JPS6023348B2 - Two-color electrophotographic copying method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a two-color electrophotographic copying method.

In recent years, a so-called color electrophotographic copying method for copying color originals in natural colors has come into practical use. However, in this color electrophotographic copying method, in order to perform color separation of the color image on the original, the photoreceptor must be exposed to light using the color-separated original image and developed at least three times. There is a problem that it takes a long time to obtain one copy, and the apparatus generally has a complicated structure and tends to be large in size, and it is difficult to reduce the cost.

On the other hand, as long as copying machines are used for office purposes, it is rarely necessary to copy multicolor originals in natural colors.

However, in daily office work, there are many opportunities to copy two-color originals, and it would be extremely convenient in practice if these could be copied in two colors.

In this case, the color of the image on the two-color original and the color of the copied image do not necessarily have to match; the point is that the parts of the information image on the original with different colors are It is sufficient if they can be separated and distinguished using different colors.

Therefore, it is expected that such copying can be performed through a simpler process and the structure of the apparatus will be simpler than that of the color electrophotographic copying method. Reflecting these circumstances, various two-color electrophotographic copying methods have been proposed recently.

Another object of the present invention is to provide a new two-color electrophotographic copying method.

The present invention will be described below with reference to the drawings.

First, the two-color original referred to in this specification is defined as follows.

In other words, a two-color original is a white background with chromatic color A and color B (
Refers to information images in chromatic colors or black. However, the white color of the background portion is not limited to pure white, and may be interpreted as a whitish color. FIG. 1 diagrammatically illustrates the process of the invention.

In the figure, reference numeral 1 indicates a photoreceptor, and this photoreceptor 1 has a three-layer structure, consisting of a conductive support 11, a first photoconductive layer 12 provided thereon, and a first photoconductive layer 12 provided thereon. Furthermore, it is constituted by a second photoconductive layer 13 provided. The first photoconductive layer 12 is one that is not sensitive to color B light.

For this purpose, a photoconductive material that is physically insensitive to color B light may be used, or a photoconductive layer 1
A thin film that absorbs or reflects color B light may be provided at the interface between photoconductive layer 2 and photoconductive layer 13. In the latter case, the above-mentioned thin film will be referred to as a first photoconductive layer. This thin film has a thickness of 1~3cm and a volume resistivity of 1~1~3cm.
Approximately 0 skin is suitable. The second photoconductive layer 13 is
A material that is not sensitive to color A light or color B light and has a property of transmitting at least color A light is used.
What should be noted here is the case where color B is black.

That is, since there is no such thing as black light, it is meaningless to be sensitive to black light.Therefore, in this case, the first photoconductive layer 12 must have photosensitivity over the visible region. Rather, the second photoconductive layer 13 only needs to satisfy the condition that it has no sensitivity to the color A light and at least allows the color A light to pass through. However, in this specification, the terms "color B light" and "sensitivity to color B light" will be used in general, including when color B is black. It is clear that even if we do this, there will be no confusion in the explanation. The electrophotographic process according to the present invention begins by uniformly charging the photoreceptor 1 with a charger 2 (FIG. 1). This charging by the charger 2 is called primary charging. However, the polarity of the primary charge is determined by the type of semiconductor of the photoconductive layer 13.

In this example, it is assumed that the polarity is negative. Note that this primary charging may be performed in the dark, or may be performed while uniformly irradiating the photoreceptor 1 with light of color A. In terms of model explanation, it seems easier to understand the case where primary charging is performed at the same time as light irradiation, so here,
The explanation will be given assuming that uniform irradiation with light of color A is performed. Now, if primary charging is performed using the conductive support 11 as a counter electrode while uniformly irradiating the photoreceptor 1 with light of color A, the negative charge imparted from the charger 2 will be applied to the surface of the photoconductive layer 13. The photoconductive layer 13 is uniformly charged, but the irradiated light of color A is transmitted through the photoconductive layer 13 without causing any physical change in the photoconductive layer 13, and the photoconductive layer is sensitive to the light of color A. 12 and turns it into a conductor, positive charges having a polarity opposite to that of the primary charge are induced on the interface between the photoconductive layer 12 and the photoconductive layer 13, and are uniformly distributed.

Of course, at this time, the surface potential of the photoreceptor 1 is uniform and negative. Next, as shown in Figure 1,
While irradiating the optical image of the original onto the primary charged photoreceptor 1, the charger 3 simultaneously applies secondary charging with the opposite polarity to the primary charging.
Apply by.

In the light image irradiation described above, the effect of this secondary charging is determined by the photoreceptor part fogged by the light from the color A part of the document, the part exposed by the light from the color B part, and the light from the white background part. Consider each exposed area.

First, considering the effect of secondary charging on the area exposed to the light of color A, the positive charge applied from the charger 3 neutralizes the negative charge caused by the primary charging on the surface of the photoreceptor, and then the The surface begins to become positively charged.

At this time, since the light of color A passes through the photoconductive layer 13 and makes the photoconductive layer 12 a conductor, the positive charges in the photoconductive layer 12 tend to dissipate to the conductive support 11, so that the final , a considerable portion of the negative charge due to primary charging on the surface of the photoreceptor is converted into positive charge, and due to the influence of this positive charge, the surface potential of the photoreceptor changes from negative polarity to positive polarity at this location. Reverse to . Next, considering the effect of secondary charging on the photoreceptor portion exposed to color B light, since neither photoconductive layers 12 nor 13 have sensitivity to color B light, both photoconductive layers 12 and 13 have no sensitivity to color B light. Both the light guiding layer acts as an insulator.

That is, the positive charges in the photoconductive layer 12 do not move.
The positive charge applied from the charger 3 attempts to neutralize the negative charge on the photoreceptor and positively charge the surface of the photoreceptor, but
Here, since there is a repulsion effect of the positive electricity in the photoconductive layer 12, as a result, only a part of the negative charges on the surface of the photoreceptor are replaced with positive charges. At this time, a considerable amount of negative charge due to primary charging remains on the surface of the photoconductor, but due to the influence of the positive charge in the photoconductive layer 12 and the newly applied positive charge, the surface potential of the photoconductor decreases. , also at this location, the polarity is reversed from negative to positive. On the other hand, what happens to the area illuminated with light from the white background, that is, white light, is that the photoconductive layer 13 absorbs light of colors other than color A and becomes a conductor.

Furthermore, since the photoconductive layer 13 transmits at least the light of color A, the photoconductive layer 12 absorbs the light transmitted through the photoconductive layer 13 and becomes a conductor. In this way, both photoconductive layers 12
, 13 become conductors, the negative charges caused by the primary charging and the positive charges in the photoconductive layer 12 disappear through neutralization and dissipation, and the positive charges imparted by the charger 3 also charge the photoreceptor at this location. I won't let you. Therefore, the surface potential of the photoreceptor 1 is zero at this location. Next, as shown in FIG. 1, the photoreceptor 1 after being irradiated with a light image is
Uniform irradiation with color A light.

Then, in the area exposed to the light of color A during the light image irradiation, the photoconductive layer 13 behaves as an insulator, and the charges on the front and back sides of the photoconductive layer 13 are balanced, so there is no electrical charge in this area. Almost no change occurs. However, in the area exposed to light of color B, when the photoconductive layer 12 becomes a conductor, the excess positive charge dissipates to the conductive support 11, thereby reducing the positive charge in the photoconductive layer 12. The remaining charge and the charge on the surface of the light guide layer 13 are balanced. As a result, the influence of the negative charge due to the primary charge remaining on the surface of the photoreceptor becomes dominant again on the surface potential of the photoreceptor, and the surface potential of the photoreceptor changes from positive polarity to negative polarity at this location. Flip again. Of course, no electrical change occurs in the area corresponding to the white background. Then,
In this state, the potential on the photoreceptor surface is positive in the area corresponding to color A, the polarity of the same level is negative in the area corresponding to color 8, and 0 potential in the area corresponding to the white background area. be.

In this way, a static latent image corresponding to the two-color texture image of the original is formed on the photoreceptor 1. Therefore, as shown in FIG. 1 W, the static latent image portion corresponding to the color A portion is visualized using toner T colored in color AI and negatively charged, and the static latent image portion corresponding to the color B portion is visualized. When the twill portion is visualized using the positively charged toner T2 colored in the color BI, a two-color information image constituted by the colors A and B is reproduced separated and distinguished by the colors AI and BI. Of course, the colors A and AI, and the colors B and BI can be the same color, but there is no problem even if they are different colors. Further, the developing method may be completely arbitrary. later,
The visible image obtained in this way is fixed directly on the photoreceptor 1 (if the photoreceptor 1 is in the form of a sheet), or
The image may be transferred to a suitable recording sheet and then fixed on this recording sheet.

FIG. 2 shows a two-color electrophotographic reproduction process according to the present invention.
It shows the changes in the photoreceptor surface potential during each step leading to the formation of a static latent image. Note that even if the photoreceptor has a four-layer structure by interposing an insulating layer or a rectifying layer between the conductive support 11 and the first photoconductive layer 12, the same result can be obtained by the above process. can get.

However, the rectifying layer is a layer having such a property that only positive or negative charges can selectively pass therethrough. Specific examples will be described below.

Experimental Example 1 An aluminum plate with a purity of 0.99 was used as a conductive support.
The first photoconductive layer was formed by vacuum evaporating 99% selenium to a thickness of 50% at a substrate temperature of 75°C, and was further sensitized with 0.1 mole of monomer unit of the resin mononitrofluorenone. A photoreceptor was constructed by coating bromopylene resin to a thickness of 10 mm as a second photoconductive layer.

FIG. 3 shows the spectral sensitivity of the second photoconductive layer made of propylene resin. The surface of the photoreceptor thus produced was negatively charged by primary charging.

At this time, the charger has 16. A discharge voltage of Fox V was applied. Next, write the red information image on plain white paper with red ink, red pencil, and red ink ballpoint pen, and then write the red information image with red ink, red pencil, and red ink ballpoint pen.
A two-color original with a black information image written on it using a black pencil and a black ink ballpoint pen is illuminated with white light, and the reflected light is focused on a photoreceptor using an imaging lens system, thereby projecting a light image of the original. , the photoreceptor was subjected to secondary charging. At this time, the charger has 4. The discharge voltage of group V was applied to 0.
In this state, the surface potential of the photoreceptor is 1200 V at the red corresponding area and 1260 V at the black corresponding area.
, the area corresponding to the white background area became approximately OV.

Next, the above photoreceptor was uniformly irradiated with a 1OW red fluorescent lamp, and as a result, the photoreceptor surface potential distribution was 1200 V in the red corresponding area and - - in the black corresponding area.
550V, OV was achieved in the area corresponding to the white background.

The electrostatic latent image thus formed is visualized using a developer in which a positively charged black toner and a negatively charged red toner are mixed and dispersed in a dispersion medium, and a visible image is obtained. When transferred and fixed onto a recording sheet, the brightness was high.
A clear red/black two-color image without tear color was obtained.

Experimental Example 2 In place of the second photoconductive layer in Experimental Example 1 above, Cu
CdS (manufactured by Nikosha) doped with silicone resin KR
251 (manufactured by Shin-Etsu Chemical) and reversed the primary charging, secondary charging, and toner polarity, and conducted an experiment under the same conditions as in Experimental Example 1 above. The results were obtained.

FIG. 4 shows an example of an apparatus for carrying out the present invention.

However, in order to avoid complexity, it should be noted that the same reference numerals as in FIG. 1 are used for items that are unlikely to be confused. In the figure, reference numeral 4 denotes an exposure optical system;
Reference numeral 5 is a light irradiation lamp, reference numeral 6 is a developing device, and reference numeral 7 is a developing device.
is a precharger, 8 is a recording sheet, 9 is a transfer charger, 10 is a static elimination charger, 2
In the river cleaning device, reference numeral 30 indicates a turtle removal lamp.

The photoreceptor 1 is formed into a drum shape and is rotatable in the direction of the arrow.

In the copying process, while rotating the photoreceptor 1 in the direction of the arrow,
This is done by sequentially operating each part according to the copying process. That is, the circumferential surface of the photoreceptor 1 that moves due to rotation is uniformly and primarily charged by the charger 2.
The next charged peripheral surface is simultaneously irradiated with a light image by the exposure optical system 4 and subjected to secondary charging by the charger 3.

Next, by the light irradiation lamp 5 that emits light of color A,
When the circumferential surface is uniformly irradiated, a static latent image is formed on the photoreceptor 1.

This static exposure latent image is visualized in the developing device 6. In this example, different colors A are used as the developer D.
A mixed system of two types of magnetic toners, which are colored I and BI and triboelectrically charged to opposite polarities in the triboelectrification series, is used. The toner visible image formed on the circumferential surface of the photoreceptor 1 is charged to the same polarity by a precharger 7 before being transferred, and then transferred to a recording sheet 8 by a transfer charger 9.
The image is transferred onto the recording sheet 8 and fixed onto the recording sheet 8 by a fixing device (not shown). After the toner visible image has been transferred, the photoreceptor 1 is cleaned by the cleaning device 20' while being neutralized by the static eliminating charger 10 and the neutralizing lamp 30.

The above is an outline of the operation of the device.

As described above, according to the present invention, it is possible to provide a two-color electrophotographic copying method that can be carried out with a simple device and can perform good two-color copying without warm colors.

[Brief explanation of the drawing]

1 to 3 are diagrams for explaining the present invention, and FIG. 4 is a diagram for explaining the present invention.
The figure is a front view schematically showing only essential parts of an example of a device for carrying out the present invention. 1... Photoreceptor, 11... Conductive support, 1
2...First photoconductive layer, 13...Second photoconductive layer, 2...Charger for primary charging, 3
・・・・・・Charger for secondary charging, T,, T2・
·····toner. Boar illustration 2 illustration 5 illustration 4 illustration

Claims (1)

[Claims] 1. A copying method for reproducing information images of chromatic colors A and B (chromatic colors or black) on a white background in different colors, the method comprising: a conductive support; and the conductive support. A first photoconductive layer that is laminated directly or through an insulating layer or a rectifying layer and is insensitive to color B light; Light of,
The surface of the photoreceptor, which is composed of a second photoconductive layer that is not sensitive to color B light and transmits at least color A light, is uniformly coated in the dark or with color A light. While being exposed to light, the surface of the photoreceptor is firstly charged to a predetermined polarity, and then, while being irradiated with the optical image of the original, the surface of the photoreceptor is secondarily charged with the opposite polarity to the primary charge, thereby increasing the surface potential on the surface of the photoreceptor. polarity,
The parts corresponding to color A and the parts corresponding to color B are inverted, and the part corresponding to the white background part is set to approximately 0 potential,
Next, the photoreceptor is uniformly irradiated with light of color A to produce the color B.
By reversing the polarity of the photoreceptor surface potential at the portion corresponding to the white background portion, the surface potential at the portion corresponding to the white background portion is approximately 0, and the surface potential at the portion corresponding to color A and the surface potential at the portion corresponding to color B are reduced. The potentials form an electrostatic latent image of opposite polarity to each other, and this electrostatic latent image is colored A1,
A two-color electrophotographic copying method characterized in that visualization is performed using two types of toner colored B1 and charged with opposite polarities.