JP2017007143A - Method for producing resin film, and supporting body for producing resin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a resin film capable of producing a resin film of high quality, and a supporting body for producing the resin film.SOLUTION: Provided is a method for producing a resin film including: a flow casting step of flow-casting a resin solution containing a transparent resin from a flow-casting die onto a running supporting body 11 to form a flow casting film; and a peeling step of peeling the flow casting film from the supporting body 11, in which a width W of the supporting body 11 is 1,500 to 2,500 mm, the thickness of the supporting body 11 is 1.4 to 1.8 mm, and a first difference between a maximum value L1 and a minimum value L2 in a distance to a central line 31 in the width direction from one tip 32 in the width direction of the supporting body 11 and a second difference between a maximum value L3 and a minimum value L4 in a distance to the central line 31 in the width direction from the other tip 33 in the width direction of the supporting body 11 are 15 mm or less in both cases.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for producing a resin film and a support for producing a resin film.

  Resin films are used in various fields, such as liquid crystal display devices, in view of their chemical characteristics, mechanical characteristics, electrical characteristics, and the like. Specifically, various resin films such as a transparent protective film for protecting the polarizing element of the polarizing plate are disposed as optical films in the image display region of the liquid crystal display device. As such a resin film, for example, a resin film excellent in transparency such as a cellulose ester film is widely used.

  A resin film such as a cellulose ester film can be produced using, for example, a resin solution (dope) obtained by dissolving a raw material resin such as a cellulose ester resin in a solvent. Specific examples of the method for producing a resin film using such a dope include a solution casting film forming method. With the solution casting film forming method, a dope is cast on a traveling support to form a casting film (web), dried to a peelable extent, and then peeled off from the support as a film. This is a method for producing a long resin film by drying or stretching the peeled film while being transported by a transport roller.

  On the other hand, an image display device, particularly an image display device used as an image display member of a television receiver or a notebook computer, is required to be thin and light, have a large screen, and have high definition. Resin films applied as optical films to image display devices are increasingly required to be thinner, wider and have higher quality in accordance with these requirements.

  Moreover, in order to manufacture a thin resin film, it is possible to make thin dope (casting ribbon) discharged from a casting die in ribbon shape. When the casting ribbon is thinned as described above, the properties of the obtained resin film are easily affected by the external environment such as wind blown on the casting ribbon. Specifically, as the support travels, the casting ribbon sways in the vicinity of the surface of the support due to the wind blowing toward the casting ribbon, resulting in uneven thickness of the manufactured resin film. There are things to do. Moreover, when manufacturing a wide resin film, it is easy to receive the influence of the vibration of a support body, and thickness unevenness may generate | occur | produce in the manufactured resin film.

  Also from this, as a resin film applied as an optical film to an image display device, a higher quality film with less thickness unevenness is required. Further, even when a thin resin film or a wide resin film is manufactured, it has been demanded that a high-quality resin film having a small thickness unevenness can be manufactured.

  Examples of a method for producing such a resin film include the methods described in Patent Document 1 and Patent Document 2.

  In Patent Document 1, in a solution casting method using a casting band, a solution suction method is provided in which a back suction device is provided behind a casting die, and a distance between the back suction device and the casting band is set to a predetermined interval. A method is described.

  Further, Patent Document 2 discloses a casting process in which a dope containing a polymer and a solvent is cast on a traveling endless support using a casting die, and the casting die by the dope. A suction step of sucking air on the back side of the casting bead formed between the support and the support from the opening of the decompression chamber; and after forming a cast film on the support, from the support The casting film is peeled off and dried to produce a film, the back side of the casting bead is communicated with the inside, a flow path having a predetermined width is provided, and the suction process is performed. A solution casting method to perform is described.

JP 2002-144357 A JP 2008-221760 A

  According to Patent Document 1, it is disclosed that production efficiency for producing a cellulose acetate film using a casting band can be improved.

  Moreover, according to Patent Document 2, it is disclosed that a film can be efficiently manufactured while suppressing occurrence of uneven thickness failure and planar failure.

  The method for producing such a resin film is the above-mentioned solution casting film forming method, wherein the casting die is supported by a decompression chamber or the like provided on the upstream side of the casting die in the running direction. The atmosphere on the upstream side in the travel direction is reduced. By doing so, in the casting process, a dope (casting ribbon) discharged from the casting die in a ribbon shape is suitably formed on the support in the casting process, and a high-quality resin film is obtained. It is thought that it is going to be. Specifically, in the casting process, a wind blown toward the casting ribbon near the surface of the support, that is, an accompanying wind, is generated in the vicinity of the surface of the support as the support travels. This is considered to reduce the problem.

  On the other hand, as described above, the resin film is required to have a higher quality such as less uneven thickness. For this reason, in order to manufacture a higher quality resin film, methods other than the methods described in Patent Document 1 and Patent Document 2 are also required.

  This invention is made | formed in view of this situation, Comprising: It aims at providing the manufacturing method of the resin film which can manufacture a high quality resin film, and the support body for resin film manufacture.

  In order to further reduce the thickness unevenness of the obtained resin film, the present inventor paid attention to the vibration of the support on which the dope, which is a resin solution containing a transparent resin, is cast when the resin film is produced. . In particular, attention was paid to the vibration of the support at the point where the casting ribbon lands. The present inventor has conceived the following present invention by paying attention to this point and studying in detail.

  The method for producing a resin film according to an aspect of the present invention includes a casting step of casting a resin solution containing a transparent resin from a casting die on a traveling support to form a casting film, A peeling step of peeling the cast film from the support, the width of the support is 1500 to 2500 mm, the thickness of the support is 1.4 to 1.8 mm, and the width direction of the support The first difference between the maximum value and the minimum value of the distance from one tip of the substrate to the center line in the width direction, and the maximum value and the minimum of the distance from the other tip in the width direction of the support to the center line in the width direction Both of the second differences from the values are 15 mm or less.

  According to such a structure, the manufacturing method of the resin film which can manufacture a high quality resin film can be provided.

  This is considered to be due to the following. First, as a support used when producing a resin film, the vibration of the support is suitably suppressed by using the above support. Specifically, even if the casting ribbon lands on the support, vibration of the support at the point where the casting ribbon lands is suitably suppressed. For this reason, it is thought that it can suppress that the thickness nonuniformity accompanying the vibration of a support body generate | occur | produces in the cast film formed on the support body. Therefore, as a result, it is considered that a high-quality resin film with little thickness unevenness can be manufactured.

  In the method for producing a resin film, the support is an endless belt stretched between a pair of rollers, and the belt is supported by a plurality of support rollers from the inner peripheral side, and the adjacent supports It is preferable to have a region where the distance between the rollers is 100 to 6000 mm.

  According to such a structure, a higher quality resin film can be manufactured. This is considered to be because the vibration of the support can be further suppressed by supporting the endless belt used as the support from the inner peripheral side by the support roller arranged as described above. For this reason, it is thought that a higher quality resin film with less thickness unevenness can be manufactured.

  In the resin film manufacturing method, it is preferable that at least one of the plurality of support rollers is a rubber roller.

  According to such a structure, a higher quality resin film can be manufactured. In addition, wear of the support can be reduced, and a high-quality resin film can be produced over a longer period of time.

  Further, the support for producing a resin film according to another aspect of the present invention is a casting film formed by casting a resin solution containing a transparent resin on a surface of the support while running from a casting die. Is a support for producing a resin film used when producing a resin film, the width is 1500 to 2500 mm, the thickness is 1.4 to 1.8 mm, and one end in the width direction The first difference between the maximum value and the minimum value of the distance from the center to the width direction and the second difference between the maximum value and the minimum value of the distance from the other end of the width direction to the center line in the width direction are: Both are characterized by being 15 mm or less.

  According to such a configuration, a casting step in which a resin solution containing a transparent resin is cast from a casting die on a traveling support to form a casting film, and the casting film is supported by the casting process. In a method for producing a resin film comprising a peeling step for peeling from a body, that is, a solution casting film forming method, a high-quality resin film can be produced by using this support for producing a resin film.

  Moreover, in the said support body for resin film manufacture, it is preferable that it was obtained by grind | polishing the one front-end | tip of the said width direction and the other front-end | tip of the said width direction.

  According to such a structure, if a resin film is manufactured using this support body for resin film manufacture, a higher quality resin film will be obtained. This is considered to be because the support for producing a resin film satisfying the above configuration can be suitably obtained while sufficiently suppressing deterioration of the state such as the smoothness of the end of the support for producing a resin film.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the resin film which can manufacture a high quality resin film, and the support body for resin film manufacture can be provided.

FIG. 1 is a schematic diagram illustrating an example of a basic configuration of a resin film manufacturing apparatus according to an embodiment of the present invention. FIG. 2 is a schematic sectional view of a casting die provided in the resin film manufacturing apparatus shown in FIG. FIG. 3 is a top view of the endless belt support provided in the resin film manufacturing apparatus shown in FIG. 1. FIG. 4 is a schematic view showing the arrangement of support rolls provided in the resin film manufacturing apparatus shown in FIG. 1.

  Hereinafter, although the embodiment concerning the present invention is described, the present invention is not limited to this.

  According to the study of the present inventor, the method of reducing the atmosphere upstream of the casting die in the running direction of the casting die as in Patent Literature 1 and Patent Literature 2 suppresses unevenness in the thickness of the resulting resin film. In some cases, this was insufficient. Specifically, in the methods described in Patent Document 1 and Patent Document 2, even if the occurrence of the problem due to the accompanying wind can be suppressed, the thickness unevenness of the resulting resin film may not be sufficiently suppressed. For this reason, in order to obtain a resin film with less thickness unevenness, it was thought that examination of methods other than such a method was necessary. Therefore, the inventors pay attention to the vibration of the support on which the dope, which is a resin solution containing a transparent resin, is cast when manufacturing the resin film in order to further reduce the thickness unevenness of the obtained resin film. did. In particular, attention was paid to the vibration of the support at the point where the casting ribbon lands.

  On the other hand, the support used in the solution casting film forming method has not been studied so much. Specifically, little consideration has been given to increasing the thickness of the support. Further, the support is often run by using an endless belt and rotating it. For this reason, too much consideration has not been given to increasing the thickness of the support in consideration of the hindrance to smooth rotation. Nevertheless, the present inventor has focused on increasing the thickness of the support and reducing the vibration of the support in order to reduce the uneven thickness of the resin film. Furthermore, the inventor paid attention not only to the thickness of the support, but also to the width of the support and the state of the tip in the width direction of the support. The present inventor has conceived the following present invention by paying attention to these points and examining them in detail.

  In the method for producing a resin film according to an embodiment of the present invention, a resin solution (dope) containing a transparent resin is cast from a casting die on a traveling support to form a casting film (web). It is a manufacturing method by a so-called solution casting film forming method, comprising a casting step and a peeling step for peeling the casting film from the support. Furthermore, as a method for producing a resin film, in addition to the above steps, a stretching step for stretching the peeled film and a drying step for drying the peeled film may be provided. And as a manufacturing method of a resin film, the method etc. which are performed with the manufacturing apparatus etc. of the resin film by the solution casting film forming method as shown in FIG. 1 etc. are mentioned, for example. In addition, the manufacturing apparatus of a resin film is not limited to what is shown in FIG. 1, The thing of another structure may be sufficient. FIG. 1 is a schematic diagram illustrating an example of a basic configuration of a resin film manufacturing apparatus according to an embodiment of the present invention. The term “film” as used herein refers to a film after a cast film (web) made of a dope cast on a support is dried on the support and can be peeled off from the support.

  Moreover, the said support body used in the manufacturing method of the resin film which concerns on this embodiment is 1500-2500 mm in width, and is 1.4-1.8 mm in thickness. The support body has a first difference between a maximum value and a minimum value of the distance from one end in the width direction to the center line in the width direction, and a distance from the other end in the width direction to the center line in the width direction. The second difference between the maximum value and the minimum value is 15 mm or less. By using such a support (support for manufacturing a resin film) in the solution casting film forming method as described above, vibration of the support is suitably suppressed. Specifically, even if the casting ribbon lands on the support, vibration of the support at the point where the casting ribbon lands is suitably suppressed. For this reason, it is thought that it can suppress that the thickness nonuniformity accompanying the vibration of a support body generate | occur | produces in the cast film formed on the support body. Therefore, as a result, it is considered that a high-quality resin film with little thickness unevenness can be manufactured. In addition, other embodiment of this invention is such a support body for resin film manufacture.

  The apparatus for producing a resin film includes an endless belt support 11, a casting die 20, a peeling roller 13, a stretching device 16, a drying device 17, a winding device 19, and the like. The casting die 20 discharges a resin solution (dope) 14 containing a transparent resin in a ribbon shape and casts it on the surface of the endless belt support 11. The endless belt support 11 is supported by a pair of rollers 12 so as to be drivable. The endless belt support 11 forms a casting film (web) made of a resin solution 14 cast from a casting die 20 and conveys the peeling roller. 13 to the extent that it can be peeled off. Then, the peeling roller 13 peels the cast film dried to some extent from the endless belt support 11 to obtain a film 15. The peeled film 15 is stretched in a predetermined direction such as a width direction by a stretching device 16. The stretched film 15 is further dried by a drying device 17 and wound into a roll by a winding device 19 using the dried film F as a resin film.

  The casting die 20 is not particularly limited as long as the dope 14 can be discharged onto the surface of the endless belt support 11 by discharging the dope 14 in a ribbon shape. The casting die 20 includes a casting die body 21 and a dope supply pipe 22 as shown in FIG. The dope supply pipe 22 is connected to the upper end portion of the casting die body 21 and supplies the dope 26 (14) into the casting die body 21. The casting die main body 21 is used for casting the dope 26 to the endless belt support 11 by discharging the manifold portion 21 a and the dope 26 for stably casting the dope to the endless belt support 11. A discharge port 21b and a slit portion 21c that is formed between the manifold portion 21a and the discharge port 21b and that allows the dope 26 to pass from the manifold portion 21a toward the discharge port 21b are provided. 2 is a schematic cross-sectional view of a casting die provided in the resin film manufacturing apparatus shown in FIG. The resin solution (dope) 14 discharged from the casting die 20 is also called a casting ribbon until the resin solution (dope) 14 is discharged from the casting die 20 and is grounded on the endless belt support 11. After being grounded on the support 11, it is also called a cast film (web).

  As shown in FIG. 1, the endless belt support 11 is an endless belt that travels indefinitely. For example, a metal endless belt that travels infinitely and has a mirror surface is preferably used. As the endless belt, for example, a belt made of stainless steel or the like is preferably used from the viewpoint of peelability of the cast film. FIG. 3 is a top view of the endless belt support provided in the resin film manufacturing apparatus shown in FIG. 1. Note that the end in the width direction of the endless belt support is not necessarily a straight line parallel to the running direction, and has some unevenness. FIG. 3 exaggerates the state of the end of the endless belt support in the width direction. The endless belt support 11 satisfies the following dimensions. In the present embodiment, an endless belt support will be described as an example of the support. However, the support is not limited to the endless belt support, as long as the following dimensions are satisfied. Also good.

  As described above, the width W of the endless belt support 11 is 1500 to 2500 mm, preferably 1700 to 2300 mm, and more preferably 1800 to 2100 mm. If the width W is too small, the width of the resulting resin film becomes narrow, and a wide resin film tends to be not obtained. Further, when the end portion is warped or the like, if the end portion is cut and removed, the end portion of the resin film that is not originally wide is cut, so that the influence tends to increase. On the other hand, if the width W is too large, the end portion of the endless belt support tends to warp. From these facts, when the width W is within the above range, it is possible to obtain a resin film having a wide width while suppressing the influence of the warp of the end portion of the endless belt support.

  The width W is the length in the direction orthogonal to the running direction and the thickness direction of the endless belt support, and is an average value of the width. Specifically, considering the unevenness at the tip in the width direction of the endless belt support, the average value of the length in the width direction of the endless belt support is the width W. Examples of the method for measuring the width W include the following methods. For example, while running the endless belt support, a laser-type dimension measuring device (LS-9000 manufactured by Keyence Co., Ltd.) is used, and the laser irradiated from this measuring device is run from the outside in the width direction to the endless running. By applying the contact to the end of the belt support, the positional information of the two ends of one end and the other end of the endless belt support is continuously measured at intervals of 1 second for one round of the belt. By doing so, the distances L9 and L10 between the measuring device and the tip can be measured. And the length between one front-end | tip of the endless belt support body and the other front-end | tip can be calculated from the distance between measuring instruments, and L9 and L10. Then, an average value of the obtained values is calculated as the width W.

  Further, the thickness T of the endless belt support 11 is 1.4 to 1.8 mm as described above, preferably 1.45 to 1.7 mm, and more preferably 1.5 to 1.6 mm. It is more preferable. If the thickness T is too thin, the effect of suppressing the vibration of the endless belt support tends to be insufficient. Specifically, when the endless belt support is traveling, a phenomenon that the endless belt support undulates, that is, buckling tends to occur. In addition, when the thickness T is too thick, buckling hardly occurs, but the influence when buckling occurs tends to increase. For these reasons, if the thickness T is within the above range, buckling hardly occurs, and even if buckling occurs, the influence is small. For this reason, the vibration of the support can be effectively suppressed.

  The thickness T is the length in the direction orthogonal to the running direction and the width direction of the endless belt support, and is an average thickness. As this measuring method, for example, with a contact-type film thickness meter manufactured by Mitutoyo Corporation, the film thickness is measured at a distance of 1 m in the longitudinal direction at a position 20 mm from the belt end, and the average value of the measured values is the film thickness. Calculate as

  The endless belt support 11 has a first difference between a maximum value and a minimum value of a distance from one end in the width direction to the center line in the width direction, and a center line in the width direction from the other end in the width direction. The second difference between the maximum value and the minimum value of the distance to each other is 15 mm or less. That is, the larger of the first difference and the second difference is 15 mm or less, preferably 10 mm or less, and more preferably 5 mm or less. The first difference and the second difference are preferably as small as possible, but in practice, about 1 mm is the limit. From this, the larger one of the first difference and the second difference is 15 mm or less, preferably 1 to 10 mm, more preferably 1 to 5 mm. Further, since the first difference and the second difference are distances between the convex portions and the concave portions at the tip in the width direction, the larger one of the first difference and the second difference is simply the peak-to-peak distance. Also called (pp distance).

  In FIG. 3, the first difference is a difference (L1−L2) between the maximum value L1 and the minimum value L2 of the distance from one end 32 in the width direction to the center line 31 in the width direction. The second difference is a difference (L3−L4) between the maximum value L3 and the minimum value L4 of the distance from the other tip 33 in the width direction to the center line 31 in the width direction. If these differences are too large, buckling tends to occur locally on the endless belt support. This is considered to be due to the following. For example, paying attention to the case where the endless belt support and the roller are in contact, the endless belt support and the roller have a tip that is convex and concave. The contact area changes suddenly. This sudden change in the contact area between the endless belt support and the roller is considered to cause local buckling. For this reason, it is thought that buckling tends to occur near the end of the endless belt support. Therefore, if the difference is within the above range, the occurrence of this local buckling can be suitably suppressed.

  The first difference and the second difference can be measured as follows. For example, while running the endless belt support, for example, using a laser dimension measuring device (LS-5000 series manufactured by Keyence Corporation), the laser emitted from this measuring device is running from the outside in the width direction. The position information of the tip of the endless belt support is continuously measured by being applied to the end of the endless belt support. By doing so, it is possible to measure the maximum value L12 and the minimum value L11 of the distance from the measuring instrument to one tip 32 in the width direction. Further, the maximum value L14 and the minimum value L13 of the distance from the measuring device to the other tip 33 in the width direction can be measured. From the L11 to L14, the first difference and the second difference can be calculated. Specifically, the difference between L12 and L11 corresponds to the first difference between the maximum value and the minimum value of the distance from one tip in the width direction to the center line in the width direction. L12-L11 is the same value as L1-L2. The difference between L14 and L13 corresponds to the second difference between the maximum value and the minimum value of the distance from the other end in the width direction to the center line in the width direction. L14-L13 is the same value as L3-L4.

  Moreover, the method for manufacturing the endless belt support 11 is not particularly limited as long as the endless belt support 11 can be manufactured. Specifically, first, in the manufacturing method of an endless belt support generally used in the solution casting film forming method, it is manufactured under the conditions such that the width W and the thickness T are within the above ranges. The tip in the width direction of the product thus obtained is polished so that the first difference and the second difference are within the range. By doing so, the endless belt support 11 is obtained. Moreover, the endless belt support obtained by polishing can satisfy the above-described configuration while sufficiently suppressing deterioration of the smoothness and the like of the end of the support. Therefore, when a resin film is produced using such a support, a higher quality resin film can be obtained. Further, instead of the polishing, it is conceivable to cut the convex portion or to reinforce the concave portion by welding.

  The endless belt support 11 is an endless belt that is stretched around a pair of rollers 12 as described above. As shown in FIG. 4, the endless belt support 11 preferably has a region supported by a plurality of support rollers 41 from the inner peripheral side. And in the area | region currently supported by this some support roller 41, it is preferable that the distance (distance between centers) L5-L8 between the adjacent support rollers 41 is 100-6000 mm, and it is 200-5000 mm. More preferably, it is 300-4000 mm. By having such a region supported by the plurality of support rollers 41, vibration of the endless belt support 11 can be suitably suppressed. The region supported by the plurality of support rollers 41 may be a partial region of the endless belt support 11 or the entire region of the endless belt support 11. When it is a partial area of the endless belt support 11, the area supported by the plurality of support rollers 41 causes vibration of the endless belt support 11 such as the vicinity of a point where the casting ribbon lands. It is preferable that it is easy. FIG. 4 is a schematic view showing the arrangement of support rolls provided in the resin film manufacturing apparatus shown in FIG.

  Further, if the distance between the centers in the region supported by the plurality of support rollers 41 is too short, the support rollers are arranged too densely, which may hinder the travel of the endless belt support. If the distance between the centers is too long, the effect of suppressing the vibration of the endless belt support by the support roller tends to be insufficient. For these reasons, having the region where the center-to-center distance is within the above range can sufficiently suppress the vibration of the endless belt support while suppressing the running of the endless belt support.

  The center-to-center distances L5 to L8 are each preferably within the above range, and the center-to-center distance is preferably shorter as the distance from the casting ribbon is closer. That is, it is preferable that L5 which is the distance between the support rollers 41a and 41b is the shortest. The distance L6 between the support rollers 41b and 41c is longer than L5, the distance L7 between the support rollers 41c and 41d is longer than L6, and the distance L8 between the support rollers 41d and 41e is It is preferably longer than L7. By doing so, the vibration of the endless belt support can be more suitably suppressed. Moreover, in FIG. 4, although the support roller 41 is five, it is not limited to this, It may be less than five and may be more than five.

  The support roller 41 is not particularly limited as long as it is a roller capable of supporting the endless belt support 11. Examples of the support roller 41 include a metal roller that is a metal roller and a rubber roller that is a rubber roller. The plurality of support rollers 41 may be all metal rollers or all rubber rollers, but at least one is preferably a rubber roller. When a rubber roller is used as the support roller, wear of the endless belt support can be suppressed. Further, among the plurality of support rollers 41, it is preferable to use a metal roller as the roller having a relatively high load from the endless belt support, specifically, the support roller 41a near the landing point of the casting ribbon. . Among the plurality of support rollers 41, it is preferable to use a rubber roller as a high roller having a relatively low load from the endless belt support, specifically, as the support roller 41e far from the landing point of the casting ribbon. . By doing so, vibration of the endless belt support can be suppressed while suppressing not only the wear of the endless belt support but also the wear of the support roller. Therefore, a high quality resin film can be manufactured over a longer period.

  The width of the casting film cast by the casting die 20 is 80 to 99% with respect to the width W of the endless belt support 11 from the viewpoint of effectively using the width W of the endless belt support 11. It is preferable. A drum support may be used instead of the endless belt support. As this drum support, for example, a rotating metal drum having a mirror surface is preferably used.

  And the endless belt support body 11 dries the solvent in dope, conveying the cast film (web) formed on the surface. The drying is performed, for example, by heating the endless belt support 11 or blowing heated air on the web.

  The traveling speed of the endless belt support 11 is not particularly limited, but is preferably about 50 to 200 m / second, for example. The draft ratio, which is the ratio of the traveling speed of the endless belt support 11 to the discharge speed of the dope 14 from the casting die 20, is not particularly limited, but is preferably about 0.8 to 5, for example. When the draft ratio is within this range, the cast film can be stably formed. For example, if the draft ratio is too large, there is a tendency to cause a phenomenon called neck-in in which the cast film is reduced in the width direction, and it becomes difficult to form a wide resin film.

  The peeling roller 13 is disposed in the vicinity of the surface of the endless belt support 11 on which the dope is cast, and the distance between the endless belt support 11 and the peeling roller 13 is preferably 1 to 100 mm. . Further, the peeling roller 13 is used when peeling a web that has been dried to some extent on the endless belt support 11. Using the peeling roller 13 as a fulcrum, the dried web is peeled as a film 15 by pulling the dried web with tension. Moreover, when peeling a film from the endless belt support body 11, the film 15 is extended | stretched in the conveyance direction (Machine Direction: MD direction) of a film with peeling tension | tensile_strength and subsequent conveyance tension | tensile_strength.

  The stretching device 16 stretches the film 15 peeled from the endless belt support 11 in a direction (Transverse Direction: TD direction) orthogonal to the web conveyance direction. Specifically, both ends in a direction perpendicular to the film transport direction are gripped with a clip or the like, and the distance between the opposing clips is increased to extend in the TD direction.

  The drying device 17 includes a plurality of transport rollers, and dries the film while transporting the film between the rollers. At that time, as shown in FIG. 1, the heated air 18 may be dried by circulating it in the drying device 17, or may be dried using infrared rays, or the heated air and infrared rays. And may be dried together. It is preferable to use heated air from the viewpoint of simplicity.

  The winding device 19 winds the film F having a predetermined residual solvent ratio in the drying device 17 around a winding core. Moreover, you may emboss by a hot embossing mechanism in the width direction both ends before winding up the film F to a winding core. In addition, it is preferable that the temperature at the time of winding is cooled to room temperature in order to prevent scratching due to shrinkage after winding and loosening of winding. The winding device to be used can be used without particular limitation, and may be a commonly used winding device, such as a constant tension method, a constant torque method, a taper tension method, a program tension control method with a constant internal stress, or the like. It can be wound up by the method.

  Moreover, the manufacturing apparatus of a resin film will not be specifically limited if the manufacturing method of the resin film which concerns on this embodiment can be implemented. Specifically, the apparatus for producing a resin film may not include a stretching apparatus or a drying apparatus, and may be provided with a plurality of apparatus instead of one each.

  Moreover, although the apparatus provided with the endless belt support body was illustrated as a support body in the aspect demonstrated above, the manufacturing apparatus of the resin film illustrated the drum support body. Specifically, instead of the endless belt support 11, a resin film manufacturing apparatus similar to the resin film manufacturing apparatus shown in FIG. Moreover, as a drum support body, the rotation drive drum made from stainless steel etc. which gave the hard chrome plating process to the surface is mentioned, for example.

  Hereinafter, the composition of the resin solution (dope) used in the present embodiment will be described.

  The resin solution (dope) used in this embodiment is obtained by dissolving a transparent resin in a solvent.

  The transparent resin is not particularly limited as long as it is a resin having transparency when formed into a substrate by a solution casting film forming method or the like, but is easily manufactured by a solution casting film forming method or the like. It is preferable that the adhesive property with other functional layers such as a hard coat layer is excellent and that it is optically isotropic. Here, the transparency means that the visible light transmittance is 60% or more, preferably 80% or more, and more preferably 90% or more.

  Specific examples of the transparent resin include cellulose ester resins such as cellulose diacetate resin, cellulose triacetate resin, cellulose acetate butyrate resin, and cellulose acetate propionate resin; polyethylene terephthalate resin and polyethylene naphthalate resin. Acrylic resins such as polymethyl methacrylate resins; Polysulfone (including polyether sulfone) resins, polyethylene resins, polypropylene resins, cellophane, polyvinylidene chloride resins, polyvinyl alcohol resins, ethylene vinyl alcohol resins, Shinji Vinyl resins such as tactic polystyrene resins, cycloolefin resins and polymethylpentene resins; polycarbonate resins; polyarylate resins Polyetherketone resins; polyether ketone imide resin; can be mentioned fluorine-based resin or the like; a polyamide resin. Among these, cellulose ester resins, cycloolefin resins, polycarbonate resins, and polysulfone (including polyethersulfone) resins are preferable. Furthermore, cellulose ester resins are preferred, and among cellulose ester resins, cellulose acetate resins, cellulose propionate resins, cellulose butyrate resins, cellulose acetate butyrate resins, cellulose acetate propionate resins, and cellulose triacetate resins are preferred, Cellulose triacetate resin is particularly preferred. Moreover, the said transparent resin may use the transparent resin illustrated above independently, and may use it in combination of 2 or more type.

  Next, the cellulose ester resin will be described.

  The number average molecular weight of the cellulose ester-based resin is preferably 30,000 to 200,000 in view of high mechanical strength when formed into a resin film and an appropriate dope viscosity in the solution casting film forming method. Further, the weight average molecular weight (Mw) / number average molecular weight (Mn) is preferably in the range of 1 to 5, and more preferably in the range of 1.4 to 3.

  The average molecular weight and molecular weight distribution of a resin such as a cellulose ester resin can be measured using gel permeation chromatography or high performance liquid chromatography. Therefore, the number average molecular weight (Mn) and the weight average molecular weight (Mw) can be calculated using these, and the ratio can be calculated.

  The cellulose ester resin preferably has an acyl group as a substituent, specifically, an acyl group having 2 to 4 carbon atoms. As a substitution degree of this acyl group, it is preferable that it is 2.2-2.95, for example. As the degree of substitution, for example, when the substitution degree of the acetyl group is X and the substitution degree of the propionyl group or butyryl group is Y, the total value of X and Y is 2.2 or more and 2.95 or less. X is preferably greater than 0 and less than or equal to 2.95.

  In addition, the portion not substituted with an acyl group usually exists as a hydroxyl group. These cellulose ester resins can be synthesized by a known method. The measuring method of the substitution degree of an acyl group can be measured according to the provisions of ASTM-D817-96.

  As the solvent used in the present embodiment, a solvent containing a good solvent for the transparent resin can be used. The good solvent varies depending on the transparent resin used. For example, when the transparent resin is a cellulose ester resin, the good solvent and the poor solvent change depending on the acyl group substitution degree of the cellulose ester. For example, when acetone is used as the solvent, the cellulose ester acetate ester (acetyl group substitution degree 2) .4), cellulose acetate propionate is a good solvent, and cellulose acetate (acetyl group substitution degree 2.8) is a poor solvent. Therefore, since the good solvent and the poor solvent differ depending on the transparent resin used, the case of a cellulose ester resin will be described as an example.

  Examples of good solvents for cellulose ester resins include organic halogen compounds such as methylene chloride, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, dioxolane derivatives, cyclohexanone, Ethyl formate, 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, etc. Can be mentioned. Among these, organic halogen compounds such as methylene chloride, dioxolane derivatives, methyl acetate, ethyl acetate, acetone and the like are preferable. Among these, methylene chloride is preferable. These good solvents may be used alone or in combination of two or more.

  The dope may contain a poor solvent as long as the transparent resin does not precipitate. Examples of poor solvents for cellulose ester resins include alcohols having 1 to 8 carbon atoms such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol, methyl ethyl ketone, and methyl isobutyl. Examples include ketones, propyl acetate, monochlorobenzene, benzene, cyclohexane, tetrahydrofuran, methyl cellosolve, and ethylene glycol monomethyl ether. Among these, ethanol is preferable. These poor solvents may be used alone or in combination of two or more.

  In addition, the resin solution used in the present embodiment may contain other components (additives) other than the transparent resin and the solvent as long as the effects of the present invention are not impaired. Examples of the additive include fine particles, plasticizers, antioxidants, ultraviolet absorbers, heat stabilizers, conductive substances, flame retardants, lubricants, and matting agents.

  Next, as an example of a method for preparing a dope, a case where a cellulose ester resin is used as a transparent resin will be described.

  The method for dissolving the cellulose ester resin when preparing the dope is not particularly limited, and a general method can be used. By combining heating and pressurization, it is possible to heat above the boiling point of the solvent at normal pressure, and it is possible to dissolve the cellulose ester resin in the solvent above the boiling point at normal pressure. It is preferable from the viewpoint of preventing the occurrence of. In addition, a method in which a cellulose ester resin is mixed with a poor solvent and wetted or swollen, and then a good solvent is added and dissolved is also preferably used.

  Next, the obtained cellulose ester resin solution is filtered using a suitable filter medium such as filter paper.

  According to the method for producing a resin film according to the present embodiment as described above, a high-quality resin film can be produced. Furthermore, even if the width is wide or the film thickness is thin, a high-quality resin film can be produced.

  Moreover, it is preferable that the thickness (film thickness) of the said resin film is 40 micrometers or less, It is more preferable that it is 10-40 micrometers, It is further more preferable that it is 15-30 micrometers. Such a film thickness is preferable from the viewpoint of thinning the liquid crystal display device and stable productivity of the resin film. On the other hand, when trying to produce a resin film having a small film thickness, there is a tendency that unevenness in thickness tends to occur. Even if it is so, if it is the manufacturing method of the resin film which concerns on this embodiment, generation | occurrence | production of thickness nonuniformity can fully be suppressed. Therefore, a resin film capable of suitably realizing thinning of the liquid crystal display device is obtained. In addition, a film thickness here is an average film thickness. As this measuring method, for example, the film thickness is measured at 20 to 200 locations in the width direction of the optical film with a contact film thickness meter manufactured by Mitutoyo Corporation, and the average value of the measured values is calculated as the film thickness.

(Polarizer)
The resin film obtained by the method for producing a resin film according to this embodiment can be used as a protective film for a polarizing plate. Thus, the polarizing plate using the resin film as a protective film includes a polarizing element and a transparent protective film disposed on the surface of the polarizing element, and the transparent protective film is the resin film. The polarizing element is an optical element that emits incident light converted to polarized light.

  As the polarizing plate, for example, a completely saponified polyvinyl alcohol aqueous solution is used on at least one surface of a polarizing element produced by immersing and stretching a polyvinyl alcohol film in an iodine solution. A laminate is preferred. Further, the resin film may be laminated on the other surface of the polarizing element, or a transparent protective film for another polarizing plate may be laminated.

  As described above, the polarizing plate uses the resin film as a protective film laminated on at least one surface side of the polarizing element. In that case, when the said resin film works as a phase difference film, it is preferable to arrange | position so that the slow axis of a resin film may be substantially parallel or orthogonal to the absorption axis of a polarizing element.

  Such a polarizing plate uses the resin film according to the present embodiment as a transparent protective film. This resin film is of high quality with little thickness unevenness. Further, as this resin film, a high quality film can be obtained even if the film thickness is reduced. For this reason, the obtained polarizing plate is also high quality, and even if it is thin, a high quality thing can be obtained by using a thin resin film. Therefore, when the obtained polarizing plate is applied to, for example, a liquid crystal display device, high image quality of the liquid crystal display device can be realized.

(Liquid crystal display device)
Moreover, the said polarizing plate can be used as a polarizing plate of a liquid crystal display device. The liquid crystal display device provided with the polarizing plate includes a liquid crystal cell and two polarizing plates arranged so as to sandwich the liquid crystal cell, and at least one of the two polarizing plates is the polarizing plate. is there. Note that the liquid crystal cell is a cell in which a liquid crystal substance is filled between a pair of electrodes, and by applying a voltage to the electrodes, the alignment state of the liquid crystal is changed and the amount of transmitted light is controlled. Such a liquid crystal display device uses the polarizing plate as a transparent protective film for the polarizing plate. By doing so, a high-quality liquid crystal display device with improved contrast and the like can be obtained.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[Example 1]
(Preparation of dope)
First, 100 parts by mass of cellulose triacetate resin (acetyl group substitution degree 2.88) was added as a transparent resin to a dissolution tank containing 418 parts by mass of methylene chloride and 23 parts by mass of ethanol, and further 8 masses of triphenyl phosphate. Part, 2 parts by mass of ethylphthalylethyl glycol, 1 part by mass of Tinuvin 326 (BASF Japan Ltd.) and 0.1 part by mass of Aerosil 200V (Nippon Aerosil Co., Ltd.) were added. And after raising the liquid temperature to 80 ° C., the mixture was stirred for 3 hours. By doing so, a resin solution was obtained. Then, stirring was complete | finished and it was left until the liquid temperature became 43 degreeC. And the resin solution after standing was filtered using filter paper with a filtration accuracy of 0.005 mm. Air bubbles in the resin solution were degassed by allowing the resin solution after filtration to stand overnight. Using the resin solution thus obtained as a dope, a resin film was produced as follows.

(Manufacture of resin film)
First, the temperature of the obtained dope was adjusted to 35 ° C., and the temperature of the endless belt support was adjusted to 20 ° C. Then, using a resin film manufacturing apparatus as shown in FIG. 1, a dope was cast from a casting die (coat hanger die) onto an endless belt support having a running speed (casting speed) of 70 m / min. The slip interval of the casting die was adjusted in advance so that the finally obtained resin film had a thickness of 40 μm.

  The endless belt support is made of stainless steel (SUS316) and an endless belt having a three-dimensional surface roughness (Ra) measured by a scanning atomic force microscope (AFM) polished to a super mirror surface with an average of 1.0 nm. An endless belt support was used. As the endless belt support, the end in the width direction of the endless belt having a width W of 1500 mm, a thickness T of 1.4 mm, and a length of one round of 40 m is a pp distance of 15 mm. What was grind | polished so that it might become.

  In addition, L9 and L10 at one front end and the other front end in the width direction are supported by a laser dimension measuring instrument (LS-9000 manufactured by Keyence Corporation) and the laser emitted from this measuring instrument is being supported. L9 and L10 were measured by applying to the body edge, and the width W was calculated from the measured L9 and L10 and the distance between the measuring devices. The width W is an average value of values obtained from measurement values obtained by measurement at intervals of 1 second for one belt revolution. The thickness T is an average value of the measured values obtained by measuring the film thickness at a distance of 1 m in the longitudinal direction at a position 20 mm from the belt end by a contact film thickness meter manufactured by Mitutoyo Corporation. Moreover, L11-L14 in one front-end | tip of the width direction and the other front-end | tip is using the laser dimension measuring device (LS-5000 series made from Keyence Corporation), and the laser irradiated from this measuring device is running. L11 to L14 were measured by applying to the end of the support, and the pp distance was calculated from the measured L11 to L14.

  And a web is dried by sending 30 degreeC drying air to the web on an endless belt support body from the dryer of an endless belt support body side. The dried web was peeled off as a film from the endless belt support.

  While the peeled film was transported by a transport roller, the residual solvent ratio was dried to 80% by mass. The dried film was stretched 6% in the TD direction while gripping both ends of the film with a clip in an environment of 100 ° C. using a stretching device (tenter), and then the clip was released. Then, the stretched film was dried at 125 ° C. using a drying apparatus while being conveyed by a conveyance roller. Then, the dried film was wound up with a winding device, and the resin film wound up in roll shape was obtained.

  The resin film thus obtained was a cellulose triacetate film having a thickness of 25 μm, a width of 1400 mm, and a winding length of 3000 m.

[Examples 2 to 9, Comparative Examples 1 to 28]
The endless belt support used is the same as in Example 1 except that the endless belt support shown in Table 1 has a width W, a thickness T, and a pp distance.

[Evaluation (thickness unevenness)]
The thickness of the obtained resin film was continuously measured in the longitudinal direction (conveying direction) of the resin film using a film thickness meter (film thickness measuring device DH-150 manufactured by Tokyo Seimitsu Co., Ltd.). From the measured value (chart) obtained by this continuous measurement, the difference between the maximum value and the minimum value of the thickness of the resin film and the average film thickness were calculated. Using this calculated value, an evaluation value used for evaluating thickness unevenness (lateral unevenness) was calculated from the following formula.

Evaluation value (%) = difference between maximum value and minimum value / average film thickness × 100
A horizontal stage is a stage which extends perpendicularly to a conveyance direction on a resin film. From this, by using the ratio of the difference between the maximum value and the minimum value of the thickness continuously measured in the longitudinal direction (conveying direction) of the resin film to the average film thickness as an evaluation value, It can be evaluated as well. That is, the larger the evaluation value, the larger the horizontal stage and the greater the thickness unevenness (lateral unevenness).

  Specifically, if this evaluation value is less than 0.4%, it is evaluated as “◎”, and if it is 0.4% or more and less than 0.6%, it is evaluated as “◯”, and 0.6% If it is less than 0.8%, it is evaluated as “Δ”, if it is 0.8% or more and less than 1.0%, it is evaluated as “X”, and if it is 1.0% or more, “XX”. "

  The evaluation results are shown in Table 1 together with the width W, the thickness T, and the pp distance of the infinite belt support.

表１から、幅Ｗが１５００〜２５００ｍｍであり、厚みＴが１．４〜１．８ｍｍであり、ｐ−ｐ距離が１５ｍｍ以下である無端ベルト支持体を用いた場合（実施例１〜９）は、そうでない場合（比較例１〜２８）と比較して、厚みむらの少ない樹脂フィルムを製造できることがわかった。なお、上記実施例１〜９及び比較例１〜２８は、無端ベルト支持体の１周分の長さが４０ｍのものを用いたが、１２０ｍのものを用いても、同様の結果であった。

From Table 1, when using an endless belt support having a width W of 1500 to 2500 mm, a thickness T of 1.4 to 1.8 mm, and a pp distance of 15 mm or less (Examples 1 to 9). It was found that a resin film with less thickness unevenness can be produced as compared with the case where this is not the case (Comparative Examples 1 to 28). In Examples 1 to 9 and Comparative Examples 1 to 28, the length of one end of the endless belt support was 40 m, but the same result was obtained even when the length of 120 m was used. .

[Reference Example 1]
The same procedure as in Comparative Example 1 was performed except that a decompression chamber was provided upstream of the casting die in the running direction of the support and the decompression chamber was decompressed to a decompression value of −200 Pa.

  The thickness unevenness of the obtained resin film was “x”.

[Reference Example 2]
The same procedure as in Reference Example 1 was performed except that the pressure was reduced so that the reduced pressure value was −400 Pa.

  The thickness unevenness of the obtained resin film was “Δ”.

[Reference Example 3]
The same procedure as in Reference Example 1 was performed except that the pressure was reduced so that the reduced pressure value was −600 Pa.

  The thickness unevenness of the obtained resin film was “Δ”.

  As can be seen from the above Reference Examples 1 to 3, when an endless belt support having a pp distance exceeding 15 mm is used, the thickness of the casting die can be reduced even if the atmosphere on the upstream side in the running direction of the support is reduced. Unevenness cannot be sufficiently suppressed. Also from this, it is possible to suppress uneven thickness by using an endless belt support having a width W of 1500 to 2500 mm, a thickness T of 1.4 to 1.8 mm, and a pp distance of 15 mm or less. It turns out to be effective.

11 Support 12 Roller 13 Peeling Roller 14 Resin Solution (Dope)
DESCRIPTION OF SYMBOLS 15 Film 16 Stretching device 17 Drying device 18 Heating air 19 Winding device 20 Casting die 21 Casting die main body 21a Manifold part 21b Discharge port 21c Slit part 22 Dope supply pipe 26 Dope 31 Center line 32, 33 Tip 41 Support roller

Claims (5)

A casting step of casting a resin solution containing a transparent resin from a casting die on a traveling support to form a casting film;
A peeling step of peeling the cast film from the support,
The width of the support is 1500 to 2500 mm;
The support has a thickness of 1.4 to 1.8 mm,
The first difference between the maximum value and the minimum value of the distance from one end in the width direction of the support to the center line in the width direction, and from the other end in the width direction of the support to the center line in the width direction. A method for producing a resin film, wherein the second difference between the maximum value and the minimum value of the distance is 15 mm or less. The support is an endless belt stretched between a pair of rollers;
The method for producing a resin film according to claim 1, wherein the belt has a region that is supported by a plurality of support rollers from the inner peripheral side, and a distance between the adjacent support rollers is 100 to 6000 mm.   The method for producing a resin film according to claim 2, wherein at least one of the plurality of support rollers is a rubber roller. Support for resin film production used when producing a resin film by peeling off a cast film formed by casting a resin solution containing a transparent resin on the surface from a casting die while running. Body,
The width is 1500-2500 mm,
The thickness is 1.4 to 1.8 mm,
The first difference between the maximum value and the minimum value of the distance from one end in the width direction to the center line in the width direction, and the maximum value and the minimum value of the distance from the other end in the width direction to the center line in the width direction Both of the second differences are 15 mm or less. The support for manufacturing a resin film according to claim 4, which is obtained by polishing one tip in the width direction and the other tip in the width direction.

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