US3494789A - Photoconductive insulating material - Google Patents

Photoconductive insulating material Download PDF

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Publication number
US3494789A
US3494789A US554840A US3494789DA US3494789A US 3494789 A US3494789 A US 3494789A US 554840 A US554840 A US 554840A US 3494789D A US3494789D A US 3494789DA US 3494789 A US3494789 A US 3494789A
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Prior art keywords
photosensitive
photoconductive
powder
photoconductive insulating
insulating material
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US554840A
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English (en)
Inventor
Katsuo Makino
Iwao Sawato
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Fujifilm Holdings Corp
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Fuji Photo Film Co Ltd
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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
    • G03G5/087—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being inorganic and being incorporated in an organic bonding material

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  • the invention is directed to a photoconductive insulating material mainly used for electrophotography.
  • Said material comprises an electrically insulating binder material having a bulk resistivity of at least ohm-cm. at room temperature, and dispersed therein finely divided particles of the reaction product of cadmium carbonate and sulfur.
  • This invention relates to a photoconductive insulating material mainly used for electrophotogrpahy.
  • Such substances for example, as sulfur, selenium, and further compounds, such as oxides, sulfides, or selenides of zinc, cadmium, mercury, bismuth, lead, etc., and also titanium oxide are known.
  • Those substances are coated stratiformly on a plate, e.g., a metal plate, paper and so on.
  • the photoconductive insulating layer could be formed by dispersing these substances in the electric insulating resin binder.
  • selenium and zinc oxide are the best known and are practically used up to now.
  • the procedure to get an electrophotographic image on the electrophotographic sensitive body having a photoconductive insulating layer employing these substances first begins with the placing of an electrostatic charge on the surface of the photoconductive insulating layer to bestow photosensitivity by corona discharge for instance, in the dark. Next follows exposure by usual photorgaphic procedure. The latent image got by exposure is then developed with charged toning powder into the visible image. The toning powder image is fixed intact upon the layer of photoconductive insulating material or alternatively transferred upon other suitable supporting body and fixed. When the image is transferred, the residual toning powder on the layer of the photoconductive insulating material is swept away so that the said layer could be reused.
  • Selenium now Widely known and employed for practical use, is employed as a reusable photosensitive material coated on a metal plate, particularly on an aluminum plate, in the form of vitreous selenium layer.
  • the photosensitivity of it corresponds to ASA 2-10 which is considered to be the highest among those electrophotographic sensitive materials up to now.
  • the vitreous selenium is exceedingly well fitted for practical reuse because it has a very hard, mirror surface.
  • another practically utilized zinc oxide is used to form an electrographic sensitive body, called a photosensitive paper, by a process of dispersing it in an electric insulating resin binder and coating it on a sheet of paper 3,494,789 Patented Feb. 10, 1970 which is then dried.
  • This photosensitive paper having a photosensitivity in the range of about ASA 0.01-0.2, looks almost white so that an image could be formed and fixed directly upon the paper.
  • the said dispersed layer of zinc oxide could be also coated on a metal body, but it has not been used as a reusable photosensitive material for the reasons that it is far inferior to a photosensitive material employing selenium in such properties as lower film hardness and lower photosensitivity. Moreover, once exposed to light, the properties of the layer are impaired to a state unfit for continuous and repeated use. Other than selenium and Zinc oxide, only the properties of titanium oxide in practical use have been reported.
  • the direct image producing process comprising fixing the toning powder directly on the layer of photoconductive insulating material.
  • Another method may be designated the indirect image producing process. This comprises either fixing the transferred image on other transferring material which is formed on the layer of photoconductive insulating material or developing and fixing on the transferred material, after transferring of the latent electrostatic image, formed on the layer of the photoconductive insulating material, to other transferring material, i.e., the method to form an image on other material with an aid of the layer of photoconductive insulating material.
  • the layer of photoconductive insulating material imposes limitations in regard to the whiteness which is possible in copying the documents and the pliability of the coated sheet, for example, a paper.
  • the whiteness of photoconductive insulating layer does no cause any problem in getting a copy image consisting of black and white, but it becomes a fatal defect in copying color printed matter. It could be understood that the limitation of employing a supporting body of paper and the like prevents the material from fully exhibiting the special properties of a photoconductive insulating layer.
  • vitreous selenium As an electrophotographic sensitive material for continuous and repeated use.
  • the said material has excellent properties such as photosensitivity, film hardness and pre-exposure effect, as the photoconductive insulating layer.
  • some defects for example, the extreme difificulty in producing it, exist.
  • it is formed by depositing on a plate by vacuum deposition as a film of uniform vitreous selenium, and the necessity of a large sized vacuum evaporating apparatus for manufacturing it has become the cause of lowering production efficiency.
  • controlling additive elements added for improving the properties, such as photosensitivity becomes extremely difiicult by vacuum evaporating process.
  • vitreous selenium being a sort of solid phase of selenium in a super-cooled state, tends to crystallize by heat, the moisture in air or contamination with other substances, which bring undesirable results to its properites with accelerated impairment of qualities and shortened life when used in high temperature and high humidity.
  • some trials for promoting photosensitivity by adding certain dyes have been done, but those dyes are thermally weak, and the deterioration of properties by corona discharge and light radiation in continuous and repeated use is relatively rapid.
  • the material still is inferior to selenium sensitive material at the point of short life for useful time.
  • a layer of photoconductive insulating material has been developed and prepared by dispersing a photoconductive powder of cadmium sulfide whose mean particle size is about 0.2 in a solvent solution of a thermosetting resin having volume specific resistivity at least more than 10" ohm-cm, and coating it on a suitable plate, i.e., a metal plate, and promoting the hardening by baking while the heat treatment of the powder of cadmium sulfide and the resin system is done simultaneously.
  • the photoconductive cadmium sulfide employed in this desirably does not contain any impurity and is a stoichiometrically perfect compound.
  • An object of this invention is to overcome these disadvantages inherent in vitreous selenium, zinc oxide and cadmium sulfide, etc., and further lies in proposing an improved photoconductive insulating material which has a photosensitivity equal to or more than that of vitreous selenium, and which is thermally stable, having a sufficiently low pre-exposure effect, being endurable in repeated and continuous use, as well as proposing a simple method of producing the said material.
  • FIG. 1 shows the decay of the electrostatic potential of the surface of the electrophotographic sensitive materials of an example according to this invention and the prior art known hitherto;
  • FIG. 2 shows the relation between the initial surface potential and the exposure time for half decay, of the electrophotographic materials prepared according to one example of the invention and made of pure cadmium sulfide;
  • FIG. 3 illustrates the comparison of the variation of the surface potential immediately after charging (LP) in the case of employing continuously and repeatedly with the period of 10 sec. for one cycle, and that of the surface potential after exposure (R.P.) in repeated and continuous use, each for the photosensitive materials made of pure cadmium sulfide and of the example according to the invention; and
  • FIG. 4 shows the diagrammatic record of the X-ray diffraction analysis for the photoconductive powder used in an example of the invention, compared with that of pure cadmium sulfide.
  • an electrophotographic photosensitive body which is prepared by coating a photoconductive insulating material onto a supporting member, is charged in one polarity by a corona discharger and it is not used in another polarity.
  • the charging polarity is decided by the potential acceptance and the light sensitivity of the photosensitive member.
  • Vitreous selenium for example, is charged with positive ions and zinc oxide and cadmium sulfide with negative ions.
  • tellurium to vitreous selenium some new electrophotographic sensitive material is considered whose photosensitivity is almost equal when charged either positive and negative and whose charge ability is almost equal in positive and negative charge by inserting an inter-layer between the supporting body and photo-conductive insulating layer.
  • an advantage lies in being able to get the directly developed image (negative negative or positivepositive) and the reversably developed image (negative psitive or positivenegative) by only changing the polarity of the corona scharge.
  • a further object of this invention exists in offering a photoconductive insulated material fitted for the use in either the positive and the negative charge.
  • a cylindrical electrographic sensitive body which is coated with photoconductive insulating substance on its surface, is forced to rotate at constant speed in continuously and repeated use. It completes one cycle of the process by steps consisting of (1) charging, (2) exposing, (3) developing, (4) transferring, (5) cleaning off, (6) pre-exposing.
  • the step of (6) pre-exposing is for the sake of accomplishing the preparation for proceeding the operation into the next cycle by discharging all the residual surface charges.
  • the photosensitive body rotates a round in about 11 seconds. That is, within the period of 11 seconds, the process is performed repeatedly. It takes 10.4 secs.
  • the electrophotographic sensitive material must at least be able to reach the state in 0.6 sec. where nothing of the influence of the exposing effect is left.
  • the photosensitive material prepared by dispersing the powder of pure cadmium sulfide in a thermosetting resin and coating it on a metal plate which then is hardened by a heat treatment could not be employed satisfactorily in Xerox Processor Model 914. However, electric charge ability in the dark and the photosensitivity is sufficiently high.
  • the decaying time constant of photocurrent is approximately 2 sec., by half value time, so that though the dark resistance has remained in a lower state at the time of charging (1), after pre-exposure (6) of the pre vious cycle, and the chargeability is lowered, the surface charge of the place that corresponds to the shadow part of the exposure decreases rapidly during a period of 34 see. until the end of developing process, after charging process. Thus, electrostatic contrast is lowered respectively and consequently.
  • a disadvantage is the lowering of the contrast of the copied image.
  • FIG. 3 should be employed where the abscissa represents the number of continuous repetitions in the case of using in the course of the aforementioned process with the period of 10 sec., and the ordinate represents the degree of surface potential immediately after the charging (l) designated LR,
  • the said LP decreases rapidly after only a few times of use.
  • a material comprising cadmium sulfide incorporated with cadmium carbonate has a relatively rapid response time to photocurrent and an electrophotosensitive member produced by dispersing it in an insulating resin and coating on a metal supporting body has sufficient potential acceptance in the dark as well as high photosensitivity.
  • photosensitive material could be charged either in positive or in negative polarity, as well as having sufi'icient photosensitivity.
  • the powder consisting of cadmium sulfide and cadmium carbonate can be produced by firing cadmium carbonate with sulfur powder at the temperature range between 400- 600 C.
  • EXAMPLE 1 6 found that the potential acceptance increases in proportion to the film thickness, but the photosensitivity decreases as the film thickness increases.
  • FIG. 1 also shows the desurface potential i di l aft r h h i Proscrease of surface Potential of an p 'aphi ess (1) (LR) decreases rapidly early in several repeated member employing vitr u Selenium, member #1001 uses in the case when photosensitive member #A-13 comprising CdS and a binder, and the member #BZC made of pure cadmium sulfide is used, but in the case comprising a dye-sensitized ZnO and a binder.
  • LR desurface potential
  • Each 40 of employing #A25, according to an example of this ordinate of FIG. 1 is plotted logarithmically with a value i vention, such variation can be scarcely observed in reof the surface potential for each sensitive member.
  • the surface potential after exposure (R.P.) a s a is Plotted wtih a time by Sec unit, Passed after at the time point corresponding to the finished time of charging. developing is shown only for #A13, but for #A-25, it
  • Selenium is a most excellent material at the surface poi too small to be illustrated and it hardly varies during tential property in the dark and p otosensitivity but, it repeated use.
  • the values at the first time and the thirtieth is said so only when selenium is charged with positive and time of repeated use are all as follows, as shown in when charged negative, its property is very undesirable, Table 1.
  • corona Photosensitive discharge 1st 30th 1st 30th member kv. time, volts time,volts time,volts time,vo ts 93? 553 it; it 53 --i 9:? as $18 2 2 though not shown in FIG. 1.
  • CdS and ZnO exhibit ex- FIG. 3 and Table 1 show that in a photosensitive memcellent properties in negative charge.
  • the response the photosensitive member #1445, an eXamPIe of h time of the photocurrent and, particularly, the decaying invention, eXhihits exerting Properties either in Poslth/e time constant of the photocurrent have been improved to and negative charg
  • the measurements above cases be shorter than that of aphotosensitive member employing e peffermefl under the following condltlons: the CdS, and to a degree where no inconvenience exists in FPPhed potential. for th chargmg corona'dlsczharge practical use with such a repeating period as is encountered 1s 7.0 kv.
  • the intensity of the illumination on the surface of a sample was about 15 lux.
  • Example 1 As employed in Example 1 is used.
  • an insulating binder there is used a mixture of a silicone resin KR-211 (available from Shinetsu Chemical Industries Co. Ltd.), a room temperature driable resin binder, and an epoxyester (avail able from Nippon Oil and Fats Co. Ltd.).
  • the photoconductive powder and the binder mixed at a ratio shown in Table 2, were mixed and kneaded in a porcelain ballmill to disperse the powder, and thus photosensitive paints were produced.
  • the said photosensitive paints were coated on an aluminum sheet of 0.1 mm. thickness by a spraymethod, and were dried at room temperature. The amount of coated film after drying weighed 3.54.0 mg./cm.
  • photosensitive insulating material comprising a photoeonductive powder and a resin binder in which many other kinds of thermoplastic resins and thermoset-ting resins are widely usable.
  • a glass material could be employed.
  • the photosensitivity is shown as a value of time which is required for half decay of the surface potential when the said body is illuminated at 15 lux of light intensity of 2.660" K. tungsten lamp, after being charged at -7.0 kv. 'by a corona discharge.
  • a method for producing a photoeonductive insulating material comprising firing a mixture of cadmium carbonate and sulfur to produce a material represented by the formula CdSnCdCO where n is greater than 0 and has a value up to about 4,
  • a photoconductive insulating material comprising an electrically insulating binder material having a bulk resistivity of at least 10 ohms-cm. at room temperature, and finely divided particles of a photoeonductive material dispersed in said binder material, said photoeonductive material being represented by the formula CdC-n(CdCO in which n represents O n54.

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  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Photoreceptors In Electrophotography (AREA)
  • Glass Compositions (AREA)
US554840A 1965-06-02 1966-06-02 Photoconductive insulating material Expired - Lifetime US3494789A (en)

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US (1) US3494789A (de)
DE (1) DE1522598C3 (de)
FR (1) FR1564467A (de)
GB (1) GB1120091A (de)
NL (1) NL6607651A (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4063811A (en) * 1975-04-11 1977-12-20 Minolta Camera Kabushiki Kaisha Electrophotographic copier
US4142889A (en) * 1976-12-27 1979-03-06 Minolta Camera Kabushiki Kaisha Electrophotographic process using a cadmium sulfide photoconductor having hystereses character
US4175955A (en) * 1976-09-24 1979-11-27 Minolta Camera Kabushiki Kaisha Electrophotographic processes using a pre-exposure
US4252883A (en) * 1972-04-28 1981-02-24 Canon Kabushiki Kaisha Process for producing electrophotographic photosensitive member
US4275135A (en) * 1978-03-08 1981-06-23 Minolta Camera Kabushiki Kaisha Electrophotographic CdS.nCdCO3 containing manganese stearate

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS602658B2 (ja) * 1976-08-19 1985-01-23 バリアン・アソシエイツ・インコ−ポレイテツド 汚染物のない光導電絶縁材

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2959481A (en) * 1958-12-18 1960-11-08 Bruning Charles Co Inc Electrophotographic recording member and process of producing same
US3234017A (en) * 1959-11-05 1966-02-08 Agfa Ag Process for the production of developed electrophotographic images including application of a breakdown potential to discrete small areas of a photoconductor
US3251714A (en) * 1961-07-13 1966-05-17 Philips Corp Method of preparing a cadmium oxide photoconductor

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2959481A (en) * 1958-12-18 1960-11-08 Bruning Charles Co Inc Electrophotographic recording member and process of producing same
US3234017A (en) * 1959-11-05 1966-02-08 Agfa Ag Process for the production of developed electrophotographic images including application of a breakdown potential to discrete small areas of a photoconductor
US3251714A (en) * 1961-07-13 1966-05-17 Philips Corp Method of preparing a cadmium oxide photoconductor

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4252883A (en) * 1972-04-28 1981-02-24 Canon Kabushiki Kaisha Process for producing electrophotographic photosensitive member
US4063811A (en) * 1975-04-11 1977-12-20 Minolta Camera Kabushiki Kaisha Electrophotographic copier
US4175955A (en) * 1976-09-24 1979-11-27 Minolta Camera Kabushiki Kaisha Electrophotographic processes using a pre-exposure
US4142889A (en) * 1976-12-27 1979-03-06 Minolta Camera Kabushiki Kaisha Electrophotographic process using a cadmium sulfide photoconductor having hystereses character
US4275135A (en) * 1978-03-08 1981-06-23 Minolta Camera Kabushiki Kaisha Electrophotographic CdS.nCdCO3 containing manganese stearate

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DE1522598B2 (de) 1974-01-31
GB1120091A (en) 1968-07-17
FR1564467A (de) 1969-04-25
DE1522598A1 (de) 1969-09-18
DE1522598C3 (de) 1974-08-29
NL6607651A (de) 1966-12-05

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