Electrophoretic fluids

Patent metadata

Field	Value
Publication number	US-10007165-B2
Application number	US-201314418465-A
Country	US
Kind code	B2
Filing date	Jul 22, 2013
Priority date	Aug 1, 2012
Publication date	Jun 26, 2018
Grant date	Jun 26, 2018

Abstract

This invention relates to electrophoretic fluids, the use of these fluids for the preparation of an electrophoretic display device, and electrophoretic displays comprising such fluids.

First claim

The invention claimed is:

1. An electrophoretic fluid comprising at least one solvent, at least one set of coloured particles, at least one highly absorbing dye, at least one set of white reflective particles, and at least one set of transparent particles, wherein the coloured particles and the white reflective particles have opposite electric charge signs and wherein the white reflective particles and the transparent particles have the same electric charge sign and wherein electrophoretic mobilities of the white reflective particles and the transparent particles differ at most by 50%, and wherein the white reflective particles, and the transparent particles comprise a polymeric shell adsorbed onto the particle wherein the polymeric shell consists of a random copolymer having monomer or macromonomer building blocks, and the random polymer comprises at least one hydrocarbon insoluble, charged or chargeable structural unit and at least one hydrocarbon soluble, stabilising structural unit;
wherein the electrophoretic fluid comprises at least one highly absorbing dye according to Formula I, Formula II, Formula III, Formula IV or Formula V

wherein
X and X′ are independently of one another H or an electron-withdrawing group;
R 1 and R 2 are independently of one another groups are linear or branched, substituted or unsubstituted alkyl groups where one or more non-adjacent carbon atoms may be replaced by O, S and/or N;
R 3 and R 4 are independently of one another groups are linear or branched, substituted or unsubstituted alkyl groups where one or more non-adjacent carbon atoms may be replaced by O, S and/or N;
R5 is a methyl or methoxy group;
and the dye comprises at least one electron-withdrawing group;

wherein
R 6 and R 7 are independently of one another groups are linear or branched, substituted or unsubstituted alkyl groups where one or more non-adjacent carbon atoms may be replaced by O, S and/or N;

wherein
X″ is an electron-withdrawing group;
R 8 is a methyl or methoxy group;
R 9 and R 10 are independently of one another groups are linear or branched, substituted or unsubstituted alkyl groups where one or more non-adjacent carbon atoms may be replaced by O, S and/or N;

wherein
R 12 and R 13 are independently of one another groups are linear or branched, substituted or unsubstituted alkyl groups where one or more non-adjacent carbon atoms may be replaced by O, S and/or N;
R 11 is an alkyl or alkoxy group with at least 3 carbon atoms;

wherein
R 14 and R 15 are independently of one another groups are linear or branched, substituted or unsubstituted C8-C20 alkyl groups where one or more non-adjacent carbon atoms may be replaced by O, S and/or N;

wherein
X′″ is an electron-withdrawing group;
R 16 and R 17 are independently of one another groups are linear or branched, substituted or unsubstituted alkyl groups where one or more non-adjacent carbon atoms may be replaced by O, S and/or N;
R 18 is NHCOR with R=linear or branched C1-C10 alkyl groups.

2. The electrophoretic fluid according to claim 1 , wherein the electrophoretic fluid comprises the highly absorbing dye, wherein the coloured particles are black particles, a set of white reflective particles, and a set of transparent particles.

3. The electrophoretic fluid according to claim 1 , wherein the electrophoretic mobilities of the white reflective particles and the transparent particles differ at most by 5%.

4. The electrophoretic fluid according to claim 1 , wherein the dye or a dye mixture has an absorbance of at least 0.3 a.u. in a cell thickness of 50 microns.

5. The electrophoretic fluid according to claim 1 , wherein the electrophoretic fluid comprises silica particles or polytetrafluoroethylene particles as transparent particles.

6. The electrophoretic fluid according to claim 1 , wherein the least one set of white reflective particles is selected from the group consisting of titanium dioxide in the rutil, anatase, or amorphous modification, surface coated titanium dioxide, titanium dioxide based particles, and white polymer particles.

7. The electrophoretic fluid according to claim 1 , wherein the coloured particles are black particles and are selected from the group consisting of carbon black, surface coated carbon black, carbon black based particles, and black polymer particles.

8. The electrophoretic fluid according to claim 1 , wherein the white reflective particles, and the transparent particles comprise a polymeric shell adsorbed onto the particle wherein the polymeric shell consists of a random copolymer selected from random copolymers comprising mono-terminated polydimethylsiloxan methacrylate, (2,3-epoxypropyl)-methacrylat, and 2-tert-butylaminoethylmethacrylate or graft copolymers comprising polystearate methacrylate, (2,3-epoxypropyl)-methacrylat, and 2-tert-butylaminoethylmethacrylate or random copolymers comprising dodecylmethacrylate, and (2-(methylacryloyloxy) ethyltrimethyl ammonium methylsulfate.

9. The electrophoretic fluid according to claim 1 , wherein the solvent comprises at least one non-polar solvent having a dielectric constant <10, volume resistivity about 10 15 ohm-cm, viscosity <5 cst, and a boiling point >80° C.

10. The electrophoretic fluid according to claim 1 , wherein the electrophoretic fluid further comprises at least one surfactant.

11. A method for the preparation of a mono, bi or polychromal electrophoretic device comprising utilizing the electrophoretic fluids according to claim 1 .

12. A method comprising displaying an image with an electrophoretic fluid according to claim 1 .

13. An electrophoretic display device comprising an electrophoretic fluid according to claim 1 .

14. The Electrophoretic display device according to claim 13 , wherein the electrophoretic fluid is applied by a technique selected from inkjet printing, slot die spraying, nozzle spraying, and flexographic printing, or any other contact or contactless printing or deposition technique.

Assignees

• Merck Patent Gmbh

Inventors

• Greinert Nils
• Bauer Thomas
• Koch Matthias
• Hechler Wolfgang
• Smith Nathan

Classifications

• G02F2001/1678

  characterised by the composition or particle type · CPC title

• G02F1/167 Primary

  by electrophoresis · CPC title

• G02F2202/04

  dye · CPC title

• C09B69/106

  containing an azo dye · CPC title

• C09B69/101

  containing an anthracene dye · CPC title