Patent ID: 6659615
Filing Date: 2003-12-09
Classification: G02B,Y10S

Abstract:
A light pipe comprising:a transparent resin plate having an average in-plane retardation of not larger than 20 nm; a transparent film having an average in-plane retardation of not larger than 20 nm; and an adhesive layer having a refractive index different by 0.1 or less from that of said transparent film, wherein said transparent film is bonded to said transparent resin plate through said adhesive layer, and wherein said transparent film includes a repetitive prismatic structure constituted by optical path control slopes which are disposed on an outer surface of said transparent film and which are aligned in a substantially predetermined direction so that each of said optical path control slopes is inclined at an inclination angle in a range of from 35 to 48 degrees with respect to a film plane, wherein a projected area, onto said film plane, of flat surfaces each having an inclination angle of not larger than 5 degrees with respect to said film plane is not smaller than 10 times as large as a projected area, onto said film plane, of slopes each having an inclination angle of not smaller than 35 degrees with respect to said film plane.