Wire-grid polarizer and process for producing the same

Abstract

Provided are a wire-grid polarizer, which has not only a high degree of polarization, a high p-polarized light transmittance and a high s-polarized light reflectance but also a low angle dependency and a low wavelength dependency in terms of optical properties in a visible light region, and a process for producing the same. A wire-grid polarizer 10 comprising a light-transmitting substrate 14 having a plurality of ridges 12 formed in parallel to one another at certain pitches Pp through respective flat portions 13 disposed between adjacent ridges 12 , each of the ridges having a width gradually reduced from a base portion to a top portion thereof, and a metal layer 20 composed of metal or a metal compound, the metal layer covering the entirety of a first lateral face 16 of each ridge 12 and a part of the flat portion 13 adjacent to the first lateral face 16 such that a second lateral face 18 of each ridge 12 is covered with no metal layer or is partially covered with the metal layer; and a process for forming the metal layer 20 by vapor-depositing metal or a metal compound on the first lateral face from a direction that is substantially orthogonal to a longitudinal direction of the ridges 12 and forms an angle of from 25 to 40 degrees toward the first lateral face 16 with respect to a height direction of the ridge 12 under conditions where the metal layer is disposed at a deposition amount of from 40 to 60 nm.

1 . A wire-grid polarizer comprising:
 a light-transmitting substrate having a plurality of ridges formed in parallel to one another at certain pitches through respective flat portions disposed between adjacent ridges, each of the ridges having a width gradually reduced from a base portion to a top portion thereof; and   a metal layer composed of metal or a metal compound, the metal layer covering the entirety of a first lateral face of each ridge and a part of the flat portion adjacent to the first lateral face such that a second lateral face of each ridge is covered with no metal layer or is partially covered with the metal layer.   
     
     
         2 . The wire-grid polarizer according to  claim 1 , wherein the ratio (Hm 1 /Hp) of the height Hm 1  of the metal layer covering the first lateral face of each ridge to the height Hp of the ridge is from 1 to 2. 
     
     
         3 . The wire-grid polarizer according to  claim 1 , wherein each ridge is formed in a triangular or trapezoidal shape in section in a direction orthogonal to a longitudinal direction thereof. 
     
     
         4 . The wire-grid polarizer according to  claim 1 , wherein each ridge is formed in a trapezoidal shape in section in the direction orthogonal to the longitudinal direction: and
 the top portion of the ridge has a width Dtp set to at most half of a width Dbp of the base portion of the ridge.   
     
     
         5 . The wire-grid polarizer according to  claim 1 , wherein each pitch Pp is at most 300 nm. 
     
     
         6 . The wire-grid polarizer according to  claim 1 , wherein the ratio (Dbp/Pp) of the width Dbp of the base portion of the ridge to each pitch Pp is from 0.1 to 0.7. 
     
     
         7 . A process for producing a wire-grid polarizer comprising a light-transmitting substrate having a plurality of ridges formed in parallel to one another at certain pitches through respective flat portions disposed between adjacent ridges, each of the ridges having a width gradually reduced from a base portion to a top portion thereof; and a metal layer composed of metal or a metal compound, the metal layer covering the entirety of a first lateral face of each ridge and a part of the flat portion adjacent to the first lateral face such that a second lateral face of each ridge is covered with no metal layer or is partially covered with the metal layer; the process comprising vapor-depositing the metal or the metal compound on the first lateral face from a direction that is substantially orthogonal to a longitudinal direction of the ridges and forms an angle of from 25 to 40 degrees toward the first lateral face with respect to a height direction of the ridges under conditions where the metal layer is disposed at a deposition amount of from 40 to 60 nm. 
     
     
         8 . The process according to  claim 7 , wherein the ratio (Hm 1 /Hp) of the height Hm 1  of the metal layer covering the first lateral face of each ridge to the height Hp of the ridge is from 1 to 2. 
     
     
         9 . The process according to  claim 7 , wherein each ridge is formed in a triangular or trapezoidal shape in section in a direction orthogonal to a longitudinal direction thereof. 
     
     
         10 . The process according to  claim 7 , wherein each ridge is trapezoidal in section in the direction orthogonal to the longitudinal direction; and
 the top portion of the ridge has a width Dtp set to at most half of the width Dbp of the base portion of the ridge.   
     
     
         11 . The process according to  claim 7 , wherein each ridge is composed of a photocurable resin or a thermoplastic resin and is formed by imprinting technology.