Coated carrier

A carrier comprised of a core and a polymer coating of (1) styrene/monoalkylaminoalkyl methacrylate or (2) styrene/dialkylaminoalkyl methacrylate.

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 components, or coated carrier particles that can be 
prepared by, for example, dry powder processes. More specifically, the 
present invention relates to carrier compositions comprised of a core and 
thereover copolymers of styrene and a monoalkylaminoalkyl methacrylate, or 
styrene and a dialkylaminoalkyl methacrylate. 
More specifically, the present invention relates to carrier particles 
comprised of a core with a coating thereover of copolymers of styrene and 
diisopropylaminoethyl methacrylate, styrene copolymers with monoalkyl or 
dialkyl aminoethyl methacrylate, t-butylaminoethyl methacrylate, and the 
like. The carrier may include the copolymer coating thereover in admixture 
with other suitable polymers, and more specifically, with a second 
polymer, such as a fluoropolymer, polymethylmethacrylate, poly(urethane), 
especially a crosslinked polyurethane, such as a poly(urethane)polyester 
and the like, and moreover the copolymer, or mixture of polymer coatings 
may contain a conductive component, such as carbon black, and which 
conductive component is preferably dispersed in the copolymer coating. 
With the conductive component, there are enabled carriers with increased 
developer triboelectric response, that is, stable triboelectric values up 
to about 80 microcoulombs per gram at relative humidities of from about 20 
to about 90 percent, improved image quality performance, excellent high 
conductivity ranges of, for example, from about 10.sup.-10 to about 
10.sup.-7 (ohm-cm).sup.-1, and the like. The carrier triboelectrical 
charge may be, for example, a carrier tribo range of from about a plus 
(positive charge) 25 to about 80, and preferably from about a positive 35 
to about a positive 70 microcoulombs per gram as determined by the known 
Faraday Cage method. 
The carrier particles of the present invention can be selected for a number 
of different xerographic copiers and printers, such as high speed color 
xerographic copies, in the range of, for example, about 70 to about 135 
impressions per minute, printers, digital copiers, and more specifically, 
wherein colored copies with excellent and substantially no background 
deposits are achievable in copiers, printers, digital copiers, and the 
combination of xerographic copiers and digital systems. Developer 
compositions comprised of the carrier particles illustrated herein and 
prepared, for example, by a dry coating process are generally useful in 
electrostatographic or electrophotographic imaging systems, especially 
xerographic imaging and printing processes, and digital processes. 
Additionally, the invention developer compositions comprised of 
substantially conductive carrier particles are useful in imaging methods 
wherein relatively constant conductivity parameters are desired. 
Furthermore, in the aforementioned imaging processes the triboelectric 
charge on the carrier particles can be preselected depending on the 
polymer composition and dispersant component applied to the carrier core 
and the type and amount of the conductive component selected. 
PRIOR ART 
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. 
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 can contain various cores, including 
steel, with a coating thereover of fluoropolymers, and terpolymers of 
styrene, methacrylate, and silane compounds. A number of these coatings 
can deteriorate rapidly, especially when selected for a continuous 
xerographic process where part of, or 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, usually adversely affect 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, and relatively low tribo as compared to the 
high tribo carriers of the present invention. 
There are 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 is 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 
5.0 percent by weight, based on the weight of the coated carrier 
particles, of thermoplastic or thermosetting resin particles. The 
resulting mixture is then dry blended until the 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 resin particles to melt and fuse on the carrier 
core. 
There is illustrated in U.S. Pat Nos. 4,937,166 and 4,935,326, the 
disclosures of which are totally incorporated herein by reference, carrier 
containing a mixture of polymers, such as two polymers, not in close 
proximity in the triboelectric series. Moreover, in U.S. Pat. No. 
4,810,611, the disclosure of which is totally incorporated herein by 
reference, there is disclosed the addition to carrier coatings of 
colorless conductive metal halides in an amount of from about 25 to about 
75 weight percent, such halides including copper iodide, copper fluoride, 
and mixtures thereof. The present invention has the advantage overthis 
prior art of for example achieving high triboelectric, especially positive 
charge on the carrier particles, that is, high negative triboelectric 
charge is imparted to the toner particles developed onto a photoreceptor 
in, for example, a xerographic development environment. Further, a full 
range of electrical properties of the carrier particles can be achieved at 
high triboelectric charging values, from carrier conductivities of 
10.sup.-17 mho/cm to 10.sup.-6 mho/cm, that is, from the insulative to the 
conductive regime. 
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 will usually 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 processing excessive quantities 
of solvents, and further, usually these processes result in low product 
yields. Also, solution coated carrier particles, when combined and mixed 
with finely divided toner particles, provide in some instances 
triboelectric charging values which are too low for many uses. The powder 
coating processes of the present invention overcome these disadvantages, 
and further enable developers that are capable of generating high 
triboelectric charging values with finely divided toner particles; and 
also wherein the carrier particles in embodiments are of substantially 
constant conductivity. 
When resin coated carrier particles are prepared by powder coating process 
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 process of the 
present invention and the carriers thereof, 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. Specifically, therefore, with 
the carrier compositions and process of the present invention there can be 
formulated developers with selected high triboelectric charging 
characteristics and/or conductivity values in a number of different 
combinations. Thus, for example, there can be formulated in accordance 
with the invention of the present application developers with 
conductivities of from about 10.sup.-6 (ohm-cm).sup.-1 to about 10.sup.-17 
(ohm-cm).sup.-1, preferably from about 10.sup.-10 (ohm-cm).sup.-1 to about 
10.sup.-6 (ohm-cm).sup.-1, and most preferably from about 10.sup.-8 
(ohm-cm).sup.-1 to about 10.sup.-6 (ohm-cm).sup.-1, determined in a 
magnetic brush conducting cell, and high carrier triboelectric charging 
value of from a positive triboelectric charge of positive about 20 to a 
positive of about 80, and for example, from a positive about 30 to a 
positive about 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 conductivity values in a 
certain range with different triboelectric charging characteristics by, 
for example, maintaining the same total coating weight on the carrier 
particles and contained therein conductive particles of, for example, 
carbon black. 
Other U.S. Patents that may be of interest include U.S. Pat. No. 3,939,086, 
which illustrates steel carrier beads with polyethylene coatings, see 
column 6; U.S. Pat. No. 5 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, the 
disclosures of each of these patents being totally incorporated herein by 
reference. 
SUMMARY OF THE INVENTION 
It is a feature of the present invention to provide toner and developer 
compositions with carrier particles containing polymer coatings. 
In another feature of the present invention there are provided dry coating 
processes for generating carrier particles of substantially constant 
conductivity parameters. 
In yet another feature of the present invention there are provided dry 
coating processes for generating carrier particles of substantially 
constant conductivity parameters, and excellent triboelectric charging 
values. 
Further, in yet another feature of the present invention there are provided 
carrier particles with tribo values of at least about 30 microcoulombs per 
gram, and wherein the carrier includes thereover a copolymer coating of a 
copolymer of polystyrene/monoalkyl or dialkylaminoethylmethacrylate, and 
poly(urethane), and a second polymer. 
Aspects of the invention include a carrier comprised of a core and a 
polymer coating of (1) styrene/monoalkylaminoalkyl methacrylate or (2) 
styrene/dialkylaminoalkyl methacrylate; a carrier wherein each of said 
alkyls contain from 1 to about 25 carbon atoms; a carrier wherein each of 
said alkyls contain from 1 to about 6 carbon atoms; a carrier wherein said 
polymer is a copolymer of styrene, and dimethylaminoethyl methacrylate, a 
copolymer of styrene and diethylaminoethyl methacrylate, a copolymer of 
styrene and t-butylaminoethyl methacrylate, or a copolymer of styrene and 
diisopropylaminoethyl methacrylate; a carrier wherein the polymer is (1) a 
copolymer of t-butyl styrene, and dimethylaminoethyl methacrylate, (2) a 
copolymer of t-butyl styrene and diethylaminoethyl methacrylate, a 
copolymer of t-butyl styrene and t-butylaminoethyl methacrylate, or a 
copolymer of t-butyl styrene and diisopropylaminoethyl methacrylate; a 
carrier wherein said polymer is selected from the group consisting of (1) 
polystyrene/monoalkyl or dialkylaminoalkyl methacrylate, and (2) poly 
t-butyl styrene/monoalkyl or poly t-butyl dialkylaminoalkyl methacrylate; 
a carrier wherein polymer (1) contains from about 50 to about 95 weight 
percent of styrene, and from about 5 to about 50 weight percent of said 
monoalkyl or dialkylaminoalkyl methacrylate, and wherein polymer (2) 
contains t-butyl of styrene in an amount of from about 50 to about 95; a 
carrier wherein polymer (1) possesses an M.sub.w of from about 20,000 to 
about 800,000, and an M.sub.n of from about 12,000 to about 350,000, and 
polymer (2) possesses an M.sub.w of from about 20,000 to about 800,000, 
and of an M.sub.n of from about 12,000 to about 350,000 as measured by gel 
permeation chromatography; a carrier wherein the polymer coating weight is 
from about 0.1 to about 20 weight percent; a carrier wherein the polymer 
coating weight is from about 1 to about 3 weight percent; a carrier 
wherein the polymer coating contains a conductive component; a carrier 
wherein the conductive component is a metal oxide, or is carbon black; a 
carrier wherein said conductive component is carbon black selected in an 
amount of from about 10 to about 60 weight percent; a carrier wherein said 
core is a metal, a metal oxide, or a ferrite; a carrier with a 
triboelectric charge of from about a positive 30 to about a positive 80 
microcoulombs per gram; a carrier with a triboelectric charge of from 
about a positive 35 to about a positive 50 microcoulombs per gram; a 
developer comprised of the carrier and toner; a developer wherein the 
toner is comprised of a thermoplastic resin and colorant; a developer 
wherein the colorant is a pigment or a dye; a developer comprised of a (1) 
carrier core and coating of a polymer of styrene/monoalkylaminoalkyl 
methacrylate or styrene/dialkylaminoalkyl methacrylate, and (2) a toner; a 
developer wherein the carrier core is selected from the group consisting 
of iron, ferrites, steel and nickel; a carrier wherein said 
dialkylaminoalkyl methacrylate is diisopropylaminoethyl methacrylate; a 
carrier with a carrier triboelectric charge of from about a positive 30 to 
about a positive 80 microcoulombs per gram, and a toner triboelectric 
charge of from about a negative 30 to about a negative 80 microcoulombs 
per gram, or with a carrier triboelectric charge of from about a positive 
35 to about a positive 50 microcoulombs per gram and a toner triboelectric 
charge of from about a negative 35 to about a negative 50 microcoulombs 
per gram; a carrier with a volume average diameter of from about 50 to 
about 200 microns; a carrier containing a second polymer coating; a 
carrier wherein said polymer coating is poly(styrene/diisopropylaminoethyl 
methacrylate) with a diisopropylaminoethyl methacrylate content of from 
about 27 weight percent to about 40 weight percent, the coating weight of 
polymer on said core is from about 0.3 to about 1.0 percent, the carrier 
volume median diameter is from about 65 to about 120 microns, and the core 
is steel or a ferrite; a carrier wherein said core is a metal of spherical 
or atomized steel, a metal oxide, or magnetite, Cu/Zn-ferrite, 
Ni/Zn-ferrite, Sr (strontium)-ferrite, or Ba-ferrite; a carrier comprised 
of a core and a polymer of styrene/alkylaminoalkyl methacrylate, 
styrene/dialkylaminoalkyl methacrylate, or mixtures thereof; a carrier 
wherein said alkyl contains from 1 to about 12 carbon atoms; a process 
wherein an image is developed with the composition; a carrier wherein said 
polymer comprises a mixture of polymers; and 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 5 percent by weight, based 
on the weight of the coated carrier particles, of the polymer, and which 
polymer may optionally contain dispersed therein carbon black or a similar 
conductive component until adherence thereof of the polymer to the carrier 
core by mechanical impaction or electrostatic attraction; heating the 
resulting mixture of carrier core particles and polymer to a temperature, 
for example, of between from about 200.degree. F. to about 625.degree. F., 
preferably about 400.degree. F. for an effective period of, for example, 
from about 10 minutes to about 60 minutes enabling the polymer 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 of, for example, from about 50 to about 200 microns in 
diameter; a carrier composition comprised of a core, and thereover a 
polymer as indicated herein, such as a styrene dialkylaminoalkyl 
methacrylate present in an amount of, for example, from about 0.05 to 
about 5 weight percent of the total carrier composition, and which coating 
may optionally contain a conductive component, such as a metal oxide, a 
conductive component like carbon black, and wherein the conductive 
component is selected in an amount of from about 10 to about 75 weight 
percent, and preferably from about 15 to about 50 weight percent; a 
carrier with two polymers thereover, wherein the first polymer is as 
indicated herein, and wherein the conductive component for the first or 
second polymer is a metal oxide, or a pigment like carbon black selected 
in an amount of from about 10 to about 50 weight percent; and wherein the 
second polymer is as illustrated herein in the U.S. patents incorporated 
herein by reference, for example a fluorocarbon, polymethylmethacrylate 
(PMMA), a thermosetting polymer such as a thermosetting polyurethane, a 
polyester, or a styrene polymer, and wherein the first polymer is selected 
in an amount of from about 1 to about 100, or from about 10 to about 75 
weight percent, based on the total weight of the polymers and conductive 
components present in the carrier and the second polymer is selected in an 
amount of from about 99 to about 0, or from about 90 to about 25 weight 
percent, based on the total weights of all polymers and conductive 
components present in the carrier; or wherein the carrier core is a metal, 
a ferrite, a metal oxide, and the like, such as known carrier cores. 
Various suitable solid core carrier materials can be selected for the 
carriers and developers of the present invention. Characteristic core 
properties of importance 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 magnetic 
brush development processes; and also wherein the carrier cores possess 
desirable mechanical aging characteristics; and also, for example, a 
suitable core surface morphology to permit high electrical conductivity of 
the developer comprising the carrier and a suitable toner. Examples of 
carrier cores that can be selected include iron or steel, such as atomized 
iron or steel powders available from Hoeganaes Corporation or Pomaton 
S.p.A (Italy), ferrites such as Cu/Zn-ferrite containing, for example, 
about 11 percent copper oxide, 19 percent zinc oxide, and 70 percent iron 
oxide and available from D.M. Steward Corporation or Powdertech 
Corporation, Ni/Zn-ferrite available from Powdertech Corporation, Sr 
(strontium)-ferrite, containing, for example, about 14 percent strontium 
oxide and 86 percent iron oxide and available from Powdertech Corporation 
and Ba-ferrite, magnetites, available, for example, from Hoeganaes 
Corporation (Sweden), nickel, mixtures thereof, and the like. 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. 
Examples of polymer coatings selected for the carrier include copolymers of 
styrene and a monoalkyl, or dialkyl amino alkyl methacrylate such as a 
dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, 
diisopropylaminoethyl methacrylate, or t-butylaminoethyl methacrylate. 
Specific examples of copolymer coatings are poly(styrene/dimethyl 
aminoethylmethacrylate), poly(styrene/tertiary-butylaminoethyl 
methacrylate), poly(styrene/diethylaminoethylmethacrylate), 
poly(styrene/diisopropylamino ethylmethacrylate), copolymers of styrene 
with other monoalkyl or dialkylaminoethyl methacrylates Akyl contains, for 
example, from about 1 to about 25, and preferably from 1 to about 10 
carbon atoms, such as methyl, ethyl, propyl, butyl, pentyl, heptyl, hexyl, 
and the like. 
The monomers for synthesizing the above polymers are obtained from Aldrich 
Chemical Company with regard to styrene, dimethylaminoethyl methacrylate, 
and diethylaminoethyl methacrylate, and Scientific Polymer Products with 
regard to diisopropylaminoethyl methacrylate and t-butylaminoethyl 
methacrylate. Synthetic methods for the preparation of polymers and 
copolymers from these monomers may be bulk polymerization, solution 
polymerization, emulsion polymerization, suspension or semisuspension 
polymerization, or any other known suitable polymerization methods. 
The polymers can also be prepared by bulk polymerization which can be 
accomplished with monomers in the absence of solvent, and by solution 
polymerization can be effected in a solvent medium such as toluene in 
which the monomer or mixture of monomers is combined with a suitable 
initiator such as 2,2'-azobis(2-methylpropionitrile), referred to as AIBN, 
and reacted for an effective period of time, for example from about 7 to 
about 15, and preferably about 11 hours, at an elevated temperature, for 
example from about 65.degree. C. to about 80.degree. C. From this 
reaction, a solution with a solids content of about 25 to 30 percent by 
weight polymer can be obtained, in which the polymer has a glass 
transition of about 60.degree. C. to about 130.degree. C. and molecular 
weight by gel permeation chromatography of about M.sub.w =50,000 to about 
700,000 with molecular weight dispersibility, that is the ratio of M.sub.w 
/M.sub.n, or MWD=about 1.6 to about 3.0. 
The suspension polymerization method involves mixing monomers and initiator 
to obtain a clear organic phase. The monomer mixtures can contain, for 
example, from about 50 to about 98 weight percent of styrene or t-butyl 
styrene or other derivatives of styrene, and from about 2 to about 50 
weight percent of said monoalkyl or dialkylaminoalkyl methacrylate, and 
more preferably from 2 to 30 weight percent of said monoalkyl or 
dialkylaminoalkyl methacrylate. A suitable polymerization initiator, such 
as 2,2'-azobis(2-methylpropionitrile), referred to as AIBN, is used from 
about 0.1 to 2.0 weight percent based on monomer, and more preferably from 
0.2 to 1.0 weight percent. The organic phase is then combined with an 
aqueous solution containing about 0.5 to about 5.0 weight percent of an 
appropriate monomer suspending agent like polyvinylalcohol, such as Air 
Products Airvol 603 polyvinyl alcohol, and more preferably from 1.5 to 3.0 
weight percent of polyvinyl alcohol and an aqueous phase inhibitor such as 
potassium iodide of from about 1.5 to about 5.0 weight percent on monomer. 
The desired particle size is obtained by homogenizing the two phases with 
a Brinkmen homogenizer equipped with a Polytron Generator with three 
stationary and three moving rings of flat rotor design for five minutes at 
about 4,000 to 14,000 RPM and more preferably from 6,000 to 10,000 RPM. 
The resulting suspended organic phase is then transferred to the preheated 
reactor and stirred at about 65 to 100 RPM to maintain stability of the 
suspension. The suspension is then held at about 70.degree. C. for about 4 
to 8 hours to complete the polymerization. The polymer suspension is then 
cooled, removed from the reactor, washed and centrifuged 5 times with a 
90/10 volume ratio of methanol/water and finally washed with water only. 
The wet polymer suspension is then air dried, placed in a vacuum oven at 
from about 40.0.degree. C. to about 80.0.degree. C. to complete drying, 
and further broken down to its primary particle size by ball milling 
followed by screen sieving. This process yields a polymer particle size 
having a volume median of about 1.50 20 .mu.m to about 10.0 .mu.m, and a 
molecular weight by gel permeation chromatography ranging from, for 
example, about 100,000 to about 700,000. 
Emulsion polymerization is accomplished by the continuous addition to a 
suitable reaction vessel containing water, and providing mechanical 
stirring, nitrogen atmosphere, and thermostatic control, a mixture of 
monomers and an initiator, such as ammonium persulfate initiator, as 
obtained from the Aldrich Chemical Company, (0.2 to 0.6 percent by weight 
of monomers). The polymerization can be effected by heating to, for 
example, between about 55.degree. C. and about 65.degree. C. to achieve 
molecular weights, M.sub.w by gel permeation chromatography ranging from, 
for example, about 200,000 to about 500,000. The polymer or copolymer 
powder is isolated by, for example, freeze drying in vacuo. The resulting 
polymer particle diameter size is, for example, 0.1 to 2.0 microns in 
volume average diameter. 
The polymer coating preferably has dispersed therein in embodiments 
conductive components, such as metal oxides like tin oxide, conductive 
carbon blacks, and the like, in effective amounts of, for example, from 
about 0 to about 70 and preferably from about 15 to about 60 weight 
percent. Specific examples of conductive components include the conductive 
carbon black SC Ultra available from Conductex, Inc., and antimony-doped 
tin oxide Zelec ECP3005-XC manufactured by E.I. DuPont. 
The process for incorporating the polymer onto a carrier core can be 
sequential, a process in which one of the two polymers, when two polymers 
are selected, is fused to the surface in a first step and the second 
polymer is fused to the surface in a subsequent fusing operation. 
Alternatively, the process for incorporation can comprise a single fusing. 
Also, the carrier coating can have incorporated therein various known 
charge enhancing additives, such as quaternary ammonium salts, and more 
specifically, distearyl dimethyl ammonium methyl sulfate (DDAMS), bis[1 
-[(3,5-disubstituted-2-hydroxyphenyl)azo]-3-(mono-substituted)-2-naphthale 
nolato(2-)] chromate(1-), ammonium sodium and hydrogen (TRH), cetyl 
pyridinium chloride (CPC), FANAL PINK.RTM. D4830, and the like, including 
those as specifically illustrated herein, and other effective known charge 
agents or additives, such as E84 zinc complex of 3,5-ditertiary butyl 
salicylic acid and E-88 tris(3,5-di-tertiary butyl sallicylato) aluminum, 
which are commercially available from Orient Chemical Company, TRH 
ammonium bis[1-(3,5-dinitro-2-hydroxy phenyl) 
azo-3-(N-phenylcarbamoyl)-2-naphthalenolate] chromate, which is 
commercially available from Hodogaya Chemicals, and aluminum complexes 
such as those disclosed in U.S. Pat. No. 324,613 and hydroxy 
bis(3,5-di-tertiary butyl salicylic) aluminate monohydrate disclosed in 
U.S. Pat. No. 5,223,368 the disclosures of which are totally incorporated 
herein by reference. The charge additives are selected in various 
effective amounts, such as from about 0.05 to about 15, and from about 0.1 
to about 3 weight percent, based on the sum of the weights of all polymer, 
conductive additive. The addition of various known charge enhancing 
additives can act to further increase the positive triboelectric charge 
imparted to the carrier, and therefore, further increase the negative 
triboelectric charge imparted to the toner in, for example, a xerographic 
development subsystem. 
Examples of second polymers selected can include polymonoalkyl or dialkyl 
methacrylates or acrylates, polyurethanes, fluorocarbon polymers such as 
polyvinylidenefluoride, polyvinylfluoride, and polypentafluorostyrene, 
polyethylene, polyethylene-co-vinylacetate, 
polyvinylidenefluoride-co-tetrafluoroethylene, and the like. Other known 
related polymers not specifically mentioned herein may also be selected, 
such as those illustrated in the U.S. Pat. No. 4,937,166 and U.S. Pat. No. 
4,935,326 patents mentioned herein. 
Another second polymer is comprised of a thermosetting polymer, more 
specifically a poly(urethane) thermosetting resin which contains, for 
example, from about 75 to about 95, and preferably about 80 percent by 
weight of a polyester polymer, which, when combined with an appropriate 
crosslinking agent such as isopherone diisocyannate and initiator such as 
dibutyl tin dilaurate, forms a crosslinked poly(urethane) resin at 
elevated temperatures. An example of a polyurethane is 
poly(urethane)/polyester polymer or Envirocron (product number PCU10101, 
obtained from PPG Industries, Inc.). This polymer has a melt temperature 
of between about 210.degree. F. and about 266.degree. F., and a 
crosslinking temperature of about 345.degree. F. This second polymer is 
mixed together with the first copolymer polymer, generally prior to mixing 
with the core, which when fused forms a uniform coating of the first and 
second polymers on the carrier surface. The second polymer is present in 
an amount of from about 0 percent to about 99 percent by weight, based on 
the total weight of the first and second polymers and the conductive 
component in the first polymer. 
Advantages of the carriers of the present invention include, for example, 
excellent robust carrier tribo charge of a positive value, excellent 
admix, for example from about 1 to about 30 seconds as determined in the 
charge spectrograph, and the like. 
Other advantages of the present invention include increased resistance of 
the carrier to mechanical aging in a xerographic environment and a 
decreased sensitivity of the carrier triboelectric value to the relative 
humidity of the environment. With respect to high toner tribo charge of a 
negative value, this property is important to xerographic, especially 
color applications, primarily because there is enabled development of 
toner particles into regions of the imaging member, such as a 
photoreceptor where strong fringe electrical fields exist, that is, at the 
borders of solids areas and lines. Developing toner particles through 
these fringe fields minimizes or eliminates the untoned part of the image 
which appears between two adjacent colors in an image. 
Various effective suitable processes can be selected to apply the polymer, 
or mixture, for example from 2 to about 5, and preferably 2, of polymer 
coatings to the surface of the carrier particles. Examples of typical 
processes for this purpose include combining the carrier core material, 
and the polymers and conductive component by cascade roll mixing, or 
tumbling, milling, shaking, electrostatic powder cloud spraying, fluidized 
bed, electrostatic disc processing, and an electrostatic curtain. 
Following application of the polymers, 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, and the parameters 
of the heating step may be selected to enable the formation of a 
continuous film of the coating polymers 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.-7 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. Moreover, known solution 
processes may be selected for the preparation of the coated carriers. 
Illustrative examples of toner binders, include thermoplastic resins, which 
when admixed with the carrier generates developer compositions, such 
binders including styrene based resins, styrene acrylates, styrene 
methacrylates, styrene butadienes, polyamides, epoxies, polyurethanes, 
diolefins, vinyl resins, polyesters, such as those obtained by the 
polymeric esterification products of a dicarboxylic acid and a diol 
comprising a diphenol. Specific vinyl monomers that can be selected 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; styrene 
butadiene copolymers; mixtures thereof; and other similar known resins. 
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 dimethyl terephthalate, 
1,3-butanediol, 1,2-propanediol and pentaerythritol. Also, the crosslinked 
and reactive extruded polyesters of U.S. Pat. No. 5,376,494, the 
disclosure of which is totally incorporated herein by reference, may be 
selected as the toner resin. Polyester resins obtained from the reaction 
of propoxylated and ethoxylated bisphenol A diols with dicarboxylic 
acids/esters, i.e. isophthalic acid and terephthalic acid, which may or 
may not be branched/crosslinked by multifunctional hydroxyl or carboxylic 
acid containing branching agents and which may or may not be unsaturated 
due to reaction with maleic anhydride/fumaric acid structures. 
Generally, from about 1 part to about 5 parts by weight of toner particles 
are mixed with from about 10 to about 300 parts by weight of the carrier 
particles. 
Numerous well known suitable colorants, such as pigments dyes, or mixtures 
thereof, and preferably pigments can be selected as the colorant for the 
toner particles including, for example, carbon black, nigrosine dye, lamp 
black, iron oxides, magnetites, and mixtures thereof. The colorant, which 
is preferably carbon black, should be present in a sufficient amount to 
render the toner composition highly colored. Thus, the colorant is present 
in amounts of for example, from about 1 percent by weight to about 20, and 
preferably from about to about 12 percent by weight, based on the total 
weight of the toner components, however, lesser or greater amounts of 
pigment may be selected. Colorants include dyes, pigments, mixtures 
thereof, mixtures of dyes, mixtures of pigments, and the like. 
When the colorant particles are comprised of magnetites, which are a 
mixture of iron oxides (FeO.multidot.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 
like REGAL 330.RTM., is contained therein, about 90 percent by weight of 
binder material is selected. Generally, 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 colorant particles such as carbon black. 
Also, there may be selected colored toner compositions comprised of toner 
resin particles, carrier particles and as colorants, such as pigments, 
dyes, and mixtures thereof, and preferably magenta, cyan and/or yellow 
particles, and mixtures thereof. More specifically, illustrative examples 
of magentas that may be selected include 1,9-dimethyl-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 
Cl 26050, Cl Solvent Red 19, and the like. Examples of cyans that may be 
used include copper tetra-4-(octadecyl 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 
yellows 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. Other known suitable 
colorants, such as reds, blues, browns, greens, oranges, and the like can 
be selected. These colorants, especially pigments are generally present in 
the toner composition in an amount of from about 1 weight percent to about 
15, and for example, from about 2 to about 12 weight percent based on the 
weight of the toner components of binder and pigment. 
For further enhancing the charging characteristics of the developer 
compositions described herein, and as optional components, there can be 
incorporated therein with respect to 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; 
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; U.S. Pat. No. 4,560,635, 
the disclosure of which is totally incorporated herein by reference; and 
other similar known charge enhancing additives, such as metal complexes, 
BONTRON E-84.TM., BONTRON E-88.TM., and the like. These additives are 
usually selected in an amount of from about 0.1 percent by weight to about 
20, and for example, from about 3 to about 12 percent by weight. These 
charge additives can also be dispersed in the carrier polymer coating as 
indicated herein. 
The toner composition of the present invention can be prepared by a number 
of known methods including melt blending the toner resin particles, and 
colorants of the present invention followed by mechanical attrition, in 
situ emulsion/aggregation/coalescence, reference U.S. Pat. Nos. 5,370,963; 
5,344,738; 5,403,693; 5,418,108; 5,364,729 and 5,405,728, and the like. 
Other methods include those well known in the art such as spray drying, 
melt dispersion, dispersion polymerization and suspensione polymerization. 
In one dispersion polymerization method, a solvent dispersion of the resin 
particles and the pigment particles are spray dried under controlled 
conditions to result in the desired product. Toner particles sizes and 
shapes are known and include, for example, a toner size of from about 2 to 
about 25, and preferably from about 6 to about 14 microns in volume 
average diameter as determined by a Coulter Counter; shapes of irregular, 
round, spherical, and the like may be selected. 
The toner and developer compositions 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. Nos. 4,265,990; 4,585,884; 4,584,253 and 4,563,408, the disclosure of 
each patent being totally incorporated herein by reference, and other 
similar layered photoresponsive devices. Examples of generating layers are 
trigonal selenium, metal phthalocyanines, metal free phthalocyanines, 
titanyl phthalocyanines, hydroxygallium phthalocyanines, and vanadyl 
phthalocyanines. As charge transport molecules there can be selected the 
aryl diamines disclosed in the aforementioned patents, such as the '990 
patent. These layered members are conventionally charged negatively thus 
requiring a positively charged toner. 
Images, especially colored images obtained with this developer composition 
possess, for example, acceptable solids, excellent halftones, and 
desirable line resolution with acceptable or substantially no background 
deposits excellent chroma, superior color intensity, constant color chroma 
and intensity over extended time periods, such as 1,000,000 imaging 
cycles, and the like. 
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.

SYNTHETIC EXAMPLE I 
A copolymer of 60 weight percent styrene and 40 percent 
diisopropylaminoethyl methacrylate (DIAEMA) was synthesized by an emulsion 
copolymerization which involved initiation and growth of copolymer latex 
particles by the continuous addition of an emulsified monomer mixture, and 
more specifically, a mixture of 60 weight percent styrene and 40 weight 
percent diisopropylaminoethyl methacrylate monomers to provide a product 
with a solids content of from about 15 percent by weight to about 40 
percent by weight, which solids content were comprised of the copolymer 
poly(styrene-co-DIAEMA) at approximately a 60/40 monomer ratio. A process 
known as "seed and growth" emulsion polymerization was utilized, whereby a 
solution of 1.0 gram of ammonium persulfate, together with 21 grams of 
Triton X-405 surfactant, in 1 liter of distilled water was prepared in a 
suitable reaction vessel, and thereafter there was provided mechanical 
stirring, a nitrogen atmosphere, and a thermostatic control. Initiation 
and growth of latex particles was accomplished by the addition of 
approximately 25 percent of the monomer mixture with the temperature at 
50.degree. C. Rapid stirring (170 to 180 RPM) was continued until any 
exotherm was completed. This was followed by a continuous and metered 
addition of the remaining monomer mixture at a rate of 1.0 to 2.0 
grams/minute. This polymerization stage was accomplished between 
55.degree. C. to 56.degree. C., with heating continued for an additional 1 
to 3 hours. The copolymer powder was isolated by freeze drying the residue 
free latex in vacuo. The resulting number median particle diameter of the 
above copolymer product was 0.10 to 0.50 micron, as determined by light 
scattering measurement. 
Molecular weight (M.sub.w) of the product polymer was determined by gel 
permeation chromatography and was typically in the range of 200,000 to 
500,000, and more specifically, a polystyrene equivalent molecular weight 
of M.sub.w =346,000 was achieved. 
SYNTHETIC EXAMPLE II 
A copolymer of 60 weight percent styrene and 40 percent 
diisopropylaminoethyl methacrylate (DIAEMA) was synthesized by an emulsion 
copolymerization which involved initiation and growth of copolymer latex 
particles by the continuous addition of a monomer mixture, and more 
specifically, a mixture of 60 weight percent styrene and 40 weight percent 
diisopropylaminoethyl methacrylate monomers, to which had been introduced 
0.22 gram of divinyl benzene, as a branching and crosslinking agent. A 
product with solids content of from 15 percent by weight to about 30 
percent by weight was composed of the copolymer poly(styrene-co-DIAEMA) at 
approximately a 60/40 monomer ratio. A process known as "seed and growth" 
emulsion polymerization was utilized, whereby a solution of 1.0 gram of 
ammonium persulfate with 21 grams of Triton X-405 surfactant in 1 liter of 
distilled water, was prepared in a suitable reaction vessel with 
mechanical stirring, a nitrogen atmosphere, and a thermostatic control. 
Initiation and growth of latex particles was accomplished by the addition 
of approximately 25 percent of the styrene/DIAEMA monomer mixture, with 
the temperature at 50.degree. C. Rapid stirring was continued until any 
exotherm was completed. This was followed by a continuous and metered 
addition at a rate of 1.0 to 2.0 grams/minute of the remaining monomer 
mixture, to which had been introduced 0.22 gram of divinyl benzene. This 
polymerization stage was accomplished at 55.5.degree. C., with heating 
continued for an additional 3.5 hours. 
The copolymer powder was isolated by freeze drying the residue free latex 
in vacuo. The resulting number median particle diameter of the above 
copolymer product was 0.10 to 0.50 micron, as determined by light 
scattering measurement. 
Molecular weight (M.sub.w) of the isolated polymer was determined by gel 
permeation chromatography and was typically in the range of 200,000 to 
500,000. The specific M.sub.w in this Example could only be estimated, as 
a turbid solution in THF was observed, which could effect GPC 
determination. 
SYNTHETIC EXAMPLE III 
Poly(t-butylstyrene-co-diisopropylaminoethyl-methacrylate) with a 
composition of 72.86 t-butylstyrene and 27.14 diisopropylaminoethyl 
methacrylate was prepared by suspension polymerization as follows. 
A 2.5 liter jacketed glass reactor was fitted with a stainless steel 
stirrer, thermal couple temperature probe, water cooled condenser with 
nitrogen outlet, a nitrogen inlet, internal/external cooling capabilities, 
and heated at 70.degree. C. with a hot water circulating bath. The 
monomers were all passed through a column of basic aluminum oxide to 
remove inhibitors and purged with nitrogen gas to remove oxygen. The 
polymerization initiator 2,2'- azobis(2-methylpropionitrile), referred to 
as AIBN, was used as received. 
To a suitable mixing vessel were added 89.16 grams of diisopropylaminoethyl 
methacrylate, 239.34 grams of t-butylstyrene, and 1.31 grams of AIBN. This 
mixture was then stirred to dissolve the AIBN until a clear organic phase 
was obtained. The organic phase was then transferred to a 3.0 liter vessel 
that contained 1.00 kilogram of a 2.5 percent by weight Air Products 
Airvol 603 polyvinyl alcohol, and 10.90 grams of potassium iodide aqueous 
phase inhibitor. The desired particle size was obtained by homogenizing 
the two phases with a Brinkman homogenizer equipped with a Polytron 
Generator with three stationary and three moving rings of flat rotor 
design. Homogenization was conducted for five minutes at about 8,000 RPM. 
The resulting suspended organic phase was then transferred to the 
preheated reactor and stirred at about 80 RPM to maintain stability of the 
suspension. The suspension was then maintained at 70.degree. C. 
+/-1.0.degree. C. for 5 hours and 46 minutes to complete polymerization. 
The polymer suspension was then cooled to about room temperature, about 
25.degree. C. throughout the Examples, unless otherwise indicated, removed 
from the reactor, washed and centrifuged 5 times with a 90/10 volume ratio 
of methanol/water and then a final washed with water only. The wet polymer 
suspension was then air dried, placed in a vacuum oven at from about 
40.0.degree. C. to 80.0.degree. C. to complete drying, and further broken 
or attrited down to its primary particle size by ball milling followed by 
screening with a 65 .mu.m sieve. The resulting suspension polymerized 
polymer had a volume median of about 5.0 .mu. (microns) and a second pass 
glass transition onset of 93.0.degree. C. Molecular weight of the 
copolymer product by gel permeation chromatography was M.sub.w =405,000, 
M.sub.n =144,000, and MWD =2.8. Percent nitrogen by CHN analysis was 1.85 
and 28 percent amine monomer content by NMR. 
CARRIER EXAMPLE I 
In the first step of the carrier coating process, 22.46 grams of the 
copolymer of Synthetic Example I, and more specifically, a copolymer of 60 
weight percent styrene and 40 percent diisopropylaminoethyl methacrylate 
(DIAEMA) synthesized by an emulsion copolymerization, and 2,246 grams of a 
spherical steel core with a volume median diameter of 100 microns (Nuclear 
Metals, Inc.) were mixed. The mixing was accomplished in a V-Cone blender 
with the following process conditions: blender speed of 23.5 rotations per 
minute and a blend time of 30 minutes. There resulted uniformly 
distributed and electrostatically attached polymer on the core as 
determined by visual observation. In the second step, the resulting 
carrier particles were inserted into a rotating tube furnace for a period 
of 30 minutes. This furnace was maintained at a temperature of 400.degree. 
F. thereby causing the polymer to melt and fuse to the core. The product 
from the kiln was screened through an 84 TBC (Tensile Bolt Cloth) mesh 
screen to remove any large agglomerates, specifically agglomerates larger 
than about 210, for example about 225 microns. The final product was 
comprised of a carrier core of spherical steel with a total of 1.0 percent 
coating weight polymer of poly(DIAEMA-co-styrene) (40 percent/60 percent 
monomer ratio) by weight on the surface, and the resulting carrier volume 
median diameter size was 100 microns. 
A developer composition was then prepared by mixing 200 grams of the above 
prepared carrier with 10 grams of a 9 micron volume median diameter 
(volume average diameter) toner composition comprised of a 30 percent (by 
weight) gel content of a partially crosslinked polyester resin, reference 
U.S. Pat. No. 5,376,494, the disclosure of which is totally incorporated 
herein by reference, obtained by the reactive extrusion of a linear 
bisphenol A propylene oxide fumarate polymer, and about 10 percent by 
weight of REGAL 330.RTM.. Thereafter, the triboelectric charge on the 
carrier particles was determined by the known Faraday Cage process, and 
there was measured on the carrier a charge of 39.2 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 was 2.75 
E.sup.11 mho-cm.sup.-1. Therefore, these carrier particles were 
semiconductive. 
CARRIER EXAMPLE II 
In the first step of the carrier coating process, 22.46 grams of the 
copolymer of Synthetic Example II, and more specifically, a copolymer of 
60 weight percent styrene and 40 percent diisopropylaminoethyl 
methacrylate (DIAEMA) synthesized by an emulsion copolymerization and 
containing divinyl benzene as a network or crosslink forming agent, and 
2,246 grams of a spherical steel core with a particle size of 100 microns 
(Nuclear Metals, Inc.) were mixed. The mixing and fusing process steps 
were accomplished using the same conditions as carrier Example I. The 
final product was comprised of a carrier core of the spherical steel with 
a total of 1.0 percent coating weight polymer of poly(DIAEMA-co-styrene) 
(40 percent/60 percent monomer ratio) by weight on the surface. The 
resulting carrier volume median diameter size was 100 microns. 
A developer composition was then prepared by the same process as carrier 
Example I. Thereafter, the triboelectric charge on the carrier particles 
was determined by the known Faraday Cage process, and there was measured 
on the carrier a charge of 44.1 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 was 9.06 E.sup.-15 
mho-cm.sup.-1. Therefore, these carrier particles were insulative. 
CARRIER EXAMPLE III 
In the first step of the carrier coating process, 22.7 grams of a copolymer 
of Synthetic Example III, and more specifically, a copolymer of about 73 
weight percent t-butylstyrene and 27 percent diisopropylaminoethyl 
methacrylate (DIAEMA) and 2,270 grams of a spherical steel core with a 
volume median diameter of 100 microns (Nuclear Metals, Inc.) were mixed. 
The mixing and fusing process steps were accomplished using the same 
conditions as carrier Example I. The final product was comprised of a 
carrier core of spherical steel with a total of 1.0 percent coating weight 
polymer of poly(t-butylstyrene-co-diisopropylaminoethyl methacrylate) (73 
percent/27 percent monomer ratio) by weight on the surface and a resulting 
carrier volume median diameter size of 100 microns. 
A developer composition was then prepared by the same process as Example I. 
Thereafter, the triboelectric charge on the carrier particles was 
determined by the known Faraday Cage process, and there was measured on 
the carrier a charge of 33.9 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 was 2.20 E.sup.15 
mho-cm.sup.-1. Therefore, these carrier particles were insulative. 
CARRIER EXAMPLE IV 
In the first step of the carrier coating process, 44.91 grams of a 
copolymer of poly(t-butylstyrene-co-diisopropylaminoethyl methacrylate) in 
a 60/40 weight percent monomer ratio with a particle size of about 5.4 
microns were mixed with 4,491.09 grams of a spherical steel core with a 
volume median diameter of 100 microns (Nuclear Metals, Inc.). The mixing 
and the remainder of the carrier coating process were accomplished in the 
same manner as carrier Example III. The final product was comprised of a 
spherical steel carrier core with a total of 1.0 percent by weight 
copolymer composed of poly(t-butylstyrene-co-diisopropylaminoethyl 
methacrylate) in a 60/40 weight percent monomer ratio on the surface of 
the carrier and the resulting carrier volume median diameter size was 100 
microns. 
A developer composition was then prepared by the process of Carrier Example 
I. Thereafter, the triboelectric charge on the carrier particles was 
determined by the known Faraday Cage process, and it was believed that a 
high triboelectric value would be obtained, based on the measured 
difference between the triboelectric values of the carrier in Carrier 
Example III and the known low triboelectric value, i.e., near zero, of a 
styrene coated carrier, in conjunction with an increase in 
dimethylaminoethyl methacrylate concentration. Specifically, it was 
believed that a triboelectric value of between 60 and 80 microcoulombs per 
gram would be obtained. Further, it was believed that 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, would be too insulating to be measured 
(&gt;10.sup.-15 mho-cm-.sup.-1). Therefore, these carrier particles were 
insulative. Additional adjustments to the dimethylaminoethyl methacrylate 
concentration, specifically to values intermediate to the 27 percent 
concentration of Carrier Example III and the 40 percent concentration of 
the current Example, were believed to yield triboelectric values of any 
magnitude between 33 and 80 microcoulombs per gram. 
Other modifications of the present invention may occur to those of ordinary 
skill in the art subsequent to a review of the present application, and 
these modifications, including equivalents thereof, are intended to be 
included within the scope of the present invention.