Electrophotographic photoreceptor, method for manufacturing an electrophotographic photoreceptor, process cartridge, and image forming apparatus

Abstract

This electrophotographic photoreceptor comprises a conductive substrate (2), a photoreceptive layer (3), and a protective layer (5). The photoreceptive layer (3) contains a charge generating agent, a hole transport agent, and a binder resin. The hole transport agent has two or fewer chain ethene-1,2-diyl groups or does not have any chain ethene-1,2-diyl groups. The protective layer (5) is the outermost surface layer of the electrophotographic photoreceptor and contains a photocurable resin. If a first absorbance of the protective layer (5) is A and a second absorbance thereof is B, as measured by Fourier transform infrared spectroscopy, the ratio A / B of the first absorbance to the second absorbance is 0.160 or less. The first absorbance is the highest absorbance within the wavelength range from 1627 cm−1 to 1647 cm−1. The second absorbance is the highest absorbance within the wavelength range of greater than 1647 cm−1 to 1800 cm−1.

Description

[Technical Field]

[0001] The present invention relates to an electrophotographic photoreceptor, a method for manufacturing 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 electrophotographic photoreceptor described in Patent Document 1 has a photosensitive layer on a conductive support containing a charge generating material and a charge transporting material in the same layer. A protective layer is provided on the photosensitive layer. The volume resistivity of the protective layer is smaller than the volume resistivity of the photosensitive layer. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2010-286707 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, the electrophotographic photoreceptor described in Patent Document 1 is not intended to contain a photocurable resin in its protective layer. Our research has revealed that when a photocurable resin is included in the protective layer, it is likely to cause a decrease in the potential stability of the electrophotographic photoreceptor and poor curing of the protective layer.

[0005] The present invention has been made in view of the above problems, and its object is to provide an electrophotographic photoreceptor that can sufficiently cure the protective layer and has excellent potential stability even when the protective layer contains a photocurable resin, and a method for manufacturing the same. Another object of the present invention is to provide a process cartridge and an image forming apparatus equipped with such an electrophotographic photoreceptor. [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, a hole transporter, and a binder resin. The hole transporter has two or fewer chain-like ethene-1,2-diyl groups, or it does not have chain-like ethene-1,2-diyl groups. The protective layer is the outermost layer of the electrophotographic photoreceptor and contains a photocurable resin. If the first absorbance of the protective layer, measured by Fourier transform infrared spectroscopy, is A and the second absorbance is B, then the ratio of the first absorbance to the second absorbance, A / B, is 0.160 or less. The first absorbance is measured at a wavenumber of 1627 cm⁻¹. -1 The above is 1647cm. -1 The highest absorbance is observed within the following range: The second absorbance is at wavenumber 1647 cm⁻¹. -1 Super 1800cm -1 The absorbance is highest within the following range.

[0007] The present invention relates to a method for manufacturing an electrophotographic photoreceptor, which is the method for manufacturing an electrophotographic photoreceptor described above. The present invention relates to a method for manufacturing an electrophotographic photoreceptor, which includes a protective layer forming step of forming the protective layer containing the photocurable resin on the photosensitive layer. In the protective layer forming step, the photocurable resin is formed by irradiating at least one of the monomers and oligomers on the photosensitive layer with ultraviolet light to polymerize at least one of the monomers and oligomers.

[0008] 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.

[0009] 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]

[0010] The electrophotographic photoreceptor of the present invention, and the electrophotographic photoreceptor manufactured by the manufacturing method of the present invention, can sufficiently cure the protective layer and exhibit excellent potential stability, even when the protective layer contains a photocurable resin. Furthermore, the process cartridge of the present invention and the image forming apparatus of the present invention are equipped with an electrophotographic photoreceptor that can sufficiently cure the protective layer and exhibit excellent potential stability, even when the protective layer contains a photocurable resin. [Brief explanation of the drawing]

[0011] [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 is the absorption spectrum of the protective layer of the photoreceptor according to Example 2, measured by Fourier transform infrared spectroscopy. [Figure 7]This is the absorption spectrum of a hole transporter before and after irradiation with a predetermined ultraviolet light, measured by ultraviolet-visible spectroscopy. This hole transporter is contained in the photosensitive layer of the photoreceptor according to Example 4. [Figure 8] This figure shows an example of an image forming apparatus according to a third embodiment of the present invention. [Figure 9] Figure 8 shows an example of the configuration of a developing apparatus. [Modes for carrying out the invention]

[0012] 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.

[0013] Acrylic and methacrylic may be collectively referred to as "(meth)acrylic." Acrylate and methacrylate may be collectively referred to as "(meth)acrylate." Acryloyl and methacryloyl may be collectively referred to as "(meth)acryloyl." 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-average 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-average 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 term "system" may be added after a compound name to comprehensively refer to the compound and its derivatives. Similarly, when "system" is added after a compound name to represent a polymer name, it means that the repeating units of the polymer originate from the compound or its derivatives. Furthermore, "general formula" and "chemical formula" are collectively referred to as "formula." In the description of a formula, "each independently" means that they may represent the same group or different groups. Unless otherwise specified, each component described herein may be used alone or in combination of two or more. For example, "at least one of A, B, and C" and "at least one of A, B, and C" are synonymous with "at least one selected from the group consisting of A, B, and C." "At least one of A, B, and C" and "at least one of A, B, and C" are synonymous with "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.

[0014] [First Embodiment: Electrophotographic Photoreceptor] A first embodiment of the present invention relates to an electrophotographic photoreceptor (hereinafter sometimes referred to as "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, a hole transporter, and a binder resin. The hole transporter has two or fewer chain-like ethene-1,2-diyl groups. Alternatively, the hole transporter does not have chain-like ethene-1,2-diyl groups. The protective layer is the outermost surface layer of the photoreceptor. The protective layer contains a photocurable resin. If the first absorbance of the protective layer, measured by Fourier transform infrared spectroscopy, is A and the second absorbance is B, then the ratio A / B of the first absorbance (hereinafter sometimes referred to as "first absorbance A") to the second absorbance (hereinafter sometimes referred to as "second absorbance B") is 0.160 or less. The first absorbance A is at wavenumber 1627 cm⁻¹. -1 The above is 1647cm. -1 The highest absorbance is observed within the following range: Absorbance B (second highest) occurs at wavenumber 1647 cm⁻¹. -1 Super 1800cm -1 The highest absorbance is observed within the following range. Hereinafter, "chain-like ethene-1,2-diyl group" may be referred to as "specified double bond." "The ratio A / B of the first absorbance A to the second absorbance B of the protective layer, measured by Fourier transform infrared spectroscopy" may simply be referred to as "ratio A / B."

[0015] The photoreceptor of the first embodiment, by having the above configuration, can sufficiently cure the protective layer even when the protective layer contains a photocurable resin, and exhibits excellent potential stability. The reason for this is presumed to be as follows.

[0016] The protective layer of the photoreceptor in the first embodiment contains a photocurable resin. In the protective layer formation process, at least one of the monomers and oligomers on the photoreceptor layer is irradiated with ultraviolet light to cause a polymerization reaction (photocuring reaction) of at least one of the monomers and oligomers, thereby forming a photocurable resin. As a result, the protective layer hardens, and a protective layer containing the photocurable resin is formed. Hereinafter, "monomers and oligomers" may be referred to as "monomers, etc." The protective layer formation process will be described later in the second embodiment.

[0017] However, ultraviolet light irradiated during the protective layer formation process can break predetermined double bonds in the hole transporter contained in the photosensitive layer, causing the hole transporter to decompose. When the hole transporter decomposes, the potential stability of the photoreceptor decreases. The inventors have conducted diligent research and found that hole transporters having two or fewer predetermined double bonds, and hole transporters without predetermined double bonds, are less susceptible to decomposition by ultraviolet light. By incorporating a hole transporter having two or fewer predetermined double bonds or a hole transporter without predetermined double bonds into the photosensitive layer, the decomposition of the hole transporter by ultraviolet light can be suppressed. As a result, holes can be transported smoothly by the hole transporter, and the potential stability of the photoreceptor in the first embodiment is improved.

[0018] Furthermore, the ratio A / B of the protective layer on the photoreceptor of the first embodiment is 0.160 or less. The first absorbance A is the absorbance of the peak based on the polymerizable functional group that reacts in the above photocuring reaction (for example, the vinyl group if the photocuring reaction is an addition polymerization reaction of vinyl groups). As the photocuring reaction progresses, the number of polymerizable functional groups decreases, and the first absorbance A decreases. On the other hand, the second absorbance B is the absorbance of the peak based on the non-polymerizable functional group that does not react in the photocuring reaction (for example, the carbonyl group if the photocuring reaction is an addition polymerization reaction of vinyl groups). Even as the photocuring reaction progresses, the number of non-polymerizable functional groups remains unchanged, and the second absorbance B remains constant. From the above, the ratio A / B indicates the progress of the photocuring reaction. The smaller the ratio A / B, the fewer the number of polymerizable functional groups, indicating that the photocuring reaction is progressing. If the ratio A / B is 0.160 or less, the number of polymerizable functional groups is sufficiently reduced, making it difficult for radicals generated in the photocuring reaction to remain in the protective layer. As a result, the decrease in the potential stability of the photoreceptor can be suppressed. Also, if the ratio A / B is 0.160 or less, the photocuring reaction has progressed sufficiently, allowing the protective layer to cure completely.

[0019] The above explains why the photoreceptor of the first embodiment can sufficiently cure the protective layer and exhibit excellent potential stability, even when the protective layer contains a photocurable resin. 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 photosensitive layer (hereinafter sometimes referred to as a single-layer photosensitive layer) 3a. In the example shown in Figure 1, the single-layer photosensitive layer 3a is provided on the conductive substrate 2, and the protective layer 5 is provided on the single-layer photosensitive layer 3a. The single-layer photosensitive layer 3a is provided directly 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, and even more preferably 2 μm to 10 μm. In the examples 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 a photocurable resin. 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] Since the protective layer 5 included in the layered photoreceptor 10 is the same as the protective layer 5 included in the single-layer photoreceptor 1, the description thereof will be omitted. As described above, the structure of the layered photoreceptor 10, which is an example of a photoreceptor, has been described with reference to FIGS. 3 to 5.

[0030] <Protective layer> The protective layer contains a photocurable resin. The protective layer preferably further contains a metal oxide. Further, the protective layer may contain a polymerization initiator used for the photocuring reaction. The protective layer may further contain an additive as necessary.

[0031] (Ratio A / B) As described above, the ratio A / B is 0.160 or less. In order to sufficiently cure the protective layer, the ratio A / B is preferably 0.155 or less, and more preferably 0.150 or less. In order to preferably suppress the decomposition of the hole transport agent by ultraviolet irradiation in the protective layer forming step, the ratio A / B is preferably 0.000 or more, and more preferably 0.100 or more.

[0032] Hereinafter, the method for measuring the ratio A / B will be described with reference to FIG. 6. FIG. 6 is an absorption spectrum of the protective layer of the photoreceptor according to Example 2 described later. This absorption spectrum is measured by Fourier transform infrared spectroscopy (FT-IR). The horizontal axis in FIG. 6 indicates the wave number (unit: cm -1 ), and the vertical axis indicates the transmittance (%). In the spectrum shown in FIG. 6, the peak P -1 showing the lowest transmittance in the range of 1627 cm -1 or more and 1647 cm A or less, and the peak P -1 showing the lowest transmittance in the range of more than 1647 cm -1 and 1800 cm B or less are confirmed. From the spectrum shown in FIG. 6, the transmittance %T A of the peak P A and the transmittance %T B of the peak P B are read. According to Lambert-Beer's law, based on the calculation formula "absorbance = -Logt", the peak PA Transmittance %T A The first absorbance A is calculated from this, and the transmittance %T is calculated. B The second absorbance B is calculated from this. Note that t in the calculation formula is a value that has not been converted to a percentage (for example, %T). A / 100, or %T B Substitute ( / 100). The calculated first absorbance A is at wavenumber 1627 cm⁻¹. -1 The above is 1647cm. -1 The highest absorbance corresponds to the following range. The calculated second absorbance B corresponds to wavenumber 1647 cm⁻¹. -1 Super 1800cm -1 The highest absorbance within the following range corresponds to the ratio A / B. The ratio A / B is calculated from the first absorbance A and the second absorbance B based on the formula "Ratio A / B = First absorbance A / Second absorbance B". Note that although the example shown in Figure 6 was measured in transmittance mode of the FT-IR analyzer, the ratio A / B may also be determined directly by measuring in absorbance mode.

[0033] In the protective layer formation process, the higher the light energy of the ultraviolet light irradiated, the more the photocuring reaction progresses, and the lower the ratio A / B tends to be. Furthermore, the ratio A / B can also be adjusted by changing at least one of the monomers or other components used to form the photocurable resin.

[0034] (light curing 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 UV irradiation also stops the photocuring reaction, making it easy to control the progress of the photocuring reaction.

[0035] The photocurable resin preferably has vinyl groups and carbonyl groups. When such a photocurable resin is contained in the protective layer, the first absorbance A is, for example, the absorbance of the peak based on the vinyl group (more specifically, the C=C stretching vibration of the vinyl group), and the second absorbance B is, for example, the absorbance of the peak based on the carbonyl group (more specifically, the carbonyl absorption). An example of a photocurable resin having vinyl groups and carbonyl groups is a (meth)acrylic resin.

[0036] The photocurable resin contains repeating units derived from (meth)acrylic acid ester, and this (meth)acrylic acid ester preferably has 2 to 6 vinyl groups. Hereinafter, "(meth)acrylic acid ester having 2 to 6 vinyl groups" may be referred to as "polyfunctional acrylic acid ester". The polyfunctional acrylic acid ester preferably has 3 to 6 vinyl groups.

[0037] 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.

[0038] 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.

[0039] Pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate are compounds represented by formulas (EA-1), (EA-2), (EA-3), and (EA-4), respectively.

[0040] [ka]

[0041] 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.

[0042] [ka]

[0043] Y in equation (EA-1a) 1 ~Y 3At least one of them represents a group represented by formula (Yb), and Y 1 ~Y 3 The remaining part represents the base expressed by equation (Ya). Y in equation (EA-2a) 4 ~Y 7 At least one of them represents a group represented by formula (Yb), and Y 4 ~Y 7 The remaining part represents the group expressed by equation (Ya). Y in equation (EA-3a) 8 ~Y 12 At least one of them represents a group represented by formula (Yb), and Y 8 ~Y 12 The remaining part represents the group represented by equation (Ya). Y in equation (EA-4a) 13 ~Y 18 At least one of them represents a group represented by formula (Yb), and Y 13 ~Y 18 The remaining part represents the base expressed by formula (Ya).

[0044] [ka]

[0045] * in equations (Ya) and (Yb) 1 * is a bond that attaches to the carbon atom of the carbonyl group in formulas (EA-1a) to (EA-4a). 2 This is the base represented by formula (Yb) that other repeating units have * 2 This is a bond that connects to the group represented by formula (Yb) of a repeating unit. 2 and the base represented by formula (Yb) of the other repeating units * 2 They are connected to each other.

[0046] 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.

[0047] 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.

[0048] The content of repeating units derived from polyfunctional acrylic acid esters in the total repeating units of the photocurable resin is preferably 60% by mass or more (i.e., 60% by mass or more and 100% by mass or less), more preferably 70% by mass or more and 100% by mass or less, even more preferably 80% by mass or more and 100% by mass or less, even more preferably 90% by mass or more and 100% by mass or less, and particularly preferably 100% by mass. If the content of repeating units derived from polyfunctional acrylic acid esters is 60% by mass or more, there are many polymerizable functional groups that react in the photocuring reaction, which can promote the photocuring reaction.

[0049] The photocurable resin may further contain repeating units derived from urethane (meth)acrylate in addition to repeating units derived from polyfunctional acrylic acid ester. Urethane (meth)acrylate has a urethane bond (-O-CO-NH-) and a (meth)acryloyloxy group. The number of vinyl groups in urethane (meth)acrylate is less than the number of vinyl groups in polyfunctional acrylic acid ester. For example, urethane (meth)acrylate has one vinyl group. Note that the polyfunctional acrylic acid ester mentioned above does not have a urethane bond.

[0050] Commercially available urethane (meth)acrylate products that can be used include U-2PPA, U-6LPA, U-200PA, UA-33H, U-10HA, U-10PA, and U-15HA from Shin-Nakamura Chemical Industry Co., Ltd., and 8FS-001 and 8SS-723 from Taisei Fine Chemical Co., Ltd.

[0051] When the photocurable resin further contains repeating units derived from urethane (meth)acrylate, the content of repeating units derived from urethane (meth)acrylate to the total of repeating units derived from polyfunctional acrylic acid ester and repeating units derived from urethane (meth)acrylate is preferably 40% by mass or more and 60% by mass or less. Furthermore, the total content of repeating units derived from polyfunctional acrylic acid ester and repeating units derived from urethane (meth)acrylate to the total repeating units of the photocurable resin is preferably 90% by mass or more, more preferably 95% by mass or more, and particularly preferably 100% by mass.

[0052] In addition to polyfunctional acrylic acid esters and urethane (meth)acrylates, other monomers (hereinafter sometimes referred to as "other monomers") may be further included as monomers for forming the photocurable resin. Examples of other monomers include acrylic acid esters having one vinyl group. The content of the photocurable 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, based on the mass of the protective layer.

[0053] (Metal oxides) Examples of metal oxides include alumina, zinc oxide, titanium oxide, and conductive metal oxides (e.g., phosphorus-doped tin oxide and antimond-doped tin oxide). Preferably, at least one metal oxide is selected from the group consisting of alumina, phosphorus-doped tin oxide, and antimond-doped tin oxide, and more preferably two. The metal oxide is contained in the protective layer, for example, as metal oxide particles.

[0054] The protective layer preferably contains two types of metal oxides. Preferably, the two types of metal oxides are a first metal oxide that is conductive and a second metal oxide that has lower conductivity (in other words, higher volume resistivity) than the first metal oxide.

[0055] The first metal oxide is preferably phosphorus-doped tin oxide or antimond-doped tin oxide, and the second metal oxide is preferably alumina. That is, it is preferable that one of the two metal oxides contained in the protective layer is alumina. It is preferable that the other of the two metal oxides is phosphorus-doped tin oxide or antimond-doped tin oxide. The ratio M2 / M1 of the mass of phosphorus-doped tin oxide or antimond-doped tin oxide to the mass M1 of alumina is preferably 1 or more and 10 or less, more preferably 1 or more and 5 or less, and even more preferably 1 or more and 3 or less.

[0056] The BET specific surface area of ​​metal oxide particles is 30 m². 2 / g or more 200m 2 It is preferable that it be less than or equal to / g, and 55m 2 / g or more 130m 2 It is more preferable that the amount is less than or equal to / g. The number-average primary particle diameter of the metal oxide particles is preferably 5 nm to 50 nm, and more preferably 20 nm to 35 nm.

[0057] The content of metal oxides 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.

[0058] (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.

[0059] (Additives) Examples of additives contained in the protective layer include leveling agents (e.g., silicone oil and leveling agents having halogen atoms) and silica. As for the leveling agent, a leveling agent having halogen atoms is preferred, an acrylic polymer having halogen atoms is more preferred, a fluorosilicone-modified acrylic polymer is even more preferred, and a UV-curable fluorosilicone-modified acrylic polymer is particularly preferred. The leveling agent preferably has polymerizable functional groups. When the leveling agent has polymerizable functional groups, the photocurable resin has repeating units derived from the leveling agent as repeating units. When the leveling agent has polymerizable functional groups, the polymerizable functional group equivalent (e.g., vinyl group equivalent) of the leveling agent is preferably 100 g / mol to 500 g / mol, and more preferably 260 g / mol to 450 g / mol. Furthermore, it is preferable that the protective layer does not contain charge generating agents, hole transporters, and electron transporters.

[0060] <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.

[0061] When 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, since the photoreceptor of the first embodiment can suppress the decomposition of the hole transport agent even without containing a radical acceptor compound, the charge generation layer and the charge transport layer may each not contain a radical acceptor compound.

[0062] (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.

[0063] 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).

[0064] [ka]

[0065] 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).

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] (Hole transport agent) The hole transporter has two or fewer (one or two) predetermined double bonds, or it does not have any predetermined double bonds. 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. The predetermined double bond (i.e., a linear ethene-1,2-diyl group) is a double bond that constitutes a linear group because it is linear. Because the predetermined double bond is linear, it is not a double bond that constitutes a ring such as a benzene ring.

[0071] [ka]

[0072] 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.

[0073] [ka]

[0074] 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 48 Each 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

[0075] 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 42These 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.

[0076] 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.

[0077] 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 53 Each 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.

[0078] 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 51may represent the same group as each other or different groups. When f5 represents an integer of 2 or more and 5 or less, a plurality of R 54 may represent the same group as each other or different groups.

[0079] In formula (2), R 50 , R 51 , and R 54 each preferably independently represents an alkyl group having 1 to 8 carbon atoms, more preferably represents an alkyl group having 1 to 3 carbon atoms, and even more preferably represents a methyl group. R 52 and R 53 each 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 8 carbon atoms is preferably an alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group. f3, f4, and f5 each preferably independently represents 0 or 1.

[0080] In formula (3), R 11 , R 12 , R 13 , and R 14 each independently represents an alkyl group having 1 to 8 carbon atoms or a phenyl group. a1, a2, a3, and a4 each independently represents an integer of 0 or more and 5 or less.

[0081] In formula (3), when a1 represents an integer of 2 or more and 5 or less, a plurality of R 11 may represent the same group as each other or different groups. When a2 represents an integer of 2 or more and 5 or less, a plurality of R 12 may represent the same group as each other or different groups. When a3 represents an integer of 2 or more and 5 or less, a plurality of R 13 [[ID=三十八]]may represent the same group as each other or different groups. When a4 represents an integer of 2 or more and 5 or less, a plurality of R 14 may represent the same group as each other or different groups.

[0082] 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.

[0083] 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). The predetermined number of double bonds in hole transporters (HT-2), (HT-3), and (HT-4) is 2, 0, and 0, respectively.

[0084] [ka]

[0085] The photosensitive layer may further contain hole transporters having three or more predetermined double bonds (hereinafter sometimes referred to as other hole transporters). However, in order to suitably suppress the decomposition of hole transporters by ultraviolet irradiation in the protective layer formation process, it is preferable that the photosensitive layer does not contain other hole transporters. 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.

[0086] When the photoreceptor is a single-layer photoreceptor, the content of the hole transport agent in the single-layer photosensitive layer, which is the photosensitive layer, is preferably 10 parts by mass or more and 200 parts by mass or less, more preferably 80 parts by mass or more and 130 parts by mass or less, based on 100 parts by mass of the binder resin. When the photoreceptor is a laminated photoreceptor, the content of the hole transport agent in the photosensitive layer (specifically, the charge transport layer) is preferably 10 parts by mass or more and 200 parts by mass or less, more preferably 50 parts by mass or more and 100 parts by mass or less, based on 100 parts by mass of the binder resin.

[0087] (Electron transport agent) Examples of the electron transport agent 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 dibromo maleic anhydride. Examples of the quinone compounds include diphenoquinone compounds, azoquinone compounds, anthraquinone compounds, naphthoquinone compounds, nitroanthraquinone compounds, and dinitroanthraquinone compounds.

[0088] 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 described as electron transport agents (11), (12), (13), (14), (15), and (16), respectively.

[0089]

Chemical formula

[0090] Q in formula (11) 1 and Q 2 in formula (12), Q21 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 Each independently represents 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), Y 1 and Y 2 This represents an oxygen atom.

[0091] 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 Preferably, each of these independently represents a hydrogen atom, an alkyl 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.

[0092] 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.

[0093] 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.

[0094] 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).

[0095] [ka]

[0096] 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. When the photoreceptor is a single-layer photoreceptor, the content of electron transporters in the single-layer photosensitive 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, based on 100 parts by mass of binder resin.

[0097] (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).

[0098] 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).

[0099] [ka]

[0100] (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.

[0101] (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.

[0102] <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.

[0103] 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).

[0104] 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.

[0105] <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.

[0106] [Second Embodiment: Method for Manufacturing a Photoreceptor] Next, an example of a method for manufacturing a photoreceptor according to the second embodiment of the present invention will be described. The method for manufacturing a photoreceptor according to the second embodiment includes, for example, a photosensitive layer formation step and a protective layer formation step.

[0107] (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.

[0108] (Photosensitive layer formation process for stacked photoreceptors) The photosensitive layer formation process for a stacked photoreceptor will be 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.

[0109] 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.

[0110] 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.

[0111] (Protective layer formation process) In the protective layer formation process, a protective layer containing a photocurable resin 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 at least one monomer or the like for forming the photocurable resin, a polymerization initiator, a solvent, a metal oxide if necessary, and additives if necessary. The protective layer coating solution is prepared by mixing these. Next, the protective layer coating solution is applied onto the photosensitive layer. Then, ultraviolet light is irradiated onto the protective layer coating solution on the photosensitive layer (more specifically, at least one monomer or the like contained in the protective layer coating solution) to polymerize at least one monomer or the like. Polymerization forms a photocurable resin, which is a polymer.

[0112] The ultraviolet light irradiated in the protective layer formation process is, for example, irradiated from a light-emitting diode light source. In order to suitably advance the photocuring reaction, 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, and even more 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 it is 100,000 mW·s or less, the decomposition of the hole transporter contained in the photosensitive layer can be further suppressed and the potential stability of the photoreceptor can be improved. In order to improve the potential stability of the photoreceptor, it is preferable to set the light energy of the ultraviolet light to a value such that the remaining percentage Z of the hole transporter, described later, is 80% or more.

[0113] If the remaining percentage of the hole transporter is denoted as Z, it is preferable that the remaining percentage of the hole transporter (hereinafter sometimes referred to as "remaining percentage of the hole transporter Z") be 80% or higher. The remaining percentage of the hole transporter Z is calculated by formula (I). Z = 100 × (A2 / A1) ... (I)

[0114] In formula (I), A1 is the absorbance of the hole transporter at a predetermined wavelength before irradiation with the predetermined ultraviolet light (hereinafter sometimes referred to as "absorbance A1"). A2 is the absorbance of the hole transporter at a predetermined wavelength after irradiation with the predetermined ultraviolet light (hereinafter sometimes referred to as "absorbance A2"). In this specification, the predetermined ultraviolet light is defined as ultraviolet light having the same wavelength and the same light energy as the ultraviolet light irradiated in the protective layer formation process. In this specification, the predetermined wavelength is defined as the same wavelength as the predetermined ultraviolet light. Therefore, the wavelength of the ultraviolet light irradiated in the protective layer formation process, the wavelength of the predetermined ultraviolet light irradiated in the measurement of the remaining rate Z of the hole transporter, and the predetermined wavelength are all the same value.

[0115] At least a portion of the ultraviolet light irradiated onto the protective layer coating solution during the protective layer formation process passes through the protective layer coating solution and reaches the photosensitive layer. Hole transporters with a remaining percentage Z of 80% or more are less likely to decompose due to the ultraviolet light irradiated during the protective layer formation process. By incorporating a hole transporter with a remaining percentage Z of 80% or more into the photosensitive layer, the decomposition of the hole transporter by ultraviolet light can be suppressed, and the potential stability of the photoreceptor can be improved. Therefore, it is preferable to use a hole transporter with a remaining percentage Z of 80% or more in the photosensitive layer.

[0116] To suppress the decomposition of the hole transporter and improve the potential stability of the photoreceptor, the remaining percentage Z of the hole transporter is preferably 85% or more, and more preferably 90% or more. For example, the remaining percentage Z of the hole transporter is 100% or less.

[0117] The method for measuring the residual rate Z of the hole transporter will be explained below with reference to Figure 7. Figure 7 shows the absorption spectra of the hole transporter (HT-3) contained in the photosensitive layer of the photoreceptor according to Example 4, described later, before and after irradiation with a predetermined ultraviolet light. This absorption spectrum is measured by ultraviolet-visible spectroscopy. In Figure 7, the horizontal axis represents wavelength (unit: nm), and the vertical axis represents absorbance. To measure the residual rate Z of the hole transporter, first, a 3 μm thick measurement sample containing 25 parts by mass of hole transporter and 100 parts by mass of binder resin is prepared. An ultraviolet-visible spectrophotometer is used to measure the ultraviolet-visible light absorption spectra of the measurement sample before and after irradiation with a predetermined ultraviolet light. In the example shown in Figure 7, the wavelength of the predetermined ultraviolet light is set to 365 nm. From the ultraviolet-visible light absorption spectrum measured before irradiation with the predetermined ultraviolet light (spectrum shown by the solid line in Figure 7), the absorbance A1 at a predetermined wavelength W (i.e., the same wavelength as the predetermined ultraviolet light, 365 nm in the example shown in Figure 7) is determined. The absorbance A2 at a predetermined wavelength W is determined from the ultraviolet-visible light absorption spectrum (shown as a dashed line in Figure 7) measured after irradiation with a predetermined ultraviolet light. Then, the remaining percentage Z of the hole transporter is calculated from absorbances A1 and A2 according to formula (I). Details of the remaining percentage Z of the hole transporter will be described later in the examples.

[0118] The photosensitive layer formation process and the protective layer formation process have been described above. The method for manufacturing the photoreceptor according to the second embodiment will now be described further.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] The method for manufacturing a photoreceptor according to the second 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.

[0124] [Third Embodiment: Image Forming Apparatus] Next, with reference to Figure 8, an image forming apparatus 100, which is an example of an image forming apparatus according to the third embodiment of the present invention, will be described. Figure 8 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 color printer.

[0125] As shown in Figure 8, the image forming apparatus 100 comprises a control unit 15, an operation 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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 third 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.

[0133] 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.

[0134] 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.

[0135] 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 8, the reference numerals are omitted for the components of the second image forming unit 62C to the fourth image forming unit 62K.

[0136] The image carrier 65 is the photoreceptor of the first embodiment (more specifically, the single-layer photoreceptor 1 and the multilayer photoreceptor 10). As described in the first embodiment, the photoreceptor of the first embodiment can sufficiently cure the protective layer and has excellent potential stability, even when the protective layer contains a photocurable resin. Therefore, the image forming apparatus 100 of the third embodiment may be equipped with a photoreceptor that can sufficiently cure the protective layer and has excellent potential stability, even when the protective layer contains a photocurable resin.

[0137] In the third embodiment, the image carrier 65 rotates in the direction indicated by arrow R1 in Figure 8 (clockwise in Figure 8). 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.

[0138] 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.

[0139] 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.

[0140] 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.

[0141] In the third 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.

[0142] 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.

[0143] 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.

[0144] 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.

[0145] 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 third 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.

[0146] 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 8. The driven roller 74 is rotationally driven in accordance with the drive of the intermediate transfer belt 72.

[0147] 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 third 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.

[0148] 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 third 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".

[0149] 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 third 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.

[0150] 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.

[0151] 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.

[0152] Next, the configuration of the developing apparatus 64 will be described in detail with reference to Figure 9. Figure 9 is a diagram showing an example of the configuration of the developing apparatus 64. Specifically, Figure 9 shows the developing apparatus 64 of the first image forming unit 62Y. In Figure 9, the image carrier 65 is shown with a dashed line for ease of understanding. In the third embodiment, the developing apparatus 64 employs a two-component developing method using a two-component developer and a touchdown developing method.

[0153] As already explained with reference to Figure 8, 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.

[0154] As shown in Figure 9, 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.

[0155] 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.

[0156] 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 9, yellow toner is supplied to the first stirring chamber 640a.

[0157] The second stirring chamber 640b houses the second stirring screw 644. The second stirring chamber 640b contains a carrier which is a magnetic material.

[0158] 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).

[0159] 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.

[0160] 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.

[0161] 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.

[0162] 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 third embodiment, the magnetic roller 642 rotates in the direction indicated by arrow R3 in Figure 9 (counterclockwise in Figure 9). 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.

[0163] 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.

[0164] The developing roller 641 rotates in the direction indicated by arrow R2 in Figure 9 (counterclockwise in Figure 9). 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.

[0165] The developing device 64 of the first image forming unit 62Y has been described above with reference to Figure 9. The configuration of the developing device 64 of each of the first image forming units 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.

[0166] The image forming apparatus 100, an example of an image forming apparatus of the third embodiment, has been described above with reference to Figures 8 and 9. However, the image forming apparatus of the third 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 corotron 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 developing roller and the magnetic roller also serves as the developing 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 third embodiment has been described above.

[0167] [Fourth Embodiment: Process Cartridge] Next, with continued reference to Figure 8, the first process cartridge 101, the second process cartridge 102, the third process cartridge 103, and the fourth process cartridge 104, which are examples of process cartridges according to the fourth embodiment of the present invention, will be described. The first to fourth process cartridges 101 to 104 of the fourth 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 the photoreceptor of the first embodiment (more specifically, the single-layer photoreceptor 1 and the stacked photoreceptor 10).

[0168] As described in the first embodiment, the photoreceptor of the first embodiment can sufficiently cure the protective layer and exhibit excellent potential stability, even when the protective layer contains a photocurable resin. Therefore, the process cartridge of the fourth embodiment may be equipped with a photoreceptor that can sufficiently cure the protective layer and exhibit excellent potential stability, even when the protective layer contains a photocurable resin.

[0169] The process cartridge of the fourth 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.

[0170] The first process cartridge 101, second process cartridge 102, third process cartridge 103, and fourth process cartridge 104 shown in Figure 8 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 fourth embodiment are not limited to the first process cartridge 101 to the fourth process cartridge 104. As described above, the process cartridge of the fourth 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 fourth embodiment only needs to include the photoreceptor of the first embodiment as the image carrier 65.

[0171] The process cartridge of the fourth 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, the image carrier 65 can be easily and quickly replaced along with the process cartridge. The process cartridge of the fourth embodiment has been described above with reference to Figure 8.

[0172] [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).

[0173] 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 8 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, and 2-methylpentyl group. Examples include the heptyl group, 3-methylpentyl group, 4-methylpentyl group, 1,1-dimethylbutyl group, 1,2-dimethylbutyl group, 1,3-dimethylbutyl group, 2,2-dimethylbutyl group, 2,3-dimethylbutyl group, 3,3-dimethylbutyl group, 1,1,2-trimethylpropyl group, 1,2,2-trimethylpropyl group, 1-ethylbutyl group, 2-ethylbutyl group, 3-ethylbutyl group, linear and branched heptyl groups, and linear and branched octyl groups. Examples of 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, respectively, groups having the corresponding number of carbon atoms from the groups described as examples of alkyl groups having 1 to 8 carbon atoms.

[0174] 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.

[0175] 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.

[0176] 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]

[0177] 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.

[0178] [Manufacturing of single-layer photoreceptors] A single-layer photoreceptor having the configurations shown in Tables 1 to 3 below was manufactured.

[0179] [Table 1]

[0180] [Table 2]

[0181] [Table 3]

[0182] The terms used in Tables 1 to 3 are as follows: Actual: Example Comparison: Comparative Example CGM: Charge Generator HTM: Hole transport agent ETM: Electronic Transport Agent HTM+ETM content: The total content of hole transporters and electron transporters relative to the mass of the single-layer photosensitive layer. Curing conditions: The light energy of ultraviolet light irradiated onto the protective layer coating solution during the protective layer formation process (unit: mW·s) 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 EA: Polyfunctional acrylic acid ester (A-DPH, manufactured by Shin-Nakamura Chemical Industry Co., Ltd., a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate, hydroxyl value 10 mg KOH / g) UA: Urethane (meth)acrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd., "U-200PA") PTO: Phosphate-doped tin oxide (Mitsubishi Materials Electronic Chemicals Co., Ltd. "SP-2", BET specific surface area 105±25m²) 2 / g) ATO: Antimond-doped tin oxide (manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd., "T-1", BET specific surface area: 77.5 ± 7.5 m²) 2 / g, number average primary particle diameter: 0.02μm) Alumina: Alumina (Al2O3 manufactured by CIK Nanotech Co., Ltd., BET specific surface area 55m²) 2 / g, number average primary particle diameter 31 nm) Monomer mass ratio: The percentage of the monomer in question relative to the total mass of monomers used to form the photocurable resin. Hole transporter (HT-1): A compound represented by the following formula (HT-1). The predetermined number of double bonds in this compound is 4.

[0183] [ka]

[0184] <Manufacturing of single-layer photoreceptor (A-1)> (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.

[0185] (Formation of a single-layer photosensitive layer) Mixture b was prepared by mixing 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 using a rod-shaped ultrasonic oscillator for 20 minutes. Mixture b was prepared by filtering the prepared mixture b through a 5 μm mesh filter to obtain a coating solution for a single-layer photosensitive layer. Next, the coating solution for the single-layer photosensitive layer was applied to an intermediate layer on a conductive substrate by dip-coating. The applied coating solution 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.

[0186] (Formation of a protective layer) 3.5 parts by mass of alumina, 9.3 parts by mass of tin-doped tin oxide (PTO), 90 parts by mass of a polyfunctional acrylate as a monomer, 1 part by mass of a leveling agent, 10 parts by mass of a polymerization initiator, and 110 parts by mass of methanol were mixed using a bead mill for 10 hours to obtain a mixed solution c. As the alumina, tin-doped tin oxide, and polyfunctional acrylate, those described in the above table were used. As the leveling agent, a UV-curable fluorine-silicon-modified acrylic polymer having a vinyl group ("8FS-001" manufactured by Dainippon Fine Chemical Co., Ltd., double bond equivalent (vinyl group equivalent): 420 g / mol) was used. As the polymerization initiator, a compound represented by the following formula (ST-1), that is, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide ("OMNIRAD TPO" manufactured by IGM RESINS) was used. The obtained mixed solution c was filtered using a filter with a pore size of 5 μm to obtain a coating solution for the protective layer. Next, the coating solution for the protective layer was applied onto the single-layer photosensitive layer by the dip coating method. The applied coating solution for the protective layer 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 60300 mW·s. By the irradiation of ultraviolet light, the polyfunctional acrylate and the leveling agent in the coating solution for the protective layer were polymerized (photo-curing reaction) to form 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 a photocurable resin cured by a photo-curing reaction, alumina, tin-doped tin oxide, and a polymerization initiator.

[0187] [Chemical formula]

[0188] <Manufacture of single-layer photoreceptors (A-2) to (A-33) and (B-1) to (B-12)> Single-layer photoreceptors (A-2) to (A-33) and (B-1) to (B-12) were manufactured in the same manner as the manufacture of the single-layer photoreceptor (A-1), except that the following points were changed.

[0189] (Formation of single-layer photosensitive layer) In the formation of the single-layer photosensitive layer, a charge generator, a hole transport agent, an electron transport agent, and a binder resin described in Tables 1 to 3 were used. The hole transport agent and the electron transport agent were added in amounts such that the total content ratio of the hole transport agent and the electron transport agent to the mass of the single-layer photosensitive layer in the single-layer photosensitive layer was the value shown in Tables 1 to 3. For example, when the total content ratio of the above-described hole transport agent and electron transport agent was 40% by mass with respect to the mass of the single-layer photosensitive layer, 36.70 parts by mass of the hole transport agent in total and 30.80 parts by mass of the electron transport agent in total were used. When the total content ratio of the above-described hole transport agent and electron transport agent was 60% by mass with respect to the mass of the single-layer photosensitive layer, 84.00 parts by mass of the hole transport agent in total and 70.30 parts by mass of the electron transport agent in total were used. When using two kinds of hole transport agents (HT-2) and (HT-3), each hole transport agent was used in an amount such that the mass ratio HT-2 / HT-3 was 1 / 1. When using two kinds of electron transport agents (ET-1) and (ET-6), each electron transport agent was used in an amount such that the mass ratio ET-1 / ET-6 was 1 / 1.

[0190] (Formation of the protective layer) In the formation of the protective layer, the monomers described in Tables 1 to 3 were used in the mass ratios described in Tables 1 to 3. For example, when the monomer type was “EA” and the monomer mass ratio was described as “100”, 90 parts by mass of a polyfunctional acrylate was used. When the monomer type was “UA” and the monomer mass ratio was described as “100”, 90 parts by mass of urethane (meth) acrylate was used. When the monomer type was “EA / UA” and the monomer mass ratio was described as “60 / 40”, 54 parts by mass of a polyfunctional acrylate and 36 parts by mass of urethane (meth) acrylate were used. When the monomer type was “EA / UA” and the monomer mass ratio was described as “40 / 60”, 36 parts by mass of a polyfunctional acrylate and 54 parts by mass of urethane (meth) acrylate were used. In the formation of the protective layer, the metal oxides described in Tables 1 to 3 were used. In the formation of the protective layer, ultraviolet rays were irradiated with the light energy described in Tables 1 to 3. In addition, in the formation of the protective layer, the wavelength of the irradiated ultraviolet rays was not changed from 365 nm.

[0191] [Measurement of single-layer photoreceptor] The ratio A / B of each single-layer photoreceptor and the remaining hole transporter Z were measured using the following method. The measurement results are shown in Tables 4 to 6.

[0192] <Ratio A / B> Except for applying the protective coating solution directly onto the conductive substrate instead of onto the single-layer photoreceptor layer, the protective layers of the single-layer photoreceptors (A-1) to (A-33) and (B-1) to (B-12) were formed in the same manner as described above. The protective layers were peeled off the conductive substrate, and the peeled protective layers were used as Fourier transform infrared spectroscopy (FT-IR) measurement samples. Using an FT-IR analyzer (Perkin Elmer "Spectrum one"), the FT-IR measurement samples were measured under the following measurement conditions, and FT-IR spectra were obtained. From the FT-IR spectra, the wavenumber 1627 cm⁻¹ was obtained. -1 The above is 1647cm. -1 The highest absorbance (first absorbance A) within the following range, and wavenumber 1647 cm⁻¹ -1 Super 1800cm -1 The highest absorbance (second absorbance B) within the following range was determined. Then, the ratio A / B was calculated using the formula "Ratio A / B = First absorbance A / Second absorbance B".

[0193] (FT-IR measurement conditions) Method: Total internal reflection (ATR) method Angle of incidence: 45 degrees Internal reflective element: Germanium Measurement wavefrequency range: 650cm -1 From 4000cm -1 up to range Number of scans: 4 Resolution: 4cm -1

[0194] <Percentage of hole transporter remaining Z> 100 parts by mass of binder resin, 25 parts by mass of hole transporter, and 2400 parts by mass of tetrahydrofuran were mixed using a rotating device for 24 hours to obtain a coating solution for UV-Vis measurement. Next, the UV-Vis measurement coating solution was applied onto an overhead projector (OHP) film using a wire bar and heated at 120°C for 50 minutes. In this way, a hole transporter-containing layer (film thickness 3 μm) was formed on the OHP film. A sample comprising the hole transporter-containing layer and the OHP film was used as a UV-Vis measurement sample. Two UV-Vis measurement samples were prepared, and each of the two prepared samples was designated as UV-Vis measurement sample S1 and UV-Vis measurement sample S2.

[0195] A UV-Vis measurement sample S1 was placed in the film holder of a UV-Vis spectrophotometer (Hitachi, Ltd. "U-3010"). Using the above UV-Vis spectrophotometer, the UV-Vis measurement sample S1 was measured under the following measurement conditions. The ultraviolet-visible light absorption spectrum (spectrum before UV irradiation) was then obtained.

[0196] Next, the UV-Vis measurement sample S2 was irradiated with a predetermined ultraviolet light. The wavelength of the predetermined ultraviolet light was set to 365 nm, and the light energy was set to the same value as the light energy of the ultraviolet light irradiated in the protective layer formation process. The UV-Vis measurement sample S2 after irradiation with the predetermined ultraviolet light was placed in the film holder of the ultraviolet-visible spectrophotometer. Using the ultraviolet-visible spectrophotometer, the UV-Vis measurement sample S2 after irradiation with the predetermined ultraviolet light was measured under the following measurement conditions, and the ultraviolet-visible light absorption spectrum (spectrum after UV irradiation) was obtained.

[0197] The absorbance A1 at a predetermined wavelength W (365 nm, the same wavelength as the predetermined ultraviolet light) was determined from the spectrum before ultraviolet irradiation. The determined absorbance A1 was considered to be the absorbance A1 of the hole transporter before the predetermined ultraviolet irradiation. Next, the absorbance A2 at a predetermined wavelength W was determined from the spectrum after ultraviolet irradiation. The determined absorbance A2 was considered to be the absorbance A2 of the hole transporter after the predetermined ultraviolet irradiation. The remaining percentage Z of the hole transporter was calculated from the absorbance A1 of the hole transporter before the predetermined ultraviolet irradiation and the absorbance A2 of the hole transporter after the predetermined ultraviolet irradiation, based on the calculation formula (I) described in the second embodiment.

[0198] (UV-Vis measurement conditions) Measurement wavelength range: 320.00 nm to 600.00 nm Sampling interval: 1.00 nm Slit width: 1 nm Scanning speed: 300 nm / min

[0199] The hole transporter and binder resin used in the preparation of the UV-Vis measurement samples were the same as those used in the manufacture of each single-layer photoreceptor shown in Tables 1 to 3. When two types of hole transporters were used, the amount of hole transporter was set to match the mass ratio used in the manufacture of each single-layer photoreceptor shown in Tables 1 to 3, and to a total amount of 25 parts by mass. The light energy of the predetermined ultraviolet light irradiated onto the UV-Vis measurement sample S2 was set to the same value as the light energy of the ultraviolet light irradiated during the manufacture of each single-layer photoreceptor shown in Tables 1 to 3. For example, in measuring the remaining percentage Z of the hole transporter in the single-layer photoreceptor (A-1), a hole transporter (HT-2) and binder resin (bisphenol Z type polycarbonate resin) were used, and the light energy of the ultraviolet light irradiated onto the UV-Vis measurement sample S2 was set to 60300 mW·s. Furthermore, the wavelength of the predetermined ultraviolet light irradiated onto the UV-Vis measurement sample S2, and the predetermined wavelength W used for reading the absorbance, remained unchanged at 365 nm.

[0200] [Evaluation of single-layer photoreceptors] The dot reproducibility and potential stability of each single-layer photoreceptor were evaluated using the following method. The evaluation results are shown in Tables 1 to 3.

[0201] <Evaluation machine and evaluation form> For the evaluation of dot reproducibility and potential stability, a modified color multifunction printer ("Taskalfa 356ci" manufactured by Kyocera Document Solutions Inc.) was used as the evaluation machine. This evaluation machine was equipped with a charging roller made of epichlorohydrin resin with dispersed conductive carbon. The charging polarity of the charging roller was positive, and the applied voltage to the charging roller was a DC voltage. The development method was a two-component development method. The transfer method was an intermediate transfer method. This evaluation machine was equipped with a cleaning blade, a friction roller, and a static eliminator. For these evaluations, copy paper ("Multi Paper Super Economy+" sold by ASKUL Corporation) was used as the paper.

[0202] <Dot Reproducibility> Dot reproducibility was evaluated under high-temperature and high-humidity conditions of 32°C and 80% RH relative humidity. A single-layer photoreceptor was installed in the evaluation machine. Using the evaluation machine, image G1 (image with 1.6% image density) was printed on one sheet of paper. The image density (ID) of 10 randomly selected dots from the printed dots was measured, and the average number of these measurements was used as the evaluation value. A reflectance densitometer (TC-6MC, manufactured by Tokyo Denshoku Co., Ltd.) was used to measure the image density.

[0203] (Criteria for dot reproducibility) Good (A): The evaluation value is 0.01 or higher and less than 0.02. Poor (B): The evaluation value is less than 0.01.

[0204] <Potential stability> The potential stability was evaluated under conditions of 23°C and 50% 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 a solid image was set to 1.08 μJ / cm². 2 I set it to that.

[0205] Using an evaluation machine, an image G2 (solid image) was printed on a single sheet of paper. During printing, the surface potential of the single-layer photoreceptor after exposure (post-exposure potential VL1) was measured. Next, using the evaluation machine, an image G3 (image with a 5% printing rate) was printed continuously for 60 minutes. Then, after printing for 60 minutes, using the evaluation machine, an image G2 (solid image) was printed on a single sheet of paper. During printing, the surface potential of the single-layer photoreceptor after exposure (post-exposure potential VL2 after printing durability) was measured. The absolute value ΔVL of the change amount of the post-exposure potential before and after printing durability was obtained from the calculation formula "ΔVL = |VL2 - VL1|". Then, the potential stability was evaluated according to the following criteria.

[0206] (Criteria for potential stability) Good: ΔVL is 20 V or less. Poor: ΔVL exceeds 20 V.

[0207]

Table 4

[0208]

Table 5

[0209]

Table 6

[0210] The terms in Tables 4 to 6 are as follows. Note that "actual" and "ratio" have the same meaning as the explanations of the terms in Tables 1 to 3 above. HTM residual rate Z: Residual rate Z of the hole transport agent Poor curing: Although ultraviolet rays were irradiated in the protective layer formation process, the curing of the photocurable resin did not proceed well, resulting in poor curing of the protective layer and inability to evaluate the single-layer photoreceptor

[0211] As shown in Tables 1 to 3, the number of predetermined double bonds in the hole transporter contained in the single-layer photoreceptor layers of single-layer photoreceptors (B-1), (B-2), (B-5), and (B-9) was 3 or more. As shown in Tables 4 to 6, the ratio A / B of the protective layer present in single-layer photoreceptors (B-1), (B-3), (B-4), (B-6), (B-7), (B-8), (B-10), (B-11), and (B-12) was greater than 0.160. As shown in Tables 4 to 6, single-layer photoreceptors (B-1), (B-6), (B-7), (B-10), and (B-11) suffered from poor curing of the protective layer and could not form single-layer photoreceptors. As shown in Tables 4 to 6, single-layer photoreceptors (B-2), (B-3), (B-4), (B-5), (B-8), (B-9), and (B-12) exhibited poor potential stability.

[0212] On the other hand, as shown in Tables 1 to 3, the hole transporter contained in the single-layer photosensitive layer of single-layer photoreceptors (A-1) to (A-33) had two or fewer predetermined double bonds, or did not have any predetermined double bonds. The ratio A / B of the protective layer of single-layer photoreceptors (A-1) to (A-33) was 0.160 or less. As shown in Tables 1 to 3, even when the protective layer of single-layer photoreceptors (A-1) to (A-33) contained a photocurable resin, the protective layer could be sufficiently cured and exhibited excellent potential stability. Furthermore, the dot reproducibility of single-layer photoreceptors (A-1) to (A-33) was maintained without any decrease.

[0213] [Manufacturing of stacked photoreceptors] A stacked photoreceptor having the configuration shown in Table 7 below was manufactured.

[0214] [Table 7]

[0215] <Manufacturing of stacked photoreceptor (C-1)> (Formation of the intermediate layer) The intermediate layer was formed in the same manner as the intermediate layer of the single-layer photoreceptor (A-1), except that the coating conditions of the dip-coating method (the speed at which the conductive substrate is pulled out of the intermediate layer coating solution) were changed to change the thickness of the intermediate layer to 0.5 μm.

[0216] (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.

[0217] (Formation of a 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.

[0218] (Formation of a protective layer) The protective layer was formed in the same manner as for the protective layer of the single-layer photoreceptor (A-1), except that the protective coating solution was applied to the charge transport layer instead of the single-layer photoreceptor, and ultraviolet light was irradiated with the light energy described in Table 7.

[0219] <Manufacturing of stacked photoreceptor (C-2)> A stacked photoreceptor (C-2) was manufactured in the same manner as the stacked photoreceptor (C-1), except that 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)) was changed to a total of 150.00 parts by mass of hole transporter (more specifically, 90.00 parts by mass of hole transporter (HT-2) and 60.00 parts by mass of hole transporter (HT-3)). The total content of hole transporter in the charge transport layer of the stacked photoreceptor (C-2) was 60% by mass relative to the mass of the charge transport layer.

[0220] [Measurement of stacked photoreceptors] The ratio A / B of each stacked photoreceptor and the remaining hole transporter Z were measured using the following method. The measurement results are shown in Table 8.

[0221] <Ratio A / B> Except for the use of the following samples as FT-IR measurement samples, the ratio A / B of the multilayer photoreceptor was measured in the same manner as the measurement of the ratio A / B of the single-layer photoreceptor. The protective layers of the multilayer photoreceptors (C-1) to (C-2) were formed in the same manner as the formation of the protective layers of the multilayer photoreceptors (C-1) to (C-2) described above, except that the protective layer coating solution was applied directly to the conductive substrate instead of on the charge transport layer. The protective layers were peeled off from the conductive substrate, and the peeled protective layers were used as FT-IR measurement samples.

[0222] <Percentage of hole transporter remaining Z> Except for the following modifications, the residual rate Z of the hole transporter in the multilayer photoreceptor was measured using the same method as for measuring the residual rate Z of the hole transporter in the single-layer photoreceptor. The hole transporter and binder resin used in measuring the residual rate Z of the hole transporter in each multilayer photoreceptor were the hole transporter and binder resin shown in Table 7 that were used in the manufacture of each multilayer photoreceptor. When two types of hole transporters were used, the amount of hole transporter was set so that the total amount of hole transporter was 25 parts by mass, according to the mass ratio of the hole transporters used in the manufacture of each multilayer photoreceptor shown in Table 7. The light energy of the ultraviolet light irradiated onto the UV-Vis measurement sample S2 was set to the same value as the light energy of the ultraviolet light irradiated during the manufacture of each multilayer photoreceptor shown in Table 7.

[0223] [Evaluation of stacked photoreceptors] The dot reproducibility and potential stability of each stacked photoreceptor were evaluated using the following method. The evaluation results are shown in Table 8.

[0224] <Evaluation machine and evaluation form> 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.

[0225] <Dot Reproducibility> The dot reproducibility of a stacked photoreceptor was evaluated using the same method as for evaluating the dot reproducibility of a single-layer photoreceptor.

[0226] <Potential stability> The potential stability of the stacked photoreceptor was evaluated using the same method as for evaluating the potential stability of the single-layer photoreceptor, except that the evaluation machine was set so that the charging potential of the stacked photoreceptor was -500V.

[0227] [Table 8]

[0228] In Table 8, "Actual" and "HTM Remaining Rate Z" have the same meaning as the terms explained in Tables 1 to 6 above.

[0229] As shown in Table 7, the hole transporter contained in the charge transport layer of the multilayer photoreceptors (C-1) to (C-2) had two or fewer predetermined double bonds, or no predetermined double bonds. As shown in Table 8, the ratio A / B of the protective layer of the multilayer photoreceptors (C-1) to (C-2) was 0.160 or less. As shown in Table 8, even when the protective layer of the multilayer photoreceptors (C-1) to (C-2) contained a photocurable resin, the protective layer could be sufficiently cured and exhibited excellent potential stability. Furthermore, the dot reproducibility of the multilayer photoreceptors (C-1) to (C-2) was maintained without any decrease.

[0230] From the above, it has been shown that the photoreceptors of the present invention, which include single-layer photoreceptors (A-1) to (A-33) and multilayer photoreceptors (C-1) to (C-2), can sufficiently cure the protective layer and exhibit excellent potential stability, even when the protective layer contains a photocurable resin. Furthermore, because such a photoreceptor is provided, it is determined that the process cartridge and image forming apparatus of the present invention are equipped with a photoreceptor that can sufficiently cure the protective layer and exhibit excellent potential stability, even when the protective layer contains a photocurable resin. [Industrial applicability]

[0231] 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, a hole transporting agent, and a binder resin. The hole transporter has two or fewer chain-like ethene-1,2-diyl groups, or does not have chain-like ethene-1,2-diyl groups. The protective layer is the outermost layer of the electrophotographic photoreceptor and contains a photocurable resin. If the first absorbance of the protective layer, measured by Fourier transform infrared spectroscopy, is A and the second absorbance is B, then the ratio of the first absorbance to the second absorbance, A / B, is 0.160 or less. The first absorbance is at wavenumber 1627 cm⁻¹. －１ The above is 1647 cm. －１ The highest absorbance is found within the following range: The second absorbance is at wavenumber 1647 cm⁻¹. －１ Super 1800cm －１ The highest absorbance is found within the following range: The photocurable resin comprises repeating units derived from (meth)acrylic acid ester and repeating units derived from urethane (meth)acrylate, wherein the (meth)acrylic acid ester has two to six vinyl groups, and is an electrophotographic photoreceptor.

2. An electrophotographic photoreceptor comprising a conductive substrate, a photosensitive layer, and a protective layer, The photosensitive layer contains a charge generating agent, a hole transporting agent, and a binder resin. The hole transporter has two or fewer chain-like ethene-1,2-diyl groups, or does not have chain-like ethene-1,2-diyl groups. The protective layer is the outermost layer of the electrophotographic photoreceptor and contains a photocurable resin. If the first absorbance of the protective layer, measured by Fourier transform infrared spectroscopy, is A and the second absorbance is B, then the ratio of the first absorbance to the second absorbance, A / B, is 0.160 or less. The first absorbance is the highest absorbance in the wavenumber range of 1627 cm⁻¹ to 1647 cm⁻¹. The aforementioned second absorbance is the highest absorbance in the range of wavenumbers greater than 1647 cm⁻¹ and less than or equal to 1800 cm⁻¹. The hole transporter comprises at least one compound represented by formulas (1), (2), and (3) in an electrophotographic photoreceptor. 【Chemistry 1】 (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 of 0 or 1. 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. The electrophotographic photoreceptor according to claim 1 or 2, wherein the ratio A / B is 0.100 or more and 0.160 or less.

4. The electrophotographic photoreceptor according to claim 1, wherein the hole transporter comprises at least one of the compounds represented by formulas (1), (2), and (3). 【Chemistry 2】 (In the above formula (1), R ４１ , R ４２ , R ４３ , R ４４ , R ４５ , and R ４６ each independently represents an alkyl group having 1 to 8 carbon atoms or a phenyl group, and R ４７ and R ４８ each independently represents 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 represents an integer of 0 or more and 5 or less, and e ５ and e ６ each independently represents an integer of 0 or more and 4 or less, In the above formula (2), R ５０ , R ５１ , and R ５４ Each independently represents an alkyl group having 1 to 8 carbon atoms, or a phenyl group, R ５２ , and R ５３ Each 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, and f ３ , f ４ , and f ５ Each of these independently represents an integer between 0 and 5, In the above formula (3), R １１ , R １２ , R １３ , and R １４ Each independently represents an alkyl group having 1 to 8 carbon atoms, or a phenyl group, a １ a ２ a ３ , and a ４ Each of these independently represents an integer between 0 and 5 (inclusive).

5. The aforementioned photocurable resin has a vinyl group and a carbonyl group, The first absorbance is the absorbance of the peak based on the vinyl group, The electrophotographic photoreceptor according to claim 2, wherein the second absorbance is the absorbance of the peak based on the carbonyl group.

6. The electrophotographic photoreceptor according to claim 2, wherein the photocurable resin contains repeating units derived from a (meth)acrylic acid ester, and the (meth)acrylic acid ester has two to six vinyl groups.

7. The electrophotographic photoreceptor according to claim 6, wherein the content of repeating units derived from the (meth)acrylic acid ester in relation to the total repeating units of the photocurable resin is 60% by mass or more.

8. The electrophotographic photoreceptor according to claim 1 or 2, wherein the protective layer further contains two types of metal oxides.

9. The electrophotographic photoreceptor according to claim 8, wherein one of the two metal oxides is alumina.

10. The electrophotographic photoreceptor according to claim 9, wherein the other of the two metal oxides is phosphorus-doped tin oxide or antimond-doped tin oxide.

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

12. The electrophotographic photoreceptor according to claim 1 or 2, wherein the charge generating agent contained in the photosensitive layer comprises titanyl phthalocyanine or metal-free phthalocyanine.

13. The process includes forming a protective layer containing the photocurable resin on the photosensitive layer, A method for producing an electrophotographic photoreceptor according to claim 1 or 2, wherein in the protective layer formation step, the photocurable resin is formed by irradiating at least one of the monomer and oligomer on the photosensitive layer with ultraviolet light to polymerize at least one of the monomer and oligomer.

14. 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 claim 1 or 2.

15. 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 claim 1 or 2.

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