Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-04-18
2003-05-13
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S319000
Reexamination Certificate
active
06562889
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a stable, non-film-forming dispersion of particles in a liquid, non-polar solvent, preferably a fluorinated solvent, that includes a dispersant selected from the group consisting of highly fluorinated polyethers, having an atomic ratio of carbon to oxygen of between 2 and 4 inclusive, and bearing at least one polar functional group.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 5,397,669 (Minnesota Mining & Manufacturing) discloses liquid toners for use with perfluorinated solvents. The patent discloses that the compositions are film-forming, allowing them to function properly as toners. ('669 at p. 8 Ins. 3-5). The '669 patent discloses pigment particles bound to a polymer that is highly fluorinated in specific parts, and that includes monomer units having groups that bind polyvalent metal ions. The '669 patent also discloses pigment particles bound to a polymer that is highly fluorinated in its entirety, without requiring monomers having groups that bind polyvalent metal ions.
U.S. Pat. No. 5,530,053 (Minnesota Mining & Manufacturing) also discloses liquid toners for use with perfluorinated solvents. The toners of '053 are polymeric dyes that are highly fluorinated in specified parts and have attached chromophoric groups. The '053 patent discloses that the toner can form a latex in perfluorinated solvent, where the toner takes a core-shell form with the hydrocarbon portion in the core and the fluorocarbon portion in the shell.
U.S. Pat. No. 5,919,293 (Hewlett-Packard) discloses ink jet inks composed of colorants in Fluorinert™ solvents (Minnesota Mining & Manufacturing Co., St. Paul, Minn.), which are perfluorinated or nearly-perfluorinated alkanes.
U.S. Pat. No. 5,573,711 (Copytele) discloses the use of certain polymeric fluorosurfactants in electrophoretic image displays. The '711 patent teaches the use of Fluorad™ surfactants (Minnesota Mining & Manufacturing Co., St. Paul, Minn.), including FC-171, having the structure R
f
—SO
2
N(C
2
H
5
)(CH
3
CH
3
O)
n
CH
3
, where n is about 8 and R
f
is a fluorocarbon portion.
U.S. Pat. No. 4,356,291 (Du Pont) discloses hexafluoropropylene oxide polymers terminating in a variety of end groups and methods of making same.
Co-assigned patent applications U.S. Ser. No. 09/604,894, 09/604,889 and 09/605,211 are currently pending. The disclosures of those applications are incorporated herein by reference.
SUMMARY OF THE INVENTION
Briefly, the present invention provides a stable, non-film-forming dispersion comprising a) dispersed particles, b) a liquid, non-polar solvent, and c) a dispersant selected from the group consisting of highly fluorinated polyethers, having an atomic ratio of carbon to oxygen of between 2 and 4 inclusive, and bearing at least one polar functional group which is preferably an ionizable group such as a carboxylic acid group.
What has not been described in the art, and is provided by the present invention, is the highly stable dispersion achieved by use of the dispersant according to the present invention which is particularly useful in an electrophoretic display device.
In this application:
“highly fluorinated”, means containing fluorine in an amount of 40 wt % or more, but preferably 50 wt % or more and more preferably 60 wt % or more, and refers to the fluorine content of a population of chemical moieties where applicable, such as in the term, “one or more highly fluorinated macromers”;
“non-fluorinated”, means containing substantially no fluorine, i.e. containing fluorine in an amount of 5 wt % or less, but preferably 1 wt % or less and most preferably 0 wt %, and refers to the fluorine content of a population of chemical moieties where applicable, such as in the term, “one or more non-fluorinated free-radically-polymerizable monomers”;
“ionizable functional group”, means a functional group that may ionize in water, such as carboxyl groups, acidic sulfur-containing groups such as —SO
3
H and —SO
2
H, acidic phosphorus-containing groups such as —PO
3
H
2
, and the like;
“hydrogen bonding functional group”, means a functional group having a hydrogen atom available for hydrogen bonding, such as functional groups containing —OH, —NH or —SH moieties, including hydroxyl groups, amino groups, and the like;
“polar functional group”, means an ionizable functional group or a hydrogen bonding functional group, preferably being an ionizable functional group and most preferably being carboxyl;
“C(number)” refers to a chemical moiety containing the indicated number of carbon atoms;
“(meth)acrylate” means acrylate and methacrylate; and
“substituted” means, for a chemical species, substituted by conventional substituents that do not interfere with the desired product or process, e.g., substituents can be alkyl, alkoxy, aryl, phenyl, halo (F, Cl, Br, I), cyano, etc.
It is an advantage of the present invention to provide a highly stable dispersion of pigment or dyed latex particles that is particularly useful in an electrophoretic display device.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention provides a stable, non-film-forming dispersion comprising a) dispersed particles, b) a liquid, non-polar solvent, and c) a dispersant selected from the group consisting of highly fluorinated polyethers, having an atomic ratio of carbon to oxygen of between 2 and 4 inclusive, and bearing at least one polar functional group which is preferably an ionizable group such as a carboxylic acid group.
The dispersed particles according to the present invention may be any suitable particles. Preferably the particles have an average diameter of 1000 nm or less, more preferably 350 nm or less, more preferably 300 nm or less, more preferably 250 nm or less, and most preferably 200 nm or less. Preferably the particles are organic. Preferably the particles are non-fluorinated. In one preferred embodiment, the dispersed particles are particles of pigment material. Preferably the pigment particles consist of pigment crystalite aggregates. These aggregates are preferably encapsulated, either partially or fully, by dispersant that is anchored or adsorbed to the particle surface. In another preferred embodiment, the dispersed particles are latex particles, more preferably (meth)acrylic latex particles. The latex particles may contain dyes that may be dispersed in the latex particles or covalently bound. The latex particles may be homogeneous or may have a core-shell structure. The latex particles are preferably encapsulated, either partially or fully, by dispersant that is anchored or adsorbed to the particle surface.
The solvent may be any suitable non-polar solvent that is liquid at room temperature. Preferably, the solvent is a hydrocarbon solvent, more preferably a fluorinated hydrocarbon solvent. More preferably, the solvent is a highly fluorinated solvent, especially a branched or unbranched, cyclic or non-cyclic fluoroalkane. Most preferably the solvent is perfluorinated. Preferred solvents include FLUORINERT™ fluorinated solvents available from 3M Company, St. Paul, Minn. Two especially preferred solvents are FLUORINERT FC-75, a perfluorinated C
8
solvent, CAS No. 86508-42-1, and FLUORINERT FC-84, a perfluorinated C
7
solvent, CAS No. 86508-42-1. The solvent preferably has a dielectric constant of 3.0 or less.
The density of particles in solvent (solids content) may be any level at which the dispersion is stable and does not significantly coagulate. For use of the dispersion in an electrophoretic display, the solids content may be any level that allows proper functioning over repeated cycles. Preferably, the solids content is less than 10 wt %, more preferably less than 5 wt %, and most preferably less than 2 wt %.
The dispersant is a highly fluorinated polyether having an atomic ratio of carbon to oxygen of between 2 and 4 inclusive, preferably about 3, and bearing at least one polar functional group. Preferably the dispersant is perfluorinated in its backbone. Preferred dispersants are described by Formula I:
n—C
3
F
7
O—(CF(CF
3
)—CF
2
O)
n
—CF(CF
3
)—C
Dahl Philip Y.
Michl Paul R.
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