JPS61252561A - Multicolor electrophotographic developing method - Google Patents

Abstract

PURPOSE:To obtain a multicolor print by changing the constraining force of a toner generated by the magnet roll of a developing device by the color of the toner, making a developed toner different by the potential difference of a latent image generated by the strength and weakness of a write beam, and executing a multicolor development. CONSTITUTION:A development is executed by a toner 13 whose magnetic susceptibility is large first by using the magnetic toner of two colors whose magnetic susceptibility is different from each other. Since this toner has a large magnetic susceptibility, the toner is attracted to only a deep part of a latent image by sticking firmly to the magnetic roll of a developing device 2a by the magnetic force. Subsequently, the second development is executed by a developing device 2b by using a toner 14 whose color is different from that of the first development, and whose magnetic susceptibility is also low. This toner 14 is developed against the whole latent image because its force sticking to the magnetic roll is weaker than that of the first development. Accordingly, the first toner 13 and the second toner 14 are mixed and developed to the deep part of the latent image and only the second toner 14 is developed to the shallow part of the latent image. In this way, a small-sized multicolor printing device can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multicolor developing method in electrophotography.

With the spread of electronic computers, output devices have become faster, smaller, and
In response to the demand for low noise, non-impact type printers have been developed, and among these, electrophotographic printers are attracting a lot of attention because of their high speed, high quality, and low noise.

In particular, electrophotographic printers tend to be used for a wider range of purposes, as they can not only output information processing results, but also process and edit those results as images, as well as tabulate and draw diagrams. Therefore, it has become necessary to change the recorded image of a printed document and the color of the document as necessary.

[Conventional technology and problems]

Conventional multicolor printing devices employ the following method. Here, FIG. 5 shows an outline of a conventional multicolor printer, and FIG. 6 shows the potential on the surface of the photosensitive drum 50 during development.

In a conventional printing apparatus, the surface K of the photosensitive drum 5 is first uniformly charged by the charger 3.

A writing section 1/α' writes a latent image in the area where the -th color is to be developed. FIG. 6 (α) represents the latent image potential at this time. A developing device 2α containing toner of a negative color forms a negative color image on this latent image. This is shown in FIG. 5(b). Next, a latent image is written on the area to be developed in the second color from the writing section 1'AK, and the second color is developed in the developing device 2b. This is represented by (c) and (bl) in FIG. 6. By repeating the same process, it is possible to print in even more colors.

In the figure, 4 is a cleaner, 6 is a transfer device, 8 is a fixing device, 9 is a static eliminator, 10 is a transfer paper, 11 and 12 are toners, and 2o is the rotation direction of the photosensitive drum 50.

However, in this conventional example, one optical writing device is required for one color of toner, so when performing multicolor development, writing devices are required for the number of toner colors.
The device becomes large-scale.

Furthermore, since it is necessary to assemble toner images of each color into a single image, optical control also becomes necessary.

In addition, in order to solve the above problems,
As seen in Publication No. 61, a method has been proposed in which multicolor development is performed by setting the latent image potential in stages and changing the bias applied to the developing device. It is necessary to apply as many different types of power as there are colors, which complicates the power supply system.

[Problem that the invention seeks to solve]

The present invention solves these problems and provides an electrophotographic developing method that uses a simple device and allows multicolor printing.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention - In component development, the binding force of the toner by the magnetic roll of the developing device is changed depending on the color of the toner, and the writing light is The toner to be developed is varied depending on the potential difference of the latent image caused by the strength of the latent image, thereby making it possible to perform multicolor development.

[Effect]

When developing by electrophotography, especially in reversal development, a bias is applied to the developing device, so that the relationship between the bias potential and the latent image potential is as shown in FIG. 2 (α). +1 here
1 is the latent image potential of the weakly exposed area, and (2) is the latent image potential of the strongly exposed area.

During development, as shown in Figure 3, there is a Coulomb force A between the toner and the latent image! ,! ) are attracted to the latent image side. On the other hand, a force B (a force in the opposite direction of the Coulomb force) due to the magnetic force from the magnet roll is applied to the toner, and when the Coulomb force A exceeds the magnetic force B, the toner
For the first time, it is deposited on top of the latent image and development is performed. Now, magnetic force B
Assume that development is performed in a state where the image is large. If the latent image at this time is in the state shown in Figure 2 (α), the toner will not be developed in the shallow part of the latent image in (1), but will be developed only in the deep part of the latent image in (1). Ru. This state is shown in FIG.

Next, when development is performed with the magnetic force B being weak, the toner is developed over almost the entire latent image, resulting in the state shown in FIG. 2(C).

When such a method is used, it is possible to print in two colors: (1) the color of the toner of the second development and (2) the mixed color of the toner of the first and second development.

By increasing the potential difference of the latent image and the toner yield, this method can also be used for multicolor printing.

〔Example〕

Next, an embodiment of the present invention will be described in the case of two-color reversal development (hereinafter referred to as two-color development). FIG. 1 shows the outline of the apparatus, and in the case of two colors, the developing device 2C is not necessary. FIG. 2 shows the relationship between the surface potential of the photosensitive drum and the toner attached when two-color development is performed.

First, the writing unit 1 performs optical writing on the photosensitive drum 5 which has been charged by the charger 3 . At this time, the writing light is modulated depending on the color of the image to be developed, and the potential of the latent image is divided into two levels. The potential diagram of the two-stage latent image created by this method is shown in FIG. 2 (α). Here, (1) the weakly exposed area (2) is the electrostatic latent image of the strongly exposed area.

Next, the developing process of this latent image is shown in diagram t44. The development is
This is carried out using two colors of magnetic toner (hereinafter referred to as toner) with different magnetic susceptibilities. First, the first development is also performed using the toner 13 having a high magnetic susceptibility.

Since this toner has a high magnetic susceptibility, it strongly adheres to the magnet roll of the developing device 2α due to magnetic force.

Therefore, when the previous latent image is developed with this toner, the toner is attracted only to the deeper side of the latent image, as shown in (2) of the second m < b+. Looking at this in FIG. 4, the area where the 10's are in two rows corresponds to a deep latent image, and only this area is developed by the developer 2a.

Next, a second development is performed by the developing device 2b using a toner 14 that is different in color from the first development and has a lower magnetic susceptibility. Since it is weaker than the first development, the entire latent image is developed. As a result, as shown in FIG. 2(C) and FIG.
The second toner 14 is mixed and developed, and only the second toner 14 is developed in the shallow portion of the latent image.

In this way, if two color toners with different magnetic susceptibilities are used, two-color development can be performed depending on the latent image depth. Another method is to use a developing magnetic roll with a high magnetic flux density for the developing device 2α and a low magnetic flux density for the developing device 2b without changing the magnetic susceptibility of the toner. A method of developing by changing the adhesion force is also considered.

Further, in the present invention, the height of the spikes of toner is regulated to a predetermined height by a blade (not shown) provided in advance in the developing device.

〔Effect of the invention〕

The multi-layer development method according to the present invention requires only one writing system, which simplifies the equipment.Since the development bias remains constant, the power supply etc. can also be simplified, making it possible to print small multi-color prints. device is possible. It goes without saying that this method has similar effects in regular development used in copying machines and the like.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the electrophotographic printing apparatus of the present invention, and FIG.
The figure is an explanatory diagram showing the relationship between the latent image potential and the developing bias in the case of two-color development in the present invention, Figure 3 is a schematic diagram of the force acting on the toner during development, and Figure 4 is a diagram showing the toner potential during development. FIG. 5 is an explanatory diagram of the process of adhesion to an image; FIG. 5 is an explanatory diagram of a conventional multicolor printing apparatus; and FIG. 6 is a diagram showing the relationship between potentials in two-color development in a conventional example. 1.1'α, 1'b, 1'C...Writing section,
2α. 2b, 2c...Developer, 3...Charger, 5...Photosensitive drum, 6...Transfer device, 11-14...・Toner, 15°15α, 1
5b... Magnet roll, A... Coulomb force acting on the latent image and toner, B... Magnetic force between toner and magnet roll. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (3)

[Claims] (1) In a one-component multicolor electrophotographic developing method in which an electrostatic latent image is formed on a photosensitive drum and this is developed with multicolor toner to print a multicolor image, on the photosensitive drum,
When forming an electrostatic latent image, the intensity of the exposing light is changed depending on the color of the image, the potential of the latent image is graded, and toners with different magnetic binding forces are used depending on the color. 1. A multicolor electrophotographic development method, characterized in that the color of the toner to be developed differs depending on the potential of the latent image. (2) A multicolor electrophotographic developing method according to claim (1), characterized in that the binding force due to the magnetic force of the toner is varied depending on the difference in magnetic susceptibility of the toner. (3) A multicolor electrophotographic developing method according to claim (1), characterized in that the magnetic binding force of the toner is varied depending on the magnetic flux density of a magnet roll.