Patent ID: 7936422

Claim:
An optical element comprising: a first transparent substrate; a second transparent substrate arranged opposite to said first transparent substrate; a liquid crystal layer arranged between said first transparent substrate and said second transparent substrate; a first transparent electrode and a first alignment layer which are arranged between said liquid crystal layer and said first transparent substrate; a second transparent electrode and a second alignment layer which are arranged between said liquid crystal layer and said second transparent substrate; a first polarizing layer arranged on the side of said first transparent substrate, as viewed from said liquid crystal layer; and a second polarizing layer arranged on the side of said second transparent substrate, as viewed from said liquid crystal layer; wherein: absorption axes of said first polarizing layer and said second polarizing layer are intersected to each other at a right angle; said liquid crystal layer is constituted by nematic liquid crystal whose dielectric anisotropy is positive; an alignment axis of said liquid crystal layer is located parallel to, or perpendicular to the absorption axes of said first polarizing layer and said second polarizing layer and are twisted; and a value of “Δnd” of said liquid crystal layer is larger than, or equal to 2000 nm, and smaller than, or equal to 5000 nm, wherein “Δnd” is a refractive index anisotropy of said liquid crystal layer and “d” is a film thickness of said liquid crystal layer.