DE2428732B2 - METHOD AND DEVICE FOR ELECTROPHOTOGRAPHIC COLOR REPRODUCTION - Google Patents

Description

The invention relates to a method according to the preamble of claim 1 and a Device for carrying out the method.

Various olectrophotographic processes have so far been used for color reproduction, such as the Carlson process, in which an electrostatic charge image is created on a photosensitive Material is formed, the NP process, in which an electrostatic charge image is relatively high Contrast is created with the help of a photosensitive material that has an insulating cover layer on top of a light-sensitive layer, the TESI process, in which the electrostatic charge image Transferring recording paper and then developing it, or the grid method the first on a light-sensitive grid with a large number of small openings an electrostatic Charge image is formed and then a recording material is opposed to the grid in order to this for generating an image corresponding to the charge image on the grid with toner particles or To apply coronaions through the grid openings.

As is well known, these electrophotographic processes can also be grouped according to two systems, namely, according to the direct system in which the reproduced image is as it is on the recording material is fixed, and the transfer system in which the on the light-sensitive material The generated image is transferred to an image receiving material and is only fixed there. In detail will the image in the case of a colored original according to the direct system by repeating one three or four times electric charging, exposure through color decomposition filters, development and fixing obtained while the color image in the transfer system by repeating the cleaning of the photosensitive Recording material, electrical charging, exposure through color separation filters, des Developing and transferring the color separation to the image receiving material.

This arises in the case of the devices for carrying out the above-mentioned process steps Problem that the color developing agents used for color reproduction easily move in the developing area and mix in the cleaning area of the recording material. So far it has been customary for such Discharge of developing agent mixtures as waste, as they are able to reproduce the hue of the generated Affect the image. However, the accumulation of such waste requires additional maintenance on the device and difficulties in disposing of waste. In addition, the Very high consumption of developing agents.

The invention is based on the object of a method according to the preamble of the patent claim 1, which is characterized by low consumption of developing agent and a allows low-maintenance device to carry out the method.

According to the invention, this object is given in the characterizing part of claim 1. -, en means resolved.

The developing agents removed from the surface of the recording material are thus processed in the following manner It is generated that they are mixed with black developing agent and used as black developing agent can be used again. This brings an extraordinary saving in developing agent, since as a rule The need for black and white copies is likely to be greater Is the need for color copies. With a device for Implementation of the method according to the invention, which is between multicolored copying and monochrome Copying can be switched, so there are considerable amounts of black developing agent, tel, whereby the removal of the Recording material from this developing agent obtained as waste is completely eliminated.

If at least developing agents are used in the three primary colors, the proportion to the 2 »the black developing agent mixed recovered developing agent of three primary colors preferably 65 wt .-% of the mixture does not überchreiten so that the developed image of the resultant developing agent mixture actually than y, to be addressed in black. Advantageously, when the recovered developing agent is mixed with black developing agent and this mixture is stored, the color tone thereof is detected and the mixing of black developing agent is controlled as a function of the measured color tone. In this way it is automatically ensured that images that appear black enough are always developed even if the individual color developing agents are contained in the mixture in widely differing concentrations.

The device according to claim 4 for performing the method works very economically and is easy to maintain, with virtually no loss of developer. It can be used for mask reproduction and used for monochrome reproduction.

The invention is described below with reference to the description of exemplary embodiments explained in more detail on the drawing.

Fig. 1 shows a vertical section of the invention Color reproduction device in schematic

Depiction; ,, ^ n j

Fig. 2 is a perspective view of the color developing agent recovery device is provided on the cleaning device of the reproduction apparatus;

3 is a block diagram for explaining an embodiment for the recovery of the mixed Re-use developing agents;

Fig. 4 is a circuit diagram of an embodiment the means for determining the hue of the mixture of the color developing agent and black Developing agent.

Fig. 1 shows the construction of a reproduction device which works with wet development and a photoconductive recording material with an insulating cover layer auiwcisi u., _U ^.,. V ..- .. ·. ~~. _e reproduction or reproduction of a color original can be obtained. The color original 2, which lies on a transparent support 1, is irradiated by a light source 3. The light emitted by the light source 3 passes through mirrors 4 and 5 through an objective and passes through a color separation filter 7a, which is supported by a turret 7 for the color separation filter, which is switched over as a function of the respective color separation; The light is then reflected by means of mirrors 8 and 9 through an AC charger 12 onto the drum 10 carrying the recording material.

In the above optical system, the light source 3 and the mirrors 4 and 5 become synchronous with the Rotation of the drum 10 shifted to their positions 3 ', 4' and 5 '. The recording material on the drum 10 is cleaned by a cleaning blade 24, electrically charged by means of a primary charger U and discharged by means of the AC charger 12 simultaneously with the image exposure.

The recording material exposed in this way is then subjected to a roller exposure of its entire surface by means of a further light source 13 and developed by one of the developing tanks 14, 15, 16 and 17. Each of these developing tanks is supplied with a specific developing agent from one of the developing tanks 14 ', 15', 16 'and 17'. The developing tanks are constructed to slide to the developing position and back in synchronism with the movement of each of the respective color separation filters 7a, Tb, Tc and 7din of the turret 7. The excess amount of developer adhering to the recording material is squeezed off with the aid of an electric charger provided for 2um squeezing or stripping. On the other hand, a copy paper 19 is set in motion by a roller 20 and held on an image transfer drum 21 adjacent to the drum 10. The image developed on the recording material on the drum 10 is therefore transferred to the copy paper held on the drum 21 at the tangential contact line between the two drums.

In the event that a color reproduction is made Should be 0, the aforementioned procedural steps are repeated three or four times, whereupon the Copy paper 19 detached from the transfer drum 21 and by means of a conveyor belt 22 to a Image fixing device 23 is worn where the overran frozen image to complete the copy. The transfer drum 21 is otherwise by a movable cleaning blade 25 cleaned, so that the reverse side of the subsequent copy paper does not come through any foreign matter left on the drum can become dirty.

If, on the other hand, a monochrome copy is to be obtained, the exposure is carried out through the filter To, with the charge image on the recording material being developed through the developing container 17. In this case, it goes without saying that the copying paper is detached from the transfer drum 21 after a transfer operation has been completed, the fixing device is fixed and output.

In the course of the aforementioned development

no and cleaning processes take place at the Reini

supply blade 24 of the reproduction device unver

Mixing or mixing of the development can be avoided

lungsmiitel st; itt. Such mixing also occurs in de

Close the developer tanks 14, 15, 16 and 17, d

h ^r ) the developing agent at these points tends to

to drip down. Furthermore, the development '

medium, which with the help of the electric charger 18 from dt

Surface of the photosensitive drum 10 abgt

be streaked, a mixture of colors. The mixed ones or mixed developing agents are recovered by various kinds of auxiliary agents. For example, on each of the developing tanks, the electric charger for scraping, the cleaning blade is attached etc. a collecting vessel is provided so that the dripping and Entwieklungsmitiel collected therein and supplied to the black toner developing container or the black developing agent storage tanks by piping can be. As explained below, it is of course possible to use these collected developing agents first then to lead into the desired container, if the color tone and concentration are set appropriately are.

A diluent for the developing agent can be applied to the cleaning blade 24 Let the liquid supply pipe 26 flow so as to prevent the recovered developing agent from flowing adheres to the cleaning blade so that the developing agent along with the diluent is recovered. The toner caught by the cleaning blade 25 can also be used a colorless diluent for the developing agent on this cleaning blade 25 flow away and recover it so that the copy paper held on the transfer drum is not is polluted. For this liquid recovery is detailed in the description of the British Patent 13 26 786 (DT-AS 20 47 130) explained construction of the photosensitive body for example particularly suitable.

It is also possible that the recovered liquid is initially collected in a collecting container and then a specific concentration with a concentrated black developing liquid for reuse, or that the recovered liquid is placed directly in a container for introduced the black developing agent and adding the concentrated black developing agent is used again depending on the need for this.

F i g. Fig. 3 illustrates an embodiment of a control mechanism for adjusting the concentration of the developing agent. According to this control mechanism, the recovered developing agent is collected in a collecting tank 31 and then fed into a mixing tank 35 through a valve 33 . The mixing tank 35 is provided with an end detector 351 of the control circuit to detect and control the color tone and an agitator 352 to make the concentration of the developing agent uniform.

F i g. 4 shows an embodiment of a mechanism for determining the color shade and for control, in which the end detector 351 is provided with a plurality of photocells CdS \ .CdS2 and CdS3 which have a red, a blue and a green filter f \, fl and / "3 and to which a single white light source LP 1 is common. With this circuit configuration of the end detector 351 , the valve 33 of the collecting tank 31 or the valve 34 of the reservoir 32 for black developing agent shown in FIG closed.

When the output of each photocell is substantially the same. For example, valve 33 is opened in the hue control.

while if any of the photocells provides a different output signal, valve 34 is opened. Otherwise, valve 33 is constantly open and an upper value is set for the strength of each hue, and if any of the detent elements exceeds the upper limit of the set value, valve 34 is opened so that the desired result of hue adjustment is obtained. The embodiment shown in Fig. 4 corresponds to this design, in which each set value can be set as desired by regulating one of the input terminal potentials of each operational amplifier by means of each variable resistor VR 1, VR ₂ or VRi.

In this way, the developing agent present in the mixing tank 35 shown in FIG. 3 can always be black or held to a hue recognized to be substantially black.

On the other hand, opening and closing of a valve 37 provided between the mixing tank 35 and a developing unit 38 is controlled by the output of another end detector 381 provided in the developing unit 38 , whereby the concentration of the developing agent can be kept at a constant level.

Although the above description is based on liquid development, it is of course possible that almost the same construction, function and effect can be achieved in the case of using a dry developer. In this case, the recovery blades, etc. may also be constructed as shown in the drawing, although particular attention should be paid to the layout of the recovery and conveying devices for the developing agent which is in powder form. As in Fig. As shown in Fig. 2, a screw 28, the total length of which corresponds to the drum width, is positioned just in front of the cleaning blade 24 and transversely transports the powdery developing agent which has been stripped from the blade. The powder developer transported sideways in this way is then collected in a channel 29 through which it is conveyed to the development unit. On the other hand, the collected powder developer can also be fed into the development unit via a pipe with the aid of a suction fan. Finally, a funnel-shaped container 291 for storing a certain amount of the transported developing agent is provided at the end of the chute or tube 29, if a valve is opened and closed by the operation of a solenoid SDL when a predetermined amount of the transported powder developer is opened with the aid of a lamp LP and a photocell CdS is detected.

For a better understanding of the invention as described above, see ™ below the result of an experiment with the critical amount of each of the color developing agents has been determined experimentally, which may be present in the ι black developing agent.

There were color developing agents for blue, red around yellow, and each of these developing agents was added in a certain amount for each of the below cases listed with black development mitu, mixed. Then using de above-described reproduction device carried out a monochrome reproduction to the critical To find out the amount of admixture at which the color is de

reproduced image is no longer recognized as truly black. The results are as follows:

I colored developing agent, Critical mixed quantity the one with black development with black was mixed medium Developing agent blue 200/0 Red 10% yellow 200/0 blue + red (*) 30% red + yellow (*) 200/0 yellow + blue (·) 25% blue + red + yellow (*) 65%

(*) Each development agent in an equivalent amount.

As described in detail above, the reproduction apparatus is able to handle the mixed development

treatment compositions to regenerate so that no occurring after developing developer waste is to be feared and any loss can be reduced at developing agent, resulting in a ^r> very economical maintenance and operation contributes to the reproduction device.

Incidentally, in a reproduction apparatus for office use, both multicolor reproduction as well as monochrome reproduction,

ι »the mixed developing agent as it is, can be used without requiring any complicated color tint control when in the case of monochrome reproduction, the color tone of the copies produced is not important.

I ¹ J Further, if the mixed developing agent is mixed with black developing agent for reuse, a good black tone can easily be obtained if a detector and control element of known type is used, which greatly simplifies the construction of the device.

For this purpose 3 sheets / attachments

Claims (7)

Patent claims: 1. Process for electrophotographic reproduction, in the case of electrostatic air images on an electrophotographic recording material are formed, the charge images each with a developing agent from a Selection of developing agents of different color to be developed and the surface of the Recording material after the transfer of the respectively developed image for reuse is cleaned, characterized in that that the after and optionally before de / image transfer from the surface of the recording material removed developing agent can be regenerated by mixing with black developing agent and the developing agent mixture thus obtained for developing charge images in black is used. 2. The method according to claim 1, wherein at least developing agents are used in the three primary colors are characterized in that the proportion of the black developing agent mixed recovered developing agent of the three primary colors 65% by weight of the mixture does not exceed. 3. The method of claim 1 or 2, wherein at least developing agents in the three primary colors are used, characterized in that when mixing the recovered developing agents the color tone of the same with black developing agent and storing the mixture detected and the admixing of black developing agent as a function of the measured Tint is controlled. 4. Device for performing the method according to one of the preceding claims I to 3 having developing means for developing electrostatic charge images on electrophotographic Recording material in different colors and a cleaning device for cleaning of the recording material after the transfer of the developed images, characterized in that that the developing device comprises a unit (17; 38) for developing charge images in black, to which the developing agents can be fed via a transport device, which from recovery means (31 to 36) from the developing agents removed from the recording material different color can be recovered. 5. Device according to claim 4, characterized in that the transport device (28, 29) has a device (CdS, LP) for determining the amount of the recovered different colored developing agent and a device (SDL) for the amount-dependent control of the transport. 6. Apparatus according to claim 4 or 5, characterized in that the recovery device recovered developing agent storage means (35) and means (15!) For detecting the color tone of the developing agent in the storage device. 7. Apparatus according to claim 6, characterized ι indicates that the recovery device includes means (32, 34, 36) for feeding and Adding an additional amount of black developing agent depending on the color tone having.