JP2011248310A - Optical compensation film and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical compensation film which can improve optical compensation performance through control of optical axis.SOLUTION: An optical compensation film 1 comprises a base film 2, and an optical anisotropic layer 3 layered on at least one of surfaces of the base film 2. On a surface 2a of the base film 2 on which the optical anisotropic layer 3 is layered, multiple grooves, whose width and depth are 5 μm or less, are provided. The optical anisotropic layer 3 is formed by coating of resin solution with viscosity of 500 mPa s or less.

Description

  The present invention is an optical compensation film having optical compensation performance, which is used in, for example, a liquid crystal display device and the like, and can display images on the liquid crystal display device with high quality, and the optical compensation film It relates to the manufacturing method.

  A liquid crystal display (LCD) is configured by adhering an optical film and a polarizing plate to a liquid crystal cell in which liquid crystal molecules are enclosed and electrodes are incorporated. As an operation method of the liquid crystal display device, there are a TN (Twisted Nematic) mode, an STN (Super Twisted Nematic) mode, a VA (Vertical Alignment) mode, an IPS (In-Plane Switching) mode, an OCB (Optically Compensated Bend, etc.). Various schemes mainly defined by the alignment form of liquid crystal molecules have been proposed. Each of these displays an image using the electro-optical characteristics of liquid crystal molecules.

  In the liquid crystal display device, optical films having various functions are used for the purpose of improving the image quality of the display viewed through the polarizing plate. The optical film needs to have various optical characteristics depending on applications, including transparency and optical compensation. In particular, optical anisotropy is applied as the above optical film in order to eliminate the optical distortion caused by the birefringence inherent in liquid crystals and the viewing angle dependency such as the coloration of the display depending on the visual direction. Compensation films are widely used.

  In various liquid crystal display devices, the optical compensation film is used as, for example, a wavelength conversion element or a viewing angle improvement element. Usually, the phase difference plate is used in a state of being laminated with a polarizing plate.

  In order to develop optical anisotropy and the like in the optical compensation film, a method of stretching the film by a heat stretching method and controlling the orientation of resin molecules is known. However, the heat stretching method cannot stretch the film uniformly over the entire width of the film. In addition, it is difficult to produce a large optical compensation film for use in a large liquid crystal display device, which is in great demand in recent years, by the heat stretching method.

  In addition, the optical axis of the optical compensation film produced by the above heat stretching method is generally in the longitudinal direction of the film or in a direction orthogonal to the longitudinal direction. However, in many cases, when the polarizing plate and the retardation plate are bonded, the optical axis of the polarizing plate and the optical axis of the retardation plate are bonded so as to form a predetermined angle that is neither orthogonal nor parallel. ing. Accordingly, a polarizing plate slightly larger than the size of the product and a retardation plate are prepared by cutting in advance, and the polarizing plate and the retardation plate are arranged so that the optical axes of the polarizing plate and the retardation plate intersect at a predetermined angle. After bonding the phase difference plate, the ends of the polarizing plate and the phase difference plate are cut so as to have a predetermined size. In this method, it is necessary to individually perform a cutting step for obtaining a slightly larger polarizing plate, a cutting step for obtaining a slightly larger retardation plate, and a step of bonding the polarizing plate and the retardation plate. For this reason, the work process is complicated, the productivity is low, and there is a portion that is removed by cutting and discarded, so that the cost increases.

  In order to solve such a problem, various methods for orienting resin molecules in a direction that is not in the longitudinal direction of the film but in a direction that is not perpendicular to the longitudinal direction have been proposed. For example, Patent Document 1 below discloses an optical compensation film in which resin molecules are oriented in an oblique direction by stretching the film in an oblique direction.

  As a method different from the heat stretching method, a resin or compound having a refractive index anisotropy and expressing a specific optical compensation performance is optically applied on a resin film or a glass substrate using a coating solution in which an organic solvent is dissolved. A method for forming an anisotropic layer has also been proposed. For example, in Patent Document 2 below, a homeotropic alignment side chain type liquid crystal polymer is coated on a substrate, and then the polymer is homeotropically aligned in a liquid crystal state and fixed in a state where the alignment state is maintained. The optical compensation film obtained by making it be disclosed is disclosed. Patent Document 3 below discloses an optical compensation film in which a film layer formed using a liquid crystal material in which a liquid crystal compound is dissolved in an organic solvent is formed on a support such as a plastic film. ing.

  For such a resin-laminated optical compensation film by coating, it is important to control the optical axis in consideration of the step of laminating the polarizing plate and the phase difference plate as in the stretched film. In Patent Document 4 below, in order to control the alignment state of liquid crystal molecules, a solution containing a liquid crystal molecule having a nematic phase in the liquid crystal state and in a glass state at a temperature below the glass transition, A second direction which forms an angle of 45 to 90 ° with respect to the first direction by aligning liquid crystal molecules in the first direction by the alignment regulating force of the substrate using a certain substrate and applying a magnetic field. Discloses an optical compensation film in which liquid crystal molecules are aligned.

JP 2001-281442 A JP 2003-149441 A JP 2007-152173 A JP 2007-55193 A

  In the optical compensation film obtained by the heating and stretching method as described in Patent Document 1, even if it is possible to incline the molecular orientation axis, that is, the optical axis, in an oblique direction with respect to the longitudinal direction of the film, It is difficult to obtain a film with uniform quality. Further, since the deformation stress acts on the film not only in the desired tilt angle direction in the film plane but also in other directions such as the width direction and the thickness direction of the film, the optical anisotropy cannot be controlled with high accuracy and desired. It is difficult to obtain an optical compensation film having the following optical performance.

  In a technique using a coating method such as Patent Documents 2 and 3, generally, an optical compensation film in which the orientation of resin molecules is controlled in a longitudinal direction or a direction orthogonal to the longitudinal direction, and the molecular orientation is controlled in an arbitrary direction. It is difficult to get. Further, even the optical compensation film described in Patent Document 4 has insufficient reproducibility to control the orientation of resin molecules in an arbitrary direction, and the optical compensation performance of the optical compensation film is not always stable.

  An object of the present invention is to provide an optical compensation film capable of increasing the optical compensation performance by controlling the optical axis in an arbitrary direction within the film plane, and a method for producing the optical compensation film.

  According to a wide aspect of the present invention, the surface includes a base film and an optical anisotropic layer laminated on at least one surface of the base film, and the surface on which the optical anisotropic layer of the base film is laminated. In addition, a plurality of grooves having a width of 5 μm or less and a depth of 5 μm or less are provided, and the optically anisotropic layer is formed by applying a resin solution having a viscosity of 500 mPa · s or less. An optical compensation film is provided.

  In a specific aspect of the optical compensation film according to the present invention, the optical compensation film has a longitudinal direction and a lateral direction, and the optical axis is inclined with respect to the longitudinal direction.

  In another specific aspect of the optical compensation film according to the present invention, the resin solution includes a resin having lyotropic liquid crystallinity.

  In another specific aspect of the optical compensation film according to the present invention, the groove is formed by polishing the surface of the base film with an abrasive that is a particle, and the abrasive that is the particle is a metal particle. , At least one selected from the group consisting of metal oxide particles, metal carbide particles, and carbon particles.

  The method for producing an optical compensation film according to the present invention includes a step of forming a groove having a width of 5 μm or less and a depth of 5 μm or less on at least one surface on which the optical film of the substrate film is laminated; Applying a resin solution having a viscosity of 500 mPa · s or less to the surface of the film on which the groove is formed to form an optically anisotropic layer.

  A specific aspect of the method for producing an optical compensation film according to the present invention is that the groove is formed by polishing the surface of the base film with an abrasive that is particles, and the abrasive that is the particles includes metal particles, At least one selected from the group consisting of metal oxide particles, metal carbide particles, and carbon particles is used.

  In the optical compensation film according to the present invention, a plurality of grooves having a width of 5 μm or less and a depth of 5 μm or less are provided on the surface of the base film on which the optical anisotropic layer is laminated. Since the layer is formed by applying a resin solution having a viscosity of 500 mPa · s or less, by controlling the direction in which the groove extends, it can be adjusted in any direction in the film plane along the fine groove. The optical axis can be controlled and the optical compensation performance can be enhanced.

  In the method for producing an optical compensation film according to the present invention, after forming a groove having a width of 5 μm or less and a depth of 5 μm or less on at least one surface on which the optical anisotropic layer of the base film is laminated, A resin solution having a viscosity of 500 mPa · s or less is applied to the surface of the material film on which the grooves are formed to form an optically anisotropic layer. Therefore, by controlling the direction in which the grooves extend, The optical axis can be controlled in any direction in the film plane along the groove, and an optical compensation film having high optical compensation performance can be obtained.

FIG. 1 is a cross-sectional view showing an optical compensation film according to an embodiment of the present invention.

  Hereinafter, the present invention will be clarified by describing specific embodiments and examples of the present invention with reference to the drawings.

  In FIG. 1, the optical compensation film which concerns on one Embodiment of this invention is shown with sectional drawing.

  The optical compensation film 1 shown in FIG. 1 includes a base film 2 and an optical anisotropic layer 3 laminated on the first surface 2 a of the base film 2. The optical anisotropic layer 3 is not laminated on the second surface 2 b opposite to the first surface 2 a of the base film 2. The optical anisotropic layer should just be laminated | stacked on the at least single side | surface of the base film 2, and the optical anisotropic layer 3 may be laminated | stacked also on the 2nd surface 2b. The optical compensation film 1 is an optical compensation laminated film in which a base film 2 and an optical anisotropic layer 3 are laminated.

  In the present embodiment, a plurality of grooves having a width of 5 μm or less and a depth of 5 μm or less are provided on the first surface 2 a on which the optical anisotropic layer 3 of the base film 2 is laminated. Since the groove is fine, the illustration of the groove is omitted in FIG. The optically anisotropic layer 3 is formed by applying a resin solution to the first surface 2 a of the base film 2. Specifically, for example, after applying a resin solution to the first surface 2 a of the base film 2, the optical anisotropic layer 3 is formed by drying to remove the solvent.

  The main feature of the present invention is that a plurality of fine grooves having a width of 5 μm or less and a depth of 5 μm or less are provided on the surface of the base film on which the optical anisotropic layer is laminated. The optically anisotropic layer is formed by applying a resin solution having a viscosity of 500 mPa · s or less on the surface provided with the groove. Thereby, the optical compensation performance can be enhanced by controlling the optical axis in any direction in the film plane along the fine groove. By using the optical compensation film according to the present invention, the display image of the liquid crystal display device can be improved.

  Further, the inventor has selected the groove provided on the surface of the base film from the group consisting of abrasive particles, particularly metal particles, metal oxide particles, metal carbide particles, and carbon particles. It has been found that when formed by polishing with at least one type of abrasive, the orientation of the resin molecules can be controlled more precisely in any direction to make the optical axis more uniform.

(Resin solution)
The resin solution is preferably a solution containing a resin having lyotropic liquid crystallinity. As the resin solution, a resin solution obtained by dissolving a resin having lyotropic liquid crystallinity in a solvent is preferably used. The resin contained in the resin solution is a polymer having a structure exhibiting lyotropic liquid crystallinity in the main chain (main chain type polymer liquid crystal compound) or a polymer having a structure exhibiting liquid crystallinity in the side chain (side chain type high molecular weight). Molecular liquid crystal compound). As for the said resin and resin solution, respectively, only 1 type may be used and 2 or more types may be used together. By using a resin having lyotropic liquid crystallinity, the lyotropic liquid crystal molecules effectively respond to the orientation regulating force of the fine grooves provided on the surface of the base film, and in any direction on the surface of the base film. The molecules can be oriented along the provided grooves.

  Examples of the main chain type polymer liquid crystal compound include polyamide, polyester, polycarbonate, polyimide, polyurethane, polybenzimidazole, polybenzoxazole, polybenzthiazole, polyazomethine, and polyesteramide. , Polymer liquid crystal compounds such as polyester carbonate type and polyester imide type, and mixtures thereof.

  Examples of the side-chain polymer liquid crystal compound include a skeleton having a linear or cyclic structure such as polyacrylate, polymethacrylate, polyvinyl, polysiloxane, polyether, polymalonate, and polyester. Examples thereof include a polymer liquid crystal compound having a mesogen group bonded as a chain, and a mixture thereof.

  When the liquid crystal expression temperature is lower than 80 ° C., when applied to a liquid crystal display, the alignment state of the liquid crystalline polymer cannot be maintained depending on the use environment of the liquid crystal display, and the optical compensation performance may be lost. is there. If the liquid crystal expression temperature is too high, deformation or alteration may occur depending on the material of the substrate film, which may significantly reduce the value of the optical compensation film. Therefore, the resin contained in the resin solution is particularly preferably an aromatic polyamide. A polyamide resin having an aromatic ring group is a resin exhibiting high optical anisotropy, and has excellent optical compensation performance including front retardation. Moreover, compared with general purpose resin, it has the big characteristics that melting | fusing point and glass transition temperature are high and it is excellent in heat resistance. Since the aromatic polyamide resin has an aromatic ring and an amide bond, it is excellent in rigidity, toughness and chemical resistance, and exhibits high adhesiveness. These resin properties are particularly advantageous in optical compensation films. When an optical compensation film using the aromatic polyamide resin is incorporated into a liquid crystal display device, stable optical compensation performance is exhibited and a display image can be maintained at a high quality. In particular, the retardation value is difficult to change even when exposed to a high temperature by backlight light in the panel. Further, since the optical anisotropic layer is rigid and tough, the optical anisotropic layer is difficult to peel from the base film, and the optical anisotropic layer is not easily chipped. For this reason, the value of an optical compensation film can be raised.

  The solvent contained in the resin solution is not particularly limited. When water is used as a solvent, the cost is reduced and the occupational health and workability are also improved as compared with the case where an organic solvent is used. Further, the resin solution can be easily prepared, and the hygiene and maintenance are particularly improved, so that the productivity of the optical compensation film is remarkably increased. Furthermore, by using water instead of an organic solvent as the main solvent, the residual amount of the organic solvent can be reduced in the coating film in which water is volatilized after coating the resin solution, and the commercial value of the resulting optical compensation film is increased. can do. However, the resin solution may contain an organic solvent in order to improve the solubility or dispersibility of the resin and improve the wettability to the base film.

  The viscosity at the time of application of the resin solution (coating viscosity) is important for ensuring the fluidity of the resin solution. In addition, the coating viscosity of the resin solution is such that the resin molecules effectively respond to the orientation regulating force by the fine grooves provided in the arbitrary direction on the surface of the base film, and the molecules are oriented along the fine grooves. Is important above. Therefore, the coating viscosity of the resin solution is very important for controlling the optical axis of the optical compensation film. In order to effectively control the optical axis, the coating viscosity of the resin solution is 500 mPa · s or less. Moreover, it is preferable that the viscosity at 20 degreeC of the said resin solution is 500 mPa * s or less. The coating viscosity of the resin solution is preferably 2 mPa · s or more, and preferably 100 mPa · s or less. The viscosity of the resin solution at 20 ° C. is preferably 2 mPa · s or more, and preferably 100 mPa · s or less. When the viscosity at the time of coating of the resin solution is 2 mPa · s or more and 100 mPa · s or less, the fluidity of the resin solution after being coated on the base film is increased, and the resin solution with respect to the base film is increased. The wettability becomes even higher. For this reason, the control of the molecular orientation of the resin by the fine grooves provided on the surface of the base film becomes easy. When the viscosity of the resin solution is too high, the fluidity of the resin molecules is insufficient. Furthermore, if the viscosity of the resin solution is too high, a resin that undergoes molecular orientation in response to shear stress during coating, such as a lyotropic liquid crystal, is oriented by the coating shear force rather than the orientation regulating force of the base film. When the regulation becomes dominant, the optical axis control becomes difficult, and the optical compensation performance is impaired.

  The solid content concentration of the resin solution affects the viscosity of the resin solution. When the solid content concentration of the resin solution is high, the viscosity of the resin solution is high, and when the solid content concentration of the resin solution is low, the viscosity of the resin solution is low. Therefore, the solid content concentration of the resin solution is important. The solid concentration of the resin solution is preferably 1 to 20% by weight. The solid content concentration of the resin solution is more preferably 3% by weight or more, and more preferably 10% by weight or less. When the solid content concentration is not less than the above lower limit and not more than the above upper limit, the viscosity of the resin solution becomes more appropriate, and an optical compensation film having more desirable optical anisotropy can be obtained.

  The temperature at which the resin solution is applied (coating temperature) affects the viscosity of the resin solution, and thus is important together with the solid content concentration of the resin solution. The resin solution is applied in a state where the viscosity is 500 mPa · s or less. The application temperature of the resin solution is appropriately adjusted so that the viscosity of the resin solution is 500 mPa · s or less. When the temperature of the resin solution is high, the viscosity of the resin solution is lowered, the fluidity of the resin solution coated on the base film is increased, and the effect of the orientation regulating force due to the grooves of the base film is increased. The application temperature of the resin solution is not particularly limited as long as it adjusts the viscosity at the time of application of the resin solution and does not impair the applicability of the resin solution to the base film. The coating temperature of the resin solution is preferably lower than the boiling point of the solvent used for the resin solution and higher than the working environment temperature at the time of coating. The coating temperature of the resin solution is preferably 15 to 95 ° C. The coating temperature of the resin solution is more preferably 20 ° C. or higher, more preferably 80 ° C. or lower. When the solvent of the resin solution is water, it is particularly preferable that the coating temperature of the resin solution is within the above range.

  The viscosity of the resin solution can be adjusted by using an additive. Specifically, the viscosity of the resin solution can be lowered by using, as an additive, a surfactant having both a hydrophilic functional group and a hydrophobic functional group in the molecular structure. Moreover, the wettability of the said resin solution can also be improved by use of surfactant. As the surfactant, various surfactants such as anionic, cationic, amphoteric and nonionic can be used. Nonionic surfactants are preferred because problems such as poor coating due to foaming are relatively unlikely to occur. The content of the surfactant in the resin solution is appropriately adjusted within a range not deteriorating the effect of the present invention. In 100% by weight of the resin solution, the content of the surfactant is preferably 0.01 to 0.1% by weight.

  In the resin solution, an antistatic agent, an antioxidant, an inorganic lubricant, an organic lubricant, an emulsifier, a pH adjuster, an ultraviolet absorber, an antifoaming agent, a facial dye, and a crystal nucleating agent are provided as long as the effects of the present invention are not reduced. Various additives such as these may be blended.

(Base film)
The base film is preferably optically transparent and has little residual retardation. Examples of the material for the base film include acrylic, polyester, polypropylene, triacetyl cellulose, cycloolefin, polycarbonate, polysulfone, polyarylate, and glass.

  The average thickness of the base film is not particularly limited. In consideration of the weight reduction of a member that is important when laminated on a liquid crystal display device so that the predetermined optical compensation performance is not impaired and has a certain mechanical strength, the above base film The thickness of is appropriately set. The average thickness of the substrate film is preferably 20 to 200 μm. The average thickness of the substrate film is more preferably 40 μm or more, and more preferably 100 μm or less.

  Fine grooves are provided on the surface of the base film. For the resin molecules arranged on the surface of the base film provided with the groove, the groove exerts an alignment regulating force and becomes a molecular alignment starting point. Therefore, the molecular orientation of the optically anisotropic layer can be controlled in any direction by shaping the fine grooves in any direction. By controlling the direction in which the groove extends, the molecular orientation of the optical anisotropic layer can be controlled including the direction inclined from the longitudinal direction, without being limited to the longitudinal direction of the film or the direction orthogonal to the longitudinal direction. . For this reason, various optical axes can be provided to the optical compensation film.

  In order for the groove to exhibit a certain alignment regulating effect, the width and depth of the groove are important. Further, depending on the width and depth of the groove, the transparency of the optical compensation film is impaired mainly by light scattering at the interface between the base film and the optical anisotropic layer. For this reason, it is preferable that the width and depth of the groove are small as long as the object of the present invention is not impaired. The width and depth of the groove are 5.0 μm or less, and more preferably 1.0 μm or less.

  It is preferable that the groove | channel provided in the surface of the said base film is formed by grind | polishing with the abrasive | polishing material which is particle | grains. It is preferable to form grooves on the surface of the base film by polishing the surface of the base film with an abrasive that is particles. The abrasive that is the particles is preferably at least one selected from the group consisting of metal particles, metal oxide particles, metal carbide particles, and carbon particles. Specific examples of the abrasive include aluminum oxide particles, chromium oxide particles, silicon carbide particles, and diamond particles.

  For the polishing, it is preferable to use a tape having an abrasive on the surface (hereinafter also referred to as an abrasive tape). For example, by applying a slurry in which the abrasive is dispersed in a binder resin on a substrate, a polishing tape having a polishing layer supported on the substrate can be obtained. The method for producing the polishing tape is specifically described in, for example, JP-A-07-1000076. In addition, you may use the said polishing tape, adjusting a dimension by slit process etc. according to a utilization form.

  Examples of the material of the base material used for the polishing tape include polyester, nylon, polyolefin, and acrylic. As the base material, a foam molded body, a woven fabric, a nonwoven fabric, and a composite thereof may be used.

  The average particle diameter of the abrasive that is the particles is preferably 0.2 to 3 μm. The average particle diameter of the abrasive is more preferably 0.5 μm or more, and more preferably 2 μm or less. The particle diameter indicates a diameter when the abrasive is a true sphere, and indicates a maximum diameter when the abrasive is a shape other than a true sphere. When the average particle size of the abrasive is equal to or more than the lower limit, contact friction does not become excessive when the surface of the base film is polished, and it is difficult for the base film to be conveyed during polishing. When the average particle diameter of the abrasive is not more than the above upper limit, the width and depth of the groove do not become too large, and the transparency of the optical compensation film can be further enhanced.

  In general, in order to apply a liquid crystal material on a substrate film and align liquid crystal molecules, a substrate film having an alignment film is usually used. The optical axis determined by the alignment direction is controlled by aligning liquid crystal molecules in a specific direction by the alignment film using the substrate film having the alignment film. However, in this case, it is necessary to form an alignment film, which is not economical.

  Further, when forming the alignment film, an undercoat layer made of polyimide or polyvinyl alcohol is formed on the surface of the base film, and a buffing roll in which fiber bundles are radially attached to the undercoat layer is brought into contact with the surface of the base material. A method of polishing is performed. This polishing method is also called buffing. Thus, fine grooves are formed along the longitudinal direction of the base film, that is, the conveying direction. This groove serves as an alignment starting point for liquid crystal molecules. The surface of the base film may be directly buffed. However, when such buffing is performed, fiber fragments derived from defects in the buffed fiber bundle often remain on the surface of the base film after the processing. The fiber fragments become foreign matters in the optical compensation film, and cause optical defects in the obtained optical compensation film. For this reason, when a buff process is performed, the product value of an optical compensation film will fall. Moreover, in order to eliminate the said optical fault, it is necessary to provide the process of wash | cleaning the surface of base films, such as water washing, and productivity falls. Furthermore, since the fiber bundle has a roll shape, grooves are formed only in a direction substantially parallel to the transport direction of the base film, and the direction inclined with respect to the longitudinal direction of the base film, or the longitudinal direction, and It is impossible to continuously form grooves so that the grooves extend in a direction inclined from the short direction. Therefore, it is preferable that the base film is not polished by the buffing roll to which the fiber bundle is attached.

  On the other hand, when the surface of the substrate film is polished with the polishing tape, the portion of the polishing tape that contacts the surface of the substrate film is substantially spherical and uniform. For this reason, if it grind | polishes using the said polishing tape, a very uniform and fine groove | channel can be formed. Therefore, the optical compensation performance of the obtained optical compensation film can be enhanced even when a base film having no alignment film is used or a base film that is not rubbed is used. Furthermore, by using a composite carrier substrate in which a resin film and a foam molded body, a resin film and a woven fabric, or a resin film and a nonwoven fabric are combined, a foam structure or a fine fiber bundle structure becomes a pocket, and Polishing debris such as resin pieces generated when the surface of the material film is polished is taken in. For this reason, the generation | occurrence | production prevention performance of the optical defect which cannot be obtained by the said rubbing process is fully acquired, and the commercial value as an optical compensation film can further be raised.

  The plurality of grooves provided on the surface of the base film are preferably arranged in a certain direction, and preferably arranged in parallel in the certain direction. The plurality of grooves are preferably arranged substantially parallel to each other. The optical compensation film has a longitudinal direction (length direction) and a lateral direction (width direction), and the plurality of grooves are preferably parallel or inclined with respect to the longitudinal direction of the film, It is preferable to be inclined with respect to the longitudinal direction, and it is preferable to be inclined with respect to the longitudinal direction and the lateral direction. The direction in which each of the plurality of grooves extends (longitudinal direction of the groove) is preferably parallel to or inclined with respect to the longitudinal direction of the film, and is preferably inclined with respect to the longitudinal direction. It is preferable to incline with respect to the short direction. If the groove that is the starting point of orientation is tilted with respect to the longitudinal direction of the film, that is, if the groove is shaped obliquely with respect to the longitudinal direction of the film, it is formed on the surface of the base film by coating. The optical axis of the optically anisotropic layer can be inclined with respect to the film longitudinal direction. Therefore, when the optical compensation film according to the present invention is used as, for example, an original film of a retardation plate, the optical film may be laminated on the original film of a polarizing plate so that the longitudinal direction of the film coincides. A laminated structure arranged so that both optical axes intersect can be easily obtained. Therefore, for example, when obtaining a wavelength conversion element or a viewing angle improvement element of a liquid crystal display device, the number of steps and cost can be reduced, and the optical characteristics of the wavelength conversion element or the viewing angle improvement element can be improved.

  The method of forming a plurality of grooves on the surface of the base film with the abrasive is not particularly limited. In particular, it is important to form fine grooves in parallel and uniformly in a direction inclined with respect to the longitudinal direction or the short direction of the base film. As a specific method for forming the groove, for example, the above-mentioned base is obtained by bringing the polishing tape into line contact while applying a certain pressure to the surface of the base film in a direction perpendicular to the transport direction of the base film to be transported. The method of forming the groove | channel inclined in the film conveyance direction, ie, a longitudinal direction, on the material film surface is mentioned. In that case, it is preferable to hold | maintain a base film with the support roll formed with the raw material which has fixed elasticity, such as rubber | gum, in the contact part of a base film and an abrasive tape. When polishing with the above-mentioned abrasive tape, in order to prevent the conveyance state of the base film from becoming unstable due to contact friction, the tension is as high as possible without causing any trouble in film conveyance. It is preferable to hold a base film with a roll at a wrap angle.

  For example, the polishing tape is brought into contact with the base film while running in a direction orthogonal to the transport direction of the base film. Thereby, the surface of a base film is grind | polished. In that case, the conveyance method of a polishing tape and the contact method to a base film are important. As a method for conveying the polishing tape, for example, a method for supporting and conveying the polishing tape on the belt surface of the conveyor unit including an endless belt formed of a material having a certain elasticity such as rubber, and a smooth support roll having a small diameter are provided. And a method of supporting and transporting the polishing tape with a plurality of roll conveyor units. Further, as a method of bringing the polishing tape into contact with the surface of the base film, the surface of the polishing tape is brought to the surface of the base film while conveying the polishing tape while applying a certain pressure to the entire conveyor device and the roll unit. Without contacting the polishing tape with the transport contact device, the polishing tape is applied to the surface of the base film by applying high-pressure air from the back of the polishing tape to the contact surface of the base film. The method of making a pressure contact etc. can be illustrated.

  The direction in which the groove is formed is determined by the ratio of the transport speed of the base film and the transport speed of the polishing tape. That is, when the base film transport speed is faster than the polishing tape transport speed, the polishing direction, that is, the groove forming direction, is controlled within an angle range of 0 to 45 ° with respect to the base film transport direction. On the other hand, when the polishing tape transport speed is faster than the base film transport speed, the groove forming direction is controlled in the range of 45 to 90 ° with respect to the base film transport direction. If the conveyance speeds of the base film and the polishing tape are the same, the groove forming direction is 45 ° with respect to the base film transport direction. The direction of groove formation by polishing is not particularly limited, and can be appropriately selected according to the optical characteristics of the polarizing plate and the liquid crystal display device to be compensated. In view of the working efficiency and product yield in the bonding process of the polarizing plate, the groove forming direction, that is, the longitudinal direction of the groove is inclined by 40 to 50 ° with respect to the longitudinal direction or the short direction of the base film. It is preferable. Therefore, the conveyance speed ratio between the base film and the polishing tape is preferably in the range of 0.84 to 1.20.

  The conveyance speed of the base film and the polishing tape is important because it affects the contact load with the polishing tape when the groove is formed. In particular, if the transport speed is too high, the contact load between the base film and the polishing tape becomes large, which may hinder the transport of the base film. Therefore, it is preferable that the conveyance speeds of the base film and the polishing tape are 50 m / min or less, respectively.

  The contact load of the polishing tape on the base film is important because it affects the groove formation density and the transport state of the base film. The contact of the polishing tape with the base film is performed by the method described above. At that time, the contact pressure of the polishing tape is preferably adjusted, and the contact pressure is preferably 0.2 to 0.8 MPa. When the contact pressure is 0.2 MPa or more, the contact of the polishing tape with the substrate film does not become too loose, and the grooves can be formed more uniformly. When the contact pressure is 0.8 MPa or less, the dynamic friction between the base film and the polishing tape does not become too large, and it is difficult for the base film to be transported.

  In order to further enhance the optical compensation performance of the optical compensation film, the base film may have an orientation film on the surface, and grooves may be formed on the surface of the orientation film of the base film. The alignment film is formed by undercoating a resin to be an alignment film on the surface of the base film. Examples of the resin that becomes the alignment film include polyimide and polyvinyl alcohol.

  Before and after the polishing treatment, the substrate film may be subjected to surface activation treatment such as corona treatment, plasma treatment, ultraviolet irradiation or various chemical treatments. Further, by performing various functional coatings or laminations by coating or vapor deposition, various performances can be added to the base film, and the utility value of the base film can be further improved.

  The above-mentioned base film may contain conventionally known additives such as an antioxidant, an ultraviolet absorber, a lubricant, an antistatic agent, a flame retardant aid, and a plasticizer, as long as the object of the present invention is not impaired. May be included.

(Optical anisotropic layer and optical anisotropic layer forming method)
The method for applying the resin solution on the base film is not particularly limited. As the coating method, various coating methods capable of forming an optically transparent and homogeneous film are appropriately used. Examples of the coating method include die coating method, bar coating method, roll coating method, knife coating method, gravure coating method, micro gravure coating method, offset gravure coating method, lip coating method, dipping method, spray coating method and spin coating method. Examples thereof include a coating method. One of these coating methods may be used, or two or more methods may be used.

  After coating the resin solution on the base film, the optical anisotropic layer can be formed by drying and removing water in the coating film. It is preferable that a drying temperature is below the glass transition temperature of the said base film. The drying temperature is preferably not higher than the boiling point of the solvent in the resin solution. When the solvent in the resin solution is water, the drying temperature is preferably not higher than the boiling point of water. It is preferable to dry so as not to break the orientation of the liquid crystal resin molecules after coating. The drying temperature is preferably 10 to 100 ° C. The drying temperature is more preferably 20 ° C or higher, more preferably 60 ° C or lower.

  In the case of drying by applying hot air or the like to the coating film, the wind pressure is not disturbed by the mechanical load on the undried coating film, and the thermal load on the base film and coating film is not disturbed. It is set appropriately so as not to become too large. The wind pressure is preferably 0.1 to 1.0 MPa. The wind pressure is preferably 0.3 MPa or more, and preferably 0.8 MPa or less.

  The drying time is preferably 5 seconds to 1 hour. The drying temperature is more preferably 10 seconds or more, further preferably 20 seconds or more, more preferably 30 minutes or less, and even more preferably 10 minutes or less. If the drying time is too short, the solvent becomes insufficiently volatilized and the coating film becomes brittle. If the drying time is too long, the orientation of the liquid crystal resin molecules constituting the optical anisotropic layer is relaxed, and the optical compensation performance tends to be lowered.

  The thickness of the optical anisotropic layer is not particularly limited. It is determined according to the optical compensation performance and thickness required for the optical compensation film. The optical anisotropic layer preferably has an average thickness of 0.2 to 10 μm. The average thickness of the optically anisotropic layer is more preferably 0.5 μm or more, and more preferably 5 μm or less.

  The method for applying the resin solution on the base film is not particularly limited. As the coating method, various coating methods capable of forming an optically transparent and homogeneous film are appropriately used. Examples of the coating method include die coating method, bar coating method, roll coating method, knife coating method, gravure coating method, micro gravure coating method, offset gravure coating method, lip coating method, dipping method, spray coating method and spin coating method. Examples thereof include a coating method. One of these coating methods may be used, or two or more methods may be used.

  The coating speed when the resin solution is applied on the surface of the base film is preferably 1-1000 m / min. The coating speed is more preferably 5 m / min or more, and more preferably 30 m / min or less. Resin having lyotropic liquid crystallinity is molecularly oriented by the coating shear force, so if the coating speed is too fast, the resin molecules will be oriented in preference to the coating direction and are provided on the surface of the base film. It becomes difficult to control the orientation by the groove.

(Optical compensation film)
The optical compensation film according to the present invention has a longitudinal direction and a transverse direction, and the optical axis is preferably parallel or inclined with respect to the longitudinal direction, and is inclined with respect to the longitudinal direction. It is preferable to incline with respect to the longitudinal direction and the lateral direction. The optical axis of the optical compensation film can be appropriately selected according to the optical characteristics of the polarizing plate to be compensated and the liquid crystal display device. In view of work efficiency and product yield in the polarizing plate laminating step, the optical axis of the optical compensation film is preferably inclined by 40 to 50 ° with respect to the longitudinal or lateral direction of the film. For example, when the optical compensation film according to the present invention is used as an original film of a retardation plate, both optical films are laminated on the original film of a polarizing plate so that the longitudinal directions of the films coincide with each other. It is possible to easily obtain a laminated structure arranged so that the optical axes of the two intersect. Therefore, for example, when obtaining a wavelength conversion element or a viewing angle improvement element of a liquid crystal display device, the number of steps and cost can be reduced, and the optical characteristics of the wavelength conversion element or the viewing angle improvement element can be improved.

  In the optical compensation film according to the present invention, the optical axis variation accuracy with respect to the main optical axis direction of the film is preferably within 0.5 °. For example, when the optical compensation film according to the present invention is used as an original film of a retardation plate, both optical films are laminated on the original film of a polarizing plate so that the longitudinal directions of the films coincide with each other. It is possible to easily obtain a laminated structure arranged so that the optical axes of the two intersect. Therefore, for example, when obtaining a wavelength conversion element or a viewing angle improvement element of a liquid crystal display device, the optical characteristics can be improved. If the variation accuracy of the optical axis exceeds 0.5 °, display unevenness may occur when each optical axis deviates from a desired angle when it is bonded to a polarizing plate and incorporated in a liquid crystal display device. The display image quality is lowered, and the commercial value as an optical compensation film is lowered.

  The optical compensation film according to the present invention preferably has a front retardation R0 (nm) defined by the following formula (1) of 50 to 500 nm.

R0 (nm) = | nx−ny | × d (1)
In the above formula (1), nx represents the maximum refractive index in the optical compensation film plane, ny represents the refractive index in the direction orthogonal to the nx direction in the optical compensation film plane, and d represents the average thickness ( nm).

  When the front retardation R0 is 50 to 500 nm, when the optical compensation film is incorporated into a liquid crystal display device, the display image can be made high quality. When the front retardation R0 is out of the range of 50 to 500 nm, birefringence when passing through the liquid crystal cannot be compensated, and the commercial value as an optical compensation film is lowered.

  In the optical compensation film according to the present invention, the Nz coefficient defined by the following formula (2) is preferably 0.0 to 5.0.

Nz coefficient = (nx−nz) / (nx−ny) (2)
In the above formula (2), nx represents the maximum refractive index in the optical compensation film surface, ny represents the refractive index in the direction orthogonal to the nx direction in the optical compensation film surface, and nz is orthogonal to the nx direction and the ny direction. Refractive index in the direction of

  When the Nz coefficient is 0.0 to 5.0, when the optical compensation film is incorporated in the liquid crystal display device, the viewing angle of the liquid crystal display device can be widened and the contrast can be increased. Therefore, the display image of the liquid crystal display device can be improved.

  The haze value of the optical compensation film is preferably 5% or less, more preferably 3% or less, and particularly preferably 2% or less. As the haze value is lower, light leakage or the like is less likely to occur when the optical compensation film is used for a polarizing plate protective film or the like.

  It is also possible to further enhance the film strength or appearance of the optically anisotropic layer by immersing the optical compensation film in various treatment liquids and performing chemical treatment. The surface of the optical compensation film may be subjected to surface activation treatment such as corona treatment, plasma treatment, ultraviolet irradiation and various chemical treatments. By performing various functional coatings or laminations by coating or vapor deposition on the surface of the optical compensation film, various performances can be added to the optical compensation film, and the utility value of the optical compensation film can be further improved.

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to these examples.

(Preparation example 1 of base film)
A polyethylene terephthalate resin (melting point: 259 ° C., glass transition temperature: 69 ° C., manufactured by Unitika Ltd., hereinafter sometimes referred to as PET) was prepared. This polyethylene terephthalate resin was supplied to a uniaxial melt extrusion molding apparatus at 280 ° C., melt-kneaded, and melt-extruded into a film form from a T die attached to the tip of the extrusion apparatus. The melt-extruded film was brought into close contact with a rotating drum at a surface temperature of 20 ° C. and a speed of 20 m / min by a pinning wire method and quenched. The obtained resin sheet was supported at a wrap angle of 180 degrees with respect to a 180 mm diameter urethane rubber roll having a durometer hardness of 90 A measured in accordance with JIS K6253. On the other hand, a roll of 100 mm wide abrasive tape (abrasive material average particle diameter: 1 μm, manufactured by Nihon Micro Coating Co., Ltd.) carrying an abrasive that is aluminum oxide particles is continuously fed out, and the resin sheet is moved in the running direction. The tape conveyance line was arrange | positioned so that it might convey in the orthogonal direction and might be wound up by the winding core at roll shape. Furthermore, the polishing tape is supported on the belt surface of a conveyor device equipped with a urethane rubber belt conveyance mechanism having a hardness of 90A and a high-pressure cylinder mechanism in the middle of the polishing tape conveyance line, and the polishing tape is applied at a conveyance speed of 20 m / min. While transporting, the conveyor device unit was moved by the cylinder to the surface of the resin sheet supported and transported by the rubber roll, whereby the surface of the polishing tape was brought into pressure contact with a load of 0.2 MPa to polish the surface of the resin sheet. On the surface of the resin sheet after polishing, a 25 μm-thick biaxially stretched PET film (manufactured by Mitsubishi Chemical Polyester Film Co., Ltd.) is laminated as a sandwich paper for preventing blocking, and rolled up into a roll shape. The width is 650 mm and the average thickness is 100 μm. A base film (A) (non-oriented PET film) was prepared.

(Production Example 2 of base film)
The polyethylene terephthalate resin was changed to a norbornene-based resin (trade name “ZEONOR 1600”, glass transition temperature: 168 ° C., manufactured by Nippon Zeon Co., Ltd., hereinafter sometimes referred to as COP), and the extrusion temperature was changed from 280 ° C. to 300 ° C. A substrate film (B) (non-oriented COP film) having a width of 650 mm and an average thickness of 80 μm was produced in the same manner as in Production Example 1 except that the temperature was changed to ° C.

(Production Example 3 of Base Film)
A substrate film (C) (non-oriented PET film) having a width of 650 mm and an average thickness of 100 μm was produced in the same manner as in Production Example 1 except that the polishing treatment was not performed.

(Production Example 4 of Base Film)
After buffing the surface of the base film (C) obtained in Production Example 3 using a nylon 6 felt, the treated surface was washed with shower water, and residual moisture on the surface was removed with compressed air. A base film (D) (non-oriented PET film) was produced.

Example 1
An aromatic polyamide resin having a lyotropic liquid crystallinity (polycondensate of 50 mol% of a terephthalate component and 50 mol% of a disulfonylbenzidine component) is added to ion-exchanged water to obtain a resin solution having a solid content concentration of 5 wt%. It was.

The substrate film (A) was corona-treated at an output of ² kW / m ² while being continuously unwound by roll conveyance at a constant speed of 20 m / min. Thereafter, using the slot die coater whose flow rate was adjusted to 150 g / min, the resin solution was applied at 20 ° C. on the surface of the base film to form a coating film. Thereafter, the base film on which the coating film was formed was immediately introduced into a heating furnace, and the surface of the coating film was subjected to a drying treatment for 20 seconds with hot air compressed at a temperature of 50 ° C. and a wind pressure of 0.5 Mpa. After cooling to room temperature, the film was wound into a roll around a winding core at a winding tension of 100 N / m to obtain an optical compensation film.

(Examples 2 to 8)
Except for changing the type of base film, the average particle diameter of abrasive particles, the conveying speed of the polishing tape, the solid content concentration of the resin solution, and the viscosity of the resin solution as shown in Table 1 below. An optical compensation film was obtained in the same manner as in Example 1.

(Comparative Example 1)
An optical compensation film was obtained in the same manner as in Example 1 except that the solid content concentration of the resin solution was changed as shown in Table 1 below, and the discharge amount of the resin solution was changed to 60 g / min.

(Comparative Example 2)
An optical compensation film was obtained in the same manner as in Example 1 except that the base film (A) was changed to the base film (C).

(Comparative Example 3)
An optical compensation film was obtained in the same manner as in Example 1 except that the base film (A) was changed to the base film (D).

(Evaluation)
(1) Solution viscosity The temperature of the resin solution is kept at 20 ° C., which is the application temperature of the resin solution, and a B-type viscometer (manufactured by Toki Sangyo Co., Ltd., model number “BLII”) is used according to JIS K7117. The viscosity of the resin solution was measured.

(2) Width and depth of grooves formed on the surface of the base film The surface of the base film was observed using an atomic force microscope (manufactured by Keyence Corporation, model number “VN-8000”). From the film cross section of the obtained three-dimensional enlarged image, the width of 10 grooves formed on the base film was measured, and the obtained numerical values were averaged to obtain the groove width. Further, the center line average surface roughness Ra was measured and set as the groove depth.

(3) Optical axis of optical compensation film With respect to the film width, a strip-shaped film piece was sampled with a longitudinal direction of 50 mm and a full width in the width direction. Using an automatic birefringence measuring apparatus (manufactured by Otsuka Electronics Co., Ltd., model number “RETS”), the film pieces were measured at intervals of 25 mm in the width direction, and the average value of the absolute values of the orientation angle measured values at each position was taken as the optical axis. . The optical axis in the film width direction was based on the longitudinal direction.

(4) Front retardation value R0 of optical compensation film
Using an automatic birefringence measuring device (manufactured by Oji Scientific Instruments, model number “KOBRA-WR”), the wavelength of the measuring light is set to 550 nm, the axis orthogonal to the longitudinal direction of the optical compensation film is used as a reference axis, and the optical compensation film is Measurement was made at intervals of 50 mm in the width direction, and the average value was calculated as the front retardation value R0 of the optical compensation film.

(5) Haze of optical compensation film Haze meter (manufactured by Tokyo Denshoku Co., Ltd., model number “TC-H3DPK”) was used to measure the optical compensation film at intervals of 50 mm in the width direction, and calculate the average value. It was set as the haze of the compensation film.

(6) Appearance of optical compensation film The obtained optical compensation film was sandwiched between polarizing plates arranged in crossed Nicols and observed visually, and the appearance of the optical compensation film was evaluated according to the following criteria.

[Appearance of optical compensation film]
○: Color unevenness and light leakage of any shape of dot shape, line shape, and planar shape were not recognized, and the appearance was homogeneous. ×: At least within point shape, line shape or surface color unevenness and light leakage. One was confirmed and had a partially heterogeneous appearance.

  The results are shown in Table 1 below.

DESCRIPTION OF SYMBOLS 1 ... Optical compensation film 2 ... Base film 2a ... 1st surface 2b ... 2nd surface 3 ... Optical anisotropic layer

Claims (6)

A base film;
An optical anisotropic layer laminated on at least one surface of the base film,
A plurality of grooves having a width of 5 μm or less and a depth of 5 μm or less are provided on the surface of the base film on which the optical anisotropic layer is laminated,
An optical compensation film, wherein the optically anisotropic layer is formed by applying a resin solution having a viscosity of 500 mPa · s or less. Having a longitudinal direction and a transverse direction,
The optical compensation film according to claim 1, wherein the optical axis is inclined with respect to the longitudinal direction.   The optical compensation film according to claim 1, wherein the resin solution contains a resin having lyotropic liquid crystallinity. The groove is formed by polishing the surface of the base film with an abrasive that is a particle,
The abrasive | polishing material which is the said particle | grain is at least 1 sort (s) selected from the group which consists of a metal particle, a metal oxide particle, a metal carbide particle, and a carbon particle. Optical compensation film. Forming a groove having a width of 5 μm or less and a depth of 5 μm or less on at least one surface of the base film;
Applying a resin solution having a viscosity of 500 mPa · s or less to the surface of the base film on which the grooves are formed to form an optically anisotropic layer. Forming the groove by polishing the surface of the base film with an abrasive that is particles,
The method for producing an optical compensation film according to claim 5, wherein at least one selected from the group consisting of metal particles, metal oxide particles, metal carbide particles, and carbon particles is used as the abrasive that is the particles.

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