JPH0554111B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for forming an electrostatic latent image in electrophotography.

Prior Art The Carlson process, which is a method of copying to obtain ordinary black-and-white images, uses an electrophotographic photoreceptor with a photoconductive layer provided on a conductive substrate.
A latent image is formed by imagewise exposure, and after this latent image is developed, the toner image is transferred to a transfer paper or the like and fixed to obtain a copy. On the other hand, the toner remaining on the surface of the photoreceptor after transfer is cleaned, and
A process is employed to remove surface charges and prepare for the next copying cycle.

Photoreceptors that can be applied to such processes include Se-based photoreceptors or PV photoreceptors on Se-based photoconductive layers.
A photoreceptor provided with a charge transport layer such as K.

By the way, black-and-white copying is sometimes performed from a multicolored original including black and chromatic colors using the above-mentioned photoreceptor, but in this case, the copied image area corresponding to the chromatic color area of the original is the background area or There were some flaws, such as the black part not being distinguishable from the original, and part of the manuscript information being lost. Furthermore, when making a two-color copy from a multicolor original, the above-mentioned process of charging the photoreceptor, image exposure, development, and copying must be repeated twice. Also,
This method requires exposure corresponding to each chromatic color of the original, resulting in slow copying speed.
There were drawbacks such as difficulty in producing clear colors due to overlapping colors and color shift.

In addition, as a two-color electrophotographic method, a second photoconductive layer is formed on a conductive substrate, and is sensitive to chromatic colors in a part of the visible light region, and transmits wavelengths in other regions. A photoreceptor laminated with a first photoconductive layer that is sensitive to a wavelength range that transmits the After uniformly holding charges of different polarities in the photoconductive layer, a latent image is formed by performing image exposure through an original having both chromatic parts and black parts, and then it is developed and transferred with toner of a different color. Proposed. This method has advantages over the color electrophotographic method, such as simpler steps and equipment, and no need for color overlapping. However, in this method, as is clear from the diagram showing the charge distribution of the final latent image in FIG. 1 of the accompanying drawings, the surface of the second photoconductive layer 10 on the conductive substrate 1 and A latent image having a different polarity is formed at the interface between the first photoconductive layer and the first photoconductive layer 9. (The latent image formed at the interface of The disadvantage is that edges that appear as if they are

Similarly, a photoreceptor in which a photoconductive layer and an evergreen layer are sequentially provided on a conductive substrate is subjected to primary charging, and uniform exposure is performed at the same time or after that to form a black area and a chromatic area, such as a red area. After stacking originals and exposing them imagewise through a filter that has a complementary color relationship with red, at the same time applying secondary charging with the opposite polarity to the primary charging, imagewise exposing them again through a red transmission filter. Accordingly, a method has been proposed in which two types of latent images, red and black, of different polarity are formed on the corresponding color portions of a document, and the image is developed and transferred using red and black toners charged to opposite polarities to the latent image polarity. In this method as well, as is clear from the diagram showing the charge distribution of the final latent image in FIG. Latent images with different polarities are formed at the interface with the photoconductive layer 11, and an internal latent image formed at the interface between the never-green layer 5 and the photoconductive layer 11 and an external latent image formed on the surface of the never-green layer 5 are formed. There is a drawback that the thin line formed by the internal latent image is reversed due to interaction with the image.

Therefore, at present, a photoreceptor is used in which a photoconductive layer and a fast-green layer are sequentially provided on a conductive substrate, and this is subjected to primary charging, and then uniformly exposed to light at the same time or afterwards, and then the black and chromatic areas are exposed. For example, originals with red parts are overlapped and image-exposed through a filter having a complementary color relationship with red, and at the same time, a secondary charge with a polarity opposite to the primary charge is applied, and then the document is passed through a red transmission filter again. By performing simultaneous image exposure with tertiary charging with a polarity opposite to that of secondary charging, and then uniform exposure, two kinds of red and black latent images with mutually different polarities are formed on the parts corresponding to each color of the original, and the polarity of the latent image is A method has been proposed in which a two-color copy is obtained by developing, transferring, and fixing red and black toners charged with opposite polarities. In this method, unlike the above-mentioned method, there is no interaction between the external latent image formed on the surface and the interface and the internal latent image, and therefore, there is no interaction between the external latent image and the internal latent image formed on the surface and the interface, and therefore there is no problem such as inversion of thin lines formed by the internal latent image, white spots etc. It does not cause the edge effect. However, in this latent image forming method, including many other latent image forming methods, it is necessary for bipolar carriers of holes and electrons to flow through the photoreceptor during the latent image forming process. There is a problem in that it is very difficult to find a photosensitive material that allows both holes and electrons to easily flow through the photoreceptor. For example, in an inorganic amorphous system, it is possible to add donor and acceptor materials to Se to cause hopping conduction at both sites. A huge increase occurs, which is assumed to be due to the movement of sexual carriers.

OBJECTS OF THE INVENTION In view of the problems of the prior art as described above, an object of the present invention is to provide a method for forming an electrostatic latent image in electrophotography that can easily form a latent image without causing edge effects such as inversion and white spots. Our goal is to provide the following.

Structure of the Invention According to the method for forming an electrostatic latent image in electrophotography according to the present invention, on a conductive substrate, a never-green layer, a first photoconductive layer sensitive to a first chromatic color, and a first photoconductive layer sensitive to a first chromatic color are provided. For an electrophotographic photoreceptor formed by successively laminating a second photoconductive layer that transmits a chromatic color and is sensitive to a second chromatic color different from the first chromatic color, and a surface green layer, a first
As a step, uniform exposure and primary charging are performed, and as a second step, secondary charging with a polarity opposite to the primary charging and image exposure through a transmission filter that transmits the first chromatic color is performed, and a third step is performed. As a step, tertiary charging or alternating current charging with a polarity opposite to that of the secondary charging and image exposure through the first chromatic complementary color filter are carried out, and as a fourth step, uniform exposure is carried out to obtain a charge of a different polarity. Two types of electrostatic latent images are formed.

Embodiments Next, the present invention will be described in more detail with respect to embodiments of the present invention based on FIGS. 3, 4, and 5 of the accompanying drawings.

FIG. 3 is a schematic sectional view schematically showing the structure of an example of an electrophotographic photoreceptor used in an electrophotographic electrostatic latent image forming method according to an embodiment of the present invention. Third
As shown in the figure, this electrophotographic photoreceptor has a conductive substrate 1, an evergreen layer 2, a first photoconductive layer 3 that is sensitive to a first chromatic color A and generates charge, and a first A second chromatic color A that is different from the first chromatic color A is transmitted through the second chromatic color A.
A second photoconductive layer 4 and a surface insulating layer 5, which are sensitive to the chromatic color B and generate charges, are laminated in sequence. The second photoconductive layer 4 may have a two-layer structure consisting of a charge generation layer and a charge transport layer.

The constituent materials and forming methods of each layer of the photoreceptor having such a structure will be explained in order below.

First, the conductive substrate 1 is made of stainless steel,
Al, Mo, Au, In, Nb, Ta, Ni, V, Ti, Pt,
A conductive plate made of metals such as Pd, Cr, Pb, or alloys thereof may also be used. In addition, for insulating supports such as polyimide films, synthetic resin films such as PET, or supports such as resin molded products,
In addition to In ₂ O ₃ and SnO ₂ , Cu, Ag, Al, Pb, Zn, Nl,
Conductive treatment using metals such as Au, Cr, Mo, Ir, Nb, Ta, V, Ti, Pt, W, etc. by vacuum evaporation, EB evaporation, sputtering, etc., or lamination treatment with the above metals, and further conductive Conductive substrate 1 is a material whose surface has been subjected to conductive treatment by applying a conductive resin.
It may also be used as The shape of the conductive substrate 1 may be any of a cylindrical shape, a flat plate shape, a sheet shape, or a screen shape.

The insulating layer 2 is an electrically insulating layer having a resistance value of 10 ¹⁴ Ωcm or more, and includes organic resin materials such as PET, polycarbonate, polyurethane, Teflon, polyester, and polystyrene. , MgF ₂ , MgO, S ₂ O,
A layer having a thickness of 0.05 to 20 μm may be formed using a high-resistance inorganic compound such as SlO ₂ by a dipping method, a plaid method, a spray method, a vapor deposition method, or a sputtering method.

Usually, the photoconductive layer is formed by Se on the surface of the aforementioned support.
Alternatively, it can be manufactured by vapor depositing a Se-based alloy film. Materials for the first photoconductive layer 3 sensitive to the first chromatic color A include alloys such as SeTe, As ₂ Se ₃ , AsSe, SeTeAs, and these Se alone or Se alloys with Bl, Sb,
A material doped with S or the like may also be used. Furthermore, impurities such as halogen may be added. This Se-based charge generation layer is formed by depositing a film of Se-based material on the surface of the above-mentioned support to have a thickness of 0.1 to 50 μm, preferably 0.5 to 5 μm. Moreover, as this photoconductive layer,
Sensitized ZnO, sensitized CdS, sensitized P.
VK-sensitized TiO ₂ , a-Si, CdSe, azo pigments, cyanine pigments, phthalocyanine pigments, etc. are used. The photoconductive layer 3 sensitive to the first chromatic color A is advantageously formed of a panchromatic, ie, optical semiconductor sensitive to the entire visible light region. The second photoconductive layer 4 that is sensitive to the second chromatic color B may be a single layer or a laminated layer. , ZnO, perylene pigments, etc. are used.
In the case of a laminated type, a photoconductive layer made of these photoconductive materials is used as a charge generation layer, and a charge transport layer is laminated thereon. PVK aromatic amine or the like is used as a material for forming this charge transport layer.
As a method for forming the photosensitive layer, a dipping method, a blade method, or a spray method is usually used in the case of an organic material, and a vapor deposition method or a sputtering method is used in the case of an inorganic material.

The surface insulating layer 5 is made of a material that transmits electromagnetic waves that excite the photoconductive layers 3 and 4, and has a resistance of 10 ¹⁴ Ωcm.
or more, and is formed to a film thickness of 5 to 50μ by dipping, blading, spraying, laminating, etc. using organic resin materials such as PET polyester, polycarbonate, polyurethane, Teflon, and polystyrene. good.

Furthermore, the steps for manufacturing the photoreceptor are not limited to the order described above; for example, the second photoconductive layer 4, the first photoconductive layer 3, An insulating layer 2 is provided and these are connected to a conductive substrate 1.
You can also laminate it on top. Alternatively, a second photoconductive layer 4, a first photoconductive layer 3, an insulating layer 2, and a conductive layer 1 may be provided on the light-transmitting surface insulating layer 5, and these may be laminated on an insulating support. .

Next, we will discuss an example in which two types of electrostatic latent images of different polarities are formed by the electrostatic latent image forming method of the present invention using such an electrophotographic photoreceptor, especially the fourth example. This will be explained with reference to the figures.

The photoreceptor used in this electrostatic latent image forming method is
It has a configuration as shown in FIG. 3, and is sensitive to the entire chromatic color range of the original.

Therefore, as a first step, a photoreceptor having such properties is first subjected to positive or negative primary charging, and then the photosensitive layer becomes sensitive. The photosensitive layer is polarized by uniform exposure at the exposure wavelength. The exposure wavelength does not have to be monochromatic, but at least chromatic color A or chromatic color B can be irradiated depending on whether only holes or only electrons are used as carriers moving inside the photoreceptor. It is preferable to select . Further, the uniform exposure may be performed simultaneously with the primary charging. Figure 4A shows the charge distribution in each layer of the photoreceptor when positive charging is performed as primary charging and the second photoconductive layer 4 is excited with chromatic color B as uniform exposure to move holes. There is.

Next, as a second step, an excessive secondary charge having a polarity opposite to that of the primary charge is applied to the optical image of the original 6 through a chromatic color A transmission filter 7 which has a property of transmitting the chromatic color A contained in the original. This is done at the same time as image exposure or before image exposure. FIG. 4B shows the charge distribution state of the photoreceptor after the second step is performed by applying image exposure and corona charging simultaneously using a constant voltage mode power supply. That is, FIG. 4B shows a case where a negative charge is applied to secondary charging, and the first photoconductive layer 3 sensitive to chromatic color A is excited using the chromatic transmission filter 7 to move holes. ing. Figure 4B
As shown in FIG. 2, in the second step, the charge distribution in the portion corresponding to the black portion of the original 6 is such that the charge on the light-transmitting surface insulating layer 5 is eliminated.
Further, the charges at the interface between the surface insulating layer 5 and the second photoconductive layer 4 and the interface between the second photoconductive layer 4 and the first photoconductive layer 3 at this position of the surface insulating layer 5 vary. There is no. On the other hand, the charge distribution of the components corresponding to the white part of the document and the chromatic color A part is such that the first photoconductive layer 3 is excited by the chromatic color A that has passed through the second photoconductive layer 4, and free carriers are generated. Since the inside of the photosensitive layer is made conductive, the transparent surface insulating layer 5 is charged with a charge having a polarity opposite to that of the primary charge. Furthermore, the charge distribution inside the photosensitive layer is also polarized in accordance with the charges on the surface insulating layer 5 to have a polarity opposite to the internal charge distribution after primary charging.

Next, as a third step, tertiary charging, which is opposite to secondary charging, is applied to the optical image of the original 6 through image exposure through a filter 8, which has a complementary color relationship to the chromatic color A contained in the original. Let's do it. The tertiary charge in this case is
It is carried out at a lower potential than the secondary charging potential, to the extent that the white part is neutralized. FIG. 4C shows the charge distribution when the second photoconductive layer 4 of chromatic color B is excited and holes are moved by positively charging the tertiary charging and using the chromatic color A complementary color filter 8. . In this case, there is no change in the charge distribution within the photosensitive layer in the portions corresponding to the black portion and the chromatic color A portion of the original 6. On the other hand, the charge on the light-transmitting surface insulating layer 5 is affected by the charges inside the photosensitive layer, resulting in a difference in the amount of charge between the black part and the red part. On the other hand, the charge distribution in the area corresponding to the white part of the original excites the second photoconductive layer 4, generates free carriers, and the inside of the photosensitive layer becomes conductive, so that the charges disappear.

Finally, in the fourth step, the entire surface of the photoreceptor is uniformly exposed. The exposure wavelength in this case does not need to be monochromatic light, but a wavelength in a range that includes both chromatic colors A and chromatic colors B is advantageous from the viewpoint of the electrostatic latent image. Figure 4D shows the charge distribution after this uniform exposure.
As shown in FIG. 4D, electrostatic latent images having different polarities corresponding to the black and chromatic portions A of the original 6 are formed on the transparent surface insulating layer 5 on the photoreceptor.
Thereafter, two-color copies are obtained by sequentially performing development, transfer, and fixing using two-color toners charged with different polarities.

In the above explanation, the primary charge is assumed to be positive, the secondary charge to be negative, and the tertiary charge to be positive. However, as long as the conditions are satisfied, even if the charge polarity is reversed, the black and chromatic A portions of the original will be Electrostatic latent images having correspondingly different polarities are formed on the surface insulating layer 5. Furthermore, tertiary charging may be alternating current charging.

Furthermore, this photoreceptor is not only applicable to the above-mentioned forming method, but also allows a black and white normal image to be obtained by, for example, excluding the third step as shown in FIG. 4C. Further, the original document is not limited to two colors, but may be multicolored.

Next, in order to confirm the effect of the electrostatic latent image forming method for electrophotography of the present invention, the results of actual implementation will be explained below. 7 parts of urethane resin, 1 part of curing agent and 10 parts of xylene
Dissolve 40%
After 5μ of SeTe was deposited, 50μ of Se was formed. after that,
As a surface insulating layer taken out from the vapor deposition tank, 7 parts of urethane resin and 1 part of curing agent were dissolved in 10 parts of xylene, and the solution was coated to a thickness of 25 μm and dried to obtain a photoreceptor. While uniformly exposing the photoreceptor made in this way to 100W W light, primary corona charging of +65KV was performed.
Next, while performing secondary corona charging of -61KV,
An original having red and black colors was imagewise exposed through a red filter, and then imagewise exposed through a cyan filter, simultaneously with +5.4 KV tertiary corona charging. After that, uniform exposure to 100W tungsten light caused the phenomenon to occur sequentially in positively charged red toner and negatively charged black toner. Next, when the obtained two-color image was aligned to have the same polarity and transferred to a transfer paper and fixed, a high-quality two-color image without white lines or edge effects was obtained.

Example 2 1μ of Se was deposited on a 24μ thick PET substrate, then taken out from the deposition tank, a solution of 1 part by weight of PVK and 10 parts by weight of THF was applied with a blade and dried to form a charge transport layer with a thickness of 50μ, and then the substrate was deposited again. Loaded into vapor deposition tank and reduced to 40%
SeTe was evaporated to 5μ, then PARYLENE was evaporated to a thickness of 3μ as an insulating layer on the conductive support side, an Al-evaporated conductive layer was laminated, and the obtained sheet was laminated on an epoxy molded pipe and exposed to light. As a body.

When the photoreceptor thus obtained was developed, transferred and fixed in the same manner as in Example 1, a two-color image of good quality was similarly obtained.

Furthermore, when 500 sheets were continuously copied using this photoreceptor, no decrease in density in black areas, decrease in density in red areas, or background smearing in white areas was observed. The graph in FIG. 5 shows the change in latent image potential when 500 copies were continuously made using the photoreceptor of the present invention.

Effects of the Invention According to the latent image forming method of the present invention, electrostatic latent images with different polarities corresponding to each color of the original are formed on the surface insulating layer, and an external latent image on the surface of the photoreceptor and an electrostatic latent image inside the photoreceptor are formed. An ideal latent image without interaction with the internal latent image is provided, and therefore a latent image without edge effects such as inversion and white spots can be formed.

[Brief explanation of the drawing]

Figure 1 shows the charge distribution of the final latent image when using an example of the conventional two-color color process, and Figure 2 shows the charge distribution of the final latent image when using another example of the conventional two-color color process. FIG. 3 is a cross-sectional view schematically showing the structure of an electrophotographic photoreceptor used in an embodiment of the present invention, and FIG. 4 is a diagram showing a method for forming an electrostatic latent image in electrophotography according to the present invention. FIG. 5, which is a diagram for explaining one embodiment, is a diagram showing changes in latent image potential when 500 copies are continuously made by the electrostatic latent image forming method of the present invention. DESCRIPTION OF SYMBOLS 1... Conductive base, 2... Insulating layer, 3... First
4... second photoconductive layer, 5... surface insulating layer.

Claims (1)

[Claims] 1. On a conductive substrate, an evergreen layer, a first photoconductive layer sensitive to a first chromatic color, a second chromatic color that transmits the first chromatic color and is different from the first chromatic color. As a first step, uniform exposure and primary charging are performed on an electrophotographic photoreceptor formed by sequentially laminating a second photoconductive layer and a surface-fastening layer that exhibit sensitivity to
As a step, secondary charging with a polarity opposite to that of the primary charging and image exposure through a transmission filter that transmits the first chromatic color is performed, and as a third step, tertiary charging with a polarity opposite to that of the secondary charging is performed. Alternatively, AC charging and image exposure through the first chromatic complementary color filter are performed, and as a fourth step, uniform exposure is performed to form two layers of electrostatic latent images of different polarities. A method for forming electrostatic latent images in electrophotography.