Optical sheet for use in an edge light type backlight unit

摘要

A substrate film for an optical sheet is made of a transparent resin and is formed into a rectangular shape. The substrate film for the optical sheet has an optical anisotropy and has an absolute value of the angle of the crystal orientation with respect to the short side orientation which is π/16 or greater and 3π/16 or less.

主权项

1. An edge light type back light for use in a liquid crystal display device in which rays of light are dispersed and lead to a front face side, the edge light type back light comprising:
a rectangular optical waveguide plate; a lamp disposed along an edge of a longer side of the optical waveguide plate and that emits said rays of light; a light diffusion sheet formed into a rectangular shape, provided with the lamp along an edge of a longer side thereof, and overlaid on a surface of the optical waveguide plate; and a prism sheet overlaid on a surface of the light diffusion sheet; and the light diffusion sheet comprising:
a substrate film for the light diffusion sheet which is made of a transparent resin and which is formed into a rectangular shape, the substrate film for the light diffusion sheet having an optical anisotropy, and having an absolute value of the angle of the crystal orientation with respect to a short side orientation being greater than or equal to π/16 and less than or equal to 3π/16; andan optical layer overlaid on one face of the substrate film for the light diffusion sheet and formed by a polymer composition coating; and wherein the transparent resin is polyethylene terephthalate; wherein a retardation value of the substrate film is greater than 680 nm; wherein the optical layer comprises multiple particles of a light diffusing agent, and a binder therefor; wherein an amount of the light diffusing agent, included per 100 parts of substrate polymer in the polymer composition coating, is 10 parts or greater and 200 parts or less as determined on a basis of solid content; and wherein the multiple particles of the light diffusing agent are spherical beads.