Solution coated carrier particles

A process for the preparation of carrier particles with substantially stable conductivity parameters which comprises providing a carrier core and applying thereto from a solution mixture thereof a mixture of polymers not in close proximity thereto in the triboelectric series.

BACKGROUND OF THE INVENTION 
This invention is generally directed to developer compositions, and more 
specifically, the present invention relates to developer compositions with 
coated carrier particles prepared by a solution process. In one embodiment 
of the present invention, the carrier particles are comprised of a core 
with coating thereover generated from a solution mixture of polymers that 
are not in close proximity thereto in the triboelectric series. In another 
aspect of the present invention, the carrier particles are prepared by a 
solution coating process wherein a mixture of two polymers, at least one, 
and preferably one, of which is substantially soluble in the solvent 
selected, are applied to the carrier core enabling insulating particles 
with relatively constant conductivity parameters; and also wherein the 
triboelectric charge, either positive or negative on the carrier can vary 
significantly depending on the coatings selected. Developer compositions 
comprised of the carrier particles prepared by the solution coating 
process of the present invention are useful in electrostatographic or 
electrophotographic imaging systems, especially xerographic imaging 
processes. Additionally, developer compositions comprised of substantially 
insulating carrier particles prepared in accordance with the process of 
the present invention are useful in imaging methods wherein relatively 
constant conductivity parameters are desired. Furthermore, in the 
aforementioned imaging processes the triboelectric charge, and/or the 
conductivity of the carrier particles can be preselected depending on the 
polymer composition applied to the carrier core. 
The electrostatographic process, and particularly the xerographic process, 
is well known. This process involves the formation of an electrostatic 
latent image on a photoreceptor, followed by development, and subsequent 
transfer of the image to a suitable substrate. 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 developer compositions is the appropriate 
triboelectric charging values associated therewith as it is these values 
that can enable continued constant developed images of high quality and 
excellent resolution. 
In a patentability search report, the following United States Patents were 
recited: U.S. Pat. No. 4,331,756 which discloses that a carrier core can 
be coated with a solution containing a mixture of butadiene/acrylonitrile 
rubber and polyurethane, and also see column 8, lines 1 to 7, and column 
5, lines 14 to 30; U.S. Pat. Nos. 3,778,262; 3,873,355 and 3,873,356 
wherein there is indicated that the very negative tribo that would result 
from a carrier coated with PTFE is raised to a more positive tribo by 
mixing another type of resin with the PTFE and solution coating the mixed 
resins on the carrier core, and note as indicated in the Abstract of the 
Disclosure that the carrier core is coated with a continuous film of a 
fluoropolymer and a modifying resin, see the U.S. Pat. No. 3,778,262 
patent and also note Examples 1 and 2 in columns 5 and 6; and U.S. Pat. 
Nos. 4,937,166 and 4,935,326 wherein there are illustrated carrier 
compositions comprised of a core with a coating thereover comprised of a 
mixture of a first and second polymer that are not in close proximity 
thereto in the triboelectric series, which coatings are applied by a dry 
coating process, reference the '166 patent, and a developer containing a 
toner with a suspension polymerized styrene butadiene and other components 
in a carrier with a coating, which carrier is similar to the carrier as 
illustrated in the '166 patent. The disclosures of each of the 
aforementioned patents are totally incorporated herein by reference. 
Carrier particles for use in the development of electrostatic latent images 
are described in many patents including, for example, U.S. Pat. No. 
3,590,000. These carrier particles may be comprised of various cores, 
including steel, with a coating thereover of fluoropolymers, and 
terpolymers of styrene, methacrylate, and silane compounds. 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. A number of the present commercial carrier 
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 
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 provides developed images of lower 
quality, and with background deposits. 
There are also illustrated in U.S. Pat. No. 4,233,387, the disclosure of 
which is totally incorporated herein by reference, 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 
320.degree. F. to about 650.degree. F. for a period of 20 minutes to about 
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, the disclosure of which has 
been totally incorporated herein by reference, are suitable for their 
intended purposes, the conductivity values of the resulting particles are 
not 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 with regard to the'387 
patent, in many situations carrier and developer mixtures with only 
specific triboelectric charging values can be generated when certain 
conductivity values or characteristics are contemplated. With the 
invention of the present application, the conductivity of the resulting 
carrier particles can be substantially constant, and moreover the 
triboelectric values can be selected to vary significantly, for example, 
from less than -15 microcoulombs per gram to greater than -70 
microcoulombs per gram, or from less than a positive 15 microcoulombs per 
gram to greater than a positive 70 microcoulombs per gram depending, for 
example, on the carrier core and polymer mixture selected for affecting 
the coating process. 
There are illustrated in U.S. Pat. No. 4,937,166 and 4,935,326, the 
disclosures of which are totally incorporated herein by reference, carrier 
particles with, for example, a mixture of coatings, such as two coatings 
not in close proximity in the triboelectric series to enable control of 
the conductivity thereof independent of the triboelectric charging values 
for example. The aforementioned carriers according to the aforementioned 
patents are prepared by dry coating processes. Advantages associated with 
the solution coated carriers of the present invention as compared to the 
dry coated carriers of the '166 and 326 patents include independence from 
particle size constraint, that is for example the polymers selected for 
the aforementioned dry coating can be of a small particle size, for 
example about 1 micron in average diameter, to enable the polymers to 
effectively fuse to the core, a greater variety of polymers are available 
for solution coatings enabling a more complete control of the carrier 
characteristics, and the like. 
It is known that carriers obtained by applying a single insulating resinous 
coating to porous metallic carrier cores using solution coating techniques 
can be undesirable from many viewpoints. For example, the coating material 
may reside in the pores of the carrier cores, rather than at the surfaces 
thereof; and therefore is not available for triboelectric charging when 
the coated carrier particles are mixed with finely divided toner 
particles. Attempts to resolve this problem by increasing the carrier 
coating weights, for example, to as much as 3 percent or greater to 
provide an effective triboelectric coating to the carrier particles 
necessarily involves handling excessive quantities of solvents, and 
further these processes can result in low product yields. When resin 
coated carrier particles are prepared by powder coating processes, 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 dry coating process 
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. Pat. 
No. 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. 
Other patents that may be of interest include U.S. Pat. No. 3,939,086, 
which teaches steel carrier beads with polyethylene coatings, see column 
6; U.S. Pat. No. 4,264,697, which discloses dry coating and fusing 
processes; U.S. Pat. Nos. 3,533,835; 3,658,500; 3,798,167; 3,918,968; 
3,922,382; 4,238,558; 4,310,611; 4,397,935; and 4,434,220. 
There can be formulated in accordance with the invention of the present 
application developers with conductivities of from about 10.sup.-6 mho 
(cm).sup.-1 to 10.sup.-17 mho (cm).sup.-1 as determined in a magnetic 
brush conducting cell, and triboelectric charging values of from about a 
positive or negative 8 to 80 microcoulombs per gram on the carrier 
particles as determined by the known Faraday Cage technique. Thus, the 
developers of the present invention 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. 
SUMMARY OF THE INVENTION 
It is a feature of the present invention to provide toner and developer 
compositions with carrier particles containing a polymer mixture coating. 
In another feature of the present invention there are provided solution 
coating processes for generating carrier particles of substantially 
constant conductivity parameters. 
In yet another feature of the present invention there are provided solution 
coating processes for generating carrier particles of substantially 
constant conductivity parameters, and a wide range of preselected 
triboelectric charging values. 
In yet a further feature of the present invention there are provided 
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, and wherein the polymers 
are applied from a solution mixture, and wherein one polymer is soluble 
therein. 
Further, in an additional feature of the present invention there are 
provided carrier particles comprised of a core with a coating thereover 
generated from a solution mixture of polymers wherein the triboelectric 
charging values are from about a positive, with a mixture of coatings of, 
for example, polymethylmethacrylate and polystyrene, or negative with a 
mixture of coatings of, for example, polyvinylidene fluoride and 
polymethylmethacrylate 10 microcoulombs to about 70 microcoulombs per gram 
at the same coating weight. 
In another object of the present invention there are provided methods for 
the development of electrostatic latent images wherein the developer 
mixture comprises carrier particles with a coating thereover consisting of 
a mixture of polymers that are not in close proximity in the triboelectric 
series. 
Also, in another feature of the present invention there are provided 
positively charged toner compositions, or negatively charged toner 
compositions having incorporated therein carrier particles with a coating 
thereover obtained from a solution mixture of polymers. 
These and other features of the present invention can be accomplished by 
providing developer compositions comprised of toner particles, and carrier 
particles wherein the coating thereover is comprised of a mixture of 
polymers obtained from a solution thereof. In one embodiment 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 solution mixture of 
polymers present in a solvent until adherence thereof to the carrier core. 
The polymers can be applied to the carrier core by, for example, known 
solution coating techniques, fluidized bed coating, immersion, coating bar 
coating, spray coating, and the like, followed by evaporation for the 
purposes of removing the solution solvent. Usually two polymers are 
selected, one of which is soluble in the solvent selected for solution 
formation, however, it is believed that up to, for example, about 10 
polymers may be utilized. 
In a specific embodiment of the present invention, there are provided 
carrier particles comprised of a core with a coating thereover comprised 
of a mixture of a first polymer component and a second polymer component, 
which are not in close proximity in the triboelectric series, and wherein 
the polymers are applied to the carrier from a solution comprised of 
solvent and polymer coatings, preferably two, as indicated herein; 
thereafter drying by heating to remove the solvent; and cooling the coated 
carrier particles obtained followed by screening primarily for the purpose 
of removing any formed agglomerates. The aforementioned carrier 
compositions can be comprised of known core materials including iron with 
a polymer coating mixture thereover. Subsequently, developer compositions 
of the present invention can be generated by admixing the aforementioned 
carrier particles with a toner composition comprised of resin particles 
and pigment particles. 
Various suitable solid core carrier materials can be selected, including 
those illustrated in the prior art, such as the U.S. patents mentioned 
herein. Characteristic core properties include 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 for the process of the present invention include iron, 
steel, ferrites, including semiconductive ferrites, reference U.S. Ser. 
No. 572,207 (D/90176), the disclosure of which is totally incorporated 
herein by reference, 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. 
Illustrative examples of known polymer coatings selected for the carrier 
particles of the present invention are illustrated in a number of patents, 
such as U.S. Pat. No. 3,923,503, the disclosure of which is totally 
incorporated herein by reference. Specific examples of coatings include 
natural and synthetic resins, such as caoutchouc, colophony, copal, 
dammer, dragons blood, jalep, storax, mixtures thereof, and the like. 
Typical synthetic resins are polyolefins, such as polypropylene, 
polyethylene, halogenated polyolefins, chlorinated polyethylene, 
polyethylene, poilyvinyls, and polyvinylidenes, such as polystyrene, 
polymethylstyrene, polyvinylbutyral, polyvinylchloride, polyvinylidene 
fluoride, polytetrafluoroethylene, polytrichlorofluoroethylene; 
polyesters; polyurethanes; polysulfides; polycarbonates; mixtures thereof; 
and the like. Known coating techniques can be utilized as indicated herein 
and, for example, U.S. Pat. No. 2,618,551, the disclosure of which is 
totally incorporated herein by reference. The polymer coating can be 
comprised of from about 99 to about 1 weight percent of a first polymer, 
and from about 1 to about 99 weight percent of a second polymer, and 
preferably from about 40 to about 60 and about 60 to about 40, 
respectively, and wherein the coating weight can be, for example, from 
about 0.05 to about 2 weight percent of polymethylmethacrylate and 
copolyethylenevinylacetate; copolyvinylidenefluoride tetrafluoroethylene 
and polyethylene; polymethylmethacrylate and copolyethylene vinylacetate; 
and polymethylmethacrylate and polyvinylidenefluoride. Other related 
polymer mixtures not specifically mentioned herein may be selected, 
including for example polystyrene and tetrafluoroethylene; polyethylene 
and polyvinyl chloride; polyvinyl acetate and tetrafluoroethylene; 
polyvinyl acetate and polyvinyl chloride; polyvinyl acetate and 
polystyrene; polystyrene and polyvinylchloride; styrene methylmethacrylate 
organosilane terpolymers and polyvinylchloride; polymethylmethacrylate and 
polyvinylchloride; and the like providing that one of the polymers 
selected is soluble in the solvent utilized to form the solution mixture. 
The solution selected can be comprised of the polymer coating mixture and a 
solvent which will dissolve at least one of the polymer coatings selected, 
such as organic solvents like methylethylketone, acetone, toluene, ethyl 
acetate, dimethylformamide, dimethylacetamide, dimethyl-2-pyrrolidone, 
triethylphosphate, and the like. Preferably two polymers are selected 
wherein one of the polymers is soluble in the solvent. Typical 
concentrations of polymer mixture present in the solvent are from about 5 
to about 25 weight percent, and preferably from about 10 to about 15 
weight percent. 
With further reference to the polymer coating mixture, by close proximity 
as used herein refers, for example, that the choice of the polymers 
selected are dictated by their position in the triboelectric series, 
reference U.S. Pat. No. 4,937,166, therefore for example, one may select a 
first polymer with a significantly lower triboelectric charging value than 
the second polymer. For example, the triboelectric charge of a steel 
carrier core with a polyvinylidenefluoride coating is about -75 
microcoulombs per gram. However, the same carrier, with the exception that 
there is selected a coating of polymethacrylate, has a triboelectric 
charging value of about -12 microcoulombs per gram. 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 
disclosure of which is totally incorporated herein by reference. 
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 1 to about 99 percent of the first polymer, and from 
about 99 to about 1 percent by weight of the second polymer. Preferably, 
there are selected two polymers with from about 40 to 65 percent by weight 
of the first polymer, and from about 60 to 35 percent by weight of a 
second polymer. In one embodiment of the present invention, when a high 
carrier triboelectric charging value is desired, that is, exceeding -50 
microcoulombs per gram, there is selected from about 90 percent by weight 
of the first polymer such as polyvinylidene fluoride, and 10 percent by 
weight of the second polymer such as polymethylacrylate. In contrast, when 
a lower carrier triboelectric charging value is desired, less than about 
-20 microcoulombs per gram, there can be selected from about 10 percent by 
weight of the first polymer, and 90 percent by weight of the second 
polymer. The coating ratio amount can be adjusted to control or preselect 
the tribo of the carrier, and the carrier polymer coating weight can be 
adjusted to control or preselect the carrier conductivity. 
Also, these results, in accordance with an embodiment of the present 
invention, carrier particles of relatively constant conductivities from 
between about 10.sup.-15 mho-cm.sup.-1 to from about 10.sup.-9 
mho-cm.sup.-1 at, for example, a 10 volt potential across a 0.1 inch gap 
containing carrier beads held in place by a magnet; and wherein the 
carrier particles are of a triboelectric charging value of from -15 
microcoulombs per gram to -70 microcoulombs per gram, these parameters 
being dependent on the coatings selected, and the percentage of each of 
the polymers used as indicated hereinbefore. Following application of the 
polymer mixture, heating is initiated to permit evaporation of the solvent 
present. The concentration of the coating material particles 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 metal 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.sup.-9 to 
about 10.sup.-17 mho-cm.sup.-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. 
Illustrative examples of finely divided toner resins selected for the 
developer compositions of the present invention include polyamides, 
epoxies, polyurethanes, diolefins, styrene acrylates, styrene 
methacrylates, styrene butadienes, crosslinked toner resins, vinyl resins, 
polymeric esterification products of a dicarboxylic acid and a diol 
comprising a diphenol and the like. Specific vinyl monomers that can be 
used, which monomers are polymerized, are styrene, p-chlorostyrene vinyl 
naphthalene, unsaturated mono-olefins such as ethylene, propylene, 
butylene and isobutylene; vinyl halides such as vinyl chloride, vinyl 
bromide, vinyl fluoride, vinyl acetate, vinyl propionate, vinyl benzoate, 
and vinyl butyrate; vinyl esters like the esters of monocarboxylic acids 
including methyl acrylate, ethyl acrylate, n-butylacrylate, isobutyl 
acrylate, dodecyl acrylate, n-octyl acrylate, 2-chloroethyl 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-vinyl pyrrolidene; mixtures thereof; and other similar 
components. 
As one toner resin there can be selected the esterification products of a 
dicarboxylic acid and a diol comprising a diphenol, reference U.S. Pat. 
No. 3,590,000 the disclosure of which is totally incorporated herein by 
reference. Other specific toner resins include styrene/methacrylate 
copolymers; styrene/butadiene copolymers; polyester resins obtained from 
the reaction of bisphenol A and propylene oxide; and branched polyester 
resins resulting from the reaction of dimethylterephthalate, 
1,3-butanediol, 1,2-propanediol and pentaerythritol; PLIOLITES.RTM. 
available from Goodyear Chemical Company, PLIOTONES.RTM. available from 
Goodyear Chemical Company, styrene acrylates crosslinked with, for 
example, divinylbenzene; styrene methacrylates crosslinked with, for 
example, divinylbenzene; and the like. 
Generally, from about 1 part to about 5 parts by weight of toner particles 
are mixed in a suitable mixing apparatus such as a Munsen mixer with from 
about 100 to about 300 parts by weight of the carrier particles prepared 
in accordance with the process of the present invention. 
Numerous well known suitable pigments or dyes can be selected as the 
colorant for the toner particles including, for example, carbon black, 
such as REGAL.RTM. 330, nigrosine dye, lamp black, iron oxides, 
magnetites, and mixtures thereof. The pigment, which is preferably carbon 
black, should be present in a sufficient amount to render the toner 
composition highly colored. The pigment particles can thus be present in 
effective amounts of, for example, from about 2 percent by weight to about 
20 percent by weight, and preferably from about 3 percent by weight to 
about 11 percent by weight based on the total weight of the toner 
composition, however, lesser or greater amounts of pigment particles may 
be selected. 
When the pigment particles are comprised of magnetites, which are comprised 
of a mixture of iron oxides (FeO.Fe.sub.2 O.sub.3) including those 
commercially available as MAPICO BLACK.RTM., they are present in the toner 
composition in an amount of from about 10 percent by weight to about 70 
percent by weight, and preferably in an amount of from about 20 percent by 
weight to about 50 percent by weight. 
The resin particles are present in a sufficient, but effective amount, thus 
when 10 percent by weight of pigment, or colorant such as carbon black is 
contained therein, about 90 percent by weight of resin material is 
selected. Generally, however, providing the objectives of the present 
invention are achieved, the toner composition is comprised of from about 
85 percent to about 97 percent by weight of toner resin particles, and 
from about 3 percent by weight to about 15 percent by weight of pigment 
particles such as carbon black. 
Also encompassed within the scope of the present invention are colored 
toner compositions comprised of toner resin particles, carrier particles 
obtained by the solution processes illustrated herein, and as pigments or 
colorants, magenta, cyan and/or yellow particles, as well as mixtures 
thereof. More specifically, illustrative examples of magenta materials 
that may be selected as pigments include 1,9-dimethylsubstituted 
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 
Cl 26050, Cl Solvent Red 19, and the like. Examples of cyan materials that 
may be used as pigments include copper tetra-4-(octaecyl sulfonamido) 
phthalocyanine, X-copper phthalocyanine pigment listed in the Color Index 
as Cl 74160, Cl Pigment Blue, and Anthrathrene Blue, identified in the 
Color Index as Cl 69810, Special Blue X-2137, and the like; while 
illustrative examples of yellow pigments that may be selected are 
Diarylide Yellow 3,3-dichlorobenzidene acetoacetanilides, a monoazo 
pigment identified in the Color Index as Cl 12700, Cl Solvent Yellow 16, a 
nitrophenyl amine sulfonamide identified in the Color Index as Foron 
Yellow SE/GLN, Cl Dispersed Yellow 33, 2,5-dimethoxy-4-sulfonanilide 
phenylazo-4'-chloro-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 enhancing the positive charging characteristics of the developer 
compositions described herein, and as optional components there can be 
incorporated in the toner charge enhancing additives inclusive of alkyl 
pyridinium halides, reference U.S. Pat. No. 4,298,672, the disclosure of 
which is totally incorporated herein by reference; quaternary ammonium 
organic sulfate or sulfonate compositions, reference U.S. Pat. No. 
4,338,390, the disclosure of which is totally incorporated herein by 
reference; distearyl dimethyl ammonium sulfate, reference U.S. Pat. No. 
4,560,635, the disclosure of which is totally incorporated herein by 
reference; bisulfates and mixtures of charge additives, reference for 
example U.S. Pat. Nos. 4,904,762 and 4,937,157, and copending application 
U.S. Ser. No. 396,497, and other similar known charge enhancing additives. 
These additives are usually incorporated into the toner in an amount of 
from about 0.05 percent by weight to about 20 percent by weight, and 
preferably are present in an amount of from about 1.0 percent by weight to 
about 5 percent by weight. 
The toner composition of the present invention can be prepared by a number 
of known methods including melt blending the toner resin particles, and 
pigment particles or colorants in, for example, a Banbury Mill followed by 
mechanical attrition including classification. Other methods include those 
well known in the art such as spray drying, melt dispersion, extrusion, 
dispersion polymerization and suspension polymerization. In one dispersion 
polymerization method, a solvent dispersion of the resin particles, 
pigment particles, and additives are spray dried under controlled 
conditions to result in the desired product. Toner particles are, it is 
known, usually of an average diameter of from about 10 to about 25 
microns. The toner particles formed may also contain thereon surface 
additives such as colloidal silicas, such a R972 and metal salts of fatty 
acids such as zinc stearate in effective amounts of, for example, from 
about 0.1 to about 1 weight percent. 
The 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. Pat. No. 4,265,990, the disclosure of which is 
totally incorporated herein by reference, and other similar layered 
photoresponsive devices. Examples of generating layers are trigonal 
selenium, metal phthalocyanines, metal free phthalocyanines and vanadyl 
phthalocyanines. As charge transport molecules there can be selected the 
aryl diamines 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. Pat. Nos. 4,394,429 and 4,368,970, the disclosures of which 
are totally incorporated herein by reference. 
Images obtained with this developer composition had acceptable solids, 
excellent halftones and desirable line resolution with acceptable or 
substantially no background deposits. 
One photoreceptor imaging member that may be selected is comprised of an 
aluminum substrate, a photogenerating layer of trigonal selenium dispersed 
in polyvinyl carbazole thereover, and a hole transport layer of 
N,N'-diphenyl-N,N'-bis(3-methylphenyl)[1,1-biphenyl]-4,4'-diamine, 50 
percent by weight dispersed in 50 percent by weight of a polycarbonate. 
In an embodiment the coating solution is comprised of the polymer coatings 
at a concentration of from about 5 to about 25 weight percent solids. The 
first polymer can be present in the solution mixture in an amount of from 
about 0.05 to about 4.95 percent by weight, and the second polymer can be 
present in the solution mixture in an amount of from about 4.95 to about 
0.05 percent by weight. The solution mixture of polymers can be metered 
until, for example, the core is fully wetted by a mixture, followed by 
agitation in, for example, a vibrating tub or fluid bed, followed by 
drying in an oven by heating at, for example, a temperature of from about 
50.degree. to about 150.degree. C., and screened to provide carrier 
particles with an average particle diameter of from 30 about to about 450 
microns. A slurry containing two polymers, one of which is substantially 
insoluble, may also be selected in an embodiment of the present invention, 
it is believed.

The following examples are being supplied to further define the present 
invention, it being noted that these examples are intended to illustrate 
and not limit the scope of the present invention. Parts and percentages 
are by weight unless otherwise indicated. Comparative Examples are also 
presented. 
EXAMPLE I 
There are prepared coated carrier particles, 0.75 weight percent coating 
weight as follows. A solution of 119 grams of polymethylacrylate in 850 
grams of the solvent methylethylketone is prepared by mixing in a 1,000 
milliliter flask. There are placed 15,876 grams of Toniolo atomized steel, 
120 microns in average diameter, in a Vibra Tub Mixer. To the mixer is 
then added the aforementioned prepared solution, and mixing is continued 
for a period of about 25 minutes, at which tme the carrier steel core is 
completely wet. Thereafter, the mixture is dried by heating at a 
temperature of about 60.degree. C. for about 15 minutes, followed by 
cooling. 
A developer composition is then prepared by mixing 97.5 grams of the above 
prepared carrier particles with 2.5 grams of a toner composition comprised 
of 88 percent by weight of a styrene n-butylmethacrylate copolymer resin, 
58 percent by weight of styrene, 42 percent by weight of 
n-butylmethacrylate, and 10 percent by weight of carbon black, and 2 
percent by weight of the charge additive cetyl pyridinium chloride. 
Thereafter, the triboelectric charge on the carrier particles is 
determined by the known Faraday Cage process, or in the known charge 
spectrograph, reference U.S. Pat. No. 4,375,673, the disclosure of which 
is totally incorporated herein by reference, and there is measured on the 
carrier a charge of -12 microcoulombs per gram. Further, 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 is 10.sup.-15 mho-cm.sup.-1. Therefore, 
these carrier particles are insulating. 
In all the working examples, the triboelectric charging values and the 
conductivity numbers are obtained in accordance with the aforementioned 
procedure. 
EXAMPLE II 
The procedure of Example I is repeated with the exception that 32 grams of 
polymethylmethacrylate, and 850 milliliters of methylketone are utilized 
resulting in carrier particles with a 0.2 weight percent coating. There 
results on the carrier particles a triboelectric charge thereon of -9 
microcoulombs per gram. Also, the carrier particles have a conductivity of 
10.sup.-9 mho-cm.sup.-1. Thus, these particles are considered conductive. 
EXAMPLE III 
A developer composition of the present invention is prepared by repeating 
the procedure of Example I with the exception that there is selected for 
the solution 12 grams of polyvinylidene fluroide, 107 grams of 
polymethylmethacrylate, and 1,000 milliliters of methyl ethyl ketone 
solvent. There results carrier particles with a steel core containing a 
coating of 0.75 weight percent (ratio of polymers 1:9). There results on 
the carrier particles a triboelectric charge of -18 microcoulombs per 
gram. Also, the carrier particles are insulating in that they had a 
conductivity of 10.sup.-15 mho-cm.sup.-1. 
EXAMPLE IV 
A developer composition is prepared by repeating the procedure of Example 
III with the exception that there is selected as the carrier coating of a 
polymer mixture, ratio 9:1, of 107 grams polyvinylidene fluoride, 
KYNAR.RTM. 301F, and 12 grams of polymethylmethacrylate in 1,200 
milliliters of methyl ethyl ketone solvent. There results on the carrier 
particles a triboelectric charge of -58 microcoulombs per gram, and the 
insulating carrier particles has a conductivity of 10.sup.-15 
mho-cm.sup.-1. The coating weight is 0.75 weight percent. 
EXAMPLE V 
A developer composition was prepared by repeating the procedure of Example 
III with the exception that there was selected as the carrier coating a 
blend, ratio 3:2, of a polymer mixture of 71 grams of polyvinylidene 
fluoride, KYNAR.RTM. 301F, and 48 grams of polymethylmethacrylate. There 
resulted on the carrier particles a triboelectric charge of -31 
microcoulombs per gram. Also, the resulting insulating carrier particles 
had a conductivity of 10.sup.-14 mho-cm.sup.-14. The coating weight was 
0.75 weight percent. 
EXAMPLE VI 
A developer composition was prepared by repeating the procedure of Example 
III with the exception that there was selected as the carrier coating a 
blend, ratio 7:3, of a polymer mixture of polymethylmethacrylate, 36 
grams, and 83 grams of polyvinylidene fluoride. There resulted on the 
carrier particles a triboelectric charge of -48 microcoulombs per gram. 
Also, the resulting insulating carrier particles had a conductivity of 
10.sup.-14 mho-cm.sup.-1. The coating weight was 0.75 weight percent. 
EXAMPLE VII 
A developer composition was prepared by repeating the procedure of Example 
VI with the exception that there was selected as the carrier coating a 
blend, ratio 7:3, of a polymer mixture of 83 grams of 
trifluorochloroethylene/vinylchloride copolymer obtained from Occidential 
Chemical Company as OXY 461, and 36 grams of polymethylacrylate in 1,000 
milliliters of solvent. There resulted on the carrier particles a 
triboelectric charge of -38 microcoulombs per gram. Also, the resulting 
insulating carrier particles had a conductivity of 10.sup.-15 
mho-cm.sup.-1. 
EXAMPLE VIII 
A developer composition was prepared by repeating the procedure of Example 
VII with the exception that there were selected 36 grams of methyl 
terpolymer in place of the polymethylmethacrylate. There resulted on the 
carrier particles a triboelectric charge of -28 microcoulombs per gram. 
Also, the resulting insulating carrier particles had a conductivity of 
10.sup.-15 mho-cm.sup.-1. 
Other modifications of the present invention may occur to those skilled in 
the art based upon a reading of the present disclosure and these 
modifications are intended to be included within the scope of the present 
invention.