JP6601414B2 - Manufacturing method of resin film - Google Patents

Description

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

  Resin films are used in various fields such as liquid crystal display devices in view of their chemical characteristics, mechanical characteristics, electrical characteristics, and the like. Specifically, various resin films such as a transparent protective film for protecting the polarizing element of the polarizing plate are disposed as optical films in the image display region of the liquid crystal display device. As such a resin film, for example, a resin film excellent in transparency such as a cellulose ester film is widely used.

  A resin film such as a cellulose ester film can be produced using, for example, a resin solution (dope) obtained by dissolving a raw material resin such as a cellulose ester resin in a solvent. Specific examples of a method for producing a resin film using such a dope include a solution casting film forming method. With the solution casting film forming method, a dope is cast on a traveling support to form a casting film (web), dried to a peelable extent, and then peeled off from the support as a film. This is a method for producing a long resin film by drying or stretching the peeled film while being transported by a transport roller.

  As a manufacturing method of such a resin film, the manufacturing method of patent document 1 is mentioned, for example.

  Patent Document 1 discloses a casting process in which a polymer film raw material solution (dope) is cast from a casting die onto a rotationally driven metal support by a solution casting film forming method to form a dope film (web). And a peeling step for peeling the web formed on the support from the support, a drying step for drying the web peeled from the support through a plurality of transport rolls, and a web in the drying step. A method for producing a polymer film formed by drying is described. And in patent document 1, after 3 second or more passes after casting dope on a support body in a casting process, the dry wind blowing apparatus arrange | positioned above the support body ahead of a casting die | dye WHEREIN: It is described that dry air is applied to the dope film (web). According to Patent Document 1, it is disclosed that a high-quality polymer film can be obtained.

  On the other hand, image display devices are required to be thin and light, have a large screen, and have high definition. Resin films applied as optical films to image display devices are increasingly required to be thinner, wider and have higher quality in accordance with these requirements. For example, in order to produce a thin resin film, it is conceivable to thin the dope (casting ribbon) discharged from the casting die in a ribbon shape. When the casting ribbon is thinned as described above, the properties of the obtained resin film are easily affected by the external environment such as wind blowing on the casting ribbon. For example, as the support travels, the casting ribbon sways near the surface of the support due to the wind blowing toward the casting ribbon, which may cause unevenness in the produced resin film. .

  There is a need for a manufacturing method that can provide a high-quality resin film even when manufacturing a thin resin film that is easily affected by the external environment.

JP 2005-111669 A

  This invention is made | formed in view of this situation, Comprising: Even if it is a resin film with thin thickness, it aims at providing the manufacturing method of the resin film which can manufacture a high quality resin film. .

  One aspect of the present invention includes a casting step of casting a resin solution containing a transparent resin from a casting die on a traveling support to form a casting film, and drying air blown from a drying device. The casting die on the support, and a drying step for drying the casting membrane, and a peeling step for peeling the dried casting membrane from the support. Prevention of the flow of the drying air toward the casting ribbon until the resin solution discharged from the casting die is grounded on the support above the casting film with the drying device It is a manufacturing method of the resin film characterized by using a mechanism.

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

FIG. 1 is a schematic diagram illustrating an example of a basic configuration of a resin film manufacturing apparatus according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing the periphery of a casting die and a casting film drying apparatus in the resin film manufacturing apparatus shown in FIG. FIG. 3 is a schematic cross-sectional view showing the periphery of a casting die and a casting film drying apparatus in the resin film manufacturing apparatus shown in FIG.

  When this inventor used the drying apparatus which blows off drying air in order to dry the casting film on a support body as described in patent document 1, the drying air influences a casting ribbon. The inventors have arrived at the present invention as follows.

  Hereinafter, although the embodiment concerning the present invention is described, the present invention is not limited to these.

  The method for producing a resin film according to the present embodiment is a casting method in which a resin solution (dope) containing a transparent resin is cast from a casting die on a traveling support to form a casting film (web). It is a manufacturing method by what is called a solution casting film-forming method provided with the process and the peeling process which peels the said cast film as a film from the said support body. Further, the method for producing a resin film according to the present embodiment applies the drying air blown from a drying apparatus (casting film drying apparatus) before peeling the casting film on the support, and the casting film is cast. A drying step (a casting membrane drying step) for drying the membrane is provided. And the manufacturing method of the resin film which concerns on this embodiment WHEREIN: The resin solution discharged from the said casting die above the said casting film between the said casting die and the said casting film drying apparatus is the said. A prevention mechanism for preventing the flow of the dry air toward the casting ribbon until it contacts the support is used. Furthermore, as a method for producing a resin film, in addition to the above steps, a stretching step for stretching the peeled film and a drying step (film drying step) for drying the peeled film may be provided. And as a manufacturing method of a resin film, the method etc. which are performed with the manufacturing apparatus etc. of the resin film by the solution casting film forming method as shown in FIG. 1 etc. are mentioned, for example. In addition, the manufacturing apparatus of a resin film is not limited to what is shown in FIG. 1, The thing of another structure may be sufficient. FIG. 1 is a schematic diagram illustrating an example of a basic configuration of a resin film manufacturing apparatus according to an embodiment of the present invention. The film here refers to a film after a cast film (web) made of a dope cast on a support is dried on the support and can be peeled off from the support.

  The apparatus for producing a resin film includes an endless belt support 11, a casting die 20, casting film drying devices 31, 32, a peeling roller 13, a stretching device 16, a film drying device 17, a winding device 19, and the like. The casting die 20 discharges a resin solution (dope) 14 containing a transparent resin in a ribbon shape and casts it on the surface of the endless belt support 11. The endless belt support 11 is supported by a pair of rollers 12 to be drivable, and forms and conveys a casting film (web) made of the resin solution 14 cast from the casting die 20. The cast film drying devices 31 and 32 apply drying air to the endless belt support 11 and the cast film on the endless belt support 11 to dry the cast film. The cast film on the endless belt support 11 is dried to the extent that it can be peeled off by the peeling roller 13 by drying at the time of transporting the cast film or by the cast film drying devices 31 and 32. Then, the peeling roller 13 peels the cast film dried to some extent from the endless belt support 11 to obtain a film 15. The peeled film 15 is stretched in a predetermined direction such as a width direction by a stretching device 16. Further, the stretched film 15 is further dried by a film drying device 17, and the dried film F is wound into a roll shape by a winding device 19 using the dried film F as a resin film.

  The casting die 20 is not particularly limited as long as the dope 14 can be discharged onto the surface of the endless belt support 11 by discharging the dope 14 in a ribbon shape. The casting die 20 includes a casting die main body 21 and a dope supply pipe 22 as shown in FIGS. The dope supply pipe 22 is connected to the upper end portion of the casting die body 21 and supplies the dope 14 into the casting die body 21. The casting die body 21 has a manifold part 21a for stably casting the dope onto the endless belt support 11, and a dope 14 for casting the dope 14 onto the endless belt support 11 by discharging the dope 14. A discharge port 21b and a slit portion 21c that is formed between the manifold portion 21a and the discharge port 21b and that allows the dope 14 to pass from the manifold portion 21a toward the discharge port 21b are provided. 2 and 3 are schematic cross-sectional views showing the periphery of a casting die and a casting membrane drying apparatus in the resin film manufacturing apparatus shown in FIG. The resin solution (dope) 14 discharged from the casting die 20 is also called a casting ribbon 14a until the resin solution (dope) 14 is discharged from the casting die 20 and is grounded on the endless belt support 11. After being grounded on the belt support 11, it is also referred to as a casting membrane (web) 14b.

  As shown in FIG. 1, the endless belt support 11 is an endless belt that travels indefinitely. For example, a metal endless belt that travels infinitely and has a mirror surface is preferably used. As the endless belt, for example, a belt made of stainless steel or the like is preferably used from the viewpoint of peelability of the cast film. The width of the casting film cast by the casting die 20 is preferably 80 to 99% with respect to the width of the endless belt support 11 from the viewpoint of effectively utilizing the width of the endless belt support 11. For example, in order to finally obtain a resin film having a width of 1500 to 4000 mm, the width of the endless belt support 11 is preferably 1800 to 4500 mm. A drum support may be used instead of the endless belt support. As this drum support, for example, a rotating metal drum having a mirror surface is preferably used.

  The traveling speed of the endless belt support 11 is not particularly limited, but is preferably about 50 to 200 m / min, for example. The draft ratio, which is the ratio of the traveling speed of the endless belt support 11 to the discharge speed of the dope 14 from the casting die 20, is not particularly limited, but is preferably about 0.8 to 5.0, for example. . When the draft ratio is within this range, the cast film can be stably formed. For example, if the draft ratio is too large, there is a tendency to cause a phenomenon called neck-in in which the cast film is reduced in the width direction, and if so, a wide film cannot be formed.

  And the endless belt support body 11 dries the solvent in dope, conveying the cast film (web) 14b formed on the surface. When the cast film 14b is first transported by the rotation of the endless belt support 11, the solvent in the dope is gradually evaporated and dried. In the resin film manufacturing method according to the present embodiment, the drying film blown from the casting film drying device 31 is applied to the casting film 14b on the endless belt support 11, and the casting film 14b is dried. To do. Further, in the resin film manufacturing method according to the present embodiment, not only the drying air from the casting membrane drying device 31 but also the surface of the endless belt support 11 on the side where the casting membrane 14b is not formed, It dries using the cast film drying apparatus 32 which applies a drying wind. In this embodiment, the casting membrane drying device 32 is used, but the casting membrane drying device 32 may not be used. In this embodiment, the drying apparatus that blows the drying air applied to the casting film is the casting film drying apparatus 31.

  The casting membrane drying device 31 is a device that applies drying air to the casting membrane 14b on the endless belt support 11 to dry the casting membrane 14b. The casting membrane drying device 31 is located above the casting membrane 14b, and has an apparatus main body 31a in which a plurality of slits 34 are formed on the casting film side, and for supplying the drying air 35 into the apparatus main body 31a. A drying air supply pipe 33. When the drying air 35 is supplied from the drying air supply pipe 33 into the apparatus main body 31a, the supplied drying air is blown out from the slit 34 toward the casting film 14b. . When this drying air hits the casting film 14b, the casting film is dried. The drying air may be a heating air in order to improve the drying property of the cast film.

  The slit 34 is not particularly limited as long as the dry air is blown toward the casting film 14b, but the flow direction of the dry air is inclined toward the downstream of the running direction of the endless belt support 11. It is preferable that the slit is blown out from the viewpoint that the influence of the drying air on the casting ribbon 14a is reduced. Moreover, it is preferable that the angle which the dry wind blown off from the said slit 34 and the surface of the said endless belt support body 11 make is 0-45 degrees, and it is more preferable that it is 15-30 degrees. If this angle is too small, the distance until the drying air blown from the slit 34 reaches the casting film 14b on the endless belt support 11 becomes long, and the speed at which the drying air collides with the casting film 14b is increased. It tends to be too slow and the drying efficiency decreases. If the angle is too large, the flow direction of the drying air is less inclined toward the downstream side in the running direction of the endless belt support 11, and if the angle is increased, the flow direction of the drying air is changed to the endless belt support. The body 11 is blown out with an inclination toward the upstream in the traveling direction. In such a case, the drying air tends to flow toward the casting ribbon, and it tends to be difficult to prevent the drying air from moving toward the casting ribbon.

  The cast film drying device 32 is a device for drying the cast film by applying drying air to the surface (back surface) of the endless belt support 11 on which the cast film is not formed. . The casting membrane drying device 32 has the same configuration as the casting membrane drying device 31, and is used to supply a device main body 32a having a plurality of slits 37 and a drying air 38 into the device main body 32a. And a dry air supply pipe 36. Since the drying air 38 is not directly applied to the casting membrane, it is preferably a heating air capable of heating the endless belt support 11 in order to contribute to the drying of the casting membrane. In addition, since it is not necessary to consider the influence of the drying air on the casting ribbon, the slit 37 in the casting membrane drying device 32 blows out the drying air in a direction perpendicular to the endless belt support 11. May be.

  When drying with the above-described cast film drying apparatuses 31 and 32, the web temperature varies depending on the solvent of the dope, but in consideration of the conveyance speed and productivity associated with the evaporation time of the solvent, for example, −5 It is preferable to raise the temperature of the drying air so that it becomes ˜70 ° C. Moreover, it is more preferable to raise the temperature of drying air so that the temperature of a web may be 0-60 degreeC. The higher the temperature of the web, the higher the drying speed of the solvent, which is preferable. However, when the web temperature is too high, foaming and flatness tend to deteriorate.

  The wind pressure of the drying air is preferably 50 to 5000 Pa, for example, considering the uniformity of solvent evaporation.

  Further, the resin film manufacturing apparatus includes the prevention mechanism 40. As the prevention mechanism 40, if the flow of the drying air toward the casting ribbon 14a above the casting film 14b between the casting die 20 and the casting film drying device 31 can be prevented, It is not limited. As the prevention mechanism 40, for example, the side closer to the casting membrane drying device 31 (the side far from the casting die 20) is the casting die 20 between the casting die 20 and the casting membrane drying device 31. The mechanism which can make atmospheric | air pressure lower than the near side (side far from the casting film drying apparatus 31) is mentioned. By such a mechanism, it is possible to suppress the drying air blown from the cast film drying device 31 from flowing toward the upstream in the traveling direction of the endless belt support 11. Further, the difference in pressure between the vicinity of the casting film drying device 31 and the vicinity of the casting die 20 is a pressure difference that suppresses the flow of the drying air toward the upstream in the traveling direction of the endless belt support 11. . If this pressure difference is too large, the drying air can be prevented from flowing toward the upstream in the running direction of the endless belt support 11, but between the casting die 20 and the casting membrane drying device 31. Above the casting membrane 14b, the air flow toward the casting membrane drying device 31 tends to increase.

  Specific examples of the prevention mechanism 40 include the prevention mechanism 40 shown in FIGS. 2 and 3.

  Specifically, as shown in FIG. 2, the prevention mechanism 40 is provided between the casting die 20 and the casting film drying device 31, on the side close to the casting film drying device 31, and on the casting die 20. A mechanism is provided in which a partition plate 41 that is divided into a close side is provided and the side close to the casting membrane drying apparatus 31 is decompressed. The partition plate 41 is provided at a predetermined interval from the endless belt support 11. Then, the casting membrane drying device 31 side is decompressed so that the casting membrane drying device 31 side is depressurized from the partition plate 41 to the casting die 20 side. As a method of reducing the pressure, for example, a method of reducing the pressure on the entire side of the casting membrane drying apparatus 31 with a decompression device provided on the casting membrane drying apparatus 31 from the partition plate 41 can be cited. In this way, by reducing the space near the casting membrane drying device 31 partitioned by the partition plate 41, the drying air blown from the casting membrane drying device 31 flows toward the casting ribbon 14a. To prevent. Therefore, the flow of the drying air toward the casting ribbon 14a above the casting film 14b between the casting die 20 and the casting film drying device 31 can be prevented.

  Further, as shown in FIG. 3, the prevention mechanism 40 includes a decompression chamber 42 having an endless belt support side opened on the upstream side in the running direction of the endless belt support 11 of the cast film drying device 31, and a decompression chamber. And an intake pipe 43 for sucking the inside of the air intake 42. In this manner, by sucking the inside of the decompression chamber 42 from the intake pipe 43, the inside of the decompression chamber 42 provided on the upstream side in the traveling direction of the endless belt support 11 of the casting membrane drying device 31 is decompressed. This prevents the drying air blown from the casting film drying device 31 from flowing toward the casting ribbon 14a. Therefore, the flow of the drying air toward the casting ribbon 14a above the casting film 14b between the casting die 20 and the casting film drying device 31 can be prevented.

  In the resin film manufacturing method according to the present embodiment, as described above, the drying air for drying the casting film 14b on the endless belt support 11 is directed toward the casting ribbon 14a by the prevention mechanism 40. Can be prevented. For this reason, it can fully suppress that a casting ribbon shakes with the wind resulting from dry wind, and, thereby, the nonuniformity generate | occur | produces in the manufactured resin film. From this, even if it is a case where a thin resin film is manufactured, a high quality resin film can be manufactured by manufacturing with the said manufacturing method.

  In addition, above the casting film 14b between the casting die 20 and the casting film drying device 31, as described above, the drying air is prevented from blowing toward the casting ribbon 14a. And as above-mentioned, as a wind speed which goes to the said casting film drying apparatus 31 from the said casting ribbon 14a above the casting film 14b between the casting die 20 and the casting film drying apparatus 31, it is drying. Although it is only necessary to prevent the wind from blowing toward the casting ribbon 14a, for example, it is preferably 0 to 2 m / sec, and more preferably 0 to 1 m / sec. If the wind speed from the casting ribbon toward the drying device is too high, the generation of streaks due to wind tends not to be sufficiently suppressed even though the wind caused by the drying wind can be prevented from hitting the casting ribbon. Moreover, when the wind speed toward the said drying apparatus from the said casting ribbon is too low, it cannot fully prevent that a drying wind blows toward a casting ribbon. Note that the wind speed here is, for example, the wind speed at a height of 10 mm from the surface of the endless belt support 11. More specifically, the air velocity at a position of 10 mm from the surface of the endless belt support 11 and 10 mm from the discharge port 21 b of the casting die 20 toward the casting film drying device 31 may be mentioned. . Moreover, this wind speed can be measured with an anemometer, for example.

  Further, the position of the casting membrane drying device 31 is preferably such that the upstream end surface in the running direction of the endless belt support 11 is 500 to 1500 mm from the discharge port 21 b of the casting die 20. If the casting membrane drying device 31 is too close to the casting die 20, the casting membrane that has reached the casting membrane drying device 31 is insufficiently dried. Therefore, the drying air blown from the casting membrane drying device 31 There is a tendency for defects to occur due to hitting. For this reason, there is a tendency that streaks occur in the obtained resin film. Moreover, when the casting film drying apparatus 31 is too far from the casting die 20, the casting film is excessively dried before reaching the casting film drying apparatus 31, and the casting film cannot be appropriately dried. Tend. For this reason, there exists a tendency for the flatness of the obtained resin film to fall.

  The peeling roller 13 is disposed in the vicinity of the surface of the endless belt support 11 on which the dope is cast, and the distance between the endless belt support 11 and the peeling roller 13 is preferably 1 to 100 mm. Further, the peeling roller 13 is used when peeling a web that has been dried to some extent on the endless belt support 11. Using the peeling roller 13 as a fulcrum, the dried web is peeled as a film 15 by pulling the dried web with tension. Moreover, when peeling a film from the endless belt support body 11, the film 15 is extended | stretched in the conveyance direction (Machine Direction: MD direction) of a film with peeling tension | tensile_strength and subsequent conveyance tension | tensile_strength.

  The stretching device 16 stretches the film 15 peeled from the endless belt support 11 in a direction (Transverse Direction: TD direction) orthogonal to the web conveyance direction. Specifically, both ends in a direction perpendicular to the film transport direction are gripped with a clip or the like, and the distance between the opposing clips is increased to extend in the TD direction.

  The film drying device 17 includes a plurality of transport rollers, and dries the film while transporting the film between the rollers. At that time, as shown in FIG. 1, the heated air 18 may be dried by circulating it in the film drying device 17, or may be dried using infrared rays, or the heated air and infrared rays. And may be dried together. It is preferable to use heated air from the viewpoint of simplicity.

  The winding device 19 winds the film F having a predetermined residual solvent ratio in the film drying device 17 around the winding core. Moreover, you may emboss by a hot embossing mechanism in the width direction both ends before winding up the film F to a winding core. In addition, it is preferable that the temperature at the time of winding is cooled to room temperature in order to prevent scratching due to shrinkage after winding and loosening of winding. The winding device to be used can be used without particular limitation, and may be a commonly used winding device, such as a constant tension method, a constant torque method, a taper tension method, a program tension control method with a constant internal stress, or the like. It can be wound up by the method.

  Moreover, the manufacturing apparatus of a resin film will not be specifically limited if the manufacturing method of the resin film which concerns on this embodiment can be implemented. Specifically, the apparatus for producing a resin film may not include a stretching apparatus or a drying apparatus, and may be provided with a plurality of apparatus instead of one each.

  Moreover, although the apparatus provided with the endless belt support body was illustrated as a support body in the aspect demonstrated above, the manufacturing apparatus of the resin film illustrated the drum support body. Specifically, instead of the endless belt support 11, a resin film manufacturing apparatus similar to the resin film manufacturing apparatus shown in FIG. Moreover, as a drum support body, the rotation drive drum made from stainless steel etc. which gave the hard chrome plating process to the surface is mentioned, for example.

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

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

  The transparent resin is not particularly limited as long as it is a resin having transparency when formed into a substrate by a solution casting film forming method or the like, but is easily manufactured by a solution casting film forming method or the like. It is preferable that the adhesive property with other functional layers such as a hard coat layer is excellent and that it is optically isotropic. Here, the transparency means that the visible light transmittance is 60% or more, preferably 80% or more, and more preferably 90% or more.

  Specific examples of the transparent resin include cellulose ester resins such as cellulose diacetate resin, cellulose triacetate resin, cellulose acetate butyrate resin, and cellulose acetate propionate resin; polyethylene terephthalate resin and polyethylene naphthalate resin. Acrylic resins such as polymethyl methacrylate resins; Polysulfone (including polyether sulfone) resins, polyethylene resins, polypropylene resins, cellophane, polyvinylidene chloride resins, polyvinyl alcohol resins, ethylene vinyl alcohol resins, Shinji Vinyl resins such as tactic polystyrene resins, cycloolefin resins and polymethylpentene resins; polycarbonate resins; polyarylate resins Polyetherketone resins; polyether ketone imide resin; can be mentioned fluorine-based resin or the like; a polyamide resin. Among these, cellulose ester resins, cycloolefin resins, polycarbonate resins, and polysulfone (including polyethersulfone) resins are preferable. Furthermore, cellulose ester resins are preferred, and among cellulose ester resins, cellulose acetate resins, cellulose propionate resins, cellulose butyrate resins, cellulose acetate butyrate resins, cellulose acetate propionate resins, and cellulose triacetate resins are preferred, Cellulose triacetate resin is particularly preferred. Moreover, the said transparent resin may use the transparent resin illustrated above independently, and may use it in combination of 2 or more type.

  Next, the cellulose ester resin will be described.

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

  The average molecular weight and molecular weight distribution of a resin such as a cellulose ester resin can be measured using gel permeation chromatography or high performance liquid chromatography. Therefore, the number average molecular weight (Mn) and the weight average molecular weight (Mw) can be calculated using these, and the ratio can be calculated.

  The cellulose ester resin preferably has an acyl group as a substituent, specifically, an acyl group having 2 to 4 carbon atoms. As a substitution degree of this acyl group, it is preferable that it is 2.2-2.95, for example. As the degree of substitution, for example, when the substitution degree of the acetyl group is X and the substitution degree of the propionyl group or butyryl group is Y, the total value of X and Y is 2.2 or more and 2.95 or less. X is preferably greater than 0 and less than or equal to 2.95.

  In addition, the portion not substituted with an acyl group usually exists as a hydroxyl group. These cellulose ester resins can be synthesized by a known method. The measuring method of the substitution degree of an acyl group can be measured according to the provisions of ASTM-D817-96.

  As the solvent used in the present embodiment, a solvent containing a good solvent for the transparent resin can be used. The good solvent varies depending on the transparent resin used. For example, when the transparent resin is a cellulose ester resin, the good solvent and the poor solvent change depending on the acyl group substitution degree of the cellulose ester. For example, when acetone is used as the solvent, the cellulose ester acetate ester (acetyl group substitution degree 2) .4), cellulose acetate propionate is a good solvent, and cellulose acetate (acetyl group substitution degree 2.8) is a poor solvent. Therefore, since the good solvent and the poor solvent differ depending on the transparent resin used, the case of a cellulose ester resin will be described as an example.

  Examples of good solvents for cellulose ester resins include organic halogen compounds such as methylene chloride, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, dioxolane derivatives, cyclohexanone, Ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3- Hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, etc. Can be mentioned. Among these, organic halogen compounds such as methylene chloride, dioxolane derivatives, methyl acetate, ethyl acetate, acetone and the like are preferable. Among these, methylene chloride is preferable. These good solvents may be used alone or in combination of two or more.

  The dope may contain a poor solvent as long as the transparent resin does not precipitate. Examples of poor solvents for cellulose ester resins include alcohols having 1 to 8 carbon atoms such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol, methyl ethyl ketone, and methyl isobutyl. Examples include ketones, propyl acetate, monochlorobenzene, benzene, cyclohexane, tetrahydrofuran, methyl cellosolve, and ethylene glycol monomethyl ether. Among these, ethanol is preferable. These poor solvents may be used alone or in combination of two or more.

  In addition, the resin solution used in the present embodiment may contain other components (additives) other than the transparent resin and the solvent as long as the effects of the present invention are not impaired. Examples of the additive include fine particles, plasticizers, antioxidants, ultraviolet absorbers, heat stabilizers, conductive substances, flame retardants, lubricants, and matting agents.

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

  The method for dissolving the cellulose ester resin when preparing the dope is not particularly limited, and a general method can be used. By combining heating and pressurization, it is possible to heat above the boiling point of the solvent at normal pressure, and it is possible to dissolve the cellulose ester resin in the solvent above the boiling point at normal pressure. It is preferable from the viewpoint of preventing the occurrence of. In addition, a method in which a cellulose ester resin is mixed with a poor solvent and wetted or swollen, and then a good solvent is added and dissolved is also preferably used.

  Next, the obtained cellulose ester resin solution is filtered using a suitable filter medium such as filter paper.

  According to the manufacturing method of the resin film which concerns on this embodiment as mentioned above, even if it is a resin film with thin thickness, a high quality resin film can be manufactured. Therefore, even if the obtained resin film is thin, it is of high quality.

  The thickness (film thickness) of the resin film is more preferably 10 to 40 μm. Such a film thickness is preferable from the viewpoint of thinning the liquid crystal display device and stable productivity of the resin film. On the other hand, when trying to manufacture a resin film having a small film thickness, there is a tendency that a problem occurs when the draft ratio is low and a problem occurs when the draft ratio is high. Even if it is so, if it is the manufacturing method of the resin film which concerns on this embodiment, generation | occurrence | production of these malfunctions can fully be suppressed. Therefore, a resin film capable of suitably realizing thinning of the liquid crystal display device is obtained. In addition, a film thickness here is an average film thickness. As this measuring method, for example, the film thickness is measured at 20 to 200 locations in the width direction of the optical film with a contact film thickness meter manufactured by Mitutoyo Corporation, and the average value of the measured values is calculated as the film thickness.

  Moreover, it is preferable that the width | variety of the resin film obtained here is 1000-4000 mm from the point of the use to a large sized liquid crystal display device, the use efficiency of the resin film at the time of polarizing plate processing, and production efficiency.

(Polarizer)
The resin film obtained by the method for producing a resin film according to this embodiment can be used as a protective film for a polarizing plate. Thus, the polarizing plate using the resin film as a protective film includes a polarizing element and a transparent protective film disposed on the surface of the polarizing element, and the transparent protective film is the resin film. The polarizing element is an optical element that emits incident light converted to polarized light.

  As the polarizing plate, for example, a completely saponified polyvinyl alcohol aqueous solution is used on at least one surface of a polarizing element produced by immersing and stretching a polyvinyl alcohol film in an iodine solution. A laminate is preferred. Further, the resin film may be laminated on the other surface of the polarizing element, or a transparent protective film for another polarizing plate may be laminated.

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

  Such a polarizing plate uses the resin film according to the present embodiment as a transparent protective film. Even if this resin film is thin, it is of high quality. For this reason, even if the obtained polarizing plate is thin, it is high quality. Therefore, when the obtained polarizing plate is applied to, for example, a liquid crystal display device, high image quality of the liquid crystal display device can be realized.

(Liquid crystal display device)
Moreover, the said polarizing plate can be used as a polarizing plate of a liquid crystal display device. The liquid crystal display device provided with the polarizing plate 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. is there. Note that the liquid crystal cell is a cell in which a liquid crystal substance is filled between a pair of electrodes, and by applying a voltage to the electrodes, the alignment state of the liquid crystal is changed and the amount of transmitted light is controlled. Such a liquid crystal display device uses the polarizing plate as a transparent protective film for the polarizing plate. By doing so, a high-quality liquid crystal display device with improved contrast and the like can be obtained.

  As described above, the present specification discloses various modes of technology, of which the main technologies are summarized below.

  One aspect of the present invention includes a casting step of casting a resin solution containing a transparent resin from a casting die on a traveling support to form a casting film, and drying air blown from a drying device. The casting die on the support, and a drying step for drying the casting membrane, and a peeling step for peeling the dried casting membrane from the support. Prevention of the flow of the drying air toward the casting ribbon until the resin solution discharged from the casting die is grounded on the support above the casting film with the drying device It is a manufacturing method of the resin film characterized by using a mechanism.

  According to such a structure, even if it is a resin film with thin thickness, the manufacturing method of the resin film which can manufacture a high quality resin film can be provided. Specifically, it is thought to be as follows.

  Drying air for drying the cast film on the support can be prevented from going to the cast ribbon by the prevention mechanism. For this reason, it is possible to reduce the influence of the drying air on the casting ribbon which is the casting film discharged from the casting die. Specifically, it is possible to sufficiently suppress the occurrence of unevenness in the produced resin film due to shaking of the casting ribbon due to the wind caused by the drying air. Therefore, according to the said structure, even if it is a thin resin film, a high quality resin film can be manufactured.

  Moreover, in the manufacturing method of the said resin film, the wind speed which goes to the said drying apparatus from the said casting ribbon above the said casting film between the said casting die and the said drying apparatus is 0-2 m / sec. It is preferable.

  According to such a structure, even if it is a resin film with thin thickness, a higher quality resin film can be manufactured. That is, if the wind speed above the casting film is within the above range, the influence of the wind caused by the dry wind on the casting ribbon can be suitably suppressed. Therefore, the occurrence of unevenness due to shaking of the casting ribbon can be sufficiently suppressed, and a higher quality resin film can be produced.

  Moreover, in the manufacturing method of the said resin film, it is preferable that the distance of the running direction upstream end surface of the said support body and the discharge outlet of the said casting die of the said drying apparatus is 500-1500 mm.

  According to such a configuration, the drying air blown from the drying device can suitably dry the cast film on the support while suppressing the occurrence of unevenness. Therefore, a higher quality resin film can be manufactured.

  Further, in the method for producing the resin film, the prevention mechanism includes a partition plate that partitions the casting die and the drying device, and an atmospheric pressure of the partition plate on the downstream side in the running direction of the support body, It is preferable that the pressure be lower than the pressure on the upstream side.

  According to such a configuration, the casting is performed above the casting film between the casting die and the drying device by creating a pressure difference in the adjacent space separated by the partition plate. The flow of the dry air toward the ribbon can be prevented. Therefore, even if the resin film is thin, a high-quality resin film can be easily manufactured.

  Further, in the method for producing the resin film, the prevention mechanism includes a decompression chamber having the support side opened on the upstream side of the drying device in the running direction of the support, and decompressing the decompression chamber. preferable.

  According to such a configuration, the decompression chamber provided on the upstream side of the support in the traveling direction of the drying device is decompressed, so that the casting film between the casting die and the drying device is reduced. It is possible to prevent the drying air from flowing toward the casting ribbon above. Therefore, even if the resin film is thin, a high-quality resin film can be easily manufactured.

  Moreover, in the manufacturing method of the said resin film, it is preferable that the thickness of the said resin film is 10-40 micrometers.

  When the thickness of the resin film is thin, as described above, the resin film is easily affected by the external environment such as wind blown on the casting ribbon. And the thin resin film as mentioned above tends to generate the trouble based on the influence of such an external environment. Even if it is a thin resin film which is easy to generate | occur | produce such a malfunction, according to the manufacturing method of the resin film of the said structure, a high quality resin film can be manufactured.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a resin film with thin thickness, the manufacturing method of the resin film which can manufacture a high quality resin film can be provided.

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

[Example A]
First, the case of manufacturing a resin film having a film thickness of 40 μm was examined.

Example 1
(Preparation of dope)
First, 100 parts by mass of cellulose triacetate resin (acetyl group substitution degree 2.88) as a transparent resin was added to a dissolution tank containing 418 parts by mass of methylene chloride and 23 parts by mass of ethanol, and further 8 masses of triphenyl phosphate. Part, 2 parts by mass of ethylphthalylethyl glycol, 1 part by mass of Tinuvin 326 (manufactured by BASF Japan Ltd.), and 0.1 part by mass of Aerosil 200V (manufactured by Nippon Aerosil Co., Ltd.) were added. And after raising the liquid temperature to 80 ° C., the mixture was stirred for 3 hours. By doing so, a resin solution was obtained. Then, stirring was complete | finished and it was left until the liquid temperature became 43 degreeC. And the resin solution after standing was filtered using filter paper with a filtration accuracy of 0.005 mm. Air bubbles in the resin solution were degassed by allowing the resin solution after filtration to stand overnight. Using the resin solution thus obtained as a dope, a resin film was produced as follows.

(Manufacture of resin film)
First, the temperature of the obtained dope was adjusted to 35 ° C., and the temperature of the endless belt support was adjusted to 20 ° C. Then, using a resin film manufacturing apparatus as shown in FIG. 1, a dope was cast from a casting die (coat hanger die) onto an endless belt support having a running speed (casting speed) of 70 m / min. The slit interval of the casting die was adjusted in advance so that the finally obtained resin film had a thickness of 40 μm. The endless belt support is an endless belt made of stainless steel (manufactured by SUS316) and an endless belt having a three-dimensional surface roughness (Ra) measured by a scanning atomic force microscope (AFM) polished to a super mirror surface with an average of 1.0 nm. A belt support was used. Then, a casting film drying apparatus for applying drying air to the casting film on the endless belt support, the end face of the endless belt support upstream in the running direction has a distance L from the discharge port of the casting die. And 500 mm. Further, by the prevention mechanism as shown in FIG. 3, casting is performed so that the wind velocity V from the casting ribbon to the drying device is 0 m / sec above the casting film between the casting die and the drying device. The flow of dry air toward the ribbon was prevented. The wind speed V is a height of 10 mm from the surface of the endless belt support, and is a wind speed measured using an anemometer at a position 10 mm from the discharge port of the casting die toward the casting film drying apparatus. is there.

  And a web is dried by sending 30 degreeC drying air to the web on an endless belt support body from a casting film drying apparatus. The dried web was peeled off as a film from the endless belt support.

  While the peeled film was transported by a transport roller, the residual solvent ratio was dried to 80% by mass. The dried film was stretched 6% in the TD direction while gripping both ends of the film with a clip in an environment of 100 ° C. using a stretching device (tenter), and then the clip was released. Then, the stretched film was dried at 125 ° C. using a drying apparatus while being conveyed by a conveyance roller. Then, the dried film was wound up with a winding device, and the resin film wound up in roll shape was obtained.

  The resin film thus obtained was a cellulose triacetate film having a film thickness of 40 μm, a width of 2000 mm, and a winding length of 3000 m.

(Examples 2 to 6, Comparative Examples 1 and 2)
Examples 2 to 6 and Comparative Examples 1 and 2 are the same as Example 1 except that the distance L and the wind speed V are changed to the values in Table 1 below.

(Example 7)
Example 7 is the same as Example 1 except that the prevention mechanism shown in FIG. 2 is used.

[Evaluation]
Using the obtained resin film, a polarizing plate was prepared by the following method, which was attached to an image display device, and the appearance was evaluated.

(Preparation of polarizing plate)
A 120 μm thick polyvinyl alcohol film was immersed in 100 g of an aqueous solution containing 1 g of iodine and 4 g of boric acid, and stretched 6 times at 50 ° C. to prepare a polarizing film. The obtained resin film is subjected to the following alkali saponification treatment, and the resin film subjected to the alkali saponification treatment is bonded to both the front and back surfaces of the polarizing film, using a 5% aqueous solution of a fully saponified polyvinyl alcohol as an adhesive, A polarizing plate was produced.

(Alkaline saponification treatment)
Process Treatment liquid Treatment temperature Treatment time Saponification process 2 mol / L-NaOH 50 ° C. 90 seconds Water washing process Water 30 ° C. 45 seconds Neutralization process 10 mass% HCl 30 ° C. 45 seconds Water washing process Water 30 ° C. 45 seconds

  The said resin film was performed in order of the said saponification process, the water washing process, the neutralization process, and the water washing process, and then dried at 80 degreeC.

  A liquid crystal display device was produced by attaching the produced polarizing plate to a liquid crystal layer of the liquid crystal display device. Specifically, it was as follows.

(Liquid crystal display device)
Of the two pairs of polarizing plates installed on the liquid crystal display device (manufactured by NEC Corporation, color liquid crystal display MultiSync LCD1525J: model name LA-1529HM) with the liquid crystal layer sandwiched between them, the polarizing plate on one side on the viewer side It peeled off and the said polarizing plate which matched the polarization direction was affixed here, and the liquid crystal display device was produced.

  The following evaluation was performed using the obtained liquid crystal display device.

  Regarding the liquid crystal display device, under illumination with a white LED, the unevenness of reflected light and the displayed image were observed as an optical characteristic at an angle of 35 ° from the normal direction. As a result, if the unevenness considered to be caused by the step extending perpendicular to the resin film conveying direction could not be confirmed at all, and the displayed image was not uneven and clear, it was evaluated as “◎”. Moreover, although the unevenness considered to be caused by the above-mentioned stage can be confirmed slightly, when the displayed image is clear and clear, it was evaluated as “◯”. In addition, when the unevenness considered to be caused by the steps can be confirmed and the displayed image can also be confirmed, it was evaluated as “Δ”. Moreover, when the nonuniformity considered to be originated from the said stage can be confirmed clearly, it evaluated as "*", and when the nonuniformity was clearer than it, it evaluated as "XX".

  The results are shown in Table 1 together with the film thickness, distance L, and wind speed V of the resin film.

  As can be seen from Table 1, when the prevention mechanism for preventing the flow of dry air toward the casting ribbon is used (Examples 1 to 7), the flow of the dry air toward the casting ribbon is not prevented ( From Comparative Examples 1 and 2, it was found that a resin film in which the occurrence of unevenness was suppressed could be produced. From this, it turned out that Examples 1-7 can fully suppress generation | occurrence | production of the nonuniformity based on a dry wind.

  Further, when the wind speed from the casting ribbon toward the casting membrane drying apparatus is 2 m / sec or less (Examples 1 to 4), the case where the wind speed exceeds 2 m / sec (Examples 5 and 6) is more uneven. It turned out that generation | occurrence | production can be suppressed more. From this, it can be seen that it is preferable to prevent the flow of the drying air by the prevention mechanism so that the wind speed A is 2 m / sec or less, that is, the wind speed A is 0 to 2 m / sec.

[Example B]
Next, the case of manufacturing a resin film having a film thickness of 10 μm, which is more likely to cause unevenness, than the case of manufacturing a resin film having a film thickness of 40 μm was examined.

(Examples 8 to 13, Comparative Examples 3 and 4)
Examples 8 to 13 and Comparative Examples 3 and 4 were the same as Example 1 except that the film thickness of the resin film was 10 μm, and the distance L and the wind speed V were changed to the values shown in Table 2 below. It is.

  The same evaluation as in Example A was performed. The results are shown in Table 2 together with the film thickness, distance L, and wind speed V of the resin film.

  As can be seen from Table 2, the flow of drying air toward the casting ribbon even when producing a resin film with a film thickness of 10 μm, which is more likely to cause unevenness, than when producing a resin film with a film thickness of 40 μm. In the case of using a prevention mechanism for preventing water (Examples 8 to 13), the resin in which the occurrence of unevenness is suppressed is less than in the case of not preventing the flow of dry air toward the casting ribbon (Comparative Examples 3 and 4). It has been found that a film can be produced. From this, it was found that in Examples 8 to 13, even when a resin film having a film thickness of 10 μm was produced, the occurrence of unevenness due to dry air could be sufficiently suppressed.

  Further, when the wind speed from the casting ribbon toward the casting membrane drying apparatus is 2 m / sec or less (Examples 8 to 11), it is more uneven than when it exceeds 2 m / sec (Examples 12 and 13). It turned out that generation | occurrence | production can be suppressed more. From this, it can be seen that it is preferable to prevent the flow of the drying air by the prevention mechanism so that the wind speed A is 2 m / sec or less, that is, the wind speed A is 0 to 2 m / sec.

[Example C]
Next, the influence of the distance L was examined.

(Examples 14 to 17)
Examples 14-17 are the same as Example 1 except having changed the film thickness of the resin film, distance L, and the wind speed V into the value of Table 3 below.

  In Examples 14 and 15, although the occurrence of unevenness due to the drying wind was sufficiently suppressed, the casting film drying apparatus was too close to the casting die, and the casting film reached the casting film drying apparatus was not dried. Since it was insufficient, streaks generated by the drying air blown from the cast film drying apparatus were confirmed.

  Further, in Examples 16 and 17, although the generation of unevenness due to the drying air was sufficiently suppressed, the flow of the casting film drying apparatus was too far from the casting die and reached the casting film drying apparatus. The drying of the cast film progressed too much, and the flatness of the resin film was lowered.

  From these, it was found that the distance L between the upstream end surface in the running direction of the endless belt support and the discharge port of the casting die of the casting membrane drying apparatus is preferably 500 to 1500 mm.

  This application is based on Japanese Patent Application No. 2014-228253 filed on November 10, 2014, the contents of which are included in the present application.

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

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a resin film with thin thickness, the manufacturing method of the resin film which can manufacture a high quality resin film is provided.

Claims (5)

A casting step of casting a resin solution containing a transparent resin from a casting die on a traveling support to form a casting film;
A drying step in which drying air blown from a drying device is applied to the casting film on the support, and the casting film is dried; and
A peeling step of peeling the dried cast film from the support,
Above the casting film between the casting die and the drying device, the drying air flows toward the casting ribbon until the resin solution discharged from the casting die contacts the support. Using a prevention mechanism to prevent flow ,
The prevention mechanism includes a partition plate that partitions between the casting die and the drying device, and the pressure on the downstream side of the partition plate in the running direction of the support is lower than the pressure on the upstream side. A method for producing a resin film. A casting step of casting a resin solution containing a transparent resin from a casting die on a traveling support to form a casting film;
A drying step in which drying air blown from a drying device is applied to the casting film on the support, and the casting film is dried; and
A peeling step of peeling the dried cast film from the support,
Above the casting film between the casting die and the drying device, the drying air flows toward the casting ribbon until the resin solution discharged from the casting die contacts the support. Using a prevention mechanism to prevent flow,
The method for producing a resin film, wherein the prevention mechanism includes a decompression chamber having the support side opened on the upstream side of the drying device in the running direction of the support, and decompresses the decompression chamber. 10 mm high from the surface of the support above the casting film between the casting die and the drying device, and 10 mm from the outlet of the casting die toward the drying device. The method for producing a resin film according to claim 1 or 2 , wherein the wind speed at the position from the casting ribbon toward the drying device is 0 to 2 m / sec. The production of the resin film according to any one of claims 1 to 3 , wherein a distance between an end surface on the upstream side in the running direction of the support and a discharge port of the casting die of the drying device is 500 to 1500 mm. Method. The thickness of the said resin film is 10-40 micrometers, The manufacturing method of the resin film of any one of Claims 1-4 .

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