JP4881749B2 - Coating film drying method and drying apparatus - Google Patents

Description

  The present invention relates to a coating film drying method and apparatus, and in particular, in the production of an optical compensation sheet or the like, a long and wide coating film surface formed by applying a coating liquid containing an organic solvent to a long support. The present invention relates to a drying method and apparatus for drying.

  In order to improve viewing angle characteristics in a liquid crystal display device, an optical compensation sheet is provided as a retardation plate between a pair of polarizing plates and a liquid crystal cell. For example, Patent Document 1 discloses a method for producing a long optical compensation sheet. In the method disclosed in Patent Document 1, a coating liquid containing an alignment film forming resin is applied to the surface of a long transparent film, and then a rubbing treatment is performed to form the alignment film. In this method, a coating liquid containing a liquid crystalline discotic compound is applied to the coating film, and the applied coating film is dried.

  In the method for drying a coating solution of Patent Document 1, after applying a coating solution containing a liquid crystalline discotic compound on an alignment film, initial drying is performed under indoor air-conditioning conditions until drying with a regular drying device. The organic solvent inside is evaporated.

  In the optical compensation sheet produced by this method, the broad spots A (shown by thin lines) and the sharp spots B (shown by thick lines) as shown in FIG. These two types of spots (unevenness) A and B occur, which is not desirable because the yield of the product may be lowered in some cases.

  As a result of analyzing these two types of plaques A and B, the following was found. As shown in FIG. 8, the broad spots A were found to have a thin layer of the coating liquid film 2 containing a liquid crystalline discotic compound. Reference numeral 3 in FIG. 8 denotes a long support, and 4 denotes an alignment film layer. On the other hand, the orientation direction 6 of the orientation portion 5 (dark color portion) where the sharp spots B are generated is shifted from the orientation portion 8 in the other normal orientation direction 7 as shown in FIG. I understood.

  As a method generally used as an effective measure against the spots (unevenness) A and B generated by such initial drying, the concentration of the coating liquid is increased or a thickener is added. Thus, there is a method for preventing the occurrence of spots by increasing the viscosity of the coating liquid and thereby suppressing the flow of the coating film surface immediately after coating by the drying air. As another method, there is a method of preventing the occurrence of spots by using a high-boiling solvent to produce a leveling effect even if the coating surface immediately after coating is flowed by the drying air.

In Patent Document 2, a drying zone is provided immediately after coating to surround a coating film surface to be dried of the traveling long support, and the drying zone is moved from one end side to the other end in the width direction of the long support. Disclosed is a drying method and apparatus capable of uniformly drying a coating film by changing the physical properties such as the viscosity of the coating liquid and the type of solvent by generating a unidirectional flow of drying air flowing to the side.
JP-A-9-73081 JP-A-2001-170547

  However, the method of increasing the viscosity of the coating solution by increasing the concentration of the coating solution or adding a thickener is to apply ultra-thin precision coating that forms an ultra-thin coating film by high-speed coating. There is a disadvantage that it cannot be done. Moreover, since the limit coating speed (the limit of the coating speed at which stable coating can be performed) decreases as the coating solution viscosity increases, high-speed coating becomes impossible as the viscosity increases, so that production efficiency is extremely deteriorated. .

  On the other hand, the method using a high boiling point solvent has the disadvantage that the drying time is increased and the amount of residual solvent remaining in the coating film is increased, and the production efficiency is deteriorated because the drying time increases accordingly.

  In the method shown in Patent Document 2, drying is delayed on the collecting side at the other end of the wind supply. Therefore, in order to complete the drying in the drying apparatus, the drying on the wind supply side must be accelerated. As a result, the spots generated by the initial drying sometimes worsen.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a drying method and apparatus capable of uniformly drying a coating film without changing the physical properties such as the viscosity of the coating liquid and the type of solvent. To do.

  In order to achieve the above object, the present invention provides a drying zone disposed immediately after application of the coating liquid in a coating film drying method formed by applying a coating liquid containing an organic solvent to a traveling long support. And passing the elongate support to the drying zone, supplying and exhausting 0.01 to 0.7 m / s of drying air to the drying zone, and supplying the drying air exhausted from the drying zone to the drying zone again. At the same time, 50% to 90% of the dry air is circulated through the bypass path.

  In order to achieve the above object, the present invention provides a coating film drying apparatus formed by applying a coating solution containing an organic solvent to a traveling long support by a coating machine, immediately after the coating machine. A drying apparatus main body that forms a drying zone for drying the coating film surface of the long support that travels, and a drying air that supplies and exhausts 0.01 to 0.7 m / s of drying air in the drying zone. Supply exhaust device, circulation path for supplying the dry air exhausted from the dry zone connected to the dry air supply exhaust device to the dry zone, and 50% to 90% of the dry air is circulated by bypass And a bypass path.

  According to the present invention, the coating film can be dried while maintaining the organic solvent concentration in the vicinity of the coating film surface in a constant state as soon as possible by circulating the drying air and further bypassing it. As a result, it is possible to prevent the above-mentioned two types of spots (unevenness) from occurring during drying and to perform uniform drying.

  Hereinafter, preferred embodiments of a coating film drying method and apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a plan view of a coating film drying apparatus of the present invention, and FIG. 2 is a side view of FIG. 1 viewed from the side.

  As shown in FIGS. 1 and 2, the coating film drying apparatus 10 of the present invention forms a drying zone 14 in which the coating film is dried by passing through a support 12 (hereinafter referred to as “web 12”). A drying device main body 16 is provided. In order to dry the coating film in the drying zone 14, the drying apparatus 10 includes a blower 21 for supplying and exhausting drying air to the drying zone 14. A circulation conduit 23 that forms a circulation path for circulating the drying air is provided in the drying apparatus 10. Further, a bypass conduit 25 is provided in the circulation conduit 23 for bypass-circulating the drying air circulating through the circulation conduit 23.

  The circulation conduit 23 includes an outside air port 27 for taking outside air into the circulation path and a waste outlet 29 for discharging the dry air in the circulation path to the outside of the circulation path.

  The drying apparatus 10 is provided immediately after a coating machine 20 that applies a coating solution containing an organic solvent to a traveling web 12. As the applicator 20, for example, a bar applicator provided with a wire bar 20A can be used, and an application liquid is applied to the lower surface of the web 12 supported by a plurality of backup rollers 22, 24, and 26. A coating film is formed.

  The drying device main body 16 is provided immediately after the coating machine 20, and is formed in a long rectangular box shape along the coating film surface side (the lower surface side of the web) of the traveling web 12, and among the sides of the box body The side of the coated film surface side (the upper side of the box) is cut off. As a result, a drying zone 14 is formed at a position facing the coating film surface to be dried of the traveling web 12. The drying zone 14 divides the drying apparatus main body 16 with a plurality of partition plates 28, 28... Orthogonal to the traveling direction of the web 12, thereby dividing the plurality of divided zones 14 A, 14 B, 14 C, 14 D, 14 E, 14 F, 14 G ( In this embodiment, the image is divided into seven divided zones. In this case, the distance between the upper end of the partition plate 28 that divides the drying zone 14 and the coating film surface formed on the web 12 is preferably in the range of 0.5 mm to 12 mm, more preferably in the range of 1 mm to 10 mm. .

  The drying apparatus 10 according to the embodiment is configured such that a unidirectional flow of drying air flowing from one end side to the other end side in the width direction of the web 12 is supplied and exhausted in the drying zone 14. In order to generate airflow in one direction, air supply ports 18A, 18B, 18C, 18D, 18E, 18F, and 18G formed on one side of both sides of the drying apparatus main body 16, and air supply ports 18A to 18G on the other side And exhaust ports 18H, 18I, 18J, 18K, 18L, 18M, and 18N formed to face each other. The air supply ducts 19A to 19G are connected to the air supply ports 18A to 18G. The exhaust ducts 19H to 19N are similarly connected to the other exhaust ports 18H to 18N.

  The air supply ducts 19A to 19G and the exhaust ducts 19H to 19N are connected to a circulation conduit 23 that constitutes a circulation path for dry air.

  By driving the blower 21 installed in the circulation conduit 23, the dry air supplied from the air supply ports 18A to 18G to the divided zones 14A to 14G is exhausted from the exhaust ports 18H to 18N. In each of the divided zones 14 </ b> A to 14 </ b> G, dry air flowing in one direction is generated from one end side (air supply port side) in the width direction of the web 12 toward the other end side (exhaust port side).

  In addition, by providing a blower, a circulation conduit, and a bypass conduit for each divided drying zone, the supply / exhaust amount can be individually controlled for each of the divided zones 14A to 14G.

  The circulation conduit 23 includes a bypass conduit 25 for circulating and bypassing the dry air. The flow of the drying air of the drying apparatus 10 will be described in the direction of the arrow shown in FIG. By driving the blower 21, the drying air A is supplied to the drying zone 14, and the drying air B is discharged from the drying zone 14. The drying air B discharged from the drying zone 14 is mixed with the outside air C introduced from the outside air port 27 in the circulation conduit 23. The mixed dry air D is further mixed with the dry air E from the bypass conduit 25 and travels through the circulation conduit 23. A part of the drying air F in which the drying air D and the drying air E are mixed is discharged from the disposal port 29 as the disposal air G. The remaining drying air H is divided into a drying air A sent to the circulation conduit 23 and a drying air E sent to the bypass conduit 25. In the present invention, there are two paths of drying air, that is, the drying air circulating through the drying zone 14 and the drying air circulating through the bypass conduit 25. According to a preferred embodiment of the present invention, it is preferable to circulate 50% to 90% of the circulated dry air by bypass.

  Next, based on FIG. 1, the relationship of the magnitude | size of the flow volume of each drying wind AH is shown. When it is considered that unexpected intrusion of air or the like into the drying zone 14 can be ignored, the following expression is satisfied.

[formula]
A = B
D = B + C
F = E + D = G + H
H = A + E
C = G
F: E = 1: 0.5 to 0.9
In particular, the present invention is characterized in that the flow rate of E flowing through the bypass conduit 25 is circulated at 50% to 90% of the flow rate of F flowing through the circulation conduit 23.

  FIG. 3 is a sectional view of the drying zone 14 </ b> B among the divided drying zones 14. The width of the drying device main body 16 is configured to be larger than the width of the web 12. A part of the open portion facing the coating film surface of the drying main body device 16 is covered with the air conditioning plate 32. The air conditioning plate 32 is provided to ensure a distance from the air supply port 18B to the coating film end and a distance from the coating film end to the exhaust port 18I. The air conditioning plate 32 prevents the drying air supplied to the drying zone 14B from making a rapid flow of drying air in the vicinity of the air supply port 18B and the exhaust port 18I. The length of the air conditioning portion, that is, the air conditioning plate 32, is preferably in the range of 50 mm or more and 150 mm or less on both the air supply side and the exhaust port side.

  The air conditioning plate 32 is installed at a certain distance from the coating film 36 formed on the web 12. This distance is determined by appropriately considering the type of coating film, the supply amount of dry air, and the like. Further, the material of the air conditioning plate 32, the size of the opening that is not covered with the material of the air conditioning plate 32, and the like are similarly determined according to the purpose.

  A shielding plate 34 is disposed at a position opposite to the coating film 36 across the web 12 so that stable running of the web 12 is not hindered by air such as air-conditioning air.

  Although not shown, a shield member may be provided between the air-conditioning plate 32 and the shielding plate 34 in order to prevent a flow caused by wind such as conditioned air from the side to the web 12.

  An air supply port 18 </ b> B and an exhaust port 18 </ b> I are provided in the drying apparatus main body 16. The supply duct 19B and the exhaust duct 19I are connected to the supply port 18B and the exhaust port 18I. Dry air is supplied from the air supply duct 19B through the air supply port 18B to the space below the air conditioning plate 32, and is discharged from the exhaust duct 19I through the exhaust port 18I. Since the air supply port 18 </ b> B and the exhaust port 18 </ b> I are provided at positions opposed to the width direction of the web 12, it is possible to supply dry air that flows in one direction in the width direction of the web 12.

  Among the divided zones 14A to 14G, the divided zone 14A closest to the coating machine is a zone where fresh air outside the drying zone 14, for example, the above-described conditioned air is dried immediately after the coating liquid is applied to the web 12. It is important to make it difficult to enter 14. For this purpose, the division zone 14A is arranged so as to be adjacent to the applicator 20, and the position of the wire bar 20A of the applicator 20 and the position of the backup roller 24 are adjusted in addition to the air conditioning plate 32 described above, It is preferable that the web 12 travels in the immediate vicinity of the divided zone 14 </ b> A so that the web 12 covers the open portion of the divided zone 14 </ b> A.

  Next, the operation of the drying apparatus 10 configured as described above will be described.

  The web 12 will be described as having a layer that becomes an alignment film by rubbing a previously applied alignment film forming resin, and the coating liquid is an organic solvent-based coating liquid containing a liquid crystalline discotic compound.

  Immediately after the coating liquid is applied to the web 12 supported by the backup rollers 22, 24, and 26 by the wire bar 20 </ b> A of the coating machine 20, the coating film surface is initially dried by the drying device 10. In this initial drying, it is preferable to start drying with a drying air immediately after application, and immediately after application within 5 seconds at the latest.

  In this initial drying, the coating film surface immediately after coating is in a state that the organic solvent is sufficiently contained. In particular, in the initial drying immediately after coating the coating solution containing the organic solvent, the evaporation distribution (fluctuation) of the organic solvent. As a result, a temperature distribution is generated on the coating film surface. This causes a distribution of surface tension, causing the coating liquid to flow in the surface of the coating film, and the coating film in the slow-drying portion becomes thin, resulting in broad spots (unevenness) A.

  In addition, the alignment direction of the liquid crystalline discotic compound is determined by rubbing the surface of the alignment film forming resin, but in the initial drying, when the wind speed is different from the rubbing direction, When the vortex is generated and the wind hits the coating film surface, a part of the coating film surface is displaced in the orientation direction, which causes sharp spots (unevenness) B.

  From this, in order to prevent spots (unevenness) A, B on the coating film surface during the initial drying, during the initial drying from the coating until the coating liquid stops flowing on the coating film surface, It is important to prevent the non-uniform wind from coming into contact with the coating film surface and to keep the organic solvent concentration in the vicinity of the coating film surface constant at all times.

There is a subordinate relationship between the broad spots A and the sharp spots B, and when the broad spots A are improved, the sharp spots B are improved. Broad spots A are generated in the early stage of drying, and the more quickly they are dried, the more the spots can be prevented. On the other hand, sharp spots are reduced-rate drying after the middle of drying, and the better the dryness is. Therefore, sharp spots B are generated when the entire length of the drying zone is rapidly dried, and broad spots A are generated when the entire length is de-dried. Therefore, it is preferable that the drying is performed immediately before the rate-reduction drying, and the drying is performed after the rate-reduction drying. However, the position where the drying changes from a constant rate to a decreasing rate has a distribution in the width direction, and the closer to the air supply side, the quicker the tendency to dry. Or may be de-dried where sharp spots B are likely to appear. Under the conditions of this trade-off, when the broad spots A are improved, the degree of rapid drying applied as a countermeasure against the broad spots A can be suppressed. Therefore, if broad spots can be improved by circulation bypass, sharp spots can be improved to follow.

  By providing the drying zone 14, a dry environment is formed in which the organic solvent evaporated from the coating film surface covers the coating film surface. When the blower 21 is driven in a dry environment, dry air is supplied from the air supply ports 18A to 18G to the divided zones 14A to 14G. Since the supplied dry air is exhausted from the exhaust ports 18H to 18N, each of the divided zones 14A to 14G is directed from one end side (suction port side) to the other end side (exhaust port side) in the web width direction. Dry air flowing in one direction is generated. Thereby, the dry wind containing the evaporated organic solvent is discharged | emitted from the exhaust ports 18H-18N with the coating film surface covered with the organic solvent. The dry air containing the organic solvent is mixed with the dry air from the outside air and the bypass conduit 25 while circulating through the circulation conduit 23, and a part thereof is discharged from the waste outlet 29 as waste air. The remaining drying air is sent to the bypass conduit 25 and the drying zone 14.

  However, if the wind speed of the drying air to the drying zone 14 is too high, the organic solvent is not evenly covered on the coating film surface, so it is necessary to adjust the drying air. Therefore, it is preferable to supply a fine wind having a wind speed of 0.01 to 0.7 m / s to the drying zone. Since the organic solvent concentration in the vicinity of the coating film surface can be made uniform, the organic solvent can be uniformly evaporated from each part of the coating film surface.

  The reason for circulating the drying air in the present invention is to make the concentration of the organic solvent near the coating film surface of the drying zone 14 as constant as possible.

  If only the outside air is supplied to the drying zone without circulating the drying air, the drying air does not contain an organic solvent. When this dry air is supplied to the coating film surface, the concentration of the organic solvent is low in the vicinity of the air supply port, and the environment becomes easy to dry. On the other hand, in the vicinity of the exhaust port, the drying air containing the organic solvent is supplied to the coating film surface, which makes it difficult to dry. Therefore, the distribution (fluctuation) of the organic solvent concentration occurs in the vicinity of the coating film surface, and a situation in which spots are easily generated occurs.

  By supplying the drying air containing an organic solvent having a constant concentration to the drying zone, the concentration distribution in the drying zone can be made uniform.

  Next, the reason why the outside air (new wind) is mixed with the circulating drying air is to prevent the organic solvent contained in the drying air from reaching equilibrium. This is because when the evaporated organic solvent contained in the drying air reaches equilibrium, the drying efficiency of the organic solvent decreases and the productivity decreases.

  In the present invention, a bypass conduit 25 is further provided in the circulation conduit 23. The reason for providing a bypass conduit to circulate and bypass the drying air is as follows. The present invention is configured to circulate the drying air through the circulation conduit 23 and supply the drying air to the drying zone 14. However, the drying air supplied to the drying zone 14 is a fine wind having a wind speed in the range of 0.01 to 0.7 m / s so as not to cause spots on the coating film surface. Since the drying air is fine, when the drying air is circulated through the circulation conduit 23 so that the concentration of the organic solvent in the drying zone is constant, it takes a lot of time to circulate the drying air. This is not preferable from the viewpoint of productivity. In particular, at the initial stage of drying, time is required until the concentration of the organic solvent in the drying air is stabilized.

  Therefore, the bypass conduit 25 is provided in the circulation conduit 23 and is circulated at a wind speed faster than the wind speed of the dry wind supplied in the drying zone in the bypass path, thereby stabilizing the concentration of the organic solvent. By sending a part of the drying air circulated at high speed in the circulation bypass path to the drying zone, it is possible to supply the drying air with a stable organic solvent concentration to the drying zone in a relatively short time. In particular, the bypass circulation wind is intended to shorten the dead time (path volume / air volume), so that it can be calmed down by bypassing more than half, preferably 10 times. The present invention has a configuration in which 50% to 90% of the dry air is circulated through the bypass path.

  In the present invention, the drying device 10 having the above-described configuration is provided for initial drying immediately after the coating liquid is applied to the web 12. By forming the drying zone 14 immediately after coating, it is possible to prevent the non-uniform strength and direction of the wind outside the drying zone 14 from hitting the coating film surface that contains a large amount of organic solvent and in which the coating liquid tends to flow. Thereby, spots (unevenness) can be prevented and uniform drying can be performed.

  Further, in order to control the flow of the drying air, the interval between the upper end of the partition plate 28 and the coating film surface is set to 0.5 mm to 12 mm, and each partition is made as narrow as possible in the range where the coating film surface does not contact the partition plate 28. The individual exhaust accuracy of the exhaust means 18P to 18W provided in the zones 14A to 14G can be improved. Further, an air conditioning plate 32 is provided under the webs on both sides of the drying zone 14 to rectify the air flowing in from the suction ports 18A to 18G and the air exhausted from the exhaust ports 18H to 18N, thereby coating the film surface. The flow of the wind containing the solvent flowing through was made uniform.

  [Web] As 12 used in the present invention, polyethylene terephthalate, polyethylene-2,6 naphthalate having a width of 0.3 to 5 m, a length of 45 to 10,000 m and a thickness of 5 to 200 μm, cellulose diacetate, cellulose triacetate, Cellulose acetate propionate, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyimide, polyamide and other plastic films, paper, polyethylene, polypropylene, ethylene butene copolymer and other α-polyolefins coated with 2-10 carbon atoms Or the laminated paper, metal foils, such as aluminum, copper, and tin, or what formed the preliminary process layer on the surface of a strip | belt-shaped base material is contained.

  [Coating Solution] In the present invention, the web 12 is coated with an optical compensation sheet coating solution, a magnetic coating solution, a photographic photosensitive coating solution, a surface protecting, antistatic or slippery coating solution on the surface and dried. After that, those which are cut to a desired length and width are included, and representative examples thereof include optical compensation sheets, various photographic films, photographic paper, magnetic tape and the like. In particular, when the viscosity of the coating film is 1 to 5 mPas, the thickness immediately after coating is 3 to 10 μm, the boiling point is 40 to 85 ° C., and the temperature of the web 12 before coating is 20 to 30 ° C., spots easily occur. . If the present invention is applied when the coating film and the web satisfy the above requirements, preferable results can be obtained.

  [Coating method] In addition to the bar coating method described above, the coating solution is applied by the curtain coating method, extrusion coating method, roll coating method, dip coating method, spin coating method, print coating method, spray coating method and slide coating method. The method can be used. In particular, a bar coating method, an extrusion coating method, and a slide coating method are preferably used.

  In the present invention, the number of coating layers of the coating solution applied simultaneously is not limited to a single layer, and can be applied to a simultaneous multilayer coating method as necessary.

  In the present invention, it is preferable that gas concentration detectors are provided in the supply ducts 19A-19G and the exhaust ducts 19H-19N for dry air. Moreover, it is preferable that the inflow amount of outside air (fresh air) can be adjusted with a damper or the like.

  The present invention can be applied not only to the drying apparatus described in this embodiment but also to a condensation type drying apparatus. Condensation-type drying equipment condenses and collects organic solvent in the coating film to dry it. To achieve spot-free drying, the distribution of the organic solvent in the vicinity of the coating film surface must be uniform. Desired. By providing the circulation conduit and the bypass conduit of the present invention in a condensation type drying apparatus, the occurrence of spots can be suppressed.

  FIG. 4 shows that the drying apparatus 10 of the present invention is incorporated into the optical compensation sheet manufacturing process. The state of occurrence of unevenness (unevenness) in the optical compensation sheet manufactured by supplying a drying air having a wind speed of 0.01 to 0.5 m / s with this drying apparatus 10 was investigated. The experimental conditions were described in detail in the examples, and the description of the same conditions was omitted in the comparative example.

[Example]
As shown in FIG. 4, the optical compensation sheet manufacturing process to which the drying apparatus 10 of the present invention is applied is such that the web 12 sent out by the unloader 40 is supported by a plurality of guide rollers 42, 42. The coating machine 20 passes through the drying device 10 of the present invention that performs initial drying, the drying zone 46 that performs main drying, the heating zone 48, and the ultraviolet lamp 50, and is wound by a winder 52.

As the web 12, triacetyl cellulose (Fujitack, manufactured by Fuji Photo Film Co., Ltd.) having a thickness of 80 μm was used. Then, the surface of the web 12, the long chain alkyl-modified Poval (MP-203, manufactured by Kuraray Co., Ltd.) 2 weight percent solution after the film 1 m ² per 25ml application was made by drying for 1 minute at 60 ° C The web 12 on which the alignment layer resin layer was formed was rubbed on the surface of the resin layer while being transported at 30 m / min to form an alignment layer.

And, on the alignment film obtained by rubbing the alignment film resin layer, the coating liquid is 4: 1 by weight ratio of (3) of the discotic compound TE-8 and (5) of TE-8. A coating liquid containing a liquid crystalline compound to be a 40 wt% methyl ethyl ketone solution of a mixture obtained by adding 1 wt% of a photopolymerization initiator (Irgacure 907, manufactured by Ciba Geigy Japan Co., Ltd.) to the mixture was used. While running the web 12 at a running speed of 30 m / min, this coating solution was applied onto the alignment film with a wire bar 20A so that the amount of the coating solution was 5 ml per 1 m ^{2 of the} web.

  Immediately after application, initial drying was performed using the drying apparatus 10 of the present invention shown in FIG. The drying device 10 includes a blower 21, a circulation conduit 23, a bypass conduit 25, an outside air port 27, a waste port 29, and a drying device body 16 that forms a drying zone 14, and an air supply duct 19A to 19G and an air supply port 18A to 18G. Then, the drying air circulated in the bypass conduit 25 is supplied to the drying zone, and the supplied drying air is discharged from the exhaust ports 18H to 18N and the exhaust ducts 19H to 19N.

  The web 12 initially dried by the drying apparatus 10 of the present invention is passed through a drying zone 46 adjusted to 100 ° C. and a heating zone 48 adjusted to 130 ° C., and a nematic phase is formed on the web 12. . The web 12 coated with the alignment film and the liquid crystal compound is continuously conveyed, and the surface of the liquid crystal layer is irradiated with ultraviolet rays from the ultraviolet lamp 50.

  In the table, in the situation of the occurrence of spots, x indicates that spots have occurred, and ◯ indicates that spots have not occurred. The dry state and spots were visually determined. Overall, these were unacceptable products as x, acceptable products as Δ, acceptable products as good as ○.

  In addition, the time required for the gas concentration to settle in the gas concentration system installed in the system is described. The calming here is the time to reach 95% of the steady value. For wind unevenness, the surface state of the coating film sampled at a position corresponding to 200 seconds after application was visually evaluated.

[Comparative Example 1]
FIG. 5 shows a drying device 60 of Comparative Example 1. The drying device 60 has a drying device main body in which the outside air taken in from the outside air port 74 forms a drying zone 62A-G as dry air through the air supply ducts 68A-68G and the air supply ports 66A-66G by driving the blower 72. 64. The supplied dry air is discharged from the exhaust ports 66H-66N and the exhaust ducts 68H-68N, and is discharged as waste air from the waste port 76 without being circulated. As is clear from FIG. 5, the drying air is supplied so as to flow in one direction from one end direction (outside air port) to the other end direction (discard port) without being circulated.

[Comparative Example 2]
FIG. 6 shows a drying apparatus of Comparative Example 2. The drying device includes a circulation conduit 94, a blower 92, an outside air port 96, a waste outlet 98, and a drying body device 84 that forms a drying zone 82A-G. The air supply ducts 88A to 88G and the air supply ports 86A to 86G are connected to each other. Then, the drying air is supplied to the drying zone 82, and the supplied drying air is discharged from the exhaust ports 86H to 86BN and the exhaust ducts 88H to 88N. The dry air discharged from the exhaust ducts 88H to 88N and the outside air from the outside air port 96 are mixed, and a part of the mixed dry air is discharged from the disposal port 98. A circulation path is constituted by the circulation conduit 94 so that the remaining dry air is supplied again to the drying zone 82 via the air supply ducts 88A to 88G and the air supply ports 86A to 86G.

In the comparative example 1 and the comparative example 2, except having changed the structure of the drying apparatus, it performed on the same conditions as an Example, and evaluation was also performed on the same conditions.

  As shown in the table, broad spots (A) and sharp spots (B) were improved in Example 1 using the circulating wind and bypass circulating wind. In particular, when the concentration of the gas concentration was 200 sec, only the circulation air (Comparative Example 2) was insufficient, but in Example 1 using the bypass circulation air, the concentration of the gas concentration was improved and the wind unevenness was good. It was.

  Thus, it turned out that it is effective in order to suppress the spot which generate | occur | produces in a drying process to dry with a circulation wind and a bypass circulation wind.

  As described above, according to the coating film drying method and apparatus of the present invention, spots (unevenness) generated in the initial drying process immediately after coating can be suppressed, and uniform drying can be achieved. Accordingly, since it is not necessary to change the physical properties such as the viscosity of the coating liquid and the type of the solvent as in the prior art, the range of types of the coating liquid that can be used and the range of the types of the solvent can be widened.

Plan view of the drying apparatus of the present invention Side view of the drying apparatus of the present invention Sectional view of the drying apparatus of the present invention Process diagram incorporating the drying device of the present invention into the optical compensation sheet manufacturing process Plan view of the drying apparatus of Comparative Example 1 Plan view of the drying apparatus of Comparative Example 2 Spots (unevenness) generated by the conventional drying method Explanatory drawing explaining broad spots (unevenness) Explanatory drawing explaining sharp spots (unevenness)

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Drying device, 12 ... Web, 14 ... Drying zone, 14A-14G ... Dividing zone, 16 ... Drying device main body, 18A-18G ... Air supply port, 18H-18N ... Exhaust port, 19A-19G ... Air supply duct, 19H to 19N: exhaust duct, 20 ... coating machine, 21 ... blower, 22, 24, 26 ... backup roller, 23 ... circulation conduit, 25 ... bypass conduit, 27 ... outside air outlet, 28 ... partition plate, 29 ... Abandonment port, 32 ... Air conditioning plate, 34 ... Shield plate, A ... Broad spots, B ... Sharp spots

Claims (6)

In the drying method of the coating film formed by applying a coating solution containing an organic solvent to the long support that travels,
Pass the elongate support through a drying zone arranged immediately after application of the coating solution, and supply and exhaust 0.01 to 0.7 m / s of drying air to the drying zone,
A drying method of a coating film, wherein the drying air exhausted from the drying zone is supplied again to the drying zone, and 50% to 90% of the drying air is circulated through a bypass path.   2. The coating film according to claim 1, wherein the drying air is supplied to the drying zone by supplying a one-way flow of drying air flowing from one end side to the other end side in the width direction of the elongated support. Drying method. 2. The elongate support is a layer that becomes an alignment film by rubbing a previously applied alignment film forming resin, and the coating liquid contains a liquid crystalline discotic compound. Or the drying method of the coating film of 2 . In a coating film drying apparatus formed by applying a coating solution containing an organic solvent to a long supporting body traveling by a coating machine,
A drying apparatus main body which is provided immediately after the coating machine and forms a drying zone for drying the coating film surface of the long support traveling;
A drying air supply / exhaust device for supplying and exhausting 0.01 to 0.7 m / s of drying air into the drying zone;
A circulation path for supplying the drying air exhausted from the drying zone connected to the drying air supply / exhaust device to the drying zone;
A bypass path for circulating 50% to 90% of the dry air by bypass;
An apparatus for drying a coating film, comprising: 5. The coating film drying apparatus according to claim 4, wherein the drying air supply / exhaust device supplies a unidirectional flow of drying air flowing from one end side to the other end side in the width direction of the elongated support. The elongated support is a layer serving as alignment film by rubbing the previously coated orientation film forming resin, according to claim 4 wherein the coating liquid, characterized in that those comprising a liquid crystalline discotic compound Or the drying apparatus of the coating film of 5 .

Images