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
• • 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
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
  • Y10T428/2982—Particulate matter [e.g., sphere, flake, etc.]
  • Y10T428/2991—Coated
  • Y10T428/2998—Coated including synthetic resin or polymer

Definitions

• the invention relates to an electrostatographic suspension developer, based on pigment particles coated with polycyanoacrylate, and to a method for producing the developer.
• Dry and wet development methods are known for developing electrostatic images on electrostatographic recording materials.
• the wet development processes are superior to the dry development processes with regard to edge sharpness and resolving power, especially in color copying processes.
• 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 pigments used are, for example, conventional azo dyes, xanthene dyes, Phthalocyanine dyes, as described, inter alia, in DE-A 29 44 021. Carbon black types are predominantly 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 which are composed of less polar monomers (for example C 6 -C 20 -alkyl (meth) acrylate) and more polar monomers (for example aminomethacrylates or vinylpyrrolidone) has been widely described (for example 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 (for example 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 (for example 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 2 157 343, GB-A 2 029 049 or US-A 4033890.
• polymers contain ionic groups, these can play a role in the build-up of the toner charge generated by metal salts of organic acids with long aliphatic residues.
• 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 in combination with conventional toner polymers is that the electrical properties of the liquid developers, such as conductivity and particle charge, are not stable when the concentration changes and are influenced to a large extent by water traces (e.g. 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 further improved positive toner charge, high charge stability and low conductivity of the dispersion medium.
• an electrostatographic suspension developer which contains a dispersed pigment in an electrically insulating carrier liquid with a volume resistance of at least 10 9 Ohm.cm and a dielectric constant below 3 and which is characterized in that the pigment is coated with polycyanoacrylate .
• Another object of the invention is a method for producing an electrostatographic suspension developer, which is characterized in that a dispersed basic or neutral pigment is coated in a non-polar carrier liquid with polycyanoacrylate by anionic polymerization.
• hydrocarbons As a carrier liquid with a volume resistance of min. least 10 9 Ohm.cm and a dielectric constant below 3 can hydrocarbons. Fluorocarbons or silicone oils are used; preference is given to hydrocarbon-based liquids, for example aromatic hydrocarbons such as benzene, toluene or xylenes or aliphatic C 6 -C 15 -hydrocarbons. like 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.
• the black and color pigments usually used for suspension developers are suitable as pigments. if they have neutral or basic surfaces.
• the suitability of a pigment can be determined in a simple manner by measuring the pH with the aid of a glass electrode in a pigment-water suspension. This method is described in detail in DIN 53 200, for example.
• Suitable pigments have pH values of 6-12, preferably 7-11. It is possible in many cases. by a preferably alkaline pretreatment of the Pi g- mentes to affect the pH value, ie, to adjust the desired pH.
• the water content of the pigments is also important for their use according to the invention.
• pigments with a low water content preferably with a water content of less than 1, particularly preferably less than 0.10%, of water are used.
• Black pigments are primarily soot types. Carbon black with a primary particle size of 20-80 nm, a BET surface area of 20-150 m 2 / g and a pH value of 8-10 is preferred. Color pigments suitable without pretreatment are CI No. 74160, CI No. 45160 and CI No. 21100.
• Cyanoacrylates of the following general formula are preferably used to coat the pigments: in the R is alkyl, in particular having 1 to 10 carbon atoms, cycloalkyl, in particular cyclohexyl, alkenyl, in particular allyl, aryl, in particular phenyl and aralkyl, in particular benzyl.
• substituents mentioned can in turn be substituted with substituents customary in the field of polycyanoacrylates, e.g. Alkoxy groups, especially methoxy and ethoxy.
• substituents customary in the field of polycyanoacrylates e.g. Alkoxy groups, especially methoxy and ethoxy.
• Different cyanoacrylates can also be used at the same time to form appropriate copolymers.
• cyanoacrylates are ethyl, methyl, butyl, isobutyl, amyl and lauryl cyanoacrylate as well as methoxyethyl cyanoacrylate and ethoxyethyl cyanoacrylate, the isobutyl cyanoacrylate being particularly suitable.
• Special. Mixtures containing 5-50% by weight of allyl cyanoacrylate are particularly favorable.
• the amount of polycyanoacrylate is 2.5-350% by weight, preferably 10-250% by weight, based on the amount of pigment.
• the pigment is coated with an additional shell made from a copolymer of A) cationic monomers and B) free-radically polymerizable, olefinically unsaturated compounds.
• the copolymer generally acts as a charge-determining substance, i.e. it effects or increases the positive electrostatic charge of the coated pigment particles.
• 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).
• the cationic monomers contain onium groups, preferably ammonium, phosphonium or sulfonium groups; the negative counterions are derived from CH-acidic or sulfur or phosphorus-containing acidic compounds with at least one hydrocarbon radical having 6 to 24 carbon atoms.
• hydrocarbon radicals mentioned can be linear or branched alkyl, aryl, arylalkyl or alkylaryl radicals, which can optionally be substituted.
• the cationic monomers described above can be used directly to produce the additional copolymer shell. However, it is also possible first to prepare a copolymer with the basic monomers on which the cation part is based and then to introduce the positive charge by protonation or quaternization with, if appropriate, subsequent anion exchange.
• 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 (meth) acrylic esters 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, also dienes such as butadiene 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 G 24 hydrocarbon radical in the alcohol part and styrene. Mixtures of different monomers are also suitable. Good installation rates who which is achieved especially when at least some (meth) acrylic acid esters are used as comonomers. Copolymers which are not crosslinked or crosslinked by using polyfunctional monomers such as, for example, ethylene dimethacrylate or divinylbenzene can be built up.
• the copolymer not only charges the dispersed pigment coated with polycyanoacrylate, but also increases the dispersion stability of the pigment dispersion by 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 example stearyl methacrylate, lauryl methacrylate or 2 -Ethylhexyl methacrylate, these comonomers preferably being used in amounts of 10 to 70% by weight (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 basic or neutral pigment is dispersed in a non-polar solvent.
• the solvents described above as the carrier liquid are particularly suitable as solvents.
• the solvents are dried well before use.
• the pigment concentration should preferably be 0.1 to 40% by weight. It is advisable to use a dispersing agent in the preparation of the dispersion.
• 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 dispersants.
• Particularly suitable dispersing aids are block copolymers, e.g. Styrene-stearyl methacrylate block copolymers or mercaptan-modified styrene-butadiene block copolymers (DE-A 34 12 085).
• the pigment is coated by adding the monomeric cyanoacrylates, preferably in the form of a feed process, for example over a period of 10 to 120 minutes.
• the anionic polymerization takes place under the catalytic action of the pigment and leads to high polymer conversions in short reaction times, generally from more than 70%, the polymer formed is formed in the form of a shell on the pigment surface.
• the polymerization temperature is not critical per se, the temperature range from 0 to 80 ° C. is preferred for practical reasons.
• the known control agents can be used to regulate the electrical charge of the pigment particles coated with polycyanoacrylate.
• These are e.g. Oil-soluble ionic compounds such as metal salts of long-chain organic acids.
• Mixtures of different control agents e.g. a mixture of different control agents with opposite charge effects can be used so that the strength of the charge on the toner or its polarity can be adjusted by changing the mixing ratio of the two control agents (GB-PS 1 411 287, 1 411 537 and 1 411 739).
• Particularly suitable, positive working control materials are described in GB-PS 1 151 141.
• These control substances are divalent or trivalent metal salts of an oxyacid derived from phosphorus and containing an organic radical.
• the positive charge of the pigment particles is generated or enhanced by applying an additional shell made of a copolymer of the cationic monomers A and comonomers B described above.
• This additional polymer shell is applied by a radical polymerization process in which the dispersion of the pigment coated with polycyanoacrylate with the monomer A or the basic monomer on which the cationic monomer A is based and comonomers B as well as a radical generator is added as starting component and the polymerization at a temperature of preferably 50 to 120 C is passed up to conversions of at least 70% *.
• the known per-compounds and preferably azo compounds can be used as radical formers.
• the monomers and radical formers are metered in, preferably by a feed process.
• the dispersion obtained by the present process can be diluted to the desired working concentration, for example to 0.01% to 1%, by adding further solvent as carrier liquid. On this occasion, if this should be desired, the solvent present can be replaced by another carrier liquid, for example by centrifugation and then redispersion.
• other 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 dispersing aids based on soluble high-molecular compounds are primarily suitable for increasing the dispersion stability.
• Resins which are compatible with the binder of the recording material are suitable as fixing substances. so that good adhesion of the generated image to the substrate is obtained after development.
• 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 alkyd resins, polyacrylic and polymethacrylic resin, polystyrene, poly (vinyl acetate).
• Specific examples of such resins can be found in the literature on electrostatographic suspension developers, e.g. in BE-PS 699 157 and in GB-A 1 151 141.
• the suspension developer showed very good storage stability.
• the particle size and conductivity were unchanged after 6 months of storage.
• Example 1 B 100 g of the pigment dispersion from Example 1 B are transferred to a stirred reactor with exclusion of moisture. With effective stirring, a solution of 36 g of isobutyl cyanoacrylate, 4 g of allyl cyanoacrylate and 50 g of isododecane is added dropwise within 30 minutes. Subsequently, the temperature to 80 * C is increased, and in 400 mg azobisisobutyronitrile was added. A solution of 10 g of N, N-dimethylaminoethyl methacrylate, 5 g of styrene, 5 g of butyl acrylate, 40 g of toluene and 40 g of isododecane is added while flushing with nitrogen.
• PTDCCP pentaisotridecyloxycarbonylcyclopentadiene
• Suspension developers A, B and C have a positive toner charge. They show excellent developer properties. Conductivity and particle size do not change during storage.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Liquid Developers In Electrophotography (AREA)

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• 1985
  • 1985-04-25 DE DE19853514867 patent/DE3514867A1/de not_active Withdrawn
• 1986
  • 1986-04-14 US US06/851,489 patent/US4719164A/en not_active Expired - Fee Related
  • 1986-04-14 EP EP86105087A patent/EP0200067A3/fr not_active Withdrawn
  • 1986-04-23 JP JP61092454A patent/JPS61249060A/ja active Pending

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