Retardation film and method for producing the same, optical functional film, polarizing film, and display device

Abstract

The main object of the present invention is to provide a highly reliable biaxial retardation film without the problems of peeling off of the retardation layer from the base material or the like generated in the case of forming the retardation layer, capable of enlarging the range of the thickness direction and in-plane direction retardation values to be obtained, easily obtaining optional thickness direction and in-plane direction retardation values even for a small amount, a method for producing the same, an optical functional film using the retardation layer, a polarizing film and a display device. In order to achieve the above-mentioned object, an optically biaxial retardation film, comprising a polymer film containing a material having refractive index anisotropy, wherein the material having refractive index anisotropy has a concentration gradient in a thickness direction of the polymer film, is provided.

1 . A retardation film which is optically biaxial, comprising a polymer film containing a material having refractive index anisotropy, wherein the material having refractive index anisotropy has a concentration gradient in a thickness direction of the polymer film.  
     
     
         2 . The retardation film according to  claim 1 , wherein the polymer film is oriented.  
     
     
         3 . The retardation film according to  claim 1 , which has refractive indices satisfying the condition of nx>ny>nz, wherein nx is a refractive index along a slow axis in plane of the film, ny is a refractive index along a fast axis in plane of the film, and nz is a refractive index along a thickness direction of the film.  
     
     
         4 . The retardation film according to  claim 1 , which has a direction of a principal refractive index inclined with respect to in-plane directions of the film and a thickness direction of the film.  
     
     
         5 . The retardation film according to  claim 1 , wherein the polymer film has regularity in the refractive index.  
     
     
         6 . The retardation film according to  claim 1 , wherein the material having refractive index anisotropy is a material having liquid crystallinity.  
     
     
         7 . The retardation film according to  claim 1 , wherein the molecular structure of the material having refractive index anisotropy is in a shape of a rod.  
     
     
         8 . The retardation film according to  claim 1 , wherein the material having refractive index anisotropy has a polymerizable functional group.  
     
     
         9 . The retardation film according to  claim 1 , wherein the material having refractive index anisotropy comprises a material having a polymerizable functional group and a material having no polymerizable functional group.  
     
     
         10 . The retardation film according to  claim 1 , wherein the concentration gradient of the material having refractive index anisotropy in a thickness direction of the polymer film has high concentration on one surface side of the polymer film and becomes low concentration toward the other surface side.  
     
     
         11 . The retardation film according to  claim 10 , wherein contact angles of the retardation film to pure water are different between one surface and the other surface.  
     
     
         12 . The retardation film according to  claim 1 , wherein the concentration gradient of the material having refractive index anisotropy in a thickness direction of the polymer film has high concentration on both surface sides of the polymer film and becomes low concentration toward a central part.  
     
     
         13 . The retardation film according to  claim 1 , wherein the concentration gradient of the material having refractive index anisotropy in a thickness direction of the polymer film varies continuously.  
     
     
         14 . The retardation film according to  claim 1 , which has a region in which the concentration gradient of the material having refractive index anisotropy is gentle and a region in which the concentration gradient of the material having refractive index anisotropy is steep.  
     
     
         15 . The retardation film according to  claim 1 , which has a region containing no material having refractive index anisotropy.  
     
     
         16 . The retardation film according to  claim 1 , which shows a thickness direction retardation of 100 to 300 nm and a in-plane direction retardation of 10 to 150 nm, wherein the thickness direction retardation is represented by the following Rth, Rth[nm]={(nx+ny)/2−nz}×d, and the in-plane direction retardation is represented by the following Re, 
 Re[nm]=(nx−ny)×d, wherein nx is a refractive index along a slow axis in plane of the film, ny is a refractive index along a fast axis in plane of the film, nz is a refractive index along a thickness direction of the film and d is the thickness of the film.    
     
     
         17 . The retardation film according to  claim 1 , which shows an in-plane direction retardation of 10 to 150 nm and has a haze value of 1% or less measured in accordance with JIS-K7136.  
     
     
         18 . The retardation film according to  claim 1 , wherein the retardation value, in the visible light range, of the retardation film on the shorter wavelength side is larger than that of the longer wavelength side.  
     
     
         19 . The retardation film according to  claim 1 , wherein the retardation value, in the visible light range, of the retardation film on the longer wavelength side is larger than that of the shorter wavelength side.  
     
     
         20 . The retardation film according to  claim 1 , which is capable of being rolled into a cylindrical form having a minimum diameter of 6 inches or less.  
     
     
         21 . The retardation film according to  claim 1 , comprising two or more sheets of the retardation film laminated together.  
     
     
         22 . A retardation film which is optically biaxial, comprising a polymer film infiltrated with a material having refractive index anisotropy.  
     
     
         23 . The retardation film according to  claim 22 , wherein the polymer film is oriented.  
     
     
         24 . The retardation film according to  claim 22 , which has refractive indices satisfying the condition of nx>ny>nz, wherein nx is a refractive index along a slow axis in plane of the film, ny is a refractive index along a fast axis in plane of the film, and nz is a refractive index along a thickness direction of the film.  
     
     
         25 . The retardation film according to  claim 22 , which has a direction of a principal refractive index inclined with respect to in-plane directions of the film and a thickness direction of the film.  
     
     
         26 . The retardation film according to  claim 22 , wherein the polymer film has regularity in the refractive index.  
     
     
         27 . The retardation film according to  claim 22 , wherein the material having refractive index anisotropy is a material having liquid crystallinity.  
     
     
         28 . The retardation film according to  claim 22 , wherein the molecular structure of the material having refractive index anisotropy is in a shape of a rod.  
     
     
         29 . The retardation film according to  claim 22 , wherein the material having refractive index anisotropy has a polymerizable functional group.  
     
     
         30 . The retardation film according to  claim 22 , wherein the material having refractive index anisotropy comprises a material having a polymerizable functional group and a material having no polymerizable functional group.  
     
     
         31 . The retardation film according to  claim 22 , wherein the concentration gradient of the material having refractive index anisotropy in a thickness direction of the polymer film has high concentration on one surface side of the polymer film and becomes low concentration toward the other surface side.  
     
     
         32 . The retardation film according to  claim 31 , wherein contact angles of the retardation film to pure water are different between one surface and the other surface.  
     
     
         33 . The retardation film according to  claim 22 , wherein the concentration gradient of the material having refractive index anisotropy in a thickness direction of the polymer film has high concentration on both surface sides of the polymer film and becomes low concentration toward a central part.  
     
     
         34 . The retardation film according to  claim 22 , wherein the concentration gradient of the material having refractive index anisotropy in a thickness direction of the polymer film varies continuously.  
     
     
         35 . The retardation film according to  claim 22 , which has a region in which the concentration gradient of the material having refractive index anisotropy is gentle and a region in which the concentration gradient of the material having refractive index anisotropy is steep.  
     
     
         36 . The retardation film according to  claim 22 , which has a region containing no material having refractive index anisotropy.  
     
     
         37 . The retardation film according to  claim 22 , which shows a thickness direction retardation of 100 to 300 nm and a in-plane direction retardation of 10 to 150 nm, wherein the thickness direction retardation is represented by the following Rth, 
 Rth[nm]={(nx+ny)/2−nz}×d, and the in-plane direction retardation is represented by the following Re,    Re[nm]=(nx−ny)×d, wherein nx is a refractive index along a slow axis in plane of the film, ny is a refractive index along a fast axis in plane of the film, nz is a refractive index along a thickness direction of the film and d is the thickness of the film.    
     
     
         38 . The retardation film according to  claim 22 , which shows an in-plane direction retardation of 10 to 150 nm and has a haze value of 1% or less measured in accordance with JIS-K7136.  
     
     
         39 . The retardation film according to  claim 22 , wherein the retardation value, in the visible light range, of the retardation film on the shorter wavelength side is larger than that of the longer wavelength side.  
     
     
         40 . The retardation film according to  claim 22 , wherein the retardation value, in the visible light range, of the retardation film on the longer wavelength side is larger than that of the shorter wavelength side.  
     
     
         41 . The retardation film according to  claim 22 , which is capable of being rolled into a cylindrical form having a minimum diameter of 6 inches or less.  
     
     
         42 . The retardation film according to  claim 22 , comprising two or more sheets of the retardation film laminated together.  
     
     
         43 . A retardation film, comprising a polymer film containing a material having refractive index anisotropy, wherein the material having refractive index anisotropy has a concentration gradient in a thickness direction of the polymer film, and the polymer film is oriented.  
     
     
         44 . A retardation film, comprising a polymer film infiltrated with a material having refractive index anisotropy, wherein the polymer film is oriented.  
     
     
         45 . An optical functional film, comprising the retardation film according to  claim 1  directly laminated to an optical functional layer other than a retardation film.  
     
     
         46 . An optical functional film, comprising the retardation film according to  claim 22  directly laminated to an optical functional layer other than a retardation film.  
     
     
         47 . A polarizing film, comprising the retardation film according to  claim 1  directly laminated to a polarizing layer.  
     
     
         48 . A polarizing film, comprising the retardation film according to  claim 22  directly laminated to a polarizing layer.  
     
     
         49 . A display device comprising the retardation film according to  claim 1  disposed in a light path of the display device.  
     
     
         50 . A display device comprising the retardation film according to  claim 22  disposed in a light path of the display device.  
     
     
         51 . A display device comprising the optical functional film according to  claim 45  disposed in a light path of the display device.  
     
     
         52 . A display device comprising the optical functional film according to  claim 46  disposed in a light path of the display device.  
     
     
         53 . A display device comprising the polarizing film according to  claim 47  disposed in a light path of the display device.  
     
     
         54 . A display device comprising the polarizing film according to  claim 48  disposed in a light path of the display device.  
     
     
         55 . A method for producing a retardation film comprising: 
 a coating process of coating a retardation reinforcing region forming coating solution, in which a material having refractive index anisotropy is dissolved or dispersed in a solvent, on at least one surface of a polymer film;    an infiltration process of infiltrating the material having the refractive index anisotropy, in the retardation reinforcing region forming coating solution coated in the coating process, into the polymer film;    a drying process of drying the solvent in the retardation reinforcing region forming coating solution coated in the coating process; and    an orientation process of orienting the polymer film.    
     
     
         56 . The method for producing a retardation film according to  claim 55 , wherein the infiltration process is carried out during the drying process.  
     
     
         57 . The method for producing a retardation film according to  claim 55 , further comprising, as a process after the drying process, a fixing process of fixing the refractive index anisotropic material infiltrated into the polymer film.  
     
     
         58 . The method for producing a retardation film according to  claim 57 , the orientation process of orienting the polymer film is carried out after the fixing process.  
     
     
         59 . The method for producing a retardation film according to  claim 55 , the orientation process of orienting the polymer film is carried out after the drying process.  
     
     
         60 . The method for producing a retardation film according to  claim 59 , further comprising, as a process after the orientation process, a fixing process of fixing the refractive index anisotropic material infiltrated into the polymer film.  
     
     
         61 . The method for producing a retardation film according to  claim 55 , the coating process of coating a retardation reinforcing region forming coating solution is carried out after the orientation process of orienting the polymer film.