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
  • G03G9/12—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
• • 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
  • G03G9/13—Developers with toner particles in liquid developer mixtures characterised by polymer components
  • G03G9/131—Developers with toner particles in liquid developer mixtures characterised by polymer components obtained by reactions only involving carbon-to-carbon unsaturated bonds
• • 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
  • Y10S430/00—Radiation imagery chemistry: process, composition, or product thereof
  • Y10S430/001—Electric or magnetic imagery, e.g., xerography, electrography, magnetography, etc. Process, composition, or product
  • Y10S430/105—Polymer in developer

Definitions

• the invention relates to an improved electrostatographic suspension developer which contains an ionic copolymer to produce a positive toner charge, and to a process for producing the developer.
• Dry and wet development methods are known for developing electrostatic images on electrostatographic recording materials.
• the wet development processes using suspension developers are superior to the dry development processes in terms of edge definition and resolving power.
• Suspension developers generally consist of a highly insulating carrier liquid, a pigment, a charge-determining substance (also called a control agent) and a polymer.
• the carrier liquid preferably has a volume resistance of at least 10 9 Ohm.cm and a dielectric constant below 3.
• Pigments are e.g. B. conventional azo dyes, xanthene dyes, phthalocyanine dyes, as described, inter alia, in DE-A 29 44 021, but also triphenylmethane dyes, acridine dyes or quinoline dyes.
• Carbon black pigments are preferably used as black pigments.
• the primary function of the polymer is to impart sufficient steric stabilization to the pigment dispersion and to ensure that the pigment particles adhere or are fixed to the image carrier.
• Numerous differently structured polymers can be used as components of electrostatographic suspension developers.
• the use of statistical copolymers composed of less polar monomers (e.g. C 6 -C 20 alkyl (meth) acrylate) and more polar monomers (e.g. aminomethacrylates or vinyl pyrrolidone) has been widely described (e.g. DE-A 19 27 592, DE-A 19 38 001, BE-A 784 367, JP-A 49 129 539 or JP-A 73 431 54).
• the use of styrene-butadiene copolymers is also possible (e.g. DE-A 23 37 419, DE-A 24 52 499 or JP-A 73 290 72).
• graft copolymers have also been used to build up suspension developers (e.g. DE-A 20 42 804, DE-A 21 03 045, DE-A 24 21 037, DE-A 25 32 281, DE-A 24 32 288, DE-A 29 35 287, GB-A 2 157 2343, GB-A 2 029 049 or US-A 4033890. From DE-OS 3232 062 it is known to sterically stabilize the pigment particles of a suspension developer by building up a crosslinked polymer shell by means of precipitation polymerization.
• the polymers contain ionic groups, these can play a role in the build-up of the toner charge.
• the charge of the toner particles by oil-soluble ionogenic compounds such.
• carbon black pigments in liquid isoparaffin can be positively charged by organic phosphorus compounds (GB-A 1 151 141).
• a negative charge build-up is possible by adding basic metal alkyl sulfonates (GB-A 1 571 401).
• a disadvantage of the use of the known charge-determining substances is that the electrical properties of the liquid developer, such as conductivity and particle charge, are not stable when there are changes in concentration and are influenced to a large extent by traces of water (for example atmospheric humidity). Furthermore, such liquid developers generally show a high electrical conductivity of the dispersion medium, which affects the electrophoretic deposition of the toner particles.
• the invention has for its object to provide an electrostatographic suspension developer with positive toner charge, high charge stability and low conductivity of the dispersion medium.
• a suspension developer which contains a dispersed pigment and at least one copolymer in an electrically insulating carrier liquid with a volume resistance of at least 10 9 ohm.cm and a dielectric constant below 3, characterized in that the copolymer comprises
• A. cationic monomers which contain ammonium, phosphonium or sulfonium groups and whose anions are derived from acidic compounds containing CH-azides or sulfur or phosphorus and having at least one hydrocarbon radical having 6 to 24 carbon atoms, and
• Hydrocarbons, fluorocarbons or silicone oils can be used as the carrier liquid with a volume resistance of at least 10 9 ohm.cm and a dielectric constant below 3; preference is given to hydrocarbon-based liquids, for example aromatic hydrocarbons such as benzene, toluene or xylenes or aliphatic C 6 -C 15 tubes. Hydrogen, such as n-hexane, cyclohexane, n-heptane, n-octane or decalin. Mixtures of different hydrocarbons can also be used. Branched aliphatic hydrocarbons such as isodecane and isododecane are particularly suitable.
• Suitable pigments are the blacks mentioned above, which are usually used for suspension developers. and color pigments.
• Spirit black (CI No. 50415), aniline black (CI No. 50440), cyanine blue (CI No. 74250), brilliant carmine 6 B (CI 15850), real red (CI No. 15865), benzidine orange (CI 21110) are particularly suitable ) or permanent yellow GR 52 (CI 21100).
• Carbon black especially basic types of carbon black
• Helio real blue HG CI No. 74160
• Fanalrosa B CI No. 45160
• Helio real yellow GRN (CI No. 21100) are particularly preferred.
• the copolymer contains 0.1 to 80, preferably 0.5 to 50 and particularly preferably 2 to 20% by weight of polymerized cationic monomers (A).
• R 2 a hydrocarbon radical with 1 to 18 carbon atoms
• R 3 and R 4 identical or different and a hydrocarbon radical having 1 to 18 carbon atoms, or the radicals R 3 and R 4 together form a 5- or 6-membered ring
• R 5 a hydrogen atom or a hydrocarbon radical with 1 to 18 carbon atoms
• X one of the groups
• Y the atoms required to complete a 5- or 6-membered heterocyclic ring.
• hydrocarbon radicals mentioned can be linear or branched alkyl, aryl, arylalkyl or alkylaryl radicals.
• Particularly preferred cations are derivatives of acrylic acid and methacrylic acid according to formulas VII and VIII.
• R 1 , R 2 , R 3 , R 4 and R 5 has the meaning given above.
• Suitable anions of the ionic monomers (A) are those which are derived from acidic compounds containing CH-azides or sulfur or phosphorus and having at least one hydrocarbon radical having 6 to 24 carbon atoms.
• Anions in which branched hydrocarbon radicals are present are particularly suitable.
• the ionic compound can be synthesized by direct reaction in the sense of an acid-base reaction.
• the ionic monomer can be obtained from this aqueous reaction mixture in a high purity by extraction, toluene, isobutanol and mixtures of both solvents being particularly suitable extraction agents.
• Quaternized compounds are generally synthesized in a two-stage process. In the first stage, the N, P or S compound on which the cation is based is quaternized using known methods.
• the quaternization reaction is preferably carried out at temperatures from 0 to 90 ° C. in the presence of organic solvents. It is expedient to add known polymerization inhibitors such as hydroquinone, hydroquinone monomethyl ether or 2,6 di-tert-butyl-p-methylphenol to this stage.
• the quaternized compound is reacted with an alkali salt of the desired anion in aqueous solution.
• the isolation of the ionic monomers can in turn advantageously be carried out by extraction with the solvents mentioned above.
• the preferred synthetic route for the copolymers is the radical polymerization of the ionic monomers.
• the polymerization can be initiated using conventional radical formers such as peroxides and preferably azo compounds.
• Redox polymerization for example using a peroxide / amine system, or photopolymerization is also possible.
• Suitable comonomers (B) are in principle all free-radically polymerizable, olefinically unsaturated compounds, in particular the known vinyl and vinylidene compounds.
• examples include: (meth) acrylic acid and its derivatives such as. B. (meth) acrylic acid ester with C 1 - to C 24 hydrocarbon radicals in the alcohol part, (meth) acrylic acid amide, (meth) acrylonitrile, vinyl esters such as vinyl acetate, vinyl propionate, vinyl aromatics such as styrene or ⁇ -methyl styrene, and also dienes such as Bu tadiene and isoprene, and halogen-containing monomers, such as vinyl chloride and vinylidene chloride.
• Preferred comonomers are (meth) acrylic acid esters with at least one C 1 to C 24 hydrocarbon radical in the alcohol part and styrene. Mixtures of different monomers are also suitable. Good installation rates are achieved above all if (meth) acrylic acid esters are used as comonomers, at least in part. It can both uncrosslinked and by using multifunctional monomers such.
• the copolymer not only charges the dispersed pigment, but also increases the dispersion stability of the pigment dispersion through steric shielding.
• Comonomers which improve the dispersant properties of the copolymer are, for example, vinyl or vinylidene monomers with a C 6 - to C 24 -hydrocarbon radical, in particular (meth) acrylic acid ester with C 6 - to C 24 -hydrocarbon radicals in the alcohol part, for. B.
• these comonomers are preferably used in amounts of 10 to 70 wt .-% (based on the copolymer). In this case it is advantageous to combine the comonomers mentioned here with those with C 1 to C 5 hydrocarbon radicals.
• the copolymer can be synthesized in the absence of the pigment by known processes, such as bulk, solution, precipitation, suspension or emulsion polymerization.
• the copolymer is synthesized in the presence of the dispersed pigment, the copolymer formed at least partially forming a firm physical or chemical bond with the pigment.
• the pigment is used in the form of a non-aqueous 0.5-40% by weight dispersion.
• Aromatic and aliphatic hydrocarbons such as, for example, benzene, toluene, xylene, linear and branched C 6 -C 15 alkanes and cyclohexane or decalin, are primarily suitable as the dispersing medium.
• a polymerization process is preferred in which the pigment dispersion, which may optionally contain a stabilizing agent, is mixed with the ionic monomers and comonomers and the polymerization is initiated as a starting component by means of a radical generator.
• Soluble, high molecular weight compounds such as homopolymers or copolymers of (meth) acrylic acid esters, for example a 1: 1 copolymer of isobutyl methacrylate and lauryl, can be used as stabilizers methacrylate can be used.
• Copolymers with a proportion of 0.1-10% by weight of copolymerized monomers with -OH, -COOH, -NH 2 , -NHR, -NR 2 groups, such as, for example, are also very suitable.
• Particularly suitable stabilizers are block copolymers, for example styrene-stearyl methacrylate block copolymers or mercaptan-modified styrene-butadiene block copolymers (DE-A 34 12 085).
• the polymerization reaction can be carried out according to a "batch process".
• the monomers and the starting component are added to the pigment dispersion all at once and the reaction is initiated by increasing the temperature. In this way, a largely uniform polymer shell is produced.
• the monomers and the starting components are metered in during the polymerization (feed process).
• This embodiment opens up a number of technically very interesting possibilities. You can e.g. B. change the monomer composition over the dosing period to achieve special effects. It has proven to be advantageous to add the above-mentioned suitable comonomers without the addition of ionic monomers at the beginning of the metering period and to add the ionic monomers in a mixture with further comonomers only after a polymerization conversion of 10 to 50%.
• the starting component is also advantageously metered in over the reaction period.
• Solid starting components are expediently dissolved in solvents or monomers.
• the copolymer is used in amounts of 10 to 300, preferably 10 to 100% by weight, based on pigment.
• polymeric additives can be used to prepare the suspension developer according to the invention, for example to increase the dispersion stability or to improve the adhesive and fixing properties of the dispersed pigment.
• the above-mentioned stabilizers based on soluble high-molecular compounds are primarily suitable for increasing the dispersion stability.
• Suitable fixing substances are resins which are compatible with the binder of the photoconductive recording material, e.g. B. with the binder of a photoconductive zinc oxide layer, so that a good adhesion of the generated image on the substrate is obtained after development.
• suitable resins are esters of hydrogenated rosin and fatty oil varnish ("long-oil"), rosin-modified phenol-formaldehyde resin, pentaerythritol esters of rosin, glycerol esters of hydrogenated rosin, Ethyl cellulose, various alkyd resins, polyacrylic and polymethacrylic resin, polystyrene, polyketone resin and polyvinyl acetate. Specific examples of such resins can be found in the literature on electrostatographic suspension developers, e.g. B. in BE-PS 699 157 and in GB-A 1 151 141.
• the suspension developers according to the invention can be prepared using conventional dispersion methods. Good results are achieved using ball mills, bead mills, colloid mills and high-speed stirrers. It may be advantageous to first produce a mixture of the pigment, the polymer and the other polymeric additives, for example by melting in a kneader, and to disperse this mixture in the carrier liquid in a second process step.
• a stable dispersion is generally obtained directly, so that an additional dispersion step can be dispensed with. It is expedient first of all to prepare a toner concentrate from carrier liquid, pigment and polymer with a content of 5 to 50% by weight, preferably 10 to 25% by weight, of solid, which is adjusted to the use concentrations of 0.05 to by adding further carrier liquid 2%, preferably 0.1 to 1% is diluted.
• 2-methacryloxyethyldimethylammonium-1,2,3,4,5-pentaisotridecyloxycarbonylcyclopentadienid is formed as a green oil; 5.45 g (quantitative).
• Example 4 a copolymer is prepared from 2 g of ionic monomer from Example 3, 9 g of styrene and 9 g of lauryl methacrylate. Yield: 15 g, [ ⁇ ]: 0.72 dl / g in toluene, at 25 ° C
• the suspension developer is filled into an electrophoresis cell with 2 planar electrodes, each with a surface area of 20 cm 2 and an electrode spacing of 0.15 cm.
• the electrical current that occurs when a voltage of 500 V is applied for 0.5 s is measured.
• the integral of the current over the period of 0.5 s is the Q T value.
• Q T is a measure of the charge on the toner particles.
• the deposition of the toner particles (blackening) on the negative electrode (cathode) shows that they are positively charged.
• the charge stability of the toner particles was checked by measuring Q T1 immediately after the liquid developer was prepared and Q T2 after 7 days of storage:
• Example 6 was repeated using 5 g of the copolymer from Example 5 and 5 g of carbon black pigment with a BET surface area of 90 m 2 2 / g:
• 80 g of a carbon black pigment with a BET surface area of 30 m 2 / g are mixed with 20 g of a copolymer of equal parts of lauryl methacrylate and isobutyl methacrylate with a molecular weight of 120,000 and dispersed in 100 g of isododecane using a ball mill.
• 250 g of the dispersion obtained are transferred to a stirred reactor and heated to 80 ° C.
• 250 mg of azoisobutyronitrile are first added with stirring, and immediately after that a solution of 75 g of toluene, 7.5 g of lauryl methacrylate, 7.5 g of isobutyl methacrylate, 5 g of divinylbenzene and 5 g of the ionic monomer from Examples 1 and 100 is added over a period of 60 minutes mg of azoisobutyronitrile evenly metered in.
• the dispersion is kept under stirring for 1 hour at 80 ° C. and 3 hours at 90 ° C.
• the dispersion is centrifuged for cleaning using a cup centrifuge; the solid formed is isolated and redispersed in 250 g of pure isododecane using a shaker. This process is repeated once. The dispersion is then adjusted to 0.4% by weight solids by adding further isododecane:
• 100 g of the dispersion obtained are diluted with 150 g of isododecane, transferred to a stirred reactor and heated to 80.degree. While stirring, 250 mg of azoisobutyronitrile and then solution I are metered in uniformly over a period of 30 minutes.
• solution II is metered in.
• the dispersion is kept at 80 ° C. for 1 hour and at 90 ° C. for 3 hours with further stirring.
• the dispersion is centrifuged for cleaning using a cup centrifuge, the solid formed is isolated and redispersed in 250 g of pure isododecane using a shaker. This process is repeated once. The disperson is then adjusted to 0.4% by weight of solid by adding further isododecane and tested. average particle size: 780 nm
• Example 9 is repeated using the ionic monomer from Example 2
• Example 5 is repeated using the ionic monomer from Example 1
• 80 g of a carbon black pigment with a BET surface area of 95 m 2 / g are dispersed in 300 g of isododecane using 20 g of the copolymer described in Example 8 using a ball mill.
• solution II is metered in.
• the dispersion is kept at 80 ° C. for 1 hour and at 90 ° C. for 3 hours with further stirring.
• the dispersion is centrifuged using a cup centrifuge, the solid formed is isolated and redispersed in 300 g of pure isododecane. This process is repeated once. The dispersion is then adjusted to a solids content of 0.4% and added by adding further isododecane.
• a dispersion is prepared in a ball mill from 4 g of carbon black pigment with a BET surface area of 30 m 2 / g, 1 g of a copolymer made from 85% isobutyl methacrylate and 15% stearyl methacrylate with a molecular weight Mw of 170,000 and in 45 g of isododecane.
• the dispersion is diluted to 0.4% solids, mixed with 80 mg of zinc (2-butyl) octyl phosphate (preparation according to GB-PS 1 151 141) and tested.
• the table shows that the suspension developers according to the invention have no conductivity of the carrier liquid.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Liquid Developers In Electrophotography (AREA)
• Polymerisation Methods In General (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

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• 1984
  • 1984-07-17 DE DE19843426256 patent/DE3426256A1/de not_active Withdrawn
• 1985
  • 1985-07-05 US US06/752,095 patent/US4639403A/en not_active Expired - Fee Related
  • 1985-07-09 EP EP85108465A patent/EP0168748B1/fr not_active Expired - Lifetime
  • 1985-07-09 DE DE8585108465T patent/DE3580798D1/de not_active Expired - Fee Related
  • 1985-07-12 JP JP15257285A patent/JPS6139058A/ja active Pending

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