CA1117803A - Carrier particle with outer layer containing vinyl polymer and tetroheptyl ammonium bromide - Google Patents
Carrier particle with outer layer containing vinyl polymer and tetroheptyl ammonium bromideInfo
- Publication number
- CA1117803A CA1117803A CA000299407A CA299407A CA1117803A CA 1117803 A CA1117803 A CA 1117803A CA 000299407 A CA000299407 A CA 000299407A CA 299407 A CA299407 A CA 299407A CA 1117803 A CA1117803 A CA 1117803A
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- Prior art keywords
- carrier
- carrier particle
- weight
- surface active
- percent
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G9/00—Developers
- G03G9/08—Developers with toner particles
- G03G9/10—Developers with toner particles characterised by carrier particles
- G03G9/113—Developers with toner particles characterised by carrier particles having coatings applied thereto
- G03G9/1138—Non-macromolecular organic components of coatings
Abstract
Developers for Humidity-Insensitive Development ABSTRACT OF THE DISCLOSURE
Carrier materials for development of electrostatic latent images comprising an outer surface or outer coating of an insulating material containing a surface active additive.
When mixed with finely-divided toner particles, the carrier materials generate the same triboelectric charge at low and high relative humidity conditions thereby avoiding humidity-induced copy defects in electrostatographic processes.
Carrier materials for development of electrostatic latent images comprising an outer surface or outer coating of an insulating material containing a surface active additive.
When mixed with finely-divided toner particles, the carrier materials generate the same triboelectric charge at low and high relative humidity conditions thereby avoiding humidity-induced copy defects in electrostatographic processes.
Description
BACKGROUND OF T~E INVENTION
This invention re}ates, in general, to electrostato- -graphic imaging systems, and, in particular, to improved developer materials and theix uses.
The formation and development of images on the surface of photoconductive materials by electrostatic means is well known. The basic electrophotographic process, as taught by C. F. Carlson in U.S. Patent 2,297,691, involves placing a uni~orm electrostatic charge on a photoconductive insulating layer, exposins the layer to a light and shadow image to dissipate -the charge on the areas of the layer exposed to the light and developing the resulting electrostatic latent image by depositing on the image a finely-divided electroscopic material referred to in the art as "toner".
~he toner will normally be attracted to those areas of the layer which retain a charge thereby forming a toner image corresponding to the electrostatic latent image. This powder image may then be transferred to a support surface such as paper. The transferred image may subsequently be permanently affixed to the support surface as by heat. Instead of latent image formation by uniformly charging the photoconductive layer and then exposing the layer to a light and shadow image, one may form the latent image by directly charging the layer in image configuration. The powder image may be fixed to the photoconductive layer if elimination of the powder image transfer step is desired. Other suitabla fixing means such as solvent or overcoa~ing treatment may be substituted for the foregoing heat fixing step.
Many methods are known for applying the electroscopic particles to the electrostatic latent image to be developed.
This invention re}ates, in general, to electrostato- -graphic imaging systems, and, in particular, to improved developer materials and theix uses.
The formation and development of images on the surface of photoconductive materials by electrostatic means is well known. The basic electrophotographic process, as taught by C. F. Carlson in U.S. Patent 2,297,691, involves placing a uni~orm electrostatic charge on a photoconductive insulating layer, exposins the layer to a light and shadow image to dissipate -the charge on the areas of the layer exposed to the light and developing the resulting electrostatic latent image by depositing on the image a finely-divided electroscopic material referred to in the art as "toner".
~he toner will normally be attracted to those areas of the layer which retain a charge thereby forming a toner image corresponding to the electrostatic latent image. This powder image may then be transferred to a support surface such as paper. The transferred image may subsequently be permanently affixed to the support surface as by heat. Instead of latent image formation by uniformly charging the photoconductive layer and then exposing the layer to a light and shadow image, one may form the latent image by directly charging the layer in image configuration. The powder image may be fixed to the photoconductive layer if elimination of the powder image transfer step is desired. Other suitabla fixing means such as solvent or overcoa~ing treatment may be substituted for the foregoing heat fixing step.
Many methods are known for applying the electroscopic particles to the electrostatic latent image to be developed.
-2-~k .
One development method, as disclosed by E.~. Wlse in U.S~
Patent 2,618,552 is well known as "cascade" development. In this method, a developer material comprising relatively large carrier particles having finely-divided toner particles electro-statically clinging to the surface of the carrier particles is conveyed to and rolled or cascadad across the electrostatic latent image bearing surface. The composition of the toner particles is so chosen as to have a triboelectric polarity opposite that of the carrier particles. As the mixture cascades or rolls across the image bearing surface, khe toner particles are electrostatically deposited and secured to the charged portion of the latent image and are not deposited on the uncharged or background portions of the image. Most of the toner particles accidentally deposited in the background are removed by the rolling carrier, due apparently, to the greater electrostatic attraction between the toner and the carrier than between the toner and the discharged background. The carrier particles and unused toner particles are then recycled. The technique is extremely good for the development of line copy images.
The cascade development process is the most widely used -- commercial electrostatographic development technique. A general purpose office copying machine incorporating this technique is described in U~S. Patent 3,099,943.
Another technique for developing electrostatic latent images is the "magnetic brush" process as disclosed, for example, in U.S. Patent 2,874,063. In this method, a developer material containing toner and magnetic carrier particles is carried by a magnet. The magnetic field of the magnet causes alignment of the magnetic carriers in a brush-like configuration. This "magnetic brush" is engaged with an electrostatic latent image bearing surface and the toner particles are drawn from the brush to the electrostatic latent image b~ electrostatic attraction.
Another technique for developing electrostatic latent images is the "touchdown" process as disclosed, for example, in U.S. Patents 2,~95,847 and 3,245,823 to Mayo.
In this method, a developer material is carried to a latent image bearing surface by a support layer such as a web or sheet and is deposited thereon in conformity with said image.
While ordinarily capable of producing good quality images, conventional developing materials suffer serious deficiencies in certain areas. The developing materials must flow freely to facilitate accurate metering and even distribution during the development and developer recycling phases of the electro-statographic process. Some developer materials, though possessing desirable properties such as proper triboelectric character-istics, are unsuitable because they tend to cake, bridge and agglomerate during handling and storate. The tendency o~
carrier particles to adhere to imaging surfaces is aggravated when the carrier surfaces are rough and irregular. The coatings of most carrier particles deteriorate rapidly when employed in continuous processes which require the recycling of carrier particles by bucket conveyors partially su~merged in the developer supply such as disclosed in U~S~ Patent
One development method, as disclosed by E.~. Wlse in U.S~
Patent 2,618,552 is well known as "cascade" development. In this method, a developer material comprising relatively large carrier particles having finely-divided toner particles electro-statically clinging to the surface of the carrier particles is conveyed to and rolled or cascadad across the electrostatic latent image bearing surface. The composition of the toner particles is so chosen as to have a triboelectric polarity opposite that of the carrier particles. As the mixture cascades or rolls across the image bearing surface, khe toner particles are electrostatically deposited and secured to the charged portion of the latent image and are not deposited on the uncharged or background portions of the image. Most of the toner particles accidentally deposited in the background are removed by the rolling carrier, due apparently, to the greater electrostatic attraction between the toner and the carrier than between the toner and the discharged background. The carrier particles and unused toner particles are then recycled. The technique is extremely good for the development of line copy images.
The cascade development process is the most widely used -- commercial electrostatographic development technique. A general purpose office copying machine incorporating this technique is described in U~S. Patent 3,099,943.
Another technique for developing electrostatic latent images is the "magnetic brush" process as disclosed, for example, in U.S. Patent 2,874,063. In this method, a developer material containing toner and magnetic carrier particles is carried by a magnet. The magnetic field of the magnet causes alignment of the magnetic carriers in a brush-like configuration. This "magnetic brush" is engaged with an electrostatic latent image bearing surface and the toner particles are drawn from the brush to the electrostatic latent image b~ electrostatic attraction.
Another technique for developing electrostatic latent images is the "touchdown" process as disclosed, for example, in U.S. Patents 2,~95,847 and 3,245,823 to Mayo.
In this method, a developer material is carried to a latent image bearing surface by a support layer such as a web or sheet and is deposited thereon in conformity with said image.
While ordinarily capable of producing good quality images, conventional developing materials suffer serious deficiencies in certain areas. The developing materials must flow freely to facilitate accurate metering and even distribution during the development and developer recycling phases of the electro-statographic process. Some developer materials, though possessing desirable properties such as proper triboelectric character-istics, are unsuitable because they tend to cake, bridge and agglomerate during handling and storate. The tendency o~
carrier particles to adhere to imaging surfaces is aggravated when the carrier surfaces are rough and irregular. The coatings of most carrier particles deteriorate rapidly when employed in continuous processes which require the recycling of carrier particles by bucket conveyors partially su~merged in the developer supply such as disclosed in U~S~ Patent
3,099,943. Print deletion and poor print quality occur when carrier having damaged coatings are not replaced. Fines and grit formed from carrier disintegration tend to drift and form unwanted deposits on critical machine parts~
Many carrier coatings having high compressive and tensile strength either do not adhere well to the carrier core or do not possess the desired triboelectric character- `
istics. The triboelectric and flow characteristics of many t3 carriers are adversely affected when relative humidity is high. For example, the triboelectric values of some carrier coatings fluctuate with changes in relative humidity and are not desirable for employment in xerographic systems, particularly in automatic machines which require carriers having stable and predictable triboelectric values. Another factor affecting the stability of carrier triboelectric properties i5 the susceptibility of carrier coatings to "toner impaction". When carrier particles are employed in automatic machines and recycled through many cycles, the many collisions which occur between the carrier particles and other surfaces in the machine cause the toner particles carried on the surface of the carrier particles to be welded or otherwise forced into ~he carrier coatings. The gradual accumulation of permanently attached toner material on- the surface of the carrier particles causes a change in the triboelectric value of the carrier particles and directly contributes to the degradation of copy quality by eventual destruction of the toner carrying capacity of the carrier. Thus, there is a continuing need for a better system for devel-oping latent electrostatic images.
It is, therefore, an object of an aspect of this invention to provide developing materials which overcome the above noted deficiencies.
It is an object of an aspect of this invention to provide carrier particles which possess improved electrostatographic properties for efficient and prolonged use in electrostatographic reproduction processes.
It is an object of an aspect of this invention to provide carrier particles having coatings which are more resistant to toner impaction.
It is an object of an aspect of this invention to provide developing materials which flow more freely.
It is an object of an aspect of this invention to provide carrier coatings havlng more stable tribo-electric values.
It is an object of an aspect of this invention to provide carrier particles which are less sensitive to changes in relative humidity conditions.
It is an object of an aspect of this invention to provide developer materials having greatly increased developer life.
It is an object of an aspect of this invention to provide developers having physical and chemical proper-ties superior to those of known developer materials.
An aspect of this invention is as follows:
A carrier particle for electrostatographic developer mixtures, said carrier particle comprising a core having an outer layer comprising an electrically insulating vinyl polymer and an effective amount of a surface active additive dissolved or dispersed in said polymer and capable of providing a desired magnitude of negative triboelectric charging potential to said carrier particle, said surface active additive consisting essentially of tetraheptylammonium bromide.
In accordance with this invention, it is believed that copy quality defects found in electrostatographic dev-elopment which are due to atmospheric conditions are humidity-induced. Thus, it has been found that a developer mixture which generates the same triboelectric charge at low and high ~ i~
11~7~3~3 relative humidity conditions will avoid humidity-induced copy defects in electrostatographic development processes.
Further, the triboelectric charge of carrier particles having an outer surface or outer coating of an insulating material may be controllably altered by incorporation therein of surface active additives such as ionic additives selected from quaternary ammonium salts. In addition to providing the aforementioned properties to the carrier compositions of this invention, the surface active additive also provides carrier compositions which have anti-stick or low surface energy properties thereby minimizing their filming by impaction of toner particles thereon.
It has been found that properties desired of carrier materials may be attained by coating carrier particles 1~ with an insulating polymer having dissolved or dispersed therein a surface active additive. That is, the surface active additive may be homogeneously dissolved or dispersed in the insulating polymer and the components employed as a carrier or applied as a coating to a carrier core. In preparation of the carrier composition of this invention, it is preferred that the resin component be melted followed by the addition of the surface active additive thereto and the mixture thoroughly mixed to yield a uniformly dissolved or dispersed composition of the additive in the resin body.
Although the actual mechani~m is not entirely clear, the relative position of a specific carrier material in the tribo-electric series is changed when the surface active additive is incorporated in at least the surface of the carrier substrate and the triboelectric charge generated on the carrier material is stable even at high relative humidity conditions.
The surface active additive employed in the carrier compositions of this invention may be selected from highly fluorinated materials~ Typical materials include fluorinated surfactants or "pentamers" commercially available under the m~ Monflor available from ICI America, Zonyl from E. I. duPont, and Fluorad from 3M. These materials contain anionic, cationic, or nonionic groups providing a wide range of surface active behavior. These surface active additives, by virtue of their low surface energy or the extent of their compatibility or association with the polymer matrix, will preferentially reside close to the polymer-air interface, so long as thermodynamic equilibrium is allowed to occur within the processing time period.
The surfa~e active additive is preferably selected from additives such as monomers and polymers containing ionic groups; for example, tetraheptylam~onium bromide, neutralized acrylic acid or vinyl pyridine containing copolymers, and silicones. However, the preferred surface active additive of this invention with respect to modification of the tribo-electric charge of the carrier material is tetraheptylammonium bromide because the additive will cause a styrene methyl methacrylate-vinyltriethoxysilane terpolymer coating material to triboelectrically charge more negatively relative to a vinyl-based toner composition. Without the surface active additive in the carrier composition, the -terpolymer-based carrier * ~r~
~0 -8--~17~
coating material charges strongly positively with the 9inyl-based toner material. The preferred surface active additive with respect to stabilization of the triboelectric charge generated on a carrier material at varying relative humidity 5 ~ conditions is Luxol Fast slue AR (C.I. Solvent slue 37, C.I.
No. 13390, available from E~I. duPont de Nemours & Co., Wilmington, Delaware).
In accordance with this invention, electrostatographic carrier compositions which generate less strongly positive tribo-electric charges are provided when the sur~ace active additives are present therein in an amount of from between about 0.5 and about 3 parts by weight based on the weight of the carrier composition. However, lt is preferred that the electrostato-graphic carrier compositions of this invention comprise from ; 15 between about 3 and about ~ parts by weight of the surface active additives based on the weight of the carrier composition because a greater effect on the triboelectric properties of the carrier material is provided, and owing to the sensitivity to moisture of polymer materials, the triboelectric properties of the carrier compositions are more stable under various relative humidity conditions. Optlmum results are generally obtained when the electrostatographic carrier compositions of this invention comprise from between about 6 and about 10 parts by weight of the surface active additives based on the weight of the carrier composition.
; 25 When the carrier compositions of this invention have an outer coating, any suitable coating thickness may be employed.
However, a coating having a thickness at least sufficient to form a continuous film is preferred because the carrier coating will then possess sufficient thickness to resist abrasion and prevent pinholes which adversely affect the triboelectric properties of the coated carrier particles. Generally, for cascade and magnetic brush development, the carrier coating may comprise from about 0.1 percent to about 2.0 percent by ~ ~rJ~
weight based on the weight of the coated carrier particles.
Preferably, the coating should comprise from about 0.2 per-cent to about 0.9 percent by weight based on the weight of the coated particle because maximum coating durability, toner S impaction resistance, and copy quality are achieved. If a partially polymerized linear or crosslinked prepolymer is to be used as the coating material, polymerization may be completed in situ on the surface of the carrier by further application of heat.
Factors affecting the quantity of surface ac~ive additive to be incorporated in at least the surface of carrier particles include: the separation in the triboelectric series between the toner particies and the carrier material;
- the concentration of the surface active additive at the sur-face of the carrier particles; and the average diameter of the carrier particle.
The surface active additive may be distributed only at the ~urface of a coated or uncoated carrier particle or ~ uniformly distributed throughout an uncoated carrier particle or throughout the external coating of a coated carrier particle.
When the surface active additive is dispersed throughout the carrier particle or carrier particle coating rather than only contiguous to the surface of the carrier particle, propor-tionally more surface active additive at the surface of the carrier particle. The additional amount of surface active additive necessary depends to a large extent on the surface area of the carrier particles, hence, upon the particle diameter selected. Obviously, as the quantity of surface active additive actually available at the surface of the carrier particle is reduced to a negligible amount, the tribo-electric properties of the carrier surface are substantially the same as a carrier which does not contain surface active additive. Obviously, with a given quantity of surface active additive based on the weight of the carrier, a greater volume of surface active additive is available at the surface of the carrier when the surface active additive is located only at the surface of the carrier particles than when the surface active additive is intLmately dispersed thxoughout each carrier particle.
In a preferred embodiment, the surface active -~ additive is incorporated into at least the outer surface of coated or uncoated carrier beads by bringing -the surface active additive into contact with the external surface of coated or uncoated beads.
Where the surface active additive is to be incor-~- porated into a carrier bead having a preformed soft outer surface which is capable of being subsequently hardened, the carrier bead or carrier bead coating should comprise a material such as a soft curable prepolymer resin, gelled plastisol or certain softened materials. The materials may comprise materials softened by heat or solvents. The solvent or heat softenable material may include natural resinæ, thermoplastic resins, and hard partially cured thermosetting resins. The soft curable prepolymers may comprise any suitable polymerized thermoplastic or thermosetting resins. Typical natural resins include: caoutchouc, colophony, copal, dammar, Dragon's Blood, jalap, storax, and the like. Typical thermoplastic resins include:
B~3 the polyolefins such as polyethylene, polypropylene, chlorinated polyethylene, and chlorosulfonated propylene, chlorinated polyethylene, and chlorosulfonated polyethylene, poly~inyls and polyvinylidenes such as polystyrene, polymethylstyrene, poly-methyl methacrylate, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ethers, and polyvinyl ketones;
fluorocarbons such as polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride; and polychlorotrifluoroethylene;
polyamides such as polycroproloctamo and polyhexamethylene adipamide; polyesters such as polyethylene terephthalate;
polyrethanes; polysulides; polycarbonates; and the li~e.
Typical thermosetting resins include: phenolic resins such as phenol-formaldehyde, phenol-furfural and resorcinol formaldehyde; amino resins such as urea-formaldehyde and melamineformaldehyde; polyester resins; epoxy resins; and the like.
Alternatively, the surface active additives of this invention may be dispersed, dissolved or suspended throughout a carrier bead or carrier bead coating mat~rial prior to bead or bead coating formation. The dispersion, solution, or suspension may be prepar~d by conventional techniques. It is to be understood that the material employed to form the matrix of the carrier bead or carrier bead coating may be in any suitable form such as a hot molt, a solution, an emulsion, a liquid monomer or a dispersion. When the ultimate product is to be a coated carrier bead, the carrier coating compositions with or without the surface active additive may be applied to a carrier core by any conventional method such as spraying, dipping, fiuidized bed coating, tumbling, brushing and the ~ ` ~
like. The coating compositions may be applied as a powder, a dispersion, solution, emulsion or hot melt. When applied as a solution, any suitable solvent may be employed. Solvents having relatively low boiling points are preferred because less energy and time is required to remove the solvent sub-sequent to application of the coating to the carrier core.
If desired, the coating may comprise resin monomers which are polymerized in situ on the surface of the bead cores or plastisols gelled in situ to a non-~lowable state on the sur-face of the bead cores. Any suitable coating thickness may be employed. However, the carrier coating should be sufficiently thick to resist flaking and chipping.
Any suitable well known coated or uncoated electro-~, statographic carrier bead material may be employed as the core of the carrier particles of this invention. ~ypical carrier core materials include sodium chloride, ammonium chloride, aluminum potassium chloride, Rochelle salt, sodium nitrate, potassium chlorate, granular zircon, granular silicon, methyl ; methacrylate, glass, silicon dioxide, flintshot, iron, steel, ferrite, nickel,~Carborundum and mixtures thereof. Many of the foregoing and other typical carriers are described by .E. Walkup in U.S. Patent 2,618,551; ~.E. Walkup et al. in U.S. Patent 2,638,416 and E.N. Wise in U.S. Patent 2,618,552.
~n ultimate homogeneous or coated carrier bead diameter between about 30 microns to about 1,000 microns is preferred for electrostatographic use because the carrier particles then possess sufficient density and inertia to avoid adherence to the electrostatic latent images during the cascade or mag-netic brush development process.
-13~
Any suitable pigmented or dyed electroscopic toner material may be employed with the carriers of this invention.
Typical toner materials include: gum copal, gum sandarac, rosin, cumaroneindene resin, asphaltum, gilsonite, phenol formal-dehyde resins, rosin~modified phenol-formaldehyde resins, methacryl c resins, polystyrene resins, polypropylene resins, polyesters, epoxy resins, polyethylene resins and mixtures thereof. The particular toner material to be employed obviously depends upon the separation of the toner particles from the treated carrier beads in the triboelectric series.
Among the patents describing electroscopic toner compositions are U.S. Patent 2,659,670 to Copley; U.S. Patent 2,753,309 to Landrigan; U.S. Patent 3,079,342 to Insalaco; U.S. Patent Reissue 25,136 to Carlson and U.S. Patent 2,788,288 to Rheinfrank et al. These toners generally have an average particle diameter between about 1 and about 30 microns.
Any suitable conventional toner concentratLon may be employed with the carriers of this invention. Typical toner concentrations include about 1 part toner with about 10 to 200 parts by weight of carrier.
Any suitable well-known electrophotosensitive material may be employed as the photoreceptor with the carriers o~ this invention. Well-kno~n photoconductive materials include vitreous selenium, organic or inorganic photoconductors embedded in a non-photoconductive matrix, or~anic or inorganic photoconductors embedded in a photocon-ductive matrix, or the like. Representative patents in which photoconductive materials are disclosed include U.S. Patent 2,803,542 to Ullrich, U.S. Patent 2,970,906 to Bixby, U.S.
Patent 3,12L,006 to Moddleton, U.S. Patent 3,121,007 to Middleton, and U.S. Patent 3,151,982 to Corrsin.
The surprisingly better results obtained with the carrier materials of this invention may be due to many factors.
For example, developer mixtures prepared with the carrier materials of this invention provide improved solid area develop-ment. In addition, greater flexibility is available in the use of different coating polymers for control of triboelectric charging properties of the carrier particles. The tribo- -e~ectric charging properties of developer mixture prepared with these carrier materials are humidity-insensitive there~y avoiding copy defects when employed at high relative humidity conditions. The carrier materials are easily prepared and exhibit improved stability during extended periods o~ usage.
The carrier coatings employed in the present invention are non-tacky and have sufficient hardness at normal operating tempera-tures to prevent toner impaction, form strong adhesive coatings which do not flake under normal operating conditions; and have triboelectric values such that they can be used with a wide variety of presently available toners in present electro-statographic processes. Thus, the carrier materials of this invention have desirable properties which permit their wide use in presently available alectrostatographic processes.
DESCRILPTION OF PREFERRED EMBODIMENTS
The following examples, other than the control examples, further define, describe and compare preferred methods of utilizing the carrier materials of the present invention in electrostatographic applications. Parts and percentages are by weight unless otherwise indicated.
In the following, the relative triboelectric values generated by contact of carrier beads with toner particles is measured by means of a Faraday Cage. The device comprises a brass cylinder having a diameter of one inch and a length of one inch. A 100-mesh screen is positioned at each end of the cylinder. The cylinder is weighed, charged with 0.5 gram of a mixture of carrier and toner particles and connected to ground through a capacitor and an electrometer connected in parallel.
Dry compre~sed air is then blown through the brass 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 micro-coulombs per gram of toner. Since tribo-electric measurements are relative, the measurements should, for comparative purposes, be conducted under substantially identical conditions. Thus, a toner comprising a styrene-n-butyl methacrylate copolymer, and carbon black is used as a contact triboelectrification standard in all the examples.
Obviously other suitable toners such as those listed above may be substituted for the toner used in the examples.
EXAMPLE I
A control developer mixture i5 prepared by applying a coating solution containing about 15 parts by weight of styrene, about 80 part~ by weight of methyl methacrylate, and about 5 parts by weight of vinyl triethoxy silane dis-solved in methyl ethyl ketone to 100 micron steel carrier cores.
The carrier cores and the coating solution are simultaneously heated and suspended in a vibrating drum. The coating solution , is applied to provide about 0.6 percent by weight of the terpolymer coating based on the weight of the coated cores.
After removal of the solvent and drying the coated cores, the coated cores are mixed with the toner material described above wherein the toner material has an average particle size of between 10 and 15 microns~ The coated cores are blended with the toner material in an amount of about 1 part toner material per about 100 parts by weight o~ carrier material. The developer mixture is used to develop a photoconductive sur-face bearing an electrostatic latent image. The relative triboelectric value of the carrier measured by means of a Faraday Cage is about 29 micro-coulombs per gram of toner.
EXAMPLE II
A developer mixture is prepared by applying a coating solution containing about 15 parts by weight of styrene, about 80 parts by weight of methyl methacrylate, about 5 parts by weight o~ vinyl triethoxy silane, and about 4 parts by weight of a surface activa additive consisting of tetraheptylammonium bromide dissolved in methyl ethyl ketone to 100 micron steel carrier cores. The carrier cores and the coating solution are simultaneously heated and suspended in a vibrating drum. The coating solution is applied to provide about 0.6 percent by weight of the coating materials based on the weight of the coated cores. A~ter removal of the solvent and drying ~he coated cores, the coated cores are mixed with the same toner material as in Example I.
The coated cores are blended with the toner material in an amount of about 1 part toner material per about 100 parts by weight of carrier material. The developer mixture is used to 7~
develop a photoconductive surface bearing an electrostatic latent image. The relative triboelectric value o~ the carrier material measured by means of a Faraday Cage is about 0 micro-soulombs per gram of toner.
EXAMPLE III
A developer mixture is prepared by applying a coating solution containing about 15 parts by weight of styrene, about 80 parts by weight of methyl methacrylate, and about 5 parts by weight of vinyl triethoxy silane, and about 8 parts by weight of a surface active additive consisting of tetraheptylammonium bromide dissolved in methyl ethyl ketone to lO0 micron steel carrier cores. The carrier cores and the coating solution are simultaneously heated and suspended in a vibrating drum4 The coating solution --is applied to provide about 0.6 percent by weight of the coating materials based on the weight of the coated cores. After re-; moval of the solvent and drying the coated cores, the coated cores are mixed with the same toner material as in Example I.
The coated cores are blended with the toner material in an amount of about 1 part toner material per about lO0 parts by weight of carrier material. The developer mixture is used to develop a photoconductive surface bearing an electrostatic latent imageO The relative triboelectric value of the carrier measured by means of a Faraday Cage is about -24 micro-coulombs per gram of toner.
EXAMPLE_IV
A co~trol developer mixture is prepared by applying a coating solution con~aining about 87 parts by weight of vinyl chloride and about 12 parts by weight or vinyl acetate ~ 7~3 ", dissolved in methyl ethyl ketone to lO0 micron steel carrier cores. The carrier cores and the coating solution are simultaneously heated and suspended in a vibrating drum.
The coating solution is applied to provide about 1.0 percent by weight of the coating materials based on the weight of the coated cores. After removal of the solvent and drying the coated cores, the coated cores are mixed with the same toner material as in Example I. The coated cores are blended with the toner material in an amount of about l part toner material per about lO0 parts by weight of carrier material.
The developer mixture is used to develop a photoconductive surface baaring an electrostatic latent image at a relative humidity of about 20% and about ~5%, respectively. The relative triboelectric value of the carrier measured by means of a Faraday Cage is about -15 and about ~25 micro-coulombs per gram of toner, respectively, indicating a fluctuation in tri`boelectric value at high relative humidity conditions.
EXAMPLE V
A developer mixture is prepared by applying a coating solution containing about 87 parts by weight of vinyl chloride and about 12 parts by weight of vinyl acetate and about 5 parts by weight of Luxol Fast slue AR, (C.I. Solvent slue 37, C.I. No. 13390, available from E.I. duPont de Nemours & Co., Wilmington, Delawar~ dissolved in methyl ethyl ketone to lO0 micron steel carrier cores. The carrier cores and the coating solution are simultaneously heated and suspended in a vibrating drum. The coating solution is applied to provide about l.0 percent by weight of the coating materials based on the weight of the coated cores. After removal of the solvent and drying the coated cores, the coated cores are mixed with the same toner toner material as in Example I. The coated cores are blended with the toner material in an amount of about 1 part toner material per about lO0 parts by weight of carrier material.
The developer mixture is used to develop a photoconductive surface bearing an electrostatic latent image at a relative humidity of about 20% and about 75%, respectively. The relative triboelectric value of the carrier measured by means of a Faraday Cage is about -16 and about -23 micro-coulombs per gram of toner, respectively, indicating no substantial 10` improvement in stability of triboelectric charge at high ~-relative humidity conditions.
EXAMPLE VI
;
A developer mixture is prepared by applying a coating solution containing about 87 parts by weight of vinyl chloride and about 12 parts by weight of vinyl acetate and about 10 parts by weight of Luxol Fast Blue AR (C.I. Solvent slue 37, C.I. No. 13390, available from E.I. duPont de ~emours &
Co., Wilmington, Delaware) dissolved in methyl ethyl ketone to lO0 micron steel carrier cores. The carrier cores and the coating solution are simultaneously heated and suspended in a vibrating drum. The coating solution is applied to provide about 1.0 percent by weight of the coating materials based on the weight of the coated cores. After removal of the solvent and drying the coated cores, the coated cores are mixed with the same toner material as in Example I. The coated cores are blended with the toner material in an amount of about l part toner material per about lO0 parts by weight of carrier material.
The developer mixture is used to develop a photoconductive sur-face bearing an electrostatic latent image at a relative humidity o about 20% and about 75%, respectively. The relative triboelectric value of the carrier measured by means of a Faraday Cage is about -20 and -20 micro-coulboms per gram of toner, respectively, indicating no fluctuation ~n tribo-electric charge value at high relative humidity conditions.
EXAMPLE VII
A developer mixture is prepared by applying a coating solution containing about 87 parts by weight of vinyl chloride and about 12 parts by weight of vinyl acetate and about 15 parts by weight of Luxol Fast Blue AR (C.I. Solvent slue 37, C.I. No. 13390, available from E. I. duPont de Nemours & Co., Wilmington, Delaware) dissolved in methyl ethyl ketone to 100 micron steel carrier cores. The carrier cores and the coating solution are simultaneously heated and suspended in a vibrating drum. The coating solution is applied to provide about 1.0 percent by weight of the coating materials based on the weight of the coated cores. After removal oE the solvent and drying the coated cores, the coated cores are mixed with the same toner material as in Example I. The coated cores are blended ~ith the toner material in an amount of about 1 part toner material per about 100 parts by weight of carrier material. The developer mixture is used to develop a photoconductive surface bearing an electrostatic latent image at a relative humidity of about 20% and about 75%, respectively.
The relative triboelectric value of the carrier measured by means of a Faraday ~age is about -22 and -17 micro-coulombs per gram of toner, respectively, indicating that the optimum amount of triboelectric charge stabilizing agent has been surpassed.
Thus, from Examples I-III, it can be seen that the use of a surface active additive such as tetraheptylammonium ~51~B~33 bromide in a carrier composition provides a viable mode of controllably altering the triboelectric charging magnitude and polarity of the carrier material; and from Examples IV-VII, that the use of a surface active additive such as Luxol Fast Blue provides a means of providing a carrier material having a stable triboelectric charge at low and high relative humidity conditions.
Although specific materials and conditions were set forth in the above exemplary processes in making and using the developer material of the invention, these are merely intended as illustrations of the present invention. Various other toners, carrier cores, substituents and processes such as those listed above may be sub~tituted for those in the examples with similar results.
Other modifications of the present invention will occur to those skilled in the art upon a reading of the present disclosure. These are intended to be included with the scope of this invention.
Many carrier coatings having high compressive and tensile strength either do not adhere well to the carrier core or do not possess the desired triboelectric character- `
istics. The triboelectric and flow characteristics of many t3 carriers are adversely affected when relative humidity is high. For example, the triboelectric values of some carrier coatings fluctuate with changes in relative humidity and are not desirable for employment in xerographic systems, particularly in automatic machines which require carriers having stable and predictable triboelectric values. Another factor affecting the stability of carrier triboelectric properties i5 the susceptibility of carrier coatings to "toner impaction". When carrier particles are employed in automatic machines and recycled through many cycles, the many collisions which occur between the carrier particles and other surfaces in the machine cause the toner particles carried on the surface of the carrier particles to be welded or otherwise forced into ~he carrier coatings. The gradual accumulation of permanently attached toner material on- the surface of the carrier particles causes a change in the triboelectric value of the carrier particles and directly contributes to the degradation of copy quality by eventual destruction of the toner carrying capacity of the carrier. Thus, there is a continuing need for a better system for devel-oping latent electrostatic images.
It is, therefore, an object of an aspect of this invention to provide developing materials which overcome the above noted deficiencies.
It is an object of an aspect of this invention to provide carrier particles which possess improved electrostatographic properties for efficient and prolonged use in electrostatographic reproduction processes.
It is an object of an aspect of this invention to provide carrier particles having coatings which are more resistant to toner impaction.
It is an object of an aspect of this invention to provide developing materials which flow more freely.
It is an object of an aspect of this invention to provide carrier coatings havlng more stable tribo-electric values.
It is an object of an aspect of this invention to provide carrier particles which are less sensitive to changes in relative humidity conditions.
It is an object of an aspect of this invention to provide developer materials having greatly increased developer life.
It is an object of an aspect of this invention to provide developers having physical and chemical proper-ties superior to those of known developer materials.
An aspect of this invention is as follows:
A carrier particle for electrostatographic developer mixtures, said carrier particle comprising a core having an outer layer comprising an electrically insulating vinyl polymer and an effective amount of a surface active additive dissolved or dispersed in said polymer and capable of providing a desired magnitude of negative triboelectric charging potential to said carrier particle, said surface active additive consisting essentially of tetraheptylammonium bromide.
In accordance with this invention, it is believed that copy quality defects found in electrostatographic dev-elopment which are due to atmospheric conditions are humidity-induced. Thus, it has been found that a developer mixture which generates the same triboelectric charge at low and high ~ i~
11~7~3~3 relative humidity conditions will avoid humidity-induced copy defects in electrostatographic development processes.
Further, the triboelectric charge of carrier particles having an outer surface or outer coating of an insulating material may be controllably altered by incorporation therein of surface active additives such as ionic additives selected from quaternary ammonium salts. In addition to providing the aforementioned properties to the carrier compositions of this invention, the surface active additive also provides carrier compositions which have anti-stick or low surface energy properties thereby minimizing their filming by impaction of toner particles thereon.
It has been found that properties desired of carrier materials may be attained by coating carrier particles 1~ with an insulating polymer having dissolved or dispersed therein a surface active additive. That is, the surface active additive may be homogeneously dissolved or dispersed in the insulating polymer and the components employed as a carrier or applied as a coating to a carrier core. In preparation of the carrier composition of this invention, it is preferred that the resin component be melted followed by the addition of the surface active additive thereto and the mixture thoroughly mixed to yield a uniformly dissolved or dispersed composition of the additive in the resin body.
Although the actual mechani~m is not entirely clear, the relative position of a specific carrier material in the tribo-electric series is changed when the surface active additive is incorporated in at least the surface of the carrier substrate and the triboelectric charge generated on the carrier material is stable even at high relative humidity conditions.
The surface active additive employed in the carrier compositions of this invention may be selected from highly fluorinated materials~ Typical materials include fluorinated surfactants or "pentamers" commercially available under the m~ Monflor available from ICI America, Zonyl from E. I. duPont, and Fluorad from 3M. These materials contain anionic, cationic, or nonionic groups providing a wide range of surface active behavior. These surface active additives, by virtue of their low surface energy or the extent of their compatibility or association with the polymer matrix, will preferentially reside close to the polymer-air interface, so long as thermodynamic equilibrium is allowed to occur within the processing time period.
The surfa~e active additive is preferably selected from additives such as monomers and polymers containing ionic groups; for example, tetraheptylam~onium bromide, neutralized acrylic acid or vinyl pyridine containing copolymers, and silicones. However, the preferred surface active additive of this invention with respect to modification of the tribo-electric charge of the carrier material is tetraheptylammonium bromide because the additive will cause a styrene methyl methacrylate-vinyltriethoxysilane terpolymer coating material to triboelectrically charge more negatively relative to a vinyl-based toner composition. Without the surface active additive in the carrier composition, the -terpolymer-based carrier * ~r~
~0 -8--~17~
coating material charges strongly positively with the 9inyl-based toner material. The preferred surface active additive with respect to stabilization of the triboelectric charge generated on a carrier material at varying relative humidity 5 ~ conditions is Luxol Fast slue AR (C.I. Solvent slue 37, C.I.
No. 13390, available from E~I. duPont de Nemours & Co., Wilmington, Delaware).
In accordance with this invention, electrostatographic carrier compositions which generate less strongly positive tribo-electric charges are provided when the sur~ace active additives are present therein in an amount of from between about 0.5 and about 3 parts by weight based on the weight of the carrier composition. However, lt is preferred that the electrostato-graphic carrier compositions of this invention comprise from ; 15 between about 3 and about ~ parts by weight of the surface active additives based on the weight of the carrier composition because a greater effect on the triboelectric properties of the carrier material is provided, and owing to the sensitivity to moisture of polymer materials, the triboelectric properties of the carrier compositions are more stable under various relative humidity conditions. Optlmum results are generally obtained when the electrostatographic carrier compositions of this invention comprise from between about 6 and about 10 parts by weight of the surface active additives based on the weight of the carrier composition.
; 25 When the carrier compositions of this invention have an outer coating, any suitable coating thickness may be employed.
However, a coating having a thickness at least sufficient to form a continuous film is preferred because the carrier coating will then possess sufficient thickness to resist abrasion and prevent pinholes which adversely affect the triboelectric properties of the coated carrier particles. Generally, for cascade and magnetic brush development, the carrier coating may comprise from about 0.1 percent to about 2.0 percent by ~ ~rJ~
weight based on the weight of the coated carrier particles.
Preferably, the coating should comprise from about 0.2 per-cent to about 0.9 percent by weight based on the weight of the coated particle because maximum coating durability, toner S impaction resistance, and copy quality are achieved. If a partially polymerized linear or crosslinked prepolymer is to be used as the coating material, polymerization may be completed in situ on the surface of the carrier by further application of heat.
Factors affecting the quantity of surface ac~ive additive to be incorporated in at least the surface of carrier particles include: the separation in the triboelectric series between the toner particies and the carrier material;
- the concentration of the surface active additive at the sur-face of the carrier particles; and the average diameter of the carrier particle.
The surface active additive may be distributed only at the ~urface of a coated or uncoated carrier particle or ~ uniformly distributed throughout an uncoated carrier particle or throughout the external coating of a coated carrier particle.
When the surface active additive is dispersed throughout the carrier particle or carrier particle coating rather than only contiguous to the surface of the carrier particle, propor-tionally more surface active additive at the surface of the carrier particle. The additional amount of surface active additive necessary depends to a large extent on the surface area of the carrier particles, hence, upon the particle diameter selected. Obviously, as the quantity of surface active additive actually available at the surface of the carrier particle is reduced to a negligible amount, the tribo-electric properties of the carrier surface are substantially the same as a carrier which does not contain surface active additive. Obviously, with a given quantity of surface active additive based on the weight of the carrier, a greater volume of surface active additive is available at the surface of the carrier when the surface active additive is located only at the surface of the carrier particles than when the surface active additive is intLmately dispersed thxoughout each carrier particle.
In a preferred embodiment, the surface active -~ additive is incorporated into at least the outer surface of coated or uncoated carrier beads by bringing -the surface active additive into contact with the external surface of coated or uncoated beads.
Where the surface active additive is to be incor-~- porated into a carrier bead having a preformed soft outer surface which is capable of being subsequently hardened, the carrier bead or carrier bead coating should comprise a material such as a soft curable prepolymer resin, gelled plastisol or certain softened materials. The materials may comprise materials softened by heat or solvents. The solvent or heat softenable material may include natural resinæ, thermoplastic resins, and hard partially cured thermosetting resins. The soft curable prepolymers may comprise any suitable polymerized thermoplastic or thermosetting resins. Typical natural resins include: caoutchouc, colophony, copal, dammar, Dragon's Blood, jalap, storax, and the like. Typical thermoplastic resins include:
B~3 the polyolefins such as polyethylene, polypropylene, chlorinated polyethylene, and chlorosulfonated propylene, chlorinated polyethylene, and chlorosulfonated polyethylene, poly~inyls and polyvinylidenes such as polystyrene, polymethylstyrene, poly-methyl methacrylate, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ethers, and polyvinyl ketones;
fluorocarbons such as polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride; and polychlorotrifluoroethylene;
polyamides such as polycroproloctamo and polyhexamethylene adipamide; polyesters such as polyethylene terephthalate;
polyrethanes; polysulides; polycarbonates; and the li~e.
Typical thermosetting resins include: phenolic resins such as phenol-formaldehyde, phenol-furfural and resorcinol formaldehyde; amino resins such as urea-formaldehyde and melamineformaldehyde; polyester resins; epoxy resins; and the like.
Alternatively, the surface active additives of this invention may be dispersed, dissolved or suspended throughout a carrier bead or carrier bead coating mat~rial prior to bead or bead coating formation. The dispersion, solution, or suspension may be prepar~d by conventional techniques. It is to be understood that the material employed to form the matrix of the carrier bead or carrier bead coating may be in any suitable form such as a hot molt, a solution, an emulsion, a liquid monomer or a dispersion. When the ultimate product is to be a coated carrier bead, the carrier coating compositions with or without the surface active additive may be applied to a carrier core by any conventional method such as spraying, dipping, fiuidized bed coating, tumbling, brushing and the ~ ` ~
like. The coating compositions may be applied as a powder, a dispersion, solution, emulsion or hot melt. When applied as a solution, any suitable solvent may be employed. Solvents having relatively low boiling points are preferred because less energy and time is required to remove the solvent sub-sequent to application of the coating to the carrier core.
If desired, the coating may comprise resin monomers which are polymerized in situ on the surface of the bead cores or plastisols gelled in situ to a non-~lowable state on the sur-face of the bead cores. Any suitable coating thickness may be employed. However, the carrier coating should be sufficiently thick to resist flaking and chipping.
Any suitable well known coated or uncoated electro-~, statographic carrier bead material may be employed as the core of the carrier particles of this invention. ~ypical carrier core materials include sodium chloride, ammonium chloride, aluminum potassium chloride, Rochelle salt, sodium nitrate, potassium chlorate, granular zircon, granular silicon, methyl ; methacrylate, glass, silicon dioxide, flintshot, iron, steel, ferrite, nickel,~Carborundum and mixtures thereof. Many of the foregoing and other typical carriers are described by .E. Walkup in U.S. Patent 2,618,551; ~.E. Walkup et al. in U.S. Patent 2,638,416 and E.N. Wise in U.S. Patent 2,618,552.
~n ultimate homogeneous or coated carrier bead diameter between about 30 microns to about 1,000 microns is preferred for electrostatographic use because the carrier particles then possess sufficient density and inertia to avoid adherence to the electrostatic latent images during the cascade or mag-netic brush development process.
-13~
Any suitable pigmented or dyed electroscopic toner material may be employed with the carriers of this invention.
Typical toner materials include: gum copal, gum sandarac, rosin, cumaroneindene resin, asphaltum, gilsonite, phenol formal-dehyde resins, rosin~modified phenol-formaldehyde resins, methacryl c resins, polystyrene resins, polypropylene resins, polyesters, epoxy resins, polyethylene resins and mixtures thereof. The particular toner material to be employed obviously depends upon the separation of the toner particles from the treated carrier beads in the triboelectric series.
Among the patents describing electroscopic toner compositions are U.S. Patent 2,659,670 to Copley; U.S. Patent 2,753,309 to Landrigan; U.S. Patent 3,079,342 to Insalaco; U.S. Patent Reissue 25,136 to Carlson and U.S. Patent 2,788,288 to Rheinfrank et al. These toners generally have an average particle diameter between about 1 and about 30 microns.
Any suitable conventional toner concentratLon may be employed with the carriers of this invention. Typical toner concentrations include about 1 part toner with about 10 to 200 parts by weight of carrier.
Any suitable well-known electrophotosensitive material may be employed as the photoreceptor with the carriers o~ this invention. Well-kno~n photoconductive materials include vitreous selenium, organic or inorganic photoconductors embedded in a non-photoconductive matrix, or~anic or inorganic photoconductors embedded in a photocon-ductive matrix, or the like. Representative patents in which photoconductive materials are disclosed include U.S. Patent 2,803,542 to Ullrich, U.S. Patent 2,970,906 to Bixby, U.S.
Patent 3,12L,006 to Moddleton, U.S. Patent 3,121,007 to Middleton, and U.S. Patent 3,151,982 to Corrsin.
The surprisingly better results obtained with the carrier materials of this invention may be due to many factors.
For example, developer mixtures prepared with the carrier materials of this invention provide improved solid area develop-ment. In addition, greater flexibility is available in the use of different coating polymers for control of triboelectric charging properties of the carrier particles. The tribo- -e~ectric charging properties of developer mixture prepared with these carrier materials are humidity-insensitive there~y avoiding copy defects when employed at high relative humidity conditions. The carrier materials are easily prepared and exhibit improved stability during extended periods o~ usage.
The carrier coatings employed in the present invention are non-tacky and have sufficient hardness at normal operating tempera-tures to prevent toner impaction, form strong adhesive coatings which do not flake under normal operating conditions; and have triboelectric values such that they can be used with a wide variety of presently available toners in present electro-statographic processes. Thus, the carrier materials of this invention have desirable properties which permit their wide use in presently available alectrostatographic processes.
DESCRILPTION OF PREFERRED EMBODIMENTS
The following examples, other than the control examples, further define, describe and compare preferred methods of utilizing the carrier materials of the present invention in electrostatographic applications. Parts and percentages are by weight unless otherwise indicated.
In the following, the relative triboelectric values generated by contact of carrier beads with toner particles is measured by means of a Faraday Cage. The device comprises a brass cylinder having a diameter of one inch and a length of one inch. A 100-mesh screen is positioned at each end of the cylinder. The cylinder is weighed, charged with 0.5 gram of a mixture of carrier and toner particles and connected to ground through a capacitor and an electrometer connected in parallel.
Dry compre~sed air is then blown through the brass 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 micro-coulombs per gram of toner. Since tribo-electric measurements are relative, the measurements should, for comparative purposes, be conducted under substantially identical conditions. Thus, a toner comprising a styrene-n-butyl methacrylate copolymer, and carbon black is used as a contact triboelectrification standard in all the examples.
Obviously other suitable toners such as those listed above may be substituted for the toner used in the examples.
EXAMPLE I
A control developer mixture i5 prepared by applying a coating solution containing about 15 parts by weight of styrene, about 80 part~ by weight of methyl methacrylate, and about 5 parts by weight of vinyl triethoxy silane dis-solved in methyl ethyl ketone to 100 micron steel carrier cores.
The carrier cores and the coating solution are simultaneously heated and suspended in a vibrating drum. The coating solution , is applied to provide about 0.6 percent by weight of the terpolymer coating based on the weight of the coated cores.
After removal of the solvent and drying the coated cores, the coated cores are mixed with the toner material described above wherein the toner material has an average particle size of between 10 and 15 microns~ The coated cores are blended with the toner material in an amount of about 1 part toner material per about 100 parts by weight o~ carrier material. The developer mixture is used to develop a photoconductive sur-face bearing an electrostatic latent image. The relative triboelectric value of the carrier measured by means of a Faraday Cage is about 29 micro-coulombs per gram of toner.
EXAMPLE II
A developer mixture is prepared by applying a coating solution containing about 15 parts by weight of styrene, about 80 parts by weight of methyl methacrylate, about 5 parts by weight o~ vinyl triethoxy silane, and about 4 parts by weight of a surface activa additive consisting of tetraheptylammonium bromide dissolved in methyl ethyl ketone to 100 micron steel carrier cores. The carrier cores and the coating solution are simultaneously heated and suspended in a vibrating drum. The coating solution is applied to provide about 0.6 percent by weight of the coating materials based on the weight of the coated cores. A~ter removal of the solvent and drying ~he coated cores, the coated cores are mixed with the same toner material as in Example I.
The coated cores are blended with the toner material in an amount of about 1 part toner material per about 100 parts by weight of carrier material. The developer mixture is used to 7~
develop a photoconductive surface bearing an electrostatic latent image. The relative triboelectric value o~ the carrier material measured by means of a Faraday Cage is about 0 micro-soulombs per gram of toner.
EXAMPLE III
A developer mixture is prepared by applying a coating solution containing about 15 parts by weight of styrene, about 80 parts by weight of methyl methacrylate, and about 5 parts by weight of vinyl triethoxy silane, and about 8 parts by weight of a surface active additive consisting of tetraheptylammonium bromide dissolved in methyl ethyl ketone to lO0 micron steel carrier cores. The carrier cores and the coating solution are simultaneously heated and suspended in a vibrating drum4 The coating solution --is applied to provide about 0.6 percent by weight of the coating materials based on the weight of the coated cores. After re-; moval of the solvent and drying the coated cores, the coated cores are mixed with the same toner material as in Example I.
The coated cores are blended with the toner material in an amount of about 1 part toner material per about lO0 parts by weight of carrier material. The developer mixture is used to develop a photoconductive surface bearing an electrostatic latent imageO The relative triboelectric value of the carrier measured by means of a Faraday Cage is about -24 micro-coulombs per gram of toner.
EXAMPLE_IV
A co~trol developer mixture is prepared by applying a coating solution con~aining about 87 parts by weight of vinyl chloride and about 12 parts by weight or vinyl acetate ~ 7~3 ", dissolved in methyl ethyl ketone to lO0 micron steel carrier cores. The carrier cores and the coating solution are simultaneously heated and suspended in a vibrating drum.
The coating solution is applied to provide about 1.0 percent by weight of the coating materials based on the weight of the coated cores. After removal of the solvent and drying the coated cores, the coated cores are mixed with the same toner material as in Example I. The coated cores are blended with the toner material in an amount of about l part toner material per about lO0 parts by weight of carrier material.
The developer mixture is used to develop a photoconductive surface baaring an electrostatic latent image at a relative humidity of about 20% and about ~5%, respectively. The relative triboelectric value of the carrier measured by means of a Faraday Cage is about -15 and about ~25 micro-coulombs per gram of toner, respectively, indicating a fluctuation in tri`boelectric value at high relative humidity conditions.
EXAMPLE V
A developer mixture is prepared by applying a coating solution containing about 87 parts by weight of vinyl chloride and about 12 parts by weight of vinyl acetate and about 5 parts by weight of Luxol Fast slue AR, (C.I. Solvent slue 37, C.I. No. 13390, available from E.I. duPont de Nemours & Co., Wilmington, Delawar~ dissolved in methyl ethyl ketone to lO0 micron steel carrier cores. The carrier cores and the coating solution are simultaneously heated and suspended in a vibrating drum. The coating solution is applied to provide about l.0 percent by weight of the coating materials based on the weight of the coated cores. After removal of the solvent and drying the coated cores, the coated cores are mixed with the same toner toner material as in Example I. The coated cores are blended with the toner material in an amount of about 1 part toner material per about lO0 parts by weight of carrier material.
The developer mixture is used to develop a photoconductive surface bearing an electrostatic latent image at a relative humidity of about 20% and about 75%, respectively. The relative triboelectric value of the carrier measured by means of a Faraday Cage is about -16 and about -23 micro-coulombs per gram of toner, respectively, indicating no substantial 10` improvement in stability of triboelectric charge at high ~-relative humidity conditions.
EXAMPLE VI
;
A developer mixture is prepared by applying a coating solution containing about 87 parts by weight of vinyl chloride and about 12 parts by weight of vinyl acetate and about 10 parts by weight of Luxol Fast Blue AR (C.I. Solvent slue 37, C.I. No. 13390, available from E.I. duPont de ~emours &
Co., Wilmington, Delaware) dissolved in methyl ethyl ketone to lO0 micron steel carrier cores. The carrier cores and the coating solution are simultaneously heated and suspended in a vibrating drum. The coating solution is applied to provide about 1.0 percent by weight of the coating materials based on the weight of the coated cores. After removal of the solvent and drying the coated cores, the coated cores are mixed with the same toner material as in Example I. The coated cores are blended with the toner material in an amount of about l part toner material per about lO0 parts by weight of carrier material.
The developer mixture is used to develop a photoconductive sur-face bearing an electrostatic latent image at a relative humidity o about 20% and about 75%, respectively. The relative triboelectric value of the carrier measured by means of a Faraday Cage is about -20 and -20 micro-coulboms per gram of toner, respectively, indicating no fluctuation ~n tribo-electric charge value at high relative humidity conditions.
EXAMPLE VII
A developer mixture is prepared by applying a coating solution containing about 87 parts by weight of vinyl chloride and about 12 parts by weight of vinyl acetate and about 15 parts by weight of Luxol Fast Blue AR (C.I. Solvent slue 37, C.I. No. 13390, available from E. I. duPont de Nemours & Co., Wilmington, Delaware) dissolved in methyl ethyl ketone to 100 micron steel carrier cores. The carrier cores and the coating solution are simultaneously heated and suspended in a vibrating drum. The coating solution is applied to provide about 1.0 percent by weight of the coating materials based on the weight of the coated cores. After removal oE the solvent and drying the coated cores, the coated cores are mixed with the same toner material as in Example I. The coated cores are blended ~ith the toner material in an amount of about 1 part toner material per about 100 parts by weight of carrier material. The developer mixture is used to develop a photoconductive surface bearing an electrostatic latent image at a relative humidity of about 20% and about 75%, respectively.
The relative triboelectric value of the carrier measured by means of a Faraday ~age is about -22 and -17 micro-coulombs per gram of toner, respectively, indicating that the optimum amount of triboelectric charge stabilizing agent has been surpassed.
Thus, from Examples I-III, it can be seen that the use of a surface active additive such as tetraheptylammonium ~51~B~33 bromide in a carrier composition provides a viable mode of controllably altering the triboelectric charging magnitude and polarity of the carrier material; and from Examples IV-VII, that the use of a surface active additive such as Luxol Fast Blue provides a means of providing a carrier material having a stable triboelectric charge at low and high relative humidity conditions.
Although specific materials and conditions were set forth in the above exemplary processes in making and using the developer material of the invention, these are merely intended as illustrations of the present invention. Various other toners, carrier cores, substituents and processes such as those listed above may be sub~tituted for those in the examples with similar results.
Other modifications of the present invention will occur to those skilled in the art upon a reading of the present disclosure. These are intended to be included with the scope of this invention.
Claims (9)
1. A carrier particle for electrostatographic developer mixtures, said carrier particle comprising a core having an outer layer comprising an electrically insulating vinyl polymer and an effective amount of a surface active additive dissolved or dispersed in said polymer and capable of providing a desired magnitude of negative triboelectric charging potential to said carrier particle, said surface active additive consisting essentially of tetraheptylammonium bromide.
2. A carrier particle for electrostatographic developer mixtures in accordance with claim 1 wherein said surface active additive is present in an amount of from about 0.5 percent to about 3 percent by weight based on the weight of said carrier particle.
3. A carrier particle for electrostatographic developer mixtures in accordance with claim 1 wherein said surface active additive is present in an amount of from about 3 percent to about 6 percent by weight based on the weight of said carrier particle.
4. A carrier particle for electrostatographic developer mixtures in accordance with claim 1 wherein said surface active additive is present in an amount of from about 6 percent to about 10 percent by weight based on the weight of said carrier particle.
5. A carrier particle for electrostatographic developer mixtures in accordance with claim 1 wherein said electrically insulating polymer comprises a styrene-methyl methacrylate-vinyltriethoxysilane terpolymer.
6. A carrier particle for electrostatographic developer mixtures in accordance with claim 1 wherein said electrically insulating polymer comprises vinyl chloride and vinyl acetate.
7. A carrier particle for electrostatographic developer mixtures in accordance with claim 1 wherein said core is selected from the group consisting of iron, steel, and ferrites.
8. A carrier particle for electrostatographic developer mixtures in accordance with claim 1 wherein said outer layer is present in an amount of from between about 0.1 percent to about 2.0 percent by weight based on the weight of said carrier particle.
9. An electrostatographic developer mixture com-prising finely-divided toner particles electrostatically clinging to the surface of carrier particles having an average particle diameter of from between about 30 microns and about 1,000 microns, each of said carrier particles comprising a core having an outer layer com-prising an electrically insulating vinyl polymer and an effective amount of a surface active additive dissolved or dispersed in said polymer and capable of providing a desired magnitude of negative triboelectric charging potential to said carrier particles, said surface active additive consisting essentially of tetraheptylammonium bromide.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US78447277A | 1977-04-04 | 1977-04-04 | |
| US784,472 | 1977-04-04 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1117803A true CA1117803A (en) | 1982-02-09 |
Family
ID=25132540
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000299407A Expired CA1117803A (en) | 1977-04-04 | 1978-03-21 | Carrier particle with outer layer containing vinyl polymer and tetroheptyl ammonium bromide |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS53123935A (en) |
| CA (1) | CA1117803A (en) |
| FR (1) | FR2386846A1 (en) |
| GB (1) | GB1603024A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS54158930A (en) * | 1978-06-06 | 1979-12-15 | Konishiroku Photo Ind Co Ltd | Carrier for developing electrostatic charge images and production thereof |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3533835A (en) * | 1966-10-11 | 1970-10-13 | Xerox Corp | Electrostatographic developer mixture |
| US4066563A (en) * | 1975-09-29 | 1978-01-03 | Xerox Corporation | Copper-tetra-4-(octadecylsulfonomido) phthalocyanine electrophotographic carrier |
-
1978
- 1978-03-21 CA CA000299407A patent/CA1117803A/en not_active Expired
- 1978-03-28 JP JP3593678A patent/JPS53123935A/en active Pending
- 1978-03-31 FR FR7809670A patent/FR2386846A1/en not_active Withdrawn
- 1978-04-03 GB GB1297978A patent/GB1603024A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS53123935A (en) | 1978-10-28 |
| GB1603024A (en) | 1981-11-18 |
| FR2386846A1 (en) | 1978-11-03 |
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