P1-111 / G. S. Ryu
• IMID 2009 DIGEST
Abstract
We fabricated flexible electronic paper display(EPD) by using toner particles on plastic (PC) substrate. We observed the relationship between contrast ratio and changes of rib structures. One is a fabrication of ribs on bottom substrate. The display with ribs on bottom substrate had higher contrast ratio about 46% than display with ribs on top substrate. The other is a change of density of rib. The less density of ribs fabricated, the higher the contrast ratio become.
1. Introduction
The electronic paper displays have been applied to signage, e- books, e-newspaper, etc. In the past few years, several types of electronic paper displays have been proposed1-4. Each technology is unique and leads us to believe that the realization of electronic paper display will be in the near future. The requirement to realize an electronic paper display is readability and the ease of use. The latter includes paper-like appearance robustness, flexibility and ultra low power consumption 5.
In this paper, we observed the dependence of contrast ratio on ribs structure in flexible toner type EPD
2. Experimental
The EPD using toner particles is comprised of two substrates which have an electrode, ribs, and toner particles. The structure of EPD using toner particles is shown in Fig. 1. The electrodes of two substrates are face each other and ribs are between electrodes. The ribs maintain space between electrodes to provide particles for move free and keep up uniformity of
display to restrict side movement of particles. Toner particles are micro-size one that has an electric charge and color. In this paper, we used black positive charge particles and white negative charge particles.
Fig. 1.The schematic representation of structure and the driving principles of electronic paper display using toner particles.
We fabricated flexible electronic paper display (EPD) by using toner particles on plastic (PC) substrate. The fabricated electronic paper display was generated a diffused reflection from edge of ribs in Fig. 2. It had a low contrast ratio because of increased luminance both white state and black state.
Dependence of contrast ratio on rib structure in flexible
toner type EPD
Gi Seong Ryu
1, Chang Bin Lee
1, Sang Kwuon Han
2, Seung Hee Chun
2and Chung Kun Song
11Dept. of Electronics Eng., media device lab, Dong-A University, Busan, Korea
Phone: +82-51-200-7363 , E-mail: gsryu@dau.ac.kr
2Human Interface Technology Development Team, Institute of Future Technology, SK
Telecom, Seoul, Korea
P1-111 / G. S. Ryu
IMID 2009 DIGEST •
Fig. 2. The diffused reflection from edge of ribs
We suggested two methods for improvement of contrast ratio. One is a fabrication of ribs on bottom substrate. The lower area of ribs made by photo lithography process was narrower than upper one. So, fabricating ribs on bottom substrate have more advantages in Fig. 3 and Fig. 4. We had measured contrast ratio of fabricated display, separately. The display with ribs on bottom substrate had higher contrast ratio about 46% than display with ribs on top substrate.
Fig. 3. The profile of processed ribs
(a) (b)
Fig. 4. The feature of reflection dependence of substrate position with fabricated ribs. (a) The ribs on top substrate. (b) The ribs on bottom substrate
The other is a change of density of rib which decide aperture ratio of panel. Fig. 6 shows the relationship between pixels per cell and contrast ratio. The less density of ribs fabricated, the higher the contrast ratio become.
Fig. 5. The change of pixels per cell and ribs width for reducing rib density
1 x 1 2 x 2 3 x 3 0.5 1.0 1.5 2.0 2.5 Cotr a st r a ti o Pixels / Cell
Fig. 6. The relationship between pixels per cell and contrast ratio
3. Results and discussion
We fabricated flexible electronic paper display by using toner particles on plastic substrate. In this paper, we suggested two methods for improvement of contrast ratio. One is a fabrication of ribs on bottom substrate. The display with ribs on bottom substrate had higher contrast ratio about 46% than display with ribs on top substrate. The other is a change of density of rib. The less density of ribs fabricated, the higher the contrast ratio become. It is based on two reasons. One is reducing density of ribs, so aperture ratio of display is high. The other is particles share in a cell. A cell which is composed ribs had several pixels. The pixels share with particles which can move between pixel and pixel. But, when different electric field
P1-111 / G. S. Ryu
• IMID 2009 DIGEST
exists between the pixels such as driving images, we think that particles in a cell are interrupted the movement. So, contrast ratio of panel can be reduced. We want to confirm the next study.
Acknowledgement
This work was supported by SK telecom.
5. References
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2. H.Fujikake, T.Murashige, H.Sato, H.Kikuchi, T.Kunita and Y.Suzuki, Euro Display Symoposium Digest, p.510-513(2005)
3. C.Joubert, J.Angele, N.Bollenbach, J.D.Laffitte, B.Pecout and Z.Zenati, SID Symposium Digest, p.1766-1799(2005).
4. G.T.McCollough, C.M.Rankin and M.L.Weiner, SID Symposium Digest, p.64-67(2005).
5. R.Sakurai, S.Ohno, S.Kita and Y.Masuda, SID Symposium Digest, p.1922-1925(2006).
