or 2, wherein the alkali saponification solution contains 0.2 to 5 mol / L of at least one of sodium hydroxide, potassium hydroxide, and lithium hydroxide. The method for producing a cellulose ester film according to claim 1, wherein the alkali saponification solution has a carbonate ion concentration of 3500 mg / L or less. The alkali saponification solution has a surface tension of 15 to 65 mN / m and a viscosity of 0. 6~20mPa · s, density of ^{0.9g / cm 3 ~1.4g / cm 3} , specific conductivity is 20mS / cm~2S / cm, the cellulose ester film according to claim 1 Manufacturing method. The method for producing a cellulose ester film according to any one of claims 1 to 5, wherein an alkali saponification treatment is performed with an alkali saponification solution at 10 to 90 ° C for 5 to 600 seconds. The alkali saponification treatment is carried out at 5 to 90 ° C. for 5 to 1200 seconds, at least once with a water washing treatment, and / or with at least one acid treatment. Of manufacturing cellulose ester film. The film-like cellulose ester is preliminarily heated to room temperature or higher, and includes a step of applying an alkali saponification aqueous solution to the film-like cellulose ester to saponify the cellulose ester and then removing the cellulose ester. The manufacturing method of the cellulose-ester film of description. 9. The cellulose according to claim 1, wherein the film-like cellulose ester has a surface contact angle of 45 ° or less at 25 ° C. and 60% relative humidity after being treated with an alkali saponification solution. A method for producing an ester film. The method for producing a cellulose ester film according to claim 1, wherein the film-like cellulose ester is solution cast or melt cast. The film-like cellulose ester is an organic solvent selected from halogenated organic solvents, ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, and esters having 3 to 12 carbon atoms. The method of producing a cellulose ester film according to claim 10, wherein the solution is cast using The cellulose ester film has a degree of polymerization of the cellulose ester of 140 to 400, a plasticizer content of 0.5 to 20% by mass, a UV agent content of 0.1 to 10% by mass, and an increase in retardation. The manufacturing method of the cellulose-ester film in any one of Claims 1-11 containing 0.5-15 mass% of an agent. (1) a step of swelling cellulose ester dispersed in an organic solvent at −10 to 55 ° C., heating the cellulose ester dispersion solution to 0 to 57 ° C., and dissolving the cellulose ester in the heated solution; 2) After swelling the cellulose ester dispersed in the organic solvent at −10 to 55 ° C., the cellulose ester dispersion solution is cooled to −100 to −10 ° C., and the cooled cellulose ester solution is added to 0 to 57 ° C. A step of warming and dissolving the cellulose ester in the heated solvent, or (3) swelling the cellulose ester dispersed in the organic solvent at −10 to 55 ° C. Heating at 60 to 240 ° C., cooling the heated cellulose ester solution to 0 to 57 ° C., and dissolving the cellulose ester in the cooled solution. The method for producing a cellulose ester film described in any one of claims 1 to 12. Including a step of casting the cellulose ester on a support, and the maximum peeling load when peeling the cellulose ester from the support is 1 to 30 g / cm, and the peelable time is 30 to 600 seconds. The method for producing a cellulose ester film according to claim 1, wherein A step of stretching the film-like cellulose ester by 1.03 to 3 times in at least one direction of the transport direction and / or the width direction, and the slow axis of the cellulose ester film is 0 ± The manufacturing method of the cellulose-ester film of Claims 1-14 which is 5 degrees or 90 degreeC +/- 5 degrees. The cellulose ester film has an in-plane retardation (Re) of 0 ≦ Re ≦ 300 nm, a thickness direction retardation (Rth) of −100 ≦ Rth ≦ 500 nm, and a film thickness of 20 to 200 μm. The manufacturing method of the cellulose-ester film in any one of Claims 1-15. The cellulose-ester film manufactured by the manufacturing method of the cellulose-ester film in any one of Claims 1-16. An optical film using the cellulose ester film according to claim 17.