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WO1988003669A2 - Imprimante couleur de haute qualite - Google Patents

Imprimante couleur de haute qualite

Info

Publication number
WO1988003669A2
WO1988003669A2 PCT/US1987/002813 US8702813W WO8803669A2 WO 1988003669 A2 WO1988003669 A2 WO 1988003669A2 US 8702813 W US8702813 W US 8702813W WO 8803669 A2 WO8803669 A2 WO 8803669A2
Authority
WO
WIPO (PCT)
Prior art keywords
dyestuff
set forth
hydrophobic polymer
polymer surface
liquid electrostatic
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US1987/002813
Other languages
English (en)
Other versions
WO1988003669A1 (fr
Inventor
Kenneth W. Gardiner
Ronald Swidler
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
SRI International Inc
Original Assignee
SRI International Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by SRI International Inc filed Critical SRI International Inc
Priority to GB08814495A priority Critical patent/GB2204419A/en
Publication of WO1988003669A1 publication Critical patent/WO1988003669A1/fr
Publication of WO1988003669A2 publication Critical patent/WO1988003669A2/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Definitions

  • the invention relates to a liquid electrostatic dyestuff or toner composition useful in electrostatic transferring printers and capable of producing multicolor images upon a hydrophobic polymer surface and to an electrostatic printing method using the aforementioned liquid electrostatic dyestuff.
  • Electrographic color copiers have been under development for many years but are only on the market in limited numbers.
  • the high gamma of most photconductor materials combined with the normal optical imaging and associated electrostatic toners (both dry and wet) have resulted in color copies that are not of photographic quality.
  • Such color copiers have used pigmented toners or dye toners with binders which serve to bind the pigments and/or dyes to paper. This reduces the brilliance of color on the prints.
  • the present invention is directed to solving one or more of the problems as set forth above.
  • a liquid electrostatic dyestuff consisting essentially of (1) an inert hydrophobic solvent; (2) dye particles dispersed in said solvent, the particles being substantially insoluble in the solvent but being selected to be soluble in a hydrophobic polymer surface at temperatures above a selected temperature and (3) a charge control agent which preferentially partitions onto the dye particles.
  • the dyestuff is substantially binder-free.
  • a method of electrostatic printing comprises contacting an imaged liquid electrostatic dyestuff as set forth above with a polymeric surface of a sheet.
  • the polymeric surface is heated to a dissolving temperature above the selected temperature, the dissolving temperature being such that the dye particles dissolve into said polymeric surface at the dissolving temperature.
  • the color printer of the present invention makes use of the electrostatic copying process and can use any of the basic electrostatic processing techniques.
  • the three major types of electrostatic processing techniques are: (1) a photoconductor coated sheet is successively charged, imaged and toned with, generally, three or four toners, for example yellow, cyan, magenta and black. This sheet then becomes the output copy; (2) a photoconductor drum, belt, or other configuration is successively charged, imaged, and the resulting charge image transferred to a dielectric receiving sheet which is again successively toned with the colored toners; and (3) a photoconductor drum, belt, or other configuration is successfully charged, imaged and then toned, with each of the toner images being transferred to a final receiving sheet.
  • the toner is binder-free and consists essentially of small physical particles of a dispersed dye.
  • the dye is dispersed in a hydrophobic solvent which may be, for example, a simple hydrocarbon solvent such as petroleum ether, benzene, or one of the Isopars (Trademark of Exxon Corporation) .
  • the chemical makeup of the solvent is unimportant so long as it does not deleteriously effect the dye, the equipment or the sheet and so long as it will not dissolve the dye sufficiently to lead to coloring of the solvent and resulting coloring of the sheet where contacted by the solvent, but not by the dye particles.
  • the dye particles themselves must be selected so as to be substantially insoluble in the solvent at the temperature that they are at when dispersed in the solvent (generally below about 40 ⁇ C) but at the same time to be soluble in a hydrophobic polymer surface when the polymer surface is sufficiently softened, as by being heated above a softening temperature.
  • This temperature is generally in the neighborhood of the glass transition temperature of the hydrophobic polymer surface and will prefereably be at or slightly above the glass transition temperature, but can also be somewhat below that temperature.
  • the dye particles must be such that they will be soluble in the hydrophobic polymer surface at a dissolving temperature which is above the temperature of application of the toner to the hydrophobic polymer surface and which is above said selected temperature.
  • the surface of the output copy be a hydrophobic polymer surface.
  • a number of hydrophobic polymers may form this surface.
  • the surface may consist of polyamide ⁇ , cellulose esters or polyesters.
  • the chemical nature of the polymer is relatively unimportant so long as the polymer is hydrophobic, will dissolve the dye particles at the dissolving temperature and will not deleteriously effect the dye.
  • the hydrophobic polymer surface will be a polyester surface.
  • the polymer be selected so as to be such that the dye particles will dissolve therein at a dissolving temperature in the range from about 150 ⁇ C to about 250°C.
  • the particles have an average particle size whch falls in a range from about 0.1 micron to about 10 microns. More preferably, the particle size will fall within a range from about 0.1 micron to about 1 micron.
  • the toner must include a charge control agent which preferentially partitions away from the hydrophobic solvent and into the dye particles.
  • the - charge control agent may be, for example, lethicin, a metallic sulfonate, a. soap or a detergent.
  • useable charge control agents include Aerosol OT (Trademark of American Cyanamid Co.) , Aerosol TR 70 (Trademark of American Cyanamid Co.), salts of long chain alkyl napthalene sulfonates, calcium and barium salts of long chain dialkyl sulfosuccinates, metal salts of fatty acids and the like.
  • the dye particles not be soluble in the inert hydrophobic solvent at the temperature at which they are dispersed in the solvent. This is important to ensure that the resulting colors appear clean and distinct. If the dye particles did dissolve somewhat in the solvent, then when the dye particles were contacted with the hydrophobic polymer surface and the hydrophobic polymer surface was heated the color would appear not only at the spots where the particles were located, but also to a lesser extent in any area which was covered by the inert hydrophobic solvent. Thus, when the requirement is set forth that the dye particles be substantially insoluble in the solvent what is meant is that the dye particles be sufficiently insoluble in the solvent (at the relevant temperature) so that the color is not noticeably smeared due to dissolved dye in the solvent.
  • the dissolving temperature whereat the hydrophobic polymer surface is sufficiently softened so that the dye is soluble therein.
  • this temperature will be about the glass transition temperature as mentioned above.
  • the dissolving of the dye into the hydrophobic polymer surface will take from about 20 seconds to about 2 minutes, more usually from about 30 seconds to about 90 seconds. This time can, however, be greatly reduced if the surface is melted.
  • the dye particles be of a sublimable dye, generally one wherein the dye particles sublime at a temperature above about 120 ⁇ C. This is necessary wherein the printed upon copy with the hydrophobic polymer surface is one to which the dye must be transferred during the heating process. This takes place in the situation wherein a photoconductor drum, belt, or other configuration is successively charged, imaged and then , toned with each of the toner images then being transferred to the final receiving sheet.
  • liquid electrostatic dyestuff When the liquid electrostatic dyestuff is spoken of as consisting essentially of an inert hydrophobic solvent, the aforementioned dye particles, and the aforementioned charge control agent, this language is not meant to exclude other components which may be present. If an additional component or components are present such additional component or components must be electrostatically compatible and practically compatible with the other components. It is a part of the present invention that a binder is not present in the liquid electrostatic dyestuff of the present invention since this interferes with the dissolving of the dyestuff into the hydrophobic polymer surface, the sublimation of the dyestuff, its diffusion into the hydrophobic polymer surface, and/or the like.
  • hydrophobic polymer surface when a hydrophobic polymer surface is spoken of herein it should be understood that this includes not only sheets which are completely made of hydrophobic polymer material, but also sheets which are made of other materials, hydrophobic or hydrophilic, and which are coated with the required hydrophobic polymer surface. For example, thin layers of a hydrophobic polymer upon ordinary paper will provide an appropriate hydrophobic polymer surface. This allows the production of opaque copies. Opaque copies can also be obtained when the sheet is made of hydrophobic polymer material having appropriate opaque, e.g., white, fillers. When the hydrophobic polymer surface is part of an overall hydrophobic polymer sheet which does not include opaque fillers, one can obtain clear copies, for example transparencies.
  • One particular advantage of the present invention is that the exposure of the charged photoconductor can be made by laser or other array of small modulated light sources to create an image from an electronic source such as a computer memory.
  • the computer may have been used to process the image, data to correct for the gamma characteristics of the electrostatic photoconductor in use in order to match the exposure of the photoconductor to achieve the gray scale range of the image being printed.
  • the photoconductor is charged and is imagewise discharged by a directed light beam with the image being created from the computer which controls the light beam.
  • Gray scale modulation can be achieved by the normal reduction of the photoconductor charge voltage, by controlled exposure of the charge image or by the creation of half tone-like dots of variable size at a fixed voltage level. A combination of these two processes can also be incorporated.
  • the heating of the hydrophobic polymer surface to the dissolving temperature may take place following the imaging of each color or following imaging of all of a series of colors if successive toning is accomplished without a heating step following each toning step.
  • the resulting color image will generally consist of well mixed pure dyes dissolved into a thin clear layer of the hydrophobic polymer.
  • the hydrophobic polymer can be coated over a white reflecting sublayer.
  • the color quality achieved is equal to that or exceeds that of photographic color prints and quality color printers.
  • the thickness of the hydrophobic polymer surface on the white reflecting sublayer can be of any value.
  • the white or other desired color may be incorporated in the polymer surface.
  • white pigmented polyester may be employed.
  • the liquid electrostatic dyestuff and the method of the present invention are such as to produce very high quality color prints onto hydrophobic polymer surface. They can be used to produce very high quality color reproductions of, for example, displays on CRT monitors.

Abstract

Un colorant électrostatique liquide comporte essentiellement un solvant hydrophobe inerte dans lequel sont dispersées des particules de matière tinctoriale, ces particules étant pratiquement insolubles dans le solvant et étant solubles dans une surface polymère hydrophobe à des températures supérieures à la température de ramollissement de cette dernière, ainsi qu'un agent de modulation de fonçage qui de préférence se répartit sur les particules de matière tinctoriale. Est également décrit un procédé d'impression électrostatique consistant à mettre en contact avec la surface polymère hydrophobe d'une feuille un colorant électrostatique liquide imagé du type décrit, la surface polymère hydrophobe présentant une température de ramollissement, et à chauffer la surface polymérique à au moins la température de ramollissement précitée. On obtient ainsi des images couleur très nettes. La reproduction d'images en couleur pure à partir d'une mémoire d'ordinateur est une caractéristique particulière de la présente invention.
PCT/US1987/002813 1986-11-05 1987-10-28 Imprimante couleur de haute qualite Ceased WO1988003669A2 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB08814495A GB2204419A (en) 1986-11-05 1987-10-28 High-quality color printer

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US92732886A 1986-11-05 1986-11-05
US927,328 1986-11-05

Publications (2)

Publication Number Publication Date
WO1988003669A1 WO1988003669A1 (fr) 1988-05-19
WO1988003669A2 true WO1988003669A2 (fr) 1988-05-19

Family

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