Methods and compositions for improved electrophoretic display performance
View Patent ↗The invention is directed to novel methods and compositions useful for improving the performance of electrophoretic displays. The methods comprise adding a high absorbance dye or pigment, or conductive particles, or a conductive filler in the form of nanoparticles and having a volume resistivity of less than about 10 4 ohm cm, or a charge transport material into an electrode protecting layer of the display.
1. A method for improving performance of an electrophoretic display, wherein said electrophoretic display comprises
(i) display cells filled with an electrophoretic fluid comprising charged pigment particles dispersed in a solvent or solvent mixture wherein said display cells are sandwiched between a first electrode layer and a second electrode layer,
(ii) a sealing layer on the open side of each of said display cells,
(iii) a primer layer between the display cells and the second electrode layer, and
(iv) an adhesive layer between the sealed display cells and the first electrode layer;
which method comprises adding a first conductive material into the sealing layer, and
adding a dye or pigment, a second conductive material, or a charge transport material into the primer layer or into the adhesive layer.
2. The method of claim 1 , where the first or second conductive materials are independently selected from a group consisting of organic conducting compounds or polymers, carbon black, carbonaceous particles, graphite, metals, metal alloys and conductive metal oxides.
3. The method of claim 2 , wherein said metal is selected from the group consisting of Au, Ag, Cu, Fe, Ni, In, Al and alloys thereof.
4. The method of claim 2 , wherein said metal oxide is selected from the group consisting of indium-tin-oxide (ITO), indium-zinc-oxide (IZO), antimony-tin oxide (ATO) and barium titanate (BaTiO 3 ).
5. The method of claim 2 , wherein said organic conducting compound or polymer is selected from the group consisting of poly(p-phenylene vinylene), polyfluorene, poly(4,3-ethylenedioxythiophene), poly(1,2-bis-ethylthio-acetylene), poly(1,2-bis benzylthio-acetylene), 5,6,5′,6′-tetrahydro-[2,2′]bi[1,3]dithiolo[4,5-b][1,4]dithiinylidene], 4,5,6,7,4′,5′,6′,7′-octahydro-[2,2′]bi[benzo[1,3]dithiolylidene, 4,4′-diphenyl-[2,2′]bi[1,3]dithioylidene, 2,2,2′,2′-tetraphenyl-bi-thiapyran-4,4′-diylidene, and hexakis-bezylthio-benzene.
6. The method of claim 1 , wherein said first or second conductive material is organic or inorganic particles overcoated with a conductive material.
7. The method of claim 1 , wherein the first conductive material is in the range of from about 0.1% to about 40% by weight of the total solid content of the sealing layer.
8. The method of claim 1 , herein said dye or pigment has an absorption band in the range of 320-800 nm.
9. The method of 1 , wherein said dye or pigment is selected from the group consisting of metal phthalocyanines, metal naphthalocyanines, metal porphines, azo dyes, squaraine dyes, perylene dyes and croconine dyes.
10. The method of claim 9 , wherein said metal in said metal phthalocyanines or metal naphthalocyanies is Cu, Al, Ti, Fe, Zn, Co, Mg, Sn, In, Ti, V or Pb.
11. The method of claim 9 , wherein said metal in porphines is Co, Ni or V.
12. The method of claim 1 , wherein the dye or pigment is in the range of from about 0.1% to about 30% by weight of the total solid content of the primer layer or the adhesive layer.
13. The method of claim 1 , wherein charge transport material is a compound having an oxidation potential less than 1.4 V.
14. The method of claim 1 , wherein said charge transport material is a compound having an oxidation potential between 0.5-0.9 V.
15. The method of claim 1 , wherein said charge transport material is selected from the group consisting of pyrazolines, hydrazones, oxazoles, oxadiazoles, enamines, carbazoles, arylamines, triarylmethanes, biphenyls, dienes, dienones and triazoles.
16. The method of claim 1 , wherein said charge transport material is selected from the group consisting of fluorenones and nitriles.
17. The method of claim 1 , wherein said charge transport material is in the range of from about 0.1% to about 30% by weight of the total solid content of the primer layer or the adhesive layer.