# US 9,428,649 B2 · Electrophoretic dispersion

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- Number: US 9,428,649 B2
- Document ID: US9428649B2
- Status: Granted
- Kind: B2
- Application number: 13/287,704
- Filed: 2011-11-02
- Published: 2012-05-10
- Granted: 2016-08-30
- Earliest claimed: 2010-11-05
- Assignees: E Ink California, LLC
- Applicants: Yu Li; Hui Du; Yayong Liu; Haiyan Gu; HongMei Zang
- Inventors: Yu Li; Hui Du; Yayong Liu; Haiyan Gu; HongMei Zang
- Web page: https://patentgrep.com/patent/US9428649B2

## CPC

- C09C 1/3676: {Treatment with macro-molecular organic compounds}
- C08F 292/00: Macromolecular compounds obtained by polymerising monomers on to inorganic materials
- C09C 1/3669: {Treatment with low-molecular organic compounds}
- C09C 1/3692: {Combinations of treatments provided for in groups C09C1/3615 - C09C1/3684}
- C09C 1/56: Treatment of carbon black {; Purification}
- G02F 1/167: by electrophoresis
- C08F 2438/03: Use of a di- or tri-thiocarbonylthio compound, e.g. di- or tri-thioester, di- or tri-thiocarbamate, or a xanthate as chain transfer agent, e.g . Reversible Addition Fragmentation chain Transfer [RAFT] or Macromolecular Design via Interchange of Xanthates [MADIX]
- G02F 2001/1678: {characterised by the composition or particle type}
- C09C: TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES (treatment of materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone C04B14/00, C04B18/00, C04B20/00); PREPARATION OF CARBON BLACK {; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS}
- C08F: MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS

## Abstract

The present invention is directed to an electrophoretic dispersion comprising pigment particles dispersed in a solvent or solvent mixture, wherein said pigment particles comprises at least one polymer chain comprising a terminal thiocarbonylthio group, attached to the particle surface. The invention also relates to pigment particles suitable for use in an electrophoretic dispersion and methods for their preparation through a RAFT polymerization technique.

## Claims

### Claim 1

An electrophoretic dispersion, comprising polymer coated charged pigment particles dispersed in a hydrocarbon solvent, wherein said polymer coated charged pigment particle comprises polymer chains attached to the particle surface and said polymer chain comprises:
(a) an outer polymer layer formed from monomers consisting of first monomers, the outer polymer layer is compatible with the hydrocarbon solvent,
(b) an inner polymer layer formed from monomers consisting of second monomers each comprising a charged functional group to provide charges to the pigment particles, and different from the first monomers, and
(c) a terminal thiocarbonylthio group attached to the outer polymer layer.

### Claim 2 (depends on 1)

The dispersion of claim 1, wherein said first monomer is selected from the group consisting of: lauryl acrylate, lauryl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, hexyl acrylate, hexyl methacrylate, n-octyl acrylate, n-octyl methacrylate, n-octadecyl acrylate, and n-octadecyl methacrylate.

### Claim 3 (depends on 1)

The dispersion of claim 1, wherein said second monomer is selected from the group consisting of: vinyl pyridine, 2-hydoxyethyl acrylate, 2-hydroxyethyl methacrylate, dimethylaminoethyl methacrylate, vinylb enzylaminoethylaminopropyl-trimethoxysilane, acrylic acid, methacrylic acid, and vinyl phosphoric acid.

### Claim 4 (depends on 1)

The dispersion of claim 1, wherein said functional group is amine, hydroxy, carboxylate, sulfonate, phosphonate, or phosphate.

### Claim 5 (depends on 1)

The dispersion of claim 1, wherein said charged pigment particles are of the same color.

### Claim 6 (depends on 1)

The dispersion of claim 1, further comprising second pigment particles having a contrasting color from the charged pigment particles of claim 1.

### Claim 7 (depends on 6)

The dispersion of claim 6, wherein the second pigment particle comprises at least one polymer chain comprising a terminal thiocarbonylthio group, attached to the particle surface.