Classifications

• • 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
  • G03G9/0819—Developers with toner particles characterised by the dimensions of the particles
• • 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

Definitions

• This invention relates to an electrostatographic developer mixture, and to an electrostatographic imaging process using the developer mixture.
• the mixture comprises finely-divided toner particles electrostatically clinging to the surface of carrier particles.
• the formation and development of images on the surface of photoconductive materials by electrostatic means is well-known.
• the basic electrostatographic process as taught by C.F. Carlson in U.S. Pat. No. 2,297,691, involves placing a uniform electrostatic charge on a photoconductive insulating layer, exposing 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".
• One technique for developing an electrostatic latent image is the "magnetic brush” process as disclosed, for example, in U.S. Pat. No. 2,874,063.
• 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 image by electrostatic attraction.
• Many other methods such as "touchdown" development as disclosed by C.R. Mayo in U.S. Pat. No. 2,895,847 are known for applying electroscopic particles to the electrostatic latent image to be developed.
• the image density may be improved by increasing the toner concentration in the developer mixture, undesirably high background toner deposition as well as increased toner impaction and agglaneration is encountered when the toner concentration in the developer mixture is excessive.
• the initial electrostatographic plate charge may be increased to improve the density of the deposited powder image, but the plate charge would ordinarily have to be excessively high in order to attract the electroscopic powder away from the carrier particle.
• Excessively high electrostatographic plate charges are riot only undesirable because of the high power consumption necessary to maintain the electrostatographic plate at high potentials, but also because the high potential causes the carrier particles to adhere to the electrostatographic plate surface rather than merely roll across and off the electrostatographic plate surface.
• U.S. Patent 3,942,979 there is disclosed a developer mixture comprising classified toner materials having a particle size distribution wherein less than about 30% by number of the toner particles have an average particle size diameter of less than about 5 microns, less than about 30% of the particles have a diameter between about 5 microns and about 8 microns, at least about 25% of the particles have a diameter between about 8 microns and about 12 microns, at least about 10% of the particles have a diameter between about 12 microns and about 20 microns, and about 5% by number of the toner particles have an average particle diameter greater than about 20 microns.
• the high surface area carrier materials have a specific surface of at least about 150cm 2 /gram. It is also indicated therein that for cascade and magnetic brush development, the carrier particles generally have an average diameter between about 30 microns and 1000 microns, and between about 30 and about 250 microns, respectively.
• Toner particles employed with these carrier particles typically have a distribution of particle sizes that vary from 1 to 30 microns.
• Experience with the aforementioned developer materials reveals degradation of copy quality as reflected by blurred and mottled prints having poor edge acuity and resolution.
• the invention as claimed is intended to provide developer materials which overcome the above noted deficiencies. This is achieved by the use of a developer mixture which is characterised in that substantially all the toner particles are of a size between a lower size limit of 3 microns and 'an upper size limit of between 8 and 15 microns, and in that the carrier particles have a mean size which is not less than the upper size limit of the toner particles and not greater than 65 microns.
• toner materials have a particle size in the range of between 3 microns and 10 microns and the carrier materials have a mean particle size in the range of between 10 microns and 40 microns.
• Optimum results are obtained when the toner materials have a particle size in the range of between 3 microns and 8 microns and the carrier materials have a mean particle size in the range of between 8 microns and 24 microns.
• the invention offers the advantages of developer materials having more stable electrostatographic properties, improved triboelectric properties and a longer useful life. These developer materials are less susceptible to toner impaction, they are more resistant to film formation on electrostatographic recording surfaces, and enable the attainment of copied images having greatly improved quality.
• toner particles having a diameter below 3 microns usually encompass free colorant such as carbon black, and unpigmented platelets which are undesirable since they inhibit proper triboelectric charging and reduce ': the active carrier surface area resulting in high background deposition of such particles.
• toner particles having a diameter below 3 microns are triboelectrically charged too highly and they tend to not be developed as easily as the larger particles and also prevent the larger partic les from being charged high enough. These lower charged larger particles are difficult to control in a developer mixture and will usually undesirably develop onto the background areas of an electrostatic latent image.
• the background deposit is not perceivable by the naked eye.
• the carrier particles employed in the developer mixtures of this invention it is now possible for the carrier particles to carry sufficient toner particles to enable developnent of large solid areas without employing excessively high toner concentrations which previously led to unacceptably high image background deposits.
• the enhanced surface/volume ratio of the developer mass provides increased toner carrying capacity and consequently improved toner concentration latitude.
• the developer materials of this invention provide improved insulation between adjacent carrier beads when the carrier particles are made of a conductive metal and the carrier particles do not contain a coating of an insulating material. This is due to the increased population of toner particles between contacting carrier particles which improves the resistance to shorting between conductive carrier particles and the photoreceptor thus allowing for higher bias field latitude.
• the carrier material should preferably be conductive to realize the virtual electrode effect for maximum development and to prevent build-up of net electrical charge.
• the combination of developer materials of this invention has been found to provide prints of outstanding high quality which are indistinguishable from offset prints.
• the developer compositions of this invention provide developed images having a more uniform and lower pile height than achieved with conventional electrostatographic developer compositions.
• the developed, unfused image toner pile height is between about 45 and 55 microns.
• the developed, unfused image toner pile height is only about 18 microns.
• the image density is about 1.3 but the lower toner pile height obtained with the compositions of this invention is due to their greater covering power; that is, a greater number of toner particles are packed closer together, occluding more image area, absorbing more reflected light, and therefore the perceived image density is the same in both cases yet the toner pile height is much less with these new developer materials.
• This finding is significant since there has conventionally been a substantial disparity in toner pile height between developed, unfused solid image areas and developed, unfused line image areas. However, with the developer compositions of this invention, the toner pile height of developed, unfused solid image areas and that of developed, unfused line image areas is substantially the same.
• any suitable particle classification method may be employed to obtain the toner materials of this invention.
• Typical particle classification methods include air classification, screening, cyclone separation, elutriation, centrification, and combinations thereof.
• the preferred method of obtaining the toner materials of this invention is by centrifugal air classification.
• air or some other gas flows inwards in a spiral path through a flat, cylindrical chamber. Particles contained in the air flow are exposed to two antagonistic forces, viz., to the inwardly directed tractive force of the air, and to the outwardly directed centrifugal force of the particle.
• the "cut size" both forces are in equilibrium.
• the "cut size" usually depends upon the gradient of the spiral, the peripheral component, and the absolute dimension of the classifying chamber. Adjustment of the cut size may be effected through variation of the two factors first mentioned, while the range of the cut size may be determined by the respective dimension of the classifying chamber.
• any suitable particle classification method may be employed to obtain the carrier materials of this invention.
• Typical particle classification methods include air classification, screening, cyclone separation, elutriation, centrification, and combinations thereof.
• the preferred method of obtaining the carrier materials of this invention is by screening or sieving.
• Any suitable vinyl resin having a melting point of at least about 110°F may be employed in the toner canpositions.
• the vinyl resin may be a hanopolymer or a copolymer of two or more vinyl monomers.
• Typical moncmeric units which may be employed to form vinyl polymers include: styrene, p-chloro-styrene, vinyl naphthalene; ethylenically unsaturated mono-olefins such as ethylene, propylene, butylene, isobutylene and the like; vinyl esters such as vinyl chloride, vinyl bromide, vinyl fluoride, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate and the like; esters of alphamethylene aliphatic monocarboxylic acids such as methyl acrylate, ethyl acrylate, n-butylacrylate, isobutyl acrylate, dodecyl acrylate, n-octyl
• Toner resins containing relatively high percentages of a styrene resin are preferred.
• the presence of a styrene resin is preferred because a greater degree of image definition is generally achieved upon latent image development. Further, denser images are obtained when at least about 25 percent by weight, based on the total weight of resin in the toner, of a styrene resin is present in the toner.
• the styrene resin may be a homopolymer of styrene or styrene homologues or copolymers of styrene with other monaneric groups containing a single methylene group attached to a carbon atom by a double bond.
• typical monomeric materials which may be copolymerized with styrene by addition polymerization include: P-chlorostyrene, vinyl naphthalene, ethylenically unsaturated monoolefins such as ethylene, propylene, butylene, isobutylene and the like; vinyl esters such as vinyl chloride, vinyl bromide, vinyl fluoride, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate and the like; esters of alpha-methylene aliphatic mono-carboxylic acids such as methyl acrylate, ethyl acrylate, n-butylacrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl-alpha-chloroacrylate, methyl methacrylate, ethyl methacrylate, butyl methacryl
• the styrene resins may also be formed by the polmeriza- tion of mixtures of two or more of these unsaturated monomeric materials with a styrene monaner.
• additional polymerization is intended to include known polymerization techniques such as free radical, anionic and cationic polymerization processes.
• the vinyl resins including styrene type resins, may also be blended with one or more other resins if desired.
• the added resin is preferably another vinyl resin because the resulting blend is characterized by especially good triboelectric stability and uniform resistance against physical degradation.
• the vinyl resins employed for blending with the styrene type or other vinyl resin may be prepared by the addition polymerization of any suitable vinyl monaner such as the vinyl monomers described above.
• Other thermoplastic resins may also be blended with the vinyl resins of this invention.
• Typical non-vinyl type thermoplastic resins include: rosin modified phenol formaldehyde resins, oil modified epoxy resins, polyurethane resins, cellulosic resins, polyether resins and mixtures thereof.
• a styrene canponent of at least about 25 percent by weight based on the total weight of the resin present in the toner is preferred because denser images are obtained and a greater degree of image definition is achieved with a given quantity of toner 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, Rose Bengal and mixtures thereof.
• the pigment or. dye should be present in the toner in a quantity sufficient to render it highly coloured so that it will form a clearly visible image on a recording member.
• the toner may comprise a black pigment such as carbon black, for example, furnace black or channel black, or a black dye such as Amaplast Black dye, available from the National Aniline Products, Inc.
• a black pigment such as carbon black, for example, furnace black or channel black
• a black dye such as Amaplast Black dye, available from the National Aniline Products, Inc.
• the pigment is employed in an amount from about 1 percent to about 20 percent by weight based on the total weight of the coloured toner. If the toner colorant employed is a dye, substantially smaller quantities of colorant may be used.
• concentration preferably should be less than about 10 percent by weight of the coloured toner.
• toner and developer materials include U.S. Patent 2,788,288, U.S. Patent 3,079,342, U.S. Reissue Patent 25,136, U.S. Patent 3,577,345, U.S. Patent 3,653,893, U.S. Patent 3,590,000, U.S. Patent 3,655,374, U.S. Patent 3,720,617, and U.S. Patent. 3,819,367.
• Particular preferred for use in the present invention are those compositions disclosed in U.S. Reissue Patent 25,136 and U.S. Patent 3,079,342 containing a copolymer of styrene and alkyl methacrylate; the compositions disclosed in U.S.
• Patent 3,590,000 comprising a solid, stable hydrophilic metal salt of a fatty acid such as zinc stearate, and a polymeric esterification product of a dicarboxylic acid and a diol comprising a diphenol; and the compositions disclosed in U.S. Patent 3,819,367 containing a minor proportion of submicroscopic silicon dioxide additive particles.
• the toner compositions may be prepared by a well-known toner mixing and conminution technique.
• the ingredients may be thoroughly mixed by blending, mixing and milling the components and thereafter micropulverizing the resulting mixture.
• Another well-known technique for forming toner particles is to spray-dry a ball-milled toner composition comprising a colorant, a resin, and a solvent.
• any suitable coated or uncoated electrostatographic carrier bead material may be Employed as the carrier material of this invention.
• Typical carriers include sodium chloride, ammonium chloride, aluminium potassium chloride, Rochelle salt, sodium nitrate, aluminium nitrate, potassium chlorate, granular zircon, granular silicon, methyl methacrylate, glass and silicon dioxide.
• Typical magnetic brush development process carriers include nickel, steel, iron, ferrites, and the like, and are preferred in the compositions of this invention. The carriers may be employed with or without a coating. Many of the foregoing and other typical carriers are described by L.E. Walkup, et al in U.S. Pat. No. 2,638,416 and E.N. Wise in U.S. Pat.
• the carrier materials have semiconductive to conductive properties.
• the carrier materials of this invention may be coated with any suitable insulating material.
• Typical electrostatographic carrier particle coating materials include vinyl chloride-vinyl acetate copolymers, styrene-acrylate-organosilicon terpolymers, natural resins such as caoutchouc, colophony, copal, dammar, jalap, storax; thermoplastic resins including the polyolefins such as polyethylene, polypropylene, chlorinated polyethylene, and chlorosulfonated polyethylene; polyvinyls and polyvinylidenes such as polystyrene, poly- methylstyrene, polymethyl methacrylate, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ethers, and polyvinyl ketones; fluoride-vinyl acetate copo
• any suitable electrostatographic carrier coating thickness may be employed.
• a carrier coating having a thickness of at least sufficient to form a thin film on the carrier particle 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.
• the carrier coating may canprise from about 0.1 percent to about 10.0 percent by weight based on the weight of the coated carrier particles.
• the carrier coating should comprise from about 0.3 percent to about 1.5 percent by weight based on the weight of the coated carrier particles because maximum durability, toner impaction resistance, and copy quality are achieved.
• additives such as plasticizers, reactive and non-reactive polymers, dyes, pigments, wetting agents and mixtures thereof may be mixed with the coating materials and the coating may be continuous or discontinuous.
• the carrier coating composition may be applied to the carrier cores by any conventional method such as spraying, dipping, fluidized bed coating, tumbling, brushing, and the like.
• the coating compositions may be applied as a powder, a dispersion, solution, emulsion or hot melt.
• 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 subsequent to application of the coating to the carrier cores.
• the coating may comprise resin monomers which are polymerized in situ on the surface of the cores or plastisols gelled in situ to a non-flowable state on the surface of the cores.
• any suitable organic or inorganic photoconductive material may be employed as the recording surface with the developer materials of this invention.
• Typical inorganic photoconductor materials include: sulfur, selenium, zinc sulfide, zinc oxide, zinc cadmium sulfide, zinc magnesium oxide, cadmium selenide, zinc ⁇ silicate, calcium strontium sulfide, cadmium sulfide, mercuric iodide, mercuric oxide, mercuric sulfide, indium trisulfide, gallium selenide, arsenic disulfide, arsenic trisulfide, arsenic triselenide, antimony trisulfide, cadmium sulfo- selenide and mixtures thereof.
• Typical organic photoconductors include: quinacridone pigments, phthalocyanine pigments, triphenylamine, 2,4-bis(4,4'-diethylamino-phenol)-1,3,4-oxadiazol, N-isopropylcarbazole, triphenylpyrrole, 4,5-diphenylimidazolidinone, 4,5-diphenyl-imidazolidin- ethione, 4,5-bis(4' -amino-phenyl)-imidazolidinone, 1,5-dicyanonaphthalene, 1,4-dicyanonapthalene, aminophthalodinitrile, nitrophthalodinitrile, 1,2,5,6-tetraazacyclooctatetracene-(2,4,6,8), 2-mercaptobenzothiazole-2-phenyl-4-bisphenylideneoxazolone, 6-hydroxy-2,3-di(p-methoxyphenyl)-benzofurane, 4-di
• photoconductive materials include U.S. Pat. No. 2,803,542 to Ullrich, U.S. Pat. No. 2,970,906 to Bixby, U.S. Pat. No. 3,121,006 to Middleton, and U.S. Pat. No. 3,151,982 to Corrsin.
• a control developer mixture is prepared by mixing a toner composition comprising a mixture of about 90 parts by weight of a copolymer of about 58.0 percent by weight of styrene and about 42.0 percent by weight of n-butyl methacrylate, and about 10 parts by weight of a furnace carbon black with carrier particles.
• the toner particles were determined to have a particle size of between 8 and 30 microns.
• the carrier particles comprised 100 micron nickel-zinc ferrite coated with about 0.6 percent by weight, based on the weight of the core material, of a carrier coating composition comprising styrene, a methacrylate ester, and an organosilicon compound as disclosed in U.S. Pat. No. 3,526,533.
• the coated ferrite carrier material was determined to have a specific surface area of about 151 cm 2 /gram.
• a developer mixture was prepared by mixing about 3 parts of the toner material employed in Example I with about 100 parts of carrier material except that the toner particles were selected to have a particle size of between about 3 and 10 microns.
• the carrier particles were selected to comprise 35 micron nickel powder.
• the nickel powder was determined to have a specific surface area of about 450cm 2 /gram.
• the developer mixture was used to develop an electrostatic latent image under substantially the same'conditions as in Example I.
• I-c was found that the developer mixture performed satisfactorily up to about 300,000 copies after which the test was suspended. No photoreceptor filming was observed as print-out on the copies. The rate of toner impaction was insignificant and not measurable using existing techniques.
• the copies produced contained images free of blur and edge acuity was excellent. Grey scale and half-tone reproduction quality was excellent. Copy resolution was about 10 line pairs per millimetre and no hollow characters were evident.
• a developer mixture was prepared by mixing about 3 parts by weight of a toner composition comprising a mixture of about 88.5 parts by weight of a polymeric esterification product of a dicarboxylic acid and a diol comprising a diphenol, and about 11.5 parts by weight of a carbon black as disclosed in U.S. Patent 3,590,000 with about 100 parts by weight of carrier particles.
• the toner particles were selected to have a particle size of. between 3 and 10 microns.
• the carrier particles comprised 35 micron nickel powder. By calculation, the nickel powder was determined to have a specific surface area of about 450 cm 2 / gram.
• the developer mixture was used to develop an electrostatic latent image under substantially the same conditions as in Example I. It was found that the developer mixture performed satisfactorily up to about 300,000 copies after which the test was suspended. No photoreceptor filming was observed as print-out on the copies. The rate of toner impaction was insignificant and not measurable using existing techniques.
• the copies produced contained images free of blur and edge acuity was excellent. Grey scale and half-tone reproduction quality was excellent. Copy resolution was about 10 line pairs per millimetre and no hollow characters were evident.
• a developer mixture was prepared by mixing about 3 parts of the toner material employed in Example III with about 100 parts of the carrier material employed in Example III except that about 0.65 parts by weight of submicroscopic silicon dioxide particles (Aerosil R-972) based on the weight of the toner particles as described in U.S. Patent 3,819,367 was added to the developer mixture.
• submicroscopic silicon dioxide particles Aerosil R-972
• the developer mixture was used to develop an electrostatic latent image under substantially the same conditions as in Example I. It was found that the developer mixture performed satisfactorily up to about 300,000 copies after which the test was suspended. No photoreceptor filming was observed as print-out on the copies. The rate of toner impaction was excellent and not measurable using existing techniques.
• the copies produced contained images free of blur and edge acuity was excellent. Grey scale and half-tone reproduction quality was excellent. Copy resolution was about 10 line pairs per millimetre and no hollow characters were evident.
• a developer mixture was prepared as in Example IV except that about 0.35 parts by weight of zinc stearate based on the weight of the toner particles as described in U.S. Patent 3,590,000 was added to the developer mixture.
• the developer mixture was used to develop an electrostatic latent image under substantially the same conditions as in Example I. It was found that the developer mixture performed satisfactorily up to about 300,000 copies after which the test was suspended. No photoreceptor filming was observed as print-out on the copies. The rate of toner impaction was insignificant and was not measurable using existing techniques.
• the copies produced contained images free of blur and edge acuity was excellent. Grey scale and half-tone reproduction quality was excellent. Copy resolution was about 10 line pairs per millimetre and no hollow characters were evident.
• a developer mixture was prepared by mixing about 3 parts by weight of a toner composition comprising a mixture of about 80 parts by weight of styrene, about 20 parts by weight of isobutyl methacrylate, and about 10 parts by weight of a carbon black with about 100 parts by weight of carrier particles.
• the toner particles were determined to have a particle size of between 3 and 10 microns.
• the carrier particles comprised 35 micron nickel powder.
• the developer mixture was used to develop an electrostatic latent image under substantially the same conditions as in Example 1. It was found that the developer mixture performed satisfactorily up to about 300,000 copies after which the test was suspended. No photoreceptor filming was observed as print-out on the copies. The rate of toner impaction was insignificant and not measurable using existing techniques.
• the copies produced contained images free of blur and edge acuity was excellent. Grey scale and half-tone reproduction quality was excellent. Copy resolution was about 10 line pairs per millimetre and no hollow characters were evident.
• a developer mixture was prepared by mixing about 3 parts by weight of a toner composition comprising a mixture of about 80 parts by weight of styrene, about 20 parts by weight of isobutyl methacrylate, about 15 parts by weight of diphenyl isophthalate, and about 10 parts by weight of a carbon black with about 100 parts by weight of carrier particles.
• the toner particles were determined to have a particle size of between 3 and 10 microns.
• the carrier particles comprised 35 micron nickel powder.
• the developer mixture was used to develop an electrostatic latent image under substantially the same conditions as in Example I. It was found that the developer mixture performed satisfactorily up to about 300,000 copies after which the test was suspended. No photoreceptor filming was observed as print-out on the copies. The rate of toner impaction was insignificant and not measurable using existing techniques.
• the copies produced contained images free of blur and edge acuity was excellent. Grey scale and half-tone reproduction quality was excellent. Copy resolution was about 10 line pairs per millimetre and no hollow characters were evident.
• the developer materials of this invention are characterized as providing substantially improved copy quality in the development of electrostatic latent images. It is believed that developed image resolution is improved due to the toner particle size range. The improved edge acuity is believed to result from less edge raking by the smaller carrier particles in the present developer mixtures. The reduced mottle appearance and absence of hollow characters of copied images obtained appears to result from more uniform latent image development and image transfer due to more uniform triboelectric charge of the developer materials. Improved grey scale and half-tone reproduction obtained with the developer materials of this invention appears to be due to the high developability of these smaller toner particles and the virtual electrode effect at the photoreceptor surface of the smaller conductive carrier particles.
• developer materials of this invention are further characterized as resulting in improved machine performance with longer systems life, that is, these developer materials provide substantially improved triboelectric charging properties of the developer mixtures for substantially longer periods of time thereby increasing the developer life of the developer mixtures and decreasing the time intervals between replacement of the developer materials.
• the developer materials of this invention may be characterized as providing dense images and are particularly useful in magnetic brush development systems.
• the developer materials of this invention may be further characterized as experiencing substantially reduced impaction rates resulting in more stable triboelectric charging properties of the developer mixtures for substantially longer periods of time thereby increasing the developer life of the developer mixtures and decreasing the time intervals between replacement of the developer materials.
• developer material and "developer mixture” as employed herein are intended to include toner material or combinations of toner material and carrier material.

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• 1979
  • 1979-02-28 CA CA000322602A patent/CA1147192A/fr not_active Expired
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