JPH0778655B2 - Color electrophotographic device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color electrophotographic apparatus that can be used in a hard copy apparatus such as a color copying machine or a printer.

2. Description of the Related Art In recent years, a plurality of toner images of different colors are formed on an electrophotographic photosensitive member (hereinafter referred to as a photosensitive member) by repeating charging, exposure, and development a plurality of times, and then the toner images are collectively transferred to a paper to perform color printing. A color electrophotographic apparatus for obtaining an image has been actively studied. Unlike the conventional color electrophotographic method, this method has an advantage that the apparatus can be downsized without a transfer drum.

An example of this type of color electrophotographic apparatus is an apparatus proposed by the inventors (Japanese Patent Application No. 62-4367). Embodiments of the present invention will be described below with reference to the drawings.

The developing devices 1, 2 and 3 are non-contact type non-magnetic one-component developing devices that fly the toner by a DC electric field, and the toner is triboelectrically charged by the conductive fur brushes 4, 5 and 6 in contact with the developing roller, A thin layer of toner is formed on the developing rollers 7, 8, 9 made of aluminum by the blades 10, 11, 12. The developing device 1 contains yellow (Y), the developing device 2 contains magenta (M), and the developing device 3 contains cyan (C) insulating toner. The developing device 13 is a contact type developing device containing a two-component developer. Then, each developing device was installed opposite to the periphery of the photoconductor 15 while keeping the gap (development gap) between the developing rollers 7, 8, 9, 14 and the photoconductor 15 constant. Each developing device is provided with a separating / contacting mechanism that approaches the photoconductor during development and separates it during non-development.

An amorphous Se-Te photosensitive drum 15 having a diameter of 152 mm, which is sensitized to a long wavelength in the infrared region, is used as a photosensitive member, and is rotated at a peripheral speed of 160 mm / s. The photoconductor 15 is charged to a charging potential + 900V by a charger 16 (scorotron charger, corona voltage: + 7kV, grid voltage: 1kV). Next, the semiconductor laser 17 having a wavelength of 790 nm is emitted and exposed. Using this semiconductor laser 17, a negative black signal is exposed on the photoconductor 15 to form an electrostatic latent image. The latent image is reversely developed by the black developing device 13 in the developing state in which + 600V is applied to the developing roller 14 to form a black toner image, and then the photoconductor 15 is neutralized by the static elimination lamp 18.

Next, the photoreceptor 15 is charged to + 600V again by the corona charger 16. After that, the semiconductor laser 17 exposes the signal light corresponding to the yellow to the photoconductor 15 to form a yellow electrostatic latent image. Next, this photoreceptor is passed through the yellow developing device 1 in the developing state in which + 600V is applied to the developing roller 7, the magenta developing device 2 in the non-developing state, the cyan developing device 3 and the black developing device 13 to pass the yellow toner image. To form. Next, without removing the charge on the photoconductor 15, the corona charger is used again.
The photosensitive member 15 was charged to + 810V by 16. Then, the semiconductor laser 17 exposes signal light corresponding to magenta to form a magenta electrostatic latent image. Next, the photoconductor 15 is passed through the yellow developing device 1 in the non-developing state and the magenta developing device 2 in the developing state in which + 800V is applied to the developing roller 8 to form a magenta toner image. After that, the photoconductor 15 is passed through the non-developed cyan developing device 3 and the black developing device 14.

Next, this time, the photoconductor 15 is exposed to corona by the AC corona charger 19 (applied voltage; 5 kVrms), and the corona charger 16 charges the photoconductor 15 to +800 V again. After that, the semiconductor laser 17 exposes signal light corresponding to cyan to form a cyan electrostatic latent image. Next, the photoconductor 15 is added to the yellow developing device 1 in the non-developing state, the developing device 2 for magenta, and the developing roller 9.
It is passed through a developing cyan developing device 3 to which 800 V is applied to form a cyan toner image to complete a color image on the photoconductor.

The color toner image thus obtained on the exposure body 15 is transferred onto the paper 21 by the transfer charger 20, and then is thermally fixed by the fixing device 22. On the other hand, after the transfer, the surface of the photoconductor 15 is positively charged by the pre-cleaning charger 23 (corona voltage +5.5 kV), and then the conductive fur brush 24 to which a voltage of −150 V is applied is pressed against the photoconductor 15. To clean.

Problems to be Solved by the Invention In the conventional example described above, two chargers, that is, the AC corona charger 19 and the DC corona charger 23 are used in the image forming process. Each of them is used according to a different purpose,
The AC corona charger 19 is used for the purpose of preventing the occurrence of color turbidity due to the reduction of the charging potential of the red portion, and the DC corona charger 23 is used for aligning the polarities of the toner remaining on the photoconductor after transfer and for assisting the cleaning. There is. These two corona chargers use one when not the other. The use of these two chargers complicates the configuration, and requires two types of high-voltage power supplies of direct current and alternating current, which increases the cost of the device.

In view of such a point, the present invention shares the same charger to achieve a plurality of image forming purposes, and by switching the voltage of the high-voltage power source applied to the charger according to the purpose,
It is an object of the present invention to provide a color electrophotographic apparatus having a very simple apparatus configuration.

Means for Solving the Problems According to the present invention, a main charger for charging a photoconductor, a yellow, magenta, and cyan color developing device, a pre-cleaner charger, and a DC bias component A and a DC bias component B are switched to generate a DC voltage. A color electrophotographic apparatus, comprising: a power source for applying a voltage to the pre-cleaner charger and a cleaner; and a charging step, an exposing step, a developing step, and the DC bias component A for each image forming step. AC voltage is superimposed on the AC voltage is applied to the cleaner pre-charger to repeat the AC corona radiating step to form a color toner image on the photoconductor and transfer it to paper, and then to the toner remaining on the photoconductor. After the voltage in which the DC bias component B is superimposed on the AC voltage is applied to the cleaner pre-charger, an AC corona is emitted, and then the cleaner is used to clean the photoreceptor. It is a color electrophotographic device for training.

Action With one corona charger, set the AC voltage so that a constant voltage is applied, and reduce only the DC bias component superimposed on it to reduce the DC bias component for the purpose of preventing red charging potential drop, and perform cleaning. For the above purpose, the problem can be solved by increasing the size.

Example First, a functional description will be given. That is, in the conventional example, the purpose of use of the charger 19 is to overlap the yellow toner and the magenta toner on the photoreceptor by exposing the AC corona, that is, when the photoreceptor in the red portion is recharged by the charger 16. It is used for the purpose of preventing dielectric breakdown and lowering the surface potential. Therefore, at this time the charger
It is desirable that the AC voltage applied to 19 has no DC bias component or is small. One of the chargers 23 is a pre-cleaner charger, and is a charger for the purpose of corona bombardment in order to align the polarity of the toner remaining on the photoconductor after transfer in one direction. In the above-mentioned conventional example, a positive DC voltage is applied to the charger 23. Here, even if an AC voltage having a DC bias component superposed to positively charge the photoconductor is applied to the charger 23, the polarities of the toners on the photoconductor can be made uniform and similarly as a cleaner pre-charger. It turns out that the effect of is obtained. However, it has been found that there is almost no effect even if the AC voltage on which the DC bias component is superposed is applied to the charger 23 as it is for the purpose of preventing the reduction of the charging potential of the target red portion of the charger 19.

Therefore, the power source applied to the corona charger used in the present invention is preferably within the range described below. Here, the DC bias component A means a voltage used for the purpose of preventing dielectric breakdown when the red part is recharged, and the DC bias component B means a voltage used for the pre-cleaner charging. The specific circuit configuration of such an AC power supply is well known in the art and will not be described.

● Range of AC voltage: 3.5 to 6 kVrms Range of superposed DC bias component A: 0 to +400 V Range of superposed DC bias component B: +400 to +1200 V Corona discharge is a direct current bias component A to the photoreceptor at least after the magenta developing step and before the cyan charging step.
It is effective to explode the AC corona with a charger to which an AC voltage that superimposes is applied, but the same effect can be obtained if the exposure is continued during all image forming processes of black, yellow, magenta, and cyan. . The effect of this corona exposure was particularly effective when the photoconductor was an amorphous selenium photoconductor. It was also effective when the photoreceptor was an amorphous selenium arsenide-based photoreceptor. Needless to say, the polarity of the superimposed DC bias component becomes negative in an organic photoconductor having a negative charging polarity.

Hereinafter, an embodiment of the improved invention will be described again with reference to the drawings.

In this device, the charging device 19 is removed from the device described in the conventional example, and the power supply connected to the charging device 23 is replaced with a high-voltage alternating-current power supply that switches the direct-current bias component from the high-voltage power supply.

The developing devices 1, 2 and 3 are non-contact type non-magnetic one-component developing devices that fly the toner by a DC electric field, and the toner is triboelectrically charged by the conductive fur brushes 4, 5 and 6 in contact with the developing roller, A thin layer of toner is formed on the developing rollers 7, 8, 9 made of aluminum by the blades 10, 11, 12. The developing device 1 contains yellow (Y), the developing device 2 contains magenta (M), and the developing device 3 contains cyan (C) insulating toner. The developing device 13 is a contact-type developing device containing a two-component developer composed of an insulating toner and a magnetic carrier, which is widely used in electrophotographic apparatuses. Then, each developing device was installed opposite to the periphery of the photoconductor 15 while keeping the gap (development gap) between the developing rollers 7, 8, 9, 14 and the photoconductor 15 constant. Each developing device is provided with a separation / contact mechanism that is close to the photoconductor 15 during development and is separated during non-development.

The specifications and development conditions of the black developing device 13 and the physical properties of the toner are shown below.

● Specifications of developing device and developing conditions Diameter of developing roller 14: 22 mm Peripheral speed of developing roller 14: 320 mm / s Developer layer thickness on developing roller 14: 400 μm Rotating direction of developing roller 14: Opposite to photoconductor 15 (Same direction of travel) Development gap (gap between the surface of the developing roller and the surface of the photoconductor): 300 μm during development, 2 mm during non-development [Physical properties of developer] Type of developer: Two-component developer of toner and carrier Average of carrier Particle size: Approx. 50 μm Carrier type: Teflon coated ferrite Toner charge amount: +10 μC / g Toner average particle size: 8 μm Toner dielectric constant: Approx. 2 Yellow, magenta and cyan developing device specifications and developing conditions It is shown below.

● Developer specifications and development conditions Development roller diameter: 20mm Development roller peripheral speed: 160mm / s Development roller rotation direction: Opposite to photoreceptor 15 (same direction) Toner layer thickness on development roller: 30μm Development gap (gap between the surface of the developing roller and the surface of the photoconductor): 150 μm during development, 2 mm during non-development [Physical properties of toner] Toner charge amount: +3 μC / g Average particle size: 10 μm Dielectric constant: about 2 As a photoconductor Amorphous Se-Te photosensitive drum 15 with a diameter of 152.8 mm that is sensitized to long wavelengths in the infrared region (photosensitive layer thickness of 63 μm, relative dielectric constant of about 7, long-wavelength sensitized function-separated selenium photoconductor, A half-exposure dose of 0.6 μJ / cm ² at a wavelength of 790 nm was used, and rotation was performed at a peripheral speed of 160 mm / s. Charge this photoreceptor 15 to charger 1.
6 (Scorotron charger, corona voltage: + 7kV, grid voltage: 1kV) was charged to a charging potential of + 900V. next,
A semiconductor laser 17 having a wavelength of 790 nm was emitted and exposed.

At this time, the light intensity on the photoreceptor surface was 1.2 mW.
Using this semiconductor laser 17, a negative black signal was exposed on the photoconductor 15 to form an electrostatic latent image. The latent image is reversely developed by the black developing device 13 in the developing state in which + 600V is applied to the developing roller 14 to form a black toner image, and then the AC corona charger 23
(AC voltage: 5 kVrms, DC bias component A: +200 V), the AC corona was exposed to an explosion, and then the photoconductor 15 was discharged by the discharge lamp 18.

At this time, the thickness of the black toner layer developed on the photoconductor 15 was 1 to 2 layers, and the thickness of the toner layer was 10 to 20 μm.

Next, again use the corona charger 16 (scorotron charger, corona voltage: +7 kV, grid voltage: 600 V) to move the photoconductor 15 to +60.
It was charged to 0V. At this time, the photoconductor 15 with the black toner attached
Has a charging potential of 600V. After that, the photoconductor 15 was exposed to the signal light corresponding to yellow by the semiconductor laser 17 to form a yellow electrostatic latent image. Here, the exposure amount of the semiconductor laser was set to 1.2 mW on the surface of the photoconductor. Next, this photoreceptor is passed through the yellow developing device 1 in the developing state in which + 600V is applied to the developing roller 7, the magenta developing device 2 in the non-developing state, the cyan developing device 3 and the black developing device 13 to pass the yellow toner image. Was formed. After that, AC corona charger 23 (AC voltage; 5
After exposing the AC corona with kVrms, DC bias component A; + 200V), the corona charger 16 (scorotron charger,
The photoconductor 15 was charged to + 850V with a corona voltage of + 7kV and a grid voltage of 900V. At this time, the charging potential of the photoconductor 15 to which the black and yellow toner adhered became 870V. Then, the semiconductor laser 17 exposed the signal light corresponding to magenta to form a magenta electrostatic latent image.

The photoconductor 15 is a yellow developing device 1 and a developing roller 8 in a non-developing state.
Then, it is passed through a magenta developing device 2 in the developing state in which +830 V is applied to form a magenta toner image. At this time the photoconductor
The toner layer on the part where yellow and magenta overlap on 15
There were 2 to 4 layers, and the thickness was 20 to 40 μm.
After that, the photoconductor 15 was passed through the non-developed cyan developing device 3 and the black developing device 13. Next, the photoconductor 15 is again charged with the AC corona charger 23 (AC voltage; 5 kVrms, DC bias component A; +2).
00V) and exposed again to the photoconductor 15 by the corona charger 16.
Was charged to + 850V. At this time, the charging potential of the photoconductor 40 to which only the black, yellow, and magenta toner adhere is +87.
It became 0V. In addition, the charging potential of the photoconductor 15 in the portion where the yellow and magenta toners were overlapped was + 800V. afterwards,
The signal light corresponding to cyan was exposed by the semiconductor laser 17 to form a cyan electrostatic latent image.

The photoconductor 15 is passed through the yellow developing device 1 in the non-developing state, the magenta developing device 2, and the developing cyan developing device 3 in which + 830V is applied to the developing roller 9 to form a cyan toner image to form a color image on the photoconductor. Completed the image.

The color toner image thus obtained on the photoconductor 15 was transferred onto the paper 21 by the transfer charger 20, and then heat-fixed by the fixing device 22. On the other hand, after transfer, the surface of the photoconductor 15 is replaced with an AC corona charger 23 (AC voltage: 5 kVrms, DC bias component B: +800
After charging the surface potential of the photosensitive member to +300 V with V), the conductive fur brush 24 to which a voltage of −350 V was applied was pressed against the photosensitive member 15 for cleaning.

As a result, the color density of the composite color of the solid areas of red, green and blue is 1.5.
As described above, a clear color image with high color purity was obtained without the cyan toner being mixed in the red part. Further, the toner remaining on the photoconductor could be completely cleaned. This image forming process was repeated 1000 times in succession, but cyan fogging on the red portion did not occur, and the background stain due to poor cleaning did not occur.

EFFECTS OF THE INVENTION As described above, according to the present invention, the same charger is commonly used to achieve a plurality of image forming purposes, and the voltage of the high voltage power source applied to the charger is switched according to the purpose. As a result, it is possible to obtain a color electrophotographic apparatus having an extremely simple apparatus configuration.

[Brief description of drawings]

FIG. 1 is a block diagram of a color electrophotographic apparatus according to an embodiment of the present invention. 1,2,3 ... Developer, 13 ... Developer (black), 15 ... Photoreceptor, 16 ... Corona charger, 17 ... Semiconductor laser, 23 ...
… AC corona charger.

Claims (1)

[Claims] 1. A main corona charger for charging a photoconductor, a yellow, magenta, and cyan color developing device, a corona charger before cleaner, a DC bias component A for discharging toner, and a DC bias component B for charging toner. A color electrophotographic apparatus comprising a power supply for switching and superimposing on an AC voltage to apply a voltage to the pre-cleaner corona charger, and a cleaner, wherein a corona charging step, an exposing step, and a developing step are performed for each image forming step. The alternating current corona radiating step in which a voltage obtained by superimposing the direct current bias component A on the alternating current voltage is applied to the corona charger before the cleaner is repeated, and the powder color toner images are superposedly formed on the photoconductor and transferred to paper. After that, a voltage in which the DC bias component B is superimposed on the AC voltage is applied to the toner remaining on the photoconductor to the corona charger before the cleaner. A color electrophotographic apparatus that cleans the photoconductor using the cleaner after radiating a flow corona.