JPH10319613A - Electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor having satisfactory electrification ability and sensitivity and excellent in stability at the time of repetitive use. SOLUTION: This electrophotographic photoreceptor contains an electric charge generating material, an electric charge transferring material and a bonding resin in the same photosensitive layer. The electron affinity (EAg ) of the electric charge generating material is higher than that (EAc ) of an electron transferring material and the ionization potential (Ipg ) of the electric charge generating material is lower than that (Iph ) of a hole transferring material. It is preferable that the electric charge generating material contains a titanium phthalocyanine compd. from the viewpoint of characteristics.

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 having good chargeability and sensitivity and excellent stability when repeatedly used.

[0002]

2. Description of the Related Art Generally, an electrophotographic photoreceptor is formed by forming a photosensitive layer made of a photoconductive material on a conductive substrate. In many cases, a laminated electrophotographic photoreceptor having a function-separated photoconductive layer composed of a photoconductive layer and a charge transport layer is used.

[0003] However, a general laminated electrophotographic photoreceptor generally has a charge transport layer composed of a relatively thick layer laminated on a thin charge generation layer having a thickness of 1 μm or less.
The difficulty in forming a thin film of the charge generation layer is a factor that lowers the yield. The charge transport material used for the charge transport layer is
Because of the abundance of compounds, electrical stability, and safety as a material, it is common to use a hole-transporting material.
Inevitably, sensitivity can be expressed only by negative charging.

In recent years, simplification of the production process has become a major issue in order to meet cost reduction demands. In addition, the influence of a large amount of ozone generated during negative corona discharge is considered to be an environmental problem, and it is desired to realize a positively charged electrophotographic photoreceptor that can be used in positive corona discharge with a small amount of generated ozone.

[0005] In response to such a demand for an electrophotographic photoreceptor, a conventional single-layer type electrophotographic photoreceptor is re-evaluated due to its advantages such as its simple layer structure and the possibility of use in positive charging. It is becoming. Therefore, attempts to realize a practical single-layer type electrophotographic photoreceptor have been actively made again, but none which can sufficiently satisfy the demand has not yet been realized.

For example, for a single-layer type electrophotography using a poly-N-vinylcarbazole (PVK) / trinitrofluorenone (TNF) complex disclosed in US Pat. No. 3,484,237, which was first practically used as an organic compound. The photoreceptor has problems such as insufficient mechanical strength of PVK as a main component, poor sensitivity due to low charge mobility, and strong toxicity of TNF.

[0007] Also, "Journal of Applied
Physics ”(Journal of Applied Physics) No. 49
No. 11, pp. 5543-5564 (1978), the electrophotographic photoreceptor in which a hole transport material is used in combination with a eutectic of a thiapyrylium salt and a polycarbonate resin is limited in usable materials. Because of this, it is difficult to improve the characteristics, and the sensitivity wavelength range is narrow, and there is no sensitivity in the long wavelength range. .

Further, as in the phthalocyanine / resin-dispersion type electrophotographic photoreceptor disclosed in US Pat. No. 3,397,086, for electrophotography, a photoconductive pigment is dispersed in an electrically insulating binder. The photoreceptor has a so-called induction effect in which charge traps, which are inevitably formed on the pigment surface, are present in the photosensitive layer at a high density, causing a delay from light irradiation to potential decay, and the photoresponse characteristics are greatly improved. There is a drawback that the optical decay curve itself is completely different from a normal laminated photoreceptor, and compatibility cannot be obtained. In addition, when used repeatedly, electric charge is accumulated in the trap, causing a change in the induction effect itself, and there has been a problem that stable characteristics cannot be continuously obtained. For this reason, this type of electrophotographic photosensitive member is currently used only as a disposable plate-making photosensitive member.

Thus, for example, Japanese Patent Application Laid-Open No. 54-1633 discloses that a charge-generating substance such as phthalocyanine is combined with a hole-transporting substance such as oxadiazole and an electron-transporting substance such as dinitrofluorenone in a binder resin. A single-layer type electrophotographic photosensitive member in which a dispersed photosensitive layer is provided on a conductive support is disclosed. This type of electrophotographic photoreceptor is different from the conventional phthalocyanine / resin dispersion type single-layer type electrophotographic photoreceptor in that charge generation and charge transport are performed by the same material, unlike charge transport and charge generation. Is applied to different materials, so that the concentration of the charge-generating substance can be significantly reduced as compared to the past.
In addition, there is an advantage that a photosensitive member having both positive and negative charges can be realized.
For this reason, an electrophotographic photoconductor having such a configuration is
For example, JP-A-61-48861, JP-A-63-8861
No. 246,749, JP-A-1-107266,
As seen in Japanese Patent Application Laid-Open No. 2-7059, active practical studies are being made.

[0010]

Conventionally, in a function-separated type electrophotographic photoconductor, for example, "IEEE Transactions on Industry Applications"
IA-17, Vol. 4, No. 382-386 (198
1 year), it is necessary that the ionization potential of the charge-generating substance is larger than that of the charge-transporting substance so as to prevent a barrier for charge injection from the charge-generating substance to the charge-transporting substance. It has been considered common sense. However, in the case of a photoreceptor having a configuration in which a charge generating material is dispersed in a charge transporting material as described above, for example, JP-A-2-37354 discloses that the ionization potential of the charge transporting material is larger than that of the charge generating material. It has been disclosed that such a relationship between the magnitudes of the ionization potentials does not always show a good result, as disclosed in Japanese Patent Application Laid-Open No. H11-27566, by which the potential stability of the photoreceptor can be improved.

Further, the value of the ionization potential indicates the HOMO level of the material, and originally relates to the transport of positive charges, and is an important factor for the photoelectric conversion function of such a photoconductor. No clue was obtained regarding the relationship with the LUMO level involved in the transport of negative charges. Therefore, as shown in the examples described later, it is apparent that the photoreceptor performance satisfying the required characteristics cannot be obtained only by specifying the magnitude relation of the ionization potential.

The problem to be solved by the present invention is to improve various problems which have been encountered in the conventionally proposed single-layer type electrophotographic photoreceptor, and to improve electrical characteristics such as chargeability, sensitivity and repetition stability. An object of the present invention is to provide a means for realizing an excellent and preferable electrophotographic photosensitive member.

[0013]

According to the present invention, there is provided an electrophotographic photosensitive member containing a charge generating material, an electron transporting material and a hole transporting material in the same photosensitive layer. When the electron affinity and ionization potential of the generated substance are E _Ag and I _pg , respectively, and the electron affinity of the electron transport substance and the ionization potential of the hole transport substance are E _Ae and I _ph , respectively, E _Ag is E _Ae greater than, and I _pg to provide an electrophotographic photoreceptor, characterized in that less than I _ph.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The electrophotographic photoreceptor of the present invention contains a charge generating substance, an electron transporting substance and a hole transporting substance in the same photosensitive layer so as to satisfy the above relationship. It is only necessary that a photosensitive layer containing these is formed on the conductive substrate.

The photosensitive layer may be composed of only a charge generating substance, an electron transporting substance, and a hole transporting substance. When a higher degree of adhesiveness to the substrate is required in terms of properties, a binder resin is used in combination. In the present invention, a typical photosensitive layer is composed of each of the above substances and a binder resin.

FIG. 1 shows an example of the structure of the photosensitive layer of the electrophotographic photosensitive member of the present invention. Here, the thickness of the photosensitive layer is 5 to 50.
The range of μm is preferred. When the photosensitive layer is formed by dip coating, a desired thickness can be easily obtained by adjusting various physical properties such as a coating speed, a viscosity of a paint, and a cutting power. In addition, in addition to the single-layered photosensitive layer, a functional layer such as an intermediate layer or a surface protective layer may be appropriately used.

In the electrophotographic photoreceptor of the present invention, a mixture of an electron transporting substance and a hole transporting substance is used.

Examples of the electron transport material include organic compounds such as benzoquinone, tetracyanoethylene, tetracyanoquinodimethane, fluorenone, xanthone, phenanthraquinone, phthalic anhydride, and diphenoquinone. , Amorphous silicon, amorphous selenium, tellurium, selenium-tellurium alloy, cadmium sulfide,
Examples include inorganic materials such as antimony sulfide, zinc oxide, and zinc sulfide.

As the hole transport material, low-molecular compounds include, for example, pyrene, carbazole, hydrazone, oxazole, oxadiazole, pyrazoline, arylamine, arylmethane, benzidine and thiazole compounds. , Stilbene compounds, butadiene compounds and the like. Examples of the polymer compound include, for example, poly-N-vinylcarbazole, halogenated poly-
Examples thereof include N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, pyrene-formaldehyde resin, ethylcarbazole-formaldehyde resin, ethylcarbazole-formaldehyde resin, triphenylmethane polymer, and polysilane.

The charge transport material used in the present invention is not limited to those listed here, and can be used alone or as a mixture of two or more.

The charge generating substance used in the present invention includes:
For example, azo pigments, quinone pigments, perylene pigments,
Indigo pigment, thioindigo pigment, bisbenzimidazole pigment, phthalocyanine pigment, quinacridone pigment, quinoline pigment, lake pigment, azo lake pigment, anthraquinone pigment, oxazine pigment, dioxazine pigment, triphenylmethane pigment Various organic pigments and dyes such as pigments, azulenium dyes, squarium dyes, pyrylium dyes, triallylmethane dyes, xanthene dyes, thiazine dyes, cyanine dyes, and amorphous silicon, amorphous selenium,
Inorganic materials such as tellurium, selenium-tellurium alloy, cadmium sulfide, antimony sulfide, zinc oxide, and zinc sulfide can be mentioned, and titanium phthalocyanine compounds are particularly preferable in terms of characteristics.

As the charge generating substance, the ones listed here can be used alone, or two or more kinds of charge generating substances can be used in combination.

The ratio of the charge generating substance to the solid content in the coating material is preferably in the range of 0.2 to 5% by weight. If the ratio of the charge generating substance to the solid content in the paint is less than 0.2% by weight, the sensitivity of the obtained electrophotographic photoreceptor tends to decrease. When the ratio of the charge generating substance to the total amount is more than 5% by weight, the obtained electrophotographic photoreceptor tends to have a reduced charge holding ability and a reduced charge transportability, which is not preferable.

The binder resin is preferably a high molecular polymer capable of forming an electrically insulating film. Such polymers include, for example, polycarbonate, polyester,
Methacrylic resin, acrylic resin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl acetate, styrene-butadiene copolymer, vinylidene chloride
Acrylonitrile polymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicon resin, silicon-alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-N-vinylcarbazole , Polyvinyl butyral, polyvinyl formal, polysulfone, casein, gelatin, polyvinyl alcohol, ethyl cellulose, phenolic resin, polyamide, carboxy-methyl cellulose, vinylidene chloride-based polymer latex, polyurethane, and the like, but are not limited thereto. These binder resins are used alone or in combination of two or more.

In addition to these binder resins, additives such as a dispersion stabilizer, a plasticizer, a surface modifier, an antioxidant, and a light deterioration inhibitor can be used.

Examples of the plasticizer include biphenyl, biphenyl chloride, terphenyl, dibutyl phthalate, diethylene glycol phthalate, dioctyl phthalate, triphenylphosphoric acid, methylnaphthalene, benzophenone, chlorinated paraffin, polypropylene, polystyrene, and various fluorohydrocarbons. No.

Examples of the surface modifier include silicone oil, fluororesin and the like.

Examples of the antioxidant include phenol-based, sulfur-based, phosphorus-based, and amine-based antioxidants.

Examples of the photo-deterioration inhibitor include benzotriazole compounds, benzophenone compounds, hindered amine compounds and the like.

Examples of the solvent used in the paint for forming the photoreceptor of the present invention by a coating method include alcohols such as methanol, ethanol and n-propanol; ketones such as acetone, methyl ethyl ketone and cyclohexanone; Amides such as dimethylformamide and N, N-dimethylacetamide; ethers such as tetrahydrofuran, dioxane and methyl cellosolve; esters such as methyl acetate and ethyl acetate; sulfoxides and sulfones such as dimethyl sulfoxide and sulfolane; methylene chloride; Examples include aliphatic halogenated hydrocarbons such as chloroform, carbon tetrachloride, and trichloroethane; and aromatics such as benzene, toluene, xylene, monochlorobenzene, and dichlorobenzene.

As the conductive substrate on which the photosensitive layer is provided, any known and commonly used conductive substrate can be used, for example, aluminum, copper, zinc, various alloys, or paper or synthetic resin film on which they are adhered. Can be used. The shape may be arbitrary, and examples thereof include a flat plate and a cylinder.

The ionization potential defined in the present invention means the amount of energy required to extract one electron from the ground state of a material. In order to measure this characteristic value, for example, methods such as a vacuum ultraviolet absorption method, an electron impact method, a photoionization method, and a photoelectron spectrum method are known, and the absolute value shows a slight variation depending on the measurement method. In some cases, however, the relative magnitude relationship does not reverse in principle. In general, a device for measuring a photoelectron spectrum emitted by irradiating ultraviolet rays in an air atmosphere (for example, a surface analysis device AC-1 manufactured by Riken Keiki Co., Ltd.) is widely used because of its simplicity, and will be described later. All the measured values of the ionization potential in the examples were measured by the same method.

The electron affinity defined in the present invention is:
It means the amount of energy required to extract one electron from the negative ions of the material. It is usually difficult to directly measure this characteristic value, and it is common to indirectly determine it by an electrochemical method. In the present invention, based on the assumption that the electron affinity is equivalent to the LUMO level, the ionization potential (HOMO level), which can be easily measured, and the H
The difference in the value calculated from the absorption edge wavelength of the optical spectrum of a material considered to represent the OMO-LUMO transition energy was defined as the electron affinity. That is, it is considered that the following equation holds between the optical absorption coefficient α, the light energy hν, and the transition energy E ₀ .

[0034]

[Equation 1] αhν = B (hν−E ₀ ) ² (where B is a constant)

A plot of (αhν) ^1/2 versus hν (the so-called Tauc
Plot) and extrapolate the linear section to h
next value transition energy E ₀ of the [nu, electron affinity E _A can be determined from the ionization potential I _p, the following equation.

[0036]

[Equation 2] E _A = I _p −E ₀

In the electrophotographic photoreceptor of the present invention, the charge generating substance has a higher electron affinity than the electron transporting substance.
Further, the ionization potential of the charge generating substance must be smaller than that of the hole transporting substance. In order for the electron affinity and ionization potential to be in the magnitude relationship specified in the present invention, it is necessary to perform the above measurement for each material and select a combination of materials that satisfies these measurements. When used, the effect can be obtained even if only the functional main components satisfy the range defined by the present invention.

The present invention includes the following embodiments: 1. In an electrophotographic photoreceptor containing a charge generating substance, an electron transporting substance and a hole transporting substance in the same photosensitive layer,
A charge electron affinity and the ionization potential each E _Ag of generating substance, I _pg, electron affinity of the electron transporting material, and the ionization potential each E _Ae of the hole transport material, when it is I _ph, the E _Ag Larger than E _Ae ,
And an electrophotographic photoconductor, wherein I _pg is smaller than I _ph .

2. An electrophotographic photoreceptor containing a charge generating substance, an electron transporting substance, a hole transporting substance, and a binder resin in the same photosensitive layer, wherein the charge generating substance has an electron affinity and an ionization potential of E _Ag and I, respectively. _pg , and when the electron affinity of the electron transport material and the ionization potential of the hole transport material are E _Ae and I _ph , respectively,
An electrophotographic photoconductor, wherein E _Ag is larger than E _Ae and I _pg is smaller than I _ph .

3. 3. The photoconductor according to the above 1 or 2, wherein the charge generating substance contains a titanium phthalocyanine compound.

A preferred embodiment of the present invention is as follows. First, the electron affinity and the ionization potential of the charge generating substance composed of a titanium phthalocyanine-based compound were E _Ag and I _pg , respectively, and the electron affinity of the electron transport substance and the ionization potential of the hole transport substance were E _Ae and I _ph , respectively. At this time, each is selected such that E _Ag is larger than E _Ae and I _pg is smaller than I _ph .

Next, an electrically insulating film-forming polymer capable of dispersing the charge generating material and dissolving the electron transporting material and the hole transporting material, and dissolving the polymer. Select a solvent. A paint is prepared by mixing these as essential components, but per solid content in the paint,
0.2 to 5% by weight of the charge generating material, 5 to 20% by weight of the electron transporting material, 30 to 45% by weight of the hole transporting material, 45 to 80% by weight of the polymer, Mix so as to obtain a weight percent and make it uniform. If necessary, an antioxidant, a photodegradation inhibitor and the like are included.

The coating material thus obtained is uniformly applied on a cylindrical conductive substrate so as to have a thickness of 5 to 50 μm after drying, and is sufficiently dried, whereby the photosensitive layer is supported. A single-layer electrophotographic photoreceptor sufficiently adhered to the body can be obtained. If necessary, on the photosensitive layer, a surface protective layer having more excellent adhesion and more excellent durability is provided.

[0044]

In the electrophotographic photoreceptor of the present invention, the electron affinity of the charge generating substance is larger than the electron affinity of the electron transport substance, and the ionization potential of the photoreceptor is smaller than that of the conventional general photoreceptor. It has the characteristic that it is smaller than the ionization potential, thereby realizing favorable electrical characteristics in terms of chargeability, sensitivity, repetition stability and the like. The reason will be described below.

In a photoconductor such as the electrophotographic photoconductor of the present invention in which a charge generating substance, a hole transporting substance and an electron transporting substance are contained in the same photosensitive layer, the bonding of the charge generating substance and the charge transporting substance is performed. The state becomes the pigment surface from the interface of the layers in the ordinary laminated photoreceptor, and the contact area thereof increases by orders of magnitude. Therefore, the energy compatibility of the charge injection from the charge generating material to the charge transporting material has a further influence on the characteristics. For example, in the conventional photoreceptor, it has been considered that in the relationship between the ionization potential of the charge generation material and the hole transport material, if the charge generation material side is large, there is no barrier for hole injection and high sensitivity can be obtained. In the case of the photoreceptor having the structure as in the present invention, it has been found that, on the contrary, since there is no injection barrier, a defect that free charge is easily injected and charge retention is deteriorated is caused. In addition, it was also found that the electron affinity between the charge generating material and the electron transporting material also required that the charge generating material side be large in order to have appropriate charge retention. That is, the photoreceptor of the present invention is greatly characterized in that a barrier against charge injection is positively introduced to suppress the movement of free charges which causes a reduction in chargeability.

This structural feature is particularly remarkable in the potential stability during repeated use. Normally, the repetition characteristics of a single-layer type photoreceptor are particularly likely to be accompanied by a decrease in chargeability. This can be interpreted as that electrons trapped in the traps at the deep level act on the interface between the charge generating material and the charge transporting material, lowering the energy barrier due to the heterojunction, and eliminating free charge binding. In the configuration of the present invention, since a stable barrier is formed at the same time with respect to the injection of electrons and holes in terms of energy level, it can be assumed that relatively stable charge retention can be achieved even after repetition. Is done.

Satisfaction of the energy state defined by the present invention depends on electrons from the charge generating substance to the charge transporting substance,
Since a barrier is provided when holes are injected, the sensitivity is expected to be disadvantageous according to the conventional theory, but it is surprising that the sensitivity actually increases. found. This is because, in the case of a laminated photoreceptor, the local electric field due to the Schottky junction at the interface between the substrate and the charge generation layer contributes to ion pair dissociation, resulting in a sensitizing effect. Since charge generation is performed on the light incident surface side, it is considered that such a bonding state does not exist there. In other words, in the dissociation of the ion pair in this case, only the electric field formed by charging and the heterojunction at the interface between the charge generating substance and the charge transporting substance function, so by providing an appropriate energy difference here, It is considered that the formation of an effective local electric field causes sensitization.

[0048]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the examples. In the following examples and comparative examples, “parts” indicates “parts by weight”.

(Measurement of Ionization Potential) The ionization potentials of the charge generating substance, the electron transporting substance and the hole transporting substance used in each of the examples and comparative examples were measured using an air atmosphere type ultraviolet photoelectron analyzer (AC manufactured by Riken Keiki Co., Ltd.). −
Using 1), the measurement was performed under the environmental conditions of 23 ° C. and 50% RH.

(Measurement of Electron Affinity) The ultraviolet and visible light absorption spectra of the charge generating substance and the electron transporting substance used in each of Examples and Comparative Examples were measured using a spectrophotometer (U-3410 manufactured by Hitachi, Ltd.). And then (αhν) ^1/2
Is plotted, and the value of hν at α = 0 is obtained by extrapolating a straight line section, and HOMO-L
UMO transition energy was obtained. The value obtained by subtracting this value from the value of the ionization potential obtained earlier was used as the respective electron affinity.

(Example 1) 0.3 parts of α-type titanyl phthalocyanine (I _pg = 5.35 eV, E _Ag = 4.00 eV), formula (1)

[0052]

Embedded image

The electron transport material represented by the formula (E _Ae = 2.83e)
V) 3 parts, formula (2)

[0054]

Embedded image

The hole transport material represented by the formula (I _ph = 5.50 eV)
10 parts and 14 parts of a polycarbonate resin (“Iupilon Z-200” manufactured by Mitsubishi Gas Chemical Company) were mixed with chloroform 7
The resultant was dissolved in 6 parts and dispersed using a vibration mill to prepare a coating for a photoreceptor.

Using this coating material, dip coating was applied to the surface of an aluminum pipe having a diameter of 30 mm so that the film thickness after drying was 20 μm, and then dried to form a photosensitive layer. A photoreceptor was obtained.

(Example 2) In Example 1, the formula (3) was used as an electron transporting substance.

[0058]

Embedded image

An electrophotographic photoreceptor was obtained in the same manner as in Example 1, except that the compound represented by the formula (E _Ae = 3.24 eV) was used.

(Example 3) In Example 1, the compound represented by the formula (4) was used as the hole transport material.

[0061]

Embedded image

An electrophotographic photoreceptor was obtained in the same manner as in Example 1 except that the compound represented by the following formula (I _ph = 5.45 eV) was used.

(Examples 4 to 6) In Examples 1 to 3,
Formula (5)

[0064]

Embedded image

An electrophotographic photoreceptor was obtained in the same manner except that a pigment (I _pg = 5.20 eV, E _Ag = 3.82 eV) comprising a titanium phthalocyanine-based compound represented by the following formula was used.

(Comparative Example 1) In Example 1, an electron transporting material represented by the formula (6)

[0067]

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An electrophotographic photoreceptor was obtained in the same manner as in Example 1 except that the compound represented by the formula (E _Ae = 4.12 eV) was used.

Comparative Example 2 In Example 1, the compound represented by the formula (7) disclosed in JP-A-62-134651 was used as a hole transport material.

[0070]

Embedded image

An electrophotographic photoreceptor was obtained in the same manner as in Example 1 except that the compound represented by the formula (I _pg = 5.26 eV) was used.

(Comparative Example 3) In Example 4, as the electron transporting substance, the formula (8) disclosed in "Journal of Imaging Science and Technology", Vol. 39, No. 1,

[0073]

Embedded image

An electrophotographic photoreceptor was obtained in the same manner as in Example 4 except that the compound represented by the following formula (E _Ae = 3.85 eV) was used.

Comparative Example 4 In Example 4, the compound represented by the formula (9) disclosed in JP-A-62-30255 was used as a hole transporting substance.

[0076]

Embedded image

A photoconductor for electrophotography was obtained in the same manner as in Example 4, except that the compound represented by the following formula (I _pg = 5.10 eV) was used.

Table 1 shows the relationship between the electron affinity and the ionization potential of the charge generating substance, electron transporting substance and hole transporting substance of each photoreceptor.

[0079]

[Table 1]

(Electrical Characteristics) In order to evaluate the electrical characteristics of the electrophotographic photoreceptors obtained in each of the examples and comparative examples, each of the drum photoreceptors was tested by using a drum photoreceptor test apparatus (“Cynthia” manufactured by Gentec Corporation). 30 ") was used to measure the electrophotographic properties. The measuring method was such that the drum photoreceptor was charged by corona discharge at an applied voltage of +6 kV while rotating at 60 rpm in a dark place, and the surface potential immediately after this was used as an initial potential V ₀ for evaluation of charging ability. Next, to measure the potential V ₁₀ after leaving for 10 seconds in the dark, was evaluated potential holding ability by V ₁₀ / V _0. Next, the exposure intensity on the surface was set to 1 μW / cm ² with 780 nm monochromatic light, and the photosensitive layer was irradiated with light, and the decay curve of the surface potential was recorded.
Here, the surface potential by light irradiation determined amount of exposure until reduced to 1/2 of V _10, were evaluated sensitivity as half decay exposure E _1/2. Immediately after repeating the process of removing electricity by applying energy of 150 erg / cm ² with a light emitting diode having a wavelength of 700 nm after charging 500 times, the same measurement was performed to evaluate the repetition stability. The results are summarized in Tables 2 and 3.

[0081]

[Table 2]

[0082]

[Table 3]

As is clear from the results shown in Tables 2 and 3, the electrophotographic photoreceptors obtained in Examples 1 to 6 of the present invention naturally show differences in characteristics depending on the types of charge generating substances. However, in comparison between photoreceptors using the same charge generating substance, all showed excellent charging ability, sensitivity, and repetition stability. On the other hand, Comparative Examples 1 and 2 in which the same charge-generating substance as in Examples 1 to 3 were used and the electron affinity of the electron-transporting substance was larger than that of the charge-generating substance, and Comparative Examples in which the ionization potential of the hole-transporting substance was smaller than that of the charge-generating substance Each of the electrophotographic photoreceptors No. 2 had a low charging ability and was significantly inferior in sensitivity. In addition, the repetition stability was remarkably inferior, and the practicability was found to be extremely poor.

This tendency was the same in the electrophotographic photosensitive members obtained in Comparative Examples 3 and 4 in which the kind of the charge generating material was changed. Both the electron transporting material and the hole transporting material used in these comparative examples have been confirmed to have good charge transportability, and it is clear that they are not inferior in terms of charge transport. These results demonstrate the specific effects of the configuration of the present invention.

[0085]

The electrophotographic photoreceptor of the present invention has excellent productivity, high image quality in which no defects appear on the image, and good electrostatic characteristics showing excellent sensitivity and chargeability. It is a photosensitive member for electrophotography that is excellent in stability during use and is practically preferable.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating an example of a layer configuration of an electrophotographic photoconductor of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 conductive support (conductive substrate) 2 charge generating substance 3 electron transporting substance + hole transporting substance + binder resin 4 photosensitive layer

Claims (3)

[Claims] 1. An electrophotographic photoreceptor containing a charge generating substance, an electron transporting substance and a hole transporting substance in the same photosensitive layer, wherein the charge generating substance has an electron affinity and an ionization potential of E _Ag and I _pg , respectively. When the electron affinity of the electron transport material and the ionization potential of the hole transport material are E _Ae and I _ph , respectively, it is determined that E _Ag is larger than E _Ae and I _pg is smaller than I _ph. A photoconductor for electrophotography, characterized by: 2. An electrophotographic photosensitive member containing a charge generating substance, an electron transporting substance, a hole transporting substance and a binder resin in the same photosensitive layer, wherein the charge generating substance has an electron affinity and an ionization potential. When E _Ag and I _pg are respectively, and the electron affinity of the electron transport material and the ionization potential of the hole transport material are E _Ae and I _ph , respectively, E _Ag is larger than E _Ae and I _pg is I _pg. An electrophotographic photoreceptor characterized by being smaller than _ph . 3. The photoconductor according to claim 1, wherein the charge generating substance contains a titanium phthalocyanine compound. [0001]