Light diffusion film, surface illuminant device and liquid crystal display device

Abstract

A transmissive display apparatus 21 comprises a liquid crystal display unit 22 and a plane light source unit 23. The unit 23 comprises a tubular light source 24, a light guide 25 having a wedge-shaped reflecting groove formed at the bottom thereof, and a light-diffusing film 27 having anisotropy and/or ultraviolet (UV) absorbability. In the film, a light-scattering characteristic F(θ) representing the relationship between the light-scattering angle θ and a scattered light intensity F fulfills Fy(θ)/Fx(θ)≧1.01 over a range of θ=4 to 30°, wherein Fx(θ) and Fy(θ) represent the light-scattering characteristics in the X-axial direction and the Y-axial direction of the film, respectively. The film comprises a light-diffusing layer composed of a plurality of resins which are different from each other in refractive index, and a transparent layer laminated on at least one side thereof. The transparent layer at least may contain a UV absorber. Such a light-diffusing film ensures simplification of structures of a plane light source device and a liquid crystal display apparatus. When the film has anisotropy, the luminance in the display surface can be uniformized. A UV absorbable light-diffusing film absorbs UV from a light source (fluorescent tube) of the plane light source device (backlight), and can prevent deterioration of a prism sheet and a liquid crystal display cell.

Dependencies are inferred from the claim text.