WO1995013600A1

WO1995013600A1 - Display electrodes

Info

Publication number: WO1995013600A1
Application number: PCT/US1994/012846
Authority: WO
Inventors: James Patrick Coleman
Original assignee: Monsanto Company
Priority date: 1993-11-08
Filing date: 1994-11-08
Publication date: 1995-05-18

Abstract

Electrodes for fabricating pixels for electrically activated displays, e.g. electrochromic displays, electrically heated thermochromic displays and electrochemiluminescent displays, comprise interdigitated conducting lines of repeating cruciforms comprising a plurality of transverse areas along an extended leg. Alternating lines are electrically connected to each other and adjacent lines are electrically insulated from each other. The width of the insulating area between interdigitated lines is preferably less than the width of the conducting lines. Displays can be fabricated using the electrodes of this invention fabricated into shaped pixels or as an array of pixels.

Description

DISPLAY ELECTRODES Disclosed herein are display electrodes useful in electrically activated optical displays and methods of making and using such electrodes, e.g. in pixels of electrochromic displays.

Electrically activated displays, including electrochromic, electrically heated thermochromic and electrochemiluminescent displays, typically have picture elements, known as pixels, which are either a simple shape, e.g. straight lines, or complex shapes in the form of a fixed image to be generated. A disadvantage of complex shapes is limited utility for a display; that is, the display can generate only the fixed complex image. A disadvantage of simple shapes, e.g. straight lines, is poor image quality. For instance, many electrically activated display materials exhibit poor quality images by perceptibly slow color change from edges or incomplete color change over the pixel. Many electrochromic displays are fabricated using transparent electrode layers in a laminate structure. Other electrochromic displays are fabricated using side by side electrodes. An object of this invention is to provide displays fabricated with side by side electrodes with higher quality images. SUMMARY OF THE INVENTION

This invention provides electrodes- for fabricating pixels for electrically activated displays including electrochromic displays, electrically heated thermochromic displays and electrochemiluminescent displays. The electrodes of this invention comprising interdigitated conducting lines of repeating cruciforms comprising a plurality of transverse areas along an extended leg. Alternating lines are electrically connected to each other and adjacent lines are electrically insulated from each other. The width of the insulating area between interdigitated lines is preferably less than the width of the conducting lines. Displays can be fabricated using the electrodes of this invention fabricated into shaped pixels or as and array of pixels. BRIEF DESCRIPTION OF THE DRAWINGS

Figures 1A, IB and 1C illustrate electrode patterns of this invention.

Figure 2 illustrates the use of electrode patterns of this invention in a seven-segment numeric display.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As used herein the term pixel means a picture element for a display. The electrodes of this invention comprising interdigitated conducting lines of repeating cruciforms comprising a plurality of transverse areas along an extended leg. Alternating lines are electrically connected to each other and adjacent lines are electrically insulated from each other. The width of the insulating area between interdigitated lines is preferably less than the width of the conducting lines. At the edges of a pixel it is generally convenient to provide a semi-cruciform line. Reference is made to the drawings illustrating pixels made with electrodes of this invention. Figures 1A, IB and 1C each illustrate a pixel 10 comprised of interdigitated electrodes extending as cruciforms from conductor strips 12 and 13. A continuous insulating area running from point 16 to point 17 separates the electrodes. Connectors 14 and 15 allow electrical connection to an image activating switch. The cruciforms can be in a variety of shapes. For instance, in Figures 1A and IB the alternating interdigitated lines are staggered cruciforms of similar shape. In Figure 1C the interdigitated lines are staggered cruciforms of dissimilar shape; more particularly, one of the alternating interdigitated lines has a shape where the transverse area of the cruciform is generally square and is about at least ten times larger that the area of the extended leg. Figure 2 illustrates a seven-segment numerical display 20 comprising seven pixels 21-28 according to this invention. In Pixel 21 a large electrode for generating an image comprising two adjacent cruciform lines 31 and 32 separated by a smaller electrode area comprising a central cruciform line 33 and two semi- cruciform lines 34 and 35 at the edges. Line 35 is forms part of a common electrode 36 for all of the pixels and terminates at signal connector 40. Pixels 21-27 are connected to signal connectors 41-47 by conducting lines 51-57, respectively.

The electrodes of this invention can be applied to a variety of substrates, e.g. rigid substrates such as glass or flexible substrates such as polyester or polyimide film. The conductor material of the electrodes can be selected from a large number of known conductors including metals, metal oxides and composites. Useful metals include aluminum, copper, nickel, gold, silver, tin or combinations thereof. Useful metal oxides included tin oxides, especially doped tin oxides such as antimony tin oxide and indium tin oxide. Useful composites include conductive inks filled with silver flake, carbon, metallized microspheres, etc.

Depending of the choice of substrate and conductor material, the electrodes of this invention can be fabricated by any of- a- variety- o -methods,- e-.g. y- silk screen printing of conductive ink such as silver filled ink, by electroless deposition of metal such as copper onto a catalytic image, by vapor deposition of metal or metal oxide through a mask, by etching metal foil through a photoresist mask, etc.

The electrodes of this invention can be used for a variety of electrically activated display applications. Preferred applications include the fabrication of electrochromic displays using well known electrochromic materials. Especially preferred applications are electrochromic displays as disclosed in United States application Serial No. 07/994,813, incorporated herein by reference.

While specific embodiments have been described herein, it should be apparent to those skilled in the art that various modifications thereof can be made without departing from the true spirit and scope of the invention. Accordingly, it is intended that the following claims cover all such modifications within the full inventive concept.

Claims

WHAT IS CLAIMED IS:

1. An electrode for electrically activated displays comprising interdigitated conducting lines of repeating cruciforms comprising a plurality of transverse areas along an extended leg, wherein alternating lines are electrically connected to each other and adjacent lines are electrically insulated from each other and wherein the width of the insulating area between interdigitated lines is less than the width of the conducting lines.

2. An electrode according to claim 1 wherein alternating interdigitated lines are staggered cruciforms of similar shape.

3. An electrode according to claim 1 wherein alternating interdigitated lines are staggered cruciforms of dissimilar shape.

4. An electrode according to claim 3 wherein one of alternating interdigitated lines has a shape where the transverse area of the cruciform is at least ten times larger that the area of the extended leg.