JP4716036B2 - Method for producing optical compensation film - Google Patents

Description

  The present invention relates to a method for producing an optical compensation film and an optical compensation film, and in particular, is a compensation film for expanding a viewing angle used in a liquid crystal display device, and a liquid crystalline compound is formed on a transparent film in which alignment films are laminated. The present invention relates to an optical compensation film manufacturing method and an optical compensation film.

  In order to improve the viewing angle characteristics of the liquid crystal display device, an optical compensation film is disposed as a retardation plate between the pair of polarizing plates and the liquid crystal cell. In recent years, with the improvement of the contrast ratio and screen brightness of liquid crystal display devices, it is strongly required to reduce the shift and variation of the slow axis of the optical compensation film. As a countermeasure, the following methods have been proposed.

  For example, in Patent Document 1, in the production process of a stretched cellulose acylate film used for an optical compensation film, when the amount of residual solvent in the web is in the range of 10 to 30% by mass, the downstream temperature is the upstream temperature. A method of drying through a web in a drying zone divided into two or more temperatures set higher by 10 to 50 ° C. has been proposed. Thereby, the retardation unevenness of the stretched cellulose acylate film and the variation of the slow axis angle are reduced.

  Moreover, in patent document 2, in the manufacturing process of the same stretched cellulose acylate film, when the difference in residual volatile content is X and the average stretching speed is Y, -5.0 <0.27X + 1.01XY-21. A method of stretching and relaxing so as to satisfy 2 <5.0 has been proposed. Thereby, the retardation unevenness of the stretched cellulose acylate film and the variation of the slow axis angle are reduced.

  In Patent Document 3, in a liquid crystal display device using a retardation film and a polarizing plate on both sides of a liquid crystal cell, the slow axis shift of the retardation film is improved by improving the adhesion method between the retardation film and the polarizer. A method for eliminating the variation has been proposed.

  In Patent Document 4, the retardation value Re in the film plane and the retardation value Rth in the film thickness direction satisfy a specific range so that the polarizing plate performance (slow axis shift, light leakage) is excellent. It is described that it is possible to obtain a liquid crystal display device that does not cause light leakage or color change even if environmental changes such as temperature and humidity occur.

By the way, in an optical compensation film provided with a coating layer containing a liquid crystalline compound on a transparent film on which an alignment film is laminated, after applying a coating liquid containing a liquid crystalline compound on the alignment film, the coating film is dried and cured. As a result, the liquid crystal compound is maintained in a predetermined alignment state.
JP 2004-163802 A JP 2005-313614 A JP 2006-3640 A JP 2006-91527 A

  However, since the coating layer of the liquid crystalline compound is in a dry film state in the late stage of the drying process, it takes a relaxation time (after the disturbance of the alignment state of the liquid crystalline compound due to the influence of the disturbance, it takes to return to the original alignment state) Time). For this reason, it has been a problem that the disturbance due to the drying air is easily fixed to the coating layer, which causes a shift or variation in the slow axis of the optical compensation film.

  On the other hand, in Patent Documents 1 to 4, in the production process of an optical compensation film in which a coating layer containing a liquid crystalline compound is formed on a transparent film in which an alignment film is laminated, Variations cannot be suppressed.

  This invention is made | formed in view of such a subject, and it aims at providing the manufacturing method of the optical compensation film which can reduce the shift | offset | difference and dispersion | variation of a slow axis.

  In order to achieve the above object, claim 1 of the present invention, after applying a coating liquid containing a liquid crystalline compound on a transparent belt-like film on which an alignment film layer is formed, the coating layer is dried and dried. In the method for producing an optical compensation film comprising the step of curing the coating layer, the steps from drying until the solid content concentration in the coating layer is 80% or more until the curing of the coating layer is completed are as follows: The method for producing an optical compensation film is characterized in that the wind speed of the dry wind component in the width direction of the strip film in the vicinity of the coating layer of the strip film is 0.7 m / second or less.

  Before the coating layer containing the liquid crystal compound is cured, the coating layer is dried until the solid content concentration in the coating layer becomes 80% or more. The inventors of the present invention have found that the coating layer in such a dry state is likely to be fixed with turbulence by a drying wind, particularly a drying wind component in the width direction generated in the vicinity of the coating layer of the belt-like film.

  The present invention has been made on the basis of the above knowledge, and according to claim 1, the curing of the coating layer is completed after drying until the solid content concentration in the coating layer becomes 80% or more. In the steps described above, the wind speed of the dry wind component in the width direction in the vicinity of the coating layer of the belt-like film is set to 0.7 m / second or less. Thereby, it can suppress that the disturbance by a dry wind is fixed to the coating layer surface, and the shift | offset | difference and dispersion | variation in the slow axis of an optical compensation film can be reduced.

  In addition, in Claim 1, the dry wind component of the width direction means the wind speed in the range within 40 mm from the application layer of a strip | belt-shaped film. In addition, the dry wind component in the width direction includes a dry wind component that is generated in the vicinity of the coating layer as a result of the dry wind flowing on the non-coated surface side of the belt-like film.

  Claim 2 is the process according to claim 1, in which the solid content in the coating layer is dried until the solid content concentration is 80% or more and the curing of the coating layer is completed. The step of measuring the wind speed of the dry wind component in the width direction and, based on the measurement result, control the blowing speed of the dry wind so that the wind speed of the dry wind component in the width direction is 0.7 m / sec or less. And a step of performing.

  According to the second aspect, the wind speed can be controlled to be 0.7 m / second or less while monitoring the wind speed of the dry wind component in the width direction in the vicinity of the coating layer of the belt-like film.

  A third aspect of the present invention is characterized in that, in the first or second aspect, the dry air is blown to the non-coated surface side of the strip-shaped film.

  According to the third aspect, the dry wind component in the width direction can be prevented from being generated as much as possible in the vicinity of the coating layer of the belt-like film.

  A fourth aspect of the present invention is characterized in that, in any one of the first to third aspects, the coating layer has a width of 0.5 to 3 m.

  In such a wide film, the slow axis tends to be shifted or varied in the width direction, and the present invention is particularly effective.

  A fifth aspect of the present invention is an optical compensation film in which an alignment film layer and a coating layer containing a liquid crystalline compound are sequentially formed on a transparent film in order to achieve the above object. An optical compensation film produced by the method according to any one of the above.

  According to the fifth aspect, it is possible to obtain an optical compensation film with little shift and variation in the slow axis.

  A sixth aspect of the present invention according to the fifth aspect is characterized in that the dispersion in the width direction of the slow axis angle of the optical compensation film is 1.0 ° or less.

  In Claim 6, it is preferable that the dispersion in the width direction of the slow axis of the optical compensation film is ± 0.5 ° or less.

  According to the present invention, it is possible to reduce the shift and variation of the slow axis of the optical compensation film.

  Hereinafter, preferred embodiments of the method for producing an optical compensation film and the optical compensation film of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram showing a schematic configuration of an optical compensation film manufacturing apparatus 10 for carrying out the present invention.

  As shown in FIG. 1, a web 14 on which a transparent resin layer for forming an alignment film is formed in advance is sent out from a feeder 12. The web 14 is fed to a rubbing processing device 18 disposed on the downstream side while being guided by a guide roller 16, and the rubbing roller 20 performs a rubbing process on the transparent resin layer. Thereby, an alignment film is formed.

  In the rubbing processing device 18, rubbing rolls 20 and 20 are arranged between two transport rolls in the continuous transport process of the web 14. Then, the web 14 is continuously rubbed by being wrapped and conveyed by the rotating rubbing rolls 20 and 20. In this case, the rubbing rolls 20 and 20 may be arranged such that the rotation shaft thereof is inclined with respect to the conveyance direction of the web 14.

  A dust remover 22 is disposed on the downstream side of the rubbing treatment device 18 to remove dust adhering to the surface of the web 14. Further, a gravure coating device 24 is disposed on the downstream side of the dust remover 22, and a coating liquid containing a liquid crystalline compound is coated on the alignment film of the web 14. As the liquid crystal compound, a liquid crystal discotic compound having a crosslinkable functional group is preferably used.

  The gravure coating device 24 includes a gravure roller 26 and a liquid receiving pan 28 disposed below the gravure roller 26 and filled with a coating liquid containing a liquid crystal compound. Is immersed in a coating solution. Further, a blade 29 is disposed at about 10 o'clock position of the gravure roller 26. As a result, the coating liquid is supplied to the cells on the surface of the gravure roller 26, and excess coating liquid is scraped off by the blade 29 and then applied to the surface of the web 14.

  The upstream guide roller 17 and the downstream guide roller 19 are arranged in a state substantially parallel to the gravure roller 26. Further, it is preferable that the upstream guide roller 17 and the downstream guide roller 19 are rotatably supported at both ends by a bearing member (ball bearing or the like) (not shown) and have no drive mechanism. The gravure coating device 24 is preferably provided in a clean atmosphere such as a clean room. The cleanliness is preferably class 1000 or less, more preferably class 100 or less, and still more preferably class 10 or less.

  As an example of the coating apparatus, FIG. 1 shows an example of the gravure coating apparatus 24, but the present invention is not limited to this. For example, methods such as a dip coating method, an air knife coating method, a curtain coating method, a roller coating method, a wire bar coating method, a micro gravure method, and an extrusion coating method can be used as appropriate.

  The web 14 on which the coating layer containing the liquid crystal compound is formed is dried by an initial drying zone 30 provided immediately downstream.

  Further, a drying zone 32 and a heating zone 34 are provided on the downstream side of the initial drying zone 30, and the coated layer of the dried web 14 is further dried and aged. In this case, in the heating zone 34, it is preferable to apply hot air or far-infrared rays or contact a heating roller to the side of the web 14 where the liquid crystal layer is not formed. Then, it is dried so that the solid content concentration in the coating layer becomes 80% or more before reaching the ultraviolet irradiation means 40 on the downstream side.

  Further, the web 14 exiting the drying zone 32 passes through the ultraviolet irradiation zone 36 provided on the downstream side thereof, and is continuously irradiated with light to cure the discotic liquid crystal. Then, the web 14 on which the coating layer containing the liquid crystalline compound is formed on the alignment film is wound up by the winder 38.

  Next, the configuration around the ultraviolet irradiation zone 36 will be described.

  FIG. 2 is a schematic cross-sectional view of an essential part for explaining a schematic configuration in the vicinity of the ultraviolet irradiation zone 36 of FIG. In the present embodiment, an example in which drying air for drying the coating layer is supplied also in the ultraviolet irradiation zone 36 will be described. However, when the drying up to the heating zone 34 is completed, only ultraviolet irradiation may be performed. it can.

  As shown in FIG. 2, an ultraviolet irradiation zone 36 provided on the downstream side of the drying zone 32 and the heating zone 34 is provided in the ultraviolet irradiation chamber 39 and the upper portion of the ultraviolet irradiation chamber 39, and the web 14 to be conveyed. And an ultraviolet irradiation means 40 for irradiating the coating layer with ultraviolet rays.

  The ultraviolet irradiation chamber 39 has a blow-off portion 42 for blowing dry air into the ultraviolet irradiation chamber 39 on the non-application surface side of the web 14 (the lower side of the web 14 in the figure), and the drying air outside the ultraviolet irradiation chamber 39. And a discharge portion 46 for discharging the water. This drying air is used to dry the coating layer of the web 14 to a state suitable for curing or to maintain the dry state. Furthermore, by setting the inside of the ultraviolet irradiation chamber 39 to an appropriate temperature with dry air, the generation of wrinkles of the web 14 due to heating is prevented and thermosetting is promoted. The drying air can be supplied similarly in the drying zone 32 and the heating zone 34.

  The blowout part 42 is provided on the upstream side surface of the ultraviolet irradiation chamber 39. The opening of the blow-out portion 42 is formed wider than the web 14 (front-depth direction in FIG. 2), and uniform drying air is blown out in the width direction as indicated by a two-dot chain line arrow in FIG. At this time, it is preferable that the dry air is supplied so that the locality (variation) of the air volume and the temperature distribution becomes small.

  The discharge portion 46 is formed on the bottom surface on the downstream side of the ultraviolet irradiation chamber 39, and the indoor drying air is discharged to the outside. As a result, the drying air blown from the blowing unit 42 flows along the conveyance direction of the web 14 and is then discharged from the discharge unit 46.

  As the ultraviolet irradiation means 40, a known one can be used, for example, an ultraviolet lamp or the like. Although FIG. 2 shows an example in which three ultraviolet irradiation means 40 are arranged, the installation form and number are not particularly limited.

  Here, in the process from the drying zone 32 to the end of the ultraviolet irradiation in the ultraviolet irradiation zone 36, the solid component in the coating layer of the web 14 is dried to 80% or more and fixed in a normal arrangement state. . When a dry wind in the width direction directly hits the coating layer in such a dry film state, the alignment of the liquid crystal compound is disturbed, and the time required to return to the original alignment state (relaxation time) becomes long. When light irradiation is performed while the alignment state of the liquid crystal compound is disturbed, the compound is cured while the alignment of the slow axis of the compound is disturbed, which causes light leakage and shift of the slow axis. In particular, in the thickness direction, on the alignment film surface, the liquid crystal compound is regulated by a groove formed by rubbing treatment, but the regulation by the groove becomes weaker and unstable as it goes to the opposite side (air interface direction). It has become. Further, in the case of the wide web 14, the variation of the slow axis in the width direction becomes large.

  Therefore, in the present invention, in the process from the drying zone 32 to the end of the ultraviolet irradiation in the ultraviolet irradiation zone 36, the wind speed of the drying wind, particularly the widthwise drying wind component generated in the vicinity of the coating layer of the web 14 is 0.7 m. The turbulence and distortion caused by drying air are not fixed to the coating layer before being cured.

  That is, as shown in FIG. 2, in the heating zone 34 and the ultraviolet irradiation zone 36, the anemometers 48 and 48 for measuring the wind speed of the dry wind component in the width direction in the vicinity of the coating layer surface, and the anemometers 48 and 48, respectively. And a control means 50 for controlling the blowing speed of the drying air from the air supply means 41 and 43 based on the result.

  The anemometer 48 is not particularly limited as long as it can measure the wind speed of the dry wind component in the width direction. For example, a “Kurimo Master anemometer” manufactured by Nippon Kanomax Co., Ltd. can be used. A “crimo master anemometer type 6531 or 6541” having directivity can be preferably used. Thereby, the control means 50 controls the blowing speed of the dry air in the blowing part 42 via the air supply means 41 based on the measurement result in the anemometer 48.

  In the embodiment of FIG. 2, one anemometer is arranged in each of the heating zone 34 and the ultraviolet irradiation zone 36, but the installation zone and the number of installations of the anemometer are not limited to this. Moreover, although the example which controls the air supply means 41 and 43 by the one control means 50 was shown, the control form is not limited to this, You may provide one control means for every air supply means. Although not shown in FIG. 2, an anemometer, an air supply unit, and a control unit similar to those described above may be provided on the downstream side of the drying zone 32.

  The width of the coating layer on the web 14 is preferably 0.5 to 3 m in order to widely correspond to the size of the liquid crystal display device.

  In the optical compensation film thus produced, it is preferable that the deviation of the slow axis angle is 0.3 ° or less. Moreover, it is preferable that the dispersion | variation in the width direction of a slow axis angle is 1.0 degrees or less, and it is more preferable that it is 0.5 degrees or less.

  Next, the operation of the manufacturing apparatus 10 in FIG. 1 will be described focusing on the process from the drying zone 32 to the ultraviolet irradiation zone 36.

  As shown in FIG. 1, the web 14 delivered from the delivery device 12 is guided by a guide roller 16 and sent to a rubbing processing device 18. The conveyance speed of the web 14 is preferably 5 to 200 m / min.

Next, the surface of the web 14 is rubbed by the rubbing treatment device 18, and then a coating liquid containing a liquid crystalline compound is coated on the web 14 by the gravure coating device 24. The coating amount of the coating solution is preferably 10 mL / m ² or less. Further, the width of the coating layer formed on the web 14 is preferably 0.5 to 3 m.

  Next, the web 14 on which the coating layer containing the liquid crystal compound is formed is initially dried in the initial drying zone 30 and then further dried in the drying zone 32 and the heating zone 34. Immediately before leaving the drying zone 32 and the heating zone 34, the coating layer is dried until the solid component becomes 80% or more. As shown in FIG. 2, in the process until the ultraviolet irradiation by the ultraviolet irradiation means 40 is completed, the dry wind component in the width direction in the vicinity of the coating layer is controlled to be 0.7 m / second or less.

  That is, as shown in FIG. 2, in the heating zone 34 and the ultraviolet irradiation zone 36, the dry wind component in the width direction in the vicinity of the coating layer is measured by the anemometer 48 (measurement step), and based on the measurement result, The blowing speed of the drying air blown out to the heating chamber 35 and the ultraviolet irradiation chamber 39 through the air supply means 41 and 43 is controlled by the control means 50 (control process).

  Thus, not only does the drying air not directly hit the coating layer, but also the drying air does not circulate from the non-application surface side of the web 14 and the flow of the drying air is not disturbed, thereby increasing the width of the drying air component. There is no fear.

  The web 14 from which the coating layer has been dried is continuously irradiated with ultraviolet rays in the ultraviolet irradiation zone 36, so that the coating layer is cured and wound by a winder 38.

  As described above, since the disturbance due to the drying wind is not fixed to the coating layer immediately before the ultraviolet irradiation, the liquid crystal compound can be cured while keeping the alignment state uniform and normal. Therefore, it is possible to suppress the occurrence of deviations and variations in the slow axis.

  Further, since the influence of the turbulence due to the dry wind component in the width direction is reduced, even the wide web 14 can reduce the shift and variation of the slow axis.

  As mentioned above, although preferable embodiment of the manufacturing method of the optical compensation film which concerns on this invention was described, this invention is not limited to the said embodiment, Various aspects can be taken.

  For example, in the above-described embodiment, the example applied to the method for producing an optical compensation film has been described. However, the present invention is not limited to this, and includes a step of applying a coating solution on a belt-like film, followed by drying and curing, with high accuracy. The present invention can also be applied to methods for producing various optical films that require surface quality, such as antiglare films and antireflection films.

  Next, various materials used in the present invention will be described.

  As the discotic compound (liquid crystal compound) used in the present embodiment, those described in JP-A-7-267902, JP-A-7-281028, and JP-A-7-306317 can be used. According to these, the optically anisotropic layer (coating layer containing a liquid crystalline compound) is a layer formed from a compound having a discotic structural unit. That is, the optically anisotropic layer is a polymer layer obtained by polymerization (curing) of a low molecular weight liquid crystal discotic compound layer such as a monomer or a polymerizable liquid crystal discotic compound.

  Examples of discotic (discotic) compounds include C.I. Destrade et al., Mol. Cryst. 71, 111 (1981), benzene derivatives described in C.I. Destrade et al., Mol. Cryst. 122, 141 (1985), Physics lett, A, 78, 82 (1990); Kohne et al., Angew. Chem. 96, 70 (1984) and the 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), such as 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. In addition, in the above publication, the term “formed from a discotic compound” does not require that the final product be the compound, for example, the low molecular discotic liquid crystal has a group that reacts with heat, light, or the like. As a result, it may be polymerized or cross-linked by reaction with heat, light, etc., to have a high molecular weight and lose liquid crystallinity. Furthermore, it is preferable to use a compound containing at least one discotic compound capable of forming a discotic nematic phase or a uniaxial columnar phase and having optical anisotropy. The discotic compound is preferably a triphenylene derivative. Here, the triphenylene derivative is preferably a compound represented by (Chemical Formula 2) described in JP-A-7-306317.

  A cellulose acylate film is preferably used as the web 14 serving as a support for the alignment layer. Specifically, those described in detail in JP-A-9-152509 can be used. That is, the alignment film is provided on the cellulose acylate film or on an undercoat layer coated on the cellulose acylate film. The alignment film functions to define the alignment direction of the liquid crystalline discotic compound provided thereon. Here, the alignment film may be any layer as long as it can impart orientation to the optically anisotropic layer.

  Preferred examples of the alignment film include a layer subjected to a rubbing treatment of an organic compound (preferably a polymer), an oblique deposition layer of an inorganic compound, and a layer having a microgroove, and ω-tricosanoic acid, dioctadecylmethylammonium chloride and stearyl. Examples thereof include a cumulative film formed by Langmuir-Blodgett method (LB film) such as methyl acid, or a layer in which a dielectric is oriented by applying an electric field or a magnetic field.

  Examples of the organic compound for the alignment film include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleimide copolymer, polyvinyl alcohol, poly (N-methylolacrylamide), and styrene / vinyltoluene copolymer. Polymers such as chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, carboxymethyl cellulose, polyethylene, polypropylene and polycarbonate, and Examples of the compound include a silane coupling agent. Examples of preferable polymers include polyimide, polystyrene, polymers of styrene derivatives, gelatin, polyvinyl alcohol, and alkyl-modified polyvinyl alcohol having an alkyl group (preferably having 6 or more carbon atoms).

Among them, alkyl-modified polyvinyl alcohol is particularly preferable and has an excellent ability to uniformly align a liquid crystal discotic compound. This is presumably because of the strong interaction between the alkyl chain on the alignment film surface and the alkyl side chain of the discotic liquid crystal. In addition, the alkyl group preferably has 6 to 14 carbon atoms, and further, polyvinyl alcohol via —S—, — (CH ₃ ) C (CN) — or — (C ₂ H ₅ ) N—CS—S—. It is preferable that it is couple | bonded with. The alkyl-modified polyvinyl alcohol has an alkyl group at the end, and preferably has a saponification degree of 80% or more and a polymerization degree of 200 or more. Moreover, the polyvinyl alcohol which has an alkyl group in the said side chain can utilize commercial items, such as Kuraray Co., Ltd. product MP103, MP203, R1130.

  A polyimide film (preferably a fluorine atom-containing polyimide) widely used as an alignment film of a liquid crystal display (LCD) is also preferable as the organic alignment film. This is done by applying polyamic acid (for example, LQ / LX series manufactured by Hitachi Chemical Co., Ltd., SE series manufactured by Nissan Chemical Co., Ltd.) to the web surface and baking at 100 to 300 ° C. for 0.5 to 1 hour. And then obtained by rubbing.

  Furthermore, alignment films applied to cellulose acylate films cure these polymers by introducing reactive groups into the polymers or using the polymers with crosslinkers such as isocyanate compounds and epoxy compounds. It is preferable that it is a cured film obtained by this.

  It is preferable that the polymer used for the alignment film and the liquid crystalline compound of the optically anisotropic layer are chemically bonded via the interface between these layers. The polymer of the alignment film is preferably formed from polyvinyl alcohol in which at least one hydroxyl group is substituted with a group having a vinyl part, an oxiranyl part or an aziridinyl part. A group having a vinyl moiety, an oxiranyl moiety or an aziridinyl moiety is preferably bonded to the polymer chain of the polyvinyl alcohol derivative via an ether bond, a urethane bond, an acetal bond or an ester bond. It is preferred that the group having a vinyl moiety, an oxiranyl moiety or an aziridinyl moiety does not have an aromatic ring. The polyvinyl alcohol is preferably (Chemical Formula 22) described in JP-A-9-152509.

  For the rubbing treatment, a treatment method widely used as a liquid crystal alignment treatment process of the LCD can be used. That is, a method of obtaining alignment by rubbing the surface of the alignment film in a certain direction using paper, gauze, felt, rubber, nylon, polyester fiber or the like can be used. In general, it is carried out by rubbing several times using a cloth in which fibers having a uniform length and thickness are flocked on average.

Moreover, as a vapor deposition material of the inorganic oblique vapor deposition film, SiO is representative, and metal oxides such as TiO ₂ and ZnO ₂ , fluorides such as MgF ₂ , and metals such as Au and Al can be given. The metal oxide can be used as an oblique deposition material as long as it has a high dielectric constant, and is not limited to the above. The inorganic oblique deposition film can be formed using a deposition apparatus. An inorganic oblique vapor deposition film can be formed by performing vapor deposition with the web fixed or by moving the long web to perform continuous vapor deposition. Examples of a method for aligning an optical anisotropic layer without using an alignment film include a method of applying an electric field or a magnetic field while heating the optical anisotropic layer on the web to a temperature at which a discotic liquid crystal layer can be formed. .

  As an application method of an optical compensation film having an optically anisotropic layer formed on a cellulose acylate film to a liquid crystal display device, the optical compensation film is bonded to one side of a polarizing plate via an adhesive, or a polarizing element It is preferable that the above optical compensation film is bonded to one side of the film with an adhesive as a protective film. The optically anisotropic element preferably has at least a discotic structural unit (preferably a discotic liquid crystal).

  The disc surface of the discotic structural unit is inclined with respect to the cellulose acylate film surface, and the angle formed by the disc surface of the discotic structural unit and the cellulose acylate film is the depth direction of the optical anisotropic layer. It is preferable that it changes in.

Preferred embodiments of the optical compensation film are as follows.
(A1) The average value of the angles increases as the distance from the bottom surface of the optical anisotropic layer increases in the depth direction of the optical anisotropic layer.
(A2) The said angle changes in the range of 5-85 degrees.
(A3) The minimum value of the angle is in the range of 0 to 85 ° (preferably 0 to 40 °), and the maximum value is in the range of 5 to 90 ° (preferably 50 to 85 °).
(A4) The difference between the minimum value and the maximum value of the angle is in the range of 5 to 70 degrees (preferably 10 to 60 °).
(A5) The angle continuously changes (preferably increases) in the depth direction of the optical anisotropic layer and with an increase in the distance from the bottom surface of the optical anisotropic layer.
(A6) The optically anisotropic layer further contains cellulose acylate.
(A7) The optically anisotropic layer further contains cellulose acetate butyrate.
(A8) An alignment film (preferably a polymer cured film) is formed between the optically anisotropic layer and the transparent web 14.
(A9) An undercoat layer is formed between the optically anisotropic layer and the alignment film.
(A10) The optically anisotropic layer has a minimum absolute value of retardation other than 0 in a direction inclined from the normal direction of the optical compensation film.
(A11) The optical compensation film according to (a8), wherein the alignment film is a rubbed polymer layer.

  It is preferable to include an organic compound that can be added to the optical anisotropic layer to change the orientation temperature of the optical anisotropic layer. The organic compound is preferably a monomer having a polymerizable group.

  The optical compensation film is particularly preferably used for a transmissive liquid crystal display device. The transmissive liquid crystal display device includes a liquid crystal cell and two polarizing plates disposed on both sides thereof. The liquid crystal cell carries a liquid crystal between two electrode substrates. One optical compensation film is disposed between the liquid crystal cell and one polarizing plate, or two optical compensation films are disposed between the liquid crystal cell and both polarizing plates. The mode of the liquid crystal cell is preferably a VA mode, a TN mode, or an OCB mode.

  Hereinafter, practical effects of the present invention will be described by way of examples.

  Using the production apparatus 10 according to the present invention, late drying was performed under the conditions shown in Table 1, and the shift of the slow axis due to the dry wind component in the width direction of the web 14 was observed.

As the web 14, triacetyl cellulose (Fujitack, manufactured by Fuji Photo Film Co., Ltd.) having a thickness of 80 μm was used. Then, the surface of the web 14, 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 formed by drying for 1 minute at 60 ° C orientation While the web 14 on which the film resin layer was formed was conveyed at 30 m / min, the surface of the alignment film resin layer was rubbed to form an alignment film.

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 that is a 40 wt% methyl ethyl ketone solution of a mixture obtained by adding 1 wt% of a photopolymerization initiator (Irgacure 907, manufactured by Nippon Ciba Geigy Co., Ltd.) to the mixture was used. While running the web 14 at 30 m / min, this coating solution was applied onto the alignment film by the gravure coating device 24 so that the amount of the coating solution was 5 to 7 mL per 1 m ^{2 of the} web. Then, after the initial drying in the initial drying zone 30 immediately after coating, drying was further performed in the drying zone 32 adjusted to 100 ° C. and the heating zone 34 adjusted to 130 ° C. Thereafter, ultraviolet rays were irradiated by an ultraviolet lamp while continuously transporting the web 14 coated with the alignment film and the liquid crystal compound.

  Here, the values shown in Table 1 show the wind speed of the dry wind component in the width direction in the vicinity of the coating layer from the heating zone 34 to the time when the ultraviolet irradiation chamber 39 is irradiated with the ultraviolet light, and the blowing speed of the drying air in the ultraviolet irradiation chamber 39. The amount of shift of the slow axis angle (axis shift angle) was measured.

表１に示すように、幅方向の乾燥風成分が０．７ｍ/秒以下である実施例１〜３では、遅相軸の軸ズレ角度が、基準値０．３（図１参照）よりも低い０．２０°以下と極めて小さくすることができた。これに対して、幅方向の乾燥風成分が０．７ｍ/秒を超える比較例１〜３では、軸ズレ角度が０．６０°以上と大きくなった。 The wind speed was measured using a crimomaster anemometer in the line operation state. The slow axis angle was measured with KOBRA 21DH (manufactured by Oji Scientific Instruments). The results are shown in Table 1 and FIG. In addition, about the tolerance determination, it performed on the following references | standards.
(Acceptance judgment)
○: Acceptable as a product and very good surface shape △: Acceptable as a product ×: Not acceptable as a product

As shown in Table 1, in Examples 1 to 3 in which the dry wind component in the width direction is 0.7 m / sec or less, the axis shift angle of the slow axis is more than the reference value 0.3 (see FIG. 1). It was as low as 0.20 ° or less and could be extremely small. On the other hand, in Comparative Examples 1 to 3 in which the dry wind component in the width direction exceeds 0.7 m / sec, the axial deviation angle is as large as 0.60 ° or more.

  As shown in FIG. 1, when the dry wind component in the width direction is 0.7 m / second or less, the deviation of the slow axis is within a certain range, which is lower than 0.7 m / second. It can be seen that the deviation of the slow axis increases rapidly.

  Further, in Comparative Examples 4 and 5 in which the coating layer having a solid content concentration of less than 80% was irradiated with ultraviolet rays, even if the wind velocity in the width direction was as small as less than 0.7 m / second, the axis deviation angle of the slow axis was large. It was. From this, it can be seen that when the drying is insufficient, the disorder of the alignment of the liquid crystal compound is easily fixed by the drying air.

  Next, the variation in the slow axis angle in the width direction and the conveyance direction when the wind speed of the drying wind in the width direction was changed was measured. The slow axis angle was measured by the same method as described above.

[Example 5]
First, the wind speed of the drying air in the width direction was set to 0.5 m / second. Then, eight measurement positions were randomly selected in the transport direction (Tests 1 to 8), and the slow axis angles at the five points of the left end, the left middle, the center, the right middle, and the right end in the width direction were measured for each measurement position. The distribution of the slow axis angles in the transport direction and the width direction is summarized in FIG.

  Further, the difference between the maximum value and the minimum value in the width direction of the slow axis angle at each measurement position (Tests 1 to 8) was determined as the variation (R) of the slow axis angle. The results are shown in Table 2.

[Comparative Example 6]
The same operation as in Example 5 was performed except that the wind speed of the drying air in the width direction was 1.1 m / sec. In addition, the eight positions selected at random in the conveyance direction were set as comparative tests 1 to 8. The results are shown in FIG.

なお、図４、５において、横軸はウエブ幅方向の遅相軸角度の測定位置を示し、縦軸は各測定位置での遅相軸角度（°）を示している。

4 and 5, the horizontal axis indicates the measurement position of the slow axis angle in the web width direction, and the vertical axis indicates the slow axis angle (°) at each measurement position.

  As shown in FIG. 4, in Example 5 (Tests 1 to 8) in which the wind speed of the drying air in the width direction was 0.5 m / sec, the variation of the slow axis angle in both the transport direction and the width direction was ± 1.0. Most of them were small, less than ± 0.5 °. On the other hand, as shown in FIG. 5, in Comparative Example 6 (Comparative Tests 1 to 8) in which the wind speed of the drying air in the width direction was 1.1 m / sec, the slow axis angle was both in the transport direction and the width direction. The variation was large exceeding ± 1.0 °.

  As shown in Table 2, in tests 1 to 8, the slow axis angle variation (R) is 0.6 or less and the variation due to the position in the transport direction is small. ˜8, the variation (R) of the slow axis angle is as large as 1 or more, and the variation due to the position in the transport direction is large.

  From the above, it has been confirmed that the shift of the slow axis can be reduced by reducing the drying wind component in the width direction in the vicinity of the coating layer from the heating zone 34 to the time when the ultraviolet irradiation chamber 39 is irradiated with the ultraviolet rays.

It is a schematic diagram which shows schematic structure of the manufacturing apparatus 10 of the optical compensation film which concerns on this invention. It is a principal part cross-sectional schematic diagram explaining the schematic structure of the ultraviolet irradiation zone 36 vicinity of FIG. It is a figure which shows the result of an Example. It is a figure which shows the result of an Example. It is a figure which shows the result of an Example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Optical compensation film manufacturing apparatus, 14 ... Web, 32 ... Drying zone, 34 ... Heating zone, 36 ... Ultraviolet irradiation zone, 39 ... Ultraviolet irradiation chamber, 40 ... Ultraviolet irradiation means, 42 ... Outlet part, 46 ... Discharge part 48 ... Anemometer, 50 ... Control means, 41, 43 ... Air supply means

Claims (4)

A step of applying a coating liquid containing a liquid crystalline compound on a transparent belt-like film on which an alignment film layer is formed to form a coating layer, drying the coating layer, and curing the dried coating layer In the manufacturing method of the optical compensation film,
After drying until the solid content concentration in the coating layer reaches 80% or more, the process until the curing of the coating layer is completed,
Supplying dry air with a wind speed of 1.40 m / sec or more to the side where the coating liquid of the belt-like film is not applied in the ultraviolet irradiation chamber for irradiating the belt-like film with ultraviolet rays;
In the ultraviolet irradiation chamber, the coating layer having a solid content concentration of 80% or more is irradiated with ultraviolet rays,
The dry air is discharged from the side of the ultraviolet irradiation chamber where the coating solution of the strip film is not applied,
A method for producing an optical compensation film, characterized in that a wind speed of a dry wind component in a width direction of the strip film in the vicinity of the coating layer of the strip film is 0.7 m / sec or less. In the process from the drying until the solid content concentration in the coating layer is 80% or more until the curing of the coating layer is completed,
Measuring the wind speed of the dry wind component in the width direction in the vicinity of the coating layer of the belt-shaped film;
Based on the measured results, the step of controlling the blowing speed of the drying wind so that the wind speed of the drying wind component in the width direction of the strip film is 0.7 m / second or less,
The method for producing an optical compensation film according to claim 1, comprising: Supplying the drying air into the ultraviolet irradiation chamber from the opening of the blowing portion formed on the side of the ultraviolet irradiation chamber that is wider than the width of the belt-shaped film and not coated with the coating liquid of the belt-shaped film. And
The drying air is discharged out of the ultraviolet irradiation chamber from a discharge portion formed on the side of the ultraviolet irradiation chamber where the coating solution of the strip film is not applied.
The method for producing an optical compensation film according to claim 1 or 2.   4. The method for producing an optical compensation film according to claim 1, wherein a width of the coating layer is 0.5 to 3 m.

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