JPH03189659A - Image forming device - Google Patents

Abstract

PURPOSE:To obtain high speed recording in a monochrome image by making the moving speed of an image carrier in a mode forming the monochrome image different from that of an image carrier in a mode forming a plural-color image. CONSTITUTION:The surface of a photosensitive body 1 is uniformly electrified by an electrifier 2, and irradiated with laser beams 3 as optical information modulated according to image information, and an electrostatic latent image is formed. This electrostatic latent image is developed with the first color toner of a developing unit 4, and the surface of the drum 1 is reelectrified by an electrifier 5. The developed image part and the potential of a non-image part are lifted up, and then, the same processing is repeated with respect to the following image information. Plural toner images are transferred on a recording material P by a transfer electrifier 8 en bloc, and the recording material P is separated from the drum 1 by a separating/destaticizing unit 9. The toner image is fixed on the recording material P by a fixing unit 10. At this time, the moving speed of the drum 1 is changed in the mode to form the monochrome image or the plural-color image, so that the upper surface of the drum 1 is smoothed and high-speed recording is attained in the monochrome image.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, and particularly to an image forming apparatus that can selectively perform multi-color overlapping development and monochrome development. Regarding.

[Prior Art] Conventionally, overlapping development of multiple colors has been carried out using the multiple development method described in JP-A No. 52-106743, and the method described in JP-A No. 60-76.
766, in which charging and exposure are performed in the same device with the cleaner released to sequentially create electrostatic latent images, and developing devices selected for each color are sequentially used. A developing method has been proposed. In both of these methods, developed images of a plurality of colors are transferred onto a recording material at once.

[Problem that the invention seeks to solve] However,
In the former Japanese Patent Application Laid-Open No. 52-106743, multiple sets of charging, exposure, and developing devices are arranged around the image carrier, and when multiple images are superimposed to obtain a recorded image, the image carrier is When the circumferential speed is the same as the recording speed, there is an advantage that it is approximately concave speed compared to a monochrome printer (or monochrome copying machine), but the same is true when obtaining a monochrome image such as a black and white image using this multiple development method. It has the disadvantage that you can only print as many copies as you like.

On the other hand, in the latter Japanese Patent Application Laid-Open No. 60-76766, when obtaining a monochrome image, it is possible to obtain a recorded image at a high print speed, or when obtaining a multi-color image, for example, four colors of yellow, magenta, cyan, and black. If a full-color image is to be obtained, the recording speed will be 4 to 5 minutes as required by the former multiple development method, which is not preferable. In addition, when the image carrier is moved at a faster speed to improve the recording speed, for example, in order to obtain about 4 to 5 sheets of A4 size recording paper per minute, it is necessary to move the image carrier at a high speed of 200 to 300 square meters per second. However, it does not move at this circumferential speed.

2. It is necessary to increase the sensitivity of the image carrier.

3. Toner (colored charged particles) on the image carrier is disturbed,
scatter.

4. It has drawbacks such as increased toner scattering from the developing device.

[Means for Solving the Problems] The present invention is an improvement on the image forming method described in the above-mentioned Japanese Patent Application Laid-Open No. 52-106743, in which the moving speed of the image carrier is switched between monochrome and multiple colors. This eliminates the drawbacks of the prior art example.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention, and in FIG. 1, the image carrier l is, for example, a drum-shaped electrophotographic photoreceptor,
It can be freely rotated in the direction of the arrow. The surface of the photoreceptor drum l is uniformly charged by a first charger 2, and is then irradiated with laser light 3 as optical information modulated according to the first image information, thereby generating a first electrostatic charge. After the first electrostatic latent image is formed, the first electrostatic latent image is visualized and developed using the first color toner by the first developing device 4. Next, the photoreceptor drum l
The surface of is recharged by the second charger 5, and the developed first image area potential and non-image area potential are respectively raised, and subsequently, as optical information modulated according to the second image information. is irradiated with laser light 6, and a second electrostatic latent image is formed. This second electrostatic latent image is then developed by a second developing device 7 with a second color toner.

The two-color developed image, that is, the toner image, formed on the photoreceptor drum l as described above is transferred all at once onto the recording material P by the transfer charger 8. The recording material P on which the toner image has been transferred is separated from the photoreceptor drum L by a separating static eliminator 9 and transferred to a fixing device 1.
At 0, the toner image is fixed onto the recording material P by means such as heating or pressure.

Further, residual toner on the photosensitive drum l is scraped off by a cleaner 11. Furthermore, the photoreceptor tram l, which has non-uniform charges received in the optical memory, transfer process, etc., is uniformly irradiated by the pre-exposure lamp 12, and the charge is removed to approximately Ov, and the next image forming process is repeated again.

There is no problem when a two-color image is obtained in the above explanation, but as mentioned above, in a single-color image, the moving speed of the photosensitive drum 1 remains the same, which is not preferable.

Therefore, in order to solve this drawback, the present inventors have developed a method for forming single-color images (first mode) and multi-color images (second mode).
The circumferential speed of the photosensitive drum 1 is changed depending on the mode.

Note that M is a motor that drives the photosensitive drum, and N is a means for switching the speed of the photosensitive drum depending on a single color or multiple colors. Specifically, the circumferential speed of the photosensitive drum is made faster when forming a single color image than when forming a multicolor image.

Here, it will be explained in more detail.

The image carrier 1 is a conductive metal cylinder, for example, aluminum, on which a phthalocyanine-based organic semiconductor is coated as a photoconductor layer. By the way, the photoconductor is zinc oxide! Semiconductors such as amorphous silicon and selenium can also be used. Two-color recording and monochrome recording using this image carrier will be explained.

This image carrier l is moved at a rate of 88 cm per second in the direction of the arrow using the apparatus shown in FIG.
The battery is rotated by the charger 2 and charged to approximately -600 (V). Next, the first image information is modulated by a laser diode (hereinafter referred to as LD), and the recording width in the direction of the image carrier is transmitted by using a combination of a high-speed polygon mirror and a lens group, which are usually numerically known. Image formation 3 to create an electrostatic latent image.

This first electrostatic latent image is subjected to reversal development by the first developing device 4. Reversal development is a development method in which colored charged particles (hereinafter referred to as toner) are attached to the areas on the image carrier l irradiated with the laser beam 3 where the potential has attenuated.

This causes the first toner image to be formed.

Next, the second charger 5 uniformly charges the image bearing member L with a charge of 65%.
Recharge to 0v. Then, similarly to the first image, the laser diode LD2 emits second image information, and the image carrier l
An image 6 is formed on the first image, and a toner of a color different from that of the first image is reversely developed by a developing device 7.

Next, when the image signal is of only one color, the peripheral speed of the image carrier 1 is set to 176 mm/sec. Next, even if the first charger 2 was operated, the moving speed of the image carrier l became faster, so
The surface potential of the upper surface of the image carrier 1 is -350 V due to the ability of the first charger 2. Next, as a means for stopping the operation of the first developing device 4, the first developing device 4 may be separated from the image carrier l, or the first developing device 4 may be moved away from the image carrier l.
It is preferable to apply a bias voltage approximately equal to the surface potential of the toner to prevent toner adhesion. Then, when the upper surface of the image carrier 1 is further charged by the second charger 5, the surface potential becomes approximately -650V. By forming an image 6 of the monochromatic image signal with the second exposure device, an electrostatic latent image corresponding to the monochromatic image signal can be formed on the image carrier l. Toner may be applied to this by the second developing device 7. (In this example, black toner was used). In this case, the circumferential speed of the image carrier 1 increases, and in order to improve the developing ability accordingly, it is preferable to increase the speed of the toner carrier 7b.

From the above explanation, it is possible to improve the recording speed of a monochrome image, and even if the peripheral speed of the image carrier l is increased when forming a monochrome image,
Because the distance from the development position to the transfer position is short, the image carrier l
The image above is distorted and toner scattering is not observed for a long period of time.

[Other Embodiments] FIG. 2 shows another embodiment. The same numbers as in FIG. 1 indicate the same parts, and this is an example that can form a full-color image.

The image carrier 1 is made by depositing ITO (indium thene oxide) as a conductive layer on PET (polyester film) and coating it with the photoconductor material described above.

The first developing device 4 uses yellow toner, the second developing device M7 uses magenta toner, the third developing device 14 uses cyan toner, and the fourth developing device 17 uses black toner. The magenta image signal is inputted to the LD2, the cyan image signal is inputted to the LD3, and the black image signal is inputted to the LD4. 15 and repeats charging, exposure, and development on the image carrier l a plurality of times as described in FIG. 1, thereby forming a color image on the upper surface of the image carrier l.

This is transferred all at once onto the recording material P by the transfer charger 8,
Full-color recording is possible by heating and fixing.

Next, when obtaining a black monochromatic image, the circumferential speed of the front image carrier 1 is increased to 4 times the speed, and the chargers 2, 5, 12. I
By operating s, the upper surface of the image carrier l is uniformly charged, image exposure is performed with the black signal light LD4, and toner is deposited by the black toner developing device 17, thereby producing an image without a decrease in the density of the black image. It became possible to obtain.

[Further Other Embodiments] FIG. 3 shows another embodiment, in which the same numbers as in FIG. 2 indicate the same machine parts.

The differences from Fig. 2 are image signal light, LDI, LD2
.

LD3. LD4 is arranged on the inner surface of the image carrier l, and the image carrier l
Image exposure is performed from the back side (conductive layer side). Yellow, magenta, cyan, and black image signals are transmitted through laser diodes LDI, LD2, respectively. LD: l.

The emitted light is input to the LD 4, and the emitted light is irradiated onto the high speed rotating polygon mirror (polygon mirror) 18, and this reflected light is passed through the fθ lens (
(not shown), scanning exposure is performed from the back surface of the image carrier 1 via a reflecting mirror 19. Also, chargers 2, 5, 12. The developing devices 4, 7, 14, and 17 can form a full-color image by performing operations similar to those described in FIG. 2, and this image is transferred onto the recording material P at once. In addition, in the case of a black monochrome image, as in the explanation in FIG. By operating the developing device 17, a black image can be obtained at high speed.

In the above explanation, examples of two-color recording and four-color recording have been explained, but this operation does not need to be particularly limited as long as there are multiple sets of charging, exposure, and development other than those described above, and the moving speed of the image carrier is It is not limited to multiple sets.

In addition, among multiple sets of charging, exposing, and developing devices, this embodiment describes the case where a black developing device (black toner) is placed at the most downstream side in the moving direction of the image bearing member 1. The toner in the developing device may be a developing device containing the most frequently used toner.

Furthermore, although the above-mentioned exposure forming means has been described as a combination of a laser diode and a polygon mirror, similar effects can be obtained by combining other light emitting elements such as an array of LEDs or a liquid crystal shutter array.

In addition, in all the operation explanations, all charging devices are operated, but the charging capacity of the most downstream side charger may be increased and the operation of other chargers may be stopped, or the most downstream charger may be a downstream charger, and at least one other charger operation.

[Effects of the Invention] As explained above, according to the present invention, by switching the moving speed of the image carrier between monochrome image formation (first mode) and multicolor image formation (second mode), monochrome image formation is possible. Images can be recorded at high speed.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing a first embodiment of the present invention, Fig. 2 is a sectional view of a second embodiment of the invention, and Fig. 3 is a sectional view of a third embodiment of the invention. It is a sectional view showing an example. 1 is an image carrier 2.5, 12.15 is a charger 4.7, 14. For the magazine, the developing device P is the recording material.

Claims (4)

[Claims] (1) A first mode in which a monochromatic developed image is formed by forming and developing a latent image on an image carrier and is transferred onto a recording material to form a monochrome image, and a latent image is formed on the image carrier. , a second mode in which a multi-color image is formed by collectively transferring a multi-color developed image formed by performing development multiple times onto a recording material, the image carrier in the first mode; An image forming apparatus characterized in that a moving speed of the image carrier in the second mode is different from a moving speed of the image carrier in the second mode. (2) The image forming apparatus according to claim 1, wherein the moving speed of the image carrier is faster in the first mode than in the second mode. (3) A frequently used developing device is disposed on the most downstream side in the moving direction of the image carrier, and in the first mode, all chargers are operated to produce a monochromatic image of the frequently used developing device. The image forming apparatus according to claim 1 or 2, wherein the image forming apparatus forms an image. (4) The image forming apparatus according to claim 3, wherein the developing device is for black color.