JPH03149570A - Image forming method and bipolar photosensitive body - Google Patents

Abstract

PURPOSE:To allow the easy execution of two kinds of image formation with a simple process by subjecting the bipolar photosensitive body, which is electrified in primarily exposed parts to the polarity reverse from the polarity at the time of primary electrifying and is subjected to secondary electrifying by holding the polarity in the unexposed parts, to secondary exposing at the wavelength different from the wavelength of the primary exposing to form secondary latent images in the primarily exposed parts. CONSTITUTION:The bipolar photosensitive body 1, which is electrified in the primarily exposed parts to the polarity reverse from the polarity at the time of the primary electrifying and is subjected to the secondary electrifying so as to hold charges in the polarity at the time of the primary electrifying in the unexposed parts, is subjected to the secondary exposing at the wavelength different from the wavelength of the primary exposing to form the secondary latent images in the exposed parts of the primary exposing. The bipolar photosensitive body 1 constituted by laminating a charge generating layer 1b contg. a charge generating material consisting of a phthalocyanine compd. and a photosensitive layer 1c contg. a charge transfer material for transferring positive holes and a charge generating material consisting of an azo compd. on a conductive base 1a and further, forming a surface protective layer 1d thereon is used for the above-mentioned purpose. Two kinds of the images are easily formed with one time of process in this way.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an image forming method using an electrophotographic process and a bipolar photoreceptor used in this image forming method. In a single electrophotographic process using a sensitive bipolar photoreceptor,
The feature is that two types of image formation are performed.

[Prior Art and its Problems] Conventionally, in electrophotographic devices such as copying machines and printers that utilize an electrophotographic process, a photoreceptor is generally exposed only once in one electrophotographic process, and one type of photoreceptor is exposed. It was supposed to form an image.

However, in recent years, electrophotographic devices have been developed that have the functions of both a copying machine and a printer. There has been a growing demand for things such as being able to write on a digital image at once, or writing two types of digital images.

In addition, various studies have been conducted on photoreceptors used in electrophotographic devices such as those mentioned above, and research has been conducted on photoreceptors used in electrophotographic devices such as those described above.
In addition to improving characteristics such as sensitivity, photoreceptors having various variations such as those for PPC, LDP, positive charging, and negative charging have been developed.

In recent years, photoreceptors such as CdS, in which one photosensitive layer is sensitive to both positive and negative polarities, and photoreceptors in which a photosensitive layer sensitive to positive polarity and a photosensitive layer sensitive to negative polarity are laminated have been developed. Bipolar photoreceptors that are sensitive to both positive and negative polarities have been developed, such as photoreceptors having a charge transport layer between two charge generating layers.

Furthermore, various studies have been conducted on exposure means for exposing the photoreceptor, including using light emitting diodes as light sources in addition to semiconductor lasers, and using optical shutters such as liquid crystals and PLZT to produce various types of light with different wavelengths. Digital images can now be written onto photoreceptors.

In recent years, in addition to using bipolar photoreceptors that are sensitive to both positive and negative polarities as described above, two types of exposure means with different wavelengths have been used in a single electrophotographic process. , two types of images are now being formed.

However, when forming two types of images in a single electrophotographic process using a bipolar photoreceptor that is sensitive to both positive and negative polarities as described above, conventionally As shown in Japanese Patent No. 15859, two types of images are formed in a single electrophotographic process through complicated steps, which poses problems such as difficulty in controlling the process.

In addition, as mentioned above, when forming two types of images in a single electrophotographic process, it has been commonly used.
In the case of the above-mentioned bipolar photoreceptor, the characteristics such as spectral sensitivity to two types of light with different wavelengths are insufficient, and it is necessary to use two types of exposure means with different wavelengths to produce two types of images. However, there was a problem in that it was not possible to obtain a satisfactory image quality.

[Problems to be Solved by the Invention] This invention uses a bipolar photoreceptor that is sensitive to both positive and negative polarities, and in a single electrophotographic process,
The object of the present invention is to solve the above-mentioned problems when forming two types of images.

That is, the present invention uses a bipolar photoreceptor that is sensitive to both positive and negative polarities, and forms two types of images in a single electrophotographic process using two types of exposure means with different wavelengths. The object of the present invention is to enable two types of image formation to be easily performed in a simple process and to obtain satisfactory image quality.

[Means and effects for solving the problem] In order to solve the above problems, the present invention includes a step of primary charging a bipolar photoreceptor having sensitivity in both positive and negative polarities using a primary charger. , a step of primarily exposing the primarily charged bipolar photoconductor to form a primary latent image on the bipolar photoconductor; and exposing the bipolar photoconductor on which the primary latent image is formed to a polarity opposite to that of the primary charger. a second step of secondarily charging the unexposed portion of the primary exposure so that it retains the charge with the polarity at the time of the primary charging, while using a secondary charger to Next, the charged bipolar photoreceptor is subjected to secondary exposure at a wavelength different from that of the primary exposure, and a secondary latent image is formed in the exposed area of the primary exposure. In this electrophotographic process, two types of image formation were performed.

In this way, in the image forming method according to the present invention,
Through the steps described above, two types of images can be easily formed in a single electrophotographic process.

Further, in the present invention, the bipolar photoreceptor used in the image forming method as described above includes at least a charge generation layer containing a charge generation material made of a phthalocyanine compound and a charge transport material on a conductive support. A bipolar photoreceptor is formed by laminating a photosensitive layer containing a charge generating material made of an azo compound, and a charge generating layer containing at least a charge generating material made of a phthalocyanine compound on a conductive support; A bipolar photoreceptor is used in which a charge transport layer containing a transport material and a charge generation layer containing a charge generation material made of an azo compound are laminated.

Here, the bipolar photoreceptor of the present invention as described above has excellent spectral sensitivity characteristics for two types of exposure means having different wavelengths, and can produce two types of images in a single electrophotographic process by the process described above. When formed, a good image can be obtained.

In addition, in the above-mentioned bipolar photoreceptor of the present invention, in order to provide a subbing layer on the conductive support, improve the abrasion resistance of the photoreceptor, and maintain stable photoreceptor performance over a long period of time. , a surface protective layer can be provided on the surface.

In the above bipolar photoreceptor of the present invention, the conductive support may be a foil or plate of copper, aluminum, gold, silver, platinum, iron, palladium, nickel, etc. in the form of a sheet or drum. These metals are attached to plastic films by vacuum evaporation, electroless plating, etc., or layers of conductive compounds such as conductive polymers, indium oxide, and tin oxide are attached to paper or plastic. A material formed by coating or vapor deposition on a support such as a film can be used.

In addition, in the above bipolar photoreceptor of the present invention, the phthalocyanine compound to be contained in the charge generation layer as a charge generation material may be any phthalocyanine compound as long as it is a known metal or metal-free phthalocyanine and its derivatives. can be used even if
Specifically, those shown in the following structural formula [1] can be used.

(R) * 1 Ha 1 (R)t [wherein R is a hydrogen atom, an alkyl group, an alkoxy group,
Aryl group, aryloxy group, halogen, nitro group,
Indicates a cyano group and an amino group.

Moreover, M is H, Be, Mg, AI, SL.

Ca,) i, V, Cr, Mn, Fe, Co.

Ni, Cu, Zn, Ga, Ge, As, Pb.

Ag, Cd, In, Sn, Sb, X, Y represent halogen, oxygen, alkoxyl group, t represents a number from 1 to 4, n- represents a number of 0 or 1, m represents the number 0 or 1. ] In the above-mentioned bipolar photoreceptor of the present invention, examples of the azo compound to be contained as a charge-generating material in the photosensitive layer or charge-generating layer include monoazo pigments, bisazo pigments, trisazo pigments, and tetrakiss, which are known per se. It is made of an azo pigment, and its spectral absorption on the long wavelength side is the oscillation wavelength of a semiconductor laser (approximately 780
Any azo compound may be used as long as the azo compound does not extend to 100 nm), and in short, any azo compound may be used as long as it can be separated from the wavelength of light that is spectrally absorbed by the above-mentioned phthalocyanine compound.

In the above-mentioned bipolar photoreceptor of the present invention, charge transport materials used in the photosensitive layer and charge transport layer include, for example, anthracene derivatives, pyrene derivatives, carbazole derivatives, tetrazole derivatives, metallocene derivatives, and phenothiazine derivatives. , pyrazoline compound,
Hydrazone compounds, styryl compounds, styrylhydrazone compounds, enamine compounds, butarinin compounds, distyryl compounds, oxazole compounds, oxadiazole compounds, thiazole compounds, imidazole compounds, triphenylamine derivatives, phenylenediamine derivatives, aminostilbene derivatives, triphenylmethane derivatives Hole transporting materials such as and polymerized versions of these can be used = Then, in forming the charge generating layer as described above, the charge generating material is deposited on the conductive support by vapor deposition or plasma polymerization. or by dispersing the charge-generating material in a solution in which a binder resin is dissolved in a suitable solvent, coating this dispersion on a conductive support, and drying it to form a charge-generating layer. ing. Note that when the charge generation layer is formed in this way, the thickness of the charge generation layer is 0.01 to 2.
ttm, preferably 0.1 to 1 μm.

In addition, in forming the above-mentioned photosensitive layer, a coating liquid for the photosensitive layer is usually prepared by dissolving or dispersing the above-mentioned azo compound and charge transporting material together with a suitable binder resin in a suitable solvent. The material is prepared, applied, and dried.

In addition, in forming the above charge transport layer, a coating liquid for the charge transport layer is usually prepared by dissolving or dispersing the charge transport material as described above in a solvent together with an appropriate binder resin. It is then applied and dried to form the structure.

Here, the binder resin used to prepare the coating liquids for the charge generation layer, photosensitive layer and charge transport layer as described above is an electrically insulating resin and a thermosetting resin which is known per se. resin,
Thermosetting resins, photocurable resins, photoconductive resins, etc. can be used, and suitable binder resins include, for example, polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinyl acetate copolymer, chloride Vinyl-vinyl acetate-maleic anhydride copolymer, ethylene-vinyl acetate copolymer, polyvinyl butyral, polyvinyl acetal, polyester, phenoxy resin, (meth)acrylic resin, polystyrene.

Thermoplastic resins such as polycarbonate, polyarylate, polysulfone, polyethersulfone, ABS resin, phenol resin, epoxy resin, urethane resin, melamine resin, isocyanate resin, alkyd resin, silicone resin.

Examples include thermosetting resins such as thermosetting acrylic resins, and photoconductive resins such as polyvinylcarbazole, polyvinylanthracene, and polyvinylpyrene, but are not particularly limited to these.

In addition, the solvents used to prepare each coating liquid as described above include alcohols such as methanol, ethanol, and isopropanol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, and N.

Amides such as N-dimethylformamide, N,N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, ethers such as tetrahydrofuran, dioxane, cellosolve, calpitol, esters such as methyl acetate, ethyl acetate, chloroform, dichloromethane , aliphatic halogenated hydrocarbons such as dichloroethane, carbon tetrachloride, trichloroethane, benzene, toluene,
Organic solvents such as aromatics such as xylene, ligluin, monochlorobenzene, dichlorobenzene, etc. can be used.

In addition, methods for applying each coating liquid prepared as above include dip coating method, ring coating method,
Spray coating method.

Various coating methods can be used, such as spray coating, blade coating, roller coating, and wire bar coating.

Furthermore, when forming an undercoat layer on a conductive substrate as described above, the material used for the undercoat layer may be polymers such as polyimide, polyamide, nitrocellulose, polyvinyl butyral, polyvinyl alcohol, etc. as is, or Curable acrylic, urethane, and epoxy.

It is appropriate to use a resin such as melamine in which a low-resistance compound such as tin oxide, indium oxide, antimony oxide, titanium pentoxide, etc. is dispersed, or a vapor-deposited film of aluminum oxide, zinc oxide, silicon oxide, zirconium oxide, etc. can be,
It is desirable to form the film so that its thickness is 10 μm or less.

In addition, when forming a surface protective layer on the surface of the bipolar photoreceptor on which the charge generation layer and charge transport layer have been formed as described above, for example, thermosetting resin, room temperature curing resin, ultraviolet curing resin, etc. .

Alternatively, a resin-based protective layer can be formed using a coating method using a resin containing metallocene or conductive filler to reduce resistance, or a resin-based protective layer can be formed using a vacuum deposition method, sputtering method, ion blating method, plasma CVD method, etc. In particular, amorphous carbon films produced by plasma CVD have excellent light transmittance, abrasion resistance, and adhesion, and are therefore suitable for use as surface protection layers. can do.

As a primary charger for primarily charging the bipolar photoreceptor formed as described above, a charger such as a scorotron charger that can charge the entire photoreceptor to a constant and uniform voltage is used. On the other hand, as a secondary charger to secondarily charge the bipolar photoreceptor after the primary exposure, a charger such as a corotron charger that can give a constant charge to the photoreceptor is used. do.

Note that when the bipolar photoreceptor as described above is primarily charged by a primary charger, the polarity thereof may be either positive or negative.

Here, when the above-mentioned bipolar photoconductor is primarily charged to negative polarity by a primary charger, the phthalocyanine compound contained in the charge generation layer located on the conductive substrate side of the bipolar photoconductor is The above-mentioned bipolar photoreceptor is primarily exposed to light having a long wavelength, for example, a semiconductor laser (approximately 780 nm) to which only the photoreceptor is sensitive, and a primary latent image is formed on the bipolar photoreceptor.

Note that when a bipolar photoreceptor is primarily exposed in this way to form a primary latent image, the unexposed areas usually remain as a latent image, so when performing digital exposure, a backlighting method is used. Exposure should be performed using

In order to form a primary latent image on the bipolar photoreceptor in this way, a positive charge is applied to the bipolar photoreceptor using a secondary charger, and the primary exposed area is made to have a positive polarity opposite to that during the primary charging. While being charged, the unexposed portion of the primary exposure where the primary latent image has been formed is secondarily charged so that the potential is maintained at the same negative polarity as that during the primary charging.

When performing secondary exposure on the bipolar photoconductor that has been secondarily charged in this way, an azo compound contained in the photosensitive layer or charge generation layer located on the surface side of the bipolar photoconductor is used. Secondary exposure is performed using short-wavelength light such as a light-emitting diode that has sensitivity or white light that has been cut off from long-wavelength light, and the secondary exposure is applied to the positively charged exposed area of the primary exposure as described above. Form a latent image.

Here, the unexposed part of the primary exposure where the primary latent image was formed holds a potential with negative polarity as described above, and the photosensitive layer located on the surface side containing the azo compound and the charge generating area. Since the layer is not sensitive to negative polarity, even if this primary latent image area is irradiated with light on the short wavelength side of secondary exposure, this primary latent image will not be erased by secondary exposure. .

Note that even when forming a secondary latent image as described above, the unexposed portion of the secondary exposure remains as a latent image, so
As this secondary exposure, analog exposure or digital exposure using a backlighting method is performed.

On the other hand, - if the bipolar photoconductor as described above is primarily charged to positive polarity by a primary charger, it is opposite to the above case in which the bipolar photoconductor is primarily charged to negative polarity by a primary charger. , this bipolar photoconductor is primarily exposed using light on the short wavelength side to which the azo compound contained in the photosensitive layer and charge generation layer located on the surface side of the bipolar photoconductor is sensitive. A primary latent image is formed on the unexposed portion of the positively charged bipolar photoreceptor.

Then, a secondary charger applies a negative charge to the bipolar photoconductor on which the primary latent image has been formed, and the primary exposed area is charged with a negative polarity opposite to that during the primary charging, while the primary latent image is The formed unexposed area is secondarily charged so as to maintain the same positive polarity as the primary charge.
Thereafter, the bipolar photoreceptor is secondarily exposed to light on the long wavelength side to which only the phthalocyanine compound contained in the charge generation layer located on the conductive substrate side is sensitive. Form a latent image.

Note that even when the bipolar photoreceptor is subjected to secondary exposure in this way and a secondary latent image is formed on the bipolar photoreceptor, the unexposed portions are left as a latent image, as in the case described above. Therefore, when performing digital exposure, exposure should be performed using a backlighting method.

In addition, when secondary exposure is performed with light on the long wavelength side as described above, the photosensitive layer and charge generation layer located on the surface side containing the azo compound are exposed to such light on the long wavelength side. However, the charge generation layer, which is located on the conductive substrate side and contains a phthalocyanine compound, does not show sensitivity to the primary latent image portion that maintains a positive polarity potential as described above. Therefore, even if the primary latent image portion is irradiated with the secondary exposure light, this primary latent image will not be erased by the secondary exposure.

After forming primary and secondary latent images with positive and negative polarities on the bipolar photoreceptor as described above by any of the methods described above, in developing each of these latent images, After these latent images are transferred to transfer paper, a developer in which a positively charged toner and a negatively charged toner are mixed and dispersed in a dispersion solvent is used to create primary and negative images formed with positive and negative polarities. A wet method may be used to visualize the secondary latent images by supplying oppositely charged toner to the secondary latent images, or the primary Alternatively, a dry method may be used in which a positively charged toner and a negatively charged toner are sequentially supplied to a secondary latent image area for development, and then these toners are transferred to a transfer paper.

In the dry method as described above, after development is performed by supplying positively charged toner and negatively charged toner to the primary and secondary latent image locations, respectively, in order to transfer these to transfer paper, In addition to sequentially transferring the positively charged toner and negatively charged toner to the transfer paper as described above, it is also possible to simultaneously transfer positively charged and negatively charged bipolar toners onto the transfer paper. .

In addition, when transferring positively charged toner and negatively charged toner of both polarities onto the transfer paper at the same time, a DC charger with a superimposed AC component is used to control the charging polarity of both the positively charged toner and the negatively charged toner. After aligning the toner to either one, the toner can be transferred onto the recording paper using a transfer charger with the opposite polarity, or the toner of both polarities supplied to the photoreceptor can be pressure-transferred onto the transfer paper, or the positively charged toner can be It is possible to use magnetic toners as the type toner and the negatively charged toner so that the toner can be transferred to the transfer paper by magnetic force. '-[Example] Hereinafter, an example of the present invention will be described in detail based on the accompanying drawings.

(Example 1) In this example, as shown in FIG. 1, a charge generation layer (1b) containing a charge generation material made of a phthalocyanine compound and a charge generation layer (1b) containing a charge generation material made of a phthalocyanine compound were formed on a conductive support (1a). An ambipolar photoreceptor (1) in which a photoreceptor layer (1c) containing a charge transport material to be transported and a charge generation material made of an azo compound is laminated, and a surface protective layer (1d) is further formed on the surface of the photoreceptor layer (1c).
).

Here, in manufacturing the bipolar photoreceptor (1) as described above, in this example, the conductive support (1a)
In forming the charge generation layer (lb) on the aluminum drum (la), a τ-type metal-free phthalocyanine is used as the phthalocyanine compound, and this τ-type metal-free lid cyanine is used as the phthalocyanine compound. A mixture consisting of 1 part by weight of polyvinyl butyral (Nislec BL-S manufactured by Sekisui Chemical ■) and 98 parts by weight of tetrahydrofuran was treated with a paint conditioner for 2 hours to prepare a coating solution for the charge generation layer. .

Then, the coating liquid for the charge generation layer prepared in this way is applied onto the aluminum drum (1a) by a dipping method so that the film thickness after drying becomes 0.25 μm, and this is dried. A charge generation layer (1b) was formed on an aluminum drum (1a).

Next, in forming the photosensitive layer (1c) on the charge generation layer (lb) thus formed on the aluminum drum (1a), a hydrazone-based material represented by the following chemical formula [2] is used as a charge transport material. In addition to using the compound, the following chemical formula [
Using the bisazo pigment shown in No. 31, 10 parts by weight of the above hydrazone compound, and polycarbonate (manufactured by Teijin Kasei ■).
K-1300) and 10 parts by weight are dissolved in 80 parts by weight of dichloromethane, the above bisazo pigment is mixed,
It was treated with a paint conditioner for 4 hours to prepare a dispersion for a photosensitive layer.

[31 Then, the dispersion liquid for the photosensitive layer prepared in this way was applied onto the previously formed charge generation layer (1b) so that the film thickness after drying was 3.
The photosensitive layer (1c) is coated on the above charge generation layer (lb) by coating by dipping to a thickness of 0 μm and drying.
was formed.

Next, on the thus formed photosensitive layer (1c), a surface protective layer made of an amorphous carbon film with a film thickness of about 1000 nm was applied by plasma CVD under the plasma conditions shown below. (1d) was formed.

[Plasma conditions] Raw material gas and gas flow rate Hydrogen gas 300 seconds Butadiene gas 15 seconds Vacuum chamber pressure 0
．． 3Toor・Substrate temperature: 50°C・Discharge frequency: 80 kHz・Discharge power: 150 W・Discharge time: 3.5 minutes Then, the bipolar photoconductor (1) manufactured in this way was transferred to a photoconductor having the same configuration as a commercially available copying machine. After attaching the bipolar photoreceptor (1) to a body tester and charging it with a charger so that the initial charging potential becomes +500V, it is exposed to white light using a filter, and the exposure amount is reduced by half E l/2 and spectral sensitivity characteristics were measured.

As a result, the half-reduced exposure amount E 1/2 is 1, Olux-
The color was purple, and its spectral sensitivity characteristics were as shown by the solid line 0 in FIG.

Next, change the polarity of the charger, and then change the polarity of the charger to the bipolar photoreceptor (
After charging 1) so that the initial charging potential becomes -500V, measure its spectral sensitivity characteristics in the same manner as above, and use a semiconductor laser with a wavelength of 780 nm as a light source to reduce the spectral sensitivity by half. The exposure amount E□72 was measured.

As a result, the spectral sensitivity characteristics when negatively charged are as shown by Δ and the dashed line in FIG. 2, and the half-decreased exposure amount E1/
2 was 2,5 erg/aj.

As described above, the bipolar photoreceptor (1) has high sensitivity in positive, positive, and negative polarities, and also has spectral sensitivity characteristics in different wavelength regions. For example, when negatively charged, it has high sensitivity. , the wavelength is 780 as above
While exposure is performed using a semiconductor laser with a wavelength of 650 nm, when charging is positive, exposure is performed using a light-emitting diode with a wavelength of about 650 nm or white light whose long wavelength component of 650 nm or more is cut off by a filter. It becomes possible to form two types of images by forming latent images separately for each polarity.

In this embodiment, when forming two types of images in one electrophotographic process using the bipolar photoreceptor (1) as described above, first, the images shown in FIG.
As shown in (B), a scorotron charger (2) is used as the primary charger (2), and this scorotron charger (2) charges the bipolar photoreceptor (1) to -1000
■It was primarily charged.

Next, the bipolar photoreceptor (1) that has been primarily charged in this way
As shown in Fig. 4 (A) and (B), the wavelength is 780
A digital image was primarily exposed using a backlighting method using a nm semiconductor laser (not shown), and a primary latent image was formed in the unexposed portion of the primary exposure.

Then, the bipolar photoreceptor (1) on which the primary latent image has been formed is placed in a corotron for positive charging as a secondary charger (3), as shown in FIGS. 5(A) and (B). Charger (
3), the corotron charger (3) was used to perform secondary charging so that the potential of the primary exposed area became +400V, while the potential of the unexposed area where the primary latent image was formed became -350V. .

After the bipolar photoreceptor (1) is secondarily charged in this way, as shown in FIGS. 6(A) and (B), 650 n
An analog image is secondarily exposed on the bipolar photoreceptor (1) using white light whose long wavelength components of m or more are cut off by a filter, and the positively charged primary exposed portion is exposed based on the analog image as described above. A secondary latent image of positive polarity was formed.

In addition, when secondary exposure is performed on the bipolar photoreceptor (1) in this way to form a secondary latent image, the light of the secondary exposure is transmitted to the unexposed area of the primary exposure where the primary latent image was formed. Even if a portion of the primary latent image is irradiated, the primary latent image will not be erased by secondary exposure because it is negatively charged and has no sensitivity even during secondary charging as described above. .

As a result, in this example, in the bipolar photoreceptor (1), the primary latent image based on the digital image by the backlighting method is formed with negative polarity, while the primary latent image based on the analog image of the secondary exposure is formed with negative polarity. A secondary latent image was formed with positive polarity.

Then, for the bipolar photoreceptor (1) in which the primary latent image based on the digital image is formed with positive polarity and the secondary latent image based on the analog image is formed with negative polarity,
Development is performed using red toner with positive polarity and black toner with negative polarity, and while the red toner with positive polarity is supplied to the primary latent image area based on the digital image, the negative toner is supplied to the secondary latent image area based on the analog image. A polar black toner was supplied and both latent images were visualized with each of the above toners.

Next, the polarity of one toner supplied to the bipolar photoreceptor (1) in this way is aligned with the polarity of the other toner by a DC charger (not shown) with an AC component superimposed, and then Each toner with the same polarity is transferred from the bipolar photoconductor (1) onto a transfer paper (not shown) using a transfer charger (not shown) with a polarity opposite to that of the toner, and this is heated. It took root.

As a result, on the transfer paper, the digital image part based on the primary exposure is displayed in red, while the analog image part based on the secondary exposure is displayed in black. Two types of images were formed: red and black.

In addition, when a 10-way printing durability test was conducted on the bipolar photoconductor (1), it was found that the bipolar photoconductor (1) had a surface made of an amorphous carbon film as described above. Since the protective layer (1d) was formed, there was no abrasion of the film, and good electrostatic properties and image properties were obtained even after the printing durability test.

(Example 2) In this example, as shown in FIG. 7, a charge generation layer (lb) containing a charge generation material made of a phthalocyanine compound and a charge generation layer (lb) containing a charge generation material made of a phthalocyanine compound were formed on a conductive support (la). A charge transport layer (le) containing a charge transport material to be transported and a charge generation layer (1f) containing a charge generation material made of an azo compound are laminated, and a surface protective layer (1f) is further layered on the surface thereof.
1d) was used.

In manufacturing such a bipolar photoreceptor (1), in this example, as in the case of Example 1, an aluminum drum (1a) was used as the conductive support (la), and , this aluminum drum (
1a) A τ-type metal-free phthalocyanine is used as the phthalocyanine compound to be contained in the charge generation layer (1b) formed on the aluminum drum (1a) in the same manner as in Example 1. A charge generation layer (1b) containing a phthalocyanine compound having a thickness of 0.25 μm was formed.

In forming the charge transport layer (le) on the charge generation layer (1b) thus formed, the hydrazone represented by the chemical formula [2] used in Example 1 was used as the charge transport material. A coating solution for the charge transport layer is prepared by dissolving 10 parts by weight of this hydrazone-based compound and 10 parts by weight of polycarbonate (K-1300 manufactured by Teijin Kasei ■) in 80 parts by weight of dichloromethane. A coating liquid is applied onto the charge generation layer (1b) by a dipping method so that the film thickness after drying is 30 μm, and this is dried to form a charge transport layer (1e) on the charge generation layer (lb). ) was formed.

Next, in forming a charge generation layer (1f) containing a charge generation material made of an azo compound on the charge transport layer (1d) thus formed, the azo compound in Example 1 was used as the azo compound. The above chemical formula used [3
1 part by weight of this bisazo pigment, 1 part by weight of polyvinyl butyral (Nislec BL-S manufactured by Sekisui Chemical ■), and 98% by weight of n-butyl alcohol.
parts by weight are treated with a paint conditioner for 4 hours to prepare a coating solution for the charge generation layer, and this coating solution is applied onto the charge transport layer (1e) so that the film thickness after drying is 0.3 μm. The charge generation layer (1f) was formed by coating by a dipping method and drying.

Then, on the charge generation layer (le) thus formed, a surface made of an amorphous carbon film with a film thickness of approximately 1000 nm is formed by plasma CVD, as in the case of Example 1 above. A protective layer (1d) was formed.

Then, the bipolar illuminant (1) produced in this way,
It was attached to a photoreceptor tester having a configuration similar to that of a commercially available copying machine, and the half-decrease exposure amount E, 72 and spectral sensitivity characteristics during positive charging and negative charging were measured in the same manner as in Example 1 above. Regarding these, the same results as the bipolar photoreceptor (1) used in Example 1 above were obtained.

Further, using the bipolar photoreceptor (1) of this example manufactured as described above, two types of images were formed in a single electrophotographic process in the same manner as in Example 1 above. However, as in the case of Example 1 above, in one electrophotographic process, the digital image part based on the primary exposure was displayed in red, and the analog image part based on the secondary exposure was displayed in black. Image obtained.

Furthermore, even when a 10-sided printing durability test was conducted,
In the above-mentioned bipolar photoreceptor (1), there is no scraping of the film,
Good electrostatic properties and image properties were obtained even after the printing durability test.

[Effects of the Invention] As detailed above, in the image forming method according to the present invention, a bipolar photoreceptor having sensitivity to both positive and negative polarities is used, and a single electrophotographic process is performed. In forming two types of images, there is no need to perform complicated processes as in the past, and after a primary latent image is formed on a bipolar photoconductor by primary exposure, a secondary exposure is performed on this bipolar photoconductor. In this case, even if the area where the primary latent image is formed is irradiated with the secondary exposure light, the primary latent image will not be erased by the secondary exposure, and image formation can be easily controlled. Two types of images can now be easily formed using the electrophotographic process.

Further, the bipolar photoreceptor as described above in this invention is
It has high sensitivity in both positive and negative polarities, and has excellent spectral sensitivity characteristics in different wavelength regions, and can form two types of images in a single electrophotographic process using two types of exposure means with different wavelengths. If you do this, you can now get better images.

[BRIEF DESCRIPTION OF THE DRAWINGS] The drawings all show embodiments of the present invention; FIG. 1 is a partial cross-sectional view of a bipolar photoreceptor used in Embodiment 1 of the invention, and FIG. Figures 3 (A) and 3 (B) are diagrams showing the spectral sensitivity characteristics of the bipolar photoreceptor in the same example, and diagrams showing the potential of the photoreceptor during primary charging and the state in which the photoreceptor is primarily charged in the same example. Figure (A). (8) is a diagram showing the state in which the photoconductor is subjected to primary exposure in the same example and the potential of the photoconductor during the primary exposure, and Figures 5 (A) and (B) are diagrams showing the secondary charging of the photoconductor in the same example. FIGS. 6A and 6B are diagrams showing the state and the potential of the photoreceptor during secondary charging, and FIGS. 6A and 6B show the state where the photoreceptor is subjected to secondary exposure and the potential of the photoreceptor during the secondary exposure in the same example. 7 are partial cross-sectional views of the bipolar photoreceptor used in Example 2 of the present invention. (1) - photoreceptor, (la) - conductive support,
(lb)...charge generation layer, (lc)...photosensitive layer,
(le)...Charge transport layer. (1f)...-charge generation layer, (2)...-primary charger (
Scorotron Charger), (3)...Secondary charger (Corotron Charger).

Claims (1)

[Scope of Claims] 1. A step of primarily charging an bipolar photoconductor having sensitivity in both positive and negative polarities using a primary charger; a step of forming a primary latent image on a photoconductor; and a step of forming a primary latent image on the bipolar photoconductor on which the primary latent image is formed, using a secondary charger having a polarity opposite to that of the primary charger, so that the primarily exposed portion has a polarity opposite to that during the primary charging. A step of secondarily charging the bipolar photoreceptor so that the unexposed portion of the first exposure retains the charge with the polarity at the time of the first charge, and a step of exposing the secondarily charged bipolar photoreceptor to a wavelength different from that of the first exposure. 1. An image forming method comprising the step of performing secondary exposure in step 1 and forming a secondary latent image in the exposed portion of the primary exposure. 2. At least a charge generation layer containing a charge generation material made of a phthalocyanine compound and a photosensitive layer containing a charge generation material made of a charge transport material and an azo compound are laminated on a conductive support. A bipolar photoreceptor characterized by: 3. At least a charge generation layer containing a charge generation material made of a phthalocyanine compound, a charge transport layer containing a charge transport material, and a charge generation layer containing a charge generation material made of an azo compound on a conductive support. A bipolar photoreceptor characterized by being made by laminating layers.