JPS6114654A - Color electrostatic developing method - Google Patents

Abstract

PURPOSE:To enable the execution of color electrostatic development in order of desired developing solns. without color mixing with a simple construction by developing plural kids of toners for developing the electrostatic latent image on a recording medium in order of the larger charge quantity of the toners. CONSTITUTION:The toner c13 charged positive sticks to the electrostatic latent image 12 on an electrostatic recording paper 11 and the toner a14 having the smaller charge quantity than the charge quantity of the toner c13 for the 1st color is brought near the point where, for example, above 20V residual potential is shown. The electrical attraction force F1 between the image 12 and the toner a14 and the electrical repulsive force F2 between the toner c13 and the toner a14 act respectively on the toner a14. The toner a14 is not stuck to the electrostatic latent image as the forces are F1<F2. The image is developed in order of the larger charge quantity of the toners by which the color electrostatic development is executed in order of the desired developing solns. without color mixing with the simple construction.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a color electrostatic development method for developing an electrostatic latent image on an electrostatic recording medium.

Structure of the conventional example and its problems As shown in FIG. 1, a conventional apparatus using an electrostatic recording method and performing color liquid development forms an electrostatic latent image on an electrostatic recording paper 1 with an electrostatic recording head 2. After that, the paper is transported by the transport roller 3 in the direction of the arrow, and at this time, a predetermined developing device, for example, the developing device 4a which is supplied with a cyan liquid developer, is brought into contact with the electrostatic recording paper 1 to form an electrostatic latent. The image is visualized. The fixing method uses vacuum pressure and wipes off excess liquid color toner using airflow flowing in from the gap between the electrostatic recording paper 1 and the developing device 4. It has a central configuration in which development and fixing are performed in a container.

The electrostatic recording paper 1, which has been recorded and developed for the required length, is stopped, then transported in the opposite direction (arrow B) by the rewind roller 6, and returned to the recording start position. is,
Development is carried out in the same manner as for the second and first colors.
The process used was to develop the image by bringing it into contact with a color image, and repeating this process three times or four times, including black, to obtain a color image.

1. [2. In this way, 111 recordings and development are performed repeatedly by the reciprocating movement of the electrostatic recording paper 1, and the developing ability is important! l1 (l. This is because development is carried out by bringing the latent image potential of recording paper 1 into contact with a developer having an opposite polarity of charge. However, if the latent image potential of the same level, for example 0110 (2) When developing a latent image potential of 120 V, the time required to neutralize the latent image potential to OV varies depending on the characteristics of the developer of each color, as shown in FIG.

Therefore, for the same development time, that is, the same recording paper speed, even if a developer with the same development rl in the paper feeding direction is brought into contact with the electrostatic latent image, the potential after development (herein referred to as residual potential) As shown in Figure 2, the contact time ranges from very high to low depending on the type of developer, so the contact time is 0.22
In the case of seconds, if a developer with characteristics as shown in Figure 2 & is used for the first color, and a developer as shown in Figure 2 is used for the second color,
Since the residual potential of the first color is about 50V higher than in Figure 2, when the developer of the second color is brought into contact with it, the image of the first color is originally desired to be 11 of the first color. The toner of the second color adheres to the residual potential of the first color, resulting in color mixing.

To solve this problem, conventional methods have been used to reduce the residual potential to OV after one development.
There are ways to make this happen.

For example, depending on the characteristics of the developer used, if the residual potential is large, the voltage applied to the electrostatic head 2 may be lowered to lower the potential of the electrostatic latent image itself, or after development, Methods have been considered in which the residual potential is neutralized by using a MuC corona or the like, but in either case, the equipment becomes complicated and is not practical.

There has also been a proposal to develop cyan, magenta, and yellow in the order of cyan, magenta, and yellow using a specific developer, but this method cannot correct the difference in hiding rate depending on the type of developer, and it is difficult to express the desired hue. It had the disadvantage that it was difficult to

[1] The present invention solves the above-mentioned conventional problems, and aims to provide a color electrostatic development method that allows development in a desired order of developing solutions without complicating the structure of the device. shall be.

Structure of the Invention The present invention applies an electrostatic latent image for each color by reciprocating an electrostatic recording medium using at least one electrostatic recording head, and develops the electrostatic latent image one color at a time with toner of a plurality of colors. In this method, the electrostatic latent image on the recording medium is developed with toner of each color in descending order of charge amount.

Explanation of Examples As one of the experiments, we thought that the reason why the residual potential differs greatly depending on the type of developer as shown in Fig. 2 is because the voltage at which the developer starts adhering to the electrostatic latent image differs, and we performed electrostatic recording. The voltage applied to the head was gradually lowered to reduce the potential of the electrostatic latent image, and at the same time, the image was plotted using a reflection densitometer. This is shown in FIG. As is clear from FIG. 3, there were some differences in recording density depending on the type of developer, but no phenomenon was observed where the development start voltage differed depending on the developer.

Next, in order to see what would happen if the residual potentials were the same in Figure 2, we changed the contact time (development time) for developers a and b, which have different characteristics, until the residual potentials were the same. At residual potentials of 40 V and 2 oV, each developer was brought into contact with these residual potentials and developed. The results were as follows: 6b7.

It was found that when the residual voltage was 40 V, colors were mixed even if either developer a or b was used for the first color. However, when developing b first and then developing with developer a, the color mixture is slight. Residual potential is 40V
At a lower voltage of 20V, even if developer A is brought into contact with the latent image after the first color is developed using developer A, the colors do not mix.
On the other hand, develop with Development Ronin as the first color, and the residual potential and -1
- After setting the voltage to 20V, which is the same as described above, the result was that colors were mixed when developing with a developer.

From this result, we believe that the amount of charge of the developer has an effect.
I tried measuring the amount of charge. As a result, developer 1 = 1s
μa/ct + developer b = 58 μO/−. From this, it was found that developer solution S had a larger charge amount than developer solution A.

From this, we can see that the phenomenon occurs when the residual potential is 20V, that is, when development is performed using a developer with a large amount of charge, the residual potential is Ov.
Despite the fact that the color is very high, even when developed with a developer & having a smaller charge than this, no mixed 7, -7 color was produced; on the other hand, after developing with a developer a with a smaller charge,
The phenomenon of color mixing when developing with a developer having a large amount of charge can be thought of as follows.

The developer is generally placed in a highly insulating solvent with a diameter of 0.2 to 0.
．． A charge control agent is added to fine toner particles of about 3 microns, and the toner particles are charged and dispersed in a solvent.

Unlike monochrome toner, color toner has a high resistance value and is close to an insulator. Therefore, even if such toner particles are charged and are electrophoretically attracted to and adhere to an electrostatic latent image with a polarity opposite to that of the toner particles, there is an instantaneous exchange of charges between the electrostatic recording paper and the toner particles. It is difficult to imagine that it will be neutralized and become Ov.

From this, the above phenomenon can be considered as follows.

Even if charged toner is attracted to and adheres to a latent image of opposite polarity during electrophoresis, all of the toner's own charge will be transferred between it and the electrostatic latent image in a short period of time. It does not mean that the charge is lost due to the exchange, but as the toner adheres to the electrostatic latent image, the lines of electric force of the toner itself and the lines of electric force of the electrostatic latent image of opposite polarity cancel each other out, creating an apparent two-potential. will go down.

FIG. 4 (to) shows that 0.13 of charged toner adheres to the electrostatic latent image 12 of a certain electrostatic recording paper 11, and 20
Suppose that a residual potential of about V is exhibited. To a place like this, the second
When toner a, 14, which has a smaller charge than the first color toner 0.13, is brought closer to develop a color, toner a, 1
Two forces act on 4, one is an electric attractive force F1 that acts between the electrostatic latent image 12 and the toner &, 14, and the other is:
This is an electrical repulsive force F2 that acts between the toner C313 and the toners a and 14. The toners a and 14 are attracted by the attraction force F1 with the electrostatic latent image 12 and try to adhere to the electrostatic latent image 12, but
Since the repulsive force F2 due to the charge of 0.13 of the first color toner 11 is larger than that of 21, it cannot adhere to the electrostatic latent image 12. In such a case, in FIG. 2, there is no color mixing at a residual potential of 20V.

Next, in Figure 4 (a), under the same conditions as above, charges 9,
<.

This shows the case where a large amount of toner b, 15 is used as the second color. In the case of toner b, 16, which has a large charge amount,
The attraction force F1 acting between the electrostatic latent image 12 is the first
Repulsion force F2 that acts between the toner 0.13 used for coloring
Since it becomes larger, it is attracted to and adheres to the electrostatic latent image 12. In other words, colors will be mixed.

This point is considered to be the location where colors are mixed at a residual potential of 20 V in FIG. 2.

Therefore, by developing the toner with a larger amount of charge first, a barrier is formed by the charge of the first color toner, and the second color toner with a smaller amount of charge is repelled and does not adhere. it is conceivable that. on the other hand,
It is thought that when developing from a toner with a small amount of charge, the force between the amount of charge of the second color toner and the electrostatic latent image is stronger, and the barrier effect is less, causing adhesion and color mixing. on the other hand,
When the residual potential is as high as 40 V or more, even if a toner with a large amount of charge is used for the first color, its barrier effect is weak.

This is thought to be due to the high residual potential. Therefore, after developing the first color using a material with a charge amount of 10,000 yen, so that the residual potential is 4 ov or less, an image without color mixture can be obtained by sequentially developing the materials with a larger charge amount. be able to. Note that the amount of charge on the toner can generally be controlled by the amount of charge control agent.

Effects of the Invention According to the present invention, by developing toners in descending order of charge amount, it is possible to obtain a good color image by mixing colors without setting the residual potential to OV. Therefore, there is no need to increase the contact time of the developing device. Further, since the charge amount of which color should be increased can be freely determined by l+ of the 'ilK load control process, it can be determined based on the color tone of the desired image.

In the second embodiment, the case of liquid development has been explained, but it goes without saying that the invention can be similarly applied to the case of powder development.

[Brief explanation of drawings]

FIG. 1 is a side view of essential parts of a color electrostatic developing device, and FIG. 2 is a graph showing the relationship between the contact time (development time) of an electrostatic latent image on electrostatic recording paper and toner and the residual potential, 111, - Fig. 3 t [Graph showing the relationship between latent image potential and toner adhesion density; Fig. 4 (7) is the charge of the first color toner) Explanation of development in the case of the charge of the toner of the second color. Figure, Figure 4 (
A) is an explanatory diagram of development in the case where the charge of the first color toner is smaller than the charge of the second color 11 toner. 11 =°=-electrostatic recording paper, 12...electrostatic latent image, 13...first color toner, 14.15...
...Second color toner. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 4
Figure FI〈rg F,〉F2

Claims (1)

[Claims] At least one recording head reciprocates the electrostatic recording medium to apply an electrostatic latent image for each color, and the order of toners of each color for developing the electrostatic latent image on the recording medium is determined from the toner with the largest amount of charge. A color electrostatic development method in which development is performed in sequence.