JP2010023312A - Film and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film in which curling is prevented enough in the end parts in the width direction of the film and a method for producing the film. <P>SOLUTION: In the method for producing the film, an end part heating process in which a solution containing a polymeric material is cast on a support and dried, and the outside surfaces 100a and 100b of the curling parts 13a and 13b curved in the end parts in the width direction of the film 12 are heated after the film is peeled off is implemented. The film produced by the method is provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a film and a manufacturing method thereof, and more particularly to an optical film useful for a liquid crystal image display device and a manufacturing method thereof.

  The solution casting method is a method in which a solution containing a polymer material is cast on a support, dried, and the film is peeled off. This method has a problem that after the film is peeled from the support, the end in the width direction of the film is turned up and a curling phenomenon occurs. The curl phenomenon is caused by a difference in shrinkage based on the difference in the amount of solvent evaporation between the support surface in contact with the support in the film and the opposite support surface opposite to the support surface.

  For example, when the amount of evaporation from the support surface side in the film is relatively large, the shrinkage on the support surface side is relatively large, and a curl that is curved toward the support surface side is generated at the end. Further, for example, when the amount of evaporation from the anti-support surface side in the film is relatively large, the shrinkage on the anti-support surface side becomes relatively large, and a curl curved toward the anti-support surface side is generated at the end.

  From the viewpoint of curling prevention, it is ideal to make the evaporation amount equal in order to equalize the shrinkage amount on the support surface side and the anti-support surface side in the film. It was not possible to prevent it sufficiently.

  If curling is not sufficiently prevented, when the film is guided by a roll, the curled portion at the end of the film is broken and wrinkles are generated, which may lead to cutting of the film. Further, when drying or stretching is performed while holding the film end with a tenter, there is a problem that the curled portion of the film end cannot be smoothly held with the tenter. Even if the curl portion can be gripped by the tenter, there is also a problem that the film meanders during conveyance and causes conveyance failure. Furthermore, the trimming for cutting and removing the film end portion could not be carried out smoothly.

  An object of this invention is to provide the film in which the curl was fully reduced and eliminated in the edge part in the width direction of a film, and its manufacturing method.

  The present invention provides an end that heats the outer surface of a curled portion that is curved at the end in the width direction of the film after casting a solution containing a polymer material on a support, drying and peeling the film The present invention relates to a film production method characterized by carrying out a heating step and a film produced by the method.

  According to the present invention, curl generated at the end in the width direction of the film is sufficiently reduced or eliminated. For this reason, when the film is guided by a roll, it is possible to prevent the end of the film from being bent and from being cut. Moreover, when drying and extending | stretching, hold | grip a film edge part with a tenter, a film edge part can be smoothly hold | gripped with a tenter. In addition, since the film meandering can be prevented during conveyance, the conveyance performance is improved. Furthermore, trimming can be performed smoothly.

  The method for producing a film according to the present invention is based on a solution casting method, that is, a solution containing a polymer material is cast on a support, dried, and the film is peeled off. After peeling off the film in the present invention, a specific edge heating step is performed. Thereafter, if desired, the stretching step, the drying step, and the winding step may be sequentially performed, or the drying step, the stretching step, the drying step, and the winding step may be sequentially performed. Hereafter, each process is demonstrated in detail using FIGS. 1-4. FIG. 1 and FIG. 3 are schematic configuration diagrams of an example of an apparatus for carrying out the film manufacturing method of the present invention. FIGS. 2 and 4 are schematic views showing an example of the end heating step in FIGS. 1 and 3, respectively, and are perpendicular to the film conveyance direction shown in the direction from left to right in FIGS. A cross section (hereinafter simply referred to as “vertical cross section”) is shown. 1-4, the common code | symbol shall show the same member or process.

(Casting process)
The solution containing the polymer material used in the casting step is a solution obtained by dissolving at least a polymer material described later in a solvent, and is hereinafter referred to as a dope.

  The casting process is a process in which the dope is cast on the support 1, for example, the dope is fed to the die 2 through a pressurized metering gear pump and supported at the casting position as shown in FIGS. A dope is cast from the die 2 onto the body 1. As the die 2, it is preferable to use a pressure die from the viewpoint that the slit shape of the base portion can be adjusted and the film thickness can be made uniform easily. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used. In order to increase the film forming speed, two or more pressure dies may be provided on the support, and the dope amount may be divided to form a multilayer film. As a method for adjusting the film thickness, for example, a doctor blade method for adjusting the film thickness of the cast dope film with a blade, or a reverse roll coater method for adjusting the film thickness with a reverse rotating roll may be employed. . The film thickness can be adjusted by appropriately adjusting the dope concentration, the pumped liquid amount, the slit gap of the die base, the extrusion pressure of the die, the speed of the support, etc. so as to obtain a desired thickness. it can.

  The support 1 is preferably an endless one that is infinitely transported, and more preferably has a mirror surface. The support is preferably made of a metal, and specific examples include a stainless steel belt, a stainless steel belt, or a rotating metal drum.

(First drying step)
The drying process on the support 1 is a first drying process, which is a preliminary drying process in which the web is heated on the support 1 and the solvent is evaporated. The web means a dope film after the dope is cast on the support 1. In order to evaporate the solvent, for example, as shown in FIGS. 1 and 3, a method in which heated air is blown from the web side and the back side of the support by the dryers 3 and 4, and heat is transferred from the back side of the support by the heating liquid. Examples thereof include a method and a method of transferring heat from the front and back by radiant heat. A method of appropriately selecting and combining them is also preferable. Drying is quicker if the web is thin. The surface temperature of the support is usually 20 ° C. or higher and is preferably set to a temperature at which the solvent does not foam. The temperature of the heating air is preferably 10 to 80 ° C.

  In the first drying step, it is preferable to dry the web until the residual solvent amount is 150% by weight or less, particularly 80 to 120% by weight, from the viewpoint of film peeling and transportability after peeling.

In the present specification, the amount of residual solvent can be represented by the following formula.
Residual solvent amount (% by weight) = {(M−N) / N} × 100
Here, M is the mass of the film at a predetermined point, and N is the mass when M is dried at 110 ° C. for 3 hours. In particular, M when calculating the amount of residual solvent achieved in the first drying step is the mass of the film immediately before the peeling step.

(Peeling process)
A peeling process is a process of peeling the film formed by evaporating the organic solvent from a web on a support body, before a support body goes around. The position at which the film is peeled from the support is referred to as the peeling point, and the roll 5 that assists in peeling is referred to as the peeling roll.

(End heating process)
The peeled film has a curling phenomenon in which the edge in the width direction is curved, and therefore an end heating process is performed to reduce or eliminate the curling phenomenon. In detail, for example, as shown in FIGS. 2A and 2B, the curl phenomenon is curved in a substantially arc shape in a vertical section with the end in the width direction W as an axis substantially parallel to the film conveyance direction. -Deformation phenomenon. The end portion where such a curl phenomenon has occurred is referred to as a curled portion 13 (13a, 13b).

Since the film 12 shown in FIG. 2A has a relatively large amount of evaporation from the support surface side in the film, the shrinkage on the support surface side becomes relatively large, and the curled portion 13 (13a) curved toward the support surface side. , 13b). The support surface means a surface in contact with the support 1 in the film, and is indicated by 10.
The film 12 shown in FIG. 2B has a relatively large amount of evaporation from the anti-support surface side in the film, so that the shrinkage on the anti-support surface side is relatively large, and the curled portion curved to the anti-support surface side 13 (13a, 13b). The anti-support surface means a surface opposite to the support surface 10 in the film, and is indicated by 11.

  In this step, the outer surface 100 (100a, 100b) of the curled portion 13 (13a, 13b) is heated while the film is conveyed. From the viewpoint of obtaining a sufficient curl reduction / elimination effect, usually only the outer surface 100 (100a, 100b) of the curled portion 13 (13a, 13b) is heated in this step. For example, as shown in FIG. 2A, when the curled portion 13 (13a, 13b) is curved toward the support surface 10 in the film 12, only the anti-support surface side 100 (100a, 100b) in the curled portion. Heat. For example, as shown in FIG. 2B, when the curled portion 13 (13a, 13b) is curved toward the anti-support surface 11 in the film 12, the support surface side 100 (100a, 100b) in the curl portion. Only heat. When the inner side surface of the curled portion is also heated, the inner shrinkage further proceeds, so that a sufficient curling reduction / elimination effect cannot be obtained.

As the heating method, the following method (I) or (II) can be employed.
(I) a method of irradiating the outer surface of the curled portion at the film edge with infrared rays;
(II) A method in which a film end is sandwiched between a pair of nip rolls and a roll in contact with the outer surface of the curled part is heated.

  In the method (I), for example, as shown in FIGS. 1 and 2A and 2B, an infrared (IR) heater 61 (61a, 61b) is used to remove the curled portion 13 (13a, 13b). Only the side surface 100 (100a, 100b) is irradiated with infrared rays. In particular, FIG. 2A corresponds to an enlarged schematic view of the film in the end portion heating step 6A of FIG.

  The infrared (IR) heater 61 (61a, 61b) is disposed outside the curled portions 13a, 13b so that the longitudinal direction is substantially parallel to the transport direction, and heats only the outer surface of the curled portion. Infrared rays are useful for selectively heating a specific surface as in the present invention because they do not go inside the curled portion like hot air and heat the inner surface.

  Any IR heater can be used as long as it is commercially available as an IR heater, and a bar heater is particularly preferable. The total length in the longitudinal direction of the IR heater is not particularly limited as long as the heating time described below can be secured in relation to the film transport speed, and for example, a length of 500 mm or more, particularly 700 to 1200 mm is preferably used. The output of the IR heater is not particularly limited as long as the object of the present invention is achieved. For example, the heating temperature described later may be achieved.

  The installation position of the IR heater is not particularly limited as long as only the outer surface of the curled portion can be heated outside the curled portions 13a and 13b. It is installed so that the curled portion outer surface at the end in the range of 5 to 3% can be heated. Specifically, the IR heater has a curled outer surface as shown in FIGS. 2A and 2B, where x is the end width from the edge in the width direction of the film to the above range in the vertical cross section. It is installed at a position where the distance from the closest point P to the IR heater at 100a, 100b to the edge in the width direction of the film is x / 2.

  The IR heater is preferably installed in a place where IR is not irradiated on the inner side surface of the curled portion when the curled portion is present even when the curled portion is eliminated and becomes flat.

  The heating temperature is not particularly limited as long as the object of the present invention is achieved. For example, the heating is performed so that the temperature at the closest point P is 5 to 20 ° C., preferably 10 to 15 ° C. higher than the conveying atmosphere temperature. The The transport atmosphere temperature is the temperature of the ambient atmosphere in which this step is performed, and the temperature at the center in the width direction on the support surface 10 of the film is used.

The temperature of the closest point P is usually 35 to 120 ° C, and particularly preferably 35 to 80 ° C.
The conveying atmosphere temperature is usually from 30 to 100 ° C, particularly preferably from 30 to 80 ° C.

  The heating time is not particularly limited as long as the object of the present invention is achieved. For example, when the closest point P on the outer side surface of the curled portion is heated at a temperature within the above range, 0.5 second or more, particularly 0. 8 to 1.6 seconds is preferred. The heating time depends on the longitudinal length of the IR heater and the film conveyance speed, and is the time for the film to pass between the IR heaters 61a and 61b.

  In the method (II), for example, as shown in FIGS. 3 and 4 (A) and 4 (B), only the film end portion is sandwiched between a pair of nip rolls 62 (62a, 62b), 63 (63a, 63b) to curl the film. Only the roll in contact with the outer surface 100 (100a, 100b) of the portion 13 (13a, 13b) is heated. 4 (A) and 4 (B) correspond to the enlarged schematic view of the film in the end heating step 6B of FIG. 3, and the dotted lines indicate the curled portions 13 (13a, 13b) generated at the ends. It is.

For example, as shown in FIG. 4A, when a curled portion 13 (13a, 13b) is generated on the support surface 10 side of the film 12, when the curled portion is sandwiched, the outer surface 100 of the curled portion is inserted. Only the lower roll 62 (62a, 62b) in contact with (100a, 100b) is heated.
For example, as shown in FIG. 4B, when a curled portion 13 (13a, 13b) is generated on the anti-support surface 11 side of the film 12, when the curled portion is sandwiched, Only the upper roll 63 (63a, 63b) in contact with the side surface 100 (100a, 100b) is heated.

  The lower roll 62 and the upper roll 63 may have any configuration independently. For example, the lower roll 62 and the upper roll 63 may be a roll made of a metal such as stainless steel, stainless steel, and aluminum, or fluorine or the like on the surface of the metal roll. It may be a roll having a resin layer. The resin layer may be a layer made of a resin whose softening temperature exceeds the surface temperature described later.

  The diameters of the lower roll 62 and the upper roll 63, particularly the diameter of the heated roll, are not particularly limited as long as the heating time described below can be secured in relation to the film transport speed. 100-300 mm is suitable.

  The installation positions of the lower roll 62 and the upper roll 63 are not particularly limited as long as the end portions where the curled portions 13a and 13b are generated can be sandwiched. Usually, in the vertical section, from the edge in the width direction of the film to the film width length. It is installed so that the edge part of the range of 0.5 to 3% can be inserted | pinched.

  Of the lower roll 62 and the upper roll 63, the heating temperature of the heated roll is not particularly limited as long as the object of the present invention is achieved. For example, the surface temperature is 5 to 20 ° C., preferably 10 to 10 ° C. from the conveying atmosphere temperature. Heated to a temperature higher by 15 ° C. The transport atmosphere temperature is the temperature of the ambient atmosphere in which this step is performed, and the temperature at the center in the width direction on the support surface 10 of the film is used.

The surface temperature of the roll to be heated is usually 35 to 120 ° C, particularly preferably 35 to 80 ° C.
The conveying atmosphere temperature is usually from 30 to 100 ° C, particularly preferably from 30 to 80 ° C.

  The heating means of the roll to be heated is not particularly limited as long as the surface temperature can be set within the above range, for example.

  The surface temperature of a roll different from the roll to be heated is usually maintained within the same range as the above-mentioned transport atmosphere temperature.

  The heating time is not particularly limited as long as the object of the present invention is achieved. The heating time depends on the circumference of the heating roll and the film conveyance speed, and is the time for the film to contact the surface of the heating roll.

  3 and 4 (A) and 4 (B), one end of the film is heated with one set of nip rolls 62 and 63, but is not limited to this, and two or more sets are used. The nip roll may be used for heating. Thereby, the heating time can be easily secured.

  The film whose outer surface is heated in this step effectively reduces or eliminates curling of the end portion, and thereafter, the step of gripping the end portion of the film, for example, the stretching step and the drying step are smoothly performed. be able to. The order of performing each step is not particularly limited, and the film subjected to the end heat treatment may be directly sent to the stretching step 16 as shown in FIGS. 1 and 3, for example, or may be a second drying (not shown). You may send to the extending | stretching process 16 via a process.

(Second drying step)
The 2nd drying process 9 is a drying process which heats the film by which edge part heat processing was carried out entirely, and also evaporates a solvent. The drying means is not particularly limited, and for example, hot air, infrared rays, heating rolls, microwaves and the like can be used. From the viewpoint of simplicity, for example, it is preferable to dry with hot air or the like while transporting the film with rolls arranged in a staggered manner. The drying temperature varies depending on the residual solvent of the film at the time of entering the stretching process, but considering the condensation on the surface of the film, the stretching rate, the foaming of the solvent, etc. due to the evaporation of the solvent, the drying temperature is in the range of 20-80 ° C. It is preferable to gradually increase the temperature in five stages.

  The residual solvent amount to be achieved in the second drying step may be in the same range as the residual solvent amount to be achieved in the first drying step. M when calculating the amount of residual solvent achieved in the second drying step is the mass of the film immediately after the second drying step.

(Stretching process)
The stretching step is a step of stretching and holding the film at least in the width direction under heating, and is indicated by 16 in FIGS.

  In the stretching process, relaxation is usually performed after stretching and holding. That is, this process includes a stretching stage for stretching the film in the width direction, a holding stage for retaining the film in the width direction, and a film in the width direction. The mitigation steps to mitigate are performed in these order.

  In the stretching step, the film is stretched by applying tension to the film in the width direction or both the width direction and the transport direction under heating. The stretching method is not particularly limited, and conventionally known stretching methods can be employed in the field of optical film production methods. Examples of the stretching method in the width direction include a pin tenter method and a clip tenter method. Examples of the stretching method in the transport direction include a method of varying the peripheral speed of the transport drive roll between the upstream side and the downstream side, a method of varying the transport tension, and the like.

  In the holding step, the drawing at the draw ratio achieved in the drawing step is held at the drawing temperature in the drawing step.

  In the relaxation stage, the stretching in the stretching stage is held in the holding stage, and then the stretching is relaxed by releasing the tension for stretching. The relaxation may be performed at a temperature lower than the stretching temperature in the stretching step.

(Third drying step)
The third drying step 17 is a drying step in which the stretched film is heated and the solvent is further evaporated. The drying means is not particularly limited, and for example, hot air, infrared rays, heating rolls, microwaves and the like can be used. From the viewpoint of simplicity, for example, as shown in FIGS. 1 and 3, it is preferable to dry with hot air or the like while transporting the film with rolls 171 arranged in a staggered manner. The drying temperature is preferably in the range of 40 to 150 ° C. and divided into 3 to 5 stages, and the drying temperature is preferably gradually increased. Further, the drying temperature is preferably in the range of 80 to 140 ° C. It is preferable for realizing the characteristics.

  In the third drying step, it is preferable to dry the film until the residual solvent amount is 0.5% by weight or less. In particular, M when calculating the amount of residual solvent achieved in the third drying step is the mass of the film immediately after the third drying step.

(Trimming process)
After finishing the third drying process, after performing a trimming process (not shown in FIGS. 1 and 3), a winding process may be performed, or the winding process may be performed without performing the trimming process. You may implement a process.

  The trimming step is a step of cutting and removing the end of the film in the width direction. What is necessary is just to cut | disconnect with the cutter etc., and collect | recover the cut | disconnected edge part, conveying a film.

(Winding process)
The winding process 18 is a process in which the obtained film is wound and cooled to room temperature. The winder 181 may be a commonly used one, and can be wound by a winding method such as a constant tension method, a constant torque method, a taper tension method, or a program tension control method with a constant internal stress. .

  The thickness of the film is not particularly limited, but when used as an optical film, usually 20 to 200 μm is preferable. In particular, in the present invention, the thickness is preferably 20 to 90 μm, and more preferably 30 to 85 μm, from the viewpoint of reducing the thickness and weight of a polarizing plate used for LCDs and the like.

  Each process from the casting process to the winding process described above may be performed in an air atmosphere or in an inert gas atmosphere such as nitrogen gas. Moreover, each process, especially a drying process and an extending process, are implemented in consideration of the explosion limit concentration of the solvent in the atmosphere.

(Dope)
The polymer material contained in the dope is not particularly limited, and a polymer material known in the field of film can be used. In particular, in the case of producing an optical film, a cellulose ester is preferably used. Hereinafter, although the case where an optical film is manufactured using a cellulose ester is demonstrated in detail, a film can be manufactured using polymeric materials other than a cellulose ester by applying the said description mutatis mutandis.

  The cellulose ester is not particularly limited as long as it is a cellulose ester conventionally used in the field of optical films. For example, cellulose triacetate, cellulose diacetate, cellulose acetate propionate, cellulose acetate butyrate, or cellulose acetate propionate. Butyrate can be used. Cellulose triacetate and cellulose acetate propionate are preferred.

The cellulose ester can be obtained by acylating a cellulose raw material. For example, when the acylating agent is an acid anhydride (acetic anhydride, propionic anhydride, butyric anhydride), an organic acid such as acetic acid or an organic solvent such as methylene chloride is used, and a protic catalyst such as sulfuric acid is used. To synthesize. For example, when the acylating agent is acid chloride (CH ₃ COCl, C ₂ H ₅ COCl, C ₃ H ₇ COCl), the reaction is carried out using a basic compound such as an amine as a catalyst. Specifically, it can be synthesized by the method described in JP-A-10-45804. The acyl group is reacted with the hydroxyl group of the cellulose molecule. Cellulose molecules are composed of many glucose units linked together, and the glucose unit has three hydroxyl groups. The number of acyl groups derived from these three hydroxyl groups is called the degree of substitution. For example, cellulose triacetate has an acetyl group bonded to all three hydroxyl groups of the glucose unit. The degree of acyl group substitution can be measured according to ASTM-D817-96.

  The cellulose raw material is not particularly limited, and examples thereof include cotton linter, wood pulp (coniferous pulp, hardwood pulp), kenaf and the like. These cellulose raw materials can be mixed and used at an arbitrary ratio.

  The number average molecular weight Mn of the cellulose ester is usually 50,000 to 200,000, and Mw is usually 150,000 to 400,000.

For the measurement of the molecular weight distribution, high performance liquid chromatography can be used, and the number average molecular weight can be calculated using this.
An example of measurement conditions is shown below.
Solvent: Methylene chloride column: Shodex K806, K805, K803G (3 used by Showa Denko Co., Ltd. connected)
Column temperature: 25 ° C. Sample concentration: 0.1% by mass Detector: RI Model 504 (manufactured by GL Sciences)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min Calibration curve: Standard polystyrene STK standard Polystyrene (manufactured by Tosoh Corp.) Mw = 100000 to 500 Sample calibration curves are used. It is preferable to obtain 13 samples at approximately equal intervals.

  The concentration of the cellulose ester is preferably 10 to 30% by mass, and more preferably 15 to 25% by mass. The cellulose ester concentration is a ratio with respect to the whole dope.

  The dope may contain additives such as a plasticizer, an ultraviolet absorber, a matting agent, and an antioxidant.

  Although it does not specifically limit as a plasticizer, For example, a phosphoric acid ester compound, a phthalic acid ester compound, a glycolic acid compound etc. can be used. Specific examples of the phosphate ester compound include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, and the like. Specific examples of the phthalic acid ester compound include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, and the like. Specific examples of glycolic acid ester compounds include, for example, triacetin, tributyrin, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate and the like. Two or more plasticizers may be used in combination as required.

  The use ratio of the phosphoric ester compound is preferably 50% by mass or less with respect to the cellulose ester because hydrolysis of the cellulose ester film hardly occurs and the durability is excellent. It is more preferable that the ratio of the phosphoric acid ester compound is small, and it is particularly preferable to use only the phthalic acid ester compound or the glycolic acid ester compound. As addition amount with respect to the cellulose ester of a plasticizer, 0.5-30 mass% is preferable, and 2-15 mass% is especially preferable.

  As an ultraviolet absorber, there is an ultraviolet absorber having an excellent ability to absorb ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of the liquid crystal, and absorption of visible light having a wavelength of 400 nm or more is as small as possible from the viewpoint of good liquid crystal display properties. Preferably used. In particular, the transmittance at a wavelength of 370 nm needs to be 10% or less, preferably 5% or less, more preferably 2% or less. Examples of the ultraviolet absorber that can be used in the present invention include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. A benzotriazole-based compound with little coloring is preferable. As commercially available UV absorbers based on benzotriazole, for example, Tinuvin 109, Tinuvin 171, Tinuvin 326, Tinuvin 327, Tinuvin 328 and the like manufactured by Ciba Specialty Chemicals can be preferably used, but are not limited thereto. Two or more kinds of ultraviolet absorbers may be used.

  As a method for adding the ultraviolet absorber to the dope, the ultraviolet absorber may be added after being dissolved in an organic solvent such as alcohol, methylene chloride, methyl acetate, dioxolane, or directly during the dope composition. For an inorganic powder that does not dissolve in an organic solvent, a dissolver or a sand mill is used in the organic solvent and cellulose ester to disperse and then added to the dope. In this invention, the usage-amount of a ultraviolet absorber can be added in 0.5-20 mass% with respect to a cellulose ester, 0.6-5.0 mass% is preferable, Especially preferably, 0.6- 2.0% by mass.

  Examples of the matting agent include inorganic fine particles such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, kaolin, talc, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. It is preferable to contain crosslinked polymer fine particles. Among these, silicon dioxide is preferable because it can reduce the haze (devitrification) of the film. The secondary particles of fine particles are preferably 0.01 to 1.0 μm in average particle size. The content of the matting agent is preferably 0.005 to 0.5 mass% with respect to the cellulose ester. In many cases, fine particles such as silicon dioxide are surface-treated with an organic material, but such a material is preferable because the haze of the film can be reduced. Preferable organic substances for the surface treatment include halosilanes, alkoxysilanes, silazanes, siloxanes and the like. As the average particle size of the matting agent, the larger the mat effect, the larger the mat effect, and the smaller the average particle size, the better the transparency. Therefore, the average particle size of the primary particles of the preferred fine particles is preferably 5 to 50 nm, more preferably. 7-20 nm. These fine particles are usually present as aggregates in the cellulose ester film, and it is preferable to form irregularities of 0.01 to 1.0 μm on the surface of the cellulose ester film. Examples of the fine particles of silicon dioxide include AEROSIL 200, 200V, 300, R972, R972V, R974, R202, R812, OX50, TT600 manufactured by Nippon Aerosil Co., Ltd., preferably AEROSIL200V, R972, R972V. , R974, R202, R812. Two or more of these matting agents may be used in combination. When using 2 or more types together, it can mix and use in arbitrary ratios. In this case, matting agents having different average particle sizes and materials, for example, AEROSIL 200V and R972V can be used in a mass ratio of 0.1: 99.9 to 99.9 to 0.1.

(Preparation method of dope)
While stirring an organic solvent mainly composed of a good solvent for cellulose ester in a dissolution vessel, flaky cellulose ester is added and dissolved to form a dope. Examples of the dissolution method include a method performed at normal pressure, a method performed at a temperature lower than the boiling point of the main solvent, a method performed while pressurizing at a temperature higher than the boiling point of the main solvent, and JP-A-9-95544 and 9-95557. Alternatively, various dissolution methods such as a method performed by a cooling dissolution method as described in JP-A-9-95538 and a method performed at a high pressure as described in JP-A No. 11-21379 can be exemplified. The dissolved cellulose ester solution, so-called dope, is then filtered through a filter medium, defoamed, and sent to the next step by a pump.

  The good solvent that can be used in the present invention is an organic solvent having good solubility in cellulose ester, for example, methyl acetate, ethyl acetate, amyl acetate, ethyl formate, acetone, cyclohexanone, methyl acetoacetate, Tetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,4-dioxane, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1 , 3-Difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, 2-pyrrolidone, N-methyl-2-pyrrolidone, , 3-dimethyl-2-imidazolidinone, there may be mentioned methylene chloride, bromo propane, in particular, methyl acetate, acetone, are preferably used methylene chloride. In view of environmental problems in recent years, it is more preferable to use a non-chlorine organic solvent. It is preferable to use a lower alcohol such as methanol, ethanol, or butanol together with these organic solvents because the solubility of the cellulose ester in the organic solvent can be improved and the dope viscosity can be reduced. In particular, ethanol having a low boiling point and low toxicity is preferable. The organic solvent used for the dope according to the present invention is preferably used by mixing a good solvent and a poor solvent of cellulose ester in terms of production efficiency, and the preferred range of the mixing ratio of the good solvent and the poor solvent is a good solvent. Is 70 to 98% by mass, and the poor solvent is 2 to 30% by mass. With the good solvent and the poor solvent used in the present invention, those that dissolve the cellulose ester used alone are defined as good solvents, and those that do not dissolve alone are defined as poor solvents. Although it does not specifically limit as a poor solvent used for dope which concerns on this invention, For example, methanol, ethanol, n-butanol, cyclohexane, acetone, cyclohexanone etc. can be used preferably. As described above, when an additive is used, it can be performed by a normal addition method. The additive may be added directly to the dope, or the additive is dissolved / dispersed in an organic solvent in advance. May be poured into the dope.

  When adding a solution or dispersion of various additives as described above to the cellulose ester dope, it is transferred from the respective transfer series, and when the transfer pipes join, each additive element is combined as a dope solution, immediately after that. A method of sufficiently mixing with an in-tube mixer is also preferable. For example, it is preferable to use an in-line mixer such as a static mixer SWJ (Toray static type in-pipe mixer Hi-Mixer manufactured by Toray Engineering). When an in-line mixer is used, it can be applied to a dope obtained by concentrating and dissolving a cellulose ester under high pressure.

  In the present invention, the film is preferably used as an optical film. In particular, the cellulose ester film can be preferably used for a liquid crystal display member. The liquid crystal display member as used in the present invention is a member used in a liquid crystal image display device. For example, a polarizing plate, a protective film for a polarizing plate, a retardation plate, a reflector, an optical compensation film, and a viewing angle improving film. , Antiglare film, non-reflective film, antistatic film and the like. Among the above description, it is preferably used for a polarizing plate or a protective film for a polarizing plate.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to this.

<Example 1>
(Preparation of dope)
Cellulose triacetate 100 parts by weight (acetyl substitution degree 2.88, number average molecular weight 150,000)
Triphenyl phosphate 10 parts by weight Ethylphthalyl ethyl glycolate 2 parts by weight Tinuvin 326 (manufactured by Ciba Specialty Chemicals) 1 part by weight AEROSIL 200V (manufactured by Nippon Aerosil Co., Ltd.) 0.1 part by weight Methylene chloride 660 parts by weight Ethanol 40 parts by weight Part The above materials are sequentially put into a sealed container, the temperature in the kettle is raised from 20 ° C. to 80 ° C., and the mixture is stirred for 3 hours while maintaining the temperature at 80 ° C. to completely dissolve the cellulose triacetate. did. Thereafter, the stirring was stopped, the liquid temperature was lowered to 40 ° C., and then immediately sent through a connected pipe to the filtration step. Using a filter paper with an absolute filtration accuracy of 0.005 mm, a filtration flow rate of 300 L / m ² · h Filtration was performed at a filtration pressure of 1.0 × 10 ⁶ Pa.

(Manufacture of cellulose ester film)
The dope prepared as described above was formed into a film by a solution casting method, and a cellulose ester film was manufactured at a conveyance speed of 30 m / min.
Specifically, in the manufacturing apparatus shown in FIG. 1, the dope was cast on a support 1 made of a stainless steel endless belt through a casting die 2 that was kept at 30 ° C. by circulating hot water (casting step). ). The dope viscosity at the time of casting was 50 poise. Next, 40 ° C. wind is obliquely applied at a wind speed of 10 m / sec from the dryer 4 on the film F side, and 45 ° C. wind is vertically applied at 10 m / sec from the dryer 3 on the support 1 side to Was dried (first drying step). The film obtained by drying the web was peeled off by the peeling roll 5 (peeling step). The amount of residual solvent in the web immediately before the peeling step was 110% by weight. The width of the film in the width direction was 1600 mm.

As shown in FIG. 2A, the peeled film had curls that were curved toward the support surface 10 side at the ends. The edge heat processing shown below were implemented with respect to such a film.
As shown in FIG. 1 and FIG. 2 (A), an IR heater 61 (61a, 61b) having a longitudinal length of 500 mm is arranged in parallel with the conveying direction outside the curled portion 13 (13a, 13b). While conveying the film, only the outer side surface 100 (100a, 100b) of the curled portion was heated. The heating time was 1 second. The installation position of the IR heater 61 (61a, 61b) is a position where the distance from the closest approach point P to the IR heater on the outer surface of the curl portion to the edge in the width direction of the film is x / 2 in the vertical section. Met. In this example, the anti-support surface at the end where the end width x was 2.3% was heated. The end width x is a value expressed as a ratio to the film width length. When the temperature of the closest point P was measured with a non-contact thermometer, it was 38 ° C. during the end portion heat treatment. When the temperature of the central part in the width direction on the support surface 10 of the film was measured with a non-contact thermometer, it was 30 ° C. during the end heat treatment.

  After the end-heat-treated film was introduced into the stretching step 16, it was introduced into the drying step 17 (third drying step). In the stretching step 16, a clip tenter method was adopted, and the end portion was gripped with a clip and stretched 1.2 times in the width direction and then relaxed. In the drying step 17, drying was performed at 100 ° C. using an apparatus in which rolls 171 were arranged in a staggered manner.

  Next, in the winding process 18, the film was wound up by a winder 181 and finally cooled to 20 ° C to obtain a cellulose ester film having a thickness of 80 µm.

<Example 2>
A cellulose ester film was obtained by the same method as in Example 1 except that the edge heat treatment was performed on the peeled film according to the following method.
As shown in FIG. 3 and FIG. 4 (A), only the film end was sandwiched between a pair of stainless steel nip rolls 62 (62a, 62b) and 63 (63a, 63b) while transporting the film. By heating only the lower roll 62 (62a, 62b) to 47 ° C., only the outer surface 100 (100a, 100b) of the curled portion 13 (13a, 13b) was heated. The upper roll 63 (63a, 63b) was maintained at 30 ° C. The installation position of the nip roll was such a position that the width from the edge in the width direction of the film on the outer surface of the curled portion was x in the vertical cross section. That is, in the present example, the surface of the support opposite to the end where the end width x is 0.9% was heated. The end width x is a value expressed as a ratio to the film width length. When the temperature of the central part was measured with a non-contact thermometer in the width direction on the support surface 10 of the film in the vertical cross section, it was 30 ° C. during the end portion heat treatment.

<Example 3>
A cellulose ester film was obtained in the same manner as in Example 2 except that the value of x and the heating temperature were changed as shown in Table 1.

<Example 4>
A cellulose ester film was obtained in the same manner as in Example 1 except that the value of x and the heating temperature were changed as shown in Table 1.

<Comparative Example 1>
A cellulose ester film was obtained in the same manner as in Example 1 except that the IR heater was not used.

<Comparative example 2>
The value of x was changed, and a hot air generator was used instead of the IR heater, and hot air of 46 ° C. was blown on the vertical cross section at x / 2 from the edge in the width direction on the anti-support surface 11 of the film. A cellulose ester film was obtained in the same manner as in Example 1 except that.

<Evaluation>
(warp)
The amount of warpage at the end of the support surface before the stretching step was observed, and compared with the center in the width direction of the support surface and evaluated according to the following criteria.
A: End warping amount ≦ 0.5 mm;
○: 0.5 mm <warping amount of end portion ≦ 1.0 mm;
Δ: 1.0 mm <warping amount of end portion ≦ 2.0 mm (no problem in practical use);
×: 2.0 mm <warping amount of end portion ≦ 3.0 mm (practical problem);
XX: 3.0 mm <warping amount at the end.

(Transportability)
The amount of meandering at the end in the width direction of the film immediately before the stretching step was observed and evaluated according to the following criteria.
A: The meandering amount of the end portion ≦ 2.0 mm;
○: 2.0 mm <the meandering amount of the end portion ≦ 3.0 mm;
Δ: 3.0 mm <the amount of meandering at the end ≦ 4.0 mm (no problem in practical use);
X: 4.0 mm <the meandering amount of the end portion ≦ 5.0 mm (there is a practical problem);
XX: 5.0 mm <Meandering amount mm at the end.

(optical properties)
Using the cellulose ester film, a polarizing plate was prepared by the following method, and was attached to a panel, and optical properties were evaluated by visual appearance evaluation.
(Preparation of polarizing plate)
A 120 μm-thick polyvinyl alcohol film was immersed in 100 g of an aqueous solution containing 1 g of iodine and 4 g of boric acid, and stretched 6 times at 50 ° C. to form a polarizing film. Each polarizing plate was prepared by bonding each cellulose ester film subjected to the following alkali saponification treatment to the front and back surfaces of this polarizing film using a 5% aqueous solution of completely saponified polyvinyl alcohol as an adhesive.

(Alkaline saponification treatment)
Each cellulose ester film was saponified, washed with water, neutralized and washed with water under the following conditions, and then dried at 80 ° C.

(Evaluation with polarizing plate attached to liquid crystal display panel)
The polarizing plate pasted on both the front and back surfaces of the LCD cell glass of a commercially available liquid crystal display panel (manufactured by NEC, color liquid crystal display MultiSync LCD1525J: model name LA-1529HM) is carefully peeled off, and the polarizing plate with the polarization direction adjusted here A liquid crystal display panel was prepared, and the appearance was evaluated by the following method.
With respect to the liquid crystal display panel, under the illumination by the white LED, as the optical characteristics, the unevenness of the reflected light and the uniformity of the screen were observed from an angle of 35 ° from the normal direction and evaluated according to the following criteria.
A: There is no stripe unevenness in the reflected light, and the image is not even, and the image is extremely clear;
○: There is no stripe unevenness of reflected light, and the image is clear with no unevenness;
Δ: Slight unevenness of reflected light is recognized, but the image is not uneven and can be clearly recognized (no problem in practical use);
×: Obviously unevenness of streaks of reflected light and unevenness of image are recognized (practical problem);
XX: Streaky unevenness of reflected light and image unevenness are conspicuous, and the screen is difficult to see.

It is a schematic block diagram of an example of the apparatus which enforces the manufacturing method of the film which concerns on this invention. (A) And (B) is a schematic schematic diagram which respectively shows an example of the edge part heating process in FIG. It is a schematic block diagram of an example of the apparatus which enforces the manufacturing method of the film which concerns on this invention. (A) And (B) is a schematic schematic diagram which respectively shows an example of the edge part heating process in FIG.

Explanation of symbols

  1: support, 2: die, 3: 4: dryer, 5: peeling roll, 6: 6A: 6B: edge heating step, 10: support surface, 11: anti-support surface, 16: stretching step, 17: Drying process (third drying process), 18: winding process, 61: 61a: 61b: IR heater, 62: 62a: 62b: lower roll, 63: 63a: 63b: upper roll, 100: 100a: 100b: curled portion Outside.

Claims (8)

  A solution containing a polymer material is cast on a support, dried, peeled off the film, and then subjected to an end heating process that heats the outer surface of the curled portion at the end in the width direction of the film. A method for producing a film, comprising: When the curled portion is curved to the side of the support surface that was in contact with the support in the film, the side of the anti-support surface opposite to the support surface in the curl portion is heated in the end heating step,
The method for producing a film according to claim 1, wherein when the curled portion is curved toward the side of the anti-support surface in the film, the side of the support surface in the curled portion is heated in the end heating step. The manufacturing method of the film of Claim 1 or 2 which employ | adopts the heating method of (I) or (II) shown below in an edge part heating process;
(I) a method of irradiating the outer surface of the curled portion at the film edge with infrared rays;
(II) A method in which a film end is sandwiched between a pair of nip rolls and a roll in contact with the outer surface of the curled part is heated.   The manufacturing method of the film in any one of Claims 1-3 which heats the outer surface of the curl part in the edge part to 0.5 to 3% with respect to the film width length from the edge of the width direction of a film.   The method for producing a film according to any one of claims 1 to 4, wherein the edge heating step is carried out while the film is conveyed, and the heating temperature is 5 to 20 ° C higher than the conveying atmosphere temperature.   The manufacturing method of the film in any one of Claims 1-5 which hold | grips a film edge part after an edge part heating process.   The method for producing a film according to claim 1, wherein the polymer material is a cellulose ester.   The film manufactured by the method in any one of Claims 1-7.

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