Electrophotographic photoreceptor, method for manufacturing the same, and image forming apparatus including the same

Abstract

To provide an electrophotographic photoreceptor that uses a known titanyl phthalocyanine adduct of 2,3-butanediol as a charge generating material, and that has excellent light resistance, prevents a reduction in sensitivity through its life even in long-term repeated energization fatigue, and can maintain stable image characteristics for a long period, a method for manufacturing the same, 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 titanyl phthalocyanine added with 2,3-butanediol as a charge generating material. The titanyl phthalocyanine in the laminated photosensitive layer has the maximum absorption at wavelengths of 750-780 nm in a spectral absorption spectrum, and the absorbance Abs780 at a wavelength of 780 nm and the absorbance Abs750 at a wavelength of 750 nm satisfy the relationship of Abs750<Abs780.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an electrophotographic photoreceptor, a method for manufacturing the same, 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 with a photosensitive layer whose main component is an organic photoconductive material (also called "organic photoreceptors") is progressing, and these now account for the mainstream of photoreceptors.

[0003] As organic photoreceptors, a structure has been proposed in which a single-layer type photosensitive layer is provided on a substrate (also called an "electroconductive support"), 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] Among these, Y-type titanyl phthalocyanine, a specific crystal type, is widely used as a charge generating material because of its highly sensitive electrical properties. However, it is known that the dissociation of carriers from Y-type titanyl phthalocyanine is promoted by moisture in the air, and the sensitivity characteristics change due to the fluctuation of humidity in the external environment, which has been an issue. For example, if a photoconductor is left in an image forming apparatus under high humidity conditions at night during the rainy season, and the room is dehumidified the next day on a sunny day or with air conditioning, a difference in sensitivity characteristics may occur between the part of the photoconductor that is open to the external environment and the part that is sealed off from the external environment, such as the developing tank, resulting in poor image quality. This problem has become more serious as the demand for higher image quality increases.

[0005] In order to solve the humidity dependency of such sensitivity characteristics, a titanyl phthalocyanine adduct of 2,3-butanediol has been proposed as a charge generating material (JP Patent Publication 2011-186118 A: Patent Document 1). The titanyl phthalocyanine adduct is a product in which butanediol having a hydroxyl group is added in place of water in a titanyl phthalocyanine crystal, and it is presumed that the high sensitivity of the photoreceptor is maintained even in a low moisture environment by introducing butanediol into the crystal as a unit that functions in place of water.

[0006] In addition, the titanyl phthalocyanine adduct is easily affected by short-wavelength light since the spectroscopic absorption spectrum of the titanyl phthalocyanine adduct is shifted to shorter wavelengths by adding butanediol to the titanyl phthalocyanine crystal, as compared with Y-type titanyl phthalocyanine. During normal use, photoconductors are exposed to external light not only from the light source inside an image forming device such as a copier, but also when performing maintenance on peripheral parts such as replacement parts and when paper jams occur inside the device. Such optical fatigue of the photoconductor caused by external light is more damaging than electrical fatigue inside the device, and is the cause of image degradation. In addition, in the production process, due to the photodegradation of the photoconductor, it is necessary to work under fluorescent lights that cut short wavelengths and to take careful care. For this reason, the use of titanyl phthalocyanine adducts as charge generating materials poses the issue of reduced productivity.

[0007] To address these issues, a technique has been proposed in which an ultraviolet absorber having a maximum absorption wavelength in the wavelength range of 380 to 480 nm is added to the photosensitive layer (JP Patent Publication No. 10-048856: Patent Document 2), and a technique has been proposed in which an electron transport material (electron transport substance) of a specific structure having a maximum absorption wavelength in the wavelength range of 300 to 370 nm and no absorption wavelength in the wavelength range of 730 to 800 nm is added (JP Patent Publication No. 2010-164639: Patent Document 3). However, all of these methods involve the addition of additives to the photosensitive layer, and although the impact varies, they pose the problem of charge transport being trapped. In addition, even a small amount of low-molecular-weight additive added to the photosensitive layer poses the problem of reduced printing durability. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2011-186118 A [Patent Document 2] Japanese Patent Application Publication No. 10-048856 [Patent Document 3] JP 2010-164639 A Summary of the Invention [Problem to be solved by the invention]

[0009] Therefore, the present disclosure aims to provide an electrophotographic photoreceptor that uses a titanyl phthalocyanine adduct of 2,3-butanediol, which is known as a charge generating substance, has excellent light resistance, does not lose sensitivity even when fatigued by repeated electrical current over a long period of time throughout the product's life, and is capable of maintaining stable image characteristics over a long period of time, a manufacturing method thereof, and an image forming apparatus equipped with the same. [Means for solving the problem]

[0010] As a result of intensive research by the present inventors to solve the above problems, they have found that in a photoreceptor using a titanyl phthalocyanine adduct of 2,3-butanediol as a charge generating substance, the light resistance of the photoreceptor is significantly improved and stable image characteristics can be maintained for a long period of time even without adding an ultraviolet absorber to the photoreceptor or even if the amount of ultraviolet absorber added is reduced, because the titanyl phthalocyanine in the photosensitive layer has a specific spectral absorption spectrum, and thus they have completed the present invention.

[0011] 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 transport layer contains, as a charge generating material, at least one selected from the group consisting of titanyl phthalocyanine to which (2R,3R)-2,3-butanediol is added and titanyl phthalocyanine to which (2S,3S)-2,3-butanediol is added; The titanyl phthalocyanine in the laminated photosensitive layer has a maximum absorption at a wavelength of 750 to 780 nm in a spectroscopic absorption spectrum, and an absorbance Abs at 780 nm 780 and absorbance at 750 nm Abs 750 And Abs 750 <Abs 780 The electrophotographic photoreceptor is characterized in that it satisfies the following relationship.

[0012] 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.

[0013] Further, according to the present disclosure, there is provided a method for producing the electrophotographic photoreceptor, A step of forming the charge generating layer by applying a coating liquid for the charge generating layer, The present invention provides a method for producing an electrophotographic photoreceptor, comprising the step of dispersing at least one selected from the group consisting of titanyl phthalocyanine having (2R,3R)-2,3-butanediol added thereto and titanyl phthalocyanine having (2S,3S)-2,3-butanediol added thereto and a binder resin, using a dispersion medium made of soda-lime glass material, to prepare a coating liquid for the charge generating layer. Effect of the Invention

[0014] According to the present disclosure, it is possible to provide an electrophotographic photoreceptor that uses a titanyl phthalocyanine adduct of 2,3-butanediol, which is known as a charge generating substance, and that has excellent light resistance, does not lose sensitivity even when fatigued by repeated current application over a long period of time throughout its life, and is capable of maintaining stable image characteristics over a long period of time, a manufacturing method thereof, and an image forming apparatus equipped with the same. [Brief description of the drawings]

[0015] [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

[0016] 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, at least one selected from the group consisting of titanyl phthalocyanine to which (2R,3R)-2,3-butanediol is added and titanyl phthalocyanine to which (2S,3S)-2,3-butanediol is added; The titanyl phthalocyanine in the laminated photosensitive layer has a maximum absorption at a wavelength of 750 to 780 nm in a spectroscopic absorption spectrum, and an absorbance Abs at 780 nm 780 and absorbance at 750 nm Abs 750 And Abs 750 <Abs 780 It is characterized in that the above relationship is satisfied. This has been found to improve the light resistance of the photoconductor.

[0017] Below, the characteristic constituent features of the photoreceptor of the present disclosure will be described, followed by a description of (1) the photoreceptor, (2) an image forming apparatus, and (3) a method for manufacturing the photoreceptor. 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.

[0018] In order to improve the light resistance of the photoconductor, the following two measures are required for titanyl phthalocyanine. (1) A crystal structure that reduces the stability of excess carriers generated by external light and promotes their rapid recombination (2) Crystal structure that can suppress carrier generation in response to external light When the maximum absorption wavelength (λmax) of the spectral absorption satisfies the above condition, it is considered that the interaction between titanyl phthalocyanines is strong.

[0019] When the photosensitive layer is exposed to external light, it is activated and becomes excited by an amount equivalent to the absorbed light energy, and the more stable this excited state is, the greater the effect on the image. Therefore, it is considered that the light resistance of the photosensitive layer is affected by how quickly a structure can be formed that can quickly deactivate from this excited state to the ground state. It is presumed that, when the titanyl phthalocyanine in the laminated photosensitive layer has the above-mentioned spectral absorption spectrum, the charge that is exposed to external light and becomes excited moves between the ππ bonds of the titanyl phthalocyanine, and is easily quickly deactivated to the ground state, resulting in the formation of a photosensitive layer with good light resistance.

[0020] In the photoreceptor of the present disclosure, titanyl phthalocyanine in the laminated photosensitive layer has, in its spectral absorption spectrum, in addition to a maximum absorption at wavelengths of 750 to 780 nm, a maximum absorption at wavelengths of 650 to 680 nm, and when the absorbance at 870 nm is 0, it is preferable that the absorbance Abs of the maximum absorption at wavelengths of 650 to 680 nm and the absorbance Abs810 at wavelength 810 nm satisfy the relationship Abs < Abs810. It has been found that this improves the light resistance more. The presence of the maximum absorption at wavelengths of 650 to 680 nm indicates that the π-π bond between titanyl phthalocyanine adducts is underdeveloped. Due to the presence of this maximum absorption, carrier generation with respect to external light is suppressed even immediately after the photosensitive layer is exposed to external light, and it is presumed that overall, damage to the charge generation layer by light is suppressed.

[0021] In the photoreceptor of the present disclosure, it is preferable that titanyl phthalocyanine in the laminated photosensitive layer has a maximum absorption at wavelengths of 770 to 780 nm in its spectral absorption spectrum. It has been found that this improves the recoverability of damage received from external light. When the maximum absorption wavelength is less than 770 nm, the recoverability of damage by external light may become insufficient. On the other hand, when the maximum absorption wavelength exceeds 780 nm, the content of titanyl phthalocyanine in which butanediol could not be added in the titanyl phthalocyanine adduct increases, and the humidity fluctuation range of sensitivity may deteriorate.

[0022] In the photoreceptor of the present disclosure, titanyl phthalocyanine in the laminated photosensitive layer has, in its spectral absorption spectrum, maximum absorptions at wavelengths of 750 to 780 nm and at wavelengths of 650 to 680 nm, and when the absorbance at 870 nm is 0, the absorbance Abs of the maximum absorption at wavelengths of 750 to 780 nm 1 and the absorbance Abs of the maximum absorption at wavelengths of 650 to 680 nm 2 and the ratio Abs 2 / Abs 1 is preferably 0.20 to 0.60. Thereby, the light resistance immediately after exposure to external light is further improved. In particular, the ratio Abs 2 / Abs 1It has been found that within the above-specified range, the light resistance is most improved. Ratio Abs 2 / Abs 1 If the ratio Abs is less than 0.2, the structure of the underdeveloped ππ bonds becomes insufficient, and the generation of carriers immediately after exposure to external light is large, which may have a large effect on the image. 2 / Abs 1 If the ratio Abs exceeds 0.6, the number of structures in which the ππ bonds are underdeveloped may be too large, and the recovery from damage may decrease. 2 / Abs 1 is greater than or equal to 0.3 and less than 0.5.

[0023] Titanyl phthalocyanine has an average particle size D of 0.15 to 0.4 μm. 50 (50%). Average particle size of titanyl phthalocyanine D 50 If the average particle size D of titanyl phthalocyanine (50%) is reduced to less than 0.15 μm, the dispersion shear is too great in the preparation process of the coating solution containing it, causing damage and making it more susceptible to aggregation, which may cause concerns about the long-term dispersion stability of the coating solution. 50 If (50%) exceeds 0.3 μm, the sensitivity characteristics in a low humidity environment may deteriorate, and the humidity fluctuation range of the sensitivity may become large. More preferred average particle size D of titanyl phthalocyanine 50 (50%) is 0.23 to 0.30 μn.

[0024] The spectral absorption spectrum (absorbance) of titanyl phthalocyanine in such a laminated photosensitive layer can be controlled by adjusting the shear conditions (dispersion method, dispersion time, media diameter, media amount, media material) during synthesis of the charge generating material and during dispersion of the coating liquid for the charge generating layer. In the synthesis of charge generating materials, it is important to reduce impurities as much as possible. For example, in the washing step of the deacidification step of titanyl phthalocyanine synthesis, it is important to reduce the sulfate ion concentration to a pH closer to 7.0, and if impurities are left in this step, the addition reaction with butanediol in the subsequent step becomes difficult to proceed, and it becomes difficult to control the spectral absorption spectrum within the range specified in the present disclosure. The presence of impurities results in a crystal structure with weak interactions between titanyl phthalocyanine particles, making it difficult to control the spectral absorption during dispersion.

[0025] When adjusting the spectral absorption spectrum of titanyl phthalocyanine by the dispersion shear conditions, the shear is preferably a spherical media with a media diameter (particle size) of 0.1 to 3.0 mm, preferably 0.1 to 2.0 mm, and it is preferable to reduce the shear applied to the pigment as much as possible, and it has been found that glass beads with a low specific gravity are suitable for grinding. If the media diameter exceeds 3.0 mm, the shear applied to the pigment increases, the collision frequency decreases, and the pulverization efficiency tends to decrease. Therefore, the spectral absorption spectrum cannot be adjusted within the range specified in the present disclosure, and excessive shear is applied to the titanyl phthalocyanine by extending the dispersion time, which may cause problems such as deterioration of characteristics, failure to reduce the particle diameter, and generation of aggregates. On the other hand, if the media diameter is less than 0.1 mm, the shear applied to the pigment may be too weak, and when dispersion is required for a long time, the amount of contamination caused by the media increases, which may cause problems in charge generation.

[0026] In addition, the grinding efficiency changes depending on the media material. The optimum conditions are influenced by titanyl phthalocyanine, so it is necessary to select the optimum dispersion conditions for each material. As long as the spectral absorption spectrum is within the range specified in the present disclosure, there are no particular limitations on the adjustment from the synthesis process, the adjustment from the shear conditions, etc., and the effects of the present disclosure can be maintained.

[0027] <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.

[0028] The raw material, titanyl phthalocyanine, is represented by the following formula (A). [ka]

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] In synthesizing the titanyl phthalocyanine adduct of 2,3-butanediol used in the present disclosure, the synthesis can be easily optimized by appropriately selecting each production condition such as the reaction molar ratio, reaction temperature, reaction time, selection of the solvent type, and crystallization method.

[0035] (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.

[0036] <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.

[0037] <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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] <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.

[0045] 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 preferable that the content is at least 80%.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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. It is preferable to form the charge generating layer by applying a coating liquid for the charge generating layer, which will be described in item (3) Method for producing an electrophotographic photoreceptor.

[0052] 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.

[0053] 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.

[0054] <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 an electron transport material as described below, and will be described separately from the hole transport material which also transports charges.

[0055] 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.

[0056] 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 comprises, as a hole transport material, a compound represented by the general formula (I): [ka] (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 (II):

[0057] [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:

[0058] The substituents and indices in the general formulae (I) and (II) are described below. R in general formula (I) 1 , R 2 , R 5 and R 6 and R in the general formula (II) 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 (I) 1 , R 2 , R5 and R 6 and R in the general formula (II) 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 (I) 1 , R 2 , R 5 and R 6 and R in the general formula (II) 8 and R 9 Examples of the aryl group include phenyl, naphthyl, anthryl, phenanthryl, fluorenyl, biphenylyl, and o-terphenyl. R in general formula (I) 1 , R 2 , R 5 and R 6 and R in the general formula (II) 8 and R 9 Examples of the aralkyl group include benzyl, phenethyl, benzhydryl, and trityl. R in general formula (I) 1 , R 2 , R 5 and R 6 and R in the general formula (II) 8 and R 9 The halogen atoms include fluorine, chlorine, bromine and iodine atoms. R in general formula (I) 1 , R 2 , R 5 and R 6 and R in the general formula (II) 8 and R 9 As the aryl group, methyl and ethyl are preferred, and methyl is particularly preferred.

[0059] R in general formula (I) 3 and R 4 and R in the general formula (II) 7 Examples of the alkyl group include the above-mentioned alkyl groups. R in general formula (I)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 (II) 7 As the alkyl group, a hydrogen atom and methyl are preferable, and methyl is particularly preferable.

[0060] In the general formula (I), 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 (II), 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.

[0061] Materials having skeletons represented by general formulas (I) and (II) 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 additive added can be reduced, and stable electrophotographic characteristics can be expressed over a long period of time.

[0062] The stilbene compound represented by general formula (I) can be synthesized, for example, by the method described in Japanese Patent No. 3272257. Examples of the stilbene derivatives represented by the general formulas (I) and (II) include the compounds (a) and (b) represented by the following structural formulas described in the Examples, which are preferably used. [ka]

[0063] [ka]

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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 absorbents for improving light resistance, and specifically, perimidine compounds such as those used in the examples. 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.

[0068] In the photoreceptor of the present disclosure, the charge transport layer contains, as an electron transport material, a compound represented by general formula (III): [ka]

[0069] (In the formula, R a and R bare 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. It is preferable that the compound contains a pyrazolone compound represented by the following formula:

[0070] The substituent R in the general formula (I) a and R b 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.

[0071] 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 groups having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, and the above-mentioned halogen atoms.

[0072] The electron transport material of the present disclosure is, in terms of solubility and interaction with a resin, a and R b are the same or different and are 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 is 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 bare particularly preferred. For example, the following compounds 1-1 to 1-4 can be mentioned, and in terms of mobility and the wavelength of light absorbed, the compound 1-1 (wherein Ph represents a phenyl group) used in CT Production Example 4 is particularly preferred.

[0073] [ka]

[0074] 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.

[0075] (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.

[0076] 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).

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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).

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] (3) Manufacturing method of electrophotographic photoreceptor The method for producing a photoreceptor according to the present disclosure includes a step of forming the charge generating layer by applying a coating liquid for the charge generating layer, The method is characterized by including a step of dispersing at least one selected from titanyl phthalocyanine having (2R,3R)-2,3-butanediol added thereto and titanyl phthalocyanine having (2S,3S)-2,3-butanediol added thereto, and a binder resin, using a dispersion medium made of soda-lime glass, to prepare a coating liquid for a charge generating layer.

[0090] The photoreceptor of the present disclosure can be produced by forming an undercoat layer, as desired, on a substrate as described above, and then forming a charge generating layer and a charge transport layer in this order. For example, the charge generating layer can be formed by applying a coating liquid for the charge generating layer. The coating liquid for the charge generating layer can be prepared by dispersing the titanyl phthalocyanine adduct of 2,3-butanediol and the binder resin as described above. As the dispersion treatment, known treatment methods can be applied as described above, but among these, treatment using a dispersion medium made of soda-lime glass material is particularly preferred. The conditions for the dispersion treatment may be appropriately set depending on the constituent materials and solvent of the coating liquid for the charge generating layer, as described in the Examples. EXAMPLES

[0091] 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.

[0092] [Production Example 1] <Preparation of titanyl phthalocyanine> Titanyl phthalocyanine with (2R,3R)-2,3-butanediol added thereto or titanyl phthalocyanine with (2S,3S)-2,3-butanediol added thereto, represented by the following structural formula, used as a charge generating material, was prepared according to the method described in Japanese Patent No. 5609167.

[0093] [ka]

[0094] 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 with chloroform, 2% aqueous hydrochloric acid solution, water, and methanol, and dried to obtain 25.5 g (yield: 89%) of crude titanyl phthalocyanine as a blue-purple crystal.

[0095] 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%).

[0096] [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°.

[0097] [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).

[0098] [CG manufacturing example 1] As charge generating substances, 3 parts by mass of the titanyl phthalocyanine adducts (CGM-2 / CGM-4 = 1 / 1) obtained in Production Examples 2 and 3 and 2 parts by mass of butyral resin (manufactured by Sekisui Chemical Co., Ltd., product name: S-LEC BX-1) were added to 95 parts by mass of methyl ethyl ketone, and 28 g of a coating solution for the charge generating layer was prepared by dispersing the mixture for 5 minutes using soda-lime glass beads (hereinafter also referred to as "glass beads") having a particle size of 0.1 mm in a paint shaker.

[0099] 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. The average particle diameter D of the titanyl phthalocyanine adduct of 2,3-butanediol in the charge generating layer of the photoreceptor of Example 1 50 (50%) was 0.26 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.

[0100] [CG production example 2] A coating liquid for a charge generating layer was prepared in the same manner as in CG Production Example 1, except that the coating liquid for a charge generating layer was prepared using glass beads having a particle size of 0.4 mm as a dispersion medium.

[0101] [CG manufacturing example 3] A coating liquid for a charge generating layer was prepared in the same manner as in CG Production Example 1, except that the titanyl phthalocyanine adducts (CGM-1 / CGM-4=1 / 1) obtained in Production Examples 2 and 3 were used as the charge generating substance when preparing the coating liquid for the charge generating layer.

[0102] [CG production example 4] A coating solution for a charge generating layer was prepared in the same manner as in CG Production Example 1, except that the coating solution for a charge generating layer was prepared by dispersing for 30 minutes using glass beads having a particle size of 1.0 mm as a dispersion medium.

[0103] [CG production example 5] A coating liquid for a charge generating layer was prepared in the same manner as in CG Production Example 1, except that the titanyl phthalocyanine adducts (CGM-2 / CGM-3=1 / 1) obtained in Production Examples 2 and 3 were used as the charge generating substance when preparing the coating liquid for the charge generating layer.

[0104] [CG production example 6] A coating liquid for a charge generating layer was prepared in the same manner as in CG Production Example 1, except that in preparing the coating liquid for a charge generating layer, zirconia beads having a particle size of 0.2 mm were used as a dispersion medium for the dispersion treatment.

[0105] [CG production example 7] A coating liquid for a charge generating layer was prepared in the same manner as in CG Production Example 1, except that the coating liquid for a charge generating layer was prepared by dispersing using glass beads having a particle size of 0.2 mm as a dispersion medium.

[0106] [CG production example 8] The coating liquid for the charge generating layer was prepared in the same manner as in CG Production Example 1, except that when preparing the coating liquid for the charge generating layer, zirconia beads having a particle size of 0.4 mm were used as the dispersion medium and the dispersion treatment was carried out in a ball mill for one day (1,440 minutes).

[0107] [CG comparison manufacturing example 1] A coating solution for a charge generating layer was prepared in the same manner as in CG Production Example 1, except that the coating solution for a charge generating layer was prepared by dispersing for 120 minutes using glass beads having a particle size of 1.0 mm as a dispersion medium.

[0108] [CG comparison manufacturing example 2] The coating liquid for the charge generating layer was prepared in the same manner as in CG Production Example 1, except that when preparing the coating liquid for the charge generating layer, a butyral resin (manufactured by Sekisui Chemical Co., Ltd., product name: S-LEC BL-1) was used as the binder resin, and glass beads having a particle size of 1.0 mm were used as the dispersion medium for 120 minutes for dispersion treatment.

[0109] [CG comparative manufacturing example 3] The coating liquid for the charge generating layer was prepared in the same manner as in CG Production Example 1, except that, when preparing the coating liquid for the charge generating layer, 4.5 parts by mass of the titanyl phthalocyanine adduct (CGM-2 / CGM-4 = 1 / 1) obtained in Production Examples 2 and 3 and 0.5 parts by mass of a butyral resin (manufactured by Sekisui Chemical Co., Ltd., product name: S-LEC BL-1) were used as the charge generating substance, and glass beads having a particle size of 1.0 mm were used as the dispersion medium for 120 minutes for dispersion treatment.

[0110] [CT manufacturing example 1] 10 parts by mass of a stilbene derivative (compound (a)) 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 30 g 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.

[0111] [ka]

[0112] [CT manufacturing example 2] A charge transport coating solution was prepared in the same manner as in CT Production Example 1, except that a stilbene derivative represented by the following structural formula (compound (b), manufactured by Takasago Chemical Co., Ltd., product name: T925) was used as the hole transport material when preparing the coating solution for the charge transport layer. [ka]

[0113] [CT manufacturing example 3] A charge transport coating solution was prepared in the same manner as in CT Production Example 1, except that a triphenylamine compound represented by the following structural formula (Compound (C), TPD, manufactured by Tokyo Chemical Industry Co., Ltd., product name: D2448) was used as the hole transport material when preparing the charge transport layer coating solution. [ka]

[0114] [CT manufacturing example 4] A 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, 1 part by mass of a pyrazolone compound (compound (1-1)) represented by the following structural formula (wherein Ph represents a phenyl group) was further added as an electron transport material. The pyrazolone compound represented by the following structural formula was prepared in advance based on the method described in Japanese Patent No. 4041741. [ka]

[0115] [CT manufacturing example 5] A charge transport coating liquid was prepared in the same manner as in CT Production Example 1, except that 0.5 parts by weight of a perimidine compound (CI Solvent Red 179, American Dyestuff, product name: Amesolve Red A) used as a compound having a maximum absorption wavelength at 470 to 490 nm (toluene) in Example 1 of JP-A-10-048856 (Patent Document 2) was further blended as an additive when preparing the coating liquid for the charge transport layer.

[0116] [CT manufacturing example 6] A charge transport coating solution was prepared in the same manner as in CT Production Example 1, except that, when preparing the coating solution for the charge transport layer, the hole transport substance was changed from 10 parts by mass of a stilbene derivative (compound (a)) to 8 parts by mass of a triphenylamine compound (compound (C)), and from 104 parts by mass of tetrahydrofuran to 98 parts by mass.

[0117] [Example 1] (Formation of Undercoat Layer) Three parts by weight of titanium oxide (manufactured by Ishihara Sangyo Kaisha, Ltd., product name: Tiebaque TTO-D-1) and two 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 eight hours using a paint shaker to prepare 3 liters 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 conductive support F1 was immersed in it and then removed. The obtained coating film was allowed to dry naturally, thereby forming an undercoat layer F21 with a thickness of 1 μm on the conductive support F1.

[0118] (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 0.3 μm.

[0119] (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 120°C for 1 hour to form a charge transport layer F23 with a thickness of 30 μm, thereby obtaining the photoreceptor shown in Figure 2.

[0120] 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.

[0121] 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 in the laminated photosensitive layer of the photoreceptor of Example 1 has a maximum absorption in the wavelength range of 750 to 780 nm, and an absorbance Abs 780 and absorbance at 750 nm Abs 750 And Abs 750 <Abs 780 The relationship is satisfied, and the maximum absorption is at a wavelength of 650 to 680 nm, and the absorbance Abs of the maximum absorption at a wavelength of 650 to 680 nm and the absorbance Abs of the wavelength of 810 nm are 810 And Abs <Abs 810 The maximum absorbance Abs at wavelengths of 750 to 780 nm is calculated by assuming the absorbance at a wavelength of 870 nm to be 0. 1 and the maximum absorption at wavelengths of 650 to 680 nm, Abs 2 Ratio to Abs 2 / Abs 1 It can be seen that the range is 0.20 to 0.60.

[0122] [Examples 2 to 12 and 14] The photoreceptors of Examples 2 to 12 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 1.

[0123] [Examples 13 and 15] The photoreceptors of Examples 13 and 15 were obtained in the same manner as in Example 1, except that no undercoat layer was formed, and that the charge generation layer and the charge transport layer were formed using the coating liquid for the charge generation layer obtained in Production Example CG and the coating liquid for the charge transport layer obtained in Production Example CT shown in Table 1, respectively.

[0124] [Comparative Examples 1 to 4] The photoreceptors of Comparative Examples 1 to 4 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 1.

[0125] [evaluation] The photoreceptors produced in Examples 1 to 15 and Comparative Examples 1 to 4 were evaluated for the following items. In the following evaluations 1 and 2, each photoconductor was attached to a unit of a digital copying machine (model: MX-2600, manufactured by Sharp Corporation) that had been modified for the test, and the evaluation was carried out.

[0126] [Evaluation 1: Light resistance] The photoreceptor (drum) to be evaluated was wrapped in light-shielding paper, a 10mm x 30mm window was opened in the light-shielding paper, and a fluorescent light with an illuminance of 400 Lux was irradiated through the window for 0.5 hours to expose the toner to light. After that, halftone printing was performed using a test copier. The images before and after the light exposure were visually compared and evaluated together with the halftone printing results performed before the light exposure, and the light resistance of the photoreceptor was judged according to the following criteria. VG: The effect on the image cannot be confirmed. G: Immediately after exposure, some traces of exposure can be seen, but they are restored in about 5 minutes and have no effect on image characteristics. NB: Slight exposure marks can be seen immediately after exposure, and some exposure marks can still be seen 5 minutes later, but the effect on image characteristics is minor and there is no problem in practical use. B: The exposed area clearly affects image characteristics, making it unsuitable for practical use.

[0127] [Evaluation 2: Sensitivity characteristics] The photoconductor (drum) to be evaluated was placed in a test copier, and the sensitivity potential VL was measured in a low humidity (NL) environment (temperature 25°C / relative humidity 10%) and a high humidity (NH) environment (temperature 25°C / relative humidity 85%). NL (-V) and VL NH (-V) and measure the difference ΔVL NL-HH The sensitivity (-V) was used as an index of humidity fluctuation. The results were judged according to the following criteria. NL " and "ΔVL NL-HH " is judged as satisfying the two requirements of that criterion, and if one requirement of a certain criterion is met and the other requirement is not met, the judgment is made based on the lower criterion that is met. VG:VL NL<200 and 0≦ΔVL NL-HH <10 Can be used without problems in high-speed multifunction devices or printers that require high sensitivity G: 200≦VL NL <220 and 10≦ΔVL NL-HH <25 Can be used without problems on low to medium speed multifunction devices or printers NB:220≦VL NL <240 and 25≦ΔVL NL-HH <35 Although the density is slightly low, it can be used without problems on slow, inexpensive multifunction machines or printers. B: 240≦VL NL And 35≦ΔVL NL-HH Poor sensitivity, low concentration, and problematic for practical use

[0128] [Evaluation 3: Adhesion] The surface of the photoreceptor (drum) to be evaluated was scratched with a cutter knife in a checkerboard pattern with a pitch of 1 mm on each side of 10 mm. Then, adhesive tape (manufactured by Nichiban Co., Ltd., product name: Nichiban Cellotape (registered trademark)) was applied to the scratches, and the adhesive tape was instantly peeled off to evaluate the adhesion of the photoreceptor according to the following criteria. VG: The area of ​​the missing part is within 5% of the total square area Can be used without problems in high-speed multifunction devices or printers that require high sensitivity G: The width of the peeling in the cut is wider than 4 points, and the area of ​​the missing part is more than 5% but less than 35% of the total square area Can be used without problems on low to medium speed multifunction devices or printers NB: The width of the peeling in the cut is wider than 4 points, and the area of ​​the missing part is 35% to 65% of the total square area. Although the density is slightly low, it can be used without problems on slow, inexpensive multifunction machines or printers. B: The area of ​​the defect due to peeling is 65% or more of the total square area Poor sensitivity, low concentration, and problematic for practical use

[0129] [comprehensive evaluation] Based on the results of evaluations 1 to 3, an overall evaluation was made according to the following criteria. VG: All rated VG G: No judgments NB and B NB: There is no B rating. B: There is a judgment B

[0130] The constituent layers of the photoreceptor, preparation of the coating solutions for forming them, and the main constituent materials and their physical properties are shown in Table 1. The measured spectral absorption spectrum of the titanyl phthalocyanine adduct of 2,3-butanediol in the laminated photosensitive layer and the calculated values ​​based on the measured spectral absorption spectrum are shown in Table 2. The evaluation results are shown in Table 3. The abbreviations in Table 1 have the following meanings. SLG: Soda lime glass Zr: Zirconia PS: Paint shaker BM: Ball mill The materials of the binder resins in the charge generating layer and the charge transport layer are indicated by their product names, and the hole transport material and the electron transport material are indicated by the compound names of their structural formulas. R stands for CI Solvent Red 179.

[0131] [Table 1]

[0132] [Table 2]

[0133] [Table 3]

[0134] The following can be seen from Tables 1 to 3: (1) According to the results of Evaluation 1, the photoreceptors (Examples 1 to 15) containing, as a charge generating material, a titanyl phthalocyanine adduct of 2,3-butanediol that satisfies the requirements of the spectral absorption spectrum of the present disclosure tend to have improved light resistance compared to conventional photoreceptors (Comparative Examples 1 to 4). (2) The titanyl phthalocyanine in the laminated photosensitive layer has a maximum absorption at wavelengths of 650 to 680 nm in the spectroscopic absorption spectrum, and the absorbance Abs of the maximum absorption at wavelengths of 650 to 680 nm and the absorbance Abs of the wavelength of 810 nm are taken as 0 in the spectroscopic absorption spectrum. 810 And Abs <Abs 810 The photoconductors (Examples 1 and 3 to 5) that satisfy the above relationship have improved light resistance compared to the photoconductors (Examples 2 and 6 to 8) that do not satisfy this requirement.

[0135] (3) The photoreceptors (Examples 1 and 6) in which the titanyl phthalocyanine in the laminated photosensitive layer has a maximum absorption at a wavelength of 770 to 780 nm in the spectral absorption spectrum have better sensitivity characteristics than the photoreceptors (Examples 3 to 5) that do not satisfy this requirement. (4) The titanyl phthalocyanine in the laminated photosensitive layer has maximum absorption at wavelengths of 750 to 780 nm and 650 to 680 nm in the spectroscopic absorption spectrum, and the absorbance Abs of the maximum absorption at wavelengths of 750 to 780 nm when the absorbance at a wavelength of 870 nm is set to 0 1 and the maximum absorption at wavelengths of 650 to 680 nm, Abs 2 Ratio to Abs 2 / Abs 1 The photoreceptors (Examples 1 and 3 to 5) having a value of 0.20 to 0.60 have better light resistance than the photoreceptor (Example 2) that does not satisfy this requirement.

[0136] (5) Average particle size D of titanyl phthalocyanine adduct of 2,3-butanediol 50 The photoconductors (Examples 1 to 4 and 6) that satisfy the requirement that D(50%) is 0.15 to 0.40 μm have better sensitivity characteristics and a smaller humidity fluctuation range than the photoconductor (Example 5) that does not satisfy the requirement and has a too large D(50%).50 If the ratio (50%) is too small, excessive shear is applied during dispersion, and when a charge generating layer is formed, lattice defects are likely to occur, and the effect on light resistance tends to decrease. (6) A photoconductor having a charge generating layer formed by applying a coating liquid for a charge generating layer, the charge generating layer being prepared by dispersing a titanyl phthalocyanine adduct of 2,3-butanediol and a binder resin using a dispersion medium made of soda-lime glass (Example 1), has better light resistance than a photoconductor not satisfying the requirements (Example 6).

[0137] (7) Photoconductors (Examples 1 and 7) using a stilbene compound satisfying the requirements of the present disclosure as a hole transport material have better light resistance and sensitivity characteristics than a photoconductor (Example 10) that does not satisfy these requirements. (8) A photoreceptor (Example 11) using a pyrazolone compound satisfying the requirements of the present disclosure as an electron transport material has better light resistance than a photoreceptor (Example 6) that does not satisfy those requirements, and tends to have a worsening sensitivity characteristic as a drawback, and has superior light resistance to a photoreceptor (Example 12) that uses a light resistance additive that does not satisfy the requirements of the present disclosure.

[0138] (9) Photoreceptors having an undercoat layer between the substrate and the laminated photosensitive layer (Examples 1 and 14) have poorer adhesion of the photosensitive layer than photoreceptors not satisfying the requirements (Examples 13 and 15); when the hole transport substance in the photosensitive layer is reduced, the charge transport layer shrinks more and the adhesion of the photosensitive layer tends to become weaker (Example 15); and when the content of the binder resin in the charge generating layer is reduced, the adhesion to the substrate and the adhesion to the charge transport layer tends to deteriorate, and the adhesion tends to become extremely poor (Comparative Example 4).

[0139] 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]

[0140] 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

[0141] 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, at least one selected from the group consisting of titanyl phthalocyanine to which (2R,3R)-2,3-butanediol is added and titanyl phthalocyanine to which (2S,3S)-2,3-butanediol is added; The titanyl phthalocyanine in the laminated photosensitive layer has a maximum absorption at a wavelength of 750 to 780 nm in a spectroscopic absorption spectrum, and an absorbance Abs at 780 nm 780 and absorbance at a wavelength of 750 nm, Abs 750 Toga Abs 750 <Abs 780 The electrophotographic photoreceptor satisfies the relationship:

2. The titanyl phthalocyanine in the laminated photosensitive layer has a maximum absorption at wavelengths of 650 to 680 nm in a spectroscopic absorption spectrum, and the absorbance Abs of the maximum absorption at wavelengths of 650 to 680 nm and the absorbance Abs at a wavelength of 810 nm are set to 0 when the absorbance at 870 nm is set to 0. 810 and Abs < Abs 810 2. The electrophotographic photoreceptor according to claim 1, which satisfies the relationship:

3. 3. The electrophotographic photoreceptor according to claim 1, wherein the titanyl phthalocyanine in the laminated photosensitive layer has a maximum absorption in a wavelength range of 770 to 780 nm in a spectroscopic absorption spectrum.

4. The titanyl phthalocyanine in the laminated photosensitive layer has maximum absorption at wavelengths of 750 to 780 nm and 650 to 680 nm in a spectroscopic absorption spectrum, and the absorbance Abs of the maximum absorption at wavelengths of 750 to 780 nm when the absorbance at 870 nm is set to 0 1 and the absorbance Abs of the maximum absorption at wavelengths of 650 to 680 nm 2 Ratio to Abs 2 / Abs 1 3. The electrophotographic photoreceptor according to claim 1, wherein the σ is 0.20 to 0.

60.

5. The titanyl phthalocyanine has an average particle diameter D of 0.15 to 0.4 μm. 50 3. The electrophotographic photoreceptor according to claim 1, wherein the total molecular weight is 50%.

6. The charge transport layer contains, as a hole transport material, a compound represented by the general formula (I): 【Chemistry 1】 (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 2】 (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:

7. The charge transport layer contains, as an electron transport material, a compound represented by the general formula (III): 【Chemistry 3】 (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.

3. The electrophotographic photoreceptor according to claim 1, further comprising a pyrazolone compound represented by the formula:

8. 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.

9. A method for producing an electrophotographic photoreceptor according to claim 1 or 2, A step of forming the charge generating layer by applying a coating liquid for the charge generating layer, a step of dispersing at least one selected from the group consisting of titanyl phthalocyanine having (2R,3R)-2,3-butanediol added thereto and titanyl phthalocyanine having (2S,3S)-2,3-butanediol added thereto, and a binder resin, using a dispersion medium made of soda-lime glass, to prepare a coating liquid for the charge generating layer.

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