Electrophoretic medium comprising a mixture of charge control agents

• US 10,040,954 B2
• Filed: 09/18/2017
• Issued: 08/07/2018
• Est. Priority Date: 05/28/2015
• Status: Active Grant

• Current Assignee: E Ink Corporation (E Ink Holdings Incorporated)
• Original Assignee: E Ink California, LLC (E Ink Holdings Incorporated)
• Inventors: Du, Hui, Ritchey, Joshua A, Barykina-Tassa, Olga Vladimirovna, Sofiyev, Vladimir
• Primary Examiner(s): Ahvazi, Bijan
• Application Number:
  US15/707,159
• Publication Number:
  US 20180002543A1
• Time in Patent Office: 323 Days
• CPC Class Codes: C08F 10/10 Isobutene
• CPC Class Codes: C08F 8/44 Preparation of metal salts or ammonium salts
• CPC Class Codes: C09D 5/4407 with polymers obtained by polymerisation reactions involving only carbon-to-carbon unsaturated bonds
• CPC Class Codes: C09D 5/448 characterised by the additives used C09D5/4403 - C09D5/4476, C09D5/4492 take precedence
• CPC Class Codes: G02F 1/167 by electrophoresis
• CPC Class Codes: G02F 2001/1678 characterised by the composition or particle type

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.

Claims

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 (CH₃)₃C—

[—

CH₂—

C(CH₃)₂—

]_n-L-NR¹R²R³⁺ X⁻

, wherein L is a linking moiety, R¹, R² and R³ 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 —

CH₂—

CH₂—

CH₂—

, —

CH₂—

CH═

CH—

CH₂—

, —

CH₂—

CH₂—

CH(CH₃)—

, —

CH₂—

CH(CH₃)—

CH₂—

, or —

NHC(O)—

CH₂—

CH₂—

CH₂—

.

6. The electrophoretic medium of claim 1, wherein L is —

CH₂—

CH₂—

CH(CH₃)—

.

7. The electrophoretic medium of claim 1, wherein R¹, R² and R³ are methyl.

8. The electrophoretic medium of claim 1, wherein X⁻

is F⁻

, Cl⁻

, Br⁻

, I⁻

, R′

SO₃⁻

, R'"'"'SO₄⁻

or R′

CO₃⁻

, 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'"'"'SO₃⁻

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 —

CH₂—

CH₂—

CH(CH₃)—

, R¹, R², and R³ are methyl, and the counter ion is CH₃SO₄⁻

.

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.