JPH035588B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming an electrostatic latent image, which is a composite of two optical images, in an electronic copying apparatus.

An electronic copying device irradiates a photosensitive layer with a charged photosensitive layer to form an electrostatic latent image, and this electrostatic latent image is developed and transferred onto a sheet of paper. In addition, recently a method has been developed in which two light images are reproduced and copied onto a single sheet of paper, but it is not possible to directly form a negative image and a positive image on the surface of the photosensitive layer using this type of conventional method. Since this was difficult, a composite image was obtained by combining one image with another image through a light image conversion device to form a positive or negative image, but the device was expensive. Moreover, there was a drawback of increasing the size. In addition, a negative composite electrostatic latent image is formed using both the first and second light images as negative images, and this electrostatic latent image is developed using a developer having the same polarity as the charge on the surface of the photosensitive layer. There are also known methods of producing visual images, but since these methods all use negative images, it is impossible to use them as a general copying machine to reproduce positive images. When using this method, a specially prepared negative original must be prepared, which is very troublesome. As described above, the conventional methods are unsuitable for outputting images expected in the future and for forming electrostatic latent images in playback devices.

This invention was made to improve the above situation, and by using the first optical image as a negative image and the second optical image as a positive image, a composite electrostatic charge is created by superimposing the two optical images. In addition to being able to form latent images,
Since a positive image is used as one of the optical images, it is an object of the present invention to provide a method for forming an electrostatic latent image in an electronic copying apparatus that can be used as a general copying machine to reproduce a positive image.

The present invention will be explained below with reference to an embodiment shown in FIG. 1 in the figure is a photosensitive drum, and this drum 1
is composed of a drum body 2 that rotates in the direction of the arrow, and a photosensitive layer 3 formed on the outer peripheral surface of this drum body 2, and various devices are installed on the outside of this drum 1. Each of these devices will be explained in sequence along the direction of movement of the drum 1. In the figure, reference numeral 4 denotes a charging corona discharger provided close to the photosensitive layer 3 of the drum 1. When the discharger 4 supplies electric power from the DC voltage power source 5 to the discharge wire 6,
Corona discharge occurs between the discharge wire 6 and the shield electrode 7, and the photosensitive layer 3 of the drum 1 is charged. A negative image irradiation device (not shown) is provided on the side of the discharge device 4 to irradiate the photosensitive layer 3 of the drum 1 with a negative light image, and this device reflects the negative image by a laser beam onto the rotating mirror 9. After this, the surface of the photosensitive layer 3 is irradiated through the focus lens 10, and the potential of the irradiated area is attenuated to form an electrostatic latent image corresponding to a negative image. ing. The above negative image irradiation section 8
A first developing device 11 is provided on the side of the developing device 11, which has a developer magnetic brush 12 having the same polarity as the surface charge of the photosensitive layer 3, and a non-magnetic brush 13 provided inside this brush 12. is connected to a bias power source 15 via a current collector piece 14, and a part of the outer side of the developer magnetic brush 12 is covered with a cover 16. Powder is attached to the potential attenuation portion and developed to form a powder image. A positive image irradiation device 16 is provided on the side of the first developing device 11, which irradiates the photosensitive layer 3 with a positive light image. 19 and this manuscript 19
The positive image of
The electrostatic latent image corresponding to a positive image is formed by irradiating the surface of the photosensitive layer 3 through the photosensitive layer 3.
A first cleaning device 25 is provided on the side of the positive image irradiation device 16, which scrapes and removes the powder adhering to the surface of the powder image with a blade 26, and receives it on a tray 27. When this powder is removed, an electrostatic latent image corresponding to both the negative image and the positive image is combined and formed on the surface of the photosensitive layer 3. . A second developing device 28 is provided on the side of the first cleaning device 25, which has a developer magnetic brush 29 having a polarity opposite to the surface charge of the photosensitive layer 3, and has a non-magnetic material inside the brush. A body sleeve 30 and a magnetic roll shaft 31 are provided, and
A part of the outer side of the brush 29 is covered with a cover 32, and the second developing device 28 attaches powder to the composite electrostatic latent image to form a composite powder image. I'm starting to do that.
A paper path 34 is provided on the side of the second developing device 28.
a paper feeding device 33 for feeding paper 35 along
A transfer corona discharger 36 that transfers the powder image onto the paper 35 fed onto the drum 1, a fixing roll heater 37 that fixes the transferred powder image onto the paper 35, and a fixing roll heater 37 that fixes the transferred powder image onto the paper 35. A copy paper holder 39 receives the copy paper 38 fixed to the photosensitive layer 3, and a second cleaning device 40 removes the residue on the photosensitive layer 3. It is becoming more and more popular.

The operation of the device configured as described above is performed in a second manner.
This will be explained with reference to the figures. First, the photosensitive drum 1 is rotated in the direction of the arrow, and the surface of the photosensitive layer 3 of the drum 1 is uniformly charged in the dark by the charging corona discharger 4, as shown in a in FIG. Charge with a uniform voltage Vo. Subsequently, a negative image formed by the laser beam is transferred to the charged photosensitive layer 3 via a rotating mirror 9 and a focus lens 10.
When the surface of the light beam is irradiated, the potential of the portion corresponding to the light image is attenuated to _V1 as shown in FIG. 2b, and an electrostatic latent image corresponding to the first light image is formed as a negative image. Then, as shown in Figure 2c, the developing bias Vb
The developer magnetic brush of the first developing device 11 applied with the powder adheres the powder to the potential attenuation part (the part irradiated with the light image of the negative image) of the photosensitive layer 3 and develops this part. Forms a powder image covered with powder. Next, the original 19 is scanned by the light source 17, and the first mirror 20, the second mirror 21, and the third mirror 2 are scanned.
2, a positive image corresponding to the original document 19 is irradiated onto the surface of the photosensitive layer 3 through a lens 23 and a fourth mirror 24. Then, as shown in Figure 2d, the surface potential of the non-image area corresponding to the second optical image of the positive image is attenuated to almost zero, but the surface potential of the area corresponding to the image area is not irradiated with light. Not attenuated. In addition, the part corresponding to the first light image of the negative image is covered by the powder image and is in a masked state, so even if the part of the powder image is irradiated with light, its surface potential will change. There's nothing to do. Next, the powder of the powder image in the first optical image section based on the negative image is removed from the blade 26 of the first cleaning device 25.
scrape it off to expose the potential of this part to the surface. Then, a composite electrostatic latent image in which the first optical image as a negative image and the second optical image as a positive image are superimposed is formed on the surface of the photosensitive layer 3. Note that the surface potential difference (V ₀ −V ₁ ) between the first optical image as a negative image and the second optical image as a positive image as shown in FIG. 2d is equal to the potential of the developer magnetic brush −
By appropriately selecting the concentration characteristics (γ characteristics),
The density difference on the reproduced image can be ignored as shown in FIG. 2e. When the photosensitive layer 3 is developed by the developer magnetic brush 29 of the second developing device 28, a powder image corresponding to the composite electrostatic latent image is formed, and this powder image is supplied by the paper supply device 33. When the paper 35 is attached and discharged by the transfer corona discharger 36, the powder image of the composite electrostatic latent image is transferred onto the paper 35, and the powder image is fixed on the paper 35 by the fixing roll 37. Then, the negative image and the positive image are combined and transferred onto the paper 35. The photosensitive layer 3 after the transfer is transferred to a second cleaning device 39
When the photosensitive layer 3 is reached, the residue on the photosensitive layer 3 is removed, and the above operation is repeated to form a composite static image of the first optical image of the negative image and the second optical image of the positive image. By forming an electrostatic latent image on the photosensitive layer 3, developing this composite electrostatic latent image, and transferring and fixing it onto the paper 35, separate images can be superimposed and copied.

Next, a method for reproducing only the first negative image will be described. The blade 26 of the first cleaning device 25 and the developer magnetic brush 29 of the second developing device 28 are separated from the photosensitive layer 3, and the light source 17 is turned off. The sheet 35 is attached to the powder image corresponding to the negative image formed by the first developing device 11, and the transfer corona discharger 36 discharges a corona of opposite polarity to the powder. By copying and fixing the image onto the paper 35, a negative image can be copied onto the paper 35. Another method for reproducing only the first negative image is to expose the entire surface of the photosensitive layer 3 at a predetermined location between the first developing device 11 and the blade 26 of the first cleaning device 25. , and a powder image corresponding to the negative image can be copied in the same manner as the composite image described above.

A method for reproducing only the second positive image is to move the developer magnetic brush 12 of the first developing device 11 away from the photosensitive layer 3, stop irradiation with the negative image, and irradiate the positive image with the light source 17. By developing this with the second developing device 28 and transferring it onto the paper 35, it is also possible to copy only a positive image. In this way, in addition to transferring a composite image of a negative image and a positive image, it is also possible to transfer only a negative image or only a positive image.

In addition, if the first optical image produced by the laser beam is a negative image as in the above embodiment, most of the printed objects are non-image areas as in general text, so it is also possible to make mistakes in erasing non-image areas (unswept areas). In addition, when a semiconductor laser is used as a laser light source, the on-period of the laser diode is shortened, so changes in the amount of light due to temperature rise can be reduced, and the life of the laser diode can be extended. It also becomes. In addition, since the second optical image is a positive image, it can function as a general copying machine, which means that when creating a composite image, there is no need to create a special negative original as in the past. A manuscript used for general copying is sufficient. Furthermore, since it is possible to overlay and copy separate images, compared to the format overlay method using a laser beam, format specifications can be changed more freely. This has the effect of reducing costs and operating costs.

As described in detail above, this invention irradiates a charged photosensitive layer with a negative image to generate a predetermined potential difference between the irradiated area and the non-irradiated area of the light image, and adheres powder to the potential attenuation area. After that, the photosensitive layer is irradiated with a positive image to attenuate the potential of the irradiated part of the light image, and then the powder image is removed. It is possible to reliably form a composite electrostatic latent image by superimposing two light images, and since a positive image is used as one of the light sources, there is no need to create a special negative original, and it can be used generally. It has excellent effects such as being able to be used as a copying machine.

[Brief explanation of drawings]

FIG. 1 is a schematic side view illustrating an embodiment of the present invention, and FIGS. 2 a, b, c, and d show changes in the surface potential of the photosensitive layer in each process, where a shows the change in surface potential of the photosensitive layer after charging;
b shows the negative image after exposure, c shows the development process of the negative image, d shows the surface potential after the positive image is exposed, and e shows the density of the retouched image on the paper. DESCRIPTION OF SYMBOLS 1... Photosensitive drum, 3... Photosensitive layer, 4... Charging corona discharger, 11... First developing device, 1
6... Positive image irradiation device, 25... First cleaning device, 28... Second developing device, 33... Paper supply device, 36... Transfer corona discharger, 37
... Fixing roll heater, 39 ... Copy paper holder, 40 ... Second cleaning device.

Claims (1)

[Claims] 1. In an electronic copying device that charges a photosensitive layer and irradiates a light image to form an electrostatic latent image on the photosensitive layer, develops this electrostatic latent image and transfers it onto paper, A predetermined negative image is irradiated onto the charged photosensitive layer, a predetermined potential difference is created between the irradiated part and the non-irradiated part of the light image, and powder is attached to the potential attenuation part to form a powder image. After that, a positive image is irradiated onto the photosensitive layer, and the potential is attenuated in the non-irradiated area to form an electrostatic latent image, thereby forming a composite negative image and a positive image on the photosensitive layer. 1. A method for forming an electrostatic latent image in an electronic copying apparatus, characterized in that an electrostatic latent image is formed.