JP2006028478A - Polymer film, solution film-forming method and equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polymer film, a solution film-forming method, and film-forming equipment, which can suppress optical nonuniformity when the polymer film is used for a high luminance mode display. <P>SOLUTION: Air is blown from an air supply duct 61 to a cast film 59 on a support 53, and at the same time, air is discharged from an exhaust duct 62. A plurality of guide plate 64 is provided between the air supply duct 61 and the exhaust duct 62 to control a direction of the wind so that air flows along the traveling direction of the cast film 59. When thickness of the obtained film is measured two or more times in a direction crossing the longitudinal direction, the variation in the thickness is within ±2 μm relative to an average thickness. A dispersion value V=Σä(dYn)/(dXn)}<SP>2</SP>/n which can be obtained from a rate of change in the thickness dYn relative to a distance dXn from a start point of the measurement to each measurement point is <300×10<SP>-5</SP>. The film, when used as a protection film, etc. of a polarizing plate for the high luminance mode display, does not create optical nonuniformity in vertical and horizontal directions, and exhibits good display performance. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polymer film, a solution casting method, and equipment, and more particularly, to a polymer film used for a polarizing plate, a liquid crystal display device, and the like, and a solution casting method and equipment as a production method thereof.

  The liquid crystal display device includes a polarizing plate and an optical compensation film. In many cases, the polarizing plate has a structure having protective films on both surfaces of the polarizing film. In recent years, the optical compensation film may be replaced with one of the protective films of the polarizing plate, for example, an elliptically polarizing plate. As a result, the front contrast of the liquid crystal display device can be improved, and the display device can be made thinner.

  On the other hand, the demand for liquid crystal display devices is rapidly expanding, and in particular, the demand for liquid crystal television display devices is increasing. In the liquid crystal television, higher brightness and a larger screen are demanded for the display device as compared with various measuring instruments and computers having a liquid crystal display device that have been used conventionally.

  By the way, various optical films including an optical compensation film and a protective film used for a liquid crystal display device are manufactured by either a solution film forming method or a melt film forming method according to the type of material. In particular, a cellulose acylate film produced by a solution casting method is representative as a protective film having an optical compensation function due to transparency, optical isotropy, appropriate moisture permeability, and the like.

In addition, the optical compensation film in the TN mode liquid crystal display device and the polymer film used in the optical application exemplified by the viewing angle widening film used in the other liquid crystal display device have conventionally exhibited a predetermined optical function. Therefore, many proposals have been made to suppress the thickness variation (thickness variation). For example, in the method proposed in Patent Document 1, the solid content concentration of the polymer solution to be cast is set to a predetermined value in order to improve foam flatness by suppressing foaming or peeling off from the support. The component ratio of the solvent and the support temperature are set to predetermined values.
Japanese Patent Publication No. 5-17844

  However, although the polymer film manufactured by the conventional method including Patent Document 1 exhibits satisfactory performance for the conventional liquid crystal display device, the liquid crystal display having a high brightness and a large screen as described above. When used in an apparatus, there is a problem that many display unevenness (optical unevenness) is confirmed. And this display nonuniformity often appears linearly in both the vertical and horizontal directions of the liquid crystal display device.

  Here, the manufacturing method of the film for liquid crystal displays is demonstrated. FIG. 8 is an explanatory diagram of a cutting method when a film manufactured by the solution casting method is used for a liquid crystal display device. In the solution casting method, a polymer film is continuously produced by casting and stripping a polymer solution on a running substrate and drying it. In the drying step, in order to keep the orientation of the polymer molecules in a predetermined state, tension is usually applied in the width direction while holding both side ends of the film with holding means. Cutting is performed in consideration of the orientation of this orientation. In FIG. 8, the X direction indicates the longitudinal direction, the Y direction indicates the width direction, and the broken line indicates a cutting line. As shown in FIG. 8, it cut | disconnects so that several polymer film sheets may be obtained at an angle of 45 degrees with respect to the elongate direction. In addition, 45 degrees with respect to the longitudinal direction means that it is 45 degrees with respect to the width direction. FIG. 8 shows, as an example, a case where five sheets (a) to (e) are obtained along a direction of 45 ° with respect to the longitudinal direction.

  When optical unevenness is examined for these sheets, optical unevenness is detected in all the sheets (a) to (e), and the optical unevenness becomes more conspicuous from the center in the width direction of the film 201 toward the side edge. There is a problem that appears. The optical unevenness is inspected by a known method of observing with a sheet sample sandwiched between two polarizing plates arranged in a crossed Nicol arrangement.

  Therefore, the present inventors further examined the cause of optical unevenness in the above sheet. Of the sheet of the film shown in FIG. 8, the relationship between the optical unevenness and the film thickness was examined for the sheet (c) surrounded by a two-dot broken line. And it marked with respect to the optical nonuniformity recognized in the sheet | seat (c). The enlarged view in FIG. 8 shows the marking state. According to this enlarged view, it can be seen that the marking is made in a direction of 45 ° with respect to the X direction and the Y direction. When the thickness was measured along this marking, that is, in the direction of 45 °, the thickness unevenness was remarkably confirmed as compared with the portion without the marking.

  The film for optical use as described above preferably has an average thickness of 20 to 100 μm. In FIG. 9, the film having an average thickness of 90 μm was measured along the direction of the 45 ° angle. Thickness data is shown. (A) is the thickness data of the film 201 shown in FIG. 8, (b) is the thickness data of another film. As can be seen from the data (a) and (b), the thickness variation is about 1 μm, and the ratio of the variation width to the average thickness is about 12%, which is very small. However, even if such a film is used in a high-brightness, large-screen LCD television, for example, there is optical unevenness as described above, and a predetermined display state is manifested simply by making the thickness variation within a predetermined range. I knew that I couldn't do that.

  Therefore, based on the above examination results, a polymer film that does not exhibit optical unevenness even when used in a liquid crystal display device with high brightness and a large screen has been provided as follows. That is, the polymer film of the present invention is produced in a long shape by a solution casting method or a melt extrusion casting method, and continuously along a direction intersecting with the longitudinal direction (however, an angle other than 90 °). The variation width of the measured thickness is within ± 2 μm with respect to the average thickness.

The polymer film of the present invention is produced in a long shape by a solution casting method or a melt extrusion casting method, and continuously along a direction intersecting (however, an angle other than 90 °) with the longitudinal direction. The number of measurement values N arbitrarily extracted from the measured thickness data is n (where n is a natural number of 5 or more), and the measurement start position PS and the measurement corresponding to each of the extracted measurement values V = Σ {(dYn) / (dXn) where (dYn) / (dXn) is the rate of change of each thickness Yn (unit; μm) with respect to each distance Xn (unit; mm) )} V determined by ² / n is less than 300 × 10 ⁻⁵ .

  Provided in the polarizing plate of a liquid crystal display device having a light emitter and a polarizing plate, and used as the protective film of the polarizing plate having a protective film on the surface of the polarizing film, and the luminance of the light emitter is 5000 candela or more It is preferably 50000 candela or less.

  The present invention also provides a casting apparatus for casting a polymer solution onto a support traveling from a casting die to form a casting film, and peeling the casting film to form a film containing a solvent. In a solution casting apparatus including a drying device for drying a film, an air supply unit that blows air onto the casting film, and the air containing a solvent evaporated from the casting film is exhausted downstream of the air supply unit. An exhaust means is provided in the vicinity of the support, and a plurality of guide plates for flowing the wind along the running direction of the casting membrane are provided between the air supply means and the exhaust means. It is configured.

  Furthermore, the present invention provides a solution casting method in which a polymer solution is cast on a traveling support to form a cast film, the film is peeled off to form a film containing a solvent, and then the film is dried. In the above, the wind is blown by the air supply means on the cast film solidified to a predetermined hardness, and the wind is made to flow along the running direction of the cast film by the guide means for controlling the flow direction of the wind, It is characterized by collecting the wind containing the solvent evaporated from the casting film by the exhaust means.

  Until the cast film reaches the predetermined hardness, it is preferable that no wind is generated in the vicinity of the cast film, and the evaporated solvent is condensed from the cast film under the no wind by the condensing means for condensing and recovering the evaporated solvent. It is more preferable to promote the drying of the cast film by this condensation. Moreover, it is preferable to dry the casting film under the windlessness to the predetermined hardness by heating the side opposite to the casting surface of the support with a heating means.

  According to the present invention, optical unevenness can be suppressed. By applying this to a high-luminance, large-screen liquid crystal display device, display unevenness, particularly display unevenness appearing in the horizontal and vertical directions can be effectively suppressed.

[material]
Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments described here. First, the film of the present invention will be described, and then the method for producing the film will be described.

  FIG. 1 is a plan view for explaining a film of the present invention, and FIG. 2 shows a part of thickness data measured along a predetermined direction of the film. The film of the present invention can be obtained in a long shape by a solution casting method described later. In FIG. 1, the X direction and the Y direction intersect at 90 °, the X direction is the long direction, and the Y direction is It is the width direction. Further, reference numeral 81 is attached to the film. About this film 81, thickness measurement is continuously implemented along the direction which cross | intersects X direction and excludes Y direction. In FIG. 1, the line to be measured is indicated by a broken line ML. Further, it is preferable that both the thickness measurement start point PS and the measurement end point PE are determined so as to include a range that is cut and used according to the application, but is not necessarily limited thereto, and is not necessarily limited to this. In the case of a film to be used, it may be determined for each range including one sheet.

  As shown in FIG. 1, a plurality of points are arbitrarily extracted on the measurement line ML. The number N of extracted points (hereinafter referred to as extraction points) is n (where n is a natural number equal to or greater than 2), and each extraction point is sequentially labeled P1, P2,. P (n-1) and Pn are attached. The distances from the measurement start point PS to the respective extraction points P1, P2,..., P (n-1), Pn are X1, X2, ..., X (n-1), Xn.

In the thickness data of FIG. 2, the vertical axis indicates the thickness (unit: μm), and the horizontal axis indicates the distance (unit: mm) from the measurement start point PS along the measurement line ML. Then, the rate of change in thickness at each extraction point P1, P2,..., P (n−1), Pn is obtained. In FIG. 2, the rate of change of the thickness is the distance X1, X2,..., X (from the measurement start point PS of each extraction point P1, P2,..., P (n-1), Pn. n-1), the change rate with respect to Xn, which is the slope at a predetermined point on the graph of FIG. 2, and is dY ₁ / dX ₁ , dY ₂ / dX ₂ ,..., dY _n-1 / dX _{n -1,} a value determined by dY _n / dX _n.

And the film of this invention is less than 300 * 10 < ^-5 > when the dispersion value V of the said change rate is calculated | required by V = (SIGMA) {(dYn) / (dXn)} < ² > / n. When the value of V is 300 × 10 ⁻⁵ or more, when used as part of a liquid crystal display device having a light emitter with a predetermined luminance or more, optical unevenness occurs in the horizontal direction or the vertical direction of the display device. End up. The value of V is preferably as small as possible, and more preferably less than 150 × 10 ⁻⁵ . In addition, when this film 81 is used as a protective film for a polarizing plate in a liquid crystal display device including a light emitter having a luminance of 5000 candela or more and 50000 candela or less, optical unevenness is suppressed and excellent display performance is exhibited. Moreover, it can use suitably as an optical compensation film other than the protective film of a polarizing plate, for example.

  In this embodiment, the thickness was measured continuously in an oblique direction using a commercially available thickness measuring machine (model; electronic micrometer, manufactured by Anritsu Co., Ltd.). As long as the rate of change in thickness at n measurement points corresponding to P1, P2,..., P (n-1), Pn can be obtained, continuous measurement is not necessarily required. In this case, if the distance from one end of the predetermined measurement line ML to each measurement point is Xn and the thickness at each measurement point is Yn, the rate of change (dYn) / (thickness Yn with respect to the distance Xn from the predetermined position. dXn) and V is also obtained.

  An example of the thickness data of the film of the present invention is shown in FIG. (A) is the thickness data of the said film 81, (b) is the thickness data of another film. In both (a) and (b), the vertical axis indicates the thickness variation (unit: μm), and the horizontal axis is the same as in FIG. For the vertical axis, the average thickness is shown with zero thickness variation. As shown in FIGS. 3 (a) and 3 (b), the film of the present invention has a thickness variation width F within ± 2 μm with respect to the average thickness in the oblique direction. As a result, optical unevenness in the oblique direction is suppressed. Therefore, even when these films are used in a liquid crystal display device with high brightness and high image quality, there is an effect that display unevenness in the vertical and horizontal directions does not occur.

Further, comparing (a) and (b), it can be seen that the peaks and valleys of both graphs appear at substantially the same pitch. The variance values V of the change rate at any point on the graph are all less than 300 × 10 ⁻⁵ . When these films are evaluated using a protective film for a polarizing plate in a liquid crystal display device including a light emitter having a luminance of 5000 to 50000 candela, no optical unevenness is observed in any case, and both are excellent. Display performance. Note that in a liquid crystal display device including a light emitter with a luminance of less than 5000 candela, optical unevenness in the oblique direction of the film hardly causes a problem, and a conventional film can also be used. In addition, when the film of the present invention is used for a light emitter having a luminance higher than 50000 candela, there is a problem in terms of durability.

  Next, a method for manufacturing the film 81 will be described. However, the manufacturing method and manufacturing apparatus described below are examples of the present invention, and the present invention is not limited thereto.

[material]
In the present embodiment, cellulose acylate is used as the polymer, and triacetyl cellulose (TAC) is particularly preferable as the cellulose acylate. The TAC may be obtained from either linter cotton or pulp cotton, but is preferably obtained from linter cotton. Among cellulose acylates, those in which the substitution degree of the acyl group substituted with the hydroxyl group of cellulose satisfies all of the following formulas (I) to (III) are more preferable. In the following formulas (I) to (III), A and B represent the substitution degree of the acyl group substituted with the hydroxyl group of cellulose, A is the substitution degree of the acetyl group, and B is 3 carbon atoms. The substitution degree of the acyl group of ˜22. In addition, it is preferable that 90 mass% or more of TAC is a particle | grain of 0.1 mm-4 mm.
(I) 2.5 ≦ A + B ≦ 3.0
(II) 0 ≦ A ≦ 3.0
(III) 0 ≦ B ≦ 2.9

  Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by esterifying some or all of these hydroxyl groups with an acyl group having 2 or more carbon atoms. The degree of acyl substitution means the ratio at which the hydroxyl group of cellulose is esterified at each of the 2-position, 3-position and 6-position (100% esterification has a substitution degree of 1).

  The total acyl substitution degree, that is, DS2 + DS3 + DS6 is preferably 2.00 to 3.00, more preferably 2.22 to 2.90, and particularly preferably 2.40 to 2.88. Further, D6S / (DS2 + DS3 + DS6) is preferably 0.32 or more, more preferably 0.322 or more, and particularly preferably 0.324 to 0.340. Here, DS2 is the degree of substitution of the hydroxyl group at the 2-position of the glucose unit with an acyl group (hereinafter also referred to as “degree of acyl substitution at the 2-position”), and DS3 is the degree of substitution of the hydroxyl group at the 3-position with an acyl group (hereinafter, referred to as “acyl group”). DS6 is the substitution degree of the hydroxyl group at the 6-position with an acyl group (hereinafter also referred to as “acyl substitution degree at the 6-position”).

  Only one type of acyl group may be used in the cellulose acylate of the present invention, or two or more types of acyl groups may be used. When two or more types of acyl groups are used, one of them is preferably an acetyl group. DSA + DSB where DSA is the total substitution degree of hydroxyl groups at the 2nd, 3rd and 6th positions with an acetyl group and DSB is the total substitution degree with an acyl group other than the acetyl group at the 2nd, 3rd and 6th hydroxyl groups. The value of is more preferably 2.2 to 2.86, and particularly preferably 2.40 to 2.80. The DSB is preferably 1.50 or more, particularly preferably 1.7 or more. Further, 28% or more of the DSB is a substituent at the 6-position hydroxyl group, more preferably 30% or more is a substituent at the 6-position hydroxyl group, more preferably 31%, and particularly 32% or more is a 6-position hydroxyl group. A substituent is also preferred. Furthermore, it is preferable to use a cellulose acylate having a DSA + DSB value of 6-position of cellulose acylate of 0.75 or more, more preferably 0.80 or more, and particularly preferably 0.85 or more. . With these cellulose acylates, a solution having a preferable solubility (dope) can be produced. In particular, in a non-chlorine organic solvent, a good solution can be produced. Furthermore, it is possible to prepare a solution having a low viscosity and good filterability.

  The acyl group having 2 or more carbon atoms of the cellulose acylate of the present invention may be an aliphatic group or an aryl group and is not particularly limited. These are, for example, cellulose alkylcarbonyl esters, alkenylcarbonyl esters, aromatic carbonyl esters, aromatic alkylcarbonyl esters, and the like, each of which may further have a substituted group. Preferred examples of these include propionyl group, butanoyl group, keptanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octadecanoyl group, iso-butanoyl group , T-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like. Among these, a propionyl group, a butanoyl group, a dodecanoyl group, an octadecanoyl group, a t-butanoyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, a cinnamoyl group, and the like are more preferable, and a propionyl group and a butanoyl group are particularly preferable. is there.

  However, the present invention is also applicable to other polymers. For example, polyethylene terephthalate, polyethylene naphthalate, polymethyl methacrylate, polycarbonate, regenerated cellulose ester, diacetyl cellulose, triacetyl cellulose, norbornene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyether sulfone, polyether ketone, Examples thereof include polyethylene, polypropylene, polyimide, polyamide, and poly-4-methyl-1-pentene. Whether to produce a film by solution casting or melt extrusion casting may be appropriately selected according to the type of polymer.

  Moreover, as a solvent for preparing the dope, aromatic hydrocarbons (for example, benzene, toluene, etc.), halogenated hydrocarbons (for example, dichloromethane, chlorobenzene, etc.), alcohols (for example, methanol, ethanol, n-propanol, Examples thereof include n-butanol, diethylene glycol, etc., ketones (eg, acetone, methyl ethyl ketone, etc.), esters (eg, methyl acetate, ethyl acetate, propyl acetate, etc.) and ethers (eg, tetrahydrofuran, methyl cellosolve, etc.). Here, the dope is a polymer solution or dispersion obtained by dissolving or dispersing a polymer in a solvent.

  Among these, halogenated hydrocarbons having 1 to 7 carbon atoms are preferably used, and dichloromethane is most preferably used. And from the viewpoint of properties such as the solubility of TAC, the peelability of the cast film from the support, the mechanical strength of the film, and the optical properties of the film, one or several kinds of alcohols having 1 to 5 carbon atoms are selected. It is preferable to use it mixed with dichloromethane. At this time, the content of the alcohol is preferably 2% by mass to 25% by mass and more preferably 5% by mass to 20% by mass with respect to the entire solvent. Specific examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol, etc. Among them, methanol, ethanol, n-butanol, or a mixture thereof is more preferably used.

  By the way, recently, for the purpose of minimizing the influence on the environment, studies have been conducted on the solvent composition when dichloromethane is not used. For this purpose, ethers having 4 to 12 carbon atoms, carbon atoms A ketone having 3 to 12 carbon atoms and an ester having 3 to 12 carbon atoms are preferable, and these may be 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 a solvent. The solvent may have another functional group such as an alcoholic hydroxyl group in the chemical structure.

  The details of cellulose acylate are described in paragraphs [0140] to [0195] of Japanese Patent Application No. 2004-264464, and these descriptions can also be applied to the present invention. Similarly, for additives such as solvents and plasticizers, deterioration inhibitors, ultraviolet absorbers, optical anisotropy control agents, dyes, matting agents, release agents, etc., from paragraph [0196] of Japanese Patent Application No. 2004-264464. [0516] is described in detail in the paragraph.

  The ultraviolet absorber preferably used in the present invention will be described. The cellulose acylate film of the present invention is used for a polarizing plate or a liquid crystal display member because of its high dimensional stability, but an ultraviolet absorber is preferably used from the viewpoint of preventing deterioration of the polarizing plate or the liquid crystal. As the ultraviolet absorber, those excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less and having little absorption of visible light having a wavelength of 400 nm or more are preferably used from the viewpoint of good liquid crystal display properties. Specific examples of ultraviolet absorbers preferably used in the present invention include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like.

  Although the specific example as a benzotriazole type ultraviolet absorber is listed below, this invention is not limited to these. 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) benzotriazole, 2- (2′-hydroxy-3) '-Tert-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3', 5'-di-tert-butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy -3 ′-(3 ″, 4 ″, 5 ″, 6 ″ -tetrahydrophthalimidomethyl) -5′-methylphenyl) benzotriazole, 2,2-methylenebis (4- (1,1,3,3-tetramethyl) Butyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl)- -Chlorobenzotriazole, 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, bis (2-methoxy-4-hydroxy-5-benzoyl) Phenylmethane), (2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine, 2 (2'-hydroxy- 3 ′, 5′-di-tert-butylphenyl) -5-chlorobenzotriazole, (2 (2′-hydroxy-3 ′, 5′-di-tert-amylphenyl) -5-chlorobenzotriazole, 2, 6-di-tert-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-tert- Til-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3 , 5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3 , 5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl- 4-hydroxyphenyl) propionate, N, N′-hexamethylenebis (3,5-di-tert-butyl-4-hydroxy-) Hydrocinnamide), 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-tert-butyl-4) -Hydroxybenzyl) -isocyanurate and the like. In particular, (2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-tert-butylanilino) -1,3,5-triazine, 2 (2′-hydroxy-3 ′, 5'-di-tert-butylphenyl) -5-chlorobenzotriazole, (2 (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) -5-chlorobenzotriazole, 2,6-di -Tert-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-tert-butyl -5-methyl-4-hydroxyphenyl) propionate], for example, N, N'-bis [3- (3,5-di-tert-butyl-4 Hydrazine-based metal deactivators such as (hydroxyphenyl) propionyl] hydrazine and phosphorus-based processing stabilizers such as tris (2,4-di-tert-butylphenyl) phosphite may be used in combination. The amount is preferably 1 ppm to 2.0%, more preferably 10 ppm to 5000 ppm in terms of mass ratio with respect to cellulose acylate.

Moreover, the ultraviolet absorbers described in JP-A-6-148430 and JP-A-7-11056 can also be preferably used. The ultraviolet absorber described above preferably used in the present invention has high transparency, is excellent in the effect of preventing the deterioration of the polarizing plate and the liquid crystal element, and is particularly preferably a benzotriazole-based ultraviolet absorber with less unnecessary coloring. The amount of the UV absorber used is not uniform depending on the type of compound and the use conditions, but is usually preferably 0.2 to 5.0 g, more preferably 0.4 to 1.5 g per 1 m ^{2 of the} cellulose acylate film. Preferably, 0.6g-1.0g is especially preferable.

  In addition, the light stabilizers listed in the catalog “Adeka Stub”, an outline of additives for Asahi Denka Plastics, can be used. Light stabilizers and UV absorbers from Ciba Special Chemicals' Tinuvin Product Guide can also be used. SEESORB, SEENOX, SEETEC, etc. described in the catalog of SHIPRO KASEI KAIYA can also be used. Jouhoku Chemical's UV absorbers and antioxidants can also be used. UV absorbers from Kyosho's VIOSORB and Yoshitomi Pharmaceutical can also be used.

  Regarding the spectral transmittance in the ultraviolet region, Japanese Patent Application Laid-Open No. 2003-043259 discloses a 390 nm necessary for obtaining an optical film, a polarizing plate and a display device excellent in color reproducibility and durability in ultraviolet irradiation. An optical film having a spectral transmittance of 50% to 95% at 350 nm and a spectral transmittance of 350% at 350 nm is described.

  Furthermore, the compound used as an optical anisotropy control agent (retardation control agent) will be described in detail.

In general formula (2) shown in Chemical formula ¹ , R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ and R ¹⁰ are each independently a hydrogen atom or a substituent. Represents a group, and the substituent T described below can be applied to the substituent. At least one of R ¹ , R ² , R ³ , R ⁴ and R ⁵ represents an electron donating group. Preferably, one of R ¹ , R ³ or R ⁵ is an electron donating group, and R ³ is more preferably an electron donating group.

  An electron donating group is one having a Hammett σp value of 0 or less. Rev. , 91, 165 (1991) having a Hammett σp value of 0 or less is preferably applicable, and more preferably −0.85 to 0. Examples thereof include an alkyl group, an alkoxy group, an amino group, and a hydroxyl group.

  The electron donating group is preferably an alkyl group or an alkoxy group, more preferably an alkoxy group (preferably having 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, still more preferably 1 to 6 carbon atoms, particularly preferably carbon). 1 to 4).

R ¹ is preferably a hydrogen atom or an electron donating group, more preferably an alkyl group, an alkoxy group, an amino group, or a hydroxyl group, and still more preferably an alkyl group having 1 to 4 carbon atoms or a carbon number 1 to 12 Particularly preferably an alkoxy group (preferably having 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, still more preferably 1 to 6 carbon atoms, and particularly preferably 1 to 4 carbon atoms). Most preferred is a methoxy group.

R ² is preferably a hydrogen atom, an alkyl group, an alkoxy group, an amino group or a hydroxyl group, more preferably a hydrogen atom, an alkyl group or an alkoxy group, still more preferably a hydrogen atom or an alkyl group (preferably a carbon number). 1 to 4, more preferably a methyl group), an alkoxy group (preferably having 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, still more preferably 1 to 6 carbon atoms, and particularly preferably 1 to carbon atoms). 4). Particularly preferred are a hydrogen atom, a methyl group and a methoxy group.

R ³ is preferably a hydrogen atom or an electron donating group, more preferably a hydrogen atom, an alkyl group, an alkoxy group, an amino group, or a hydroxyl group, still more preferably an alkyl group or an alkoxy group, particularly preferably. An alkoxy group (preferably having 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, still more preferably 1 to 6 carbon atoms, and particularly preferably 1 to 4 carbon atoms). Most preferred are n-propoxy group, ethoxy group and methoxy group.

R ⁴ is preferably a hydrogen atom or an electron donating group, more preferably a hydrogen atom, an alkyl group, an alkoxy group, an amino group, or a hydroxyl group, and still more preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. , An alkoxy group having 1 to 12 carbon atoms (preferably having 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, still more preferably 1 to 6 carbon atoms, and particularly preferably 1 to 4 carbon atoms), particularly preferably. Is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms, and most preferably a hydrogen atom, a methyl group, or a methoxy group.

R ⁵ is preferably a hydrogen atom, an alkyl group, an alkoxy group, an amino group or a hydroxyl group, more preferably a hydrogen atom, an alkyl group or an alkoxy group, still more preferably a hydrogen atom or an alkyl group (preferably a carbon number). 1 to 4 is more preferably a methyl group), an alkoxy group (preferably having 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, still more preferably 1 to 6 carbon atoms, and particularly preferably 1 to 4 carbon atoms). It is. Particularly preferred are a hydrogen atom, a methyl group and a methoxy group.

R ⁶ , R ⁷ , R ⁹ and R ¹⁰ are preferably a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or a halogen atom, more preferably a hydrogen atom or a halogen atom. More preferably a hydrogen atom.

R ⁸ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or an aryloxy having 6 to 12 carbon atoms. Group, an alkoxycarbonyl group having 2 to 12 carbon atoms, an acylamino group having 2 to 12 carbon atoms, a cyano group, or a halogen atom, which may have a substituent if possible. The group T can be applied.

R ⁸ is preferably an alkyl group having 1 to 4 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, and an aryloxy group having 2 to 12 carbon atoms. And more preferably an aryl group having 6 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, and an aryloxy group having 6 to 12 carbon atoms, still more preferably an alkoxy group having 1 to 12 carbon atoms (preferably Is preferably 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, still more preferably 1 to 6 carbon atoms, particularly preferably 1 to 4 carbon atoms, and particularly preferably a methoxy group, an ethoxy group, n-propoxy group, iso-propoxy group and n-butoxy group.

  Of the general formula (2), the following general formula (2-A) is more preferable.

R ¹¹ in the general formula (2-A) represents an alkyl group. R ¹ , R ² , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁹ and R ¹⁰ each independently represent a hydrogen atom or a substituent. R ⁸ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or an aryloxy having 6 to 12 carbon atoms. Group, an alkoxycarbonyl group having 2 to 12 carbon atoms, an acylamino group having 2 to 12 carbon atoms, a cyano group, or a halogen atom. In general formula (2-A), R ¹ , R ² , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ and R ¹⁰ have the same meanings as those in general formula (2), and The preferable range is also the same.

In the general formula (2-A), R ¹¹ represents an alkyl group having 1 to 12 carbon atoms, and the alkyl group represented by R ¹¹ may be linear or branched, and further has a substituent. However, it is preferably an alkyl group having 1 to 12 carbon atoms, more preferably an alkyl group having 1 to 8 carbon atoms, still more preferably an alkyl group having 1 to 6 carbon atoms, and particularly preferably an alkyl group having 1 to 4 carbon atoms. (For example, methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, tert-butyl group and the like can be mentioned).

  Of the general formula (2), the following general formula (2-B) is more preferable.

In the general formula (2-B), R ¹ , R ² , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁹ and R ¹⁰ each independently represent a hydrogen atom or a substituent. R ¹¹ represents an alkyl group having 1 to 12 carbon atoms. X is an alkyl group having 1 to 4 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, a carbon number A 2-12 alkoxycarbonyl group, a C2-C12 acylamino group, a cyano group, or a halogen atom is represented.

In the general formula (2-B), R ¹ , R ² , R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁹ and R ¹⁰ have the same meanings as those in the general formula (2), and the preferred range is also It is the same. R ¹¹ in the general formula (2-B) has the same meaning as R ¹¹ in the general formula (2-A), the preferred ranges are also the same.

  In general formula (2-B), X is an alkyl group having 1 to 4 carbon atoms, an alkynyl group having 2 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, and the number of carbon atoms. It represents a 6-12 aryloxy group, a C2-C12 alkoxycarbonyl group, a C2-C12 acylamino group, a cyano group or a halogen atom.

When all of R ¹ , R ² , R ⁴ and R ⁵ are hydrogen atoms, X is preferably an alkyl group, alkynyl group, aryl group, alkoxy group or aryloxy group, more preferably an aryl group, alkoxy group Group, aryloxy group, more preferably alkoxy group (preferably having 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, still more preferably 1 to 6 carbon atoms, particularly preferably 1 to 4 carbon atoms). And particularly preferably a methoxy group, a methoxy group, an n-propoxy group, an iso-propoxy group or an n-butoxy group.

When at least one of R ¹ , R ² , R ⁴ or R ⁵ is a substituent, X is preferably an alkynyl group, an aryl group, an alkoxycarbonyl group, or a cyano group, more preferably an aryl group (preferably Is a cyano group or an alkoxycarbonyl group (preferably a carbon number of 2 to 12), more preferably an aryl group (preferably an aryl group of 6 to 12 carbon atoms, more preferably a phenyl group). , P-cyanophenyl group and p-methoxyphenyl group), an alkoxycarbonyl group (preferably having a carbon number of 2-12, more preferably having a carbon number of 2-6, still more preferably having a carbon number of 2-4, particularly preferably methoxy. Carbonyl, ethoxycarbonyl, n-propoxycarbonyl), cyano group, particularly preferably phenyl group, methoxy group. A sicarbonyl group, an ethoxycarbonyl group, an n-propoxycarbonyl group, and a cyano group.

  Of the general formula (2), the following general formula (2-C) is more preferable.

In the general formula (2-C), R ¹ , R ² , R ⁴ , R ⁵ , R ¹¹ and X have the same meanings as those in the general formula (2-B), and preferred ranges are also the same.

Among the compounds represented by the general formula (2), a compound represented by the following general formula (2-D) is preferable.

In the general formula (2-D), R ² , R ⁴ and R ⁶ have the same meanings as those in the general formula (2-C), and preferred ranges are also the same. R ²¹ and R ²² are each independently an alkyl group having 1 to 4 carbon atoms. X ¹ is an aryl group having 6 to 12 carbon atoms, an alkoxycarbonyl group having 2 to 12 carbon atoms, or a cyano group.

R ²¹ represents an alkyl group having 1 to 4 carbon atoms, preferably an alkyl group having 1 to 3 carbon atoms, and more preferably an ethyl group or a methyl group. R ²² represents an alkyl group having 1 to 4 carbon atoms, preferably an alkyl group having 1 to 3 carbon atoms, more preferably an ethyl group or a methyl group, and still more preferably a methyl group.

X ¹ is an aryl group having 6 to 12 carbon atoms, an alkoxycarbonyl group having 2 to 12 carbon atoms, or a cyano group, preferably an aryl group having 6 to 10 carbon atoms, an alkoxycarbonyl group having 2 to 6 carbon atoms, or a cyano group. More preferably a phenyl group, a p-cyanophenyl group, a p-methoxyphenyl group, a methoxycarbonyl group, an ethoxycarbonyl group, an n-propoxycarbonyl group, and a cyano group, still more preferably a phenyl group, a methoxycarbonyl group. , An ethoxycarbonyl group, an n-propoxycarbonyl group, and a cyano group.

  Of the general formula (2), the following general formula (2-E) is most preferable.

In the general formula (2-E), R ² , R ⁴ and R ⁵ have the same meanings as those in the general formula (2-D), and the preferred range is also the same, but one of them is represented by —OR ¹³ . (R ¹³ is an alkyl group having 1 to 4 carbon atoms). R ²¹ , R ²² and X ¹ have the same meanings as those in formula (2-D), and preferred ranges are also the same.

In the general formula (2-E), R ² , R ⁴ and R ⁵ have the same meanings as those in the general formula (2-D), and the preferred range is also the same, but one of them is represented by —OR ¹³ . (R ¹³ is an alkyl group having 1 to 4 carbon atoms), preferably R ⁴ and R ⁵ are groups represented by —OR ¹³ , more preferably R ⁴ is —OR ^13. It is group represented by these. R ¹³ represents an alkyl group having 1 to 4 carbon atoms, preferably an alkyl group having 1 to 3 carbon atoms, more preferably an ethyl group or a methyl group, and still more preferably a methyl group.

  The aforementioned substituent T will be described below. Examples of the substituent T include an alkyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, and particularly preferably 1 to 8 carbon atoms such as methyl, ethyl, iso-propyl, tert-butyl, and n-octyl, n-decyl, n-hexadecyl, cyclopropyl, cyclopentyl, cyclohexyl, etc.), an alkenyl group (preferably having 2 to 20 carbon atoms, more preferably 2 to 12 carbon atoms, and particularly preferably carbon number). 2 to 8, for example, vinyl, allyl, 2-butenyl, 3-pentenyl, etc.), an alkynyl group (preferably having 2 to 20 carbon atoms, more preferably 2 to 12 carbon atoms, and particularly preferably carbon number). 2-8, and examples thereof include propargyl and 3-pentynyl).

  For example, an aryl group (preferably having 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, and particularly preferably 6 to 12 carbon atoms, such as phenyl, p-methylphenyl, naphthyl, etc.), substitution Or an unsubstituted amino group (preferably having 0 to 20 carbon atoms, more preferably 0 to 10 carbon atoms, particularly preferably 0 to 6 carbon atoms, such as amino, methylamino, dimethylamino, diethylamino, dibenzylamino, etc. An alkoxy group (preferably having 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, and particularly preferably 1 to 8 carbon atoms, such as methoxy, ethoxy, butoxy, etc.), An aryloxy group (preferably having 6 to 20 carbon atoms, more preferably 6 to 16 carbon atoms, particularly preferably 6 to 12 carbon atoms, Phenyloxy, 2-naphthyloxy and the like.), And also like.

  For example, an acyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, and examples thereof include acetyl, benzoyl, formyl, pivaloyl and the like), alkoxycarbonyl. A group (preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 12 carbon atoms, such as methoxycarbonyl, ethoxycarbonyl, etc.), an aryloxycarbonyl group (preferably 7 to 20 carbon atoms, more preferably 7 to 16 carbon atoms, particularly preferably 7 to 10 carbon atoms, such as phenyloxycarbonyl, etc.), acyloxy group (preferably 2 to 20 carbon atoms, more preferably Has 2 to 16 carbon atoms, particularly preferably 2 to 10 carbon atoms, such as acetoxy, benzo Aryloxy and the like.) May also be mentioned, such as.

  For example, an acylamino group (preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 10 carbon atoms, and examples thereof include acetylamino and benzoylamino), alkoxycarbonylamino group (Preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 12 carbon atoms, such as methoxycarbonylamino), aryloxycarbonylamino group (preferably having carbon number) 7 to 20, more preferably 7 to 16 carbon atoms, particularly preferably 7 to 12 carbon atoms, such as phenyloxycarbonylamino, and the like, and sulfonylamino groups (preferably 1 to 20 carbon atoms, more preferably Has 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms. Amino, such as benzenesulfonylamino and the like.), And also like.

  For example, a sulfamoyl group (preferably having 0 to 20 carbon atoms, more preferably 0 to 16 carbon atoms, particularly preferably 0 to 12 carbon atoms, such as sulfamoyl, methylsulfamoyl, dimethylsulfamoyl, phenylsulfamoyl ), A carbamoyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as carbamoyl, methylcarbamoyl, diethylcarbamoyl, phenylcarbamoyl, etc. An alkylthio group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as methylthio and ethylthio), an arylthio group. (Preferably 6-20 carbon atoms, more preferably 6-6 carbon atoms. 6, particularly preferably 6 to 12 carbon atoms, such as phenylthio and the like.), And also like.

  For example, a sulfonyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms such as mesyl, tosyl, etc.), sulfinyl group (preferably carbon 1 to 20, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as methanesulfinyl, benzenesulfinyl, etc.), ureido group (preferably 1 to 20 carbon atoms, more Preferably it is C1-C16, Most preferably, it is C1-C12, for example, a ureido, methylureido, phenylureido etc. are mentioned), phosphoric acid amide groups (preferably C1-C20, More preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as diethyl phosphoric acid amide and phenyl phosphoric acid amide And the like.) It may also be mentioned, such as.

  For example, hydroxy group, mercapto group, halogen atom (eg fluorine atom, chlorine atom, bromine atom, iodine atom), cyano group, sulfo group, carboxyl group, nitro group, hydroxamic acid group, sulfino group, hydrazino group, imino group A heterocyclic group (preferably having a carbon number of 1 to 30, more preferably 1 to 12, and examples of the hetero atom include a nitrogen atom, an oxygen atom and a sulfur atom. Specific heterocyclic groups include: For example, imidazolyl, pyridyl, quinolyl, furyl, piperidyl, morpholino, benzoxazolyl, benzimidazolyl, benzthiazolyl, etc.), a silyl group (preferably having 3 to 40 carbon atoms, more preferably 3 to 30 carbon atoms, Particularly preferably, it has 3 to 24 carbon atoms, for example, trimethylsilyl, triphenyl Such as silyl and the like), and the like. These substituents may be further substituted. Moreover, when there are two or more substituents, they may be the same or different. If possible, they may be linked together to form a ring.

  Hereinafter, the compound represented by the general formula (2) will be described in detail with specific examples, but the present invention is not limited to the following specific examples.

  The compound represented by the general formula (2) can be synthesized by a general ester reaction of a substituted benzoic acid and a phenol derivative, and any reaction may be used as long as it is an ester bond forming reaction. Examples thereof include a method of converting a substituted benzoic acid to an acid halide and then condensing with phenol, a method of dehydrating the substituted benzoic acid and a phenol derivative using a condensing agent or a catalyst, and the like. In view of the production process and the like, a method in which the substituted benzoic acid is functionally converted to an acid halide and then condensed with phenol is preferable.

  Reaction solvents include hydrocarbon solvents (preferably toluene and xylene), ether solvents (preferably dimethyl ether, tetrahydrofuran, dioxane, etc.), ketone solvents, ester solvents, acetonitrile, dimethylformamide, dimethyl Acetamide or the like can be used. These solvents may be used alone or in admixture of several kinds, and preferred reaction solvents are toluene, acetonitrile, dimethylformamide and dimethylacetamide.

  The reaction temperature is preferably 0 to 150 ° C, more preferably 0 to 100 ° C, still more preferably 0 to 90 ° C, and particularly preferably 20 ° C to 90 ° C. In this reaction, it is preferable not to use a base. When a base is used, either an organic base or an inorganic base may be used, preferably an organic base such as pyridine, tertiary alkylamine (preferably triethylamine, ethyldiisopropyl). Pyramine and the like).

The optical properties of the cellulose acylate film of the present invention are as follows:
Formula (IV): Re (λ) = (nx−ny) × d,
Formula (V): Rth (λ) = {(nx + ny) / 2−nz} × d,
It is preferable that the Re retardation value and Rth retardation value represented by the following formulas (VI) and (VII) are satisfied.
Formula (VI): 46 nm ≦ Re (630) ≦ 200 nm
Formula (VII): 70 nm ≦ Rth (630) ≦ 350 nm
[In the formula, Re (λ) is a front retardation value (unit: nm) at a wavelength λnm, and Rth (λ) is a retardation value (unit: nm) in a film thickness direction at a wavelength λnm. Further, nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the fast axis direction in the film plane, nz is the refractive index in the thickness direction of the film, and d is the thickness of the film. That's it. More preferably, the following formulas (VIII) and (IX) are satisfied.
Formula (VIII): 46 nm ≦ Re (630) ≦ 100 nm
Formula (IX): 180 nm ≦ Rth (630) ≦ 350 nm

The optical characteristic values of Re and Rth change with changes in humidity, mass changes and dimensional changes with time. The smaller the values of Re and Rth, the better. In addition to using cellulose acylate with a high degree of acyl substitution at the 6-position in order to reduce changes in optical properties due to humidity, by using various hydrophobic additives (plasticizer, retardation developer, ultraviolet absorber, etc.) Reduce the moisture permeability and equilibrium moisture content of the film. The preferred moisture permeability is 400 to 2300 g per square meter at 60 ° C. and 95% RH for 24 hours. A preferable equilibrium water content is 3.4% or less at 25 ° C. and 80% RH. When the humidity at 25 ° C. is changed from 10% RH to 80% RH, the amount of change in optical characteristics is preferably 12 nm or less in Re value and 32 nm or less in Rth value. A preferred amount of the hydrophobic additive is from 10% to 30%, more preferably from 12% to 25%, particularly preferably from 14.5% to 20%, based on cellulose acylate. When the additive is volatile or decomposable and changes in the mass or dimensionality of the film occur, optical properties change. Therefore, it is preferable that the mass change amount of the film after aging at 80 ° C. and 90% RH for 48 hours is 5% or less. Similarly, the dimensional change after 24 hours at 60 ° C. and 95% RH is preferably 5% or less. Even if there is a small dimensional change or mass change, if the photoelastic coefficient of the film is small, the amount of change in optical characteristics is small. Accordingly, the photoelastic coefficient of the film is preferably 50 × 10 ⁻¹³ cm ² / dyne or less.

  The method for producing the dope used in the present invention is not particularly limited. A specific example will be described. A mixed solvent to which alcohol is added using dichloromethane as a main solvent is used. TAC and a plasticizer (for example, triphenyl phosphate, biphenyl diphenyl phosphate) are added to the mixed solvent and dissolved by stirring to obtain a dope (hereinafter referred to as a raw material dope). In addition, when melt | dissolving, solubility can be improved by heating or cooling. Further, an additive solution (hereinafter referred to as an additive solution) is prepared by mixing and dissolving a raw material dope, a mixed solvent, and an ultraviolet absorber (for example, a benzotriazole compound is preferable). Further, an additive solution (hereinafter referred to as a matting agent solution) is prepared by mixing and dispersing a raw material dope, a mixed solvent, and a matting agent (for example, silica particles). Furthermore, an additive solution containing a deterioration inhibitor, an optical anisotropy control agent (retardation control agent), a dye, a pigment, a release agent, and the like may be prepared and used according to the purpose.

[Dope production method]
First, a dope is manufactured using the above raw materials. FIG. 4 shows a dope production facility 10. The dope manufacturing facility 10 includes a solvent tank 11 for storing a solvent, a dissolution tank 13 for mixing the solvent and TAC, a hopper 14 for supplying TAC, and an additive for storing the additive. An additive tank 15, a heating device 26 for heating the swelling liquid described later, a temperature controller 27 for adjusting the temperature of the heated swelling liquid, filtration devices 28, 35, A flash device 31 for adjusting the dope concentration is arranged. The dope manufacturing facility 10 is further provided with a recovery device 32 for recovering the solvent and a regeneration device 33 for regenerating the recovered solvent. The dope manufacturing equipment 10 is connected to the stock tank 30 of the solution casting equipment 40.

  In the present embodiment, the dope is manufactured by the following method using the manufacturing line 10 described above. First, the valve 12 is opened, and the solvent is sent from the solvent tank 11 to the dissolution tank 13. Next, the TAC contained in the hopper 14 is fed into the dissolution tank 13 while being measured. In addition, the required amount of the additive solution is sent from the additive tank 15 to the dissolution tank 13 by opening and closing the valve 16.

  In addition to the method of sending the additive as a solution, for example, when the additive is liquid at room temperature, it can be sent to the dissolution tank 13 in the liquid state. Further, when the additive is solid, a method of feeding into the dissolution tank 13 using a hopper or the like is also possible. When a plurality of types of additives are added, a solution in which a plurality of types of additives are dissolved can be placed in the additive tank 15. Alternatively, a solution in which an additive is dissolved can be put in each of a plurality of additive tanks and sent to the dissolution tank 13 through independent pipes.

  In the above description, the order of putting into the dissolution tank 13 is the solvent (used in the meaning including the case of the mixed solvent), TAC, and additive, but it is not limited to this order. For example, a preferred amount of solvent can be fed after the TAC is metered into the dissolution tank 13. Further, it is not always necessary to add the additive to the dissolution tank 13 in advance, and it can be mixed with a mixture of TAC and a solvent (hereinafter, these mixtures may also be referred to as a dope) in a later step.

  As shown in FIG. 4, the dissolution tank 13 is provided with a jacket 17 that wraps the outer surface thereof, and a first stirrer 19 that is rotated by a motor 18. Furthermore, as shown in FIG. 4, a second stirrer 21 that is rotated by a motor 20 is preferably attached to the melting dunk 13. The first stirrer 19 is preferably provided with an anchor blade, and the second stirrer 21 is preferably a dissolver type eccentric stirrer. And the melting tank 13 used by this embodiment is temperature-controlled by flowing a heat-transfer medium inside the jacket 17, The preferable temperature range is the range of -10 degreeC-55 degreeC. By appropriately selecting and using the types of the first stirrer 19 and the second stirrer 21, the swelling liquid 22 in which the TAC is swollen in the solvent is obtained.

  Next, the swelling liquid 22 is sent to the heating device 26 by the pump 25. The heating device 26 is preferably a pipe with a jacket, and further preferably has a configuration capable of pressurizing the swelling liquid 22. By using such a heating device 26, the solid content in the swelling liquid 22 is dissolved under heating conditions or pressure heating conditions. In addition, it is preferable that the temperature in swelling and melt | dissolution is 0 to 97 degreeC. Moreover, the well-known cooling dissolution method which cools the swelling liquid 22 to the temperature of -100 degreeC--10 degreeC without using the heating apparatus 26 can also be performed. TAC can be sufficiently dissolved in a solvent by appropriately selecting the heating dissolution method and the cooling dissolution method. After the dope is brought to about room temperature by the temperature controller 27, the dope is filtered by the filtering device 28 to remove impurities contained in the dope. The filtration filter used in the filtration device 28 preferably has an average pore diameter of 100 μm or less. The filtration flow rate is 50 liters / hr. The above is preferable. The dope after filtration is sent to the stock tank 30 in the solution casting equipment 40 through the valve 29 and stored therein.

  By the way, as mentioned above, once the swelling liquid 22 is prepared and then the swelling liquid 22 is used as a solution, the time required increases as the concentration of TAC is increased, which is a problem in terms of manufacturing cost. There is. In that case, it is preferable to prepare a dope having a concentration lower than the target concentration and then perform a concentration step for obtaining the target concentration. When using such a method, the dope filtered by the filtering device 28 is sent to the flash device 31 through the valve 29, and a part of the solvent in the dope is evaporated in the flash device 31. The solvent gas generated by the evaporation is condensed by a condenser (not shown) to become a liquid and is recovered by the recovery device 32. The recovered solvent is regenerated and reused as a solvent for dope preparation by the regenerator 33. This reuse is effective in terms of cost.

  Further, the concentrated dope 36 is extracted from the flash unit 31 by the pump 34. Furthermore, it is preferable that a bubble removal process for removing bubbles generated in the dope 36 is performed. As this defoaming method, various known methods are applied, for example, an ultrasonic irradiation method. The dope 36 is subsequently sent to the filtering device 35 to remove foreign matter. In addition, it is preferable that the temperature of dope 36 at the time of filtration is 0 degreeC-200 degreeC. Then, the dope 36 is sent to the stock tank 30 and stored. Then, the dope in the stock tank 30 is sent to the solution casting apparatus 40.

  It is preferable to mix the raw material dope 16 and an additive liquid (for example, an ultraviolet absorber liquid) added to the raw material dope 16 using an in-line mixer (for example, a static mixer) that mixes during the transfer. It is more preferable to perform mixing by connecting a plurality of in-line mixers having different mixing methods in series.

  As the in-line mixer, it is preferable to include at least one of a static mixer and a through the mixer. When the static mixer is provided, the number of elements of the static mixer is preferably 6 or more and 9 or less, and more preferably 6 or more and 60 or less.

  In the case where both a static mixer and a slew mixer are provided, the slew mixer is preferably arranged on the upstream side of the static mixer. Further, the distance between the through-the-mixer and the addition port for adding the additive liquid is preferably 5 mm or more and 150 mm or less, and further, the distance between the through-the-mixer and the addition port for adding the additive liquid is 5 mm or more and 15 mm or less. Is more preferable. Moreover, it is preferable that the upstream edge part of the element which comprises a through-zer mixer is located in the inner wall vicinity of the piping through which the said raw material dope flows.

  Furthermore, it is preferable that a first filtration device for filtering the raw material dope is provided on the upstream side of the in-line mixer, and an additive is added to the raw material dope after filtration by the first filtering device, and further, the downstream side of the in-line mixer It is more preferable that a second filtering device for filtering the dope is provided, and the dope mixed by the in-line mixer is filtered by the second filtering device.

In addition, the present invention preferably satisfies the following.
(1) When the flow rate of the additive solution is V1 and the flow rate of the raw material dope is V2, 1 ≦ V1 / V2 ≦ 5.
(2) The additive ratio of the additive liquid is 0.1% to 50% in flow rate ratio.
(3) When the viscosity of the additive solution is N1 and the viscosity of the raw material dope is N2, 1000 ≦ N2 / N1 ≦ 100000 is satisfied, and at 20 ° C., 5000 cP ≦ N1 ≦ 500000 cP, and 0 .1 cP ≦ N2 ≦ 100 cP.
(4) The shear rate of the raw material dope is 0.1 (1 / s) to 30 (1 / s).
(5) The polymer is cellulose acylate.
(6) The additive solution is a solution containing the main solvent of the polymer solution.
(7) The additive solution is a solution containing the main solvent of the polymer solution and has a composition different from that of the raw material dope.
(8) The additive solution is a solution containing the main solvent of the polymer solution, and contains at least one ultraviolet absorber.
(9) The additive solution is a solution containing the main solvent of the polymer solution, and is formed by dispersing at least one kind of inorganic or organic fine particles.
(10) The additive solution is a solution containing the main solvent of the polymer solution and contains at least one type of peeling accelerator.
(11) The additive solution is a solution containing the main solvent of the polymer solution and contains at least one kind of poor solvent.

  By the above method, the dope whose TAC density | concentration is 5 mass%-40 mass% can be manufactured. In addition, about the raw material in the solution casting method which obtains a TAC film, a raw material, the dissolution method of an additive, the filtration method, defoaming, and the addition method, the paragraphs [0517] to [0616] of Japanese Patent Application No. 2004-264464 are detailed. These descriptions can also be applied to the present invention.

[Solution casting method]
Next, a method for producing a film using the dope 36 obtained above will be described. FIG. 5 is a schematic view showing the solution casting equipment 40. However, the present invention is not limited to the solution casting apparatus as shown in FIG. The solution casting apparatus 40 includes a stock tank 30, a filtration device 44, a casting die 50, a casting band 53 stretched between rotating rollers 51 and 52, and a tenter 80. The ear clip device 82, the drying chamber 85, the cooling chamber 87, and the winding chamber 90 are arranged.

  A stirrer 42 that is rotated by a motor 41 is attached to the stock tank 30. The stock tank 30 is connected to the casting die 50 via a pump 43 and a filtration device 44.

The material of the casting die 50 is preferably two-layer stainless steel or precipitation hardening type stainless steel, and preferably has a thermal expansion coefficient of 2 × 10 ⁻⁵ (° C. ⁻¹ ) or less. And what has corrosion resistance substantially equivalent to SUS316 in the forced corrosion test with electrolyte aqueous solution can be used as the material of the casting die 50, and further immersed in a mixed solution of dichloromethane, methanol and water for 3 months. Even if it has corrosion resistance, no pitting (perforation) occurs at the gas-liquid interface. Furthermore, it is preferable that the casting die 50 is manufactured by grinding a material that has passed one month or more after casting. Thereby, the surface shape of the dope flowing in the casting die 50 is kept constant. The finishing accuracy of the wetted surface between the casting die 50 and the feed block described later is preferably 1 μm or less in terms of surface roughness and the straightness is 1 μm / m or less in any direction. The slit clearance of the casting die 50 can be adjusted within a range of 0.5 mm to 3.5 mm by automatic adjustment. About the corner | angular part of the liquid-contact part of the lip | tip end of the casting die 50, the R shall be 50 micrometers or less over the whole width. The shear rate inside the casting die 50 is preferably adjusted to be 1 (1 / sec) to 5000 (1 / sec).

  The width of the casting die 50 is not particularly limited, but is preferably about 1.0 to 2.0 times the width of the film as the final product. Moreover, it is preferable to attach a temperature controller to the casting die 50 so that the temperature during film formation is maintained at a predetermined temperature. The casting die 50 is preferably a coat hanger type. Furthermore, it is more preferable that thickness adjusting bolts (heat bolts) are provided at predetermined intervals in the width direction of the casting die 50 and the casting die 50 is provided with an automatic thickness adjusting mechanism using a heat bolt. The heat bolt is preferably formed by setting a profile according to the amount of pump 43 (preferably a high precision gear pump) according to a preset program. Further, feedback control may be performed by an adjustment program based on a profile of a thickness meter (for example, an infrared thickness meter) (not shown) in the film forming line 40. It is preferable that the thickness difference between any two points except the casting edge is adjusted within 1 μm, and the maximum difference in the width direction thickness is adjusted to 3 μm or less. In addition, it is preferable to use a lip gap whose accuracy is adjusted to ± 50 μm or less.

More preferably, a cured film is formed at the lip tip of the casting die 50. A method for forming the cured film is not particularly limited, and examples thereof include ceramic coating, hard chrome plating, and a nitriding method. In the case of using ceramics as the cured film, it is preferable to use a ceramic that can be ground, has a low porosity, is not brittle, has good corrosion resistance, and does not adhere to the casting die 50. Specific examples include tungsten carbide (WC), Al ₂ O ₃ , TiN, Cr ₂ O _{3 and the} like, among which WC is particularly preferable. The WC coating can be performed by a thermal spraying method.

  In order to prevent the dope flowing out to the slit end of the casting die 50 from locally drying and solidifying, it is preferable to attach a solvent supply device (not shown) to the slit end. In this case, a solvent for solubilizing the dope (for example, a mixed solvent of 86.5 parts by mass of dichloromethane, 13 parts by mass of acetone, and 0.5 parts by mass of n-butanol) is supplied to both ends of the casting bead. Is preferred. In addition, as a pump which supplies this liquid, it is preferable to use a pump with a pulsation rate of 5% or less.

  Below the casting die 50, there is provided a casting band 53 that spans the rotating rollers 51 and 52. The rotating rollers 51 and 52 are rotated by a driving device (not shown), and the casting band 53 travels endlessly with the rotation. It is preferable that the casting band 53 can move at a moving speed, that is, a casting speed of 10 m / min to 200 m / min. In order to set the surface temperature of the casting band 53 to a predetermined value, it is preferable that a heat transfer medium circulation device 54 is attached to the rotary rollers 51 and 52, and the surface temperature of the casting band 53 is It is preferable that the temperature can be adjusted to -20 ° C to 40 ° C. A heat transfer medium flow path (not shown) is formed in the rotating rollers 51 and 52 used in the present embodiment, and the heat transfer medium maintained at a predetermined temperature passes through the flow path. Thus, the temperature of the rotating rollers 51 and 52 is maintained at a predetermined value.

It is also possible to use the rotating rollers 51 and 52 directly as a support. In this case, it is preferable that the rotation can be performed with high accuracy so that the rotation speed variation is 0.2% or less. In this case, it is preferable that the average roughness of the surfaces of the rotary rollers 51 and 52 be 0.01 μm or less. It is preferable to perform a hard chrome plating process on the surfaces of the rotating rollers 51 and 52, thereby further providing sufficient hardness and durability. In addition, it is preferable to suppress the surface defects of the support (the casting band 53 and the rotating rollers 51 and 52) to the minimum. Specifically, there is no pinhole of 30 μm or more, and the number of pinholes of 10 μm or more and less than 30 μm is 1 / m ² or less, and the number of pinholes of less than 10 μm is preferably ² / m ² or less.

  Casting devices such as the casting die 50 and the casting band 53 are accommodated in the casting chamber 55. The casting chamber 55 is provided with a temperature controller 56 for maintaining the internal temperature at a predetermined value, and a first condenser (condenser) 57 for condensing and recovering the volatile organic solvent. . A recovery device 58 for recovering the condensed and liquefied organic solvent is provided outside the casting chamber 55. Further, it is preferable that a decompression chamber 60 for controlling the pressure of the back surface of the casting bead formed from the casting die 50 to the casting band 53 is disposed, and this is also used in the present embodiment. .

  Further, an air supply duct 61 for blowing wind to evaporate the solvent of the casting film 59 and an exhaust duct 62 for exhausting the evaporated solvent from the casting film 59 together with the wind are provided above the band 53. A guide plate is provided between the air supply duct 61 and the exhaust duct 62. The air supply duct 61, the exhaust duct, and the guide plate 64 will be described in detail later using another drawing.

  The crossover portion 70 is provided with a blower 71, and the ear clip device 82 downstream of the tenter 80 is provided with a crusher 83 for finely cutting the side edge scraps of the cut film 81.

  The drying chamber 85 is provided with a number of rollers 84, and an adsorption / recovery device 86 for adsorbing and recovering the solvent gas generated by evaporation is attached. In FIG. 2, the cooling chamber 87 is provided downstream of the drying chamber 85, but a humidity control chamber (not shown) may be provided between the drying chamber 85 and the cooling chamber 87. A forced neutralization device (static neutralization bar) 88 for adjusting the charged voltage of the film 81 to be within a predetermined range (for example, −3 kV to +3 kV) is provided downstream of the cooling chamber 87. In FIG. 2, the forced static eliminating device 88 is illustrated on the downstream side of the cooling chamber 87, but is not limited to this installation position. Furthermore, in this embodiment, a knurling application roller 89 for applying knurling to both edges of the film 81 by embossing is appropriately provided downstream of the forced static elimination device 88. The take-up chamber 90 is provided with a take-up roller 91 for taking up the film 81 and a press roller 92 for controlling the tension during the take-up.

  Next, an example of a method for producing a film using the solution casting apparatus 40 as described above will be described below. The dope 36 is always made uniform by the rotation of the stirrer 42. The dope 36 may be mixed with additives such as a plasticizer and an ultraviolet absorber during the stirring.

Then, the dope 36 is sent to the filtration device 44 by the pump 43 and filtered there, and then cast from the casting die 50 to the casting band 53. The driving of the rotary rollers 51 and 52 is preferably adjusted so that the tension generated in the casting band 53 is 1.5 × 10 ⁴ kg / m. Further, the relative speed difference between the casting band 53 and the rotary rollers 51 and 52 is adjusted to be 0.01 m / min or less. It is preferable that the speed fluctuation of the casting band 53 is 0.5% or less, and the meandering in the width direction that occurs when the casting band 53 rotates once is 1.5 mm or less. In order to suppress this meandering, it is more preferable to provide a detector (not shown) for detecting the positions of both ends of the casting band 53 and to control the speed of the rotating roller by feedback control based on the measured value. Furthermore, it is preferable to adjust the casting band 53 immediately below the casting die 50 so that the vertical position fluctuation accompanying the rotation of the rotary roller 51 is 200 μm or less. The temperature of the casting chamber 55 is preferably set to −10 ° C. to 57 ° C. by the temperature controller 56. The solvent evaporated inside the casting chamber 55 is recovered by the recovery device 58 and then regenerated and reused as a dope preparation solvent.

  A casting bead is formed from the casting die 50 to the casting band 53, and a casting film 59 is formed on the casting band 53. The temperature of the dope 36 during casting is preferably −10 ° C. to 57 ° C. In order to stabilize the casting bead, the back surface of the bead is preferably controlled to a predetermined pressure value by the decompression chamber 60. It is preferable that the bead back surface is depressurized by −10 Pa to −1500 Pa than the front surface. Furthermore, it is preferable to attach a jacket (not shown) to the decompression chamber 60 and to control the temperature so that the internal temperature is kept at a predetermined temperature. In order to keep the shape of the casting bead desired, it is preferable to attach a suction device (not shown) to the edge portion of the casting die 50. This edge suction air volume is 1 L / min. ~ 100 L / min. It is preferable that it is the range of these.

  After the casting film 59 has self-supporting properties, the casting film 59 is peeled off from the casting band 53 while being supported by the peeling roller 65 as a wet film 66. After that, after the transfer section 70 provided with a large number of rollers is conveyed, the wet film 66 is fed into the tenter 80. In the transfer part 70, the drying of the wet film 66 is advanced by sending the drying air of desired temperature from the air blower 71. FIG. At this time, the temperature of the drying air is preferably 20 ° C to 250 ° C.

  The wet film 66 sent to the tenter 80 is dried while its both ends are held by clips and conveyed. Moreover, it is preferable to divide the inside of the tenter 80 into different temperature zones and adjust the drying conditions appropriately for each of the zones. In the tenter 80, the wet film 66 can be stretched in the width direction. As described above, in at least one of the crossover portion 70 and the tenter 80, it is preferable to stretch at least one direction of the wet film 66 in the casting direction and the width direction by 100.5% to 300%.

  The wet film 66 is dried to a predetermined residual solvent amount by the tenter 80 and then sent out downstream as a film 81. Both edges of the film 81 are cut at both edges by the edge cutting device 82, and the cut side edges are sent to the crusher 83 by a cutter blower (not shown). By the crusher 83, the side end portion is crushed into chips. Since this chip is reused for dope preparation, this method is effective in terms of cost. In addition, although it can also abbreviate | omit about the cutting process of this both-sides edge part, it is preferable to carry out in any one from the said casting process to the process of winding up the said film.

  On the other hand, in this embodiment, the film 81 from which both end portions have been cut and removed is sent to the drying chamber 85 and further dried. The temperature in the drying chamber 85 is not particularly limited. In the drying chamber 85, the film 81 is conveyed while being wound around a roller 84, and the solvent gas generated by evaporation here is adsorbed and recovered by an adsorption recovery device 86. The air from which the solvent component has been removed is blown again as dry air inside the drying chamber 85. The drying chamber 85 is more preferably divided into a plurality of sections in order to change the drying temperature. In addition, when a preliminary drying chamber (not shown) is provided between the ear opener 82 and the drying chamber 85 and the film 81 is preliminarily dried, the film temperature is prevented from rising rapidly in the drying chamber 85. The shape change of the film 81 can be further suppressed.

  The film 81 is cooled to approximately room temperature in the cooling chamber 87. Note that a humidity control chamber (not shown) may be provided between the drying chamber 85 and the cooling chamber 87, and in this humidity control chamber, air adjusted to a desired humidity and temperature can be blown onto the film 81. It is preferable. Thereby, generation | occurrence | production of the curling of the film 81 and the winding-up defect at the time of winding can be suppressed.

  In the solution casting method, various steps such as a drying step and a side edge cutting and removing step are performed before the film (polymer film) peeled off from the support is wound up. In each of these processes or between each process, the film is mainly supported or conveyed by a roller. These rollers include a driving roller and a non-driving roller, and the non-driving roller is mainly used for determining a film conveyance path and improving conveyance stability.

  On the other hand, the drive roller is used to transmit drive to the film and convey it downstream, and a suction roller is usually used. In film transport in film formation, separation of transport tension may be necessary within each process such as casting process, stripping process, drying process, winding process, etc., and in that case, suction Separation of conveyance tension is achieved by applying a driving force to the film by a roller. This suction roller has a large number of air suction holes on the peripheral surface of the roller for adsorbing and transporting the film to itself.

  When a suction roller is used, the film is more easily deformed than a non-driven roller because a complex force whose directionality cannot be specified acts on the film. The film is also deformed by a difference in tension before and after the conveyance applied to the film. Furthermore, a large number of air suction holes are formed on the peripheral surface of the suction roller. If the film slips or contracts or deforms when the film is in contact with the edge of the suction holes, Fine scratches occur.

  The driving roller used in the transporting process is a roller whose peripheral surface is previously cured by nitriding treatment, cured chrome plating, or quenching treatment. The surface hardness of the circumferential surface is 500 to 2000 in terms of Vickers hardness. Or less, more preferably 800 or more and 1200 or less.

  The drive roller used is a suction roller, and this suction roller has a large number of air suction holes on its peripheral surface. At this time, the surface roughness Ry of the peripheral surface of the suction roller is preferably 0.3 μm or more and 1.0 μm or less, more preferably 0.5 μm or more and 0.8 μm or less. As for the surface roughness Ry of the peripheral surface, the surface roughness of the smooth portion having no hole in the roller is the peripheral surface roughness. The hole diameter is preferably 1 mm or more and 6 mm or less, more preferably 2 mm or more and 4 mm or less, and the chamfering amount of the hole is preferably 2% or more and 20% or less of the hole diameter.

  When using the suction roller, it is preferable to control the peripheral surface temperature, and therefore, it is preferable to have at least one temperature adjusting device for one suction roller. It is preferable to form the film while making the peripheral surface temperature of the roller higher than the film temperature immediately before contacting the suction roller.

  Moreover, the charged voltage while the film 81 is conveyed is set to a predetermined range (for example, −3 kV to +3 kV) by the forced charge removal device (charge removal bar) 88. In the drawing, an example provided on the downstream side of the cooling chamber 87 is illustrated, but the position is not limited thereto. Furthermore, it is preferable to provide a knurling roller 89 and to impart knurling to both edges of the film 81 by embossing. In addition, it is preferable that the unevenness | corrugation of the knurled location is 1 micrometer-200 micrometers.

  Finally, the film 81 is wound up by the winding roller 91 in the winding chamber 90. At this time, it is preferable to wind the sheet while applying a desired tension with the press roller 92. More preferably, the tension is gradually changed from the start to the end of winding. The film 81 to be wound is preferably at least 100 m in the longitudinal direction (casting direction). Moreover, it is preferable that the width | variety of a film is 600 mm or more, and it is more preferable that they are 1400 mm or more and 1800 mm or less. The present invention is also effective when it is larger than 1800 mm. The present invention is also applied when manufacturing a thin film having a thickness of 15 μm or more and 100 μm or less.

  In the present invention, when casting the dope, a method of simultaneously laminating two or more types of dopes or co-casting sequentially may be used. When performing simultaneous lamination and co-casting, a casting die to which a feed block is attached may be used, or a multi-manifold casting die may be used. In the film composed of multiple layers by co-casting, it is preferable that either the thickness of the layer on the air surface side or the thickness of the layer on the support side is 0.5% to 30% of the thickness of the entire film. Furthermore, when performing simultaneous lamination co-casting, it is preferable that the high-viscosity dope is wrapped with the low-viscosity dope when the dope is cast from the die slit to the support. Moreover, when performing simultaneous lamination | stacking co-casting, it is preferable that the dope which contact | connects an external world among the beads formed from a die slit to a support body has a larger alcohol composition ratio than an internal dope.

  From casting die, vacuum chamber, support structure, co-casting, peeling method, stretching, drying conditions for each process, handling method, curl, winding method after flatness correction, solvent recovery method, film recovery method The details are described in paragraphs [0617] to [0889] of Japanese Patent Application No. 2004-264464. These descriptions can also be applied to the present invention.

  Next, the casting process will be described in detail with reference to FIGS. 6 is a plan view of the band 59 as viewed from above the casting die 50 side, and FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. However, the illustration of the decompression chamber provided on the upstream side of the casting die is omitted to avoid the complexity of the illustration.

  In the following description, the downstream side from the casting start position PS indicated by the broken line in FIG. 6 and the point in FIG. 7 is referred to as a casting film 59. As described above, the air supply duct 61 and the exhaust duct 62 are provided above the casting film 59 and in the vicinity of the casting film 59, and the guide plate 64 is provided between them. A plurality of guide plates 64 are arranged in the width direction of the casting film 59. The air supply duct 61 is provided with an air supply opening 61a along the width direction so that air is blown against the casting film 59 and is directed from the upstream side toward the downstream side. The exhaust duct 62 is provided with an exhaust port 62a along the width direction in order to effectively collect and exhaust the flowing wind.

  The air supply duct 61 is provided with a blower controller 111 and a blower 112, and the exhaust duct 62 is provided with an exhaust controller 114 and an exhaust processing unit 115. Then, the wind from the blower 112 is sent from the air supply duct 61 to the casting film 59 while the temperature and the wind speed are controlled by the blower controller. Further, the exhaust force by the exhaust duct 62 is controlled by the exhaust controller 114, and the exhaust processing unit 115 condenses and recovers the solvent from the exhaust that has been sent, and the air from which the evaporated solvent is removed is sent to the blower 112.

  In the present embodiment, the guide plate is provided close to the air supply port 61a and the exhaust port 62a so as to divide the air supply port 61a and the air exhaust port 62a into a plurality in the width direction. 61a and the exhaust port 62a may be in contact. By providing the guide plate 64 in this way, it is possible to suppress the wind from the air supply port 61a from flowing in the width direction of the casting film, and external air from the side end portion of the air supply duct 61. Entrainment on the top is suppressed. Thereby, it can suppress that the thickness nonuniformity of the diagonal direction which cross | intersects a elongate direction generate | occur | produces in the film after drying. In particular, the guide plate 64 having both end portions arranged on the outermost sides has a thickness unevenness that becomes stronger toward the side edge of the film in order to prevent wind from flowing in the width direction on the side edge of the film. Can be more effectively suppressed, and the film 81 (see FIG. 1) having no optical unevenness as described above can be manufactured. Even in applications with high luminance and high image quality, such as a VA (Vertically Aligned) liquid crystal display device and an OCB (Optically Compensated Birefringence) liquid crystal display device in which minute optical unevenness is also a problem. it can.

  The position of the air supply duct 61 is not a position immediately after the casting start point PS but a position where the casting film 59 has a predetermined hardness. Thereby, it is possible to suppress the traces of the casting film from being blown by the wind and the like on the casting film 59.

  And, it is more preferable in order to suppress thickness unevenness between the casting die 50 and the air supply duct 61 in order to suppress thickness unevenness, and in order to make this region a windless region range indicated by a symbol R in FIG. In the present embodiment, a wind shielding plate 121 is provided. This wind shield valve is provided above the casting film 59 and suppresses the flow of wind above the casting film. This restraining effect winds the labyrinth structure along the traveling direction of the casting film 59. By providing the plate 121, it can be further improved. That is, the labyrinth structure enhances the effect of suppressing the air entrainment flow and the air volume of the band traveling. Or the effect of this invention improves by combining the method of drying the back surface of the casting film 59, and the method of using a cooling condensation collection | recovery system etc. and a windless state. It is preferable that the windless region R is from when the cast film 59 is formed until the residual solvent is dried to an extent of about 150%. 6 and 7, the cooling condensation recovery system is provided with a second condensing plate 122 above the casting film 59, and the solvent volatilized from the casting film is cooled by the second condensing plate. The method of condensing. Further, as a method for drying the back surface of the casting film 59 as described above, there is a method of drying the casting film 59 by providing a heating plate 124 on the side opposite to the casting film of the band 53 as shown in FIG. Yes, this embodiment is also implemented. Furthermore, by using a co-casting method that forms multiple layers, the concentration of the dope that becomes the surface layer of the film is smaller than that of the intermediate layer excluding the surface layer. Since the thickness fluctuation which may occur can be buffered, it is possible to perform casting at a higher speed.

[Performance / Measurement method]
(Curl degree / thickness)
The performance of the wound cellulose acylate film and the measuring method thereof are disclosed in Japanese Patent Application No. 200.
No. 4-264464, paragraphs [0112] to [0139]. These can also be applied to the present invention.

[surface treatment]
It is preferable that at least one surface of the cellulose acylate film is surface-treated. The surface treatment is preferably at least one of vacuum glow discharge treatment, atmospheric pressure plasma discharge treatment, ultraviolet irradiation treatment, corona discharge treatment, flame treatment, acid treatment or alkali treatment.

[Functional layer]
(Antistatic, hardened layer, antireflection, easy adhesion, antiglare)
At least one surface of the cellulose acylate film may be undercoated.

  Furthermore, the cellulose acylate film can be preferably used for a functional material obtained by using the cellulose acylate film as a base film and adding another functional layer to the base film. The functional layer is preferably at least one layer selected from an antistatic layer, a cured resin layer, an antireflection layer, an easy adhesion layer, an antiglare layer, and an optical compensation layer. In addition, in the paragraphs [0890] to [1087] of Japanese Patent Application No. 2004-264464, the method for applying the functional layer is described including detailed conditions and methods. These are also applicable to the present invention.

(Use)
The cellulose acylate film is particularly useful as an optical compensation film that also functions as a polarizing plate protective film. Usually, two polarizing plates each having a cellulose acylate film bonded to a polarizer are bonded to a liquid crystal layer to produce a liquid crystal display device. However, the arrangement of the liquid crystal layer and the polarizing plate is not limited, and various known arrangements can be employed. Japanese Patent Application No. 2004-264464 describes in detail TN type, STN type, VA type, OCB type, reflection type, and other examples of liquid crystal display devices. This method can also be applied to the present invention. The application also describes a cellulose acylate film provided with an optically anisotropic layer and a cellulose acylate film provided with antireflection and antiglare functions. Furthermore, the use as an optical compensation film is also described as a biaxial cellulose acylate film imparted with appropriate optical performance. This can also be used as a polarizing plate protective film. These descriptions can be applied to the present invention. Details are described in paragraphs [1088] to [1265] of Japanese Patent Application No. 2004-264464.

  The resulting film can be used as a polarizing plate protective film or a base film for a photographic photosensitive material. Furthermore, it can also be used as an optical compensation film for improving the viewing angle dependency of a liquid crystal display device for television applications. In particular, it is effective for applications that also serve as a protective film for a polarizing plate. Therefore, it is used not only for the conventional TN mode but also for the IPS mode, OCB mode, VA mode, and the like. Moreover, you may comprise a polarizing plate using the said film for polarizing plate protective films.

  In the present invention, as described above, depending on the type of polymer, a film may be produced by melt casting instead of solution casting. In this case, it is preferable to use a melt extrusion process instead of the casting process, melt the polymer with various commercially available melt extrusion dies and extrude it into a film shape, and cool the extruded film under predetermined conditions to produce a film. . About the film extruded in the elongate shape, you may extend | stretch in a predetermined direction as needed. In addition, as the said cooling method of the extruded film, natural cooling may be sufficient and cooling by a predetermined cooling device may be sufficient.

Next, examples of the present invention will be described. The production conditions were changed as shown in Table 1, and the experiment names under the respective conditions were set to Experiment 1 to Experiment 14 and Comparative Experiment 1 to Comparative Experiment 3. First, the formulation for preparing the polymer solution (dope) used for film production is shown below.
[composition]
Cellulose triacetate (substitution degree 2.84, viscosity average polymerization degree 306, water content 0.2 mass%, viscosity 6 mass% in dichloromethane solution 315 mPa · s, average particle diameter 1.5 mm with standard deviation 0.5 mm Some powders) 100 parts by mass dichloromethane (first solvent) 320 parts by mass methanol (second solvent) 83 parts by mass 1-butanol (third solvent) 3 parts by mass plasticizer A (triphenyl phosphate) 7.6 parts by mass Plasticizer B (diphenyl phosphate) 3.8 parts by mass UV agent a: 2 (2′-hydroxy-3 ′, 5′-di-tert-butylphenyl) benzotriazole 0.7 part by mass UV agent b: 2 ( 2′-Hydroxy-3 ′, 5′-di-tert-amylphenyl) -5-chlorobenzotriazole 0.3 parts by mass of citric acid ester mixture (citric acid, citric acid Monoethyl ester, citric acid diethyl ester, citric acid triethyl ester mixture) 0.006 parts by weight fine particles (silicon dioxide (particle size 15 nm), Mohs hardness: about 7) 0.05 parts by weight

  Furthermore, in order to control the optical characteristics, a compound represented by the following chemical formula 57 was added in various amounts. In addition, each addition amount is as showing in the column of chemical | drug | medicine 57 addition rate (unit; weight%) of Table 1, and this addition rate is a weight ratio with respect to the said cellulose triacetate.

[Cellulose triacetate]
The cellulose triacetate used here has a residual acetic acid content of 0.1% by mass or less, a Ca content of 58 ppm, a Mg content of 42 ppm, a Fe content of 0.5 ppm, a free acetic acid of 40 ppm, It contained 15 ppm of sulfate ions. The degree of substitution of the 6-position acetyl group was 0.91, 32.5% of the total acetyl. Moreover, the acetone extraction part which extracted this TAC with acetone was 8 mass%, and the weight average molecular weight / number average molecular weight ratio was 2.5. The obtained TAC has a yellow index of 1.7, a haze of 0.08, a transparency of 93.5%, a Tg (glass transition point; measured by DSC) of 160 ° C., and a crystallization calorific value of It was 6.4 J / g. This TAC is synthesized using cellulose collected from cotton as a raw material. In the following description, this is called cotton raw material TAC.

(1-1) Dope Preparation A dope 36 was prepared using a dope manufacturing facility 10 shown in FIG. In a 4000 L stainless steel dissolution tank having a stirring blade, the plurality of solvents were mixed and stirred well to obtain a mixed solvent. In addition, all the solvents used that the water content is 0.5 mass% or less. Next, TAC flaky powder was gradually added from the hopper of the dissolution tank. The TAC powder was put into a dissolution tank and dispersed under a predetermined stirring condition for 30 minutes by a dissolver type eccentric stirrer 21 equipped with an anchor blade 19 on a rotating shaft. The temperature at the start of dispersion was 25 ° C., and the final temperature reached 48 ° C. Further, an additive solution prepared in advance was adjusted from the additive tank to the dissolution tank by adjusting the amount of liquid fed with a valve so that the total amount was 2000 kg. After the dispersion of the additive solution was completed, high-speed stirring was stopped, and then the peripheral speed of the anchor blade 19 was set to a predetermined value and further stirred for 100 minutes to swell the TAC flakes to obtain a swelling liquid. The tank was pressurized to 0.12 MPa with nitrogen gas until the end of swelling. The inside of the dissolution tank at this time was kept in a state where there was no problem in terms of explosion prevention because the oxygen concentration was less than 2 vol%. The amount of water in the swelling liquid was 0.3% by mass.

(1-2) Dissolution / filtration The swelling liquid was fed from the dissolution tank to the jacketed pipe using a pump. The swelling liquid was heated to 50 ° C. with a jacketed pipe, and further heated to 90 ° C. under a pressure of 2 MPa to completely dissolve. The heating time at this time was 15 minutes. Next, the temperature of the dissolved liquid was lowered to 36 ° C. with a temperature controller, and the dope (hereinafter referred to as pre-concentration dope) was obtained by passing through a filtration device equipped with a filter medium having a nominal pore diameter of 8 μm. At this time, the primary pressure in the filtration device was 1.5 MPa, and the secondary pressure was 1.2 MPa. As the filter, housing, and piping exposed to a high temperature, those having a jacket made of Hastelloy alloy having excellent corrosion resistance and circulating a heat transfer medium for heat insulation heating were used.

(1-3) Concentration / Filtration / Defoaming / Additive The dope before concentration thus obtained is flash-evaporated in a flash apparatus at 80 ° C. and normal pressure, and the evaporated solvent is condensed in a condenser. And recovered. In this way, the dope concentration was adjusted as shown in Table 1. The condensed solvent was recovered by a recovery device to be reused as a dope preparation solvent, regenerated by a regeneration device, and then sent to a solvent tank. Distillation and dehydration are performed in the recovery device and the regeneration device. The flash tank of the flash unit was provided with a stirrer having an anchor blade on the stirring shaft, and the flashed dope was stirred by this stirrer to perform defoaming. The temperature of the dope in this flash tank was 25 ° C., and the average residence time of the dope in the tank was 50 minutes. The shear viscosity measured at 25 ° C. after collecting this dope was 450 Pa · s at a shear rate of 10 (sec ⁻¹ ).

  Next, bubbles were removed by irradiating the dope with weak ultrasonic waves. Thereafter, the filter was passed through the pump while being pressurized to 1.5 MPa using a pump. In the filtration apparatus, first, a sintered fiber metal filter having a nominal pore diameter of 10 μm was passed, and then a sintered fiber filter having a same pore diameter of 10 μm was passed. Respective primary pressures were 1.5 MPa and 1.2 MPa, and secondary pressures were 1.0 MPa and 0.8 MPa. The dope temperature after filtration was adjusted to 36 ° C., and the dope 36 was fed into a 2000 L stainless steel stock tank and stored therein. The stock tank has a stirrer having an anchor blade on the central axis, and the inside is constantly stirred by this stirrer. Incidentally, no problem such as corrosion occurred at all in the wetted part of the dope from the dope before concentration to the preparation of the dope 36.

  Moreover, the mixed solvent A of 86.5 mass parts of dichloromethane, 13 mass parts of acetone, and 0.5 mass part of 1-butanol was produced.

(1-4) Discharge / Previous Addition / Casting / Bead Depressurization A film 81 was manufactured using the solution casting apparatus 10 shown in FIG. The dope 36 in the reserve tank 12 was sent to the filtration device by the high precision gear pump 15. This pump 15 has a function of increasing the pressure on the primary side of the pump 15 and feeds it by performing feedback control on the upstream side of the pump 15 with an inverter motor so that the pressure on the primary side becomes 0.8 MPa. . The pump 15 has a volume efficiency of 99.2% and a discharge rate variation rate of 0.5% or less. The discharge pressure was 1.5 MPa. Then, the dope 36 that passed through the filtration device was fed to the casting die 50.

  The casting die 50 was cast by adjusting the flow rate of the dope 36 at the outlet of the die 50 so that the width of the casting die 50 was 1.8 m and the thickness of the film 81 after drying was 80 μm. The casting width of the dope 36 from the discharge port of the die 50 was 1700 mm. In order to adjust the temperature of the dope 36 to 36 ° C., a jacket (not shown) is provided on the casting die 50 and the inlet temperature of the heat transfer medium supplied into the jacket is set to 36 ° C.

  The casting die 50 and the piping were all kept at 36 ° C. during operation. The casting die 50 is a coat hanger type die. And as this die | dye 50, the thickness adjustment bolt was provided in 20 mm pitch, and the thing equipped with the automatic thickness adjustment mechanism by a heat bolt was used. The heat bolt can set a profile corresponding to the pumping amount by a preset program, and is feedback controlled by an adjustment program based on a profile of an infrared thickness meter (not shown) installed in the solution casting apparatus 40. Also used were those having possible performance. In the film 81 excluding the casting side end 20 mm, the difference in thickness between two arbitrary points separated by 50 mm was within 1 μm, and the thickness variation in the width direction was adjusted to 3 μm / m or less. The overall thickness was adjusted to ± 1.5% or less.

  In addition, a decompression chamber 60 for decompressing this portion was installed on the primary side of the casting die 50. The degree of decompression of the decompression chamber 60 is adjusted so that a pressure difference of 1 Pa to 5000 Pa is generated before and after the casting bead from the casting die 50 until reaching the casting start position PS. Made according to speed. At that time, the pressure difference on both sides of the bead was set so that the length of the bead became a predetermined value. Further, the decompression chamber was provided with a mechanism that can be set to a temperature higher than the condensation temperature of the gas around the casting part. Labyrinth packings (not shown) were provided on the front and back portions of the beads at the die discharge port, and openings were provided at both ends of the die discharge port. Further, the die 50 is provided with an edge suction device (not shown) for adjusting the disturbance of both edges of the casting bead.

(1-5) Casting Die The material of the casting die 50 is a two-layer stainless steel having a coefficient of thermal expansion of 2 × 10 ⁻⁵ (° C. ⁻¹ ) or less. This is a material that has almost the same corrosion resistance as that of SUS316 in the forced corrosion test with an aqueous electrolyte solution, and it is also pitting at the gas-liquid interface even if immersed in a mixture of dichloromethane, methanol, and water for 3 months. Corrosion resistance that does not cause (perforation). The finishing accuracy of the wetted surface of the casting die 50 was 1 μm or less in terms of surface roughness, the straightness was 1 μm / m or less in any direction, and the slit clearance was adjusted to 1.5 mm. The corner portion of the liquid contact portion at the tip of the lip of the die 50 is processed so that R is 50 μm or less over the entire width of the slit. The shear rate inside the die was in the range of 1 (1 / sec) to 5000 (1 / sec). Further, a WC (tungsten carbide) coating was performed on the lip end of the casting die 50 by a thermal spraying method to provide a cured film.

  Further, in order to prevent the dope 36 flowing out from being locally dried and solidified at the discharge port of the casting die 50, the mixed solvent A for solubilizing the dope 36 is provided on both side ends of the casting bead. 0.5 ml / min. For each interface with the discharge port. Supplied one by one. The pulsation rate of the pump supplying the mixed solvent A was 5% or less. Further, the pressure on the back side of the bead was reduced by 150 Pa from the front side by the decompression chamber 60. In addition, a jacket (not shown) was attached in order to keep the internal temperature of the decompression chamber 60 constant at a predetermined temperature. A heat transfer medium adjusted to 35 ° C. was supplied into the jacket. The edge suction device is 1 L / min. ~ 100 L / min. The edge suction air volume can be adjusted so as to fall within the range of 30 L / min. ~ 40 L / min. It adjusted suitably so that it might become the range of.

(1-6) Metal Support A stainless steel endless band 53 having a width of 2.1 m and a length of 70 m was used as a support. The casting band 53 was polished so that the thickness was 1.5 mm and the surface roughness was 0.05 μm or less. The material is made of SUS316 and has sufficient corrosion resistance and strength. The thickness unevenness of the entire casting band 53 was 0.5% or less. The casting band 53 was transported by two backup rollers 51 and 52. At that time, the relative speed difference between the casting band 53 and the backup rollers 51 and 52 is 0.01 m / min or less so that the tension in the conveying direction of the casting band 53 is 1.5 × 10 ⁵ N / m ^2. It was adjusted to become. Moreover, the speed fluctuation of the casting band 53 was 0.5% or less. Further, both end positions of the casting band 53 were detected and controlled so that the meandering in the width direction of one rotation was limited to 1.5 mm or less. Further, the positional fluctuation in the vertical direction between the lip tip of the die 50 and the casting band 53 immediately below the casting die 50 was set to 200 μm or less. The casting band 53 is installed in a casting chamber (not shown) having wind pressure fluctuation suppressing means (not shown). The dope 36 was cast from the casting die 50 on the casting band 53.

As the backup rollers 51 and 52, those capable of feeding a heat transfer medium therein were used so that the temperature of the casting band 53 could be adjusted. A 5 ° C. heat transfer medium was passed through the backup roller 32 on the casting die 50 side, and a 40 ° C. heat transfer medium was passed through the other backup roller 36 for drying. The surface temperature of the central part of the casting band 53 immediately before casting was 15 ° C., and the temperature difference between both side ends was 6 ° C. or less. The casting band 53 preferably has no surface defects, has no pinholes of 30 μm or more, has 1 pinhole of 10 μm to 30 μm / m ² or less, and ² pinholes of less than 10 μm / Those with m ² or less were used.

(1-7) Casting Drying The temperature of the casting chamber 55 was kept at 35 ° C. by the temperature controller 56. Wind was sent from the air supply duct 61 to the casting film 59 formed from the dope 36 cast on the casting band 53. The exhaust duct 62 exhausted air and the guide plate 64 controlled the flow of wind. The air volume VS (m ³ / min) from the air supply duct 61 and the wind temperature TS (° C.) were changed as shown in Table 1. Further, the lower part of the casting band 53 was blown from a blower (not shown) so as to be 65 ° C. The saturation temperature of each drying wind was around -8 ° C. The oxygen concentration in the dry atmosphere on the casting band 53 was kept at 5 vol%. In order to maintain this oxygen concentration at 5 vol%, the air was replaced with nitrogen gas. Further, in order to condense and recover the solvent in the casting chamber, a condenser (condenser) was provided, and its outlet temperature was set to -10 ° C.

In order to prevent the air flow from directly hitting the dope 36 and the casting film 59 during the casting time of 5 seconds from the casting start point PS, a wind shielding plate (not shown) is provided, and the casting die 50 is in the immediate vicinity. Was suppressed to ± 1 Pa or less. When the solvent ratio in the casting film 59 reached 50% by mass on the dry basis, the film was peeled off as the film 81 while being supported by the peeling roller 65 from the casting band 53. The solvent content based on the dry weight standard is a value obtained by {(xy) / y} × 100, where x is the film weight at the time of sampling and y is the weight after the sampling film is dried. . The stripping tension at this time is 1 × 10 ² N / m ² , and the stripping speed (stripping roller draw) relative to the speed of the casting band 53 is 100.1% to 110% in order to suppress stripping failure. Adjusted appropriately within the range. The surface temperature of the peeled film was 15 ° C. The drying rate on the casting band 53 was 60% by mass on the basis of dry weight reference solvent / min. Met. The solvent gas generated by the drying was condensed and liquefied with a -10 ° C. condenser and recovered with a recovery device (not shown). The recovered solvent was adjusted so that the water content was 0.5% or less. The drying air from which the solvent has been removed is heated again and reused as drying air. The film 81 was conveyed through a roller and sent to the tenter 80. At the time of this conveyance, 40 degreeC dry air was sent with respect to the film 81 from the air blower (not shown). It should be noted that a predetermined value of tension is applied to the wet film 66 during conveyance by the roller at the crossover portion.

(1-8) Tenter Transport / Drying / Ear Cutting The film 81 sent to the tenter 80 is transported in the drying zone of the tenter 80 while being fixed at both ends with clips, and is dried by drying air during this time. The clip was cooled by supplying a heat transfer medium at 20 ° C. The clip of the tenter 80 was conveyed by a chain, and the speed fluctuation of the sprocket was 0.5% or less. The gas composition of the drying air was set to a saturated gas concentration at −10 ° C. The average drying speed in the tenter 80 was 120% by mass (dry weight reference solvent) / min. The conditions of the drying zone were adjusted so that the residual solvent amount of the film 81 at the outlet of the tenter 80 was 7% by mass. In the tenter 80, the film 81 was conveyed and stretched in the width direction. In addition, when the width | variety of this film 81 before extending | stretching was 100%, it extended | stretched so that the width | variety after extending | stretching might be 103%. The stretching ratio (tenter drive draw) from the peeling roller to the entrance of the tenter 80 was 102%. The ratio of the length from the clip nipping start position to the nipping release position with respect to the length from the tenter inlet to the outlet was 90%. The solvent evaporated in the tenter 80 was condensed and liquefied at a temperature of −10 ° C. and recovered. A condenser (condenser) was provided for condensation recovery, and the outlet temperature was set to -8 ° C. The condensed solvent was reused after adjusting the water content to 0.5% by mass or less.

  Then, the ear cut of the film 81 was performed by the ear cut device 82 within 30 seconds from the exit of the tenter 80.

(1-9) Post-drying / static elimination The film 81 was dried at high temperature by the roller dryer 23. The roller drying device 23 was divided into four sections, and drying air at 120 ° C., 130 ° C., 130 ° C., and 130 ° C. was supplied from a blower (not shown) from the upstream side. The conveyance tension of the film 81 by the roller 23a was controlled to a predetermined value, and the film 81 was dried for about 10 minutes until the residual solvent amount finally reached 0.3% by mass. The wrap angle (film winding center angle) in the roller 23a was 90 ° and 180 °. The material of the roller 23a was made of aluminum or carbon steel, and the surface was hard chrome plated. As the surface shape of the roller 23a, a flat one and a mat formed by blasting were used. All film position fluctuations due to the rotation of the roller 23a were 50 μm or less. The roller deflection under a predetermined tension condition was selected to be 0.5 mm or less.

  The solvent gas contained in the drying wind was removed by adsorption using an adsorption / recovery device (not shown). The adsorbent used here was activated carbon, and desorption was performed using dry nitrogen. The recovered solvent was adjusted to a water content of 0.3% by mass or less and reused as a dope preparation solvent. Since the drying air contains solvent gas, plasticizer, UV absorber, and other high-boiling substances, these were removed by a cooler and a pre-adsorber for cooling and removing them, and recycled and used. And adsorption / desorption conditions were set so that VOC (volatile organic compound) in the outdoor exhaust gas was finally 10 ppm or less. Moreover, the solvent amount collect | recovered by a condensation method among all the evaporation solvents was 90 mass%, and most of the remainder was collect | recovered by adsorption collection.

  The dried film 81 was conveyed to a first humidity control chamber (not shown). A drying air of 110 ° C. was supplied to the transition portion between the roller dryer and the first humidity control chamber. Air having a temperature of 50 ° C. and a dew point of 20 ° C. was supplied to the first humidity control chamber. Further, the film 81 was conveyed to a second humidity control chamber (not shown) for suppressing the curling of the film 81. In the second humidity control chamber, air of 90 ° C. and humidity 70% was directly applied to the film 81.

(1-10) Knurling and Winding Conditions The film 81 after humidity control was subjected to ear cutting by the second ear cutting device 22 after being cooled to 30 ° C. or lower in the cooling chamber. A forced static eliminator (static neutralization bar) was installed so that the charged voltage of the film 81 during conveyance was always in the range of -3 kV to +3 kV. Further, knurling was applied to both ends of the film 81 with a knurling roller. The knurling is imparted by embossing from one side of the film 81, the width for imparting the knurling is 10 mm, and the knurling is pushed by a knurling roller so that the height of the unevenness is 12 μm higher than the average thickness of the film 81. The pressure was set.

  Then, the film 81 was conveyed to the winding chamber 90. The winding chamber 90 is maintained at an apparatus internal temperature of 28 ° C. and a humidity of 70%. Further, an ion wind static elimination device (not shown) was also installed in the winding chamber 90 so that the charged voltage of the film 81 was −1.5 kV to +1.5 kV. The product width of the film 81 thus obtained is 1475 mm. The diameter of the winding roller in the winding chamber 90 is 169 mm. The tensions at the start and end of winding were controlled so as to have predetermined values. The total length of the wound film 81 was 3940 m. The fluctuation range of winding deviation (sometimes referred to as oscillating width) during winding was ± 5 mm, and the winding deviation period with respect to the winding axis was 400 m. Further, the pressing pressure of the press roller against the winding shaft was set to a predetermined value. The temperature of the film 81 at the time of winding was 25 ° C., the water content was 1.4% by mass, and the residual solvent amount was 0.3% by mass. The average drying rate was 20% by mass (dry weight reference solvent) / min throughout the entire process. Moreover, there was no winding looseness and wrinkles, and no winding slip occurred in the impact test at 10G. Moreover, the external appearance of the film roll was also favorable. The average thickness (unit: μm) of the obtained film is shown in Table 1.

  The film roll was stored in a storage rack at 25 ° C. and a relative humidity of 55% (hereinafter referred to as 55% RH) for one month and further examined in the same manner as described above. As a result, no change was observed. Further, no film adhesion was observed in the film roll. Further, after the film 81 was formed, no peeling residue of the cast film formed from the dope 36 was found on the cast band 53.

(1-11) Evaluation and Results For the films obtained by the above experiments 1 to 14 and comparative experiments 1 to 3, the in-plane retardation value Re, the dispersion value V and the optical unevenness were evaluated, and the results are shown in Table 1. . The dispersion value V is a value obtained based on thickness data measured along a direction of 45 ° with respect to the casting direction. Moreover, about the optical nonuniformity, the obtained film was affixed on the glass plate, it distribute | arranged between the polarizing plates of the crossed Nicols state, the backlight was applied, and visual sensory evaluation was implemented. In Table 1, ◎ indicates that no optical unevenness is confirmed, ○ indicates that there is no problem even though it is slightly confirmed, Δ indicates that it is slightly visible but there is no problem, and × is clearly It is confirmed that.

  From the results of the above examples, it can be seen that optical unevenness is confirmed at locations where the variation in thickness is large and the dispersion value V of the rate of change in thickness relative to the measurement position is large. Thus, according to the present invention, since the optical unevenness of the film can be suppressed, when this is applied to a high-brightness, large-screen liquid crystal display device, display unevenness, particularly, appears in the horizontal and vertical directions. Display unevenness can be effectively suppressed.

It is a top view explaining the film of this invention. It is explanatory drawing of a part of thickness data measured along the predetermined direction of a film. (A) is the thickness data of the film which is embodiment, (b) is the thickness data of the film as another embodiment. It is the schematic of dope manufacturing equipment. It is the schematic of solution casting apparatus. It is a top view of the casting membrane vicinity. It is sectional drawing along the VII-VII line of FIG. It is explanatory drawing of the optical nonuniformity which generate | occur | produces in the conventional film. (A) and (b) are thickness data of different conventional film products.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Solution casting equipment 36 Dope 50 Casting die 59 Casting film 61 Supply duct 62 Exhaust duct 64 Guide plate 81 Film ML Thickness measurement line PS Measurement start point

Claims (8)

Produced in a long shape by solution casting method or melt extrusion casting method,
A polymer film characterized in that a variation range of thickness continuously measured along a direction intersecting with the longitudinal direction (excluding 90 °) is within ± 2 μm with respect to an average thickness. Produced in a long shape by solution casting method or melt extrusion casting method,
The number of measurement values N arbitrarily extracted from the thickness data continuously measured along the direction crossing the long direction (however, excluding 90 °) (n is a natural number of 5 or more) And a change in each thickness Yn (unit: μm) with respect to each distance Xn (unit: mm) between the measurement start position PS and the measurement position Pn corresponding to each of the extracted measurement values. A polymer film characterized in that when the rate is (dYn) / (dXn), V obtained by V = Σ {(dYn) / (dXn)} ² / n is less than 300 × 10 ⁻⁵ . It is provided in the polarizing plate of a liquid crystal display device having a light emitter and a polarizing plate, and is used as the protective film of the polarizing plate having a protective film on the surface of the polarizing film,
3. The polymer film according to claim 1, wherein the luminous body has a luminance of 8000 candela or more and 50000 candela or less. A casting apparatus for casting a polymer solution on a support traveling from a casting die to form a casting film, peeling the casting film to form a film containing a solvent, and a drying apparatus for drying the film In solution casting equipment comprising:
An air supply means for blowing air to the casting film and an exhaust means for exhausting the wind containing the solvent evaporated from the casting film on the downstream side of the air supply means are provided in the vicinity of the support. As well as
A solution casting apparatus characterized in that a plurality of guide plates for flowing the wind along the running direction of the casting film are provided between the air supply means and the exhaust means. In a solution casting method in which a polymer solution is cast on a traveling support to form a cast film, and after the cast film is peeled to form a film containing a solvent, the film is dried.
Blowing the cast film that has been hardened to a predetermined hardness with air supply means,
While flowing the wind along the running direction of the cast film by the guide means for controlling the flow direction of the wind,
A solution casting method, wherein the air containing the solvent evaporated from the casting film is collected by an exhaust means.   6. The solution casting method according to claim 5, wherein no wind is generated in the vicinity of the casting film until the casting film reaches the predetermined hardness.   The solution casting method according to claim 6, wherein drying of the casting film is promoted by condensing the solvent evaporated from the casting film under the windless state by a condensing unit. The solution casting according to claim 6 or 7, wherein the casting film under windlessness is dried to the predetermined hardness by heating the counter casting surface side of the support by a heating means. Method.

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