JP2008285625A - Method for alkali saponification of polymer film, surface saponified cellulose ester film, and optical film using the same - Google Patents

Abstract

Method for alkali saponification of polymer film by extracting hydrophobic component from polymer film with organic solvent without affecting coating film formation and alignment of liquid crystal molecule layer and liquid crystal molecule layer to be applied later The present invention provides a surface saponified cellulose ester film and an optical film using the same.
An application step of applying an alkaline aqueous solution to a polymer film, a saponification reaction step of saponifying a polymer film with an alkaline aqueous solution applied in the application step, a reaction stopping step of stopping the saponification reaction step, and an alkaline aqueous solution In the method for alkali saponification of a polymer film comprising a washing step of washing with a washing solution, the washing solution contains at least a surfactant, and the amount of the surfactant contained in the washing solution is determined after the saponification reaction step. The hydrophobic component extracted from the polymer film in the saponification treatment solution is 0.5 times or more and 5.0 times or less.
[Selection figure] None

Description

  The present invention relates to a method for alkali saponification of a polymer film, and more particularly to a method for alkali saponification of a polymer film used as a transparent support for an optical compensation sheet.

  A liquid crystal display device is employed as a flat image display device (FPD). The liquid crystal display device includes a sheet material (optical film) having an optical function such as a liquid crystal cell, a polarizing plate, and an optical compensation sheet (retardation plate).

  The polarizing plate is generally composed of a polarizing film and two transparent protective films provided on both sides thereof. A polarizing film is generally obtained by impregnating polyvinyl alcohol with an aqueous solution of iodine or a dichroic dye and stretching it uniaxially.

  The optical compensation sheet has a function of improving the display quality of the liquid crystal display device by eliminating image coloring and widening the viewing angle, and is therefore used in various liquid crystal display devices.

  As a transparent support for polarizing plates and optical compensation sheets, it is typified by cellulose acetate film having excellent light transmittance, optical non-orientation, excellent physical and mechanical properties, and characteristics with little change in temperature and humidity. Cellulose ester film is employed.

  As the optical compensation sheet, an optical compensation sheet having an optically anisotropic layer formed of liquid crystalline molecules (particularly discotic liquid crystalline molecules) on a transparent support is used in place of the conventionally used stretched birefringent film. It has been proposed. This optically anisotropic layer is formed by aligning liquid crystalline molecules and fixing the alignment state. By using liquid crystal molecules, particularly discotic liquid crystal molecules, optical compensation sheets having various optical characteristics corresponding to various display modes of the liquid crystal cell can be produced.

  For example, TN mode liquid crystal cell optical compensation sheet, IPS mode or FLC mode liquid crystal cell optical compensation sheet, OCB mode or HAN mode liquid crystal cell optical compensation sheet, STN mode liquid crystal cell optical compensation sheet, VA mode liquid crystal An optical compensation sheet for cells has been proposed. Furthermore, in order to reduce the weight of the liquid crystal display device, an integrated elliptical polarizing plate using an optical compensation sheet as one protective film of the polarizing plate has been proposed.

  In a polarizing plate and an optical compensation sheet, a polarizing film and an optical anisotropic layer are provided on a cellulose ester film which is a transparent support through an adhesive layer and an alignment film (usually polyvinyl alcohol). As one means for improving the adhesion between the adhesive layer and the alignment film and the transparent support, a method has been proposed in which a cellulose ester film is immersed in an alkaline aqueous solution to saponify and hydrophilize the surface (Patent Document). 1-4). In addition, a method of selectively saponifying one surface of the film by applying an alkaline aqueous solution to the cellulose ester film has been proposed (see Patent Documents 5 and 6).

Furthermore, in recent years, a method for producing an optical compensation sheet with high productivity and no display defects by uniformly saponifying the entire surface has been proposed (see Patent Documents 7 to 12). For example, in Patent Document 7, saponification treatment with an alkaline aqueous solution includes (1) a wet / static charge / dust removal process, (2) a heating process, (3) a coating process, (4) a saponification reaction process, and (5) a reaction stop process. And (6) a washing step, and it is disclosed that the saponification reaction is performed at a predetermined temperature. Patent Document 8 discloses that the adhesiveness between the transparent support of the optical compensation sheet and the alignment film is improved by setting the alkaline aqueous solution to pH 10 or more. Furthermore, Patent Document 9 discloses that the display quality of the optical compensation sheet is improved by setting the carbonate ion concentration in the alkali diluted solution and the neutralized solution used in the cleaning step to a predetermined value. Patent Document 10 discloses a film that can easily produce an optical sheet free from display defects by saponification with an alkaline aqueous solution containing an amphoteric surfactant. Patent Document 11 discloses that the surface treatment characteristics are improved by using an alkali saponification solution after electron beam irradiation. Patent Document 12 discloses an alkaline diluent used in the cleaning process.
Paragraph No. [0008] of JP-A-7-151914 Paragraph No. [0033] of JP-A-8-94838 Paragraph No. [0083] of Japanese Patent Laid-Open No. 2001-166146 Paragraph No. [0042] of JP 2001-188130 A Paragraph number [0034] of Japanese Patent Laid-Open No. 2002-82226 WO02 / 46809 Publication JP 2003-313326 A JP 2004-182893 A JP 2004-203965 A JP 2004-225002 A JP 2006-232892 A JP 2006-307056 A

  However, in the conventional saponification method, the polymer film is not dissolved by the alkaline aqueous solution, but the additive substance in the polymer film may be extracted. Since the extracted additive substance is a hydrophobic substance, there is a problem in that it affects the alignment film to be applied later and the coating film formation of the liquid crystal molecular layer and the alignment of liquid crystal molecules.

  The present invention has been made in view of such circumstances. By extracting a hydrophobic component from a polymer film with an alkaline aqueous solution, the alignment film to be applied later and the formation of a liquid crystal molecule layer and the alignment of liquid crystal molecules can be achieved. An object of the present invention is to provide an alkali saponification method of a polymer film, a surface saponified cellulose ester film, and an optical film using the same without affecting the polymer film.

  To achieve the above object, a coating step of applying an alkaline aqueous solution to the polymer film, a saponification reaction step of saponifying the polymer film with the alkaline aqueous solution applied in the coating step, and a reaction stop for stopping the saponification reaction step In the method for alkaline saponification of a polymer film comprising a step and a washing step of washing an alkaline aqueous solution with a washing solution, the washing solution contains at least a surfactant, and the surfactant contained in the washing solution The addition amount is 0.5 times or more and 5.0 times or less with respect to the hydrophobic component extracted from the polymer film in the saponification treatment solution after the saponification reaction step.

  The present invention focuses on the extraction amount of the hydrophobic component in the saponification solution after the saponification reaction step. The present inventor has found that this hydrophobic component can be washed off by adding a surfactant to the cleaning liquid, and further, the amount of the surfactant contained in the cleaning liquid is the amount of saponification after the saponification reaction step. It has been found that poor cleaning in the cleaning step can be suppressed by setting the ratio to 0.5 to 5.0 times the ratio of the hydrophobic component extracted from the polymer film in the treatment liquid. Here, the “saponification solution” refers to an alkaline aqueous solution after the polymer film is saponified with an alkaline aqueous solution.

  That is, the cleaning liquid contains at least a surfactant, and the amount of the surfactant included in the cleaning liquid is larger than the hydrophobic component extracted from the polymer film in the saponification treatment liquid after the saponification reaction step. When the ratio is 0.5 times or more and 5.0 times or less, there is no cleaning failure in the cleaning process, and the deterioration of the surface characteristics of the polymer film can be prevented. Accordingly, the present invention provides an alkali saponification method of a polymer film that does not affect the formation of a coating film of a liquid crystal molecular layer and a liquid crystal molecule layer and the orientation of liquid crystal molecules by extracting a hydrophobic component from the polymer film. Can do. The addition amount of the surfactant contained in the cleaning solution is 1.0 to 4.0 times the hydrophobic component extracted from the polymer film in the saponification treatment solution after the saponification reaction step. Further preferred.

  In the alkali saponification method of the polymer film of the present invention, the liquid temperature of the cleaning liquid in the cleaning step is preferably 30 ° C. or higher and 60 ° C. or lower.

  This regulates the mobility of the surfactant, and when the temperature of the cleaning liquid is 30 ° C. or higher and 60 ° C. or lower, the hydrophobic component extracted from the polymer film can be effectively cleaned. it can.

  In the alkali saponification method of the polymer film of the present invention, the polymer film is preferably a cellulose ester film.

  The surface saponified cellulose ester film of the present invention is obtained by the alkali saponification method described above.

  The surface saponified cellulose ester film obtained by the above-described alkali saponification method is effectively used as a transparent support for optical sheets. In particular, the surface saponified cellulose ester film has few cleaning defects after the saponification reaction step, and thus contributes to the quality improvement of the optical sheet.

  The optical film of the present invention is characterized by a surface saponified cellulose ester film obtained by the alkali saponification method described above.

  Since the optical sheet is produced using the surface saponified cellulose ester film obtained by the alkali saponification method described above, a high-quality optical sheet can be obtained.

  According to the present invention, the extraction of hydrophobic components from a polymer film with an organic solvent does not affect the orientation of the alignment film to be applied later and the coating film formation of the liquid crystalline molecular layer and the alignment of the liquid crystal molecules. A saponification method, a surface saponified cellulose ester film, and an optical film using the same can be provided.

[Polymer film]
As the polymer film, it is preferable to use a polymer film having a light transmittance of 80% or more. As the polymer film, a film in which birefringence hardly occurs due to external force is preferable. The polymer film contains a hydrolyzable bond (bond to be saponified) such as an ester bond or an amide bond. An ester bond is preferred, and it is more preferred that the ester bond be present on the side chain of the polymer. A typical example of the polymer having an ester bond in the side chain is a cellulose ester. Lower fatty acid esters of cellulose are more preferable, cellulose acetate is more preferable, and cellulose acetate having an acetylation degree of 59.0 to 61.5% is most preferable. The degree of acetylation means the amount of bound acetic acid per unit mass of cellulose. The degree of acetylation follows the measurement and calculation of the degree of acetylation in ASTM: D-817-91 (test method for cellulose acetate and the like).

  The viscosity average polymerization degree (DP) of the cellulose ester is preferably 250 or more, and more preferably 290 or more. The cellulose ester used in the present invention preferably has a narrow molecular weight distribution of Mw / Mn (Mw is a mass average molecular weight, Mn is a number average molecular weight) by gel permeation chromatography. The specific value of Mw / Mn is preferably 1.0 to 1.7.

When using a polymer film for an optical compensation sheet, the polymer film preferably has a high retardation value. The Re retardation value and Rth retardation value of the film are defined by the following formulas (I) and (II), respectively.
(I) Re = | nx−ny | × d
(II) Rth = {(nx + ny) / 2−nz} × d
In the formulas (I) and (II), nx is the refractive index in the slow axis direction in the film plane (direction in which the refractive index is maximum), ny is the fast axis direction in the film plane (the refractive index is minimum) Nz is the refractive index in the thickness direction of the film, and d is the thickness of the film with the unit of nm. The Re retardation value of the polymer film is preferably 1 to 200 nm, and the Rth retardation value is preferably 70 to 400 nm. A specific value is obtained by extrapolating from the measurement result in which the incident direction of the measurement light is inclined with respect to the vertical direction of the film film surface. The measurement can be carried out using an ellipsometer (for example, M-150, manufactured by JASCO Corporation). As a measurement wavelength, 632.8 nm (He—Ne laser) is adopted.

  It is preferable to produce a polymer film by a solvent cast method. In the solvent cast method, a film is produced using a solution (dope) in which a polymer material is dissolved in an organic solvent. The organic solvent is a solvent selected from ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, esters having 3 to 12 carbon atoms, and halogenated hydrocarbons having 1 to 6 carbon atoms. It is preferable to contain. The ether, ketone and ester may have a cyclic structure. A compound having two or more functional groups of ether, ketone and ester (that is, —O—, —CO— and —COO—) can also be used as the organic solvent. The organic solvent may have another functional group such as an alcoholic hydroxyl group. In the case of an organic solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group.

  Examples of the ether having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole. Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone. Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate. Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol. The number of carbon atoms of the halogenated hydrocarbon is preferably 1 or 2, and most preferably 1. The halogen of the halogenated hydrocarbon is preferably chlorine. The proportion of halogen atoms substituted by halogen in the halogenated hydrocarbon is preferably 25 to 75 mol%, more preferably 30 to 70 mol%, and more preferably 35 to 65 mol%. More preferably, it is most preferable that it is 40-60 mol%. Methylene chloride is a representative halogenated hydrocarbon. Further, two or more kinds of organic solvents may be mixed and used.

  A polymer solution can be prepared by a general method. The general method means that the treatment is performed at a temperature of 0 ° C. or higher (room temperature or high temperature). The solution can be prepared using a dope preparation method and apparatus in a normal solvent cast method. In the case of a general method, it is preferable to use a halogenated hydrocarbon (particularly methylene chloride) as the organic solvent. The amount of the polymer is adjusted so as to be contained in the obtained solution in an amount of 10 to 40% by mass. The amount of the polymer is more preferably 10 to 30% by mass. Arbitrary additives described later may be added to the organic solvent (main solvent). The solution can be prepared by stirring the polymer and the organic solvent at room temperature (0 to 40 ° C.). High concentration solutions may be stirred under pressure and heating conditions. Specifically, the polymer and the organic solvent are put in a pressure vessel and sealed, and stirred while heating to a temperature not lower than the boiling point of the solvent at normal temperature and in a range where the solvent does not boil. The heating temperature is usually 40 ° C. or higher, preferably 60 to 200 ° C., and more preferably 80 to 110 ° C.

  Each component may be coarsely mixed in advance and then placed in a container. Moreover, you may put into a container sequentially. The container needs to be configured so that it can be stirred. The container can be pressurized by injecting an inert gas such as nitrogen gas. Moreover, you may utilize the raise of the vapor pressure of the solvent by heating. Or after sealing a container, you may add each component under pressure. When heating, it is preferable to heat from the outside of the container. For example, a heating device having a jacket structure can be used. The entire container can also be heated by providing a plate heater outside the container and piping to circulate the liquid. It is preferable to provide a stirring blade inside the container and stir using this. The stirring blade preferably has a length that reaches the vicinity of the wall of the container. A scraping blade is preferably provided at the end of the stirring blade in order to renew the liquid film on the vessel wall. Instruments such as a pressure gauge and a thermometer may be installed in the container. Each component is dissolved in a solvent in the container. The prepared dope is cooled and then taken out from the container, or taken out and then cooled using a heat exchanger or the like.

  A solution can also be prepared by a cooling dissolution method. In the cooling dissolution method, the polymer can be dissolved in an organic solvent that is difficult to dissolve by a normal dissolution method. In addition, even if it is a solvent which can melt | dissolve a polymer with a normal melt | dissolution method, there exists an effect by which a uniform solution can be obtained rapidly according to a cooling melt | dissolution method. In the cooling dissolution method, first, a polymer is gradually added to an organic solvent with stirring at room temperature. The amount of the polymer is preferably adjusted so as to be contained in the mixture in an amount of 10 to 40% by mass. The amount of the polymer is more preferably 10 to 30% by mass. Furthermore, you may add the arbitrary additive mentioned later in a mixture.

  Next, the mixture is cooled to -100 to -10 ° C, preferably -80 to -10 ° C, more preferably -50 to -20 ° C, and most preferably -50 to -30 ° C. The cooling can be performed, for example, in a dry ice / methanol bath (−75 ° C.) or a cooled diethylene glycol solution (−30 to −20 ° C.). Upon cooling in this way, the mixture of polymer and organic solvent solidifies. The cooling rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and most preferably 12 ° C./min or more. The cooling rate is a value obtained by dividing the difference between the temperature at the start of cooling and the final cooling temperature by the time from the start of cooling to the final cooling temperature.

  Furthermore, when this is heated to 0 to 200 ° C., preferably 0 to 150 ° C., more preferably 0 to 120 ° C., and most preferably 0 to 50 ° C., the polymer dissolves in the organic solvent. The temperature may be increased by simply leaving it at room temperature or in a warm bath. The heating rate is preferably 4 ° C./min or more, more preferably 8 ° C./min or more, and most preferably 12 ° C./min or more. The heating rate is the value obtained by dividing the difference between the temperature at which heating starts and the final heating temperature by the time from the start of heating until the final heating temperature is reached. is there. A uniform solution is obtained as described above. If the dissolution is insufficient, the cooling and heating operations may be repeated. Whether or not the dissolution is sufficient can be determined by merely observing the appearance of the solution with the naked eye.

  In the cooling dissolution method, it is desirable to use a sealed container in order to avoid moisture mixing due to condensation during cooling. In the cooling and heating operation, when the pressure is applied during cooling and the pressure is reduced during heating, the dissolution time can be shortened. In order to perform pressurization and decompression, it is desirable to use a pressure-resistant container. In addition, according to differential scanning calorimetry (DSC), a 20 mass% solution obtained by dissolving cellulose acetate (acetylation degree: 60.9%, viscosity average polymerization degree: 299) in methyl acetate by a cooling dissolution method was 33. There exists a quasi-phase transition point between a sol state and a gel state in the vicinity of ° C., and a uniform gel state is obtained below this temperature. Therefore, it is necessary to keep the solution at a temperature equal to or higher than the pseudo phase transition temperature, preferably about 10 ° C. plus the gel phase transition temperature. However, this pseudo phase transition temperature varies depending on the degree of acetylation of cellulose acetate, the degree of viscosity average polymerization, the concentration of the solution, and the organic solvent used.

  A polymer film is formed from the prepared polymer solution (dope) by a solvent cast method. The dope is cast on a drum or band and the solvent is evaporated to form a film. The concentration of the dope before casting is preferably adjusted so that the solid content is 18 to 35%. The surface of the drum or band is preferably processed into a mirror surface state. The casting and drying methods in the solvent casting method are described in U.S. Pat. Nos. 2,336,310, 2,367,603, 2,429,078, 2,429,297, 2,429,978, 2,607,704, 2,739,69, British Patent 6,407,331, No. 736892, JP-B Nos. 45-4554, 49-5614, JP-A-60-176834, No. 60-203430, and No. 62-1115035. The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less. After casting, it is preferable to dry it by applying air for 2 seconds or more. The obtained film can be peeled off from the drum or band, and further dried by high-temperature air whose temperature is successively changed from 100 to 160 ° C. to evaporate the residual solvent. The above method is described in Japanese Patent Publication No. 5-17844. According to this method, it is possible to shorten the time from casting to stripping. In order to carry out this method, it is necessary for the dope to gel at the surface temperature of the drum or band during casting.

(Plasticizer)
A plasticizer can be added to the polymer film in order to improve mechanical properties or increase the drying speed. As the plasticizer, phosphoric acid ester or carboxylic acid ester is used. Specifically, detailed compounds and the like can be mentioned on page 16 of the Japan Institute of Invention Disclosure Technical Report (Public Technical Number 2001-1745, published on March 15, 2001, Japan Institute of Invention). The addition amount of the plasticizer is preferably 0.1 to 25% by mass of the amount of cellulose ester, more preferably 1 to 20% by mass, and most preferably 3 to 15% by mass.

  Specifically, the following materials are preferably used as the plasticizer.

  As these preferably added plasticizers, phosphate esters or carboxylic acid esters are 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 diethylhexyl phthalate (DEHP). Examples of citrate esters include triethyl O-acetyl citrate (OACTE) and tributyl O-acetyl citrate (OACTB), acetyl triethyl citrate, acetyl tributyl citrate. These preferred plasticizers are liquid except for TPP (melting point: about 50 ° C.) at 25 ° C. and have a boiling point of 250 ° C. or higher.

  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, butyl phthalyl butyl glycolate, methyl phthalyl methyl glycolate, propyl phthalyl Examples include propyl glycolate, butyl phthalyl butyl glycolate, and octyl phthalyl octyl glycolate. Of these, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, tributyl phosphate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, diethyl hexyl phthalate, triacetin, and ethyl phthalyl ethyl glycolate are preferable. In particular, triphenyl phosphate, diethyl phthalate, and ethyl phthalyl ethyl glycolate are preferable. These plasticizers may be used alone or in combination of two or more.

(Retardation increasing agent)
In order to adjust the retardation of the polymer film, a method of applying an external force such as stretching is generally used. A retardation increasing agent for adjusting optical anisotropy is optionally added. In order to adjust the retardation of the cellulose acylate film, an aromatic compound having at least two aromatic rings is preferably used 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 cellulose acylate. Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic heterocyclic ring in addition to the aromatic hydrocarbon ring. Examples thereof include compounds described in European Patent 0911656A2, JP-A Nos. 2000-1111914 and 2000-275434. The molecular weight of the retardation increasing agent is preferably 300 to 800. Examples of the retardation increasing agent include compounds described in JP-A-2005-104148.

(Ultraviolet ray prevention agent, deterioration prevention agent)
Deterioration inhibitors (eg, antioxidants, peroxide decomposers, radical inhibitors, metal deactivators, acid scavengers, amines) and UV inhibitors may be added. Examples of the UV inhibitor and the deterioration inhibitor include compounds described in JP-A-2005-104148.

  Furthermore, various additives (for example, fine particles, release agents, antistatic agents, infrared absorbers, etc.) can be added to the polymer film of the present invention, and these may be solid or oily. But you can. Moreover, when a film is formed from a multilayer, the kind and addition amount of the additive of each layer may differ. For these details, the materials described in detail on pages 17 to 22 of the technique No. 2001-1745 described above are preferably used. The amount of these additives to be used is not particularly limited as long as the amount of each material is manifested, but it is preferably used in the range of 0.001 to 20% by mass in the entire polymer film composition.

  The retardation of the polymer film can be further adjusted by stretching treatment. The draw ratio is preferably 3 to 100%. The thickness of the polymer film is preferably 30 to 200 μm, more preferably 40 to 120 μm.

[Alkaline saponification]
The method for alkali saponification of a polymer film of the present invention comprises a coating step of applying an alkaline aqueous solution to the polymer film, a saponification reaction step of saponifying the polymer film with the alkaline aqueous solution applied in the coating step, and stopping the saponification reaction step. A reaction stopping step and a washing step of washing an alkaline aqueous solution with a washing liquid, and a step of heating to room temperature or higher in advance, a step of applying an alkaline aqueous solution to a polymer film, and a step of maintaining the temperature of the polymer film above room temperature An alkali saponification treatment is performed. It is preferable to carry out these steps and the steps before and after that while transporting the polymer film.

  Any conventionally known method may be used for the saponification treatment of the polymer film using an aqueous alkali solution. For example, a dipping method, a spraying method, a coating method, and the like can be given. In particular, when only one surface of the film is uniformly saponified without unevenness, a coating method is preferable. As a coating method, a conventionally known coating method can be used as described later.

  In the present invention, the cleaning liquid needs to contain at least a surfactant. Then, with respect to the hydrophobic component extracted from the polymer film in the saponification treatment solution after the saponification reaction step, the addition amount of the surfactant contained in the cleaning solution contains at least the surfactant is 0. It is important that it is 5 times or more and 5.0 times or less.

  Here, the hydrophobic component refers to a substance having a weak interaction with water and a weak affinity (standard chemical terminology second edition). Although the polymer film is not dissolved by the organic solvent in the alkaline aqueous solution, the additive substance in the polymer film may be extracted. Since the extracted additive substance is a hydrophobic substance, it affects the alignment film to be applied later, the coating film formation of the liquid crystalline molecular layer, and the alignment of liquid crystal molecules. It is effective to improve the quality / characteristics of an optical film using a polymer film by reducing the amount of the additive substance extracted from the polymer film, particularly the amount of the hydrophobic substance extracted.

  An experiment was conducted to investigate the relationship between the amount of hydrophobic substance extracted in the saponification solution and the occurrence of white turbidity caused by the aggregation of the extract on the polymer film. As described above, the polymer film contains a hydrophobic additive such as a retardation increasing agent for adjusting optical anisotropy, a plasticizer, an ultraviolet ray preventing agent and a deterioration preventing agent.

The total extraction amount of 1 m ² of the hydrophobic component polymer film contained in the saponification solution after the saponification reaction step was measured. Hydrophobic components include triphenyl phosphate (TPP) used as a plasticizer, biphenyl diphenyl phosphate (BDP) used as a plasticizer, and (L004) used as a retardation increasing agent. ing.

  The saponification treatment of the present invention includes at least a step of heating in advance to room temperature or higher, a step of applying an alkaline aqueous solution to the polymer film, a step of maintaining the temperature of the polymer film at room temperature or higher and an appropriate humidity, and an aqueous alkaline solution from the polymer. It consists of carrying out an alkali saponification process by a washing-off process. In addition, in order to remove dust and to make the wettability of the film surface more uniform before the step of heating the polymer film to room temperature or higher in advance, or the step of applying the alkaline aqueous solution to the polymer film, These methods that can also carry out dust removal treatment or wet treatment can use generally known methods. Examples of the charge removal method include the method described in JP-A-62-1131500 and the dust removal method. Can include the method described in JP-A-2-43157. In the step of heating the polymer film to room temperature or higher in advance, impact of warm / hot air, contact heat transfer using a heating roll, induction heating using microwaves, or radiant heat heating using an infrared heater can be preferably used. In particular, contact heat transfer using a heating roll is preferable in terms of high heat transfer efficiency and a small installation area, and fast rise in film temperature at the start of conveyance. A general double jacket roll or electromagnetic induction roll (manufactured by Tokuden) can be used. The film surface temperature after heating is preferably 30 ° C. or higher and 50 ° C. or lower, more preferably 35 ° C. or higher and 50 ° C. or lower, and most preferably 40 ° C. or higher and 50 ° C. or lower.

In the process of applying alkaline aqueous solution to polymer film, die coater (extrusion coater, slide coater), roll coater (forward roll coater, reverse roll coater, gravure coater), rod coater (rod wrapped with thin metal wire) It 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 aqueous alkali solution is desirably not excessively large considering the extraction amount of the hydrophobic component by the organic solvent, preferably 8 g / m ² or more and 16 g / m ² or less, and 8 g / m ² or more and 12 g / m. ² or less is more preferable. A rod coater, gravure coater, blade coater, and die coater that can be stably operated even in a small coating amount range are particularly preferred. Moreover, it is preferable to apply the aqueous alkaline solution to the lower surface of the polymer film in order to easily wash off the aqueous alkaline solution after applying the aqueous alkaline solution and saponifying the polymer film. It is preferable to suppress the variation in the coating amount to less than 30% with respect to the width direction of the polymer film and the coating time. Moreover, a continuous application method can also be adopted. In the present invention, the polymer film is preferably saponified in an atmosphere having an oxygen concentration in the range of 0 to 18%. The oxygen concentration is more preferably 0 to 15%, and most preferably 0 to 10%. By applying a saponification coating solution (alkaline aqueous solution) under a low oxygen concentration, the surface characteristics of the film can be controlled, and a surface with high adhesion can be obtained. The gaseous component other than oxygen in the atmosphere is preferably an inert gas (eg, nitrogen, helium, argon), and particularly preferably nitrogen.

  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 polymer 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.

  The temperature of the alkaline aqueous solution is desirably equal to the reaction temperature (= the temperature of the polymer film). Depending on the type of organic solvent used, the reaction temperature may exceed the boiling point of the alkaline aqueous solution. In order to perform stable coating, the temperature is preferably lower than the boiling point of the aqueous alkali solution, more preferably 5 ° C. lower than the boiling point, and most preferably 10 ° C. lower than the boiling point. .

  In the alkali saponification method of the present invention, the temperature of the polymer film is kept at room temperature or higher until the saponification reaction is completed after applying the alkaline aqueous solution. In the present invention, room temperature is 15 ° C. The means for heating is selected considering that one side of the polymer film is wet with an alkaline aqueous solution. Collision of hot air with the opposite surface of the coating, contact heat transfer with a heating roll, induction heating with microwaves, radiant heat heating with an infrared heater, etc. can be preferably used. Infrared heaters are preferable because they can be heated without contact and without the flow of air, so that the influence on the surface to which the alkaline 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 polymer film may be the same as or different from the temperature heated before application of the alkaline aqueous solution. Further, the temperature may be changed continuously or stepwise during the saponification reaction. The film surface temperature is preferably 30 ° C. or higher and 50 ° C. or lower, more preferably 35 ° C. or higher and 50 ° C. or lower, and most preferably 40 ° C. or higher and 50 ° C. or lower. For the detection of the film temperature, a commercially available non-contact infrared thermometer can be used, and feedback control may be performed on the heating means in order to control the temperature within the above range.

  The dew point temperature during the saponification reaction step is preferably in the range of 10 ° C. (DP) to 25 ° C. (DP), more preferably 12 ° C. (DP) to 23 ° C. (DP), and 14 ° C. ( Most preferred is DP) or higher and 21 ° C. (DP) or lower.

  The wind speed during the saponification reaction step is preferably in the range of 0.3 m / second to 1.0 m / second, and most preferably 0.5 m / second to 1.0 m / second.

  The time for which the alkaline aqueous solution is applied and kept in the temperature range before washing off depends on the conveying speed described later, but is preferably maintained for 10 seconds to 30 seconds.

  It is preferable to carry out each step treatment while carrying the polymer film to carry out an alkali saponification treatment. The conveyance speed of the polymer film is determined by the combination of the composition of the alkaline aqueous solution and the coating method. Generally, 10 to 500 m / min is preferable, and 20 to 300 m / min is more preferable, but in the present invention, it is possible to cope with 100 m / min or more.

  Further, as the liquid property of the alkali saponification solution, the absorbance of the liquid at a measurement wavelength of 400 nm is preferably less than 2.0. It is necessary to determine the size of the liquid feeding system and the coater so that the additive in the polymer film is extracted at the time of coating so that the absorbance of the liquid does not increase. If a liquid having a high absorbance is used, the additive of the polymer film dissolved in the liquid adheres to the polymer film and causes a bright spot failure. For controlling the absorbance of the alkaline saponification 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. A method of directly putting activated carbon into an alkaline aqueous solution tank or a method of circulating a saponification solution between a saponification solution tank and a purifier filled with activated carbon may be used.

  There are the following methods for stopping the saponification reaction between the aqueous alkali solution and the polymer film. The first method is a method of diluting the applied alkaline aqueous solution to lower the alkali concentration and reducing the reaction rate, and the second method is to lower the temperature of the polymer film coated with the alkaline aqueous solution, The third method is a method of neutralizing with an acidic liquid. As another method, a bar (rod) may be brought into contact with the application surface to scrape off the alkaline aqueous solution.

  In order to dilute the applied alkaline aqueous solution, a method of applying a dilution solvent, a method of spraying the dilution solvent, and a method of immersing the polymer film in a container containing the dilution solvent can be employed. The method of applying the diluting solvent and the method of spraying are preferable methods for carrying out the continuous transportation of the polymer film. The method of applying the diluting solvent is most preferable because it can be carried out using the minimum necessary amount of diluting solvent.

  The application of the diluting solvent is desirably a system that can be continuously applied so that the diluting solvent can be applied again onto the polymer film already coated with the alkaline aqueous solution. For the application, the same die coater (extrusion coater, slide coater), roll coater (forward roll coater, reverse roll coater, gravure coater) and rod coater as described in the application step of the alkaline aqueous solution can be preferably used. In order to reduce the alkali concentration by quickly mixing the aqueous alkali solution and the diluting solvent, the flow is more laminar than the die coater where the diluting solvent is applied (sometimes called coating beads). A roll coater or a rod coater in which the flow is not uniform is preferable.

  The purpose of the diluting solvent is to lower the alkali concentration, so it must be a solvent that dissolves the alkaline agent in the alkaline aqueous solution. Therefore, it is preferable to use water or a mixed solution of an organic solvent and water, and two or more organic solvents may be mixed and used. The organic solvent used in the alkali saponification solution described above can be used advantageously. A preferred solvent is water.

  The coating amount of the dilution solvent is determined according to the concentration of the alkaline 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 1.5 to 10 times the original alkali concentration, and more preferably 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, mixing of the alkaline aqueous solution and the diluting solvent occurs, and the mixed liquid is recoated. Therefore, in this case, since the dilution rate cannot be specified by the application amount of the dilution solvent, it is necessary to measure the alkali concentration after application of the dilution solvent. Also in the roll coater and the rod coater, the coating amount is preferably diluted 1.5 to 10 times the original alkali concentration, more preferably 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, sulfuric acid, phosphoric acid, chromic acid, methanesulfonic acid and citric acid are particularly preferred.

  In order to neutralize the applied aqueous alkali solution with an acid, a method of applying an acid solution, a method of spraying an acid solution, or a method of immersing the polymer film together in a container containing the acid solution can be employed. The method of applying the acid solution and the method of spraying are preferable for carrying out the continuous transportation of the polymer film. The method of applying the acid solution is most preferable because it can be carried out using the minimum necessary acid solution.

  It is desirable that the acid solution is applied in such a manner that the acid solution can be reapplied on the polymer film on which the alkaline aqueous solution has already been applied. Application is the same die coater (extrusion coater, slide coater), roll coater (forward roll coater, reverse roll coater, gravure coater), rod coater (rod wrapped with a thin metal wire) as described in the coating step. It can be preferably used. In order to reduce the alkali concentration by quickly mixing the aqueous alkali solution and the diluting solvent, the flow is more laminar than the die coater where the diluting solvent is applied (sometimes called coating beads). A roll coater or a rod coater in which the flow is not uniform is preferable.

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

  The temperature of the polymer film can be lowered to stop the saponification reaction. 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 polymer film is determined taking into consideration that one side of the polymer 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.

  The cleaning step is performed in order to remove the alkaline aqueous solution with the cleaning liquid. If the alkaline aqueous solution remains, not only the saponification reaction proceeds, but also affects the alignment film and the coating film formation of the liquid crystalline molecular layer and the alignment of the liquid crystal molecules.

  In the present invention, a surfactant is contained in the cleaning liquid. By including a surfactant in the cleaning liquid, the hydrophobic component extracted from the polymer film can be effectively cleaned. This hydrophobic component can be washed off by adding a surfactant to the cleaning solution. Furthermore, the hydrophobic component is added to the cleaning solution with respect to the proportion of the hydrophobic component extracted from the polymer film in the saponification treatment solution after the saponification reaction step. When the amount of the surfactant contained is 0.5 times or more and 5.0 times or less, poor cleaning in the cleaning process can be suppressed. Here, the “saponification solution” refers to an alkaline aqueous solution after the polymer film is saponified with an alkaline aqueous solution.

  That is, at least the surfactant is contained in the cleaning liquid, and the addition amount of the surfactant contained in the cleaning liquid is 0 with respect to the hydrophobic component extracted from the polymer film in the saponification treatment liquid after the saponification reaction step. When the ratio is 5 times or more and 5.0 times or less, there is no cleaning failure in the cleaning process, and the deterioration of the surface characteristics of the polymer film can be prevented. Accordingly, the present invention provides an alkali saponification method of a polymer film that does not affect the formation of a coating film of a liquid crystal molecular layer and a liquid crystal molecule layer and the orientation of liquid crystal molecules by extracting a hydrophobic component from the polymer film. Can do.

  Cleaning can be performed by a method of applying a cleaning solution, a method of spraying the cleaning solution, or a method of immersing the polymer film in a container containing the cleaning solution. The method of applying the cleaning liquid and the method of spraying are preferable for carrying out the continuous conveyance of the polymer film. The method of spraying the cleaning liquid is particularly preferable because turbulent mixing of the cleaning liquid on the polymer film and the alkaline coating liquid can be obtained by a jet.

  The cleaning liquid 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 air humidification, painting, or automatic tank cleaning. 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 polymer 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.

  Higher turbulent mixing is obtained when the cleaning liquid spray speed is higher. However, if the speed is high, the transport stability of the polymer film that is continuously transported 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 amount of water used for cleaning with the cleaning liquid is an amount exceeding the theoretical dilution rate defined below. Theoretical dilution ratio = amount of washing water used [cc / m ² ] ÷ amount of coating of alkaline saponification solution [cc / m ² ], that is, all of the water used for washing contributed to the dilution and mixing of the alkaline coating solution. Define the assumed theoretical dilution factor. In practice, since complete mixing does not occur, a washing water amount exceeding the theoretical dilution rate is used. Although depending on the alkali concentration of the alkaline coating solution used, the secondary additives, and the type of the solvent, a theoretical dilution of at least 100 to 1000 times, preferably 500 to 10,000 times, more preferably 1000 to 100,000 times is obtained. Use flush water.

  It is preferable to control the variation in the spray amount of the cleaning liquid to less than 30% with respect to the width direction of the traveling polymer film and the coating time. However, at both ends in the width direction of the polymer film, it often occurs that the coating amount of the alkaline aqueous solution or the coating amount of the acid solution used for neutralization is large. In order to ensure the cleanability of the portion where the coating amount is large, the amount of cleaning liquid sprayed at both ends in the width direction can be increased. When using a coating head, the clearance of the slit from which the cleaning liquid is discharged is set so as to increase the flow rate at both ends. In addition, a coater having a narrow width may be separately provided in order to locally supply the cleaning liquid film to both ends. Multiple coaters with a narrow width can be installed. Also when using a spray nozzle, a nozzle for locally spraying water is installed at both ends.

  In the washing, a batch washing method in which the whole amount is applied at a time and divided into several times is preferable. That is, the amount of the cleaning liquid is divided into several parts and supplied to a plurality of cleaning means installed in tandem in the transport direction of the polymer film. An appropriate time (distance) is provided between one cleaning means and the next cleaning means, and the dilution of the alkaline coating liquid by diffusion proceeds. More preferably, if the polymer film to be conveyed is provided with an inclination so that 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 cleaning dilution efficiency can be further enhanced by providing a cleaning liquid cutting means for removing the cleaning liquid film on the polymer film between the cleaning means and the cleaning means. Specific cleaning liquid cutting means include a blade used for a blade coater, an air knife used for an air knife coater, a rod used for a rod coater, and a roll used for a roll coater. A larger number of cleaning means arranged in tandem is advantageous. However, from the viewpoint of installation space and equipment cost, usually 2 to 10 stages, preferably 2 to 5 stages are used.

  The thickness of the cleaning liquid film after the cleaning liquid cutting means is preferably thin, but the minimum cleaning liquid film thickness is limited depending on the type of the cleaning liquid cutting means used. In methods such as blades, rods, and rolls that physically contact a solid with a polymer film, even if the solid is an elastic body with low hardness such as rubber, the film surface is scratched or the elastic body is polished. Therefore, it is necessary to leave a finite cleaning liquid film as a lubricating fluid. Usually, a cleaning liquid film of several μm or more, preferably 10 μm or more is left as a lubricating fluid.

  An air knife is preferable as the cleaning liquid cutting means that can reduce the cleaning liquid film thickness to the limit. By setting a sufficient air volume and air pressure, the thickness of the cleaning liquid film 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 polymer film, such as flapping and deviation, so there is a preferable range. Although depending on the original cleaning liquid film thickness on the polymer film and the film transport speed, a wind speed of 10 to 500 m / sec, preferably 20 to 300 m / sec, more preferably 30 to 200 m / sec is used. In order to remove the water film uniformly, the air supply to the air knife outlet and the air knife should be adjusted so that the wind speed distribution in the width direction of the polymer film is usually within 10%, preferably within 5%. adjust. The narrower the gap between the surface of the polymer film to be conveyed and the air knife outlet, the better the ability to cut the cleaning liquid, but there is an appropriate range because the possibility of damage due to contact with the polymer film increases. Usually, an air knife is installed with a gap of 10 μm to 10 cm, preferably 100 μm to 5 cm, more preferably 500 μm to 1 cm. Furthermore, by setting a backup roll on the side opposite to the cleaning surface of the polymer 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. Therefore, it is preferable.

  In the alkali saponification method of the polymer film of the present invention, the liquid temperature of the cleaning liquid in the cleaning step is preferably 30 ° C. or higher and 60 ° C. or lower. This regulates the mobility of the surfactant, and when the temperature of the cleaning liquid is 30 ° C. or more and 60 ° C. or less, the hydrophobic component extracted from the remer film can be effectively washed. it can.

  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 the polymer film is wound into a roll, it is heated and dried to adjust to a preferred moisture content. 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.

  In the alkaline saponification method of the present invention, the functional layer can be applied continuously after the saponification reaction step described above. By applying saponification treatment on one side by coating and coating the functional layer on it, even if the film is wound into a roll after providing the functional layer, it is between the functional layer surface and the opposite surface of the film. It can prevent sticking.

"Alkaline aqueous solution"
The alkaline aqueous solution used for the saponification treatment of the present invention will be described. The aqueous alkali solution of the present invention can be prepared by dissolving an alkali in water or a mixture of an organic solvent and water. Preferred organic solvents are one or more selected from alcohols having 8 or less carbon atoms, ketones having 6 or less carbon atoms, esters having 6 or less carbon atoms, and polyhydric alcohols having 6 or less carbon atoms. It is an organic solvent.

[Organic solvent]
The solvent of the alkaline aqueous solution of the present invention comprises a mixed solution of water and an organic solvent. Any organic solvent that is miscible with water can be used. Among them, preferred organic solvents are those having an inorganic / organic value (I / O value) of 0.5 or more and a solubility parameter in the range of 16 to 40 [mJ / m ³ ] 1/2. More preferably, the I / O value is 0.6 to 10 and the solubility parameter is 18 to 31 [mJ / m ³ ] 1/2. If the I / O value is more inorganic than this range or the solubility parameter is low, the alkali saponification rate decreases and the overall uniformity of the saponification degree is unsatisfactory. On the other hand, when the I / O value is on the organic side of the above range or the solubility parameter is highly soluble, the saponification rate is fast, but haze is likely to occur. Dissatisfied. Examples of organic solvents that have solubility parameters and I / O values within the above ranges and can be preferably used in the present invention include the following solvents.

  The organic solvent is described in the new edition solvent pocket book (Ohm, published in 1994). Specific examples of the organic solvent include monohydric alcohols (eg, methanol, ethanol, n-propanol, isopropanol, n-butanol, isopropanol). Butanol, 2-butanol, cyclohexanol, benzyl alcohol, fluorinated alcohol, etc.), ketones (eg, acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.), esters (eg, methyl acetate, ethyl acetate, butyl acetate, etc.), polyhydric alcohols (Eg, ethylene glycol, diethylene glycol, propylene glycol, glycerin, etc.), amides (eg, N, N-dimethylformamide, dimethylformamide), sulfoxides (eg, dimethylsulfoxide) and ethers (eg, methyl cellulose) Cellosolve, ethylene glycol diethyl ether) and the like. Particularly preferred are methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, 2-butanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl acetate, ethyl acetate, ethylene glycol, diethylene glycol, propylene glycol, glycerin. is there.

  The organic solvent must not dissolve or swell the polymer film. It is also desirable to select an organic solvent having a moderately low surface tension as described in the section of the liquid physical properties of the alkaline aqueous solution so that the application of the alkaline saponification solution is facilitated. Moreover, the usage-amount in the solvent of an organic solvent is determined according to the kind of solvent, miscibility (solubility) with water, reaction temperature, and 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 solvent concentration is too high, components (plasticizer, etc.) in the polymer film may be extracted or the film may swell excessively, so that the selection is appropriately made. The mixing ratio of water and organic solvent is preferably 3/97 to 85/15 mass ratio. More preferably, it is 5 / 95-60 / 40 mass ratio, More preferably, it is 15 / 85-40 / 60 mass ratio. In this range, the entire film surface can be easily saponified uniformly without impairing the optical properties of the film.

[Alkaline agent]
Either an inorganic base or an organic base can be used as the alkaline agent in the alkaline aqueous solution. Strong bases are preferred for carrying out saponification reactions at low concentrations. Alkali metal hydroxides (eg, NaOH, KOH, LiOH), amines (eg, perfluorotributylamine, triethylamine, diazabicyclononene, diazabicycloundecene, etc.), tetraalkylammonium hydroxides (as alkyl groups, Methyl group, ethyl group, propyl group, butyl group, etc.) and free bases of complex salts (eg, [Pt (NH3) 6] (OH) 4) are preferred, alkali metal hydroxides are more preferred, NaOH and KOH Is most preferred.

  The concentration of the aqueous alkali solution is determined according to the type of alkali 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 aqueous alkali solution is impaired, and it may precipitate during long-time application. The concentration of the alkaline aqueous solution is preferably 0.1 to 5 N (N), more preferably 0.5 to 5N, and most preferably 0.5 to 3N.

The high-concentration alkaline aqueous solution absorbs CO ₂ in the environmental atmosphere and becomes carbonic acid in the solution to lower the pH and easily generate carbonate precipitates. Therefore, the CO ₂ concentration in the environmental atmosphere is preferably 5000 ppm or less. In order to suppress the absorption of CO _{2 in} the environmental atmosphere, it is more preferable that the coating solution coater of the alkaline aqueous solution has a semi-sealed structure, or is covered with organic solvent saturated vapor of dry air, inert gas or alkaline aqueous solution.

[Surfactant]
The alkaline aqueous solution of the present invention can also contain a surfactant. By adding the surfactant, even if the organic solvent extracts the film-containing material, it is stably present in the alkaline aqueous solution, and the extracted material does not precipitate and solidify in the subsequent water washing step. The concentration of the surfactant is set so that the hydrophobic additive extracted from the polymer film into the aqueous alkaline solution can be stably dispersed. If the organic solvent used in the alkaline aqueous solution does not dissolve or swell the polymer film, the additive extracted from the film is only from the vicinity of the film surface. The extraction amount of the hydrophobic additive is estimated to be 1% by mass at the maximum in the application amount of the alkaline aqueous solution of 1 to 50 cc / m ² applied in the present invention. It was found that sufficient dispersion characteristics can be obtained by adding 10% by mass of the surfactant concentration, which is 10 times the extraction amount. 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 hinder the bonding (adhesion) between the film and the alignment film when the alignment film is applied on the polymer film later. is there. 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. 0.1-10 mass% is preferable and, as for the addition density | concentration of surfactant, 0.5-5 mass% is more preferable. 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, ionic surfactants (anions, cations, amphoteric surfactants) and the like 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 singly or in combination with one or more different anionic surfactants or nonionic surfactants, or a combination of anionic and nonionic surfactants.

  Hereinafter, the surfactants that can be used in the present invention will be sequentially described.

(Nonionic surfactant)
Examples of nonionic surfactants include 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, fat Diethanolamides, N, N-bis-2-hydroxyalkylamines, polyoxyethylene alkylamines, triethanolamine fatty acid esters, trialkylamine oxides and the like.

  Preferable nonionic surfactants include compounds represented by the following general formula (1).

General formula (1) R1-L1-Q1
In the formula, R1 represents a linear or branched alkyl group having 8 or more carbon atoms (which may have a substituent), preferably an alkyl group having 8 to 22 carbon atoms, particularly preferably 10 to 10 carbon atoms. 18 alkyl groups. The alkyl group may have a suitable substituent. Examples of the substituent include a halogen atom, aryl group, heterocyclic group, alkoxyl group, aryloxy group, alkylthio group, arylthio group, acyl group, hydroxyl group, acyloxy group, amino group, alkoxycarbonyl group, acylamino group, oxycarbonyl Group, carbamoyl group, sulfonyl group, sulfamoyl group, sulfonamido group, sulfolyl group, carboxyl group and the like. L1 represents a group for linking RI and Q1, and represents a direct bond or a divalent linking group, preferably a single bond, —O—, —CO—, —NR11—, —S—, —SO ₂ —, It is a divalent linking group formed by —PO (OR12) —, an alkylene group, an arylene group or a combination thereof. Here, R11 represents a hydrogen atom, an alkyl group, an aryl group, or an aralkyl group. R12 represents an alkyl group, an aryl group, or an aralkyl group. L1 preferably contains a direct bond, —O—, —CO—, —NR11—, —S—, —SO ₂ —, an alkylene group, or an arylene group, and —CO—, —O—, —NR11— , An alkylene group, or an arylene group is particularly preferable. When L1 contains an alkylene group, the alkylene group preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and particularly preferably 1 to 6 carbon atoms. Specific examples of particularly preferred alkylene groups include methylene, ethylene, trimethylene, tetrabutylene, hexamethylene groups and the like. When L1 contains an arylene group, the carbon number of the arylene group is preferably 6 to 24, more preferably 6 to 18, and particularly preferably 6 to 12. Specific examples of particularly preferred arylene groups include phenylene and naphthalene groups. When L1 contains a divalent linking group (that is, an aralkylene group) obtained by combining an alkylene group and an arylene group, the carbon number of the aralkylene group is preferably 7 to 34, more preferably 7 to 26, and particularly preferably. 7-16. Specific examples of particularly preferred aralkylene groups include a phenylenemethylene group, a phenyleneethylene group, and a methylenephenylene group. The group exemplified as L1 may have an appropriate substituent. Examples of such a substituent include the same substituents as those described above as the substituent for R11. Q1 represents a nonionic hydrophilic group.

More preferably, the compound represented by General formula (2) is mentioned.
General formula (2) R2-L2-Q2
In the formula, R2 and L2 respectively represent the same contents as R1 and L1 in formula (1). Q2 is preferably a nonionic hydrophilic group selected from a polyoxyethylene unit (polymerization degree of 5 to 150), a polyglycerin unit (polymerization degree of 3 to 30), and a hydrophilic sugar chain unit. In particular, hydrophilic sugar chain units such as glucose, arabinose, fructose, sorbitol, and mannose are preferred in addition to polyoxyethylene units having a polymerization degree of 10-50 and polyglycerin units having a polymerization degree of 5-15.

  Specifically, polyethylene glycol, polyoxyethylene lauryl ether, polyoxyethylene nonyl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene behenyl ether, polyoxyethylene polyoxypropylene Cetyl ether, polyoxyethylene polyoxypropylene behenyl ether, polyoxyethylene phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene stearylamine, polyoxyethylene oleylamine, polyoxyethylene stearamide, polyoxyethylene oleic acid amide, Polyoxyethylene castor oil, polyoxyethylene ethylene abiethyl ether, polyoxy Ethylene nonine ether, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene glyceryl monooleate, polyoxyethylene glyceryl monostearate, polyoxyethylene propylene glycol monostearate, oxyethylene oxypropylene block polymer, Examples include distyrenated phenol polyethylene oxide adducts, tribenzylphenol polyethylene oxide adducts, octylphenol polyoxyethylene polyoxypropylene adducts, glycerol monostearate, sorbitan monolaurate, polyoxyethylene sorbitan monolaurate, and the like. The mass average molecular weight of these nonionic surfactants is preferably from 300 to 50,000, particularly preferably from 500 to 5,000.

(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, linear alkyl benzene sulfonic acid salts, and branched alkyl benzene. Sulfonates, alkylnaphthalenesulfonates, alkylphenoxypolyoxyethylenepropylsulfonates, polyoxyethylenealkylsulfophenyl ether salts, N-methyl-N-oleyl taurine sodium salt, N-alkylsulfosuccinic acid monoamide disodium salt , Petroleum sulfonates, sulfated beef tallow oil, sulfate esters of fatty acid alkyl esters, alkyl sulfate esters, polyoxyethylene alkyl ether sulfate esters, fatty acids Noglyceride sulfates, polyoxyethylene alkylphenyl ether sulfates, polyoxyethylene styrylphenyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkylphenyl ether phosphates Preferable examples include salts, partially saponified products of styrene / maleic anhydride copolymer, partially saponified products of olefin / maleic anhydride copolymer, and naphthalene sulfonate formalin condensates.

Preferable anionic surfactants include compounds in which Q1 represents an anionic group in the general formula (1). More preferred examples include compounds represented by the following general formula (3).
General formula (3) R3-L3-Q3
In the formula, R3 represents a linear or branched alkyl group having 8 or more carbon atoms (which may have a substituent), preferably an alkyl group having 8 to 22 primaries, particularly preferably 10 to 10 18 alkyl groups. The alkyl group may have a suitable substituent. Examples of the substituent include a halogen atom, aryl group, heterocyclic group, alkoxyl group, aryloxy group, alkylthio group, arylthio group, acyl group, hydroxyl group, acyloxy group, amino group, alkoxycarbonyl group, acylamino group, oxycarbonyl Group, carbamoyl group, sulfonyl group, sulfamoyl group, sulfonamido group, sulfolyl group, carboxyl group and the like. L3 represents a divalent linking group, and preferably a divalent linking group having a polar partial structure obtained by combining units selected from the following group.

Units: —O—, —CO—, —NR 5 — (R 5 is an alkyl group having 1 to 5 carbon atoms), —OH, —CH═CH—, —SO ₂ —,
Specifically, the structure may be selected so as to always include at least one of the above units in L3 in the general formula (3). Particularly preferred is a case where the polar partial structure has an ester group (—COO—, —OCO—), an amide group (—CONR 5 —, —NR 5 CO—), a hydroxyl group (—OH), or —CH═CH—. Q3 represents an anionic hydrophilic group, preferably -COOM, -OSO3M, -P (= O ) (OR21) OM, a is M groups (here represented by -SO ₃ M cation, R21 is M or single Represents an alkyl group having 1 to 3 prime numbers, and —SO ₃ M is particularly preferable. M represents a counter cation of an anionic group, preferably a hydrogen ion, an alkali metal ion (such as lithium, sodium or potassium) or an ammonium ion. Particularly preferred are sodium ion, potassium ion and ammonium ion.

(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.

  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. In addition to these surfactants, a fluorine surfactant containing a perfluoroalkyl group in the molecule may be used in combination. For example, perfluoroalkyl carboxylate, perfluoroalkyl sulfonate, anion type such as perfluoroalkyl phosphate ester, amphoteric type such as perfluoroalkyl betaine, cation type such as perfluoroalkyltrimethylammonium salt, perfluoroalkyl Amine oxide, perfluoroalkyl ethylene oxide adduct, oligomer containing perfluoroalkyl group and hydrophilic group, oligomer containing perfluoroalkyl group and lipophilic group, oligomer containing perfluoroalkyl group, hydrophilic group and lipophilic group, perfluoroalkyl Nonionic types such as a group and a lipophilic group-containing urethane.

  In the alkaline aqueous solution, a nonionic active agent and an anionic active agent or a nonionic active agent and a cationic active agent can be used together.

  The amount of these surfactants added to the aqueous alkali solution is preferably 0.001 to 20% by mass, more preferably 0.01 to 10% by mass, and particularly preferably 0.03 to 3% by mass. %. When the addition amount is less than 0.001% by mass, it is difficult to obtain the effect of adding the surfactant. When the addition amount is more than 20% by mass, the saponification property tends to decrease.

[Defoaming agent]
Further, the alkaline aqueous solution in the present invention preferably contains an antifoaming agent. This additive can be contained in the alkaline aqueous solution at a concentration of preferably 0.001 to 5 mass%, particularly preferably 0.005 to 3 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. In particular, it is effective for processing a long film continuously and rapidly.

  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-t- 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. Amide series, Aluminum stearate, Calcium stearate, Potassium oleate, Wool oleic acid calcium salt and other metal soap series, Sodium lauryl sulfate ester sulfate series, Dimethylpolysiloxane, Methylphenyl Silicone defoaming agents such as resiloxane, methylhydrogen polysiloxane, fluoropolysiloxane, dimethylpolysiloxane and polyalkylene oxide copolymer, and solution type, emulsion type, paste type silicone oil, etc. Can be mentioned.

An organic solvent other than the organic solvents described above can be added to the aqueous alkali solution used in the present invention as a solubilizing agent for the surfactant and antifoaming agent in the aqueous alkali solution. There is no particular limitation as long as it is preferably a solvent having solubility in water. For example, N- phenyl ethanolamine and N- phenyl diethanolamine, fluorinated alcohols _{(e.g., Cn F 2 n + 1 (} CH 2) k OH (n is 3-8 integer, k is an integer of 1 or 2), 1 2,2,3,3-heptafluoropropanol, hexafluorobutanediol, perfluorocyclohexanol, etc.). The content of these organic solvents is preferably 0.1 to 5% with respect to the total mass of the liquid used.

[Antidepressant / Antimicrobial agent]
The alkaline aqueous solution used in the present invention preferably further contains an antifungal agent and / or an antibacterial agent. 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, the disinfectant described in LEWest, “Water Quality Criteria” Phot. Sci. And Eng., Vol 9 No. 6 (1965), JP-A 57-8542, 58-105145, 59-126533. , 55-111942, and 57-157244, “Bacterial and fungicidal chemistry” by Horiguchi Hiroshi, Sankyo Publishing (Sho 57), “Bacterial and fungicidal technology handbook” Chemicals as described in the Japanese Society for Bacteriological Diseases and Gihodo (Sho 61) can be used. The addition amount of these antifungal agents and / or antibacterial agents is preferably 0.01 to 50 g / L, more preferably 0.05 to 20 g / L in the alkaline aqueous solution.

[Other additives]
In addition, you may use another additive together for the alkaline aqueous solution used for this invention. For example, alkaline solution stabilizers (antioxidants and the like) and water-soluble compounds (polyalkylene glycols, natural water-soluble resins and the like) can be mentioned. In the present invention, the additive of the alkaline aqueous solution is not limited to these.

[water]
In addition, as water used for the alkaline aqueous solution, the Japanese Waterworks Law (Act No. 177 of 1957) and the ministerial ordinance on water quality standards based on it (August 31, 1978 Ministry of Health and Welfare Ordinance No. 56), It is preferable to be based on the effects on each element, mineral, etc. in the state of contamination in water specified by the Law No. 125 of July 10, 2011 and its separate table) and the WHO specified tap water standard.

  In order to more reliably achieve the effect of the present invention, it is preferable to use the water described above, and the calcium concentration of the alkaline aqueous solution is preferably 0.001 to 400 mg / L, and 0.001 to 150 mg / L. Is more preferable, and 0.001 to 10 mg / L is particularly preferable. The magnesium concentration is preferably 0.001 to 400 mg / L, more preferably 0.001 to 150 mg / L, and particularly preferably 0.001 to 10 mg / L. It is preferable that other polyvalent metal ions other than calcium and magnesium are not included. The concentration of the polyvalent metal ion is preferably 0.002 to 1000 mg / L. On the other hand, it is preferable that the alkaline aqueous solution does not contain anions such as chloride ions and carbonate ions. The chloride ion concentration is preferably 0.001 to 500 mg / L, more preferably 0.001 to 300 mg / L, and particularly preferably 0.001 to 100 mg / L. Moreover, it is preferable that carbonate ions are not included. The carbonate ion concentration is preferably 0.001 to 3500 mg / L, more preferably 0.001 to 1000 mg / L, and particularly preferably 0.001 to 200 mg / L. In these concentration ranges, generation of insoluble matter in the solution is suppressed.

[Liquid properties of alkaline aqueous solution]
The aqueous alkaline solution used in the present invention is composed of the composition described above, but is preferably adjusted so as to fall within the range of the liquid physical properties described below. The alkaline aqueous solution preferably has a surface tension of 45 mN / m or less and a viscosity of 0.8 to 20 mPa · s. More preferably, the surface tension is 20 to 40 mN / m and the viscosity is 1 to 15 mPa · s. Within this range, the aqueous alkaline solution can be easily applied in a stable manner according to the conveying speed, and the wettability of the liquid on the film surface, the retention of the solution applied on the film surface, and the saponification treatment The alkali liquid is sufficiently removed from the film surface. Moreover, it is preferable that the density of aqueous alkali solution is 0.65-1.05 g / cm < ³ >. More preferably from 0.70~1.00g / cm ^3, and particularly preferably even at 0.75~0.95g / cm3. In this viscosity range, the saponification treatment is uniformly performed without causing wind unevenness due to the wind pressure during conveyance and coating stripes parallel to the conveyance direction due to its own weight. Furthermore, the electrical conductivity of the alkaline aqueous solution of the present invention is preferably 1 mS / cm to 100 mS / cm, more preferably 2 mS / cm to 50 mS / cm, and 3 mS / cm to 50 mS / cm. It is particularly preferred. Within this electric conductivity range, the saponification reaction proceeds uniformly, and the saponification solution after the saponification reaction can be easily removed from the film surface. If the electrical conductivity is less than 1 mS / cm, many bright spot failures occur due to impurities remaining on the film surface after the saponification treatment, and poor adhesion of the optical compensation layer is liable to occur. Further, as the liquid property of the alkali saponification solution, the absorbance of the liquid at a measurement wavelength of 400 nm is preferably less than 2.0.

"Cleaning liquid"
As the water used for the cleaning liquid, as in the case of the alkaline aqueous solution, the Japanese Waterworks Law (Act No. 177 of 1957) and the ministerial ordinance on water quality standards based on it (August 31, 1978 Ministry of Health Ordinance No. 56), the country's hot springs Based on the Act (July 10, 1948, Law No. 125 and its separate table), and the influence on each element and mineral, etc. in the state of mixing in water prescribed by the WHO regulation tap water standard Is preferred.

  The cleaning liquid according to the present invention contains a surfactant. Further, the addition amount of the surfactant contained in the cleaning liquid is 0.5 times or more and 5.0 times or less with respect to the hydrophobic component extracted from the polymer film in the saponification treatment liquid after the saponification reaction step.

  The surfactant that is preferably used is not particularly limited as long as the hydrophobic component can be washed. Any of nonionic surfactants, ionic surfactants (anions, cations, amphoteric surfactants) and the like can be suitably used. These surfactants may be added singly or in combination with one or more different anionic surfactants or nonionic surfactants, or a combination of anionic and nonionic surfactants.

"Surface characteristics of cellulose ester film"
Saponification by coating can improve “bright spot failure” and “display unevenness”, but in order to improve “bright spot failure” reliably, it is necessary to adjust the surface properties of the film after saponification. I understood it. Conversely, if the surface properties of the film after saponification are not adjusted, a bright spot failure may occur even if the saponification treatment is performed, and a “cloud failure” may occur after a liquid crystal display device has been used for a long time. I understood it.

  The “bright spot failure” is a star-like defect generated on the screen of the liquid crystal display device and can be easily observed when the screen is black. As a result of investigating such a bright spot failure, it has been found that the bright spot is generated by adhesion of debris such as an alignment film or an optically anisotropic layer. These scraps are generated when the alignment film (at the same time as the optically anisotropic layer) peels off slightly from the film due to the impact when cutting (or punching) the optical compensation sheet according to the dimensions of the liquid crystal display device. I understood.

  The “cloud fault” is an alignment quality defect in which unevenness that appears to be cloudy appears on the screen of the liquid crystal display device, and is a defect that is easy to observe when the screen displays white. This cloud failure is unlikely to occur immediately after the liquid crystal display device is manufactured, and is likely to occur after a long period of time. As a result of investigating such cloud-like unevenness, the cloud-like unevenness is caused by the fact that the low molecular weight compound (for example, plasticizer) in the cellulose ester film used for the optical compensation sheet is formed between the alignment film and the optically anisotropic layer after a long time. It was found that it occurs when it precipitates to the interface. Furthermore, it was also found that the cloud-like failure is more likely to occur when the saponification treatment is performed than the conventional saponification treatment by immersion.

  The surface property of the surface of the cellulose ester film that has been saponified by coating satisfies at least one (preferably plural) of the following surface properties (1) to (6). In addition to the advantages of using saponification (such as maintaining a smooth surface of the film), it was found that bright spot failures when using optical compensation sheets in liquid crystal display devices can be improved without the occurrence of cloud failures. . The surface characteristics of the film that can suppress the occurrence of “bright spot failure” and “cloud failure” when the cellulose ester film is saponified by coating are described below.

  (1) The saponification depth of the film surface is in the range of 0.010 to 0.8 μm. The saponification depth is preferably in the range of 0.020 to 0.6 μm, and more preferably in the range of 0.040 to 0.4 μm.

  (2) The C = O / C—O ratio indicating the ratio of the amount of chemical bonds present on the surface is in the range of 0 to 0.6, and the C—C / C—O ratio is 0.45 to 0.75. Be in the range. The C═O / C—O ratio is preferably in the range of 0 to 0.55, and more preferably in the range of 0 to 0.5. The C—C / C—O ratio is preferably in the range of 0.5 or more and 0.7, and more preferably in the range of 0.5 to 0.65.

  (3) When a phosphorus compound is added as a plasticizer to the cellulose ester film, the O / C ratio indicating the ratio of the abundance of elements on the surface is in the range of 0.62 to 0.75, and the P / C ratio Is in the range of 0.007 to 0.015. The surface O / C ratio is preferably in the range of 0.63 to 0.73, and more preferably in the range of 0.64 to 0.71. The P / C ratio on the surface is preferably in the range of 0.008 to 0.0145, and more preferably in the range of 0.009 to 0.014.

  (4) When a cellulose acetate film is used as the cellulose ester film, the degree of acetyl substitution on the film surface is in the range of 1.8 to 2.7. The degree of acetyl substitution is preferably in the range of 1.85 to 2.5, and more preferably in the range of 1.9 to 2.4.

  (5) The contact angle with water on the film surface is in the range of 20 to 55 degrees. The contact angle with water is preferably in the range of 25 to 50 degrees, and more preferably in the range of 30 to 45 degrees.

  (6) The surface energy on the film surface is preferably in the range of 55 to 75 mN / m.

  The reason why bright spot failure and cloud failure can be suppressed by achieving these surface characteristics is not known, but is presumed as follows. For example, when the saponification depth is too deep, it is presumed that the main chain of the cellulose ester near the surface is broken. It is considered that the molecular weight of the cellulose ester on the film surface is lowered and the brittleness is caused by the cleavage of the main chain, and the adhesion between the film and the alignment film is lowered. Then, it is considered that the surface of the film is excessively saponified (from the surface to the deep), so that low molecular weight compounds (plasticizers, etc.) are generated more and adhere to the surface. It is presumed that a cloud-like failure occurs when a low molecular weight compound precipitates on the surface of the alignment film after a long period of time. On the other hand, when the saponification depth is too shallow, it is considered that the adhesion between the film and the alignment film is lowered due to insufficient saponification treatment. Since the saponification depth is extremely shallow, it is considered that low molecular weight compounds (such as plasticizers) present in a very small amount in the vicinity of the surface of the cellulose ester film are likely to be deposited on the surface of the alignment film after a long period of time.

  The surface property of the cellulose ester film can be adjusted to the above range by adjusting the conditions of the saponification treatment by coating. The most important point for adjusting the surface characteristics is to apply an alkaline aqueous solution to the cellulose ester film under a low oxygen atmosphere of 18% or less, and thereafter wash the alkaline aqueous solution at 30 ° C to 80 ° C (preferably hot water). It is to wash with.

"Evaluation method of surface characteristics"
About the evaluation method of the surface characteristics (1)-(5) of a cellulose-ester film, it can carry out by the method as described in pages 27-30 of WO02 / 46809 specification. The surface energy (evaluation item (6)) evaluation method of the surface characteristics can be obtained by the contact angle method, the wet heat method, and the adsorption method described in “Basics and Application of Wetting” (Realize, 1989). I can do it. In the case of the cellulose ester film of the present invention, it is preferable to use a contact angle method. Specifically, a solvent having a known surface energy is dropped on the cellulose ester film, and at the intersection of the droplet surface and the film surface, the angle between the tangent line drawn on the droplet and the film surface is the one containing the droplet. The angle is defined as the contact angle, and the surface energy of the film can be calculated by calculation.

"Optical compensation sheet"
The saponified polymer film is preferably used as a transparent support for the optical compensation sheet. The optical compensation sheet has a layer structure in which a polymer film saponified by applying an alkaline aqueous solution, an alignment film forming resin layer, and an optically anisotropic layer in which the alignment of liquid crystal molecules is fixed are laminated in this order. . In the formation of the alignment film, the step of heating the polymer film, the step of applying the alkaline aqueous solution to the surface of the alignment film side of the polymer film, the step of maintaining the temperature of the alkaline aqueous solution coating surface, the step of stopping the reaction, Following the step of washing and removing from the surface of the film, a step of applying and drying the alignment film can also be added. 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 not only by saponification of the polymer film but also by consistently forming an alignment film and a liquid crystalline molecular layer. Furthermore, there is no time elapsed from saponification treatment to alignment film coating, there is little deterioration of the activated saponification surface, and the water washing process of saponification treatment is combined with wet dust removal. It is an advantage that no loss occurs.

  The optical compensation sheet includes a transparent support made of a saponified polymer film, an alignment film provided thereon, and an optical anisotropic layer having a disk-like structural unit formed on the alignment film. 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. Discotic compounds (discotic compounds) can generally be roughly classified into compounds having a discotic liquid crystal phase (that is, a discotic nematic phase) and compounds having no discotic liquid crystal phase. Discotic compounds generally have negative birefringence. 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 kinds 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 into which a functional group is introduced, between the polymers by light, heat, or pH change, or by forming 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 between the polymers.

  Crosslinking of the polymer can be performed 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, it is heated and dried, and then a rubbing treatment is performed to form an alignment film, 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, Examples include chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, carboxymethyl cellulose, polyethylene, polypropylene and polycarbonate. Silane coupling agents can be used as the polymer. Water-soluble polymers (eg, poly (N-methylolacrylamide), carboxymethylcellulose, gelatin, polyvinyl alcohol, modified polyvinyl alcohol) are preferred, gelatin, polyvinyl alcohol and modified polyvinyl alcohol are more preferred, and polyvinyl alcohol and modified polyvinyl alcohol are most preferred. . 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 modifying groups include hydrophilic groups (carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, amino groups, ammonium groups, amide groups, thiol groups, etc.), hydrocarbon groups having 10 to 100 carbon atoms, fluorine atoms Substituted hydrocarbon groups, thioether groups, polymerizable groups (unsaturated polymerizable groups, epoxy groups, azirinidyl groups, etc.), alkoxysilyl groups (trialkoxy, dialkoxy, monoalkoxy) and the like can be mentioned. As specific examples of these modified polyvinyl alcohol compounds, for example, paragraph numbers [0022] to [0145] in JP-A No. 2000-155216 and paragraph numbers [0018] to [0018] in JP-A No. 2002-62426 are described. 022] and the like.

  Examples of polymers (preferably water-soluble polymers, more preferably polyvinyl alcohol or modified polyvinyl alcohol crosslinking agents include aldehydes, N-methylol compounds, dioxane derivatives, compounds that act by activating carboxyl groups, active vinyl compounds In addition, active halogen compounds, isoxazole and dialdehyde starch may be used, and two or more kinds of crosslinking agents may be used in combination, for example, paragraph number [0023] in JP-A-2002-62426. To [024] The aldehyde having a high reaction activity, particularly glutaraldehyde is preferable.

  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 polymer on the transparent support containing the alignment film forming material and the crosslinking agent, followed by drying by heating (crosslinking) and rubbing treatment. As described above, the crosslinking reaction may be performed at an arbitrary 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 (eg, 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 layer surface of an alignment film and also an optical 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 preferably 0.1 to 10 μm. Heating and drying can be performed at 15 ° 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 particularly preferable. The drying time can be 1 minute to 36 hours, preferably 1 minute to 30 minutes. The pH is preferably set to an optimum value for the crosslinking agent to be used. When glutaraldehyde is used, the pH is 4.5 to 5.5, and 5 is particularly preferable.

  The alignment film is provided on the transparent support or the undercoat layer. 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 liquid crystalline 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 the orientation by rubbing the surface of the orientation 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.

"Optical 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 having negative birefringence composed of a compound having a discotic structural unit. The optically anisotropic layer is a layer of a low molecular weight liquid crystalline discotic compound (monomer) or a polymer layer obtained by polymerization (curing) of a polymerizable liquid crystalline discotic compound. Discotic compounds include benzene derivatives described in C. Destrade et al., Mol. Cryst. Vol. 71, 111 (1981), C. Destrade et al., Mol. Cryst 122, 141 (1985), Physics lett, A, 78, 82 (1990), a research report by B. Kohne et al., Angew. Chem. 96, 70 ( (1984) and JMLehn et al., J. Chem. Commun., 1794 (1985), J. Zhang et al., J. Am. Chem. Soc. 116, 2655 Azacrown and phenylacetylene macrocycles described on page (1994). A discotic (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 crystal exhibiting liquid crystallinity. Some optically anisotropic layers formed from discotic compounds have lost their liquid crystallinity by polymerizing or crosslinking by reacting with a low molecular discotic liquid crystal having a group that reacts with heat or light. 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 discotic structural unit, and the surface of the discotic structural unit is inclined with respect to the transparent support surface, and the discotic structural unit 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 discotic structural unit increases or decreases in the depth direction of the optical anisotropic layer and with an increase in the distance from the bottom surface of the alignment film of the optical anisotropic layer. 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, then heating to a discotic nematic phase formation temperature, and then aligning the state (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, particularly preferably 70 to 170 ° C.

  The tilt angle of the discotic unit on the support side can be generally adjusted by selecting a discotic compound or an alignment film material, or by selecting a rubbing treatment method. In addition, the inclination angle of the discotic unit on the surface side (air side) is generally selected from the discotic compound or other compounds (eg, plasticizer, surfactant, polymerizable monomer and 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, polymerizable monomers (eg, compounds having a vinyl group, a vinyloxy group, an acryloyl group, and a methacryloyl group) are preferable. The above compound is generally used in an amount of 1 to 50% by mass, preferably 5 to 30% by mass, based on 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 crystal 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 generally 0.1 to 10% by mass, preferably 0.1 to 8% by mass, particularly preferably 0.1 to 5% by mass based on the discotic compound so as not to inhibit the alignment of the liquid crystalline discotic compound. Used in an amount of mass%.

"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 optically 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 case of TN, MVA or OCB, 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, 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 orienting a discotic compound (or rod-like liquid crystal compound) and fixing its orientation 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 a discotic compound 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. It is disclosed in the specifications of Japanese Patent Nos. 45882525 and 5410422. 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 called 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.

  Examples are shown below, but the present invention is not limited thereto.

The polymer film was saponified and the hydrophobic film shown in Table 1 was expressed. A cleaning solution containing the amount of W agent (surfactant) shown in Table 1 (for Experiments 1 to 21, the liquid temperature was 35 ° C. With respect to 22 to 26, the orientation quality of the polymer film washed at a liquid temperature of 20 to 70 ° C. was evaluated. The evaluation is made visually, and a 1 × 1 m ² sample is observed with a microscope. If the light leakage failure (= orientation defect failure) of 70 μ or more is less than 5, ◎ if less than 10, ○ if less than 15, The case was evaluated as Δ, and the case of 15 or more was evaluated as ×.

  As can be seen from Table 1, the cleaning liquid contains at least a surfactant, and the surfactant contained in the cleaning liquid with respect to the hydrophobic component extracted from the polymer film in the saponification treatment liquid after the saponification reaction step. When the addition amount of the agent was 0.5 times or more and 5.0 times or less, the evaluation was Δ to ◎. From Experiments 23 to 27, it is found that the liquid temperature of the cleaning liquid in the cleaning process is preferably 30 ° C. or higher and 60 ° C. or lower.

Claims (5)

An application step of applying an alkaline aqueous solution to the polymer film; a saponification reaction step of saponifying the polymer film with the alkaline aqueous solution applied in the application step; a reaction stopping step of stopping the saponification reaction step; In a method for alkali saponification of a polymer film comprising a washing step for washing,
The cleaning liquid contains at least a surfactant,
The addition amount of the surfactant contained in the cleaning liquid is 0.5 to 5.0 times the hydrophobic component extracted from the polymer film in the saponification treatment liquid after the saponification reaction step. A method for alkali saponification of a polymer film.   The method for alkali saponification of a polymer film according to claim 1, wherein the temperature of the cleaning liquid in the cleaning step is 30 ° C or higher and 60 ° C or lower.   The method for alkali saponification of a polymer film according to claim 1 or 2, wherein the polymer film is a cellulose ester film.   A surface saponified cellulose ester film obtained by the alkali saponification method according to claim 3.   An optical film using the surface saponified cellulose ester film according to claim 4.