Self-supporting pigment layers for electrochromic display

Abstract

An electrochromic data display and imaging device which may be formed by sandwich arrangement of the imaging area and the counter-electrode area, with a suitable self-supporting ion-conductive layer between.

I claim: 
     
       1. A varaible light transmission device which comprises light transmitting substrate having a persistent electrochromic material as a light modulating material, a counter-electrode, and a .[.self-supporting.]. .Iadd.porous separator .Iaddend.layer comprising a pigment and an ion-conducting material .Iadd.in a binding medium .Iaddend.in contact with said .Iadd.light modulating .Iaddend.material and counter-electrode. 
     
     
       2. A variable light transmission device as in claim 1, which comprises two layers, one with said electrochromic material, and the other of said counter-electrode separated by said .[.self-supporting.]. .Iadd.porous separator .Iaddend.layer, disposed between a pair of conductive electrodes. 
     
     
       3. The device of claim 2, wherein said counter-electrode is the type of the persistent electrochromic material. 
     
     
       4. The device of claim 3, wherein the electrochromic materials in each said layer are identical. 
     
     
       5. The device of claim 2, wherein at least one of the electrodes is substantially transparent. 
     
     
       6. The device of claim 4, wherein said electrochromic materials are WO 3 . 
     
     
       7. A device of claim 1, wherein said .[.self-supporting.]. .Iadd.porous separator .Iaddend.layer contains a color pigment. 
     
     
       8. The device of claim 1, wherein said .[.self-supporting.]. .Iadd.porous separator .Iaddend.layer is a porous sheet saturated with an electrolyte. .Iadd. 9. The device of claim 1 wherein said porous separator layer is self-supporting. .Iaddend..Iadd. 10. The device of claim 9 wherein the self-supporting porous layer is a separate pre-cut element. .Iaddend. .Iadd. 11. In an electrochromic display of the type having a first substrate with selectively actuatable transparent electrodes and first electrochromic layers thereon, and also having a second substrate with counter-electrode and second electrochromic layer thereon, the improvement comprising: porous separator means applied as a layer and uniformly and closely spacing said first and second substrate members, the pores of said separator means being filled with liquid electrolyte, and   pigment means held by said separator means and selected to provide contrast with said first electrochromic layers and disposed to hide said second electrochromic layer. .Iaddend..Iadd. 12. The combination according to claim 11, wherein said porous separator means comprises porous polypropylene. .Iaddend..Iadd. 13. The combination according to claim 11, wherein said pigment means is premixed in said separator means. .Iaddend.