JPH02219074A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To form plural electrostatic latent images on a image carrier by providing each image exposing means on the upper surface (a photo conductive layer side) and the back surface (light transmitting layer side) of the image carrier, and exposing at least second or third and subsequent images from the back side. CONSTITUTION:The image carrier 1 is rotated and is uniformly electrified by an electrifier 2. First information is image-formed, and the electrostatic latent image is formed to perform reversal development. Then, the surface of the image carrier 1 is uniformly re-electrified by the electrifier 5. The second information in inputted to an LED head array 16, and light is emitted as an image pattern. The emitted light 6 is image-formed on the back of the image carrier 1 by a selfoc lens array 17 to form the second electrostatic latent image, and color toner different from the first image is reversely developed. Therefore, a non-priority image which is easy to decipher, and an image whose gradation reproducibility is excellent can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic apparatus that uses an electrophotographic process to obtain a multicolored recorded image using a laser beam, an LED, an LCD, etc. A multicolor electrophotographic device that can perform multicolor printing by repeating the exposure and development steps according to image information multiple times to form a multicolor visible image on a latent image carrier and then transferring it onto a recording material. Regarding.

[Prior Art] Currently, printers using electrophotography are computers,
It has been widely used as an output device for facsimile, CAD, etc.

These devices form image information as a latent image on an electrostatic latent image carrier using a laser LED, LCD, etc., convert it into a visible image using a developing device, and then
A recorded image is obtained by transferring a visible image onto a recording material and fixing it, but in conventional printers, the recorded image is of one color, for example, black. However, recently, for reasons such as recording images becoming clearer and information easier to understand, for example, the color of the format and the color of the calculated value or data value are expressed in different colors, or output using CAD. It is desired to obtain a recorded image by distinguishing it by two or more colors, such as outputting a part of a printed drawing in another color.

As an example of an electrophotographic device capable of such multicolor recording, a two-color printer will be described as an example.1 For example, an image forming process using an image forming device as shown in FIG. (See Publication No. 52-106743).

In the image forming process of this image forming apparatus, for example, the surface of the photosensitive drum l, which is a latent image carrier, is uniformly charged by the first charger 2 and modulated according to the first image information. An electrostatic latent image is formed by being irradiated with the laser beam 3, and then the electrostatic latent image is developed with the first color toner by the first developing device 4, and is converted into an image. The potential of the first image area and the non-image area are respectively leveled up, that is, raised, by the device 5, and then a laser beam 6 modulated according to the second image information is irradiated to develop the image. A second color electrostatic latent image is formed. This electrostatic latent image is converted into a second image by the second developing device 7.
The electrostatic latent image is developed with colored toner to form a ii image.

The two-color toner image formed on the photoreceptor drum l in the manner described above is transferred onto the recording material P supplied by the transfer charger 8. This recording material P is separated from the photoreceptor tram 1 by a separation static eliminator 9 and conveyed to a fixing device (not shown), where the toner image is fixed. Further, the residual toner on the photosensitive drum 1 is scraped off by the cleaner IO, and the same image forming process is repeated again.

However, in the conventional example described above, after the first image is formed on the image carrier, when recharging is performed and the second image is exposed,
In the overlapping portion of the first image and the second image, the exposure light of the second image cannot reach the image carrier surface due to the toner of the first image, and when the second image is formed as a latent image, the second image is chipped.

In order to compensate for this drawback, as detailed in Japanese Patent Application Laid-Open No. 62-81668, images are selected according to the priority of the first image and the second image, and priority is always given so that the priority image is not missing. Some methods have been considered, such as providing a means for erasing a part of the non-priority image that overlaps with the image, or forming an image by setting priorities as detailed in Japanese Patent Publication No. 63-42785.

[Problem that the invention seeks to solve] However,
In the conventional example above, this is to select between a priority image and a non-priority image.

l) A circuit for discriminating electrical signals between priority images and non-priority images is required.

2) It becomes difficult to decipher non-priority images of recorded images.

3) It is difficult to form images that involve gradation reproduction.

It has the following disadvantages.

[Means for Solving the Problems] According to the present invention, image exposing means are provided on the upper surface (photoconductive layer side) and the rear surface (light transparent layer side) of the image carrier, and at least the second or third This is an attempt to create a plurality of electrostatic latent images on an image carrier by exposing the area after the image to light from the back side.

[Embodiment] FIG. 1 is an embodiment of the present invention, and FIG. 3 is a partially enlarged view of the first image carrier l.

As shown in FIG. 3, the image carrier 1 has conductive ITO (indium thene oxide) 14 deposited on the upper surface of a cylindrical glass 13 as a light-transmitting conductive base layer, and a phthalocyanine-based organic material as a photoconductor layer 15. A semiconductor was used. Note that photoconductors such as zinc oxide, amorphous silicon, and selenium can also be used as the photoconductor.

This image carrier 1 is rotated in the direction of the arrow in the apparatus shown in FIG. 1. By combining a generally known high-speed polygonal mirror and a lens group, an image is formed over a recording width in one axis direction of an image carrier, and an electrostatic latent image is created. This first electrostatic latent image is subjected to reversal development by the first developing device 4. In zero reversal development, colored charged particles (hereinafter referred to as toner) are applied to an uncharged area of the image carrier 1 irradiated with the laser beam 3. ) is a developing method. This forms a first toner image.

Then, the recharging device 5 uniformly charges the image carrier l to -650
Charged to (V). In addition, the second image information, which is different for both @i images, is input to the LED head array 16 (using ROHM's product name R eye + 3008ss) to emit light in an image pattern, and this emitted light 6 is transmitted to the SELFOC lens array 17 (
A second electrostatic latent image is formed by forming an image on the back surface of the image carrier 1 using Nippon Sheet Glass (trade name), and a developer 7 reversely develops the toner of a different color from the first image.

The two-color toner image formed on the image carrier L as described above is transferred onto the transfer material P at once by the transfer charger 8. The toner image on this transfer material P is fixed and fixed by means of pressure, heating, etc., by means of a device 10 comprising an image carrier 1, by means of a separation static eliminator 9.

Further, residual toner on the image carrier l is cleaned by a cleaner device 11 such as a rubber blade or a fur brush.

The non-uniform electrostatic state on the image carrier l is neutralized by the pre-discharge exposure 12, and the same image forming process is repeated again.

As explained above, the first image is formed from the top surface of the image carrier 1, and the second image is formed by exposure from the back surface (light-transmitting layer side) of the image carrier 1. effective.

l) A clear image with no image defects can be obtained even at the intersection of the first image and the second image.

2) Since it is not necessary to mount two optical systems outside the image carrier as in the conventional case, the mounting density inside the main body is reduced.

3) Since a laser optical system can be used to form the first image, brightness modulation can be performed at low cost (although in the case of an LED head array, the modulation circuit becomes complicated if all the light emitting elements are modulated in brightness).
It is possible to obtain a high gradation image in the first image (the rotating polygonal mirror laser optical system only needs to be modulated to one D line and is inexpensive).

[Other Embodiments] FIG. 4 shows another embodiment in which the same numbers as in FIG. 1 indicate the same functions. In FIG. Modulates the LD according to the image pattern and emits modulated light 3
is formed on the image carrier L, reversely developed using the toner color selected by the developing device 4 or 7, and in the next cycle, the toner color is formed on the charging device 2.
The image carrier l is recharged by the LED
A second image latent image is created by causing the array 6 to emit light and performing back exposure 6 through the lens 17, and developing the second image latent image with a second toner (developing unit 7 or 4) different from the first image color. A color image may also be formed.

In this case, the first image is not disturbed by releasing the cleaner device 11 to the dashed line shown at 11' until the end of l cycle (passing of the first image). According to this method, by applying pulse modulation to the LD in the first image, it is not only possible to form a high-density, high-gradation image, but also to freely select hues.

FIG. 5 shows yet another embodiment. The same numbers as in FIG. 4 indicate the same functions.

In FIG. 5, the image carrier l is uniformly charged by the charger 2 in accordance with the first image pattern, D is modulated, a first latent image is formed on the image carrier l, and the developing device Form a toner image selected from 4, 7, 18, and 19, then release the cleaner device 11 as shown in 11', re-charge the image carrier 1 with the charger 2, and if high gradation, If high density is required, D
LED array 16 for modulation or normal line reproduction
is selected to create an electrostatic latent image on the image carrier l, and a second color toner different from the first color toner is applied to the developing devices 4, 7, 1.
8. Image formation is performed by selecting from among 19, and this cycle is repeated in the third. By performing the fourth step, a multicolor image is obtained on the image carrier l, and a method of transferring it to the transfer material P using the transfer device 8 is also possible.

In this case, the toner (T,
T2T, T4) may be any combination of red, green, blue, black, cyan, magenta, yellow, black, etc.

[Effects of the Invention] As explained above, by performing the first exposure from the photoconductive layer side of the image carrier and the second or third exposure from the light transmitting layer side of the image carrier, The priority image can be easily decoded, the device can be made smaller, and images with good gradation reproduction can be formed.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, and FIG. 2 is a schematic diagram showing a conventional example. FIG. 3 is a partial sectional view showing the layer structure of an image carrier used in the present invention, and FIGS. 4 and 5 are schematic views showing other embodiments of the present invention. 1 is an image carrier 3, modulated light 16 from a laser optical system is an LED array 4, and a developer 7 is a developer containing toner of a different hue from that of 4.

Claims (1)

[Claims] (1) In an electrophotographic apparatus that sequentially forms a plurality of color images on an image carrier having a light-transmitting layer and a photoconductive layer, and then transfers the images to a recording material, the first image is an image carrier. An electrophotographic apparatus characterized in that exposure is performed from the photoconductive layer side of the body, and the second or third image and subsequent images are exposed from the light-transmissive layer side of the image carrier.