Manufacturing method for electrophotographic photoreceptors

Abstract

To provide a method for manufacturing an electrophotographic photoreceptor that suppresses coating defects such as blistering and cracking on the surface of the charge transport layer, and the inclusion of foreign matter on the surface of the coating film. [Solution] A method for manufacturing an electrophotographic photoreceptor, comprising: applying a coating liquid for forming a charge generation layer onto a conductive substrate and drying the coating film to form a charge generation layer; and applying a coating liquid for forming a charge transport layer to the surface of the charge generation layer and drying the coating film to form a charge transport layer, wherein the coating liquid for forming the charge transport layer contains a binder resin, a charge transport material, and a solvent; the ratio (V / SC) of the vibratory viscosity V (mPa·s) of the coating liquid for forming the charge transport layer to the solid content SC (mass%) at 20°C is 3,000 or more and 8,000 or less; and the drying conditions of the coating film of the coating liquid for forming the charge transport layer satisfy the relationship of the following formula (T1). Formula (T1): 10≦(T DRY -B MAX ) / B AVG ×H R ≤30

Description

[Technical Field]

[0001] This disclosure relates to a method for manufacturing an electrophotographic photoreceptor. [Background technology]

[0002] Patent Document 1 discloses "a method for manufacturing an electrophotographic photoreceptor having, in this order, an intermediate layer in which an inorganic pigment is dispersed on a conductive support, and a photosensitive layer formed by coating it using a coating solution for a photosensitive layer containing one or more solvents selected from cyclic ether compounds, ketone compounds, and aromatic hydrocarbon compounds, wherein there are two or more drying steps for drying the coated photosensitive layer, and the maximum heating rate of the conductive support in the first drying step for drying the photosensitive layer immediately after coating is 5°C / sec or less, and the average heating rate is 0.05°C / sec or less." Patent Document 2 discloses a conductive member comprising a conductive support and a coating layer formed on its outer circumference, characterized in that a coating liquid containing two or more solvents with different boiling points is applied to the outer surface of the conductive support, drying is performed in a range from a temperature 40°C lower than the boiling point of a solvent contained in an amount of 60% to 95% by mass relative to the total weight of the solvent, to a temperature below the boiling point of the solvent contained in an amount of 60% to 95% by mass relative to the total weight of the solvent, and drying is performed at a temperature above the boiling point of the solvent having the highest boiling point among the solvents contained in an amount of 5% to 40% by mass relative to the total weight of the solvent, thereby forming the coating layer on the outer surface of the conductive support. Patent Document 3 discloses "a method for manufacturing an electrophotographic photoreceptor in which at least one functional layer for a photoreceptor is formed on a cylindrical conductive substrate by immersion coating from a coating solution, characterized in that at least one of the functional layers for the photoreceptor is formed by first forming a coating film on the substrate from the coating solution, then holding the coating film in a temperature environment lower than the boiling point of the solvent in the coating solution until the solvent content in the coating film becomes 30% by weight or less, and then drying it at a temperature higher than the boiling point of the solvent." [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2006-072090 [Patent Document 2] Japanese Patent Publication No. 2004-354595 [Patent Document 3] Japanese Patent Publication No. 2003-114541 [Overview of the project] [Problems that the invention aims to solve]

[0004] The object of this disclosure is to provide a method for manufacturing an electrophotographic photoreceptor that suppresses coating defects such as blistering and cracking on the surface of the charge transport layer and the inclusion of foreign matter on the coating film surface, compared to cases where "the ratio (V / SC) of the vibrational viscosity V (mPa·s) of the charge transport layer forming coating liquid at 20°C to the solid content SC (mass%) is less than 3,000 or greater than 8,000" or "the drying conditions after coating the charge transport layer forming coating liquid do not satisfy the relationship of formula (T1)". [Means for solving the problem]

[0005] The following embodiments are included as specific means for solving the aforementioned problems. <1> The process involves applying a charge generation layer forming solution onto a conductive substrate, drying the coating film, and forming a charge generation layer. The process involves applying a coating liquid for forming a charge transport layer to the surface of the charge generating layer, and drying the coating film to form a charge transport layer. The coating liquid for forming the charge transport layer comprises a binder resin, a charge transport material, and a solvent. The ratio (V / SC) of the vibrational viscosity V (mPa·s) to the solid content SC (mass%) of the charge transport layer forming coating liquid at 20°C is 3,000 or more and 8,000 or less. A method for manufacturing an electrophotographic photoreceptor, wherein the drying conditions of the coating film of the charge transport layer forming coating solution satisfy the relationship of the following equation (T1). Formula (T1): 10≦(T DRY -B MAX) / B AVG ×H R ≤30 (In the above formula (T1), T DRY is the average drying temperature (°C), <0OO0160>B MAX is the boiling point (°C) of the solvent with the highest boiling point contained in the coating solution for forming the charge transport layer, B AVG is the average boiling point (°C) of all solvents contained in the coating solution for forming the charge transport layer, H R represents the average temperature rising rate (°C / min) when drying the coating film of the coating solution for forming the charge transport layer.) <2> The average temperature rising rate H when drying the coating film of the coating solution for forming the charge transport layer R [[ID= / / ]] (°C) is 3°C / min or more and 40°C / min or less, and the method for manufacturing an electrophotographic photoreceptor according to <1>. <3> The average temperature rising rate H when drying the coating film of the coating solution for forming the charge transport layer R (°C) is 15°C / min or more and 25°C / min or less, and the method for manufacturing an electrophotographic photoreceptor according to <2>. <4> After applying the coating solution for forming the charge transport layer and before drying, the residual solvent amount V1 in the coating film is more than 30% by mass and less than 70% by mass, and the method for manufacturing an electrophotographic photoreceptor according to any one of <1> to <3>. <5> The content of the binder resin having a weight average molecular weight Mw of 80,000 or more and 130,000 or less in the entire binder resin is 20% by mass or more and 100% by mass or less, and the method for manufacturing an electrophotographic photoreceptor according to any one of <1> to <4>. <6> The oscillatory viscosity V of the coating solution for forming the charge transport layer at 20°C is 700 mPa·s or more and 1200 mPa·s or less, and the method for manufacturing an electrophotographic photoreceptor according to any one of <1> to <5>. <7> The oscillatory viscosity V of the coating solution for forming the charge transport layer at 20°C is 700 mPa·s or more and 1000 mPa·s or less, and the method for manufacturing an electrophotographic photoreceptor according to <6>. <8> The value of the solid content ratio SC is 15% by mass or more and 22% by mass or less, and the method for manufacturing an electrophotographic photoreceptor according to any one of <1> to <7>. <9> The average boiling point B of all solvents contained in the aforementioned charge transport layer forming coating liquid. AVG The value is 65°C or higher and 80°C or lower. <1> ~ <8> A method for manufacturing an electrophotographic photoreceptor as described in any one of the following. [Effects of the Invention]

[0006] <1> According to the report, a method for manufacturing an electrophotographic photoreceptor is provided that suppresses coating defects such as blistering and cracking on the surface of the charge transport layer and the inclusion of foreign matter on the coating film surface, compared to cases where "the ratio (V / SC) of the vibrational viscosity V (mPa·s) of the charge transport layer forming coating solution at 20°C to the solid content SC (mass%) is less than 3,000 or greater than 8,000" or "the drying conditions after coating the charge transport layer forming coating solution do not satisfy the relationship of formula (T1)". <2> According to this, the average heating rate H when drying the coating film of the charge transport layer forming coating liquid is R A method for manufacturing an electrophotographic photoreceptor is provided that suppresses coating defects such as blistering and cracking on the surface of the charge transport layer and the inclusion of foreign matter on the coating film surface, compared to cases where the temperature (°C) is less than 3°C / min or greater than 40°C / min. <3> According to this, the average heating rate H when drying the coating film of the charge transport layer forming coating liquid is R A method for manufacturing an electrophotographic photoreceptor is provided that suppresses coating defects such as blistering and cracking on the surface of the charge transport layer and the inclusion of foreign matter on the coating film surface, compared to cases where the temperature (°C) is less than 15°C / min or greater than 25°C / min. <4> According to this, a method for manufacturing an electrophotographic photoreceptor is provided that suppresses coating defects such as blistering and cracking on the surface of the charge transport layer and the inclusion of foreign matter on the surface of the coating film, compared to the case where the amount of residual solvent V1 in the coating film after applying the charge transport layer forming coating liquid and before drying is 30% by mass or less or 70% by mass or more. <5> According to the above, the content of the binder resin having a weight-average molecular weight Mw of 80,000 to 130,000 in the total binder resin is 20% by mass to 100% by mass, <1> ~ <4> A method for manufacturing an electrophotographic photoreceptor as described in any one of the following. <6> According to this, a method for manufacturing an electrophotographic photoreceptor is provided that suppresses coating defects such as blistering and cracking on the surface of the charge transport layer and the inclusion of foreign matter on the coating film surface, compared to cases where the vibrational viscosity V of the charge transport layer forming coating liquid at 20°C is less than 700 mPa·s or greater than 1200 mPa·s. <7> According to this, a method for manufacturing an electrophotographic photoreceptor is provided that suppresses coating defects such as blistering and cracking on the surface of the charge transport layer and the inclusion of foreign matter on the coating film surface, compared to cases where the vibrational viscosity V of the charge transport layer forming coating liquid at 20°C is less than 700 mPa·s or greater than 1000 mPa·s. <8> According to this, a method for manufacturing an electrophotographic photoreceptor is provided that suppresses coating defects such as blistering and cracking on the surface of the charge transport layer and the inclusion of foreign matter on the coating film surface, compared to cases where the solid content SC value is less than 15% by mass or greater than 22% by mass. <9> According to this, the average boiling point B of all solvents contained in the charge transport layer forming coating liquid AVG A method for manufacturing an electrophotographic photoreceptor is provided that suppresses coating defects such as blistering and cracking on the surface of the charge transport layer and the inclusion of foreign matter on the coating film surface, compared to cases where the value is less than 65°C or more than 80°C. [Brief explanation of the drawing]

[0007] [Figure 1] This is a partial cross-sectional view showing an example of the layer structure of an electrophotographic photoreceptor. [Modes for carrying out the invention]

[0008] The embodiments of this disclosure are described below. These descriptions and embodiments are illustrative and do not limit the scope of the embodiments.

[0009] In this disclosure, the numerical range indicated using "~" represents a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described in stages within this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in numerical ranges described within this disclosure, the upper or lower limit of that range may be replaced with the values ​​shown in the examples.

[0010] In this disclosure, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, provided that their objectives are achieved.

[0011] When embodiments are described in this disclosure with reference to the drawings, the configuration of such embodiments is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each figure are conceptual, and the relative relationships between the components are not limited thereto.

[0012] In this disclosure, each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition in this disclosure, if there are multiple types of the substance corresponding to each component in the composition, it means the total amount of those multiple types of substances present in the composition unless otherwise specified. In this disclosure, each component may contain multiple types of particles. If multiple types of particles corresponding to each component are present in the composition, the particle size of each component refers to the value for a mixture of such multiple types of particles present in the composition, unless otherwise specified.

[0013] In this disclosure, ppm stands for parts per million and is based on mass.

[0014] <Manufacturing method for electrophotographic photoreceptors> The manufacturing method according to this embodiment is a method for manufacturing an electrophotographic photoreceptor comprising a conductive substrate and a photosensitive layer having a charge generating layer and a charge transport layer disposed on the conductive substrate. Hereinafter, "electrophotographic photoreceptor" will also be referred to as "photoreceptor".

[0015] Figure 1 is a schematic partial cross-sectional view showing an example of the layer structure of a photoreceptor. The photoreceptor 10A shown in Figure 1 has a structure in which an undercoat layer 2, a charge generation layer 3, and a charge transport layer 4 are stacked in this order on a conductive substrate 1, with the charge generation layer 3 and the charge transport layer 4 constituting the photosensitive layer 5 (a so-called functionally separated photosensitive layer). The photoreceptor 10A may have an intermediate layer (not shown) between the undercoat layer 2 and the charge generation layer 3. The photoreceptor 10A may have a protective layer (not shown) on the charge transport layer 4. The undercoat layer 2 may or may not be present.

[0016] The method for manufacturing an electrophotographic photoreceptor according to this embodiment comprises: applying a coating liquid for forming a charge generation layer onto a conductive substrate and drying the coating film to form a charge generation layer; and applying a coating liquid for forming a charge transport layer onto the surface of the charge generation layer and drying the coating film to form a charge transport layer, wherein the coating liquid for forming the charge transport layer contains a binder resin, a charge transport material, and a solvent; the ratio (V / SC) of the vibrational viscosity V (mPa·s) of the coating liquid for forming the charge transport layer to the solid content SC (mass%) at 20°C is 3,000 or more and 8,000 or less; and the drying conditions of the coating film of the coating liquid for forming the charge transport layer satisfy the relationship of the following formula (T1).

[0017] Formula (T1): 10≦(T DRY -B MAX ) / B AVG ×H R ≤30 In the above equation (T1), T DRY This is the average drying temperature (°C). B MAX This is the boiling point (°C) of the solvent with the highest boiling point contained in the coating solution for forming the charge transport layer. B AVG This is the average boiling point (°C) of all solvents contained in the coating solution for forming the charge transport layer. H R These represent the average heating rate (°C / min) when drying the coating film of the charge transport layer forming solution.

[0018] Hereinafter, in this specification, the vibratory viscosity V will also be simply referred to as viscosity.

[0019] In a stacked electrophotographic photoreceptor comprising a photosensitive layer consisting of a charge generation layer and a charge transport layer, a coating solution for forming the charge transport layer is applied to the surface of the charge generation layer, and the coating film is dried to form the charge transport layer. If an excessive amount of solvent remains during this coating film drying process, blistering may occur on the surface of the charge transport layer. To suppress this blistering, conventional manufacturing methods employ a method of slowly and gradually increasing the heating temperature during the drying process (for example, a method of heating and drying by increasing the temperature at 5°C / sec or less for several hours immediately after coating film formation, and at an average heating rate of 0.05°C / sec or less). However, with this gradual heating, the drying process tends to be lengthy, and foreign matter such as dust from the atmosphere is likely to be mixed into the coating film during this time. In other words, in conventional manufacturing methods, there is a trade-off between suppressing coating defects in the charge transport layer and suppressing the incorporation of foreign matter. When an image is formed using an electrophotographic photoreceptor with coating defects or foreign matter incorporation into the coating film, image quality defects tend to occur in the defective or foreign matter-contaminated areas.

[0020] The method for manufacturing an electrophotographic photoreceptor according to this embodiment, having the above configuration, suppresses coating defects such as blistering and cracking on the surface of the charge transport layer and the incorporation of foreign matter on the coating film surface. The mechanism of action is not entirely clear, but it is presumed to be as follows.

[0021] When the ratio (V / SC) of the vibrational viscosity V (mPa·s) of the charge transport layer forming coating solution to the solid content SC (mass%) at 20°C is 3,000 or higher, the proportion of low solids is kept relatively small, and the viscosity of the coating solution is prevented from becoming excessively low. As a result, the coating film is easily formed evenly across the entire surface of the charge generation layer, and the formation of bubbles from the solvent inside the surface layer of the coating film is suppressed. Consequently, coating defects such as blistering and cracking are suppressed. When the ratio (V / SC) is 8,000 or less, excessively high solid content is suppressed. As a result, unevenness in the thickness of the coating film (hereinafter also referred to as "uneven coating film thickness") is suppressed, and coating defects such as blistering and cracking are suppressed.

[0022] The above equation (T1) represents the precise correlation between the boiling points of various solvents in the charge transport layer forming coating solution and the drying conditions during coating film drying. A value of 10 or greater in equation (T1) means that, when viewed from the perspective of the entire coating solution, configurations that result in an excessively slow drying rate of the coating film are eliminated. This suppresses the incorporation of foreign matter into the coating film during drying. Conversely, a value of 30 or less in equation (T1) means that configurations that result in an excessively fast drying rate of the coating film are eliminated. This suppresses the incorporation of foreign matter into the coating film during drying. Furthermore, coating film defects such as blistering and cracking caused by a faster drying rate are suppressed.

[0023] Furthermore, the method for manufacturing an electrophotographic photoreceptor according to this embodiment, having the above configuration, offers superior productivity compared to conventional methods for manufacturing electrophotographic photoreceptors. In addition, the method for manufacturing an electrophotographic photoreceptor according to this embodiment suppresses coating defects and foreign matter contamination in the charge transport layer, resulting in a smooth surface and reduced film thickness unevenness, thus providing superior abrasion resistance.

[0024] [Coating solution for forming a charge transport layer] The ratio (V / SC) of the vibrational viscosity V (mPa·s) of the charge transport layer forming coating liquid to the solid content SC (mass%) at 20°C is preferably 3,000 to 8,000, more preferably 3,100 to 6,000, and more preferably 3,200 to 4,500. When the ratio (V / SC) is 3,000 or higher, the proportion of low-solid content is kept relatively small, and the viscosity of the coating solution is prevented from becoming excessively low. As a result, the coating film is easily formed evenly across the entire surface of the charge generation layer, and the formation of bubbles from the solvent inside the surface layer of the coating film is suppressed. Consequently, coating defects such as blistering and cracking are suppressed. This also leads to a reduction in manufacturing time and improved manufacturing efficiency. Furthermore, the suppression of uneven coating film thickness and improved film formation results in superior abrasion resistance. When the ratio (V / SC) is 8,000 or less, excessively high solid content is suppressed. As a result, unevenness in coating film thickness is suppressed, and coating defects such as blistering and cracking are suppressed. Furthermore, because unevenness in coating film thickness is suppressed and film formation is improved, abrasion resistance is superior.

[0025] There are no particular limitations on the specific methods used to set the ratio (V / SC) within the above range, but examples include methods that set the viscosity and solid content values ​​of the coating solution within the preferred range mentioned above; and methods that use the solvent described below as the solvent in the coating solution.

[0026] The drying conditions for the coating film of the charge transport layer forming coating solution preferably satisfy the relationship of formula (T1), preferably the relationship of formula (T2), and more preferably the relationship of formula (T3). Formula (T1): 10≦(T DRY -B MAX ) / B AVG ×H R ≤30 Formula (T2): 12≦(T DRY -B MAX ) / B AVG ×H R ≤27 Formula (T3): 14≦(T DRY -B MAX ) / B AVG ×H R ≤18

[0027] There are no particular limitations on the specific methods used to satisfy the specifications of equations (T1) to (T3), but examples include methods that set the viscosity and solid content values ​​of the coating solution to the preferred range described above; and methods that use the solvent described below as the solvent in the coating solution.

[0028] The vibrational viscosity V of the coating liquid for forming the charge transport layer at 20°C is preferably greater than 600 mPa·s and less than or equal to 1200 mPa·s, more preferably between 700 mPa·s and 1200 mPa·s, and even more preferably between 700 mPa·s and 1000 mPa·s. When the vibrational viscosity V exceeds 600 mPa·s, the excessive low viscosity of the coating film is further suppressed. As a result, the coating film is more easily formed evenly across the entire surface of the charge generation layer, and the formation of bubbles from the solvent inside the surface layer of the coating film is suppressed. Consequently, coating film defects such as blistering and cracking are further suppressed. When the vibrational viscosity V is 1200 mPa·s or less, excessive viscosity of the coating film is suppressed. As a result, unevenness in the coating film thickness is suppressed, and coating defects such as blistering and cracking are reduced.

[0029] There are no particular limitations on the specific methods used to set the value of the vibrational viscosity V within the above range, but examples include using one of the solvents described below in the coating solution, or using one of the proportions of the solvent (i.e., solid content) in the coating solution as described below.

[0030] The vibratory viscosity V at 20°C is measured using a vibratory viscometer (VM-10A, manufactured by Sekonic).

[0031] The solid content ratio SC is preferably 10% by mass or more and less than 30% by mass, more preferably 10% by mass or more and less than 26% by mass, and even more preferably 15% by mass or more and 22% by mass or less. When the solid content ratio (SC) is 10% by mass or higher, the proportion of low-solid content is kept relatively small. As a result, the coating film is more easily formed evenly across the entire surface of the charge generation layer, and the formation of bubbles from the solvent inside the surface layer of the coating film is suppressed. Consequently, coating defects such as blistering and cracking are suppressed. When the solid content ratio (SC) is less than 30% by mass, excessively high solid content is suppressed. As a result, unevenness in the coating film thickness is suppressed, and coating defects such as blistering and cracking are reduced.

[0032] Average drying temperature T DRY (°C) is preferably "the boiling point of the solvent with the highest boiling point + 20°C to 70°C", more preferably "the boiling point of the solvent with the highest boiling point + 30°C to 65°C", and even more preferably "the boiling point of the solvent with the highest boiling point + 40°C to 60°C". Average drying temperature T DRY The temperature (°C) is preferably, for example, 140°C to 180°C, more preferably 145°C to 175°C, and even more preferably 155°C to 170°C. Average drying temperature T DRY If the value is above the lower limit mentioned above, configurations that cause the coating film to dry excessively slowly are more likely to be eliminated when considering the entire coating solution. This further suppresses the incorporation of foreign matter into the coating film during drying. Average drying temperature T DRY If the value is below the above upper limit, configurations that dry the coating film excessively quickly are more likely to be eliminated. This further suppresses the incorporation of foreign matter into the coating film during drying. In addition, coating defects such as blistering and cracking caused by a faster drying speed are further suppressed.

[0033] Average drying temperature T DRY This refers to the process of heating the coating film of the charge transport layer formation solution at the average heating rate H described later. R This refers to the highest holding temperature reached after heating.

[0034] The boiling point B of the solvent with the highest boiling point contained in the coating solution for forming a charge transport layer. MAX The temperature (°C) is preferably 65°C to 145°C, more preferably 80°C to 125°C, and even more preferably 100°C to 120°C. The boiling point B of the solvent with the highest boiling point MAX If the value is above the lower limit mentioned above, configurations that dry the coating film excessively slowly are more likely to be eliminated. This further suppresses the incorporation of foreign matter into the coating film during drying. The boiling point B of the solvent with the highest boiling point MAX If the value is below the above upper limit, configurations that dry the coating film excessively quickly are more likely to be eliminated. This further suppresses the incorporation of foreign matter into the coating film during drying. In addition, coating defects such as blistering and cracking caused by a faster drying speed are further suppressed.

[0035] Average boiling point B of all solvents contained in the charge transport layer forming coating solution AVGThe temperature (°C) is preferably 50°C to 120°C, more preferably 65°C to 110°C, and even more preferably 65°C to 80°C. Average boiling point B AVG If the value is above the lower limit mentioned above, configurations that cause the coating film to dry excessively slowly are more likely to be eliminated when considering the entire coating solution. This further suppresses the incorporation of foreign matter into the coating film during drying. Average boiling point B AVG When this value is below the above upper limit, the components that cause the coating film to dry excessively quickly are more likely to be eliminated when viewed from the perspective of the entire coating solution. This further suppresses the incorporation of foreign matter into the coating film during drying. In addition, coating film defects such as blistering and cracking caused by a faster drying speed are further suppressed.

[0036] Average heating rate H when drying the coating film of the charge transport layer forming coating solution R Preferably, the temperature (°C / min) is greater than 3°C / min and less than 40°C / min, more preferably greater than 10°C / min and 35°C / min or less, and even more preferably 15°C / min or more and less than 25°C / min.

[0037] Average heating rate H R If the value is above the lower limit mentioned above, configurations that dry the coating film excessively slowly are more likely to be eliminated. This further suppresses the incorporation of foreign matter into the coating film during drying. It also leads to a reduction in manufacturing time and improved manufacturing efficiency. Average heating rate H R If the value is below the above upper limit, configurations that dry the coating film excessively quickly are more likely to be eliminated. This further suppresses the incorporation of foreign matter into the coating film during drying. In addition, coating defects such as blistering and cracking caused by a faster drying speed are further suppressed.

[0038] Average heating rate H RThis refers to the average heating rate (°C / min) during the process from immediately after applying the charge transport layer forming solution until the coating film is dried and the charge transport layer is formed. In the charge transport layer formation process, the heating may be at a constant rate, or it may be a stepwise heating with a varying heating rate. From the viewpoint of further suppressing the incorporation of foreign matter into the coating film, further suppressing coating film defects such as blistering and cracking, and from the viewpoint of manufacturing cost and manufacturing simplification, it is preferable for the heating to be at a constant rate, and the average heating rate H described above is preferable. R It is more preferable that the temperature rises at a constant rate that satisfies the specified range.

[0039] After applying the charge transport layer forming coating solution and before drying, the amount of residual solvent V1 in the coating film is preferably more than 30% by mass and less than 70% by mass, more preferably more than 40% by mass and less than 70% by mass, and even more preferably 50% by mass or more and less than 70% by mass, relative to the charge transport layer forming coating solution. When the amount of residual solvent is above the lower limit, the drying rate of the coating film is prevented from becoming excessively fast. This further reduces coating film defects such as blistering and cracking caused by rapid drying. It also leads to shorter manufacturing times and improved manufacturing efficiency. If the amount of residual solvent is below the above upper limit, the drying rate of the coating film will not become excessively slow. This will further suppress the incorporation of foreign matter into the coating film during drying.

[0040] The amount of residual solvent mentioned above is quantified using a gas chromatograph-mass spectrometer. First, prepare the solvent to be used in the preparation of the coating solution, heat it at 300°C to vaporize it, and measure the retention time to create a calibration curve that includes the range of 0.05 ppm to 1500 ppm. Next, accurately weigh the undried coating film, which will be the measurement sample, after applying the charge transport layer forming coating solution. Heat this coating film at 300°C and measure the retention time of the volatile components. Based on the peak area of ​​the corresponding component that appears in the chromatograph and the calibration curve, determine the amount of residual solvent (ppm) contained in the coating film. Then, determine the ratio (mass%) of the amount of residual solvent to the charge transport layer forming coating solution.

[0041] The specific method for keeping the amount of residual solvent within the above range is not particularly limited, but examples include methods for setting the viscosity and solid content of the coating solution within the preferred range described above; and methods for using the solvent described below in the coating solution.

[0042] The following provides a detailed explanation of the layer structure of the photoreceptor.

[0043] [Conductive substrate] Examples of conductive substrates include metal plates, metal drums, and metal belts containing metals (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.). Other examples of conductive substrates include paper, resin films, belts, etc., coated, vapor-deposited, or laminated with conductive compounds (e.g., conductive polymers, indium oxide, etc.), metals (e.g., aluminum, palladium, gold, etc.), or alloys. Here, "conductive" refers to a volume resistivity of 1 × 10⁻⁶. 13 This refers to a value less than Ωcm.

[0044] When an electrophotographic photoreceptor is used in a laser printer, the surface of the conductive substrate is preferably roughened to a center-line average roughness Ra of 0.04 μm to 0.5 μm in order to suppress interference fringes that occur when irradiated with laser light. When non-interfering light is used as the light source, roughening to prevent interference fringes is not particularly necessary, but it is suitable for a longer lifespan because it suppresses the occurrence of defects due to surface irregularities of the conductive substrate.

[0045] Methods for roughening a surface include, for example, wet honing, which involves suspending an abrasive in water and spraying it onto a conductive substrate; centerless grinding, which involves pressing a conductive substrate against a rotating grinding wheel and continuously grinding it; and anodizing.

[0046] One method for roughening the surface is to disperse conductive or semiconductive powder in a resin without roughening the surface of the conductive substrate, to form a layer on the surface of the conductive substrate, and then roughen the surface with the particles dispersed in that layer.

[0047] Anodizing roughening treatment involves forming an oxide film on the surface of a conductive substrate (e.g., aluminum) by anodizing it in an electrolyte solution. Examples of electrolyte solutions include sulfuric acid solution and oxalic acid solution. However, the porous anodic oxide film formed by anodizing is chemically active, easily contaminated, and exhibits large resistance fluctuations depending on the environment. Therefore, it is preferable to perform a sealing treatment on the porous anodic oxide film to block the micropores of the oxide film by volume expansion due to a hydration reaction using pressurized steam or boiling water (metal salts such as nickel may be added), thereby converting it into a more stable hydrated oxide.

[0048] The thickness of the anodic oxide film is preferably, for example, 0.3 μm to 15 μm. When the film thickness is within this range, it tends to exhibit barrier properties against injection and tends to suppress the increase in residual potential due to repeated use.

[0049] The conductive substrate may be treated with an acidic treatment solution or with boehmite. Treatment with an acidic solution is carried out, for example, as follows: First, an acidic solution containing phosphoric acid, chromic acid, and hydrofluoric acid is prepared. The mixing ratio of phosphoric acid, chromic acid, and hydrofluoric acid in the acidic solution is, for example, in the range of 10% to 11% by mass for phosphoric acid, 3% to 5% by mass for chromic acid, and 0.5% to 2% by mass for hydrofluoric acid, and the total concentration of these acids is preferably in the range of 13.5% to 18% by mass. The treatment temperature is preferably, for example, 42°C to 48°C. The film thickness is preferably 0.3 μm to 15 μm.

[0050] The boehmite treatment is carried out, for example, by immersing the material in pure water at 90°C to 100°C for 5 to 60 minutes, or by contacting it with heated steam at 90°C to 120°C for 5 to 60 minutes. The film thickness is preferably 0.1 μm to 5 μm. This can be further treated with anodic oxidation using an electrolyte solution with low film solubility, such as adipic acid, boric acid, borate, phosphate, phthalate, maleate, benzoate, tartrate, or citrate.

[0051] [Sublayer] The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

[0052] As for inorganic particles, for example, powder resistance (volume resistivity) 1 × 10 2 Ωcm or more, 1 × 10 11 Examples of inorganic particles with a resistance of Ωcm or less include metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles, with zinc oxide particles being particularly preferred.

[0053] The specific surface area of ​​inorganic particles using the BET method is, for example, 10 m². 2 A value of 1g or more is preferable. The volume-average particle size of the inorganic particles is preferably between 50 nm and 2000 nm (preferably between 60 nm and 1000 nm).

[0054] The inorganic particle content is preferably 10% by mass or more and 80% by mass or less relative to the binder resin, and more preferably 40% by mass or more and 80% by mass or less.

[0055] The inorganic particles may be surface-treated. Two or more types of inorganic particles with different surface treatments or particle sizes may be mixed and used.

[0056] Examples of surface treatment agents include silane coupling agents, titanate-based coupling agents, aluminum-based coupling agents, and surfactants. Silane coupling agents are particularly preferred, and silane coupling agents having an amino group are more preferred.

[0057] Examples of silane coupling agents having an amino group include, but are not limited to, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane.

[0058] Silane coupling agents may be used in combination of two or more types. For example, a silane coupling agent having an amino group may be used in combination with another silane coupling agent. Examples of other silane coupling agents include, but are not limited to, vinyltrimethoxysilane, 3-methacrylateoxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and 3-chloropropyltrimethoxysilane.

[0059] The surface treatment method using the surface treatment agent may be any known method, and may be either a dry or wet method.

[0060] The amount of surface treatment agent applied is preferably, for example, 0.5% by mass or more and 10% by mass or less relative to the inorganic particles.

[0061] The underlying layer should contain electron-accepting compounds along with inorganic particles, which is desirable from the viewpoint of improving the long-term stability of electrical properties and carrier blocking ability.

[0062] Examples of electron-accepting compounds include quinone compounds such as chloranil and bromonil; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone and 2,4,5,7-tetranitro-9-fluorenone; oxadiazole compounds such as 2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole, 2,5-bis(4-naphthyl)-1,3,4-oxadiazole, and 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole; xanthone compounds; thiophene compounds; and diphenoquinone compounds such as 3,3',5,5'-tetra-t-butyldiphenoquinone; as well as other electron-transporting substances. In particular, compounds having an anthraquinone structure are preferred as electron-accepting compounds. Examples of compounds having an anthraquinone structure include hydroxyanthraquinone compounds, aminoanthraquinone compounds, and aminohydroxyanthraquinone compounds. Specifically, examples of preferred compounds include anthraquinone, alizarin, quinizalin, anthralphine, purpurin, and their derivatives.

[0063] The electron-accepting compound may be dispersed in the underlayer together with inorganic particles, or it may be present attached to the surface of the inorganic particles.

[0064] Methods for attaching electron-accepting compounds to the surface of inorganic particles include, for example, dry methods or wet methods.

[0065] The dry method involves, for example, adding an electron-accepting compound, either directly or dissolved in an organic solvent, dropwise while stirring inorganic particles with a mixer that has a high shear force, or spraying it with dry air or nitrogen gas, to adhere the electron-accepting compound to the surface of the inorganic particles. When adding or spraying the electron-accepting compound, it is preferable to do so at a temperature below the boiling point of the solvent. After adding or spraying the electron-accepting compound, further baking at 100°C or higher may be performed. The baking temperature and time are not particularly limited as long as electrophotographic characteristics can be obtained.

[0066] The wet method involves dispersing inorganic particles in a solvent using methods such as stirring, ultrasound, sand milling, attritoring, and ball milling, while adding an electron-accepting compound. After stirring or dispersion, the solvent is removed to adhere the electron-accepting compound to the surface of the inorganic particles. Solvent removal methods include, for example, filtration or distillation. After solvent removal, further baking at 100°C or higher may be performed. The baking temperature and time are not particularly limited as long as electrophotographic characteristics can be obtained. In the wet method, the water content of the inorganic particles may be removed before adding the electron-accepting compound. Examples of this include removing water while stirring and heating in the solvent, or removing water by azeotrope with the solvent.

[0067] The electron-accepting compound may be applied before or after surface treatment with a surface treatment agent to the inorganic particles, or it may be applied simultaneously with the surface treatment with the surface treatment agent.

[0068] The content of the electron-accepting compound is preferably, for example, 0.01% by mass or more and 20% by mass or less relative to the inorganic particles, and more preferably 0.01% by mass or more and 10% by mass or less.

[0069] Examples of known polymer compounds used as the binder resin for the undercoat include acetal resin (e.g., polyvinyl butyral), polyvinyl alcohol resin, polyvinyl acetal resin, casein resin, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, unsaturated polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, urea resin, phenol resin, phenol-formaldehyde resin, melamine resin, urethane resin, alkyd resin, epoxy resin, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, and silane coupling agents. Examples of binder resins used in the undercoat include charge-transporting resins having charge-transporting groups, conductive resins (e.g., polyaniline), and the like.

[0070] Among these, a resin insoluble in the coating solvent of the upper layer is preferred as the binder resin used for the undercoat layer. In particular, a resin obtained by the reaction of a curing agent with at least one resin selected from the group consisting of thermosetting resins such as urea resin, phenol resin, phenol-formaldehyde resin, melamine resin, urethane resin, unsaturated polyester resin, alkyd resin, and epoxy resin is preferred. When using two or more of these binder resins in combination, the mixing ratio is set as needed.

[0071] The undercoat may contain various additives to improve electrical properties, environmental stability, and image quality. Examples of known additives include electron-transporting pigments such as polycyclic condensation and azo pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, and silane coupling agents. As mentioned above, silane coupling agents are used for surface treatment of inorganic particles, but they may also be added to the undercoat as additives.

[0072] Examples of silane coupling agents used as additives include vinyltrimethoxysilane, 3-methacrylateoxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and 3-chloropropyltrimethoxysilane.

[0073] Examples of zirconium chelate compounds include zirconium butoxide, ethyl zirconium acetate, zirconium triethanolamine, acetylacetonate zirconium butoxide, ethyl acetate zirconium butoxide, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octanoate, zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, methacrylate zirconium butoxide, stearate zirconium butoxide, and isostearate zirconium butoxide.

[0074] Examples of titanium chelate compounds include tetraisopropyl titanate, tetran-butyl titanate, butyl titanate dimer, tetra(2-ethylhexyl) titanate, titanium acetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate ammonium salt, titanium lactate, titanium lactate ethyl ester, titanium triethanolamine, and polyhydroxytitanium stearate.

[0075] Examples of aluminum chelating compounds include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, diethylacetoacetate aluminum diisopropylate, and aluminum tris(ethylacetoacetate).

[0076] These additives may be used individually or as a mixture or polycondensate of multiple compounds.

[0077] The underlayer should ideally have a Vickers hardness of 35 or higher. The surface roughness (ten-point average roughness) of the undercoat layer should be adjusted to between 1 / (4n) (where n is the refractive index of the upper layer) and 1 / 2 of the exposure laser wavelength λ used, in order to suppress moiré patterns. Resin particles may be added to the undercoat to adjust the surface roughness. Examples of resin particles include silicone resin particles and cross-linked polymethyl methacrylate resin particles. The surface of the undercoat may also be polished to adjust the surface roughness. Polishing methods include buffing, sandblasting, wet honing, and grinding.

[0078] The formation of the undercoat is not particularly limited, and known formation methods can be used. For example, it can be carried out by forming a coating film of an undercoat-forming solution obtained by adding the above components to a solvent, drying the coating film, and heating it if necessary.

[0079] Solvents for preparing the coating solution for forming the undercoat include known organic solvents such as alcohol-based solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone-based solvents, ketone alcohol-based solvents, ether-based solvents, and ester-based solvents. Specific examples of these solvents include common organic solvents such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene.

[0080] Known methods for dispersing inorganic particles when preparing a coating solution for forming an undercoat include, for example, roll mills, ball mills, vibrating ball mills, attritors, sand mills, colloid mills, and paint shakers.

[0081] Conventional methods for applying the undercoating solution onto a conductive substrate include, for example, the blade coating method, wire bar coating method, spray coating method, immersion coating method, bead coating method, air knife coating method, and curtain coating method.

[0082] The thickness of the undercoat layer is preferably set to a range of 15 μm or more, and more preferably 20 μm to 50 μm.

[0083] [Middle class] An intermediate layer may be further provided between the undercoat layer and the photosensitive layer. The intermediate layer is, for example, a layer containing a resin. Examples of resins used in the intermediate layer include polymer compounds such as acetal resin (e.g., polyvinyl butyral), polyvinyl alcohol resin, polyvinyl acetal resin, casein resin, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, and melamine resin. The intermediate layer may contain an organometallic compound. Examples of organometallic compounds used in the intermediate layer include those containing metal atoms such as zirconium, titanium, aluminum, manganese, and silicon. The compounds used in these intermediate layers may be used individually, as a mixture of multiple compounds, or as polycondensates.

[0084] Among these, the intermediate layer is preferably a layer containing an organometallic compound that contains zirconium atoms or silicon atoms.

[0085] The formation of the intermediate layer is not particularly limited, and known formation methods can be used. For example, it can be carried out by forming a coating film of an intermediate layer-forming coating solution obtained by adding the above components to a solvent, drying the coating film, and heating it if necessary. Conventional coating methods such as immersion coating, push-up coating, wire bar coating, spray coating, blade coating, air knife coating, and curtain coating (a coating method for forming the intermediate layer of an FB photoreceptor) are used to form the intermediate layer.

[0086] The thickness of the intermediate layer is preferably set to a range of 0.1 μm to 3 μm, for example. The intermediate layer may also be used as a base layer.

[0087] [Charge generation layer] The charge generation layer is, for example, a layer containing a charge generation material and a binder resin.

[0088] Examples of charge-generating materials include azo pigments such as bisazo and trisazo; fused aromatic pigments such as dibromoanthonthrone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; and trigonal selenium.

[0089] Among these, in order to accommodate laser exposure in the near-infrared region, it is preferable to use a metallic phthalocyanine pigment or a metal-free phthalocyanine pigment as the charge generating material. Specifically, at least one selected from the group consisting of hydroxygallium phthalocyanine, chlorogallium phthalocyanine, dichlorotin phthalocyanine, and titanyl phthalocyanine is preferred, hydroxygallium phthalocyanine and / or chlorogallium phthalocyanine is more preferred, and hydroxygallium phthalocyanine is even more preferred.

[0090] On the other hand, to accommodate laser exposure in the near-ultraviolet region, preferred charge-generating materials include fused aromatic pigments such as dibromoanthoten; thioindigo pigments; porphyrazine compounds; zinc oxide; trigonal selenium; and bisazo pigments.

[0091] The above charge generating material may also be used when using non-coherent light sources such as LEDs and organic EL image arrays, which have a central emission wavelength between 450 nm and 780 nm.

[0092] When n-type semiconductors such as fused aromatic pigments, perylene pigments, and azo pigments are used as charge-generating materials, dark currents are less likely to be generated, and image defects called black spots can be suppressed even in thin films. The n-type is determined using the commonly used time-of-flight method, which is determined by the polarity of the photocurrent that flows, and materials that readily carry electrons as carriers rather than holes are classified as n-type.

[0093] The binder resin used in the charge generation layer can be selected from a wide range of insulating resins, or it may be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, and polysilane. Examples of binder resins include polyvinyl butyral resin, polyarylate resin (hereinafter also referred to as PAR), polycarbonate resin (hereinafter also referred to as PC), polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyamide resin, acrylic resin, polyacrylamide resin, polyvinylpyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, and polyvinylpyrrolidone resin. Here, "insulating properties" refer to a volume resistivity of 1 × 10⁻⁶. 13 This refers to a density of Ωcm or greater. These binder resins can be used individually or in mixtures of two or more types.

[0094] The mixing ratio of the charge-generating material to the binder resin is preferably within the range of 10:1 to 1:10 by mass ratio.

[0095] The charge generation layer may also contain other known additives.

[0096] The charge generation layer is formed by coating. An embodiment of the coating process includes, for example, preparing a coating solution for forming the charge generation layer by dissolving or dispersing the above components in a solvent, applying the coating solution for forming the charge generation layer to the surface of a conductive substrate, the surface of an undercoat layer, or the surface of an intermediate layer to form a coating film, and drying the coating film.

[0097] Solvents for preparing the coating solution for forming the charge generation layer include methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene. These solvents may be used individually or in mixtures of two or more.

[0098] Methods for dispersing particles (e.g., charge-generating materials) in a coating solution for forming a charge-generating layer include, for example, media dispersers such as ball mills, vibrating ball mills, attritors, sand mills, and horizontal sand mills, as well as media-less dispersers such as stirrers, ultrasonic dispersers, roll mills, and high-pressure homogenizers. Examples of high-pressure homogenizers include collision methods, which disperse the dispersion by causing liquid-liquid collisions or liquid-wall collisions under high pressure, and penetration methods, which disperse the dispersion by penetrating fine channels under high pressure. During this dispersion, it is effective to set the average particle size of the charge-generating material in the coating solution for forming the charge-generating layer to 0.5 μm or less, preferably 0.3 μm or less, and more preferably 0.15 μm or less.

[0099] Conventional methods for applying the charge-generating layer forming coating solution onto the undercoat (or intermediate layer) include, for example, the blade coating method, wire bar coating method, spray coating method, immersion coating method, bead coating method, air knife coating method, and curtain coating method.

[0100] The drying temperature of the coated film is adjusted according to the boiling point of the solvent used to prepare the coating solution for forming the charge generation layer, so that the amount of solvent contained in the charge generation layer after drying is between 0.1 ppm and 500 ppm. When the boiling point of the solvent with the lowest boiling point among the solvents used to prepare the coating solution is defined as BP1°C, and the boiling point of the solvent with the highest boiling point is defined as BP2°C (if there is only one type of solvent, BP1 = BP2), the drying temperature of the coating film is preferably (BP1 - 30)°C or higher and (BP2 + 30)°C or lower, more preferably (BP1 - 20)°C or higher and (BP2 + 20)°C or lower, and even more preferably (BP1 - 10)°C or higher and (BP2 + 10)°C or lower.

[0101] The thickness of the charge generation layer is preferably set to a range of 0.1 μm to 5.0 μm, more preferably 0.2 μm to 2.0 μm.

[0102] [Charge transport layer] The charge transport layer is a layer containing a charge transport material and a binder resin. The charge transport layer may also contain a polymer charge transport material.

[0103] Examples of charge transport materials include quinone compounds such as p-benzoquinone, chloranil, bromanil, and anthraquinone; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthone compounds; benzophenone compounds; cyanovinyl compounds; and ethylene compounds, which are electron transport compounds. Other examples of charge transport materials include hole transport compounds such as triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted ethylene compounds, stilbene compounds, anthracene compounds, and hydrazone compounds. These charge transport materials may be used individually or in combination of two or more, but are not limited to these.

[0104] As charge transport materials, from the viewpoint of charge mobility, the triarylamine derivative shown in the following structural formula (a-1) and the benzidine derivative shown in the following structural formula (a-2) are preferred.

[0105] [ka]

[0106] In structural formula (a-1), Ar T1 Ar T2 , and Ar T3 Each is independently a substituted or unsubstituted aryl group, -C6H4-C(R T4 )=C(R T5 )(R T6 ), or -C6H4-CH=CH-CH=C(R T7 )(R T8 ) indicates R T4 , R T5 , R T6 , R T7 , and R T8 Each of these independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Substituents for each of the above groups include halogen atoms, alkyl groups having 1 to 5 carbon atoms, and alkoxy groups having 1 to 5 carbon atoms. Furthermore, substituted amino groups substituted with alkyl groups having 1 to 3 carbon atoms are also examples of substituents for each of the above groups.

[0107] [ka]

[0108] In structural formula (a-2), R T91 and R T92 Each of these independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. T101 , R T102 , R T111 and R T112 Each of these independently consists of a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 to 2 carbon atoms, a substituted or unsubstituted aryl group, and -C(R T12 )=C(R T13 )(R T14 ), or -CH=CH-CH=C(R T15 )(R T16 ) shows R T12 , R T13 , R T14 , R T15 and R T16 Each of these independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Tm1, Tm2, ​​Tn1, and Tn2 each independently represent an integer between 0 and 2. Substituents for each of the above groups include halogen atoms, alkyl groups having 1 to 5 carbon atoms, and alkoxy groups having 1 to 5 carbon atoms. Furthermore, substituted amino groups substituted with alkyl groups having 1 to 3 carbon atoms are also examples of substituents for each of the above groups.

[0109] Here, among the triarylamine derivative represented by structural formula (a-1) and the benzidine derivative represented by structural formula (a-2), in particular, "-C6H4-CH=CH-CH=C(R T7)(R T8 Triarylamine derivatives having ")" and "-CH=CH-CH=C(R T15 )(R T16 A benzidine derivative having ) is preferred from the viewpoint of charge mobility.

[0110] As polymer charge transport materials, known charge transport materials such as poly-N-vinylcarbazole and polysilane can be used. Polyester-based polymer charge transport materials are particularly preferred. The polymer charge transport material may be used alone, or it may be used in combination with a binder resin.

[0111] Examples of binder resins used in the charge transport layer include polyarylate resin (hereinafter also referred to as PAR), polycarbonate resin (hereinafter also referred to as PC), polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer, vinylidene chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-N-vinylcarbazole, and polysilane. Among these, it is preferable that the binder resin contains polycarbonate resin or polyarylate resin, and more preferably polyarylate resin. These binder resins may be used individually or in combination of two or more.

[0112] Preferably, the content of the binder resin having a weight-average molecular weight Mw of 80,000 to 130,000 in the total binder resin is 20% to 100% by mass, more preferably 50% to 100% by mass, and even more preferably 80% to 100% by mass.

[0113] When the binder resin content with a weight-average molecular weight (Mw) of 80,000 to 130,000 is 20% by mass or more, excessively low viscosity of the coating film and low solid content of the coating solution are further suppressed. As a result, the coating film is more easily formed evenly across the entire surface of the charge generation layer, and the formation of bubbles from the solvent inside the surface layer of the coating film is suppressed. Consequently, coating defects such as blistering and cracking are further suppressed. In addition, the abrasion resistance of the charge transport layer is improved. When the weight-average molecular weight (Mw) of the resin is 130,000 or less, excessive viscosity of the coating film and excessive solid content of the coating solution are suppressed. As a result, unevenness in the film thickness is suppressed, and coating defects such as blistering and cracking are reduced.

[0114] The weight-average molecular weight Mw of the resin contained in the coating solution for forming the charge transport layer is preferably 50,000 to 130,000, and more preferably 80,000 to 130,000.

[0115] When the weight-average molecular weight (Mw) of the resin is 80,000 or higher, excessively low viscosity of the coating film and low solid content of the coating solution are further suppressed. As a result, the coating film is more easily formed evenly across the entire surface of the charge generation layer, and the formation of bubbles from the solvent inside the surface layer of the coating film is suppressed. Consequently, coating defects such as blistering and cracking are further suppressed. When the weight-average molecular weight (Mw) of the resin is 130,000 or less, excessive viscosity of the coating film and excessive solid content of the coating solution are suppressed. As a result, unevenness in the film thickness is suppressed, and coating defects such as blistering and cracking are reduced.

[0116] The weight-average molecular weight is measured by gel permeation chromatography (GPC). GPC molecular weight measurement is performed using a Tosoh GPC-HLC-8120GPC analyzer, a Tosoh TSKgel SuperHM-M (15cm) column, and THF solvent. The weight-average molecular weight is then calculated from these measurement results using a molecular weight calibration curve prepared with monodisperse polystyrene standard samples.

[0117] The preferred mixing ratio of the charge transport material to the binder resin is between 10:1 and 1:5 by mass.

[0118] The charge transport layer may also contain other well-known additives.

[0119] Examples of solvents included in the coating solution for forming the charge transport layer include common organic solvents such as aromatic hydrocarbons like benzene, toluene, xylene, and chlorobenzene; ketones like acetone and 2-butanone; halogenated aliphatic hydrocarbons like methylene chloride, chloroform, and ethylene chloride; cyclic or linear ethers like tetrahydrofuran (also known as THF) and ethyl ether; and terephthalic acids like dimethyl terephthalate (also known as DMT). Among the above, the solvent is preferably an organic solvent that satisfies formulas (T1) to (T3) mentioned above, and is preferably an organic solvent that is at least one of aromatic hydrocarbons and ethers, and more preferably at least one of toluene and tetrahydrofuran.

[0120] The solvent may be a single solvent or a combination of two or more solvents. When the solvent is a combination of two or more solvents, it is preferable that the solvent is a combination of two to three solvents, and more preferably a combination of two solvents, from the viewpoint of satisfying the aforementioned formulas (T1) to (T3) and from the viewpoint of manufacturing cost. When two or more solvents are used in combination, the proportion of the solvent with the highest boiling point is preferably more than 0% by mass and 30% by mass or less, and more preferably 1% by mass or more and 15% by mass or less, relative to the total amount of solvent, from the viewpoint of satisfying the aforementioned equations (T1) to (T3) and from the viewpoint of manufacturing costs.

[0121] Conventional methods for applying a charge transport layer forming coating solution onto a charge generation layer include blade coating, wire bar coating, spray coating, immersion coating, bead coating, air knife coating, and curtain coating.

[0122] The coating speed of the charge transport layer forming coating solution (also called the withdrawal speed in the case of immersion coating) is preferably 50 mm / min or more and 250 mm / min or less, and more preferably 100 mm / min or more and 200 mm / min or less, from the viewpoint of suitably adjusting the thickness of the coating film.

[0123] The thickness of the charge transport layer is set, for example, preferably within the range of 5 μm or more and less than 40 μm, and more preferably within the range of 10 μm or more and 30 μm or less.

[0124] The thickness of the charge transport layer may be 40 μm or more. When the thickness of the charge transport layer increases (for example, to 40 μm or more), coating defects such as blistering and cracking tend to occur during the drying process of the coating film. In contrast, the method for manufacturing an electrophotographic photoreceptor according to this embodiment has the above-described configuration, which suppresses coating defects such as blistering and cracking even when the film thickness is 40 μm or more.

[0125] [Protective layer] A protective layer is provided on the photosensitive layer as needed. The protective layer is provided, for example, to prevent chemical changes in the photosensitive layer during electrostatic charging, or to further improve the mechanical strength of the photosensitive layer. Therefore, it is preferable to apply a protective layer composed of a cured film (crosslinked film). Examples of such layers include those shown in 1) or 2) below.

[0126] 1) A layer composed of a cured film of a composition containing a reactive group-containing charge transport material having a reactive group and a charge transport skeleton within the same molecule (i.e., a layer containing a polymer or crosslinked form of the reactive group-containing charge transport material). 2) A layer composed of a cured film of a composition comprising a non-reactive charge transport material and a non-charge transport material containing reactive groups that does not have a charge transport skeleton but has reactive groups (i.e., a layer comprising a non-reactive charge transport material and a polymer or crosslinked form of the non-charge transport material containing reactive groups).

[0127] Examples of the reactive group of the reactive group-containing charge transport material include chain polymerizable groups, epoxy groups, -OH, -OR [where R represents an alkyl group], -NH2, -SH, -COOH, -SiR Q1 3-Qn (OR Q2 ) Qn [where R Q1 represents a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group, and R Q2 represents a hydrogen atom, an alkyl group, or a trialkylsilyl group. Qn represents an integer from 1 to 3] and other well-known reactive groups.

[0128] The chain polymerizable group is not particularly limited as long as it is a functional group capable of radical polymerization. For example, it is a functional group having a group containing at least a carbon-carbon double bond. Specifically, groups containing at least one selected from vinyl groups, vinyl ether groups, vinyl thioether groups, styryl groups, vinylphenyl groups, acryloyl groups, methacryloyl groups, and their derivatives can be mentioned. Among them, since it has excellent reactivity, the chain polymerizable group is preferably a group containing at least one selected from vinyl groups, styryl groups, vinylphenyl groups, acryloyl groups, methacryloyl groups, and their derivatives.

[0129] The charge transport skeleton of the reactive group-containing charge transport material is not particularly limited as long as it is a known structure in the electrophotographic photoreceptor. For example, skeletons derived from nitrogen-containing hole transport compounds such as triarylamine compounds, benzidine compounds, and hydrazone compounds, and structures conjugated with nitrogen atoms can be mentioned. Among these, a triarylamine skeleton is preferred.

[0130] These reactive group-containing charge transport materials having these reactive groups and charge transport skeletons, non-reactive charge transport materials, and reactive group-containing non-charge transport materials may be selected from well-known materials. <0000​​​​​​There are no particular restrictions on the formation of the protective layer, and well-known formation methods can be used. For example, it can be formed by adding the above components to a solvent to create a protective layer coating solution, drying the coating, and then performing a curing treatment such as heating as necessary.

[0133] Solvents for preparing coating solutions for forming a protective layer include aromatic solvents such as toluene and xylene; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester solvents such as ethyl acetate and butyl acetate; ether solvents such as tetrahydrofuran and dioxane; cellosolve solvents such as ethylene glycol monomethyl ether; and alcohol solvents such as isopropyl alcohol and butanol. These solvents can be used individually or in combination of two or more. The coating solution for forming the protective layer may be a solvent-free coating solution.

[0134] Conventional methods for applying a protective layer-forming coating solution onto a photosensitive layer (e.g., a charge transport layer) include immersion coating, push-up coating, wire bar coating, spray coating, blade coating, air knife coating, and curtain coating (a coating method for forming an intermediate layer in an FB photoreceptor).

[0135] The thickness of the protective layer is set, for example, preferably within the range of 1 μm to 20 μm, and more preferably within the range of 2 μm to 10 μm. [Examples]

[0136] The embodiments of the invention will be described in detail below with reference to examples, but the embodiments of the invention are not limited to these examples. In the following explanation, unless otherwise specified, "parts" and "%" refer to mass. In the following descriptions, unless otherwise specified, synthesis, manufacturing, processing, and measurements were performed at room temperature (25°C ± 3°C).

[0137] The abbreviations used herein have the following meanings: T DRY :Average drying temperature (℃), B MAX : Boiling point (°C) of the solvent with the highest boiling point contained in the coating liquid for forming the charge transport layer. B AVG : Average boiling point (°C) of all solvents contained in the coating liquid for forming the charge transport layer. H R : Average heating rate (°C / min) when drying the coating film of the coating liquid for forming the charge transport layer. V1: Residual solvent amount (mass%) in the coating film before drying in the charge transport layer forming process. V: Vibration viscosity (mPa·s) of the coating liquid for forming the charge transport layer at 20°C. SC: Solids content ratio (mass%) of the coating liquid for forming the charge transport layer at 20°C.

[0138] <Examples 1 to 4, Examples 8 to 9, Example 21, Example 23, Example 31, Example 32, Examples 34 to 38, Example 42, Comparative Example 1, Comparative Example 3, Comparative Example 5, and Comparative Example 8> [Formation of Underlayer] As a conductive substrate, an aluminum cylindrical tube with an outer diameter of 30 mm, a length of 365 mm, and a wall thickness of 2 mm was prepared.

[0139] 100 parts of zinc oxide (average particle size 70 nm, specific surface area 15 m 2 / g, Tayca Corporation) were stirred and mixed with 500 parts of toluene, 1.3 parts of a silane coupling agent (trade name: KBM603, Shin-Etsu Chemical Co., Ltd., N-2-(aminoethyl)-3-aminopropyltrimethoxysilane) were added, and stirring was carried out for 2 hours. Next, toluene was distilled off under reduced pressure, and baking was performed at 120°C for 3 hours to obtain zinc oxide surface-treated with a silane coupling agent.

[0140] 110 parts of the surface-treated zinc oxide were stirred and mixed with 500 parts of tetrahydrofuran, a solution in which 0.6 parts of alizarin were dissolved in 50 parts of tetrahydrofuran was added, and stirring was carried out at 50°C for 5 hours. Next, the solid content was filtered off by vacuum filtration, and vacuum drying was performed at 60°C to obtain alizarin-imparted zinc oxide.

[0141] 60 parts of alizarin-modified zinc oxide, 13.5 parts of a curing agent (blocked isocyanate, trade name: Sumijule 3175, Sumitomo Bayer Urethane Co., Ltd.), and 15 parts of butyral resin (trade name: Esrec BM-1, Sekisui Chemical Co., Ltd.) were dissolved in 68 parts of methyl ethyl ketone. 100 parts of this solution were mixed with 5 parts of methyl ethyl ketone, and the mixture was dispersed for 2 hours using a sand mill with 1 mm diameter glass beads to obtain a dispersion. To the dispersion, 0.005 parts of dioctyl tin dilaurate and 4 parts of silicone resin particles (trade name: Tospar 145, Momentive Performance Materials, Inc.) were added as catalysts to obtain a coating solution for forming an undercoat. The undercoat solution was applied to the outer surface of a conductive substrate by immersion coating, and dried and cured at 170°C for 40 minutes to form an undercoat with a thickness of 20 μm.

[0142] [Formation of charge generation layer] • Charge generating material: Hydroxygallium phthalocyanine...3 parts • Binding resin: Vinyl chloride / vinyl acetate copolymer... 2 parts • Solvent: n-butyl acetate ···66.5 parts • Solvent: Methyl isobutyl ketone ···28.5 parts The above materials were mixed and dispersed using 1 mm diameter glass beads in a sand mill for 4 hours to obtain a coating solution for forming a charge generation layer. The coating solution for forming a charge generation layer was applied by immersion onto a base layer and dried at a temperature of 110°C to form a charge generation layer with a thickness of 0.2 μm.

[0143] [Formation of charge transport layer] Solvents A and B of the types shown in Tables 1 and 2 were mixed in the mass ratios shown in Tables 1 and 2 to prepare a mixed solvent. To this mixed solvent, binder resins of the weight-average molecular weight Mw and types shown in Tables 1 and 2, and 7.2 parts of charge transport material CTM-1 were added and stirred to obtain a coating solution for forming a charge transport layer. The various conditions for the coating solution for forming a charge transport layer are as shown in Tables 1 and 2. Next, the obtained coating solution for forming the charge transport layer was applied to the charge generation layer by immersion. During this process, the withdrawal speed of the immersion coating was controlled as the coating speed as shown in Tables 1 and 2. The coating film was then dried to form a charge transport layer with a thickness of 40 μm. The drying conditions are as shown in Tables 1 and 2. During this process, the heating rate was kept constant at the average heating rate shown in Tables 1 and 2. In this way, a photoreceptor was obtained in which the undercoat layer, charge generation layer, and charge transport layer were arranged on an aluminum substrate.

[0144] In Tables 1 and 2, the polyarylate resin referred to as PAR is the polyarylate resin (1) having the following structure. The structure of the charge transport material CTM-1 is as follows. [ka]

[0145] In Tables 1 and 2, the polycarbonate resin referred to as PC is a polyarylate resin (1) having the following structure. [ka]

[0146] <Evaluation of photoreceptor performance> Each example's photoreceptor was mounted in an electrophotographic image forming apparatus, the DocuCentre-V C7775 (manufactured by Fujifilm Business Innovation Co., Ltd.), and 40,000 full-screen cyan halftone images with a density of 30% were continuously printed on A3-sized plain paper under conditions of 24°C and 55% relative humidity.

[0147] [Coating defects] For each example of electrophotographic photoreceptor, the surface of the photoreceptor (i.e., the surface of the charge transport layer) was visually inspected, and the details of coating defects were evaluated according to the following criteria. The results are shown in Tables 1 and 2. S: Surface observation of 10 photoreceptors revealed no coating defects on any of them. A: One blister was observed in a small area of ​​one of the 10 photoreceptors, but it is within acceptable limits. B: Two areas of blistering were observed in a portion of the 10 photoreceptors, but these are within acceptable limits. C: Of the 10 photoreceptors, three to four blisters were observed in certain areas, but this is within the acceptable range. D: In 10 photoreceptors, swelling and cracks were observed in multiple areas.

[0148] [Foreign substance contamination] For each example of electrophotographic photoreceptor, the HEPA filter on the air supply side of the coating chamber was removed to simulate the risk of foreign matter contamination under stressful conditions, and the likelihood of foreign matter adhering was evaluated according to the following criteria. The results are shown in Tables 1 and 2. S: Surface observation of 10 photoreceptors revealed no coating defects on any of them. A: Among the 10 photoreceptors, foreign matter was found in one to three locations in some areas, but this is within acceptable limits. B: Of the 10 photoreceptors, foreign matter was found in 4 to 6 locations in some areas, but this is within the acceptable range. C: Among the 10 photoreceptors, foreign matter was found in 7 to 9 locations in certain areas, but this is within the acceptable range. D: In a total of 10 photoreceptors, foreign matter was found adhering to multiple areas in several of them.

[0149] [Abrasion resistance] Before and after image formation, the thickness of the charge transport layer was measured at four locations at 90° intervals in the circumferential direction at the center of the photoreceptor in the axial direction. An electromagnetic film thickness gauge (Fischer Instruments, Permascope) was used for measurement. The layer thickness at the four locations was averaged, and the amount of wear was calculated by subtracting the average value after image formation from the average value before image formation. The wear rate (nm / kcy) was calculated by dividing the amount of wear by the number of photoreceptor cycles, and evaluated according to the following criteria. The results are shown in Tables 1 and 2. S: Wear rate less than 15 nm / kcy A: Wear rate between 15 nm / kcy and less than 20 nm / kcy B: Wear rate of 20 nm / kcy or more, less than 30 nm / kcy C: Wear rate of 30 nm / kcy or more, less than 35 nm / kcy. D: Wear rate of 35 nm / kcy or higher

[0150] [productivity] The faster the withdrawal speed when applying the charge transport layer by immersion, the faster the production line speed and the higher the productivity. The withdrawal speed when applying the charge transport layer by immersion was classified as follows. The results are shown in Tables 1 and 2. S: Lifting speed of 150 mm / min or more A: Lifting speed less than 150 mm / min, 135 mm / min or more B: Lifting speed less than 135 mm / min, 120 mm / min or more C: Lifting speed less than 120 mm / min, or 105 mm / min or more. D: Lifting speed less than 105 mm / min

[0151] <Examples 5-7, 10-20, 22, 24-30, 33, 39-41, Comparative Example 2, Comparative Example 4, Comparative Example 6-7, and Comparative Example 9-11> [Formation of the lower layer] As a conductive substrate, prepare an aluminum cylindrical tube with an outer diameter of 30 mm, a length of 365 mm, and a wall thickness of 2 mm.

[0152] Zinc oxide (average particle size 70 nm, specific surface area 15 m²) 2 100 parts of (Teika Co., Ltd.) are mixed with 500 parts of toluene and stirred. 1.3 parts of a silane coupling agent (product name: KBM603, Shin-Etsu Chemical Co., Ltd., N-2-(aminoethyl)-3-aminopropyltrimethoxysilane) are added and stirred for 2 hours. Then, the toluene is removed by distillation under reduced pressure, and the mixture is baked at 120°C for 3 hours to obtain zinc oxide surface-treated with the silane coupling agent.

[0153] 110 parts of surface-treated zinc oxide are mixed with 500 parts of tetrahydrofuran by stirring. A solution of 0.6 parts of alizarin dissolved in 50 parts of tetrahydrofuran is added, and the mixture is stirred at 50°C for 5 hours. The solids are then filtered off by vacuum filtration, and the mixture is dried under reduced pressure at 60°C to obtain alizarin-treated zinc oxide.

[0154] 100 parts of a solution prepared by dissolving 60 parts alizarin-modified zinc oxide, 13.5 parts curing agent (blocked isocyanate, trade name: Sumijule 3175, Sumitomo Bayer Urethane Co., Ltd.), and 15 parts butyral resin (trade name: Esrec BM-1, Sekisui Chemical Co., Ltd.) in 68 parts methyl ethyl ketone, are mixed with 5 parts methyl ethyl ketone and dispersed in a sand mill for 2 hours using 1 mm diameter glass beads to obtain a dispersion. To the dispersion, 0.005 parts dioctyl tin dilaurate as a catalyst and 4 parts silicone resin particles (trade name: Tospar 145, Momentive Performance Materials, Inc.) are added to obtain a coating solution for forming an undercoat. The undercoat solution is applied to the outer surface of a conductive substrate by immersion coating and dried and cured at 170°C for 40 minutes to form an undercoat with a thickness of 20 μm.

[0155] [Formation of charge generation layer] • Charge generating material: Hydroxygallium phthalocyanine...3 parts • Binding resin: Vinyl chloride / vinyl acetate copolymer... 2 parts • Solvent: n-butyl acetate ···66.5 parts • Solvent: Methyl isobutyl ketone ···28.5 parts The above materials are mixed and dispersed using 1 mm diameter glass beads in a sand mill for 4 hours to obtain a coating solution for forming a charge generation layer. The coating solution for forming a charge generation layer is applied by immersion onto the base layer and dried at a temperature of 110°C to form a charge generation layer with a thickness of 0.2 μm.

[0156] [Formation of charge transport layer] Mix solvent A and solvent B of the types shown in Tables 1 and 2 in the mass ratios shown in Tables 1 and 2 to prepare a mixed solvent. Add the binder resin of the weight-average molecular weight Mw and type shown in Tables 1 and 2, and 7.2 parts of charge transport material CTM-1 to this mixed solvent, and stir-mix to obtain a coating solution for forming the charge transport layer. The various conditions for the coating solution for forming the charge transport layer are as shown in Tables 1 and 2. Next, the obtained charge transport layer forming coating solution is applied to the charge generation layer by immersion. Then, the coating film is dried to form a charge transport layer with a thickness of 40 μm. The drying conditions are as shown in Tables 1 and 2. During this process, the heating rate is kept constant at the average heating rate shown in Tables 1 and 2. In this way, a photoreceptor is obtained in which the undercoat layer, charge generation layer, and charge transport layer are arranged on an aluminum substrate.

[0157] In Tables 1 and 2, the polyarylate resin referred to as PAR is the polyarylate resin (1) having the following structure. The structure of the charge transport material CTM-1 is as follows. [ka]

[0158] In Tables 1 and 2, the polycarbonate resin referred to as PC is a polyarylate resin (1) having the following structure. [ka]

[0159] <Evaluation of photoreceptor performance> For the photoreceptors of Examples 5-7, 10-20, 22, 24-30, 33, 39-41, Comparative Example 2, Comparative Example 4, Comparative Example 6-7, and Comparative Example 9-11, the coating defects, foreign matter contamination, abrasion resistance, and productivity were evaluated by simulation. The evaluation criteria were the same as those described above. The results are shown in Tables 1 and 2.

[0160] [Table 1]

[0161] [Table 2]

[0162] As shown in Tables 1 and 2, the manufacturing method of the electrophotographic photoreceptor in the examples was found to suppress both coating defects such as blistering and cracking on the surface of the charge transport layer and foreign matter contamination on the surface of the coating film, compared to the manufacturing method of the electrophotographic photoreceptor in the comparative example.

[0163] The method for manufacturing an electrophotographic photoreceptor according to this disclosure includes the following embodiments. (((1))) Applying a coating liquid for forming a charge generation layer onto a conductive substrate and drying the coating film to form a charge generation layer, The process involves applying a coating liquid for forming a charge transport layer to the surface of the charge generating layer, and drying the coating film to form a charge transport layer. The coating liquid for forming the charge transport layer comprises a binder resin, a charge transport material, and a solvent. The ratio (V / SC) of the vibrational viscosity V (mPa·s) to the solid content SC (mass%) of the charge transport layer forming coating liquid at 20°C is 3,000 or more and 8,000 or less. A method for manufacturing an electrophotographic photoreceptor, wherein the drying conditions of the coating film of the charge transport layer forming coating solution satisfy the relationship of the following equation (T1). Formula (T1): 10≦(T DRY -B MAX ) / B AVG ×H R ≤30 (In the above formula (T1), T DRY This is the average drying temperature (°C). B MAX This is the boiling point (°C) of the solvent with the highest boiling point contained in the coating solution for forming the charge transport layer. B AVG This is the average boiling point (°C) of all solvents contained in the coating solution for forming the charge transport layer. H R This represents the average heating rate (°C / min) when drying the coating film of the charge transport layer forming solution. (((2))) The average rate of temperature rise H when drying the coating film of the charge transport layer forming coating liquid. R A method for manufacturing an electrophotographic photoreceptor as described in (((1))) above, wherein the temperature (°C) is 3°C / min or more and 40°C / min or less. (((3))) The average rate of temperature rise H when drying the coating film of the charge transport layer forming coating liquid.R A method for manufacturing an electrophotographic photoreceptor according to (((2))) above, wherein the temperature (°C) is 15°C / min or more and 25°C / min or less. (((4))) A method for manufacturing an electrophotographic photoreceptor according to any one of (((1))) to (((3))), wherein the amount of residual solvent V1 in the coating film after applying the charge transport layer forming coating solution and before drying is greater than 30% by mass and less than 70% by mass. (((5))) A method for producing an electrophotographic photoreceptor according to any one of (((1))) to (((4))) above, wherein the content of the binder resin having a weight-average molecular weight Mw of 80,000 or more and 130,000 or less in the total binder resin is 20% by mass or more and 100% by mass or less. (((6))) The method for manufacturing an electrophotographic photoreceptor according to any one of (((1))) to (((5))), wherein the vibrational viscosity V of the charge transport layer forming coating liquid at 20°C is 700 mPa·s or more and 1200 mPa·s or less. (((7))) The method for manufacturing an electrophotographic photoreceptor according to (((6))), wherein the vibrational viscosity V of the charge transport layer forming coating liquid at 20°C is 700 mPa·s or more and 1000 mPa·s or less. (((8))) A method for producing an electrophotographic photoreceptor according to any one of (((1))) to (((7))) above, wherein the value of the solid content SC is 15% by mass or more and 22% by mass or less. (((9))) The average boiling point B of all solvents contained in the charge transport layer forming coating liquid. AVG A method for manufacturing an electrophotographic photoreceptor according to any one of the above (((1))) to (((8))), wherein the value of is 65°C or more and 80°C or less.

[0164] According to (((1))), a method for manufacturing an electrophotographic photoreceptor is provided that suppresses coating defects such as blistering and cracking on the surface of the charge transport layer and the inclusion of foreign matter on the coating film surface, compared to cases where "the ratio (V / SC) of the vibrational viscosity V (mPa·s) of the charge transport layer forming coating liquid at 20°C to the solid content SC (mass%) is less than 3,000 or greater than 8,000" or "the drying conditions after coating the charge transport layer forming coating liquid do not satisfy the relationship of formula (T1)". According to (((2))), the average heating rate H when drying the coating film of the charge transport layer forming coating liquid R A method for manufacturing an electrophotographic photoreceptor is provided that suppresses coating defects such as blistering and cracking on the surface of the charge transport layer and the inclusion of foreign matter on the coating film surface, compared to cases where the temperature (°C) is less than 3°C / min or greater than 40°C / min. According to (((3))), the average heating rate H when drying the coating film of the charge transport layer forming coating liquid R A method for manufacturing an electrophotographic photoreceptor is provided that suppresses coating defects such as blistering and cracking on the surface of the charge transport layer and the inclusion of foreign matter on the coating film surface, compared to cases where the temperature (°C) is less than 15°C / min or greater than 25°C / min. According to (((4))), a method for manufacturing an electrophotographic photoreceptor is provided that suppresses coating defects such as blistering and cracking on the surface of the charge transport layer and the inclusion of foreign matter on the surface of the coating film, compared to the case where the amount of residual solvent V1 in the coating film after applying the charge transport layer forming coating liquid and before drying is 30% by mass or less or 70% by mass or more. According to (((5))), the method for producing an electrophotographic photoreceptor according to any one of (((1))) to (((4))), wherein the content of the binder resin having a weight-average molecular weight Mw of 80,000 or more and 130,000 or less in the total binder resin is 20% by mass or more and 100% by mass or less. According to (((6))), a method for manufacturing an electrophotographic photoreceptor is provided that suppresses coating defects such as blistering and cracking on the surface of the charge transport layer and the inclusion of foreign matter on the coating film surface, compared to cases where the vibrational viscosity V of the coating liquid for forming the charge transport layer at 20°C is less than 700 mPa·s or greater than 1200 mPa·s. According to (((7))), a method for manufacturing an electrophotographic photoreceptor is provided that suppresses coating defects such as blistering and cracking on the surface of the charge transport layer and the inclusion of foreign matter on the coating film surface, compared to cases where the vibrational viscosity V of the coating liquid for forming the charge transport layer at 20°C is less than 700 mPa·s or greater than 1000 mPa·s. According to ((8)), a method for manufacturing an electrophotographic photoreceptor is provided that suppresses coating defects such as blistering and cracking on the surface of the charge transport layer and the inclusion of foreign matter on the coating film surface, compared to cases where the solid content SC is less than 15% by mass or greater than 22% by mass. According to (((9))), the average boiling point B of all solvents contained in the charge transport layer forming coating liquid AVG A method for manufacturing an electrophotographic photoreceptor is provided that suppresses coating defects such as blistering and cracking on the surface of the charge transport layer and the inclusion of foreign matter on the coating film surface, compared to cases where the value is less than 65°C or more than 80°C.

[0165] 1 conductive substrate, 2 subbing layer, 3 charge generation layer, 4 charge transport layer, 5 photosensitive layer, 10A photoreceptor

Claims

1. The process involves applying a charge generation layer forming solution onto a conductive substrate, drying the coating film, and forming a charge generation layer. The process involves applying a coating liquid for forming a charge transport layer to the surface of the charge generating layer, and drying the coating film to form a charge transport layer. The coating liquid for forming the charge transport layer comprises a binder resin, a charge transport material, and a solvent. The ratio (V / SC) of the vibrational viscosity V (mPa·s) of the charge transport layer forming coating liquid at 20°C to the solid content SC (mass%) is 3,000 or more and 8,000 or less. A method for manufacturing an electrophotographic photoreceptor, wherein the drying conditions of the coating film of the charge transport layer forming coating solution satisfy the relationship of the following formula (T1). Formula (T1): 10 ≤ (T ＡＶＧ , Ｒ - B ＭＡＸ ) / B ＡＶＧ × H Ｒ ≤ 30 (In the above formula (T1), T ＤＲＹ はAverage drying temperature (℃), B ＭＡＸ This refers to the boiling point (°C) of the solvent with the highest boiling point contained in the coating solution for forming the charge transport layer. B ＡＶＧ This is the average boiling point (°C) of all solvents contained in the coating solution for forming the charge transport layer. H Ｒ This represents the average heating rate (°C / min) when drying the coating film of the charge transport layer forming solution.

2. The average temperature increase rate H Ｒ (°C) when drying the coating film of the coating liquid for forming the charge transport layer is 3 °C / min or more and 40 °C / min or less, and the method for manufacturing an electrophotographic photoreceptor according to claim 1.

3. The average heating rate H when drying the coating film of the charge transport layer forming coating liquid. Ｒ A method for manufacturing an electrophotographic photoreceptor according to claim 2, wherein the temperature (°C) is 15°C / min or more and 25°C / min or less.

4. A method for manufacturing an electrophotographic photoreceptor according to claim 1 or 2, wherein the amount of residual solvent V1 in the coating film after applying the charge transport layer forming coating solution and before drying is greater than 30% by mass and less than 70% by mass.

5. A method for producing an electrophotographic photoreceptor according to claim 1 or claim 2, wherein the content of the binder resin having a weight-average molecular weight Mw of 80,000 or more and 130,000 or less is 20% by mass or more and 100% by mass or less of the total binder resin.

6. A method for manufacturing an electrophotographic photoreceptor according to claim 1 or claim 2, wherein the vibrational viscosity V of the charge transport layer forming coating liquid at 20°C is 700 mPa·s or more and 1200 mPa·s or less.

7. The method for manufacturing an electrophotographic photoreceptor according to claim 6, wherein the vibrational viscosity V of the coating liquid for forming the charge transport layer at 20°C is 700 mPa·s or more and 1000 mPa·s or less.

8. A method for producing an electrophotographic photoreceptor according to claim 1 or claim 2, wherein the value of the solid content SC is 15% by mass or more and 22% by mass or less.

9. The average boiling point B of all solvents contained in the charge transport layer forming coating liquid. ＡＶＧ A method for manufacturing an electrophotographic photoreceptor according to claim 1 or claim 2, wherein the value of is 65°C or higher and 80°C or lower.

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