JPH0123779B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multicolor development method that prevents deterioration in the quality of development results due to multicolor development and simplifies maintenance.

Conventionally, multicolor development using an electrophotographic apparatus such as a copying machine has been performed, for example, as follows. That is, the first toner as a developer is frictionally charged to a negative polarity by the carrier. Then, the first electrostatic latent image of positive polarity formed on the photoreceptor is developed using the toner. Next, while the first toner image formed in the first developing step remains on the photoreceptor, a second electrostatic latent image of positive polarity newly formed on the photoreceptor is transferred. is developed using a second toner that is negatively charged. Similarly, while leaving the previously formed toner image on the photoreceptor,
Each of the positive electrostatic latent images newly formed on the photoreceptor is developed for each color using each negatively charged toner to obtain a multicolor toner image.

However, in the conventional developing process as described above, it is difficult to avoid the toner of the toner image previously formed on the photoreceptor from getting mixed in during the development of each developing device used after the second developing process. Katta. Therefore, the mixed toner as described above is triboelectrically charged by the carrier to the same polarity as the toner unique to each developing device. Therefore, as the amount of mixed toner increases, the color of the toner (developed color) adhering to the electrostatic latent image becomes cloudy, resulting in deterioration of the quality of the toner image.

Therefore, when the amount of mixed toner (toner of other colors) exceeds a predetermined amount, the developer must be replaced with a new one, which is not economical and requires extremely complicated maintenance.

This invention was made in view of the above circumstances, and its purpose is to prevent mixed toner of other colors from adhering to the electrostatic latent image and to develop only a single color without color mixture. The object of the present invention is to realize and provide a multicolor developing method that can be used in a variety of applications and that also facilitates maintenance of the device.

This invention involves repeating the steps of forming an electrostatic latent image on a photoreceptor and developing the electrostatic latent image using a developer containing toner charged to the opposite polarity to the electrostatic latent image. In a multicolor development method that produces a multicolor image, in the second and subsequent development steps, the toner in the developer is transferred in the opposite direction to the electrostatic latent image using a developing device different from that used in the previous development step. It is characterized in that it is charged to the same polarity as the electrostatic latent image, and at the same time, the toner mixed in the developer and used in the previous development process is charged to the same polarity as the electrostatic latent image.

More specifically, for example, when a mixture of toner and carrier is used as a developer and the toner is charged by friction with the carrier, the toner in the developer is charged by friction with the carrier to have a polarity opposite to that of the electrostatic latent image. What is necessary is to select a material that simultaneously charges the toner mixed into the developer and used in the previous development process to the same polarity as the electrostatic latent image.

Next, the principle of an embodiment of the present invention will be explained with reference to FIG. Note that the description will be made assuming that a negative electrostatic latent image is formed on the photoreceptor. In addition, the toner of the developer is indicated by T, and the carrier is indicated by C, and the charging series is expressed using an inequality sign such as C<T, and the open side of the inequality sign is positive polarity, and the closed side of the inequality sign is negative polarity. explain.

First, a first electrostatic latent image formed on a photoreceptor is charged using a first carrier and a first toner whose charging series is (C ₁ <T ₁ ) as shown in FIG. 1a. Developed to form a first toner image. next,
A second electrostatic latent image newly formed on the photoreceptor while leaving this first toner image on the photoreceptor is shown in FIG.
As shown in , the charging series is (C ₂ < T ₂ ) and (C ₂
>T ₁ ) using a second toner and a second carrier to form a second toner image. Similarly, as shown in Fig. 1c, the n-th electrostatic latent image has a charging series of (Cn<Tn) and (Cn>T ₁
〜T _o-1 ) and the nth toner such that
The n-th toner image is formed, and the entire development process is completed.

In other words, in each development process, only the toner specific to that process is positively charged, and the toner used in other development processes, that is, the mixed toner of other colors, is charged to the same polarity as the electrostatic latent image. Development is carried out by preparing carriers that are charged to a polarity (negative polarity). Therefore, only the toner unique to each developing process adheres to each electrostatic latent image.
The mixed toner of other colors is electrically repelled by the electrostatic latent image and therefore does not adhere to the electrostatic latent image. Therefore, each toner image formed in each developing step is of only a single color.

By the way, as a method of controlling the charging series of the carrier and toner as described above, there is a method such as coating the surface of the resin with another resin or the like. For example, if Teflon (tetrafluoroethylene resin trade name) is used as a material for coating the surface of a resin, the resin carrier coated with this Teflon will be negatively charged with respect to most resins. Also, oil blue #603 is used for styrene-acrylic resin.
(Resin coloring material trade name: manufactured by Orient Chemical Industry Co., Ltd.) is used as a toner, the charge polarity with respect to a carrier such as stainless steel becomes positive. Therefore, by appropriately selecting resin materials, coating materials, additive materials, etc., and varying the combinations and mixing amounts, an appropriate charging series can be set. .

Next, an embodiment of the present invention will be described with reference to FIG. FIG. 2 is a schematic diagram of a multicolor developing device employing the method of the embodiment, and is constructed as follows. That is, the first and second electrostatic latent images of negative polarity formed on the photosensitive surface of the photosensitive drum 1 are
are developed by the second developing device 2 and the second developing device 3, respectively. The first developing device 2 is a magnetic brush developing device as shown, and is used to develop the first electrostatic latent image described above using black toner. Further, the second developing device 3 is comprised of a pressure developing device constructed by combining the magnetic brush developing device and a conductive rubber roller as shown in the figure. This pressure developing device is configured to develop the second electrostatic latent image using red toner. In other words, such a developing device is a device that performs two-color development consisting of black and red.

The operation of the above device will be explained below. First, T-30P was used as the black toner in the magnetic brush developing device 2.
(Black toner product name: manufactured by Toshiba) is prepared, and TEFV200/300 (carrier product name: manufactured by Nippon Steel Powder) is used as a carrier to positively charge this T-30P.
Prepare a surface coated with Teflon. Then, the first electrostatic latent image of negative polarity formed on the photoreceptor drum 1 is transferred to the black toner (T-
30P) to form a black toner image on the photoreceptor drum 1, and the first development step is completed. Next, TM-5 was used as the red toner for the pressure development 3.
(red toner product name: manufactured by Sakata Shokai) is prepared, this TM-5 is further charged to positive polarity, and the black toner (T-5 used in the previous development process) is prepared.
30P) as a carrier to negatively charge the
TEFV200/300 (Carrier product name: Nippon Iron Powder)
Prepare. Then, while leaving the black toner image formed in the first developing step on the photoreceptor drum 1, a second electrostatic latent image of negative polarity newly formed on the photoreceptor drum 1 is transferred to the positive electrode. Develop using a sexually charged red toner (TM-5). and,
A red toner image is formed on a photosensitive drum 1. Here, as mentioned earlier, the carrier (TEFV200/300) prepared in pressure developer 3 is the red toner (TM
-5) has a property of positively charging the black toner (T-30P) and negatively charging the black toner (T-30P). In other words, the charging series can be expressed as Tr>Cr>Tb. However, Cr: the above carrier, Tr: red toner (TM-5), and Tb: black toner (T-30P). Therefore, the black toner Tb mixed into the red toner Tr of the pressure developing device 3
is electrically repelled to the second electrostatic latent image (negative polarity) and does not adhere to the second electrostatic latent image. As a result, black toner Tb in red toner Tr
Even if the mixed amount increases, only the red toner Tr adheres to the second electrostatic latent image, and development is performed using only a single color.

In this way, two-color toner images of black and red are formed on the same photosensitive drum 1 using only a single color, and the entire development process is completed.

By the way, when the present inventors conducted experiments using such a developing method, even after performing the image printing operation on several thousand sheets, no color mixing with black appeared in the red area, and the original clear red color remained. was kept. In other words, the effectiveness of this invention was proven.

In this development method, in the red development process, the red toner, which is the toner specific to this process, is charged to a positive polarity, which is different from the polarity of the electrostatic latent image, and the black toner, which is the mixed toner of another color, is statically charged. Development is performed using a carrier that is charged to the same negative polarity as the latent image. Therefore,
Only red toner, which is a specific toner, adheres to the electrostatic latent image, and black toner, which is another color toner, does not adhere because it is electrically repelled to the electrostatic latent image. Therefore, even if the amount of black toner mixed into the red developer increases, the black toner does not adhere to the electrostatic latent image, and development is performed using only the red toner.
As a result, even after copying a large number of sheets, clear red color development can be performed and high quality development results can be obtained. In addition, as mentioned above, even if the amount of black toner mixed into the red developer increases, it does not affect development, so there is no need to replace the developer frequently, making maintenance extremely easy. Become.

Note that this invention is not limited to the above embodiments. For example, when forming a positive electrostatic latent image on a photoreceptor drum, this can be done by charging a toner specific to each development process to a negative polarity, and charging mixed toners of other colors to a positive polarity. can. Further, in the above embodiment, the explanation was given of an apparatus that forms multicolor toner images on the same photoconductor and transfers and fixes these toner images simultaneously, but it is possible to transfer and fix the toner images each time a toner image is formed on the photoconductor. It can also be applied to a device that obtains a multicolor image by repeating this operation. This makes it possible to prevent mixed color development even if the toner scatters during the operation of each developing device and mixes into the developer of another developing device. Furthermore, in addition to black and red, blue, green, yellow, etc. may be used as the color of the toner, and combinations of these colors can also be determined arbitrarily. Further, the multicolor image is not limited to two colors, but may be three or more colors, and the development order can be freely selected and implemented. Further, in the developing device used in each developing step, means other than the frictional charging of the carrier and toner may be used as the toner charging means only in the first developing step. For example, a corona charger may be used. In addition, the configuration of each developing device can be modified in various ways without departing from the gist of the present invention.

As detailed above, according to the present invention, in the second and subsequent development steps, the toner in the developer is charged to a polarity opposite to that of the electrostatic latent image, and at the same time, the toner from the previous development mixed in the developer is charged. By charging the toner used in the process to the same polarity as the electrostatic latent image,
It is possible to prevent mixed toners of other colors from adhering to the electrostatic latent image, and to perform development without color mixture. In this case, since the toner in the developer and the mixed toner of other colors are charged with opposite polarities, it is necessary to consider the possibility that both toners will stick together due to electrostatic attraction. This is because the particles are mixed into the developer, and the amount thereof is extremely small. Therefore, there is almost no risk of color development due to both toners adhering to each other due to electrostatic attraction and adhering together to the electrostatic latent image. Furthermore, in the present invention, since development with toner of each color is performed using a separate developing device, it is possible to easily grasp the toner consumption status for each color, and it is possible to accurately control (replenish) the amount of toner. Can be done. Therefore, maintenance of the device becomes easy.

Further, according to the present invention, since the electrostatic latent images formed in each electrostatic latent image forming process have the same polarity, it is possible to transfer the developed images of each color in the same process or at once. . Therefore, the time required for a series of multicolor image forming processes can be shortened, and the apparatus can be downsized.

[Brief explanation of drawings]

1A to 1C are configuration diagrams for explaining the principle of the method of this invention, and FIG. 2 is a schematic diagram of a multicolor developing apparatus for explaining an embodiment of the method of this invention. 1... Photosensitive drum, 2... First developing device (magnetic brush developing device), 3... Second developing device (pressure developing device).

Claims (1)

[Scope of Claims] 1. An electrostatic latent image forming step of forming an electrostatic latent image on a photoreceptor, and a toner in which the electrostatic latent image formed by this step is charged to the opposite polarity to the electrostatic latent image. In a multicolor development method for obtaining a multicolor image by repeating a development step of developing using a developer containing: In the second and subsequent development steps, the toner in the developer is charged to the opposite polarity to the electrostatic latent image using a developer different from that used in the previous development step, and at the same time, the toner in the developer is charged to the opposite polarity to the electrostatic latent image. A multicolor development method characterized by charging mixed toner used in a previous development process to the same polarity as the electrostatic latent image. 2. A mixture of toner and carrier is used as the developer, and the toner in the developer is charged as the carrier to a polarity opposite to that of the electrostatic latent image by frictional charging, and at the same time, the toner mixed in the developer is removed from the previous development image. 2. The multicolor developing method according to claim 1, wherein the toner used in the process is selected from a material that charges to the same polarity as the electrostatic latent image.