JP4625587B2 - Method for producing cellulose acylate film - Google Patents

Description

【００８５】
［残留溶媒量の測定］
フィルムの残留溶媒量は、以下式に従って求めた。
残留溶媒量（％）＝（Ａ−Ｂ）／Ｂ×１００
ここで、
Ａ：フィルムサンプルの重量（ｇ）
Ｂ：１１５℃空気恒温槽にて１時間乾燥後のフィルムサンプルの重量（ｇ）
【００８６】
［面積膨張率の測定］
フィルムの長手方向及び幅手方向に沿って１２０ｍｍ長の短冊状にカットした２枚のサンプルをあらかじめ２３℃，６５％ＲＨで２時間以上放置した後、両端に直径６ｍｍの穴を１００ｍｍ間隔に開け、間隔の原寸（Ｌ１）を最小目盛り１／１０００ｍｍまで測定する。次に、２０℃の水に３０分浸漬した後、パンチ間隔の寸法（Ｌ２）を測定し、長手方向及び幅手方向の膨張を以下式により求める。
膨張＝Ｌ２／Ｌ１
【００８７】
長手方向、幅方向について得られた膨張を以下式に従って計算し、面積膨張率を得る。
面積膨張率（％）＝｛膨張（長手）×膨張（幅手）−１｝×１００
【００８８】
［熱収縮率の測定］
１２０ｍｍ長の短冊状にカットしたサンプルをあらかじめ２３℃，６５％ＲＨで２時間以上放置した後、両端に直径６ｍｍの穴を１００ｍｍ間隔に開け、間隔の原寸（Ｌ１）を最小目盛り１／１０００ｍｍまで測定する。次に、９０℃恒温槽にて１２０時間処理後、パンチ間隔の寸法（Ｌ２）を測定し、以下式により求める。
収縮率（％）＝（Ｌ１−Ｌ２）／Ｌ１×１００
【００８９】
［額縁現象の評価］
作製した偏光板を、吸収軸を対角線として１４．１×１４．１ｃｍの正方形にカットし、粘着剤を介してガラス板の両面にクロスニコル状態で貼り合わせた。
これをシャーカステンで背面より光をあてて暗室内で目視観察すると、すべてのサンプルについて額縁現象は観察されなかった。
【００９０】
これらのサンプルを、６０℃，９０％ＲＨの恒温恒湿室に４８ｈ入れ、さらに常温常湿に１ｈ置いた後、同様にシャーカステン光により暗室内で額縁現象を目視観察した。
【００９１】
額縁現象の程度は以下の基準で判定した。
Ａ…目視では全く額縁現象が観察されない。
Ｂ…縁から１〜２ｍｍ程度にわずかに額縁現象がみられるが、注意してみないとわからない。
Ｃ…縁から５ｍｍ程度、薄いが額縁現象が見られる。
Ｄ…縁から１０ｍｍ程度額縁が発生し、目視で顕著に観察される。
【００９２】
以上のように、実施例は、比較例に対し明らかに額縁現像の改良効果が見られた。また、実施例のうちでも、延伸倍率が高く、吸水膨張率の低い実施例２、４、及び膜厚が薄い実施例５に特に改良効果が顕著であった。
【００９３】
【発明の効果】
本発明は、以上のように構成したので、セルロースアシレートフィルムを用いた偏光板をパネルに貼合した場合において、額縁状の光漏れを抑制することができる。また、限定された条件でフィルムを延伸することにより、望ましい吸水膨張率、熱収縮率のセルロースアシレートフィルムを製造することができる。
【図面の簡単な説明】
【図１】 流延ドラム形式の溶液製膜法によりフィルムを製造する装置の概略図である。
【図２】 流延バンド形式の溶液製膜法によりフィルムを製造する装置の概略図である。
【符号の説明】
１０…流延部
１１…乾燥室
１２…流延ダイ
１３…流延バンド
２０…延伸乾燥部
２１…乾燥室
２２…保持部
３０…乾燥部
３１…搬送ロール
４０…巻き芯
５０…流延部
５１…乾燥室
５２…流延ダイ
５３…流延バンド
６０…延伸乾燥部
６１…乾燥室
６２…保持部
７０…乾燥部
７１…搬送ロール
８０…巻き芯[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cellulose acylate film capable of improving frame-like light leakage, a method for producing the same, and a polarizing plate using the cellulose acylate film.
[0002]
[Prior art]
The importance of polarizing plates has been increasing rapidly with the spread of liquid crystal display devices (LCD). In general, the polarizing plate is configured by attaching a protective film to both surfaces or one surface of a polarizing film having polarizing ability via an adhesive layer. This polarizing film is mainly made of polyvinyl alcohol (hereinafter referred to as “PVA”). After the PVA film is uniaxially stretched, it is dyed with iodine or a dichroic dye, or vice versa. It is produced by stretching and further crosslinking with a boron compound.
[0003]
In general, a cellulose acylate film is used as a polarizing plate protective film to be bonded to a polarizing film, and in particular, cellulose acetate film is the most widely used because of its transparency, low birefringence, appropriate moisture permeability, and appropriate rigidity. It is used. This cellulose acetate film is usually produced by a solution casting method. That is, a dope obtained by dissolving cellulose acetate in a solvent is cast on an endless support such as a drum or a band to provide self-supporting properties. It is peeled and further dried by a drying device using a tenter or a roller.
[0004]
[Problems to be solved by the invention]
However, when a polarizing plate using a cellulose acylate film as a polarizing plate protective film is attached to both sides of the panel with a crossed Nicol via an adhesive and placed in wet heat conditions such as 60 ° C. and 90% RH, There is a case where a light leakage phenomenon (hereinafter referred to as a frame phenomenon) is observed, and the deterioration of display quality is a problem.
[0005]
By the way, as a method for producing a cellulose acylate film used for a polarizing plate protective film or the like, various means have been proposed. For example, JP-A Nos. 62-46625, 11-48271, and 4- No. 1009. However, the means proposed in these publications are intended to promote drying, improve the flatness, etc., and are used to suppress shrinkage or stretch in the width direction by a width regulating means such as a tenter, and the frame phenomenon described above. It was something that could not be improved.
[0006]
That is, the means proposed in Japanese Patent Application Laid-Open No. 11-48271 is such that the volatile content X (%) at the start of stretching is 12 ≦ X <50 and the stretching ratio Y (%) is Y ≧ −10 log (X + 40) +20. The flatness can be improved by stretching with a relatively low residual solvent amount. However, the frame phenomenon cannot be improved, and the film is relatively hard in the region of less than 50% on the basis of the dry amount of the film, and the force required for stretching becomes large, and the film breaks easily. It is. In addition, stretching with a low residual solvent has various problems such as an increase in film haze and a decrease in thermal dimensional stability due to an increase in residual stress.
[0007]
Further, the means proposed in Japanese Patent Application Laid-Open No. 4-1009 is to suppress the width shrinkage rate within a certain range according to the film volatile content in the drying process. This means that the frame phenomenon cannot be improved.
[0008]
In addition, when a polymer film having low birefringence such as polyolefin is used for the polarizing plate protective film, the frame phenomenon is alleviated. However, since the polyolefin film is hydrophobic, the moisture contained in the polarizing film in the manufacturing process and the moisture contained in the adhesive cannot be removed during the drying process, resulting in deterioration of durability and productivity. It was not preferable.
[0009]
An object of the present invention is to provide a cellulose acylate film capable of solving the above-described problems and alleviating the frame phenomenon. Moreover, it aims at providing the manufacturing method of the cellulose acylate film which can manufacture this cellulose acylate film.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the present inventor has intensively studied the relationship between the cellulose acylate film and the frame phenomenon, and that the frame phenomenon is improved when the cellulose acylate film has specific physical properties. The title and the present invention have been completed. Further, the inventors have found a method capable of suitably producing a cellulose acylate film having this specific physical property and completed the present invention.
[0012]
  Further, the method for producing a cellulose acylate film according to the present invention comprises preparing a dope by dissolving a plasticizer containing at least cellulose acylate and an aromatic ring structure in an organic solvent, and continuously casting the dope on an endless support. It is a method for producing a film by drying the peeled film,
  i) a width stretching step of stretching the film in the width direction by 1.5% or more from the endless support to the completion of the film after peeling;
  ii) a longitudinal stretching step of stretching the film in the longitudinal direction by 0.5% or more from the endless support to the completion of the film after peeling;
  iii) a heating step for heating the film surface temperature to 120 ° C. or higher from the endless support to the completion of the film after peeling.And
  The width stretching step applies tension in the width direction while holding both ends of the film with holding means, and the residual solvent amount of the film at the start of applying the tension is 50% by weight or more based on the dry film, and The residual solvent amount at the end of applying the tension is less than 20% by weight based on the dry film,
  The longitudinal stretching step is provided from when the film is peeled off from the endless support until it is introduced into the width stretching step.It is configured as a feature.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The cellulose acylate film according to the present invention is a film containing 80% by weight or more of cellulose acylate, and the area expansion X (%) after being immersed in water at 20 ° C. for 30 minutes is equivalent to the film thickness Y (μm). It has the relationship of the following formula (1),
0 ≦ X <7.2 / √Y Equation (1)
Preferably, it has the relationship of the following formula (2).
0 ≦ X <3.6 / √Y (2)
[0014]
The film thickness Y (μm) of the cellulose acylate film is not particularly limited, but is preferably 60 μm or more, particularly in the range of 70 to 90 μm, where frame failure is particularly remarkable. When the film thickness exceeds 90 μm, the frame becomes prominent and cannot be used for a large-screen LCD.
[0015]
In the cellulose acylate film according to the present invention, the thermal shrinkage rate in each of the film longitudinal direction and the width direction at 90 ° C. and 120 h is preferably 0.2% or less, more preferably 0.18% or less. Preferably, it is most preferably 0.15% or less. When the thermal shrinkage rate exceeds 0.2%, the polarization degree, transmittance, and color change of the polarizing plate are remarkably changed in use under high temperature, and high quality display cannot be performed.
[0016]
The retardation value of the cellulose acylate film is not particularly limited, but is preferably 0 to 200 nm, particularly preferably 0 to 5 nm. The direction of the slow axis is preferably substantially perpendicular or parallel to the longitudinal direction of the film from the viewpoint of avoiding elliptical polarization. Substantially perpendicular or parallel refers to 0 ± 1 ° or 90 ± 1 °.
[0017]
The cellulose acylate film of the present invention is composed mainly of cellulose acylate. Details of the cellulose acylate are described below. Preferred cellulose acylates are those in which the substitution degree of the hydroxyl group of cellulose satisfies all of the following formulas (1) to (4).
(1) 2.6 ≦ A + B ≦ 3.0
(2) 2.0 ≦ A ≦ 3.0
(3) 0 ≦ B ≦ 0.8
(4) 1.9 <AB
[0018]
Here, A and B represent the substituent of the acyl group substituted by the hydroxyl group of cellulose, A is the substitution degree of an acetyl group, and B is the substitution degree of a C3-C5 acyl group. . Cellulose has three hydroxyl groups in one glucose unit, and the above number represents the degree of substitution with respect to the hydroxyl group 3.0, and the maximum degree of substitution is 3.0. Cellulose triacetate generally has a substitution degree of A of 2.6 or more and 3.0 or less (in this case, there is a maximum of 0.4 hydroxyl groups not substituted), and B = 0 is cellulose triacetate. The cellulose acylate of the present invention has a cellulose triacetate in which all acyl groups are acetyl groups, an acetyl group of 2.0 or more, an acyl group of 3 to 5 carbon atoms of 0.8 or less, and an unsubstituted hydroxyl group. A cellulose triacetate having a substitution degree of 2.6 to 3.0 is particularly preferable. The degree of substitution can be obtained by calculation by measuring the degree of binding of acetic acid substituted with a hydroxyl group of cellulose and a fatty acid having 3 to 5 carbon atoms. As a measuring method, it can carry out according to ASTM D-817-91.
[0019]
Other acyl groups having 3 to 5 carbon atoms of the acetyl group are propionyl groups (C₂H₅CO-), butyryl group (C₃H₇CO-) (n-, iso-), valeryl group (C₄H₉CO-) (n-, iso-, sec-, tert-), of which n-substituted ones are preferred from the viewpoint of mechanical strength when formed into a film, ease of dissolution, etc., and in particular, an n-propionyl group Is preferred. Moreover, when the substitution degree of an acetyl group is low, mechanical strength and heat-and-moisture resistance deteriorate. When the degree of substitution of the acyl group having 3 to 5 carbon atoms is high, the solubility in an organic solvent is improved. However, if the degree of substitution is within the above range, good physical properties are exhibited.
[0020]
The degree of polymerization (average viscosity) of cellulose acylate is preferably from 200 to 700, particularly preferably from 250 to 550. The viscosity average degree of polymerization (DP) can be determined with an Ostwald viscometer, and is determined from the measured intrinsic viscosity [η] of cellulose acylate according to the following formula.
DP = [η] / Km (where Km is a constant 6 × 10^-4)
[0021]
Examples of cellulose as a cellulose acylate raw material include cotton linter and wood pulp. Any cellulose acylate obtained from any raw material cellulose may be used, or these may be used in combination.
[0022]
Examples of organic solvents that dissolve cellulose acylate include hydrocarbons (eg benzene, toluene), halogenated hydrocarbons (eg methylene chloride, chlorobenzene), alcohols (eg methanol, ethanol, diethylene glycol), ketones (eg : Acetone), esters (eg, ethyl acetate, propyl acetate), ethers (eg, tetrahydrofuran, methyl cellosolve) and the like.
[0023]
A halogenated hydrocarbon having 1 to 7 carbon atoms is preferably used, and methylene chloride is most preferably used. From the viewpoint of physical properties such as solubility of cellulose acylate, peelability from the support, mechanical strength of the film, optical properties, etc., in addition to methylene chloride, one or several alcohols having 1 to 5 carbon atoms are mixed. It is preferable. The content of alcohol is preferably 2 to 25% by weight, more preferably 5 to 20% by weight, based on the entire solvent. Specific examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol, etc., but methanol, ethanol, n-butanol, or a mixture thereof is preferably used.
[0024]
Recently, a solvent composition not using methylene chloride has been proposed in order to minimize the influence on the environment. For this purpose, ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, and esters having 3 to 12 carbon atoms are preferable, and these are used by appropriately mixing them. These ethers, ketones and esters 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 ethers 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, cyclopentanone, 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.
[0025]
In addition to cellulose acylate, the components that become solid after drying include plasticizers, UV absorbers, inorganic fine particles, heat stabilizers such as alkaline earth metal salts such as calcium and magnesium, antistatic agents, A flame retardant, a lubricant, an oil agent, a peeling accelerator from the support, a cellulose acylate hydrolysis inhibitor, and the like can optionally be included.
[0026]
As a plasticizer to be preferably added, phosphate ester or carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP), cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc. Can be given. Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters. Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethyl hexyl phthalate (DEHP). Examples of citrate esters include triethyl O-acetylcitrate (OACTE) and tributyl O-acetylcitrate (OACTB), acetyltriethyl citrate, and acetyltributyl citrate.
[0027]
Examples of other carboxylic acid esters include trimellitic acid esters such as butyl oleate, methyl acetyl ricinoleate, dibutyl sebacate, and trimethyl trimellitate. Examples of glycolic acid esters include triacetin, tributyrin, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, and butyl phthalyl butyl glycolate.
[0028]
Among the plasticizers exemplified above, triphenyl phosphate, biphenyl diphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, tributyl phosphate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, diethyl hexyl phthalate , Triacetin, ethyl phthalyl ethyl glycolate, trimethyl trimellitate and the like are preferably used. In particular, triphenyl phosphate, biphenyl diphenyl phosphate, diethyl phthalate, ethyl phthalyl ethyl glycolate, and trimethyl trimellitate are preferable. These plasticizers may be used alone or in combination of two or more. The addition amount of the plasticizer is preferably 5 to 30% by weight, particularly preferably 8 to 16% by weight or less based on the cellulose acylate. These compounds may be added together with cellulose acylate and a solvent during the preparation of the cellulose acylate solution, or may be added during or after the solution preparation.
[0029]
As the ultraviolet absorber, any type can be selected according to the purpose, and salicylic acid ester-based, benzophenone-based, benzotriazole-based, benzoate-based, cyanoacrylate-based, nickel complex-based absorbers and the like can be used. However, benzophenone series, benzotriazole series, and salicylic acid ester series are preferred. Examples of benzophenone ultraviolet absorbers include 2,4-dihydroxybenzophenone, 2-hydroxy-4-acetoxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2′-di-hydroxy-4-methoxybenzophenone, 2, 2′-di-hydroxy-4,4′-methoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2-hydroxy-4- (2-hydroxy-3- And methacryloxy) propoxybenzophenone. As a benzotriazole ultraviolet absorber, 2 (2′-hydroxy-3′-tert-butyl-5′-methylphenyl) -5-chlorobenzotriazole, 2 (2′-hydroxy-5′-tert-butylphenyl) ) Benzotriazole, 2 (2′-hydroxy-3 ′, 5′-di-tert-amylphenyl) benzotriazole, 2 (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -5 And chlorobenzotriazole, 2 (2′-hydroxy-5′-tert-octylphenyl) benzotriazole, and the like. Examples of salicylic acid esters include phenyl salicylate, p-octylphenyl salicylate, and p-tert-butylphenyl salicylate. Among these exemplified ultraviolet absorbers, in particular, 2-hydroxy-4-methoxybenzophenone, 2,2′-di-hydroxy-4,4′-methoxybenzophenone, 2 (2′-hydroxy-3′-tert-butyl- 5'-methylphenyl) -5-chlorobenzotriazole, 2 (2'-hydroxy-5'-tert-butylphenyl) benzotriazole, 2 (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) ) Benzotriazole, 2 (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) -5-chlorobenzotriazole is particularly preferred.
[0030]
A combination of a plurality of absorbents having different absorption wavelengths is particularly preferable because a high blocking effect can be obtained in a wide wavelength range. The amount of the ultraviolet absorber is preferably from 0.01 to 5% by weight, particularly preferably from 0.1 to 3% by weight, based on the cellulose acylate. The ultraviolet absorber may be added simultaneously with the dissolution of cellulose acylate, or may be added to the dope after dissolution. In particular, a mode in which an ultraviolet absorbent solution is added to the dope immediately before casting using a static mixer or the like is preferable because the spectral absorption characteristics can be easily adjusted.
[0031]
As the inorganic fine particles to be added to the cellulose acylate, silica, kaolin, talc, diatomaceous earth, quartz, calcium carbonate, barium sulfate, titanium oxide, alumina and the like can be arbitrarily used depending on the purpose. These fine particles are preferably dispersed in the binder solution by any means such as a high-speed mixer, a ball mill, an attritor, or an ultrasonic disperser before being added to the dope. As the binder, cellulose acylate is preferable. It is also preferable to carry out dispersion together with other additives such as ultraviolet absorbers. The dispersion solvent is arbitrary, but a composition close to that of the dope solvent is preferable. The number average particle diameter of the dispersed particles is preferably from 0.01 to 100 μm, particularly preferably from 0.1 to 10 μm. The above dispersion may be added simultaneously to the cellulose acylate dissolving step, or may be added to the dope in any step, but a form of addition just before casting using a static mixer or the like is preferable as with the ultraviolet absorber.
[0032]
As the peeling accelerator from the support, a surfactant is effective, and is not particularly limited, such as a phosphoric acid type, a sulfonic acid type, a carboxylic acid type, a nonionic type, and a cationic type. These are described, for example, in JP-A-61-243837.
[0033]
The polarizing plate protective film of the present invention is preferably imparted with hydrophilicity by means such as saponification, corona treatment, flame treatment, glow discharge treatment, etc., on the surface of the film in order to enhance the adhesion with the PVA resin. Alternatively, a hydrophilic resin may be dispersed in a solvent having affinity for cellulose acylate and applied in a thin layer. Among the above means, saponification is particularly preferable because the flatness and physical properties of the film are not impaired. The saponification treatment is performed, for example, by immersing the film in an alkaline aqueous solution such as caustic soda. In order to remove excess alkali after the treatment, it is preferable to neutralize with a low-concentration acid and sufficiently wash with water.
[0034]
The cellulose acylate film according to the present invention can be used as an optical compensation film by applying a polarizing plate protective film, a retardation film, and an optically anisotropic layer, and is particularly effective for a polarizing plate protective film.
[0035]
The cellulose acylate film of the present invention is bonded to at least one surface of a polarizing film as a polarizing plate protective film and used as a polarizing plate. A polarizing plate is generally produced by adhering a protective film to at least one surface of a polarizing film produced by adsorbing and orienting a dichroic substance on a base film. As the base polymer, a PVA polymer is generally used. As the dichroic substance, iodine or a dichroic dye is used alone or in combination.
[0036]
The cellulose acylate film as described above can be suitably produced by the method for producing a cellulose acylate film according to the present invention.
[0037]
In the method for producing a cellulose acylate film according to the present invention, a dope is prepared by dissolving a plasticizer containing at least cellulose acylate and an aromatic ring structure in an organic solvent, and the dope is continuously cast on an endless support. A method of peeling off and drying the peeled film to produce a film,
i) a width stretching step of stretching the film in the width direction by 1.5% or more from the endless support to the completion of the film after peeling;
ii) a longitudinal stretching step of stretching the film in the longitudinal direction by 0.5% or more from the endless support to the completion of the film after peeling;
iii) a heating step of heating the film surface temperature of the film to 120 ° C. or higher from the endless support to the completion of the film after peeling.
[0038]
In addition, in the said manufacturing method, until a film completion is until it winds up a film on a winding core.
[0039]
The ratio between the stretching ratio in the width direction in the width stretching process and the stretching ratio in the longitudinal direction in the longitudinal stretching process is not particularly limited and can be arbitrarily selected.
[0040]
The width stretching step is provided until the film is completed after the film is peeled off from the endless support, and tension is applied in the width direction while holding both ends of the film with holding means (such as a tenter). This width extending step may be newly provided as a width extending step or may be combined with a conventional step. For example, the width stretching step is preferably used in the width regulating step (tenter step). In addition, when performing in the width regulation step, while regulating the width direction, it is not always necessary to continue to stretch the film in the width direction, for example, after reducing the width in a range where the film does not sag in the first half, In the latter half, the film can be stretched in the width direction.
[0041]
In the width stretching step, the residual amount of solvent in the film at the start of application of tension in the width direction of the film is preferably 50% by weight or more, more preferably 60% by weight or more based on the dry film. Moreover, it is preferable that the residual solvent amount at the time of completion | finish of tension | tensile_strength is less than 20 weight% on a dry film basis, and it is more preferable that it is less than 15 weight%.
[0042]
The longitudinal stretching step is provided until the film is completed after peeling the film from the endless support, and a new longitudinal stretching step may be provided, or a conventional step may be used. For example, after peeling the film from the endless support, it can be used in the roller drying process provided at the subsequent stage of the conveying process and the width regulating process until it is introduced into the width regulating process. After that, the transporting process until it is introduced into the width regulating process is preferable because the film residual solvent is high and the film can be stretched without leaving an unnecessary residual stress.
[0043]
As described above, the residual solvent content of the film in the longitudinal stretching step is preferably high from the viewpoint of residual stress, and is preferably 50% or more, more preferably 60% or more on the dry film basis.
[0044]
Although the specific example of the manufacturing apparatus which enforces the manufacturing method of the cellulose acylate film by this invention is shown in FIG.1 and FIG.2, this invention is not limited to these examples.
[0045]
FIG. 1 is a schematic view showing an example of a drum casting method in an apparatus for producing a cellulose acylate film. In this figure, 10 is a casting part for casting a dope onto an endless support to form a film, 20 is a stretching / drying part for stretching and drying the film formed by the casting part 10, and 30 is a film for further drying. A drying section 40 for drying to obtain a product, 40 is a winding core for winding the completed film.
[0046]
The casting part 10 is provided with a casting die 12 in a drying chamber 11, a casting drum 13 as an endless support, and a peeling roll 14 for peeling off the film. Yes. The stretching / drying unit 20 is provided with holding means 22 that stretches in the width direction while holding both ends of the film in the drying chamber 21, and the drying unit 30 includes a large number of transport rolls 32 in the drying chamber 31. ing.
[0047]
In order to produce a film using the production apparatus of the drum casting method as described above, first, the dope is extruded from the casting die 12 and cast onto the casting drum 13. It is preferable that the casting drum 13 is cooled to 10 ° C. or less in order to quickly remove the casting drum 13. The film is dried in an appropriate atmosphere, and when the dope has a self-supporting property, it is peeled off as a film containing a residual solvent through a peeling roll 14. The peeled film is sent to the drying chamber 21 and is stretched in the longitudinal direction in this process (longitudinal stretching step). In the drying chamber 21, both ends of the introduced film are held by the holding means 22, and dried while being conveyed while being stretched by applying tension in the width direction (width stretching step). The holding means 22 can be any means such as a clip or a pin. As the drying means, hot air blowing is generally used, but any means such as infrared rays and microwaves can be used. It is preferable to dry until the residual solvent becomes 20% or less with the regulation in the width direction. This film is further transported to the drying chamber 31, wound around a transport roll 32 and transported, and further dried and wound into a roll form by the winding core 40. The amount of residual solvent during winding is preferably 0.8% or less, and more preferably 0.5% or less.
[0048]
FIG. 2 is a schematic view showing an example of the band casting method. In this figure, 50 is a casting part for casting a dope onto an endless support to form a film, 60 is a stretching and drying part, 70 is a drying part, and 80 is a winding core.
[0049]
The casting part 50 is provided with a casting die 52 in a drying chamber 51, a casting band 53 as an endless support, and a stripping roll 54 for stripping the film. Yes. The stretch drying unit 60, the drying unit 70, and the winding core 80 are substantially the same as those in the drum casting method shown in FIG.
[0050]
In order to produce a film using the production apparatus of the band casting method as described above, first, the dope is extruded from the casting die 52 and cast onto the casting band 53. The film is dried on the casting band 53 by means of hot air or the like, and when the dope has a self-supporting property, it is peeled off as a film containing a residual solvent through a peeling roll 54. The peeled film is sent to the drying chamber 61, and is stretched in the longitudinal direction in this process (longitudinal stretching step). In the drying chamber 61, both ends of the introduced film are held by the holding means 62, and dried while being conveyed while being stretched by applying tension in the width direction (width stretching step). The film is further transported to the drying chamber 71, wound around a transport roll 72 and transported, and further dried and wound into a roll form by the winding core 40.
[0051]
The drying chambers 11, 21, 31, 51, 61, and 71 do not need to have a single drying condition, and may be divided into several parts and dried in different atmospheres. Moreover, it is preferable to perform the film heating for improving the heat shrinkage rate in the latter half of the drying sections 30 and 70.
[0052]
【Example】
In order to describe the present invention in detail, examples will be described below, but the present invention is not limited thereto.
[0053]
[Preparation of raw material dope]
(Preparation of fine particle dispersion a)
Silica (Nippon Aerosil Co., Ltd., “Aerosil R972”) 0.67% by weight
Cellulose acetate (substitution degree 2.8) 2.93% by weight
Triphenyl phosphate 0.23% by weight
Biphenyl diphenyl phosphate 0.12% by weight
Methylene chloride 88.37% by weight
Methanol 7.68% by weight
A solution was prepared and dispersed with an attritor so that the volume average particle size was 0.7 μm.
[0054]
(Preparation of raw material dope A)
Cellulose triacetate (substitution degree 2.8) 89.3% by weight
Triphenyl phosphate 7.1% by weight
Biphenyl diphenyl phosphate 3.6% by weight
17.9 parts by weight of the fine particle dispersion a is added to 100 parts by weight of the solid content,
Dichloromethane 92% by weight
8% by weight of methanol
The dope was prepared by appropriately adding a mixed solvent to be dissolved under stirring. The solid content concentration of the dope was 18.5%. This dope is filtered through a filter paper (Toyo Filter Paper Co., Ltd., “# 63”), then filtered through a sintered metal filter (Nihon Seisen Co., Ltd., “06N”, nominal pore size 10 μm), and further a mesh filter. (Nippon Pole Co., Ltd., “RM”, nominal pore diameter 45 μ).
[0055]
(Preparation of UV absorber solution b)
2 (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5
Chlorbenzotriazole 5.83 wt%
2 (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) benzo
Triazole 11.66% by weight
Cellulose acetate (substitution degree 2.8) 1.48% by weight
Triphenyl phosphate 0.12% by weight
Biphenyl diphenyl phosphate 0.06% by weight
Methylene chloride 74.38% by weight
Methanol 6.47% by weight
An ultraviolet absorber solution was prepared according to the above formulation, and filtered through “Astrpore 10 Filter” manufactured by Fuji Photo Film Co., Ltd.
[0056]
(Preparation of raw material dope B)
Cellulose triacetate (substitution degree 2.8) 89.5% by weight
Triphenyl phosphate 7.0% by weight
Biphenyl diphenyl phosphate 3.5% by weight
To the solid content
82% by weight of methylene chloride
15% by weight of methanol
n-butanol 3% by weight
The mixed solvent to be added was appropriately added and dissolved by stirring to prepare a dope. The solid content concentration of the dope was 23.5%. This dope is filtered with a filter paper (Toyo Filter Paper Co., Ltd., “# 63”), further filtered with a sintered metal filter (Nihon Seisen Co., Ltd., “06N”), and further with a sintered metal filter (Nihon Seisen). The product was filtered with “12N” (nominal pore diameter 40 μ) manufactured by Co., Ltd.
[0057]
(Fine particle dispersion, preparation of ultraviolet absorber solution c)
2 (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) -5
Chlorbenzotriazole 5.40% by weight
2 (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) benzo
Triazole 10.79% by weight
Silica (Nippon Aerosil Co., Ltd., “Aerosil R972”) 0.39% by weight
Cellulose acetate (substitution degree 2.8) 2.58% by weight
Triphenyl phosphate 0.28% by weight
Biphenyl diphenyl phosphate 0.14% by weight
Methylene chloride 67.71% by weight
Methanol 10.86% by weight
n-butanol 1.85% by weight
A solution was prepared and dispersed with an attritor so that the volume average particle diameter of the silica particles was 0.6 μm. The solution after dispersion was filtered through “Astropore 10 filter” manufactured by Fuji Photo Film Co., Ltd., and further filtered through a sintered metal filter (manufactured by Nippon Seisen Co., Ltd., “07N”).
[0058]
<Measurement of volume average particle diameter>
The volume average particle size in the fine particle dispersion a and the fine particle dispersion / ultraviolet absorber solution c was measured by “Mastersizer MS20” manufactured by MALVERN.
[0059]
<Measurement of dope solid content concentration>
The dope solid content concentration (%) in the raw material dope A and the raw material dope B is based on the moisture amount,
(Weight loss of dope heated at 120 ° C. for 2 hours) / (original dope weight) × 100
I asked for it.
[0060]
[Example 1]
For the dope A, using a static mixer, adjusting the ultraviolet absorbent solution b so that the amount of the ultraviolet absorbent is 1.04% by weight with respect to the solid content in the dope, Added and mixed.
[0061]
Using this dope, a film was produced with the production apparatus of the band casting method shown in FIG. That is, the dope was cast from the casting die 52 to the casting band 53, dried with hot air until self-supporting, and peeled off as a film. The peeled film was sent to the stretching / drying unit 60. At this time, tension was applied in the longitudinal direction of the film, and the film was stretched by 0.8% in the longitudinal direction.
[0062]
Both ends of the film introduced into the stretching / drying unit 60 are held by the holding means 62 of the tenter dryer, and the film is conveyed while tension is applied in the width direction. As a result, the film was stretched 3.0% with respect to the width of the film at the entrance of the stretch drying unit 60. In addition, in the extending | stretching drying part 60, the film was always extended | stretched and the film was not shrunk | reduced. Further, the residual solvent at the start of application of tension in the width direction (tenter inlet) was 55% by weight, and the residual solvent at the end of application of tension (tenter outlet) was 13.7% by weight.
[0063]
Next, the film was introduced into the roller drying unit 70 and heated until the surface temperature of the film reached a maximum of 130 ° C. In the roller drying unit 70, no stretching occurred in the width direction and the longitudinal direction. The film thickness of the completed film was 80 μm.
[0064]
[Example 2]
The longitudinal stretch rate until peeling from the casting band 53 and introduction into the stretch drying unit 60 is 10.0%, the stretch rate in the width direction in the stretch drying unit 60 is 12.0%, and the residual solvent amount at the outlet is 14%. A film was produced in the same manner as in Example 1 except that the content was 3% by weight.
[0065]
[Example 3]
For the dope B, using a static mixer, the ultraviolet absorber solution c is added in the dope piping path while adjusting the amount of the ultraviolet absorber to 1.04% by weight with respect to the solid content in the dope, Mixed.
[0066]
Using this dope, a film was produced by a drum casting method production apparatus shown in FIG. That is, the dope was cast from the casting die 12 to the casting drum 13, dried with hot air until self-supporting, and peeled off as a film. At this time, the surface temperature of the casting drum 13 was −3 ° C. The peeled film was sent to the stretching / drying unit 20. At this time, a tension was applied in the longitudinal direction of the film and the film was stretched by 8.0% in the longitudinal direction.
[0067]
  Both ends of the film introduced into the stretch drying unit 20 are held by the holding means 62 of the tenter dryer, and the width is first reduced by 5.3% in the first half of the process, and then the rest Width direction in the process2. Stretched 0%. At the time when the 2/3 contraction process in the first half was completed, no loose film was visually observed. Further, the residual solvent at the start of applying the tension in the width direction (tenter inlet) was 240% by weight, and the residual solvent at the end of applying the tension (tenter outlet) was 12.0% by weight.
[0068]
Next, the film was introduced into the roller drying unit 30 and heated until the surface temperature of the film reached a maximum of 137 ° C. In the roller drying unit 30, no stretching occurred in the width direction and the longitudinal direction. The film thickness of the completed film was 80 μm.
[0069]
[Example 4]
12.0% of the stretching ratio in the longitudinal direction until peeling from the casting drum 13 and introduction into the stretching and drying section 20, and 5.7% of the stretching ratio in the width direction in the latter third of the processes in the stretching and drying section 20. A film was produced in the same manner as in Example 3 except that the amount of residual solvent at the outlet was 12.7% by weight.
[0070]
[Example 5]
The amount of the UV absorber is 2.08% by weight, the film thickness of the finished film is 40 μm, the residual solvent at the inlet of the stretch drying unit 60 is 52% by weight, the residual solvent at the outlet is 8.3% by weight, inside the roller drying unit 70 A film was produced in the same manner as in Example 1 except that the maximum temperature was 125 ° C.
[0071]
[Comparative Example 1]
A film was produced in the same manner as in Example 1 except that the stretching ratio in the width direction in the stretching and drying unit 60 was 0.5% and the residual solvent at the outlet of the stretching and drying unit 60 was 14.0% by weight.
[0072]
[Comparative Example 2]
A film was produced in the same manner as in Example 1 except that the maximum film surface temperature in the roller drying unit 70 was set to 110 ° C.
[0073]
[Comparative Example 3]
Example 3 except that in the latter half of the third step of the stretch drying unit 20, the shrinkage was 3.0% without stretching in the width direction, and the residual solvent at the outlet of the stretch drying unit 20 was 13.0% by weight. A film was produced in the same manner as above.
[0074]
[Comparative Example 4]
A film was produced in the same manner as in Example 1 except that the temperature of the stretching / drying unit 60 was lowered and the residual solvent at the outlet of the stretching / drying unit 60 was changed to 22% by weight.
[0075]
[Comparative Example 5]
The residual solvent at the entrance of the stretch drying unit 60 was 25% by weight, and an attempt was made to produce a film in the same manner as in Example 2. However, the tenter clip part was broken, and the stretch rate in the width direction was the same as in Example 2. It was not obtained.
[0076]
[Comparative Example 6]
A film was produced in the same manner as in Example 5 except that the film was not stretched in the stretch drying unit 60, the width was shrunk by 1.2%, and the residual solvent at the outlet was 9.0%.
[0077]
[Comparative Example 7]
The film is not stretched in the longitudinal direction until it is introduced into the stretching / drying unit 60 from peeling of the film, and is shrunk by 0.5%. In the stretching / drying unit 60, the stretching ratio in the width direction is 2.0%. A film was produced in the same manner as in Example 1 except that the residual solvent was changed to 13.8% by weight.
[0078]
[Saponification of film]
The films of Examples 1 to 5 and Comparative Examples 1 to 4, 6 and 7 were treated with a 1.5N NaOH aqueous solution at 50 ° C. for 180 seconds, then neutralized and washed with water, and dried.
[0079]
[Preparation of polarizing plate]
“PVA film” (75 μm) manufactured by Kuraray Co., Ltd. was immersed in an aqueous solution of 0.3 g / l iodine and 18.0 g / l potassium iodide at 25 ° C., and further 80 g / l boric acid and 30 g potassium iodide. / L, zinc chloride 10 g / l, stretched 5.0 times in an aqueous solution at 50 ° C. Examples 1 to 5 and Comparative Examples 1 to 4 and 6 which were subjected to saponification treatment using a 4% aqueous solution of PVA (manufactured by Kuraray Co., Ltd., “PVA-117H”) as an adhesive after drying at 60 ° C. for 5 minutes. , 7 films were bonded to both sides and further dried at 80 ° C. to obtain polarizing plates.
The polarization degree of the obtained polarizing plate was 99.7 to 99.9%.
[0080]
<Measurement of degree of polarization>
The degree of polarization was calculated by the following formula.
Polarization degree P (%) = {(Tp−Tc) / (Tp + Tc)}^1/2× 100
Where Tp is the transmittance (%) when the absorption axes of the two polarizing plates are superposed in parallel in the sample of the two polarizing plates, and Tc is perpendicular to the absorption axis of the two polarizing plates. It is the transmittance (%) when superimposed.
[0081]
Further, the film immersion time in the staining solution was adjusted so that the transmittance of the polarizing plate was 42 ± 0.5%.
[0082]
<Transparency of polarizing plate>
The transmittance of the polarizing plate was calculated according to the following formula from the spectral transmittance τ (λ) obtained every 10 nm by measuring the transmittance with a Shimadzu spectrophotometer UV-3100PC. In the equation, P (λ) is a spectral distribution of the standard light D65 light source according to JIS Z 8720, and y (λ) is a color matching function based on the two-degree field X, Y, Z system according to JIS Z 8701.
Transmittance T (%) = A / B × 100
A = ∫_visP (λ) · y (λ) · τ (λ) dλ
B = ∫_visP (λ) · y (λ) dλ
(Vis: 400-700 nm)
[0083]
Table 1 shows the results of testing Examples 1 to 5 and Comparative Examples 1 to 4, 6, and 7.
[0084]
[Table 1]

[0085]
[Measurement of residual solvent content]
The amount of residual solvent in the film was determined according to the following formula.
Residual solvent amount (%) = (A−B) / B × 100
here,
A: Weight of film sample (g)
B: Weight (g) of film sample after drying for 1 hour in a 115 ° C air constant temperature bath
[0086]
[Measurement of area expansion coefficient]
  Along the longitudinal and lateral directions of the filmCut into strips 120mm long2 sheetsThe sample is left to stand for 2 hours or more at 23 ° C. and 65% RH in advance, then holes with a diameter of 6 mm are formed at both ends at 100 mm intervals, and the original size (L1) of the interval is measured to a minimum scale of 1/1000 mm. Next, after being immersed in water at 20 ° C. for 30 minutes, the dimension (L2) of the punch interval was measured, and the longitudinal direction and width were measured.handThe expansion in the direction is obtained by the following formula.
        Expansion = L2 / L1
[0087]
The expansion obtained in the longitudinal direction and the width direction is calculated according to the following formula to obtain the area expansion rate.
Area expansion rate (%) = {expansion (longitudinal) × expansion (width) −1} × 100
[0088]
[Measurement of heat shrinkage]
Samples cut into 120 mm long strips are left in advance at 23 ° C. and 65% RH for 2 hours or more, then 6 mm diameter holes are opened at both ends at 100 mm intervals, and the original distance (L1) is set to the minimum scale of 1/1000 mm taking measurement. Next, after processing in a 90 ° C. constant temperature bath for 120 hours, the dimension (L2) of the punch interval is measured and obtained by the following equation.
Shrinkage rate (%) = (L1-L2) / L1 × 100
[0089]
[Evaluation of frame phenomenon]
The produced polarizing plate was cut into a square of 14.1 × 14.1 cm with the absorption axis as a diagonal line, and bonded to both surfaces of the glass plate in a crossed Nicol state via an adhesive.
When this was visually observed in the dark room by applying light from the back with a Schaukasten, no frame phenomenon was observed for all samples.
[0090]
These samples were placed in a constant temperature and humidity chamber at 60 ° C. and 90% RH for 48 hours, and further placed at room temperature and humidity for 1 hour, and then the frame phenomenon was visually observed in the dark room similarly with Schaukasten light.
[0091]
The degree of the frame phenomenon was judged according to the following criteria.
A ... The frame phenomenon is not observed at all visually.
B: Although a frame phenomenon is slightly seen about 1-2 mm from the edge, it is not understood unless attention is paid.
C: The frame phenomenon is seen although it is thin about 5 mm from the edge.
D: A frame of about 10 mm is generated from the edge, and is visually observed visually.
[0092]
As described above, in the example, the effect of improving the frame development was clearly seen as compared with the comparative example. Further, among the examples, the improvement effect was particularly remarkable in Examples 2 and 4 having a high draw ratio and a low water absorption expansion coefficient and Example 5 having a thin film thickness.
[0093]
【The invention's effect】
Since this invention was comprised as mentioned above, when the polarizing plate using a cellulose acylate film is bonded to a panel, frame-shaped light leakage can be suppressed. In addition, by stretching the film under limited conditions, a cellulose acylate film having a desirable water absorption expansion coefficient and thermal contraction coefficient can be produced.
[Brief description of the drawings]
FIG. 1 is a schematic view of an apparatus for producing a film by a casting drum type solution casting method.
FIG. 2 is a schematic view of an apparatus for producing a film by a casting band type solution casting method.
[Explanation of symbols]
10 ... Casting part
11 ... Drying room
12 ... Casting die
13 ... Casting band
20 ... Stretching and drying section
21 ... Drying room
22 ... holding part
30 ... Drying section
31 ... Conveying roll
40 ... winding core
50 ... Casting part
51. Drying room
52 ... Casting die
53 ... Casting band
60 ... Stretching and drying section
61 ... Drying room
62 ... Holding part
70 ... Drying section
71 ... Conveying roll
80 ... winding core

Claims (3)

A plasticizer containing at least a cellulose acylate and an aromatic ring structure is dissolved in an organic solvent to prepare a dope, and the dope is continuously cast on an endless support and peeled off. A method for manufacturing
i) A width stretching step of stretching the film in the width direction by 1.5% or more from the endless support to the completion of the film after peeling;
ii) a longitudinal stretching step of stretching the film by 0.5% or more in the longitudinal direction from the endless support to the completion of the film after peeling;
iii) a heating step of heating the film surface temperature of the film to 120 ° C. or higher from the endless support to the completion of the film after peeling,
The width stretching step applies tension in the width direction while holding both ends of the film with holding means, and the residual solvent amount of the film at the start of applying the tension is 50% by weight or more based on the dry film, and The residual amount of solvent at the end of applying the tension is less than 20% by weight based on the dry film,
The method for producing a cellulose acylate film, wherein the longitudinal stretching step is provided from when the film is peeled off from the endless support until it is introduced into the width stretching step. Stretching in the width direction of the film in the width stretching step is 5% or more of stretching, according to claim 1, wherein the longitudinal stretching of the film in the longitudinal stretching step is the stretching of 5% or more A method for producing a cellulose acylate film. The width stretching step applies tension in the width direction while holding both ends of the film with holding means, and after the start of tension application, the film width is reduced within a range in which the film does not become slack, and then the film is the method for producing a cellulose acylate film according to claim 1 or 2, characterized in that stretching in the width direction.

Images