Date Visited: October 7, 1991

Report Author: M. Slusarczuk





Hiroshi Kobayashi
Shosaku Tanaka

Tottori University performs research on electroluminescent materials. Their focus is on improving the performance of color and white phosphors. Their laboratory, which is about 600 ft2, contains the following deposition equipment:

Sputtering - hot wall epitaxy - electron beam evaporation.

The general thrust of their research is using potassium, sodium, or lithium as the charge- compensating material. The following single-color phosphor combinations are presently under study;

The white phosphor combinations are

They have shown reasonable progress in both blue and white phosphors, especially using an Ar-S atmosphere anneal at 630 degrees centigrade. They have shown three colors using the white phosphor with both dye and interference filters. The dye filters provided better viewing angle. Brightness achieved has been 50 nits at 60 Hz and 900 nits at 1000 Hz. The efficiency is about 0.4 1/W.

We were also shown a laser laboratory that had a dye laser with femto second optics for measuring nonlinear optic properties.

Answers to direct questions: In order for EL technology to be viable, a 5- to 6-factor improvement in blue brightness is necessary.

They felt that RGB and white with color filters each offer different trade-offs. They believed that EL could support 1000 x 1000 pixels without serious cross-talk problems. Gray scale and cross-talk minimization are both areas that require additional work.

DC EL powder/thin-film hybrid is being studied by Nippon Sheet Glass, which has shown a 640 x 480 display with 16 levels of gray with pulse-width modulation.

ITO resistivity is not something that Tottori's researchers have given much thought to.

Tottori University works with a number of industries: Sharp, NEC Kansai, Oki, Fuji Electric, Nippon Sheet Glass, Matsushita, Komatsu, and Toso--all companies with some level of EL research.

The University chooses to publish its results rather than to patent the discoveries. Part of the motive is to further the status of EL relative to other display technologies.


We had a discussion with Professor Muneo Oka on the sources of funding for universities and the nature of the industry-university interaction. Each research group gets 3.5 million yen from the Ministry of Education. This money covers one professor, one assistant professor, and one lecturer. If the group is part of a PhD-granting department, then the amount increases to 6.5 million yen. Tottori University has no PhD program in engineering yet but is in the process of trying to establish one. These funds constitute the "even distribution" money.

If a particular professor has been performing excellent work and the Ministry of Education feels that this work is in an important area, then it awards a larger sum--on the order of 100 million yen. This money covers the work of multiple professors, about 10, from across several research groups. Half of the money goes for equipment, the rest for operational costs, excluding salaries. The projects are usually for three years. They are not renewable.

Selection of the larger projects is done through consensus, which "bubbles up" through meetings at societies, universities, etc. Final selections are made by a committee of about 10 senior professors from around the country (though in reality they are mostly from the Tokyo area.) There is currently an initiative to start including smaller universities in the process. Until recently, most such grants went to the major universities only.

Graduate students are supported by a "stipend" at a rate of about 5,000 yen per day for up to 30 days.


  1. Shosaku Tanaka, Haruyuki Morita, Kimihiko Yamada, and Hiroshi Kobayashi, "Luminance Improvement of Blue- and White-Emitting SrS TFEL Devices by Annealing in Ar-S Atmosphere" to be presented at IRDC '91.

Published: June 1992; WTEC Hyper- Librarian