| 摘要 |
PROBLEM TO BE SOLVED: To provide a surface light source unit of simple structure that illuminates a display panel of a liquid crystal display device uniformly, even though equipped with a tubular light source having anisotropy in luminance distribution. SOLUTION: This surface light source unit arranges an anisotropic light scattering film 7 composed of a continuous phase (crystalline resin) and dispersing phase (amorphous resin) having mutually different refractive indexes between a light guide member 5 where the light from the tubular light source 4 enters through the side and goes out from the flat outgoing surface and the display panel 2 illuminated by the light from the outgoing surface of the light guide member, and illuminates the display panel 2 uniformly. In the light scattering characteristics F (θ) that show the relations between a scattering angle θ and intensity F of scattered light, when taking the light scattering characteristics of X axis direction as Fx (θ) and taking the light scattering characteristics of Y axis direction as Fy (θ), the anisotropic light scattering film satisfies the following equation. Fy (θ)/Fx (θ)>5 (θ=4-30 deg.), Fy (θ)/Fx (θ)>10 (θ=2-30 deg.) Moreover, when θ=0-30 deg., the light scattering characteristics Fy (θ) decrease gently with the increase of θ, and typically, Fy (0 deg.)/Fy (30 deg.)<200. |
