| 摘要 |
PURPOSE:To provide a lighting device which is capable of irradiating the right-side diffusion plate uniformly with diffuse light originally radiated from a straight-pipe-type light source disposed along the side face of a light guiding plate, and usable in a transmission type liquid crystal display device by providing a reverse-side diffusion plate on the reflection plate. CONSTITUTION:Light emitted by a tubular light source 4 is incident on the side face of a light guiding plate 1 and is transmitted through the inside thereof and, when the incident angle of light incident on an outgoing surface 7 is bigger than its critical angle, the former light is wholly reflected there and is further transmitted through the inside of the light guiding plate 1. The light having been transmitted through the inside of the light guiding plate 1 and incident on a reverse surface diffusion plate 2 is diffused if there is a protrusion 21 on the reverse surface diffusion plate 2 which protrusion is made to abut against the reverse surface of the light guiding plate 1, and the light is allowed to go out upwardly from the outgoing surface 7. Because the abutting area per unit area of the protrusion 21 of the reverse surface diffusion plate 2 against the reverse surface of the light guiding plate 1 becomes larger as it is distant from the light source, the amount of outgoing light 8 allowed to go out from the light outgoing surface 7 is properly controlled and so such a lighting device is formed that the whole surface of the surface diffusion plate 5 uniformly shines regardless of its distance from the light source. |
