Process cartridge and image forming apparatus

Abstract

To provide a process cartridge which nicely suppresses appearance of fine color lines on obtained images.SOLUTION: A process cartridge provided herein comprises a photoreceptor comprising a conductive base material, a photosensitive layer provided on the conductive base material, and a protective layer provided on the photosensitive layer, and a roll-shaped charging member configured to contact the photoreceptor for charging, where electrical charge required to charge the photoreceptor is 1.65 μC / (m2 V) or greater.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] A conventional image forming apparatus is the one described in Patent Document 1. Patent Document 1 discloses an image forming apparatus comprising a photoreceptor and a charging means for uniformly charging the surface of the photoreceptor, wherein the photoreceptor has a conductive support, a photosensitive layer and a protective layer provided on the conductive support, the protective layer contains a curable resin hardened by electron beam irradiation and conductive particles, the photoreceptor has a Taber wear of 0.1 to 1.0 (mg / 1000 rpm), the charging means comprises a charging member placed in contact with the surface of the photoreceptor, a charging bias application power supply that charges the surface of the photoreceptor by applying a charging bias in which a DC voltage and an AC voltage are superimposed on the charging member, and a control means for controlling the charging bias with an AC voltage, wherein the control means determines the AC voltage value when performing the AC voltage control based on the application time of the charging bias. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2004-205581 [Overview of the project] [Problems that the invention aims to solve]

[0004] This disclosure relates to a process cartridge comprising a photoreceptor having a conductive substrate, a photosensitive layer provided on the conductive substrate, and a protective layer provided on the photosensitive layer, and a roll-shaped charging member that contacts the photoreceptor to perform charging, wherein the charge required to charge the photoreceptor is 1.65 μC / (m 2The objective is to provide a process cartridge that exhibits superior suppression of minute color lines in the resulting image compared to cases where the value is less than V. [Means for solving the problem]

[0005] The means for solving the aforementioned problem include the following embodiments. <1> The device comprises a photoreceptor having a conductive substrate, a photosensitive layer provided on the conductive substrate, and a protective layer provided on the photosensitive layer, and a roll-shaped charging member that charges the photoreceptor by contacting it, wherein the charge required to charge the photoreceptor is 1.65 μC / (m 2 Process cartridges of type V or higher. <2> The thickness of the protective layer is 1 μm or more. <1> Process cartridge as described above. <3> The thickness of the protective layer is 3 μm or more and 8 μm or less. <2> Process cartridge as described above. <4> The thickness of the photosensitive layer is 9 μm or more. <1> ~ <3> The process cartridge listed in one of the following. <5> The thickness of the photosensitive layer is 9.5 μm or more and 15 μm or less. <4> Process cartridge as described above. <6> The sum of the value of the thickness of the photosensitive layer (μm) / the relative permittivity of the photosensitive layer and the value of the thickness of the protective layer (μm) / the relative permittivity of the protective layer is 4.0 or more and 7.0 or less. <1> ~ <5> The process cartridge listed in one of the following. <7> The sum of the value of the thickness of the photosensitive layer (μm) / the relative permittivity of the photosensitive layer and the value of the thickness of the protective layer (μm) / the relative permittivity of the protective layer is 4.5 or more and 6.0 or less. <6> Process cartridge as described above. <8> The charge required to charge the photoreceptor is 1.65 μC / (m 2 ·V) or more 2.30μC / (m 2 • V) is less than or equal to <1> ~ <7> The process cartridge listed in one of the following. <9> The charge required to charge the photoreceptor is 1.65 μC / (m 2 ·V) or more 2.10μC / (m 2• V) is less than or equal to <8> Process cartridge as described above. <10> <1> ~ <9> An image forming apparatus comprising: a process cartridge as described in any one of the above; an electrostatic latent image forming means for forming an electrostatic latent image on the surface of the charged photoreceptor; a developing means for developing the electrostatic latent image formed on the surface of the photoreceptor with a developer containing toner to form a toner image; and a transfer means for transferring the toner image to the surface of a recording medium. [Effects of the Invention]

[0006] <1> According to the invention, a process cartridge comprises a photoreceptor having a conductive substrate, a photosensitive layer provided on the conductive substrate, and a protective layer provided on the photosensitive layer, and a roll-shaped charging member that contacts the photoreceptor to perform charging, wherein the charge required to charge the photoreceptor is 1.65 μC / (m 2 A process cartridge is provided that offers superior suppression of minute color lines in the resulting image compared to the case where the value is less than V. <2> According to the invention, a process cartridge is provided that is superior in suppressing the generation of minute color lines in the resulting image compared to the case where the thickness of the protective layer is less than 1 μm. <3> According to the invention, a process cartridge is provided that is superior in suppressing the generation of minute color lines in the resulting image compared to cases where the thickness of the protective layer is less than 3 μm or greater than 8 μm. <4> According to the invention, a process cartridge is provided that is superior in suppressing the generation of minute color lines in the resulting image compared to the case where the thickness of the photosensitive layer is less than 9 μm. <5> According to the invention, a process cartridge is provided that is superior in suppressing the generation of minute color lines in the resulting image compared to cases where the thickness of the photosensitive layer is less than 9.5 μm or greater than 15 μm. According to the invention according to <6>, a process cartridge is provided that is superior in suppressing the generation of minute color lines in the resulting image as compared with the case where the sum of the value of the thickness (μm) of the photosensitive layer / the relative permittivity of the photosensitive layer and the value of the thickness (μm) of the protective layer / the relative permittivity of the protective layer is less than 4.0 or more than 7.0. According to the invention according to <7>, a process cartridge is provided that is superior in suppressing the generation of minute color lines in the resulting image as compared with the case where the sum of the value of the thickness (μm) of the photosensitive layer / the relative permittivity of the photosensitive layer and the value of the thickness (μm) of the protective layer / the relative permittivity of the protective layer is less than 4.5 or more than 6.0. According to the invention according to <8>, the process cartridge is provided that is superior in suppressing the generation of minute color lines in the resulting image as compared with the case where the charge required to charge the photoreceptor is less than 1.65 μC / (m 2 ·V) or more than 2.30 μC / (m 2 ·V). According to the invention according to <9>, the process cartridge is provided that is superior in suppressing the generation of minute color lines in the resulting image as compared with the case where the charge required to charge the photoreceptor is less than 1.65 μC / (m 2 ·V) or more than 2.10 μC / (m 2 ·V). According to the invention according to <10>, an image forming apparatus is provided that is superior in suppressing the generation of minute color lines in the resulting image as compared with the case of using a process cartridge including a photoreceptor having a conductive substrate, a photosensitive layer provided on the conductive substrate, and a protective layer provided on the photosensitive layer, and a roll-shaped charging member that contacts the photoreceptor to perform charging, and where the charge required to charge the photoreceptor is less than 1.65 μC / (m 2 ·V).

Brief Description of the Drawings

[0007] [Figure 1] It is a schematic configuration diagram showing an example of the charging member used in the present embodiment. [Figure 2] It is a schematic partial cross-sectional view showing an example of the layer configuration of the photoreceptor used in the present embodiment. [Figure 3] This is a schematic diagram showing an example of an image forming apparatus according to this embodiment. [Figure 4] This is a schematic diagram showing another example of the image forming apparatus according to this embodiment. [Figure 5] This is a schematic diagram showing another example of the image forming apparatus according to this embodiment. [Figure 6] This is a schematic diagram showing an example of a process cartridge according to this embodiment. [Modes for carrying out the invention]

[0008] Embodiments of the invention are described below. These descriptions and embodiments are illustrative and do not limit the scope of the invention.

[0009] In this specification, when referring to the amount of each component in a composition, if there are multiple substances corresponding to each component in the composition, unless otherwise specified, it refers to the total amount of those multiple substances present in the composition. In this specification, "electrophotographic photoreceptor" is also referred to simply as "photoreceptor." In this specification, "axial direction" of a charged member means the direction in which the axis of rotation of the charged member extends. "Circumferential direction" means the direction of rotation of the charged member. Furthermore, in this specification, "conductive" means that the volume resistivity at 20°C is 1 × 10⁻⁶. 14 This means it is less than or equal to Ωcm.

[0010] <Processing Cartridge> The process cartridge according to this embodiment comprises a photoreceptor having a conductive substrate, a photosensitive layer provided on the conductive substrate, and a protective layer provided on the photosensitive layer, and a roll-shaped charging member that contacts the photoreceptor to perform charging, wherein the charge required to charge the photoreceptor is 1.65 μC / (m 2 • V) That is the case.

[0011] Conventional process cartridges, which include a photoreceptor and a roll-shaped charging member that charges the photoreceptor in contact with it, had a problem in that when charged with a DC power supply, minute color lines could be generated when the process cartridge was used for image formation. As a result of detailed investigations by the present inventors, it was found that the above-mentioned minute color lines are caused by residual charge due to uneven discharge after the charged material comes into contact with the photoreceptor, and that this portion becomes a minute color line (also simply called a "minute color line") in the resulting image, with a width of several tens of micrometers and a length of several tens of micrometers to several centimeters. In the process cartridge according to this embodiment, a photoreceptor is provided having a conductive substrate, a photosensitive layer provided on the conductive substrate, and a protective layer provided on the photosensitive layer, wherein the charge required to charge the photoreceptor is 1.65 μC / (m 2 • When the potential is V or higher, the amount of discharge required to obtain the surface potential of the photoreceptor is large, which suppresses discharge unevenness and reduces the occurrence of minute color lines in the resulting image.

[0012] The details of the process cartridge according to this embodiment will be described below.

[0013] [Charge required to charge the photoreceptor] The process cartridge according to this embodiment has a charge of 1.65 μC / (m³) required to charge the photoreceptor. 2 • V) or higher, and from the viewpoint of suppressing the generation of minute color lines in the resulting image, 1.65 μC / (m 2 ·V) or more 2.30μC / (m 2 It is preferable that the value be less than or equal to 1.65 μC / (m 2 ·V) or more 2.10μC / (m 2 It is more preferable that it be less than or equal to 1.70 μC / (m 2 ·V) or more 2.10μC / (m 2 It is even more preferable that it be less than or equal to 1.80 μC / (m 2 ·V) or more 2.10μC / (m 2 It is especially preferable that it be V or less. In this embodiment, "the charge required to charge the photoreceptor" refers to the value obtained by multiplying the current flowing to the photoreceptor during charging by the charging time (peripheral contact time of the charging roll), and then converting this to a value per unit area.

[0014] The charge required to charge the photoreceptor is 1.65 μC / (m 2 There are no particular limitations on the means to achieve V) or higher, but preferred means include adjusting the thickness of the photosensitive layer of the photoreceptor, the thickness of the protective layer, and the sum of the value of the thickness of the photosensitive layer (μm) / relative permittivity and the value of the thickness of the protective layer (μm) / relative permittivity, as described later.

[0015] The charge required to charge the photoreceptor in this embodiment shall be measured by the following method. The photoreceptor and charging roll are brought into contact and rotated in the same manner as in the actual machine, and while measuring the surface potential using a surface potential meter (Trek Model 344) until the target surface potential is achieved, a current is applied to the charging roll using a Trek 610C high-voltage power supply, and the value of this current is measured. This value is multiplied by the charging time (charging roll circumferential contact time = contact width / photoreceptor rotation speed), and this value is further divided by the contact area between the charging roll and the photoreceptor (contact width between charging roll and photoreceptor × charging roll length) and the surface potential of the photoreceptor after charging to determine the charge required to charge the photoreceptor.

[0016] [Relationship between the thickness of each layer and the relative permittivity] The value of the thickness of the photosensitive layer (μm) / the relative permittivity of the photosensitive layer is preferably 1 to 8, more preferably 2.0 to 6.0, and particularly preferably 2.5 to 5.0, from the viewpoint of suppressing the generation of minute color lines in the resulting image. The value of the thickness (μm) of the protective layer and the relative permittivity of the protective layer is preferably 0.5 or more and 5 or less, more preferably 1.0 or more and 4.0 or less, and particularly preferably greater than 1.0 and 3.0 or less, from the viewpoint of suppressing the generation of minute color lines in the obtained image.

[0017] The sum of the value of the thickness of the photosensitive layer (μm) / the relative permittivity of the photosensitive layer and the value of the thickness of the protective layer (μm) / the relative permittivity of the protective layer is preferably 4.0 to 7.0, more preferably 4.2 to 6.0, even more preferably 4.5 to 6.0, and particularly preferably 4.5 to 5.3, from the viewpoint of suppressing the generation of minute color lines in the resulting image.

[0018] In this embodiment, the thickness of each layer of the photoreceptor or charged member is measured using a FisherSCOPE MMS PC2 eddy current film thickness gauge manufactured by Fisher.

[0019] The relative permittivity of the photosensitive layer or protective layer in this embodiment shall be measured by the following method. A single layer is coated onto a photosensitive substrate, and a φ5 mm gold electrode is fabricated by vapor deposition. The impedance is measured using a Schlumberger Solartron 1260 Impedance Gain-Phase Analyzer, and the relative permittivity is calculated. The measurement value at 2.5 Hz is used.

[0020] [Charging components] The shape of the charging member used in this embodiment is not particularly limited, but examples include roll-shaped, brush-shaped, belt (tube-shaped), and blade-shaped members. Among these, a roll-shaped charging member, as illustrated in Figure 1, that is, a so-called charging roll, is preferred.

[0021] Figure 1 shows an example of a charging member used in this embodiment. The charging member 208A shown in Figure 1 has a conductive substrate 30 which is a hollow or non-hollow cylindrical member, an elastic layer 31 disposed on the outer circumferential surface of the conductive substrate 30, and a surface layer 32 disposed on the outer circumferential surface of the elastic layer 31.

[0022] (Conductive base material) The charging member preferably has a roll-shaped conductive substrate. The conductive substrate functions as an electrode and support for the charged component. Examples of conductive substrates include metals or alloys such as aluminum, copper alloys, and stainless steel; iron plated with chromium, nickel, etc.; and conductive resins. In this embodiment, the conductive substrate functions as an electrode and support member of the charging roll, and examples of its material include metals such as iron (free-cutting steel, etc.), copper, brass, stainless steel, aluminum, and nickel. In this embodiment, the conductive substrate is a conductive rod-shaped member, and examples of conductive substrates include members with a plated outer surface (e.g., resin or ceramic members) and members in which a conductive agent is dispersed (e.g., resin or ceramic members). The conductive substrate may be a hollow member (cylindrical member) or a non-hollow member.

[0023] (Elastic layer) The charging member preferably has an elastic layer on a conductive substrate. The elastic layer is, for example, a conductive layer containing an elastic material and a conductive agent. The elastic layer may also contain other additives as needed.

[0024] The elastic layer may be a single layer or a laminate of multiple layers. The elastic layer may be a conductive foamed elastic layer, a conductive non-foamed elastic layer, or a conductive foamed elastic layer and a conductive non-foamed elastic layer may be laminated together.

[0025] Examples of elastic materials include polyurethane, nitrile rubber, isoprene rubber, butadiene rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, epichlorohydrin rubber, epichlorohydrin-ethylene oxide rubber, epichlorohydrin-ethylene oxide-allyl glycidyl ether rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, chloroprene rubber, chlorinated polyisoprene, hydrogenated polybutadiene, butyl rubber, silicone rubber, fluororubber, natural rubber, and elastic materials made by mixing these. Among these elastic materials, polyurethane, silicone rubber, nitrile rubber, epichlorohydrin rubber, epichlorohydrin-ethylene oxide rubber, epichlorohydrin-ethylene oxide-allyl glycidyl ether rubber, ethylene-propylene-diene rubber, acrylonitrile-butadiene rubber, and elastic materials made by mixing these are preferred.

[0026] Examples of conductive materials include electronic conductive materials and ionic conductive materials. Examples of electronically conductive agents include powders such as carbon black (furnace black, thermal black, channel black, Ketjen black, acetylene black, color black, etc.), pyrolysis carbon, graphite, metals or alloys such as aluminum, copper, nickel, and stainless steel, metal oxides such as tin oxide, indium oxide, titanium oxide, tin oxide-antimony oxide solid solution, and tin oxide-indium oxide solid solution, and materials whose insulating surfaces have been treated to become conductive. Examples of ionic conductive agents include perchlorates or chlorates such as tetraethylammonium, lauryltrimethylammonium, and benzyltrialkylammonium; and perchlorates or chlorates of alkali metals or alkaline earth metals such as lithium and magnesium. The conductive agent may be used individually or in combination of two or more types. The conductive agent preferably has an average primary particle size of 1 nm or more and 200 nm or less.

[0027] The content of the electronically conductive agent in the elastic layer is preferably 1 to 30 parts by mass, and more preferably 15 to 25 parts by mass, per 100 parts by mass of the elastic material. The content of the ion conductive agent in the elastic layer is preferably 0.1 parts by mass or more and 5 parts by mass or less, and more preferably 0.5 parts by mass or more and 3 parts by mass or less, per 100 parts by mass of the elastic material. The average particle size is calculated by observing a sample cut from the elastic layer using an electron microscope, measuring the diameter (maximum diameter) of 100 conductive particles, and averaging them. Alternatively, the average particle size may be measured using, for example, a Zetasizer Nano ZS manufactured by Sysmex Corporation.

[0028] There are no particular restrictions on the content of the conductive agent, but in the case of the electronic conductive agent, it is preferably in the range of 1 to 30 parts by mass, and more preferably in the range of 15 to 25 parts by mass, per 100 parts by mass of the elastic material. On the other hand, in the case of the ionic conductive agent, it is preferably in the range of 0.1 to 5.0 parts by mass, and more preferably in the range of 0.5 to 3.0 parts by mass, per 100 parts by mass of the elastic material.

[0029] Other additives that can be incorporated into the elastic layer include, for example, softeners, plasticizers, hardening agents, vulcanizing agents, vulcanization accelerators, vulcanization accelerators, antioxidants, surfactants, coupling agents, and fillers (silica, calcium carbonate, clay minerals, etc.).

[0030] The thickness of the elastic layer is preferably 1 mm to 10 mm, and more preferably 2 mm to 5 mm. The volume resistivity of the elastic layer is 1 × 10⁻⁶ 3 Ωcm or more, 1 × 10 14 A value of Ωcm or less is preferable.

[0031] The volume resistivity of the elastic layer was measured using the following method. A sheet-like sample is taken from the elastic layer, and a voltage adjusted to produce an electric field (applied voltage / composition sheet thickness) of 1000 V / cm is applied to the sample for 30 seconds using a measuring jig (R12702A / B Resistivity Chamber: Advantest Corporation) and a high-resistance measuring instrument (R8340A Digital High-Resistance / Micro-Ammeter: Advantest Corporation) in accordance with JIS K 6911 (1995). The current value is then calculated using the following formula. Volume resistivity (Ωcm) = (19.63 × applied voltage (V)) / (current value (A) × sample thickness (cm))

[0032] The morphology of the surface-forming particles contained in the elastic layer can be similar to that of the surface-forming particles contained in the surface layer. The elastic layer preferably contains unevenness-forming particles having a volume-average particle size of 5 μm to 20 μm in an amount of 5 to 30 parts by mass per 100 parts by mass of the elastic material. More preferably, the elastic layer contains unevenness-forming particles having a volume-average particle size of 5 μm to 10 μm in an amount of 8 to 20 parts by mass per 100 parts by mass of the elastic material.

[0033] Methods for forming an elastic layer on a conductive substrate include, for example, extruding an elastic layer-forming composition, which is a mixture of an elastic material, a conductive agent, and other additives, and a cylindrical conductive substrate together from an extrusion molding machine to form a layer of the elastic layer-forming composition on the outer surface of the conductive substrate, and then heating the layer of the elastic layer-forming composition to cause a crosslinking reaction and form an elastic layer; or extruding an elastic layer-forming composition, which is a mixture of an elastic material, a conductive agent, and other additives, from an extrusion molding machine onto the outer surface of an endless belt-shaped conductive substrate to form a layer of the elastic layer-forming composition on the outer surface of the conductive substrate, and then heating the layer of the elastic layer-forming composition to cause a crosslinking reaction and form an elastic layer. The conductive substrate may have an adhesive layer on its outer surface.

[0034] (Surface layer) The charging member according to this embodiment further has a surface layer on an elastic layer. The surface layer is, for example, a layer containing resin. The surface layer may also contain other additives as needed. Examples of binder resins that can be used for the surface layer include urethane resin, polyester, phenol, acrylic, polyurethane, epoxy resin, cellulose, and the like. Conductive particles are often included to adjust the resistivity of the surface layer to an appropriate value. The conductive particles have a particle size of 3 μm or less and a volume resistivity of 10 9 It is preferable that the particle size is Ωcm or less. For example, particles made of metal oxides such as tin oxide, titanium oxide, zinc oxide, or alloys thereof, or carbon black may be used.

[0035] The thickness of the surface layer is preferably 2 μm to 15 μm, more preferably 2 μm to 10 μm, and even more preferably 3 μm to 8 μm. The volume resistivity of the surface layer is 1 × 10⁻⁶ 5 Ωcm or more, 1 × 10 8 A value of Ωcm or less is preferable.

[0036] From the viewpoint of charging performance, wear resistance, and film suppression, it is preferable that the surface of the charged member has irregularities formed by the particle size, content, and dispersion state of various particles contained in the surface layer.

[0037] In this embodiment, from the viewpoint of charging performance, wear resistance, and film suppression, the average spacing Sm of the irregularities on the surface of the charging member is preferably in the range of 50 μm to 300 μm, and more preferably in the range of 70 μm to 250 μm. Here, the average spacing Sm of the irregularities on the surface of the charged material is an index indicating the surface roughness of the charged material as defined in JIS B 0601 (1994). In this embodiment, the average spacing Sm of the irregularities is obtained by taking a sample of a reference length from the roughness curve in the direction of the average line, calculating the sum of the lengths of the average lines corresponding to one peak and one adjacent valley in this sampled portion, and expressing the arithmetic mean of the spacing of these numerous irregularities in micrometers (μm).

[0038] The average spacing Sm of surface irregularities on the charged material was measured using a contact-type surface roughness measuring device (Surfcom 70, manufactured by Tokyo Seimitsu Co., Ltd.) under conditions of 23°C and 55% relative humidity. The measurement distance was set to 2.5 mm, and a contact needle with a diamond tip (5 μmR, 90° cone) was used. The average value of three repeated measurements at different locations was defined as the average spacing Sm of the irregularities.

[0039] Conventional methods such as roll coating, blade coating, wire bar coating, spray coating, dipping, bead coating, air knife coating, and curtain coating can be used for coating the surface layer. Roll coating is preferable for this invention because it does not cause sagging at the edges, thus making the edges thicker than the center. Although dipping coating does cause sagging at the edges, it is preferable because it can efficiently form a film with few defects.

[0040] (adhesive layer) The charging member used in this embodiment may have an adhesive layer between the conductive substrate and the elastic layer. Examples of adhesive layers interposed between the elastic layer and the conductive substrate include resin layers, specifically, resin layers such as polyolefin, acrylic resin, epoxy resin, polyurethane, nitrile rubber, chlorine rubber, vinyl chloride resin, vinyl acetate resin, polyester, phenolic resin, and silicone resin. The adhesive layer may also contain a conductive agent (for example, the aforementioned electronic conductive agent or ionic conductive agent).

[0041] From the viewpoint of adhesion, the thickness of the adhesive layer is preferably 1 μm to 100 μm, more preferably 2 μm to 50 μm, and particularly preferably 5 μm to 20 μm.

[0042] [Photoreceptor] The process cartridge according to this embodiment comprises a photoreceptor (also referred to as an "electrophotographic photoreceptor") having a conductive substrate, a photosensitive layer provided on the conductive substrate, and a protective layer provided on the photosensitive layer.

[0043] Figure 2 is a schematic cross-sectional view showing an example of the layer structure of the photoreceptor used in this embodiment. The photoreceptor 7A shown in Figure 2 has a structure in which an undercoat layer 1, a charge generation layer 2, and a charge transport layer 3 are laminated in that order on a conductive substrate 4. The charge generation layer 2 and the charge transport layer 3 constitute the photosensitive layer 5. Although not shown in the figure, the photoreceptor 7A is further provided with a protective layer 6 on top of the charge transport layer 3.

[0044] In the photoreceptor used in this embodiment, the photosensitive layer may be a laminated photoreceptor in which the charge generation layer 2 and the charge transport layer 3 are separated, as shown in the photoreceptor 7A in Figure 2, or it may be a single-layer photoreceptor having charge generation and charge transport capabilities instead of the charge generation layer 2 and the charge transport layer 3. When the photosensitive layer is a laminated photoreceptor, the order of the charge generation layer and the charge transport layer is not particularly limited, but it is preferable that the photoreceptor has a configuration in which the charge generation layer, the charge transport layer and the protective layer are arranged in this order on a conductive substrate. The photoreceptor may also include layers other than these.

[0045] (protective layer) The protective layer is provided on the photosensitive layer. The protective layer is a layer composed of a cured film of a composition containing a reactive group-containing charge transport material having both a reactive group and a charge transport skeleton within the same molecule, or a cured film of a composition containing a non-reactive charge transport material and a reactive group-containing non-charge transport material that does not have a charge transport skeleton but has a reactive group, and preferably the ratio of the degree of curing of the conductive substrate side surface to the degree of curing of the outer peripheral surface side surface is 75% or more.

[0046] The protective layer preferably has a ratio of the degree of hardening B of the conductive substrate side to the degree of hardening A of the outer peripheral surface (= B / A × 100) of 75% or more, more preferably 80% to 100%, and even more preferably 90% to 100%. When the above ratio is 75% or more (preferably 80% to 100%), the difference in the degree of curing of the cured film from the outer surface side to the conductive substrate side is kept small, so the variation in the amount of wear of the protective layer per rotation of the photoreceptor is kept small, and it is thought that the long-term variation in the wear resistance of the protective layer is suppressed.

[0047] The protective layer preferably has a hardening degree A on the outer surface side of 55% to 95%, more preferably 68% to 88%, and even more preferably 74% to 82%. If the degree of hardening A of the outer surface is 55% or higher, the outer surface will not become excessively soft, resulting in superior abrasion resistance of the protective layer. If the degree of hardening A of the outer surface is 95% or lower, the outer surface will not become excessively hard, and the difference in the degree of hardening of the cured film from the outer surface to the conductive substrate side will be kept smaller. As a result, fluctuations in the amount of wear of the protective layer per rotation of the photoreceptor will be kept smaller, and fluctuations in the long-term abrasion resistance of the protective layer will be further suppressed.

[0048] The protective layer preferably has a curing degree B of 41% to 95% on the conductive substrate side, more preferably 54% to 88%, and even more preferably 67% to 82%. When the degree of hardening A on the outer peripheral surface is 55% or higher, the conductive substrate side does not become excessively soft, and the outer peripheral surface does not become excessively soft, resulting in superior abrasion resistance of the protective layer. Furthermore, when the degree of hardening B is 41% or higher, the difference in the degree of hardening of the hardened film from the outer peripheral surface to the conductive substrate side is kept smaller, which is thought to reduce fluctuations in the amount of wear of the protective layer per rotation of the photoreceptor and further suppress fluctuations in the long-term abrasion resistance of the protective layer. If the degree of hardening A on the conductive substrate side is 95% or less, the outer surface side will not become excessively hard, and the difference in the degree of hardening of the hardened film from the outer surface side to the conductive substrate side will be kept smaller. As a result, fluctuations in the amount of wear of the protective layer per rotation of the photoreceptor will be kept smaller, and fluctuations in the long-term wear resistance of the protective layer will be further suppressed.

[0049] The method for controlling the degree of hardening of the outer peripheral surface, the degree of hardening of the conductive substrate side, and the ratio thereof is not particularly limited, but examples include having a hot air drying step (for example, heating at a temperature of 155°C or higher for 15 minutes or more) in the protective layer formation step.

[0050] The degree of hardening is measured as follows. (1) The photoreceptor surface is cut diagonally from the substrate to the surface, exposing the conductive substrate side without separating the protective layer, and a 20mm x 20mm test piece is obtained. (2) For the obtained test specimens, the remaining percentage of cured reactive groups is measured by infrared absorption spectroscopy on the outer surface and the conductive substrate side, respectively, under the following conditions. Measurement conditions: Infrared spectrometer (manufactured by PerkinElmer) Measurement conditions: ATR(Ge) method, area ratio of the absorption peak at the curing reaction group detection wavelength to the absorption peak at the base wavelength.

[0051] The protective layer is the layer shown in 1) or 2) below. If the protective layer is one of the layers shown in 1) or 2) below, chemical changes in the photosensitive layer during static charge are prevented, and the protective layer exhibits excellent abrasion resistance.

[0052] 1) A layer composed of a cured film of a composition containing a reactive group-containing charge transport material having a reactive group and a charge transport skeleton within the same molecule (i.e., a layer containing a polymer or crosslinked form of the reactive group-containing charge transport material). 2) A layer composed of a cured film of a composition comprising a non-reactive charge transport material and a reactive group-containing non-charge transport material that does not have a charge transport skeleton but has reactive groups (i.e., a layer comprising a non-reactive charge transport material and a polymer or crosslinked form of the reactive group-containing non-charge transport material).

[0053] The layer described in 1) above may further contain a non-reactive charge transport material in the composition.

[0054] The reactive groups in the reactive group-containing charge transport material include chain polymerizable groups, epoxy groups, -OH, -OR [where R represents an alkyl group], -NH2, -SH, -COOH, and -SiR. Q1 3-Qn (OR Q2 ) Qn [However, R Q1 R represents a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group. Q2 Examples of well-known reactive groups include hydrogen atoms, alkyl groups, and trialkylsilyl groups, where Qn is an integer from 1 to 3. Furthermore, these known reactive groups can also be used as reactive groups in non-charge transport materials containing reactive groups.

[0055] The chain polymerizable group is not particularly limited as long as it is a functional group capable of radical polymerization, for example, a functional group having at least one carbon double bond. Specifically, examples include groups containing at least one selected from vinyl groups, vinyl ether groups, vinyl thioether groups, styryl groups, acryloyl groups, methacryloyl groups, and their derivatives. Among these, the chain polymerizable group is preferably a group containing at least one selected from vinyl groups, styryl groups (vinylphenyl groups), acryloyl groups, methacryloyl groups, and their derivatives, due to its excellent reactivity.

[0056] The charge-transporting skeleton is not particularly limited as long as it is a known structure in the image holder. Examples include skeletons derived from nitrogen-containing hole-transporting compounds such as triarylamine compounds (compounds having a triarylamine skeleton), benzidine compounds (compounds having a benzidine skeleton), and hydrazone compounds (compounds having a hydrazone skeleton), in which the structure is conjugated with a nitrogen atom. Among these, it is preferable that the charge-transporting skeleton includes a triarylamine skeleton.

[0057] These reactive groups and charge-transporting skeletons, including reactive group-containing charge transport materials, non-reactive charge transport materials, and reactive group-containing non-charge transport materials, can be selected from well-known materials.

[0058] The reactive group-containing charge transport material may be a reactive group-containing charge transport material having a chain polymerizable group as the reactive group (hereinafter also referred to as "specific reactive group-containing charge transport material (a)"). The reactive group-containing non-charge transport material may be used alone or in combination of two or more types.

[0059] The specific reactive group-containing charge transport material (a) is preferably a compound represented by the following general formula (A) because it exhibits excellent charge transport properties.

[0060] [ka]

[0061] In the above general formula (A), Ar 1 ~Ar 4 Each of these independently represents a substituted or unsubstituted aryl group, Ar 5 represents a substituted or unsubstituted aryl group, or a substituted or unsubstituted arylene group; D represents an organic group having a chain polymerizable group; c1 to c5 each independently represent an integer between 0 and 2; k represents 0 or 1; d represents an integer between 0 and 5; e represents 0 or 1; and the total number of D is 4 or more.

[0062] In general formula (A), Ar 1 ~Ar 4 Each of these independently represents a substituted or unsubstituted aryl group. 1 ~Ar 4 These may be the same or they may be different. Here, examples of substituents in the substituted aryl group include, other than organic groups having a chain polymerizable group (D), alkyl or alkoxy groups having 1 to 4 carbon atoms, and substituted or unsubstituted aryl groups having 6 to 10 carbon atoms. Ar 1 ~Ar 4 Preferably, it is one of the following formulas (1) to (7). Note that formulas (1) to (7) below are Ar 1~Ar 4 "-(D)" can be linked to each of these. C1 " or "-(D) C4 "-(D)" is a comprehensive representation of " C This is shown together with ".

[0063] [ka]

[0064] In formulas (1) to (7) above, R 1 R represents one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group substituted with an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms, an unsubstituted phenyl group, and an aralkyl group having 7 to 10 carbon atoms. 2 ~R 4 Each of these independently represents one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a phenyl group substituted with an alkoxy group having 1 to 4 carbon atoms, an unsubstituted phenyl group, an aralkyl group having 7 to 10 carbon atoms, and a halogen atom; Ar represents a substituted or unsubstituted arylene group; D represents an organic group having a chain polymerizable group; c represents 1 or 2; s represents 0 or 1; and t represents an integer between 0 and 3.

[0065] Here, the Ar in formula (7) is preferably represented by the following structural formula (8) or (9).

[0066] [ka]

[0067] In equations (8) and (9) above, R 5 and R 6Each of these independently represents one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a phenyl group substituted with an alkoxy group having 1 to 4 carbon atoms, an unsubstituted phenyl group, an aralkyl group having 7 to 10 carbon atoms, and a halogen atom, and t' represents an integer between 0 and 3.

[0068] Furthermore, in formula (7), Z' represents a divalent organic linking group, preferably one represented by any of the following formulas (10) to (17). Also, in formula (7), s represents either 0 or 1.

[0069] [ka]

[0070] In formulas (10) to (17) above, R 7 and R 8 Each of the following independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms or a phenyl group substituted with an alkoxy group having 1 to 4 carbon atoms, an unsubstituted phenyl group, an aralkyl group having 7 to 10 carbon atoms, and a halogen atom; W represents a divalent group; q and r independently represent an integer between 1 and 10; and t'' independently represent an integer between 0 and 3.

[0071] In formulas (16) to (17), W is preferably one of the divalent groups represented by the following formulas (18) to (26). However, in formula (25), u represents an integer between 0 and 3.

[0072] [ka]

[0073] Also, in general formula (A), Ar 5 When k is 0, it is a substituted or unsubstituted aryl group, and this aryl group is Ar 1 ~Ar 4Examples similar to the aryl group exemplified in the explanation include Ar 5 When k is 1, it is a substituted or unsubstituted arylene group, and this arylene group is Ar 1 ~Ar 4 From the aryl group exemplified in the explanation, -N(Ar 3 -(D) C3 )(Ar 4 -(D) C4 An example is an arylene group in which one hydrogen atom is removed from the position where the substituted group is located.

[0074] The content of the reactive group-containing charge transport material is preferably 30% to 100% by mass, more preferably 40% to 100% by mass, and even more preferably 50% to 100% by mass, relative to the composition (solid content) used when forming the protective layer. By setting the content within this range, the electrical properties of the cured film are excellent, and the cured film can be made thicker.

[0075] Examples of non-reactive charge transport materials include quinone compounds such as p-benzoquinone, chloranil, bromanil, and anthraquinone; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthone compounds; benzophenone compounds; cyanovinyl compounds; and electron transport compounds such as ethylene compounds. Examples of charge transport materials include hole transport compounds such as triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted ethylene compounds, stilbene compounds, anthracene compounds, and hydrazone compounds. Non-reactive charge transport materials may be used individually or in combination of two or more.

[0076] Examples of non-charge transport materials containing reactive groups include thermosetting resins and curing agents. These materials may be used individually or in combination of two or more types. Examples of thermosetting resins include guanamine resin, melamine resin, phenolic resin, urea resin, and alkyd resin. Examples of curing agents include compounds having a guanamine structure (hereinafter also referred to as "guanamine compounds") and compounds having a melamine structure (hereinafter also referred to as "melamine compounds"). When the protective layer is a cured film composed of, for example, a reactive group-containing charge transport material and a crosslinked body (crosslinked product) of a thermosetting resin (more preferably guanamine resin, melamine resin, etc.), a guanamine compound, and a melamine compound, a cured film with a higher degree of curing is more easily obtained and exhibits superior abrasion resistance compared to cases where the thermosetting resin (more preferably guanamine resin, melamine resin, etc.), a guanamine compound, and a melamine compound are not included.

[0077] The protective layer is preferably composed of a cured product of a composition containing a reactive group-containing charge transport material having both the reactive group and the charge transport skeleton within the same molecule, among the layers described in 1) and 2). When the protective layer is the layer described in 1), the hardness of the protective layer tends to be higher and the wear resistance is superior compared to the layer described in 2).

[0078] -Fluororesin particles- The protective layer may further contain fluororesin particles. Adding fluororesin particles further creates a moderately uneven surface on the outer periphery of the protective layer, resulting in superior abrasion resistance. The protective layer contains fluororesin particles in an amount of 5% to 15% by mass relative to the total solid content of the protective layer. The content of fluororesin particles is preferably 5% to 15% by mass, and more preferably 7% to 12% by mass, relative to the total solid content of the layer.

[0079] Fluororesin particles are not particularly limited, but examples include polytetrafluoroethylene (PTFE, also known as "tetrafluoroethylene resin"), perfluoroalkoxy fluororesins, polychlorotrifluoroethylene, polyvinylidene fluoride, polydichlorodifluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer, and tetrafluoroethylene-perfluoroalkoxyethylene copolymer.

[0080] In particular, polytetrafluoroethylene and copolymers of tetrafluoroethylene and perfluoroalkoxyethylene are preferred from the viewpoint of wear resistance and cleanability of the electrophotographic photoreceptor. Fluororesin particles may be used individually or in combination of two or more types.

[0081] The weight-average molecular weight of the fluororesin constituting the fluororesin particles should, for example, be between 3,000 and 5,000,000.

[0082] The average primary particle size of the fluororesin particles is preferably, for example, 0.05 μm or more and 10 μm or less, and more preferably 0.1 μm or more and 5 μm or less. The average primary particle size of fluororesin particles is measured using a laser diffraction / scattering particle size distribution analyzer LA-920 (manufactured by Horiba, Ltd.) at a refractive index of 1.35, with the measurement solution diluted in the same solvent as the dispersion in which the fluororesin particles were dispersed.

[0083] Examples of commercially available fluoropolymer particles include the LeBron® series (manufactured by Daikin Industries, Ltd.), the Teflon® series (manufactured by DuPont), and the Dynion series (manufactured by Sumitomo 3M).

[0084] -Method for forming a protective layer- There are no particular restrictions on the formation of the protective layer, and well-known formation methods can be used. For example, it can be formed by adding the above components to a solvent to create a protective layer coating solution, drying the coating, and then performing a curing treatment such as heating as necessary.

[0085] Solvents for preparing coating solutions for forming a protective layer include aromatic solvents such as toluene and xylene; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester solvents such as ethyl acetate and butyl acetate; ether solvents such as tetrahydrofuran and dioxane; cellosolve solvents such as ethylene glycol monomethyl ether; and alcohol solvents such as isopropyl alcohol and butanol. These solvents can be used individually or in combination of two or more.

[0086] Conventional methods for applying a protective layer-forming coating solution onto a photosensitive layer (e.g., a charge transport layer) include immersion coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating, and curtain coating.

[0087] - thickness - From the viewpoint of suppressing the generation of minute color lines in the resulting image, the thickness of the protective layer is preferably 1 μm or more, more preferably 1 μm to 20 μm, even more preferably 2 μm to 10 μm, and particularly preferably 3 μm to 8 μm.

[0088] (Conductive base material) In this embodiment, the photoreceptor has a conductive substrate thickness of 3 mm or more, which may be 4 mm to 20 mm or 4 mm to 10 mm.

[0089] As mentioned above, when the thickness of the conductive substrate is 3 mm or more (especially 4 mm to 10 mm), compared to photoreceptors with a conductive substrate thickness of less than 3 mm, heat is less easily transferred from the outer surface side to the conductive substrate side when forming the protective layer. Consequently, the difference in the degree of hardening of the cured film from the outer surface side to the conductive substrate side becomes larger. Therefore, the amount of wear per rotation of the photoreceptor gradually decreases, and the long-term fluctuation in the wear resistance of the protective layer becomes larger. On the other hand, in the photoreceptor according to this embodiment, even if the thickness of the conductive substrate is 3 mm or more (especially 4 mm to 10 mm), the difference in the degree of hardening of the cured film from the outer surface side to the conductive substrate side is kept small when forming the protective layer. Therefore, the long-term fluctuation in the wear resistance of the protective layer is suppressed.

[0090] Examples of conductive substrates include metal plates, metal drums, and metal belts containing metals (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.). Other examples of conductive substrates include paper, resin films, and belts coated, vapor-deposited, or laminated with conductive compounds (e.g., conductive polymers, indium oxide, etc.), metals (e.g., aluminum, palladium, gold, etc.) or alloys. Here, "conductive" refers to a volume resistivity of 10⁻¹⁰. 13 This refers to a value less than Ωcm.

[0091] When an electrophotographic photoreceptor is used in a laser printer, the surface of the conductive substrate is preferably roughened to a center-line average roughness Ra of 0.04 μm to 0.5 μm in order to suppress interference fringes that occur when irradiated with laser light. While roughening to prevent interference fringes is not particularly necessary when using non-interfering light as the light source, it is beneficial for extending the lifespan of the conductive substrate by suppressing the occurrence of defects due to surface irregularities.

[0092] Methods for roughening a surface include, for example, wet honing, which involves suspending an abrasive in water and spraying it onto a conductive substrate; centerless grinding, which involves pressing a conductive substrate against a rotating grinding wheel and continuously grinding it; and anodizing.

[0093] One method for roughening the surface is to disperse conductive or semiconductive powder in a resin without roughening the surface of the conductive substrate, to form a layer on the surface of the conductive substrate, and then roughen the surface with the particles dispersed in that layer.

[0094] Anodizing roughening treatment involves forming an oxide film on the surface of a conductive substrate by anodizing a metal (e.g., aluminum) conductive substrate in an electrolyte solution. Examples of electrolyte solutions include sulfuric acid solution and oxalic acid solution. However, the porous anodic oxide film formed by anodizing is chemically active, easily contaminated, and exhibits large resistance fluctuations depending on the environment. Therefore, it is preferable to perform a sealing treatment on the porous anodic oxide film, which involves sealing the micropores of the oxide film by volume expansion due to a hydration reaction using pressurized steam or boiling water (metal salts such as nickel may be added), thereby converting it into a more stable hydrated oxide.

[0095] The thickness of the anodic oxide film is preferably, for example, 0.3 μm to 15 μm. When the film thickness is within this range, it tends to exhibit barrier properties against injection and tends to suppress the increase in residual potential due to repeated use.

[0096] The conductive substrate may be treated with an acidic treatment solution or with boehmite. Treatment with an acidic solution is carried out, for example, as follows: First, an acidic solution containing phosphoric acid, chromic acid, and hydrofluoric acid is prepared. The mixing ratio of phosphoric acid, chromic acid, and hydrofluoric acid in the acidic solution is, for example, in the range of 10% to 11% by mass for phosphoric acid, 3% to 5% by mass for chromic acid, and 0.5% to 2% by mass for hydrofluoric acid, and the total concentration of these acids is preferably in the range of 13.5% to 18% by mass. The treatment temperature is preferably, for example, 42°C to 48°C. The film thickness is preferably 0.3 μm to 15 μm.

[0097] The boehmite treatment is carried out, for example, by immersing the material in pure water at 90°C to 100°C for 5 to 60 minutes, or by contacting it with heated steam at 90°C to 120°C for 5 to 60 minutes. The film thickness is preferably 0.1 μm to 5 μm. This can be further treated with anodic oxidation using an electrolyte solution with low film solubility, such as adipic acid, boric acid, borate, phosphate, phthalate, maleate, benzoate, tartrate, or citrate.

[0098] (subbing layer) The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

[0099] As for inorganic particles, for example, powder resistance (volume resistivity) 10 2 Ωcm or more 10 11 Examples include inorganic particles smaller than Ωcm. Among these, suitable inorganic particles having the above-mentioned resistance values ​​include metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles, with zinc oxide particles being particularly preferred.

[0100] The specific surface area of ​​inorganic particles using the BET method is, for example, 10 m². 2 A value of 1g or more is preferable. The volume-average particle size of the inorganic particles is preferably between 50 nm and 2000 nm (preferably between 60 nm and 1000 nm).

[0101] The inorganic particle content is preferably 10% by mass or more and 80% by mass or less relative to the binder resin, and more preferably 40% by mass or more and 80% by mass or less.

[0102] The inorganic particles may be surface-treated. Two or more types of inorganic particles with different surface treatments or particle sizes may be mixed and used.

[0103] Examples of surface treatment agents include silane coupling agents, titanate-based coupling agents, aluminum-based coupling agents, and surfactants. Silane coupling agents are particularly preferred, and silane coupling agents having an amino group are more preferred.

[0104] Examples of silane coupling agents having an amino group include, but are not limited to, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane.

[0105] Silane coupling agents may be used in combination of two or more types. For example, a silane coupling agent having an amino group may be used in combination with another silane coupling agent. Examples of other silane coupling agents include, but are not limited to, vinyltrimethoxysilane, 3-methacrylateoxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and 3-chloropropyltrimethoxysilane.

[0106] The surface treatment method using the surface treatment agent may be any known method, and may be either a dry or wet method.

[0107] The amount of surface treatment agent applied is preferably, for example, 0.5% by mass or more and 10% by mass or less relative to the inorganic particles.

[0108] In this case, it is preferable for the underlayer to contain electron-accepting compounds (acceptor compounds) along with inorganic particles, from the viewpoint of improving the long-term stability of electrical properties and carrier blocking ability.

[0109] Examples of electron-accepting compounds include quinone compounds such as chloranil and bromonil; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone and 2,4,5,7-tetranitro-9-fluorenone; oxadiazole compounds such as 2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole, 2,5-bis(4-naphthyl)-1,3,4-oxadiazole, and 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole; xanthone compounds; thiophene compounds; and diphenoquinone compounds such as 3,3',5,5'-tetra-t-butyldiphenoquinone; as well as other electron-transporting substances. In particular, compounds having an anthraquinone structure are preferred as electron-accepting compounds. Examples of compounds having an anthraquinone structure include hydroxyanthraquinone compounds, aminoanthraquinone compounds, and aminohydroxyanthraquinone compounds, and specifically, for example, anthraquinone, alizarin, quinizalin, anthralphine, and purpurin are preferred.

[0110] The electron-accepting compound may be dispersed in the underlayer together with inorganic particles, or it may be present attached to the surface of the inorganic particles.

[0111] Methods for attaching electron-accepting compounds to the surface of inorganic particles include, for example, dry methods or wet methods.

[0112] The dry method involves, for example, adding an electron-accepting compound, either directly or dissolved in an organic solvent, dropwise while stirring inorganic particles with a mixer that has a high shear force, or spraying it with dry air or nitrogen gas, to adhere the electron-accepting compound to the surface of the inorganic particles. When adding or spraying the electron-accepting compound, it is preferable to do so at a temperature below the boiling point of the solvent. After adding or spraying the electron-accepting compound, further baking at 100°C or higher may be performed. The baking temperature and time are not particularly limited as long as electrophotographic characteristics can be obtained.

[0113] The wet method involves dispersing inorganic particles in a solvent using methods such as stirring, ultrasound, sand milling, attritoring, and ball milling, while adding an electron-accepting compound. After stirring or dispersion, the solvent is removed to adhere the electron-accepting compound to the surface of the inorganic particles. Solvent removal methods include, for example, filtration or distillation. After solvent removal, further baking at 100°C or higher may be performed. The baking temperature and time are not particularly limited as long as electrophotographic characteristics can be obtained. In the wet method, the water content of the inorganic particles may be removed before adding the electron-accepting compound. Examples of this include removing water while stirring and heating in the solvent, or removing water by azeotrope with the solvent.

[0114] Furthermore, the attachment of the electron-accepting compound may be performed before or after surface treatment with a surface treatment agent on the inorganic particles, or it may be performed simultaneously with the attachment of the electron-accepting compound and surface treatment with the surface treatment agent.

[0115] The content of the electron-accepting compound is preferably, for example, 0.01% by mass or more and 20% by mass or less relative to the inorganic particles, and more preferably 0.01% by mass or more and 10% by mass or less.

[0116] Examples of known polymer compounds used as the binder resin for the undercoat include acetal resin (e.g., polyvinyl butyral), polyvinyl alcohol resin, polyvinyl acetal resin, casein resin, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, unsaturated polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, urea resin, phenol resin, phenol-formaldehyde resin, melamine resin, urethane resin, alkyd resin, epoxy resin, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, and silane coupling agents. Examples of binder resins used in the undercoat include charge-transporting resins having charge-transporting groups, conductive resins (e.g., polyaniline), and the like.

[0117] Among these, a resin insoluble in the coating solvent of the upper layer is preferred as the binder resin used for the undercoat layer. In particular, a resin obtained by the reaction of a curing agent with at least one resin selected from the group consisting of thermosetting resins such as urea resin, phenol resin, phenol-formaldehyde resin, melamine resin, urethane resin, unsaturated polyester resin, alkyd resin, and epoxy resin is preferred. When using two or more of these binder resins in combination, the mixing ratio is set as needed.

[0118] The undercoat may contain various additives to improve electrical properties, environmental stability, and image quality. Examples of known additives include electron-transporting pigments such as polycyclic condensation and azo pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, and silane coupling agents. As mentioned above, silane coupling agents are used for surface treatment of inorganic particles, but they may also be added to the undercoat as additives.

[0119] Examples of silane coupling agents used as additives include vinyltrimethoxysilane, 3-methacrylateoxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and 3-chloropropyltrimethoxysilane.

[0120] Examples of zirconium chelate compounds include zirconium butoxide, ethyl zirconium acetate, zirconium triethanolamine, acetylacetonate zirconium butoxide, ethyl acetate zirconium butoxide, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octanoate, zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, methacrylate zirconium butoxide, stearate zirconium butoxide, and isostearate zirconium butoxide.

[0121] Examples of titanium chelate compounds include tetraisopropyl titanate, tetran-butyl titanate, butyl titanate dimer, tetra(2-ethylhexyl) titanate, titanium acetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate ammonium salt, titanium lactate, titanium lactate ethyl ester, titanium triethanolamine, and polyhydroxytitanium stearate.

[0122] Examples of aluminum chelating compounds include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, diethylacetoacetate aluminum diisopropylate, and aluminum tris(ethylacetoacetate).

[0123] These additives may be used individually or as a mixture or polycondensate of multiple compounds.

[0124] The underlayer should ideally have a Vickers hardness of 35 or higher. The surface roughness (ten-point average roughness) of the undercoat layer should be adjusted to between 1 / (4n) (where n is the refractive index of the upper layer) and 1 / 2 of the exposure laser wavelength λ used, in order to suppress moiré patterns. Resin particles may be added to the undercoat to adjust the surface roughness. Examples of resin particles include silicone resin particles and cross-linked polymethyl methacrylate resin particles. The surface of the undercoat may also be polished to adjust the surface roughness. Polishing methods include buffing, sandblasting, wet honing, and grinding.

[0125] There are no particular restrictions on the formation of the undercoat layer, and well-known formation methods can be used. For example, it can be carried out by forming a coating film of an undercoat-forming solution obtained by adding the above components to a solvent, drying the coating film, and heating it if necessary.

[0126] Solvents for preparing the coating solution for forming the undercoat include known organic solvents such as alcohol-based solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone-based solvents, ketone alcohol-based solvents, ether-based solvents, and ester-based solvents. Specific examples of these solvents include common organic solvents such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzyl alcohol, methyl cellsolve, ethyl cellsolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene.

[0127] Known methods for dispersing inorganic particles when preparing a coating solution for forming an undercoat include, for example, roll mills, ball mills, vibrating ball mills, attritors, sand mills, colloid mills, and paint shakers.

[0128] Conventional methods for applying the undercoating solution onto a conductive substrate include, for example, the blade coating method, wire bar coating method, spray coating method, immersion coating method, bead coating method, air knife coating method, and curtain coating method.

[0129] The thickness of the undercoat layer is preferably set to a range of 15 μm or more, and more preferably 20 μm to 50 μm.

[0130] (Middle class) Although not shown in the diagram, an intermediate layer may be further provided between the undercoat layer and the photosensitive layer. The intermediate layer is, for example, a layer containing a resin. Examples of resins used in the intermediate layer include polymer compounds such as acetal resin (e.g., polyvinyl butyral), polyvinyl alcohol resin, polyvinyl acetal resin, casein resin, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, and melamine resin. The intermediate layer may contain an organometallic compound. Examples of organometallic compounds used in the intermediate layer include those containing metal atoms such as zirconium, titanium, aluminum, manganese, and silicon. The compounds used in these intermediate layers may be used individually, as a mixture of multiple compounds, or as polycondensates.

[0131] Among these, the intermediate layer is preferably a layer containing an organometallic compound that contains zirconium atoms or silicon atoms.

[0132] There are no particular restrictions on the formation of the intermediate layer, and well-known formation methods can be used. For example, it can be carried out by forming a coating film of an intermediate layer-forming coating solution obtained by adding the above components to a solvent, drying the coating film, and heating it if necessary. Conventional methods such as immersion coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating, and curtain coating are used to form the intermediate layer.

[0133] The thickness of the intermediate layer is preferably set to a range of 0.1 μm to 3 μm, for example. The intermediate layer may also be used as a base layer.

[0134] (Charge generation layer) The charge generation layer is, for example, a layer containing a charge generation material and a binder resin. Alternatively, the charge generation layer may be a vapor-deposited layer of the charge generation material. A vapor-deposited layer of the charge generation material is suitable when using non-coherent light sources such as LEDs (Light Emitting Diodes) or organic EL (Electro-Luminescence) image arrays.

[0135] Examples of charge-generating materials include azo pigments such as bisazo and trisazo; fused aromatic pigments such as dibromoanthonthrone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; and trigonal selenium.

[0136] Among these, in order to accommodate laser exposure in the near-infrared region, it is preferable to use a metal phthalocyanine pigment or a metal-free phthalocyanine pigment as the charge generating material. Specifically, for example, hydroxygallium phthalocyanine; chlorogallium phthalocyanine; dichlorotin phthalocyanine; and titanyl phthalocyanine are more preferable.

[0137] On the other hand, to accommodate laser exposure in the near-ultraviolet region, preferred charge-generating materials include fused aromatic pigments such as dibromoanthoten; thioindigo pigments; porphyrazine compounds; zinc oxide; trigonal selenium; and bisazo pigments.

[0138] Even when using non-coherent light sources such as LEDs and organic EL image arrays with a central emission wavelength between 450 nm and 780 nm, the above charge generating materials may be used. However, from the viewpoint of resolution, when using a thin film of 20 μm or less for the photosensitive layer, the electric field strength in the photosensitive layer becomes high, making it easier for charge reduction due to charge injection from the substrate to occur, resulting in image defects known as black spots. This is particularly noticeable when using charge generating materials that are p-type semiconductors that easily generate dark current, such as trigonal selenium and phthalocyanine pigments.

[0139] In contrast, when n-type semiconductors such as fused aromatic pigments, perylene pigments, and azo pigments are used as charge-generating materials, dark currents are less likely to occur, and image defects called black spots can be suppressed even in thin films. Furthermore, the n-type is determined using the commonly used time-of-flight method, based on the polarity of the photocurrent that flows. Those that are more likely to carry electrons as carriers than holes are classified as n-type.

[0140] The binder resin used in the charge generation layer can be selected from a wide range of insulating resins, or it may be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, and polysilane. Examples of binder resins include polyvinyl butyral resin, polyarylate resin (polycondensate of bisphenols and aromatic divalent carboxylic acids, etc.), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyamide resin, acrylic resin, polyacrylamide resin, polyvinylpyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, and polyvinylpyrrolidone resin. Here, "insulating properties" refers to a volume resistivity of 10 13 This refers to a value of Ωcm or greater. These binder resins can be used individually or in combination of two or more types.

[0141] Furthermore, the mixing ratio of the charge-generating material to the binder resin is preferably within the range of 10:1 to 1:10 by mass ratio.

[0142] The charge generation layer may also contain other well-known additives.

[0143] The formation of the charge generation layer is not particularly limited, and well-known formation methods can be used. For example, it can be carried out by forming a coating film of a charge generation layer forming solution obtained by adding the above components to a solvent, drying the coating film, and heating it as necessary. The charge generation layer may also be formed by vapor deposition of the charge generation material. Formation of the charge generation layer by vapor deposition is particularly suitable when using fused aromatic pigments or perylene pigments as the charge generation material.

[0144] Solvents for preparing the coating solution for forming the charge generation layer include methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellsolve, ethyl cellsolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene. These solvents may be used individually or in mixtures of two or more.

[0145] Methods for dispersing particles (e.g., charge-generating materials) in a coating solution for forming a charge-generating layer include, for example, media dispersers such as ball mills, vibrating ball mills, attritors, sand mills, and horizontal sand mills, as well as media-less dispersers such as stirrers, ultrasonic dispersers, roll mills, and high-pressure homogenizers. Examples of high-pressure homogenizers include collision methods, which disperse the dispersion by causing liquid-liquid collisions or liquid-wall collisions under high pressure, and penetration methods, which disperse the dispersion by penetrating fine channels under high pressure. Furthermore, during this dispersion, it is effective to set the average particle size of the charge-generating material in the coating solution for forming the charge-generating layer to 0.5 μm or less, preferably 0.3 μm or less, and more preferably 0.15 μm or less.

[0146] Conventional methods for applying the charge-generating layer forming coating solution onto the undercoat (or intermediate layer) include, for example, the blade coating method, wire bar coating method, spray coating method, immersion coating method, bead coating method, air knife coating method, and curtain coating method.

[0147] The thickness of the charge generation layer is preferably set to a range of 0.1 μm to 5.0 μm, more preferably 0.2 μm to 2.0 μm.

[0148] (charge transport layer) The charge transport layer is, for example, a layer containing a charge transport material and a binder resin. The charge transport layer may also be a layer containing a polymer charge transport material.

[0149] Examples of charge transport materials include quinone compounds such as p-benzoquinone, chloranil, bromanil, and anthraquinone; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthone compounds; benzophenone compounds; cyanovinyl compounds; and ethylene compounds, which are electron transport compounds. Other examples of charge transport materials include hole transport compounds such as triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted ethylene compounds, stilbene compounds, anthracene compounds, and hydrazone compounds. These charge transport materials may be used individually or in combination of two or more, but are not limited to these uses.

[0150] As charge transport materials, from the viewpoint of charge mobility, the triarylamine derivative shown in the following structural formula (a-1) and the benzidine derivative shown in the following structural formula (a-2) are preferred.

[0151] [ka]

[0152] In structural formula (a-1), Ar T1 Ar T2 , and Ar T3 These are, independently, substituted or unsubstituted aryl groups, -C6H4-C(R T4 )=C(R T5 )(R T6 ), or -C6H4-CH=CH-CH=C(R T7 )(R T8 ) indicates R T4 , RT5 , R T6 , R T7 , and R T8 each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Examples of the substituent of each of the above groups include a halogen atom, an alkyl group having 1 to 5 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms. Further, examples of the substituent of each of the above groups also include a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

[0153]

Chemical formula

[0154] In structural formula (a-2), R T91 and R T92 each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. R T101 , R T102 , R T111 and R T112 each independently represents a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted with an alkyl group having 1 to 2 carbon atoms, a substituted or unsubstituted aryl group, -C(R T12 )=C(R T13 )(R T14 ), or -CH=CH-CH=C(R T15 )(R T16 ), and R T12 , R T13 , R T14 , R T15 and R T16 each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Tm1, Tm2, Tn1, and Tn2 each independently represent an integer of 0 or more and 2 or less. Examples of the substituent of each of the above groups include a halogen atom, an alkyl group having 1 to 5 carbon atoms, and an alkoxy group having 1 to 5 carbon atoms. Further, examples of the substituent of each of the above groups also include a substituted amino group substituted with an alkyl group having 1 to 3 carbon atoms.

[0155] Here, among the triarylamine derivative represented by structural formula (a-1) and the benzidine derivative represented by structural formula (a-2), in particular, "-C6H4-CH=CH-CH=C(R T7 )(R T8 Triarylamine derivatives having ")" and "-CH=CH-CH=C(R T15 )(R T16 A benzidine derivative having ) is preferred from the viewpoint of charge mobility.

[0156] As polymer charge transport materials, known charge transport materials such as poly-N-vinylcarbazole and polysilane can be used. Polyester-based polymer charge transport materials are particularly preferred. The polymer charge transport material may be used alone, or it may be used in combination with a binder resin.

[0157] Examples of binder resins used in the charge transport layer include polycarbonate resin, polyester resin, polyarylate resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer, vinylidene chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-N-vinylcarbazole, and polysilane. Among these, polycarbonate resin or polyarylate resin is preferred as the binder resin. These binder resins can be used individually or in combination of two or more. The preferred mixing ratio of the charge transport material to the binder resin is between 10:1 and 1:5 by mass.

[0158] The charge transport layer may also contain other well-known additives.

[0159] The formation of the charge transport layer is not particularly limited, and well-known formation methods can be used. For example, it can be carried out by forming a coating film of a charge transport layer forming solution obtained by adding the above components to a solvent, drying the coating film, and heating it if necessary.

[0160] Suitable solvents for preparing the coating solution for forming the charge transport layer include common organic solvents such as aromatic hydrocarbons like benzene, toluene, xylene, and chlorobenzene; ketones like acetone and 2-butanone; halogenated aliphatic hydrocarbons like methylene chloride, chloroform, and ethylene chloride; and cyclic or linear ethers like tetrahydrofuran and ethyl ether. These solvents can be used individually or in mixtures of two or more.

[0161] Conventional methods for applying a charge transport layer forming coating solution onto a charge generation layer include blade coating, wire bar coating, spray coating, immersion coating, bead coating, air knife coating, and curtain coating.

[0162] The thickness of the charge transport layer is preferably set within the range of 5 μm to 50 μm, more preferably 8 μm to 30 μm, and particularly preferably 9 μm to 14 μm.

[0163] (Single-layer photosensitive layer) A single-layer photosensitive layer (charge generation / charge transport layer) is, for example, a layer comprising a charge generation material, a charge transport material, and, if necessary, a binder resin and other well-known additives. These materials are the same as those described for the charge generation layer and the charge transport layer. Furthermore, the content of the charge-generating material in the single-layer photosensitive layer is preferably 0.1% to 10% by mass, and more preferably 0.8% to 5% by mass, relative to the total solid content. In addition, the content of the charge-transporting material in the single-layer photosensitive layer is preferably 5% to 50% by mass, relative to the total solid content. The method for forming a single-layer photosensitive layer is the same as the method for forming a charge generation layer or a charge transport layer.

[0164] - thickness - The thickness of the photosensitive layer, that is, the thickness of a stacked photosensitive layer in which a charge generation layer and a charge transport layer are stacked, or a single-layer photosensitive layer, is preferably 9 μm or more, more preferably 9 μm to 20 μm, even more preferably 9 μm to 17 μm, and particularly preferably 9.5 μm to 15 μm, from the viewpoint of suppressing the generation of minute color lines in the resulting image.

[0165] The process cartridge according to this embodiment is preferably a cartridge that can be attached to and detached from an image forming apparatus. The process cartridge according to this embodiment may further include at least one device selected from the group consisting of a developing device, a photoreceptor cleaning device, a photoreceptor static elimination device, and a transfer device.

[0166] The process cartridge according to this embodiment may be one of the following: a method that applies only a DC voltage (DC charging method), a method that applies only an AC voltage to the charging member (AC charging method), or a method that applies a voltage obtained by superimposing an AC voltage on a DC voltage to the charging member (AC / DC charging method).

[0167] <Image forming apparatus> The image forming apparatus according to this embodiment is not particularly limited as long as it has a process cartridge according to this embodiment, and preferably comprises an electrostatic latent image forming means that forms an electrostatic latent image on the surface of the charged photoreceptor, a developing means that develops the electrostatic latent image formed on the surface of the photoreceptor with a developer containing toner to form a toner image, and a transfer means that transfers the toner image to the surface of a recording medium.

[0168] Furthermore, the image forming apparatus according to this embodiment may further include at least one selected from the group consisting of a cleaning device for cleaning the surface of the photoreceptor after the transfer of the toner image and before charging, and a static elimination device for irradiating the surface of the photoreceptor with light to remove static charge after the transfer of the toner image and before charging.

[0169] The image forming apparatus according to this embodiment may be either a direct transfer apparatus that directly transfers a toner image formed on the surface of an electrophotographic photoreceptor to a recording medium, or an intermediate transfer apparatus that first transfers a toner image formed on the surface of an electrophotographic photoreceptor to the surface of an intermediate transfer body, and then secondarily transfers the toner image transferred to the surface of the intermediate transfer body to the surface of a recording medium.

[0170] The configurations of the charging apparatus, image forming apparatus, and process cartridge according to this embodiment will be described below with reference to the drawings.

[0171] Figure 3 is a schematic diagram showing an example of an image forming apparatus according to this embodiment. Figure 3 is a schematic diagram showing a direct transfer type image forming apparatus. Figure 4 is a schematic diagram showing another example of an image forming apparatus according to this embodiment. Figure 4 is a schematic diagram showing an intermediate transfer type image forming apparatus.

[0172] The image forming apparatus 200 shown in Figure 3 comprises an electrophotographic photoreceptor (also simply called a "photoreceptor") 207, a charging device 208 for charging the surface of the photoreceptor 207, a power supply 209 connected to the charging device 208, an exposure device 206 for exposing the surface of the photoreceptor 207 to form a latent image, a developing device 211 for developing the latent image on the photoreceptor 207 with a developer containing toner, a transfer device 212 for transferring the toner image on the photoreceptor 207 to a recording medium 500, a fixing device 215 for fixing the toner image to the recording medium 500, a cleaning device 213 for removing toner remaining on the photoreceptor 207, and a static elimination device 214 for removing static electricity from the surface of the photoreceptor 207. The static elimination device 214 is optional.

[0173] The image forming apparatus 210 shown in Figure 4 comprises a photoreceptor 207, a charging device 208, a power supply 209, an exposure device 206, a developing device 211, a primary transfer member 212a and a secondary transfer member 212b for transferring the toner image on the photoreceptor 207 to the recording medium 500, a fixing device 215, and a cleaning device 213. The image forming apparatus 210 may also be equipped with a static elimination device, similar to the image forming apparatus 200.

[0174] The charging device 208 is a contact-charging type charging device consisting of a roll-shaped charging member that contacts the surface of the photoreceptor 207 to charge the surface of the photoreceptor 207. The charging device 208 is supplied with either a DC voltage only, an AC voltage only, or a voltage obtained by superimposing an AC voltage on a DC voltage from the power supply 209.

[0175] Examples of exposure apparatus 206 include optical systems equipped with light sources such as semiconductor lasers and LEDs (light-emitting diodes).

[0176] The developing device 211 is a device that supplies toner to the photoreceptor 207. The developing device 211, for example, brings a roll-shaped developer holder into contact with or close to the photoreceptor 207 to deposit toner onto the latent image on the photoreceptor 207 and form a toner image.

[0177] Examples of the transfer device 212 include a corona discharge generator and a conductive roll that presses against the photoreceptor 207 via the recording medium 500.

[0178] Examples of the primary transfer member 212a include a conductive roll that rotates in contact with the photoreceptor 207. Examples of the secondary transfer member 212b include a conductive roll that presses against the primary transfer member 212a via the recording medium 500.

[0179] Examples of fixing devices 215 include a heating fixing device that includes a heating roll and a pressure roll that presses against the heating roll.

[0180] The cleaning device 213 may include a device equipped with cleaning components such as blades, brushes, and rolls. The material of the cleaning blade may include urethane rubber, neoprene rubber, and silicone rubber.

[0181] The static elimination device 214 is, for example, a device that irradiates light onto the surface of the photoreceptor 207 after transfer to eliminate the residual potential of the photoreceptor 207. The static elimination device 214 is not required to be provided.

[0182] Figure 5 is a schematic diagram showing another example of an image forming apparatus according to this embodiment. Figure 5 is a schematic diagram showing a tandem and intermediate transfer type image forming apparatus in which four image forming units are arranged in parallel.

[0183] The image forming apparatus 220 comprises, within a housing 400, four image forming units corresponding to each color of toner, an exposure apparatus 403 equipped with a laser light source, an intermediate transfer belt 409, a secondary transfer roll 413, a fixing apparatus 414, and a cleaning apparatus having a cleaning blade 416.

[0184] Since the four image forming units have the same configuration, the configuration of the image forming unit including the photoreceptor 401a will be described as representative of them. Around the photoreceptor 401a, in the direction of rotation of the photoreceptor 401a, are arranged in the following order: a charging roll 402a, a developing device 404a, a primary transfer roll 410a, and a cleaning blade 415a. The primary transfer roll 410a presses against the photoreceptor 401a via an intermediate transfer belt 409. The developing device 404a is supplied with toner contained in a toner cartridge 405a.

[0185] The charging roll 402a is a contact-charging device that charges the surface of the photoreceptor 401a by contacting it. The charging roll 402a is supplied with either a DC voltage only, an AC voltage only, or a DC voltage superimposed with an AC voltage.

[0186] The intermediate transfer belt 409 is stretched by a drive roll 406, a tension roll 407, and a back roll 408, and travels by the rotation of these rolls.

[0187] The secondary transfer roll 413 is positioned to press against the back roll 408 via the intermediate transfer belt 409.

[0188] The fixing device 414 is, for example, a heating fixing device that includes a heating roll and a pressure roll.

[0189] The cleaning blade 416 is a component that removes toner remaining on the intermediate transfer belt 409. The cleaning blade 416 is located downstream of the back roll 408 and removes toner remaining on the intermediate transfer belt 409 after transfer.

[0190] A tray 411 for holding the recording medium 500 is provided inside the housing 400. The recording medium 500 in the tray 411 is transported by a transport roll 412 to the contact point between the intermediate transfer belt 409 and the secondary transfer roll 413, and then transported to a fixing device 414, where an image is formed on the recording medium 500. After image formation, the recording medium 500 is discharged to the outside of the housing 400.

[0191] Figure 6 is a schematic diagram showing an example of a process cartridge according to this embodiment. The process cartridge 300 shown in Figure 6 is attached to, for example, the main body of an image forming apparatus that includes an exposure device, a transfer device, and a fixing device.

[0192] The process cartridge 300 integrates a photoreceptor 207, a charging device 208, a developing device 211, and a cleaning device 213 within a housing 301. The housing 301 is provided with a mounting rail 302 for attaching and detaching from an image forming apparatus, an opening 303 for exposure, and an opening 304 for static elimination exposure.

[0193] The charging device 208 of the process cartridge 300 consists of a roll-shaped charging member and is a contact-charging type charging device that contacts the surface of the photoreceptor 207 to charge the surface of the photoreceptor 207. When the process cartridge 300 is mounted in the image forming apparatus and image forming is performed, the charging device 208 is supplied with either only a DC voltage, only an AC voltage, or a voltage obtained by superimposing an AC voltage on a DC voltage from the power supply.

[0194] <Developers, Toners> The developer used in the image forming apparatus according to this embodiment is not particularly limited. The developer may be a one-component developer containing only toner, or a two-component developer containing a mixture of toner and carrier.

[0195] The toner contained in the developer is not particularly limited. The toner includes, for example, a binder resin, a colorant, and a release agent. Examples of binder resins for the toner include polyester and styrene-acrylic resin.

[0196] Toner may have external additives added to it. Examples of external additives for toner include inorganic particles such as silica, titania, and alumina.

[0197] Toner is prepared by manufacturing toner particles and then adding external additives to these toner particles. Methods for manufacturing toner particles include kneading and grinding, agglomeration and coalescence, suspension polymerization, and dissolution and suspension. The toner particles may be single-layer toner particles, or they may be so-called core-shell toner particles consisting of a core (core particle) and a coating layer (shell layer) covering the core.

[0198] The volume-average particle size (D50v) of the toner particles is preferably 2 μm or more and 10 μm or less, and more preferably 4 μm or more and 8 μm or less.

[0199] The carrier contained in the two-component developer is not particularly limited. Examples of carriers include coated carriers in which a resin is coated on the surface of a core material made of magnetic powder; magnetic powder dispersed carriers in which magnetic powder is dispersed in a matrix resin; and resin-impregnated carriers in which resin is impregnated into porous magnetic powder.

[0200] In a two-component developer, the mixing ratio (mass ratio) of toner and carrier is preferably toner:carrier = 1:100 to 30:100, and more preferably 3:100 to 20:100. [Examples]

[0201] Hereinafter, embodiments of the invention will be described in detail with reference to examples, but the embodiments of the invention are not limited to these examples in any way. In the following description, unless otherwise specified, "parts" are based on mass.

[0202] <Example 1> [Production of Charging Member 1] (Production of Elastic Layer) The following mixture for forming an elastic layer was kneaded with an open roll, and the outer peripheral surface of a roll-shaped conductive base material made of SUS416 with a diameter of 9 mm was cylindrically coated to a thickness of 1.5 mm. This was placed in a cylindrical mold with an inner diameter of 12.0 mm, vulcanized at 170 °C for 30 minutes, taken out of the mold, and then the surface was polished. As a result, a cylindrical conductive elastic layer formed on the outer peripheral surface of the conductive base material was obtained.

[0203] - Mixture for Forming Elastic Layer - · Rubber material (epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber, GECHRON 3106, manufactured by Nippon Zeon Co., Ltd.): 100 parts by mass · Conductive agent (carbon black, Asahi Thermal, manufactured by Asahi Carbon Co., Ltd.): 25 parts by mass · Conductive agent (Ketjen Black EC, manufactured by Lion Corporation): 8 parts by mass · Ion conductive agent (lithium perchlorate): 1 part by mass · Vulcanizing agent (sulfur, 200 mesh, manufactured by Tsurumi Chemical Industry Co., Ltd.): 1 part by mass · Vulcanization accelerator (Nocceler DM, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.): 2.0 parts by mass · Vulcanization accelerator (Nocceler TT, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.): 0.5 parts by mass

[0204] (Formation of Surface Layer) The following mixture for forming a surface layer was dispersed with a bead mill, and the resulting dispersion was diluted with methanol. This was dip-coated on the surface (outer peripheral surface) of the conductive elastic layer prepared above, and then heated and dried at 140 °C for 15 minutes. As a result, a charging member 1 having a surface layer with a thickness of 4 μm on the surface of the conductive elastic layer was obtained. The average spacing Sm of the surface irregularities on the obtained charged member 1 was 90 μm.

[0205] -Surface layer forming mixture- • Polymer material (N-alkoxymethylated polyamide, Trezin, manufactured by Nagase ChemteX Corporation): 100 parts by mass • Conductive agent (Carbon Black Monarch 1000, manufactured by Cabot): 30 parts by mass • Solvent (methanol): 500 parts by mass • Solvent (butanol): 240 parts by mass

[0206] [Preparation of photoreceptor 1] (Formation of the lower layer) Zinc oxide (average particle size 70nm: manufactured by Teika Co., Ltd.: specific surface area value 15m²) 2 100 parts by mass of zinc oxide ( / g) was mixed with 500 parts by mass of toluene and stirred. 1.3 parts by mass of silane coupling agent (KBM503: manufactured by Shin-Etsu Chemical Co., Ltd.) was added and the mixture was stirred for 2 hours. The toluene was then removed by vacuum distillation, and the mixture was baked at 120°C for 3 hours to obtain zinc oxide with surface treatment using the silane coupling agent. 110 parts by mass of the surface-treated zinc oxide was mixed with 500 parts by mass of tetrahydrofuran and stirred. A solution of 0.6 parts by mass of alizarin dissolved in 50 parts by mass of tetrahydrofuran was added and the mixture was stirred at 50°C for 5 hours. The zinc oxide with alizarin was then filtered off by vacuum filtration, and further dried under vacuum at 60°C to obtain zinc oxide with alizarin. 60 parts by mass of zinc oxide treated with alizarin, 13.5 parts by mass of a curing agent (blocked isocyanate, Sumijule 3175, manufactured by Sumitomo Bayern Urethanes), and 15 parts by mass of butyral resin (Eslec BM-1, manufactured by Sekisui Chemical Co., Ltd.) were mixed with 85 parts by mass of methyl ethyl ketone. 38 parts by mass of this mixture was mixed with 25 parts by mass of methyl ethyl ketone, and the mixture was dispersed for 2 hours using a sand mill with 1 mm diameter glass beads to obtain a dispersion. To the obtained dispersion, 0.005 parts by mass of dioctyl tin dilaurate and 40 parts by mass of silicone resin particles (Tospar 145, manufactured by Momentive Performance Materials) were added as catalysts to obtain a coating solution for forming an undercoat. This undercoat solution was applied to a 5 mm thick conductive aluminum substrate by immersion coating, and dried and cured at 170°C for 40 minutes to obtain an undercoat with a thickness of 20 μm.

[0207] (Formation of a charge generation layer) As a charge-generating material, hydroxygallium phthalocyanine was prepared, having diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.5°, 16.3°, 25.0°, and 28.3° in its X-ray diffraction spectrum using Cukα characteristic X-rays. A mixture of 15 parts by mass of hydroxygallium phthalocyanine, 10 parts by mass of vinyl chloride / vinyl acetate copolymer resin (VMCH, manufactured by Nippon Unicar Co., Ltd.), and 200 parts by mass of n-butyl acetate was dispersed for 4 hours using glass beads with a diameter of 1 mm in a sand mill. 175 parts by mass of n-butyl acetate and 180 parts by mass of methyl ethyl ketone were added to the resulting dispersion and stirred to obtain a coating solution for forming the charge-generating layer. This coating solution was immersed onto the undercoat and dried at 150°C for 10 minutes to form a charge-generating layer with a thickness of 0.2 μm.

[0208] (Formation of a charge transport layer) 38 parts by mass of charge transport agent (HT-1), 10 parts by mass of charge transport agent (HT-2), and 52 parts by mass of polycarbonate (A) (viscosity-average molecular weight 48,000) were dissolved in 800 parts by mass of tetrahydrofuran to obtain a coating solution for forming a charge transport layer. This coating solution was applied to a charge generating layer by immersion and dried at 140°C for 40 minutes to form a charge transport layer with a thickness of 10.8 μm.

[0209] [ka]

[0210] [ka]

[0211] (Formation of a protective layer) A protective layer was formed by a thermosetting film of a composition containing a reactive group-containing charge transport material having both a reactive group and a charge transport skeleton within the same molecule, as described below.

[0212] 70 parts by mass of compound (2), represented by the structural formula shown below, which is a reactive group-containing charge transport material; 15 parts by mass of compound (3), represented by the structural formula shown below, which is a reactive group-containing charge transport material; and 4.4 parts by mass of a curable resin, benzoguanamine resin (Nicalac BL-60, manufactured by Sanwa Chemical Co., Ltd.; (H)-17 as described above), which is a reactive group-containing non-charge transport material, were added to 220 parts by mass of 2-propanol, mixed and dissolved, and then 0.1 parts by mass of NACURE5225 (manufactured by King Industries Co., Ltd.) was added as a curing catalyst to obtain a coating solution for forming a protective layer. The protective layer forming solution was applied to the charge transport layer by immersion, air-dried at room temperature (25°C) for 30 minutes, and then heated under a nitrogen stream with an oxygen concentration of 110 ppm from room temperature to the heating temperature (target temperature) shown in Table 1. This was then held for the heating time (holding time) shown in Table 1 to cure the layer. A protective layer with a film thickness of 10 μm was formed. In this manner, photoreceptor 1 was obtained.

[0213] [ka]

[0214] The obtained charged member 1 and the photoreceptor 1 were combined to fabricate a process cartridge that is detachable from a DocuCentre-V C2263 (manufactured by Fujifilm Business Innovation Co., Ltd.), which is an image forming apparatus.

[0215] <Examples 2 to 6 and Comparative Examples 1 to 3> As shown in Table 1, process cartridges of each example were fabricated in the same manner as in Example 1, except that the thicknesses and relative dielectric constants of the protective layer and the photosensitive layer of the photoreceptor were changed.

[0216] <Evaluation of suppression of generation of minute color lines> A DocuCentre-V C2263 manufactured by Fujifilm Business Innovation Co., Ltd. was prepared, and the obtained process cartridge was set to print a halftone image with a density of 30%. The appearance state of minute color lines was graded with G0 to G4 shown below using a gray scale sample (classified by the density and average length of the color lines). It is preferable that it is G0, G0.5 or G1. G0: 0 color lines per 25 cm in density of minute color lines 2 , 0 mm in length of minute color lines G0.5: 0 color lines per 25 cm in density of minute color lines 2 exceeding 0 and 1 color line per 25 cm 2 hereinafter, average length of minute color lines less than 20 mm G1: 1 color line per 25 cm in density of minute color lines 2 exceeding 1 and 5 color lines per 25 cm 2 hereinafter, average length of minute color lines less than 20 mm G2: 1 color line per 25 cm in density of minute color lines 2 exceeding 1 and 5 color lines per 25 cm 2 hereinafter, average length of minute color lines 20 mm or more G3: 5 color lines per 25 cm in density of minute color lines 2 exceeding 5 and 10 color lines per 25 cm 2 hereinafter, average length of minute color lines 20 mm or more G4: density of minute color lines exceeding 10, and average length of minute color lines 20 mm or more 2 and average length of minute color lines 20 mm or more Furthermore, if the average length of the minute color lines is less than 20 mm in grades G3 or G4, the grade will be G2 or G3, respectively.

[0217] The evaluation results are summarized in Table 1.

[0218] [Table 1]

[0219] From the above results, it can be seen that this embodiment is superior to the comparative example in suppressing the generation of minute color lines in the resulting image. [Explanation of Symbols]

[0220] 1 Undercoat layer, 2 Charge generation layer, 3 Charge transport layer, 4 Conductive substrate, 5 Photosensitive layer, 7A Electrophotographic photoreceptor

[0221] 208A Charging member, 30 Conductive substrate, 31 Elastic layer, 32 Surface layer

[0222] 200, 210, 220 Image forming apparatus, 206 Exposure apparatus, 207 Electrophotographic photoreceptor (photoreceptor), 208 Charging apparatus, 209 Power supply, 211 Developing apparatus, 212 Transfer apparatus, 212a Primary transfer member, 212b Secondary transfer member, 213 Cleaning apparatus, 214 Static eliminator, 215 Fixing apparatus, 500 Recording medium

[0223] 400 Housing, 401a, 401b, 401c, 401d Photoreceptor, 402a, 402b, 402c, 402d Charging Roll, 403 Exposure Unit, 404a, 404b, 404c, 404d Developer, 405a, 405b, 405c, 405d Toner Cartridge, 406 Drive Roll, 407 Tension Roll, 408 Back Roll, 409 Intermediate Transfer Belt, 410a, 410b, 410c, 410d Primary Transfer Roll, 411 Tray, 412 Transport Roll, 413 Secondary Transfer Roll, 414 Fixing Unit, 415a, 415b, 415c, 415d Cleaning Blade, 416 Cleaning Blade

[0224] 300 Process cartridge, 301 Housing, 302 Mounting rail, 303 Aperture for exposure, 304 Aperture for static elimination exposure

Claims

1. A photoreceptor having a conductive substrate, a photosensitive layer provided on the conductive substrate, and a protective layer provided on the photosensitive layer, The system comprises a roll-shaped charging member that contacts the photoreceptor to perform charging, The thickness of the photosensitive layer is 9.5 μm or more and 15 μm or less. The thickness of the protective layer is 3 μm or more and 8 μm or less. The sum of the value of the thickness of the photosensitive layer (μm) / the relative permittivity of the photosensitive layer and the value of the thickness of the protective layer (μm) / the relative permittivity of the protective layer is 4.5 or more and 6.0 or less. The protective layer is a cured film of a composition containing a reactive group-containing charge transport material having a reactive group and a charge transport skeleton within the same molecule. The charge required to charge the photoreceptor is between 1.65 μC / (m²·V) and 2.10 μC / (m²·V). Process cartridge.

2. The process cartridge according to claim 1, An electrostatic latent image forming means for forming an electrostatic latent image on the surface of the charged photoreceptor, A developing means that develops the electrostatic latent image formed on the surface of the photoreceptor with a developer containing toner to form a toner image, The system includes a transfer means for transferring the toner image onto the surface of a recording medium. Image forming apparatus.

Images