JP5408894B2 - Electrophotographic photoreceptor and image forming apparatus provided with the same - Google Patents

Description

  The present invention relates to an electrophotographic photosensitive member and an image forming apparatus including the same.

As an electrophotographic photosensitive member used in an image forming apparatus or the like, an electrophotographic photosensitive member having a conductive substrate and a photosensitive layer provided on the conductive substrate is known. In recent years, an electrophotographic photoreceptor in which an undercoat layer is interposed between a conductive substrate and a photosensitive layer has been proposed as a photoreceptor that is insulated to suppress leakage.
In such an electrophotographic photoreceptor, a coating solution in which a charge generator, a charge transport agent, and a binder resin are dissolved in a solvent is applied onto a conductive substrate or an undercoat layer, and dried to form a photosensitive layer. It is manufactured by.

  An enamine compound is known as a charge transport agent. As the enamine compound, for example, a compound represented by the following general formula (15) and an electrophotographic photoreceptor using the compound have been proposed (for example, see Patent Document 1).

In the general formula (15), R ¹ represents a hydrogen atom, an alkyl group, or a halogen atom. Ar ^{1 to} Ar ⁵ each represents an aryl group or a heterocyclic group which may have a substituent.
JP 2003-195542 A

  However, the compound represented by the general formula (15) has poor solubility in a solvent and compatibility with a binder resin, and a part of the charge transport agent is easily crystallized and precipitated during production of the electrophotographic photosensitive member. It was not practical. In addition, the electrophotographic photosensitive member produced in this manner was liable to deteriorate electrical characteristics such as sensitivity. In particular, the electrical characteristics of the electrophotographic photosensitive member are likely to deteriorate under a high temperature and high humidity environment. In addition, in an image forming apparatus provided with an electrophotographic photosensitive member having insufficient electrical characteristics, the quality of an obtained image is easily deteriorated.

  The present invention has been made in view of the above circumstances, and can be produced without crystallization and precipitation of the charge transport agent, and is excellent in electrical characteristics even in a high-temperature and high-humidity environment, and image formation provided with the same. The purpose is to realize the device.

The present inventors have found a result of intensive studies, the Ar ⁴ of the compound represented by the general formula (15) was replaced by a hydrogen atom, Ar ⁴ is an aryl group or a heterocyclic group as described in Patent Document 1 It has been found that characteristics as a charge transport agent (for example, mobility) are further improved as compared with the compound. When a charge transfer agent having excellent mobility is used, an electrophotographic photoreceptor having good electrical characteristics can be obtained.
However, the charge transfer agent in which Ar ⁴ in the compound represented by the general formula (15) is replaced with a hydrogen atom is remarkably easily reduced in solubility in a solvent and compatibility with a binder resin.

Therefore, as a result of further intensive studies, the present inventors have selected and used an aryl group having a specific substituent as Ar ³ of the compound represented by the general formula (15), whereby solubility in a solvent, And it discovered that compatibility with binder resin improved.
In addition, by selecting and using an aryl group having a specific substituent as Ar ³ , even if Ar ⁴ in the compound represented by the general formula (15) is replaced with a hydrogen atom, solubility in a solvent and binder It has been found that the properties as an electron transport agent can be improved without lowering the compatibility with the resin, and the present invention has been completed.

That is, the electrophotographic photosensitive member of the present invention is an electrophotographic photosensitive member in which a photosensitive layer containing a charge generating agent, a charge transporting agent, and a binder resin is formed on a conductive substrate. among the enamine butadiene compound represented by the following general formula (1) as a transport agent, and characterized in that it contains one kind selected from compounds represented by the later-described formula (1-1) to (1-5) To do.

In Formula (1), R ¹ is an alkyl group having 2 or more carbon atoms, Ar ¹ is a hydrogen atom, an aryl group, or an alkyl group, and Ra, Rb, Rc, and Rd are the same or different, and An alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 30 carbon atoms, an alkenyl group having 6 to 30 carbon atoms, or —OR ² (wherein R ² is an alkyl group having 1 to 10 carbon atoms and 1 to 10 carbon atoms) A perfluoroalkyl group or an aryl group having 6 to 30 carbon atoms), m representing an integer of 0 to 4 and n, o, and p are integers of 0 to 5.

The Ar ¹ is preferably a hydrogen atom.
Furthermore, R ¹ is preferably an alkyl group having 4 or more carbon atoms.
The binder resin is preferably a polycarbonate resin having at least one structural unit selected from the group consisting of structural units represented by the following general formulas (2) to (4).

In the formulas (2) to (4), Rf, Rg, and Rh are the same or different and are each an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 30 carbon atoms, an alkenyl group having 6 to 30 carbon atoms, or —OR ² (wherein R ² is an alkyl group having 1 to 10 carbon atoms, a perfluoroalkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 30 carbon atoms), and the number of substituents is R, s, and t shown are each an integer of 0 to 4.

Moreover, it is preferable that the photosensitive layer has a single layer structure containing the charge generating agent, the charge transporting agent, and the binder resin in the same layer.
Furthermore, it is preferable that the photosensitive layer has a laminated structure having a charge generation layer containing at least the charge generation agent and a charge transport layer containing the charge transfer agent and the binder resin.

  The image forming apparatus of the present invention includes an image carrying unit, a charging unit that charges the surface of the image carrying unit, an exposure unit that exposes the surface of the image carrying unit to form an electrostatic latent image, Discharging means comprising developing means for developing an electrostatic latent image as a toner image and transfer means for transferring the toner image from the image carrying means to a transfer target, and for removing charges on the surface of the image carrying means. In the image forming apparatus that does not include the above, the image carrying means is the electrophotographic photosensitive member.

The electrophotographic photoreceptor of the present invention can be produced without the charge transfer agent being crystallized and precipitated, and is excellent in electrical characteristics even in a high temperature and high humidity environment.
Further, since the image forming apparatus of the present invention includes the electrophotographic photosensitive member of the present invention, a high quality image can be obtained.

[Electrophotographic photoreceptor]
In the electrophotographic photoreceptor of the present invention, a photosensitive layer containing a charge generator, a charge transport agent, and a binder resin is formed on a conductive substrate.

<Conductive substrate>
Examples of the material of the conductive substrate include metals such as iron, aluminum, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, brass, and the like. An oxide film formed by oxidation treatment; a plastic material on which the metal is deposited or laminated; a glass coated with aluminum iodide, tin oxide, indium oxide, etc .; a plastic material in which conductive fine particles such as carbon black are dispersed Etc.
In the present invention, “conductive” means that the resistance value is 1.0 × 10 ⁸ Ω · cm or less.

Examples of the shape of the conductive substrate include a sheet shape and a drum shape. The shape of the conductive substrate may be appropriately determined according to the structure of the image forming apparatus.
The surface of the conductive substrate may be roughened. Thereby, generation | occurrence | production of an interference fringe can be prevented. Examples of the surface roughening treatment include etching, anodizing, wet blasting, sand blasting, rough cutting, and centerless cutting.

<Photosensitive layer>
The photosensitive layer contains a charge generator, a charge transport agent, and a binder resin.

(Charge generator)
A known charge generating agent can be used as the charge generating agent. Specifically, phthalocyanine pigments, perylene pigments, bisazo pigments, diketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaraine pigments, trisazo pigments, indigo pigments, azurenium pigments, cyanine pigments, pyrylium Organic photoconductors such as pigments, ansanthrone pigments, triphenylmethane pigments, selenium pigments, toluidine pigments, pyrazoline pigments, quinacridone pigments; selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, amorphous silicon, etc. An inorganic photoconductive agent etc. are mentioned. A charge generating agent may be used individually by 1 type, and may use 2 or more types together.
In addition, as the charge generating agent, compounds (11-1) to (11-4) are preferable.

(Charge transport agent)
In the present invention, the photosensitive layer contains an enamine budadiene compound represented by the following general formula (1) as a charge transfer agent. Hereinafter, the compound represented by the general formula (1) is referred to as a compound (1). Other compounds are described in the same manner.

R ¹ is an alkyl group having 2 or more carbon atoms.
As the alkyl group, ethyl group, propyl group, isopropyl group, n-butyl group, t-butyl group, pentyl group, isopentyl group, neopentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group And a dodecyl group.
R ¹ is particularly preferably an alkyl group having 4 or more carbon atoms.

Ar ¹ is a hydrogen atom, an aryl group, or an alkyl group. These aryl groups and alkyl groups may or may not have a substituent.
Examples of the aryl group include phenyl group, tolyl group, xylyl group, mesityl group, naphthyl group, anthryl group, phenanthryl group and the like.
As an alkyl group, the alkyl group illustrated previously and a methyl group are mentioned.
As Ar ¹ , a hydrogen atom is particularly preferable.

Ra, Rb, Rc, and Rd are the same or different and are each an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 30 carbon atoms, an alkenyl group having 6 to 30 carbon atoms, or —OR ² . These alkyl group, aryl group, and alkenyl group may or may not have a substituent.
As an alkyl group, the alkyl group illustrated previously and a methyl group are mentioned.
Examples of the aryl group include the aryl groups exemplified above.
Examples of the alkenyl group include a vinyl group, an allyl group, a 1-propenyl group, an isobutenyl group, a 1-butenyl group, and a 2-butenyl group.
-OR ² is, ^{R 2} is an alkyl group, a perfluoroalkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 30 carbon atoms, having 1 to 10 carbon atoms. As an alkyl group and an aryl group, each alkyl group and aryl group which were illustrated previously are mentioned.
As Ra, Rb, Rc and Rd, a methyl group is preferable.

  m, n, o, and p each represent the number of substituents. m is an integer of 0 to 4, and n, o, and p are integers of 0 to 5. From the viewpoint of synthesis, m, n, and o are preferably 0, and p is preferably 0 or 1.

  Examples of compound (1) include compounds (1-1) to (1-5).

Compound (1) is produced, for example, as follows. In the reaction formula, X ¹ is a halogen atom, and R ¹ , Ar ¹ , Ra, Rb, Rc, Rd, m, n, o, and p are the same as those in the formula (1).

(A) Process:
In the presence of an acid catalyst, a secondary amine compound (5) and an aldehyde compound (6) are reacted in an organic solvent to form an enamine intermediate (7), and the enamine intermediate (7) is extracted and purified.

The reaction ratio (molar ratio) between the secondary amine compound (5) and the aldehyde compound (6) is preferably 1: 1 to 1: 2.5. If the amount of the aldehyde compound (6) is too small, the secondary amine compound (5) remains and purification becomes difficult. When there are too many aldehyde compounds (6), it will become a cost increase.
The reaction temperature is preferably 60 to 120 ° C., and the reaction time is preferably 1 to 5 hours. By setting it as this range, a desired reaction can be efficiently carried out with a relatively simple production facility.

Examples of the acid catalyst include p-toluenesulfonic acid, camphorsulfonic acid, pyridinium-p-toluenesulfonic acid and the like.
0.05-10 mass parts is preferable with respect to 100 mass parts of aldehyde compounds (6), and, as for the addition amount of an acid catalyst, 0.2-4 mass parts is more preferable. If the addition amount of the acid catalyst is less than 0.05 parts by mass, the reactivity between the secondary amine compound (5) and the aldehyde compound (6) may be significantly reduced. If the addition amount of the acid catalyst exceeds 10 parts by mass, it may be difficult to control the reaction between the secondary amine compound (5) and the aldehyde compound (6).

Examples of the organic solvent include toluene, xylene, chlorobenzene, butanol, diethylene glycol dimethyl ether, and the like.
In the step (a), water is generated as a by-product during the reaction. However, since this water hinders the reaction, it is preferable to remove the generated water from the reaction system by azeotropic distillation with an organic solvent. .

(B) Process:
Enamine intermediate (7) is added to Vilsmeier reagent, and formylation is performed by Vilsmeier reaction. After completion of the reaction, alkaline aqueous solution such as sodium hydroxide aqueous solution is added and hydrolyzed to obtain enamine-aldehyde intermediate (8). obtain.

The reaction ratio (mass ratio) between the enamine intermediate (7) and the Vilsmeier reagent is preferably 1: 1 to 1: 1.5. If there is too little Vilsmeier reagent, the enamine intermediate (7) remains and purification becomes difficult. If there is too much Vilsmeier reagent, the cost increases.
The reaction temperature is preferably 60 to 120 ° C., and the reaction time is preferably 1 to 10 hours. By setting it as this range, a desired reaction can be efficiently carried out with a relatively simple production facility.

Vilsmeier reagent can be prepared by adding N, N-disubstituted formamide and acid chloride in a solvent.
Examples of the solvent include N, N-dimethylformamide, 1,2-dichloroethane and the like.
Examples of the N, N-disubstituted formamide include N, N-dimethylformamide, N-methyl-N-phenylformamide, N, N-diphenylformamide and the like.
Examples of the acid chloride include phosphorus oxychloride, thionyl chloride, oxalyl chloride and the like.

(C) Process:
The compound (9) is reacted with triethyl phosphite to obtain the compound (10), and unreacted triethyl phosphite is distilled off under reduced pressure.

  The reaction ratio (molar ratio) between the compound (9) and triethyl phosphite is preferably 1: 1 to 1: 2.5. If there is too little triethyl phosphite, unreacted compound (9) remains and purification becomes difficult. If there is too much triethyl phosphite, the cost increases. The reaction temperature is preferably 120 to 200 ° C., and the reaction time is preferably 2 to 6 hours. By setting it as this range, a desired reaction can be efficiently carried out with a relatively simple production facility.

(D) Process:
In the presence of a base, the enamine-aldehyde intermediate (8) and the compound (10) are reacted in an organic solvent to obtain the compound (1), and the compound (1) is extracted and purified.

The reaction ratio (molar ratio) between the enamine-aldehyde intermediate (8) and the compound (10) is preferably 1: 1 to 1: 1.3. When there is too little compound (10), the yield of compound (1) will become small. When there are too many compounds (10), there will be many unreacted compounds (10) and there exists a possibility that the refinement | purification of a compound (1) may become difficult by side reaction etc.
The reaction temperature is preferably 15 to 60 ° C., and the reaction time is preferably 1 to 10 hours. By setting it as this range, a desired reaction can be efficiently carried out with a relatively simple production facility.

Examples of the base include metal alkoxides such as sodium methoxide, sodium ethoxide and potassium t-butoxide. A base may be used individually by 1 type and may be used in combination of 2 or more type.
The amount of the base added is preferably 1 to 1.8 mol with respect to 1 mol of the enamine-aldehyde intermediate (8). If the addition amount of the base is less than 1 mol, the reactivity between the enamine-aldehyde intermediate (8) and the compound (10) may be significantly reduced. When the addition amount of the base exceeds 1.8 mol, it may be difficult to control the reaction between the enamine-aldehyde intermediate (8) and the compound (10).

  Examples of the solvent include toluene, xylene, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, dimethyl sulfoxide, N, N-dimethylformamide and the like.

The compound (1) described above is specified as an alkyl group having 2 or more carbon atoms as R ¹ of the general formula (1), that is, as Ar ³ of the compound represented by the general formula (15), By selecting and using an aryl group (phenyl group) having an alkyl group having 2 or more carbon atoms, crystallinity is lowered, and as a result, solubility in a solvent and compatibility with a binder resin described later are improved. . In particular, when R ¹ is an alkyl group having 4 or more carbon atoms, the crystallinity is more likely to be lowered, so that the solubility and the compatibility are further improved.
Although the solvent is described in detail later, it is a solvent used in preparing a coating solution by dissolving each component constituting the photosensitive layer, and specifically includes an aromatic hydrocarbon or halogenated carbonization. Examples thereof include hydrogen and ethers.

By the way, when Ar ^{4 of the} compound represented by the general formula (15) (corresponding to Ar ¹ in the general formula (1)) is replaced with a hydrogen atom, steric hindrance in the molecule is small, and π in the molecule is small. Since the conjugated system becomes more planar, the properties as a charge transfer agent (for example, mobility) are further improved, but the solubility in a solvent and the compatibility with a binder resin are remarkably lowered.
However, according to the present invention, by specifying an alkyl group having 2 or more carbon atoms as R ^{1 in the} general formula (1), solubility in a solvent and compatibility with a binder resin are improved. Therefore, even if Ar ¹ in the general formula (1) is a hydrogen atom, the characteristics as an electron transport agent can be improved without reducing the solubility in a solvent and the compatibility with a binder resin.

In the present invention, the compound (1) described above is used as a charge transport agent, but a charge transport agent other than the compound (1) may be used in combination.
By the way, charge transport agents can be broadly classified into hole transport agents and electron transport agents. The compound (1) described above is classified as a hole transport agent.

  Among other charge transport agents, examples of the hole transport agent include benzidine compounds, phenylenediamine compounds, naphthylenediamine compounds, phenanthrylenediamine compounds, oxadiazole compounds, styryl compounds, and carbazole compounds. , Pyrazoline compounds, hydrazone compounds, triphenylamine compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, triazole compounds, butadiene compounds Compound, pyrene-hydrazone compound, acrolein compound, carbazole-hydrazone compound, quinoline-hydrazone compound, stilbene compound, stilbene-hydrazone compound, and dipheni Njiamin based compounds. A hole transport agent may be used individually by 1 type, and may use 2 or more types together.

  On the other hand, as electron transport agents, quinone derivatives, anthraquinone derivatives, malononitrile derivatives, thiopyran derivatives, trinitrothioxanthone derivatives, 3,4,5,7-tetranitro-9-fluorenone derivatives, dinitroanthracene derivatives, dinitroacridine derivatives, nitroant Araquinone derivatives, dinitroanthraquinone derivatives, tetracyanoethylene, 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroanthracene, dinitroacridine, nitroanthraquinone, dinitroanthraquinone, succinic anhydride, maleic anhydride, dibromomaleic anhydride, etc. Is mentioned. An electron transfer agent may be used individually by 1 type, and may be used in combination of 2 or more type.

  Among these electron transfer agents, since the electron-accepting property and the matching with the charge generating agent are excellent and an electrophotographic photoreceptor excellent in sensitivity characteristics and durability can be obtained, the compounds (12-1) to (12- 5) is particularly preferred.

(Binder resin)
As binder resin, polycarbonate resin such as bisphenol Z type, bisphenol ZC type, bisphenol C type, bisphenol A type, polyarylate resin, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer , Acrylic copolymer, styrene-acrylic acid copolymer, polyethylene resin, ethylene-vinyl acetate copolymer, chlorinated polyethylene resin, polyvinyl chloride resin, polypropylene resin, ionomer resin, vinyl chloride-vinyl acetate copolymer, Thermoplastic resins such as alkyd resin, polyamide resin, polyurethane resin, polysulfone resin, diallyl phthalate resin, ketone resin, polyvinyl acetal resin, polyvinyl butyral resin, polyether resin; silicone resin, epoxy resin Resins, phenol resins, urea resins, thermosetting resins such as melamine resin, epoxy acrylate, urethane - photocurable resins such as acrylate. Binder resin may be used individually by 1 type, and may use 2 or more types together.

  Among these binder resins, from the viewpoint of the film strength of the photosensitive layer and the compatibility with the hole transport agent and the electron transport agent, from the group consisting of structural units represented by the following general formulas (2) to (4) Polycarbonate resins having at least one selected structural unit are particularly preferred.

Rf, Rg, and Rh are the same or different and each represents an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 30 carbon atoms, an alkenyl group having 6 to 30 carbon atoms, or —OR ² . These alkyl group, aryl group, and alkenyl group may or may not have a substituent.
Examples of the alkyl group, aryl group, and alkenyl group include the alkyl groups, aryl groups, and alkenyl groups exemplified above.
-OR ² is, ^{R 2} is an alkyl group, a perfluoroalkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 30 carbon atoms, having 1 to 10 carbon atoms. As an alkyl group and an aryl group, each alkyl group and aryl group which were illustrated previously are mentioned.
r, s, and t each represent the number of substituents. r, s, and t are integers of 0 to 4, and 0 is preferable from the viewpoint of synthesis.

(Other)
The photosensitive layer may contain known additives as long as the electrophotographic characteristics are not affected. Examples of additives include antioxidants, light stabilizers, radical scavengers, singlet quenchers, deterioration inhibitors such as ultraviolet absorbers, softeners, plasticizers, surface modifiers, extenders, thickeners, Examples include dispersion aids, waxes, acceptors, donors and the like.
In order to improve the sensitivity of the photoreceptor layer, known sensitizers such as terphenyl, halonaphthoquinones, and acenaphthylene may be used in combination with the charge generator.
Specific examples of these additives include biphenyl compounds. By adding a biphenyl compound, the generation of cracks can be suppressed and the photosensitive layer can be prevented from cracking. Examples of the biphenyl compound include (13-1) to (13-20).

  Moreover, as a dispersion adjuvant, a compound (13-21) can be illustrated.

<Structure of photosensitive layer>
The photosensitive layer may have a single layer structure containing the above-described charge generating agent, charge transporting agent, and binder resin in the same layer, and includes at least a charge generating layer including a charge generating agent, a charge transporting agent, and a binder resin. A stacked structure including a charge transport layer may be used.
The order of stacking the charge generation layer and the charge transport layer in the multilayered photosensitive layer is not particularly limited. However, since the charge generation layer is thinner than the charge transport layer, it is preferable to provide a charge transport layer on the charge generation layer in order to protect the charge generation layer.
Here, in the present invention, an electrophotographic photosensitive member having a photosensitive layer having a single-layer structure is referred to as a “single-layer type electrophotographic photosensitive member”, and an electrophotographic photosensitive member having a laminated structure is referred to as a “multi-layered electrophotographic photosensitive member”. And

(Photosensitive layer with a single layer structure)
0.1-50 mass parts is preferable with respect to 100 mass parts of binder resins, and, as for content of a charge generating agent, 0.5-30 mass parts is more preferable.
20-500 mass parts is preferable with respect to 100 mass parts of binder resin, and, as for content of a hole transport agent, 30-200 mass parts is more preferable.
5-100 mass parts is preferable with respect to 100 mass parts of binder resins, and, as for content of an electron transport agent, 10-80 mass parts is more preferable.
The thickness of the photosensitive layer is preferably 5 to 100 μm, more preferably 10 to 50 μm.

(Photosensitive layer with a laminated structure)
The charge generation layer includes the above-described charge generation agent and binder resin. In addition, a known additive may be contained as long as the electrophotographic characteristics are not adversely affected.
The content of the charge generation agent in the charge generation layer is preferably 5 to 1000 parts by mass, more preferably 30 to 500 parts by mass with respect to 100 parts by mass of the binder resin.
The thickness of the charge generation layer is preferably from 0.01 to 5 μm, and more preferably from 0.1 to 3 μm.

The charge transport layer includes the above-described charge transport agent and binder resin. In addition, a known additive may be contained as long as the electrophotographic characteristics are not adversely affected.
10-500 mass parts is preferable with respect to 100 mass parts of binder resin, and, as for content of the hole transport agent of a charge transport layer, 25-200 mass parts is more preferable.
When the electron transport agent is contained in the charge transport layer, the content of the electron transport agent is preferably 5 to 200 parts by weight, and more preferably 10 to 100 parts by weight with respect to 100 parts by weight of the binder resin.
The thickness of the charge transport layer is preferably 2 to 100 μm, and more preferably 5 to 50 μm.

<Other layers>
In the electrophotographic photoreceptor of the present invention, an undercoat layer may be interposed between the conductive substrate and the photosensitive layer. An electrophotographic photosensitive member having an undercoat layer can effectively suppress the occurrence of leakage. Further, a protective layer may be provided on the photosensitive layer.
The undercoat layer contains inorganic particles. By containing the inorganic particles, an increase in resistance can be suppressed by flowing a current smoothly when the electrophotographic photosensitive member is exposed while suppressing the occurrence of leakage. Examples of the inorganic particles include metals and metal oxides. Specific examples include aluminum, iron, copper, titanium oxide, silica, alumina, zirconium oxide, tin oxide, zinc oxide, and indium oxide. Among these, titanium oxide is preferable. In particular, rutile type titanium oxide is preferable from the viewpoint of imparting appropriate insulating properties.

  The undercoat layer contains a binder resin in addition to the inorganic particles described above. As the binder resin, one or more of the binder resins exemplified above in the description of the photosensitive layer can be selected and used.

The thickness of the undercoat layer is preferably from 0.1 to 10 μm, more preferably from 0.5 to 5 μm.
10-1000 mass parts is preferable with respect to 100 mass parts of binder resin, and, as for content of an inorganic particle in an undercoat layer, 30-400 mass parts is more preferable.

<Production of electrophotographic photoreceptor>
The electrophotographic photoreceptor of the present invention can be produced, for example, as follows.
(Single layer type electrophotographic photoreceptor)
A coating solution in which a hole transporting agent, a charge generating agent, a binder resin and, if necessary, an electron transporting agent are dissolved or dispersed in a solvent is applied onto a conductive substrate, dried, and then exposed on the conductive substrate. An electrophotographic photosensitive member having a layer formed thereon is prepared.
The coating liquid is prepared by dissolving or dispersing each component in a solvent using a roll mill, a ball mill, an attritor, a paint shaker, an ultrasonic disperser or the like.

  Examples of the solvent include alcohols such as methanol, ethanol, isopropanol and butanol; aliphatic hydrocarbons such as n-hexane, octane and cyclohexane; aromatic hydrocarbons such as benzene, toluene and xylene; dichloromethane, dichloroethane, Halogenated hydrocarbons such as chloroform, carbon tetrachloride and chlorobenzene; ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, 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 Dimethylformaldehyde, dimethylformamide, dimethyl sulfoxide and the like. A solvent may be used individually by 1 type and may be used in mixture of 2 or more types.

Examples of the coating method include known methods such as dip coating, spray coating, spin coating, and bar coating.
Examples of the drying device include a high-temperature dryer and a vacuum dryer. The drying temperature is preferably 60 to 150 ° C.
An undercoat layer may be formed on the conductive substrate before forming the photosensitive layer. In this case, each component contained in the undercoat layer is dissolved or dispersed in the above-described solvent to prepare a coating solution for the undercoat layer, and the coating solution is applied onto a conductive substrate and dried to form the undercoat layer. What is necessary is just to form.
The method for preparing the coating solution, the coating method, the drying conditions, and the like are the same as those for forming the photosensitive layer.

(Laminated electrophotographic photoreceptor)
First, each component contained in the charge generation layer is dissolved or dispersed in the solvent described above to prepare a charge generation layer coating solution. Similarly, each component contained in the charge transport layer is dissolved or dispersed in the solvent described above to prepare a charge transport layer coating solution.
Next, the above-described coating liquids are sequentially applied and dried on the conductive substrate to form a charge generation layer and a charge transport layer.
The order of application and drying of each coating solution is not particularly limited. Moreover, the preparation method, coating method, drying conditions, etc. of the coating solution are the same as in the case of forming the photosensitive layer of the single-layer type electrophotographic photoreceptor.
Further, as in the case of the single-layer type electrophotographic photoreceptor, an undercoat layer may be formed on the conductive substrate before forming the charge generation layer and the charge transport layer.

The electrophotographic photoreceptor of the present invention thus obtained is produced using the specific compound (1), which is excellent in solubility in a solvent and compatibility with a binder resin, as a charge transport agent. It is possible to suppress crystallization of a part of the charge transfer agent and hardly precipitate. Therefore, the electrophotographic photosensitive member of the present invention is excellent in electrical characteristics such as sensitivity.
The electrophotographic photoreceptor of the present invention can maintain electrical characteristics even when used in a high temperature and high humidity environment.

[Image forming apparatus]
FIG. 1 is a schematic configuration diagram showing an example of an image forming apparatus of the present invention. The image forming apparatus 10 in this example includes an image carrying unit 11, a charging unit 12, an exposure unit 13, a developing unit 14, a transfer unit 15, and a cleaning unit 16.

The image carrying means 11 is the multilayer electrophotographic photosensitive member of the present invention, and a charge generation layer and a charge transport layer are laminated on a drum-like conductive substrate.
The charging unit 12 is a unit that charges the surface of the image carrying unit 11, and examples thereof include a corona charging device, a charging roller, and a charging brush.
The exposure unit 13 is a unit that exposes the surface of the image carrying unit 11 to form an electrostatic latent image.
The developing unit 14 is a unit that develops an electrostatic latent image as a toner image using toner.
The transfer unit 15 is a unit that transfers the toner image from the image carrying unit 11 to a transfer target (not shown).
The cleaning means 16 is means for removing paper dust and the like adhering to the photosensitive drum, and examples thereof include an elastic blade and a fur brush.

In general, the image forming apparatus is often provided with a charge eliminating unit that removes the charge on the surface of the image carrying unit.
However, in the case of the image forming apparatus of the present invention, since the electrophotographic photosensitive member of the present invention is used as the image carrying means, charges generated by exposure are not easily accumulated in the photosensitive layer. For this reason, even if the static eliminating means is not provided, the surface potential difference between the exposed portion and the non-exposed portion is small when the photoreceptor is charged in the next cycle. Therefore, it is not necessary to provide a static elimination means such as a static elimination lamp, and the manufacturing cost can be reduced.
In the image forming apparatus of the present invention, since the photosensitive layer has sufficient film strength and leakage resistance, a charging roller can be used as the charging means. By using the charging roller, discharge of active gas such as ozone and nitrogen oxide generated from the charging means can be suppressed.

In the image forming apparatus described above, the crystallization of the charge transport agent in the charge transport layer is suppressed and the electrophotographic photoreceptor of the present invention having excellent electrical characteristics is used. High-quality images can be obtained with less image fogging. In addition, since the electrophotographic photosensitive member of the present invention can maintain electrical characteristics even in a high temperature and high humidity environment, a high quality image can be obtained.
Examples of such an image forming apparatus include a copying machine, a facsimile, and a laser beam printer.

[Synthesis of charge transport agent]
<Synthesis of Compound (1-1)>
(A) Process:
In a reaction vessel, p-toluenesulfonic acid, secondary amine compound (5-1) 22.5 g (0.1 mol), aldehyde compound (6-1) 19.6 g (0.1 mol), and toluene were placed, and the temperature was 80 ° C. The mixture was stirred for 4 hours while being heated at, and reacted while removing water from the system azeotropically with water and toluene. After cooling to room temperature, the enamine intermediate (7-1) was extracted and purified.

(B) Process:
First, N-dimethylformamide and phosphorus oxychloride were added to N, N-dimethylformamide to prepare a Vilsmeier reagent.
To 40 g of the obtained Vilsmeier reagent, 32.3 g (0.08 mol) of enamine intermediate (7-1) was added, stirred for 6 hours while heating at 80 ° C., formylation was performed by Vilsmeier reaction, and after completion of the reaction, An aqueous sodium hydroxide solution was added and hydrolyzed to obtain an enamine-aldehyde intermediate (8-1).

(C) Process:
In a reaction vessel, 30.5 g (0.2 mol) of the compound (9-1) and 49.8 g (0.3 mol) of triethyl phosphite were added and stirred for 3 hours while heating at 30 ° C. After cooling to room temperature, excess triphosphorous acid triethyl ester was distilled off under reduced pressure to obtain compound (10-1).

(D) Process:
In a reaction vessel, sodium methoxide, 21.6 g (0.05 mol) of enamine-aldehyde intermediate (8-1), 15.3 g (0.06 mol) of compound (10-1), and tetrahydrofuran are placed and heated at 30 ° C. The mixture was stirred for 5 hours while being reacted. After cooling to room temperature, the compound (1-1) was extracted and purified.

<Synthesis of Compound (1-2)>
In the step (a), synthesis was performed in the same manner as in the compound (1-1) except that 23.9 g (0.1 mol) of the compound (5-2) was used instead of the compound (5-1). Compound (1-2) was obtained.

<Synthesis of Compound (1-3)>
In the step (a), synthesis was performed in the same manner as in the compound (1-1) except that 26.7 g (0.1 mol) of the compound (5-3) was used instead of the compound (5-1). Compound (1-3) was obtained.

<Synthesis of Compound (1-4)>
In the step (c), the compound (9-1) was synthesized in the same manner as the compound (1-1) except that 51.3 g (0.2 mol) of the compound (9-2) was used instead of the compound (9-1). Compound (1-4) was obtained.

<Synthesis of Compound (1-5)>
In the step (a), the compound (5-1) was synthesized in the same manner as the compound (1-1) except that 19.7 g (0.1 mol) of the compound (5-4) was used instead of the compound (5-1). Compound (1-5) was obtained.

<Synthesis of Compound (15-1)>
In the step (a), the compound (5-1) was synthesized in the same manner as in the compound (1-1) except that 18.3 g (0.1 mol) of the compound (5-5) was used instead of the compound (5-1). Compound (15-1) was obtained.

<Synthesis of Compound (15-2)>
In the step (a), 18.3 g (0.1 mol) of the compound (5-5) is used instead of the compound (5-1), and in the step (c), the compound is used instead of the compound (9-1). (9-2) The compound (15-2) was obtained by synthesis in the same manner as in the compound (1-1) except that 51.3 g (0.2 mol) was used.

[Synthesis of Charge Generator (Titanyl Phthalocyanine)]
(Pigmentation pretreatment)
In a flask purged with argon, 25 g of o-phthalonitrile, 28 g of titanium tetrabutoxide, and 300 g of quinoline were added, and the temperature was raised to 150 ° C. while stirring.
Next, while evaporating the vapor generated from the reaction system, the temperature was raised to 215 ° C. while distilling out of the system, and the mixture was further stirred for 2 hours while maintaining this temperature.
After completion of the reaction, when the reaction mixture is cooled to 150 ° C., the reaction mixture is taken out from the flask and filtered through a glass filter. The obtained solid is washed successively with N, N-dimethylformamide and methanol, and then dried in vacuo. 24 g of a violet solid was obtained.

10 g of the obtained blue-violet solid was added to 100 mL of N, N-dimethylformamide, heated to 130 ° C. with stirring, and stirred for 2 hours.
Next, after 2 hours had elapsed, heating was stopped, and after cooling to 23 ± 1 ° C., stirring was also stopped. In this state, the liquid was allowed to stand for 12 hours for stabilization treatment.
The stabilized liquid was filtered off with a glass filter, and the obtained solid was washed with methanol and then vacuum-dried to obtain 9.83 g of a crude crystal of a titanyl phthalocyanine compound.

(Pigmentation treatment)
5 g of the crude crystal of the obtained titanyl phthalocyanine compound was dissolved in 100 mL of concentrated sulfuric acid.
Next, this solution was added dropwise to ice-cooled water, stirred at room temperature for 15 minutes, and further allowed to stand at about 23 ± 1 ° C. for 30 minutes for recrystallization.
Next, the above liquid is filtered off with a glass filter, and the obtained solid is washed with water until the washing liquid becomes neutral. Then, without drying, in the presence of water, dispersed in 200 mL of chlorobenzene and heated to 50 ° C. And stirred for 10 hours.
And after filtering a liquid with a glass filter, the obtained solid was vacuum-dried at 50 degreeC for 5 hours, and 4.1g of crystals (blue powder) of titanyl phthalocyanine (11-2) were obtained.

  The obtained titanyl phthalocyanine (11-2) has an initial Bragg angle of 2θ ± 0.2 ° = 7.4 ° and 26.2 ° even when immersed in 1,3-dioxolane or tetrahydrofuran for 7 days. It was confirmed that no peak was generated and that no peak of temperature change was observed from 50 ° C. to 400 ° C. except for a peak near 90 ° C. accompanying vaporization of adsorbed water.

[Test 1: Laminated electrophotographic photoreceptor]
<Example 1>
(Production of multilayer electrophotographic photoreceptor)
After surface treatment with alumina and silica, 2 parts by mass of titanium oxide (manufactured by Teica, “SMT-02”, number average primary particle size 10 nm) surface-treated with methyl hydrogen polysiloxane while being wet-dispersed, and copolymerized 1 part by mass of polyamide resin (“Daiamide X4585” manufactured by Daicel Degussa) was dispersed in 10 parts by mass of ethanol and 2 parts by mass of butanol for 5 hours using a bead mill to prepare a coating solution for an undercoat layer.
The obtained undercoat layer coating solution was filtered through a 5 μm filter, and then applied to an aluminum drum-shaped substrate having a diameter of 30 mm and a total length of 238.5 mm as a conductive substrate by a dip coating method. And an undercoat layer having a thickness of 1.5 μm was formed.

Next, 1 part by mass of titanyl phthalocyanine (11-2) previously synthesized as a charge generator, 1 part by mass of polyvinyl butyral resin (manufactured by Denki Kagaku Kogyo Co., Ltd., “Denka Butyral # 6000EP”) as a binder resin, and propylene glycol as a dispersion medium 40 parts by mass of monomethyl ether and 40 parts by mass of tetrahydrofuran were mixed and dispersed in a bead mill for 2 hours to prepare a charge generation layer coating solution.
The obtained coating solution for charge generation layer was filtered through a 3 μm filter, and then applied on the undercoat layer prepared above by dip coating, dried at 50 ° C. for 5 minutes, and a film thickness of 0. A 3 μm charge generation layer was formed.

Next, 70 parts by mass of the compound (1-1) as a hole transport agent, 5 parts by mass of Yoshix BHT (di-t-butyl-p-cresol) as an additive, and meta-terphenyl (13-3) 3 100 parts by mass of a polycarbonate resin (14-1) having a viscosity average molecular weight of 50,500 shown below as a binder resin and a binder resin, 430 parts by mass of tetrahydrofuran and 430 parts by mass of toluene are mixed and dissolved, and a coating solution for a charge transport layer is prepared. Prepared.
The prepared charge transport layer coating solution is applied onto the charge generation layer in the same manner as the charge generation layer coating solution and dried at 130 ° C. for 30 minutes to form a charge transport layer having a thickness of 20 μm. An electrophotographic photosensitive member was produced.

(Evaluation 1: Electrical property test)
Laminate type electrophotographic photosensitive member is installed in a printer (Oki Data Corporation, “MicroLine-22N”, without static elimination means) employing a negatively charged reversal development process, and in a normal temperature and humidity environment (23 ° C., 40 RH%). 10000 sheets were printed. After printing, the potential at the development position was measured using a surface potentiometer, and the electrical characteristics (surface potential, bright potential, exposure memory) were evaluated. The surface potential is the blank portion potential (V ₀ ), the bright potential is the solid portion potential (V _L ), and the exposure memory is (V ₀ -V _0b ) from the next blank portion potential (V _0b ) of the front exposure portion. Asked. The results are shown in Table 1.

(Evaluation 2: Image cover)
In the same manner as in the electrical property test, the laminated electrophotographic photosensitive member was installed in a printer, and 20 blank paper images were printed in a high temperature and high humidity environment (35 ° C., 85 RH%). For the tenth blank paper image, a fog value (FD value) was measured using a Macbeth reflection densitometer ("SPM-50" manufactured by Gretag Macbeth). The results are shown in Table 1.

<Examples 2-14, Comparative Examples 1-2>
Example 1 except that a charge generation layer coating solution was prepared using the charge generation agent shown in Table 1 and a charge transport layer coating solution was prepared using the hole transport agent and binder resin shown in Table 1. In the same manner, a laminated electrophotographic photoreceptor was prepared and evaluated. The results are shown in Table 1.
In addition, binder resin (14-2)-(14-6) is shown below.

  As is clear from Table 1, the multilayer electrophotographic photoreceptors obtained in the examples have lower light potential and exposure memory than the multilayer electrophotographic photoreceptors obtained in the comparative examples, and are excellent in electrical characteristics. It was. Further, the fogging value is low, and a high quality image can be formed. In Example 5, a slight turbidity was confirmed in the coating solution for charge transport layer, but the photoconductor could be produced without precipitation of the hole transport agent.

On the other hand, in the laminated electrophotographic photoreceptor obtained in Comparative Example 1, the hole transport agent crystallized and deposited on the surface of the photoreceptor when the charge transport layer coating solution was applied. Could not be measured. Therefore, the evaluation test was not performed.
In the multilayer electrophotographic photoreceptor obtained in Comparative Example 2, the hole transport agent was easily crystallized and deposited when the charge transport layer coating solution was applied. For this reason, the bright potential and the exposure memory were higher than those of the examples and the sensitivity was inferior. Moreover, the fogging value was high.

[Test 2: Single-layer type electrophotographic photosensitive member]
<Example 15>
(Production of single layer type electrophotographic photoreceptor)
First, 3 parts by mass of an x-type metal-free phthalocyanine (11-1) as a charge generator, 50 parts by mass of a compound (1-1) as a hole transport agent, and 40 parts by mass of a diphenoquinone compound (12-1) as an electron transport agent. Parts, 3 parts by mass of meta-terphenyl (13-3) as an additive, 100 parts by mass of a polycarbonate resin (14-1) as a binder resin, and 750 parts by mass of tetrahydrofuran as an organic solvent, mixed and dispersed with an ultrasonic disperser A photosensitive layer coating solution was prepared.
Next, the obtained coating solution for forming a photosensitive layer was applied by a dip coating method onto an undercoat layer formed on a conductive substrate in the same manner as in Example 1, and then heated with hot air at 130 ° C. for 40 minutes. It was dried to form a photosensitive layer having a thickness of 25 μm, and a single layer type electrophotographic photosensitive member was produced.

(Evaluation 3: Electrical property test)
The single-layer type electrophotographic photosensitive member was installed in a printer (“Printer DP-560” manufactured by Kyocera Mita Co., Ltd.), and 10,000 sheets were printed in a normal temperature and humidity environment (23 ° C., 40 RH%). After printing, the potential at the development position was measured using a surface potentiometer, and the electrical characteristics (bright potential, exposure memory) were evaluated. The bright potential was determined as (V ₀ -V _0b ) from the solid portion potential (V _L ) and the exposure memory from the blank portion potential (V _0b ) next to the front exposure portion. The results are shown in Table 2.
The rotational speed of the electrophotographic photosensitive member of the printer was 60 mm / sec, and the light quantity was 1.0 μJ / cm ² . The printer is an image forming apparatus using a simultaneous development cleaning system, and includes a scorotron charger, an exposure device, a developing device, and a transfer roller. The printer was used after removing the static elimination lamp.

(Evaluation 4: Image cover)
In the same manner as in the electrical property test (Evaluation 3), the single-layer electrophotographic photosensitive member was installed in a printer, and 20 blank paper images were printed in a high temperature and high humidity environment (35 ° C., 85 RH%). For the tenth blank paper image, a fog value (FD value) was measured using a Macbeth reflection densitometer ("SPM-50" manufactured by Gretag Macbeth). The results are shown in Table 2.

<Examples 16 to 28>
A single-layer electrophotographic photosensitive member is produced in the same manner as in Example 15 except that the coating solution for the photosensitive layer is prepared using the charge generating agent, hole transporting agent, electron transporting agent and binder resin shown in Table 2. And evaluated. The results are shown in Table 2.
In Example 24, 3 parts by mass of titanyl phthalocyanine (11-2) as a hole transporting agent and C.I. I. 2 parts by mass of Pigment Yellow 93 (PY93) was used.

  As is clear from Table 2, the single-layer electrophotographic photosensitive member obtained in the examples had low light potential and low exposure memory, and excellent electrical characteristics. Further, the fogging value is low, and a high quality image can be formed.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus of the present invention.

Explanation of symbols

10: image forming apparatus, 11: image carrying means (electrophotographic photosensitive member), 12: charging means, 13: exposure means, 14: developing means, 15: transfer means.

Claims (5)

In an electrophotographic photosensitive member in which a photosensitive layer containing a charge generating agent, a charge transporting agent, and a binder resin is formed on a conductive substrate,
It said photosensitive layer, the charge transport agent were lower following formula and (1-1) to an electrophotographic photoreceptor, characterized by containing one kind selected from compounds represented by (1-5).

Said binder resin is an electron according to claim 1, characterized in that it is a polycarbonate resin having at least one structural unit selected from the group consisting of a structural unit represented by the following general formula (2) to (4) Photoconductor.

In the formulas (2) to (4), Rf, Rg, and Rh are the same or different and are each an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 30 carbon atoms, an alkenyl group having 6 to 30 carbon atoms, or —OR ² (wherein R ² is an alkyl group having 1 to 10 carbon atoms, a perfluoroalkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 30 carbon atoms), and the number of substituents is R, s, and t shown are each an integer of 0 to 4. Said photosensitive layer, the charge generating material, electric charge transferring material, and an electrophotographic photosensitive member according to claim 1 or 2, characterized in that the binder resin is a single-layer structure containing the same layers. The said photosensitive layer is a laminated structure which has a charge generation layer containing the said charge generation agent at least, and a charge transport layer containing the said charge transfer agent and the said binder resin, The Claim 1 or 2 characterized by the above-mentioned. Electrophotographic photoreceptor. Image carrying means, charging means for charging the surface of the image carrying means, exposure means for exposing the surface of the image carrying means to form an electrostatic latent image, and developing the electrostatic latent image as a toner image In an image forming apparatus comprising: a developing unit; and a transfer unit that transfers the toner image from the image carrying unit to a transfer target, and no charge removing unit that removes the charge on the surface of the image carrying unit.
An image forming apparatus, wherein the image carrying means is the electrophotographic photosensitive member according to claim 4 .

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