Patent ID: 6822710
Filing Date: 2004-11-23
Classification: G02F

Abstract:
A backlight device for a liquid crystal display device, comprising:a light source providing light; a light waveguide plate guiding light from the light source, said light waveguide plate having an emitting surface, a front surface and a bottom surface, the emitting surface being adjacent to the light source; a reflector arranged under the bottom surface of the light waveguide plate, reflecting light; and at least one single layer cholesteric liquid crystal (CLC) film arranged on the front surface of the light waveguide plate, selectively collimating light by controlling a helical pitch P of said CLC film according to the equation: &lgr;0=P(no+ne)/2, where &lgr;0 is a wavelength of incident light, P is a helical pitch, no is an ordinary refractive index, and ne is an extraordinary refractive index.