US3215528A - Photoconductive layers for electrophotography - Google Patents

Photoconductive layers for electrophotography Download PDF

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US3215528A
US3215528A US234926A US23492662A US3215528A US 3215528 A US3215528 A US 3215528A US 234926 A US234926 A US 234926A US 23492662 A US23492662 A US 23492662A US 3215528 A US3215528 A US 3215528A
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photoconductive
terphenyl
compound
layers
compounds
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Schaum Gustav
Haydn Hildegard
Seibert Heinrich
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Agfa Gevaert NV
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    • 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
    • G03G5/0622—Heterocyclic compounds
    • G03G5/0624—Heterocyclic compounds containing one hetero ring
    • G03G5/0635—Heterocyclic compounds containing one hetero ring being six-membered
    • G03G5/0637—Heterocyclic compounds containing one hetero ring being six-membered containing one hetero atom
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D221/00—Heterocyclic compounds containing six-membered rings having one nitrogen atom as the only ring hetero atom, not provided for by groups C07D211/00 - C07D219/00
    • C07D221/02—Heterocyclic compounds containing six-membered rings having one nitrogen atom as the only ring hetero atom, not provided for by groups C07D211/00 - C07D219/00 condensed with carbocyclic rings or ring systems
    • C07D221/04—Ortho- or peri-condensed ring systems
    • C07D221/06—Ring systems of three rings
    • C07D221/10—Aza-phenanthrenes
    • 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
    • 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
    • G03G5/0601—Acyclic or carbocyclic compounds
    • G03G5/0605—Carbocyclic compounds
    • 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
    • G03G5/0601—Acyclic or carbocyclic compounds
    • G03G5/0609—Acyclic or carbocyclic compounds containing oxygen
    • 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
    • G03G5/0601—Acyclic or carbocyclic compounds
    • G03G5/0612—Acyclic or carbocyclic compounds containing nitrogen
    • 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
    • G03G5/0601—Acyclic or carbocyclic compounds
    • G03G5/0618—Acyclic or carbocyclic compounds containing oxygen and nitrogen
    • 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
    • G03G5/0622—Heterocyclic compounds
    • G03G5/0624—Heterocyclic compounds containing one hetero ring
    • G03G5/0635—Heterocyclic compounds containing one hetero ring being six-membered
    • G03G5/0638—Heterocyclic compounds containing one hetero ring being six-membered containing two hetero atoms
    • 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
    • G03G5/0666—Dyes containing a methine or polymethine group
    • G03G5/0668—Dyes containing a methine or polymethine group containing only one methine or polymethine group
    • G03G5/067—Dyes containing a methine or polymethine group containing only one methine or polymethine group containing hetero rings
    • 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
    • G03G5/0666—Dyes containing a methine or polymethine group
    • G03G5/0672—Dyes containing a methine or polymethine group containing two or more methine or polymethine groups
    • G03G5/0674—Dyes containing a methine or polymethine group containing two or more methine or polymethine groups containing hetero rings

Definitions

  • the present invention relates to photoconductive layers for electrophotography.
  • photoconductive layers for eletrophotography For the production of photoconductive layers for eletrophotography it is known to use certain inorganic or organic photoconductive materials.
  • examples of such materials are sulphur, selenium, oxides, sulphides and selenides of zinc, cadmium, mercury, antimony, bismuth, and lead, and also anthracene and anthraquinone.
  • These substances are applied to an electrophotographic plate, especially a plate consisting of metal or another material, for example paper, or to a sheet or foil produced from a fihn-forming plastic. If necessary, the photoconductive substance can be held dispersed in an electrically isolating, layer-forming binder.
  • Such layers being produced by means of coating solutions in which the binders are either dissolved or dispersed and in which the electro-conductive substances are dispersed.
  • Such photoconductive layers are for instance disclosed in United States Patents No. 2,297,691; 2,357,809; 2,727,807; 2,727,808; 2,735,784; and 2,735,785, and in French Patents No. 1,113,933; 1,122,275; 1,125,235; and 1,136,146.
  • acylchloride with terphenyl in the presence of a Fn'edel-Crafts catalyst such as AlCl
  • Suitable acyl groups are, for example, lower aliphatic acyl groups or benzoyl, the benzene rings of which can be further substituted, for example, by halogen, chlorine or bromine or by further phenyl rings.
  • the photoconductive compounds according to the invention are advantageous over prior art because they are more sensitive to longer wavelength. It is furthermore possible to sensitize these substances for still longer wavelengths by suitable compounds as they are for instance disclosed in French Patent No. 1,125,235.
  • the coating solution which is used for the production of the photoconductive layers comprises at least one of the aforementioned substances and a film-forming binding agent, the electrical specific resistance of which must be higher than that of the photoconductive substance and also higher than that of the layer support.
  • binding agents the electrical specific resistance of which amounts to at least 10 ohm-centimeters.
  • Particularly suitable binding agents are silicone resins such as alkylpolysiloxanes and arylpolysiloxanes, especially phenyl and methyl polysiloxanes as they are disclosed in German Patents No. 853,351 and 865,975.
  • binding agents are for instance cellulose, cellulose esters, cellulose ethers, polyvinyl chlo ride, polyurethanes, polyesters, polyamides, polycarbonates with a base of di-(monohydroxyaryl)-alkanes, especially 4,4'-di(m0nohydroxyaryl)-alkanes according to German Patents No. 971,790 and 971,777.
  • Photoconductive compounds can be present in the electrophotographic layers, homogeneously in dissolved form or heterogeneously in a suspended form whereby the particle size of the suspended photoconductor should be as small as possible.
  • the quantitative ratios between the photoconductive substances and the binding agents may vary within wide limits. It is preferred to use the photoconductive substance in amounts between 1 part for each 0.3 to 2 parts by weight of binding agent which is the equivalent of 0.5 to 3.33 parts by weight of the photoconductive substance to each part by weight of the binding agent, and amounts between about 5 and about 40 grams per square meter of photoconductive layer.
  • the solvent or solvent mixture used for the production of electrophotographic layers containing a photoconductive compound, heterogeneously dispersed therein must be good solvents for the binding agent but non-solvents or poor solvents for the photoconductive compounds. Suitable layers of this type can be produced as follows: An organic solvent is used which dissolves both the photoconductive substance and the binding agent layer former.
  • This solution has added thereto another organic solvent in which the layer former is soluble but the photoconductive substance is insoluble.
  • the photoconductive compound is deposited in a state of particularly fine distribution, so that layers with a particularly smooth surface are obtained.
  • a support for the photoconductive layer there may be used paper or metal plates, such as zinc, aluminum, or brass plates.
  • thin foils of cellulose hydrate, cellulose esters or of polyamide come into question.
  • said material is electrostatically charged in the dark, for instance, by meaning of a corona discharge device. The charged layer is then exposed with light through a nega tive photographic film, positive film or mask or otherwise to a light image, to receive a latent electrostatic image.
  • the latent electrostatic image can be developed by any developing process known per se, for example, by dusting a developing powder whereby the powder adheres to the areas where the electrostatic charges remain, forming thereby a powder image corresponding to the electrostatic image. Thereafter the powder image can be fixed by melting the developing powder or can be transferred to a sheet of transfer material resulting in a positive or negative print as the case may be.
  • the photoconductive layers can also be produced from aqueous dispersions of photoconductive substances and binding agents, for instance by the process disclosed in French Patent No. 1,136,146. If necessary, the cast dispersions or emulsions are subjected to a final condensation or final polymerization by heat treatment at temperatures of about 80-150 C. for about 2 to 30 minutes after being dried.
  • Aqueous dispersions of polymeric substances such as melamineformaldehyde or urea-formaldehyde resins, xylene-formaldehyde resins, polymers based on vinyl chloride, vinylidene chloride, vinyl ethers, acrylic esters, methacrylic esters, acrylic amides, such for example as methacrylic amide, aromatic vinyl compounds, such for example as styrene, isoolefins, such for example as isobutylene, copolymers based on the aforementioned compounds, such for example as copolymers of vinyl chloride and butyl acrylate vinylidene chloride and butyl acrylate synthetic elastorners, such for example as copolymers of butadiene and styrene, butadiene and acrylonitrile, and also copolymers of dienes with a preponderant proportion of styrene and/ or acrylonitrile or other vinyl compounds, as well
  • Example 1 40 g. of 4,4-"-diacetyl-p-terphenyl,
  • the resulting mixture is then cast on a paper support and dried.
  • Example 2 30 g. of 4,4"-di(2,5-dichlorobenzoyl)-p-terphenyl are added to a mixture of 100 cc. of a 30% aqueous dispersion of a heat-hardenable melamine-formaldehyde condensation product and 80 cc. of water. The mixture is treated for 2 hours in a ball mill and thereafter coated on a paper support. After drying at room temperature the material is heated to 80 C. for minutes.
  • Example 3 In this example the electrophotographic properties of several compounds according to the invention are compared with known photoconductive compounds.
  • the sensitivity of a electrophotographic material depends essentially on the difference between the photoconductivity and the dark-conductivity. The more electrostatic charge drains off by a given exposure the higher is the contrast and the quality of the resulting image.
  • the graphs attached thereto present the draining off of the charge by exposure as a function of time. The steeper the slope of the curve the more suitable is the compound for electro-photographic purposes.
  • the axis of abscissa shows the relative charge per unit area in logarithmic scale in arbitrary units and the axis of ordinate the time in arbitrary units.
  • the electrophotographic material to be tested where prepared according to Example 2 by mixing each 40 g. of photoconductive compounds with 64 g. of a solvent of the silicone resin described in that example. With each compound the processing, charging and exposure used identical technique.
  • FIGURES 1 and 2 represent the following photoconductive compounds:
  • FIGURE 1 Known photoconductive compounds.
  • Curve 1 anthracene
  • Curve 2 p-terphenyl
  • Curve 3 anthraquinone
  • FIGURE 2 Photoconductors according to the invention.
  • Curve 1 4,4"-dibenzoyl-p-terphenyl
  • Curve 2 4,4"di-(4-chlorobenzoyl)-p-terphenyl.
  • An electrotophotographic material comprising a support, and a photoconducting insulating layer coated thereon composed of a dielectric film forming organic resin and a photoconductive organic compound dispersed therein, said organic compound being a polynuclear aryl compound which contains between 2 and 3 benzene rings connected to each other by single carbon to carbon bonds and substituted by at least 1 acyl radical.
  • photoconducting insulating layer contains as a photoconductive compound 4,4"-diacetyl-p-terphenyl.
  • said photoconducting insulating layer contains as a photoconductive compound 4,4"-di-(2,5-dichlorobenzoyl -p-terphenyl.
  • photoconducting insulating layer contains as a photoconductive compound 4,4-di-(4-chlorobenzoyl)- p-terphenyl.
  • an electrophotographic reproduction process which comprises exposing an electrostatically charged supported photoconductive insulating layer to light under a master to discharge the layer in proportion to the intensity of light to which any given area is exposed and developing the resulting latent electrostatic image with an electrophotographic developer, the improvement according to which the photoconductive insulating layer has as photoconductive ingredient a polynuclear aryl compound which contains between 2 and 3 benzene rings connected to each other by single carbon to carbon bonds and substituted by at least 1 acyl radical.
  • said photoconductive layer contains as a photoconductive compound 4,4"-di-(2,5-dichlorobenzoyl)-p-terphenyl.
  • said photoconductive layer contains as a photoconductive compound 4, 4"-di (4-chl orobenzoyl -p-terphenyl.

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Description

Nov. 2, 1965 sc M ETAL 3,215,528
PHOTOGONDUCTIVE LAYERS FOR ELECTROPHOTOGRAPHY Filed Nov. 2, 1962 INVENTORS GUSTAV SCHAUM, H/LDEGAPD HAYDEN, AN/M VON KON/G, HEINRICH SE/BERT.
BY CM 463.1. ATTO NE United States Patent Office 3,215,523 Patented Nov. 2, 1965 3,215,528 PHOTOCONDUCTEVE LAYERS FOR ELECTROPHOTOGRAPHY Gustav Schaurn, Hildegard Haydn, Anita von Kiinig, and Heinrich Seibert, Leverkusen, Germany, assignors to Agfa Aktiengesellschaft, Leverkusen, Germany, a corporation of Germany Filed Nov. 2, 1962, Ser. No. 234,926 Claims priority, application Germany, Nov. 14, 1956, A 26,007 9 Claims. (Cl. 96-1) This application is a continuation-in-part of our application Serial No. 696,032, filed November 13, 1957, now abandoned.
The present invention relates to photoconductive layers for electrophotography.
For the production of photoconductive layers for eletrophotography it is known to use certain inorganic or organic photoconductive materials. Examples of such materials are sulphur, selenium, oxides, sulphides and selenides of zinc, cadmium, mercury, antimony, bismuth, and lead, and also anthracene and anthraquinone. These substances are applied to an electrophotographic plate, especially a plate consisting of metal or another material, for example paper, or to a sheet or foil produced from a fihn-forming plastic. If necessary, the photoconductive substance can be held dispersed in an electrically isolating, layer-forming binder. Such layers being produced by means of coating solutions in which the binders are either dissolved or dispersed and in which the electro-conductive substances are dispersed. Such photoconductive layers are for instance disclosed in United States Patents No. 2,297,691; 2,357,809; 2,727,807; 2,727,808; 2,735,784; and 2,735,785, and in French Patents No. 1,113,933; 1,122,275; 1,125,235; and 1,136,146.
It has now been found that electrophotographic layers with excellent properties and which are only slightly colored are obtained if polynuclear aryl compounds which contain at least 2 benzene rings connected to each other by a single carbon-to-carbon bond and which are substituted by at least 1 acyl or substituted acyl radical are used as photoconductive compounds in such electrophotographic layers.
The following compounds are, for example, suitable for the instant process:
M.P. 4-b enzoyl-p-terphenyl 214 4 4-chlorobenzoyl) -p-terphenyl 2 69-70 4 (2,5-dichlorobenzoyl p-tertphenyl 184-85 4-acetyl-p-terphenyl 200-201 4,4"-diacetyl-p-pterphenyl 283-84 4,4"dibenzoyl-p-terphenyl 294-95 4,4di (4-chlorobenzoyl) p-terphenyl 300 4(p-phenylbenzoyl)p-terphenyl 299-300 4,4-di-(2,5-dichlorobenzoyl)-p-terphenyl 241-42 The method for the preparation of 4-benzoyl-p-terphenyl is described in J. Org. Chem. 19, 730 (1954). The other compounds are prepared accordingly by the reaction of an acylchloride with terphenyl in the presence of a Fn'edel-Crafts catalyst such as AlCl Suitable acyl groups are, for example, lower aliphatic acyl groups or benzoyl, the benzene rings of which can be further substituted, for example, by halogen, chlorine or bromine or by further phenyl rings.
The photoconductive compounds according to the invention are advantageous over prior art because they are more sensitive to longer wavelength. It is furthermore possible to sensitize these substances for still longer wavelengths by suitable compounds as they are for instance disclosed in French Patent No. 1,125,235.
The coating solution which is used for the production of the photoconductive layers comprises at least one of the aforementioned substances and a film-forming binding agent, the electrical specific resistance of which must be higher than that of the photoconductive substance and also higher than that of the layer support. The best results are obtained with binding agents the electrical specific resistance of which amounts to at least 10 ohm-centimeters.
Particularly suitable binding agents are silicone resins such as alkylpolysiloxanes and arylpolysiloxanes, especially phenyl and methyl polysiloxanes as they are disclosed in German Patents No. 853,351 and 865,975.
Further suitable binding agents are for instance cellulose, cellulose esters, cellulose ethers, polyvinyl chlo ride, polyurethanes, polyesters, polyamides, polycarbonates with a base of di-(monohydroxyaryl)-alkanes, especially 4,4'-di(m0nohydroxyaryl)-alkanes according to German Patents No. 971,790 and 971,777. Photoconductive compounds can be present in the electrophotographic layers, homogeneously in dissolved form or heterogeneously in a suspended form whereby the particle size of the suspended photoconductor should be as small as possible.
The quantitative ratios between the photoconductive substances and the binding agents may vary within wide limits. It is preferred to use the photoconductive substance in amounts between 1 part for each 0.3 to 2 parts by weight of binding agent which is the equivalent of 0.5 to 3.33 parts by weight of the photoconductive substance to each part by weight of the binding agent, and amounts between about 5 and about 40 grams per square meter of photoconductive layer. The solvent or solvent mixture used for the production of electrophotographic layers containing a photoconductive compound, heterogeneously dispersed therein must be good solvents for the binding agent but non-solvents or poor solvents for the photoconductive compounds. Suitable layers of this type can be produced as follows: An organic solvent is used which dissolves both the photoconductive substance and the binding agent layer former. This solution has added thereto another organic solvent in which the layer former is soluble but the photoconductive substance is insoluble. By this means, the photoconductive compound is deposited in a state of particularly fine distribution, so that layers with a particularly smooth surface are obtained. As a support for the photoconductive layer there may be used paper or metal plates, such as zinc, aluminum, or brass plates. Furthermore, thin foils of cellulose hydrate, cellulose esters or of polyamide come into question. In processing of the electrophotographic materials said material is electrostatically charged in the dark, for instance, by meaning of a corona discharge device. The charged layer is then exposed with light through a nega tive photographic film, positive film or mask or otherwise to a light image, to receive a latent electrostatic image. If the electrophotographic material has been properly prepared, the charges leak 01? rapidly to the support in proportion to the intensity of light to which any given area is exposed. After such exposure, the latent electrostatic image can be developed by any developing process known per se, for example, by dusting a developing powder whereby the powder adheres to the areas where the electrostatic charges remain, forming thereby a powder image corresponding to the electrostatic image. Thereafter the powder image can be fixed by melting the developing powder or can be transferred to a sheet of transfer material resulting in a positive or negative print as the case may be.
The photoconductive layers can also be produced from aqueous dispersions of photoconductive substances and binding agents, for instance by the process disclosed in French Patent No. 1,136,146. If necessary, the cast dispersions or emulsions are subjected to a final condensation or final polymerization by heat treatment at temperatures of about 80-150 C. for about 2 to 30 minutes after being dried. Aqueous dispersions of polymeric substances, such as melamineformaldehyde or urea-formaldehyde resins, xylene-formaldehyde resins, polymers based on vinyl chloride, vinylidene chloride, vinyl ethers, acrylic esters, methacrylic esters, acrylic amides, such for example as methacrylic amide, aromatic vinyl compounds, such for example as styrene, isoolefins, such for example as isobutylene, copolymers based on the aforementioned compounds, such for example as copolymers of vinyl chloride and butyl acrylate vinylidene chloride and butyl acrylate synthetic elastorners, such for example as copolymers of butadiene and styrene, butadiene and acrylonitrile, and also copolymers of dienes with a preponderant proportion of styrene and/ or acrylonitrile or other vinyl compounds, as well as polyamides, polyurethanes, polyesters of polycarboxylic acids and polyhydric alcohols, polycarbonates, cellulose ester, rubber and the like, are for example employed.
Example 1 40 g. of 4,4-"-diacetyl-p-terphenyl,
64 g. of a 60% solution of a silicon resin in toluene, for instance a silicone resin according to Example 1, German Patent No. 853,351,
97 cc. toluene are thoroughly mixed and ground for several hours in a ball mill.
The resulting mixture is then cast on a paper support and dried.
By usual processing which comprises charging by corona discharge exposing and developing the resulting electrostatic latent image, a developed powder image is obtained having excellent detail and quality.
Example 2 30 g. of 4,4"-di(2,5-dichlorobenzoyl)-p-terphenyl are added to a mixture of 100 cc. of a 30% aqueous dispersion of a heat-hardenable melamine-formaldehyde condensation product and 80 cc. of water. The mixture is treated for 2 hours in a ball mill and thereafter coated on a paper support. After drying at room temperature the material is heated to 80 C. for minutes.
By usual processing which comprises charging by corona discharge exposing and developing the resulting electrostatic latent image, a developed powder image is obtained having excellent detail and quality.
Example 3 In this example the electrophotographic properties of several compounds according to the invention are compared with known photoconductive compounds.
The sensitivity of a electrophotographic material depends essentially on the difference between the photoconductivity and the dark-conductivity. The more electrostatic charge drains off by a given exposure the higher is the contrast and the quality of the resulting image. The graphs attached thereto present the draining off of the charge by exposure as a function of time. The steeper the slope of the curve the more suitable is the compound for electro-photographic purposes. The axis of abscissa shows the relative charge per unit area in logarithmic scale in arbitrary units and the axis of ordinate the time in arbitrary units.
The electrophotographic material to be tested where prepared according to Example 2 by mixing each 40 g. of photoconductive compounds with 64 g. of a solvent of the silicone resin described in that example. With each compound the processing, charging and exposure used identical technique.
The curves in FIGURES 1 and 2 represent the following photoconductive compounds:
FIGURE 1: Known photoconductive compounds. Curve 1: anthracene Curve 2: p-terphenyl Curve 3: anthraquinone FIGURE 2: Photoconductors according to the invention. Curve 1: 4,4"-dibenzoyl-p-terphenyl Curve 2: 4,4"di-(4-chlorobenzoyl)-p-terphenyl.
We claim:
1. An electrotophotographic material comprising a support, and a photoconducting insulating layer coated thereon composed of a dielectric film forming organic resin and a photoconductive organic compound dispersed therein, said organic compound being a polynuclear aryl compound which contains between 2 and 3 benzene rings connected to each other by single carbon to carbon bonds and substituted by at least 1 acyl radical.
2. An electrophotographic material according to claim 1, wherein said photoconducting insulating layer contains as a photoconductive compound 4,4"-diacetyl-p-terphenyl.
3. An electrophotographic material according to claim 1,-wl1erein said photoconducting insulating layer contains as a photoconductive compound 4,4"-di-(2,5-dichlorobenzoyl -p-terphenyl.
4. An electrophotographic material according to claim 1, wherein said photoconducting insulating layer contains as a photoconductive compound 4,4-di-(4-chlorobenzoyl)- p-terphenyl.
5. In an electrophotographic reproduction process which comprises exposing an electrostatically charged supported photoconductive insulating layer to light under a master to discharge the layer in proportion to the intensity of light to which any given area is exposed and developing the resulting latent electrostatic image with an electrophotographic developer, the improvement according to which the photoconductive insulating layer has as photoconductive ingredient a polynuclear aryl compound which contains between 2 and 3 benzene rings connected to each other by single carbon to carbon bonds and substituted by at least 1 acyl radical. I
6. The combination of claim 5, wherein said photoconductive layer contains as a photoconductive compound 4,4"-diacetyl-p-terphenyl.
7. The combination of claim 5, wherein said photoconductive layer contains as a photoconductive compound 4,4"-di-(2,5-dichlorobenzoyl)-p-terphenyl.
8. The combination of claim 5, wherein said photoconductive layer contains as a photoconductive compound 4, 4"-di (4-chl orobenzoyl -p-terphenyl.
9. The combination of claim 1 in which the polynuclear aryl compound is present in a concentration of between about 5 and 40 grams per square meter of photoconductive layer, and between about 0.5 to 3.33 parts by weight to each part of the resin by weight.
No references cited NORMAN G. TORCHIN, Primary Examiner.

Claims (1)

1. AN ELECTROTOPHOTOGRAPHIC MATERIAL COMPRISING A SUPPORT, AND A PHOTOCONDUCTING INSULATING LAYER COATED THEREON COMPOSED OF A DIELECTRIC FILM FORMING ORGANIC RESIN AND A PHOTOCONDUCTIVE ORGANIC COMPOUND DISPERSED THEREIN, SAID ORGANIC COMPOUND BEING A POLYNUCLEAR ARYL COMPOUND WHICH CONTAINS BETWEEN 2 AND 3 BENZENE RINGS CONNECTED TO EACH OTHER BY SINGEL CARBON TO CARBON BONDS AND SUBSTITUTED BY AT LEAST 1 ACYL RADICAL.
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