JPH0343621B2 - - Google Patents

Description

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

(Prior Art) As a color electrophotographic method, a method that combines the Carlson process and color separation is well known. That is, an electrostatic latent image corresponding to the color separated image of a color image separated by one of the three primary colors is formed on a photoreceptor having panchromatic photosensitivity, and this electrostatic latent image is Visualization is performed using toner colored in a complementary color to the separation color, and the resulting visible image is transferred onto a recording medium such as paper. This process is repeated for the other two colors of the three primary colors, and the three colors are superimposed and transferred onto the same recording medium.
A color image is synthetically reproduced using the different colored visible images of the seeds.

This method has a problem in that it is necessary to repeat the Carlson process as many times as there are color separations to obtain one color electrophotographic image, making it difficult to improve the efficiency of the color electrophotographic process.

To solve this problem, we used as many photoreceptors as there were color separations, performed the Carlson process required for each color separation simultaneously on each photoreceptor, and recorded images of different colors obtained on each photoreceptor on the same recording medium. A method has also been proposed in which the images are transferred onto each other by overlapping them, but this method requires multiple equipment for the Carlson process, including a photoreceptor, so there is a problem in that the equipment required to achieve this becomes larger. be.

Furthermore, both of the above methods require a process of transferring visible images of different colors onto the same recording medium in mutually aligned positions, and perfect alignment is impossible; A common problem is that a color electrophotographic image with good resolution cannot be obtained due to significant positional deviation.

(Objective) Therefore, an object of the present invention is to provide a completely new color electrophotographic method that does not have the above-mentioned alignment problem, is highly efficient, and can be implemented with a compact device.

(composition) The present invention will be explained below.

One of the features of the present invention lies in the configuration of the photoreceptor used.

That is, this photoreceptor has 5
It is constructed by laminating photoconductive layers. One of these five photoconductive layers has photosensitivity only to red light, the other layer has photosensitivity only to blue light, and the still other layer has photosensitivity only to green light. the other 2
The photoconductive layer of the layer is photosensitivity to one or more of blue, red, green, and other colors of light. However, the spectral sensitivities of these two photoconductive layers are different from each other.

Here, additional explanation will be added regarding the above red, blue, and green. That is, in this specification, the above-mentioned red, blue, and green are used in a special meaning. That is, these are used as colors representative of the three primary colors. Therefore, herein:
When we say red, blue, and green, these can be replaced with the other three primary colors.

When red, blue, and green actually and literally mean red, blue, and green, this will be specifically stated.

The five photoconductive layers described above are laminated so that the two layers with overlapping photosensitive regions are in direct contact with each other.

Of the photoconductive layer of this photoreceptor, only red light
The three layers sensitive only to blue light and only green light are charged to a predetermined polarity, and the other two layers are charged to the opposite polarity.

After each photoconductive layer is charged in this manner, the photoreceptor is illuminated with a color image.

Development is then carried out with a toner colored complementary to the color to which the top photoconductive layer, ie the fifth photoconductive layer, is photosensitized.

Next, the top two photoconductive layers, i.e. the fourth
First, the photoreceptor is uniformly irradiated with light that makes only the photoconductive layer conductive. Following this,
Development is performed with a toner colored complementary to the color to which the third photoconductive layer is photosensitized.

Further, the photoreceptor is uniformly irradiated with light that makes only the third and second photoconductive layers conductive, and finally, a toner colored in a complementary color to the color to which the first photoconductive layer has photosensitivity is applied. Development is performed by

As a result, a color visible image corresponding to the above color image is obtained on the photoreceptor.

This color visible image is either fixed on the photoreceptor as it is and used for recording (if the photoreceptor itself is in the form of a sheet), or transferred and fixed onto a recording medium such as paper.

Hereinafter, a detailed description will be given with reference to the drawings.

In FIG. 1, reference numeral 1 indicates a photoreceptor used for carrying out the present invention as an explanatory diagram.

The photoreceptor 1 includes five photoconductive layers P1, P2, P3, P4, and P5 laminated in this order on a conductive substrate B. photoconductive layers P1 to P5,
This order will be referred to as first to fifth photoconductive layers.

These first to fifth photoconductive layers are, respectively,
In Fig. 2, the symbols 2-1, 2-2, 2-3, 2-
It has a spectral sensitivity as shown by 4,2-5.

That is, the first photoconductive layer P1 actually has photosensitivity only to blue light, and the third and fifth photoconductive layers actually have photosensitivity only to green light and only red light, respectively. Further, the second photoconductive layer emits blue light;
The fourth photoconductive layer has a photosensitivity to light having a shorter wavelength than that, and the fourth photoconductive layer has a photosensitivity that overlaps with the third photoconductive layer P3, and has photosensitivity in a wavelength region of 700 nm or more.

The first photoconductive layer P1 and the second photoconductive layer P2 are provided so as to be in direct contact with each other because their photosensitivity overlaps with each other in the blue light region. Further, the third photoconductive layer P3 and the fourth photoconductive layer P4 have spectral sensitivities that overlap each other in the green light region, so they are provided so as to be in contact with each other.

Each of these photoconductive layers is formed by sequentially or simultaneously coating an organic photoconductor or a dye-sensitized zinc oxide-resin binder by a dipping method or a spray method. Further, the thickness of each photoconductive layer is about 3 to 20 μm, preferably about 5 to 10 μm.

Now, the color electrophotographic process according to the present invention will be explained below.

First, the photoreceptor 1 is uniformly irradiated with light obtained by removing the green light component from white light. Such light can be easily obtained by filtering white light through a bandpass filter that does not transmit the green light component. A bandpass filter as described above can be easily produced using a vapor-deposited multilayer film. When irradiated with such light, all four photoconductive layers in the photoreceptor 1 except for the third photoconductive layer P3 become conductive, as can be easily seen by looking at the distribution of spectral sensitivities in Figure 2. It will be understood.

In such a state, if a positive corona discharge is applied to the photoreceptor, a state as shown in FIG.
A state in which multiple layers are formed is realized. Therefore, the third
The photoconductive layer P3 is likened to a capacitor, and this state is said to be that the photoconductive layer P3 is charged. Also, considering the direction of charging, that is, the direction of the dipole moment in the electric double layer, let us say, for example, that this state is that the photoconductive layer P3 is positively charged. Next, when the photoreceptor 1 is irradiated with light in a wavelength range of 700 nm or more,
As a result, only the fifth photoconductive layer P5 becomes a conductor.

In this state, if a negative corona discharge is performed,
A situation as shown in FIG. 3 can be realized. however,
Here, it is assumed that there is rectification of holes between the conductive substrate B and the first photoconductive layer P1. According to the previous expression, the state shown in FIG. 3 is a state in which both the second photoconductive layer P2 and the fourth photoconductive layer P4 are negatively charged.

Next, when a positive corona discharge is applied in the dark, a state as shown in FIG. 3 is realized.
In this state, the first, third, and fifth photoconductive layers P1,
P3 and P5 are charged to positive polarity, and the second and fourth photoconductive layers are charged to negative polarity.

Note that the initial positive corona discharge is called primary charging,
The next negative polarity corona discharge is called secondary charging, and the third positive polarity corona discharge is called tertiary charging. It is assumed that the surface potential of the photoreceptor is, for example, +800V after primary charging, -200V after secondary charging, and +500V after tertiary charging.

In this state, as shown in FIG.
image exposure.

Assume that on a color original O, there are a white area W, a black area N, a cyan area C, a magenta area M, a yellow area Y, a red area R, a green area G, and a blue area B.

First, considering the part of the photoreceptor corresponding to the black area N, this part is hardly exposed to light, so the surface potential of this part is maintained at about +500V. On the other hand, in the portion corresponding to the white portion W, the charged state of each photoconductive layer is canceled by the photoconductive phenomenon, so the surface potential of this portion becomes approximately V.

Next, considering the part corresponding to the cyan part C, the wavelength region of cyan light is an intermediate region between green and blue, and the wavelength region is the spectral sensitivity region of the first to fourth photoconductive layers P1 to P4. , the charged state of these four photoconductive layers is canceled, and the fifth photoconductive layer P
Only the charging state of 5 remains, and the surface potential is 400 ~
It becomes 500V.

Similarly, in the portion corresponding to the magenta portion M, the charged states of the first, second, and fifth photoconductive layers P1 and P5 are eliminated, and the surface potential is reversed to a negative polarity of about -100V. In the portion corresponding to the yellow portion Y, the charged state of the third, fourth, and fifth photoconductive layers P3, P4, and P5 is eliminated, and the surface potential becomes about -100V.
Further, at the portion corresponding to the red portion R, the charged state of the fifth photoconductive layer is eliminated, and the surface potential becomes approximately -100V.

In the portion corresponding to the green portion G, the charged state of the third and fourth photoconductive layers P3 and P4 is eliminated, and the surface potential becomes +400 to 500V. Finally, in the portion corresponding to the blue portion B, the charged state of the first and second photoconductive layers P1 and P2 is eliminated, and the surface potential becomes +400 to 500V.

Therefore, if the first photoconductive layer P5 is developed using a color to which it has photosensitivity, that is, a complementary color of red, that is, cyan and negatively charged cyan toner TC, black part N, cyan part C, green part The photoreceptor parts corresponding to part G and blue part B are developed. This state is shown in FIG.

Next, as shown in FIG. 3, the fourth and fifth photoconductive layers P4 and P5 are uniformly irradiated with light L ₄₅ that turns only the fourth and fifth photoconductive layers P4 and P5 into conductors, that is, light with a wavelength of 600 nm or more.
When the charged state of the fifth photoconductive layer is released, the surface potential of the portion corresponding to the cyan portion C becomes 0, and the surface potential of the portion of the photoreceptor corresponding to the black portion N, magenta portion M, red portion R, and blue portion B becomes zero. Surface potential +400~500V,
In the portions corresponding to the yellow portion Y and the green portion G, the surface potential is approximately −100V. This uniform irradiation is called primary exposure.

Therefore, Magenta Toner TM is colored magenta, which is a complementary color to the photosensitive edge of the third photoconductive layer P3, and is negatively charged.
(FIG. 3), and then with light L ₂₃ to make the second and third photoconductive layers P2 and P3 conductive.
The photoreceptor 1 is uniformly irradiated (FIG. 3). This light L ₂₃
is obtained by removing components in the wavelength range of 400 to 500 nm from light in the wavelength range of 300 to 600 nm using a bandpass filter. As a result of this uniform exposure, the charged state of the first photoconductive layer P1 remains only in the parts corresponding to the black part N, yellow part Y, red part R, and green part G, and the surface potential of the photoreceptor in these parts becomes +
400-500V, approximately 0V in other parts. This uniform irradiation is called secondary exposure.

Therefore, the first photoconductive layer is colored yellow, which is a complementary color to the blue light to which it is sensitive, and is developed with yellow toner TY, which is negatively charged.

As a result, a color visible image of the original O is obtained on the photoreceptor 1 (FIG. 3).

In this color image, black is cyan toner TC, magenta toner TM, yellow toner TY
Red is expressed by a mixture of yellow toner TY and magenta toner TM. Furthermore, green is expressed by a mixture of yellow toner TY and cyan toner TC, and blue is expressed by a mixture of magenta toner TM and cyan toner TC.

All that remains is to fix this color visible image on the photoreceptor 1 and use it for recording (when the photoreceptor 1 itself is in the form of a sheet), or transfer and fix it on another suitable recording medium, such as paper. and submit it for recording.

Ultimately, the characteristics of the color electrophotography according to the present invention are as follows:
It can be said as follows. On the other hand, an electrostatic latent image corresponding to a color-separated image that would be obtained by color separation using a blue filter is formed on the first photoconductive layer P1.
Furthermore, electrostatic latent images corresponding to color-separated images that would be obtained by color separation using a green filter and color-separated images that would be obtained from color separation using a red filter are formed on the third and fifth photoconductive layers P3, In P5, the color image exposure stage (third
Figure). However, the electrostatic latent image corresponding to the color-separated image formed by the blue filter is also formed as a negative charge on the second photoconductive layer P2, and the electrostatic latent image corresponding to the color-separated image formed by the green filter is
The fourth photoconductive layer P4 is also formed in the form of negative polarity charging.

Therefore, at the stage of color image exposure (FIG. 3), the electrostatic latent image corresponding to the color-separated images produced by the blue filter and the green filter does not appear on the surface.
This is visualized by sequentially extracting it with light irradiation alternating with development, that is, with first and second exposure.

FIG. 4 shows the steps in each step shown in FIG.
This diagram schematically shows changes in the surface potential of a photoreceptor. N,C,
G, B, W, M, R, and Y indicate the surface potentials of the portions corresponding to the same reference numerals shown in FIG.

FIG. 5 schematically shows only the essential parts of an example of an apparatus for carrying out the present invention.

Reference numeral 10 indicates a drum-shaped photoreceptor, and this photoreceptor 10 rotates in the direction of the arrow. It is assumed that the spectral sensitivity of each photoconductive layer is as shown in FIG.

Symbols 11, 12, and 13 are primary and secondary, respectively.
Next, a charger for tertiary charging is shown. The chargers 11 and 12 are composed of a charger, a light source, and a filter.

15, 17, 19 are developing devices; 16,
Reference numeral 18 denotes lamps for primary and secondary exposure, each having filters F16 and F18.

Reference numeral 20 is a transfer charger, reference numeral S is a recording paper, reference numeral 21 is a cleaner, and reference numeral 14 is a color image.

While rotating the photoreceptor 1 in the direction of the arrow, chargers 11, 12, and 13 perform primary or tertiary charging, then image exposure is performed using a color image 14, and development using cyan toner TC is performed using a developing device 15. , a lamp 16 performs primary exposure, and a developing device 17 performs development using magenta toner TM. Next, secondary exposure is performed using the lamp 18 and development using yellow toner is performed using the developing device 19. Each process shown in FIG. transfer charger 20
By transferring the image to recording paper S, which is a recording medium, and fixing it using a fixing device (not shown), a desired color electrophotograph can be obtained.

(Effects) As described above, according to the present invention, a novel color electrophotographic method can be provided. In this color electrophotographic method, a color electrophotograph can be obtained with a single image exposure, so the process is efficient.Also, since color images are formed on the same photoreceptor, each color image has a different color. High-resolution color images can be obtained without the need for alignment.

[Brief explanation of drawings]

1 to 4 are diagrams for explaining the present invention, and FIG. 5 is an explanatory front view schematically showing only essential parts of an example of an apparatus for carrying out the present invention. 1... Photoreceptor, B... Conductive substrate, P1 to P5
...First to fifth highly conductive layers, O...Color original,
TC...Cyan toner, TM...Magenta toner,
TY...Yellow toner.

Claims (1)

[Scope of Claims] 1. A photoconductive layer having photosensitivity only to red light, a photoconductive layer having photosensitivity only to blue light, a photoconductive layer having photosensitivity only to green light, and a photoconductive layer having photosensitivity only to red light, blue light, and blue light. Two photoconductive layers having different spectral sensitivities and having photosensitivity to one or more of light, green light, and light of colors other than these are placed on a conductive substrate, and the two layers have overlapping photosensitive regions. The three photoconductive layers of the five-layer photoreceptor, which are sensitive to only red light, only blue light, and only green light, are charged to a predetermined polarity so that they are in direct contact with each other. ,
After charging the other two photoconductive layers to opposite polarities to the above-mentioned predetermined polarity, image exposure is performed by irradiating the photoreceptor with a color image, so that the uppermost photoconductive layer is exposed to a color image to which it has photosensitivity. Development is carried out with complementary colored toner, followed by uniform exposure of the photoreceptor with light that makes only the top photoconductive layer and the fourth photoconductive layer below it conductive, followed by a third photoconductive layer. Development is performed with a toner colored complementary to the color to which the conductive layer exhibits photosensitivity, and then the photoreceptor is uniformly exposed to light that makes only the second and third photoconductive layers conductive. Developed with a toner colored complementary to the color to which the photoconductive layer has photosensitivity, and then deposited on the photoreceptor.
A color electrophotographic method, characterized in that a color electrophotographic image corresponding to the above-mentioned color image is obtained.