JP5522164B2 - Manufacturing method of optical film - Google Patents

Description

  The present invention is also used for various functional films such as an antireflection film used for various image display devices such as a protective film for polarizing plates, a retardation film, a viewing angle widening film, and a plasma display device used for liquid crystal display devices. The present invention relates to a method for producing an optical film, an optical film obtained by the production method, a polarizing plate using the optical film, and a liquid crystal display device including the polarizing plate.

  Image display devices, particularly liquid crystal display devices, have been widely used due to improvements in image quality, high definition technology, and the like. Further, a liquid crystal display device, particularly a liquid crystal display device used as a television receiver, is further required to have a large screen and high image quality. For this reason, the optical film provided in a liquid crystal display device, for example, a protective film for a polarizing plate, is not only improved in visibility, but also needs to be widened in order to cope with an increase in screen size. And in order to respond to the cost reduction of a liquid crystal display device, the increase in the demand of a liquid crystal display device, etc., it is also calculated | required to raise the production efficiency of an optical film.

  In order to increase the production efficiency of the optical film, it is conceivable to continuously produce the optical film. Examples of the method for continuously producing an optical film include a solution casting film forming method and a melt casting film forming method. The solution casting film forming method is a method in which a resin solution obtained by dissolving a raw material resin in a solvent is cast on a traveling support, and the film obtained by drying to some extent is peeled off from the support, and the peeled film Is a method of producing a resin film by drying while transporting the film with a transport roller. The melt casting film forming method is a method in which a molten resin obtained by heating and melting a raw material resin is cast on a support, the film obtained by cooling and solidifying to some extent is peeled off from the support, and the peeled film is conveyed. This is a method for producing a resin film by further cooling and solidifying while being conveyed by a roller.

  In the resin film obtained by the above method, curling or wrinkling may occur at the end during conveyance. In such a case, in order to use the obtained resin film as an optical film, there is a problem that the production efficiency is lowered unless the film end is separately cut. Further, in the above-described method, particularly when a widened resin film is manufactured, the resin film manufacturing is stopped by folding the end portion of the resin film into the transport roller during the transport of the resin film. There was also a problem that there was a risk of doing.

  In order to eliminate these problems, for example, after the resin film is peeled off from the support, the end of the resin film is conveyed while being transported at a predetermined position until the resin film is rolled up as an optical film. The part is cut (trimmed) with a trim cutter. That is, during the production of the resin film, the end portion is cut and the film remaining by separating the cut end film is used as an optical film.

  However, unless the end film after cutting is smoothly transported, the transport of the resin film before cutting and the transportability of the optical film after separating the end film are affected. Specifically, for example, even if the end film is broken during conveyance, the end film is detached from the predetermined conveyance path, or is not conveyed from the predetermined conveyance path, In some cases, the end film is not smoothly conveyed due to clogging of the end film. In addition, since the end film is not smoothly conveyed, for example, the tension of the optical film or the like after being separated from the end film is lowered, and there is a problem that the conveyance of the optical film is hindered. There was something to do.

  Specific examples of conventional methods for cutting the edge of such a film include the methods described in Patent Documents 1 to 3 below.

  In the following Patent Document 1, a cutting-edge automatic that automatically processes an ear (end film) generated when a traveling wide web is cut in the traveling direction to obtain a plurality of narrow webs having a desired width. A processing apparatus, which is movable in the width direction of the traveling wide web and which cuts the cutting ear in the width direction, and the cutting ear cut by the ear cutting means is separated from the wide web. An ear conveying means that is movable in the width direction of the traveling wide web, and a width of the wide web and a position of the cutting ear that varies depending on the width and number of the narrow web to be cut. And a method using an automatic cutting ear processing apparatus comprising the ear cutting means and a control means for positioning the ear conveying means.

  According to Patent Document 1, since the control means for positioning the ear cutting means and the ear conveying means according to the position of the cutting ear is provided, it is possible to cope with various changes such as the width of the original fabric (resin film). It is disclosed that it can respond automatically. That is, the cutting position of the resin film can be automatically changed depending on the width of the resin film and the like, and the cutting of the resin film can be performed stably.

Further, Patent Document 2 below has a first step of blowing a film side end portion (end portion film) cut from a continuously conveyed film in a long shape, and uses the first step. In the method of blowing the side end portion to the recovery portion, a roller pair for sandwiching the side end portion is provided in the first step, and the side end portion immediately before being sandwiched by the roller pair is provided. However, there is described an air feeding method in which a tension of 3 N / m ² or more and 45 N / m ² or less is applied in the longitudinal direction.

  According to Patent Document 2, the end film cut from the film is held between a pair of rollers, and by applying a certain tension, the end film is cut from the film until the end film is recovered. It is disclosed that the end film can be aired without clogging the airflow path between them.

  Patent Document 3 below is provided with a guide roller for guiding the sheet-like material, a trim cutter for cutting the vicinity of both ends of the sheet-like material along the traveling direction of the sheet-like material, and downstream of the guide roller. An edge of a sheet-like material comprising: a traverse cutter that cuts an edge (end film) cut by the trim cutter in the width direction of the edge; and an air feeding device that sucks and discharges the edge cut in the width direction In the trimming device, a guide unit for conveying the edge cut in the width direction to the air blowing device is interposed between the guide roller and the air blowing device, and the guide unit is provided on a surface thereof. Has a casing provided with a slit for injecting compressed air at an injection angle of 3 to 45 ° in a downstream direction from the surface of the sheet material. Method using the edge trimming of a sheet comprising a pressure supply means for supplying compressed air to the ring have been described.

  According to Patent Document 3, the edge trimming can be automatically performed regardless of the thickness of the sheet-like material, and the cut edge (end film) can be smoothly conveyed into the suction box, It is disclosed that automation is achieved.

JP-A-8-257990 JP 2005-238801 A JP-A-5-131398

  The present invention relates to a method for producing an optical film by cutting an end portion of a film while transporting the film, so that the optical film obtained by separating the end film is smoothly transported. It aims at providing the manufacturing method of a high optical film.

  One aspect of the present invention is to form an optical film by cutting at least one end in a direction perpendicular to the film transport direction while separating the film, and separating the cut end film. A cutting step and a conveying step of inserting the separated end film into the pipe and conveying the inside of the pipe by air sending, and in the conveying step, the wind speed of the wind blowing used for the air sending is The method for producing an optical film is characterized in that the speed increases from the upstream side to the downstream side of the pipe.

  Another aspect of the present invention is an optical film obtained by the method for producing an optical film.

  Another aspect of the present invention is a polarizing plate including a polarizing element and a transparent protective film disposed on at least one surface of the polarizing element, wherein the transparent protective film is the optical film. It is a polarizing plate characterized by being.

  Another aspect of the present invention is a liquid crystal display device including 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 a liquid crystal display device characterized by being the polarizing plate.

  Objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings.

It is the schematic which shows the basic composition of the manufacturing apparatus 11 of the optical film by the solution casting film forming method in one Embodiment of this invention. It is a schematic perspective view which shows the periphery of the cutting device 16 with which the said optical film manufacturing apparatus 11 is equipped. It is the schematic which shows the periphery of the cutting device 44 with which the said optical film manufacturing apparatus 11 is equipped. It is the schematic which shows the fundamental structure of the manufacturing apparatus 21 of the optical film by the melt casting film forming method in other one Embodiment of this invention.

  According to the studies by the present inventors, even if the resin film can be stably cut by the method described in Patent Document 1, the end film is clogged in the pipe as described above. There was something to do. If the end film after the cutting is not smoothly conveyed, there may be a problem that the optical film is not smoothly conveyed.

  Moreover, in the method described in Patent Document 2, the tension applied to the film is too strong and the film may be broken. This breakage of the film is particularly likely to occur in the case of a thin film or a film having a low tensile strength. Further, when the film broke, the downstream end of the end film transported in the air feed path becomes a free end, so that it is easily affected by the wind blown in the air feed path and easily fluttered greatly. Furthermore, the vibration from the cutting device for cutting the end film in the pipe is easily transmitted to the end film, and the end film is more likely to flutter. When the end film fluctuates greatly as described above, there is a problem that the end film is clogged or the end film is further broken.

  Moreover, in the method of patent document 3, although the method of blowing a wind at a certain angle from the upstream of piping to the end film was taken, the end film became easy to flutter large downstream. When the end film fluctuates greatly as described above, there is a problem that the end film is clogged or the end film is further broken. In particular, when the end of the film is cut after the film is stretched by a film stretching device called a tenter, the surface of the cut end film is uneven by the tenter clip deformation by gripping the film with the clip in the tenter. Therefore, there is a problem that it becomes more difficult to smoothly convey the end film because the air flow is greatly affected by the unevenness.

  The present invention has been made based on the results of the above studies. Hereinafter, although the embodiment concerning the manufacturing method of the optical film of the present invention is described, the present invention is not limited to these.

  The method for producing an optical film according to the present embodiment cuts at least one end in a direction perpendicular to the transport direction of the film while transporting the film, and separates the cut end film. A cutting step for forming an optical film; and a transporting step for inserting the separated end film into a pipe and transporting the inside of the pipe by air blowing, and used in the air feeding in the transporting step. The wind speed of wind blowing increases from the upstream side to the downstream side of the pipe.

  According to the above configuration, since the optical film is manufactured by cutting the end of the film while conveying the film, the optical film can be continuously produced. And in the continuous production of such an optical film, the manufacturing method of an optical film with high production efficiency in which the optical film obtained by isolate | separating the cut edge part film can be smoothly conveyed can be provided.

  This is considered to be due to the following.

  First, since the cut end film is inserted into the pipe and transported through the pipe, it is possible to suppress the end film from coming off from a predetermined transport path even when the optical film is continuously produced. it is conceivable that.

  Moreover, generally the end part film which conveys the inside of the piping tends to have a large flutter from the upstream side to the downstream side of the piping. If the fluttering of the end film is large, smooth transport of the end film is hindered, and smooth transport of the optical film obtained by separating the end film is hindered. And in order to suppress this fluttering, if the wind speed of a wind ventilation is raised as a whole, even if flapping can be suppressed, there exists a tendency for the edge part film to generate | occur | produce. When the end film is broken, smooth transfer of the end film is further hindered. Therefore, by increasing the wind speed of the wind blowing used when conveying the end film from the upstream side to the downstream side of the pipe, the fluttering is large without increasing the overall wind speed of the wind blowing. On the downstream side, it is considered that the direction of the wind blows toward the central portion of the pipe so as to suppress fluttering of the end film. It is considered that fluttering can be effectively suppressed by such air blowing toward the center of the pipe. Furthermore, since the wind speed of wind blowing is not increased as a whole, it is considered that the breakage of the end film can be suppressed. From the above, it is considered that the end film transported in the pipe can be smoothly transported.

  Therefore, the conveyance of the optical film can be prevented from being obstructed by the fact that the conveyance of the end film is not smoothly performed, so that the optical film is cut by cutting the edge of the film while conveying the film. In the method for producing an optical film, it is considered that a method for producing an optical film with high production efficiency in which the optical film obtained by separating the end film is smoothly conveyed can be provided.

  And it is preferable to further provide the cutting process cut | disconnected in the direction perpendicular | vertical to the conveyance direction of the said edge part film, conveying the said edge part film.

  The manufacturing method of the optical film which concerns on this embodiment will not be specifically limited if the said cutting process and the said conveyance process are provided. Specifically, for example, in the solution casting film forming method and the melt casting film forming method, after the film is peeled from the support, the cutting step is performed at a predetermined position until the film is wound into a roll. The method etc. which manufacture an optical film are mentioned.

  (Solution casting film forming method)

  First, the case where an optical film is manufactured by the solution casting film forming method (first embodiment) will be described.

  The method for producing an optical film according to the first embodiment includes a casting step of casting a resin solution (dope) containing a transparent resin on a traveling support to form a film, and the support for the film. A peeling step for peeling from the body, a stretching step for stretching the peeled film, and a winding step for winding the stretched film into a roll, wherein the cutting step is between the peeling step and the winding step. To be done. For example, it is performed by an optical film manufacturing apparatus as shown in FIG. In addition, as an optical film manufacturing apparatus, if the said each process is performed, it will not specifically limit to what is shown in FIG. 1, The thing of another structure may be sufficient. Here, the film means 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.

  FIG. 1 is a schematic diagram showing a basic configuration of an optical film manufacturing apparatus 11 by a solution casting film forming method. The optical film manufacturing apparatus 11 includes an endless belt support 12, a casting die 13, a peeling roller 14, a stretching device 15, a cutting device 16, a drying device 17, a winding device 18, and the like. The casting die 13 casts a resin solution (dope) 19 in which a transparent resin is dissolved onto the surface of the endless belt support 12. The endless belt support 12 is formed into a film by forming a web made of the dope 19 cast from the casting die 13 and drying it while being conveyed. The peeling roller 14 peels the film from the endless belt support 12. The stretching device 15 stretches the peeled film. The drying device 17 dries the stretched film while being transported by a transport roller. The said winding apparatus 18 winds up the dried film in roll shape, and makes it a film roll. Further, as shown in FIG. 1, the cutting device 16 is provided between the peeling roller 14 and the stretching device 15, between the stretching device 15 and the drying device 17, and between the drying device 17 and the winding device. 18 is provided. And the said cutting device 16 cuts the edge part of the film in each location, and performs a predetermined process with respect to the cut edge part film.

  Further, the optical film manufacturing method according to the present embodiment is not limited to the manufacturing apparatus 11 provided with three cutting devices 16 as shown in FIG. Or four or more places may be sufficient.

  As shown in FIG. 1, the casting die 13 is supplied with a dope 19 from a dope supply pipe connected to the upper end of the casting die 13. Then, the supplied dope is discharged from the casting die 13 to the endless belt support 12, and a web is formed on the endless belt support 12.

  As shown in FIG. 1, the endless belt support 12 is a metal endless belt having a mirror surface and traveling infinitely. As the belt, for example, a belt made of stainless steel or the like is preferably used from the viewpoint of peelability of the film. The width of the casting film cast by the casting die 13 is not particularly limited, but is 80 to 99% of the width of the endless belt support 12 from the viewpoint of effectively utilizing the width of the endless belt support 12. It is preferable that And in order to finally obtain an optical film with a width of 1000 to 4000 mm, the width of the endless belt support 12 is preferably 1800 to 5000 mm. Further, instead of the endless belt support, a rotating metal drum (endless drum support) having a mirror surface may be used.

  And the said endless belt support body 12 dries the solvent in dope, conveying the cast film (web) formed on the surface. The drying is performed by, for example, heating the endless belt support 12 or blowing heated air on the web. At that time, although the temperature of the web varies depending on the dope solution, the range of −5 to 70 ° C. is preferable and the range of 0 to 60 ° C. is preferable in consideration of the conveyance speed and productivity accompanying the evaporation time of the solvent. More preferred. The higher the temperature of the web, the higher the drying speed of the solvent, which is preferable. However, when the temperature is too high, foaming and flatness tend to be deteriorated.

  When heating the endless belt support 12, for example, a method of heating the web on the endless belt support 12 with an infrared heater, a method of heating the back of the endless belt support 12 with an infrared heater, the back of the endless belt support 12 And a method of heating by blowing heated air, and the like can be selected as needed.

  In addition, when blowing heated air, the wind pressure of the heated air is preferably 50 to 5000 Pa in consideration of the uniformity of solvent evaporation and the like. The temperature of the heating air may be dried at a constant temperature, or may be supplied in several steps in the running direction of the endless belt support 12.

  The time from casting the dope on the endless belt support 12 to peeling the web from the endless belt support 12 varies depending on the film thickness of the optical film to be produced and the solvent used. In consideration of the peelability from the belt support 12, it is preferably in the range of 0.5 to 5 minutes.

  The transport speed of the cast film by the endless belt support 12 is not particularly limited, but is preferably about 50 to 200 m / min, for example, from the viewpoint of productivity. Moreover, it is preferable that ratio (draft ratio) of the conveyance speed of the cast film with respect to the traveling speed of the endless belt support 12 is about 0.8 to 1.2. 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 if so, a wide film cannot be formed.

The peeling roller 14 is in contact with the surface of the endless belt support 12 on which the dope 19 is cast, and the dried web (film) is peeled by applying pressure to the endless belt support 12 side. . When the film is peeled from the endless belt support 12, the film is stretched in the film conveyance direction (Machine Direction: MD direction) by the peeling tension and the subsequent conveyance tension. For this reason, it is preferable that the peeling tension and the conveyance tension when peeling the film from the endless belt support 12 are, for example, 50 to 400 N / m ² .

  Further, the total residual solvent amount of the film when the film is peeled off from the endless belt support 12 is formed after the peelability from the endless belt support 12, the residual solvent amount at the time of peeling, the transportability after peeling, and the transport / drying. In consideration of physical properties of the optical film and the like, the content is preferably 30 to 200% by mass.

  The cutting device 16 cuts at least one end in a direction (width direction) substantially perpendicular to the film conveying method, and performs a predetermined process on the cut end film to make a strip. . Specifically, the cutting device 16 is, for example, as shown in FIG. FIG. 2 is a schematic perspective view showing the periphery of the cutting device 16.

  The cutting device 16 includes a trim cutter (not shown), a guide roller 53, a guide roller pair 42, a first pipe 43, a cutting device 44, a second pipe 45, and the like. The trim cutter cuts an end portion in a direction (width direction) substantially perpendicular to the transport method of the film 41 that has been transported, and cuts the remaining portion of the cut film to become an optical film as a shipping product. At that time, the cut end is processed as an end film 46. The guide roller 53 and the guide roller pair 42 guide the end film 46 from the upstream end of the first pipe 43 into the first pipe 43. The first pipe 43 sucks the end film 46 and conveys it to the cutting device 44 by air blowing. The cutting device 44 is connected to the downstream end of the first pipe 43, and is cut into pieces 47 in a direction substantially perpendicular to the conveying direction of the end film 46. One end of the second pipe 45 is connected to the cutting device 44, and the strip 47 is connected to the other end by air blowing to store the strip 47. To a storage tank (not shown).

  The trim cutter is not particularly limited as long as the end of the conveyed film can be cut off. As the trim cutter, it is preferable that the depth of cut with respect to the film can be arbitrarily adjusted in order to appropriately cut the end of the film. For example, the trim cutter includes a cutting blade composed of an upper round blade and a lower round blade. Rotating disc type or knife type.

  The guide roller 53 and the guide roller pair 42 are not particularly limited as long as the end film 46 can be guided into the first pipe 43. The guide roller 53 is not particularly limited as long as the end film 46 can be guided into the first pipe 43 from the upstream end of the first pipe 43, and the driven roller that follows the conveyance of the end film 46. Examples include rollers. As the guide roller pair 42, for example, the end film 46 is sandwiched, and at least one of the rollers is driven so as to apply tension to the end film 46 immediately before being sandwiched in the transport direction. The thing etc. which are rollers are mentioned. The guide roller 42 may be a driven roller that follows the conveyance of the end film 46, but the one using the driving roller as described above is provided in the first pipe 43. It is preferable because tension can be applied to the end film 46 before being guided in the transport direction, and by doing so, occurrence of flapping of the end film 46 can be suppressed. In addition, it is preferable that the rollers of the guide roller pair 42 are made of rubber or metal on which an unevenness for suppressing slippage of the end film is formed.

  The first piping 43 is connected to the cutting device 44 at the downstream end, and the inside of the first piping 43 is sucked toward the cutting device 44. That is, the first piping 43 is for conveying the end film 46 inserted into the first piping 43 to the cutting device 44 by air blowing. Thus, since the cut end film 46 is inserted into the first pipe 43 and conveyed through the first pipe 43, the end film 46 is used even when the optical film is continuously produced. It is considered that can be prevented from deviating from a predetermined conveyance path. And this suction | inhalation generate | occur | produces the wind ventilation which goes inside the 1st piping 43 toward the said cutting device 44. FIG. Specifically, for example, a compressor (compressor) or the like sends air toward the downstream side in the second pipe 45 connected via the cutting device 44 to the downstream side of the first pipe 43. The air blowing may be generated by inflow.

  Then, the inside of the first pipe 43 is sucked so that the wind speed of the wind blow used for the air feeding increases from the upstream side to the downstream side of the first pipe 43. The method for increasing the wind speed of the wind blowing from the upstream side to the downstream side is not particularly limited. Specifically, for example, the first pipe 43 may be provided with a wind speed adjusting valve or a wind suction port, but the cross-sectional area of the portion of the first pipe 43 through which the wind air flows circulates on the upstream side. It is preferable to make it small from the downstream side. By doing so, the wind speed from the upstream side to the downstream side of the first pipe 43 can be increased without using a means for increasing the wind speed of the wind blowing from the upstream side to the downstream side, for example, a wind speed adjusting valve or a wind suction port. The wind speed of blowing can be increased. The ratio of the cross-sectional area at the downstream end to the cross-sectional area at the upstream end of the first pipe 43 (downstream / upstream) is preferably 10 to 95%. % Is more preferable. The wind speed of the wind can be measured using an anemometer, specifically, a hybrid anemometer DP70 manufactured by Hiyoshi Co., Ltd.

  As described above, by increasing the wind speed on the downstream side rather than on the upstream side, the cut end film 46 is smoothly conveyed in the first pipe 43, and thus obtained by separating the end film 46. The obtained optical film can be smoothly conveyed.

  This is considered to be due to the following.

  In general, a long film such as an end film transported in a pipe tends to have a large flutter from the upstream side to the downstream side of the pipe. When the fluttering of the end film is large in this way, the smooth conveyance of the end film is hindered, and the smooth conveyance of the optical film obtained by separating the end film is hindered. And in order to suppress this fluttering, if the wind speed of a wind ventilation is raised as a whole, even if flapping can be suppressed, there exists a tendency for the edge part film to generate | occur | produce. When the end film is broken, smooth transfer of the end film is further hindered.

  Therefore, the wind speed of the air blow used when the end film 46 is conveyed is increased from the upstream side to the downstream side of the first pipe 43. Specifically, for example, the first pipe 43 having a downstream sectional area smaller than the upstream sectional area is used. By doing so, on the downstream side where the fluttering increases without increasing the overall wind speed of the wind blowing, it is considered that the direction of the wind blowing goes toward the center of the pipe so as to suppress the fluttering of the end film. . It is considered that fluttering can be effectively suppressed by such air blowing toward the center of the pipe. Furthermore, since the wind speed of wind blowing is not increased as a whole, it is considered that the breakage of the end film can be suppressed. From the above, it is considered that the end film 46 transported in the first pipe 43 can be smoothly transported. Therefore, since conveyance of the end film 46 is not performed smoothly, it is possible to suppress the conveyance of the optical film, so that the film edge is cut while conveying the film, In continuous production for producing an optical film, it is considered that the production efficiency of the optical film being smoothly conveyed is high.

  Moreover, it is preferable that the wind speed difference of the wind ventilation of the wind speed in the upstream edge part of the said 1st piping 43 and the wind speed in the downstream edge part of the said 1st piping 43 is 0.5-50 m / sec. . By doing so, flapping can be effectively suppressed by fast air blowing on the downstream side where flapping tends to increase without increasing the overall wind speed of the air blowing. That is, fluttering of the end film can be further suppressed, the end film can be transported more smoothly, and the optical film obtained by separating the end film can be transported more smoothly.

  The cutting device 44 is connected to a downstream end of the first pipe 43 and cuts the end film 46 into a strip 47 by cutting it into a direction substantially perpendicular to the conveying direction of the end film 46. There is no particular limitation as long as it can be used. Specifically, for example, as shown in FIG. 3, a long edge film provided with a rotary blade 51 and a fixed blade (not shown) and conveyed in the first pipe 43 is rotated. The thing etc. which can be cut | disconnected continuously by pinching between the rotating blade 51 and fixed blade which are present are mentioned. More specifically, for example, the rotary blade 51 includes a rotary shaft arranged along the width direction of the end film 46 that has been conveyed in the first pipe 43, and a circumferential surface of the rotary shaft. And a plurality of elongated blades extending along the rotation axis direction. The fixed blade is provided so as to face the peripheral surface of the rotation shaft of the rotary blade 51, and the long blade of the rotary blade 51 comes close by the rotation of the rotary blade 51. The cutting device 44 rotates the rotary blade 51 so that the long blade and the fixed blade of the rotary blade 51 come close to each other at predetermined intervals, and the long end film is rotated. It can be continuously cut by being sandwiched between the rotating blade 51 and the fixed blade. FIG. 3 is a schematic view showing the periphery of the cutting device 44.

  Further, as shown in FIG. 3, the cross-sectional area of the portion of the cutting device 44 through which the air blast flows is smaller than the cross-sectional area of the portion of the first pipe 43 through which the air blast flows. It is preferable. The method of reducing the cross-sectional area of the portion of the cutting device 44 through which the wind air flows is not particularly limited. Specifically, for example, as shown in FIG. By making the rotating shaft thicker, the cross-sectional area of the cutting device 44 through which the wind blows may be reduced, or the cutting device 44 itself may be reduced as shown in FIG. That is, the housing that houses the rotary blade 51 and the fixed blade may be made small. By doing so, since the cross-sectional area of the part through which the wind blowing flows of the cutting device 44 connected to the downstream end of the first pipe 43 is reduced, the wind used for the wind sending is reduced. The wind speed of blowing becomes faster from the upstream side to the downstream side of the first pipe 43. Further, the end film 46 may flutter even by a cutting process by the cutting device 44, and the fluttering may hinder smooth conveyance of the end film 46. Therefore, by making the cutting device 44 as described above, fluttering of the end film 46, which is generated by the cutting process by the cutting device 44, can be suppressed. Therefore, fluttering of the end film 46 can be further suppressed, and the optical film obtained by separating the end film 46 can be transported more smoothly.

  The second pipe 45 is connected to the cutting device 44, and the inside of the second pipe 45 is sucked from the cutting device 44 toward, for example, a storage tank for storing the strips 47. ing. That is, the second pipe 45 is for conveying the strips 47 cut by the cutting device 44 to a storage tank or the like for storing the strips 47 by air blowing. And the said thin piece 47 stored by the storage tank etc. may be used again as a film raw material. At that time, it is preferable that the strip 47 is further finely crushed.

  The cutting device 16 is provided between the peeling roller 14 and the stretching device 15, between the stretching device 15 and the drying device 17, and between the drying device 17 and the winding device 18. It is done.

  The stretching device 15 stretches the film peeled from the endless belt support 12 (the film whose end is cut by the cutting device 16) in a direction (Transverse Direction: TD direction) perpendicular 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. In addition, in 1st Embodiment, although the extending | stretching apparatus 15 was provided, it does not need to be provided. The total residual solvent amount of the film stretched by the stretching device 15 is not particularly limited, but is preferably 1 to 20% by mass from the viewpoint of cutting properties by the cutting device 16 and the like. When the stretching device 15 is not provided, it is preferable that the total residual solvent amount of the film is 1 to 20% by mass before the film is supplied to the cutting device 16.

  The drying device 17 includes a plurality of transport rollers, and dries the film while transporting the film between the rollers. In that case, you may dry using heating air, infrared rays, etc. independently, and you may dry using heating air and infrared rays together. It is preferable to use heated air from the viewpoint of simplicity. The drying temperature varies depending on the amount of residual solvent in the film, but is determined by appropriately selecting the amount of residual solvent in the range of 30 to 180 ° C. in consideration of drying time, shrinkage unevenness, stability of the amount of expansion and contraction, etc. That's fine. Moreover, it may be dried at a constant temperature, or may be divided into two to four stages of temperature, and may be divided into several stages of temperature. Further, the film can be stretched in the MD direction while being conveyed in the drying device 17. The amount of residual solvent in the film after the drying treatment in the drying device 17 is preferably 0.01 to 15% by mass in consideration of the load of the drying process, the dimensional stability expansion / contraction ratio during storage, and the like.

  The winding device 18 winds the film having a predetermined residual solvent amount on the winding core to a required length by the drying device 17. The temperature at the time of winding is preferably cooled to room temperature in order to prevent scratches and loosening due to shrinkage after winding. The winder to be used can be used without particular limitation, and may be a commonly used one, such as a constant tension method, a constant torque method, a taper tension method, or a program tension control method with a constant internal stress. Can be wound up.

  The optical film manufacturing apparatus 11 according to the first embodiment includes the cutting device 16 between the peeling roller 14 and the stretching device 15, between the stretching device 15 and the drying device 17, and the drying device. Although it provided between 17 and the said winding device 18, as above-mentioned, it is not limited to this.

  Generally, the width of a film changes due to shrinkage, drying, or the like. On the other hand, various apparatuses such as the stretching apparatus 15 and the drying apparatus 17 may have restrictions on the film width. Therefore, if three or more cutting devices 16 are provided, the film can be made to have a film width suitable for various devices even if the width of the film changes due to shrinkage or drying. Specifically, for example, the film peeled off by the peeling roller 14 changes the width of the film due to heat shrinkage, but the cutting device 16 is provided between the peeling roller 14 and the stretching device 15. Thus, the film width can be adjusted before the film is conveyed to the stretching device 15. Further, by providing the cutting device 16 between the stretching device 15 and the drying device 17, it is possible to cut an end portion having a clip mark or the like that has been deformed by a stretching process by the stretching device 15. . Further, by providing the cutting device 16 between the drying device 17 and the winding device 18, the film dried by the drying device 17 can be adjusted to a desired product width. Moreover, it is preferable that the cutting process by the cutting apparatus 16 is performed after the stretching process by the stretching apparatus 15. By doing so, the optical film in which the edge part deform | transformed by the extending process was cut can be manufactured easily with high production efficiency. For example, when the cutting device 16 is provided in one place, it is preferable to provide the cutting device 16 between the stretching device 15 and the drying device 17.

  In addition, the optical film manufacturing apparatus 11 according to the first embodiment cuts the end portions where the film thickness, the optical value, and the like are likely to be non-uniform during the manufacturing of the optical film by the above-described steps. Therefore, an optical film having a uniform film thickness, optical value and the like can be obtained.

  Moreover, it is preferable that the width | variety of an optical film is 1000-4000 mm from the point of the use to a large sized liquid crystal display device, the use efficiency of the film at the time of polarizing plate processing, and production efficiency. Moreover, it is preferable that the film thickness of a film is 30-90 micrometers from points, such as a viewpoint of thickness reduction of a liquid crystal display device, and the production stabilization of a film. Moreover, if it is the conventional optical film manufacturing apparatus, even if it is the film thickness of 30-50 micrometers which is easy to generate | occur | produce problems, such as a fracture | rupture of a film, if it is an optical film manufacturing apparatus which concerns on 1st Embodiment, it will be a malfunction. An optical film can be produced while suppressing the occurrence of. Here, the film thickness is an average film thickness, and 20 to 200 locations in the film width direction are measured with a contact-type film thickness meter manufactured by Mitutoyo Corporation, and the average value of the measured values is calculated. Shown as film thickness.

  Hereinafter, the composition of the resin solution used in the first embodiment will be described.

  The transparent resin used in the first embodiment 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. It is preferable that the production by the method is easy, the adhesiveness with the hard coat layer and the like is excellent, the optically isotropic property, and the like. 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 triacetate resin. The dope used in the first embodiment may contain fine particles. In this case, the fine particles to be used are appropriately selected according to the purpose of use, but are preferably fine particles that can scatter visible light when contained in a transparent resin. The fine particles may be inorganic fine particles such as silicon oxide or organic fine particles such as acrylic resin. As the solvent used in the first embodiment, a solvent containing a good solvent for the transparent resin can be used, and a poor solvent may be contained as long as the transparent resin does not precipitate. Examples of the good solvent for the cellulose ester resin include organic halogen compounds such as methylene chloride. Moreover, as a poor solvent with respect to a cellulose-ester-type resin, C1-C8 alcohols, such as methanol, etc. are mentioned, for example. The resin solution used in the first embodiment may contain other components (additives) other than the transparent resin, fine particles and solvent as long as the effects of the present invention are not impaired. Examples of the additive include a plasticizer, an antioxidant, an ultraviolet absorber, a heat stabilizer, a conductive substance, a flame retardant, a lubricant, and a matting agent.

  Moreover, the solution of a cellulose-ester-type resin is obtained by mixing said each composition. The obtained cellulose ester resin solution is preferably filtered using a suitable filter medium such as filter paper.

  (Melt casting method)

  Next, a case where an optical film is manufactured by a melt casting film forming method (second embodiment) will be described.

  The method for producing an optical film according to the second embodiment includes a casting step of casting a resin melt obtained by melting a transparent resin on a traveling support to form a casting film, and the casting film. A cooling process for cooling the film, a peeling process for peeling the film from the support, a stretching process for stretching the peeled film, and a winding process for winding the stretched film into a roll. The cutting step is performed between the peeling step and the winding step. For example, it is performed by an optical film manufacturing apparatus as shown in FIG. The optical film manufacturing apparatus is not particularly limited to the one shown in FIG. 4 as long as it performs each of the above steps, and may have other configurations. Here, the film means 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.

  FIG. 4 is a schematic view showing a basic configuration of an optical film manufacturing apparatus 21 by a melt casting film forming method. The optical film manufacturing apparatus 21 includes a first cooling roller 22, a casting die 23, a touch roller 24, a second cooling roller 25, a third cooling roller 26, a peeling roller 27, a conveying roller 28, a stretching apparatus 29, and a cutting apparatus 30. And a winding device 31 and the like. The casting die 23 casts a resin melt (dope) obtained by melting a transparent resin onto the surface of the first cooling roller 22. The first cooling roller 22 forms a casting film made of dope cast from the casting die 23, cools the casting film while transporting it, and transports the casting film to the second cooling roller 25. At that time, the thickness of the cast film is adjusted and the surface is smoothed by the touch roller 24 provided in contact with the first cooling roller 22. The second cooling roller 25 cools the cast film while transporting the cast film, and transports the cast film to the third cooling roller 26. By doing so, the said casting film is made into a film. The peeling roller 27 peels the film from the third cooling roller 26. The conveyance roller 28 extends in the MD direction while conveying the film. The stretching device 29 stretches the film in the TD direction. The cutting device 30 cuts the end of the stretched film, and performs a predetermined process on the cut end film. The winding device 31 winds the cooled and solidified film in a roll shape to obtain a film roll.

  The casting die 23 has the same configuration as the casting die 13 except that a resin melt is discharged as a dope instead of a resin solution.

  The first cooling roller 22, the second cooling roller 25, and the third cooling roller 26 are metal rollers having a mirror surface. As each of the rollers, for example, a roller made of stainless steel or the like is preferably used from the viewpoint of peelability of a cast film or a film. The width of the cast film cast by the casting die 23, the transport speed of the cast film by the first cooling roller 22, the second cooling roller 25, and the third cooling roller 26 are the same as in the first embodiment. It is.

  The touch roller 24 has an elastic surface, is deformed along the surface of the first cooling roller 22 by a pressing force to the first cooling roller 22, and between the first cooling roller 22, Form a nip. The touch roller 24 can be used without particular limitation as long as it is a touch roller conventionally used in the melt casting film forming method. Specifically, the thing made from stainless steel is mentioned, for example.

  The peeling roller 27 is in contact with the third cooling roller 26, and the film is peeled by applying pressure.

  The conveyance roller 28 is composed of a plurality of conveyance rollers, and can be stretched in the MD direction of the film by setting a different rotation speed for each conveyance roller.

  Further, the stretching device 29, the cutting device 30, and the winding device 31 can be the same as the stretching device 15, the cutting device 16, and the winding device 18 in the first embodiment.

  In the optical film manufacturing apparatus 21 according to the second embodiment, the cutting apparatus 30 is provided between the stretching apparatus 29 and the winding apparatus 31, but the invention is not limited thereto, and the peeling is performed. What is necessary is just to provide between the roller 27 and the said winding device 31. FIG. However, it is preferable that the cutting process by the cutting apparatus 16 is performed after the stretching process by the stretching apparatus 29. By doing so, the optical film in which the edge part deform | transformed by the extending process was cut can be manufactured easily with high production efficiency. Moreover, although the manufacturing apparatus 21 of the optical film which concerns on this 2nd Embodiment is provided with the said conveyance roller 29 and the said extending | stretching apparatus 29, it does not need to be provided and each is provided in two or more places. May be.

  In addition, the optical film manufacturing apparatus 21 according to the second embodiment cuts the end portions where the film thickness, the optical value, and the like are likely to be non-uniform during the manufacturing of the optical film by the above-described steps. Therefore, as with the optical film formed by the optical film manufacturing apparatus 11 according to the first embodiment, an optical film having a uniform film thickness, optical value, and the like can be obtained.

  Moreover, it is preferable that the width | variety of an optical film is 1000-4000 mm from the point of the use to a large sized liquid crystal display device, the use efficiency of the film at the time of polarizing plate processing, and production efficiency. Moreover, it is preferable that the film thickness of a film is 30-90 micrometers from points, such as a viewpoint of thickness reduction of a liquid crystal display device, and the production stabilization of a film. Moreover, if it is the conventional optical film manufacturing apparatus, even if it is the film thickness of 30-50 micrometers which is easy to generate | occur | produce problems, such as a fracture | rupture of a film, if it is an optical film manufacturing apparatus which concerns on 1st Embodiment, it will be a malfunction. An optical film can be produced while suppressing the occurrence of. Here, the film thickness is an average film thickness, and 20 to 200 locations in the film width direction are measured with a contact-type film thickness meter manufactured by Mitutoyo Corporation, and the average value of the measured values is calculated. Shown as film thickness.

  Hereinafter, the composition of the resin melt used in the second embodiment will be described.

  The transparent resin used in the second embodiment can be the same as the transparent resin in the first embodiment as long as it can be heated and melted. In addition, the same composition as in the first embodiment can be used for other compositions.

  Moreover, this invention is not limited to the said 1st Embodiment and 2nd Embodiment, It can apply to the method of manufacturing an optical film by cutting an edge part, conveying a film continuously.

  (Polarizer)

  The polarizing plate according to the present embodiment includes a polarizing element and a transparent protective film disposed on the surface of the polarizing element, and the transparent protective film is an optical film according to the present embodiment. 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. Moreover, the said optical film may be laminated | stacked also on the other surface of the said polarizing element, and the transparent protective film for another polarizing plate may be laminated | stacked. As the transparent protective film for the polarizing plate, for example, as a commercially available cellulose ester film, KC8UX2M, KC4UX, KC5UX, KC4UY, KC8UY, KC12UR, KC8UY-HA, KC8UX-RHA (above, manufactured by Konica Minolta Opto) Is preferably used. Or you may use resin films, such as cyclic olefin resin other than a cellulose-ester film, an acrylic resin, polyester, a polycarbonate. In this case, since the saponification suitability is low, it is preferable to perform an adhesive process on the polarizing plate through an appropriate adhesive layer.

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

  Moreover, as a specific example of the said polarizing element, a polyvinyl alcohol-type polarizing film is mentioned, for example. Polyvinyl alcohol polarizing films include those obtained by dyeing iodine on polyvinyl alcohol films and those obtained by dyeing dichroic dyes. As the polyvinyl alcohol film, a modified polyvinyl alcohol film modified with ethylene is preferably used.

  The polarizing element is obtained as follows, for example. First, a film is formed using a polyvinyl alcohol aqueous solution. The obtained polyvinyl alcohol film is uniaxially stretched and then dyed or dyed and then uniaxially stretched. And preferably, a durability treatment is performed with a boron compound.

  The thickness of the polarizing element is preferably 5 to 40 μm, more preferably 5 to 30 μm, and more preferably 5 to 20 μm.

  When the cellulose ester resin film is laminated on the surface of the polarizing element, it is preferable to bond the cellulose ester resin film with an aqueous adhesive mainly composed of completely saponified polyvinyl alcohol or the like. Moreover, in the case of resin films other than a cellulose ester-type resin film, it is preferable to carry out the adhesive process to a polarizing plate through a suitable adhesion layer.

  Since the polarizing plate as described above uses the optical film according to the present embodiment as a transparent protective film of the polarizing element, the optical film has a uniform film thickness, optical value, and the like as a whole. When applied to a liquid crystal display device, a polarizing plate capable of realizing high image quality of a liquid crystal display device excellent in contrast and the like can be obtained. Furthermore, when a wide optical film obtained by a stretching process or the like is used as an optical film used as a transparent protective film of a polarizing element, it can be applied to a liquid crystal display device having a large screen.

  (Liquid crystal display device)

  The liquid crystal display device according to this embodiment 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. . 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. Since such a liquid crystal display device uses the optical film according to the present embodiment as a transparent protective film for a polarizing plate, the optical film has a uniform film thickness, optical value, and the like as a whole. A high-quality liquid crystal display device with improved contrast and the like can be provided. Further, by using a wide film as the optical film according to this embodiment, a large screen can be obtained.

  As mentioned above, although embodiment concerning the present invention was described in detail, the above-mentioned explanation is illustration in all the aspects, and the present invention is not limited to these. It is understood that countless variations that are not illustrated can be envisaged without departing from the scope of the present invention.

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

  Example A

  In Example A, the case where two types of pipes having different cross-sectional areas are connected so that the cross-sectional area of the portion of the first pipe through which the wind air flows circulates from the upstream side to the downstream side is examined. did.

  [Example 1]

  (Preparation of dope)

  First, 100 parts by mass of cellulose triacetate resin (acetyl group substitution degree: 2.88) is added as a transparent resin to a dissolution tank containing 418 parts by mass of methylene chloride, and further 8 parts by mass of triphenyl phosphate and biphenyl diphenyl phosphate. (Liquid plasticizer) 4 parts by mass, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxyphenyl) -2H-benzotriazole (liquid UV absorber) 1 part by mass, silicon dioxide 0.1 parts by mass of fine particles (Aerosil R972V) and 23 parts by mass of ethanol were added. The silicon dioxide fine particles were added in a state dispersed in ethanol. And after raising the liquid temperature to 80 ° C., the mixture was stirred for 3 hours. By doing so, a cellulose triacetate resin solution was obtained. Then, stirring was complete | finished and it was left until the liquid temperature became 43 degreeC. Then, the obtained resin solution was filtered using a filter paper having 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. The resin solution thus obtained was used as a dope to produce an optical film as follows.

  (Manufacture of optical film)

First, the temperature of the obtained dope was adjusted to 35 ° C., and the temperature of the endless belt support was adjusted to 25 ° C. Then, using an optical film manufacturing apparatus as shown in FIG. 1, an endless belt support made of an endless belt made of stainless steel and polished to a super-mirror surface, with a conveyance speed of 60 m / min from a casting die (coat hanger die). The dope was cast. By doing so, a web was formed on the endless belt support and conveyed while drying. Then, the web is peeled off from the endless belt support as a film, dried while being conveyed in a roll at 90 ° C., and when the residual solvent amount is 10%, the film is drawn at 100 ° C. using a stretching device (tenter). The film was stretched 1.40 times in the width direction while holding both ends of the film with clips. Then, using the cutting device, the area (60 mm width from the film end) held by the clip was cut to obtain an optical film having a thickness of 40 ± 10 μm. At that time, the cut end film having a thickness of 40 ± 10 μm was inserted into the first pipe and cut into strips by a cutting device. As the first piping, a 150A steel pipe (with a cross-sectional area of the hollow portion of about 18900 mm ² ) is connected to the upstream side, and a steel pipe with a cross-sectional area of the hollow portion of about 2700 mm ² is connected to the downstream side, and the downstream end is used. A cutting device was connected. In addition, it was made to attract | suck so that the wind speed in the upstream of 1st piping might be 10 m / sec.

  [Examples 2 to 6 and Comparative Example 1]

  Examples 2 to 6 and Comparative Example 1 are the same as Example 1 except that the steel pipe used on the downstream side is replaced with a steel pipe having a cross-sectional area of the hollow portion shown in Table 1.

  Examples 1 to 6 and Comparative Example 1 were evaluated as follows.

  (Tension applied to end film)

  The tension of the end film conveyed between the guide roller 53 and the guide roller pair 42 was measured with a tensiometer, and the tension was evaluated as the tension applied to the end film.

  (Swing width)

  The end film transported in the first pipe was photographed by photographing means installed in the vicinity of the connection part between the upstream steel pipe and the downstream steel pipe in the first pipe. And the maximum moving distance of the film conveyed in the 1st piping from the reference | standard position was measured from the image | photographed image on the basis of the film of the state which has not fluttered at all. The flutter width (mm) was defined as twice the measured maximum moving distance.

  (Film tears)

  It was visually confirmed whether or not the end film was broken before the end film transported in the first pipe was transported to the cutting device.

  (Transportability)

  The transportability of the end film was evaluated according to the following criteria.

A: No film tearing occurs and the flapping width is 10 mm or less. ○: The fluttering width exceeds 10 mm and is 30 mm or less.

  The evaluation results are shown in Table 1.

  As can be seen from Table 1, in the first pipe, compared to the case where the wind blown in the first pipe becomes faster from the upstream part to the downstream part (Examples 1 to 6) and the case where it does not become faster (Comparative Example 1). The transportability of the end film transported to the surface is excellent.

  This means that the wind speed of the air blowing used for transporting the end film is increased from the upstream side to the downstream side of the first pipe without increasing the overall wind speed of the wind blowing. In the downstream side where fluttering increases, it is considered that this is an effect of the direction of the wind blowing toward the center of the first pipe so as to suppress fluttering of the end film. It is thought that fluttering could be effectively suppressed by such wind blowing toward the center of the pipe.

  In addition, when the wind ventilation in 1st piping did not become quick from an upstream part to a downstream part (comparative example 1), the film tearing generate | occur | produced. This indicates that the fluttering of the end film is large when the wind blowing in the first pipe does not increase from the upstream part to the downstream part (Comparative Example 1). The state in which the end film is fluttered is a state in which a force, that is, tension, is applied to the end film in a direction perpendicular to the conveying direction of the end film. Therefore, when the end film is transported in a state where the fluttering is large, it is considered that the tension generated by the fluttering of the end film is applied to the end film in a direction perpendicular to the transport direction of the end film. That is, it is considered that the tension generated by the flapping is added to the end film, and the tension applied to the end film is increased.

  Moreover, the ratio (downstream side / upstream side) of the cross-sectional area on the downstream side (downstream side end part) to the cross-sectional area on the upstream side (upstream side end part) is 15 to 85% (Example 2). 5) Compared with the case where it is less than 15% (Example 1) and the case where it exceeds 85% (Example 6), the transportability of the end film transported into the first pipe is excellent.

  Example B

  In Example B, the section of the cutting device connected to the downstream end of the first pipe through which the wind blast flows is the portion through which the wind blast flows downstream of the first pipe. The case where it was smaller than the cross-sectional area of was examined.

  [Example 7]

(Preparation of dope)
A dope was prepared in the same manner as in Example 1.

  (Manufacture of optical film)

First, the temperature of the obtained dope was adjusted to 35 ° C., and the temperature of the endless belt support was adjusted to 25 ° C. Then, using an optical film manufacturing apparatus as shown in FIG. 1, an endless belt support made of an endless belt made of stainless steel and polished to a super-mirror surface, with a conveyance speed of 60 m / min from a casting die (coat hanger die). The dope was cast. By doing so, a web was formed on the endless belt support and conveyed while drying. Then, the web is peeled off from the endless belt support as a film, dried while being conveyed in a roll at 90 ° C., and when the residual solvent amount is 10%, the film is drawn at 100 ° C. using a stretching device (tenter). The film was stretched 1.40 times in the width direction while holding both ends of the film with clips. Then, using the cutting device, the area (60 mm width from the film end) held by the clip was cut to obtain an optical film having a thickness of 40 ± 10 μm. At that time, the cut end film having a thickness of 40 ± 10 μm was inserted into the first pipe and cut into strips by a cutting device. At that time, as a cutting device connected to the downstream end portion of the first pipe, a cutting device having a cross-sectional area of about 2700 mm ² in a portion through which the wind air circulates was used. Moreover, it was made to attract | suck so that the wind speed in a 1st piping might be 10 m / sec.

  [Examples 8 to 12 and Comparative Example 2]

  Examples 8 to 12 and Comparative Example 2 are the same as Example 7 except that the cutting device is replaced by a cutting device in which the cross-sectional area of the portion through which the wind air flows is the cross-sectional area shown in Table 2.

  Examples 7 to 12 and Comparative Example 2 were evaluated as follows.

  (Tension applied to end film)

  The tension of the end film conveyed between the guide roller 53 and the guide roller pair 42 was measured with a tensiometer, and the tension was evaluated as the tension applied to the end film.

  (Swing width)

  The end film transported in the first pipe was photographed by photographing means installed in the vicinity of the connection part between the first pipe and the cutting device. And the maximum moving distance of the film conveyed in the 1st piping from the reference | standard position was measured from the image | photographed image on the basis of the film of the state which has not fluttered at all. The flutter width (mm) was defined as twice the measured maximum moving distance.

  (Transportability)

  The transportability of the end film was evaluated according to the following criteria.

A: The flapping width is 10 mm or less. B: The fluttering width exceeds 10 mm and is 30 mm or less. X: The flapping width exceeds 30 mm.

  The evaluation results are shown in Table 2.

  As can be seen from Table 2, in the first pipe, when the wind speed of the wind blowing increases from the upstream portion to the downstream portion (Examples 7 to 12), compared with the case where it does not increase (Comparative Example 2), the first The transportability of the end film transported into the pipe is excellent.

  This means that the wind speed of the air blowing used for transporting the end film is increased from the upstream side to the downstream side of the first pipe without increasing the overall wind speed of the wind blowing. In the downstream side where fluttering increases, it is considered that this is an effect of the direction of the wind blowing toward the center of the first pipe so as to suppress fluttering of the end film. It is thought that fluttering could be effectively suppressed by such wind blowing toward the center of the pipe.

  In addition, when the wind ventilation in 1st piping did not become quick from an upstream part to a downstream part (comparative example 2), the film tearing generate | occur | produced. This indicates that the fluttering of the end film is large when the wind blowing in the first pipe does not increase from the upstream part to the downstream part (Comparative Example 2).

  Moreover, when the ratio (cutting device / first piping) of the cross-sectional area of the portion through which the wind blower of the cutting device circulates relative to the sectional area of the first piping is 15 to 85% (Examples 8 to 11), Compared with the case where it is less than 15% (Example 7) and the case where it exceeds 85% (Example 12), the transportability of the end film transported into the first pipe is excellent.

  Moreover, although the said Example gave and demonstrated the Example of manufacture by a solution casting method, the same result was obtained even if it was manufacture by the melt casting method.

  The present specification discloses various aspects of the technology as described above, and the main technologies are summarized below.

  One aspect of the present invention is to form an optical film by cutting at least one end in a direction perpendicular to the film transport direction while separating the film, and separating the cut end film. A cutting step and a conveying step of inserting the separated end film into the pipe and conveying the inside of the pipe by air sending, and in the conveying step, the wind speed of the wind blowing used for the air sending is The method for producing an optical film is characterized in that the speed increases from the upstream side to the downstream side of the pipe.

  According to the above configuration, since the optical film is manufactured by cutting the end of the film while conveying the film, the optical film can be continuously produced. And in the continuous production of such an optical film, the manufacturing method of an optical film with high production efficiency in which the optical film obtained by isolate | separating the cut edge part film can be smoothly conveyed can be provided.

  This is considered to be due to the following.

  First, since the cut end film is inserted into the pipe and transported through the pipe, it is possible to suppress the end film from coming off from a predetermined transport path even when the optical film is continuously produced. it is conceivable that.

  Moreover, generally the end part film which conveys the inside of the piping tends to have a large flutter from the upstream side to the downstream side of the piping. If the fluttering of the end film is large, smooth transport of the end film is hindered, and smooth transport of the optical film obtained by separating the end film is hindered. And in order to suppress this fluttering, if the wind speed of a wind ventilation is raised as a whole, even if flapping can be suppressed, there exists a tendency for the edge part film to generate | occur | produce. When the end film is broken, smooth transfer of the end film is further hindered. Therefore, by increasing the wind speed of the wind blowing used when conveying the end film from the upstream side to the downstream side of the pipe, the fluttering is large without increasing the overall wind speed of the wind blowing. On the downstream side, it is considered that the direction of the wind blows toward the central portion of the pipe so as to suppress fluttering of the end film. It is considered that fluttering can be effectively suppressed by such air blowing toward the center of the pipe. Furthermore, since the wind speed of wind blowing is not increased as a whole, it is considered that the breakage of the end film can be suppressed. From the above, it is considered that the end film transported in the pipe can be smoothly transported.

  Therefore, the conveyance of the optical film can be prevented from being obstructed by the fact that the conveyance of the end film is not smoothly performed, so that the optical film is cut by cutting the edge of the film while conveying the film. In the method for producing an optical film, it is considered that a method for producing an optical film with high production efficiency in which the optical film obtained by separating the end film is smoothly conveyed can be provided.

  Moreover, in the manufacturing method of the optical film, the wind speed difference between the wind speed at the upstream end of the pipe and the wind speed at the downstream end of the pipe is 0.5 to 50 m / sec. Is preferred.

  According to such a configuration, flapping of the end film can be further suppressed, and the end film can be transported more smoothly. Therefore, the optical film obtained by separating the end film can be transported more smoothly.

  Moreover, in the manufacturing method of the said optical film, it is preferable that the cross-sectional area of the part which the said wind ventilation distribute | circulates becomes small from the upstream to the downstream.

  According to such a configuration, it is possible to increase the wind speed of the wind blowing from the upstream side to the downstream side of the pipe without separately using means for increasing the wind speed of the wind blowing from the upstream side to the downstream side. That is, fluttering of the end film can be more easily suppressed, and the end film can be transported more smoothly. Therefore, smooth conveyance of the optical film obtained by separating the end film can be realized more easily.

  Moreover, in the manufacturing method of the optical film, the cutting unit connected to the downstream end of the pipe includes a cutting step of cutting while conveying the end film, and the wind blowing of the cutting unit It is preferable that the cross-sectional area of the part which distribute | circulates is smaller than the cross-sectional area of the part which the said wind ventilation in the downstream of the said piping distribute | circulates.

  According to such a configuration, flapping of the end film can be further suppressed, and the end film can be transported more smoothly. Therefore, the optical film obtained by separating the end film can be transported more smoothly.

  First of all, since the cross-sectional area of the portion through which the wind blowing flows of the cutting means connected to the downstream end of the pipe is small, the wind speed of the wind blowing used for the wind sending is low. This is considered to be because it becomes faster from the upstream side to the downstream side of the pipe.

  In general, the conveyance of the end film is also affected by the fluttering of the end film generated by the cutting step. That is, according to the above configuration, it is considered that the fluttering of the end film, which is generated by the cutting means connected to the downstream end of the pipe, can be suppressed.

  Therefore, it is considered that the fluttering of the end film can be further suppressed, and the optical film obtained by separating the end film can be transported more smoothly.

  Further, in the method for producing an optical film, a casting step of casting a resin solution containing a transparent resin on a traveling support to form a film, and a peeling step of peeling the film from the support And a stretching step for stretching the peeled film, and a winding step for winding the stretched film into a roll, and the cutting step is performed after the peeling step and before the winding step. Are preferred.

  In such a solution casting film forming method capable of continuous production of a film, an optical element having an edge cut by performing the cutting step after the peeling step and before the winding step. The film can be easily produced with high production efficiency.

  Moreover, in the manufacturing method of the optical film by the solution casting film forming method as mentioned above, it is preferable that the said cutting process is performed after the said extending process. According to such a structure, the optical film in which the edge part deform | transformed by the extending process was cut can be manufactured easily with high production efficiency.

  Further, in the method for producing an optical film, a casting step of casting a resin melt obtained by melting a transparent resin on a traveling support to form a casting film, and cooling the casting film. A cooling step for forming a film, a peeling step for peeling the film from the support, a stretching step for stretching the peeled film, and a winding step for winding the stretched film into a roll. It is preferable that the process is performed after the peeling process and before the winding process.

  In such a melt casting film forming method capable of continuous production of a film, an optical element having an edge cut by applying the cutting step after the peeling step and before the winding step. The film can be easily produced with high production efficiency.

  In the method for producing an optical film by the melt casting film forming method as described above, it is preferable that the cutting step is performed after the stretching step. According to such a structure, the optical film in which the edge part deform | transformed by the extending process was cut can be manufactured easily with high production efficiency.

  Another aspect of the present invention is an optical film obtained by the method for producing an optical film.

  According to such a configuration, since the end portion where the film thickness, the optical value, etc. are likely to be non-uniform is cut during the production of the optical film, the film thickness, the optical value, etc. are uniform throughout. Can be provided.

  Another aspect of the present invention is a polarizing plate including a polarizing element and a transparent protective film disposed on at least one surface of the polarizing element, wherein the transparent protective film is the optical film. It is a polarizing plate characterized by being.

  According to such a configuration, an optical film having a uniform film thickness, optical value, and the like is applied as a transparent protective film of the polarizing element, so that, for example, when applied to a liquid crystal display device, contrast, etc. A polarizing plate capable of realizing high image quality of an excellent liquid crystal display device is obtained. Furthermore, when a wide optical film obtained by a stretching process or the like is used as an optical film used as a transparent protective film of a polarizing element, it can be applied to a liquid crystal display device having a large screen.

  Another aspect of the present invention is a liquid crystal display device including 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 a liquid crystal display device characterized by being the polarizing plate.

  According to such a configuration, a polarizing plate provided with an optical film having a uniform film thickness, optical value, and the like is used, so that high image quality of a liquid crystal display device excellent in contrast and the like can be realized. Furthermore, when a wide optical film obtained by a stretching process or the like is used as a transparent protective film for a polarizing plate, a large screen can be realized.

  According to the present invention, in the method for producing an optical film by cutting an end of the film while transporting the film, the optical film obtained by separating the end film is smoothly transported. A method for producing an optical film with high efficiency is provided. Moreover, the optical film obtained by the manufacturing method of such an optical film, the polarizing plate which used the said optical film as a transparent protective film, and the liquid crystal display device provided with the said polarizing plate are provided.

Claims (8)

A cutting step of forming an optical film by cutting at least one end in a direction perpendicular to the film transport direction while transporting the film, and separating the cut end film;
A separation step of inserting the separated end film into the pipe and conveying the inside of the pipe by air sending;
The method for producing an optical film characterized in that, in the transporting step, the wind speed of the air blow used for the air feeding increases from the upstream side to the downstream side of the pipe.   The wind speed difference between the wind speed at the upstream end of the pipe and the wind speed at the downstream end of the pipe is 0.5 to 50 m / sec. Manufacturing method of optical film.   3. The method for producing an optical film according to claim 1, wherein a cross-sectional area of a portion of the pipe through which the wind air flows is reduced from an upstream side to a downstream side. The cutting means connected to the downstream end of the pipe comprises a cutting step of cutting while conveying the end film,
The cross-sectional area of the part where the wind blower circulates in the cutting means is smaller than the cross-sectional area of the part where the wind blower circulates on the downstream side of the pipe. The manufacturing method of the optical film of any one. A casting step of casting a resin solution containing a transparent resin on a traveling support to form a film;
A peeling step of peeling the film from the support;
A stretching step of stretching the peeled film;
A winding step of winding the stretched film into a roll,
The method for producing an optical film according to claim 1, wherein the cutting step is performed after the peeling step and before the winding step.   The method for producing an optical film according to claim 5, wherein the cutting step is performed after the stretching step. A casting step of casting a resin melt obtained by melting the transparent resin on a traveling support to form a casting film;
A cooling step of cooling the cast film to form a film;
A peeling step of peeling the film from the support;
A stretching step of stretching the peeled film;
A winding step of winding the stretched film into a roll,
The method for producing an optical film according to claim 1, wherein the cutting step is performed after the peeling step and before the winding step. The method for producing an optical film according to claim 7, wherein the cutting step is performed after the stretching step.

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