JPH0285873A - Color image forming apparatus - Google Patents

Abstract

PURPOSE:To reduce the total number of the rotations of a photosensitive drum chargeable to both polarities and to shorten the time required for color copying and to suppress stains due to toners by using the photosensitive drum and providing auxiliary chargers between plural developing devices together with a main charger. CONSTITUTION:A first color image forming process is executed by rotating the photosensitive drum 18 in the direction (t), charging it to +650V by the charge 20, exposing it to blue light in an exposing section 21, applying development bias and adding a yellow toner in the developing device 22, destaticizing it with a lamp 33, and thus finishing the first rotation. The process in the second rotation is executed likewise by exposing the drum 1 to green light in the exposing section 23, adding a magenta toner in the developing device 24, then, charging it to -600V in the charger 26, exposing it to red light in an exposing section 27, adding a cyan toner in the developing device 28 to form a color toner image. The 3 color toner image can be completed by the 2 rotations, thus permitting color copying speed to be enhanced, scattering of the toner and staining of the apparatus also to be reduced.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Field of Application) The present invention relates to a color image in which a plurality of toners are superimposed on a photoreceptor that can be charged to one polarity in an electrophotographic device or the like to obtain a color image. This invention relates to improvements in forming devices.

(Prior Art) In an image forming apparatus such as a copying machine or a laser beam printer, a device as shown in FIG. 6 has conventionally been used to obtain a color image by superimposing a plurality of toners of different colors on the same photoreceptor. It is used.

That is, the second yellow toner in the first developing device (10)
When trying to obtain a color image using the magenta toner in the third developing device (II) and the cyan toner in the third developing device (12), the photoreceptor (9) is rotated in the direction of arrow S, and the photoreceptor (9) is rotated in the direction of arrow S, ) is charged by the post-exposure section (14
) is first exposed to blue light, and then developed by a first developing device (10) with yellow toner, which is a complementary color to blue. Thereafter, the photoreceptor (9) is neutralized by the static elimination lamp (16), charged again by the charger (13), then exposed to green light, and then transferred to the second developing device (
11), the image is developed with magenta toner, which is a complementary color to green, and then static electricity is removed.

Finally, photoconductor 0 is connected to another 4F electric charger (1
After being charged in step 3), it is exposed to red light and developed with cyan toner, which is a complementary color to red, by a third developing device (12), and after obtaining a color image with all the toners on the photoreceptor (9), While the image is transferred onto a sheet of paper (not shown), the photoreceptor (9) is cleaned by a cleaning blade (17) and is further neutralized to enable the next color copy.

However, in such an apparatus, in order to obtain one color copy, the photoreceptor (1) must be rotated three times, which slows down the copying speed and also causes the photoreceptor (0) to rotate with the toner image formed. Since the toner is rotated three times, there is a problem in that toner scatters and stains the inside of the device.

(Problems to be Solved by the Invention) Conventionally, in order to obtain a color image, the photoreceptor had to be rotated three times with a toner image formed thereon, which reduced the copying speed and further caused problems with the device due to toner scattering. This is causing contamination.

Therefore, the present invention aims to eliminate the above-mentioned problems. By reducing the number of rotations of the photoreceptor during color image formation, copying speed can be increased, and furthermore, reliable color can be achieved without causing stains due to toner scattering. The purpose is to provide an image forming device.

[Structure of the invention]

(Means for Solving the Problems) In order to solve the above problems, the present invention uses an image bearing member that can be charged to both positive and negative polarities, and provides a main charging device that charges the image bearing member at the start of copying. A sub-charging device is provided at any position between the plurality of developing devices to charge the image carrier to a polarity opposite to that of the main charging device.

(Function) The present invention uses the above means to reduce the number of rotations of the image carrier for obtaining color copies, increase copying speed, and prevent staining due to toner scattering.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 4. (18) is a photoreceptor drum that is an image carrier, and around it, a first photoreceptor drum (18) is placed.
A first charger (20), which is a main charging device, to which a voltage of +6 (KV) is applied in order to be charged to a positive polarity, which is the polarity of
a first developing device (22) having a first magnetic brush (22a) to which a developing bias of +200 (V) is applied, and containing negatively charged yellow toner (22b); A second exposure section (23) exposed to green light (23a), a second magnetic brush (24a) to which a developing bias of +270 (V) is applied, and negatively charged magenta toner (24b). Built-in second developing device (24), photosensitive drum (18)
-7 [KV] to charge to a negative polarity opposite to the first polarity.
A second charging charger (26), which is a secondary charging device, is applied with a voltage of , and a third exposure section (27) is exposed to red light (27a), to which a developing bias of -200 [V] is applied. A third developing device (28) having a third magnetic brush (28a) and containing positively charged cyan toner (28b), a transfer charger (30), a peeling charger (31), and a cleaning device (32). ), and a static elimination lamp (33) are provided in this order. In addition, blue light (21a), green light (23a), red light (
Each part of 27a) is obtained by color-separating the light from the light source or the image using an optical device (not shown).

When copying starts, the photosensitive drum (18)
is rotated in the direction of the arrow, and first the first charger (
20) uniformly +650 as shown in Figure 2 (a).
(V), then exposed to blue light in the first exposure section (21) as shown in FIG. The yellow toner (22b) is applied by the first developing device (22) to which a developing bias shown in is applied, and the static electricity is further removed by the static elimination lamp (33) as shown in FIG. 18) is rotated once and the yellow toner (
When the second rotation of the photoreceptor drum (18) is started, the photoreceptor drum (18) is charged with the first charger (22b). ), the undeveloped area is uniformly charged to +650 (V) as shown in FIG.
After green exposure is performed as shown in FIG. 3(B) in the exposure section (23) of FIG. The magenta toner (24b) is applied by the second developing device (24), and the second color toner image forming process is completed. Then, when the photosensitive drum (18) is further rotated in the direction of the arrow,
Photosensitive drum! , (1a) is the second charger (26
), the undeveloped area is uniformly - as shown in Figure 4 (a).
The first and third exposed parts (27) are charged to 600 (V).
As shown in Figure 4 (b), red exposure was carried out.
Furthermore, as shown in FIG. 4(C), a cyan toner (28b) is applied by the third developing device (28) to which a developing bias indicated by a two-dot chain line [C] is applied, and a toner image forming process of all colors is completed. is completed, and a color toner image is formed on the surface of the photoreceptor drum (18). When the photoreceptor drum (18) reaches the transfer charger (30) in this state, the color toner image is transferred onto a sheet of paper (not shown) that is fed in synchronization with the toner image. After the sheet paper (not shown) is peeled off by a peeling charger (31), a color copy is completed through a fixing device (not shown). on the other hand.

After the sheet paper is peeled off, the photosensitive drum (18) has residual toner removed by a cleaning device (32), and then static electricity is removed by a static elimination lamp (33), completing the second rotation and making the fifth copy possible. .

With this configuration, the photoreceptor drum (18) can be charged to both forward and reverse polarities during the second rotation of the photoreceptor drum (18), so even though there are three types of toner, each toner During development, the potential difference between the exposed area and unexposed area on the photoreceptor drum (18) and the developing bias can be set well, and each developing device (22), (24)
), (2g) can prevent toner color mixing. or,
A color image can be formed using three types of toner by rotating the photoreceptor drum (18) only twice, and since the number of rotations of the photoreceptor drum (18) can be reduced compared to the conventional method, copying speed can be increased, and toner Scattering can also be reduced, and contamination within the main body can also be reduced.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and can be modified in various ways.1 For example, the polarity of the surface of the photoreceptor drum by the charging charger, the charging potential, the magnitude of the developing bias, etc. can be changed arbitrarily, and the installation of a sub-charging device can be changed. The location and number of installations are also arbitrary. Furthermore, depending on the development bias and developer selection, it is possible to further increase the copying speed by reducing the number of rotations of the photosensitive drum to one during color toner image formation. That is, for example, as in another modification shown in FIG. 5, the first developing device F11 (22) and the second developing device (24) in the embodiment
), a third charging charger (34) having a higher applied voltage than the first charging charger (20) is provided, and the photosensitive drum (18) is transferred to the third developing device (22) following development by the first developing device (22). The charging charger (34) charges the battery to +700 (V), which is higher than that of the first charging charger (20), and after green exposure in the second exposure section (23), the second magnetic brush (24a) The developing bias of +320 (
V) and the second developing device (24) set higher, and then the third developing device (28) is used as in the embodiment.
) to develop the image.

It becomes possible to obtain a color toner image during one rotation of the photoreceptor.

〔Effect of the invention〕

As explained above, according to the present invention, when forming a color toner image, color mixing of toners does not occur in the developing device, and
Compared to the conventional method, the number of rotations of the image bearing member can be reduced, so copying speed can be increased, and the rotation of the image bearing member with toner attached is also reduced.
Contamination of the device due to toner scattering is reduced, maintenance frequency can be reduced, and furthermore, the life of the device can be extended.

[Brief explanation of the drawing]

1 to 4 show an embodiment of the present invention, FIG. 1 is a schematic explanatory diagram thereof, and FIG. 2 shows the surface potential of the photosensitive drum during the first rotation. (b) is a graph showing the time of exposure, (c) is a graph showing the time of development, (d) is a graph showing the time of static electricity removal,
Figure 3 shows the surface potential from the start of the second rotation of the photosensitive drum until development with magenta toner.
C) is a graph showing the time of development, and FIG. b) is a graph showing the exposure time, (
C) is a graph showing the development time, FIG. 5 is a schematic explanatory diagram showing another modification of the present invention, and FIG. 6 is a schematic explanatory diagram showing a conventional apparatus. 18... Photosensitive drum, 20... First electrification charger, 21... First exposure section, 22... First developing device. 23... Second exposure section, 24... Second developing device. 26... Second electrification charger, 27... Third exposure section, 28... Third developing device, 30... Transfer charger, 31... Peeling charger, 32... Cleaning device . 33... Static elimination lamp. Agent Patent Attorney Nori Ogo Husband A side @ + Oka, A1 Kasumi (I) (Ron No. 2) (2nd →

Claims (1)

[Claims] Using color-separated light, an image carrier that can be charged to a first polarity and a second polarity opposite to the first polarity is sequentially charged for each color of the separated light. , in which a color image is obtained by repeating an exposure step and a developing step, a plurality of developing devices each having a developer corresponding to each color of light, and a plurality of developing devices provided upstream of the developing step of the plurality of developing devices. a main charging device that charges the image carrier to a first polarity; and at least one secondary charging device that is provided between any of the developing steps in the plurality of developing devices and charges the image carrier to a second polarity; A color image forming apparatus characterized by comprising a charging device.