Developer compositions with coated carrier particles having incorporated therein colorless additives

A developer composition comprised of a toner composition having dispersed therein resin particles, pigment particles, and carrier particles comprised of a core with a coating thereover, which coating has incorporated therein colorless copper iodide enabling carriers with a conductivity of from about 10.sup.-6 to 10.sup.-8 ohm-cm.

BACKGROUND OF THE INVENTION 
This invention is generally directed to developer compositions, and more 
specifically the present invention is directed to the incorporation of 
specific carrier particles into developer compositions. Therefore, in one 
embodiment the present invention is directed to coated carrier particles 
having incorporated therein colorless components, such as certain metal 
halides, primarily for the purpose of achieving a specific conductivity 
value range for the aforementioned particles. In one embodiment of the 
present invention, the developer compositions are comprised of toner resin 
particles, pigment particles, carrier particles with a coating thereover 
such as those selected from polymeric compositions especially those 
derived from vinyl homopolymers and copolymers, and incorporated into the 
coating specific metal halides. The aforementioned developer compositions, 
which are particularly useful in electrophotographic imaging processes, 
provide developers which substantially eliminate contamination of the 
imaging apparatus within which they are incorporated; and also these 
compositions have desirable conductivity values and excellent charge 
admixing times. 
The xerographic process involves the development of latent images by 
developer compositions comprised of toner resin particles, pigment 
particles, and carrier particles. Numerous different developer 
compositions are described in the prior art, inclusive of those with toner 
resin particles comprised of styrene acrylate copolymers, styrene 
butadiene copolymers, styrene methacrylate copolymers, polyesters, and the 
like. Additionally, there is disclosed in the prior art the selection of 
various carrier particles, both coated and uncoated, for use as a 
component in a developer composition. Moreover, it is known that charge 
enhancing additives can be incorporated into various developer 
compositions for the purpose of imparting the desired charge polarity to 
the toner resin particles. 
There are disclosed in U.S. Pat. No. 3,795,617 carrier particles containing 
magnetically attractable core particles with a resinous vinylidene 
chloride copolymer coating thereon. Illustrative examples of copolymeric 
materials selected are outlined in column 5, beginning at line 4, and 
include, for example vinylidene chloride, acrylonitrile, and acrylic acid 
terpolymers. Additionally, it is indicated in this patent that useful 
results can be obtained by substituting one or more alkyl esters of 
acrylic or methacrylic acid for the acrylonitrile component of the 
copolymer, which esters typically have from about 1 to 18 carbon atoms in 
the alkyl group, inclusive of methyl methacrylate, ethyl methacrylate, and 
butyl methacrylate. 
Further, there are disclosed in U.S. Pat. No. 4,310,611 novel magnetic 
carrier components comprised of a mass of passivated particles of magnetic 
stainless steel with a thin tightly adherent chromium rich layer. It is 
indicated in column 2, beginning at line 35 of this patent, that 
optionally the passivated particles can have a coating of a resin which 
aids in the triboelectrical charging of the toner, but which is 
discontinuous or thin enough to allow the particle mass to remain 
conductive. Also, examples of resins selected as carrier coatings include 
those described in U.S. Pat. Nos. 3,795,617; 3,795,618; and 4,076,857. 
Specific examples of carrier coatings listed in column 4 of the U.S. Pat. 
No. 3,795,617 include fluorocarbon polymers such as 
polytetrafluoroethylene, polyvinylidene fluoride, and 
polyvinylidenefluoride-co-tetrafluoroethylene. 
In U.S. Pat. No. 4,374,192 there are disclosed novel carrier coatings with 
miscible mixtures of a butadiene acrylonitrile rubber, and containing from 
about 20 percent to about 40 percent of acrylonitrile together with a 
polyurethane elastomer. These coatings, according to the teachings of this 
patent, are tough, tenacious, and not tacky, reference the disclosure in 
column 4, beginning at line 3. 
Many other patents are in existence disclosing toner and carrier particles, 
representative of which include U.S. Pat. No. 4,051,077, relating to 
developer compositions with various additives; U.S. Pat. No. 4,298,672, 
the disclosure of which is totally incorporated herein by reference, which 
discloses positively charged developer compositions comprised of resin 
particles, pigment particles, alkyl pyridinium charge enhancing additives, 
and carrier particles; U.S. Pat. No. 3,627,522, the disclosure of which is 
totally incorporated herein by reference, directed to developer 
compositions with carrier particles coated with terpolymer resins of 
styrene, methylmethacrylate, and an organo silane; U.S. Pat. No. 
3,923,503, the disclosure of which is totally incorporated herein by 
reference, disclosing methods of imaging with developer compositions 
comprised of steel carrier particles coated with various resins, such as 
polymethylmethacrylate, polyvinylidene fluoride, and terpolymers of 
styrene; and U.S. Pat. No. 3,526,533, the disclosure of which is totally 
incorporated herein by reference, directed to carriers with coatings of 
linear addition copolymers of polymerized polystyrene, polymerized 
acrylates, or polymerized methacrylates, and polymerizable organo silicon 
compositions. 
Of particular interest with respect to the invention of the present 
application are the carrier particles illustrated in U.S. Pat. No. 
3,533,835, the disclosure of which is totally incorporated herein by 
reference, which particles are comprised of a core with a coating 
thereover, and wherein the coating contains therein numerous conductive 
substances such as silver iodide, which iodide decomposes into an 
undesirable black color as contrasted to copper iodide which is colorless, 
and does not decompose. While the substances of the U.S. Pat. No. 
3,533,835 are suitable for their intended purposes, they generally are not 
colorless as is the situation with the additive incorporated into the 
carrier coatings of the present invention; and furthermore, with the 
invention of the present application, there are enabled other advantages 
such as avoiding contamination of the imaging apparatus, excellent 
admixing times in some embodiments, and acceptable conductivity values. 
Also of interest are U.S. Pat. No. 4,133,933, which discloses 
electrosensitive recording sheets in which cupric iodide is selected as an 
electroconductive material, which iodide particles can be whitened by an 
aqueous akaline material; U.S. Pat. No. 4,275,103, which discloses an 
electographic recording sheet wherein metal oxide semiconductors that are 
virtually colorless are selected, examples of such semiconductors 
including tin oxide, dye indium trioxide, and zinc oxide; and U.S. Pat. 
No. 4,601,967 directed to toner particles consisting of an 
electroconductive core in a coating layer, which coating layer may 
comprise copper iodide in the form of a powder iron, nickel, cobalt, or 
manganese, reference for example column 3, lines 3 to 9. 
Accordingly, there is a need for developer compositions wherein there are 
selected carrier coatings having incorporated therein colorless conductive 
additives. There is also a need for carrier particles that possess 
desirable conductivity values which are achievable by incorporating into 
the carrier coatings specific colorless components thereby avoiding color 
contamination, a problem with some prior art carrier coatings wherein, for 
example, carbon black is selected as the conductivity controlling 
component that is incorporated into the carrier coating. In addition, 
there is a need for developer compositions with carrier coatings having 
incorporated therein specific colorless conductive components, which 
compositions maintain their triboelectric charging characteristics for 
extended time periods. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide developer compositions 
with many of the above advantages. 
In another object of the present invention there are provided developer 
compositions with coated carrier particles having incorporated therein 
colorless components. 
Furthermore, in another object of the present invention there are provided 
developer compositions with coated carrier particles having incorporated 
therein certain colorless metal halide conductive components thereby 
permitting specific acceptable conductivity values for the carrier 
particles. 
Moreover, in yet another object of the present invention there are provided 
for incorporation into developer compositions durable carrier particles 
with coatings of specific vinyl polymers including vinyl homopolymers and 
vinyl copolymers, and wherein there is incorporated into these coatings 
certain colorless metal halide conductive components. 
Additionally, in another object of the present invention there are provided 
developer compositions useful for the development of electrostatic latent 
images in xerographic imaging processes. 
In addition, another object of the present invention resides in the 
provision of coated carrier particles having incorporated therein specific 
colorless conductive components thereby resulting in carrier particles 
with conductivity values of from about 10.sup.-6 to about 10.sup.-8 
ohm-cm. 
These and other objects of the present invention are accomplished by the 
provision of improved developer compositions comprised of resin particles, 
pigment particles, and specific carrier particles. More specifically, in 
accordance with the present invention there are selected coated carrier 
particles having incorporated therein specific colorless conductive 
components. Accordingly, in one embodiment of the present invention there 
are provided improved developer compositions comprised of resin particles, 
pigment particles, and carrier particles comprised of a core with a 
coating thereover, which coating has incorporated therein colorless copper 
iodide components. 
With further respect to the present invention, similar developer 
compositions are illustrated in related application U.S. Ser. No. 751,922, 
entitled Developer Composition With Specific Carrier Particles, wherein 
there are selected coated carriers having incorporated therein various 
dopants such as carbon black for the primary purpose of controlling the 
conductivity of carrier particles, the disclosure of the aforementioned 
application being totally incorporated herein by reference. Some of the 
coatings of the aforementioned application, particularly carbon black, are 
not colorless and thereby could have a tendency to contaminate the 
developer composition causing undesirable modifications of these 
compositions including, for example, a reduction in the conductivity 
parameters, and a decrease in the triboelectric charging properties. 
Various suitable known toner compositions can be selected for the developer 
compositions of the present invention including compositions comprised of 
resin particles and pigment particles. Examples of suitable toner resins 
selected are as illustrated in U.S. Pat. No. 4,298,672, the disclosure of 
which is totally incorporated herein by reference, inclusive of styrene 
polymers, styrene methacrylates, styrene acrylates, and styrene 
acrylonitriles, as well as styrene butadiene polymers and polyesters, 
reference U.S. Pat. No. 3,590,000, the disclosure of which is totally 
incorporated herein by reference. Various styrene butadienes can be 
selected especially those commercially available from Goodyear Chemical as 
Pliolite.sup.R. Generally, the styrene butadiene resin used comprises from 
about 80 percent by weight to about 92 percent by weight of styrene, and 
from about 8 percent by weight to about 20 percent by weight of butadiene. 
Particularly preferred are styrene butadiene resins of a molecular weight 
of from about 80,000 to about 140,000, a glass transition temperature of 
from about 51.degree. to about 63.degree. C., and a molecular weight 
distribution of from about 5.5 to 8.5. Other examples of styrene 
butadiene resin copolymers useful as a component in the developer 
composition of the present invention include those as prepared by the 
process as described in U.S. Pat. Nos. 4,558,108 and 4,469,770, the 
disclosures of each of the aforementioned patents being totally 
incorporated herein by reference. 
Numerous known suitable pigments or dyes can be selected as the colorant 
for the toner particles including, for example, carbon black, magnetites, 
nigrosine dye, chrome yellow, DuPont oil red, phthalocyanine blue, and 
mixtures thereof. These pigments, excluding magnetites, should be present 
in a sufficient amount to render the toner composition highly colored, 
thus enabling the formation of a clearly visible image on a recording 
member. For example, where conventional xerographic copies of documents 
are desired, the pigment particles are present in amounts of from about 3 
percent by weight to about 20 percent by weight, based on the total weight 
of the toner composition; however, lesser or greater amounts of pigment 
particles can be selected providing the objectives of the present 
invention are achieved. Preferably, from about 5 percent by weight to 
about 15 percent by weight of pigment particles are incorporated into the 
toner compositions of the present invention. 
With respect to magnetite pigments comprised of iron oxides, they are 
present in the toner composition in various amounts inclusive of, for 
example, from about 5 percent by weight to about 25 percent by weight, and 
preferably from about 10 percent by weight to about 20 percent by weight, 
based on the weight of the toner composition. Moreover, there can be 
incorporated into the developer composition of the present invention flow 
aid additives inclusive of Aerosil, and aluminum oxides, especially 
Al.sub.2 O.sub.3 and Cabosil.sup.R. These flow additives can be blended 
into the toner composition or are present as external materials in amounts 
of from about 0.1 percent by weight to about 5 percent by weight, and 
preferably in an amount of from about 0.1 percent by weight to about 2 
percent by weight. 
Various suitable cores can be selected for the carrier particles including 
steel, iron, ferrites, especially nickel-zinc-ferrites, and the like. The 
preferred carrier core is steel. Generally, the carrier core is of a 
diameter of from about 35 microns to about 500 microns, and preferably is 
of a diameter of from about 80 microns to about 150 microns. 
Coatings selected for the carrier particles of the present invention are 
comprised of certain vinyl polymers, and other components, reference the 
patents and copending application mentioned herein. Examples of polymers 
include copolymers and homopolymers of vinylchloride and 
trifluorochloroethylene; Saran F-310; vinylchloride/maleate ester; 
vinylchloride and vinylacetate; trifluorochloroethylene and 
vinylidenefluoride; vinylchloride and acrylonitrile; 
vinylchloride/chlorotrifluoroethylene (FP461); and other equivalent 
coatings. One preferred coating is comprised of a copolymer of 
vinylchloride and trifluorochloroethylene with about 65 percent by weight 
of vinylchloride, and 35 percent by weight of trichlorofluoroethylene 
monomer. Moreover, the coating polymers of the present invention are 
preferably of a weight average molecular weight exceeding 10,000, and more 
preferably are of a weight average molecular weight of from about 40,000 
to about 80,000. 
The coatings applied to the carrier cores can be of any suitable thickness 
providing the objectives of the present invention are achieved, however, 
generally the coating is present in a thickness of from about 0.1 to about 
1 micron, and preferably from about 0.1 to about 0.5 micron. Usually the 
coating is present on the entire surface of the carrier core, that is it 
is continuous; however, the coating can also be semicontinuous providing 
each of the carrier core particles have a minimum of about 0.3 percent by 
weight of the polymeric coating composition. 
Incorporated into the aforementioned carrier coatings are colorless 
components selected from certain colorless conductive metal halides, which 
components are added in an amount of from about 25 percent by weight to 
about 75 percent by weight, and preferably in an amount of from about 50 
percent by weight to about 70 percent. Examples of metal halides that may 
be selected include copper iodide, copper fluoride, mixtures thereof, and 
the like. 
Although it is not desired to be limited by theory, it is believed that the 
colorless coatings enable developer compositions with the improved 
characteristics as detailed herein including, for example, triboelectric 
charging values of from about 15 microcoulombs per gram to about 30 
microcoulombs per gram for extended time periods; a conductivity of from 
about 10.sup.-6 to about 10.sup.-8 (ohm-cm).sup.-1 ; and more importantly, 
the conductive additives selected for the carrier coatings are colorless 
thereby eliminating any contamination of the resulting developer 
compositions. 
There can also be incorporated into the toner compositions of the present 
invention comprised of resin particles and pigment particles charge 
enhancing additives such as alkyl pyridinium halides, organic sulfate and 
sulfonate compositions, and other charge enhancing additives, reference 
the U.S. patents previously mentioned herein. Particularly preferred 
charged enhancing additivies include cetyl pyridinium chloride, distearyl 
dimethyl ammonium methyl sulfate, stearyl phenethyl dimethyl ammonium 
tosylate, and the like. These additives assist in providing a positive 
charge to the resulting toner compositions enabling such compositions to 
be especially useful in xerographic imaging apparatuses having 
incorporated therein negatively charged layered photoresponsive imaging 
members as illustrated in U.S. Pat. No. 4,265,990, the disclosure of which 
is totally incorporated herein by reference. 
Normally, from about 3 to about 5 parts by weight of toner composition are 
added to about 100 to 200 parts by weight of carrier particles for 
enabling formation of the developer composition. Specifically, the 
developer compositions are prepared by mixing together in a suitable 
vessel from about 3 to 10 parts by weight of toner particles with from 100 
to 200 parts by weight of carrier particles. 
The toner composition of the present invention can be prepared by a number 
of known methods, including melt blending the toner resin particles, 
pigment particles, and charge enhancing additive followed by mechanical 
attrition. Other methods include those well known in the art, such as 
spray drying, melt dispersion, dispersion polymerization, extrusion 
processing, and suspension polymerization. In one dispersion 
polymerization method, a solvent dispersion of the resin particles, the 
pigment particles, and the charge enhancing additive are spray dried under 
controlled conditions resulting in the desired product. 
Also, the toner and developer compositions of the present invention may be 
selected for use in electrophotographic imaging apparatuses, including 
those as described in U.S. Pat. Nos. 4,368,970 and 4,394,429, the 
disclosure of each of these patents being totally incorporated herein by 
reference. According to the teachings of these patents, there is selected 
a development system for incorporation into a xerographic imaging 
apparatus comprised of a moving deflected tensioned flexible imaging 
member, a moving transporting member, a development zone situated between 
the imaging member and transporting member, these members being maintained 
at a distance of from about 0.5 millimeter to about 1.5 millimeters, 
wherein toner particles are desirably agitated in the development zone, 
thereby allowing these particles to be readily available in a continuous 
manner to the imaging member. 
Examples of photoconductive members selected for the imaging apparatuses 
within which the toner and developer compositions of the present invention 
are incorporated include amorphous selenium, selenium alloys, such as 
selenium arsenic, selenium tellurium, selenium antimony, and the like; and 
organic photoreceptors, illustrative examples of which include layered 
photoresponsive devices comprised of transport layers and photogenerating 
layers, reference U.S. Pat. No. 4,225,990, the disclosure of which is 
totally incorporated herein by reference, and other similar layered 
photoresponsive devices. Illustrative examples of generating layers 
include trigonal selenium, metal phthalocyanines, metal free 
phthalocyanines, and vanadyl phthalocyanines, while examples of charge 
transport layers include the diamines as disclosed in the U.S. Pat. No. 
4,225,990.

The following examples are being submitted to further define various 
species of 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. 
EXAMPLE I 
There was prepared a toner composition by admixing in a Banbury apparatus 
94 percent by weight of a styrene n-butyl methacrylate copolymer 
containing 58 percent by weight of styrene, and 42 percent by weight of 
n-butyl methacrylate; and 6 percent by weight of Regal.RTM. 330 carbon 
black. Subsequently, the resulting toner composition was classified to 
remove particles smaller than 5 microns average diameter. Thereafter, the 
aforementioned prepared toner composition, 2 parts by weight, was mixed 
with carrier particles, 100 parts by weight, consisting of a nickel, zinc, 
ferrite core available from Titan Advance Materials, Indiana, which 
contain a continuous coating of a copolymer of vinyl 
chloride/chlorotrifluorethylene (65/35), and a coating thickness of about 
1 micron. About 50 percent by weight of copper iodide was incorporated 
into the copolymer prior to accomplishing the coating enabling a carrier 
with a conductivity of 3.9.times.10.sup.-7 (ohm-cm).sup.-1. 
When this developer mixture was roll milled for 1 hour and evaluated in a 
charge spectrograph, it had an average charge level for 10 micron size 
particles of 0.77 femtocoulomb per micron, and a standard deviation in the 
charge of 0.11 femtocoulomb per micron enabling a sharpness value (the 
average charge divided by the standard deviation) of 7.3. Also, the time 
for added uncharged toner compositions comprised of the same components 
identified above to achieve a single peak in a charge spectrograph was 
about 10 minutes. In addition, the aforementioned developer can be 
selected for incorporation into a xerographic imaging test fixture with an 
amorphous selenium photoreceptor, and it is believed that there can be 
obtained images of excellent resolution with no background deposits. 
EXAMPLE II 
A toner composition was prepared by repeating the procedure of Example I 
with the exception that there was selected 92 percent by weight of the 
copolymer, and further this toner composition had incorporated therein 2 
percent by weight of the charge enhancing additive cetyl pyridinium 
chloride. 
Subsequently, the aforementioned prepared toner, 2 parts by weight, was 
mixed with 100 parts by weight of the carrier particles of Example I, 
followed by roll milling the resulting developer composition for 1 hour. 
Thereafter, this developer was evaluated in the charge spectrograph and 
the average charge level for 10 micron particles (average diameter) was 
0.74 femtocoulombs per micron, while the sharpness value was 6.8. In 
addition, the admix time was 15 seconds. Moreover, when the aforementioned 
developer composition is incorporated into the imaging test fixture of 
Example I, it is believed that substantially similar results can be 
obtained. 
EXAMPLE III 
A toner composition was prepared by mixing in an extruder device 80 percent 
by weight of a styrene butadiene copolymer consisting of 90 percent by 
weight of styrene, and 10 percent by weight of butadiene; which toner had 
incorporated therein 16 percent by weight of Mapico magnetite, and 4 
percent by weight of Regal.RTM. 330 carbon black. The resulting toner was 
then subsequently classified to remove particles having an average 
particle diameter of less than 5 microns. 
Thereafter, a developer composition was prepared by admixing 2 parts by 
weight of the above prepared toner with 100 parts by weight of the carrier 
particles of Example I. Subsequently, the developer composition was roll 
milled for 1 hour, and the developer was evaluated in a charge 
spectrograph. The average charge level for 10 micron particles was 0.63 
femtocoulombs per micron, and the sharpness value was 6.1. In addition, 
the admix time for uncharged toner comprised of the same components, and 
added to the above prepared toner was 4 minutes. 
EXAMPLE IV 
A toner composition was prepared by repeating the procedure of Example I 
with the exception that there was selected 79 percent by weight of the 
copolymer, and there was incorporated into the toner composition 1 percent 
by weight of the charge enhancing additive dimethyl distearyl ammonium 
methyl sulfate. 
Thereafter, a developer composition was prepared by admixing 2 parts by 
weight of the above prepared toner with 100 parts of the carrier of 
Example I. This developer was then roll milled for 1 hour, and the 
developer was evaluated in a charge spectrograph. The average charge level 
for 10 micron particles was 0.66 femtocoulombs per micron, and the 
sharpness value was 5.3. In addition, the admix time for this developer 
was 15 seconds. Further, when the aforementioned developer composition is 
incorporated into the imaging test fixture of Example I, it is believed 
that substantially similar results can be obtained. 
EXAMPLE V 
There was prepared a toner composition by repeating the procedure of 
Example III with the exception that a polyester resin was selected in 
place of the styrene butadiene resin. Thereafter, two parts of this toner 
were admixed with 100 parts of the carrier particles of Example I. The 
resulting developer was then roll milled for 1 hour, and the developer was 
evaluated in the charge spectrograph. The average charge level for 10 
micron particles was 0.52 femtocoulombs per micron, and the sharpness 
value was 3.6. In addition, the admix time for uncharged developer was 15 
seconds. 
Other modifications of the present invention may occur to those skilled 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.