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
  • G03G5/06—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

Definitions

• This invention relates to electrophotographic elements in the form of copy sheets having photoconductive coatings for use in electrostatic image development and it relates more particularly to an improvement in photocon ductive compositions used in the preparation of light sensitive photoconductive coatings.
• a typical electrostatic process includes the preparation of an electrophotographic element such as a paper base sheet having a photoconductive coating formed of a photoconductive insulating material, such as zinc oxide, dispersed in an insulating binder, such as a silicone or modified alkyl resin.
• the recording element is subjected to corona discharge at high voltage to produce an electrostatic charge over tire photoconductive surface.
• corona discharge at high voltage to produce an electrostatic charge over tire photoconductive surface.
• the portions irradiated by the light rays are rendered conductive to discharge the electrostatic charge to leave the remainder of the surface in a charged condition which defines a latent electrostatic image.
• the image is rendered visible by application of a developing powder or liquid whereby the colored particles adhere electrostatically to the charged areas of the sheet and the image is subsequently fixed directly to the photoconductive coating, as by means of heat, adhesive, vapor or the like. Instead, use can be made of a reverse toner whereby the colored particles are deposited on the uniriaged portions of the copy sheet.
• a detailed description of a typical electrostatic printing process is set forth in the Greig Patent No. 2,874,063.
• the patent describes a process in which a copy sheet having a photoconductive coating containing a relatively pure zinc oxide is charged by corona discharge to a potential of approximately 600-800 volts.
• a latent image is formed by hoto graphic exposure and the image is developed with a developer composition such as iron particles mixed with a powed of carbon pigmented resin.
• An electrostatic recording element of the type described is usually prepared by first mixing a finely divided photoconductor, such as zinc oxide, and the electrically insulating film forming vehicle, such as a silicone resin, with a volatile solvent. The mixture is coated onto the base sheet, dried and then cut to size.
• a finely divided photoconductor such as zinc oxide
• the electrically insulating film forming vehicle such as a silicone resin
• the photoconductive layers heretofore produced are slow in response to light whereby considerable time is required during the exposure period to form the latent electrostatic image and other limitations are imposed from the standpoint of the time and intensity of the exposure.
• the art has sought to sensitize the photoconductive materials, such as the zinc oxide used in the photoconductive coating, as by the addition of certain sensitizing dyestufl's which are capable of absorbing radiant energy in bands of wave lengths to which the photoconductive material is substantially insensitive and which are capable of transferring the absorbed energy to the zinc oxide or other photoconductive material.
• certain sensitizing dyestufl's which are capable of absorbing radiant energy in bands of wave lengths to which the photoconductive material is substantially insensitive and which are capable of transferring the absorbed energy to the zinc oxide or other photoconductive material.
• the sensitizing dyes that have been used with zinc oxide are fluorescent dyes, eosin dyes, erythrosin dyes, rose bengal, malachite green, crystal violet, basic fushin, methyl green, brilliant green, methylene blue, acridine orange, aldzarin red and other dye systems more fully described in the following US.
• Such dye sensitized systems are also deficient from the standpoint of the high speed required for the more recently developed copying machines employing electrostatic techniques. While increased speed might be achieved by increase in dye concentration, the corresponding increase in color would be objectionable and even then adequate speed is difiicult to achieve.
• the term speed is used to define light sensitivity of the electrophotographic coating and it is measured by the amount of light in foot candle seconds required to decay the charge on the paper to a very low or zero residual potential.
• the term dark decay measured in volts per second, relates to the loss of charge of the electrophotographic coating in the dark.
• Another property used to measure electrophotographic coatings is charge. acceptance which is measured in volts.
• Electrophotographic coating employed in present practice are formulated of photoconductive materials, such as zinc oxide of the type marketed by the New Jersey Zinc Company under the trade name Photox zinc oxide, or of the type marketed by the American Zinc Company under the trade name Azo-ZZZ-661 zinc oxide, with an insulating resinous binder such as styrene-ethyl acrylate, silicone resins, modified urethane-oil silicone resins, modified polyvinyl acetate, and the like, or other film forming insulating resins and pigments as described in US. Pats. 3,052,539; 3,121,006; 3,121,007, and 3,132,241.
• Dyestuffs which have been used to increase light sensitivity of the described electrophotographic coatings include Bromo Phenol'Bl'ue, Dibromofiuorescein, ErythrosineB, Rose BengaL'Sulpho Rhodamine, Rhodamine B Extra, Eosin OJ concentrate, Auromine '0 concentrate, Quin'oline Yellow, Bromo Cresol Purple, Phloxine B, Acradine Orange, Fuchsin, Methylene Blue, Kiton Blue, Tartrazine concentrate, or others of the dyestuffs described in the aforementioned list of patents.
• photoconductive coatings with or without dye sensitization, can be markedly increased in speed without addition of color by the formulation of the coating to contain one or more cyanine compounds represented by the following structural formula:
• R R and R are selected of hydrogen or an alkyl group having from 1 to 2 carbon atoms, such as methyl and ethyl; R and R are selected of an alkyl or dimethyl-2,2'-carbocyanine iodide; l,1-diethyl-2,2'-quinocyanine iodide; 3-ethyl-2-[5- ('3-ethyl-2 benzothiazolinyli- (idene)-1,3-pentadienyl]-benzothiazolium iodide; 3,3-diallylthiacarbocyanine iodide; 3,3-diethyl-9-methylthiacarbocyanine iodide; 3,3'-diethyloxacarbocyanine iodide.
• the desirable effect can be achieved when the cyanine compound is present in the photoconductive coating composition in an amount of at least 0.0001% by weight of the coating composition and little, if any, additional benefit is secured when present in the coating composition in an amount greater than 0.2% by weight.
• the amount of cyanine compound based upon the -weight percent of the coating composition is within the range of 0.005% to 0.05% by weight.
• the amount of cyanine compound or mixtures thereof may be employed within the range of 0.003% to 0.3% by weight and preferably within the range of 0.01% to 0.1% by weight.
• a sensitizing dye component When a sensitizing dye component is employed in the composition with the cyanine compound or compounds in the photoconductive coating, the amount thereof will correspond to that conventionally employed, as described in the aforementioned patents which are addressed to sensitization with dyestuffs.
• the cyanine compounds are unique in that the marked increase in speed is noticeable primarily in photoconductive coatings formulated with a binder component selected of a polyvinyl acetate, a mixture of polyvinyl acetate, polystyrene and polyethyl acrylate, or a mixture of polystyrene and polyethyl acrylate, in which the polyethyl acrylate component can be substituted with other polyalkyl aci'ylates or in which the alkyl groups have from 1 to 3 carbon atoms.
• a binder component selected of a polyvinyl acetate, a mixture of polyvinyl acetate, polystyrene and polyethyl acrylate, or a mixture of polystyrene and polyethyl acrylate, in which the polyethyl acrylate component can be substituted with other polyalkyl aci'ylates or in which the alkyl groups have from 1 to 3 carbon atoms.
• Example 3 The compositions are the same as in Example 1 except that in Example 3 the compound 1,1-diethyl-2,2'-dicarbo cyanine iodide is substituted for the compound 3-ethyl-2- [5 (3-ethyl-2-benzothiazolinylidene) 1,3 pentadienyl]- benzothiazolium iodide.
• Example 4 the compound pinacyanol iodide is substituted for the compound -3-ethyl- 2-[5 (3-ethyl-2-benzothiazolinylidene)-1,3-pentadienyl]- benzothiazolium iodide.
• Example 5 the compound 1,1- diallyl-6,6-dimethyl-2,2'-carbocyanine iodide is substituted for the compound 3-ethyl-2-[ 5-(3-ethyl-2-benzothiazolinylidene) 1,3 pentadienyl]-benzothiazolium iodide.
• Example 6 the compound 1,1'-diethyl-2,2-quinocyanine iodide is substituted for the compound 3-ethyl-2-[5-(3-ethyl- 2-benzothiazolinylidene)-1,35pentadienyl] benzothiazolium iodide.
• Example 7 the compound 3,3'-diallylthiacarbocyanine iodide is substituted for the compound 3-ethyl-2-[5-(3-ethyl 2 benzothiazolinylidene)-1,3-pentadienyl]-benzothiazolium iodide.
• Example 8 the compound 3,3'-diethyl-9-methylthiacarbocyanine iodide is substituted
• Example 10 The composition is the same as: in Example 1 except that polyvinyl acetate is substituted for the De Soto resin in equivalent amounts.
• Example 11 The composition is the same as in Example 1- except -that a polystyrene-polyethyl acrylate is substituted for.
• the zinc oxide, toluene and resinous binder are mixed for three minutes. Thereafter addition is made of thedye blend, when used, followed by the addition of the cyanine solution with mixture in an Osterizerfor another three minutes.
• the prepared coating composition is applied as a coating onto conductive paper base stock (Weyerhaeuser Plainwell 35'pound paper) in a coating weightof 20 pounds per 3000 square feet of surface area.
• the coated paper is air dried or drying can be accelerated by air drying at an elevated temperature from room temperature to 350 F.
• the coated paper electrophotographic printing element can be charged and exposed in the conventional manner and developed to provide a visible image with conventional liquid or powder developers used in the electro static printing.
• the electrometer data run on sheets prepared with the composition of Example 1 gives a speed 3.7 times greater than the speed of paper coated with the same composition but without the cyanine compound and without loss in charge acceptance.
• the invention permits the use of resinous binder systems in the photoconductive coating which is capable of accepting a high charge, andthe ability to sensitize these resins to so-called fast systems. Because of the increase in speed and high charge acceptance, use can be made of lower coating weight of 8 to 25 pounds per 3000 square feet of surface area without undesirable effect on copy quality. Thus the amount of coating applied to the sheet can be reduced by at least 40% compared to conventional coating weights applied in current construction. This not only reduces the weight of the Electrofax type paper but it also operates markedly to reduce the cost of the photoconductive element while also improving the feel and appearance thereof. The ability to reduce or eliminate the colored dye sensitizers also permits the production of whiter sheets with better contrast between the developed image and background.
• An electrophotographic printing element comprising a conductive base sheet and a coating on the base sheet containing a photoconductive zinc oxide, an insulating resinous binder of a mixture of polyvinyl acetate, poly styrene and a polyalkyl acrylate in which the alkyl group contains 1-3 carbon atoms, and a cyanine compound having the structural formula:
• R R and R are groups selected from the group consisting of hydrogen and an alkyl group containing from 1 to 2 carbon atoms
• R and R are groups selected from the group consisting of an alkyl group and an alkylene group containing from 1 to 2 carbon atoms
• Y is a halogen group
• X is a group selected from the group consisting of oxygen, sulfur and an ethylenic group
• n is an integer of 0, 1, 2 or 3.
• cyanine compound is selected from the group consisting of 1,1'-diethyl-2,2-dicarbocyanine iodide; pinacyanol iodide; 1,1-diallyl-6,6-dimethyl -2,2'-carbocyanine iodide; 1,l'-diethyl-2,2'-quinocyanine iodide;
• An electrophotographic printing element as claimed in claim 1 in which the cyanine compound is present in the coating in an amount within the range of 0.003% to 0.3% by weight of the photoconductive compound.
• An electrophotographic printing element as claimed in claim 1 in which the cyanine compound is present in the coating in an amount within the range of 0.01% to 0.1% by weight of the photoconductive compound.
• An electrophotographic printing element as claimed in claim 1 which includes a dye sensitizer to increase the light sensitivity of the coating.
• the electrophotographic recording element comprises a conductive base sheet and a coating on the base sheet con taining photoconductive zinc oxide, an insulating resinous binder of a mixture of polyvinyl acetate, polystyrene and a polyalkyl acrylate in which the alkyl contains 1-3 carbon atoms and mixtures of polystyrene and a cyanine compound having the structural formula:
• R R and R are groups selected from the group consisting of hydrogen and an alkyl group containing from 1 to 2 carbon atoms, R;, and R are groups selected from the group consisting of an alkyl group and an alkylene group containing from 1 to 2 carbon atoms, Y is a halogen group, X is a group selected from the group consisting of oxygen, sulfur and an ethylenic group, and n is an integer of 0, l, 2 or 3.
• the cyanine compound is selected from the group consisting of 1,1'-diethyl-2,2'-dicarbocyanine iodide; pinacyanol iodide; 1,1-diallyl-6,6-dimethyl-2,2-carbocyanine iodide; 1,1'-diethy1-2,2-quinocyanine iodide; 3-ethyl-2-[-(3-ethyl-2-benzothiazolinylidene)-1,3-pentadienyl]-benzothiazolium iodide; 3,3'-diallylthiacarbocyanine iodide; 3,3'-diethyl-9-methylthiacarbocyanine iodide; and 3,3'-diethyloxacarbocyanine iodide.
• the coating composition includes a dye sensitizer to increase the light sensitivity of the coating.

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

Applications Claiming Priority (1)

Publications (1)

Family

ID=21938714

Family Applications (1)

Country Status (5)

Cited By (7)

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• 1970
  • 1970-06-11 US US45577A patent/US3682630A/en not_active Expired - Lifetime
• 1971
  • 1971-06-08 FR FR7120641A patent/FR2096037A5/fr not_active Expired
  • 1971-06-09 BE BE768322A patent/BE768322A/xx unknown
  • 1971-06-09 DE DE19712128759 patent/DE2128759A1/de active Pending
  • 1971-06-11 NL NL7108020A patent/NL7108020A/xx unknown

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