US 3542682 A
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United States Patent Ofice 3,542,682 Patented Nov. 24, 1970 US. Cl. 252-621 9 Claims ABSTRACT OF THE DISCLOSURE A positive-working liquid toner composition comprising in an electrically insulating carrier liquid, a pigment, e.g. carbon black, a metal soap and a dispersing agent comprising an alkylated polymer of a heterocyclic N- vinyl monomer.
The present invention relates to a liquid toner composition for use in electrostatic printing processes; more particularly, the present invention relates to a positiveworking liquid toner system comprising in addition to an electrically conductive carrier liquid, a pigment, and a metal soap, a dispersant comprising an alkylated polymer of a heterocyclic N-vinyl monomer.
Although a great number of liquid toner compositions or systems for use in electrostatic printing processes have been disclosed in the literature, many of such compositions or systems have not been found completely satisfactory in view of their inability to remain in suspension adequately or to give copies which have uniform fill and are free from bleeding or similar streaking characteristics.
With respect to electrophotographic processes in general, it is known that various liquid developing agents or toners are capable of producing electrophotographic images on photoconductive surfaces in various colors. Thus, for example, if the photoconductive surface comprises zinc oxide, which substance is not capable of supporting a positive electrostatic charge, it is necessary for the developer particles suspended in a liquid carrier to assume positive polarity with respect to the latent electrostatic image formed on the zinc oxide surface. This is because the latent image formed on the zinc oxide surface can be formed essentially by a negative electrostatic charge only. Accordingly, there has been a great desire for the production of a positive-working electrostatic developer or toner composition or system which the positive-Working polarity characteristics so as to effect the necessary development of the latent image on the zinc oxide or similar surface yet will be free of the inherent deficiencies of non-uniformity and bleeding and streaking characteristics associated with the employment of previously utilized materials.
It has now been found in accordance with the present invention that excellent, positive-working electrostatic toners free from the disadvantages and deficiencies of prior art materials, i.e. their ability to remain in suspension and give copies having uniform fill and free from bleeding and streaking characteristics are provided by a system comprising in an electrically insulating carrier liquid, a coloring agent, a metal soap, and a dispersing agent comprising an alkylated polymer of a heterocyclic N-vinyl monomer.
Accordingly, it is a principal object of the present invention to provide a positive-working electrostatic toner or developer free from the inherent deficiencies and disadvantages of prior art compositions or systems.
A further object of the present invention comprises a positive-working electrostatic toner containing in an electrically insulating carrier liquid a coloring agent, a metal soap, and a dispersing agent.
A still further object of the present invention comprises a new and improved liquid electrostatic toner having an improved ability to remain in suspension and yielding uniform prints and copies free from bleeding and streaking characteristics comprising in an electrically insulating carrier liquid a colorng agent, e.g. carbon black, a metal soap and a dispersing agent comprising an alkylated polymer of a heterocyclic 'N-vinyl monomer.
Still further objects and advantages of the novel liquid toner systems of the present invention will become more apparent from the following more detailed description thereof.
The above objects and advantages of the present invention are provided by a liquid positive-working electrostatic toner comprising an electrically insulating carrier liquid containing a coloring agent, e.g. carbon black, a metal-organic salt or soap and a dispersing agent comprising an alkylated polymer of a heterocyclic N-vinyl monomer.
Thus, while various metal-organic salts have been described in the preparation of liquid toners as charge agents or drying agents, e.g. US. Pat. 3,259,581, it has been discovered in accordance with the present invention that the use of certain metal salts or soaps in combination with a dispersant comprising an alkylated polymer of a heterocyclic N-vinyl monomer in an electrically insulating carrier liquid containing a dispersed pigment or dye that a liquid electrostatic toner is produced, which toner does not suffer from an inability to remain in suspension or a failure to provide a uniform fill and a copy free from bleeding and streaking characteristics such as associated with prior art systems. In this respect, it has now been discovered in accordance with the present invention that certain liquid toner systems containing certain metal soaps even in amounts less than 1% by weight are extremely efiective positive-Working toner systems when a dispersant is incorporated within the system comprising an alkylated polymer of a heterocyclic N-vinyl monomer. It is pointed out that the use of such dispersant alone in a liquid toner system absent the employment of the metal soap provides a negative-working electrostatic toner, and accordingly, it is surprising that an exceptionally positive-working toner eliminating the inherent deficiencies and disadvantages of the prior art is provided by the employment of the combination of the particular metal soaps and dispersing agents in accordance with the present invention.
Thus, in accordance with the present invention the liquid toner composition or system comprises as a base iluid any of the conventional electrically insulating carrier liquids generally employed in liquid developer and toner compositions. Such electrically insulating carrier liquids generally comprise hydrocarbon solvent materials having the necessary di-electric constant, e.g. less than 3 and volume resistivity, e.g. in excess of 10 ohm centimeter so as to be acceptably employed in the electrostatic reproduction process. Thus, for example the solvent can comprise various hydrocarbon solvents, e.g. toluene, kerosene and mixtures thereof as well as various commercial petroleum and hydrocarbon solvents, e.g. Isopar having a boiling range of from ISO-182 C. or Solvesso having a boiling range of from -174 0., Shell X4 having a boiling range of from 58-70 C., or Shell X55 having a boiling range of from 58140 C., can be effectively employed as the electrically insulating carrier liquid of the liquid toner system.
The coloring agent or pigment employed in accordance with the liquid electrostatic toner of the present invention can again comprise any of those conventionally employed in such conventional electrostatic toners. Thus, for example, the coloring agent or pigment can comprise carbon black, channel black, alkali blue, nigrosine dyes,
3 etc. In this respect, any conventional coloring agent or pigment which is dispersible in the carrier liquid can be employed in the liquid electrostatic toner of the present invention.
The pigment, e.g. carbon black suspended in the carrier liquid as the toner is employed in that amount necessary when attracted to the negative electrostatic lmage through the positive-working of the metal soap and dispersing agent in the toner system to be deposited on the image areas only and provide the desired positive print or copy. Generally, the pigment comprises from about .001% to about of the toner system or composition. Of course, slightly lesser or greater amounts can be employed where desired for particular purposes.
Since the pigments would by themselves in the insulating carrier liquid assume fully or partially negative polarity in respect to the negative electrostatic latent image, such pigments would tend to deposit onto the non-image areas to a greater or lesser degree or would deposit both onto the image and non-image areas. For this reason, therefore, it is necessary to modify the characteristics of the pigmented insulated carrier liquid so as to provide a positive-working system wherein the pigment particles. are deposited only onto the image areas of the negative electrostatic latent image by assuming a positive electrostatic charge. This is accomplished in accordance with the present invention by including within the pigmented electrically insulated carrier liquid both a metal soap which tends to be absorbed on the pigment particle surfaces, and an alkylated polymer of a heterocyclic N-vinyl monomer, which as a dispersing agent provides a uniform dispersion of the toner so as to allow the production of a copy having a uniform fill and free from bleeding or streaking characteristics not heretofore attainable by prior art systems. The metal soaps or salts employed in accordance with the present invention are the hydrocarbon solvent soluble salts of the metals cerium, iron, nickel, cobalt, zirconium, cadmium, lithium, magnesium, manganese, calcium, barium, strontium, chromium and indium, the salts or soaps of such metals in the liquid toner system of the present invention providing copies having no tendency to bleed or streak. The use of salts of lead, zinc or antimony, for example, tend to give relatively poor copies. Accordingly, the salts or soaps of these metals are not preferably employed in accordance with the present invention.
As indicated previously, the salts or soaps generally employed in accordance with the present invention are those which are soluble in the carrier liquid which is generally a hydrocarbon fraction. In this respect, suitable soaps include the metal linoleates, naphthenates, resinates, palmetates, stearates, oleates, octoates, etc.
In accordance with the present invention, alkylated polymers of heterocyclic N-vinyl monomers are utilized as the dispersants. These dispersants are those prepared by alkylation of a homopolymer or copolymer of a heterocyclic N-vinyl monomer, preferably an N-vinyl lactam monomer and most preferably an N-vinyl pyrrolidone monomer with an alpha-olefin containing from 2 carbon atoms to 2000 carbon atoms, preferably in the range of from 2 to 200 carbon atoms, and most preferably in the range of from 8 to 42 carbon atoms, said alkylation process being more fully described in General Aniline & Film Corporations co-pending patent application, Ser. No. 508,547, filed Nov. 18, 1965 and now U.S. Pat. No. 3,417,054, or by simultaneously polymerizing and alkylating a mixture containing a heterocyclic N-vinyl monomer, a monoethylenically unsaturated polymerizable monomer and an alpha-olefin containing from 2 carbon atoms to 2000 carbon atoms or a mixture of the same or two different heterocyclic N-vinyl monomers and an alphaolefin containing from 2 carbon atoms to 2000 carbon atoms, said simultaneous polymerization and alkylation process being more fully described in General Aniline &
4 Film Corporations co-pending patent application, Ser. No. 525,374, filed Feb. 7, 1966 and now U.S. Pat. No. 3,423,367.
As examples of heterocyclic N-vinyl monomers which contain a carbonyl function adjacent to the nitrogen in the heterocyclic moiety, whose alkylated polymer derivatives produced as described in said applications, Ser. Nos. 508,547 and 525,374, may be employed in practicing the present invention, that may be mentioned are N-vinyl succinimide, N-vinyl diglycolylimide, N-vinyl glutarimide, N-vinyl-3-morpholinone, N-vinyl-S-methyl 3-morpholinone, N-vinyl-5-ethyl-3-morpholinone, N-vinyl oxazolidone, etc., and N-vinyl ring-oxygenated lactams as disclosed in U.S. Pat. 3,231,548, and especially the N-vinyl 5-, 6- and 7-membered lactams, particularly N- vinyl pyrrolidone, characterized by the following formula:
wherein R and R are selected from the group consisting of hydrogen, methyl and ethyl, n is an integer of from 1 to 3, and m represents the average molecular weight as determined by relative viscosity measurements which are designated as K values.
The viscosity coefiicient, K, which is fully described in Modern Plastics, vol. 23, No. 3, pp. 157-61, 212, 214, 216 and 218 (1945) is calculated as follows:
log 71" l 751(0 where c is the concentration in grams per ml. of polymer in solution and the 1 is the viscosity of the solution compared to solvent.
There may also be used the alkylated polymers of comparable monomers of N-vinyl 5-, 6- and 7-membered thiolactams, N-acryloylpyrrolidone, -piperidone and -caprolactam; N-acryloyl 5 methyl-pyrrolidone, N-acryloyl-6- methyl piperidone and N-acryloyl-7-methyl caprolactam and their corresponding 5-, 6- and 7-ethyl derivatives; N-acryloxy-methyl-pyrrolidone, -piperidone and -caprolactam; N-methacryloxy ethyl-pyrrolidone, -piperidione and -caprolactam; N-methacryloxy-methyl-5-methyl pyrrolidone, -6-methyl-piperidone and -7-methyl-caprolactam; N-methacrylamido-methyh, N-methacrylamidoethyl-, N-methacrylamidopropyland N-(N-phenylacrylamidopropyl)-pyrrolidones, -piperidones and caprolactams.
The homopolymers of the N-vinyl lactams characterized by the foregoing formula (whose alkylated derivatives obtained, for example, as described in said application Ser. No. 508,547, are suitable for use in practicing the present invention) are readily obtained by homopolymerizing N-vinyl pyrrolidone; N-vinyl-5-methyl pyrrolidone; N-vinyl-S-ethyl pyrrolidone; N-vinyl-5,5-dimethyl pyrrolidone; N-vinyl-5,5-diethyl pyrrolidone and N-vinyl-S-methyl-S-ethyl pyrrolidone; N-vinyl piperidone; N-vinyl-6-methyl piperidone; N-vinyl-6-ethyl piperidone; N-vinyl-6,6-dimethyl piperidone; N-vinyl-6,6-diethyl piperidone and N-vinyl-6-methyl-6-ethyl piperidone; N- vinyl caprolactam, N-vinyl-7-methyl caprolactam; N-vinyl- 7,7-dimethyl caprolactam; N-vinyl-7-ethyl caprolactam; N-vinyl-7,7-diethyl caprolactam and N-vinyl-7-methyl-7- ethyl caprolactam.
For the purpose of the present invention I employ alkylated derivatives of homopolymers of heterocyclic N- vinyl monomers having a K value from about 10 to 140, preferably from about 30 to 100. These homopolymers are readily obtained by conventional homopolymerization procedures of the foregoing heterocyclic N-vinyl monomers described in U.S. Pats. 2,265,450; 2,3l7,804; 2,335,- 454 and many others too numerous to mention in which working examples are given.
Copolymers obtained by copolymerizing to 99 mole percent of the foregoing heterocyclic N-vinyl monomers with 1 to 95 mole percent of a monoethylenically unsaturated polymerizable monomer and having a K value from about to 140 are readily alkylated in accordance with the present invention to yield products having solubility characteristics dictated by the end use.
The various monoethylenically unsaturated polymerizable monomers, which are copolymerized with any one of the aforementioned heterocyclic N-vinyl monomers in the conventional manner and which will yield copolymers that are readily alkylated in accordance with said application, Ser. No. 508,547, to produce alkylated copolymers suitable for use in practicing the present invention, include vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl lactate, vinyl caproate, vinyl caprylate, vinyl oleate and vinyl stearate; acrylonitrile; vinyl ketones; vinyl cyclohexane; styrene; 2-vinyl pyridine, 4-vinyl pyridine; acrylic acid, acrylate ester monomers of the formula:
CH =CHCOOR wherein R represents either a straight or branched alkyl of from 1 to 18 carbon atoms or an alkoxyalkyl in which the total number of carbon atoms in the alkyl groups range from 3 to 6.
As examples of such acrylate esters the following are illustrative: methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, Z-methyl-l-butyl, 3-methyl-1-butyl, 2-ethyll-butyl, amyl, 3-pentyl, Z-methyl-l-pentyl, 4-methyl-2- pentyl, hexyl, 2-ethyl-hexyl, heptyl, 2-heptyl, octyl, 2-octyl, nonyl, 5-ethyl-2-nonyl, decyl, 2-methyl-7-ethyl-4-undecyl, dodecyl, tetradecyl, hexadecyl, octadecyl, 2-methoxyethyl, 2-ethoxyethyl and 2-butoxyethyl acrylate; methacrylic monomers such as methacrylic acid, methyl methacrylate, cyclohexyl methacrylate, isobutyl methacrylate, isoamyl methacrylate, fl-methoxy ethyl methacrylate and a-(o-chlorophenyl) ethyl methacrylate, B- phenoxy ethyl methacrylate, a-phenyl ethyl methacrylate, phenyl methacrylate, o-cresol methacrylate, p-cyclohexylphenyl methacrylate, 2-nitro-2-methyl propyl methacrylate, diethylamino-ethylmethacrylate, ethylidene acetate methacrylate and glycidyl methacrylate, including esters of halo acrylic acids, such as methyl-2-chloro-acrylate, ethyl-a-chloro-acrylate, phenyl-u-chloroacrylate, tar-ethylacrylic acid; methacrylonitrile; N-alkyl and N-aryl substituted acrylamides such as N-methyl acrylamide, N- ethyl acrylamide, N-propyl acrylamide, N-n-butyl acrylamide, N-n-dodecyl acrylamide, N-n-octadecyl acrylamide, N,N-dimethyl acrylamide, N,N-diethyl acrylamide, N-N-di-n-butyl acrylamide, N-N-di-isobutyl acrylamide, N-cyclohexyl acrylamide, N-N-dicyclohexyl acrylamide, N-phenyl acrylamide, N-p-nitro-phenyl acrylamide, N-anaphthyl acrylamide, N-fi-naphthyl acrylamide, N-methyl-N-phenyl acrylamide, N,N-diphenyl acrylamide, N- benzyl acrylamide, N,N-di-benzyl acrylamide; and grafted monomers of the type disclosed in US. Pats. 3,029,219; 3,035,009; 2,036,033 and the like.
A mixture consisting of from 5 to 99 mole percent of any one of the foregoing heterocyclic N-vinyl monomers and from 1 to 95 mole percent of a different heterocyclic N-vinyl monomers, such as for example, N-vinyl lactam with either N-vinyl succinimide, N-vinyl-3-morpholinone, and the like, may also be copolymerized and the resulting copolymer alkylated for use in the present invention.
From numerous experiments connected with the present invention, it has been found that the configuration of the foregoing monoethylenically unsaturated monomers, and numerous others, is immaterial since they all copolymerize in the aforementioned proportions with the heterocyclic N-vinyl monomers and yield copolymers which are soluble in the organic solvent or mixture thereof and which are readily alkylated.
With regard to the u-olefins employed for producing the alkylated polymers used in practicing this invention, it is to be noted at the outset that any a-olefins having a molecular weight from about 28 to as high as about 28,000, may be employed as the alkylating agent for the alkylated polymers of the various heterocyclic N-vinyl monomers. As examples of such a-olefins, the following are illustrative: ethylene, propylene, l-butene, l-pentene, 2-ethyl-1-butene, 2-methyl-l-pentene, l-hexane, 5-methyl-l-hexene, 2-methyl-l-pentene, 3-ethyl-1-pentene, l-heptene, l-octene, l-nonene, 2-ethyl-l-hexene, l-decone, 1- dodecone, l-tetradecene, l-hexadecene, l-heptadecene, loctadecene, l-nonadecene, l-eicosene, l-docosene, l-tetracosene, l-pentacosene and polybutenes of molecular weight of 400 to 2500 may be employed.
While linear u-olefins are preferred because of their commercial availability, numerous isomers of a-olefins ranging from l-pentene to l-pentacosene as well as polybutenes may also be employed in the alkylation reaction. The only requirement in such case is that the isomer contained in ethylenic unsaturation in the a-position thereof.
Instead of employing any of the foregoing individual a-olefins, a mixture of commercially available linear ocolefins produced by cracking petroleum wax or by polymerizing lower olefins may also be used as the alkylating agent. Alpha-olefins in the carbon range of from C -C C -C C C11; C -C and C -C are commercially available and may be used. A mixture of a-olefins containing from 65 to percent of a-olefins of from C to C carbon atoms having an average molecular weight of 366 is also commercially available and such mixture is employed in the alkylation reaction.
The quantity of the alkylated polymers of the heterocyclic N-monomonomers employed for a given amount of pigment or coloring agent is not critical in accordance with the present invention, such dispersing agent need only be employed in that amount sufficient to provide a stable suspension or dispersion of the pigment. Generally, the dispersing agent is employed in the range of 0.01 to 2-3 times the weight of the pigment, and preferably within the range of 1 to parts per 100 parts of the pigment employed.
The dispersing agents employed in accordance with the present invention act to provide a stable, uniform dispersion of the pigment particles within the liquid electrostatic toner system so as to provide a copy having a uni form fill and free from bleeding or streaking characteristics. It is theorized that the salts or soaps employed im part strong, electrical charges to the toner or pigment particles by being absorbed on the particle surfaces thus causing the particles to be drawn to the sensitized paper with suflicient attraction to firmly fix the particles on the image. Since excessive amounts of the metal salts or soaps tend to result in weak images, a fact possibly explained in that the organic salt or soap molecules themselves are drawn to the paper surface and thus satisfy the electrical charge of the area without imparting a color at that point, it is generally disadvantageous to employ more than about 3% by weight of the metal salts or soaps. However, in contradistinction to that set forth in US. Pat. 3,259,581 wherein it is disclosed at least 1% of metal based on the pigment is required it has been found in accordance with the present invention that the salt concentration can be considerably lower than this prior art recognized lower limit. In this respect, in accordance with the present invention, when employing a dispersing agent comprising an alkylated polymer of a heterocyclic N-vinyl monomer it is possible to employ a metal soap in an amount ranging from about 0.5% to about 3% by weight. Again, the beneficial results associated with the present invention, i.e. the production of copies having uniform fill and free from bleeding or streaking characteristics is associated with the combined employment of the metal soap or salt and the dispersing agent comprising the alkylated polymer of a heterocyclic N-vinyl monomer.
In accordance with the present invention, the manner by which the dispersion is produced is in no way critical. In this respect, it has been found that 3-roll mill, ball mills, colloid mills, high speed shear mixers, etc., are all applicable in the production of the dispersions employed in the liquid electrostatic toner systems of the present invention. In addition, as used throughout the instant specification and in the appending claims the expression coloring agent is meant to embrace all and any pigments and dyestuffs applicably employed in the present and like electrostatic liquid toner systems. Thus, for example, such term embraces carbon blacks including furnace blacks, lamp blacks, channel blacks and other black materials made by processes well known in the art. Similarly embraced are colored pigments including the phosphotungstate and phosphomolybdate colors, alkali blue and many azo pigments as well as nigrosine dyestuffs and triphenylmethine dyes in particular. Of course, any and all pigments and dyestuifs capable of yielding color copies when attracted to the negative latent image by the action of the metal soaps and dispersing agents can be advantageously employed.
The present invention will now be described by reference to the following specific examples. It is to be understood that such examples are presented for purposes of illustration only, and the present invention is in no way to be deemed as limited thereo.
EXAMPLE I The following materials were mixed on a 3-roll mill to obtain a uniform dispersion as a heavy ink.
1 On olefin-alkylated polyvinylpyrrolidone of an average olefin carbon chain length of 16 carbon atoms and 20% vinylpyrrolidone residue.
-An aliphatic petroleum solvent having a boiling range of The ink was adjusted to carbon black content with additional Isopar M. Then 7 cc. of the 5% toner was added to 1 liter of additional aliphatic petroleum solvent to produce the final liquid toner system.
Prior to use in an electrostatic reproduction process a few drops of the following solutions were added; when employed in an SCM-33 copier, resulted in excellent copies of uniform fill and no streaking or bleeding characteristics.
Cerium naphthanate (0.6%) 1 Strontium naphthenate (0.6%) Chromium naphthenate (0.6%) Indium naphthenate (0.6%) Nickel octoate (1.0%) Zirconium octoate 0.6%) Cadmium octoate (1.6%) Magnesium naphthenate (1%) Manganese naphthenate (0.6%) Barium octoate (0.6%)
1 Approximate metal content of toner.
EXAMPLE II The following materials were charged to a ball mill.
G. Carbon black 2O Ganex 220 1 20 Isopar M 370 Zirconium octoate (6%) 5 1 An olefin alkylated polyvinylpyrrolidone of an araryl olefin length of 20 carbon atoms and 20% vinylpyrrolidone residue.
This toner when tested at a concentration of about 6 cc.
per liter of aliphatic petroleum solvent gave excellent pr1nts.
8 EXAMPLE III The following materials were mixed and passed over a 3-roller mill to make an ink. The concentration of Spirit Nigrosine was adjusted to about 5% by mixing the above ink with additional petroleum solvent.
G. Spirit Nigrosine 10 Ganex 216 5 Isopar M 5 This 5% toner when tested had a charge opposite to that needed. However, by adding a few drops of Zr octoate (0.6% Zr) an excellent toner with proper polarity resulted. Again, copies of uniform fill without any tendency to bleed or streak resulted.
EXAMPLE IV This mixture was then mixed with Zr octoate at a ratio of about 25 cc. of toner to 1 cc. of 6% (Zr) octoate solution.
This mixture when tested gave excellent blue prints.
EXAMPLE V The following materials were mixed and passed over a 3-roller mill to make an ink. The ink was adjusted to 5% pigment concentration with additional petroleum solvent.
Gms. 15 7.5 27.5
When 10 cc. of the above was mixed with 2 cc. of zirconium octoate solution, a toner that gave excellent prints resulted.
While the present invention has been described primarily with respect to the foregoing specific examples, it is to be understood that the present invention is in no way to be deemed as limited thereto, but must be com strued as broadly as all or any equivalents thereof.
1. A positive working electrostatic liquid toner comprising (a) an electrically insulating carrier liquid having a dielectric constant of less than three and a volume resistivity in excess of 10 ohm centimeter; (b) a coloring agent dispersible in said carrier liquid and capable of yielding color copies when attracted to a negative latent image; (c) a metal soap of a fatty acid soluble in said carrier liquid; and (d) as a dispersant for said coloring agent an alkylated polymer of a heterocyclic N-vinyl monomer in which the alkyl radical of said polymer contains from 2 to 2000 carbon atoms, and said polymer has a K value of about 10 to 140.
2. The electrostatic liquid toner of claim 1 wherein said alkyl radical of said polymer contains from 8 to 42 carbon atoms.
3. The electrostatic liquid toner of claim 2 wherein said alkylated polymer is an alkylated polymer of an N-vinyl pyrrolidone monomer.
4. The electrostatic liquid toner of claim 1 wherein said metal soap comprises a soap selected from the group consisting of the linoleates, naphthenates, resinates, palmetates, stearates, oleates and octoates of a metal selected from the group consisting of cerium, iron, nickel, cobalt, zirconium, cadmium, lithium, magnesium, manganese, calcium, barium, strontium, chromium and indium.
Pyrazolone Red B Ganex 220 Isopar M 5. The electrostatic liquid toner of claim 4 wherein said electrically insulating carrier liquid is a hydrosaid alkyl radical of said polymer contains from 8 to 42 carbon. carbon atoms. References Cited 6. The electrostatic liquid toner of claim 5 wherein I said alkylated polymer is an alkylate polymer of an N- UN TED PATENTS vinyl pyn-olidone monomen 5 3,231,374 1/ 1966 Sc1amb1 252-621 7. The electrostatic liquid toner of claim 3 wherein 3,079,270 2/1963 Cortez 252-621 said coloring agent comprises carbon black.
8. The electrostatic liquid toner of claim 6 wherein GEORGE LESMES Pnmary Exammer said coloring agent comprises carbon black. 10 I. P. BRAMMER, Assistant Examiner 9. The electrostatic liquid toner of claim 1 wherein