JPS60237467A - Image formation - Google Patents

Abstract

PURPOSE:To enable formation of multiple layers of images consisting of several layers on a photosensitive body by executing several times the process for electrifying uniformly the surface of the photosensitive body, subjecting the body to exposing by a semiconductor laser than to reversal development during one rotation of the photosensitive body. CONSTITUTION:The surface of the photosensitive body 51 having a transparent conductive electrode substrate 1a on the rear is uniformly electrified by a corona electrifier 3 and is then subjected to the exposing corresponding to the color signal of the 1st color by the semiconductor laser La from the rear of the photosensitive body. The surface potential of the exposed part is decreased from the initial surface potential down to the prescribed potential and the exposed part thereof is similarly subjected to reversal development. The exposing corresponding to the color signal of the 2nd color is executed similarly from the rear side and the exposed part thereof is similarly subjected to reversal development. Such process is repeated plural times during one rotation of the photosensitive body, by which the images of the multiple colors consisting of several layers are formed on the photosensitive body. The color images having good reproducibility of the medium contrast are thus obtd. at a high speed without resist deviation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming method, and more particularly to an image forming method for obtaining an image based on a plurality of different latent images.

Traditionally, full-color No\-Tocobee images were yellow.
It is composed of 3M colors of magenta and cyan, and color reproduction has been performed by so-called subtractive color mixing. FIG. 4 shows a color laser beam printer that has been proposed so far.

The laser light La modulated by the image signal is converted into a laser light having a predetermined beam diameter by the beam expander 41 and is incident on the polyhedral reflecting mirror 42 . Polyhedral reflector 4
2 has a plurality of reflecting mirrors and is rotated at a predetermined speed by a constant speed rotation motor 43, so that the incident laser beam La is scanned substantially horizontally.

The light is then imaged as a spot light onto the photosensitive drum 51 through the slit of the secondary charger 54 by the imaging lens 44 having f-θ characteristics. Note that a part of the output laser light from the imaging lens 44 is reflected by a reflecting mirror 45 and transmitted to a beam detector 46.
The timing of the modulation operation of the semiconductor laser 40 is controlled in order to provide predetermined optical information on the photoreceptor drum 51 based on the output signal.

The photosensitive drum 51 has, for example, a CdS photosensitive member having a three-layer structure including a conductive support, a photoconductive layer, and an insulating layer, and is rotatably supported. The photosensitive drum 51 is cleaned in advance by a cleaning unit 52, and then the influence of a previously formed latent image is removed by an AC charger (not shown). Further, as the surface rotates in the direction of the arrow shown in the figure, the surface is uniformly positively charged by the primary charger 53, and then the secondary charger 5
While being negatively charged by 4, it is scanned by a laser beam, and is further uniformly exposed by a lamp 55 to form an electrostatic latent image.

This latent image is developed by the corresponding color developing device among the developing devices 56, 57, and 58 having yellow, magenta, and cyan developers, respectively. Of the above, the polarity of charging is merely an example, and the polarity differs depending on the conductivity type of the photoreceptor.

The transfer material 60 stored in the cassette 59 is transferred to the photosensitive drum 51.
The tip of the transfer material 60 is held by the gripper 62a of the transfer drum 62, which has the same diameter as the photosensitive drum 51, by the paper feed roller 61 in synchronization with the rotation of the photosensitive drum 51. It is wrapped around the surface of the polyester mesh screen 62b. Transfer charger 6
2c transfers the developed image on the photosensitive drum 51 to a transfer material 60.
At the same time, the back surface of the mesh screen 62b is charged, thereby causing the transfer material to be electrostatically attracted to the surface thereof.

After the developed image on the photosensitive drum 51 is multiple-transferred to the transfer material 60 on the transfer drum 62 with three-color alignment, the gripper 62a is released and the separation claw 62d is operated to remove the transfer material 60. To separate. The transfer material 60 is guided by a conveyor belt 63 to a heating roller fixing device 64, where the transferred image is heated and fixed, and then the transfer material 60 is discharged onto a paper discharge tray 65. In this way, a full-color image is formed on the transfer material 60, and document information corresponding to the color signals input to the color laser printer is faithfully reproduced.

In this way, in conventional color laser printers, in order to form full colors, toner images of each of the three primary colors are superimposed and fixed on transfer paper by repeating the above five steps of charging, exposure, development, transfer, and cleaning. .

Therefore, there are problems in that the time required for one copy is long and the apparatus becomes complicated and large.

The present invention has been made in view of these points, and it is an object of the present invention to provide an image forming method that is fast, that requires only registration, and that can obtain color images with good halftone reproducibility.

That is, in the present invention, a photoreceptor having a transparent conductive electrode substrate on the back surface is uniformly charged with a corona charger, and then exposed from the back surface of the photoreceptor with a semiconductor laser according to the color signal of the first color. The surface potential of the exposed area is lowered from the initial surface potential to a predetermined potential, and the exposed area is reversely developed. Next, exposure according to the color signal of the second color is similarly performed from the back side of the photoreceptor, and the exposed area is similarly subjected to reversal development.

By repeating this process multiple times during one rotation of the photoreceptor, a multicolor image consisting of several layers is formed on the photoreceptor.

Hereinafter, details of the present invention will be explained using specific examples with reference to the drawings.

FIG. 1 is a diagram illustrating an embodiment of the process according to the present invention, and 7 to 6 are schematic diagrams showing the surface potential Vs of the photoreceptor and the developed image in each step. FIG. 2 is a schematic diagram of an apparatus for carrying out the method of the present invention, in which a photosensitive drum 1 has a transparent conductive electrode substrate 1a and a photoconductor layer tb.

(2) Step A charge is uniformly applied to the surface of the photoreceptor by the corona charger 3, and the surface potential Vs is charged to approximately 600V, for example.

(2) Step In accordance with the first color signal, exposure is performed from the back surface of the photoreceptor through the transparent conductive electrode substrate 1a using a semiconductor laser La. In this case, exposure is performed according to the logic shown in the semiconductor laser output logic table (1) in Figure 3. In other words, in this example, the potential of the surface of the photoreceptor at the exposed portion (represented by ON in the table) drops to 400■. As in, semiconductor laser L
The light amount of aI is set.

(2) Process Development is performed by the developing device 4 using toner having a complementary color to the color signal of the first color. For example, when the color signal of the first color is blue, reversal development is performed using developer Y of yellow, which is its complementary color.

At this time, the developing sleeve 41 is coated with yellow one-component insulating toner Y, and the charge pattern is reversely developed by a non-contact developing method. At this time, the polarity of the toner is positive.

During this first development, alternating current and direct current developing bias voltages are applied to the developing sleeve 41. The developing bias in this case is an AC voltage component (Example 2-3KHz - 1000-1500
V p p ) t*, which is the value at which a notonaka powder cloud can be formed on the sleeve and transferred according to the potential of the photoreceptor. Further, the DC voltage component is set to a potential that can prevent fogging of the back ground (in the embodiment, it is set close to the value of the surface potential of 600 cm).

Ultrasonic waves can also be used as a powder cloud generation method. In addition, as another non-contact developing method,
The method described in No. 1180fiO may be applied.

The above-mentioned development conditions are the same in the following steps, so their description will be omitted below.

Step (2) A charge pattern corresponding to the color signal of the second color is applied onto the surface of the photoreceptor having the toner image Y of the first color by the semiconductor laser La2. The output of the semiconductor laser La2 based on the second color signal is determined by the logic shown in the third diagram (2). That is, it is determined by the relationship between the target potential of the second color and the potential of the first color.

For example, in the case of a dot that is not developed in the second color, that is, in the case that development is OFF during the surface, the potential e of the first color is
Regardless of the value of oov or 400V, the semiconductor laser La2 is exposed so that the potential of the second color becomes 400V. In addition, in the case of dots to be developed in the second color,
That is, when development is ON, the potential of the first color is 800V.
, 400V, exposure is performed so that the potential of the second color becomes 200V. In other words, the potential for developing the second color is 20QV, and the potential for not developing is 4QOV. To obtain this potential, the amount of change in surface potential is 200V (8
00V-400V, 400V-200V),
Reduce the laser output to Low and change the surface potential by 400
V (600V → 200V) If not, increase the laser output to Middle. Note that in a semiconductor laser, the output of the laser beam changes depending on the change in the injection current, so the injection current may be controlled in order to change the laser exposure amount.

The above example assumes that the potential of the first color does not attenuate due to development with the first color toner. However, in reality, this potential attenuation occurs to some extent, so the output of the semiconductor laser must take this amount of attenuation into consideration.

Further, in this case, the DC voltage component of the developing bias is set close to the value of the surface potential of 400 V in the area on which toner is not to be attached, and the other developing conditions are as described above.

(2) Process Developing is performed in the developing unit 5 using toner having a complementary color to the color signal of the second color. In this case, for example, when the color signal of the second color is green, the toner of the developer is magenta, which is a complementary color.

■Process Semiconductor laser La
3, a charge pattern corresponding to the color signal of the third color is applied.

The output of the semiconductor laser is determined according to the logic in the third diagram (3), similar to the logic in the third diagram (3), similar to the table (2) showing the logic in the step (2).

In other words, in the area where development is ON, the potential of the second color is 400V or 200V, which is OV the target potential of the third color, and in the area where development is OFF, the potential of the second color is 400V or 200V, whichever is OV. However, the semiconductor laser is exposed so that the target potential of the third color is 200V. Laser output LawφMid when the amount of potential change between the potential of the second color and the target potential of the third color is 200V/400V
The relationship of dle is the same as in the case of step (2).

■Process Developing is performed in the developing device 6 using toner having a complementary color relationship to the color signal of the third color.
When the color signal of the color is red, the toner of the developer is cyan C, which is a complementary color.

In this case, the DC voltage component of the developing bias may be set close to the value of the surface potential of 200 V on the area where toner is not desired to adhere.

In the above configuration, since jumping development is performed with a spacing of 300 pLm between the sleeve and the photoreceptor, the previously developed toner image is developed faithfully to the charge pattern without overflowing during subsequent development.

When the step L is completed, the three-color toner images of yellow, magenta, and cyan on the photosensitive drum l are simultaneously transferred onto the transfer material 8 by the transfer charger 7. The surface of the photosensitive drum after the transfer is cleaned by a cleaner 2. On the other hand, the toner on the transfer material 8 is fixed by a fixing device 9.

Note that in order to increase the transfer efficiency, the toner image on the photoreceptor may be charged with the same polarity as the toner using the charger 10 before the transfer.

Although the above embodiment is a case of overlapping colors, a multicolor image can be obtained as a multicolor printer that does not perform overlapping colors.

In other words, in the example in Figure 1, the yellow Y (yellow) that appears in the final step (■) and the mixed color (red) of yellow Y and magenta M
, a mixed color of yellow Y, magenta M, and cyan C (black),
Each latent image is developed using toner of four colors, a mixed color (blue) of magenta M and cyan C.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the steps of the method of the present invention, Fig. 2 is a schematic diagram of an apparatus for carrying out the method of the present invention, Fig. 3 is an output logic diagram of a semiconductor laser, and Fig. 4 is a conventional color image forming apparatus. A perspective view of. 1 is a photosensitive drum, 1a is a transparent conductive electrode substrate, 1b is a photoconductor layer, 3 is a charger, 4, 5, and 6 are developing devices, 7 is a transfer charger, 8 is a transfer material, Lal La2 φLa3 is a laser beam. Figure 2 9 Figure 1

Claims (2)

[Claims] (1) On the photoreceptor having a transparent conductive electrode substrate on the back side,
After uniformly charging, laser exposure is performed from the back side to form a charge pattern, and the process of reversing and developing the charge pattern is repeated several times during one rotation of the photoreceptor, thereby creating different patterns on the photoreceptor. An image forming method characterized by forming a developed image. (2) After developing the charge pattern corresponding to the first color, the second
After the color, the output of the laser that performs exposure from the back surface is adjusted according to the relationship between the potentials of the charge pattern of the first color and the (i-1)th color so that the potential of the target charge pattern of the first color is obtained. The image forming method according to claim 1, wherein the image forming method is determined logically.