JP2010078904A - Monolayer type electrophotographic photosensitive member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a monolayer type electrophotographic photosensitive member capable of forming a high quality image stably with high sensitivity. <P>SOLUTION: The monolayer type electrophotographic photosensitive member contains titanyl phthalocyanine having the maximum peak at a Bragg angle of 2&theta;&plusmn;0.2&deg;=27.2&deg; in &alpha; characteristic X-ray diffraction spectrum of CuK as an electric charge generator, having the maximum peak at a Bragg angle of 2&theta;&plusmn;0.2&deg;=27.2&deg; after being immersed in an organic solvent for 24 hours, and having no peak at 26.2&deg; and contains bisazo pigment expressed in formula (1) as an electric charge generating adjuvant. The content of titanyl phthalocyanine is larger than that of the bisazo pigment. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a single layer type electrophotographic photosensitive member.

  In recent years, the electrophotographic system is used not only in the field of copying machines but also in fields where photographic technology has been used conventionally, such as printing plate materials, slide films, and microfilms. Application to high-speed printers using lasers, LEDs, or CRTs as light sources is also being studied. Furthermore, applications of photoconductive materials other than electrophotographic photoreceptors such as electrostatic recording elements, sensor materials, EL elements, etc. have begun to be studied. For this reason, demands for photoconductive materials and electrophotographic photoreceptors using the same (hereinafter, sometimes simply referred to as “photoreceptors”) are becoming high and wide.

  As electrophotographic photoreceptors, inorganic photoconductive substances such as selenium, cadmium sulfide, zinc oxide, silicon and the like are known, and these have been widely studied and put into practical use. However, these inorganic photoconductive materials have many advantages and various drawbacks. For example, selenium has the disadvantages that the production conditions are difficult and that it is easily crystallized by heat and mechanical shock, and cadmium sulfide and zinc oxide have the disadvantages of being inferior in moisture resistance and durability. It has been pointed out that silicon is insufficiently charged and difficult to manufacture. In addition, selenium and cadmium sulfide also had toxicity problems.

In order to solve these problems, a photoreceptor using an organic photoconductive material has been put into practical use. Organic photoconductive materials have advantages such as excellent film formability and flexibility, light weight, good transparency, and easy design of a photoreceptor for a wide range of wavelengths by an appropriate sensitization method. Have.
Known organic photoconductive materials include photoconductive polymers such as polyvinyl carbazole, organic low molecular photoconductive compounds, and the like.

By the way, the following matters are generally required as basic properties for a photoreceptor used in electrophotographic technology. That is, (1) high chargeability with respect to corona discharge in a dark place, (2) little leakage (dark decay) of the obtained charged charge in the dark place, and (3) charged charge due to light irradiation. (4) The residual charge after light irradiation is small, and the like.
However, the photoconductive polymer does not necessarily have sufficient film properties, flexibility, and adhesiveness, and it is difficult to say that the photoconductive polymer has sufficient basic properties as the above-described photoreceptor.
For organic low-molecular photoconductive compounds, a photoconductor excellent in mechanical strength such as film property, adhesiveness, and flexibility can be obtained by selecting a binder resin or the like used for forming the photoconductor. Although it was possible, it was difficult to find a low molecular photoconductive compound suitable for maintaining high sensitivity characteristics.

  In order to improve such a point, a photoconductor in which a charge generation function and a charge transport function are assigned to different substances has been proposed. Among these, various substances such as phthalocyanine pigments, squalium dyes, azo pigments, and perylene pigments have been studied as substances responsible for the charge generation function, and charge generation materials with high charge generation efficiency have been developed. It has been broken.

  In recent years, laser beam printers that use laser light as a light source instead of conventional white light and have the advantages of high speed, high image quality, and non-impact have become widespread in conjunction with advances in information processing systems. Therefore, there is a demand for the development of materials that can withstand these requirements. In particular, semiconductor lasers, whose application to compact discs, optical discs, and the like, among the laser beams is increasing and whose technological progress is remarkable, are actively applied in the printer field as a compact and highly reliable light source material. Since the wavelength of the light source in this case is around 650 to 830 nm, development of a photoreceptor having high sensitivity characteristics from red to the near infrared region is strongly desired. In particular, development of photoreceptors using phthalocyanine pigments that absorb light from red to the near infrared region has been actively conducted. In particular, a layered type in which a substance (charge generating agent) responsible for charge generation function, a charge generation layer containing a substance responsible for charge transport function (charge transport agent) and a charge transport layer are laminated on a conductive substrate. These photoconductors are also mass-produced.

Taking titanyloxyphthalocyanine (hereinafter abbreviated as “TiOPc”) as an example of the phthalocyanine pigment, for example, in Patent Document 1, the Bragg angle (2θ ± 0.2 °) in the X-ray diffraction spectrum is 7. Α-type TiOPc having main diffraction peaks at 5 °, 12.3 °, 16.3 °, 25.3 °, and 28.7 ° is disclosed.
In Patent Document 2, Bragg angles (2θ ± 0.2 °) in an X-ray diffraction spectrum are 9.3 °, 10.6 °, 13.2 °, 15.1 °, 15.7 °, 16 Β-type TiOPc having main diffraction peaks at .1 °, 20.8 °, 23.3 °, 26.3 ° and 27.1 ° is disclosed.

However, the TiOPc described in Patent Documents 1 and 2 does not always satisfy the required high characteristics sufficiently.
Further, even if the X-ray diffraction spectrum has a Bragg angle (2θ ± 0.2 °) having a peak at 27.2 °, type II TiOPc reported in Patent Document 2 is inferior in chargeability. The sensitivity was low.

Therefore, as TiOPc showing good sensitivity, Patent Document 3 discloses that the Bragg angle (2θ ± 0.2 °) in the X-ray diffraction spectrum is 9.5 °, 9.7 °, 11.7 °, 15.0. Y-type TiOPc having main diffraction peaks at °, 23.5 °, 24.1 ° and 27.3 ° is disclosed.
JP-A-61-217050 JP-A 62-67094 JP-A 64-17066

However, when the Y-type TiOPc described in Patent Document 3 is used as a charge generating agent, the single layer type photosensitive member in which the charge generating agent and the charge transporting agent are contained in one layer (photosensitive layer) has high sensitivity. Is insufficient and does not necessarily satisfy the electrical characteristics. For this reason, the quality of the obtained image is likely to deteriorate due to the occurrence of fogging.
Further, if the coating solution for forming the photosensitive layer is stored for a long period of time, the Y-type TiOPc may aggregate or precipitate, which may make it difficult to efficiently manufacture the photoreceptor.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to realize a single-layer type electrophotographic photosensitive member capable of forming a high-quality image stably with high sensitivity.

  As a result of intensive studies, the present inventors have found that Y-type TiOPc is likely to aggregate or precipitate in the organic solvent used in the coating solution for forming the photosensitive layer, so that the dispersibility in the organic solvent is insufficient. In the case of producing a single-layer type photoreceptor, Y-type TiOPc is difficult to uniformly disperse in the photosensitive layer, and as a result, an excellent charge generation function is not fully exhibited, and a high-sensitivity single-layer type photosensitive body is produced. It was found that the body was difficult to obtain. In particular, in the case of a single layer type photoreceptor, since the types of binder resin and organic solvent that can be selected are less than those of a laminated type photoreceptor, the dispersibility of the charge generating agent tends to decrease.

  Therefore, the present inventors use a specific titanyl phthalocyanine as a charge generator in a monolayer type electrophotographic photoreceptor, and prevent the titanyl phthalocyanine from aggregating or precipitating in an organic solvent. For the purpose, it has been found that by containing a specific bisazo pigment, the dispersibility of titanyl phthalocyanine can be improved, and a highly sensitive single layer type electrophotographic photoreceptor can be easily produced, and the present invention has been completed.

  That is, the single-layer electrophotographic photosensitive member of the present invention has a single layer provided with a photosensitive layer containing a charge generating agent, a charge generating auxiliary agent, a hole transporting agent, an electron transporting agent, and a binder resin on a conductive substrate. The electrophotographic photosensitive member has a maximum peak at a Bragg angle of 2θ ± 0.2 ° = 27.2 ° in the CuKα characteristic X-ray diffraction spectrum as the charge generating agent, and the photosensitive layer is In the CuKα characteristic X-ray diffraction spectrum after being immersed in the organic solvent used for the coating liquid to be formed for 24 hours, it has a maximum peak at least at a Bragg angle 2θ ± 0.2 ° = 27.2 °, and 26.2 °. Containing a titanyl phthalocyanine having no peak, a bisazo pigment represented by the following general formula (1) as the charge generation auxiliary agent, and the content of the titanyl phthalocyanine is More than the content of the bisazo pigment.

In Formula (1), A ¹ is a hydrogen atom, an alkyl group, an alkoxy group, an alkylthio group, an aryl group, an aralkyl group, or a heterocyclic group, Cp ¹ and Cp ² are the same or different coupler residues, and X ¹ is a hydrogen atom or an aryl group, m is an integer of 0 to 2, and n is 0 or 1.

Further, it is preferable that an undercoat layer is provided between the conductive substrate and the photosensitive layer.
Furthermore, the undercoat layer preferably contains at least titanium oxide and a binder resin.
The titanium oxide is preferably surface-treated with alumina and silica and further surface-treated with an organosilicon compound.

Furthermore, it is preferable that the titanyl phthalocyanine has the characteristics shown in the following (a) or (b).
(A): In the differential scanning calorimetry, no peak is present in the range of 50 ° C. or higher and 400 ° C. or lower except for the peak accompanying vaporization of adsorbed water.
(B): In the differential scanning calorimetry, there is no peak in the range of 50 ° C. or more and less than 200 ° C., and there is one peak in the range of 200 ° C. or more and 400 ° C. or less, except for the peak accompanying vaporization of adsorbed water. Have a peak.

According to the present invention, a high-sensitivity single layer type electrophotographic photosensitive member can be obtained.
Further, according to the single layer type electrophotographic photosensitive member of the present invention, a high quality image can be stably formed.

Hereinafter, the present invention will be described in detail.
The single-layer electrophotographic photoreceptor of the present invention (hereinafter sometimes simply referred to as “photoreceptor”) has a charge generating agent, a charge generating auxiliary agent, a hole transporting agent, an electron transporting agent on a conductive substrate. A photosensitive layer containing a binder resin is provided.

<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 support 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>
(Charge generator)
The photoreceptor of the present invention contains titanyl phthalocyanine as a charge generator.
The titanyl phthalocyanine used in the present invention is preferably a titanyl phthalocyanine crystal obtained by crystallizing a titanyl phthalocyanine compound. Moreover, titanyl phthalocyanine has the following optical properties.

That is, the CuKα characteristic X-ray diffraction spectrum has a maximum peak at least at a Bragg angle 2θ ± 0.2 ° = 27.2 °. By having such optical characteristics, the storage stability in an organic solvent (hereinafter simply referred to as “organic solvent”) used in a coating solution for forming a photosensitive layer is improved.
Further, in the CuKα characteristic X-ray diffraction spectrum after being immersed in an organic solvent for 24 hours, it has a maximum peak at least at a Bragg angle 2θ ± 0.2 ° = 27.2 ° and 2θ ± 0.2 ° = 26. It shall not have a peak at 2 °. By having such optical characteristics, even when immersed in an organic solvent for 24 hours, the crystal transition in the organic solvent (crystal transition to α-type crystal or β-type crystal) can be easily controlled. Thus, a photosensitive member having high sensitivity and excellent electrical characteristics can be obtained.
The crystal form of titanyl phthalocyanine having a maximum peak at a Bragg angle 2θ ± 0.2 ° = 27.2 ° and no peak at 26.2 ° is a Y-type.

The CuKα characteristic X-ray diffraction spectrum can be measured using, for example, an X-ray diffraction apparatus “RINT1100” manufactured by Rigaku Corporation.
Moreover, the immersion experiment evaluation in the organic solvent used as the reference | standard which evaluates the storage stability of titanyl phthalocyanine is the conditions which actually store the coating liquid which forms a photosensitive layer (henceforth "the coating liquid for photosensitive layers"), for example. It is preferable to implement on the same conditions. Specifically, it is preferable to evaluate the storage stability of titanyl phthalocyanine in a closed system under conditions of a temperature of 23 ± 1 ° C. and a relative humidity of 50 to 60% RH. The organic solvent for evaluating the storage stability is preferably the same as the organic solvent used for the coating solution for forming the photosensitive layer. Specifically, tetrahydrofuran, dichloromethane, toluene, 1,4-dioxane, and 1 It is preferably at least one selected from the group consisting of -methoxy-2-propanol.

The titanyl phthalocyanine preferably has the characteristics shown in the following (a) or (b).
(A): In the differential scanning calorimetry, no peak is present in the range of 50 ° C. or higher and 400 ° C. or lower except for the peak accompanying vaporization of adsorbed water.
(B): In the differential scanning calorimetry, there is no peak in the range of 50 ° C. or more and less than 200 ° C., and there is one peak in the range of 200 ° C. or more and 400 ° C. or less, except for the peak accompanying vaporization of adsorbed water. Have a peak.
By having such thermal characteristics, crystal transition in an organic solvent can be easily controlled. As a result, a photosensitive layer coating solution having excellent storage stability can be obtained, and a photoreceptor excellent in electrical characteristics and image characteristics can be produced, and a high-quality image can be stably formed.

More specifically, when titanyl phthalocyanine has the characteristic (a), such titanyl phthalocyanine tends to be a stable crystal that hardly undergoes crystal transition.
That is, even when the photosensitive layer coating solution is prepared and used after being stored for a certain period, titanyl phthalocyanine is changed from Y-type to α-type or β-type by the action of the organic solvent contained in the photosensitive layer coating solution. Little crystal transition to mold. Accordingly, it is possible to retain the Y-type, which is a crystal type in which titanyl phthalocyanine is excellent in charge generation.

In addition, when titanyl phthalocyanine has the characteristics (b), the titanyl phthalocyanine has improved temporal stability and dispersibility, so that it can suppress crystal transition in an organic solvent, and in the photosensitive layer coating solution, Particularly excellent dispersibility can be exhibited.
That is, the titanyl phthalocyanine used in the present invention has a crystal form that does not transfer to α or β type when preparing a coating solution for a photosensitive layer, and can retain the Y type, and has a dispersibility in the coating solution for the photosensitive layer. Since it is particularly excellent, it is possible to generate charges at the time of exposure in the formed photosensitive layer very efficiently. Furthermore, the excellent dispersibility enables efficient charge transport between the titanyl phthalocyanine and the charge transporting agent (hole transporting agent and electron transporting agent) to be described later. In addition to the improvement, generation of a residual potential in the photosensitive layer can be prevented, and the exposure memory can be effectively suppressed.

In addition, it is more preferable that one peak appearing in the range of 200 to 400 ° C. other than the peak accompanying vaporization of the adsorbed water appears in the range of 270 to 400 ° C., and the range of 300 to 400 ° C. More preferably, it appears within.
The differential scanning calorimetry can be analyzed using, for example, a differential scanning calorimeter “TAS-200 type” manufactured by Rigaku Corporation.

  Such titanyl phthalocyanine is, for example, a crystal of a titanyl phthalocyanine compound represented by the following general formula (2) having a Y-type or a similar crystal form from the viewpoint of stability and ease of production. Is preferred.

In formula (2), Y ^{1 to} Y ⁴ are the same or different and are a halogen atom, an alkyl group, an alkoxy group, a cyano group, or a nitro group, and a to d are the same or different and are integers of 0 to 4. . The alkyl group, alkoxy group, cyano group, or nitro group may or may not have a substituent.
Examples of the halogen atom include fluorine, chlorine, bromine and iodine.
Examples of the alkyl group include 1 to 6 carbon atoms such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, and hexyl group. Of the alkyl group.
Alkoxy groups include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy, hexyloxy, etc. 1-6 alkoxy groups are mentioned.

Preferable examples of the titanyl phthalocyanine compound, wherein in the general formula (2) in the Y ¹ to Y ⁴ are all the same group Y, and it is a~d same number both have e indicating the number of the substituents, The compound represented by the following general formula (21) is mentioned.

In formula (21), Y represents a halogen atom, an alkyl group, an alkoxy group, a cyano group, or a nitro group, and e represents an integer of 0 to 4.
Among these, a compound represented by the following general formula (21-1) in which e is 0 is most preferable.

  The titanyl phthalocyanine crystal represented by the general formula (21) and having the optical characteristics described above is manufactured, for example, as follows. In the reaction formula, R is an alkyl group having 1 to 6 carbon atoms (particularly n-butyl is preferable), and Y and e are the same as those in the general formula (21).

Production Example 1:
By reacting phthalonitrile or its derivative (21a) with titanium alkoxide (21b), a titanyl phthalocyanine compound (21) is synthesized.

Production Example 2:
1,3-diiminoindoline or its derivative (21c) is reacted with titanium alkoxide (21b) to synthesize a titanyl phthalocyanine compound (21).

  Next, the titanyl phthalocyanine compound (21) obtained in Production Example 1 or Production Example 2 is added to a water-soluble organic solvent, and after stirring for a certain time under heating, the temperature is lower than that of the stirring treatment. The pigmentation pretreatment is performed in which the liquid is allowed to stand for a certain period of time for stabilization treatment.

Examples of the water-soluble organic solvent used in the pretreatment for pigmentation include alcohols such as methanol, ethanol, and isopropanol, N, N-dimethylformamide, N, N-dimethylacetamide, propionic acid, acetic acid, N-methylpyrrolidone, and ethylene. 1 type, or 2 or more types, such as glycol, are mentioned. Note that a water-insoluble organic solvent may be added to the water-soluble organic solvent in a small amount. The conditions for the agitation treatment in the pre-pigmentation treatment are not particularly limited, but it is preferable to carry out the agitation treatment for about 1 to 3 hours under a constant temperature condition in a temperature range of about 70 to 200 ° C.
Further, the conditions for the stabilization treatment after the stirring treatment are not particularly limited, but are about 10 to 50 ° C., particularly preferably about 5 to 10 hours under a constant temperature condition in the temperature range of about 23 ± 1 ° C. It is preferable to stabilize by standing.

Next, after completion of the pre-pigmentation treatment, the crude crystal of the titanyl phthalocyanine compound obtained by removing the water-soluble organic solvent is further dissolved in a solvent according to a conventional method and then dropped into a poor solvent for recrystallization. Then, it is pigmented through steps such as filtration, washing with water, milling, filtration, and drying.
In this way, a titanyl phthalocyanine crystal having the optical characteristics described above is produced.

  The milling process is a process of dispersing and stirring in a non-aqueous solvent in a state where water is present without drying the solid after washing with water. Examples of the solvent for dissolving the crude crystals include halogenated hydrocarbons such as dichloromethane, chloroform, ethyl bromide and butyl bromide, trihaloacetic acids such as trifluoroacetic acid, trichloroacetic acid and tribromoacetic acid, and sulfuric acid. Or arbitrary combinations of 2 or more types are mentioned.

  Moreover, examples of the poor solvent for recrystallization include water, alcohols such as methanol, ethanol, and isopropanol, and water-soluble organic solvents such as acetone and dioxane. Alternatively, two or more arbitrary combinations are used. Furthermore, examples of non-aqueous solvents for milling include halogen solvents such as chlorobenzene and dichloromethane.

The titanyl phthalocyanine crystal can also be produced by the following method.
That is, after the pre-pigmentation treatment, the crude crystal of the titanyl phthalocyanine compound obtained by removing the water-soluble organic solvent is first treated by the acid paste method. Specifically, the above crude crystal is dissolved in an acid, this solution is added dropwise to ice-cooled water, stirred for a certain time, and further allowed to stand at around 23 ± 1 ° C. for recrystallization.

Next, the low crystalline titanyl phthalocyanine compound obtained by the above treatment is filtered, washed with water, and then dispersed in a non-aqueous solvent in the presence of water without being dried, and the milling treatment is performed. When the solid after the treatment is filtered and dried, a titanyl phthalocyanine crystal having the optical characteristics described above is obtained.
Examples of the acid used in the acid paste method include concentrated sulfuric acid and sulfonic acid. The non-aqueous solvent used for the milling treatment is the same as described above.

In the present invention, other charge generating agents other than titanyl phthalocyanine may be used in combination.
As other charge generating agents, known charge generating agents can be used. Specific examples include phthalocyanine pigments other than titanyl phthalocyanine, naphthalocyanine pigments, squalium compounds, and perylene pigments. Other charge generating agents may be used alone or in combination of two or more.

(Charge generation aid)
The photoreceptor of the present invention contains a bisazo pigment represented by the following general formula (1) as a charge generation aid.

A ¹ is a hydrogen atom, an alkyl group, an alkoxy group, an alkylthio group, an aryl group, an aralkyl group, or a heterocyclic group. These alkyl group, alkoxy group, alkylthio group, aryl group, aralkyl group and heterocyclic group may or may not have a substituent.
Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a t-butyl group.
Examples of the alkoxy group include a methoxy group, an ethoxy group, an n-propoxy group, and an isoproxy group.
Examples of the alkylthio group include a methylthio group and an ethylthio group.
Examples of the aryl group include phenyl group, tolyl group, biphenyl group, naphthyl group, 3-ethylphenyl group, 3-propylphenyl group, 3-butylphenyl group, 3-methoxyphenyl group, and 3-ethoxyphenyl group. .
Examples of the aralkyl group include a benzyl group and a naphthylmethyl group.
Examples of the heterocyclic group include a furyl group and a thienyl group.
The A ^1, aryl group having a substituent, a phenyl group is particularly preferable to having a substituent.

Cp ¹ and Cp ² are the same or different coupler residues.
Here, the “coupler residue” is a group corresponding to a part of a coupler bonded to an azo group by a coupling reaction between a diazo component and a coupler component in obtaining a bisazo pigment.

X ¹ is a hydrogen atom or an aryl group. Examples of the aryl group include the aryl groups exemplified above. X is preferably a hydrogen atom.
m is an integer of 0 to 2, and n is 0 or 1.

  By containing the above-mentioned bisazo pigment as a charge generation auxiliary agent, the bisazo pigment particles adhere around the titanyl phthalocyanine pigment particles, so that the above-mentioned titanyl phthalocyanine can be prevented from aggregating and precipitating in an organic solvent. The dispersibility of titanyl phthalocyanine in an organic solvent is improved. Accordingly, the titanyl phthalocyanine is easily dispersed uniformly in the photosensitive layer, and exhibits an excellent charge generation function, so that a highly sensitive photoreceptor can be obtained.

In the present invention, other charge generation auxiliary agents other than bisazo pigments may be used in combination.
As other charge generation auxiliary agents, known charge generation agents can be used. Specific examples include naphthalocyanine pigments, squarium compounds, and perylene pigments. Other charge generation aids may be used alone or in combination of two or more.

(Hole transport agent)
As the hole transport agent, a known hole transport agent can be used. Specifically, benzidine compounds, phenylenediamine compounds, naphthylenediamine compounds, phenanthrylenediamine compounds, oxadiazole compounds, styryl compounds, carbazole compounds, pyrazoline compounds, hydrazone compounds, tri Phenylamine compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, triazole compounds, butadiene compounds, pyrene-hydrazone compounds, acrolein compounds Compounds, carbazole-hydrazone compounds, quinoline-hydrazone compounds, stilbene compounds, stilbene-hydrazone compounds, diphenylenediamine compounds, and the like. A hole transport agent may be used individually by 1 type, and may use 2 or more types together.

(Electron transfer agent)
A known electron transport agent can be used as the electron transport agent. Specifically, quinone derivatives, anthraquinone derivatives, malononitrile derivatives, thiopyran derivatives, trinitrothioxanthone derivatives, 3,4,5,7-tetranitro-9-fluorenone derivatives, dinitroanthracene derivatives, dinitroacridine derivatives, nitroantharaquinone derivatives , Dinitroanthraquinone derivatives, tetracyanoethylene, 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroanthracene, dinitroacridine, nitroanthraquinone, dinitroanthraquinone, succinic anhydride, maleic anhydride, dibromomaleic anhydride, etc. . An electron transfer agent may be used individually by 1 type, and may be used in combination of 2 or more type.

(Binder resin)
A known binder resin can be used as the binder resin. Specifically, 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, phenol resin Lumpur 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.

(Other)
The photosensitive layer may contain known additives as long as the electrophotographic characteristics are not affected. Examples of additives include leveling agents, antioxidants, light stabilizers, radical scavengers, singlet quenchers, UV absorbers and other deterioration inhibitors, softeners, plasticizers, surface modifiers, extenders, Examples thereof include a sticking agent, a dispersion stabilizer, a wax, an acceptor, and a donor.

(Photosensitive layer structure)
The photosensitive layer has a single layer structure containing the above-described charge generating agent, charge generating auxiliary agent, hole transporting agent, electron transporting agent, and binder resin in the same layer.
In the present invention, the content of the above-mentioned titanyl phthalocyanine is larger than the content of the bisazo pigment. Thereby, the dispersibility of titanyl phthalocyanine becomes sufficient, and the influence of the bisazo pigment is reduced, so that the generation of fog can be suppressed with high sensitivity.
The content of titanyl phthalocyanine is preferably 1.1 to 10 times, more preferably 1.5 to 5 times that of the bisazo pigment. If it is less than 1.1 times, the content of the bisazo pigment is increased with respect to titanyl phthalocyanine, and fog tends to occur. On the other hand, when it exceeds 10 times, the prevention of aggregation of titanyl phthalocyanine becomes insufficient, and titanyl phthalocyanine tends to aggregate, which tends to cause fogging or decrease in sensitivity.

The content of titanyl phthalocyanine is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the binder resin. In addition, when containing another charge generating agent, the content is preferably 0.1 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the binder resin.
0.01-10 mass parts is preferable with respect to 100 mass parts of binder resin, and, as for content of a bisazo pigment, 0.1-5 mass parts is more preferable.

20-500 mass parts is preferable with respect to 100 mass parts of binders, 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 binders, 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.

<Underlayer>
In the photoreceptor of the present invention, an undercoat layer may be formed between the conductive substrate and the photosensitive layer. The photoreceptor on which the undercoat layer is formed can effectively suppress the occurrence of leakage.
The undercoat layer contains at least titanium oxide and a binder resin. By containing titanium oxide, an increase in resistance can be suppressed by flowing a current smoothly when the electrophotographic photosensitive member is exposed while suppressing generation of leakage and appropriately insulating.

As the titanium oxide, rutile type titanium oxide is preferable from the viewpoint of imparting appropriate insulating properties.
Further, as titanium oxide, it is preferable to use titanium oxide that has been surface-treated with alumina and silica and further surface-treated with an organosilicon compound from the viewpoint of obtaining appropriate insulation and dispersibility in the coating solution. Examples of the organosilicon compound include methyl hydrogen polysiloxane.
As a surface treatment method, a known method can be used. Specifically, after titanium oxide is surface-treated with alumina and silica, it is mixed and dispersed with an organosilicon compound by a wet method or a dry method, The method of crushing is mentioned.

  Titanium oxide preferably has an average primary particle size of 100 nm or less, more preferably 10 to 30 nm. When the average primary particle diameter exceeds 100 nm, the undercoat layer tends to become cloudy. As a result, the light is likely to be diffusely reflected, so that it is difficult for the light to pass through the undercoat layer. For this reason, even if the reflection absorbance of the undercoat layer is measured, only the vicinity of the surface is measured, so that it is difficult to accurately measure the reflection absorbance.

  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 undercoat layer may contain inorganic particles other than titanium oxide. Examples of the inorganic particles include aluminum, iron, copper, silica, alumina, zirconium oxide, tin oxide, zinc oxide, and indium oxide.

10-1000 mass parts is preferable with respect to 100 mass parts of binder resin, and, as for content of the titanium oxide in an undercoat layer, 30-400 mass parts is more preferable.
Moreover, when the undercoat layer contains inorganic particles other than titanium oxide, the content is preferably 10 to 500 parts by mass, and more preferably 30 to 200 parts by mass with respect to 100 parts by mass of the binder resin.
The thickness of the undercoat layer is preferably from 0.1 to 10 μm, more preferably from 0.5 to 5 μm.

[Production of single-layer electrophotographic photoreceptor]
The electrophotographic photoreceptor of the present invention can be produced, for example, as follows.
A photosensitive layer coating solution is prepared by dissolving or dispersing the above-described charge generating agent, charge generating auxiliary agent, hole transporting agent, electron transporting agent, and binder resin in an organic solvent, and the photosensitive layer coating solution is made conductive. An electrophotographic photosensitive member having a photosensitive layer formed on a conductive substrate is prepared by coating on a substrate and drying.
The photosensitive layer coating solution is prepared by dissolving or dispersing each component in an organic solvent using a roll mill, ball mill, attritor, paint shaker, ultrasonic disperser or the like.

  Examples of the organic 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 and dichloroethane. Halogenated hydrocarbons such as chloroform, carbon tetrachloride, chlorobenzene; ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether; ketones such as acetone, methyl ethyl ketone, cyclohexanone; ethyl acetate, methyl acetate, etc. Esters include dimethylformaldehyde, dimethylformamide, dimethyl sulfoxide and the like. An organic solvent may be used individually by 1 type, and 2 or more types may be mixed and used for it.

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 organic solvent to prepare a coating solution for the undercoat layer, and the undercoat layer coating solution is applied onto the conductive substrate and dried. Then, an undercoat layer may be formed.
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.

  The electrophotographic photoreceptor obtained in this way has a high sensitivity because it contains a specific Y-type titanyl phthalocyanine as a charge generator, which has good storage stability in an organic solvent and hardly undergoes crystal transition in an organic solvent. Excellent electrical characteristics and stable and high quality images can be formed.

Usually, Y-type titanyl phthalocyanine tends to aggregate or precipitate in an organic solvent, and its dispersibility in the organic solvent is insufficient. Therefore, when manufacturing a single-layer type photoreceptor, Y-type titanyl phthalocyanine is difficult to uniformly disperse in the photosensitive layer, and an excellent charge generation function is not fully exhibited, and a highly sensitive single-layer type electron It was difficult to obtain a photographic photoreceptor.
However, according to the present invention, a specific bisazo pigment is included as a charge generation auxiliary agent for the purpose of preventing the titanyl phthalocyanine from aggregating or precipitating in an organic solvent. Thus, a highly sensitive single-layer type electrophotographic photosensitive member can be easily manufactured. In particular, in the case of a single layer type electrophotographic photosensitive member, the dispersibility of titanyl phthalocyanine tends to decrease because the types of binder resins and organic solvents that can be selected are less than those of a laminated type photosensitive member. If so, since the bisazo pigment is contained, the dispersibility of the titanyl phthalocyanine can be improved without depending on the kind of the binder resin or the organic solvent.

  The image forming apparatus provided with the electrophotographic photoreceptor of the present invention has good photoreceptor characteristics and can form an image with excellent quality. Examples of such an image forming apparatus include a copying machine, a facsimile machine, and a laser beam printer.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to a following example.
[Synthesis of titanyl phthalocyanine compound]
<Synthesis Example 1>
In a flask purged with argon, 25 g of 1,3-diiminoisoindoline, 22 g of titanium tetrabutoxide, and 300 g of diphenylmethane were added, and the temperature was raised to 150 ° C. while stirring.
Next, after evaporating the steam generated from the reaction system, the temperature was raised to 215 ° C. while maintaining this temperature, and the reaction was further continued for 4 hours while stirring.
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 purple solid was obtained.

(Pigmentation pretreatment)
10 g of the obtained purple solid was added to 100 mL of N, N-dimethylformamide, heated to 130 ° C. while stirring, and further 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 reaction solution was allowed to stand for 12 hours for stabilization treatment.
And the reaction liquid after stabilization was separated by filtration with a glass filter, and the obtained solid was washed with methanol and then vacuum dried to obtain 9.85 g of a crude crystal of a titanyl phthalocyanine compound.

(Pigmentation treatment)
5 g of the obtained crude crystals of titanyl phthalocyanine compound were dissolved in 100 mL of a mixed solvent of dichloromethane and trifluoroacetic acid (volume ratio 4: 1).
Next, this solution was dropped into a mixed poor solvent of methanol and water (volume ratio 1: 1), stirred at room temperature for 15 minutes, and further allowed to stand at room temperature for 30 minutes for recrystallization.
Thereafter, the mixed poor solvent containing the crystals of titanyl phthalocyanine was filtered off with a glass filter, and the resulting solid was washed with water until the washing solution became neutral, and then in 200 mL of chlorobenzene in the presence of water without drying. Dispersed and stirred for 1 hour.
And after filtering a liquid with a glass filter, the obtained solid was vacuum-dried at 50 degreeC for 5 hours, and 4.2 g of crystals (blue powder) of the following unsubstituted titanyl phthalocyanine (21-1) shown below. Got.
In the present invention, “room temperature” means 18 to 25 ° C.

<< CuKα characteristic X-ray diffraction spectrum >>
0.5 g of titanyl phthalocyanine crystals obtained in Synthesis Example 1 within 60 minutes after synthesis were filled in a sample holder of an X-ray diffractometer (“RINT1100” manufactured by Rigaku Corporation), and CuKα characteristic X-ray diffraction was performed. The spectrum was measured. This is an initial measurement, and the results are shown in FIG.
Next, 0.5 g of titanyl phthalocyanine crystals are dispersed in 5 g of tetrahydrofuran, and stored in a closed system for 24 hours under conditions of a temperature of 23 ± 1 ° C. and a relative humidity of 50 to 60%. A CuKα characteristic X-ray diffraction spectrum was measured in the same manner as the initial measurement. This was remeasured and the results are shown in FIG.
The measurement conditions in the initial measurement and remeasurement were as follows.
X-ray tube: Cu,
Tube voltage: 40 kV,
Tube current: 30 mA,
Start angle: 3.0 °
Stop angle: 40.0 °
Scanning speed: 10 ° / min.

As a result, the crystals of titanyl phthalocyanine within 60 minutes after synthesis had strong peaks at Bragg angles 2θ ± 0.2 ° = 9.5 °, 24.1 °, and 27.2 °, as shown in FIG. And having no peak at 26.2 °, it was confirmed to have a Y-type crystal form.
Further, even when the titanyl phthalocyanine crystal is immersed in tetrahydrofuran for 24 hours, it has a maximum peak at a Bragg angle 2θ ± 0.2 ° = 27.2 ° and a peak at 26.2 ° as shown in FIG. Therefore, it was confirmed that the crystal maintained the Y type and did not transition to another crystal type such as the β type.

《Differential scanning calorimetry》
Differential scanning calorimetry of the titanyl phthalocyanine crystal obtained in Synthesis Example 1 was performed using a differential scanning calorimeter (manufactured by Rigaku Corporation, “TAS-200 type, DSC8230D”). The results are shown in FIG. Measurement conditions were as follows.
Sample pan: Al,
Temperature increase rate: 20 ° C./min or more.

  As a result, as shown in FIG. 3, the titanyl phthalocyanine crystal shows no temperature change peak from 50 ° C. to 400 ° C. except for the peak near 90 ° C. accompanying vaporization of the adsorbed water, and thus does not cause crystal transition. It was confirmed that it was stable.

<Synthesis Example 2>
4.2 g of crystals of titanyl phthalocyanine (21-1) were obtained in the same manner as in Synthesis Example 1 except that the pigmentation treatment was not performed.
In the same manner as the titanyl phthalocyanine crystal obtained in Synthesis Example 1, measurement of CuKα characteristic X-ray diffraction spectrum and differential scanning calorimetry were performed. FIG. 4 shows the results of initial measurement of the CuKα characteristic X-ray diffraction spectrum, FIG. 5 shows the results of remeasurement, and FIG. 6 shows the results of differential scanning calorimetry.

As a result, the titanyl phthalocyanine crystal obtained in Synthesis Example 2 had a maximum peak at a Bragg angle 2θ ± 0.2 ° = 27.2 ° in the initial measurement as shown in FIG. As shown in FIG. 3, the peak of Bragg angle 2θ ± 0.2 ° = 27.2 ° was reduced by immersion in tetrahydrofuran for 24 hours, and instead a strong peak was generated at 26.2 °. It was confirmed that the Y-type could not be maintained and the β-type was transferred.
Further, the differential scanning calorimetric analysis of the titanyl phthalocyanine crystal obtained in Synthesis Example 2 showed a peak near 247 ° C. in addition to the peak around 90 ° C. accompanying vaporization of adsorbed water, as shown in FIG. It was confirmed that crystal transition occurred.

[Example 1]
<Manufacture of single layer type electrophotographic photoreceptor>
(Formation of undercoat layer)
After surface treatment with alumina and silica, 3 parts by mass of titanium oxide (“SMT-022”, number average primary particle size 10 nm, manufactured by Teika Co., Ltd.) surface-treated with methylhydrogenpolysiloxane while being wet-dispersed, 1 part by mass of polymerized polyamide resin (manufactured by Daicel Degussa, “Daiamide X4585”) was dispersed in 10 parts by mass of ethanol and 2 parts by mass of butanol for 5 hours using a bead mill. Then, it filtered with a 5-micrometer filter and prepared the coating liquid for undercoat layers.
As a conductive substrate, an undercoat layer coating solution obtained was applied to an aluminum drum-shaped substrate having a diameter of 30 mm and a total length of 246 mm by dip coating, and heat-treated at 130 ° C. for 30 minutes to obtain a film thickness. A 2.0 μm subbing layer was formed.

(Formation of photosensitive layer)
100 parts by mass of the polycarbonate resin (3-1) shown below as the binder resin, 3 parts by mass of the crystal of titanyl phthalocyanine (21-1) obtained in Synthesis Example 1 as the charge generating agent, and the following as the charge generating auxiliary agent 2.0 parts by mass of the bisazo pigment (1-1) shown, 50 parts by mass of the compound (4-1) shown below as a hole transporting agent, and 40 parts by mass of the compound (5-1) shown below as an electron transporting agent And 0.1 parts by weight of a leveling agent (manufactured by Shin-Etsu Chemical Co., Ltd., “KF-96-50CS”) are added to 420 parts by weight of tetrahydrofuran as an organic solvent, dissolved and dispersed with an ultrasonic disperser, and coated for a photosensitive layer. A liquid was prepared.
The resulting photosensitive layer coating solution was allowed to stand at room temperature for 20 days, and then applied onto the undercoat layer by dip coating, followed by drying with hot air at 130 ° C. for 40 minutes, and a photosensitive layer having a thickness of 28 μm. To form a single layer type electrophotographic photosensitive member.

<Evaluation 1>
(Measurement of bright potential)
When the obtained single-layer type electrophotographic photosensitive member was installed in an electrostatic copying apparatus (“FS-1010” manufactured by Kyocera Mita Co., Ltd.), charged to +400 V, and exposed to a red semiconductor laser beam having a wavelength of 780 nm. The surface potential (bright potential) was measured. This wavelength is 780 nm. The results are shown in Table 1. As the value of the bright potential increases, the sensitivity of the electrophotographic photosensitive member tends to be inferior. In the present invention, the case of +80 V or less is accepted.

(Image evaluation)
A single-layer electrophotographic photosensitive member was installed in an electrostatic copying apparatus in the same manner as the measurement of the bright potential, and 20 blank paper images were printed in a high temperature and high humidity environment (temperature 35 ° C., relative humidity 85%). With respect to the tenth blank paper image, the density FD ₁ value was measured using a Macbeth reflection densitometer (manufactured by Gretag Macbeth, “SPM-50”). Similarly, the density FD ₀ value in a blank image that has not been output was measured, and the density FD ₀ value was subtracted from the density FD ₁ value to obtain an FD value (fogging value). The results are shown in Table 1. The determination is “場合” when the FD value is 0.005 or less, “◯” when it is greater than 0.005 and 0.010 or less, “x” when it is greater than 0.010, and “◎” and “ “Yes” was accepted.

<Evaluation 2>
(Measurement of bright potential)
The light potential was measured in the same manner as in Evaluation 1 except that the electrostatic copying apparatus used in Evaluation 1 was a modified machine in which the laser wavelength was changed to 650 nm and the light amount was changed to 2.0 μJ / cm ² . The results are shown in Table 1.

(Image evaluation)
Image evaluation was performed in the same manner as in Evaluation 1 except that the modified machine used in Evaluation 2 was used. The results are shown in Table 1.

[Examples 2 to 13]
Single-layer electrophotography in the same manner as in Example 1 except that the polycarbonate resin, bisazo pigment, hole transport agent, and electron transport agent shown in Table 1 were used and the content of the bisazo pigment was changed to the values shown in Table 1. Photoconductors were manufactured and evaluated. The results are shown in Table 1.
In addition, polycarbonate resin (3-2), bisazo pigments (1-2) to (1-3), hole transport agents (4-2) to (4-4), and electron transport agents (5-2) to (5-4) used the following compounds.

[Example 14]
An electrophotographic photosensitive member was produced and evaluated in the same manner as in Example 1 except that the undercoat layer was not formed. The results are shown in Table 1.

[Comparative Example 1]
An electrophotographic photoreceptor was produced and evaluated in the same manner as in Example 1 except that the bisazo pigment was not used. The results are shown in Table 1.

[Comparative Example 2]
An electrophotographic photoreceptor was produced and evaluated in the same manner as in Example 1 except that the content of the bisazo pigment (1-1) was changed to the values shown in Table 1. The results are shown in Table 1.

[Comparative Example 3]
An electrophotographic photosensitive member was produced and evaluated in the same manner as in Example 1 except that titanyl phthalocyanine (2-1) obtained in Synthesis Example 2 was used as the charge generator. The results are shown in Table 1.

  As is apparent from Table 1, the single-layer electrophotographic photosensitive member obtained in each example had a bright potential value of +80 V or less and excellent sensitivity. Further, a high quality image could be formed with a low FD value. In particular, a single layer type electrophotographic photosensitive member formed with an undercoat layer has a low FD value and is suitable for forming a high-quality image.

On the other hand, the single layer type electrophotographic photosensitive member obtained in Comparative Example 1 had a bright potential and an FD value higher than those in Examples, and was inferior in sensitivity. This is because the photosensitive layer contains no bisazo pigment, so the dispersibility of the charge generator (titanyl phthalocyanine) in the coating solution for the photosensitive layer is reduced, and it becomes difficult for the titanyl phthalocyanine to be uniformly dispersed in the photosensitive layer. As a result, it is considered that the excellent charge generation function was not sufficiently exhibited.
The monolayer type electrophotographic photoreceptor obtained in Comparative Example 2 had a high FD value and was likely to cause fogging because the content of the bisazo pigment was higher than the content of titanyl phthalocyanine.
The single layer type electrophotographic photosensitive member obtained in Comparative Example 3 had a bright potential and an FD value higher than those of the Examples, and the sensitivity was inferior. This is because the titanyl phthalocyanine used as the charge generating agent changed from Y-type to β-type by storing the coating solution for the photosensitive layer, so that the sensitivity of the obtained single-layer type electrophotographic photosensitive member was lowered. It is considered a thing.

2 is a graph showing a CuKα characteristic X-ray diffraction spectrum of a titanyl phthalocyanine crystal obtained in Synthesis Example 1 immediately after synthesis. It is a graph which shows the CuK (alpha) characteristic X-ray-diffraction spectrum measured again, after immersing the crystal | crystallization of the titanyl phthalocyanine obtained by the synthesis example 1 in tetrahydrofuran for 24 hours. 4 is a graph showing the results of differential scanning calorimetry analysis of the titanyl phthalocyanine crystal obtained in Synthesis Example 1. 6 is a graph showing a CuKα characteristic X-ray diffraction spectrum of a titanyl phthalocyanine crystal obtained in Synthesis Example 2 immediately after synthesis. It is a graph which shows the CuK (alpha) characteristic X-ray-diffraction spectrum measured again, after immersing the crystal | crystallization of titanyl phthalocyanine obtained by the synthesis example 2 in tetrahydrofuran for 24 hours. 6 is a graph showing the results of differential scanning calorimetric analysis of the titanyl phthalocyanine crystal obtained in Synthesis Example 2.

Claims (5)

A monolayer type electrophotographic photosensitive member comprising a photosensitive layer containing a charge generating agent, a charge generating auxiliary agent, a hole transporting agent, an electron transporting agent, and a binder resin on a conductive substrate,
As the charge generator, an organic solvent having a maximum peak at least at a Bragg angle 2θ ± 0.2 ° = 27.2 ° in a CuKα characteristic X-ray diffraction spectrum and used for a coating solution for forming the photosensitive layer In a CuKα characteristic X-ray diffraction spectrum after being immersed in the solution for 24 hours, titanyl phthalocyanine having a maximum peak at least at a Bragg angle 2θ ± 0.2 ° = 27.2 ° and no peak at 26.2 ° Contains,
As the charge generation auxiliary agent, containing a bisazo pigment represented by the following general formula (1),
And the content of the said titanyl phthalocyanine is more than content of the said bisazo pigment, The single layer type electrophotographic photoreceptor characterized by the above-mentioned.

In Formula (1), A ¹ is a hydrogen atom, an alkyl group, an alkoxy group, an alkylthio group, an aryl group, an aralkyl group, or a heterocyclic group, Cp ¹ and Cp ² are the same or different coupler residues, and X ¹ is a hydrogen atom or an aryl group, m is an integer of 0 to 2, and n is 0 or 1.   The single-layer electrophotographic photosensitive member according to claim 1, further comprising an undercoat layer between the conductive substrate and the photosensitive layer.   The single-layer electrophotographic photosensitive member according to claim 2, wherein the undercoat layer contains at least titanium oxide and a binder resin.   The single-layer electrophotographic photosensitive member according to claim 3, wherein the titanium oxide is surface-treated with alumina and silica and further surface-treated with an organosilicon compound. The single-layer electrophotographic photosensitive member according to any one of claims 1 to 4, wherein the titanyl phthalocyanine has the following properties (a) or (b).
(A): In the differential scanning calorimetry, no peak is present in the range of 50 ° C. or higher and 400 ° C. or lower except for the peak accompanying vaporization of adsorbed water.
(B): In the differential scanning calorimetry, there is no peak in the range of 50 ° C. or more and less than 200 ° C., and there is one peak in the range of 200 ° C. or more and 400 ° C. or less, except for the peak accompanying vaporization of adsorbed water. Have a peak.

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