JP4710160B2 - Optical compensation cellulose ester film manufacturing equipment for liquid crystal display - Google Patents

Description

【００３９】
表１の結果からわかるように、エンドレスベルト２の上部移行部２ａの裏面に接触するサポートロール３，３の距離Ｌ1 、及び同エンドレスベルト２の下部移行部２ｂの裏面に接触するサポートロール３，３の距離Ｌ2 が１０００〜５０００ｍｍの範囲内の場合（参考例１〜３、実施例１〜２）では、セルロースエステルフィルムのレターデーション値のばらつきΔＲは小さいものであるが、Ｌ1 及びＬ2 が５０００ｍｍを越えると、レターデーション値のばらつきΔＲが増大することがわかった（比較例１）。なお、Ｌ1 及びＬ2 が１０００ｍｍ（参考例１）でのレターデーション値のばらつきΔＲは、Ｌ1 及びＬ2 が２０００〜５０００ｍｍの範囲内の実施例１〜２および参考例２〜３の場合と大きく変わらないが、このように１０００ｍｍ間隔でサポートロール３を配置した場合は、ロール本数が増えることによるコスト負担が大きくなるため、サポートロール３，３の距離Ｌ1 及びＬ2 は、２０００ｍｍ〜５０００ｍｍの範囲内が好ましい。
【００４０】
さらに、表１の実施例３〜５及び比較例２と３の結果からわかるように、相互に隣り合うサポートロール３，３間の距離Ｌ1 及びＬ2 が、２ｍより大きく、５ｍ以下の範囲内でかつロール周長Ｓ×整数ｎ、及びその±５％以内であると、レターデーション値のばらつきΔＲが大きくなり（比較例２と３）、サポートロール３，３間の距離Ｌ1 及びＬ2 が、２ｍ以上、５ｍ以下の範囲で、ロール周長の整数倍の±５％の範囲外の長さであれば、得られるセルロースエステルフィルムのレターデーション値のばらつきΔＲを小さくすることができる（実施例３〜５）ことがわかった。
【００４１】
【発明の効果】
本発明によれば、溶液流延製膜法により液晶表示装置用光学補償セルロースエステルフィルムを製造する装置において、セルロースエステル溶液を流延して膜を形成する駆動エンドレスベルトが掛け渡された一対のドラム同士の中間に配置されかつエンドレスベルトの上部及び下部移行部をそれぞれ裏側より支えている複数のサポートロールの配置に関して、使用するベルトの長さと搬送速度に対して必要なサポートロールの距離を、２ｍ以上、５ｍ以下の範囲で、ロール周長の整数倍の±５％の範囲外の長さに規定することにより、高速搬送でのベルトの振動を抑制し、安定した製膜を可能として、液晶表示装置用光学補償セルロースエステルフィルムの面品質及び光学特性を改善することができ、レターデーション値のばらつきが少なくかつ目標とするレターデーション値を持つ品質の優れた液晶表示装置用光学補償セルロースエステルフィルムを効率よく、常時、高品質で製造することを可能であるという効果を奏する。
【図面の簡単な説明】
【図１】 本発明の実施の形態を示す液晶表示装置用光学補償セルロースエステルフィルムの製造装置の平面略図である。
【図２】 同セルロースエステルフィルムの製造装置の縦断面略図である。
【図３】 従来のセルロースエステルフィルムの製造装置の縦断面略図である。
【符号の説明】
１ ドラム
２ エンドレスベルト
２ａ エンドレスベルトの上部移行部
２ｂ エンドレスベルトの下部移行部
３ サポートロール
４ ダイ
５ ウェブ
６ 剥離ロール[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for producing an optically compensated cellulose ester film for a liquid crystal display device .
[0002]
[Prior art]
In general, a liquid crystal image display device is widely used as a display device such as a word processor or a personal computer. The basic configuration of the liquid crystal image display device is one in which polarizing plates are provided on both sides of a liquid crystal cell. Since a polarizing plate allows only light of a polarization plane in a certain direction to pass, it plays an important role in visualizing changes in the orientation of the liquid crystal display device due to an electric field in a liquid crystal image display device. The performance of the display device is greatly affected.
[0003]
In recent years, liquid crystal image display devices have been developed for a large screen and high image quality as a monitor instead of a CRT. Along with this, the demand for protective films for polarizing plates for liquid crystals has also become severe. In particular, it is strongly desired to improve the surface quality and optical property problems that occur with the surface roughness of the protective film.
[0004]
As a protective film used for a polarizing plate of a liquid crystal image display device, a cellulose ester film such as triacetyl cellulose is suitable because it has a small birefringence and is often used.
[0005]
The polarizing plate generally has a configuration in which a transparent resin layer is laminated on one or both sides of a polarizing film made of polyvinyl alcohol film or the like on which iodine or dye is adsorbed and oriented. It is often used as this transparent resin layer.
[0006]
By the way, since the liquid crystal image display device tends to be further thinned, a thinner film is also required for the cellulose ester film used for the polarizing plate. Here, the cellulose ester film used for the film base of the conventional silver halide photographic light-sensitive material is manufactured using, for example, an ordinary solution casting film forming apparatus as shown in FIG.
[0007]
First, the cellulose ester is dissolved in a mixed solvent of a good solvent that dissolves the cellulose ester and a poor solvent that does not dissolve the cellulose ester, and a cellulose ester solution (hereinafter referred to as “dope”) is prepared by adding a plasticizer and an ultraviolet absorber. Is cast from a die (12) onto a drive stainless steel endless belt (13) having a mirror-finished surface to obtain a dope film or web (11), and the web (11) is placed on the lower surface of the endless belt (13). When it is almost complete, it is peeled off by the peeling roll (14), transferred by a plurality of transfer rolls (20) arranged in a staggered manner as viewed from the side, and introduced into the drying device (15). In the drying device (15), the web (11) is meandered by a plurality of drying rolls (16) arranged alternately on the top and bottom, and the web (11) is moved forward of the bottom of the drying device (15). The air is blown from the portion, dried by the dry gas (17) discharged from the rear portion of the ceiling of the drying device (15), and wound on the winder (18) as the cellulose ester film (21). The drying device (15) uses a drying gas, but may be dried by infrared rays. Although not shown in the figure, while the web (11) is peeled off by the peeling roll (14) and introduced into the drying device (15), the both side edges of the web are held with clips and stretched. A tenter dryer (not shown) for drying may be interposed.
[0008]
As described above, in recent years, light and thin features have been evaluated, and as liquid crystal display devices have been actively developed, there is a demand for cellulose ester films having excellent optical properties. Increasingly.
[0009]
One of the important optical properties of the cellulose ester film is retardation. Retardation is represented by the product of birefringence and film thickness. Retardation is largely related to the compensation of a liquid crystal display device incorporating a cellulose ester film, resulting in a deviation in retardation of the cellulose ester film, If this deviation exceeds a certain range, there is a problem that sufficient compensation of the liquid crystal display element cannot be performed. In particular, when the deviation from the target retardation value in the width direction becomes large, even in one cellulose ester film cut out according to the size of the liquid crystal display element, there is a problem that uniform screen display cannot be performed due to partially different optical characteristics. In addition, the problem that optical characteristics are different between the cut cellulose ester films becomes remarkable.
[0010]
[Problems to be solved by the invention]
An object of the present invention is an apparatus for producing an optically-compensated cellulose ester film for a liquid crystal display device, in particular, by a solution casting film forming method, and is disposed between a pair of front and rear drums holding an endless belt, and an upper portion of the endless belt With regard to the arrangement of multiple support rolls that are in contact with the back surface of the lower transition part, belt vibration during high-speed conveyance is suppressed by defining the required support roll distance for the belt length and conveyance speed to be used. , Enabling stable film formation, improving the surface quality and optical properties of the optically compensated cellulose ester film for liquid crystal display devices, with little variation in retardation values and excellent quality with target retardation values liquid crystal display device for optical compensation cellulose ester film efficiently at all times, high - In in attempts to provide an apparatus for manufacturing a liquid crystal display device for optical compensation cellulose ester film makes it possible to produce.
[0011]
[Means for Solving the Problems]
The apparatus for producing an optically compensated cellulose ester film for a liquid crystal display device of the present invention is an apparatus for producing an optically compensated cellulose ester film for a liquid crystal display device by a solution casting film forming method, and a film is formed by casting a cellulose ester solution. Among a plurality of rolls arranged between a pair of drums around which a driving endless belt is stretched and supporting the upper and lower transition portions of the endless belt from the back side, between the support rolls adjacent to each other The distance is in the range of 2 m or more and 5 m or less, and the length is outside the range of ± 5% of an integral multiple of the roll circumference .
The cellulose ester film produced by the apparatus of the present invention is excellent in optical isotropy, and is suitable for a member of a liquid crystal display device, particularly an optical compensation film.
[0012]
The film thickness of the optically compensated cellulose ester film for a liquid crystal display device produced by the device of the present invention is, for example, in the range of 20 to 200 μm.
[0013]
In the above, as the endless belt, a driving metal endless belt such as a driving stainless steel endless belt is usually used.
[0014]
The cellulose ester used in the cellulose ester film is obtained by reacting cellulose with acetic anhydride, propionic anhydride or butyric anhydride by a conventional method using cellulose selected from the group of linter pulp, wood pulp and kenaf pulp. Among them, cellulose triacetate, cellulose acetate propionate, cellulose acetate butyrate and cellulose acetate propionate butyrate having a substitution degree of all acyl groups with respect to hydroxyl groups of cellulose of 2.5 to 3.0 are preferable. The substitution degree of the acetyl group of the cellulose ester is preferably at least 1.5. As a measuring method of the substitution degree of the acyl group of a cellulose ester, it can implement according to ASTM-D-817-91. The molecular weight of the cellulose ester is preferably 70,000 to 300,000, particularly 80,000 to 200,000 as the number average molecular weight in view of mechanical strength when formed into a film. Usually, cellulose ester becomes flakes after treatment such as water washing after the reaction, and is used in that shape, but the solubility can be accelerated by making the particle size 0.05 to 2.0 mm.
[0015]
By including plasticizers such as phthalate esters and phosphate esters, ultraviolet absorbers, antioxidants and matting agents in the cellulose ester film, silver halide photographic light-sensitive materials and liquid crystal images resulting from the cellulose ester film The performance of the display device can be improved. Moreover, you may contain dye etc. in a cellulose-ester film. In addition, an antistatic agent, a flame retardant, a lubricant and an oil agent may be added to the cellulose ester film. These additives may be added together with the cellulose ester and the solvent during the preparation of the cellulose ester solution, or may be added during or after the solution preparation.
[0016]
Next, a method for preparing the dope will be described. A dope is formed by dissolving a flaky cellulose ester in an organic solvent mainly containing a good solvent for the cellulose ester while stirring in a dissolving kettle. As a dissolution method, a method performed at normal pressure, a method performed below the boiling point of the main solvent, a method performed under pressure above the boiling point of the main solvent, JP-A-9-95544, JP-A-9-95557, and JP-A-9- There are a method of carrying out by a cooling dissolution method as disclosed in each publication of Japanese Patent No. 95538 and a method of carrying out at a high pressure as disclosed in JP-A No. 11-21379. After dissolution, the dope is filtered with a filter medium, defoamed, and sent to the next process with a pump. The concentration of the cellulose ester in the dope is about 10 to 35%, preferably 15 to 25%. In order to contain a useful polymer in the dope, it may be added after dissolving the polymer in an organic solvent in advance, or may be added directly to the dope. In this case, the polymer is added so as not to become cloudy or phase-separated in the dope.
[0017]
Examples of organic solvents as good solvents for cellulose esters include methyl acetate, ethyl acetate, amyl acetate, ethyl formate, acetone, cyclohexanone, methyl acetoacetate, tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,4-dioxane, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3 , 3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, Nitroethane, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, methylene chloride and It can be exemplified bromo propane. Of these, methyl acetate, acetone or methylene chloride is preferred, but a non-chlorine organic solvent is more preferred in view of recent environmental problems. In addition, it is preferable to use a lower alcohol such as methanol, ethanol and butanol in combination with the organic solvent because the solubility of the cellulose ester in the organic solvent can be improved and the dope viscosity can be reduced. Especially, the boiling point is low and the toxicity is low. Ethanol is particularly preferred. The organic solvent used for the dope is preferably used by mixing a good solvent and a poor solvent of cellulose ester from the viewpoint of production efficiency. The preferred range of the mixing ratio of the good solvent and the poor solvent is 70 to 98 for the good solvent. %, And the poor solvent is 2 to 30%. A good solvent refers to a solvent that dissolves the cellulose ester used alone, and a poor solvent refers to a solvent that does not dissolve alone. Examples of the poor solvent used for the dope include methanol, ethanol, n-butanol, cyclohexane, acetone, and cyclohexanone. As the organic solvent for the useful polymer, a good solvent for cellulose ester is selected. As described above, when using a low molecular weight plasticizer, it can be carried out by a usual addition method, but it may be added directly into the dope, and after dissolving in an organic solvent in advance, it is poured into the dope. Also good.
[0018]
The cellulose ester dope must be filtered to remove foreign substances, particularly foreign substances that are easily recognized as an image in a liquid crystal image display device. It can be said that the quality of the protective film for polarizing plates is determined by this filtration. Filter media used for filtration should have low absolute filtration accuracy. However, if the absolute filtration accuracy is too small, the filter media is likely to be clogged, and the filter media must be replaced frequently, reducing productivity. There is a problem of making it. For this reason, the filter medium used for the dope is preferably one having an absolute filtration accuracy of 0.001 to 0.008 mm, and particularly preferably 0.003 to 0.006 mm.
[0019]
Next, of the manufacturing process of the cellulose ester film, a process of casting the dope on the drive endless belt, a drying process on the endless belt, a peeling process of peeling the web from the endless belt, and a process of drying the web will be described.
[0020]
In the casting process, for example, as shown in FIGS. 1 and 2, the dope is fed to the pressurizing die 4 through the pressurization type fixed gear pump, and the dope is supplied from the pressurizing die 4 onto the drive endless belt 2 at the casting position. It is a process of casting.
[0021]
In the figure, a drive endless belt 2 is stretched around a pair of drive drums 1 and a driven drum 1, and the endless belt 2 is rotated in a fixed direction by a drive generating means (not shown). A plurality of support rolls 3 supporting the upper transition portion 2a and the lower transition portion 2b of the endless belt 2 from the back side are provided in the middle between the pair of front and rear drums 1 and 1 around which the endless belt 2 is stretched. The drums 1 and 1 are arranged so that the long axes thereof are parallel to each other, and the endless belt 2 is rotatably and held in a tension state. Then, the cellulose ester solution cast from the die 4 onto the upper transition part 2a of the endless belt 2 is dried on the endless belt 2 and continuously transferred in the direction of the arrow in the figure. When it returns to the vicinity of the drum 1 on the casting side again through the transition part 2b, it is peeled off from the endless belt 2 by the peeling roll 6, and sent to the subsequent drying step.
[0022]
As other casting methods for casting the dope, there are a doctor blade method in which the film thickness of the cast web is adjusted with a blade and a reverse roll coater method in which the film thickness is adjusted with a reverse rotating roll. A pressure die is preferred in that the slit shape of the portion can be adjusted and the film thickness can be made uniform easily. The pressure die includes a coat hanger die and a T die, both of which are preferably used. In order to increase the film forming speed, two or more pressure dies may be provided on the endless belt, and the dope amount may be divided and stacked. In order to adjust the film thickness, it is preferable to control the dope concentration, the pumping amount, the slit gap of the die base, the extrusion pressure of the die, the speed of the endless belt, and the like so as to obtain a desired thickness.
[0023]
The drying process on the endless belt is a process in which the web is heated on the endless belt to evaporate the solvent. In order to evaporate the solvent, a method of sending warm air from the web side and the back side of the endless belt, a method of heating from the back side of the endless belt with a heating liquid, a method of heating from the web side and the back side of the endless belt by radiant heat, There are ways to combine them. Of course, if the web film is thin, it dries quickly. The temperature of the endless belt may be the same as a whole or may be different depending on the position.
[0024]
The peeling process is a process of evaporating the organic solvent on the endless belt and peeling the web before the endless belt makes a full circuit. After this process, the web is sent to the drying process. The position at which the web is peeled from the endless belt is called a peeling point, and a roll that helps the peeling is called a peeling roll. Although it depends on the thickness of the web, if the residual solvent amount of the web at the peeling point is too large, it will be difficult to peel off, or conversely, if it is peeled off after sufficiently drying on the endless belt, a part of the web will be halfway The web may be peeled off when the residual solvent amount is 10 to 150%.
[0025]
In the present invention, a plurality of endless belts, which are arranged in the middle of a pair of drums over which a driving endless belt is cast to cast a cellulose ester solution and support the upper and lower transition portions of the endless belt from the back side. The distance between the support rolls adjacent to each other is within a range of 2 m or more and 5 m or less. For example, since the total length of the upper and lower transition portions of the endless belt is usually 20 to 60 m, when the support rolls are arranged at intervals of 1 m, for example , the cost burden increases due to the increase in the number of rolls. The distance between the support rolls is preferably 2 m or more. Further, if the distance between the support rolls adjacent to each other exceeds 5 m, the retardation value variation ΔR increases, which is not preferable.
[0026]
In the present invention, the distance between the support rolls adjacent to each other is limited to a length outside the range of ± 5% of an integral multiple of the roll circumference in the range of 2 m to 5 m. ing. The reason is that if the distance between the support rolls adjacent to each other is roll circumference S × integer n, the wave of vibration due to roll transfer is amplified, and as a result, the retardation value of the resulting cellulose ester film This is because it is not preferable because the dispersion ΔR of the roller increases, and even when the distance between the support rolls adjacent to each other is within a range of ± 5% of the roll circumferential length S × integer n, it is obtained similarly. This is because the dispersion ΔR of the retardation value of the obtained cellulose ester film increases, which is not preferable.
[0027]
Here, the diameter of the support roll is 100 to 250 mm, preferably 100 to 200 mm.
[0028]
In the present invention, the distance between the support rolls adjacent to each other among the support rolls supporting the upper transition part of the endless belt from the back side is the distance between the support rolls supporting the lower transition part of the endless belt from the back side. Of these, the distance is preferably narrower than the distance between the support rolls adjacent to each other . The reason for this is that the distance between the support rolls on the upper transition part side of the endless belt is made narrower than the distance between the support rolls on the lower transition part side of the endless belt, and thus the optically compensated cellulose for a liquid crystal display device is obtained. This is because the variation ΔR in the retardation value of the ester film can be reduced.
[0029]
The polarizing plate can be produced by a conventionally known method. For example, a cellulose ester film is subjected to a surface saponification treatment with a 2.5 mol / l sodium hydroxide aqueous solution at 40 ° C. for 60 seconds, washed with water for 3 minutes and dried to obtain a protective film for polarizing plate. . Separately, 120 μm-thick polyvinyl alcohol is immersed in 100 parts by mass of an aqueous solution containing 1 part by mass of iodine and 4 parts by mass of boric acid, and stretched four times in the longitudinal direction at 50 ° C. to obtain a polarizing film. A cellulose ester film subjected to the above surface saponification treatment is bonded to one surface or both surfaces of this polarizing film with an adhesive made of a completely saponified 5% aqueous solution of polyvinyl alcohol to form a polarizing plate.
[0030]
The cellulose ester film produced by the apparatus of the present invention is a cellulose ester film particularly used for an optical compensation film for liquid crystal display devices . According to the apparatus of the present invention, it is possible to suppress the vibration of the belt during high-speed conveyance, enable stable film formation, and improve the surface quality and optical characteristics of the optically compensated cellulose ester film for liquid crystal display devices. In addition, it is possible to efficiently produce an optically compensated cellulose ester film for a liquid crystal display device having a small retardation value variation and having a target retardation value, with high quality.
[0031]
The cellulose ester film produced by the apparatus of the present invention is excellent in optical isotropy, and is suitable for a member of a liquid crystal display device, particularly an optical compensation film.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Example In producing a cellulose ester film using the apparatus of the present invention, a dope was first prepared. That is, the following blended composition in which triacetyl cellulose was dissolved in a solvent was put into a sealed container, dissolved with stirring to prepare a dope, and the prepared dope was filtered with a filter paper.
[0033]
(Dope composition)
Cellulose triacetate with a degree of acetyl substitution of 2.88 (number average molecular weight 150,000) 100 parts by weight Triphenyl phosphate 10 parts by weight Ethylphthalyl ethyl glycolate 2 parts by weight Tinuvin 326 1 part by weight AEROSIL 200V 0.1 part by weight Methylene chloride 475 parts by weight Ethanol 25 parts by weight Next, using the dope after filtration, a cellulose ester film was produced by the apparatus of the present invention shown in FIGS. 1 and 2 as follows.
[0034]
The drive endless belt 2 is stretched around a pair of front and rear drums 1 and 1, and the endless belt 2 is rotated in a fixed direction at a transition speed of, for example, 50 m / min by a drive generating means (not shown). A plurality of support rolls 3 supporting the upper transition part 2a and the lower transition part 2b of the endless belt 2 from the back side are provided between the pair of drums 1 and 1 on which the endless belt 2 is stretched. The drums 1 and 1 are arranged so that the long axes thereof are parallel to each other, and the endless belt 2 is rotatably held in a tension state.
[0035]
The cellulose ester solution cast from the die 4 onto the upper transition portion 2a of the endless belt 2 is continuously transferred in the direction of the arrow while being dried on the endless belt 2, and the lower transition portion 2b of the endless belt 2 is transferred. Then, when it returns to the vicinity of the drum 1 on the casting side again, it is peeled off from the endless belt 2 by the peeling roll 6, and the remaining solvent is dried in the drying chamber to produce a cellulose ester film.
[0036]
Here, the circumferential length of the support roll 3 disposed between the pair of drums 1 and 1 is S, and the support rolls 3 adjacent to each other among the support rolls 3 supporting the upper transition portion 2a of the endless belt 2 from the back side. When the distance between the support rolls 3 and 3 adjacent to each other among the support rolls 3 supporting the lower transition portion 2b of the endless belt 2 from the back side is L1, the distance between the three is S, Films were formed by changing the conditions of L1 and L2, and a cellulose ester film having a thickness of about 80 μm was obtained. The variation ΔR of the retardation value of the obtained cellulose ester film was measured, and the results obtained are shown in Table 1.
[0037]
In addition, the measurement of retardation measured the arbitrary 30 points of the sample formed into a film with the automatic birefringence meter COBRA-21ADH by Oji Scientific Instruments, and made the standard deviation the dispersion | variation ((DELTA) R) of retardation value.
[0038]
Reference Examples 1-3, Examples 1-5, and Comparative Examples 1-3
[Table 1]

[0039]
As can be seen from the results in Table 1, the distance L1 of the support rolls 3 and 3 in contact with the back surface of the upper transition portion 2a of the endless belt 2 and the support roll 3 in contact with the back surface of the lower transition portion 2b of the endless belt 2 are shown. When the distance L2 of 3 is in the range of 1000 to 5000 mm ( Reference Examples 1 to 3 and Examples 1 to 2 ), the retardation value variation ΔR of the cellulose ester film is small, but L1 and L2 are 5000 mm. It was found that the dispersion ΔR of the retardation value increases when the value exceeds (Comparative Example 1). The retardation value variation ΔR when L1 and L2 are 1000 mm ( Reference Example 1 ) is not significantly different from the case of Examples 1-2 and Reference Examples 2-3 where L1 and L2 are in the range of 2000 to 5000 mm. However, when the support rolls 3 are arranged at intervals of 1000 mm in this way, the cost burden due to the increase in the number of rolls increases, so the distances L1 and L2 of the support rolls 3 and 3 are preferably in the range of 2000 mm to 5000 mm. .
[0040]
Further, as can be seen from the results of Examples 3 to 5 and Comparative Examples 2 and 3 in Table 1, the distances L1 and L2 between the support rolls 3 and 3 adjacent to each other are within a range of more than 2 m and less than 5 m. When the roll circumference S × integer n and within ± 5% thereof, the retardation value variation ΔR becomes large (Comparative Examples 2 and 3), and the distances L1 and L2 between the support rolls 3 and 3 are 2 m. As long as the length is outside the range of ± 5% of an integral multiple of the roll circumference in the range of 5 m or less, the retardation value variation ΔR of the resulting cellulose ester film can be reduced ( Example 3). ~ 5) was found.
[0041]
【The invention's effect】
According to the present invention, in an apparatus for producing an optically compensated cellulose ester film for a liquid crystal display device by a solution casting film forming method, a pair of drive endless belts are formed on which a cellulose ester solution is cast to form a film. Regarding the arrangement of a plurality of support rolls arranged in the middle of the drums and supporting the upper and lower transition portions of the endless belt from the back side, the distance of the support rolls required for the length of the belt to be used and the conveying speed is determined. By defining the length outside the range of ± 5% of an integral multiple of the roll circumference in the range of 2 m or more and 5 m or less, the vibration of the belt at high speed conveyance is suppressed, enabling stable film formation. It can improve the surface quality and optical characteristics of the liquid crystal display device for optical compensation cellulose ester film, less variation in the retardation value One goal to retardation efficiently excellent liquid crystal display device for optical compensation cellulose ester films of quality having always an effect that it is possible to produce high quality.
[Brief description of the drawings]
FIG. 1 is a schematic plan view of an apparatus for producing an optically compensated cellulose ester film for a liquid crystal display device according to an embodiment of the present invention.
FIG. 2 is a schematic longitudinal sectional view of the cellulose ester film production apparatus.
FIG. 3 is a schematic longitudinal sectional view of a conventional cellulose ester film production apparatus.
[Explanation of symbols]
1 Drum 2 Endless Belt 2a Endless Belt Upper Transition 2b Endless Belt Lower Transition 3 Support Roll 4 Die 5 Web 6 Peeling Roll

Claims (1)

In an apparatus for producing an optically compensated cellulose ester film for a liquid crystal display device by a solution casting film forming method, it is arranged between a pair of drums over which a driving endless belt is formed that casts a cellulose ester solution to form a film. Among the plurality of rolls that support the upper and lower transition portions of the endless belt from the back side (hereinafter referred to as “support rolls”), the distance between the adjacent support rolls is 2 m or more and 5 m or less. An apparatus for producing an optically compensated cellulose ester film for a liquid crystal display device , wherein the length is outside the range of ± 5% of an integral multiple of the roll circumference .

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