JPS6251467B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic method and apparatus capable of arbitrarily erasing and reproducing an image of one color of a two-color original.

The applicant of the present application has so far made numerous proposals as two-color image reproduction methods. The outline of this method is to use a photoreceptor in which two photoconductive layers with different spectral sensitivities are laminated on at least a conductive substrate, and the surface of the photoreceptor is subjected to primary charging and secondary charging with opposite polarity. , a light image of a two-color original is irradiated to form two latent images with opposite polarities, and these are developed with two-color toner charged with opposite polarities. This was born out of the need to faithfully reproduce these two colors, as manuscripts are often used for general office work that consist primarily of black text with areas to be emphasized in red.

However, recently, if the part to be particularly emphasized is a secret matter, there has been a demand for reproduction with that part deleted. For example, this is the answer part of an exam question. Conventionally, when copying and distributing test questions and their answers,
It was necessary to create two originals, the question and the answer part, separately. For example, it would be extremely convenient to create one original in which the questions are represented in black and the answers in red, and the red answer parts can be arbitrarily deleted and copied.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an electrophotographic method and apparatus that can arbitrarily erase and reproduce an image of one color of a two-color original.

Hereinafter, the present invention will be described with reference to the attached drawings. FIG. 1 schematically shows an example of a two-color electrophotographic process, and FIG. 2 shows changes in the surface potential of a photoreceptor in each process. The photoreceptor P has a first layer on the conductive substrate 1 that is sensitive to blue light, which is a first color of light, and is not sensitive to red light, which is a second color of light. A photoconductive layer 2 and a second photoconductive layer 3 that is substantially sensitive to red light and insensitive to blue light are laminated. The term "substantially" means
The meaning is not limited to the case where each photoconductive layer has a sharp sensitivity to each color, but also includes the case where the sensitivity is relative.
First, in step (1), the surface of such a photoreceptor is subjected to positive primary charging by the charger 4 while being irradiated with red light. The charging polarity in this step is determined by the characteristics of the photoreceptor used. Second
Since the photoconductive layer 3 is sensitive to red light, it becomes conductive, and the positive charges applied to the surface are distributed at the interface with the first photoconductive layer 2 that has moved within the layer, and are also transferred to the conductive substrate 1. An equal amount of negative charges is distributed to form an electric double layer, and the first photoconductive layer 2 is positively charged. Next, in step (2), a negative secondary charge is applied to the surface of the photoreceptor by a corona discharger 5 to which a negative voltage slightly lower than the primary charging voltage is applied. As a result, negative charges are distributed on the surface of the second photoconductive layer 3, forming an electric double layer together with the internal positive charges, and the second photoconductive layer 3 is negatively charged. In step (3), the surface of such a photoreceptor is irradiated with a light image of a two-color original 6 having black and red images on a white background. In the area Pa of the photoreceptor corresponding to the black part 6a of the document, the light does not reach the black part 6a.
Since it is absorbed by a and has almost no effect on the photoreceptor surface, the photoreceptor surface potential in this area Pa is:
A negative potential of approximately the same value as at the end of secondary charging is maintained. On the other hand, in the photoreceptor area Pb corresponding to the white part 6b of the original, both the second and first photoconductive layers 3, 2 are made conductive by the white light from the original, and the charge makes them conductive. Since almost all of the charges accumulated in the conductive substrate 1 are discharged through the conductive substrate 1, the surface potential of the photoreceptor in this region Pb becomes almost zero. On the other hand, the red part 6c of the original
In the photoreceptor area Pc corresponding to , since the second photoconductive layer 3 is sensitive to red light, the negative charges accumulated in the second photoconductive layer 3 are discharged by the red light from the original. , a positive charge equal to the negative charge of the conductive substrate 1 is held on the first photoconductive layer 2, and the surface potential of the photoreceptor in this region Pc becomes positive. In step (4), negatively charged red toner 7 and positively charged black toner 8 are sequentially supplied to the surface of the photoreceptor to develop the area Pc in red color.
Develop Pa to black and reproduce the two-color image of the original on the photoreceptor. The reproduced two-color image on the photoreceptor is
The image may be fixed as is, or if necessary, after aligning its polarity to one side, it may be transferred to transfer paper and fixed.

In order to carry out the present invention in a two-color electrophotographic method having such steps, as shown in FIG. 3, steps (1), (2), (3) similar to those shown in FIG. Next, in step (3'), the surface of the photoreceptor is uniformly irradiated with blue light using a blue filter 9 or by a blue light source. The condition for this step (3') is that colored light is used which is substantially sensitive only to the photoconductive layer in which there are both charges forming two latent images corresponding to the red and black parts. In the case of this embodiment, as is clear in step (3), the photoconductive layer in which the charges of the two latent images are both present is the first photoconductive layer 2, and substantially only in the first photoconductive layer. The colored light to which we are sensitive is blue light. Therefore, when the entire surface is irradiated with blue light, the first photoconductive layer 2 becomes conductive, and the positive charges accumulated there are discharged, except for those bound by the negative charges on the surface. The latent image corresponding to the black part in Pa is left behind by the charges distributed in the second photoconductive layer 3, and the latent image corresponding to the red part in area Pc is erased. The potential of the latent image corresponding to the black area is changed to
As shown in step (3') in the figure, the value increases further on the negative side. When the positively charged black toner 8 and the negatively charged red toner 7 are supplied to the surface of such a photoreceptor, only the black toner 8 falls into the area.
It is attracted to Pa, and only a black image is reproduced.
At this time, it is of course better if only the black toner 8 is supplied without the red toner 7, since the red toner 7 will not affect the image.

The second photoconductive layer of the photoreceptor used in this example is a eutectic layer, and its spectral transmittance has a peak in the blue light region with a wavelength of 400 to 500 nm, as shown in FIG. The photoconductive layer is a selenium layer, and its spectral transmittance has a peak in the red light region with a wavelength of 600 to 700 nm, as shown in FIG. In addition, the relative values of the spectral sensitivities of the respective photoconductive layers are as shown in Figure 7. The eutectic layer shown by the solid line shows a dip in the blue light region with a wavelength of 400 to 500 nm, and the selenium layer shown by the broken line shows a dip in the blue light region of wavelength 400 to 500 nm. , in the red light region of wavelength 600-700nm,
Although there are small peaks, there is a substantial decline. Therefore, in this photoreceptor, the surface second photoconductive layer is sensitive to red light and does not transmit it, and is substantially insensitive to blue light and transmits it. , the inner first photoconductive layer is substantially insensitive to and transmits red light, and is sensitive to and does not transmit blue light;
It can be said that. Therefore, the colored light to which only the first photoconductive layer is sensitive is blue light, which is why the colored light used in the above step (3') is blue light. From this, it is clear that the colored light used in step (3') depends on the spectral characteristics of the photoreceptor. In addition, in the case of a process in which the charges forming the latent images corresponding to the red part and the black part are both distributed in the second photoconductive layer, the above step (3') is performed so that the sensitivity is applied only to the second photoconductive layer. It will also be clear that this can be done using colored light having a . Furthermore, it will be clear that the two-color original is not limited to red and black, and the developing toner is not limited to red and black.

In the above embodiment, instead of irradiating the entire surface with blue light in step (3'), only the red latent image portion can be irradiated with blue light. For example, if the latent image corresponding to red is distributed in a direction parallel to the direction of relative movement of the photoreceptor with a blue light lamp, small blue light lamps are arranged in a row in the horizontal direction perpendicular to that direction. This is possible by selectively lighting up the . Furthermore, if the red latent image is distributed in the horizontal direction perpendicular to the direction of relative movement between the photoreceptor and the blue light lamp, it is only necessary to turn on the blue light lamp when that portion is reached.

FIG. 8 shows an example of an electrophotographic apparatus that makes it possible to carry out the above method. In the center of the apparatus main body 11, there is a three-layer photoreceptor endless belt 12 having the above-mentioned spectral characteristics, which is composed of a drive roller 13 and support rollers 14, 15, 16 so that its upper side is horizontal. It is arranged to extend around the roller group and to be rotatable in a counterclockwise direction. A guide plate 17 is arranged below the upper horizontal portion of the photoreceptor belt 12, and a transparent original platen 18 is placed on the upper surface of the apparatus body above the guide plate 17.
An opaque document holding plate 19 is arranged to cover this plate in an openable and closable manner. Above the support roller 16, an optical system unit 20 that moves forward to the left and back to the right is arranged. This optical system unit 20 includes a first charger 23 for primary charging of an open-top type having a red filter 21 and an incandescent lamp 22 at the top, which are arranged in order from left to right, and a first charger 23 having a polarity opposite to that of the first charger. A second charger 24 for secondary charging to which a negative voltage is applied, a vertically arranged focusing light transmitting body imaging element 25, and a blue lamp 2 for irradiating the photoreceptor.
6 and image exposure halogen lamps 27 and 2 arranged on both sides of the upper part of the focusing light transmitting body imaging element 25.
8, which are integrally connected and reciprocate in the horizontal direction.

A first developing device 30 containing a two-component first developer 29 containing red toner is disposed at the lower left of the drive roller 13, and a two-component second developer containing black toner is arranged at the lower left of the support roller 14. A second developing device 32 containing a developing device 31 is disposed. These developing devices are conventional magnetic brush developing devices in which the red toner is negatively charged and the black toner is positively charged by friction with the carrier in each developer, but does not contain carrier. One-component developers can also be used. Support rollers 14 and 15
A transfer paper container 34 containing a transfer paper 33 is disposed below between and a paper feed roller 35 and a guide plate 36 are disposed on the upper right side thereof. A corona discharger 37 for toner image polarity adjustment is disposed below and on the left side of the support roller 15, and a corona discharger 38 for transfer is disposed on the right side thereof, facing the photoreceptor belt. On the right side of the transfer corona discharger 38, a transfer paper separation device 39,
A fixing device 40 and a paper discharge tray 41 are arranged. A cleaning device 42 is installed on the right side of the support roller 16, and a corona discharger 43 for static elimination is installed above it.
are respectively arranged facing the photoreceptor belt. A positive voltage is applied to the adjustment corona discharger 37, a negative voltage is applied to the transfer corona discharger 38, and an alternating current voltage is applied to the static elimination corona discharger 43.

In this copying apparatus, in order to perform the two-color copying process as shown in FIG.
This is done by turning off the blue light lamp 26 placed on the right side of the screen. The home position of the optical system unit 20 is above the support roller 16 and on the right side of the document table 18 as shown. Exposure of the photoreceptor belt to the two-color original placed on the original platen 18 is performed by stopping the photoreceptor belt 12 and moving the optical system unit 20 forward to the left. By moving the optical system unit to the left, the photoreceptor belt 12
are positive primary charging by the first charger 23 while receiving red light irradiation from the red filter 21 and the white light source 22, negative secondary charging by the second charger 24, exposure lamps 27 and 28, and the imaging element. child 25
image exposure. By this,
A positive latent image corresponding to the red portion of the two-color original and a negative latent image corresponding to the black portion are sequentially formed on the photoreceptor. The imaging element 25 is known as a self-occurring lens array, and is composed of a large number of rod-shaped lenses with a diameter of about 1 mm whose refractive index changes quadratically in the radial direction, and is arranged in a row. It is possible to form a life-sized image.

When the optical system unit 20 completes its forward stroke, the photoreceptor belt 12 begins to rotate counterclockwise, and the optical system unit 20 moves to the right in its backward stroke. Of the two latent images formed on the photoreceptor belt, the positive latent image corresponding to red is first developed by being supplied with negatively charged red toner from the first developing device 30, and then developed by the second developing device 30. Positively charged black toner is supplied from the device 32 to develop a negative latent image corresponding to black. The two-color toner image on the photoreceptor belt obtained by the development is made to have a positive polarity by the adjusting corona discharger 37, and then is transferred from the transfer paper container 34 by the paper feed roller 35. Transfer paper 44 that has been fed
The toner images are superimposed under the transfer corona discharge device 38 and transferred onto the transfer paper 44 by corona discharge of opposite polarity to the toner image produced by the transfer corona discharge device 38 .
Subsequently, the transfer paper 44 is separated from the photoreceptor belt by the separation device 39, enters the fixing device 40, receives the fixation of the toner image, and then is transferred to the paper discharge tray 4.
1. On the other hand, after the toner remaining on the surface of the photoreceptor belt is removed by the cleaning device 42, the charge remaining on the surface and inside of the photoreceptor is removed by the action of the charge-eliminating corona discharger 43.

In order to make a copy with the red image erased as shown in FIG. 3 using this copying device, the same operation must be performed with the blue light lamp 26 placed on the right side of the imaging element 25 turned on. Bye. The blue light lamp 26 uses a white light source via a blue filter, or a blue fluorescent lamp having a peak wavelength around 450 nm. In addition, in order to perform partial erasure as described above, a blue light lamp 26 is used.
A lighting control device may be attached to the drawing, or a large number of small blue light lamps may be arranged in a direction perpendicular to the paper surface on which the drawing is drawn, and each may be configured to be turned on as desired. By irradiating the surface of the photoreceptor belt with this blue light, the latent image corresponding to red among the two latent images formed on the photoreceptor belt is erased, so that the red toner is removed from the first developing device 30. Even if it is supplied, no red color development is performed, and only black color development is performed by the second developing device 32. At this time, it is better to stop the operation of the first developing device so that the red toner is not supplied onto the photoreceptor belt. This blue light irradiation is normally performed when the optical system unit 20 moves forward, but when the amount of light is larger than the amount of light for image exposure, the blue light lamp 26 is irradiated to correspond to the amount of light for image exposure. It is recommended to use an ND filter etc. Conversely, this blue light irradiation is transmitted to optical system unit 2.
0, the blue light lamp 26 is activated by increasing the return speed of the optical system unit.
Even if the amount of light is large, it can be made to correspond to the image exposure amount.

In this embodiment, the blue light lamp 26 is used for erasing the latent image, but this is because, as mentioned above, the spectral characteristics of the photoreceptor belt 12 used require this, and the blue light lamp 26 is used for erasing the latent image. Different colors of light may be used if they have different spectral properties.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing an example of a two-color electrophotographic process to which the present invention is applied, FIG. 2 is a diagram showing changes in the surface potential of a photoreceptor in each step, and FIG. Process diagram showing one example, No. 4
5 shows the spectral transmittance of the surface photoconductive layer of the photoreceptor used in one embodiment of the present invention. FIG. Figure 7 showing the spectral transmittance of the internal photoconductive layer of the photoreceptor used in one example of the present invention.
The figure shows the relative values of the spectral sensitivities of the surface and inner photoconductive layer of the photoreceptor used in an embodiment of the present invention, and Figure 8 shows an electrophotographic apparatus using an embodiment of the method of the present invention. It is a block diagram which shows an example. P... Photoreceptor, 1... Conductive substrate, 2... First photoconductive layer, 3... Second photoconductive layer, 6... Two-color original, 7... Red toner, 8... Black toner, 9... Blue filter,
12... Photoreceptor belt, 20... Optical system unit.

Claims (1)

[Scope of Claims] 1. A first photoconductive layer on a conductive substrate that is sensitive to light of a first color and insensitive to light of a second color; A photoreceptor having a second photoconductive layer laminated thereon that is sensitive to light of a color and insensitive to light of a first color is used. A primary charge is applied while irradiating light, and then a secondary charge is applied which is slightly lower than the primary charge voltage and has a polarity opposite to the primary charge, and then a light image of a two-color original containing a second color is applied. In an electrophotographic method in which two latent images with opposite polarities are formed and developed with two-color toner containing a second color charged with opposite polarities, the two latent images are formed. An electrophotographic method comprising: thereafter, irradiating the surface of the photoreceptor with light of a first color to erase a latent image of a second color. 2 a first photoconductive layer substantially sensitive to light of a first color and insensitive to light of a second color on a conductive substrate; and a photoconductive layer substantially sensitive to light of a second color; an endless photoreceptor belt laminated with a second photoconductive layer that is insensitive to light of a first color; and the endless photoreceptor belt is rotatably supported with its upper side maintained horizontally. a group of rollers, a first charger and a first charger integrally disposed on the upper side of the endless photoreceptor belt so as to be able to reciprocate horizontally;
An optical system unit including a second charger to which a voltage slightly lower than the voltage applied by the charger is applied, a focusing light transmitter imaging element, an image exposure lamp, and a photoreceptor illumination lamp, the optical system unit comprising: and an optical system unit to which voltages of opposite polarity are applied to the second chargers, and the photoreceptor irradiation lamp has colored light that is substantially sensitive only to the first photoconductive layer; a transparent document mounting table disposed above the optical system unit; and first and second developing devices for developing a first color and a second color disposed facing the endless photoreceptor belt. , a transfer device, a cleaning device, and a static eliminator, and by keeping the photoreceptor endless belt stationary and moving the optical system unit forward, two colors including a second color placed on the document table are transferred. Two latent images corresponding to the original are formed, and the second color latent image is erased by arbitrarily operating the photoreceptor irradiation lamp, and then the photoreceptor endless belt is rotated to erase the second color latent image. An electrophotographic device that develops two or a first color latent image and transfers the developed image to transfer paper.