Particles for electrophoretic displays

Patent metadata

Field	Value
Publication number	US-9645416-B2
Application number	US-201314400660-A
Country	US
Kind code	B2
Filing date	May 7, 2013
Priority date	May 14, 2012
Publication date	May 9, 2017
Grant date	May 9, 2017

Abstract

This invention relates to particles comprising a core particle and a polymeric shell, a process for their preparation, electrophoretic fluids comprising such particles, and electrophoretic display devices comprising such fluids.

First claim

The invention claimed is:

1. A fluid comprising particles comprising organic or inorganic pigment core particles encapsulated by a polymeric shell consisting of monomer units of:
a) at least one polymerisable steric stabiliser,
b) at least one coupling reagent,
c) at least one co-monomer,
d) optionally at least one charged co-monomer,
e) optionally at least one polymerisable dye, and
f) optionally at least one crosslinking co-monomer,
wherein the amount of coupling reagent is between 75-125% by weight, based on the pigment particle, and wherein the fluid is an electrophoretic fluid, and
wherein the particles are formed from a polymerisable composition comprising 0.1-75% by weight of at least one organic or inorganic pigment particle, 0.1-50% by weight of at least one polymerisable steric stabiliser, and 20-95% by weight of co-monomer, all percentages are based on the total weight of the polymerisable composition except solvent.

2. The fluid according to claim 1 , wherein the pigment core particle is titanium dioxide in the rutile, anatase, or amorphous modification or carbon black.

3. The fluid according to claim 1 , wherein the coupling reagent is a polymerisable alkoxysilane or chlorosilane.

4. The fluid according to claim 1 , wherein the polymerisable steric stabiliser is a poly(dimethylsiloxane) macromonomer with at least one polymerisable group and a molecular weight in the range of 1000-50000.

5. The fluid according to claim 1 , wherein the polymerisable steric stabiliser is a mono-methacrylate terminated poly-dimethylsiloxane.

6. The fluid according to claim 1 , wherein the percentage of polymerisable steric stabiliser is at least 5% by weight based on the weight of the particle.

7. The fluid according to claim 1 , wherein the particles have a diameter of 400-1000 nm.

8. A process for the preparation of the fluid according to claim 1 comprising
a) dispersing at least one organic or inorganic pigment particle in a solution of at least one polymerisable steric stabiliser in a non-polar organic solvent, wherein the pigment particle is un-funtionalized;
b) adding at least one co-monomer, at least one coupling reagent, at least one initiator, optionally at least one polymerisable dye, and optionally at least one chain transfer agent;
c) subjecting the dispersion of step b) to heating and sonication for polymerisation,
d) optionally washing by repeated centrifugation and redispersion in fresh solvent, and
e) optionally isolating the resulting coated particles.

9. The process according to claim 8 , wherein the non-polar organic solvent is a non-polar hydrocarbon.

10. A method comprising utilizing the fluid prepared by a process according to claim 8 in optical, electrooptical, electronic, electrochemical, electrophotographic, electrowetting and electrophoretic displays and/or devices, and in security, cosmetic, decorative, and diagnostic applications.

11. A method comprising utilizing the particles according to claim 1 in optical, electrooptical, electronic, electrochemical, electrophotographic, electrowetting and electrophoretic displays and/or devices, and in security, cosmetic, decorative, and diagnostic applications.

12. An electrophoretic display device comprising the electrophoretic fluid according to claim 1 .

13. An electrophoretic display device according to claim 12 , wherein the electrophoretic fluid is applied by a technique selected from inkjet printing, slot die spraying, nozzle spraying, and flexographic printing, contact or contactless printing or deposition technique.

14. The fluid according to claim 1 , wherein the amount of pigment core particles is between 20-60% by weight, based on the total particle.

15. The fluid according to claim 1 , wherein the coupling reagent is at least one polymerisable organosilane, -titanate and/or zirconate of the general formula
(X) 4-n-m Z(R) n (B—Y) m

wherein
X=OH, halogen, alkoxy, aryloxy;
Z=Si, Ti, Zr;
R=alkyl, phenyl or hydrogen;
B=single bond, or an organic, at least bifunctional group;
Y=vinyl, styryl, acrylamide, methacrylamide, acryloyl, and/or methacryloyl group;
n=0,1,2,3 and m=1,2,3 where n+m≦3.

16. The fluid according to claim 15 , wherein Z is Si and X is an alkoxy group.

17. The fluid according to claim 1 , wherein the coupling reagent is selected from the group consisting of are vinyltrimethoxysilane, vinyltriethoxysilane, 3-(Trichlorosilyl)propyl methacrylate, (methacryloxymethyl)trimethoxysilane, (methacryloxymethyl)triethoxysilane, (methacryloxymethyl)methyldimethoxysilane, (methacryloxymethyl)ethyldimethoxysilane, and 3-(trimethoxy silyl)propyl methacrylate (MPS).

18. The fluid according to claim 1 , wherein the percentage of polymerisable steric stabiliser is at least 20% by weight based on the weight of the particle.

Assignees

• Merck Patent Gmbh

Inventors

• Blackman Lewis
• Farrand Louise Diane
• Wilson Jonathan Henry
• Biggs Simon
• Cayre Olivier
• Lawson Simon
• Richez Alexandre

Classifications

• C09C3/12

  Treatment with organosilicon compounds {(C09C3/006 takes precedence)} · CPC title

• C08F2/44

  Polymerisation in the presence of compounding ingredients, e.g. plasticisers, dyestuffs, fillers · CPC title

• C09B69/106

  containing an azo dye · CPC title

• C01P2004/84

  one phase coated with the other · CPC title

• C08F220/04

  Acids; Metal salts or ammonium salts thereof · CPC title