KR20160148455A - Method for manufacturing resin films - Google Patents

Abstract

The present invention relates to a method for producing a resin film. According to an embodiment of the present invention, the method for producing the resin film comprises the following processes: a supplying process for supplying a long film; and an elongation process for elongating the film while sending back the film through a plurality of grip holes formed by gripping both lateral end portions in the width direction of the film. The film is gripped by the grip holes, so that the thickness (d) of the gripping region gripped by the grip holes ranges from 0.012 to 0.045 mm, and the distance (L) from a front end in the width direction of the film to a spot farthest from the front end on a portion held by the grip holes of the film satisfies inequation 1, 2.5 mm<= L <= (1200 x d - 10.5) mm.

Description

[0001] METHOD FOR MANUFACTURING RESIN FILMS [0002]

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

BACKGROUND ART Resin films are used in various fields, for example, liquid crystal display devices, in consideration of their chemical properties, mechanical properties, and electrical characteristics. Specifically, in the image display area of the liquid crystal display device, various resin films are disposed as optical films such as a transparent protective film for protecting the polarizing elements of the polarizing plate. 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 by using a resin solution (dope) in which a raw resin such as a cellulose ester resin is dissolved in a solvent. Specific examples of the method for producing the resin film using such a dope include a solution casting film forming method and the like. The solution casting film forming method is a method in which a dope is formed on a support to be run to form a flexible film (web), dried to the extent that it can be peeled off, peeled from the support as a film, Followed by drying or stretching to obtain a long resin film.

As a method of producing such a resin film, for example, the production method described in Patent Document 1 is exemplified by stretching a film during production.

Patent Document 1 discloses a technique of detecting the absolute position of the tenter clip in the web width direction at the point of the tentacle clip of the edge of the running web and detecting the absolute position in the web width direction of the edge of the web And obtains a web holding amount of the tenter clip at the point of wave from the absolute position of the detected tenter clip in the web width direction and the absolute position of the web in the web width direction, A web is stretched in the web width direction by the tenter clip while controlling the position of the tenter clip so that the grip amount becomes equal to a preset predetermined amount of web grip. According to Patent Document 1, it is disclosed that the gripping position of the tenter clip can be controlled to a grip amount designated with high accuracy.

Further, in the method for producing a resin film, when the film is stretched during the production, whitening may occur in the film at the time of stretching.

Japanese Patent Laid-Open No. 8-12144

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for producing a resin film in which whitening which can occur in a film during stretching is sufficiently suppressed.

One aspect of the present invention is a film forming apparatus comprising: a supply step of supplying a long film; and a stretching step of stretching the film while conveying the film into a plurality of holding holes holding both side ends in the width direction of the film Wherein a thickness d of a grip region gripped by the gripping portion of the film is 0.012 to 0.045 mm and a tip end in the width direction of the film and a position furthest from the tip end of the portion of the film, Is held by the gripper so that the distance L of the film satisfies the following formula (1): &quot; (1) &quot;

These and other objects, features and advantages of the present invention will be apparent from the following detailed description and the accompanying drawings.

1 is a schematic view showing an example of a basic configuration of a resin film production apparatus using a resin film production method according to an embodiment of the present invention.
Fig. 2 is a schematic view showing an example of a stretching device provided in an apparatus for producing a resin film using the method for producing a resin film in the present embodiment. Fig.
3 is a cross-sectional view of a waveguide (clip) viewed from a cutting plane line III-III in the drawing apparatus shown in Fig.
Fig. 4 is a schematic view showing another example of a stretching apparatus provided in an apparatus for producing a resin film using the method for producing a resin film in the present embodiment. Fig.

According to the study by the present inventors, it has been found that when a resin film such as a cellulose acetate film is produced by the method for producing a web described in Patent Document 1, whitening or the like occurring around the waveguide such as a tenter clip can be sufficiently suppressed There was no case.

Patent Document 1 discloses an example in which a polyester film having a thickness of 13 占 퐉 is stretched so that the gripping amount is set to 14 mm as an example, but there is no description to adjust the gripping amount depending on the film thickness of the film . The method of manufacturing a web described in Patent Document 1 can not be adjusted to a desired holding amount depending on the film thickness even if it can be controlled with high precision with a predetermined holding amount.

As described above, whitened and hazed portions are unsuitable for use as optical films, so that the resin film on which whitening has occurred provides the optical film with the remaining portion that has been whitened. As a result, as the whitened portion becomes larger, the cut-off portion increases, which can not cope with widening or the manufacturing efficiency is lowered.

In view of the above, there is a demand for a method for producing a resin film which sufficiently suppresses whitening which may occur in a film during stretching.

According to the study by the inventor of the present invention, it has been found that whitening occurring around the waveguide when a film is stretched using a plurality of waveguides such as clippers is apt to occur when stretching is performed without replacing the waveguide for a long period of time I found out. In other words, it has been found that after the exchange of a wave earth for a new one, whitening occurs more easily after a certain period of time, for example, one year after the exchange, even though the whitening does not occur. This was presumed to be due to the following reasons. The film is generally stretched in a high-temperature environment. Under such a high temperature environment, it is considered that the wave earth used over a long period of time is deformed or abraded. It is considered that this deformation is the cause of whitening. Specifically, the deformation of the waveguide causes a discrepancy between the stress applied to the waveguide of the film at the time of stretching and the originally assumed stress, and this discrepancy is considered to cause whitening.

Thus, in the production method of the resin film, when the stretching using the breaking core is performed, the breaking core is periodically replaced. For this reason, whitening caused by the use of a wave earth used over a long period of time has not been a big problem. However, the inventors of the present invention have pointed out that as the resin film becomes thinner, the period until the occurrence of whitening is shortened. From this, the inventor of the present invention has studied the period of time required for the occurrence of this whitening to be prolonged.

Conventionally, the gripping position of the waveguide is relatively deeply held so that the film does not come off from the waveguide at the time of stretching. However, the inventors of the present invention have studied the grip position, and found that the period until the occurrence of whitening differs depending on the grip position. In other words, it has been found that the fact that the grip position is relatively shallow is effective in suppressing occurrence of whitening. Further, it has been found that even if it is a thin film, occurrence of whitening can be suppressed.

From the above, the present inventors paid attention to the conditions at the time of stretching in the production method of the resin film, and have reached the present invention as described below.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.

A method of producing a resin film according to an embodiment of the present invention is a method of manufacturing a resin film comprising a feeding step of feeding a long film and a feeding step of feeding the film in a plurality of gripping ways holding both end portions in the width direction of the film, And a stretching step of stretching the film. The thickness d of the holding region of the film held by the holding means is 0.012 to 0.045 mm (12 to 45 mu m). That is, in the method for producing a resin film, in the stretching step, a resin film having a film thickness at the time of stretching and having a grip region gripped by the gripper is 12 to 45 μm.

In the stretching step, a gripping position for gripping the film with the gripping tool may be a distance L between a tip of the film in the width direction and a position farthest from the tip of the portion of the film sandwiched by the waveguide Is a position that satisfies the following expression (1). That is, the distance L from the end on the widthwise center side of the film to the tip of the film in the width direction of the portion of the film sandwiched by the waveguide is a position satisfying the following expression (1). In the stretching step, the film is gripped by the gripper so that the gripping position is obtained.

&Quot; (1) &quot;

A relatively thin resin film is finally obtained because the thickness of the grip region grasped by the gripper is relatively small, 0.012 to 0.045 mm, in the film during manufacture. Even in the case of producing such a thin resin film, by setting the gripping position as the gripping position as described above, it is possible to make the period from the replacement of the waveguide to the occurrence of bleeding around the waveguide for a long period of time. That is, even if a wave earth used for a relatively long period of time in the drawing process is used, whitening occurring around the wave earth can be sufficiently suppressed. On the other hand, if the distance L is too short, the film tends to escape from the waveguide during stretching. Further, if the distance L is excessively long in order to suppress the deviation of the film from the wave earth, there is a tendency that the effect of making the period until the occurrence of whitening around the wave earth of the film becomes long can not be sufficiently exhibited. Therefore, by grasping and stretching the film with a gripper so as to satisfy the expression (1), the whitening that may occur in the film during stretching can be sufficiently suppressed.

As described above, the thickness d of the grip region gripped by the gripper of the film is preferably 12 to 45 占 퐉, more preferably 16 to 40 占 퐉, and more preferably 18 to 32 占 퐉. Since the thickness d of the grip region gripped by the gripper is relatively small as described above in the film during manufacture, a resin film having a relatively small thickness is finally obtained. In addition, when such a thin resin film is produced, whitening tends to occur around the wave earth. Nevertheless, in the case of the method for producing a resin film according to this embodiment, that is, if the stretching step is provided, even when such a thin resin film is produced, whitening may occur It is possible to make the period to be long.

The gripping position for gripping the film with the gripping tool is a position at which the distance L satisfies the expression (1). It is preferable that the distance L satisfies the following expression (2). By doing so, it is possible to further suppress the occurrence of whitening around the wave earth, and the period from the wave earth exchange to the occurrence of the whitewash around the wave earth can be made longer.

The stretching step is a step of stretching the film while conveying the film into a plurality of holding holes holding both side ends in the width direction of the film supplied in the feeding step, It is not particularly limited.

The supplying step is not particularly limited as long as it can supply a long film. As the supplying step, there can be mentioned, for example, a step of continuously supplying a film having a long shape by solution casting film forming method as described later. Specifically, it is preferable that the supplying step is a step of supplying a resin solution containing a transparent resin to a flexible support on a running support to form a flexible film, and a peeling step of peeling the flexible film from the support to obtain the film . If such a supplying step is provided, the film provided in the stretching step can be continuously supplied. Therefore, a resin film in which occurrence of whitening is suppressed can be continuously produced.

The distance L in the waveguide holding one end of the film and the distance L in the waveguide holding the other end of the film may be the same or different. Further, depending on the state of the wave earth, the distance can be changed on one side and the other side. For example, the distance can be changed according to the period of time used in the stretching process.

The method for producing a resin film according to the present embodiment is not particularly limited as long as it includes the feeding step and the drawing step. Specifically, for example, a method in which a film is peeled from a support in a solution casting film-forming method, and then the above-mentioned stretching process is performed on the peeled film to produce a resin film. Specifically, the manufacturing method of the resin film according to the present embodiment is characterized by comprising a softening step of forming a flexible film (web) on a support on which a resin solution (dope) containing a transparent resin is run, A peeling step of peeling the support film as a film from the support, and the stretching step performed on the peeled film. The resin film may be produced by a drying step for drying the peeled film or a winding step for winding the finally obtained resin film into a roll form. Further, the stretching step may be a step of stretching the film and drying the film. In such a process, the film is stretched in the step of drying, so that it is preferable in that a resin film can be efficiently produced. In addition, if the film is stretched and the film is dried, generally whitening is likely to occur in the film. With the stretching process according to the present embodiment, even when the film is dried in this way, the occurrence of whitening can be sufficiently suppressed. Therefore, a resin film in which occurrence of whitening is suppressed can be efficiently produced.

Such a solution casting film forming method is performed, for example, by a resin film producing apparatus using a solution casting film forming method as shown in Fig. Further, the apparatus for producing a resin film is not limited to the one shown in Fig. 1 and may have other constitution as long as each step is carried out. Here, the term &quot; film &quot; refers to a film after the flexible film (web) including the dope softened on the support is dried on the support and can be peeled off from the support.

Fig. 1 is a schematic view showing an example of a basic configuration of a resin film production apparatus using the resin film production method according to the present embodiment. The apparatus for producing a resin film includes an endless belt support 11, a flexible die 15, a peeling roller 13, a stretching device 21, a drying device 17, a winding device 19 and the like. The flexible die 15 discharges a resin solution (dope) 14 containing a transparent resin in the form of a ribbon, and is flexible on the surface of the endless belt support 11. The endless belt support 11 is supported so as to be able to be driven by a pair of rollers 12 and forms a flexible film (web) including a flexible resin solution 14 from the flexible die 15, And is dried to the extent that it can be peeled off by the peeling roller (13). The peeling roller 13 peels the dried flexible film from the endless belt support 11 to obtain a film 16. The peeled film 16 is stretched in a predetermined direction such as a width direction by the stretching device 21. [ Further, the stretched film 16 is further dried by the drying device 17, and the dried film F is wound as a resin film in the form of a roll by a winding device 19.

The flexible die 15 is not particularly limited as long as it can discharge the dope 14 in the form of a ribbon and be flexible on the surface of the endless belt support 11. [ The flexible die 15 is supplied with dope from a dope supply pipe connected to the upper end portion. Then, the supplied dope is discharged from the flexible die 15 to the endless belt support body 11, and a web is formed on the endless belt support body 11.

As shown in Fig. 1, the endless belt support 11 is an endless belt running infinitely. For example, an endless belt running on an endless surface of which surface is mirror-finished is preferably used. As the endless belt, for example, a belt including stainless steel or the like is preferably used from the viewpoint of releasability of the flexible film. Further, a drum support may be used instead of the endless belt support. As the drum support, for example, a rotating metal drum or the like whose surface is mirror-finished is preferably used.

Then, the endless belt support 11 carries the flexible film (web) formed on its surface, and dries the solvent in the dope. The drying is performed, for example, by heating the endless belt support 11 or spraying the heated air onto the web.

The running speed of the endless belt support 11 is not particularly limited, but is preferably about 50 to 200 m / min, for example. The draft ratio, which is the ratio of the running speed of the endless belt support body 11 to the discharge speed of the dope 14 from the flexible die 15, is not particularly limited, but is preferably about 0.8 to 5.0, for example . When the draft ratio is within this range, a flexible film can be stably formed. For example, if the draft ratio is too large, the flexible film tends to cause a phenomenon called a neck in which the film is reduced in the width direction, and as a result, a wide film can not be formed.

The distance between the endless belt support 11 and the peeling roller 13 is preferably 1 to 100 mm. The peeling roller 13 is disposed near the surface of the endless belt support 11 where the dope is softened. The peeling roller 13 is used for peeling the dried web to some extent on the endless belt support 11. Using the peeling roller 13 as a fulcrum, tension is applied to the dried web to pull it, and the dried web is peeled off as the film 16. Further, when the film is peeled from the endless belt support 11, the film 16 is stretched in the machine direction (machine direction: MD direction) by the peeling tension and the subsequent transport tension.

The elongating device 21 is provided with a plurality of waveguides for gripping both end portions in the width direction of the film 16 and is capable of performing the elongating process by the plurality of waveguides, It does not. As the stretching device 21, for example, there can be mentioned a stretching device which stretches the film 16 in a direction (Transverse Direction: TD direction) perpendicular to the carrying direction, as shown in Fig. Specifically, as shown in Fig. 2, such a stretching device is configured such that both ends in the direction (width direction) perpendicular to the carrying direction of the film 16 are gripped by the grips 24 and 25, By extending the distance between the clips 24 and 25, the film is stretched in the TD direction.

Fig. 2 is a schematic view showing an example of a stretching device provided in an apparatus for producing a resin film using the method for producing a resin film in the present embodiment. Fig. The elongating device 21 includes a first rail 22, a second rail 23, and a plurality of clips 24 and 25. 2 is a schematic view, and the number of the clips 24, 25 is generally larger than that shown in Fig.

The first rail 22 extends along one end of the film 16 and defines the running direction of the clip 24, as described below. The second rail 23 extends along the other end of the film 16 and determines the running direction of the clip 25, as will be described later.

The clips (24, 25) each grip an end portion in the width direction of the film (16). Further, the clips 24 and 25 are disposed at predetermined intervals on an endless chain (not shown), respectively. The endless chain in which the clip (24) is arranged spans a pair of sprockets (26, 28). The endless chain in which the clip (25) is disposed is extended over a pair of sprockets (27, 29). The sprockets 28 and 29 are rotationally driven by a drive source such as a stepping motor to impart driving force for continuously rotating the endless chains. The sprockets 26 and 27 are rotatably mounted and are driven to rotate in response to the endless rotation of the endless chain by the sprockets 28 and 29. The endless rotation of each endless chain is guided by the first rail (22) and the second rail (23). Thus, the endless chain in which the clip 24 and the clip 25 are arranged is continuously rotated in a state of being guided by the first rail 22 and the second rail 23, so that the clip 24 And 25 sequentially run on the first rail 22 and the second rail 23 in the transport direction of the film 16 while holding the end portions in the width direction of the film 16.

The traveling directions of the clips 24 and 25 are determined as follows.

First, each of the clips 24 and 25 moves only along the longitudinal direction of the film 16 while grasping both end portions in the width direction of the film. That is, the distance between the clip 24 and the clip 25 is changed so as to be hardly changed.

Each of the clips 24 and 25 then moves along the longitudinal direction of the film 16 and moves between the clip 24 and the clip 25 in the width direction of the film 16 It moves in the direction of gradually expanding. By doing so, the film 16 is stretched in the width direction. At this time, the angle? 1 formed between the longitudinal direction of the film 16 before stretching and the clip 24 or the clip 25 at the time of stretching is preferably 1 to 50 degrees. If the angle [theta] 1 is too small, the elongation becomes low and the resin film can not sufficiently be widened. If the angle? 1 is too large, distortion tends to occur at the periphery of the position gripped by the grips 24 and 25, and in some cases, the film 16 may be torn.

Finally, each of the clips 24 and 25 moves so as to hardly change the distance therebetween. In other words, it moves so as to maintain the extended gap by stretching. By doing so, the shrinkage of the film 16 in the width direction after the clips 24, 25 are opened is suppressed.

When the film 16 is stretched, the film 16 is usually heated. The heating of the film 16 is not particularly limited. For example, the film 16 may be heated by blowing heated air onto the film, or may be heated by a heating device such as infrared rays. The temperature of the film at the time of stretching varies depending on the composition of the film and the like, but is preferably 100 to 150 ° C, for example. The film may be dried by such heating. Concretely, as described above, it is preferable that the stretching step is a step of stretching the film and drying the film. As described above, since the film is stretched in the step of drying, the resin film can be efficiently produced. In addition, if the film is stretched and the film is dried, generally whitening is likely to occur in the film. In the case of the production method of the resin film according to the present embodiment, occurrence of whitening can be sufficiently suppressed even in such a process. Therefore, a resin film in which occurrence of whitening is suppressed can be efficiently produced.

The structure of the gripping clips 24 and 25 is not particularly limited as long as the film can be gripped. Specifically, for example, a clip having the structure shown in Fig. 3 can be cited. 3 is a cross-sectional view of the clips 24, 25 viewed from the cutting plane line III-III of the elongating apparatus 21 shown in Fig.

As shown in Fig. 3, the clips 24 and 25 include a movable portion 31 and a pedestal 32. As shown in Fig. The movable part 31 is rotatably supported by the pedestal 32. The clips 24 and 25 hold the film 17 by rotating the movable part 31 and fitting the film 16 into the pedestal 32 with the movable part 31. [

The gripping positions of the clips 24 and 25 are set such that the tip 16a of the film 16 in the width direction and the tip 16a of the portion of the film 16 engaging the clip 24 and 25 16a from the farthest position 16b is a position that satisfies the above-mentioned formula (1). A position 16b farthest from the front end 16a of the portion of the film 16 that is engaged with the clips 24 and 25 means that the film 16 is positioned between the movable portion 31 and the pedestal 32 And is located farthest from the tip 16a. That is, the position is the farthest from the tip 16a of the portion where the movable portion 31 and the pedestal 32 are in contact with the film 16. Further, the position 16b farthest from the tip 16a of the portion of the film 16 that is engaged with the clip 24, 25 is not limited to the position shown in Fig. 3 if it is the above position.

3, a second contact surface 34 of the pedestal 32, which contacts the film 16, contacts a first contact surface (not shown) of the movable part 31 that contacts the film 16 33 to the center side in the width direction of the film 16. In this case, a position 16b farthest from the tip end 16a of the portion of the film 16 that is engaged with the clip 24, 25 is located at a portion of the film 16 that is in contact with the movable portion 31 Is the farthest position from the tip (16a) When the first contact surface 33 is wider than the second contact surface 34 to the widthwise center side of the film 16, the film 16 and the pedestal 32 are contacted with each other Is the farthest position from the tip (16a) of the portion where the tip is located.

The film 16 gripped by the clips 24 and 25 is formed such that the thickness d of the grip region gripped by the clips 24 and 25 is smaller than the thickness d of the grip region It is preferable that the thickness d 'is 4 to 28 탆 thicker than the thickness d' of the central side region, and more preferably 8 to 22 탆 thick. Whitening generated in the film at the time of stretching tends to occur in the vicinity of the clip which is a grip. In addition, such white papers tend to be more likely to occur as the film is thinner. In this respect, by making the thickness of the gripping region thicker than the thickness of the central region, the effect of suppressing the occurrence of whitening can be further exerted. Further, even when a thin resin film is produced, whitening can be suppressed by making the grip region grasped by the gripper portions thick. In this respect, even when a thin resin film is produced, whitening that may occur in the film during stretching can be sufficiently suppressed. Even if the thickness d of the gripping region is larger than the thickness d 'of the central region, if the difference is small, the effect of the difference in thickness becomes small. Further, if the thickness d of the gripping region is too thick with respect to the thickness d 'of the central region, the deformation in the vicinity of the waveguide after stretching tends to become large. The thickness d of the holding region of the film 16 is preferably 16 to 40 mu m, more preferably 18 to 32 mu m. Further, the thickness d 'of the central region of the film 16 is preferably 8 to 36 μm, more preferably 10 to 24 μm.

The method for producing a film having the thickness d of the grip region larger than the thickness d 'of the central region as described above is not particularly limited. Such a film may be formed in the forming step. For example, in the case of forming a film by a solution casting film forming method, a flexible die in which bolts for adjusting the gap width of the slit (discharge port) for discharging the dope in the flexible width direction (the width direction of the discharge port) The thickness of the grip region d is greater than the thickness d 'of the center side region by forming the film by softening the dope in a state in which the end portion in the width direction is greatly expanded in comparison with the center portion with respect to the gap width of the slit, .

The stretching step may be not only the case of stretching in the TD direction but also the case of oblique stretching as described above. Specifically, there may be mentioned a stretching process in which both end portions in the width direction of the film are held while being gripped by a plurality of gripping portions, and the carrying direction is changed while maintaining the holding state. A plurality of third waveguides for gripping one end of the film among a plurality of waveguides for holding both side ends in the width direction of the film by changing the conveying direction as described above; Distribute the moving distance to the fourth wave earth. By doing so, the film is obliquely stretched in the direction larger than 0 DEG and less than 90 DEG with respect to the width direction. The stretching step may be a step of oblique stretching. With such a stretching process, the film can be stretched properly in an oblique direction, and occurrence of whitening can be sufficiently suppressed at the time of oblique stretching.

Fig. 4 is a schematic view showing another example of a stretching apparatus provided in an apparatus for producing a resin film using the method for producing a resin film in the present embodiment. Fig. The film 16 whose direction is controlled by the guide roll 41 on the tenter inlet side is positioned at the position of the outer film holding start point 42-1 and the inner film holding start point 42-2, (Clip), and is transported and stretched in the oblique direction indicated by the locus 44-1 of the film holding and holding means on the outer side and the locus 44-2 of the film holding and holding means on the outer side by the oblique drawing tenters 43, The gripping is released by the outer film holding end point 45-1 and the inner film holding end point 45-2 and the conveying is controlled by the guide roll 46 on the outlet side of the tenter, The film 16 is formed. That is, the film 16 is obliquely stretched at an angle (orientation angle? 2) of the stretching direction 52 of the film with respect to the transport direction 51 of the film. 2 is stretched so as to be larger than 0 DEG and less than 90 DEG.

The drying apparatus 17 has a plurality of conveying rollers, and dries the film while conveying the film between the rollers. At this time, as shown in Fig. 1, the heating air 18 may be dried by circulating it in the drying device 17, or may be dried by using infrared rays or the like, or may be dried by using heated air and infrared rays in combination . It is preferable to use heated air in view of simplicity.

The winding device 19 winds the film F having a predetermined residual solvent ratio in the drying device 17 to the winding core. Before the film F is wound around the winding core, embossing may be performed on both ends in the width direction of the film by a hot embossing mechanism. The temperature at the time of winding is preferably cooled to room temperature to prevent scratches due to shrinkage after winding, relaxation of winding, and the like. The winding device to be used can be used without particular limitation and can be a commonly used winding device and can be wound by a winding method such as a constant tension method, a constant torque method, a taper tension method, a program tension control method with a constant internal stress have.

The apparatus for producing a resin film may be provided with a cutting device for cutting and removing the end portion of the film 16 before winding the resin film with the winding device 19. [ By cutting off the end portion in this way, the portion gripped by the gripping portion in the stretching step can be removed. At this time, in the case of the production method of the resin film according to the present embodiment, occurrence of whitening around the wave earth can be suppressed, so that only the portion deformed by the wave earth can be cut, . Concretely, it is preferable to cut a position of 4.5 cm from the tip of the film in the width direction. By doing so, the portion deformed by the wave earth can be removed. Further, in order to use the resin film as a product after being wound up by the winding device 19, the end may be cut off when the resin film is unwound.

Further, the apparatus for producing a resin film is not particularly limited as long as the method for producing the resin film according to the present embodiment can be carried out. Specifically, the apparatus for producing a resin film does not need to be provided with a stretching device or a drying device, and may be provided with a plurality of not each one.

In the above-described embodiment, the apparatus for producing a resin film is provided with the endless belt support as the support, but it may be provided with the drum support. Specifically, in addition to the drum support body in place of the endless belt support body 11, the same resin film production apparatus as the resin film production apparatus shown in Fig. 1 and the like can be given. Examples of the drum support include a rotary drive drum made of stainless steel and subjected to a hard chrome plating treatment on its surface.

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

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

The transparent resin is not particularly limited and may be a resin having transparency when formed into a substrate shape by a solution casting film forming method or the like. However, the transparent resin can be easily produced by a solution casting film forming method or the like, Is preferably an optically isotropic one, and the like. The transparency herein means that the transmittance of visible light 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; Polyester resins such as polyethylene terephthalate resin and polyethylene naphthalate resin; Acrylic resins such as polymethyl methacrylate resin; But are not limited to, polysulfone (including polyethersulfone) resin, polyethylene resin, polypropylene resin, cellophane, polyvinylidene chloride resin, polyvinyl alcohol resin, ethylene vinyl alcohol resin, syndiotactic polystyrene resin, cycloolefin resin, Vinyl resins such as polymethylpentene resin; Polycarbonate resin; Polyarylate resins; Polyetherketone resins; Polyether ketone imide resins; Polyamide based resin; Fluorine-based resins, and the like. Among them, a cellulose ester resin, a cycloolefin resin, a polycarbonate resin, and a polysulfone (including polyethersulfone) resin are preferable. Among them, a cellulose acetate resin, a cellulose propionate resin, a cellulose butyrate resin, a cellulose acetate butyrate resin, a cellulose acetate propionate resin, and a cellulose triacetate resin are preferable, and among these, Cellulose triacetate resins are particularly preferred. As the transparent resin, the above-mentioned transparent resins may be used alone, or two or more of them may be used in combination.

Next, the cellulose ester resin will be described.

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

The average molecular weight and the molecular weight distribution of a resin such as a cellulose ester resin can be measured by 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-based resin preferably has an acyl group, specifically, an acyl group having 2 to 4 carbon atoms as a substituent. The degree of substitution of the acyl group is preferably 2.2 to 2.95, for example. The degree of substitution is, for example, when the substitution degree of the acetyl group is X, the degree of substitution of the propionyl group or the butyryl group is Y, the total value of X and Y is not less than 2.2 and not more than 2.95, And is preferably 2.95 or less.

In addition, the portion not substituted with an acyl group usually exists as a hydroxyl group. This cellulose ester resin can be synthesized by a known method. The degree of substitution degree of the acyl group can be measured in accordance with ASTM-D817-96.

As the solvent used in the present embodiment, a solvent containing a good solvent for the transparent resin may be used. The above-mentioned two solvents differ depending on the transparent resin used. For example, when the transparent resin is a cellulose ester-based resin, the good solvent and the poor solvent are changed depending on the acyl group substitution degree of the cellulose ester. For example, when acetone is used as the solvent, the acetate ester of the cellulose ester Degree of substitution 2.4). In cellulose acetate propionate, it becomes a two-solvent. Acetate ester of cellulose (acetyl group substitution degree 2.8) becomes a poor solvent. Therefore, since the good solvent and the poor solvent differ depending on the transparent resin to be used, the case of the cellulose ester resin will be described as an example.

Examples of suitable solvents for the cellulose ester resin include organic halogen compounds such as methylene chloride and the like; organic solvents such as methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, , 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, and nitroethane. Of these, organic halogen compounds such as methylene chloride, dioxolane derivatives, methyl acetate, ethyl acetate, and acetone are preferred. Of these, methylene chloride is preferred. These two solvents may be used alone or in combination of two or more.

In addition, a poor solvent may be contained in the dope within such a range that the transparent resin is not precipitated. Examples of the poor solvent for the cellulose ester resin include alcohols having 1 to 8 carbon atoms such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, Ketone, methyl isobutyl ketone, propyl acetate, monochlorobenzene, benzene, cyclohexane, tetrahydrofuran, methyl cellosolve, and ethylene glycol monomethyl ether. Of these, ethanol is preferable. These poor solvents may be used alone or in combination of two or more.

The resin solution used in the present embodiment may contain the above-mentioned transparent resin and other components (additive) other than the solvent within the range that does not impair the effect of the present invention. Examples of the additives include microparticles, plasticizers, antioxidants, ultraviolet absorbers, heat stabilizers, conductive materials, flame retardants, lubricants, and matting agents.

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

As a method of dissolving the cellulose ester resin in preparing the dope, a general method can be used without particular limitation. The combination of heating and pressurizing to dissolve the cellulose ester resin in the solvent at a temperature higher than the boiling point at normal pressure by using the solvent which can be heated to the boiling point or higher of the solvent at normal pressure is not particularly limited, And the like. It is also preferable to use a method in which the cellulose ester resin is mixed with a poor solvent to wet or swell the solution, followed by addition of a good solvent to dissolve the cellulose ester resin.

Next, the solution of the obtained cellulose ester resin 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, the occurrence of whitening can be suppressed and a resin film in which the occurrence of whitening is suppressed can be produced over a long period of time. Further, in the method for producing a resin film according to the present embodiment, it is preferable to produce a cellulose acetate film as a resin film. By doing so, a cellulose acetate film suitably used for an optical film or the like can be produced by suppressing occurrence of whitening. Therefore, a high-quality optical film can be produced over a long period of time.

The thickness (film thickness) of the resin film is preferably 5 to 25 mu m. Such a film thickness is preferable because of the thinness of the liquid crystal display device and the stable productivity of the resin film. Here, the film thickness here is an average film thickness. As the measuring method, for example, the film thickness is measured at 20 to 200 positions in the width direction of the optical film by a contact type film thickness measuring apparatus manufactured by Mitsutoyo Corporation, and the average value of the measured values is used as a film thickness . The width of the resin film obtained here is preferably 1000 to 4000 mm from the viewpoint of use in a large-sized liquid crystal display apparatus, efficiency of use of the resin film in production of a polarizing plate, and production efficiency.

(Polarizer)

The resin film obtained by the method for producing a resin film according to the present embodiment can be used as a protective film for a polarizing plate. The polarizing plate using the resin film as a protective film as described above has 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 converts incident light into polarized light and emits it.

As the polarizing plate, it is preferable that the resin film is bonded to at least one surface of a polarizing element produced by, for example, immersing a polyvinyl alcohol film in an iodine solution and stretching it, using a fully saponified polyvinyl alcohol aqueous solution . The resin film may be laminated on the other surface of the polarizing element, or a transparent protective film for a 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. At that time, when the resin film functions as a retardation film, it is preferable that the slow axis of the resin film is disposed so as to be substantially parallel or orthogonal to the absorption axis of the polarizing element.

Such a polarizing plate uses a resin film according to the present embodiment as a transparent protective film. This resin film is high in quality even if it is thin. Therefore, even if the obtained polarizing plate is thin, it is of high quality. Therefore, when the polarizing plate thus obtained is applied to, for example, a liquid crystal display device, the quality of the liquid crystal display device can be improved.

(Liquid crystal display device)

The resin film or the polarizing plate may be used in a liquid crystal display device. Specifically, the polarizing plate can be used as a polarizing plate of a liquid crystal display device. The liquid crystal display device having the polarizing plate has 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. The liquid crystal cell is a liquid crystal material filled between a pair of electrodes. By applying a voltage to this electrode, 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 above polarizing plate as a transparent protective film for a polarizing plate. By doing so, a high-quality liquid crystal display device with improved contrast and the like can be obtained.

Although the present specification discloses various types of techniques as described above, the main techniques are summarized below.

One aspect of the present invention is a film forming apparatus comprising: a supply step of supplying a long film; and a stretching step of stretching the film while conveying the film into a plurality of holding holes holding both side ends in the width direction of the film Wherein a thickness d of a grip region gripped by the gripping portion of the film is 0.012 to 0.045 mm and a tip end in the width direction of the film and a position furthest from the tip of the portion of the film sandwiched by the waveguide Is held by the gripper so that the distance L of the film satisfies the following formula (1): &quot; (1) &quot;

&Quot; (1) &quot;

According to such a constitution, it is possible to provide a method for producing a resin film in which whitening which may occur in the film during stretching is sufficiently suppressed. The thickness of the grip region gripped by the gripping portion of the film in manufacturing is 0.012 to 0.045 mm, and the finally obtained resin film becomes relatively thin. Even in the case of producing such a thin resin film, the period from the exchange of the wave earth to the occurrence of white matter around the wave earth can be made longer. In addition, even if a wave earth used for a relatively long period of time in the stretching process is used, whitening occurring around the wave earth can be sufficiently suppressed. In this respect, whitening that may occur in the film during stretching can be sufficiently suppressed.

In the method for producing a resin film, it is preferable that the film includes the grip region and a central region on the center side in the width direction of the film than the grip region, and the thickness of the grip region is greater than the thickness of the central region Is preferably 4 to 28 탆 thick.

According to such a constitution, whitening that may occur in the film during stretching can be further suppressed. That is, by making the gripping region gripped by the gripping portion of the film thicker than the region closer to the center than the gripping region, the occurrence of whitening can be further suppressed. In addition, even when a thin resin film is produced, whitening can be suppressed by making the gripping region grasped by the gripping portions thick. In this respect, even when a thin resin film is produced, whitening that may occur in the film during stretching can be sufficiently suppressed.

Further, in the above-mentioned method of producing a resin film, the stretching step may be performed such that the waveguide moves in the longitudinal direction of the film while grasping both side ends in the width direction of the film with a plurality of holding means, A step of moving a distance between a plurality of first waveguides holding one end of the film in the earth and a second waveguide holding the other end of the film in a direction of gradually expanding in the width direction of the film .

According to such a constitution, the film can be stretched properly in the width direction of the film, and the occurrence of whitening can be sufficiently suppressed at the time of stretching.

In the method of producing the resin film, the stretching step may be carried out while grasping both end portions in the width direction of the film with a plurality of gripping portions and changing the carrying direction while maintaining the gripped state, A plurality of third waveguides for holding one end of the film among a plurality of waveguides for holding both side ends in the width direction and a fourth waveguide for holding the other end of the film are different from each other And a step of obliquely stretching the film in a direction larger than 0 DEG and less than 90 DEG with respect to the width direction.

According to such a constitution, the film can be stretched properly in the oblique direction, and occurrence of whitening can be sufficiently suppressed at the time of oblique stretching.

In the manufacturing method of the resin film, it is preferable that the supplying step includes a flexible step of forming a flexible film by pouring a resin solution containing a transparent resin from a flexible die onto a running support, and removing the flexible film from the support And a peeling step of obtaining the film.

According to this configuration, the film provided in the stretching process can be continuously supplied. From this, it is possible to continuously produce a resin film in which occurrence of whitening is suppressed.

In the method for producing a resin film, it is preferable that the stretching step is a step of stretching the film and drying the film.

With such a constitution, since the film is stretched in the step of drying, the resin film can be efficiently produced. In addition, if the film is stretched and the film is dried, generally whitening is likely to occur in the film. In the case of the method for producing a resin film according to one aspect of the present invention, even in such a step, occurrence of whitening can be sufficiently suppressed. Therefore, a resin film in which occurrence of whitening is suppressed can be efficiently produced.

In the method for producing a resin film, it is preferable that the film is a cellulose ester film.

With such a constitution, a cellulose ester film preferable as an optical film can be produced while suppressing occurrence of whitening.

It is preferable that the distance L in the waveguide holding one end of the film and the distance L in the waveguide holding the other end of the film are the same Or may be different. Further, the distance may be changed on one side and the other side depending on the state of the wave earth. For example, the distance can be changed according to the period of time used in the stretching process.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for producing a resin film in which whitening which may occur in a film during stretching is sufficiently suppressed.

Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited thereto.

[Example]

[Examples 1 to 11, Comparative Examples 1 to 3]

(Preparation of dope)

First, 100 parts by mass of cellulose triacetate resin (acetyl group substitution degree 2.88) as a transparent resin was added to a dissolution tank containing 418 parts by mass of methylene chloride and 23 parts by mass of ethanol, and further, 8 parts by mass of triphenyl phosphate, 2 parts by mass of ethyl glycol, 1 part by mass of Tinuvin 326 (manufactured by BASF Japan K.K.) and 0.1 part by mass of Aerosil 200V (manufactured by Nippon Aerosil Co., Ltd.) were added. Then, the mixture was heated to a liquid temperature of 80 deg. C and stirred for 3 hours. By doing so, a resin solution was obtained. Thereafter, stirring was terminated, and the solution was allowed to stand until the liquid temperature reached 43 캜. The resin solution after being left standing was filtered using a filter paper with a filtration accuracy of 0.005 mm. The resin solution after filtration was allowed to stand overnight to bubble out the bubbles in the resin solution. Using the thus obtained resin solution as a dope, a resin film was produced as follows.

(Production of resin film)

First, the temperature of the obtained dope was adjusted to 35 캜 and the temperature of the endless belt support was adjusted to 20 캜. Then, by using the apparatus for producing a resin film as shown in Fig. 1, the discharge slot slit interval and the like of the flexible die were adjusted so that the thickness of the film at the time of stretching became the thicknesses shown in Tables 1 and 2, The film was made to have a width of 1160 mm.

First, the dope was made flexible from the flexible die (coat hanger die) to the endless belt support. As the endless belt support, a stainless steel (made of SUS316) and an endless belt including an endless belt polished with a superficially average three-dimensional surface roughness (Ra) of 1.0 nm by a scanning type atomic force microscope (AFM) Support was used.

Then, the web is dried by sending the drying air of 30 DEG C from the dryer on the endless belt support side to the web on the endless belt support. The dried web was peeled off as a film from an endless belt support. The peeled film was conveyed by a conveying roller and dried until the residual solvent ratio became 80% by mass.

The dried film was stretched 22% in the TD direction while gripping both ends of the film with a clip under an environment of 140 占 폚 by using a stretching device (tenter), and the clip was released.

The gripping position of the film by the clip is preferably a distance L between the tip of the film in the width direction and the farthest position from the tip of the portion of the film that is sandwiched between the clips The distance L from the end on the center side to the tip in the width direction of the film) was L as shown in Tables 1 and 2 below.

Thereafter, the dried film was wound up with a winding device to obtain a roll-wound resin film.

[Evaluation (White)]

The obtained resin film was evaluated as follows.

After replacing the clip as a holding tool with a new one, the haze of the resin film obtained by using the clip at the use time of 2100 hours and at the time of 2800 hours was measured. Ten points different from each other in the longitudinal direction were measured at a position of 4.5 cm from the tip in the width direction of the resin film before cutting the end portion. The measurement was performed using a haze meter (NDH2000 manufactured by Nippon Denshoku Kogyo K.K.) under the environment of 23 ° C and 55% RH. The results are shown in Table 1.

Further, the distal end side of 4.5 cm from the tip in the width direction of the resin film before cutting the end portion has a deformation of the film held by the clip. For this reason, this portion is often cut off. When the haze is 0.6% or more, it is not suitable as a transparent protective film for a polarizing plate. In this regard, when the haze is 0.6% or more, it is necessary to cut and remove the portion more than the portion where the film is deformed due to holding by the clip.

From Table 1 and Table 2, it can be seen that, even when the film having the thickness of 0.012 to 0.045 mm in the grip region gripped by the clip is stretched, the position where the film is gripped by the clip is determined when the distance L satisfies the above- (Examples 1 to 11), it was found that the occurrence of whitening can be suppressed as compared with the case where the distance L does not satisfy the expression (1) (Comparative Examples 1 to 4).

Further, in the case where the thickness of the grip region gripped by the clip is thicker than the central region on the center side than the grip region (Examples 5 to 11), in the case where the grip region and the central region have the same thickness (Examples 1 to 4) , And the occurrence of whitening can be suppressed. Further, it was found that the occurrence of whitening can be suppressed more than in the case where the difference in thickness is 4 to 28 mm (Examples 5 to 8) than in the case where the difference in thickness is less than 4 mm (Examples 9 to 11).

This application is based on Japanese Patent Application No. 2015-120989 filed on June 16, 2015, the contents of which are incorporated herein.

Although the present invention has been adequately and sufficiently described in the foregoing for the purpose of expressing the present invention through the embodiments with reference to the drawings in the foregoing description, those skilled in the art will recognize that modifications and / or improvements to the above- do. It is therefore to be understood that changes or modifications thereof that fall within the scope of the appended claims are intended to be encompassed within the scope of the appended claims.

According to the present invention, there is provided a method for producing a resin film which sufficiently suppresses whitening that may occur in a film during stretching.

Claims (8)

A supply step of supplying a long film,
And a stretching step of stretching the film while conveying the film with a plurality of holding means holding both side ends in the width direction of the film,
The thickness d of the grip region held by the gripping portion of the film is 0.012 to 0.045 mm,
Characterized in that the film is gripped by the gripper so that a distance L between a tip of the film in the width direction and a position farthest from the tip of the portion sandwiched by the waveguide of the film satisfies the following expression By weight based on the total weight of the resin film.
&Quot; (1) &quot;

The film according to claim 1, wherein the film includes the grip region and a central region on the center side in the width direction of the film than the grip region,
And the thickness of the gripping region is 4 to 28 占 퐉 thicker than the center-side region. The method according to claim 1, wherein the stretching step is a step of stretching the film in a longitudinal direction of the film while holding both side ends in the width direction of the film with a plurality of holding means, Which is a step of moving a distance between a plurality of first waveguides holding one end and a second waveguide holding the other end of the film in a direction of gradually expanding in the width direction of the film, Way. The film stretching method according to claim 1, wherein the stretching process is carried out while grasping both side ends in the width direction of the film with a plurality of gripping parts and changing the carrying direction while maintaining the holding state, A plurality of third waveguides for holding one end of the film among a plurality of waveguides for holding the end portion and a fourth waveguide for holding the other end of the film are made to have different moving distances, Which is greater than 0 DEG and less than 90 DEG with respect to the width direction. The method of claim 1,
A softening step of softening a resin solution containing a transparent resin from a flexible die on a running support to form a flexible film,
And peeling the flexible film from the support to obtain the film. The method for producing a resin film according to claim 1, wherein the stretching step is a step of stretching the film and drying the film. The method for producing a resin film according to claim 1, wherein the film is a cellulose ester film. The method for producing a resin film according to claim 1, wherein the distance L in the waveguide holding one end of the film is different from the distance L in the waveguide holding the other end of the film.

Images