JPS5860755A - Electrophotographic method - Google Patents

Abstract

PURPOSE:To form a high-quality bicolor picture in a short time with an easy adjustment, by changing only the first optical image exposure to adjust the density. CONSTITUTION:An original 3 is scanned and irradiated by light sources 6a and 6b in different positions, and reflected lights 27a and 27b become exposure lights of a black part and a red part of the original through cyan and red filters 13 and 14 respectively, and a photosensitive drum 1 is exposed to these lights. By this constitution, only the exposure of the drum 1 corresponding to the black part of the original 3 is adjusted when only the quantity of light of the light source 6a is changed, and the exposure corresponding to the red part of the original 3 is not changed, and the density of a black latent image formed on the drum 1 is adjusted without the influence upon a red latent image in accordance with the variance of unevenness of the density of the black part due to pencil-written or printed data on the original 3. The red latent image on the drum 1 is developed in a red developing device 15, and the black latent image formed by an overall exposure lamp 16 following the device 15 is developed with a black toner having the polarity opposite to that of the device 15 by a black developing device 16, and thus, a high-quality bicolor picture is formed in a short time during one rotation of the photosensitive drum with a simple constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is based on the electrophotographic method, in particular, the reproduction of two color components of an original image, for example, black and chromatic colors, by two development steps after the original image. This is related to the electrophotographic method that is possible.

Conventional color copying requires multiple process repetitions for the number of colors (primary colors and black), and therefore requires a large amount of time to produce a single copy. was difficult. Furthermore, color shift caused by repeated operations is also a major problem, and it has been extremely difficult to prevent this.

On the other hand, most of the demand for copying machines in the market is for making copies of documents, conference materials, etc.

Therefore, it is very rare that natural colors (multicolors sm>) are required for copies, and two colors such as black and red are sufficient when copying documents and the like.

For example, it is often the case that a document with black text is copied with corrections or annotations added using a red pen.In such cases, multiple colors are not necessary, but it is possible to make a copy by dividing it into two colors. , the effect of evoking attention, etc. is a dog. In this respect as well, two-color color reproduction is extremely useful.

The present applicant has previously proposed a method as described in Japanese Patent Application Laid-open No. 51-146832. This method differs from the method in which an electrostatic image having predetermined color components is formed and the process of developing it is repeated.After forming an electrostatic image of the original image, two-color brightness is applied to the exposure i of the original optical image. Based on the conventional method (compared to one hour for color copying, it takes an extremely short time to image)
It enables color reproduction.

The outline of the =I notation method will be explained below with reference to the drawings.

In FIG. 1, a manuscript to be read by Ald 4M is shown.

The manuscript consists of a white background for A, a red image for the mouth, and a black image for ). B indicates an electrophotographic photoreceptor, with insulation +1t
s Photoconductivity/#I[, the basic structure is a conductive layer I.

Explain the process step by step.

(1) The surface of the insulating layer of photoreceptor B is uniformly primary charged with a corona discharger Ct (positive charging in the illustrated example).

This process induces a negative charge having a polarity opposite to that of the vertical stack in the back layer of the insulating layer 1.

(2) After the above process has been completed, the photoconductor is charged with a polarity opposite to the primary charge, or is secondary charged with alternating current using a corona discharger Q.
The two-color original image A is irradiated through a cyan filter (αF) that completely blocks only red light. Through this process, in area a, light other than red out of the light coming from document A passes through the filter (QFJ) and acts on the original conductive layer ■, so the resistance of the original conductive layer ■ decreases, and the back side of the insulating layer The negative charge induced in the insulating layer escapes, and the positive primary charge on the surface of the insulating layer disappears due to reverse polarity charging.

On the other hand, in the area where the red light coming from the image aperture is blocked by the filter (CAF), the resistance of the original conductive layer I does not decrease. As a result, the electric potential of the insulating layer Asada 1 becomes near zero while the induced charge on the back surface of the insulating layer JII remains in a retained state.

The potential on the surface of the line layer is near zero.

(3) Next, a red filter (λF) is applied to the entire surface of the photoreceptor, except for those restricted by the charges, which escape to conductivity -■.

- In the universal color image corresponding area (e), the induced negative charge is
It is held near the interface between the insulating layer and the photoconductive layer.

As a result, the surface of the insulating layer rises to a positive potential in the region Φ) corresponding to the red image (b), and remains at near zero potential in the region C corresponding to the -universal color image (c).

(4) The latent image generated by the above process is developed with red toner.

When white and irradiated metal are uniformly applied to the surface, the photosensitive area C of the center or center becomes conductive, and the induced negative charge near the interface layer escapes to the conductive layer π side, resulting in the photosensitive plate in the black image area. A positive potential appears on the surface.

(6) The photosensitive plate is developed using negatively charged black toner to obtain a two-color oak image on the photosensitive member.

For example, this is transferred to a transfer material such as paper to provide a two-color image copy.

As described above, the method described above is useful because a latent image corresponding to a two-color image is formed by one electrostatic latent image formation, and the latent image yJ can be visualized as a two-color phenomenon. However, in order to reproduce various original documents without fog, such as those with high image density such as printed characters and those with low image density such as pencil characters, it is generally necessary to adjust the exposure ftf. In this case, by changing the exposure amount of the first M light means, the exposure amount of the second exposure means must be adjusted accordingly.

In other words, when the first exposure amount is reduced, the latent image potential corresponding to black increases, but the latent image potential corresponding to red does not increase much if the second jl light amount decreases according to the first exposure amount. As a result, the developed image will have a different balance of red and black. Alternatively, when the first g element amount is increased, the second exposure amount increases in accordance with the first exposure amount, and when it exceeds a certain level, the black latent image potential increases due to the increase in the amount of reflected light from the original black part or the amount of flare light. appears, and during red development, the black areas will also be developed.

An object of the present invention is to provide an electrophotographic method that satisfies the above-mentioned point Vcs and makes it possible to obtain color images with good quality.

The present invention is characterized in that density adjustment is performed by exposing the photoreceptor to a first light image and by making small changes in the exposure i of the second light image.

The following is a drawing showing a specific example of the measurement of the present invention. I will explain while referring to it.

FIG. 3 shows a specific example of an apparatus for carrying out the process of the present invention. 1 is a photoreceptor drum, which has a conductive layer as described above;
The basic structure is a photoconductive layer and an insulating layer. The original 3 (for example, a two-color image consisting of black and red) placed on the original platen glass 2 is
It is irradiated by an illumination light source 6 having two illumination lamps 6a and 6b, and the reflected light is divided into light beams 27a and 27b and passes through the movable mirrors 4 and 5, the lens 7, and the mirror 8°9.
It is projected onto the surface of the photoreceptor drum 1 via each of the cyan and filter 13 (αF), and the red and filter 14 (&F).

The illumination distribution on the document surface by the two illumination lamps 6a and 6bK is different from each other as shown in FIG. 4, and the reflected light is made to correspond to 27a and 27b, respectively.

Even if the illumination lamp 6a is adjusted to adjust the first exposure amount 27a, the second exposure amount 27b hardly changes as shown by the broken line in FIG.

That is, the above effect can be obtained by configuring only the illumination lamp 6a to be adjustable.

Since the document table 2 is moved in the direction of the arrow X, each point on the lateral side of the original first passes through the path of the light beam 27a, and then through the path of the light beam 27b, and is projected onto the photosensitive drum. The photoreceptor drum 1 is subjected to primary cleaning in the -order corona discharger 1.1, and then simultaneously subjected to original f-quadrant exposure (cyan, filter) from the path of the light beam 27a, and at the same time, -order charging and opposite polarity charging or A
C corona discharge is provided by a secondary corona discharger 12.

The document is scanned in synchronization with the # movement of the photoreceptor drum 4!
Of course, the photoreceptor-drum 1, which has been subjected to a secondary charge of opposite polarity, is irradiated with red light, which has passed through the filter 14, through the path of the light beam 27b. That is, as a result, a light image in which all light other than red is cut is irradiated, and a developable potential image is formed in the red corresponding portion of the formed electrostatic latent image. The image is rendered red by the gap device 15.

The photoreceptor drum 1 is then illuminated with a full exposure rung 16 to form a high potential image on the photoreceptor portion corresponding to the black color of the original document. Next, the negatively charged black toner is supplied to the developing device 17, and the image is developed by the paper feed roller 19.
Alternatively, the image is transferred by the corona transfer device 22 onto a transfer material 21 or 21' such as plain paper fed by the paper 19'. 18 is a transfer material feeding timing roller. After the transfer is completed, the transfer material of the transfer method is separated from the drum 1 by a separation roller 23. The powder image is fixed onto the transfer material by a contact heat fusing device 20 and is discharged onto a tray 30 by a paper discharge roller 25. 24 is a static eliminator that removes residual charges on the transfer material.

After the transfer is completed, residual toner on the drum surface is removed by a cleaning device 26 and accumulated at - locations.

Next, a modification of the present invention will be explained with reference to FIGS. 6 and 7. As shown in FIG. 6, when the illumination distribution on the document surface by the two illumination lamps 6a and 6b is almost the same, the original source can be narrowed down to a narrow range, and the photographing lens etc. can be used with a relatively small diameter. It has the advantage that it can be used even in However, it is difficult to separate these two parties using an optical system, so lighting,
In front of the lamps 6a and 6b, there are cyan and n filters, respectively.
Set up a red filter.

In this way, in FIG.
3. Since the irradiation field passes through the red filter 12, the first
Even if the source f of the illumination lamp 6a is changed in order to change the exposure amount, the second exposure amount is hardly affected.

Another modification of the present invention will be explained with reference to FIG.

As shown in FIG. 8, a red filter 31 is provided on the entrance side or exit side of the photographic lens 70.

By sliding this red filter in the direction of the arrow, the cyan component in the light beam can be made variable. On the other hand, the red wavelength component changes slightly due to the insertion of the red filter, but the change is small. In such a method, the number of illumination lamps shown as 6a and 6b in FIG.
On the other hand, the second island light amount hardly changes.

As a method of inserting the filter, the first exposure field may be adjusted by rotating the element 31, which employs a red filter only in half, as shown in FIG. 9 with respect to the optical path. That is, it is sufficient to rearrange a disk filter, half of which is transparent and the other half of which is a red filter, with respect to the lens 7 as shown in the figure, and adjust the rotation around the center of the disk filter.

As a modification of the method shown in FIG. 8, a guest-host type liquid crystal cell in which a dichroic dye is mixed with the liquid crystal may be used. Dichroic dyes have an elongated molecular shape as shown in the principle diagram in Figure 10, and when the molecular length axis and the polarization direction of the incident light match as shown in (a), there is a large absorption at the absorption wavelength of the dye. However, in cases where they do not match as in (b) and (C), the original absorption is small.

As such dichroic dyes, azo dyes and anthraquinone dyes are known.

When such a dichroic dye is mixed into the liquid crystal, the dichroic dye 31 can be aligned in the same direction as the liquid crystal 32. To orient the liquid crystal 32, there are methods such as rubbing the glass substrate 33 having the transparent electrode 34 in one direction with a cloth, or diagonally depositing SiO to give directionality to the glass substrate. It has been known. This type of liquid crystal cell is generally called a guest-host cell, but when a voltage is applied to it, the liquid crystal aligns in the direction of the electric field due to its dielectric constant anisotropy, and this type of liquid crystal is known as a P-type liquid crystal. ,
Liquid crystals arranged perpendicular to the reverse 1c electric field are called n-type liquid crystals. Although the embodiment will be described using an electro-type liquid crystal, an n-type liquid crystal can also be used.

Now, since the liquid crystals are arranged in the direction 32 in FIG. 11(b), the dichroic dye 31 is also arranged in the same direction, and in such a case, no light is absorbed and the cell is transparent.

An example of such a cell is the spectral transmittance of a guest-host cell in which an anthraquinone dichroic dye is mixed with a mixed liquid crystal of BBCA (parabutoxybenzylidene cyanoaniline) (!: MBBA (paramethoxybenzylidene parabutylaniline). This is shown in Figure 12.By changing the applied voltage to the cell in this way, the blue-green light component can be changed without changing the transmittance of red light.Also, in Figure 12, the applied voltage Ov However, the reason why the transmission of light is not O is because polarized light in the direction perpendicular to the long axis of the dichroic dye molecule is not absorbed. It is sufficient to use W+ only in the long axis direction of the dichroic dye molecule.

By employing such a guest-host cell, the light amount can be adjusted by changing the first exposure light i by the applied voltage and hardly changing the second exposure f.

Although black and red have been described with respect to the original color and reproduced color, it is needless to say that the original image and the developed color do not have to be the same, as well as the original image having scales having any of the color components.

As described above in detail in the specific examples, the present invention is an excellent method that makes it possible to obtain good color images with simple adjustments.

Furthermore, the configuration of the apparatus for carrying out the present invention is extremely simple and enables formation of a good image.

[Brief explanation of the drawing]

Figures 1 (1) to (6) and Figure 2 illustrate the prior art method; Figures 1 (1) to (6) are explanatory diagrams of each process step in image formation; A surface potential characteristic diagram, FIG. 3 is a side view of a specific example device based on the present invention, FIG. 4 is an explanatory diagram of the light intensity distribution on the document surface of the third illustrated device of the present invention, and FIG. 5 Fi
An explanatory diagram of the light amount distribution on the photoreceptor in the case of the light amount distribution in FIG. 4,
6 and 7 are explanatory diagrams of the light quantity distribution on the document surface and the light quantity distribution on the photoreceptor surface in a modified example based on the present invention, and FIG.
9 is an explanatory diagram of another specific example of the light amount regulating means, FIG. 9 is an explanatory diagram of a further modified example, and FIG.
Explanatory diagram of the principle of chromatic pigments, Fig. 11 (a), (b) ld
, guest, and host cells. (a) is when no voltage is applied to the liquid crystal, (b) is an explanatory diagram when the voltage is applied, and Figure 12 is the spectral transmittance of the guest 5 host cell. Characteristic diagram. In the figure, 1: Photoreceptor drum, 2: Original table glass, 3: Original, 4, 5: Movable mirror, 6: Illumination light source, 7: Lens, 8
, 9; Mirror; 10; Control device; 16; Full-surface exposure lamp; 17; Black phenomenon device. "!4-121 Figure 1 '5'

Claims (1)

[Claims] (1) First light image exposure and second ft, gII on the photoreceptor.
An electrophotographic method for forming a color image gI by exposure, characterized in that the first light image exposure & is adjusted, and the density of the second light image is adjusted with a small change in exposure amount. Photography method. (2. In the invention described in claim 1, the electrophotographic method is characterized in that the photoreceptor has a basic structure of a conductive layer, a photoconductive layer, and an insulating layer. (3) In the invention set forth in claim 1 or 2, the first optical image exposure includes applying a voltage having a polarity component opposite to that of the uniform charging to the surface of the photoreceptor that has been uniformly charged in advance. An electrophotographic method characterized in that the first light image exposure is carried out at the same time. An electrophotographic method characterized in that a chromatic image is formed by exposing a light image. (phrase Clause 1, 2, 3, or 4 of the scope of claims)
2. The electrophotographic method according to the invention, wherein the second light image exposure comprises a light image exposure having a predetermined chromatic color gII. (6) The invention according to any one of claims 1) to 5, further comprising a first developing step using a predetermined color developer following the second light image^light. Characteristic electrophotographic method. (7) An electrophotographic method according to the invention as set forth in claim 6, characterized in that the first developing/imaging step is followed by a full-surface exposure step. (8) In the invention described in claim 7, in the invention described in electronic photography, the invention further comprises a second development step using a different developer following the entire surface exposure step. An electrophotographic method characterized in that a common optical lens means is used for a first optical image g source, a second ft, image layer ft, and t. In the invention described in any one of the first to ninth terms, the first optical image j! An electrophotographic method comprising a first illumination means for exposing an original image and a second illumination means for exposing a second light image. 0υ An electrophotographic method according to claim 10, characterized in that the first illumination means is variable. (I2, in the invention set forth in claim 10, an electrophotographic method characterized in that the first illumination means has colored light according to the first light image exposure. +ld) In the invention described in scope 10, the electrophotographic method is characterized in that the second illumination means has colored light according to the second light image exposure. (14) In the invention set forth in claim 9, the amount of light that regulates the colored light of the first optical image exposure to the common optical path of the optical lens biomembrane and allows the colored light of the second optical image exposure to pass through. An electrophotographic method characterized in that it has a regulating means. (15j) In the invention described in claim 14, the electrophotographic method is characterized in that the regulating means has a guest/host hill.