Electrophoretic medium comprising a mixture of charge control agents

Patent metadata

Field	Value
Publication number	US-10040954-B2
Application number	US-201715707159-A
Country	US
Kind code	B2
Filing date	Sep 18, 2017
Priority date	May 28, 2015
Publication date	Aug 7, 2018
Grant date	Aug 7, 2018

Abstract

An electrophoretic medium including a mixture of charge control agents, for example quaternary amine salts of polyisobutylene combined with quaternary amine salts of polyesters. The described electrophoretic medium exhibits improved color saturation as compared to similar electrophoretic media having only one of the charge control agents.

First claim

What is claimed is:

1. An electrophoretic medium comprising:
a first set of charged particles;
a non-polar fluid;
a first charge control agent comprising a quaternary amine and a branched hydrocarbon tail of between 20 and 1000 carbon atoms in length; and
a second charge control agent comprising a quaternary amine and a linear polyisobutylene tail of between 12 and 500 carbon atoms in length,
wherein the branched hydrocarbon tail of the first charge control agent comprises a polyester or a poly secondary alcohol;
wherein the second charge control agent comprises a species of (CH 3 ) 3 C—[—CH 2 —C(CH 3 ) 2 —] n -L-NR 1 R 2 R 3+ X − , wherein L is a linking moiety, R 1 , R 2 and R 3 are independently alkyl having 1-4 carbon atoms, n is an integer from 2 to 40, and X − is a counter ion; and
wherein the electrophoretic medium exhibits color saturation for red and yellow color states in an electrophoretic display.

2. The electrophoretic medium of claim 1 , wherein n is between 5 and 20.

3. The electrophoretic medium of claim 1 , wherein L is a saturated or unsaturated alkylene or amide-alkylene chain of 2 to 6 carbon atoms.

4. The electrophoretic medium of claim 1 , wherein L is —CRR—CR═CR—CRR—, —CRR—CRR—CRR—, or —NHC(O)—CRR—CRR—CRR—, wherein the R's are independently hydrogen or an alkyl of 1-4 carbon atoms.

5. The electrophoretic medium of claim 1 , wherein L is —CH 2 —CH 2 —CH 2 —, —CH 2 —CH═CH—CH 2 —, —CH 2 —CH 2 —CH(CH 3 )—, —CH 2 —CH(CH 3 )—CH 2 —, or —NHC(O)—CH 2 —CH 2 —CH 2 —.

6. The electrophoretic medium of claim 1 , wherein L is —CH 2 —CH 2 —CH(CH 3 )—.

7. The electrophoretic medium of claim 1 , wherein R 1 , R 2 and R 3 are methyl.

8. The electrophoretic medium of claim 1 , wherein X − is F − , Cl − , Br − , I − , R′SO 3 − , R'SO 4 − or R′CO 3 − , wherein R′ is an alkyl of 1-4 carbon atoms or an aryl of 6 to 18 carbon atoms optionally substituted with an alkyl of 1-4 carbon atoms.

9. The electrophoretic medium of claim 1 , wherein X − is R'SO 3 − wherein R′ is a phenyl optionally substituted with an alkyl of 1-4 carbon atoms.

10. The electrophoretic medium of claim 1 , wherein L is —CH 2 —CH 2 —CH(CH 3 )—, R 1 , R 2 , and R 3 are methyl, and the counter ion is CH 3 SO 4 − .

11. The electrophoretic medium of claim 1 , wherein a concentration of the first charge control agent is 0.05% to 0.6% by weight of the electrophoretic medium.

12. The electrophoretic medium of claim 1 , wherein a concentration of the second charge control agent is 0.05% to 0.6% by weight of the electrophoretic medium.

13. The electrophoretic medium of claim 1 , wherein a total concentration of both the first and the second charge control agents is between 0.1% and 0.4% by weight of the electrophoretic medium.

14. The electrophoretic medium of claim 1 , wherein a ratio of the first charge control agent to the second charge control agent is from 5:1 to 1:5.

15. The electrophoretic medium of claim 14 , wherein the ratio of the first charge control agent to the second charge control agent is from 2:1 to 1:2.

16. The electrophoretic medium of claim 1 , further comprising a second set of charged particles dispersed in the non-polar fluid, wherein the first and the second sets of charged particles have opposite charges.

17. The electrophoretic medium of claim 16 , further comprising a third set of charged particles dispersed in the non-polar fluid, wherein the third set of charged particles is not white and not black.

18. The electrophoretic medium of claim 17 , wherein the third set of charged particles is yellow or red.

Assignees

• E Ink Corp
• E Ink California Llc

Inventors

• Du Hui
• Ritchey Joshua A
• Barykina-Tassa Olga Vladimirovna
• Sofiyev Vladimir

Classifications

• G02F2001/1678

  characterised by the composition or particle type · CPC title

• C09D5/448

  characterised by the additives used (C09D5/4403 - C09D5/4476, C09D5/4492 take precedence) · CPC title

• C08F8/44

  Preparation of metal salts or ammonium salts · CPC title

• C09D5/4407 Primary

  with polymers obtained by polymerisation reactions involving only carbon-to-carbon unsaturated bonds · CPC title

• G02F1/167 Primary

  by electrophoresis · CPC title