Charger having discharge wire, drum cartridge, and image forming apparatus

Abstract

To suppress peeling of a coating layer containing silver from a core material of a discharge wire SOLUTION: The charger includes a discharge wire 102, a grid electrode, and a pair of shields. The grid electrode faces the discharge wire 102. The pair of shields are electrically connected to the grid electrode. The pair of shields are disposed with the discharge wire 102 interposed therebetween. The discharge wire 102 includes a conductive core material 102A and a coating layer 102A that coats the core material 102B and contains silver and graphene.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a charger using a discharge wire, a drum cartridge, and an image forming apparatus. [Background technology]

[0002] Conventionally, among discharge wires used in chargers, those with a double structure in which a linear core is coated with a conductive metal are known (see Patent Document 1). Chargers generate ozone (O3) when they discharge, and it is desirable to generate as little ozone as possible. Patent Document 1 discloses that by selecting silver (Ag) for the coating layer, ozone is decomposed by the oxidation-reduction reaction of silver, thereby reducing the amount of ozone generated from the charger. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 63-177859 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when a wire-shaped core material is coated with silver in a discharge wire used in a charger, there is a problem in that the coating layer is easily peeled off from the core material.

[0005] Therefore, an object of the present invention is to prevent the coating layer containing silver from peeling off from the core material of the discharge wire. [Means for solving the problem]

[0006] In order to achieve the above object, a charger for charging a photosensitive drum includes a discharge wire, a grid electrode, and a pair of shields. The grid electrode faces the discharge wire. The pair of shields are electrically connected to the grid electrode. The pair of shields are disposed with the discharge wire sandwiched between them. The discharge wire has a conductive core material and a coating layer that coats the core material and contains silver and graphene.

[0007] Since the discharge wire has a conductive core material and a coating layer containing silver and graphene, peeling of the coating layer containing silver from the core material of the discharge wire can be suppressed.

[0008] The coating layer may be configured as a composite silver plating film containing graphene in silver.

[0009] Since the coating layer is a composite silver plating film containing graphene in silver, the coating layer can be formed as a plating film by dispersing graphene in the plating solution.

[0010] The graphene may include graphene oxide.

[0011] By including graphene oxide in the graphene coating layer, it is easily dispersed in the plating solution, making it possible to form a coating layer in which graphene is uniformly dispersed.

[0012] The graphene oxide may have a structure including multiple layers of graphene oxide.

[0013] When the graphene oxide contains multiple layers of graphene oxide, the particle size of the graphene oxide can be controlled.

[0014] The proportion of graphene in the coating layer may be 0.5 to 7 vol %.

[0015] Since the proportion of graphene in the coating layer is 0.5 to 7 vol %, the coating layer containing silver can be prevented from peeling off from the core material of the discharge wire without reducing the conductivity of the coating layer.

[0016] The particle size of the graphene may be equal to or smaller than the thickness of the coating layer.

[0017] When the particle size of the graphene is equal to or smaller than the thickness of the coating layer, the coating layer becomes a smooth film, improving the adhesion between the coating layer and the core material.

[0018] The coating layer may have a thickness of 1.5 μm or more.

[0019] Since the coating layer has a thickness of 1.5 μm or more, the durability of the coating layer can be increased.

[0020] The coating layer may have a thickness of 10 μm or less.

[0021] Since the thickness of the coating layer is 10 μm or less, the cost of the coating layer can be reduced.

[0022] The core material may be made of tungsten.

[0023] Since the core material is made of tungsten, the strength and discharge characteristics of the discharge wire can be improved.

[0024] To achieve the above object, the drum cartridge includes a drum frame, a photosensitive drum, and a charger. The photosensitive drum is supported by a drum frame and rotates around a rotation axis. The charger charges the photosensitive drum and includes a discharge wire, a grid electrode, and a pair of shields. The discharge wire extends along the rotation axis and has a conductive core material and a coating layer that coats the core material and includes silver and graphene. The grid electrode is disposed between the photosensitive drum and the discharge wire. The pair of shields is electrically connected to the grid electrode and is disposed with the discharge wire between them.

[0025] Since the discharge wire has a conductive core material and a coating layer containing silver and graphene, peeling of the coating layer containing silver from the core material of the discharge wire can be suppressed.

[0026] The drum cartridge may further include a cleaner that cleans foreign matter adhering to the discharge wire, the cleaner being slidable between one end and the other end of the discharge wire, and a rail extending in a first direction and holding the cleaner so that it can slide.

[0027] By providing the charger with a cleaner, foreign matter adhering to the discharge wire can be cleaned.

[0028] In order to achieve the above object, the image forming apparatus includes a main body housing, a drum cartridge, and a voltage application circuit. The drum cartridge is detachably attached to the main body housing and includes a drum frame, a photosensitive drum, and a charger. The photosensitive drum is supported by a drum frame and rotates around a rotation axis. The charger charges the photosensitive drum and includes a discharge wire, a grid electrode, and a pair of shields. The discharge wire extends along the rotation axis and has a conductive core material and a coating layer that coats the core material and includes silver and graphene. The grid electrode is disposed between the photosensitive drum and the discharge wire. The pair of shields is electrically connected to the grid electrode and is disposed with the discharge wire between them. The voltage application circuit applies a voltage to the discharge wire.

[0029] Since the discharge wire has a conductive core material and a coating layer containing silver and graphene, peeling of the coating layer containing silver from the core material of the discharge wire can be suppressed.

[0030] The voltage application circuit may be configured to apply a positive voltage to the discharge wire.

[0031] Since the voltage application circuit applies a positive voltage, the amount of ozone generated can be reduced compared to when a negative voltage is applied.

[0032] The image forming apparatus may further include an exhaust fan that exhausts air from inside the main body housing to the outside of the main body housing.

[0033] Since the image forming apparatus is provided with an exhaust fan, even if ozone is generated by the discharge wire, the generated ozone can be prevented from remaining in the charger.

[0034] The image forming apparatus may further include an intake fan that draws air from outside the main body housing into the main body housing.

[0035] Since the image forming apparatus is provided with an intake fan, air from outside the main body housing can be taken into the charger. [Effects of the Invention]

[0036] According to the present disclosure, it is possible to prevent the coating layer containing silver from peeling off from the core material of the discharge wire. [Brief explanation of the drawings]

[0037] [Figure 1] 1 is a cross-sectional view of an image forming apparatus according to an embodiment. [Figure 2] FIG. 2 is a perspective view showing the drum cartridge. [Figure 3] FIG. 2 is a partially enlarged view of FIG. 1, showing the periphery of the charger. [Figure 4] FIG. 10 is a perspective view showing the charger with the cleaner removed from the rail. [Figure 5] FIG. 2 is a diagram illustrating application of a voltage by a voltage application circuit. [Figure 6] 2A and 2B are a cross-sectional perspective view and a partially enlarged view of the cross section of the discharge wire; [Figure 7] The structural formula of graphene (a) and graphene oxide (b). [Figure 8] 10 is a table showing the results of a durability test on a plating layer to which graphene is not added and a plating layer to which graphene is added. DETAILED DESCRIPTION OF THE INVENTION

[0038] Next, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, directions are described relative to the user when using the image forming apparatus 1. That is, in Fig. 1, the left side of the paper is the "front," the right side of the paper is the "rear," the near side of the paper is the "right," and the far side of the paper is the "left." The up-down direction of the paper is also referred to as the "vertical direction."

[0039] 1, the image forming apparatus 1 is a color printer and includes a main body housing 10, a supply unit 20, an image forming unit 30, a fixing unit 80, and a discharge unit 90.

[0040] The main body housing 10 has a front cover 12 and a discharge tray 14. The front cover 12 is disposed on the front surface of the main body housing 10. The front cover 12 can be opened and closed. The discharge tray 14 is disposed on the top surface of the main body housing 10. The discharge tray 14 holds the sheets S discharged from the main body housing 10.

[0041] The supply unit 20 is provided in the lower part of the main body housing 10. The supply unit 20 has a supply tray 21 and a supply mechanism 22. The supply tray 21 stores sheets S. The supply mechanism 22 supplies the sheets S stored in the supply tray 21 to the image forming unit 30.

[0042] The image forming section 30 includes an exposure unit 40, a drum cartridge 50, and a transfer unit .

[0043] The exposure unit 40 is provided in the upper part of the main body housing 10. The exposure unit 40 has a laser light source (not shown), a polygon mirror (not shown), multiple lenses, and multiple reflecting mirrors. The laser light emitted from the laser light source is reflected by the polygon mirror and the reflecting mirror, passes through the lens, and is scanned at high speed over the surface of each photosensitive drum 52.

[0044] The drum cartridge 50 is detachably attached to the main body housing 10. In this embodiment, the drum cartridge 50 can be pulled out through an opening 10A formed in the front surface of the main body housing 10 with the front cover 12 open. As shown in FIG. 2 , the drum cartridge 50 is a drawer that can be pulled out from the main body housing 10.

[0045] Returning to FIG. 1 , when the drum cartridge 50 is attached to the main body casing 10, it is positioned between the supply tray 21 and the exposure unit 40. The drum cartridge 50 includes a drum frame 51, four photosensitive drums 52, four developing cartridges 61, four chargers 100, and four cleaning units 140.

[0046] The photosensitive drums 52 are each supported by a drum frame 51. The photosensitive drums 52 rotate about a rotation axis extending in the left-right direction.

[0047] The developing cartridge 61 is detachable from the drum cartridge 50 pulled out through the opening 10A (not shown). As shown in FIG. 3, the developing cartridge 61 includes a developing roller 63, a supply roller 64, a layer thickness regulating blade 65, and a toner storage chamber 66.

[0048] The developing roller 63 carries toner on the photosensitive drum 52. The supply roller 64 supplies toner in a toner storage chamber 66 to the developing roller. A layer thickness regulating blade 65 regulates the layer thickness of the toner supplied to the developing roller 63. The toner storage chambers 66 store toner therein. Each of the four toner storage chambers 66 stores toner of a different color.

[0049] The chargers 100 are disposed opposite the corresponding photosensitive drums 52. The chargers 100 are scorotron chargers. The chargers 100 charge the surfaces of the photosensitive drums 52.

[0050] The cleaning unit 140 is a member that cleans the surface of the photosensitive drum 52. The cleaning unit 140 is provided upstream of the charger 100 in the rotation direction of the photosensitive drum 52. The cleaning unit 140 includes a cleaner case 141, a cleaning blade 145, a seal member 148, and an auger 149.

[0051] The cleaning blade 145 has a support plate 146 and a blade 147. The support plate 146 is fixed to the upper end of the cleaner case 141. The base end of the blade 147 is adhered to the support plate. The tip of the blade 147 comes into contact with the surface of the photosensitive drum 52. When the photosensitive drum 52 rotates with the tip of the blade 147 in contact with the surface of the photosensitive drum 52, residual toner and foreign matter on the photosensitive drum 52 are scraped off and moved into the cleaner case 141.

[0052] The base end of the seal member 148 is fixed to the bottom of the cleaner case 141. The tip of the seal member 148 contacts the surface of the photosensitive drum 52. The seal member 148 prevents residual toner and foreign matter from falling out of the cleaner case 141.

[0053] The auger 149 transports the residual toner and foreign matter to a waste toner box (not shown).

[0054] 1, the transfer unit 70 is provided between the supply unit 20 and the drum cartridge 50. The transfer unit 70 includes a drive roller 71, a driven roller 72, a conveyor belt 73, and four transfer rollers 74.

[0055] The drive roller 71 and the driven roller 72 are arranged at a distance from each other in the front-to-rear direction. The conveyor belt 73 is an endless belt. The conveyor belt 73 is stretched between the drive roller 71 and the driven roller 72. Four transfer rollers 74 are arranged side by side in the front-to-rear direction inside the conveyor belt 73. Each transfer roller 74 is arranged opposite the corresponding photosensitive drum 52, and the conveyor belt 73 is sandwiched between the transfer roller 74 and the corresponding photosensitive drum 52.

[0056] The fixing unit 80 is provided behind the drum cartridge 50. The fixing unit 80 has a heating roller 81 and a pressure roller 82. The heating roller 81 has an internal heater and heats the sheet S. The pressure roller 82 is disposed opposite the heating roller 81 and presses the sheet S together with the heating roller 81.

[0057] In the image forming section 30 configured as described above, the surface of each photosensitive drum 52 is first uniformly charged by the charger 100, and then exposed to laser light from the exposure unit 40, thereby forming an electrostatic latent image based on image data on the photosensitive drum 52. In addition, a certain thickness of toner is carried on the developing roller 63 by the developing cartridge 61.

[0058] The toner carried on the developing roller 63 is then supplied to the photosensitive drum 52 on which the electrostatic latent image is formed, thereby making the electrostatic latent image visible and forming a toner image on the photosensitive drum 52. Thereafter, the sheet S supplied from the supply unit 20 is transported between the photosensitive drum 52 and the transport belt 73, whereby the toner images carried on the photosensitive drums 52 are sequentially superimposed and transferred onto the sheet S. The sheet S onto which the toner image has been transferred in the image forming unit 30 is transported between the heating roller 81 and the pressure roller 82, whereby the toner image is thermally fixed.

[0059] The sheet S on which the image has been formed is conveyed by conveyance rollers 83 to a conveyance path 91 of a discharge section 90, and then discharged by discharge rollers 92 to the outside of the main body housing 10 and placed on a discharge tray 14.

[0060] 1, the image forming apparatus 1 further includes an intake fan F1, an exhaust fan F2, and a voltage application circuit VC. The intake fan F1 and the exhaust fan F2 are disposed on the side wall of the main body housing 10.

[0061] The intake fan F1 draws air from the outside of the main body housing 10 into the main body housing 10. In this embodiment, the intake fan F1 is provided in front of and below the drum cartridge 50.

[0062] The exhaust fan F2 exhausts the air inside the main body housing 10 to the outside of the main body housing 10. In this embodiment, the exhaust fan F2 is provided behind and above the drum cartridge 50.

[0063] The air taken into the main body housing 10 by the intake fan F1 flows through the drum cartridge 50 to the exhaust fan F2 as shown by the arrows in Figure 1. The air that reaches the exhaust fan F2 is exhausted to the outside of the main body housing 10.

[0064] Here, a small amount of ozone is generated as a by-product of corona discharge in the charger 100 of each drum cartridge 50. The generated ozone remains around the charger 100.

[0065] The air passing through the drum cartridge 50 also passes around the charger 100. Therefore, when the air taken into the main body housing 10 by the intake fan F1 passes around the charger 100, it washes away the ozone generated in the charger 100. The washed-out ozone is then exhausted to the outside of the main body housing 10 by the exhaust fan F2.

[0066] 3, the drum cartridge 50 further includes a charger frame 120. The charger frame 120 is fixed to the drum frame 51.

[0067] The charger 100 is disposed opposite the photosensitive drum 52. The charger 100 is held by a charger frame 120. As shown in FIG. 4, the charger frame 120 has a cleaner 110 and a rail 123R. The charger 100 also has a discharge wire 102 and a counter electrode 104.

[0068] In the following description, the direction in which the discharge wire 102 extends is referred to as the "first direction." In this embodiment, the first direction is the left-right direction, which is the same direction as the extension of the rotation axis of the photosensitive drum 52. The direction from the discharge wire 102 toward the rotation axis of the photosensitive drum 52 is referred to as the "second direction." The second direction is a direction perpendicular to the first direction. The direction perpendicular to the first and second directions is referred to as the "third direction."

[0069] The charger frame 120 supports the discharge wire 102, the counter electrode 104, and the cleaner 110. The charger frame 120 extends in a first direction. The charger frame 120 is a plate-like member having a U-shaped cross section. The charger frame 120 has a first wall 121, a second wall 122, and a third wall 123.

[0070] The first wall 121 is provided upstream of the discharge wire 102 in the rotation direction of the photosensitive drum 52, and extends in the second direction.

[0071] The second wall 122 is provided downstream of the discharge wire 102 in the rotation direction of the photosensitive drum 52, and extends in the second direction.

[0072] The third wall 123 extends in the third direction. The third wall 123 is located on the opposite side of the photosensitive drum 52 in the second direction, with the discharge wire 102 sandwiched between them. The third wall 123 forms a rail 123R. The rail 123R extends from one end to the other end of the charger frame 120 in the first direction. The rail 123R holds the cleaner 110 so that it can slide.

[0073] The cleaner 110 is a member for cleaning foreign matter adhering to the discharge wire 102. The cleaner 110 has a sponge 112 and a support frame 114. The sponge 112 comes into sliding contact with the discharge wire 102 to clean foreign matter adhering to the discharge wire 102. The support frame 114 has a sponge holding portion 114A, a rail engaging portion 114B, and a contact portion 114C.

[0074] The sponge holding portion 114A holds the sponge 112. The sponge holding portion 114A is a groove into which the sponge 112 fits. The sponge 112 is folded in half and held by the sponge holding portion 114A with the discharge wire 102 sandwiched inside. The rail engaging portion 114B engages with the rail 123R. By engaging the rail engaging portion 114B with the rail 123R, the cleaner 110 can slide between one end and the other end of the discharge wire 102. The contact portion 114C is a portion that the user comes into contact with. The user slides the cleaner 110 by contacting the contact portion 114C.

[0075] The discharge wire 102 extends in the direction of the rotation axis of the photosensitive drum 52. The discharge wire 102 extends in a first direction. Both ends of the discharge wire 102 are supported by the charger frame 120.

[0076] The counter electrode 104 extends in a first direction. The counter electrode 104 is a plate-shaped electrode that is bent into a U-shape in cross section so as to face the discharge wire 102. The counter electrode 104 has a grid electrode 106 and a pair of shields 108.

[0077] The grid electrode 106 is an electrode in which a plurality of slits SR are formed. The grid electrode 106 is disposed between the photosensitive drum 52 and the discharge wire 102. In this manner, the grid electrode 106 faces the discharge wire 102 in the second direction. The second direction is a direction from the discharge wire 102 toward the rotation axis of the photosensitive drum 52.

[0078] The pair of shields 108 are electrically connected to the grid electrode 106. The pair of shields 108 are arranged opposite each other in the rotation direction of the photosensitive drum 52, sandwiching the discharge wire 102 therebetween. In other words, the pair of shields 108 are arranged in the third direction, sandwiching the discharge wire 102 therebetween. The pair of shields 108 face each other. In this embodiment, the pair of shields 108 extend parallel to each other.

[0079] The voltage application circuit VC is disposed inside the main body housing 10. As shown in FIG. 5, the voltage application circuit VC is a circuit that applies voltages to the charger 100, the developing roller 63, and the transfer roller 74. The voltage application circuit VC applies a positive voltage to the discharge wire 102. The voltage application circuit VC applies a voltage to the discharge wire 102 so that the voltage of the counter electrode 104 becomes a predetermined target value. The voltage application circuit VC applies a positive voltage to the developing roller 63. The voltage application circuit VC applies a negative voltage to the transfer roller 74.

[0080] As shown in FIG. 6, the discharge wire 102 has a core material 102A and a coating layer 102B.

[0081] The core 102A is made of a conductive material. In this embodiment, the core is made of tungsten. In this embodiment, a tungsten wire with a diameter of 60 μm is used.

[0082] The coating layer 102B contains silver and graphene and coats the core material 102A. Specifically, the coating layer 102B is a composite silver plating film containing graphene particles 102D in a silver matrix 102C. The coating layer 102B is manufactured by plating a tungsten wire with a silver plating solution containing graphene or graphene oxide.

[0083] As shown in Figure 7(a), graphene is a material with a sheet-like structure in which carbon atoms are densely bonded in a hexagonal pattern. In this embodiment, graphene includes graphene oxide, as shown in Figure 7(b). Graphene oxide is graphene to which carboxyl groups, hydroxyl groups, and epoxy groups are added.

[0084] Furthermore, graphene and graphene oxide include not only single-layer graphene and multi-layer graphene and graphene oxide.

[0085] The particle size of graphene and graphene oxide is preferably 0.1 to 3 μm, and more preferably 0.2 to 0.5 μm.

[0086] The thickness of the coating layer 102B is preferably 1.5 μm or more, and more preferably 10 μm or less.

[0087] The particle diameter of graphene and graphene oxide is preferably smaller than the thickness of coating layer 102B. In this embodiment, as an example, the particle diameter of graphene and graphene oxide is set to 0.2 to 3 μm, and the film thickness of coating layer 102B is set to 3 to 10 μm.

[0088] The proportion of graphene and graphene oxide in the coating layer 102B is preferably 0.5 to 7 vol %. In this embodiment, the proportion of graphene and graphene oxide in the coating layer 102B is 3 vol %.

[0089] As described above, the following effects can be obtained in this embodiment. In the charger 100, drum cartridge 50, and image forming apparatus 1 of this embodiment, the coating layer 102B of the discharge wire 102 contains silver, which reduces the amount of ozone generated by discharge. Furthermore, the coating layer 102B contains graphene, which prevents the coating layer 102B from peeling off from the core material of the discharge wire 102.

[0090] The coating layer 102B is a composite silver plating film containing graphene in silver, and therefore, by dispersing graphene in a plating solution, the coating layer 102B can be formed as a plating film.

[0091] Furthermore, since the coating layer 102B contains graphene oxide, the graphene is easily dispersed in the plating solution when the coating layer 102B is formed, and therefore the coating layer 102B in which the graphene is uniformly dispersed can be formed.

[0092] Furthermore, since the graphene oxide contains multiple layers of graphene oxide, the particle size of the graphene oxide can be controlled when the coating layer 102B is formed.

[0093] Furthermore, since the proportion of graphene in the coating layer 102B is 0.5 to 7 vol %, it is possible to prevent the coating layer 102B, which contains silver, from peeling off from the core material 102A of the discharge wire 102, without reducing the conductivity of the coating layer 102B. In other words, since the proportion of graphene in the coating layer 102B is 0.5 to 7 vol %, it is possible to achieve both strength and conductivity of the coating layer 102B.

[0094] Furthermore, since the particle size of the graphene is equal to or smaller than the thickness of the coating layer 102B, the graphene particles are prevented from protruding from the coating layer 102B, which results in the coating layer 102B being a smooth film and improving the adhesion between the coating layer 102B and the core material 102A.

[0095] Furthermore, since the thickness of the coating layer 102B is 1.5 μm or more, the durability of the coating layer 102B can be increased.

[0096] Furthermore, since the thickness of the coating layer 102B is 10 μm or less, the cost of the coating layer 102B can be reduced.

[0097] Furthermore, since the core material 102A is made of tungsten, the strength and discharge characteristics of the discharge wire 102 can be improved.

[0098] Furthermore, the charger 100 has the cleaner 110, so that foreign matter adhering to the discharge wire 102 can be cleaned.

[0099] Furthermore, since the voltage application circuit VC applies a voltage of positive polarity, the amount of ozone generated can be reduced compared to when a voltage of negative polarity is applied.

[0100] Furthermore, the image forming apparatus 1 is provided with an exhaust fan F2. Therefore, even if ozone is generated by the discharge wire 102, the generated ozone can be prevented from remaining in the charger 100.

[0101] The image forming apparatus 1 is also provided with an intake fan F1, which allows the charger 100 to take in air from outside the main body housing 10.

[0102] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. The specific configuration can be appropriately changed without departing from the spirit of the present invention. In the following description, the same reference numerals will be used to designate components that are substantially the same as those in the above embodiment, and a description thereof will be omitted.

[0103] In the above-described embodiment, the drum cartridge 50 is removed from the main body casing 10 by pulling it forward from the front cover 12, but it may also be removed from above, behind, right, left, etc.

[0104] In the above-described embodiment, the drum cartridge 50 has four photosensitive drums 52, but the drum cartridge may have one photosensitive drum.

[0105] In the above-described embodiment, the cleaning unit 140 has the cleaning blade 145, but the cleaning unit may have a cleaning roller. Also, the cleaning unit may be omitted.

[0106] In the above-described embodiment, the intake fan F1 is provided in front of and below the drum cartridge 50, but the intake fan may be provided behind or above the drum cartridge 50, or near the drum cartridge 50. Furthermore, multiple intake fans may be provided.

[0107] In the above-described embodiment, the exhaust fan F2 is provided behind and above the drum cartridge 50, but the exhaust fan may be provided in front of or below the drum cartridge 50, or may be provided near the drum cartridge 50. Furthermore, multiple exhaust fans may be provided.

[0108] In the above-described embodiment, the core material of the discharge wire is made of tungsten, but the core material may be made of other materials such as stainless steel or other alloys, graphite, etc., as long as it is conductive. Furthermore, the diameter of the tungsten wire and other wires may be determined arbitrarily.

[0109] In the above-described embodiment, the discharge wire has a configuration including a core material and a coating layer, but it may further include an intermediate layer between the core material and the coating layer, or may further include a surface layer outside the coating layer.

[0110] In the above-described embodiment, the pair of shields extend parallel to each other, but they do not have to extend parallel to each other.

[0111] In the above-described embodiment, the voltage application circuit VC applies a positive voltage to the discharge wire 102, but it may also apply a negative voltage. In this case, a negatively charged voltage is also applied to the developing roller 63, and a positive voltage is applied to the transfer roller 74.

[0112] In the above-described embodiment, the present invention is applied to the image forming device 1 which is a color printer, but it may also be applied to a monochrome printer, or to other image forming devices such as a copier or multifunction device.

[0113] The elements described in the above-described embodiment and modifications may be implemented in any combination. [Example]

[0114] Next, with reference to the table in FIG. 8, the results of a durability test performed when graphene was added to a plating layer containing silver (Examples 1 to 3) and when graphene was not added (Comparative Example) will be described.

[0115] The durability test was carried out using an image forming apparatus 1 equipped with the charged wires of Examples 1 to 3 and the comparative example, and the number of printed sheets was counted. After each count of printed sheets, the appearance of the discharge wire was observed. The charged wire was observed using a magnifying glass to check for cracks and peeling of the plating layer. The evaluation results were ranked A to D as follows. A: No peeling B: Cracked C: Partial peeling (less than 30% peeled area) D: Peeling occurs throughout the entire surface (30% or more of the surface is peeled off) In addition, image formation could be carried out without any problems in all of the states A to D. In all of the states A to C, ozone generation could be reduced.

[0116] [Comparative Example] Plating thickness: 3 μm Graphene added: None 1000 prints: Rating "D"

[0117] [Example 1] Plating thickness: 3 μm Graphene addition: particle size 1-3 μm, 3 vol% Print count 0-7500 sheets: Rating "A" Print count: 1,000-30,000 sheets: Rating "C"

[0118] [Example 2] Plating thickness: 5 μm Graphene addition: particle size 0.2 to 0.5 μm, 3 vol% Print count 0-10,000 sheets: Rating "A" Print count: 15,000-30,000 sheets: Rating "B" [Example 3] Plating thickness: 10 μm Graphene addition: particle size 0.2 to 0.5 μm, 3 vol% Print count 0-80,000 sheets: Rating "A" 90,000 prints: Rating "B"

[0119] From the above results, it was confirmed that when graphene was not added to the silver-containing coating layer, the plating peeled off completely after 1,000 printed sheets, whereas by adding graphene to the coating layer, the durability of the silver-containing coating layer increased to at least 7,500 sheets, significantly improving the durability of coating layer 102B. [Explanation of symbols]

[0120] 1. Image forming device 50 drum cartridges 100 Charger 102 Discharge wire 102A Core material 102B Covering layer 106 Grid electrode 108 Shield 110 Cleaner

Claims

1. A charger that charges a photosensitive drum, A discharge wire; a grid electrode facing the discharge wire; a pair of shields electrically connected to the grid electrode and disposed on either side of the discharge wire; The discharge wire is A conductive core material; a coating layer that coats the core material and contains silver and graphene.

2. The charger according to claim 1 , wherein the coating layer is a composite silver plating film containing graphene in silver.

3. The charger according to claim 2 , wherein the graphene includes graphene oxide.

4. The charger according to claim 3 , wherein the graphene oxide comprises multi-layer graphene oxide.

5. 2. The charger according to claim 1, wherein the graphene accounts for 0.5 to 7 vol % of the coating layer.

6. The charger according to claim 1 , wherein the particle diameter of the graphene is equal to or smaller than the thickness of the coating layer.

7. 2. The charger according to claim 1, wherein the coating layer has a thickness of 1.5 [mu]m or more.

8. 8. The charger according to claim 7, wherein the coating layer has a thickness of 10 [mu]m or less.

9. 2. The charger according to claim 1, wherein the core material is made of tungsten.

10. Drum frame and a photosensitive drum supported by the drum frame and rotating around a rotation axis; A charger that charges the photosensitive drum, a discharge wire extending along the rotation axis, the discharge wire having a conductive core material and a coating layer coating the core material and including silver and graphene; a grid electrode disposed between the photosensitive drum and the discharge wire; a charger including a pair of shields electrically connected to the grid electrode and disposed with the discharge wire interposed therebetween; A drum cartridge comprising:

11. a cleaner for cleaning foreign matter adhering to the discharge wire, the cleaner being slidable between one end and the other end of the discharge wire; 11. The drum cartridge according to claim 10, further comprising a rail extending in the first direction and supporting the cleaner so that the cleaner can slide.

12. A main body housing; A drum cartridge detachably attached to the main body housing, Drum frame and a photosensitive drum supported by the drum frame and rotating around a rotation axis; A charger that charges the photosensitive drum, a discharge wire extending along the rotation axis, the discharge wire having a conductive core material and a coating layer coating the core material and including silver and graphene; a grid electrode disposed between the photosensitive drum and the discharge wire; a drum cartridge including a charger having a pair of shields electrically connected to the grid electrode and disposed on either side of the discharge wire; a voltage application circuit that applies a voltage to the discharge wire.

13. 13. The image forming apparatus according to claim 12, wherein the voltage application circuit applies a positive voltage to the discharge wire.

14. 13. The image forming apparatus according to claim 12, further comprising an exhaust fan that exhausts air from inside the main body housing to the outside of the main body housing.

15. 13. The image forming apparatus according to claim 12, further comprising an intake fan that draws air from the outside of the main body housing into the main body housing.

Images