JP5457811B2 - Manufacturing method of optical film - Google Patents

Description

  The present invention relates to an optical film manufacturing method and an optical film, and more particularly to an optical film manufacturing method including a drying step, and an optical film manufactured by the manufacturing method.

  A coating film containing a volatile organic solvent applied to a substrate is generally dried by exposing it to hot air or the like in a drying apparatus to evaporate the organic solvent. And the high temperature exhaust gas containing the organic solvent evaporated from the coating film is discharged | emitted out of a drying apparatus. Since the amount of heat of exhaust gas is large, it is known to use the energy effectively.

  Patent Document 1 discloses that the exhaust gas from the inside of the furnace of the drying apparatus is combusted, heat is exchanged between the air (outside air) taken from the outside and the exhaust gas, and the outside air is preheated using the heat of the exhaust gas. doing.

Japanese Patent Laid-Open No. 9-94511

  By the way, the problem when recovering heat from high-temperature exhaust gas containing volatile organic solvents to produce an optical film is that additives with a high melting point among volatiles in the exhaust gas adhere to the heat exchanger. is there. When an additive or the like adheres to the heat exchanger, the exhaust gas path is blocked. As a result, the heat exchange rate of the heat exchanger decreases, and finally heat exchange by the heat exchanger becomes impossible.

  As another problem, when the concentration of the photopolymerization initiator contained in the exhaust gas is low, the fuel cost is high in the method of burning the exhaust gas shown in Patent Document 1.

  The present invention has been made in view of such circumstances, and provides an optical film manufacturing method capable of easily removing deposits attached to a heat exchanger, and an optical film manufactured by the manufacturing method. For the purpose.

  In order to achieve the above object, an optical film manufacturing method of the present invention includes a step of feeding a strip-shaped support, a step of forming a coating film containing an additive and a solvent on the strip-shaped support, and the coating film A process of spraying heated outside air onto the coating film to evaporate the solvent and drying the coating film, a process of discharging the evaporated solvent containing the additive as exhaust gas, and a heat medium oil in the circulation path using the exhaust gas The heat medium oil is circulated in the circulation path, and the outside air is heated by the heat medium oil to exchange heat between the outside air and the exhaust gas via the heat medium oil, and drying. A method for producing an optical film, comprising a step of irradiating actinic rays to the subsequent coating film and a step of winding the belt-like support, wherein the heating medium oil is heated by a heater, and the heated heating medium oil Attached to the circuit Melting and liquefying the serial additive, characterized in that it comprises a step of removing the additive from the circulation path.

  Heat medium oil used for heat exchange between outside air and exhaust gas is heated by a heater and circulated in the circulation path. The circulation path is heated by the heat medium oil. Thereby, the deposit adhering to the circulation path is heated, and the deposit is redissolved and liquefied. The liquefied deposit falls by its own weight. Thereby, the deposit can be removed from the circulation path. Here, the circulation path includes an exhaust wind heat medium cooler that performs heat exchange between the exhaust gas and the heat medium oil, and a fresh wind heat medium heater that performs heat exchange between the outside air and the heat medium oil.

  The film includes a film to which a coating film containing an additive that closes the heat exchanger in the drying step is applied, and includes, for example, an optical film and a hard coat film. An optical film means a film having a coating film that exhibits an optical function on a support, and a hard coat film is a film having a coating film that is cured on a support regardless of the expression of the optical function. means.

  In the method for producing an optical film of the present invention, in the invention, in the step of removing the additive, a circulation path that does not perform heat exchange between the heat medium oil and the outside air, which is different from the circulation path, is formed. It is preferable that the heat medium oil circulates in the circulation path.

  Since the heat medium oil is heated in the circulation path that does not exchange heat with the outside air, heat loss of the heat medium oil can be reduced. Deposits adhering to the circulation path can be removed by the heated heat medium oil.

  In the method for producing an optical film of the present invention, in the invention, the additive is a photopolymerization initiator.

  In the method for producing an optical film of the present invention, in the invention described above, the step of removing the additive is preferably performed in a dark room. When an additive hardens | cures by irradiation of light, a deposit can be removed before hardening by removing it in a dark room.

  In the method for producing an optical film of the present invention, in the above invention, the heat medium oil preferably has a boiling point of exhaust gas temperature + 15 ° C. or higher.

  Preferably, the method for producing an optical film of the present invention further includes a step of cooling the heat medium oil in the step of exchanging heat between the outside air and the exhaust gas via the heat medium oil.

  According to the manufacturing method of the present invention, deposits attached to the heat exchanger can be easily removed.

The block diagram which shows the manufacturing line of an optical film. The block diagram which shows the periphery of a heat exchanger.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. The present invention will be described by the following preferred embodiments, but can be modified in many ways without departing from the scope of the present invention, and other embodiments can be used in the same manner as this embodiment. can do. Accordingly, all modifications within the scope of the present invention are included in the claims.

  FIG. 1 shows a production line for producing an optical film as an example of the present embodiment. In the optical film production line 10, the web 26, which is a belt-like flexible support, is sent out from a feeding machine 73. The web 26 is guided by the guide roller 75 and passes through the dust remover 25A. Dust adhering to the surface of the web 26 is removed by the dust remover 25A.

  A bar coating device 21A is provided downstream of the dust remover 25A. A coating solution containing alignment film forming resin is applied to the web 26 by the bar coating device 21A. Downstream of this, a drying zone 76A and a heating zone 78A are sequentially provided. An alignment film forming material layer is formed on the web 26.

  Note that other application means may be employed in the same manner as the bar coating apparatus 21A. As other coating means, a gravure coater, roll coater (transfer roll coater, reverse roll coater, etc.), die coater, extrusion coater, fountain coater, curtain coater, dip coater, spray coater or slide hopper can be employed.

  After applying and drying the coating liquid, the web 26 is guided by the guide roller 75 and conveyed to the rubbing processing device 70. The rubbing treatment device 70 is a device for performing a rubbing treatment on the alignment film forming material layer. In the present embodiment, the rubbing processing device 70 includes a one-stage rubbing roller 72. A rubbing cloth woven with pile yarn is attached to the rubbing roller 72. In addition, the rubbing processing apparatus 70 can also be configured to include a plurality of stages of rollers.

  The rubbing processing device 70 can control the rotational speed of the rubbing roller 72 in the direction of the arrow, that is, in the direction opposite to the traveling direction of the web 26 to about 10 to 1000 rpm. The rubbing roller 72 has a roller shape, for example, an outer diameter of 50 to 500 mm. The length is set to be slightly longer than the width of the web 26 even when the rubbing angle is applied. In addition, the rubbing treatment device 70 is configured to be rotatable in a horizontal plane with respect to the traveling direction of the web 26 so that the rubbing treatment device 70 can be adjusted to an arbitrary rubbing angle.

  An air nozzle 74 is provided above the rubbing roller 72. The air nozzle 74 can spray gas (air, nitrogen gas, etc.) on the back side of the web 26. The web 26 is pressed against the rubbing roller 72 by the gas from the air nozzle 74.

  In the rubbing process, the alignment film forming material layer is rubbed with the pile yarn of the rubbing cloth while rotating the rubbing roller 72 in the direction opposite to the running direction of the web 26, thereby imparting the alignment regulating force to the alignment film forming material layer. Is done.

  A dust remover 25 </ b> B is provided downstream of the rubbing treatment device 70. Dust adhering to the surface of the web 26 is removed by the dust remover 25B. A bar coating device 21B is provided downstream of the dust remover 25B, and a coating liquid containing a disconematic liquid crystal is applied to the web 26. The configuration of the bar coating device 21B may be the same as that of the previously described bar coating device 21A.

  In the optical film, a liquid crystal layer having a discotic nematic phase is formed on the alignment film. The liquid crystal layer is a layer having negative birefringence obtained by cooling and solidifying a liquid crystalline discotic compound after alignment or by polymerization (curing) of a polymerizable liquid crystalline discotic compound.

  Examples of the above discotic compounds include C.I. Destrade et al., Mol. Cryst. 71, 111 (1981), benzene derivatives, C.I. Destrade et al., Mol. Cryst. 122, 141 (1985), Physicslett. A, 78, p. 82 (1990); Kohne et al., Angew. Chem. 96, page 70 (1984), and cyclohexane derivatives described in J. Am. M.M. Lehn et al. Chem. Commun. 1794 (1985), J. Am. Zhang et al., J. Am. Chem. Soc. 116, 2655 (1994), and azacrown and phenylacetylene macrocycles.

  The above discotic (discotic) compounds generally have a structure in which these are used as a mother nucleus at the center of a molecule, and a linear alkyl group, an alkoxy group, a substituted benzoyloxy group, etc. are radially substituted as the linear chain. , Which shows liquid crystallinity and is generally called a discotic liquid crystal. However, the molecule itself is not limited to the above description as long as the molecule itself has negative uniaxiality and can give a certain orientation.

  The aligned liquid crystal molecules can be fixed while maintaining the alignment state. Immobilization is performed by a photopolymerization reaction.

  Examples of additives include photopolymerization initiators such as α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ethers (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatics. Group acyloin compounds (described in US Pat. No. 2,722,512), polynuclear quinone compounds (described in US Pat. Nos. 3,046,127 and 2,951,758), combinations of triarylimidazole dimers and p-aminophenyl ketone (described in US Pat. No. 3,549,367) ), Acridine and phenazine compounds (described in JP-A-60-105667, US Pat. No. 4,239,850) and oxadiazole compounds (described in US Pat. No. 4,212,970). The amount of the photopolymerization initiator used is preferably in the range of 0.01 to 20% by mass, more preferably in the range of 0.5 to 5% by mass, based on the solid content of the coating solution.

  A drying zone 76B and a heating zone 78B are sequentially provided downstream of the bar coating device 21B. The organic solvent containing the photopolymerization initiator in the coating solution evaporates by passing through the drying zone 76B and the heating zone 78B. As a result, the coating liquid is dried and a liquid crystal layer is formed on the web 26.

  A drying method in the drying zone 76B and the heating zone 78B will be described. Outside air is taken into the duct 32 by the air supply fan 31 from the air supply port 30. The outside air is heated by the heater 33. Next, the outside air is heated by a fresh wind heat medium heater 50 a constituting the heat exchanger 50. The duct 32 branches into a duct 32a connected to the drying zone 76B and a duct 32b connected to the heating zone 78B. A heater 34 and a fan 35 are provided in the duct 32a. The outside air flowing into the duct 32a is heated by the heater 34 and supplied to the drying zone 76B by the fan 35. Similarly, a heater 36 and a fan 37 are provided in the duct 32b. The outside air flowing into the duct 32b is heated by the heater 36 and supplied to the heating zone 78B by the fan 37.

  The duct 32a is further connected to a nozzle (not shown) in the drying zone 76B. The heated outside air (hot air) is sprayed from the nozzle onto the coating solution on the web 26. Similar to the drying zone 76B, the duct 32b is connected to a nozzle (not shown) in the heating zone 78B. The heated outside air is sprayed from the nozzle onto the coating solution on the web 26. This hot air evaporates the organic solvent contained in the coating solution. As described above, the coating liquid contains a photopolymerization initiator as an additive.

  For this reason, a gas that evaporates from the coating solution, so-called exhaust gas, contains a photopolymerization initiator having a relatively high melting point. In addition, when the concentration of the photopolymerization initiator contained in the exhaust gas is low, there is a problem that burning the organic material increases the combustion cost.

  Duct 40a is connected to drying zone 76B, and duct 40b is connected to heating zone 78B. Exhaust gas from the drying zone 76B is discharged through the duct 40a. Exhaust gas from the heating zone 78B is discharged through the duct 40b. The duct 40a and the duct 40b are connected to one duct 40. An exhaust fan 41 is provided in the duct 40. The exhaust fan 41 sends exhaust gas to the exhaust air heat medium cooler 50 b that constitutes the heat exchanger 50. The exhaust gas is cooled by the exhaust air heat medium cooler 50b. The exhaust gas whose temperature has decreased is discharged from the exhaust port 42. In addition, in order to connect the duct 40a and the duct 32a, the bypass duct 40c is installed between the duct 40a and the duct 32a. In order to connect the duct 40b and the duct 32b, a bypass duct 40d is installed between the duct 40b and the duct 32b. Part of the exhaust gas discharged from the drying zone 76B and the heating zone 78B circulates in the drying zone 76B and the heating zone 78B via the bypass ducts 40c and 40d. The heat energy of the exhaust gas is used to dry the coating liquid in the drying zone 76B and the heating zone 78B.

  The heat exchange between the exhaust gas and the outside air by the heat exchanger 50 will be described. The heat exchanger 50 includes a fresh air heat medium heater 50a, an exhaust air heat medium cooler 50b, a pipe 52 that forms a circulation path between the fresh air heat medium heater 50a and the exhaust air heat medium cooler 50b, and a heat medium provided in the pipe 52. A pump 54 is provided. The pipe 52 stores heat medium oil as a heat medium. As the heat medium oil, for example, a synthetic organic heat medium oil can be used. The synthetic organic heat medium oil has a boiling point of 176 ° C. or higher. In the exhaust air heat medium cooler 50b, the heat medium oil in the pipe 52 is heated by the exhaust gas. Here, heat exchange is performed between the exhaust gas and the heat medium oil, and the temperature of the exhaust gas decreases. The heated heat medium oil is sent to the fresh air heat medium heater 50a via the pipe 52 by the heat medium pump. Outside air is heated by the heated heat medium oil in the pipe 52 in the fresh air heat medium heater 50a. Here, heat is exchanged between the outside air and the heat medium oil, and the temperature of the heat medium oil decreases. As described above, the heat energy of the exhaust gas is transmitted to the outside air through the heat medium oil.

  A liquid crystal layer is formed by drying the coating solution. The web 26 having the liquid crystal layer is conveyed to an ultraviolet lamp 80 that irradiates ultraviolet rays as a downstream active ray. By irradiating with ultraviolet rays, the liquid crystal is crosslinked by the photopolymerization initiator. A desired polymer layer is formed on the web 26. Then, the polymer layer is inspected by the inspection device 90. A protective film 94 sent out from a laminating machine 92 is laminated on the web 26. Next, the web 26 on which the polymer layer is formed is wound up by the winder 82.

  By the way, as described above, the coating liquid contains a photopolymerization initiator having a high melting point (70 to 75 ° C. or higher). Therefore, the photopolymerization initiator is also contained in the gas that evaporates from the coating solution, so-called exhaust gas. If the temperature of the exhaust gas is, for example, 70 to 75 ° C. or higher, the photopolymerization initiator is not deposited. However, when heat exchange with the heat medium oil is performed in the exhaust air heat medium cooler 50b of the heat exchanger 50, the temperature of the exhaust gas falls to 70 ° C. or lower. The photopolymerization initiator is condensed and liquefied in the exhaust air heat medium cooler 50b due to the temperature drop of the exhaust gas. The photopolymerization initiator finally gels and deposits on the piping and fin surfaces inside the exhaust air heat medium cooler 50b. The deposit of the photopolymerization initiator inhibits the flow of exhaust gas that passes through the exhaust air heat medium cooler 50b. Therefore, heat exchange efficiency is reduced. Eventually, the deposits will become clogged and the balance between air supply and exhaust will be lost. This leads to poor liquid crystal layer formation in the drying zone. It is important to remove deposits adhering to the exhaust air heat medium cooler 50b.

  When removing deposits in the exhaust air heat medium cooler 50b, it is conceivable to enter the exhaust air heat medium cooler 50b and clean the internal piping and fin surfaces. However, there are the following problems when the deposit is cured by, for example, ultraviolet rays. When the door of the exhaust air heat medium cooler 50b is opened, ultraviolet rays enter. The photopolymerization initiator is cured by the ultraviolet rays. Therefore, it becomes difficult to remove deposits from the piping and fin surfaces inside the exhaust air heat medium cooler 50b. Therefore, the present inventors diligently studied the removal of deposits adhering to the piping and fin surfaces inside the exhaust air heat medium cooler 50b. As a result, it has been found that the deposit can be removed from the pipe and the fin by temporarily stopping the heat recovery operation or heating the heat medium (heat medium oil) to a certain temperature during the heat recovery operation. The piping and fins are heated by heating the heat medium oil. If the deposit is not cured by ultraviolet rays, the gel-like deposit adhering to the pipes and fins whose temperature has increased is redissolved and liquefied. The liquefied deposit falls by its own weight, and the deposit is removed from the pipe and the fin.

  Next, the heat exchanger 50 will be described with reference to FIG. The heat exchanger 50 includes a fresh air heat medium heater 50a, an exhaust air heat medium cooler 50b, a pipe 52 that forms a circulation path between the fresh air heat medium heater 50a and the exhaust air heat medium cooler 50b, and a heat medium pump 54. Prepare. The pipe 52 is provided with a first valve 53. The pipe 52 is provided with a bypass pipe 56, and the pipe 56 is provided with a second valve 57. A heat medium pump 54 is provided in the pipe 52 to move the heat medium oil in the pipe 52.

  A heat medium heater 60 is provided in the pipe 52. The heat medium heater 60 is connected to the boiler 62 via a pipe 61. Saturated steam is supplied from the boiler 62 to the heat medium heater 60. The heat medium oil is heated by the saturated steam.

  A heat medium cooler 63 is provided in the pipe 52. The heat medium cooler 63 is connected to the cooling tower 65 through a pipe 64. Cooling water is supplied from the cooling tower 65 to the heat medium cooler 63. The heat medium oil is cooled by the cooling water.

  An expansion tank 66 is connected to the pipe 67. Thereby, the expansion tank 66 and the heat medium pump 54 are connected in parallel. The expansion tank 66 absorbs the expansion of the volume accompanying the temperature rise of the heat medium oil in the pipe 52. The pipe 67 is provided with a third valve 68.

  An operation sequence of the heat exchanger 50 will be described with reference to FIGS. 1 and 2. First, heat exchange between exhaust gas and outside air will be described. The air supply fan 31 and the exhaust fan 41 are driven. The heater 33 starts adjusting the temperature of the outside air. The first valve 53 is opened and the second valve 57 is closed. The piping 52 forms a circulation path between the fresh air heat medium heater 50a and the exhaust air heat medium cooler 50b. The third valve 68 is closed. The heat medium pump 54 starts operation and circulates the heat medium oil in the pipe 52. Control of the heat medium cooler 63 is started.

  Room temperature outside air is heated to 36 ° C. by the heater 33. Furthermore, it is heated to 70 ° C. by the fresh air heat medium heater 50a. The heat medium oil is sent to the fresh air heat medium heater 50a at 95 ° C., and is sent out at 65 ° C. by heat exchange with the outside air. The heat medium oil is cooled to 50 ° C. by the heat medium cooler 63. The heat medium oil is sent to the exhaust air heat medium cooler 50b at 50 ° C. The exhaust fan 41 sends exhaust gas at 100 ° C. to the exhaust air heat medium cooler 50b. Heat is exchanged between the heat medium oil and the exhaust gas in the exhaust air heat medium cooler 50b. The temperature of the heat transfer oil rises to 95 ° C. On the other hand, the exhaust gas is cooled to 60 ° C. and released into the atmosphere. At this time, the photopolymerization initiator contained in the exhaust gas is deposited on the surface of the exhaust air heat medium cooler 50b.

  Next, an operation sequence for removing deposits attached to the exhaust air heat medium cooler 50b will be described. As in normal heat exchange, the air supply fan 31 and the exhaust fan 41 are driven, and the heater 33 starts adjusting the temperature of the outside air. The first valve 53 is closed and the second valve 57 is opened. Thus, a heat medium oil circulation path is formed by the exhaust air heat medium cooler 50 b, the pipe 52, and the bypass pipe 56. In this circulation path, heat exchange is not performed between the outside air and the heat medium oil. Therefore, the heat loss of the heat medium oil can be reduced. Control of the heat medium heater 60 is started. The heat medium oil is heated to 100 ° C. by the heat medium heater 60. The heated heat medium oil is sent to the exhaust air heat medium cooler 50b. The piping inside the exhaust air heat medium cooler 50b and the fin surface are heated to 100 ° C. by the heat medium oil. Thereby, the deposits adhering to the piping and fin surfaces inside the exhaust air heat medium cooler 50b are liquefied and removed from the piping and fins. When the removal of the deposit is completed, the third valve 68 is opened and then closed.

  According to the present embodiment, deposits attached to the piping and fin surfaces inside the exhaust air heat medium cooler 50b can be easily removed. The drawings and descriptions relating to the present embodiment are intended to show examples of the present invention. Accordingly, changes can be made without departing from the scope described in the claims.

  DESCRIPTION OF SYMBOLS 10 ... Production line, 21A, 21B ... Coating device, 25A, 25B ... Dust remover, 26 ... Web, 32, 40 ... Duct, 50 ... Heat exchanger, 50a ... Fresh air heat medium heater, 50b ... exhaust air heat medium cooler, 52, 56, 61, 64, 67 ... piping, 53, 57, 58 ... valve, 54 ... heat medium pump, 60 ... Heat medium heater, 63 ... Heat medium cooler, 70 ... Rubbing processing device, 72 ... Rubbing roller, 73 ... Delivery machine, 74 ... Air nozzle, 75 ... Guide roller, 76A, 76B ... drying zone, 78A, 78B ... heating zone, 80 ... UV lamp, 82 ... winder, 86, 88 ... backup roller, 90 ... inspection device, 92 ... Laminating machine, 94 ... Protective film Beam

Claims (6)

A step of feeding the belt-shaped support;
Forming a coating film containing an additive and a solvent on the belt-shaped support;
Spraying the outside air heated on the coating film onto the coating film to evaporate the solvent, and drying the coating film;
Discharging the evaporated solvent containing the additive as exhaust gas;
The heat medium oil in the circulation path is heated by the exhaust gas, the heat medium oil is circulated in the circulation path, and the outside air is heated by the heat medium oil, so that the heat medium oil is between the outside air and the exhaust gas. Heat exchange through
Irradiating actinic rays to the coating film after drying;
A method for producing an optical film comprising a step of winding the belt-shaped support,
Production of an optical film comprising the steps of heating the heat medium oil with a heater, dissolving and liquefying the additive adhering to the circulation path with the heated heat medium oil, and removing the additive from the circulation path Method.   The step of removing the additive forms a circulation path that does not exchange heat between the heat medium oil and the outside air, which is different from the circulation path, and the heat medium oil circulates in the circulation path. 1. A method for producing an optical film according to 1.   The method for producing an optical film according to claim 1, wherein the additive is a photopolymerization initiator.   The method for producing an optical film according to claim 1, wherein the step of removing the additive is performed in a dark room.   The method for producing an optical film according to claim 1, wherein the heat medium oil has a boiling point of exhaust gas temperature + 15 ° C. or higher.   The method for producing an optical film according to claim 1, further comprising a step of cooling the heat medium oil in the step of exchanging heat between the outside air and the exhaust gas via the heat medium oil.

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