Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
  • G03G5/02—Charge-receiving layers
  • G03G5/04—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor
  • G03G5/06—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being organic
  • G03G5/0664—Dyes
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
  • G03G5/02—Charge-receiving layers
  • G03G5/04—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor
  • G03G5/09—Sensitisors or activators, e.g. dyestuffs

Definitions

• the present invention pertains to zinc oxide photoconductive materials for use in electrophotographic printing and more particularly to such materials which are panchromatically dye sensitized zinc oxide-binder coatings having the desi ed speed, balance, background and storage stability.
• the commonly practiced form of electrophotographic printing uses as a photosensitive element a thin zinc oxide photoconductive insulating layer coated on a suitably conductive base sheet.
• the zinc oxide insulating layer is then illuminated by a light and shadow pattern which represents the image to be reproduced.
• the hitherto insulating photoconductive layer becomes electrically semi-conductive and therefore any previously deposited electrostatic surface charge is dissipated conductively in consonance with the actinic radiation which each element of area receives. In this way an electrostatic latent image is formed, the greatest surface charge density remaining in unexposed areas and the least in maximally illuminated portions of the photoconductive element.
• the latent image is then rendered visible by development with electrostatically charged pigment particles or toners which may be applied to the image as powder clouds, as suspensions in insulating liquids of low di electric constant or the like.
• the toner adheres differentially to charged and discharged areas thereby rendering them visibly different.
• the visible image may be fixed to the backing member by fusion or may be transferred to another sheet to which it is fused.
• Zinc oxide is almost universally used as the photoconductor in such electrophotographic printing processes, particularly where the powder image is fused to the base of the photoconductive recording element.
• Zinc oxide has one particular property which mitigates against its most efiicient use for the intended purpose and that is its restricted or limited spectral response which is confined essentially to the ultraviolet. Because of such limitation, best results are only secured where U.V. radiation is available. Use of white light containing but a minimum amount of U.V. very materially reduces the speed of response of the photoconductor during exposure.
• the dye blends employed will not only sensitize in the visible spectrum but will give when mixed with zinc oxide a mixture which when viewed by reflected light will have a white or offwhite appearance. It is also represented that the dye blends will have several peaks in different regions of the visible spectrum.
• the recording element through which we realize our objectives comprises abacking member which may be rendered conductive, as in conventional practice, coated with an insulating binder-resin having a white zinc oxide photoconductor dispersed therein.
• the zinc oxide is treated with a dye blend to make it absorptive to light rays of the visible spectrum to ensurethat it will have proper speed and balance when irradiated imagewise with white light. Agents are also present or provide an uncolored background.
• the backing member may be any suitable paper base rendered conductive (i.e., 10 ohm cm.) by any of several means.
• the zinc oxide is French process zinc oxide such as that sold by the New JerseyZinc Sales Company Incorporated of New York under the trade name Photox 801.
• the resin binder may be any suitable hydrophobic insulating resin of the type used in the manufacture of electrophotographic materials.
• suitable hydrophobic insulating resins are silicone, polystyrene, polyvinyl acetate and the like.
• epoxy ester resins in which the ester group is supplied by a fatty acid, i.e., stearic, or a rosin acid and abietic acid.
• Particularly suitable is the modified epoxy resin which is commercially available as Epidene E 168/50 from the T. F. Washburn Co., Chicago, Ill.
• This compound can be described as an epoxy ester polymer derived from bisphenol A, the di-(4-hydroxybenzene)-dimethylmethane, which is further modified by a fatty acid, preferably oleic acid.
• a fatty acid preferably oleic acid.
• Epoxy polymers modified by abietic acid or stearic acid are equally suitable.
• Fatty acid mixtures containing oleic and linoleic acid and derived from tall oil are especially preferred.
• the contemplated recording elements may be prepared by mixing a solution of an epoxy ester resin in toluene or xylene with small quantities of metallic driers, such as the naphthenates of cobalt and maganese.
• metallic driers such as the naphthenates of cobalt and maganese.
• Typical pigment resin ratios range from 5.5 to 6.0.
• plasticizer with the resin.
• a plasticizer for this purpose we prefer to use a petroleum-derived polymeric hydrocarbon with a fair degree of aromaticity and relatively low iodine value.
• a suitable plasticizer meeting these prerequisites is the product sold as Velsicol TPO #1 by Velsicol Chemical Corp., 535 5th Ave., New York, NY.
• This product is a resinous, dark polymeric material of low molecular weight derived from a petroleum hydrocarbon and prepared from a mixture of styrene, a lower styrene homolog, such as a-methylstyrene and a naphthol by the use of a suitable polymerization catalyst.
• This mixture is then dispersed in any of several means to reduce agglomerates to less than 1p. average particle size. This can be accomplished by ball milling or by the use of dispersing equipment as is found throughout the paint industry.
• the dispersed slurry is sensitized by adding a small quantity of an alcoholic solution of the desired mixture of organic dyes.
• the slurry may be coated on to the paper base by various methods using either a two-step application by an oxide or a one-step application by wire wound bar or gravure roller. After drying the coating is ready for use in the conventional xerographic or electrophotographic process.
• the dye blend which we use absorbs for the primary colors and therefor has a magenta component, a cyan component and a yellow component. It has been ascertained that the magenta component is nicely supplanted by Rose Bengal either alone or in ad mixture with Merthiolate and Eosin Y. A better balance results with the mixture than with the Rose Bengal per se.
• Merthiolate which is sodium ethyl mercury thiosalicylate as a catalyst. This compound is colorless but is dyed magenta by Eosin Y.
• a yellow component for the absorption may be added to the dye blend and for this purpose we may use the sodium salt of Fluorescein.
• absorption for the blue and red may be obtained by a mixture of Chlorophyll and Patent Blue V with or without the Fluorescein.
• Patent Blue V it is possible to supplant the Patent Blue V by Patent Blue A sold as Alphazurine A by National Division, Biological Stains Department, 40 Rector Street, New York. It is, of course, understood that inmodifying the blends by substituting one dye for another an adjustment in concentration must be provided for.
• the dye components discussed above provide the necessary sensitization and as a matter of fact when using Patent Blue A for Patent Blue V and by varying the concentration of the Patent Blue A, provision is made for avoiding the tendency of the background to yellow. It is preferred however to effect this result by incorporation of a separate masking component such as a blue pigment or a mixture of a coupling component and a sensitized diazoamino compound which forms a blue dye on coupling.
• a separate masking component such as a blue pigment or a mixture of a coupling component and a sensitized diazoamino compound which forms a blue dye on coupling.
• Such materials are available on the open market. Suitable materials comprise a mixture of a Naphthol AS coupling component and a stabilized diazoamino compound of a 2, S-dialkoxy-4-benzoylamino aniline.
• Blue Masking Dye Component 2 Preferably, we use Naphthol ASBG in admixture with the diazos from 2,5-dimethoxy-4-benzoylamino aniline and 2,5-diethoxy-4-benzoylamino aniline, the azo groups being stabilized by N- methyl taurine.
• This mixture will hereinafter be referred to as Blue Masking Dye Component.
• Another method for reducing the visible yellowing of background is to add an inert light-fast blue dye not in the alcoholic sensitizing solution but dissolved in a solvent common to the resin, such as toluene or xylene.
• a dye such as Heliogen Blue Oil Soluble, a phthalocyanine type available from Antara Chemicals, New York. This solution will hereinafter be referred to as Blue Masking Dye Component 2.
• the ratios of the various components in the sensitizing composition will not vary to any substantial degree. We have found that by utilizing the component in the following proportion per pound of zinc oxide that a recording paper meeting the full requirements of the trade can be produced:
• the product after drying was sensitive to the visible spectrum, gave a gray appearance by reflected light, had high speed and excellent balance.
• the usual loss of memory encountered in pre-illumination of the zinc oxide coatings was absent.
• the product obtained was superior in color balance to that of Example I.
• the background moreover was noticeably free from yellow stain.
• EXAMPLE IV The procedure was the same as in Example II except that a toluene solution of 2.7 mgs. Heliogen Blue Oil Soluble per 100 grs. zinc oxide, was added in place of Blue Masking Dye Component 1.
• a storage stable electrophotographic recording element having adequate speed and balance for whitelight exposure comprising a backing member coated with finely divided photoconductive zinc oxide dispersed in an insulating resin binder, said zinc oxide being sensitized to light rays corresponding to the primary colors by a blend of organic dyes in which the component absorptive of the green rays is selected from the class consisting of Rose Bengal and mixtures thereof with Merthiolate and Eosin Y and the components absorptive of the red and blue rays are selected from the class consisting of (1) a mixture of Chlorophyll and Patent Blue V, (2) a mixture of Chlorophyll and Patent Blue A, and (3) mixtures of (1) and (2) with Fluorescein wherein the concentration of the components is adjusted so that when viewed by reflected light the sensitized zinc oxide appears white to neutral gray in color.
• the blend of organic dyes includes a blue dye for masking a yellow background, said blue dye being formed in situ from a particulate mixture of a Naphthol AS coupling component and a diazo compound obtained from a 2,5-di-alkoxy- 4-benzoylamino aniline, the azo group of which is stabilized by N-methyltaurine.
• the insulating resin-binder is modified by a terpolymer derived from styrene, a lower styrene homolog and a naphthol.
• a storage stable electrophotographic recording element having adequate speed and balance for white light exposure comprising a backing member coated with finely divided photoconductive zinc oxide dispersed in an insulating resin binder, said zinc oxide :having adsorbed to the surface thereof and being sensitized by a composition consisting of Rose Bengal, Chlorophyll, Patent Blue V and Fluorescein wherein the concentration of the components is adjusted so that when viewed by reflected light the sensitized zinc oxide appears white to neutral gray in color.
• a storage stable electrophotographic recording ele-' ment having adequate speed and balance for white light exposure comprising a backing member coated with finely divided photoconductive zinc oxide dispersed in an insulating resin binder, said zinc oxide having adsorbed to the surface thereof and being sensitized by a composition consisting of Rose Bengal, Merthiolate, Eosin Y, Chlorophyll, Patent Blue V and the blue dye formed from a particulate mixture of a Naphthol AS coupling component, the diazo of a 2,5-di-alkoxy-3-benzoylamino aniline, the azo group of which is stabilized by N-methyl taurine wherein the concentration of the components is adjusted so that when viewed by reflected light the sensitized zinc oxide appears white to neutral gray in color.
• a storage stable electrophotographic recording element having adequate speed and balance for white light exposure comprising a backing member coated with finely divided photoconductive zinc oxide dispersed in an insulating resin binder, said zinc oxide having adsorbed to the surface thereof and being sensitized by a composition consisting of Merthiolate, Eosin Y, Rose Bengal, Chlorophyll and Patent Blue A wherein the concentration of the components is adjusted so that when viewed by reflected light the sensitized zinc oxide appears whiteto neutral gray in color.
• a photoconductive composition comprising finely divided photoconductive zinc oxide having a spectral response to white light suspended in an electrically insulating resin binder and having incorporated therein a blend of organic dyes in which the component absorptive of the green rays is selected from the class consisting of Rose Bengal and mixtures thereof with Merthiolate and Eosin Y and the component absorptive of the red and blue rays are (1) a mixture of Chlorophyll and Patent Blue V, (2) a mixture of Chlorophyll and Patent Blue A, and (3) mixtures of (1) and (2) with Fluorescein wherein the concentration of the components is adjustedso that when viewed by reflected light the sensitized zinc-oxide appears white to neutral gray in color.-
• composition as defined in claim 11 wherein component, and a diazo compound from a 2,5-di-a1koxy.--

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Photoreceptors In Electrophotography (AREA)

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Cited By (4)

Citations (3)

• 1965
  • 1965-05-14 US US455971A patent/US3403023A/en not_active Expired - Lifetime
• 1966
  • 1966-05-11 NL NL6606414A patent/NL6606414A/xx unknown
  • 1966-05-12 DE DE19661522621 patent/DE1522621A1/de active Pending

Patent Citations (3)

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