JPH0523434B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an image forming apparatus that can obtain color copies of natural colors (hereinafter referred to as full color), and particularly relates to an image forming apparatus that uses three color toners that can produce other colors. The present invention relates to a color image forming apparatus which can obtain full color copies by rotating a photoreceptor twice.

(Prior Art) As a conventional full-color image forming apparatus using a regular development method, there is one shown in FIG. This color image format device includes a laser oscillator 2 that oscillates a light beam 1 modulated according to an image signal, a lens 3 that focuses the light beam 1, and a rotating polygon mirror 4 that diffuses the light beam 1 in the scanning direction. However, a photosensitive drum 5 exposed to the light beam 1 is provided below it. The photosensitive drum 5 is in contact with the transfer drum 10 at the transfer section 5a (20 is a transfer corotron),
A paper feed tray 14 is provided for supplying copy paper 13 to the transfer section 5a. Further, around the photosensitive drum 5, a charging corotron 6 and a developing section 8 (green, blue, etc.) for developing the electrostatic latent image on the photosensitive drum 5 are provided.
A cleaner 9 is provided for removing toner from the photosensitive drum 5 after it has been transferred. Furthermore, a transport belt 11 and a fixing section 12 are provided downstream of the transfer section 5a.

To explain the operation in the above configuration,
Photosensitive drum 5 by first charging corotron 6
After charging, the photosensitive drum 5 is exposed to the light beam 1 from the laser oscillator corresponding to the green component, and the developing section 8a develops the latent image resulting from the exposure with magenta toner, and this developed image is fed to paper. Copy paper 13 fed from tray 14 and held by transfer drum 10 is transferred by transfer section 5a. The toner transferred onto the photosensitive drum 5 is removed by a cleaner 9. Thereafter, after the second charging of the photosensitive drum 5, the photosensitive drum 5 is exposed to light corresponding to the blue component by the light beam 1 from the laser oscillator 2, and the developing section 8b converts the latent image resulting from the exposure into a yellow toner. The developed image is transferred to transfer drum 1.
The image is transferred to the copy paper 13 held by the transfer unit 5a. The toner transferred onto the photosensitive drum 5 is removed by a cleaner 9. Finally, after the photosensitive drum 5 is charged for the third time, the photosensitive drum 5 is exposed to light corresponding to the red component by the light beam 1 from the laser oscillator 2, and a latent image resulting from the exposure is transferred to the developing section 8c.
is developed with cyan toner, and this developed image is transferred to the copy paper 13 held by the transfer drum 10.
is transferred at the transfer section 5a. In this way, the three-color superimposed copy paper 13 is transferred to the fixing section 12 via the transport belt 11, where it undergoes a fixing process and is then discharged.

However, in the case of a full-color image forming apparatus using a conventional regular development method, each step of charging, exposure, development, and transfer is repeated at least three times, depending on the number of color toners, and the multiple Since one color copy is obtained by fixing the transferred image, it takes time to complete the copying process, which may impede a speedy copying process.

(Object and structure of the invention) The present invention has been made in view of the above,
In order to enable rapid copy processing operations to obtain full-color copies using regular development methods, uniform charging is required when producing full colors other than black using three color toners. A latent image formed by exposure on the photoreceptor according to the first color image information is developed using a first color toner, and then a latent image is developed on the photoreceptor using the re-charged first color toner. After developing the latent image formed by exposure using the second color image information using the second color toner, the first and second
The image formed using the color toner is transferred, and then a third color image formed using the third color toner based on the third color image information is transferred onto the newly uniformly charged photoreceptor. The present invention provides a full-color image forming apparatus using a regular development method in which the image is transferred onto the transferred image.

EMBODIMENT OF THE INVENTION Hereinafter, one embodiment of the present invention will be described in detail based on the accompanying drawings.

(Embodiment) FIG. 2 shows an embodiment of the present invention. The same parts as in FIG. 1 to 4th charged corotrons 6a to 6d, and the first
Further, fourth laser oscillators 2a to 2d and developing machines 8a to 8d for cyan toner, black toner, magenta toner, and yellow toner for developing the latent image on the photosensitive drum 5 are provided. Among the toners used here, at least cyan toner,
The magenta toner used is a light-transmitting one, and the developing machines 8b, 8c, and 8d in the second and subsequent stages have a non-contact developing structure. As shown in FIG. 3, the non-contact developing method has a configuration in which a toner supply roll 21 and a developing roll 22 are provided in a developing machine 8b having a toner supply port 23.
and the photosensitive drum 5 are in a non-contact state with a predetermined interval, and the developing roll 22 is at a predetermined potential Vo.
connected to the positive terminal of a power supply with (The potential Vo is made smaller than the charging voltage of the photosensitive drum 5). Further, the charging corotrons 6a to 6d are controlled by a control unit 25 (e.g., a microcomputer), and in the first and second transfer steps, the charging corotron 6 that operates to develop the second color toner does not operate to develop the first color toner. (Figure 4 A and B show the discharge cut-off voltage Vo in the case of "DC constant voltage" and "AC + DC bias", and the second color The discharge cut-off voltage Vo of the charged corotron
lower than the photosensitive drum charging voltage of the first color).
In addition to the charging corotrons 6a to 6d, the control unit 25 also controls the respective laser oscillators 2a to 2d and developing machines 8a to 6d.
It also controls the operation of 8d. The control unit 25 includes an input interface 25a that inputs sensor signals from various sensors in the copying machine or operation command signals from a console (not shown), and a ROM 25b that stores programs necessary for arithmetic processing of input signals.
CPU2 that performs predetermined calculations based on the program
5c and temporarily store calculation results and data.
It has a RAM 25d and an output interface 25e that outputs control signals to various control objects such as laser oscillators 2a to 2d and charging corotrons 6a to 6d or to a display section of a console (not shown) based on calculation results.

In the above configuration, the operation is shown in Figures 5 and 6.
This will be explained based on the diagram. FIG. 5 is a drawing regarding subtractive color mixing of colors. According to this, the following relationship holds true.

C (cyan) + M (magenta) + Y (yellow) = BL (black) C (cyan) + M (magenta) = B (blue) C (cyan) + Y (yellow) = G (green) M (magenta) + Y (yellow) ) = R (Red) Based on the above relationship, full color is produced. In this embodiment, a black toner is provided separately, and C (cyan), M (magenta), Y (yellow) are produced. ) is used to produce colors other than black by mixing the two colors. However, black can also be produced by combining the three colors. FIG. 6 shows a copying operation consisting of a first stage 1 to a fourteenth stage 14. In the following explanation, R is red, G
represents green, B represents blue, C represents cyan, M represents magenta, Y represents yellow, K represents black, and W represents white. As a first step, the surface of the photosensitive drum 5 (photosensitive layer 5a, conductive layer 5b) is charged to (+) using the charging corotron 6a. In the second step, the R, M, Y, K, and W portions are exposed by the laser oscillator 2a. As a result, only the G, B, and C portions of the (+) charge remain. In the third step, the G, B, and C portions are developed with a transparent cyan toner c using the developing device 8a. In the fourth step, the surface of the photosensitive drum 5 is again charged to (+) by the charging corotron 6b (the cut-off voltage is lowered than the charging voltage to prevent the cyan toner c from detaching). As the fifth step,
Expose the R, G, B, C, M, Y, and W parts.
As a result, only the K portion of the (+) charge remains. As the sixth step, the developing machine 8b
Develop the area with black toner K. As a seventh step, the transfer portion 5a is placed on the copy paper 13 fed from the paper feed tray 14 and held by the transfer drum 10.
Cyan toner C and black toner K are transferred. The residual toner on the photosensitive drum 5 after transfer is removed by a cleaner 9. In the eighth step, the surface of the photosensitive drum 5 is charged to (+) by the charging corotron 6c. As the ninth stage, G, C,
The Y, K, and W portions are exposed by the laser oscillator 2c. As a result, only the R, B, and M portions of the (+) charge remain. As the 10th step,
The R, B, and M portions are developed with transparent magenta toner M by the developing device 8c. In the eleventh step, the surface of the photosensitive drum 5 is again charged to (+) by the charging corotron 6d. As the 12th step, B, C,
Expose the M, K, and W parts. As a result, (+)
The charges remain only in the R, G, and Y portions. As the 13th step, R, G,
Develop the Y portion with yellow toner Y. In the 14th step, magenta toner M and yellow toner Y are transferred onto the copy paper 13 held by the transfer drum 10 by the transfer unit 5a, and as a result, the copy 13 is colored R (red) and G (green) from the left edge. , B (blue), C (cyan), M (magenta), Y (yellow)
,
The colors K (black) and W (white) are colored. Furthermore, among the toners used here, at least magenta toner and cyan toner are light-transmissive, so even after development with the toner on the photosensitive drum 5, there is no effect on the second exposure process. Furthermore, since the developing machines 8b, 8c, and 8d have a non-contact developing structure, the developing roller 2
It is possible to prevent toner peeling and development due to contact between the photosensitive drum 2 and the photosensitive drum 5.

Next, in such an apparatus, the transfer drum 1
The reason why it is difficult to create full color with one rotation of the photosensitive drum 5 without having a zero color will be explained below.

FIG. 7 shows the first stage 1 to the sixth stage 6a, 6b. As a first step, the surface of the photosensitive drum 5 is charged to (+) by the charging corotron 6a. In the second step, the R, M, Y, K, and W portions are exposed by the laser oscillator 2a. the result,
The (+) charge remains only in the G, B, and C portions. In the third step, the G, B, and C portions are developed with cyan toner c by the developing device 8a. In the fourth step, the surface of the photosensitive drum 5 is again charged to (+) by the charging corotron 6b. In the first case of the fifth step, the C, Y, K, and W portions are exposed by the laser oscillator 2b, as shown in FIG. 7A. Therefore, the (+) charge remains in the R and M parts in addition to the G and B parts to which the cyan toner is attached. As a result, Fig. 7 6a
As shown in FIG. 3, when developing with magenta toner in the developing device 8c, the magenta toner also adheres to the G portion, making it impossible to create green. On the other hand, in the second case of the fifth stage, as shown in FIG. 7, 5b, when the C, Y, and K color toner parts are exposed to the G part, the (+) charge in the G part is The magenta toner disappears, and as shown in FIG. 7 6b, the magenta toner does not adhere, but the yellow toner of the subsequent developing device 8d also does not adhere, and green cannot be created. Therefore, as shown in the above embodiment, it is necessary to rotate the photosensitive drum 5 twice and perform the transfer twice.

(Effects of the Invention) As explained above, according to the full-color image forming apparatus using the regular development method of the present invention, the regular development method is adopted, and at least During one rotation of the photoreceptor, three charging means are used to form and transfer two-color toner images on the photoreceptor, accompanied by a charging step by the charging means provided upstream of the exposure means, respectively, and the photoreceptor is rotated once. The photoreceptor is developed so that, while the photoreceptor is rotated one more time, a toner image of another color is formed and transferred on the photoreceptor through a charging process by a charging means provided before the exposure means. By providing a control means for controlling the image forming apparatus, the exposure means, and the charging means, full-color copies with a wide color reproduction range can be obtained, and rapid image forming processing operations can be performed.

[Brief explanation of drawings]

FIG. 1 is a structural explanatory diagram of a conventional color image forming apparatus, FIG. 2 is a structural explanatory diagram of a color image forming apparatus according to the present invention, FIG. 3 is a structural explanatory diagram of a non-contact color development system, and FIG. , b are graphs showing the discharge characteristics of the charged corotron for the second color development process (Fig. 4 a shows "DC constant voltage", Fig. 4 b shows "AC + DC bias"), and Fig. 5 shows the color characteristics. FIG. 6 is an explanatory diagram of the steps of charging, exposure, development, and transfer according to the present invention, and FIG. 7 is an explanatory diagram of subtractive color mixing, and FIG.
FIG. 2 is an explanatory diagram of the steps of charging, exposure, development, and transfer, showing that it is difficult to create full color with one rotation of the photosensitive drum. Explanation of symbols, 2a to 2d...laser oscillator,
5...Photoreceptor, 6a-6d...Charged corotron,
8a to 8d...Development method.

Claims (1)

[Scope of Claims] 1. A color image forming apparatus that forms a full-color image using a regular development method by combining color toners of at least three colors, comprising: a rotating photoreceptor; at least three developing machines that perform development with color toner; at least three exposing units that are arranged upstream of each developing machine and that expose the photoreceptor to light based on color signals corresponding to the respective colors; and each exposing unit. at least three charging means disposed upstream of the photoconductor to charge the photoconductor, and forming and transferring two-color toner images on the photoconductor during one rotation of the photoconductor; The invention further comprises a control means for controlling the photoreceptor, the developing device, the exposing means, and the charging means so that a toner image of another color is formed and transferred on the photoreceptor during one more rotation. color image forming device.