Electrophotographic photoreceptor and image forming apparatus including the same

Abstract

To provide an electrophotographic photoreceptor using a known titanyl phthalocyanine adduct of 2,3-butanediol as a charge generating substance, the photoreceptor achieving acceleration, miniaturization, and a reduction in the diameter of the photoreceptor, preventing a reduction in charging due to optical fatigue caused by static eliminating light and pre-exposure caused by external light, and capable of providing stable images, and an image forming apparatus including the same.SOLUTION: An electrophotographic photoreceptor comprises, on a substrate, at least a laminated photosensitive layer in which a charge generating layer and a charge transport layer are laminated in this order. The charge generating layer contains, as charge generating substances, 2,3-butanediol-added titanyl phthalocyanine having the maximum absorption in wavelengths of 745-780 nm in a spectral absorption spectrum, and a specific pyrazolone compound.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an electrophotographic photoreceptor and an image forming apparatus including the same. [Background technology]

[0002] Electrophotographic image forming apparatuses that form images using electrophotographic technology are widely used in copying machines, printers, facsimile machines, and the like. An electrophotographic photoreceptor (hereinafter also referred to as "photoreceptor") used in an electrophotographic process is configured by laminating a photosensitive layer containing a photoconductive material on a substrate. Currently, research and development of photoreceptors having a photosensitive layer whose main component is an organic photoconductive material (also called "organic photoreceptors") is progressing, and they now account for the majority of photoreceptors in practical image forming devices.

[0003] As organic photoreceptors, a structure has been proposed in which a single-layer type photosensitive layer is provided on a substrate, in which a charge generating material and a charge transporting material (also called a "charge transfer material") are dispersed in a binder resin (also called a "binder resin" or "binder resin"), and a laminated type photosensitive layer is provided in which a charge generating layer in which a charge generating material is dispersed in a binder resin and a charge transporting layer in which a charge transporting material is dispersed in a binder resin are laminated in that order. Of these, the latter function-separated type photoreceptor is widely used because it has excellent electrophotographic properties and durability, has a high degree of freedom in material selection, and is easy to design various photoreceptor properties.

[0004] Various materials have been proposed as constituent materials of photoreceptors, and as a charge generating substance (pigment), a titanyl phthalocyanine adduct of 2,3-butanediol has been proposed, which is highly sensitive and shows little change in sensitivity characteristics due to external environment, particularly humidity fluctuations (JP Patent Publication 7-173405: ​​Patent Document 1). However, photoconductors containing a titanyl phthalocyanine adduct of 2,3-butanediol as a charge generating material have strong absorption at a wavelength of around 600 nm in the spectroscopic spectrum, and when the processes of charging, exposure, development, transfer and static elimination are repeatedly performed inside an image forming apparatus (actual machine), they are affected by electrical fatigue or light fatigue due to static elimination light. In addition, when repeatedly used, the charging potential at the first rotation after being left alone does not rise to a predetermined potential, and a difference in surface potential (hereinafter also referred to as "FV0") occurs between the area of ​​the photoconductor at the first rotation and the area at the second rotation and thereafter in the first copy image, resulting in uneven image density and background fogging, leading to a problem of deterioration in image quality.

[0005] During normal use, photoconductors are exposed to external light not only from the light source inside image forming devices such as copiers, but also when peripheral parts are replaced for the second maintenance or when paper gets jammed inside the device. Such photo-fatigue of photoconductors caused by external light is more damaging than electrical fatigue inside the device, and is the cause of image degradation. It is believed that such photo-fatigue is caused by excess carriers generated in the charge generating layer.

[0006] To address these issues, a technique has been proposed in which a specific ultraviolet absorber having a maximum absorption wavelength in the range of 380 to 480 nm is added to the charge transport layer, and a technique has also been proposed in which an additive (electron transport material) having a specific structure that has a maximum absorption wavelength in the range of 300 to 370 nm and no absorption wavelength in the range of 730 to 800 nm is added to the charge transport layer (JP Patent Publication (Kokai) No. 2010-164639: Patent Document 2). However, in either case, additives are used in the photosensitive layer, and although the effect varies, the effect of trapping charge transport remains the same. In addition, adding even a small amount of low molecular weight compound to the photosensitive layer brings about the problem of reduced printing durability. For the reasons mentioned above, the current situation is that image forming apparatuses such as copying machines are still insufficient in terms of meeting the demands for higher speed, smaller size, smaller diameter photoconductors, and longer life. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 7-173405 [Patent Document 2] JP 2010-164639 A Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, an object of the present disclosure is to provide an electrophotographic photoreceptor and an image forming apparatus equipped therewith, which are capable of providing stable images in a photoreceptor using a titanyl phthalocyanine adduct of 2,3-butanediol, which is known as a charge generating substance, in response to increased speed, smaller size, and smaller diameter of the photoreceptor, and which is resistant to charge reduction due to photofatigue caused by static elimination light and pre-exposure to external light. [Means for solving the problem]

[0009] As a result of intensive research conducted by the present inventors to solve the above-mentioned problems, they discovered that the above-mentioned problems can be solved by having a charge generating layer containing, as charge generating materials, a titanyl phthalocyanine adduct of 2,3-butanediol having a maximum absorption at wavelengths of 745 to 780 nm in its spectral absorption spectrum and a specific pyrazolone compound, and thus completed the present invention.

[0010] Thus, according to the present disclosure, there is provided a photosensitive layer including a charge generating layer and a charge transport layer laminated in this order on a substrate, The charge generating layer contains, as a charge generating material, a compound represented by the general formula (I): [ka]

[0011] and at least one selected from the group consisting of titanyl phthalocyanine to which (2R,3R)-2,3-butanediol has been added and titanyl phthalocyanine to which (2S,3S)-2,3-butanediol has been added, which has a maximum absorption at a wavelength of 745 to 780 nm in a spectroscopic absorption spectrum, and a titanyl phthalocyanine to which (2S,3S)-2,3-butanediol has been added, represented by the general formula (II): [ka]

[0012] (In the formula, R a and R b are the same or different and each is a hydrogen atom, a halogen atom, a cyano group, a nitro group, a hydroxyl group, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group which may have a substituent, a heterocyclic group which may have a substituent, an ester group, a cycloalkyl group, an aralkyl group which may have a substituent, an allyl group, an amide group, an amino group, an acyl group, an alkenyl group, an alkynyl group, a carboxyl group, a carbonyl group, a carboxylic acid group, or a halogenated alkyl group, and the substituent is a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a hydroxyl group, a cyano group, an amino group, a nitro group, or a halogenated alkyl group. The present invention provides an electrophotographic photoreceptor comprising a pyrazolone compound represented by the following formula:

[0013] Furthermore, according to the present disclosure, there is provided an image forming apparatus comprising at least the above-mentioned electrophotographic photosensitive member, a charging means for charging the electrophotographic photosensitive member, an exposure means for exposing the charged electrophotographic photosensitive member to light to form an electrostatic latent image, a developing means for developing the electrostatic latent image to form a toner image, and a transfer means for transferring the toner image onto a recording medium. Effect of the Invention

[0014] According to the present disclosure, it is possible to provide an electrophotographic photoreceptor and an image forming apparatus equipped therewith, which are capable of providing stable images in a photoreceptor using a titanyl phthalocyanine adduct of 2,3-butanediol, which is known as a charge generating substance, in response to increased speed, smaller size, and smaller diameter of the photoreceptor, and which is resistant to charge reduction due to photofatigue caused by static elimination light and pre-exposure to external light.

[0015] The inventors surmise that by incorporating a specific pyrazolone compound in the charge generation layer, electron traps captured in lattice defects are efficiently transported, the accumulation of excess carriers is suppressed more than in the past, and even with continuous use, the generation of excess carriers in the charge generation layer is suppressed, the occurrence of charging reduction due to excess carriers is suppressed, and a stable image can be provided. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 is a diagram showing a spectral absorption spectrum of a photosensitive layer of a photoreceptor (Example 1) of the present disclosure. [Diagram 2] FIG. 1 is a schematic cross-sectional view showing the configuration of a main part of a photoreceptor (laminated photoreceptor) F01 according to the present disclosure. [Diagram 3] 1 is a schematic side view showing a configuration of a main part of an image forming apparatus 100 according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The photoreceptor of the present disclosure includes at least a laminated photosensitive layer in which a charge generating layer and a charge transport layer are laminated in this order on a substrate, The charge generating layer contains, as a charge generating material, a compound represented by the general formula (I): [ka]

[0018] and having a maximum absorption at a wavelength of 745 to 780 nm in a spectroscopic absorption spectrum, at least one selected from the group consisting of (2R,3R)-2,3-butanediol-added titanyl phthalocyanine and (2S,3S)-2,3-butanediol-added titanyl phthalocyanine, and a general formula (II): [ka]

[0019] (In the formula, R a and R b are the same or different and each is a hydrogen atom, a halogen atom, a cyano group, a nitro group, a hydroxyl group, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group which may have a substituent, a heterocyclic group which may have a substituent, an ester group, a cycloalkyl group, an aralkyl group which may have a substituent, an allyl group, an amide group, an amino group, an acyl group, an alkenyl group, an alkynyl group, a carboxyl group, a carbonyl group, a carboxylic acid group, or a halogenated alkyl group, and the substituent is a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a hydroxyl group, a cyano group, an amino group, a nitro group, or a halogenated alkyl group. The composition is characterized in that it contains a pyrazolone compound represented by the following formula:

[0020] Below, the constituent features that characterize the photoreceptor of the present disclosure will be described, and then (1) the photoreceptor and (2) the image forming apparatus will be described. It should be noted that the embodiments and examples described below are merely specific examples of the present invention, and the present invention is not limited thereto.

[0021] <Method for synthesizing titanyl phthalocyanine to which (2R,3R)-2,3-butanediol has been added and titanyl phthalocyanine to which (2S,3S)-2,3-butanediol has been added (collectively referred to as "titanyl phthalocyanine adduct of 2,3-butanediol")> The titanyl phthalocyanine adduct of 2,3-butanediol of the present disclosure can be synthesized by heating and reacting titanyl phthalocyanine with (2R,3R)-2,3-butanediol or (2S,3S)-2,3-butanediol in various solvents based on the method described in Japanese Patent No. 5609167.

[0022] The raw material, titanyl phthalocyanine, is represented by the following formula (A). [ka]

[0023] The oxotitanium phthalocyanine represented by formula (A) can be produced by known synthesis methods described, for example, in JP-A-6-293769, JP-A-2003-183534, JP-A-7-271073, and Phthalocyanine Compounds by Moser, Frank H and Arthur L. Thomas, Reinhold Publishing Corp., New York, 1963. In known synthesis methods, there are cases where a titanium halide is used as a starting material and cases where a titanium halide is not used as a starting material. However, the present inventors have confirmed that, as long as a titanyl phthalocyanine adduct of 2,3-butanediol having the above-mentioned spectral absorption spectrum characteristics can be synthesized, the excellent effects of the present disclosure can be obtained regardless of the starting material or synthesis method. The inclusion of halogens such as chlorine in (2R,3R)-2,3-butanediol or (2S,3S)-2,3-butanediol can adversely affect the charging performance of a photoreceptor, and therefore titanyl phthalocyanine derived from raw materials that do not contain halogens such as chlorine is preferred.

[0024] The synthesis method is exemplified below. However, the synthesis route below is only an example and is not intended to be limiting. Phthalonitrile and titanium alkoxide such as tetrabutoxytitanium are reacted in the presence of urea while maintaining the temperature at 150°C for at least 5 hours under stirring. After the reaction is completed, the titanyl phthalocyanine produced is filtered off. The resulting product is washed with a solvent such as alcohols such as methanol, ethanol, n-propanol, butanol, chlorine-based hydrocarbons such as dichloroethane and chloroform, ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, ketones such as acetone and methyl ethyl ketone, to obtain titanyl phthalocyanine. Titanyl phthalocyanine does not dissolve in these solvents, but impurities attached to titanyl phthalocyanine do dissolve, so by repeating the washing, the remaining impurities can be reduced to the minimum.

[0025] Furthermore, isoindoline is reacted with titanium tetraalkoxide such as tetrabutoxytitanium in a suitable solvent such as N-methylpyrrolidone under heating to obtain oxotitanium phthalocyanine. This titanyl phthalocyanine may contain a phthalocyanine derivative in which the hydrogen atom of the benzene ring is substituted with a substituent such as chlorine, fluorine, nitro, cyano, or sulfone. The titanyl phthalocyanine thus obtained can be treated with a water-immiscible organic solvent such as dichloroethane in the presence of water to obtain crystalline titanyl phthalocyanine, which is a raw material for the titanyl phthalocyanine adduct of 2,3-butanediol used as a charge generating substance in the present disclosure.

[0026] Examples of the treatment method (crystal conversion method) include a method in which titanyl phthalocyanine is swollen with water and then treated with an organic solvent, and a method in which water is added to an organic solvent without performing a swelling treatment, and titanyl phthalocyanine powder is then added thereto. As a method for swelling titanyl phthalocyanine with water, for example, titanyl phthalocyanine is dissolved in 10 to 30 times concentrated sulfuric acid, and if any insoluble matter is generated, it is removed by filtration or the like, and the precipitate is precipitated in cooled water. The obtained titanyl phthalocyanine is then filtered with ion-exchanged water or the like to remove the acid, and washing operations are repeated until it becomes neutral to obtain a wet cake. When titanyl phthalocyanine is swollen with water, it is washed using known stirring and dispersing equipment such as a homomixer, paint mixer, ball mill, and sand mill. If sulfuric acid remains in the wet cake, it is difficult to proceed with the reaction with butanediol in the next step, so careful washing is required. After the washing step, the wet cake is filtered and dried to obtain amorphous titanyl phthalocyanine.

[0027] Add 1 to 3.5 times the molar equivalent of butanediol to the obtained amorphous titanyl phthalocyanine. If the amount of butanediol is less than 1, it is not possible to obtain a spectral absorption spectrum within the range specified in the present disclosure, and the humidity dependency of the sensitivity specific to titanyl phthalocyanine may become insufficient. On the other hand, if the amount of butanediol exceeds 3.5 times, the amount of butanediol becomes excessive, making it difficult to remove unreacted butanediol, and it has been found that the stability against repeated current fatigue is significantly reduced. The organic solvent used here is not particularly limited as long as it can give the desired crystal form, and examples thereof include chlorobenzene, dichlorobenzene, anisole, chloronaphthalene, quinoline, and tetrahydrofuran. The organic solvent may be one or a mixed solvent of two or more selected from these.

[0028] In synthesizing the titanyl phthalocyanine adduct of 2,3-butanediol used in the present disclosure, various production conditions such as the reaction molar ratio, reaction temperature, reaction time, selection of the solvent type, and crystallization method can be appropriately selected, and thus the synthesis can be easily optimized.

[0029] In terms of the effect of improving the light resistance of photoconductors, the titanyl phthalocyanine adduct of 2,3-butanediol has an absorbance of 780 nm and 750 nm in the spectral absorption spectrum of Abs 780 and Abs 750 When Abs 750 <Abs 780 It is preferable that the following relationship is satisfied. Furthermore, as a result of the examples described later, for example, 750 / Abs 780 As is clear from the results of Example 2, where Abs is 0.70, as is the case for Example 1, where Abs is 1.19. 780 Abs 750 It is more preferable that the relationship be 1.1 times or more. The measurement of absorbance will be specifically described in the Examples.

[0030] The titanyl phthalocyanine adduct of 2,3-butanediol preferably has an average particle size D (50%) of 0.15 to 0.45 μm. If the average particle size D of the titanyl phthalocyanine adduct is less than 0.15 μm, excessive shear is applied during dispersion, and when a charge generation layer is formed, lattice defects are likely to occur. The effect on light resistance tends to decrease. On the other hand, if the average particle size D of the titanyl phthalocyanine adduct exceeds 0.45 μm, the charge generation efficiency decreases, which may induce a decrease in sensitivity and a decrease in concentration due to an increase in VL over long-term use. The average particle size D of the titanyl phthalocyanine adduct is more preferably 0.15 to 0.03 μm, and particularly preferably 0.20 to 0.30 μm. The measurement of the average particle diameter D(50%) will be specifically explained in the Examples.

[0031] <Pyrazolone compounds> The charge generating layer of the photoreceptor of the present disclosure contains the pyrazolone compound represented by general formula (II) together with the titanyl phthalocyanine adduct of 2,3-butanediol represented by general formula (I) above.

[0032] The substituent R in the general formula (I) a and Rb The substituents which may be present will be described below. Examples of the alkyl group include alkyl groups having 1 to 6 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, and n-hexyl, and alkyl groups having 7 to 12 carbon atoms, such as n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, and n-dodecyl. Examples of the alkoxy group include alkoxy groups having 1 to 6 carbon atoms, such as methoxy, ethoxy, n-propoxy, isopropoxy, tert-butoxy, n-pentyloxy, and n-hexyloxy, and alkoxy groups having 7 to 12 carbon atoms, such as n-hexyloxy, n-octyloxy, n-nonyloxy, n-decyloxy, n-undecyloxy, and n-dodecyloxy. Examples of the aryl group include phenyl, naphthyl, anthryl, phenanthryl, fluorenyl, biphenylyl, and o-terphenyl.

[0033] Heterocyclic groups include, for example, pyridyl, indolyl, carbazole, thiophene, and the like. Cycloalkyl groups include, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and the like. Aralkyl groups include, for example, benzyl, phenethyl, benzhydryl, trityl, and the like. Examples of the acyl group include acetyl, propanoyl, and benzyl. Alkenyl groups include, for example, vinyl, propenyl, allyl, butenyl, pentenyl, hexenyl, and the like. Alkynyl groups include, for example, ethynyl, propynyl, butynyl, pentynyl, hexynyl, and the like. Carboxylic acid groups include, for example, formyl, acetyl, propionyl, butyryl, isobutyryl, valeryl, isovaleryl, and the like. Examples of the halogen atom include fluorine, chlorine, bromine, and iodine. Examples of the substituent that may be possessed include the above-mentioned alkyl group having 1 to 6 carbon atoms, alkoxy group having 1 to 6 carbon atoms, and the above-mentioned halogen atoms.

[0034] The pyrazolone compound of the present disclosure has a substituent R a and R b are the same or different and each represents an alkyl group having 1 to 12 carbon atoms or an aryl group which may have a substituent, and the substituent is preferably a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a hydroxyl group, a cyano group, an amino group, a nitro group or a halogenated alkyl group, and the substituent R b represents an aryl group which may have a substituent, and the substituent is preferably a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a hydroxyl group, a cyano group, an amino group, a nitro group, or a halogenated alkyl group, and the substituent R a and R b Particularly preferred are compounds in which both are optionally substituted aryl groups.

[0035] Since general fluorescent lamps have strong light wavelength components around 550 (~600), these lights act on charge generating materials and generate charge traps. On the other hand, light sources such as LEDs and laser light that expose photoconductors to form electrostatic latent images, or LEDs that remove residual surface charges on photoconductors, often have an emission range of 600 to 650 nm, so if light of this wavelength is blocked, the residual potential will rise and it will become impossible to maintain stable potential repeatedly. Therefore, the pyrazolone compound represented by the general formula (II) has a maximum absorption at wavelengths of 515 to 560 nm in the spectral absorption spectrum even in the wavelength range of 500 to 600 nm (λ max = 515 to 560 nm) is preferable.

[0036] Furthermore, the pyrazolone compound is preferably a compound having the structure of general formula (II) and the above-mentioned optical properties, and not inhibiting the effects of the present disclosure, and is preferably a compound in which the substituent Ra in general formula (II) is a phenyl group which may have a substituent.

[0037] Examples of pyrazolone compounds include the following compounds 2-1 to 2-4 (wherein Ph represents a phenyl group). In terms of mobility and wavelength of light absorbed, compounds 2-1 to 2-3 used in the CT manufacturing examples are preferred, and compound 2-1 is particularly preferred in terms of sensitivity characteristics and charging properties after repeated current fatigue.

[0038] [ka]

[0039] The pyrazolone compound is preferably contained in the charge generating layer in a proportion of 10 to 100 parts by mass, and more preferably 30 to 60 parts by mass, per 100 parts by mass of the charge generating substance. By including the pyrazolone compound in the charge generating layer in the above range, electrons generated from the charge generating material upon exposure can be transported more efficiently to the outside of the charge generating layer. If the amount of the pyrazolone compound is less than 10 parts by mass per 100 parts by mass of the charge generating substance, the amount is insufficient, and FV0 due to fatigue caused by electrical current may increase, whereas if the amount of the pyrazolone compound is more than 100 parts by mass per 100 parts by mass of the charge generating substance, charge generation may be inhibited.

[0040] If the pyrazolone compound is contained in the charge transport layer, it becomes a trap for hole transport, and the residual potential cannot be suppressed, so it is most effective to add the pyrazolone compound only to the charge generation layer.Therefore, even if the pyrazolone compound is added to the charge transport layer (if the pyrazolone compound added to the charge generation layer seeps into the charge transport layer), it is preferable that the charge transport layer contains the pyrazolone compound at a ratio of 0.35 mass % or less, preferably 0.2 mass % or less, based on the total solid content of the charge transport layer. Therefore, the charge transport layer preferably contains the pyrazolone compound in an amount of 0.2% by mass or less based on the total solid content of the charge transport layer.

[0041] (1) Electrophotographic Photoreceptor The photoreceptor of the present disclosure includes at least a laminated photosensitive layer in which a charge generating layer and a charge transport layer are laminated in this order on a substrate. The photoreceptor of the present disclosure will be described below with reference to the drawings, but the present invention is not limited thereto. FIG. 2 is a schematic cross-sectional view showing the configuration of a main part of the photoreceptor (multilayer type photoreceptor) F01 of the present disclosure. The multi-layer photoreceptor F01 is provided with a multi-layer photosensitive layer in which an undercoat layer F21, a charge generating layer F22 containing a charge generating material, and a charge transport layer F23 containing a charge transport material are laminated in this order on a substrate F1. In the drawing, Fa indicates the surface of the photoreceptor.

[0042] <Base F1> The substrate (also referred to as "conductive substrate" or "conductive support") functions as an electrode for the photoreceptor and as a support member, and the material constituting the substrate is not particularly limited as long as it is a material used in the relevant technical field. Specific examples include metal materials such as aluminum, aluminum alloys, copper, zinc, stainless steel, and titanium, as well as polymer materials such as polyethylene terephthalate, nylon, and polystyrene, whose surfaces are laminated with metal foil, subjected to metal vapor deposition, or vapor-deposited or coated with a layer of a conductive compound such as a conductive polymer, tin oxide, or indium oxide, as well as hard paper and glass. Among these, aluminum is preferred from the viewpoint of ease of processing, and aluminum alloys such as JIS 3003, JIS 5000, and JIS 6000 are particularly preferred. The shape of the substrate is not limited to a cylindrical shape (drum shape) as shown in FIG. 3, but may be a sheet shape, a columnar shape, an endless belt shape, or the like. In addition, the surface of the substrate may be subjected to a diffuse reflection treatment such as anodizing, surface treatment with chemicals or hot water, coloring, or surface roughening, as necessary, to prevent interference fringes caused by laser light, within a range that does not affect image quality.

[0043] <Undercoat layer F21> The photoreceptor of the present disclosure preferably includes an undercoat layer (also called an "intermediate layer") between the substrate and the laminated photosensitive layer. The undercoat layer generally covers the unevenness of the surface of the substrate to make it uniform, improves the film-forming property of the laminated photosensitive layer, suppresses the peeling of the photosensitive layer from the substrate, and improves the adhesion between the substrate and the photosensitive layer. Specifically, it prevents the injection of electric charge from the substrate into the photosensitive layer, prevents the chargeability of the photosensitive layer from decreasing, and prevents fogging of the image (so-called black spots). The undercoat layer can be formed, for example, by dissolving a binder resin in a suitable solvent to prepare a coating liquid for the undercoat layer, coating this coating liquid on the surface of the substrate, and then drying to remove the organic solvent.

[0044] Examples of the binder resin include acetal resin, polyamide resin, polyurethane resin, polyester resin, acrylic resin, epoxy resin, phenol resin, melamine resin, urethane resin, etc. The binder resin is required to have properties such as not dissolving or swelling in the solvent used when forming the photoconductor layer on the undercoat layer, excellent adhesion to the substrate, and flexibility. Among the above binder resins, polyamide resin is preferred, and alcohol-soluble nylon resin and polyamide resin containing a piperazine compound are particularly preferred. Examples of alcohol-soluble nylon resins include homopolymer or copolymer nylons such as 6-nylon, 66-nylon, 610-nylon, 11-nylon, and 12-nylon, and chemically modified nylons such as N-alkoxymethyl modified nylons. A curing agent that crosslinks the binder resin may be used to form a cured film. As the curing agent, blocked isocyanate is preferred from the viewpoint of storage stability and electrical properties of the coating liquid.

[0045] Examples of the solvent include lower alcohols such as water, methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, 2-butanol, and isobutanol, ketones such as acetone, cyclohexanone, and 2-butanone, ethers such as tetrahydrofuran, dioxane, ethylene glycol, and diethyl ether, and halogenated hydrocarbons such as methylene chloride and ethylene chloride. An appropriate solvent is selected from these solvents based on the solubility of the binder resin and the surface smoothness of the undercoat layer, and one type may be used alone or two or more types may be used in combination. Among these solvents, for example, non-halogenated organic solvents can be preferably used in consideration of the global environment.

[0046] The coating solution for the undercoat layer may contain metal oxide particles, which can easily adjust the volume resistivity of the undercoat layer, further suppress the injection of charges into the charge generating layer, and maintain the electrical properties of the photoreceptor under various environments. Materials that can be used for the metal oxide particles include, for example, titanium oxide, aluminum oxide, aluminum hydroxide, and tin oxide. In the coating liquid for forming an undercoat layer, the ratio (A / B) of the total mass A of the binder resin and metal oxide particles to the mass B of the solvent is, for example, preferably about 1 / 99 to 30 / 70, and particularly preferably about 2 / 98 to 40 / 60. The ratio (C / D) of the mass C of the binder resin to the mass D of the metal oxide particles is, for example, preferably about 1 / 99 to 90 / 10, and particularly preferably about 5 / 95 to 70 / 30.

[0047] The coating method for the undercoat layer coating liquid may be appropriately selected from among the most suitable methods taking into consideration the physical properties of the coating liquid and productivity, and examples of the method include spraying, bar coating, roll coating, blade coating, ring coating, and dip coating. Among these, the dip coating method is a method in which a substrate is immersed in a coating tank filled with a coating liquid, and then pulled up at a constant speed or a gradually changing speed to form a layer on the surface of the substrate, and is relatively simple and has excellent productivity and cost, so that it can be suitably used for manufacturing photoreceptors. The apparatus used for the dip coating method may be provided with a coating liquid dispersion device, typically an ultrasonic generator, in order to stabilize the dispersibility of the coating liquid.

[0048] The solvent in the coating film may be removed by natural drying, but the solvent in the coating film may also be removed forcibly by heating. The temperature in such a drying step is not particularly limited as long as it is a temperature at which the solvent used can be removed, but a temperature of about 50 to 140°C is appropriate, and a temperature of about 80 to 130°C is particularly preferable. If the drying temperature is less than 50°C, the drying time may be long and the solvent may not evaporate sufficiently and remain in the photoreceptor layer, while if the drying temperature exceeds about 140°C, the electrical characteristics of the photoreceptor may deteriorate during repeated use, resulting in poor quality of the obtained image. Such temperature conditions are common not only to the formation of the undercoat layer, but also to the formation of layers such as the photosensitive layer, which will be described later, and other treatments.

[0049] The thickness of the undercoat layer is not particularly limited, but is preferably 0.01 to 20 μm, and more preferably 0.05 to 10 μm. If the thickness of the undercoat layer is less than 0.01 μm, sufficient blocking effect against electron injection from the conductive substrate and sufficient effect against interference fringes due to light scattering may not be obtained. On the other hand, if the thickness of the undercoat layer exceeds 20 μm, the change in sensitivity during continuous printing may become large, which may result in a large change in image density.

[0050] <Charge generation layer F22> The charge generation layer has the function of generating charges by absorbing light irradiated by a light emitting device such as a light beam from a semiconductor laser in an electrophotographic device such as an image forming device, and contains a charge generation substance as a main component and, as necessary, a binder resin and additives.

[0051] As the charge generating material, at least one selected from the above-mentioned titanyl phthalocyanine with (2R,3R)-2,3-butanediol added thereto and titanyl phthalocyanine with (2S,3S)-2,3-butanediol added thereto is used, and other charge generating materials known in the art may be used in combination within a range that does not impair the effect of the charge generating material. However, since the photoreceptor of the present disclosure has improved characteristics depending on the content of titanyl phthalocyanine, the higher the content, the better, and it is preferably at least 80% or more.

[0052] As the charge generating material, either one of titanyl phthalocyanine with (2R,3R)-2,3-butanediol added and titanyl phthalocyanine with (2S,3S)-2,3-butanediol added can be used alone or in a mixture thereof. The mixture is preferred because it is convenient for synthesizing and obtaining the titanyl phthalocyanine adduct of 2,3-butanediol, and the mixing ratio is preferably 1:1 as described in the examples.

[0053] Other charge generating substances include α-type, β-type, Y-type, and amorphous oxo-titanyl phthalocyanine having a crystal type different from that of the above-mentioned oxo-titanyl phthalocyanine, other metal phthalocyanines such as gallium, azo pigments such as monoazo pigments, bisazo pigments, and trisazo pigments, indigo pigments such as indigo and thioindigo, perylene pigments such as perylene imide and perylene acid anhydride, polycyclic quinone pigments such as anthraquinone and pyrene quinone, phthalocyanine pigments such as metal phthalocyanines and metal-free phthalocyanines such as oxotitanium phthalocyanine, organic photoconductive materials such as squarylium dyes, pyrylium salts, thiopyrylium salts, and triphenylmethane dyes, and inorganic photoconductive materials such as selenium and amorphous silicone, and the like, and those having sensitivity in the exposure wavelength region can be appropriately selected and used.

[0054] A preferred method for forming the charge generating layer is to disperse the charge generating material in a binder resin solution obtained by mixing a binder resin in a solvent by a conventionally known method, and then coat the coating liquid for the charge generating layer on the undercoat layer. This method will be described below.

[0055] The binder resin is not particularly limited, and may be any of the resins having binding properties used in the art and the binder resins exemplified for the undercoat layer above. Preferably, the binder resin has excellent compatibility with the charge generating material. Specifically, polyester, polystyrene, polyurethane, phenol resin, alkyd resin, melamine resin, epoxy resin, silicone resin, acrylic resin, methacrylic resin, polycarbonate, polyarylate, phenoxy resin, polyvinyl butyral (PVB), polyvinyl formal, copolymer resin containing two or more of the repeating units constituting these resins, etc. Examples of the copolymer resin include insulating resins such as vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, and acrylonitrile-styrene copolymer resin. These binder resins can be used alone or in combination of two or more.

[0056] In the present disclosure, among the above binder resins, a resin obtained by an acetalization reaction between two or more types of aldehyde and polyvinyl alcohol and having a mass average molecular weight of 60,000 or more and 200,000 or less is preferred. If the mass average molecular weight is less than 60,000, the dispersibility of the titanyl phthalocyanine of the present disclosure may be poor, film-forming defects may easily occur, and problems may occur in dispersion stability during long-term storage. On the other hand, if the mass average molecular weight exceeds 200,000, the viscosity of the dispersion coating liquid increases, and the crystal system of the titanyl phthalocyanine may collapse. A more preferable range of the mass average molecular weight is 80,000 or more and 120,000 or less. The mass average molecular weight can be measured by a known method.

[0057] Examples of the solvent include halogenated hydrocarbons such as dichloromethane and dichloroethane, ketones such as acetone, methyl ethyl ketone and cyclohexanone, esters such as ethyl acetate and butyl acetate, ethers such as tetrahydrofuran (THF) and dioxane, alkyl ethers of ethylene glycol such as 1,2-dimethoxyethane, aromatic hydrocarbons such as benzene, toluene and xylene, and aprotic polar solvents such as N,N-dimethylformamide and N,N-dimethylacetamide. These solvents can be used alone or in combination of two or more. Among these solvents, for example, non-halogenated organic solvents can be preferably used in consideration of the global environment.

[0058] As with the undercoat layer, a dispersing machine such as a paint shaker, a ball mill, or a sand mill can be used to dissolve or disperse the charge generating material in the binder resin solution. In this case, it is preferable to set the dispersion conditions appropriately so that impurities generated by wear or the like from the members constituting the container and dispersing machine are not mixed into the coating liquid.

[0059] The ratio (E / F) of the mass E of the charge generating substance to the mass F of the binder resin is preferably, for example, about 55 / 45 to 80 / 20. If the ratio (E / F) exceeds 80 / 20, i.e., if the mass E of the charge generating substance becomes large, there will be too much charge generating substance, and the dispersion stability in the binder resin may deteriorate. On the other hand, if the ratio (E / F) is less than 55 / 45, i.e., if the mass E of the charge generating substance becomes small, the charge generation efficiency may decrease and the sensitivity may deteriorate. A more preferable ratio is about 60 / 40 to 70 / 30.

[0060] The thickness of the charge generating layer is not particularly limited, but is preferably 0.05 to 5 μm, and more preferably 0.1 to 1 μm. If the thickness of the charge generating layer is less than 0.05 μm, the efficiency of light absorption decreases, and the sensitivity of the photoconductor may decrease. On the other hand, if the thickness of the charge generating layer is more than 5 μm, the charge transfer inside the charge generating layer becomes the rate-limiting step in the process of erasing the charge on the surface of the photoconductor, and the sensitivity of the photoconductor may decrease.

[0061] <Charge transport layer F23> The charge transport layer has the function of receiving the charges generated by the charge generation substance and transporting them to the surface of the photoreceptor (Fa in FIG. 2), and contains a charge transport substance, a binder resin, and additives as required. The charge transport layer of the photoreceptor of the present disclosure may contain a small amount of an electron transport material, which is described separately from the hole transport material, which also transports charges.

[0062] The hole transport material is not particularly limited, and any compound used in the art can be used. Specific examples thereof include carbazole derivatives, pyrene derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, polycyclic aromatic compounds, indole derivatives, pyrazoline derivatives, oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, triarylmethane derivatives, phenylenediamine derivatives, stilbene derivatives, enamine derivatives, benzidine derivatives, polymers having groups derived from these compounds in the main chain or side chain (poly-N-vinylcarbazole, poly-1-vinylpyrene, ethylcarbazole-formaldehyde resin, triphenylmethane polymer, poly-9-vinylanthracene, etc.), and polysilanes. These hole transport materials can be used alone or in combination of two or more.

[0063] Among these hole transporting materials, stilbene derivatives are particularly preferable in terms of electrical properties, durability and chemical stability. The photoreceptor of the present disclosure contains, as a hole transport material, a compound represented by the general formula (III): [ka]

[0064] (In the formula, R 1 , R 2 , R 5 and R 6 are the same or different and each is an alkyl group, an alkoxy group, an aryl group, an aralkyl group, or a halogen atom; m, n, p, and q are the same or different and each is an integer of 0 to 3; R 3 and R 4 are the same or different and are a hydrogen atom or an alkyl group. and a stilbene derivative represented by the general formula (IV):

[0065] [ka] (In the formula, R 7 is a hydrogen atom or an alkyl group, and R 8 and R 9 are the same or different and each is an alkyl group, an alkoxy group, an aryl group, an aralkyl group, or a halogen atom, and r, s, and t are the same or different and each is an integer of 0 to 3. It is preferable that the compound contains at least one stilbene derivative represented by the following formula:

[0066] The substituents and indices in general formulae (III) and (IV) are described below. R in general formula (III) 1 , R 2 , R 5 and R 6 and R in general formula (IV) 8 and R 9 Examples of the alkyl group include alkyl groups having 1 to 6 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, and n-hexyl. R in general formula (III) 1 , R 2 , R 5 and R 6 and R in general formula (IV) 8 and R 9 Examples of the alkoxy group include alkoxy groups having 1 to 6 carbon atoms, such as methoxy, ethoxy, n-propoxy, isopropoxy, tert-butoxy, n-pentyloxy, and n-hexyloxy. R in general formula (III) 1 , R 2 , R 5 and R 6 and R in general formula (IV) 8 and R 9 Examples of the aryl group include phenyl, naphthyl, anthryl, phenanthryl, fluorenyl, biphenylyl, and o-terphenyl. R in general formula (III) 1 , R 2 , R 5 and R 6 and R in general formula (IV) 8 and R 9 Examples of the aralkyl group include benzyl, phenethyl, benzhydryl, and trityl. R in general formula (III) 1 , R 2 , R 5 and R 6 and R in general formula (IV) 8 and R 9 The halogen atoms include fluorine, chlorine, bromine and iodine atoms. R in general formula (III) 1 , R 2 , R 5 and R 6 and R in general formula (IV) 8 and R 9 As the aryl group, methyl and ethyl are preferred, and methyl is particularly preferred.

[0067] R in general formula (III) 3 and R 4 and R in general formula (IV) 7Examples of the alkyl group include the above-mentioned alkyl groups. R in general formula (III) 3 and R 4 As the group, a hydrogen atom and methyl are preferable, and a hydrogen atom is particularly preferable. R in general formula (IV) 7 As the alkyl group, a hydrogen atom and methyl are preferable, and methyl is particularly preferable.

[0068] In the general formula (III), m, n, p and q are the same or different and are integers of 0 to 3, and when this index is 2 or more, each substituent may be different from each other. It is preferably 0 to 2, and more preferably 1 or 2. In the general formula (IV), r, s and t are the same or different and are integers of 0 to 3, and when this index is 2 or more, each substituent may be different from each other. It is preferably 0 or 1, and more preferably 1.

[0069] Materials having skeletons represented by general formulas (III) and (IV) are useful materials with small sensitivity and charge fluctuations due to repeated use. On the other hand, as a drawback, they are materials with poor light resistance, and usually require use in combination with a light resistance additive. However, by using them in combination with the charge generating substance of the present disclosure, light resistance can be guaranteed without using a light resistance additive, and the material can be compatible with light resistance without impairing the inherent advantage of high response. In addition, when greater light resistance is required depending on the usage environment, it is possible to use them in combination with a light resistance additive, but the amount of addition can be suppressed, and stable electrophotographic characteristics can be expressed over a long period of time.

[0070] The stilbene compound represented by general formula (III) can be synthesized, for example, by the method described in Japanese Patent No. 3272257. Examples of the stilbene derivatives represented by the general formulas (III) and (IV) include compounds (3-1) and (4-1) represented by the following structural formulas described in the Examples, which are preferably used. [ka]

[0071] [ka]

[0072] A preferred method for forming the charge transport layer is to disperse a hole transport material in a binder resin solution obtained by mixing a binder resin in a solvent by a conventionally known method, and then coat the charge transport layer coating liquid on the charge generating layer. This method is described below. The binder resin is not particularly limited, and any resin having binding properties that is used in the art can be used, and it is preferable that the binder resin has excellent compatibility with the hole transport material. Specific examples include vinyl polymer resins such as polymethyl methacrylate, polystyrene, and polyvinyl chloride, and copolymer resins thereof, as well as resins such as polycarbonate, polyester, polyester carbonate, polysulfone, phenoxy resin, epoxy resin, silicone resin, polyarylate, polyamide, polyether, polyurethane, polyacrylamide, phenol resin, and polyphenylene oxide, and thermosetting resins obtained by partially crosslinking these resins. These binder resins can be used alone or in combination of two or more. Among these, polystyrene, polycarbonate, polyarylate and polyphenylene oxide have a volume resistivity of 10 13 It is preferable because it has a hardness of Ω or more, is excellent in electrical insulation, and is also excellent in film-forming properties and potential characteristics, and polycarbonate is particularly preferable.

[0073] Examples of the solvent include aromatic hydrocarbons such as benzene, toluene, xylene, and monochlorobenzene; halogenated hydrocarbons such as dichloromethane and dichloroethane; ethers such as tetrahydrofuran, dioxane, and dimethoxymethyl ether; and aprotic polar solvents such as N,N-dimethylformamide. If necessary, a solvent such as alcohols, acetonitrile, or methyl ethyl ketone can also be added. These solvents can be used alone or in combination of two or more. Among these solvents, for example, non-halogenated organic solvents can be preferably used in consideration of the global environment.

[0074] The ratio (G / H) of the mass G of the hole transport material to the mass H of the binder resin is preferably, for example, about 10 / 30 to 10 / 12. If the ratio G / H is less than 10 / 30 and the ratio of the binder resin is high, when the charge transport layer is formed by the dip coating method, the viscosity of the coating liquid increases, which leads to a decrease in the coating speed and a significant decrease in productivity. In addition, if the amount of solvent in the coating liquid is increased to suppress the increase in the viscosity of the coating liquid, a blushing phenomenon may occur, causing the formed charge transport layer to become cloudy. On the other hand, if the ratio G / H exceeds 10 / 12 and the ratio of the binder resin is low, the printing durability may be lower than when the ratio of the binder resin is high, and the amount of wear of the photosensitive layer may increase.

[0075] The charge transport layer may contain additives as long as the additives do not impair the effects of the present disclosure. The additives include, for example, ultraviolet absorbers for improving light resistance, and specifically, perinone dyes. However, the addition of an additive to the charge transport layer may result in the formation of charge transport traps, which may adversely affect the properties of the photoreceptor, and the amount of additive added is about 1 to 10 parts by mass relative to the hole transport substance. In addition, the charge transport layer may contain inorganic fine particles such as silica or aluminum oxide to improve printing durability, and may contain fluorine-based resin fine particles to improve surface lubricity, as long as the effects of the present disclosure are not impaired.

[0076] The charge transport layer may contain additives such as plasticizers and leveling agents as necessary to improve film-forming properties, flexibility, and surface smoothness. Examples of plasticizers include dibasic acid esters such as phthalic acid esters, fatty acid esters, phosphoric acid esters, chlorinated paraffins, and epoxy-type plasticizers. Examples of leveling agents include silicon-based leveling agents. Examples of solvents include aromatic hydrocarbons such as benzene, toluene, xylene, and monochlorobenzene; halogenated hydrocarbons such as dichloromethane and dichloroethane; ethers such as THF, dioxane, and dimethoxymethyl ether; and aprotic polar solvents such as N,N-dimethylformamide. If necessary, solvents such as alcohols, acetonitrile, and methyl ethyl ketone may also be added and used. Among these solvents, non-halogenated organic solvents are preferably used in consideration of the global environment. These solvents may be used alone or in combination of two or more.

[0077] The charge transport layer is formed, for example, in the same manner as in the case of forming the charge generation layer described above, by preparing a coating liquid for the charge transport layer by dissolving or dispersing a hole transport material, a binder resin, and, if necessary, the additives described above in an appropriate solvent, and applying this coating liquid onto the charge generation layer by a spray method, a bar coating method, a roll coating method, a blade method, a ring method, a dip coating method, etc. Among these coating methods, the dip coating method is particularly preferable in the case of forming the charge transport layer, since it is superior in various respects as described above.

[0078] The thickness of the charge transport layer is not particularly limited, but is preferably about 5 to 50 μm, and more preferably about 10 to 40 μm. If the thickness of the charge transport layer is less than 5 μm, the charge retention ability of the photoreceptor surface may decrease, whereas if the thickness of the charge transport layer is more than 50 μm, the resolution of the photoreceptor may decrease.

[0079] (2) Image forming apparatus 100 The image forming apparatus of the present disclosure is characterized by comprising at least the photoconductor of the present disclosure, a charging means for charging the photoconductor, an exposure means for exposing the charged photoconductor to light to form an electrostatic latent image, a developing means for developing the electrostatic latent image to form a toner image (make it visible), and a transfer means for transferring the toner image onto a recording medium. The image forming apparatus of the present disclosure may include a fixing means for fixing the transferred toner image onto a recording medium to form an image, a cleaning means for removing and recovering toner remaining on the photosensitive member, and a discharging means for discharging surface charges remaining on the photosensitive member. The image forming apparatus of the present disclosure and its operation will be described below with reference to the drawings, but the image forming apparatus of the present disclosure is not limited thereto.

[0080] FIG. 3 is a schematic side view showing the configuration of a main part of the image forming apparatus 100 of the present disclosure. The image forming apparatus (laser printer) 100 in Fig. 3 includes the photoreceptor 1 (corresponding to F01 in Fig. 2) of the present disclosure, an exposure means (semiconductor laser) 31, a charging means (charger) 32, a developing means (developer) 33, a transfer means (transfer charger) 34, a conveyor belt (not shown), a fixing means (fixer) 35, and a cleaning means (cleaner) 36. Reference numeral 51 denotes a recording medium (recording paper or transfer paper).

[0081] Photoreceptor 1 is rotatably supported by the main body of image forming apparatus 100, and is driven to rotate around rotation axis 44 in the direction of arrow 41 by driving means (not shown). The driving means includes, for example, an electric motor and a reduction gear, and transmits its driving force to a base that constitutes the core of photoreceptor 1, thereby driving and rotating photoreceptor 1 at a predetermined peripheral speed. Charging means 32, exposure means 31, developing means 33, transfer means 34, and cleaning means 36 are provided in this order along the outer circumferential surface of photoreceptor 1 from the upstream side to the downstream side in the rotation direction of photoreceptor 1 indicated by arrow 41.

[0082] The charger 32 is a charging means for uniformly charging the outer circumferential surface of the photoreceptor 1 to a predetermined potential. Examples of the charging means include a non-contact charging method such as a corona charging method using a charging device, and a contact charging method using a charging roller or a charging brush.

[0083] The exposure means 31 has a semiconductor laser as a light source, and irradiates the surface of the photoreceptor 1 between the charger 32 and the developer 33 with a laser beam light output from the light source, thereby exposing the charged outer peripheral surface of the photoreceptor 1 according to image information. The light is repeatedly scanned in the direction of extension of the rotation axis 44 of the photoreceptor 1, which is the main scanning direction, and these are focused to sequentially form electrostatic latent images on the surface of the photoreceptor 1. In other words, the charge amount of the photoreceptor 1, which has been uniformly charged by the charger 32, differs depending on whether it is irradiated with the laser beam or not, and an electrostatic latent image is formed.

[0084] The developing device 33 is a developing means that develops the electrostatic latent image formed on the surface of the photoconductor 1 by exposure with a developer (toner), and is provided facing the photoconductor 1. The developing device 33 includes a developing roller 33a that supplies toner to the outer peripheral surface of the photoconductor 1, and a casing 33b that rotatably supports the developing roller 33a about a rotation axis parallel to the rotation axis 44 of the photoconductor 1 and contains a developer including toner in its internal space.

[0085] The transfer charger 34 is a transfer means that transfers a toner image, which is a visible image formed on the outer peripheral surface of the photoconductor 1 by development, onto a transfer paper 51, which is a recording medium, supplied between the photoconductor 1 and the transfer charger 34 from the direction of the arrow 42 by a transport means (not shown). The transfer charger 34 is, for example, a contact type transfer means that includes a charging means and transfers the toner image onto the transfer paper 51 by applying a charge of the opposite polarity to that of the toner to the transfer paper 51.

[0086] The cleaner 36 is a cleaning means for removing and recovering the toner remaining on the outer peripheral surface of the photoreceptor 1 after the transfer operation by the transfer charger 34, and includes a cleaning blade 36a for removing the toner remaining on the outer peripheral surface of the photoreceptor 1, and a recovery casing 36b for containing the toner removed by the cleaning blade 36a. The cleaner 36 is also provided together with a static elimination lamp (not shown).

[0087] Furthermore, in the image forming apparatus 100, a fixing device 35, which is a fixing means for fixing a transferred image, is provided downstream of the conveyance of the transfer paper 51 that has passed between the photoconductor 1 and the transfer charger 34. The fixing device 35 includes a heating roller 35a having a heating means (not shown), and a pressure roller 35b that is provided opposite the heating roller 35a and is pressed against the heating roller 35a to form a contact portion. Reference numeral 37 denotes a separating means for separating the transfer paper from the photosensitive member, and reference numeral 38 denotes a housing for accommodating the various means of the image forming apparatus.

[0088] The image forming operation by this image forming apparatus 100 is carried out as follows. First, when the photoconductor 1 is rotated in the direction of arrow 41 by the driving means, the surface of the photoconductor 1 is uniformly charged to a predetermined positive potential by the charger 32, which is provided upstream of the image-forming point of the light by the exposure means 31 in the rotational direction of the photoconductor 1.

[0089] Next, light according to image information is irradiated from exposure means 32 onto the surface of photoreceptor 1. This exposure removes surface charge from the areas of photoreceptor 1 irradiated with light, creating a difference in surface potential between the areas irradiated with light and the areas not irradiated with light, forming an electrostatic latent image. Toner is supplied from a developing device 33, which is provided downstream in the rotational direction of the photoconductor 1 from the imaging point of the light by the exposure means 33, to the surface of the photoconductor 1 on which the electrostatic latent image is formed, thereby developing the electrostatic latent image and forming a toner image.

[0090] In synchronization with the exposure of the photoconductor 1, a transfer paper 51 is supplied between the photoconductor 1 and the transfer charger 34. The transfer charger 34 gives the supplied transfer paper 51 a charge of the opposite polarity to that of the toner, and the toner image formed on the surface of the photoconductor 1 is transferred onto the transfer paper 51. The transfer paper 51 onto which the toner image has been transferred is transported by the transport means to the fixing device 35, and is heated and pressurized as it passes through the contact area between the heating roller 35a and the pressure roller 35b of the fixing device 35, and the toner image is fixed onto the transfer paper 51 to form a robust image. The transfer paper 51 on which the image has been formed in this way is discharged to the outside of the image forming apparatus 100 by the transport means.

[0091] Meanwhile, the toner remaining on the surface of the photoreceptor 1 after the transfer of the toner image by the transfer charger 34 is peeled off from the surface of the photoreceptor 1 and collected by the cleaner 36. The charge on the surface of the photoreceptor 1 from which the toner has been removed in this manner is removed by light from a discharging lamp, and the electrostatic latent image on the surface of the photoreceptor 1 disappears. The photoreceptor 1 is then rotated again, and the series of operations starting with charging are repeated again to form images continuously.

[0092] The image forming apparatus 100 is a monochrome image forming apparatus (printer), but may be, for example, a color image forming apparatus of an intermediate transfer type capable of forming a color image. Specifically, it may be a so-called tandem type full-color image forming apparatus in which a plurality of electrophotographic photosensitive members on which toner images are respectively formed are arranged in a predetermined direction (for example, the horizontal direction H or the approximately horizontal direction H). The image forming apparatus 100 may also be another color image forming apparatus, a copying machine, a multifunction machine, or a facsimile machine. EXAMPLES

[0093] The present disclosure will be specifically described below with reference to Production Examples, Comparative Production Examples, Examples, and Comparative Examples. However, the present invention is not limited to the following Examples as long as it does not depart from the gist of the present invention.

[0094] [Production Example 1] <Preparation of titanyl phthalocyanine 1> Titanyl phthalocyanine with (2R,3R)-2,3-butanediol added thereto or titanyl phthalocyanine with (2S,3S)-2,3-butanediol added thereto, which are represented by the following structural formula and used as a charge generating material, was prepared according to the method described in Japanese Patent No. 5609167 (Production Examples 1 to 3).

[0095] [ka]

[0096] 29.2 g of diiminoisoindoline and 200 ml of sulfolane were mixed, and 17.0 g of titanium tetraisopropoxide was added and reacted under a nitrogen atmosphere at 140° C. for 2 hours. The resulting reaction mixture was allowed to cool, and the precipitate was collected by filtration, washed successively with chloroform and a 2% aqueous hydrochloric acid solution, then washed successively with water and methanol, dried, washed again with water, and dried to obtain 25.5 g (yield: 89%) of crude titanyl phthalocyanine as a blue-purple crystal.

[0097] Five parts by mass of the resulting crude titanyl phthalocyanine that had been washed with hot water was stirred in 100 parts by mass of sulfuric acid at 3 to 5°C, gradually dissolved, and filtered. If the reaction temperature exceeded 5°C, there was a possibility that the phthalocyanine would decompose, so the temperature was strictly controlled to 5°C or less. The obtained sulfuric acid solution was added dropwise to 3500 parts by mass of ice water while stirring. During this time, the temperature of the ice water was always controlled to 5°C or less. The precipitated crystals were filtered, and then repeatedly suspended and washed in a washing solution, to obtain 250 g of the desired titanyl phthalocyanine wet cake. The pH of the washing solution was measured to be 6.8, confirming that deacidification washing had been performed. The obtained wet cake was frozen in a freezer to prepare wet cake A. In addition, when freezing, the wet paste was spread to an even thickness on a flat tray, and wet paste B was prepared with care to prevent uneven freezing throughout. The frozen wet pastes were thawed, filtered, washed with water, filtered repeatedly, and dried to obtain 23.9 g of amorphous titanyl phthalocyanine (yield: 82%).

[0098] [Production Example 2] <Preparation of (2R,3R)-2,3-butanediol titanyl phthalocyanine adducts (CGM-1 and CGM-2)> 10.0 g of amorphous titanyl phthalocyanine derived from wet cake A and wet cake B obtained in Production Example 1 and 2.50 g of (2R,3R)-2,3-butanediol were mixed in 200 ml of orthodichlorobenzene (ODB) and heated and stirred at 80 to 90 ° C for 6.0 hours. After standing overnight, 100 ml of water was added to the resulting reaction liquid, and the mixture was heated and stirred at 60 to 70 ° C for 6.0 hours to perform hydrolysis. Thereafter, the reaction liquid was allowed to cool, methanol was added, and the resulting crystals were filtered. The filtered crystals were washed with methanol to obtain 12.2 g of titanyl phthalocyanine adducts of (2R,3R)-2,3-butanediol (CGM-1 and CGM-2, respectively). In the X-ray diffraction spectrum of the resulting adduct, it was confirmed that it had diffraction peaks at 8.3°, 24.7°, 25.1° and 26.5°.

[0099] [Production Example 3] <Preparation of (2S,3S)-2,3-butanediol titanyl phthalocyanine adducts (CGM-3 and CGM-4)> Except for using (2S,3S)-2,3-butanediol instead of (2R,3R)-2,3-butanediol for the amorphous titanyl phthalocyanine derived from wet cake A and wet cake B, the same procedure as in Production Example 2 was carried out to obtain 12.5 g of a titanyl phthalocyanine adduct of (2S,3S)-2,3-butanediol (CGM-3 and CGM-4, respectively).

[0100] [Production Example 4] <Preparation of titanyl phthalocyanine 2> Titanyl phthalocyanine crystals used as the charge generating material in Comparative Example 1 were prepared according to the method described in Japanese Patent No. 3907112.

[0101] [CG manufacturing example 1] As the charge generating substance, 1.5 parts by mass of each of the titanyl phthalocyanine adducts CGM-1 and CGM-3 obtained in Production Examples 2 and 3 (mass ratio 1:1, total 3.0 parts by mass) was used, and as a pyrazolone compound, compound 2-1 (λ max = 528 nm) (50 parts by mass per 100 parts by mass of charge generating material) and 2.0 parts by mass of butyral resin (manufactured by Sekisui Chemical Co., Ltd., product name: S-LEC BX-1) as a binder resin (charge generating material / binder resin = 6 / 4) were added to 98 parts by mass of methyl ethyl ketone, and the mixture was dispersed for 20 minutes using a paint shaker with glass beads having a particle size (media diameter) of 0.4 mm, to prepare 3 liters of coating liquid for the charge generating layer. Compound 2-1 was prepared in advance based on the method described in Japanese Patent No. 4041741.

[0102] [ka]

[0103] The average particle diameter D of the titanyl phthalocyanine adduct of 2,3-butanediol in the coating liquid for the charge generating layer was measured using a laser diffraction particle size distribution analyzer (manufactured by Nikkiso Co., Ltd. (now Microtrack Bell Co., Ltd.), model: Microtrack MT-3000II). 50 (50%) was measured. As a result, the average particle diameter D 50 (50%) was 0.30 μm. The average particle diameter D of the titanyl phthalocyanine adduct of 2,3-butanediol for the charge generating layer coating liquid of the following CG Production Example and CG Comparative Production Example was similarly measured. 50 (50%) was measured.

[0104] [CG production example 2] In preparing the coating solution for the charge generating layer, 1.5 parts by mass of each of the titanyl phthalocyanine adducts CGM-2 and CGM-4 obtained in Production Examples 2 and 3 were used as the charge generating material (mass ratio 1:1, total 3.0 parts by mass), 2.0 parts by mass of butyral resin (manufactured by Sekisui Chemical Co., Ltd., product name: S-LEC BM-2) was used as the binder resin (charge generating material / binder resin = 6 / 4), and glass beads with a particle size (media diameter) of 0.4 mm were used and dispersed for 10 minutes with a paint shaker. The same procedure as in CG Production Example 1 was used to prepare 3 liters of the coating solution for the charge generating layer. The average particle diameter D of the titanyl phthalocyanine adduct 50 was 0.31 μm.

[0105] [CG manufacturing example 3] When preparing the coating solution for the charge generating layer, the compound 2-2 (λ max 3 liters of the charge generating layer coating solution was prepared in the same manner as in CG Production Example 1, except that 1.5 parts by mass of the titanyl phthalocyanine adduct (D = 509 nm) was used, glass beads having a particle size (media diameter) of 0.4 mm were used, and the dispersion treatment was performed for 10 minutes using a paint shaker. 50 was 0.29 μm. Compound 2-2 was prepared in advance based on the method described in Japanese Patent No. 4041741.

[0106] [ka]

[0107] [CG production example 4] When preparing the coating solution for the charge generating layer, the compound 2-3 (λ max 3 liters of the charge generating layer coating solution was prepared in the same manner as in CG Production Example 1, except that 1.5 parts by mass of the titanyl phthalocyanine adduct (D = 553 nm) was used, glass beads having a particle size (media diameter) of 0.4 mm were used, and the dispersion treatment was performed for 10 minutes using a paint shaker. 50was 0.30 μm. Compound 2-3 was prepared in advance based on the method described in Japanese Patent No. 4041741.

[0108] [ka]

[0109] [CG manufacturing example 5] When preparing the coating solution for the charge generating layer, the compound 2-4 (λ max Three liters of a coating solution for a charge generating layer was prepared in the same manner as in CG Production Example 1, except that 1.5 parts by mass of a phthalocyanine copolymer (D50 = 580 nm) was used, glass beads having a particle size (media diameter) of 0.4 mm were used, and dispersion treatment was performed for 10 minutes using a paint shaker. The average particle size D50 of the titanyl phthalocyanine adduct was 0.31 μm.

[0110] [ka]

[0111] [CG manufacturing example 6] The same procedure as in CG Production Example 1 was repeated except that the coating solution for the charge generating layer was prepared by dispersing for 20 minutes using glass beads having a particle size of 0.2 mm as a dispersion medium. The average particle diameter D of the titanyl phthalocyanine adduct was 50 was 0.14 μm.

[0112] [CG manufacturing example 7] The same procedure as in CG Production Example 1 was repeated except that the coating solution for the charge generating layer was prepared by dispersing for 20 minutes using glass beads having a particle size of 0.6 mm as a dispersion medium. The average particle diameter D of the titanyl phthalocyanine adduct was 50 was 0.46 μm.

[0113] [CG production example 8] When preparing the coating solution for the charge generating layer, compound 2-1 (λmax 3 liters of the coating solution for the charge generating layer was prepared in the same manner as in CG Production Example 1, except that 3.0 parts by mass (100 parts by mass per 100 parts by mass of the charge generating substance) of titanyl phthalocyanine adduct (D = 509 nm) was used. 50 was 0.30 μm.

[0114] [CG production example 9] When preparing the coating solution for the charge generating layer, compound 2-1 (λ max 3 liters of the coating solution for the charge generating layer was prepared in the same manner as in CG Production Example 1, except that 1.95 parts by mass (65 parts by mass per 100 parts by mass of the charge generating material) of titanyl phthalocyanine adduct (D = 509 nm) was used. 50 was 0.30 μm.

[0115] [CG production example 10] When preparing the coating solution for the charge generating layer, compound 2-1 (λ max 3 liters of the coating solution for the charge generating layer was prepared in the same manner as in CG Production Example 1, except that 0.75 parts by mass (25 parts by mass per 100 parts by mass of the charge generating material) of titanyl phthalocyanine adduct (D = 509 nm) was used. 50 was 0.30 μm.

[0116] [CG production example 11] In preparing the coating solution for the charge generating layer, 3.0 parts by mass of the titanyl phthalocyanine adduct CGM-1 obtained in Production Example 2 was used as the charge generating material in the same manner as in CG Production Example 1, and 3 liters of the coating solution for the charge generating layer was prepared. 50 was 0.30 μm.

[0117] [CG production example 12] In preparing the coating solution for the charge generating layer, 3.0 parts by mass of the titanyl phthalocyanine adduct CGM-3 obtained in Production Example 3 was used as the charge generating material in the same manner as in CG Production Example 1, and 3 liters of the coating solution for the charge generating layer was prepared.50 was 0.30 μm.

[0118] [CG comparison manufacturing example 1] In preparing the coating solution for the charge generating layer, 3 liters of the coating solution for the charge generating layer was prepared in the same manner as in CG Production Example 1, except that the titanyl phthalocyanine crystal obtained in Production Example 4 was used as the charge generating material. 50 was 0.30 μm.

[0119] [CG comparison manufacturing example 2] In preparing the coating solution for the charge generating layer, a butyral resin (manufactured by Sekisui Chemical Co., Ltd., product name: S-LEC BM-SH) was used as the binder resin, glass beads having a particle size (media diameter) of 2.0 mm were used, and dispersion treatment was performed for 120 minutes with a paint shaker. The same procedure as in CG Production Example 1 was used to prepare 3 liters of the coating solution for the charge generating layer. The average particle diameter D of the titanyl phthalocyanine crystals was 50 was 0.50 μm.

[0120] [CG comparative manufacturing example 3] The same procedure as in CG Production Example 1 was repeated except that the charge generating layer coating solution was prepared by dispersing for 30 minutes using zirconia beads having a particle size of 0.4 mm as a dispersion medium. The average particle diameter D of the titanyl phthalocyanine adduct was 50 was 0.29 μm.

[0121] [CG comparison manufacturing example 5] In preparing the coating solution for the charge generating layer, the compound (B) represented by the following structural formula was used as the electron transport material instead of the pyrazolone compound, a butyral resin (manufactured by Sekisui Chemical Co., Ltd., product name: S-LEC BM-SH) was used as the binder resin, glass beads with a particle size (media diameter) of 2.0 mm were used, and dispersion treatment was performed for 120 minutes with a paint shaker. The same procedure as in CG Production Example 1 was repeated to prepare 3 liters of the coating solution for the charge generating layer. The average particle size D of the titanyl phthalocyanine crystals was 50 was 0.30 μm.

[0122] [ka]

[0123] [CG comparative manufacturing example 6] In preparing the coating solution for the charge generating layer, the compound (C) represented by the following structural formula was used as the electron transport material instead of the pyrazolone compound, a butyral resin (manufactured by Sekisui Chemical Co., Ltd., product name: S-LEC BM-SH) was used as the binder resin, glass beads with a particle size (media diameter) of 2.0 mm were used, and dispersion treatment was performed for 120 minutes with a paint shaker. The same procedure as in CG Production Example 1 was repeated to prepare 3 liters of the coating solution for the charge generating layer. The average particle size D of the titanyl phthalocyanine crystals was 50 was 0.30 μm.

[0124] [ka]

[0125] [CT manufacturing example 1] 10 parts by mass of a stilbene derivative (compound 3-1) represented by the following structural formula as a hole transport material and 20 parts by mass of Z-type polycarbonate (manufactured by Teijin Chemical Co., Ltd., product name: TS2020) as a binder resin were added to 104 parts by mass of tetrahydrofuran, and the mixture was stirred and mixed to prepare 3 kg of a coating solution for forming a charge transport layer. The stilbene derivative represented by the following structural formula was prepared in advance based on the method described in Japanese Patent No. 3272257.

[0126] [ka]

[0127] [CT manufacturing example 2] 3 kg of the charge transport coating liquid was prepared in the same manner as in CT Production Example 1, except that when preparing the coating liquid for the charge transport layer, 0.2 mass % of compound 2-1 represented by the above structural formula was added as an electron transport substance (pyrazolone compound) based on the solid content of the charge transport layer.

[0128] [CT manufacturing example 3] 3 kg of the charge transport coating liquid was prepared in the same manner as in CT Production Example 1, except that when preparing the coating liquid for the charge transport layer, 3.9 mass % of compound 2-1 represented by the above structural formula was added as an electron transport substance (pyrazolone compound) based on the solid content of the charge transport layer.

[0129] [CT manufacturing example 4] In preparing the coating solution for the charge transport layer, 3 kg of the coating solution for charge transport was prepared in the same manner as in CT Production Example 1, except that compound 4-1 represented by the following structural formula was used as the hole transport material. Compound 4-1 represented by the following structural formula was prepared in advance based on the method described in Japanese Patent No. 4041741.

[0130] [ka]

[0131] [CT manufacturing example 5] In preparing the coating solution for the charge transport layer, 3 kg of the coating solution for charge transport was prepared in the same manner as in CT Production Example 1, except that the compound (D) represented by the following structural formula was used as the hole transport material.

[0132] [ka]

[0133] [Example 1] (Formation of Undercoat Layer) 3 parts by weight of titanium oxide (manufactured by Ishihara Sangyo Kaisha, Ltd., product name: Tiebaque TTO-D-1) and 2 parts by weight of copolymer polyamide (nylon) (manufactured by Toray Industries, Inc., product name: Amilan (registered trademark), grade: CM8000) were added to 25 parts by weight of methyl alcohol, and the mixture was dispersed for 8 hours using a paint shaker to prepare 3 kg of a coating solution for the undercoat layer. The obtained coating liquid for the undercoat layer was filled into a coating tank, and an aluminum drum-shaped support having a diameter of 30 mm and a length of 255 mm as the substrate F1 was immersed in it and then removed. The obtained coating film was allowed to dry naturally to form an undercoat layer F21 with a thickness of 1.0 mm on the substrate F1.

[0134] (Formation of Charge Generation Layer) The coating liquid for the charge generating layer obtained in CG Production Example 1 was applied onto the undercoat layer F21 by the same immersion method as in the case of forming the undercoat layer, and the resulting coating film was allowed to dry naturally to form a charge generating layer F22 with a thickness of 0.2 μm.

[0135] (Formation of charge transport layer) The coating solution for the charge transport layer obtained in CT Production Example 1 was applied onto the charge generation layer F22 by the same immersion method as in the case of forming the undercoat layer, and the resulting coating film was dried at 130°C for 1 hour to form a charge transport layer F23 with a thickness of 34 μm, thereby obtaining the photoreceptor shown in Figure 2.

[0136] The photosensitive layer of the obtained photoreceptor was peeled off, and the spectral absorption spectrum of the titanyl phthalocyanine adduct of 2,3-butanediol in the photosensitive layer was measured using an ultraviolet-visible spectrophotometer (Shimadzu Corporation, UV-VIS SPECTROPHOTOMETER, model: UV-2450) in the wavelength range of 400 to 900 nm. The spectral absorption spectra in the wavelength region of 400 to 900 nm were also measured for the photoreceptors of the following Examples and Comparative Examples in the same manner.

[0137] FIG. 1 is a diagram showing the spectral absorption spectrum obtained for the photosensitive layer of Example 1. According to FIG. 1, the titanyl phthalocyanine adduct of 2,3-butanediol contained in the charge generating layer of the photoreceptor of Example 1 has a maximum absorption wavelength at 772 nm in the wavelength range of 745 to 780 nm, and the absorbance at wavelengths of 780 nm and 750 nm is Abs 780 and Abs 750 When Abs 750 <Abs 780 Relationship between (Abs 780 / Abs 750= 1.19).

[0138] [Examples 2 to 16] The photoreceptors of Examples 2 to 16 were obtained in the same manner as in Example 1, except that the charge generation layer and the charge transport layer were formed using the coating liquid for the charge generation layer obtained in the CG production example and the coating liquid for the charge transport layer obtained in the CT production example, respectively, as shown in Table 2.

[0139] [Comparative Examples 1 to 7] The photoreceptors of Comparative Examples 1 to 7 were obtained in the same manner as in Example 1, except that the charge generation layer and the charge transport layer were formed using the coating liquid for the charge generation layer obtained in the CG comparative production example and the coating liquid for the charge transport layer obtained in the CT production example, respectively, as shown in Table 2.

[0140] [evaluation] The photoreceptors produced in Examples 1 to 16 and Comparative Examples 1 to 7 were evaluated for the following items. The evaluation was carried out by placing each photoconductor in a digital copying machine (manufactured by Sharp Corporation, product name: MX-60DR) that had been modified for the test.

[0141] [Rating 1] The photoconductor (drum) to be evaluated was placed in a test copier, and the process of charging, exposing, and discharging was repeated 600,000 times in a high humidity (NH) environment (temperature 25°C / relative humidity 85%), and the sensitivity potential after electrical fatigue was measured. The surface potential difference ΔVL between the initial sensitivity potential measured beforehand and the sensitivity potential after electrical fatigue was calculated. From the results obtained, the sensitivity characteristics in a high humidity environment were judged according to the following criteria.

[0142] <Judgment criteria> VG:0≦|ΔVL|<30 (very good) Can be used without problems even in high-speed multifunction machines or printers that require high sensitivity G :30≦|VL|<60(Good) Can be used without problems on low to medium speed multifunction devices or printers NB: 60≦|VL|<90 (fairly good) Although the density is slightly low, it can be used without problems on slow, inexpensive multifunction machines or printers. B :90≦|VL|(Bad) Poor sensitivity, low concentration, and problematic for practical use

[0143] [Rating 2] The photoconductor (drum) to be evaluated was placed in a test copier, and the process of charging, exposing, and discharging was repeated 600,000 times in a low humidity (NL) environment (temperature 25°C / relative humidity 10%), and the sensitivity potential after electrical fatigue was measured. The surface potential difference ΔV0 between the initial sensitivity potential measured beforehand and the sensitivity potential after electrical fatigue was calculated. From the results obtained, the sensitivity characteristics in a low humidity environment were judged according to the following criteria.

[0144] <Judgment criteria> VG: Very good (0≦ΔV0<60) Can be used without problems in high-speed multifunction devices or printers that require high sensitivity G :60≦ΔV0<80 (good) Can be used without problems on low to medium speed multifunction devices or printers NB: 80≦ΔV0<100 (slightly better) Although the density is slightly low, it can be used without problems on slow, inexpensive multifunction machines or printers. B :100≦ΔV0(defective) Poor sensitivity, low concentration, and problematic for practical use

[0145] [Rating 3] The photoconductor (drum) to be evaluated was wrapped in light-shielding paper, a 10mm x 30mm window was opened in the light-shielding paper, and light from a white fluorescent lamp with an illuminance of 1000 Lux was irradiated from the window for 10 minutes, and then the drum was left for 10 minutes. After that, a halftone image was printed using a test copier, and the prints on the irradiated and non-irradiated areas were compared and evaluated, and the light resistance of the photoconductor was judged according to the following criteria.

[0146] <Judgment criteria> VG: No difference between irradiated and non-irradiated areas G: There is a slight difference between the irradiated and non-irradiated areas, but the difference is not significant. NB: There is a slight difference between the irradiated and non-irradiated areas, but this does not affect the actual use. B: There is a large difference between the irradiated and non-irradiated areas, which is problematic in practical use.

[0147] [comprehensive evaluation] Based on the results of evaluations 1 to 3, an overall evaluation was made according to the following criteria. VG: All judgements are VG Can be used without problems even in high-speed multifunction machines or printers that require high sensitivity G: No judgment B or NB Can be used without problems on low to medium speed multifunction devices or printers NB: There is a NB decision. Although the density is slightly low, it can be used without problems on slow, inexpensive multifunction machines or printers. B: There is a judgment B Poor sensitivity, low concentration, and problematic for practical use

[0148] Table 1 shows the constituent layers and main constituent materials of the photoreceptor and their physical properties. Table 2 shows the preparation conditions of the coating solutions for forming each constituent layer. Table 3 shows the evaluation results of the photoreceptor. The abbreviations in Tables 1 to 3 have the following meanings. SLG: Soda lime glass Zr: Zirconia PS: Paint shaker Furthermore, the materials of the binder resins in the charge generating layer and the charge transporting layer are indicated by their product names, and the hole transporting materials and the electron transporting materials are indicated by the compound names of their structural formulas. For P100: for 100 parts by mass of charge generating material For P100: for 100 parts by mass of charge generating material M: relative to the total solid content (hole transport material) of the charge transport layer "Production" and "Comparison" in the charge generating layer: CG production example and CG comparison production example, respectively "Production" in charge transport layer: CT manufacturing example

[0149] [Table 1]

[0150] [Table 2]

[0151] [Table 3]

[0152] The following can be seen from Tables 1 to 3: (1) A photoconductor having a charge generating layer containing a titanyl phthalocyanine adduct of 2,3-butanediol represented by general formula (I) and having a specific spectral absorption spectrum and a pyrazolone compound represented by general formula (II) as a charge generating material suppresses an increase in high humidity sensitivity characteristic ΔVL, while significantly improving the charge reduction and light resistance of low humidity sensitivity characteristic ΔV0 (Examples 1 to 13). (2) The titanyl phthalocyanine adduct of 2,3-butanediol has absorbances at wavelengths of 780 nm and 750 nm in the spectroscopic absorption spectrum, respectively. 780 and Abs 750 When Abs 750 <Abs 780 When the above relationship is satisfied, the light resistance of the photoconductor is further improved (Comparison between Example 1 and Example 2).

[0153] (3) In response to the issue of excess carriers accumulated due to repeated electrical fatigue being trapped in lattice defects, which deteriorates FV0, the incorporation of a pyrazolone compound as an electron transport material with a specific structure makes it possible to suppress the accumulation of residual carriers at the interface. (4) The lattice defects in the crystal types of the charge generating materials are different, suggesting that the optimal structures of the electron transport materials are also different (comparison of Examples 1, 5, 6, and 7 with Comparative Examples 6 and 7), and the combination of Example 1 is the optimal combination.

[0154] (5) From the results of the Examples and Comparative Examples 4, 6, and 7, it was found that FV0 due to repeated fatigue was reduced by incorporating a titanyl phthalocyanine adduct of 2,3-butanediol as the charge generating material of the present disclosure and a pyrazolone compound as the electron transport material in the charge generating layer. This is thought to be a defect in which FV0 occurs when excess carriers accumulated due to repeated electrical fatigue are trapped in lattice defects, and it is thought that in the photoreceptor of the present disclosure, an electron transport material having a specific structure is contained in the vicinity of the charge generation substance, thereby effectively eliminating the excess carriers trapped in lattice defects. (6) In addition, as in Comparative Examples 6 and 7, the same effect is not exhibited when electron transport materials have different structures, and as in Comparative Example 1, when the charge generating material is Y-type titanyl phthalocyanine, the same effect is not exhibited even when the electron transport material of the present disclosure is contained, but is exhibited only when the charge generating material and the charge transport material of the present disclosure are combined.

[0155] (7) Furthermore, when an electron transport material is added to the charge transport layer, the additive itself becomes a hole transport trap, and damage to the charge generation layer caused by external light is improved, but it is difficult to achieve both this and the suppression of the increase in ΔVL (Comparison between Examples 3 and 4 and Comparative Example 5). (8) The average particle diameter D(50%) of the titanyl phthalocyanine adduct of 2,3-butanediol is preferably 0.15 to 0.45 μm. When it is less than 0.15 μm (Example 8), FV0 becomes high. This is presumably because too much shear is applied to the pigment, resulting in many lattice defects in the charge generation layer. When it exceeds 0.45 μm (Example 9), the shear to the pigment is reduced, so FV0 is good, but the carrier generation efficiency in the charge generation layer decreases, sensitivity deteriorates, and VL increase due to long-term use tends to deteriorate. Therefore, by adjusting the average particle diameter D(50%) to the range of 0.15 to 0.45 μm, it is possible to achieve both characteristics.

[0156] (9) In combination with a charge transport layer, when Compound 3-1 is used as the charge transport material, it is advantageous in terms of light resistance and increase in VL in a high humidity environment (Comparison between Example 1 and Examples 10 and 11). (10) When the charge generating material is titanyl phthalocyanine, the addition of a pyrazolone compound as an electron transport material according to the present disclosure only results in a small improvement in FV0, whereas the charge generating material is a titanyl phthalocyanine adduct of 2,3-butanediol and has a greater improvement in FV0 (Comparison with Example 1 and Comparative Example 1). This is presumably because the structure was such that electrons of trapped carriers were easily removed due to lattice defects occurring in the charge transport layer. (11) The absorbance at wavelengths of 780 nm and 750 nm in the spectroscopic absorption spectrum is Abs 780 and Abs 750 When Abs 750 <Abs 780 The condition satisfying the above relationship is most excellent in terms of FV0 and light resistance (comparison with Examples 1 and 2 and Comparative Examples 2 and 3).

[0157] (12) By setting the content of the pyrazolone compound added to the charge generating layer within the range of 30 to 60 parts by mass per 100 parts by mass of the charge generating substance, it is possible to achieve both an increase in ΔVL and a reduction in FV0 due to fatigue caused by electrical current (compare with Examples 12, 13, and 14). If the content is less than 30 parts by mass, the contribution to the reduction in FV0 is small, whereas if the content exceeds 60 parts by mass, charge generation may be inhibited and the increase in ΔVL due to fatigue caused by repeated electrical current tends to be large.

[0158] The present invention is not limited to the above-described embodiment, but can be embodied in various other forms. Therefore, the embodiment is merely illustrative in all respects and should not be interpreted as being limited. The scope of the present invention is indicated by the claims, and is not restricted in any way by the text of the specification. Furthermore, all modifications and changes within the scope of the claims are within the scope of the present invention. [Explanation of symbols]

[0159] F01 Multilayer electrophotographic photoreceptor (multilayer photoreceptor, photoreceptor) F1 Substrate (conductive support) F21 Undercoat layer (middle layer) F22 Charge generation layer F23 Charge transport layer Fa Photoconductor surface

[0160] 1 photoreceptor 31 Exposure means (semiconductor laser) 32 Charging means (charger) 33 Developing means (developer) 33a Developing roller 33b Casing 34 Transfer means (transfer charger) 35 Fixing means (fixing device) 35a Heating roller 35b Pressure roller 36 Cleaning means (cleaner) 36a cleaning blade 36b Recovery casing 37 Separation means 38 Housing 41, 42 arrow mark 44 Rotation axis 51 Recording media (recording paper or transfer paper) 100 Image forming apparatus (laser printer)

Claims

1. The electrophotographic recording medium comprises at least a laminated photosensitive layer in which a charge generating layer and a charge transport layer are laminated in this order on a substrate, The charge generating layer contains, as a charge generating material, a compound represented by the general formula (I): 【Chemistry 1】 and having a maximum absorption at a wavelength of 745 to 780 nm in a spectroscopic absorption spectrum, at least one selected from the group consisting of (2R,3R)-2,3-butanediol-added titanyl phthalocyanine and (2S,3S)-2,3-butanediol-added titanyl phthalocyanine, and a general formula (II): 【Chemistry 2】 (In the formula, R ａ and R ｂ are the same or different and each represents a hydrogen atom, a halogen atom, a cyano group, a nitro group, a hydroxyl group, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group which may have a substituent, a heterocyclic group which may have a substituent, an ester group, a cycloalkyl group, an aralkyl group which may have a substituent, an allyl group, an amide group, an amino group, an acyl group, an alkenyl group, an alkynyl group, a carboxyl group, a carbonyl group, a carboxylic acid group, or a halogenated alkyl group, and the substituent is a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a hydroxyl group, a cyano group, an amino group, a nitro group, or a halogenated alkyl group.

2. An electrophotographic photoreceptor comprising a pyrazolone compound represented by the formula:

2. The titanyl phthalocyanine has an absorbance of Abs at wavelengths of 780 nm and 750 nm in the spectroscopic absorption spectrum. ７８０ and Abs ７５０ When this is done, Abs ７５０ <Abs ７８０ 2. The electrophotographic photoreceptor according to claim 1, which satisfies the relationship:

3. 3. The electrophotographic photoreceptor according to claim 1, wherein the pyrazolone compound has a maximum absorption in a wavelength range of 515 to 560 nm in a spectroscopic absorption spectrum.

4. 3. The electrophotographic photoreceptor according to claim 1, wherein the pyrazolone compound is contained in the charge generating layer in an amount of 30 to 60 parts by weight per 100 parts by weight of the charge generating substance.

5. 3. The electrophotographic photoreceptor according to claim 1, wherein the charge transport layer contains the pyrazolone compound in an amount of 0.2% by mass or less based on the total solid content of the charge transport layer.

6. 3. The electrophotographic photoreceptor according to claim 1, wherein the pyrazolone compound is a compound represented by formula (II) in which the substituent Ra is a phenyl group which may have a substituent.

7. The pyrazolone compound has the following formula: 【Chemistry 3】 7. The electrophotographic photoreceptor according to claim 6, wherein the compound is represented by the formula:

8. 3. The electrophotographic photoreceptor according to claim 1, wherein the titanyl phthalocyanine has an average particle diameter D (50%) of 0.15 to 0.45 μm.

9. The charge transport layer contains, as a hole transport material, a compound represented by the general formula (III): 【Chemistry 4】 (In the formula, R １ , R ２ , R ５ and R ６ are the same or different and each is an alkyl group, an alkoxy group, an aryl group, an aralkyl group, or a halogen atom; m, n, p, and q are the same or different and each is an integer of 0 to 3; R ３ and R ４ are the same or different and each is a hydrogen atom or an alkyl group. and a stilbene derivative represented by the general formula (II): 【Chemistry 5】 (In the formula, R ７ is a hydrogen atom or an alkyl group, R ８ and R ９ are the same or different and each is an alkyl group, an alkoxy group, an aryl group, an aralkyl group, or a halogen atom, and r, s, and t are the same or different and each is an integer of 0 to 3.

3. The electrophotographic photoreceptor according to claim 1, further comprising at least one stilbene derivative selected from the group consisting of stilbene derivatives represented by the following formula:

10. 3. An image forming apparatus comprising at least the electrophotographic photoreceptor according to claim 1 or 2, a charging unit which charges the electrophotographic photoreceptor, an exposure unit which exposes the charged electrophotographic photoreceptor to light to form an electrostatic latent image, a developing unit which develops the electrostatic latent image to form a toner image, and a transfer unit which transfers the toner image onto a recording medium.

Images