KR101618387B1 - Optical film manufacturing method and optical film - Google Patents

Abstract

The present invention provides an optical film manufacturing method which is excellent in conveyability by a conveying roller and is suppressed from being scratched due to slippage on a conveying roller during conveyance. Also provided is an optical film obtained by the method for producing such an optical film. The method for producing an optical film includes an embossed portion forming step of forming a strip-shaped embossed portion having a plurality of convex portions on at least one end portion in a direction perpendicular to the transport direction of the film, The embossed portion is formed in a non-contact manner during transport of the film.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of manufacturing an optical film,

The present invention relates to a process for producing an optical film and an optical film obtained by the process.

As optical films in various image display devices such as a liquid crystal display device and a plasma display device, a resin film excellent in translucency such as a cellulose ester resin film is used. Such a resin film is produced by, for example, a solution casting film forming method and a melt casting film forming method. The solution casting film forming method refers to a method in which a film obtained by pliability on a support on which a resin solution in which a raw resin is dissolved in a solvent is run and which is dried to some extent is peeled from a support and the peeled film is conveyed Thereby producing a resin film. The melt soft-film-forming method is a method in which a resin melt obtained by heating and melting a raw resin is softened on a support, cooled and solidified to a certain extent, and the resulting film is peeled off from the support. While the peeled film is conveyed by the conveying roller, Followed by cooling and solidification to produce a resin film.

There has been a problem in that when the film is conveyed by the conveying roller and the friction between the conveying roller and the film is insufficient, the film slips on the conveying roller, and the film is damaged by the minute unevenness on the conveying roller. In particular, when the film is left in a solvent state or in a state in which it is not completely solidified, as in the above-described manufacturing method, the film is likely to be damaged when the film is transported by the transport roller.

Therefore, studies have been made to improve the transportability of the film by raising the friction between the transport roller and the film by processing the end portion of the film. For example, Patent Document 1 discloses a method for producing a cellulose acetate film by a solution casting film forming method in which, in a step of drying a film peeled from a support while conveying it by a conveying roller, In which the kneading is performed by a solution casting method. Herein, it is described that the knurling is performed by contact-type processing in which a film in which the solvent remains is sandwiched by the engraving roller.

Japanese Patent Application Laid-Open No. 2003-175522

According to Patent Document 1, it is disclosed that abrasion and wrinkles can be suppressed. However, as in Patent Document 1, when the contact of the end portion of the film in a state in which the solvent is left is subjected to the contact-type processing as described above, the film tends to be pierced, There was a case where the film was broken due to only slight deviation between the processing speeds. In addition, the processing by imprinting rollers is a physical irregularity process, and the irregularities formed may be crushed due to the tension and temperature of the film during transportation.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and provides a manufacturing method of an optical film which is excellent in transportability by a transport roller and is suppressed from being scratched by sliding on a transport roller during transport. It is another object of the present invention to provide an optical film obtained by such a method for producing an optical film.

A method of manufacturing an optical film according to an aspect of the present invention includes an embossed portion forming step of forming a strip-shaped embossed portion having a plurality of convex portions on at least one end portion in a direction perpendicular to the transport direction of the film, And the embossed portion forming step forms the embossed portion in a non-contact manner during transportation of the film.

According to this configuration, since the embossed portion is formed in a non-contact manner, the convex portion of the formed embossed portion is prevented from being crushed or the film is broken even when the film forming the embossed portion is in a state where the solvent remains or is not completely solidified. Therefore, it is possible to increase the friction with the conveying roller and to improve the conveyability with the conveying roller. During embedding of the film, an embossing portion capable of raising the friction with the conveying roller is sequentially formed on the end portion of the film, so that even if the film is continuously conveyed, the film is prevented from sliding on the conveying roller. Therefore, the conveyance synchronization between the rotation speed of the conveying roller and the conveying speed of the film becomes good. Further, since the conveying roller comes into contact with the embossing portion having a plurality of convex portions, the air interposed between the conveying roller and the film escapes from between the convex portions, and air is prevented from intervening between the conveying roller and the film. This also improves the conveyability by the conveying roller.

Therefore, the conveyability by the conveying roller is excellent, and the occurrence of abrasion due to the film slipping on the conveying roller is suppressed.

In addition, in the above manufacturing method, it is preferable that the method further comprises: a flexible step of forming a film on a support on which a resin solution containing a transparent resin is run to form a film; a peeling step of peeling the film from the support; And a drying step of drying the film by conveying by a roller, wherein the embossed part forming step is preferably performed between the peeling step and the drying step.

Even in the case of the solution casting film forming method in which the film with the solvent remaining is conveyed by the conveying roller, the conveying property of the film can be improved by performing the embossing portion forming step between the peeling step and the drying step, The occurrence of abrasion due to sliding on a plurality of conveying rollers in the conveying direction is suppressed.

In the above manufacturing method, it is preferable that the manufacturing method further comprises: a flexible step of forming a flexible film on the support on which the resin melt is melted to form a flexible film; a cooling step of cooling the flexible film to form a film; And a stretching step of stretching the film by conveying the peeled film by a plurality of conveying rollers, wherein the embossing portion forming step is preferably carried out between the peeling step and the stretching step.

Even in the case of the melt softening film forming method in which the film in a state of not fully solidified is conveyed by the conveying roller, the conveying property of the film can be improved by carrying out the embossing portion forming step between the peeling step and the drawing step, Occurrence of abrasion due to sliding on the roller is suppressed.

The ratio of the height of the convex portion before the winding is carried out by the conveying roller to the height of the convex portion immediately after forming the embossed portion by the conveying roller is 50 to 90% And the height of the convex portion is preferably 10 占 퐉 or more. According to this configuration, even when the film is transported by the transport roller, the transportability of the film can be sufficiently secured.

It is preferable that the embossed portion forming step is a step of forming the embossed portion by irradiating a laser beam on the film before forming the embossed portion. According to such a configuration, it is more suppressed that the convex portion of the embossed portion is crushed, and the breakage of the film is further suppressed.

It is also preferable that the embossed portion forming step moves the irradiating position of the laser beam during the transportation of the film. According to this configuration, the position at which the embossed portion is formed can be appropriately adjusted during transport of the film.

It is preferable that the embossed portion forming step forms an embossed portion by applying a liquid material for forming the embossed portion by an inkjet method. According to such a configuration, it is more suppressed that the convex portion of the embossed portion is crushed, and the breakage of the film is further suppressed.

Further, an optical film according to another aspect of the present invention is characterized by being obtained by the above-mentioned method for producing an optical film. According to this configuration, since the transportability of the film when the optical film is produced is improved, the film is produced without slipping on the transport roller. Thus, an optical film in which the occurrence of abrasion caused by sliding on the conveying roller is suppressed is obtained.

According to the present invention, there is provided a production method of an optical film which is excellent in transportability by a transport roller and in which the occurrence of abrasion is suppressed. Also provided is an optical film obtained by the method for producing such an optical film.

1 is a schematic view showing a basic constitution of an optical film production apparatus 11 by solution casting film-forming method.
2 is a schematic view showing a basic configuration of an apparatus 21 for producing an optical film by a melt soft-film-forming method.
3 is a schematic view showing a basic configuration of an optical film production apparatus 41. Fig.
4 is a plan view of the film immediately after the embossed portion is formed in the embodiment;
Fig. 5 is a cross-sectional view taken along the line AA in Fig. 4, Fig. 4 (A) is a schematic view, and Fig.
6 is a cross-sectional view of a film showing another embodiment of the embossing portion;

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

The method for producing an optical film according to the present invention includes an embossed portion forming step of forming a strip-shaped embossed portion having a plurality of convex portions on at least one end in a direction perpendicular to the transport direction of the film, The process is to form the embossed portion in a non-contact manner during transport of the film. The method for producing an optical film according to the present invention is not particularly limited as long as it includes the embossed portion forming step. Specifically, for example, a method of producing an optical film by carrying out the embossed portion forming step before transporting the film by the conveying roller in the solution softening film forming method, the melt softening film forming method and the like.

(Solution flexible film-forming method)

First, a case (first embodiment) in which an optical film is produced by a solution casting film forming method will be described.

The method for producing an optical film according to the first embodiment is a method for producing an optical film comprising a flexible step of forming a film on a support on which a resin solution (dope) containing a transparent resin is run, and a peeling step of peeling the film from the support And a drying step of drying the film by conveying the peeled film by a plurality of conveying rollers, wherein an embossing portion forming step is performed between the peeling step and the drying step. For example, by an apparatus for producing an optical film as shown in Fig. The apparatus for producing an optical film is not particularly limited to the one shown in Fig. 1 and may be of any other configuration as long as it carries out the above steps. Here, the term " film " refers to a film after the flexible film (web) formed of softened dope on the support is dried on the support and is ready to be peeled off from the support.

Fig. 1 is a schematic view showing the basic constitution of an optical film production apparatus 11 by solution casting film-forming method. The optical film production apparatus 11 includes an endless belt support 12, a flexible die 13, a peeling roller 14, a stretching device 15, an embossing portion forming device 16, a drying device 17, Device 18 and the like. The flexible die 13 softens the surface of the endless belt support 12 with a resin solution (dope) 19 in which a transparent resin is dissolved. The endless belt supporter 12 is formed into a film by forming a web comprising a flexible dope 19 from the flexible die 13 and drying it while being transported. The peeling roller 14 peels the film from the endless belt support 12. The stretching device (15) stretches the peeled film. The embossing portion forming device 16 forms an embossed portion at an end portion of the stretched film. The drying apparatus 17 dries the film having the embossed portion formed thereon while conveying it by the conveying roller. The winding device 18 winds the dried film into a film roll.

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

As shown in Fig. 1, the endless belt support 12 is an endless belt made of metal running on an infinitely curved surface. As the belt, a belt made of, for example, stainless steel is preferably used from the viewpoint of film peelability. The width of the flexible film which is flexible by the flexible die 13 is preferably 80 to 99% with respect to the width of the endless belt support body 12 from the viewpoint of effectively utilizing the width of the endless belt support body 12. [ In order to finally obtain an optical film having a width of 1000 to 4000 mm, the width of the endless belt support 12 is preferably 1800 to 5000 mm. Instead of the endless belt support, a rotating metal drum (endless drum support) whose surface is mirror-finished may be used.

Then, the endless belt support 12 dries the solvent in the dope while conveying the flexible film (web) formed on the surface thereof. The drying is performed, for example, by heating the endless belt support 12 or spraying heated air onto the web. At this time, the temperature of the web varies depending on the solution of the dope, but is preferably in the range of -5 to 70 캜, more preferably in the range of 0 to 60 캜, in consideration of the conveying speed and productivity depending on the evaporation time of the solvent Do. The higher the temperature of the web is, the faster the drying speed of the solvent can be, but the higher the temperature, the higher the web tends to foam or deteriorate in planarity.

For example, a method of heating the web on the endless belt support 12 with an infrared heater, a method of heating the back surface of the endless belt support 12 with an infrared heater, a method of heating the endless belt support 12 A method of spraying hot air on the back surface of the honeycomb structure 12 and heating it, and the like, and it is possible to appropriately select it if necessary.

When the heating air is sprayed, the wind pressure of the heating air is preferably 50 to 5000 Pa in consideration of the uniformity of the evaporation of the solvent. The temperature of the heated wind may be dried at a constant temperature or may be divided into several temperature stages in the running direction of the endless belt support body 12. [

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

The transporting speed of the flexible film by the endless belt support 12 is preferably about 50 to 200 m / min, for example. In addition, even if the conventional optical film production apparatus has a transporting speed of 100 to 200 m / min, which tends to cause problems such as breakage of the film, the optical film production apparatus according to the first embodiment, Can be prepared. It is preferable that the ratio of the conveying speed of the flexible film to the running speed of the endless belt support 12 (draft ratio) is about 0.8 to 1.2. When the draft ratio is within this range, a flexible film can be stably formed. For example, if the draft ratio is excessively large, the flexible film tends to cause a phenomenon that it is a neck that is contracted in the width direction, and if so, a wide film can not be formed.

The peeling roller 14 abuts against the surface of the endless belt support 12 on the side where the dope 19 is flexible and presses the endless belt support 12 toward the endless belt support 12 to peel the dried web (film). When the film is peeled from the endless belt support 12, the film is stretched in the machine direction (machine direction: MD direction) by the peeling tension and the subsequent transporting tension. Therefore, the peel tension and the transport tension when peeling the film from the endless belt support 12 are preferably 50 to 400 N / m.

The amount of the residual solvent in the film when peeling the film from the endless belt support body 12 depends on the peelability from the endless belt support 12, the amount of residual solvent at the time of peeling, the transportability after peeling, It is preferably 30 to 200% by mass in consideration of the physical properties and the like of the completed optical film.

The stretching device 15 stretches the film peeled off from the endless belt support 12 in a direction (Transverse Direction: TD direction) perpendicular to the conveying direction of the web. Concretely, both ends in the direction perpendicular to the carrying direction of the film are gripped with a clip or the like, and the distance between the opposed clips is increased to stretch in the TD direction. The stretching device 15 may be provided with a device for cutting the area gripped by the clip. Although the drawing apparatus 15 is provided in the first embodiment, it may be omitted.

The total amount of residual solvent in the film stretched by the stretching device 15 is preferably 1 to 20% by mass in order to form a suitable embossed portion by the embossing portion forming device 16. When the stretching device 15 is not provided, it is preferable that the total amount of the residual solvent in the film is 1 to 20% by mass until the film is supplied to the embossing portion forming device 16.

The embossing portion forming device 16 forms an embossed portion in a non-contact manner during conveyance of the film on at least one end in a direction (width direction) perpendicular to the conveying direction of the film. The embossed portion is a band-like shape having a plurality of convex portions, and at least one end portion in the width direction of the film is enlarged.

The width of the embossed portion differs depending on the width of the film and the like, but is preferably 5 to 50 mm, more preferably 10 to 40 mm, from the viewpoint of enhancing the transportability of the film. If the width of the embossed portion is excessively narrow, the transportability of the film tends not to be sufficiently improved. In addition, if the width of the embossed portion is excessively wide, the area where the embossed portion is not formed, that is, the area used as the optical film becomes narrow. It is preferable that the ratio of the height of the convex portion before the winding of the film with the embossed portion to the height of the convex portion just after forming the embossed portion by the conveying roller described later is 50 to 90% And more preferably 60 to 85%. If the ratio is too low, the conveying performance by the conveying roller tends to be gradually lowered. If the ratio is too high, the convex portion may be too hard, and the film or conveying roller may be damaged. In addition, the height of the convex portion before carrying and winding is preferably 10 占 퐉 or more, more preferably 15 占 퐉 or more. If the height of the convex portion before conveying and winding is excessively low, the conveyability tends not to be sufficiently secured in the second half of the conveyance. Therefore, by adjusting the height of the convex portion of the embossed portion within the above-mentioned range, it is possible to sufficiently secure the transportability of the film even if the film is conveyed by the conveying roller. That is, the conveying roller can ensure a sufficient conveyance property to the end. The height of the convex portion immediately after the embossed portion is formed may be as long as it satisfies the above condition, but it is preferably about 15 to 40 占 퐉, for example, in order to secure initial transportability.

The embossing portion forming device 16 is not particularly limited as long as the embossing portion can be formed in a noncontact manner. Concretely, for example, there are laser processing and ink jet printing methods as described later.

The embossing portion forming device by the laser processing is not particularly limited as long as the embossing portion can be formed by irradiating the film before forming the embossing portion with a laser beam. Specifically, for example, a CO ₂ laser light irradiation apparatus, a YAG laser light irradiation apparatus, and the like can be given. It is preferable that laser light which can be irradiated with a circular cross-sectional shape in the direction perpendicular to the laser light irradiation direction is provided. A focal point is provided in front of the laser light irradiation direction, and the diameter of the circular shape is reduced And a laser beam can be irradiated. The means for condensing the laser light is not particularly limited, and for example, means commonly used by a lens, a prism, a mirror, or the like can be used. In addition, it is preferable that the laser beam irradiating device is capable of moving the irradiating position of the laser beam during transport of the film. The film temperature at the laser light irradiation position is preferably about 300 to 600 DEG C from the viewpoint of processing. The temperature of the film immediately before the laser processing is not particularly limited as long as a good embossed portion can be formed. Concretely, it is preferably about 10 to 150 占 폚, for example. In order to heighten the height of the convex portion immediately after formation of the embossed portion, the film temperature immediately before the laser processing is preferably set to a high temperature of about 40 to 150 DEG C. By heating the film immediately before laser processing, the embossing formed when the laser is irradiated can be further increased. Further, if a convex portion having a sufficient height is formed at a film temperature of about 10 to 40 DEG C, this temperature range is preferable from the viewpoint of drivability of the laser light irradiation apparatus.

The temperature of the film just before the laser processing becomes substantially equal to the temperature around the film. However, when the temperature is excessively high or too low, distortion occurs in the optical system and the driving system, and operation and driving are not stable. Therefore, when the temperature around the film is in the range of 10 to 40 ° C, it is necessary to control the temperature of the laser light irradiating device to be maintained at about 10 to 40 ° C, which increases facility cost. Further, if the film temperature is higher than 150 캜, it affects the optical performance of the film, which is not preferable. Further, when the film is partially heated to a high temperature, the film is twisted, causing the film to be skewed and broken due to uneven tension.

4 is a plan view of the film immediately after the embossed portion is formed in the embodiment. Fig. 5 is a view showing a cross section in a direction (AA line) perpendicular to the transport direction of the film of Fig. Fig. 5A is a schematic cross-sectional view taken along the line AA in Fig. 4, and Fig. 5B is a diagram showing an enlarged cross-sectional photograph taken along the line AA in Fig.

4, the film 111 is a strip-shaped long film having a predetermined substantially constant width and a predetermined substantially constant film thickness, and is provided with at least two side ends 112 and 112 thereof along the carrying direction X Embossed portions 113 and 113 are formed in a substantially linear shape. The embossing portion 113 may be formed between the both side ends 112 and 112 as well as the both side ends 112 and 112 and in a substantially straight line along the conveying direction X. [ For example, the embossed portion 113 may be further formed along the transport direction X at a substantially central portion of the width direction Y of the film 111. [ The embossing portion 113 may be formed over the entire length of the film 111 or may be intermittently formed.

4 and 5, the embossing portion 113 includes a pair of convex portions 113b and 113b formed substantially in a straight line along the conveying direction X and a pair of convex portions 113b and 113b formed along the conveying direction X (First concave portion) 113a formed in a rectilinear shape and the concave portion 113a has a pair of convex portions 113b and 113b between the pair of convex portions 113b and 113b, (Back surface) 114b opposite to one main surface (surface) 114a of the film 111 on which the electrodes 111a and 113b are formed. On one main surface 114a of the resin film 111 on which the pair of convex portions 113b and 113b are formed between the pair of convex portions 113b and 113b, A second concave portion 113c having a substantially straight shape is further formed.

As the embossing portion forming apparatus by laser machining, there may be one laser light irradiating apparatus, but two or more laser light irradiating apparatuses may be provided, and the position of the laser light irradiated by each laser light irradiating apparatus may be And may be arranged so as to be arranged in a direction perpendicular to the transport direction of the film. By forming the embossed portion by such two or more laser light irradiation devices, it is possible to form a wide embossed portion, and the width of the embossed portion can be adapted. Therefore, even if the film is flapped or meandered, it is difficult to cause winding displacement or the like when the film is wound. Even in the case of a single laser irradiation apparatus, the width of the embossed portion can be adjusted by adjusting the diameter of the laser beam, but it is difficult to form a convex portion having a shape suitable for enhancing the transportability. In addition, although the width of the embossed portion can be matched by reflecting laser light at various angles by a mirror or the like, it can not cope with the case where the film transport speed is increased.

As the embossing portion forming device by laser machining, the embossing portion may be formed as described above, and the outside of the embossing portion may be cut with laser light. Specifically, for example, in an embossing portion forming apparatus provided with two or more laser light irradiating devices, the output of the laser light of the laser light irradiating device for irradiating laser light to a position near the end of the film is increased . By doing so, for example, the stretching device 15 can cut the area gripped by the clip.

The embossing portion forming device by laser machining may be an apparatus for irradiating the transferred film with laser light, but it is preferable to lower the oxygen concentration around the film when irradiating the laser light. It is possible to suppress generation of dust and gas generated when the film is irradiated with laser light. Specifically, for example, there is a configuration in which a film is transported into a housing having an inlet and an outlet through which an inert gas can flow, and a laser beam is irradiated in the housing. The oxygen concentration around the film can be lowered by introducing the inert gas from the inlet and discharging the gas from the outlet through the outlet. As the inert gas, for example, rare gas such as argon and neon, nitrogen gas and the like can be mentioned, and nitrogen gas is preferably used from the viewpoint of cost. It is also preferable that the inert gas is introduced so that the oxygen concentration in the laser beam machining portion for processing the film by the laser beam irradiated from the laser beam irradiating device is, for example, 15 vol% or less.

The embossing portion forming device by the inkjet method is not particularly limited as long as it can form the embossing portion by applying a liquid material for forming the embossing portion by an inkjet method. Specifically, for example, a known inkjet apparatus can be used. The ink jet apparatus is also preferable in that the thickness of the embossed portion can be changed by changing the application amount of the liquid material in accordance with the conveying speed of the film.

In addition, the embossing portion may be cut before being used as an optical film, and is often actually cut. Therefore, the material of the embossed portion is not particularly limited as long as it can improve the transportability of the film. Specifically, for example, in the case of using an embossing portion forming apparatus by laser processing, since the film is deformed by laser light, it is the same material as the film. In the case of using the embossing portion forming device by the ink jet method, for example, a known resin layer and the like can be mentioned as the embossing portion. The resin layer preferably has high adhesion with a film.

The shape of the embossing portion is not particularly limited. For example, the number of the embossing portions may be one or two or more. The embossing portion may be provided with a convex portion capable of increasing the transportability of the film. Concretely, for example, a concave portion may be formed between adjacent convex portions, or a hole 115 may be formed between adjacent convex portions as shown in Fig. In the case of forming a hole between adjacent convex portions, air interposed between the conveying roller and the film is easily released from between the convex portions, and air is further prevented from intervening between the conveying roller and the film. From this, the conveyability by the conveying roller is further improved. In the case of the contact method, if a hole is to be formed, the film is broken from the portion as a starting point. On the other hand, in the case of the non-contact type, since no physical force is applied to the hole when the hole is formed, the hole can be formed without being broken.

It is preferable that the embossing portion is formed at both end portions of the film in order to increase the transportability of the film and prevent the occurrence of biasing in the transport of the film.

In the film, the surface on which the embossed portion is formed may be formed on the surface where abrasion is likely to occur by the conveying roller, or may be formed on both surfaces.

The drying apparatus 17 has a plurality of conveying rollers, and dries the film while conveying the film between the rollers. At that time, heating air, infrared light, etc. may be used alone or in combination with heated air and infrared light. It is preferable to use heated air in view of simplicity. The drying temperature may be appropriately selected depending on the amount of the residual solvent in the range of 30 to 180 占 폚 in consideration of the drying time, the shrinkage unevenness, the stability of the elongation and expansion, and the like, though it varies depending on the residual solvent amount of the film. Further, it may be dried at a constant temperature, or may be divided into two to four stages and dried at several temperatures. Further, while being conveyed into the drying apparatus 17, the film may be stretched in the MD direction. The residual solvent amount of the film after the drying treatment in the drying apparatus 17 is preferably 0.01 to 15% by mass in consideration of the load of the drying step, the dimensional stability expansion ratio at the time of storage, and the like.

The winding device 18 winds the film having a predetermined residual solvent amount in the drying device 17 onto the winding core in a required length. The temperature at the time of winding is preferably cooled to room temperature to prevent rubbing due to shrinkage after winding, relaxation of winding, and the like. The winding machine to be used is not particularly limited and may be generally used, and may be wound by a winding method 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.

Further, a cutting device for cutting the embossed portion from the film dried by the drying device 17 may be separately provided. Further, the embossed portion may be wound by the winding device 18 while the embossed portion is formed, and the embossed portion may be cut off immediately before use as an optical film. Further, by winding the film with the embossed portion formed thereon by the winding device 18, it is possible to suppress occurrence of abrasion due to contact between the films when the film is stored in a wound film roll state.

By the above process, an optical film in which the occurrence of abrasion due to sliding on the conveying roller is suppressed is obtained.

The width of the optical film is preferably 1000 to 4000 mm in view of the use in a large-sized liquid crystal display device, the efficiency of use of the film at the time of polarizing plate processing, and the production efficiency. The film thickness of the film is preferably 30 to 90 mu m from the viewpoint of thinning of the liquid crystal display device and stabilization of production of the film. Even in the conventional apparatus for producing an optical film, even in the case of a film thickness of 30 to 50 占 퐉 in which problems such as breakage of the film are liable to occur, in the apparatus for producing an optical film according to the first embodiment, Can be manufactured. Here, the term "film thickness" means an average film thickness, which is measured by a contact type film thickness measuring machine manufactured by Kabushiki Kaisha Mitsudoyo Co., Ltd., in 20 to 200 film thicknesses in the width direction of the film, .

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

The transparent resin used in the first embodiment may be any resin having transparency when formed into a substrate shape by a solution casting film forming method or the like and is not particularly limited and may be easily produced by a solution casting film forming method or the like, Is preferably an optically isotropic one, and the like. Here, the transparency means that the transmittance of visible light is 60% or more, preferably 80% or more, and more preferably 90% or more.

Specific examples of the transparent resin include a cellulose ester resin such as cellulose triacetate resin. The dope used in the first embodiment may contain fine particles. At this time, the fine particles to be used are appropriately selected according to the purpose of use, but are preferably fine particles capable of scattering visible light 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 first embodiment, a solvent containing a good solvent for the above-mentioned transparent resin may be used, and a poor solvent may be contained in the range that the transparent resin is not precipitated. Examples of suitable solvents 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 and the like. The resin solution used in the first embodiment may contain other components (additive) other than the transparent resin, the fine particles and the solvent within the range that does not impair the effect of the present invention. Examples of the additives include plasticizers, antioxidants, ultraviolet absorbers, heat stabilizers, conductive materials, flame retardants, lubricants and matting agents.

In addition, a solution of the cellulose ester-based resin is obtained by mixing the respective compositions. The solution of the obtained cellulose ester resin is preferably filtered using a suitable filter medium such as a filter paper.

(Melt flexible film forming method)

Next, a case (second embodiment) in which an optical film is produced by the melt soft-film-forming method will be described.

A manufacturing method of an optical film according to a second embodiment of the present invention is a manufacturing method of an optical film comprising a flexible step of forming a flexible film on a support on which a molten resin melt is melted to form a flexible film, A peeling step of peeling the film from the support, and a stretching step of stretching the film by conveying the peeled film by a plurality of conveying rollers, wherein the embossing part forming step comprises: And the drawing step. For example, by an apparatus for producing an optical film as shown in Fig. The apparatus for producing an optical film is not particularly limited to that shown in Fig. 2 as far as it carries out the above-described steps, and may be of another constitution. Here, the term " film " refers to a film after a flexible film (web) formed of a flexible dope on a support is dried on a support and can be peeled off from the support.

2 is a schematic view showing a basic configuration of the optical film production apparatus 21 by the melt soft film formation method. The optical film production apparatus 21 includes a first cooling roller 22, a flexible die 23, a touch roller 24, a second cooling roller 25, a third cooling roller 26, a peeling roller 27 An embossing portion forming device 28, a conveying roller 29, an elongating device 30 and a winding device 31, The flexible die 23 softens the resin melt (dope) obtained by melting the transparent resin onto the surface of the first cooling roller 22. The first cooling roller 22 forms a flexible film composed of flexible dope from the flexible die 23 and cools it while conveying and conveys the flexible film to the second cooling roller 25. At this time, the thickness of the flexible film is adjusted and the surface is smoothed by the touch roller 24 installed outside the first cooling roller 22. The second cooling roller 25 conveys the flexible film to the third cooling roller 26 by cooling the flexible film while conveying it. By doing so, the flexible film is made into a film. The peeling roller 27 peels the film from the third cooling roller 26. The embossing portion forming device 28 forms an embossed portion at an end portion of the peeled film. The conveying roller 29 extends in the MD direction while conveying the film on which the embossed portion is formed. The stretching device (30) stretches the film in the TD direction. The winding device (31) winds the cooled and solidified film into a film roll.

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

The first cooling roller 22, the second cooling roller 25 and the third cooling roller 26 are metallic rollers whose surfaces are mirror-finished. As the rollers, rollers made of, for example, stainless steel are preferably used from the viewpoint of peelability of the flexible film or film. The width of the flexible film which is flexible by the flexible die 23 and the conveying speed of the flexible film by the first cooling roller 22, the second cooling roller 25 and the third cooling roller 26, This is the same as the embodiment.

The surface of the touch roller 24 is resilient and deforms along the surface of the first cooling roller 22 by the pressing force applied to the first cooling roller 22, Thereby forming a nip therebetween. As the touch roller 24, a touch roller conventionally used in the melt softening method can be used without particular limitation. Specifically, for example, stainless steel can be used.

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

The embossing portion forming device 28 can be the same as the embossing portion forming device 16 in the first embodiment. By forming the embossed portion here, the occurrence of abrasion on the film during conveyance by the conveying roller 29 is suppressed.

The conveying roller 29 is composed of a plurality of conveying rollers, and can be stretched in the MD direction of the film by rotating the conveying rollers at different rotational speeds. Such a conveying roller 29 is liable to cause slippage on the conveying rollers and the film. When the conveying property of the film is low, abrasion or the like easily occurs. In the present embodiment, however, since the conveying property of the film is high, .

The stretching device 30 and the winding device 31 may be the same as the stretching device 15 and the winding device 18 in the first embodiment.

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 melted by heating. The same composition as in the first embodiment can be used for other compositions.

In addition to the first and second embodiments, a method for producing an optical film in which another functional layer such as an antireflection layer is formed on a film substrate may be used. The film substrate is not particularly limited and may be, for example, an optical film produced by the first embodiment or the second embodiment, or may be a film produced by a conventional solution casting film forming method, a melt casting film forming method, good.

As such an embodiment (third embodiment), for example, there are a coating step of applying a liquid resin composition to at least one surface of a film substrate, and a layer forming step of forming a functional layer by curing or drying the resin composition And an embossed portion forming step is performed after the layer forming step. For example, by an apparatus for producing an optical film as shown in Fig. The apparatus for producing an optical film is not limited to the one shown in Fig. 3, but may be of another constitution.

Fig. 3 is a schematic view showing a basic configuration of the optical film production apparatus 41. Fig. The optical film production apparatus 41 includes an unwinding device 42, a coating device 43, a drying device 44, a hardening device 45, an embossing portion forming device 46, a transport device 47, (48) and the like.

The unwinding device 42 supplies the film base material to the application device 43 or the like. The winding device 42 is, for example, a device which includes a winding roller wound so as to be able to unwind a film base material and supplies the film base material to the coating device 43 or the like by rotating the winding roller.

The application device 43 applies the liquid resin composition onto the surface of the film base material supplied from the winding device 42. The coating device 43 may be any conventional coating device without any limitations. Examples of the coating device include an extrusion method, a dip coating method, an air knife coating method, a curtain coating method, a roller coating method, a rod coating method, An ink-jet method or the like. Further, in the case of forming a plurality of layers on the film base material, it is possible to apply a plurality of layers simultaneously by one coating device like an extrusion die having a multi-manifold, . In the present embodiment, the step of applying the liquid resin composition by the coating device 43 corresponds to the application step.

The drying device 44 dries the liquid resin composition applied on the film substrate. The drying device 44 may adopt, for example, a convection drying method using hot air or a radiation drying method using radiant heat such as infrared rays. In the drying device 44, it is not necessary to dry completely.

The curing device 45 cures the liquid resin composition applied on the film substrate. The curing device 45 is different depending on whether the liquid resin composition contains an active ray curable resin such as an ultraviolet curable resin or an electron beam curable resin or a thermosetting resin. Specifically, for example, when the liquid resin composition contains an active ray curable resin, an active ray irradiating device such as an ultraviolet ray irradiating device may be used. When the liquid resin composition contains a thermosetting resin, a heat treatment apparatus is exemplified.

The embossing portion forming device 46 may be the same as the embossing portion forming device 16 in the first embodiment. Here, the surface forming the embossed portion may be the side coated with the resin composition, or may be the side not coated. Further, both surfaces may be used.

The film on which the embossed portion is formed by the embossed portion forming device 46 is conveyed to the winding device 48 by the conveying device 47. The transport device 47 is composed of a plurality of transport rollers. Even if the film is conveyed by such a conveying device, since the embossing portion is formed, the film is prevented from being scratched due to sliding on the conveying roller.

The winding device 48 winds the optical film obtained as described above. The winding device 48 is, for example, a device provided with a rotatable winding roller and winding the optical film by rotating the winding roller.

Example

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

[Example A]

In Example A, the effect of the type of the embossing portion forming apparatus in the solution casting film forming method of the first embodiment was examined.

(Preparation of Dope)

First, a cellulose acetate propionate resin (acetyl group degree of substitution: 1.5, propionyl group degree of substitution: 1.0, total acyl group degree of substitution: 2.5) was added as a transparent resin to a dissolution tank containing 400 parts by mass of methylene chloride and 45 parts by mass of ethanol, , 5.5 parts by weight of triphenyl phosphate and 5.5 parts by weight of ethyl phthalyl ethyl glycol were further added. Then, the temperature was raised until the liquid temperature reached 80 ° C, and then the mixture was stirred for 3 hours. By doing so, a cellulose acetate propionate resin solution was obtained. Thereafter, stirring was terminated, and the solution was allowed to stand until the liquid temperature reached 43 캜. Then, the obtained resin solution was filtered using a filter paper having a filtration accuracy of 0.005 mm. The resin solution after filtration was allowed to stand overnight to bubble out the bubbles in the resin solution. Using the thus obtained resin solution as a dope, a film (cellulose acetate propionate film) was produced as follows.

(Preparation of cellulose acetate propionate film)

First, the temperature of the obtained dope was adjusted to 35 캜 and the temperature of the endless belt support was adjusted to 25 캜. Then, using the apparatus for producing an optical film as shown in Fig. 1, the dope was flexibly fed from the flexible die to the endless belt support at a conveying speed of 60 m / min. By doing so, a web was formed on the endless belt support, and the web was transported while being dried. Then, the web was peeled off as a film from the endless belt support, and the peeled film was stretched while gripping both ends of the film by a stretching device (tenter). Then, the region gripped by the clip was cut to obtain a film having a width of 1500 mm.

Thereafter, an embossing portion having a width of 30 mm was formed at both end portions of the film by each of the following embossing portion forming devices (laser processing, ink jetting, and hot embossing). Then, after being conveyed by a conveying roller in a drying apparatus heated to 120 占 폚, the embossed portion was cut. The obtained film was wound in a length of 4000 m.

(Laser processing)

A laser light was irradiated to both ends of the film using a CO ₂ laser light irradiation device (wavelength: 10.6 탆, laser light output: 60 W). The laser machining was performed in Example 1.

(Inkjet method)

A liquid having the same composition as that of the dope was discharged onto both end portions of the film by using an ink jet apparatus (having a nozzle with a diameter of 100 mu m) and dried. The embossing portion was formed in the manner described above,

(Hot emboss processing)

Both ends of the film were sandwiched between engraved engraved rollers while conveying the film. In this way, Comparative Example 1 was obtained by processing (hot-embossing) with engraved rollers on both sides of the film.

The height A (占 퐉) of the convex portion immediately after forming the embossed portion of the optical film (Examples 1 and 2 and Comparative Example 1) obtained as described above and the height B (占 퐉) of the convex portion after conveyed by the conveying roller in the drying apparatus, And the following evaluation (abrasion evaluation) was carried out. The results are shown in Table 1.

(Abrasion evaluation)

100 rolled films were produced, scratches were visually observed, and evaluated according to the following criteria.

○: No abrasion was observed.

X: abrasion was confirmed.

As can be seen from Table 1, in the case of using the non-contact type embossing portion forming apparatus (Examples 1 and 2), even when conveyed by the conveying roller, the height of the convex portion did not change greatly, and no abrasion occurred. From this, it can be seen that the conveyability by the conveying roller is sufficiently high. On the other hand, in the case of using the contact type embossing portion forming apparatus (Comparative Example 1), when conveyed by the conveying roller, the height of the convex portion was reduced and abrasion occurred. From this, it can be seen that when the embossed portion is formed by the contact method, the embossed portion is crushed during transportation.

[Example B]

In Example B, a film was produced in the same manner as in Example A, and a width of 50 mm at both ends of the film was locally heated to a predetermined temperature, and then an embossing portion having a width of 30 mm was formed at both ends of the film by laser processing. Then, after being conveyed by a conveying roller in a drying apparatus heated to 120 占 폚, the embossed portion was cut. The obtained film was wound in a length of 4000 m.

(Laser processing)

The laser light was irradiated onto both ends of the film by using a CO ₂ laser light irradiation apparatus (wavelength: 10.6 탆, laser light output: 60 W) while changing the temperature of the film immediately before the laser light irradiation to 30 캜, 40 캜, 150 캜, I investigated. When the temperature of the film was 150 占 폚 and 160 占 폚, the laser light irradiation apparatus was equipped with a facility for controlling the temperature to 40 占 폚 or less.

The height A (占 퐉) of the convex portion immediately after forming the embossed portion of the optical film thus obtained was measured, and the deformation of the film was evaluated according to the following criteria. The results are shown in Table 2.

≪ Film deformation &

?: Deformation of the film edge is 1 mm or more.

?: Deformation of the film edge is 1 mm or less.

It can be seen from Table 2 that if the temperature of the film is 40 DEG C or higher, the height A after processing can be made higher. It is also understood that, when the film temperature is 150 占 폚 or less, the deformation amount of the film end portion can be suppressed to be small.

[Example C]

In Example C, the effect of the type of the embossing portion forming apparatus in the melt softening film forming method of the second embodiment was examined.

(Preparation of Dope)

First, a cellulose resin propionate resin (acetyl group degree of substitution: 1.5, propionyl group degree of substitution: 1.0, total acyl group degree of substitution: 2.5) was used as a transparent resin, . Using the thus obtained dope, a film (cellulose acetate propionate film) was produced as follows.

(Preparation of cellulose acetate propionate film)

First, the dope was flexed from the flexible die to the first cooling roller at a conveying speed of 40 m / min to a width of 1400 mm using an apparatus for producing an optical film as shown in Fig. Then, the surface was smoothed with a touch roller, and cooled and solidified while being conveyed with the second cooling roller and the third cooling roller. The cooled and solidified film was peeled off from the third cooling roller, and embossed portions each having a width of 30 mm were formed at both end portions of the peeled film by the following embossing portion forming devices (laser processing, inkjet method and hot embossing).

Then, the film was stretched in the MD direction by a plurality of conveying rollers. Thereafter, the film was stretched in the TD direction while gripping both ends of the film with a clip by using a stretching device (tenter). Then, the region gripped by the clip was cut to obtain a film having a width of 1350 mm. The obtained film was wound in a length of 4000 m.

(Laser processing)

A laser light was irradiated to both ends of the film using a CO ₂ laser light irradiation device (wavelength: 10.6 탆, laser light output: 60 W). This laser processing was performed in Example 3.

(Inkjet method)

A liquid having the same composition as the dope used in the solution casting method was discharged onto both ends of the film by using an ink jet apparatus (having a nozzle having a diameter of 100 mu m) and dried. The embossing portion was formed in this manner to obtain Example 4.

(Hot emboss processing)

Both ends of the film were sandwiched between engraved engraved rollers while conveying the film. In this manner, Comparative Example 2 was obtained by machining (hot-embossing) with engraved rollers on both sides of the film.

The height A (占 퐉) of the convex portion immediately after forming the embossed portion of the optical film (Examples 3 and 4 and Comparative Example 2) obtained as described above and the height B (占 퐉) of the convex portion after conveyed by the conveying roller in the drying apparatus, And the following evaluations (retardation evaluation) were carried out. The results are shown in Table 3.

(Evaluation of retardation)

The retardation Rth in the thickness direction of the film immediately after the stretching in the MD direction and at a point 600 mm from the center to the end was measured as follows.

The measurement of the thickness direction retardation Rth (nm) (= ((nx + ny) / 2-nz) x d was carried out using an automatic birefringence system KOBRA-21ADH (Oji Keisei Kikuchi) Refractive index is measured at a wavelength of 590 nm under an environment of 55% RH to obtain refractive indices nx, ny and nz.

The obtained retardation was evaluated according to the following criteria.

?: The difference in the retardation Rth in the thickness direction of the central portion from the central portion toward the end portion of 600 mm is within 0.5 nm.

X: Difference in retardation Rth in the thickness direction of the central portion and a point 600 mm away from the central portion toward the end is larger than 0.5 nm.

As can be seen from Table 3, in the case of using the non-contact type embossing portion forming apparatus (Examples 3 and 4), the height of the convex portion did not change greatly even when conveyed by the conveying roller, and the difference in retardation was small. From this, it can be seen that the conveyability by the conveying roller is sufficiently high. Regarding retardation, since the transportability is high, it indicates that the film was not flaky or meandering at the time of transportation. On the other hand, in the case of using the contact-type embossing portion forming apparatus (Comparative Example 2), the height of the convex portion was reduced when conveyed by the conveying roller, and the difference in retardation was large. From this, it can be seen that when the embossed portion is formed by the contact method, the embossed portion is crushed during transportation.

11, 21, 41: Optical film production apparatus
12: endless belt support
13, 23: Flexible die
14, 27: peeling roller
15, 30: stretching device
16, 28, 46: embossing part forming device
17, 44: Drying device
18, 31, 48: winding device
22: first cooling roller
24: touch roller
25: second cooling roller
26: second cooling roller
29: conveying roller
42:
43: dispensing device
45: Curing device
47:
111: Film
113: Embossing section
113a: concave portion (first concave portion)
113b: convex portion
113c: second concave portion
115: hole

Claims (8)

delete A softening step of forming a film by pliing on a support on which a resin solution containing a transparent resin runs,
A peeling step of peeling the film from the support,
And a drying step of drying the film by conveying the peeled film by a plurality of conveying rollers,
And an embossed portion forming step of forming a strip-shaped embossed portion having a plurality of convex portions on at least one end in a direction perpendicular to the carrying direction of the film between the peeling step and the drying step,
Wherein the embossed portion forming step forms the embossed portion in a non-contact manner during transportation of the film. A softening step of forming a flexible film by being softened on a support on which a resin melt in which a transparent resin is melted is run,
A cooling step of cooling the flexible film to form a film,
A peeling step of peeling the film from the support,
And a stretching step of stretching the film by conveying the peeled film by a plurality of conveying rollers,
And an embossed portion forming step of forming a strip-shaped embossed portion having a plurality of convex portions on at least one end in a direction perpendicular to the carrying direction of the film between the peeling step and the drawing step,
Wherein the embossed portion forming step forms the embossed portion in a non-contact manner during transportation of the film. The method according to claim 2 or 3, wherein the ratio of the height of the convex portion before the film is conveyed by the conveying roller to the height of the convex portion immediately after forming the embossed portion, %, And the height of the convex portion before conveyance and winding is 10 占 퐉 or more. The method of manufacturing an optical film according to claim 2 or 3, wherein the embossed portion forming step is a step of forming the embossed portion by irradiating a laser beam on the film before forming the embossed portion. The method of manufacturing an optical film according to claim 5, wherein the embossed portion forming step moves the irradiating position of the laser beam during transport of the film. The method of manufacturing an optical film according to claim 2 or 3, wherein the embossed portion forming step forms an embossed portion by applying a liquid material for forming the embossed portion by an inkjet method. An optical film obtained by the method for producing an optical film according to claim 2 or 3.

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