An Edge-lit Backlight Unit for Small Portable Liquid Crystal Displays with a Newly Designed Single Pyramid Sheet

Abstract

In recent years, owing to the rapid development of liquid crystal display (LCD) technology, LCDs are being used in different applications ranging from small portable information display devices to large televisions (TVs) [1]. However, to ensure that LCDs continue to be used widely, their performance should be consistently improved, and manufacturing costs should be reduced. Recently, in the field of portable information displays such as smart phones, there has been intense competition between LCDs and organic light-emitting diodes (OLEDs). LCDs require a backlight unit (BLU) because they do not emit light themselves, in contrast to OLEDs. A BLU is generally composed of many optical components, such as a light source, a light guide plate, a reflective sheet, a diffusive sheet, and two prism sheets [2,3]. Therefore, the BLU is thought to be an impediment to the manufacture of brighter, slimmer, lighter, and cheaper LCDs [4]. In a BLU, incident light from a light source propagates via a light guide plate by total internal reflection. The light is then reflected from the light guide plate by the scattering of a pattern formed on the surface of the light guide plate opposite the LCD panel. The light is then reflected toward the LCD panel and diffused through a diffusive sheet. Once diffused, the light is then collimated through two orthogonally -placed prism sheets in