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Publication numberUS3797930 A
Publication typeGrant
Publication dateMar 19, 1974
Filing dateApr 17, 1972
Priority dateMay 18, 1971
Also published asDE2223934A1, DE2223934B2, DE2223934C3
Publication numberUS 3797930 A, US 3797930A, US-A-3797930, US3797930 A, US3797930A
InventorsEnoguchi Y, Fujiwara T, Inoue M, Tanaka S, Wada K
Original AssigneeMinolta Camera Kk
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Electrophotographic copier
US 3797930 A
Abstract
A copier comprises a photosensitive member substantially in the form of an endless belt and composed of a flexible base subjected to electric conductive treatment, and inorganic semiphotoconductive layer and organic semiphotoconductive layer superposed on the base; an exposure station for exposing the electrically charged sensitive surface of the photosensitive member to reflected light from the face of an original document to form an electrostatic latent image thereon; drive means for driving the photosensitive member during each cycle of transfer operation; means for driving transfer paper in synchronism with the travelling photosensitive member formed with the latent image so as to bring the paper into fitting contact with the member, the transfer paper being composed of an electroconductive base and a dielectric coating thereon; means for electrically grounding the bases of both photosensitive member and transfer paper fitted together to transfer the electrostatic latent image onto the transfer paper; and developing means for supplying toner to the transfer paper bearing the transferred electrostatic latent image to visualize the image. The copier further includes color separation filters in the exposure station and developing sections for three or four colors to be operated in accordance with the change of the filters. A color copy is obtained by repeating a copying cycle three or four times.
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Tanaka et al.

[ Mar. 19, 1.974

ELECTROPHOTOGRAPHIC COP] ER Inventors: Susumu Tanaka: Masayoshi lnoue;

Yuji Enoguchi, all of Osaka; Kenichi Wada, Toyokawa; Takao Fujiwara, Osaka. all of Japan Primary ExaminerJohn M. Horan Attorney, Agent. or Firmwolder & Gross [57] ABSTRACT A copier comprises a photosensitive member substantially in the form of an endless belt and composed of a flexible base subjected to electric conductive treatment. and inorganic semiphotoconductive layer and organic semiphotoconductive layer superposed on the base; an exposure station for exposing the electrically charged sensitive surface of the photosensitive member to reflected light from the face of an original document to form an electrostatic latent image thereon; drive means for driving the photosensitive member during each cycle of transfer operation; means for driving transfer paper in synchronism with the travelling photosensitive member formed with the latent image so as to bring the paper into fitting contact with the member, the transfer paper being composed of an electroconductive base and a dielectric coating thereon; meansfor electrically grounding the bases of both photosensitive member and transfer paper titted together to transfer the electrostatic latent image onto the transfer paper; and developing means for supplying toner to the transfer paper bearing the transferred electrostatic latent image to visualize the image. The copier further includes color separation filters in the exposure station and developing sections for three or four colors to be operated in accordance with the change of the filters. A color copy is obtained by repeating a copying cycle three or four times.

PATENTEUHAR 1 9 1914 7 9 sum 2 BF 5 Fig.2

PATENTEIJ m 19 um SHEET 3 [IF 5 PATENTEU MAR 1 9 I974 SHEET 0F 5 PAIENTEUHAR 19 I974 SHEET 5 BF 5 ELECTROPHOTOGRAPHIC COPIER BACKGROUND OF THE INVENTION The present invention relates to an electrophotographic copier, more particularly to an electrophotographic copier of the electrostatic latent image transfer type.

According to the copying process involving transfer of electrostatic latent image, the electrically charged sensitive face of photosensitive member is exposed to reflected light from the face of an original document to form on the sensitive face an electrostatic latent image, which is then electrically transferred onto the dielectric face of dielectric coated paper (hereinafter referred to as transfer paper") and the latent image on the transfer paper is then developed with toner. This process is generally called process of transfer of electrostatic image," which includes various processes and which may be classified into two broad groups: those employing external electric field and those which do not use such field.

In producing a color copy by the conventional electrophotographic copier, predominantly employed is Electrofax process in which zinc oxide paper is used. According to this process, the image of original is subjected to color separation by red, blue and green filters and a process involving charging, exposure, development and drying is repeated three times with the development conducted with cyan, magenta and yellow toners respectively for the superposition of the three colors, followed by a final process including charging, exposure, development and drying. Thus a finished copy is obtained through four cycles of copying process. However this process has a serious drawback "that due to the memory effect inherent to the zinc oxide paper there arises a difference between the charge amounts in the first cycle and the subsequent cycle, along with a further difference in light decay rate. Accordingly, it is very difficult to control the amount of the respective toners and amount of exposures and color reproducibility becomes unstable. Further since it is impossible to completely eliminate fogging due to the foregoing reasons and because of four cycles of copying operation conducted in repetition which result in superposed fog, the background will be stained. Further the need to obtain spectral sensitivity that is almost panchromatic requires use of various sensitizing dyes, so that the consequent absorption of the dyes inevitably renders the surface of the zinc oxide paper faint gray.

Therefore it follows that highlight portion gets deteriorated and colors are reproduced with lower brightness and purity. Further even if the zinc oxide paper is sensitized with dyes, the resulting improvement will be as low as about 20 1x-sec., requiring a prolonged processing time and greater power.

Further various photosensitive members have heretofore been proposed for use in the electrophotographic copier of the type described, as in the form of a drum, belt or sheet suitably disposed on the surface of a belt. To subject the sensitive member or the sensitive face thereof to an exposure and to transfer an electrostatic latent image onto transfer paper, the photosensitive member may be moved in a path of various shapes such as a circular. eliptical or modified annular form.

It is noted however that whatever type of photosensitive member may be employed. chargeability of the photosensitive member will lower to prevent formation of electrostatic latent image of good quality. if the number of exposures. namely, the number of copying operations exceeds a certain level. ln other words. the sensitive member has a limited life and has to be replaced usually if it becomes unserviceable. It is desired that such replacement be as seldom as possible to assure easy maintenance of the copier and improved copying efficiency.

In the case where a plurality of photosensitive members are disposed on a belt and used one after another. the photosensitive members must be so arranged that at least until transfer of the electrostatic latent image has been completed, with a photosensitive member moved from the exposure station into fitting contact with transfer paper, the subsequent photosensitive member will not reach the exposure station. Consequently, an attempt to space the photosensitive members by a smaller distance to increase the number of the photosensitive members will encounter a considerable limitation, with the result that the number of photosensitive members to be mounted on the belt is relatively small as compared with the length of the belt, leaving a rather large dead space on the belt.

SUMMARY OF THE INVENTION An object of this invention is to provide an electrophotographic copier of the electrostatic latent image transfer type which is capable of producing copy images with high quality and high contrast.

Another object of this invention is to provide an electrophotographic copier capable of giving color copies having excellent color reproducibility and free from fogging in the background and any of the drawbacks heretofore experienced with color copying by Electrofax process.

Another object of this invention is to provide a compact electrophotographic color copier which permits a greater freedom in process design and easy to practice the process.

Another object of this invention is to provide an electrophotographic copier of the type described wherein a plurality of photosensitive members are provided on an endless belt with the smallest possible dead space left on the belt so as to increase the number of the photosensitive members.

In order to fulfil the foregoing objects, there is provided a photosensitive member composed of a flexible film base subjected to electric conductive treatment and an inorganic semiphotoconductive layer and an organic semiphotoconductive layer superposed on the base, the photosensitive member being supported on drive means so as to be moved in a circular or elliptical path or the like. The photosensitive member is charged and then exposed to reflected light from the face of an original document to form an electrostatic latent image. The transfer face of transfer paper composed of an electroconductive base and a dielectric coating thereon is brought into fitting contact with the sensitive face of the photosensitive member which is driven with the electrostatic latent image thereon to cause the image to be transferred onto the paper by grounding both bases of the photosensitive member and transfer paper. The electrostatic latent image on the paper is then developed with toner.

It is noted that there is a lower limit for the surface potential of the charge on the photosensitive member when the charge (electrostatic latent image) is to be transferred. Experiments have revealed that the charge is about 300 volts. Thus in accordance with this invention, the photosensitive member is negatively charged. The experiments have also indicated that the surface potential on the photosensitive member can be determined at a controlled value as desired. this making it possible to selectively transfer the electrostatic latent image from the photosensitive member without transferring unwanted stain in the background. Thus copies free from any background fog can be obtained. In other words, images of enhanced contrast can be obtained.

Further according to this invention, the sensitive face and image receiving face (i.e., transfer face) are formed separately on the sensitive member and transfer paper which can be handled entirely independently of each other, permitting much greater freedom in process design and making it possible to select and use sensitive material and image receiving material in combination to achieve optimum results.

With the electrophotographic color copier of this invention, the optical exposure system for the photosensitive member incorporates therein color separation filters. such as WRATTEN filter already known in color printing, which are used in succession for respective copying cycles in subjecting the sensitive member to exposures.

The photosensitive member is driven every time an exposure is made. In synchronism with each turn of rotation of the sensitive member, transfer paper driving means carrying the transfer paper on the peripheral face of a drum is driven one turn to bring the transfer paper into fitting contact with the surface of the sensitive member and to thereby effect transfer of 'ihe electrostatic latent image, with bases of both sensitive member and transfer paper grounded. After the transfer of image, the remaining charge is removed from the sensitive member by charge erasing means. The photosensitive member is charged again and then subjected to a subsequent exposure through another filter. On the other hand, the transfer paper formed with the image is supplied by developing means with a toner corresponding to the color selected upon separation through the filter. Development thus effected is then followed by fixing. The transfer paper is further retained on the drum and brought into snug-fit contact with the travelling sensitive face again, subsequent to the next exposure through another filter. The following development causes toner of another color to be superposed on the already developed face. Repetition of such process gives a finished copy.

The developing means comprises cyan. magenta, yellow and black developing sections which are shifted in response to the selection of the filter so as to supply the transfer paper with toners respectively corresponding to the colors separated by the filters.

Thus the present invention employs in combination a photosensitive member which is highly sensitive. panchromatic and free of memory effect and which has spectral sensitivity over the entire range of visible rays and electrostatic transfer paper composed of pure white high quality paper and transparent dielectric coating thereon, whereby all of the drawbacks heretofore experienced with color copying by the Electrofax process can be eliminated to give. with .lower power and shorter exposure time, clear color copies free of background fogging and having colors very close to natural colors.

According to this invention. a plurality of photosensitive members are arranged in the path of travel thereof in an endless form and are carried on the drive means therefor. Further provided are control means for selectively positioning a particular photosensitive member or a particular section of the photosensitive member at the position for effecting copying operation and changeover means for switching the position control means to bring another photosensitive member or another section thereof into operation in place of the foregoing member or section. Thus when the particular sensitive member or section gets deteriorated in chargeability due to fatigue, another member or section can be put into copying operation.

In this way, the photosensitive member(s) can be made serviceable for a prolonged period before replacement and the respective sensitive members or sections thereof can be spaced with a remarkably reduced dead space, with the resulting increase in the sensitive area relative to the whole length of the endless belt to provide a compact copier.

Other objects and features of this invention will become more apparent from the preferred embodiments of this invention to be described below.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view showing the principal part of an electrophotographic color copier embodying this invention;

FIGS. 2 (A) and (B) are views illustrating the construction of photosensitive members;

FIG. 3 is a view showing the construction of transfer paper;

FIG. 4 is a perspective view showing drive means for the photosensitive member;

FIG. 5 is a perspective view showing the principal part of a construction for associating the photosensitive member with the drive means;

FIG. 6 is a diagram showing an arrangement of switches for the copier which serve also to indicate colors and indications of synthesized colors;

FIG. 7 is a front view showing the principal part of an embodiment of means for controlling the position of the photosensitive member;

FIG. 8 is a diagram showing an electric circuit serving as means for changing over the position control means;

FIG. 9 is a sectional view showing the principal part of another embodiment of this invention; and

FIG. 10 is a diagram showing an electric circuit for controlling the embodiment of FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a frame 1 of the copier has at a left hand portion of its top a document table 3 made of a glass plate for receiving an original document 2 with its face down. An independnt compartment 4 under the document table 3 is provided. on the opposite sides of and below the table 3, with light sources 5 to be turned on by depression of an unillustrated start switch of the copier. A mirror M opposes the document table 3 and directs reflected light from the original document face to an exposure station when the light sources 5 are lighted. The wall 40 of the independent chamber 4 carries an image forming lens 6 for the reflected light. Disposed in front of the lens 6 is a filter 7 such as a WRAT- TEN filter to be moved in operative relation to a copying operation or to be operated manually for separating the color of the original image into three colors. The light passing through the lens 6 is projected onto an exposure station 8 by way of a mirror M to expose a photosensitive member P.

As shown in FIG. 2 (A), the photosensitive member P comprises a flexible base plate a having a thickness of about 100 microns and made of a polyethylene telephthalate film. The base film is provided thereon with an electroconductive layer b formed by depositing an electroconductive metal such as aluminum by vacuum evaporation. The electroconductive layer b is coated by vacuum evaporation with an inorganic semiphotoconductive layer c having a thickness of about 0.5 to 1.0 micron. The inorganic semiphotoconductive layer c is further formed on its surface with an organic semiphotoconductive layer d. The construction is such that the inorganic semiphotoconductive layer c will substantially exhibit photosensitivity.

Accordingly, it is preferable that the inorganic semiphotoconductive layer 0 be made of a material which is of high sensitivity and has a wide range of spectral sensitivity. For example, use of a selenium alloy containing at least 20 percent by weight of tellurium will assure spectral sensitivity not lower than 7,000 A, and a selenium alloy incorporating at least 30 percent by weight of tellurium will give an increased spectral sensitivity of up to about 8,000 A, ensuring panchromatic properties for electrophotographic color copying operation.

The organic semiphotoconductive layer d may be made of a transparent organic semiphotoconductor such as polyvinylcarbazole (hereinafter referred to as PVK). The layer d is formed on the inorganic semiphotoconductor c to a thickness of 10 to 30 microns.

Since the photosensitive member P thus constructed has no memory effects, it is highly stable in forming a latent electrostatic image upon exposure during repeated use. Further it has five to ten times the sensitivity of zinc oxide paper heretofore used as a photosensitive member, in addition to an extended range of spectral sensitivity. Thus the photosensitive member P is very advantageous from the viewpoint of power and ruduction of copying time. Further the photosensitive member P may comprise a flexible base a having a thickness of 75 microns and made of a polyester film, a thin electroconductive layer b of aluminum film deposited on the base by vacuum evaporation and serving as an electrode, an inorganic semiphotoconductive layer 0 of a very thin amorphous selenium film formed I on the layer b by vacuum evaporation and an organic semiconductive layer d covering the layer c and made of PVK containing diphenyl trichloride serving as a plasticizer and monochlorobenzene serving as a solvent. The uppermost PVK film d serves to retain the charge and to provide a passage for holes, while the thin selenium film 0 produces charge carriers upon absorption of the light. The aluminum film b forms a high rectifying barrier at the boundary between the film b and selenium film c to completely prevent hole injection into the latter. When the photosensitive member is exposed with a negative charge on its surface, the holes produced on the thin selenium film c are injected into the PVK film d and move to the surface to neutralize the charge on the surface to form an electrostatic latent image. Thus a useful photosensitive member capable of providing images of improved density and contrast is obtained.

Further FIG. 2 (B) shows a photosensitive member P including a thin selenium film c and a thin seleniumtellurium alloy film 0' formed by vacuum evaporation which are interposed between a thin aluminum film serving as the foregoing electroconductive layer b and a PVK film acting as the organic semiphotoconductive layer d. in this case the selenium film 0 does not absorb light but the selenium-aluminum interface merely acts as a rectifying barrier and prevents holes from being injected into the selenium film. It is possible to use about 10 to 60 percent by weight of tellurium in forming the selenium-tellurium alloy film c to thereby provide a photosensitive member having a remarkably improved sensitivity. The selenium film and the seleniumtellurium alloy film in these photosensitive members have a thicknes of not more than 1 micron and the PVK film is made of a high molecular weight material. The aluminum film and selenium film are adhered to each other firmly by exposing the aluminum film to ion bombardment in glow discharge to forcibly oxidize the same and then depositing selenium thereon by vacuum evaporation. For these reasons, the selenium film will not be peeled off the aluminum film, for instance even when the photosensitive member P or P is used in the form of a belt and is passed around two rollers having a diameter of 30 mm and driven at a high speed of lm/sec for 1,000 hours without interruption. Thus, it has been ascertained that the present photosensitive member is very useful even when used in the form of a belt.

FIG. 3 shows an example of transfer paper T having a transfer face serving as a face for receiving the electrostatic latent image. The transfer paper T comprises wood free paper e subjected to electroconductive treatment and a transparent dielectric layer f formed on the surface of paper e. To provide the dielectric layer f, the paper e is coated to a thickness of about 5 microns with a highly dielectric substance such as acrylic resin, vinyl chloride, polyethylene, etc.

It is possible for the transfer paper T of such construction to have a high degree of whiteness, with the result that the image can be reproduced on the transfer paper T in very bright colors.

The transfer paper T may comprise paper e having a thickness of 25 to microns and subjected to dielectric treatment and a synthetic resin film f on the paper e obtained by coating the paper to a thickness of 2 to 10 microns with a synthetic resin serving as a highly dielectric substance such as polyethylene wax, alkyd resin, cellulose acetate, epoxy resin, copolymer of vinyl chloride and vinyl acetate, etc.

The transfer paper T'of such construction is pressed into contact by an electroconductive roller with the surface of the photosensitive member P formed with an electrostatic latent image, with both bases of the photosensitive member and transfer paper grounded for the transfer of the latent image, and the transfer paper T is then subjected to liquid development. it has been ascertained by this operation that a copy of greatly improved quality can be obtained which is superior to those made by copiers heretofore used. In particular, a photosensitive member using the thin seleniumtellurium alloy film can be charged with a negative charge in excess of l,000 volts and an exposure at several lx-sec. gives a very distinct visible image background-free and having high contrast and high resolving power (in excess of 50 lines/mm).

A plurality of the photosensitive member P are mounted in an endless manner on a pair of belts 11 reeved around rollers 9 and 10, or the photosensitive member per se may be reeved around the rollers 9 and 10 in an endless fashion. In the illustrated embodiment, the roller 9 is grounded as an electroconductive roller, while the roller 10 keeps the photosensitive member P taut as a tension roller. As shown in FIGS. 4 and 5, apertured belts 12 extend over sprockets 11 on the opposite ends of both rollers 9 and 10. A bar 13 is fixed to one end of the photosensitive member P which has an exposure area required for one copying operation. The bar 13 is caught on hooks 14 on the belts. The other end of the photosensitive member P is connected to one end of each spring the other end of which is secured to the bar 13 of the adjacent photosensitive member P. In this way, the photosensitive members P are retained on the belts 12 in an endless fashion in their entirety.

The belts 12 extend horizontally below the mirror M and one of the rollers 9 and 10 is driven to bring the photosensitive member P to the exposure station 8. Upon completion of an exposure, the photosensitive member P is moved to a transfer station to be described later. where the electrostatic latent image on the photosensitive member is transferred onto the transfer paper T. After transference, the charge remaining on the photosensitive member P is removed by charge eraser 16. On the way to the exposure station 8, the photosensitive member P is charged by charging means 17. To sum up, the photosensitive member P is subjected to a series of processes of charging. exposure transfer, and charge removal while being driven by the rollers 9 and 10 and is brought to a halt upon returning to the original position.

in the case where a plurality of photosensitive members P are retained on the belts 12 or the photosensitive member P per se is in the form of a belt to provide a plurality of exposure sections on the sensitive face thereof, a particular sensitive face or section of the photosensitive member P will be used in repetition with the other faces or sections kept out of use, if the photosensitive member is so arranged as to be driven by the rollers'9 and 10 to the original position upon finishing each cycle of the foregoing copying operation. Accordingly, there arises a need to operate position control means to shift the sensitive face when a particular sensitive face undergoes fatigue or is deteriorated through repeated use. The position control means will be described later. Instead of using a particular section in repitition, the photosensitive member P may be stopped at a desired position every time a cycle of copying operation has been completed so as not to specify the sensitive face to be used. Alternatively, sensitive faces or sections may be put to use one after another during several cycles of copying operation.

An electroconductive drum 18 is so disposed as to cause the image receiving face of the transfer paper T to come into contact with the sensitive face of the photosensitive member P at the position opposing the electroconductive roller 9. The drum 18 is grounded like the electroconductive roller 9 and provides a transfer station at the place where the transfer paper T comes into fitting contact with the photosensitive member P.

The drum 18 is equipped with paper clamp means 19 as well-known in offset press and has a circumference equal to the length of the endless belts 12. To obtain a color copy according to this invention. the drum 18 has to be rotated a number of turns equal to the number of copying cycles (four cycles in maximum) required for a color copying operation to effect transfer. developing and fixing in repetition. with the transfer paper T on the surface of the drum 18. Accordingly, it is preferred that the transfer paper T be secured to the drum 18 not only by causing the clamp means 19 to clamp the leader end of the paper but also by clamping the opposite sides and rear end of paper with suitable clamp means. The drum 18 may further incorporate therein vacuum means (not shown) so as to attract the transfer paper onto the surface of the drum 18.

The photosensitive member P and transfer paper T are driven at the same speed. In the case where a particular photosensitive member P or a particular sensitive section is to be used in repetition, it is so arranged that the endless belts 12 make one turn of rotation while permitting the drum to make one turn of rotation to ensure registration of the respective colors for a color copying operation.

The transfer paper T is supplied to the drum 18 by transfer paper supply means comprising a paper feed roller 20 and transport rollers 21 and 22 in timed relation to the operation of the photosensitive member P which is initiated with a start signal as by the closing of a start switch (not shown) for charging, exposure, transfer and removal of the charge. (During exposure, the photosensitive member in this embodiment is temporarily stopped for a period of time required for exposure and the stop signal turns on the light sources for making an exposure.) The transfer paper is retained on the drum surface for transfer, development and fixing.

The exposure of the photosensitive member P is ad justed by varying the exposure time. For a color copying operation, it is necessary to adjust the color temperature of the light source to a definite level, while the differences in sensitivity to blue, green, red and black are corrected by N.D. filter, or by presetting exposure time and exposure amount for each color or by some other means so that a proper exposure can be assured for each color by one exposure control dial.

Indicated at 23 is developing means for the transfer paper T onto which the electrostatic latent image has been transferred. As already well-known in color printing, the developing means includes liquid developing sections 23a, 23b, 23c and 23d using toners of yellow, magenta, cyan and black respectively. For each cycle of copying operation, a liquid developing section corresponding to the color of that cycle of operation comes into contact with the transfer paper on the drum 18 to visualize the electrostatic latent image corresponding to the copy color successively. For this purpose, the developing means is movable under the drum l8 and beltlike photosensitive member P from the solid line position to the broken line position in the drawing in corresponding relation to the copy color. This movement may be effected in operative relation to the color setting of the filter 7.

Each of the liquid developing sections 23a, 23b, 23c and 23d is independent of another so as to prevent mixture of colors. To assure quick drying and fixing of the image to the transfer paper, it is preferable to.use a liquid of insulating properties and high volatility such as ISOPAR G, DIFLON (both being trade name) or the like. To prevent evaporation, the developing section is of airtight construction. The developing section includes an applicator 24 comprising a roller covered with a liquid absorbing sponge, felt or the like for applying the developer to the transfer paper.

The developer applicator 24 may alternatively be in the form of a belt or a pump for forcing the developer against the transfer paper T. These means may further be used in combination.

Drying and fixing means 25 is so arranged as to be actuated immediately after the transfer paper T on the drum 18 has been developed by the developing means 23 to force warm air against the paper and to thereby effect drying and fixing. For color copying. the drying and fixing means is operated for each cycle of transferring and developing the image of each color to dry and fix the reproduced image.

Copy discharge means 26 includes a separating pawl 27 and discharge rollers 28. The pawl 27 is located at the position where the dried and fixed transfer paper T is sent out. The discharge rollers 28 further send out the copy paper onto a copy receiver 29 outside the frame 1 after it has been removed from the drum 18 by the separating pawl 27. While the drum 18 is rotated a number of turns corresponding to the number of cycles required for color copying, the separating pawl 27 is kept away from the drum face, and upon completion of the last cycle of copying operation the separating pawl 27 is brought'close to the drum surface. For instance, if a four-color copy is to be made, the pawl is brought toward the drum simultaneously when the transfer paper is released from the clamp means 19 after completion of a fourth cycle of operation including transfer of electrostatic latent image. development, drying and fixing. Thus, the pawl 27 separates the transfer paper T from the drum surface and guides the same to the discharge rollers 28, which in turn forward the paper onto the copy receiver 29.

In the foregoing construction. the paper feed roller 20 is adapted to be stopped or rotated idly so as not to supply transfer paper T while the drum 18 with the transfer paper T thereon rotates a required number of turns for color copying operation. When the copy with the respective colors completely developed and fixed thereon is delivered onto the copy receiver, the paper feed roller supplies the transfer paper T to the drum 18 for the subsequent operation with the desired timing after closing of the start switch.

The filter 7 is switched to filtration of the next color in operative relation to the movement of the photosensitive member P when it has reached a standby position after completion of a cycle of copying operation. For black color copying, the filter 7 is positioned out of the light path of the lens 6.

Color copying operation by the present embodiment is conducted in the following manner. Upon closing of the start switch, the photosensitive member P in the standby position and drum 18 are initiated into operation. The photosensitive member P is negatively charged on its sensitive surface by the charging means, and the drum 18 is supplied with transfer paper T and retains the same thereon. The photosensitive member and the drum comes to a temporary halt for an exposure upon the photosensitive member reaching an ex- -posure position. Thus an electrostatic latent image is formed by a given period of exposure. Through the subsequent movement of both the sensitive member and drum, transfer of the latent image, development and drying and fixing are conducted. The charge is removed from the photosensitive member, which then returns to the above-mentioned standby position. This is followed by second, third and fourth copying cycles to effect transfer, development and drying and fixing of images of respective colors, whereby a color copying operation is completed as desired. Upon completion of each copying cycle, the developing means 23 is moved from the solid line position to the broken line positions in FIG. 1 in operative relation to the change of the filter 7 and is returned to the solid line position when the last copying cycle is completed.

The foregoing respective movements can be controlled in programmatic manner by an electric control circuit which may incorporate a timer or a combination of cam and microswitch for mechanical operation or a combination of relay and microswitch for successive operation as already known.

Further the frame 1 may be provided with an operation panel (not shown) equipped with selection switches for respective colors. The switches may be so adapted as to move the filter 7 out of operation and permit a developing section of the color corresponding to the selected switch to operate. Thus various single color copies can be obtained. Selection switches in such arrangement may include a switch Y for the yellow developing section 23a, a switch M for the magenta developing station 23b, a switch C for a cyan developing station 230 and a switch B for the black developing section 23b. Depression of one or two of these switches will then give four kinds of single color copy and three kinds of color copies through combination of colors other than black, hence seven kinds of color copies. For this operation, it is meaningless to depress three or more switches. If a copying operation is conducted without depressing these selection switches, four copying cycles are conducted as already described with the filter 7 acting to separate colors for a color copying, whereas if two selection buttons are depressed, the filter will be brought out of operation to effect two cycles of copying operation.

The selection switches are arranged for example as illustrated in FIG. 6. The synthesized colors may be indicated by indicating members G, R and B' disposed between each pair of switches other than the switch B for black color. This will readily indicate to the operator the relationship between the colors in providing synthesized colors.

FIGS. 4, 7 and 8 show means for driving the photosensitive member P and for controlling the position of the same. A gear 30 is mounted at the end of one of the rollers 9 and 10 for carrying the photosensitive member P through the belts 12. The gear carrying roller may be one other than the tension roller. In the drawing, the gear is on the shaft of the roller 9. An electromagnetic clutch 30 is mounted on a shaft for a sprocket 31 to be driven through chain transmission means by an unillustrated main motor which is driven all the time when unillustrated main switch is closed. Further there is provided a gear 33 for effecting or interrupting transmission of torque of the sprocket 31 by energization or deenergization of the electromagnetic clutch. The gears 30 and 33 mesh with each other.

The gears 30 and 33 are so constructed as to mesh with each other when the photosensitive member P is reeved around by means of belts 12 on rollers 9 and on a frame 34 and the assembly is mounted in position within the main body of the copier.

Further mounted on the shaft of the roller 9 is a gear 35 which drives a gear 39 on a shaft 38 through intermediate gears 36 and 37. The shaft 38 is supported on the frame 34 and carries a cam plate 40. The cam 40 is therefore driven in operative relation to the photosensitive member P.

The gear ratios are so determined that the cam plate 40 makes one turn of rotation in synchronism with one turn of rotation of the photosensitive member P, namely with one cycle of movement of the photosensitive member P during which it is initiated into movement from the standby position thereof and returned to the standby position after charging, exposure, transfer of electrostatic image and removal of charge.

Disposed around the cam plate 40 are detectors such as microswitches M51, M82, M53, M54 which are identical in number to the photosensitive members P on the belts 12 or to the sections of the sensitive face where the photosensitive member P per se is in the form of a continuous belt. Detecting members 41,, 41 41 41, of the detectors are in resilient contact with the periphery of the cam plate 40. A notch 40a is formed in the periphery of the cam plate 40. Thus the angular position of the cam plate 40 is detected by the detecting members 41,, 41 41 41, The result of mechanical detection thus effected is converted to an electrical signal by the microswitches M81, M82, M53,

The detecting members 41,, 41 41 41, are so arranged along the periphery of the cam as to detect the notch 40a as each different one of the photosensitive members P or each section of the sensitive face is shifted to the aforesaid standby position. Accordingly, where the photosensitive members P or sensitive sections are equidistantly spaced, the detecting members are arranged along the cam periphery in equidistant relationship.

The standby position of a particular photosensitive member P to be repeatedly subjected to charging, exposure. transfer and removal of charge is determined at a suitable position within such range that the leader end thereof with respect to the direction X of its travel (see FIG. 7) is positioned before the charging means '17 or not beyond the means 17 and the rear end has already passed the transfer portion.

Thus closing of the start switch brings the charging means 17 and electromagnetic clutch 31 into operation and causes the main motor to drive the roller 9, whereby the photosensitive member P kept at the standby position is initiated into movement by the belts toward the exposure station 8 while being subjected to a charging action, causing the cam plate 40 to rotate and push out the detecting member 41, from the cutout 40a.

When the notch 40a has rotated to the position of the detecting member 41,, the detecting member 41 is actuated, whereupon the microswitch MSZ gives a detecting signal to a position detecting circuit B1 shown in FIG. 8 to deenergize the electromagnetic clutch 31 and thereby stop the photosensitive member P and turn off the charging means 17. Thus the photosensitive member P stops at the exposure position and is subjected to an exposure. Upon lapse of a predetermined period of exposure time, a timer or the like acting on the position detecting circuit Bl energizes the electromagnetic clutch 31 again, permitting the photosensitive member P to move forward and causing the electrostatic latent image to be transferred from the photosensitive member P onto transfer paper T at the transfer station. The charging means 16 erases the residual charge and the notch 40a of the cam plate 40 actuates the detecting member 41, of the microswitch MSl, which in turn feeds a signal to a position detecting circuit B2 to deenergize the electromagnetic clutch 31 and thereby keep the photosensitive member P at its standby position. In this way one cycle of copying operation is completed.

During one turn of rotation of the cam plate 40, the notch 40a will actuate the detecting members 41,, and 41, of the microswitches M83 and M54, but these are cut off from the electric circuit by switching means to be described later so as not to emit electrical signal. If a particular photosensitive member undergoes fatigue, other photosensitive members will be put into use one after another and an electrical signal will be produced for controlling the position of the new photosensitive member.

in the case where two to four cycles of copying operation are conducted in repetition, the position detecting circuit B2 is designed in such manner that it will not deenergize the electromagnetic clutch 31 until a predetermined number of cycles of copying operation are completed.

The changeover means serves to render two of the microswitches electrically operable, disconnecting the rest from the electric circuit for controlling the position of the photosensitive member P. Thus the changeover means acts to determine which of the plurality of photosensitive members to use for copying operation. For instance, where four photosensitive members P1, P2, P3 and P4 are mounted on the belts 12, four microswitches MSl, M52, M53 and M84 are arranged along the periphery of the cam plate 40 as seen in FIGS. 7 and 8 and the changeover means is provided to cause these switches to energize the position detecting circuits B1 and B2.

During one cycle of operation of the photosensitive member P, there is a need to produce an electrical signal twice in order to operate the position detecting circuits B1 and B2 in succession as already described. Accordingly, each pair of the microswitches are provided for detection of position of each photosensitive member, more specifically microswitches M51 and M52 for photosensitive member P1, M82 and M83 for P2, M53 and M54 for P3 and M54 and MSI for P4. The changeover means is adapted to enable these pairs of microswitches to emit electrical signals to the position detecting circuits B1 and B2.

As illustrated in FIG. 8, the changeover means comprises a rotary member 43 to be rotated by a knob 42 and contact members 43, and 43 fixed to the rotary member 43 and electrically insulated from each other. The contact member 43, is electrically connected to the position detecting circuit B1, and the contact member 43 to the position detecting circuit B2. Disposed around the contacting members 43, and 43, are contact points 44,, 44 44 and 44, which are electrically connected to the microswitches M81, M52, M83 and M54 respectively, the arrangement being such that the contacting members 43, and 43 will selectively contact the contact points. The microswitches M81, M52, M53 and M84 are connected to an input terminal 45 so that when the detecting members 41 41 41 and 41, detect the notch 40a of the cam plate 40, the microswitches are closed and are otherwise kept open.

By moving the knob 42 to rotate the rotary member 43, the parts will be brought to the position shown in FIG. 8 wherein the contacting member 43, is in contact with the contact point 44 with the contacting member 43 in contact with the contact point 44 In this state, when the detecting member 41, of the microswitch MS2 detects the notch 40a of the cam plate 40, an electrical signal will be sent to the position detecting circuit B1 through the contact member 43 if the detecting member 41 of the microswitch MSl detects the notch 400, the resulting electrical signal will be applied to the position detecting circuit B2 through the contact member 43, to control the position of the photosensitive member P1 in the already described manner. Since the contact points 44 and 44; are in off state, the other microswitches M83 and MS4 are electrically out of operation despite the action of the detecting members 41 and 41 If repeated use renders the photosensitive member P1 deteriorated or damaged and therefore unserviceable, the rotary member 43 will be operated by the knob 42 to bring the contact member 43 into contact with the contact point 44 and the contact member 43 with the contact point 44,, leaving the contact points 44 and 44 in off position. The microswitches M82 and M53 will then control the position of the photosensitive member P2. In like manner, changeover manipulation of the knob 42 will bring fresh photosensitive members into operation one after another.

The knob 42 may be operated manually or automatically. To indicate on the operation panel which photosensitive member P1, P2 is in operation, the knob 42 may be provided with a mark or the like.

Instead of employing the foregoing electrical control means. the changeover operation may be such that a fresh photosensitive member will be brought to the standby position mechanically every time the photosensitive member is deteriorated. lndicated at 46 in F l6. 4 is a plate for keeping the photosensitive member P in planar position.

FIG. 9 shows the principal parts of an embodiment of an electrophotographic single color copier. At the top of a frame 51 there is positioned a document table 53 made of a transparent glass plate for placing an original document 52 with its face down. Disposed under the document table 53 is an independent compartment 54 housing lamps 55 and a mirror Ml. An image-forming lens 56 is mounted in a wall 54a. An image of original document reflected from the mirror Ml passes through the lens 56, is reflected from a mirror M2 above an exposure station 57 and projected onto the exposure station 57.

At the exposure station 57, photosensitive members P1, P2, P3 to be driven in the direction of X under the control of the position control means described above are supported on belts 60 reeved around an electroconductive roller 58 and a tension roller 59 and kept planar by a plate 61. In the path of travel of the photosensitive members there are disposed charging means 62, electroconductive roller 63 for transfer and charge removing means 64. The electroconductive rollers 58 and 63 are both grounded. The photosensitive member P bearing an electrostatic latent image and the transfer paper T are brought into snug-fit contact with each other between the rollers 58 and 63, permitting the latent image to be transferred onto the image receiving face of the paper The belt is driven in the direction of X by gear transmission means 66 and 67 associated with chain transmission means by way of an electromagnetic clutch (not shown) to be energized or deenergized by the already described position control means, the chain transmission means 65 being driven by a main motor MM all the time.

if the transfer paper T is in the form of a roll of paper TR. the transfer paper roll TR is mounted on a rotary shaft 68 within the machine and the paper is pulled out by drawing out rollers 71 and 72 driven by a paper feed motor MT through a chain transmission 69, electromagnetic clutch and the like. The paper is cut off to a copy size by a cutter 73 and supplied between a transfer roll 63 and photosensitive member P by paper feed rollers 74 and 75 likewise driven by the paper feed motor MT.

In the case where a sheet of transfer paper TS is used as the transfer paper T, the transfer paper TS supplied from an inlet 78 is sent into the copier by transport rollers 76 and 77 driven by the paper feed motor MT and is fed into the transfer station (i.e. between the photosensitive member and transfer roller) by means of paper feed rollers 74 and 75. At this time, a microswitch MSS prevents unwinding of the transfer paper TR by being actuated by the sheet of transfer paper TS to deenergize the electromagnetic clutch 70 and stop the operation of the drawing out rollers 71 and 72.

The transfer paper T fed to the transfer station is brought into fitting contact with the photosensitive member P, and the bases of the paper T and the photosensitive member P are grounded through the rollers 63 and 58, causing the electrostatic latent image to be transferred from the sensitive member P onto the image receiving face of the transfer paper T.

The transfer paper T thus bearing the latent image transferred thereon is peeled off the photosensitive member P and sent to a developing station 81 by transport rollers 79 an 80 which are driven by the main motor MM all the time through the chain transmission 65 as shown.

The developing station 81 includes a developing tray 82, a transfer paper transport belt 83 in the tray 82, an inlet 84 for forcing out a developer, a pump 86 for supplying the developer to the inlet 84 through a pipe 85, a developer tank 87 incorporating the pump 86, a conduit 88 for returning excess developer from the developing tray 82 to the developer tank 87, and a group of squeeze rollers to be driven through a chain trans mission 89 by the main motor MM. The developer containing toner is supplied to the transfer paper T forwarded by the belt 83 to cause the toner to be absorbed to the electrostatic latent image on the transfer paper and to thereby visualize the image. Excess developer is removed by the squeeze rollers 90.

The transfer paper T from which excess developer has been removed by the squeeze rollers 90 is sent by a belt 91 driven by the main motor MM through the chain transmission 89 to a drying and fixing station 92, where it is subjected to air forced out by a fan 93 and warmed by a heater 94 for drying and fixing and is sent out onto a copy receiver 95.

FIG. 10 shows an example of electric circuit for controlling the apparatus of FIG. 9. Closing of the main switch SM energizes the main motor MM, a motor MP for driving the developer pump 86, and a motor MP for the drying and fixing fan 93 and also supplies current to the heater 94 to warm the air from the fan 93. Further the charge removing means 64 is turned on to light a charge removal lamp.

Energization of the main motor MM drives the transport rollers 79 and 80, developing belt 83, squeeze rollers 90 and drying and fixing belt 91. The belt for the photosensitive member P, however. is not driven because the electromagnetic clutch 31 is kept deenergized by the position control means. The energization of the pump motor MP circulates the developer and the fan motor MF drives the fan 93.

When the start switch SW is depressed with the original document 52 placed on the document table 53, a first control circuit F1 is energized to energize the electromagnetic clutch 31 to initiate the photosensitive members P1, P2, P3, and P4 into movement, energizing at the same time a high voltage transformer HV to cause the charging means 62 to effect corona discharge. Accordingly the photosensitive member PI, for example, which has been shifted to the standby position by the changeover means and position control means is charged while passing the position of the charging means 62 and is rendered sensitive.

Upon the charged photosensitive member P1 reaching the exposure position, a position detecting circuit Bl operates in response to an electric signal from the position control circuit to energize a second control circuit F2, which in turn deenergizes the high voltage transformer HV to stop the operation of the charging means 62. The clutch 31 is also deenergized to stop the photosensitive number Pl at the exposure position. At the same time, the light sources 55 are lighted to project the image of the original onto the sensitive member Pl for exposure, whereby an electrostatic latent image is formed on the photosensitive member P1.

The second control circuit F2 is controlled by an exposure amount control circuit J to be adjusted by an exposure adjusting dial (not shown) so as to control the amount (time) of the exposure.

When the second control circuit F2 has completed its operation in accordance with a predetermined program. a third control circuit F3 is energized to turn off the light sources 55 and energizes the electromagnetic clutch 31 again to further move the photosensitive members P1, P2, forward. Simultaneously with the energization of the electromagnetic clutch 31, the paper feed motor MT is driven to energize the paper size control circuit G, which in turn energizes the electromagnetic clutch 70 to drive the drawing out rollers 71 and 72 and unwind the transfer paper roll TR. Simultaneously when a predetermined length of transfer paper has been sent out. the paper size control circuit G is turned off to deenergize the electromagnetic clutch 70 and stop the unwinding of the paper. At the same time. the cutter 73 is actuated to cut the transfer paper TR to a predetermined size.

If a sheet of transfer paper TS is used as the transfer paper T. the contact point of the microswitch MSS is opened, leaving the paper size control circuit G out of operation as already described, with the electromagnetic clutch 70 and cutter 73 also kept out of operation.

In timed relation to the travel of the photosensitive member P1 subsequent to exposure, the transfer paper T is brought into contact with the sensitive face of the photosensitive member P1 by the paper feed rollers 74 and 75 driven by the paper feed motor MT. The paper and the sensitive member are fitted together snugly by the rollers 58 and 63 and the transfer of image is effected by the action of the transfer effecting unit R which grounds both rollers 58 and 63. Through further movement. the photosensitive member P1 reaches the original standby position. The position control means operates to energize the position detecting circuit B2. whereby one copying cycle is completed with the photosensitive member P1 brought to a halt.

The transfer paper T bearing the transferred image is subjected to development and drying and fixing in the already described manner, whereupon a finished copy is sent out onto a copy receiver.

The control circuit described may be operated by any of the known methods as by timer, combination of cam and microswitch or combination of relay and microswitch for effecting operations in succession.

When all the photosensitive members P1, P2 become unserviceable due to fatigue and deterioration after they have been used one after another through the action of the changeover means, the photosensitive members are taken out of the machine together with the frame 34, the photosensitive members are all replaced with fresh members and a new assembly is set in position. The drive means can be readily separated by unmeshing the gear 30 from the gear 33 to facilitate the above-mentioned procedure.

What is claimed is:

1. An electrophotographic copier comprising in combination:

a photosensitive member substantially in the form of an endless belt traversing forward and return runs about a pair of laterally spaced rollers and composed of a flexible film base having an electrically conductive face and an inorganic semiphotoconductive layer of a thickness of 0.5 to L0 micron and an organic semi-photoconductive layer of a thickness of IO to 30 microns superposed on the conductive face, exposure means for projecting the full light image of an original document to the electrically charged sensitive member lying in the full image-focal plane along a run of the belt which is parallel to the plane of the original to expose the surface to the light and thereby form an electro-.

static latent image thereon,

drive means for driving the photosensitive member from its standby position during each cycle of transfer operation, means for bringing the image receiving face of transfer paper into snug-fit contact with the latent image bearing sensitive face of the travelling photosensitive member and driving the transfer paper at the same speed as the photosensitive member, the transfer paper being composed of a base having an electrically conductive face and a dielectric coating formed thereon,

means for grounding the bases of both photosensitive member and transfer paper, the grounding means acting to electrically ground both an electroconductivc roller included in the photosensitive member driving means and the transfer paper driving means, the roller and the latter driving means acting to bring the image receiving face of the transfer paper into snug-fit-contact with the face of the photosensitive member, and

developing means for supplying toner to the transfer paper bearing the transferred electrostatic latent image so as to visualize the latent image.

2. An electrophotographic copier comprising in combination:

a photosensitive member substantially in the form of an endless belt and composed of a flexible film base having an electrically conductive face, and inorganic semiphotoconductive layer and organic semiphotoconductive layer superimposed on the conductive face,

exposure means for guiding reflected light from the face of an original document to the electrically charged sensitive surface of the photosensitive member to expose the surface to the light and thereby form an electrostatic latent image thereon,

drive means for driving the photosensitive member from its standby position during each cycle of transfer operation,

means for bringing the image receiving face of transfer paper into snug-fit contact withthe latent image bearing sensitive face of the travelling photosensitive member and driving the transfer paper at the same speed as the photosensitive member, the transfer paper being composed of a base having an electrically conductive face and a dielectric coating formed thereon,

means for grounding the bases of both photosensitive member and transfer paper, the grounding means acting to electrically ground both an electroconductive roller included in the photosensitive member driving means and the transfer paper driving means, the roller and the latter driving means acting to bring the image receiving face of thetransfer paper into snug-fit contact with the face of the photosensitive member, and

developing means for supplying toner to the transfer paper bearing the transferred electrostatic latent image so as to visualize the latent image, said photosensitive member including a plurality of photosensitive sheets arranged in an endless belt reeved around the photosensitive member driving means, with the photosensitive faces on the faces of the photosensitive sheets arranged substantially in the form of an endless belt, so as to provide a photosensitive face divided into a plurality of sections.

3. The copier as set forth in claim 2 wherein the photosensitive member driving means and the transfer paper driving means give to the photosensitive member and transfer paper rotational movement for copying cycles identical in number to the number of colors of the copying operation.

4. An electrophotographic copier comprising in combination:

a photosensitive member substantially in the form of an endless belt and composed of a flexible film base having an electrically conductive face and inorganic semiphotoconductive layer and organic semiphotoconductive layer superimposed on the con ductive face exposure means for guiding reflected light from the face of an original document to the electrically charged sensitive surface of the photosensitive member to expose the surface to the light and thereby 7 form an electrostatic latent image thereon.

drive means for driving the photosensitive member from its standby position during each cycle of transfer operation,

means for bringing the image receiving face of transfer paper into snug-fit contact with the latent image bearing sensitive face of the travelling photosensitive member and driving the transfer paper at the same speed as the photosensitive member. the transfer paper being composed of a base having an electrically conductive face and a dielectric coating formed thereon,

means for grounding the bases of both photosensitive member and transfer paper. the grounding means acting to electrically ground both an electroconductive roller included in the photosensitive member driving means and the transfer paper driving means, the roller and the latter driving means acting to bring the image receiving face of the transfer paper into snug-fit contact with the face of the photosensitive member,

developing means for supplying toner to the transfer paper bearing the transferred electrostatic latent image so as to visualize the latent image,

position control means for returning the photosensitive member to the original standby position for each cycle of copying operation and including a cam plate to be rotated one turn for each cycle of copying operation, means for giving an electrical signal to position detecting circuits upon detecting under the control of the cam plate that the photosensitive member has reached an exposure position, and means for giving an electrical signal to the position detecting circuits upon detecting that one copying cycle has been completed.

5. The copier as set forth in claim 4 wherein the photosensitive member driving means and the transfer paper driving means give to the photosensitive member and transfer paper rotational movement for copying cycles identical in number to the number of colors of the copying operation.

6. An electrophotographic copier comprising in combination:

a photosensitive member substantially in the form of an endless belt and composed of a flexible film base having an electrically conductive face and inorganic semiphotoconductive layer and organic semiphotoconductive layer superimposed on the conductive face exposure means for guiding reflected light from the face of an original document to the electrically charged sensitive surface of the photosensitive member to expose the surface to the light and thereby form an electrostatic latent image thereon,

drive means for driving the photosensitive member from its standby position during each cycle of transfer operation,

means for bringing the image receiving face of transfer paper into snug-fit contact with the latent image bearing sensitive face of the travelling photosensitive member and driving the transfer paper at the same speed as the photosensitive member, the transfer paper being composed of a base having an electrically conductive face and a dielectric coating formed thereon,

means for grounding the bases of both photosensitive member and transfer paper, the grounding means acting to electrically ground both an electroconductive roller included in the photosensitive member driving means and the transfer paper driving means, the roller and the latter driving means acting to bring the image receiving face of the transfer paper into snug-fit contact with the face of the photosensitive member,

developing means for supplying toner to the transfer paper bearing the transferred electrostatic latent image so as to visualize the latent image,

position control means for returning the photosensitive member to the original standby position for each cycle of copying operation. and

changeover means for changing over the position control means to change the sensitive face to be used for a copying operation from a particular sensitive face to another sensitive face in succession and including a cam plate to be rotated one turn for each copying cycle, detecting members arranged around the cam plate and identical in number to the number of the sections of the photosensitive face and a switching member for selectively giving an electrical signal produced by the operation of the detecting member to the position detecting circuits, the detecting member being operable to emit electric signal upon detecting the angular position of the cam plate, the switching member being operable to give only the selected electrical signal to the position detecting circuits.

7. The copier as set forth in claim 6, wherein the photosensitive member driving means and the transfer paper driving means give to the photosensitive member and transfer paper rotational movement for copying cycles identical in number to the number of colors of the copying operation.

8. An electrophotographic copier comprising in combination: a photosensitive member substantially in the form of an endless belt and composed of a flexible film base having an electrically conductive face and an inorganic semi-photoconductive layer, and an organic semi-photoconductive layer, superposed on the conductive face exposure means for guiding reflected light from the face of an original document to the electrically charged sensitive surface of the photosensitive member to expose the surface to the light and thereby form an electrostatic latent image thereon.

drive means for driving the photosensitive member from its standby position during each cycle of transfer operation, means for bringing the image receiving face of transfer paper into snug-fit contact with the latent image bearing sensitive face of the travelling photosensitive member and driving the transfer paper at the same speed as the photosensitive member, the transfer paper being composed of a base having an electrically conductive face and a dielectric coating formed thereon.

means for grounding the bases of both photosensitive member and transfer paper, the grounding means acting to electrically ground both an electroconductive roller included in the photosensitive member driving means and the transfer paper driving means, the roller and the latter driving means acting to bring the image receiving face of the transfer paper into snug-fit contact with the face of the pho tosensitive member, and

developing means for supplying toner to the transfer paper bearing the transferred electrostatic latent image so as to visualize the latent image,

the exposure means including a filter for separating the original image into three color images; the transfer paper driving means comprising a drum having a circumference equal to the entire peripheral length of the photosensitive member in the form of an endless belt, the drum being operable to retain the transfer paper on its peripheral face and move the same in synchronism with the photosensitive member with the transfer paper in snug-fit contact with the sensitive face of the member;

and the developing means including liquid developing sections of three or four colors, the developing section of each color being positionable at a developing position of the transfer paper in corresponding relation to the change of the filter, the photosensitive member driving means and the transfer paper driving means giving to the photosensitive member and transfer paper rotational movement for copying cycles identical in number to the number of colors of the copying operation.

i IF i t UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION 3,797,933 DATED March 19 197 INVENTOR(S) PATENT NO.

TA'EARA a].

Itis certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:

--[3D] Foreign Application Priority l -ata Hay 1.8, 1.97}. Japan 46-33807 Signed and Scaled this Twenty-sixth D a) f Se tember 1978 [SEAL] Attest:

Anesting Officer Commissioner of Patents grid Trademarks UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 797 ,93-13 DATED March 1 1974 INVENTOR(S) TAtI'IA, e; a].

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

--[3")] Foreign Application Priority lkata 1s, 1.271 Japan ire-33m? Signed and Scaled this T wenty-sixt D y of September I 978 [SEAL] A nest:

RUT MASON DONALD W. BANNER Arresting Ojficer Commissioner of Patents and Trademarks

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Classifications
U.S. Classification399/90, 399/154, 399/178
International ClassificationG03G15/01, G03G15/18
Cooperative ClassificationG03G15/18, G03G15/0142
European ClassificationG03G15/01S, G03G15/18