Browse Prior Art Database

Electrochromic Display Device Operable in Both Passive and Active Mode

IP.com Disclosure Number: IPCOM000083092D
Original Publication Date: 1975-Mar-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 3 page(s) / 46K

Publishing Venue

IBM

Related People

Chang, IF: AUTHOR

Abstract

An improved electrochromic display device is obtained by the use of an opacifier in the liquid electrochromic material.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 3

Electrochromic Display Device Operable in Both Passive and Active Mode

An improved electrochromic display device is obtained by the use of an opacifier in the liquid electrochromic material.

Although electrochromic display devices are advantageous from the standpoint that they require low voltages for switching, and no power for display, they suffer from the fact that when erased the color image at the front electrode is reproduced at the back electrode. Thus, as shown in Fig. 1A, when a voltage of the polarity shown is applied to electrodes 1 and 3 a color pattern is formed at the front electrode 3.

As is evident, electrode 3 is transparent, and may be fabricated from any of a variety of transparent conductors such as SnO(2). Likewise, face plate 5 is a transparent plate made from any of a variety of materials, such as glass. Likewise, backplate 7 may be fabricated from glass, with the liquid electrochromic material with color forming species sealed between plate 7 and plate 5.

When the voltage polarity is reversed, as shown in Fig. 1b, the color pattern is erased from electrode 3 and recreated at electrode 1. The fact that the pattern is recreated at the back electrode 1 makes the device not feasible for use in either the transmission mode or the reflective mode, when the electrodes are arranged on separate plates in sandwich configuration, as for example, as typically employed in an X-Y orthogonal-line matrix arrangement. Accordingly, conventional configurations are constrained to planar electrode arrangements as shown in Fig. 1, which fact tends to limit the usefulness of this type of display device.

In order to obviate this problem, any of a variety of opacifiers may be suspended in the liquid electrochromic material, so as to thereby mask the view of the back electrode 1 as would otherwise be seen through the transparent front electrode 3. By so doing, an image switched on the front electrode 1 can be erased by a potential of opposite polarity, without revealing the consequent image developed at the back electrode 3. Such an arrangement permits the electrochromic material to be matrix addressed.

As shown in Fig. 2, then, liquid electrochromic material 9 has suspended therein an opacifier. When a potential is applied between Y line 11 and X line 13, the color forming species of liquid electrochromic 9 forms on selected line 13 where it intersects with line 11. Typically, the electrochromic liquid material may comprise a tungstate solution or an organic salt solution. The opacifier may typically comprise a solid powder, suc...