Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

This electrophotographic photoreceptor comprises an electrically conductive substrate (2), a photosensitive layer (3), and a protective layer (5). The photosensitive layer (3) contains a charge generating agent and a hole transport agent. The protective layer (5) is an outermost surface layer of the electrophotographic photoreceptor. The protective layer (5) contains first particles having n-type conductivity and second particles not having n-type conductivity. The volume resistivity of the second particles is preferably higher than the volume resistivity of the first particles.

Description

[Technical Field]

[0001] The present invention relates to an electrophotographic photoreceptor, a process cartridge, and an image forming apparatus. [Background technology]

[0002] When images are repeatedly formed using an image forming apparatus equipped with an electrophotographic photoreceptor, the electrophotographic photoreceptor may gradually wear down. To suppress wear and extend the lifespan of the electrophotographic photoreceptor, a hard protective layer may be provided on the surface of the electrophotographic photoreceptor. For example, the protective layer provided on the electrophotographic photoreceptor described in Patent Document 1 contains a composition. This composition is obtained by reacting silica fine particles having at least polymerizable unsaturated groups with an organic compound having reactive groups capable of forming chemical bonds with polymerizable unsaturated groups. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2010-14948 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, in order to manufacture the electrophotographic photoreceptor described in Patent Document 1, it is necessary to react silica fine particles having polymerizable unsaturated groups with an organic compound having reactive groups capable of forming chemical bonds with polymerizable unsaturated groups. Therefore, the manufacturing process for the electrophotographic photoreceptor described in Patent Document 1 is complicated. Furthermore, our investigations have revealed that the electrophotographic photoreceptor described in Patent Document 1 has room for improvement in terms of sensitivity characteristics and dot reproducibility in the formed image.

[0005] The present invention has been made in view of the above problems, and its objective is to provide an electrophotographic photoreceptor, a process cartridge, and an image forming apparatus that can be easily manufactured, have excellent sensitivity characteristics, and can form images with excellent dot reproducibility. [Means for solving the problem]

[0006] The electrophotographic photoreceptor of the present invention comprises a conductive substrate, a photosensitive layer, and a protective layer. The photosensitive layer contains a charge generating agent and a hole transporting agent. The protective layer is the outermost layer of the electrophotographic photoreceptor. The protective layer contains first particles having n-type conductivity and second particles not having n-type conductivity.

[0007] The process cartridge of the present invention comprises at least one selected from the group consisting of a charging device, an exposure device, a developing device, a transfer device, a cleaning member, a rubbing roller, and a static elimination device, and the electrophotographic photoreceptor.

[0008] The image forming apparatus of the present invention comprises an image carrier, a charging device for charging the surface of the image carrier, an exposure device for exposing the charged surface of the image carrier to form an electrostatic latent image on the surface of the image carrier, a developing device for supplying toner to the surface of the image carrier to develop the electrostatic latent image as a toner image, and a transfer device for transferring the toner image from the image carrier to a transfer target. The image carrier is the electrophotographic photoreceptor described above. [Effects of the Invention]

[0009] The electrophotographic photoreceptor, process cartridge, and image forming apparatus of the present invention can be easily manufactured, have excellent sensitivity characteristics, and can form images with excellent dot reproducibility. [Brief explanation of the drawing]

[0010] [Figure 1] This is a partial cross-sectional view of a single-layer electrophotographic photoreceptor, which is an example of an electrophotographic photoreceptor according to the first embodiment of the present invention. [Figure 2] This is a partial cross-sectional view of a single-layer electrophotographic photoreceptor, which is an example of an electrophotographic photoreceptor according to the first embodiment of the present invention. [Figure 3] This is a partial cross-sectional view of a stacked electrophotographic photoreceptor, which is an example of an electrophotographic photoreceptor according to the first embodiment of the present invention. [Figure 4] This is a partial cross-sectional view of a stacked electrophotographic photoreceptor, which is an example of an electrophotographic photoreceptor according to the first embodiment of the present invention. [Figure 5] This is a partial cross-sectional view of a stacked electrophotographic photoreceptor, which is an example of an electrophotographic photoreceptor according to the first embodiment of the present invention. [Figure 6] This figure shows an example of an image forming apparatus according to a second embodiment of the present invention. [Figure 7] Figure 6 shows an example of the configuration of a developing apparatus. [Modes for carrying out the invention]

[0011] The embodiments of the present invention will be described in detail below. However, the present invention is not limited to the following embodiments and can be implemented with appropriate modifications within the scope of the object of the present invention.

[0012] First, let's explain the terminology used in this specification. Acrylics and methacrylics are sometimes collectively referred to as "(meth)acrylics." Unless otherwise specified, the hydroxyl value is the value measured according to "JIS (Japanese Industrial Standards) K0070-1992." Unless otherwise specified, the number-mean primary particle diameter is the number-mean value of the equivalent circle diameter (Heywood diameter: the diameter of a circle having the same area as the projected area of ​​the primary particle) of primary particles measured using a scanning electron microscope. For example, the number-mean primary particle diameter is the number-mean value of the equivalent circle diameter of 100 primary particles. Unless otherwise specified, the BET specific surface area is the value measured by the BET method using nitrogen adsorption, in accordance with "JIS (Japanese Industrial Standards) Z8830:2001 Method for measuring the specific surface area of ​​powders (solids) by gas adsorption." The compound name is sometimes followed by "system" to collectively refer to the compound and its derivatives. Also, when "system" is followed by a compound name to represent a polymer name, it means that the repeating units of the polymer originate from the compound or its derivative. Furthermore, "general formula" and "chemical formula" will be collectively referred to as "formula." In the description of a formula, "each independently" means that they may represent the same group or different groups. "At least one of A, B, and C" and "at least one of A, B, and C" mean "at least one selected from the group consisting of A, B, and C." "At least one of A, B, and C" means "at least one selected from the group consisting of A, B, and C." Note that A, B, and C are examples and may be replaced with other terms as appropriate. Unless otherwise specified, each component described herein may be used alone or in combination of two or more. The terms used in this specification have now been explained.

[0013] [First Embodiment: Electrophotographic Photoreceptor] A first embodiment of the present invention relates to an electrophotographic photoreceptor (hereinafter sometimes referred to as a photoreceptor). The photoreceptor of the first embodiment comprises a conductive substrate, a photosensitive layer, and a protective layer. The photosensitive layer contains a charge generating agent and a hole transporting agent. The protective layer is the outermost surface layer of the photoreceptor. The protective layer contains first particles having n-type conductivity and second particles not having n-type conductivity.

[0014] The photoreceptor of the first embodiment, by having the above configuration, can form images with excellent sensitivity characteristics and excellent dot reproducibility. The reason for this is presumed to be as follows. Note that dot reproducibility is the characteristic that dots can be printed on the recording medium in the same position as the dots in the image input to the image forming apparatus.

[0015] The protective layer of the photoreceptor in the first embodiment contains first particles having n-type conductivity. In this specification, "n-type conductivity" refers to conductivity in which the primary charge carrier is electrons. The inclusion of first particles having n-type conductivity in the protective layer improves the sensitivity characteristics.

[0016] For example, if the photoreceptor is a positively charged photoreceptor, the outer surface of the protective layer (the surface opposite to the inner surface on the conductive substrate side) is positively charged by the charging device. In the first embodiment, since the protective layer contains first particles having n-type conductivity, electrons are suitably transported from the inner surface to the outer surface of the protective layer by the first particles. Then, the holes on the outer surface of the protective layer that are added by the charging are suitably canceled out by the transported electrons. As a result, the sensitivity characteristics of the photoreceptor are improved.

[0017] On the other hand, for example, if the photoreceptor is a negatively charged photoreceptor, the outer surface of the protective layer is negatively charged by a charging device. In the first embodiment, since the protective layer contains first particles having n-type conductivity, electrons on the outer surface of the protective layer that are imparted by the charging are accepted by the first particles. This makes it easier for holes to reach the outer surface from the inner surface of the protective layer. Then, the electrons on the outer surface of the protective layer are suitably canceled out by the holes that have reached it. As a result, the sensitivity characteristics of the photoreceptor are improved.

[0018] However, if the protective layer contains only first particles having n-type conductivity, lateral charge flow may occur between the first particles. This lateral charge flow can cause a misalignment between the dot positions of the image input to the image forming apparatus and the dot positions of the electrostatic latent image formed on the surface of the photoreceptor. As a result, the dot reproducibility in the formed image may decrease. Therefore, in the first embodiment, the protective layer contains second particles that do not have n-type conductivity in addition to the first particles. Since the second particles do not have n-type conductivity, lateral charge flow can be suppressed. As a result, the dot reproducibility in the formed image is improved.

[0019] The above explains why the photoreceptor of the first embodiment can form images with excellent sensitivity characteristics and dot reproducibility. The photoreceptor will be described further below.

[0020] The photoreceptor is, for example, a single-layer electrophotographic photoreceptor (hereinafter sometimes referred to as a single-layer photoreceptor) or a multilayer electrophotographic photoreceptor (hereinafter sometimes referred to as a multilayer photoreceptor).

[0021] The structure of a single-layer photoreceptor 1, an example of a photoreceptor, will be described below with reference to Figures 1 and 2. Figures 1 and 2 show partial cross-sectional views of the single-layer photoreceptor 1, respectively. As shown in Figure 1, the single-layer photoreceptor 1 comprises, for example, a conductive substrate 2, a photosensitive layer 3, and a protective layer 5. The photosensitive layer 3 is a single layer. Hereinafter, "single-layer photosensitive layer" may be referred to as "single-layer photosensitive layer." In the example shown in Figure 1, a single-layer photosensitive layer 3a is provided on the conductive substrate 2, and a protective layer 5 is provided on the single-layer photosensitive layer 3a. The single-layer photosensitive layer 3a is directly provided on the conductive substrate 2. The protective layer 5 is the outermost layer of the single-layer photoreceptor 1.

[0022] As shown in Figure 2, the single-layer photoreceptor 1 may further include an intermediate layer 4 (undercoat layer) in addition to the conductive substrate 2, the single-layer photoreceptor layer 3a, and the protective layer 5. In the example shown in Figure 2, the intermediate layer 4 is provided on the conductive substrate 2, the single-layer photoreceptor layer 3a is provided on the intermediate layer 4, and the protective layer 5 is provided on the single-layer photoreceptor layer 3a. The single-layer photoreceptor layer 3a is provided on the conductive substrate 2 via the intermediate layer 4.

[0023] The thickness of the single-layer photosensitive layer 3a is not particularly limited, but is preferably 5 μm or more and 100 μm or less, and more preferably 10 μm or more and 50 μm or less.

[0024] The thickness of the protective layer 5 is not particularly limited, but is preferably 2 μm or more, more preferably 2 μm to 30 μm, even more preferably 2 μm to 10 μm, and even more preferably 2 μm to 4 μm. In the example shown in Figures 1 and 2, the protective layer 5 is a single layer. However, the protective layer 5 may be multiple layers. If the protective layer 5 is multiple layers, at least the outermost layer of the multiple layers contains the first and second particles. The structure of a single-layer photoreceptor 1, which is an example of a photoreceptor, has been described above with reference to Figures 1 and 2.

[0025] The structure of a multilayer photoreceptor 10, an example of a photoreceptor, will be described below with reference to Figures 3 to 5. Figures 3 to 5 each show a partial cross-sectional view of the multilayer photoreceptor 10. As shown in Figure 3, the multilayer photoreceptor 10 comprises, for example, a conductive substrate 2, a photosensitive layer 3, and a protective layer 5. The photosensitive layer 3 includes a charge generation layer 3b and a charge transport layer 3c. In the example shown in Figure 3, the charge generation layer 3b is provided on the conductive substrate 2, the charge transport layer 3c is provided on the charge generation layer 3b, and the protective layer 5 is provided on the charge transport layer 3c. However, as shown in Figure 4, in the multilayer photoreceptor 10, the charge transport layer 3c may be provided on the conductive substrate 2, the charge generation layer 3b may be provided on the charge transport layer 3c, and the protective layer 5 may be provided on the charge generation layer 3b. In the examples shown in Figures 3 and 4, the photosensitive layer 3 is provided directly on the conductive substrate 2. The protective layer 5 is the outermost layer of the stacked photoreceptor 10.

[0026] As shown in Figure 5, the stacked photoreceptor 10 may further include an intermediate layer 4 (undercoat layer) in addition to the conductive substrate 2, the photosensitive layer 3, and the protective layer 5. In the example shown in Figure 5, the intermediate layer 4 is provided on the conductive substrate 2, the charge generation layer 3b is provided on the intermediate layer 4, the charge transport layer 3c is provided on the charge generation layer 3b, and the protective layer 5 is provided on the charge transport layer 3c. The photosensitive layer 3 (for example, the charge generation layer 3b) is provided on the conductive substrate 2 via the intermediate layer 4.

[0027] The thickness of the charge generation layer 3b is not particularly limited, but is preferably 0.01 μm or more and 5 μm or less, and more preferably 0.1 μm or more and 3 μm or less. In the examples shown in Figures 3 to 5, the charge generation layer 3b is a single layer. However, the charge generation layer 3b may consist of multiple layers.

[0028] The thickness of the charge transport layer 3c is not particularly limited, but is preferably 2 μm to 100 μm, and more preferably 5 μm to 50 μm. In the examples shown in Figures 3 to 5, the charge transport layer 3c is a single layer. However, the charge transport layer 3c may consist of multiple layers.

[0029] The protective layer 5 of the stacked photoreceptor 10 is the same as the protective layer 5 of the single-layer photoreceptor 1, so its explanation is omitted. The structure of the stacked photoreceptor 10, which is an example of a photoreceptor, has been explained above with reference to Figures 3 to 5.

[0030] <Protective layer> The protective layer contains a first particle and a second particle. Preferably, the protective layer further contains a resin. Hereinafter, "resin contained in the protective layer" may be referred to as "protective layer resin". The protective layer may further contain, if necessary, one or both of a polymerization initiator and / or an additive.

[0031] (First particle and second particle) The first particle has n-type conductivity. That is, the first particle has conductivity in which the main charge carrier is an electron. On the other hand, the second particle does not have n-type conductivity. That is, the second particle does not have conductivity in which the main charge carrier is an electron. The second particle does not have n-type conductivity, but rather has, for example, p-type conductivity, intrinsic conductivity, or insulating properties. In this specification, p-type conductivity refers to conductivity in which the main charge carrier is a hole.

[0032] In order to effectively suppress the lateral flow of charge between the first particles, it is preferable that the volume resistivity of the second particle is higher than that of the first particle.

[0033] To effectively suppress the lateral flow of charge between the first particles, the volume resistivity of the first particle-containing sheet containing the first particles is preferably 0.1 Ω·cm or more and less than 12.0 Ω·cm, and more preferably 9.0 Ω·cm or more and 11.0 Ω·cm or less. The first particle-containing sheet is composed of 9.3 parts by mass of first particles, 89.0 parts by mass of photocurable resin, 10.0 parts by mass of polymerization initiator, and 1.0 part by mass of leveling agent.

[0034] To effectively suppress the lateral flow of charge between the first particles, the volume resistivity of the second particle-containing sheet containing the second particles is preferably 12.0 Ω·cm or more and 50.0 Ω·cm or less, and more preferably 12.5 Ω·cm or more and 14.5 Ω·cm or less. The second particle-containing sheet is composed of 9.3 parts by mass of second particles, 89.0 parts by mass of photocurable resin, 10.0 parts by mass of polymerization initiator, and 1.0 part by mass of leveling agent.

[0035] For the first particle-containing sheet and the second particle-containing sheet, the components other than the first and second particles (for example, 89.0 parts by mass of photocurable resin, 10.0 parts by mass of polymerization initiator, and 1.0 part by mass of leveling agent) are identical. Therefore, the relative volume resistivity of the first particle-containing sheet and the second particle-containing sheet corresponds to the relative volume resistivity of the first and second particles. For example, if the volume resistivity of the second particle-containing sheet is higher than that of the first particle-containing sheet, then the volume resistivity of the second particle will be higher than that of the first particle. Volume resistivity is measured, for example, by applying a voltage of +100V and a frequency of 33.3mHz using an electrical resistance meter in an environment with a temperature of 23°C and a relative humidity of 50%RH.

[0036] Examples of the first particles include metal oxide particles having n-type conductivity, more specifically, zinc oxide particles, titanium oxide particles, and tin oxide particles. In order to improve the sensitivity characteristics of the photoreceptor, tin oxide particles are preferred as the first particles. The tin oxide particles may be undoped. However, in order to enhance n-type conductivity and improve the sensitivity characteristics of the photoreceptor, the tin oxide particles are preferably doped. As doped tin oxide particles, phosphorus-doped tin oxide particles or antimond-doped tin oxide particles are preferred.

[0037] To improve dot reproducibility in the formed image, alumina particles, silica particles, or silicone particles are preferred as the second particle.

[0038] One or both of the first and second particles do not need to have polymerizable functional groups that can react with the photocurable resin. Because the protective layer contains the first particles, the photoreceptor of the first embodiment can improve sensitivity characteristics even if one or both of the first and second particles do not react with the photocurable resin.

[0039] The BET specific surface area of ​​the first and second particles is 30 m². 2 / g or more 200m 2 It is preferable that it be less than or equal to / g, 45m 2 / g or more 130m 2It is more preferable that it be less than or equal to / g, 70m 2 / g or more 130m 2 It is even more preferable that the value be less than or equal to / g.

[0040] The number-average primary particle diameter of the first and second particles is preferably 5 nm to 500 nm, more preferably 30 nm to 200 nm, and even more preferably 100 nm to 200 nm.

[0041] If the mass of the first particle is M1 and the mass of the second particle is M2, then the ratio of the mass of the first particle (M1) to the mass of the second particle (M2), M1 / M2, is preferably 1 or more and 10 or less, more preferably 1 or more and 5 or less, and even more preferably 2 or more and 3 or less.

[0042] The content of the first particles in the protective layer is preferably 1% by mass or more and 15% by mass or less, and more preferably 5% by mass or more and 10% by mass or less, relative to the mass of the protective layer. The content of the second particles in the protective layer is preferably 1% by mass or more and less than 5% by mass, relative to the mass of the protective layer. The total content of the first and second particles in the protective layer is preferably 1% by mass or more and 20% by mass or less, and more preferably 10% by mass or more and 15% by mass or less, relative to the mass of the protective layer.

[0043] (Protective layer resin) Examples of protective layer resins include photocurable resins, thermoplastic resins, and thermosetting resins. Photocurable resins are preferred as the protective layer resin. Examples of photocurable resins include (meth)acrylic resins and epoxy resins. Photocurable resins have polymerizable functional groups. (Meth)acrylic resins have vinyl groups as polymerizable functional groups. Epoxy resins have epoxy groups as polymerizable functional groups. (Meth)acrylic resins are preferred as photocurable resins because stopping ultraviolet irradiation stops the photocuring reaction, making it easy to control the progress of the photocuring reaction.

[0044] The photocurable resin preferably has repeating units derived from a compound having two or more polymerizable functional groups and repeating units derived from a compound having one polymerizable functional group. Hereinafter, "compounds having two or more polymerizable functional groups" may be referred to as "polyfunctional monomers," and "compounds having one polymerizable functional group" may be referred to as "monofunctional monomers."

[0045] As the polyfunctional monomer, (meth)acrylic acid esters having 2 to 6 vinyl groups are preferred. Hereinafter, "(meth)acrylic acid esters having 2 to 6 vinyl groups" may be referred to as "polyfunctional acrylic acid esters." The polyfunctional acrylic acid esters preferably have 3 to 6 vinyl groups.

[0046] Examples of polyfunctional acrylic acid esters include trimethylolpropane triacrylate, glycerin triacrylate, tris-(2-acryloxyethyl) isocyanurate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate. These polyfunctional acrylic acid esters may be ethoxylated.

[0047] The polyfunctional acrylic acid ester is preferably at least one selected from the group consisting of pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate, and more preferably one or two. The polyfunctional acrylic acid ester is preferably a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate. The content of pentaerythritol triacrylate in the mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate is preferably 40% by mass or more and 60% by mass or less. The polyfunctional acrylic acid ester is also preferably a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate.

[0048] Pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate are compounds represented by formulas (EA-1), (EA-2), (EA-3), and (EA-4), respectively.

[0049] [ka]

[0050] Through a photocuring reaction (more specifically, an addition polymerization reaction of vinyl groups), repeating units represented by formulas (EA-1a), (EA-2a), (EA-3a), and (EA-4a) are formed from the monomer compounds represented by formulas (EA-1), (EA-2), (EA-3), and (EA-4), respectively.

[0051] [ka]

[0052] Y in equation (EA-1a) 1 ~Y 3At least one of them represents a group represented by the formula (Y-b), and Y 1 ~Y 3 The rest of them represent a group represented by the formula (Y-a). Y in the formula (EA-2a) 4 ~Y 7 At least one of them represents a group represented by the formula (Y-b), and Y 4 ~Y 7 The rest of them represent a group represented by the formula (Y-a). Y in the formula (EA-3a) 8 ~Y 12 At least one of them represents a group represented by the formula (Y-b), and Y 8 ~Y 12 The rest of them represent a group represented by the formula (Y-a). Y in the formula (EA-4a) 13 ~Y 18 At least one of them represents a group represented by the formula (Y-b), and Y 13 ~Y 18 The rest of them represent a group represented by the formula (Y-a).

[0053]

Chemical formula

[0054] The * in the formulas (Y-a) and (Y-b) 1 is a bond that binds to the carbon atom of the carbonyl group in the formulas (EA-1a) to (EA-4a). The * in the formula (Y-b) 2 is a bond that binds to the * 2 that another repeating unit has or the *<y 3 described later. That is, the * 2 of the group represented by the formula (Y-b) that one repeating unit has and the * 2 of the group represented by the formula (Y-b) that another repeating unit has or the * 3 in the formula (EB-1a) described later are bonded to each other.

[0055] Through a photocuring reaction (more specifically, an addition polymerization reaction of vinyl groups), the double bond of the group represented by formula (Ya) is cleaved, and the group represented by formula (Yb) is formed. Therefore, as the photocuring reaction (more specifically, the addition polymerization reaction of vinyl groups) proceeds, the number of groups represented by formula (Ya) decreases and the number of groups represented by formula (Yb) increases.

[0056] The hydroxyl value of the polyfunctional acrylic acid ester is preferably 1 mg KOH / g or more and 50 mg KOH / g or less, and more preferably 5 mg KOH / g or more and 15 mg KOH / g or less.

[0057] As the monofunctional monomer, a (meth)acrylic acid ester having one vinyl group is preferred. Hereinafter, "(meth)acrylic acid ester having one vinyl group" may be referred to as "monofunctional acrylic acid ester".

[0058] The monofunctional acrylic acid ester is preferably a compound represented by formula (EB-1).

[0059] [ka]

[0060] In formula (EB-1), R 1 R represents a base represented by formula (b1) or (b2). 2 represents a hydrogen atom or a methyl group.

[0061] [ka]

[0062] In equation (b1), m represents 0 or 1, and n represents an integer between 1 and 3 (inclusive). 3 R represents a hydrogen atom or a fluorine atom. In formula (b2), R 4 * represents an alkyl group having 1 to 18 carbon atoms. In formulas (b1) and (b2), * represents a bond.

[0063] In formula (b1), m preferably represents 1. n preferably represents 1 or 3. 3 It is preferable that R represents a hydrogen atom. In formula (b2), R 4 R preferably represents an alkyl group having 10 to 18 carbon atoms, more preferably an alkyl group having 15 to 18 carbon atoms, and even more preferably an alkyl group having 18 carbon atoms. 2 It is preferable that this represents a hydrogen atom.

[0064] Preferred examples of compounds represented by formula (EB-1) include those represented by formulas (EB-11), (EB-12), and (EB-13). In formula (EB-13), "iso-C 18 H 37 " represents the isooctadecyl group.

[0065] [ka]

[0066] Through a photocuring reaction (more specifically, an addition polymerization reaction of vinyl groups), repeating units represented by formula (EB-1a) are formed from the monomer compound represented by formula (EB-1).

[0067] [ka]

[0068] * in equation (EB-1a) 3 This is the * that other repeating units have 2 or * 3 It is a bonding hand that connects to . R in equation (EB-1a) 1 and R 2 R in equation (EB-1) 1 and R 2 It is synonymous with [the above].

[0069] To promote the photocuring reaction and increase the hardness of the protective layer, the ratio M4 / M3 of the mass of repeating units derived from monofunctional acrylic acid esters to the mass M3 of repeating units derived from polyfunctional acrylic acid esters is preferably 0.1 to 0.9, more preferably 0.5 to 0.8, and even more preferably 0.6 to 0.7.

[0070] The content of repeating units derived from polyfunctional acrylic acid esters in the total repeating units of the photocurable resin is preferably 50% by mass or more and 90% by mass or less, and more preferably 60% by mass or more and 70% by mass or less. The content of repeating units derived from monofunctional acrylic acid esters in the total repeating units of the photocurable resin is preferably 10% by mass or more and 50% by mass or less, and more preferably 30% by mass or more and 40% by mass or less. The total content of polyfunctional acrylic acid esters and monofunctional acrylic acid esters in the total repeating units of the photocurable resin is preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 100% by mass.

[0071] The content of the protective layer resin in the protective layer is preferably 50% by mass or more and 99% by mass or less, and more preferably 70% by mass or more and 90% by mass or less, relative to the mass of the protective layer.

[0072] (Polymerization initiator) The polymerization initiator is, for example, a photopolymerization initiator. Examples of photopolymerization initiators include acylphosphine oxide compounds, acetophenone compounds, ketal compounds, benzoin ether compounds, anthraquinone compounds, and thioxanthone compounds. Due to their high UV absorption efficiency, acylphosphine oxide compounds are preferred as photopolymerization initiators. Examples of acylphosphine oxide compounds include 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and lithiumphenyl(2,4,6-trimethylbenzoyl)phosphonate. The content of the polymerization initiator in the protective layer is preferably 1% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 10% by mass or less, relative to the mass of the protective layer.

[0073] (Additives) Examples of additives contained in the protective layer include leveling agents (e.g., silicone oil) and other known additives. Preferably, the protective layer does not contain charge generating agents, hole transporters, or electron transporters.

[0074] <Photosensitive layer> The photosensitive layer contains a charge generating agent, a hole transporter, and a binder resin. When the photoreceptor is a single-layer photoreceptor, the single-layer photosensitive layer contains a charge generating agent, a hole transporter, and a binder resin. Preferably, the single-layer photosensitive layer further contains an electron transporter. The single-layer photosensitive layer may further contain additives as needed.

[0075] If the photoreceptor is a multilayer photoreceptor, the charge generation layer included in the photosensitive layer contains a charge generating agent. The charge transport layer included in the photosensitive layer contains a hole transport agent and a binder resin. The charge generation layer may further contain a base resin as needed. The charge generation layer and the charge transport layer may each further contain additives as needed. The charge generation layer and the charge transport layer may each contain a radical acceptor compound. However, the charge generation layer and the charge transport layer do not each contain a radical acceptor compound.

[0076] (Charge-generating agent) Examples of charge generating agents include phthalocyanine pigments, perylene pigments, bisazo pigments, trisazo pigments, dithioketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metallic naphthalocyanine pigments, squaline pigments, indigo pigments, azulenium pigments, cyanine pigments, powders of inorganic photoconductive materials (e.g., selenium, selenium-tellurium, selenium-arsenide, cadmium sulfide, and amorphous silicon), pyryllium pigments, ancencelon pigments, triphenylmethane pigments, surene pigments, toluidine pigments, pyrazoline pigments, and quinacridone pigments.

[0077] Phthalocyanine pigments have a phthalocyanine structure. Examples of phthalocyanine pigments include metallic phthalocyanines and metal-free phthalocyanines. Examples of metallic phthalocyanines include titanyl phthalocyanine, hydroxygallium phthalocyanine, and chlorogallium phthalocyanine. Titanyl phthalocyanine is preferred as the metallic phthalocyanine. Titanyl phthalocyanine is represented by formula (CG-1). Metal-free phthalocyanines are represented by formula (CG-2).

[0078] [ka]

[0079] Phthalocyanine pigments may be crystalline or amorphous. Examples of metal-free phthalocyanine crystals include X-type crystals of metal-free phthalocyanine (hereinafter sometimes referred to as X-type metal-free phthalocyanine). Examples of titanyl phthalocyanine crystals include α-type, β-type, and Y-type crystals of titanyl phthalocyanine (hereinafter sometimes referred to as α-type, β-type, and Y-type titanyl phthalocyanine, respectively).

[0080] For example, in digital optical image forming apparatuses (e.g., laser beam printers or facsimile machines using light sources such as semiconductor lasers), it is preferable to use a photoreceptor that is sensitive to wavelengths of 700 nm or more. As a charge generating agent, phthalocyanine-based pigments are preferred because they have a high quantum yield in the wavelength range of 700 nm or more, with titanyl phthalocyanine or metal-free phthalocyanine being more preferred, and Y-type titanyl phthalocyanine or X-type metal-free phthalocyanine being particularly preferred.

[0081] Y-type titanyl phthalocyanine has a major peak at, for example, 27.2° of the Bragg angle (2θ±0.2°) in its CuKα-characterized X-ray diffraction spectrum. The major peak in a CuKα-characterized X-ray diffraction spectrum is the peak with the first or second highest intensity in the range where the Bragg angle (2θ±0.2°) is between 3° and 40°. Y-type titanyl phthalocyanine does not have a peak at 26.2° in its CuKα-characterized X-ray diffraction spectrum.

[0082] The CuKα characteristic X-ray diffraction spectrum can be measured, for example, by the following method. First, the sample (titanyl phthalocyanine) is placed in the sample holder of an X-ray diffractometer (for example, RIGAK Corporation's "RINT(registered trademark) 1100"), and the X-ray diffraction spectrum is measured under the following conditions: X-ray tube Cu, tube voltage 40kV, tube current 30mA, and CuKα characteristic X-ray wavelength 1.542Å. The measurement range (2θ) is, for example, 3° to 40° (start angle 3°, stop angle 40°), and the scanning speed is, for example, 10° / min. The main peak is determined from the obtained X-ray diffraction spectrum, and the Bragg angle of the main peak is read.

[0083] When the photoreceptor is a single-layer photoreceptor, the content of the charge generating agent in the single-layer photoreceptor layer is preferably 0.1 parts by mass or more and 50 parts by mass or less, and more preferably 0.5 parts by mass or more and 30 parts by mass or less, per 100 parts by mass of the binder resin. When the photoreceptor is a multilayer photoreceptor, the content of the charge generating agent in the photoreceptor layer (specifically the charge generating layer) is preferably 10 parts by mass or more and 300 parts by mass or less, and more preferably 100 parts by mass or more and 200 parts by mass or less, per 100 parts by mass of the base resin.

[0084] (Hole transport agent) Examples of hole transporters include triphenylamine derivatives, diamine derivatives (e.g., N,N,N',N'-tetraphenylbenzidine derivatives, N,N,N',N'-tetraphenylphenylenediamine derivatives, N,N,N',N'-tetraphenylnaphthylenediamine derivatives, N,N,N',N'-tetraphenylphenantolylenediamine derivatives, and di(aminophenylethenyl)benzene derivatives), oxadiazole compounds (e.g., 2,5-di(4-methylaminophenyl)-1,3,4-oxadiazo Examples include oxymethylcellulose, styryl compounds (e.g., 9-(4-diethylaminostyryl)anthracene), carbazole compounds (e.g., polyvinylcarbazole), organic polysilane compounds, pyrazoline compounds (e.g., 1-phenyl-3-(p-dimethylaminophenyl)pyrazoline), hydrazone compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, and triazole compounds.

[0085] To improve the sensitivity characteristics of the photoreceptor, the hole transporter preferably contains at least one compound represented by formulas (1), (2), and (3). Hereinafter, the compounds represented by formulas (1), (2), and (3) may be referred to as hole transporters (1), (2), and (3), respectively.

[0086] [ka]

[0087] In formula (1), R 41 , R 42 , R 43 , R 44 , R 45 , and R 46 Each of these independently represents an alkyl group having 1 to 8 carbon atoms, or a phenyl group. 47 and R 48Each of these independently represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a phenyl group. Each of these independently represents an integer between 0 and 5, and each of these independently represents an integer between 0 and 4

[0088] In equation (1), when e1 represents an integer between 2 and 5, multiple R 41 These may represent the same base or different bases. When e2 represents an integer between 2 and 5, multiple R 42 These may represent the same base or different bases. When e3 represents an integer between 2 and 5, multiple R 43 These may represent the same base or different bases. When e4 represents an integer between 2 and 5, multiple R 44 These may represent the same base or different bases. When e5 represents an integer between 2 and 4, multiple R 45 These may represent the same base or different bases. When e6 represents an integer between 2 and 4, multiple R 46 These may represent the same group or different groups.

[0089] In formula (1), R 41 ~R 46 Each of these groups preferably independently represents an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably a methyl group or an ethyl group. 47 and R 48 e1, e2, e3, and e4 each preferably represent an integer between 0 and 2, with e1 and e2 representing 0 and e3 and e4 representing 2. e5 and e6 preferably represent 0.

[0090] In formula (2), R 50 , R 51 , and R 54 Each of these independently represents an alkyl group having 1 to 8 carbon atoms, or a phenyl group. 52 , and R 53Each of these independently represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a phenyl group which may be substituted with an alkyl group having 1 to 8 carbon atoms. Each of these independently represents an integer between 0 and 5.

[0091] In equation (2), when f3 represents an integer between 2 and 5, multiple R 50 These may represent the same base or different bases. When f4 represents an integer between 2 and 5, multiple R 51 These may represent the same base or different bases. When f5 represents an integer between 2 and 5, multiple R 54 These may represent the same group or different groups.

[0092] In formula (2), R 50 , R 51 , and R 54 Each of these groups preferably independently represents an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably a methyl group. 52 and R 53 Each of these preferably independently represents a hydrogen atom, an unsubstituted phenyl group, or a phenyl group substituted with an alkyl group having 1 to 8 carbon atoms. When the phenyl group is substituted with an alkyl group having 1 to 8 carbon atoms, such an alkyl group having 1 to 3 carbon atoms is preferred, and a methyl group is more preferred. Each of f3, f4, and f5 preferably independently represents 0 or 1.

[0093] In formula (3), R 11 , R 12 , R 13 , and R 14 Each of these independently represents an alkyl group having 1 to 8 carbon atoms, or a phenyl group. Each of a1, a2, a3, and a4 independently represents an integer between 0 and 5.

[0094] In equation (3), when a1 represents an integer between 2 and 5, multiple R 11These may represent the same base or different bases. When a2 represents an integer between 2 and 5, multiple R 12 These may represent the same base or different bases. When a3 represents an integer between 2 and 5, multiple R 13 These may represent the same base or different bases. When a4 represents an integer between 2 and 5, multiple R 14 These may represent the same group or different groups.

[0095] In formula (3), R 11 , R 12 , R 13 , and R 14 Each of these preferably independently represents an alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group or an ethyl group. Each of a1, a2, a3, and a4 preferably independently represents an integer between 1 and 3, and more preferably 1.

[0096] Preferred examples of hole transporters include compounds represented by formulas (HT-2), (HT-3), and (HT-4) (hereinafter, these may be referred to as hole transporters (HT-2), (HT-3), and (HT-4), respectively).

[0097] [ka]

[0098] The content of hole transporters (1) to (3) in the total hole transporters in the photosensitive layer is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass, based on the total mass of hole transporters in the photosensitive layer.

[0099] When ultraviolet irradiation is performed in the protective layer formation process, it is preferable that the hole transporter has two or fewer (one or two) linear ethene-1,2-diyl groups, or does not have linear ethene-1,2-diyl groups, in order to suppress the decomposition of the hole transporter by ultraviolet irradiation. Hereinafter, "linear ethene-1,2-diyl group" may be referred to as "predetermined double bond". The predetermined double bond is a bond represented by the following formula (DB). In formula (DB), * represents a bond. The predetermined double bond is an unsubstituted ethene-1,2-diyl group. Since the predetermined double bond is linear, it is a double bond that constitutes a linear group. Since the predetermined double bond is linear, it is not a double bond that constitutes a ring such as a benzene ring.

[0100] [ka]

[0101] When ultraviolet irradiation is performed in the protective layer formation process, in order to suppress the decomposition of hole transporters due to ultraviolet irradiation, the content of hole transporters having two or fewer predetermined double bonds, or not having predetermined double bonds, in the photosensitive layer is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass, based on the total mass of hole transporters.

[0102] When the photoreceptor is a single-layer photoreceptor, the content of the hole transporter in the single-layer photoreceptor, which is the photosensitive layer, is preferably 10 parts by mass or more and 200 parts by mass or less, and more preferably 80 parts by mass or more and 130 parts by mass or less, per 100 parts by mass of the binder resin.

[0103] To improve the sensitivity characteristics of the photoreceptor, when the photoreceptor is a single-layer photoreceptor, the total content of hole transporters and electron transporters in the single-layer photoreceptor layer is preferably 40% by mass or more, and more preferably 40% by mass or more and 60% by mass or less, relative to the mass of the single-layer photoreceptor layer.

[0104] When the photoreceptor is a laminated photoreceptor, the content of the hole transporter in the photosensitive layer (specifically the charge transport layer) is preferably 10 parts by mass or more and 200 parts by mass or less, and more preferably 50 parts by mass or more and 100 parts by mass or less, per 100 parts by mass of the binder resin.

[0105] To improve the sensitivity characteristics of the photoreceptor, when the photoreceptor is a multilayer photoreceptor, the content of the hole transporter in the charge transport layer is preferably 40% by mass or more, and more preferably 40% by mass or more and 60% by mass or less, relative to the mass of the charge transport layer.

[0106] (Electron transport agent) Examples of electron transport agents include quinone compounds, diimide compounds, hydrazone compounds, malononitrile compounds, thiopyran compounds, trinitrothioxanthone compounds, 3,4,5,7-tetranitro-9-fluorenone compounds, dinitroanthracene compounds, dinitroacridine compounds, tetracyanoethylene, 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroacridine, succinic anhydride, maleic anhydride, and dibromomaleic anhydride. Examples of quinone compounds include diphenoquinone compounds, azoquinone compounds, anthraquinone compounds, naphthoquinone compounds, nitroanthraquinone compounds, and dinitroanthraquinone compounds.

[0107] The electron transport agent preferably contains at least one of the compounds represented by formulas (11), (12), (13), (14), (15), and (16). Hereinafter, the compounds represented by formulas (11), (12), (13), (14), (15), and (16) may be referred to as electron transport agents (11), (12), (13), (14), (15), and (16), respectively.

[0108] [ka]

[0109] Q in equation (11)1 and Q 2 Q in formula (12) 21 Q 22 Q 23 and Q 24 Q in formula (13) 31 and Q 32 Q in formula (14) 41 Q 42 and Q 43 Q in formula (15) 71 Q 72 Q 73 Q 74 Q 75 and Q 76 and Q in formula (16) 61 and Q 62 each independently represents an aryl group having 6 to 14 carbon atoms which may be substituted with at least one substituent selected from the group consisting of a hydrogen atom, a halogen atom, a cyano group, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an alkyl group having 1 to 6 carbon atoms and a halogen atom. Y in formula (15) 1 and Y 2 represents an oxygen atom.

[0110] Q in formula (11) 1 and Q 2 Q in formula (12) 21 Q 22 Q 23 and Q 24 Q in formula (13) 31 and Q 32 Q in formula (14) 41 Q 42 and Q 43 Q in formula (15) 71 Q 72 Q 73 [[ID=?]]Q 74 ?Q [[ID=?]] 75 ? and Q 76 and Q in formula (!6) 61 and Q 62 It seems there are some tags that might be incorrect or incomplete in the original. I've translated as accurately as possible based on what's provided. If you can clarify those parts, it would be great for a more precise translation.Preferably, each of these independently represents an aryl group having 6 to 14 carbon atoms, which may be substituted with a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or at least one substituent selected from the group consisting of an alkyl group having 1 to 6 carbon atoms and a halogen atom.

[0111] Q in equation (11) 1 and Q 2 Q in equation (12) 21 Q 22 Q 23 , and Q 24 Q in equation (13) 31 and Q 32 Q in equation (14) 41 Q 42 , and Q 43 Q in equation (15) 71 Q 72 Q 73 Q 74 Q 75 , and Q 76 , and Q in equation (16) 61 and Q 62 The alkyl group having 1 to 6 carbon atoms represented by is preferably an alkyl group having 1 to 5 carbon atoms, and preferably a methyl group, ethyl group, propyl group, butyl group, or pentyl group, and particularly preferably a methyl group, tert-butyl group, or 1,1-dimethylpropyl group.

[0112] Q in equation (11) 1 and Q 2 Q in equation (12) 21 Q 22 Q 23 , and Q 24 Q in equation (13) 31 and Q 32 Q in equation (14) 41 Q 42 , and Q 43 Q in equation (15) 71 Q 72 Q 73 Q 74 Q 75 , and Q 76 , and Q in equation (16) 61 and Q 62The aryl group having 6 to 14 carbon atoms represented by is preferably an aryl group having 6 to 10 carbon atoms, and more preferably a phenyl group. The aryl group having 6 to 14 carbon atoms may be substituted with at least one substituent selected from the group consisting of alkyl groups having 1 to 6 carbon atoms and halogen atoms. The alkyl group having 1 to 6 carbon atoms is preferably an alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group or an ethyl group. The halogen atom used as a substituent is preferably a fluorine atom, a chlorine atom, or a bromine atom, and particularly preferably a chlorine atom. When the aryl group having 6 to 14 carbon atoms is substituted with a substituent, the number of substituents is preferably one to five, and more preferably one or two. The aryl group having 6 to 14 carbon atoms substituted with at least one substituent selected from the group consisting of alkyl groups having 1 to 6 carbon atoms and halogen atoms is preferably a chlorophenyl group, a dichlorophenyl group, or an ethylmethylphenyl group, and more preferably a 4-chlorophenyl group, a 2,5-dichlorophenyl group, or a 2-ethyl-6-methylphenyl group.

[0113] More preferred examples of electron transport agents include compounds represented by formulas (ET-1) to (ET-7) (hereinafter, these may be referred to as electron transport agents (ET-1) to (ET-7), respectively).

[0114] [ka]

[0115] The content of electron transporters (11) to (16) in the total electron transporters in the photosensitive layer is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass, based on the total mass of electron transporters in the photosensitive layer.

[0116] When the photoreceptor is a single-layer photoreceptor, the content of the electron transport agent in the single-layer photoreceptor layer is preferably 5 parts by mass or more and 150 parts by mass or less, and preferably 10 parts by mass or more and 50 parts by mass or less, per 100 parts by mass of the binder resin.

[0117] (Binder resin) Examples of binder resins include thermoplastic resins (more specifically, polyarylate resins, polycarbonate resins, styrene-based resins, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers, styrene-acrylic acid copolymers, acrylic copolymers, polyethylene resins, ethylene-vinyl acetate copolymers, chlorinated polyethylene resins, polyvinyl chloride resins, polypropylene resins, ionomers, vinyl chloride-vinyl acetate copolymers, polyester resins, alkyd resins, polyamide resins, polyurethane resins, polysulfone resins, diallyl phthalate resins, ketone resins, polyvinyl butyral resins, polyvinyl acetal resins, and polyether resins), thermosetting resins (more specifically, silicone resins, epoxy resins, phenolic resins, urea resins, melamine resins, and other crosslinkable thermosetting resins), and photocurable resins (more specifically, epoxy-acrylic acid resins and urethane-acrylic acid copolymers).

[0118] Among these resins, polycarbonate resin is preferred because it provides a single-layer photosensitive layer and charge transport layer with an excellent balance of processability, mechanical strength, optical properties, and abrasion resistance. Examples of polycarbonate resins include bisphenol Z type polycarbonate resin, bisphenol B type polycarbonate resin, bisphenol ZC type polycarbonate resin, bisphenol C type polycarbonate resin, and bisphenol A type polycarbonate resin. As the binder resin, bisphenol Z type polycarbonate resin or bisphenol B type polycarbonate resin is preferred. Bisphenol Z type polycarbonate resin is a resin having repeating units represented by the formula (BisZ). Bisphenol B type polycarbonate resin is a resin having repeating units represented by the formula (BisB).

[0119] [ka]

[0120] (Base resin) The base resin contained in the charge generation layer is the same as the binder resin contained in the charge transport layer. However, in order to suitably form the charge generation layer and the charge transport layer, it is preferable to select a resin as the base resin that is different from the resin used as the binder resin from the above examples of binder resins. The base resin is, for example, polyvinyl acetal resin.

[0121] (Additives) Additives contained in the photosensitive layer include, for example, UV absorbers, antioxidants, radical scavengers, singlet quenchers, softeners, surface modifiers, bulking agents, thickening agents, dispersion stabilizers, waxes, donors, surfactants, plasticizers, sensitizers, electron acceptor compounds, and leveling agents. Examples of leveling agents include silicone oil, and more specifically, dimethyl silicone oil.

[0122] <Middle class> The presence of an intermediate layer allows for a degree of insulation sufficient to suppress leakage while facilitating the flow of current generated when the photoreceptor is exposed, thereby suppressing an increase in resistance. The intermediate layer (undercoat) contains, for example, one or both of inorganic particles and organic particles, and a resin used in the intermediate layer (hereinafter sometimes referred to as "intermediate layer resin"). Hereinafter, the inorganic particles and organic particles contained in the intermediate layer will be collectively referred to as intermediate layer particles. The ratio of the mass of intermediate layer particles to the mass of intermediate layer resin is, for example, 1 to 4. The thickness of the intermediate layer is, for example, 0.1 μm to 5 μm.

[0123] Examples of inorganic particles for the intermediate layer include white pigments (more specifically, titanium dioxide, zinc oxide, zinc oxide, zinc sulfide, lead white, and lithopone, etc.) and extender pigments (more specifically, alumina, calcium carbonate, and barium sulfate, etc.). Examples of organic particles for the intermediate layer include fluororesin particles, benzoguanamine resin particles, and styrene resin particles. The number-mean primary particle size of the intermediate layer particles is preferably 100 nm or less, and more preferably 1 nm to 50 nm. Inorganic particles are preferred for the intermediate layer particles, and titanium dioxide is more preferred. Titanium dioxide may be surface-treated. Surface treatment of titanium dioxide may be performed once or multiple times (for example, twice). Examples of surface treatment agents used for surface treatment of titanium dioxide include alumina, silica, and organosilicon compounds (for example, polysiloxane, more specifically, methylhydrogenpolysiloxane).

[0124] Examples of intermediate layer resins are the same as examples of binder resins contained in the photosensitive layer. However, in order to suitably form the photosensitive layer, it is preferable to select an intermediate layer resin from the above examples of binder resins that is different from the resin used as the binder resin. The intermediate layer resin is, for example, a polyamide resin.

[0125] <Conductive substrate> The conductive substrate is not particularly limited, and only needs to be composed of a material whose surface is conductive. An example of a conductive substrate is a conductive substrate composed of a conductive material. Another example of a conductive substrate is a conductive substrate coated with a conductive material. Examples of conductive materials include aluminum, iron, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, and indium. Two or more conductive materials may be combined to form an alloy (more specifically, an aluminum alloy, stainless steel, or brass, etc.). Aluminum and aluminum alloys are preferred as conductive materials because they allow for good charge transfer from the photosensitive layer to the conductive substrate. The shape of the conductive substrate is appropriately selected according to the structure of the image forming apparatus. Examples of conductive substrate shapes include sheet-like and drum-like shapes. The thickness of the conductive substrate is appropriately selected according to the shape of the conductive substrate.

[0126] <Method for manufacturing photoreceptors> Next, an example of a method for manufacturing a photoreceptor according to the first embodiment will be described. The method for manufacturing a photoreceptor according to the first embodiment includes, for example, a photosensitive layer formation step and a protective layer formation step.

[0127] (Photosensitive layer formation process for single-layer photoreceptors) The photosensitive layer formation process for a single-layer photoreceptor is described below. The photosensitive layer formation process for a single-layer photoreceptor includes a single-layer photosensitive layer formation process. In the single-layer photosensitive layer formation process, a coating solution for forming a single-layer photosensitive layer (hereinafter sometimes referred to as a single-layer photosensitive layer coating solution) is prepared. The single-layer photosensitive layer coating solution contains, for example, a charge generating agent, a hole transporter, a binder resin, a solvent, an electron transporter if necessary, and additives if necessary. The single-layer photosensitive layer coating solution is prepared by mixing these. Next, the single-layer photosensitive layer coating solution is applied onto a conductive substrate. Then, at least a portion of the solvent contained in the applied photosensitive layer coating solution is removed to form a single-layer photosensitive layer.

[0128] (Photosensitive layer formation process for stacked photoreceptors) The photosensitive layer formation process for a stacked photoreceptor is described below. The photosensitive layer formation process for a stacked photoreceptor includes a charge generation layer formation process and a charge transport layer formation process.

[0129] In the charge generation layer formation step, a coating solution for forming the charge generation layer (hereinafter sometimes referred to as the charge generation layer coating solution) is prepared. The charge generation layer coating solution contains, for example, a charge generating agent, a base resin, a solvent, and additives as needed. The charge generation layer coating solution is prepared by mixing these components. Next, the charge generation layer coating solution is applied onto a conductive substrate. Then, at least a portion of the solvent contained in the applied charge generation layer coating solution is removed to form the charge generation layer.

[0130] In the charge transport layer formation process, a coating solution for forming the charge transport layer (hereinafter sometimes referred to as the charge transport layer coating solution) is prepared. The charge transport layer coating solution contains a hole transport agent, a binder resin, a solvent, and additives as needed. The charge transport layer coating solution is prepared by mixing these components. Next, the charge transport layer coating solution is applied onto the charge generating layer. Then, at least a portion of the solvent contained in the applied charge transport layer coating solution is removed to form the charge transport layer.

[0131] (Protective layer formation process) In the protective layer formation process, a protective layer is formed on the photosensitive layer. First, a coating solution for forming the protective layer (hereinafter sometimes referred to as the protective layer coating solution) is prepared. The protective layer coating solution contains a first particle, a second particle, at least one of an oligomer and a monomer for forming the protective layer resin, a solvent, a polymerization initiator if necessary, and additives if necessary. The protective layer coating solution is prepared by mixing these. Hereinafter, "oligomer and monomer" may be referred to as "monomer, etc." Next, the protective layer coating solution is applied onto the photosensitive layer. Then, at least one of the monomer, etc. contained in the protective layer coating solution on the photosensitive layer is polymerized. By polymerization, a protective layer resin, which is a polymer, is formed.

[0132] When the protective layer resin is a photocurable resin, at least one monomer or the like contained in the protective layer coating solution is polymerized by irradiating the protective layer coating solution with ultraviolet light. The ultraviolet light irradiated in the protective layer formation process is, for example, irradiated from a light-emitting diode light source. In order to allow the photocuring reaction to proceed favorably, the wavelength of the ultraviolet light irradiated in the protective layer formation process is preferably 200 nm to 420 nm, more preferably 270 nm to 420 nm, even more preferably 270 nm to 400 nm, and particularly preferably 365 nm. The light energy of the ultraviolet light irradiated in the protective layer formation process is preferably 10,000 mW·s to 100,000 mW·s, and more preferably 60,300 mW·s to 86,400 mW·s. If the light energy of the ultraviolet light is 10,000 mW·s or more, the photocuring reaction will proceed sufficiently and the protective layer can be sufficiently cured. If the power is 100,000 mW·s or less, the decomposition of the hole transporter contained in the photosensitive layer can be further suppressed, and the sensitivity characteristics of the photoreceptor can be improved.

[0133] In the first embodiment, one or both of the first and second particles may not have polymerizable functional groups. Furthermore, in the production of the photoreceptor of the first embodiment, it is not necessary to react the polymerizable functional groups (e.g., polymerizable unsaturated groups) of one or both of the first and second particles with the polymerizable functional groups of the organic compound (e.g., protective layer resin, or monomer for forming the protective layer resin) to form a chemical bond. For this reason, the photoreceptor of the first embodiment can be easily manufactured.

[0134] The photosensitive layer formation process and the protective layer formation process have been described above. The method for manufacturing the photoreceptor according to the first embodiment will now be described further.

[0135] The solvents contained in the above-mentioned single-layer photosensitive layer coating solution, charge generation layer coating solution, charge transport layer coating solution, and protective layer coating solution (hereinafter, these may be collectively referred to as "coating solution") are not particularly limited, as long as they can dissolve or disperse each component contained in the coating solution. Examples of solvents include alcohols (more specifically methanol, ethanol, isopropanol, and butanol), aliphatic hydrocarbons (more specifically n-hexane, octane, and cyclohexane), aromatic hydrocarbons (more specifically benzene, toluene, and xylene), halogenated hydrocarbons (more specifically methylene chloride, chloroform, ethylene chloride, dichloromethane, dichloroethane, carbon tetrachloride, and chlorobenzene), ethers (more specifically dioxane, dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, propylene glycol monomethyl ether, and diethylene glycol dimethyl ether), ketones (more specifically acetone, methyl ethyl ketone, 2-butanone, and cyclohexanone), esters (more specifically ethyl acetate and methyl acetate), dimethylformaldehyde, dimethylformamide, and dimethyl sulfoxide.

[0136] The coating solution is prepared by mixing each component and dissolving or dispersing them in a solvent. For mixing, for example, a bead mill, ball mill, roll mill, paint shaker, or ultrasonic disperser can be used.

[0137] The method of applying the coating solution is not particularly limited, as long as it allows for uniform application of the coating solution. Examples of application methods include dip coating, spray coating, bead coating, blade coating, and roller coating.

[0138] Methods for removing at least a portion of the solvent contained in the above-mentioned single-layer photosensitive layer coating solution, charge generation layer coating solution, and charge transport layer coating solution include, for example, heating, reduced pressure, or a combination of heating and reduced pressure. More specifically, a method of heat treatment (hot air drying) using a high-temperature dryer or a reduced-pressure dryer is used. The heat treatment temperature is, for example, 40°C to 150°C. The heat treatment time is, for example, 3 minutes to 150 minutes.

[0139] The method for manufacturing a photoreceptor according to the first embodiment may further include an intermediate layer formation step of forming an intermediate layer on a conductive substrate, if necessary. The intermediate layer formation step may be carried out by appropriately selecting a known method.

[0140] [Second Embodiment: Image Forming Apparatus] Next, with reference to Figure 6, an image forming apparatus 100, which is an example of an image forming apparatus of a second embodiment of the present invention, will be described. Figure 6 is a diagram showing an example of the configuration of the image forming apparatus 100. The image forming apparatus 100 is, for example, a tandem-type color printer.

[0141] As shown in Figure 6, the image forming apparatus 100 comprises a control unit 15, an operating unit 20, a paper feeding unit 30, a transport unit 40, a toner supply unit 50, an image forming unit 60, a transfer device 70, a fixing device 80, and a discharge unit 90.

[0142] The control unit 15 controls the operation of each part of the image forming apparatus 100. The control unit 15 includes a processor (not shown) and a storage unit (not shown). The processor includes, for example, a CPU (Central Processing Unit). The storage unit includes memory such as semiconductor memory, and may also include an HDD (Hard Disk Drive). The processor controls the operation of the image forming apparatus 100 by executing a control program. The storage unit stores the control program.

[0143] The operation unit 20 receives instructions from the user. Upon receiving instructions from the user, the operation unit 20 transmits a signal indicating the user's instructions to the control unit 15. As a result, the image forming operation by the image forming apparatus 100 is started.

[0144] The paper feeding unit 30 includes a paper feeding cassette 31 and a group of paper feeding rollers 32. The paper feeding cassette 31 can accommodate multiple recording media P (for example, paper). The group of paper feeding rollers 32 feeds the recording media P stored in the paper feeding cassette 31 one sheet at a time to the transport unit 40.

[0145] The transport unit 40 is equipped with rollers and guide members. The transport unit 40 extends from the paper feeding unit 30 to the discharge unit 90. The transport unit 40 transports the recording medium P from the paper feeding unit 30 to the discharge unit 90, passing through the image forming unit 60 and the fixing device 80.

[0146] The toner supply unit 50 supplies toner to the image forming unit 60. The toner supply unit 50 comprises a first mounting unit 51Y, a second mounting unit 51C, a third mounting unit 51M, and a fourth mounting unit 51K.

[0147] The first toner container 52Y is mounted in the first mounting section 51Y. Similarly, the second toner container 52C is mounted in the second mounting section 51C, the third toner container 52M is mounted in the third mounting section 51M, and the fourth toner container 52K is mounted in the fourth mounting section 51K.

[0148] The first toner container 52Y, the second toner container 52C, the third toner container 52M, and the fourth toner container 52K each contain toner. In the second embodiment, the first toner container 52Y contains yellow toner. The second toner container 52C contains cyan toner. The third toner container 52M contains magenta toner. The fourth toner container 52K contains black toner.

[0149] The image forming unit 60 comprises an exposure apparatus 61, a first image forming unit 62Y, a second image forming unit 62C, a third image forming unit 62M, and a fourth image forming unit 62K.

[0150] Each of the first image forming units 62Y to the fourth image forming unit 62K includes a charging device 63, a developing device 64, an image carrier 65, a cleaning device 66, and a static elimination device 67.

[0151] Note that the configurations of the first image forming unit 62Y to the fourth image forming unit 62K are the same except for the type of toner supplied from the toner supply unit 50. Therefore, in Figure 6, the reference numerals are omitted for the components of the second image forming unit 62C to the fourth image forming unit 62K.

[0152] The image carrier 65 is the photoreceptor of the first embodiment (more specifically, the single-layer photoreceptor 1 and the stacked photoreceptor 10). As described in the first embodiment, the photoreceptor of the first embodiment can form an image with excellent sensitivity characteristics and excellent dot reproducibility. Therefore, the image forming apparatus 100 of the second embodiment can form an image with excellent sensitivity characteristics and excellent dot reproducibility.

[0153] In the second embodiment, the image carrier 65 rotates in the direction indicated by arrow R1 in Figure 6 (clockwise in Figure 6). The charging device 63, developing device 64, cleaning device 66, and static elimination device 67 are arranged along the circumferential surface of the image carrier 65 in the order listed from the upstream side in the rotational direction of the image carrier 65.

[0154] The charging device 63 charges the surface (circumferential surface) of the image carrier 65. The charging device 63 uniformly charges the image carrier 65 to a predetermined polarity by discharge. The charging device 63 is, for example, a charging roller.

[0155] The exposure apparatus 61 exposes the surface of the charged image carrier 65. More specifically, the exposure apparatus 61 irradiates the surface of the charged image carrier 65 with laser light. As a result, an electrostatic latent image is formed on the surface of the image carrier 65.

[0156] The developing device 64 receives toner from the toner supply unit 50. The developing device 64 supplies the toner supplied from the toner supply unit 50 to the surface of the image carrier 65. As a result, the electrostatic latent image formed on the surface of the image carrier 65 is developed as a toner image.

[0157] In the second embodiment, the developing device 64 of the first image forming unit 62Y is connected to the first toner container 52Y. Therefore, yellow toner is supplied to the developing device 64 of the first image forming unit 62Y. As a result, a yellow toner image is formed on the surface of the image carrier 65 of the first image forming unit 62Y.

[0158] Similarly, the developing device 64 of the second image forming unit 62C, the developing device 64 of the third image forming unit 62M, and the developing device 64 of the fourth image forming unit 62K are connected to the second toner container 52C, the third toner container 52M, and the fourth toner container 52K, respectively. Therefore, the developing devices 64 of the second image forming unit 62C, the third image forming unit 62M, and the fourth image forming unit 62K are supplied with cyan toner, magenta toner, and black toner, respectively. As a result, cyan toner images, magenta toner images, and black toner images are formed on the surfaces of the image carrier 65 of the second image forming unit 62C, the third image carrier 65 of the third image forming unit 62M, and the fourth image carrier 65 of the fourth image forming unit 62K, respectively.

[0159] The cleaning device 66 includes a cleaning member 661 and a scraping roller 662. After transfer by the primary transfer roller 71, which will be described later, the cleaning member 661 is pressed against the surface of the image carrier 65 to collect toner adhering to the surface of the image carrier 65. The cleaning member 661 is, for example, a cleaning blade. The scraping roller 662 scrapes the surface of the image carrier 65 to polish the surface of the image carrier 65.

[0160] The static elimination device 67 irradiates the surface of the image carrier 65 with static elimination light to eliminate static electricity from the surface of the image carrier 65.

[0161] The transfer device 70 transfers the toner image from the image carrier 65 to the recording medium P, which is the object to be transferred. Specifically, the transfer device 70 transfers each toner image formed on the surface of each image carrier 65 of the first image forming unit 62Y to the fourth image forming unit 62K onto the recording medium P. In the second embodiment, the transfer device 70 transfers each toner image onto the recording medium P using a secondary transfer method (intermediate transfer method). The transfer device 70 has four primary transfer rollers 71, an intermediate transfer belt 72, a drive roller 73, a driven roller 74, and a secondary transfer roller 75.

[0162] The intermediate transfer belt 72 is an endless belt stretched over four primary transfer rollers 71, a drive roller 73, and a driven roller 74. The intermediate transfer belt 72 is driven in accordance with the rotation of the drive roller 73. The intermediate transfer belt 72 rotates counterclockwise in Figure 6. The driven roller 74 is rotationally driven in accordance with the drive of the intermediate transfer belt 72.

[0163] The first image forming unit 62Y to the fourth image forming unit 62K are arranged facing the lower surface of the intermediate transfer belt 72. In the second embodiment, the first image forming unit 62Y to the fourth image forming unit 62K are arranged in the order of the first image forming unit 62Y to the fourth image forming unit 62K from the upstream side to the downstream side in the driving direction D of the lower surface of the intermediate transfer belt 72.

[0164] Each primary transfer roller 71 is positioned opposite each image carrier 65 via an intermediate transfer belt 72 and is pressed toward each image carrier 65. As a result, the toner images formed on the surface of each image carrier 65 are sequentially transferred to the intermediate transfer belt 72 by each primary transfer roller 71. In the second embodiment, yellow toner images, cyan toner images, magenta toner images, and black toner images are transferred to the intermediate transfer belt 72 in this order. Hereinafter, the toner image formed by the superimposition of yellow toner images, cyan toner images, magenta toner images, and black toner images may be referred to as a "layered toner image".

[0165] The secondary transfer roller 75 is positioned opposite the drive roller 73 via the intermediate transfer belt 72. The secondary transfer roller 75 is pressed toward the drive roller 73. This forms a transfer nip between the secondary transfer roller 75 and the drive roller 73. As the recording medium P passes through the transfer nip, the secondary transfer roller 75 transfers the laminated toner image on the intermediate transfer belt 72 to the recording medium P. In the second embodiment, the yellow toner image, cyan toner image, magenta toner image, and black toner image are transferred to the recording medium P in this order, from top to bottom. The recording medium P on which the laminated toner image has been transferred is transported toward the fuser 80 by the transport unit 40.

[0166] The fixing device 80 includes a heating element 81 and a pressurizing element 82. The heating element 81 and the pressurizing element 82 are arranged facing each other to form a fixing nip. The recording medium P, transported from the image forming unit 60, is heated to a predetermined fixing temperature and pressurized as it passes through the fixing nip. As a result, the stacked toner image is fixed to the recording medium P. The recording medium P is transported from the fixing device 80 to the discharge unit 90 by the transport unit 40.

[0167] The discharge unit 90 includes a pair of discharge rollers 91 and a discharge tray 93. The pair of discharge rollers 91 transports the recording medium P to the discharge tray 93 via a discharge port 92. The discharge port 92 is formed on the upper part of the image forming apparatus 100.

[0168] Next, the configuration of the developing apparatus 64 will be described in detail with reference to Figure 7. Figure 7 is a diagram showing an example of the configuration of the developing apparatus 64. Specifically, Figure 7 shows the developing apparatus 64 of the first image forming unit 62Y. In Figure 7, the image carrier 65 is shown with a dashed line for ease of understanding. In the second embodiment, the developing apparatus 64 employs a two-component developing method using a two-component developer and a touchdown developing method.

[0169] As already explained with reference to Figure 6, the developing container 640 of the developing device 64 is connected to the first toner container 52Y. Therefore, yellow toner is supplied to the developing container 640 of the developing device 64 through the toner supply port 640h.

[0170] As shown in Figure 7, the developing apparatus 64 has a developing roller 641, a magnetic roller 642, a first stirring screw 643, a second stirring screw 644, and a blade 645 inside the developing container 640. Specifically, the developing roller 641 is positioned opposite the magnetic roller 642. The magnetic roller 642 is positioned opposite the second stirring screw 644. The blade 645 is positioned opposite the magnetic roller 642.

[0171] The developing container 640 is divided into a first stirring chamber 640a and a second stirring chamber 640b by a partition wall 640c. The partition wall 640c extends in the axial direction of the developing roller 641. The first stirring chamber 640a and the second stirring chamber 640b are in communication with each other at the outer ends of the longitudinal direction of the partition wall 640c.

[0172] The first stirring chamber 640a houses the first stirring screw 643. The first stirring chamber 640a contains a carrier, which is a magnetic material. The first stirring chamber 640a is supplied with toner, which is a non-magnetic material, through the toner supply port 640h. In the example shown in Figure 7, yellow toner is supplied to the first stirring chamber 640a.

[0173] The second stirring chamber 640b houses the second stirring screw 644. The second stirring chamber 640b contains a carrier which is a magnetic material.

[0174] The yellow toner is agitated with the carrier by the first agitation screw 643 and the second agitation screw 644. As a result, a two-component developer containing the carrier and the yellow toner is formed. This two-component developer is then placed in the developing container 640 (more specifically, the first agitation chamber 640a and the second agitation chamber 640b).

[0175] The first stirring screw 643 and the second stirring screw 644 agitate the two-component developer between the first stirring chamber 640a and the second stirring chamber 640b while circulating it. As a result, the toner becomes charged to a predetermined polarity due to friction with the carrier.

[0176] When the image carrier 65 is a single-layer photoreceptor 1, the surface of the image carrier 65 and the toner are charged with, for example, a positive polarity. When the image carrier 65 is a multilayer photoreceptor 10, the surface of the image carrier 65 and the toner are charged with, for example, a negative polarity.

[0177] The magnetic roller 642 consists of a non-magnetic rotating sleeve 642a and a magnet body 642b. The magnet body 642b is fixedly positioned inside the rotating sleeve 642a. The magnet body 642b contains multiple magnetic poles. The two-component developer is attracted to the magnetic roller 642 by the magnetic force of the magnet body 642b. As a result, magnetic brushes are formed on the surface of the magnetic roller 642.

[0178] The blade 645 is positioned upstream of the magnetic roller 642 in the direction of rotation of the magnetic roller 642, above the position where the magnetic roller 642 and the developing roller 641 face each other. In the second embodiment, the magnetic roller 642 rotates in the direction indicated by arrow R3 in Figure 7 (counterclockwise in Figure 7). By rotating, the magnetic roller 642 transports the magnetic brush to a position facing the blade 645. The blade 645 is positioned such that a gap is formed between it and the magnetic roller 642. The blade 645 is made of a magnetic material. Therefore, the thickness of the magnetic brush is regulated by the magnetic force of the blade 645.

[0179] After the thickness of the magnetic brush on the magnetic roller 642 is regulated, a predetermined voltage is applied to the magnetic roller 642 and the developing roller 641. When the predetermined voltage is applied and a predetermined potential difference is reached between the magnetic roller 642 and the developing roller 641, the yellow toner contained in the two-component developer is transferred to the developing roller 641. As a result, a thin layer of yellow toner is formed on the surface of the developing roller 641.

[0180] The developing roller 641 rotates in the direction indicated by arrow R2 in Figure 7 (counterclockwise in Figure 7). This transports the thin layer of toner formed on the surface of the developing roller 641 to a position facing the image carrier 65, where it adheres to the image carrier 65. In this way, the developing device 64 supplies toner, which has been charged by friction with the carrier, to the surface of the image carrier 65.

[0181] The developing device 64 of the first image forming unit 62Y has been described above with reference to Figure 7. The configuration of the developing device 64 of each of the first image forming unit 62Y to the fourth image forming unit 62K is the same except for the type of toner supplied from the toner supply unit 50. Therefore, the configuration of the developing device 64 of the second image forming unit 62C to the fourth image forming unit 62K will not be described.

[0182] The image forming apparatus 100, an example of an image forming apparatus of the second embodiment, has been described above with reference to Figures 6 and 7. However, the image forming apparatus of the second embodiment is not limited to the image forming apparatus 100. For example, the image forming apparatus may be a monochrome image forming apparatus. In this case, the image forming apparatus only needs to have one image forming unit. The image forming apparatus may employ a rotary system. The charging device may be a charging device other than a charging roller (for example, a scorotron charger, a charging brush, or a scorotron charger). The image forming apparatus may employ a one-component development method using a one-component developer. The image forming apparatus may employ a development method other than the touchdown development method (for example, a development method in which there is no development roller and the magnetic roller also serves as the development roller). The image forming apparatus may employ a direct transfer method. When the image forming apparatus employs a direct transfer method, the toner image is directly transferred from the image carrier to the recording medium while the image carrier is in contact with the recording medium. The image forming apparatus does not need to be equipped with a cleaning device. The image forming apparatus does not need to be equipped with a static elimination device. The image forming apparatus of the second embodiment has been described above.

[0183] [Third Embodiment: Process Cartridge] Next, with continued reference to Figure 6, a first process cartridge 101, a second process cartridge 102, a third process cartridge 103, and a fourth process cartridge 104, which are examples of process cartridges according to a third embodiment of the present invention, will be described. The first to fourth process cartridges 101 to 104 of the third embodiment correspond to the first to fourth image forming units 62Y to 62K, respectively. Each of the first to fourth process cartridges 101 to 104 comprises an image carrier 65. The image carrier 65 is a photoreceptor according to the first embodiment (more specifically, a single-layer photoreceptor 1 and a stacked photoreceptor 10).

[0184] As described in the first embodiment, the photoreceptor of the first embodiment can form images with excellent sensitivity characteristics and excellent dot reproducibility. Therefore, the process cartridge of the third embodiment, which includes the photoreceptor of the first embodiment, can form images with excellent sensitivity characteristics and excellent dot reproducibility.

[0185] The process cartridge of the third embodiment may further include, in addition to the image carrier 65, at least one (for example, one to seven) selected from the group consisting of a charging device 63, an exposure device 61, a developing device 64, a transfer device 70 (particularly a primary transfer roller 71), a cleaning member 661, a rubbing roller 662, and a static elimination device 67.

[0186] The first process cartridge 101, second process cartridge 102, third process cartridge 103, and fourth process cartridge 104 shown in Figure 6 each include an image carrier 65, a charging device 63, a developing device 64, a cleaning device 66 having a cleaning member 661 and a rubbing roller 662, and a static elimination device 67, similar to the first image forming unit 62Y, second image forming unit 62C, third image forming unit 62M, and fourth image forming unit 62K. However, the process cartridges of the third embodiment are not limited to the first process cartridge 101 to the fourth process cartridge 104. As described above, the process cartridge of the third embodiment may further include at least one of the exposure device 61 and the transfer device 70, or it may include only one of the cleaning member 661 and the rubbing roller 662 (for example, only the cleaning member 661). In any case, the process cartridge of the third embodiment only needs to include the photoreceptor of the first embodiment as the image carrier 65.

[0187] The process cartridge of the third embodiment is designed to be detachably attached to the image forming apparatus 100. Therefore, the process cartridge is easy to handle, and if the sensitivity characteristics of the image carrier 65 deteriorate, it can be easily and quickly replaced, including the image carrier 65. The process cartridge of the third embodiment has been described above with reference to Figure 6.

[0188] [Substituent] The substituents used in this specification are described below. Examples of halogen atoms (halogen groups) include fluorine atoms (fluoro groups), chlorine atoms (chloro groups), bromine atoms (bromo groups), and iodine atoms (iodine groups).

[0189] Alkyl groups having 1 to 18 carbon atoms, alkyl groups having 10 to 18 carbon atoms, alkyl groups having 15 to 18 carbon atoms, alkyl groups having 18 carbon atoms, alkyl groups having 1 to 8 carbon atoms, alkyl groups having 1 to 6 carbon atoms, alkyl groups having 1 to 5 carbon atoms, and alkyl groups having 1 to 3 carbon atoms are, unless otherwise specified, linear or branched and unsubstituted. Examples of alkyl groups having 1 to 18 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, 1-methylbutyl group, 2-methylbutyl group, 3-methylbutyl group, 1-ethylpropyl group, 2-ethylpropyl group, 1,1-dimethylpropyl group, 1,2-dimethylpropyl group, 2,2-dimethylpropyl group, n-hexyl group, 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group, 1,1-dimethylbutyl group, 1,2-dimethylbutyl group, 1,3-dimethylbutyl group, 2,2-dimethylbutyl group, and 2,3-dimethylbutyl group. Examples include butyl groups, 3,3-dimethylbutyl groups, 1,1,2-trimethylpropyl groups, 1,2,2-trimethylpropyl groups, 1-ethylbutyl groups, 2-ethylbutyl groups, 3-ethylbutyl groups, linear and branched heptyl groups, linear and branched octyl groups, linear and branched nonyl groups, linear and branched decyl groups, linear and branched undecyl groups, linear and branched dodecyl groups, linear and branched tridecyl groups, linear and branched tetradecyl groups, linear and branched pentadecyl groups, linear and branched hexadecyl groups, linear and branched heptadecyl groups, and linear and branched octadecyl groups. Examples of alkyl groups having 10 to 18 carbon atoms, alkyl groups having 15 to 18 carbon atoms, alkyl groups having 18 carbon atoms, alkyl groups having 1 to 8 carbon atoms, alkyl groups having 1 to 6 carbon atoms, alkyl groups having 1 to 5 carbon atoms, and alkyl groups having 1 to 3 carbon atoms are, each, groups having the corresponding number of carbon atoms from the groups described as examples of alkyl groups having 1 to 18 carbon atoms.

[0190] Unless otherwise specified, alkoxy groups having 1 to 6 carbon atoms are linear or branched and unsubstituted. Examples of alkoxy groups having 1 to 6 carbon atoms include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, n-pentoxy, 1-methylbutoxy, 2-methylbutoxy, 3-methylbutoxy, 1-ethylpropoxy, 2-ethylpropoxy, 1,1-dimethylpropoxy, 1,2-dimethylpropoxy, 2,2-dimethylpropoxy, n-hexyloxy, and 1-methylpropoxy. Examples include the methylpentyloxy group, 2-methylpentyloxy group, 3-methylpentyloxy group, 4-methylpentyloxy group, 1,1-dimethylbutoxy group, 1,2-dimethylbutoxy group, 1,3-dimethylbutoxy group, 2,2-dimethylbutoxy group, 2,3-dimethylbutoxy group, 3,3-dimethylbutoxy group, 1,1,2-trimethylpropoxy group, 1,2,2-trimethylpropoxy group, 1-ethylbutoxy group, 2-ethylbutoxy group, and 3-ethylbutoxy group.

[0191] Unless otherwise specified, aryl groups having 6 to 14 carbon atoms and aryl groups having 6 to 10 carbon atoms are unsubstituted. Examples of aryl groups having 6 to 14 carbon atoms include the phenyl group, naphthyl group, indacenyl group, biphenylenyl group, acenaphthyrenyl group, anthryl group, and phenanthryl group. Examples of aryl groups having 6 to 10 carbon atoms are those groups among the examples of aryl groups having 6 to 14 carbon atoms that have the corresponding number of carbon atoms.

[0192] Alkenyl groups having 2 to 6 carbon atoms are linear or branched and unsubstituted unless otherwise specified. Alkenyl groups having 2 to 6 carbon atoms have one to three double bonds. Examples of alkenyl groups having 2 to 6 carbon atoms include ethenyl, propenyl, butenyl, butadienyl, pentenyl, hexenyl, hexadienyl, and hexatrinyl groups. The substituents used in this specification have been described above. [Examples]

[0193] The present invention will be described in more detail below using examples, but the present invention is not limited in any way to the scope of these examples.

[0194] [First particle and second particle] The following particles were used as the first and second particles. The conductivity mechanisms of these particles are shown in Table 1. • Tin oxide: "S-2000" manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd. (undoped tin oxide, BET specific surface area 52.5 ± 7.5 m²) 2 / g) • Phosphate-doped tin oxide: "SP-2" manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd. (BET specific surface area 105±25m²) 2 / g) • Antimond-doped tin oxide: "T-1" manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd. (BET specific surface area 77.5 ± 7.5 m²) 2 / g, number average primary particle diameter 200nm) • Zinc oxide: "NanoTek ZnO" manufactured by CIK Nanotech Co., Ltd. (number average primary particle size 65.9 nm) • Titanium dioxide: "MT-500B" manufactured by Teika Co., Ltd. (number mean primary particle size 40 nm) • Alumina: "Nanotek Al2O3" manufactured by CIK Nanotech Co., Ltd. (BET specific surface area 55m²) 2 / g, number average primary particle diameter 31 nm) • Silica: "Nanotek SiO2" manufactured by CIK Nanotech Co., Ltd. (BET specific surface area 110 m²) 2 / g, number average primary particle diameter 11 nm) • Silicone: "MSP-N050" manufactured by Nikko Rica Co., Ltd. (number mean primary particle size 500nm)

[0195] <Measurement of volume resistivity> Sheets containing each of the eight types of particles were prepared using the following method, and the volume resistivity of the eight prepared sheets was measured. The measurement results are shown in Table 1. Since the components other than the particles are the same for all eight sheets, there is a correlation between the volume resistivity of the eight particle-containing sheets and the volume resistivity of the particles contained in each sheet. For example, the higher the volume resistivity of the particle-containing sheet, the higher the volume resistivity of the particles contained in that sheet.

[0196] (Preparation of particle-containing sheets) 9.3 parts by mass of particles (any one of the above tin oxide, phosphorus-doped tin oxide, antimony-doped tin oxide, zinc oxide, titanium oxide, alumina, silica, and silicone), 56.0 parts by mass of a polyfunctional acrylate ester, 33.0 parts by mass of a monofunctional acrylate ester, 1.0 part by mass of a leveling agent, 10.0 parts by mass of a polymerization initiator, and 110.0 parts by mass of methanol were mixed using a bead mill for 10 hours to obtain a mixed solution s. As the polyfunctional acrylate ester, "A-DPH" manufactured by Shin-Nakamura Chemical Co., Ltd. was used. As the monofunctional acrylate ester, "Viscote 8F" manufactured by Osaka Organic Chemical Industry Co., Ltd. was used. As the leveling agent, dimethyl silicone oil ("KF96-50CS" manufactured by Shin-Etsu Chemical Co., Ltd.) was used. As the polymerization initiator, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide ("OMNIRAD TPO" manufactured by IGM RESINS) was used. The obtained mixed solution s was filtered using a filter with a pore size of 5 μm to obtain a coating solution for samples. Next, the coating solution for samples was applied onto a conductive substrate by the dip coating method. The applied coating solution for samples was irradiated with ultraviolet light having a wavelength of 365 nm from a light-emitting diode light source under the condition of a light energy of 86400 mW·s. By the irradiation of ultraviolet light, the polyfunctional acrylate ester and the monofunctional acrylate ester in the coating solution for samples were polymerized (photo-curing reaction) to form a photo-curable resin. In this way, a particle-containing sheet (film thickness: 3 μm) was formed on the conductive substrate. The particle-containing sheet contained a photo-curable resin cured by the photo-curing reaction, the above particles, a leveling agent, and a polymerization initiator. A circular mask with a diameter of 5 mm was placed on the formed particle-containing sheet, and silver paste was applied thereto to obtain a measurement sample for volume resistivity.

[0197] (Measurement of the volume resistivity of the particle-containing sheet) The volume resistivity was measured under the environment of a temperature of 23°C and a relative humidity of 50%RH. First, a high-voltage power amplifier ("MODEL 677B" manufactured by TREK), a function generator ("AG2062F" manufactured by OWON), and a picoammeter ("MODEL 485" manufactured by KETHLEY) were connected in series to the measurement sample. Subsequently, a voltage was applied between both electrodes under the conditions of +100V and a frequency of 33.3mHz, and the electrical resistance value 1 minute after the start of the application was measured. Then, based on the measured value of the electrical resistance and the dimensions of the particle-containing sheet, the volume resistivity of the particle-containing sheet was determined according to the following formula. Volume resistivity [Ω·cm] = Electrical resistance value × Cross-sectional area of the current path / Length of the current path

[0198]

Table 1

[0199] [Polyfunctional acrylate] As the polyfunctional acrylate, the following were used. · EA-3 / EA-4: "A-DPH" manufactured by Shin-Nakamura Chemical Co., Ltd. (a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate, the number of polymerizable functional groups of dipentaerythritol pentaacrylate is 5, the number of polymerizable functional groups of dipentaerythritol hexaacrylate is 6, hydroxyl value 10mgKOH / g) · EA-1 / EA-2: "A-TMM-3LM-N" manufactured by Shin-Nakamura Chemical Co., Ltd. (a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate, the number of polymerizable functional groups of pentaerythritol triacrylate is 3, the number of polymerizable functional groups of pentaerythritol tetraacrylate is 4, the content rate of pentaerythritol triacrylate in the mixture is 57% by mass)

[0200] [Monofunctional acrylate] As the monofunctional acrylate, the following were used. · R in formula (EB-1) 1is -CH2-(CF2)3CHF2 and R 2 Compounds where H is present: "Viscoat 8F" manufactured by Osaka Organic Chemical Industry Co., Ltd. (compound represented by formula (EB-12)) ·R in formula (EB-1) 1 -iso-C 18 H 37 And R 2 Compounds where H is present: "ISTA" (compound represented by formula (EB-13)) manufactured by Osaka Organic Chemical Industry Co., Ltd. ·R in formula (EB-1) 1 is -CH2-(CF2)CHF2 and R 2 Compounds where H is present: "Viscoat 4F" manufactured by Osaka Organic Chemical Industry Co., Ltd. (compound represented by formula (EB-11))

[0201] [Manufacturing of single-layer photoreceptors] Single-layer photoreceptors (P-A1) to (P-A49) and (P-B1) to (P-B8) were manufactured using the following method. The configurations of these single-layer photoreceptors are shown in Tables 2 to 6 below. Furthermore, the configurations of the single-layer photosensitive layers (A-1) to (A-23) shown in Tables 2 to 6 are shown in Table 7 below.

[0202] <Manufacturing of single-layer photoreceptor (P-A1)> (Formation of the intermediate layer) Two parts by mass of titanium dioxide, one part by mass of polyamide resin, ten parts by mass of methanol, one part by mass of butanol, and one part by mass of toluene were mixed using a bead mill for 5 hours to obtain mixture a. As titanium dioxide, prototype "SMT-A" manufactured by Teika Co., Ltd. (number average primary particle size of 10 nm, titanium dioxide primary surface-treated with alumina and silica, and then secondary surface-treated with methylhydrogenpolysiloxane) was used. As polyamide resin, "Amiran® ​​CM8000" manufactured by Toray Industries, Inc. (a quaternary copolymer polyamide resin of polyamide 6, polyamide 12, polyamide 66, and polyamide 610) was used. The obtained mixture a was filtered using a 5 μm mesh filter to obtain an intermediate layer coating solution. Next, the intermediate layer coating solution was applied to the surface of a conductive substrate by dip coating. An aluminum drum-shaped support was used as the conductive substrate. Next, the applied intermediate layer coating solution was dried at 130°C for 30 minutes to form an intermediate layer (film thickness: 2 μm) on the conductive substrate.

[0203] (Formation of a single-layer photosensitive layer) Next, a single-layer photosensitive layer was formed as shown in the (A-1) column of Table 7. Specifically, 1.31 parts by mass of Y-type titanyl phthalocyanine, 36.70 parts by mass of hole transporter (HT-2), a total of 30.80 parts by mass of electron transporter (more specifically, 15.40 parts by mass of electron transporter (ET-1) and 15.40 parts by mass of electron transporter (ET-6)), 100.00 parts by mass of bisphenol Z-type polycarbonate resin, and 500.00 parts by mass of tetrahydrofuran were mixed for 20 minutes using a rod-shaped ultrasonic oscillator to obtain mixture b. The obtained mixture b was filtered using a 5 μm mesh filter to obtain a coating solution for the single-layer photosensitive layer. Then, the coating solution for the single-layer photosensitive layer was applied to the intermediate layer on the conductive substrate by dip-coating. The coating solution for the single-layer photosensitive layer was dried at 110°C for 60 minutes to form a single-layer photosensitive layer (film thickness: 25 μm) on the intermediate layer. The total content of hole transporters and electron transporters in the single-layer photosensitive layer was 40% by mass relative to the mass of the single-layer photosensitive layer.

[0204] (Formation of a protective layer) Next, a protective layer was formed on the single-layer photosensitive layer (A-1), as shown in the protective layer column for the single-layer photoreceptor (P-A1) in Table 2. Specifically, the first particle was tin oxide 9.3 parts by mass, the second particle was alumina 3.5 parts by mass, polyfunctional acrylic acid ester (EA-3 / EA-4) 56.0 parts by mass, and monofunctional acrylic acid ester (R in formula (EB-1)) 1 is -CH2-(CF2)3CHF2 and R 2 34.0 parts by mass of a compound (where H is present), 10.0 parts by mass of a polymerization initiator, 1.0 part by mass of a leveling agent, and 110.0 parts by mass of methanol were mixed using a bead mill for 10 hours to obtain mixture c. As the polymerization initiator, a compound represented by the following formula (ST-1), namely 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (OMNIRAD TPO, manufactured by IGM RESINS), was used. Dimethyl silicone oil (KF96-50CS, manufactured by Shin-Etsu Chemical Co., Ltd.) was used as the leveling agent. The obtained mixture c was filtered using a 5 μm mesh filter to obtain a protective layer coating solution. Next, the protective layer coating solution was applied onto a single-layer photosensitive layer by dip-coating. The applied protective layer coating solution was irradiated with ultraviolet light of wavelength 365 nm from a light-emitting diode light source under conditions of light energy 86400 mW·s. Upon irradiation with ultraviolet light, the polyfunctional acrylic acid esters and monofunctional acrylic acid esters in the protective coating solution polymerized (photocuring reaction), forming a photocurable resin. In this way, a protective layer (film thickness: 3 μm) was formed on the single-layer photosensitive layer. The protective layer contained the photocurable resin cured by the photocuring reaction, tin oxide, alumina, a polymerization initiator, and a leveling agent.

[0205] [ka]

[0206] <Manufacturing of single-layer photoreceptors (P-A2) to (P-A49) and (P-B1) to (P-B8)> Single-layer photoreceptors (P-A2) to (P-A49) and (P-B1) to (P-B8) were manufactured using the same method as the single-layer photoreceptor (P-A1), with the following modifications.

[0207] (Formation of single-layer photosensitive layers in single-layer photoreceptors (P-A2) to (P-A49) and (P-B1) to (P-B8)) In forming the single-layer photosensitive layer, the single-layer photosensitive layers shown in the single-layer photosensitive layer column of Tables 2 to 6 were formed. For the formation of these single-layer photosensitive layers, the charge generating agent, hole transporter, electron transporter, and binder resin shown in Table 7 were used. Furthermore, the hole transporter and electron transporter were added in amounts such that the total content of the hole transporter and electron transporter relative to the mass of the single-layer photosensitive layer was the value shown in Table 7. For example, when the total content of the hole transporter and electron transporter mentioned above was 40% by mass relative to the mass of the single-layer photosensitive layer, a total of 36.70 parts by mass of hole transporter and a total of 30.80 parts by mass of electron transporter were used. When the total content of the hole transporter and electron transporter mentioned above was 60% by mass relative to the mass of the single-layer photosensitive layer, a total of 84.00 parts by mass of hole transporter and a total of 70.30 parts by mass of electron transporter were used. When using two types of hole transporters (HT-2) and (HT-3), each hole transporter was used in an amount such that the mass ratio of HT-2 / HT-3 was 1 / 1. When using two types of electron transporters (ET-1) and (ET-6), each electron transporter was used in an amount such that the mass ratio of ET-1 / ET-6 was 1 / 1.

[0208] (Formation of protective layer for single-layer photoreceptors (P-B1) to (P-B3)) In forming the protective layer of the single-layer photoreceptors (P-B1) to (P-B3), the first particle described in Table 2 was used. The second particle was not added.

[0209] (Formation of protective layer for single-layer photoreceptors (P-B4) to (P-B6)) In forming the protective layer of the single-layer photoreceptors (P-B4) to (P-B6), the first particle was not added. The second particle described in Table 2 was used.

[0210] (Formation of the protective layer of single-layer photoreceptors (P-A2) to (P-A49) and (P-B7) to (P-B8)) In the formation of the protective layer of single-layer photoreceptors (P-A2) to (P-A49) and (P-B7) to (P-B8), the first particles, second particles, polyfunctional acrylate, and monofunctional acrylate described in Tables 2 to 6 were used.

[0211] [Evaluation of single-layer photoreceptors] The dot reproducibility and sensitivity characteristics of each single-layer photoreceptor were evaluated by the following method. The evaluation results are shown in Tables 2 to 6.

[0212] <Evaluation equipment and evaluation paper> For the evaluation of dot reproducibility and sensitivity characteristics, a modified version of a color multifunction machine ("Taskalfa 356ci" manufactured by Kyocera Document Solutions Co., Ltd.) was used as the evaluation equipment. This evaluation equipment had a charging roller composed of an epichlorohydrin resin in which conductive carbon was dispersed. The charging polarity of the charging roller was positive, and the applied voltage of the charging roller was a DC voltage. The developing method was a two-component developing method. The transfer method was an intermediate transfer method. This evaluation equipment had a cleaning blade, a rubbing roller, and a charge removal device. For these evaluations, copy paper ("Multi Paper Super Economy +" sold by Askul Corporation) was used as the paper.

[0213] <Dot reproducibility> The evaluation of dot reproducibility was performed in a high-temperature and high-humidity environment at a temperature of 32°C and a relative humidity of 80%RH. A single-layer photoreceptor was mounted on the evaluation equipment. Using the evaluation equipment, Image G1 (an image with an image density of 1.6%) was printed on one sheet of paper. Among the printed dots, the image densities (ID) of 10 randomly selected locations were measured, and the average value of these was used as the evaluation value. For the measurement of image density, a reflection densitometer ("TC-6MC" manufactured by Tokyo Denshoku Co., Ltd.) was used.

[0214] (Criteria for dot reproducibility) Good (A): The evaluation value is 0.01 or more and less than 0.02. Poor (B): The evaluation value is less than 0.01.

[0215] <Sensitivity Characteristics> The sensitivity characteristics were evaluated under low-temperature, low-humidity conditions of 10°C and 10% RH relative humidity. A single-layer photoreceptor was mounted in the evaluation machine. The evaluation machine was set so that the charging potential of the single-layer photoreceptor was +500V. The exposure dose of the exposure device when printing solid images was set to 1.08 μJ / cm². 2 The settings were adjusted as follows. Using an evaluation machine, image G2 (solid image) was printed on a single sheet of paper, and the surface potential (post-exposure potential VL) of the single-layer photoreceptor after exposure was measured. Then, the sensitivity characteristics of the single-layer photoreceptor were evaluated from the post-exposure potential according to the following criteria.

[0216] (Sensitivity characteristics standard) Particularly good: VL is below +200V. Good: VL is between +200V and +270V. Defect: VL is above +270V.

[0217] [Table 2]

[0218] [Table 3]

[0219] [Table 4]

[0220] [Table 5]

[0221] [Table 6]

[0222] [Table 7]

[0223] The terms used in Tables 2 to 7 are as follows: Actual: Example Comparison: Comparative Example -: Does not contain the relevant ingredient. PTO: Phosphorus-doped tin oxide ATO: Antimond-doped tin oxide Polyfunctional group: Polyfunctional acrylic acid ester Monofunctional group: Monofunctional acrylic acid ester R1: R in equation (EB-1) 1 The base represented by R2: R in equation (EB-1) 2 The base represented by CGM: Charge Generator HTM: Hole transport agent ETM: Electronic Transport Agent HTM+ETM ratio: The total content of hole transporters and electron transporters relative to the mass of the single-layer photosensitive layer (unit: mass%) CG-1: Y-type titanyl phthalocyanine CG-2:X-type metal-free phthalocyanine BisZ: Bisphenol Z-type polycarbonate resin BisB: Bisphenol B type polycarbonate resin

[0224] As shown in Table 2, the protective layer of the single-layer photoreceptors (P-B1) to (P-B3) did not contain the second particle. The dot reproducibility of the single-layer photoreceptors (P-B1) to (P-B3) was evaluated as poor.

[0225] As shown in Table 2, the protective layer of the single-layer photoreceptors (P-B4) to (P-B6) did not contain the first particle. The sensitivity characteristics of the single-layer photoreceptors (P-B4) to (P-B6) were evaluated as poor.

[0226] As shown in Tables 2 and 3, the protective layer of the single-layer photoreceptors (P-B7) to (P-B8) contained silica as the first particle, but as shown in Table 1, the silica did not have n-type conductivity. The sensitivity characteristics of the single-layer photoreceptors (P-B7) to (P-B8) were evaluated as poor.

[0227] On the other hand, as shown in Tables 2 to 6, the protective layer of the single-layer photoreceptors (P-A1) to (P-A49) contained a first particle having n-type conductivity and a second particle not having n-type conductivity. The dot reproducibility of the single-layer photoreceptors (P-A1) to (P-A49) was evaluated as good, and the sensitivity characteristics were evaluated as good or particularly good.

[0228] [Manufacturing of stacked photoreceptors] A stacked photoreceptor (P-C1) was manufactured using the following method. The configuration of this stacked photoreceptor is shown in Table 8 below.

[0229] <Manufacturing of stacked photoreceptors (P-C1)> (Formation of the intermediate layer) The intermediate layer of the multilayer photoreceptor (P-C1) was formed in the same manner as the intermediate layer of the single-layer photoreceptor (P-A1), except that the coating conditions of the dip-coating method (the speed at which the conductive substrate is pulled out from the coating solution for the intermediate layer) were changed to change the thickness of the intermediate layer to 0.5 μm.

[0230] (Formation of a charge generation layer) 1.5 parts by mass of Y-type titanyl phthalocyanine, 1 part by mass of polyvinyl acetal resin (Sekisui Chemical Co., Ltd.'s "Eslec BX-5") as a base resin, 40 parts by mass of propylene glycol monomethyl ether, and 40 parts by mass of tetrahydrofuran were mixed using a bead mill for 12 hours to obtain mixture d. The obtained mixture d was filtered using a 3 μm mesh filter to obtain a coating solution for the charge generation layer. Next, the coating solution for the charge generation layer was applied to the intermediate layer on a conductive substrate by dip coating. The applied coating solution for the charge generation layer was dried at 50°C for 5 minutes to form a charge generation layer (film thickness: 0.3 μm) on the intermediate layer.

[0231] (Formation of charge transport layer) A total of 68.00 parts by mass of hole transporter (more specifically, 45.30 parts by mass of hole transporter (HT-2) and 22.70 parts by mass of hole transporter (HT-3)), 100.00 parts by mass of bisphenol Z type polycarbonate resin, 0.05 parts by mass of leveling agent, 340.00 parts by mass of tetrahydrofuran, and 60.00 parts by mass of toluene were mixed using a roll mill for 24 hours to obtain a coating solution for the charge transport layer. Dimethyl silicone oil (Shin-Etsu Chemical Co., Ltd. "KF96-50CS") was used as the leveling agent. Next, the coating solution for the charge transport layer was applied to the charge generation layer by dip coating. The applied coating solution for the charge transport layer was dried at 120°C for 40 minutes to form a charge transport layer (film thickness: 25 μm) on the charge generation layer. The total content of hole transporter in the charge transport layer was 40% by mass relative to the mass of the charge transport layer.

[0232] (Formation of a protective layer) The protective layer of the stacked photoreceptor (P-C1) was formed in the same manner as the protective layer of the single-layer photoreceptor (P-A1), except that the protective coating solution was applied to the charge transport layer instead of the single-layer photoreceptor, and the tin oxide was changed to phosphorus-doped tin oxide.

[0233] [Evaluation of stacked photoreceptors] The dot reproducibility and sensitivity characteristics of each stacked photoreceptor were evaluated using the following method. The evaluation results are shown in Table 8.

[0234] <Evaluation equipment and evaluation forms> Except for modifying the charging roller's polarity from positive to negative, the same evaluation machine used for evaluating single-layer photoreceptors was used for evaluating multilayer photoreceptors. The same evaluation paper used for evaluating single-layer photoreceptors was used for evaluating multilayer photoreceptors.

[0235] <Dot Reproducibility> The dot reproducibility of the stacked photoreceptor was evaluated using the same method as for evaluating the dot reproducibility of the single-layer photoreceptor.

[0236] <Sensitivity Characteristics> The sensitivity characteristics of the stacked photoreceptor were evaluated using the same method as for the evaluation of the sensitivity characteristics of the single-layer photoreceptor, except that the evaluation machine was set so that the charging potential of the stacked photoreceptor was -500V, and the evaluation criteria were changed as follows.

[0237] (Sensitivity characteristics standard) Particularly good: VL is -200V or higher. Good: VL is between -270V and -200V. Defect: VL is below -270V.

[0238] [Table 8]

[0239] In Table 8, "Actual" and "PTO" have the same meaning as the terms explained in Tables 2 to 7 above.

[0240] As shown in Table 8, the protective layer of the stacked photoreceptor (P-C1) contained a first particle having n-type conductivity and a second particle not having n-type conductivity. The dot reproducibility of the stacked photoreceptor (P-C1) was evaluated well, and the sensitivity characteristics were particularly good.

[0241] From the above, it has been shown that the photoreceptor of the present invention, which includes single-layer photoreceptors (P-A1) to (P-A49) and stacked photoreceptor (P-C1), can form images with excellent sensitivity characteristics and excellent dot reproducibility. Furthermore, because such a photoreceptor is provided, it is determined that the process cartridge and image forming apparatus of the present invention can form images with excellent sensitivity characteristics and excellent dot reproducibility of the photoreceptor. [Industrial applicability]

[0242] The photoreceptor according to the present invention can be used in an image forming apparatus. The process cartridge and image forming apparatus according to the present invention can be used to form an image on a recording medium.

Claims

1. An electrophotographic photoreceptor comprising a conductive substrate, a photosensitive layer, and a protective layer, The photosensitive layer contains a charge generating agent and a hole transporting agent, The protective layer is the outermost layer of the electrophotographic photoreceptor, The protective layer contains first particles having n-type conductivity and second particles not having n-type conductivity. The protective layer further contains a photocurable resin, The photocurable resin has repeating units derived from a compound having two or more polymerizable functional groups, and repeating units derived from a compound having one polymerizable functional group. The compound having one polymerizable functional group is an electrophotographic photoreceptor represented by formula (EB-1). 【Chemistry 1】 (In formula (EB-1) above, R1 represents a group represented by formula (b1) or (b2), and R2 represents a hydrogen atom or a methyl group.) 【Chemistry 2】 (In formula (b1) above, m represents 0 or 1, n represents an integer between 1 and 3, and R3 represents a hydrogen atom or a fluorine atom.) In formula (b2) above, R4 represents an alkyl group having 1 to 18 carbon atoms.

2. An electrophotographic photoreceptor comprising a conductive substrate, a photosensitive layer, and a protective layer, The photosensitive layer contains a charge generating agent and a hole transporting agent, The protective layer is the outermost layer of the electrophotographic photoreceptor, The protective layer contains first particles having n-type conductivity and second particles not having n-type conductivity. An electrophotographic photoreceptor wherein the hole transport agent contained in the photosensitive layer comprises at least one of the compounds represented by formulas (1), (2), and (3). 【Transformation 3】 (In formula (1) above, R 41, R 42, R 43, R 44, R 45, and R 46 each independently represent an alkyl group having 1 to 8 carbon atoms, or a phenyl group; R 47 and R 48 each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a phenyl group; e 1, e 2, e 3, and e 4 each independently represent an integer between 0 and 5; e 5 and e 6 each independently represent an integer between 0 and 4; In formula (2), R 50, R 51, and R 54 each independently represent an alkyl group having 1 to 8 carbon atoms, or a phenyl group; R 52 and R 53 each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a phenyl group which may be substituted with an alkyl group having 1 to 8 carbon atoms; and f 3, f 4, and f 5 each independently represent an integer between 0 and 5. In formula (3) above, R11, R12, R13, and R14 each independently represent an alkyl group or phenyl group having 1 to 8 carbon atoms, and a1, a2, a3, and a4 each independently represent an integer between 0 and 5.

3. An electrophotographic photoreceptor comprising a conductive substrate, a photosensitive layer, and a protective layer, The photosensitive layer contains a charge generating agent and a hole transporting agent, The protective layer is the outermost layer of the electrophotographic photoreceptor, The protective layer contains first particles having n-type conductivity and second particles not having n-type conductivity. The aforementioned photosensitive layer is a single layer, The aforementioned photosensitive layer further contains an electron transport agent, The electron transport agent comprises at least one compound represented by formulas (11), (12), (13), (14), (15), and (16) in an electrophotographic photoreceptor. 【Chemistry 4】 (Q1 and Q2 in formula (11), Q21, Q22, Q23, and Q24 in formula (12), Q31 and Q32 in formula (13), Q41, Q42, and Q43 in formula (14), Q71, Q72, Q73, Q74, Q75, and Q76 in formula (15), and Q61 and Q62 in formula (16) each independently represent a hydrogen atom, a halogen atom, a cyano group, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 14 carbon atoms which may be substituted with at least one substituent selected from the group consisting of an alkyl group having 1 to 6 carbon atoms and a halogen atom.) In formula (15) above, Y1 and Y2 represent oxygen atoms.

4. The electrophotographic photoreceptor according to any one of claims 1 to 3, wherein the volume resistivity of the second particle is higher than the volume resistivity of the first particle.

5. The electrophotographic photoreceptor according to any one of claims 1 to 3, wherein the first particle is a metal oxide particle.

6. The electrophotographic photoreceptor according to any one of claims 1 to 3, wherein the first particle is a tin oxide particle.

7. The electrophotographic photoreceptor according to any one of claims 1 to 3, wherein the first particle is phosphorus-doped tin oxide particle or antimond-doped tin oxide particle.

8. The electrophotographic photoreceptor according to any one of claims 1 to 3, wherein the second particle is alumina particle, silica particle, or silicone particle.

9. The protective layer further contains a photocurable resin, The electrophotographic photoreceptor according to claim 2 or 3, wherein the photocurable resin comprises repeating units derived from a compound having two or more polymerizable functional groups and repeating units derived from a compound having one polymerizable functional group.

10. The electrophotographic photoreceptor according to claim 9, wherein the compound having two or more polymerizable functional groups is at least one selected from the group consisting of compounds represented by formulas (EA-1), (EA-2), (EA-3), and (EA-4). 【Transformation 5】

11. The electrophotographic photoreceptor according to any one of claims 1 to 3, wherein the thickness of the protective layer is 2 μm or more.

12. The electrophotographic photoreceptor according to any one of claims 1 to 3, wherein the charge generating agent contained in the photosensitive layer comprises titanyl phthalocyanine or metal-free phthalocyanine.

13. At least one selected from the group consisting of a charging device, an exposure device, a developing device, a transfer device, a cleaning member, a friction roller, and a static elimination device, A process cartridge comprising an electrophotographic photoreceptor according to any one of claims 1 to 3.

14. Image carrier and, A charging device for charging the surface of the image carrier, An exposure apparatus for exposing the surface of the charged image carrier to form an electrostatic latent image on the surface of the image carrier, A developing apparatus that supplies toner to the surface of the image carrier and develops the electrostatic latent image as a toner image, The system comprises a transfer device for transferring the toner image from the image carrier to the transfer target, An image forming apparatus wherein the image carrier is an electrophotographic photoreceptor according to any one of claims 1 to 3.

Images