Note: Descriptions are shown in the official language in which they were submitted.
2076840
,
IMPROVED TONER AND PROCESS FOR FORMING
TWO-COLOR IMAGES
BACKGROUND OF THE INVENTION
The present invention is directed to improved toner
compositions and to an improved process for forming two-color images.
More specifically, the present invention is directed to a process for forming
two-color images which comprises creating on an imaging member a latent
image comprising areas of high, medium, and low potential, developing
the low areas of potential with a developer comprises a toner of a first color
comprising a res n, a colorant, a charge control additive selected from the
group consisting of (a) zinc 3,5-di-tert-butyl salicylate compounds; (b)
mixtures of a zinc 3,5-di-tert-butyl salicylate compound and an alkyl
pyridinium halide; (c) mixtures of a zinc 3,5-di-tert-butyl salicylate
compound and distearyl dimethyl ammonium methyl sulfate; (d) mixtures
of a zinc 3,5-di-tert-butyl salicylate compound and distearyl dimethyl
ammonium bisulfate; (e) mixtures of an aluminum 3,5-di-tert-butyl
salicylate compound and an alkyl pyridinium halide; (f) mixtures of an
aluminum 3,5-di-tert-butyl salicylate compound and distearyl dimethyl
ammonium methyl sulfate; (g) mixtures of an aluminum 3,5-di-tert-butyl
salicylate comp~und and distearyl dimethyl ammonium bisulfate; and
mixtures thereof, a colloidal silica external additive, and a metal salt of a
fatty acid external additive, and a carrier, subsequently developing the high
areas of potential with a developer comprising a toner of a second color
and a carrier, transferring the developed two-color image to a substrate,
and optionally permanently affixing the image to the substrate. Another
.... . .
-2- 2076810
embodiment of the present invention is directed to a toner composition
comprising a resin, a colorant, a charge control additive setected from the
group consisting of (a) mixtures of a zinc 3,5-di-tert-butyl salicylate
compound and an alkyl pyridinium halide; (b) mixtures of a zinc 3,5~i-tert-
butyl salicylate compound and distearyl dimethyl ammonium methyl
sulfate; (c) mixtures of a zinc 3,5-di-tert-butyl salicylate compound and
distearyl dimethyl ammonium bisulfate; (d) mixtures of an aluminum 3,5-
di-tert-butyl salicylate compound and an alkyl pyridinium halide; (e)
mixtures of an aluminum 3,5-di-tert-butyl salicylate compound and
distearyl dimethyl ammonium methyl sulfate; (f) mixtures of an aluminum
3,5-di-tert-butyl salicylate compound and distearyl dimethyl ammonium
bisulfate; and mixtures thereof, a colloidal silica external additive, and a
metal salt of a fatty acid external additive
U.S. Patent 4,845,003 (Kiriu et al.) discloses a toner for
developing electrostatic latent images characterized in that the
toner comprises an aluminum compound of a hydroxycarboxylic acid
which may be substituted with alkyl and/or aralkyl.
U.S. Patent 4,656,112 (Kawagishi et al.) discloses a toner
for developing electrostatic latent images which is characterized in
that the toner comprises as a charge control agent a zinc complex
compound of an aromatic hydroxycarboxylic acid having or not having
a substituent.
U.S. Patent 4,314,017 (Takahashi et al.) discloses a developer
composed of colored insulating particles for developing an electrostatic
image wherein ;3t least the external surface of each particle comprises two
different areas of which one area constitutes a major portion of the
external surface and comprises an element which defines the polarity of the
triboelectric charge of the particle to a determined polarity while the other
area comprises an element capable of being easily separated from the
particle, transferred to a surface of a developing device and charged to a
polarity opposite to that of the particle.
~ -F
3 20768~0
-
U.S. Patent 4,604,338 (Gruber et al.) discloses a positively
charged dry electrostatic colored toner composition comprising first resin
particles, crosslinked second resin particles, colored pigment particles
excluding black and selected from the group consisting of cyan, magenta,
yellow, blue, red, and brown, a low molecular weight wax, and a charge
enhancing additive selected from the group consisting of alkyl pyridinium
halides, organic sulfonate compositions, and organic sulfate compositions
of specified formulas, including distearyl dimethyl ammonium methyl
su If ate.
U.S. Patent 4,206,064 (Kiuchi et al.) discloses a toner
for developing electrostatic images which comprises a metal
complex of salicylic acid or a metal complex of an alkyl salicylic
acid as a charge control agent.
U.S. Patent 4,902,598 (Winnik et al.) discloses a process for the
preparation of silica based charge enhancing additives which comprises the
reaction of a tetraalkoxysilane with an alcoholic alkaline solution in the
presence of a soluble charge enhancing amine.
U.S. Patent 4,824,750 (Mahalek et al.) discloses a developer
composition which comprises crosslinked styrene copolymers with an
insoluble gel content of from about 20 to about 60 percent, pigment
particles, low molecular weight wax components, first external additive
particles of colloidal silica, second external additive particles of fatty acid
metal salts, and carrier particles.
U.S. Patent 4,904,762 (Chang et al.) discloses a toner composition
which comprises resin, pigment, and a mixture of charge enhancing
additives comprising a first additive of distearyl dimethyl ammonium
methyl sulfate, and a second additive comprising a tetraalkyl ammonium
bisu If ate.
The process of charging a photoresponsive imaging member to a
single polarity and creating on it an image consisting of at least three
different levels of potential of the same polarity is disclosed in U.S. Patent
4,078,929. This patent discloses a method of creating two colored images
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~4~ 20768~0
by creating 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. According to the teachings of this
patent, however, the images produced are of inferior quality compared to
those developed in two successive development steps. Also of interest with
respect to the tri-level process for generating images is U.S. Patent
4,686, 1 63.
U.S. Patent 4,525,447 discloses an image forming method
which comprises forming on a photosensitive member an electrostatic
latent image having at least three different levels of potential, or
comprising first and second latent images and developing the first and
second latent imdges with a three component developer. The developer
comprises a magnetic carrier, a first toner chargeable to one polarity by
contact with the magnetic carrier, and a second toner chargeable to a
polarity opposite to that of the first toner by contact with the first toner,
but substantially not chargeable by contact with the magnetic carrier.
U.S. Patent 4,640,883 discloses a method of forming composite
or dichromatlc images which comprises forming on an imaging member
electrostatic latent images having at least three different potential levels,
the first and secclnd latent images being represented respectively by a first
potential and a second potential relative to a common background
potential. The first and second images are developed by a first magnetic
brush using two kinds of toners, at least one of which is magnetic, and both
of which are chargeable to polarities opposite to each other, with
application to a developing electrode of a bias voltage capable of
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~5~ 2a76840
depositing the magnetic toner on the backdround potential area, to
deposit selectively the two toners on the first and second latent images and
to deposit the magnetic toner on the background potential area, while
collecting the deposited magnetic toner at least from the background
potential area by second magnetic brush developing means.
U.S. Patent 4,948,686 (Koch et al.) discloses 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 with a developer comprising a colored first toner
comprising a first resin selected from the group consisting of polyesters,
styrene-butadiene polymers, styrene-acrylate polymers, styrene-
methacrylate polymers, and mixtures thereof; a first pigment; a charge
control agent; colloidal silica surface external additives present; and
external additives comprising metal salts or metal salts of fatty acids; and a
first carrier comprising a core 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 polymethylmethacrylate
and from about 35 to about 65 percent by weight of
chlorotrifluoroethylene-vinyl chloride copolymer, wherein the coating
contains from O to about 40 percent by weight of the coating of conductive
particles; (4) subsequently developing the high areas of potential with a
developer comprising a black second toner comprising a second resin
present selected from the group consisting of polyesters, styrene-butadiene
polymers, styrene-acrylate polymers, styrene-methacrylate polymers, and
mixturesthereof; a second pigment; and a second charge control additive;
and a second carrier comprising a core and a coating selected from the
group consisting of chlorotrifluoroethylene-vinyl chloride copolymer
containing from O to about 40 percent by weight of conductive particles;
polyvinylfluorlde; and polyvinylchloride; and (5) transferring the
developed two-color image to a substrate.
.,
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207S8~0
U.S. Patent 5,223,368, issued June 29, 1993, Roger N.
Ciccarelli et al, entitled "Toner and Developer Compositions"
discloses a toner composition comprising a resin, a pigment,
and a charge enhancing additive of the formulas
/~OH
(R1)n t Al OH
\~CO~
--2
/ ~OH
(Rl)n~ AI OH
~CO~
--2
wherein R1 is selected from the group consisting of hydrogen, methyl,
ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, Cs alkyl and isomers
thereof, and C6 to C20 alkyl and isomers thereof, and wherein n is 0 to 4.
Aithough known compositions and processes are suitable for
their intended purposes, a need remains for toners, developers, and
imaging processes that enable generation of high quality two-color images
in a single development pass, particularly as a result of the absence of
interaction between the black and color developers. A need also remains
for toners, developers, and imaging.processes that enable reduction or
elimination of frmge-field development (the development of a halo of one
color toner surrounding an image developed with the other color toner).
There is also a need for toner compositions that enable improved developer
conductivity. Further, there is a need for toner compositions that enable
7 2 0768~D
improved developer admix properties (the amount of time required for
new toner particles added to the mixture of toner particles and
carrier particles to acquire the desired triboelectric charge).
SUMMARY OF THE INVENTION
It is an object of an aspect of the present invention to provide
toners, developers, and imaging processes that enable generation of high
quality two-color images in a single development pass.
It is an object of an aspect of the present invention to provide
toners, developers, and imaging processes that enable reduction or
elimination of fringe-field development.
It is an object of an aspect of the present invention to provide
toner compositions that enable improved developer conductivity.
It is an object of an aspect of the present invention to provide
toner compositions that enable improved developer admix properties.
These and other objects of the present invention (or specific
embodiments thereofl can be achieved by providing a process for forming
two-color images which comprises charging an imaging member, creating
on the member a latent image comprising areas of high, medium, and low
potential, developing the low areas of potential with a developer
comprises a toner of a first color comprising a resin, a colorant, a charge
control additive selected from the group consisting of (a) zinc 3,5-di-tert-
butyl salicylate compounds; (b) mixtures of a zinc 3,5-di-tert-butyl salicylate
compound and an alkyl pyridinium halide; (c) mixtures of a zinc 3,5-di-tert-
butyl salicylate compound and distearyl dimethyl ammonium methyl
sulfate; (d) mixtures of a zinc 3,5-di-tert-butyl salicylate compound and
distearyl dimethyl ammonium bisulfate; (e) mixtures of an aluminum 3,5-
di-tert-butyl salicylate compound and an alkyl pyridinium halide; (f)
mixtures of an aluminum 3,5-di-tert-butyl salicylate compound and
distearyl dimethyl ammonium methyl sulfate; (g) mixtures of an aluminum
3,5-di-tert-butyl salicylate compound and distearyl dimethyl ammonium
bisulfate; and mixtures thereof, a colloidal silica external additive, and a
metal salt of a fatty acid external additive, and a carrier, subsequently
, .
2~76~34~
developing the high areas of potential with a developer comprising a toner
of a second color and a carrier, transferring the developed two-color image
to a substrate, and optionally permanently affixing the image to the
substrate. Another embodiment of the present invention is directed to a
process for forming two-color images which comprises (1) creating on an
imaging member in an imaging apparatus a latent image comprising areas
of high, intermediate, and low potential; (2) developing the low areas of
potential by conductive magnetic brush development with a developer
comprising a first toner of a first color comprising a first resin present in anamount 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 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, substituted copper phthalocyanine pigments,
halogenated phthalocyanine pigments, quinacridone pigments, azo
pigments, rhodamine pigments, and mixtures thereof; a charge control
agent present in an amount of from about 0.1 to about 5 percent by weight
and selected from ~he group consisting of (a) zinc 3,5-di-tert-butyl salicylate
compounds; (b) mlxtures of a zinc 3,5-di-tert-butyl salicylate compound and
an alkyl pyridinium halide; (c) mixtures of a zinc 3,5-di-tert-butyl salicylate
compound and distearyl dimethyl ammonium methyl sulfate; (d) mixtures
of a zinc 3,5-di-tert-butyl salicylate compound and distearyl dimethyl
ammonium bisulfate; (e) mixtures of an aluminum 3,5-di-tert-butyl
salicylate compound and an alkyl pyridinium halide; (f) mixtures of an
aluminum 3,5-di-tert-butyl salicylate compound and distearyl dimethyl
ammonium methyl sulfate; (g) mixtures of an aluminum 3,5-di-tert-butyl
salicylate compound and distearyl dimethyl ammonium bisulfate; and
mixtures thereof; 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
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2û7~8~
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 polymethylmethacrylate 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; (3)
subsequently developing the high areas of potential by conductive
magnetic brush development with a developer comprising a second toner
of a second color 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
chlorotrifluoroeth~lene-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 (4)
transferring the developed two-color image to a substrate. Yet another
embodiment of the present invention is directed to a toner composition
comprising a resin, a colorant, a charge control additive selected from the
group consisting of (a) mixtures of a zinc 3,5-di-tert-butyl salicylate
compound and an alkyl pyridinium halide; (b) mixtures of a zinc 3,5-di-tert-
butyl salicylate compound and distearyl dimethyl ammonium methyl
sulfate; (c) mixtures of a zinc 3,5-di-tert-butyl salicylate compound and
distearyl dimethyl ammonium bisulfate; (d) mixtures of an aluminum 3,5-
di-tert-butyl salicylate compound and an alkyl pyridinium halide; (e)
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2076840
mixtures of an aluminum 3,5-di-tert-butyl salicylate compound and
distearyl dimethyl ammonium methyl sulfate; (f) mixtures of an aluminum
3,5-di-tert-butyl salicylate compound and distearyl dimethyl ammonium
bisulfate; and mixtures thereof, a colloidal silica external additive, and a
metal salt of a fatty acid external additive. Still another embodiment of the
present invention is directed to an imaging process which comprises
forming an electrostatic latent image on an imaging member, developing
the latent image with a toner composition comprising a resin, a colorant, a
charge control additive selected from the group consisting of (a) mixtures
of a zinc 3,5-di-tert-butyl salicylate compound and an alkyl pyridinium
halide; (b) mixtures of a zinc 3,5-di-tert-butyl salicylate compound and
distearyl dimethyl ammonium methyl sulfate; (c) mixtures of a zinc 3,5-di-
tert-butyl salicylate compound and distearyl dimethyl ammonium bisulfate;
(d) mixtures of an aluminum 3,5-di-tert-butyl salicylate compound and an
alkyl pyridinium halide; (e) mixtures of an aluminum 3,5-di-tert-butyl
salicylate compound and distearyl dimethyl ammonium methyl sulfate; (f)
mixtures of an aluminum 3,5-di-tert-butyl salicylate compound and
distearyl dimethyl ammonium bisulfate; and mixtures thereof, a colloidal
silica external additive, and a metal salt of a fatty acid external additive,
transferring the developed image to a substrate, and optionally
permanently affixing the transferred image to the substrate.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Toners of the present invention generally comprise a resin or
resins, one or more pigments, a charge control agent selected from the
group consisting of (a) zinc 3,5-di-tert-butyl salicylate compounds; (b)
mixtures of a zinc 3,5-di-tert-butyl salicylate compound and an alkyl
pyridinium halide; (c) mixtures of a zinc 3,5-di-tert-butyl salicylate
compound and distearyl dimethyl ammonium methyl sulfate; (d) mixtures
of a zinc 3,5-di-tert-butyl salicylate compound and distearyl dimethyl
ammonium bisulfate; (e) mixtures of an aluminum 3,5-di-tert-butyl
salicylate compound and an alkyl pyridinium halide; (f) mixtures of an
aluminum 3,5-di~tert-butyl salicylate compound and distearyl dimethyl
2~i768kO
ammonium methyl sulfate; (g) mixtures of an aluminum 3,5-di-tert-butyl
salicylate compound and distearyl dimethyl ammonium bisulfate; and
mixtures thereof, a colloidal silica external additive, and a metal salt of a
fatty acid external additive. Suitable resins include polyesters and 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, 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, preferably about 12 percent by weight, such as the
resins commercially available as Pliolite~ or Pliotone~ from Goodyear. Also
suitable are styrene acrylate polymers and styrene-n-butylmethacrylate
polymers, particularly those styrene-n-butylmethacrylate copolymers
wherein the styrene portion 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 portion 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 are also suitable. Also particularly suitable for
inclusion in the toners for the present invention are styrene-n-
butylmethacrylate uolymers wherein the styrene portion is present in an
amount of from about 50 to about 80 percent by weight, preferably about
65 percent by weight, and the n-butylmethacrylate portion is present in an
amount of from about S0 to about 20 percent by weight, preferably about
35 percent by weight. The resin is generally present in an amount of from
about 80 to about 98.8 percent by weight.
Suitable toner pigments include copper phthalocyanine
pigments, substituted copper phthalocyanine pigments, halogenated
phthalocyanine pigments, quinacridone pigments, azo pigments,
rhodamine pigments, and mixtures thereof. Specific examp~es include
Fanal Pink, commercially available from BASF, Sudan Blue OS, commercially
available from BASF, Neopen Blue, commercially available from BASF, PV
Fast Blue, commercially available from Hoechst-Celanese, Lithol Scarlet,
commercially available from BASF, Heliogen Green K-9360, commercially
available from BASF, Hostaperm Pink E pigment, commercially available
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2076840
from Hoechst-Celanese, Fanchon Fast Red R-6226, commercially available
from Mobay Chemical Company, Permanent Yellow FGL, commercially
available from Hoechst-Celanese, monoazo pigments such as Pigment Red
48: l, and the like. Generally, the pigment is present in an amount of from
about 1 to about 15 percent by weight, and preferably from about 2 to
about 10 percent by weight.
Suitable charge control agents for the toners of the present
invention include zinc 3,5-di-tert-butyl salicylate compounds, such as
Bontron E-84, available from Orient Chemical Company of Japan, or zinc
compounds as disclosed in U.S. Patent 4,656,112; mixtures of a zinc
3,5-di-tert-butyl salicylate compound with a second charge control agent
such as alkyl pyridinium halides, including cetyl pyridinium chloride
and others as disclosed in U.S. Patent 4,298,672, distearly dimethyl
ammonium methyl sulfate as disclosed in U.S. Patent 4,560,635, and
distearyl dimethyl ammonium bisulfate as disclosed in U.S. Patent
4,937,157 and U.S. Patent 4,560,635; mixtures of an aluminum 3,5-
di-tert-butyl salicylate compound, such as Bontron E-88TM, available
from Orient Chemical Company of Japan, or aluminum compounds as
disclosed in U.S. Patent 4,845,003 with a second charge control agent
such as alkyl pyridinium halides, including cetyl pyridinium
chloride and others, distearyl dimethyl ammonium methyl sulfate,
and distearyl dimethyl ammonium bisulfate; and mixtures thereof.
The zinc compound charge control additives are compounds of
zinc with 3,5-ditertiary-butyl salicylic acid as disclosed in U.S. Patent
4,656,112.
The aluminum compound charge control additives are
compounds of aluminum with 3,5-di-tertiary-butyl salicylic acid, and
according to U.S. Patent 4,845,003 are prepared from an aromatic
, .
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20768~o
hydroxycarboxylic acid with an alkyl and/or aralkyl by treating the acid with
an aluminum imparting agent by a known method.
The charge control agent or mixture of charge control agents is
generally present in a total amount of from about 0.1 to about 10 percent
by weight, and preferably from about 0.25 to about 3 percent by weight,
although other amounts may be present provided that the objectives of the
present invention are achieved. In one preferred embodiment, the charge
control agent is a mixture of either a zinc compound of 3,5-di-tert-butyl
salicylate or an aluminum compound of 3,5-di-tert-butyl salicylate with one
of the second charge control agents, wherein the second charge control
agent is present in the toner in an amount of from about 0.1 percent by
weight to about 1 percent by weight, and preferably from about 0.25
percent by weight to about 0.75 percent by weight.
In addition, external additives of colloidal silica, such as Aerosil~
R972, Aerosil~ R976, Aerosil~ R812, and the like, available from Degussa,
and metal salts or metal salts of fatty acids, such as zinc stearate,
magnesium stearate, aluminum stearate, cadmium stearate,`and the like,
are blended on the surface of the toners of the present invention. In
general, toners with these additives blended on the surface are disclosed in
U.S. Patent 3,590,000, U.S. Patent 3,720,617, U.S. Patent 3,900,588, and U.S.
Patent 3,983,045. Generally, the silica is present in an amount of from
about 0.1 to about 2 percent ~y weight, and preferably about 0.3 percent
by weight, of the toner and the metal salt additive such as zinc stearate is
present in an amount of from about 0.1 to about 2 percent by weight, and
preferably about 0.~ percent by weight, of the toner. Varying the amounts
of these two external additives enables ad justment of the charge levels and
conductivities of the toners. For example, increasing the amount of silica
generally adjusts the triboelectric charge in a negative direction and
improves admix times, which are a measure of the amount of time required
for fresh toner to become triboelectrically charged after coming into
contact with the carrier. In addition, increasing the amount of zinc stearate
improves admix times, renders the developer composition more conductive,
~ ;,
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~076~10
adjusts the triboelectric charge in a positive direction, and improves
humidity insensitivity.
One particularly preferred embodiment of the present invention
is directed to a toner comprising 9O percent by weight of a styrene-
butadiene resin, such as Pliolite~, 7 percent by weight of a pigment, such as
PV Fast Blue B2G-A, and 3 percent by weight of a zinc 3,5-di-tert-butyl
salicylate compound, such as Bontron E-84, with external additives colloidal
silica, such as Aerosil0 R-972, present in an amount of about 0.3 percent by
weight of the toner, and metal salts of fatty acids, such as zinc stearate,
present in an amount of about 0.3 percent by weight of the toner. Another
particularly preferred embodiment of the present invention is directed to a
toner comprising 90.5 percent by weight of a styrene-butadiene resin, such
as Pliolite0, 7 percent by weight of a pigment, such as PV Fast Blue, 2
percent by weight of a zinc 3,5-di-tert-butyl salicylate compound, such as
Bontron E-84, and 0.5 percent by weight of an alkyl pyridinium halide, such
as cetyl pyridinium chloride, with external additives colloidal silica, such as
Aerosil~ R-972, present in an amount of about 0.3 percent by weight of the
toner, and metal salts of fatty acids, such as zinc stearate, present in an
amount of about 0.3 percent by weight of the toner. Yet another
particularly preferred embodiment of the present invention is directed to a
toner comprising 90.5 percent by weight of a styrene-butadiene resin, such
as Pliolite~, 7 percent by weight of a pigment, such as PV Fast Blue, 2
percent by weight of an aluminum 3,5-di-tert-butyl salicylate compound,
such as Bontron E-88, and 0.5 percent by weight of an alkyl pyridinium
halide, such as cetyl pyridinium chloride, with external additives colloidal
silica, such as Aerosil~ R-972, present in an amount of about 0.3 percent by
weight of the toner, and metal salts of fatty acids, such as zinc stearate,
present in an amount of about 0.3 percent by weight of the toner.
Colored developers suitable for the imaging processes of the
present invention comprise a toner of the present invention and a carrier.
Any suitable electrophotographic carrier can be used. When the developer
is used to develop two-color images according to the process of the present
invention, preferred carriers are generally conductive, and generally exhibit
- - 20758~0
a conductivity of, for example, from about 10-14 to about 10-6 (ohm-cm)-1,
and preferably from about 10-1 1 to about 10-7 (ohm-cm)-1. Conductivity is
generally controlled by the choice of carrier core and coating; by partially
coating the carrier core, or by coating the core with a coating of a material
containing carbon black, the carrier is rendered conductive. In addition,
irregularly shaped carrier particle surfaces and toner concentrations of
from about 0.2 to about 5 will generally render a developer conductive.
Addition of a surface additive such as zinc stearate to the surface of the
toner particles also renders a developer conductive with the level of
conductivity rising with increased concentrations of the additive. Preferred
carriers for the developers of the present invention generally comprise a
steel core, preferably unoxidized, such as Hoeganoes Anchor Steel Grit,
with an average diameter of from about 25 to about 215 microns,
preferably from 50 to 150 microns, available from Hoeganoes, Riverton, NJ,
or Toniolo non-round steel with an average diameter of from about 25 to
about 215 microns, preferably from 50 to 150 microns, available from
Pometom S.P.A. (Toniolo), Venezia, Italy. The carrier particles are coated
with a solution coating of methyl terpolymer containing from 0 to about 40
percent by weight of conductive particles such as carbon black or
other conductive particles as disclosed in U.S. Patent 3,533,835,
issued October 13, 1970, Robert J. Hagenbach et al, homogeneously
dispersed in the coating material with the coating weight being from about
0.2 to about 3 percent by weight of the carrier, and preferably from about
0.4 to about 1.5 percent by weight of the carrier. Alternatively, the carrier
coating may comprise polymethylmethacrylate containing conductive
particles in an amount of from 0 to about 40 percent by weight of the
polymethylmethacrylate, and preferably from about 10 to about 20 percent
by weight of the polymethylmethacrylate, wherein the coating weight is
from about 0.2 to about 3 percent by-weight of the carrier and preferably
about 1 percent by weight of the carrier. A third possible carrier coating for
the carrier of the developer comprises a blend of from about 35 to about 65
percent by weight of polymethylmethacrylate and from about 35 to about
65 percent by weight of chlorotrifluoroethylene-vinyl chloride copolymer,
- - 20768~0
commercially available as OXY 461TM from Occidental Petroleum Company
containing conductive particles in an amount of from 0 to about 40 percent
by weight, and preferably from about 20 to about 30 percent by weight,
wherein the coating weight is from about 0.2 to about 3 percent by weight
of the carrier, and preferably about 1 percent~by weight of the carrier.
Preferably, the carrier coatings are placed on the carrier cores by a solution
coating process.
Colored developer compositions of the present invention
prepared from this toner and carrier generally comprise from about 0.5 to
about S percent by weight of the toner and from about 95 to about 99.5
percent by weight of the carrier. The ratio of toner to carrier may vary,
however, provided that the objectives of the present invention are
achieved. For example, an imaging apparatus employed for the process of
the present invention may be replenished with a colored developer
comprising about 55 percent by weight toner and about 45 percent by
weight carrier. The triboelectric charge of the colorèd toners generally is
from about -10 to about -30, and preferably from about -15 to about -20
microcoulombs per gram, although the value may be outside of this range
provided that the ob~ectives of the present invention are achieved. Particle
size of the colored toners is generally from about 7 to about 20 microns in
volume average diameter, and preferably about 13 microns in volume
average diameter, although the value may be outside of this range
provided that the objectives of the present invention are achieved.
The color developers of the present invention are particularly
suitable for two-color imaging processes wherein a latent image
comprising areas of high, medium, and low potential is developed with two
different color developers. Imaging members suitable for use with the
process of the present invention may be of any type capable of maintaining
three distinct levels of potential. Generally, various dielectric or
photoconductive insulating material suitable for use in xerographic,
ionographic, or other electrophotographic processes may be used, and
suitable photoreceptor materials include amorphous silicon, layered
2076890
organic materials as disclosed in U.S. Patent 4,265,990.
The photoresponsive imaging member can be negatively
charged, positively charged, or both, and the latent image formed on the
surface may consist of either a positive or a ne,gative potential, or both. In
one embodiment, the image consists of three distinct levels of potential, all
being of the same polarity. The levels of potential should be well
differentiated, such that they are separated by at least 100 volts, and
preferably 200 volts or more. For example, a latent image on an imaging
member can consist of areas of potential at -800, -400, and -100 volts. In
addition, the levels of potential may consist of ranges of potential. For
example, a latent image may consist of a high level of potential ranging
from about -500 to about -800 volts, an intermediate level of potential of
about -400 volts, and a low level ranging from about -100 to about -300
volts. An image having levels of potential that range over a broad area may
be created such that gray areas of one color are developed in the high
range and gray areas of another color are developed in the low range with
100 volts of potential separating the high and low ranges and constituting
the intermediate, un~leveloped range. In this situation, from 0 to about
100 volts may separate the high level of potential from the intermediate
level of potential, and from 0 to about 100 volts may separate the
intermediate level of potential from the low level of potential. When a
layered organic photoreceptor is employed, preferred potential ranges are
from about -700 to about -850 volts for the high level of potential, from
about -350 to about -450 volts for the intermediate level of potential, and
from about -100 to about -180 volts for the low level of potential. These
values will differ, depending upon the type of imaging member selected.
The latent image comprising three levels of potential,
hereinafter referred to as a tri-level image, may be formed on the imaging
member by any of various suitable methods, such as those disclosed in U.S.
Patent 4,078,929, the disclosure of which is totally incorporated herein by
reference. For example, a tri-level charge pattern may be formed on the
imaging member by the xerographic method of first uniformly charging
s
-18-
20768~0
the imaging member in the dark to a single polarity, followed by exposing
the member to an original having areas both lighter and darker than the
background area, such as a piece of gray paper having both white and
black images thereon. In a preferred embodiment, a tri-level charge
pattern may be formed by means of a raster output scanner, optically
modulating laser light as it scans a uniformly charged photoconductive
imaging member. In this embodiment, the areas of high potential are
formed by turning the light source off, the areas of intermediate potential
are formed by exposing the imaging member to the light source at partial
power, and the areas of low potential are formed by exposing the imaging
member to the light source at full power. Other electrophotographic and
ionographic methods of generating latent images are also acceptable.
Generally, in the process of the present invention the
highlighted areas of the image are developed with a developer of the
present invention having a first color, usually other than black, while the
remaining portions of the image are developed with a developer of a
second color, usually black, although another color can also be selected.
For the purpose of simplicity in describing the present invention, the first
color toner will be re~erred to as the "color toner" or the "colored toner"
and the second color toner will be referred to as the "black toner",
although either developer may be of any color. In general, the highlighted
color portions are developed first to minimize the interaction between the
two developers, thereby maintaining the high quality of the black image.
Development is generally by the magnetic brush development process
disclosed in U.S. Patent 2,874,063. This method entails the carrying of a
developer material containing toner and magnetic carrier particles by a
magnet. The magn~tic field of the magnet causes alignment of the
magnetic carriers in a brushlike 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
_. . ,
-19-
207684~
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. Conductive
magnetic brush development is generally employed for the process of the
present invention in view of the relatively small development potentials of
around 200 volts that are generally available for the process; conductive
development ensures that sufficient toner is laid on the photoreceptor
under these development potentials to result in acceptable image density.
Conductive development is also preferred to ensure that fringe fields
occurring around the edges of images of one color are not developed by
the toner of the other color.
During the development process, the developer housings are
biased to a voltage between the level of potential being developed and the
intermediate level of charge on the imaging member. For example, if the
latent image consists of a high level of potential of about -800 volts, an
intermediate level of potential of about -400 volts, and a low level of about
-100 volts, the develoDer housing containing the positively charged toner
that develops the high areas of potential may be biased to about -500 volts
and the developer housing containing the negatively charged toner that
develops the low areas of potential may be biased to about -300 volts.
These biases result in a development potential of about -200 volts for the
high areas of potential, which will be developed with a positively charged
toner, and a development potential of about + 200 volts for the low areas
of potential, which will be developed with a negatively charged toner.
Background deposits are suppressed by keeping the background
intermediate voltage ~etween the bias on the color developer housing and
the bias on the black developer housing. Generally, it is preferred to bias
the housing containing the positive toner to a voltage of from about 100 to
about 150 volts above the intermediate level of potential and to bias the
housing containing the negative toner to a voltage of from about 100 to
about 150 volts below the intermediate level of potential, although these
-20-
2076~0
values may be outside these ranges provided that the objectives of the
present invention are achieved.
The developed image is then transferred to any suitable
substrate, such as paper, transparency material, and the like. Prior to
transfer, it is preferred to apply a charge by means of a corotron to the
developed image in order to charge both toners to the same polarity, thus
enhancing transfer. 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.
Black developers suitable for the process of the present
invention comprise a toner and a carrier. A preferred carrier generally
comprises a steel core, such as Hoeganoes Anchor Steel Grit, with an
average diameter of from about 25 to about 215 microns, preferably from
about 50 to about 150 microns, with a coating of chlorotrifluoroethylene-
vinyl chloride copolymer, commercially available as OXY 461 from
Occidental Petroleum Company, said coating containing from 0 to about 40
percent by weight of conductive particles homogeneously dispersed in the
coating, at a coating weight of from about 0.4 to about 1.5 percent by
weight. This coating is generally solution coated onto the carrier core from
a suitable solvent, such as methyl ethyl ketone or toluene. Alternatively,
the carrier coating may comprise a coating of polyvinyl fluoride,
commercially available as Tedlar~ from E.l. Du Pont de Nemours and
Company, present in a coating weight of from about 0.01 to about 0.2, and
preferably about 0.05, percent by weight of the carrier. The polyvinyl
fluoride coating is generally coated onto the core by a powder coating
process, wherein the carrier core is coated with the polyvinyl fluoride in
powder form and subsequently heated to fuse the coating. In one
preferred embodiment, the carrier comprises an unoxidized steel core
which is blended with polyvinyl fluoride (Tedlar~), wherein the polyvinyl
fluoride is present in an amount of about 0.05 percent by weight of the
core. This mixture is then heat treated in a kiln at about 400F to fuse the
20768~0
polyvinyl fluoride coating to the core. The resulting carrier exhibits a
conductivity of about 7.6x10-10 (ohm-cm)-1. Optionally, an additional
coating of polyvinylidene fluoride, commercially available as Kynar~ from
Pennwalt Corporation, may be powder coated on top of the other coating
of the carrier in the black developer at a coating weight of from about 0.01
to about 0.2 percent by weight. The carrier for the black developer
generally has a conductivity of from about 10-14 to about 10-7, and
preferably from about 10-12 to about 10-9 (ohm-cm)-1 .
Black toners suitable for development of the image generally
comprise a resin, a pigment, and a charge control additive. Suitable resins
include polyesters, styrene-butadiene polymers, styrene acrylate polymers,
and styrene-methacrylate polymers, and particularly styrene-n-
butylmethacrylate copolymers wherein the styrene portion is present in an
amount of from about 50 to about 80 percent by weight, preferably about
58 percent by weight, and the n-butylmethacrylate portion is present in an
amount of from about 20 to about 50 percent by weight, preferably about
42 percent by weight. Generally, the resin is present in an amount of from
about 80 to about 98.8 percent by weight, and preferably in an amount of
92 percent by weight Suitable pigments include those such as carbon
black, including Regal~ 330, commercially available from Cabot
Corporation, as well as any pigment colored other than black. Generally,
the pigment is present in an amount of from about 1 to about 15 percent
by weight, and preferably in an amount of abowt 6 percent by weight.
Suitable charge control agents for the black toner of the present
invention include distearyl dimethyl ammonium methyl sulfate and alkyl
pyridinium halides such as cetyl pyridinium chloride and the like. The
charge control agent is present in an amount of from about 0.1 to about 6
percent by weight, and preferably in an amount of about 2 percent by
weight. In addition, the black toner may contain magnetite, such as
Mapico Black, in an amount of from about 8 to about 20, and preferably
about 15 or 16 percent by weight. A toner suitable for the present
invention containing magnetite generally comprises from about ~1.25 to
about 87.8 percent by weight of the resin, from about 8 to about 20
-22-
207684~
percent by weight of the magnetite, from about 4 to about 7 percent by
weight of carbon black, and from about 0.2 to about 1.75 percent by
weight of the charge control additive.
In addition, external additives of colloidal silica, such as Aerosil~
R972, Aerosil~ R976, Aerosil0 R812, and the like, available from Degussa,
and metal salts or metal salts of fatty acids, such as zinc stearate,
magnesium stearate, and the like, may optionally be blended on the
surface of the black toner. Generally, the silica is present in an amount of
from about 0.1 to about 2 percent by weight of the toner and the zinc
stearate is present in an amount of from about 0.1 to about 2 percent by
weight of the toner. These additives function in the manner described for
the color toners with respect to charge control, admix control, conductivity
control, and the like.
The black toners of the present invention may also optionally
contain as an external additive a linear polymeric alcohol comprising a fully
saturated hydrocarbon backbone with at least about 80 percent of the
polymeric chains terminated at one chain end with a hydroxyl group. The
linear polymeric alcohol is of the general formula CH3(CH2)nCH2OH,
wherein n is a number from about 30 to about 300, and preferably from
about 30 to about 50. Linear polymeric alcohols of this type are generally
available from Petrolite Chemical Company as UnilinTM. The linear
polymeric alcohol is generally present in an amount of from about 0.1 to
about 1 percent by weight of the toner.
Black developer compositions for the present invention
generally comprise from about 1 to about 5 percent by weight of the toner
and from about 95 to ~bout 99 percent by weight of the carrier. The ratio
of toner to carrier may vary, however, provided that the objectives of the
present invention are achieved. For example, an imaging apparatus
employed for the process of the present invention may be replenished with
a colored developer comprising about 65 percent by weight toner and
about 35 percent by weight carrier. The triboelectric charge of the black
toners generally is from about + 10 to about + 30, and preferably from
about + 13 to about + 18 microcoulombs per gram, although the value may
-23- 2076843
be outside of this range provided that the objectives of the present
invention are achieved. Particle size of the black toners is generally from
about 8 to about 13 microns in volume average diameter, and preferably
about 11 microns in volume average diameter, although the value may be
outside of this range provided that the objectives of the present invention
are achieved.
Coating of the carrier particles for the black developer may be by
any suitable process, such as powder coating, wherein a dry powder of the
coating material is applied to the surface of the carrier particle and fused to
the core by means of heat, solution coating, wherein the coating material is
dissolved in a solvent and the resulting solution is applied to the carrier
surface by tumbling, or fluid bed coating, in which the carrier particles are
blown into the air by means of an air stream, and an atomized solution
comprising the coating material and a solvent is sprayed onto the airborne
carrier particles repeatedly until the desired coating weight is achieved.
The black toners may be prepared by processes such as extrusion,
which is a continuous process that entails dry blending the resin, pigment,
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. External additives such aslinear polymeric alcohols, silica, or zinc stearate are then blended with the
classified toner in a powder blender. Subsequent admixing of the toners
with the carriers, generally in amounts of from about 0.5 to about 5 percent
by weight of the toner and from about 95 to about 99.5 percent by weight
of the carrier, yields the developers suitable for the two-color imaging
process of the present invention.
Specific embodiments of the invention will now be described in
detail. These examples are intended to be illustrative, and the invention is
not limited to the materials, conditions, or process parameters set forth in
these embodiments. All parts and percentages are by weight unless
othervvise indicated.
-24-
207684~3
EXAMPLE I
A toner composition was prepared containing 90.5 percent by
weight of Pliotone~ resin (available from Goodyear), 7.0 percent by weight
of PV Fast Blue B2G-A pigment (available from Hoechst-Celanese), 2.0
percent by weight of Bontron E-88 aluminum compound charge control
agent (available from Orient Chemical, Japan), and 0.5 percent by weight
of cetyl pyridinium chloride charge control agent (available from Hexcel
Corporation) The toner components wer~ first dry blended and then melt
mixed in an extruder. The extruder strands were cooled, chopped into
small pellets, ground into toner particles, and then classified to narrow the
particle size distribution. The toner particles had a particle size of 13.0
microns (by volume median). Subsequently, the toner particles were dry
blended with silica particles (Aerosil~ R972, available from Degussa) in an
amount of 0.3 percent by weight of the toner particles, and zinc stearate
(available from Synthetic Products) in an amount of 0.3 percent by weight
of the toner particles.
A carrier composition was prepared by coating Hoeganoes Steel
Grit cores (available from Hoeganoes) with a coating comprising 80 percent
by weight of polymethyl methacrylate (available from E.l. Du Pont de
Nemours & Company) and 20 percent by weight of Vulcan carbon black
(available from Cabot Corp), wherein the core was present in an amount of
99.2 percent by weight and the coating was present in an amount of 0.8
percent by weight. Coating was carried out by a solution coating process
from methyl ethyl ketone.
EXAMPLE II
A developer composition was prepared by mixing together 3
parts by weight of the toner with 100 parts by weight of the carrier
particles. The developer thus prepared containing Bontron E-88 aluminum
compound charge control agent was incorporated into a printer testfixture
comprising an organic imaging member and two developer housings,
wherein a two-color image can be developed in a single pass by having the
imaging member bearing a tri-level latent image pass both developer
-25- 20768~0
housings sequentially, and the conductivity of the developer was measured
as the printer test fixture was operated with a tri-level electrostatic latent
image on the imaging member having voltages of -700 V, -400 V, and -lO0
V, with the image at -100 V being developed by the blue toner containing
the Bontron E-88TM. The log (base lO) of the developer conductivity (mho)
was -9Ø For comparison purposes, the same measurement was made on a
developer of the same composition with the exception that the toner
contained no cetyl pyridinium chloride, 3 percent by weight of the Bontron
E-88TM, and 90 percent by weight of the Pliotone~ resin. The developer
containing no cetyl pyridinium chloride exhibited a lower value of the
logarithm tbase 10) of the developer conductivity of -11Ø Thus, the
developer containing both cetyl pyridinium chloride and the aluminum
compound charge control agent exhibited a higher conductivity, as
indicated by the lower absolute value of the logarithm of the developer
conductivity. Higher conductivity is generally desirable for developer
compositions employed in conductive development processes.
EXAMPLE lll
Four developers were prepared by preparin~ toners as described
in Example I containing Bontron E-88TM aluminum compound charge control
agent. Each toner contained the amounts of pigment and external
additives described for the toner in Example 1. The toners contained,
respectively, 2 percent by weight of Bontron E-88TM aluminum compound
charge control agent, 0.25 percent cetyl pyridinium chloride, and 90.75
percent by weight of Pliotone~; 2 percent by weight of Bontron E-88TM
aluminum compound charge control agent, 0.5 percent by weight of cetyl
pyridinium chloride, and 90.5 percent by weight of Pliotone~; 3 percent by
weight of Bontron E-88TM aluminum compound charge control a~ent, 0.25
percent by weight of cetyl pyridinium chloride, and 89.75 percent by
wei~ht of Pliotone~; and 3 percent by weight of Bontron E-88TM aluminum
compound char~e control agent, 0.5 percent by wei~ht of cetyl pyridinium
chloride, and 89.5 percent by weight of Pliotone~. For comparison
purposes, a fifth toner was prepared containing 3 percent by weight of
~,~
B~
-26- 207-6~
Bontron E-88 aluminum compound charge control agent and 90 percent by
weight of Pliotone~. Each of the five toners was then admixed with a
carrier as described in Example I to form five developer compositions.
The developers were incorporated into the printer test fixture
described in Example II and the toner-to-carrier ratios of the five
developers were varied to determine the maximum amount of toner
concentration that could be contained in each developer before fringe field
development occurred. Fringe field devetopment occurred when the blue
developer formed a blue halo surrounding the black images formed during
the two-color development process. In the test fixture, a tri-level image
was generated on the imaging member. The color image was developed
first with the blue developer containing the Bontron E-88 aluminum
compound charge control additive, followed by development of the black
image with a black developer. The black developer contained a toner
comprising 2 percent by weight of cetyl pyridinium chloride, 6 percent by
weight of Regal~ 330 carbon black (available from Cabot Corporation), and
92 percent by weight of a styrenetn-butylmethacrylate polymer containing
58 percent by weight of styrene and 42 percent by weight of n-
butylmethacrylate. The toner particles had a particle size of 11.4 microns
(by volume median). The black carrier comprised a Hoeganoes steel core (as
described for the carrier in Example I) coated with a polyvinyl fluoride
(Tedlar~, available from E.l. Du Pont de Nemours 8 Company) coating in a
coating weight such that the carrier comprised 0.05 percent by weight of
the coating and 99.95 percent by weight of the core. The black toner and
black carrier were mixed together in relative amounts of 3 parts by weight
of toner to 100 parts by weight of carrier. The maximum toner
concentration possible without fringe field development for the blue
developer containing no cetyl pyridinium chloride was 4.5 percent by
weight of toner. In contrast, for the blue developers containing both the
aluminum compound cl~arge control agent and cetyl pyridinium chloride,
the maximum toner concentrations possible without fringe field
development were, respectively: greater than 8.6 percent by weight (toner
containing 2 percent by weight of Bontron E-88 and 0.25 percent by weight
-27- 20768~
of cetyl pyridinium chloride); greater than 6.5 percent by weight (toner
containing 2 percent by weight of Bontron E-88 and 0.5 percent by weight
of cetyl pyridinium chloride); greater than 6.5 percent by weight (toner
containing 3 percent by weight of Bontron E-88 and 0.25 percent by weight
of cetyl pyridinium chloride); and greater than 6.7 percent by weight (toner
containing 3 percent by weight of Bontron E-88 and 0.5 percent by weight
of cetyl pyridinium chloride). These results indicate that the toner-to-
carrier ratio of the developers containing both the aluminum compound
charge control agent and cetyl pyridinium chloride can be varied over a
wider range than the toner-to-carrier ratio of the developer containing
only the aluminum compound charge control agent. This wider range over
which toner-to-carrier ratio can be varied enables the developer to be
adjusted to the varying temperature and relative humidity conditions
under which development occurs without the occurrence of fringe field
development.
EXAMPLE IV
The four developers in which the toners contained both the
aluminum compound chdrge control agent and cetyl pyridinium chloride
described in Example m were each roll milled for 30 minutes at a milling
speed of 90 linear feet per minute, after which the charging characteristics
of the toners were measured. For comparison purposes, the charging
characteristics of a developer in which the toner contained the al~minum
compound charge control agent but no cetyl pyridinium chloride as
described in Example m were also measured subsequent to milling. The At
values of the four toners containing both the aluminum compound charge
control additive and cetyl pyridinium chloride ranged from 75 to 83% ~lc/g;
in contrast, the At value of the toner containing no cetyl pyridinium
chloride was 70% ~c/g, indicating that the toners containing both the
aluminum compound charge control agent and cetyl pyridinium chloride
were capable of becoming more highly charged than the toner containing
no cetyl pyridinium chloride. At is a measure of triboelectric charging, and
-28- 2076340
is calculated from the triboelectric charge in microcoulombs per gram and
the toner concentration as follows:
At=tribo(llc/g) x [tonerconcentration(%) + 1l
EXAMPLE V
The admix performances of the developer in which the toner
contained the aluminum compound charge control agent but no cetyl
pyridinium chloride and the four developers in which the toners contained
both the aluminum compound charge control agent and cetyl pyridinium
chloride described in Example III were measured by introducing each
developer into a roll mill at a toner concentration of 2.5 parts by weight of
toner to 100 parts by weight of carrier, adding to the developer mixture
fresh uncharged toner particles in an amount of 1 part by weight of toner,
and roll milling the developer at 90 linear feet per minute until the fresh
toner particles became fully charged. For the four developers in which the
toners contained both the aluminum compound charge control agent and
cetyl pyridinium chloride, admix was accomplished in 15 seconds. In
contrast, for the developer in which the toner contained the aluminum
compound charge control agent but no cetyl pyridinium chloride, admix
was accomplished in 30 seconds, indicating that the presence of both the
aluminum compound charge control agent and cetyl pyridinium chloride in
the toner enabled more rapid admix.
E~tAMPLE Vl
A toner compos~tion was prepared as described in Example I
with the exception that the toner contained 3 percent by weight of
Bontron E-84 zinc compound charge control agent (available from Orient
Chemicals, Japan), 0.5 pe~rcent by weight of cetyl pyridinium chloride, and
89.5 percent by weight of Pliotone~. This toner was admixed with the
carrier prepared as described in Example I and the admix time for the
resulting developer was measured by the process described in Example V.
The admix time for this developer was 15 seconds.
2~768~0
EXAMPLE VII
Three developers were prepared by preparing toners as
described in Example I but containing Bontron E-84 zinc compound charge
control agent instead of Bontron E-88 aluminum compound charge control
agent. Each toner contained the amounts of pigment and external
additives described for the toner in Example I. The toners contained,
respectively, 3 percent by weight of Bontron E-84 zinc compound charge
control agent, 0.5 percent cetyl pyridinium chloride, and 89.5 percent by
weight of Pliotone~; 2 percent by weight of Bontron E-84 zinc compound
charge control agent, 0.5 percent by weight of cetyl pyridinium chloride,
and 90.5 percent by weight of Pliotone~; and 2 percent by weight of
Bontron E-88 aluminum compound charge control agent, 0.5 percent by
weight of cetyl pyridinium chloride, and 90.5 percent by weight of
Pliotone~ (prepared by a process wherein the toner pellets obtained from
the extruder were converted to powder particles with an Alpine Fluid Bed
Grinder). The toner particles had a particle size of 13.0 microns (by volume
median). Each of the three toners was then admixed with a carrier as
described in Example I to form three developer compositions.
The developen were incorporated into the printer test fixture
described in Example II and the toner-to-carrier ratios of the three
developers were varied to determine the maximum amount of toner
concentration that could be contained in each developer before fringe field
development occurred, as described in Example m. The maximum toner
concentration possible without fringe field development for all three
developers was greater than 6.5 percent by weight of toner. In contrast,
the developer described in Example III containing only Bontron E-88
aluminum compound charge control agent and no cetyl pyridinium
chloride had a maximum toner concentration of 4 95 percent without
fringe field development. These results indicate that the toner-to-carrier
ratio of the developers cc~ntaining both the zinc compound charge control
agent and cetyl pyridinium chloride can be varied over a wider range than
the toner-to-carrier ratio of the developer containing only the aluminum
compound charge control agent.
-30-
~076840
EXAMPLE VIII
A developer was prepared by preparing a toner as described in
Example I but containing Bontron E-84 zinc compound charge control
agent instead of Bontron E-88 aluminum compound charge control agent
and containing no cetyl pyridinium chloride. The toner contained 3 percent
by weight of Bontron E-84 zinc compound charge control agent, 90 percent
by weight of Pliotone~, and the amounts of pigment and external additives
set forth for the toner in Example I. The toner was then admixed with a
carrier as described in Example I to form a developer composition.
The developer was incorporated into the printer test fixture
described in Example II and the toner-to-carrier ratio of the developer was
varied to determine the maximum amount of toner concentration that
could be contained in the developer before fringe field development
occurred, as described in Example m. The maximum toner concentration
possible without fringe field development for this developer containing the
zinc compound charge control agent was greater than 6.5 percent by
weight of toner. In contrast, the developer described in Example m
containing only Bontron E-88 aluminum compound charge control agent
and no cetyl pyridinium chloride had a maximum toner concentration of
4.95 percent without fringe field development. These results indicate that
the toner-to-carrier ratio of the developer containing the zinc compound
charge control agent can be varied over a wider range than the toner-to-
carrier ratio of the developer containing only the aluminum compound
charge control agent.
EXAMPLE IX
Four developers in which the toners contained both the Bontron
E-88 aluminum compounc charge control agent and distearyl dimethyl
ammonium bisulfate were prepared by the method described in Example I.
Each toner contained the amounts of pigment and external additives
described for the toner In Example I. The toners contained, respectively: 2
percent by weight of Bontron E-88 aluminum compound charge control
-31-
20768~0
agent,0.25 percent distearyl dimethyl ammonium bisulfate (available from
Hexcel Corporation), and 90.75 percent by weight of Pliotone~9; 2 percent
by weight of Bontron E-88 aluminum conpound charge control agent, 0.75
percent by weight of distearyl dimethyl ammonium bisulfate, and 90.25
percent by weight of Pliotone~; 3 percent by weight of Bontron E-88
aluminum compound charge control agent, 0.25 percent by weight of
distearyl dimethyl ammonium bisulfate, and 89.75 percent by weight of
Pliotone~; and 3 percent by weight of Bontron E-88 aluminum compound
charge control agent, 0.75 percent by weight of distearyl dimethyl
ammonium bisulfate, and 89.25 percent by weight of Pliotone~D. For
comparison purposes, a fifth toner was prepared containing 3 percent by
weight of Bontron E-88 aluminum compound charge control agent and 90
percent by weight of Pliotone~. Each of the five toners was then admixed
with a carrier as described in Example I to form five developer
compositions. The five developers were each roll milled for 30 minutes at a
milling speed of 90 linear feet per minute, after which the charging
characteristics of the toners were measured. The At values of the four
toners containing both the aluminum compound charge control additive
and distearyl dimethyl ammonium bisulfate ranged from 82 to 90% ~c/g; in
contrast, the At value of the toner containing only the Bontron E-88
aluminum compound charge control agent was 70% ~c/g, indicating that
the toners containing both the aluminum compound charge control agent
and distearyl dimethyl ammonium bisulfate were capable of becoming
more highly charged than the toner containing no distearyl dimethyl
ammonium bisulfate.
EXAMPLE X
The admix performances of the developer in which the toner
contained the aluminum compound charge control agent but no distearyl
dimethyl ammonium bisulfate and the four developers in which the toners
contained both the aluminum compound charge control agent and
distearyl dimethyl ammonium bisulfate described in Example IX were
measured by introducing each developer into a roll mill, adding to the
-32-
~76840
developer mixture fresh uncharged toner particles, and roll milling the
developer at 90 linear feet per minute until the fresh toner particles
became fully charged. For the four developers in which the toners
contained both the aluminum compound charge control agent and
distearyl dimethyl ammonium bisulfate, admix was accomplished in 15
seconds. In contrast, for the developer in which the toner contained the
aluminum compound charge control agent but no distearyl dimethyl
ammonium bisulfate, admix was accomplished in 30 seconds, indicating
that the presence of both the aluminum compound charge control agent
and distearyl dimethyl ammonium bisulfate in the toner enabled more
rapid admix.
Other embodiments and modifications of the present invention
may occur to those skilled in the art subsequent to a review of the
information presented herein; these embodiments and modifications, as
well as equivalents thereof, are also included within the scope of this
invention.
