JPS638666A - Dichromatic copying method - Google Patents

Abstract

PURPOSE:To easily execute a layout around a photosensitive body by switching the polarity of discharge voltage from a single charger to execute electrostatic charge with different polarity. CONSTITUTION:A recording sheet S to which a visual image with color A is transferred is regressively carried again to a transfer part. During the period, a photosensitive body 10 continues rotation and charging with different polarity for reversely charging respective photoconductive layers is executed by a charger 121 used for a process obtaining the visual image with the color A. Thereby, the discharging polarity of the charger 121 is switched. Then, the photosensitive body 10 is exposed and developed to form a visual image based upon toner with color B on the photosensitive body 10 and the visual image is transferred to the recording sheet S to be regressively carried to the transfer part.

Description

[Detailed description of the invention] (Technical field) The present invention relates to a two-color copying method.

(Prior art) Two-color copying uses a composite photoreceptor, that is, a photoreceptor having two photoconductive layers on a conductive substrate, and utilizes the difference in spectral sensitivity of these photoconductive layers to perform two-color copying. Copying methods are known.

In implementing such a two-color copying method, it is necessary to charge the two photoconductive layers on the photoreceptor in opposite directions. It is necessary to perform charging and negative charging. Conventionally, this charge of different polarity is divided into two types: one for positive charging and one for negative charging.
This was done using two chargers, which made it difficult to find a layout for arranging each piece of equipment around the photoconductor. In other words, in the two-color copying system, as a developing device, one for each color toner and a charger for the above-mentioned positive and negative charging are required. This results in one more device and one more charger, which makes the layout around the photoreceptor that much more difficult.

On the other hand, in the above-mentioned two-color copying method, if two-color visible images are simultaneously exploded on the photoreceptor, the previously developed visible image may be disturbed or the edge A unique phenomenon called effect may occur. In order to solve this problem, a method has been proposed in which the formation and transfer of a visible image are performed with shifts for each color. For convenience, such a two-color copying method is referred to as a solid development method.

(Objective) The present invention provides a novel two-color copying method that effectively reduces the difficulty of the layout described above in two-color copying using the solid development method described above.
The purpose is to provide a color copying method.

(composition〕 The present invention will be explained below.

In the two-color copying method of the present invention, a composite photoreceptor formed in the shape of a drum or belt is used, and the photoreceptor has enough sections to form an entire electromagnetic switch corresponding to the original to be copied. have The copying process is performed while rotating the photoreceptor in a fixed direction.

While being rotated, the photoconductor is first charged to a predetermined polarity by a charger, and then exposed to Vc and developed, a visible image corresponding to the black paper on the document is formed on the photoconductor by A color toner. It is formed. Here, black information means, in addition to normal black information, information on colors in which none of the photoconductive layers of the photoreceptor are made into conductors, or information on colors that are made into black information using an appropriate filter. including. Furthermore, color A is generally black, but it may be a different color depending on preference.

The A-color visible image is then transferred onto a recording sheet, ie, a sheet-like mound-bearing medium that ultimately bears the reproduced image.

The recording sheet onto which the A-color visual image has been transferred is re-rolled and recursively conveyed to the transfer section.

While the recording sheet is recursively I'c'I& fed to the transfer section, the photoreceptor continues to rotate and is charged with different polarities to charge each photoconductive layer in the opposite direction. Positive charging and purchasing charging are performed by the charger described above, that is, the same charger as the charger used in the process of obtaining the A-color town image. Therefore, the discharge polarity of the charger is switched.

After that, the photoreceptor is exposed and developed, and the
A visible image is formed with three color toners.

This B-color visual image is transferred onto a recording sheet that is recursively conveyed to a transfer section.

It should be noted that when the A-color i5T Shukushin image and the B-color Machi visual image are developed by the dry development method, they are fixed on the recording sheet.

At this time, the A color town vision 1 family may be fixed prior to the transfer of the B color town vision image, or may be fixed together with the B color town vision image.

Hereinafter, specific embodiments will be described with reference to the drawings.

Referring to Fig. 3, Figs. 3-6 schematically illustrate only the mounting part of an example of a device for carrying out the invention.

In the figure, 10 is a photoreceptor, 12 is a charger with a lamp, 14.16 is a developing device, 18 is a transfer device,
20 is a separator, 22 is a fixing device, 24 is a cleaning device, 26 is a stocker, 28 is a delivery roller, 60 is a return conveyance path, and 32 is a return conveyance path for duplex copying.

The photoreceptor 10 is formed into a drum shape and can be rotated four times in the direction of the arrow.

The charger with lamp 12 is a combination of a charger 121 and a lamp 122.
21, the polarity of the discharge voltage and its absolute value can be switched. Further, the lamp 122 is a lamp that emits red light, and by lighting the lamp 122 and discharging the charger 121, the photoreceptor 10 can be charged while being irradiated with red light.

Note that the apparatus of this embodiment converts a red and black two-color image on a document into
This is a device that reproduces copies in two colors, red and black.

The developing devices 14 and 16 are both of the magnetic brush type, and the developing device 14 is for black development, and the developing device 16 is for red development.

Now, here, referring to Figure 1, the photoreceptor 10
consists of two photoconductive layers 10B and 10C laminated on the outer peripheral surface of a conductive substrate 10A (aluminum drum).The photoconductive layer 10B is a layer of Se--Te alloy, and The conductive layer IOC is eutectic OPC (organic optical semiconductor)
This is the layer of When this photoreceptor 10 is irradiated with white light,
Both the photoconductive layer 10B and the IOC become conductive, but when red light is irradiated, mainly only the photoconductive layer 10C becomes conductive. In addition, the conductive silkworm body 10A and the photoconductive layer 10B
There is rectification between the two, and holes are easily injected from the former to the latter, but electrons are hardly injected.

The copying process takes place as follows.

In Figure 3, the photoreceptor 10 rotates in the direction of the arrow, and the charger 121 of the charger 12 with a lamp performs electrical charging. At this time, the lamp 122
is off, and charger 121 has -5,5KV.
A discharge voltage of is applied. Due to this charging, the surface potential of the photoreceptor becomes -700V.

Figure 1 (1) shows this charged state. The negative charge applied from the charger 121 is uniformly distributed on the surface of the photoconductive layer 10C.

Due to the action of the electric field formed by this negative charge and the above-mentioned rectification, holes are injected from the conductive substrate 10A to the photoconductive layer 10B, and the injected holes are transferred to the photoconductive layers 10B, 10.
0 is trapped at the boundary surface. Therefore, in this state, an electric double layer is formed through the photoconductive layer 10Cv, and in this state, the photoconductive layer 10C is charged by viewing the photoconductive layer 10C as a capacitor.

The photoreceptor 10 is then subjected to slit exposure by an imaging light beam as shown in FIG. As an optical system for slit exposure, any known suitable optical system can be used. During this slit exposure, the light mound of the document ○ is irradiated onto the photoreceptor 10 through the red filter F, as shown in Figure 1 (I[).

Assume that document ○ has black and red images on a white background. In this image exposure, the photoreceptor 10 is irradiated with red light at the white background portion of the document ○ and the portion corresponding to the red image. However, since the red light turns the photoconductive layer ioc into a conductor, the charged state of the photoconductive layer 10C is released in the photoreceptor area corresponding to the white background area and red image of the original O, and this area becomes electrically conductive. The surface potential is -50V at the area corresponding to the white background and -100V at the area corresponding to the red image. On the other hand, the photoreceptor portion corresponding to the black image of the original O is not irradiated with light during image exposure.

Therefore, this portion maintains a surface potential of approximately -650V.

Figure 2 (II) shows changes in the surface potential of the photoreceptor due to charging by the charger 121 and image exposure. In the figure, 1-1 shows the charging process shown in Figure 1 (1) VC, and 1-■ shows the artist exposure process shown in Figure 1 (II).

Thus, an electrostatic latent image corresponding to the black image of the original O is formed on the photoreceptor 10. This electrostatic a image is developed with black toner from the developing device 14Vc shown in FIG. 3, and thus a black visible image is formed by the black toner TNVc as shown in FIG. Ru. Note that while the developing device 14 is performing the first development, the developing device 16 is retracted from the developing position, and the magnetic brush made of red toner does not come into contact with the photoreceptor 10, so that the black visible image is It is not disturbed by the brush. Also, black toner T
N is positively charged, and the developing bias voltage is -1s.
It is ov.

The black visible image obtained in this way is Figure 1 (ff).
As shown in K, the image is transferred onto transfer paper S, which is a recording sheet.

That is, when the transfer paper S is fed from the cassette, the spear 5
As shown in the figure, it is sent to the transfer section 5, and a black visible image is electrostatically transferred by the action of the transfer device 18. Transfer device 18Vc
is applied with a discharge voltage of -6, OKV. black visible 1
．． &! The transferred paper S is separated from the photoreceptor 10 by a splitter 20, first has a black visible image fixed by a fixing device 22, and then passes through a return conveyance path 60 and is stocked by a stonker 26vc.

On the other hand, the photoreceptor 10 subjected to the OT image transfer is charged by a static eliminator (not shown) at °C and cleaned by the cleaning device 24, and then enters the second rotation.

At the second rotation of this spear, the charger with lamp 12
The lamp 122 is lit, and a discharge voltage of +6.8 KV is applied to the charger 121 VC. In addition,
The developing device 14 retreats from the developing position after completing the development of the electrolyte film formed by the exposure process shown in FIG. 3-1 CD) IC.

Now, when charging the photoreceptor 1002, the lamp 122 is turned on and the photoreceptor 10 is irradiated with red light, so the photoconductive layer 10C becomes a conductor, and this charging causes the 1,1- As shown in Figure i (V), the photoconductive layer 10B
A state in which the battery is charged is realized. Photoreceptor surface potential is +1oo
It becomes ov.

Furthermore, when the photoreceptor 10 enters the sixth rotation, the lamp 122 of the lamp-equipped charger 12 is turned off, and the charge-?
-121 is applied with a -4.7 KV (7) discharge voltage. At this time, the negative charges applied from the charger 121 are distributed on the surface of the photoconductive layer 10C. Thus spear 1
As shown in the figure (Vl), a state in which both the photoconductive layers 10B1ioc are charged is realized. However, since the directions of the electric fields in each photoconductive layer 11c are opposite to each other, this state is a state in which the photoconductive layers 10B and ioc are charged in opposite directions. The photoconductive layer 10B is charged at +500 VK, the photoconductive layer IOC is charged at -600 VIC, and the photoreceptor surface potential becomes -ioov.

Subsequently, the photoreceptor 10 is subjected to imagewise exposure using the optical image of the original, but the second exposure is performed without using a filter, as shown in Figure 1 (■).

As a result, in the photoconductor portion corresponding to the black image of document O,
The surface potential becomes -70V, and in the area corresponding to the white background,
-30V, and the surface potential of the red image corresponding area becomes +400V as the charged state of the photoconductive layer 10C is eliminated. The developing device 16 occupies the developing position in time with the movement of the electrostatic m image obtained on the photoreceptor 10.

The electrostatic layer image formed on the photoreceptor 10 is then transferred to a developing device 1.
Developed with red toner by 6, Figure 1 (Vllll
), a red visible image is formed on the photoreceptor 10 by the red toner TR. Note that the red toner TR is negatively charged, and therefore only the positive potential distribution on the photoreceptor 10 is visualized.

Figure 2 (1) shows changes in the surface potential of the photoreceptor corresponding to the charging process and Katazuka exposure process during the second and sixth rotations of the photoreceptor. In the figure, i-y, i-■, 1
-■ denotes the processes shown in FIG. 1, (W) and (■), respectively.

In this way, a red visible image is obtained on the photoreceptor 10, but during this time, the transfer paper S stocked in the stocker 26 is fed by the delivery roller 28, passes through the return conveyance path 30, and returns to the transfer section. The red visible image is sent in synchronization with the movement of the red visible image, electrostatically transferred by the transfer device 18, separated from the photoreceptor 10 by the separator 20, and then fixed by the fixing device 22Vc. After that, it is discharged from the device. Note that the discharge voltage applied to the transfer device 1BVc is +6.0 KV.

FIG. 2-1 (IX) shows a state in which the red visible image has been transferred onto the transfer paper S. Symbol indicates a black copy image that was previously transferred and fixed.

The photoreceptor 10 after the red visible color transfer is destaticized and cleaned.

(Effects) As described above, according to the present invention, a novel two-color copying method can be provided. This method performs charging with different polarities by switching the polarity of the discharge voltage of a single charger, so there is no need for dedicated chargers for positive charging and negative charging, and the layout around the ℃ photoreceptor is easy. becomes.

Depending on the length of the return conveyance path, the red image copying process may be performed during the third or fourth rotation of the photoreceptor, or during several hundred other rotations.

Additionally, circuits that switch between applying positive and negative voltages to the same charger are well known.

In addition, in the embodiment shown in Figure 3, if the transfer paper S after the black visible image has been transferred is returned via the return conveyance path 32 for double-sided copying, the black image and the red image are separated into the front and back sides of the transfer paper. You can also make copies.

Furthermore, instead of the processes shown in (V) and (V1) of Fig. 1, negative charging is first performed, and then positive charging is performed to form the photoconductive layer 10.
B. If you charge the ioc in the opposite direction, lamp 1
22 can be omitted.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams for explaining one embodiment of the present invention, and Figure 5 is a diagram of an apparatus for carrying out the above embodiment.
FIG. 2 is an explanatory diagram schematically showing only important parts of an example. 10... Composite photoreceptor, 12... Charger with lamp, 60... Return transport path

Claims (1)

[Claims] While rotating a drum-shaped or belt-shaped composite photoreceptor in a fixed direction, a charger charges it to a predetermined polarity, and after exposure and development, a visible image made of A color toner is transferred onto a recording sheet. Then, use this recording sheet again.
While recursively conveying to the transfer section, while rotating the photoreceptor, charging of different polarities is performed by the charger to charge each photoconductive layer of the photoreceptor in the opposite direction, by switching the discharge polarity, A two-color copying method characterized in that after exposure and development, a visible image of B color toner is transferred onto the recording sheet.