GB2245376A

GB2245376A - Toner compositions

Info

Publication number: GB2245376A
Application number: GB9111090A
Authority: GB
Inventors: Robert A Nelson
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1990-06-01
Filing date: 1991-05-22
Publication date: 1992-01-02
Also published as: GB9111090D0; JPH04232964A

Abstract

A toner comprised of a resin blend containing (1) at least one resin which is crosslinked (2); pigment (3); wax component and (4) charge enchancing additive; and (5) an additive on the surface of the resin blend particle. The resin (1) may be a styrene acrylate or styrene butadiene crass-linked with a divinyl benzene and the resin may be admixed with an uncrosslinked polymer such as a styrene butadiene. The wax component (3) may be a polyethylene or polypropylene wax, the charge enhancer (4) may be a quaternary ammonium salt and the surface additive (5) may be silica, a metal oxide or a metal soap. The addition of (5) improves the toner flow.

Description

TONER AND DEVELOPER COMPOSITIONS BACKGROUND OF THE INVENTION This invention is generally directed to toner and developer compositions, for use especially in electrostatographic or electrophotographic imaging and printing systems.

The electrostatographic process, and particularly the xerographic process, is well known. This process usually involves the formation of an electrostatic latent image on a photoreceptor, followed by development, subsequent transfer of the image to a suitable substrate, and fixing thereto. Numerous different types of xerographic imaging processes are known wherein, for example, insulative developer particles or conductive toner compositions are selected depending on the development systems used. Moreover, of importance with respect to the aforementioned toner compositions is the appropriate triboelectric charging values associated therewith, as they can enable for example continued constant developed images of high quality and excellent resolution.

Additionally, carrier particles for use in the development of electrostatic latent images are described in many patents including, for example U.S. 3,590,000. These carrier particles may be comprised of various cores, including steel, with a coating thereover of fluoropolymers; terpolymers of styrene, methacrylate, and silane compounds, and the like.

Recently efforts have focused on the attainment of coatings for carrier particles, for the purpose of improving development quality; and also to permit particles that can be recycled, and that do not adversely effect the imaging member in any substantial manner. Some of the present commercial coatings can deteriorate rapidly, especially when selected for a continuous xerographic process where the entire coating may separate from the carrier core in the form of chips or flakes; and fail upon impact, or abrasive contact with machine parts and other carrier particles.These flakes or chips, which cannot generally be reclaimed from the developer mixture, have an adverse effect on the triboelectric charging characteristics of the carrier particles thereby providing images with a lower resolution in comparison to those compositions wherein the carrier coatings are retained on the surface of the core substrate. Further, another problem encountered with some prior art carrier coatings resides in fluctuating triboelectric charging characteristics, particularly with changes in relative humidity. The aforementioned modification in triboelectric charging characteristics can provide developed images of lower quality, and with background deposits.

There are illustrated in U.S. Patent 4,233,387, coated carrier components for electrostatographic developer mixtures comprised of finely divided toner particles clinging to the surface of the carrier particles. Specifically, there are disclosed in this patent coated carrier particles obtained by mixing carrier core particles of an average diameter of from between about 30 microns to about 1,000 microns with from about 0.05 percent to about 3.0 percent by weight, based on the weight of the coated carrier particles, of thermoplastic resin particles. The resulting mixture is then dry blended until the thermoplastic resin particles adhere to the carrier core by mechanical impaction and/or electrostatic attraction.Thereafter, the mixture is heated to a temperature of from about 3200F to about 6500F for a period of 20 minutes to aix > ut 120 minutes enabling the thermoplastic resin particles to melt and fuse on the carrier core.While the developer and carrier particles prepared in accordance with the process of this patent, are suitable for their intended purposes, the conductivity values of the resulting particles may not be constant in all instances, for example, when a change in carrier coating weight is accomplished to achieve a modification of the triboelectric charging characteristics; and further -~. th regard to the '387 patent, in some situations carrier and developer mixtures with only specific :tboelectric charging values can be generated when certain conductivity values or characterstcs are contemplated .

With further reference to the prior art, carriers obtained by applying insulating resinous coatings to porous metallic carrier cores using solution coating techniques are undesirable from many viewpoints. For example, the coating material can reside n the pores of the carrier cores, rather than at the surfaces thereof, and therefore is not availab e for triboelectric charging when the coated carrier particles are mixed with finely di X ded toner particles. Attempts to resolve this problem by increasing the carrier coating weights to provide an effective triboelectric coating to the carrier particles can involve handling excess We quantities of solvents, and further usually these processes result in low product yields.Also, so jtion coated carrier particles, when combined and mixed with finely divided toner particles, provide in some instances toner triboelectric charging values which can be too low for many uses Toner compositions with crosslinked resins and second resins, toge-#er with waxes and charge enhancing additives are also known, reference for example U.S. Patent 4,556,624, and some of the prior art references mentioned thereon, and cited against this paters Toners with crosslinked toner resins are also illustrated in U.S. Paterts 3,941,898; 3,938,992 and Reissue U.S. Patent 31,072.

Other patents of interest include 3,939,086, which teaches steel cater beads with polyethylene coatings, see column 6; 4,264,697, which discloses dry coating and using processes; 3,533,835; 3,658,500; 3,798,167; 3,918,968; 3,922,382; 4,238,558; 4,310,611; 4,337,935; and 4,434,220.

The present invention provides a toner comprising a mixture of res r particles, wherein at least one of the resins is a crosslinked resin, pigment particles, wax, a charge enhancing additive, and surface additives. Carrier particles admixed with the tone- to form a developer are comprised of a core of, for example, steel, iron powder, iron, fern es, other known cores, and the like, which core may contain a polymer thereover at typical coating weights of, for example, from about 0.05 to about 3 weight percent, such as a fluorinated polymer like Kynar, polyvinylidene fluoride/vinylchloride, trifluorochloroethylene/vinylchloride, available from Occidential Chemical as FP-461, methyl terpolymers, and the like.Also, there may be selected as carriers, particles comprised of a core with a coating thereover comprised of a mixture of polymers. More specifically. the carrier particles selected can be prepared by mixing low density porous magnetic, or magnetically attractable metal core carrier particles with from, for example, between about 0.05 percent and about 3 percent by weight, based on the weight of the coated carrier particles, of a mixture of polymers until adherence thereof to the carrier core by mechanical impaction or electrostatic attraction; heating the mixture of carrier core particles and polymers to a temperature, for example, of between from about 200 F to about 5500F for a period of from about 10 minutes to about 60 minutes enabling the polymers to melt and fuse to the carrier core particles; cooling the coated carrier particles; and thereafter classifying the obtained carrier particles to a desired particle size.

In another aspect, the present invention provides developers with carrier particles comprised of a core with a coating thereover comprised of a mixture of a first dry polymer component and a second dry polymer component, which are not in close proximity in the triboelectric series. The aforementioned carrier compositions can be comprised of known core materials including iron, ferrites, steel, and the like, with a dry polymer coating mixture thereover. Developer compositions of the present invention can be generated by admixing the aforementioned carrier particles with a toner composition comprised of resin particles, pigment particles, low molecular weight waxes, a charge enhancing additive, and toner surface additives.

Various suitable carrier materials can be selected as indicated herein. Characteristic core properties include, for example, those that will enable the toner particles to acquire a positive charge or a negative charge, and carrier cores that will permit desirable flow properties in the developer reservoir present in the xerographic imaging apparatus. Also of value with regard to the carrier core properties are, for example, suitable magnetic characteristics that will permit magnetic brush formation in mag brush development processes; and also wherein the carrier cores possess desirable mechanical aging characteristics. Examples of carrier cores that can be selected include iron, steel, ferrites, magnetites, nickel, and mixtures thereof. Preferred carrier cores include ferrites and sponge iron, or steel grit with an average particle size diameter of from between about 30 microns to about 200 microns, and preferably from about 100 to about 150 microns.

Illustrative examples of polymer coatings selected for the carrier particles of a developer composition the present invention include those that are not in close proximity in the triboelectric series. Specific examples of polymer mixtures used are polyvinylidenefluoride with polyethylene, polymethylmethacrylate and copolyethylenevi nylacetate, copolyvinylidenefluoride tetrafluoroethylene and polyethylene, polymethyl methacrylate and copolyethylene vinylacetate, and polymethylmethacrylate and polyvinylidenefluoride. Other related polymer mixtures not specifically mentioned herein can be selected including, for example. polystyrene and tetrafluoroethylene, polyethylene and tetrafluoroethylene, polyethylene and polyvinyl chloride, polyvinyl acetate and tetrafluoroethylene, polyvinyl acetate and polyvinyl chloride, polyvinyl acetate and polystyrene, and polyvinyl acetate and polymethyl methacrylate.

With further reference to the polymer coating mixture, by close proximity is meant, for example, that the choice of the polymers selected is dictated by their position in the triboelectric series, therefore for example, one may select a first polymer with a significantly lower triboelectric charging value than the second polymer. More specifically, not in close proximity refers to first and second polymers that are at different electronic work function values, that is they are not at the same electronic work function value; and further, the first and second polymers are comprised of different components.Additionally, the difference in electronic work functions between the first and second polymer is at least 0.2 electron volt, and preferably is about 2 electron volts; and moreover, it is known that the triboelectric series corresponds to the known electronic work function series for polymers, reference "Electrical Properties of Polymers", Seanor, D.A., Chapter 17, Polymer Science, A.D. Jenkins, Editor, North Holland Publishing (1972).

The percentage of each polymer present in the carrier coating mixture can vary depending on the specific components selected, the coating weight and the properties desired.

Generally, the coated polymer mixtures used contain from about 10 to about 90 percent of the first polymer, and from about 90 to about 10 percent by weight of the second polymer.

Preferably, there are selected mixtures of polymers with from about 40 to 60 percent by weight of the first polymer, and from about 60 to 40 percent by weight of a second polymer. In one embodiment of the present invention, there can be selected from about 90 percent by weight of the first polymer, such as polyvinylidenefluoride, and 10 percent by weight of the second polymer, such as polyethylene.

There result carrier particles of relatively constant conductivities from between about 10-5 mho-cm-1 to from about 10-9 mho-cm-1 at, for example, a 10 volt impact across a 0.1 inch gap containing carrier beads held in place by a magnet, and the like, these parameters being dependent, for example, on the coatings selected, and the percentage of each of the polymers used as indicated herein before.

Various effective suitable means can be used to apply the polymer mixture coatings to the surface of the carrier particles. Examples of typical means for this purpose include combining the carrier core material and the mixture of polymers by cascade roll mixing, or tumbling, milling, shaking, electrostatic powder cloud spraying, fluidized bed process, electrostatic disc processing, and an electrostatic curtain. Following application of the polymer mixture, heating is initiated to permit flow out of the coating material over the surface of the carrier core. The concentration of the coating material powder particles, as well as the parameters of the heating step, may be selected to enable the formation of a continuous film of the coating material on the surface of the carrier core, or permit only selected areas of the carrier core to be coated.When selected areas of the carrier core remain uncoated or exposed, the carrier particles will possess electrically conductive properties when the core material comprises a metal. The aforementioned conductivities can include various suitable values. Generally, however, this conductivity is from about 10-9 to about 10-17 mho-cm-1 as measured, for example, across a 0.1 inch magnetic brush at an applied potential of 10 volts; and wherein the coating coverage encompasses from about 10 percent to about 100 percent of the carrier core. The aforementioned carriers with polymer coatings not in close proximity in the tribo series are illustrated U.S. Patents Nos. 935 326 and 4937 166.

The toner in an embodiment of the present invention is comprised of a resin blend of two polymers, a first crosslinked polymer, a second uncrosslinked polymer, a pigment such as carbon black, or a mixture of pigments of, for example, carbon black and magnetites, a wax component, and a charge enhancing additive; and present on the toner surface additive components. In another embodiment of the present invention, the toner is comprised of a polymer blend of two polymers, a first crosslinked polymer, a second uncrosslinked polymer, pigment particles, a low molecular wax component, and a charge enhancing additive; and surface additive components such as silicas, metal salts, metal salts of fatty acids, and the like.

Illustrative examples of toner polymers which are subsequently crosslinked include, for example, styrene acrylates, styrene methacrylates, styrene butadienes, polyesters, it is believed, and the like, reference U.S. Patent 4,556,624. Specific crosslinked resins that may be selected include polyesters, reference U.S. Patents 3,590,000 and 3,655,374; Pliotones, available from Goodyear Chemical Company; styrene butadienes, especially those with a styrene content of from about 70 to about 95 weight percent, and preferably from about 85 to 93 weight percent; suspension polymerized styrene butadienes, reference U.S. Patent 4,558,108; emulsion polymerized styrene butadienes, reference U.S. Patent 4,469,770; and the like. Also, examples of crosslinked resins that may be selected for the toners of the present invention are illustrated in U.S. Patents and U.S.Reissue Patents 3,941,898; 3,938,992; Reissue 31,072 .

Crosslinking of the toner polymer can be effected by a number of processes, including those as illustrated in the prior art. In one embodiment, crosslinking is accomplished by adding to a suitable monomer a crosslinking component, such as divinylbenzene in an effective amount, of, for example, from about 0.05 to about 1.0 weight percent, and reacting at a suitable temperature of, for example, from about 350C to about 150 C, until crosslinking is accomplished, followed by cooling. The degree and extent of crosslinking can be determined by glass transition temperature measurements of the product, gel content, rheology characteristics, and the like.

The aforementioned crosslinked polymer is present in the toner in various effective amounts, including, for example, from about 5 to about 80 weight percent, and preferably from about 15 to about 45 weight percent. While not desired to be limited by they, it is believed that the crosslinked polymer assists in the reinforcement of the second uncrosslinked polymer in the polyblend mixture, thereby enabling a significant reduction in toner ofsetting of the developed image to fuser rolls,Crosslinking components also include aromatic and nonaromatic substances such as alkylene glycol methacrylates, such as ethylene glycol dimethylmethacrylate, and the like.

Examples of uncrosslinked toner polymers or resins in tme toner polymer blend include polyamides, epoxies, polyurethanes, diolefins, vinyl resins and polymeric esterification products of a dicarboxylic acid and a diol comprising a diphenol; styrene methacrylates, styrene acrylates, styrene butadienes, especially those with a high styrene content, and the like.Specific vinyl monomers that can be selected for polymer formation are styrene; p-chlorostyrene vinyl naphthalene, unsaturated mono-olefins such as ethylene, propylene, tutylene and isobutylene, vinyl halides such as vinyl chloride, vinyl bromide, vinyl fluoride, vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl butyrate; vinyl esters; esters of monocarboxyic acids including methyl acrylate, ethyl acrylate, n-butylacrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2chloroethyl acrylate, phenyl acrylate, methylalphachloracrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate; acrylonitrile, methacrylonitrile, acrylamide, vinyl ethers, inclusive of vinyl methyl ether, vinyl isobutyl ether, and vinyl ethyl ether. vinyl ketones inclusive of vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone; vinylidene halides such as vinylidene chloride and vinylidene chlorofluoride; N-vinyl indole, N-v7yl pyrrolidene; mixtures thereof; and other similar components. Although it is not desired to se limited by theory it is believed that the uncrosslinked polymer assists in controlling tte toner minimum fuse temperature, and permits adjustments in the tonertribo.

As one uncrosslinked toner resin, there can be selected the esterification products of a dicarboxylic acid and a diol comprising a diphenol, reference U.S Patent 3,590,000. Other uncrosslinked toner polymers or resins include those illustrated herein with reference to the crosslinked polymers, and those disclosed in the U.S. patents mentioned herein, such as ttyrene/methacrylates, styrene/acrylates, styrene/butadienes, and the like.

The uncrosslinked toner resin is present in various effective amounts, such as, for example. from about 95 to about 40, and preferably from about 70 to about 55 weight percent.

Generally, from about 1 part to about 5 parts by weight o toner particles are mixed with 100 parts by weight of the carrier particles to enable the developer The toner can be subjected to known attrition and classification for the purpose of enabling the toner particles with a known average size diameter of from about 5 to about 25 micons, and preferably from about 9 to about 15 microns.

Numerous well known suitable pigments or dyes can be selected as the colorant for the toner particles including, for example, carbon black, nigrosine dye, lamp black, and mixtures thereof. The pigment, which is preferably carbon black, should be present in a sufficient amount to render the toner composition highly colored. Thus, the pigment particles are present in amounts of from about 5 percent by weight to about 15 percent by weight, and preferably from about 2 to about 10 weight percent based on the total weight of the toner composition, however, lesser or greater amounts of pigment particles can may selected.

When the above illustrated pigment particles are mixed with magnetites, which magnetites are known and can be comprised of a mixture of iron oxides (FeO.Fe2O3) including those commercially available as Mapico Black, the mixtures are present in the toner composition in for example, an amount of from about 10 percent by weight to about 50 percent by weigh, and preferably in an amount of from about 12 percent by weight to about 25 percent by weight In an embodiment of the present invention, the toner can be comprised of a mixture of magnetite, of from about 12 to about 20 weight percent, and pigment, such as carbon black, in an amount of from about 4 to about 15 weight percent.In another embodiment of the present invention, the toner can be comprised of a mixture of magnetite of from about 25 to about 35 weight percent, and pigment, such as carbon black, in an amount of from about 2 to about 10 weight percent.

Also encompassed within the scope of the present invention are colored torer compositions comprised of a toner blend and as pigments or colorants, red, blue, green, brown, magenta, cyan and/or yellow particles, as well as mixtures thereof. More specifically, illustrat ie examples of magenta materials that may be selected as pigments include 1,9-dimetl substituted quinacridone and anthraquinone dye identified in the Color Index as Cl 60720, Cl Dispersed Red 15, a diazo dye identified in the Color Index as CI 26050, Cl Solvent Red 19, and re like.Examples of cyan materials that may be used as pigments include copper tetra-4-(octade sulfonamido) phthalocyanine, X-copper phthalocyanine pigment listed in the Color Index as Ci 74160, Cl Pigment Blue, and Anthrathrene Blue, identified in the Color Index as CI 69810, Speca Blue X-2137, and the like' while illustrative examples of yellow pigments that may be selected ze diarylide yellow 3,3-dichlorobenzidene acetoacetanilides, a monoazo pigment identified in e Color Index as Cl 12700, Cl Solvent Yellow 16, a nitrophenyl amine sulfonamide identified in Ine Color Index as Foron Yellow SE/GLN, CI Dispersed Yellow 33, 2,5#dimethoxy-4-sulfonaniIi#e phenylazo-4' < hloro-2,5-dimethoxy acetoacetanilide, permanent yellow FGL, and the like. These pigments are generally present in the toner composition in an amount of from about 1 weight percent to about 15 weight percent based on the weight of the toner resin particles.

For further enhancing the positive charging characteristics of the developer compositions described herein, there can be incorporated in the toner charge enhancing additives, inclusive of alkyl pyridinium halides, reference U.S. Patent 4,298,672; organic sulfate or sulfonate compositions, reference U.S. Patent 4,338,390; distearyl dimethyl ammonium sulfa-e, reference U.S. Patent 4,560,635; and other similar known charge enhancing additives include other quaternary ammonium salts. These additives are usually incorporated into the toner in an amount of from about 0.1 percent by weight to about 10, and preferably in an amount of from about 0.1 to about 5, and more preferably from about 0.3 to about 1.0 percent by weight.The triboelectric charge of the toner as determined, for example, by the known Faraday Cage process, or a charge spectrograph is from about 10 to about 40, and preferably from about 15 to about 25 microcoulombs per gram.

The wax selected generally has an average molecular weight of from about 500 to about 20,000 and preferably from about 1,000 to about 6,000, examples of which include polyethylenes, polypropylenes, and the like, reference for example British Patent 1,442,835, and U.S. Patent 4,556,624 Specific waxes include Viscol 660-P, Viscol 55OP available from Sanyo Kasei K.K., Epolene N-15, and the like. Generally, the wax is present in an effective amount of, for example, from about 1 to about 15, and preferably from about 2 to about 10 weight percent.

While not being desired to be limited by theory, it is believed that the wax has a number of functions including enabling an increased fusing lattitude, 2500F for example, increased stripping performance, and as a lubricant.

The toner includes surface additives, in an effective amount of, for example, from about 0.1 to about 5, and preferably from about 0.1 to about 1.5 weight percent, such as silicas, including Aerosil R972, metal salts such as titanium oxide, magnesium oxide, tin oxide, and the like, which metal oxides can assist in enabling negatively charged toners, and metal salts of fatty acids, such as zinc stearate, magnesium stearate, and the like, reference U.S. Patents 3,655,374; 3,720,617; 3,900,588 and 3,983,045. While not being desired to be limited by theory, it is believed that the surface additives, especially the silicas, enable excellent toner flow characteristics, enhanced and stable triboelectric values, improved stable admix characteristics, and the like.

Toner compositions of the present invention can be prepared by a number of known methods including melt blending the toner resin blend particles and pigment particles, or colorants, wax, and charge additive, in an extruder followed by mechanical attrition. Other methods include those well known in the art such as spray drying, Banbury melt mixing, and the like. In one extrusion method, a dry bend of the toner components is added to the extruder feeder, followed by heating, to enable a melt mix, which heating in some instances is accomplished at 450 F, and shearing in an extruder, such as the Wemer Pfleiderer ZSK 53, cutting the strands of toner exiting from the extruder, and cooling the resulting toner in, for example, water.Thereafter, the toner may be attrited with, for example, an attritor available from Alpine Inc., and classified with, for example, a Donaldson classifier, resulting in toner particles with an average diameter as indicated herein, and in an embodiment of from about 9 to about 20 microns, for example. There can then be added to the resulting toner product surface additives by mixing, for example, in a Lodige Blender the toner and additives, such as Aerosil, wherein the surface additives are mechanically impacted on and into the toner surface. The developer compositions can then be prepared by mixing in a Lodige Blender the toner with surface additives and carrier particles for effective mixing times of, for example, from about 1 to about 20 minutes.

Toner and developer compositions of the present invention may be selected for use in electrostatographic imaging processes containing therein conventional photoreceptors including inorganic and organic photoreceptor imaging members. Examples of imaging members are selenium, selenium alloys, and selenium or selenium alloys containing therein additives or dopants such as halogens. Furthermore. there may be selected organic photoreceptors, illustrative examples of which include layered photoresponsive devices comprised of transport layers and photogenerating layers, reference U.S. Patent 4,265,990, and other similar layered photoresponsive devices. Examples of generating layers are trigonal selenium, metal phthalocyanines, metal free phthalocyanines and vanadyi phthalocyanines.As charge transport molecules, there can be selected the aryl diarnines disclosed in the '990 patent. Also, there can be selected as photogenerating pigments, squaraine compounds, thiapyrillium materials, and the like. These layered members are conventionally charged negatively, thus requiring a positively charged toner. Moreover, the developer compositions of the present invention are particularly useful in electrostatographic imaging processes and apparatuses wherein there is selected a moving transporting means and a moving charging means; and wherein there is selected a deflected flexible layered imaging member, reference U.S. Patents 4,394,429 and 4,368,970.

Images obtained with this developer composition had acceptable solids, excellent halftones and desirable line resolution with acceptable or substantially no background deposits at, for example, a relative humidity of from about 10 to about 90 percent as determined, for example, by known standard visual and optical copy quality characterization methods.

With further reference to the process for generating the carrier particles for a developer composition, there are initially obtained, usually from commercial sources, the uncoated carrier core and the polymer powder mixture coating. The individual components for the coating are available, for example, from Pennwalt as 301F Kynar, Allied Chemical as Polyrnist B6, and other sources. Generally, these polymers are blended in various proportions as mentioned hereinbefore as, for example, in a ratio of 1:1,0.1 to 0.9, and 0.9 to 0.1. The blending can be accomplished by numerous known methods including, for example, a twin shell mixing apparatus. Thereafter, the carrier core polymer blend is incorporated into a mixing apparatus, about 1 percent by weight of the powder to the core by weight in a preferred embodiment, and mixing is affected for a sufficient period of time until the polymer blend is uniformly distributed over the carrier core, and mechanically or electrostatically attached thereto.Subsequently, the resulting coated carrier particles are metered into a rotating tube furnace, which is maintained at a sufficient temperature to cause melting and fusing of the polymer blend to the carrier core Illustrated in Figure 1 of the tJ.S. Patent No. 4 935 326 is a graph plotting the negative triboelectric charge of the carrier In microcoulombs per gram versus imaging cycles in thousands with a developer composition comprised of 4 percent by weight of a toner composition containing styrene butadiene, 78 percent by weight; magnetite commercially available as Mapico Black, 16 percent by weight; 4 percent by weight of carbon black; 2 percent by weight of the charge enhancing additive distearyl dimethyl ammonium methyl sulfate; and 96 percent by weight of carrier particles consisting of a steel core with a coating thereover; 0.7 percent by weight of a polymer blend consisting of 40 percent by weight of polyvinylidenefluoride; and 60 percent by weight of polymethylmethacrylate. The values reported on this graph were obtained in a Xerox Corporation imaging test fixture with a photoreceptor imaging member comprised of aluminum, a photogenerating layer of trigonal selenium dispersed in polyvinyl carbazole thereover, and a charge transport layer of N,N'diphenyl-N,N'-bis(3#methylphenyl)(1,1.biphenyli- 4A'-diamine, 50 percent by weight dispersed in 50 percent by we ght of polycarbonate.

Illustrated in Figure 2 of the U.S. Patent No. 4935 326 is a plot generated in a Faraday Cage, in accordance with the procedure illustrated hereinafter, of the negative triboelectric charging values of carrier particles comprised of a steel core witt various polymer ratios thereover of 301F polyvinylidenefluoride, and polyethylene B available from Allied Chemical, which values were at a 1 percent coating weight.

The following examples are being supplied to further illustrate the present invention, it being noted that these examples are not intended to limit the scope of the present invention. Parts and percentages are by weight unless otherwise indicated.

EXAMPLE I There was prepared a toner by melt mixing in a twin screw W/P extruder ZSK53, obtained from Werner Pfleiderer, followed by cooling in waver after cutting 63.4 percent by weight of a suspension polymerized styrene butadiene (89 11), 21.1 weight percent of a crosslinked styrene n-butyl methacrylate (58/42) crosslinked with 0.2 weight percent of divinylbenzene, 10 weight percent of Regal 330 (Trade Mark) carbon black, 5 weight percent of the low molecular weight polypropylene wax Viscol 660-P, and 0.5 weight percent of the charge additive distearyl dimethyl ammonium methyl sulfate. The toner product, which contained 84.5 weight percent of the above polymer blend mixture, resulting was then micronized to about 11 microns average diameter in an Alpine grinder and classified in a Donaldson classifier.The toner resulting, 11 microns average diameter, was then blended by mixing with 0.3 weight percent of 'Aerosil" (Trade Mark) R972 in a Lodige Blender.

Polymeric coated carrier particles were prepared by dry coating a Toniolo atomized steel core, 120 microns in diameter, at 0.7 coating weight percent with a mixture, 50 weight percent of each (1:1 ratio) of Kynar 301F and polymethacrylate by mixing these components for 60 minutes in a Munson MX-1 Minimixer rotating at 27.5 RPM. There resulted uniformly distributed and electrostatically attached, as determined by visual observation, on the carrier core the aforementioned polymeric mixture. Thereafter, the resulting carrier particles were metered into a rotating tube furnace at a rate of 105 grams/minute. This furnace was maintained at a temperature of 5030F thereby causing the polymers to melt and fuse to the core.The conductivity of the carrier, as determined by forming a 0.1 inch long magnetic brush of the carrier particles, and measuring the conductivity by imposing a 10 volt potential across the brush, was 1015 mho cm-1.

A developer composition was then prepared by mixing on a paint shaker for 10 minutes 100 parts of the above prepared carrier particles with 4.0 parts of the above prepared toner composition.

The toner had a triboelectric charge thereon as determined by the known Faraday Cage process, and after 10 minutes of mixing on a Red Devil paint shaker a positive 5.4 microcoulombs per gram, and a flow angle of 44 degrees as determined by known standard techniques for determining particulate flow wherein, for example, a predetermined amount of toner is dispersed to a flat surface from a small orifice tube and the resulting angle of the toner pile conical wall to the flat surface is measured. The admix time for fresh, new uncharged toner comprised of the above components and prepared by the above method when added to the above prepared developer was 15 seconds as determined by a charge spectrograph, that is for example a unimodal charge distribution curve resulted at 15 seconds.

The above prepared developer was then incorporated into a xerographic imaging test fixture as illustrated in U.S. Patents 4,394,429 and 4,368,970, with a moving layered imaging member, reference for example the aforementioned '970 or '429 patent, or U.S. Patent 4,265,990, and a toner transporting means; and there resulted excellent quality images with no background deposits for 500,000 imaging cycles, at which time the test was terminated. The developer tribo for the entire imaging test of 500,000 imaging cycles was stable, and the dispense behaviour of the toner was acceptable, a flow angle of 44 degrees. Transfer of the toned image was about 95 percent as determined by quantitative weight measurements.The MFT (mirimum fix temperature) of the toner was 315 F, and the above toner characteristics were maintained for a relative humidity of from 10 to about 90 percent. At 3 percent toner concentration, the triboelectric charge of a toner sample obtained from the above prepared developer was 17 microcoulombs per gram as determined by the Faraday Cage method. The At was 70. The At typically is calculated as follows: At equals the toner tribo multiplied by (the toner corwentration + a constant, which is a number such as 1).

A developer prepared by repeating the above process, with the exception that the toner prepared did not contain the "Aerosil" R972 as a surface additive, had a toner flow angle of 60 degrees, and an admix time greater than two minutes. The prepared toner would nct dispense from the toner hopper in the above imaging apparatus, toner transfer was about 75 percent, and bridging/blocking of the cleaning system resulted. Also, images developed witn the above prepared developer with no "Aerosil" were of low quality, and these images contained substantial unwanted, and undesirable background deposits.

In all the working Examples, the triboelectric charging values, the conductivity numbers, and the other toner, carrier and developer characteristics were obtained in accordance with the aforementioned procedure.

EXAMPLE II Toners were prepared by repeating the process of Example I, with the exceptions that no "Aerosil" R972 was utilized and the wax amounts were 3,5 (same as Example I), and 7.5 percent, respectively, with the amount of resin blend being 86.5 when 3 weight percent of wax was present and 82 weight percent of the resin blend when 7.5 weight percent of wax was present. The tribo product, which represents the product of the triboelectric charge on the toner multiplied by the toner concentration, was 80.3,98.4 and 128.2 with the 3,5 and 7.5 weight percent wax. This indicates that the addition of wax can cause the toner tribo to become more positive.

EXAMPLE Ill Toners were prepared by repeating the procedure of Example I, with the exceptions that the amount of "Aerosil" R972 selected was 0,0.1, 0.25,0.3 and 0.4 weight percent, respectively, and the resulting toner flow angles were 60, 51,47, 45 and 41 degrees, respectively, with 5 weight percent of wax present in each of the prepared toners.

Toners were then prepared by repeating the above procedure with the exceptions that no "Aerosil" was utilized and the amount of wax selected was 0,3,5 and 7.5 weight percent, respectively, with a resin blend ratio of 75 weight percent styrene butadiene, and 25 weight percent of crosslinked styrene n-butylmethacrylate. The resulting toners had toner flows of 49,54,60 and greater than 60 degrees, respectively.

EXAMPLE IV Toners were prepared by repeating the procedure of Example I with the exceptions that there was utilized 3 weight percent of the wax, and 0.1,0.25,0.30 and 0.40 weight percent of the "Aerosil surface additive. The tribo product for the resulting toners was 108.6,92.1,80.3 and 68.1, respectively.

Toners were then prepared by repeating the procedure of Example I with 5 weight percent of wax, and 0.3 weight percent of "Aerosil", and with the exceptions that 8 and 15 weight percent of carbon black were selected. The toner dielectric constant K' as determined by standard ASTM procedures was 2.66,3.23 and 4.49 with 8,10 and 15 weight percent of carbon black, respectively, (toner blend amounts were 86.5,84.5 and 79.5, respectively). Higher amounts of carbon black in this Example translates into an increase in the dielectric constant, which in turn permits improved toner charging admix response.

EXAMPLE V The developer composition of Example I (4 percent toner concentration, that is 4 grams of toner per 100 grams of carrier) with the surface additive "Aerosil", 0.3 weight percent and without the surface additive "Aerosil" was mixed on a Red Devil paint shaker, and the following characteristics thereof were measured in a charge spectrograph for each developer.

With the "Aerosil", the average Q/D was 0.423, the standard Q/D was 0.257, and relative standard deviation was 0.607; the corresponding characteristics for the same developer without "Aerosil" were 0.673,0.312 and 0.464. Q refers to the triboelectric charge on the toner in Femtocoulombs per micron, and D refers to the average diameter of the toner particles in microns Also, for the toner with "Aerosil" the charge spectrograph curves were unimodal, and of narrow and acceptable charge distribution.

Subsequently there was added to the developer with "Aerosil" and the developer without "Aerosil" 1 percent by weight of fresh uncharged toner of Example I, and the characteristics thereof were determined in a charge spectrograph after mixing for 15 seconds on a Red Devil paint shaker. With "Aerosil" the average Q/D was 0.347, the standard Q'D was 0.254, and the relative standard deviation was 0.732; the corresponding characteristics for the developer without "Aerosil" were 0.432, 0.490 and 1.134. Also, with no "Aerosil" the developers had a bimodal distribution; while the "Aerosil" containing developers had a desirable unimodal distribution as determined on the charge spectrograph, and excellent admix of 15 seconds.

Mixing of the developers was continued on the paint shaker for a total of 2 minutes, and the following was measured with "Aerosil" and without "Aerosil", respectively; with the "Aerosil", the Q/D was 0.371, the standard OlD was 0.267, and the relative standard deviation was 0.718; the corresponding characteristics for the developer without "Aerosil" were 0.434,0.455 and 1.408.

The above data evidences that the toner with "Aerosil" had excellent admix, about 15 seconds, that is there were no bimodal distribution curves. Without the "Aerosil", the admix spectra exhibited bimodal distribution peaks, which are not acceptable in that, for example, image background on the copy results, and the print density could not be maintained; these disadvantages were avoided or minimized with the above "Aerosil" developers.

It is believed that the following toners and developers can also be prepared. The procedure of Example I is repeated with the exception that there is selected as the toner with surface additive 62 percent by weight of a copolymer resin of styrene-n-butylmethacrylate, containing 58 percent by weight of styrene and 42 percent by weight of n-butylmethacrylate, 25 percent by weight of a styrene-nbutylmethacrylate copolymer, (58/42) crosslinked with 0.2 percent by weight of divinylbenzene, 6 percent by weight of carbon black Regal 330, 2 percent by weight of cetyl pyridinium chloride, and 5 percent by weight of polypropylene of a molecular weight of about 5,000, commercially available as Viscol 550-P from Sanyo Corporation, and as the carrier coating a polymer blend at a 1.0 percent coating weight of a polymer mixture, ratio 1::9 of polyvinylidenefluoride Kynar 301F and polyethylene available as Polymist B6 from Allied Chemical; a developer composition of Example I with the exception that there is selected as the carrier coating a polymer mixture, ratio 9:1, of polyvinylidenefluoride Kynar 301F and polyethylene available as Polymist B6, coating weight 1.0 percent; a developer composition of Example I with the exception that there is selected as the carrier coating, 0.5 weight percent, a blend, ratio 3:2, of a polymer mixture of polyvinylidenefluoride Kynar 301 F, and high density polyethylene FA520 available from USI Chemical Company; a developer composition of Example I with the exception that there is selected as the carrier coating a blend, ratio 7:3, of a polymer mixture, 0.4 weight percent, of copolyvinylidenefl uoride tetrafluoroethylene available from Pennwalt as Kynar 7201, and a high density polyethylene available as Microthene FA520 from USI Chemicals Company; a developer composition of Example I with the exception that there is selected as the carrier coating a blend, ratio 7:3, of a polymer mixture of copolyvinylidenefluoride tetrafluoroethylene available from Pennwalt as Kynar 7201, and a low density polyethylene available from USI Chemicals Company as FN510, 0.7 percent coating weight; a developer composition of Example I with the exception that there is selected as the carrier coating a blend, ratio 7:3, of a polymer mixture of Kynar 7201, and a copolyethylene vinylacetate available from USI Chemical Company as FE532, 0.7 percent coating weight; and similar developers with the carriers of U.S. Patent No. 4 937 166 and U.S. Patent No. 4 935 326.

In an embodiment of the present invention, the toners can be comprised, it is believed, of the components illustrated herein, and wherein the charge additive is sorbed on the surface additives, such as the "Aerosils", and the like. The relative standard Q/D was arrived at by dividing the standard Q/D by the average QUID. Also, it is believed that with Banbury mixing for the preparation of the toners in embodiments of the present invention control of the amount of free wax in the final toner product can be achieved, for example, preferably to provide little or no free wax since free wax may in some instances adversely effect the electrographic, especially xerographic, imaging or printing cleaning subsystems.

Developer compositions in accordance with the invention and as described above are useful in electrostatographic or eletrophotographic imaging and printing systems, especially xerographic imaging processes, including high speed processes, that is those generating over 100 copies per minute. In particular, they are useful in imaging methods wherein relatively constant conductivity parameters are desired. Furthermore, the triboelectric charge on the carrier particles can be preselected depending, for example, on the polymer composition applied to the carrier core.Advantages associated with toners and developers of the present invention as described above include desirable toner triboelectric charging characteristics, excellent toner flow properties, excellent toner admix characteristics, stable performance for extended time periods exceeding, for example, 500,000 imaging test cycles in a xerographic imaging test fixture including those as illustrated in U.S.Patents 4,394,429 and 4,368,970, acceptable dielectric values (generally the higher the dielectric value the better the admix), the capability to vary the triboelectric charge on the carrier independent of the conductivity thereof; varying the conductivity on the carrier independent of the triboelectric charge thereof; use of the developer in imaging processes wherein a release fluid such as silicone oil is present; use of the developer in imaging processes wherein a minimum amount, or no release fluid, such as silicone oil is present; selection of the developer for electrophotographic, especially xerographic, heated fuser and pressure systems wherein the fuser roll coating is a silicone, reference for example the commercially available Xerox Corporation 1075 (Trade Mark) and 1090 (Trade Mark) imaging apparatuses; and the like.

Further, when polymer coated carrier particles are prepared for a developer by the powder coating process of the aforementioned U.S. Patents Nos. 935 326 and 4937 166, the majority of the coating materials are fused to the carrier surface thereby reducing the number of toner impaction sites on the carrier material. Additionally, there can be achieved with the carriers of the aforementioned, independent of one another, desirable triboelectric charging characteristics and conductivity values; that is, for example the triboelectric charging parameter is not dependent on the carrier coating weight as is believed to be the situation with the process of U.S. Patent 4,233,387 wherein an increase in coating weight on the carrier particles may function to also permit an increase in the triboelectric charging characteristics.Specifically, therefore, with the carrier compositions of the aforementioned U.S. Patents Nows. 935 326 and 4937 166 there can be formulated developers with selected triboelectric charging characteristics and/or conductivity values in a number of different combinations. Thus, for example, there can be formulated in accordance with the aforementioned copending applications, developers with conductivities of from about 10 6mho (cm)- to 10-17 mho (cm)-1 as determined in a magnetic brush conducting cell. The developers of the aforementioned copending applications can be formulated with constant conductivity values with different triboelectric charging characteristics by, for example, maintaining the same coating weight on the carrier particles and changing the polymer coating ratios.Similarly, there can be formulated developer compositions wherein constant triboelectric charging values are achieved and the conductivities are altered by retaining the polymer ratio coating constant and modifying the coating weight for the carrier particles.

The present invention as described above enables the provision of toners with many advantages including, in addition to excellent flow characteristics, especially for dispensed toner, and desirable admix: low minimum fix temperatures of for example from about 300 to about 325, and in an embodiment 315 F; excellent offset fusing latitude depending on the toner components, and the like; and as measured in a Xerox Corporation 1075 (Trade Mark) fuser system of in excess of 500F with no or minimum release fluid, and up to 950F with a release fluid such as a silicone oil present in the imaging apparatus; stable toner tribo; resistance to a relative humidity of from about 10 to about 90 percent; and the formation of developed images with excellent quality, high image resolution, which images are free or substantially free of undesirable background deposits, and the like.

A further feature is the provision of a toner with a mixture of resins, preferably two resins or polymers, one of which is crosslinked, and surface additives thereon, which toner has many advantages including superior flow characteristics in combination with other desirable properties.

Another feature is the provision of developers with many of the advantages described and comprised of toners with surface additives and carrier particles, including carrier particles containing a polymer coating.

Another feature is the provision of developers that can be selected for imaging processes wherein a release oil such as a silicone oil is present, or is substantially avoided, and wherein the toner is comprised of the components of U.S. Patent 4,556,624 with surface additives thereon.

Another feature is the provision of developers wherein carrier particles of substantially constant conductivity parameters are generated by a dry coating processes.

Yet another feature is the provision of developers with carrier particles of substantially constant conductivity parameters, and a wide range of preselected triboelectric charging values.

Yet a further feature is the provision of developers with the toner of the 4,556,624 patent with surface additives, and carrier particles comprised of a coating with a mixture of polymers that are not in close proximity, that is for example a mixture of polymers from different positions in the triboelectric series.

Still a further feature is the provision of developers with carrier particles of insulating characteristics comprised of a core with a coating thereover generated from a mixture of polymers.

Another feature resides in the provision of developers with stable At, that is for example an At of from about 50 to about 125, and more specifically from about 60 to about 80, wherein, for example, the toner tribo is from about 15 to about 25 microcoulombs per gram at a toner concentration of from about 1 to about 4 percent in embodiments of the present invention.

As already mentioned, the At typically is calculated as follows: 4tequals the toner tribo multiplied by (the toner concentration + a constant, which is a number such as 1). For the toners of the present invention, when the constant is 1 and with the appropriate toner concentrations, the toner tribo will remain relatively constant for an extensive number of imaging and development cycles, thus permitting, for example, final developed copies of excellent quality with substantially no, or with the absence of any background deposits; and excellent solid area development for an extended number of imaging cycles, such as, for example, 500,000.

Another feature is the provision of methods for the development of electrostatic latent images wherein the developer mixture comprises toner and carrier particles, preferably with a coating thereover comprised of a mixture of polymers that are not in dose proximity in the triboelectric series.

Another feature is the provision of developers with positively charged toner compositions, or negatively charged toner compositions having admixed therewith carrier particles with a coating thereover comprised, for example, of a mixture of certain polymers.

Claims

CLAIMS:

1. A toner comprised of a resin blend wherein at least one resin is crosslinked, p gment, wax component, and charge enhancing additive; and surface additive.

2 A toner comprised of polyblend mixture of crosslinked copolymer composition, and second polymer, pigment particles, wax component, and charge enhancing additive; and surface additive.

3. A toner comprised of polyblend mixture of a crosslinked polymer composition, and a second polymer, pigment particles, a wax component of a molecular weight of from 500 to about 20,000, and a charge enhancing additive; and a surface additive.

4. A toner comprised of polyblend mixture of crosslinked copolymers, and second uncrosslinked polymers, pigment particles, wax components, and charge enhancing additives; and surface additives.

5. A toner comprised of polyblend mixture of a crosslinked copolymer composition, and a second uncrosslinked polymer, pigment particles, a wax component of a rrolecular weight of from 500 to about 20,000, and a charge enhancing additive; and a surface additive.

6. A toner in accordance with any one of claims 1 to 3, wherein the surface additives are present in an amount of from about 0.05 to about 3.0 weight percent.

7. A toner in accordance with any one of claims 1 to 3, wherein the surface additive is present in an amount of from about 0.1 to about 0.6 weight percent.

8. A toner in accordance with claim 1 or claim 2, wherein the surface additive is present in an amount of 0.3 weight percent.

9. A toner in accordance with claim 2, wherein the crosslinked polymer is selected from the group consisting of styrene methacrylates, styrene acrylates, and styene bjtadienes.

10. A toner in accordance with claim 2, wherein the second polymer is selected from the group consisting of styrene methacrylates, styrene acrylates, and styene butadienes.

11. A toner in accordance with claim 2, wherein the crossllnked polymer is a styrene butyl methacrylate.

12. A toner in accordance with claim 2, wherein the crosslinked polymer is a styrene butadiene with from about 70 to about 95 weight percent of styrene.

13. A toner in accordance with claim 2, wherein the second polymer is a styrene butadiene with from about 70' to about 95 weight percent of styrene.

14. A toner in accordance with claim 1 or claim 2, where n the crosslinked polymer is present in an amount of from about 5 to 80 weight percent.

15. A toner in accordance with claim 2, wherein the second polymer is present in an amount of from about 20 to 95 weight percent.

16. A toner in accordance with claim 2, wherein the c osslinking component for the crosslinked resin is divinyl benzene.

17. Atoner in accordance with claim 2, wherein the crosslinking component is present in an amount of from about 0.05 to about 1.0 percent

18. A toner in accordance with claim 2, wherein the crosslinked polymer is a styrene n-butylmethacrylate crosslinked with divinylbenzene, and the second polymer is a styrene butadiene.

19. A toner in accordance with claim 12 or claim t3, wherein the styrene butadiene is prepared by suspension polymerization.

20. A toner in accordance with claim 2, wherein the wax is selected from the group consisting of polypropylene and polyethylene.

21. A toner in accordance with claim 2, wherein the v ax is present in an amount of from about 1 to about 10 weight percent.

22. A toner in accordance with claim 2, wherein the wax is present in an amount of from about 3 to about 7 weight percent.

23. A toner in accordance with claim 2, wherein the charge additive is present in an amount of from about 0.1 to about 10 weight percent.

24. A toner in accordance with claim 2, wherein the charge additive is selected from the group consisting of quaternary ammonium salts.

25. A toner in accordance with claim 2, wherein the charge additive is distearyl dimethyl ammonium methyl sulfate.

26. A toner in accordance with claim 2, wherein the charge additive is an alkyl pyridinium halide.

27. A toner in accordance with any one of claims 1 to 5, wherein the pigment is carbon black.

28. A toner in accordance with any one of claims 1 to 5, wherein the pigment is selected from the group consisting of red, blue, green, cyan, yellow, magenta, or mixtures thereof.

29. A toner in accordance with claim 1 or claim 2, wherein the pigment is present in an amount of from about 2 to about 20 weight percent.

30. A toner in accordance with claim 3, wherein the pigment is present in an amount of from about 3 to about 20 weight percent.

31. A toner in accordance with any one of claims 1 to 5, wherein the surface additive is colloidal silica.

32. A toner in accordance with claim 1 to claim 2, wherein the surface additive is metal oxide.

33. A toner in accordance with claim 1, wherein there is present from about 5 to about 80 percent by weight of the crosslinked resin, and a second thermoplastic resin present In an amount of from about 20 to about 95 weight percent.

34. A toner in accordance with claim 1 or claim 2, wherein the surface additive is metal salt of fatty acids.

35. A toner in accordance with claim 1 or claim 2, wherein the surface additive is metal salt.

36. A toner in accordance with claim 34, wherein the surface additives are present in an amount of from about 0.05 to about 3 weight percent.

37. A toner in accordance with claim 1 or claim 2, wherein the surface additive is comprised of mixtures of colloidal silicas and metal salts of fatty acids.

38. A toner in accordance with any one of claims 1 to 5, wherein the crosslinked polymer is present in an amount of from about 15 to about 45 weight percent.

39. A toner in accordance with claim 2 or claim 3, wherein the second polymer is present in an amount of from about 40 to about 95 weight percent.

40. A toner in accordance with claim 2 or claim 3, wherein the second polymer is present in an amount of from about 55 to about 70 weight percent.

41. A toner comprised of a mixture of two polymers comprised of a first crosslinked polymer, and second uncrosslinked polymer, pigment particles, wax component and charge enhancing additive; and surface additive.

42. A toner in accordance with claim 41, wherein the wax is of a molecular weight of from 500 to about 20,000.

43. A toner in accordance with claim 41, wherein the wax is polypropylene.

44. A toner in accordance with claim 41, wherein the surface additive is comprised of collioidal silica.

45. A toner in accordance with claim 41, wherein the surface additive is comprised of metal salt of fatty acids.

46. A toner in accordance with claim 41, wherein the surface additive is comprised of metal salt.

47. A toner in accordance with claim 41, wherein the surface additive is comprised of "Aerosil".

48. A toner in accordance with claim 41, wherein the surface additive is comprised of zinc stearate.

49. A toner in accordance with claim 41, wherein the charge enhancing additive is distearyl dimethyl ammoniumm methyl sulfate.

50. A toner comprised of a mixture of two polymers comprised of a first crosslinked polymer, and a second uncrosslinked polymer, a mixture of pigment particles, a wax component and a charge enhancing additive; and surface additive.

51. A toner in accordance with claim 50, wherein the pigment mixture is comprised of carbon black and magnetites.

52. A toner in accordance with claim 51, wherein the magnetite is present in an amount of from about 3 to about 40 weight percent.

53. A developer composition comprised of the toner of any one of claims 1 to 6 and carrier particles.

54. A developer composition comprised of the toner of any one of claims 1 to 4, and carrier particles comprised of a core with a coating thereover comprised of a mixture of first and second polymers that are not in close proximity thereto in the triboelectric series.

55. A developer composition in accordance with claim 54, wherein the carrier core is selected from the group consisting of iron, ferrites, steel and nickel.

56. A developer composition in accordance with claim 53 when appended to claim 2 or claim 3, wherein the second toner polymer is a styrene alkyl methacrylate.

57. A developer composition in accordance worth claim 53, wherein the toner charge enhancing additive is stearyl dimethyl phenethyl arr.~nonium paratoluene sulfonate, distearyl dimethyl ammonium methyl sulfate, or cetyl pyridinium chloride.

58. A developer composition in accordance wim claim 53 when appended to any one of claims 2 to 5, wherein the first polymer is present in an amount of from about 40 percent by weight to about 60 percent by weight, and the second polymer is present in an amount of from about 60 percent by weight to about 40 percent by weight.

59. A developer in accordance with claim 54 wherein the coating is continuous, and is present in a thickness of from about 0.2 micron to about 1 5 microns.

60. A developer in accordance with claim 54 Wherein the carrier core particles have an average particle diameter of between about 30 microns and about 200 microns.

61. A developer composition comprised of a toner comprised of a polyblend mixture of a crosslinked copolymer composition and a second polymer, pigment particles, a wax component of a molecular weight of from 500 to about 20,000 and a charge enhancing additive, and surface additive; and carrier particles coated with a polymer

62. A developer in accordance with claim 6', wherein the polymer mixture selected is comprised of from about 40 percent by weight to about 60 percent by weight of the first polymer, and from about 60 percent by weight to about ID percent by weight of the second polymer.

63. A developer composition in accordance v th claim 61, wherein the second toner resin particles are selected from the group consisting of styrene methacrylate copolymers, styrene butadiene copolymers, styrene acrylate copolymers, an: polyesters.

64. A developer composition in accordance vbth claim 61, wherein the charge enhancing additives are selected from the group consisting o' alkyl pyridinium halides, organic sulfate compositions, organic sulfonate compositions, distearyl dimethyl ammonium methyl sulfate, and quaternary ammonium compounds.

65. A developer in accordance with claim 54, wherein the difference in electronic work function values between the first and second carrier polymer is at least 0.2 electron volts.

66. A developer composition in accordance with claim 54, wherein the first and second polymers are selected from the group consisting of polystyrene and tetrafluoroethylene, polyethylene and tetrafluoroethylene, polyethylene and polyvinyl chloride, polyvinyl acetate and tetrafluoroethylene, polyvinyl acetate and polyvinyl chloride, polyvinyl acetate and polystyrene, and polyvinyl acetate and polymethyl methacrylate.

67. A method of formulating images which comprises generating an electrostatic latent image on a photoconductive imaging member; thereafter developing this image with a toner composition in accordance with any one of claims 1 to 3; subsequently transfering the developed image to a supporting substrate; and thereafter affixing the image thereto.

68. A method in accordance with claim 67, wherein fixing is accomplished by silicone soft roll fusing.

69. A method in accordance with claim 67 or claim 68, wherein sequential image development is accomplished by continuously generating electrostatic latent images on the imaging member and thereafter developing each of the images formed.

70. A method in accordance with any one of claims 67 to 69, wherein the toner composition selected contains colloidal silica surface additives.

71. A method in accordance with any one of claims 67 to 70, wherein the charge enhancing additives of the toner are selected from the group consisting of alkyl pyridinium halides, organic sulfate compositions, organic sulfonate compositions, and distearyi dimethyl ammonium methyl sulfate.

72. A toner comprised of a mixture of two resins comprised of a crosslinked resin and a noncrosslinked resin, carbon black pigment, wax, and a distearyl dimethyl ammonium methyl sulfate charge enhancing additive; and colloidal silica surface additive.

73. A toner in accordance with claim 72, wherein the crosslinked resin is a styrene acrylate, a styrene methacrylate, or a styrene butadiene.

74. A toner in accordance with claim 72 or 73, wherein the noncrosslinked resin is a styrene acrylate, a styrene methacrylate, or a styrene butadiene.