JP4060267B2 - Single layer type electrophotographic photoreceptor - Google Patents

Description

  The present invention relates to a monolayer type electrophotographic photoreceptor using titanyl phthalocyanine as a charge generating agent.

  In recent years, digital technology has been widely adopted in image forming apparatuses such as electrostatic copying machines, laser beam printers, and plain paper facsimiles. Generally, a semiconductor laser (LD) or a light emitting diode (LED) is used as an exposure light source for a digital image forming apparatus, and the wavelength thereof is a long wavelength region around 680 to 830 nm (hereinafter, this wavelength region is referred to as “near wavelength”). "Infrared region") is the mainstream. Therefore, development of electrophotographic photoreceptors using phthalocyanines having high sensitivity in the near infrared region, in particular, titanyl phthalocyanine (TiOPc) as a charge generating agent has been actively conducted.

At present, an electrophotographic photoreceptor using TiOPc is put into practical use in a laminated type. However, in the present situation, a single-layer type photoreceptor that has a simple structure and is easy to manufacture compared to the laminated type has not been obtained with excellent electrical characteristics. This is considered to be due to the following reason. The multilayer photoreceptor usually has a large charge transport layer disposed on the outer side, so that the charge generation layer does not need to have such a large mechanical strength, and therefore, polyvinyl butyral and polyvinyl acetal having excellent affinity with TiOPc. A vinyl polymer such as can be used as the binder resin. On the other hand, in a single-layer type photosensitive layer requiring mechanical strength, a resin having poor affinity with TiOPc, such as polycarbonate, polyester, polyarylate, and polystyrene, must be used as the binder resin. Therefore, the stability over time of the coating solution is lowered, and TiOPc is likely to aggregate and precipitate, making it difficult to form a high-performance single-layer type photosensitive layer.
Japanese Patent Laid-Open No. 7-13370 JP-A-8-234460

  An object of the present invention is to improve the stability of a coating solution for a single layer type photosensitive layer containing titanyl phthalocyanine, so that a single layer type capable of realizing high sensitivity even when titanyl phthalocyanine is used as a charge generating agent. An electrophotographic photosensitive member is provided.

In order to achieve the above object, a single layer type electrophotographic photosensitive member according to the present invention comprises:
A single photosensitive layer containing titanyl phthalocyanine as a charge generating agent, a charge transport agent, a binder resin, and an isoindolinone derivative on a conductive substrate,
The binder resin contains at least one resin selected from the group consisting of polycarbonate, polyester, polyarylate and polystyrene,
The content of the isoindolinone derivative is 30 to 80% by weight based on the total content of the charge generating agent .

  In the single-layer electrophotographic photoreceptor according to the present invention, the isoindolinone derivative has the formula (1):

(In the formula, R ¹ represents an alkyl group having 1 to 6 carbon atoms which may have a substituent, or an arylene group having 6 to 20 carbon atoms which may have a substituent. X represents a halogen atom.)
It is preferable that it is the isoindolinone pigment represented by these.
In the single-layer electrophotographic photosensitive member according to the present invention, an isoindolinone derivative [preferably an isoindolinone pigment represented by the above formula (1)] is contained in the photosensitive layer together with titanyl phthalocyanine as a charge generator. Is blended.

  Here, the isoindolinone derivative [or isoindolinone pigment (1)] not only has an affinity for titanyl phthalocyanine but also a binder such as polycarbonate, polyester, polyarylate, polystyrene or the like that forms a single-layer type photosensitive layer. It is a compound that also has an affinity for a resin. Therefore, the isoindolinone derivative [or isoindolinone pigment (1)] blended in the photosensitive layer exhibits the action of a titanyl phthalocyanine as a dispersant in the coating solution for forming the photosensitive layer. Further, the dispersibility of titanyl phthalocyanine can be stabilized, and the temporal stability of the coating solution for a single-layer type photosensitive layer containing titanyl phthalocyanine can be maintained.

Moreover, the isoindolinone derivative [or isoindolinone pigment (1)] blended in the photosensitive layer of the single-layer electrophotographic photoreceptor according to the present invention has an absorbance with respect to light having a wavelength of 680 nm, which is 680 nm of the titanyl phthalocyanine. Therefore, the charge generation function of titanyl phthalocyanine is not hindered.
Therefore, according to the single layer type electrophotographic photosensitive member according to the present invention, high sensitivity can be realized as a single layer type photosensitive member even though titanyl phthalocyanine is used as a charge generating agent.

  The photoreceptor described in Patent Document 1 uses at least one selected from the group consisting of phthalocyanine and isoindolinone as a charge generation compound (charge generation agent) (see claim 1). However, this photoreceptor is a multilayer photoreceptor, and both phthalocyanine and isoindolinone are used as charge generating agents. Furthermore, titanyl phthalocyanine has poor affinity for the binder resin for the single layer type photosensitive layer, and the titanyl phthalocyanine is dispersed in the binder resin for the single layer type photosensitive layer together with the specific isoindolinone. There is no description or suggestion in the same document regarding the ability to improve the stability and the temporal stability of the coating solution for forming a photosensitive layer.

  Further, in the electrophotographic photoreceptor described in Patent Document 2, the chromophore residue in a known pigment (charge generating agent) that is originally insoluble is substituted with a soluble group capable of being chemically removed. It is realized that the photosensitive layer is finely dispersed with a very small particle diameter (Claim 1, Claim 2, Paragraph [0005], Paragraph [0008], etc.). Furthermore, claim 2 of the same document includes phthalocyanines and isoindolinones as chromophore residues. However, even in this document, titanyl phthalocyanine has poor affinity for a binder resin for a single-layer type photosensitive layer, and by dispersing titanyl phthalocyanine in a binder resin for a single-layer type photosensitive layer together with specific isoindolinone. There is no description or suggestion that the dispersibility of titanyl phthalocyanine and the stability over time of the coating solution for forming a photosensitive layer can be improved. In addition, isoindolinone is used as a charge generating agent in the electrophotographic photoreceptor of this document.

  In the single-layer electrophotographic photosensitive member according to the present invention, titanyl phthalocyanine has an α having a main diffraction peak at 27.6 ° at least 7.6 ° in the Bragg angle (2θ ± 0.2 °) in the X-ray diffraction spectrum. It is preferable to be type titanyl phthalocyanine or Y type titanyl phthalocyanine having a main diffraction peak at 27.3 °. Both the α-type titanyl phthalocyanine (α-TiOPc) and the Y-type titanyl phthalocyanine (Y-TiOPc) have excellent charge generation ability in the near infrared region, and thus the sensitivity of the photoreceptor in the near infrared region is improved. It can be made even better.

  The titanyl phthalocyanine used in the single-layer electrophotographic photosensitive member according to the present invention has an endothermic peak other than the peak accompanying vaporization of adsorbed water when the temperature is raised from 50 ° C. to 400 ° C. in differential scanning calorimetry. It is preferable not to. In the temperature rise measurement in the range of 50 to 400 ° C. by differential scanning calorimetry (DSC), the fact that no endothermic peak other than the peak accompanying vaporization of adsorbed water is observed means that the crystal transition of titanyl phthalocyanine hardly occurs, It shows that the crystal form is stable. Therefore, by using such titanyl phthalocyanine, the dispersibility in the binder resin can be further improved, and the temporal stability of the sensitivity of the photoreceptor can also be improved.

  The single-layer type electrophotographic photoreceptor according to the present invention is suitable as a photoreceptor for an image forming apparatus using light having a wavelength in the range of 680 to 830 nm as an exposure light source. As described above, titanyl phthalocyanine (TiOPc) used as a charge generating agent in the present invention, particularly α-TiOPC and Y-TiOPc, which are preferably used, all exhibit excellent charge generating ability in the near infrared region. Therefore, when the wavelength of the exposure light source is 680 to 830 nm (near infrared region), a highly sensitive electrophotographic photosensitive member can be provided. As described above, semiconductor lasers (LD) and light-emitting diodes (LEDs) that are generally used as exposure light sources for digital image forming apparatuses often have a near infrared region with a wavelength of around 680 to 830 nm. The single-layer electrophotographic photoreceptor according to the present invention is particularly suitable as a photoreceptor for a digital image forming apparatus.

Hereinafter, embodiments of the present invention will be described in detail.
[Formation material of electrophotographic photosensitive member]
(Charge generator)
In the single-layer electrophotographic photoreceptor according to the present invention, titanyl phthalocyanine is used as a charge generating agent blended in the photosensitive layer.

  Titanyl phthalocyanine is classified into several types according to its crystal form. The crystal form of titanyl phthalocyanine that can be used in the present invention is not particularly limited, and any known crystal form such as α-type, Y-type, β-type, and C-type can be used. However, as described above, from the viewpoint of further improving the sensitivity in the near-infrared region, the Bragg angle (2θ ± 0.2 °) in the X-ray diffraction spectrum is at least 7.6 °, 28.6. It is preferable to use α-type titanyl phthalocyanine (α-TiOPc) having a main diffraction peak at 0 ° or Y-type titanyl phthalocyanine (Y-TiOPc) having a main diffraction peak at 27.3 °.

Among these, Y-type titanyl phthalocyanine (Y-TiOPc) having a main diffraction peak at 27.3 ° at a Bragg angle (2θ ± 0.2 °) in an X-ray diffraction spectrum is described in (i) or (ii) below. It can manufacture by the method of.
(I) Titanyl phthalocyanine is added to a water-soluble organic solvent, and stirred for a certain time under heating. Next, the reaction solution is allowed to stand for a certain period of time under a temperature condition lower than that at the time of the stirring treatment to stabilize (pigmentation pretreatment). Further, after dissolving the crude crystal of titanyl phthalocyanine obtained by removing the water-soluble organic solvent in the solvent and dropping it into a poor solvent for recrystallization, the steps of filtration, washing with water, milling, filtration, drying, etc. It turns into a pigment.

(Ii) After the pigmentation pretreatment similar to (1) above, the crude crystal of titanyl phthalocyanine obtained by removing the water-soluble organic solvent is treated by the acid paste method, and the low crystalline titanyl phthalocyanine thus obtained is treated with water. After being milled in the existing state, it is filtered and dried.
On the other hand, α-type titanyl phthalocyanine (α-TiOPc) having a main diffraction peak of at least 7.6 ° and 28.6 ° at a Bragg angle (2θ ± 0.2 °) in the X-ray diffraction spectrum is shown in (iii) below. It can be produced by the method described.

(Iii) A sulfuric acid solution containing at least titanyl phthalocyanine and, if necessary, added with metal-free phthalocyanine is prepared and treated by an acid paste method in which it is poured into water to form a pigment. Further, the α-TiOPc thus obtained may be wet milled in the presence of a chlorinated solvent.
In the monolayer type electrophotographic photoreceptor according to the present invention, the above-exemplified titanyl phthalocyanine is used as the charge generating agent. However, as long as the effects of the present invention are not inhibited, metal-free phthalocyanine, hydroxygallium phthalocyanine Other phthalocyanine pigments such as chlorogallium phthalocyanine may be used in combination.

(Isoindolinone derivative)
In the single layer type electrophotographic photoreceptor according to the present invention, the isoindolinone derivative blended in the photosensitive layer has an absorbance with respect to light having a wavelength of 680 nm as described above, and the wavelength of 680 nm of titanyl phthalocyanine used as a charge generator. 1/3 or less with respect to the light absorbency with respect to light.

Specific examples of the isoindolinone derivative used in the present invention include an isoindolinone pigment represented by the general formula (1). In the isoindolinone pigment (1), as R ^1, as described above, the alkylene group having 1 to 6 carbon atoms which may have a substituent, or the carbon group having 6 to 20 carbon atoms which may have a substituent, as described above. An arylene group is mentioned. That is, for example, alkylene groups such as methylene, ethylene, trimethylene, propylene, tetramethylene, ethylethylene, dimethylethylene, pentamethylene, hexamethylene, o-phenylene, m-phenylene, p-phenylene, 1,4-naphthylene, , 6-naphthylene, biphenyl-4,4′-diyl, and arylene groups such as 2,7-phenanthrylene. Examples of the group that may be substituted on the alkylene group include an alkoxy group having 1 to 4 carbon atoms (methoxy, ethoxy, etc.), halogen (chloro, bromo, etc.) and the like. Examples of the group that may be substituted with the arylene group include, for example, an alkyl group having 1 to 6 carbon atoms (methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, etc.), and an alkoxy having 1 to 4 carbon atoms. Group, halogen and the like.

  Specific examples of the isoindolinone pigment represented by the general formula (1) are not limited thereto. For example, Pigment Yellow 109 represented by the following formula (1-1), the following formula (1- Pigment yellow 110 represented by 2), pigment orange 42 represented by the following formula (1-3), pigment red 180 represented by the following formula (1-4), and the like.

(Charge transport agent)
In the single-layer electrophotographic photoreceptor according to the present invention, various conventionally known electron transport agents and / or hole transport agents can be used as the charge transport agent. Whether to use an electron transfer agent or a hole transfer agent is selected according to the charging polarity of the photoreceptor. In the case where no charge transfer complex is formed between the two, it is preferable that both be mixed and contained in the photosensitive layer.

(Electron transfer agent)
The electron transporting agent that can be used in the single-layer electrophotographic photosensitive member according to the present invention is not particularly limited, and can be appropriately selected from conventionally known electron transporting agents. Specifically, diphenoquinone derivatives represented by the following general formulas (ETM1) and (ETM2), stilbenequinone derivatives represented by the following general formula (ETM3), the following general formulas (ETM4), (ETM5), (ETM6) And naphthoquinone derivatives represented by (ETM7), dinaphthoquinone derivatives represented by the following general formulas (ETM8) and (ETM9), represented by the following general formulas (ETM10), (ETM11), (ETM12) and (ETM13). Azoquinone derivatives, naphthalenetetracarboxylic acid diimide derivatives represented by the following general formula (ETM14), and the like can be used. These may be used alone or in combination of two or more.

[In the general formulas (ETM1) to (ETM14), R ^{e1 to} R ^e11 , R ^{e13 to} R ^e26 , R ^{e32 to} R ^e37 , R ^e40 and R ^e41 are the same or different, and are each a hydrogen atom having 1 to 8 carbon atoms. An alkyl group or an aryl group having 12 or less carbon atoms is shown. R ^e12 is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group having 12 or less carbon atoms, an alkylcarbonyl group having 1 to 9 carbon atoms, an alkoxycarbonyl group having 1 to 9 carbon atoms, or an arylcarbonyl having 13 or less carbon atoms. Group or an aryloxycarbonyl group having 13 or less carbon atoms. R ^e27 , R ^e29 and R ^e31 are the same or different and each represents an alkyl group having 1 to 8 carbon atoms, an aryl group having 12 or less carbon atoms, a chlorine atom or a nitro group. R ^e28 , R ^e30 , R ^e38 and R ^e39 are the same or different and represent an alkyl group having 1 to 8 carbon atoms or an aryl group having 12 or less carbon atoms. a represents an integer of 0 to 3, and b represents an integer of 0 to 4. The aryl group, arylcarbonyl group and aryloxycarbonyl group may further have a substituent such as a nitro group in the aryl portion. ]
The azoquinone derivative represented by the above general formula (ETM12) is obtained by adding concentrated hydrochloric acid to an aniline derivative [having a substituent (R ^e31 ) _a ] and sodium nitrite to form a diazonium compound. And 9-hydroxy-10- ^{methylanthracene} derivative [comprising substituent (R ^e30 ) _b ], and then obtained by oxidizing the hydroxy group of the product thus obtained.

(Hole transport agent)
The hole transporting agent that can be used in the single-layer electrophotographic photosensitive member according to the present invention is not particularly limited, and can be appropriately selected from conventionally known hole transporting agents. Among them, a diamine derivative represented by the following general formula (HTM1), a diamine derivative represented by the general formula (HTM2), a stilbene derivative represented by the general formula (HTM3), or a general formula (HTM4) It is preferred to use a stilbeneamine-hydrazone derivative. These hole transport agents may be used alone or in combination of two or more.

[X ^h1 of formula (HTM1) represents any of the following formulas (A) ~ (C), indicate either X ^h2 the following formula of formula (HTM2) (A) ~ ( D). ]

[In the formulas (HTM1) to (HTM4), R ^{h1 to} R ^h18 and R ^{h20 to} R ^h25 are the same or different and are an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or 12 or less carbon atoms. An aryl group of R ^h19 represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an aryl group having 12 or less carbon atoms. a and b are the same as described above. k represents an integer of 0 to 3. ]
The hole transport agent exemplified above has a high charge transport ability, is difficult to form a charge transfer complex with the electron transport agent exemplified above, and has good compatibility with a binder resin described later. Have.

(Binder resin)
In the single-layer electrophotographic photosensitive member according to the present invention, the binder resin forming the photosensitive layer includes one containing at least one resin selected from the group consisting of polycarbonate, polyester, polyarylate and polystyrene. The above-exemplified resins are suitable for forming a single-layer type photosensitive layer because the properties such as strength and abrasion resistance of the photosensitive layer can be further improved. In addition, since the binder resin exemplified above is excellent in compatibility with the charge transport agent and does not have a site in the molecule that interferes with the charge transport capability of the charge transport agent, it is highly sensitive. It is also suitable for obtaining an electrophotographic photoreceptor.

  Suitable examples of the binder resin include, but are not limited to, for example, the general formula (I):

[In General Formula (I), R ²⁰ and R ²¹ are the same or different and each represents an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or a halogen atom. Show. α and β are the same or different and represent an integer of 0 to 2. ]
Or a repeating unit represented by formula (II):

[In General Formula (II), R ²² and R ²³ are the same or different and each represents an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or a halogen atom. Show. γ and δ are the same or different and represent an integer of 0 to 2. X represents a 1,1-cycloalkylene group having 5 to 11 carbon atoms, an α, ω-alkylene group having 2 to 10 carbon atoms, —O—, —S—, —SO—, —SO ₂ —, or the following formula: (II-1), formula (II-2) or formula (II-3):

(In formula (II-1), R ²⁴ and R ²⁵ are the same or different and are a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a perfluoroalkyl having 1 to 6 carbon atoms. In formula (II-2), R ²⁶ and R ²⁷ are the same or different and each represents an alkyl group having 1 to 6 carbon atoms, in formula (II-3), R ²⁸ , R ²⁹ , R ^30. And R ³¹ are the same or different and each represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms.)
The bivalent group represented by these is shown. ]
A polycarbonate resin having a repeating unit represented by

Such a polycarbonate is a copolymer having a plurality of repeating units included in the range of the general formula (II), or a repeating unit included in the range of the general formula (I) and a repeating unit included in the range of the general formula (II). It may be a copolymer having both units.
In the copolymer polycarbonate resin having both the repeating unit represented by the general formula (I) and the repeating unit represented by the general formula (II), the copolymerization ratio of both units is m for the former, When the content ratio is n, the formula:
0.05 <m / (m + n) <0.4
It is preferable to set so as to satisfy.

Carbon number of the alkyl group corresponding to R ^{20 to} R ²³ in the general formulas (I) and (II) is preferably 1 to 6, more preferably 1 to 4. Such an alkyl group may be linear or branched.
(Dispersion medium)
In preparing a coating solution for forming a photosensitive layer by dispersing and dissolving the charge generator, isoindolinone derivative, charge transport agent, binder resin and the like exemplified above, as a dispersion medium used for the coating solution, Various organic solvents conventionally used in coating solutions for single-layer type photosensitive layers can be used. Specifically, from the viewpoint of the solubility of the binder resin, aliphatic hydrocarbons such as n-hexane, octane and cyclohexane; aromatic hydrocarbons such as benzene, toluene and xylene, dichloromethane, dichloroethane, chloroform, tetrachloride Halogenated hydrocarbons such as carbon and chlorobenzene; ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, dioxane, dioxolane, 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.

  In addition, although not limited thereto, tetrahydrofuran, dioxane, dioxolane, cyclohexanone, among various organic solvents, are preferable for stably dispersing each component such as a charge generator, a charge transport agent, and a binder resin. It is preferable to use at least one organic solvent selected from the group consisting of toluene, xylene, dichloromethane, dichloroethane and chlorobenzene.

(Other ingredients)
In the coating solution for forming the photosensitive layer, in addition to the above-mentioned components, various conventionally known additives such as an antioxidant, a radical scavenger, a singlet quencher are used as long as they do not adversely affect the electrophotographic characteristics. Deterioration inhibitors such as char and ultraviolet absorbers, softeners, plasticizers, surface modifiers, extenders, thickeners, dispersion stabilizers, waxes, acceptors, donors, and the like can be blended. In order to improve the sensitivity of the photosensitive layer, a known sensitizer such as terphenyl, halonaphthoquinones, and acenaphthylene may be used in combination with the charge generator. Further, a surfactant, a leveling agent or the like may be used in order to improve the dispersibility of the charge transport agent or charge generator and the smoothness of the photosensitive layer surface.

(Conductive substrate)
In the single layer type electrophotographic photosensitive member according to the present invention, various conductive materials can be used for the conductive substrate on which the photosensitive layer is formed. The conductive substrate is not particularly limited as long as the substrate itself has conductivity or the surface of the substrate has conductivity. Specific examples thereof include simple metals such as iron, aluminum, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, and brass; Examples thereof include glass coated with plastic materials, aluminum iodide, tin oxide, indium oxide, etc .; resin substrates in which conductive fine particles such as carbon black are dispersed. The shape of the conductive substrate may be any of a sheet shape, a drum shape and the like according to the structure of the image forming apparatus to be used.

  The conductive substrate used in the present invention is not limited to this, but the surface thereof may be subjected to an oxide film treatment or a resin film treatment. The oxide film treatment for the conductive substrate includes, for example, a process of forming an anodic oxide film (anodic oxide film) on the surface of the conductive substrate when aluminum or titanium is used as the conductive substrate. The anodic oxide coating is formed by anodizing in an acidic bath such as chromic acid, sulfuric acid, oxalic acid, boric acid, sulfamic acid, etc., and the treatment is performed in sulfuric acid, especially in the acidic baths exemplified above. Is preferred. The method of anodizing treatment, the method of degreasing treatment performed prior to the anodizing treatment, and the like are not particularly limited, and may be performed according to a conventional method. Examples of the resin coating treatment on the conductive substrate include a treatment in which nylon resin, phenol resin, melamine resin, alkyd resin, polyvinyl acetal resin, etc. are dissolved in an appropriate solvent and applied to the surface of the conductive substrate. It is done. As the resin material used for the resin coating treatment, it is particularly preferable to use nylon resin or resol type phenol resin among the resins exemplified above.

(Method for producing electrophotographic photoreceptor)
The single-layer electrophotographic photosensitive member according to the present invention includes a charge generator, an isoindolinone derivative, a charge transport agent, a binder resin, and other components as needed dispersed in an appropriate dispersion medium. Alternatively, it is obtained by dissolving and applying the thus obtained coating solution for forming a photosensitive layer on a conductive substrate and drying it to form a photosensitive layer.

In the coating solution for forming the photosensitive layer, the charge generating agent may be blended in an amount of 0.1 to 50 parts by weight, preferably 0.5 to 30 parts by weight with respect to 100 parts by weight of the binder resin. Isoindolinone derivative in the total electric charge generating material (titanyl phthalocyanine) are blended so that 30 to 80 wt%. What is necessary is just to mix | blend a hole transport agent in the ratio of 20-100 weight part with respect to 100 weight part of binder resin, Preferably 30-80 weight part. What is necessary is just to mix | blend an electron transport agent in the ratio of 10-80 weight part with respect to 100 weight part of binder resin, Preferably it is 20-60 weight part. In the case where the electron transport agent and the hole transport agent are used in combination, the total amount of the electron transport agent and the hole transport agent is 20 to 500 parts by weight, preferably 30 to 200 parts by weight with respect to 100 parts by weight of the binder resin. It is appropriate to do.

  The thickness of the photosensitive layer is preferably set to 5 to 100 μm, particularly 10 to 50 μm. For the photosensitive layer, the charge generators, isoindolinone derivatives, charge transfer agents, binder resins and the like exemplified above are added to the solvent, and this is used using known means such as a roll mill, a ball mill, an attritor, a paint shaker, and an ultrasonic disperser. After the dispersion and mixing, the dispersion thus prepared is applied on a conductive substrate by a known means and dried.

  Although not particularly limited in the present invention, an undercoat layer (barrier layer) may be formed between the conductive substrate and the photosensitive layer as long as the characteristics of the photoreceptor are not impaired. Further, a protective layer may be formed on the surface of the photoreceptor.

Next, the present invention will be described with reference to examples and comparative examples.
[Reference Example: Production of titanyl phthalocyanine]
(1) Synthesis of titanyl phthalocyanine compound 25 g of 1,3-diiminoisoindoline, 22 g of titanium tetrabutoxide, and 300 g of diphenylmethane were added to an argon-substituted flask, 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 stirring, and the reaction was further continued for 4 hours while maintaining this temperature. After completion of the reaction, when the reaction mixture is cooled to 150 ° C., the reaction mixture is removed from the flask, filtered through a glass filter, and the resulting solid is washed successively with N, N-dimethylformamide and methanol, and further dried in vacuo to give a purple solid. 24 g was obtained.

(2) Pre-pigmentation treatment 10 g of the purple solid obtained in (1) above was added to 100 mL of N, N-dimethylformamide, heated to 130 ° C. with stirring, and stirred for 2 hours. When 2 hours had passed, heating was stopped, and after cooling to 23 ± 1 ° C., stirring was also stopped, and in this state, the reaction solution was allowed to stand for 12 hours for stabilization treatment. Thereafter, the reaction solution was filtered off 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.

(3) Pigmentation treatment 5 g of crude crystals of the titanyl phthalocyanine compound obtained by the pretreatment in (2) above were added to 100 mL of a mixed solvent of dichloromethane and trifluoroacetic acid (volume ratio 4: 1) and dissolved. Subsequently, 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 then allowed to stand at room temperature for 30 minutes for recrystallization. Subsequently, the mixed poor solvent containing titanyl phthalocyanine crystals was filtered off with a glass filter, and the obtained solid was washed with water until the washing solution became neutral, and then dispersed in 200 mL of chlorobenzene in the presence of water without drying. And allowed to stir for 1 hour. The liquid was filtered off with a glass filter, and the obtained solid was vacuum dried at 50 ° C. for 5 hours to obtain 4.2 g of unsubstituted titanyl phthalocyanine (TiOPc) crystals (blue powder).

  TiOPc thus obtained is a so-called Y-type crystal, and as a result of analysis by X-ray diffraction spectrum, it has a main diffraction peak when the Bragg angle (2θ ± 0.2 °) is 27.2 °, There was no peak when the Bragg angle (2θ ± 0.2 °) was 26.2 °. As a result of differential scanning calorimetry (DSC), no endothermic peak other than the peak accompanying vaporization of adsorbed water was observed when the temperature was raised from 50 ° C. to 400 ° C.

[Production of single-layer electrophotographic photoreceptor]
Example 1
As the charge generating agent, Y-type titanyl phthalocyanine (Y-TiOPc) obtained in the above Reference Example was used. As the isoindolinone derivative, an isoindolinone pigment (Pigment Yellow 109) represented by the above formula (1-1) was used.

  A bisstilbene compound represented by the following formula (HTM1-1) was used as the hole transporting agent, and a dinaphthylquinone compound represented by the following formula (ETM8-1) was used as the electron transporting agent.

  Further, dimethyl silicone oil (product name “KF96-50CS” manufactured by Shin-Etsu Chemical Co., Ltd.) is used as the leveling agent, and the polycarbonate resin having a repeating unit represented by the following formula [Z-type polycarbonate, viscosity] Average molecular weight 50000] was used.

  Y-TiOPc 2.5 parts by weight, isoindolinone pigment (1-1) 2.0 parts by weight, bis-stilbene compound 50 parts by weight, dinaphthylquinone compound 30 parts by weight, dimethyl silicone oil 0.1 part by weight And 100 parts by weight of the above polycarbonate were added to 750 parts by weight of tetrahydrofuran (THF), and dissolved and dispersed with an ultrasonic disperser to obtain a coating solution for a single-layer type photosensitive layer.

Next, the single layer type photosensitive layer coating solution is applied on an aluminum base tube (conductive substrate) by a dip coating method and dried with hot air at 140 ° C. for 20 minutes, thereby providing a single layer having a photosensitive layer thickness of 25 μm. A mold photoreceptor was obtained.
(Example 2)
As an isoindolinone derivative, instead of the compound of the above formula (1-1), 2.0 parts by weight of an isoindolinone pigment (Pigment Yellow 110) represented by the above formula (1-2) was used. A single layer type electrophotographic photosensitive member was produced in the same manner as in Example 1.

(Comparative Example 1)
A single-layer electrophotographic photosensitive member was produced in the same manner as in Example 1 except that no isoindolinone derivative was blended in the single-layer photosensitive layer coating solution.
[Evaluation of physical properties of electrophotographic photosensitive member / photosensitive layer forming coating solution]
(1) Sensitivity test The single layer type electrophotographic photoreceptors obtained in the above examples and comparative examples were charged by a drum sensitivity tester using corona discharge, and the surface potential was set to + 850V. Next, light having a wavelength of 780 nm, a half-value width of 20 nm, and an intensity of 8 μW / cm ² monochromatized using a bandpass filter is exposed on the surface of the electrophotographic photosensitive member for 1.5 seconds, and 0.5 seconds from the start of exposure. The surface potential after the lapse was measured as the post-exposure potential (V). The measurement results are shown in Table 1 as “photosensitivity (V) immediately after dispersion”.

An electrophotographic photosensitive member was produced in the same manner as in the above Examples and Comparative Examples except that the single layer type photosensitive layer coating solution was allowed to stand for 1 day. The post-exposure potential (V) was measured by the same method as described above. The measurement results are shown in Table 1 as “photosensitivity after standing (V)”.
(2) Evaluation of stability over time of coating solution Whether the coating solution for a single-layer type photosensitive layer obtained in the above Examples and Comparative Examples is allowed to stand for 1 day, then precipitates are generated in the coating solution. Was visually observed.

  The evaluation results in the above (1) and (2) are shown in Table 1 together with the type of isoindolinone pigment used.

As is clear from Table 1, according to Examples 1 and 2 in which a predetermined isoindolinone pigment was blended with titanyl phthalocyanine, no precipitation was observed in the coating solution for forming the photosensitive layer, and therefore its stability was good. In addition, the sensitivity of the single-layer electrophotographic photosensitive member can be made excellent.
The present invention is not limited to the above description, and various design changes can be made within the scope of the matters described in the claims.

Claims (5)

A single photosensitive layer containing titanyl phthalocyanine as a charge generating agent, a charge transport agent, a binder resin, and an isoindolinone derivative on a conductive substrate,
The binder resin contains at least one resin selected from the group consisting of polycarbonate, polyester, polyarylate and polystyrene,
A single-layer electrophotographic photoreceptor, wherein the content of the isoindolinone derivative is 30 to 80% by weight based on the total content of the charge generating agent . The isoindolinone derivative is represented by the formula (1):

(In the formula, R ¹ represents an alkylene group having 1 to 6 carbon atoms which may have a substituent, or an arylene group having 6 to 20 carbon atoms which may have a substituent. X represents a halogen atom.)
The single-layer electrophotographic photosensitive member according to claim 1, which is an isoindolinone pigment represented by the formula:   The titanyl phthalocyanine is an α-type titanyl phthalocyanine having a main diffraction peak at 27.6 ° at a Bragg angle (2θ ± 0.2 °) in an X-ray diffraction spectrum, or a main diffraction at 27.3 °. 3. The single-layer electrophotographic photosensitive member according to claim 1, which is a Y-type titanyl phthalocyanine having a peak.   The said titanyl phthalocyanine does not have an endothermic peak other than the peak accompanying vaporization of adsorbed water at the time of temperature rising from 50 degreeC to 400 degreeC in differential scanning calorimetry. Single layer type electrophotographic photoreceptor.   The single-layer electrophotographic photoreceptor according to any one of claims 1 to 4, which is a photoreceptor for an image forming apparatus using light having a wavelength in the range of 680 to 830 nm as an exposure light source.