JPS63292155A - Color recording method - Google Patents

Abstract

PURPOSE:To facilitate the removal of a toner which has been mixed into a developing device, and to contrive the improvement of the picture quality by forming a toner image of two colors or more on a photosensitive body, and attracting selectively and electrostatically a mixed toner electrified to the opposite polarity to the toner used for its developing device, to a prescribed part on the photosensitive body, when the toner of the toner image formed previously has been mixed into the developing device in the subsequent developing process. CONSTITUTION:Materials of a toner and a carrier are selected in advance so that the toner of a developing device 6 is electrified to the positive polarity, and the mixed toner is electrified to the negative polarity. A photosensitive body 1 suspends the formation of an electrostatic latent image at the time of a cleaning work of the developing device 6, and during that time, the position electrode of a DC power source 64 is connected thereto. Also, a developing roller 61 is grounded. In this state, the photosensitive body 1 rotates in the direction as indicated with an arrow 63. In such a way, the mixed toner 32 electrified to the negative polarity is attracted electrostatically to the photosensitive body 1. On the other hand, the toner 31 electrified to the positive polarity sticks to the carrier 30 as it is and remains in a second developing device 6. In such a way, the mixed toner 32 which has been attracted selectively to the photosensitive body 1 is removed from the outer peripheral surface of the photosensitive body 1 by a cleaning device thereafter.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a color recording method for recording a color image on recording paper using an electrophotographic recording method.

``Prior Art'' In the conventionally well-known electrophotographic recording method, a photoreceptor is uniformly charged, and a light image is formed on the photoreceptor for exposure, thereby forming an electrostatic latent image. After that, the electrostatic latent image is developed to form a corresponding toner image, and the toner image is transferred onto recording paper.

Various methods of recording color images using such electrophotographic recording methods have been developed as described below, but each method has its own problems.

"Problems to be Solved by the Invention" First, FIG. 6 shows a schematic diagram of the so-called overlap transfer method.

In this method, the photoreceptor is charged, exposed, developed, and transferred multiple times. For example, the first time is a black image, the second time is a red image, and the third time is a blue image. In this method, an electrostatic latent image corresponding to an image of a certain color is formed, and development and transfer thereof are repeatedly performed using toner of a corresponding color (Japanese Patent Application Laid-open No. 48871/1983).

This device includes a pre-clean corotron 2, a cleaning device 3, a charger 4, and a first developer 5 on the outer periphery of a photoreceptor 1.
, a second developing device 6, a third developing device 7, and a transfer device 8 are arranged. Furthermore, an exposure section 10 is provided between the charger 4 and the first developer 50. Furthermore, photoreceptor 1
A hollow transfer drum 9 is disposed so as to be circumscribed by the transfer portion 11 . The recording paper 12 is wound around the transfer drum 9, and as the transfer drum 9 rotates, the recording paper 12 passes through the transfer B11 repeatedly.

In this apparatus, first, when a black image is exposed, the electrostatic latent image is developed by a developing device 5 containing black toner. The toner image is transferred onto recording paper 12 by transfer section 11 . Next, a red image is exposed, and the electrostatic latent image is developed by a developing device 6 containing red toner. The toner image is transferred in the transfer section 11 onto the recording paper 12 that has been wrapped around the transfer drum 9 and made one revolution. Similarly, when the blue toner image is transferred onto the recording paper 12, the recording paper 12 is released from the transfer drum 9 and heads toward the fixing device 13. In this way, a total of three color images can be recorded.

However, in an apparatus with such a configuration, the space for installing the transfer drum 9 is relatively large, which leads to an increase in the size of the apparatus.Also, the process from exposure to transfer is repeated for the number of colors used, resulting in a slow copying speed. The problem is that it is late.

FIG. 7 shows a schematic diagram of an apparatus employing a different sequential transfer method.

In this method, a separate photoreceptor is prepared for each color, and the charging, exposure, development, and transfer of the photoreceptor are performed in separate steps.For example, the first step is to create a black image, and the second step is to create a red image. This is a method of sequentially transferring data onto recording paper 12 (Japanese Patent Application Laid-Open No. 1983-1999)
-36767).

In this device, a pre-clean corotron 2, a cleaning device 3, a charger 4, and a black toner developer 5 or a red toner developer 6 are arranged around the outer periphery of each photoreceptor 1. Furthermore, exposure sections 10 and 20 are provided between the charger 4 and the developer 5 or 6, respectively. Furthermore, a transfer device 8 is arranged below each photoreceptor l.

The recording paper 12 has two transfer parts 11a in the direction of the arrow in the figure;
llb to the fixing device 13.

In this way, a total of two color images can be recorded.

Although an apparatus having such a configuration does not have the disadvantage that the copying speed is slow, it has the disadvantage that the apparatus becomes larger because a plurality of photoreceptors 1 and the like are provided for each color.

Furthermore, in both of the above two methods, toner images of different colors are superimposed on the recording paper, so if the transfer position is not aligned accurately during the second and subsequent transfers, color misregistration will occur, resulting in so-called high precision. It also has the disadvantage of requiring registration.

Now, FIG. 8 shows a schematic diagram of an apparatus employing the so-called overlapping development method (Japanese Patent Application Laid-Open No. 124354/1983).

This device includes a Briclean corotron 2, a cleaning device 3, a charger 4, a first developer 5, a second developer 6, a pre-transfer corotron 14, and a transfer device 8 on the outer periphery of the photoreceptor 1.
and are arranged. Also, a charger 4 and a first developer 5
A first exposure section 10 is provided between the first developing unit 5 and the first developing unit 5.
A second exposure section 20 is provided between the first developing device 6 and the second developing device 6 .

In this device, after uniformly charging the photoreceptor 1, an electrostatic latent image is formed with positive polarity in the first exposure section 10, and an electrostatic latent image with negative polarity is formed in the second exposure section 20, based on the charged potential. Electrostatic latent images are formed and developed with different colored toners of different polarity. In this way, two-color toner images are formed on the photoreceptor 1, and these toner images are transferred to the recording paper 12 all at once.

Since this method develops a two-color image by forming a so-called ternary latent image, there is no reduction in copying speed, and there is no need for highly accurate registration.

However, there is an upper limit to the charging potential of the photoreceptor, and when that potential is divided into two and charged to opposite polarities, the potential contrast of both the first electrostatic latent image and the second electrostatic latent image is The problem was that it was half of the normal amount. moreover,
In order to carry out such exposure, a special photoreceptor must be used, and there is also the drawback that it requires modulation of the energy of the light.

On the other hand, FIG. 9 shows a schematic configuration diagram of an apparatus employing a color recording method using a similar overlapping development method but forming a latent image using a different method.

This device includes a pre-clean corotron 2, a cleaning device 3, a first charger 4, a first developer 5, a second charger 15, a second developer 6, and a transfer device on the outer periphery of the photoreceptor 1. A front corotron 14 and a transfer device 8 are arranged. Also,
A first exposure section 10 is provided between the first charger 4 and the first developer 50, and a second exposure section is provided between the second charger 15 and the second developer 60. 20 are provided.

In this device, after the photoreceptor 1 is uniformly charged by the first charger 4, an electrostatic latent image is formed in the first exposure section 10, and the first developer 5 uses, for example, black toner to form an electrostatic latent image. Develop. Next, after the photoreceptor 1 is uniformly charged again by the second charger 15, an electrostatic latent image is formed in the second exposure section 20, and a second
The image is developed using, for example, a red toner in a developing device 6. In this way, two-color toner images are formed on the photoreceptor 1, and these toner images are transferred to the recording paper 12 all at once.

This method also does not reduce copying speed and does not require highly accurate registration.

However, in the second developing device 6, the toner image already formed on the photoreceptor 1 may be disturbed and the developed density may be reduced, or the toner may be mixed into the second developing device 6 and the toner image already formed on the photoreceptor 1 may be disturbed. This has had the disadvantage of causing problems such as a shortened lifespan of the developer. Therefore, a method is adopted in which a roll for removing mixed toner is provided in the second developing device 6, and a voltage of opposite polarity to that of the mixed toner is applied to the roll to electrostatically attract and collect the mixed toner. was.

However, this method has the disadvantage that many parts are added to the second developing device, resulting in an increase in the size of the device. Therefore, it becomes impossible to achieve miniaturization of the apparatus, which is an advantage of the overlapping development method.

The present invention was made with attention to the above points, and uses the overlapping development method to enable small-sized and high-speed copying, and further improves image quality by making it easier to remove toner mixed into the developing device. The object of the present invention is to provide a color recording method that allows for color recording.

"Means for Solving the Problems" The color recording method of the present invention involves forming an electrostatic latent image on a charged photoreceptor, and developing the electrostatic latent image to form a toner image. The process is repeated multiple times to form toner images of two or more colors on the photoreceptor, and when the toner of the previously formed toner image gets mixed into the developing device in the later developing process,
This system is characterized by selectively electrostatically adsorbing mixed toner that is charged to the opposite polarity to the toner used in the developing device on a predetermined portion of the photoreceptor, and collecting this toner with a cleaning device. be.

"Operation" In the above method, the toner mixed in the developing device is removed as follows, and the quality of the toner in the developing device is maintained.

That is, the material of the carrier is selected so that when toner from another developing device mixes into the developing device, the mixed toner will be charged to the opposite polarity to that of the toner itself. When a constant electric field is applied between the developing device and the photoreceptor at a predetermined timing, only the mixed toner is electrostatically attracted to the photoreceptor.

An electrostatic latent image is formed on the photoreceptor for the recording operation, and a toner image is formed thereon.After this operation is completed, while the photoreceptor is running idle, the mixed toner is deposited on the surface of the photoreceptor. Make it adhere.

By cleaning this with a cleaning device, toner mixed in the developing device can be immediately removed from the developing device.

Embodiment FIG. 2 shows a schematic diagram of an apparatus suitable for carrying out the color recording method of the present invention.

This device includes a pre-clean corotron 2, a cleaning device 3, a first charger 4, a first developer 5, a second charger 15, a second developer 6, A pre-transfer corotron 14 and a transfer device 8 are arranged. Also,
A first exposure section 1o is provided between the first charger 4 and the first developer 50, and a first exposure section 1o is provided between the first charger 4 and the second developer 6.
A second exposure section 20 is provided between them. The recording paper 12 is sent out from the paper feed tray 16 and transferred to the transfer device 8.
and the photoreceptor 10, and is discharged via the fixing device 13.

Note that the first exposure section 10 and the second exposure section 20 of this apparatus
For this purpose, a so-called imaging optical system using a mirror or lens system, or a so-called optical writing device such as a laser diode array, a light emitting diode array, a liquid crystal shutter array, or a fluorescent display element array is used.

This apparatus performs a color recording operation as shown in FIG. 3, for example.

In FIG. 3, lines a to f show changes in the potential of the photoreceptor surface in each step. In addition, as shown in the upper part of the figure, the recorded image has a white background (W) and a black area (B).
and a red part (R).

First, the photoreceptor 1 is uniformly charged by the first charger 4 (FIG. 3a).

Next, in the first exposure section 10, the photoreceptor 1 is exposed to light by an imaging optical system through a red filter.

As a result, the black portion B of the photoreceptor 1 is set to a high potential 21, and the other portions are neutralized. The red portion R is neutralized to a potential 23 close to the background potential 22 (FIG. 3b).

Next, a developing bias 25 is set between the electrostatic latent image potential 21 of the black portion B and the background potential 22, and development is performed using negatively charged black toner in the first developing device 5. As a result of this development, toner adheres to the areas where the potential of the electrostatic latent image is high (the areas corresponding to the black areas), and development is performed (FIG. 3C).

After the first development is completed, the second charger 15 uniformly charges the photoreceptor 1 again. In this case, a scorotron, for example, is used as the second charger 15.

The grid potential of this scorotron is set to approximately the same potential as the background potential 22. As a result, all the surface areas of the photoreceptor 10 have a potential equal to or higher than that of the grid (FIG. 3d).

There is also a method of applying an AC high voltage to the corotron wire of the scorotron. In this case, the photoreceptor surface is uniformly recharged equal to the grid potential.

Thereafter, a second electrostatic latent image corresponding to the red area R is formed in the second exposure section 20 (FIG. 3e). (FIG. 3f). At this time, the developing bias potential 26 is set between the background potential 22 and the red electrostatic latent image potential 23. In this way, two color toners are deposited on the photoreceptor 1. An image is formed, and these toner images are transferred all at once onto the recording paper 12.Before this transfer, both the black toner and the red toner are charged to the same polarity by the pre-transfer corotron 14.

Now, in such an apparatus, when developing the second electrostatic latent image in the second developing device 6, all toner images formed in the first development are of negative polarity and are not used for the second development. As long as the toner is of positive polarity, there is little possibility that the toner of negative polarity will be mixed into the second developing device 6. However, during the recharging process after the first development (FIG. 3d), some of the toner may be reversed to positive polarity (FIG. 3e). In this case, since the positive polarity toner has the same polarity as the toner in the second developing device 6, it is easy to mix into the second developing device 6.

The method of the present invention for removing such mixed toner will be explained with reference to an enlarged view of main parts in FIG.

The illustrated apparatus is an enlarged view of the main part of the second developing device 6.

Normally, in a two-component developing device, toner and carrier rub against each other and the toner becomes electrically charged. In the present invention, this developing device 6
The materials for the toner and carrier are selected in advance so that the toner in the carrier is positively charged and the mixed toner is negatively charged. Therefore, at the outer periphery of the current (10-rule 61) in the figure,
The carrier 30 to which the toner 31 of the second developing device 6 and the mixed toner 32 are attached is attracted. Note that this carrier 30 is magnetically attracted by a magnet housed inside the developing roll 61. When the developing roll 61 rotates in the direction of the arrow 62 in this state, the toners 31 and 32 attached to the carrier 30 are both transported to the side facing the photoreceptor 1.

On the other hand, the photoreceptor 1 stops forming an electrostatic latent image during cleaning of the developing device 6, and the positive electrode of the DC power source 64 is connected to it during that time. Further, the developing roll 61 is grounded. The photoreceptor 1 rotates in the direction of arrow 63 in this state. As a result, the negatively charged mixed toner 32 is electrostatically attracted to the photoreceptor 1. On the other hand, the positively charged toner 31 adheres to the carrier 30 and remains in the second developing device 6 . The mixed toner 32 selectively adsorbed onto the photoreceptor 1 in this manner is then removed from the outer peripheral surface of the photoreceptor 1 by a cleaning device 3 (FIG. 2).

Incidentally, as shown in FIG. 4, the DC power source 64 may be arranged so that its negative electrode is connected to the developing roll 61, and the photoreceptor 1 may be grounded.

Furthermore, as shown in FIG. 5, when the second developing device 6 uses toner 31 of negative polarity, the materials of the toner and carrier are adjusted so that the mixed toner 32 is positively charged. In addition, in a multicolor recording device equipped with three or more developing devices, the materials of the toner and carrier are selected so that the toner that is most likely to get mixed into each developing device is charged to the opposite polarity to the toner in that developing device. Just do it.

In the above examples, the specific configurations and materials of each part were selected as follows.

<In the case of Examples> ☆ Photoreceptor - Se (selenium) type photoreceptor - Drum diameter 200 mm ☆ First developer - Two-component system - Carrier ferrite carrier average particle size 100 μm - Black toner styrene-n-butyl methacrylate copolymer 92 parts of combined and 8 parts of carbon black #4000 (manufactured by Mitsubishi Chemical Corporation),
Charge control agent (Bon).

5-34 (manufactured by Orient Kagaku Co., Ltd.), melt-kneaded, and finely pulverized to an average particle size of 9.8 μm. Charges negatively with respect to the carrier.

☆Second developer, two-component system, carrier 35 parts of styrene-n-butyl methacrylate copolymer and 65 parts of magnetite were mixed, melted and kneaded, and then finely ground to form a magnetic powder dispersion type. Average particle size is 30μm, density is 2.2
g/cm'.

・Red toner 92 parts of styrene-n-butyl methacrylate copolymer, 8 parts of red pigment Resource Cult (BASF), and 2 parts of cetylpyridinium chloride as a charge control agent were mixed and melted and kneaded to obtain an average particle size of 9.8μ.
Finely ground to m.

Charges positively to the carrier.

☆Process speed 150mm/sec☆Development parameters (first developer and second developer) TG (rimming gap) 0.9mm DR3 (drum/roll space) l, Qmm MSA (magnetic pole tilt) +5° Vd (rotational speed of developing roll) 450 mm/sec Magnetic pole scraping 50 G Rotation of developing roll WITH (in the forward direction of the photoreceptor in the developing nip) "Effects of the Invention" According to the color recording method of the present invention described above, the second Even if toner gets mixed into the second developing device during the charging process, it is quickly electrostatically removed, so that the quality of the developer in the second developing device can be stably maintained. Further, since a special mixed toner removal roll or the like is not required, the apparatus can be made smaller.

[Brief explanation of the drawing]

FIG. 1 is an enlarged explanatory diagram of the main parts of an apparatus showing an embodiment of the color recording method of the present invention, FIG. 2 is a schematic configuration diagram of a recording apparatus suitable for carrying out the color recording method of the present invention, and FIG. Explanatory diagrams of the potential of each part of the photoreceptor to explain the operation, Figures 4 and 5
The figures are explanatory diagrams of other embodiments of the present invention, and FIGS. 6 to 9 are schematic configuration diagrams of an apparatus employing a conventional color recording method. 1...Photoreceptor, 30...Carrier, 3
2...Contaminated toner, 61...Developing roll.

Claims (1)

[Claims] The process of forming an electrostatic latent image on a charged photoreceptor and developing the electrostatic latent image to form a toner image is repeated multiple times to form toner images of two or more colors on the photoreceptor. When the toner of the previously formed toner image gets mixed into the developing device in the later development process, the mixed toner, which is charged to the opposite polarity to the toner used in the developing device, is removed from a predetermined area on the photoreceptor. A color recording method characterized in that the toner is selectively electrostatically attracted to the toner and the toner is collected by a cleaning device.