JPH01271777A - Color image recording method - Google Patents

Abstract

PURPOSE:To obtain image density without color mixture and image irregularity by performing developing by means of a 2nd developing roll around midway between the developing main pole of the developing roll and a magnetic pole adjacent to the main pole. CONSTITUTION:Two developing rolls are disposed so that developing by means of a 1st developing roll 31 is performed near the magnetic pole of a developing main pole facing a latent image carrier and developing by means of the 2nd developing roller 32 is performed around midway between the developing main pole and the magnetic pole adjacent to the main pole. Therefore, among toner images, the one with the lowest electric charge level formed by developing by means of the 1st developing roll in a 1st developing stage is scavanged when developing by means of the 2nd developing roll is performed. The amount of the electric charges of a formed toner image is high and the toner image is closely packed. Thus, in a 2nd developing stage, when developing is performed by toner according to a 2nd color, the toner image according to the 2nd color can be formed with high density without disturbing the toner image corresponding to a 1st color formed in the 1st developing process.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of recording color images using electrostatic latent images.

Conventional technology Conventionally, color recording methods using electrophotography include:
Various methods are known, one of which is the overlapping development method. In the overlapping development method, after a first latent image on a photoconductor having a binary or ternary latent image is developed in a first developing machine, a second latent image is subsequently developed on the photoconductor. The final toner image developed by a second developing machine is transferred all at once to obtain a color image.This method is effective because the device is compact and the copying speed is extremely high. .

In such an overlapping development method, in the second and subsequent development steps, the photoreceptor carrying the toner image is rubbed again by the developer in the first development step.
The toner image formed in the first development step may be significantly disturbed by the second or subsequent development steps, or a second toner may be newly developed on top of the toner image, causing color mixture or disturbance. This causes troubles such as toner entering the developing device and shortening the life of the second developer. And the first
(Image of toner image formed in the developing process) When the agricultural yield is increased, in the second developing process, (1) Disturbance of the toner image is likely to occur.Conditions for balancing both the problems of image density and toner image disarray The problem is that the range is narrow.

As a method for developing the toner image on the photoconductor-F without disturbing it, there are two ways to develop the toner image on the photoreceptor-F in the later development step: (1) Non-contact development method
6-144452) and (2) using a magnetic brush development method in which the rubbing force is weakened may be considered. (Unexamined Japanese Patent Publication No. 55
-36889 Publication, Publication No. 57-79970, Publication No. 6
0-126665) Problem to be Solved by the Invention In the method (1) above, for example,
44.52 @ As disclosed in the publication, when the non-contact AC flying method is adopted in the second development step, considering the flying phenomenon of the already developed toner due to the AC electric field, the 11th toner image disturbance, This cannot be said to be a 1q solution in terms of mixing of the second developer into the first toner image.

In addition, in the method (2), since the developing efficiency or developing ability of the second inkstone image step is used in a degraded state, there is a problem that it is difficult to develop a sufficient image density. 1. The present invention has been made in view of the above-mentioned problems in the conventional technology.

An object of the present invention is to obtain a color image having sufficient image density without color mixture or image disturbance, without causing any disturbance in the toner image formed in the first development step, even in the second development step. In order to provide a color image recording method that can 62-88629@
). According to this method, the above problems can be solved to some extent, but as a result of further investigation, if the amount of charge of the toner image formed in the first developing step is high, as shown in FIG. have found that image disturbance is less likely to occur even in the second development step. FIG. 4 shows the relationship between the charge amount of the toner image formed in the first developing step and the disturbance of the 1 to toner images caused by the second developing step, and the vertical axis is the disturbance of the toner image (the first The ratio of the width of the line drawing obtained in the first developing step after the second developing step to the width of the line drawing obtained in the developing step is shown, and (a) and (b) on the horizontal axis represent the width of the line drawing obtained in the first developing step, respectively.
The cases where the charge amount of the toner image by development is -20.7 μC/g and -9.7 μc/q are shown. line)
This is the case where * is the case where there is a horizontal line (line in the axial direction of the photosensitive drum) in the toner image after the same process. As is clear from FIG. 4, when the amount of charge of the 1-hener image in the first developing step is high, the disturbance of the toner image in the second developing step is reduced.

Means for Solving the Problem The inventors of the present invention focused on this fact and proceeded with the preposition, and as a result,
It has been discovered that in order to increase the amount of charge of the toner image formed in the first development step, it is sufficient to carry out development using a plurality of development rolls under different conditions as shown below. The present invention has now been completed.

The present invention includes a latent image forming step in which an electrostatic latent image is formed on a latent image carrier by a latent image forming means, and a developing step in which the formed electrostatic latent image is visualized with two or more different toner colors. and a transfer step, in which a developed color toner image is transferred to a transfer material after repeating at least the latent image forming step and the developing step multiple times, Of the multiple development steps, the first [
Two developing rolls are used in the first developing step;
Development by the first developing roll of the developing rolls is performed near the magnetic pole of the main developing pole facing the latent image carrier, and development by the second developing roll is performed between the main developing pole of the developing roll and the magnetic pole thereof. It is characterized by being carried out near the middle between adjacent magnetic poles.

The color image recording method of the present invention will be explained below with reference to the drawings.

FIG. 1 shows an example of a color recording apparatus used to carry out the present invention, in which a color image is formed by forming a binary latent image. In FIG. 1, 1 is a charger;
2a is a first exposure means, 3a is a first developing means, 2b is a second
exposure means, 3b a second developing means, 4 a transfer corotron,
5 (a static eliminating corotron, 6 a cleaner, 7 an optical static eliminator, 8 a recording paper, 9 a pre-transfer corotron, 10 a photoreceptor drum, and 10a a photoreceptor 1).

The photosensitive drum 10 is rotating in the direction of the arrow.

First, the photosensitive layer 10a on the surface of the photosensitive drum 10 is uniformly charged by the charger 1.

Next, the first exposure means 2a irradiates light according to image information corresponding to the first color, and an electrostatic latent image corresponding to the first color is formed on the photoreceptor. Note that any exposure means can be selected. Next, a first photosensitive layer 10a having a first electrostatic latent image formed by the first exposure means is coated with a first photosensitive layer 10a.
The developing means 3a supplies toner corresponding to the first color and visualizes it.

Two developing rolls 31 and 32 are present in the first developing means.

In the present invention, these two developing rolls are arranged so that development by the first developing roll 31 is performed near the magnetic pole of the main developing pole facing the latent image carrier,
The development by the second developing roll 32 is arranged near the middle between the main developing pole of the second developing roll and the adjacent Wt pole.

FIG. 2 shows an example of this. FIG. 2(a) shows the first developing roll, and FIG. 2(b) shows the second developing roll. It is composed of an eight-pole symmetrical magnet roll 12. In the first developing roll, the magnetic pole of the main developing pole facing the photosensitive layer 10a is at an angle of, for example, 0 to ±10 degrees with respect to the plane of the shortest distance connecting the central axis of the developing roll and the latent image carrier. Arrange it so that

(Hereinafter, the angle θ of the magnetic pole of the main developing pole with respect to the plane of the shortest distance connecting the central axis of the developing roll and the latent image carrier is referred to as the "magnet fixed angle".)
The magnet is arranged so that the magnet fixing angle θ is, for example, an angle of ±<15 to 30) degrees.

Subsequently, the second exposure means 2b irradiates light according to the image information corresponding to the second color, and a second light is irradiated onto the photosensitive layer 10a.
An electrostatic latent image is formed according to the color of the image.

The exposure means and writing method are optional. Next, the photosensitive layer 10 having the second electrostatic latent image formed by the second exposure means
A toner corresponding to the second color is supplied by the second developing means 3b to form an image. The pre-transfer corotron 9 is used to align the polarities of the first toner and the second toner carried on the photoreceptor before transfer, but this can also be omitted in certain processes. The first toner image and the second toner image may be transferred onto the recording paper 8 by the transfer corotron 4, or may be transferred using a means other than electrostatic transfer.

The recording paper is then fixed in a fixing section (not shown).

Further, the photoreceptor that has passed through the transfer section is cleaned by a static eliminator corotron 5, a cleaner 6, and an optical static eliminator 7 for reuse.

The first and second exposure means may include a light illumination means, an original scanning means, and an optical system, such as those used in a normal copying machine, an optical writing device capable of modulating light according to image information, such as a laser. Writing device, liquid crystal light valve consisting of one light source and one liquid crystal micro shutter, LED
Arrays, optical fibers, etc. can be used depending on the purpose. In some cases, a second charging means may be provided before the second exposing means.

According to the present invention, in the first development step, among the images 1 to 2 formed by the development by the first development roll, those with a low electric charge are scanned during development by the second development roll. As a result, the toner image formed by the second developing roll has a high charge amount and is densely packed.

Therefore, in the second development step, when developing with the toner corresponding to the second color, the toner image corresponding to the first color formed in the first development step is not disturbed.
A toner image corresponding to the second color is formed at high density.

Example The present invention will be explained below with reference to Examples.

Example 1 A copy test was conducted using a color image recording apparatus as shown in FIG. 1 above.

A selenium-based drum with an outer diameter of 200 mm was used as the photosensitive drum, and was uniformly charged to 1oooy by a first charger. Next, regular exposure was performed using an exposure lamp to form an electrostatic latent image having a surface potential of 200 V in exposed areas and 1000 V in non-exposed areas. This electrostatic latent image was developed by a first developing means under a developing bias of 300 V using a negatively charged black developer. Subsequently, the second charger charges 90
It was uniformly charged to 0V.

Furthermore, reverse exposure is performed using the LED array, and the non-exposed area 9 is exposed.
00V, an electrostatic latent image having a surface potential of 200V at the exposed portion is formed, and a developing bias of 60V is applied by the second developing means.
Development was performed using a positively charged red developer under 0 V. The operating conditions in this case were as follows.

The moving speed of the photosensitive drum was set to 50 mm/Sec.

In the first developing means, the developing roll has an outer diameter of 4
Two rolls consisting of a 0 mm stainless steel sleeve and an 8-pole symmetrical magnetized roll with an outer diameter of 20 mm were used.

The first developing roll of these two developing rolls is
The magnet is fixed at a fixed angle of 5 degrees, and the second developing roll is
The first developing step was carried out with the magnet fixed angle fixed at 20 degrees. Further, the negatively charged black developer used in the first developing means is a two-component developer consisting of black toner and ferrite carrier particles with a particle size of 80 μm in both the first developing roll and the second developing roll. Met.

In the second developing means, a developing roll was used which formed a repelling magnetic field in the developing nip region by a stainless steel sleeve with an outer diameter of 40 mm and an 8-pole symmetrical magnet roll with an outer diameter of 20 mm. The positively charged red developer used in the second developing means is a two-component developer consisting of a red toner and carrier particles having a density of 2.2(]/cm3 and a particle size of 40 pm, in which magnetic powder is dispersed in a binder resin.

When the operation was performed using the above-mentioned strip A41, no color mixing or image disturbance of the toner image occurred even at 20 kC/V.

Further, the density of the toner image formed in the second development was sufficiently high.

Comparative Example 1 When the C operation was carried out in the same manner as in Example 1 except that the second developing roll was omitted in the first developing means in Example 1, color mixing of the toner image occurred at about 5 kC/V.

Example 2 Operations were performed under the same conditions as in Example 1 above, and the amount of charge and image density of the toner image formed in the first development step were measured.

The amount of charge of the toner image formed in the first development step is
-14μC/Q.

For comparison, the second development [
When development with the 1-roll was carried out under the same conditions as the first development with the development roll, that is, with the magnet fixed angle θ -5 degrees, the amount of charge of the formed toner image was -8 μC.
I got it at /g.

Further, the image density of the formed toner image was as shown in FIG. 3. In FIG. 3, the vertical axis indicates image density, and the horizontal axis indicates the difference between the latent image potential and the developing bias potential. In FIG. 3, each curve shows the image density of the toner image formed in the first development step, and curve A shows the image density of the toner image formed in the first development step. 1 to 2 images formed with the developing roll set at a fixed magnet angle of θ-20 degrees; C indicates a 1 to toner image formed using only the second developing roll (magnet fixed angle θ = 20 degrees), D indicates a toner image formed by the second developing roll The toner image is shown when the development is carried out under the same conditions as the first development using the development roll, that is, with the magnet fixed angle θ-5 degrees.

As is clear from the above results, in the case of the present invention,
The toner image formed by development by the first development roll is developed by the second development roll, and the amount of charge of the toner increases without much change in development density. Therefore, since the 1 to 3 images are firmly adhered to the photosensitive layer in a tightly packed state, they are not disturbed by the developing operation in the second developing step.

On the other hand, the development by the first development roll and the second development roll is performed under the same conditions, that is, from magnet I to fixed angle θ.
-5 degrees, the formed toner image is
Although the amount of charge of the toner is low and the image density is increased, the layer height of the toner image is increased, which is easily disturbed by the developing operation in the second developing step.

Effects of the Invention As described above, the present invention uses two developing rolls in the first developing step among multiple developing steps,
Then, the development by the first of the two developing rolls is carried out near the magnetic pole of the main developing pole facing the latent image carrier (
Since the development by the second development roll is carried out near the middle between the main development pole of the development roll and the adjacent magnetic pole, the thick image formed in the first development process is highly charged. It has sufficient image density and is therefore not disturbed even in the second development step. Once upon a time,
According to the present invention, it is possible to obtain a color image that is free from color mixture and image disturbance and has sufficient image density.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a color image recording apparatus used to carry out the present invention, FIG. 2 is an explanatory diagram of an example for explaining the first developing step of the present invention, and FIG. FIG. 4 is a graph showing the image density in the developing step, and is a graph explaining the disturbance of the toner image formed in the first developing step due to the second developing step. DESCRIPTION OF SYMBOLS 1... Charger, 2a... 1st exposure means, 2b...
Second exposure means, 3a...First developing means 1.3b...
Second developing means, 4... Transfer corotron, 8... Recording paper, 10-... Photosensitive drum, 10a... Photosensitive layer, 1
1... Developing sleeve 11. 12... 8-pole symmetrical magnet 1 to roll, 31 and 32... Developing roll. Prayer end 1 pile J-()-* Q <I(jgu

Claims (1)

[Claims] (1) A latent image forming step in which an electrostatic latent image is formed on a latent image carrier by a latent image forming means, and a developing step in which the formed electrostatic latent image is visualized with two or more different toner colors. , a transfer step, and after repeating at least the developing step of the latent image forming step and the developing step multiple times, a developed color toner image is transferred to a transfer material. Two developing rolls are used in the first developing process, and the development by the first of the two developing rolls is carried out on the main developing pole facing the latent image carrier. A color image recording method characterized in that development is performed near a magnetic pole of the second developing roll, and development by a second developing roll is performed near the middle between a main developing pole of the developing roll and a magnetic pole adjacent thereto.