JP4346258B2 - Method for producing film having stretching process - Google Patents

Description

【００６９】
【発明の効果】
本発明のフィルムの製造方法は、叙上の如く構成されているので、幅方向に極めて均一な光学特性を持つ偏光板保護フィルムや光学補償フィルムを提供できる。
【図面の簡単な説明】
【図１】 本発明の方法を実施する溶液製膜装置の一実施形態の概略図である。
【図２】 本発明の方法で製造できるフィルムを概略的に示す断面図である。
【図３】 本発明の方法に利用することができるダイの概略断面図である。
【図４】 本発明の方法に利用することができるフィードブロックの概略断面図である。
【図５】 本発明による偏光板用フィルムを製膜する単層ダイ及びフィードブロックの断面図である。
【図６】 本発明による偏光板用フィルムの製膜に用いるフィードブロックのベーン及びディストリビューションピンの斜視図である。
【図７】 本発明による偏光板用フィルムの製膜に用いるフィードブロックのディストリビューションピンの側面図である。
【図８】 本発明の方法に利用することができるダイの概略断面図である。
【図９】 本発明の方法に利用することができるダイの概略断面図である。
【図１０】 本発明の方法に利用することができる溶液製膜装置の概略図である。
【図１１】 本発明の方法に利用することができる溶液製膜装置の概略図である。
【図１２】 本発明の方法に利用することができる溶液製膜装置の概略図である。
【図１３】 本発明の方法に利用することができる溶液製膜装置の概略図である。
【図１４】 本発明の方法に利用することができる溶液製膜装置の概略図である。
【図１５】 本発明の方法に利用することができる溶液製膜装置の概略図である。
【図１６】 本発明の方法に利用することができる溶液製膜装置の概略図である。
【図１７】 本発明の方法に利用することができる溶液製膜装置の概略図である。
【図１８】 本発明の方法に利用することができる溶液製膜装置の概略図である。
【図１９】 本発明の方法に利用することができる溶液製膜装置の概略図である。
【符号の説明】
１…ミキシングタンク
２…送液ポンプ
３…フィルタ
４…流延ダイ
５…流延バンド
６、７…回転ドラム
８…ガイドロール
９…剥ぎ取りロール
１０…ガイドロール
１１…巻き取りロール
１２…乾燥部
１４…フィルム
ａ…剥離点
ｂ…接触点
ｈ…接線方向
ｖ…法線方向
θ…剥ぎ取り角度[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing an optical functional film such as a polarizing plate protective film and an optical compensation film, which are required to have uniform optical characteristics in the width direction of the film.
[0002]
[Prior art]
An optical functional film such as a polarizing plate protective film or an optical compensation film needs to have uniform optical characteristics in the width direction and the film longitudinal direction in addition to the film thickness. On the other hand, the demand for optical functionality for films is increasing, and the functionality is improved by stretching during film formation.
[0003]
However, in the stretching process, it is easy to suffer from stretching unevenness, and the required uniformity of optical properties tends to be impaired. Therefore, it is desired to maintain the uniformity of the optical characteristics.
[0004]
In order to realize this, conventionally, a technology for preheating by applying a temperature gradient of 0.1 to 2 ° C. in the width direction of the film before the stretching step (Japanese Patent Application No. 11-160536), a film at the time of stretching A technique in which the temperature distribution in the width direction is within ± 1 ° C. (Japanese Patent Application No. 10-58227), and a technique in which a temperature gradient is provided in the width direction of the film in the preheating process after stretching (Japanese Patent Application No. 9 No. 245836) has been developed. However, it is difficult to control the temperature of the drying process on a large scale, and in order to realize this, large-scale equipment and highly accurate control equipment are required.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for producing a film having uniform optical properties, wherein the in-plane retardation distribution in the width direction of the film is within 5 nm by simple means.
[0006]
[Means for Solving the Problems]
The present invention has been made to solve the above problems, and in the method for producing a film by stretching, the stretched film contains a retardation increasing agent, and the weight concentration thereof is from the ends of the film ears to the center. This object is achieved by a film manufacturing method characterized by having a higher density distribution as it gets closer.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The film to which the present invention is applied is based on a polymer, and this polymer is composed of cellulose esters such as cellulose acetate, cellulose propionate, and cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate. Such as mixed fatty acid esters. Further, polycarbonate, aramid resin, norbornene resin, polysulfone, polyethersulfone, polyarylate, polyethylene terephthalate, polystyrene, polymethyl methacrylate, polypropylene, polyvinyl chloride, polystyrene, polyvinyl alcohol may be used.
[0008]
The film is preferably produced by a solvent cast method.
[0009]
In the solvent cast method, a film is produced using a solution (dope) in which the polymer 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.
[0010]
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 halogenated hydrocarbon hydrogen atoms substituted with halogen is preferably 25 to 75 mol%, more preferably 30 to 70 mol%, and more preferably 35 to 65 mol%. More preferably, it is 40 to 60 mol%, and most preferably. Methylene chloride is a representative halogenated hydrocarbon. Two or more organic solvents may be mixed and used.
[0011]
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 by 10 to 40% by weight in the obtained solution. The amount of the polymer is more preferably 10 to 30% by weight. 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 placed in a pressure vessel and sealed, and stirred while being heated to a temperature equal to or higher 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., more preferably 80 to 110 ° C.
[0012]
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 jacket type heating device 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 taken out of the container after cooling, or taken out and then cooled using a heat exchanger or the like.
[0013]
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 (an organic solvent other than the halogenated hydrocarbon) that is difficult to dissolve by a normal dissolution method. In addition, even if it is a solvent (for example, halogenated hydrocarbon) which can melt | dissolve a polymer with a normal melt | dissolution method, there exists an effect that a uniform solution can be obtained rapidly according to a cooling melt | dissolution method. Further, when the cooling dissolution method is used, the retardation of the polymer film to be produced becomes high. 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 at 10 to 40% by weight. The amount of the polymer is more preferably 10 to 30% by weight. Furthermore, you may add the arbitrary additive mentioned later in a mixture.
[0014]
The mixture is then cooled to -100 to -10 ° C (preferably -80 to -10 ° C, more preferably -50 to -20 ° C, 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.). When cooled 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 faster the cooling rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. 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 until the final cooling temperature is reached.
[0015]
Further, when this is heated to 0 to 200 ° C. (preferably 0 to 150 ° C., more preferably 0 to 120 ° C., most preferably 0 to 50 ° C.), the polymer is dissolved 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 higher the heating rate, the better. However, 10,000 ° C./second is the theoretical upper limit, 1000 ° C./second is the technical upper limit, and 100 ° C./second is the practical upper limit. The heating rate is a value obtained by dividing the difference between the temperature at the start of heating and the final heating temperature by the time from the start of heating until the final heating temperature is reached. . 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.
[0016]
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 wt% solution obtained by dissolving cellulose acetate (acetylation degree: 60.9%, viscosity average polymerization degree: 299) in methyl acetate by the 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, this solution needs to be stored at a temperature equal to or higher than the pseudo phase transition temperature, preferably about the gel phase transition temperature plus about 10 ° C. However, this pseudo phase transition temperature varies depending on the average degree of acetylation, the degree of viscosity average polymerization, the concentration of the solution, and the organic solvent used.
[0017]
A polymer film is produced 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. It is preferable to adjust the concentration of the dope before casting so that the solid content is 18 to 35%. The surface of the drum or band is preferably finished in a mirror state. The casting and drying methods in the solvent casting method are described in U.S. Pat. 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. It is preferable that the cast is dried for 2 seconds or longer after being cast. 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. The solution (dope) prepared according to the present invention satisfies this condition. In addition, the extending | stretching process mentioned later can also be implemented simultaneously with this drying process.
[0018]
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. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP). Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethyl hexyl phthalate (DEHP). Examples of citrate esters include triethyl O-acetylcitrate (OACTE) and tributyl O-acetylcitrate (OACTB). Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Phthalate plasticizers (DMP, DEP, DBP, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularly preferred. The amount of the plasticizer added is preferably 0.1 to 25% by weight, more preferably 1 to 20% by weight, and most preferably 3 to 15% by weight of the amount of the polymer.
[0019]
Retardation increasing agents, deterioration inhibitors (eg, antioxidants, peroxide decomposers, radical inhibitors, metal deactivators, acid scavengers, amines) and UV inhibitors as described below are used for the polymer film. It may be added. The deterioration preventing agents are described in JP-A-3-199201, JP-A-51907073, JP-A-5-194789, JP-A-5-271471, and JP-A-6-107854. The addition amount of the deterioration preventing agent is preferably 0.01 to 1% by weight of the solution (dope) to be prepared, and more preferably 0.01 to 0.2% by weight. When the addition amount is less than 0.01% by weight, the effect of the deterioration preventing agent is hardly recognized. When the added amount exceeds 1% by weight, bleed-out (bleeding) of the deterioration preventing agent to the film surface may be observed. As a particularly preferred example of the deterioration preventing agent, butylated hydroxytoluene (BHT) can be mentioned. The ultraviolet ray preventing agent is described in JP-A-7-11056. In addition, the cellulose acetate whose average acetylation degree is 55.0 to 58.0% is more stable than the cellulose triacetate whose average acetylation degree is 58.0% or more, and the film produced. There is a disadvantage that the physical properties are inferior. However, this drawback can be substantially eliminated by using the above-described deterioration preventing agent, particularly an antioxidant such as butylated hydroxytoluene (BHT).
[0020]
[Retardation raising agent]
A retardation increasing agent is added to the polymer film stretched in the present invention. As a retardation increasing agent that provides a method for producing a film having uniform optical properties with an in-plane retardation distribution in the width direction of the film within 5 nm by simple means, it has at least two aromatic rings, A compound having a molecular structure that does not sterically hinder the conformation of two aromatic rings can be used. The retardation increasing agent is preferably used in the range of 0.01 to 20 parts by weight with respect to 100 parts by weight of the polymer. A compound having at least two aromatic rings has a π-bonding plane of 7 or more carbon atoms. Unless the steric hindrance of the conformation of the two aromatic rings, the two aromatic rings form the same plane. According to the inventor's research, in order to increase the retardation of the polymer film, it is important to form the same plane by a plurality of aromatic rings. In the present specification, the “aromatic ring” includes an aromatic hetero ring in addition to an aromatic hydrocarbon ring. The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring).
[0021]
The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring. As the aromatic ring, benzene ring, furan ring, thiophene ring, pyrrole ring, oxazole ring, thiazole ring, imidazole ring, triazole ring, pyridine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring are preferable.
[0022]
The number of aromatic rings contained in the retardation increasing agent is preferably 2 to 20, more preferably 2 to 12, still more preferably 2 to 8, and most preferably 2 to 6. preferable. In the case of having three or more aromatic rings, the conformation of at least two aromatic rings should not be sterically hindered. The bond relationship between two aromatic rings can be classified into (a) a condensed ring, (b) a direct bond with a single bond, and (c) a bond through a linking group (for aromatic rings). , Spiro bonds cannot be formed). From the viewpoint of the retardation increasing function, any of (a) to (c) may be used. However, in the case of (b) or (c), it is necessary not to sterically hinder the conformation of the two aromatic rings.
[0023]
Examples of the condensed ring of (a) (condensed ring of two or more aromatic rings) include an indene ring, a naphthalene ring, an azulene ring, a fluorene ring, a phenanthrene ring, an acetracene ring, an acenaphthylene ring, a biphenylene ring, a naphthacene ring, Pyrene ring, indole ring, isoindole ring, benzofuran ring, benzothiophene ring, indolizine ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring, purine ring, indazole ring, chromene ring, quinoline ring, isoquinoline Ring, quinolidine ring, quinazoline ring, cinnoline ring, quinoxaline ring, phthalazine ring, pteridine ring, carbazole ring, acridine ring, phenanthridine ring, xanthene ring, phenazine ring, phenothiazine ring, phenoxathiin ring, phenoxazine ring and thiant It includes emissions ring. Naphthalene ring, azulene ring, indole ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring and quinoline ring are preferred. The single bond (b) is preferably a bond between carbon atoms of two aromatic rings. Two aromatic rings may be bonded with two or more single bonds to form an aliphatic ring or a non-aromatic heterocyclic ring between the two aromatic rings.
[0024]
The linking group in (c) is also preferably bonded to carbon atoms of two aromatic rings. The linking group is preferably an alkylene group, an alkenylene group, an alkynylene group, —CO—, —O—, —NH—, —S—, or a combination thereof. Examples of linking groups composed of combinations are shown below. In addition, the relationship between the left and right in the following examples of the linking group may be reversed.
[0025]
c1: -CO-O-
c2: —CO—NH—
c3: -alkylene-O-
c4: —NH—CO—NH—
c5: —NH—CO—O—
c6: —O—CO—O—
c7: -O-alkylene-O-
c8: -CO-alkenylene-
c9: -CO-alkenylene-NH-
c10: -CO-alkenylene-O-
c11: -alkylene-CO-O-alkylene-O-CO-alkylene-
c12: -O-alkylene-CO-O-alkylene-O-CO-alkylene-O-
c13: -O-CO-alkylene-CO-O-
c14: -NH-CO-alkenylene-
c15: -O-CO-alkenylene-
[0026]
The aromatic ring and the linking group may have a substituent. However, the substituent is required not to sterically hinder the conformation of the two aromatic rings. In steric hindrance, the type and position of substituents are problematic. As the type of the substituent, a sterically bulky substituent (for example, a tertiary alkyl group) tends to cause steric hindrance. As the position of the substituent, steric hindrance is likely to occur when a position adjacent to the bond of the aromatic ring (ortho position in the case of a benzene ring) is substituted. Examples of the substituent include halogen atom (F, Cl, Br, T), hydroxyl, carboxyl, cyano, amino, nitro, sulfo, carbamoyl, sulfamoyl, ureido, alkyl group, alkenyl group, alkynyl group, aliphatic acyl group , Aliphatic acyloxy group, alkoxy group, alkoxycarbonyl group, alkoxycarbonylamino group, alkylthio group, alkylsulfonyl group, aliphatic amide group, aliphatic sulfonamido group, aliphatic substituted amino group, aliphatic substituted carbamoyl group, aliphatic Substituted sulfamoyl groups, aliphatic substituted ureido groups and non-aromatic heterocyclic groups are included.
[0027]
The alkyl group preferably has 1 to 8 carbon atoms. A chain alkyl group is preferable to a cyclic alkyl group, and a linear alkyl group is particularly preferable. The alkyl group may further have a substituent (eg, hydroxy, carboxy, alkoxy group, alkyl-substituted amino group). Examples of alkyl groups (including substituted alkyl groups) include methyl, ethyl, n-butyl, n-hexyl, 2-hydroxyethyl, 4-carboxybutyl, 2-methoxyethyl and 2-diethylaminoethyl. The alkenyl group preferably has 2 to 8 carbon atoms. A chain alkenyl group is preferable to a cyclic alkenyl group, and a linear alkenyl group is particularly preferable. The alkenyl group may further have a substituent. Examples of alkenyl groups include vinyl, allyl and 1-hexenyl. The alkynyl group preferably has 2 to 8 carbon atoms. A chain alkynyl group is preferable to a cyclic alkynyl group, and a linear alkynyl group is particularly preferable. The alkynyl group may further have a substituent. Examples of alkynyl groups include ethynyl, 1-butynyl and 1-hexynyl.
[0028]
The aliphatic acyl group preferably has 1 to 10 carbon atoms. Examples of the aliphatic acyl group include acetyl, propanoyl and butanoyl. The aliphatic acyloxy group preferably has 1 to 10 carbon atoms. Examples of the aliphatic acyloxy group include acetoxy. The number of carbon atoms of the alkoxy group is preferably 1 to 8. The alkoxy group may further have a substituent (eg, alkoxy group). Examples of alkoxy groups (including substituted alkoxy groups) include methoxy, ethoxy, butoxy and methoxyethoxy. The alkoxycarbonyl group preferably has 2 to 10 carbon atoms. Examples of the alkoxycarbonyl group include methoxycarbonyl and ethoxycarbonyl. The number of carbon atoms of the alkoxycarbonylamino group is preferably 2 to 10. Examples of the alkoxycarbonylamino group include methoxycarbonylamino and ethoxycarbonylamino.
[0029]
The alkylthio group preferably has 1 to 12 carbon atoms. Examples of the alkylthio group include methylthio, ethylthio and octylthio. The alkylsulfonyl group preferably has 1 to 8 carbon atoms. Examples of the alkylsulfonyl group include methanesulfonyl and ethanesulfonyl. The aliphatic amide group preferably has 1 to 10 carbon atoms. Examples of the aliphatic amide group include acetamide. The aliphatic sulfonamide group preferably has 1 to 8 carbon atoms. Examples of the aliphatic sulfonamido group include methanesulfonamido, butanesulfonamido and n-octanesulfonamido. The number of carbon atoms of the aliphatic substituted amino group is preferably 1 to 10. Examples of the aliphatic substituted amino group include dimethylamino, diethylamino and 2-carboxyethylamino. The aliphatic substituted carbamoyl group preferably has 2 to 10 carbon atoms. Examples of the aliphatic substituted carbamoyl group include methylcarbamoyl and diethylcarbamoyl. The aliphatic substituted sulfamoyl group preferably has 1 to 8 carbon atoms. Examples of the aliphatic substituted sulfamoyl group include methylsulfamoyl and diethylsulfamoyl. The number of carbon atoms in the aliphatic substituted ureido group is preferably 2 to 10. Examples of the aliphatic substituted ureido group include methylureido. Examples of non-aromatic heterocyclic groups include piperidino and morpholino. The molecular weight of the retardation increasing agent is preferably 300 to 800. The boiling point of the retardation increasing agent is preferably 260 ° C. or higher.
[0030]
This retardation (Re) is obtained, for example, by using an ellipsometer (Ellipsometer AEP-100: manufactured by Shimadzu Corporation) and multiplying the longitudinal and lateral refractive index difference in the plane at a wavelength of 632.8 nm by the film thickness. It is obtained by the following formula.
Re = (nx−ny) × d
nx: refractive index in the horizontal direction ny: refractive index in the vertical direction
A smaller retardation (Re) indicates that there is no optical anisotropy in the in-plane direction.
[0032]
The solvent casting method itself may be the same as the conventional one, and the support may be either a drum or a band. Moreover, as a method of ensuring the self-supporting property necessary for peeling off from the support, either a method of cooling and gelling the support or drying by hot air or the like may be used. The stretch ratio in the film longitudinal direction or the width direction to be performed after the peeling is about 0.1 to 300%, usually about 1 to 150%.
[0033]
Moreover, the film residual volatile content at the time of extending | stretching of a film longitudinal direction or the width direction is 3 to 300 wt% by dry quantity reference | standard volatile matter, and 50 to 250 wt% is more preferable.
[0034]
The final film thickness of these films is preferably 10 to 200 μm, and more preferably 30 to 120 μm.
[0035]
Regarding the optical properties in the film width direction, as a means of the present invention to ensure the uniformity, first, the stretched film contains a retardation increasing agent, and the content thereof is from the edge of the film toward the center. Do by increasing. That is, in the stretching process, the cross section of the deformation width direction that the film receives by stretching is substantially arc-shaped in the film width direction, and the amount thereof is the smallest at the film ear end and slightly increases as it approaches the center. For this reason, the final film thickness of the film is slightly thinner at the center of the film in the width direction than at both ends. This thickness difference is [(ear end portion thickness−center portion thickness) / center portion thickness] × 100, which is about 0.1 to 5%, usually about 0.1 to 3%, most of which is about 0.1 to 2%. is there. Also, the birefringence distribution is determined in proportion to the amount of deformation and the concentration of the retardation increasing agent. The in-plane retardation value is determined by the product of the film thickness and the birefringence. As a result, the in-plane retardation value of the film is offset by the distribution of the retardation increasing agent and the birefringence distribution due to stretching unevenness, so that the distribution in the width direction of the optical properties is offset, and uniformity in the film width direction can be secured. At this time, the final film thickness distribution of the film is set to a level that can be ignored in terms of product quality. As for the level, when the film width is 2000 mm, the thickness difference between the center and both ends of the ear is about 0.1 to 2 μm. Moreover, this thickness distribution improves the film transportability in the next process, and is useful for improving the quality of the film in total.
[0036]
As described above, the method of the present invention compensates for the change in the optical property due to the change in thickness generated between the film center and the ear end due to stretching by providing a distribution in the content of the retardation increasing agent. is there. Since this varies depending on the material, thickness, stretch ratio, etc. of each film, the thickness change and birefringence distribution in the width direction due to stretching are obtained for each film, and the retardation increasing agent is included in the width direction to compensate for this. It adjusts the distribution of quantities. The content of the retardation increasing agent is per unit area.
[0037]
In order to adjust the content distribution in the width direction of the retardation increasing agent, a method of providing a distribution in the concentration of the retardation increasing agent in the film, the concentration of the retardation increasing agent in the film is kept constant, and the distribution is distributed over the film thickness. There are a method for adjusting the thickness and a method for adjusting both the concentration and the thickness, and any of them can be used.
[0038]
As a means for giving the film width direction distribution of the retardation increasing agent, the film is composed of two or more laminated films, at least one layer of which includes the retardation increasing agent, and the thickness distribution in the width direction of the layer is the film edge. This can be realized by giving a distribution in which the thickness increases from the both end portions toward the center. Each layer thickness control method includes a multi-manifold die system having two or more pockets in a die that can form a laminated film of two or more layers, a feed block system having a block that joins two or more layers at the entrance of the die, or There is a method of sequentially forming a film using two or more dies.
[0039]
In the case of the feed block method, the thickness distribution of each layer is controlled by using a pin having a notch and a vane that determines the confluence ratio of each layer in the cross-sectional profile of each confluence, The total film thickness distribution is controlled by the slit clearance distribution at the tip of the die lip. In the case of the multi-manifold die method, the thickness distribution of each layer is adjusted by the slit clearance of each layer at the junction, and the total film thickness distribution is controlled by the slit clearance distribution at the tip of the die lip. In the case of the sequential film formation method, the thickness of each layer is controlled in correspondence with the total thickness by the slit clearance distribution at the tip of the die lip of each die.
[0040]
As an effect similar to the above-described addition of a retardation increasing agent, there is a means for lowering the average degree of acetylation of cellulose acetate. In this case, the average degree of acetylation of cellulose acetate is preferably 58 to 62.5%, particularly 59.5 to 61.0%, and in this range, the average degree of acetylation of at least one layer of cellulose acetate is It can be realized by lowering 0.5% or more, preferably 1.0% or more from other layers. Each layer thickness distribution control can be similarly controlled by the above-described methods. This cellulose acetate may consist of either wood pulp or cotton linter, or a mixture thereof.
[0041]
An embodiment of a solution casting apparatus for carrying out the method of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of a solution casting apparatus.
[0042]
In FIG. 1, reference numeral 1 denotes a mixing tank, which is prepared by adding cellulose triacetate, an additive and a solvent. The mixing tank 1 is connected to a casting die 4 via a liquid feed pump 2 and a filter 3. The dope liquid feeding step including the mixing tank 1, the liquid feed pump 2, and the filter 3 is provided in three sets so that a film having a three-layer structure can be manufactured. Below the casting die 4, a casting band 5 made of stainless steel as a casting support is disposed. The casting band 5 is wound around the rotating drums 6 and 7 and is rotated. A plurality of guide rolls 8 are provided between the drum 6 and the rotating drum 7. Further, above and below the casting band 5, drying air blowing means (not shown) is provided for blowing hot air on the dope cast on the casting band 5 to dry the dope. A stripping roll 9 is provided adjacent to the rotary drum 6 on the casting die 4 side, a number of guide rolls 10 and a winding roll 11 are further provided, and a drying unit is provided between the stripping roll 9 and the winding roll 11. 12
[0043]
In order to form a film with the solution casting apparatus as described above, the dope is discharged from the casting die 4, cast into the casting band 5, and conveyed while being dried on the casting band 5. The film dried to some extent on the casting band 5 is peeled off from the casting band 5 by a peeling roll 9.
[0044]
A film that can be produced by the method of the present invention will be described with reference to FIG. FIG. 2 is a cross-sectional view schematically showing the film.
[0045]
The film 22A shown in FIG. 2 has a two-layer structure, and the surface layer 22a on one side contains a retardation increasing agent. The film 22B has a three-layer structure, and the surface layers 22a and 22c on both sides contain a retardation increasing agent.
[0046]
In addition, this invention is not limited to these layer structures, For example, the multilayered structure of four or more layers may be sufficient.
[0047]
An example of a co-casting die that can be used in the solution casting method of the present invention will be described with reference to FIGS.
[0048]
FIG. 3 is a schematic sectional view of the die, and FIG. 4 is a schematic sectional view of the feed block. In the co-casting method shown in FIG. 3, a co-casting die 30 provided with a feed block 31 as shown in FIG. 4 is used, and the dopes 32 are joined by the feed block 31 before the co-casting die 30. Then, the dope 32 is discharged from the co-casting die 30 onto the support 33 moving at a constant speed in the direction of the arrow and simultaneously cast.
[0049]
FIG. 5 is a cross-sectional view of a casting die using a feed block, FIG. 6 is a perspective view of vane and distribution pin portions of the feed block, and FIG. 7 is a side view of the distribution pin of the feed block.
[0050]
In FIG. 5, reference numeral 40 denotes a single-layer casting die, in which one manifold 41 is formed and a slit 42 is formed. A feed block 50 is provided in close contact with the upper portion of the casting die 40, and an inner layer channel 51 is formed on the feed block 50, and an outer layer channel 52 is formed on both sides thereof. The outer layer flow path 52 joins the inner layer flow path 51 at the joining portion a.
[0051]
The junction a is provided with a vane 53 and a distribution pin 54. The vane 53 is rotatably provided around a shaft 55, and the flow rate can be adjusted by changing the opening degree of the vane 53 with respect to the distribution pin 54. The distribution pin 54 is provided so as to be rotatable about an axis, and a groove 56 is formed on the surface thereof. The groove 56 is formed in a trapezoidal shape whose width is narrowed from one side to the other side, and for the outer layer joined from the outer layer flow path 52 to the inner layer flow path 51 by the portion of the groove 56 facing the vane 53. The width of the dope can be changed.
[0052]
FIG. 8 is a schematic sectional view of a die showing an example of another co-casting method. The co-casting method shown in FIG. 8 is a multi-manifold die in which the co-casting die 60 has three manifolds 61, 62, 63, and after the dope 64 is joined inside the co-casting die 60, In this method, the dope 64 is discharged from the rolling die 60 onto the support 65 and cast at the same time.
[0053]
Next, a sequential casting method that can be used in the solution casting method of the present invention will be described with reference to FIG.
[0054]
FIG. 9 is a schematic sectional view of the die. In the sequential casting method shown in FIG. 9, three dies 70, 80, 90 are arranged on the support 100, and the dopes 71, 81, 91 are flowed from the dies 70, 80, 90 to the support 100, respectively. At this time, the die 80 on the downstream side casts the dope 81 on the upper surface of the dope 71 cast by the die 70 on the upstream side, and the die 90 on the downstream side is upstream. The dope 91 is cast on the upper surface of the dope 81 cast by the die 80 on the side, and a film having a three-layer structure can be formed.
[0055]
Moreover, the example of the solution casting apparatus which can be utilized for the solution casting method of this invention is shown to FIGS.
[0056]
The solution casting apparatus shown in FIG. 10 uses a casting band as a casting support. The solution casting apparatus shown in FIG. 11 uses a casting band as a casting support and also uses a tenter. The solution casting apparatus shown in FIG. 12 also uses a casting band as a casting support and also uses a tenter. The solution casting apparatus shown in FIG. 13 also uses a casting band as a casting support and also uses a tenter. The solution casting apparatus shown in FIG. 14 also uses a casting band as a casting support, and also uses a tenter and heat transfer means. The solution casting apparatus shown in FIG. 15 also uses a casting band as a casting support, and also uses a tenter and heat transfer means. The solution casting apparatus shown in FIG. 16 also uses a casting band as a casting support, and also uses a tenter and heat transfer means. The solution casting apparatus shown in FIG. 17 uses a cooling drum as a casting support and also uses a tenter. The solution casting apparatus shown in FIG. 18 also uses a cooling drum as a casting support and a tenter. The solution casting apparatus shown in FIG. 19 uses a drying drum as a casting support and also uses a tenter.
[0057]
In the above solution casting apparatus, 81 is a die, 82 is a casting support, 83 is a drying apparatus, and 84 is a tenter.
[0058]
【Example】
Three types of solutions having the following compositions were prepared.
[0059]
[Polymer solution 1]
Cellulose ester solution composition Cellulose acetate with an acetylation degree of 60.9% 100 parts by weight Triphenyl phosphate (plasticizer) 7.8 parts by weight Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by weight Methylene chloride (first solvent) 300 parts by weight Part methanol (second solvent) 65 parts by weight
[Polymer solution 2]
Cellulose ester solution composition Cellulose acetate having an acetylation degree of 59.7% 100 parts by weight Triphenyl phosphate (plasticizer) 7.8 parts by weight Biphenyl diphenyl phosphate (plasticizer) 3.9 parts by weight Methylene chloride (first solvent) 300 parts by weight Part methanol (second solvent) 65 parts by weight
[Retardation raising agent solution 1]
Retardation increasing agent solution composition 2-hydroxy-4-benzyloxybenzophenone 12 parts by weight (retardation increasing agent)
2,4-benzyloxybenzophenone 4 parts by weight (retardation increasing agent)
Methylene chloride 80 parts by weight Methanol 20 parts by weight [0062]
Using these three kinds of solutions, a film was formed under the following conditions.
[0063]
<Comparative Example 1>
The following single-layer film formation was carried out using a solution in which 22 parts by weight of retardation increasing agent solution 1 was uniformly mixed with 474 parts by weight of polymer solution 1.
(Film forming conditions)
Final film average film thickness: 80 μm
Longitudinal stretch (film longitudinal direction) amount: 150%
Stretched film volatiles: 200wt%
[0064]
<Example 1>
Two layers of films were formed according to the following solutions A and B and film forming conditions.
(Each layer solution)
Solution A: Polymer solution 1 / Retardation raising agent solution 1 = 474/44 mixed solution B: Polymer solution 1 only (film forming conditions)
Final film average film thickness: 80 μm
Two layer average film thickness ratio: A layer (solution A) / B layer (solution B) = 40/40
Width direction thickness distribution during stretching of layer A (solution A): ear end / center portion = 38/42
Longitudinal stretch (film longitudinal direction) amount: 150%
Stretched film volatiles: 200wt%
[0065]
<Example 2>
Three layers of films were formed according to the following solutions A and B and film forming conditions.
(Each layer solution)
Solution A: Polymer solution 1 / Retardation raising agent solution 1 = 474/44 mixed solution B: Polymer solution 1 only (film forming conditions)
Final film average film thickness: 80 μm
Three-layer average film thickness ratio: A layer (solution A) / B layer (solution B) / A layer (solution A) = 20/40/20
Width direction thickness distribution during stretching of both A layers (solution A): ear end / center = 19/21
Longitudinal stretch (film longitudinal direction) amount: 150%
Stretched film volatiles: 200wt%
[0066]
<Example 3>
Two layers of films were formed according to the following solutions A and B and film forming conditions.
(Each layer solution)
Solution A: Polymer solution 2 only Solution B: Polymer solution 1 only (film forming conditions)
Final film average film thickness: 80 μm
Two layer average film thickness ratio: A layer (solution A) / B layer (solution B) = 40/40
Width direction thickness distribution during stretching of layer A (solution A): ear end / center portion = 35/45
Longitudinal stretch (film longitudinal direction) amount: 150%
Stretched film volatiles: 200wt%
[0067]
Table 1 shows the results of evaluating the obtained films.
[0068]
[Table 1]

[0069]
【The invention's effect】
Since the film manufacturing method of the present invention is configured as described above, a polarizing plate protective film and an optical compensation film having extremely uniform optical characteristics in the width direction can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic view of an embodiment of a solution casting apparatus for carrying out the method of the present invention.
FIG. 2 is a cross-sectional view schematically showing a film that can be produced by the method of the present invention.
FIG. 3 is a schematic cross-sectional view of a die that can be used in the method of the present invention.
FIG. 4 is a schematic cross-sectional view of a feed block that can be used in the method of the present invention.
FIG. 5 is a cross-sectional view of a single-layer die and a feed block for forming a polarizing plate film according to the present invention.
FIG. 6 is a perspective view of vanes and distribution pins of a feed block used for forming a polarizing plate film according to the present invention.
FIG. 7 is a side view of a distribution pin of a feed block used for forming a polarizing plate film according to the present invention.
FIG. 8 is a schematic cross-sectional view of a die that can be used in the method of the present invention.
FIG. 9 is a schematic cross-sectional view of a die that can be used in the method of the present invention.
FIG. 10 is a schematic view of a solution casting apparatus that can be used in the method of the present invention.
FIG. 11 is a schematic view of a solution casting apparatus that can be used in the method of the present invention.
FIG. 12 is a schematic view of a solution casting apparatus that can be used in the method of the present invention.
FIG. 13 is a schematic view of a solution casting apparatus that can be used in the method of the present invention.
FIG. 14 is a schematic view of a solution casting apparatus that can be used in the method of the present invention.
FIG. 15 is a schematic view of a solution casting apparatus that can be used in the method of the present invention.
FIG. 16 is a schematic view of a solution casting apparatus that can be used in the method of the present invention.
FIG. 17 is a schematic view of a solution casting apparatus that can be used in the method of the present invention.
FIG. 18 is a schematic view of a solution casting apparatus that can be used in the method of the present invention.
FIG. 19 is a schematic view of a solution casting apparatus that can be used in the method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Mixing tank 2 ... Liquid feed pump 3 ... Filter 4 ... Casting die 5 ... Casting band 6, 7 ... Rotary drum 8 ... Guide roll 9 ... Stripping roll 10 ... Guide roll 11 ... Winding roll 12 ... Drying part 14 ... film a ... peeling point b ... contact point h ... tangential direction v ... normal direction θ ... peeling angle

Claims (9)

In a film production method for producing a film based on cellulose ester by stretching, the film to be stretched contains a retardation increasing agent, and the concentration of weight increases as the weight concentration approaches the center from both ends of the film ear. In the final film thickness of the stretched film, the distribution in the width direction becomes thinner as it approaches the center from both ends of the film ear, and the difference in thickness is [(ear end thickness−center thickness) / center thickness]. ] the method for producing a full Irumu you characterized in that at × 100 is 0.1% to 5% In the film production method for producing a film based on cellulose ester by stretching, the film to be stretched is composed of two or more laminated films in the thickness direction, and at least one of the layers has a retardation increasing agent. In addition, the thickness distribution in the width direction of the layer containing the retardation increasing agent is closer to the center from both ends of the film ear, and in the final film thickness of the stretched film, the width direction distribution is thinner the closer the film ear opposite ends in the center, the thickness difference is - you characterized in that 0.1 to 5% in the [(ear end thickness center portion thickness) / central thickness] × 100 off Film manufacturing method In the method for producing a film produced by stretching a film based on cellulose acetate, the cellulose acetate film is composed of two or more laminated films in the thickness direction, and at least one of the layers is relative to the other layers. In the final film thickness of the stretched film, the thickness distribution in the width direction of the layer composed of the cellulose acetate polymer solution having a low average degree of acetylation is closer to the center from both ends of the film ears, in the width direction. The distribution becomes thinner as it approaches the center from both ends of the film ear, and the difference in thickness is [(ear end portion thickness−center portion thickness) / center portion thickness] × 100, which is 0.1 to 5%. method of manufacturing to that full Irumu When the film is a film with a solvent casting method, the film residual volatile content during stretching, on a dry basis volatiles film production method of claim 1 or 2 wherein the 3～300Wt% Using a multi-manifold die system having two or more pockets into the die The process of claim 2 Symbol placement of the film by stretching a laminate of two or more films to produce a film Using a feed block method with block for combining two or more layers at the entrance of the die, the manufacturing method according to claim 2 Symbol placement of the film by stretching a laminate of two or more films to produce a film Using two or more dies, by using a method of sequentially de-casting process according to claim 2 Symbol placement of the film by stretching a laminate of two or more films to produce a film A process according to claim 1, 2 or 4, wherein the film to produce a polarizing plate protective film A process according to claim 1, 2 or 4, wherein the film to produce an optical compensation film

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