US3788738A

US3788738A - Method for recording a visible image on a substrate by using an electroconductive toner

Info

Publication number: US3788738A
Application number: US00845040A
Authority: US
Inventors: S Takeuchi; H Saito
Original assignee: Dai Nippon Printing Co Ltd
Current assignee: Dai Nippon Printing Co Ltd
Priority date: 1968-08-15
Filing date: 1969-07-25
Publication date: 1974-01-29
Anticipated expiration: 1991-01-29
Also published as: DE1941241A1; DE1941241B2

Abstract

This invention relates to a method for recording a visible image by forming an electrostatic charge image or an electric field image on a photoconductive insulating layer or a dielectric layer which is disposed on a substrate or a dielectric sheet or film and connecting said electrostatic charge image or said electric field image to said visible image by contacting said electrostatic charge image or said electric field image with an electroconductive toner sprinkled on said photoconductive insulating layer or said dielectric layer or said dielectric sheet or film, thereby to form said visible image, and fixing said visible image on said photographic insulating layer or said dielectric layer or said dielectric sheet or film under heating or in the presence of a solvent vapor.

Description

Takeuchi et a1.

METHOD FOR RECORDING A VISIBLE IMAGE ON A SUBSTRATE BY USING AN ELECTROCONDUCTIVE TONER Inventors: Satoshi Takeuchi, Iruma District,

Saitama Prefecture; Hachiro Saito, Narashino, Chiba Prefecture, both of Japan Dai Nippon Insatsu Kabushiki Kaisha, Tokyo, Japan Filed: July 25, 1969 Appl. No.: 845,040

Assignee:

Foreign Application Priority Data Aug. 15, 1968 Japan 43-58340 Aug. 15, 1968 Japan 43-58341 References Cited UNITED STATES PATENTS 1/1962 Carlson 118/637 Jan. 29, 1974 3,630,608 12/1971 Sage ass/17 3,311,490 3/1967 Fauser 355/10 X 2,624,652 l/1953 Carlson 355/3 X 3,002,434 10/1961 Reuter 355/3 x 3,263,649 8/1966 Heyl 118/637 Primary Examiner-John M. Horan Attorney, Agent, or Firm-Wenderoth, Lind and Ponack 5 7] ABSTRACT This invention relates to a method for recording a visible image by forming an electrostatic charge image or an electric field image on a photoconductive insulating layer or a dielectric layer which is disposed on a substrate or a dielectric sheet or film and connecting said electrostatic charge image or said electric field image to said visible image by contacting said electrostatic charge image or said electric field image with an electroconductive toner sprinkled on said photoconductive insulating layer or said dielectric layer or said dielectric sheet or film, thereby to form said visible image, and fixing said visible image on said photographic insulating layer or said dielectric layer or said dielectric sheet or film under heating or in the presence of a solvent vapor.

4 Claims, No Drawings METHOD FOR RECORDING A VISIBLE IMAGE ON A SUBSTRATE BY USING AN ELECTROCONDUCTIVE TONER Also this invention relates to a method for recording a visible image by forming an electrostatic charge image on a photoconductive insulating layer or a dielectric layer which is disposed on a substrate or a dielectric sheet or film, and transferring said electrostatic charge image to a fresh photoconductive insulating layer or a fresh dielectric layer or a fresh dielectric sheet or film, and then converting said transferred electrostatic charge image to said visible image by contacting said electrostatic charge image with an electroconductive toner sprinkled on said fresh phoconductive insulating layer or said fresh dielectric layer or said fresh dielectric sheet or film thereby to form said visible image, and fixing said visible image on said fresh photoconductive insulating layer or said fresh dielectric layer or said fresh dielectric sheet or film under heating or in the presence of a solvent vapor.

Furthermore, this invention relates to a method for recording a visible image by transferring the visible image which is disposed on a photoconductive insulating layer or'a dielectric layer which is disposed on a substrate to a fresh photoconductive insulating layer or a fresh dielectric layer or a fresh dielectric sheet or film before said visible image is fixed to said photoconductive insulating layer or said dielectric layer, and then fixing said transferred visible image on said fresh photoconductive insulating layer or said fresh dielectric layer or said dielectric sheet or film under heating or in the presence of a solvent vapor.

This invention relates to an improvement of the electrophotography or the electrography for recording a visible image on a photoconductive insulating layer disposed on a substrate or on a dielectric layer disposed on a substrate or on a dielectric sheet or film.

In particular, this invention relates to improved methods as summarized hereinafter.

l. A method for recording a visible image by forming an electrostatic charge image by exposing a light pattern on a photoconductive insulating layer disposed on a substrate after it was sensitized by a corona discharge, and converting said electrostatic charge image to said visible image by contacting said electrostatic charge image with an electroconductive toner sprinkled on said photoconductive insulating layer.

2. A method for recording a visible image by forming an electrostatic charge image on a dielectric layer disposed on a substrate or by forming an electrostatic charge image on a dielectric film or sheet by using a suitable charged electrode and converting said electrostatic charge image to said visible image by contacting said electrostatic charge image with an electroconductive toner sprinkled on said dielectric layer or said dielectric sheet or film.

3. A method for recording a visible image by forming an electrostatic charge image on a photoconductive insulating layer or a dielectric layer which is disposed on a substrate or a dielectric sheet on film by the conventional procedures, transferring said electrostatic charge image to a fresh photoconductive insulating layer or a fresh dielectric layer or a fresh dielectric sheet or film by the conventional techniques such as TESI process, and converting said transferred electrostatic charge image to a visible image by contacting said transferred electrostatic charge image with an electroconductive toner sprinkled on said fresh photoconductive insulating layer or said fresh dielectric layer or said fresh dielectric sheet or film.

4. A method for recording a visible image by forming an electrostatic charge image on a photo conductive insulating layer or dielectric layer which is disposed on a substrate or a dielectric sheet or film by the conventional procedures, contacting said photoconductive insulating layer or said dielectric layer or said dielectric sheet of film with a fresh dielectric sheet or film in tightly or placing said photoconductive insulating layer or said dielectric layer or said dielectric sheet or film at a place slightly apart from a fresh dielectric sheet or film thereby to produce an electric field image corresponding to said electrostatic charge image and then supply an electroconductive toner on said fresh dielectric sheet or film to convert said electric field image to said visible image.

5. A method for recording a visible image by placing a dielectric sheet or film on the convex patterns disposed on a plate, forming an electric field image corresponding to said convex patterns on said dielectric sheet or film by applying an electric voltage to said plate and then converting said electric field image to said visible image by supplying an electroconductive toner on said dielectric sheet or film.

6. A method for recording a visible image by transferring the visible image which was formed on a photoconductive insulating layer or a dielectric layer which is disposed on a substrate ora dielectric sheet or film by the procedures as mentioned above to such a member as a fresh photoconductive insulating layer or a fresh dielectric layer which is disposed on a substrate or a fresh dielectric sheet or film by contacting said visible image with said fresh members to which said visible image is to be transferred in tightly in the presence of an electric field or by supplying a corona discharge to a back surfaceoof said fresh member, or by placing said visible image at the place slightly apart from said fresh member which said visible image is to be transferred in presence of electric field or by supplying a corona discharge to a back surface of said fresh member.

7. In the methods as mentioned above, it is noted that the visible image is fixed under heating or in the presence of vapor of a solvent such as a water or an organic solvent.

Heretofore, there were proposed in the art various kinds of the electrophotographic techniques which are exemplifed by xerography and electrofax and therefore the basic principles of such techniques are known in the art. The prior electrophotography is characterized by forming an electrostatic charge image on a photoconductive insulating layer disposed on substrate by using a conventional technique by exposing a light image on said photoconductive insulating layer after said layer was sensitized by a corona discharge, and then by developing said electrostatic charge image by using a developing technique in which a colored and triboelectrically charged electro-insulating powder is used as a toner. In carrying out such developing technique, it is conventional to use a relatively coarse granule, which is the so-called carrier, such as a plastic bead, an iron powder or the like in addition to the colored and triboelectrically charged electro-insulating powder as in the cascade process and a magnetic brush process. Also, a fur-brush developing process is practiced by using a hair-like carrier, and a powder-cloud process is practised in which no carrier is used.

In carrying out an electrographic process, an electrostatic charge image is formed on a dielectric sheet or film by using suitable electrodes or an electron beam and then the electrostatic charge image is developed by using the developing technique mentioned above in which the colored and triboelectrically charged electro-insulating toner is used.

In carrying out a xeroprinting process, an electrocharge is induced on an electro-insulating pattern disposed on an electroconductive material by a corona discharge and then the electro-charge is developed in the same manner as mentioned above.

It is therefore noted that the common feature of the prior known techniques reside in the use of a colored and triboelectrically charged electro-insulating toner. Such prior known techniques have a common defect, which is referred to as an edge effect, causing the degradation of the visible image formed. The edge effect results in the visible image having a non-uniform density because the electric line of force is concentrated on the outline of the electrostatic charge image and the density is increased on the outline of the visible image. The edge effect is greater enhanced if the electrostatic charge image having a broad area is developed. Therefore, when an original pattern having the broad area is copied by the prior techniques, the resultant copy is subjected to the edge effect and suffers degradation. Also it is impossible to produce a copy of originals having a continuous tone by using the prior techniques due to the presence of the edge defect. Such defect was a fatal obstacle to the development of the prior electrophotographic or electrographic technique.

In order to remove the above mentioned defects inherent to the prior electrophotographic or electrographic techniques, many investigations have been made in the field of dry and wet developing methods but they do not yield good results.

The object of this invention is to provide new methods for satisfactorily removing the edge effect so as to be able to copy the originals having a continuous tone. For achieving the object of this invention, it is characterized by the use of a colored and electroconductive powder as a toner which is contrary to the colored and electric-insulating toner used in the prior electrophotographic or electrophotographic techniques.

In the prior electrophotographic r electrographic techniques, it is also proposed to use a developing electrode for removing the edge-effect and preventing the concentration of the electric line of force on the outline marked with the electrostatic charge image. In such a case, the edge effect is reduced when an electroconductive carrier such as a metal powder, for example, an iron powder is used because such a carrier acts as an electrode for developing the electrostatic charge image. The edge effect is remarkable when an electroinsulating carrier such as a plastic bead or metal powder coated with an electro-insulating material is used.

In prior magnet brush developing process, it is sometimes observed that fine particles of ferromagnetic powders (carrier) adhered to the electrostatic charge image which was formed on the photoconductive insulating layer or dielectric layer. This is considered that because the ferromagnetic powders are charged with an electric charge contrary to the electric charge of electrostatic charge image by the electrostatic induction phenomenon, the attractive force acts between the electrostatic charge image and the ferromagnetic powder. It is considered that the attractive force between the electrostatic charge image and the ferromagnetic powders is generally not too powerful and'so large size particles of ferromagnetic powders are easily removed by the magnet, but small size particles of ferromagnetic powders are retained on the electrostatic charge image.

It is assumed that any powdered materials having good electro-conductivity can be adhered to the electrostatic charge image by using the electro-charge which is induced by the electrostatic induction phenomenon and it was found by the inventors that this is realized and also that the electrostatic charge image can be developed by such powdered materials. Namely, it was found by the inventors that when such an electroconductive powdered material (electroconductive toner) is sprinkled on the electrostatic charge image under such a condition as that if the external force can be neglected, it can be adhered to the electrostatic charge image in an amount varied depending on the amount of the electro-charge of the electrostatic charge image.

In such a case, the'photoconductive insulating layer or the dielectric sheet or film on which the electrostatic charge image is formed can be dipped in the electroconductive toner which is stored in electroconductive container or the electroconductive toner can be uniformly sprinkled on the electrostatic charge image in a large amount and so such an electroconductive toner itself does not adhere to the electrostatic and consequently a good visible image from which the edge effect I can be completely eliminated is obtained.

As is obvious from the foregoing, the electroconductive toner is used in accordance with this invention. Such an electroconductive toner is not electrically charged under normal conditions and has no ability to adhere electrically to any materials under normal conditions. As is well known when an object is placed near an electro-charged material, the object is charged with an electro-charge, which is contrary to the electrocharge of the electro-charged material, at one end near the electro-charged material and the object is simultaneously charged with an electro-charge, which is the same electro-charge as that of the electro-charged material, at the other end of the object far from the electro-charged material. This phenomenon occurs by electric-conductivity when the object is made of an electroconductive material. Also, this phenomenon caused by polarizing action when the object is made of a dielectric material. When an electroconductive object is placed near an electro-charged material and then said object is electrically grounded to the earth, said electroconductive object is charged with an electro-.

charge which is contrary to the electro-charge of the electro-charged material. When the electric circuit between the electroconductive object and the earth is cut off, the electroconductive object can retain an electrocharge which is contrary to'electro-charge of the electro-charged material. This principle is well known and it is illustrated by the mechanisms of an electrophorus and an electrostatical generator.

This invention can also be illustrated by referring to the above principle. For example, an electrostatic charge image is formed on a photoconductive insulating member such as an amorphous selenium plate or a zinc oxide-resin paper by subjecting said photoconductive insulating member to the corona discharge, exposing a light pattern on said photoconductive insulating member, sprinkling an electroconductive toner all over said member and then sweeping an excess amount of the electroconductive toner by inclining or vibrating said photoconductive insulating member or by using other procedures while the electroconductive toner is adhered to and retained on said electrostatic charge image. The adhesion and retension of the electroconductive toner on the electrostatic charge image is based on the fact that the toner is charged with an electrocharge which is contrary to the electro-charge of the electrostatic charge image after the excess amount of said toner is removed from the photoconductive insulating member.

The electroconductive toner used in this invention is selected from electroconductive water-soluble high molecular substances such as polyvinyl alcohol, polyvinyl pyrrolidone, gelatine, polyacrylic amides and the like, organic compounds such as urea, starch, sodium alginate, sugar and the like, and inorganic materials such as Fe, Cu, Al, sodium chloride and cupric sulfate. Also, certain materials having less electric-resistance can be used as the electroconductive toner. Such an electroconductive toner is used in the powdered state and the bulk conductivity of the particles of such a toner can be practically neglected because the surface electric conductivity of the particles or the easy mobility of the electro-charge induced by the electrostatic induction phenomenon is effectively utilized in accordance with this invention. Therefore, certain materials having high electric reistance can also be used in this invention when the outer surface of their particles is treated to have the electro-conductivity orto reduce the surface electric resistance of the particles.

The prior electrophotographic or electrographic developing technique is based on the phenomenon of triboelectrification. Thus, it is common sense that the toner must have triboelectric charge of polarity contrary to that of the electrostatic charge image which is formed on a photoconductive insulating or dielectric layer or a dielectric sheet or film. For instance, for positive-to'positive development, it is necessary to use a electronegatively charged toner in the xerographic process and also it is necessary to use a electropositively charged toner in the electrofax process. When the electropolarity of the toner is the same as that of electro static charge image, positive-to-negative development is accomplished but the obtained visible image is not of good quality. Thus, in the prior technique, it is necessary to control the triboelectric charge of toner used in order to obtain a good visible image; therefore it is necessary to select the material for the toner-carrier combination higher in the triboelectric series, and also it is necessary to mix the charge control agents with the toner or apply a specific treatment on the surface of a carrier. Also, the material for the toner itself must have a high electric resistance in the prior technique.

On the contrary, the electroconductive toner used in this invention is not required to be triboelectrically charged, because the negative electric charge is induced in the electroconductive toner when it comes near to or contacts with the electrostatic charge image which is electrically positive, also the positive electric charge is induced in the electroconductive toner when it comes near to or contacts the electrostatic charge image which is electrically negative. Consequently,

there is produced an electrostatic attractive force between the electrostatic charge image which is disposed on a dielectric layer or an electrophotographic layer or a dielectric sheet or film and the electroconductive toner which has an electrostatically induced charged, and therefore the toner adhered to the charge image. Thus, the positive-to-positive development is always accomplished in this invention, no matter whether the electrostatic charge image is electrically negative or positive, therefor the material for the toner used in this invention can be widely varied and easily selected independently of their triboelectric characteristics. It is most preferable to use a dipping procedure for carrying out a developing step in accordance with this invention. The dipping procedure is carried out by dipping the dielectric layer or the photoconductive insulating layer which is disposed on a substrate or the dielectric sheet or film, on which the electrostatic charge image is formed, into the electroconductive toner and then by sweeping the excess amount of said toner from said substrate or said sheet or film by vibrating or inclinating said substrate or said sheet or film. Also, the electroconductive toner can be sprinkled uniformly and continuously on the surface of said substrate or said sheet or film on which the electrostatic charge image is formed or contacted with the surface of said substrate or said sheet or film on which the electrostatic charge image is formed.

As mentioned above, the electroconductive toner is electrically adhered to the electrostatic charge image and therefore care must be taken not to rub the surface of said member by applying an unnecessarily strong mechanical force in order to produce a good visible im age. Thus, it is desired that the electroconductive toner is contacted with the electrostatic charge image under the static condition without rubbing the surface of the electrostatic charge image. In such a case, the development can not be carried out with high speed but such a developing procedure is very simple. It is, however, possible to carry out the development with high speed by moving the electroconductive toner at the same speed as that of the photoconductive insulating layer or dielectric sheet or film having the electrostatic charge image as illustrated in Examples because the electroconductive toner is in the static condition relative to' the photoconductive insulating layer or the dielectric sheet or film.

Now it is necessary to fix a visible image on the dielectric layer or the photoconductive insulating layer or the dielectric sheet or film in order to complete the improved electrophotographic or electrographic technique of this invention. In the conventional fixing steps, the electroconductive toner which consists of powdered metals or their compounds can not be used because they can not be melted under the usual heating or in the presence of a solvent vapor. It is, however, possible to use the powdered metals in this invention for fixing the visible image when such powdered metals are coated with a good electroconductive and easily fusible or a water-soluble material such as an organic substance or a high molecular substance such as sugar, a phenol resin, an alkyd resin and a polystyrene resin. Japanese Pat. Publication No. 2633/68 discloses that the saturated fatty acids can be used as the coating materials and also Japanese Pat. Publication No. 2634/68 discloses that the thermoplastic or fusible resins and the saturated fatty acids can be used as the coating materials. It is, however, noted that such saturated fatty acids and such resins are electro-insulative materials which are different from the electroconductive materials used in this invention. Also it is noted that the conventional powdered materials having high electric resistance can also be used'in this invention after they were coated with any electro-conductive material because such conventional powdered materials are fusible under heating or soluble in the presence of a solvent vapor and such powdered material can be leached out and fixed on the dielectric or photoconductive insulating layer or the dielectric sheet or film when the electroconductive material is broken during the fixing step of the visible image.

Thus, the visible image is fixed on the dielectric or photoconductive insulating layer or the dielectric sheet or film and the copy of the original is made. When the visible image is transferred to the other member by using the conventional transferring procedure, the visible image disposed on the dielectric or photoconductive insulating layer or dielectric sheet or film is put on the other member in layers tightly bonded and then the visible image is subjected to the corona discharge or rolled with an electrode .such as a roller which is supplied with an external electric voltage.

It should be noted that the electro-insulative toner used in the prior electrophotographic techniques can be tightly adhered to the electrostatic charge image by the electric force in light but that in this invention the electroconductive toner can not be tightly adhered to the electrostatic charge image in light because the electric charge of the electrostatic charge image escapes and also the electric charge induced on the electroconductive toner vanishes in light. Therefore, the transferring step of this invention can be carried out in the same manner as in the conventional transferring procedures in the dark, and the transferring step of this invention can be carried out more easily when it is carried out in the light.

Further, it is an interesting matter that when the toner is an electroconductive ferromagnetic powder, the electroconductive magnetic toner adhered to the electrostatic charge image can be transferred by the action of a magnet to the other member which is spaced apart from the member which has visible image composed of the electroconductive ferromagnetic toner, because the magnetic attractive force to electroconductive ferromagnetic toner is very powerful.

It is obvious from the foregoing that this invention can be applied to the dielectric sheet or film on which the electric field image is formed. in accordance with this invention, the visible image can be produced on a dielectric sheet or film by putting it on a member on which the electrostatic charge image is formed and by supplying the electroconductive toner on said dielectric sheet or film because the electroconductive toner is charged with the electric charged by action of the electric field which is produced through said dielectric sheet or film due to the electric charge of said electrostatic charge image which is disposed on said member and the electroconductive toner adheres to the area of surface of said electrostatic charge image. Then the dielectric sheet or film on which the visible image was produced is removed from the member which has the electrostatic charge image. In such a case the member which has the electrostatic charge image can be repeatedly used because the visible image is not produced directly on said member.

This invention is illustrated by the following Examples.

EXAMPLE 1 A paper was coated with a photoconductive insulating layer having thickness of 2 to 4 by applying a photoconductor-resin paint to said paper. The photoconductor-resin paint was prepared by mixing zinc oxide, silicone resin and rose bengal in the weight ratio of 50 l0 0.1. The photoconductive insulating layer had good photoconductivity but it can be replaced by a commercial electrofax paper. The photoconductive insulating layer was sensitized by the negative corona discharge in the dark and then the sensitized layer was ex posed to a light image having the broad area of picture to form an electrostatic charge image. 200 grams of an iron powder of**300"to"500"mesh"was coated with a fixing material which was prepared by mixing with shel lac, methyl alochol and sorbitan monolaurate in the weight ratio of 10 50 0.01, and had a melting point of C to C. The coated iron powder was sprinkled on the electrostatic charge image disposed on the paper and then the excess amount of the coated iron powder was swept from the paper by inclining said paper to develope the electrostatic charge image into a visible image having no edge effect. The visible image was good but it was damaged when it was placed in the light and rubbed. Therefore, the visible image was fixed under heating at a temperature ,of 100 to 150C in the dark.

EXAMPLE 2 Example 1 was repeated with the exception that the photoconductive insulating layer used in Example 1 was replaced by an aluminum plate having a thin layer of amorphous selenium which was sensitized by the positive corona discharge. Also it can be replaced by a commercial zerographic plate. The resultant visible image was good as in Example 1.

Further, it was observed that the similar results are achieved when the iron powder used in Examples 1 and 2 was replaced by at least one powder selected from the group consisting of Al, Zn, Sn, Ni, Cu, brass and their alloys or at least one powdered metal which was prepared by electrically plating or electroless-plating a powder selected from the group consisting of Al, Zn, Sn, Ni, Cu and Cr with at least one of such metals.

EXAMPLE 3 Examples 1 and 2 were repeated with the exception that the coated iron powder used in Examples 1 and 2 was replaced by a graphite powder coated with a fixing material used in Example 1 for producing a good visible image.

Further, it was observed that the similar results are achieved by using a powdered material selected from the group consisting of carbon black, gelatine, shellac, casein, gum arabic, starch, methyl cellulose, hydroxyethyl cellulose, polyacrylamide, polyvinyl pyrrolidone, polyvinyl, alcohol, water soluble resin, in oxide, silver chloride, iron phosphate, lead acetate, crystalline inorganic compounds, pigments and dyestuffs. Some of the materials mentioned above could not be fixed on the electrostatic charge image under heating but it was found that they can be fixed on the electrostatic charge image under heating after they were treated with the fixing material as shown in Example 1.

EXAMPLE 4 A colored and electric insulating polystyrene powder was prepared by dissolving 100 grams of polystyrene resin, which is referred to Picolastic D-l (ESSO Company), in 200 cc of methylethyl ketone, adding grams of carbon black to the solution, ball-milling the mixture for 24 hours, evaporating methylene ketone under heating and pulverizing the mixture into fine particles by using a jet mixer after the mixture was cooled. The polystyrene powder thus produced was treated with an aqueous solution containing 1 to 5 grams of gelatine, 100 grams of water and 0.0] gram of polyoxyeth ylene sorbitan monostearate for imparting electric conductivity to the surface of the polystyrene powder. The coated powder was dried and was then used as a toner in the same manner as in Example 1 for obtaining a black visible image. The black visible image was fixed on the photoconductive insulating layer disposed on the paper in the same manner as in Example 1 by heating it at a temperature of 100 to 150C to fuse the polystyrene resin.

Further, it was found that any colored, pulverizable insulating resin can be used in this invention after it was powdered into fine particles and then the particles were coated for improving their electric conductivity. Also, it was found that it is preferable to use an antistatic agent in course of the preparation of the polystyrene powder for reducing its electric insulating resistance.

EXAMPLE 5 Example 2 was repeated with the exception that the coated iron powder was replaced by a toner which was prepared as follows.

grams of gelatine and 2 grams of aniline blue were throughly dissolved in 100 cc of hot water and the solution was dried and the resultant mixture was pulverized into fine particles. The surfaces of the particles were treated with an alcohol solution containing 20 percent shellac and a small amount of titanous chloride and then the treated particles were dried to form the electroconductive toner.

EXAMPLE 6 A capsulated powder was prepared from a solution containing a dyestuff (or a coloring material) by using the coacervation technique disclosed in the Fuji Shashin Film Report, No. 14, pages 77 to 84 published in the year 1966. The capsulated powder was treated with the fixing material as shown in Example 1 and the treated powder was used as a toner in the same manner as in Example 1 for obtaining a good visible image.

EXAMPLE 7 An iron powder was treated with an electroconductive fixing material which was prepared by using a mixture of 10 weight parts of a copolymer of polyvinyl acetate and crotonic acid, 50 weight parts of water and 0.01 weight part of an antistatic agent (alkylbenzene sulfonate), and the treated iron powder was used as a toner for converting an electrostatic charge image into a visible image. It was observed that the visible image was almost not transferred to a polystyrene sheet when the visible image was spaced from the polystyrene sheet at the distance of l to 3 millimeters in the dark room and a negative or a positive corona discharge was applied to said sheet atbehind said sheet. Also, it was observed that the visible image was almost not transferred to the polystyrene sheet when an electrode was placed behind said sheet and 500 to 10,000 volts were applied to the electrode.

It was, however, observed that the visible image was effectively transferred to the polystyrene sheet when the visible image was closely contacted with said sheet and the corona discharge was applied at behind said sheet. The transferred visible image was fixed under heating at temperature of to C.

A further experiment was carried out by spacing the visible image from the polystyrene sheet at the distance of 1 to 3 millimeters in the light. It was found that the visible image was effectively transferred to the polystyrene sheet and the visible image was fixed under heating at a temperature of 100 to 150C.

Still further, it was observed that when a toner was made by treating a ferromagnetic powder (iron powder) with the fixing material as mentioned above and the toner was used in the same manner as mentioned above, the visible image can be transferred to the polystyrene sheet by using not only the electric transferring technique but also by using the magnetic transferring technique in which a magnet is used.

EXAMPLE 8 An electrostatic charge image was formed on the commercial electrofax paper and then the electrostatic charge image was transferred to a polyester sheet by using the conventional techniques. The transferred electrostatic charge image was developed by using the toner as mentioned in Example 4. It was found that the transferred electrostatic charge image can be converted into a good visible image.

EXAMPLE? A copy of an original having a continuous tone was made by using the toner as mentioned in Example 5 and a photoconductive member made of an inorganic photoconductor such as zinc oxide, amorphous selenium, cadmium sulfide or an organic photoconductor such as polyvinylcarbazol. It was found that the quality of the copy varied depending on the property of the photoconductor used and also that the copy was affected by gamma (7) values of the photoconductive member. For example, the commercial electrofax paper or zerox plate gave the copy having high contrast but the photoconductive member made of cadmium sulfide or polyvinylcarbazole gave the copy having low contrast. it was found that the best photoconductor was the powdered pure cadmium sulfide which was doped with copper in an amount of 10 10 molar percent. Such a photoconductor was dispersed in an adhesive such as epoxy resin and the dispersion was used for forming a photoconductive insulating layer.

EXAMPLE 10 An electrostatic charge image was formed on a commercial electrostatic recording paper which has a dielectric layer on a paper by using a needle-like electrode which was applied with 200 to 1,500 volts and then the electrostatic charge image was developed by using the toner as mentioned in Example 5. it was found that a good visible image was formed even if the electrode was given either negative voltage or positive voltage.

Also, it was found that a good visible image was formed when an electrostatic charge image was formed on a commercial electrostatic recording paper by using a plate having the convex patterns which was applied with 200 to 2,000 volts and then the electrostatic charge image was developed by using the toner as mentioned in Example 5.

EXAMPLE 1 1 An electrostatic charge image was formed on a commercial electrofax paper and then cellophane was adhered to the electrostatic charge image without forming the static marks and the toner as mentioned in Example 4 was sprinkled on the cellophane. It was found that a visible image was formed on the surface of the cellophane. The visible image was fixed under heating at a temperature of 100 to 150C, and then the electrofax paper was stripped out from the cellophane. The stripped electrofax paper can be re-used.

Also, it was found that the visible image can be fixed in the cellophane by using the above toner without damage after the visible image was placed in the light.

EXAMPLE 12 An electrofax paper was sensitized by the corona discharge and then the sensitized electrofax paper was covered with a transperent polypropylene sheet. An electrostatic charge image was formed on the sensitized electrofax paper by exposing it to a light image passing through the polypropylene sheet. A toner as mentioned in Example 4 was sprinkled on the polypropylene sheet to produce a visible image on the polypropylene sheet and then the visible image was placed in the light room. The polypropylene sheet was stripped out from the electrofax paper and then the visible image was fixed on said polypropylene sheet by using conventional fixing techniques.

EXAMPLE 13 A xeroprinting plate was sensitized by exposing it to positive or the negative corona discharge and an electrostatic charge image was formed and then it was developed with the toner in the same manner as in Example 5. A good visible image was formed on the zeroprinting plate, and then it was transferred to a paper by conventional method. Resultant visible image was fixed on the paper under heating at a temperature of 100 to 150C.

EXAMPLE 14 A plate having the convex patterns was used as an electrode and the plate was contacted with a polystyrene sheet and then 200 to 2,000 volts were applied to the plate. Then the toner as mentioned in Example was sprinkled on the back surface of polystyrene sheet while the voltage was held at 200 to 2,000. It was found that a visible image was formed in accordance with the convex pattern on the back area of the sheet which is contacted with the convex area of the plate by the action of the electric field.

The present Example shows the fact that the visible image can be recorded by the action of the electric field and also that the toner is electrostatically bonded to the electric field image. The visible image was fixed on the polystyrene sheet by the conventional techniques after the electric field vanished.

EXAMPLE 15 An electrofax paper was sensitized by exposing it to the negative corona discharge in the same manner as in the conventional techniques and then the sensitized paper was exposed to a light image to form an electrostatic charge image on the electrofax paper. The electrostatic charge image formed on the electrofax paper was immersed in a powdered electroconductive magnetic toner having a size of 5 to 50 p.. The magnetic toner was prepared as follows.

grams of finely powdered magnetic oxide of iron were mixed with 20 to 30 grams of polystyrene resin which is referred to Piccolastic D-lOO and sold by ESSO Company and the mixture was pulverized. l0 grams of the pulverized powder was dispersed in 100 grams of a water solution containing 5 grams of lauryl trimethylammonium chloride (an antistatic agent). The resultant dispersion was dried to produce the electroconductive magnetic toner.

An excess amount of the toner retained on the electrofax paper was swept from said paper by vibrating it and a good visible image was formed on the electrofax paper. The visible image disposed on the electrofax paper was placed in the light room and the visible image was covered with a cellulose paper and then a magnet was placed near behind of the cellulose paper. It was found that the visible image is effectively transferred to the cellulose paper. The visible image can be fixed on the cellulose paper under heating at a temperature of 100 to C.

EXAMPLE 16 Example 15 was repeated with the exception that a coarse powder of iron was additionally added to the toner used in Example l5. The coarse powder of iron has a size of l00 to 500 u. The present Example proved that the step for sweeping an excess of the toner retained on the electrofax paper can easily carried out.

Further, it was observed that the similar results are achieved by using glass particles which are treated with stannous chloride or glass particles on which metallic aluminum was deposited under vacuum evaporation or glass particles on which copper was plated without the use of electric current.

EXAMPLE 17 In carrying out of Example 15, it was observed that the excess amount of the toner can not be completely removed from the surface of the electrofax paper but it was found that the toner retained on the area on which the toner must not be adhered can easily be swept by cascading the coarse powder used in Example 16.

In this Example, the density of the visible image was slightly reduced but it was found that there is no defect in practice.

EXAMPLE 18 An electrostatic charge image formed on an electrofax paper was loosely contacted with the toner, which is mentioned in Example 1 and sprinkled over the surface of an aluminium plate. It was found that a good visible image is formed on the electrofax paper after the paper was removed from the aluminium plate. A slight contamination due to the toner retained on a part of the electrofax paper not having the visible image can be removed by vibrating said paper or cascading the coarse powder used in Example 16. The visible image was fixed on the electrofax paper at the place but the visible image can be transferred to a cellulose paper in the same manner as in the conventional techniques and then the transferred visible image can be fixed on the cellulose paper.

EXAMPLE 19 Example 18 was repeated with the exception that the aluminium plate was replaced by a napped cloth such as velvet goods. It was found that a good visible image is formed on the electrofax paper.

EXAMPLE 20 A concave portion of a photogravure-like copper plate was fed with the toner as mentioned in Example 5 and the copper plate was contacted with an electrofax paper having an electrostatic charge image. The copper plate was made by known plate-making process to have gravure cells having a size of 100 to 200 lines per inch and the toner was fed into the concave portion of the copper plate. When the copper plate was contacted with the electrofax paper, the toner adheres to the electrostatic charge image to develope it into a netlike visible image. It is noted that the gravure cells can be replaced by grained cells, mosaic cells and other desired types of cells.

EXAMPLE 21 In the present Example, a movable and rotary copper drum which is provided with the gravure cells having a size of 100 to 200 lines per inch was used for carrying out the method of this invention at high speed. The drum was moved and rotated at high speed in contact with an electrostatic charge image disposed on an electrofax paper while the gravure cells were continuously fed with the toner as mentioned in Example 5 by using the doctor members. It was found that a good visible image is formed on the electrofax paper.

Also, the present Example can be modified by using a rotary copper drum which is stationary. The electrofax paper having the electrostatic charge image was passed through the space between the drum and a rubber roller.

It was found that the developing can be carried out at a speed of 50 to meters per minutes.

We claim:

1. A method for recording a visible image, characterized by:

a. sensitizing a photoconductive insulating layer disposed on a suitable substrate by corona discharge,

b. placing a transparent dielectric sheet onto the sensitized photoconductive insulating layer;

0. projecting a light image on said sensitized photoconductive insulating layer by passing a light through said transparent dielectric sheet, thereby producing an electrostatic charge image on said sensitized photoconductive insulating layer, said electrostatic charge image causing an electric field image corresponding to said electrostatic charge image on said transparent dielectric sheet;

d. converting said electric field image into a visible image by contacting said electric field image with an electroconductive toner sprinkled on said transparent di-electric sheet, and

e. fixing said visible image on said transparent dielectric sheet by heating.

2. A method for recording a visible image, according to claim 1, wherein the step for converting the electrostatic charge image or the electric field image to said visible image is carried out by contacting a plate or drum having concave cells in which the electroconductive toner is fed, with the surface of the fresh dielectric layer having the transferred electrostatic charge image or the transparent dielectric sheet having the electric field image.

3. A method for recording the visible image according to claim 1, wherein the step for converting the electrostatic charge image or the electric field image to said visible image is carried out by cascading or flowing a mixture of the electroconductive toner and electroconductive coarse granules over the surface of the fresh dielectric layer having the transferred electrostatic charge image or the transparent dielectric sheet having the electric field image.

4. A method for recording the visible image according to claim 1, wherein the step for fixing the visible image on the fresh dielectric layer or the transparent dielectric sheet is carried out in the presence of a solvent vapor.

Claims

2. A method for recording a visible image, according to claim 1, wherein the step for converting the electrostatic charge image or the electric field image to said visible image is carried out by contacting a plate or drum having concave cells in which the electroconductive toner is fed, with the surface of the fresh dielectric layer having the transferred electrostatic charge image or the transparent dielectric sheet having the electric field image.
3. A method for recording the visible image according to claim 1, wherein the step for converting the electrostatic charge image or the electric field image to said visible image is carried out by cascading or flowing a mixture of the electroconductive toner and electroconductive coarse granules over the surface of the fresh dielectric layer having the transferred electrostatic charge image or the transparent dielectric sheet having the electric field image.
4. A method for recording the visible image according to claim 1, wherein the step for fixing the visible image on the fresh dielectric layer or the transparent dielectric sheet is carried out in the presence of a solvent vapor.