JP2013063569A - Method for extending film and method for forming solution film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a variation of an optical axis.SOLUTION: A tentering device 2 includes: a clip 5; a pair of rails disposed at both sides of a film transportation path, respectively; a chain traveling along the pair of rails; and a clip attaching mechanism for attaching the clip 5 to the chain. The clip 5 includes: a clamper 31; a substantially U-shaped frame 35; and a blade spring 37 serving as an urging member. The clamper 31 is rotatable between an abutting position where a gripping part 31B abuts on a side edge of a polymer film 3, and a separated position where gripping parts 31B, 32B are separated from the side edge of the polymer film 3. The blade spring 37 urges respective clampers 31, 32 toward the abutting position.

Description

  The present invention relates to a film stretching method and a solution casting method.

  In recent years, due to the rapid development and spread of liquid crystal displays and the like, there is an increasing demand for polymer films, particularly cellulose acylate films, used as protective films for these liquid crystal displays. With this increase in demand, improvement in productivity is desired.

  A solution casting method for producing a cellulose acylate film (hereinafter referred to as a film) is a film forming step in which a dope containing a polymer and a solvent is cast on a support, and a cast film made of the dope is formed on the support. And a membrane drying step of evaporating the solvent from the casting membrane by applying dry air to the membrane surface of the casting membrane, a peeling step of peeling the casting membrane from the support to form a wet film, and a solvent from the wet film. A film drying step for evaporating the film, and a stretching step for adjusting the optical properties of the film by stretching the film in the width direction. According to such a solution casting method, a film having no foreign matter and excellent optical characteristics can be obtained as compared with a casting method by melt extrusion.

  A tenter device is used in the film drying process and the stretching process (for example, Patent Document 1). The tenter device includes a rail disposed on both sides of the film conveyance path and a clip that travels along the rail. In the film drying process, drying air can be applied to both surfaces of the wet film gripped on both side edges by the clip. Therefore, compared with the film drying process performed on the cast film on the support, Evaporation can be performed efficiently. Moreover, at a extending | stretching process, a film can be extended | stretched in the width direction by running a clip so that the space | interval of the clip which hold | gripped the both-sides edge part of the film may become large. By appropriately setting the stretching conditions, the optical properties of the film can be adjusted.

  Patent Document 1 describes a tenter device that can suppress variations in optical axes by reducing the interval between clips that run along one rail.

Japanese Patent Application No. 2011-042186

  However, even when the tenter device disclosed in Patent Document 1 is used, variations in the optical axis remain in the polymer film, and improvement has been demanded.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a film stretching method and a solution casting method that suppress variations in optical axes with a simple configuration.

  In order to achieve the above object, the film stretching method of the present invention was supported so as to lie on the upper side of the base that supports the widthwise side edge of the belt-like film containing the polymer and the solvent from below. A gripping portion capable of gripping the widthwise side edge portion by a rotation shaft and the base is provided at the tip, and a contact position where the gripping portion abuts on the widthwise side edge portion and the gripping portion is in the width direction. A clamper attached to the rotating shaft so as to be freely rotatable between separated positions away from the side edge portions, and to suppress the lifting of the gripper due to play of the clamper and the rotating shaft. The film is stretched using a clip tenter having a biasing member that biases the clamper to a contact position, the clip tenter has a plurality of the clampers, and the clampers are arranged in the longitudinal direction of the film. Et , Characterized in that distance between the adjacent damper is 4.5mm or 1 mm.

  It is preferable that the solvent content of the film in which the side edge is gripped by the base and the clamper is 1% by mass or more and 80% by mass or less.

  The solution casting method of the present invention includes a film forming step of forming a cast film comprising a dope containing the polymer and the solvent on a support, a film drying step of evaporating the solvent from the cast film, and the support. It has the peeling process which peels off the said casting film from a body to make the said film, and the extending process which performs the extending | stretching method of said film, It is characterized by the above-mentioned.

  According to the present invention, the variation of the optical axis can be suppressed to an extremely low level.

It is a top view which shows the outline | summary of a tenter apparatus. It is sectional drawing which shows the outline | summary of the tenter apparatus in a tenter entrance. It is a perspective view of a clip. It is sectional drawing of the clip of a holding state. It is sectional drawing of the clip of an open state. It is sectional drawing which shows the outline | summary of the tenter apparatus which hold | grips the side edge part of a polymer film. It is the schematic of a 1st solution casting apparatus. It is the schematic of the 2nd solution casting apparatus. It is explanatory drawing of intersection angle (theta) 1 of a 1st linear part and an inclination part. It is a side view of the clip 5 when it sees from the film conveyance path 7. FIG.

  As shown in FIG. 1, the tenter device 2 grips both side edges of the polymer film 3 with clips 5 and stretches in the film width direction B while transporting in the film transport direction A, and dries the polymer film 3. It is.

  As shown in FIGS. 1 and 2, the tenter device 2 travels along the clip 5, the first rail 11 and the second rail 12 disposed on both sides of the film transport path 7, and the rails 11 and 12. First and second chains (endless chains) 13 and 14 and a clip attachment mechanism 16 for attaching the clip 5 to the first and second chains 13 and 14 are provided. A number of clips 5 are attached to the first and second chains 13 and 14 at a constant pitch by the clip attachment mechanism 16 (see FIG. 1).

  The rails 11 and 12 are bent by the first straight portions 11A and 12A extending in the film transport direction A, the first bent portions 11B and 12B bent outward in the film width direction B, and the first bent portions 11B and 12B. Inclined portions 11C, 12C extending linearly at the inclined angle, second bent portions 11D, 12D bent inward in the film width direction B, and second straight portions 11E, 12E extending in the film transport direction A are provided. . The shapes of the rails 11 and 12 are substantially symmetric with respect to the film transport path 7.

  The tenter device 2 is disposed in a drying chamber (not shown). The drying chamber is divided into a preheating zone 2A, a stretching zone 2B, and a stretching relaxation zone 2C in the film transport direction A. In the preheating zone 2A that is the range of the first straight portions 11A and 12A of the rails 11 and 12, the polymer film 3 is preheated at, for example, 80 ° C. or more and 200 ° C. or less. In the preheating zone 2A, the distance between the pair of clips is constant.

  In the stretching zone 2B that is the range of the inclined portions 11C and 12C of the rails 11 and 12, the polymer film 3 is heated at, for example, 80 ° C. or more and 200 ° C. or less. In the stretching zone 2 </ b> B, the distance between the pair of clips gradually increases as the clip 5 moves along the inclined portions 11 </ b> C and 12 </ b> C, and the polymer film 3 is stretched in the film width direction B by the clip 5. In the stretching relaxation zone 2C that is in the range of the second straight portions 11E and 12E, the distance between the pair of clips is constant, and stretching relaxation is performed to relieve strain caused by stretching. In addition, a draw ratio is suitably changed according to a desired optical characteristic etc.

  Driving sprockets 21 and 22 are provided on the downstream ends of the rails 11 and 12, that is, on the tenter outlet 2E side. The driving sprockets 21 and 22 are rotationally driven by a driving mechanism (not shown). Further, driven sprockets 23 and 24 are provided at the upstream ends of the rails 11 and 12, that is, at the tenter inlet 2I side.

  The first chain 13 is stretched between the driving sprocket 21 and the driven sprocket 23. The first chain 13 travels along the first rail 11 by the rotational drive of the driving sprocket 21. Similarly, the second chain 14 is stretched between the driving sprocket 22 and the driven sprocket 24, and travels along the second rail 12 by the rotational driving of the driving sprocket 22. As the chains 13 and 14 travel, the clip 5 travels along the rails 11 and 12.

  As shown in FIGS. 2 and 3, the clip 5 includes a clamper 31, a substantially U-shaped frame 35, and a leaf spring 37 that is an urging member.

  As shown in FIGS. 4 and 5, the clamper 31 includes a shaft portion 31A that is rotatably attached to the frame 35, and extends from the shaft portion 31A toward the base 35B. A grip portion 31B that grips the edge portion and a head portion 31C that extends from the shaft portion 31A in the opposite direction to the grip portion 31B are provided. The shaft portion 31A is provided with an insertion hole 31AO into which a mounting shaft (described later) of the frame 35 can be inserted. The diameter of the insertion hole 31AO is obtained by adding a play amount to the diameter of the mounting shaft, and is slightly larger than the diameter of the mounting shaft.

  The frame 35 includes a base 35B that supports the side edge of the polymer film 3 from the lower surface side, an arm 35A that is provided to stand up from the base 35B, and an attachment shaft 35AX that is provided at the tip of the arm 35A.

  The clamper 31 is attached to the frame 35 by passing the attachment shaft 35A through the insertion hole 31AO. Thereby, the clamper 31 has a contact position (see FIG. 4) where the grip portion 31B contacts the side edge portion of the polymer film 3, and a separation position where the grip portion 31B is separated from the side edge portion of the polymer film 3 (see FIG. 4). 5)). Thus, the clip 5 can be changed between a gripping state (see FIG. 6) in which the polymer film 3 is gripped by the base 35B and an open state (see FIG. 2) in which the gripping is released.

  The leaf spring 37 is for urging the clamper 31 toward the contact position, and one end is attached to the grip portion 31B of the clamper 31 and the other end is attached to the arm 35A.

  Returning to FIG. 2, the clip attachment mechanism 16 includes an attachment frame 16F and rollers 16RA, 16RB, and 16RC. The first chain 13 or the second chain 14 is attached to the attachment frame 16F. The rollers 16RA to 16RC rotate by contacting each support surface of the driving sprockets 21 and 22 or by contacting the support surface of the first rail 11 or the second rail 12. The clip attachment mechanism 16 can guide the clip 5 along the rails 11 and 12 without dropping from the sprockets 21 to 24 and the rails 11 and 12.

  Returning to FIG. 1, the grip start position PA is set on the travel path of the first and second chains 13 and 14 at the tenter inlet 2I, and on the travel path of the first and second chains 13 and 14 at the tenter outlet 2E. A grip opening position PB is set.

  The clip opener 40 is for opening the clip 5 and is provided at the tenter inlet 2I and the tenter outlet 2E. The clip opener 40 provided at the tenter inlet 2I extends from the grip start position PA toward the upstream side in the travel direction of the clip 5 on the travel path of the clip 5. The clip opener 40 provided at the tenter outlet 2E26 extends from the grip opening position PB toward the downstream side in the traveling direction of the clip 5 on the traveling path of the clip 5.

  When the head portion 31C comes into contact with the clip opener 40 on the upstream side of the grip start position PA, the clip 5 is opened (see FIG. 2). Thereby, the clip 5 will be in the state which can accept the side edge part of the polymer film 3. FIG. Thereafter, the side edge of the polymer film 3 is supported by the base 35B until the clip 5 reaches the grip start position PA. Since the head 31C is separated from the clip opener 40 when the clip 5 passes the grip start position PA, the clip 5 is set from the open state to the grip state by its own weight and the leaf spring 37, and the polymer film 3 side The edge is gripped (see FIG. 6). Similarly, at the grip open position PB of the driving sprockets 21 and 22, the head 5C contacts the clip opener 40, so that the clip 5 is in an open state. Thereby, the grip of the side edge part of the polymer film 3 is released.

  In the tenter device 2, the stretching of the polymer film 3 is started at the stretching start position PC, and the stretching of the polymer film 3 is completed at the stretching end position PD. In the preheating zone 2A from the grip start position PA to the stretching start position PC, the polymer film 3 is conveyed without being stretched. Furthermore, the polymer film 3 is conveyed without being stretched even in the stretching relaxation zone 2C from the stretching end position PD to the grip opening position PB.

  As shown in FIGS. 4 and 5, since there is a certain amount of play Z1 between the shaft portion 31A and the rotating shaft 33A, when the clip 5 is set from the open state to the gripping state only by the weight of the clamper 31, As a result of part of the grip portion 31 </ b> B floating from the side edge portion of the polymer film 3, the entire grip portion 31 </ b> B may not contribute to gripping the side edge portion of the polymer film 3. If the polymer film 3 is stretched in the width direction B in such a state, the optical axis of the polymer film 3 varies.

  In the present invention, since the clip 5 is set from the open state to the gripping state using its own weight and the leaf spring 37, a part of the gripping portion 31B is prevented from floating from the side edge of the polymer film 3, and the entire gripping portion 31B is Can contribute to the gripping of the side edges of the polymer film 3. Therefore, variations in the optical axis in the polymer film 3 can be suppressed.

  As an urging force of the leaf spring 37, any force may be used as long as the entire gripping portion 31 </ b> B can contact the side edge of the polymer film 3. As the urging member, a known member such as a spring may be used in addition to the leaf spring. Further, as the urging member, the clamper 31 is urged toward the contact position with respect to the clamper 31 near the contact position, and the clamper 31 is urged toward the separation position with respect to the clamper 31 near the separation position. A so-called toggle spring may be used.

  Next, the manufacturing method of the polymer film 3 is demonstrated. However, the manufacturing method and manufacturing apparatus described below are examples of the present invention, and the present invention is not limited thereto.

  As shown in FIG. 7, the solution casting apparatus 50 includes a dope 51, a casting chamber 52, two tenter apparatuses 2, a drying chamber 54, a cooling chamber 55, and a winding chamber 56. In the present embodiment, of the two tenter apparatuses 2, the one that performs film stretching first (the left side in FIG. 7, ie, the upstream side) is referred to as the first tenter apparatus 2, and the film stretching is performed later (FIG. 7). The right tenter device 2 is called the second tenter device 2.

  The dope 51 is for producing the polymer film 3 and includes a polymer and a solvent which are raw materials for the polymer film. The dope 51 is sent to the casting die 60.

  The casting chamber 52 includes a casting die 60, two rotating drums 61, a casting band 62 that moves across the two rotating drums 61, a drying device 63, a peeling roller 64, and a decompression chamber 65. Is installed. The rotating drum 61 is rotated by a driving device (not shown). The casting band 62 is moved by the rotation of the rotating drum 61. The casting die 60 continuously flows out the dope 51 from the casting die 60 toward the moving casting band 62. In this way, a film forming process is performed in which the casting film 66 made of the dope 51 is formed on the casting band 62.

  The drying device 63 applies drying air to the casting film to evaporate the solvent from the casting film 66. Thus, a film drying process for evaporating the solvent from the cast film 66 is performed. The cast film having self-supporting property due to evaporation of the solvent is peeled off from the cast band 62 by the stripping roller 64 to become a wet film 68.

  The decompression chamber 65 is disposed on the upstream side in the traveling direction of the casting band 62 with respect to the casting die 60, and maintains the inside of the decompression chamber 65 at a negative pressure. As a result, the back surface of the casting bead (the surface that comes into contact with the casting band 62 later) is depressurized to a desired pressure, and the influence of the accompanying air generated by the casting band 62 traveling at high speed is reduced. .

  On the downstream side of the casting chamber 52, a crossing portion 71, a first tenter device 2, and a second tenter device 2 are installed in this order. The transfer section 71 introduces the wet film 68 peeled off by the transport roller 72 into the first tenter device 2 and the second tenter device 2 in order. In the first tenter device 2, the wet film 68 is stretched and dried, and a film drying process to become the polymer film 3 is performed. In the second tenter device 2, the polymer film 3 is stretched and dried, and a stretching process for imparting desired optical properties to the polymer film 3 is performed.

  The solvent content of the wet film 68 introduced into the first tenter device 2 is more preferably 20% by mass or more and 80% by mass or less, for example. The solvent content of the wet film 68 introduced into the second tenter device 2 is, for example, 1% by mass or less.

  Here, the solvent content indicates the amount of the solvent contained in the cast film or each film on a dry basis. A sample is taken from the target film, the weight of this sample is x, When the weight after drying is y, it is represented as {(xy) / y} × 100.

  The film drying process in the first tenter device 2 is performed in order to suppress the drying of the wet film 68 and the generation of wrinkles of the wet film due to this drying. The stretching process in the second tenter device 2 is performed for adjusting the optical properties of the polymer film.

  Ear openers 73 are provided downstream of the first and second tenter devices 2, respectively. The edge-cutting device 73 cuts the ears at both ends of the film. The cut ears are sent by air to the crusher 74, where they are crushed and reused as raw materials for dopes and the like.

  The drying chamber 54 is provided with a plurality of rollers 77, and the polymer film 3 is wound around and transported by the rollers 77. An adsorption recovery device 78 is connected to the drying chamber 54, and the solvent evaporated from the polymer film 3 is absorbed and recovered.

  A cooling chamber 55 is provided on the outlet side of the drying chamber 54, and the polymer film 3 is cooled to room temperature in the cooling chamber 55. A forced neutralization device (static neutralization bar) 79 is provided downstream of the cooling chamber 55 to neutralize the polymer film 3. Further, a knurling application roller 80 is provided on the downstream side of the forced static elimination device 79, and knurling is applied to both side edges of the polymer film 3. In the winding chamber 56, a winding machine 81 having a press roller 82 is installed, and the polymer film 3 is wound around the winding core in a roll shape.

  As shown in FIG. 8, the second tenter device 2 may be omitted. In this case, in the first tenter device 2, the film drying process may be performed, or the film drying process and the stretching process may be performed sequentially. Further, in the solution casting apparatus 50 shown in FIG. 7, the first tenter device 2 may be omitted.

  As shown in FIG. 9, the bending angle at the first bent portions 11B and 12B, that is, the intersection angle θ1 between the first straight portions 11A and 12A and the inclined portions 11C and 12C is, for example, 0.01 ° or more and 10 ° or less. is there. The bending angle at the second bent portions 11D and 12D, that is, the intersection angle θ2 between the inclined portions 11C and 12C and the second straight portions 11E and 12E is, for example, 0.01 ° or more and 10 ° or less. Here, the intersection angle θ1 is an angle from the extension line of the first straight portions 11A and 12A to the inclined portions 11C and 12C, and 180 degrees from the extension line of the first straight portions 11A and 12A toward the outside in the width direction B. A positive value is taken when the angle is up to °, and a negative value is taken when the angle is 180 ° from the extension of the first straight portions 11A and 12A toward the inside in the width direction B. Similarly, the intersection angle θ2 is an angle from the extended line of the inclined portions 11C and 12C to the second straight line portions 11E and 12E, and from the extended line of the inclined portions 11C and 12C to 180 ° toward the outside in the width direction B. In this case, a positive value is taken, and a negative value is taken from the extended line of the inclined portions 11C, 12C to 180 ° inward in the width direction B. The bending radius (curvature radius) in the first bent portions 11B and 12B and the second bent portions 11D and 12D is, for example, not less than 1000 mm and not more than 10,000 mm.

As shown in FIG. 10, the clamper interval L1 is preferably 1 mm or more and 4.5 mm or less, and more preferably 1 mm or more and 3.5 mm or less. The clip interval L2 is
It is preferably 0.5 mm or more and 4 mm or less, and more preferably 0.5 mm or more and 3.0 mm or less. Here, the clamper interval L1 is a gap between adjacent clampers 31, and the clip interval L2 is an interval between adjacent clips 5.

(polymer)
The polymer used as the raw material for the polymer film is not particularly limited, and examples thereof include cellulose acylate and cyclic polyolefin.

(Cellulose acylate)
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 kinds of acyl groups are used, it is preferable that one of them is an acetyl group. The ratio in which the hydroxyl group of cellulose is esterified with carboxylic acid, that is, the substitution degree of the acyl group satisfies all of the following formulas (I) to (III) is preferable. In the following formulas (I) to (III), A and B represent the substitution degree of the acyl group, A is the substitution degree of the acetyl group, and B is the substitution degree of the acyl group having 3 to 22 carbon atoms. It is. In addition, it is preferable that 90 weight% or more of a triacetyl cellulose (TAC) is 0.1 mm-4 mm particle | grains.
(I) 2.0 ≦ A + B ≦ 3.0
(II) 1.0 ≦ A ≦ 3.0
(III) 0 ≦ B ≦ 2.0

  The total substitution degree A + B of the acyl group is more preferably 2.20 or more and 2.90 or less, and particularly preferably 2.40 or more and 2.88 or less. Further, the substitution degree B of the acyl group having 3 to 22 carbon atoms is more preferably 0.30 or more, and particularly preferably 0.5 or more.

  Cellulose, which is a raw material for cellulose acylate, may be obtained from either linter or pulp.

  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, butanoyl, pentanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl, iso-butanoyl, t-butanoyl, cyclohexanecarbonyl, oleoyl, benzoyl , Naphthylcarbonyl, cinnamoyl group and the like. Among these, propionyl, butanoyl, dodecanoyl, octadecanoyl, t-butanoyl, oleoyl, benzoyl, naphthylcarbonyl, cinnamoyl and the like are more preferable, and propionyl and butanoyl are particularly preferable.

(solvent)
Solvents for preparing the dope include aromatic hydrocarbons (eg, benzene, toluene, etc.), halogenated hydrocarbons (eg, dichloromethane, chlorobenzene, etc.), alcohols (eg, methanol, ethanol, n-propanol, 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.). In the present invention, the dope means 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. In addition to dichloromethane, one kind of alcohol having 1 to 5 carbon atoms is used from the viewpoint of physical properties such as solubility of polymer, peelability from cast film support, mechanical strength of film and optical properties of film. It is preferable to mix several kinds. The content of the alcohol is preferably 2% by weight to 25% by weight and more preferably 5% by weight to 20% by weight with respect to the whole solvent. Specific examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol and the like, but methanol, ethanol, n-butanol or a mixture thereof is 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, an ester having 3 to 12 carbon atoms, and an alcohol having 1 to 12 carbon atoms are preferably used. These may be used in combination as appropriate. For example, a mixed solvent of methyl acetate, acetone, ethanol, and n-butanol can be mentioned. These ethers, ketones, esters and alcohols may have a cyclic structure. A compound having two or more functional groups of ether, ketone, ester, and alcohol (that is, —O—, —CO—, —COO—, and —OH) can also be used as the solvent.

  The details of cellulose acylate are described in paragraphs [0140] to [0195] of JP-A-2005-104148. These descriptions are also applicable to the present invention. The same applies to additives such as solvents and plasticizers, deterioration inhibitors, ultraviolet absorbers (UV agents), optical anisotropy control agents, retardation control agents, dyes, matting agents, release agents, and release accelerators. JP-A-2005-104148 describes in detail in paragraphs [0196] to [0516].

  In order to confirm the effect of the present invention, the following experiments 1 to 6 were performed.

(Experiment 1)
In the solution casting apparatus 50 shown in FIG. 7, a casting film 66 was formed on the surface of the casting band 62 by casting a dope 51 containing cellulose acylate and a solvent. The casting film 66 having self-supporting property was peeled off while being supported by the peeling roller 63, and a wet film 68 was obtained.

  Thereafter, a wet film 68 having a solvent content of 40% by mass was introduced into the first tenter device 2. The outline of the first tenter device 2 is as follows. The bending angle θ1 (see FIG. 9) in the first bent portions 11B and 12B was 2 °. The bending angle θ2 at the second bent portions 11D and 12D was −2 °. The bending radius at the first bent portions 11B and 12B was 7000 mm. The bending radii at the second bent portions 11D and 12D were the same as those of the first bent portions 11B and 12B. The clamper interval L1 and clip interval L2 (see FIG. 10) of the first tenter device 2 were as shown in Table 1.

  In the first tenter device 2, the wet film 68 is sent to the preheating zone 2A, the stretching zone 2B, and the stretching relaxation zone 2C having a drying temperature of 140 ° C., and the wet film 68 is preheated, stretched, and stretched to relax. It was. When the width of the wet film 68 before stretching was 100%, the stretching ratio in the stretching zone 2B of the first tenter device 2 was 105%. The polymer film 3 exiting from the first tenter device 2 had a solvent content of 1% by mass.

  Thereafter, the polymer film 3 having a solvent content of 1% by mass or less was introduced into the second tenter device 2 having the same structure as that of the first tenter device 2. In the second tenter device 2, the polymer film 3 was sent to the preheating zone 2 </ b> A, the stretching zone 2 </ b> B, and the stretching relaxation zone 2 </ b> C having a drying temperature of 140 ° C., and preheating, stretching, and stretching relaxation were performed on the polymer film 3. When the width of the polymer film 3 before the introduction of the second tenter device 2 was 100%, the stretching ratio in the stretching zone 2B of the second tenter device 2 was 105%. The polymer film 3 exiting from the second tenter device 2 had a solvent content of 1% by mass.

  After cutting both side ends of the polymer film 3 with the edge-cutting device 73 installed downstream of the second tenter device 2, the polymer film 3 is dried while being wound around a plurality of rollers 77 and conveyed in the drying chamber 54. It was fully promoted. After the polymer film 3 was cooled to approximately room temperature in the cooling chamber 55, the polymer film 3 was sent to the winding chamber 56 and wound around the winding core while being pressed by the press roller 82, thereby obtaining a roll-shaped polymer film 3. In addition, before winding up, the charged voltage was adjusted by the forced static eliminating device 79, and knurling was imparted by the knurling imparting roller 80.

(Experiments 2-6)
In Experiments 2 to 6, a polymer film 3 was produced in the same manner as in Experiment 1 except that it was shown in Table 1. Further, in Experiments 4 to 6, the second tenter device 2 and the ear-cutting device 73 downstream of the second tenter device 2 were omitted, and a polymer was obtained in the same manner as in Experiment 1 except that it was shown in Table 1. Film 3 was made.

(Evaluation)
The obtained polymer film 3 was evaluated as follows.

(Fluctuation amount of in-plane retardation Re)
A sample film (length 10 mm) was cut out from the roll-shaped polymer film 3, and the in-plane retardation Re was continuously measured in the longitudinal direction of the sample film using an automatic birefringence meter. Table 1 shows the fluctuation amount of the measured value of the in-plane retardation Re.

(Measurement method of in-plane retardation Re)
From the extrapolated value of the retardation value measured from the vertical direction at 589.3 nm with an automatic birefringence meter (KOBRA21ADH Oji Scientific Co., Ltd.) It calculated according to the following formula.
Re = | nX−nY | × d
nX is the refractive index in the slow axis direction, nY is the refractive index in the fast axis direction, and d is the film thickness (film thickness).

(Fluctuation amount of thickness direction retardation Rth)
The sample film was cut out, and the thickness direction retardation Rth was continuously measured in the longitudinal direction of the sample film using an automatic birefringence meter. Table 1 shows the fluctuation amount of the measured value of the thickness direction retardation Rth.

(Measurement method of thickness direction retardation Rth)
The sample film was conditioned for 2 hours at a temperature of 25 ° C. and a humidity of 60% RH, and the value measured from the vertical direction at 589.3 nm with an automatic birefringence meter (KOBRA21ADH Oji Scientific Co., Ltd.) and the film surface tilted It calculated according to the following formula from the extrapolated value of the retardation value measured similarly.
Rth = {(nX + nY) / 2−nZ} × d
nZ represents the refractive index in the thickness direction.

(Fluctuation amount of optical axis)
The fluctuation amount of the optical axis in the longitudinal direction was determined by an automatic birefringence meter. Table 1 shows the obtained fluctuation amount of the optical axis.

  Note that the fluctuation amount of each measurement value is obtained by subtracting the minimum measurement value from the maximum measurement value.

2 Tenter Device 3 Polymer Film 5 Clip 31 Clamper 31A Shaft Part 31AO Insertion Hole 35 Frame 35AX Rotating Shaft 35A Arm 35B Base 37 Plate Spring

Claims (3)

The base in the width direction is gripped by the base that supports the side edge of the band-shaped film containing the polymer and the solvent from below, the rotation shaft that is supported so as to lie above the base, and the base. A possible gripping portion is provided at the tip, so that the gripping portion can freely rotate between a contact position where the gripping portion touches the widthwise side edge portion and a separation position where the gripping portion is separated from the widthwise side edge portion. A clamper attached to the pivot shaft, and a biasing member that biases the clamper to a contact position so as to prevent the gripper from floating due to play of the clamper and the pivot shaft. Stretched the film using a clip tenter,
The clip tenter has a plurality of the clampers,
The clampers are arranged in the longitudinal direction of the film,
The film stretching method, wherein an interval between the adjacent clampers is 1 mm or more and 4.5 mm.   2. The film stretching method according to claim 1, wherein a solvent content of the film in which the side edge is gripped by the base and the clamper is 1 mass% or more and 80 mass% or less. A film forming step of forming a cast film made of a dope containing the polymer and a solvent on a support;
A film drying step of evaporating the solvent from the cast film;
A peeling step of peeling off the casting film from the support to form the film;
A solution casting method comprising: a stretching step of performing the film stretching method according to claim 1.

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