JPS6310828B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for eliminating static electricity from a composite photoreceptor for electrophotography, and more specifically, the present invention relates to a method for eliminating static electricity from a composite photoreceptor for electrophotography, and more specifically, even if a composite photoreceptor in which one photoconductive layer is made of a eutectic complex formed from a pyrylium dye and an electrically insulating polymer is used repeatedly. The present invention relates to a method for eliminating static electricity from a composite photoreceptor for electrophotography, which allows good image characteristics to be obtained without residual potential appearing. 2. Description of the Related Art Electrophotographic photoreceptors in which a photoconductive layer mainly composed of a eutectic complex is provided on a conductive substrate are known. usually,
These photoreceptors have a photoconductive layer on an aluminum substrate, and a eutectic complex formed from a pyrylium dye (pyryllium, thiapyrylium, selenapyrylium, etc.) and an electrically insulating polymer (an electrically insulating resin having an alkylidene diarylene moiety). It was formed as follows. Incidentally, such a eutectic complex photoreceptor has higher photosensitivity when positively charged than when negatively charged. However, the residual potential shows a larger potential in the case of positive charging than in the case of negative charging, which has the drawback of causing background smearing. On the other hand, unlike the above-mentioned photoconductor having a single photoconductive layer, two photoconductive layers, each sensitive to light of different wavelengths, are laminated on a conductive substrate such as an aluminum plate for use in electrophotography. A composite photoreceptor is used, and it is subjected to primary charging, secondary charging with a polarity different from the primary charging, or after or simultaneously with such primary charging, one of the photoconductive layers is charged with light of a wavelength at which it can become a conductor. After performing uniform exposure, secondary charging is performed to maintain charges of different polarities in each photoconductive layer, and then image exposure is performed through the original having black areas and chromatic areas, so that each color of the original is An electrostatic latent image with surface potentials of different polarities corresponding to the areas appears on the photoreceptor, this is sequentially developed with different color toners of different polarity, and this toner image is transferred to image receiving paper (for example, plain paper) and fixed. to obtain a two-color copy.
A new electrophotographic method is in the spotlight. One of the typical photoreceptors used in this two-color electrophotography method has two photoconductive layers having the above properties on an aluminum substrate, and one of the photoconductive layers is made of a eutectic complex. The main component is However, even with this composite photoreceptor,
In repeated image characteristics, carriers are accumulated inside, resulting in a so-called residual potential, which tends to result in poor image quality. The direct cause of this poor image quality is the lack of exposure during static electricity removal. Therefore, in order to prevent this, it is conceivable to increase the amount of exposure light (cleaning light) during charge removal, but in such a case, there is a problem that the photoreceptor itself may deteriorate. An object of the present invention is to provide a static neutralization system for an electrophotographic composite photoreceptor in which the above-mentioned eutectic complex photosensitive layer is used as one of the photoconductive layers, and which eliminates the risk of deterioration of the photoreceptor itself, has no residual potential, and provides good copies. The purpose is to provide a method. Another object of the present invention is to provide a method for removing static electricity from a composite photoreceptor for electrophotography which has particularly excellent repeatable image characteristics. That is, the method for removing static electricity from a composite photoreceptor for electrophotography according to the present invention includes a second photoconductive layer that is sensitive to some chromatic light in the visible light region and transmits other chromatic light, and the second photoconductive layer. a first photoconductive layer sensitive to chromatic light transmitted through the transparent conductive substrate, the first photoconductive layer, an optional intermediate layer, and a second photoconductive layer being laminated in this order, and One of these two photoconductive layers is mainly composed of a photoconductive compound and a eutectic complex formed of a pyrylium dye and an electrically insulating polymer, and is charged with a positive or negative primary corona charge. The first photoconductive layer or the second photoconductive layer is made into a conductor by a process of applying secondary corona charging with a polarity different from the polarity of the primary charging, or after or simultaneously with the primary corona charging. A process of uniformly exposing each photoconductive layer to chromatic light that can be chromatic, followed by a similar secondary corona charging process to maintain charges of different polarities on each of the photoconductive layers, and then exposing the original having black and chromatic areas to An electronic device characterized in that static electricity is removed from a composite photoreceptor whose surface potentials corresponding to each color portion appear as different polarities when imagewise exposed to light by irradiating cleaning light from both the front and back surfaces of the photoreceptor. Method for removing static electricity from photographic photoreceptors. It is. The method of the present invention will be explained in more detail below with reference to the accompanying drawings. 1 and 2 are cross-sectional views of two examples of composite photoreceptors used in the method of the present invention, and the numbers 1' and 1'' are the photoreceptors, 2 is the transparent conductive substrate, and 3 is the photoreceptor. is a photoconductive layer, 31'
32' represents the first photoconductive layer, and 32' represents the second photoconductive layer. The transparent conductive substrate 2 here has a volume resistance of 10 ¹⁰ Ω.
It has conductivity of less than cm and is transparent in the visible light range, and examples include indium oxide, tin oxide, plastic film coated with indium oxide-tin oxide, and glass. These materials are not suitable as substrates here. coated
The thickness _{of In2O3} , _SnO2 , _{In2O3 −SnO2 is} 0.1~0.01μ
It is about m. As mentioned above, the photoconductive layer 3 shown in FIG.
It is made mainly from pyrylium dyes (pyryllium, thiapyrylium, selenapyrylium, etc.), electrically insulating polymers (electrically insulating resins with alkylidene diarylene moieties), and photoconductive compounds. A eutectic complex is formed with the insulating polymer. Pyrylium dye has the following general formula. In the above formula, R ^a , R ^b , R ^c , R ^d and R ^e each represent (a) a hydrogen atom (b) an alkyl group, typically methyl, ethyl, propyl, isopropyl, butyl, t-butyl,
_C1 - _C15 alkyl groups such as amyl, isoamyl, hexyl, octyl, nonyl, dodecyl, etc. (c) Alkoxy groups such as methoxy, ethoxy, propoxy, butoxy, amyloxy, hexoxy, octoxy, etc. (d) Phenyl, 4-diphenyl, Alkylphenyls such as 4-ethylphenyl and 4-propylphenyl; 4-ethoxyphenyl, 4-methoxyphenyl, 4-amyloxyphenyl, 2-hexoxyphenyl, 2-methoxyphenyl,
Alkoxyphenyls such as 3,4-dimethoxyphenyl; β such as 2-hydroxyethoxyphenyl and 3-hydroxyethoxyphenyl
-Hydroxyalkoxyphenyl; 4-hydroxyphenyl, 2,4-dichlorophenyl,
Halophenyls such as 3,4-dibromophenyl, 4-chlorophenyl, 3,4-dichlorophenyl; azidophenyl, nitrophenyl, 4
-Aminophenyls such as diethylaminophenyl and 4-dimethylaminophenyl; naphthyl, styryl, methoxystyryl, diethoxystyryl, dimethylaminostyryl, 1-butyl-4-p-dimethylaminophenyl-1,3
- represents an aryl group including substituted aryl groups such as vinyl-substituted aryl groups such as butadienyl, β-ethyl-4-dimethylaminostyryl, X is a sulfur, oxygen or selenium atom, and Z ^- is perchlorate, Anionic functional groups such as fluoroborate, iodide, chloride, bromide, sulfate, periodide, p-toluenesulfonate, hexafluorophosphate. Furthermore
R ^a , R ^b , R ^c , R ^d and R ^e may be atoms necessary to jointly complete the aryl ring fused to the pyrylium nucleus. Representative examples of such pyrylium dyes are shown below.

[Table] Chlorate

Table - Chlorate Particularly useful pyrylium dyes are those having the general formula: In the formula, R ¹ and R ² are C ₁ to C ₅ alkyl groups and C ₁ to
It is an aryl group such as a substituted phenyl group having one substituent selected from a _C5 alkoxy group, and ^R3 is an alkylamino-substituted phenyl group whose alkyl moiety is _C1 to _C5 , dialkylamino-substituted and haloalkyl. An amino-substituted phenyl group may also be used. X
is an oxygen or sulfur atom, and Z ^- is as described above. As an electrically insulating polymer, the main chain (repeat unit)
Particularly useful are those having an alkylidene diarylene moiety represented by the following formula. In the formula, R ⁴ and R ⁵ each represent a hydrogen atom, methyl containing a substituted alkyl group such as trifluoromethyl,
Ethyl, propyl, isopropyl, butyl, t-
Aryl groups such as phenyl and naphthyl, including alkyl groups such as butyl, bentyl, hexyl, heptyl, octyl, nonyl, decyl, substituted aryl groups having substituents such as halogen, C1 _{- C5} alkyl groups, Furthermore, R ⁴ and R ⁵ may be carbon atoms necessary to jointly form a cyclic hydrocarbon group including cycloalkanes such as cyclohexyl and polycycloalkanes such as norbornyl. R ⁶ and R ⁷ are hydrogen, a C ₁ to C ₅ alkyl group, or a halogen such as chloro, bromine, iodine, and R ⁸ is

【formula】 【formula】

【formula】

【formula】

【formula】

【formula】 as well as

[Formula] is a divalent group selected from the group consisting of: Hydrophobic carbonate polymers (polycarbonates) comprising repeating units of the following formula are also useful and preferred. In the formula, R ⁹ is a phenylene group including halo-substituted phenylene groups and alkyl-substituted phenylene groups, and R ⁴ and R ⁵ are as described above. These polymers are disclosed in USP 3,028,365 and USP 3,317,466. Preferably, a compound containing an alkylidene diarylene moiety in the repeating unit, such as produced from bisphenol A, is produced by transesterification between diphenyl carbonate and 2,2-bis(4-hydroxyphenyl)propane. Polycarbonates containing such polymers are useful. Such polymers are disclosed in USP2999750, USP3038874,
Same No. 3038880, No. 3106544, No. 3106545, Same No.
It is disclosed in No. 3106546 etc. In any case, film-forming polycarbonate resins can be used in a wide variety of ways. Satisfactory results are obtained especially when using those having an intrinsic viscosity of about 0.5 to 1.8. Specific examples of the electrically insulating polymer are as follows. No. Polymer Material 1 Poly(3,3'-ethylenedioxyphenylenethiocarbonate) 2 Poly(4,4'-isopropylidene diphenylene carbonate) 3 Poly(4,4'-isopropylidene phenylenethiocarbonate) ) 4 Poly(2,2-butanebis-4-phenylene carbonate) 5 Poly[4,4'-isopropylidene bis(2-methylphenylene) carbonate] 6 Poly[4,4'-methylenebis(2-methylphenylene) carbonate] In addition, the following general formula is used as a photoconductive compound: (However, R ¹⁰ , R ¹¹ , R ¹² and R ¹³ are hydrogen, alkyl groups, phenyl groups, alkyl group-substituted phenyl groups, halo-substituted phenyl groups, alkylamino-substituted phenyl groups, dialkylaminophenyl-substituted, haloalkylamino-substituted Polyarylalkane derivatives represented by the following are preferred, and typical examples thereof include the following. (1) 1,3-diphenyl-2-p-diethylaminophenyl-tetrahydroimidazole (2) Bis(p-(N,N-dibenzyl)aminophenyl)methane (3) 1-bis(p-(N,N- dibenzyl)aminophenyl)propane(4) 4,4'-bis(diethylamino)-2,2'-
Dimethyltriphenylmethane (5) 4,4'-bis(diethylamino)-2,2'-
Dimethyl-2″-chlorotriphenylmethane (6) α,α-bis(2-methyl-4-diethylaminophenyl)-2-methylthiophene (7) α,α-bis(2-methyl-4-diethylaminophenyl) enyl)-2-picoline(8) α,α-bis(2-methyl-4-diethylaminophenyl)-2-methylfuran(9) α,α-bis(2-methyl-4-diethylaminophenyl)- 2-Methylpyrrole (10) α,α-bis(2-methyl-4-diethylaminophenyl)-2-methylindole(11) α,α-bis(2-methyl-4-diethylaminophenyl)-2- Methylbenzothiophene (12) α,α-bis(2-methyl-4-diethylaminophenyl)-2-methylbenzofuran (13) 4,4′,4″-tris(diethylamino)-
2,2'-Dimethyltriphenylmethane These photoconductive compounds are present in the photoconductive layer (photosensitive layer) 3 and act as a conductive carrier transport medium generated within the photosensitive layer by light irradiation, and the photoconductive layer It is effective in reducing the surface charge of . The composite photoreceptor 1' in the method of the present invention is prepared by combining the pyrylium dye, the electrically insulating polymer, and the photoconductive compound in a suitable solvent such as methylene chloride, chloroform, methylene dichloride, 1,1,2-trichloroethane (these The first photoconductive layer 31' is coated on the transparent conductive substrate 2 and dried to form a first photoconductive layer 31'. It can be manufactured by further forming a second photoconductive layer 32' thereon. Further, the composite photoreceptor 1'' shown in FIG. 2 can be manufactured by providing an intermediate layer 4 between the first photoconductive layer 31' and the second photoconductive layer 32'. The appropriate thickness of the photoconductive layer 31' is about 5 to 30 μm.The proportions of each component are 2 to 5% by weight of the dye, 30 to 80% by weight of the electrically insulating polymer, and 20 to 50% of the photoconductive compound. The composite photoreceptor 1', shown in FIGS. 1 and 2, is about % by weight.
1'' can of course be applied to the Carlson process, but since it is applied to the original two-color image forming method, the second photoconductive layer 32' has poor or no sensitivity to red light and is not sensitive to blue light. It is desirable that the second photoconductive layer 32' is made of a sensitive photosemiconductor.Specifically, the second photoconductive layer 32' is made of (a) a charge transfer complex (CT): the charge transfer substance here is It is transparent to visible light or has a faint color even if it is colored, such as a charge transfer complex of polyvinylcarbazole, polyarylalkane, etc. and TNF (trinitrofluorenone). (2) Charge transfer layer (CTL) / CdS , CTL/Se or
Composed of CTL/organic pigment dispersion system, etc.: Here, charges generated in the CdS layer, Se layer, or organic pigment dispersion layer are well injected into the CTL. (c) Azo pigment (disazo pigment, trisazo pigment)
Dispersed in a resin binder (d) Cu-CdS: CdS content is about 1 to 92% by weight,
Cu-sensitized CdS dispersed in a resin binder. (e) ZnO dye-sensitized dispersion system: Examples include zinc oxide sensitized with fluorescein. When the second photoconductive layer 32' is formed as a single layer, it is preferably not a vapor deposited layer or a sputtered layer. This is because if such a layer structure is adopted, the resulting photoreceptor will have poor flexibility. The intermediate layer 4 is effective in preventing charge leakage. This intermediate layer 4 is made of (a) SiO, SiO ₂ , Al ₂ O ₃ ,
White or transparent high-resistance inorganic compounds such as MgO and MgF ₂ are applied by vapor deposition or sputtering, (b) polyester, polycarbonate, polyamide, acrylic resin, vinyl chloride resin, polyvinylidene chloride, polystyrene, styrene-butadiene, etc. polymer, butyral resin, formal resin,
Thin films of phenolic resin, polyurethane resin, epoxy resin, melamine resin, silicone resin, polyimide resin, cellulose resin, polyamino acid, etc.
It is formed by etc. Furthermore, as described above, an appropriate pigment or dye may be added to the intermediate layer 4 in order to control the wavelength of light incident on the first photoconductive layer 31'. The dyes and pigments used here are preferably red, and therefore, the pigments include indigo pigments such as indigo and thioindigo, azo pigments such as pyrazolone red, anthraquinone pigments such as indanthrene blue, and organic pigments such as quinacridone pigments. Pigments: copper sulfate, potassium ferrocyanide, (metal) phthalocyanine, barium dichromate, cobalt sulfate,
Examples include inorganic pigments such as cobalt carbonate, trichloromolybdenum, potassium ferricyanide, selenium powder, tin iodide, red iron, silver vermilion, and cobalt blue. Dyes include diphenylmethane dyes such as auramine, triphenylmethane dyes such as crystal violet and malachite green, xanthene dyes such as fluorescein, rose bengal and rhodamine B, acridine dyes such as acridine orange, phenosafranin, methylene violet, etc. Thiazine dyes such as azine dyes, phenothiazine, and methylene blue are 1, 3,
Examples include pyrylium salts such as 5-triphenylpyrylium perchlorate, and thiapyrylium salts such as 1,3,5-triphenylthiapyrylium perchlorate. Photoreceptor 1' (or 1'') in the present invention
After providing a first photoconductive layer 31' mainly composed of a eutectic complex and a photoconductive compound on a transparent conductive substrate 2, an intermediate layer having a thickness of about 1 to 5 μm is provided if necessary,
Furthermore, a second photoconductive layer 32' as described in (a) to (e) above may be provided on this. The intermediate layer 4 is formed using a vapor deposition method.
It is formed by a sputtering method or a resin dispersion (dissolution) coating method. Further, the second photoconductive layer 32' can be formed by a similar method, and its thickness is suitably about 10 to 50 .mu.m. In addition, when a binder is used in providing the second photoconductive layer 32', examples of the binder material include polyethylene, polystyrene, polybutadiene, styrene-butadiene copolymer, acrylic ester, or methacrylic ester. Polymers and copolymers, polyester, polyamide, polycarbonate, epoxy resin, urethane resin, silicone resin, alkyd resin, cellulose resin and polycarbonate
N-vinylcarbazole and its derivatives (for example, halogens such as chlorine and bromine in the carbazole core,
(having substituents such as methyl group or amino group),
Polyvinylpyrene, polyvinylanthracene, pyrene-formaldehyde condensation polymers and derivatives thereof (for example, those having substituents such as halogen such as bromine or nitro group in the pyrene core), poly-γ-carbazolylethyl-L-glutamate, Styrene resin, chlorinated polyethylene, acetal resin,
Examples include melamine resin. A plasticizer can be used in combination with this binder. As the plasticizer, those commonly used as plasticizers for resins, such as dibutyl phthalate and dioctyl phthalate, can be used as they are. The appropriate amount to be used is 0 to 30% by weight based on the binder. Moreover, the organic solvent used here is of course not intended to dissolve the binder, for example, toluene,
Tetrahydrofuran, 1,2-dichloroethane,
Methylene chloride, benzene, methanol, etc. are applicable. 2 and 3 above, the eutectic complex photosensitive layer is used as the first photoconductive layer 31', but a composite photoreceptor using this eutectic complex layer as the second photoconductive layer 32' can also be applied to the method of the present invention. It is applicable. In this case, the material of the second photoconductive layer 32' can be used as it is as the first photoconductive layer, but an intermediate layer 4 is provided and a coloring agent (for example, copper phthalocyanine, methylene blue, etc.) that absorbs red light is added to the intermediate layer 4. If added,
The underlying first photoconductive layer may have panchromatic properties. As mentioned above, a photoreceptor having a eutectic complex layer as a photoconductive layer has a considerable residual potential. Therefore,
The inventors of the present invention have investigated in detail the relationship between removal of residual potential and cleaning light, and have found that even in composite photoreceptors, the problem of erasing residual potential occurs in the case of positive charge or positive charge. Therefore, in the method of the present invention, erasing of residual potential by cleaning light is solved by a photoelectron emission phenomenon (a phenomenon in which electrons are emitted when a metal surface is irradiated with light). That is, in the case of a composite photoreceptor in which the first photoconductive layer 31' is a eutectic complex layer, the first photoconductive layer 31' becomes conductive by applying cleaning light from the back surface of the photoreceptor. The positive charges that had been charged there will now flow in the direction of the transparent conductive substrate 2, and at the same time, the positive charges that cannot be moved will be neutralized by the electrons coming out of the substrate 2. When the photoconductive layer 3 is negatively charged and is irradiated with this cleaning light, the negative charges move well through the conductive first photoconductive layer 31' and flow to the transparent conductive substrate 2. . Here, even if either positive or negative charge exists as a residual potential on the photoconductor 1, the residual potential can be eliminated by irradiating cleaning light from the back side (front side 2) of the photoconductor. The above-mentioned tendency is also observed in the composite photoreceptors 1' and 1'' in which the eutectic complex layer is used as the second photoconductive layer 32', and the effect of cleaning light irradiation is exhibited. It was confirmed that the effect is better when each photoconductive layer 31', 32' is irradiated with cleaning light.
The photoconductive layers 31' and 32' have different photosensitive wavelength ranges, and when irradiating cleaning light only from the side of the transparent conductive substrate 2 or only from the surface of the photoreceptor, for example, white light that includes the photosensitive wavelength of both photoconductive layers is used. However, when irradiating from one side, the amount of irradiation must be increased to remove the residual charge on the photoconductive layer on the side opposite to the irradiated side. In this case, the photoconductive layer on the irradiation side is irradiated with a large amount of light, which temporarily deteriorates the characteristics of the photoconductive layer and reduces the amount of charge etc. in the next image forming step. Therefore, in composite photoreceptors such as those used in the method of the present invention, it is advantageous to irradiate each photoconductive layer with the required amount of cleaning light from both sides. As described above, the present invention is a good method for removing static electricity from a composite photoreceptor having a photoconductive layer mainly composed of a eutectic complex and a photoconductive compound, and according to this method, copies without background stains can be obtained. . Here, we will investigate the static elimination effect of a photoconductive layer mainly composed of a eutectic complex and a photoconductive compound. 0.2 g of 4-p-dimethylaminophenyl-2,6-diphenylthiapyrylium perchlorate 4,4'-bis(diethylamino)-2, on a plastic film (transparent conductive substrate) coated with a conductive substance. A solution consisting of 2'-dimethyltriphenylmethane 2g, polycarbonate resin (Panlite K-1300, manufactured by Teijin KK) 3g, and dichloromethane 80g was applied using a doctor blast method, dried at 80°C for 2 minutes, and then exposed to a layer of about 8μm thick. A conductive layer was formed. The thus-prepared photoconductor was experimentally subjected to each step of dark charging, dark attenuation, light attenuation, and cleaning light irradiation from the photoconductor surface using a paper analyzer (manufactured by Kawaguchi Denki KK). The results are shown in Figure 3. and as shown in Table 1. In addition, in FIG. 3, the solid line shows the case of negative charging, and the broken line shows the case of positive charging.

[Table] In this experiment, it was confirmed that when the photoreceptor was positively charged, no potential decay occurred even when irradiated with cleaning light of about 100,000 lux. Therefore, especially in the case of positive charging, the sample with residual potential is turned over and the cleaning light is irradiated from the transparent conductive substrate side (with Kawaguchi Electric KK's Paper Analyzer, light irradiation from the front and back sides of the photoreceptor is done at the same time). After that, I returned to normal measurement using the paper analyzer and measured the residual surface potential, and found that the initial residual potential was 0.
It had become a bolt. For comparison, the sample with residual potential was turned over so that the cleaning light could be irradiated from the transparent conductive substrate side. After leaving it in the dark, the paper analyzer was returned to normal measurement and the residual surface potential was measured, and the initial residual potential remained at the same value. For further comparison, a photoreceptor manufactured in the same manner except that the conductive material of the substrate was replaced with aluminum (film thickness approximately 9.0 μm) was subjected to the same test operations as above. The following results were obtained.

[Table] Example 0.2 g of 4-p-dimethylaminophenyl-2,6-diphenylthiapyrylium perchlorate on a plastic sheet (transparent conductive substrate) coated with indium oxide to a thickness of about 0.005 μm 4,4 '-Bis(diethylamino)-2,2'-dimethyltriphenylmethane 2g Polycarbonate resin (Panlite K-1300)
A solution consisting of 2.8 g dichloromethane and 60 g was applied by a doctor blade method and dried at 80° C. for 15 minutes to form a first photoconductive layer with a thickness of about 29 μm. On top of this, a polyester resin layer (intermediate layer) having a thickness of about 1 μm was provided. Furthermore, a selenium vapor deposition layer (charge generation layer) with a thickness of about 2 μm is provided on this intermediate layer, and then a layer of bis(p-N,N-dibenzyl)aminophenylpropane and polycarbonate resin (Panlite K-1300) is formed. A second photoconductive layer was formed by providing a charge transfer layer having a thickness of about 11 μm and having a weight ratio of :1. The thus prepared composite photoreceptor was uniformly irradiated from the back side through an R-60 filter (red filter, manufactured by Hoya Glass KK), and primary corona charging of -6.5 KV was performed from the front side. Then in the dark +
After performing secondary corona charging of 5.0KV from the surface,
Image exposure was performed. This is sequentially developed with positively charged red toner and negatively charged black toner, and image receiving paper (plain paper) is
When the image was transferred and fixed, a good two-color image copy was obtained. On the other hand, after performing the above-mentioned charging (primary charging, secondary charging) and image exposure, white light (100,000 lux/sec) is irradiated from the surface of the photoconductor as cleaning light, and at the same time, white light (100,000 lux/second) is irradiated from the back surface. Lux/sec) was irradiated as a cleaning light. These operations of charging, image exposure, and cleaning were repeated. As a result, no residual potential was observed even after repeated operations 100 times, and satisfactory copies could be obtained for a long time without any deterioration of the photoreceptor. For comparison, when the cleaning light irradiation from the back side was omitted, it was found that the image on the photoreceptor gradually deteriorated as copies were repeatedly made. In addition, the cleaning light irradiation from the back side is omitted and the cleaning light irradiation from the front side is used instead.
When the intensity was increased to 200,000 lux·sec, similar results were observed.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of an electrophotographic photoreceptor applied to the method of the present invention, and FIG. 3 is a graph showing the electrophotographic characteristics of a single-layer photoreceptor. 1', 1''...Photoreceptor, 2...Transparent conductive substrate,
3... Photoconductive layer, 4... Intermediate layer, 31'... First photoconductive layer, 32'... Second photoconductive layer.

Claims (1)

[Claims] 1. A second photoconductive layer that is sensitive to some chromatic light in the visible light range and transmits other chromatic light, and a first photoconductive layer that is sensitive to chromatic light that passes through the second photoconductive layer. A photoconductive layer is laminated on a transparent conductive substrate in the order of a first photoconductive layer, an optional intermediate layer, and a second photoconductive layer, and one of the two photoconductive layers is coated with a pyrylium dye. It is mainly composed of a eutectic complex formed with an electrically insulating polymer and a photoconductive compound, and after being subjected to positive or negative primary corona charging, it is charged with a polarity different from that of the primary charging. By the process of applying secondary corona charging, or similarly after or simultaneously with applying primary corona charging, uniform exposure to chromatic light capable of making the first photoconductive layer or the second photoconductive layer conductive is carried out, followed by Similarly, by the process of applying secondary corona charging, each of the photoconductive layers is made to maintain charges of different polarity, and then when an image is exposed through an original having a black part and a chromatic part, the surface potential corresponding to each color part is 1. A method for eliminating static electricity from a composite photoconductor for electrophotography, characterized in that static elimination of the composite photoconductor, which appears as different polarities, is carried out by irradiating cleaning light from both the front and back surfaces of the photoconductor.