WO2016203835A1

WO2016203835A1 - Method for producing optical film

Info

Publication number: WO2016203835A1
Application number: PCT/JP2016/062415
Authority: WO
Inventors: 研一風間
Original assignee: コニカミノルタ株式会社
Priority date: 2015-06-19
Filing date: 2016-04-19
Publication date: 2016-12-22
Also published as: JPWO2016203835A1; JP6737270B2

Abstract

The present invention pertains to a method for producing an optical film including an air-transport step for cutting the edge parts of a film manufactured by a melt-casting film-formation method or solution-casting film-formation method and transporting the edge parts by air to a recovery pipe, the method for producing an optical film characterized in that openings are present in the walls of a suction duct for delivering the edge parts to the recovery pipe used in the air-transport step, and the ratio of the opening area due to the openings to the total opening area combining a suction port area of the suction duct and the openings is 40-70%.

Description

Manufacturing method of optical film

The present invention relates to a method for producing an optical film, and more particularly to a method for producing an optical film used in a liquid crystal image display device.

Liquid crystal display devices have been widely used due to improvements in image quality and high definition technology. 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 optical films, it is conceivable to continuously produce optical films. 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 resin obtained by heating and melting a raw material resin is cast on a support, and the film obtained by cooling and solidifying to some extent is peeled off from the support, and the peeled film is removed with a transport roller. This is a method for producing a resin film by further cooling and solidifying while being conveyed.

The resin film obtained by the method as described above sometimes had curls or wrinkles 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 risk.

In order to solve 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 wound as a roller as an optical film. A part (ear part) is cut out (trimmed) with a trim cutter. That is, during the production of the resin film, the film that remains by cutting the ear portion and separating the cut end film is used as the optical film.

However, unless the end film (ear part) 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, There is a concern that the end film after cutting 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 is also a case.

As a method for cutting and transporting the ear portion of such a film, a method for preventing the clogging of the discharge pipe by performing static elimination on the ear portion (Patent Document 1), or a suction port inlet of the ear portion. A method of blowing wind toward the outside (Patent Document 2) has been reported.

According to Patent Document 1, it is possible to prevent clogging of the ear part to some extent in the pipe for discharging the ear part. However, even if this method is used, it is difficult to prevent the ear portion from adhering to the inner wall of the suction duct.

Further, according to Patent Document 2, the ears of the film can be efficiently collected. However, in the case of a thin film that is in high demand in recent years, the ears sometimes flutter by blowing air.

As described above, in the conventional technology, when the cut ear portion is blown to the suction duct, the ear portion flutters due to the suction air, and the ear portion adheres to the inner wall of the suction duct, thereby changing the tension of the ear portion. May occur. If this fluctuation in tension is transmitted to the upstream slitting section, the slitting that cuts off the ear becomes unstable, and there is a risk of generating chips. When the chips adhere to the product, there is a problem that the quality of the obtained film is deteriorated.

The present invention has been made in view of such circumstances, and in a method for producing an optical film by cutting off a film ear using a melt casting film forming method or a solution casting film forming method, It is an object of the present invention to provide a method for producing an optical film having a high production efficiency in which the ear portion is smoothly collected without causing a flutter or the like.

JP 2002-370242 A JP 2010-46932 A

As a result of intensive studies, the present inventor has found that the above problem can be solved by a method for producing an optical film having the following configuration, and has further completed the present invention based on such findings.

The method for producing an optical film according to one embodiment of the present invention includes a step of obtaining a polymer film by a melt casting film forming method or a solution casting film forming method, cutting out the ears of the obtained film, and collecting the ears An optical film manufacturing method including an air blowing process for air blowing to a pipe, wherein the suction duct wall for sending the ear part to the recovery pipe used in the air blowing process has an opening, In addition, the ratio of the opening area by the opening is 40% to 70% with respect to the total opening area including the suction opening area of the suction duct and the opening.

According to the present invention, in the method for producing an optical film by cutting off the film ears while conveying the film, the film ears can be stably cut off, and the chips to the obtained film, etc. It is possible to provide a high-quality optical film by suppressing the adhesion of.

FIG. 1 is a schematic diagram showing a basic configuration of an example of an apparatus for producing an optical film by a solution casting film forming method in the present embodiment. FIG. 2 is a schematic perspective view showing an example of a suction duct for collecting the ear portion in the present embodiment.

Hereinafter, embodiments according to the method for producing an optical film of the present invention will be specifically described, but the present invention is not limited thereto.

(Optical film manufacturing method)
The method for producing an optical film according to the present embodiment includes a step of obtaining a polymer film by a melt casting film forming method or a solution casting film forming method, cutting out the ears of the obtained film, and using the ears to a recovery pipe. A method for producing an optical film including an air blowing step for air blowing, wherein an opening is present in a wall of a suction duct for feeding an ear portion to a recovery pipe used in the air blowing step, and The ratio of the opening area by the opening is 40% to 70% with respect to the total opening area including the suction opening area of the suction duct and the opening.

The manufacturing method of the optical film according to the present embodiment is not particularly limited as long as it includes the step of obtaining the film and the air feeding step. Specifically, for example, in the case of a solution casting film forming method, a method for producing an optical film by performing the air blowing process at a predetermined position after the film is peeled off from the support and wound up into a roller shape. Etc.

In the following, a solution flow including a peeling step of peeling a web formed by casting a polymer dope on a support from the support, and a drying step of drying the web peeled from the support to obtain a film. Although an embodiment including a step of obtaining a polymer film by a casting film forming method will be described, the present invention is not limited to this, and the film obtained by the melt casting film forming method is cut off at the ear portion of the obtained film. The manufacturing method of the optical film including the air feeding process which air-winds the ear | edge part to collection | recovery piping may be sufficient.

The optical film manufacturing method according to the present embodiment is formed by casting a resin solution (dope) containing a transparent resin (polymer) on a traveling support by, for example, a solution casting film forming method. Provided with a peeling step for peeling the peeled web from the support, a drawing step for drawing the peeled film, a winding step for winding the drawn film into a roller, and the like. It can implement by performing between a process and the said winding-up process. More specifically, for example, it is performed by an optical film manufacturing apparatus as shown in FIG. In addition, as an optical film manufacturing apparatus, if it performs each said process, it will not specifically limit to what is shown in FIG. 1, The manufacturing apparatus of another structure may be sufficient. Moreover, in this specification, a film is 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. To tell. The position of the air blowing process may be anywhere as long as it is between the peeling process and the winding process.

FIG. 1 shows one embodiment of an apparatus for carrying out the manufacturing method of the present embodiment, and FIG. 2 shows its main part (suction duct of the ear part).

1 and 2, each symbol indicates the following. 1: support, 5: peeling roller, 6: drying device, 8: trimming device, 9: suction duct, 10: film winding device, 12: suction port, 13: opening, 102: winding core, 200, 201: Static elimination blower, F: Film, F1: Ear, F2: Rolled film, W: Web.

In FIG. 1, an optical film manufacturing apparatus includes a support 1 made of an endless belt, a dope casting die 2 for casting a resin solution (dope) containing a transparent resin on the support 1, and a support 1. The heating and

drying devices

3 and 4 for forming the web by heating and drying the dopes casted on the front and back sides of the upper and lower transfer paths and cast on the support 1, and the web (W) from the support 1. The web peeling roller 5 to be peeled off, the drying device 6 for obtaining the film F by drying the web (W) peeled off from the support 1, and the width of the film F in the width direction both sides of the obtained film F are gripped. A tenter device 7 that keeps the film F constant or stretches the film F in the width direction, and a trimming device 8 that cuts the film ear F1 whose width is restricted by the tenter device 7 and finishes the film F to the final product dimensions. , Cut Suction duct (ear part discharge conduit) 9 for discharging the taken ear part F1 and embossing for forming a number of micro protrusions having a height of several μm on both side edges in the width direction of the film F finished to the final product dimensions A processing device (not shown) and a film winding device 10 for winding the embossed film F are provided.

As shown in FIG. 1, the endless belt support 1 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 2 is not particularly limited. However, from the viewpoint of effectively utilizing the width of the endless belt support 1, the width of the endless belt support 1 is 80 to 99%. It is preferable that In addition, as a support body, you may use what consists of metal drums instead of an endless belt.

Further, the trimming device 8 may be installed at one place as shown in FIG. 1 or at a plurality of places.

Examples of the heating and

drying devices

3 and 4 include a method of heating the web on the endless belt support 1 with an infrared heater, a method of heating the back surface of the endless belt support 1 with an infrared heater, and a web on the endless belt support 1. There are a method of heating by blowing heated air, a method of heating by blowing heated air to the back surface of the endless belt support 1, and the like, which can be appropriately selected as necessary.

The transport speed of the cast film by the endless belt support 1 is not particularly limited, but is preferably about 50 to 200 m / min, for example, from the viewpoint of productivity. Further, the ratio (draft ratio) of the transport speed of the cast film to the travel speed of the endless belt support 1 is preferably about 0.8 to 5.0. 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 dried web (film) is peeled off by the peeling roller 5. When the film is peeled from the endless belt support 1, the film is stretched in the film transport direction (machine direction: MD direction) by the peeling tension and the subsequent transport tension. For this reason, it is preferable that the peeling tension and the conveying tension when peeling the film from the endless belt support 1 are, for example, 50 to 400 N / m ² .

Further, the total residual solvent amount of the film when the film is peeled from the endless belt support 1 is obtained after the peelability from the endless belt support 1, the residual solvent amount at the time of peeling, the transportability after peeling, and the transport / drying. Considering the physical properties of the optical film, it is preferably 10 to 200% by mass.

The drying device 6 may be, for example, one in which a plurality of transport rollers 63 are provided in a staggered arrangement in a housing 60 having a hot air blowing port 61 and a discharge port 62. In the drying device 6, the web W is transported by being hung on the transport roller 63 in the housing 60, and is dried by hot dry air blown from the hot air blowing port 61 during the transport. Also, a tenter that is provided with a plurality of drying devices 6 and regulates the width by holding the web width side edge portions between the drying devices 6 to keep the web width constant or by stretching the web in the width direction. A (stretching) device 7 may be provided. Furthermore, the tenter device 7 may have a drying function, and the film F may be obtained by finally drying the tenter device 7.

The drying device 6 may be dried by using heated air, infrared rays, or the like alone, or may be dried by using heated air and infrared rays in combination. 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. However, the drying temperature is appropriately selected in the range of 30 to 180 ° C. depending on the amount of residual solvent in consideration of drying time, shrinkage unevenness, stability of expansion and contraction, and the like. That's fine. Further, 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. In addition, the film can be stretched in the MD direction while being transported in the drying device 6.

Further, the tenter device 7 stretches the film peeled from the endless belt support 1 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.

Next, the trimming device 8 is provided between the tenter device 7 and the winding device 10 and includes, for example, a roller 80 provided with round blades (trim cutters, not shown) at both ends of the peripheral surface. The film winding apparatus 10 may include a plurality of transport rollers 101 and one winding core 102 provided in the housing 100. Then, the film F finished to the final product size in the trimming device 8 is conveyed on the conveyance roller 101 in the housing 100 and is wound on the winding core 102.

The trim cutter of the trimming device 8 cuts off the end in the direction (width direction) substantially perpendicular to the transport method of the transported film so that the remaining portion of the cut film becomes an optical film as a shipping product. Cut. The edge part cut off in that case is processed as the ear | edge part film F1.

The suction duct 9 sucks the ear part F1 and blows it to the ear part collecting part. The collected ears are finely cut by a cutting device (not shown) or the like and transported to a storage tank (not shown) or the like as a fine piece.

The configuration of 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.

In the present embodiment, the suction duct 9 is a pipe for blowing the film ears cut by the trimming device 8 to the collection unit, and the wall has an opening, and The ratio of the opening area by the opening is 40% to 70% with respect to the total opening area including the suction port area of the suction duct and the opening.

Thus, since the flow of the wind which goes to the center part of a duct from the wall surface of a duct generate | occur | produces by providing the opening part in the wall of the suction duct 9 in a predetermined ratio, it is for sending an ear | edge part into collection | recovery piping. It is thought that the fluttering, adhesion, and entanglement of the ears in the suction duct can be suppressed more than before. Thereby, it is possible to stably cut out the ears of the film and transport and collect the ears, and to suppress the adhesion of chips and the like to the obtained film, thereby providing a high-quality optical film. It is considered possible.

The inside of the suction duct 9 is sucked toward the downstream, and this suction is performed by generating wind blown toward the downstream inside the suction duct 9. Specifically, for example, by installing a blower or the like on the downstream side of the suction duct 9, the air blowing can be generated by flowing air toward the downstream side.

FIG. 2 is a schematic perspective view showing an example of the suction duct 9 for collecting the ear portion in the present embodiment. An opening 13 exists in the wall of the suction duct 9, and the opening 13 has a total opening area that is the sum of the area of the suction port 12 of the suction duct and the area of the opening 13. The ratio of the opening area is 40% to 70%.

FIG. 2 shows an example in which a circular opening 13 is provided in a suction duct 9 having a rectangular cross-sectional shape, but the suction duct of the present embodiment is not limited to this, and the cross-sectional shape of the duct may be circular. However, the shape of the opening may be other than circular.

In the case of a suction duct as shown in FIG. 2, the ratio of the area of the opening 13 can be calculated as follows.

When r is the radius of the opening, and N is the total number of openings,
Total area of openings S1 = πr ² × N
Opening area S2 of suction duct suction port: a × b
(A and b show the inner method of each side of the suction duct suction port as shown in FIG. 2.)
Ratio (%) of opening area S1 due to the opening to the total opening area:
S1 / (S1 + S2) × 100

When the ratio of the opening area of the opening calculated in this way is less than 40%, sufficient wind speed toward the center of the duct cannot be obtained, and the ears of the film to be blown flutter, and the wall surface of the duct There is a risk of sticking. On the other hand, if the ratio of the opening area of the opening portion exceeds 70%, the wind speed at the suction port of the duct becomes low, the suction force for sucking the ear portion becomes weak, and the ear portion may flutter. If the ratio of the opening area of the opening is in the range of 40% to 70%, the air volume entering from the suction port and the air volume entering from the opening of the wall surface can be balanced, so that the flutter of the ear is suppressed and stable. The ear portion can be sent to the collecting portion. More preferably, the ratio of the opening area of the opening is in the range of 50 to 60%.

As shown in FIG. 2, it is desirable that the openings 13 of the present embodiment are provided evenly without the plurality of openings 13 being biased toward the wall surface of the suction duct 9. The number and size of the openings are not particularly limited, but the number and size of the openings are, for example, so that the combined air volume from the openings 13 and the inlet 12 is about 0.5 m ³ / min to 80 m ³ / min. Etc. are preferably adjusted.

In the suction duct, the total air volume of the air entering from the opening and the suction port is more preferably about 1 m ³ / min to 50 m ³ / min. The wind speed of the wind can be measured using an anemometer, specifically, for example, a hybrid anemometer DP70 manufactured by Hiyoshi Corporation.

In a preferred embodiment, the size of each opening is preferably about 3 to 85 mm ² per opening, although it depends on the size of the suction duct. If it is in such a range, it is thought that the effect of the present invention can be obtained more reliably by suppressing the fluttering of the ear part and stably blowing the ear part to the recovery part. More preferably, the area per opening is about 7 to 20 mm ² .

For example, when the opening is circular as shown in FIG. 2, the diameter of the opening is desirably about 2 to 10 mm, preferably about 3 to 5 mm.

Further, it is preferable that the opening is present in a range of 500 mm or less from the suction port of the suction duct toward the downstream. Thus, it is considered that by providing an opening near the suction port of the suction duct, it becomes easier to balance the amount of air entering from the suction port and the amount of air entering from the opening of the wall surface. More preferably, it is desirable that the opening is in the range of 5 to 400 mm downstream from the suction port of the suction duct.

Further, a neutralizing blower 200 for neutralizing the film F by blowing ion wind over the entire width from the upper surface side of the film F in the trimming process may be provided above the roller 80 of the trimming device 8. Moreover, between the trimming roller 80 and the inlet of the suction duct 9, the static elimination blower 201 which neutralizes the ear | edge part F1 by spraying an ion wind from the single side | surface side of the cut-off ear | edge part F1 may be provided.

The winding device 10 winds a film having a predetermined residual solvent amount around the core to a required length. 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 any particular limitation. It may be one generally used in optical film manufacturing methods, 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 controller method with a constant internal stress, or the like. .

(Optical film manufacturing method)
In the manufacturing method of the optical film according to the present embodiment, the ears (ends) where the film thickness, the optical value, etc. are likely to be non-uniform are cut during the manufacturing of the optical film by the steps as described above. Therefore, an optical film having a uniform film thickness, optical value and the like can be obtained. Of course, the optical film obtained by such a production method of the present invention is also included in the present invention.

The width of the obtained optical film is preferably 1000 to 3000 mm from the viewpoint of use in a large liquid crystal display device, use efficiency of the film during polarizing plate processing, and production efficiency. The film thickness after drying is preferably 15 to 85 μm from the viewpoint of thinning the liquid crystal display device and stabilizing the production of the film. In addition, the manufacturing method of the present embodiment can manufacture an optical film while suppressing the occurrence of defects even when the film thickness is as thin as 15 to 45 μm. Here, the film thickness is an average film thickness. For example, the film thickness is measured at 20 to 200 locations in the width direction of the film with a contact-type film thickness meter manufactured by Mitutoyo Corporation. Values are shown as film thickness.

Next, the composition of the polymer dope (resin solution) used in this embodiment will be described.

The transparent resin used in the present 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 is easy, the adhesiveness with the hard coat layer and the like is excellent, and the optical isotropy is. 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 polymer include cellulose ester resins such as cellulose triacetate resin. The dope used in this 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 present 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. Examples of the poor solvent for the cellulose ester resin include alcohols having 1 to 8 carbon atoms such as methanol. The dope used in the present embodiment may contain 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.

A cellulose ester resin solution is obtained by mixing the above-mentioned compositions. The obtained cellulose ester resin solution is preferably filtered using a suitable filter medium such as filter paper.

(Polarizer)

The optical film obtained by the manufacturing method according to this embodiment is useful as a protective film for a polarizing plate. The polarizing plate includes a polarizing element and a transparent protective film disposed on the surface of the polarizing element, and the transparent protective film is preferably 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. 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 even 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. 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)

Furthermore, the polarizing plate using the optical film of the present embodiment as described above can be used for a liquid crystal display device. Such a liquid crystal display device 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.

This specification discloses various modes of technology as described above, and the main technologies are summarized below.

That is, the method for producing an optical film according to one aspect of the present invention includes a step of obtaining a polymer film by a melt casting film forming method or a solution casting film forming method, and cutting off an ear portion of the obtained film. A method of manufacturing an optical film including an air blowing process for air blowing a part to a recovery pipe, wherein an opening exists in a wall of a suction duct for feeding an ear part to the recovery pipe used in the air blowing process In addition, the ratio of the opening area by the opening to the total opening area including the suction port area of the suction duct and the opening is 40% to 70%.

With such a configuration, it is possible to suppress the fluttering, adhesion, and entanglement of the ears in the suction duct for sending the ears to the recovery pipe as compared with the conventional case. As a result, it is thought that the ear | edge part of a film can be cut out stably and adhesion of chips etc. to a film can be suppressed and a high quality optical film can be provided.

Further, in the method for producing an optical film, a film is obtained by peeling a web formed by casting a polymer dope on a support from the support, and drying the web peeled from the support. It is more preferable to include a step of obtaining a film by a solution casting film forming method including a drying step and an air feeding step of cutting out the ear portion of the film and blowing the ear portion to a recovery pipe. In such an embodiment, it is considered that the effect of the present invention is more exhibited.

Furthermore, in the method for producing an optical film, the area per one opening in the suction duct is preferably 3 to 85 mm ² . Thereby, it is thought that the effect mentioned above can be acquired more reliably.

Furthermore, in the manufacturing method of the optical film, it is preferable that the opening is present in a range within 500 mm from the suction port of the suction duct toward the downstream. Thereby, it is thought that the effect mentioned above can be acquired more reliably.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

[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 films)
First, the temperature of the obtained dope was adjusted to 34 ° C., and the temperature of the endless belt support was adjusted to 30 ° 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 80 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 from the endless belt support as a film, dried while being conveyed by a roller at 30 ° C., and when the residual solvent amount is 9%, the film is drawn at 180 ° C. using a stretching device (tenter). The film was stretched 1.15 times in the width direction while holding both ends of the film with clips. Then, using the trimming apparatus, the area | region (width of 120 mm from the film end) currently hold | gripped with the clip was cut off, and the optical film with a thickness of 20 micrometers was obtained. In that case, the ear | edge part of the cut-out film was air-fed to the suction duct, and it cut | disconnected to the strip (strip shape) with the cutting device downstream. As the suction duct, a stainless steel square duct (the cross-sectional area of the hollow portion at the suction port is about 10,000 mm ² ) was used. In addition, it was made to attract | suck so that the air volume of the wind which enters from the suction inlet and opening part of a suction duct might be set to 30 m < ³ > / min.

The opening has an area per opening of 20 mm ² , and the ratio of the opening area by the opening to the total opening area of the suction duct area and the opening area is 40% (opening) The total number of parts was 333), and the opening was present in the range of 5 to 400 mm downstream from the suction port of the suction duct. The ratio of the opening area was obtained by the following formula. The total number of openings was 333.
Opening area of the opening: 20 × 333 / (20 × 333 + 10000) = 40%

[Examples 2 to 9 and Comparative Examples 1 and 2]
In Examples 2 to 9 and Comparative Examples 1 and 2, except that the percentage area of the opening, the opening area per opening, the number of openings, and the position of the opening were changed as shown in Table 1, In the same manner as in Example 1, an optical film was produced.

Examples 1 to 9 and Comparative Examples 1 and 2 were evaluated as follows.

(Foreign matter adhesion)
Using an optical surface inspection apparatus (“LSC-6000” manufactured by MEC Co., Ltd.), the number of foreign matters having a size of 10 μm or more adhering to the obtained optical film was measured. A film length of 300 m was measured, and the number per 1 m ² was calculated. The evaluation results are shown in Table 1. The evaluation criteria are as follows:
A: Less than 0.2 foreign matter / m ² ○: Less than 0.2-2 foreign matter / m ² ×: More than 2 foreign matter / m ²

As can be seen from Table 1, it was confirmed that the optical film obtained by the production method of the present embodiment suppressed the adhesion of foreign matters and a high-quality film was obtained. In contrast, in Comparative Example 1 in which the area ratio of the opening was less than the range of the present invention and Comparative Example 2 in which the range of the present invention exceeded the range of the present invention, foreign matter adhered to the obtained film. .

Furthermore, the adhesion area of the foreign matter can be further suppressed when the opening area per piece is in the range of 3 to 85 mm ² and / or the position of the opening is within 500 mm from the suction port of the suction duct. Were also shown by the results of Examples 5 and 8 and Example 9.

This application is based on Japanese Patent Application No. 2015-123490 filed on June 19, 2015, the contents of which are included in this application.

In order to express the present invention, the present invention has been described appropriately and sufficiently through the embodiments with reference to the drawings and the like. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that it can be done. Therefore, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not limited to the scope of the claims. To be construed as inclusive.

The present invention has wide industrial applicability in the technical field of optical films used in display devices and the like and manufacturing methods thereof.

Claims

An optical film comprising: a step of obtaining a polymer film by a melt casting film forming method or a solution casting film forming method; and an air blowing step of cutting off an ear portion of the obtained film and blowing the ear portion to a recovery pipe. A manufacturing method comprising:
The wall of the suction duct for sending the ear part to the recovery pipe used in the air blowing process has an opening, and the total opening area that combines the suction port area of the suction duct and the opening. On the other hand, the ratio of the opening area by the opening is 40% to 70%.
A peeling step of peeling the web formed by casting a polymer dope on the support from the support;
A drying step of drying the web peeled from the support to obtain a film;
The method for producing an optical film according to claim 1, further comprising a step of obtaining a film by a solution casting film forming method including an air blowing step of cutting out an ear portion of the film and blowing the ear portion to a recovery pipe.
The method for producing an optical film according to claim 1 or 2, wherein an area per one opening in the suction duct is 3 to 85 mm 2 .
The method for producing an optical film according to any one of claims 1 to 3, wherein the opening is present within a range of 500 mm or less downstream from the suction port of the suction duct.