JP2008203345A - Method of manufacturing liquid crystal film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a liquid crystal film by which the variation of the optical characteristics in the liquid crystal film is satisfactorily suppressed. <P>SOLUTION: The method of manufacturing the liquid crystal film includes a coating step for applying a liquid crystal polymer solution 22 on an aligning substrate film 20 and a drying step for drying by passing the aligning substrate film 20 on which the liquid crystal polymer solution 22 is applied successively into adjacent drying furnaces 31a, 31b, 31C while introducing a gas for drying the solution into the respective drying furnaces 31a, 31b, 31c to dry the solution. In the drying step, the discharge quantity of a gas discharged from the drying furnaces 31a, 31b, 31c is controlled so that the pressure difference among the drying furnaces 31a, 31b and 31c reaches zero. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a liquid crystal film.

  Liquid crystal displays (LCDs) use liquid crystal films to improve contrast and viewing angle. In this liquid crystal film, it is necessary to align liquid crystal molecules in a predetermined direction in order to have optical anisotropy. In general, the rubbing process in which the surface of the alignment substrate film, which is the base layer of the liquid crystal layer, is rubbed along a certain direction (rubbing direction) by lightly contacting a rubbing roll wound with a rubbing cloth made of fiber such as rayon. Is adopted. After this rubbing treatment step, liquid crystal molecules are applied through a coating step in which a solution containing a liquid crystal polymer is applied onto the alignment substrate film, a drying step in which the solution is dried to volatilize the solvent, and a heat treatment step in which the liquid crystal phase is developed by heating. Can be obtained on the alignment substrate film. A liquid crystal film is thus obtained.

  By the way, the liquid crystal film is usually manufactured in a long shape with a length of several hundred meters. Therefore, in the drying step, the elongated alignment substrate film coated with the liquid crystal polymer solution is continuously moved in a drying furnace, and the drying of the liquid crystal polymer solution is performed from one end to the other end of the alignment substrate film. It goes sequentially. At this time, the long alignment substrate film coated with the liquid crystal polymer solution is generally passed through a plurality of drying ovens adjacent to each other for the purpose of drying with high accuracy and uniformity. Here, in each drying furnace, it is possible to individually control the temperature, the blowing amount of hot air, and the like, and different drying conditions are set for each drying furnace. By drying in this way, the alignment substrate film coated with the liquid crystal polymer solution can be dried with high accuracy and uniformity.

  In general, a hot-air drying apparatus is widely used as an apparatus for drying a coating film applied to a film-like or sheet-like substrate. This type of drying apparatus includes a drying space through which a substrate to be dried passes, a drying furnace inlet and outlet through which the substrate enters and exits at the front and rear ends thereof, means for normally supplying hot air to the drying space, exhaust means, and further apparatus Inside temperature control means is provided.

When drying with such a hot air drying device, if there is a differential pressure inside and outside the drying device, an air flow caused by the differential pressure is generated at the entrance of the furnace, and in particular, the air flow at the entrance of the furnace through which the undried coating film passes is applied. Adversely affects the membrane. Therefore, a sensor for detecting the pressure difference inside and outside the furnace is provided, and the air flow caused by the pressure difference is suppressed by adjusting the supply / exhaust amount based on the detected value (Patent Document 1).
JP 2004-144433 A

  However, the present inventors have found that the following problems arise when the liquid crystal polymer solution applied to the alignment substrate film is dried in a plurality of drying furnaces as described above.

  That is, when the liquid crystal polymer solution is dried as described above, if a pressure difference occurs between adjacent drying furnaces, an opening for passing the alignment substrate film is formed in each drying furnace. Gas moves between adjacent drying ovens. For this reason, the actual drying conditions in each drying furnace are different from the preset drying conditions, which causes drying unevenness (non-uniform film thickness) and improves the viewing angle characteristics of the obtained liquid crystal film. The present inventors have found that optical characteristics such as color compensation vary.

  Accordingly, an object of the present invention is to provide a method for producing a liquid crystal film that can sufficiently reduce variations in optical properties of the liquid crystal film.

  In order to solve the above problems, a method for producing a liquid crystal film according to the present invention includes a solution coating step of applying a liquid crystal polymer solution to an alignment substrate film, and a plurality of adjacent alignment substrate films coated with the solution. A drying step of sequentially passing through the drying oven, introducing a gas for drying the solution in each of the plurality of drying ovens, and drying the solution by discharging the gas from each of the plurality of drying ovens, Control at least one of the amount of gas introduced into each of the plurality of drying furnaces and the amount of gas discharged from the plurality of drying furnaces so that the pressure difference between the plurality of drying furnaces approaches zero. It is characterized by.

  According to the method for producing a liquid crystal film according to the present invention, the alignment substrate film coated with the liquid crystal polymer solution is sequentially passed through a plurality of drying ovens adjacent to each other, and the liquid crystal polymer solution in each of the plurality of drying ovens. A gas for drying is introduced and discharged from each of the plurality of drying furnaces, thereby drying the solution. At this time, at least one of the amount of gas introduced into each of the plurality of drying furnaces and the amount of gas discharged from the plurality of drying furnaces so that the pressure difference between the plurality of drying furnaces approaches zero. Is controlled. Therefore, compared with the case where such control is not performed, the amount of gas movement between adjacent drying furnaces is sufficiently reduced or substantially zero. For this reason, in each drying furnace, the actual drying conditions are sufficiently prevented from fluctuating from the preset drying conditions due to the gas entering from the adjacent drying furnace. As a result, drying unevenness of the liquid crystal polymer solution is sufficiently prevented.

  In the method for producing a liquid crystal film according to the present invention, in the drying step, only the amount of gas discharged from the plurality of drying furnaces is controlled so that the pressure difference between the plurality of drying furnaces approaches zero. Is preferred.

  The drying conditions in each drying furnace are mainly determined by the temperature and amount of gas introduced into each drying furnace. Therefore, if the pressure difference between adjacent drying furnaces is controlled only by the amount of gas discharged from a plurality of drying furnaces as described above, the influence on the drying conditions in each drying furnace can be further reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the liquid crystal film which can fully reduce the dispersion | variation in the optical characteristic in a liquid crystal film is provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same elements are denoted by the same reference numerals. Moreover, the dimensional ratio in the component in a drawing and between components is not restricted to what is illustrated.

  First, a first embodiment of a method for producing a liquid crystal film according to the present invention will be described in detail with reference to FIG. (A)-(f) of Drawing 1 is a series of process drawings of the manufacturing method of the liquid crystal film concerning this embodiment.

  First, the liquid crystal film 30 obtained by the liquid crystal film manufacturing method according to the present embodiment will be described.

  As shown in FIG. 1 (f), the liquid crystal film 30 is configured such that an adhesive layer 24, a liquid crystal layer 23, an overcoat layer 28 and a protective film 29 are sequentially laminated on a transparent substrate film 26. ing.

  The liquid crystal film 30 is manufactured as follows.

  That is, as shown in FIG. 1, the liquid crystal film 30 includes a rubbing process (see FIG. 1A) in which the surface of the alignment substrate film 20 is mainly rubbed by the rubbing apparatus 10, and the alignment substrate film 20 that has been rubbed. A coating step (see FIG. 1B) for applying a liquid crystal polymer solution 22 to the surface of the substrate, a drying step for drying the liquid crystal polymer solution 22 (see FIG. 1C), and a liquid crystal polymer solution after drying. 22 is heated to develop a liquid crystal phase to obtain a liquid crystal layer 23 (see FIG. 1 (d)), and the liquid crystal layer 23 and the transparent substrate film 26 are bonded to each other through the adhesive layer 24. The alignment substrate film 20 is peeled from the liquid crystal layer 23, the transfer step (see FIG. 1E) for transferring the liquid crystal layer 23 from the alignment substrate film 20 to the transparent substrate film 26, and the transparency of the liquid crystal layer 23. The plate film 26 side on the opposite side, bonded to the overcoat layer 28 and the protective film 29 is obtained by passing through the protective layer forming step of obtaining a liquid crystal film 30 (of FIG. 1 (f) refer) to.

  Hereinafter, each step will be described in detail.

  (Rubbing process)

  First, the rubbing process will be described. As described above, the rubbing process is a process in which the rubbing apparatus 10 performs a rubbing process on the surface of the alignment substrate film 20.

  Here, the alignment substrate film 20 is subjected to rubbing treatment on the surface thereof, so that when the liquid crystal layer 23 is formed on the surface, the alignment direction of the liquid crystal molecules in the liquid crystal layer 23 is in the plane of the alignment substrate film 20. There is no particular limitation as long as it can be oriented. Examples of the material of the alignment substrate film 20 include thermosetting resins such as polyimide, epoxy resin, and phenol resin, polyamide such as nylon, polyether imide, polyether ketone, polyether ether ketone (PEEK), and polyketone. , Polyethersulfone, Polyphenylene sulfide, Polyphenylene oxide, Polyethylene terephthalate, Polyethylene terephthalate, Polyethylene naphthalate, Polybutylene terephthalate and other polyesters, Polyacetal, Polycarbonate, Poly (meth) acrylate, Cellulose resins such as triacetyl cellulose, Thermoplastics such as polyvinyl alcohol Resins etc. are mentioned, but in particular polyethylene terephthalate, polyphenylene sulfide, PEEK, polyvinyl alcohol Thermoplastic resins, such as, there is no possibility that disappear or decrease the effect of the rubbing treatment by heating to a liquid crystal phase to be developed in a subsequent step, preferred.

  FIG. 2 is a perspective view showing the rubbing apparatus 10 for rubbing the oriented substrate film 20. As shown in FIG. 2, the rubbing apparatus 10 includes a rubbing roll 1 having a roll body 1a having a columnar shape and a rubbing cloth 2 wound along the outer peripheral surface of the roll body 1a. Here, the roll body 1a can be rotated by a drive mechanism (not shown) such as a motor with the central axis as a rotation axis.

  When the rubbing treatment of the alignment substrate film 20 is performed using the rubbing device 10, the rubbing device 10 is disposed, for example, so that the rotation axis of the rubbing roll 1 is orthogonal to the conveyance direction (arrow A direction) of the alignment substrate film 20. To do.

  Then, the rubbing roll 1 is rotated in a state where the oriented substrate film 20 is conveyed on the guide roll 25 in the direction of arrow A in FIG. 2 at a constant speed by a conveying device (not shown). The rotating direction of the rubbing roll 1 at this time is set to the same direction as the conveying direction of the oriented substrate film 20 at a position where the rubbing roll 1 and the oriented substrate film 20 are in contact with each other.

  Thereby, the surface of the oriented substrate film 20 is rubbed in the same direction as the transport direction of the oriented substrate film 20 by the rubbing cloth 2.

  By this treatment, when the liquid crystal layer 23 is formed on the surface of the alignment substrate film 20 in a later step, the longitudinal direction of the liquid crystal molecules of the liquid crystal layer 23 is in a plane parallel to the surface of the alignment substrate film 20, The direction can be directed to the rubbing process.

  (Coating process)

  Next, the coating process performed after the rubbing process will be described. As shown in FIG. 1B, the coating step is a step of coating a liquid crystal polymer solution 22 on the alignment substrate film 20 that has been rubbed in the rubbing step.

  The liquid crystal polymer solution 22 is a solution obtained by dissolving a polymer of a thermotropic liquid crystal such as a nematic liquid crystal, a smectic liquid crystal, a cholesteric liquid crystal, or a discotic liquid crystal in an appropriate solvent. This liquid crystal polymer is, for example, a condensed liquid crystal polymer obtained by condensing a compound having a carboxylic acid group, an alcohol group, a phenol group, an amino group, a thiol group, etc., an acryloyl group, a methacryloyl group, a vinyl group, an allyl group, etc. Liquid crystalline vinyl polymer obtained from a liquid crystalline compound having a bond, a liquid crystalline polysiloxane synthesized from a liquid crystalline compound having an alkoxysilane group, a liquid crystalline epoxy resin synthesized from a liquid crystalline compound having an epoxy group, etc. Alternatively, a mixture of the above liquid crystal polymers can be used. Among these various liquid crystal polymers, condensed liquid crystal polymers are most preferable from the viewpoint of the optical characteristics of the liquid crystal film obtained.

  The solvent of the liquid crystal polymer solution 22 is not particularly limited as long as it can dissolve the above liquid crystal polymer. For example, ketones such as acetone, methyl ethyl ketone, isophorone, cyclohexanone, butoxyethyl alcohol, hexyloxyethyl are generally used. Alcohols, ether alcohols such as methoxy-2-propanol and benzyloxyethanol, glycol ethers such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether, esters such as ethyl acetate, ethyl lactate and γ-butyrolactone, phenols such as phenol and chlorophenol Amides such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, chloroform, tetrachloroethane, di Halogen-like or a mixture of these systems, such as chlorobenzene is preferably used. Moreover, in order to form a uniform coating film on the oriented substrate film 20, a surfactant, an antifoaming agent, a leveling agent, and the like may be added to the solution.

  In this coating step, the above-described liquid crystal polymer solution 22 is usually continuous in the longitudinal direction of the alignment substrate film 20 with respect to the surface on which the alignment substrate film 20 has been rubbed using a coating machine such as a roll coater. It is applied so that the film thickness is uniform. The film thickness of the applied liquid crystal polymer solution 22 is, for example, 0.1 to 50 μm, preferably 5 to 30 μm.

  (Drying process)

  In the drying step, as shown in FIG. 1C, the liquid crystal polymer solution 22 is heated, the liquid crystal polymer solution 22 applied to the surface is dried, and the solvent is vaporized. In this step, as shown in FIG. 3, the liquid crystal polymer solution 22 is dried by the drying unit 31.

  Here, the drying unit 31 will be described in detail.

  The drying unit 31 includes a plurality of drying furnaces 31a, 31b, and 31c. The plurality of drying furnaces 31a, 31b, 31c are adjacent to each other, and are arranged in series along the transport direction (direction of arrow A) of the alignment substrate film 20. Each drying furnace 31a, 31b, 31c has a slit-like opening 33 through which the alignment substrate film 20 coated with the liquid crystal polymer solution 22 is passed, and the opening 33 in each drying furnace 31a, 31b, 31c is also aligned. It arrange | positions in series along the conveyance direction (arrow A direction) of the board | substrate film 20. As shown in FIG.

  Also, each of the drying furnaces 31a, 31b, 31c is provided with cylindrical gas introduction portions 32a, 32b, 32c for introducing a gas for drying the liquid crystal polymer solution 22, and the gas introduction portions 32a, 32b, 32 c is arranged on the surface side of the alignment substrate film 20 on which the liquid crystal polymer solution 22 is applied. In FIG. 3, reference numeral 20 </ b> A is given to the film in which the liquid crystal polymer solution 22 is applied to the alignment substrate film 20. The liquid crystal polymer solution 22 is arranged on the gas introduction part 32a, 32b, 32c side.

  Air blowers 40a, 40b, and 40c are provided in the cylindrical gas inlets 32a, 32b, and 32c, respectively, and heating means 41a, 41b, and 41c are provided in the gas inlets 32a, 32b, and 32c, respectively. That is, the gas introduction part 32a is provided with the blowing means 40a and the heating means 41a, the gas introduction part 32b is provided with the blowing means 40b and the heating means 41b, and the gas introduction part 32c is provided with the blowing means 40c and the heating means. Means 41c are provided. Here, the heating means 41a, 41b, and 41c are provided at positions closer to the drying furnaces 31a, 31b, and 31c than the blowing means 40a, 40b, and 40c, respectively. The air blowing means 40a, 40b, 40c have a function of sending air outside the respective drying furnaces 31a, 31b, 31c into the respective drying furnaces 31a, 31b, 31c, and the air sent by the air blowing means 40a, 40b, 40c. After being heated by the heating means 41a, 41b, 41c, they are introduced into the drying furnaces 31a, 31b, 31c as the drying gases 38a, 38b, 38c. At this time, since the blowing means 40a, 40b, and 40c can independently control the blowing amount, the introduction amounts of the dry gases 38a, 38b, and 38c can be independently controlled. In addition, since the heating means 41a, 41b, and 41c can independently control the heating amount of air, the temperatures of the drying gases 38a, 38b, and 38c can be independently controlled.

  For example, a fan can be used as the air blowing means 40a, 40b, and 40c, and the air flow rate of the dry gas 38a, 38b, and 38c can be controlled by controlling the rotation speed of the fan. Moreover, as the heating means 41a, 41b, 41c, for example, an electric heater, an oil heater, a steam heater or the like can be used, and the temperature of the dry gas 38a, 38b, 38c is controlled by controlling the energization amount. be able to.

  On the other hand, in each drying furnace 31a, 31b, 31c, cylindrical gas discharge portions 36a, 36b, 36c for discharging gas from the inside are provided. The gas discharge portions 36a, 36b, and 36c may be arranged on the surface side of the alignment substrate film 20 on which the liquid crystal polymer solution 22 is applied. From the viewpoint of facilitating gas discharge, It is preferable to arrange on the side opposite to the surface. Discharge means 43a, 43b, and 43c are provided in the gas discharge portions 36a, 36b, and 36c, respectively. , 36c to the outside as exhaust gas 39a, 39b, 39c. At this time, the discharge means 43a, 43b, and 43c can control the discharge amount of the gas in the drying furnaces 31a, 31b, and 31c independently of each other.

  As the discharge means 43a, 43b, and 43c, for example, a fan can be used, and the discharge amount of the exhaust gases 39a, 39b, and 39c can be controlled by controlling the rotation speed of the fan with an inverter.

  Furthermore, pressure gauges 35a, 35b, and 35c for measuring the pressure in each of the drying furnaces 31a, 31b, and 31c are installed in each of the drying furnaces 31a, 31b, and 31c.

  Next, a drying process using the drying unit 31 will be described.

  First, each drying furnace 31a, 31b, 31c is set to a drying condition suitable for drying the liquid crystal polymer solution 22. The drying conditions are determined in advance for each of the drying furnaces 31a, 31b, 31c. For example, in the drying furnace 31a, the amount of the dry gas 38a introduced by the blowing means 40a and the temperature of the dry gas 38a by the heating means 41a are determined. Is adjusted by controlling the discharge amount of the exhaust gas 39a by the discharge means 43a. The drying conditions are similarly adjusted in the drying furnaces 31b and 31c.

  In this state, the alignment substrate film 20 coated with the liquid crystal polymer solution 22 is passed through the openings 33 of the drying ovens 31a, 31b, 31c, and sequentially passed through the drying ovens 31a, 31b, 31c. Thereby, the liquid crystal polymer solution 22 is dried.

  When the liquid crystal polymer solution 22 is dried in this way, for example, a part of the drying gas 38a introduced into the drying furnace 31a enters the adjacent drying furnace 31b through the opening 33 of the drying furnace 31a. Then, in the drying furnace 31b, the actual drying condition varies from the predetermined drying condition, and the drying unevenness of the solution 22 tends to occur.

  Therefore, in this embodiment, the pressure gauges 35a, 35b, and 35c installed in the drying ovens 31a, 31b, and 31c are used to monitor the pressure in each drying oven 31a, 31b, and 31c, and between adjacent drying ovens. Check if the pressure difference is zero. When the pressure difference is not zero, the exhaust gas 39a, 39b, 39c is adjusted so that the pressure difference approaches zero, and when the pressure difference is zero, the gas discharge amount is adjusted. Do not.

  For example, when the pressure difference Pa−Pb between the pressure Pa measured by the pressure gauge 35a in the drying furnace 31a and the pressure Pb measured by the pressure gauge 35b in the drying furnace 31b is not zero (for example, positive). In this case, the amount of exhaust gas 39a exhausted from the drying furnace 31a is increased by increasing the rotation speed of the fan as the exhaust means 43a so that Pa-Pb approaches zero, and Pa-Pb approaches zero. Like that. Further, when the pressure difference Pb-Pc between the pressures Pc and Pb measured by the pressure gauge 35c in the drying furnace 31c is not zero (for example, positive), the discharge is performed so that Pb-Pc becomes zero. The amount of exhaust gas 39b exhausted from the drying furnace 31b is increased by increasing the rotational speed of the fan serving as the means 43b, so that Pb-Pc approaches zero.

  By doing so, the amount of gas movement between adjacent drying ovens 31a, 31b, 31c is sufficiently reduced or substantially zero. For this reason, in the drying furnaces 31a, 31b, 31c, the actual drying conditions are sufficiently prevented from fluctuating from the preset drying conditions due to the gas entering from the adjacent drying furnace. As a result, drying unevenness of the liquid crystal polymer solution 22 is sufficiently prevented.

  The drying conditions in the drying furnaces 31a, 31b, 31c are mainly determined by the temperature and the amount of the drying gas 38a, 38b, 38c introduced into the drying furnaces 31a, 31b, 31c. Therefore, if the pressure difference between adjacent drying furnaces is controlled only by the discharge amount of the exhaust gases 39a, 39b, 39c from the respective drying furnaces 31a, 31b, 31c as in the present embodiment, the exhaust gas 39a, 39b, 39c Compared with the case of controlling not only the discharge amount but also the introduction amount of the drying gas 38a, 38b, 38c, the influence on the drying conditions in each of the drying furnaces 31a, 31b, 31c can be further reduced.

  In the present embodiment, the pressure values measured by the pressure gauges 35a, 35b, and 35c provided in the drying ovens 31a, 31b, and 31c are confirmed, and the discharge means 43a is set so that the pressure difference between the drying ovens becomes zero. , 43b, 43c are operated to adjust the discharge amount of the exhaust gas 39a, 39b, 39c, but the pressure gauges 35a, 35b, 35c and the discharge means 43a, 43b, 43c are electrically connected to the control device. You can also. In this case, the control device determines the amount of gas discharged by the discharge means 43a, 43b, 43c based on the pressure values measured by the pressure gauges 35a, 35b, 35c provided in the drying furnaces 31a, 31b, 31c. Adjust.

  Further, the pressure difference between adjacent drying furnaces may be adjusted so as to approach zero, and if the actual pressure difference is usually 50 Pa or less, preferably 10 Pa or less, more preferably 5 Pa or less, the adjacent drying furnace is dried. Gas movement between furnaces tends to be substantially prevented.

  (Heat treatment process)

  After the drying step, a heat treatment step is performed. In the heat treatment step, as shown in FIG. 1 (d), the liquid crystal polymer solution 22 after drying is heated to develop a liquid crystal phase and then cooled to form a liquid crystal layer 23 in which liquid crystal molecules are aligned in a predetermined direction. It is a process to obtain. Specifically, the alignment substrate film 20 is conveyed through a heat treatment furnace (not shown), and the temperature of the liquid crystal polymer solution 22 is a temperature at which the liquid crystal polymer transitions from solid to liquid crystal (hereinafter, “liquid crystal transition temperature”). Cool after the above. At this time, cooling may be performed by discharging from the heat treatment furnace.

  A liquid crystal polymer heated to a temperature higher than the liquid crystal transition temperature undergoes phase transition from a solid phase to a liquid crystal phase and has fluidity. Therefore, the liquid crystal polymer is easily aligned in the rubbing direction on the surface of the alignment substrate film 20.

  Thereafter, when the alignment substrate film 20 is cooled below the liquid crystal transition temperature, the liquid crystal polymer becomes a glass state and loses fluidity, and the liquid crystal molecules are fixed in the alignment state in the liquid crystal phase. In this way, a liquid crystal layer 23 in which liquid crystal molecules are aligned in a predetermined direction is obtained.

  (Transfer process)

  After the heat treatment step, a transfer step is performed. In the transfer step, as shown in FIG. 1E, the liquid crystal layer 23 and the isotropic transparent substrate film 26 are bonded together via the adhesive layer 24, and then the alignment substrate film 20 is peeled off from the liquid crystal layer 23. Thus, the liquid crystal layer 23 is transferred from the alignment substrate film 20 to the isotropic transparent substrate film 26.

  The isotropic transparent substrate film 26 is a film made of a material having isotropic optical characteristics and transparent to visible light, and has a function of supporting the final liquid crystal film. This material is not particularly limited as long as it satisfies the above conditions and has an appropriate flatness. For example, in addition to TAC (triacetyl cellulose), PET (polyethylene terephthalate), etc., polymethyl methacrylate, polystyrene, polycarbonate , Polyethersulfone, polyphenylene sulfide, polyarylate, amorphous polyethylene and the like can also be used. Moreover, even if it has optical anisotropy, it can be used as long as it does not give a problem to the function of the target liquid crystal film. Examples of such a film include retardation films such as stretched polyethylene terephthalate film and polycarbonate.

  The adhesive layer 24 preferably has a sufficiently low absorption rate for visible light and has optical isotropy. For example, an acrylic type, an epoxy type, an ethylene-vinyl acetate copolymer system, a rubber type, Urethane-based and mixed systems thereof can be used. Further, the adhesive layer 24 can be used without any problem with any type of adhesive such as thermosetting, photo-curing, and electron beam curing.

  The method for peeling the alignment substrate film 20 from the liquid crystal layer 23 is, for example, a method of mechanically peeling using a roll or the like, a method of mechanically peeling after dipping in a poor solvent for these constituent materials, A method of peeling by applying ultrasonic waves, a method of peeling by applying a temperature change using a difference in thermal expansion coefficient between the alignment substrate film 20 and the liquid crystal layer 23, a method of dissolving and removing the alignment substrate film 20 itself, etc. are adopted. can do. Since the peelability varies depending on the adhesion between the alignment substrate film 20 and the liquid crystal layer 23, the method for peeling the alignment substrate film 20 from the liquid crystal layer 23 is appropriately selected from the above methods.

  As described above, by adopting the step of transferring the liquid crystal layer 23 from the alignment substrate film 20 to the isotropic transparent substrate film 26, there is an advantage that the degree of freedom in selecting the material of the alignment substrate film 20 is increased. That is, the alignment substrate film 20 needs to have conditions such as having a function of aligning liquid crystal molecules and heat resistance in the heat treatment step. When the transfer process of the liquid crystal layer 23 is employed as in the present embodiment, the necessary conditions for the alignment substrate film 20 are reduced, so that a more suitable material can be selected to align liquid crystal molecules in a desired manner. Become.

  (Protective layer forming step)

  After the transfer step, a protective layer forming step is performed. The protective layer forming step is a step of bonding the overcoat layer 28 and the protective film 29 to the surface of the liquid crystal layer 23 opposite to the isotropic transparent substrate film 26 side, as shown in FIG. is there.

  The overcoat layer 28 is a layer for protecting the liquid crystal layer 23. The material of the overcoat layer 28 is not particularly limited as long as it protects the liquid crystal layer 23. However, a material having a sufficiently low absorption factor for visible light and optical isotropy is preferable. The adhesive layer 24 can be made of the same material.

  The protective film 29 is a film for further protecting the overcoat layer 28, and may be attached directly to the surface of the overcoat layer 28 or may be attached via an adhesive. The material of the protective film 29 has a low absorption factor for visible light, and preferably has optical isotropy. For example, PET, polymethyl methacrylate, polystyrene, polycarbonate, polyethersulfone, polyphenylene sulfide, Polyarylate, various ethylene-vinyl monomer copolymers, amorphous polyolefin, triacetyl cellulose and the like can be used. The thickness of the protective film 29 made of these materials and the like can be appropriately selected according to the process applied to the post-processing of the liquid crystal film 30 to be obtained, but is usually 1 to 500 μm, preferably 10 to 100 μm. is there.

  The liquid crystal film 30 is obtained through the above steps. Thus, the production of the liquid crystal film 30 is completed.

  In the liquid crystal film 30 obtained as described above, since the alignment of the liquid crystal molecules in the liquid crystal layer 23 needs to be precisely controlled, if unevenness of drying occurs during the drying process, for example, Even if it is a fine defect part, there exists a possibility of leading to the defect of the liquid crystal film 30 finally obtained. In the present embodiment, fluctuations in the drying conditions during the drying process are sufficiently prevented, so that uneven drying of the liquid crystal polymer solution 22 is sufficiently prevented. As a result, variations in optical characteristics of the finally obtained liquid crystal film 30 can be sufficiently reduced, and the yield in manufacturing can be improved.

  The present invention is not limited to the above embodiment. For example, in the introduction of the dry gas 38a, 38b, 38c, after adjusting the pressure and flow rate of the gas in the high pressure gas cylinder with a regulator and a flow rate regulator, the gas is led to the heating means 41a, 41b, 41c by the piping and heated. May be introduced into each drying furnace 31a, 31b, 31c. In this case, the introduction amounts of the dry gases 38a, 38b, and 38c are controlled by the flow rate regulator. Thereby, even if the environment (atmospheric temperature and humidity) of the place where the drying unit is installed fluctuates, the influence on the drying conditions can be reduced. Further, the discharging means 43a, 43b, 43c may be suction devices such as vacuum pumps connected to the gas discharging portions 43a, 43b, 43c, respectively, instead of the fans.

  Further, the fixing of the orientation of the liquid crystal molecules in the liquid crystal layer 23 is not limited to the method using the phase transition of the thermotropic liquid crystal having a high liquid crystal transition temperature as in the above embodiment, and the orientation is fixed by photocrosslinking or thermal crosslinking after the orientation. May be used. In such a case, it is possible to use a liquid crystal polymer having a low liquid crystal transition temperature. In this case, instead of the above-described heat treatment step, a step of performing photocrosslinking or thermal crosslinking is performed.

  Further, if the alignment substrate film 20 is a material that is optically isotropic and transparent to visible light, the alignment substrate film 20 can be used as a final support film for a liquid crystal film. That is, the above-described transfer process can be omitted, and the liquid crystal layer 23, the overcoat layer 28, and the protective film 29 can be laminated in this order on the alignment substrate film 20 to form a liquid crystal film.

  Further, the liquid crystal film 30 is not particularly limited as long as it is a film that fixes the liquid crystal molecules of the liquid crystal layer 23 in a specific alignment state and uses optical anisotropy generated from the alignment state. And those used as color compensation films.

  Moreover, in the said embodiment, although the extending direction of the rubbing roll 1 and the conveyance direction of the orientation board | substrate film 20 are orthogonal, it is not restricted to these, and you may cross | intersect with an acute angle or an obtuse angle.

  Furthermore, the liquid crystal film 30 may not necessarily have the overcoat layer 28 and the protective layer 29. Therefore, in this case, the above-described protective layer forming step may be omitted.

It is process drawing which shows a series of manufacturing processes of 1st Embodiment of the manufacturing method of the liquid crystal film which concerns on this invention. It is a perspective view which shows the rubbing apparatus used with embodiment of the manufacturing method of the liquid crystal film which concerns on this invention. It is the schematic of the drying furnace used at the drying process of the manufacturing method of the liquid crystal film which concerns on this invention.

Explanation of symbols

  20 ... Alignment substrate film, 22 ... Liquid crystal polymer solution, 30 ... Liquid crystal film, 31 ... Drying unit, 31a, 31b, 31c ... Drying furnace.

Claims (2)

A solution coating step of coating a liquid crystal polymer solution on the alignment substrate film;
The alignment substrate film coated with the solution is sequentially passed through a plurality of drying furnaces adjacent to each other, and a gas for drying the solution is introduced into each of the plurality of drying furnaces to each of the plurality of drying furnaces. Drying the solution by draining gas from the
Of the amount of gas introduced into each of the plurality of drying furnaces and the amount of gas discharged from the plurality of drying furnaces so that the pressure difference between the plurality of drying furnaces approaches 0 in the drying step Controlling at least one of them,
A method for producing a liquid crystal film. 2. The liquid crystal according to claim 1, wherein in the drying step, only a discharge amount of gas discharged from the plurality of drying furnaces is controlled so that a pressure difference between the plurality of drying furnaces approaches zero. A method for producing a film.

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