[0001] The present invention is generally directed to toners, developers, and imaging processes,
including full color processes for forming multiple color images, and more specifically,
the present invention is directed to developer compositions with surface additives.
[0002] United States patents Nos. 4,288,517; 4,301,228; 4,533,616; 4,828,954; and 4,973,540
disclose toner and developer compositions.
[0003] Toner compositions with colored pigments are known. For example, there are illustrated
in U.S. Patent 4,948,686 processes for the formation of two-color images with a colored
developer comprised of a first toner comprised of certain resin particles, such as
styrene butadiene, a first pigment such as copper phthalocyanine, a charge control
additive, colloidal silica and metal salts of fatty acid as external surface additives,
and a first carrier comprised of a steel core with, for example, a terpolymer overcoating;
and a second developer comprised of a black toner, a second charge additive and a
steel core carrier with certain polymeric overcoatings. Examples of colored toner
pigments are illustrated in column 9, lines 10 to 26, and examples of charge additives
for the toner are detailed in column 9, lines 27 to 43, of the aforementioned patent.
For the black toner, there can be selected the components as recited in columns 10
and 11, including charge additives such as distearyl dimethyl ammonium methyl sulfate,
see column 11, lines 16 to 32. Additionally, the working Examples of this patent detail
the preparation of a number of specific toners. Also, there is illustrated in the
4,948,686 patent a process for forming two-color images which comprises, for example,
(1) charging an imaging member in an imaging apparatus; (2) creating on the member
a latent image comprising areas of high, intermediate, and low potential; (3) developing
the low areas of potential by conductive magnetic brush development with a developer
comprising a colored first toner comprising a first resin present in an amount of
from about 80 to about 98.8 percent by weight and selected from the group consisting
of polyesters, styrene-butadiene polymers, styreneacrylate polymers, styrene-methacrylate
polymers, and mixtures thereof; a first pigment present in an amount of from about
1 to about 15 percent by weight and selected from the group consisting of copper phthalocyanine
pigments, quinacridone pigments, azo pigments, rhodamine pigments, and mixtures thereof;
a charge control agent present in an amount of from about 0.2 to about 5 percent by
weight; colloidal silica surface external additives present in an amount of from about
0.1 to about 2 percent by weight; and external additives comprising metal salts or
metal salts of fatty acids present in an amount of from about 0.1 to about 2 percent
by weight; and a first carrier comprising a steel core with an average diameter of
from about 25 to about 215 microns and a coating selected from the group consisting
of methyl terpolymer, polymethyl methacrylate, and a blend of from about 35 to about
65 percent by weight of polymethyl methacrylate and from about 35 to about 65 percent
by weight of chlorotrifluoroethylene-vinyl chloride copolymer, wherein the coating
contains from 0 to about 40 percent by weight of the coating of conductive particles
and wherein the coating weight is from about 0.2 to about 3 percent by weight of the
carrier; (4) subsequently developing the high areas of potential by conductive magnetic
brush development with a developer comprising a black second toner comprising a second
resin present in an amount of from about 80 to about 98.8 percent by weight and selected
from the group consisting of polyesters, styrene-butadiene polymers, styrene-acrylate
polymers, styrene-methacrylate polymers, and mixtures thereof; a second pigment present
in an amount of from about 1 to about 15 percent by weight; and a second charge control
additive present in an amount of from about 0.1 to about 6 percent by weight; and
a second carrier comprising a steel core with an average diameter of from about 25
to about 215 microns and a coating selected from the group consisting of chlorotrifluoroethylene-vinyl
chloride copolymer containing from 0 to about 40 percent by weight of conductive particles
at a coating weight of from about 0.4 to about 1.5 percent by weight of the carrier;
polyvinylfluoride at a coating weight of from about 0.01 to about 0.2 percent by weight
of the carrier; and polyvinylchloride at a coating weight of from about 0.01 to about
0.2 percent by weight of the carrier; and (5) transferring the developed two-color
image to a substrate. Imaging members suitable for use with the process of the copending
application may be of any type capable of maintaining three distinct levels of potential.
Generally, various dielectric or photoconductive insulating materials suitable for
use in xerographic, ionographic, or other electrophotographic processes may be selected
for the above process. Examples of suitable photoreceptor materials include amorphous
silicon, layered organic materials as disclosed in U.S. Patent 4,265,990 and the like.
The aforementioned colored toners may be selected for utilization with the black toner
and developer of the present invention in embodiments.
[0004] Processes for obtaining electrophotographic, including xerographic, and two-colored
images are known. In U.S. Patent 4,264,185 there is illustrated an apparatus for forming
two-color images by forming a bipolar electrostatic image of a two-color original
document on a photoconductive drum. A first developing unit applies a toner of a first
color and polarity to the drum and a second developing unit applies a toner of a second
color and polarity to the drum to form a two-color electrostatic image which is transferred
and fixed to a copy sheet. A bias voltage of the first polarity is applied to the
second developing unit to repel the toner of the first color and prevent degradation
of the first color toner image. A bias voltage of the second polarity is applied to
the first developing unit to prevent contamination of the first color toner with the
second color toner. A similar full color process can be selected for the present invention
in embodiments and wherein, for example, there are developed four images, one with
the black toner of the present invention, and the others with three different colored
toners.
[0005] Also, the following United States patents are mentioned: 4,308,821 wherein there
is disclosed a method and apparatus for forming two-color images which employs two
magnetic brushes; 4,378,415, which discloses a method of highlight color imaging which
comprises providing a layered organic photoreceptor having a red sensitive layer and
a short wavelength sensitive layer, subjecting the imaging member to negative charges,
followed by subjecting the imaging member to positive charges, imagewise exposing
the member, and developing with a colored developer composition comprising positively
charged toner components, negatively charged toner components, and carrier particles;
4,430,402, which discloses a two-component type dry developer for use in dichromatic
electrophotography which comprises two kinds of developers, each of which is comprised
of a toner and a carrier, and wherein dichromatic images can be formed by developing
a positively and negatively electrified electrostatic latent image successively with
toners different in polarity and color from each other; 4,594,302 which discloses
a developing process for two-colored electrophotography which comprises charging the
surface of a photoreceptor with two photosensitive layers of different spectral sensitivities
with one polarity, subsequently charging the photoreceptor with a different polarity,
exposing a two-colored original to form electrostatic latent images having different
polarities corresponding to the two-colored original, developing one latent image
with a first color toner of one polarity, exposing the photoreceptor to eliminate
electric charges with the same polarity as the first color toner which are induced
on the surface of the photoreceptor in the vicinity of the latent image developed
by the first color toner, and developing the other latent image with a second color
toner charged with a polarity different from that of the first color toner; 4,500,616
which discloses a method of developing electrostatic latent images by selectively
extracting colored grains of one polarity from a mixture containing colored grains
having opposite polarity to each other in the presence of an alternating field, followed
by development of the electrostatic image by the selectively extracted colored grains;
4,524,117 which discloses an electrophotographic method for forming two-colored images
which comprises uniformly charging the surface of a photoreceptor having a conductive
surface and a photoconductive layer sensitive to a first color formed on the conductive
substance, followed by exposing a two-colored original to form on the photoconductive
layer a latent image corresponding to a second color region in the original with the
same polarity as the electric charges on the surface of the photoconductive layer;
4,525,447, which discloses an image forming method which comprises forming on a photosensitive
member an electrostatic latent image having at least three different levels of potentials,
or comprising first and second latent images and developing the first and second latent
images with a three component developer; 4,539,281, which discloses a method of forming
dichromatic copy images by forming an electrostatic latent image having a first image
portion and a second image portion; 4,562,129, which illustrates a method of forming
dichromatic copy images with a developer composed of a high-resistivity magnetic carrier
and a nonmagnetic insulating toner, which are triboelectrically chargeable; 4,640,883,
which discloses a method of forming composite or dichromatic images which comprises
forming on an imaging member electrostatic latent images having at least three different
potential levels, the first and second latent images being represented, respectively,
by a first potential and a second potential relative to a common background potential;
4,045,218 and 4,572,651.
[0006] The process of charging a photoresponsive imaging member to a single polarity and
creating on it an image comprised of at least three different levels of potential
of the same polarity is illustrated in U.S. Patent 4,078,929. This patent discloses
a method of creating two-colored images by forming on an imaging surface a charge
pattern including an area of first charge as a background area, a second area of greater
voltage than the first area, and a third area of lesser voltage than the first area
with the second and third areas functioning as image areas. The charge pattern is
developed in a first step with positively charged toner particles of a first color
and, in a subsequent development step, developed with negatively charged toner particles
of a second color. Alternatively, charge patterns may be developed with a dry developer
containing toners of two different colors in a single development step. Also of interest
with respect to the trilevel process for generating images is U.S. Patent 4,686,163.
[0007] Moreover, illustrated in U.S. Patent No. 5075185 are developers, toners and imaging
processes thereof. In an embodiment of the copending application, there is provided
a process for forming two-color images which comprises (1) charging an imaging member
in an imaging apparatus; (2) creating on the member a latent image comprising areas
of high, intermediate, and low potential; (3) developing the low areas of potential
by, for example, conductive magnetic brush development with a developer comprising
carrier particles, and a colored first toner comprised of resin particles, colored,
other than black, pigment particles, and an aluminum complex charge enhancing additive;
(4) subsequently developing the high areas of potential by conductive magnetic brush
development with a developer comprising a second black developer comprised of carrier
particles and a toner comprised of resin, black pigment, such as carbon black, and
a charge enhancing additive; (5) transferring the developed two-color image to a suitable
substrate; and (6) fixing the image thereto. In an embodiment of the aforementioned
U.S. patent, the first developer comprises, for example, a first toner comprised of
resin present in an effective amount of from, for example, about 70 to about 98 percent
by weight, which resin can be selected from the group consisting of polyesters, styrene-butadiene
polymers, styrene-acrylate polymers, styrene-methacrylate polymers, PLIOLITES®, crosslinked
styrene acrylates, crosslinked styrene methacrylates, and the like, wherein the crosslinking
component is, for example, divinyl benzene, and mixtures thereof; a first colored
blue, especially PV FAST BLUE™ pigment present in an effective amount of from, for
example, about 1 to about 15 percent by weight, and preferably from about 1 to about
3 weight percent; an aluminum complex charge enhancing additive; and a second developer
comprised of a second toner comprised of resin present in an effective amount of from,
for example, about 70 to about 98 percent by weight, which resin can be selected from
the group consisting of polyesters, styrene-butadiene polymers, styrene-acrylate polymers,
styrene-methacrylate polymers, PLIOLITES®, crosslinked styrene acrylates, crosslinked
styrene methacrylates, and the like, wherein the crosslinking component is, for example,
divinyl benzene, and mixtures thereof; and a black pigment present in an effective
amount of from, for example, about 1 to about 15 percent by weight, and preferably
from about 1 to about 5 weight percent wherein the aforementioned black toner contains
a charge enhancing additive such as an alkyl pyridinium halide, and preferably cetyl
pyridinium chloride, and in a preferred embodiment the black toner is comprised of
92 percent by weight of a styrene n-butyl methacrylate copolymer (58/42), 6 percent
by weight of REGAL 330® carbon black, and 2 percent by weight of the charge enhancing
additive cetyl pyridinium chloride.
[0008] Illustrated in U.S. Patent No. 5087538 is a process for forming two-color images
which comprises (1) charging an imaging member in an imaging apparatus; (2) creating
on the member a latent image comprising areas of high, intermediate, and low potential;
(3) developing the low areas of potential by, for example, conductive magnetic brush
development with a developer comprising carrier particles, and a colored first toner
comprised of resin, a positively charging pigment, and a negatively charging pigment;
(4) subsequently developing the high areas of potential by conductive magnetic brush
development with a developer comprising a second developer comprised of carrier particles
and a toner comprised of resin, black pigment, such as carbon black, and a charge
enhancing additive; (5) transferring the developed two-color image to a suitable substrate;
and (6) fixing the image thereto.
[0009] Illustrated in EP. patent No. 516434 is, for example, a magneta toner for full color
processes, and wherein the toner may contain surface additives such as a mixture of
certain colloidal silicas, such as AEROSIL#76®, tin oxide, and a polymeric hydroxy
compound.
[0010] One of the objects of the present invention is to provide a developer with stable
triboelectrical toner characteristics which enables the generation of high quality
images subsequent to development A further objective of the present invention is to
provide a multicolor image formation wherein the developers are of a specific triboelectric
charge, charge distribution, and conductivity, and exhibit acceptable admix times
and excellent developer lifetimes.
[0011] Accordingly, there is provided a developer composition including a toner and carrier
particles, characterised in that said toner comprises resin, carbon black, magnetite,
and a charge additive, and a surface additive mixture comprised of a polymeric hydroxy
compound and a colloidal silica treated with a quaternary ammonium salt compound;
and said carrier particles comprise a core with a polymer mixture coating thereover
and wherein the polymeric hydroxy compound is of the formula
CH
3(CH
2)
nCH
2OH
wherein n is a number of from 30 to 300.
[0012] In one embodiment said carrier particles comprise a ferrite core.
[0013] The first polymer may be present in an amount of from about 25 percent by weight
to about 45 percent by weight, and the second polymer is present in an amount of from
about 25 percent by weight to about 55 percent by weight.
[0014] The toner resin may comprise styrene polymers, such as, for example, selected from
the group consisting of styrene methacrylates, styrene butadienes, and styrene acrylates.
Alternatively the toner resin comprises a polyester.
[0015] The charge enhancing additive may comprise distearyl dimethyl ammonium methyl sulfate.
The semiconductive ferrite carrier core may comprise manganese, copper, zinc, nickel,
iron and oxygen.
[0016] The first polymer may be present in an amount of from about 40 percent by weight
to about 60 percent by weight, and the second polymer is present in an amount of from
about 60 percent by weight to about 40 percent by weight.
[0017] In one embodiment the ammonium compound is dimethyloctadecyl-3-trimethoxy(silyl)propyl
ammonium chloride.
[0018] In one embodiment the semiconductive ferrite core comprises of from about 0.1 to
about 20 weight percent of copper, from about zero to about 50 weight percent of magnesium,
from about 2 to 25 weight percent of zinc, from about zero to about 12 weight percent
of nickel, from about zero to 3 weight percent of manganese, from about 22 to 35 weight
percent of oxygen, and from about 40 to 60 weight percent of iron is selected.
[0019] In one embodiment carbon black is present in an amount of from about 0.1 to about
0.4 weight percent, and the colloidal silica treated with a quarternary ammonium salt
compound is present in an amount of from about 0.8 to about 0.22 weight percent.
[0020] In another embodiment the polymeric hydroxy compound is present in an amount of from
about 0.1 to about 0.4 weight percent, and the colloidal silica treated with a quarternary
ammonium salt compound is present in an amount of from about 0.8 to about 0.22 weight
percent.
[0021] The ferrite carrier may have a volume median diameter of from about 40 to about 80
microns, and preferably from about 45 to about 60 microns.
[0022] In one embodiment the resin comprises an emulsion polymerised styrene butadiene.
[0023] One aspect of the present invention is a process for obtaining multicolor, including
four-color images, one of which is black, which in an embodiment comprises charging
and developing an imaging member four times and wherein a black toner is utilized
for one of the images. The aforementioned black toner in one embodiment of the present
invention has excellent admix characteristics, for example from about 15 to about
60 seconds as determined by a charge spectrograph, desirable triboelectric properties,
for example from about a positive 10 to about 25 microcoulombs per gram as determined
by the known Faraday Cage measurement process, acceptable and stable At and the like.
Another embodiment of the present invention relates to black toners comprised of toner
resin particles, black pigment particles, magnetite particles, a positive charge enhancing
additive, and surface additives, such as a mixture of a colloidal silica, AEROSIL
#76®, and polymeric hydroxy surface additives, such as UNILINS®, reference U.S. Patent
4,883,736, the disclosure of which is totally incorporated herein by reference, and
developers therein as illustrated herein. The black toner of the present invention
enables excellent black images with substantially no background deposits, acceptable
mottle, minimal image graininess, undesirable history image defects, avoidance or
minimization of cometing, improved toner flow characteristics in the developer housing
and in the toner dispenser, and moreover this toner is substantially inactive with
respect to the colored toners being utilized in that, for example, the triboelectric
characteristics and color intensity of the colored toners and developed images thereof
is not adversely affected. In embodiments, the toners and developers of the present
invention can be utilized in specific color imaging processes, such as process color,
and the like. Other advantages associated with the present invention include the provision
of a developer with stable positive triboelectrical toner characteristics which enables
the generation of high quality images subsequent to development, that is images with
substantially no background deposits and substantially no smearing for a broad range
of relative humidity conditions, that is for example from 20 to 80 percent relative
humidity at an effective range of temperature zones ranging, for example, from about
10°C to about 49°C (50°F to about 120°F), and preferably from about 15°C to about
32°C (60 to about 90°F).
[0024] An example of the aforementioned development process comprises a developer housing
with a twin auger transport single magnetic brush design mounted in the approximate
6 o'clock orientation. The magnetic brush roll (developer roll) is about 30 millimeters
in diameter, with a grooved surface for developer transport, and preferably operates
at about 3.0 times the speed of the photoreceptor, or imaging member. The developer
roll is spaced about 0.5 millimeter from the photoreceptor and is biased with a negative
DC bias, for example from 200 to about 500 volts. A stationary magnet is situated
internal to the rotating developer roll sleeve, and is comprised of a ferrite with
a designed magnetic pole configuration to satisfy the requirements of controlling
the developer transport and developability. The developer flow (termed Mass on the
Sleeve, or MOS) can be controlled by the location of a low permeability trimmer bar
in the magnetic field at the point of trimming. Typically, the MOS is set at from
about 25 to about 40 mg milligrams/cm
2 and is sensitive to the trim gap, toner concentration (TC) and developer tribo. The
twin augers in the developer housing sump transport the developer in opposite directions,
first past the toner dispenser, then to the developer pick up region of the developer
roll. The augers have slits built into them in order to facilitate the mixing of the
fresh toner added to the developer. Usually a number of latent images are formed,
such as four, and developed sequentially on the imaging member, first with the black
toner of the present invention, magneta toner, cyan toner, and yellow. Also, one can
develop black only, or black with one or more other colors.
[0025] In another embodiment of the present invention there are provided toners comprised
of resin particles, carbon black pigments, such as REGAL 330®, known magnetites, a
charge additive like distearyl dimethyl ammonium methyl sulfate, reference U.S. Patent
4,560,635, the disclosure of which is totally incorporated herein by reference, and
as surface additives a mixture of UNILIN® and AEROSIL #76®, a colloidal silica treated
with a quaternary ammonium compound, such as dimethyloctadecyl-3-trimethoxy(silyl)propyl
ammonium chloride available from Tayca Inc. The treated surface additives of U.S.
Patent 4,828,954, the disclosure of which is totally incorporated herein by reference,
can be selected for the toners and developers of the present invention. This patent
discloses toners which contain an inorganic powder that has been subjected to the
treatment with a compound having an onium salt structure, see the Abstract, and see
columns 2 to 8, and the working Examples.
[0026] Also, in another feature of the present invention there are provided developer compositions
with excellent electrical characteristics comprised of the black toners illustrated
herein and carrier particles preferably comprised of ferrites, especially copper zinc
ferrites. One preferred ferrite is described in U.S. patent No. 5 162 187. In the
aforementioned copending application, there is disclosed a semiconductive ferrite
core with a coating thereover comprised of a mixture of first and second polymers
that are not in close proximity thereto in the triboelectric series, and a ferrite
carrier composition with a coating of a first polymer present in an amount of from
about 10 percent by weight to about 90 percent by weight, and a second polymer is
present in an amount of from about 90 percent by weight to about 10 percent by weight
[0027] These and other features of the present invention can be accomplished in embodiments
by providing developers, toners and imaging processes thereof. In an embodiment of
the present invention, there are provided toner compositions comprised of resin particles,
black pigment particles, magnetites, a positive charge enhancing additive component,
and surface additives comprised of a mixture of certain treated colloidal silicas,
and polymeric hydroxy compounds, such as UNILIN® components available from Petrolite
Corporation. Developers can be prepared by admixing the aforementioned toners with
carriers, such as ferrites, and the like, and preferably ferrite carriers, which carriers
are coated with a polymer mixture, such as polymethyl methacrylate and KYNAR®, reference
U.S. Patents 4,937,166 and 4,935,326.
[0028] Examples of resin particles selected for the toners of the present invention include
styrene acrylates, styrene methacrylates, polyesters, crosslinked styrene methacrylates,
styrene butadienes, especially those with a high, such as from about 80 to about 95
weight percent styrene content, like the commercially available Goodyear PLIOLITES®,
PLIOTONES®, and the like. The resin is present in an effective amount of from, for
example, about 70 to about 98 percent by weight. Specific toner resins include known
styrene acrylates, styrene methacrylates (58/32), linear, and branched polyesters,
PLIOLITES®, PLIOTONES® available from Goodyear Chemical Company, styrene-butadiene
polymers, particularly styrene-butadiene copolymers wherein the styrene portion is
present in an amount of from about 83 to about 93 percent by weight, and preferably
about 88 percent by weight, and the butadiene portion is present in an amount of from
about 7 to about 17 percent by weight, and preferably about 12 percent by weight.
Also suitable are styrene-n-butylmethacrylate polymers, particularly those styrene-n-butylmethacrylate
copolymers wherein the styrene segment is present in an amount of from about 50 to
about 70 percent by weight, preferably about 58 percent by weight, and the n-butylmethacrylate
segment is present in an amount of from about 30 to about 50 percent by weight, preferably
about 42 percent by weight. Mixtures of these resins may also be selected. Preferred
as the toner resin is an emulsion polymerized styrene butadiene, reference U.S. Patent
4,469,770, preferably present in an amount of about 87 to about 89 percent by weight..
[0029] Carbon black toner pigments are known and include carbon blacks like REGAL 330®,
VULCAN®, furnace blacks, and the like. The black pigment is present in various effective
amounts such as, for example, from about 1 to about 15, and preferably from about
2 to about 10 weight percent of the toner. These pigments are part of a mixture with
known magnetites, such as MAPICO BLACK®, and the like. The mixture preferably contains
in embodiments effective amounts of carbon black, such as from about 2 to about 10
weight percent, and magnetite, such as MAPICO BLACK®, preferably from about 2 to about
10, and more preferably from about 2 to about 7 weight percent. One preferred mixture
is comprised of 5.5 percent by weight of toner of REGAL 330® carbon black and MAPICO
BLACK®, 4.5 weight percent.
[0030] Examples of positive charge enhancing additives, which are present in the toner in
various effective amounts, such as from about 0.5 to about 10, and preferably from
about 1 to about 2 weight percent, include known additives such as distearyl dimethyl
ammonium methyl sulfate, cetyl pyridinium halide, especially the chloride, bisulfides,
and mixtures thereof in embodiments. Examples of specific charge additives include
alkyl pyridinium halides, and preferably cetyl pyridinium chloride, reference U.S.
Patent 4,298,672, organic sulfates and sulfonates, reference U.S. Patent 4,338,390,
the disclosure of which is totally incorporated herein by reference; distearyl dimethyl
ammonium methyl sulfate (DDAMS), the preferred additive; 1.2 percent by weight of
the toner as it enables excellent admix characteristic, reference U.S. Patent 4,560,635,
and the like. The black toner in embodiments usually possesses a positive charge of
from about 5 to about 35 µC/g microcoulombs per gram, and preferably from about 8
to about 25 µC/g microcoulombs per gram, which charge is dependent on a number of
known factors, including the amount of charge enhancing additive present, and the
exact composition of the other compositions, such as the toner resin, the pigment,
the carrier core, and the coating selected for the carrier core; and an admix time
of from about 15 to about 60 seconds and preferably from about 15 to about 30 seconds.
In the preparation of the toner compositions, normally the products obtained comprised
of toner resin, pigment, and magnetite, and charge enhancing additive can be subjected
to micronization and classification, which classification is primarily for the purpose
of removing fines, and substantially very large particles to enable, for example,
toner particles with an average volume diameter of from about 8 to about 15 µm, and
preferably from about 8 to about 12 µm. The toners of the present invention in embodiments
may be prepared by processes such as extrusion, which is a continuous process that
comprises dry blending the resin, black pigment, magnetite, and charge control additive,
placing them into an extruder, melting and mixing the mixture, extruding the material,
and reducing the extruded material to pellet form. The pellets are further reduced
in size by grinding or jetting, and are then classified by particle size. In an embodiment
of the present invention, toner compositions with an average particle size of from
about 8 to about 15, and preferably from 8 to about 12 µm are preferred. The external
additive mixtures can then be blended with the classified toner in a known medium
intensity dry powder blender. Other known toner preparation processes can be selected
including melt mixing of the components in, for example, a Banbury, followed by cooling,
attrition and classification.
[0031] The aforementioned toners include as surface or external components additives in
an effective amount of, for example, from about 0.18 to about 1 weight percent, a
mixture of certain colloidal silicas, such as AEROSIL #76®, present in effective amounts
of from about 0.8 to about 0.22, and preferably 0.15 weight percent, and a UNILIN®
which is a polymeric hydroxy compound of the formula
CH
3 (CH
2)
n CH
2 OH
wherein n is a number of from about 30 to about 300, and preferably n is a number
of from about 30 to about 50, present in effective amounts such as from about 0.1
to about 0.4, and preferably 0.25 weight percent. One preferred hydroxy compound has
a number average molecular weight of from about 475 to about 1,400, and more preferably
a number average molecular weight of from about 475 to about 750. These hydroxy compounds
and the toners thereof are illustrated in U.S. Patent 4,883,736. Varying the amounts
of these two external additives can enable adjustment of the charge levels of the
toners. For example, increasing the amount of AEROSIL #76® and polymeric hydroxy compound
generally adjusts the triboelectric charge in a positive direction and improves admix
times, which is a measure of the amount of time required for fresh toner to become
triboelectrically charged after coming into contact with a developer.
[0032] The carrier for the developer in an embodiment of the present invention can be comprised
of a ferrite, preferably copper zinc core, obtained from D.M. Steward Company, with
an average diameter of from about 40 to about 80, and preferably about 45 to about
60 microns volume average diameter, and a polymeric coating thereover of, for example,
polyvinylidene fluoride (KYNAR®), and polymethyl methacrylate, with a preferred ratio
of 35 to 65, however, a range of about 25 to about 45 for the first polymer like KYNAR®,
and about 55 to about 75 for the second polymer like polymethyl methacrylate, 0.15
to about 1, and preferably 0.3 weight percent coating thereover. Preferred carriers
that may be selected are the ferrite carriers as illustrated in U.S. Patents 4,937,166
and 4,935,326, and copending patent application U.S. patent No. 5 162 187. The aforementioned
carriers in one embodiment comprise a core with two polymer coatings not in close
proximity in the triboelectric series. The carriers are of a particle size diameter
of from about 40 to about 80 µm, and preferably from about 45 to about 60 µm for the
semiconductive ferrites.
[0033] Examples of imaging members selected for the processes of the present invention include
various dielectric or photoconductive insulating material suitable for use in xerographic,
ionographic, or other electrophotographic processes, such as layered organic materials
as disclosed in U.S. Patent 4,265,990, and the like. The photoresponsive imaging member
can be negatively charged, positively charged, or both, and the latent images formed
on the surface may comprise either a positive or a negative potential, or both. In
one embodiment, four latent images are formed and one of the images is developed with
the black toner of the present invention as indicated herein. Known colored toners
are selected for the development of the other latent images, which toners include
magenta like FANAL PINK™, about 5 percent flushed, cyan, like PV FAST BLUE", about
2 weight percent, yellow like Permanent Yellow FGL, about 5 percent, and wherein the
resin is usually an emulsion polymerized styrene butadiene, although the other toner
resins illustrated herein may be used in embodiments. Examples of toners and pigments
are illustrated in copending patent applications U.S. Patents Nos. 5 208 129, 5 278
019, 5 212 036 and 5 275 905.
[0034] The developed images are then transferred to any suitable substrate, such as paper,
transparency material, and the like. Transfer may be by any suitable means, such as
by charging the back of the substrate with a corotron to a polarity opposite to the
polarity of the toner. The transferred image is then permanently affixed to the substrate
by any suitable means. For the toners of the present invention, fusing by application
of heat and pressure is preferred. There results on a single substrate, such as paper,
pictorial colors of black, green, blue, red, yellow, green, brown, and others.
[0035] Development is generally accomplished by the magnetic brush development process disclosed
in U.S. Patent 2,874,063. This method entails the carrying of a developer material
containing the magnetic toner and magnetic carrier particles by a magnet. The magnetic
field of the magnet causes alignment of the magnetic carriers in a brush-like configuration,
and this "magnetic brush" is brought into contact with the electrostatic image bearing
surface of the photoreceptor. The toner particles are drawn from the brush to the
electrostatic image by electrostatic attraction to the undischarged areas of the photoreceptor,
and development of the image results. For the process of the present invention, the
conductive magnetic brush process is generally preferred wherein the developer comprises
conductive carrier particles and is capable of conducting an electric field between
the biased magnet through the carrier particles to the photoreceptor.
[0036] Developer compositions selected for the present invention generally comprise various
effective amounts of carrier and toner. Generally, from about 6 to about 12, and preferably
8.5 percent by weight of developer, and from about 88 to about 94 percent, and preferably
91.5 percent by weight of developer are admixed to formulate the developer. The ratio
of toner to carrier may vary depending, for example, on the tribo charge and the like
desired. Particle size of the colored toners is generally from about 9 to about 14
µm in volume average diameter, and preferably about 11 µm in volume average diameter
in embodiments.
[0037] Embodiments of the present invention include a developer composition comprised of
a toner comprised of resin, carbon black, magnetite, and a positive charge enhancing
additive, and a surface additive mixture comprised of a polymeric hydroxy compound
of the formula CH
3(CH
2)
nCH
2OH, wherein n is a number of from 30 to 300 and a colloidal silica treated with a
quaternary ammonium salt compound; and carrier particles comprised of a ferrite core
with a polymer mixture coating thereover; and a full color imaging process which comprises
the formation of a multiplicity of separate latent images on a photoconductive imaging
member, subsequently developing one image with a black developer composition, and
thereafter sequentially developing the remaining three images with three different
toners comprised of resin and a colored pigment other than black, and wherein the
toner pigment selected for the second image is dissimilar from the toner pigment selected
for the third image, and the toner pigment selected for the third image is dissimilar
from the toner pigment selected for the fourth image, followed by transferring each
of the developed images to a suitable substrate, and fixing the images thereto.
[0038] The following Examples are provided. All parts and percentages are by weight unless
otherwise indicated.
EXAMPLE I
[0039] A black developer composition was prepared as follows. Eighty nine and eight tenths
(88.8) percent by weight of emulsion polymerized styrene butadiene (89/11), 5.5 percent
of REGAL 330® carbon black, 4.5 percent by weight of the magnetite MAPICO BLACK®,
and 1.2 percent by weight of the charge additive distearyl dimethyl ammonium methyl
sulfate were melt blended in an extruder ZSK53 wherein the die was maintained at a
temperature of between 130 and 170°C, and the barrel temperature ranged from about
70 to about 150°C, followed by cooling, micronization and air classification to yield
toner particles of a volume average diameter size of 9.5 microns. The toner particles
were then blended with 0.15 percent by weight of colloidal silica particles treated
with dimethyloctadecyl-3-trimethoxy(silyl)propyl ammonium chloride, which is believed
to be AEROSIL #76®, treated with POLON MF-50® and available from Tayca Corporation
of Japan, and 0.25 percent by weight of UNILIN®, with an average molecular weight
of 700, reference Example I of U.S. Patent 4,883,736, the disclosure of which is totally
incorporated herein by reference, which UNILIN® was obtained from Petrolite Corporation.
Subsequently, carrier particles were prepared by dry powder coating a 50 micron diameter
copper zinc ferrite carrier obtained from Steward Chemical Company, 0.3 percent coating
weight, with a mixture of KYNAR®, 35 weight percent, and polymethyl methacrylate,
65 weight percent. A black developer was then prepared by blending 100 parts by weight
of the coated carrier particles with 10 parts by weight of the black toner in a Lodige
Blender for about 15 minutes at 60 RPM resulting in a developer with a toner exhibiting
a triboelectric charge of + 13 µC/g microcoulombs per gram as determined in the known
Faraday Cage apparatus at a toner concentration of about 8.5 percent. Admix time for
substantially uncharged added toner comprised of the same components of the above
prepared toner is believed to be about 15 seconds as determined in the known charge
spectrograph.
[0040] The above black magnetic developer was then incorporated into a full four-color Xerox
Corporation 5775™ imaging device, and wherein the device included a magenta toner,
a cyan toner, and a yellow toner, and there resulted for 100,000 copies with the same
developer charge pictorial and text of black with excellent quality and substantially
no background, and red, yellow, blue, green, subsequent to transfer and fixing with
heat. The triboelectric charge of the magnetic black toner remained at about 10 to
about 15 µC/g microcoulombs per gram for the 100,000 developed black images. The imaging
member utilized was comprised of an aluminum substrate, thereover a photogenerating
layer of trigonal selenium, and a top charge transport of the aryl amine, N,N'-diphenyl-N,N'-bis(3-methyl
phenyl) 1,1 '-biphenyl-4,4'-diamine, dispersed in 45 weight percent of a MAKROLON®
polycarbonate binder, reference U.S. Patent 4,265,990, the disclosure of which is
totally incorporated herein by reference.
EXAMPLE II
[0041] A toner and developer are prepared by repeating the procedures of Example I with
the exceptions that there is selected as the pigment 12.5 weight percent of flushed
HOSTAPERM PINK E™ comprised of 40 percent of pigment, and 60 percent of a styrene
butadiene obtained from Goodyear Chemical as PLIOLITE™, and no MAPICO BLACK®. The
triboelectric charge of the toner is + 15 µC/g microcoulombs per gram. This toner
can be utilized with the toner of Example I and two other colored toners for full
color imaging processes as illustrated herein.
[0042] Examples of magenta pigments include HOSTAPERM PINK E™, available from American Hoechst,
HOSTAPERM PINK EB™, available from American Hoechst, FANAL PINK D4830™, available
from BASF, LITHOL RUBINE NBD 4573™, available from BASF, effective mixtures thereof,
such as, for example, mixtures of HOSTAPERM PINK EB™ or HOSTAPERM PINK E™ with BASONYL
RED 560™, available from BASF. The aforementioned magenta pigment is present in the
toner in various effective amounts, such as, for example, from about 0.1 to about
15 weight percent, and preferably from about 1 to about 5 weight percent. Also, in
embodiments for the magenta toner about 3.2 weight percent of HOSTAPERM PINK E™ with
0.1 to 0.3 weight percent of BASONYL RED 560™ can be selected per 100 parts of toner.
[0043] Similar toners can be prepared by utilizing cyan and yellow pigments in place of
the HOSTAPERM PINK™.
[0044] Other embodiments and modifications of the present invention may occur to those skilled
in the art subsequent to a review of the present application; these embodiments and
modifications, as well as equivalents thereof, are also included within the scope
of this invention.