Fine latex and seed method of making

Details Fine latex and seed method of making Fine latex and seed method of making

2000-06-28

2002-04-16

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...

C524S463000

Reexamination Certificate

active

06372838

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a very fine latex of dispersed particles in a highly fluorinated liquid solvent and a method of making which involves an initial seed particle formation step.
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 lns. 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 which 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.
SUMMARY OF THE INVENTION
Briefly, the present invention provides a two-step method of making a latex in a highly fluorinated liquid solvent, including a first step of polymerizing together a mixture of: i) 1-2 parts by weight of one or more non-fluorinated free-radically-polymerizable monomers, and ii) 1-9 parts by weight of one or more highly fluorinated macromers terminated at one or more sites with free-radically-polymerizable groups to form a dispersion of seed particles; and a second step of polymerizing together said seed particles with an additional 10-1,000 percent by weight, relative to the total weight of the seed particles, of one or more non-fluorinated free-radically-polymerizable monomers.
In another aspect, the present invention provides a fine latex comprising a highly fluorinated liquid solvent and dispersed particles having an average particle size of 250 nm or less and more preferably 200 nm or less.
In another aspect, the present invention provides an electrophoretic display comprising the non-film-forming latex herein, wherein said dispersed particles may be alternately a) removed from dispersion by application of an electric field, and b) redispersed by removal or reversal of said electric field.
What has not been described in the art, and is provided by the present invention, is a non-film-forming latex of hydrocarbon/fluorocarbon particles dispersed in a fluorocarbon solvent useful in an electrophoretic display having the small particle size and high conductance disclosed herein.
In this application:
“reacting dyes” means dyes which are covalently bound to the polymer;
“non-reacting dyes” means dyes which are not substantially incorporated into a polymer by polymerization, including every dye that is not a reacting dye;
“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”;
“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 which 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 latex of non-film-forming dye-bearing particles, which latex is useful in an electrophoretic display and can be used for repeated cycles of electrophoretically removing the particles of the latex from dispersion and returning them to dispersion.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention provides a two-step method of making a latex in a highly fluorinated liquid solvent, including a first step of polymerizing together a mixture of: i) 1-2 parts by weight of one or more non-fluorinated free-radically-polymerizable monomers, and ii) 1-9 parts by weight of one or more highly fluorinated macromers terminated at one or more sites with free-radically-polymerizable groups to form a dispersion of seed particles; and a second step of polymerizing together said seed particles with an additional 10-1,000 percent by weight, relative to the total weight of the seed particles, of one or more non-fluorinated free-radically-polymerizable monomers.
The latex according to the present invention is preferably a non-film-forming latex comprising a highly fluorinated liquid solvent and dispersed particles comprising a polymer comprising units according to formula I:
wherein each (fcp) is independently selected from highly fluorinated polymer chains which may terminate at the —A=group of another unit according to formula I so as to form a polymer molecule that contains two or more A groups linked by (fcp) groups; wherein each Q is independently selected from —H and straight or branched non-fluorinated polymer chains (hcp), wherein no more than one Q of each unit according to formula I may be —H, and wherein each (hcp) may terminate at the —A=group of another unit according to formula I so as to form a polymer molecule that contains two or more A groups linked by (hcp) groups. Preferably some of the (hcp) groups are branched due to the inclusion of polyfunctional crosslinkers. Preferably the particles contain reacting or non-reacting dyes. Preferably the particles additionally contain charging agents.
Preferably the —A=group is the moiety according to formula II:
wherein each R
1
is independently selected from —H, —CH
3
, —F and —Cl; wherein each —R
6
— is independently selected from divalent substituted or unsubstituted C1-C10 alkylene, cyclic alkylene, or arylene groups. The (fcp) moieties may terminate at A groups at one or both ends. The (hcp) moieties may terminate at A groups at one or both ends, or at more than two ends if the (hcp) moiety is branched due to the inclusion of a crosslinker. Thus it is contemplated that a single molecule may contain numerous A groups linked by (hcp) groups.
The fluorocarbon polymer (fcp) portions are preferably highly fluorinated macromers. Preferred macromers include macromers of monomers selected from fluoroalkyl acrylates, fluoroalkyl methacrylates, fluoroalkyl haloacrylates and fluoroalkyl halomethacrylates. Preferably these macromers are fluoropolymer chains comprising units according to formula III:
where each R
1
is independently selected from —H, —CH
3
, —F and —Cl; each n is independently selected from integers from 1 to 10; and each R
2
is selected independently from: highly fluorinated substituted or unsubstituted C1-C20 alkyl, cyclic alkyl, or aryl groups; —N(R
3
)

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