Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D13/00—Electrophoretic coating characterised by the process
• • 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
  • G03G9/12—Developers with toner particles in liquid developer mixtures
  • G03G9/135—Developers with toner particles in liquid developer mixtures characterised by stabiliser or charge-controlling agents
• • 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
  • G03G9/12—Developers with toner particles in liquid developer mixtures
  • G03G9/135—Developers with toner particles in liquid developer mixtures characterised by stabiliser or charge-controlling agents
  • G03G9/1355—Ionic, organic compounds
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
  • H01J9/20—Manufacture of screens on or from which an image or pattern is formed, picked up, converted or stored; Applying coatings to the vessel
  • H01J9/22—Applying luminescent coatings
  • H01J9/221—Applying luminescent coatings in continuous layers
  • H01J9/225—Applying luminescent coatings in continuous layers by electrostatic or electrophoretic processes
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S516/00—Colloid systems and wetting agents; subcombinations thereof; processes of
  • Y10S516/924—Significant dispersive or manipulative operation or step in making or stabilizing colloid system

Definitions

• the invention relates to a dispersion of finely divided substances in an apolar dispersing agent, to an electrophoretic method using such a dispersion and to an electrophotographic method using such a dispersion as a developer.
• Electrophoresis is understood to mean the transport of dispersed particles in an electric field, which transport is brought about because these particles carry an electric charge. Many uses of electrophoresis in polar dispersing agents are known in technology.
• Charging of the particles is based on the formation of ions by electrolytic dissociation in polar dispersing agents having a high dielectric constant such as water or alcohols whose dipolar molecules surround the ion.
• the solvation energy of this process is equal to or larger than the lattice energy of an ionic compound and renders the dissolution of such a compound in the dispersing agent possible.
• the colloidal particle itself must include dissociable groups, for example, macromolecules having built-in carboxyl or hydroxyl groups, or such particle absorbing an ion of a low molecular weight electrolyte.
• the mechanism of electrophoresis in polar dispersing agents is based on methods of depositing finely divided substances on objects which for this purpose are arranged as electrodes and have a conducting surface.
• Known technical uses are among others coating oxide cathodes and lacquering motor bodies and other objects.
• apolar organic liquids having a small dielectric constant and a high electric resistance as dispersing agents.
• the formation of ions by means of dipolar solvation in the manner described above is not possible in these dispersing agents.
• Small solid-substance particles may, however, be charged by barrier layer effects, tribe-electrical effects or contact potential differences, a particle having a dielectric constant which is higher than that of the dispersing agent being positively charged and being negatively charged 1n the converse case.
• This natural charge may be suflicient for small particles (approximately 0.1 ,um) for transport in an electric field; on the other hand larger particles cannot be deposited on a flat electrode.
• the so called dielectrophoresis in non-homogeneous electric fields occurs. This occurs in such a manner that an uncharged or a weakly charged particle in the electric field is polarized.
• a net attraction of gravity towards a higher field strength is obtained independent of the polarity of the electrode, when the dielectric constant or the polarisability is larger than that of the surrounding dispersing agent.
• Th attractive force is proportional to the polarisability and to the volume of the particle and the gradient of the square of the field strength. Larger and insufiiciently charged particles can thus be deposited on the edges of the electrodes and on irregularities and on corners and edges of charging profiles because inhomogeneous field distributions occur in these areas.
• German patent specification 1,047,616 describes a method of developing electrostatic charge images wherein a dispersion of pigment particles in apolar media such as cyclohexane is used.
• the pigment particles are electrically rendered selective for the image charge by adding a substance which controls the pigment. This substance gets to surround the particle and to influence charging by adjusting a given ratio between its dielectric constant and the dielectric constant of the solvent.
• a substance is, for example, an alkyd resin, an alkyd resin modified with linseed oil or boiled linseed oil itself.
• the two firstmentioned compounds must charge the pigment particle positively while the last-mentioned compound must charge this particle negatively. In practice, however, it is dependent on the chemical nature of the pigment substance whether this charge is obtained.
• suspensions may be stabilized both with ionic and non-ionic substances from the group of surface-active substances. It was found that solutions of ionic stabilizers have an electric conductivity which is 10 times higher than that of the pure apolar solvents. Thus it must be possible to form ions also in apolar media, even at a very slight degree of dissociation.
• micelles are formed from a lyophilic organic acid radical and a lyophobic cation, which micelles may envelope and shield a few lyophobic cations, while a few lyophilic radicals are present in the solution. If additional particles are present in a suspension the lyophobic cation can be adsorbed in polar groups at the surface of the particles.
• the charge may thus be regarded to be a dissociative adsorption wherein a certain type of ion is bound in an adsorption phase while the other ion is present in the solvent.
• Ions of the polarity which are adsorbed at the solid particle may also occur in micelles so that the charge image for the deposition cannot be utilized optimally because the micelles neutralize the charge unused.
• An object of the present invention is to provide a dispersion of solid particles in apolar solvents which does not give the above-mentioned drawbacks and wherein solid particles of an arbitrary material nature such as metals, semiconductors and dielectrics having a grain size of approximately 0.01-10 m and in special cases even larger particles are charged.
• the dispersion of a finely divided substance in an apolar dispersing agent having an electrical conductivity which is smaller than is characterized in that the dispersion includes surfaceactive ion-forming substances which are soluble in the dispersing agent and are dissociable in such a manner that their conductivity in a 10- molar solution is greater than l' SZ- cmr and preferably between 1 l0 and 1 10- .2- cm.- and that these substances comprise bivalent or multivalent ions.
• Such a multivalent compound dissociates into an ion consisting of the metal atom and the remaining lyophilic acid radical and into an oppositely charged lyophilic radical itself.
• a metal ion including a remaining lyophilic acid radical formed in this manner may be stabilised either into a micelle or into an adsorption phase built up similarly in an easier manner than a single alkali ion. Alternatively mixtures of several of these substances may yield particularly favourable results.
• the concentration of the substance to be added must lie between certain limits: When this concentration is too low dielectrophoresis occurs and when it is too high the charges of a charge pattern are compensated by micelles of the same polarity as the pigment particles so that only a small deposit thickness can be obtained. A series of simple tests enables anyone skilled in the art to determine the active concentration range for each individual case.
• this dispersion includes a substance which intensifies and stabilises the dissociative adsorption of the ionic compound due to the formation of a special adsorptive phase and which renders control of this phase within comparatively large ranges of concentration and charge possible.
• This substance comprises a soluble non-ionic macromolecular compound whose molecules include side chains of at least 4 carbon atoms. Particularly suitable are substances having side chains of 1020 carbon atoms.
• Suitable for suspension in isoparaffins are, for example, polymethacrylic acid esters having a molecular weight of 10 -10", polyacrylic acid esters, polyalkyl styrenes, polyvinyl alkyl ethers and copolymers or polymethacrylates having cyclic amides and fumarates.
• the quantities to be used are dependent on the concentration of the particles, the nature and the size of their surface and on the manner of dispersing. As a result of the synergistic action of the two additions a quantity of ionic substance is used which is much smaller than when only the last-mentioned substance is used.
• the intensifying and stabilising agent is first dispersed with the pigment, optionally together with the pigment and the added ionic substance. The optimum activity frequently cannot be obtained if this substance is added to the suspension at a later stage.
• Ionic substance which are soluble in isoparafiins are, for example: alkaline earth alkyl sulfonates containing 24-32 carbon atoms such as Ca(SO C H basic alkaline earth alkyl sulfonates such as wherein R may be a mixture of different radicals, salts of fatty acids such as Mg, Ca and Ba oleates, Conaphthenate, salts of alkyl salicylic acid such as calcium diisopropyl salicylate, alkaline earth and aluminum salts of alkyl esters of sulphosuccinic acid, such as Cadodecyl sulphosuccinate or cetyl-, octyl or stearyl titanate. Mixtures of these substances may alternatively be active.
• alkaline earth alkyl sulfonates containing 24-32 carbon atoms such as Ca(SO C H basic alkaline earth alkyl sulfonates such as wherein R may be a mixture of different
• Particularly active combinations of these ionic substances are mixtures of an alkyl salicylate including cetyl titanate or an alkyl salicylate including an alkyl sulphosuccinate.
• a dispersion has already been described hereinbefore wherein pigment particles are dispersed in cyclohexane while adding an alkyd resin, an alkyd resin modified with linseed oil or linseed oil itself including Pb or C0 naphthenate as a hardening agent, which, however, is not based on the recognition of the present invention. These combinations are therefore explicitly excluded from the rights applied for.
• the solid substance may be replaced by any other substance while the nature and the concentration of the additions may be changed and adapted to the envisaged object and to the condition of the solid substance.
• Luminescent substances which are soluble in water such as, for example, cesium iodide may be deposited advantageously in this manner.
• Metals, for example, silver may be deposited for intensifying metallic conductive paths.
• Ceramic and metallic pulverulent magnetic materials may be used for the manufacture of magnetic layers and structures.
• EXAMPLE 2 An electrophotographic developer was prepared by dispersing the following mixture:
• Zinc oxide papers which are usually charged to several hundred volts of surface potential by means of a corona discharge could be developed to full density even at 30-70 v. This technique is a condition for a high quality reproduction of half tones. Zinc oxide papers having a great charge produced stained and mottled images as a result of an imhomogeneous charge distribution and additionally showed a step gradation.
• the exposed areas are pigmented on the negatively charged zinc oxide; thus this developer is suitable for a negative-positive process.
• soot-pigmented synthetic resins or pastes having a high content of synthetic resin are used as basic material for such developers.
• Such a developer may, however, be manufactured easily from pure soot having few additions with the aid of the stabilising agents.
• This developer has, for example, the following composition:
• An interesting use of the dispersion according to the invention consists in the manufacture of the luminescent layer on the inner side of television picture tubes and particularly of a pattern comprising three luminescent materials for the screens of colour television picture tubes.
• the inner side of the picture screen is provided with a conducting layer and a photoconducting organic layer is provided on said layer; an electric charge is supplied by a corona discharge to the photoconducting layer Whereafter the charged layer is exposed in accordance with the desired pattern and is treated with the liquid dispersion of luminescent materials according to the invention. This process is repeated for the two other luminescent materials.
• the conducting layer and the photoconducting layer are finally removed by heating while simultaneously the luminescent layers are compacted by sintering.
• the dispersion obtained was dispersed in 250 gms. of isoparafiin (C C boiling range -210 C.) and was diluted to 1500 mls. for use.
• the dispersing was carried out by an ultrasonic treatment so as to expose the luminescent material as little as possible to mechanical load which reduces its light output.
• a low boiling isoparaffin was used first.
• 0.2 g. of a polymethacrylic acid alkyl ester having side chains of C H and a molecular weight of 8x10 was dispersed in isoparaffin likewise as the blue luminescent material. In this dispersion the particles were positively charged.
• the following mixture was used for the dispersion of a negatively charged (green) luminescent material.
• dispersing agent is a mixture of isoparaffins and the soluble nonionic macro-molecular compound has side chains of 10-20 carbon atoms.
• a dispersion of claim 2 containing a mixture of an OTHER REFERENCES alkyl salicylate and cetyl titanate as surface-active ion schwanz et at surface Active Agents, VOL I, Intep formmg P P science Publishers, Inc., N.Y., 1949, pp. 30-33 and 527 4.
• a dispersion of claim 2 contammg a mixture of an 7 alkyl s a1icy1ate and an alkyl sulphosuccinate as surface- 5 Schwartz et all: surface Active Agents and Damp actlve 10H formmg substancesgents, v01. 11, Interscience Publishers, Inc., N.Y., 1958,

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• Chemical & Material Sciences (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Metallurgy (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Organic Chemistry (AREA)
• Developing Agents For Electrophotography (AREA)
• Luminescent Compositions (AREA)
• Photoreceptors In Electrophotography (AREA)
• Colloid Chemistry (AREA)
• Peptides Or Proteins (AREA)
• Lubricants (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=5736250

Family Applications (1)

Country Status (9)

Cited By (6)

Families Citing this family (5)

Family Cites Families (4)

• 1969
  • 1969-06-06 DE DE1928817A patent/DE1928817C2/de not_active Expired
• 1970
  • 1970-06-02 NL NL7007936A patent/NL7007936A/xx unknown
  • 1970-06-03 SE SE07716/70A patent/SE367073B/xx unknown
  • 1970-06-03 GB GB2682770A patent/GB1318396A/en not_active Expired
  • 1970-06-03 US US00043223A patent/US3766125A/en not_active Expired - Lifetime
  • 1970-06-04 ES ES380417A patent/ES380417A1/es not_active Expired
  • 1970-06-05 CA CA084746A patent/CA926605A/en not_active Expired
  • 1970-06-05 FR FR7020757A patent/FR2064053A1/fr not_active Withdrawn
  • 1970-06-05 BE BE751585D patent/BE751585A/xx unknown

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