Optical sheet controlling external light, display device and method for producing optical sheet

Abstract

An optical sheet, which can suitably absorb external light over a wide range and can improve a contrast, a display device, and a method for producing an optical sheet. The optical sheet is disposed on an observer side relative to an image light source and includes a plurality of layers that control light emitted from the image light source to emit the light on the observer side, at least one of the plurality of layers is an optical functional sheet layer which includes prisms being arranged in parallel along the surface of the optical sheet whereby light can be transmitted and wedge portions are being arranged in parallel between the prisms whereby light can be absorbed. At least one of the plurality of layers other than the optical functional sheet layer is a light-absorbing layer.

1 . An optical sheet disposed on an observer side relative to an image light source comprising:
 a plurality of layers that control light emitted from the image light source to emit the light on the observer side,   wherein at least one of the plurality of layers is an optical functional sheet layer, which comprises prisms being arranged in parallel along a surface of the optical sheet whereby light is transmitted and wedge portions being arranged in parallel between the prisms whereby light is absorbed; and at least one of the plurality of layers other than the optical functional sheet layer is a light-absorbing layer capable of absorbing light all over the light-absorbing layer, and is capable of absorbing the part of visible light; the light-absorbing layer and the wedge portions of the optical functional sheet layer absorb a same wavelength of light; and the light-absorbing layer is formed integrally with the wedge portion.   
     
     
         2 . The optical sheet according to  claim 1 , wherein the light-absorbing layer absorbs light having a predetermined wavelength. 
     
     
         3 . The optical sheet according to  claim 1 , wherein the wedge portion is configured to show a light absorption performance having a transmittance of 40-70% when measuring the transmittance of a 6 μm thick optical sheet made only of materials for forming the wedge portion. 
     
     
         4 . The optical sheet according to  claim 1 , wherein in a cross section in a sheet thickness direction, the prism of the optical functional sheet layer has a trapezoidal shape whose short upper base is located at one sheet surface side and long lower base is located at the other sheet surface side, and the wedge portion has a triangular shape whose bottom is located at the one sheet surface side. 
     
     
         5 . The optical sheet according to  claim 1 , wherein in a cross section in a sheet thickness direction, the prism of the optical functional sheet layer has a trapezoidal shape whose short upper base is located at one sheet surface side and long lower base is located at the other sheet surface side, and the wedge portion has a trapezoidal shape whose long lower base is located at the one sheet surface side and short upper base is located at the other sheet surface side. 
     
     
         6 . The optical sheet according to  claim 4 , wherein an oblique line of the trapezoid provided between the upper base and the lower base of the prism has an angle of more than 0° and not more than 10° with respect to a normal line of the sheet surface. 
     
     
         7 . The optical sheet according to  claim 6 , wherein the oblique line comprises a polygonal line or a curved line. 
     
     
         8 . The optical sheet according to  claim 1 , wherein the wedge portion contains light-absorbing particles with an average particle diameter of not less than 1 μm. 
     
     
         9 . The optical sheet according to  claim 1 , wherein a material constituting the prism has: a refractive index of Np; a material constituting the wedge portion has a refractive index of Nb; the Np and Nb have a relation of Np ≧Nb; and the Np and Nb have a value in a range of 1.49 to 1.56. 
     
     
         10 . The optical sheet according to  claim 1 , wherein the prism and the wedge portion of the optical functional sheet layer each have a predetermined cross section and extend in a longitudinal direction and the two optical functional sheet layers are stacked such that the wedge portions of the two optical functional sheet layers are perpendicular to one another in longitudinal directions. 
     
     
         11 . A display device comprising the optical sheet according to  claim 1 . 
     
     
         12 . A method for producing the optical sheet according to  claim 1 , comprising:
 a step of forming the light-absorbing layer by coating,   wherein the step comprises a step of applying a light-absorbable resin to be cured by application of light and a step of irradiating light to the applied light-absorbable resin to cure the light-absorbable resin.   
     
     
         13 . The optical sheet according to  claim 5 , wherein an oblique line of the trapezoid provided between the upper base and the lower base of the prism has an angle of more than 0° and not more than 10° with respect to a normal line of the sheet surface. 
     
     
         14 . The optical sheet according to  claim 13 , wherein the oblique line comprises a polygonal line or a curved line.