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
  • G03G9/132—Developers with toner particles in liquid developer mixtures characterised by polymer components obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds

Definitions

• the present invention relates to self-fixing liquid electrostatic image developers comprising as a dispersed component, a compatible blend of at least one polyester binder and at least one polyester plasticizer, to images formed from such developers, and to methods of forming images with such developers.
• Electrographic imaging and development processes have been extensively described in both the patent and other literature. Generally, these processes have in common the steps of forming an electrostatic charge image, often called an electrostatic latent image, in an insulating surface, such as a photoconductive insulating layer coated on a conductive support.
• the electrostatic latent image is then rendered visible by a development step in which the charge image-bearing surface is brought into contact with a suitable electrostatic image developer composition which deposits toner particles on either the charged or uncharged image areas.
• the visible image is either heat-fixed directly to the electrostatic charge-bearing surface or it is transferred to another surface such as paper where it is there heat-fixed.
• Liquid developer compositions of the type described in U.S. Patent No. 4,202,785 are very useful for developing latent electrostatic images. These developers comprise a stable dispersion of dispersed components and dissolved components in an electrically insulating carrier liquid.
• the dispersed components include charged particles, known as toner particles, comprising a colorant or pigment, such as carbon black, generally associated with a thermoplastic resin binder.
• the dissolved components include optional organic liquids from previous steps in the preparation of the liquid developer, as well as optional charge control agents.
• Liquid developers containing polyester resin binders such as those disclosed in the aforementioned U.S. Patent No. 4,202,785 as well as developers containing other polyester resin binders are particularly useful.
• the polyesters are fixed to receiving surfaces by the application of heat.
• Heat-fixable polyesters having very high glass transition temperatures (TgJ, (i.e., above 150°C) thus require higher fixing temperatures as well as careful selection of the receiving support to avoid support distortion or charring.
• U.K. Patent 1,110,225 describes a liquid developer which is said to be self-fixing upon removal of the carrier liquid following deposition of the toner particles.
• the patent discloses the use of liquid alkyd resins which, because of their unsaturated chemical bond linkages, cure in air upon removal of the carrier liquid.
• Toner particles containing oxidizing type unsaturated alkyd resins in combination with certain phenol modified pentaerythritol ester resins are also noted in U.K. Patent 897,903.
• German Offenlegungsschrift 2313547 published 25 October 1973, describes adding monomeric or polymeric plasticizers to toner resins in order to improve considerably the capability of images developed with such toners to transfer from one surface to another. From the teachings of these patents, therefore, it would appear that the use of plastizicers will not produce a toner that self-fixes to an image-forming surface.
• U.K. Patent Application 2,003,620A relates to the use of carrier-soluble monomeric and polymeric plasticizing agents for the toner binder resin.
• carrier-soluble plasticizers however, is undesirable as they tend to leach out of the binder resin into the carrier, thus negating any potential benefit from their use.
• this document does not teach that its toners are self-fixing.
• a self-fixing liquid electrographic developer exhibiting, in its broadest aspects, several significant advantages.
• the developer is self-fixing without resort to tacky low Tg binder polymers.
• the self-fixing property moreover is exhibited specifically on an electrostatic image-bearing surface without fear of unwanted transfer to other surfaces.
• the liquid developer exhibits its self-fixing property immediately upon extraction of the image-bearing surface or element from the liquid development region, in contrast to the prior art methods relying upon further chemical reaction of included curing agents having unsaturated chemical groups.
• liquid electrographic developer composition which self-fixes to an electrostatic image-forming surface.
• a liquid electrostatic image developer composition comprising an electrically insulating organic carrier liquid containing, as a dispersed constituent, a plurality of toner particles comprising a compatible blend of at least one polyester resin and at least one polyester plasticizer, characterized in that the developer composition is self-fixable, in that the plasticizer has a glass transition temperature below -40°C, is substantially free of curable groups and is substantially insoluble in the carrier liquid, and in that the polyester resin is a polyester ionomer having ionic diacid recurring units.
• Self-fixing in the context of the present invention denotes the quality of forming a rub resistant image on an electrostatic image-bearing surface without resort to externally applied heat.
• the self-fixing property moreover, is substantially immediate, after the image-bearing surface is treated in and removed from the liquid developer, and any residual carrier evaporated to dryness.
• the rub test comprises the application of a 700 gram weighted oleic acid soaked patch approximately 5 mm in diameter to a toner-bearing image and oscillating a portion of the image back and forth underneath the absorbent patch. Oleic acid is chosen to simulate natural finger oil.
• Rub resistance is determined as a range A to B, wherein A is the number of oscillatory cycles (a cycle being one movement of the patch back and forth) it takes to first interrupt the toner image integrity while B represents the number of cycles necessary to completely remove the subjected portion of the image by such rubbing.
• Specific toner images prepared in accordance with the present invention exhibit an A value of from 1 to 9 cycles and a B value of from 2 to 12 cycles whereas control images having no polyester plasticizer are completely removed (B) in one cycle.
• higher A-B values are, of course, likely to be obtained depending on such factors as the materials used in the compatible blend of resin and plasticizer, as well as the nature of the surface to which the blend is self-fixed.
• a compatible blend of at least one polyester resin and at least one polyester plasticizer is used.
• the plasticizer is specifically free of curable groups, in contrast to prior art materials such as alkyd resins that rely on further chemical reaction of curable groups to fix.
• the plasticizer moreover, is substantially insoluble in the carrier liquid so as to prevent leaching of the plasticizer into the carrier.
• a compatible blend in this regard refers to the ability of the resin and plasticizer to form a non-hazy solid solution of one in the other.
• the ratio of components in the compatible blend varies widely in accordance with the user needs.
• a useful weight ratio of plasticizer to resin is in the range from 0.2 to 1.0.
• a preferred ratio is in the range from 0.25 to 0.5.
• polyester ionomer resins having repeating diol units and ionic diacid recurring units well known to those skilled in the art are useful in the practice of the present invention.
• Representative polyesters are disclosed, for example in U.K. Patent 1,528,950. This patent discloses a redispersible liquid developer in which the polyester binder comprises disulphonamido groups.
• polyester ionomer resins of the invention are polyesters comprising recurring diol units and recurring ionic diacid units.
• Representative preferred polyester binders have recurring diol units of the formula: wherein:
• polyester resins of the present invention have a glass transition temperature (Tg) of the from 40°C to 100°C.
• Tg glass transition temperature
• Polyester resins having a Tg in the aforementioned preferred range can be self-fixed to smooth-surfaced dielectric coated receiving elements, as well as ordinary support surfaces, such as photoconductive coated paper or film elements, without difficulty.
• the glass transition temperatures can be determined by conventional methods, such as differential scanning calorimetry (DSC).
• Useful polyester resins have an inherent viscosity of 0.01 to 0.65, preferably 0.16 to 0.31. Polyester resins having inherent viscosities in the preferred range are compatible with the preferred charge control agents, optionally used in the liquid electrographic developers of the present invention. Inherent viscosities of the polyesters are measured in a 1:1 by weight solution of phenol:chlorobenzene at 25°C at a concentration of 0.25 gram per 100 ml of solution.
• the plasticizers employed in the compatible blend of resin and plasticizer are chosen from among a variety of commercially available polyester plasticizers having a Tg below -40°C, preferably within the range from about ⁇ 45°C to about -70°C.
• the criteria of compatibility with the polyester binder is usually first employed to screen potentially useful materials. From among these materials that satisfy the compatibility criteria, one then excludes plasticizers having curable chemical groups such as oil-modified polyester plasticizers or epoxidized oils. Of the eligible plasticizers, ones are chosen that are insoluble in the electrically insulating carrier liquid as defined below.
• polyester plasticizers that are insoluble in commonly employed isoparaffinic hydrocarbon carrier liquids such as that sold under the trade mark "Isopar" G are listed in the following table by Trade Mark and commercial source.
• polyester plasticizers include those sold under the Trade Marks "Santicizer” 429, “Paraplex” G-25, “Paraplex” G-41 and “Paraplex” G-57.
• “Santicizer” 429 typifying the preferred materials, has the following physical properties:
• Preferred polyester plasticizers comprise repeating alkylene diol units having 2 to 6 carbon atoms such as diol units derived from ethylene glycol or butylene diol, and repeating aliphatic diacid units having 3 to 10 carbon atoms such as diacid units derived from malonic acid, succinic acid or adipic acid.
• a particularly preferred polyester plasticizer comprises an acetate terminated adipic acid-butylene glycol polyester.
• the polystyrene equivalent molecular weight of the preferred polyester plasticizers ranges from 7000 to 9000 as determined by gel permeation chromatography.
• the compatible blend of resin and plasticizer defined above is formed in a variety of ways that facilitate the formation of small particles, preferably of submicron size (i.e., 0.01 to 1.0 micrometer average particle size).
• a preferred method of forming the blend comprises preparing a concentrated solution of the plasticizer and resin in a common solvent such as "Solvesso" 100 (the trade mark for an alkylated aromatic having a major aromatic component and a boiling range of from 150°-185°C sold by Humble Oil & Refining Co., U.S.A.).
• Solvesso the trade mark for an alkylated aromatic having a major aromatic component and a boiling range of from 150°-185°C sold by Humble Oil & Refining Co., U.S.A.
• the carrier liquid employed according to the present invention is selected from a variety of materials that satisfy the plasticizer insolubility criteria. These materials should be electrically insulating and have a fairly low dielectric constant.
• Useful carrier liquids have a dielectric constant of less than 3, and a volume resistivity greater than 10 10 ohm/cm.
• Suitable carrier liquids include halogenated hydrocarbon solvents, for example, fluorinated lower alkanes, such as trichloromonofluoromethane and trichlorotrifluoroethane, having a boiling range typically from 2°C to 55°C.
• Other hydrocarbon solvents that are useful include isoparaffinic hydrocarbons having a boiling range of from 145°C to 185°C. such as "Isopar" G or cyclohydrocarbons, such as cyclohexane.
• Additional carrier liquids which are useful include polysiloxanes, odourless mineral spirits and octane.
• useful working strength developers of the present invention contain from 0.005 to 5% by weight of the plasticizer-resin blend. These developers contain from 99.999 to 90% by weight of the liquid carrier vehicle.
• liquid developers of the present invention without further addenda, it is often desirable to incorporate such addenda as charge control agents, waxes, and dispersing agents for the wax or colorants, in the developer.
• the developer may be used to form a colourless hydrophobic image in a lithographic printing process.
• the resultant developer composition consists essentially of the liquid carrier vehicle and the plasticizer-resin blend particles of the present invention.
• colorants such as carbon black pigments are also included in the liquid developer defined.
• images formed from toners comprising polyester resin binder and colorants exhibit a tendency to crack in a pattern resembling that of the bed of a dried lake; the so-called adobe pattern.
• This tendency is significantly reduced and often eliminated with the presently defined blend of resin-plasticizer.
• the present invention contemplates the use of colorant-containing developers to produce self-fixing and crack-resistant visible images. Useful results are obtained from virtually any of a wide variety of known dyes or pigment materials. Particularly good results are obtained by using various kinds of carbon black pigments.
• the colorant concentration when colorant is present, varies widely with a useful concentration range, by weight of the total dispersed constituents, being 10 to 90 percent.
• a preferred concentration range is from 35 to 45 percent.
• Waxes and dispersing agents for the wax are also included as optional dispersed components in the present developers.
• Suitable waxes and dispersing agents include those described in European Patent Application No. 82301671.2 based on U.S. Patent Application No. 249,330 filed on 31st March 1981, by P.
• Alexandrovich and Upson which describes liquid electrographic developers comprising an electrically insulating organic carrier liquid containing dispersed constituents and dissolved constituents, said dissolved constituents comprising an electrically insulating organic dispersing liquid which forms a solution with said carrier liquid, said dispersed constituents comprising at least one thermoplastic resin and wax particles, and characterized in that said developer also contains a dispersing agent for said wax particles which is insoluble in said solution of carrier liquid and dispersing liquid, but soluble in said dispersing liquid alone.
• the wax particles are a polyolefin wax, carnauba wax, an ester wax or an amide wax.
• the dispersing liquid used with these waxes is preferably an alkylated aromatic liquid when the carrier liquid is an iso-paraffinic hydrocarbon.
• the developers of the present invention include various charge control agents to enhance uniform charge polarity on the developer toner particles.
• charge control agents have been described heretofore in the liquid developer art. Examples of such charge control agents may be found in U.S. Patent No. 3,788,995 which describes various polymeric charge control agents.
• Other useful charge control agents include phosphonate materials described in U.S. Patent No. 4,170,563 and quaternary ammonium polymers described in U.S. Patent No. 4,229,513.
• a partial listing of preferred representative polymeric charge control agents for use in the present invention includes poly(styrene - co - lauryl methacrylate - co - sulphoethyl methacrylate), poly(vinyltoluene - co - lauryl methacrylate - co - lithium methacrylate - co - methacylic acid), poly(styrene - co - lauryl methacrylate - co - lithium sulphoethyl methacrylate), poly(vinyltoluene - co - lauryl methacrylate - co - lithium methacrylate), poly(styrene - co - lauryl methacrylate - co - lithium methacrylate), poly(tyrene - co - lauryl methacrylate - co - lithium methacrylate), poly(t - butylstyrene - co - lauryl methacrylate
• the amount of charge control agent used will vary depending upon the particular charge control agent and its compatibility with the other components of the developer. It is usually desirable to employ an amount of charge control agent within the range of from 0.01 to 10.0 weight percent based on the total weight of a working strength liquid developer composition.
• the charge control agent may be added in the liquid developer simply by dissolving or dispersing the charge control agent in the liquid carrier vehicle at the time concentrates of the components are combined with the liquid carrier vehicle to form a working strength developer.
• a working strength developer comprising the aforementioned plasticizer-binder blend.
• a concentrate is a concentrated solution or dispersion of one or more developer components in a suitable electrically insulating liquid vehicle not necessarily the developer carrier liquid.
• the concentrates are then admixed in a preselected sequence, the admixture slurried with the carrier liquid to dilute the components, and the slurry homogenized to form the working strength developer.
• the present liquid developers are employed to develop electrostatic charge patterns carried by various types of elements.
• Such elements are either photoconductive themselves, i.e. image-forming surfaces, or adapted to receive charge images, i.e. image receiving surfaces, as disclosed in U.S. Patent No. 3,519,819.
• the developers may be used with photoconductive film elements containing arylmethane photoconductor compositions such as those disclosed in European Patent Application 11980.
• the film element comprises a film support, an electrically conducting layer overlying the support and a photoconductive layer overlying the conductive layer.

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

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• 1982
  • 1982-04-08 WO PCT/US1982/000435 patent/WO1982003700A1/en active IP Right Grant
  • 1982-04-08 JP JP50149982A patent/JPS58500541A/ja active Pending
  • 1982-04-08 DE DE8282901480T patent/DE3274907D1/de not_active Expired
  • 1982-04-08 CA CA000400733A patent/CA1174886A/en not_active Expired
  • 1982-04-08 EP EP19820901480 patent/EP0076316B1/en not_active Expired

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