Antireflection structure and optical device including the same

Abstract

A diffusing plate has a surface including a plurality of fine concave/convex portions regularly arranged within a cycle equal to or smaller than a predetermined wavelength. The surface has a larger surface roughness than the predetermined wavelength. An average value for an angle between a normal vector of the tangent plane of a roughness shape of the surface and a normal vector of a reference plane of the surface is 5 degrees or more.

1 . An antireflection structure for suppressing reflection of light having a wavelength equal to or larger than a predetermined wavelength, the antireflection structure comprising a surface including a plurality of fine concave/convex portions regularly arranged within a cycle equal to or smaller than the predetermined wavelength,
 wherein the surface has a larger surface roughness than the predetermined wavelength and an average value for an angle between a normal vector of a tangent plane of a roughness shape of the surface and a normal vector of a reference plane of the surface is 5 degrees or more.   
     
     
         2 . The antireflection structure of  claim 1 , wherein the antireflection structure transmits the light of which reflection is suppressed. 
     
     
         3 . The antireflection structure of  claim 1 , wherein the fine concave/convex portions are approximately conical/pyramidal concaves and convexes, or filiform concaves and filiform convexes. 
     
     
         4 . The antireflection structure of  claim 1 , wherein a surface roughness of the surface in terms of a maximum height roughness Rz defined by ISO4287:1997 is larger than the predetermined wavelength. 
     
     
         5 . The antireflection structure of  claim 1 , wherein a surface roughness of the surface in terms of a maximum height roughness Rz defined by ISO4287:1997 is smaller than 100 μm. 
     
     
         6 . The antireflection structure of  claim 1 , wherein a surface roughness of the surface in terms of a maximum height roughness Rz defined by ISO4287:1997 is smaller than 50 μm. 
     
     
         7 . The antireflection structure of  claim 1 , wherein a surface roughness of the surface in terms of a maximum height roughness Rz defined by ISO4287:1997 is smaller than 30 μm. 
     
     
         8 . The antireflection structure of  claim 1 , wherein respective heights of the plurality of fine concave/convex portions from the surface in a normal direction of the reference plane are approximately the same. 
     
     
         9 . The antireflection structure of  claim 1 , wherein the surface is substantially formed of a plane in which an angle between a normal vector of the tangent plane of the roughness shape and a normal vector of a reference plane of the surface is 90 degrees or less. 
     
     
         10 . The antireflection structure of  claim 1 , wherein each of the plurality of fine concave/convex portions is a conical/pyramidal concave or convex and respective center axises of the plurality of fine concave/convex portions are parallel to each other, each of the center axises connecting a center of a base and a top point of each of the concave/convex portions. 
     
     
         11 . The antireflection structure of  claim 1 , wherein each of the plurality of fine concave/convex portions has a height equal to or larger than 0.4 times as large as a wavelength of light of which reflection is suppressed. 
     
     
         12 . An optical device comprising the antireflection structure of  claim 1 . 
     
     
         13 - 24 . (canceled) 
     
     
         25 . An antireflection structure for suppressing reflection of light having a wavelength equal to or larger than a predetermined wavelength, the antireflection structure comprising a surface including a plurality of fine concave/convex portions regularly arranged within a cycle equal to or smaller than the predetermined wavelength,
 wherein the surface has a larger surface roughness than the predetermined wavelength and a percentage of an area per unit area of part in which an angle between a normal vector of a tangent plane of a roughness shape of the surface and a normal vector of a reference plane of the surface is 5 degrees or less is less than 80%.   
     
     
         26 . The antireflection structure of  claim 25 , wherein the antireflection structure transmits the light of which reflection is suppressed. 
     
     
         27 . The antireflection structure of  claim 25 , wherein the fine concave/convex portions are approximately conical/pyramidal concaves and convexes, or filiform concaves and filiform convexes. 
     
     
         28 . The antireflection structure of  claim 25 , wherein a surface roughness of the surface in terms of a maximum height roughness Rz defined by ISO4287:1997 is larger than the predetermined wavelength. 
     
     
         29 . The antireflection structure of  claim 25 , wherein a surface roughness of the surface in terms of a maximum height roughness Rz defined by ISO4287:1997 is smaller than 100 μm. 
     
     
         30 . The antireflection structure of  claim 25 , wherein a surface roughness of the surface in terms of a maximum height roughness Rz defined by ISO4287:1997 is smaller than 50 μm. 
     
     
         31 . The antireflection structure of  claim 25 , wherein a surface roughness of the surface in terms of a maximum height roughness Rz defined by ISO4287:1997 is smaller than 30 μm. 
     
     
         32 . The antireflection structure of  claim 25 , wherein respective heights of the plurality of fine concave/convex portions from the surface in a normal direction of the reference plane are approximately the same. 
     
     
         33 . The antireflection structure of  claim 25 , wherein the surface is substantially formed of a plane in which an angle between a normal vector of the tangent plane of the roughness shape and a normal vector of a reference plane of the surface is 90 degrees or less. 
     
     
         34 . The antireflection structure of  claim 25 , wherein each of the plurality of fine concave/convex portions is a conical/pyramidal concave or convex and respective center axises of the plurality of fine concave/convex portions are parallel to each other, each of the center axises connecting a center of a base and a top point of each of the concave/convex portions. 
     
     
         35 . The antireflection structure of  claim 25 , wherein each of the plurality of fine concave/convex portions has a height equal to or larger than 0.4 times as large as a wavelength of light of which reflection is suppressed. 
     
     
         36 . An optical device comprising the antireflection structure of  claim 25 . 
     
     
         37 - 48 . (canceled)