TN, STN, and ECB Materials

Low-molecular-weight nematic liquid crystalline materials for TN, STN, and ECB displays are well developed, and substantial improvements in such features as reduced viscosity, enhanced dielectric anisotropy, and birefringence are not expected. Major European nematic materials producers have established joint ventures in Japan to tailor-make mixtures for display manufacturers. Japanese companies are taking an increasing role in designing, synthesizing, and patenting new nematic materials, while European companies are protecting their strength by keeping their research and development efforts at home and only making mixtures in their joint ventures in Japan.

Most improvements in the TN and STN displays are expected to come from other materials such as retardation films and improved alignment layers. Retardation films are a Japanese innovation, and Japanese companies are currently the only suppliers of such films. There is room for substantial improvement in retardation films. Alignment layers that do not require rubbing would be welcome in the industry. Innovative materials and techniques for molecular surface alignment are primarily being explored in Japanese universities such as the laboratory of Professor S. Kobayashi, who is working on Langmuir-Blodgett films and conducting polymers.

FLC Display Materials

Improvements are expected to come from the synthesis and design of new low- molecular-weight LC materials for FLC displays, and several Japanese companies are studying new molecular forms. Discussion with several companies did not indicate as much enthusiasm in Japan as in Europe for new antiferroelectric LC materials. There did not appear to be any new solutions to the surface stabilization problem, other than that mentioned by Fujitsu, which has been approaching the problem by designing FLC materials that stimulate the bookshelf-ordering structure. Gray scale was perceived to be a major problem by most of the Japanese companies the JTEC team visited.

PDLC Materials

Most Japanese display companies visited had research programs on PDLC materials, and there appeared to be wide interest in these materials for projection applications. Some companies also viewed these materials as having potential for brighter direct-view displays. Drive voltage and resistivity problems in the use of these materials on the active matrix are reported to be nearing solution. Asahi Glass and Dainippon Ink show PDLC materials with impressive characteristics. Improvements in the polymer binder and in the nematic materials used in the dispersions are responsible for these advances.

EL and PDP Materials

Research on materials for light-emissive displays is perceived to be de- emphasized in Japan because of the strong commitment to LCD manufacturing. Advances are being made in the development of blue and white EL phosphors. In PDP displays, new designs and success in discharge cell structure are expected to give new focus to materials research.

University Materials Research

University researchers in Japan are more aware of display materials problems and industrial needs than are their counterparts in the United States and Europe. University research is more basic in general, and approaches to industrial problems more innovative. In Japan, basic research on liquid crystals is more driven by the display technology than in the United States and Europe. There are joint industry/government research support programs that encourage university/industry interactions.

Published: June 1992; WTEC Hyper-Librarian