Electrophoretic fluid

1. An electrophoretic fluid comprising at least one solvent, at least one dye, and a) white particles, and at least one set of colored particles or b) at least two sets of colored particles having different colors and optionally white particles, wherein the colored particles in a) and b) are selected from red, green, blue, magenta, cyan, and yellow particles, and mixtures thereof;

wherein the electrophoretic fluid comprises at least one dye according to Formula I, Formula II, Formula III, Formula IV, Formula V or Formula VI

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 in a) transmissive colored particles and in b) reflective coloured particles.

3. The electrophoretic fluid according to claim 1 , wherein the electrophoretic fluid comprises at least one solvent, at least one dye, white particles, and a set of colored particles selected from red, green, blue, magenta, cyan, and yellow particles.

4. The electrophoretic fluid according to claim 1 , wherein the electrophoretic fluid provides different color states on vertical movement of the particles and increased or reduced spacing between particles.

5. The electrophoretic fluid according to claim 1 , wherein the electrophoretic fluid has a first color state based on the color of the dye, and a second color state based on the color of the dye and on the colored particles.

6. The electrophoretic fluid according to claim 1 , wherein the electrophoretic fluid has a first color state based on the color of the dye, a second color state based on the colour color of the dye and on the colored particles, and a third color state based on the white particles.

7. 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.

8. The electrophoretic fluid according to claim 1 , wherein the electrophoretic fluid comprises at least two dyes wherein each dye comprises at least one chromophoric group and at least one solubilizing group and wherein at least two dyes comprise different solubilizing groups.

9. The electrophoretic fluid according to claim 1 , wherein the electrophoretic fluid 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 colored particles are colored polymer particles.

11. The electrophoretic fluid according to claim 1 , wherein the electrophoretic fluid comprises white particles selected from titanium dioxide in the rutil, anatase, or amorphous modification, surface coated titanium dioxide, titanium dioxide based particles, and white polymer particles.

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

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

14. A method comprising displaying different color states in an electrophoretic display according to claim 13 by moving the particles vertically and increasing or reducing the spacing between white particles and/or colored particles.

15. The method according to claim 14 comprising

a) achieving a first color state based on the color of the dye by increasing the spacing between the white particles,

b) achieving a second color state based on the color of the dye and on the color of the colored particles by increasing the spacing between the colored particles, and optionally c) achieving a white color state by reducing the spacing between the white particle.

16. A method comprising displaying different color states in an electrophoretic display comprising an electrophoretic fluid comprising at least one solvent, at least one dye, and a) white particles, and at least one set of colored particles or b) at least two sets of colored particles having different colors and optionally white particles, wherein the colored particles in a) and b) are selected from red, green, blue, magenta, cyan, and yellow particles, and mixtures thereof by moving the particles vertically and increasing or reducing the spacing between white particles and/or colored particles; said method comprising:

a) achieving a first color state based on to the color of a first set of particles by reducing the spacing between the particles of the first set of particles,

b) achieving a second color state based on the color of a second set of particles by reducing the spacing between the colored particles of the second set of particles,

c) achieving a third color state based on the color of the dye and on the color of the first set of coloured colored particles by increasing the spacing between the colored particles of the first set of particles,

d) achieving a fourth color state based on the color of the dye and on the color of the second set of colored particles by increasing the spacing between the colored particles of the second set of particles, and optionally

e) achieving a white color state by reducing the spacing between the white particles.

17. 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.