JP2000019746A - Negatively charged single layer type electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a defect in a photoreceptor mounted directly with a negative charge type single layer photosensitive layer on a conductive substrate, and to form an image of high quality without generating a fog and a black point. SOLUTION: In this photoreceptor, a conductive substrate has a work function (w) satisfying a formula LETH+α<=W<=HHTM-β, where the LETM represents ionization energy (eV) corresponding to the lowest unoccupied orbit of an electron transporting agent, α is 0.35 eV, HHTM represents ionization energy corresponding to the highest occupied orbit of a positive hole transporting agent, βis 0.14 eV, in a single layer type electrophotographic photoreceptor mounted directly on the conductive substrate with a photosensitive layer in which at least a charge generating pigment, the electron transporting agent and the positive hole transporting agent are dispersed in a binder resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negatively charged single-layer type electrophotographic photoreceptor which is easy to manufacture, has no fog or black spots, and can form a high quality image. Negatively charged single-layer type electrophotographic photoreceptor for use in printers, printers, and plain paper fax machines.

[0002]

2. Description of the Related Art In an electrophotographic method, an electrophotographic photosensitive member is charged, an image is exposed to form an electrostatic latent image, and the electrostatic latent image is developed with toner while a developing bias voltage is applied. The formed toner image is transferred onto a transfer paper or the like and fixed to form an image. This electrophotographic method is widely used for digital or analog copying, printers, and plain paper FAX.

A selenium photoreceptor and an amorphous silicon photoreceptor have conventionally been used as a photoreceptor used in the electrophotography, but an organic photoreceptor (OPC) has recently been widely used. Organic photoreceptors include a charge generator (CG
M) and a charge-transporting agent (CTM) are stacked as separate layers, and a function-separated-type stacked photoconductor and a single-layer photoconductor provided with CGM and CTM as a single dispersion layer are typical examples. . A positive charging type and a negative charging type are known as the laminated photoreceptor and the single-layer photoreceptor, respectively.

[0004] In a single-layer type photoreceptor, the use of a combination of an electron transporting agent and a hole transporting agent as a charge transporting agent has been quite generalized.
No. 1474 discloses a single-layer organic photoreceptor provided directly or via an undercoat layer on a conductive substrate, and the photosensitive layer comprises at least a charge generation material, an electron transport material, and a hole transport material. A negatively charged single-layer type electrophotographic photoreceptor is disclosed in which the ratio of the electron transporting substance to the hole transporting substance is 3: 2 to 50: 1 (weight ratio) dispersed in an adhesive.

[0005]

However, the above-mentioned negatively charged laminated photoreceptor requires two or more coatings of the photosensitive layer, even though the performance is generally satisfactory.
There is a problem that productivity is low.

In addition, although a single-layer type photoreceptor has a subbing layer provided on a conductive substrate, there is also a problem that productivity is low because the coating process is performed twice. Thus, from the viewpoint of productivity, it is desirable to provide the photoconductor layer directly on the conductive substrate.

However, when a negatively charged single-layer photosensitive layer is provided directly on a conductive substrate, depending on the material of the substrate,
It is often observed that fog and black spots occur. The occurrence of such fog and black spots is a peculiar phenomenon observed only when the negatively charged single-layer photosensitive layer is provided directly on the conductive substrate. This is never observed in a single-layer type photoreceptor provided with a drawing layer.

Accordingly, an object of the present invention is to eliminate the above-mentioned disadvantages of a photoreceptor in which a negatively charged single-layer photosensitive layer is provided directly on a conductive substrate, and to provide a high-quality image without fogging or black spots. An object of the present invention is to provide a negatively charged single-layer type electrophotographic photosensitive member that can be formed. Another object of the present invention is to provide a negatively charged single-layer type electrophotographic photoreceptor excellent in productivity, in which a photosensitive layer is formed by only one coating operation.

[0009]

According to the present invention, there is provided a photoconductor comprising at least a photosensitive layer in which at least a charge generating pigment, an electron transporting agent and a hole transporting agent are dispersed in a binder resin, which is directly provided on a conductive substrate. In the layer-type electrophotographic photoreceptor, the conductive substrate is formed by the following formula (I) L _ETM + α ≦ W ≦ H _HTM -β (I) where L _ETM is an energy level corresponding to the lowest unoccupied orbit of the electron transporting agent. (EV), α is 0.35 eV,
H _HTM represents an energy level (eV) corresponding to the highest occupied orbit of the hole transporting agent, and β has a work function (W) satisfying 0.14 eV. A layer type electrophotographic photoreceptor is provided. According to the present invention, there is also provided a single-layer type electrophotographic photoreceptor comprising a photosensitive layer in which at least a charge generation pigment, an electron transporting agent and a hole transporting agent are dispersed in a binder resin, and which is directly provided on a conductive substrate. When the conductive substrate has the following formula (II): L _CG + K ≦ W ≦ H _CG -J (II) where L _CG represents an energy level (eV) corresponding to the lowest unoccupied orbit of the charge-generating pigment; Is 0.48 eV,
H _CG represents energy level (eV) corresponding to the highest occupied molecular orbital of the photogenerating pigment, negatively charged single-layer, wherein J is has a work function (W) satisfying the a 0.05eV An electrophotographic photoreceptor is provided.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Operation] The negatively charged single-layer type electrophotographic photoreceptor of the present invention comprises a photosensitive layer in which at least a charge generation pigment, a hole transporting agent and an electron transporting agent are dispersed in a binder resin. It is provided directly on the substrate, but is related to the energy level corresponding to the lowest unoccupied orbital (LUMO) of the electron transporting agent used and the energy level corresponding to the highest occupied orbital (HOMO) of the hole transporting agent. Conductivity or a work function in a certain range, in relation to the energy level corresponding to the lowest unoccupied orbital (LUMO) and the energy level corresponding to the highest occupied orbital (HOMO) of the charge generating pigment used A substrate is selected and combined with this single layer photosensitive layer.

The molecular orbital (MO) has an occupied orbit and an unoccupied orbit. Among the occupied orbitals, the most unstable (uppermost) orbit is the highest occupied orbit, so-called HOMO. The most stable (lowest) orbit of the orbit is the lowest empty orbit, so-called LUMO. These HOMO and L
The UMO was named the frontier orbit by the late Professor Fukui, and it has long been pointed out that it has an important meaning in reactions involving electrons.
In the molecular orbital method, the orbital energy generally shows a negative value (indicating that it is more stable than the ground state)
However, the energy level of each orbit determined by photoelectron spectroscopy is equal to the sign of the orbital energy of that orbit (Koopmans' theorem). On the other hand, the work function is a work required to transfer electrons in a solid at the Fermi level to a vacuum outside the solid, and is expressed in units of eV.

In the present specification, the above energy levels and work functions are actually measured values or calculated values based on the actually measured values, and are measured by the following method. (1) Energy level corresponding to the highest occupied orbit It is measured by atmospheric photoelectron spectroscopy.
It is measured by atmospheric photoelectron spectroscopy, specifically, directly using a low-energy electron counting method using a surface analyzer AC-1M manufactured by Riken Keiki Co., Ltd. (2) Energy level corresponding to lowest unoccupied orbit e of energy level corresponding to lowest unoccupied orbit of electron transport agent
The following is performed for the purpose of V conversion. First, measurement of the ionization potential (energy level corresponding to the highest occupied orbit) of the hole transport agent ^{* 1} and measurement of the oxidation potential of the hole transport agent in the electrolyte solution ^{* 2} are performed. The result is shown in FIG. A first order correlation was recognized between the energy unit of the hole transporting agent and the oxidation potential, and the ionization potential of the Ag / AgNO ₃ reference electrode was calculated to be 4.74 eV. * 1 By atmospheric photoelectron spectroscopy * 2 By three-electrode type cyclic voltametry (Measurement of reduction potential) The reduction potential was measured by the following materials using three-electrode type cyclic voltametry. Electrode: working electrode (glassy carbon electrode), counter electrode (platinum electrode) Reference electrode: silver silver nitrate electrode (0.1 mol / liter A)
gNO ₃ -acetonitrile solution) Measurement solution Electrolyte: 0.1 mol of t-butylammonium perchlorate Measurement substance: 0.001 mol of electron transport agent Solvent: 1 liter or more of CH ₂ Cl ₂ was prepared to prepare a measurement solution. Calculation of reduction potential:
As shown in FIG. 2, the relationship between the index voltage (V) and the current (μA) was determined, E1 and E2 shown in the figure were measured, and the reduction potential was determined by the following formula. Reduction potential = (E1 + E2) / 2 (V) Then, the reduction potential of the electron transport agent was measured ^{* 2} , and Ag / Ag
An energy unit value of the NO ₃ reference electrode of 4.74 (eV) is added to perform eV conversion. The converted value was defined as an energy level corresponding to the lowest unoccupied orbit of the electron transporting agent (Table 2). Regarding the pigment (XH ₂ Pc), the energy level with respect to the highest occupied orbit was determined by photoelectron spectroscopy under the atmosphere in the same manner as the hole transporting agent. The energy level for the lowest unoccupied orbit is the maximum absorption wavelength of the pigment (λ _max = 810 min → 1.53 eV).
). (3) Work function Measured by atmospheric photoelectron spectroscopy, specifically, directly measured using a surface analysis apparatus AC-1M manufactured by Riken Keiki Co., Ltd. using a low energy electron counting method.

According to the present invention, electron transport in the single-layer photosensitive layer
Energy level corresponding to the lowest free orbit of the agent (L_ETM)
Levels corresponding to the highest occupied orbitals of the hole transport agent
(H _HTM), A work function satisfying the above formula (I)
By using a conductive substrate having (W), an image
Prevents fogging and black spots at the time of formation
You. It also corresponds to the lowest free orbit of the charge generation pigment used.
Energy level (L_CG) And d corresponding to the highest occupied orbit.
Energy level (H_HTM) Also satisfies the formula (II).
Using a conductive substrate having an additional work function (W)
Prevents fogging and black spots during image formation
can do.

See Tables 1 to 3 in the examples described below. That is, in the case of the combination of the photosensitive layer and the conductive substrate not satisfying the formulas (I) and (II) (Comparative Examples 1 to 7), fogging and black spots are remarkably generated during image formation. On the other hand, the formula (I) and the formula (II)
It is clear that any of the combinations of the photosensitive layer and the conductive substrate satisfying the following conditions (Examples 1 to 20) can completely suppress the occurrence of fog and black spots during image formation.

The reason for this is not intended to limit the present invention in any way, but is considered as follows.

That is, in FIG. 1 for explaining the principle of forming an electrostatic latent image on a negatively charged single-layer type electrophotographic photosensitive member, FIG.
The negatively charged single-layer type electrophotographic photoreceptor 1 includes a conductive substrate 2 and a single-layer organic photosensitive layer 3. This single layer organic photosensitive layer 3
Is formed from at least a charge generation pigment, a hole transporting agent, and an electron transporting agent dispersed in a binder resin.
Prior to exposure, the surface of the photosensitive layer 3 is negatively charged,
On the other hand, the surface of the conductive substrate 2 on the photosensitive layer side is positively inductively charged. When the photosensitive layer 3 is image-exposed, the charge-generating pigment 4
Generates a pair of a hole H and an electron e, and the generated electron e is transported to the surface of the conductive group 2 by an electron transporting agent, while the generated hole H is transferred to the photosensitive layer 3 by the hole transporting agent. After being transported to the surface, the surface charge is eliminated, and an electrostatic latent image is formed.

According to the study of the present inventors, in a photoreceptor in which a negatively charged single-layer photosensitive layer is provided directly on a conductive substrate,
The occurrence of fog and black spots is a phenomenon that is observed when the charge generation pigment, electron transporting agent and hole transporting agent in the photosensitive layer are all placed in contact with the conductive substrate. It is considered that the cause is that thermoelectrons and electrons having a low energy level other than hopped electrons are injected into the conductive substrate (or conversely, holes are injected from the substrate).

On the other hand, in the case of the electron transport agent, the lowest unoccupied orbit (LUMO) of the electron transport agent is considered to be the orbit reached when the electron transport agent is excited or receives electrons. In the photoreceptor described above, there is a barrier of α (0.35 eV) or more between the energy level (L _ETM ) corresponding to the lowest unoccupied orbit and the work function (W) of the conductive substrate. It is considered that injection of electrons and low energy levels is prevented, and as a result of injection of only hopped electrons, fogging and black spots are prevented from occurring during image formation. The same is true for the relationship between the energy level (L _CG ) corresponding to the lowest unoccupied orbit of the charge generating pigment and the work function (W) of the conductive substrate.

On the other hand, in the case of the hole transporting agent, the problem with the injection of holes from the conductive substrate is that the energy level (H) corresponding to the highest occupied orbital (HOMO) of the hole transporting agent is high.
_HTM ), and between the energy level (H _HTM ) and the work function (W) of the conductive substrate, the aforementioned β (0.1
It is thought that there is a barrier of 4 eV) or more, which prevents the injection of holes at a low level, and similarly prevents fogging and black spots from occurring during image formation. The same is true for the relationship between the energy level (H _CG ) corresponding to the highest occupied orbit of the charge generating pigment and the work function (W) of the conductive substrate.

According to the present invention, even when a negatively charged single-layer photosensitive layer is directly provided on a conductive substrate, the occurrence of fogging and black spots is prevented. Thus, the photoreceptor can be formed by the above-mentioned coating, and the productivity of the photoreceptor can be improved.

[Electrophotographic Photoreceptor] As shown in FIG. 1, the electrophotographic photoreceptor of the present invention has a single-layer organic photosensitive layer 3 provided directly on a conductive substrate 2. The photosensitive layer 3 is formed of at least a charge generation pigment, a hole transport agent, and an electron transport agent dispersed in a binder resin. Prior to exposure, the surface of the photosensitive layer 3 is negatively charged, while the surface of the conductive substrate 2 on the photosensitive layer side is positively inductively charged. By exposing the photosensitive layer 3 to an image,
The formation of the electrostatic latent image is performed by the mechanism described with reference to FIG. According to the present invention, the transport of electrons and holes is effectively performed based on the principle described above, and the occurrence of fog and black spots due to extra charge injection is prevented. Hereinafter, the composition of the photosensitive layer will be described in detail.

[Composition of photosensitive layer] (1) Charge-generating pigment Examples of the charge-generating pigment include selenium, selenium-tellurium, amorphous silicon, pyrylium salts, azo pigments, disazo pigments, anthanthrone pigments, and phthalocyanine pigments. Examples include, indico-based pigments, sulene-based pigments, toluidine-based pigments, pyrazoline-based pigments, perylene-based pigments, quinacridone-based pigments, and the like. . Of course, the charge generating pigment used must satisfy the formula (2) in relation to the conductive substrate.

The following phthalocyanine pigments, perylene pigments, bisazo pigments and the like are particularly preferable for the purpose of the present invention. Examples of phthalocyanine pigments include metal-free phthalocyanine, aluminum phthalocyanine, vanadium phthalocyanine, cadmium phthalocyanine, antimony phthalocyanine, chromium phthalocyanine, copper 4-phthalocyanine, germanium phthalocyanine, iron phthalocyanine, chloroaluminum phthalocyanine, oxotitanyl phthalocyanine, chloroindium phthalocyanine, and chlorogallium. Examples include phthalocyanine, magnesium phthalocyanine, dialkyl phthalocyanine, tetramethyl phthalocyanine, tetraphenyl phthalocyanine, and the like. The crystal forms are α-type and β-type.
Any of the following types can be used: γ-type, δ-type, ε-type, σ-type, x-type, and τ-type. X-type metal-free phthalocyanines are particularly preferred.

As the perylene-based pigment, particularly, the general formula (1):

Embedded image In the formula, each of R ₁ and R ₂ is a substituted or unsubstituted alkyl group, cycloalkyl group, aryl group, alkaryl group, or aralkyl group having 18 or less carbon atoms. What is represented by Examples of the alkyl group include an ethyl group, a propyl group, a butyl group, a 2-ethylhexyl group, and the like.
Examples of the cycloalkyl group include a cyclohexyl group and the like; examples of the aryl group include a phenyl group and a naphthyl group; examples of the alkaryl group include a tolyl group, a xylyl group, and an ethylphenyl group; and an aralkyl group. Examples thereof include a benzyl group and a phenethyl group. Examples of the substituent include an alkoxy group and a halogen atom.

As the bisazo pigment, in particular, the following formula (2)

Embedded image In the formula, Y is a divalent aromatic group which may contain a heterocyclic group, and Cp is a coupler residue. Examples of the divalent aromatic group include a divalent group derived from benzene, naphthalene, anthracene, phenanthrene, chrysene, anthraquinone, a biphenol, a bisphenol, a heterocyclic ring, or a combination thereof. Examples of the heterocyclic group include a monocyclic or polycyclic saturated or unsaturated heterocyclic ring containing nitrogen, oxygen, sulfur or a combination thereof in the ring, and specifically, pyrrole, pyrazole, thiophene, Furan, imidazoline, pyrimidine,
Examples include pyrazoline, pyran, pyridine, pyrimidine, benzofuran, benzimidazoline, benzoxazole, indoline, quinoline, chromene, carbazole, dibenzofuran, xanthene, and thioxanthene.
These divalent groups may be unsubstituted or substituted, and examples of the substituent include an alkyl group, an aryl group, and a heterocyclic group. Here, as the alkyl group,
Methyl, ethyl, propyl, butyl, amyl group and the like, and the aryl group includes phenyl, naphthyl, biphenyl, anthryl, phenanthryl, fluorenyl group and the like, and the heterocyclic group includes nitrogen, oxygen, sulfur or these. A monocyclic or polycyclic saturated or unsaturated heterocyclic group containing a combination in a ring, such as a thienyl group, a furyl group, an imidazolyl group, a pyrrolyl group, a pyrimidinyl group,
Imidazole group, pyrazinyl group, pyrazolinyl group, pyrrolidinyl group, pyranyl group, piperidyl group, piperazinyl group, morpholyl group, pyridyl group, pyrimidyl group, pyrrolidinyl group, pyrrolinyl group, benzofuryl group, benzimidazolyl group, benzofuranyl group, indolyl group, quinolyl group Carbazolyl group, dibenzofuranyl group and the like. On the other hand, as the coupler residue in the formula (2),
As long as it is a residue of a coupler (azo coupling component) used in this type of azo pigment, it may be any one such as a substituted or unsubstituted phenol, naphthol, or a hydroxyl-containing heterocyclic compound. Here, examples of the substituent include a lower alkyl group, a lower alkoxy group, an aryl group, an acyloxy group, a halogen atom such as chlor, a hydroxyl group, a nitrile group, a nitro group, an amino group, an amide group, an acyloxy group, and a carboxyl group. No.

(2) Electron transporting agent As the electron transporting agent, any material having an electron transporting property is used alone or in combination of two or more. The following are known as electron transporting agents, and those having excellent electron transporting properties and excellent solubility can be selected and used. The electron transport agent used must satisfy the relationship of the formula (I) with respect to the conductive substrate. Paradiphenoquinone derivative, benzoquinone derivative, naphthoquinone derivative, tetracyanoethylene, tetracyanoquinodimethane, chloranil, bromoanil, 2,4,7
-Trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4,7-trinitro-9-dicyanomethylenefluorenone, 2,4,5
Electron-withdrawing substances such as 7-tetranitroxanthone and 2,4,8-trinitrothioxanthone, and those obtained by polymerizing these electron-withdrawing substances.

As an electron transporting agent particularly suitable for the purpose of the present invention, diphenoquinone derivatives, particularly the following formula (3)

Embedded image In the formula, each of R ₃ , R ₄ , R ₅ and R ₆ is an alkyl group, an alkoxy group or a substituted or unsubstituted aryl group, which may be the same or different from each other And diphenoquinone derivatives represented by As the alkyl group present in this derivative, an alkyl group having 1 to 8 carbon atoms, for example, a methyl group, an ethyl group, an n-propyl group, an iso-propyl group,
n-butyl group, iso-butyl group, t-butyl group, amyl group, 2-ethylhexyl group, cyclohexyl group, etc., and as the alkoxy group, methoxy group, ethoxy group, propoxy group, butoxy group, etc. No. Also,
Examples of the aryl group include a phenyl group and a naphthyl group, which may be unsubstituted or substituted with an alkyl group, an alkoxy group, a halogen atom, or the like.

Specific examples of the diphenoquinone derivative include:
These include: 3,5-dimethyl-3 ', 5'
-Di-t-butyldiphenoquinone, 3,5-dimethoxy-
3 ′, 5′-di-tert-butyldiphenoquinone, 3,3′-
Dimethyl-5,5'-di-tert-butyldiphenoquinone,
3,5′-dimethyl-3 ′, 5-di-tert-butyldiphenoquinone, 3,5,3 ′, 5′-tetramethyldiphenoquinone, 2,6,2 ′, 6′-tetra-tert-butyl Diphenoquinone, 3,5,3 ', 5'-tetraphenyldiphenoquinone, 3,5,3', 5'-tetracyclohexyldiphenoquinone

As other electron transporting agents particularly suitable for the purpose of the present invention, naphthoquinone derivatives, especially the following formula (4)

Embedded image In the formula, each of R ₇ and R ₈ is an alkyl group or a substituted or unsubstituted aryl group, and a naphthoquinone derivative represented by the formula: As the alkyl group or the aryl group, specifically, those already exemplified in the formula (3) are appropriate.

The following are specific examples of the naphthoquinone derivative. 2-phenyl-3-tbutylcarbonyl-1,4-naphthoquinone 2-phenyl-3-isobutylcarbonyl-1,4-naphthoquinone 2-pmethylphenyl-3-tbutylcarbonyl-1,4-naphthoquinone

As still another electron transporting agent particularly suitable for the purpose of the present invention, naphthalenetetracarboxylic diimide derivatives, particularly those represented by the general formula (5)

Embedded image In the formula, m and n are integers of 6 or less including zero, and may be the same or different, and R ₉ is a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom;
Each of ₁₀ and R ₁₁ is a substituted or unsubstituted alkyl group,
And a naphthalenetetracarboxylic diimide derivative represented by an aryl group, an alkoxy group or an amino group, which may be the same or different.

R ₉ present in this derivative is a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom, and the alkyl group and the alkoxy group may be the same as those exemplified above. Examples of the halogen atom include a chlorine atom and a bromine atom. Each of R ₁₀ and R ₁₁ is a substituted or unsubstituted alkyl group, an alkoxy group or an aryl group. Examples of the alkyl group or the alkoxy group include those described above, and examples of the aryl group include a phenyl group and a naphthyl group. Groups. They also unsubstituted, or an alkyl group, an alkoxy group or may be substituted by a halogen atom or the like, wherein the substituents may be those described with respect to group R _1.

The following are specific examples of the naphthalenetetracarboxylic acid diimide derivative. N,
N′-bis (2-ethyl-6-methylphenyl) naphthalene-1,4,5,8-tetracarboxylic diimide,
N, N'-bis (2,4-dimethyl-6-ethylphenyl) naphthalene-1,4,5,8-tetracarboxylic diimide, N, N'-bis (2-methyl-6-ethoxyphenyl) naphthalene -1,4,5,8-tetracarboxylic acid diimide, N, N'-bis (2-methyl-6-methoxyphenyl) naphthalene-1,4,5,8-tetracarboxylic acid diimide, N, N'- Bis (2-methyl-6-methoxyethylphenyl) naphthalene-1,4,5,8-
Tetracarboxylic diimide, N, N'-bis (1,2-
Dimethylpropyl) naphthalene-1,4,5,8-tetracarboxylic diimide, N- (2-ethoxyethyl)-
N '-(2-methyl-6-ethylphenyl) naphthalene-1,4,5,8-tetracarboxylic diimide, N-
(1,2-dimethylpropyl) -N ′-(2-methyl-
6-ethylphenyl) naphthalene-1,4,5,8-tetracarboxylic diimide, N- (2-ethoxyethyl)
-N '-(1,2-dimethylpropyl) naphthalene-
1,4,5,8-tetracarboxylic diimide.

The naphthalenetetracarboxylic diimide derivative is synthesized by reacting the corresponding naphthalenetetracarboxylic anhydride with the corresponding primary amine in a solvent under reflux. As the solvent, an aprotic polar organic solvent such as dimethylformamide or dimethylacetamide is preferably used, and the reaction temperature is preferably the boiling point of the solvent. The reaction is preferably carried out using a stoichiometric amount or more of a primary amine with respect to naphthalenetetracarboxylic anhydride.

(3) Hole transporting agent As the hole transporting substance, for example, the following are known, and among them, those having excellent solubility and hole transporting property are used. . Needless to say, the hole transporting agent used must satisfy the above formula (I) in relation to the conductive substrate. Pyrene, N-ethylcarbazole, N-isopropylcarbazole, N-methyl-N-phenylhydrazino-3-methylidene-9-carbazole, N, N
-Diphenylhydrazino-3-methylidene-9-ethylcarbazole, N, N-diphenylhydrazino-3-methylidene-10-ethylphenothiazine, N, N-diphenylhydrazino-3-methylidene-10 -Ethylphenoxazine, p-diethylaminobenzaldehyde-
N, N-diphenylhydrazone, p-diethylaminobenzaldehyde-α-naphthyl-N-phenylhydrazone, p-pyrrolidinobenzaldehyde-N, N-diphenylhydrazone, 1,3,3-trimethylindolenine-ω-aldehyde -N, N-diphenylhydrazone, p
Hydrazone salts such as -diethylbenzaldehyde-3-methylbenzthiazolinone-2-hydrazone;
Bis (p-diethylaminophenyl) -1,3,4-oxadizole, 1-phenyl-3- (p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline, 1- [quinonyl (2)]- 3- (p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazolin, 1- [pyridyl (2)]-3- (p-
Diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline, 1- [6-methoxy-pyridyl (2)]-3- (p-diethylaminostyryl) -5-
(P-diethylaminophenyl) pyrazolin, 1- [pyridyl (3)]-3- (p-diethylaminostyryl)
-5- (p-diethylaminophenyl) pyrazoline, 1
-[Lepidyl (3)]-3- (p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazolin, 1- [pyridyl (2)]-3- (p-diethylaminostyryl) -4-methyl- 5- (p-diethylaminophenyl) pyrazoline, 1- [pyridyl (2)]-3-
(Α-methyl-p-diethylaminostyryl) -3-
(P-diethylaminophenyl) pyrazoline, 1-phenyl-3- (p-diethylaminostyryl) -4-methyl-5- (p-diethylaminophenyl) pyrazoline,
Pyrazolines such as spiropyrazoline, 2- (p-diethylaminostyryl) -3-diethylaminobenzoxazole, 2- (p-diethylaminophenyl) -4-
Oxazole-based compounds such as (p-dimethylaminophenyl) -5- (2-chlorophenyl) oxazole, 2
Thiazole compounds such as-(p-diethylaminostyryl) -6-diethylaminobenzothiazole, triarylmethane compounds such as bis (4-diethylamino-2-methylphenyl) phenylmethane, 1,1-bis (4-N, N- Diethylamino-2-methylphenyl) heptane, 1,1,2,2-tetrakis (4-N,
Polyarylalkanes such as N-dimethylamino-2-methylphenyl) ethane; N, N'-diphenyl-
N, N'-bis (methylphenyl) benziben, N, N
'-Diphenyl-N, N'-bis (ethylphenyl) benzidine, N, N'-diphenyl-N, N'-bis (propylphenyl) benzidine, N, N'-diphenyl-
N, N'-bis (butylphenyl) benzidine, N, N
'-Bis (isopropylphenyl) benzidine, N, N
'-Diphenyl-N, N'-bis (secondary butylphenyl) benzidine, N, N'-diphenyl-N, N'-bis (tertiarybutylphenyl) benzidine, N, N'-diphenyl-N, N' Benzidine compounds such as -bis (2,4-dimethylphenyl) bendiben, N, N'-diphenyl-N, N'-bis (chlorophenyl) benzidine, triphenylamine, poly-N-vinylcarbazole, polyvinylpyrene, Polyvinyl anthracene, polyvinyl alicdin, poly-9-vinyl phenyl anthracene, pyrene-formaldehyde resin, ethyl carbazole formaldehyde resin.

The following are preferred as hole transport agents particularly suitable for the purpose of the present invention. The following equation (6)

Embedded image Wherein, a, each of b and c is 2 an integer including zero, it may be the same or different from each other, R _12, R
A benzidine derivative represented by the formula: wherein each of ₁₃ and R ₁₄ is a hydrogen atom, an alkyl group or an aryl group, which may be the same or different. The following are specific examples. N, N, N ′, N′-tetra-p-tolyl-3,3′-dimethylbenzidine;

The following equation (7)

Embedded image In the formula, each of d and e is an integer of 2 or less including zero, and may be the same or different, and each of R ₁₅ , R ₁₆ and R ₁₇ is a hydrogen atom, an alkyl group or an aryl group. And a phenylenediamine derivative represented by the following formula: The following are specific examples. N, N, N ′, N′-tetra-m-tolyl-metaphenylenediamine,

The following equation (8)

Embedded image In the formula, each of p and q is an integer of 2 or less including zero, and may be the same or different from each other, and R ₁₈ and R ₁₉
Is an alkyl group, an aryl group or an aralkyl group, which may be the same or different, and is a phenanthrylenediamine derivative represented by the formula: The following are specific examples. N, N'-di-p-tolyl-
N, N′-di (p-isopropylphenyl) phenanthrylene-9,10-diamine,

The following equation (9)

Embedded image In the formula, each of r and s is an integer of 2 or less including zero, and may be the same or different from each other, and R ₂₀ and R ₂₁
Is an alkyl group, an aryl group or an aralkyl group, which may be the same or different from each other. The following are specific examples. N, N, N ′, N′-tetra-m-tolyl-naphthylene-1,4-diamine;

The following equation (10)

Embedded image Wherein, t, each of u and w a 2 an integer including zero, it may be the same or different from each other, R _22, R
A stilbene derivative represented by the formula: wherein each of ₂₃ and R ₂₄ is an alkyl group, an aryl group or an aralkyl group, which may be the same or different. 1,4-bis [p
-(N-phenyl-N-2-methyl-5-ethylphenyl) aminostyryl] benzene,

(4) Binder Resin Various resins can be used as a resin medium in which the charge generating agent, the electron transporting agent and the hole transporting agent are dispersed. For example, a styrene-based polymer, an acrylic polymer, and a styrene-based resin can be used. Acrylic polymer, ethylene-vinyl acetate copolymer, polypropylene, olefin polymer such as ionomer, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyester, alkyd resin, polyamide, polyurethane, epoxy resin, polycarbonate, Various polymers such as polyarylate, polysulfone, diallyl phthalate resin, silicone resin, ketone resin, polyvinyl butyral resin, polyether resin, phenol resin, and photocurable resins such as epoxy acrylate can be exemplified. These binder resins may be used alone or in combination of two or more. Suitable resins include styrene polymers, acrylic polymers, styrene-acrylic polymers, polyester resins, alkyd resins, polycarbonates, polyarylates, and the like.

Particularly preferred resins are polycarbonate, Panlite manufactured by Teijin Chemicals Ltd., PCZ manufactured by Mitsubishi Gas Chemical Company, and the like.

Embedded image In the formula, R ₂₅ and R ₂₆ are a hydrogen atom or a lower alkyl group, and R ₂₅ and R ₂₆ may be linked to form a cyclo ring such as a cyclohexane ring together with a bonding carbon atom. Polycarbonate derived from bisphenols and phosgene.

(4) Composition The single-layer photosensitive layer used in the present invention contains the above-described charge generating pigment, electron transporting agent and hole transporting agent in a state of being dispersed in a binder resin. Generally, the concentration of the charge generation pigment in the photosensitive layer is preferably in the range of 0.1 to 1.5% by weight, particularly preferably 0.25 to 1.0% by weight based on the solid content. On the other hand, the concentration of the electron transporting agent in the photosensitive layer is generally 5 to 40% by weight based on the solid content,
In particular, it is preferably in the range of 10 to 30% by weight.
The concentration of the hole transporting agent in the photosensitive layer is generally from 10 to 50% by weight, especially from 20 to 4% by weight, based on the solid content.
It is desirably in the range of 0% by weight.

[Conductive Substrate] As the conductive substrate on which the photosensitive layer is provided, the above formula (I) or (II) may be used in relation to the electron transporting agent and hole transporting agent used or the charge generating pigment used. A conductive substrate having a work function in a range satisfying the following condition is used. For example, aluminum, copper, tin, platinum, gold, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, indium, stainless steel,
A metal simple substance such as brass, a plastic material on which the above metal is deposited or laminated, aluminum iodide, tin oxide,
Glasses coated with indium oxide or the like are exemplified, and among them, those having a work function defined in the present invention are used.

In general, a hollow or solid aluminum drum is often used in an image forming apparatus using an electrophotographic method, but this drum is rarely made of pure aluminum. Strength, rigidity,
From the viewpoint of corrosion resistance and the like, an aluminum alloy is usually used.
Alloy metals such as i, Fe, Cu, Mn, Mg, Cr, Ti, and Ni are contained.

The work function (W) of pure aluminum is 4.2
Although it is 8 eV, the work function of the aluminum alloy varies considerably depending on the type of the alloy metal, and particularly when the alloy metal is precipitated as crystal grains, the variation range tends to be considerably large. In the present invention, the use of an aluminum alloy having a constant work function corresponding to the energy levels of the charge generating pigment, the electron transporting agent and the hole transporting agent to be used enables effective generation of fog and black spots during image formation. Can be prevented.

[Preparation of Photoreceptor] The photoreceptor-forming composition used in the present invention contains various compounding agents known per se, such as antioxidants, as long as they do not adversely affect the electrophotographic properties. Radical scavenger, singlet quencher, UV absorber, softener, surface modifier, defoamer, extender, thickener,
A dispersion stabilizer, a wax, an acceptor, a donor and the like can be blended. -0.8 to-
An electron accepting compound having a reduction potential of 1.4 eV may be added.

When a sterically hindered phenolic antioxidant of 0.1 to 50% by weight based on the total solid content is blended in at least the upper layer of the photosensitive layer, the electrophotographic properties of the photosensitive layer are not adversely affected. The durability can be significantly improved.

To form a photoreceptor, a charge generating pigment,
A combination of an electron transporting agent, a hole transporting agent and a binder resin,
What is necessary is just to prepare a coating composition using a conventionally known method, for example, a roll mill, a ball mill, an attritor, a paint shaker or an ultrasonic disperser, apply by a conventionally known coating means, and dry.

As the solvent used for forming the coating solution, various organic solvents can be used, and alcohols such as methanol, ethanol, isopropanol and butanol,
n-hexane, octane, aliphatic hydrocarbons such as cyclohexane, benzene, toluene, aromatic hydrocarbons such as xylene, dichloromethane, dichloroethane, carbon tetrachloride, halogenated hydrocarbons such as chlorobenzene, dimethyl ether, diethyl ether, tetrahydrofuran, Various solvents such as ethers such as ethylene glycol dimethyl ether and diethylene glycol dimethyl ether; ketones such as acetone, methyl ethyl ketone and cyclohexanone; esters such as ethyl acetate and methyl acetate; dimethylformamide and dimethyl sulfoxide; Used as a mixture. In general, the solid content of the coating solution is preferably 5 to 50%.

The thickness of the single-layer photosensitive layer is generally 1
It is preferably in the range of 0 to 40 μm, especially 15 to 30 μm. That is, when the thickness is smaller than the above range, the charging potential is lowered, and it tends to be difficult to form an image with contrast. On the other hand, when the thickness is larger than the above range, the sensitivity is reduced or the residual potential is reduced. Tend to be high, and both are not preferred.

The image forming method using the electrophotographic photoreceptor of the present invention is not particularly limited. Generally, the photoreceptor is uniformly negatively charged, exposed to an image to form an electrostatic latent image, and then non-magnetic Development is performed using a component-based toner, a magnetic one-component-based toner, a magnetic two-component-based developer, a non-magnetic two-component-based developer, and then transferred to a transfer paper and fixed to form an image.

[0053]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the following examples.

The materials used for forming the photosensitive layer are as follows.

Charge generating pigment x-H2Pc: X type metal-free phthalocyanine L _CG = 3.67 to 3.77 eV H _CG = 5.2 to 5.3 eV

Electron transporting agent ETM-1: The following formula (12)

Embedded image 3,3′-dimethyl-5,5′-di-tert-butyl-4,4
- diphenoquinone L _ETM = 3.86eV _ETM-2 following formula (13)

Embedded image 2-phenyl-3-tbutylcarbonyl-1,4-naphthoquinone L _ETM = 3.78 eV

Hole transporting agent HTM-1: The following formula (14)

Embedded image N, N, N ′, N′-tetra-m-tolyl-metaphenylenediamine, H _HTM = 5.64 eV

Conductive Substrate As the conductive substrate, pure aluminum shown in Table 1 and an aluminum alloy containing an alloy metal shown in Table 1 were used.

[Examples 1 to 12 and Comparative Examples 1 to 4] [Preparation of Sample] <Photoreceptor> The charge generating pigment, electron transporting agent and hole transporting agent shown in Table 1 are shown in parts by weight shown in Table 1, 100 parts by weight of polycarbonate as a binder resin and 800 parts by weight of tetrahydrofuran as a solvent were dispersed in a ball mill for 50 hours to prepare a coating solution for a photosensitive layer, and the prepared solution was coated on a conductive substrate having the structure shown in Table 1. And dried by hot air at 100 ° C. for 60 minutes to obtain a 20 μm-thick negatively charged single-layer type photoconductor.

[Evaluation] <Photosensitivity> A laser printer manufactured by Seiko Epson Corporation, which uses an electrophotographic photosensitive member by charging it to a negative polarity, was used as a tester, and the photosensitive drum prepared as described above was mounted thereon. An image was output, and the presence or absence of black spots in the output image was confirmed. The results are shown in Table 1.

[0061]

[Table 1]

[Examples 13 to 16 and Comparative Examples 5 and 6] In Example 1, an electron transporting agent having a structure represented by the following formula and a lowest unoccupied energy level shown in Table 2 was used. A single-layer photoreceptor was manufactured in the same manner as in Example 1 except that the pure aluminum tube used in Example 1 was used as the conductive substrate. Table 2 shows the relationship between the lowest free orbital energy level of the electron transporting agent and the printing characteristics.

Electron transporting agent ETM-3 The following formula (15)

Embedded image N, N'-bis [1,2-dimethylpropyl] naphthalene-1,4,5,8-tetracarboxylic diimide ETM-4 of the following formula (16)

Embedded image N-2-methyl-6-ethylphenyl-N'-2-ethoxyethyl-naphthalene-1,4,5,8-tetracarboxylic diimide ETM-5 of the following formula (17)

Embedded image 3,5-dimethyl-3 ′, 5′-di-t-butyldiphenoquinone ETM-6:

Embedded image Electron transport agent ETM-7 of the following formula (19)

Embedded image Electron transport agent

[0064]

[Table 2] ^* 1 Energy level = reduction potential + 4.74

Examples 17 to 20 and Comparative Example 7 In Example 6, except that a hole transporting agent having a structure represented by the following formula and having the highest occupied orbital energy level shown in Table 3 was used. A single-layer photoreceptor was manufactured in the same manner as in Example 1. The highest occupied orbital energy level of the hole transport agent,
Table 3 shows the relationship with the printing characteristics.

Hole transporting agent HTM-2: The following formula (20)

Embedded image N, N, N ', N'-tetra-p-tolyl-3,3'
-Dimethylbenzidine, HTM-3: the following formula (21)

Embedded image N, N'-di-p-tolyl-N, N'-di (p-isopropylphenyl) phenanthrylene-9,10-diamine; HTM-4: Formula (22)

Embedded image N, N, N ', N'-tetra-m-tolyl-naphthylene-2,3-diamine, HTM-5: Formula (23) below

Embedded image 1,4-bis [p- (N-phenyl-N-2-methyl-5-ethylphenyl) aminostyryl] benzene, HTM-6: Formula (24) below

Embedded image Styryl derivatives of

[0067]

[Table 3]

According to the above Tables 1, 2 and 3, black spots were generated when a conductive substrate satisfying the formula (I) or (II) was combined with a charge generating pigment, an electron transporting agent and a hole transporting agent. It is clear that is effectively eliminated.

[0069]

According to the present invention, a negatively charged single-layer type in which a photosensitive layer in which at least a charge generation pigment, a hole transporting agent and an electron transporting agent are dispersed in a binder resin is provided directly on a conductive substrate. In the electrophotographic photoreceptor, an electric charge corresponding to the energy level corresponding to the lowest unoccupied orbit (LUMO) of the electron transporting agent used and the energy level corresponding to the highest occupied orbital (HOMO) of the hole transporting agent, or used. In relation to the energy level corresponding to the lowest unoccupied orbital (LUMO) and the energy level corresponding to the highest occupied orbital (HOMO) of the generated pigment,
By selecting a conductive substrate whose work function is within a certain range, and by combining with this single-layer photosensitive layer, the disadvantages of the conventional photosensitive member are eliminated, and no fogging or black spots are generated.
High quality images can be formed. Further, the photoreceptor of the present invention has an advantage that the formation of the photosensitive layer is performed only by one coating operation, and the productivity is excellent.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the operation of the photoconductor of the present invention at the same time.

FIG. 2 is a graph showing a relationship between an index voltage and a current.

FIG. 3 is a graph showing a relationship between an energy level and an oxidation potential.

Claims (3)

[Claims] 1. A single-layer type electrophotographic photoconductor in which a photosensitive layer in which at least a charge generation pigment, an electron transporting agent and a hole transporting agent are dispersed in a binder resin is provided directly on a conductive substrate. during sexual substrate following formula _{L ETM + α ≦ W ≦ H} HTM -β formula, L _ETM represents energy level (eV) corresponding to the lowest unoccupied molecular orbital of the electron transport agent, alpha is 0.35 eV, H _HTM Represents an energy level (eV) corresponding to the highest occupied orbit of the hole transporting agent, and β has a work function (W) satisfying 0.14 eV. Electrophotographic photoreceptor. 2. A single-layer type electrophotographic photoconductor in which a photosensitive layer in which at least a charge generation pigment, an electron transporting agent and a hole transporting agent are dispersed in a binder resin is provided directly on a conductive substrate. In the formula, L _CG represents an energy level (eV) corresponding to the lowest unoccupied orbit of the charge-generating pigment, K represents 0.48 eV, and H _CG represents the following formula: L _CG + K ≦ W ≦ H _CG −J Represents an energy level (eV) corresponding to the highest occupied orbit of the charge-generating pigment, and J has a work function (W) satisfying 0.05 eV. Photoreceptor. 3. The electrophotographic photosensitive member according to claim 2, wherein the charge generation pigment is an X-type metal-free phthalocyanine.