Image forming apparatus

Abstract

An image forming apparatus has an electrophotographic photoreceptor having a photosensitive layer on a conductive base, and on the conductive base, a lower coating layer containing a metal oxide, a charge generation layer containing a metal element provided on the lower coating layer, and a charge transport layer provided on the charge generation layer; a charging device that charges the electrophotographic photoreceptor using a charging roller that applies an alternating current; a direct transfer roller; and a recording medium peeling member that peels a recording medium from the direct transfer roller, the lower coating layer having a resistance value of 6.0 logΩ·m or more and 9.5 logΩ·m or less, and the electrophotographic photoreceptor having a current density of 0.012 μA / cm 2 or more and 0.030 μA / cm 2 or more and 0.030 μA / cm

Description

Technical Field

[0001] This invention relates to an image forming apparatus. Background Technology

[0002] Patent Document 1 discloses an image forming apparatus comprising: a plurality of image carriers; a primary transfer unit having a transfer belt unit that rotates an annular conveyor belt by at least a driven roller and a drive roller, and forming a color image on the transfer belt by transferring toner from each of the image carriers onto the transfer belt; and a secondary transfer unit having a secondary transfer member disposed opposite to the drive roller and used to transfer the color image on the transfer belt onto paper, wherein the value between the paper spacings is changed according to the number of sheets of paper simultaneously associated with the transfer belt.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2012-63740 Summary of the Invention

[0004] The objective of this invention is to provide an image forming apparatus in which the resistivity of the underlying coating is less than 6.0 logΩ·m or greater than 9.5 logΩ·m, or the current density of the electrophotographic photoreceptor at 40 V / μm is less than 0.012 μA / cm. 2 Or exceeding 0.030 μA / cm 2 Compared to other cases, it exhibits superior fog suppression and stripe discharge stripe suppression.

[0005] The specific means used to solve the problem include the following methods.

[0006] <1> An image forming apparatus comprising: an electrophotographic photoreceptor having a photosensitive layer on a conductive substrate, and having on the conductive substrate: a lower coating containing a metal oxide, a charge generating layer containing a metal element disposed on the lower coating, and a charge transport layer disposed on the charge generating layer; a charging device for applying an alternating current using a charging roller to charge the electrophotographic photoreceptor; a direct transfer roller; and a recording medium peeling member for peeling a recording medium from the direct transfer roller, wherein the resistivity of the lower coating is 6.0 log Ω·m or more and 9.5 log Ω·m or less, and the current density of the electrophotographic photoreceptor at 40 V / μm is 0.012 μA / cm. 2 Above and 0.030 μA / cm 2 the following.

[0007] <2> According to the image forming apparatus described in <1>, wherein,

[0008] The resistivity of the lower coating layer is above 7.0 logΩ·m and below 9.0 logΩ·m.

[0009] <3> The image forming apparatus according to <2>, wherein,

[0010] The resistivity of the lower coating layer is above 7.5 logΩ·m and below 9.0 logΩ·m.

[0011] <4> The image forming apparatus according to any one of <1> to <3>, wherein,

[0012] The current density of the electrophotographic photoreceptor at 40V / μm is 0.015μA / cm. 2 Above and 0.025μA / cm 2 the following.

[0013] <5> The image forming apparatus according to any one of <1> to <4>, wherein,

[0014] The voltage of the recording media stripping component is above 300V and below 800V.

[0015] <6> The image forming apparatus according to any one of <1> to <5>, wherein,

[0016] The transfer current of the direct transfer roller is above 5μA and below 15μA.

[0017] <7> The image forming apparatus according to any one of <1> to <6>, wherein,

[0018] The resistance of the recording medium used is above 4logΩ·m and below 12logΩ·m.

[0019] <8> The image forming apparatus according to any one of <1> to <7>, wherein,

[0020] After passing through the direct transfer roller, the angle between the direction of the transfer roller pair to which the recording medium is subsequently transferred and the direction of transport of the recording medium after the transfer is more than 10° and less than 30°.

[0021] <9> The image forming apparatus according to <8>, wherein,

[0022] After passing through the direct transfer roller, the angle between the direction of the transfer roller pair to which the recording medium is subsequently transferred and the direction of transport of the recording medium after the transfer is 15° or more and 30° or less.

[0023] Invention Effects

[0024] According to the invention described in <1>, an image forming apparatus is provided in which the resistance of the underlying coating is less than 6.0 logΩ·m or greater than 9.5 logΩ·m, or the current density of the electrophotographic photoreceptor at 40 V / μm is less than 0.012 μA / cm. 2 Or exceeding 0.030 μA / cm 2 Compared to other cases, it exhibits superior fog suppression and stripe discharge stripe suppression.

[0025] According to the invention described in <2>, an image forming apparatus is provided that exhibits superior fog suppression compared to cases where the resistance value of the lower coating is less than 7.0 logΩ·m or greater than 9.0 logΩ·m.

[0026] According to the invention described in <3>, an image forming apparatus is provided that exhibits superior fog suppression compared to cases where the resistance value of the lower coating is less than 7.5 logΩ·m or greater than 9.0 logΩ·m.

[0027] According to the invention described in <4>, an image forming apparatus is provided in which the current density of the electrophotographic photoreceptor at 40V / μm is less than 0.015μA / cm. 2 Or exceeding 0.025 μA / cm 2 Compared to the previous case, the stripping discharge stripe suppression performance is superior.

[0028] According to the invention described in <5>, an image forming apparatus is provided that exhibits superior suppression of stripping discharge wires compared to cases where the voltage of the recording medium stripping member is less than 300V or more than 800V.

[0029] According to the invention described in <6>, an image forming apparatus is provided that exhibits superior fog suppression and stripe discharge stripe suppression compared to cases where the transfer current of the direct transfer roller is less than 5 μA or more than 15 μA.

[0030] According to the invention described in <7>, an image forming apparatus is provided that exhibits superior stripping discharge stripe suppression compared to cases where the resistance of the recording medium used is less than 4logΩ·m or greater than 12logΩ·m.

[0031] According to the invention described in <8>, an image forming apparatus is provided that exhibits superior stripe discharge stripe suppression compared to cases where the angle between the direction of the transfer roller pair to which the recording medium is subsequently transferred after passing through the direct transfer roller and the direction of transfer of the recording medium immediately after transfer is less than 10° or more than 30°.

[0032] According to the invention described in <9>, an image forming apparatus is provided that exhibits superior stripe discharge stripe suppression compared to cases where the angle between the direction of the transfer roller pair to which the recording medium is subsequently transferred after passing through the direct transfer roller and the direction of transfer of the recording medium immediately after transfer is less than 15° or more than 30°. Attached Figure Description

[0033] The embodiments of the present invention will be described in detail with reference to the following figures.

[0034] Figure 1 This is a partial cross-sectional view showing an example of the layer structure of the electrophotographic photoreceptor used in this embodiment;

[0035] Figure 2 This is a schematic structural diagram illustrating an example of the image forming apparatus according to this embodiment;

[0036] Figure 3 This is an enlarged view of a partial cross-section of an example of the image forming apparatus according to this embodiment.

[0037] Symbol Explanation

[0038] 1-Undercoat layer, 2-charge generation layer, 3-charge transport layer, 4-conductive substrate, 7A, 7-electrophotographic photosensitive material, 8-charged device, 9-exposure device, 11-developing device, 13-cleaning device, 14-lubricant, 40-transfer device, 50-recording medium, 52-electrophotographic photosensitive material, 54-charged device, 56-direct transfer roller, 58-recording medium stripping component, 60-recording medium, 62-transfer roller pair, 100-image forming device, 131-cleaning blade, 132-fibrous component (roller-shaped), 133-fibrous component (flat brush-shaped), 300-processing box. Detailed Implementation

[0039] The following describes this embodiment. These descriptions and examples are illustrative of the embodiment and do not limit the scope of the embodiment.

[0040] In this specification, the numerical range indicated by “~” represents the range to which the values ​​before and after “~” are included, respectively, as the minimum and maximum values.

[0041] In the numerical ranges described in this specification, the upper or lower limit of a numerical range can be replaced with the upper or lower limit of other numerical ranges described in different periods. Furthermore, within the numerical ranges described in this specification, the upper or lower limit of that range can be replaced with the values ​​shown in the embodiments.

[0042] In this specification, the term "process" includes not only individual processes, but also processes that achieve the desired purpose of the process, even if they cannot be clearly distinguished from other processes.

[0043] In this specification, each component may also contain a plurality of corresponding substances. When referring to the amount of each component in the composition, unless otherwise specified, the amount refers to the total amount of the plurality of substances present in the composition, where a plurality of substances corresponding to each component are present in the composition.

[0044] In this specification, principal component refers to the main component. For example, a principal component is a component that accounts for more than 30% by mass of the total mass of a mixture of multiple components.

[0045] (Image forming apparatus)

[0046] The image forming apparatus according to this embodiment includes: an electrophotographic photoreceptor having a photosensitive layer on a conductive substrate, and having on the conductive substrate: a lower coating containing a metal oxide, a charge generating layer containing a metal element disposed on the lower coating, and a charge transport layer disposed on the charge generating layer; a charging device that applies an alternating current using a charging roller to charge the electrophotographic photoreceptor; a direct transfer roller; and a recording medium peeling member that peels the recording medium off from the direct transfer roller, wherein the resistivity of the lower coating is 6.0 log Ω·m or more and 9.5 log Ω·m or less, and the current density of the electrophotographic photoreceptor at 40 V / μm is 0.012 μA / cm. 2 Above and 0.030 μA / cm 2 the following.

[0047] In conventional image forming apparatuses with a direct transfer roller and a recording media peeling unit, after toner fixing, when the recording media, such as paper, is peeled off from the direct transfer roller, a voltage is applied to the recording media peeling unit to peel off the recording media. If the resistance of the undercoat of the electrophotographic photosensitive element is high, charge accumulates. Therefore, after passing through the direct transfer roller and the recording media peeling unit, the positive charge remaining on the paper discharges at the end of the recording media during peeling, leaving a trace of positive charge on the electrophotographic photosensitive element, resulting in transverse stripes (hereinafter also referred to as "peeling discharge stripes") during the next printing cycle. On the other hand, if the resistance of the undercoat is reduced to suppress peeling discharge stripes, a secondary defect, haze, will occur.

[0048] In the image forming apparatus of this embodiment, since the resistivity of the lower coating layer is 6.0 log Ω·m or more and 9.5 log Ω·m or less, and the current density of the electrophotographic photoreceptor at 40 V / μm is 0.012 μA / cm², 2 Above and 0.030 μA / cm 2 This reduces the overall resistance of the electrophotographic photosensitive element under high electric fields, resulting in excellent fog suppression and stripping discharge streak suppression even when a high-resistance undercoating is used.

[0049] <Resistivity of the lower coating>

[0050] Unless otherwise specified, the term "resistance value" in this invention refers to the commonly used logarithmic value of volume resistivity.

[0051] In the image forming apparatus of this embodiment, the resistivity of the lower coating layer is 6.0 log Ω·m or more and 9.5 log Ω·m or less. From the viewpoint of fog suppression, for example, it is preferable to be 6.5 log Ω·m or more and 9.2 log Ω·m or less, more preferably 7.0 log Ω·m or more and 9.0 log Ω·m or less, and even more preferably 7.5 log Ω·m or more and 9.0 log Ω·m or less.

[0052] The method for measuring the resistance value of the lower coating layer in this embodiment is as follows.

[0053] In the determination of volume resistivity using the AC impedance method, the measurement environment was set at 22°C and 55% RH. The power supply used was a SI1287 electrochemical interface (manufactured by TOYO Corporation), the ammeter used was a SI1260 impedance / gain phase analyzer (manufactured by TOYO Corporation), and the current amplifier used was a 1296 dielectric interface (manufactured by TOYO Corporation). In the AC impedance measurement samples, an aluminum substrate was used as the cathode, and a gold electrode as the anode. Starting from the high-frequency side, an AC voltage of 1Vp-p was applied in the range of 1MHz to 1mHz. The AC impedance of each sample was measured, and the volume resistivity was calculated by fitting the Cole-Cole spectrum obtained from this measurement to an RC parallel equivalent circuit.

[0054] <Current density of electrophotographic photoreceptor at 40V / μm>

[0055] In the image forming apparatus of this embodiment, the current density of the electrophotographic photoreceptor at 40V / μm is 0.012μA / cm.2 Above and 0.030 μA / cm 2 From the viewpoint of suppressing stripped discharge streaks, the following is preferably, for example, 0.012 μA / cm. 2 Above and 0.028μA / cm 2 The following is more preferably 0.015 μA / cm 2 Above and 0.025μA / cm 2 the following.

[0056] The method for measuring the current density of the electrophotographic photoreceptor at 40V / μm in this embodiment is as follows.

[0057] The photoreceptor and charged roller are brought into contact and rotated in the same manner as in the actual equipment. A high-voltage power supply (Trek 610C) is used to apply a voltage from 0V to -1500V to the charged roller in 10V increments. Simultaneously, a surface potentiometer (Trek Model 344) is used to measure the voltage value on the photoreceptor surface. The voltage value (VH1) on the photoreceptor surface is measured 75 ms after charging. The voltage value on the photoreceptor surface 339.8 ms after VH1 is defined as VH2, and the difference between VH2 and VH1 is defined as the potential dark decay value. The electric field (V / μm) is calculated by dividing VH1 at each applied voltage by the measured total film thickness of the photoreceptor (undercoat film thickness + charge generation layer film thickness + charge transport layer film thickness). The potential dark decay value relative to each applied voltage is then converted, and the potential per unit area (cm²) is calculated. 2 The current density is calculated using the above method when the photoreceptor surface potential is divided by the total film thickness to reach 40 V / μm.

[0058] <Voltage of the recording media stripping component>

[0059] From the viewpoint of suppressing stripping discharge stripes, in the image forming apparatus according to this embodiment, the voltage of the recording medium stripping member is preferably 100V or more and 1,000V or less, more preferably 200V or more and 900V or less, further preferably 300V or more and 800V or less, and particularly preferably 400V or more and 700V or less.

[0060] <Transfer current of direct transfer roller>

[0061] From the viewpoint of suppressing fog and stripe discharge streaks, in the image forming apparatus of this embodiment, the transfer current of the direct transfer roller is preferably 2 μA or more and 18 μA or less, more preferably 5 μA or more and 15 μA or less, and particularly preferably 8 μA or more and 12 μA or less.

[0062] <Resistance value of the recording medium used>

[0063] From the viewpoint of suppressing discharge stripes, in the image forming apparatus of this embodiment, the resistance value (common logarithmic value of volume resistivity) of the recording medium used is preferably 1 log Ω·m or more and 20 log Ω·m or less, more preferably 2 log Ω·m or more and 15 log Ω·m or less, further preferably 4 log Ω·m or more and 12 log Ω·m or less, and particularly preferably 4 log Ω·m or more and 10 log Ω·m or less.

[0064] <The angle between the direction of the transport roller pair on which the recording medium is subsequently transported after passing through the direct transfer roller and the direction of transport of the recording medium immediately after transfer>

[0065] From the viewpoint of suppressing stripped discharge stripes, in the image forming apparatus of this embodiment, the angle (deflection angle) between the direction of the transfer roller pair to which the recording medium is subsequently transferred after passing through the direct transfer roller and the direction of transfer of the recording medium immediately after transfer is preferably 5° or more and 40° or less, more preferably 10° or more and 30° or less, and particularly preferably 15° or more and 30° or less.

[0066] When the recording medium is conveyed after transfer, if the angle is within the specified range, a discharge to the direct transfer roller is easily generated at the end of the recording medium, thereby further enhancing the effect of this embodiment.

[0067] Figure 3 This is an enlarged view of a partial cross-section of an example of the image forming apparatus according to this embodiment.

[0068] exist Figure 3 The electrophotographic photosensitive element 52 is equipped with a charging device 54 and a direct transfer roller 56, and the direct transfer roller 56 is equipped with a recording media peeling component 58.

[0069] Recording media 60 is stripped from direct transfer roller 56 by recording media stripping component 58 and conveyed to transfer roller pair 62.

[0070] Furthermore, after passing through the direct transfer roller 56, the angle between the direction of the transfer roller pair 62 to which the recording medium 60 is subsequently transferred and the transfer direction of the recording medium 60 is θ.

[0071] The following is a detailed description of the image forming apparatus according to this embodiment.

[0072] <Electronic Photoreceptor>

[0073] The image forming apparatus according to this embodiment includes an electrophotographic photosensitive element having a photosensitive layer on a conductive substrate, and having a lower coating containing a metal oxide, a charge generating layer containing a metal element disposed on the lower coating, and a charge transport layer disposed on the charge generating layer on the charge generating layer.

[0074] Figure 1 This is a partial cross-sectional view that roughly illustrates an example of the layered structure of an electrophotographic photoreceptor.

[0075] Figure 1 The electrophotographic photoreceptor 7 shown has a stacked photosensitive layer.

[0076] As Figure 1 The electrophotographic photosensitive material 7 shown can be, for example, a photosensitive material 7 having a structure in which a lower coating layer 1, a charge generating layer 2, and a charge transport layer 3 are sequentially stacked on a conductive support 4. The charge generating layer 2 and the charge transport layer 3 constitute the photosensitive layer 5.

[0077] The following is a detailed description of each layer of an electrophotographic photoreceptor. Symbols are omitted in the description of each layer of the photoreceptor.

[0078] The electrophotographic photosensitive material of this embodiment has a lower coating containing metal oxide, a charge generating layer containing metal elements disposed on the lower coating, and a charge transport layer disposed on the charge generating layer, on a conductive substrate.

[0079] <<Undercoating>>

[0080] The undercoat is, for example, a layer containing metal oxides and a binding resin.

[0081] As a metal oxide, for example, a powder with a resistivity (volume resistivity) of 10 can be cited. 2 Ω·cm or more and 10 11 Metal oxides with an Ω·cm or less.

[0082] Among them, the metal oxide having the above-mentioned resistance value is preferably, for example, tin oxide particles, titanium oxide particles, zinc oxide particles, zirconium oxide particles, etc., and zinc oxide particles are particularly preferred.

[0083] The specific surface area of ​​metal oxide particles obtained by the BET method is, for example, 10 m². 2 / g or more is preferred.

[0084] The volume average particle size of the metal oxide particles is preferably 50 nm or more and 2,000 nm or less (more preferably 60 nm or more and 1,000 nm or less).

[0085] The content of metal oxides relative to the adhesive resin is preferably 10% by mass or more and 80% by mass or less, more preferably 40% by mass or more and 80% by mass or less.

[0086] Metal oxide particles can be surface treated. Two or more types of metal oxide particles with different surface treatments or different particle sizes can be used in combination.

[0087] Examples of surface treatment agents include silane coupling agents, titanate coupling agents, aluminum coupling agents, and surfactants. In particular, silane coupling agents are preferred, and silane coupling agents having an amino group are more preferred.

[0088] Examples of amino-containing silane coupling agents 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.

[0089] Two or more silane coupling agents can be used in combination. For example, an amino-containing silane coupling agent can be used in combination with other silane coupling agents. Other silane coupling agents include, for example, vinyltrimethoxysilane, 3-methacryloyloxypropyltris(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, 3-chloropropyltrimethoxysilane, etc., but are not limited to these.

[0090] The surface treatment method using surface treatment agents can be any known method, whether it is a dry method or a wet method.

[0091] The amount of surface treatment agent relative to the inorganic particles is preferably 0.5% by mass or more and 10% by mass or less.

[0092] From the viewpoint of improving the long-term stability of electrical properties and carrier blocking properties, the lower coating preferably contains an electron acceptor compound (acceptor compound) together with the metal oxide.

[0093] Examples of electron-accepting compounds include, for instance, compounds with anthraquinone structures; quinones such as chloroquinone and tetrabromo-p-benzoquinone; dimethyl tetracyano-p-benzodiquinone 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-tert-butylphenyl)-1,3,4-oxadiazole, 2,5-bis(4-naphthyl)-1,3,4-oxadiazole, and 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole; xanthonesone compounds; thiophene compounds; biphenylquinone compounds such as 3,3',5,5'-tetra-tert-butylbiphenylquinone; benzophenone compounds; and isoelectronic transport substances.

[0094] In particular, compounds having an anthraquinone structure are preferred as electron-accepting compounds. Among compounds having an anthraquinone structure, hydroxyanthraquinone compounds, aminoanthraquinone compounds, aminohydroxyanthraquinone compounds, etc., are preferred, specifically, anthraquinones, alizarins, quinone alizarins, anthraquinones, rutins, and their derivatives are preferred.

[0095] Electron-accepting compounds can be dispersed in the undercoat along with metal oxides, or they can be contained in the undercoat as adhering to the surface of metal oxide particles.

[0096] Methods for attaching electron-accepting compounds to the surface of metal oxide particles include, for example, dry or wet methods.

[0097] A dry method, for example, involves directly adding an electron-accepting compound or an electron-accepting compound dissolved in a solvent by stirring inorganic particles using a mixer with high shear force, and then spraying it together with dry air or nitrogen, thereby causing the electron-accepting compound to adhere to the surface of the metal oxide 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, sintering can be performed at a temperature above 100°C. There are no particular limitations on the temperature and time of sintering, as long as the electron photographic properties are obtained.

[0098] Wet processes, for example, involve dispersing metal oxide particles in a solvent using a mixer, ultrasonic disperser, sand mill, grinder, or ball mill. An electron-accepting compound is added, and the mixture is stirred or dispersed. The solvent is then removed, allowing the electron-accepting compound to adhere to the surface of the metal oxide particles. Solvent removal methods include filtration or evaporation. After solvent removal, sintering can be performed at temperatures above 100°C. The temperature and time for sintering are not particularly limited as long as the electron imaging properties are obtained. In wet processes, the moisture content of the inorganic particles can be removed before adding the electron-accepting compound. Examples include removing moisture while stirring and heating in a solvent, and removing moisture through azeotropic mixing with the solvent.

[0099] In addition, the attachment of electron-receiving compounds can be carried out before or after surface treatment of metal oxide particles based on surface treatment agents, or the attachment of electron-receiving compounds and surface treatment based on surface treatment agents can be carried out simultaneously.

[0100] The content of the electron-accepting compound relative to the metal oxide particles is preferably 0.01% by mass or more and 20% by mass or less, and more preferably 0.01% by mass or more and 10% by mass or less.

[0101] Examples of known polymeric compounds used as adhesive resins in the undercoat include acetal resins (e.g., polyvinyl butyral), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyester resins, unsaturated polyester resins, methacrylic acid resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, urea resins, phenolic resins, phenolic-formaldehyde resins, melamine resins, urethane resins, alkyd resins, and epoxy resins; zirconium chelate compounds; titanium chelate compounds; aluminum chelate compounds; titanium alkoxide compounds; organotitanium compounds; and silane coupling agents.

[0102] Examples of adhesive resins used in the undercoat include charge-transporting resins with charge-transporting groups and conductive resins (e.g., polyaniline).

[0103] The adhesive resin used in the lower coating layer is preferably a resin that is insoluble in the coating solvent of the upper layer, and is particularly preferably a resin obtained by reacting a curing agent with at least one resin selected from the group consisting of thermosetting resins such as urea resin, phenolic resin, phenolic-formaldehyde resin, melamine resin, urethane resin, unsaturated polyester resin, alkyd resin, and epoxy resin; polyamide resin, polyester resin, polyether resin, methacrylic resin, acrylic resin, polyvinyl alcohol resin, and polyvinyl alcohol acetal resin.

[0104] When using two or more of these adhesive resins in combination, set the mixing ratio as needed.

[0105] To improve electrical properties, environmental stability, and image quality, various additives can be included in the undercoat.

[0106] Examples of additives include polycyclic condensation pigments, azo pigments, zirconium chelates, titanium chelates, aluminum chelates, titanium alkoxides, organotitanium compounds, and silane coupling agents. As mentioned earlier, silane coupling agents are used for surface treatment of metal oxide particles, but they can also be added to undercoatings as additives.

[0107] Examples of silane coupling agents used as additives include vinyltrimethoxysilane, 3-methacryloyloxypropyltris(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.

[0108] Examples of zirconium chelate compounds include zirconium butoxide, ethyl zirconium acetoacetate, zirconium triethanolamine, zirconium acetylacetone butoxide, ethyl acetoacetate butoxide, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octanoate, zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, zirconium methacrylate butoxide, zirconium stearate butoxide, and zirconium isostearate butoxide.

[0109] Examples of titanium chelate compounds include tetraisopropyl titanate, tetrabutyl titanate, tetrabutyl titanate dimer, tetra(2-ethylhexyl) titanate, titanium acetylacetone, polyacetylacetone titanium, octanediol titanium, titanium ammonium lactate, titanium lactate, titanium ethyl lactate, titanium triethanolamine, and titanium polyhydroxystearate.

[0110] Examples of aluminum chelate compounds include aluminum isopropoxide, aluminum monobutoxydiisopropoxide, aluminum butoxide, aluminum diacetoacetate diisopropoxide, and aluminum triacetoacetate.

[0111] These additives can be used alone or as a mixture or condensation polymer of multiple compounds.

[0112] The undercoat is preferably coated with a Vickers hardness of 35 or higher.

[0113] To suppress moiré fringes, the surface roughness (ten-point average roughness) of the lower coating is preferably adjusted, for example, to be 1 / (4n) to 1 / 2 of the wavelength λ of the laser used for exposure (where n is the refractive index of the upper layer).

[0114] To adjust surface roughness, resin particles can be added to the undercoat. Examples of resin particles include silicone resin particles and cross-linked polymethyl methacrylate resin particles. Furthermore, to adjust surface roughness, the surface of the undercoat can be ground. Examples of grinding methods include polishing, sandblasting, wet grinding, and grinding.

[0115] There are no particular limitations on the formation of the undercoat, and known formation methods can be used. However, for example, the formation of the undercoat is carried out by adding the above-mentioned components to the solvent to form a coating film of the coating liquid, drying the coating film, and heating as needed.

[0116] As solvents used to prepare coating liquids for forming the undercoat, known organic solvents can be cited, such as alcohol solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone solvents, ketol solvents, ether solvents, ester solvents, etc.

[0117] Specifically, examples of these solvents include, for instance, methanol, ethanol, n-propanol, isopropanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, dichloromethane, chloroform, chlorobenzene, toluene, and other common organic solvents.

[0118] As a method for dispersing metal oxide particles when preparing a coating liquid for forming an undercoat, known methods such as using a roller mill, ball mill, vibratory ball mill, grinder, sand mill, colloid mill, paint mixer, etc. can be cited.

[0119] Methods for applying a coating liquid for forming an undercoat onto a conductive substrate include, for example, scraper coating, wire rod coating, spraying, dip coating, bead coating, air knife coating, curtain coating, and other common methods.

[0120] The thickness of the lower coating is preferably set to 15 μm or more, and more preferably to be in the range of 20 μm or more and 50 μm or less.

[0121] <<Intermediate Layer>>

[0122] An intermediate layer can be set between the undercoat layer and the photosensitive layer.

[0123] The intermediate layer may be, for example, a resin-containing layer. Examples of resins used in the intermediate layer include acetal resins (such as polyvinyl butyral), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, methacrylic acid resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, phenolic-formaldehyde resins, melamine resins, and other polymeric compounds.

[0124] The intermediate layer can be a layer containing an organometallic compound. Examples of organometallic compounds used as intermediate layers include those containing metal atoms such as zirconium, titanium, aluminum, manganese, and silicon.

[0125] The compounds used in these intermediate layers can be used alone or as a mixture or condensation polymer of multiple compounds.

[0126] The intermediate layer is preferably a layer containing an organometallic compound containing zirconium or silicon atoms.

[0127] There are no particular limitations on the formation of the intermediate layer, and known formation methods can be used. However, for example, the intermediate layer is formed by adding the above-mentioned components to the solvent to form a coating film of the coating liquid, drying the coating film, and heating as needed.

[0128] As a coating method for forming the intermediate layer, conventional methods such as dip coating, push coating, bar coating, spraying, scraper coating, air knife coating, and curtain coating can be used.

[0129] The thickness of the intermediate layer is preferably set in the range of 0.1 μm or more and 3 μm or less. Alternatively, the intermediate layer can be used as the lower coating layer.

[0130] <<Charge Generation Layer>>

[0131] The charge generation layer may be, for example, a layer comprising a charge generation material containing a metallic element and a binding resin. Furthermore, the charge generation layer may be a vapor-deposited layer of the charge generation material. Vapor-deposited layers of charge generation materials are suitable, for example, for use with incoherent light sources such as LED (Light Emitting Diode) and organic EL (Electro-Luminescence) image arrays.

[0132] Examples of charge-generating materials containing metallic elements include azo pigments such as diazo and triazo; fused-ring aromatic pigments such as dibromoanthracene anthrone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; and trigonal selenium.

[0133] To cope with laser exposure in the near-infrared region, metal phthalocyanine pigments are preferably used as charge-generating materials. Specifically, hydroxy gallium phthalocyanine, gallium chloride phthalocyanine, dichlorotin phthalocyanine, and titanium dioxide phthalocyanine are more preferred.

[0134] On the other hand, in order to cope with laser exposure in the near-ultraviolet region, the preferred charge-generating materials are, for example, fused-ring aromatic pigments such as dibromoanthracene; sulfur-indigo pigments; porphyrin compounds; zinc oxide; trigonal selenium; and diazo pigments.

[0135] The above-mentioned charge-generating materials can be used even when using incoherent light sources such as LEDs and organic EL image arrays with a center wavelength of light emission above 450nm and below 780nm.

[0136] When n-type semiconductors such as fused-ring aromatic pigments, perylene pigments, and azo pigments are used as charge-generating materials, dark currents are not easily generated, and even when set as thin films, image defects known as black spots can be suppressed.

[0137] Furthermore, regarding the determination of n-type, the commonly used time-of-flight method is used, and the determination is made based on the polarity of the flowing photocurrent. Semiconductors that flow more easily than holes with electrons as charge carriers are defined as n-type.

[0138] The adhesive resin used as the charge-generating layer can be selected from a wide range of insulating resins, and can also be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, and polysilane.

[0139] Examples of adhesive resins include, for example, polyvinyl butyral resin, polyarylate resin (condensates of bisphenols and aromatic dicarboxylic 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, "insulation" refers to a volume resistivity of 10 Ω·cm. 13 Ω·cm or higher.

[0140] These adhesive resins can be used alone or in combination of two or more.

[0141] In addition, the mixing ratio of the charge-generating material to the adhesive resin is preferably in the range of 10:1 to 1:10 by mass, for example.

[0142] Other known additives may be included in the charge generation layer.

[0143] There are no particular limitations on the formation of the charge-generating layer, and known formation methods can be used. For example, it can be performed by forming a coating film of a charge-generating layer forming liquid by adding the aforementioned components to a solvent, drying the coating film, and heating as needed. Alternatively, the charge-generating layer can be formed by vapor deposition of a charge-generating material. Vapor deposition is particularly suitable for situations where, for example, fused-ring aromatic pigments or perylene pigments are used as charge-generating materials.

[0144] Examples of solvents used in preparing coating solutions for forming charge-generating layers include methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, dichloromethane, chloroform, chlorobenzene, and toluene. These solvents may be used individually or in combination of two or more.

[0145] As a method for dispersing particles (e.g., charge-generating materials) in a coating liquid for forming a charge-generating layer, media dispersers such as ball mills, vibratory ball mills, grinders, sand mills, and horizontal sand mills, or medialess dispersers such as mixers, ultrasonic dispersers, roller mills, and high-pressure homogenizers can be used. For example, high-pressure homogenizers can be used for dispersion by liquid-liquid or liquid-wall collisions under high pressure, or by dispersion through fine flow paths under high pressure.

[0146] In addition, when performing this dispersion, it is effective to set the average particle size of the charge-generating material in the coating liquid for forming the charge-generating layer to 0.5 μm or less, for example, preferably 0.3 μm or less, and more preferably 0.15 μm or less.

[0147] Methods for applying a coating liquid for forming a charge generation layer onto an underlying layer (or an intermediate layer) include, for example, scraper coating, wire rod coating, spraying, dip coating, bead coating, air knife coating, curtain coating, and other common methods.

[0148] The thickness of the charge generation layer is preferably set in the range of 0.1 μm or more and 5.0 μm or less, and more preferably in the range of 0.2 μm or more and 2.0 μm or less.

[0149] <<Charge Transport Layer>>

[0150] The charge transport layer is a layer containing a bonding resin and a charge transport material.

[0151] -Charge Transport Materials-

[0152] Examples of charge-transporting materials include quinone compounds such as p-benzoquinone, chloroquinone, tetrabromo-p-benzoquinone, and anthraquinone; dimethyl compounds such as tetracyano-p-benzodiquinone; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthones; benzophenones; cyanoethylene compounds; and ethylene compounds, all of which are electron-transporting compounds. Examples of hole-transporting compounds include triarylamines, benzidines, arylalkanes, aryl-substituted ethylene compounds, piracenes, anthracenes, and hydrazones, all of which are hole-transporting compounds. These charge-transporting materials can be used individually or in combination, but are not limited to this.

[0153] From the viewpoint of charge mobility, the preferred charge transport materials are, for example, triarylamine derivatives represented by the following structural formula (a-1) and benzidine derivatives represented by the following structural formula (a-2).

[0154] [Chemical Formula 1]

[0155]

[0156] In structural formula (a-1), Ar T1 Ar T2 and Ar T3 Each independently represents a substituted or unsubstituted aryl group, -C6H4-C(R) T4 )=C(R T5 (R) T6 ) or -C6H4-CH=CH-CH=C(R T7 (R) T8 R T4 R T5 R T6 R T7 and R T8 Each of the following can be independently represented: a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.

[0157] Examples of substituents for the aforementioned groups include halogen atoms, alkyl groups having 1 or more but 5 or fewer carbon atoms, and alkoxy groups having 1 or more but 5 or fewer carbon atoms. Furthermore, examples of substituents for the aforementioned groups include substituted amino groups substituted with alkyl groups having 1 or more but 3 or fewer carbon atoms.

[0158] [Chemical Formula 2]

[0159]

[0160] In structural formula (a-2), R T91 and R T92 Each of the following can be independently represented: a hydrogen atom, a halogen atom, an alkyl group having 1 or more but less than 5 carbon atoms, or an alkoxy group having 1 or more but less than 5 carbon atoms. RT101 R T102 R T111 and R T112 Each of the following can be independently represented: a halogen atom, an alkyl group having 1 or more but less than 5 carbon atoms, an alkoxy group having 1 or more but less than 5 carbon atoms, an amino group substituted with an alkyl group having 1 or more but less than 2 carbon atoms, a substituted or unsubstituted aryl group, or a -C(R) group. T12 )=C(R T13 (R) T14 ) or -CH=CH-CH=C(R T15 (R) T16 ), R T12 R T13 R T14 R T15 and R T16 Each of these independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. T m1 T m2 T n1 and T n2 Each of the following can be used to represent an integer greater than 0 and less than 2.

[0161] Examples of substituents for the aforementioned groups include halogen atoms, alkyl groups having 1 or more but 5 or fewer carbon atoms, and alkoxy groups having 1 or more but 5 or fewer carbon atoms. Furthermore, examples of substituents for the aforementioned groups include substituted amino groups substituted with alkyl groups having 1 or more but 3 or fewer carbon atoms.

[0162] Here, among the triarylamine derivatives represented by structural formula (a-1) and the benzidine derivatives represented by said structural formula (a-2), for example, from the viewpoint of charge mobility, it is particularly preferred to have "-C6H4-CH=CH-CH=C(R T7 (R) T8 Triarylamine derivatives with "-CH=CH-CH=C(R)" and those with "-CH=CH-CH=C(R)" T15 (R) T16 )" benzidine derivatives.

[0163] Charge transport materials can be polymers.

[0164] As a polymeric charge-transporting material, known materials with charge-transporting properties such as poly-N-vinylcarbazole and polysilane can be used. In particular, polyester-based polymeric charge-transporting materials are especially preferred. Furthermore, polymeric charge-transporting materials can be used alone or in combination with a binding resin.

[0165] Examples of binder resins used in the charge transport layer include polycarbonate resins, polyester resins, polyarylate resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl acetate resins, styrene-butadiene copolymers, vinylidene chloride-acrylonitrile copolymers, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate-maleic anhydride copolymers, silicone resins, silicone alkyd resins, phenol-formaldehyde resins, styrene-alkyd resins, poly-N-vinylcarbazole, and polysilanes. Among these, polycarbonate resins or polyarylate resins are preferred as binder resins. One or more of these binder resins may be used alone.

[0166] In addition, the mixing ratio of charge transport material to binder resin by mass is preferably, for example, 10:1 to 1:5.

[0167] Other known additives may be included in the charge transport layer.

[0168] There are no particular limitations on the formation of the charge transport layer, and known formation methods can be used. However, for example, it can be carried out by forming a coating film of a coating liquid for forming a charge transport layer by adding the above-mentioned components to a solvent, drying the coating film, and heating as needed.

[0169] Examples of solvents used in preparing coating solutions for forming charge transport layers include aromatic hydrocarbons such as benzene, toluene, xylene, and chlorobenzene; ketones such as acetone and 2-butanone; halogenated aliphatic hydrocarbons such as dichloromethane, chloroform, and dichloroethane; and cyclic or linear ethers such as tetrahydrofuran and diethyl ether. These solvents can be used alone or in combination of two or more.

[0170] Common methods for applying a coating liquid for forming a charge transport layer onto a charge generation layer include scraper coating, wire rod coating, spraying, dip coating, bead coating, air knife coating, and curtain coating.

[0171] The thickness of the charge transport layer is preferably set in the range of 5 μm or more and 50 μm or less, and more preferably in the range of 10 μm or more and 30 μm or less.

[0172] The film thickness of each layer of the photosensitive layer is the arithmetic mean of the measured values ​​obtained using an eddy current film thickness gauge. The measurement sites are four points spaced 90° apart circumferentially at the center along the axial direction of the photoreceptor. For example, a Fisher SCOPE MMS PC2 eddy current film thickness gauge manufactured by Fisher Corporation can be used for the measurement.

[0173] Furthermore, the electrophotographic photoreceptor may also have a surface protective layer.

[0174] As a surface protective layer, known materials can be used.

[0175] <<Conductive Substrate>>

[0176] The electrophotographic photosensitive material involved in this embodiment preferably has a photosensitive layer on a conductive substrate.

[0177] Examples of conductive substrates include metal plates, metal drums, and metal strips containing metals (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.). Furthermore, examples of conductive substrates include substrates formed by coating, vapor-depositing, or laminating conductive compounds (e.g., conductive polymers, indium oxide, etc.), metals (e.g., aluminum, palladium, gold, etc.) or alloys onto paper, resin films, tapes, etc. Here, "conductivity" refers to a volume resistivity of less than 10 Ω·cm. 13 Ω·cm.

[0178] When an electrophotographic photosensitive material is used in a laser printer, to suppress interference fringes generated when the laser beam is irradiated, the surface of the conductive substrate is preferably roughened to, for example, 0.04 μm or more and 0.5 μm or less, based on the centerline average roughness Ra. Furthermore, when incoherent light is used as the light source, roughening to prevent interference fringes is not particularly necessary, but it can suppress the generation of defects caused by unevenness on the conductive substrate surface, thus facilitating a longer lifespan.

[0179] Examples of roughening methods include wet grinding, which involves suspending an abrasive in water and spraying it onto a conductive substrate; centerless grinding, which involves pressing a conductive substrate onto a rotating grinding wheel and continuously grinding it; and anodizing.

[0180] As a roughening method, another example is a method that disperses conductive or semi-conductive powder in a resin to form a layer on the surface of the conductive substrate without roughening the surface of the conductive substrate, and then roughens the surface by means of particles dispersed in the layer.

[0181] Anodizing roughening is a process in which a conductive metallic substrate (e.g., aluminum) is used as the anode and anodized in an electrolyte solution, thereby forming an oxide film on the surface of the conductive substrate. Examples of electrolyte solutions include sulfuric acid solution and oxalic acid solution. However, the porous anodic oxide film formed by anodizing is chemically active in its original state, easily contaminated, and exhibits significant resistance variations due to environmental factors. Therefore, it is preferable, for example, to perform a sealing treatment on the porous anodic oxide film, where the micropores are blocked by a hydration reaction induced by pressurized steam or boiling water (with the addition of metal salts such as nickel), thereby changing it into a more stable hydrated oxide.

[0182] The thickness of the anodic oxide film is preferably 0.3 μm or more and 15 μm or less. If the film thickness is within the above range, there is a tendency for it to act as a barrier against implantation, and there is a tendency for the rise in residual potential caused by repeated use to be suppressed.

[0183] Conductive substrates can be treated with acidic solutions or boehmite.

[0184] The treatment using an acidic treatment solution is carried out, for example, as follows. First, an acidic treatment solution containing phosphoric acid, chromic acid, and hydrofluoric acid is prepared. The proportions of phosphoric acid, chromic acid, and hydrofluoric acid in the acidic treatment solution are, for example, 10% by mass or more and 11% by mass or less, 3% by mass or more and 5% by mass or less, and 0.5% by mass or more and 2% by mass or less, and the total concentration of these acids is preferably 13.5% by mass or more and 18% by mass or less. The treatment temperature is preferably, for example, 42°C or more and 48°C or less. The film thickness is preferably, for example, 0.3 μm or more and 15 μm or less.

[0185] Boehmite treatment can be performed, for example, by immersion in pure water at a temperature above 90°C and below 100°C for 5 to 60 minutes, or by contact in heated steam at a temperature above 90°C and below 120°C for 5 to 60 minutes. The film thickness is preferably, for example, 0.1 μm or more and 5 μm or less. Further anodizing can be performed using electrolyte solutions with low film solubility, such as adipic acid, boric acid, borates, phosphates, phthalates, maleates, benzoates, tartrates, and citrates.

[0186] <Electrified Devices>

[0187] The image forming apparatus according to this embodiment has a charging device that uses a charging roller and applies an alternating current to charge the electrophotographic photoreceptor.

[0188] As a live device, it is possible to use known live devices.

[0189] The layer structure of the charged roller is not particularly limited. For example, a charged roller may have a conductive elastic layer, a resistive layer, and a surface layer sequentially formed on the surface of a conductive support. Adhesives may be used between the layers as needed. The resistive layer serves to ensure uniform charging performance or to prevent leakage current.

[0190] The conductive support body functions as an electrode and support component for the charged roller, and is made of metals or alloys such as aluminum, copper alloys, and stainless steel; iron plated with chromium, nickel, etc.; or conductive materials such as conductive resin. The diameter of the conductive support body is preferably 5 mm or more and 9 mm or less, more preferably 6 mm or more and 8 mm or less.

[0191] The elastic layer and resistive layer are formed, for example, by dispersing a conductive agent in a rubber material. Examples of rubber materials include isoprene rubber, chloroprene rubber, epichlorohydrin rubber, butyl rubber, polyurethane rubber, silicone rubber, fluororubber, styrene-butadiene rubber, butadiene rubber, nitrile rubber, ethylene propylene rubber, epichlorohydrin-ethylene oxide copolymer rubber, epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber, ethylene-propylene-diene ternary copolymer rubber (EPDM), acrylonitrile-butadiene copolymer rubber (NBR), natural rubber, and blends thereof. Among these, polyurethane rubber, silicone rubber, EPDM, epichlorohydrin-ethylene oxide copolymer rubber, epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber, NBR, and blends thereof can be used. In particular, in the elastic layer, these rubber materials can be either foamed or non-foamed.

[0192] As conductive agents, electronic conductive agents or ionic conductive agents can be used. Examples of electronic conductive agents include carbon black such as Ketjen black and acetylene black; thermally decomposed carbon and graphite; various conductive metals or alloys such as aluminum, copper, nickel, and stainless steel; various conductive metal oxides such as tin oxide, indium oxide, titanium oxide, tin oxide-antimony oxide solid solution, and tin oxide-indium oxide solid solution; conductive agents that have been used to make the surface of insulating materials conductive; and micro powders.

[0193] Furthermore, examples of ionic conductive agents include perchlorates and chlorates such as tetraethylammonium and lauryltrimethylammonium; and perchlorates and chlorates of alkali metals and alkaline earth metals such as lithium and magnesium.

[0194] These conductive agents can be used alone or in combination of two or more.

[0195] Furthermore, there is no particular limitation on the amount added, but in the case of the aforementioned electronic conductive agent, it is preferably in the range of 1 part by weight or more and 30 parts by weight or less relative to 100 parts by weight of the rubber material, more preferably in the range of 5 parts by weight or more and 25 parts by weight or less. On the other hand, in the case of the aforementioned ionic conductive agent, for example, it is preferably in the range of 0.1 parts by weight or more and 5.0 parts by weight or less relative to 100 parts by weight of the rubber material, more preferably in the range of 0.5 parts by weight or more and 3.0 parts by weight or less.

[0196] The thickness of the elastic layer is preferably 1.0 mm or more and 4.0 mm or less, more preferably 2.0 mm or more and 3.0 mm or less. Furthermore, the thickness of the resistive layer is preferably 200 μm or more and 1,000 μm or less, more preferably 300 μm or more and 600 μm or less.

[0197] The polymeric materials constituting the surface layer are not particularly limited, but examples include polyamide, polyurethane, polyvinylidene fluoride, tetrafluoroethylene copolymer, polyester, polyimide, silicone resin, acrylic resin, polyvinyl butyral, ethylene-tetrafluoroethylene copolymer, melamine resin, fluororubber, epoxy resin, polycarbonate, polyvinyl alcohol, cellulose, polyvinylidene chloride, polyvinyl chloride, polyethylene, ethylene-vinyl acetate copolymer, etc.

[0198] The aforementioned polymeric materials can be used alone, or two or more can be mixed or copolymerized. Furthermore, the number-average molecular weight of the polymeric materials is preferably in the range of 1,000 or more and 100,000 or less, and more preferably in the range of 10,000 or more and 50,000 or less.

[0199] The conductive agent used as a conductive agent in the elastic layer or various microparticles are mixed with the above-mentioned polymer material to form a composition, and a surface layer is formed. There is no particular limitation on the amount added, but it is preferably in the range of 1 part by weight or more and 50 parts by weight or less relative to 100 parts by weight of the polymer material, and more preferably in the range of 5 parts by weight or more and 20 parts by weight or less.

[0200] The aforementioned particles can be metal oxides such as silicon dioxide, aluminum oxide, and barium titanate, as well as composite metal oxides, and polymeric micropowders such as tetrafluoroethylene and vinylidene fluoride, used individually or in combination, but are not limited to these.

[0201] The thickness of the surface layer is preferably 1 μm or more and 50 μm or less, and more preferably 3 μm or more and 20 μm or less.

[0202] The deviation of the outer diameter of the electrified roller is greatly affected by the thickness accuracy of the elastic layer. By improving the grinding accuracy of the elastic layer or the accuracy of the mold used to form the elastic layer, the deviation of the outer diameter of the electrified roller can be set to less than 0.1 mm.

[0203] Furthermore, by appropriately combining the materials constituting the surface layer, elastic layer, and resistive layer, the resistance (commonly logarithmic value) of the charged roller can be set to below 9.0 logΩ·m. Examples of combinations of rubber materials and conductive agents constituting the elastic and resistive layers include, for example, a mixture of any polar rubber such as epichlorohydrin-ethylene oxide copolymer rubber, epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber, acrylonitrile-butadiene copolymer rubber, and polyurethane, used alone or in combination with two or more of them, as well as ionic conductive agents and carbon black. Examples of combinations of polymeric compounds constituting the surface layer and conductive agents include, for example, polyamide, polyurethane, polyester, melamine resin, and carbon black or metal oxides.

[0204] <Direct Transfer Roller>

[0205] The image forming apparatus described in this embodiment has a direct transfer roller.

[0206] As a direct transfer roller, any roller that directly transfers to the recording medium is acceptable, and there are no particular restrictions; any known transfer roller can be used.

[0207] <Recording Media Stripping Components>

[0208] The image forming apparatus according to this embodiment has a recording medium stripping member that strips the recording medium from the direct transfer roller.

[0209] The recording media peeling component is a component that peels recording media such as paper from the direct transfer roller.

[0210] There are no particular restrictions on the type of stripping component used for recording media; known stripping components such as scraper-shaped or roller-shaped components can be used.

[0211] The image forming apparatus according to this embodiment is applicable to the following known image forming apparatuses: a cleaning apparatus that brings a cleaning member into contact with the surface of the electrophotographic photosensitive body for cleaning; a fixing apparatus that fixes a toner image transferred to the surface of a recording medium; a direct transfer method apparatus that directly transfers a toner image formed on the surface of the electrophotographic photosensitive body to the recording medium; an intermediate transfer method apparatus that transfers a toner image formed on the surface of the electrophotographic photosensitive body to the surface of an intermediate transfer body in one step, and then transfers the toner image transferred to the surface of the intermediate transfer body to the surface of the recording medium in a second step; a cleaning apparatus that cleans the surface of the electrophotographic photosensitive body after transferring the toner image but before charging; an electrostatic elimination apparatus that irradiates the surface of the electrophotographic photosensitive body with electrostatic elimination light after transferring the toner image but before charging to eliminate static electricity; and an electrophotographic photosensitive body heating member that raises the temperature of the electrophotographic photosensitive body and lowers the relative temperature, etc.

[0212] The image forming apparatus described in this embodiment can be either a dry developing image forming apparatus or a wet developing image forming apparatus (a developing method that utilizes liquid developer).

[0213] Furthermore, in the image forming apparatus according to this embodiment, for example, the portion including the electrophotographic photosensitive element can be a cassette structure (processing cassette) detachable from the image forming apparatus. As the processing cassette, for example, a processing cassette including the electrophotographic photosensitive element according to this embodiment is preferably used. In addition to the electrophotographic photosensitive element, the processing cassette may also include at least one selected from the group consisting of a charging device, an electrostatic latent image forming apparatus, a developing apparatus, and a transfer apparatus.

[0214] The following describes an example of the image forming apparatus according to this embodiment, but it is not limited thereto. Furthermore, the main parts shown in the figures will be described, while descriptions of other parts will be omitted.

[0215] Figure 2 This is a schematic structural diagram illustrating an example of the image forming apparatus according to this embodiment.

[0216] like Figure 2 As shown, the image forming apparatus 100 according to this embodiment includes: a processing cartridge 300 having an electrophotographic photosensitive element 7, an exposure apparatus 9 (an example of an electrostatic latent image forming apparatus), and a transfer apparatus 40 (a direct transfer apparatus). Furthermore, in the image forming apparatus 100, the exposure apparatus 9 is positioned to expose the electrophotographic photosensitive element 7 through the opening of the processing cartridge 300, and the transfer apparatus 40 is positioned opposite the electrophotographic photosensitive element 7, transferring the image to the recording medium 50.

[0217] Figure 2 The processing cartridge 300 integrally supports the electrophotographic photoreceptor 7, the charging device 8 (an example of the charging device), the developing device 11 (an example of the developing device), and the cleaning device 13 (an example of the cleaning device) within the housing. The cleaning device 13 has a cleaning blade (an example of a cleaning component) 131, which is configured to contact the surface of the electrophotographic photoreceptor 7. Furthermore, the cleaning component may be a conductive or insulating fibrous component instead of the cleaning blade 131, and can be used alone or in conjunction with the cleaning blade 131.

[0218] In addition, Figure 2 In this example, an image forming apparatus is shown that includes a fibrous component 132 (roller-shaped) for supplying lubricant 14 to the surface of an electrophotographic photosensitive element 7 and a fibrous component 133 (flat brush-shaped) for assisting in cleaning, but these can be configured as needed.

[0219] The structure of the image forming apparatus according to this embodiment will be described below.

[0220] -Electrified devices-

[0221] As the charging device 8, for example, a contact-type belt conveyor is used, which employs a conductive or semi-conductive charging roller. Furthermore, non-contact roller belt conveyors, grid corona tube belt conveyors utilizing corona discharge, or corona tube belt conveyors, and other belt conveyors known in themselves, can also be used.

[0222] -Exposure device-

[0223] As the exposure device 9, examples include optical systems that expose the surface of an electrophotographic photosensitive object 7 with light such as semiconductor laser, LED light, or liquid crystal shutter light to form a predetermined pattern. The wavelength of the light source is set within the spectral sensitivity range of the electrophotographic photosensitive object. Near-infrared light with an oscillation wavelength around 780 nm is the mainstream wavelength for semiconductor lasers. However, it is not limited to this wavelength; lasers with an oscillation wavelength in the 600 nm band, or lasers with an oscillation wavelength in the range of 400 nm to 450 nm (as blue lasers), can also be used. Furthermore, surface-emitting laser light sources capable of outputting multiple beams for forming color images are also effective.

[0224] -Developing apparatus-

[0225] As a developing apparatus 11, for example, a conventional developing apparatus that develops by contact or non-contact with a developer can be cited. There are no particular limitations on the developing apparatus 11 as long as it has the aforementioned functions, and it can be selected according to the purpose. For example, known developing machines that use brushes, rollers, etc., to adhere a single-component or two-component developer to the electrophotographic photosensitive element 7 can be cited. Among these, a developing machine that uses a developing roller to hold the developer on the surface is preferred, for example.

[0226] The developer used in the developing apparatus 11 can be a single-component developer containing only a toner, or a two-component developer containing both a toner and charge carriers. Furthermore, the developer can be magnetic or non-magnetic. Commonly known developers are acceptable.

[0227] -Cleaning Device-

[0228] The cleaning device 13 is a device that uses a cleaning scraper with a cleaning scraper 131.

[0229] In addition to the cleaning scraper method, brush cleaning and simultaneous development and cleaning methods can also be used.

[0230] -Transfer Device-

[0231] As a transfer device 40, for example, a contact transfer belt appliance that uses rollers can be cited.

[0232] Example

[0233] Hereinafter, the embodiments of the present invention will be described in detail with reference to the examples, but the embodiments of the present invention are not limited to these examples.

[0234] Unless otherwise specified, “parts” and “%” are quality standards in the following description.

[0235] Unless otherwise specified, the following instructions shall be followed by synthesis, manufacturing, processing, and measurement at room temperature (25℃±3℃).

[0236] (Example 1)

[0237] <Formation of the undercoat>

[0238] An aluminum cylindrical tube with an outer diameter of 30 mm, a length of 340 mm, and a wall thickness of 1 mm was prepared as the conductive substrate.

[0239] In a stainless steel tray, 100 parts by weight of zinc oxide particles (trade name: Nano Tek ZnO, manufactured by CIKasei CO.,LTD.) were pre-dried by heating at 120°C for 2 hours.

[0240] Next, while stirring the pre-dried zinc oxide particles, a 4% by mass toluene solution of N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane (silane coupling agent) was sprayed onto them (40 parts by mass), and the mixture was stirred at 100°C for 1 hour. Then, after a further sintering treatment at 175°C for 1 hour, the particles were pulverized using a mortar.

[0241] Next, the obtained zinc oxide, which has been surface-treated with a surface treatment agent, is mixed as follows: 25 parts by weight; curing agent (terminated isocyanate SUMIDUR 3175, manufactured by Sumika Bayer Urethane Co., Ltd.): 10 parts by weight; butyral resin S-LEC BM-1 (manufactured by SEKISUICHEMICAL CO.,LTD.): 9 parts by weight; methyl ethyl ketone: 60 parts by weight; and additive (EDHA: 4-ethoxy-1,2-dihydroxy-9,10-anthraquinone). The glass beads were dispersed using a sand mill for 2 hours to obtain a dispersion.

[0242] The obtained dispersion was supplemented with 3 parts by weight of silica spheres "TOSPEARL120 (NISSHO SANGYO CO.,Ltd)" and 0.01 parts by weight of silicone oil SH29PA (manufactured by Dow Corning Toray Co.,Ltd). This yielded a coating solution for forming an undercoat.

[0243] The obtained undercoating solution was applied to an aluminum cylindrical conductive substrate and dried and cured at 160°C for 60 minutes. This resulted in an undercoating with a thickness of 23.5 μm.

[0244] <Formation of the charge generation layer>

[0245] A mixture consisting of 15 parts of hydroxy gallium phthalocyanine (X-ray diffraction spectra using CuKα characteristic X-rays showing diffraction peaks at Bragg angles (2θ±0.2°) of at least 7.5°, 9.9°, 12.5°, 16.3°, 18.6°, 25.1°, and 28.3°) as the charge-generating material, 10 parts of vinyl chloride-vinyl acetate copolymer resin (trade name: VMCH, manufactured by Nippon Unicar Company Limited) as the binder resin, and 200 parts of n-butyl acetate was dispersed in a sand mill for 4 hours using glass beads with a diameter of 1 mm. 175 parts of n-butyl acetate and 180 parts of methyl ethyl ketone were added to the dispersion, and the mixture was stirred to obtain a coating solution for forming a charge-generating layer. The coating solution for forming the charge-generating layer was impregnated onto the undercoat and dried at room temperature to form a charge-generating layer with a thickness of 0.25 μm.

[0246] <Formation of the charge transport layer>

[0247] • Adhesive resin (polycarbonate resin (1) (viscosity-average molecular weight 40,000, the values ​​in the structural formula represent molar ratios)): 20 parts

[0248] • Charge transport material (CTM-1): 15 parts

[0249] • Solvent (tetrahydrofuran (THF)): 600 parts

[0250] The above materials were stirred and mixed for 12 hours to obtain a coating solution for forming a charge transport layer. The coating solution was then applied to the charge generation layer at room temperature (28°C). Hot air was then blown onto the coating to dry it, forming a charge transport layer A with a thickness of 22 μm.

[0251] [Chemical Formula 3]

[0252]

[0253] The above process yields a photoreceptor.

[0254] The photoreceptor was connected to a surface electrical property evaluation device (scanner), and the current density of the photoreceptor under an electric field of 40V / μm was measured. The photoreceptor was mounted on a DocuPrint 3050 manufactured by FUJIFILM Business Innovation Corp., and the voltage of the stripping component of the printed media, the transfer current of the direct transfer roller, and the resistance of the printed media were adjusted as shown in Table 1, and an image forming apparatus was fabricated.

[0255] (Examples 2 to 10 and Comparative Examples 1 to 6)

[0256] As described in Table 1, the type of charge transport layer, the resistance of the undercoat, the current density of the photoreceptor in an electric field of 40V / μm, the voltage of the stripped part of the printing medium, the transfer current of the direct transfer roller, and the resistance of the printing medium were changed. Otherwise, the respective image forming apparatus was manufactured in the same manner as in Example 1.

[0257] In addition, charge transport layers B and C are shown below.

[0258] (charge transport layer B)

[0259] When forming charge transport layer A, the content of charge transport material was changed to 12 parts. Otherwise, charge transport layer B was formed in the same manner as charge transport layer A.

[0260] (charge transport layer C)

[0261] When forming charge transport layer A, the content of charge transport material was changed to 10 parts. Otherwise, charge transport layer C was formed in the same manner as charge transport layer A.

[0262] Furthermore, the resistance of the undercoat was adjusted by the film thickness and the amount of zinc oxide added. Increasing the film thickness of the undercoat would increase the resistance, while decreasing it would decrease it. Conversely, decreasing the amount of zinc oxide added would increase the resistance, and vice versa.

[0263] <Evaluation of Fog Suppression and Stripping Discharge Streak Suppression>

[0264] In the DocuPrint 3050 (manufactured by FUJIFILM Business Innovation Corp., an image forming apparatus that uses direct transfer printing and is equipped with a recording media stripping unit (strip discharge unit, DTS), an evaluation drum is installed on the processing unit (CRU), and five specified charts (blank paper and bicycle) are continuously output to perform a sensory evaluation of fogging and strip discharge streaks.

[0265] -Fog suppression-

[0266] A: No haze was observed.

[0267] B: Fog was observed in some areas, but there were no problems in actual use.

[0268] C: Gray fog was observed, making it unsuitable for practical use.

[0269] -Suppression of stripped discharge streaks-

[0270] A: No stripes observed

[0271] B: Stripes were observed in some areas, but there were no problems in actual use.

[0272] C: Stripes were observed, making it unsuitable for practical use.

[0273] [Table 1]

[0274]

[0275] As can be seen from the above results, compared with the image forming apparatus of the comparative example, the image forming apparatus of the embodiment has superior fog suppression and stripe discharge stripe suppression.

[0276] (1) An image forming apparatus comprising: an electrophotographic photoreceptor having a photosensitive layer on a conductive substrate, and having on the conductive substrate: a lower coating containing a metal oxide, a charge generating layer containing a metal element disposed on the lower coating, and a charge transport layer disposed on the charge generating layer; a charging device for applying an alternating current using a charging roller to charge the electrophotographic photoreceptor; a direct transfer roller; and a recording medium peeling member for peeling a recording medium from the direct transfer roller, wherein the resistivity of the lower coating is 6.0 logΩ·m or more and 9.5 logΩ·m or less, and the current density of the electrophotographic photoreceptor at 40 V / μm is 0.012 μA / cm. 2 Above and 0.030 μA / cm 2 the following.

[0277] (2) The image forming apparatus according to (1), wherein,

[0278] The resistivity of the lower coating layer is above 7.0 logΩ·m and below 9.0 logΩ·m.

[0279] (3) The image forming apparatus according to (2), wherein,

[0280] The resistivity of the lower coating layer is above 7.5 logΩ·m and below 9.0 logΩ·m.

[0281] (4) The image forming apparatus according to any one of (1) to (3), wherein,

[0282] The current density of the electrophotographic photoreceptor at 40V / μm is 0.015μA / cm. 2 Above and 0.025μA / cm 2 the following.

[0283] (5) The image forming apparatus according to any one of (1) to (4), wherein,

[0284] The voltage of the recording media stripping component is above 300V and below 800V.

[0285] (6) The image forming apparatus according to any one of (1) to (5), wherein,

[0286] The transfer current of the direct transfer roller is above 5μA and below 15μA.

[0287] (7) The image forming apparatus according to any one of (1) to (6), wherein,

[0288] The resistance of the recording medium used is above 4logΩ·m and below 12logΩ·m.

[0289] (8) The image forming apparatus according to any one of (1) to (7), wherein,

[0290] After passing through the direct transfer roller, the angle between the direction of the transfer roller pair to which the recording medium is subsequently transferred and the direction of transport of the recording medium after the transfer is more than 10° and less than 30°.

[0291] (9) The image forming apparatus according to (8), wherein,

[0292] After passing through the direct transfer roller, the angle between the direction of the transfer roller pair to which the recording medium is subsequently transferred and the direction of transport of the recording medium after the transfer is 15° or more and 30° or less.

[0293] According to the invention described in (1), an image forming apparatus is provided in which the resistance of the underlying coating is less than 6.0 logΩ·m or greater than 9.5 logΩ·m, or the current density of the electrophotographic photoreceptor at 40 V / μm is less than 0.012 μA / cm. 2 Or exceeding 0.030 μA / cm 2 Compared to other cases, it exhibits superior fog suppression and stripe discharge stripe suppression.

[0294] According to the invention involved in (2), an image forming apparatus is provided that has superior fog suppression compared to cases where the resistance value of the lower coating is less than 7.0 logΩ·m or more than 9.0 logΩ·m.

[0295] According to the invention involved in (3), an image forming apparatus is provided that has superior fog suppression compared to cases where the resistance value of the lower coating is less than 7.5 logΩ·m or more than 9.0 logΩ·m.

[0296] According to the invention involved in (4), an image forming apparatus is provided in which the current density of the electrophotographic photoreceptor at 40V / μm is less than 0.015μA / cm. 2 Or exceeding 0.025 μA / cm 2Compared to the previous case, the stripping discharge stripe suppression performance is superior.

[0297] According to the invention involved in (5), an image forming apparatus is provided that has better suppression of stripping discharge wires compared to the case where the voltage of the recording medium stripping member is less than 300V or more than 800V.

[0298] According to the invention involved in (6), an image forming apparatus is provided that has superior fog suppression and stripe discharge stripe suppression compared to cases where the transfer current of the direct transfer roller is less than 5 μA or more than 15 μA.

[0299] According to the invention involved in (7), an image forming apparatus is provided that has better stripping discharge stripe suppression compared to cases where the resistance value of the recording medium used is less than 4logΩ·m or more than 12logΩ·m.

[0300] According to the invention involved in (8), an image forming apparatus is provided that has better stripe discharge stripe suppression compared to cases where the angle between the direction of the transfer roller pair to which the recording medium is subsequently transferred after passing through the direct transfer roller and the direction of transfer of the recording medium after transfer is less than 10° or more than 30°.

[0301] According to the invention involved in (9), an image forming apparatus is provided that has better stripe discharge stripe suppression compared to cases where the angle between the direction of the transfer roller pair to which the recording medium is subsequently transferred after passing through the direct transfer roller and the direction of transfer of the recording medium after transfer is less than 15° or more than 30°.

[0302] The embodiments of the present invention described above are provided for illustrative purposes. Furthermore, these embodiments do not encompass the entirety of the invention, nor do they limit the invention to the disclosed methods. It will be apparent to those skilled in the art that various modifications and variations will be readily understood. These embodiments were chosen and described to most readily explain the principles and applications of the invention. Thus, those skilled in the art can understand the invention through various modifications that are assumed to be optimized for specific uses of various embodiments. The scope of the invention is defined by the foregoing claims and their equivalents.

Claims

1. An image forming apparatus comprising: An electrophotographic photosensitive material has a photosensitive layer on a conductive substrate, and on the conductive substrate, it has: a lower coating layer containing a metal oxide, a charge generating layer containing a metal element disposed on the lower coating layer, and a charge transport layer disposed on the charge generating layer. The charging device uses a charging roller to apply alternating current, thereby charging the electrophotographic photoreceptor. Direct transfer roller; and The recording media stripping component strips the recording media from the direct transfer roller. The resistivity of the lower coating is above 6.0 logΩ·m and below 9.5 logΩ·m, and the current density of the electrophotographic photoreceptor at 40 V / μm is 0.012 μA / cm. 2 Above and 0.030 μA / cm 2 the following.

2. The image forming apparatus according to claim 1, wherein, The resistivity of the lower coating layer is above 7.0 logΩ·m and below 9.0 logΩ·m.

3. The image forming apparatus according to claim 2, wherein, The resistivity of the lower coating layer is above 7.5 logΩ·m and below 9.0 logΩ·m.

4. The image forming apparatus according to any one of claims 1 to 3, wherein, The current density of the electrophotographic photoreceptor at 40V / μm is 0.015μA / cm. 2 Above and 0.025μA / cm 2 the following.

5. The image forming apparatus according to any one of claims 1 to 4, wherein, The voltage of the recording media stripping component is above 300V and below 800V.

6. The image forming apparatus according to any one of claims 1 to 5, wherein, The transfer current of the direct transfer roller is above 5μA and below 15μA.

7. The image forming apparatus according to any one of claims 1 to 6, wherein, The resistance of the recording medium used is above 4logΩ·m and below 12logΩ·m.

8. The image forming apparatus according to any one of claims 1 to 7, wherein, After passing through the direct transfer roller, the angle between the direction of the transfer roller pair to which the recording medium is subsequently transferred and the direction of transport of the recording medium after the transfer is more than 10° and less than 30°.

9. The image forming apparatus according to claim 8, wherein, After passing through the direct transfer roller, the angle between the direction of the transfer roller pair to which the recording medium is subsequently transferred and the direction of transport of the recording medium after the transfer is 15° or more and 30° or less.

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