Comparison Between Reflective LCDs with Diffusive Micro Slant Reflector (DMSR) and Bump Reflector
ELECTRONIC RESEARCH AND SERVICE ORGANIZATION/INDUSTRIAL TECHNOLOGY RESEARCH INST HSINCHU (TAIWAN)
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A reflective TFT-LCD with an internal asymmetric diffusive micro slant reflector DMSR is developed to enhance the light efficience. The DMSR structure is optimized to obtain a desired light distribution cone with asymmetric characteristics. In this paper, we will compare the optical properties of a reflective TFT-LCD panel with a DMSR structure and those of a reflective LCD with symmetric bump structure reflector. Since the light intensity distribution of a reflective LCD depends strongly on the behavior of the incident light source we used two different incident light sources for illumination. One is collimated light, and other is diffused light. The conoscope is then used to understand the light distribution of the panels in all directions. When the collimated light source is used for illuminating the reflective LCD panel, the brightness of a LCD panel with DMSR is about 2 times of that of a LC cell with a symmetric bump type reflector. If the incident light is the diffusive type, the reflectance of a bump reflector will be independent of the viewing angles. However, the diffusive property of the new DMSR design will redistribute the reflected light so that an asymmetric viewing cone can be generated to increase the brightness in this area. The asymmetric property of the cone is a result of the slant structure. The experimental results demonstrate that the DMSR structure can redirect the collimated light in a designated area. Due to the effect of DMSR, the peak of reflected light is shifted away from the surface specular reflection and the light distribution is wider. Normal environment contains both the collimated and diffusive light. With the DMSR structure, we can utilize both light sources and make our panel much brighter, suitable for many information applications.
- Electrooptical and Optoelectronic Devices