EP0050987B1 - One part toner powder composition - Google Patents

One part toner powder composition Download PDF

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Publication number
EP0050987B1
EP0050987B1 EP81305059A EP81305059A EP0050987B1 EP 0050987 B1 EP0050987 B1 EP 0050987B1 EP 81305059 A EP81305059 A EP 81305059A EP 81305059 A EP81305059 A EP 81305059A EP 0050987 B1 EP0050987 B1 EP 0050987B1
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EP
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Prior art keywords
particles
weight
parts
toner powder
toner
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EP81305059A
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German (de)
French (fr)
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EP0050987A1 (en
Inventor
Jan P. Roos
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3M Co
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Minnesota Mining and Manufacturing Co
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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
    • G03G9/097—Plasticisers; Charge controlling agents
    • G03G9/09733—Organic compounds
    • G03G9/09766—Organic compounds comprising fluorine

Definitions

  • This invention relates to dry powder compositions suitable for use in electrographic recording. More particularly, it relates to heat-fusible and pressure-fixable one part toner powders that have a surface treatment comprising a fluoroaliphatic compound attached to the surface of the individual toner powder particles.
  • One-part toner powder formulations (sometimes known as single- or mono-component toners) are known. They differ from two-part or two component developing powders in that they do not utilize a mixture of carrier particles and toner powder particles to make up the developing powder composition. Rather, one-part toner powders are magnetically responsive and do not utilize a carrier to develop the electrostatic image.
  • One-part toner powders may be either heat-fusible or pressure-fixable.
  • Heat-fusible toner powders are typically fixed after image formation by raising the temperature of the powders to their melting or softening point causing the powder particles to coalesce, flow together and adhere to the substrate.
  • Pressure-fixable toner powders are typically fixed after image formation by simply applying pressure to the powder particles causing them to coalesce and adhere to the substrate.
  • the flow properties and developing characteristics of such one-part toner powders are often adversely affected by conditions of high humidity. Thus, they may resist flow, e.g. by caking or forming clumps, resulting in streaking on the finished copy. Such caking or clumping may also cause clogging in the development station leading to poor development and transfer of the toner powder and, consequently, poor copy quality.
  • U.S. Patent No. 3,798,167 discloses the application of a coating of a fluoropolymer, or optionally, a mixture of a fluoropolymer and a modifying resin, to a carrier material.
  • U.S. Patent No. 4,002,570 discloses a three component developer composition that comprises carrier particles, toner particles, and a lubricant comprising a particulate, cross-linked polyvinylidene fluoride. The polyvinylidene fluoride particles are said to lubricate and act as effective photoreceptor cleaning materials.
  • U.S. Patent No. 4,073,980 discloses a two component developing composition wherein the carrier particles have a mixture of a perfluoroacid and molybdenum disulfide coated on their surface.
  • U.S. Patent Nos. 4,139,483 and 4,198,477 disclose two-part developer compositions wherein a fluorinated surface active additive is dispersed throughout, rather than coated on, the binder of the toner portion of the composition.
  • European Patent Publication No. 37,297 discloses the formation of toner powder in which thermoplastic resin and titanate are heated to obtain a melted mixture. Magnetic powder is dispersed in the mixture and the melted mixture solidified and ground into particles. A small quantity of polytetrafluoroethylene (PTFE) resin is added to the powder but the mixture is never subjected to any processing which would cause the PTFE to adhere even slightly to the magnetic powder.
  • PTFE polytetrafluoroethylene
  • thermoplastic binder thermoplastic binder, magnetically responsive material, and a fluoroaliphatic compound containing, within a single molecule, both a fluoroaliphatic group and a group which is attracted to said thermoplastic binder, in which
  • the toner powder of the present invention produces final images with sharply defined edges, substantially reduced “fuzzy fill-in”, and substantially reduced background, even in the areas between images.
  • the most preferred toner of the invention virtually eliminates “fuzzy fill-in", and background. .
  • the toner of the invention possesses improved flow properties in high humidity conditions. Thus, it does not significantly cake or clump under such conditions and the images produced therefrom have sharp edge definition, exhibit reduced "fuzzy-fill-in", and reduced background.
  • the toner powder of the invention tends to be less sensitive to changes in the size of the developing gap utilized than are the previously known one-part toners.
  • This permits the use of more generous process conditions and machine tolerances, such as doctor blade gap, may be relaxed.
  • the toner of the invention also permits the use of smooth surface developer rolls in place of the more expensive rough surface developer rolls.
  • the toner powder of the invention also possesses a less positive triboelectric characteristic than does a correspondingly non-surface treated toner powder. It is believed that this property accounts at least in part for the ability of the developing powder compositions of the invention to provide such high resolution images.
  • the powder of the present invention preferably comprises essentially spherical particles wherein at least 95 number percent of the particles have a maximum dimension in the range of about 4 to 30 microns.
  • the particles each comprise a blend of from about 35 to 45 parts by weight thermoplastic binder, and correspondingly, from about 65 to 55 parts by weight magnetically responsive material.
  • the particles each comprise a homogeneous blend of the binder and magnetically responsive material.
  • the surprising improvements in copy quality obtained by using the toner powder of the invention is the result of treating the surface thereof so that the treatment composition is attached to the surface of the individual particles.
  • the exact mechanism of attachment is not completely understood, it is believed that attachment is achieved by at least partially embedding the mixture into the surface of the particles to provide a layer or zone of the treatment around the particles.
  • the fluoroaliphatic compound useful as the surface treatment composition may be monomeric or polymeric and, preferably, contains in the same molecule both a fluoroaliphatic group and a group which may contain an aliphatic group, an aromatic group, or both and which is attracted to the thermoplastic binder used in the toner powder of the invention.
  • the particular structure of the fluoroaliphatic compound is not critical to the invention.
  • the preferred fluoroaliphatic compound may be represented as R f Q m Z where R f is a fluoroaliphatic group, Q m is a linking group, and Z is a terminal group.
  • the fluoroaliphatic group may be generally described as a fluorinated, monovalent, non-aromatic group of at least 3 carbon atoms.
  • the aliphatic chain may be saturated, unsaturated, straight, branched, or, if sufficiently large, cyclic and may include oxygen or trivalent nitrogen atoms bonded only to carbon atoms.
  • a fully fluorinated group is preferred, but hydrogen or chlorine atoms may be present as substituents provided that not more than one atom of either is present for every two carbon atoms, and preferably, the group contains at least a terminal perfluoromethyl group.
  • fluoroaliphatic groups containing a larger number of carbon atoms will function adequately, those containing not more than about 20 carbon atoms are preferred since larger groups usually represent a less efficient utilization of fluorine than is possible with shorter chains. Fluoroaliphatic groups containing about 5 to 12 carbon atoms are most preferred.
  • linking group Q m is an integer from 0 to 2
  • Q represents a direct bond between R f and Z when m is zero, or a multifunctional, generally difunctional, linking group such as alkylene, arylene, sulfonamido alkylene, carbonamido alkylene and the like.
  • more than one R, group may attach to a single Q group and in other instances, a single R f group may be linked to more than one Q group, or may be linked by a single Q group to more than one Z group.
  • the Z group represents an anionic, a cationic, a non-ionic or an ampholytic moiety or combinations thereof.
  • Typical anionic groups would include -C0 2 M, -S0 2 M, -S0 3 M, -OPOOM, and -OP(OM) 2 , where M is hydrogen or a metallic ion, such as sodium, potassium, calcium, etc.
  • Typical cationic groups would include -NH 2 , -NHR, where R is a lower alkyl group such as methyl, ethyl or butyl, -NR3°A°, where R' is a lower alkyl group or hydrogen and A is an anion, such as iodide, chloride, sulphate, phosphate, hydride, etc.
  • Typical non-ionic groups would include ⁇ NR 2 ⁇ 0 and those derived from polyethylene oxide and mixed polyethylene oxide-polypropylene oxide polyols.
  • Typical mixed or ampholytic groups would include ⁇ N(C 2 H 4 OH) 2 , ⁇ NHC 2 H 4 NHC 2 H 4 NH 2 , ⁇ N(CH 3 ) 2 C 2 H 4 CO 2 , ⁇ N(CH 3 )(C 2 H 4 CO 2 H) 2 ⁇ 0, and the like.
  • Polymeric fluoroaliphatic compounds are also useful in the invention.
  • Fluoroaliphatic compounds and methods for their preparation are further described in, for example, United States Patents, 2,559,751; 2,559,749; 2,559,754; 2,559,629; 2,597,702; 2,732,398; 2,759,019; 2,803,615; 2,809,999; 2,915,554; 3,129,254; 3,282,905; 3,398,182; 3,911,056; 4,171,282; British Specifications 1,270,662; 1,130,822; and Organic Fluorine Chemistry, Milas Hudlicky, Plenum Press, N.Y. (1971).
  • the fluoroaliphatic compound is preferably blended with one or more other ingredients before being applied to the surface of the particles.
  • the surface treatment may further comprise from about 0.1 to 2.5, preferably 0.5 to 2.5, parts by weight silicon dioxide per 100 parts by weight particles; from about 0.1 to 2, preferably 0.5 to 1, parts by weight carbon per 100 parts by weight particles; or both.
  • the treatment composition comprises a mixture of said fluoroaliphatic compound, said silicon dioxide, and said carbon.
  • the treatment composition preferably comprises from about 0.5 to 1 part by weight silicon dioxide, 0.4 to 0.7 part by weight fluoroaliphatic compound, and 0.7 to 0.8 part by weight carbon per 100 parts by weight particles when heat-fusing toners are made; and from about 1 to 2.5 parts by weight silicon dioxide, 0.6 to 1.2 parts by weight fluoroaliphatic compound, and 0.7 to 0.8 part by weight carbon per 100 parts by weight particles when pressure-fixing toners are made.
  • the silicon dioxide useful in the surface treatment comprises a powder having an average particle size (i.e., average diameter) smaller than that of the toner powder particles but whose exact size is otherwise not critical to the invention.
  • the silicon dioxide is a pyrogenic silica in the form of spherical particles having an average diameter in the range of 5 to 50 pm (millimicrons) (most preferably in the range of 10 to 20 pm).
  • Silicon dioxide particles per se are known and may be prepared by, for example, the hydrolysis of silicon tetrachloride in an oxygen-hydrogen flame. Pyrogenic silicon dioxide is hydrophilic as prepared. However, it can be rendered hydrophobic, if desired, by reacting the silanol groups on the particle surface with chlorosilane.
  • silicon dioxides examples include "Aerosil@” 200 (a hydrophilic, pyrogenic, white fluffy powder, 99.8% Si0 2 , average primary particle size of 12 nm (millimicron), bulk density of 200 m 2 /g, and BET surface area of 200 ⁇ 25 m 2 /G), and "Aerosil@” R972 (a hydrophobic, pyrogenic, white fluffy powder, 98.3% Si0 2 , average primary particle size of 16 millimicron, bulk density of 60 g/l, and BET surface area of 120 ⁇ 20 m 2 /g). These materials are available from Degussa, Incorporated.
  • the carbon useful in the surface treatment is also a powder whose average particle size (i.e., average diameter) is smaller than that of the toner powder particles but whose exact size is otherwise not critical to the invention.
  • Particularly useful carbons have an average diameter below about 100 nm and preferably one below about 40 nm. It is also preferred that the carbon be conductive, i.e., that it have a static electrical conductivity of at least 10- 2 reciprocal ohm-cm in a 10,000 v/cm electrical field. Static electrical conductivity may be measured as described in U.S. Patent 3,639,245 at column 3, line 47 - column 6, line 46.
  • Examples of useful carbon materials include carbon blacks such as "Vulcan” XC-72R, a conductive carbon black with a maximum particle size of 30 nm sold by Cabot Corporation; “Conductex” 950, maximum particle size of 21 nm sold by Cities Service; “Raven” 1800, maximum particle size of 18 nm sold by Columbia Chemicals; “Ketjenblack” EC sold by Noury; and “Thermax” MT sold by R. T. Vanderbilt.
  • carbon blacks such as "Vulcan” XC-72R, a conductive carbon black with a maximum particle size of 30 nm sold by Cabot Corporation; “Conductex” 950, maximum particle size of 21 nm sold by Cities Service; “Raven” 1800, maximum particle size of 18 nm sold by Columbia Chemicals; “Ketjenblack” EC sold by Noury; and “Thermax” MT sold by R. T. Vanderbilt.
  • the resulting toner powder preferably has a dynamic conductivity in the range of 2-15 (most preferably 6-9) microamperes (uA) in an electric field of 1,000 D.C. volts.
  • the dynamic conductivity referred to here is measured according to the technique described hereinafter.
  • thermoplastic binder useful in the present invention may be any thermoplastic material although organic materials are preferred. Most preferably the binder is selected from the group consisting of (a) waxes that have a melting point in the range of 45°C to 150°C as measured according to ASTM:D-127, (b) organic resins that have a ring and ball softening point above about 60°C as measured according to ASTM:E-128, and mixtures of the two.
  • Waxes useful in the binder include aliphatic waxes (e.g. natural or synthetic), fatty acids and derivatives thereof, metal salts of fatty acids, hydroxylated fatty acids or amides, low molecular weight ethylene homopolymers, or mixtures of such materials.
  • Other useful waxes include aromatic and polymeric wax-like materials.
  • useful aliphatic waxes include paraffin wax, microcrystalline wax, caranauba wax, montan wax, ouricury wax, ceresin wax, candellila wax, and sugar cane wax.
  • useful fatty acids include stearic acid, palmitic acid, and behenic acid.
  • useful metal salts of fatty acids include aluminum stearate, lead stearate, barium stearate, magnesium stearate, zinc stearate, lithium stearate, and zinc palmitate.
  • useful fatty acid derivatives include castor wax (glyceryl tris-12-hydroxy stearate), methyl hydroxystearate (commercially available under the trade name “Paracin 1 "), ethylene glycol monohydroxy stearate (commercially available under the trade name “Paracin 15”), and hydroxystearic acid.
  • useful hydroxylated fatty acids or amides include N(betahydroxyethyl)ricinole- amide (commercially available under the trade name “Flexricin 115”), N,N'ethylene-bis-ricinoleamide (commercially available under the trade name “Flexricin 185"), N(2-hydroxylethyl)-12-hydroxystearamide (commercially available under the trade name “Paracin 220”), and N,N'-ethylene-bis-12-hydroxy- stearamide (commercially available under the trade name "Paracin 285").
  • N(betahydroxyethyl)ricinole- amide commercially available under the trade name "Flexricin 115"
  • N,N'ethylene-bis-ricinoleamide commercially available under the trade name "Flexricin 185"
  • N(2-hydroxylethyl)-12-hydroxystearamide commercially available under the trade name "Paracin 220”
  • ethylene homopolymers include the low molecular weight polyethylenes such as the Bareco "Polywaxes", e.g., “Polywax” 655, 1000, and 2000 sold by the Bareco Division of Petrolite Corporation.
  • Other ethylene homopolymers include oxidized, high density, low molecular weight polyethylenes such as “Polywax” E-2018 and E-2020 sold by Bareco Division of Petrolite Corporation, and the "Epolene” series of low molecular weight polyethylene resins such as "Epolene” E-14 available from Eastman Chemical Products Incorporated.
  • useful aromatic wax-like materials include dicyclo- hexylphthalate, diphenylphthalate and the "Be Square” series of waxes from the Bareco Division of Petrolite Corporation, such as “Be Square” 195.
  • the "Be Square” waxes are high melting point waxes that consist of paraffins and naphthenic hydrocarbons.
  • thermoplastic binder examples include polyamides, polystyrenes (e.g., 2000 mol. wt.); epoxy resins (e.g., diglycidyl ether of bisphenol-A such as "Epon” 1004, commercially available from Shell Chemical Corp); acrylic resins (e.g., "Elvacite” 2044, and N-butyl methacrylate commercially available from E. I.
  • vinyl resins such as polyvinyl butyral (e.g., "Butvar” B72-A, commercially available from Monsanto Company), polyvinyl acetate resins (e.g., "Gelva” V-100, commercially available from Monsanto Company); vinyl copolymers such as vinyl chloride/vinyl acetate (e.g., "VYHH", commercially available from Union Carbide Corp.), ethylene/vinyl acetate copolymers; cellulose esters such as cellulose acetate butyrate (e.g., "EAB-171-25", commercially available from Eastman Chemical Products, Inc.), cellulose acetate propionate; and cellulose ethers.
  • vinyl resins such as polyvinyl butyral (e.g., "Butvar” B72-A, commercially available from Monsanto Company), polyvinyl acetate resins (e.g., "Gelva” V-100, commercially available from Monsanto Company);
  • the thermoplastic binder preferably comprises the organic resin.
  • the organic resin is an epoxy resin.
  • some wax may also be incorporated into the binder of a heat-fusible toner powder. The wax is added to reduce the temperature necessary to achieve satisfactory fusing of the toner to a desired surface.
  • the weight ratio of the organic resin to the wax is between about 4:1 and 20:1.
  • the thermoplastic binder comprises either the wax alone or a combination of the wax and the organic resin.
  • the weight ratio of wax to organic resin is between about 1:1 to 50:1, preferably between about 4:1 and 20:1.
  • the binder consists essentially of the wax.
  • the wax preferably is selected from microcrystalline wax, low molecular weight polyethylene resin, or a combination thereof, while the organic resin, when present, comprises an epoxy resin.
  • the magnetically responsive material employed in the developing powder composition preferably is homogeneously distributed throughout the binder. Additionally, it preferably has an average major dimension of one micron or less.
  • Representative examples of useful magnetically responsive materials include magnetite, barium ferrite, nickel zinc ferrite, chromium oxide, nickel oxide, etc.
  • binders useful for pressure-fixable toner powders are known.
  • This patent describes a binder that comprises (a) about 74 to 98 parts by volume of a thermoplastic component that has a softening point of at least about 60°C, a 10-second shear creep compliance in the range of about 1 x 10- 9 cm 2 /dyne to 1 x 10- 13 cm 2 /dyne at room temperature, and a "heat deflection temperature" below about 300°C, and (b) about 2 to 26 parts by volume of a non-volatile component having a principal glass transition temperature below about 0°C as measured by differential thermal analysis, and a 10-second shear creep compliance in the range of about 50 cm 2 /dyne to 8 x 10- 8 cm 2 /dyne at room temperature, said non-volatile component preferably being elastomeric.
  • thermoplastic components i.e., low shear creep compliance materials
  • non-volatile components i.e. high shear creep compliance materials
  • fatty acid amides containing at least about 10 carbon atoms have been found to be useful in reducing the time required to prepare the toner powders. Typically from about 0.05 to 2% by weight of the fatty acid amide is satisfactory.
  • useful fatty acid amides include erucamide, stearamide, behenamide, oleamide, N,N'-ethylene-bis(tall oil)amide, and N,N'-ethylene-bis-oleamide.
  • the developing powders of the invention may be readily prepared.
  • a dry blend of the thermoplastic binder and the magnetically responsive material is obtained by meling the thermoplastic binder, stirring in the magnetically responsive material, preferably until a homogeneous mixture is provided, allowing the mixture to cool, grinding the mixture to form particles, and classifying the resulting solid particles to the desired size (i.e., 1 to 40 pm maximum dimension).
  • the particles which are irregularly shaped, are then preferably formed into "prespheres" by first aspirating them into a moving gas stream, preferably air, thus creating an aerosol, and directing the aerosol at an angle of about 90° ⁇ 5° through a stream of gas, again preferably air, which has been heated to about 450°C and 600°C into a cooling chamber where the now substantially spherical particles settle by gravity as they cool.
  • a moving gas stream preferably air
  • the surface treatment composition is then applied to the "prespheres".
  • the treatment composition contains ingredients (e.g., silicon dioxide and/or carbon) other than the fluoroaliphatic compound
  • a mixture of the ingredients is first prepared by charging them to, for example, a "Waring" blender and mixing for about one-half hour at a medium speed. The resulting preferably homogeneous mixture is fluffy and black.
  • the prespheres and surface treatment composition are then each added to a blender (e.g., a twin shell blender from "Patterson Kelly") and cold blended a temperature less than the softening point of the thermoplastic binder (e.g., 20-30°C) until the surface treatment is at least loosely adhered to the prespheres. Typically this is accomplished within three hours.
  • a blender e.g., a twin shell blender from "Patterson Kelly
  • the prespheres may be cold blended with one of the above disclosed fatty acid amides before treating the prespheres with the surface treatment composition.
  • the treated prespheres are then "hot” blended at about the glass transition temperature of the thermoplastic binder for a time sufficient to substantially permanently attach the treatment composition to the particles. This is typically accomplished in from two to six hours.
  • the surface treatment composition is attached as a layer or zone at or near the surface of the prespheres.
  • the resultant toner powder is cooled for about one half hour, screened to remove agglomerates, and classified so that 95% by weight of the product is greater than 4 pm average diameter and only 5% by weight is greater than 30 ⁇ m average diameter.
  • the toner powder of the invention is useful in electrographic recording processes where a differential image pattern of the toner is formed and subsequently fixed by means of pressure, heat, or heat and pressure.
  • the differential image pattern may be formed by, for example, forming electrostatic image areas on a photoconductive surface and contacting the image areas with the toner.
  • the differential image pattern may be formed by contacting a passive dielectric surface with the toner; forming the image pattern by, for example, selectively exposing the uniformly toned surface to a stylus which imagewise transmits an electrical potential signal; and magnetically removing toner from uncharged areas. See U.S. Patent 3,816,840 for further description of this process.
  • the toned image areas may be transferred to another surface prior to fixing.
  • This property simulates the electrical conductivity of a toner powder when used in an electrostatic copying process.
  • Dynamic conductivity is measured on a test rig that comprises the developing station of a "Secretary III" photocopier (available from the 3M Company) except that the photoconductor drum is replaced by an aluminum drum (12.5 cm dia).
  • the developer roll comprises a stainless steel shell (3.15 cm dia) around an 8 pole circular magnet.
  • a doctor blade, a toner hopper, and a 1000 volt power supply are also supplied.
  • the gap between the developer roll and the aluminum drum is set at 0.071 cm; the gap between the doctor blade and the toner hopper at 0.05 cm; and the gap between the toner hopper and the developer roll at 0.125 cm.
  • test rig To measure conductivity, 16 ml of toner is charged to the hopper, and the test rig is started so that the developer roll and the aluminum drum are driven in opposing directions with the developer roll having a surface speed of 61.3 cm/sec and the aluminum drum having a surface speed of 19.5 cm/sec. The test rig is then run for five minutes after which the current passing through toner is measured while the toner is in the development gap and under a 1000 volt potential.
  • This property illustrates the optical output density of an image produced from an original having an optical input density of one.
  • D max is at least one.
  • D max is measured by determining the diffuse reflection optical density of the image using a conventional diffuse reflection densitometer (e.g., MacBeth Quanta-Log Diffuse Reflection Densitometer, Model RD-100). The optical density reading is taken as the D max for the toner powder being tested.
  • a conventional diffuse reflection densitometer e.g., MacBeth Quanta-Log Diffuse Reflection Densitometer, Model RD-100.
  • This property measures the sensitivity of a toner powder to changes in the size of the development gap.
  • the density of an image produced from a given toner powder decreases as the size of the development gap increases.
  • the larger the gap the lower the resultant image density. Larger decreases indicate that the toner powder is more sensitive to such changes and, therefore, requires narrower development gaps.
  • Density decay is measured on a conventional electrographic recording device (e.g., a "Secretary III") as follows.
  • the development gap is reduced to the point at which image densities on an imaged and developed photoconductive surface vary from bands of high and low image density horizontally across said photoconductive surface.
  • the development gap is then opened by turning the adjustment means two full turns from this point. A copy is produced at this opening and its image density measured using a conventional diffuse reflection densitometer such as is set forth above.
  • the development gap is then further opened by turning the adjustment means four additional (total of six) turns from said point.
  • a copy is produced at this opening and its image density measured as described above.
  • the density decay is taken as the decrease in image density from the narrower to the wider of the two development gaps.
  • This property is a measure of a toner powder's ability to distinguish between differing image densities on an original and reproduce those differences on a copy.
  • High contrast values i.e., greater than 5, indicate the toner powder's inability to distinguish and reproduce the difference between varying image densities.
  • Contrast is measured according to the following procedure. Copies of an original having a range of image densities (i.e., a step wedge) are made on an electrographic recording (e.g., a "Secretary III") machine. The output image densities are measured as described above in the D max test and plotted against the tog io of the input image densities. The log 10 of the input densities are plotted as the horizontal axis and the output densities are plotted as the vertical axis. The contrast (gamma) is taken as the slope of the straight line portion of the plot.
  • a series of examples of heat fusible toner powders were prepared. In the examples, 95% by weight of the toner powders were greater than 5 ⁇ m average diameter and only 5% by weight were greater than 22 11m average diameter. Examples 1-15 were examples of the invention while Example 16 was a toner powder that was not surface treated.
  • the prespheres were prepared as described above from 40 parts epoxy resin ("Epon" 1004 from Shell Chemical Company) and 60 parts magnetite. Examples 1-14 the prespheres were separately surface treated as described above using different treatment compositions. In example 15 the surface treatment composition was cold blended with the prespheres for 15 hours prior to hot blending.
  • the non-surface treated toner powder (Example 16) was prepared by combining 100 parts of the prespheres with 0.6 parts of conductive carbon black (Vulcan XC-72R from the Cabot Corporation) to form a mixture. The mixture was dry blended at room temperature for 3 hours and then hot blended at 65°C for about 8 hours. The carbon was then embedded into the prespheres as a layer or zone at or near the surface thereof by drawing the particles of the mixture into an air stream at a rate of 36 kg/h to form an aerosol; directing the aerosol at 90 ⁇ 5°C into a hot (650°C) air stream; allowing the powder to settle; and collecting the powder by filtration. About 0.05% by weight Si0 2 ("Aerosil" 972, Degussa, Incorporated) was blended with the toner as a separate component to aid its flow properties.
  • the powders were then used in a heat-fusing copying process in a "Secretary III" copying machine (available from the 3M Company) to provide images on plain paper substrates.
  • the exposure voltages are reported in Table 1.
  • the bias voltage was set at -200 DC volts.
  • the toner powders of the invention i.e., those used in Examples 1-15 provided copies with images that were more sharply defined than were the images provided by the toner used in Example 16.
  • the edges of the images produced in Examples 1-15 were sharp, the openings in the images (letters) had substantially reduced "fuzzy fill-in", and the spaces between the images (background) had substantially reduced blurring caused by undesired toner deposition.
  • the toners used in Examples 1, 2, 7, and 13 produced copies having virtually no "fuzzy fill-in” and virtually no background.
  • the toners of the invention generally demonstrated less density decay than did the non-surface treated toner used in Example 16.
  • the toners of the invention generally permit the use of less stringent process conditions such as gap latitude:
  • a pressure-fixable toner powder according to the invention was prepared as described above except that the prespheres were prepared from 10 parts "Polywax” 1000 (a low molecular weight, unmodified homopolymer of ethylene having a Mw/Mm of 1.2 from Bareco Division of Petrolite Corporation), 30 parts “Epolene” E-14 (an emulsifiable low molecular weight polyethylene resin from Eastman Chemical Products, Incorporated), and 60 parts Magnetite.
  • the prespheres were surface treated as described above with a treatment composition comprising 0.6 parts “Vulcan” XC-72R, 2.4 parts “Aerosil” 200, and 1.2 parts C 8 F 17 SO 2 N(C 2 H 5 )CH 2 COOH.
  • the resulting toner powder was used in a cold (room temperature) pressure-fixing copying process to provide images on a plain paper substrate.
  • the exposure voltage was 82 volts.
  • the images on the copies produced were sharp, the openings in the images had virtually no "fuzzy fill-in", and there was virtually no background.
  • the toner powder had a dynamic conductivity of 5.3 A/10 3 V, a Dmax of 1.47, and a contrast (gamma) of 4.3.
  • a heat-fusible toner powder according to the invention was prepared as described in Examples 1-14 utilizing the following surface treatment composition:
  • the resulting toner powder was used in a heat-fusing copying process in a "Secretary" III copying machine to provide images on plain paper substrates.
  • the exposure voltage was 75 volts and the bias voltage was 200 volts.
  • the images on the resultant copy were sharply defined, had virtually no "fuzzy fill-in", and the copy had virtually no background. Additionally, the toner powder had a dynamic conductivity of 9.5 A/10 3 V and produced images having a D max of 0.62 and a contrast of 0.65. While the D max and contrast values of this example are low, it still demonstrates improved edge sharpness, "fuzzy fill-in" and background.
  • a heat fusible toner according to the invention was prepared as described in Examples 1-14 except that the surface treatment composition was prepared by the following procedure.
  • a dispersion of a polymeric fluoroaliphatic compound in solvent was provided.
  • Sufficient methyl alcohol was added to the dispersion to precipitate the polymer.
  • the polymer was dried in a vacuum oven.
  • the fluoroaliphatic compound was then ground with a mortar and pestle to reduce it to a relatively fine powder.
  • the surface treatment was then prepared as described above by combining 0.6 part fluorochemical, 0.8 part "Aerosil” 200, and 0.7 part “Vulcan” XC-72R.
  • the resulting toner powder was used in a heat-fusing copying process in a "Secretary" III copying machine to provide images on plain paper substrate.
  • the exposure voltage was 78 volts and the bias voltage was 200 volts.
  • the images on the resultant copy were sharply defined, had virtually no "fuzzy fill-in", and the copy had virtually no background. Additionally, the toner powder had a dynamic conductivity of 8 pA/10 3 V and produced images having a D max of 0.98 and a contrast of 1.53.

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Description

  • This invention relates to dry powder compositions suitable for use in electrographic recording. More particularly, it relates to heat-fusible and pressure-fixable one part toner powders that have a surface treatment comprising a fluoroaliphatic compound attached to the surface of the individual toner powder particles.
  • One-part toner powder formulations (sometimes known as single- or mono-component toners) are known. They differ from two-part or two component developing powders in that they do not utilize a mixture of carrier particles and toner powder particles to make up the developing powder composition. Rather, one-part toner powders are magnetically responsive and do not utilize a carrier to develop the electrostatic image.
  • One-part toner powders may be either heat-fusible or pressure-fixable. Heat-fusible toner powders are typically fixed after image formation by raising the temperature of the powders to their melting or softening point causing the powder particles to coalesce, flow together and adhere to the substrate. Pressure-fixable toner powders are typically fixed after image formation by simply applying pressure to the powder particles causing them to coalesce and adhere to the substrate.
  • Although both heat-fusible and pressure-fixable toner powders have been widely used and have enjoyed commercial success, they often suffer from certain disadvantages. For example, the images produced with such powders generally have poor resolution. Thus, they lack sharp edge definition and openings in the images, such as in the letters A, a, B, b, D, d, and O, suffer from "fuzzy-fill-in" (i.e., there is a significant toner deposited in such openings thereby rendering them indistinct). Additionally, there is substantial deposition of toner in non-image areas, i.e. background, particularly the areas between letters. Consequently, the resultant photocopies are messy in appearance and frequently are difficult to read.
  • Additionally, the flow properties and developing characteristics of such one-part toner powders are often adversely affected by conditions of high humidity. Thus, they may resist flow, e.g. by caking or forming clumps, resulting in streaking on the finished copy. Such caking or clumping may also cause clogging in the development station leading to poor development and transfer of the toner powder and, consequently, poor copy quality.
  • The foregoing disadvantages are overcome in the present invention by surface treating the toner powder particles with a composition comprising a fluoroaliphatic compound.
  • Although the use of fluorochemical materials has been disclosed previously, see U.S. Patents 3,798,167; 4,002,570; 4,073,980; 4,139,483; 4,198,477; British Patent No. 2,034,907; copending U.S. Application Serial No. 84,607 filed October 15, 1979 and now U.S. Patent No. 4,268,598; and European Patent Publication No. 37,297, applicant is aware of no disclosure of the use of a treatment composition comprising a fluoroaliphatic compound as a surface treatment for a one-part toner powder such that the fluoroaliphatic compound is essentially permanently attached at or near the surface of the particles.
  • Of the above-mentioned patents, all except the British Patent, the copending United States Application and the European Patent Publication disclose the use of fluorochemical materials with two component developing powder compositions. For example, U.S. Patent No. 3,798,167 discloses the application of a coating of a fluoropolymer, or optionally, a mixture of a fluoropolymer and a modifying resin, to a carrier material. U.S. Patent No. 4,002,570 discloses a three component developer composition that comprises carrier particles, toner particles, and a lubricant comprising a particulate, cross-linked polyvinylidene fluoride. The polyvinylidene fluoride particles are said to lubricate and act as effective photoreceptor cleaning materials. U.S. Patent No. 4,073,980 discloses a two component developing composition wherein the carrier particles have a mixture of a perfluoroacid and molybdenum disulfide coated on their surface. U.S. Patent Nos. 4,139,483 and 4,198,477 disclose two-part developer compositions wherein a fluorinated surface active additive is dispersed throughout, rather than coated on, the binder of the toner portion of the composition.
  • Fluorochemical materials have also been previously utilized with one-part toner powders. Thus, British Patent No. 2,034,907A (published June 11, 1980) discloses a toner powder having a magnetic material distributed throughout a binder resin. A low molecular weight fluorine-containing surface active agent is applied to the surface of the magnetic material before the magnetic material is distributed throughout the binder.
  • Copending U.S. Application No. 84,607, filed October 15, 1979, now U.S. Patent No. 4,268,698 describes a mixture of a sulfonamido surface active material and a toner powder. The resultant mixture has two discrete components, i.e. the surface active material and the toner powder.
  • European Patent Publication No. 37,297 discloses the formation of toner powder in which thermoplastic resin and titanate are heated to obtain a melted mixture. Magnetic powder is dispersed in the mixture and the melted mixture solidified and ground into particles. A small quantity of polytetrafluoroethylene (PTFE) resin is added to the powder but the mixture is never subjected to any processing which would cause the PTFE to adhere even slightly to the magnetic powder.
  • According to the present invention there is provided a one-part, flowable, dry, electrostatically attractable toner powder comprising thermoplastic binder, magnetically responsive material, and a fluoroaliphatic compound containing, within a single molecule, both a fluoroaliphatic group and a group which is attracted to said thermoplastic binder, in which
    • (a) the particles each comprise a blend of from 30 to 80 parts by weight thermoplastic binder and, correspondingly from 70 to 20 parts by weight magnetically responsive material, and
    • (b) a layer of the fluoroaliphatic compound essentially permanently attached to each of said particles at or near the outer surface of said particles, said fluoroaliphatic compound comprising from 0.1 to 2 parts by weight per 100 parts by weight of said particles.
  • The toner powder of the present invention produces final images with sharply defined edges, substantially reduced "fuzzy fill-in", and substantially reduced background, even in the areas between images. The most preferred toner of the invention virtually eliminates "fuzzy fill-in", and background. . Additionally, the toner of the invention possesses improved flow properties in high humidity conditions. Thus, it does not significantly cake or clump under such conditions and the images produced therefrom have sharp edge definition, exhibit reduced "fuzzy-fill-in", and reduced background.
  • Still further, the toner powder of the invention tends to be less sensitive to changes in the size of the developing gap utilized than are the previously known one-part toners. Thus, there generally is less decrease in image density as the gap is widened with the instant toners than with such prior art toners. This permits the use of more generous process conditions and machine tolerances, such as doctor blade gap, may be relaxed. The toner of the invention also permits the use of smooth surface developer rolls in place of the more expensive rough surface developer rolls.
  • The toner powder of the invention also possesses a less positive triboelectric characteristic than does a correspondingly non-surface treated toner powder. It is believed that this property accounts at least in part for the ability of the developing powder compositions of the invention to provide such high resolution images.
    • Detailed Description of the Invention
  • The powder of the present invention preferably comprises essentially spherical particles wherein at least 95 number percent of the particles have a maximum dimension in the range of about 4 to 30 microns. Preferably the particles each comprise a blend of from about 35 to 45 parts by weight thermoplastic binder, and correspondingly, from about 65 to 55 parts by weight magnetically responsive material. Most preferably the particles each comprise a homogeneous blend of the binder and magnetically responsive material.
  • The surprising improvements in copy quality obtained by using the toner powder of the invention is the result of treating the surface thereof so that the treatment composition is attached to the surface of the individual particles. Although the exact mechanism of attachment is not completely understood, it is believed that attachment is achieved by at least partially embedding the mixture into the surface of the particles to provide a layer or zone of the treatment around the particles.
  • The fluoroaliphatic compound useful as the surface treatment composition may be monomeric or polymeric and, preferably, contains in the same molecule both a fluoroaliphatic group and a group which may contain an aliphatic group, an aromatic group, or both and which is attracted to the thermoplastic binder used in the toner powder of the invention. The particular structure of the fluoroaliphatic compound is not critical to the invention. However, the preferred fluoroaliphatic compound may be represented as RfQmZ where Rf is a fluoroaliphatic group, Qm is a linking group, and Z is a terminal group.
  • The fluoroaliphatic group, may be generally described as a fluorinated, monovalent, non-aromatic group of at least 3 carbon atoms. The aliphatic chain may be saturated, unsaturated, straight, branched, or, if sufficiently large, cyclic and may include oxygen or trivalent nitrogen atoms bonded only to carbon atoms. A fully fluorinated group is preferred, but hydrogen or chlorine atoms may be present as substituents provided that not more than one atom of either is present for every two carbon atoms, and preferably, the group contains at least a terminal perfluoromethyl group. While fluoroaliphatic groups containing a larger number of carbon atoms will function adequately, those containing not more than about 20 carbon atoms are preferred since larger groups usually represent a less efficient utilization of fluorine than is possible with shorter chains. Fluoroaliphatic groups containing about 5 to 12 carbon atoms are most preferred.
  • In the linking group Qm, m is an integer from 0 to 2, and Q represents a direct bond between Rf and Z when m is zero, or a multifunctional, generally difunctional, linking group such as alkylene, arylene, sulfonamido alkylene, carbonamido alkylene and the like. In some instances more than one R, group may attach to a single Q group and in other instances, a single Rf group may be linked to more than one Q group, or may be linked by a single Q group to more than one Z group.
  • The Z group represents an anionic, a cationic, a non-ionic or an ampholytic moiety or combinations thereof. Typical anionic groups would include -C02M, -S02M, -S03M, -OPOOM, and -OP(OM)2, where M is hydrogen or a metallic ion, such as sodium, potassium, calcium, etc. Typical cationic groups would include -NH2, -NHR, where R is a lower alkyl group such as methyl, ethyl or butyl, -NR3°A°, where R' is a lower alkyl group or hydrogen and A is an anion, such as iodide, chloride, sulphate, phosphate, hydride, etc. Typical non-ionic groups would include―NR2→ 0 and those derived from polyethylene oxide and mixed polyethylene oxide-polypropylene oxide polyols. Typical mixed or ampholytic groups would include―N(C2H4OH)2,―NHC2H4NHC2H4NH2,―N(CH3)2C2H4CO2,―N(CH3)(C2H4CO2H)2→ 0, and the like.
  • Specific examples of useful fluoroaliphatic compounds include
    Figure imgb0001
    • (C8F17SO2NHC3H6N⊕(CH3)3)I⊖
    • C8F17SO2N(CH3)H
    • C8F17SO2N(C2H5)CH2COOH
    • C8F17SO3K
    • C8F17SO2NHC2H4NHC2H4NH2
    • (C8F17SO2N(C2H5)C2H4O)2POOH
    • C8F17SO2N(C2H5)C2H4OPO(OH)2
  • Other specific examples of useful fluoroaliphatic compounds include
    Figure imgb0002
    where M is as described above, available as "MD 31" from ICI, Ltd.,
  • (CaF2a + 1C2H4O)2P(O)(ONH4), where a is an integer of from about 5-25, available as "Zonyl" FSP from E.I. duPont de Nemours), and
    Figure imgb0003
    where a and M are as described above, available as "Lodyne" S100 from Ciba-Geigy.
  • Polymeric fluoroaliphatic compounds are also useful in the invention. For example, the copolymer (95/ 5 by weight) of C8F17SO2N(C2H5)C2H5OCOC(CH3) = CH2 and butylacrylate is a useful surface treatment material.
  • Fluoroaliphatic compounds and methods for their preparation are further described in, for example, United States Patents, 2,559,751; 2,559,749; 2,559,754; 2,559,629; 2,597,702; 2,732,398; 2,759,019; 2,803,615; 2,809,999; 2,915,554; 3,129,254; 3,282,905; 3,398,182; 3,911,056; 4,171,282; British Specifications 1,270,662; 1,130,822; and Organic Fluorine Chemistry, Milas Hudlicky, Plenum Press, N.Y. (1971).
  • The fluoroaliphatic compound is preferably blended with one or more other ingredients before being applied to the surface of the particles. Thus, the surface treatment may further comprise from about 0.1 to 2.5, preferably 0.5 to 2.5, parts by weight silicon dioxide per 100 parts by weight particles; from about 0.1 to 2, preferably 0.5 to 1, parts by weight carbon per 100 parts by weight particles; or both.
  • Most preferably the treatment composition comprises a mixture of said fluoroaliphatic compound, said silicon dioxide, and said carbon. In this instance the treatment composition preferably comprises from about 0.5 to 1 part by weight silicon dioxide, 0.4 to 0.7 part by weight fluoroaliphatic compound, and 0.7 to 0.8 part by weight carbon per 100 parts by weight particles when heat-fusing toners are made; and from about 1 to 2.5 parts by weight silicon dioxide, 0.6 to 1.2 parts by weight fluoroaliphatic compound, and 0.7 to 0.8 part by weight carbon per 100 parts by weight particles when pressure-fixing toners are made.
  • The silicon dioxide useful in the surface treatment comprises a powder having an average particle size (i.e., average diameter) smaller than that of the toner powder particles but whose exact size is otherwise not critical to the invention. Preferably the silicon dioxide is a pyrogenic silica in the form of spherical particles having an average diameter in the range of 5 to 50 pm (millimicrons) (most preferably in the range of 10 to 20 pm).
  • Silicon dioxide particles per se are known and may be prepared by, for example, the hydrolysis of silicon tetrachloride in an oxygen-hydrogen flame. Pyrogenic silicon dioxide is hydrophilic as prepared. However, it can be rendered hydrophobic, if desired, by reacting the silanol groups on the particle surface with chlorosilane.
  • Examples of useful silicon dioxides include "Aerosil@" 200 (a hydrophilic, pyrogenic, white fluffy powder, 99.8% Si02, average primary particle size of 12 nm (millimicron), bulk density of 200 m2/g, and BET surface area of 200 ± 25 m2/G), and "Aerosil@" R972 (a hydrophobic, pyrogenic, white fluffy powder, 98.3% Si02, average primary particle size of 16 millimicron, bulk density of 60 g/l, and BET surface area of 120 ± 20 m2/g). These materials are available from Degussa, Incorporated.
  • The carbon useful in the surface treatment is also a powder whose average particle size (i.e., average diameter) is smaller than that of the toner powder particles but whose exact size is otherwise not critical to the invention. Particularly useful carbons have an average diameter below about 100 nm and preferably one below about 40 nm. It is also preferred that the carbon be conductive, i.e., that it have a static electrical conductivity of at least 10-2 reciprocal ohm-cm in a 10,000 v/cm electrical field. Static electrical conductivity may be measured as described in U.S. Patent 3,639,245 at column 3, line 47 - column 6, line 46.
  • Examples of useful carbon materials include carbon blacks such as "Vulcan" XC-72R, a conductive carbon black with a maximum particle size of 30 nm sold by Cabot Corporation; "Conductex" 950, maximum particle size of 21 nm sold by Cities Service; "Raven" 1800, maximum particle size of 18 nm sold by Columbia Chemicals; "Ketjenblack" EC sold by Noury; and "Thermax" MT sold by R. T. Vanderbilt.
  • When a conductive carbon is employed in the surface treatment, the resulting toner powder preferably has a dynamic conductivity in the range of 2-15 (most preferably 6-9) microamperes (uA) in an electric field of 1,000 D.C. volts. The dynamic conductivity referred to here is measured according to the technique described hereinafter.
  • The thermoplastic binder useful in the present invention may be any thermoplastic material although organic materials are preferred. Most preferably the binder is selected from the group consisting of (a) waxes that have a melting point in the range of 45°C to 150°C as measured according to ASTM:D-127, (b) organic resins that have a ring and ball softening point above about 60°C as measured according to ASTM:E-128, and mixtures of the two.
  • Waxes useful in the binder include aliphatic waxes (e.g. natural or synthetic), fatty acids and derivatives thereof, metal salts of fatty acids, hydroxylated fatty acids or amides, low molecular weight ethylene homopolymers, or mixtures of such materials. Other useful waxes include aromatic and polymeric wax-like materials.
  • Representative examples of useful aliphatic waxes include paraffin wax, microcrystalline wax, caranauba wax, montan wax, ouricury wax, ceresin wax, candellila wax, and sugar cane wax. Representative examples of useful fatty acids include stearic acid, palmitic acid, and behenic acid. Representative examples of useful metal salts of fatty acids include aluminum stearate, lead stearate, barium stearate, magnesium stearate, zinc stearate, lithium stearate, and zinc palmitate. Representative examples of useful fatty acid derivatives include castor wax (glyceryl tris-12-hydroxy stearate), methyl hydroxystearate (commercially available under the trade name "Paracin 1 "), ethylene glycol monohydroxy stearate (commercially available under the trade name "Paracin 15"), and hydroxystearic acid. Representative examples of useful hydroxylated fatty acids or amides include N(betahydroxyethyl)ricinole- amide (commercially available under the trade name "Flexricin 115"), N,N'ethylene-bis-ricinoleamide (commercially available under the trade name "Flexricin 185"), N(2-hydroxylethyl)-12-hydroxystearamide (commercially available under the trade name "Paracin 220"), and N,N'-ethylene-bis-12-hydroxy- stearamide (commercially available under the trade name "Paracin 285"). Representative examples of ethylene homopolymers include the low molecular weight polyethylenes such as the Bareco "Polywaxes", e.g., "Polywax" 655, 1000, and 2000 sold by the Bareco Division of Petrolite Corporation. Other ethylene homopolymers include oxidized, high density, low molecular weight polyethylenes such as "Polywax" E-2018 and E-2020 sold by Bareco Division of Petrolite Corporation, and the "Epolene" series of low molecular weight polyethylene resins such as "Epolene" E-14 available from Eastman Chemical Products Incorporated. Representative examples of useful aromatic wax-like materials include dicyclo- hexylphthalate, diphenylphthalate and the "Be Square" series of waxes from the Bareco Division of Petrolite Corporation, such as "Be Square" 195. The "Be Square" waxes are high melting point waxes that consist of paraffins and naphthenic hydrocarbons.
  • Representative organic resins useful as the thermoplastic binder are polyamides, polystyrenes (e.g., 2000 mol. wt.); epoxy resins (e.g., diglycidyl ether of bisphenol-A such as "Epon" 1004, commercially available from Shell Chemical Corp); acrylic resins (e.g., "Elvacite" 2044, and N-butyl methacrylate commercially available from E. I. duPont deNemours); vinyl resins such as polyvinyl butyral (e.g., "Butvar" B72-A, commercially available from Monsanto Company), polyvinyl acetate resins (e.g., "Gelva" V-100, commercially available from Monsanto Company); vinyl copolymers such as vinyl chloride/vinyl acetate (e.g., "VYHH", commercially available from Union Carbide Corp.), ethylene/vinyl acetate copolymers; cellulose esters such as cellulose acetate butyrate (e.g., "EAB-171-25", commercially available from Eastman Chemical Products, Inc.), cellulose acetate propionate; and cellulose ethers.
  • When a heat-fusible developing powder is desired, the thermoplastic binder preferably comprises the organic resin. Most preferably the organic resin is an epoxy resin. However, some wax may also be incorporated into the binder of a heat-fusible toner powder. The wax is added to reduce the temperature necessary to achieve satisfactory fusing of the toner to a desired surface. Typically the weight ratio of the organic resin to the wax is between about 4:1 and 20:1.
  • When a pressure fixable developing powder is prepared, the thermoplastic binder comprises either the wax alone or a combination of the wax and the organic resin. When the binder comprises said combination, the weight ratio of wax to organic resin is between about 1:1 to 50:1, preferably between about 4:1 and 20:1. Most preferably the binder consists essentially of the wax. In either event, the wax preferably is selected from microcrystalline wax, low molecular weight polyethylene resin, or a combination thereof, while the organic resin, when present, comprises an epoxy resin.
  • The magnetically responsive material employed in the developing powder composition preferably is homogeneously distributed throughout the binder. Additionally, it preferably has an average major dimension of one micron or less. Representative examples of useful magnetically responsive materials include magnetite, barium ferrite, nickel zinc ferrite, chromium oxide, nickel oxide, etc.
  • Other binders useful for pressure-fixable toner powders are known. Thus, for example, see U.S. Patent 3,965,022. This patent describes a binder that comprises (a) about 74 to 98 parts by volume of a thermoplastic component that has a softening point of at least about 60°C, a 10-second shear creep compliance in the range of about 1 x 10-9 cm2/dyne to 1 x 10-13 cm2/dyne at room temperature, and a "heat deflection temperature" below about 300°C, and (b) about 2 to 26 parts by volume of a non-volatile component having a principal glass transition temperature below about 0°C as measured by differential thermal analysis, and a 10-second shear creep compliance in the range of about 50 cm2/dyne to 8 x 10-8 cm2/dyne at room temperature, said non-volatile component preferably being elastomeric.
  • Examples of useful thermoplastic components (i.e., low shear creep compliance materials) and of non-volatile components (i.e. high shear creep compliance materials) are disclosed in U.S. 3,965,022. The disclosures of that patent are incorporated herein by reference for the disclosure of the binder system.
  • Other ingredients may be incorporated onto the particles used in the toner powder of the invention. Thus, fatty acid amides containing at least about 10 carbon atoms have been found to be useful in reducing the time required to prepare the toner powders. Typically from about 0.05 to 2% by weight of the fatty acid amide is satisfactory. Examples of useful fatty acid amides include erucamide, stearamide, behenamide, oleamide, N,N'-ethylene-bis(tall oil)amide, and N,N'-ethylene-bis-oleamide.
  • The developing powders of the invention may be readily prepared. Thus, a dry blend of the thermoplastic binder and the magnetically responsive material is obtained by meling the thermoplastic binder, stirring in the magnetically responsive material, preferably until a homogeneous mixture is provided, allowing the mixture to cool, grinding the mixture to form particles, and classifying the resulting solid particles to the desired size (i.e., 1 to 40 pm maximum dimension).
  • The particles, which are irregularly shaped, are then preferably formed into "prespheres" by first aspirating them into a moving gas stream, preferably air, thus creating an aerosol, and directing the aerosol at an angle of about 90° ± 5° through a stream of gas, again preferably air, which has been heated to about 450°C and 600°C into a cooling chamber where the now substantially spherical particles settle by gravity as they cool.
  • The surface treatment composition is then applied to the "prespheres". When the treatment composition contains ingredients (e.g., silicon dioxide and/or carbon) other than the fluoroaliphatic compound, a mixture of the ingredients is first prepared by charging them to, for example, a "Waring" blender and mixing for about one-half hour at a medium speed. The resulting preferably homogeneous mixture is fluffy and black.
  • The prespheres and surface treatment composition are then each added to a blender (e.g., a twin shell blender from "Patterson Kelly") and cold blended a temperature less than the softening point of the thermoplastic binder (e.g., 20-30°C) until the surface treatment is at least loosely adhered to the prespheres. Typically this is accomplished within three hours. If desired, the prespheres may be cold blended with one of the above disclosed fatty acid amides before treating the prespheres with the surface treatment composition.
  • In either event, the treated prespheres are then "hot" blended at about the glass transition temperature of the thermoplastic binder for a time sufficient to substantially permanently attach the treatment composition to the particles. This is typically accomplished in from two to six hours. The surface treatment composition is attached as a layer or zone at or near the surface of the prespheres.
  • After hot blending, the resultant toner powder is cooled for about one half hour, screened to remove agglomerates, and classified so that 95% by weight of the product is greater than 4 pm average diameter and only 5% by weight is greater than 30 µm average diameter.
  • The toner powder of the invention is useful in electrographic recording processes where a differential image pattern of the toner is formed and subsequently fixed by means of pressure, heat, or heat and pressure. The differential image pattern may be formed by, for example, forming electrostatic image areas on a photoconductive surface and contacting the image areas with the toner. Alternatively, the differential image pattern may be formed by contacting a passive dielectric surface with the toner; forming the image pattern by, for example, selectively exposing the uniformly toned surface to a stylus which imagewise transmits an electrical potential signal; and magnetically removing toner from uncharged areas. See U.S. Patent 3,816,840 for further description of this process. If desired, the toned image areas may be transferred to another surface prior to fixing.
  • The present invention is further illustrated by means of the following examples wherein the term "parts" refers to parts by weight unless otherwise indicated.
  • In these examples, several physical characteristics of the toner powders were measured. The techniques for measuring these characteristics are described below.
  • a. Dynamic Conductivity.
  • This property simulates the electrical conductivity of a toner powder when used in an electrostatic copying process. Dynamic conductivity is measured on a test rig that comprises the developing station of a "Secretary III" photocopier (available from the 3M Company) except that the photoconductor drum is replaced by an aluminum drum (12.5 cm dia). The developer roll comprises a stainless steel shell (3.15 cm dia) around an 8 pole circular magnet. A doctor blade, a toner hopper, and a 1000 volt power supply are also supplied. The gap between the developer roll and the aluminum drum is set at 0.071 cm; the gap between the doctor blade and the toner hopper at 0.05 cm; and the gap between the toner hopper and the developer roll at 0.125 cm.
  • To measure conductivity, 16 ml of toner is charged to the hopper, and the test rig is started so that the developer roll and the aluminum drum are driven in opposing directions with the developer roll having a surface speed of 61.3 cm/sec and the aluminum drum having a surface speed of 19.5 cm/sec. The test rig is then run for five minutes after which the current passing through toner is measured while the toner is in the development gap and under a 1000 volt potential.
  • b. Maximum Density (Dmax)
  • This property illustrates the optical output density of an image produced from an original having an optical input density of one. Preferably Dmax is at least one.
  • Dmax is measured by determining the diffuse reflection optical density of the image using a conventional diffuse reflection densitometer (e.g., MacBeth Quanta-Log Diffuse Reflection Densitometer, Model RD-100). The optical density reading is taken as the Dmax for the toner powder being tested.
  • c. Density Decay.
  • This property measures the sensitivity of a toner powder to changes in the size of the development gap. Generally speaking, the density of an image produced from a given toner powder decreases as the size of the development gap increases. Thus the larger the gap, the lower the resultant image density. Larger decreases indicate that the toner powder is more sensitive to such changes and, therefore, requires narrower development gaps.
  • Density decay is measured on a conventional electrographic recording device (e.g., a "Secretary III") as follows. The development gap is reduced to the point at which image densities on an imaged and developed photoconductive surface vary from bands of high and low image density horizontally across said photoconductive surface. The development gap is then opened by turning the adjustment means two full turns from this point. A copy is produced at this opening and its image density measured using a conventional diffuse reflection densitometer such as is set forth above. The development gap is then further opened by turning the adjustment means four additional (total of six) turns from said point. A copy is produced at this opening and its image density measured as described above. The density decay is taken as the decrease in image density from the narrower to the wider of the two development gaps.
  • d. Contrast (Gamma).
  • This property is a measure of a toner powder's ability to distinguish between differing image densities on an original and reproduce those differences on a copy. High contrast values, i.e., greater than 5, indicate the toner powder's inability to distinguish and reproduce the difference between varying image densities.
  • Contrast is measured according to the following procedure. Copies of an original having a range of image densities (i.e., a step wedge) are made on an electrographic recording (e.g., a "Secretary III") machine. The output image densities are measured as described above in the Dmax test and plotted against the togio of the input image densities. The log10 of the input densities are plotted as the horizontal axis and the output densities are plotted as the vertical axis. The contrast (gamma) is taken as the slope of the straight line portion of the plot.
    • Examples 1-16
  • A series of examples of heat fusible toner powders were prepared. In the examples, 95% by weight of the toner powders were greater than 5 µm average diameter and only 5% by weight were greater than 22 11m average diameter. Examples 1-15 were examples of the invention while Example 16 was a toner powder that was not surface treated.
  • In each example the prespheres were prepared as described above from 40 parts epoxy resin ("Epon" 1004 from Shell Chemical Company) and 60 parts magnetite. Examples 1-14 the prespheres were separately surface treated as described above using different treatment compositions. In example 15 the surface treatment composition was cold blended with the prespheres for 15 hours prior to hot blending.
  • The following treatment compositions, with quantities reported as parts, were used:
    Figure imgb0004
  • The non-surface treated toner powder (Example 16) was prepared by combining 100 parts of the prespheres with 0.6 parts of conductive carbon black (Vulcan XC-72R from the Cabot Corporation) to form a mixture. The mixture was dry blended at room temperature for 3 hours and then hot blended at 65°C for about 8 hours. The carbon was then embedded into the prespheres as a layer or zone at or near the surface thereof by drawing the particles of the mixture into an air stream at a rate of 36 kg/h to form an aerosol; directing the aerosol at 90 ± 5°C into a hot (650°C) air stream; allowing the powder to settle; and collecting the powder by filtration. About 0.05% by weight Si02 ("Aerosil" 972, Degussa, Incorporated) was blended with the toner as a separate component to aid its flow properties.
  • The powders were then used in a heat-fusing copying process in a "Secretary III" copying machine (available from the 3M Company) to provide images on plain paper substrates. The exposure voltages are reported in Table 1. The bias voltage was set at -200 DC volts.
  • The surface treatment compositions employed together with the results obtained (i.e., dynamic conductivity of the toner powders, the maximum density (Dmax). the density decay, and the image contrast) are given in Table 1.
    Figure imgb0005
  • The toner powders of the invention, i.e., those used in Examples 1-15 provided copies with images that were more sharply defined than were the images provided by the toner used in Example 16. Thus the edges of the images produced in Examples 1-15 were sharp, the openings in the images (letters) had substantially reduced "fuzzy fill-in", and the spaces between the images (background) had substantially reduced blurring caused by undesired toner deposition. Furthermore, the toners used in Examples 1, 2, 7, and 13 produced copies having virtually no "fuzzy fill-in" and virtually no background. The images produced from the toner used in Example 16, however, had blurry edges, substantial "fuzzy fill-in", and substantial background.
  • Additionally, the toners of the invention generally demonstrated less density decay than did the non-surface treated toner used in Example 16. Thus, the toners of the invention generally permit the use of less stringent process conditions such as gap latitude:
  • The foregoing results are achieved without adversely affecting other physical characteristics of the toner powders. Thus, dynamic conductivity, Dmax, and contrast all remain within acceptable limits.
    • Example 17
  • A pressure-fixable toner powder according to the invention was prepared as described above except that the prespheres were prepared from 10 parts "Polywax" 1000 (a low molecular weight, unmodified homopolymer of ethylene having a Mw/Mm of 1.2 from Bareco Division of Petrolite Corporation), 30 parts "Epolene" E-14 (an emulsifiable low molecular weight polyethylene resin from Eastman Chemical Products, Incorporated), and 60 parts Magnetite.
  • The prespheres were surface treated as described above with a treatment composition comprising 0.6 parts "Vulcan" XC-72R, 2.4 parts "Aerosil" 200, and 1.2 parts C8F17SO2N(C2H5)CH2COOH.
  • The resulting toner powder was used in a cold (room temperature) pressure-fixing copying process to provide images on a plain paper substrate. The exposure voltage was 82 volts. The images on the copies produced were sharp, the openings in the images had virtually no "fuzzy fill-in", and there was virtually no background.
  • The toner powder had a dynamic conductivity of 5.3 A/103V, a Dmax of 1.47, and a contrast (gamma) of 4.3.
    • Example 18
  • A heat-fusible toner powder according to the invention was prepared as described in Examples 1-14 utilizing the following surface treatment composition:
    Figure imgb0006
  • The resulting toner powder was used in a heat-fusing copying process in a "Secretary" III copying machine to provide images on plain paper substrates. The exposure voltage was 75 volts and the bias voltage was 200 volts.
  • The images on the resultant copy were sharply defined, had virtually no "fuzzy fill-in", and the copy had virtually no background. Additionally, the toner powder had a dynamic conductivity of 9.5 A/103V and produced images having a Dmax of 0.62 and a contrast of 0.65. While the Dmax and contrast values of this example are low, it still demonstrates improved edge sharpness, "fuzzy fill-in" and background.
    • Example 19
  • A heat fusible toner according to the invention was prepared as described in Examples 1-14 except that the surface treatment composition was prepared by the following procedure.
  • A dispersion of a polymeric fluoroaliphatic compound in solvent was provided. The fluoroaliphatic compound was a 95/5 by weight copolymer of C8F17SO2N(C2H5)C2H4OCOC(CH3) = CH2 and butyl acrylate. Sufficient methyl alcohol was added to the dispersion to precipitate the polymer. The polymer was dried in a vacuum oven. The fluoroaliphatic compound was then ground with a mortar and pestle to reduce it to a relatively fine powder.
  • The surface treatment was then prepared as described above by combining 0.6 part fluorochemical, 0.8 part "Aerosil" 200, and 0.7 part "Vulcan" XC-72R.
  • The resulting toner powder was used in a heat-fusing copying process in a "Secretary" III copying machine to provide images on plain paper substrate. The exposure voltage was 78 volts and the bias voltage was 200 volts.
  • The images on the resultant copy were sharply defined, had virtually no "fuzzy fill-in", and the copy had virtually no background. Additionally, the toner powder had a dynamic conductivity of 8 pA/103V and produced images having a Dmax of 0.98 and a contrast of 1.53.

Claims (7)

1. A one-part, flowable, dry, electrostatically attractable toner powder comprising thermoplastic binder, magnetically responsive material, and a fluoroaliphatic compound containing, within a single molecule, both a fluoroaliphatic group and a group which is attracted to said thermoplastic binder, characterised in that
(a) the particles each comprise a blend of from 30 to 80 parts by weight thermoplastic binder and, correspondingly from 70 to 20 parts by weight magnetically responsive material, and
(b) a layer of the fluoroaliphatic compound essentially permanently attached to each of said particles at or near the outer surface of said particles, said fluoroaliphatic compound comprising from 0.1 to 2 parts by weight per 100 parts by weight of said particles.
2. A toner powder as claimed in Claim 1, characterised in that from 0.1 to 2.5 parts by weight silicon dioxide per 100 parts by weight of said particles are essentially permanently attached to said particles at or near the outer surface of said particles, said silicon dioxide having an average diameter smaller than said particles.
3. A toner powder as claimed in Claim 1 or Claim 2, characterised in that from 0.1 to 2 parts by weight carbon per 100 parts by weight of said particles are essentially permanently attached to said particles at or near the outer surface of said particles, said carbon having an average diameter smaller than said particles.
4. A toner powder as claimed in any preceding claim, characterised in that said fluoroaliphatic compound has the formula RIQmZ where Rf is a fluoroaliphatic group of at least 3 carbon atoms, Z is a terminal group comprising an anionic, a cathionic, a non-ionic or an ampholytic moiety or combination thereof and Qm is a linking group joining Rf and Z, wherein m is an integer from 0 to 2.
5. A toner powder as claimed in Claim 4, characterised in that that said fluoroaliphatic compound is selected from
Figure imgb0007
Figure imgb0008
Figure imgb0009
Figure imgb0010
Figure imgb0011
Figure imgb0012
Figure imgb0013
Figure imgb0014
Figure imgb0015
Figure imgb0016
Figure imgb0017
Figure imgb0018
in which
M is hydrogen or a metallic ion and
a is an integer of from 5 to 25; and polymeric fluoroaliphatic compounds, in particular
a 95/5 weight copolymer of C8F17SON(C2H5)C2H5OCOC(CH3) = CH2 and butylacrylate.
6. A process for preparing a one-part, flowable, dry, electrostatically attractable toner powder as defined in any one of Claims 1 to 5 characterised by:
providing a plurality of particles each comprising a blend of from 30 to 80 parts by weight thermoplastic binder and, correspondingly, from 70 to 20 parts by weight magnetically responsive material,
providing a surface treatment composition comprising from 0.1 to 2 parts by weight per 100 parts by weight of said particles of fluoroaliphatic compound containing, within a single molecule, both a fluoroaliphatic group and a group which is attracted to said thermoplastic binder,
mixing said particles and said surface treatment composition together at a temperature less than the softening point of said thermoplastic binder for a time sufficient to at least loosely attach said surface treatment composition to the surface of said particles,
heating said particles with attached surface treatment composition to a temperature of about the glass transition temperature of said thermoplastic binder with continued mixing, and
maintaining said heating with continued mixing for a time sufficient to substantially permanently attach said surface treatment composition to said particles thereby providing said toner composition.
7. Use of the toner powder as defined in any one of Claims 1 to 5 for electrographic recording comprising:
forming an electrostatic image pattern on a surface,
developing the electrostatic pattern by contacting the pattern with the toner powder as defined in any one of Claims 1 to 5 and adhering said toner powder to the pattern, and
fixing said powder by means of heat and/or pressure.
EP81305059A 1980-10-28 1981-10-27 One part toner powder composition Expired EP0050987B1 (en)

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US201417 1980-10-28

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Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS59137956A (en) * 1983-01-27 1984-08-08 Ricoh Co Ltd Electrostatic charge image developing magnetic toner
JP2797294B2 (en) * 1987-01-29 1998-09-17 ミノルタ株式会社 Binder type carrier
US4960677A (en) * 1987-08-14 1990-10-02 E. I. Du Pont De Nemours And Company Dry nonelectroscopic toners surface coated with organofunctional substituted fluorocarbon compounds
JPH01309074A (en) * 1988-06-07 1989-12-13 Minolta Camera Co Ltd Developer composition
DE3837345A1 (en) * 1988-11-03 1990-05-10 Hoechst Ag USE OF COLORLESS HIGH GRADE FLUORATED AMMONIUM AND IMMONIUM COMPOUNDS AS LOADING AGENTS FOR ELECTROPHOTOGRAPHIC RECORDING METHODS
EP0467439B1 (en) * 1990-07-19 1996-06-12 Agfa-Gevaert N.V. Dry electrostatographic developer composition
EP0613059A1 (en) * 1993-02-22 1994-08-31 Nippon Paint Co., Ltd. Toner
WO2005076087A1 (en) * 2004-02-06 2005-08-18 Lg Chem, Ltd. Positive chargeable magnetic toner composition

Citations (1)

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Publication number Priority date Publication date Assignee Title
EP0037297A1 (en) * 1980-03-20 1981-10-07 COMPAGNIE INTERNATIONALE POUR L'INFORMATIQUE CII - HONEYWELL BULL (dite CII-HB) Powder for the development of latent images and process for its preparation

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Publication number Priority date Publication date Assignee Title
CA971026A (en) * 1969-03-24 1975-07-15 Walter Crooks Electrophotographic developer
JPS598821B2 (en) * 1978-10-09 1984-02-27 コニカ株式会社 Magnetic toner for developing electrostatic images

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0037297A1 (en) * 1980-03-20 1981-10-07 COMPAGNIE INTERNATIONALE POUR L'INFORMATIQUE CII - HONEYWELL BULL (dite CII-HB) Powder for the development of latent images and process for its preparation

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CA1158090A (en) 1983-12-06
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DE3170877D1 (en) 1985-07-11

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