Surface lighting device and portable terminal using the same

摘要

A surface lighting device has one single light source and a light-guide-board. The board includes a light-guiding-section and a light-emitting-section. A shorter side of the light-guiding-section is not more than 8 mm, and an area of the light-emitting-section is not less than 500 mm2. The light-emitting-section has the following features: (1) a ratio of min. luminance vs. max. luminance of is not less than 0.3; (2) an average luminance ranges from 1 cd/m2 to 200 cd/m2, and (3) a change value in luminance per unit length is not more than (average luminance)×100 cd/m3. Employing plural light-emitting-elements in the light source allows the lighting device to produce versatile colors. The light source, light-guide-board and a holder are structured and shaped in optimum way, so that unevenness in luminance of the device is reduced. An LCD unit incorporating this surface lighting device increases its display quality, and a portable terminal incorporating this LCD unit produces easy-to-lead display.