Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G8/00—Layers covering the final reproduction, e.g. for protecting, for writing thereon

Definitions

• This invention relates to an electrostatographic imaging method.
• this invention relates to a method to improve the mechanical properties of fixed toner images comprising several superimposed toner layers.
• Electrostatic printing methods are manifold, e.g. Direct Electrostatic Printing, wherein electrostatic printing is performed directly from a toner delivery means on a receiving substrate, the latter not bearing any imagewise latent electrostatic image, by means of an electronically addressable printhead structure.
• electrostatic printing toner images are made on an image-forming element in the form of a rotating drum provided with an electrostatic layer built up from a number of controllable electrodes in and beneath a dielectric layer.
• the voltage that is image-wise applied to said controllable electrodes attracts charged toner particles from a toner source.
• an electrostatic latent image is formed by the steps of uniformly charging a photoconductive member and imagewise discharging it by an imagewise modulated photo-exposure.
• an electrostatic latent image is formed by imagewise depositing electrically charged particles, e.g. from electron beam or ionized gas onto a dielectric substrate.
• the obtained latent images are developed, i.e. converted into visible images by selectively depositing thereon light absorbing particles, called toner particles, which usually are triboelectrically charged.
• a latent magnetic image is formed in a magnetizable substrate by a pattern wise modulated magnetic field.
• the magnetizable substrate must accept and hold the magnetic field pattern required for toner development which proceeds with magnetically attractable toner particles.
• dry development the application of dry toner powder to the substrate carrying the latent electrostatic image may be carried out by different methods known as, “cascade”, “magnetic brush”, “powder cloud”, “impression” or “transfer” development also known as “touchdown” development described e.g. by Thomas L. Thourson in IEEE Transactions on Electronic Devices, Vol. ED-19, No. 4, April 1972, pp.495-511.
• the toning developer is directly, image wise deposited on a final substrate to form a visible image.
• a latent image, electrostatic or magnetographic is developed to form a visible image.
• This visible image is the transferred, either directly or via an intermediate transfer medium, to a final substrate.
• the visible image of electrostatically or magnetically attracted toner particles, on the final substrate is not permanent and has to be fixed by causing the toner particles to adhere to each other and the substrate by softening or fusing them followed by cooling. Normally fixing proceeds on more or less porous paper by causing or forcing the softened or fused toner mass to penetrate into the surface irregularities of the paper.
• Dry-development toners essentially comprise a thermoplastic binder consisting of a thermoplastic resin or mixture of resins (ref. e.g. US-P 4,271,249) including colouring matter, e.g. carbon black or finely dispersed dye pigments or soluble dyes.
• the triboelectrically chargeability is defined by said substances and may, optionally, be modified with a charge controlling agent.
• the toner image fixed to a substrate is vulnerable and can e.g. easily be scratched.
• full colour images or black and white images wherein the tonal range is extended by the use of toner particles comprising different amounts of black pigment are vulnerable, due to the height differences in the images. These height differences occur because of the superposition of various layers of toner particles depending on the colour hue or to the grey density that has to be reproduced. This "surface relief" enhances the possibility for mechanical scratches to occur in the image. It has been disclosed to apply a layer of colourless toner particles on top of the four colour toner image to protect the image and at the same time equalize the gloss of the image.
• the objects of the invention are realized by providing a toner image fixed on a final substrate characterized in that i) said toner image comprises fused toner particles and ii) said toner image comprises on top of it a non-image wise applied radiation cured layer, said layer having a thickness between 1 ⁇ m and 20 ⁇ m.
• Toner images fixed to a final substrate, often show a "surface relief", i.e. differences in height between different parts of the image. This is so in monochrome image where the image is formed by the presence or absence of toner particles on a substrate, but it is especially so in full colour images were different colours and hues are realized by the superposition of yellow, magenta, cyan and black (YMCK) toners.
• the yellow parts are e.g. made up by one layer of toner particles and the black parts by the superposition of four layers of toner particles. This gives raise to differences in height in the image, furtheron referred to as "surface relief".
• this radiation curable composition can be either an electron beam curable composition or a UV-curable composition.
• the radiation curing can proceed off-line or on-line. When the curing proceeds off-line, there is no special preference for the curing method, when the curing proceeds on-line (i.e. in the electrostatographic printing apparatus itself), it is preferred in the present invention to use UV-curable compositions.
• Such a layer is applied in such a way that the dry thickness of it is between 1 ⁇ m and 20 ⁇ m, preferably between 4 and 12 ⁇ m.
• This thickness is achieved by applying between 1 g/m 2 and 20 g/m 2 , preferably between 4 g/m 2 and 12 g/m 2 of radiation curable composition on the image.
• Very useful UV-curable compositions for forming a protective coating in the present invention contain as primary components :
• the components of the radiation curable composition for use in this invention are chosen such the components do not, or only in to small extent penetrate, in the toner particles forming the image.
• the penetration of the components in the toner particles can be measured as follows. On an fused toner image (mono-chrome or full colour) a 6 ⁇ m thick layer of the UV-curable composition under investigation, is applied by a bar coater. Then the layer is UV-cured for 0.5 sec with a high pressure mercury lamp giving an intensity of 80 W/cm. The gloss of the layer is measured with a in a Minolta Multi-gloss 268 reflectometer (trade name of Minolta, Osaka, Japan). When this gloss was higher than 80 %, the UV-curable composition is a useful composition according to the present invention. It seems that the penetration of the UV-curable composition decreases as the cure-rate of the composition increases.
• the usual amounts of three primary components calculated on the total coating composition are 0-100 % by weight (% wt/wt), preferably between 5 and 90 % wt/wt for the prepolymer, 0-100 % wt/wt, preferably between 5 and 90 %wt/wt for the reactive diluent
• Optionally minor amounts (e.g. 5 % by weight) of non-reactive organic solvent for the prepolymer may be present.
• the oligomer (or prepolymer) and the reactive diluent monomer together account for between 30 and 100 % by weight, preferably between 35 and 95 % wt/wt of the total composition.
• an oligomer and a reactive diluent monomer are present in the radiation curable composition, then is the ratio between said oligomer (prepolymer) and said reactive diluent monomer, in compositions useful in the present invention, between 10:1 and 1:10, preferably between 5:1 and 1:5.
• Suitable prepolymers for use, either alone or in a mixture) in a radiation-curable composition applied according to the present invention are the following :
• Unsaturated polyesters useful in UV-curable compositions according to this invention, are polyester comprising more than 40 mole percent of moieties derived from unsaturated dicarboxylic acids as, e.g. maleic acid, fumaric acid.
• Epoxy acrylates are prepared by the reaction of an epoxy resin and acrylic or methacrylic acid.
• the epoxy acrylate resin comprises bisphenol 'A' diglycidyl ether moieties.
• Useful epoxyacrylate prepolymers are available in 100 % oligomer form as well as in a solution in a diluent reactive monomer. Typical 100 % oligomers are, e.g., ACTILANE 72 (trade name of Harcros Chemicals Ltd, Manchester, England), ACTOCRYL 100 (tradename of Anchor Chemical (UK), Manchester, England), EBECRYL 600, EBECRYL 3700, EBECRYL 3701 (trade names of UCB, Radcure Specialities, Drogenbos, Belgium), etc.
• Typical epoxyacrylates as prepolymer diluted in a diluent reactive monomer are, e.g. ACTILANE 7220 TP, (trade name of Harcros Chemicals Ltd, Manchester, England), wherein the diluent monomer is TriPropylene Glycol DiAcrylate (TPGDA), ACTOCRYL 10020 A, (tradename of Anchor Chemical (UK), Manchester, England), wherein the diluent monomer is also TPGDA, EBECRYL 604, wherein the diluent monomer is 1,6 HexaneDiol DiAcrylate (HDDA), EBECRYL 1940, wherein the diluent monomer is DiPropylene Glycol DiAcrylate (DGGDA) (EBECRYL is a trade name of UCB, Radcure specialities, Drogenbos, Belgium), etc.
• TPGDA TriPropylene Glycol DiAcrylate
• ACTOCRYL 10020 A
• Urethane Acrylates useful in the present invention can be prepared by the reaction of one or more organic mono- or poly-isocyanate compounds and an hydroxyacrylate or hydroxymethacrylate. These basic urethane acrylates can be modified by introducing in the reaction mixture other hydroxyl group comprising compounds together with one or more organic mono- or poly-isocyanate compounds and an hydroxyacrylate or hydroxymethacrylate.
• the other hydroxyl group comprising compound is a diol or polyol
• polyol urethane acrylates are produced; when said compound is a polyester with free hydroxylgroups, polyester urethane acrylates are formed; when said compound is a polyether polyol or diol, polyether urethane acrylates are formed.
• All modifications of the basic urethane acrylate compounds are useful in the present invention.
• poly-isocyanate compounds By using poly-isocyanate compounds, the acrylate functionality in the urethaneacrylate oligomer (prepolymer) can be enhanced.
• Typical very useful isocyanate compounds are, e.g., toluenediisocyanate, tetramethylenediisocyanate, hexamethylenediisocyanate, etc.
• the isocyanate compounds available through Bayer, Leverkusen, Germany under tradename DESMODUR are very useful for preparing urethaneacrylates to be used as oligomer in the present invention.
• Useful hydroxyacrylates for preparing said urethaneacrylates are, e.g.
• Urethaneacrylates are preferred for use as oligomers (prepolymers) in a UV-curable composition according to the present invention. These prepolymers have excellent film forming characteristics and by proper choice of the oligomer a widely varying range of film properties can be realized. Also Polyester Urethane Acrylates can be useful as oligomer (prepolymer) in UV-curable compositions for use in the present invention. Typical useful polyester urethane acrylates in accordance with this invention, consist of three major components : a polyester polyol, i.e.
• diol or polyol urethane acrylates can be used in the present invention, typical members of this group comprise a diol (ethylene glycol, 1,6 hexanediol, etc) and/or a polyol (glycerol, trimethylolpropane, etc), a multifunctional isocyanate and a hydroxyacrylate or hydroxymethacrylate.
• diol or polyol urethane acrylates can be used in the present invention, typical members of this group comprise a diol (ethylene glycol, 1,6 hexanediol, etc) and/or a polyol (glycerol, trimethylolpropane, etc), a multifunctional isocyanate and a hydroxyacrylate or hydroxymethacrylate.
• a polyol is used the resulting urethane is a "hard" urethane acrylate
• a aliphatic diol e.g.
• the resulting urethane is a "soft" urethane acrylate.
• the hardness and the brittleness of a UV-cured layer of the polyol urethanes can be controlled.
• Several urethane acrylates are commercially available in 100 % oligomer form as well as in a solution in a diluent reactive monomer.
• Typical 100 % oligomers are, e.g., ACTILANE 17 (trade name of Harcros Chemicals Ltd, Manchester, England for a flexible aromatic urethane acrylate), ACTILANE 40 (trade name of Harcros Chemicals Ltd, Manchester, England for a hard aromatic urethane acrylate), ACTOCRYL 300 (tradename of Anchor Chemical (UK), Manchester, England, for a flexible aromatic urethane acrylate with functionality 2), EBECRYL 210 an aromatic urethane acrylate with functionality 2, EBECRYL 220 an aromatic urethane acrylate with functionality 6, EBECRYL 6700 an aromatic urethane acrylate with functionality 2.3, EBECRYL 270 a flexible aliphatic urethane acrylate with functionality 2 (EBECRYL is a trade name of UCB, Radcure Specialities, Drogenbos, Belgium), etc.
• ACTILANE 17 trade name of Harcros Chemicals Ltd, Manchester, England for
• Polyester urethane acrylates are, a.o., CRAYNOR CN 960 (trade name of Cray Valley - Radiation curing and Speciality Monomers, Puteaux, France for a hard polyester urethane acrylate), CRAYNOR CN 961 (trade name of Cray Valley - Radiation curing and Speciality Monomers, Puteaux, France for a resilient polyester urethane acrylate) and CRAYNOR CN 962 (trade name of Cray Valley - Radiation curing and Speciality Monomers, Puteaux, France for a flexible polyester urethane acrylate).
• PHOTOMER 6118 (trade name of Harcros Chemicals Ltd, Manchester, England) is a typical polyether urethane acrylate.
• Comparable compounds are available, from the same companies, as solution in a diluent reactive monomer, e.g. ACTILANE 182TP (trade name of Harcros Chemicals Ltd, Manchester, England for an aromatic urethane acrylate in TPGDA), ACTILANE 2020TP (trade name of Harcros Chemicals Ltd, Manchester, England for an aliphatic urethane acrylate in TPGDA), ACTOCRYL 330X (tradename of Anchor Chemical (UK), Manchester, England, for a resilient aliphatic urethane acrylate with functionality " in TPGDA), EBECRYL 204 an aromatic urethane acrylate with functionality 3 in HDDA, EBECRYL 224 an aliphatic urethane acrylate with functionality 2 in HDDA, EBECRYL 264 an aliphatic urethane acrylate with functionality 3 in HDDA, (EBECRYL is a trade name of UCB, Radcure Specialities, Drogenbos, Belgium),
• Polyester acrylates are prepared by the condensation of acrylic acid with hydroxyl groups on a polyol or a polyester backbone or by the reaction of hydroxy acrylate (hydroxymethacrylate) with residual acid groups on a polyester structure.
• polyesters showing a hydroxyl value and/or a carboxyl value > 2.5 mg KOH/g of polyester are beneficially used.
• polyester acrylates are commercially available in diluent free form or as a solution in a diluent reactive monomer.
• Typical examples of commercial diluent free polyester acrylates are EBECRYL 657 a tetrafunctional compound, EBECRYL 870 a hexafunctional compound, (EBECRYL is a trade name of UCB, Radcure Specialities, Drogenbos, Belgium), etc.
• Acrylic resins are prepared by free radical polymerization and can proceed in four different techniques, bulk polymerisation, solution polymerisation, emulsion polymerisation and dispersion polymerisation.
• the bulk polymerisation is generally speaking quite impractical due to the exothermic nature of the free radical reaction.
• acrylic resins with pendant functionality are first prepared and then reacted with e.g. an hydroxyacrylate or hydroxymethacrylate as described above for polyester acrylates and urethane acrylates.
• Monomers with functional groups and being suitable for incorporation in the acrylic resin are,e.g., acrylic acid, methacrylic acid, maleic anhydride, glycidylacrylate, dimethylamino acrylate, allyl isocyanate, methacrylamide, etc.
• Reactive diluent monomers that preferably serve, either alone or in a mixture, as solvent for the prepolymers are chosen on the basis of several properties :
• Mono-functional diluent monomers are not necessarily applied in conjunction with unsaturated prepolymers but can be used to form a radiation-curable composition with good abrasion resistance in conjunction with saturated polyesters, e.g. polyethylene terephthalate and polyethylene isophthalate.
• Preferred mono-functional monomers for use therewith are methyl methacrylate and tetrahydrofurfuryl methacrylate.
• Suitable di-functional monomers are :
• Suitable tri- or more-functional monomers are :
• the tri- or more functional diluent reactive monomers could also be classified with the oligomers useful in the present invention.
• oligomers useful in the present invention Especially alkoxylated tetraacrylates (ATTA) and highly alkoxylated tetraacrylates (PPTTA) are considered to be rather oligomers. Therefore these compounds can be used in a radiation curable solution as oligomer (or prepolymer) and without the use of a diluent reactive monomer.
• Pentaacrylates, tetraacrylates and alkoxylated tetraacrylates hereinafter for short : multiacrylates have low viscosity, good flow characteristics and excellent cure-rates.
• a particularly useful property of these multiacrylates is the fact that they give very low irritation and have low odour. They can give hard though films with very good abrasion resistance. For all these reason said multiacrylates are very useful compounds in accordance with the present invention. Said multiacrylates have also the advantage that there is little or no penetration in the toner particles, so that a thin layer of UV-curable compound can be used to achieve the advantages of this invention, i.e. low scratchability, high even gloss, high solvent resistance and high weatherability. This thin layer has the advantage that the image on the substrate is made up of relatively thin layer, which decreases the possible brittleness of the image and improves the flexibility of the image.
• UV ultraviolet radiation
• a photoinitiator is present in the radiation curable composition to serve as a catalyst to initiate the polymerization of the monomers and their optional cross-linking with the pre-polymers resulting in curing of the coated protective layer composition.
• a photosensitizer for accelerating the effect of the photoinitiator may be present.
• Photoinitiators suitable for use in UV-curable coating compositions belong to the class of organic carbonyl compounds, for example, benzoin ether series compounds such as benzoin isopropyl, isobutylether; benzil ketal series compounds; ketoxime esters; benzophenone series compounds such as benzophenone, o-benzoylmethylbenzoate; acetophenone series compounds such as acetophenone, trichloroacetophenone, 1,1-dichloroacetophenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone; thioxanthone series compounds such as 2-chlorothioxanthone, 2-ethylthioxanthone; and compounds such as 2-hydroxy-2-methylpropiophenone, 2-hydroxy-4'-isopropyl-2-methylpropiophenone, 1-hydroxycyclohexylphenylketone, (2-acetyloxy)-1-phenyl-e
• photopolymerization initiators may be used alone or as a mixture of two or more.
• Suitable photosensitizers are particular aromatic amino compounds as described e.g. in GB-P 1,314,556, 1,486,911, US-P 4,255,513 and merocyanine and carbostyril compounds as described in US-P 4,282,309.
• the invention is concerned with providing a clear abrasion resistant layer on top of a toner image and therefore, although some pigmentation may be useful, no pigments or dyes are normally incorporated in the radiation curable compositions for use in the present invention. It can be beneficial to add some spacing particles (polymeric beads, SiO 2 particles, etc) to the radiation curable composition in order to avoid sticking of the toner images.
• a slip-agent e.g. silicone slip additives.
• the abhesive qualities, the flexibility, the abrasion resistance and oxidation resistance of cured layer according to the present invention can be controlled by not only adding a silicone slip additive to the radiation curable composition, but also by mixing a silicon acrylate with the other prepolymers used in the radiation curable composition.
• Silicone acrylates are formed by the reaction of an organic polysiloxane compound with one or more reactive groups with e.g. an hydroxyacrylate or hydroxymethacrylate.
• the invention includes also a method for producing toner images on a substrate comprising the steps of :
• the application of the radiation curable composition and/or the radiation curing thereof can proceed on-line, e.g, the radiation curing proceeds in the fusing (fixing) station itself of an electrostatographic apparatus or in a station immediately adjacent to said fusing station.
• the application of the radiation curable composition and radiation curing of it can also proceed off-line in a separate apparatus wherein the fused layer of toner particles and the radiation curable composition on top of it is irradiated with curing rays.
• a layer of clear toner particles can be applied over the image.
• a plurality of layers of different toner particles can be applied to the substrate.
• the application of a plurality of layers of different types of toner particles (adjacent to each other or superimposed) is beneficial for the formation of full colour images wherein the image is built by the superposition of yellow, magenta, cyan and black toner (YMCK) or in the formation of a black and white (monochrome) image with extended tonal range as disclosed in European Application 95202768, filed on October 13, 1995)
• the radiation curable composition can, within the scope of the present invention also be applied on toner images, covered or not with a layer of clear toner particles, before fixing said toner particles and said toner particles are fixed after application of said composition. I.e. in an other embodiment of the method according to the present invention the step of fixing said toner particles is performed after the step of applying a radiation curable composition.
• the fixing step in the method described above can beneficially comprise a non-contact fusing step.
• the methods, outlined above, are especially suited for the production of full colour images and black and white images wherein the different shades of grey are realized by the superposition of toner particles comprising different amounts of black pigment.
• the invention also includes an apparatus for producing toner images comprising :
• UV emitting means e.g. mercury lamps with giving light with an intensity between 20 W/cm and 150 W/cm.
• An apparatus can also comprise, between said means for image wise depositing toner particles on a substrate and means for fixing said toner image, means for applying a layer of clear toner particles, covering the previously applied layer.
• An apparatus wherein said means for applying said radiation curable composition precede said means for fixing said toner image, is within the scope of the present invention.
• An apparatus according to this invention and described immediately above, comprises beneficially means for non-contact fusing said toner particles.
• Said means for applying said radiation curable composition can be rollers, wicks, sprays, screen printing, offset-printing, gravure rollers, etc.
• said means for applying said radiation curable composition are rollers, it may be split rollers, e.g. when 10 g/m 2 of radiation curable composition has to be applied, there may be provided four application rollers, the first two applying together 7.5 g/m 2 and the following rollers applying the remaining 2.5 g/m 2 .
• Preferred means for applying said radiation curable composition are supply rollers with a surface in NOMEX-felt (NOMEX is a trade name of Du Pont de Nemours, Wilmington, US) as described in article titled "Innovative Release Agent Delivery Systems" by R. Bucher et al.
• the radiation curable composition can be delivered to the image directly by supply rollers as described above, or over an intermediate roller, which distributes the composition even more evenly over the image.
• said means for fixing said toner particles and said means for UV-curing said UV-curable composition are mounted in said apparatus directly adjacent to each other so that the UV-curing proceeds on the warm curable composition.
• the present invention can be practised in any electrographic or magnetographic imaging method. It can be useful in classical electrophotography, in ionography, in direct electrostatic printing (DEP), etc.
• the present invention is useful for mono-chromatic toner images as well as for multi-chromatic and full colour toner images.
• said means for image-wise depositing toner particles can be direct electrostatic printing means, wherein charged toner particles are attracted to the substrate by an electrical field and the toner flow modulated by a printhead structure comprising printing apertures and control electrodes.
• Said means for image-wise depositing toner particles can also be toner depositing means wherein first a latent image is formed.
• said means for image-wise depositing toner particles) comprise :
• Said latent image may be a magnetic latent image that is developed by magnetic toner particles (magnetography) or, preferably, an electrostatic latent image.
• an electrostatic latent image is preferably an electrophotographic latent image and the means for producing a latent image are in this invention preferably light emitting means, e.g., light emitting diodes or lasers and said latent image bearing member comprises preferably a photoconductor.
• the present invention can be practised on toner images that are formed with any electrographic imaging method and with any type of toner particles known in the art.
• the toner particles can be magnetic or non-magnetic.
• the developer used to form the image can be mono-component magnetic developer, a non-magnetic mono-component developer, a multi-component developer comprising non-magnetic toner particles and magnetic carrier particles.
• the toner particles, used to form a toner image according to the present invention can comprise any known toner resin or mixtures thereof.
• the toner resin can be a polycondensation polymer or a mixture of different polycondensation polymers as well as an addition polymer or a mixture of addition polymers. Also mixtures of polycondensation polymers and addition polymers are suitable as toner resin for toner particles according to the present invention.
• polyesters are preferred. Polyester resins suitable for use in toner particles according to the present invention are selected e.g. from the group of linear polycondensation products of (i) di-functional organic acids, e.g.
• di-functional alcohols such as ethylene glycol, triethylene glycol, an aromatic dihydroxy compound, preferably a bisphenol such as 2,2-bis(4-hydroxyphenyl)-propane called "Bisphenol A” or an alkoxylated bisphenol, e.g. propoxylated bisphenol examples of which are given in US-P 4,331,755.
• a bisphenol such as 2,2-bis(4-hydroxyphenyl)-propane called "Bisphenol A”
• an alkoxylated bisphenol e.g. propoxylated bisphenol examples of which are given in US-P 4,331,755.
• suitable polyester resins reference is made to GB-P 1,373,220.
• styrene/acrylic resins it is preferred to use styrene/acrylic resins.
• Preferred styrene-acrylic resins have a relatively high (more than 70 mol %) styrene content, and are more particularly copolymers of styrene-acrylic resins or styrene-methacrylic resins, e.g. copoly(styrene/n-butylmethacrylate) or copoly(styrene/2-ethyl-hexylacrylate).
• Toner particles useful in this invention can have an average volume diameter between 1 and 50 ⁇ m, preferably between 3 and 20 ⁇ m. When the toner particles are intended for use in colour imaging, it is preferred that the volume average diameter is between 3 and 10 ⁇ m, most preferred between 3 and 8 ⁇ m.
• the particle size distribution of said toner particles can be of any type. It is however preferred to have an essentially (some negative or positive skewness can be tolerated, although a positive skewness, giving less smaller particles than an unskewed distribution, is preferred) Gaussian or normal particle size distribution, either by number or volume, with a coefficient of variability (standard deviation divided by the average) ( ⁇ ) smaller than 0.5, more preferably of 0.3.
• the toner particles can comprise any normal toner ingredient e.g. charge control agents, pigments both coloured and black, dyes, release agents, resistivity regulating agents, anorganic fillers, etc.
• charge control agents, pigments and other additives useful in toner particles, to be used in a toner composition according to the present invention can be found in e.g. EP-A 601 235.
• the solidified mass was pulverized and milled using an ALPINE Fliessbettarnastrahlmühle type 100AFG (tradename) and further classified using an ALPINE multiplex zig-zag classifier type 100MZR (tradename).
• the average particle size of the separated toner was measured by Coulter Counter model Multisizer (tradename) was found to be 8.0 ⁇ m by volume.
• the toner particles were mixed with 0.5 % of hydrophobic colloidal silica particles (BET-value 130 m 2 /g).
• the preparation of the Yellow toner was repeated, but instead of 2 parts SICOECHTGELB PY13, 2 parts of CABOT REGAL 400 (carbon black, trade name of the Cabot Corp. High Street 125, Boston, U.S.A.) were used.
• the four toners, Y, M, C and K had a meltviscosity at 120 ° C of 250 Pas (measured at a frequency of 16 Hz in a RHEOMETRICS dynamic rheometer, RVEM-200 (One Possumtown Road, Piscataway, NJ 08854 USA).
• the viscosity measurement is carried out at a sample temperature of 120 °C.
• the sample having a weight of 0.75 g is applied in the measuring gap (about 1.5 mm) between two parallel plates of 20 mm diameter one of which is oscillating about its vertical axis at 100 rad/sec and amplitude of 10 -3 radians.
• Each of the above prepared toners were used to form carrier-toner developers by mixing said mixture of toner particles and colloidal silica in a 4 % ratio with silicone-coated Cu-Zn ferrite carrier particles having an average diameter of 55 ⁇ m.
• the composition UV2 was the same as UV1 except for the amount of EBECRYL 264 and HDDA. In UV2 35 g of EBECRYL 264 and 15 g of HDDA were used.
• the composition UV3 was the same as UV1 except for the amount of EBECRYL 264 and HDDA. In UV3 15 g of EBECRYL 264 and 35 g of HDDA were used.
• Full colour toner images were produced using a commercial CHROMAPRESS (a trade name of Agfa-Gevaert NV, Mortsel, Belgium). Off-line all UV-curable coating were applied to the images in different thicknesses. The layers were cured for 0.5 sec by a high pressure mercury lamp with intensity 80 W/cm.
• the gloss of the images was measured in a Minolta Multi-gloss 268 reflectometer (trade name of Minolta, Osaka, Japan), the abrasion resistance was measured by manually scratching the image with a stylus with rounded head having a diameter of 0.5 mm and visually evaluating the marks and ranking them from 1 (almost no scratches) to 5 (severe scratching), the solvent resistance against solvents was tested by rubbing the image 10 consecutive times with a cloth soaked with MEK (methylethyleketone) and ranked from 1 (totally resistant) to 5 (all the image away).
• MEK methylethyleketone

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Cited By (11)

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• 1996
  • 1996-08-08 EP EP96202239A patent/EP0823670A1/de not_active Withdrawn

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