Monolithic Glass Light-Guide Plate with Built-in Prism Structure for 1D Dimming Large-Area LCD Masanobu Isshiki*, Yusuke Arai*, Masahiro Inoue*, Takashi Sasaki*, and K Käläntär** *Asahi Glass Co. Ltd, Tokyo, Japan **Global Optical Solutions, Tokyo, Japan Abstract We have developed monolithic functional glass LGP (GLGP) for large-area LCD backlight unit (BLU) with built-in prism structure enabling 1D segment dimming. We simulated and optimized the prismatic GLGP, confirming the 1D dimming and light collimating characteristics of the prototyped sample. We have succeeded in fabricating prism structure on 65” GLGP with both imprint and film lamination methods. Author Keywords Glass light-guide plate; GLGP; BLU; prism structure; large-area TV; edge-lit backlight; 1D-dimming; monolithic; imprint; film lamination. 1. Introduction The International Telecommunications Union - Radio- communication, known as ITU-R, recommended and approved BT.2100-1 (06/2017), i.e., the image parameter values for high dynamic range television for use in production and international program exchange that defines peak luminance of 1000 cd/m 2 for display [1]. Since a high brightness is mandatory for large- area LCD TVs, improvement of backlight units (BLUs) are required. Edge-lit BLU have been widely used in TV sets mainly for medium and small LCDs, because the Edge-lit BLU is thin compared with direct-lit BLU. For larger display areas such as 55” and 65”, thin edge-lit BLU are more attractive. Polymer materials, e.g., PMMA, PC, COP, MS, have been common materials for LGP so far. However, the nature of the polymers, such as low stiffness, deformable by humidity, higher thermal expansion, and lower chemical and thermal durability, have been recognized as disadvantages when using for the larger size BLU. On the other hand, the glass materials have advantages for those aspects compared with the plastic materials. In addition, a thin TV set can be realized by eliminating the housing. Therefore, a GLGP is more attractive than LGP with plastic material when TV size increases. We have developed and commercialized GLGP for excellent mechanical and optical properties compared with polymer LGP (PLGP) [2,3]. In recent years, BLUs adopting prismatic PLGPs for TV sets are in the market. By employing prismatic structure on the LGP, a high brightness BLU can be achieved. The excessive luminance can be forfeited for eliminating a light collimating film and reducing the BLU cost. The realization of prismatic structure on a GLGP with high dimming index and high luminance is the objective of this study. One of the technologies that can be used to increase the luminance is the block-wise dimming. The contrast ratio and the BLU efficacy (i.e., reduction in power consumption) can be improved by segment dimming [4,5]. Furthermore, the 1D- dimming technology can enhance the moving picture quality by inserting the black segment in each frame picture or by using field-sequential-color segment [6-8]. In this paper, we report on realization of prismatic structure on our recently developed glass “XCV”, i.e. GLGP. By integrating our GLGP fabrication technology and optical design technology we develop monolithic GLGP with built-in prism for 1D dimming large-area LCD TV. The GLGPs are fabricated by two methods, (1) resin imprinting, and (2) prism film lamination technologies. 2. Functional BLU (a) Structure of BLU The structure of conventional BLU (without prism) is shown in Fig.1. The light introduced from LEDs to the GLGP propagates inside the GLGP with repeating reflection on the inner surfaces of front and back of the GLGP based on total internal reflection (TIR). A certain amount of light is scattered by the scattering dots that are printed on the back surface of the GLGP. The scattered light are emergent from the GLGP. The emergent light from the back is reflected on the reflector set on the back side of the GLGP. The emergent light from the front side enters a diffuser film and two crossed collimating prism films. In a few cases, a top diffuser with low haze is optionally used on the top prism film. (b) Issues of conventional BLU A high luminance in normal direction (z-direction in Fig.1) and horizontal viewing angle of 30~35° are required for TV applications. The extracted light from GLGP spread into a wide angle, and the luminance in surface normal direction is low on the GLGP. Therefore, two crossed prism films are indispensable to collimate the light in normal direction. Figure 1. Structure of a conventional BLU. Light sources (LEDs), a LGP, a reflector , a diffuser film and two light collimating prism films are used in the BLU structure. 14-2 / M. Isshiki SID 2018 Digest • 149 ISSN 0097-996X/18/4701-0149-$1.00 © 2018 SID