US3743609A - Process for producing photoconductive materials - Google Patents

Process for producing photoconductive materials Download PDF

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Publication number
US3743609A
US3743609A US00211726A US3743609DA US3743609A US 3743609 A US3743609 A US 3743609A US 00211726 A US00211726 A US 00211726A US 3743609D A US3743609D A US 3743609DA US 3743609 A US3743609 A US 3743609A
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United States
Prior art keywords
photoconductive
powder
dispersant
cadmium
flux
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Expired - Lifetime
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US00211726A
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English (en)
Inventor
M Hirata
N Tarumi
M Sato
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Konica Minolta Inc
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Konica Minolta Inc
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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
    • G03G5/08—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being inorganic

Definitions

  • This invention relates to a process for producing photoconductive fine powders of cadmium sulfide, cadmium selenide, cadmium sulfoselenide, etc.
  • photoconductive powders have been used in the form of resin-bound layers, sintered mass or resin-coated dusts, for a device for changing signals of light or radiation into electric signals which are useful for electrophotography, e.g. image converters, image intensifiers, photocells, etc.
  • a pure cadmium sulfide powder is mixed with an acceptor-forming activator such as copper or silver, a donor-forming coactivator such as halide, and a flux such as cadmium chloride, sodium chloride or zinc chloride, and then the resulting mixture is fired at a temperature above the melting point of the flux to carry out the atomic valence control, whereby a photoconductive powder having various characteristics can be obtained.
  • an acceptor-forming activator such as copper or silver
  • a donor-forming coactivator such as halide
  • a flux such as cadmium chloride, sodium chloride or zinc chloride
  • the degree of particle size of such photoconductive powder frequently brings about a great problem.
  • the degree of particle size influences the uniformity of the photosensitive layer. That is, if the particle size is large, the surface smoothness of the photosensitive layer is injured.
  • the dispersion should be made high in viscosity in order to lower the sedimentation velocity of the particles, with the result that there are brought about such drawbacks that not only the coating operation is extremely difiicult but also bubbles become entrained in the resulting photosensitive layer.
  • a fine photoconductive powder When applied to an electrophotographic photosensitive member, a fine photoconductive powder gives such advantages that the photosensitive member is greatly decreased in fog, increased in contact portions of individual particles, and increased in electric resistance. Further, the uniformity of the photosensitive layer due to incor- 3,743,609 Patented July 3, 1973 poration of fine photoconductive powder has such merits that the damage of photoelectric means due to local eddy currents can be prevented and the distance between electrodes can be made small.
  • the prior art photoconductive powder is further pulverized.
  • the firing is eflfected by use of no or smaller amount of flux to inhibit the growth of crystals.
  • the firing is effected at below the melting point of the flux to inhibit the growth of crystals.
  • process (1) however, the resulting crystals are far lower in photosensitivity than the prior art photoconductive crystals. Further, according to processes (2) and (3), sufiicient activation cannot be accomplished to make optional valence control impossible, with the result that no high sensitivity material can be obtained.
  • a process for producing a high sensitivity fine photoconductive powder having a particle size of less than 5 microns by mixing a cadmium sulfide powder with suitable amounts of an activator, a coactivator and pure water, and treating the resulting mixture at elevated temperature and pressure to recrystallize the cadmium sulfide.
  • the present invention is a process for producing a fine photoconductive powder by firing a mixture comprising a powder of cadmium sulfide, cadmium selenide, cadmium sulfoselenide or the like (starting material) and suitable amounts of an activator (a halide, sulfate or nitrate of gold, silver or copper), a coactivator (a halide such as ammonium chloride or the like, or a compound of a trivalent metal such as aluminum, gallium, indium or the like), a flux (a halide such as cadmium chloride, zinc chloride, sodium chloride, potassium chloride or the like), and a dispersant (sodium iodide, potassium iodide, sodium bromide, potassium bromide, sodium chloride, potassium chloride, sodium sulfate, calcium carbonate, sodium carbonate, calcium oxide or the like), whereby the degree of size of the growing crystals is controlled by the starting powder.
  • the activator used herein is a chemical which forms the acceptor level in the crystals of the starting cadmium sulfide or the like.
  • the coactivator is a chemical which forms the donor level in the crystals of the starting cadmium sulfide or the like. Both the activator and the coactivator are to provide desired properties of the photoconductor.
  • the flux is a chemical which has such property that in the firing step it melts at the firing temperature to fuse the starting powder. It should be understood that although the functions of the activator, coactivator and flux have been mentioned as above, sometimes a single chemical can perform two or three of the functions.
  • the dispersant is a chemical which has such property that in the firing step, it neither melts at the firing temperature nor fuses the starting powder.
  • the flux and the dispersant are distinguished from each other depending on the firing temperature. That is, depending on the firing temperature, there are the case where a substance is used as the flux and the case where the said substance is used as the dispersant.
  • a substance which has a melting point of 800 C. is used as the flux when the firing temperature is more than 800 C., but may be used as the dispersant when the firing temperature is too low to melt the sodium chloride.
  • the dispersant used in the present invention has such property as mentioned above.
  • One or two or more of such compounds may be used.
  • the dispersant serves to divide the activated starting material into suitable fine units to inhibit the fusion and agglomeration of the starting particles.
  • the particle size of the resulting photoconductive powder is affected by the mixing ratio of the dispersant to the starting material and by the particle size of the dispersant.
  • the particle size of the resulting photoconductive powder can suitably be controlled. Ordinarily, the dispersant is used in excess of the starting material.
  • the dispersant a substance having such properties that it is high in purity, has no chemical interaction with the starting photoconductive powder, is higher in melting point than the flux used, does not melt at the firing temperature, can disperse the photoconductive powder, and is Water-soluble.
  • the flux sodium chloride, potassium chloride, sodium bromide, potassium bromide, sodium iodide, potassium iodide, cadmium sulfate, zinc sulfate, sodium sulfate or potassium sulfate is preferable as the dispersant for the reasons that said compound is higher in melting point and lower in solubility in alcohols than cadmium chloride and hence can uniformly be dispersed by use of alcohol, and that it is water-soluble and hence can easily be separated, after firing, from the photoconductive powder by water-washing.
  • the firing temperature in the present invention may be the firing temperature adopted in the known valence control method, and should suitably be selected in consideration of the kind of the starting material and the desired characteristics of the resulting photoconductive material.
  • EXAMPLE 1 A mixture comprising 175 g. of high purity cadmium sulfide of 0.5 to 1 micron in particle size, 50 g. of cadmium chloride as a flux, 6.4 g. of ammonium chloride as a coactivator, 15 cc. of an aqueous solution of mole/ cc. of copper chloride as an activator and 140 cc. of pure water was pulverized for 6 hours in an agate-made ball mill. Thereafter, the mixture was transferred to an evaporating dish and dried at 140 C. for about hours. To the dried mixture were added 600 g. of sodium chloride as a dispersant and 400 cc. of absolute alcohol.
  • the resulting mixture was pulverized for 6 hours in an agate-made ball mill. Thereafter, the mixture was placed in an evapo rating dish and then dried at 120 C. for about 10 hours. The dried mixture was ground to the size of millet grains, and the resulting grains were charged into a quartz tube and then fired by use of an electric furnace in an air at mosphere at 590 C. for 15 minutes. After cooling to room temperature, the resulting brown fired substance was dipped in pure water, water-washed by decantation and then dried. The water-washing was terminated after repeating the decantation about 20 times to confirm that no chlorine ion had been detected in the waste liquid.
  • the fired substance after drying was a brown crystalline powder of about 1 micron in particle size and showed photoconductivity.
  • the particle size distribution of the thus obtained cadmium sulfide was measured by use of an optical microscope, and the percentage of the number of particles varying in size is shown in Table 1.
  • absolute alcohol is used for efiective dispersion, but it is not always required to be used and may be replaced by another organic solvent. However, it is effective to use a solvent which is low in solubility for the dispersant.
  • Example 1 was repeated, except that an aqueous solution of 10- mole/ cc. of AgNO was used as the activator, KI as the flux and CdSO as the dispersant, and the firing temperature was 700 C. The results obtained were as set forth in Table 1.
  • Example 1 was repeated, except that cadium selenide was used in place of the starting cadmium sulfide, and the amounts of individual compounds used were varied as shown in Table 1. The results obtained were as set forth in Table 1.
  • Example 1 was repeated, except that the starting cadmium sulfide was replaced by cadmium sulfoselenide and the amounts of the individual components used were varied as shown in Table 1. The results obtained were as set forth in Table 1.
  • the voltage at which the mium sulfide powder obtained in each of the above-men- 5 cells had been damaged was 600 to 700 volts, whereas tioned examples, there may be eifected the following treatin the case of the photoconductive powders according to ments. the present invention, said voltage was more than 2,000
  • the crystalline powder after water-washing is mixed volts. This is considered ascribable to the facts that the with 0.05 g. of cadmium chloride and 1.0 g. of ammo- 10 voltage applied had been consumed by a barrier layer nium chloride.
  • the resulting mixture is dried at 140 C. derived from resistivity contact among the particles arfor about 10 hours.
  • the dried mixture is ranged between the electrodes, and that the uniformity of charged into a quartz glass tube and fired by use of an the photosensitive layer had been increased due to the electric furnace in an air atmosphere at 590 C. for use of finer photosensitive particles. minutes.
  • the fired mixture which has been taken out of 15
  • 5 g. of the photoconductive powthe furnace after firing is in such a state that crystalline der prepared in Example 1 was subjected to sensitivityparticles, which are susbtantially in particle size with the increasing treatment, and then dispersed in a mixture particles before firing (about 1 micron), have slightly comprising 2 g. of alkyd resin and 2 g. of xylene.
  • the said soft fired mixthen dried and cured to prepare an electrophotographic ture is packed in a quartz glass tube, and fired first in a light-sensitive plate having a sensitive layer of about 70 hydrogen sulfide-nitrogen gas atmosphere at 500 C. for microns in thickness.
  • the sensitive layer of said light-sensi- 10 minutes and then in a vacuum atmosphere at 500 C. tive plate was electrically charged on the surface by use for 10 minutes.
  • the first mixture is cooled of a corona discharge electrode, to which had been applied to 100 C.
  • the produced according to the present invention is composed latent image was developed with a toner according to an of fine particles having a particle size within the range ordinary procedure and then transferred to a high quality from 1 to 5 microns, and not only the particle size dis- 30 paper, whereby a clear image free from fog was obtained.
  • tribution thereof can freely be controlled by varying the Thus, even when used as an electrophotographic lightblending amounts of the individual components (refer to sensitive layer, the photoconductive powder obtained ac- Example 2) but also the fine particles are substantially cording to the present invention gives favorable results. in the form of spheres. Accordingly, when the photocon- What we claim is: ductive powder is formed into a photosensitive layer, the 1. A process for producing a photoconductive powder charging rate of the photosensitive material can be made according to the valence control method comprising firing greater.
  • the photoconductive powder prosisting of cadmium sulfide, cadmium selenide and cadmium is not only composed mainly of a flux, and a particulate dispersant selected from the group particles having a particle size within the range from 10 consisting of sodium iodide, potassium iodide, sodium broto 30 microns but also contains particles having a peride, potassium bromide, sodium chloride, potassium chloticle size of more than 30 microns, and shows a wide parride, sodium sulfate, calcium carbonate, sodium carbonate ticle size distribution.
  • the particles are comand calcium oxide at a temperature which is below the posed of spherical, rod-shaped and L-shaped particles. melting point of the dispersant but sutlicient to melt the
  • the photoconductive powders prepared according to flux and introduce the activator and coactivator into the the aforesaid examples and comparative examples were photoconductive material, wherein the amount by weight subjected to sensitivity-increasing treatment. 5 grams of of dispersant is in excess of that of the photoconductive each of the thus treated photoconductive powders was dis material.
  • the resulting dispersion was coated on comb type electrodes (electrode distance 1 mm., length 150 mm.), 2,856,878 12/1958 BnggF et a1 252-501 X which had been prepared by the vacuum deposition of 3,238,150 3/1966 Behrmger et a1 96 1-5 X aluminum onto insulating polyester films, and then dried 3,598,760 8/1971 Nakamura et a1 961'5 X and cured. Subsequently, a voltage of 100 v.

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  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Photoreceptors In Electrophotography (AREA)
  • Light Receiving Elements (AREA)
US00211726A 1970-12-26 1971-12-23 Process for producing photoconductive materials Expired - Lifetime US3743609A (en)

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JP11905270A JPS5531633B1 (enrdf_load_stackoverflow) 1970-12-26 1970-12-26

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JP (1) JPS5531633B1 (enrdf_load_stackoverflow)
DE (1) DE2164141A1 (enrdf_load_stackoverflow)
GB (1) GB1343200A (enrdf_load_stackoverflow)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3847606A (en) * 1973-03-08 1974-11-12 Pitney Bowes Inc Protecting photoconductor surfaces
US4021237A (en) * 1974-11-14 1977-05-03 Canon Kabushiki Kaisha Process for producing cadmium sulfide for electrophotography
US4069356A (en) * 1974-08-22 1978-01-17 Westinghouse Electric Corporation Method for rapidly forming photoconductive layers for integrated circuits
US4090983A (en) * 1975-11-06 1978-05-23 Kip Corporation Photoconductive cadmium sulfide and process for producing same
US4197122A (en) * 1977-04-29 1980-04-08 Canon Kabushiki Kaisha Process for preparing raw particles of cadmium sulfide for electrophotography
US4239844A (en) * 1979-03-05 1980-12-16 Gte Products Corporation Electrophotoconductive Cd S Se materials with Cu and Cl
US4286034A (en) * 1978-10-26 1981-08-25 U.S. Philips Corporation Photoconductive structures
US4338389A (en) * 1979-10-04 1982-07-06 Canon Kabushiki Kaisha CdS-Binder member for electrophotography with Fe, Co, Ni additives
US4440735A (en) * 1981-01-28 1984-04-03 Canon Kabushiki Kaisha Process for production of photoconductive cadmium sulfide

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5013050A (enrdf_load_stackoverflow) * 1973-06-04 1975-02-10
DE3632210A1 (de) * 1985-09-25 1987-04-02 Sharp Kk Verfahren zur herstellung eines photoelektrischen umwandlungsfilms

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3847606A (en) * 1973-03-08 1974-11-12 Pitney Bowes Inc Protecting photoconductor surfaces
US4069356A (en) * 1974-08-22 1978-01-17 Westinghouse Electric Corporation Method for rapidly forming photoconductive layers for integrated circuits
US4021237A (en) * 1974-11-14 1977-05-03 Canon Kabushiki Kaisha Process for producing cadmium sulfide for electrophotography
US4090983A (en) * 1975-11-06 1978-05-23 Kip Corporation Photoconductive cadmium sulfide and process for producing same
US4197122A (en) * 1977-04-29 1980-04-08 Canon Kabushiki Kaisha Process for preparing raw particles of cadmium sulfide for electrophotography
US4286034A (en) * 1978-10-26 1981-08-25 U.S. Philips Corporation Photoconductive structures
US4239844A (en) * 1979-03-05 1980-12-16 Gte Products Corporation Electrophotoconductive Cd S Se materials with Cu and Cl
US4338389A (en) * 1979-10-04 1982-07-06 Canon Kabushiki Kaisha CdS-Binder member for electrophotography with Fe, Co, Ni additives
US4440735A (en) * 1981-01-28 1984-04-03 Canon Kabushiki Kaisha Process for production of photoconductive cadmium sulfide

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Publication number Publication date
GB1343200A (en) 1974-01-10
DE2164141A1 (de) 1972-07-13
JPS5531633B1 (enrdf_load_stackoverflow) 1980-08-19

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