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
  • G03G9/13—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
• • 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

Definitions

• the invention relates to an improved electrostatographic suspension developer which contains a basic polymer and a Bronsted acid to produce a positive toner charge, and to a process for its preparation.
• 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.
• 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 40 33 890. It is known from DE-A 32 32 062 that the pigment particles of a suspension developer can be formed by building up a cross-linked polymer shell Sterically stabilize 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 suspension developers, such as conductivity and particle charge, are not stable when the concentration changes and are influenced to a large extent by traces of water (for example atmospheric humidity). Furthermore, such suspension developers generally show a high electrical conductivity of the dispersion medium, which affects the electrophoretic deposition of the toner particles.
• the object of the invention is to provide an electrostatographic suspension developer with a positive toner charge and improved charge stability.
• a suspension developer which, in an electrically insulating carrier liquid with a volume resistance of at least 10 9 Ohm.cm and a dielectric constant below 3, contains a dispersed pigment and contains a polymer with secondary or tertiary amino groups, the secondary or tertiary amino groups being completely or partially neutralized with a Bronsted acid with at least one C 6 -C 24 hydrocarbon group.
• Hydrocarbons, fluorocarbons or silicone oils can be used as carrier liquids with a volume resistance of at least 10 9 ohm.cm and a dielectric constant below 3.
• Hydrocarbon-based liquids for example aromatic hydrocarbons such as benzene, toluene or xylenes or aliphatic C 6 -C 15 hydrocarbons, are preferred, 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 black and color pigments mentioned above, which are usually used for suspension developers.
• Spirit schwart (CI No. 50415), aniline black (CI No. 50440), cyanine blue (CI No. 74250), brilliant carmine 6 B (CI 15850), real red (CI No. 15 865), 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.
• hydrocarbon radicals mentioned can be linear or branched alkyl, aryl, arylalkyl or alkyl acryl radicals.
• (meth) acrylate here means acrylate or methacrylate.
• the basic monomers mentioned can be copolymerized with free-radically polymerizable, olefinically unsaturated comonomers. Vinyl and vinylidene compounds are primarily suitable. Examples include:
• 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 esters are used as comonomers, at least in part. It can both uncrosslinked and by using multifunctional monomers such.
• the polymer increases the dispersion stability of the pigment dispersers steric shielding.
• Comonomers which improve the dispersant properties of the polymer are, for example, vinyl or vinylidene monomers having a hydrocarbon radical having 6 to 24 carbon atoms, such as stearyl (meth) acrylate, lauryl (meth) acrylate or 2-ethylhexyl (meth) acrylate, these comonomers preferably being in Amounts of 10 to 70 wt .-% (based on the polymer) are used.
• Known ionic or radical polymerization methods can be used to prepare the polymer.
• the preferred route of synthesis 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.
• the polymer can be synthesized in the absence of the pigment by known processes such as bulk, solution, precipitation, suspension or emulsion polymerization. According to a preferred embodiment, the polymer 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. In this synthetic method, the pigment is used in the form of a non-aqueous 0.5 - 40% 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.
• Preferred is a polymerization process in which basic monomers and optionally comonomers are added to the pigment dispersion, which may optionally contain a stabilizing agent, 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 methacrylate, can be used as stabilizers.
• 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.
• Block copolymers for example styrene-stearyl meth, are particularly suitable stabilizers acrylate block copolymers or mercaptan-modified styrene-butadiene block copolymers (DE-A 3 412 085).
• 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.
• a largely uniform polymer shell is obtained in this way.
• the monomers and the starting components are metered in during the polymerization (feed process). In this embodiment it is possible to change the monomer composition over the metering period.
• 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.
• R 14 iso C 13 H 27 HC (SO 2 -R 14 ) 3
• the sulfonic acids, sulfuric acid monoesters, phosphonic acids and phosphoric acid mono- or diesters used according to the invention as Br ⁇ nsted acids are accessible from known salts, from which they can be obtained in a simple manner with the aid of ion exchangers.
• novel 1, 2, 3, 4, 5-pentaalkoxycarbonylcyclopentadienes with C 6 to C 24 hydrocarbon radicals are obtained by transesterification of the 1, 2, 3, 4, 5-pentamethoxycarbonylcyclopentadiene with the corresponding C 6 to C 24 alcohols.
• the use of a transesterification catalyst can be dispensed with.
• the dicyanoacetic acid esters are synthesized by reacting sodium malodinitrile with chloroformic acid ester in a molar ratio of 2: 1 in ethanol as the solvent.
• the sodium salt initially formed is freed from malodinitrile by digestion with, for example, methylene chloride and converted into the acid form with the aid of an ion exchanger.
• the trisalkylsulfonylmethanes with at least one C 6 to C 24 hydrocarbon radical can be synthesized by reaction of the corresponding trithioorthoformic acid esters with peracetic acid in chlorinated hydrocarbons, for example in 1,2-dichloropropane, the isolation of the compounds soluble in the chlorinated hydrocarbon by distilling off the solvent with the addition of Water takes place.
• the Br ⁇ nsted acids are generally in amounts of 0.01 to 10 wt .-%, preferably 0.1 to 5 wt .-%, be referred to the solids content of the suspension developer according to the invention used.
• the amount used is such that the secondary or tertiary amino groups contained in the polymer are completely or partially, but preferably only partially, neutralized.
• the extent of the positive toner charge can be adjusted in a simple manner via the type and the amount of Bronsted acid.
• further polymeric additives can be used to produce 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 stabilizers specified above, based on soluble high-molecular compounds, are primarily suitable for increasing the dispersion stability.
• Resins are suitable as fixing substances, which should be compatible with the binder of the photoconductive recording material, e.g. B. with the binder of a photoconductive zinc oxide layer, so that according to the invention good adhesion of the image formed on the substrate is obtained.
• suitable resins are esters of hydrogenated rosin and long-oil oil, "rosin-modified phenol-formaldehyde resin, pentaerythritol esters of rosin, glycerol esters of hydrogenated rosin, ethyl cellulose, various alkyl resins, polyacrylic and polymethacrylic resin, polystyrene, polyketone and polyvinyl acetate. Specific examples of such resins can be found in the literature on electrostatographic suspension developers, e.g. B. in BE-A 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 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.
• the sodium salt is converted into dicyanoacetic acid isodecyl ester in quantitative yield using a cation exchanger.
• the deposition of the toner particles (blue color) on the negative electrode (cathode) shows that they are positively charged.
• the charge stability of the toner particles was checked by measuring the value Q Tl immediately after the liquid developer was prepared and Q T2 after 7 days of storage:
• Example 3 was repeated, using a carbon black pigment with a BET surface area of 30 m 2 / g instead of Helioechtblau HG (CI 74160). The test showed the following values:
• 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 zinc (2-butyl) octyl phosphate (preparation according to GB-A 1 151 141) and tested.

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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)

Applications Claiming Priority (2)

Publications (3)

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• 1984
  • 1984-07-17 DE DE19843426198 patent/DE3426198A1/de not_active Withdrawn
• 1985
  • 1985-07-05 US US06/752,086 patent/US4631243A/en not_active Expired - Fee Related
  • 1985-07-09 DE DE8585108464T patent/DE3579857D1/de not_active Expired - Fee Related
  • 1985-07-09 EP EP85108464A patent/EP0168747B1/fr not_active Expired - Lifetime
  • 1985-07-12 JP JP15257385A patent/JPS6139059A/ja active Pending

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