JPH04295867A - Color electrophotgraphic copying device - Google Patents

Abstract

PURPOSE:To prevent the defect of an image caused by fogging and the unevnness of the image caused by faulty transfer from occurring by providing a 2nd electrostatic charger between a developing stage part and a transfer stage part and repeating 1st electrostatic charging, exposure, developing and 2nd electrostatic charging several times. CONSTITUTION:This device is provided with a 1st electrostatic charger 38 which electrostatically charges a photosensitive body 37, an image exposing means by a semiconductor laser 39, developing devices of plural colors 23-25 and 35, and the 2nd electrostatic charger 40 which electrostatically charges the photosensitive body 37 before transfer. After the respective stages of electrostatic charging, exposing and developing are repeated several times to form the toner image of plural colors on the photosensitive body 37, the toner image is transferred to a paper in a lump. Then, the photosensitive body 37 and the toner image are electrostatically charged to have the same polarity as the electrostatically charged polarity by the 1st electrostatic charger 38 by the 2nd electrostatic charger 40 provided between the developing stage part and the transfer stage part. Therefore, the optical memory of the photosensitive body 37 is reduced, the fogging disappears, and transfer efficiency to a paper after finishing superposing several times on the photosensitive body 37 is improved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color electrophotographic device that can be used in hard copy devices such as color copying machines and printers.

0002

[Prior Art] In recent years, charging, exposure, and development are repeated multiple times to form a plurality of toner images of different colors on an electrophotographic photoreceptor (hereinafter referred to as photoreceptor), and then the toner images are transferred all at once to paper. A color electrophotographic apparatus that obtains color images using a color image is actively being studied. This method differs from conventional color electrophotography methods in that it does not require a transfer drum and has the advantage that the apparatus can be miniaturized.

As this type of color electrophotographic apparatus, for example, there is an apparatus proposed by the inventors in Japanese Patent Application No. 62-270664. Hereinafter, an embodiment of the present invention will be described using FIG. 2.

The developing units 1, 2, and 3 are non-contact type non-magnetic one-component developing units that use a DC electric field to scatter the toner, and the toner is rubbed by conductive fur brushes 4, 5, and 6 that are in contact with the developing roller. Charged aluminum developing rollers 7, 8,
The blades 10, 11, and 12 form a thin layer of toner on the toner 9. Yellow (Y) for developer 1
, magenta (M) in developer 2, and cyan (M) in developer 3.
Contains C) insulating toner. The developing device 13 is a contact type developing device containing a two-component developer. Each developing device was disposed around the photoreceptor 15 so as to face each other with a constant gap (development gap) between the developing rollers 7, 8, 9, 14 and the photoreceptor 15. Each developing device is attached with a separation mechanism that brings it close to the photoreceptor during development and separates it when not developing.

[0005] As a photoreceptor, an amorphous Se-Te photoreceptor drum 15 having a diameter of 152 mm and sensitized to long wavelengths in the infrared region is used, and is rotated at a circumferential speed of 160 mm/s. This photoreceptor 15
Charger 16 (Scorotron charger, corona voltage: +7
kV, grid voltage: 1kV), charging potential +900
Charge it to V. Next, the semiconductor laser 17 having a wavelength of 790 nm is caused to emit light for exposure. Using this semiconductor laser 17, a negative black signal is exposed onto the photoreceptor 15 to form an electrostatic latent image. The latent image is reversely developed with the black developing device 13 in a developing state in which +600V is applied to the developing roller 14 to form a black toner image, and then the AC corona charger 18 (applied voltage: 5
The photoreceptor 15 is exposed to corona at a voltage of 100 kVrms).

Next, the photoreceptor 15 is charged again by the corona charger 16.
is charged to +600V. Thereafter, the photoreceptor 15 is exposed to signal light corresponding to yellow by the semiconductor laser 17 to form a yellow electrostatic latent image. Next, this photoreceptor is passed through a yellow developer 1 in a developing state with +600V applied to the developing roller 7, a magenta developer 2, a cyan developer 3, and a black developer 13 in a non-developing state to form a yellow toner image. form. Next, the photoreceptor 1 is charged again with the AC corona charger 18.
5 was exposed to corona, and the photoreceptor 15 was charged to +810V again by the corona charger 16. Thereafter, a semiconductor laser 17 is used to expose a signal light corresponding to magenta to form a magenta electrostatic latent image. Next, the photoreceptor 15 is passed through a yellow developing device 1 in a non-phenomenal state and a magenta developing device 2 in a developing state in which +800V is applied to the developing roller 8 to form a magenta toner image. Thereafter, the photoreceptor 15 is passed through the cyan developer 3 and the black developer 14 in a non-phenomenal state. Next, the photoreceptor 15 is exposed to corona again by the AC corona charger 18, and the photoreceptor 15 is again exposed to + by the corona charger 162.
Charge to 800V. Thereafter, a semiconductor laser 17 is used to expose the semiconductor laser 17 to signal light corresponding to cyan to form a cyan electrostatic latent image. Next, the photoconductor 15 is applied to the yellow developing device 1, magenta developing device 2, and developing roller 9 in a non-developing state at +800V.
The toner image is passed through a cyan developing device 3 in a developed state to which a cyan toner image is applied, thereby forming a cyan toner image to complete a color image on the photoreceptor.

After the color toner image thus obtained on the photoreceptor 15 is transferred to the paper 20 by the transfer charger 19,
The image is thermally fixed by the fixing device 21. On the other hand, after transfer, photoreceptor 1
After applying a direct current voltage (corona voltage +5.5 kV) to the corona charger 18 to positively charge the surface of the photoconductor 5, the conductive fur brush 22 to which a voltage of -150V was applied was applied to the photoconductor. 15 and clean it.

[0008]

[Problems to be Solved by the Invention] In this conventional example, after development, an optical memory of the photoreceptor occurs, which causes a difference in charging potential in the next process between the exposed area and the unexposed area, and depending on the photoreceptor, the developing device It was found that fogging occurred in unexposed areas due to It was also found that since charging with an AC corona charger is repeated after each color has been developed, the amount of charge on the toner on the photosensitive layer decreases, causing image unevenness due to poor transfer in color overlapping areas and black image areas. Ta.

An object of the present invention is to eliminate image defects due to fog and image unevenness due to poor transfer in a color electrophotographic device that synthesizes toner images of multiple colors on a photoreceptor and then transfers them all at once to paper to obtain a color image. An object of the present invention is to provide a color electrophotographic device that does not generate.

0010

[Means for Solving the Problems] The present invention includes a first charging means for charging a photoreceptor, an image exposure means, a plurality of color developing devices, and a second charging means for charging the photoreceptor before transfer. A color electrophotographic device that repeats the steps of charging, exposing, and developing multiple times to form toner images of multiple colors on a photoreceptor, and then transfers the toner images all at once to paper, and develops each color. The color electrophotographic apparatus is characterized in that after the step, the second charging means charges the photoreceptor and the toner image to the same polarity as the main charge.

[0011]

[Operation] With the above-described configuration, the present invention charges the photoreceptor and toner image after development by the second charger provided between the development process section and the transfer process section to the same polarity as the charge polarity by the first charger. As a result, the optical memory of the photoreceptor is reduced and fog is eliminated. Moreover, the transfer efficiency to paper after the overlapping phenomenon has been completed multiple times on the photoreceptor is also improved.

0012

Embodiments Hereinafter, embodiments of the present invention will be explained in detail with reference to FIG.

The developing devices 23, 24, and 25 are non-contact type non-magnetic one-component developing devices that spray toner using a DC electric field.
Conductive fur brushes 26, 27 in contact with the developing roller
, 28 to frictionally charge the toner, and blades 32, 33, 34 are placed on aluminum developing rollers 29, 30, 31.
The structure is such that a thin layer of toner is formed. The developer 23 has yellow (Y), and the developer 24 has magenta (M).
), the developing device 25 contains cyan (C) insulating toner. The developing device 35 is a contact type developing device containing a two-component developer. Each developing device was disposed around the photoreceptor 37 so as to face each other with a constant gap (development gap) between the developing rollers 29, 30, 31, and 36 and the photoreceptor 37. Each developing device is attached with a separation mechanism that brings it close to the photoreceptor during development and separates it when not developing.

The specifications and developing conditions of the black developing device 35 and the physical properties of the toner are shown below. ●Developer specifications and development conditions Diameter of developing roller 36: 22 mm Peripheral speed of developing roller 36: 320 mm/s developing roller 36
Thickness of the developer layer on the surface: 400 μm Direction of rotation of the phenomenon roller 36: Opposite direction to the photoreceptor 39 (same traveling direction) Development gap (gap between the surface of the developing roller and the surface of the photoreceptor): 300 μm during development, during non-development 2mm ●Developer physical properties Type of developer: Two-component developer of toner and carrier Average particle size of carrier: Approximately 50 μm Type of carrier: Teflon coated ferrite Toner charge amount: +15 μC/g Average particle size of toner: 12 μm Toner dielectric constant : Approximately 2 The specifications and development conditions of the yellow, magenta, and cyan developing devices and physical properties of the toners are shown below. ●Developer specifications and development conditions Developing roller diameter: 20 mm Developing roller circumferential speed: 160 mm/s Developing roller rotation direction: Opposite direction to photoreceptor 37 (same traveling direction) Toner layer thickness on developing roller: 30 μm Development gap (
Gap between the developing roller surface and the photoreceptor surface): 150 μm during development, 2 mm when not developed Toner physical properties Toner charge amount: 3 μC/g Average particle size: 12 μm Relative dielectric constant: Approx. 2 As a photoreceptor, in the infrared region Long wavelength sensitized diameter 152mm
Using an amorphous Se-Te photoreceptor drum 37, the circumferential speed is 16
Rotate at 0 mm/s. This photoreceptor 37 is charged by a charger 38.
(Scorotron charger, corona voltage: +6.5 kV, crid voltage 900 V) to charge to a charging potential of +900 V. Next, the semiconductor laser 39 with a wavelength of 790 nm is caused to emit light for exposure. Using this semiconductor laser 39, a negative black signal is exposed onto the photoreceptor 37 to form an electrostatic latent image. The latent image is reversely developed by the black developing device 35 in a developing state in which +600V is applied to the developing roller 36 to form a black toner image, and then a charger 40 (Scorotron charger, corona voltage: 6.5 kV, grid voltage :900V) and the photoreceptor 37
was charged again to +900V.

Next, the photoreceptor 37 is charged again by the corona charger 38.
was charged to +600V. Thereafter, the photoreceptor 37 was also exposed to signal light corresponding to yellow by the semiconductor laser 39 to form a yellow electrostatic latent image. Next, this photoconductor is passed through a yellow developer 23 in a developing state with +600V applied to the developing roller 7, a magenta developer 24 in a non-developing state, a cyan developer 27, and a black developer 35 to form a yellow toner image. After forming, the photoreceptor 37 was charged to +600V by the corona charger 40. Next, corona charger 3 again
At step 8, the photoreceptor 37 was charged to +900V. Thereafter, a semiconductor laser 39 was used to expose signal light corresponding to magenta to form a magenta electrostatic latent image. Next, the photoconductor 37 is placed in the non-phenomenal state of the yellow developing device 23 and the developing roller 30 at +8
A magenta toner image was formed by passing through a magenta phenomenon device 24 in a phenomenon state to which 00V was applied. Thereafter, the photoreceptor 37 is transferred to the cyan developer 25 and the black developer 3 in a non-developing state.
5, the photoreceptor 3 is charged by a corona charger 40.
7 was charged to +600V. Next, corona charger 3 again
8, the photoreceptor 37 was charged to +800V. Thereafter, a semiconductor laser 39 was used to expose signal light corresponding to cyan to form a cyan electrostatic latent image. Next, the photoreceptor 37 is transferred to the yellow developing device 23 in a non-developing state and the magenta developing device 2.
4. A cyan toner image was formed by passing through the cyan developing device 25 in a developing state in which +800V was applied to the developing roller 31, thereby completing a color image on the photoreceptor.

The color toner image thus obtained on the photoreceptor 37 is charged by a corona charger 40 to +80
After being charged to 0V, the transfer charger 41 (corona voltage: -5
kV), and then thermally fixed by a fixing device 43. On the other hand, after the transfer, the surface of the photoreceptor 37 is positively charged with a pre-cleaning charger 44 (corona voltage +5.5 kV), and then a conductive fur brush 45 to which a voltage of -150V is applied is pressed against the photoreceptor 37. Cleaned. Note that when the charging potential of the charger 40, which is the second charging means, is made higher than the charging potential of the charger 38, which is the first charging means, a portion where the potential of the photoreceptor is higher than the charging potential by the first charging means occurs, Density unevenness occurred in the image. Therefore, the second
The charging potential of the charging means needs to be equal to or lower than the charging potential of the first charging means.

[0017]

According to the present invention, it is possible to provide a color electrophotographic apparatus which combines toner images on a photoreceptor to obtain a color image, and which does not suffer from fogging due to the optical memory of the photoreceptor and image unevenness due to poor transfer. I was able to get it.

[Brief explanation of drawings]

FIG. 1 is a side view of a color electrophotographic apparatus according to the present invention.

[Figure 2] Side view of a conventional electrophotographic device

[Explanation of symbols]

23 Yellow developer 24 Magenta developer 25 Cyan developer 35 Black developer 37 Photoreceptor 38 Corona charger 39 Semiconductor laser 40 Corona charger 41 Transfer charger 43 Heat fixing device

Claims (4)

[Claims] [Claim 1] A photoreceptor, a first charger, an exposure means,
It is equipped with a plurality of color developing devices, a black developing device, a transfer device, and a cleaning device, and after repeating the steps of charging, exposure, and development multiple times to form a color toner image on the photoreceptor, the color toner image is produced. In a color electrophotographic method that transfers all images onto paper in one go, a second charger is provided between the development process section and the transfer process section, and the first charge, exposure, development, and second charge are repeated multiple times to achieve exposure. A color electrophotographic device that forms color toner images on the body. 2. The color according to claim 1, wherein the photoreceptor and the toner image are charged to the same polarity as the charging polarity by the first charger by a second charger provided between the development process section and the transfer process section. Electrophotographic equipment. 3. The color electrophotographic apparatus according to claim 1, wherein the second charging means is a scorotron. 4. The color electrophotographic apparatus according to claim 1, wherein the potential charged on the photoreceptor by the second charging means is lower than the potential charged on the photoreceptor by the first charging means.