JPS62234171A - Color electrophotographic method - Google Patents

Abstract

PURPOSE:To enable color correction by using a photosensitive body having 5 layers of photoconductive layer by forming a cyan latent image having a prescribed polarity and magenta and yellow latent images having a positive polarity and negative polarity, developing the latent images with a cyan toner, then uniformly exposing the photoconductive layer body with a yellow toner. CONSTITUTION:The cyan latent image is formed by image exposing on the photoconductive layer P5, the magenta latent image of the negative polarity on the photoconductive layer P4, the magenta latent image of the positive polarity on the photoconductive layer P3, and the yellow latent images of the negative polarity and positive polarity are formed on the photoconductive layers P2 and P1, respectively. The latent images are developed in this stage by the cyan toner TC electrostatically charged negative. The photosensitive body is then uniformly irradiated with prescribed light L1 to erase the magenta latent image of the positive polarity and the latent images are developed with the magenta toner TM electrostatically charged positive. The photosensitive body is subjected to uniform secondary exposing to erase the weakened cyan latent image and yellow latent image of the negative polarity. The latent images are then developed by the yellow toner TY electrostatically charged negative. The toner deposition decreases in the part where the yellow latent image and the magenta latent image overlap.

Description

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

(Prior Art) As a color electrophotographic method for obtaining color electrophotographic images without color separation of an original, a method using a photoreceptor having five photoconductive layers is known (Japanese Unexamined Patent Publication No. 59-1213
Publication No. 56).

Incidentally, in recent years, there has been a strong demand for improved color expression in color electrophotographic images, and so-called color correction has also been performed.

In the prior art described above, color correction is not performed at all.

(Objective) Therefore, the object of the present invention is to improve the above-mentioned conventional technology and to provide a novel color electrophotographic method that uses a photoreceptor having five photoconductive layers and is capable of color correction. be.

(composition) The present invention will be explained below.

In practicing the present invention, a photoreceptor having five photoconductive layers is used. Five photoconductive layers are laminated onto a conductive substrate. The photoreceptor is prepared such that the five photoconductive layers have different sensitivities within the photoreceptor.

In this photoreceptor, first, the five photoconductive layers are alternately charged in opposite directions.

Thereafter, image exposure is performed on the photoreceptor. This image exposure forms a cyan latent image, a magenta latent image, and a yellow latent image. The cyan latent image has a predetermined polarity, but the magenta latent image and the yellow latent image have positive and negative polarities.

That is, after image exposure, a cyan latent image of a predetermined polarity, magenta and yellow latent images of positive polarity, and magenta and yellow latent images of negative polarity are formed on the photoreceptor.

In this state, first, development is performed using cyan toner.

Through this development, the cyan latent image is visualized with cyan toner.

Next, the photoreceptor is uniformly exposed to light of a predetermined color. This uniform exposure is performed as follows.

That is, among magenta latent images of positive and negative polarities, those having the same polarity as the cyan latent image are erased, and at the same time, the cyan latent image is weakened. How much does the cyan latent image weaken?

The remaining magenta latent image, that is, the magenta latent image having the opposite polarity to the cyan latent image, is determined so as to be appropriately color corrected.

Subsequently, development is performed using magenta toner to visualize the magenta latent image.

Next, the photoreceptor is uniformly exposed to light of a different color from the previous uniform exposure to erase the cyan latent image.

At the same time, the yellow latent image, which has the opposite polarity to the cyan latent image, is also erased. Additionally, the magenta latent image is weakened so that proper color correction can be made to the remaining yellow latent image.

Then, it was developed using yellow toner.

A visible color image is obtained using cyan, magenta, and yellow toners on a photoconductor, and this is transferred onto a recording sheet.
By fixing, a desired color electrophotographic image is obtained.

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

The inventor prototyped a photoreceptor having the structure shown in FIG.

In Fig. 2, the symbol BS is a conductive substrate, and the symbol P1゜P
2. P3. P4. P5 is a photoconductive layer, symbol Bl,
B2. B3. B4 indicates one barrier layer, and symbols FV and FR indicate one filter layer, respectively. The conductive substrate BS is made of aluminum.

The photoconductive IPI is a 10 μm thick layer of Se, which is deposited at a substrate temperature of 72° C.

The photoconductive layer P2 is also a 10 μm thick Se layer, but this one is vacuum deposited at a substrate temperature of 20° C.

The photoconductive layer P3 is a 10 μm thick layer of eutectic OPC and is formed by coating. Eutectic OPC is a eutectic of thiapyrylium salt and polycarbonate.

The photoconductive layer P4 is a negatively charged ZnO resin layer sensitized with rose bengal, and is coated and has a thickness of 10 μm.
It is m.

The photoconductive layer P5 is a positively charging ZnO resin layer sensitized with methylene blue, and is coated and has a thickness of 10 μm.
It is m.

Barrier layer Bl, B2. B3. [14] All are cellulose resin layers formed as a coating, and each has a thickness of approximately 1 μm.

Further, the filter image FV is a multilayer film filter formed by vacuum deposition, has a thickness of more than 1 μm, and has a function of cutting near ultraviolet light.

The filter single layer FR is formed by coating.

It is approximately 1 μm thick and has the function of cutting red light. Note that the specific shape of the photoreceptor was a drum shape.

Each of the above photoconductive layers P1 to P5 has a spectral sensitivity as shown in FIG. That is, the photoconductive layers P1 and P2 have spectral sensitivities as shown by curve 3-1 in FIG. 3, and the photoconductive layers P3. P4. P5 is curve 3-3.3-4.
It has a spectral sensitivity of 3-5. However, the spectral sensitivity shown in FIG. 3 is for the case where each photoconductive layer exists alone, and due to the absorption characteristics of each layer and the presence of filters FV and FR, the spectral sensitivity of each photoconductive layer P1 to P5 is The sensitivity in the body may differ from the curve in FIG. 3.

For example, photoconductive layers P1 and Pl may be
Although it has a spectral sensitivity as shown by curve 3-1 in the figure, since the single layer V of the filter blocks near ultraviolet light from the photoconductive layer PL, the photoconductive layer pi does not have sensitivity to near ultraviolet light within the photoreceptor. Therefore, the photoconductive layer P2 has a photosensitivity different from that of the photoconductive layer P2, which has photosensitivity to near-ultraviolet light.

The process will be explained below with reference to FIG.

In addition, in this FIG. 1, the illustration of the photoreceptor is simplified,
The barrier layer and the filter layer are omitted from illustration.

First, a photoreceptor is uniformly irradiated with white light through a filter that cuts only green light. Then, from the relationship between the spectral sensitivities, among the photoconductive layers pt to P5, PI,
Pl, P4. P5 is made into a conductor and only the photoconductive layer P3 acts as an insulating layer. In this state, when uniform charging with positive polarity (referred to as -order charging) is performed, as shown in Fig. 1 (1).
As shown in FIG. 2, an electric double layer of positive charges and negative charges is formed via the photoconductive layer P3. In this state, the photoconductive layer P3 is likened to a capacitor, and the photoconductive layer is said to be charged.

Due to this negative charge, the photoconductive layer P3 is charged to +2000V.

Next, the photoreceptor is uniformly irradiated with red light. Then, since the filter FR cuts red light from the photoconductive layers P1 to P4, only the photoconductive layer P5 is made conductive in this state. However, the photoconductive layer P1 has a conductive substrate B
There is a rectifying property between S and S, and holes are easily injected from the conductive substrate BS into the photoconductive layer pt.

When holes are injected into the photoconductive layer PL, they easily move through the same layer Pl.

Therefore, when the photoreceptor is secondarily charged to a negative polarity under irradiation with red light, a charge distribution as shown in FIG. 1 (II) is realized within the photoreceptor. Photoconductive layer PI.

The positive charges trapped on the Pl interface are holes injected from the conductive substrate BS. At this stage, the photoconductive layer WJP4 is -800V, and the photoconductive layer P2 is the same <-aOO
V, and photoconductive layer P3 (7) is charged [1st place is +400V
becomes.

Next, perform positive tertiary charging in the dark,
A charge distribution as shown in FIG. 1(m) is realized. In this state, the photoconductive layers Pl, Pl, P3 . P4. The photoconductive layers PI, P3 . P5 is +400v, photoconductive layer P2. P4 has 1400V. Therefore, in the state shown in FIG. 1(m), the surface potential of the photoreceptor is +400V.

Subsequently, as shown in FIG. 1 (IV), the photoreceptor is exposed to image light using the light image of document 0. Manuscript O is black on white,
Assume that there are images in seven colors: cyan, magenta, yellow, red, green, and blue.

This image exposure causes the charge distribution on the photoreceptor to change to the first
It will look like Figure Hv).

A cyan latent image, that is, an electrostatic latent image corresponding to an image containing cyan as a component of the original image, that is, an image of black, cyan, green, and blue, is an electrostatic latent image corresponding to the charge distribution of the photoconductive layer P5 (charged distribution of parts). This means that a cyan latent image is formed on the photoconductive layer 1)1. Charging of the charged portion of the photoconductive layer P1 11! ft position is +400v
Therefore, the polarity of this cyan latent image is positive.

Next, looking at the charging distribution of the photoconductive layer P4, this distribution corresponds to an image having a magenta color component in the original O, and since the charging potential of the photoconductive layer P4 is -400V,
This means that a magenta latent image of negative polarity is formed on the photoconductive layer.

Similarly, light guide? ! M! A magenta latent image of positive polarity is formed on IP3, and yellow latent images of negative polarity and positive polarity are formed on photoconductive layers P2 and P1, respectively.

In the state shown in FIG. 1 (IV), the magenta latent image and the yellow latent image are inside the photoconductor, and since the positive and negative polarities cancel each other out, these magenta and yellow latent images are in this state. It does not appear as a photoreceptor surface potential.

Therefore, in this state, the negatively charged cyan toner T
When developing with C, only the cyan latent image becomes visible as shown in FIG. 1(V).

Next, as shown in FIG. 1 (Vl), 600 to 8000
The photoreceptor is uniformly irradiated with light LL having a wavelength range of m.

As shown in FIG.
The photoconductive layer P3 has a function of making it conductive, but the degree of making the photoconductive layer P3 a conductor by the light L1 is greater than that of P5, and therefore,
When the light L1 is continued to be irradiated, the charged state of the photoconductive layer P3 is first eliminated, and later, the charged state of the photoconductive layer P5 is eliminated. The cancellation of the charged state of the photoconductive layer P3 means that the positive magenta latent image is erased.

Therefore, by adjusting the amount of light irradiation by the light LL, the positive magenta latent image is erased, but the charging potential of the cyan latent image is reduced to about 1/2 to 1/3 of its original value. do. This operation on the cyan latent image is called weakening the cyan latent image.

When the positive polarity of the magenta latent image is erased, the charging potential of the negative polarity magenta latent image appears as the photoreceptor surface potential. Therefore, this surface potential distribution is developed using magenta toner TM which is positively charged (FIG. 1 (■)). At this time, in the part where the magenta latent image and the cyan latent image overlap (parts corresponding to the black image and blue image), a repulsive force acts on the magenta toner due to the weakened cyan latent image as described above. Toner adhesion amount is 1/3
The area is smaller than other parts.

Note that the uniform exposure of the photoreceptor by the light L1 will be referred to as primary uniform exposure.

Next, as shown in FIG. 1 (■), light L2 is applied to the photoreceptor.
Perform secondary uniform exposure using Light L2 is 300-400
It is a mixed light of no+ light and 500 to 600 nn+ light.

Therefore, this light L2 is transmitted to the photoconductive layer P2. P4. It has the effect of making P5 a conductor.

Therefore, this secondary uniform exposure is performed as follows. That is, the cyan latent image weakened by the previous primary uniform exposure is erased, and the yellow latent image of negative polarity, that is, the charging distribution of the photoconductive layer P2 is erased. At the same time, the magenta latent image (charging potential distribution of the photoconductive layer P4) is weakened, and its charging potential is reduced to 172 to 1/3 of the original value. As a result, a positive yellow latent image (charge distribution of the photoconductive layer P1) is filled f! ! The potential appears as the photoreceptor surface potential.

Subsequently, development is performed using negatively charged yellow toner TY. At this time, in areas of the yellow latent image that overlap with the magenta latent image (black image, red image corresponding area), the magenta latent image (
Although it is weakened, it has a negative polarity and exerts a repulsive force on the yellow toner), so that the amount of yellow toner adhered to other areas (the yellow latent image area that does not overlap with the magenta latent image) is 172. It becomes 2/3.

In this way, a color visible image corresponding to the document ○ is obtained on the photoreceptor (FIG. 1 (■)).

Thereafter, by transferring this visible image onto a recording sheet and fixing it, a desired color electrophotographic image can be obtained.

As is clear from the above explanation, when developing with magenta toner, the cyan latent image was weakened by the second uniform exposure, and when developing with yellow toner, the cyan latent image was weakened by the second uniform exposure. Since each magenta latent image acts as a mask in the masking method, the resulting color electrophotographic image is color-corrected by the masking method.

FIG. 4 schematically shows the transition of the photoreceptor surface potential in the process of the present invention described above.

Black, cyan, magenta, yellow, red, green, blue.

White indicates the potential of the corresponding portion of the photoreceptor of the original image of these colors.

FIG. 5 shows an example of an apparatus for implementing the present invention in an explanatory diagram of only the main parts.

In the figure, 10 is a photoreceptor, 12.14 is a charger with a lamp, 16 is a charger, and 18°22
, 26 is a developing device, 20.22 is a lamp with a filter, 28 is a transfer device, and 3o is a cleaning device.

This device was prototyped by the inventor and is capable of carrying out the process specifically explained above.

The photoreceptor IO is formed into a drum shape and is rotatable in the direction of the arrow, and its specific configuration is as described in conjunction with FIG. 2.

While rotating the photoreceptor 10 in the direction of the arrow, chargers 12 and 14 with lamps perform sequential charging and secondary charging, charger 16 performs tertiary charging, and then image exposure is performed using a beam of exposure light.

Next, development is performed using cyan toner in a developing device [18], and then primary uniform exposure is performed using a lamp 20 with a filter.

Further, a developing device 22 performs development with magenta toner, a lamp with a filter 24 performs secondary uniform exposure, and a developing device 26 performs development with yellow toner.

The color visible image thus obtained on the photoreceptor 10 is electrostatically transferred onto the transfer paper S, which is a recording sheet, by the transfer device 28, and fixed onto the transfer paper S by a fixing device (not shown).

After the visible image has been transferred, the photoreceptor 10 is cleaned by a cleaning device 30.

A color electrophotographic image is thus obtained.

In this way, the hue of the color electrophotographic image obtained with the prototype device shown in FIG. 5 was well improved due to the effect of color correction. Comparing the color differences for each color on a document between a color electrophotographic image obtained by the conventional technique described in JP-A-59-121356 and a color electrophotographic image produced according to the present invention, the results are as shown in the following table.

Even when simply comparing the average color difference in the table, the color difference in the present invention has been improved to 172 or less compared to the conventional method.

Note that the photoreceptor 10 is rotated three times for one process,
In the first rotation, primary or tertiary charging, image exposure, and development with cyan toner are carried out, in the second rotation, primary uniform exposure and development with magenta toner are carried out, and in the third rotation, secondary uniform exposure and development with yellow toner are carried out. , visible image transfer/fixing, and cleaning may be performed.

(Effects of the Invention) As described above, according to the present invention, a novel color electrophotographic method can be provided.

Since color correction is performed in this method as described above, a color electrophotographic image with good hue can be obtained. Note that the leading 711 layers PI to P5 may be arranged in combinations other than those shown in FIG. 1, and the magenta and yellow positive and negative latent images do not necessarily have to be adjacent to each other.

[Brief explanation of drawings]

Figure 1 is a diagram for explaining the present invention, Figures 2 and 3 are diagrams for explaining the present invention.
The figure is a diagram for explaining a photoconductor used in carrying out the present invention, Figure 4 is a diagram showing changes in the surface potential of the photoconductor in the color electrophotographic process of the present invention, and Figure 5 is a diagram for carrying out the present invention. FIG. 2 is an explanatory diagram schematically showing only essential parts of an example of the device. BS: conductive substrate of photoreceptor, PI, P2. P3
．． P4゜P5...Photoconductive layer, 0...Original, TC.
... Cyan toner, TM... Magenta toner, TY.
...Yellow toner. Shape 7 In 17f) 2 Illustration sale 3 Insu wo (n Hiroshi 2 Ryo 4 Figure 5 Inna Tekai ρ Yukuchi Seisho (Method) % expression % 1 Incident indication Patent Order No. 77732 of 1985 2 Invention Name of Color Electrophotographic Method 3 Relationship with the person making the amendment Case Name of patent applicant (674) Ricoh Co., Ltd. 4th generation
person

Claims (1)

[Claims] In a photoreceptor, five photoconductive layers are laminated on a conductive substrate, and each photoconductive layer is prepared in such a way that each photoconductive layer exhibits a different sensitivity. After charging in the same direction, image exposure is performed to form a cyan latent image with a predetermined polarity, a magenta latent image and a yellow latent image with a positive polarity, and a magenta latent image and a yellow latent image with a negative polarity, and then developed with cyan toner. After that, uniform exposure with light of a predetermined color is performed to erase the magenta latent image of the same polarity as the cyan latent image, and at the same time, the cyan latent image is removed so that the remaining magenta latent image is properly color-corrected. Then, development is performed with magenta toner, and uniform exposure is performed again with light of another color to erase the cyan latent image and the yellow latent image, which has the opposite polarity, and at the same time remove the remaining yellow latent image. Color electrophotography characterized by weakening the magenta latent image so that the image is properly color-corrected, then developing with yellow toner, and transferring the resulting color visible image onto a recording sheet and fixing it. Method.