JPS63303374A - Color recording method - Google Patents

Abstract

PURPOSE:To prevent the toner image formed in a 1st development from being disturbed at the time of the 2nd development in a color image forming method in which toner image forming stages are repeated twice by varying the electrostatic polarities of the toners in the 1st and 2nd developing stages. CONSTITUTION:For example, a photosensitive body 10 is electrostatically charged by a 1st electrostatic charger 1a and is subjected to normal exposing with a 1st exposing device 2a, following which the image is developed with the black toner having negative electrostatic chargeability. The image is then electrostatically charged by the 2nd electrostatic charger 1b in the 2nd stage and is subjected to reversal exposing with the 2nd exposing device 2b. This image is developed with the red toner having positive chargeability. The color images are formed on transfer paper 8 by a transfer corotron 4. The charge polarities of the toner of the 1st developing device 3a and the toner of the 2nd developing device 3b are varied and the polarity of the 2nd charger 1b is made the same as the polarity of the toner image formed by the 1st developing device 3a. The adhesion power of the toner image formed in the 1st development to the photosensitive body is, therefore, increased in the 2nd development and the color images are satisfactorily formed without being scraped away in the 2nd development.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a color recording method using an electrostatic latent image, and particularly to a color recording method that does not cause image disturbance or color mixture even when recording is performed continuously. Regarding.

2. Description of the Related Art The overlapping development method, which is one of the conventional color recording methods, is a method in which the steps of forming a binary latent image and developing it are sequentially repeated to perform one transfer. With this method, the copying speed is the same as when using one color (the device is also smaller, but during the second development, it may disturb the already developed toner image or the toner may get mixed into the developing machine). There were some problems, such as color mixing. In addition, in the second charging step, when a charge of a polarity different from that of the first ring toner image already formed on the latent image carrier is applied, the fq charge of the toner to the latent image carrier is The problem was that the strength of the film was reduced and the film was easily scraped off during the second development. Particularly, in a copying machine having an analog optical system that uses reflected light from the original for the first exposure, the first developed toner image formed on the electrostatic latent image corresponding to the low-density part of the original is There is a problem in that the adhesive is easily scratched off due to the decrease in adhesion, and it is difficult to obtain good reproduction of parts of the document with extremely low density.

As a solution to the above problems, JP-A-60-15
Japanese Patent No. 9763 discloses a method of increasing only the charge amount of the toner image that has already been formed without changing the potential of the photosensitive layer of the drum at the adhering part by carrying out charging and exposure simultaneously with a scorotron. In addition, JP-A-59-124354 describes a method of reversing the polarity of the charge of the first toner and setting the surface potential of the photosensitive layer to a predetermined value through a recharging process. 59-116
Publication No. 763 describes the use of a scorotron as a recharging means, and JP-A-58-116553 discloses that a recharging process is provided between the first development and the second exposure. It is already stated.

Problems to be Solved by the Invention Incidentally, in these devices, both the first exposure and the second exposure perform negative writing by reversal exposure, and both the first development and the second development involve lFj] polar l hener. I am using it. However, in these cases, additional development (
At the same time, color mixing due to overlapping development becomes a problem, and at the same time, the first toner image is scraped off in the second developing process and mixed into the second developing machine, reducing the life of the second developing machine. A drawback was that the toner was developed together with the second toner.

Furthermore, when the first exposure and the second exposure are normal exposure and reverse exposure, or vice versa, since the polarity of the first developing toner and the second developing toner is different, color mixing basically does not occur. There is a problem in that the formed first toner image is scraped off in the second developing step, the density of the first toner image decreases, and the resulting first toner image is mixed into the second developing machine.

The present invention has been made in view of the problems mentioned in the prior art.

Therefore, it is an object of the present invention to provide a technique for preventing an already developed toner image from being disturbed or being mixed into a developing machine in an overlapping development type color recording method using two types of toner having different charging polarities. Write the purpose.

Means for Solving the Problems The present invention provides a charging step for supplying an electric charge onto a latent image carrier;
The toner formed after repeating the toner image forming process twice, which consists of three steps: an exposure process to form an electrostatic latent image on the latent image carrier and a development process to visualize the electrostatic latent image. In a color recording method in which an image is transferred to recording paper, the toner used in the first developing step and the toner used in the second developing step have very different charging polarities, and the toner used in the second developing step is characterized in that the toner image formed in the first developing step is given an electric charge of the same polarity as that of the toner.

The present invention will be described below with reference to the drawings. FIG. 1 shows an example of a color image recording apparatus used to carry out the present invention, in which 1a is a first charger, 2a is a first exposure device, and 3a
1b is the first developing means, 1b is the second charger, 2b is the second exposing means, 3b is the second developing means, 4 is the transfer roller 1 to ron, 5 is the static elimination roller 1 to ron, 6 is the cleaner, and 7 is the light Static eliminator, 8
9 is a recording paper, 9 is a photosensitive layer before transfer, 10 is a photosensitive drum, and 10a is a photosensitive layer.

The photosensitive drum 10 is rotating in the direction of the arrow. First, the photosensitive layer 1 of the photosensitive drum 10 is charged by the first charger 1a.
0a is uniformly charged. Next, the first exposure means 2a performs normal exposure (or reverse exposure) according to the image information corresponding to the first color, and -6= an electrostatic latent image corresponding to the first color is formed on the photoreceptor. It is formed.

Next, the first developing means 3a supplies toner corresponding to the first color to visualize the image. Note that the color of the toner may be different from the first color.

Next, the photosensitive layer 10a is charged by the second charger 1b, and the charging polarity is made to be the same as the polarity of the toner image formed by the first development. Subsequently, the second exposure means 2b performs inversion exposure (regular exposure) according to the image information corresponding to the second color, and the exposure 1i1J
An electrostatic latent image corresponding to the second color is formed on 10a. A toner corresponding to the second color is supplied onto this photosensitive layer by the second developing means 3b, and the toner to be removed has a charge polarity different from that of the toner used for the first development. need to be different. Note that the color of the toner may be the same as the second color.

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. The first toner image and the second toner image may be transferred onto the recording paper 8 by the rotron 4, or may be transferred using 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 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 imaging optical system as used in a normal copying machine, an optical writing device capable of light modulation according to image information, etc. , laser writing device, liquid crystal light valve consisting of uniform light source and liquid crystal micro shutter, LE
Any type of D array, optical fiber, etc. can be used depending on the purpose.

Further, as the second charger, for example, a scorotron is used, an example of which is shown in FIG.

A metal wire having a diameter of about 50 to 150 micrometers is provided as a corona wire 12 inside the installed metal case 11, and a high voltage of 4 to 9 KV is applied. In addition, a grid wire 13 with a diameter of 50 to 15 mm is placed in the opening of the metal case 11.
A plurality of 0 μm metal wires are provided so that the pitch is approximately 1 to 3 #. A voltage is applied to the grid voltage by the DC high-voltage power supply 15, or a voltage approximately the same as the charging potential to be obtained on the photoreceptor is applied. Corona discharge starts when the voltage applied to the corona wire 12 by the power source 14 is about 4 KV, and it becomes possible to charge the photosensitive layer 10a. When the corona applied voltage becomes about 4 to 9 KV, corona discharge becomes active, a large amount of corona ions are generated, and a light emission phenomenon is observed around the corona wire 12. However, even if a large amount of corona ions are generated, the controllability of the grid wire 13 allows the photosensitive layer 10a to be charged to an arbitrary potential.

In the present invention, when a positive latent image is formed as a first electrostatic latent image, it is normally developed, a negative latent image is formed as a second electrostatic latent image, and it is reversely developed, The potential of the area to which toner is not attached after the second charging should be 300 V or more in order to provide a range of potential contrast between the image area and the non-image area during the second development, and to perform good development. is necessary.

In addition, when a negative latent image is formed as the first electrostatic latent image, it is reversely developed, a positive latent image is formed as the second electrostatic latent image, and it is normally developed, the second exposure is performed. As for the surface potential of the subsequent photosensitive layer, it is desirable that the potential of the area to which the toner is attached due to the first development is lower than the potential of the background area of the second latent image (see FIG. 4(d)). ). This is to prevent the toner image from being easily scraped off by the magnetic brush in the second development due to the reduction in the adhesion of the toner due to the action of the electric field.

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

Example 1 A test was conducted using the color image recording apparatus shown in FIG. 1 above, with the first development being regular development and the second development being reversal development. In the first development, the developer used was a negatively charged black toner and an average particle size of 100 μm.
In the second development, it is a two-component system consisting of positively charged red toner and particles with an average particle size of 40 μm in which magnetic powder is dispersed in resin. there were.

A selenium drum with an outer diameter of 200 m was used as the photoreceptor drum, and the first charger was used to uniformly charge it to 900 V (Fig. 3 (a)), and then regular exposure (non-image area exposure) was performed using a He-Ne laser. The potential of the exposed part was 450V.
A positive latent image was formed. This positive latent image is negatively charged by the first developing means using a two-component magnetic brush method under a developing bias of 600 μm; ~
The film was developed using a dye (FIG. 3(b)).

Next, charging was carried out using a second charger, and the second charger used was the S]RoI-Ron shown in FIG. That is, by applying a voltage of 450 to the grid 13 by the DC high voltage power supply 15 and applying a voltage of -4.5 KV to the corona wire 12 by the DC high voltage power supply 14, a negative potential was supplied to the image area with a high potential. . The potential of the image area was 550V, and the potential of the non-image area was 450V (
Figure 3 (C>). Subsequently, reversal exposure (image area exposure) was performed using a He-Ne laser to form a negative latent image whose potential at the exposed area was attenuated to 100μ.This negative latent image was developed by a two-component magnetic brush method using a second developing means. , development was carried out using a positively charged red toner under a developing bias of 300 V (Fig. 3(d)).

In this example, during the second development, the black toner image obtained by the first development is given a negative charge by the second charger, increasing the amount of charge and increasing the adhesion force to the surface of the photosensitive layer. Therefore, a good image could be obtained without being scraped off during the second development.

Furthermore, when an analog optical system that utilizes reflected light from the original is used as the first exposure means, the toner image formed on the electrostatic latent image corresponding to the low-density portion of the original is not scraped off. We were able to achieve good image reproducibility.

Example 2 Using the color image recording apparatus shown in FIG. 1 above, Tests 1 to 1 were conducted such that the first development was reverse development and the second development was regular development. In the first development, the developer used was a positively charged red toner and an average particle size of 100 μm.
It is a two-component system consisting of ferrite particles of m, and in the second development, it is a two-component system consisting of negatively chargeable black 1 to toner and particles with an average particle size of 40 μm in which magnetic powder is dispersed in resin. It happened.

A selenium drum with an outer diameter of 200# was used as the photosensitive drum, and it was uniformly charged to 800V by a first charger (
Figure 4(a)). Next, reversal exposure (image area exposure) is performed using a je-Ne laser, and the exposed area potential is set to 200mm.
, a negative latent image with a potential of 800 cm in the unexposed area was formed. This negative latent image was developed by the first developing means by a two-component magnetic brush method using a positively charged red toner under a developing bias of 650 V (FIG. 4(b)).

Next, a positive charge was applied by a second charger so that the potential of the image area was 300 V and the potential of the non-image area was 800 V (FIG. 4(C)). Subsequently, regular exposure (non-image area exposure) was carried out using a 1e-\e laser to form a positive latent image with a potential of 300 V in the exposed area, a potential of 800 V in the non-exposed area, and 200 V in the red toner-attached area. This positive latent image,
FIG. 4(d>) is developed using negatively charged black toner under a developing bias of 450 V by the second developing means by a two-component magnetic brush method.

In this example, during the second glare image, the red 1 to toner images formed by the first development are given a positive charge by the second charger, and the amount of charge is increased, so that they are not attached to the surface of the photosensitive layer. The adhesion was increased, and a good image could be obtained without being scraped off during the second development.

Effects of the Invention In the present invention, as described above, the toner used in the first developing step and the toner used in the second developing step have different charging polarities, and the second charging step 1st
Since it is characterized in that the toner image formed by the developing step is given an electric charge of the same polarity as the polarity of the toner in No. 1 to No. 1, the adhesion of the toner image by the first development to the surface of the photosensitive layer is strengthened, and the adhesion of the toner image by the first development is strengthened, and the second development step It is no longer scraped off during development, and a color image of good quality without image disturbance or color mixture can be obtained.

[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 a sufrotron used in the second charging in the present invention, and FIG. 3 is a photosensitive diagram in Example 1. FIG. 4 is an explanatory diagram illustrating the surface potential of the layer and the conditions of development. 1a...first charging means, 1b...second charging means, 2
a...first exposure means, 2b...second exposure means, 3a
...first developing means, 3b...second developing means, 4...
- Transfer corotron, 8... Recording paper, 10... Photosensitive drum, 10a... Photosensitive layer, 11... Metal case,
12... Corona wire, 13... Grid wire. Figure 1 10a 15 Figure 2 (C) Figure 3 Figure 4

Claims (4)

[Claims] (1) Three steps: a charging step for supplying electric charge onto the latent image carrier, an exposure step for forming an electrostatic latent image on the latent image carrier, and a developing step for making the electrostatic latent image visible. In a color recording method in which the formed toner image is transferred to recording paper after repeating the toner image forming step twice, the toner used in the first developing step and the toner used in the second developing step have charge polarities with respect to each other. A color recording method characterized in that the second charging step applies a charge having the same polarity as that of the toner to the toner image formed in the first developing step. (2) forming a positive latent image as a first electrostatic latent image, developing it regularly, and forming a negative latent image as a second electrostatic latent image;
2. The color recording method according to claim 1, wherein the color recording method is subjected to reversal development. (3) The color recording method according to claim 2, wherein after the second charging step, the absolute value potential of the portion of the latent image carrier to which toner is not attached is 300 volts or more. . (4) forming a negative latent image as a first electrostatic latent image, reversing it and forming a positive latent image as a second electrostatic latent image;
2. The color recording method according to claim 1, wherein the color recording method is subjected to regular development.