<title>Holographic diffusive reflectors for reflective color LCDs</title>

Abstract

ABSTRACT A diffusive color reflector using volume hologram was examined to implement a diffusive reflector to be employed inreflective color LCDs, with high brightness due to gain reflection and with high color purity and high light efficiency. Inholographic exposure experiment a micro-lens-array was introduced to generate object lights and to define an abrupt gainprofile and to control the magnitude of the angular profile. The DuPont materials were used to obtain high color purity ofreflection lights. The high light efficiency was realized by broadening the reflection width to the value of about 100 urnunder an optimized color tuning process.Keywords: Reflective LCD, Hologram, Diffusive reflection, Reflection gain, Micro-lens-array, Chirp structure, Broad bandreflection, Color purity 1. INTRODUCTION A sheet of polarizer in the LCDs absorbs half of the incident lights and a color filter of the absorption type utilizes one thirdof the lights since the filter was divided into RGB regions in space. The light efficiency of current reflective LCDs assumes20% at the better case. On the other hand, the brightness of future reflective color LCDs is expected to be as high as a copypaper. To this end there is a way to increase the light efficiency by using a RGB layer or CMY layer structure for brightreflective LCDs. However, many interfaces in the device structure deteriorate the efficiency and the display quality remainspoor due to parallax. Another way to get the bright reflective display quality is to use a gain reflector. There have beenproposed different kinds of diffusive reflectors.