Charging device, process cartridge and electro-photographic image formation apparatus

Abstract

To provide a charging device that can stably charge a charging object over a long period of time.SOLUTION: A charging device includes a plasma actuator. The plasma actuator includes: a dielectric body; a first electrode which is provided on the first surface of the dielectric body; and a second electrode which is arranged with the dielectric body held between the first electrode and itself. The plasma actuator applies the AC voltage between the first electrode and the second electrode to generate an inductive flow from the edge of the first electrode along an exposed part that is not covered by the first electrode of the first surface of the dielectric body. The plasma actuator is arranged so that the inductive flow is supplied directly to the surface of the charging object, and applies the DC voltage between the first electrode and the charging object.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In electrophotographic image forming apparatuses, a contact charging method using a charging roller is widely adopted as a method for charging a photosensitive drum. In the contact charging method, developer remaining on the photosensitive drum (hereinafter also referred to as transfer residual toner) may adhere to the surface of the charging roller, preventing stable discharge from the charging roller. In order to solve such problems of the contact charging method, a non-contact charging method has been proposed in which the surface of the electrophotographic photosensitive member is brought into contact with the electrophotographic photosensitive member without contacting a member such as a charging roller with the electrophotographic photosensitive member. Patent Document 1 discloses a charging device using a solid discharge element having an induction electrode and a discharge electrode sandwiching a dielectric. In this charging device, the induction electrode is provided at a position away from the straight line connecting the center of the discharge electrode and the closest position to the non-charged surface. In other words, a charging device is disclosed that can perform uniform charging by arranging the induction electrode and the discharge electrode without overlapping and using a solid discharge element that suppresses dielectric breakdown. Patent Document 2 discloses a charging device using a non-contact charging roller. Furthermore, Patent Document 3 discloses a charged body device equipped with a scorotron type charger. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 7-084435 [Patent Document 2] JP 2006-039288 A [Patent Document 3] JP 2003-140438 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present inventors have attempted to perform a durability evaluation equivalent to long-term use by using the charging devices according to Patent Documents 1 to 3 in an electrophotographic process, which has been made longer-lasting in recent years. As a result, even in a non-contact manner, dirt accumulates on the charging member, causing uneven discharge, which may result in uneven charging of the charged body (for example, an electrophotographic photosensitive body such as a photosensitive drum).

[0005] At least one aspect of the present disclosure is directed to providing a charging device capable of stably charging a charged body for a long period of time. At least one aspect of the present disclosure is directed to providing a process cartridge that contributes to forming high-quality electrophotographic images for a long period of time. At least one aspect of the present disclosure is directed to providing an electrophotographic image forming apparatus that can form high-quality electrophotographic images for a long period of time. [Means for solving the problem]

[0006] According to at least one aspect of the present disclosure, there is provided a charging device for charging a body to be charged, comprising: A plasma actuator is provided. The plasma actuator comprises: A dielectric material; a first electrode provided on a first surface of the dielectric; a second electrode disposed between the first electrode and the dielectric, The plasma actuator generates an induced flow from an edge of the first electrode along an exposed portion of the first surface of the dielectric material that is not covered by the first electrode by applying an AC voltage between the first electrode and the second electrode; the plasma actuator is disposed so that the induced flow is directly supplied to a surface of the body to be charged; A charging device is provided that applies a DC voltage between the first electrode and the member to be charged.

[0007] According to at least one aspect of the present disclosure, there is provided a process cartridge detachably mountable to a main body of an electrophotographic image forming apparatus, the process cartridge including the charging device described above. According to at least one aspect of the present disclosure, there is provided an electrophotographic image forming apparatus including the above-described charging device. Effect of the Invention

[0008] According to at least one aspect of the present disclosure, a charging device capable of stably charging a charged body over a long period of time can be obtained. According to at least one aspect of the present disclosure, a process cartridge contributing to high-quality electrophotographic image formation over a long period of time can be obtained. Furthermore, according to at least one aspect of the present disclosure, an electrophotographic image forming apparatus capable of forming high-quality electrophotographic images over a long period of time can be obtained. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram illustrating a configuration of a charging device according to at least one embodiment of the present disclosure. [Diagram 2] FIG. 2 is a schematic diagram showing an example of the configuration of a plasma actuator and a charging device. [Diagram 3] FIG. 1 is an explanatory diagram of static electricity removal from dirt using an induced flow. [Figure 4] FIG. 4 is an explanatory diagram of overlap between a first electrode and a second electrode. [Diagram 5] FIG. 13 is an explanatory diagram of suppression of electric field concentration by overlapping. [Figure 6] FIG. 4 is an explanatory diagram of the uneven shape of the edge of the first electrode. [Figure 7] FIG. 4 is an explanatory diagram regarding the arrangement of a plasma actuator. [Figure 8] FIG. 4 is a schematic diagram showing the positional relationship between a photosensitive drum, a dielectric body, and a first electrode. [Figure 9] FIG. 1 is a schematic diagram showing an example of the configuration of a plasma actuator. [Figure 10] FIG. 2 is a schematic configuration diagram of a process cartridge using the charging device according to the present disclosure. [Figure 11] 1 is a schematic configuration diagram of an electrophotographic image forming apparatus using a charging device according to the present disclosure. [Figure 12] An explanatory diagram of how wind speed is measured using PIV. [Figure 13] FIG. 4 is an explanatory diagram regarding the arrangement of a plasma actuator. [Figure 14] FIG. 4 is an explanatory diagram regarding the arrangement of a scorotron charger. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, with reference to the drawings, specific examples of the embodiments for carrying out this disclosure will be described. However, the dimensions, materials, shapes, and relative positions of the components described in these embodiments should be appropriately changed depending on the configuration of the member to which the disclosure is applied and various conditions. In other words, it is not intended to limit the scope of this disclosure to the following embodiments. In the present disclosure, the description of a numerical range such as "XX or more and YY or less" or "XX to YY" means a numerical range including the lower and upper limits, which are the endpoints, unless otherwise specified. When a numerical range is described in stages, the upper and lower limits of each numerical range can be combined in any combination.

[0011] After extensive research, the inventors have discovered that by using a plasma actuator as a charging member and positioning the plasma actuator so that the induced flow generated by discharge is supplied directly to the surface of the body to be charged (for example, an electrophotographic photosensitive member such as a photosensitive drum), it is possible to suppress the flying of dirt and inhibit the adhesion of dirt to the charging member. In the present disclosure, the term "contamination" refers to, for example, when the charged body is an electrophotographic photosensitive body, during a transfer process in an electrophotographic image forming process, when toner is transferred to paper or an intermediate transfer body, the entire amount of toner is not transferred and remains on the surface of the electrophotographic photosensitive body, and is directed toward a charging member. It should be noted that, in the case where the electrophotographic image forming apparatus has a cleaning member, the contaminants include substances that pass through the cleaning member and fly toward and adhere to the charging member. Examples of contaminants include toner and external additives.

[0012] As a result of investigations, the present inventors speculate that the reason why image defects occur due to the adhesion of dirt to the charging members according to Patent Documents 1 to 3 in the electrophotographic process with a long life is as follows. The present inventors believe that the reason why the charging member not in contact with the electrophotographic photoreceptor according to Patent Documents 1 to 3 is soiled is that the dirt flies toward the charging member due to the electrostatic force between the charging member and the dirt. The dirt such as toner and external additives needs to have a certain charge in order to be properly transferred to the electrophotographic photoreceptor in the development process. Therefore, they often have insulating properties. The toner and external additives that are not transferred to the paper or intermediate transfer member and remain on the electrophotographic photoreceptor are affected by friction and the like before reaching the charging member, so that they do not have a charge of polarity that is largely biased toward positive or negative in the developing container, but have a certain distribution of positive and negative charges. On the other hand, the charging member is a member that applies a voltage to the electrophotographic photosensitive member to generate discharge and generates a potential difference between the charging member and the surface of the electrophotographic photosensitive member, and therefore, since dirt having a polarity opposite to that of the charging bias flies toward the charging member side due to electrostatic attraction, it is difficult to prevent the dirt from adhering to the electrophotographic photosensitive member.

[0013] In addition, once dirt adheres to the charging member, it adheres strongly due to electrostatic force, and it is difficult to return the dirt to the electrophotographic photoreceptor. Therefore, it is generally known that the charging member may have a cleaning member. However, providing a cleaning member for the charging member in the electrophotographic image forming apparatus is not preferable in terms of further miniaturizing the electrophotographic image forming apparatus. Therefore, the present inventors recognized that in a non-contact charging process, in order to reduce the adhesion of dirt to the charging member, it is effective to prevent the dirt from flying to the charging member.

[0014] With this in mind, the inventors conducted research and discovered that with a charging device having the configuration according to the present disclosure, dirt is less likely to adhere to the discharge portion of the charging member even with long-term use, and the charged body can be charged stably for a longer period of time.

[0015] That is, a charging device according to at least one embodiment of the present disclosure includes a plasma actuator. The plasma actuator includes a dielectric, a first electrode provided on a first surface of the dielectric, and a second electrode arranged to sandwich the dielectric with respect to the first electrode. The plasma actuator generates an induced flow from an edge of the first electrode along an exposed portion of the first surface of the dielectric that is not covered by the first electrode by applying an AC voltage between the first electrode and the second electrode. The plasma actuator is arranged so that the induced flow is directly supplied to the surface of the charged body. The charging device applies a DC voltage between the first electrode and the charged body.

[0016] The charging device of the present disclosure will be described in detail below. <Charging device and plasma actuator> 1 shows a charging device 101 that charges an electrophotographic photosensitive member 104 as a member to be charged according to at least one embodiment of the present disclosure. The charging device 101 includes a plasma actuator 102. In FIG. 1, reference numeral 105 denotes dirt (residual toner after transfer) remaining on a surface 104-1 of a photosensitive drum as an electrophotographic photosensitive member, and reference numeral 106 denotes an induced flow. FIG. 2 shows a cross-sectional structure of at least one embodiment of the plasma actuator 102 and at least one embodiment of the charging device. In FIG. 2, plasma actuator 102 includes dielectric body 201 and first electrode 203 provided on one surface of dielectric body 201 (hereinafter also referred to as the "first surface"). The plasma actuator 102 includes a second electrode 205 sandwiching the dielectric 201 with respect to the first electrode 203. That is, the second electrode 205 is provided with the dielectric 201 sandwiched with respect to the first electrode 203. Here, the second electrode 205 is preferably arranged diagonally opposite the first electrode 203 with the dielectric 201 sandwiched therebetween. By arranging the first electrode 203 and the second electrode 205 with the dielectric 201 sandwiched therebetween diagonally, the induced flow 106 can be more reliably supplied in a desired direction. As a result, it is possible to further increase the charging efficiency of the charged body. The embodiment in which the second electrode 205 is provided with the dielectric 201 sandwiched with respect to the first electrode 203 includes an embodiment as shown in FIG. 2 and an embodiment as shown in FIG. 9B. The embodiment as shown in FIG. 9B will be described later.

[0017] The plasma actuator 102 may have a configuration in which a second electrode 205 is provided on a surface (hereinafter also referred to as a "second surface") opposite to the first surface. The plasma actuator 102 is a so-called Dielectric Barrier Discharge (DBD) plasma actuator (hereinafter sometimes simply referred to as "DBD-PA"). In FIG. 2, reference numeral 206 denotes a dielectric substrate, reference numeral 207 denotes an AC power source, reference numeral 208 denotes a DC power source, and reference numeral 209 denotes an edge of the second electrode. In the plasma actuator 102, the first electrode 203 and the second electrode 205 are arranged, for example, diagonally opposite each other with the dielectric 201 in between. By applying an AC voltage between these electrodes (between both electrodes), plasma 202 is generated from the first electrode 203 toward the second electrode 205. Then, an induced flow 106, which is a jet-like flow by the plasma (surface plasma) 202, is induced from the edge 204 of the first electrode 203 along the exposed portion (portion not covered by the first electrode) 201-1 of the first surface of the dielectric 201.

[0018] The plasma actuator 102 is disposed so that an induced flow 106 is directly supplied to a surface 104-1 of an electrophotographic photosensitive member serving as a member to be charged. That is, in this embodiment, the induced flow 106 having electric charge from the plasma actuator 102 is directly supplied to the surface of the electrophotographic photoreceptor.

[0019] Positively charged particles, negatively charged particles, and electrically neutral particles are present in the induced flow 106, which are generated by ionization caused by the discharge of the plasma actuator. In the charging device, a DC voltage is applied between the first electrode 203 and the body to be charged 104. For example, a positive or negative DC voltage may be applied between the first electrode 203 and the body to be charged 104. By applying a positive DC voltage or a negative DC voltage between the first electrode 203 and the photosensitive drum 104 as a charged body, an electric field is formed, and among the positive charges and negative charges generated by ionization due to the discharge of the plasma actuator, charges of the same polarity as the DC voltage can be preferentially supplied to the photosensitive drum surface 104-1. In other words, by superimposing the discharge of the plasma actuator by the AC voltage and the DC voltage, the charge supplied to the photosensitive drum 104 can be controlled, the photosensitive drum surface 104-1 can be charged, and dirt (not shown) can be charged or neutralized. Furthermore, the higher the applied DC voltage, the more charges of the same polarity as the applied voltage are supplied to the photosensitive drum surface 104-1 and the dirt, improving the charging and neutralization performance.

[0020] As shown in Fig. 3, when the charged body is a photosensitive drum, dirt 105 having a charge of the opposite polarity to the polarity of the charging bias is transported by the transfer roller as the photosensitive drum 104 rotates, and receives an induced flow 106 containing a charge of the same polarity as the charging bias. As a result, dirt 105-1 that has received the induced flow can be neutralized or charged to the same polarity as the photosensitive drum 104 by the charge of the same polarity as the charging bias contained in the induced flow. By charging the dirt with the same polarity as that of the plasma actuator 104, the electrostatic attraction between the dirt and the plasma actuator 102 can be reduced, and the dirt can be prevented from flying toward the charged member. In addition, the induced flow 106 flows in a direction that presses the dirt against the photosensitive drum surface, so that the dirt can be physically prevented from flying, which also effectively prevents the dirt from adhering to the charging device. As a result, the charging device according to the present disclosure can suppress the flying of dirt onto the charging member, which is unavoidable in non-contact charging, and can suppress the adhesion of dirt to the discharge portion of the charging member, thereby enabling high-quality image formation for a long period of time.

[0021] The induced flow 106 flows in the direction of a jet-like flow caused by the surface plasma from the edge 204 of the first electrode 203 along the exposed portion 201-1 of the first surface of the dielectric 201, that is, in the direction from the edge 204 of the first electrode 203 along the exposed portion 201-1 of the first surface of the dielectric. This induced flow is a gas flow having a speed of about several m / s to several tens of m / s.

[0022] The velocity of the induced flow at a position 1.0 mm away from the tip of the plasma actuator in the supply direction of the induced flow, measured by particle image velocimetry, is preferably 0.10 to 1.00 m / sec, more preferably 0.15 to 1.00 m / sec, and even more preferably 0.20 to 0.40 m / sec. The position 1.0 mm away from the tip is a position 1.0 mm away from the tip 701a on the second electrode side in the supply direction of the induced flow, on an extension line (line 700) in the direction along the exposed portion 201-1 of the first surface of the dielectric from the edge of the first electrode of the plasma actuator in FIG. 7A. When the velocity is in the above range, a more sufficient induced flow can be supplied to charge the electrophotographic photosensitive member and to charge and de-electrify dirt.

[0023] In addition, whether or not the transfer residual toner and other contaminants have been discharged or charged to the same polarity as the photosensitive drum can be known by, for example, measuring the surface potential of the transfer residual toner group on the photosensitive drum or measuring the charge amount. Specifically, for example, by using a means for quantifying the charge amount distribution of the transfer residual toner group, which will be described later, it is possible to know that the transfer residual toner has been discharged. More specifically, for example, a method can be used to confirm the proportion of toner particles that have changed to the polarity opposite to polarity A after irradiation of the induced flow 106 on the transfer residual toner among toner particles that have the same polarity as the polarity of the voltage applied to the transfer member (hereinafter also referred to as polarity A) before irradiation of the induced flow 106 on the transfer residual toner.

[0024] The amount of residual toner when checking the change in polarity can be determined by measuring the change in charge polarity of the residual toner caused by the plasma actuator under transfer process conditions under which the fog value obtained by the following measurement method is 5%, for example. Specifically, the fog value can be measured, for example, as follows. First, while a solid black image is being printed, the printing operation is stopped, and the residual toner adhering between the contact portion of the transfer member on the photosensitive drum surface and the contact portion of the charging member is peeled off with tape (product name: CT18, manufactured by Nichiban Co., Ltd.). Next, the reflectance is measured with a reflection densitometer (product name: TC-6DS / A, manufactured by Tokyo Denshoku Co., Ltd.), and the reflectance of the tape is used as a reference. The amount of decrease (%) in reflectance when the light is turned on is measured and this is taken as the fog value.

[0025] Furthermore, for the transfer residual toner group under the transfer process conditions that result in the above fog value, the number ratio of the toner group that has changed from the same polarity as the polarity of the voltage applied to the transfer member to the opposite polarity before and after irradiation with the plasma actuator is measured. The number ratio is based on the number of toner particles that have the same polarity as the polarity of the voltage applied to the transfer member before irradiation. It is preferable that the change rate Δ after irradiation described below is 50% or more. It is more preferable that the change rate Δ is 80% to 100%. Within this range, the electrostatic attraction with the photosensitive drum can be suppressed, and the cleaning performance can be improved.

[0026] <Electrode arrangement> FIG. 4 shows a first electrode 203 and a second electrode 204 of a plasma actuator, which is a charged member. 4 is an explanatory diagram of the overlap of FIG. 5. In FIG. 4, the first electrode 203 and the second electrode 205 are arranged diagonally opposite each other with the dielectric 201 in between. Here, when the plasma actuator is seen through from the first surface side, it is preferable that at least a part of the first electrode and the second electrode have an overlapping portion. In other words, in the first electrode 203 and the second electrode 205 arranged diagonally opposite each other with the dielectric 201 in between, it is preferable that when the dielectric is seen through from the surface side of the first electrode, the edge of the first electrode is present in the formation portion of the second electrode. In other words, it is preferable that the first electrode and the second electrode are provided so as to overlap with the dielectric in between. By overlapping the first and second electrodes with a dielectric between them, the distance between the electrodes is minimized and the electric field strength is maximized, which allows a strong induced flow to be generated. In this case, it is preferable to prevent dielectric breakdown when a voltage is applied in the portion where the first and second electrodes overlap with the dielectric between them.

[0027] Furthermore, if the edge of the second electrode is exposed, plasma may also be generated from the edge of the second electrode, generating an induced flow in the opposite direction to the induced flow 106 originating from the first electrode. It is preferable not to blow the induced flow to an area other than the surface of the photosensitive drum. Therefore, it is preferable not to generate an induced flow originating from the second electrode. Therefore, it is preferable that the second electrode 205 is covered with a dielectric such as a dielectric substrate 206 as shown in Figs. 2 and 9, or embedded in a dielectric 201 to prevent plasma generation from the edge of the second electrode.

[0028] From the viewpoint of uniformly discharging and charging dirt, it is preferable that the induced flow is generated from one side of the first electrode when the plasma actuator is viewed from the first electrode side. For example, it is preferable that the induced flow is generated in one direction toward the photoconductor surface from one side of the first electrode facing the surface of the photoconductor. The other side of the first electrode may be covered with a dielectric material so that the induced flow is not generated from the other sides of the first electrode other than the one side.

[0029] <Overlap> FIG. 4 is an explanatory diagram (cross-sectional view) of the overlap between the first electrode 203 and the second electrode 205 of the plasma actuator. The length of the overlapping portion between the edge of the first electrode and the edge of the second electrode is defined as length A, and the overlapping length is defined as positive. That is, when the plasma actuator is seen through from the first surface side, at least a part of the first electrode and the second electrode have an overlapping portion, and the length A between the edge of the first electrode and the edge of the second electrode forming the overlapping portion is preferably 0 to 1200 μm, more preferably 80 to 1000 μm, even more preferably 100 to 1000 μm, and even more preferably 400 to 1000 μm. By overlapping the first electrode and the second electrode, the convex shape of the electrode edges (described below) can be used to suppress electric field concentration, thereby making it possible to suppress streaks on the image caused by uneven discharge and uneven dirt adhesion caused by uneven induced flow.

[0030] The convex shape of the edge of the electrode will be explained. FIGS. 5A to 5D show cross-sectional views and overhead views of the plasma actuator. When the first electrode and the second electrode are separated and do not overlap as in FIG. 5A, and the edge of the first electrode has a convex portion, as shown in FIG. 5C, the electric field concentrates at the apex of the convex portion of the edge of the first electrode, and unevenness in the discharge and the strength of the induced flow may occur in the longitudinal direction (501a). On the other hand, when the first electrode and the second electrode overlap as in FIG. 5B, the electric field strength formed between the two electrodes is governed by the thickness of the dielectric layer. As a result, as shown in FIG. 5D, unevenness in the discharge in the longitudinal direction can be alleviated (501b). Furthermore, since local concentration of the electric field on the convex portion can be suppressed, insulation breakdown can be suppressed even when the distance between the two electrodes is short. When the electrodes have a convex shape, the length A is determined by the distance between the edge of the first electrode closest to the second electrode and the edge of the second electrode closest to the first electrode. This is the length between the first electrode side.

[0031] <Electrode thickness> The thickness of the electrodes, both the first electrode and the second electrode, is not particularly limited, but can be 10 μm to 1000 μm. If it is 10 μm or more, the resistance is low and plasma is easily generated. If it is 1000 μm or less, electric field concentration is likely to occur, making plasma easily generated.

[0032] <Electrode material> The material constituting the first electrode and the second electrode is not particularly limited as long as it is a material with good electrical conductivity. For example, metals such as copper, aluminum, stainless steel, gold, silver, platinum, and the like, and those plated or vapor-deposited thereon, conductive carbon materials such as carbon black, graphite, and carbon nanotubes, and composite materials in which these are mixed with resins, etc. can be used. The material constituting the first electrode and the material constituting the second electrode may be the same or different.

[0033] Among these, from the viewpoint of avoiding electrode corrosion and achieving uniform discharge, the material constituting the first electrode is preferably aluminum, stainless steel, or silver, and for the same reason, the material constituting the second electrode is preferably aluminum, stainless steel, or silver.

[0034] <Electrode shape> The first electrode and the second electrode may have any shape, such as a flat plate, a wire, or a needle, without any particular limitation. The first electrode is preferably shaped like a flat plate. The second electrode is preferably shaped like a flat plate. When at least one of the first electrode and the second electrode is shaped like a flat plate, the aspect ratio of the flat plate (length of long side / length of short side) is preferably 2 or more.

[0035] 6A to 6C are schematic diagrams showing non-limiting examples of electrode shapes. The edge of the first electrode and the edge of the second electrode are preferably linear or approximately linear. The term "approximately linear" does not necessarily mean an exact straight line, but may be linear enough to uniformly discharge the material and suppress electric field concentration, and some irregularities may be tolerated. Specifically, as shown in FIG. 6A, a linear shape without irregularities is preferable. The linear shape of the electrode edges allows uniform discharge and uniform charge supply in the longitudinal direction. If the edge has a convex portion, the discharge becomes non-uniform in the longitudinal direction, and the surface potential on the photosensitive drum becomes non-uniform. Therefore, streaky images are likely to be obtained. Therefore, the edge of the first electrode may have a convex portion, and the edge of the second electrode may have a convex portion, but the shape of the convex portion is preferably such that image defects do not occur even if the discharge becomes non-uniform. The shape of the edge may have at least one convex portion (FIG. 6C). From the viewpoint of strengthening the induced flow, it is preferable that the edge has many convex portions, and it is preferable that the convex portions are arranged regularly. In addition, the edge may have discontinuous convex portions, but it is preferable that the convex portions are arranged continuously (FIG. 6B).

[0036] The maximum height of the convex portion is not particularly limited, but is preferably 100 μm or less, more preferably 70 μm or less, even more preferably 60 μm or less, and particularly preferably 40 μm or less. The lower limit is not particularly limited, but may be 1 μm or more, may be 5 μm or more, or may be 10 μm or more. Preferred examples include 1 to 100 μm, 1 to 70 μm, 5 to 60 μm, and 10 to 40 μm. The height of the convex portion can also be referred to as the length in the length A direction. The width of the convex portion is not particularly limited, but is preferably 110 μm or less, and more preferably 95 μm or less. It is more preferable that the width is 1 μm or less, further preferably 60 μm, and particularly preferably 40 μm or less. The lower limit is not particularly limited, but may be 1 μm or more, 5 μm or more, or 10 μm or more. Preferred examples include 1 to 110 μm, 1 to 95 μm, 5 to 60 μm, and 10 to 40 μm. The width of the convex portion can also be said to be the length in a direction perpendicular to the length A direction and along the dielectric surface.

[0037] In order to reduce the height and width of the maximum convex portion to the above range, the edge of the first electrode may be formed into a shape with as few projections and recesses as possible. For example, when forming an electrode while masking, such as by liquid application such as screen printing or metal deposition, a method of printing using a masking member whose edge shape is polished or cut with a sharp blade so that there are no projections and recesses in the longitudinal direction on the dielectric surface on which the electrode is formed can be mentioned. In addition, a metal sheet whose edge shape is polished or cut with a sharp blade so that there are no projections and recesses in the longitudinal direction, or a razor can be used.

[0038] The shape of the convex portion is not particularly limited, and examples thereof include a sawtooth shape as shown in FIG. 6B, a triangular shape, an approximately triangular shape, an arc shape, an elliptical arc shape, an approximately arc shape, a sinusoidal shape, a trapezoidal shape, an approximately trapezoidal shape, a rectangular shape, or an approximately rectangular shape. As described above, the electric field concentration caused by the convex shape of the edge of the first electrode can be reduced by controlling the amount of overlap between the first electrode and the second electrode.

[0039] The method for forming the first electrode and the second electrode is not particularly limited, and examples of the method include attaching a metal plate to a dielectric, vapor deposition, screen printing, etc. In order to generate a stable discharge and uniformly supply electric charge to the electrophotographic photoreceptor over its length, it is preferable to use a conductive tape with a regular edge shape or a metal plate with a polished tip like a razor as the electrode. Methods for measuring the shape of the electrode include observing the plasma actuator from the first surface side with an optical microscope, laser microscope, electron microscope, digital camera, visual inspection, a magnifying glass, etc. To measure the shape more accurately, it is preferable to use a laser microscope or optical microscope that has a dimensional measurement function. Specifically, the height and width of the protrusions on the edge of the first electrode and the edge of the second electrode can be calculated by the following procedure.

[0040] The height and width of the convex portion can be obtained, for example, as follows. First, the step formed by the first electrode and the dielectric layer is photographed using an optical microscope, a laser microscope, a confocal microscope, or the like. Specifically, a laser microscope (product name: Color 3D Laser Microscope VK-8700, manufactured by Keyence Corporation) is used to observe and confirm the step in the longitudinal direction in a field of view of 1000 μm vertically and 1000 μm horizontally. A two-dimensional image is obtained by scanning the laser on the XY plane within the field of view. Data is obtained, and then scanning is repeated every 0.2 μm in the Z direction and in the height direction to obtain three-dimensional image data. The three-dimensional data is acquired over the entire longitudinal area of ​​the first electrode, and the height and width as shown in Fig. 6B can be calculated for the obtained three-dimensional image group using the length measurement function of the analysis software attached to the laser microscope. Note that, since the height of a protrusion is more sensitive to the electric field intensity than its width, the one with the greatest height among the measured protrusions was taken as the maximum protrusion.

[0041] <Applied voltage> There are no particular limitations on the AC voltage applied between the first electrode 203 and the second electrode 205 of the plasma actuator as long as it is possible to generate plasma in the plasma actuator. In a preferred embodiment, the voltage is a pulse voltage. Furthermore, the amplitude of the voltage can be set to 1 kV to 100 kV, more preferably 1 kV to 10 kV. Furthermore, the frequency of the voltage can be set to preferably 1 kHz or higher, more preferably 5 kHz to 20 kHz. The waveform of the AC voltage is not particularly limited, and a sine wave, a square wave, a triangular wave, etc. can be used, but from the viewpoint of the speed of the voltage rise, a square wave is preferable. The duty ratio of the voltage can be appropriately selected, but it is preferable that the voltage rises quickly. Preferably, the voltage is applied so that the rise time of the voltage from the bottom to the peak of the amplitude of the wavelength is 4,000,000 V / sec or more. The value (voltage / film thickness) obtained by dividing the amplitude of the voltage applied between the first electrode 203 and the second electrode 205 by the film thickness of the dielectric film 201 is preferably 10 kV / mm or more.

[0042] <DC voltage> By applying a DC voltage between the first electrode 203 of the plasma actuator and the electrophotographic photosensitive member 104 as the member to be charged, an induced flow can be supplied having a charge whose polarity is biased toward a component of opposite polarity relative to the charging polarity of the dirt. The DC voltage is not particularly limited as long as it is possible to preferentially supply charges of the same polarity as the DC voltage among the charges contained in the induced current 106 to the surface 104-1 of the body to be charged. The DC voltage can be appropriately set to adjust the charge amount of the electrophotographic photosensitive member 104 as the body to be charged and the dirt 105 remaining on the surface of the electrophotographic photosensitive member. From the viewpoint of controlling the charge amount of the photosensitive drum and the dirt, the DC voltage is preferably set to +200V to +1500V or -1500V to -200V. Also, it is more preferable to set it to +400V to +1200V or -1200V to -400V. Furthermore, the higher the applied DC voltage, the stronger the electric field formed between the first electrode and the electrophotographic photosensitive member as the member to be charged, and therefore more charges are supplied to the surface of the electrophotographic photosensitive member. This improves the charging performance of the electrophotographic photosensitive member and the charging / de-electrification performance of dirt remaining on the surface of the electrophotographic photosensitive member. The DC voltage increases the flow rate of the induced flow, which improves the effect of physically suppressing the flying of dirt. In other words, the higher the applied DC voltage, the easier it becomes to form high-quality images over a long period of time.

[0043] By applying a DC voltage, the plasma actuator can also be used as a charging device. That is, the charging device includes at least a plasma actuator. Then, a DC voltage is applied between a first electrode of the plasma actuator and a body to be charged. Since such a charging device can be used as a charging device for an electrophotographic photosensitive body in an electrophotographic process, a charging device such as a contact-type charging roller can be omitted.

[0044] <Dielectric> The dielectric is not particularly limited as long as it is a material having high electrical insulation. For example, resins such as polyurethane resin, polyimide, polyester, fluororesin, silicone resin, acrylic resin, and phenol resin, glass, ceramics, and composite materials in which these are mixed with resins, etc. can be used. The dielectric is preferably polyurethane resin, silicone resin, polyimide, or glass. For example, it is preferable to use a material such as silicone resin that has a high volume resistivity, a small amount of unevenness in the chemical structure and grain boundaries, a small charge bias, and a low dielectric constant, since it can further suppress the dielectric breakdown between the first electrode and the second electrode.

[0045] In addition, in the plasma actuator, the shorter the shortest distance between the first electrode and the second electrode, the easier it is to generate plasma. Therefore, the thickness of the dielectric is not particularly limited as long as it does not cause electrical breakdown, but the thinner the better. For example, it can be 10 μm to 1000 μm, and more preferably 10 μm to 200 μm. The thickness of the dielectric does not have to be uniform. For example, the thickness of the first end side of the dielectric may be 10 μm to 1000 μm, and the thickness of the second end side of the dielectric may be 1 to 5 mm. The thickness of the first end side of the dielectric is preferably 10 μm to 200 μm. There are no particular limitations on the shape of the dielectric, as long as it can be used as the dielectric of the plasma actuator. Although not limited thereto, examples thereof include a sheet shape and a flat plate shape.

[0046] <Arrangement of plasma actuator and photosensitive drum> A plasma actuator 102 that generates an induced flow is disposed so that an induced flow 106 is directly supplied to a surface 104-1 of an electrophotographic photoreceptor in order to increase the charging efficiency of the surface area of ​​a member to be charged. For example, as shown in FIG. 7, the surface 104-1 of the body to be charged may be included on an extension line extending from the edge of the first electrode of the plasma actuator 102 along the exposed portion of the first surface of the dielectric. When the charging and decharging of dirt by the induced flow 106 of the plasma actuator 102 is insufficient and the flying of dirt cannot be suppressed by the physical force of the induced flow, the dirt may fly toward the first electrode 203 of the plasma actuator 102. Therefore, in a configuration in which the charging device has a substrate and the plasma actuator is disposed on the surface of the substrate, it is preferable to dispose the substrate between the plasma actuator and the surface of the body to be charged, so that the dirt is less likely to fly to the first electrode. For example, as shown in Figs. 7A and 7C, it is preferable that the substrate 103 is disposed between the first electrode 203 and the electrophotographic photoreceptor 104 as the body to be charged. It is also preferable that the substrate 103 is disposed between the plasma actuator 102 and the electrophotographic photoreceptor 104 as the body to be charged. The substrate will be described later.

[0047] Specifically, when the body to be charged is an electrophotographic photosensitive member, when a straight line is drawn from the center of the rotation axis of the electrophotographic photosensitive member to the center of the first electrode as shown in FIG. 8, it is preferable that the straight line intersects with the surface of the electrophotographic photosensitive member, the dielectric material, and the first electrode in that order. On the other hand, as shown in Figs. 7B and 7D, a first electrode 203 may be disposed between the substrate 103 and the electrophotographic photoreceptor 104, and a plasma actuator 102 may be disposed between the substrate 103 and the electrophotographic photoreceptor 104. With such an arrangement, the airflow in the housing of the electrophotographic device is blocked by the substrate, so that it is possible to suppress the influence of the airflow on the induced flow generated by the plasma actuator. As a result, the induced flow generated by the plasma actuator is allowed to reach the photosensitive drum surface without being weakened by the airflow, so that dirt can be charged or neutralized more effectively.

[0048] <Distance between plasma actuator and photosensitive drum> Furthermore, in order to more effectively supply the charge in the induced flow to the surface of the body to be charged, it is preferable to make the distance between the plasma actuator and the body to be charged short to the extent that the discharge from the first electrode of the plasma actuator does not reach the body to be charged directly. As an example, in Fig. 7A, it is preferable to arrange them so that the distance 701 between the tip of the plasma actuator 102 on the second electrode side and a point 701b where an extension line (line 700) extending from the edge of the first electrode of the plasma actuator in the direction along the exposed portion 201-1 of the first surface of the dielectric intersects with the surface of the electrophotographic photosensitive body as the body to be charged is 1 mm to 20 mm (more preferably 1 mm to 10 mm, and even more preferably 1 mm to 5 mm).

[0049] <Orientation of plasma actuator relative to photosensitive drum rotation direction> In the charging device, the outflow direction of the induced flow of the plasma actuator is not particularly limited as long as the induced flow is directly supplied to the surface of the body to be charged. In the case where the member to be charged is an electrophotographic photosensitive member, a preferred configuration for further exerting the effects of the present disclosure will be described below.

[0050] 7, an extension line 700 extending from the edge of the first electrode along the exposed portion of the first surface of the dielectric intersects with the surface of the electrophotographic photosensitive member at point 701b. A velocity vector in the rotational direction of the electrophotographic photosensitive member on the tangent to the surface of the electrophotographic photosensitive member at point 701b is defined as a tangent vector 702. When the outflow direction vector 106a of the induced flow 106 supplied from the plasma actuator 102 is decomposed, it is preferable that the outflow direction vector has a directional component 106x that is parallel to and opposite to the tangent vector 702 (hereinafter, an arrangement of plasma actuators in which the directional component 106x is parallel to and opposite the tangent vector 702 will be referred to as counter, and an arrangement of plasma actuators in which the directional component 106x is parallel to and opposite the tangent vector 702 will be referred to as with). When the induced flow flows in the above-mentioned direction, the relative speed of the induced flow with respect to the electrophotographic photosensitive member is increased, and a stronger wind can be applied to the dirt remaining on the surface of the electrophotographic photosensitive member, so that the dirt can be rolled on the photosensitive drum surface, the electrophotographic photosensitive member can be charged more effectively, and the dirt can be charged or de-electrified more effectively.

[0051] Also, when the outflow direction vector 106a is decomposed, the outflow direction vector 106a may have a directional component parallel to and directed in the same direction as the tangent vector 702 (the With described above). In such a case, the induced flow is less likely to be disturbed by the rotation of the electrophotographic photosensitive member, and the induced flow can be kept in contact with the photosensitive drum surface and dirt for a longer period of time. As a result, the electrophotographic photosensitive member can be charged more effectively, and the dirt can be discharged and charged more effectively.

[0052] <Angle> Since the transfer residual toner, which is an example of dirt, has a shape close to a perfect sphere, it has been found that there is a suitable angle for more effectively supplying an induced flow to the gap between the surface of the electrophotographic photoreceptor as a charged body and the dirt. By supplying an induced flow to the gap between the surface of the electrophotographic photoreceptor and the dirt, the dirt on the surface of the electrophotographic photoreceptor is rolled, making it easier to charge or de-electrify the entire surface of the dirt. In addition, the surface of the electrophotographic photoreceptor covered with dirt is also more easily charged. That is, the narrow angle θ is defined as the narrow angle that an extension line extending from the edge of the first electrode of the plasma actuator in a direction along exposed portion 201-1 of the first surface of the dielectric makes with respect to tangent vector 702. The narrow angle θ is preferably 0° to 90°, more preferably 0° to 80°, and further preferably 10° to 45°. Here, the incident angle that the extension line makes with the tangent vector 702 can also be said to be the incident angle that the extension line makes with the tangent line to the surface of the electrophotographic photosensitive member at the point 701b.

[0053] <Base material> The charging device preferably has a substrate to which the plasma actuator can be attached, i.e., the plasma actuator may be disposed on a surface of the substrate. The substrate is not particularly limited, and there is no particular limit to the cross-sectional shape, width, thickness, material, etc. For example, it is possible to use a substrate in a form that allows a plasma actuator to be attached. The material of the substrate is preferably a material that does not deform under its own weight, such as metal, ceramics, or resin such as ABS resin. It is more preferable that the material has high insulating properties so that electric charge does not leak from the electrodes of the plasma actuator to the outside. In addition, the thickness of the substrate is preferably a thickness that does not deform under its own weight. In other words, the material of the substrate is preferably resin, and more preferably ABS resin. It is more preferable that the thickness of the substrate is such that electric charge does not leak from the electrodes of the plasma actuator to the outside. Also, the plasma actuator may be attached to the frame or main body of the process cartridge as a base material. Also, a configuration may be used in which the dielectric of the plasma actuator is used as the substrate, as shown in Fig. 9B. In the plasma actuator of Fig. 9B, the dielectric has a portion sandwiched between a first electrode and a second electrode, that is, the plasma actuator has a second electrode with a dielectric sandwiched between the first electrode.

[0054] <Process cartridge> FIG. 10 is a schematic cross-sectional view of a process cartridge equipped with a charging device according to the present disclosure. The process cartridge integrally includes the charging device of the present disclosure and one or more devices used in the electrophotographic process. The one or more devices used in the electrophotographic process may be, for example, a developing device. In other words, it is preferable that the process cartridge integrally includes the developing device and the charging device. In addition, it is preferable that the process cartridge is configured to be detachably attached to the main body of the electrophotographic device. The process cartridge may be an electrophotographic process cartridge. The developing device is an integrated unit of at least a developing roller 1002 and a toner container 1004, and may include at least one selected from the group consisting of a photosensitive drum 1001, a toner supply roller 1003, a toner 1007, a developing blade 1006, and an agitating blade 1008, as necessary. The charging device includes at least a plasma actuator 102. The plasma actuator 102, the photosensitive drum 1001, the developing roller 1002, the toner supply roller 1003, and the developing blade 1006 are each configured to have a voltage applied thereto.

[0055] <Electrophotographic device> FIG. 11 is a schematic diagram of an electrophotographic image forming apparatus using a charging device according to the present disclosure. The electrophotographic image forming apparatus includes a charging device according to the present disclosure. The charging device includes a plasma actuator 102. An electrophotographic image forming apparatus can be composed of an electrophotographic photosensitive member such as a photosensitive drum, a charging device that charges the photosensitive drum, a latent image forming device that exposes the electrophotographic photosensitive member to light to form an electrostatic latent image, a developing device that develops the electrostatic latent image as a toner image, a transfer device that transfers the toner image to a transfer material, a fixing device that fixes the toner image to the transfer material, and the like.

[0056] The electrophotographic photoreceptor 1101, such as a photosensitive drum, is preferably a rotating drum type having a photosensitive layer on a conductive substrate. The electrophotographic photoreceptor 1101 is rotated at a predetermined peripheral speed (process speed) in the direction of the arrow. The plasma actuator 102 applies AC and DC voltages, for example, by a charging power source 1106, to the electrophotographic photoreceptor 1101 to a predetermined potential. A latent image forming device (not shown) for forming an electrostatic latent image on the electrophotographic photoreceptor 1101 can be an exposure device such as a laser beam scanner. An electrostatic latent image is formed by irradiating the uniformly charged electrophotographic photoreceptor 1101 with exposure light 1105 corresponding to image information.

[0057] The developing device preferably has a developing sleeve or developing roller 1102 disposed in close proximity to or in contact with the electrophotographic photoreceptor 1101. The developing device develops the electrostatic latent image by reversal development with toner electrostatically treated to have the same polarity as the charged polarity of the electrophotographic photoreceptor 1101 to form a toner image. The transfer device preferably has a contact type transfer roller 1103. The transfer device transfers the toner image from the electrophotographic photoconductor 1101 onto a transfer material such as plain paper. The transfer material is transported by a paper feed system (not shown) having a transport member. The toner image transferred to the transfer material is fixed to the transfer material by passing between a fixing belt 1104 heated by a heating device (not shown) and a roller disposed opposite the fixing belt. EXAMPLES

[0058] The present disclosure will be described in further detail below using examples and comparative examples, but the aspects of the present disclosure are not limited thereto.

[0059] <Example 1> (Creating a plasma actuator) A piece of aluminum foil measuring 2.5 mm in length, 300 mm in width, and 100 μm in thickness was cut with a sharp razor and attached with adhesive tape to a first surface of a silicone resin (5 mm in length, 300 mm in width, and 150 μm in thickness) as a dielectric, to form a first electrode. A piece of aluminum foil measuring 2 mm in length, 300 mm in width, and 100 μm in thickness was also attached with adhesive tape to a second surface of the silicone resin, which is the surface opposite to the first surface, so as to be diagonally opposite the aluminum foil attached to the first surface, to form a second electrode. Furthermore, the second surface including the second electrode was covered with polyimide tape. In this way, a plasma actuator 1 was produced in which the first electrode and the second electrode were provided so as to overlap over a width of 500 μm with the dielectric (silicone resin) sandwiched therebetween. Conductors were attached to the first electrode and the second electrode so that a voltage could be applied. The convex portion of the edge of the first electrode was measured over the entire length direction using a laser microscope. The largest protrusion had a height of 20 μm and a width of 22 μm.

[0060] 2. Characterization [2-1. Induced flow velocity] Next, the speed of the induced flow generated by the plasma actuator was calculated using particle image velocimetry (PIV). Figure 12 is a schematic diagram of the PIV measurement. PIV measurement is a technique in which oil mist injected from the upstream of a wind tunnel is visualized using a PIV Laser (Kato Koken Co., Ltd., G450, 450mW) 1201 installed downstream of the measurement section, and then photographed using a USB high-speed camera (Kato Koken Co., Ltd., k4) 1202 installed above the measurement section.

[0061] The above-mentioned photographing was performed in the oil mist by applying a square wave with an amplitude of 3 kVpp and a frequency of 12 kHz between the first electrode and the second electrode of the fabricated plasma actuator 102, and a DC voltage of -600 V between the first electrode and the ground electrode of the electrophotographic device to generate an induced flow 106. The laser output was 450 mW, the camera exposure was F2.8, and the shutter speed was 1 / 800; FPS=800. The photographed image was analyzed in PIV analysis software (Flow-Expert64 ver1.3.3) to analyze the speed of the oil mist per unit time, and the flow velocity distribution of the induced flow was obtained.

[0062] Specifically, the induced flow velocity was determined as the average flow velocity of the components parallel to the outflow direction vector 106a of the induced flow 106 among the velocity vectors measured within a range of 0.2 mm x 1.0 mm in an area 1.0 mm away from the tip position of the plasma actuator. In this example, the induced flow velocity was 0.29 m / sec.

[0063] [2-2. Discharge stability evaluation] In order to confirm the discharge stability performance of this plasma actuator 1, the following evaluation was carried out. First, an electrophotographic laser printer (product name: Laser Jet Pro M203dw, manufactured by Hewlett-Packard Company) was prepared as an electrophotographic image forming apparatus, and was modified so that a predetermined voltage could be applied thereto. A conductor is connected to the first electrode and the second electrode of the plasma actuator, and a voltage is applied to generate an induced flow. Specifically, an AC voltage is applied between the first electrode and the second electrode from an AC power source, and a DC voltage is applied between the first electrode and the ground electrode of the electrophotographic device. Modifications have been made to make this possible. Next, an ABS resin sheet (30 mm long, 300 mm wide, 1 mm thick) was prepared as a base material for mounting the fabricated plasma actuator 1. Next, the previously fabricated plasma actuator 1 was attached to one surface of the ABS resin sheet. Specifically, the polyimide tape side covering the second electrode of the plasma actuator was glued and fixed. Next, Then, the ABS resin sheet with the plasma actuator 1 attached was attached to the process cartridge from which the charging roller was removed. At this time, the sheets were attached so that when a straight line was drawn from the center of the rotation axis of the photosensitive drum to the center of the first electrode, the straight line intersected the photosensitive drum surface, the dielectric, and the first electrode in that order. The plasma actuators were also attached so that they were arranged in a counter-position. Furthermore, the distance between the tip of the plasma actuator on the second electrode side and the point where an extension line from the edge of the first electrode along the direction along the exposed part of the first surface of the dielectric intersects with the photosensitive drum surface (701 in FIG. 7A) was 2 mm, and the narrow angle θ (FIG. 7A), which is the angle between the extension line along the direction along the exposed part of the first surface of the dielectric and the tangent vector, was 30°.

[0064] Next, the electrophotographic image forming apparatus and the process cartridge to which the plasma actuator 1 was attached were left in an environment of 18° C. / 30% RH for 48 hours in order to acclimate them to the evaluation environment. The process cartridge that had been left in the above environment was installed in a laser printer. Then, in the same environment, a square wave with an amplitude of 3 kVpp and a frequency of 12 kHz was applied between the first electrode and the second electrode, and a DC voltage of -600 V was applied between the first electrode and the ground electrode of the electrophotographic device, and a halftone image (an image in which horizontal lines with a width of 1 dot and an interval of 2 dots are drawn in the direction perpendicular to the rotation direction of the photosensitive drum) was output. This halftone was observed visually and with a microscope, and vertical streaks were evaluated according to the following criteria. In this embodiment, it was ranked A. A good evaluation indicates that the discharge stability performance of the plasma actuator is high.

[0065] [Evaluation of vertical stripes in halftone images] Rank A: When observed visually and under a microscope, no vertical streaks are observed on the halftone image. Rank B: No vertical streaks are visible on the halftone image when observed with the naked eye, but they are visible when observed under a microscope. Rank C: Vertical stripes are visible on some parts of the halftone image. Rank D: Vertical stripes are visible across the entire surface of the halftone image.

[0066] [2-3. Static electricity removal performance of dirt] The static electricity removal performance of the plasma actuator 1 against dirt was measured. The static electricity removing performance of the plasma actuator against dirt (residual toner after transfer) was evaluated by measuring the charge amount of the residual toner before and after the induced flow by the plasma actuator was supplied, using a charge amount distribution measuring device by the following means.

[0067] Specifically, the amount of transfer residual toner was increased by increasing the transfer current using the electrophotographic image forming apparatus used in 2-2 above.Then, the charge distribution of the transfer residual toner was measured after the induced flow was supplied by the plasma actuator driven under the same conditions as in 2-1 above.Then, the same operation was performed except that the plasma actuator was not driven, and the charge distribution of the transfer residual toner was measured.

[0068] The amount of the transfer residual toner when checking the change in the charge polarity of the transfer residual toner was controlled by adjusting the transfer bias so that the fog value obtained by the following measurement method was 5%. The fog value was specifically measured as follows. First, the printing operation was stopped while printing a solid black image, and the transfer residual toner adhering between the transfer member abutment part and the charging member abutment part on the photosensitive drum surface was peeled off with a tape (product name: CT18, manufactured by Nichiban Co., Ltd.). Next, the reflectance was measured with a reflection densitometer (product name: TC-6DS / A, manufactured by Tokyo Denshoku Co., Ltd.), and the reduction amount (%) of the reflectance based on the reflectance of the tape was measured and used as the fog value.

[0069] The charge distribution is measured using an E-spart analyzer (manufactured by Hosokawa Micron Corporation). The E-spart analyzer is a detector that simultaneously generates an electric field and an acoustic field ( This device introduces sample particles into a measuring section, measures the number-average particle size of the sample particles using the action of an acoustic field, measures the movement speed of the sample particles using the laser Doppler method, and calculates the charge of the sample particles. The air flow rate for aspirating the sample particles was 400 L / min, the voltage applied to the measurement electrode was 100 V, and the count number was 300 particles.

[0070] Then, the proportion of transfer residual toner charged with the same polarity as the polarity (polarity A) applied to the transfer member when the plasma actuator is driven is defined as X1, and the proportion of transfer residual toner charged with the same polarity as polarity A when the plasma actuator is not driven is defined as X2, and the rate of change in the proportion Δ (Δ=((X2-X1) / X2)×100) was calculated. In the examples, the proportion X of the number of positively charged transfer residual toner particles was calculated from the charge amount distribution of the transfer residual toner obtained by measurement. The proportion of the number of positively charged transfer residual toner particles to the total number of transfer residual toner particles when the plasma actuator was driven was designated as X1, and the proportion of the number of positively charged transfer residual toner particles to the total number of transfer residual toner particles when the plasma actuator was not driven was designated as X2, and the rate of change in the proportion Δ (Δ=((X2-X1) / X2)×100) was calculated. In this embodiment, X1=8.1%, X2=82.1%, and Δ=90.1%.

[0071] 3.Durability evaluation [3-1. Stain resistance] After the discharge stability evaluation in 2-2 above, a total of 50,000 images were output continuously under the same conditions. The output image was an alphabet letter "E" of 4 points on A4 size paper with a print rate of 1.0%. Then, one halftone image (an image in which horizontal lines of 1 dot width and 2 dot intervals are drawn in the direction perpendicular to the rotation direction of the photosensitive drum) was output. This halftone was observed visually and under a microscope, and evaluated under the same criteria as the criteria for vertical streaks in 2-2 above. In this embodiment, it was ranked A.

[0072] [3-2. Dirt adhesion] After the evaluation test of the stain resistance in 3-1 above, the first electrode of the plasma actuator was observed in the longitudinal direction using a laser microscope (product name: Color 3D Laser Microscope VK-8700, manufactured by Keyence Corporation). A square field of view of 1000 μm in length and 1000 μm in width was placed at the location where the stain (toner) was attached to the first electrode, and the number of toner particles attached to the first electrode within the field of view was counted. The number of stains attached was 6. In the examples in which streaks were observed in the stain resistance evaluation test in 3-1 above, the first electrode of the plasma actuator was observed by placing the above-mentioned square field of view on a portion of the first electrode corresponding to the vertical streak portion that had the largest density difference from the surrounding image.

[0073] [3-3. Dielectric breakdown evaluation] After the stain resistance evaluation test in 3-1 above, the first electrode of the plasma actuator was visually observed to check whether there were any locations where dielectric breakdown occurred between the first electrode and the second electrode, and the number of such locations was counted. In this example, no dielectric breakdown occurred. If "burning" due to dielectric breakdown is confirmed at the interface between the first electrode and the dielectric, or at the interface between the second electrode and the dielectric, it is determined that dielectric breakdown has occurred. The number of dielectric breakdowns is shown in Table 2.

[0074] <Examples 2 to 20> Plasma actuators 2 to 20 were produced in the same manner as plasma actuator 1, except that the configuration and arrangement of the plasma actuator were changed as shown in Table 1. In addition, a process cartridge similar to that of Example 1 was prepared and evaluated, except that plasma actuators 2 to 20 were used. The evaluation results are shown in Table 2. In Example 19, a polyimide resin sheet was used as the dielectric. In Examples 7 to 10, the cut aluminum foil was ground with sandpaper to form an uneven shape on the edge of the first electrode where discharge occurs, thereby forming a convex portion.

[0075] <Example 21> In Example 21, a silicone resin having different thicknesses at the front and rear ends (length 30 mm, width 300 mm, front end thickness 150 μm, rear end thickness 3 mm) was produced as shown in Fig. 9B. Plasma actuator 21 was produced in the same manner as plasma actuator 1, except that the front end side of the produced silicone resin was used as a dielectric. A process cartridge similar to that in Example 1 was prepared and evaluated, except that the rear end portion of the dielectric was attached to the process cartridge. The evaluation results are shown in Table 2.

[0076] <Example 22> A plasma actuator 22 was produced in the same manner as the plasma actuator 1, except that the configuration and arrangement of the plasma actuator were changed as shown in Table 1. Specifically, the first electrode and the second electrode of the plasma actuator were not overlapped, and were separated by a distance of 200 μm. In addition, a process cartridge similar to that of Example 1 was prepared and evaluated, except that the plasma actuator 22 was used. In this example, the two electrodes did not overlap, so the induced flow by the plasma actuator was weak, and the effect of de-electrifying and / or charging the transfer residual toner was relatively weak compared to Example 1. It is considered that this is the reason why streaky images were generated after durability testing. The evaluation results are shown in Table 2.

[0077] <Comparative Examples 1 to 3> Plasma actuators 23-25 ​​were produced in the same manner as plasma actuator 1, except that the configuration and arrangement of the plasma actuator were changed as shown in Table 1. In addition, a process cartridge similar to that of Example 1 was prepared and evaluated, except that plasma actuators 23-25 ​​were used. The evaluation results are shown in Table 2.

[0078] In Comparative Example 1, the induced flow was not directly supplied to the surface of the photosensitive drum, so the dirt negativity was poor. Therefore, in the durability evaluation, the adhesion of dirt to the charging member could not be suppressed, and vertical streaks occurred. One of the reasons for this is thought to be that the two electrodes do not overlap, and the induced flow generated is weak. In Comparative Example 2, similar to Comparative Example 1, the induced flow was not directly supplied to the surface of the photosensitive drum, so that adhesion of dirt could not be suppressed during the durability evaluation, resulting in the occurrence of vertical streaks. In Comparative Example 3, since no DC voltage was applied, the charges in the induced current were not biased and the current was electrically neutral, so the photosensitive drum surface could not be charged and an image could not be formed.

[0079] <Comparative Example 4> The evaluation was performed in the same manner as in Example 1, except that the charging roller of the process cartridge in Example 1 was not removed, a non-contact charging roller was used as the charging member, and no plasma actuator was used, a POM roller having an outer diameter of 9.8 mm was attached to the core metal part of the charging roller mounted in the process cartridge used, the charging roller was spaced 50 μm from the photosensitive drum, and the charging bias was −1500 V. The evaluation results are shown in Table 2. In Comparative Example 4, a non-contact charging roller was used, and no induced flow toward the drum surface was generated. Therefore, the flying of dirt from the photosensitive drum surface to the charging roller due to electrostatic attraction could not be suppressed, and dirt continued to accumulate on the charging member, causing vertical streaks in the durability evaluation.

[0080] <Comparative Example 5> Except for using a scorotron charger as the charging member, the evaluation was performed in the same manner as in Example 1. As shown in FIG. 14, the scorotron charger is composed of a wire 1401, a casing 1402, and a grid 1403, and is disposed so that the grid is close to the photosensitive drum 104. A wire bias voltage of 3 kVpp and a grid bias voltage of -700 V were applied to the scorotron charger. The evaluation results are shown in Table 2. In Comparative Example 5, since a Scorotron charger is used, no induced flow toward the drum surface occurs, and therefore, the flying of dirt from the photosensitive drum surface to the charging member due to electrostatic attraction cannot be suppressed, and dirt continues to accumulate on the charging member, causing vertical streaks in the durability evaluation. [Table 1] In the table, in the column of overlap length A, -200 μm indicates that the first electrode and the second electrode are not overlapped and are spaced apart by 200 μm. In the column of PA position, 1 indicates that a substrate is disposed between the first electrode and the electrophotographic photoreceptor, and 2 indicates that a plasma actuator is disposed between the substrate and the electrophotographic photoreceptor. [Table 2]

[0081] The present disclosure relates to the following configurations. (Configuration 1) A charging device for charging a body to be charged, comprising: A plasma actuator is provided. The plasma actuator comprises: A dielectric material; a first electrode provided on a first surface of the dielectric; a second electrode disposed between the first electrode and the dielectric, The plasma actuator generates an induced flow from an edge of the first electrode along an exposed portion of the first surface of the dielectric material that is not covered by the first electrode by applying an AC voltage between the first electrode and the second electrode; The plasma actuator is arranged so that the induced flow is directly supplied to the surface of the charged body. It is placed, A charging device comprising: a charging member for applying a DC voltage between the first electrode and the member to be charged. (Configuration 2) 2. The charging device according to configuration 1, wherein the first electrode and the second electrode are arranged diagonally opposite each other with the dielectric material therebetween. (Configuration 3) When the plasma actuator is seen through from the first surface side, at least a portion of the first electrode and the second electrode have an overlapping portion, 3. The charging device according to configuration 1 or 2, wherein a length A between the edge of the first electrode and the edge of the second electrode forming the overlapping portion is 0 to 1000 μm. (Configuration 4) 4. The charging device according to any one of configurations 1 to 3, wherein the height of the protrusions on the edge of the first electrode is 40 μm or less. (Configuration 5) the charging device having a substrate; The plasma actuator is disposed on a surface of the substrate, 5. The charging device according to any one of configurations 1 to 4, wherein the base material is disposed between the plasma actuator and the body to be charged. (Configuration 6) the charging device having a substrate; The plasma actuator is disposed on a surface of the substrate, 5. The charging device according to any one of configurations 1 to 4, wherein the plasma actuator is disposed between the substrate and the body to be charged. (Configuration 7) the member to be charged is an electrophotographic photoreceptor, a point where an extension line extending from an edge of the first electrode in a direction along the exposed portion of the first surface of the dielectric intersects with the surface of the electrophotographic photosensitive member, and a velocity vector in a rotational direction of the electrophotographic photosensitive member on a tangent line to the surface of the electrophotographic photosensitive member at the point is defined as a tangent vector; The charging device according to any one of configurations 1 to 6, wherein when the outflow direction vector of the discharge induced flow supplied from the plasma actuator is decomposed, the outflow direction vector has a directional component that is parallel to and points in the same direction as the tangent vector. (Configuration 8) the member to be charged is an electrophotographic photoreceptor, a point where an extension line extending from an edge of the first electrode in a direction along the exposed portion of the first surface of the dielectric intersects with the surface of the electrophotographic photosensitive member, and a velocity vector in a rotational direction of the electrophotographic photosensitive member on a tangent line to the surface of the electrophotographic photosensitive member at the point is defined as a tangent vector; The charging device according to any one of configurations 1 to 6, wherein when the outflow direction vector of the discharge induced flow supplied from the plasma actuator is decomposed, the outflow direction vector has a directional component that is parallel to and opposite to the tangent vector. (Configuration 9) the member to be charged is an electrophotographic photoreceptor, a point where an extension line extending from an edge of the first electrode in a direction along the exposed portion of the first surface of the dielectric intersects with the surface of the electrophotographic photosensitive member, and a velocity vector in a rotational direction of the electrophotographic photosensitive member on a tangent line to the surface of the electrophotographic photosensitive member at the point is defined as a tangent vector; When an extension line from the edge of the first electrode in a direction along the exposed portion of the first surface of the dielectric body forms an angle θ with respect to the tangent vector, the angle θ is 0° to 90°. The charging device according to any one of configurations 1 to 8. (Configuration 10) 10. The charging device according to claim 9, wherein the narrow angle θ is 10° to 45°. (Configuration 11) the charging device having a substrate; 11. The charging device according to any one of configurations 1 to 10, wherein the dielectric material of the plasma actuator is the substrate. (Configuration 12) 12. The charging device according to any one of configurations 1 to 11, wherein the dielectric material is a silicone resin. (Configuration 13) 13. A process cartridge detachably mountable to a main body of an electrophotographic image forming apparatus, comprising the charging device according to any one of Configurations 1 to 12. (Configuration 14) 13. An electrophotographic image forming apparatus comprising the charging device according to any one of configurations 1 to 12.

Claims

1. A charging device for charging an object to be charged, Equipped with a plasma actuator, The plasma actuator is Dielectrics and A first electrode provided on the first surface of the dielectric, The device comprises a second electrode positioned with respect to the first electrode, with the dielectric material in between. The plasma actuator generates an induced flow from the edge of the first electrode along the exposed portion of the first surface of the dielectric that is not covered by the first electrode by applying an alternating voltage between the first electrode and the second electrode. The plasma actuator is positioned such that the induced flow is directly supplied to the surface of the charged object. A charging device characterized by applying a DC voltage between the first electrode and the object to be charged.

2. The charging device according to claim 1, wherein the first electrode and the second electrode are arranged diagonally opposite each other with the dielectric in between.

3. When the plasma actuator is viewed through from the first surface side, at least a portion of the first electrode and the second electrode have an overlapping portion. The charging device according to claim 1, wherein the length A between the edge of the first electrode and the edge of the second electrode forming the overlapping portion is 0 to 1000 μm.

4. The charging device according to claim 1, wherein the height of the protrusion at the edge of the first electrode is 40 μm or less.

5. The charging device has a base material, The plasma actuator is positioned on the surface of the substrate. The charging device according to claim 1, wherein the substrate is disposed between the plasma actuator and the object to be charged.

6. The charging device has a base material, The plasma actuator is positioned on the surface of the substrate. The charging device according to claim 1, wherein the plasma actuator is disposed between the substrate and the object to be charged.

7. The charged object is an electrophotographic photoreceptor, The extension line from the edge of the first electrode along the exposed portion of the first surface of the dielectric material intersects the surface of the electrophotographic photoreceptor at a point, and the tangent vector is defined as the velocity vector in the rotational direction of the electrophotographic photoreceptor on the tangent line to the surface of the electrophotographic photoreceptor at that point. The charging device according to claim 1, wherein when the outflow direction vector of the induced flow supplied from the plasma actuator is decomposed, the outflow direction vector has a directional component that is parallel to and in the same direction as the tangent vector.

8. The charged object is an electrophotographic photoreceptor, The extension line from the edge of the first electrode along the exposed portion of the first surface of the dielectric material intersects the surface of the electrophotographic photoreceptor at a point, and the tangent vector is defined as the velocity vector in the rotational direction of the electrophotographic photoreceptor on the tangent line to the surface of the electrophotographic photoreceptor at that point. The charging device according to claim 1, wherein when the outflow direction vector of the induced flow supplied from the plasma actuator is decomposed, the outflow direction vector has a directional component that is parallel to and opposite to the tangent vector.

9. The charged object is an electrophotographic photoreceptor, The extension line from the edge of the first electrode along the exposed portion of the first surface of the dielectric material intersects the surface of the electrophotographic photoreceptor at a point, and the tangent vector is defined as the velocity vector in the rotational direction of the electrophotographic photoreceptor on the tangent line to the surface of the electrophotographic photoreceptor at that point. The charging device according to claim 1, wherein when the narrow angle θ is defined as the angle formed between the extension line extending from the edge of the first electrode along the exposed portion of the first surface of the dielectric and the tangent vector, the narrow angle θ is between 0° and 90°.

10. The charging device according to claim 9, wherein the narrow angle θ is 10° to 45°.

11. The charging device has a base material, The charging device according to claim 1, wherein the dielectric of the plasma actuator is the substrate.

12. The charging device according to claim 1, wherein the dielectric is a silicone resin.

13. A process cartridge that is detachable from the main body of an electrophotographic image forming apparatus, characterized in that it comprises a charging device as described in any one of claims 1 to 12.

14. An electrophotographic image forming apparatus comprising a charging device according to any one of claims 1 to 12.

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