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 or 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

• An electrophotographic plate which comprises a photoconductive layer comprising a photoconductive material, a binder material, and a photochromic sensitizing agent selected from the group consisting of:
• R. H ahalogen.
• a halogen, CN, OR, or COOR where R is an alkyl group having one to seven carbon atoms, providing R5 and R; do not represent H atoms simultaneously; and mixtures thereof, is disclosed. Electrophotographic processes employing these plates are also disclosed.
• images may be formed and developed on the surface of certain photoconductive insulating materials by electrostatic means.
• the basic electrophotographic process as taught by Carlson in U.S. Pat. No. 2,297,691, involves uniformly charging a photoconductive insulating layer and exposing said layer to a light-and-shadow image which dissipates the charge on the portions of the layer which are exposed to light.
• the electrostatic latent image formed on the layer corresponds to the configuration of the light-and-shadow image.
• a latent electrostatic image may be formed on the plate by charging said plate in image configuration. This image is rendered visible by depositing on the imaged layer a developing material, comprising a colorant, called a toner.
• the developing material is attracted to those portions of the layer which retain a charge, thereby forming a toner image corresponding to the latent electrostatic image.
• the toner image may be fixed directly to the plate as by heat or solvent fusing.
• the toner image may be transferred to a sheet of receiving material, such as paper, and fixed thereon.
• the photoconductive insulating layer to be eflective must be capable of holding an electrostatic charge in the dark and dissipating the charge to a conductive substrate when exposed to light.
• Another object of this invention is to provide a novel electrophotographic process devoid of the above-noted disadvantages.
• Still another object of this invention is to provide a nonreusable electrophotographic process capable of producing prints of high contrast and quality.
• a further object of this invention is to provide a novel electrophotographic plate having improved photosensitivity and panchromaticity.
• an electrophotographic plate which comprises a photoconductive material, a binder material, and a photochromic sensitizing agent selected from the group consisting of:
• R, H, a halogen, R or OR wherein: R is an alkyl group having one to seven carbon atoms, R and R an alkyl group having one to seven carbon atoms, and R (CI-1 H or (CI-1 COOH, wherein n l to 7;
• R, H, a halogen, R or OR wherein: R is an alkyl group having one to seven carbon atoms, R and R an alkyl group having one to seven carbon atoms, R, (CH SO H or (CH COOH where n l to 7, and R,, and R H, N0 a halogen, CN OR, or COOR where R is an alkyl group having one to seven carbon atoms, providing R, and R, do not represent H atoms simultaneously; and mixtures thereof.
• These agents increase the photosensitivity and panchromaticity of a photoconductive layer.
• a latent electrostatic image is formed on the surface of the above-mentioned photoconductive layer which contains a photochromic sensitizing agent of the general formulas described above, said image is first developed and then the surface of said layer is exposed uniformly to visible light in order to remove the color imparted by said sensitizing agent to the background areas of said layer.
• any suitable organic or inorganic photoconductive material may be employed in the plate of this invention.
• Typical inorganic photoconductive materials are sulfur, selenium (vitreous, amorphous alpha monoclinic), zinc sulfide, zinc oxide, zinc cadmium sulfide, zinc magnesium oxide, cadmium selenide, zinc silicate, calcium-strontium sulfide, cadmium sulfide, mercuric iodide, mercuric oxide, mercuric sulfide, indium trisulfide, gallium triselenide, arsenic disulfide, arsenic trisulfide, arsenic triselenide, antimony trisulfide, cadmium sulfoselenide, doped chalcogenides of zinc and cadmium, aluminum oxide, bismuth oxide, molybdenum oxide, lead oxide, titanium oxide, molybdenum iodide, molybden
• Typical organic photoconductive materials include aromatic polyvinyl compounds such as polyvinyl naphthalene, polyvinyl anthracene, polyvinyl biphenyl, and polyvinyl fluorene; heterocyclic polyvinyl compounds such as polyvinyl carbazole, polyvinyl quinoline, and polyvinyl furane; high molecular weight aromatic compounds such as polyacenaphthylene, polyacephenanthracene, oxadiazoles, imidazolones, imidazolethiones, triazoles, oxazoles, thiazoles, triazines, and hydrazones; low molecular weight aromatic carbocyclic or aromatic heterocyclic compounds such as imidazoles and triazoles; azomethines; amino compounds with multinuclear heterocyclic and aromatic ring system, anthracene and its derivatives, styryl compounds, thiophenes, acylhydrazones, metal compounds of
• Typical photoconductive insulating materials include films of amorphous selenium, sulfur, sulfur-selenium mixtures, arsenic-selenium mixtures, selenium-tellurium mixtures, lead oxide, cadmium sulfide, zinc sulfide and organic photoconductors (especially when these are complexed with small amounts of a suitable Lewis acids).
• organic photoconductors are polyvinylcarbazole; polyvinylanthracene; 4,5 -diphenylimidazolidinone; 4,5-diphenylimidazolidinethione; 4,5-bis-(4 aminophenyl)- imidazolidinone; 1,5-cyanonaphthalene; 1,4- dicyanonaphthalene; aminophthalodinitrile; nitrophthalidinitrile; l,2,5,6-tetraazacyclooctatetraene- (2,4,6,8 3,4-di(4'-methoxy-phenyl)-7,8-diphenyl-1,2,5,6- tetraazacyclo actatetraene-( 2,4,6,8 3 ,4-di-( 4'-phenoxyphenyl-7,8-diphenyl-l ,2,5 ,6-tetraaza-cycyloctatotraene- (2,4,6,8 3,4,7,8-tetrameth
• Typical insulating film forming binders include thermoplastic and thermoset polymers such as polyvinylchloride, polyvinylacetates, polystyrene, polystyrene-polybutadiene copolymers, polymethacrylates, polyacrylics, polyacrylonitriles, silicone resins, chlorinated rubber, epoxy resins including halogenated epoxy and phenoxy resins, phenolics, epoxy-phenolic copolymers, epoxy urea formaldehyde copolymers, epoxy melamine formaldehyde, polycarbonates, polyurethanes, polyamides, saturated polyesters, unsaturated polyesters cross-linked with vinyl monomers and epoxy esters, vinyl epoxy resins, tall-oil modified epoxys, and copolymers and mixtures thereof.
• thermoplastic and thermoset polymers such as polyvinylchloride, polyvinylacetates, polystyrene, polystyrene-polybutadiene copolymers, polymeth
• insulating film-forming binder materials includes organics such as sucrose and its derivates, resin and modified resins, etc; inorganic materials such as low melting point insulating glasses including those made from glassforming oxides, sulfides, selenides, borates, phosphates, ar' sonates, other well known glass formers and mixtures thereof.
• organics such as sucrose and its derivates, resin and modified resins, etc
• inorganic materials such as low melting point insulating glasses including those made from glassforming oxides, sulfides, selenides, borates, phosphates, ar' sonates, other well known glass formers and mixtures thereof.
• any other suitable binder may be used if desired.
• the binder for the photoconductive material used in the present invention should be of such a nature that it will not adversely affect the photochromic sensitizing agent nor will it impede the removal of color at the time of exposure to visible light.
• binder material While any suitable binder material may be used in the present invention, it is preferred to use alkyd resins, sytrenebutadiene copolymers, polymethacrylic ester resins, and epoxy resins, for excellent results. Optimum results are obtained with styrenated alkyd binder materials.
• sensitizing material represented by the above-mentioned general formulas
• these materials are most preferred.
• Typical non-conductive bases include paper, plastics, polyurethane, polyvinylchloride, polyethylene, polyethylene terephthalate, among others. If it is desired to use a conductive base in a single charging applica tion, any suitable conductive base may be utilized in accordance with the present invention.
• Typical conductive bases include NESA glass, aluminized Mylar, conductive polymers, chromium, aluminum, brass, stainless steel, copper, zinc and alloys thereof. A substantially white paper substrate is preferred in the present invention.
• the photoconductive layer of the present invention may have any suitable thickness. Thicknesses ranging from about 5 microns to about 200 microns have been found convenient. For best operation it is preferred that the layer have a thickness of about 10 microns to about microns.
• sensitizing agent represented by the above-mentioned general formulas to photoconductive material may be employed in this invention.
• a range of about 1 part to about 1,000 parts by weight of sensitizing agent to about 100,000 parts by weight of photoconductive material has been found convenient.
• a preferred ratio lies in the range of about 1 part to about 20 parts by weight of sensitizing agent to about 10,000 parts by weight of photoconductive material.
• the photoconductive material may be incorporated in a dissolved or melted binder by any suitable means, such as strong shear agitation, preferably with simultaneous grinding.
• the methods include ball milling, roller milling, sand milling, ultrasonic agitation, high speed blending, and any desirable combination of these methods.
• the photoconductive material may also be added and blended into a dry or slurried form of the powdered binder material before it is heated or dissolved to make it film forming.
• any suitable range of photoconductor-binder ratios may be used.
• the ratio between binder and photoconductive material is from about 1 part binder and 10 parts photoconductor to about 2 parts binder and 1 part photoconductor, by weight. Best results are achieved in the range of about 1 part binder and 1 part photoconductor to about 1 part binder and 9 parts photoconductor, by weight, and, accordingly, this range is preferred.
• the sensitizing agent of this invention may be added to the photoconductive material in several ways.
• said agent may be dissolved in a suitable solvent and the photoconductive material added to the resultant solution so as to permit the sensitizing substance to be deposited on the photoconductive material.
• the photoconductive material may be mixed and kneaded with the binder and the solution of sensitizing substance added to the resulting mixture.
• the nature of the surface of the photoconductive material should be known.
• zinc oxide which is comparatively basic on its surface satisfactorily absorbs a photochromic sensitizing agent possessing an acid radical.
• Titanium oxide on the other hand, is acidic on its surface, as compared to zinc oxide, and therefore tends to absorb a basic colored sensitizing agent.
• the photoconductive material comes to possess photosensitivity to the portion of wavelengths corresponding to the light absorption by the sensitizing agent.
• the sensitized photoconductor-binder-solvent slurry or the photoconductor-binder melt may be applied to substrate materials by any of the well known coating methods, including spray, flow coating, hydrolic coating, knife-coating, electrocoating, mayer bar drawdown coating, dip coating, reverse roll coating, etc. Spraying in an electric field may be preferred for smoothest finish and dip coating for convenience in the laboratory.
• the toner image may be formed by an conventional electrophotographic process.
• an electrostatic latent image is formed on a photoconductive insulating layer and is developed thereon by finely divided electroscopic developing materials.
• the developed image may then be fixed in place or transferred to a copy sheet where it is permanently fixed.
• the photoconductive insulating layer is first charged to sensitize it and is then exposed to a light image or other pattern of activated electromagnetic radiation to dissipate the charge in radiation struck areas.
• the charge pattern formed conforms to the electromagnetic radiation pattern which impinges upon the plate.
• This charge pattern may then as above discussed be developed or made visible by a charge wise deposition on the plate of an electroscopic or electrostatically attractable, finely divided colored material which is referred to in the art as toner.
• any of several known methods for applying the electroscopic particles to the electrostatic latent image to be developed may be used in this invention.
• One development method as disclosed by E. N. Wise in U.S. Pat. No. 2,618,552, is known as cascade development.
• a developer material comprising relatively large carrier particles having finely divided toner particles electrostatically coated thereon is conveyed to and rolled or cascaded across the electrostatic latent image bearing surface.
• the composition of the carrier particles is so selected as to triboelectrically charge the toner particles to the desired polarity.
• the toner particles are electrostatically deposited and secured to the charged portion of the latent image and are not deposited on the uncharged or background portions of the image. Most of the toner particles accidentally deposited in the background are removed by the rolling carrier, due apparently, to the greater electrostatic attraction between the toner and the carrier than between the toner and the discharged background. The carrier and excess toner are then recycled. This technique is extremely good for the development ofline copy images.
• Another method of developing electrostatic images is the magnetic brush process as disclosed, for example, in U.S. Pat. No. 2,874,063.
• a developer material containing toner and magnetic carrier particles are carried by a magnet.
• the magnetic field of the magnet causes alignment of the magnetic carrier into a brush-like configuration.
• This magnetic brush is engaged with the electrostatic image-bearing surface and the toner particles are drawn from the brush to the latent image by electrostatic attraction.
• Still another technique for developing electrostatic latent images is the powder cloud" process as disclosed, for example, by C.F. Carlson in U.S. Pat. No. 2,221,776.
• a developer material comprising electrically charged toner particles in a gaseous fluid is passed adjacent the surface bearing the electrostatic latent image.
• the toner particles are drawn by electrostatic attraction from the gas to the latent image. This process is particularly useful in continuous tone development.
• the fixing of the toner image may be accomplished by a heat-fixing process, a process which causes the toner to be deposited fast and solidified, or a process which provides uniform lacquering.
• the removal of color from the background areas of the sensitized photoconductive layer may be carried out before or after the fixing step.
• the exposure of the colored sensitized photoconductive layer may be accomplished by placing said layer open to sufficiently intense light emanating from a suitable light source for a short length of time. This is accomplished, for example, by exposure to sunlight, exposure to light from a tungsten light source, or exposure to light from other visible light sources.
• a light which absorbs the activated coloring matter proves effective. Where the color need not be removed at once, the fixed print may be left in a light room.
• said print may be exposed to a light having an illumination exceeding 10,000 luxes from, for example, a tungsten light source having a color temperature of about 2,800 K.
• the exposure time may, of course, be reduced where a brighter light source is void.
• a brighter light source is void.
• the print is exposed to sunlight, about I to 5 minutes of exposure time is sufficient to remove color from the background areas.
• After exposure to visible light there is obtained a final print which is excellent in image quality. This, in part, is due to a white background and a consequent high contrast.
• a substance which manifests photochromism is characterized by the fact that reversible change of color takes place quite rapidly.
• the photochromic sensitizing agents of the present invention i.e., those represented in the general formulas mentioned above, once the color is removed, it is not easily restored. In fact, such resumption of color cannot be achieved unless the decolorized layer is heated and/or exposed to ultraviolet rays.
• the background color is removed, after development of the image, through exposure to visible light, no resumption of color takes place under ordinary storage conditions. Even if the color is allowed to reappear under defective storage conditions it can be removed again by exposing the layer to visible light once more.
• the step of removing the color from the non-image areas of a print after development can be applied to electrophotographic processes other than described above. For example, it may be applied to a non-charging electrophotographic process, an electrolytic electrophotographic process, and the like.
• a binder resin lOlO34 0498 which comprises about 0.6 g. (as involatile component) of Styresol 4400 (made by Nippon Reichheld Co.) and about 4.0 g. (as involatile component) of Desmodule L (made by Bayer Co. of West Germany).
• Styresol 4400 is a styrenated alkyd resin and is marketed as a 5.0 percent toluene solution.
• Desmodule L is the reaction product of 1 mol of trimethylol propane and 3 mol of tolylenediisocyanate and is marketed as a 75 percent ethyl acetate solution.
• the resultant resin solution and the treated zinc oxide are mixed together by means of a ball mill.
• This dispersion which is obtained is then spread to a dry thickness of about 6 microns on a conductive paper. After spreading, the layer is dried and kept in an air thermostat bath at about 40 C for about 24 hours. All the preceding treatments are carried out in a darkroom.
• the photoconductive layer thus obtained assumes a light blue color by virtue of the sensitizing material.
• the reflective optical density is found to be 0.32.
• This photosensitive layer is then uniformly charged by exposure to a negative corona at 7000 V. It acquires a surface electric potential of 320 V. In this state, the sensitive layer is held directly in contact with a positive original and exposed, through the original to light from a tungsten light source at 1,000 luxes for 0.4 seconds. lmmediately after the exposure, the sensitive layer is developed with a liquid developer comprising commercial blue offset ink and cyclohexane.
• the sheet containing the sensitive layer is rinsed in a bath of clean isoparafin to wash off the remaining toner particles.
• the image is fixed by spraying thereon commercial clear lacquer. The lacquer is dried, and, subsequently, the sheet is exposed in its entire surface to the sunlight for about minutes.
• the reflective optical density falls to 0.24 in the non-image area.
• Example I is repeated using a methanol solution of the following sensitizing agent which is absorbed by zinc oxide:
• An electrophotographic member comprising a support substrate having superimposed thereon a photoconductive layer comprising an inorganic photoconductive material, a binder material, and a photochromic sensitizing agent selected from at least one member of the group consisting of:
• said inorganic photoconducting material is selected from at least one member of the group consisting of zinc oxide and titanium oxide.
• m 1034 uns photochromic sensitizing agent is the open form of said agent.
• said inorganic photoconductive material is selected from at least one member of the group consisting of zinc oxide and titanium oxide.

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

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Citations (1)

• 1969
  • 1969-01-17 JP JP44003261A patent/JPS4946264B1/ja active Pending
• 1970
  • 1970-01-02 US US394A patent/US3660086A/en not_active Expired - Lifetime
  • 1970-01-16 DE DE2001905A patent/DE2001905C3/de not_active Expired
  • 1970-01-16 GB GB1290441D patent/GB1290441A/en not_active Expired

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