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on a flexible liquid crystal display (LCD) fabricated using self-aligned microstructures of the photopolymer/spacer composite material through a wettability patterning process. The microstructures confined on the patterned alignment layer provide spacers for the uniform cell gap as well as the mechanical stability. No structural change of the substrates was observed during the fabrication process. Our flexible LCD provides good flexibility, durability, and excellent electro-optic performances. This method can be applicable to the fabrication of large plastic LCDs using a roll-to-roll process. 1. Introduction flexible display(1) is one of the most promising display devices in the ubiquitous era due to several advantages such as higher portability and better durability than existing displays. The design scheme of the flexible display has potential for realizing future applications such as wearable computers, smart cards, and display systems in small packages with totally new concepts. Among a number of flexible display technologies under development, liquid crystal displays(2,3) (LCDs) are well established compared to organic light emitting devices(4) and electrophoretic displays(5). The use of flexible substrates, however, brings various issues on the reliability of the LCD. Flexible devices might be bent or rolled up with an elastic deformation of the substrates, which results in irregular thickness of the liquid crystal (LC) layer. In addition, the accompanying flow of the in-between LC significantly affects the optical properties of the LCD. From the viewpoint of improving both the mechanical stability between the top and bottom substrates and the electro-optic (EO) properties under the bent environment, a variety of techniques have been proposed and demonstrated. Recently, polymer wall formation techniques using the isotropic/anisotropic phase separation of photopolymer and liquid crystal (LC) composite systems have been proposed and successfully demonstrated(6-12). However, these systems suffer from inevitable drawbacks that are inappropriate for large size panel and mass production. Moreover, high image quality is not guaranteed due to the deterioration of contrast ratio by the residual polymer after the phase separation process. In addiction, the fabrication of the flexible LCD needs to be carried out with no chemical etching process to avoid structural changes and damages of the substrates. Therefore, a new technology applicable for a simple process and providing better EO properties should be developed. In this work, we demonstrate a new method of improving the mechanical stability of the flexible LCDs by spontaneously forming microstructures of a photopolymer/spacer composite. The wettability patterning technique used here confines the composite in patterned array regions prepared on the LC alignment layer without the chemical etching process. The microstructures serve as columnar spacers for the uniform cell gap as well as an adhesion layer that allows for mechanical stability and reproducibility against the bending deformations after ultraviolet irradiation. The EO measurements show the fast response time of about 7 ms, and the contrast ratio of 150 : 1 in the normally white mode. Our flexible LCD provides better electro-optic properties than the polymer/ LC composite system. |
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