US3574456A

US3574456A - Apparatus for producing electrophotographic copies

Info

Publication number: US3574456A
Application number: US674241A
Authority: US
Inventors: Archie R Grace
Original assignee: Ricoh Co Ltd
Current assignee: Ricoh Co Ltd
Priority date: 1966-10-18
Filing date: 1967-10-10
Publication date: 1971-04-13
Anticipated expiration: 1988-04-13
Also published as: AU1273166A; AU419178B2

Abstract

Apparatus for electrophotographic sequential color printing by returning the sensitizable paper to the starting position a required number of times and exposing and developing with different color conditions each time, and an applicator for the developer. An exposure station and a developer station are provided and timing means select the color exposure and development.

Description

United States Patent {111 3,574,45

[72] inventor Archie R. Grace [50] Field of Search 355/4, 10; Collinswood, Australia 95/89 A l. N 674,241 rii d 0 Oct. 10,1967 References Wed [45] Patented Apr. 13, 1971 UNITED STATES PATENTS [73] Assignee Ricoh Co., Ltd. 3,192,846 7/1965 Wright 95/89X Nakamagome, Ohta-Ku, Tokyo, Japan [32] Priority Oct. 18, 1966 [3 3 Australia [3 l 12,731

Primary Examiner-Samuel S. Matthews Assistant Examiner-Richard A. Wintercom Attorney-Oldham and Oldham 1 ABSTRACT: Apparatus for electrophotographic sequential color printing by returning the sensitizable paper to the starting position a required number of times and exposing and [54] APPARATUS FOR PRODUCING ELECTROPHOTOGRAPHIC COPIES 8 Claims 3 Drawing Figs developing with different color conditions each time, and an [52] US. Cl 355/4, applicator for the developer. An exposure station and a 95/89, 355/10 developer station are provided and timing means select the [51] Int. Cl G03g 15/00 color exposure and development.

A X1 051. R

5 CHHRGER COMPUTL'R J l. I l

4 I? DVLOPR /9 APPARATUS FOR PRODUCING ELECT ROPHOTOGRAPHIC COPIES This invention relates to a method of and means for producing electrophotographic copies.

Electrophotographic copiers are finding extensive commercial use in office and other copying procedures where it is desired to rapidly copy data from sheets or books or the like.

One of the main advantages of electrophotographic copying is that dry and permanent copies are produced in a ready manner and in a relatively shon time.

One of the real problems with copying however is to be able to achieve a system whereby colored images can be effectively copied in black and white, because of the lack of distinction in the final copy of colors which have a somewhat similar value in the production of a latent electrostatic image.

Thus when for instance printing in black occurs on a red background, the contrast between the two colors is only a matter of intensity and therefore it is difficult with machines as used at the present time to produce satisfactory prints from many color images.

it is already well known in the electrophotographic art to produce colored images by utilizing a series of color selected negatives and to overpn'nt in the complimentary colors from these negatives, but many problems exist in this particular field such as the difficulty of achieving effective registering of the various images, applying a suitable developer, and generally achieving effective results, because of which the production of color prints has remained in what could be termed the expert" field and has not been available for use in machines equipped for office and similar purposes.

One of the objects of this invention is to provide a copier of the type generally termed as office copiers which can be used for the effective reproduction of images in color, thereby avoiding the difficulties which occur where the colored images are produced as black and white copies, and at the same time giving a much more effective and better copying of the original.

A further object is to provide an improved method of applying liquid developer to surfaces containing a latent electrostatic image, whether for color or monochromic work.

The method of producing color prints according to this invention can conveniently comprise the steps of fixing a sheet on which the color image is to be produced on to a movable element, moving the movable element to bring the sheet to an exposure station, effecting a light exposure through a filter of a first color, moving the element to bring the sheet to a developer station, projecting a liquid developer of selected color relative to the color of the filter on to the surface of the sheet to wash the face of the sheet with the developer, said developer containing pigment of the selected color in a volatile insulating carrier liquid and containing also a fixing medium efi'ective when the said carrier liquid is evaporated, evaporating the insulating carrier liquid to fix the image of the first color while moving the element to bring the sheet back to the said exposure station, effecting a light exposure through a filter of a second color, moving the element to bring the sheet to a developer station, projecting a liquid developer of selected color relative to the color of the second filter on to the said sheet, evaporating the second developer and so on until the required colors have been applied to the sheet to produce the color image.

The machine may comprise; means to receive and transport the sheet on which the image is to be produced sequentially through stations in a recurring path, means to effect exposure colorwise, means to effect developer colorwise by means of a liquid developer which fixes on evaporation of the carrier liquid and in which the toner is carried, and timing means to sequentially select colorwise exposure and development, whereby the copy sheet is first exposed to a selected color image, is then wet developed by the complimentary color, then returns to the exposure position while a different color image is produced and then passes through the complimentary developer and so on until the complete color values required have been reproduced.

In order however that the invention can be fully appreciated embodiments thereof will now be described with reference to the accompanying drawings, but it is to be clear that the invention need not necessarily be limited to details referred to, the scope being defined in the claims herein.

in the drawings:

FIG. 1 shows schematically a machine for carrying out this sequential development of three color images,

FIG. 2 is a schematic view showing one of the developer trays by means of which an upward flow of developer can be maintained, and

FIG. 3 shows a modified developer tray. 1

in FIG. 1 an endless conveyor 1 passes around

sprockets

2 and 3 at each end and is driven by means of a suitable motor mechanism 4 which can be variable speed or duplicated so that the endless conveyor can be moved on at different rates if this is required such for instance as the motion between one of the operations and the next could entail fast movement of the conveyor but while the image which is being treated is in the actual treatment station the conveyor can be stopped or slowed down as required.

The charging is carried out in any normal manner from a charging unit 5 which applies a corona field between the electrodes 6 and 7 so that when the photoconductor sheet is disposed in the zone 9 the surface thereof can be charged preparatory to moving to the zone 10 where the surface is light modified by the exposure device 11 which can be of any general or approved type, a projector being shown in this instance.

Associated with the projector is a carrier 12 which is movable and has on it filters 13, 14 and 15 corresponding to the primary colors generally used in color reproduction work and the carrier 12 is so movable that either the filter 13 or the filter 14 or the filter 15 can be brought into operative position.

The image so produced is projected to the zone 10 by the mirror 16 which effects the necessary image reversal.

Development is effected by means of three

separate developer units

17, 18 and 19, the developer unit 17 containing the complimentary color to the filter 13, the unit 18 containing the complimentary color to the filter 14 and the unit 19 containing the complimentary color to the filter 15.

The

developer mechanism

17, 18 and 19 can each comprise a tray 20 (see FIG. 2) having a series of inclined vanes 21 in it which are horizontally guided but are operated through a crank 22 and a connecting rod 23 in such a manner that they oscillate to cause the developer to be splashed up between and around the vanes 21 so long as the crank 22 operates.

The developer is thus upwardly projected from the trays, but preferably obliquely to the face of the sheet as shown to give a washing action over the sheet. The developer may be directed so as to move in the direction of movement of the sheet or in opposite direction to the sheet.

The agitation can of course be effected in any other manner such as by an electric vibrator or the like, or a pump could be used with fixed guide vanes, the object of this unit being simply to lift developer into the

zones

24, 25 and 26 over which the sheet 6 passes as the endless conveyor carries it around the cycle.

FIG. 3 shows a developer tray comprising a container 30 having in it a flap valve 31 with an aperture 32 with a flexible valve membrane 33 over it, the flap valve 31 being actuated from a shaft 34 of an oscillatory motor 35 such as a windscreen wiper motor, fixed vanes 36 then directing the liquid against the sheet to be developed which passes along the plane 37. The vanes direct the liquid obliquely to the sheet so that the liquid flows along the sheet and from the sheet back to the tray.

A computer 22 or similar device is coupled to the carrier 12 and to the actuating mechanisms of the

developer units

17, 18 and 19 in such a manner that the correct developer is applied in relation to the previous exposure made and this computer also controls the forward motion of the endless conveyor and actuates locking means by means of which the exact register of the images is obtained at the exposure station 10 as well as controlling the endless conveyor motion, the charging and other factors.

In this way during a typical action a color slide or the like is put into the exposing device 11 and a sheet of zinc oxide or similar paper 8 fixed to the endless conveyor 1 and on commencement of the cycle the sheet 8 is charged as it passes between the electrodes 6 and 7 which of course must be carried out in the dark, and the endless conveyor moves the sheet 8 to the exposure station 10 where after selection of the correct color filter an exposure is made.

The endless conveyor now moves the paper 10 around to the first developer station mechanism 17 and, while the conveyor continues to move, developer is projected upwardly against the face of the paper and the image is developed, drying taking place after development is completed. Paper movement continues until it again reaches the charging position, where at the station 9 it is again charged and proceeds on to the exposure station to receive the next exposure, which in this case would be through the filter 14. After exposure, development would take place from the developer mechanism 18, the subsequent travel utilizing the filter l5 and the developer mechanism 19.

It will be realized that instead of using fixed developer mechanisms these could be moved in the same manner as is suggested in the filters on the carrier 12. Instead of using a projector the device could be arranged for book copying or the like by appropriately changing the exposure device.

lt will of course be obvious that in a simple form of a machine it may be desirable to use only two colors for any particular copying or it may be that a picture can satisfactorily be produced by utilizing a single color, but it will be clear that as the sheet on which the image is being produced can pass successively through the same path, it is then possible to provide timing mechanism which will bring the appropriate color filters into position, and the latent image so produced will then be developed by the appropriate color, register of the colors being assured because the system passes the sheet through the same path until the required number of prints have been made.

It will of course in obvious that the sheets on which the printing is effected can be carried on a disc or drum or other member which will maintain the correct sequential positioning, and vice versa the sheet itself may be kept stationary and the other elements of the copier brought sequentially in relation to it, or a combination of both of these means may be used. The invention can be applied either to the system where the exposure is effected by progressive projection of the image as the sheet is carried forward, or the sheet can be stopped to allow the image to be projected while the sheet is stationary.

Refinements can be introduced such as light fatiguing by exposing to a strong light prior to the charging operation, and also it will be appreciated that with the more recently developed techniques of producing an image by the chargeless method" that the charging step could be eliminated, or it could be moved in position to occur after rather than before the forming of the latent electrostatic image. A drier which dries the surface of the sheet after each development may be used.

it will however be clear that in a copier of this type, when a color picture is to be copied, it is placed on to the window or other means whereby it is brought into position for copying, and the machine can then effect the necessary number of passages of the sheet on which the copy is being made to allow each color to be sequentially reproduced on the final copy.

Timing of such a machine presents no problems due to the sheet generally following the same path, and therefore register can be readily effected, in fact this is much simpler than in the methods used at present where either different negatives have to be used or different exposure methods resorted to, and where the sheet must be removed from the machine for development between each of the actions.

The various color filters can of course be moved by an indexing system or by a computer and the color intensities can be appropriately adjusted by a meter or the like.

The various developers can readily be positioned in trays or the like at an appropriate part of the travel of the sheet which is to have the image developed thereon, and these can be energized according to the particular color required at each stage.

The developer can be applied in any manner but preferably it is projected upwardly against an image carried on a belt or the like by movement or agitation of vanes or the like as has been described and which cause the developer to rise within the trays to effect development, it being then a simple matter to have a series of these trays with different colored developer (and if desired including biased developer), and for the mechanism to actuate only any particular required colored section so that only this color is applied at the appropriate time.

It will be realized from the foregoing that a machine which has very little more complication than an ordinary black and white copier can be produced. The charging, exposing, and developer means can all be of a construction similar to that used heretofore, and the only added matter is the color filter or exposure system and the selection of one of a series of developer colors at appropriate stages of the passage of the sheet on which the reproduction is being made.

The use of liquid developer removes the need of a fusing or fixing section, and as fixing is by evaporation of the carrier liquid, this can be readily and quickly achieved. Also the liquid developer does not give rise to problems of transport of developer dust to unwanted areas, as can be the case with dry developers, and further, liquid developers can be projected upwards readily as shown in the illustrations to allow a belt to be effectively used. Dangerous heat fusing mechanisms are unnecessary.

It will also be appreciated that while such a copier can give effective color reproduction in a simple manner and by relatively simple apparatus, the unit can at the same time be used to produce copies in a single color by simply controlling the function regulating mechanism, and in this way for instance a black developer could be used to produce copies which would be similar to those produced by machines in operation at the present time. However, by simply resetting the machine, development could take place in any particular color and with or without color filters being in operation so that the machine can be used to reproduce work in the same manner as the single color machines at present in use but has the advantage of allowing a selection of a color in which a monochromic work is produced, or allows full color reproduction in cases where this is required.

Additionally it is obvious that by simple adaptation this invention can be incorporated as an effective camera or photogravure camera.

I claim:

1. An electrophotographic color copier of the type wherein a photoconductive sheet has a latent electrostatic image produced thereon at an exposure station and then passes through a developing station, characterized by: means to receive and transport the said sheet on which the image is to be produced sequentially through said stations in a recurring path, means to efi'ect said exposure colorwise, means to effect said developer colorwise by means of a liquid developer which fixes on evaporation of the carrier liquid and in which the toner is carried, and timing means to sequentially select said colorwise exposure and development, whereby said copy sheet is first exposed to a selected color image, is then developed by the complimentary color with a liquid developer, then returns to the exposure position while a latent image conforming to a different color is produced and then passes through the complimentary developer and so on until the complete color values required have been reproduced.

2. An electrophotographic color copier according to claim 1 wherein an image is projected onto a photoconductive sheet carried on a moving member, and is developed by directing liquid developer upwardly on to the face of the photoconductive sheet as it passes face down above a tray from which the liquid projection takes place.

3. An electrophotographic color copier according to claim 1 wherein the developer is directed against the face of the photoconductive sheet by vanes which move in a tray of liquid and are shaped to direct the liquid upwards during such movement.

4. An electrophotographic color copier according to claim 1 wherein the developer is placed into motion and is then directed upwards by fixed vanes.

5. An electrophotographic color copier according to claim 4 wherein the developer is directed so that it strikes the face of the photoconductive sheet obliquely to cause the developer to move over the sheet and return to the developer tray.

6. An electrophotographic color copier according to claim 1 wherein the photoconductive sheet is subjected to a corona discharge prior or after each colorwise exposure.

7. An electrophotographic color copier of the type wherein a photoconductive sheet has a latent electrostatic image produced thereon at an exposure station and then passes through a developing station, characterized by: a belt to hold and transport the said sheet on which the image is to be produced sequentially through said stations in a recurring path, said path including movement of the belt over developer means with the face of the photoconductive sheet facing downwards, means to effect said exposure colorwise, means to effect said development colorwise by means of a liquid developer which fixes on evaporation of the carrier liquid and in which the toner is carried, said developer being projected upwardly onto the said photoconductive sheet, and timing means to sequentially select said colorwise exposure and development, whereby said copy sheet is first exposed to an image of a selected color, is then developed by liquid of the complimentary color by washing the liquid upwards against the face of the photoconductive sheet, then returns to the exposure position after drying of the developed image by evaporation of the carrier liquid of the developer where a latent image of a different color value is then produced, and then passes through the complimentary developer and so on until the complete color values required have been reproduced.

8. An electrophotographic color copier according to claim 7 wherein color filters are successively interposed in a liquid image which is projected onto the photoconductive surface, and each developer is contained in a tray provided with means which successively raises the liquid developer to a higher level to contact the sheet, and means to correlate the movement of the filters and the developer tray actuating mechanism for successive exposure and development.

Claims

2. An electrophotographic color copier according to claim 1 wherein an image is projected onto a photoconductive sheet carried on a moving member, and is developed by directing liquid developer upwardly on to the face of the photoconductive sheet as it passes face down above a tray from which the liquid projection takes place.
3. An electrophotographic color copier according to claim 1 wherein the developer is directed against the face of the photoconductive sheet by vanes which move in a tray of liquid and are shaped to direct the liquid upwards during such movement.
4. An electrophotographic color copier according to claim 1 wherein the developer is placed into motion and is then directed upwards by fixed vanes.
5. An electrophotographic color copier according to claim 4 wherein the developer is directed so that it strikes the face of the photoconductive sheet obliquely to cause the developer to move over the sheet and return to the developer tray.
6. An electrophotographic color copier according to claim 1 wherein the photoconductive sheet is subjected to a corona discharge prior or after each colorwise exposure.
7. An electrophotographic color copier of the type wherein a photoconductive sheet has a latent electrostatic image produced thereon at an exposure station and then passes through a developing station, characterized by: a belt to hold and transport the said sheet on which the image is to be produced sequentially through said stations in a recurring path, said path including movement of the belt over developer means with the face of the photoconductive sheet facing downwards, means to effect said exposure colorwise, means to effect said development colorwise by means of a liquid developer which fixes on evaporation of the carrier liquid and in which the toner is carried, said developer being projected upwardly onto the said photoconductive sheet, and timing means to sequentially select said colorwise exposure and development, whereby said copy sheet is first exposed to an image of a selected color, is then developed by liquid of the complimentary color by washing the liquid upwards against the face of the photoconductive sheet, then returns to the exposure position after drying of the developed image by evaporation of the carrier liquid of the developer where a latent image of a different color value is then produced, and then passes through the complimentary developer and so on until the complete color values required have been reproduced.
8. An electrophotographic color copier according to claim 7 wherein color filters are successively interposed in a liquid image which is projected onto the photoconductive surface, and each developer is contained in a tray provided with means which successively raises the liquid developer to a higher level to contact the sheet, and means to correlate the movement of the filters and the developer tray actuating mechanism for successive exposure and development.