| 摘要 |
<p>A surface light source having a luminous face which is excellent in whiteness and does not reflect the background of the viewer. The surface light source is advantageously applied to the back lighting of a liquid crystal display. A fluorescent lamp (L) is disposed in the proximity of a light incidence surface (2) of a light guide plate (1). A prism sheet (4') having prism surfaces formed on both its sides is disposed over a light take-out face (5). Prisms (4a, 4b) on the inner surface extend in a transverse direction of the light guide plate (1) and prisms (4c, 4d) on the outer surface extend in a vertical direction of the light guide plate (1). A reflector (3) is disposed on the back of the light guide plate (1). Outgoing light from the light take-out face (5) is guided in a front surface direction by the action of prisms (4a, 4b), shifted in the transverse direction by the prisms (4c, 4d) and then travels towards the light guide plate (1) as backward travelling light. The paths of outgoing light from the prism sheet (4') is diversified through this action, and visual characteristics are improved.</p> |
