| 摘要 |
PROBLEM TO BE SOLVED: To improve uneven brightness on a backlight surface by electrically improving optical characteristics and not using an expensive member, by increasing brightness of light emitting diodes arranged in a part where the surface is darkened in the brightness on a light transmission plate. SOLUTION: The same kind of light emitting diodes 1a-1c mounted on a light transmission plate 3 are connected with a light sources 5, driving transistors 4a-4c, and current limiting resisters 2a-2c. A control signal to turn on-off the transistors is applied to a terminal 6. Since an edge parts of the light transmission plate 3 are darkened in general, the light emitting diodes 1a and 1c are controlled so as to be increased in brightness compared with 1b. For this purpose, the current limiting resister values are set to satisfy R1=R3<R2, to bring drive currents of the light emitting diodes into a relation of I1=I3>I2. In such a manner, it is possible to uniformalize the brightness of the light transmission plate 3 by increasing the brightness of the light emitting diodes arranged on the edge parts of the light transmission plate 3. |
