Electrophoretic particles and processes for the production thereof
First Claim
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1. A process for coating a pigment particles with silica, the process comprising:
- dispersing the pigment particles in a solution of a soluble silicate at a pH above about 8 and a temperature above about 60°
C.;
adding to the dispersion of the pigment particles both a solution of an acid and a solution of a soluble silicate while maintaining the temperature of the dispersion above about 60°
C., thereby causing deposition of silica on to the particles; and
lowering the pH of the dispersion below about 4, and thereafter separating the silica-coated particles from the liquid.
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Abstract
In electrophoretic media, it is advantageous to use pigment particles having about 1 to 15 per cent by weight of a polymer chemically bonded to, or cross-linked around, the pigment particles. The polymer desirably has a branched chain structure with side chains extending from a main chain. Charged or chargeable groups can be incorporated into the polymer or can be bonded to the particles separately from the polymer. The polymer-coated particles can be prepared by first attaching a polymerizable or polymerization-initiating group to the particle and then reacting the particle with one or more polymerizable monomers or oligomers.
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Citations
10 Claims
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1. A process for coating a pigment particles with silica, the process comprising:
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dispersing the pigment particles in a solution of a soluble silicate at a pH above about 8 and a temperature above about 60°
C.;adding to the dispersion of the pigment particles both a solution of an acid and a solution of a soluble silicate while maintaining the temperature of the dispersion above about 60°
C., thereby causing deposition of silica on to the particles; andlowering the pH of the dispersion below about 4, and thereafter separating the silica-coated particles from the liquid. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification