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
  • G03G5/05—Organic bonding materials; Methods for coating a substrate with a photoconductive layer; Inert supplements for use in photoconductive layers
  • G03G5/0528—Macromolecular bonding materials
  • G03G5/0532—Macromolecular bonding materials obtained by reactions only involving carbon-to-carbon unsatured bonds
  • G03G5/0546—Polymers comprising at least one carboxyl radical, e.g. polyacrylic acid, polycrotonic acid, polymaleic acid; Derivatives thereof, e.g. their esters, salts, anhydrides, nitriles, amides
• • 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
  • G03G5/05—Organic bonding materials; Methods for coating a substrate with a photoconductive layer; Inert supplements for use in photoconductive layers
  • G03G5/0528—Macromolecular bonding materials
  • G03G5/0532—Macromolecular bonding materials obtained by reactions only involving carbon-to-carbon unsatured bonds
  • G03G5/0542—Polyvinylalcohol, polyallylalcohol; Derivatives thereof, e.g. polyvinylesters, polyvinylethers, polyvinylamines
• • 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
  • Y10S526/00—Synthetic resins or natural rubbers -- part of the class 520 series
  • Y10S526/934—Electrodeposit, e.g. electrophoretic, xerographic

Definitions

• the invention relates to photoconductive recording layers for use in electrophotography and to processes of producing same.
• An electrophotographic copying material consists of an electroconductive support having thereon a photoconductive recording layer formed of a photoconductive pigment dispersed in an insulating binder material.
• an electrostatic charge is applied to the photoconductive recording layer, which is then exposed image-wise to light.
• the electrostatic charge leaks away and the resulting latent electrostatic image is developed and thus made visible by treating with a finely divided toner material.
• the toner image can be fixed on the layer itself according to any known method such as heating or solvent fixing, or can be transferred to a receptor surface and fixed thereon.
• a photoconductive recording layer for use in electrophotography, comprising a photoconductive pigment dispersed in an electrically insulating binder therefor, said binder consisting of a copolymer of 83 to 95.5 percent by weight of vinyl acetate, 4 to 15 percent by weight of vinyl laurate and 0.5 to 2 percent by weight of an a, B-ethylenically unsaturated acid, preferably crotonic acid.
• the invention also comprises a method for producing an electrophotographic recording element, comprising the steps of preparing a photoconductive pigmentbinder composition as hereinbefore defined, applying a solution of the photoconductive binder composition to an electroconductive support, and drying to remove volatile material therefrom.
• Paper is normally used as support for the photoconductive recording layer, although other supports such as metal foils or sheets, glass, textile materials and plastic films can also be used.
• the electroconductivity of the support is not high enough, the electroconductive properties of the support can be improved by the application thereto of a known conducting layer.
• the resistivity of the support at a relative humidity of 50 percent has to be lower than approximately 1.10 Ohm/cm.
• the photoconductive recording layer composition of the invention is applied to the support by spraying, painting, roller-application, dip-coating or wiping techniques.
• the coating is then normally dried at an elevated temperature.
• the coating mixture contains zinc oxide as photoconductive pigment in a weight ratio of 90 to 75 percent by weight with respect to the total solid content of the dried photoconductive layer.
• Good recording and reproduction results are obtained with photoconductive layers of a thickness between one and 20 micron, preferably between three and 10 micron. Layers that are too thin possess an insufficient insulating power, whereas layers that are too thick present undesirable mechanical and photographic characteristics.
• the electrically insulating polymeric binder material for the photoconductive layer is a copolymer formed of vinyl acetate, vinyl laurate, and a a, B-ethylenically unsaturated acid used in the proportions as indicated.
• crotonic acid is preferred for the a, B-ethylenically unsaturated acid
• other unsaturated carboxylic acids can also'be used, e.g. acrylic acid, methacrylic acid, maleic acid, itaconic acid, and citraconic acid.
• At least 0.5 percent by weight of unsaturated acid groups are required in the copolymer to ensure sufficient adsorption of the copolymer to the zinc oxide pigment particles.
• This adsorption is necessary to improve the photographic properties of the photoconductive layer at high relative humidities. Indeed, e.g. it is known that polystyrene, although being com pletely hydrophobic, is fully inappropriate as a binding material for zinc oxide. With polystyrene a rapid dark decay of the electric charges applied to the photoconductive layer is noted at high relative humidities. And this rapid dark decay is due to the absence of polar groups in the polymer.
• Vinyl laurate is built in in the copolymer as an internal plasticizer. At least 4 percent by weight of vinyl laurate units have to be present in the copolymer to improve the plastic properties of the layer and to ensure a diminished curling of the zinc oxide layer even in extreme conditions of relative humidity. Further the vinyl laurate content of the copolymer has to be at most 15 percent by weight since it has been found that at higher relative humidities and for vinyl laurate contents above 15 percent the electrostatic chargeability rapidly di minishes.
• the electrostatic chargeability of the photoconductive layer is the charge, expressed in volts, taken up by the layer after charging with a coronadischarging apparatus having between the ground and the wires a potential difference of 6000 V.
• the voltage appearing at the electrometer terminals by passing thesamples directly after charging under the probe of a dynamic-capacitor electrometer as described by Giaimo, R.C.A. Review, 2 (1961) 780-790, is a measure of the charge density obtained.
• the dark decay is defined as the loss of charge found on the layer after charging with the same corona-discharging apparatus followed by keeping the material for 30 seconds in the dark.
• the molecular weight of the copolymer is of minor importance. In our experiments we used copolymers having molecular weights between approximatively 30.000 and 80.000.
• the photoconductive recording layers of the invention may contain, in addition to the photoconductive substance(s) and binder, optical sensitizers, e.g. those mentioned in United Kingdom Patent Specifications Nos. 1,020,504 and 1,020,506, additives known in coating techniques, eg pigments (see e.g. United Kingdom Patent Specification No. 1,007,349), compounds influencing the gloss and/or the viscosity, and compounds that counteract aging and/or oxidation of the layer, or that influence their thermal stability.
• optical sensitizers e.g. those mentioned in United Kingdom Patent Specifications Nos. 1,020,504 and 1,020,506, additives known in coating techniques, eg pigments (see e.g. United Kingdom Patent Specification No. 1,007,349), compounds influencing the gloss and/or the viscosity, and compounds that counteract aging and/or oxidation of the layer, or that influence their thermal stability.
• a very substantial increase in image density, which is probably due to an increase in sensitivity, can be obtained by the use, in the photoconductive recording layer, of substances increasing the dark-resistivity, e.g. those described'and claimed in the United Kingdom Patent Specification Nos. 1,020,504 and 1,020,506.
• 1,2-dichloroethunc 0.566 kg ethyl acetate 0.283 kg 20% solution of copolymer 1 kg photoconductive zinc oxide 1 kg solution of tetrachlorophthalic acid anhydride in ethanol 33 ml 1% solution of bromophenol in methanol '12 ml 2% solution of eosin in dimethylt'ormamide 0.6 ml 0.5% solution of fluoreseein in methanol 9.6 ml 2% solution of silicon oil in 1,2-dichloroethane 33 ml.
• the copolymer of vinyl acetate, vinyl laurate, and crotonic acid used had a molecular weight of about 50.000 and possessed different vinyl laurate and crotonic acid contents as indicated in Table l.
• the copolymer was dissolved as a percent solution in a 65:35 by volume mixture of 1,2-dichloroethane and ethyl acetate.
• the dispersion formed was applied to an electroconductive paper support at a ratio of g of zinc oxide per square meter, whereafter the material was dried and kept in the dark for 24 hours.
• copolymers of vinyl acetate, vinyl laurate. and crotonic acid had a molecular weight of approximatively 50,000 and were composed as indicated in Table 4.
• 1,2-dichloroethane 1.500 kg ethyl acetate 0.476 kg copolymer 0.160 kg photoconductive zinc oxide 1 kg 10 solution of tetrachlnrophthalic acid anhydride in ethanol 33 ml 2 solution of silicon oil in 1,2-dichloroethane ml 2 ll; solution of eosin in dimethyl- 0.6 ml formamide 0.5 solution of fluorescein 9.6 ml in methanol
• the copolymer used had a molecular weight of approximatively 50.000 and contained 90.5 percent of vinyl acetate, 8 percent of vinyl laurate, and 1.5 percent of crotonic acid.
• the sensitivity of the electrophotographic material showed to be 4 and the chargeability-dark decay at relative humidities of 50 and 70 percent respectively 430-370 and 430-250 Volts.
• EXAMPLE 7 The coating was carried out in such a way that the dried layer contained 2 g of gelatin per sq.m.
• the electrical resistivity of the coating was 1 X 10 Ohm per sq.cm.
• An electrophotographic recording material was prepared by coating onto said conductive layer a solution containing an organic photoconductor having the following structural formula:
• Rhodamine B (C.l. Basic Violet l; C.l. 45,l70) 0.020 g copolymer of vinyl acetate, vinyl Iaurate and crotonic acid (90.5:8:l.5 g methylene chloride 100 ml
• the solution was applied in such a way that the dried recording layer contained 3 g per sq.m. of said quinolin-2-0ne compound as photoconductor.
• the charged recording layer was contact-exposed for 1 see. through a positive transparency of a test chart with a tungsten filament lamp exposing the recording layer with 2400 lux and having a colour temperature of 2600K.
• EXAMPLE 8 A photoconductive recording layer as described in Example 5 was applied to an electronconductive paper support. The photoconductive recording layer was charged negatively and contact-exposed for seconds. As original a colour transparency was used. During a first exposure a green filter was laid between the original and the photoconductive recording layer, said filter transmitting only light of wavelengths around 535 nm. The latent image formed was developed with-a known electrophoretic development solution containing a magenta dye-stuff. A positive magenta separation image was obtained from the original.
• a multicoloured copy was obtained from the original.
• a photoconductive recording material for use in electrophotography comprising a conductive support and a photoconductive layer thereon comprising a photoconductive pigment dispersed in an electrically insulating binder, said binder consisting of a copolymer of 83 to 95.5percent by weight of vinyl acetate, 4 to l5 percent by weight of vinyl laurate, and 0.5 to 2 percent by weight of an a, ,B-ethylenically unsaturated acid.
• a photoconductive recording material according to any of claim 1, wherein the phtoconductive pigment is photoconductive zinc oxide.
• a photoconductive recording material according to claim 5, wherein the photoconductive pigment is a compound according to the formula:

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• Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Spectroscopy & Molecular Physics (AREA)
• General Physics & Mathematics (AREA)
• Photoreceptors In Electrophotography (AREA)

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Citations (5)

• 1971
  • 1971-06-08 GB GB1947771A patent/GB1376196A/en not_active Expired
• 1972
  • 1972-05-19 FR FR7218230A patent/FR2141084A5/fr not_active Expired
  • 1972-05-25 BE BE783908A patent/BE783908A/nl unknown
  • 1972-06-03 DE DE19722227145 patent/DE2227145A1/de active Pending
  • 1972-06-06 US US00260202A patent/US3791825A/en not_active Expired - Lifetime

Patent Citations (5)

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