JPS6343180A - Two-color developing method - Google Patents

Abstract

PURPOSE:To attain clear two-color printing by continuing the operating states of a photosensitive drum, an electrifier, 2nd developing device, an electrostatic separating/removing device arranged in a 2nd developing device, and cleaner for a fixed period at the time of non-printing. CONSTITUTION:At the time of two-color printing, the photosensitive drum 1, the charger 2, a 1st light 3, a 1st developing device 4, a 2nd light 6, the 2nd developing device 7, a transfer device 9, paper 10, and the cleaner 11 are set up to operating state. Under said status, a 1st color toner 5 gradually mixed into the device 7 is inverted at its polarity and electrostatically sucked, separated and removed by a conductive roll 13. However, time is required a little to separate and remove all the mixed toner 5. Therefore, the light 3, the device 4, the light 6, and the transfer device 9 are stopped at the time of of non printing, and the operating states of only the drum 1, the electrifier 2, the device 7, and cleaner 11 are continued for the fixed period. Thus, the toner 5 mixed into the device 7 can be effectively removed and always clear two-color printing can be obtd.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention is an electrophotographic system that continuously performs two-color printing.
This invention relates to a color development method.

[Background of the invention]

Conventionally, a two-color printing electrophotographic method as shown in FIG. 2 has been proposed. That is, after the surface of the rotating photosensitive drum 10 is charged uniformly, for example, by the charger 2, the first light beam 3 is emitted.
to form a first electrostatic latent image. This first electrostatic latent image is reversely developed using a two-component developer such as the first color toner 5 of the first developing device 4 to form an image of the first color toner 5. Subsequently, the photosensitive drum 1 is exposed to a second light beam 6 to form a second electrostatic latent image. This second electrostatic latent image is reversely developed with a two-component developer such as a second color toner 8 of a different color from the first color in a second developing device 7 to form an image of the second color toner 8. . The two-color toner image on the surface of the photosensitive drum 10 is transferred to a sheet of paper 10 by a transfer device 9, and then fixed,
Print a two-color image. On the other hand, after the two-color toner image remaining on the surface of the photosensitive drum 1 is cleaned by a cleaner 11, the photosensitive drum 1 is returned to green color and used again. A voltage 12 having the same polarity as the charging polarity of the second color toner 8 is applied to the second developing device @7, facing the developer conveyance path.
A conductive roll 13 is provided which rotates approximately in synchronism with the developing device 7 to which a voltage is applied.

Then, the first developing device 7 on which a toner image has already been formed is applied to the surface of the photosensitive drum 1 by a magnetic brush or the like of the second developing device 7.
The first color toner 5 mixed into the second color developer in the second developing device 7 by scraping off a portion of the color toner 5 is electrostatically separated and removed by the conductive roll 13. It is configured. That is, the first color toner 5.8 and the second color toner 5.8 have the same charging polarity, and the specific charge of the second color toner 8 is
If a difference is created between the characteristics of the two toners, such as by increasing the width of the toner, the first color will be mixed into the second color developer and the first color will be agitated.
The charge polarity of the color toner 5 is reversed, for example, the positive polarity becomes negative polarity. This is a method that has already been applied for, in which the mixed first color toner 5 converted into the load property is electrostatically attached to the conductive roll 13 and separated and removed.

FIG. 3 is a main operation timing chart of the configuration shown in FIG. As shown in the figure, the photosensitive drum 1, charger 2, first and second developing devices 4.5, etc. are all stopped in a print signal standby state during non-printing. In this way, the amount of the first color toner 5 mixed into the second color developer varies depending on the amount of printing of the first color toner 5, and the larger the amount, the more the amount of the first color toner 5 mixed into the second color developer increases. Moreover, it is difficult to immediately reverse the polarity of the mixed first color toner 5 and quickly separate and remove it.
Since it takes time for the mixed first color toner 5 to be completely separated and removed, the next two-color printing must be performed in a mixed color state in which the mixed first color toner 5 cannot be completely separated and removed, which has the disadvantage that the image of the second color toner 8 is mixed. . In addition, in order to overcome this drawback, it is necessary to increase the size of the device in order to improve the efficiency of separation and removal.

[Purpose of the invention]

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to enable clear two-color printing.

[Summary of the invention]

The present invention utilizes the standby time during which two-color printing is stopped in which the first color toner does not get mixed into the second developing device, and during that time only the second developing device is operated to separate and remove the mixed first color toner. The timing of the operation has been devised.

[Embodiments of the invention]

The present invention will be explained below. FIG. 1 is a main operation timing chart of a two-color printing apparatus having the configuration shown in FIG. 2, which shows one embodiment of the present invention. In Figure 1, when printing in two colors, the second
As explained in the figure, there is a photosensitive drum 1, a charger 2, a first light beam 3, a first developing device 4, a second light beam 6, a second developing device 7, and although not shown, a transfer device 9 and a sheet of paper 10. and the cleaner 11 is in operation. In this state, the second
The first color toner 5 gradually mixed into the developing device 7 has its polarity reversed, and is electrostatically attracted and separated and removed by the conductive roll 13. However, it takes some time to separate and remove all of the mixed first color toner 5. Therefore, during a non-printing period, for example, during a certain period of time when the paper ends at home, or during a two-color print signal waiting time, as shown in the figure, the first light beam 3 related to the first color development, the t41 developing device 4, and the ? :E20 ray 6
, the transfer device 9 (not shown) is stopped, and the photosensitive drum 1, charger 2, and second developing device 7 (conductive roll 13) are stopped.
) and the cleaner 11 are kept in operation for a certain period of time. During this duration, there is almost no mixing of the first color toner 5, and since it is separated and removed by the conductive roll 13, the removal efficiency is improved. Ninth, since the charged polarity of the photosensitive drum 1 and the polarity of the mixed first color toner 5 whose polarity has been reversed are different from each other, the mixed one color toner 5 adheres to the photosensitive drum 1 under normal development and is removed by the cleaner 11. Effects that are removed can also be used together.

Furthermore, in addition to the configuration shown in FIG. 2, the effect of the present invention shown in FIG. 1 is not obtained at all even in a method in which after first color development, recharging is performed, and then exposure is performed with the second light beam 6, and the second development is performed. It's the same.

In the above, an electrostatic separation/removal device including the conductive roll 13 has been described, but the present invention is not limited to this device.
It is much more effective when applied to a method with a high separation and removal effect.

Although the present invention has been described in the case where it is applied to a two-color printing method, the present invention is also effective for separating and removing toner whose polarity has been reversed due to deterioration in a general electrophotographic method of one-color printing using black toner.

〔Effect of the invention〕

According to the present invention, the first color toner mixed in the second color developer in the second developing device can be separated and removed during the non-printing time when the first color toner is not mixed. , effective. Therefore, clear two-color printing can always be performed.

[Brief explanation of the drawing]

FIG. 1 is a two-color printing operation timing chart according to the present invention. FIG. 2 is a schematic diagram of conventional two-color printing electrophotography, and FIG. 3 is a conventional two-color printing operation timing chart. In the figure, 1 is a photosensitive drum, 2 is a charger, 3 is a first light beam, 4 is a first developing device, 5 is a first color toner, 6 is a second light beam, 7 is a second developing device, 8 is the second color toner, 1
1 is a cleaner, 12 is a voltage power source having the same polarity as 8, and 13 is a conductive roll. Patent applicant name Hitachi Koki Co., Ltd.) Figure 1

Claims (1)

[Claims] 1. In an electrophotographic apparatus that obtains two-color printing by developing and transferring two colors in one rotation of one photosensitive drum, the photosensitive drum, charger, second developing device, and second A two-color developing method characterized in that an electrostatic separation/removal device and a cleaner provided in a developing device are kept in operation for a certain period of time. 2. The two-color developing method according to claim 1, characterized in that the operating state is continued for a certain period of time when the paper reaches end-home.