Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G9/00—Developers
  • G03G9/08—Developers with toner particles
  • G03G9/10—Developers with toner particles characterised by carrier particles
  • G03G9/113—Developers with toner particles characterised by carrier particles having coatings applied thereto
  • G03G9/1132—Macromolecular components of coatings
  • G03G9/1137—Macromolecular components of coatings being crosslinked
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G9/00—Developers
  • G03G9/08—Developers with toner particles
  • G03G9/10—Developers with toner particles characterised by carrier particles
  • G03G9/113—Developers with toner particles characterised by carrier particles having coatings applied thereto
  • G03G9/1132—Macromolecular components of coatings
  • G03G9/1133—Macromolecular components of coatings obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • G03G9/1134—Macromolecular components of coatings obtained by reactions only involving carbon-to-carbon unsaturated bonds containing fluorine atoms
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G9/00—Developers
  • G03G9/08—Developers with toner particles
  • G03G9/10—Developers with toner particles characterised by carrier particles
  • G03G9/113—Developers with toner particles characterised by carrier particles having coatings applied thereto
  • G03G9/1132—Macromolecular components of coatings
  • G03G9/1135—Macromolecular components of coatings obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • G03G9/1136—Macromolecular components of coatings obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds containing silicon atoms

Definitions

• This invention relates to coated particles. It relates especially to coated carrier particles to be used as carrier particles in multi-component developers for electrostatic imaging with magnetic brush development as well in cascade development.
• electrostatographic imaging carrier particles mostly magnetic carrier particles, are mixed with toner particles (and with other ingredients) to form a developer.
• the carrier particles are magnetic
• the carrier particles can be coated glass beads.
• the rubbing of the carrier particles and the toner particles induce a tribo-electric charge in the toner particles and the nature of the coating on the carrier particles determines, together with the toner ingredients, not only the polarity of the charge on the toner articles and the amount of the charge but also the stability of the charge over time, the charge distribution over the population of toner particles, etc.
• the coating of the carrier particles is very crucial to the resulting properties of the developer and thus to the image quality that can be reached with that developer.
• the speed of charging of the toner particles is to a large extent determined by the coating of the carrier particles.
• Carrier particles having an high speed of charging towards the toner particles are beneficial especially when images with high image fill (i.e. a high amount of area in an page is really occupied by toning particles) are present. Then large amounts of toner are consumed and the toner, especially in long run printing, resides only a limited time in the developer. In such a situation the toner has only a limited number of activation cycles.
• the charging properties of the developer in terms of its kinetics, i.e. the speed of the rise of the charge amount, as well as in terms of its plateau value are important.
• JP-A-10 153 886 it is disclosed to apply on carrier particles for use in electrostatograpohic developers a coating of a polyester with relatively high acid value and tri-alkyloxysilane compounds that contain groups that can react with the free acid groups of the polyester.
• WO-A 98/53372 a new type of coating has been described, consisting of chemical compounds selected from the group consisting of a monomeric polyfunctional organosilane, an hydrolysis product of a monomeric polyfunctional organosilane, a reaction product of a monomeric polyfunctional organosilane with an organosilane containing an hetero-atom and a reaction product of a monomeric, polyfunctional organosilane with an alkoxide.
• Such a coating offers interesting properties as described in said application.
• EP-A 898 206 it has been disclosed that such a coating could be applied to carrier particles in a quite simple method that requires only mechanical stirring and uses a quite low amount of solvents.
• the coating disclosed in WO-A 98/53372 combined with the method described in EP-A 898 206 has a very long lifetime and can easily be manufactured in an inexpensive method.
• the coating shows some limitations in terms of activation behaviour, i.e. the charging of the toner particles in rubbing contact with the carrier coating shows relatively low speed and thus when images with high page fill have to be printed, some problems with charging can occur.
• the objects of the invention are realised by providing carrier particles having a coating comprising a polycondensation network having moieties derived from chemical compounds selected from the group consisting of a monomeric polyfunctional organosilane, an organosilane containing an hetero-atom and an alkoxide, characterised in that said coating further comprises an amount A of a polymeric compound not containing silicon atoms so that 5% ⁇ A ⁇ 50 % by weight, with respect to the weight of the dried coating.
• the quality of a coating for carrier particles according to the chemistry disclosed in WO-A 98/53372, that is included herein by reference, could surprisingly be enhanced with respect to the activation, i.e. the speed of charge accumulation on toner particles by rubbing contact between the carrier and the toner particles, when appreciable amounts of a non silicon containing polymeric substance were included in the coating. It was found that between 5 and 50 % by weight, both limits included, of such non silicon containing polymeric compounds could be incorporated in the coating. Preferably an amount between 10 and 30 % by right, both limits included, is incorporated.
• carrier particles according to this invention comprise a coating comprising a polycondensation network having moieties derived from chemical compounds selected from the group consisting of a monomeric polyfunctional organosilane, an organosilane containing an hetero-atom and an alkoxide, characterised in that said coating further comprises an amount A of a polymeric compound not containing silicon atoms so that 5% ⁇ A ⁇ 50 % by weight, with respect to the weight of the dried coating.
• said polycondensation network is derived from 20 to 80 % by weight of polyfunctional organosilane, 20 to 80 % by weight of alkoxide, 0 to 10 % by weight of organosilane (I) which contains a hetero atom.
• said polycondensation network contains 19.9 to 80 % by weight of polyfunctional organosilane, 19.9 to 80 % by weight of alkoxide (II), 0.1 to 10 % by weight of organosilane (I) which contains a hetero atom.
• the polycondensation network can in addition to the chemicals above contain finely divided metal oxides or metal oxide-hydroxides of the elements Si, Sn, In, Tl, Zr, B or Al, e.g. silica sols, which contain organic solvents in particular.
• the preferred primary particle size thereof falls within the range from 1 to 50 nm; they are hereinafter termed "nanoparticles".
• said polycondensation network contains moieties derived from 0.1 to 100 % by weight of polyfunctional organosilane, 0 to 20 % by weight of organosilane (I) which contains a hetero atom, 0 to 99.9 % by weight of alkoxide (II) and 0 to 70 % by weight of nano-particles a.
• said polycondensation network contains 20 to 80 % by weight of polyfunctional organosilane, 20 to 80 % by weight of alkoxide (II), 0 to 10 % by weight of organosilane (I) which contains a hetero atom, and 0 to 50 % by weight of nano-particles.
• the non silicon containing polymeric compound has preferably an average molecular weight by number larger than 1000, more preferably larger than 2000. It can be addition home-polymers , e.g., polystyrene, polymethylacrylate, polymethylmethacrylate, polymethylacrylicacid, polymethylmethacrylacid, etc.. It can be copolymers as, e.g., styreneacrylic resins. It can also be vinylpolymers as polyvinylbutyral, polyvinyl acetate, polyvinylalcohol, etc.. The vinyl polymers are preferred as non silicon containing polymer for use in the present invention. Also polycondensation polymers, e.g., polyesters, polyamides, polyimides etc. can be used as well as polymers comprising fluor containing moieties.
• polycondensation polymers e.g., polyesters, polyamides, polyimides etc. can be used as well as polymers comprising fluor containing moieties
• the organosilane containing an hetero-atom for use in a carrier coating according to this invention consist of at least one silicon atom carrying an hydrolysable group and/or a group that can be cross-linked by polycondensation and at least on organic rest group, bound to the silicon atom by a carbon atom, wherein the rest group contains an hetero atom and can be an alkyl, cycloalkyl or aryl group.
• silicon atom carrying an hydrolysable group and/or a group that can be cross-linked by polycondensation can be -SiOR, wherein R can be an alkyl, cycloalkyl or aryl group and is preferably an alkyl group or -SiOH. It is preferred that R is an alkyl group.
• the hetero atoms can be N, P, S, F, Cl, Br, O, B and Al, but are more preferably N or F.
• Typical useful nitrogen containing alkoxysilane are :
• Typical useful nitrogen containing alkoxysilane are :
• the alkoxide for use in a coating according to this invention corresponds preferably to formula (II) : M 1 (OR 1 ) y Wherein
• Preferred alkoxides are Si(OC 2 H 5 ) 4 , B(OC 2 H 5 ) 3 , Al(O-i-C 3 H 7 ) 3 and Zr(O-i-C 3 H 7 ) 4 . It is highly preferred to use Si(OC 2 H 5 ) 4 as alkoxide in a polycondensation network on the carrier particles of this invention.
• Polyfunctional organosilanes for use in the present invention comprise at least 2, preferably 3 Si-atoms coupled to 1 to 3 hydrolysable groups and/or a group that can be cross-linked by polycondensation.
• the latter groups are preferably alkoxy-, acyloxy or hydroxygroups.
• the Si-atoms are preferably coupled by a Si-C bond to an organic group, e.g., to a linear or branched C1 to C10 alkylgroup, to a C5 to C10 cycloalkylgroup, to an aromatic group or combinations of these.
• Polyfunctional organosilanes useful to prepare a coating according to this invention correspond to formula (III), (IV) and (V) (R 5 ) 4-i Si[(CH 2 ) p Si(OR 6 ) a (R 7 ) 3-a ] i wherein
• Typical examples of polyfunctional organo silane useful in this invention are :
• a coating solution with the chemical compounds described above by adding an amount between 0.1 to 50 % by weight of a polyfunctional organosilane and 0 to 50 % of an alkoxide optionally together with a catalyser, which can be an organic acid e.g. formic acid, acetic acid, paratoluenesulphonic acid, etc. in a solvent ( preferably a lower C1 to C4 alcohol, most preferred isopropanol).
• a pre-reaction 0 to 20 % by weight of a organosilane containing an hetero-atom is added and the solution is further diluted with solvent.
• a polymeric compound non containing silicon atoms is added.
• said coating solution comprises 5 to 15 % of a polymeric compound non containing silicon atoms.
• the relative amounts of the constituents of the coating are adapted so has to have a total of 100 %.
• the alkoxide and the organosilane containing an hetero-atom have reacted together and have lost water and alcohol so that in the dried coating only 50 % by weight of sum of the amounts (weight) of the polyfunctional organosilane, the alkoxide and the organosilane added to the coating solution is contained in the coating.
• the non silicon atom containing polymer does not loose weight during the coating and thus when 2.5 % by weight of the non silicon atom containing polymer is added to the coating solution, 5 % by weight is present in the dried coating.
• the present invention thus encompasses a method for coating carrier particles with a polycondensation network incorporating a polymer not containing Si-atoms, comprising the steps of :
• a polyfunctional organosilane and an alkoxide between 30 and 50 % by weight, with respect to the total amount of chemicals used for forming said polycondensation network are mixed with between 30 and 50 % by weight, with respect to the total amount of chemicals used for forming said polycondensation network, of an alkylorthosilicate and in said step of adding a organosilane containing an hetero-atom 0 and 5 % by weight, with respect to the total amount of chemicals used for forming said polycondensation network, of an organo silane comprising an hetero atom are added.
• said alkylorthosilicate is tetraethylorthosimlicate (TEOS) and in said step of mixing a polymeric compound non containing silicon atoms in said solution between 5 and 15 % by weight, with respect to the total amount of chemical in said coating solution of said polymeric compound non containing silicon atoms are used.
• TEOS tetraethylorthosimlicate
• the coating solution according to this invention and described immediately above can preferably be applied to the carrier particles by the method disclosed in EP-A 898 206 and its equivalent US-A-5 888 692, that is incorporated herein by reference.
• the present invention encompasses thus also a method for coating carrier particles, having a volume average diameter between 20 and 200 ⁇ m, for use in electrostatic developers, comprising the steps of :
• Said Froude number is between 0.5 and 8 both limits included.
• Said solution with chemical compounds for coating the carrier particles contains preferably between 15 and 40 % by weight with respect to the total volume of said solution of chemical compounds for coating said particles. Said solution is preferably added to said vessel at a rate that, at any time, said solvent is present in an amount lover than 0.6 10 -4 ml per cm 2 of surface of said particles to be coated.
• said vessel with a mechanical mixer wherein the carrier particles are coated is a ploughshare mixer.
• Carrier particles coated with a coating composition according to this invention can be used in any multi-component developer comprising magnetic carrier particles and toner particles, it can be used in electrophotography, direct electrostatic printing, ionography etc.
• the solidified mass was pulverised and milled using an ALPINE Fliessbettarnastrahlmühle type 100AFG (trade name) and further classified using an ALPINE multiplex zig-zag classifier type 100MZR (trade name).
• the resulting particle size distribution of the separated toner measured by Coulter Counter model Multisizer (trade name), was found to be 6.3 ⁇ m average by number and 8.2 ⁇ m average by volume.
• the toner particles were mixed with 0.5 % of hydrophobic colloidal silica particles (BET-value 130 m 2 /g).
• An electrostatographic developer was prepared by mixing said mixture of toner particles and colloidal silica in a 4 % ratio (wt/wt) with carrier particles coated according to the examples.
• ferrite beads having an average volume diameter d v of 50 ⁇ m.
• a coating solution is prepared and is added over 25 minutes at 80 °C.
• the mixtures are post-cured during 120 minutes at 140 °C.
• the amount of agglomerates is determined by sieving over a 125 ⁇ m sieve and expressed as % wt/wt.
• the charging characteristics are measured upon admixture of 5% of toner.
• the Q/M-value is determined at different activation times, by a blow-off method. The difference of the Q/M-values is taken as an indication of the activation property of the coated carrier particles.
• a coating solution is prepared containing 39.7 g of cyclo- ⁇ OSiCH 3 [(CH 2 ) 2 Si(O C 2 H 5 ) 2 CH 3 ] ⁇ 4 and 37 g of TEOS (Si(OC 2 H 5 ) 4 ), in 15 g of isopropanol and 6.6 g of a 0.1 N solution of paratoluenesulphonic acid as a catalyst. After one hour at room temperature, 0.39 g of H 2 N-(CH 2 ) 2 -HN-(CH 2 ) 2 -HN-(CH2) 3 Si(OCH 3 ) 3 is added together with 150 g of isopropanol. This results, after reaction and coating in 38.5 grams of a polycondensation network.
• the ferrite beads were coated according the general procedure above with a solution containing ONLY non silicone containing polymeric compound.
• BUTVAR B79 trade name of polyvinyl butyral from Monsanto
• the coating solution consisted of 15% BUTVAR in a mixture 1/3 MEK-2/3 isopropanol. Amount of coated material is 0.5% relatively to ferrite carrier core.
• 50 % of agglomerates were found and when the carrier beads were mixed with the toner particles no stable charge measurements could be done.
• BUTVAR B79 trade name of polyvinyl butyral from Monsanto
• Mw weight average molecular weight
• Invention example 1 was repeated but a dispersion of carbon black (KETJEN BLACK EC) is added so that in the final coating contained 20 % by weight of Carbon Black, 20 % by weight of BUTVAR B79 and 60 % by weight of the polycondensation network.
• a dispersion of carbon black (KETJEN BLACK EC) is added so that in the final coating contained 20 % by weight of Carbon Black, 20 % by weight of BUTVAR B79 and 60 % by weight of the polycondensation network.
• the number of agglomerates was 3 % and the Q/m (charge over mass ratio) as a function of rubbing time is given in the table below : Rubbing time Q/m 2 min 15.2 10 min 15.0 30 min 14.4 60 min 15.7

Landscapes

• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• General Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Developing Agents For Electrophotography (AREA)

Priority Applications (1)

Applications Claiming Priority (3)

Publications (1)

Family

ID=26150920

Family Applications (1)

Country Status (1)

Cited By (1)

Citations (5)

• 1999
  • 1999-11-17 EP EP99203837A patent/EP1004942A1/de not_active Withdrawn

Patent Citations (5)

Non-Patent Citations (1)

Similar Documents

Legal Events