JPH01227173A - Method for forming one-exposure, multicolor image - Google Patents

Abstract

PURPOSE:To obtain a sharp, multicolor image by further increasing the potential gap between electrostatic latent images of different potentials and the potential difference between bias voltages and sequentially developing said images. CONSTITUTION:An original placed on an original platen glass 17 is scanned by an original system A, and its image is converged on an electrostatically charged photosensitive drum 1 through a mirror, a lens, etc. The drum 1 is image-exposed and forms electrostatic latent images of different potentials corresponding to the color of the original image. The developing bias voltages impressed in the order of developing process are raised in that order, and an electrostatically charging process electrostatically and uniformly charging the entire surface of the advancing photosensitive body is added between the developing processes performed by adjacent developing devices. The potential gap between the electrostatic latent images of different potentials is further increased to make larger the potential difference between impressed bias voltages, and ultimately the images are developed in order. Thus, a multicolor image of high contrast is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an improvement in a method for forming an exposure multicolor image.

"Prior art" Two or more electrostatic latent images with different potentials are formed on a photoreceptor, and the electrostatic latent images are developed by driving a plurality of developing devices each containing a different color of developer. In particular, a method has already been developed in which a multicolor image is formed in one exposure by changing the developing bias voltage applied to each developing device.

``Problems to be Solved by the Invention'' In the conventional method, for example, as shown in FIG. Differently, the potential of the black part■,
and the potential of the red part ■2 is V, = -600V, V2 = -3
00V ((a) in the same figure).

Next, the residual potential ■,
When developing by applying a developing bias voltage of Vs+=100V, which is several tens of V higher than
400V, the potential of the red part becomes 2'--200V, and more red toner adheres to the black part than to the red part ((1) in the same figure)).

Further, the developing device containing the black developer is charged with V, which is several tens of V higher than the potential of the red part (2=-2).
When developing by applying a developing bias voltage of 50 V, the black toner adheres to the red toner in the black part, but does not adhere to the red part, as shown in FIG. 3(c). However, the potential ■1' of the black portion and the developing bias voltage VB2
Because the potential difference between the two colors is small, the amount of black toner adhering to the colored area is small, and when transferred to copy paper, the proportion of red toner adhering to the black area is large, resulting in a nearly black color that is a mixture of red and black. (d)) There is a problem that the boundary between the red part and the black part becomes unclear, making it impossible to obtain a sharp image with a high contrast color boundary. The present invention was made with the aim of solving the above problems.

"Means for Solving the Problem" A specific means for achieving the above object is to form two or more electrostatic latent images of different potentials on a photoreceptor, and to form electrostatic latent images of different colors in the traveling direction of the photoreceptor. A plurality of developing devices containing developer are arranged differently from the developing device 'ft, and the developing bias voltage applied to the developing devices is increased in the order of arrangement, and
This method is characterized by adding a charging step (=) to uniformly charge the entire surface of the photoreceptor as it progresses between the developing steps performed by adjacent developing devices.

"Function" As clarified in the description of the specific means described above, the present invention increases the developing bias voltage applied in the order of the developing steps, and the entire surface of the photoconductor that is being progressed between the developing steps by adjacent developing devices. By adding a charging process to uniformly charge the Fp, the potential gap between Fp images of different potentials is further increased.
By increasing the potential difference with the applied bias voltage and sequentially developing, a multicolor image with clear image contrast is formed.

"Example" An embodiment of the present invention will be described based on the accompanying drawings.

FIG. 1 is a schematic sectional view showing an example of a copying machine which is an image forming apparatus to which the method of the present invention is applied.

Approximately in the center of the copying machine body is a counterclockwise rotation drive I.
A photoreceptor drum 1 with high performance is provided, and a main eraser lamp 2. Charger 3, LED array 7, first developer 4. Electrostatic charger 6, second developing device 5
．． Transfer charger8. Charger 9. for copy paper. A blade type cleaner device 10 and the like are arranged quaternarily.

The photoreceptor drum 1 has a negatively charged photoreceptor layer on its surface, and is irradiated with light by an eraser lamp 2 each time it is copied, charged by passing through a charger 3, and subjected to image exposure from an optical system A. receive.

The optical system A is installed below the original glass 17 so that the original image can be scanned, and includes a light source 1] and a movable mirror 12.13.
4, a lens 15, and a mirror 16.

On the other hand, there are paper feed rollers 21 on the left side of the copying machine body.
. The lower paper feed cassette 22 is installed, and a pair of rollers 24. Timing roller pair 26. Guide plate 27. Guide plate 28 just before the transfer position. Conveyor belt 29.
It is composed of a fixing device 30 and a pair of discharge rollers 31.

The original placed on the original glass 17 is scanned by the optical system A, and the original image is transferred to the charged photosensitive drum 1.
The drum 1 receives image exposure and forms an electrostatic latent image with a different potential depending on the color of the original image.

By driving the first developing device 4, the toner contained in the developing device 4 is attached to the electrostatic latent image, and then the entire surface of the photoreceptor 1, which is being rotated 1!1, is deposited by the charger 6. Furthermore, by driving the second developing device 5, the toner contained in the second developing device 5 is attached. The toner image on the photoreceptor 1 is transferred by the transfer charger 8 onto a copy sheet sent out from the timing roller pair 26 together with the toner image forming area and the leading edge. Subsequently, the toner is separated from the surface of the photoreceptor drum 1 by the separation charger 9, sent to the fixing device 30 by the conveyor belt 29, where it is fused and fixed with the toner, and then delivered onto the ejection tray 34 by the ejection roller pair 31. Others 35 are main motors, and the photosensitive drums 1. Paper feed roller 21, 23', roller pair 24
．． Timing 1 Cola vs. 26. Developing device 4.5, 6. Conveyor belt 29° Fixed gear device 30. It is configured to drive a pair of discharge rollers 31, etc., and the paper feed rollers 21, 23 . Timing roller pair 26. Laura vs. 24. The developing devices 4, 5, etc. are configured to transmit or not transmit the driving force of the main motor 35 using a solenoid, an electromagnetic spring clutch, etc. (UfA not shown) so that they can operate independently.

Said 1st. The second developing device 4.5 has almost the same configuration as shown in FIG. Starting from the body drum 1 side, the developing sleeve 42. Supply roller 44. and a screw 45 are provided.

The developing sleeve 42 is made of a non-magnetic conductive material in a cylindrical shape (φ24.
5 mm), minute irregularities are formed on the outer periphery by sandblasting, and it faces the photoreceptor drum 1 with a development gap: l) s (= 0.6 mm) and development υ1fflX, X'. A charger 6 is disposed between the developing devices χ and X′.

Further, on the back side of the developing position X of the developing sleeve 42, a brush height regulating member 49 provided on the upper inner surface of the developer tank 41 faces with a brush height regulating gap: D b (=0.41).

A magnet roller 43 with a plurality of magnets extending in the axial direction is provided inside the developing sleeve 42, and magnets %N, ~Nj are located on the outer peripheral surface of the magnets.

The magnetic forces of Sl and S2 are respectively N l= l OU
OG, N2. N5=500G, S,,52=800G(
Note that G is an abbreviation for Gauss. ) Toshishita.

Furthermore, as shown in the figure, the first. A developing bias voltage V −+ is applied to the developing sleeves 42 and 42° of the second developing device 4°5.
= 100 V and V s t = 250 V were respectively applied.

A copying machine that implements the method of the present invention has the configuration described above. The second developing device 4.5 stores red and black insulating non-magnetic positively charged toners, and the photoconductor drum 1 is used as a negative band photoconductor to copy an original having a red part and a black part by the copying machine. The operation in this case and the potential of the static latent image corresponding to the red and black portions of the original on the photoreceptor will be explained with reference to FIG.

Due to the scanning operation of optical system A, the black part of the document becomes V)=
-600V, and the red part becomes V4=300V, forming electrostatic latent images of different potentials on the photoreceptor 1 (FIG. 4(a)). Next, when developing is performed by applying a developing bias voltage of several tens of V higher than the residual potential v8 to the first developing device 4, 11 = -100 µ, the potential of the black portion Vv' = 40
0V, the potential of the red part v,' = -200V, and more red toner adheres to the electrostatic latent image in the black part than in the red part ((b) in the same figure). (see figure).

After the development knee stage by the first developing device 4, when the entire surface of the photoreceptor 1 is charged in a negative direction by the charger 6, the electrostatic latent image in the black area is formed with the amount of toner attached as described above. Because there are so many, the capacitance becomes small and charges are easily accumulated, and therefore the surface potential becomes high, and as shown in the same figure (c), the potential of each of the black and red parts becomes Vs = 8.
50 V, V*--400V. Subsequently, when developing by applying a developing bias voltage V, 2 = -450 V to the second developing device 5, the amount of black toner attached is smaller than that in the conventional case because the potential gap between V and ■8□ is large. (same & (d)), - development bias voltage V -2 = 450 V > V s =
400 V No Seki (Black toner does not adhere from A. When this is transferred to paper, the black part becomes a mixed color of red and black, but since there is a large amount of black toner M, the red can be almost ignored. The contrast between the black and red parts becomes clearer, and the color boundaries become sharper ((d) in the same figure).
.

When similarly obtaining images of three or more colors from an original of three or more colors, a uniform charging process using a charging charger is added between each development process, and the differences between the toner adhesion and density between each electrostatic latent image are added. In addition to increasing the potential gap, the developing bias voltage of each developing device may be set so as to ensure a sufficient potential gap with the n-electro latent image corresponding to the developed color. Furthermore, in this case, toners of lower brightness are used in the order of the developing steps.

In addition, by using a translucent toner as the toner stored in the first developing device 4, I
- Since the color of the color does not show through and is not hidden, it is possible to obtain a color image with clear color boundaries.

"Effects of the Invention" As clarified in the above description of the specific means and operation, the present invention increases the developing bias voltage applied in the order of the developing steps, and increases the developing bias voltage applied between the developing steps using adjacent developing devices. A charging process is added to uniformly charge the entire Ifi of the photoconductor, the potential gap between electrostatic latent images of different potentials is further increased, and the potential difference with the applied bias voltage is also increased to perform sequential development. Therefore, it is possible to provide a single-exposure multicolor image forming method in which the amount of toner adhesion increases as the process progresses to the post-process, and a clearer multicolor image can be obtained compared to the conventional method. .

[Brief explanation of the drawing]

The accompanying drawings show one embodiment of the method of the present invention, in which FIG. 1 is a sectional view showing the outline of a copying machine, FIG. 2 is an enlarged sectional view of the first and second developing units 4.5, and FIG. The figure shows the present embodiment, and FIG. 4 is an explanatory diagram showing changes in the potential of the photoreceptor 1-I: of the conventional example. 199. Photoreceptor, 48. First developing device, 5.4. Second
Developing device, 691. Electric charger. Figure 4

Claims (1)

[Claims] Two or more electrostatic latent images with different potentials are formed on a photoreceptor, and a plurality of developing units each containing a developer of a different color are arranged at different developing positions in the traveling direction of the photoreceptor. One exposure characterized in that the developing bias voltage applied to the developing devices is increased in the order in which they are arranged, and a charging step is added between the developing steps of adjacent developing devices to uniformly charge the entire surface of the photoreceptor. Multicolor image forming method.