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
  • G03G5/08—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being inorganic
  • G03G5/087—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being inorganic and being incorporated in an organic bonding material
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S430/00—Radiation imagery chemistry: process, composition, or product thereof
  • Y10S430/167—X-ray
  • Y10S430/168—X-ray exposure process

Definitions

• Electrophotographic materials consisting of a support, on which a photoconductive substance is coated together with a binder are generally known in this respect.
• photoconductive substances in such coatings specific inorganic as well as organic substances can be used, e.g., sulfur, selenium, and compounds belonging to the type of the oxides, sulfides, and selenides of zinc, cadmium, mercury, antimony, bismuth, titanium, and lead, anthracene and a great variety of other organic monomeric and polymeric photoconductors.
• photoconductive zinc oxide has been selected for its brilliant white color whereby it constitutes an excellent contrasting base for developer materials applied thereon.
• photoconductive lead(II) oxide of the tetragonal type having a color ranging from red to tan and which is particularly suited for X-ray recording (ref. US. Pat. No. 3,008,825).
• the lead (II) oxide of the orthorhombic type havinga yellow color is utilized for the same purpose according to the US. Pat. No. 3,266,932.
• the present invention provides a method for improving the contrast in color tone to black substances of photoconductive recording materials on the basis of photoconductive lead(II) oxide.
• the lead(II) oxide is treated before or after its incorporation into a photoconduc tive recording material with a compound, preferably a salt, which reacts with the lead(II) oxide and forms on its surface a product having a color, which in the chromaticity diagram is closer to the chromaticity point of daylight than the untreated lead(II) monoxide.
• Preferred halides which give a more neutral color tone to lead( 11) oxide, in particular to the red or tan type, are alkali metal halides, alkaline earth metal halides, or onium halides, particularly ammonium halides.
• Preferred salts in that respect are ammonium chloride, ammonium fluoride, ammonium iodide, sodium chloride, sodium bromide, potassium chloride, calcium chloride, magnesium chloride, barium chloride, strontium chloride, calcium bromide, magnesium fluoride, barium bromide and strontium bromide.
• calcium chloride which covers the red to tan lead(ll) oxide with a bright white product that masks the inherent color of the photoconductor.
• the halide is preferably applied in an aqueous liquid in highly concentrated dissolved form, e.g., in a concentration of at least percent by weight.
• the interaction with the colored photoconductor can be accelerated by heating the treating solution and/or photoconductor.
• the treatment can be applied before as well as after the exposure and does not markedly reduce the chargeability and the X-ray sensitivity of the lead(II) oxide.
• the sensitivity to visible light is reduced but not to such an extentthat the recording material becomes useless for recording electromagnetic radiation of this range of the wavelength spectrum.
• the decolorizing treatment is performed in a step subsequent to the development of the electrostatic image.
• This treatment can be effected by simply dipping the developed photoconductive recording material in an aqueous solution containing a said halide or a mixture thereof.
• the contacting of the decolorizing liquid with the recording material can, however, be carried out according to any coating technique, e.g., spraying, coating, whirling, by using a lick-roller, etc.
• the interaction with the lead(II) oxide is more or less effective or takes more or less time depending on the type of binding agent.
• the binding agent may not prevent wetting of the lead(II) oxide by the liquid improving the contrast of the lead(II) oxide in respect of the developing substance(s). Satisfactory results have been obtained by means of binding agents that are not very hydrophobic. 0ptimal results have been obtained hitherto with polyvinyl acetate as binding agent. Wetting can be improved by means of common wetting agents and/or by applying organic solvents that are miscible with-water, preferably those penetrating into the binder.
• wetting can also be improved by applying a voltage to the recording layer.
• the binder material when perfectly suitable from the viewpoint of not preventing the wetting of lead(II) oxide, should also be electrically insulating to the extent that an electrostatic charge applied to the recording layer must not be conducted by the binder at a rate that prevents the formation and retention of an electrostatic charge thereon for photographic processing.
• the recording materials of use in the present invention can be prepared by any of the known processes for preparing binder-pigment coatings.
• the pigment-binder composition together with a suitable solvent for the binder may be flowed on a base material or otherwise coated on the base by dipping, whirling, spraying, using a doctor blade, a dip roller, etc.
• the coating composition should preferably contain a dispersing agent preventing coagulation or flocculation of the lead(II) oxide during storage and coating of the dispersion.
• a dispersing agent preventing coagulation or flocculation of the lead(II) oxide during storage and coating of the dispersion.
• acid esters of oxyacids of phosphorus e.g., monobutyl phosphate, have proved to be particularly suited for dispersing lead(II) oxide.
• the photoconductive pigment-binder composition for use according to the present invention may contain all kinds of substances. applied in zinc oxide electrophotography and prefcrably contains 50 to percent by weight of lead(II) oxide calculated on the binder.
• the lead(II) oxide of the present invention can be mixed with other known photoconductive substances preferably those being white or only slightly colored, e.g., in order to obtain an increase in sensitivity for a particular part of the electromagnetic spectrum, e.g., photoconductive zinc oxide and other photoconductive chalcogenides and the ingredients of photoconductive coatings described in the UK. Pat. specification Nos. 1,020,504 and 1,020,506 can be used.
• the photoconductive substances which are treated to obtain a more neutral color tone can be combined with fluorescing agents and/or brightening agents as described e.g., in Phot.l(orr. 94, No. l (l958)p. 3-11 and No. 2 (1958) p. 19-26.
• the photoconductive recording materials on the basis of lead( ll) oxide treated according to the invention are particularly suitable for visible light continuous tone reproduction and for X-ray recording with or without intensifying screens such as lead screens.
• the electrostatic charge is preferably applied by means of a positive corona charging, since optimal results can be obtained therewith.
• a double corona charging may be applied, whereby there is understood that both sides of the recording material are corona-charged with charges of opposite sign.
• the physical shape or conformation of the electrostatic recording material may be widely different. It may be a plate, a sheet, or a drum, and it may be flexible as well as rigid.
• a relatively conductive support is used for the recording layer.
• an electroconductive sheet or plate, or an insulating sheet or plate covered with an electroconductive interlayer can be employed.
• electroconductive plate or sheet there is meant a plate or sheet, the electrical resistivity of which is smaller than that of the photoconductive layer i.e., preferably at least 100 times smaller.
• Suitable conductive plates or sheets can be made of metals such as aluminum, zinc, copper, tin, iron, or lead.
• Suitable electroconductive interlayers for insulating supports are, e.g., vacuum-coated metal layers such as silver or aluminum layers, conductive polymer layers e.g., applied from polymers containing quaternized nitrogen atoms such as those described in the U.K. Pat. specification No. 950,960, or layers containing in a binder dispersed particles e.g., carbon black and metal particles.
• the binder used for said particles preferably has a resistivity lower than ohm-cm.
• Paper sheets which have an insufficient electrical conductivity are coated or impregnated with substances enhancing their conductivity e.g., by means of a conductive overcoat such as a metal sheet (e.g. aluminum) laminated thereto.
• a conductive overcoat such as a metal sheet (e.g. aluminum) laminated thereto.
• Substances suitable for enhancing the conductivity of a paper sheet and which can be applied in the paper mass are hygroscopic compounds and antistatic agents as described, e.g., in the U.K. Pat. specification No. 964,877, and antistatic agents of polyionic type, e.g., a quaternized polyethylene imine.
• the photoconductive composition When the photoconductive composition is coated from organic solvents on paper sheets, the latter are preferably made organophobic i.e., are impermeabilized for organic solvents, e.g., by means of a water-soluble colloid covering layer or by a strong hydration of the cellulose fibers as in glassine paper.
• Electrostatic images in recording materials used according to the present invention can be developed according to one of the techniques known in electrophotography, wherein use is made of the electrostatic attraction or repulsion of finely divided colored substances.
• elec trophoretic development is preferred.
• an insulating liquid e.g., a hydrocarbon liquid.
• the recording materials applied in the present invention can also be developed electrolytically.
• EXAMPLE 1 A photoconductive recording layer containing 80 percent by weight of tetragonal lead(ll) oxide, dispersed in polyvinyl acetate applied to an aluminum plate was treated for 15 sec. at C. in a 25 percent by weight aqueous solution of calcium chloride. The tan color of the recording layer became masked with a white product strongly adhering thereto.
• the thus treated recording layer was charged with a positive corona and exposed to the bone skeleton of a hand by means of a medical X-ray tube of 52 kv./l00 ma.sec. placed at a distance of 50 cm.
• the residual charge image was detected by electrophoretic development.
• the developer was prepared by diluting the concentrated developer composition described hereinafter in a volume ratio of 15/],000 by means of SHELLSOL T (trade name for a hydrocarbon solvent):
• the resin binder solution was prepared by heating at 60 C. 500 g. of ALKYDAL L67 (trade name of Konverkusen, W.-Germany, for a linseed oil modified (67 percent by weight) alkyd resin and 500 cc. of white spirit containing 11 percent by weight of aromatic compounds till a clear solution was obtained. Subsequently the solution was cooled.
• ALKYDAL L67 trade name of Konverkusen, W.-Germany
• a black continuous tone image of the hand was obtained on a white background.
• Example 1 was repeated with the difference, however, that the treatment of the recording layer by means of the calcium chloride solution was carried out after the electrophoretic development.
• a method of improving the color tone of a recording layer containing photoconductive lead(ll) oxide particles dispersed in a resinous binder which comprises treating the surface of said layer in the presence of water with an alkali metal halide, an alkaline earth metal halide or an onium halide salt which is more water soluble than lead chloride; the amount of said halide being sufficient to combine with said lead(ll) oxide at said layer surface and modify the color thereof nearer to the chromaticity point of daylight in a chromaticity diagram.
• halide is ammonium chloride, ammonium fluoride, ammonium iodide, sodium chloride, sodium bromide, potassium chloride, calcium chloride, magnesium chloride, barium chloride, strontium chloride, calcium bromide, magnesium fluoride, barium bromide or strontium bromide.

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• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Photoreceptors In Electrophotography (AREA)
• Heat Sensitive Colour Forming Recording (AREA)

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Cited By (6)

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Citations (6)

• 1968
  • 1968-11-12 GB GB53672/68A patent/GB1280023A/en not_active Expired
• 1969
  • 1969-10-29 BE BE740943D patent/BE740943A/xx unknown
  • 1969-10-30 DE DE19691954633 patent/DE1954633A1/de active Pending
  • 1969-11-12 FR FR6939338A patent/FR2023143A1/fr not_active Withdrawn
  • 1969-11-12 US US876062A patent/US3642470A/en not_active Expired - Lifetime

Patent Citations (6)

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