| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a light guide plate having a high light utilization efficiency and can emit light having little luminous irregularities and can obtain a bright convex distribution in the vicinity of a central part of a screen as compared with a peripheral part, and provide a surface lighting device. <P>SOLUTION: The light guide plate includes two layers comprising a first layer and a second layer which are superimposed in an almost vertical direction to a light emission surface and have different particle concentrations of diffusion particles. The second layer has a cross-sectional shape having at least a part in which the thickness in an almost vertical direction to the light emission surface is continuously increased up to the maximum in a direction as it goes apart from a light incident surface, and the diffusion particles are dispersed so that a synthetic scattering cross-sectional area S in a direction of the two layers in a position along a direction almost parallel with the light emission surface may be continuously and monotonously increased as it goes apart from the light incident surface, and the maximum value S<SB POS="POST">max</SB>and the minimum value S<SB POS="POST">min</SB>of the synthetic scattering cross-sectional area S shall satisfy 1.25≤S<SB POS="POST">max</SB>≤2.2, and moreover 0.90≤S<SB POS="POST">min</SB>≤1.6. <P>COPYRIGHT: (C)2013,JPO&INPIT |
