US3432415A - Electrophoretic imaging process using photosensitive xanthenonium salts - Google Patents

Electrophoretic imaging process using photosensitive xanthenonium salts Download PDF

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US3432415A
US3432415A US492178A US3432415DA US3432415A US 3432415 A US3432415 A US 3432415A US 492178 A US492178 A US 492178A US 3432415D A US3432415D A US 3432415DA US 3432415 A US3432415 A US 3432415A
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pigment
xanthenonium
image
lake
particles
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Santokh S Labana
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Xerox Corp
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G17/00—Electrographic processes using patterns other than charge patterns, e.g. an electric conductivity pattern; Processes involving a migration, e.g. photoelectrophoresis, photoelectrosolography; Processes involving a selective transfer, e.g. electrophoto-adhesive processes; Apparatus essentially involving a single such process
    • G03G17/04—Electrographic processes using patterns other than charge patterns, e.g. an electric conductivity pattern; Processes involving a migration, e.g. photoelectrophoresis, photoelectrosolography; Processes involving a selective transfer, e.g. electrophoto-adhesive processes; Apparatus essentially involving a single such process using photoelectrophoresis

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  • This invention relates in general to imaging methods. More specifically, the invention concerns the use of electrically photosensitive particles in electrophotographic imaging systems.
  • the images are produced in color because mixtures of two or more differently colored sets of particles which are each sensitive only to light of a specific wavelength or narrow range of wavelengths are used. Particles used in this system must have both intense pure colors and be highly photosensitive. The materials of the prior art often lack the purity and brilliance of color, the high degree of photosensitivity, and/ or the preferred correlation between the peak spectral response and peak photosensitivity necessary for use in such a system.
  • Another imaging system which utilizes electrically photosensitive material is the xerographic process as described in US. Patent 2,297,691 to C. F. Carlson.
  • the photosensitive material must be an effective photoconductive insulator, i.e., must be capable of holding an electrostatic charge in the dark and dissipating the charge to a conductive substrate when exposed to light.
  • a base sheet of relatively low electrical resistance such as metal, paper, etc., having a photoconductive insulating surface coated thereon, is electrostatically charged in the dark. The charged coating is then exposed to a light image.
  • the coating is contacted with electrostatic marking particles in the dark. These particles adhere to the areas where the electrostatic charge remains, forming a powder image corresponding to the electrostatic latent image.
  • the base sheet is relatively inexpensive, such as paper
  • the image may be fixed directly to the plate, as by heat or solvent fusing.
  • the powder image may be transferred to a sheet of transfer material, such as paper, and fixed thereon.
  • compositions within the general formula given above are derivatives of 9-phenylxanthene containing alkylamino or arylarnino groups and belong to the class of metal oxide lakes obtained from N-substituted 3,6bis- (amino)-9,2-canboxyphenyl xanthenonium chloride.
  • compositions within this class are: phosphotungstomolybdic lake obtained from 3,6-bis(ethylamino)-9,2-carboxyphenyl xanthenonium chloride (bluish red), phosphotungstomolybdic lake obtained from 3,6-bis(et -hylamino) 9,2 carbethoxyphenyl xanthenonium chloride (bluish pink), phosphomolybdic lake obtained from 3,6- bis(ethylamino) 2,7 dimethyl-9,2-carbethoxyphenyl xanthenonium chloride (bluish red), sodium salt of 3,2- toluidine amino-6,2"-methyl-4"-sulphophenylamino-9,2"- carboxyphenyl xanthene (violet), phosphotungstomolybdic lake obtained from 3,-6-bis(diethyla-mino)-9,2'-car bethoxyphenyl xanthenonium chloride (reddish violet), phosphotungstomolybdic lake
  • compositions may be prepared by condensing two moles of m-dialkylaminophcnol with phthalic anhydride by heating to a high temperature (about 200 C.) in the absence of any condensing agent.
  • a condensing agent such as sulfuric acid may be used.
  • the dye thus produced is then precipitated with a suitable metallic compound (e.g., sodium phosphotungstate and phosphomolybdic acid) to form the relatively insoluble lake.
  • a suitable metallic compound e.g., sodium phosphotungstate and phosphomolybdic acid
  • Any conven'ional synthesis may be used to prepare the compounds of the above general formula. For example, the methods described in German Patents 403,- 002 and 449,539 may be used.
  • the phosphotungstomolybdic lake and barium salt of 3 ,6-bis diethylamino -9,2'-carboxyphenyl xanthenonium chloride, the phosphomolybdic lake obtained from 3,6 bis(ethylamino)2,7-dimethyl-9,2'-carbethoxyphenyl xanthenonium chloride and the barium salt of 3,2'-toluidine amino-6,2"-methyl-4"-sulphophenylamino-9,2-carboxyphenyl xanthene are preferred for use in electrophoretic imaging processes since they are simply and economically synthesized, have especially desirable color and have high electrical photosensitivity.
  • the optimum composition is the phosphomolybdic lake obtained from 3,6-bis(ethylamino)-2,7-dimethyl-9,2'-carbethoxyphenyl xanthenonium chloride. Since the shade or tone of the compositions and the spectral and photosensitive responses vary slightly depending upon the substituent used, intermediate values of these variables may be obtained by mixing several of the different compositions.
  • compositions within the general formula listed above, and mixtures thereof, are especially useful as photosensitive pigment particles in electrophoretic imaging processes.
  • An exemplary electrophoretic imaging system is shown in the figure.
  • a transparent electrode generally designated 1 which, in this exemplary instance, is made up of a layer of optically transparent glass 2 overcoated with a thin optically transparent layer 3 of tin oxide, commercially available under the name NESA glass.
  • This electrode will hereafter be referred to as the injecting electrode.
  • Coated on the surface of the injecting electrode 1 is a thin layer 4 of finely divided photosensitive particles dispersed in an insulating liquid carrier.
  • photosensitive for the purposes of this application, refers to the properties of a particle which, once attracted to the injecting electrode, will migrate away from it under the influence of an applied electric field when it is exposed to actinic electromagnetic radiation.
  • Liquid suspension 4 may also contain a sensitizer and/or a binder for the pigment particles which is at least partially soluble in the suspending or carrier liquid as will be explained in greater detail below.
  • Adjacent to the liquid suspension 4 is a second electrode 5, hereinafter called the blocking electrode, which is connected to one side of the potential source 6 through a switch 7.
  • the opposite side of potential source 6 is connected to the injecting electrode 1 so that when switch 7 is closed, an electric field is applied across the liquid suspension 4 between electrodes 1 and 5.
  • Electrode 5 is made in the form of a roller having a conductive central core 11 connected to the potential source 6.
  • the core is covered with a layer of a blocking electrode material 12, which may be Baryta paper.
  • the pigment suspension is exposed to the image to be reproduced while a potential is applied across the blocking and injecting electrodes by closing switch 7.
  • Roller 5 is caused to roll across the top surface of injecting electrodes 1 with switch 7 closed during the period particles originally attracted to electrode 1 to migrate through the liquid and adhere to the surface of the blocking electrode leaving behind a pigment image on the injecting electrode surface which is a duplicate of the original transparency 9.
  • the relatively volatile carrier liquid evaporates off, leaving behind the pigment image.
  • This pigment image may then be fixed in place as for example, by placing a lamination over its top surface or by virtue of a dissolved binder material in the carrier liquid such as paraffin wax or other suitable binder that comes out of solution as the carrier liquid evaporates.
  • a dissolved binder material in the carrier liquid such as paraffin wax or other suitable binder that comes out of solution as the carrier liquid evaporates.
  • the carrier liquid itself may be paraffin wax or other suitable binder.
  • the pigment image remaining on the injecting electrode may be transferred to another surface and fixed thereon.
  • this system can produce either monochromatic or polychromatic images depending upon the type and number of pigments suspended in the carrier liquid and the color of light to which this suspension is exposed in the process.
  • any suitable insulating liquid may be used as the carrier for the pigment particles in the system.
  • Typical carrier liquids are decane, dodecane, N-tetradecane, paraffin, beeswax or other thermoplastic materials, Sohio Odorless Solvent 3440 (a kerosene fraction) and Isopar-G (a long chain saturated aliphatic hydrocarbon). Good quality images have been produced with voltages ranging from 300 to 5,000 volts in the apparatus of the figure.
  • particles of a single composition are dispersed in the carrier liquid and exposed to a black-and-white image.
  • a single color image results, corresponding to conventional black-and-white photography.
  • the particles are selected so that those of different colors respond to different wavelengths in the visible spectrum corresponding to their principal absorption bands.
  • the pigments should be selected so that their spectral response curves do not have substantial overlap, thus allowing for color separation and subtractive multicolor image formation.
  • the particle dispersion should include cyan colored particles sensitive mainly to red light, magenta particles sensitive mainly to green light and yellow colored particles sensitive mainly to blue light. When mixed together in a carrier liquid, these particles produce a black appearing liquid.
  • the particles When one or more of the particles are caused to migrate from base electrode 11 toward an upper electrode, they leave behind particles which produce a color equivalent to the color of the impinging light.
  • red light exposure causes the cyan colored pigment to migrate, leaving behind the magenta and yellow pigments which combine to produce red in the final image.
  • blue and green colors are reproduced by removal of yellow and magenta, respectively.
  • white light impinges upon the mix all pigments migrate, leaving behind the color of the white or transparent substrate. No exposure leaves behind all pigments which combine to produce a black image.
  • This is an ideal technique of subtractive color imaging in that the particles are not only each composed of a single component but, in addition, they perform the dual functions of final image colorant and photosensitive medium.
  • any suitable different colored photosensitive pigment particles having the desired spectral responses may be used with the pigments of this invention to form a pigment mix in a carrier liquid for color imaging. From about 2 to about 10 percent pigment by weight have been found to produce good results. The addition of small amounts (generally ranging from 0.5 to 5 mol percent) of electron donors or acceptors to the suspensions may impart significant increases in system photosensitivity.
  • EXAMPLE I About 7 parts of the phosphomolybdic lake obtained from 3,6 bis(ethylamino)-2,7-dimethyl-9,2'-carbethoxyphenyl xanthenonium chloride is suspended in about 100 parts Sohio Odorless Solvent 3440. The mixture is coated on the NESA glass substrate and a negative potential is imposed on the roller electrode.
  • the plate is exposed through a Wratten filter 29 and the neutral density step wedge filter, thus exposing the plate to red light
  • the pig- 6 EXAMPLE v A series of tests is run as in Example I above, except that the pigment here is the phosphotungstomolybdic lake of 3,6 bis(diethylamino)-9,2'-carbethoxyphenyl xanthenonium chloride.
  • the roller electrode is held at a negative potential.
  • the pigment here is sensitive to green and white light, but has relatively low photographic speed. Results are tabulated in Table I below.
  • EXAMPLE VI A series of tests is run as in Example V above except that the roller electrode is held at a positive potential. The pigment is found to have significantly higher photographic speed with positive roller electrode potential. See Table for results.
  • EXAMPLE VII A series of tests is run as in Example I above except that the pigment here is the barium salt of 3,6-bis(diethylamino)9,2'-carboxyphenyl xanthenonium chloride. The roller is held at a negative potential. The pigment is found to be sensitive to green and white light, through having low photographic speed. See Table I for results.
  • EXAMPLE VIII A series is run as in Example VII above, except that the roller electrode is held at a positive potential. The pigment is found to have substantially the same characteristics with positive or negative roller potential. See Table I for results.
  • Example II A series of tests is run as in Example I above, except the roller electrode here is maintained at a positive potential. Again, the pigment is found to be relatively insensitive to red and blue light but sensitive to green and white light. However, the pigment is not as sensitive with positive roller potential as with negative roller potential. See Table I for results.
  • EXAMPLE III A series of tests is run as in Example I above, except that the pigment here is the photophotungstomolybdic lake of 3,6 bis(diethylamino) 9,2 carboxyphenyl xanthenonium chloride. The blocking electrode is held at a negative potential. The results are tabulated in Table I below.
  • EXAMPLE IV A series of tests is run as in Example III above except that the roller electrode is held at a positive potential. This pigment is found to have higher photographic speed with a positive roller potential than with negative potential. See Table I for results.
  • the electrophoretic sensitivity of the various pigments to red, green, blue and white light is tested according to conventional photographic methods and the results are recorded in Table I, above.
  • the first column lists the number of the test example.
  • the second column gives the positive or negative electrical potential applied to the roller electrode in volts.
  • Columns 3-6 give the photographic speed for the tested pigment in footcandles for red, green, blue and white light.
  • the photographic speed is the result of a curve of optical density plotted against the logarithm of exposure in foot-candles; ft.-c. being 0.3 gamma toe speed and ft.-c. being 0.3 gamma shoulder speed.
  • Gamma is a standard photographic term referring to the slope of the above mentioned curve.
  • the maximum and minimum reflection density produced are listed in columns 8 and 9, respectively.
  • the tested pigments are sensitive, in an electrophoretic sense, to green light only.
  • the pigments are essentially non-responsive to red and blue light.
  • the response to these pigments to white light is essentially identical to their response to green light.
  • a suspension including equal amounts of three different colored pigments is made up by dispersing the pigments in finely divided form in Sohio Odorless Solvent 3440 so that the pigments constitute about 8% by weight of the mixture.
  • This mixture may be referred to as a trimix.
  • the mixtures are individually tested by coating them on a NESA glass substrate and exposing them as in Example I above, except that a multicolor Kodachrome transparency is interposed between the light source and the plate instead of the neutral density and Wratten filters. Thus, a multicolored image is projected on the plate as the roller moves across the surface of the coated NESA glass substrate.
  • a Baryta paper blocking electrode is employed and the roller is held at a negative potential of about 2500 volts with respect to the substrate.
  • the roller is passed over the substrate six times, being cleaned after each pass. Potential application and exposure are both continued during the entire period of the six passes by the roller. After completion of the six passes, the quality of the image left on the substrate is evaluated as to density and color separation.
  • the pigments are, as magenta, the phosphotungstomolybdic lake of 3,6-bis(diethylamino)-9,2-carboxyphenyl xanthenonium chloride; as cyan, Monolite Fast Blue 6.5., the alpha form of metal-free phthalocyanine, C.I. No. 74100; and as yellow Algol Yellow GC, 1, 2, 5, 6-d -(C, C -diphenyl)-thiazole-anthraquinone, C.I. No. 67300.
  • This trimix when exposed to a multicolored image, produces a full color image with good density and color balance.
  • the pigment suspension consists of a magenta pigment, the phosphomolybdic lake of 3,6-bis(ethylamino)-2,7-dimethyl-9,2-carbethoxyphenyl xanthenonium chloride; a cyan, pigment, Cyan GTNF, the beta form of copper phthalocyanine, C.I. No. 74160, and a yellow pigment, Indofast Yellow Toner, fiavanthrone, C.I. No. 70600. This trimix is exposed to a multicolored image and produces a full color image of good density.
  • the pigment suspension consists of a magenta pigment, the phosphotungstomolybdic lake of 3,6-bis(diethyl amino-9,2'-carbethoxyphenyl xanthenonium chloride; a cyan pigment, Cyan Blue XR, the alpha form of copper phthalocyanine, and as a yellow pigment, 8,13-dioxodinaphtho(l,2 2',3')furan 6-carbox-(3"-cyano-5"-methoxy)anilide prepared as described in copending application Ser. No. 421,589, now abandoned, filed Dec. 28, 1964. This trimix is exposed to a multicolored image and produces a full color image of good density.
  • compositions of the general formula given above are also useful in xerographic imaging systems.
  • xerographic plates may be produced by coating a relatively conductive substrate, e.g., aluminum or paper, with a dispersion of particles of the photosensitive pigment of the above general formula in a resin binder.
  • the pigment-resin layer may also be cast as a self-supporting film.
  • the plate formed may be both with or without an overcoating on the photoconductive layer.
  • the photosensitive pigment-resin photoconductive layer may be used in the formation of multilayer sandwich configurations adjacent a dielectric layer, similar to that shown by Golovin et al., in the publication entitled A New Electrophotographic Process, Effected by Means at Combined Electret Layers, Doklady Akad. Nauk SSSR, vol. 129, No. 5, pp. 08- 1011, November-December 1961.
  • Suitable materials for this purpose include aluminum, steel, brass, metalized or tin oxide coated glass, semiconductive plastics and resins, paper and other convenient materials.
  • Any suitable dielectric material may be used to overcoat the photoconductive layer.
  • a typical overcoating is bichromated shellac.
  • any suitable organic binder or resin may be used in combination with the pigment to prepare the photoconductive layer of this invention.
  • the resin used in the present invention should be more resistive than about 10 and preferably more than 10 ohms per centimeter under the conditions of xerographic use.
  • Typical resins include thermoplastics such as polyvinyl chloride, polyvinyl acetates, polyvinylidene chloride, polystyrene, polybutadiene, polymethacrylates, polyacrylics, polyacrylonitrile, silicone resins, chlorinated rubber, and mixtures and copolymers thereof where applicable; and thermosetting resins such as epoxy resins including halogenated epoxy and phenoxy resins, phenolics, epoxyphenolic copolymers, epoxy ureaformaldehyde copolymers, epoxy melamine formaldehyde formaldehyde copolymers and mixtures thereof, where applicable.
  • thermoplastics such as polyvinyl chloride, polyvinyl acetates, polyvinylidene chloride, polystyrene, polybutadiene, polymethacrylates, polyacrylics, polyacrylonitrile, silicone resins, chlorinated rubber, and mixtures and copolymers thereof where applicable
  • thermosetting resins such as epoxy
  • typical resins are epoxy esters, vinyl epoxy resins, tall-oil modified epoxies and mixtures thereof, where applicable.
  • any other suitable resin may be used if desired.
  • other binders such parafiin and mineral waxes may be used if desired.
  • the pigments may be incorporated in the dissolved or melted binder resin by any suitable means such as strong shear agitation, preferably with simultaneous grinding. These include ball milling, roller milling, sand milling, ultrasonic agitation, high-speed blending and any desirable combination of these methods. Any suitable range of pigment-resin ratios may be used.
  • the pigment-resin-solvent slurry (or the pigment-resin melt) may be applied to the conductive substrate by any of the well-known painting or coating methods, including spraying, flow coating, knife coating, electrocoating, Mayer bar drawdown, dip coating, reverse foil coating, etc. Spraying in an electric fiield may be preferred for the smoothest finish and dip coating for convenience in the laboratory.
  • the setting, drying and/or curing steps for these plates are generally similar to those recommended for films of the particular binder used for other painting applications.
  • pigment-epoxy plates may be cured by adding a cross-linking agent and stoving according to approximately the same schedule as other baking enamels made with the same resins and similar pigments for painting applications.
  • a very desirable aspect of these pigments is that they are stable against chemical decomposition at the temperatures normally used for a wide variety of bake-on enamels, and therefore, may be incorporated in very hard glossy photoconductive coatings, similar to automotive or kitchen appliance resin finishes.
  • the thickness of the photoconductive films may be varied from about 1 to about 100 microns, depending on their required individaul purpose.
  • Self-supporting films for example, cannot usually be manufactured in thicknesses thinner than about 10 microns, and they are easiest to handle and use in the 15 to micron range.
  • Coatings on the other hand, are preferably formed in the 5 to 30 micron range. For certain compositions and purposes it is desirable to provide an overcoating; this should usually not exceed the thickness of the photoconductive coating, and preferably not above one-quarter of the latter. Any suitable overcoating material may be used, such as bichromated shellac.
  • Xerographic plates for use as in the following examples are prepared as follows: Mixtures using specific pigments and resin binders are prepared by ball milling the pigment or a solution of a resinous binder and one or more solvents until the pigment is well dispersed. This is done by adding the desired parts of resin solution in a suitable mixing vessel. A quantity of one-eighth inch steel balls are added and the vessel is rotated for approximately one-half hour in order to obtain a homogeneous dispersion. The cooled slurry is applied onto an aluminum substrate with a wire drawdown and force dried in an oven for about 3 minutes at about C. The coated sheets are dark rested for about 1 hour and then tested.
  • plates are tested as follows.
  • the plate is charged negative by corona discharge to about 400 volts and exposed to a light and shadow image.
  • the plate is cascade developed using Xerox 1824 developer.
  • the powder image produced on the plate corresponds to the projected image.
  • the developed image may be then either fused to the plate or may be electrostatically transferred to a receiving sheet and there fused. Where the image is transferred, the plate may be then cleaned of residual toner and may be reused as by the above described process.
  • the xerographic plate is prepared by initially mixing about 2 parts of Lucite 2042, an ethylmethacrylate polymer, about 18 parts benzene, and about 1 part of the phosphotungstomolybdic lake of 3,6-bis(diethylamino)- 9, 2'-carboxyphenyl xanthenonium chloride. This mixture is coated onto an aluminum substrate to a thickness of about microns and cured. The plate is then charged. exposed for about 60 seconds to a light and shadow image using a Simmons Omega D3 enlarger equipped with a tungsten light source operating at 2950 K. color temperature (illumination level incident on the plate is 2.8 foot candles as measured with a Weston illumination meter model No. 756), and developed as above described. The image produced is heat fused directly onto the plate. The image produced was found to be of satisfactory quality.
  • EXAMPLE XIII The xerographic plate is prepared by initially mixing a binder and a solvent as in Example XII above with about 1 part of the phosphomolybdic lake of 3,6-bis(ethylamino)-2,7 dimethyl9,2' carbethoxyphenyl xanthenonium chloride. This mixture is coated on an aluminum substrate to a thickness of about 8 microns and cured. The plate is charged, exposed for about 45 seconds to a light and shadow image using a Simmons Omega D3 enlarger equipped with a tungsten light source operating at 2950" K. color temperature (illumination level incident on the plate is 2.8 foot candles as measured with a Weston illumination meter model No. 756) and developed. An image of good quality results.
  • the xerographic plate is prepared by initially mixing about 3 parts of Lucite 2042 with about 100 parts benzene and about 10 parts of the phosphotungstomolybdic lake of 3,6 bis(diethylamino) 9,2'carbethoxyphenyl xanthenonium chloride. The mixture is coated onto an aluminum substrate to a thickness of about 8 microns and cured. The plate is charged negative in the dark by means of a corona discharge to a potential of about 400 volts. The charged plate is exposed to a film positive for about 30 seconds by means of a high intensity, long wave, ultraviolet lamp (1680 microwatts/cm of 3660 A.U. radiation at a distance of 18 inches).
  • the latent electrostatic image is developed by cascading Xerox 1824 toner over the plate.
  • the powder image on the plate is electrostatically transferred to a receiving sheet and heat fused.
  • the image on the receiving sheet is of good quality and corresponds to the original.
  • the plate is wiped clean of any residual toner and reused as in the above manner.
  • pigment compositions and/or the pigment-resin compositions of this invention may be dye sensitized, if desired, or may be mixed or otherwise combined with other photoconductors, both organic and inorganic.
  • the method of electrophoretic imaging comprising subjecting a layer of a suspension to an applied electric field between at least two electrodes, as least one of which is at least partially transparent and simultaneously exposing said suspension to an image through said partially transparent electrode with activating electromagnetic radiation whereby a pigment image made up of particles is formed on at least one of said electrodes; said suspension comprising a plurality of finely divided photosensitive particles of at least one color, at least a portion of said particles comprising a composition which is a lake of a 3,6 bis(amino)-9,2'-carboxyphenyl xanthenonium salt.
  • said lake is the phosphotungstomolybdic lake of 3,6-bis(diethylamino)- 9,2'-carboxyphenyl xanthenonium chloride.
  • said lake is the phosphomolybdic lake of 3,6-bis(ethylamino)-2,7-dimethyl-9,2'-carbethoxyphenyl xanthenonium chloride.
  • said lake is the barium salt of 3,2-toluidine amino-6,2"-methyl-4"-Sulphophenylamino-9,2'"-carboxyphenyl xanthene.
  • the method of electrophoretic imaging comprising subjecting a layer of a suspension to an applied electric field between at least two electrodes, at least one of said electrodes being a blocking electrode, and exposing said suspension to an image with activating electromagnetic radiation whereby a pigment image made up of particles is formed on at least one of said electrodes; said suspension comprising a plurality of finely divided photosensitive particles of at least one color, at least one of said particles comprising a composition which is a lake of a 3,6-bis(amino)-9,2'-carboxyphenyl xanthenonium salt.
  • said lake is the phosphotungstomolybdic lake of 3,6-bis(diethylamino)- 9,2'-carboxyphenyl xanthenonium chloride.
  • said lake is the barium salt of 3,6-bis-(diethylamino)-9,2'-carboxyphenyl xanthenonium chloride.
  • said lake is the phosphomolybdic lake of 3,6 bis(ethylamino)-2,7-dimethyl-9,2'-carbethoxyphenyl xanthenonium chloride.
  • said lake is the barium salt of 3,2-toluidine amino-6"-methyl-4"-sulphophenylamino-9,2'"-carboxyphenyl xanthene.
  • the method of electrophoretic imaging comprising subjecting a layer of a suspension to an applied electric field between two electrodes, at least one of which is at least partially transparent, said suspension comprising a plurality of finely divided particles of at least two different colors in an insulating carrier liquid, the particles of each color comprising a photosensitive pigment whose principal light absorption bands substantially coincides with its principal photosensitive response, simultaneously exposing said suspension to a light image through said transparent electrode and then separating said electrodes whereby a pigment image is formed on the surface of at least one of said electrodes; the particles of one color comprising a composition which is a lake of a 3,6-bis(amino)-9,2'-carboxyphenyl xanthenonium salt.
  • the method of electrophoretic imaging comprising subjecting a layer of a suspension to an applied electric field between two electrodes, at least one of which is a blocking electrode, said suspension comprising a plurality of finely divided particles of at least two different colors in an insulating carrier liquid, the particles of each color comprising a photosensitive pigment whose principal light absorption bands substantially coincides with its principal photosensitive response, simultaneously exposing said suspension to a light image and then separating said electrodes whereby a pigment image is formed on the surface of at least one of said electrodes; the particles of one color comprising a composition which is a lake of a 3,6-bis(amino)-9,2-car boxyphenyl Xanthenonium salt.
  • a xerographic plate comprising a photoconductive layer comprising a binder material and a composition which is a lake of a 3,6-bis(amino)-9,2-carboxyphenyl Xanthenonium salt.
  • a process for forming a latent xerographic image on a photoconductive layer comprising a photoconductive pigment in an organic binder, which comprises electrostatically charging said layer and exposing said layer to a pattern of activating electromagnetic radiation; said photoconductive pigment comprising a composition which is a lake of a 3,6-bis(amino)-9,2-carboxyphenyl xanthenonium salt.
  • An imaging process which comprises the steps of providing a p'hotoconductive layer comprising a photo conductive pigment in an organic binder, uniformly electrostatically charging said layer, exposing said layer to a pattern of activating electromagnetic radiation and contacting said layer with electroscopic marking particles whereby said particles are held to said layer in pattern configuration; said photoconductive pigment comprising a composition which is a lake of a 3,6-bis(amino)-9,2'- carboxyphenyl xanthenonium salt.

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US2758939A (en) * 1953-12-30 1956-08-14 Rca Corp Electrostatic printing
US2940847A (en) * 1957-07-03 1960-06-14 None i red
US3247081A (en) * 1964-08-07 1966-04-19 Eastman Kodak Co Electrolytic deposition of charged dyes for photoconductographic processes
US3367946A (en) * 1964-10-22 1968-02-06 Du Pont Xanthene dyes

Patent Citations (6)

* Cited by examiner, † Cited by third party
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US1006738A (en) * 1910-12-30 1911-10-24 Hoechst Ag Red acid dyestuff of the triphenylmethane series and process of making same.
US2149992A (en) * 1936-10-08 1939-03-07 Gen Electric Light-transforming screen or reflector and method of making and using the same
US2758939A (en) * 1953-12-30 1956-08-14 Rca Corp Electrostatic printing
US2940847A (en) * 1957-07-03 1960-06-14 None i red
US3247081A (en) * 1964-08-07 1966-04-19 Eastman Kodak Co Electrolytic deposition of charged dyes for photoconductographic processes
US3367946A (en) * 1964-10-22 1968-02-06 Du Pont Xanthene dyes

Also Published As

Publication number Publication date
BE743895A (OSRAM) 1970-06-30
DE1522701B2 (de) 1975-07-10
DE1522701A1 (de) 1969-10-30
GB1155747A (en) 1969-06-18

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