JPH0145916B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Technical Field of the Invention The present invention relates to a multicolor recording method in which multicolor recording is performed by sequentially repeating latent image formation and development on a latent image forming medium. The present invention relates to a multicolor recording method in which a recharging step is provided after each developing means except for the developing means.

(B) Technical background In recent years, as electronic computers have become faster, output devices such as line printers are required to meet the following requirements.

(1) High-speed printing (2) Miniaturization of the device (3) Easy maintenance (4) No noise To meet these demands, research and development of non-impact printing devices is underway.

In addition, printed matter from the output device is not only used for checking information processing results as in the past, but also for processing, editing,
There is a tendency for printed materials to be treated as official documents by tabulating tables, etc., and it is required to be able to change the color of characters, symbols, figures, etc. on printed materials as necessary.

(C) Prior Art and Problems Hereinafter, in order to simplify the explanation of the present invention, a two-color recording device using the principles of electrophotography will be used.

FIG. 1 shows a schematic diagram of a conventional two-color recording device.
Further, FIG. 2 shows the potential levels of each process for two-color recording.

In FIG. 1, a photoreceptor 1 is uniformly charged over its entire surface by an initial charger 2. As shown in FIG.

The potential at this time is set to the initial charging potential level Vs, as shown in FIG. Next, the photoreceptor 1 is exposed to an image corresponding to a first color (hereinafter referred to as black) by the exposure section 3.

At this time, the potential of the photoreceptor 1 exposed by the exposure section 3 is attenuated to approximately O [V] as shown in FIG. Thereafter, using a black toner with a positive charge, the developing bias voltage setting section 5 sets the developing bias voltage V _B1 to a value slightly lower than the initial charging potential level V _S as shown in FIG. Developing is performed by step 4.

By performing development, toner adheres to the photoreceptor 1 in areas from which the charge has been removed, as shown in FIG. 2 and 3.

Next, the exposure section 6 performs exposure of an image corresponding to a second color (hereinafter referred to as red). At this time, the potential of the photoreceptor 1 exposed by the exposure section 6 is attenuated to approximately O [V] as shown in FIG. 2 .

Next, using a toner with a positive red charge, the developing bias voltage is set by the developing bias voltage setting section 8.
V _B2 is the initial charging potential level as shown in Figure 2.5.
The two-component developer 7 performs development by setting the value to a value slightly lower than V _S. By performing development, red toner adheres to the portion from which the charge has been removed as shown in FIG. is formed. Next, the toner image is transferred onto the recording paper 10 by the transfer means 9. Next, like the printing process of a normal electrophotographic apparatus, one process is completed through heating and fixing of the toner image on the recording paper 10, a cleaning process 11, and a static elimination process 12.

Two-color recording can be performed by sequentially repeating the above steps.

However, the conventional method has the following problems.

First, in the two-component development method, the particle size is 100~
Iron powder of about 300 [μm] is used as a carrier.
This developer mixed with carrier and toner forms a spike 14 with a height of about 5 mm on the sleeve 13 as shown in FIG. 3 due to the magnetic force of a mag roll (not shown), and during development, Step 14 is carried out by contacting the photoreceptor 1 with a contact depth of about ε=d−δ=3 [mm].

In this way, in the two-component development method, development is performed by pressing the spike 14 made of developer against the photoreceptor 1 and rubbing it.

Therefore, if the contact depth ε of the ears 14 of the second developing device 7 is not set appropriately, the black image formed on the photoreceptor 1 by the first developing device 4 will be distorted when passing through the second developing device 7. may be mechanically scraped off, resulting in destruction of the black image.

FIG. 4 shows the relationship between the contact depth ε of the second developing device 7 and the developer density when black is used as the first developer and red as the second developer.
As the contact depth ε of the second developing device 7 increases, the density of the red image increases, but the density of the black image decreases.

This is because the black image is mechanically scraped off by the second developing device 7.

When two-color recording is performed by repeating latent image formation and development, in addition to the destruction of the first black image, the occurrence of color mixture as shown in FIG. 5 becomes an important problem. 5. As shown in FIGS. 1 and 2, the first exposure,
When a black image is formed on the photoreceptor 1 by performing the first development, the image portion potential V _T1 has a value lower than the development bias V _B1 because there is an unsaturated portion of the development. In this state, the second
When the exposure and second development is performed, red toner adheres to unsaturated portions of the first black image due to the second development, resulting in color mixture in the black image.

Therefore, as a method for preventing destruction of the first image, the present inventors have proposed applying one-component magnetic toner development, which is a soft development method, to the second development.

In this one-component development method, a toner having a diameter of about 10 [μm] and containing magnetic powder dispersed therein is used to form spikes of about 0.1 to 0.3 [mm] on the sleeve of a developing device.

This toner originally has no charge, but during development, a charge is injected into the toner due to electrostatic induction of the latent image, and development is performed. This one-component development method is
It can be said that this is an extremely soft developing method because it does not use a carrier with a large particle size like the two-component developing method, and because development is carried out near the point where the tip of the toner comes into contact with the photoreceptor. FIG. 6 is a diagram showing the relationship between the contact depth ε of the second developing device and the developed density when the one-component developing method is used for the second developing device. A black image can be obtained with a developed density of about 1.2 when the contact depth ε is around 0 [mm]. The density of the red image at this time does not change, unlike the conventional method, even if the contact depth ε of the second developing device increases.

This is because a soft developing method is used as the second development, and the red image is not mechanically rubbed off by the second development.

However, even in this method, as shown in FIG. 5, since the magnetic toner is developed in the unsaturated portion of the first red image, color mixture occurs in the red image.

Furthermore, this method also has the following drawbacks. When transferring magnetic toner on a photoreceptor to recording paper, the resistance of the magnetic toner must be high to some extent. As a result, the latent image strength required for magnetic toner development is greater than that of the two-component development method, and at the initial charging potential level V _S shown in FIG.
Another problem arises in that the image density in magnetic toner development becomes low and density unevenness occurs in the two-color image.

(D) Object of the Invention In view of the above-mentioned drawbacks, the object of the present invention is to prevent toners of different colors by developing the unsaturated portions of the previous development stage into the unsaturated portions of the previous development stage, when recording is performed by repeating latent image formation and development. The object of the present invention is to realize a multicolor recording method that can prevent the adhesion of color and obtain multicolor printing without color mixing.

Still another object of the present invention is that even if developing methods with different required latent image strengths are used, the developed densities obtained by each developing method can be made to be approximately the same, and multicolor recording with uniform density can be achieved. The object of the present invention is to realize a multicolor recording method that allows printing.

(E) Structure of the present invention The object is to provide a charging means for uniformly charging a latent image forming medium to one polarity, and a charging means for uniformly charging a latent image forming medium to one polarity, and an electrostatic latent image formed by irradiating light onto the latent image forming medium. A plurality of latent image forming means are provided to form a latent image, and developers of different colors charged to the same polarity as the charging means are supplied to the portions of the latent image forming medium that are irradiated with light and the charges have disappeared. In order to visualize the latent image, a plurality of developing means are provided corresponding to each of the latent image forming means, and the latent image formation and development are sequentially performed by the plurality of latent image forming means and the developing means. A multi-color recording method that obtains multi-color recording by repeating the process, wherein a recharging means is provided after each of the plurality of developing means except for the last developing means, and the recharging means is connected to the previous developing means. This is achieved by a multicolor recording method characterized by performing recharging so that the potential of the image area developed by the means is approximately the same as the potential of the non-image area.

(F) Embodiments of the present invention To simplify the multicolor recording method according to the present invention, 2
The color recording device will be explained in detail with reference to the drawings. FIG. 7 shows a schematic diagram of a two-color recording apparatus for explaining the multicolor recording method according to the present invention. In this case, a two-component magnetic brush development method is applied to the first development, and a one-component magnetic toner development method is applied to the second development. The difference between the figure and FIG. 1 is that a recharging step using a recharging device 13 is provided after the first developing device 4. The same parts as in Figure 1 are given the same numbers. FIG. 8 shows the relationship between latent image strength and developed density in the one-component development method and the two-component development method.

In Figure 8, in order to obtain a development density of 1.0,
The two-component development method requires a latent image intensity of about 500 [V], and the one-component development method requires a latent image intensity of about 800V.

FIG. 9 shows the potential levels of each process of the two-color recording apparatus according to this embodiment.

First, the entire surface of the photoreceptor 1 is uniformly charged by the initial charger 2 . The potential at this time is set to the initial charging potential level V _S as shown in FIG. Next, the photoreceptor 1 is exposed to an image corresponding to red by the exposure section 3. At this time, the surface potential of the photoreceptor 1 exposed by the exposure section 3 is attenuated to approximately O [V] as shown in FIG.

Then, using a red toner with a positive charge,
The developing bias voltage setting section 5 sets the developing bias voltage V _B1 to the initial charging potential level as shown in FIG.
Develop at a value slightly lower than V _S. By performing the development, red toner adheres to the photoreceptor 1 in the areas from which the electric charge has been removed, as shown in FIG. 9.

At this time, the image potential of the red image is lower than the development bias because there is an unsaturated part of the development.
V becomes _T1 . Next, the photoreceptor 1 is recharged by a recharger 13 placed after the first developer 4 .
In this case, by using a scorotron equipped with a grid electrode and a charging control function as the recharging device 13, the image area potential of the red image can be made comparable to the background area potential, as shown in FIG. Furthermore, the background potential V _S itself can be increased to the potential V _S '. The background potential V _S ' after recharging is a potential at which a latent image strength such that the image density becomes OD1.0 or more is obtained by one-component magnetic toner development.

Next, the photoreceptor 1 is exposed to an image corresponding to black by the exposure section 6. At this time, the surface potential on the photoreceptor 1 exposed by the exposure section 6 is the 9th
As shown in FIG. 5, the voltage is attenuated to approximately O [V]. Next, using black magnetic toner, the developing bias voltage setting section 8 sets the developing bias voltage V _B2 as shown in FIG.
Development is carried out by setting the potential level to a value equal to the recharging potential level V _S ', as shown in FIG. At this time, the magnetic toner does not adhere to the first red image, and the second
Since the black image formed by development also has sufficient density, a good two-color toner image without color mixture and density unevenness can be obtained on the photoreceptor 1.

Therefore, the good two-color toner image formed on the photoreceptor 1 is transferred to the paper 10 by the transfer means 9, and a printed matter with good print quality can be obtained.

In this embodiment, a two-component development method was used for the first development, and a one-component magnetic toner development method was used for the second development. It goes without saying that similar effects can be obtained when using development or other development methods. Even when using only two-component development, destruction of the first image can be significantly prevented by lowering the magnetic force of the magnetic roller of the developing device used for the second development or by changing the particle size of the carrier used for the developer. be able to. As a result,
As in this embodiment, even when only two-component development is used, if the present invention is used, color mixing of the first image can be prevented and the same effect can be obtained.

In addition, if the required latent image intensities in the development methods used for the first development and the second development are approximately the same, the background potential V _S
There is no need to increase the voltage, and it is sufficient to control the scorotron so that only the potential of the image area of the first image is approximately the same as the potential of the background area.

Further, in this embodiment, for the sake of simplicity, the case where two-color recording is performed has been described, but it goes without saying that similar effects can be obtained even when multi-color recording is performed using three or more colors.

(G) Effects of the Invention As explained above, according to the present invention, when performing multicolor recording by sequentially repeating latent image formation and development, the unsaturated areas of the image area have different effects depending on the next development. It prevents colored toners from adhering, making it possible to obtain good multicolor images without color mixing, and also to obtain good multicolor images without uneven density even when using developing methods with different required latent image strengths. be able to.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a conventional two-color recording device, FIG. 2 is a diagram showing the potential levels of each process in the two-color recording device shown in FIG. 1, and FIG. 3 is a diagram explaining the developing state of the developing device. , FIG. 4 and FIG. 6 are diagrams showing the relationship between contact depth and development density, FIG. 5 is a diagram for explaining the occurrence of color mixture in a two-color recording device, and FIG. 7 is a diagram showing the multicolor recording according to the present invention. A schematic diagram of a two-color recording device for explaining the method, FIG. 8 is a diagram showing the relationship between latent image intensity and developed density, and FIG. 9 is a diagram showing the potential level of each process of the two-color recording device in FIG. 7. It is a diagram. In the figure, 1 is a photoreceptor, 2 is an initial charger,
3 and 6 are exposure sections, 4 and 7 are developing devices, 5 and 8 are development bias setting sections, 9 is a transfer means, 10 is paper, 1
1 is a cleaning process, 12 is a static elimination process, and 13 is a recharger.

Claims (1)

[Scope of Claims] 1. Charging means for uniformly charging a latent image forming medium to one polarity, and a plurality of latent images forming an electrostatic latent image by irradiating light onto the latent image forming medium. An image forming means, and a developer of a different color charged to the same polarity as the charging means is supplied to the latent image portion of the latent image forming medium where the electric charge has disappeared by irradiation with light to form a visible image. A plurality of developing means are provided corresponding to each of the latent image forming means, and the latent image formation and development are sequentially repeated by the plurality of latent image forming means and the developing means. A multi-color recording method for obtaining a color record, wherein recharging means is provided at a stage subsequent to each of the plurality of developing means except for the last developing means, and the recharging means is developed by the preceding developing means. A multicolor recording method characterized by performing recharging so that the electric potential of the image area becomes approximately the same as the electric potential of the non-image area.