| 摘要 |
PROBLEM TO BE SOLVED: To provide high luminance and to eliminate luminance irregularity by forming, into a non-mirror surface, at least one surface of a transparent light guiding plate that is provided with a light diffusing-transmitting part and a back reflector on its back surface and is also provided with a diffusion plate on its front surface, by setting its height difference to a specific value or lower, and by setting its transmissivity to specific percent or more. SOLUTION: For the cross-sectional shape of a light guiding plate 1, a inclined surface part of which thickness is reduced as it part away from a linear light source 2 is formed on its back surface. At least one surface of the light guiding plate 1 is so formed into a non-mirror surface that its height difference should be set to 5 μm or less, and its transmissivity should be molded to 88% or more. Thereby, the light that is guided from the linear light source 2 into the light guiding plate 1 and reaches the non-mirror surface of the light guiding plate 1 can partially be emitted from the light guiding plate 1 not only at a position (A) close to the linear light source 2 but also at a position (B) parted away from the linear light source 2, and even the light incapable of being emitted only by a light diffusing-transmitting part 3 can be emitted, so that luminance can be improved. |
