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, 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
  • G03G5/05—Organic bonding materials; Methods for coating a substrate with a photoconductive layer; Inert supplements for use in photoconductive layers
  • G03G5/0528—Macromolecular bonding materials
  • G03G5/0532—Macromolecular bonding materials obtained by reactions only involving carbon-to-carbon unsatured bonds
  • G03G5/0542—Polyvinylalcohol, polyallylalcohol; Derivatives thereof, e.g. polyvinylesters, polyvinylethers, polyvinylamines
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G13/00—Electrographic processes using a charge pattern
  • G03G13/02—Sensitising, i.e. laying-down a uniform charge
  • G03G13/025—Sensitising, i.e. laying-down a uniform charge by contact, friction or induction
• • 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
  • G03G5/05—Organic bonding materials; Methods for coating a substrate with a photoconductive layer; Inert supplements for use in photoconductive layers
  • G03G5/0528—Macromolecular bonding materials
  • G03G5/0532—Macromolecular bonding materials obtained by reactions only involving carbon-to-carbon unsatured bonds
  • G03G5/0539—Halogenated polymers
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S430/00—Radiation imagery chemistry: process, composition, or product thereof
  • Y10S430/001—Electric or magnetic imagery, e.g., xerography, electrography, magnetography, etc. Process, composition, or product
  • Y10S430/102—Electrically charging radiation-conductive surface

Definitions

• ABSTRACT A method for electro'statically charging the surface of a photoconductive insulative layer which is formed by dispersing an inorganic n-type photoconductive powder in a binder, which is primarily a vinyl chloride-vinyl acetate ELECTROPHOTOGHIC PROCESS UTILIZING FMQTION CHGING BACKGROUND OF Tl-IE INVENTION 1 Field of the Invention
• the present invention relates to an electrophotographic method for charging a photoconductive insulative layer utilizing friction.
• a corona discharge is commonly applied, and a charging method utilizing a simple mechanical device is also available, i.e., the surface of a recording layer is rubbed with an appropriate material to achieve triboelectric charging.
• a charging method utilizing a simple mechanical device is also available, i.e., the surface of a recording layer is rubbed with an appropriate material to achieve triboelectric charging.
• Such a method is described in US. Pat. No. 2,297,691.
• a photoconductive insulative layer comprising an ntype n-type photoconductive powder, such as ZnO, which is dispersed in a vinyl chloride vinyl acetate copolymer'with a composition ratio of vinyl chloride to vinyl acetate of from 95:5 to 55:45 parts by weight, is rubbed with a friction material, such as a cotton velvet cloth, to negatively charge the layer.
• a friction material such as a cotton velvet cloth
• the invention utilizes the differences in the triboelectric properties of the materials involved.
• the friction charging is performed while the surface of the insulative layer is maintained in contact with a highly insulative liquid, such as an aliphatic hydrocarbon.
• the invention thus has as its object the provision of a process which will yield an improved image of extremely high quality when developedDESCRIPTlON OF THE PREFERRED EMBODIMENTS
• a light sensitive layer comprising an n-type photoconductive semiconductor, such as photoconductive zinc oxide, titanium dioxide, ect., dispersed in a binder comprising a vinyl chloride-vinyl acetate copolymer as its main constituent, is rubbed with a friction material which is positive in the triboelectric series with respect to said layer, a copy which is superior in quality to other combinations can be obtained.
• Suitable prior art insulative binders for use with zinc oxide are poiysiloxane resins alkyd resins, epoxy esters, polyacrylic esters, polymethacrylic esters, styrene containing polymers, and the like. With respect to triboelectric characteristics, all of these resins are relatively positive, and powdery zinc oxide is extremely positive. Extremely positive "as used above, means that using ethylcellulose (ethoxized percentage: 47.5- 49.0 percent) as an empirically typical positively chargeable resin, zinc oxide is very positive in comparison. Nitrocellulose can be selected as a typical negatively chargeable resin.
• An image of high density is also hard to obtain even if an insulative material is applied as a supporting material or provides a relatively thick insulative layer between a conductive supporting material and a sensitive layer, or even where (for the purpose of minimizing the effect of leakage) an image-exposure is first applied to a light sensitive layer and its surface is then rubbed with a friction material in a liquid developer comprising an insulative liquid as carrier liquid.
• the binder used may contain a small quantity of plasticizer, but such a component is liable to stain the surface of a friction material when used repeatedly, and therefore it is preferably preferable that a plasticize not be used.
• plasticizer a component which may be present
• polymers of nonmigrating characteristics are desirable, for instance, vegetable oil modified alkyd resins, epoxy ester resins, vinyl monomer modified alkyd resin, and thelike, are available.
• a composition of 60 parts by weight of vinyl chloride-vinyl acetate copolymer and 40 parts of other components may be regarded as being the upper limit of binder composition. If a liquid development is utilized, it is desirable to cure the aforesaid alkyd resins, epoxy ester resins and the like by means of curing agent prior to development so as to improve the charge decay characteristics in the liquid.
• vinyl chloride vinyl acetate copolymer one containing more than 5 percent and less than 45 percent (by weight) vinyl acetate is suitable. It is difficult to dissolve polyvinyl chloride homopolymer in many solvents, while a content of more than 45 percent vinyl acetate lowers the insulating properties and the advantageous friction charge characteristic of polyvinyl chloride.
• a supporting material generally one possessing good conductivity may be used, but an insulative supporting material can be utilized when the friction step occurs after exposure.
• n-type photoconductive materials useful in the present invention there are titanium dioxide, zinc oxide, cadmium sulfide, cadmium sulfide-cadmium carbonate mixtures, cadmium sulfide-zinc sulfide mialed crystals, and the like. Mixtures of these substances may also be used.
• friction charging materials for the light sensitive material the most positive in comparison to a photoconductive layer in the triboelectric series are preferred
• proper mechanical properties are preferable. For instance, cotton velvet cloth, rayon, wool, tannedleathcr, nylon cloth, polyurethane sponge, and the like are especially desirable.
• an image with high resolution can be obtained by means of a liquid development, but this type of developing process is liable to be accompanied by fog in the image element background.
• this fog the following is a specially desirable modification of the present invention. Specifically, the friction generated between the friction material and the light sensitive layer is caused to take place under an insulative liquid. This process may be carried out either prior or subsequent to image exposure. If this method is followed, the fog density will be remarkably reduced.
• the mechanism of this aspect of the invention can be explained as of follows: when a thin layer of insulative liquid is formed on the surface of the light sensitive layer, the adhesion of toners to the surface of the light sensitive layer due to forces other than electrostatic forces (i.e., adsorptive attraction, trapping" into surface irregularities, etc.) in the subsequent developing process will be remarkably reduced.
• the charge acceptance of the light sensitive layer in the insulative liquid is higher than the carrier liquid of the developer, the lifetime" of a latent image will be extended, and the image 'density will be increased due to the presence of such a thin liquid layer.
• the liquid initially applied is a purified, highly insulative nonpolar liquid, and since the developer carried liquid contains resin and other components, the above requirement is satisfied.
• the liquid which is applied at the time of the generation of the friction should be such one that can be mixed with a developer which is applied subsequently and which will not attack a light sensitive layer.
• Typical examples are aliphatic hydrocarbons, alicyclic hydrocarbons and fluorinated hydrocarbons.
• the present invention makes an extremely simple electrography possible.
• the process may be practical in a compact copying machine and therefore it has a high value from an industrial viewpoint.
• the process of this invention (herein friction charging is employed) is more profitably used in an electrophotographic process in which the photoconductive layer is charged after the image-exposure, than in the process wherein a corona discharge is employed.
• This is due to the fact that when the photoconductive layer is image-exposed prior to charging and is then charged by a corona discharge utilizing a photoconductive after effect, sharp images will not usually be obtained.
• This result may be explained as follows: at the boundary of an exposed and an unexposed area, the conductivity of the former remains high, while the latter is low, so that when both of these ares areas are subjected to a corona discharge, the charge is barely accumulated in the former area, while the potential of the latter area absorbs the charge rapidly.
• the corona discharge is continued, this will cause the preferential deposition of corona-produced ions onto the exposed area, which will be repelled by the adjacent charged area which has the same polarity as the ions. Accordingly, the exposed areas which are adjacent the unexposed areas receive a higher concentration of con corona-produced ions and recover from light fatigue more rapidly than other exposed areas. Since such a phenomenon results immediately after the beginning of the charging by the corona, an image with an indefinite edge results.
• EXAMPLE 1 A light sensitive layer comprising 100 parts of photoconductive ZnO powder and 25 parts of vinyl chloride-vinyl acetate copolymer (containing 35 percent by weight of vinyl acetate) was coated to a thickness of 5 [LOB a sheet of paper which has had been rendered conductive. After the dark adaptation of the layer, an image exposure was applied by means of a contact exposure. The light sensitive paper was then clipped into a liquid developer comprising a paste of a kneaded mixture of phthalocyanine blue pigment and rosin-modified phenol-formaldehyde resin dispersed in cyclohexane. The surface of the light sensitive layer was then lightly rubbed several times with a polyurethane sponge.
• the pigment maintained a positive charge in the liquid, while the light sensitive layer which was rubbed with polyurethane was negatively charged. Thus, an attractive" development could be achieved.
• the resultant image was quite sharp, and showed no indistinct outline along the circumference of image as would be observed in an ordinary image involving the Kalmann method of electrophotography.
• the image density was also excellent.
• EXAMPLE 2 A light sensitive layer consisting of 50 parts of photocom ductive titanium dioxide, 50 parts of photoconductive zinc oxide, 27.5 parts of a vinyl chloride-vinyl acetate copolymer (the same type as used in example I) 2.5 parts of the epoxy ester of dehydrated castor oil fatty acid (oil length 40 percent and 10 parts per 1000 parts of rosebengal, was coated to a thickness of 5 p. on a sheet of the same type base paper as used in example 1.
• the surface of the light sensitive layer was rubbed several times with a piece of cotton velvet cloth and an image exposure was applied by the projection method.
• a positive line image was chosen as the original.
• the electrostatic latent image was developed by a cascade developer containing positivelycharged toners, and a positive reproduction of the original was obtained.
• cotton velvet cloth impregnated with purified kerosene was used to rub the surface of the light sensitive layer in the same manner as described above. After subsequent exposure and development, a homogeneous image with a low fog density was obtained.
• An electrophotographic method for electrostatically charging the surface of a photoconductive insulative layer formed by dispersing an inorganic n-type photoconductive powder in a binder comprising as its main constituent a vinyl chloride-vinyl acetate copolymer with a composition ratio of vinyl chloride to vinyl acetate ranging from about :5 to about 55:45 parts by weight which comprises rubbing said insulative layer with a friction material so as to produce a negative charge on the surface of said insulative layer by friction while maintaining a highly insulative liquid on the surface of said insulative layer so that the generated friction is caused to take place within the insulative liquid.
• n-type photoconductive material is selected from the group consisting of titanium dioxide, zinc oxide, cadmium sulfide, a mixture of cadmium sulfide and cadmium carbonate, and a mixed crystal of cadmium sulfide and zinc sulfide.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Photoreceptors In Electrophotography (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=12911420

Family Applications (1)

Country Status (6)

Cited By (5)

Citations (5)

• 1968
  • 1968-08-10 CA CA027071A patent/CA925561A/en not_active Expired
  • 1968-08-12 BE BE719365D patent/BE719365A/xx unknown
  • 1968-08-14 US US752472A patent/US3569803A/en not_active Expired - Lifetime
  • 1968-08-14 FR FR1577647D patent/FR1577647A/fr not_active Expired
  • 1968-08-15 GB GB1232470D patent/GB1232470A/en not_active Expired
  • 1968-08-16 DE DE19681797099 patent/DE1797099A1/de active Pending

Patent Citations (5)

Also Published As

Similar Documents