JP6737270B2 - Method for manufacturing optical film - Google Patents

Description

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

Liquid crystal display devices have come into wide use 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 required to have a large screen and high image quality. Therefore, an optical film provided in a liquid crystal display device, for example, a protective film for a polarizing plate and the like, is required not only to have improved visibility but also to have a wider width in order to cope with a larger screen. Further, in order to meet the cost reduction of liquid crystal display devices and the increasing demand for liquid crystal display devices, it is also required to increase the production efficiency of optical films.

In order to increase the production efficiency of the optical film, it is possible 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 resin solution in which a raw material resin is dissolved in a solvent, cast on a running support, and a film obtained by drying to some extent is peeled from the support, and the peeled film Is a method for producing a resin film by drying while being transported by a transport roller. Further, the melt casting film forming method, 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 from the support, and the peeled film is conveyed by a transport roller. It is a method for producing a resin film by further cooling and solidifying while transporting.

The resin film obtained by the above method may have curls, wrinkles or the like at the edges during transportation. 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 reduced unless the film edge is separately cut. Further, in the method as described above, particularly when manufacturing a resin film having a wider width, the production of the resin film is stopped by the end portion of the resin film being folded into the transportation roller during transportation of the resin film. There was a risk that

In order to solve these problems, for example, after peeling the resin film from the support, at a predetermined position until the resin film is wound into a roller shape as an optical film, while conveying the resin film, the end of the resin film The part (ear) is cut (trimmed) with a trim cutter. That is, in the production of a resin film, the film left after cutting the ears and separating the cut end film is used as an optical film.

However, if the edge film (ear) is not smoothly conveyed after cutting, the conveyance of the resin film before cutting and the conveyance 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 separated from a predetermined conveyance path, or the end film is not separated from the predetermined conveyance path, even if the inside of the pipe is conveyed, There is a risk that the end film may not be smoothly conveyed after cutting due to clogging of the end film. And, since the conveyance of such an end film is not carried out smoothly, for example, the tension of the optical film or the like after being separated from the end film is lowered, and the conveyance of the optical film is hindered. In some cases.

As a method for cutting and transporting the ears of such a film, a method of preventing clogging of the discharge pipe by performing static elimination on the ears (Patent Document 1) or a suction port inlet of the ears has been used so far. A method of blowing air toward the target (Patent Document 2) and the like have been reported.

According to Patent Document 1, it is possible to prevent clogging of the ears to some extent in the pipe for discharging the ears. However, even with this method, it was difficult to prevent the ears from adhering to the inner wall of the suction duct.

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

As described above, in the related art, when the cut-out ear portion blows air into the suction duct, flaps of the ear portion are generated by the suction air, and when the ear portion adheres to the inner wall of the suction duct, fluctuations in the tension of the ear portion occur. May occur. If this fluctuation in tension is transmitted to the upstream slitting portion, the slitting that cuts off the ears becomes unstable and chips may be generated. 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, the melt casting film forming method, or, using the solution casting film forming method, by cutting the ears of the film, in the method of producing an optical film, An object of the present invention is to provide a method for producing an optical film with high production efficiency, in which the ears are smoothly collected without causing fluttering or the like.

JP 2002-370242A JP, 2010-46932, A

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

A method for producing an optical film according to an 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 an ear portion of the obtained film, and collecting the ear portion. A method of manufacturing an optical film including a step of blowing air into a pipe, which is used in the step of blowing air, wherein a wall of a suction duct for feeding an ear portion to a recovery pipe has an opening. Further, 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, while the film is being conveyed, the ears of the film are cut off, and in the method for producing the optical film, the ears of the film can be cut off stably, and chips etc. to the obtained film are obtained. 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 ears in the present embodiment.

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

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

The method of manufacturing 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 blowing step. Specifically, for example, in the case of a solution casting film forming method, a method of producing an optical film by performing the air blowing step at a predetermined position after peeling the film from a support and winding it into a roller shape. Etc.

In the following, a solution flow including a peeling step of peeling the web formed by casting the polymer dope on the 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 film-forming method will be described, the present invention is not limited to this, and a film obtained by the melt-casting film-forming method is cut off from the ears of the obtained film. The method for producing an optical film may include a step of blowing the ear portion to the collection pipe.

The method for producing an optical film according to the present embodiment is formed by casting a resin solution (dope) containing a transparent resin (polymer) onto a running support by, for example, a solution casting film forming method. A peeling step of peeling the formed web from the support, a stretching step of stretching the peeled film, a winding step of winding the stretched film into a roller shape, etc., and the air blowing step as described above, It can be carried out by performing between the step and the winding step. More specifically, 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 that shown in FIG. 1 as long as it can perform the above-mentioned steps, and a manufacturing apparatus having another configuration may be used. In addition, in the present specification, the film refers to a film after the casting film (web) made of the dope cast on the support is dried on the support and is ready to be peeled from the support. To tell. The position of the air blowing step may be anywhere as long as it is between the peeling step and the winding step.

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

In FIGS. 1 and 2, each reference numeral indicates the following. 1: Support, 5: Separation roller, 6: Drying device, 8: Trimming device, 9: Suction duct, 10: Film winding device, 12: Suction port, 13: Opening part, 102: Winding core, 200, 201: static eliminator blower, F: film, F1: ear, F2: roll film, W: web.

1, an optical film manufacturing apparatus includes a support 1 composed 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 which are respectively arranged on the front and back sides of the upper and lower transfer paths and which heat-dry the dope cast on the support 1 to form the web, and the web (W) from the support 1. The web peeling roller 5 for peeling, the drying device 6 for drying the web (W) peeled from the support 1 to obtain the film F, and the widthwise both side edges of the obtained film F are gripped to obtain the film F width. Constant, or a tenter device 7 that stretches the film F in the width direction, and a trimming device 8 that cuts off the ears F1 of the film whose width is restricted by the tenter device 7 to finish the film F into the final product size. The suction duct (ear discharge pipe line) 9 for discharging the cut-off ear F1 and a large number of minute protrusions having a height of several μm are formed on both side edges in the width direction of the film F finished to the final product size. An embossing 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 whose surface is a mirror surface and runs infinitely. As the belt, for example, a belt made of stainless steel or the like is preferably used from the viewpoint of film releasability. The width of the casting film cast by the casting die 2 is not particularly limited, but 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 As the support, a support made of a metal drum may be used instead of the endless belt.

Further, the trimming device 8 may be installed at one place as shown in FIG. 1 or may be installed 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. Examples of the method include a method in which heated air is blown onto the endless belt support 1, and a method in which heated air is blown onto the back surface of the endless belt support 1 to heat the same. The method can be appropriately selected as necessary.

The transport speed of the casting film by the endless belt support 1 is not particularly limited, but from the viewpoint of productivity, it is preferably about 50 to 200 m/min. The ratio (draft ratio) of the transport speed of the casting film to the running speed of the endless belt support 1 is preferably about 0.8 to 5.0. When the draft ratio is within this range, a casting film can be stably formed. For example, if the draft ratio is too high, the casting film tends to cause a phenomenon called neck-in in which the film is reduced in the width direction, and if this happens, a wide film cannot be formed.

The peeling roller 5 peels the dried web (film). When the film is peeled from the endless belt support 1, the film is stretched in the film conveying direction (Machine Direction: MD direction) by the peeling tension and the subsequent conveying tension. Therefore, the peeling tension and the conveying tension when peeling the film from the endless belt support 1 are preferably, 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 determined by the releasability from the endless belt support 1, the residual solvent amount at the time of peeling, the transportability after peeling, and the transport and drying. Considering the physical properties of the optical film and the like, 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 zigzag arrangement in a housing 60 having a hot air blowing port 61 and a hot air outlet 62. In the drying device 6, the web W is hung and conveyed by the conveyance rollers 63 in the housing 60, and is dried by the drying hot air blown from the hot air blowing port 61 during the conveyance. Further, a plurality of drying devices 6 are provided, and between the drying devices 6, a tenter that holds the widthwise both side edges of the web to keep the web width constant or stretches the web in the width direction to regulate the width. A (stretching) device 7 may be provided. Further, the film F may be obtained by providing the tenter device 7 with a drying function and finally drying it.

At the time of drying, 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. From the viewpoint of simplicity, it is preferable to use heated air. As the drying temperature, the suitable temperature varies depending on the residual solvent amount of the film, but in consideration of the drying time, shrinkage unevenness, stability of expansion and contraction amount, etc., it is appropriately selected and determined depending on the residual solvent amount in the range of 30 to 180°C. Good. Further, it may be dried at a constant temperature, or may be divided into 2 to 4 stages of temperature and divided into several stages of temperature to be dried. 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 separated from the endless belt support 1 in a direction (Transverse Direction: TD direction) orthogonal to the web transport direction. Specifically, the film is stretched in the TD direction by gripping both ends of the film in the direction perpendicular to the transport direction with clips or the like and increasing the distance between the opposing clips.

Next, the trimming device 8 is provided between the tenter device 7 and the winding device 10, and is composed of, for example, a roller 80 having round blades (trim cutters, not shown) provided at both ends of the peripheral surface. The film winding device 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 hung on the conveying roller 101 in the housing 100 and conveyed, and is wound around the winding core 102.

The trim cutter of the trimming device 8 cuts an end portion in a direction (width direction) substantially perpendicular to the method of conveying the conveyed film so that the remaining portion of the cut film becomes an optical film as a shipping product. Cut. At this time, the cut off end is processed as the ear film F1.

The suction duct 9 sucks the ear portion F1 and blows it to the ear portion collecting portion. The collected ear portion is finely cut by a cutting device (not shown) or the like, and is conveyed as a strip to a storage tank (not shown) or the like.

The configuration of the trim cutter is not particularly limited as long as it can cut off the end portion of the conveyed film. As the trim cutter, in order to appropriately cut off the end portion of the film, it is preferable that the cutting depth for the film can be arbitrarily adjusted, for example, a cutting blade including an upper round blade and a lower round blade. Examples include a rotating disk type and a knife type.

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

Since the wall of the suction duct 9 is provided with the opening portions at a predetermined ratio as described above, a flow of wind is generated from the wall surface of the duct toward the central portion of the duct, so that the ear portion is sent to the recovery pipe. It is considered that the flapping, adhesion and entanglement of the ears in the suction duct can be suppressed more than ever before. As a result, it is possible to stably cut off the ears of the film and carry and collect the ears, suppress the adhesion of cutting chips and the like to the obtained film, and provide a high-quality optical film. It is thought to be possible.

The inside of the suction duct 9 is sucked toward the downstream side, and this suction is performed by generating air blowing 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, air can be made to flow toward the downstream side to generate the air blowing.

FIG. 2 is a schematic perspective view showing an example of the suction duct 9 for collecting the ears in the present embodiment. An opening 13 is present in the wall of the suction duct 9, and the opening 13 is defined by the total 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 the suction duct 9 having a rectangular cross-sectional shape, but the suction duct of the present embodiment is not limited to this, and the duct may have a circular cross-sectional shape. However, the shape of the opening may be a shape other than a circle.

In the case of the suction duct as shown in FIG. 2, the area ratio 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 opening 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 the opening area S1 by the opening to the total opening area:
S1/(S1+S2) x 100

When the ratio of the opening area of the opening calculated in this way is less than 40%, sufficient wind speed toward the central portion of the duct cannot be obtained, and the ears of the film to be blown flutter and the wall surface of the duct is fluttered. There is a risk of adhesion. On the other hand, when the ratio of the opening area of the opening exceeds 70%, the wind speed at the suction port of the duct becomes low, the suction force for sucking the ear becomes weak, and the ear may flap. When the ratio of the opening area of the opening is in the range of 40% to 70%, the amount of air entering from the suction port and the amount of air entering from the opening of the wall surface are balanced, so that flapping of the ears is suppressed and stability is ensured. The ear part can be blown to the collecting part. 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 have a plurality of openings 13 evenly arranged on the wall surface of the suction duct 9, and the number of openings 13 and the size of each opening are large. is not particularly limited but such is, for example, air volume, so that 0.5 m 3 ^/ min ~80m 3 ^/ min extent, the number and size of the opening of the combined air entering from the opening 13 and the suction port 12 Etc. are preferably adjusted.

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

In a preferred embodiment, the size of each opening depends on the size of the suction duct, but the area per opening is preferably about 3 to 85 mm ² . Within such a range, it is considered that the effect of the present invention that the fluttering of the ears can be suppressed and the ears can be stably blown to the collecting section can be obtained more reliably. More preferably, the area per opening is preferably about 7 to ²⁰ mm ² .

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

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

Further, above the roller 80 of the trimming device 8, there may be provided a neutralization blower 200 for neutralizing the film F by blowing ion air over the entire width of the film F in the trimming process from the upper surface side. Further, between the trimming roller 80 and the inlet of the suction duct 9, a static elimination blower 201 may be provided to eliminate static electricity from the ear portion F1 by blowing ion air from one side of the cut ear portion F1.

The winding device 10 winds a film having a predetermined residual solvent amount on a core in 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 winding machine used can be used without particular limitation. It may be one generally used in the method for producing an optical film, and can be wound by a winding method such as a constant tension method, a constant torque method, a taper tension method, or a program tension controller method with a constant internal stress. ..

(Method for producing optical film)
In the method for producing an optical film according to the present embodiment, the ear portions (end portions) where the film thickness, the optical value and the like are likely to be non-uniform are cut during the production 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. The optical film obtained by such a production method of the present invention is naturally included in the present invention.

The width of the obtained optical film is preferably 1000 to 3000 mm from the viewpoints of use in a large-sized liquid crystal display device, use efficiency of the film when processing a polarizing plate, and production efficiency. The film thickness after drying is preferably 15 to 85 μm from the viewpoints of thinning the liquid crystal display device and stabilizing the production of the film. Further, according to the manufacturing method of the present embodiment, it is possible to manufacture an optical film while suppressing the occurrence of defects even with a very thin film thickness of 15 to 45 μm. Here, the film thickness means an average film thickness, and for example, a contact-type film thickness meter manufactured by Mitutoyo Corporation is used to measure the film thickness at 20 to 200 points in the width direction of the film, and the average of the measured values. The 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 may be a resin having transparency when formed into a substrate by a solution casting film forming method or the like, and is not particularly limited, but may be a solution casting film forming method or the like. It is preferable that the production is easy, that the adhesiveness with the hard coat layer and the like is excellent, and that it is optically isotropic. The term "transparency" as used herein means that the transmittance of visible light is 60% or more, preferably 80% or more, and more preferably 90% or more.

Specific examples of the transparent resin polymer include cellulose ester resins such as cellulose triacetate resin. Further, the dope used in the present embodiment may contain fine particles. At that time, the fine particles used are appropriately selected according to the purpose of use, but it is preferable that the fine particles are capable of scattering visible light when contained in the 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. Further, 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 other components (additives) other than the transparent resin, the fine particles and the 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 solution of a cellulose ester resin is obtained by mixing the above respective compositions. The obtained cellulose ester resin solution is preferably filtered using a suitable filter material 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 or the like. 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 the optical film according to the present embodiment. The polarizing element is an optical element that converts incident light into polarized light and emits it.

As the polarizing plate, for example, at least one surface of the polarizing element produced by immersing and stretching a polyvinyl alcohol-based film in an iodine solution, using a completely saponified polyvinyl alcohol aqueous solution, the optical film It is preferably pasted. Further, the optical film may be laminated on the other surface of the polarizing element, or a transparent protective film for another polarizing plate may be laminated. Alternatively, a resin film other than the cellulose ester film, such as a cyclic olefin resin, an acrylic resin, polyester, or polycarbonate, may be used. In this case, since the suitability for saponification is low, it is preferable to carry out adhesion processing to the polarizing plate via 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 optical film functions as a retardation film, it is preferable that the slow axis of the optical film is arranged so as to be substantially parallel or orthogonal to the absorption axis of the polarizing element.

Moreover, as a specific example of the polarizing element, for example, a polyvinyl alcohol-based polarizing film can be cited. Polyvinyl alcohol-based polarizing films include those obtained by dyeing a polyvinyl alcohol-based film with iodine and those obtained by dyeing a dichroic dye. As the polyvinyl alcohol-based film, a modified polyvinyl alcohol-based 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. Then, a durability treatment is preferably performed with a boron compound.

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

When a cellulose ester-based resin film is attached to the surface of the polarizing element, it is preferable to attach it with a water-based adhesive containing a completely saponified polyvinyl alcohol as a main component. Further, in the case of a resin film other than the cellulose ester resin film, it is preferable that the resin film is adhered to the polarizing plate via an appropriate adhesive layer.

The polarizing plate as described above, by using the optical film according to the present embodiment as a transparent protective film of the polarizing element, since the optical film has a uniform film thickness, optical value, etc., When applied to a liquid crystal display device, a polarizing plate that can realize high image quality of the liquid crystal display device having excellent 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)

Further, the polarizing plate using the optical film of the present embodiment as described above can be used in 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 a liquid crystal cell is a pair of electrodes filled with a liquid crystal substance, and by applying a voltage to the electrodes, the alignment state of the liquid crystal is changed and the amount of transmitted light is controlled. Such a liquid crystal display device, by using the optical film according to the present embodiment as a transparent protective film for a polarizing plate, since the optical film has a uniform film thickness, optical value, etc., It is possible to provide a high-quality liquid crystal display device with improved contrast and the like. Further, by using a wide film as the optical film according to the present embodiment, it is possible to increase the screen size.

The present specification discloses various aspects of the technique as described above, and the main techniques thereof are summarized below.

That is, the method for producing an optical film according to one aspect of the present invention comprises 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 a blowing step of blowing a part to a collection pipe, wherein an opening exists in a wall of a suction duct used for the blowing step for feeding an ear part to the collection pipe. In addition, the ratio of the opening area of the opening to the total opening area of the suction opening of the suction duct and the opening is 40% to 70%.

With such a configuration, fluttering, adhesion, and entanglement of the ears in the suction duct for feeding the ears to the collection pipe can be suppressed more than ever before. As a result, it is considered that the ear portion of the film can be stably cut off, adhesion of cutting chips and the like to the film can be suppressed, and a high-quality optical film can be provided.

In the method for producing an optical film, a peeling step of peeling a web formed by casting a polymer dope onto a support from the support, and drying the web peeled from the support to obtain a film. It is more preferable to include a step of obtaining a film by a solution casting film-forming method including a drying step and a step of cutting off an edge portion of the film and blowing the edge portion to a recovery pipe. In such an embodiment, the effect of the present invention is considered to be more exerted.

Further, in the above-mentioned method for producing an optical film, it is preferable that the area of each opening in the suction duct is 3 to 85 mm ² . Thereby, it is considered that the above-mentioned effect can be obtained more reliably.

Further, in the above-described method for producing an optical film, it is preferable that the opening is present within a range of 500 mm or less downstream from the suction port of the suction duct. Thereby, it is considered that the above-mentioned effect can be obtained more reliably.

The present invention will be specifically described below 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) was 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 ultraviolet absorber) 1 part by mass, silicon dioxide 0.1 part by weight of fine particles (Aerosil R972V) and 23 parts by weight of ethanol were added. The silicon dioxide fine particles were added in a state of being dispersed in ethanol. Then, after raising the liquid temperature to 80° C., it was stirred for 3 hours. By doing so, a cellulose triacetate resin solution was obtained. Then, the stirring was completed and the solution was left to stand until the liquid temperature reached 43°C. Then, the obtained resin solution was filtered using a filter paper having a filtration accuracy of 0.005 mm. Bubbles in the resin solution were removed 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 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 stainless steel and having an endless belt polished to a super-mirror surface is conveyed from a casting die (coat hanger die) at a transfer speed of 80 m/min. The dope was cast. By doing so, a web was formed on the endless belt support and conveyed while being dried. Then, the web is peeled off as a film from the endless belt support and dried while being conveyed by rollers in an atmosphere of 30° C. When the residual solvent amount is 9%, the film is drawn in an atmosphere of 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, a region (120 mm width from the film edge) held by the clip was cut out using a trimming device to obtain an optical film having a thickness of 20 μm. At that time, the ears of the cut film were blown into a suction duct and cut into strips (strips) by a cutting device located downstream. As the suction duct, a rectangular duct made of stainless steel (the hollow portion of the suction port has a cross-sectional area of about 10000 mm ² ) was used. In addition, the amount of wind entering from the suction port and the opening of the suction duct was suctioned to be 30 m ³ /min.

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

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

The following evaluations were performed on Examples 1 to 9 and Comparative Examples 1 and 2.

(Adhesion of foreign matter)
An optical surface inspection device (“LSC-6000” manufactured by MEC Co., Ltd.) was used to count the number of foreign matters having a size of 10 μm or more attached to the obtained optical film. 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:
◎: Foreign matter number less than 0.2/m ² ○: Foreign matter number 0.2 to less than ² /m ² ×: Foreign matter number 2/m ² or more

As can be seen from Table 1, it was confirmed that the optical film obtained by the production method of the present embodiment suppresses the adhesion of foreign matter and obtains a high quality film. On the other hand, 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 area ratio of the opening exceeded the range of the present invention, foreign matter adhered to the obtained film. ..

Furthermore, 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, so that adhesion of foreign matter can be further suppressed. Is also shown by the results of Examples 5 and 8 and Example 9.

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

In order to express the present invention, the present invention has been appropriately and sufficiently described through the embodiments with reference to the drawings and the like, but those skilled in the art can easily modify and/or improve the above embodiments. It should be recognized that this is possible. Therefore, unless a modification or improvement performed by a person skilled in the art is at a level that departs from the scope of rights of the claims recited in the claims, the modification or the improvement is covered by the scope of rights of the claims. Is understood to be included in.

INDUSTRIAL APPLICABILITY The present invention has a wide range of industrial applicability in the technical field of optical films used for display devices and the like and methods for producing the same.

Claims (4)

A step of obtaining a polymer film by a melt casting film forming method or a solution casting film forming method, including a blowing step of cutting off the ears of the obtained film and blowing the ears to a collecting pipe; A manufacturing method,
There is an opening in the wall of the suction duct for feeding the ears to the recovery pipe used in the air blowing step, and the total opening area of the suction duct and the opening. respect, Ri ratio of 40% to 70% der opening area by the opening,
Characterized Rukoto plurality of the openings have been evenly in the wall of the suction duct, method for producing an optical film. A peeling step of peeling the web formed by casting the polymer dope on the support from the support;
A drying step of drying the web separated 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 a step of cutting off 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, wherein an area of each of the openings in the suction duct is 3 to 85 mm ² . The method for producing an optical film according to claim 1, wherein the opening is present within a range of 500 mm downstream from the suction port of the suction duct.

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