JPH04217263A - Electrophotosensitive material - Google Patents

Abstract

PURPOSE:To obtain a laminated electrophotosensitive material which has high sensitivity equal to the initial period even relating to fatigue by repeated use to suppress a rise of residual potential further with small fluctuation. CONSTITUTION:In an electrophotosensitive material formed by laminating a charge generation layer and a charge transport layer on a conductive substrate, quantum efficiency of the sensitive material is set to quantum efficiency or more of the charge generation single layer. Accordingly, carrier generation efficiency of the laminated sensitive material is increased and sensitized more than the case of the single charge generation layer by presence of the charge transport layer. In a result thus obtained, that is, a light carrier in this laminated sensitive material is suggested generated between a charge generation material and a charge transport material, accordingly to increase very high also carrier injection.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor that has a high sensitivity equivalent to that of the initial state even when fatigued due to repeated use, and an increase in residual potential is suppressed.

0002

[Prior Art] In recent years, electrophotographic photoreceptors used in copiers, printers, facsimile machines, etc. have been made using organic photosensitive materials instead of inorganic photosensitive materials due to their low cost, mass productivity, and ease of use. It is beginning to be used due to its advantages such as being less polluting. Organic electrophotographic photoreceptors include photoconductive resins such as polyvinylcarbazole (PVK) and PVK-T.
There are charge transfer complex type photoreceptors represented by NF (2,4,7 trinitrofluorenone), pigment dispersion types represented by phthalocyanine binders, and functionally separated type photoreceptors that use a combination of a charge generation substance and a charge transport substance. It is known that functionally separated photoreceptors have high sensitivity and are comparable to inorganic photoreceptors.
Taking advantage of its high-speed response, it is at the center of practical application. but,
In the case of organic electrophotographic photoreceptors, even if one of the above photoreceptors is used, changes in photoreceptor characteristics over time due to repeated use cannot be avoided, and in particular, the increase in residual potential determines the lifespan of the photoreceptor. Functionally separated photoreceptors are no exception, and improvements have been strongly desired. In organic photoreceptors,
The increase in residual potential during repeated use is an important factor determining the lifespan of a photoreceptor. This point will be explained using FIGS. 8 and 9 and comparing it with the case of an inorganic photoreceptor. Figure 8 shows selenium,
FIG. 2 is a schematic diagram showing residual potential fluctuations during repeated use of an inorganic photoreceptor typified by selenium alloy, amorphous silicon, and the like. Residual potential is generated due to repeated use,
When use is discontinued, the residual potential decreases (recovers) to the initial value of use. On the other hand, as for the organic photoreceptor, as shown in FIG. 9, the residual potential increases with repeated use and increases monotonically even after discontinuation of use. This is the reason for determining the lifespan. Although there are some hypotheses, the mechanism for increasing the residual potential of such an organic photoreceptor is still not clear, and therefore, there is no guideline for designing the slope shown in FIG. 9 to be small. By the way, photoattenuation of the surface potential of a laminated photoreceptor occurs through the following processes: photocarrier generation in the charge generation layer, carrier injection at the charge generation layer-charge transport layer interface, and carrier movement in the charge transport layer. , depends on both the charge-generating material and the charge-transporting material. However, increasing the sensitivity of laminated photoreceptors has been achieved through experience-based combinations of charge-generating materials and charge-transporting materials. As described above, the sensitivity and residual potential of a laminated photoreceptor have been treated as independent characteristics, and the relationship between them has not been studied.

0003

[Problems to be Solved by the Invention] The present invention solves the above-mentioned problems of the prior art, maintains high sensitivity even after repeated use, and
Moreover, it is an object of the present invention to provide an electrophotographic photoreceptor in which the residual potential does not easily increase.

0004

[Means for Solving the Problems] The present inventors actively investigated technology for increasing the sensitivity of laminated photoreceptors while using the same materials as before, and surprisingly found that The present invention has been completed by discovering that a highly sensitive laminated photoreceptor with a suppressed increase in residual potential than before can be obtained when the quantum efficiency exceeds the quantum efficiency of a single charge generation layer constituting the laminated photoreceptor. reached. According to the present invention, in an electrophotographic photoreceptor comprising a charge generation layer and a charge transport layer laminated on a conductive substrate, the quantum efficiency of the photoreceptor is greater than or equal to the quantum efficiency of a single layer of the charge generation layer. An electrophotographic photoreceptor with features is provided. Although there is no certainty that can explain the causal relationship between increasing the sensitivity of an electrophotographic photoreceptor and suppressing an increase in residual potential, the following explanation can be given regarding increasing the sensitivity of a laminated photoreceptor and suppressing an increase in residual potential in the present invention. I can explain something like this. Figure 3
shows simultaneously the quantum efficiency of the laminated photoreceptor of Example 1 of the present invention and the quantum efficiency of the single charge generation layer used in the laminated photoreceptor, but it is clear that the quantum efficiency of the laminated photoreceptor is This exceeds that of a single charge generation layer. In general, the quantum efficiency (φD) of a laminated photoconductor and the quantum height (φS) of a single layer photoconductor are
) are given by equations (1) and (2), respectively. φD=φg×φi×φt (1)φS=
φg×φt (2) Here, φg represents carrier generation efficiency, φi represents carrier injection efficiency, and φt represents carrier transport efficiency. Under conditions where the exposure intensity is not large and carrier transport is not rate-limiting (referred to as emission limited), it can be assumed that φt = 1, so Equations (1) and (2)
can be expressed by equations (3) and (4), respectively. φD=φg×φi (3) φS=φg (4) Since the carrier injection efficiency φi can only take a value between 0 and 1,
The results of the quantum efficiency of the laminated photoreceptor and charge generation layer in Figure 3 are expressed by the formula (
3) Considering the relationship of equation (4), it is clear that φg (multilayer photoconductor) >> φg (single charge generation layer). In other words, it can be seen that the carrier generation efficiency of the laminated photoreceptor of Example 1 is increased and sensitized due to the presence of the charge transport layer than in the case of only the charge generation layer. These results suggest that the generation of photocarriers in this laminated photoreceptor occurs between the charge-generating material and the charge-transporting material, and it is therefore assumed that carrier injection is also very high. Ru. That is, when carriers are injected from the charge generation layer to the charge transport layer in this laminated photoreceptor, it is considered that the number of carriers that stagnate or accumulate in the charge generation layer is very small. On the other hand, the residual potential may be caused by the laminated photoreceptor not having the ability to neutralize surface charges, or the accumulation of carriers in the photosensitive layer. It is thought that if the carrier injection efficiency from the charge generation layer to the charge transport layer is poor, the ability to neutralize surface charges will be poor, and there is a good possibility that charges will accumulate in the photosensitive layer, resulting in residual potential. It will be done. In this way, the higher sensitivity and lower residual potential in a laminated photoreceptor seem to be simultaneously explained by the efficiency of carrier injection from the charge generation layer to the charge transport layer. The present inventors have demonstrated that in an electrophotographic photoreceptor comprising a charge generation layer and a charge transport layer laminated on a conductive substrate, the quantum efficiency of the photoreceptor is greater than or equal to the quantum efficiency of a single layer of the charge generation layer. The present invention was completed by empirically discovering that the electrophotographic photoreceptor exhibits high sensitivity and suppresses the generation of residual potential, and completed the present invention. This is considered to be due to the fact that carrier injection from the charge generation layer to the charge transport layer occurs efficiently as described above, and there is no (few) stagnation or accumulation of carriers within the charge generation layer. Next, the method for measuring quantum efficiency will be described. Quantum efficiency is defined as the number of surface charges removed by a single photon, and several measurement methods have been proposed. Among them, a photoreceptor charged with corona is irradiated with light and the rate of light decay of the surface potential is measured. The method of determining quantum efficiency from is the simplest and most reproducible method, and is therefore frequently used in various studies. This method is described, for example, in Photochemistry and Photobiology, Vol. 8, pages 429 to 440, and the following formula (5)

It is calculated by [Equation 1]. Here, C is the capacitance per unit area of a laminated photoreceptor or a single charge generation layer, e is the elementary charge of electrons, I is the absorption rate of photons, V is the surface potential, t is time, and E is the electric field. be. The quantum efficiency is preferably measured using a device based on the device described in the above-mentioned document, but it is also possible to measure the quantum efficiency by using a commercially available electrostatic copying paper test device, a device disclosed in Japanese Patent Application Laid-open No. 100167/1986, etc. can also be measured well. Incidentally, the incident light during measurement is monochromatic light having a wavelength in the region used for imagewise exposure, and is used at a relatively weak exposure amount so as not to cause rate-determining of carrier movement. Furthermore, when measuring the quantum efficiency of a laminated photoreceptor, it is desirable to measure in a region that includes an electric field range in which the photoreceptor can actually be used. Specifically, 1×105V
・cm-1 to 3×105V·cm−1, more preferably 5×104V·cm−1 to 5×105V·cm−1
It is desirable to measure in an electric field region that includes However, the electric field referred to here is an average value applied to the photoreceptor, and is a value obtained by dividing the surface potential by the photoreceptor film thickness. The quantum efficiency of a single charge generation layer can also be calculated from equation (5) using the same measurements as in the case of a laminated photoreceptor.
However, when measuring a single charge generation layer, attention should be paid to its thickness. That is, the film thickness should match the thickness of the charge generation layer of the corresponding laminated photoreceptor, and the reason for this is to prevent the movement process of carriers in the charge generation layer from being mixed in as disturbance (noise). In addition, it is preferable that the single charge generation layer be irradiated with light under the same conditions as those for the corresponding laminated photoreceptor. Next, the structure of the electrophotographic photoreceptor of the present invention will be explained with reference to the drawings. 2 and 3 are cross-sectional views showing the electrophotographic photoreceptor of the present invention, in which a charge generation layer 13 is formed on a conductive substrate 11.
It has a structure in which a charge transport layer 15 and a charge transport layer 15 are laminated. As the conductive substrate 11, materials exhibiting conductivity with a volume resistance of 1010 Ωcm or less, for example, metals such as aluminum, nickel, chromium, nichrome, copper, silver, gold, and platinum, and metal oxides such as tin oxide and indium oxide are used. , coated on film or cylindrical plastic or paper by vapor deposition or sputtering, or aluminum,
D. plates of aluminum alloy, nickel, stainless steel, etc. I. ,I. I. It is possible to use pipes that have been made into blank pipes using methods such as , extrusion, and drawing, and then have their surfaces treated by cutting, superfinishing, polishing, etc. The charge generation layer 13 is a layer containing a charge generation substance as a main component, and a binder resin can be used in combination as necessary. As the binder resin, polyamide, polyurethane, polyester, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, poly-N-vinylcarbazole, polyacrylamide, etc. are used. Examples of charge generating substances include phthalocyanine pigments, naphthalocyanine pigments, perylene pigments, perinone pigments, quinacridone pigments, quinone condensed polycyclic compounds, squaric acid dyes, azulenium dyes, azo pigments, etc. These charge generating substances may be used alone or in combination of two or more. The binder resin is suitably used in an amount of 0 to 100 parts by weight, preferably 0 to 50 parts by weight, based on 100 parts by weight of the charge generating substance. The charge generation layer is prepared by dispersing a charge generation substance together with a binder resin if necessary using a ball mill, attritor, sand mill, etc. using a solvent such as tetrahydrofuran, cyclohexane, dioxane, dichloroethane, etc., diluting the dispersion liquid appropriately and applying it. It can be formed by Application can be performed using a dip coating method, a spray coating method, a bead coating method, or the like. Further, a charge generating material having sublimation property can be provided by a vacuum thin film production method such as a vacuum evaporation method, and can be preferably used. The thickness of the charge generation layer is suitably about 0.01 to 5 .mu.m, preferably 0.1 to 2 .mu.m. The charge transport layer 22 is prepared by dissolving or dispersing a charge transport substance and a binder resin in a suitable solvent, and coating the solution on the charge generation layer.
It can be formed by drying. Moreover, a plasticizer, a leveling agent, etc. can also be added if necessary. The charge transport layer 15 is composed of a charge transport material and a binder or a polymeric charge transport material. Charge transport materials include hole transport materials and electron transport materials. Examples of electron transport substances include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinone dimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2, 4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno[1,2-
b] Electron accepting substances such as thiophen-4-one and 1,3,7-trinitrodibenzothiophene-5,5-dioxide. As a hole transport material, poly-
N-vinylcarbazole and its derivatives, poly-γ-
Carbazolylethyl glutamate and its derivatives, pyrene-formaldehyde condensate and its derivatives, polyvinylpyrene, polyvinylphenanthrene, oxazole derivatives, oxadiazole derivatives, imidazole derivatives, monoarylamine derivatives, diarylamine derivatives, triarylamine derivatives, stilbenes derivative, α
-Phenylstilbene derivatives, benzidine derivatives, diarylmethane derivatives, triarylmethane derivatives, 9-
Other known materials such as styryl anthracene derivatives, pyrazoline derivatives, divinylbenzene derivatives, hydrazone derivatives, indene derivatives, and butadiene derivatives can be used. These charge transport substances may be used alone or in combination of two or more. Binder resins include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, and polychloride. Vinylidene, polyacrylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal,
polyvinyltoluene, poly-N-vinylcarbazole,
Examples include thermoplastic or thermosetting resins such as acrylic resins, silicone resins, epoxy resins, melamine resins, urethane resins, phenolic resins, and alkyd resins. Among these binder resins, especially bisphenol A
, bisphenol C, and bisphenol Z as bisphenol components can be suitably used. As the solvent, tetrahydrofuran, dioxane, toluene, monochlorobenzene, dichloroethane, methylene chloride, etc. are used. The thickness of the charge transport layer is 5 to 50μ
A value of about m is appropriate. In the present invention, a plasticizer or a leveling agent may be added to the charge transport layer. As the plasticizer, those used as plasticizers for general resins such as dibutyl phthalate and dioctyl phthalate can be used as they are, and the amount used is 0 to 3
Approximately 0% by weight is appropriate. As the leveling agent, silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, and polymers or oligomers having perfluoroalkyl groups in the side chains are used, and the amount used is 0 to 1 weight by weight based on the binder resin. % is appropriate. In the electrophotographic photoreceptor of the present invention, a subbing layer can be provided between the conductive support 11 and the photosensitive layer. The undercoat layer generally has a resin as its main component, but considering that the photosensitive layer is coated on top of it with a solvent, these resins need to be highly solvent resistant to common organic solvents. desirable. Examples of such resins include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, alcohol-soluble resins such as copolymerized nylon, and methoxymethylated nylon, polyurethane, melamine resins, phenolic resins, alkyd-melamine resins, and epoxy resins. Examples include curable resins that form a three-dimensional network structure, such as resins. In addition, fine powder pigments of metal oxides such as titanium oxide, silica, alumina, zirconium oxide, tin oxide, and indium oxide may be added to the undercoat layer to prevent moire and reduce residual potential. These subbing layers can be formed using a suitable solvent and coating method like the photosensitive layer described above. Furthermore, a silane coupling agent, a titanium coupling agent, a chromium coupling agent, etc. can also be used as the subbing layer of the present invention. In addition, the undercoat layer of the present invention may be provided with Al2O3 by anodic oxidation,
Organic substances such as polyparaxylylene (parylene) and SiO
, SnO 2 , TiO 2 , ITO, CeO 2 , and other inorganic materials formed by a vacuum thin film forming method can also be used satisfactorily. The thickness of the undercoat layer is suitably 0 to 5 μm. In the electrophotographic photoreceptor of the present invention, a protective layer may be provided on the photosensitive layer for the purpose of protecting the photosensitive layer. Materials used for this are ABS resin, ACS resin, olefin-vinyl monomer copolymer, chlorinated polyether, allyl resin, phenol resin, polyacetal, polyamide, polyamideimide, polyacrylate, polyallyl sulfone, polybutylene, poly Butylene terephthalate, polycarbonate, polyethersulfone, polyethylene, polyethylene terephthalate, polyimide, acrylic resin, polymethylpentene, polypropylene, polyphenylene oxide, polysulfone, polystyrene, AS resin, butadiene-styrene copolymer, polyurethane, polyvinyl chloride, polychloride Examples include resins such as vinylidene and epoxy resins. In addition, fluororesins such as polytetrafluoroethylene, silicone resins, and dispersions of inorganic materials such as titanium oxide, tin oxide, and potassium titanate in these resins are added to the protective layer for the purpose of improving wear resistance. can do. A normal coating method is adopted as a method for forming the protective layer. Note that the thickness of the protective layer is suitably about 0.5 to 10 μm. In addition to the above, known materials such as i-C and a-SiC formed by a vacuum thin film forming method can also be used as the protective layer. In the present invention, it is also possible to provide another intermediate layer between the photosensitive layer and the protective layer. The intermediate layer generally contains a binder resin as a main component. Examples of these resins include polyamide, alcohol-soluble nylon resin, water-soluble polyvinyl butyral resin, polyvinyl butyral, and polyvinyl alcohol. As a method for forming the intermediate layer, the usual coating method as described above is employed. Note that the thickness of the intermediate layer is suitably about 0.05 to 2 μm. Further, in the electrophotographic photoreceptor of the present invention, an antioxidant can be added for the purpose of improving environmental resistance, particularly for the purpose of preventing a decrease in sensitivity and an increase in residual potential due to an oxidizing environment. The antioxidant may be added to any layer containing an organic substance, but good results are obtained when it is added to a layer containing a charge transport substance. As the antioxidant that can be used in the present invention, known materials can be used, and in particular, commercially available products such as rubber, plastics, oils and fats can be used.

[0005]

[Examples] Next, examples will be shown, but the examples are for explaining the present invention in detail, and the present invention is not limited by the examples. Note that all parts in the examples are parts by weight.

Example 1 A charge generation layer coating liquid and a charge transport layer coating liquid having the following compositions were sequentially applied and dried on an aluminum plate with a thickness of 0.2 mm to form a charge generation layer with a thickness of 0.2 μm. , a charge transport layer having a thickness of 23 μm was formed. Charge generation layer coating liquid Azo pigment with the following structure

Part 3

[Chemical 1] Polyvinyl butyral (Denka Butyral #4000-1 manufactured by Denki Kagaku Kogyo Co., Ltd.)

Part 2 Cyclohexanone
8
0 parts 2-butanone

70 parts Charge transport layer coating liquid Charge transport substance having the following structure

7th part

[Chemical formula 2] Polycarbonate (Teijin Kasei Ltd. Panlite L-1250) 9 parts Tetrahydrofuran
85 parts The quantum efficiency measurement of the laminated photoreceptor of Example 1 and a sample prepared in the same manner with only a charge generation layer under the same conditions was carried out using an electrostatic copying paper tester (SP-428 manufactured by Kawaguchi Electric Manufacturing Co., Ltd.).
) was used. Exposure is 700nm monochromatic light, 2μ
It was set at w/cm2. The measurement results are shown in Figure 3. The laminated photoreceptor of Example 1 shows high quantum efficiency, indicating high sensitivity, and the quantum efficiency of the laminated photoreceptor is
It is clear that the quantum efficiency greatly exceeds the quantum efficiency of the same single charge generation layer. Next, the same laminated photoreceptor as in Example 1 was placed on an aluminum cylinder with an outer diameter of 80 mm, and this was mounted on a copying machine, Recopy FT4820, into which a surface electrometer terminal was inserted so that the surface potential could be measured immediately before development. Then, 5,000 sheets were continuously copied, and the surface potentials of the exposed and non-exposed areas on the photoreceptor were measured before and after copying. Table 1 shows the results.
Shown below.

Example 2 Coating liquids having the following compositions were coated on an aluminum plate with a thickness of 0.2 mm and dried to form a subbing layer of 1.5 μm thickness, a charge generation layer of 0.2 μm thickness, and a charge generation layer of 27 μm thickness. charge transport layers were sequentially provided. Undercoat layer coating liquid TiO2 powder (manufactured by Ishihara Sangyo Co., Ltd., Tipeque R-670) 15 parts Alcohol-soluble nylon (Amiran CM-4000, manufactured by Toray Industries)
6 parts methanol

50 parts ethanol

100 parts Charge generation layer coating liquid Azo pigment with the following structure

4th part

[Chemical formula 3] Cyclohexanone

100 parts tetrahydrofuran

40 parts Charge transport layer coating liquid Charge transport substance having the following structure

10 copies

[Chemical formula 4] Polycarbonate Z resin (Mitsubishi Gas Chemical Co., Ltd.)
(manufactured by) 12 parts toluene

90 copies

Example 3 A charge generation layer coating liquid and a charge transport layer coating liquid having the following compositions were sequentially coated and dried on an aluminum plate having a thickness of 0.2 mm to form a charge generation layer having a thickness of 0.3 μm. A charge transport layer of 29 μm thickness was formed. Charge generation layer coating liquid Azo pigment with the following structure

5th part

[Chemical formula 5] Polyester (Toyobo Byron 200)
4th part
Tetrahydrofuran

90 parts 2-butanone

70 parts Charge transport layer coating liquid Charge transport substance having the following structure

10 copies

[Chemical formula 6] Polycarbonate (Panlite K-1300 manufactured by Teijin Kasei Ltd.) 11 parts Dichloromethane

90 copies

0
Comparative Example 1 A charge generation layer coating liquid and a charge transport layer coating liquid having the following compositions were sequentially applied and dried on an aluminum plate with a thickness of 0.2 mm to form a charge generation layer with a thickness of 0.4 μm. , a charge transport layer with a thickness of 28 μm was provided. Charge generation layer coating liquid X-type metal-free phthalocyanine

5 parts Polyvinyl butyral (Sekisui Chemical Co., Ltd. S-LEC BL-1) 3 parts Cyclohexanone
8
0 parts 2-butanone

30 parts Charge transport layer coating liquid Charge transport substance having the following structure

7th part

[Chemical 7] Polycarbonate (same as Example 1)
11 parts Tetrahydrofuran

80 copies

Comparative Example 2 On an aluminum plate with a thickness of 0.2 mm, a subbing layer coating liquid, a charge generation layer coating liquid, and a charge transport layer coating liquid having the following compositions were sequentially applied and dried. 0.2 μm thick subbing layer, 0.25
A .mu.m thick charge generation layer and a 24 .mu.m thick charge transport layer were provided. Undercoat layer coating liquid methanol

80 parts n-butanol

20 copies
Alcohol-soluble nylon (Alamine CM-8000
(manufactured by Toray Industries) 3 parts Alcohol-soluble nylon was dissolved in a methanol/n-butanol mixed solvent having the above composition to prepare an undercoat layer coating solution. Charge generation layer coating liquid Azo pigment with the following structure

7th part

[Chemical formula 8] Polyester (Toyobo Byron 200)
0.5 part
Tetrahydrofuran

100 parts methyl isobutyl ketone

60 parts Charge transport layer coating liquid Charge transport substance having the following structure

9th part

[Chemical formula 9] Polycarbonate Z resin (same as Example 2)
10 copies
dioxane

85 parts Each of the photoreceptors of Examples 2 and 3 and Comparative Examples 1 and 2 and a single layer of the corresponding charge generation layer (However, the samples corresponding to Example 2 and Comparative Example 2 were also provided with an undercoat layer. ) was measured in the same manner as in Example 1. However, the exposure conditions are as shown in Table 2. The measurement results of quantum efficiency are shown in FIGS. 4 to 7. It is clear from FIG. 4 that the quantum efficiency of the laminated photoreceptor of Example 2 exceeds that of the single charge generation layer. FIG. 5 shows the quantum efficiency of the laminated photoconductor of Example 3. Since the sample with a single charge generation layer does not cause any optical attenuation, the quantum efficiency can be regarded as 0. Therefore, in this case as well, the quantum efficiency of the laminated photoreceptor exceeds that of a single charge generation layer. The results of Comparative Examples 1 and 2 are shown in FIGS. 6 and 7, respectively, and it can be seen that in both cases, the quantum efficiency of the laminated photoreceptor is lower than that of a single charge generation layer. Next, each of the laminated photoreceptors of Examples 2 and 3 and Comparative Examples 1 and 2 was placed on an aluminum cylinder with an outer diameter of 80 mm, and a test using a copying machine was conducted in the same manner as in Example 1. The results are shown in Table 3. show. Table 3

[0011]

According to the present invention, when the quantum efficiency of the laminated photoreceptor is higher than the quantum efficiency of the same single charge generation layer, the increase in residual potential is suppressed and the laminated electrophotographic photoreceptor exhibits little fluctuation. is provided. That is, in positive-positive development, it is possible to prevent staining of the background area, and in negative-positive development, it is possible to prevent a decrease in image density.

[Brief explanation of the drawing]

[Figure 1]

FIG. 2 is a schematic cross-sectional diagram showing an example of the layer structure of the electrophotographic photoreceptor of the present invention;

[Figure 3]

[Figure 4]

[Figure 5]

[Figure 6]

FIG. 7 is a graph showing the relationship between electric field and quantum efficiency for the electrophotographic photoreceptor and its comparative sample explained in each example and comparative example;

[Figure 8] Shows the relationship between the number of repeated uses and residual potential of an inorganic photoreceptor

FIG. 9 is a graph showing the relationship between the number of repeated uses and residual potential of a conventional organic photoreceptor.

Claims (1)

[Claims] Claim 1: In an electrophotographic photoreceptor comprising a charge generation layer and a charge transport layer laminated on a conductive substrate, the quantum efficiency of the photoreceptor is greater than or equal to the quantum efficiency of a single layer of the charge generation layer. Characteristic electrophotographic photoreceptor.