JPS58137846A - Two-color developing method - Google Patents

Abstract

PURPOSE:To execute 2-color development exhibiting no color mixing, by changing an amt. of the first toner to be charged by mutual electrostatic action of the second toner attached to a carrier and the first toner mixed with this. CONSTITUTION:The first electrostatic latent image formed on a recording material 1 by exposure to rays 3 is reversely developed with the first toner 5 contained in a developing device 4. The second latent image formed with rays 6 is reversely developed with the second toner different in color contained in a developing device 7. Since the surface of the recording material 1 is rubbed with the magnetic brush of a 2-component type developer in developing the second image with the toner 8, the toner 5 is partially scraped off and mixed into the developer in the device 7. Charge of the toner 5 become about zero to a negative polarity by interaction of the toner 8, attracted with an opposite electrode charged positively or to recording paper and removed, and therefore, a sharp 2-color image having no color mixing is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic method, and particularly to a developing method suitable for two-color development.

The present inventors have proposed a method for obtaining a two-color image by repeatedly performing reversal development on a uniformly charged d-recording medium using a two-component dust toner consisting of toner and carrier.

In this method, the first and second toners having different colors in the phase 4 used have charges of the same polarity, so the first toner mixed in the second toner has an electrostatic latent It has the disadvantage that it adheres to the image and gradually causes color mixture, making it impossible to print a clear two-color image.

The object of the present invention is to prevent color mixture from occurring even when the first toner is mixed into the second toner.2 Tax exemption11! The purpose is to provide a method.

In order to achieve the above object, the present invention provides the following features: In the method of obtaining two-color image scratches by repeating reversal development +*' using a second toner, the first toner mixed in the $2 developer becomes more saturated due to interaction with the second toner. The amount of charged charge is changed to range from near zero to the opposite polarity. The first toner, which has become close to zero, is likely to scatter loosely from the second toner, so it is separated and removed by mechanical means such as air suction, and as soon as the polarity becomes reversed, the first toner is separated and removed by electrical means. This eliminates color mixing.

That is, the present invention provides a second
Due to the interaction between the toner and the mixed first toner,
This was done based on experimental results showing that the amount of charge on the first toner can be easily changed.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows an example of a two-color development method to which the present invention is applied. In the figure, a photoconductive recording medium 1t rotating clockwise is uniformly charged, for example, positively, by a charger 2.

Next, the first light IIi! ! 3 and irradiate the first silence 11
m 11 t- is formed, and this is reversely developed using the positively charged first toner 5 contained in the first developing device 4 .

Next, the second light @ 6 is irradiated to form a second electrostatic latent image, which is combined with the positive charge contained in the second developing device 7 and the first toner 5. is a second toner 8 of a different color.
Develop in reverse. 2 formed on the surface of the recording medium 1.
One color of toner is electrostatically transferred to the recording paper 9. This 2
In the color development method, the first toner 5 gradually mixes into the second toner 8 in the second developing device 7 via the recording medium 1, gradually creating color mixture. The present invention relates to this two-color development method.

An embodiment of the present invention will be described with reference to FIG. 2, in which the same parts as in FIG. 1 are designated by the same reference numerals. The present invention has the following features: 1. The second toners 5 and 8 are both positively charged and developed by magnetic brush development using a two-component developer used together with a negatively charged carrier. Then, compared to the average charge amount of the first toner 5, that of the second toner 8 is 5 to 20μ.
Use one with large c/g.

In FIG. 2, the first electrostatic latent image formed on the recording medium 1 by the first light beam 3 is transferred to the first toner 5 contained in the first developing device 4 (partially marked with a plus sign inside a white circle). (exaggerated)). Next is the second light! 16 is transferred to the first electrostatic latent image in the second developing device 7.
Reversal development is performed using a second toner 8 (partially shown exaggerated with black circles) of a different color from the toner 5. In the above process, when developing with the second toner 8, the surface of the recording medium 1 is rubbed with the magnetic brush of the two-component developer, so that the first toner 5 that has already been formed on the surface of the recording medium 1 is rubbed. A part of the toner image is scraped off and mixed into the developer in the second developing device 7. Most of the mixed first toner 5 changes from near-zero to negative polarity (reverse polarity) due to toner interaction with the second toner 8. This development is the first step. the second carrier is the same, the first and second toner 5,
Since this occurs when the average charge amount of No. 8 differs as described above, it can be seen that this occurs not due to the carrier but between the first and second toner. Since the second toner is more easily charged, it is thought that this is more likely to happen than other toners. Furthermore, the fact that the amount of charge of the mixed first toner 5 has changed means that the second toner mixed with the first toner 5 has changed.
Counter electrode K100OV in contact with or close to the developer of
When a certain amount of positive charge is applied, the first toner 5 adheres well to the electrode (converts to the opposite polarity), and the flow of the developer is disturbed, which will be explained in the next section. This can be confirmed from the fact that when the adhesive force is small (○ mark), the adhesion force with the carrier is small. From the above, the second phenomenon (the negative polarity of the first toner 5 mixed in the device 7 is electrostatically attracted and removed by the 11 opposing poles to which a positive charge is applied, or is attached to the recording medium) It is absorbed and removed (it is not transferred to the recording paper during transfer).

By removing by air suction those whose charge amount is near zero and are easily scattered, a clear two-color image without color mixture can always be obtained, which has a great practical effect.

It should be noted that a small amount of the mixed first toner 5 can be tasted, but the amount of charged charge hardly changes.

However, the amount of charge on the first toner 5 is the same as that on the second toner 8.
The second toner 8 is smaller and has better developability than that of the second toner 8.
It also has the effect that it is not accumulated because it is developed and consumed together.

1. Used in the present invention. The difference in the average charge amount of the second toner is important, and the absolute value has little to do with it, but the following values are preferred from practical standpoints such as scattering and developability. The first toner is around 20 (μc7g), the second toner is around 35μc
(μC/g) (same carrier).

FIG. 3 shows an embodiment of the second developing device 7 for embodying the invention described above (the same parts as in FIG. 2 are indicated by the same reference numerals). In the figure, an air suction device 1 is placed on a scraping member 11 provided close to the magnetic developing roll 10.
21, and removes by suction the toner that has become more likely to scatter due to its electrical charge being near zero, out of the mixed first toner 5. A conductive roll 13 that is rotatable and to which a positive charge is applied is provided on the lower side, and electrostatically attracts and adsorbs the toner that has become negative in the mixed first toner 5. The toner is scraped off into the container 15 by the scraping member 14 and is continuously removed. Adding the above device to a conventionally known developing device (the structure and setting position of the device are not limited)
As a result, most of the mixed first toner is removed, resulting in two clear colors with no color mixture +l! I can see the effects that can be obtained from 11 elephants.

As the second toner 8 is also used up, the amount of toner whose charge amount changes from near zero to the opposite polarity increases, but these toners are also removed by the two devices described above. Therefore,
It also has the effect of providing a good 21st layer with good developability and no fogging.

Above is the first part. Although the case where both the second toner has positive polarity has been described, the present invention can also be applied to the case where the second toner has negative polarity.

Furthermore, even if the carriers of the first and second developer are different, when the first toner is mixed in the second developer, the amount of charge of the first toner changes from near zero to the opposite polarity. If so, the same effect can be obtained. That is, when the amount of triboelectric charge of the first toner with respect to the carrier of the @2 agent is smaller than that of the second toner, a similar sound effect is produced.

Note that the present invention can be applied to any charged one-component developer that is not a two-component developer, as long as its charge polarity is reversed and the amount of charge is reduced after mixing.

As explained above, according to the present invention, in a two-color electrophotographic method, a clear two-color image without color mixture can be continuously produced, which has a practical effect.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a printing device to which the present invention is applied;
The figure is a schematic diagram of a boundary portion for explaining the present invention in detail, and Figure @3 is an explanatory diagram of a developing device implementing the present invention.

Claims (1)

[Claims] 1. A first negative exposure is performed on a uniformly charged recording medium, the formed first electrostatic latent image 1 is reversely developed with a first toner, and then a second 2. In the duty-free 1-image method, the second electrostatic latent image 1 formed by negative exposure is subjected to a reversal phenomenon with a second toner having a color different from that of the first toner.
The average charge amount of the second toner is made larger than the average charge amount of the toner, and the charge amount of the first toner mixed in the second toner is reduced to a range from near zero to the opposite polarity due to the interaction between both toners. A two-color development method characterized by changing to 2. The method according to claim 1, characterized in that the first toner having a charge amount near zero is separated and removed by mechanical means. 3. In claim 1, the band 11 of opposite polarity,
2. A tax-free and 1-parallel method, characterized in that the first toner, which has become a load, is separated and removed by electrical means.