Pigments for electrophoretic displays

Patent metadata

Field	Value
Publication number	US-11613654-B2
Application number	US-202117548863-A
Country	US
Kind code	B2
Filing date	Dec 13, 2021
Priority date	Dec 30, 2017
Publication date	Mar 28, 2023
Grant date	Mar 28, 2023

Abstract

A polysiloxane-substituted quinacridone pigment is produced by a quinacridone pigment with an epoxy-terminated polysiloxane under conditions effective to cause the epoxy group on the polysiloxane to react with, and bond the polysiloxane to, the quinacridone pigment. The quinacridone pigment thus produced has the polysiloxane grouping bonded to one of the quinacridone nitrogen atoms via a hydrocarbon linking group, which bears a hydroxyl group on a carbon atom α or β to the quinacridone nitrogen atom. These quinacridone pigments are useful in electrophoretic displays.

First claim

I claim:

1. A process for producing a quinacridone pigment having a polysiloxane-substituted quinacridone on the pigment surface, which process comprises adding an epoxy-terminated polysiloxane into a dispersion of quinacridone pigment in an organic solvent causing the epoxy group of the epoxy-terminated polysiloxane to react with a nitrogen atom of the quinacridone pigment forming the polysiloxane-substituted quinacridone of the formula

where L is a hydrocarbon linking group or a 3-alkoxypropyl linking group, Sil is a polysiloxane grouping and the broken line indicates that the hydroxyl substituent is attached to a carbon atom β to the quinacridone nitrogen atom,
wherein R is hydrogen, C 1 -C 3 alkyl group, or a halogen.

2. The process of claim 1 wherein the process for producing the quinacridone pigment involves a single reaction step.

3. The process of claim 1 wherein the polysiloxane is a polydialkylsiloxane.

4. The process of claim 1 wherein the polysiloxane has a molecular weight in the range of about 3,000 to about 30,000.

5. The process of claim 1 wherein the epoxy group of the polysiloxane forms part of an epoxyalkyl ether grouping or an epoxycycloalkyl grouping.

6. The process of claim 1 wherein the polysiloxane is of the formula:

wherein n is integer.

7. The process of claim 1 wherein the polysiloxane is of the formula:

wherein n and m are integers.

8. The process of claim 1 wherein the quinacridone pigment used is of the formula:

wherein each R independently is a hydrogen, C 1 -C 3 alkyl group, or a halogen.

9. The process of claim 8 wherein both R groups are methyl groups.

10. An electrophoretic medium comprising particles of a pigment, prepared by a process according to claim 1 , dispersed in a fluid.

11. The electrophoretic medium of claim 10 wherein the fluid comprises a hydrocarbon.

Assignees

• E Ink Corp

Inventors

• Yezek Lee

Classifications

• C09B69/008

  Dyes containing a substituent, which contains a silicium atom · CPC title

• G02F1/167

  by electrophoresis · CPC title

• C08L83/08

  containing silicon bound to organic groups containing atoms other than carbon, hydrogen and oxygen · CPC title

• C09B68/41

  Polymers attached to the pigment surface (C09B68/444, C09B68/446 take precedence) · CPC title

• G02F1/1675

  Constructional details · CPC title