| Summary: | 碩士 === 長庚大學 === 化工與材料工程研究所 === 95 === In a liquid crystal display, the backlight unit serves as the light source because liquid crystals do not emit light. A light diffuser is one of the major components of the backlight unit, whose function is to provide uniform light distribution of the backlight unit. A diffuser is typically composed of three basic parts, the diffusing beads, the resin and the substrate. In this work, particles of different sizes, different size distributions and different refractive index were mixed with an acrylic resin and coated on a 100 μm thick PET substrate using a wire-bar coater. The optical performances (haze, light transmittance) of the coated films were examined by a haze meter.
The results show that the haze value of the film increases with the increase of the normalized film thickness and the decrease of the particle size. The light transmittance value of the film increases with the decrease of the normalized film thickness and the increase of the particle size. Diffuser films coated with particles with narrow particle size distribution give better optical performance compared to the particles with wide particle size distribution. From the experimental result, we developed the correlation between the transmittance, the normalized film thickness and the bead-to-resin ratio and the correlation between the haze value, the normalized film thickness and the bead-to-resin ratio.
When mixing small particles and large particles as the diffusing beads, the size ratio of large particles to small particles have strong influence on the optical performance of the diffuser. When increasing the portion of the PS particles in the PMMA diffusing beads, the light transmittance increase with the increasing of the PS particle portion.
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