JPH0697362B2 - 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. The conductive fur brushes 4, 5 and 6 in contact with the developing roller frictionally charge the toner, and aluminum is used. A thin layer of toner is formed on the developing rollers 7, 8 and 9 made of blades by the blades 10, 11 and 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, with the gap (development gap) between the developing rollers 7, 8, 9 and 14 and the photoconductor 15 being constant, the respective developing devices are installed facing each other around the photoconductor 15. Each developing device is provided with a separation / contact mechanism that is close to the photoconductor during development and is separated during non-development.

An amorphous Se-Te photosensitive drum 15 having a diameter of 152 mm 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. This photoconductor 15 is charged by a charger 16 (a scorotron charger,
It is charged to a charging potential of + 900V by 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 +600 V 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.

Then, without discharging the photoconductor 15, the photoconductor 15 was again charged to +810 V by the corona charger 16 as it was. Then, the semiconductor laser 17 exposes signal light corresponding to magenta to form a magenta electrostatic latent image. next,
The photoconductor 15 is the yellow developing device 1 and the developing roller 8 in the undeveloped state.
Then, a magenta toner image is formed by passing it through the magenta developing device 2 in the developing state in which +800 V is applied to. Then the photoconductor
15 is passed through the cyan developing device 3 and the black developing device 14 in the non-developed state.

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 photoconductor 15 is transferred onto the paper 21 by the transfer charger 20, and then 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.

As described above, in this conventional example, black is first developed.

SUMMARY OF THE INVENTION In this method, the order of image formation on the photoconductor is black, yellow, magenta, and cyan. Here, the black developing device is a developing method in which the photoconductor and the developer come into contact with each other, and the other yellow, magenta, and cyan developing method is a DC electric field flight developing method in which the photoconductor and the developer do not come into contact with each other. In the conventional example, black development, which is a contact development method, is performed first, and then yellow.
By repeating the image forming process in the order of magenta and cyan to form a color image, the color turbidity of the developing device is prevented. However, when a paper jam occurs and the device is reset, when the developing device is pressed against the photoconductor in the order of black, yellow, magenta, and cyan in the same manner as when forming an image, other color toner is mixed in the black developing device. However, it was found that remarkable color turbidity occurred.

In view of the above point, the present invention has an object to prevent other color toners from being mixed into the black developing device when the apparatus is reset due to a trouble such as a paper jam.

MEANS FOR SOLVING THE PROBLEM The present invention repeats the charging, exposing and developing processes for each image forming process of each color of black, yellow, magenta and cyan to form a color image on the photoconductor and then transfer it to paper. In the color electrophotographic apparatus, each of the black, yellow, magenta, and cyan developing devices has a mechanism for approaching the photoconductor during development and otherwise separating from the photoconductor. Is a developing method in which a developer is in contact with the photoconductor, and each of the yellow, magenta, and cyan developing methods is a color electrophotographic apparatus in which the photoconductor and the developer are non-contact developing methods, In the image forming step, the black image forming step is performed first, and in the device resetting step, the black developing devices are brought close to the photoconductor in the last order of the developing devices.

Action In the electrophotographic device that forms a color toner image on the photoconductor and then transfers it to a sheet of paper as described in the conventional example, if the image forming process is stopped due to a paper jam or the like, all the colors will be printed on the photoconductor. Toner remains attached. When the black developing device is first brought close to the photoconductor, the black developing device comes into contact with the photoconductor to develop the color toner on the photoconductor. Resulting in. However, according to the present invention, first, the color developing device is brought close to the photoconductor. At this time, since the color developing device is a DC electric field flight developing method in which the developer and the photoconductor are not in contact with each other, the toner is not mixed in the color developing device even if the toner remains on the photoconductor. During that time, since the toner on the photoconductor is removed by the cleaning device while the photoconductor continues to rotate, it is possible to prevent the color toner from being mixed into the black developing device which is finally brought close to the photoconductor.

Example Hereinafter, an example of the present invention will be described 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 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) 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 property 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. It is shown below.

● Developer specifications and development conditions Development roller diameter: 20mm Development roller peripheral speed: 160mm / s Development roller rotation direction: Opposite direction to photoconductor 15 (same direction) Toner layer thickness on development roller: 30μm Development gap (gap between the surface of the development 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 Relative permittivity: Approx. 2 binder resin: Styrene / Acrylic resin Amorphous Se-Te photoconductor drum 15 with a diameter of 152.8 mm sensitized in the infrared region as a long wavelength (photosensitive layer thickness of 63 μm, relative dielectric constant of about 7, long wavelength sensitized in the infrared region) Using a function-separated selenium photoconductor, a half-exposure amount at a wavelength of 790 nm of 0.6 μJ / cm ² ) and rotating 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, the 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 a black developing device 13 in a developing state in which + 600V is applied to a developing roller 14 to form a black toner image, and then an AC corona charger 23 (AC voltage: 5kVrms, DC bias component: + 200V).
After exposing the AC corona to the
I removed 15 charges. At this time, the thickness of the black toner layer developed on the photoconductor 15 is 1 to 2 layers, and the thickness of the toner layer is 10 layers.
Was about 20 μm.

Again, the photoconductor 15 was charged to + 600V by the corona charger 16 (scorotron charger, corona voltage: + 7kV, grid voltage: 600V). At this time, the charging potential of the photoconductor 15 to which the black toner adhered was 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. Next, AC corona charger 23 (AC voltage: 5kVrms, DC bias component: + 200V)
After exposing the AC corona to
(Scorotron charger, corona voltage: +7 kV, grid voltage: 900 V) charged photoreceptor 15 to +850 V. 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. Next, the photoconductor 15 is added to the yellow developing device 1 and the developing roller 8 in the non-developing state.
A magenta toner image was formed by passing it through the magenta developing device 2 in the developing state to which 830 V was applied. At this time, the toner layer in the portion where the yellow and magenta overlapped on the photoconductor 15 was 2 to 4 layers, and the thickness thereof 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 an AC corona charger 23 (AC voltage: 5 kVrms, DC bias component: +200
V) and exposed the photoconductor 15 to + 850V by the corona charger 16 again. At this time, the charging potential of the photoconductor 40 to which only the black, yellow, and magenta toners are attached is 870V.
Became. In addition, the charging potential of the photoconductor 15 in the portion where the yellow and magenta toners are overlapped is also 800V.

After that, the semiconductor laser 17 exposed the signal light corresponding to cyan to form a cyan electrostatic latent image. Next, the photoconductor 15
To a non-developing yellow developing device 1 and a magenta developing device 2 and a developing developing cyan developer 3 with + 830V applied to the developing roller 9 to form a cyan toner image and complete a color image on the photoconductor. did.

When the color toner image thus obtained on the photoconductor 15 is transferred onto the paper 21 by the transfer charger 20, a paper jam occurs. A toner image in which four types of toner overlapped with each other remained on the photoconductor.

After removing the paper 21 from inside the device, the device was reset.
First rotate photoreceptor 15, then fur brush cleaner 24.
Was pressed against the photoconductor 15. After that, for each rotation of the photoconductor 15, the yellow, magenta, and cyan developing devices are sequentially turned on.
15 was pressed and finally the black developing device 13 was pressed. Since the toner image remaining on the photoconductor 15 was removed by the cleaner 24 before the black developing device 13 was pressed against the photoconductor 15,
The toner remaining on the photoconductor 15 was not mixed in the black developing device 13.

EFFECTS OF THE INVENTION According to the present invention, it is possible to prevent other color toners from being mixed into the black developing device during the reset operation of the photoconductor due to the occurrence of a trouble such as a paper jam.

[Brief description of drawings]

FIG. 1 is a schematic view 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, 24 ...
... Fur brush cleaner.

Claims (1)

[Claims] 1. A color electrophotographic apparatus in which a charging, exposing, and developing process is repeated for each image forming process of black, yellow, magenta, and cyan to form a color image on a photoconductor, and then the image is transferred to paper. Each of the black, yellow, magenta, and cyan developing devices has a mechanism that is close to the photoconductor during development and is separated from the photoconductor at other times, and is black when the developer is in contact with the photoconductor. And the development of yellow, magenta, and cyan is performed without contact between the photoconductor and the developer, and in the image forming step, the black image forming step is first performed, and the device resetting step is performed. Then, the color electrophotographic apparatus is characterized in that the black developing device is brought close to the photoconductor in the last order of the developing devices.