Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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CONDUCTIVE POWDER COAT~D ELECTROSTATOGRAP~IIC CARRIERS
This invention is generally concerned with electrostatographic
imaging systems and, more specifically, to improved imaging materials, their
5 manufacture, and use.
It is well known to form and develop images on the surface of
photoconductive materials by electrostatic methods sueh as described, for
example, in U.S. Patents 2,297,691; 2,277,013; 2,551,582; 3,220,324; and
3,220,833. In summary, these processes as described in the aforementioned
10 patents involve the formation of an electrostatic latent charged image on an
insulating electrophotographic element and rendering the la~ent image visible
by a development step whereby the charged surface of the photoconductive
element is brought into contact with a developer mixture. As described in U.S.
Patent 2,297,691, for example, the resulting electrostatic latent image is
15 developed by depositing thereon a finely-divided electroscopic material
referred to in the art as toner, the toner being generally attracted to the areas
of the layer which retain a charge thus forming a toner image corresponding to
the electrostatic latent image. Subsequently, the toner image can be
transferred to a support surface such as paper and this transferred image can
20 be permanently a~fixed to the support surface using a variety of techniques
including pressure fixing, heat fixing, solvent fixing, and the like.
Many methods are known for applying the electroscopic particles to
the latent image including cascade development, touchdown and magnetic
brush as illustrated in U.S. Patents 2,618,552; 2,895,847 and 3,245,823. One of
25 the most widely used methods is cascade development wherein the developer
material comprising relatively large carrier particles having finely-divided
toner particles electrostatically clinging to the surface of the carrier particles
is conveyed to and rolled or cascaded across the elect~ostatic latent image-
bearing surface. Magnetic brush development is also known and involves the
30 use of a developer material comprising toner and magnetic earrier particles
which are carried by a magnet so that the magnetic field produced by the
magnet causes alignment of the magnetic carriers in a brush-like configura-
tion. Subsequently, this brush is brought into contact with the electrostatic
latent image-bearing surface causing the toner particles to be attracted from
35 the brush to the eleetrostatic latent image by electrostatic attraction, as more
specifically disclosed in U.S. Patent 2,874,063.
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Carrier materials used in the development of electrostatic latent
images are described in many patents including, for example, U.S. Patent
3,590,000. The type of carrier material to be used depends on many factors
such as the type of development used, the quality of the development desired,
5 the type of photoconductive material employed and the like. Generally,
however, the materials used as carrier surfaces or carrier partieles or the
coating thereon should have a triboelectric value commensurate with the
triboelectric value of the toner in order to generate electrostatic adhesion of
the toner to the carrier. Carriers should be selected that are not brittle so as10 to cause flaking of the surface or particle break-up under the forces exertedon the carrier during recycle as such causes undesirable effects and could,for
example, be transferred to the copy surface thereby reducing the quality of
the final image.
There have been recent eforts to develop carriers and particularly
15 coatings for carrier particles in order to obtain better development quality and
also to obtain a material that can be recycled and does not cause any adverse
effects to the photoconductor. Some of the coatings commercially utilized
deteriorate rapidly especially when employed in a continuous process whereby
the ~entire coating may separate from the carrier core in the form of chips or
20 flakes as a result of poorly adhering coated material and fail upon impact and
abrasive contact with machine parts and other carrier particles. Such carrier
parffcles generally cannot be reclaimed and reused and usually provide poor
print quality results. Further, the triboelectric values of some carrier coatings
have been found to fluctuate when changes in relative humidity occur and thus
25 these carriers are not desirable for use in electrostatographic systems as they
can adversely affect the quality of the developed image.
The coating materials employed for carrier particles are generally
resins having electrically insulating properties and are usually applied by
solution or spray-drying techniques. However, it has been found that when
30 attempts are made to apply an insulating resin coating to porous carrier core materials by solution-coating techniques that the products obtained are
undesirable. This is so because most of the coating material is found to reside
in the pores of the carrier cores and not at the surface thereof so as to be
available for triboelectric charging when the coated carrier particles are
35 mixed with finely-divided toner particles. Attempts to resolve this problem by
increasing carrier coating weights, for example, to as much as up to about 3
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percent or greater to provide an effective triboelectric charging coating to thecarrier particles necessarily involves handling excessive quantities of solventsand usually results in low product yields. It has also been found that ~oner
impaction, i.e., where toner particles become welded to or impacted upon the
5 carrier particles, remains high with thus coated carrier particles producing
short developer useful lifetimes. Further, solution-coated porous carrier
particles when combined and mixed with finely-divided toner particles provide
triboelectric charging levels which are too low for practical use. In addition,
solution-coated metallic carrier particles have a high incidence of electrical
10 breakdown at low applied voltages leading to shorting between the carrier
particles and the photoreceptor.
Further, when attempting to provide carrier materials having
conductive properties such as by partially coating conductive carrier cores
with an electrically insulating resin, the amount of coating material applied
15 must be carefully controlled so that enough uncoated areas remain on the
carrier cores to provide conductive paths between the carrier material and the
photoreceptor. Such partially coated carrier materials are extremely difficult
to reproducibly control and manufacture, they produce bimodal triboelectric
charging sites, and they have narrow toner concentration latitudes quickly
20 yielding insulating developers and short developer life.
~ urther, in particular electrostatographic reproduction systems, in
order to develop a latent image comprised of negative electrostatic charges,
an electrostatic carrier and toner powder combination must be selected in
which the toner is triboelectrically charged positively relative to the granular25 carrier. Likewise, in order to develop a latent image comprised of positive
electrostatic charges such as where a selenium photoreceptor is employed, an
electroscopic toner powder and carrier mixture must be selected in which the
toner is triboelectrically charged natively relative to the carrier. Thus, wherethe latent image is formed of negative electrostatic charges such as when
30 employing an organic electrophotosensitive material as the photoreceptor, it is
highly desirable to develop the latent image with a positively charged
electroscopic powder and a negatively charged carrier material. Thus, there is
a continuing need for a better electrostatographie carrier material and an
improved method for its preparation.
3~ Summary of the Invention~ af~
,~ It is, therefore, an object of~l~?his i~vention to provide a carriermanufacturing technique and a resul~ing product which overcome the above-
: noted deficiencies.
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It is an object of an aspect of this invention
to provide carrier beads having conductive characteristics,
greatly increased useful life, and which substantially
eliminate photoreceptor shorting problems.
It is an object of an aspect o~ this invention
to provide a method for altering triboelectric values of
a carrier material without markedly changing the physical
and chemical properties of the original carrier material.
It is an object of an aspect of this invention
to provide a carrier manufacturing technique for producing
carriers having uniform triboelectric properties.
An object of an aspect of this invention is to
provide improved developer materials~ especially improved
coated carrier materials, which may be used in electrostato-
graphic development environments where the photoreceptor
is negatively charged.
An object of an aspect of this invention is to
provide carrier beads having triboelectric properties superior
to known carrier beads.
The foregoing objects and others are accomplished,
generally speaking, by providing coated carrier particles
having electrically conductive properties. More specifically,
the carrier particles of this invention comprise a core
particle having an average diameter of from between about
30 microns and about 1,000 microns coated with from between
about 0.05 percent and about 3.0 percent by weight, based
on the weight of the carrier particles, of a mixture of
thermoplastic insulating resinous material and at least
one agent possessing electrically conductive properties.
Generally speaking, the coated carrier particles of thisinvention are provided by preparing a fluid mixture of
thermoplastic insulating resinous material and at least
one electrically conductive agent, applying said mixture
in the form of dry, powdered particles having a particle
size of between about 1 micron and about 100 microns to
the aforementioned carrier core, and then heating the result-
ant aggregation to a temperature of between about 260F
and about 650F for between about 20 minutes and about
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120 minutes so that the mixture of thermoplastic insuIating
resinous material and electrically conductive a~ent fuse
to the carrier core particle.
Thus, one aspect of this invention is as follows:
A process for preparing coated carrier particles
having conductive properties useful in electrostatographic .
developer mixtures for the development of electrostatic
latent images wherein the improvement comprises the steps
of preparing a fluid mixture of insulating resinous material
and at least one electrically conductive agent, converting
said fluid mixture to a solid state, comminuting said
mixture in said solid state to dry, powdered particles
having a particle size of between about 1 micron and about
100 microns, applying said powdered particles to the surface
of carrier cores having an average particle diameter of
from between about 30 microns and about 1,000 microns,
and heating the resultant aggregation to a temperature
of between about 260F and about 650F for between about
20 minutes and about 120 minutes so that said powdered
particles fuse to said carrier cores.
In the initial step of preparing the
compositions of this invention, any suitable means may
be employed to produce the conductive material-powdered
resin mixture. Thus, for example, an insulating
resinous material is heat-melted or dissolved in a
suitable solvent to bring the resinous material to
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a fluid or tacky state. To the fluid or tacky resinous composition is added a
suitable amount of conductive material and mixed therewith until a uniform
mixture is obtained. The resultant resinous composition and conductive
material mixture is then processed to provide dry, powdered particles having a
5 particle size of between about 1 micron and about 100 microns, preferably
between 1 micron and about 50 microns. Some of the means which may be
employed to provide these dry, powdered resin-conductive material particles
include spray-drying the foregoing fluid or tacky mixture or a dispersion
thereof, precipitation of a resin-conductive material dispersion, freeze-drying
10 a resin-conductive material dispersion, air or fluid attrition of a resin-
conductive material dispersion, direct polymerization such as emulsion
polymerization of conductive material in a monomer followed by crushing,
grinding, or milling and any other suitable means to obtain the aforedescribed
particles.
Following preparation of the dry, powdered resin-conductive
material parti¢les described above, the powdered particles are applied to the
surface of a carrier core material by, for example, dry-mixing the powdered
resin-conductive material particles and the carrier core material until the
powdered particles adhere to the carrier core material by mechanical
20 impaction and/or electrostatic attraction. Any suitable means may be
employed for this purpose. Typical means for this purpose include combining
the carrier core material and the powdered particles mixture by caseade roll-
milling or tumbling, mulling, shaking, electrostatic powder cloud spraying,
employing a fluidized bed, electrostatic disc processing, and an electrostatic
25 curtain. Following application of the coating material powder particles to the
carrier core material, the mixture of carrier material and powdered particles
is heated to permit flow-out of the coating material powder parffcles over the
surface of the carrier core material. After fusion of the eoating particles to
the carrier core particles, the coated carrier particles are cooled and
30 classified to ths desired particle size. The resultant coated carrier particles
may have a fused coating over between about 15 percent and up to about 85
percent of their surface area. As will be appreciated~ the concentration of
coating material powder particles as well as the conditions of the heating step
may be selected as to form a continuous film of the coating material on the
35 surface of the carrier core material or leave selected areas of it uncoated.
Where selected areas of the carrier core material remain uncoated or e~posed,
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the carrier material will possess more strongly electrically conductive
properties when the core material comprises a metal. Thus, when such
partially coated carrier materials are provided, these earrier materials may
possess both electically insulating and electtricaIly conductive properties. Due5 to the electrically conductive properties of these carrier materials, the carrier
materials provide desirably high triboelectric charging values when mixed with
finely-divided toner particles.
Further, the dry, powdered resin-conductive material compositions
and coating technique of this invention have been found to be especially
10 effective in coating porous carrier cores to obtain coated carrier particles
capable of generating high and useful triboelectric charging values to finely-
divided toner particles and carrier particles and which possess significantly
increased resistivities. In addition, when carrier particles are prepared by thepowder coating technique of this invention, the majority of the coating
15 material particles are fused to the carrier surface and thereby reduce the
number of potential toner impaction sites on the carrier material.
Any suitable solid material having an average particle diameter of
between about 30 microns and about 1,000 microns may be employed as the
carrier core in this invention. However, it is preferred that the carrier core
20 material be selected so that the coated eore material acquire a charge havinga polarity opposite to that of the toner particles when brought into close
contact therewith so that the toner particles adhere to and surround the
carrier particles. In employing the carrier particles of this invention, it is also
preferred that the carrier particles be selected so that the toner particles
25 acquire a positive charge and the carrier particles acquire a negative
triboelectric charge. Thus, by proper selection of the developer materials in
accordance with their triboelectric properties, the polarites of their charge
when mixed are such that the electroscopic toner particles adhere to the
surface of the carrier particles and also adhere to that portion of the
30 electrostatic image-bearing surface having a greater attraction for the toner particles than the carrier particles.
In accordance with this invention, it is preferred that the carrier
core material comprise low density, porous, magnetic or magnetically-
attraetable metal particles having a gritty, oxidi2ed surface and a high surface35 area, i.e, a surface area which is at least about 200 cm2/gram and up to about
1300 cm gram of carrier material. Typical satisfactory carrier core materials
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include iron, steel, ferrite, magnetite, nickel and mixtures thereof. For
ultimate use in an electrostatographic magnetic brush development system, i~
is preferred that the carrier core materials have an average particle size of
between about 30 microns and about 250 microns. Excellent results have been
obtained when the carrier core materials comprise porous, sponge iron or steel
grit. The carrier core materials are generally produced by gas or water
atomiæation processes or by reduction of suitable sized ore to yield sponge
powder particles. The powders produced have a gritty surface, are porous, and
have high surface areas. By comparison, conventional carrier core materials
usually have a high density and smooth surface characteristics.
~ny suitable thermoplastic insulating resinous material which can
be rendered in powdered form may be employed in this invention. Typical
insulating coating materials include vinyl chloride-vinyl acetate copolymers,
styrene-acrylate-organosilicon terpolymers, natural resins such as caoutchouc,
lS carnauba, colophony, copal, dammar, jalap, storax; thermoplastic resins
including the polyolefins such as chlorinated polyethylene, chlorosulfonated
polyethylene, and copolymers and mixtures thereof; polyvinyls and polyvinyli-
denes such as polymethyl-styrene, polymethyl methacrylate, polyacrylonitrile,
polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride,
2û polyvinyl pyridine, polyvinyl carbazole, polyvinyl ethers, and polyvinyl ketones;
fluorocarbons such as polytetrafluoroethylene, polyvinyl fluoride, polyvinyli-
dene fluoride; and polychlorotrifluoroethylene; polyamides such as polycapro-
lactam and polyhexamethylene adipamide; pol~esters such as polyethylene
terephthalate; polyurethanes; polysulfides, thermosetting resins including
phenolic resins such as phenol-formaldehyde, phenol-Iurfural and resorcinol
formaldehyde; amino resins such as urea-formaldehyde and melamine-formal-
dehyde; polyester resins; and the like. Many of the foregoing and other typical
carrier eoating materials are described by L.E. WaLcup in U.S. Patent ~o.
2,618,551; B.B. Jacknow et al in U.S. Patent NQ. 3,526,433; and R.J. Hagenbach
et al in U.S. Patent Nos. 3,533,835 and 3,658,500. The preferred powdered
coating materials of this invention are selected from fluorinated ethylene,
fluorinated propylene and eopolymers, mixtures, combinations or derivatives
thereof such as fluorinated ethylene-propylene commercialIy available from
E.I. l~upont Co., Wilmington, Delaware, under the tradename FEP; trichloro-
fluoroethylene, perfluoroa1~oxy tetrafluoroethylene, polyvinylidene fluoride
and the ~inc and sodium salts of ionomer resins such as those containing
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carboxyl groups which are ionically bonded by partial neutralization with
strong bases such as sodium hydroxide and zinc hydroxide to create ionic
crosslinks in the intermolecular structure thereof and the like. Other
preferred powdered coating materials are polyethylene, polypropylene, styrene
5 and styrene copolymers or terpolymers, epoxy resins, polycarbonates, polysul-
fones, polyphenylene oxide, silicones, vinyI chloride and vinyl chloride
copolymers, halogenated resins including homopolymers, copolymers, and
terpolymers thereof. For use of the coated carrier particles in electrostato-
graphic development systems employing organic photoreceptors, it is preferred
10 that the resinous coating material be of the type capable of providing negative
triboelectric charging values to the carrier particles wherein the toner
particles obtain a positive triboelectric charge for attraction of the toner
particles to a negatively charged photoconductive surface.
Any suitable organic or inorganic electrically conductive material
15 may be employed in this invention. Typical electrically conductive materials
include metals, metal oxides, sulfides, halides, carbon, graphite, phthalo-
cyanines, charge transfer complexes, quaternary ammonium compounds, and
other conductive materials such as those described in U.S~ Patent No.
3,533,835. ~ny suitable concentration of conductive material in the carrier
20 coating may be employed. Typically, a loading of between about 3% to about
75% by weight, based on the weight of the carrier coating composition, i.e. the
powdered particles, provides adequate electrical conductivity to the carrier
particles. Coating compositions having a volume resistivity of less than about
101~ ohm-cm at 23 C are considered conductive. Some of the factors
25 affecting the quantity of conductive material to be employed in the coating
compositions include: the separation in the triboelectric series between the
toner particles and the carrier material, the average diameter of the carrier
particle; and the conductivity of the conductive material.
Any suitable inely-divided toner material may be employed with
30 the carrier materials of this invention. Typical toner materials include, forexample, gum copal, gum sandarac, rosin, asphaltum, phenol-formaldehyde
resins, rosin-modified phenol-formaldehyde resins, methacrylate resins,
polystyrene resins~ polystyrene-butadiene resins, polyester resins, polyethyleneresins, epoxy resins and copolymers and mixtures thereof. The particular type
35 of toner material to be used depends to some extent upon the separation of the
toner particles from the coated carrier particles in the triboelectric series.
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g
Patents describing typical electroscopic toner compositions include U.S.
2,659,670; 3,079,342; Reissue 25,136 and 2,788,288. Generally, the toner
materials have an average particle diameter of between about 5 and 15
microns. Preferred toner resins include those containing a high content of
5 styrene because they generate high triboelectric charging values and a greater degree of image definition is achieved when employed with the carrier
materials of this invention. Generally speaking, satisfactory results are
obtained when about 1 part by weight toner is used with about 10 to 200 parts
by weight of conductive powder coated earrier material.
Any suitable pigment or dye may be employed as the colorant for
the toner particles. Toner colorants are well known and include, for example,
carbon black, nigrosine dye, aniline blue, Calco Oil Blue, chrome yellow,
ultramarine blue, duPont Oil Red, Quinoline Yellow, methylene blue chloride,
phthalocyanine blue, Malachite Green Oxalate, lamp black, iron oxide, Rose
15 Bengal and mixtures thereof. The pigment and/or dye should be present in the
toner in a quantity sufficient to render it highly colored so that it will form a
clearly visible image on a recording member. Thus, for example, where
conventional xerographic copies of typed documents are desired, the toner may~
comprise a black pigment such as carbon black or a black dye such as Amaplast''
20 Black dye, available from National Aniline Products, Inc.. Preferably, the
pigment is employed in an amount from about 3 percent to about 20 percent by
weight, based on the total weight of the colored toner. If the toner colorant
employed is a dye, substantially smaller quantities of colorant may be used.
The developer compositions of the instant invention may be
25 employed to develop electrostatic latent images on any suitable electrostaticlatent image-bearing surface including conventional photoconductive surfaces.
Well known photoconductive materials include vitreous selenium, organic or
inorganic photoconductors embedded in a non-photoconductive matrix, organic
or inorganic photoconductors embedded in a photoconductive matrix, or the
30 like. Representative patents in which photoconductive materials are disclosedinclude U.S. Patent NO. 2,803,542 to Ullrich; U.S. Patent No. 2,970,906 to
Bixby; U.S. Patent No. 3,121,006 to Middleton; U.S. Patent No. 3,121,û07 to
Middleton; and U.S. Patent No. 3,151,982 to Corrsin.
In the following e~amples, the relative triboelectric values gene-
35 rated by contact of carrier particles with toner particles is measured by meansof a Faraday Cage. The device comprises a steel cylinder having a diameter of
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about one inch and a length of about one inch. A 400-mesh screen is positioned
at each end of the cylinder. The cylinder is weighed, charged with about 0.5
gram mixture OI carrier and toner particles and connected to ground through a
capacitor and an electrometer connected in parallel. Dry compressed air is
then blown through the steel cylinder to drive all the toner from the carrier.
The charge on the capacitor is then read on the electrometer. Next, the
chamber is reweighed to determine the weight loss. The resulting data is used
to calculate the toner concentration and the charge in microcoulombs per
gram of toner. Since the triboelectric measurements are relative, the
measurements should, for comparative purposes, be conducted under substan-
tially identical conditions.
Description of Preferred Embodiments
The following examples further define, describe and compare
methods of preparing the carrier materials of the present invention and of
utilizing them to develop electrostatic latent images. Parts and percentages
are by weight unless otherwise indicated.
Example I
A control carrier material is prepared comprising about 97 parts of
sponge iron carrier cores (available from Hoeganaes Corporation, Riverton,
New Jersey, under the tradona~c~ANCOR EH 80/150) having an average
particle diameter of about 150 microns. A coating composition comprising
about 10 percent solids of polyvinyl chloride and trifluorochloroethylene
prepared from a material commercially available as FPC 461 from Firestone
Plastics Company, Pottstown, PA., dissolved in methyl ethyl ketone is applied
to the carrier cores as to provide them with a coating weight of about 3
percent. The coating composition is applied to the carrier cores via solution
coating employing a vibratub (available from ~ibraslide, Inc., Binghamton, New
York).
About 97 parts by weight of the coated carrier particles are mixed
with about 3 parts by weight of toner particles having an average diameter of
about 12 microns. The composition of the toner particIes comprises about 87
parts of a 65/35 styrene-n~butyl methacrylate copolymer, about 10 parts of
carbon black and about 3 parts of nigrosine SSB. The mixture of carrier
particles and toner particles is employed in a magnetic brush development
testing fixture e~uipped with a photoreceptor charged to a negative polarity.
The testing fixture is set as to provide a solid area density of about 1.3 to
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developed electrostatic latent images. It is found that this developer mixture
is unsatisfactory in that the trib~electric charge generated on the toner
material is about 14 microcoulombs per gram of toner, and the image
background density is about O.û4 which is considerably above the acceptable
level of 0.01. The electrical resistivity of the developer is about 3.8 x 10"
ohm-cms.
Example II
A carrier material is prepared comprising about 99 parts of sponge
iron carrier cores as in Example I. The carrier eores are mixed for about 10
minutes with about 1.0 part of powdered polyvinyl chloride and trifluorochl~ro-
ethylene prepared from a material commercially available as FPC 461 from
Firestone Plastics Company, Pottstown, Pa.. The powdered coating material is
attrited to an average particle diameter of less than about 44 microns. The
dry mixture is placed in a muffle furnace and heated to a maximum
15 temperature of 350F and cooled to room temperature over a total process
time of about 75 minutes.
About 97 parts by weight of the coated carrier particles is mixed
with about 3 parts by weight of toner particles as in Example I. The mixture of
carrier and toner particles is employed as in Example I to develop an
20 electrostati~ latent image. It is found that this developer mixture is
unsatisfactory in that the triboelectric charge generated on the toner material
is about 16 micro~ouIombs per gram of toner, the developed image background
density is about 0.03, and the image quality is unacceptable. The electrical
resistivity of the developer is about 1.5 x 10" ohm-cms.
Example III
A carrier material is prepared in the following manner~ About 50
P grams of polyvinylidene fluoride and tetrafluoroethylene copolymer commer-cially available as Kynar~7201 from Pennwalt Corporation, King of Prussia, Pa.
is placed in a heating vessel and brought to a fluid state. About 3 grams of
30 carbon black commercially available as Ketjenblack~- EC from Armak
Corporation, Chicago, Illinois is added to the fluid resin composition and
stirred therewith until a substantially uniform mixture is obtained. ~he
mixture is then cooled and allowed to solidify into a solid mass. The solid massis then converted to dry, powdered particles having an average particle size of
35 less than about 44 microns by cryogenic grinding using liquid nitrogen to cool
the pigmented polymer composition and steel shot having a diameter of about
1/8 inch as a grinding aid.
f~ e ~ 4
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About 9 9 parts of the sponge iron carrier co~es described in
Example I is mixed for about 10 minutes with about 1 part of the aforedescribed
dry, powdered particles whereby the powdere~ coating composition electro-
statically adheres to the carrier cores. The dry mixture is placed in a muffle
5 furnace and heated to a maximum temperature of about 260F and then cooled
to room temperature over a total process time of about 15 minutes.
About 97 parts by weight of the coated carrier particles is mixed
with about 3 parts by weight of toner particles as in Example I. The mixture
of carrier and toner particles is employed as in Example I to develop an
10 electrostatic latent image. It is found that this developer mixture is
satisfactory in that the triboelectric charge generated on the toner material ishigher than that obtained with the developer mixture of Example 11, being
about 25 microcoulombs per gram of toner material. The developed image
background density is only about .008, and the image quality is excellent. The
15 electrical resistivity of the developer is about 7.8 x 10 ohm-cms.
Example IV
A carrier material is prepared in the following manner. About 50
grams of polyvinylidene fluoride commercially available as Kynar 461 from
20 Pennwalt Corporation, King of Prussia, Pa. is placed in a heating vessel and
brought to a fluid state. About 5 grams of the carbon black of Example III is
added to the fluid resin composition and stirred therewith until a substantiallyuniform mixture is obtained. The mixture is then cooled and allowed to
solidify into a solid mass. The solid mass is then converted to dry, powdered
25 particles having an average particle si~e of less than about 44 microns by
cryogenic grinding as in Example III.
About 98.5 parts of the sponge iron carrier cores described in
Example I is mixed for about 10 minutes with about 1.5 parts of the
aforedescribed dry, powdered particles whereby the powdered coating com-
30 position electrostatically adheres to the carrier cores. The dry mixture isplaced in a muffle furnace and heated to a maximum temperature of about
550 F and then cooled to room temperature over a total process time of about
90 minutes.
About 9~ parts by weight of the coated carrier particles is mixed
35 with about 3 parts by weight of toner particles as in Example I. The mixture
of carrier and toner particles is employed as in Example I to develop an
.
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electrostatic latent image. It is found that this developer mixture is
satisfactory in that the triboelectric charge generated on the toner material ishigher than that obtained with the developer mixture of Example II, being
about 28 microcoulombs per gram of toner material. The developed image
5 background is only abou-t .006, and the image quality is excellent. The
electrical resistivity of the developer is about 5.4 x 109 ohm-cms.
ExamDle V
A carrier material is prepared in the following manner. About 10
grams of polyvinylidene fluoride commercially available as Kynar 301 from
10 Pennwalt Corporation, King of Prussia, Pa. is placed in a polyethylene jar
containing about 2 grams of carbon black and about 250 ml of propylene
carbonate solvent. The mixture is placed on a Red Devil paint shaker to
disperse the pigment. Steel shot, 1/8" diameter, is present in the mixture as a
milling aid. After about 10 minutes of mixing, the mixture is sieved to remove
15 the steel shot and the dispersion is put into a beaker and heated with stirring
to about 85C to dissolve the resin. The temperature is maintained for about
15 minutes after which the dispersion is added to 500 ml of methanol with
agitation at the rate of about 50 ml/min.. Fine sized polyvinylidene fluoride
coated carbon black particles are obtained of about 3 to 10 microns after
20 filtration and washing with water.
About 98.5 parts of the sponge iron carrier cores described in
Example I is mixed for about 10 minutes with about 1.5 parts of the
aforedescribed dry, powdered particles whereby the powdered coating com-
position electrostatically adheres to the carrier cores. The dry mixture is
25 placed in a muffle furnace and heated to a maximum temperature of about
530 F and then cooled to room temperature over a total process time of about
60 minutes.
About 97 parts by weight of the coated carrier particles is mixed
with about 3 parts by weight of toner particles as in Example I. The mixture
3 0 of carrier and toner particles is employed as in Example I to develop an
electrostatic latent image. It is found that this developer mixture is
satisfactory in that the triboelectric charge generated on the toner material ishigher than that obtained with the developer mixture of Example 11, being
about 2~ microcoulombs per gram of toner material. The developed image
35 background density is only about .007, and the image quality is excellent. The
electrical resistivity of the developer is about 1.3 x 109 ohm-cms.
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Example VI
A carrier material is prepared in the following manner. About 50
grams of polyvinyl chloride and trifluorochloroethylene commercially available
as FPC 461 from Firestone Plastics Company, Pottstown, Pa. is dissolved in
5 about 300 mls of methyl ethyl ketone. About 4 grams of carbon black as in
Example III is added to the fluid resin cornposition and stirred therewith until a
substantially uniform mixture is obtained. The mixture is then spray-dried to
powdered particles having an average particle size of about 5 to 8 microns.
About 98.0 parts of the sponge iron carrier cores described in
lO Example I are mixed for about lO minutes with about 2.0 parts of the
aforedescribed dry, powdered particles whereby the powdered coating com-
position electrostatically adheres to the carrier cores. The dry mixture is
placed in a muffle furnace and heated to a rnaximum temperature of about
350 F and then cooled to room temperature over a total process time of about
lS 60 minutes.
About 97 parts by weight of the coated carrier particles is mixed
with about 3 parts by weight of toner particles as in Example I. The mixture
of carrier and toner particles is employed as in Example I to develop an
electrostatic latent image. It is found that this developer mixture is
20 satisfactory in that the triboelectric charge generated on the toner material is
higher than that obtained with the developer mixture of Example II, being
about l9 microeoulombs per gram of toner material. The developed image
background density is only about .007, and the image quality is excellent. The
electrical resistivity of the developer is about 8.7 x lO9 ohm-cms.
Example VII
A carrier material is prepared in the following manner. About 50
grams of polyvinylidene fluoride and tetrafluoroethylene c~polymer commer-
cially available as Kynar 7201 from Pennwalt Corporation, King of Prussia, Pa.
30 is placed in a heating vessel and brought to a fluid state. About 3 grams of
phthalocyanine is added to the fluid resin composition and stirred therewith
until a substantially uniform mixture is obtained. The mixture is then cooled
and allowed to solidify into a solid mass. The solid mass is then converted to
dry, powdered particles having an average particle size of less than about 44
35 microns by cryogenic grinding as in Example III.
.
:114Q7~4
-15-
About 99 parts of the sponge iron carrier cores described inExample I is mixed for about 1~ minutes with about 1 part of the aforedescribed
dry, powdered particles whereby the powdered coating composition electro-
statically adheres to the carrier cores. The dry mixture is placed in a muffle
5 furnace and heated to a maximum temperature of about 260~ F and then cooled
to room temperature over a total process time of about 15 minutes.
About 97 parts by weight of the coated carrier particles is mixed
with about 3 parts by weight of toner particles as in Example I. The mixture
of carrier and toner particles is employed as in Example I to develop an
10 electrostatic latent image. It is found that this developer mixture is
satisfactory in that the triboelectric charge generated on the toner material ishigher than that obtained with the developer mixture of Example II, being
about 23 microcoulombs per gram of toner material. The developed image
background density is only about .006, and the image quality is excellent. The
electrical resistivity of the developer is about 9.2 x 109 ohm-cms.
Example VIII
A carrier material is prepared in the following manner. About 50
grams of polyvinylidene fluoride commercially available as Kynar 201 from
Pennwalt Corporation, King of Prussia, Pa. is placed in a heating vessel and
2û brought to a fluid state. About 10 grams of aluminum commercially availableas M~796 from Alcan Metal Powders, Inc., of Elizabeth, New Jersey having
an a~erage particle size of less than about 45 microns is added to the fluid
resin composition and stirred therewith until a substantially uniform mixture isobtained. The mixture is then cooled and allowed to solidify into a solid mass.
The solid mass is then converted to dry, powdered particles having an average
particle size of less than about 50 microns by cryogenic grinding as in Example
III.
About 98 parts of the sponge iron carrier cores described in
Example I is mixed for about 10 minutes with about 2 parts of the
aforedescribed dry, powdered particles whereby the powdered coating com-
position electrostatically adheres to the carrier cores. The dry mixture is
placed in a muffle furnace and heated to a maximum temperature of about
45û F and then cooled to room temperature over a total process time of about
70 minutes.
About 97 parts by weight of the coated carrier particles is mixed
with about 3 parts by weight of toner particles as in Example 1. The mixture
7~3~
-16--
of carrier and toner particles is employed as in Example I to develop an
electrostatic latent image. It is found that this developer mixture is
satisfactory in that the triboelectric charge generated on the toner material ishigher than that obtained with the developer mixture of Example II, being
about 32 microcoulombs per gram of toner material. The developed image
background density is satisfactory and the image quality is excellent.
Example IX
A carrier material is prepared in the following manner. About 50
grams of polyvinylidene fluoride commercially available as Kynar 201 from
Pennwalt Corporation, King of Prussia, Pa. is placed in a heating vessel and
brought to a fluid state. About 10 grams of carbon black commercially
A available as Yulcan~XC-72 ~om Cabot Corporation, Boston, Mass. is added to
the fluid resin composition and stirred therewith until a substantially uniform
n~.ixture is obtained. The mixture is then cooled and allowed to solidify into asolid mass. The solid mass is then converted to dry, powder0d particles having
an average particle size of less than about 44 microns by cryogenic grinding as
in Example III.
About 98 parts of the sponge iron carrier cores described in
Example I is mixed for about lû minutes with about 2 parts of the
aforedescribed dry, powdered particles whereby the powdered coating com-
position electrostatically adheres to the carrier cores. The dry mixture is
placed in a muffle furnace and heated to a maximum temperature of about
450 ~ and then cooled to room temperature over a total process time of about
70 minutes.
About 9q parts by weight of the coated carrier particles is mixed
with about 3 parts by weight of toner particles as in Example I. The mixture
of carrier and toner particles is employed as in Example I to develop an
electrostatic latent image. It is found that this developer mixture is
satisfactory in that the triboelectric charge generated on the toner material ishigher than that obtained with the developer mixture of Example II, being
about 16 microcoulombs per gram of toner material. The developed image
background density is satisfactory and the image quality is excellent.
Example X
A carrier material is prepared in the following manner. About 50
grams of vinyl chloride/vinyl acetate/maleic acid terpolymer commercially
available as ~inylite~YNS from Union Carbide Corporation, New York, New
7~r~ A~-~
~4~7159~
-17
York is placed in a heating vessel and brought to a fluid state. About 8 grams
of earbon black as in Example IX is added to the fluid resin composition and
stirred therewith until a substantially uniform mixture is obtained. The
mixture is then cooled and allowed to solidify into a solid mass. The solid mass5 is then converted to dry, powdered particles having an average particle size of
less than about 44 microns by cryogenic grinding as in Example III.
About 97.5 parts of the sponge iron carrier cores described in
Example I is mixed for about ;0 minutes with about 2.5 parts of the
aforedescribed dry, powdered particles whereby the powdered coating com-
10 position electrostatically adheres to the carrier cores. The dry mixture isplaced in a muffle fu~nace and heated to a maximum temperature of about
275 F and then cooled to room temperature over a total process tirrle of about
30 minutes.
About 97 parts by weight of the coated carrier particles is mixed
15 with about 3 parts by weight of toner particles as in Example I. The mixture
of carrier and toner particles is employed as in Example I to develop an
electrostatic latent image. It is found that this developer mixture is
satisfactory in that the triboelectric charge generated on the toner material ishigher than that obtained with the developer mixture of Example II, being
20 about 18 microcoulombs per gram of toner material. The developed image
background density is satisfactory and the image quality is excellent. The
electrical resistivity of the developer is about 7.6 x 109 ohm-cms.
Example XI
A carrier material is prepared in the following manner. About S0
~5 grams of polyvinyl chloride and trifluorochloroethylene commercially available
as FPC 461 from ~irestone Plastics Company, Pottstown, Pa. is dissolved in
about 300 n~ls of methyl ethyl ketone. About 4 grams of cetyl pyridinium
chloride available from Hexcel Corporation, ~odi, New Jersey is added to the
fluid resin composition and stirred therewith until a substantially uniform
30 mixture is obtained. The mixture is then spray-dried to powdered particles
having an average particle size of about 5 to 8 microns.
About 98 parts of the sponge iron carrier cores described in
Example I is mixed for abou~ 10 minutes with about 2 parts of the
aforedescribed dry, powdered particles whereby the powdered coating com-
35 position electrostatically adheres to the carrier cores. The dry mixture isplaced in a muffle furnace and heated to a maximum temperature of about
~4Q~34
--18--
275 F and then cooled to room temperature over a total process time of about
30 minutes.
About 97 parts by weight of the coated carrier particles is mixed
with about 3 parts by weight of toner particles as in Example I. The mixture
5 of carrier and toner particles is employed as in Example I to develop an
electrostatic latent image. It is found that this developer mixture is
satisfactory in that the triboelectric charge generated on the toner material ishigher than that obtained with the developer mixture of 13xample II, being
about 18 microcoulombs per gram of toner material. The developed image
10 background density is satisfactory and the image quality is excellent.
Although specific materials and conditions are set forth in the
foregoing examples, these are merely intended as illustrations of the present
invention. Various other suitable thermoplastic toner resin components,
additives, colorants, and development processes such as those listed above may
15 be substituted for those in the examples with similar results. Other materials
may also be added to the toner or carrier to sensitize, synergize or otherwise
improve the fusing properties or other desirable properties of the system.
Other modifications of the present invention will occur to those
skilled in the art upon a reading of the present disclosure. These are intended
20 to be included within the scope of this invention.
