JPH067278B2 - Image forming method - Google Patents

Description

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.

Conventionally, a full-color hard copy image is composed of three primary colors of yellow, magenta, and cyan, and color reproduction has been performed by so-called subtractive color mixing. FIG. 5 shows a color laser beam printer proposed so far.

The laser beam La modulated by the image signal is made into a laser beam having a predetermined beam diameter in the beam expander 41 and is incident on the polyhedral reflecting mirror 42. Polyhedral reflector 4
Reference numeral 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.

Then, an image is formed as spot light on the photosensitive drum 51 through the slit of the secondary charger 54 by the image forming lens 44 having the f-θ characteristic. A part of the laser beam output from the imaging lens 44 is reflected by the reflecting mirror 45, and the beam detector 46
Is detected, and predetermined optical information is given to the photosensitive drum 51 by the output signal thereof, the timing of the modulation operation of the semiconductor laser 40 is controlled.

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 previously cleaned by the cleaning unit 52, and then the influence of the latent image previously formed is removed by an AC charger (not shown). Further, with the rotation in the direction of the arrow in the figure, the surface of the secondary charger 5 is uniformly positively charged by the primary charger 53, and then the secondary charger 5 is charged.
While being negatively charged by 4, the laser beam scans it, and the lamp 55 uniformly exposes it to form an electrostatic latent image.

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

The transfer material 60 stored in the cassette 59 is the photosensitive drum 51.
The transfer material 60 is fed by the paper feed roller 61 in synchronism with the rotation of the transfer drum 62, and the tip of the transfer material 60 is held by the gripper 62a of the transfer drum 62 having the same diameter as the photosensitive drum 51. It is wound around the surface of the polyester mesh screen 62b. Transfer charger 6
2c is a transfer material 60 for transferring the developed image on the photosensitive drum 51.
And the back surface of the mesh screen 62b is charged, thereby electrostatically adsorbing the transfer material on the front surface.

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

As described above, in the conventional color laser printer, in order to form a full-color image, the toner images of the three primary colors are repeatedly fixed on the transfer paper by repeating the above-mentioned five steps of charging, exposure, development, transfer, and cleaning. .

Therefore, there is a problem that the time required for one copy is long and the apparatus is complicated and large.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an image forming method capable of obtaining a high-quality color image at high speed.

That is, according to the present invention, the step of forming a latent image on the image carrier and the step of developing the latent image are repeated a plurality of times, and after the development of the first latent image, the formation of the next second latent image. In the image forming method of forming a color image by batch-transferring a plurality of developed images formed on a transfer material by performing a step of destaticizing the image carrier, the image carrier is formed on a light-transmissive conductive substrate. It is characterized in that it has a photoconductive layer, and the charge eliminating step is carried out by irradiating light from the light transmissive conductive substrate side of the image carrier.

Hereinafter, details of the present invention will be described with reference to specific examples.

FIG. 1 illustrates one embodiment of the process steps according to the present invention, in which I to VIII are schematic steps showing the surface potential Vs of the image carrier and the developing state of the toner image in each step. It is a figure. FIG. 2 is an example of an apparatus for carrying out the above steps.

Process I: A digital charge pattern is formed on the image carrier 1 by digitally driving the ion flow of the ion generator 4 described in Japanese Patent Laid-Open No. 54-78134 by a digital color image signal for the first color. To do.

Step II Charge pattern formed on the image carrier in Step I
The toner is developed by the developing device 5 with the toner of the same color as the first color.
For example, when the color signal of the first color is yellow, development is performed with the yellow developer Y. At this time, the developer has a polarity opposite to the charging polarity of the ions supplied by the ion generator 4. The developing one-component insulating toner - a developing pickpocket - after coating the blanking 5 _1, carried out at a jumping development of non-contact distance of about 300 [mu] m. That is, the developing sleeve 5 ₁
AC voltage (Example 2-3KHz, 1500Vpp) and DC voltage (Example + 10- + 50V) are applied to the toner, the toner on the sleeve does not contact the toner layer on the surface of the image carrier, and a powder cloud is formed to carry the image. Allows transfer depending on the body surface potential. At this time, the DC voltage is set to a value such that the fog toner does not transfer onto the image carrier by the powdery toner.

Step III: The surface of the image bearing member is neutralized by the static eliminator 6, and the potential of the surface of the image bearing member is neutralized to approximately 0V. However, it does not necessarily have to be 0 V and may be a uniform potential including the toner image portion. The charge is removed by a corona discharger. Step IV: The ion generator 7 is driven by the digital color image signal of the second color and the first digital charge pattern is generated.
The color toner images are formed on the image carrier 1.

V charge process The charge pattern formed in the IV process is developed with the developer M of the same color as the second color, for example, magenta.

The developing conditions are the same as those for the first color. The same applies to development in each of the steps described below.

VI process By the static eliminator 9, the first color toner and the second color toner
From the toner image of the color toner, the surface of the image bearing member is discharged in the same manner as in the step III. Step VII: The ion generator 10 is driven by the digital color image signal of the third color to form a charge pattern of the third color from the toner images of the first and second colors on the image carrier.

VIII process Depending on the charge pattern formed in the VII process, the third to third toner images from the first and second color toner images are formed.
The color toner image is developed with, for example, a cyan developer C.

By the above processes I to VIII, on the image bearing member 1,
A color developed image corresponding to the digital color image signal is formed. The color development image is simultaneously transferred onto the transfer material P by the transfer charger 12 at the same time.

The untransferred toner on the surface of the image carrier drum after the transfer is cleaned by a cleaner 2 such as a blade, and the residual charge on the image carrier is removed by a neutralizer 3.
On the other hand, the toner on the transfer material P is fixed by the fixing device 14.

The transfer is usually achieved by applying an electric charge having a polarity opposite to that of the toner to the back surface of the transfer paper. However, the toners such as yellow, magenta, and cyan that form the toner image on the image carrier 1 are charged by the digital charger and the static eliminator at least once. Therefore, the polarity of the toner may be reversed before the transfer process is reached. Therefore, it is preferable to provide a pretreatment means for returning the inversion of the toner polarity to the normal polarity. As post-processing means, the post-charger 15 shown in FIG. 2 charges the yellow, magenta and cyan triple toner images with the same polarity as the toner. After that, the transfer charger 12 applies a charge having a polarity opposite to that of the toner from the back surface of the transfer paper.

By the way, in the series of processes, when the charge is removed from the developed image formed on the surface of the image bearing member by the charge eliminator, the toner developing portion and the undeveloped portion are always discharged to a uniform potential. If possible. When a static eliminator such as the corona static eliminators 6 and 9 shown in FIG. 2 which supplies electric charges having a polarity opposite to the surface potential to the image bearing member is used, uneven static erasing b occurs in the toner developing portion and the undeveloped portion. As shown in FIGS. IV and VII of FIG. 3, there is a possibility that development unevenness (V and VIII) may occur in the second and third color toner developing portions due to the potential difference caused by the charge removal unevenness b. Therefore, the exposure type static eliminator is more effective than the charging type static eliminator.

However, even when the exposure type charge removal is used, there is no problem if the developer is a material having a good light transmittance, but when the light transmittance is poor and the light scattering effect is large, even if the exposure type charge removal is performed, After all, uneven development occurs due to uneven charge removal shown in FIG. Therefore, another embodiment of the present invention which solves such a problem is shown in FIG.

Also in the embodiment shown in FIG. 4, the ion generators 4, 7, 10, ...
16 and developing device, 5 (yellow), 8 (magenta), 1
The operations of 1 (cyan) and 17 (black) are the same as those of the embodiment shown in FIG.

That is, the drive of the ion generator can drive a digital color image signal from an external computer or a reader (not shown) through an external relay circuit, and is not shown in the image forming apparatus itself. When a reading system using a solid-state scanner such as CCD is provided, it is also possible to drive directly from a digital color image signal obtained from the reading system.
However, the ON / OFF of each ion generator must be performed with timing according to the moving speed of the image carrier.

The image carrier drum 1 shown in FIG. 4 is a conductive substrate 1a made of a transparent material.
And a photoconductive layer 1b. Further, a shaft 25 for rotatably supporting the drum 1 is made of a transparent material, and an exposure / erasing light source 24 such as a halogen lamp is housed therein. Then, the optical guide plate 26 is radially provided in a fixed manner, for example, by inserting it into the shaft 25, and between the guide plates 26 and 26 so as not to expose the charge pattern forming, developing and transferring regions. A light shielding plate 27 is provided.

With the above configuration, in the area corresponding to the static eliminators 6 and 9 in FIG. 2, the light from the light source 24 is received through the shaft 25 and the transparent electrode substrate 1a made of a transparent material, and the rear surface of the image carrier on the toner developing side. Therefore, it is possible to perform uniform charge removal without exposure unevenness and development unevenness.

As a result, a color toner image corresponding to the digital color image signal of each color is formed on the surface of the photoconductor, and is transferred at once by the transfer charger 12 onto the transfer paper P conveyed from the paper feed cassette 19. The fixing device 14 fixes the image. After the transfer process, the toner remaining on the surface of the photoconductor is removed by the cleaner 2. In FIG. 4, the exposure charge eliminator 23 is arranged on the downstream side of the cleaner in the moving direction of the image carrier. If a light source having a high heat dissipation effect is selected as the light source 24 for exposure and charge removal, it can be used as a drum heater together.

Further, in this embodiment, the color order of the developers is yellow Y, magenta M, cyan C, and black B, but this configuration can be arbitrarily selected due to the effect of improving color reproducibility. .

Further, the polarity of charging by the ion generator and the polarity of the developer may be selected so as to be opposite to each other as described above. That is, the developer of each color may be set to have a negative polarity in the case of positive charging, and the developer may be set to have a positive polarity in the case of negative charging.

As described above, one or more pairs of the ion generator and the developing device are arranged on the photoconductive side of the image carrier which moves endlessly, the ion generator is driven by the digital color image signal, and while the image carrier makes one round. Since this is a process in which the steps of charge pattern formation, development, and charge elimination are repeated at least once, a high-quality color image with no resist shift can be formed at high speed, and the apparatus can be miniaturized.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the steps of the present invention, FIGS. 2 and 4 are schematic configuration diagrams of an apparatus for carrying out the method of the present invention, FIG. 3 is a schematic diagram for explaining charge removal unevenness and development unevenness, and FIG. Is a configuration diagram of a conventional digital color printer using a laser beam method. DESCRIPTION OF SYMBOLS 1 ... Image bearing member, 2 ... Cleaner, 3/6/9 ... Electrification charger, 4/7/10/16 ... Ion generator, 5/8/11
17 ... Developer, 12 ... Transfer charger, 15 ... Post charger, 1a ... Transparent electrode, 1b Photoconductive layer, 23.24 ... Electrification removing light source, 25 ... Transparent drum shaft, 26 ... Light guide, 27 ...
Light shield.

Claims (1)

[Claims] 1. A process of forming a latent image on an image carrier,
The step of developing the latent image is repeated a plurality of times, and the step of destaticizing the image carrier is performed after the development of the first latent image and before the formation of the next second latent image. In the image forming method of forming a color image by batch-transferring to a transfer material, the image carrier has a photoconductive layer on a light transmissive conductive substrate, and the image carrier has a light transmissive conductive substrate side. An image forming method, characterized in that the static elimination step is performed by irradiating light from above.